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  • Articles: DFG German National Licenses  (607)
  • 1995-1999
  • 1985-1989  (607)
  • 1915-1919
  • 1989  (607)
  • Engineering  (566)
  • Magnetic resonance imaging
  • Nuclear reactions
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  • Articles: DFG German National Licenses  (607)
Material
Years
  • 1995-1999
  • 1985-1989  (607)
  • 1915-1919
Year
  • 1
    ISSN: 1432-1440
    Keywords: Periarteritis nodosa ; Magnetic resonance imaging ; Cerebral lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The course is reported of a patient with periarteritis nodosa who initially presented with neurological symptoms. Multiple cerebral lesions were documented by the first magnetic resonance imaging (MRI) investigation. The majority of these had disappeared completely in the follow-up MRI studies. In contrast to neurological improvement the patient eventually died due to multiorgan failure. Postmortem histological examination revealed no pathological findings in the brain except one single necrotic area already known from MRI. Remissions of histological and angiographic alterations in periarteritis nodosa have been described as “local healing” leading to fibrosis and scarring. Our findings suggest that restitutio ad integrum may occur, at least in cerebral lesions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 11 (1989), S. 155-161 
    ISSN: 1279-8517
    Keywords: Brain stem ; Magnetic resonance imaging ; Anatomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé A partir d'une exploration IRM de la fosse postérieure de 30 sujets volontaires sains une corrélation anatomoradiologique a été effectuée. L'examen fut pratiqué sur un appareil CGR Magniscan de 0,5 Tesla avec une séquence d'inversion récupération (TI: 21 ms, Tr. 2 000 ms, Ti: 500 ms). Cette séquence nous paraît être celle qui visualise le mieux la substance grise, la substance blanche et le liquide cérébrospinal. Afin d'étudier la configuration des principales structures du tronc cérébral 8 plans de coupes horizontales et 3 sagittales sont proposés.
    Notes: Summary Magnetic resonance imaging of 30 normal volunteers' posterior fossae was performed on a CGR Magniscan machine with a magnetic field strength of 0,5 Tesla. We chose the inversion recovery signal with a Tr of 2,000 ms, a TE of 21 ms and an inverse time of 500 ms. This sequence gives a better definition of the grey matter, the white matter and the CSF. To study the brain stem we suggest 8 horizontal and 3 sagittal sections.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Abdominal imaging 14 (1989), S. 308-310 
    ISSN: 1432-0509
    Keywords: Hemangioma, spleen ; Thrombocytopenia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In contrast to the only previously published description, the magnetic resonance appearance of a splenic hemangioma was markedly heterogeneous on T2-weighted images due to extensive infarction and large vascular pools. Magnetic resonance images correlated precisely with the pathological findings. The hemangioma caused thrombocytopenia, a well-documented albeit rare hematologic phenomenon associated with visceral hemangioma.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 129-133 
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Computed tomography ; Brain stem tumour ; Brain stem haemorrhage ; Brain stem infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ninety-six magnetic resonance imaging (MRI) studies demonstrating solitary brain stem lesions were reviewed in order to establish distinguishing features between tumours and other lesions. Histological confirmation of the radiological diagnoses was obtained in 33% of patients. The morphology of the lesion rather than its signal characteristics was the most useful feature in differential diagnosis, except after haemorrhage. However, areas of abnormal T2 recovery time were significantly more extensive than areas of abnormal T1 recovery time in tumours at presentation. In other lesions and in tumours following radiotherapy induced regression, the extent of abnormal T1 and T2 signal was the same. Possible reasons for this observation are discussed. The accuracy of computed tomography (CT) and MRI were similar for lesions causing brain stem expansion but for small lesions MRI was more sensitive and provided better topographical information.
