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  • Articles: DFG German National Licenses  (591)
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  • ZIB Catalog
  • Articles: DFG German National Licenses  (591)
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  • 1985-1989  (591)
  • 1965-1969
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  • 1
    ISSN: 1432-1440
    Keywords: Growth hormone-Releasing hormone ; Somatostatin ; Insulin ; Type 1 diabetic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following a mixed meal, plasma hormone responses were measured in four type 1 diabetic children and in eight short normal children. Between 60 and 150 min after ingestion of the mixed meal there was a significant increase in circulating growth hormone-releasing hormone values both in diabetic and in normal children. Mean plasma GHRH peak values were not different between diabetic patients (27.0±3.9 ng/l) and controls (24.6±4.9 ng/l). No time relationship to spontaneous growth hormone peaks was observed. Whereas normal children showed a characteristic biphasic plasma somatostatin response, somatostatin plasma levels in diabetic children did not change. In normal children plasma insulin values increased between 30 and 150 min, but remained unchanged in type 1 diabetic patients. Blood glucose response was more pronounced in diabetic children than in short normal children. These results indicate that circulating growth hormone-releasing hormone does not play a dominant role in the regulation of insulin and somatostatin.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 66 (1988), S. 924-927 
    ISSN: 1432-1440
    Keywords: Hypertension ; Insulin ; Glucagon ; Skeletal muscle ; Glycogen ; Glucose ; Glycogen synthetase ; Glycogen phosphorylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was performed to investigate as to whether peripheral insulin resistance exists in spontaneously hypertensive rats (SHR). After a 12 h fasting period, SHR had significantly higher serum glucose and higher plasma glucagon values in comparison to normotensive control rats (WKY). There was a tendency for higher serum insulin concentrations as well, but this difference did not reach significance. After oral glucose loading or glucose/insulin administration, serum glucose and insulin levels were also higher in SHR compared to WKY rats. Muscle glycogen and glucose concentrations were identical in fasted SHR and WKY rats. With an oral glucose load or glucose/insulin treatment there was a significant increase in muscle glycogen, whereas glucose values declined in skeletal muscle. Both total (a+b-form) phosphorylase activity as well as the active a-form of the enzyme were similar in skeletal muscle of SHR and WKY rats. Glucose/insulin administration or oral glucose loading induced a considerable reduction of both a+b-form and a-form activities. The decrease in muscle phosphorylase activities was almost identical in both groups of animals. There was also a comparable activity of muscle glycogen synthetase activity in all groups of rats. Despite subtile changes of glucose, glucagon and to a lesser degree insulin levels which would be suggestive of insulin resistance, the data obtained from skeletal muscle argue against peripheral insulin resistance in spontaneously hypertensive rats.
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  • 3
    ISSN: 1432-2307
    Keywords: AVP/SV40 transgenic mice ; Immunocytochemistry ; Insulin ; Pancreatic polypeptide ; Large T-antigen ; Heterochromatin ; Dysplasia ; Neoplasia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insertion into the mouse genome of the hybrid oncogene made up of bovine vasopressin gene derived 5′ upstream sequences and the coding sequences of SV40 large T-antigen promoted tumours in anterior pituitary and endocrine pancreas of mice bearing this transgene. In order to investigate the morphology of the steps in the neoplastic process, we used light and electron microscopy to study these organs in 42 animals belonging to the 3rd, 4th and 5th generations, subdivided into 4 age groups from 20 days to 100 days of life. Antibodies to large T-antigen were used to identify sites of expression of the hybrid oncogene, thus monitoring the steps in neoplastic transformation. Large T-antigen immunoreactivity was identified in dysplastic lesions of younger animals and in both dysplastic lesions and tumours of older mice. Insulin (100% of cases) and pancreatic polypeptide (25% of cases) immunoreactivities were revealed in pancreatic lesions but no hormonal immunoreactivity was detected in the pituitary lesions. The ultrastructural study confirmed that the majority cell population of the pancreatic neoplasms was B-type and that the anterior pituitary tumours were poorly granulated. The subcellular localization of large T-antigen immunoreactivity was investigated by the immunogold method and was confined to the heterochromatin of tumour cell nuclei. These findings provide evidence for the dysplasia-neoplasia sequence in the genesis of endocrine tumours of pituitary and pancreas of transgenic mice. The vasopressin-SV40 large T-antigen transgenic mice may therefore be an useful model for the study of endocrine cell oncogenesis,
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Research in experimental medicine 188 (1988), S. 27-33 
    ISSN: 1433-8580
    Keywords: Carbon tetrachloride ; Insulin ; Glucagon ; Cytochrome P450
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats given a dose of carbon tetrachloride (CCl4) immediately received injections of glucagon and insulin every 4h. They frequently died after 4h and showed a significantly higher mortality between 8h and 28h as compared to the control rats where such deaths occurred 16h later. At 8h, the derangements of SGPT values and prothrombin time were significantly greater in the hormone-treated rats than in the control rats. In these CCl4-intoxicated rats, hepatic reduced glutathione content at 4h was significantly reduced after hormone treatment. The treatment significantly enhanced CCl4 metabolism, conversion of14CCl4 into14CO2 in vitro, by microsomes isolated from the liver, whereas it did not affect the microsomal cytochrome P450 content. These results suggest that glucagon and insulin treatment increased CCl4 hepatotoxicity in rats through activating the cytochrome P450-dependent mono-oxygenase system. This would merit consideration for the clinical application of this treatment.
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  • 5
    ISSN: 1432-0568
    Keywords: Pancreatic islet ; Insulin ; Glucagon ; Ontogeny ; Immunohistochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ontogenetic appearances of glucagon, insulin and tyrosine hydroxylase (TH) were immunohistochemically investigated on developing pancreatic islets of rats. Glucagon immunoreactivity appeared first in some epithelial cells (g-cells) of the dorsal anlage of the pancreas on day 11.5 of gestation. On day 12.5, g-cells increased in number manufacturing the primitive islets, in which some cells appeared to be immunoreactive for insulin (i-cells) and about 40% of g-cells indicated also a slight immunoreactivity for insulin (g/i-cells). Afterwards, all the islet cells, especially g-cells, increased in number, and almost half of g-cells were g/i-cells. After day 16.5 of gestation, numerical increase of the cells with insulin immunoreactivity exceeded that of the cells with glucagon immunoreactivity, and about one fifth of g-cells were g/i-cells. After 20.5 days, however, no g/i cells were found. On day 16.5 of gestation, the immunoreactivity for TH appeared in occasional cells of the islets, but the cells did not show immunoreactivity for glucagon or insulin. It is concluded that the progenitor cells of the pancreatic islets appear to synthesize both glucagon and insulin by day 20.5 of gestation, but differentiate giving rise to mature A and B cells of adult isoets afterward.
