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  • 2000-2004  (35)
  • 1980-1984  (1,801)
  • Engineering General  (1,377)
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  • 101
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 129-131 
    ISSN: 1432-1041
    Keywords: aprindine ; antiarrhythmic agent ; healthy volunteers ; plasma level ; oral administration ; pharmacokinetics ; urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of aprindine following a single oral dose can best be described by a two-compartment open model. The mean plasma half-life (t1/2β) increased from 8.0±2.1 h (SD) after a 25 mg dose to 9.4±2.9 h after 50 mg and to 15.8±2.6 h after 100 mg, with a decrease in total plasma clearance (Cl/F) and volume of distribution at steady state (Vdss/F) and during β-phase (Vdβ/F). The area under plasma concentration-time curve (AUC), maximum plasma concentration (Cmax) and the amount of unchanged aprindine excreted in the urine increased in a non-linear fashion with the increase in dose. The t1/2β after multiple oral doses showed a 3-fold increase over the single dose value. These results indicate that aprindine shows dose-dependent non-linear kinetics.
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  • 102
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 191-195 
    ISSN: 1432-1041
    Keywords: furosemide ; triamterene ; drug combination ; pharmacodynamics ; pharmacokinetics ; furosemide retard ; triamterene metabolite ; urine potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacodynamics and pharmacokinetics of the combination of furosemide retard (30 mg)/triamterene (50 mg) were compared with furosemide (30 mg) in 18 healthy male volunteers aged 39.3±6.3 years. After the administration of furosemide the onset of its effect was very rapid, reaching a maximum between 1.5 to 3 h, and followed by rebound after 9 to 10.5 h. In contrast the combination furosemide retard/triamterene showed a protracted course with a duration of effect up to 12 h. The general effect over 12 h of the two preparations was equivalent with respect to the excretion of urine, sodium, chloride and calcium, but the combination caused significantly less excretion of potassium (p≤0.05) than furosemide. After a lag-phase of 33.9±5.4 min the maximum plasma concentration of furosemide was reached after 3.47±0.66 h, and the elimination half-life was approximately 2 h. After a lag-phase of 33.0±17.8 min the maximum plasma concentration of the main metabolite of triamterene, the OH-TA sulphuric acid ester, was reached after 1.7±0.59 h, and its elimination half-life amounted to 1.25±0.37 h. Because of the sustained release of furosemide from the retard-formulation, its principal pharmacokinetic parameters were better adapted to those of triamterene. The consequences were not only a protracted effect but also an improved electrolyte profile, especially with regard to reduced loss of potassium. In the case of renal insufficiency, however, the potassium level in serum might be increased to an undesirable extent.
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  • 103
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 269-270 
    ISSN: 1432-1041
    Keywords: cyclophosphamide ; cytostatic drug ; cancer therapy ; female breast cancer ; bioavailability ; rapid release formulations ; gastric juice resistant formulation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Cyclophosphamide (CP) is an alkylating cytostatic compound, which is activated to its cytotoxic form in the liver [1]. Since the therapeutic range of CP in the treatment of human tumours, is small like other cytostatics, a constant high bioavailability is essential for its oral administration. Although CP has become one of the most widely used cytostatics [2], there do not appear to have been any bioavailability investigations providing the necessary information. The development of a very sensitive gas chromatographic analytical method has now permited investigation of the pharmacokinetics of oral CP in conventional clinical doses [3, 4, 5, 6].
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  • 104
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 603-608 
    ISSN: 1432-1041
    Keywords: pinacidil ; hypertension ; pinacidil pyridine-N-oxide ; urinary excretion ; protein binding ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Preliminary investigation in 3 healthy volunteers suggested that intravenous pinacidil in a dose of 0.2 mg/kg had a potent but well-tolerated hypotensive action in the supine position. Facial flushing, uncomfortable chest sensation and distressing postural hypotension occurred at serum concentrations above 300 ng/ml. Pinacidil, 0.2 mg/kg, was given intravenously over 4 min to 15 healthy volunteers in the supine position. Maximum fall in mean arterial pressure (MAP) was 15.7±6.0 mmHg. Maximum rise in heart rate was 23.8±6.6 beats/min. Pinacidil serum distribution half-life ( $${\text{T}}_{{\raise0.7ex\hbox{${\text{1}}$} \!\mathord{\left/ {\vphantom {{\text{1}} {{\text{2}}\alpha }}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${{\text{2}}\alpha }$}}}$$ ) was 13.4±8.5 min and elimination half-life ( $${\text{T}}_{{\raise0.7ex\hbox{${\text{1}}$} \!\mathord{\left/ {\vphantom {{\text{1}} {{\text{2}}\beta }}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${{\text{2}}\beta }$}}}$$ ) was 2.13±0.49 h. The apparent volume of distribution (Vdβ) was 90.3±13.21 and total body clearance was 31.1±9.61/h. Pinacidil was approximately 40% bound to plasma protein over the concentration range 40–400 ng/ml. Urinary excretion of unchanged pinacidil accounted for 5.7 ± 1.3% of the administered dose over 24 hours and urinary excretion of the major metabolite, pinacidil pyridine-N-oxide, was 31.6±9.2% of the administered dose. It was concluded that intravenous pinacidil is a potent vasodilator hypotensive compound, with a duration of action between 1.5 and 2 h.
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  • 105
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 85-89 
    ISSN: 1432-1041
    Keywords: digitoxin ; radioimmunoassay ; pharmacokinetics ; bioavailability ; digitoxin metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of digitoxin were examined in six normal human subjects using an assay that separates digitoxin from its metabolites. After intravenous administration, the mean systemic clearance was 2.44 ml/min; the volume of distribution was 0.47 l/kg; and the elimination half-life was 6.5 days. After oral administration, the elimination half-life was 5.8 days. The bioavailability was 81.5% using the specific assay. Using a non-specific, direct serum digitoxin radioimmunoassay the bioavailability was 98.0%. Assay of aqueous fractions from extracted serum samples indicated higher levels of water-soluble metabolites following oral compared to intravenous digitoxin administration. These findings suggest that previously reported values for digitoxin bioavailability using non-specific methods may be falsely elevated due to the presence of digitoxin metabolites in serum.
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  • 106
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 85-89 
    ISSN: 1432-1041
    Keywords: digitoxin ; radioimmunoassay ; pharmacokinetics ; bioavailability ; digitoxin metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of digitoxin were examined in six normal human subjects using an assay that separates digitoxin from its metabolites. After intravenous administration, the mean systemic clearance was 2.44 ml/min; the volume of distribution was 0.47 l/kg; and the elimination half-life was 6.5 days. After oral administration, the elimination half-life was 5.8 days. The bioavailability was 81.5% using the specific assay. Using a non-specific, direct serum digitoxin radioimmunoassay the bioavailability was 98.0%. Assay of aqueous fractions from extracted serum samples indicated higher levels of water-soluble metabolites following oral compared to intravenous digitoxin administration. These findings suggest that previously reported values for digitoxin bioavailability using non-specific methods may be falsely elevated due to the presence of digitoxin metabolites in serum.