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  • 5
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Cerebral angiography ; Atrial myxoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of left atrial myxoma presenting exclusively with neurological symptoms, studied with magnetic resonance imaging (MRI) combined with cerebral angiography and computed tomography (CT) is reported. Typical angiographic findings suggested the diagnosis of myxoma. MRI showed multiple ischemic lesions disseminated throughout the entire brain, some of which had been clinically asymptomatic. Because of its sensitivity in identifying small cerebral infarcts, MRI should prove in the future to be a first-choice technique in the evaluation of the presence of and extent of cerebral involvement in embolic left atrial myxoma.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 213-216 
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Spine ; 3DFT ; Gradient echo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A prospective study of 16 patients was performed to compare quantitatively a contiguous single slice 2DFT version with a 3DFT version of a short TR, variable flip angle, gradient echo (GRASS) pulse sequence. The 3DFT GRASS scans had higher signal-to-noise ratios (SNR) of cord and CSF compared to the single slice 2DFT GRASS scans. The 3DFT GRASS scans, however, had lower CSF-cord and CSF-disc contrast than the single slice 2DFT version. The 3DFT GRASS sequence demonstrated comparable contrast only on the end slices of an imaging volume suggesting influence of an entry phenomenon. The lower CSF-cord and CSF-disc contrast of the 3DFT GRASS technique diminished its usefulness in the diagnosis of cervical disc disease compared to the single slice 2DFT GRASS technique. Two different slice thicknesses (3 mm and 5 mm) were investigated with the 2DFT GRASS technique and found to be comparable although the 3 mm scans had sharper disc and dural margins because of less partial volume artifact.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 382-385 
    ISSN: 1432-1920
    Keywords: Cervical spine ; Disk herniation ; Myelography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eleven operated herniated disks in 10 patients were evaluated preoperatively with plain films, myelography and magnetic resonance imaging. Plain X-ray was a valuable supplement to MRI for studying the bony changes. Myelography showed 7 of 11 herniated disks while MRI gave correct diagnosis in all. It is concluded that MRI can replace myelography and computerized tomography in the preoperative evaluation of cervical herniated disk. The other examinations may be supplementary in some cases.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 430-432 
    ISSN: 1432-1920
    Keywords: Amnesia ; Glioblastoma ; Hippocampal formation ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The authors report a unique case of glioblastoma which caused permanent amnesia. Magnetic resonance imaging showed the lesion to be limited to the hippocampal formation bilaterally. Although glioblastoma extends frequently into fiber pathways and expands into the opposite cerebral hemisphere, making a “butterfly” lesion, it is unusual for it to invade the limbic system selectively to this extent.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1920
    Keywords: Thoracic disc herniation ; Spine, intervertebral discs ; Spine, MR studies ; Spinal cord, compression ; Contrast media ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The Gd-DTPA-enhanced magnetic resonance findings in two patients with herniated thoracic intervertebral discs are reported. The first patient was a 56-year-old woman with a small subligamentous T6-7 disc herniation, slightly lateralized to the right. The second patient was a 51-year-old man with a central and right posterolateral disc herniation, including a large calcified fragment, at the T8-9 level. The nonenhanced MR examination revealed the presence of an extradural mass lesion in both patients, impinging upon the dural sac and compressing and displacing the spinal cord posteriorly. The lesion was slightly hypointense on both T1- and T2-weighted spin echo sequences. Following intravenous injection of Gd-DTPA in a dosage of 0.1 mmol/kg body weight, enhancement of the posterior longitudinal ligament was noted and triangular areas of contrast uptake were seen to occur in the epidural space above and below the herniated disc. At surgery, they were found to correspond to dilated and congested epidural veins.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
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    Springer
    Neuroradiology 31 (1989), S. 276-277 
    ISSN: 1432-1920
    Keywords: Cockayne syndrome ; White matter ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary MRI findings are reported from two patients with Cockayne syndrome (CS) type I, aged 11 and 37 years. Changes were compatible with diffuse white matter hypomyelination. Basal ganglia calcification was present in both, marked cerebellar atrophy in the older patient. MRI may support the diagnosis of CS in the appropriate clinical context. The view that CS is a dysmyelinating disorder is further substantiated.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 177-179 
    ISSN: 1432-1920
    Keywords: Malignant fibrous histiocytoma ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A rare case of primary MFH of the brain is described together with the CT and MRI findings. The radiological appearance of this tumor is discussed in conjunction with the material published in other case reports.