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  • 6
    ISSN: 1432-0428
    Keywords: Insulin ; glucose ; age ; children ; puberty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The pattern of insulin secretion was studied in 107 normal individuals aged 5 to 50 years. Intravenous glucose tolerance tests were performed on 64 islet-cell antibody negative siblings of diabetic children and on 43 normal adults. Puberty was staged using Tanner's criteria and subjects were grouped as follows: I — stage 1 (n=22), II — stages 2 and 3 (n=18), III — stages 4 and 5 (n=20), IV — adults 〉17 years (n=47). Basal and stimulated (incremental 0–10 and 10–60 min areas) insulin responses rose throughout puberty (Groups I–III), declined following puberty until the third decade (Groups III and IV) and then appeared constant thereafter. Insulin levels in the 17.6–22.5 year group were lower than in the 12.6–15 year group (p〈0.01). Fasting insulin to glucose ratios and incremental 0–60 min insulin to glucose area ratios produced a similar age-related pattern indicating that changes in insulin levels were independent of glucose concentrations. Gender did not affect these changes and multiple regression analysis showed that HLA haplotype sharing did not influence insulin responses in siblings of diabetic patients. Age and pubertal status must be carefully considered when interpreting intravenous glucose tolerance tests from patients suspected of having early abnormalities of carbohydrate metabolism.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 31 (1988), S. 51-53 
    ISSN: 1432-0428
    Keywords: Insulin ; erythrocyte ; diabetes ; glucose metabolism ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Alloxan-induced diabetes in rats significantly impaired the capacity of the erythrocytes to metabolise glucose in vitro to either lactic acid or CO2. Both these metabolic activities were initially insensitive to insulin in normal as well as in diabetic animals; but became responsive when these cells were subjected to insulin and glucose ‘starvation’ for 1 h through incubation in their absence. This action of insulin in starved cells showed concentration dependence and required preincubation with the hormone prior to addition of glucose.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0428
    Keywords: Insulin ; glucagon ; thyroid hormones ; glucose turnover ; glucose production ; glucose utilisation ; glucoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The glucoregulatory function of glucagon was investigated in hypo-, eu- and hyperthyroid miniature pigs. Infusion glucagon, (3 ng x kg body weight−1 · min−1) transiently increased blood glucose (p〈0.01) and hepatic glucose production (p〈0.01) in euthyroidism, but was without effect in hyperthyroidism. Infusing glucagon plus somatostatin (2 ng x kg body weight−1 · min−1 and 0.2 μg x kg body weight−1 · min−1) transiently increased blood glucose (Δ 3.0 to 4.3 mmol/l) and hepatic glucose production (Δ 3.3 to 7.7 umol x kg body weight−1 · min−1) in all thyroid states, the effect was less pronounced in hyperthyroid pigs. By contrast, hypoglucagonaemia (74 to 107 pg/ml) at basal insulin (28 to 35 μU/ml) provoked hypoglycaemia (1.4 to 2.2 mmol/l) and a fall in glucose production (Δ 4.7 to 8.3 umol x kg body weight−1 · min−1), which was independent of the thyroid state; the effect was most pronounced in hyperthyroidism (p〈0.01). Hepatic glycogen content, arterial gluconeogenic precursor concentrations as well as the glycaemic response (Δ 0.60 mmol/l) to alanine infusion (23 umol x kg body weight−1 · min−1) were all unaffected by hyperthyroidism. We conclude that moderate experimental hyperthyroidism reduces glucagon action due to reduced glycogen mobilisation. This may in part result from increased insulin sensitivity.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 44 (1988), S. 1-9 
    ISSN: 1420-9071
    Keywords: Insulin ; glucagon ; pancreatic polypeptide ; somatostatin ; fetal pancreas ; ontogeny ; immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ontogeny of insulin, glucagon, PP and somatostatin in the mammalian fetal pancreas has been examined in recent years largely by immunocytochemistry and in some instances by radioimmunoassay. Complete ontogenic data are available only for the rat, human pig and sheep. Figure 3 compares the time of appearance of the endocrine cell-types within the fetal pancreas when the periods of gestation of the four species are converted to a uniform scale. The striking ontogenic difference in the rat probably reflects the immaturity of the rodent fetus at birth compared with the human, pig and sheep. In the fetal pancreas, differences in cell number of glucagon and PP cells in the dorsal and ventral lobes become apparent from an early gestational period. Factors responsible for the functional and structural maturation of the fetal pancreatic endocrine cells and the processes involved in pancreatic organogenesis are poorly understood. Studies in these areas would have clinical implications since it may be possible in the future to employ agents for selective replication of fetal β-cells for transplantation in patients with Type I diabetes, bearing in mind that such cells must have the capacity to respond to normal stimuli and repressors when transplanted. The presence of the other islet cell-types may be obligatory for these appropriate responses. This would require a more complete knowledge of those factors which produce the normal selectivity of the four hormonal cell-types.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 412 (1988), S. 258-263 
    ISSN: 1432-2013
    Keywords: Acetylcholine ; Quanta ; Na+−K+ exchange pump ; Ouabain ; Adrenaline ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pretreatment with hypertonic solutions, insulin, or adrenaline increases the size of quanta at the frog neuromuscular junction, as determined by measurements of miniature end plate potentials or currents (Van der Kloot and Van der Kloot 1985, 1986). The increase in quantal size apparently is due to an increase in acetylcholine (ACh) content of individual quanta. These treatments, therefore, can be used to study the packaging of ACh. Previously, I reported that increases are blocked by an inhibitor of active ACh uptake into vesicles (Van der Kloot 1986b, 1987b). The present study shows that the increases in quantal size were antagonized by inhibiting the Na+−K+ exchange pump with 100 μM ouabain, 10 μM dihydroouabain, or K+-free solutions. The increases in quantal size were also antagonized by 10 μM monensin, a Na+ ionophore, or by 5 μM aconitine, which opens Na+ channels at normal resting potentials. Apparently a rise in intracellular [Na+] inhibits the addition of ACh to quanta. The mechanism by which a rise in intracellular Na+ inhibits ACh packing is unknown, but apparently it is not due to inhibition of choline reuptake into the terminals. Also consistent with the above hypothesis is that the increase in quantal size following depolarization for 2 h in elevated [K+]out was substantially enhanced when tetrodotoxin (TTX) was present, suggesting that in the absence of TTX there is a rise in [Na+]in that antagonizes the incorporation of additional ACh into the quanta.
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  • 11
    ISSN: 1432-2013
    Keywords: Nephron microdissection ; Glomeruli ; Tubules ; [125I] Insulin binding ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Binding of [125I] Tyr A14 human insulin ([125I] insulin) was measured at 4°C in glomeruli and pieces of tubule microdissected from collagenase-treated rat kidneys. For glomeruli and all segments tested, total and non specific binding increased linearly with glomeruli number or tubular length. When determined with 4.0 nM labelled hormone, the distribution of specific binding sites (expressed as 10−18 mol [125I] insulin bound per glomerulus or mm tubule length) was as follows: glomerulus, 2.5±0.3; proximal convoluted tubule (PCT), 12.6±0.6; pars recta (PR), 4.0±2.3; thin descending limb (TDL), 0.6±0.2; thin ascending limb (TAL), 0.6±0.2; medullary thick ascending limb (MAL), 0.8±0.1; cortical ascending limb (CAL), 2.1±0.1; distal convoluted tubule (DCT), 5.6±1.1; cortical collecting tubule (CCT), 3.2±0.3 and outer medullary collecting tubule (MCT), 2.3±0.1. Specific [125I] insulin binding to glomeruli and tubule segments was time- and dose-dependent, saturable, reversible after elimination of free labelled ligand, and inhibited by unlabelled human insulin. When analysed in Scatchard and Hill coordinates, the binding data revealed a negative cooperation in the interaction processes between [125I] insulin and glomerular and tubular binding sites, with apparent dissociation constants and Hill coefficients of the following values: glomerulus, 0.6 nM and 0.60; PCT, 10.0 nM and 0.55; MAL, 4.3 nM and 0.80; CAL, 2.0 nM and 0.74; CCT, 7.6 nM and 0.80 and MCT, 1.0 nM and 0.57 respectively. The stereospecificity of nephron binding sites was assessed in competitive experiments showing that unlabelled bovine and procine insulins were as efficient as human insulin for displacing [125I] insulin, whereas A and B chains of insulin and unrelated peptide hormones were almost inactive. These results indicate that the detected [125I] insulin binding sites may correspond to physiological insulin receptors.