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  • 107
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 119-121 
    ISSN: 1432-1041
    Keywords: S-adenosyl-L-methionine ; pharmacokinetics ; protein binding ; dose-dependent kinetics ; healthy volunteers ; urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary S-Adenosyl-L-methionine (AdoMet) kinetics was studied in 6 male subjects given 100 and 500 mg i. v. Drug concentrations in plasma and urine were assayed using a radioenzymatic method. Pharmacokinetic parameters were estimated according to an open two-compartment model. The apparent volumes of distribution after the 100 and 500 mg doses were 407±27 and 443±36 ml/kg (mean±SEM), terminal half-lives 81±8 and 101±7 min and body clearances 3.7±0.5 and 3.1±0.2 ml/min per kg. Urinary excretion was 34±3 and 40±2% of the administered dose. The results demonstrate that drug disposition occurs more via metabolism than via renal excretion, and it is not dependent on the administered dose. Binding of AdoMet to serum proteins is negligible.
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  • 108
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 115-117 
    ISSN: 1432-1041
    Keywords: benzodiazepine antagonist ; Ro 15-1788 ; healthy volunteers ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the selective benzodiazepine antagonist Ro 15-1788 has been studied in 6 healthy male volunteers following a single intravenous dose of 2.5 mg. The drug was only slightly bound to plasma proteins (40±8%, mean±SD). A negligible amount (〈0.2% of the dose) of unchanged drug was recovered in urine. Hepatic elimination was rapid, as shown by a short t1/2 of 0.9±0.2 h, and high total plasma and blood clearances of 691±216 ml/min and 716±199 ml/min, respectively. The fast decline of plasma levels from about 60 to 2 ng/ml accounts for the short-lasting reversal of benzodiazepine-induced sedation by Ro 15-1788.
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  • 109
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 335-339 
    ISSN: 1432-1041
    Keywords: transdihydrolisuride ; dopamine agonist ; pharmacokinetics ; pharmacodynamics ; prolactin levels ; side-effects ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels and urinary excretion of the dopamine agonist, transdihydrolisuride (TDHL), were measured by radioimmunoassay in healthy male volunteers given TDHL 50 µg i.v. and oral doses of 200, 400 and 800 µg. Plasma prolactin was also measured by radioimmunoassay. Following i.v. injection, the concentration of TDHL declined with a half-life of 37±19 min. The total clearance was 38±27 ml/min/kg and the apparent volume of distribution was 1.3±0.4 l/kg. The bioavailability of oral TDHL was proportional to the dose; after 200, 400 and 800 µg the bioavailability was 20±25%, 31±24% and 48±26%. TDHL was almost totally metabolized and less than 0.5% of the dose was excreted unchanged in urine in 24 h. Plasma prolactin levels were depressed by 66±15%, 75±11% and 80±7% after TDHL 200 µg, 400 µg and 800 µg. The effect lasted for more than 12 h after the lowest dose and for more than 24 h after 400 and 800 µg. Side effects, mainly nausea and headache, only occurred at the two highest dose levels.
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  • 110
    ISSN: 1432-1041
    Keywords: molsidomine ; vasodilators ; pharmacokinetics ; pharmacodynamics ; dose-response relationship ; haemodynamics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 12 healthy male volunteers, molsidomine 1, 2 and 4 mg i.v. increased resting heart rate and decreased systolic blood pressure, the latter still being affected after 8 hours. After single oral doses of 1 and 2 mg, systolic pressure tended to be reduced for 90 minutes and exercise heart rate tended to be increased. After oral treatment with 2 mg molsidomine three times daily for 1 week, the pharmacokinetic parameters and the effects on heart rate and blood pressure after the final dose were not different from those after the first dose. The terminal half-life was independent of dose and route of administration. Clearance and distribution volume were not dose-dependent. The bioavailability of a 2 mg oral dose of molsidomine was 44%. Inter-individual variation in heart rate, blood pressure and pharmacokinetics was observed.
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  • 111
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 349-354 
    ISSN: 1432-1041
    Keywords: tolfenamic acid ; anti-inflammatory agents ; biliary excretion ; pharmacokinetics ; intravenous administration ; bile duct cannulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To study its pharmacokinetics and especially its biliary excretion, 14C-tolfenamic acid 9.84 µCi/100 mg was infused i.v. in 8 patients with a T-tube inserted in the common bile duct at choledocholithotomy 7–10 days prior to the study. Bile was collected in fractions by continuous suction over a 24 h period. Blood samples were taken and urine collected up to 48 h after the dose. Tolfenamic acid and its metabolites were separated by TLC and were quantitated by liquid scintillation counting. The pharmacokinetics of tolfenamic acid could be described by a two compartment open model with V1 of 3.67±0.68 l and Vss of 8.0±1.0 l. The total plasma clearance of tolfenamic acid averaged 106±8 ml/min and t1/2β was 1.38±0.32 h. A three compartment open model was required to describe the kinetics of total 14C. The plasma clearance of total 14C was 15.4±3.9 ml/min and its terminal half life averaged 19.0±4.1 h. The long half-life was caused by the slow elimination of tolfenamic acid metabolites. Four metabolites were measured in plasma and bile. The principal metabolites in bile were glucuronide/sulphate conjugates of hydroxylated derivatives of tolfenamic acid. The recovery of tolfenamic acid in bile was 1.1±0.3% of the dose, whereas the recovery of total 14C was 18.6±4.9%. The biliary clearances of tolfenamic acid and total 14C were 1.2±0.3 and 5.0±2.1 ml/min, respectively. Thus, biliary excretion plays a considerable part in the pharmacokinetics of tolfenamic acid.
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  • 112
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 325-328 
    ISSN: 1432-1041
    Keywords: theophylline ; sustained release ; pharmacokinetics ; chronic administration ; healthy volunteers ; plasma levels ; GCMS assay ; stable isotope technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a new sustained-release preparation of theophylline (Dilatrane à Action Prolongée capsules filled with homogenous microgranules) has been after its studied administration to 7 healthy volunteers at 8 p.m. in order to achieve therapeutic levels at night and in the morning. In separate trials the test dose of 500 or 600 mg was administered for 7 days, once daily at 8 p.m. Plasma theophylline levels were measured by capillary gas chromatography with a mass specific detector after pentylation, using internal standards labelled with stable isotopes (15N-1,3 and 13C-2 theophylline). The new sustained-release preparation showed a monophasic regular absorption phase with very low interindividual variability. After administration, the plasma level stayed within 80% of the peak levels for 8.5±1.5 h. There was a good correlation between the dose and the steady state plasma level (r=0.9587; p〈0.05). This preparation can be chronically administered once daily day at 8 p.m. in order to achieve a therapeutic level during the night and the morning, and to provide sufficient protection during the nycterohemeral period, with a once dose a day schedule.