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  • 12
    Electronic Resource
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    Springer
    Neuroradiology 31 (1989), S. 293-298 
    ISSN: 1432-1920
    Keywords: Pituitary microadenoma ; Magnetic resonance imaging ; Gadolinium DTPA ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ten patients with biochemical evidence of a hormonally active pituitary adenoma were examined by dynamic contrast enhanced computed tomography (CT) and then by pre and post Gadolinium-DTPA (Gd-DTPA) enhanced magnetic resonance imaging (MRI). Excluding one false positive case, CT and unenhanced MRI were comparable in the detection of microadenoma. Post Gd-DTPA examination gave more clear evidence of the actual adenoma in two patients and aided in the demonstration of a third. However, in two others all imaging techniques failed to demonstrate the microadenoma subsequently found at surgery. On the post enhancement MRI it was easier to assess the relationship of a tumour to the cavernous sinus and to visualise the relationships of the parasellar carotid arteries.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 403-407 
    ISSN: 1432-1920
    Keywords: Vertebral artery ; Basilar artery ; Arterial occlusion ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Magnetic resonance (MR) images of nine patients with intracranial vertebral artery occlusion (five proved, four presumed) have been reviewed. In two of nine, both vertebral arteries were occluded and in five of the nine, the basilar artery was also blocked. All occluded arteries showed absence of flow void and were clearly demonstrated as mildly hypo-∼mildly hyperintense structures to brainstem parenchyma on the T1-weighted images. In two of five patients with basilar artery occlusion, retrograde filling of the distal basilar artery was detected. Thus, MR imaging, in particular the T1-weighted image, is a pertinent diagnostic modality for evaluating intracranial vertebral artery occlusion. Angiography does not seem to be required for confirmation.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
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    Springer
    Neuroradiology 31 (1989), S. 190-192 
    ISSN: 1432-1920
    Keywords: Epidural lipomatosis ; Lumbar myelography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Epidural lipomatosis may be unassociated with steroid use and should be considered in the differential diagnosis of lumbar radiculopathy. This may cause widening of the spinal canal on plain film and complete block on myelography. CT or MRI is diagnostic.
    Type of Medium: Electronic Resource
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  • 15
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    Springer
    Neuroradiology 31 (1989), S. 98-101 
    ISSN: 1432-1920
    Keywords: Brain cysts ; Anomalies, congenital ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cases of large asymptomatic cysts of the lateral ventricle are presented. The cyst walls or cyst contours were demonstrated well by proton density-weighted or T2-weighted spin echo images. These cysts are being detected as incidental findings in increasing frequency with the increasing use of MR imaging. Our data and review of the literature suggest that surgical intervention is not necessarily warranted, but that careful clinical evaluation is indicated. The diagnostic problem of intraventricular cysts is also discussed.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1989), S. 258-262 
    ISSN: 1432-1920
    Keywords: Neuro-Behçet's syndrome ; Behçet's syndrome ; Brain stem type neuro-Behçet's syndrome ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Brain stem type neuro-Behçet's syndrome was studied with enhanced CT and MRI during the acute and chronic stage of the illness. During the acute stage, brain CT revealed a low density lesion in the brain stem extending from the lower pons up to the midbrain ventrolaterally with marginal enhancement effect. T2-weighted image showed a high signal intensity lesion in the brain stem which mainly involved the basis ponti, tegmentum, tectum and cerebral peduncle. During the chronic stage, the lesion became low in signal intensity with T2-weighted image and reduced in its size without enhancement in brain CT. The prolonged relaxation time of the lesions was gradually normalized with steroid treatment. Sequential brain CT with enhancement and MRI study with T1- and T2-weighted images were useful to detect the lesions and to evaluate the activity in the neuro-Behçet's syndrome.
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  • 17
    ISSN: 1432-1920
    Keywords: Brain ; Magnetic resonance imaging ; Cavernous angioma ; Arteriovenous malformation ; (AVM) ; Venous angioma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twelve patients with cerebral vascular malformations (5 cavernous angiomas, 1 thrombosed arteriovenous malformation, and 6 venous angiomas) were studied with magnetic resonance (MR) imaging. All lesions were clearly depicted. Characteristic MR findings were obtained mainly on T2-weighted images: a markedly low intensity area was always seen. The margins of arteriovenous malformation (AVM) and venous angioma were irregular while those of cavernous angioma were smooth in all planes on T2-weighted images. Gradient-echo (GrE) pulse sequences were more sensitive than T2-weighted spin echo (SE) in lesion detection. MR imaging could play an important role in the differential diagnosis of cerebral vascular malformations.
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  • 18
    Electronic Resource
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    Springer
    Skeletal radiology 18 (1989), S. 253-259 
    ISSN: 1432-2161
    Keywords: Fibrous metaphyseal defect ; Magnetic resonance imaging ; Determination of origin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Sixteen patients with fibrous metaphyseal defects were examined with both plain radiography and magnetic resonance (MR) imaging. Depending on the age of the fibrous metaphyseal defects, characteristic radiomorphologic changes were found which correlated well with MR images. Following intravenous Gadolinium-DTPA injection, fibrous metaphyseal defects invariably exhibited a hyperintense border and signal enhancement. Healed lesions exhibited a transition to normal bone marrow. A line through the maximum longitudinal diameter of a fibrous metaphyseal defect invariably led to a point of tendinous or ligamentous insertion. Coronal MR images demonstrated the maximum longitudinal extension and the respective inserting tendon or ligamentous structure at the epiphyseal line.