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  • 12
    ISSN: 1432-2307
    Keywords: Insulin ; Insulinomas ; Ultrastructure ; Immunogold technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Localisation of insulin-like immunoreactivity has been studied using the immunogold staining procedure on thin sections of 6 human insulinomas, conventionally processed for electron microscopy. The labelling was restricted to the secretory granules. Depending on their morphology, these either resembled B-cell granules of human adult pancreas or belonged to the atypical (non-diagnostic) group. Within the former group, those with a crystalloid core or an amorphous dense or moderately dense core were strongly immunoreactive, whereas others, filled with a pale material, were poorly labelled. Most granules of this type were stored together within the heavily granulated cells of 3 insulinomas, presenting the classical features of clinical and biological behaviour and a typical light microscopic staining pattern. In contrast, the non-diagnostic granules, characterized by their smaller size, a very dense core and a thin halo, were mainly found within the poorly granulated cells making up the other tumours, and showed a very uneven labelling. Strongly labelled granules were found in one insulinoma that also belonged to the classical type; these were stored together with a few diagnostic granules within the same cells. Only poorly labelled atypical granules were present in two cases revealing a number of unusual features; these included moderate elevation of insulinaemia, uncertain tumour histology, as well as weak immunostaining for insulin/proinsulin and variable argyrophilia of the tumour in paraffin sections. These findings suggest that human insulinomas differ not only in storage capacity but also in their degree of granule maturation. This may involve some deficiency of either the prohormone conversion or the subsequent processing of the cleavage products.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 252 (1988), S. 9-15 
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Insulin ; Immunocytochemistry ; Lysosomes ; Crinophagy ; Mouse (NMRI)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies of pancreatic islets have suggested that crinophagy provides a possible mechanism for intracellular degradation of insulin in the insulin-producing B-cells. In the present study, a quantitative estimation of crinophagy in mouse pancreatic islets was attempted by morphometric analysis of lysosomes containing immunoreactive insulin. Isolated islets were incubated in tissue culture for one week in 3.3, 5.5 or 28 mmol/l glucose. The lysosomes of the pancreatic B-cells were identified by morphological and enzyme-cytochemical criteria and divided into three subpopulations comprising primary lysosomes and insulin-positive or insulin-negative secondary lysosomes. Both the volume and numerical density of the primary lysosomes increased with increasing glucose concentration. The proportion of insulin-containing secondary lysosomes was highest at 5.5 and lowest at 3.3 mmol/l glucose. Insulin-negative secondary lysosomes predominated at 3.3 mmol/l glucose. Studies of the dose-response relationships of glucose-stimulated insulin biosynthesis and insulin secretion of the pancreatic islets showed that biosynthesis had an apparent Km-value for glucose of 7.0 mmol/l, whereas it was 14.5 mmol/l for secretion. The pronounced crinophagic activity at 5.5 mmol/l glucose may thus be explained by the difference in glucose sensitivity between insulin biosynthesis and secretion resulting in an intracellular accumulation of insulin-containing secretory granules. The predominance of insulin-negative secondary lysosomes at 3.3 mmol/l glucose may reflect an increased autophagy, whereas the predominance of primary lysosomes at 28 mmol/l glucose may reflect a generally low activity of intracellular degradative processes.
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  • 14
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Stomach ; Intestine ; Immunohistochemistry ; Thyrotropin-releasing hormone (TRH) ; Somatostatin ; Avian pancreatic polypeptide ; Insulin ; Gastrin ; Rat ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By use of the indirect immunofluorescence technique, the cellular localization of thyrotropin-releasing hormone (TRH) was studied in the gastrointestinal tract of rats and guinea pigs of different ages. TRH-like immunoreactivity (LI) was observed in many pancreatic islet cells of young rats and guinea pigs but only in single cells of 6-month-old rats. In aged guinea pigs, a reduction in the number of TRH-positive cells was evident; however, numerous strongly fluorescent cells were still present. In the guinea pig, TRH-LI was in addition observed in gastrin cells in the stomach. TRH-positive nerve fibers occurred in the myenteric plexus of the oesophagus, stomach and intestine of the rat, and in the muscle layers of the guinea pig. These results suggest a functional role of TRH both as hormone and neuroactive compound in various portions and sites of the gastro-intestinal tract of the rat and guinea pig
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  • 15
    ISSN: 1439-6327
    Keywords: Energy metabolism ; Carbohydrate-rich diet ; Lipoprotein lipase ; Free fatty acids ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A comparison of the influence of simple and complex carbohydrate (CHO) consumption on adipose tissue- and skeletal muscle-lipoprotein lipase activity (AT-LPLA, SM-LPLA) was examined. Twenty male marathon runners were divided into two equal dietary groups: simple-CHO and complex-CHO. Half of the subjects in each group consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days. Immediately following this dietary period, the subjects consumed a CHO-rich diet (70% E intake) predominant in simple-CHO or in complex-CHO for an additional 3 days. Thereafter, all subjects returned to a normal mixed diet. Skeletal muscle biopsies, adipose tissue aspirations, and venous blood samples were obtained prior to dietary manipulation (PRE), upon completion of the 6 day diet (POST I), and 2 weeks after returning to a normal diet (POST II). The samples were analysed for AT-LPLA, SM-LPLA, serum insulin, and free fatty acids (FFA), and blood glucose, and lactate. SM-LPLA fell 71% from PRE values of 0.39±0.30 μ mol · g−1 · h−1 to POST I values of 0.11 ±0.09 μ mol · g−1 · h−1 (means±SD) (p〈0.05), after a complex-CHO diet. However, the simple-CHO diet did not alter SM-LPLA. AT-LPLA similarly decreased (p〈0.05) after the complex-CHO diet, and no significant decrease was noted after the simple-CHO diet. Serum FFA decreased significantly (p〈0.05) after a simple-CHO diet (0.82±0.13 to 0.65±0.10 mmol l−1) but were unchanged after a complex-CHO diet. Blood glucose and lactate, and serum insulin were not altered following a CHO-rich diet.
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  • 16
    ISSN: 1439-6327
    Keywords: Glucose and fat feeding ; Glycogen sparing ; Ketone bodies ; Insulin ; Lipolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to test the hypothesis that oral ingestion of lipids could increase endurance by slowing the rate of glycogen depletion. Trained rats were killed after a 2 h run on a rodent treadmill, following an intragastric infusion of water, glucose, medium chain triglycerides (MCT) or long chain triglycerides (LCT). Glucose and triglycerides were administered in equicaloric concentrations (50 kJ). The results show that oral ingestion of lipids (MCT or LCT) did not reduce glycogen depletion in liver, heart or skeletal muscle after exercise whereas the fat diet increased muscle and heart glycogen stores in resting conditions. In contrast, glucose feeding induced a significant sparing effect on endogenous carbohydrate utilization and reduced physical exercise lipolysis. These data indicated, firstly, that enhanced lipid availability induced by a single lipid meal before exercise was not able to modify the glycogen depletion occuring after exercise and, secondly, that the glucose/fatty acid cycle was not effective in these conditions. The comparison between lipids indicated that the effect on glycogen use of MCT did not differ from that of LCT, and did not seem to be of any particular importance during physical exercise.
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  • 17
    ISSN: 1573-739X
    Keywords: Absorption, transdermal ; Brilliant Blue ; Dodecyl-l-pyroglutamate ; Insulin ; Laurocapram ; N-Methyl-2-pyrrolidone ; Permeability, enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The study reports on penetration enhancers used to improve drug absorption through the skin. All experiments were carried out in permeation cellsin vitro. Insulin (2.5 mg/ml) and Brilliant Blue (50.0 mg/ml) served as model drugs. They were formulated into a 40% solution of propylene glycol with increasing concentrations ofN-methyl-2-pyrrolidone (NMP) (0.0 to 20.0%), dodecylazacycloheptan-2-one (laurocapram) and a new compound dodecyl-l-pyroglutamate (DLP; 0.0 to 0.5%). The maximum amount of insulin permeated within 24 h was almost 200 μU/ml in the case of 0.1% laurocapram, while in the case of 0.1% DLP it was approximately half of that. The optimum concentration of NMP was 12.0%. Experiments performed with Brilliant Blue showed no significant difference among formulations containing either 6.0, 12.0 or 20.0% of NMP. When NMP was omitted, flux, permeability as well as the maximum concentration estimated after 26 h reached 50% of the values obtained with NMP. The lag time was twice as long in this case in comparison with the formulations containing NMP.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Pharmacy world & science 10 (1988), S. 213-216 
    ISSN: 1573-739X
    Keywords: Adsorption ; Equipment and supplies ; Infusions, parenteral ; Insulin ; Polyethylenes ; Polyvinylchloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A comparison between human and porcine insulins with regard to their adsorption to administration sets was performed. A125I-mono(A14)-iodinated insulin was used to follow the adsorption phenomenon over time and the adsorption was quantified with radioimmunoassays of unlabelled insulin. The obtained data were similar for both methods. No relevant difference in adsorption was found between human and porcine insulin. Both insulins showed a significantly more pronounced initial drop in delivered insulin when polyethylene tubing was used. After 3 h a steady state was reached, resulting in the administration of a more predictable dose. Particularly in the initial phase an important reduction in the amount of both insulins actually delivered to the patient was observed when compared to the expected amount as calculated from the concentration present in the container and the infusion rate. Therefore, the mainstay in treatment of a patient with ketoacidosis remains frequent serum glucose measurement and making appropriate infusion rate adjustments on that basis.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 13 (1988), S. 1119-1124 
    ISSN: 1573-6903
    Keywords: Insulin ; astroglia ; cultures ; GABA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Astroglial cultures from newborn mouse cerebral cortex contain [125I]insulin binding sites. Binding was specific reversible, time dependent and reached equilibrium after 45 min. Insulin analogues compete for this [125I]Insulin binding. Incubation of cerebral cortex astroglial cultures with insulin induced a time-and dose-dependent inhibition of the [3H]GABA high affinity uptake. A decrease in theV max rather than, an effect on theK m was observed. This effect was dose-dependent and effective at 10−10 M. Autoradiographic observations on the cell monolayer showed the presence of two groups of cells: one which strongly takes up [3H]GABA and consist in smaller GFAP positive process-bearing cells and another group of much flatter and larger GFAP positive cells which uptake was lower. The smaller stellate cells were apparently the most sensitive to insulin effect. These results: 1) confirm the presence of insulin binding sites on astroglial primary cultures, 2) show an effect of insulin of [3H]GABA high affinity uptake of these cells; this effect being optimal on a stellate-like population of astrocytes, and 3) indicate, that insulin may interfere in neuromodulation through astroglial signals.