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  • 113
    Electronic Resource
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    Springer
    European journal of clinical pharmacology 27 (1984), S. 589-593 
    ISSN: 1432-1041
    Keywords: piretanide ; renal insufficiency ; furosemide ; pharmacokinetics ; loop diuretic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of piretanide was studied in 10 patients with chronic renal failure. After administration of a high oral dose (12 to 192 mg) of piretanide the kinetics behaved according to an open 2-compartment model. The elimination constant in the first phase (α) ranged from 0.385 to 0.756 h−1 and in the second phase (β) from 0.079 to 0.274 h−1. The corresponding elimination half-lives ranged from 55 to 108 min (t1/2 α) and from 152 to 524 min (t1/2 β). Only an average of 2.8% of the orally administered drug was recovered in 24 h urines. Nevertheless, a good correlation was found between urinary recovery or renal clearance of the drug and residual renal function. The elimination of piretanide by non-renal mechanisms appeared to be increased when renal function was greatly diminished.
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  • 114
    Electronic Resource
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    Springer
    Journal of mathematical biology 20 (1984), S. 95-102 
    ISSN: 1432-1416
    Keywords: pharmacokinetics ; generalized inverse Gaussian distribution ; recirculatory model ; renewal theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Based on a stochastic pharmacokinetical model (which mirrors topological properties of the circulatory system) it is shown by reinterpreting results of Wise (1974) that if the transit times of circulating drug molecules have a generalized inverse Gaussian distribution the corresponding residence times are gamma distributed. The condition that the probability of elimination of a drug molecule in a single circulatory passage is sufficiently small appears to be valid for most drugs. Thus theoretical evidence is given for fitting blood concentration-time curves following bolus injection of a single dose by power functions of time.
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  • 115
    Electronic Resource
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    Springer
    Investigational new drugs 2 (1984), S. 201-206 
    ISSN: 1573-0646
    Keywords: ASTA Z 7557 ; acute toxicity in mice and rats ; myelotoxicity ; immunosuppression ; urotoxicity ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The LD 50 of Z 7557 in mice was between 500 and 625 mg/kg after i.v. and around 2310 mg/kg after oral administration. The corresponding LD 10 was around 435 mg/kg (i.v.) or 1100–1250 mg/kg (p.o.), respectively. The LD 50 values in rats were in the range of 250–310 mg/kg after i.v. administration and around 1000–1250 mg/kg if given orally. With repeated daily i.v. injections only 70% of the daily dose contributed to lethality. A second administration of Z 7557 to rats after reversal of all toxic signs from the first administration induced the same symptoms and degree of toxicity as the initial injection. Reversible myelosuppression was the predominant feature of toxicity in mice and rats, but at equimolar doses this myelotoxicity was less than half that of cyclophosphamide (CP). First signs of immunosuppression were seen only at 100 mg/kg i.v. No severe urotoxicity was observed in rats with single i.v. doses up to 192 mg/kg. This might be due to the fast and complete renal excretion of the thiol moiety of Z 7557, whereas the activated oxazaphosphorine component occurred in the urine only to a much smaller amount, as could be shown by a pilot pharmacokinetic study. In conclusion, Z 7557 appeared to have an overall tolerance in rats and mice similar to cyclophosphamide but was clearly less toxic with respect to the bone marrow, the immune system and the urinary tract.
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  • 116
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    Springer
    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 177-191 
    ISSN: 1573-8744
    Keywords: compartmental analysis ; identification ; Michaelis-Menten kinetics ; nonlinear systems ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper deals with the deterministic identifiability of nonlinear pharmacokinetic models, namely, whether the model parameters can be identified with perfect data. It is shown that the most familiar method for analyzing the deterministic identifiability of linear models, in which the Laplace transform of the observation is examined, does not work for nonlinear models. An alternative method, in which the observation is expanded as a Taylor series about t=0,is described and is illustrated with some examples of nonlinear models familiar in the pharmacokinetics literature, in which an elimination rate is assumed capacity limited, with Michaelis-Menten kinetics.
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  • 117
    ISSN: 1573-8744
    Keywords: disopyramide ; pharmacokinetics ; pharmacodynamics ; electrophysiology ; protein binding ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and pharmacodynamics of the antiarrhythmic drug, disopyramide, were investigated in 12 volunteers who took 300 mg doses of 3 different capsule preparations and an aqueous oral solution of the drug at 1-week intervals. Concentrations of drug unbound to plasma proteins were measured by a sensitive immunoenzyme assay after ultrafiltration of plasma samples taken serially after dosing. QT interval was measured on serial ECG recordings with correction for changes in heart rate. Unbound concentrations of disopyramide were modelled by an open one-compartment pharmacokinetic model with a zero-order absorption rate and a lag time. There was no significant difference in parameter estimates between the four preparations, except for the lag time, which was significantly shorter for the solution preparation. The saturable protein binding of disopyramide was described by a hyperbolic model including a specific binding site and additional nonspecific binding. The pharmacodynamic relationship between unbound drug concentration and QT prolongation was fit by a simple linear model. This fit was better using unbound concentration of the drug than using total concentrations.
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  • 118
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 597-610 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; steady-state volume of distribution ; methotrexate pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of plasma concentration and pH on the steady-state volume of distribution, Vss,of methotrexate (MTX) were studied in five conditioned male beagle-mongrel dogs. Steady-state plasma MTX concentrations of approximately 1, 20, and 100μg/ml were targeted for by i.v. bolus doses followed by i.v. infusions. An isotonic solution of sodium bicarbonate or ammonium chloride was simultaneously infused for the purpose of inducing plasma pH change, while the infusion of an isotonic solution of sodium chloride served as a control. Plasma and urine concentrations of MTX were quantitated by a sensitive high-performance liquid chromatographic method, and the Vss of MTX was estimated by a recently reported physiologically based method of Chiou and Lam. Statistically significant (p〈0.05) concentration and plasma pHdependent Vss of MTX were observed. Concentration dependence of Vss was noted in sodium chloride and ammonium chloride infused dogs, but not in bicarbonate treated dogs. There was an average 50.0 and 44.8% increase in Vss at 1 μg/ ml relative to the two higher concentrations (20 and 100 μg/ ml) for dogs treated with ammonium and sodium chloride, respectively. However, Vss of MTX at the targeted concentrations of 20 and 100 μg/ml was relatively constant. Plasma pHdependence of Vss was observed only at the plasma concentration of 1 μg/ml, and on the average, ammonium chloride and sodium chloride treatments resulted in 50.0 and 31.3% higher Vss,respectively, when compared with the bicarbonate treatment. These phenomena appear to be adequately explained by the reported tissue uptake kinetics of MTX.
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  • 119
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 525-534 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; Michaelis-Menten model ; steady state predictions ; sensitivity analysis ; experimental design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Linear sensitivity theory is used to estimate the reliability of predictions of the minimum and maximum concentrations at steady state in the Michaelis-Menten model with i.v. bolus. The dependence of the relative errors in the predictions on the errors in the pharmacokinetic parameters is derived in an analytical form. It is shown that the quality of the predictions is not equally sensitive to all errors in parameters, and that the sensitivity factors vary with the degree of saturation of the system. An example of application for a drug, such as phenytoin, is discussed. It is suggested that sensitivity analysis may be useful in design of pharmacokinetic experiments aimed at the control of steady state levels for drugs with Michaelis-Menten kinetics.
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  • 120
    ISSN: 1573-8744
    Keywords: hydrochlorothiazide ; triamterene ; hydroxytriamterene sulfate ; pharmacokinetics ; bioavailability ; renal clearance ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate were monitored in the plasma and urine of 24 healthy young men taking single doses of a liquid preparation containing both hydrochlorothiazide and triameterene, liquid preparations containing either of these drugs alone, and a combination tablet recently formulated with a dose ratio of hydrochlorothiazide: triamterene (1∶1,5) found to give optimal potassium-sparing effect. In contradiction to a recent publication, no interaction between the drugs affecting the bioavailability or renal clearance of either could be demonstrated. The previous report of drug-drug interaction probably arose from formulationrelated problems with bioavailability from the two capsule and two tablet products which had been studied. A well-formulated hydrochlorothiazide-triamterene combination tablet promotes plasma concentrations and urinary excretion of hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate which are virtually identical to those seen after either a combination liquid dosage form or simple liquid forms containing only one of the two drugs.
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  • 121
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 289-313 
    ISSN: 1573-8744
    Keywords: protein binding ; pharmacokinetics ; bioavailability ; disopyramide ; heart failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and bioavailability of total (bound plus unbound) and unbound disopyramide were compared following the simultaneous administration of an oral dose of disopyramide and an intravenous dose of14C-disopyramide in five normal volunteers and in 11 patients with congestive heart failure. The binding of disopyramide varied between 60 and 92% in patients and between 81 and 88% in normal subjects at postequilibrium drug concentrations of 10−7M. The binding of disopyramide to serum protein was concentration-dependent in all study subjects at serum concentrations achieved following drug administration. The association constant for the first binding site in serum from normal subjects and patients averaged 8.7X105 M−1 and 4.4X10 5 M−1, respectively (p 〈 0.05). The unbound clearance of disopyramide averaged 277ml/min and 209 ml/min in normal subjects and in patients (p 〈 0.05). When normalized for body weight, the unbound clearance between patients and normal subjects was not significantly different. The elimination half-life of unbound concentrations in normal subjects and in patients averaged 4.9 and 6.1 h, respectively (p 〈 0.05). The clearance and elimination half-life of total disopyramide was the same in both groups. Although the bioavailability of disopyramide averaged 0.85 in both groups, it was more variable in patients owing to the variability in the fraction of the dose absorbed. The unbound renal clearance and volume of distribution at steady state of disopyramide was related to cardiac index. The ratio of elimination half-lives of total and unbound disopyramide was related to the extent of serum protein binding.
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  • 122
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 263-287 
    ISSN: 1573-8744
    Keywords: beta-adrenoceptor blocking agents ; pharmacokinetics ; structure ; lipophilicity ; octanol/water partition coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure and pharmacokinetics relationship of 14-beta-adrenoceptor antagonists was investigated in humans. Statistically significant linear and parabolic correlations were found to exist between standard and derived mean pharmacokinetic parameters and the apparent octanol/buffer (pH7.4) partition coefficient of the compounds. The lipophilic/hydrophilic properties were the primary determinants for the pharmacokinetic behavior of the compounds. Most of the pharmacokinetic parameters were also significantly correlated with the plasma protein/plasma water partition coefficient for the compounds. When the values of the pharmacokinetic parameters of the individual compounds were predicted from the regressions on the apparent partition coefficients in octanol/buffer (pH 7.4) and in plasma protein/plasma water, the error was on average 60%.
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  • 123
    ISSN: 1573-8744
    Keywords: methylene chloride ; pharmacokinetics ; physiological model ; hybrid model ; I.V. administrations ; mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A physiologic mathematical model was developed to describe the time course of14C-methylene chloride (14CH2Cl2) distribution and elimination in mice following single i.v. administrations of 10 and 50mg/kg. A whole-body model was used to simulate14CH2Cl2 concentrations in blood and tissues, pulmonary clearance of unchanged14CH2Cl2, and metabolic conversion to14CO2 and14CO as monitored by the appearances of these metabolites in expired breath. This diffusion-limited model was identified via a sequential optimization scheme using hybrid models for each compartment. Pulmonary elimination of unchanged14CH2Cl2 was modeled as a linear process while hepatic metabolism of14CH2Cl2 to the compounds14CO2and14CO was described by a saturable metabolic rate term. The model adequately described the dose dependence in methylene chloride distribution and metabolism when simulations were compared to experimental data.
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  • 124
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 451-461 
    ISSN: 1573-8744
    Keywords: rabbit ear chamber ; granulation tissue ; serum albumin ; sodium fluorescein ; Stokes-Einstein radius ; fluorescence ; photometric analysis ; vascular permeability ; renal clearance ; erythrocyte-free plasma layer ; two-compartment model ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Plasma pharmacokinetics of sodium fluorescein, fluorescein isothiocyanate conjugated bovine serum albumin, and a graded series of dextrans of 19,400 to 71,800 MW were monitored continuously using a noninvasive photometric technique in individual blood vessels of tissue grown in a rabbit ear chamber. The data obtained were fitted with a two-compartment open model to obtain an effective permeability and an effective clearance. Both parameters decreased with increasing molecular radius for dextrans. Values for albumin were considerably less than expected on the basis of molecular radius, presumably due to the configuration, charge, and binding characteristics of albumin.
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  • 125
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 351-365 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; model discrimination ; experiment design ; information theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The need for objective design of pharmacokinetic experiments aimed at model discrimination is argued. A sequential design strategy based on information theory is outlined. The characteristics of this strategy and its applicability to pharmacokinetic experiments is examined by means of computer simulated experiments. The limitations of the technique are discussed and alternative approaches outlined.
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  • 126
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 119-128 
    ISSN: 1573-8744
    Keywords: teicoplanin ; pharmacokinetics ; three-compartment model ; noncompartmental analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of teicoplanin, a new glycopeptide antibiotic active against gram-positive aerobic and anaerobic bacteria, was studied in adult male volunteers given 2- and 3- mg/ kg doses by a constant-rate 0.5-hr infusion. Serum and urine samples were collected up to 96 hr. Mean peak serum levels after the two doses were 15.7 and 22.4 μg/ml. Postinfusion serum teicoplanin levels showed triexponential decay. A three-compartment body model gave close values for pharmacokinetic parameters after the two doses. The mean half-life of the λ1 phase was 20.3 min, that of the λ2 phase was 2.9 hr, and the half-life of the estimated λ3 phase was 40.5 hr, in good agreement with that of the λZ phase (45.9 hr) calculated from the last urine data. The mean volume of distribution of the central compartment was 0.09 liter/kg and the steady-state volume of distribution using noncompartmental analysis was 0.84 liter/kg. Total clearance averaged 16.05 ml/hr/kg, with renal clearance arbout half this (9.51 ml/hr/kg), calculated by two different methods. The average total recovery of active teicoplanin in urine over 4 days was 52%, suggesting that both renal and nonrenal mechanisms are involved in elimination of the drug. The concentrations of teicoplanin in serum and urine exceeded the MIC (ranging from 0.02 to 2 μg/ml) on many pathogenic organisms for at least 1 day after administration.