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  • 20
    ISSN: 1573-6903
    Keywords: Insulin ; receptors ; brain ; cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The presence and specificity of insulin receptors was investigated in cultured cells obtained from 15–16 days old embryonic mouse cerebra. Developmental studies suggested that the maximum insulin binding occurred at about 11 days in vitro (DIV). Scatchard analysis of binding data revealed two types of binding sites. One type of receptor was the high affinity type (K d=7.77×10−9 M; number of receptor sites,B max=350 fmol/mg protein) while the other type was of low affinity type (K d=5.75×10−8 M;B max=1150 fmol/mg protein). The specificity of receptors for insulin was also confirmed by showing that [125I]insulin was displaced by non-radioactive insulin but not by glucagon or growth hormone. Insulin displayed a clear dose-dependent stimulation of thymidine incorporation. It also stimulated the activity of the enzyme 2′,3′-cyclic nucleotide phosphohydrolase (CNPase), which is specifically associated with myelin produced from oligodendroglia. Thus insulin has a positive influence on the proliferation and differentiation of brain cells.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 13 (1988), S. 887-892 
    ISSN: 1573-6903
    Keywords: Insulin ; streptozotocin ; diabetes ; noradrenaline ; dopamine ; p-tyrosine ; hypothalamus ; olfactory tubercles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A single intracardial injection of streptozotocin produced a significant increase in rat hypothalamic noradrenaline while no changes were observed in the olfactory tubercles. The parenteral administration of a single dose of insulin decreased rat hypothalamic noradrenaline; the effect had a rapid onset and lasted for at least six hours. Similar noradrenaline reductions were observed in the olfactory tubercles but in this tissue the depletion started later and recovered earlier. In addition, in olfactory tubercles after insulin injection, tyrosine level and dopamine metabolism were increased. The results show that the increases in hypothalamic NA observed in streptozotocin diabetic rats are counteracted by insulin administration and possibly the consequence of changes in noradrenaline turnover.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 23-42 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A very simple and reliable error estimator has recently been developed for problems of linear elasticity.1 This leads naturally toa predication of an h-mesh refinement required for a given accuracy and with a suitable mesh generator2 for an efficient adaptive process. In this paper we extend the methodology developed previously to incompresible plastic flow of metals or polymers using the ‘flow formulation’ approach.3The examples of application include steady state extrusion problems for which exact solutions are available and hence allow the efficiency of the error estimates to be tested as well as more complex problems of upsetting in which the mesh is updated. It is found that the estimator performs well under various circumstances and provides an economical adaptive process.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 373-386 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The ignition of a semi-infinite solid polymer under convective exposure is investigated. A quasi-steady approximation is used for the gas phase and the transient effect is accounted for in the solid phase only. Both surface and gas phase chemical reactions are included simultaneously. The ignition mechanism is studied in terms of the concurrent heat transfer, mass transfer, mass transfer and chemical processes at the surface as well as in the gas phase. The gas phase governing equations are integrated independently from the solid phase energy equation using the Adams-Moulton subroutine. Corrections to the iterative procedure are carried out by establishing a set of perturbation equations and using the Newton-Raphson and least-squares methods. The results indicate that ignition occurs in the heterogeneous mode within a narrow range of low flow velocities and high temperatures. An ignition phase transition point exists, and within a wide range of high flow velocities, ignition switches to the homogeneous mode.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 109-120 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Shape design sensitivity analysis (SDSA) expressions have been derived for non-linear anisotropic heat conducting solid bodies by following the material derivative concept and adjoint variable method of optimal shape design given in the literature. The variation of a general integral functional has been described in terms of primary and adjoint quantities evaluated at the varying boundaries. As an example problem in shape optimization, optimal outer boundary profiles of an orthotropic solid body are obtained by the boundary element method (BEM), after reformulating the SDSA equations in a form which is most suitable for the BEM.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 43-54 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The application of the penalty-function formulation of the finite element method is made possible for analysing visco-elastic fluid flows by the method which decouples the momentum and continuity equations from the constitutive equation. An upwind finite element scheme is combined with the method in order to solve the constitutive equation. As visco-elastic fluid models, Jaumann derivative, upper and lower convected derivatives are considered. The Poiseuille flow and the flow through a plane converging channel are analysed.
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  • 27
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 99-112 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Approximate methods for analysing steady-state cold drawing processes in polymer forming are discussed. These methods are applied to both axisymmetric and plane-strain drawing. The cold drawing process is associated with steady-state neck propagation along the specimen. Modifications are introduced in the approximate steady-state analysis which reflect the neck initiation and localization phases prior to steady-state drawing. This is accomplished without resorting to an analysis of the entire load-deformation history of the process. Finite element results are also presented and compared with those of the proposed approximate analyses. These comparisons show the approximate analysis to be an extremely efficient and quite accurate computational scheme for the analysis of steady-state cold drawing processes.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 55-66 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The cold rolling of rectangular section slabs is analysed for a range of width-to-height ratios (one to three) for which spread of the workpiece is appreciable. This necessitates the use of a three-dimensional model. An elastic-plastic finite-element method is used to provide a complete description of the slab rolling process.The pressure distribution at the workpiece/roll interface is found to show the typical ‘friction-hill’ observed in near-plane-strain experiments, but the pressure varies across the width of the interface. The shear-stress distribution at the roll interface provides detailed information about the ‘neutral line’ which is usually assumed to occur where the shear stress changes direction. The 3-D analysis shows clearly that there is a flow divide in both longitudinal and transverse directions.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 213-225 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method is introduced which is based on metal flow theory and simulates the densification of metal powder during hot isostatic pressing.The method, in which nodal velocities are variables, takes into consideration the dependence of flow stress on the temperature, strain rate and relative density of the material. The compressibility of porous metal as well as the incompressibility of fully dense metal are also taken into account.Porous specimens of the superalloy MERL76 were subjected to uniaxial compression tests at high temperature in order to determine the parameters of the equations on which the method is based. The densification behaviour of a turbine disk and two cylindrical components was numerically simulated and compared with experimental results.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. i 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 347-355 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Combined forced and free convective flows having locally complicated geometries or boundary conditions were numerically studied with a finite difference method of coarse and fine meshes. The coarse-and-fine mesh method developed can be used for numerical calculations of both unsteady and steady processes of heat and mass transfer in convective and diffusion flows which are strongly influenced by locally fine flows. The method was applied to a numerical calculation of the steady flow field of a CVD (chemical vapour deposition) reactor which has locally complicated flows caused by small inlet nozzles. The results of the calculation showed a considerable contribution of locally fine flows to the overall flow field, which is well predicted with the present method.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 357-371 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: For the solution of thermal comfort problems a coupled model is presented consisting of the thermal model of the human body and of the clothing, with boundary conditions of the third kind.For thermal modelling the human body is divided into 16 parts according to the special character of the internal heat generation, of the blood vessel system and of the sweat secretion mechanism. Part models are connected by the flow paths of arteries and veins.Transport phenomena in the clothing are treated by a coupled heat and mass transfer model which permits various kinds of clothing for the different parts of the body.The equation system of the full model has been solved numerically by using time stepping schemes. As the results of the computations an approximative temperature field of the human body is produced.Calculated results have been compared with Experimental data.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 191-212 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Rate form constitutive equations of elasto-viscoplastic type are expressed in a manner similar to that of classical metals, but the viscoplastic part, which is no longer incompressible, is related to the rate of variation of porosity. An incremental and implicit algorithm has been implemented in a finite element program in order to simulate hot isostatic pressing of an Astroloy powder. Temperature distributions are shown to induce strong density variations in real parts during hot isostatic pressing (HIP). For one particular turbine disk, we tested the sensitivity of the final shape to different processing parameters. Computed final shapes compare well with experimental ones.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 253-267 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The majority of work in numerical analyses of sheet metal forming operations is based on the simple membrane-shell theory which neglects the effect of sheet bending. While useful information can be extracted from these analyses, especially for stretch-dominated operations, the membrane theory is basically inadequate for analysing the draw-type operations where sheet metal bends, slides and unbends over a draw radius.This paper presents axisymmetric and plane-strain finite element analyses of stretch/draw of sheet metal over a die corner radius. Numerical solutions obtained from a total Lagrangian formulation of a finite-strain thin shell theory are used to indicate the relative significance of including the bending effects in various simple forming operations. Comparisons of the calculated results with available experimental data are also given.