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  • 127
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    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 193-221 
    ISSN: 1573-8744
    Keywords: compartmental analysis ; identification ; Michaelis-Menten kinetics ; nonlinear systems ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper deals with aspects of the numerical identifiability of parameters of a model with a capacity-limited elimination rate using a single dose-response curve, namely, the prospects of being able to identify model parameters with any meaning from real data. The concept of linear bounds, first proposed by Tong and Metzler, is described and it is shown that if the Michaelis-Menten constant Km is greater than all the measured concentration values, approximation by a linear model is appropriate. At the other end of the scale, if Km is small compared with measured concentration values, the nonlinear response approximates to a zero-order curve.
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  • 128
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    International Journal for Numerical Methods in Engineering 20 (1984) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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  • 129
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1-14 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The solution of dynamic contact (elastic impact) problems is complicated by the changing nature of the contact area. If a finite element approach is used, the system matrices vary with the contact area. If the problem is properly formulated, such changes are rank one. Rank one changes produce easily determinable changes in the LDLT decompositions of the system matrices. This renders a class of dynamic contact problems soluble with the same accuracy and computational effort as is associated with the solution of any dynamic problem using finite element procedures. Consideration of an example problem involving the impact of spring-mass systems confirms this claim.
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  • 130
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 101-119 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method is described to derive finite element schemes for the scalar convection equation in one or more space dimensions. To produce accurate temporal differencing, the method employs forward-time Taylor series expansions including time derivatives of second- and third-order which are evaluated from the governing partial differential equation. This yields a generalized time-discretized equation which is successively discretized in space by means of the standard Bubnov-Galerkin finite element method. The technique is illustrated first in one space dimension. With linear elements and Euler, leap-frog and Crank-Nicolson time stepping, several interesting relations with standard Galerkin and recently developed Petrov-Galerkin methods emerge and the new Taylor-Galerkin schemes are found to exhibit particularly high phase-accuracy with minimal numerical damping. The method is successively extended to deal with variable coefficient problems and multi-dimensional situations.
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  • 131
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 175-181 
    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 20 (1984), S. 169-173 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A two-noded, straight element with one-point quadrature is introduced for the unsymmetrical bending of orthotropic axisymmetric shells. The numerical results indicate that the present simple element performs accurately for both thick and thin shell applications.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 187-194 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Numerical results using uniform h-refinement approaches to the solution of a pair of elasticity problems with singularities are presented and compared to recently published results based on the uniform p-refinement approaches.
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  • 134
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 143-167 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Steady-state, free surface seepage through a heterogeneous porous medium underlain by a drain at a finite depth is solved using a fixed domain solution technique. The problems investigated are axisymmetric seepage from a circular pond and plane seepage from a symmetric channel. These ponds and channels may have variable shaped bottoms. Since the Baiocchi transformation was used to define a new dependent variable, the form of the permeability function was restricted to a product of functions of the independent variables. Herein the permeability was chosen to be a function of the depth only. For certain forms of this function, namely those having negative gradients, part of the flowfield becomes unsaturated and this violates the assumed saturation of the flowfield in the flow theory. The governing differential equation, which holds in the sense of distributions, is derived for a fixed solution domain and a simple algorithm (a finite difference successive over-relaxation scheme with projection) is given to obtain the solution to these free surface problems. Numerous comparisons are made with published results. Rigorous mathematical justification of the methods used herein can be found in the references cited.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 195-195 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 20 (1984) 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 182-186 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Bathe's basic algorithm of subspace iteration for the solution of the symmetric eigenvalue problem is improved by including a Chebyshev filtering mechanism. To obtain satisfactory convergence for the largest eigenvalues, a shifting strategy is adopted. The shift factor is approximately computed by the Lanczos process.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 479-503 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A transfer-matrix analysis is presented for determining the static behaviour of thick beams of ‘multimodular materials’ (i.e. materials which have different elastic behaviour in tension and compression, with nonlinear stress-strain curves approximated as piecewise linear, with four or more segments). To validate the transfer-matrix method results, a closed-form solution is also presented for cases in which the neutral-surface location is constant along the beam axis. Numerical results for axial displacement, transverse deflection, bending slope, bending moment, transverse shear, axial force and location of neutral surface are presented for multimodular and bimodular models of unidirectional aramid cordrubber. The transfer-matrix method results agree very well with the closed-form solutions.
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  • 139
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 523-528 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An 8-node brick element based on the assumed stress hybrid formulation is described. With three additional stress fields, the element stiffness matrix now has the required rank of 18, and the ‘bending’ response is exact with rectangular elements. Surprisingly, the 2 × 2 × 2 Gauss rule suffices for all numerical integrations, to satisfy the constant stress patch test.
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  • 140
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 529-548 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An assumed stress hybrid curvilinear triangular finite element is described which is based upon the Kirchhoff theory of plate bending. The derivation extends the assumed stress hybrid technique to curvilinear boundaries where the twelve connectors are related to those of an equilibrium rectilinear element and to Semiloof. The solution process demands only first derivatives of the shape functions.The element is subjected to various patch tests for constant bending, e.g. where the central element is in close approximation to a circle. All tests are passed for stress couples and vertex displacements, but values of the remaining connectors do not resemble exact results. Patch tests for rigid-body movements are passed exactly in every respect.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 505-514 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical technique has been developed to solve a system that consists of m linear parabolic differential equations with coupled nonlinear boundary conditions. Such a system may represent chemical reactions, chemical lasers and diffusion problems. An implicit finite difference scheme is adopted to discretize the problem, and the resulting system of equations is solved by a novel technique that is a modification of the cyclic odd-even reduction and factorization (CORF) algorithm. At each time level, the system of equations is first reduced to m nonlinear algebraic equations that involve only the m unknown grid points on the nonlinear boundary. Newton's method is used to determine these m unknowns, and the corresponding Jacobian matrix can be computed and updated easily. After convergence is achieved, the remaining unknowns are solved directly. The efficiency of this technique is illustrated by the numerical computations of two examples previously solved by the cubic spline Galerkin method.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 549-553 
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    Keywords: Engineering ; Engineering General
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    Notes: It is demonstrated that finite element discretizations may not, in general, satisfy the maximum principle; and sufficient conditions are presented to guarantee that solutions based on bilinear elements do satisfy the maximum principle.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 515-522 
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    Keywords: Engineering ; Engineering General
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    Notes: The efficiency and computational accuracy of the boundary element and finite element methods are compared in this paper. This comparison is carried out by employing different degrees of mesh refinement to solve a specific illustrative problem by the two methods.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 565-572 
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    Notes: The BEM is shown to be superior to FEM with respect to economy (man hour and data processing) and convergence (with increasing number of boundary nodes) in the elasic notch stress analysis of compact components.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 555-563 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This note discusses the numerical solution of the kinematic wave equation under those conditions when the solution contains a discontinuous shock. A finite element solution is described in which shocks are represented by discrete nodal discontinuities. The implementation of the method follows conventional finite element practice over the shockless regions of the solution domain which are coupled by frontal constraints. The basis of the method and examples of its application to the solution of the kinematic wave equation in one and two dimensions are presented.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 887-914 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A concise survey of formulation methods of geometric and material nonlinearity problems is given. Differences between existing formulations in the literature are discussed. A consistent Lagrangian and updated Lagrangian formulations are derived from the energy balance equation transformed to the proper reference configuration. Differences between the existing formulations and similar ones in the literature are found to be in specific geometric nonlinear terms in the final incremental equation as well as in the definition of the load increment vector. Specific forms of constitutive equations for elastic and elastoplastic materials are presented. Some of the forms used by other authors in application to elastoplastic materials are shown to be inconsistent. Sample numerical examples intended for checking some particular points in the formulation are presented.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 845-849 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Two numerical methods for solving two-point boundary-value problems associated with systems of first-order nonlinear ordinary differential equations are described. The first method, which is based on Lobatto quadrature, requires four internal function evaluations for each subinterval. It does not need derivatives and is of order h7, where h is the space chop. The second method, which is similar to the first but is based on Lobatto-Hermite quadrature, makes the additional use of derivatives to achieve O(h9) accuracy. Results of computational experiments comparing these methods with other known methods are given.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 915-929 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An almost linear optimization problem of importance in vibration isolation has been identified and algorithms were developed to minimize the forced vibrational response of structural systems. The constraints can be either displacements or accelerations. These algorithms have been studied for transient response, frequency response and stationary random using the direct dynamic solution. Multiple response points and loading conditions may be used.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 949-966 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: When applied to large sparse sets of simultaneous equations, classical iterative methods may yield very poor convergence rates. This paper gives an incomplete Choleski-conjugate gradient algorithm (ICCG) which has reliably good convergence rates at the expense of computing and using at each iteration an incomplete Choleski factor of the coefficient matrix. The method is applicable to any problems in which the coefficient matrix is symmetric positive definite and is likely to be advantageous with respect to elimination when it is not possible to represent the equations in a dense band form.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 931-948 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A method is presented for performing efficient and stable finite element calculations of heat conduction with quadrilaterals using one-point quadrature. The stability in space is obtained by using a stabilization matrix which is orthogonal to all linear fields and its magnitude is determined by a stabilization parameter. It is shown that the accuracy is almost independent of the value of the stabilization parameter over a wide range of values; in fact, the values 3, 2 and 1 for the normalized stabilization parameter lead to the 5-point finite difference, 9-point finite difference and fully integrated finite element operators, respectively, for rectangular meshes; numerical experiments reported here show that the three have identical rates of convergence in the L2 norm. Eigenvalues of the element matrices, which are needed for stability limits, are also given. Numerical applications are used to show that the method yields accurate solutions with large increases in efficiency, particularly in nonlinear problems.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 979-979 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 980-980 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 967-977 
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    Notes: A simple dynamic finite element algorithm for analysing a propagating mixed mode crack tip is presented. A double noding technique, which can be easily incorporated into existing dynamic finite element codes, is used together with a corrected Ĵ integral to extract modes I and II dynamic stress intensity factors of a propagating crack. The utility of the procedure is demonstrated by analysing test problems involving a mode I central crack propagating in a plate subjected to uniaxial tension, a stationary slanted central crack in a plate subjected to uniaxial inpact loading and an extending slanted-edge crack in plate subjected to uniaxial tension.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1370-1371 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1407-1414 
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    Notes: The paper describes the development of an eight-node plane rectangular finite dynamic element and presents detailed descriptions of the associated numerical formulation involving the higher order dynamic correction terms pertaining to the related stiffness and inertia matrices. Numerical test results of free vibration analyses are presented in detail for the newly developed eight-node element and also the corresponding four-node element in order to make a clear comparison of the relative efficiencies of the corresponding finite element and dynamic element procedures. Such results indicate a superior pattern of solution convergence of the presently developed dynamic element.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1415-1431 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A computational strategy for the evaluation of delamination stresses in multilayered fibre-reinforced composites is presented. The approach uses special inter-laminar shear elements and an iterative procedure in the calculation of out-of-plane stresses. Both regular and singular elements for the free edge are presented. The solutions are carried on by switching between direct matrix solution methods of small systems of equations and an iterative conjugate gradient method. The proposed discretization avoids ill-conditioning problems, modelling difficulties and large computational cost associated with three-dimensional analysis of delamination of holes, cut-outs, joints and areas of complex stress states.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1433-1441 
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    Keywords: Engineering ; Engineering General
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    Notes: A general, consistent and accurate procedure for obtaining difference equations from differential equations is presented and illustrated by several examples. The procedure is an extension of the integral method and incorporates what is known of the solution to the differential equation in the formation of the corresponding difference equation. For the same accuracy, large increases in grid size over that obtained by standard Taylor's series approximations are possible. Both boundary-value and initial-value problems are treated.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1443-1459 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The standard isoparametric transformation for finite element analysis is shown to be only a special case of a more general transformation which allows for flexibility in locating side and interior element nodes. Side nodes positioned at the same relative distance from corner nodes in both local and global space, and interior nodes positioned such that they do not affect the Jacobian of the co-ordinate transformation, provide improved accuracy over nodes positioned locally without regard for the global configuration. This concept is demonstrated in the context of two-dimensional quadratic quadrilateral isoparametrics, but is also applicable to higher orders and dimensions. In the test cases examined, the new formulation provides a reduction in error of up to three orders of magnitude and also provides accurate solutions for nodal placements which are not allowed using the standard transformations.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1461-1475 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A weighting function by which the mass matrix is made to be diagonal is deduced on the two-dimensional simplex element. Adopting the weighted residual method with the deduced weighting function for spatial domain and the two-step Lax-Wendroff method for time differentiation, the two-dimensinoal tidal flow in a model basin is calculated by means of the explicit finite element method. The water mass transport integrated over one tidal period at some cross-sections of the basin is also estimated, in order to verify the water mass conservation. It is found that the water mass is nearly conserved in the present method, although the usual lumped mass matrix technique fails to conserve.The present explicit finite element method with the conservative form of governing equations is also investigated and the water mass conservation is found to be a little more improved in this case than in the case of non-conservative forms. Application to a real bay indicates that the method with the conservative form of equations could be used for the estimation of tidal residual flow.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1477-1489 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this work, the plastic stress-strain relation and the incremental elastoplastic stiffness matrix for materials obeying the principal stress yield criterion are derived in the context of the associated theory of plasticity. Particular attention is paid to the treatment of the singularity conditions associated with this yield criterion.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1491-1506 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: It is demonstrated that the residual in a compatible (displacement) finite element solution can be partitioned into local self-equilibrating systems on each element. An a posteriori error analysis is then based on a complementary approach and examples indicate that the guaranteed upper bound on the energy of the error is preserved.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1507-1519 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The paper develops a new discrete transform pair which economizes on the number of samples of F(s) and f(t) compared with the standard pair. Whereas the standard pair used uniform sampling along the Bromwich contour, the new method allows a progressive increase in the sampling interval, thereby reducing the number of samples required to meet a specified bandwidth requirement. In the case of the computation of transient responses of physical systems, a reduction by a factor of 10 is not unrealistic. The new transform pair is based on the generalization of fundamental sampling principles. In particular, this leads to an integration contour different from the Bromwich contour.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1553-1554 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 164
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1581-1597 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A new family of coupled time integration operators of different orders is developed. It permits different time integration operators to be used simultaneously in various regions of the model. This approach has the advantage of applying a very accurate time integrator, such as Runge Kutta method of order two to four, to the local nonlinear region of interest and a simple time integrator, such as the implicit-explicit or mixed time implicit-explicit method of order one, for the remaining region. The computer implementation aspects, stability analysis as well as the numerical evaluations of these new methods are presented. This is another attractive addition to the repertoire of time integration methods.