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 283-292 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element simulation code of the sheet metal forming process has been developed. This simulation code plays an important role in the computer aided engineering (CAE) system for an automobile parts forming process, which includes the pre- and post-processes. The paper presents the development of an updated Lagrangian type finite element modelling, based on the elastic-plastic (J2 flow law) membrane shell theory. An attempt is made to calculate the strain distribution incurred by peripherally clamped or non-clamped square plates when impressed by rigid punches. These are the cases of square box-shape punch drawing and arbitrary shaped panel stretch forming.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 269-282 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The goal of mathematical modelling of sheet metal forming processes is to provide predictive tools for use in the design of stamping processes and the selection of sheet materials. Most current approaches to finite element modelling of large deformation, elastic-plastic sheet metal forming problems use a rate form of the virtual work (equilibrium) equations, and a single-field finite element representation of the displacement components. Called the incremental method, this approach does not produce approximations which satisfy the discrete equilibrium equations at all times, and consequently it demands small time steps to insure stability and numerical accuracy. This paper describes a variant of the mixed method in which displacements, stresses, effective strain and pressures are all given separate finite element representations. The equilibrium equations in non-rate form are discretized to produce a system of algebraic equations which are coupled with the constitutive equations and then integrated using state-of-the-art numerical software. When used to model rate sensitive sheet materials in hydrostatic bulging, plane strain punch stretching and hemispherical punch stretching, the new approach proved to be between 6 and 26 times as fast as the old incremental method.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 331-345 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A control-volume-based finite-difference formulation is developed for heat transfer and fluid flow in arbitrary three-dimensional parallelepiped enclosures. The governing equations in Cartesian co-ordinates are first transformed to those in non-orthogonal curvilinear co-ordinates by tensor transformations. After introducing the properties of the parallelepiped geometry, equations are obtained in the primitive variables for which all vectors and tensors are based on the curvilinear co-ordinates. With proper treatment of the heat flux and stress tensor terms, the finite-difference equations, analogous to those in the Cartesian coordinates, are formed. Examples are utilized to show the validity of the methodology and the results are found to compare well with existing experimental data. The differences in heat transfer and fluid flow inside parallelepiped enclosures and rectangular enclosures are delineated and discussed from a physical point of view.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 313-329 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Turbulent fluid flow and heat transfer in lid-driven rectangular cavities are analysed by a finite element procedure for the prediction of the turbulent forced convection in two-dimensional recirculating flows. The (k-ε) model is used to compute effective viscosities and thermal conductivities. The fluid flow and turbulence model parabolic equations are solved sequentially, one after the other. Then, the calculated velocity distribution is used in the solution of the steady state energy equation to yield the temperature field. Aspect ratios e=0·75, 1·0 and 1·5 and Reynolds numbers ranging from 5 × 104 to 4 × 105 are considered in the numerical examples.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 415-444 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Two-dimensional finite element simulations of solidification for quiescent undercooled pure metals are presented. The full non-linear, transient heat equation is used with phase front tracking which is subject to local curvature and interfacial kinetics. During early stages of the waveform instability the simulated solutions match the linear stability analysis with fidelity. Beyond the valid range of that analysis the numerical solution continues to demonstrate the physically observed exponential growth behaviour and characteristic spacing between fingers. Whereas the simulations show the sensitivity of dendritic growth to initial conditions, as expected for an unstable process, the overall pattern formation preserves the characteristic spacing. The simulations are terminated after the onset of bifurcation. Thereafter, the numerical model is inappropriate for physical comparison owing to the planar, two-dimensional limitation.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 495-515 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A Regular Indirect Boundary Element formulation is developed following a weighted residual approach. In this formulation, the fictitious source density, which appears in the integral equations of the method, is distributed on a surface which is exteriorly separated from the physical field boundary of the problem. This approach does not require the evaluation of singular integrals and produces undeteriorated solutions at geometric discontinuities. The formulation is presented here as applied to two dimensional and axisymmetric thermal problems. It includes a different subregioning scheme which treats each subregion, of a multidomain problem, separately, thereby eliminating the need for a sophisticated reduction scheme.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 231-243 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Many structural members including metallic, reinforced polymer and concrete members must be modelled, in the simplest approximation, as thin-walled beams whose cross-sections exhibit significant, out-of-plane warping owing to torsion. The elastic capabilities of the semiloof beam element are extended to include warping torsion of thin-walled open section beams. The performance of the extended element is compared with that of the original formulation.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 143-152 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The partial solution of damped structures involves the determination of only a few of the resonant frequencies and corresponding damping characteristics and mode shapes. The procedure outlined here uses a modification of the variable metric solution algorithm, in which the dicision variables are elements of the complex eigenvector and the eigenvalue. The quadratic eigenvalue problem is reformulated as a sequential unconstrained minimization problem. Both normality and orthogonality constraints are incorporated in the objective function. The method is compared to an adaptation of the subspace iteration technique, also applicable to the quadratic eigenvalue problem.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 199-215 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Mechanical computer aided engineering (CAE) implies large finite element problems due to the geometric complexity of the ‘true’ 3D designs. Application of the standard finite element technique is not practical for such problems because the direct solution of the global matrix equations is too costly. This paper considers the element-by-element implicit algorithm for the CAE application of transient heat conduction. The direct solution is avoided by an operator splitting or approximate factorization technique. This results in both the execution time and storage requirements for each time step being linearly proportional to the number of elements while retaining unconditional stability. However, the approximate factorization introduces additional truncation error and incorrect jump conditions at material interfaces. Detailed analyses and numerical experiments are carried out in one dimension to assess the nature and mechanism of these inaccuracies. A three dimensional implementation is then compared with one dimensional results. The need for an additional predictor-corrector element-by-element algorithm for 3D composite problems is also presented.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 281-282 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 291-292 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 290-290 
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 289-289 
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 361-378 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A hybrid two-dimensional finite element-Monte Carlo numerical solution method has been developed for solving complex transient non-linear gas radiation enclosure problems. Solid conducting media are coupled to conducting gaseous or particulate participating media and both may be internally energy generating. Bilinear isoparametric elements are used, allowing geometrically complex enclosures with internal objects to be present. Radiative energy transport within the gaseous enclosures is accounted for using a Monte Carlo method which permits a broad range of complexities. Included here are: diffuse-grey and specularly reflecting walls with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; absorbing/emitting gases with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; and isotropic or anisotropic scattering gases or particles. This method was verified by solving several standard steady state problems and comparing the solutions to those found using the conventional finite element, the P-N and the exchange factor methods. Solution times are comparable to those of the finite element method. A more complex transient problem solution is then given to demonstrate the versatility and power of the method.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 293-311 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A survey of methods for sensitivity analysis of the algebraic eigenvalue problem for non-Hermitian matrices is presented. In addition, a modification of one method based on a better normalizing condition is proposed. Methods are classified as Direct or Adjoint and are evaluated for efficiency. Operation counts are presented in terms of matrix size, number of design variables and number of eigenvalues and eigenvectors of interest. The effect of the sparsity of the matrix and its derivatives is also considered, and typical solution times are given. General guidelines are established for the selection of the most efficient method.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 329-347 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A C0 9-node shell element based on assumed interpolations of covariant strain components defined with respect to the element natural co-ordinate system has recently been proposed. In this formulation, the covariant strains are obtained directly from the Cartesian strains by tensor transformation without any need to compute laminar co-ordinate based strains. In the present work, the interpolated covariant strains used in this element are analysed to determine their satisfaction of the basic requirements for successful strain interpolation. These basic requirements are stated as invariance to rigid body motions and ability to represent constant and linear strain states. In the finite element formulation, the weak form of momentum balance is expressed in terms of covariant strains and contravariant stresses. The corresponding elasticity tensor is a function of the components of the metric tensor associated with the element natural co-ordinate system. The invariance properties of the metric tensor in the context of the finite element approximation are also discussed.