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  • 165
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1613-1628 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element formulation for elastoviscoplasticity problems in the presence of large strains and deformations is presented in this paper. The formulation is capable of using any of a class of combined creep-plasticity constitutive models with state variables for the description of material behaviour. The specific problem considered is plane strain extrusion using the constitutive model originally proposed by Hart. Numerical results are presented for sample problems and the important effects of extrusion speed and friction (at the die-workpiece interface) on the residual stresses in an extruded sample are investigated. The computer program developed here is quite general and can be modified to solve problems for other manufacturing processes like rolling, sheet forming, etc.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1643-1660 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A new direct search package is presented. Typical test functions solved establish the robustness and efficiency of the package. The most significant features of the package are that it works satisfactorily even in single precision and requires much less memory. It needs only the function values and the unidimensional search is totally dispensed with. Methods such as different descent techniques, the RMS procedure, the co-ordinate movement technique and the gallop-canter equalization scheme form the sequence of strategies.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1629-1641 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper attempts to answer two commonly raised questions during the preparation of a finite element mesh, for the linear elastic fracture analysis of cracked structure: how to set up the finite element mesh around the crack tip, and what level of accuracy is to be expected from such a modelling.Two test problems, with known analytical expressions for their stress intensity factors, are analysed by the finite element method using the isoparametric quadratic singular element. The modified parameters were the order of integration, aspect ratio, number of elements surrounding the crack tip, use of transition elements, the singular element length over the total crack length, the symmetry of the mesh around the crack tip. Based on these analyses, a data base is created and various plots produced. The results are interpreted, the accuracy evaluated and recommendations drawn.Contrary to previous reports, it is found that the computed stress intensity factor (SIF) remains within engineering accuracy (10 per cent) throughout a large range of l/a (singular element length over crack length) for problems with a uniform non-singular stress distribution ahead of the crack tip (i.e. double edge notch), and l/a should be less than 0·1 for problems with a non-singular stress gradient (i.e three-point bend). Also, it is found that the best results are achieved by using at least four singular elements around the crack tip, with their internal angles around 45 degrees, and a reduced (2 × 2) numerical integration.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1661-1670 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents and analyses methods for design sensitivity analysis of static response for structural systems when general boundary conditions are used during the analysis phase. The design sensitivity analysis methods where the boundary conditions are used to reduce the equilibrium equation have been presented earlier. In such procedures, the reduced stiffness matrix is non-singular. This fact is used to show differentiability of the displacement vector. When reduction procedures are not used, the global structural stiffness matrix may be singular. In such a case, differentiability of the displacement vector may be questionable. However, it is shown that the displacement vector is still differentiable. Several forms of the structural design sensitivity equations are presented. Although these equations are derived with Lagrange multiplier treatment of general boundary conditions, it is shown that they are applicable with any treatment of general boundary conditions. For example, they can also be used with co-ordinate reduction schemes. Therefore, design sensitivity analysis can be carried out with any existing finite element analysis computer code. Moreover, the procedures presented can be used to calculate sensitivity of a force of constraint can that is desired. The formulations are kept quite general such that design dependent boundary conditions can be routinely treated. An example is used to illustrate the procedures.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1671-1683 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, an efficient, exact zooming technique is developed which employs static condensation and exact structural reanalysis methods. For a multiple level of zooming such that the successive level of zooming is contained within the prior levels of zoom, repeated application of static condensation will reduce the system to one that is associated only with the degrees-of-freedom (dof) of the original model. Then, application of an exact static reanalysis technique permits the displacements at the dof of the original model that are contained in the final zoomed portion of the structure to be obtained first. Next, the response external to the zoom, as well as the response of additional dof within various levels of zooming, can be computed. With the triangular factor of the stiffness matrix of the original system available, this approach involves only the solution of a system of equations of small order. The proposed method is demonstrated by a numerical example.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1697-1702 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An inversion formula based on expansion in a Fourier sine series, proposed by Koizumi in 1935, is examined. It is found to give results of moderate accuracy with relatively little work.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1685-1695 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method for the formulation of hybrid elements by the Hellinger-Reissner principle is established by expanding the essential terms of the assumed stresses as complete polynomials in the natural coordinates of the element. The equilibrium conditions are imposed in a variational sense through the internal displacements which are also expanded in the natural co-ordinates. The resulting element possesses all the ideal qualities, i.e. it is invariant, it is less sensitive to geometric distortion, it contains a minimum number of stress parameters and it provides accurate stress calculations. For the formulation of a 4-node plane stress element, a small perturbation method is used to determine the equilibrium constraint equations. The element has been proved to be always rank sufficient.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1703-1709 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The strain space and traditional stress space formulations of plasticity theory are compared. We show how plasticity theory has been implemented numerically to solve static and dynamic problems, and conclude that the numerical loading criteria that have been used for two decades are identical to the strain space loading criteria proposed by Naghdi and co-workers.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1729-1733 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A PERQ single user computer can be used to animate structure plots, which is of great assistance when interpreting the results from finite element programs. Excellent appreciation may be obtained of a structure oscillating in complicated natural modes. The technique is also useful for studying deformations due to static forces.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1711-1728 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Simple solutions are extracted from the exact compatibility equations of inextensional bending for a special class of shell shapes, and it is speculated that these solutions provide useful criteria towards evaluating finite elements for these and closely related shapes. Curved finite elements of a quadratic parametric representation, which do not belong to the special class, are then studied. By using a series of exact inextensional bending displacements, it is concluded from numerical evidence that the criteria apply to finite element shapes in this representation when they are shallow, as is usually the case in practice. Criteria for homogeneous membrane actions follow from Gol'denveizer's static-geometric analogue.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1745-1749 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Using the partial-boundary element approach, in which only a part of the boundary in problem is discretized, the elastic torsion problem of a prismatic beam of a cracked rectangular cross-section has been solved in this brief paper, together with a numerical example to show the accuracy and versatility of the approach.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1751-1755 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The radial symmetry of the cable results in circular finite elements to evaluate the potential distribution in a multi-dielectric cable. Owing to this, a two dimensional analysis used in conjunction with triangular finite elements is reduced to one-dimensional analysis. This method therefore suggests an alternative proposal to calculate the potential distribution in a multi-dielectric cable with better accuracy.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1756-1756 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1757-1757 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1757-1758 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1758-1759 