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 413-421 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Natural convection flow of a non-Newtonian fluid between two vertical infinite parallel flat plates forms the case study of the present work. Velocity profiles for the Prandtl-Eyring and Powell-Eyring fluid models are obtained through the method of spline collocation.The applicability and reliability of the techniques employed here are discussed in detail with a suggested error estimate and analysis. Accuracy in the successive iterations in the results is of the fourth order. To maintain this accuracy the help of a computer is not required for carrying out the calculation of velocity profiles. Thus the simplicity of the spline collocation technique is demonstrated in its application to flow problems.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 423-435 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Three functionals, the modified forms of the Hu-Washizu, Hellinger-Reissner, and complementary energy principles, as developed by Pian, Chen, and Kang1.2 are stated. Finite element discretization of each is presented and the ensuing computations developed, resulting in the element stiffness matrix, with displacement degrees-of-freedom only, and the stress recovery matrices. Subroutines are presented for this purpose where the close relationship of the three principles is exploited to result in a compact hybrid element technique. The techniques herein reviewed are assumed applicable at the individual element level. The usual summation over all elements in the model is implied.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 453-465 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The accuracy of three numerical algorithms - the tangent-stiffness radial-return, secant-stiffness radial-return and simple radial-return methods - is analysed against exact solutions for the pressure-modified von Mises yield criterion with the associated flow rule. The governing equations of the exact solutions are derived using a simple and innovative geometrical approach, in terms of a pair of non-linear, first order differential equations, in rate change of the deviatoric radius and in rate change of angular locations on the deviatoric plane. For both accuracy and efficiency, and for small and large time steps, the secant-stiffness radial-return method is the best of all.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 437-452 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A three-dimensional finite element model has been developed to simulate the sliding of a rubber block over a grooved road surface. The model makes use of the symmetries of the problem to simplify the analysis, so that two-dimensional isoparametric elements of both rectangular and triangular configuration have been extended into the third dimension. A procedure for analysing the behaviour of any one groove to groove unit of the pavement is also developed, and this is extended so that the contact between the sliding rubber block and the leading edge of each raised pavement section is analysed. Preliminary comparisons between theoretical calculations and experimental measurements indicate that the finite element procedure provides an accurate and economical estimate of the behaviour of the rubber slider as it is pressed into a grooved pavement. Elastic predictions of sliding resistance seem reasonable at low sliding speeds, but viscoelastic rubber analysis appears necessary if higher speed skid resistance is to be predicted.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 467-487 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An analysis is presented for the steady state free convective flow and heat transfer from an axisymmetric heat-generating body that is embedded in a fluid-saturated, semi-infinite, porous medium. The porous medium is assumed to be rigid, homogeneous and isotropic, and be in thermal equilibrium with the fluid. The fluid is assumed to be incompressible, with the density changes contributing only towards the buoyancy forces via the Boussinesq approximation. The governing equations for the fluid consist of the equation of continuity, Darcy's law and the equation of energy. After introducing the stream function concept, the equations governing the stream function and pressure are derived. Using the non-dimensional variables, the non-dimensional equations governing the non-dimensional forms of the temperature, stream function and pressure are dervied and the appropriate boundary conditions are stated. The mathematical formulation contains two parameters; D, the non-dimensional depth of the body from the surface of the porous medium, and a product Raθs of Rayleigh number (Ra) and the non-dimensional surface temperature of the body (θs). The Galerkin finite element method, with linear, isoparametric, quadrilateral elements, is used to reduce the mathematical formulation into a set of algebraic equations. The expressions to calculate the non-dimensional surface temperature and Nusselt number of the body, and the non-dimensional velocity of the fluid, are derived. A computer code has been developed to solve the algebraic equations, using Gauss elimination procedure, in a banded matrix form. The computer code, in addition to the non-dimensional temperature, stream function and pressure, calculates the isothermal lines, non-dimensional surface temperature of the body, Nusselt number of the body, velocity field and isobars.To demonstrate the application of the code, a spherical heat-generating body is considered as an example. Numerical results are obtained for D = 3 and 6, and Raθs = 0.001, 0.1, 1 and 5, and presented.
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    International Journal for Numerical Methods in Engineering 26 (1988) 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 527-530 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 555-570 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An integrated approach to the minimum weight design of geometrically non-linear three dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The non-linear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the contraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically non-linear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 531-539 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In a recently published paper a finite element based iterative method was introduced for the solution of the eigenvalue problem of stationary cracks.1 In this paper we give the theoretical basis of this iterative method and we show why it converges and how it could be extended to more complex fracture problems. The cases of cracks at interfaces are illustrated.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 541-554 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The finite element iterative method is applied to the eigenvalue problem of a crack between dissimilar media. In this case the transfer matrix is non-symmetric, which leads to complex eigenvalues. The singularity obtained agrees with the analytical results of r(-1/2+ie). The method of evaluating the eigenfunctions is general and can be applied to more complex cases of material and geometry, which are frequently encountered in composite materials. A powerful method for evaluating stress intensities in dissimilar media is given in the Appendix. The method is also reduced for homogeneous media to give stress intensity factors for modes I, II and III.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 589-615 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper deals with elasto-plastic large deformation analysis of space-frames. It is based on a complementary energy approach. A methodology is presented wherein: (i) each member of the frame, modelled as an initially straight space-beam, is sought to be represented by a single finite element, (ii) each member can undergo arbitrarily large rigid rotations, but only moderately large relative rotations; (iii) a plastic-hinge method, with arbitrary locations of the hinges along the beam, is used to account for plasticity, (iv) the non-linear bendin-stretching coupling is accounted for in each member, (v) the applied loading may be non-conservative and (vi) an explicit expression for the tangent stiffness matrix of each element is given under conditions (i) to (v). Several examples, with both quasi-static and dynamic loading, are given to illustrate the accuracy and efficiency of the approaches presented.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 631-646 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The elastic plastic torsion problem for an elastic, perfectly plastic cylinder with multiply connected cross section twisted around its longitudinal axis is formulated as an obstacle problem for an associated stress potential, the obstacle being defined in terms of a generalized distance function. Based upon the reformulation of the obstacle problem as an equivalent linear complementarity problem, the latter is discretized by means of finite difference techniques, and a monotonically convergent iterative scheme for its numerical solution is developed. At each step of the iteration the solution of a reduced system of discrete Poisson equations is required which is done by applying multi-grid techniques with respect to a hierarchy of grid-point sets. Combined with a suitably chosen nested iteration process this results in a computationally very efficient algorithm for the approximate solution of the elastic plastic torsion problem.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 663-676 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper deals with the vibration of open cylindrical shells by the spline strip method based on Novozhilov's shell theory. Convergence of the solutions is investigated in a few examples and is found to be satisfactory. The accuracy of the results is compared with those calculated by other numerical methods and found to be in good agreement.The effect of inlcuded angles and inplane constraints on vibrating characteristics of simply supported cylindrical shells is shown.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 717-730 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A finite element of arbitrary quadrilateral shape is presented for plane elasticity analysis. The element is derived from triangular fields of compatible quadratic displacements with vertex connectors which include rotations. All rigid body movements and constant strain states are recovered exactly. Results from several test problems demonstrate that very good numerical accuracy is obtained for both displacements and stresses, even for quite coarse finite element meshes.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 695-704 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper addresses some of the theoretical aspects involved in the numerical study of non-Newtonian flow problems. We consider the second-order Rivlin-Erickson constitutive model due to the simple differential form that emerges for the system of equations that govern the flow when expressed in stream function-vorticity variables. This model describes slightly elastic fluids that exhibit a constant viscosity behaviour. A steady two-dimensional flow is studied through a planar contraction geometry.An auxiliary variable is introduced into the problem formulation producing a non-linear system of differential equations comprising two elliptic equations and one hyperbolic equation. This system is discretized by finite difference methods and the resulting system of non-linear algebraic equations is solved iteratively by successive substitutions. The simple structure of this iteration permits a convergence analysis which is presented in Section 2. This analysis is performed prior to the spatial discretization and establishes the dependence of the iteration upon the material parameters. At the discrete linearized equation level a combination of inner iterations for elliptic equations and direct marching for the hyperbolic equation is used. The stability of the marching scheme is considered in Section 4.3 and a discussion on the results is given in Section 5.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1945-1962 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A nine node finite element is presented for the analysis of thin shell structures undergoing large deflection. The finite element formulation is based on the concept of degenerate solid shell element and the Hellinger-Reissner principle with independent strain. Three versions of assumed independent strain are selected to suppress spurious kinematic modes. One version leads to a finite element model which is kinematically stable at element level while the other two give globally stable models. Numerical tests indicate that the finite element model which is stable at element level may reveal the locking effect in certain cases. However, the other two models are free of locking.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1989-2007 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An efficient implementation of finite element methods for free boundary parabolic problems in general two dimensional space domains is presented. The Stefan problem, the Hele-Shaw problem and the porous medium equation are included. Backward differences or linearization techniques are used for the time discretization of the problem. The performances of these schemes are discussed with several numerical tests.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1087-1100 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer problems. The transfinite element methodology, while retaining the modelling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this paper is to provide a viable hybrid computational methodology for applicability to general transient thermal analysis. Highlights and features of the methodology are described and developed via generalized formulations and applications to several test problems. The proposed transfinite element methodology successfully provides a viable computational approach and numerical test problems validate the proposed developments for conduction/convection/radiation thermal analysis.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1169-1184 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A new triangular plate element is presented. This new element is based on independent interpolations for slopes, displacement and shear forces, and it is shown that it does not suffer from any defect common to other Mindlin plate elements. Several examples are presented to illustrate the behaviour of this new element.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1235-1236 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1213-1233 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The paper presents a general hierarchical formulation applicable to both elliptic and hyperbolic problems. Static and eigenvalue linear elastic problems as well as convection-diffusion problems are studied. The hierarchical formulation is well suited for adaptive procedures.For the convection-diffusion problem the hierarchical approximation is made in time only. Different hierarchical functions are proposed for different types of problems. Both weighted residual and least-squares formulations are applied. A combination of these two gives a penalty method with a constraint equation corresponding to the least-squares method. A whole class of time integration formulae is obtained. These are all suitable for adaptive procedures owing to the hierarchical approximation in the time domain. If a linear discontinuous hierarchical base function is used in the Galerkin weak formulation, the method so obtained corresponds to the discontinuous Galerkin method in time and is especially suited for convection dominated problems. The streamline-diffusion method is found to be the aforementioned penalty method.This paper also examines the sequence of nested equation systems that results from a hierarchical finite element formulation. Properties of these systems arising from static problems are investigated. The paper presents some new possibilities for iterative solution of hierarchic element equations, and different procedures are compared in a numerical example. Finally, a simple ID convection-diffusion problem clearly shows that the proposed hierarchical formulation in time gives a stable and accurate solution even for convection dominated flow.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1240-1240 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 26 (1988) 
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 1201-1212 
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    Notes: Exact expressions for the distributions of the components of radiative flux density and the radiative energy source term in terms of wall and medium temperature distributions have been formulated for an emitting absorbing medium of constant properties bounded by black walls of a cylindrical enclosure. The accuracy of numerical solutions has been tested on an idealized enclosure for which exact analytical solution of the expressions is possible and shown to have six-figure accuracy. The exact expressions have then been solved numerically for an enclosure problem based on data reported previously on a large scale experimental furnace. The principal feature of the data is highly non-uniform temperature distributions which are typical of the conditions encountered in industrial furnaces. These data have been chosen because of their practical importance and the non-availability of exact solutions for such data. The resulting exact solutions have been tabulated and are intended to serve in the future as standards for testing the accuracy of the approximate predictions produced using various three-dimensional flux models in cylindrical configurations.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 67-85 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Three-dimensional finite element analysis is applied to operation sequences in open-die forging. Flat tools with rounded edges for open-die forging are geometrically modelled using Bézier curves. With this technique, the problems at the die-workpiece interface, such as the integration of frictional stress, node touching on dies and node separating from dies, can be handled effectively. It is shown that in solving general symmetric problems computation time can be saved by reducing variables and rearranging them in the stiffness matrix. One-bite operations and operation sequences for producing two-size bars and two-size pipes in several bites are investigated in regard to geometry, load, energy and deformation distribution.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 113-131 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 165-176 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The boundary element method is applied to large deformation problems typical in industrial forming problems. A form of Betti's theorem relevant to an updated Lagrangian type of solution procedure is established as the basis for the boundary element formulation. Equilibrium iterations are needed in each load step. All non-linear terms are moved to the right-hand side and the boundary element method can be used. Cross-anisotropy is assumed where Hill's yield criterion is adopted together with isotropic hardening. The investigation has shown that the boundary element method is applicable to this type of problem, giving good results within reasonable computer time.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 177-189 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The pseudo-concentration method is used to follow the flow of metal during the transient analysis of an axisymmetric forging problem. The technique requires a minimum of user interaction and appears to be ideal for computer aided design of dies. An analysis of an engine disc blocker die is presented and compared with experimental results. The same problem is analysed using a Newtonian fluid which is shown to give good qualitative results which would be acceptable in the initial stages of die design.
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 227-251 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A formal analogy between the equations of pure plastic and viscoplastic flow theory for void-containing metals and those of standard non-linear elasticity is presented. The formulation is particularized for the analysis of axisymmetric sheet metal forming problems using simple two node linear finite elements. Details of the treatment of friction and strain hardening phenomena, time increment computation and elastic effects are also given. Examples of the effect of void porosity on the hemispherical stretching of a circular sheet are presented.
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    International Journal for Numerical Methods in Engineering 25 (1988) 
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 293-311 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The extension of time-marching procedures to low Mach number and low Reynolds number conditions is considered. It is shown that the disparate speeds of the acoustic and particle waves prevent convergence at high Reynolds numbers, while the requirement that both the Courant and the von Neumann numbers be of order one prevents convergence in very viscous flows. A perturbation expansion is used to introduce pseudo-acoustic waves that propagate at speeds similar to the particle speed at high Reynolds numbers and that allows both the inviscid and viscous time step parameters to be of order one at low Reynolds numbers. The resulting algorithm is shown to give convergence rates that are independent of either Mach number or Reynolds number over a range of five orders of magnitude in both parameters. Results are shown for strong heat addition in low-speed flow encompassing this broad range of variables.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 183-197 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The problem of design of actively controlled structures subject to restrictions on the damping parameters of the closed-loop system is formulated and solved as a multiobjective optimization problem. The purpose of control is to effectively suppress structural vibrations due to initial excitation. The cross-sectional areas of the members are treated as design variables. The structural weight and the controlled system energy are considered as objective functions for minimization. The goal programming approach is used for the solution of the multiobjective optimization problems. The procedure is illustrated through numerical simulations using two-bar and twelve-bar truss structures.
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 245-262 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical study of the flow in a two-dimensional 90° circular-arc bend is presented. The study is based on the solution of the governing equations using a finite volume technique. Both laminar and turbulent flows are considered. Particular attention is given to the occurrence and size of the separation regions and, in this respect, the effects of Reynolds number and bend radius to height ratio are discussed. The study includes the effect of a guide vane, placed in the bend, on the flow characteristics. It is shown that the emerging velocity distribution is more uniform than that associated with flow in a bend without a guide vane. The presence of a guide vane is shown to suppress the formation of regions of flow separation. Comparisons are made between the effects on the flow of two different designs of guide vane.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 283-287 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 1 Ill.