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    International Journal for Numerical Methods in Engineering 20 (1984) 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1791-1796 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Contour plots of finite element solutions, especially for derivatives, often are discarded due to poor plotting algorithms. This note shows how a smoothing scheme based on a minimum surface theory can significantly improve the quality of the graphical results. The scheme proposed is compared with many other smoothing schemes, including least squares, on a simple problem.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1763-1790 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper describes the stages of development of an optimum structural design scheme. Any attempt to generate the optimum scantlings of a structure of even moderate complexity usually poses nonlinear programming problems for which there exist no universally accepted solution method. The structure considered here is a complete compartment of a single-hulled ship acted upon by multiple load cases. The elastic responses under four different load types are obtained by a quasi finite element analysis routine developed specifically for this purpose. Sequential linear programming (SLP) with appropriate artifices to achieve rapid convergence has been successfully employed as an optimization routine to minimize the object function, which in this case was the total weight of the major structural members. The test problem has 490 basic degrees-of-freedom, 21 free design variables and more than 100 mixed constraints, the majority of which are nonlinear implicit stress functions. The method is then applied to a number of cases representative of small warship designs. Suggestions for future extensions and general conclusions are included at the end of the paper.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1815-1821 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The approach of Cermak and Zlamal1 for solving quasilinear parabolic equations is modified and improved. The modified approach leads to a normal system of ODE, which may be solved with a standard program. The numerical solution of a specially selected example is compared with the exact solution. The method is applied on a system of quasilinear parabolic equations, which describes a real process - crystallization of a metal ingot.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1797-1813 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The simulation of a large-scale gas transmission network involves the numerical solution of a large system of initial valued, stiff algebraic/differential equations. Rapid changes in the solution are present due to the disturbances generated by the varying consumer demand and the operation of network controlling devices such as compressors. This paper discusses the design of an efficient variable-step integrator for the solution of the problem. Two sets of strategies are presented for implementing the variable-step integrator; one for the implicit numerical method such as the diagonally implicit Runge-Kutta methods, and the other for the linearly implicit Rosenbrock-type method. The performance of the numerical methods implemented are compared with the British Gas simulation program PAN on a number of large, realistic transmission networks.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1823-1840 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The optimality conditions for the optimal shape remodelling of linearly elastic plates are obtained by introducing the total variation of a function defined on a variable domain, although the variation of a function has been taken on a fixed domain in most literature on calculus of variations. Using these optimality conditions, a solution scheme involving an iterative algorithm is proposed, together with several numerical examples.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1863-1884 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper presents a simple scheme for analysing shells subject to the Kirchhoff-Love hypothesis. The method combines a previously developed, statically determinate truss model with the static-geometric analogy of elastic thin shell theory. In this way, both in-plane and flexural mid-surface actions are obtained by simply repeating the elementary computations performed on an essentially ‘membrane’ truss.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1841-1861 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper presents the modelling of open shells, such as those used in roof construction, by means of a single-layered, pin-jointed truss. The latter exhibits several advantages over existing framework models, such as, for example, statical determinacy and the capacity to cope with arbitrary material constants. In the present article, the truss model is developed for and applied to the numerical analysis of shells subject to the membrane hypothesis. However, the same statically determinate model forms the basis for a computational scheme for analysing shells according to the more formal, statically indeterminate bending theory; the latter application of the truss model will be presented in a subsequent paper.
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1951-1952 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1952-1952 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1957-1958 
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    International Journal for Numerical Methods in Engineering 20 (1984), S. 1953-1956 
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 1959-1964 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method for static condensation is presented. This method utilizes Choleski decomposition with some modification to obtain the effective stiffness matrix and the effective load vector. A comparison between this modified decomposition method and the usual matrix decomposition method shows that the former is more efficient than the latter.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 195
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 1965-1990 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An approach for the fully automatic generation of three-dimensional finite element meshes is presented. The method is specifically designed for use with solid modelling systems which provide a complete and unique definition of the geometry of a part. The method follows from the basic concepts of the octree encoding technique with specific modifications made to produce valid, user controllable finite element meshes. Example problems are included to demonstrate the technique.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
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  • 196
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 2065-2075 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method which combines the finite element technique and the singular-integral equation method is presented. The association of the two methods is obtained with the help of Schwarz's alternating method (SAM). The method was applied with satisfactory results to the solution of a series of problems of a circular arc crack lying inside a finite thin plate for various lengths of the circular arc and for various dimensions of the rectangular cracked sheet.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 197
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 198
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 2121-2141 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A 48 degrees-of-freedom (d.o.f.) quadrilateral thin elastic shell finite element using variable-order polynomial functions, B-spline functions and rational B-spline functions to model the shell surface is developed. This development may allow the stiffness formulation of the shell element to be linked to the geometry data bases created by computer aided design systems. The displacement functions are that of bicubic Hermitian polynomials. The displacement functions and d.o.f. are expressed and investigated in both the curvilinear and Cartesian forms. The cuivilinear form is simpler and can provide the proper solution for a certain class of shell problems. For certain highly curved shells such as bellows, however, the curvilinear form fails to properly model some rigid body modes even with either the explicit inclusion of rigid body terms or the high order displacement functions. It is suggested in this study that such difficulty can be circumvented and the rigid body modes can be properly included if a Cartesian form is used for displacement functions. The strain-displacement equations are expressed in curvilinear co-ordinates. Thus, the Cartesian displacement functions require a transformation to curvilinear displacement at each numerical integration point. Examples include a pinched cylinder, a translational shell under central load, a uniformly loaded hypar shell, a pressurized ovel shell, a semi-toroidal bellows and a U-shaped bellows. For the first four examples, geometric modellings consist of polynomials of second-order (subparametric), third-order (isoparametric), and fourth and fifth-order (both superparametric) as well as B-spline functions of fourth- and fifth-order. The geometries of the pinched cylinder, the semi-toroidal bellows, and the U-shaped bellows were modelled exactly using rational B-spline functions. All the results obtained are in good agreement with alternative existing solutions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 199
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 2175-2195 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element method for contact problems in crack mechanics is developed on the basis of the penalty function method. The method is successfully applied to three important problems in fracture mechanics: a crack propagated from a pin hole, a two-point supported specimen with an edge crack loaded by a stamp, and a thick plate with a through-wall crack under bending force.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
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  • 200
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 20 (1984), S. 2253-2281 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A total Lagrangian finite element formulation for the geometrically nonlinear analysis (large displacement/large rotations) of shells is presented. Explicit expressions of all relevant finite element matrices are obtained by means of the definition of a local co-ordinate system, based on the shell principal curvature directions, for the evaluation of strains and stresses. A series of examples of nonlinear analysis of shell and plate structures is given.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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