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  • 85
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 731-742 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The behaviour of infilled frames subjected to horizontal loads is analysed by an iterative numerical procedure. The stiffness of the structural system is determined with variations in geometrical and mechanical characteristics.The analysis is carried out utilizing the boundary element method (BEM) for the infill and opportunely dividing the frame into finite elements, so as to transform the mutual interactions of the two subsystems into stresses distributed along the boundary for the infill and into nodal actions for the frame.This makes it possible to take into account the separation arising between the two substructures when mutual tensile stresses are involved.At first, infills without openings are considered, using BEM with constant elements for two-dimensional problems in elasticity.The results are compared with those obtained using the simplified equivalent pin-jointed strut model, which is very common in the literature.Subsequently, using an analogous procedure, panels with openings are considered. For these systems, for which no satisfactory simplified models exist, the loss of stiffness in relation to the size of the opening is evaluated.
    Additional Material: 4 Ill.
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  • 86
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 87
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 766-767 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 88
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 785-803 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Combinations of the Ritz-Galerkin and finite element methods are applied to solving singularity problems of homogeneous, elliptic equations. The Ritz-Galerkin method is used in the subdomains where there exist singular points; and the finite element method is still used in the rest of the solution domains. More general coupling techniques than those of Reference 6 along the common boundary of subdomains are discussed. Numerical experiments using these kinds of coupling techniques are provided for the first time. It is interesting that the calculated results of Motz's problem have shown the simplified hybrid strategy in Reference 6 to be optimal for both error bounds and stability of numerical solutions, among all general coupling techniques.
    Additional Material: 7 Ill.
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  • 89
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 805-813 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Expansions in terms of beam functions and Chebyshev polynomials are used to compute solutions to the primary two-point boundary value problem within a spectral collocation formulation. The performance of the methods is analysed in terms of accuracy and robustness relative to the level of non-linearity. Accurate results are obtained with Chebyshev polynomials and the performance of these trial functions is insensitive to the level of non-linearity whereas the behaviour of the beam functions shows great sensitivity to the level of non-linearity. The use of Newton's method to solve the mixed linear-non-linear system for the Chebyshev coefficients is successful for highly non-linear problems without the need for parameter continuation.
    Additional Material: 4 Tab.
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  • 90
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 843-855 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The two matrix equations obtained from the mixed finite element method are uncoupled through the use of the QR decomposition. The procedure obtains the basis for the null space which is composed of solutions to the homogeneous flux-equilibrium equation. The result is that, even for statically indeterminate problems, stresses can be obtained without solving for the displacement field. Furthermore, the stress field can be decomposed directly into contributions from applied forces and from prescribed displacements. The appearance of kinetic modes can easily be monitored. The possibility of utilizing non-conventional basis functions for use in conjunction with the QR decomposition is explored briefly. Simple examples are given to illustrate the theoretical results.
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  • 91
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Householder's method for tridiagonalizing a real symmetric matrix, a major step in evaluating eigenvalues of the matrix, is modified into a parallel algorithm for a concurrent machine of message passing type. Each processor of the concurrent machine has its own CPU, communications control and local memory. Messages are passed through connections between processors. Although the basic algorithm is inherently serial, the computations can be spread over all processors by scattering different rows of the matrix into processors, hence the term “Scattered Row Decomposition”. The steps in the serial and the parallel algorithms are identified. Expressions for efficiency and speedup are given in terms of problem and machine parameters. For a concurrent machine of ring type interconnection, a selected representative problem of large order exhibits efficiency approaching 66 per cent.
    Additional Material: 2 Ill.
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  • 92
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 891-911 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An advanced implementation of the boundary element technique for the periodic and transient dynamic analyses of two-dimensional elastic or visco elastic solids of arbitrary shape and connectivity is presented. For transient dynamic analysis the problem is first solved in the Laplace transform space and then the time domain solutions are obtained by numerical inversion of transformed domain solutions.The present analysis is capable of treating very large, multi-domain problems by substructuring and satisfying the equilibrium and compatibilities at the interfaces. With the help of this substructuring capability, problems related to the layered media and soil-structure interaction can all be analysed. This paper also introduces a new type of element called ‘Enclosing Element’, which has been developed and used to model the infinitely extending boundaries of a half-space or a layered medium. A number of numerical examples are presented, and through comparisons with available analytical and numerical results, the accuracy, stability and efficiency of the present analysis are established.
    Additional Material: 12 Ill.
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  • 93
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 973-985 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper describes a full range analysis of reinforced concrete slabs, which includes the effects of both geometric and material non-linearities, using the finite element method. A computer program is described which has been used to analyse slabs previously tested by a number of investigators. The comparisons between the test results and the computer program are considered to be good.
    Additional Material: 9 Ill.
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  • 94
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1003-1003 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 95
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 987-1000 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A two-scalar-potential formulation for magnetostatic computations has been recommended4 based on a comparative study of several different formulations in terms of their accuracy and efficiency. A different study3 challenged this recommendation. It is the purpose of this report to present results which confirm the practical necessity for the two-potential formulation.The method used for the present study was to construct a simplified computer program designed to easily compare the alternative methods. This program uses the finite element method on a geometry suited for analysis of the ‘bifiliar conductor’ problem treated in both studies mentioned above. In this program, the alternative formulations are implemented with a great deal of common code. In particular, the input, stiffness matrix, matrix solution and editing routines are common to both formulations, with differences appearing only in the source terms for the stiffness matrix equation. The known analytic solution to this particular problem provides a reference with which the computed solutions is compared. The main conclusion of this study of the ‘bifiliar conductor’ problem is that for a given choice of mesh, the two-potential formulation yields significantly more accuracy than the reduced-potential formulation.
    Additional Material: 8 Ill.
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  • 96
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 9-22 
    ISSN: 0029-5981
    Keywords: Streamline Elements ; KBKZ Model ; LDPE Extrusion ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite streamline element method for use with integral type constitutive equations in viscoelastic flow simulation, including thermal effects, is presented and some new results using this method in modelling the IUPAC extrusion experiments for low-density polyethylene (LDPE), involving both long and short circular dies, are reported and discussed. It will be shown that the special streamline-based elements provide a convenient way of particle tracking and strain tensor calculation. The extrusion calculation when using a relatively realistic KBKZ type integral model with multiple relaxation times is stable, and practically important Weissenberg numbers and swelling ratios have been reached without difficulty. The agreement with experimental swelling ratios is on the whole satisfactory. In order to make the model a good fit to the Trouton viscosity experimental data of the LDPE sample, a spectrum of elongational parameters has been introduced. The second normal stress term has also been added to the integral model to examine its effect on extrusion swelling. The non-isothermal effects and the possibility of a wall slip near the die exit at high apparent shear rates are also discussed.
    Additional Material: 11 Ill.
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  • 97
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    International Journal for Numerical Methods in Engineering 25 (1988), S. 87-97 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A fully three-dimensional elastic-plastic finite-element program for the study of metalforming operations is described. Several applications are discussed, and the finite-element (FE) predictions of metal flow, strain rate and temperature distributions, and the sites of initiation of ductile fracture are presented.
    Additional Material: 10 Ill.
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  • 98
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The bulging of continuously cast steel between the support rolls has been computed using a viscoplastic finite element model. Both two-dimensional and three-dimensional models are based on the minimization of the functional associated with the Norton-Hoff law and use the streamlines integration to calculate the bulging. By using industrial data, the influence of both numerical parameters and process parameters on the extent of the calculated bulging values has been investigated. The comparison of our results with experimental measurements confirms the relevance of the hypothesis of viscoplastic behaviour.
    Additional Material: 15 Ill.
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  • 99
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    International Journal for Numerical Methods in Engineering 26 (1988), S. 263-279 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The influence of non-linear thermal parameters on moisture distribution predictions in an unsaturated soil is investigated. A fully non-linear numerical model of coupled heat and mass transfer is used to analyse the one dimensional drying of a stratum of loam. The distribution of moisture content in the upper 0.5 m of soil is the subject of interest. Assumed representative material parameters are used.The results show small but significant changes in moisture content variations when either the value of the thermal conductivity or the heat capacity alone is kept constant. When both are held constant, however, a cancellation of effects occurs. This is attributed to the fact that the thermal gradients in the soil remain largely unchanged when compared with fully non-linear values. Actual magnitudes of temperatures are different but the thermal gradients are not.These conclusions cannot be generalized at this stage beyond the problem dependent results achieved. The results are, however, viewed as a contribution to a greater overall understanding of the complex problem under consideration.
    Additional Material: 5 Ill.
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  • 100
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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