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  • 19
    ISSN: 1432-2161
    Keywords: Magnetic resonance imaging ; Pulse sequences ; Primary bone tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A prospective magnetic resonance imaging (MRI) study was carried out in 13 patients (19 examinations) with primary bone tumours to assess the relative value of each of four pulse sequences in showing the extent and nature of the lesion. The four pulse sequences used were a T1-weighted spin-echo (SE544/44), a T2-weighted spin echo (SE1500/80), a short TI inversion recovery (STIR) (IR500/100/44), and a partial saturation (PS) (PS500/22) with field echo data collection. For soft tissue disease the combination of PS and STIR gave better definition of the boundary of the tumour than the more conventional T1 and T2-weighted spin echo sequences. For the demonstration of bone cortex, periosteal change and calcification, T1 and T2-weighted spin echo sequences were better. However, for calcified tissues, plain radiographs were better than either MRI combination. On the assumption that plain films will be available in all cases, PS and STIR sequences could therefore be substituted for T1 and T2-weighted spin echo sequences allowing an increase in soft tissue detectability for lesions in both red and yellow marrow.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 18 (1989), S. 523-526 
    ISSN: 1432-2161
    Keywords: Spine ; Scheuermann disease ; Magnetic resonance imaging ; Disc degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Comparison of the radiographic signs of Scheuermann disease and the corresponding disc degeneration on thoracolumbar magnetic resonance (MR) images was made in 21 young patients. Marginal sclerosis, Schmorl nodes and narrowed disc spaces, but not irregular or wedge-shaped end-plates, were significantly associated with disc degeneration. Fifty-five percent of the discs in the patients with Scheuermann disease were abnormal on MRI, compared with 10% in asymptomatic controls. Our study confirms that thoracolumbar disc degeneration is enhanced in 20-year-old patients with low back pain who have radiological evidence of Scheuermann disease.
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  • 21
    ISSN: 1432-2161
    Keywords: Disc ; Disc disease ; Disc extrusion ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Magnetic resonance (MR) imaging is useful in evaluating a variety of spinal pathologies including intervertebral disc disease. Herniated discs are commonly believed to undergo premature degeneration and produce low intensity signal on T2-weighted images. We reviewed 154 patients who were studied for disc herniations or other pathology. Fifty-nine (38%) had disc herniations and 7 of these (5%) had a fragment that was hyperintense with respect to the adjacent intervertebral disc on T2-weighted images. It is hypothesized that some disc fragments may contain a higher water content that causes prolongation of the T2 signal. The bright signal which is therefore seen on long TR long TE (T2-weighted) images may be a useful sign suggesting herniation or extrusion.
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  • 22
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    Springer
    Skeletal radiology 18 (1989), S. 585-590 
    ISSN: 1432-2161
    Keywords: Soft tissue tumors ; Bone tumors ; Magnetic resonance imaging ; Low field strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Extremely low field magnetic resonance imaging (MRI) was evaluated in 16 patients with bone and soft tissue tumors, both benign and malignant. Twelve of the lesions were located in the lower extremity, 2 in the gluteal and 2 in the shoulder region. The findings were compared to the results of computed tomography (CT). Low signal-to-noise ratio and poor spatial resolution result in an image quality which is inferior to that obtained with MR imaging at higher field strengths. In spite of this, the diagnostic information seems to be at least comparable to that obtained from CT.
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  • 23
    ISSN: 1432-2161
    Keywords: Magnetic resonance imaging ; Gadolinium-DTPA ; Rheumatoid arthritis ; Dynamic magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thirty-four joints (19 knees, 15 wrists) of 31 patients suffering from rheumatoid arthritis and related disorders were examined prior to and following intravenous administration of Gadolinium-DTPA (0.1 mmol/kg body weight). T1-weighted spin-echo sequences and the gradient-echo technique FLASH were applied. FLASH scanning was used for the registration of the time-dependent changes of signal intensity following Gd-DTPA. Synovial proliferations exhibited a rapid and marked increase of signal intensity whereas fatty tissue, bone marrow, muscle and synovial effusion demonstrated only minor changes, causing enhanced contrast between synovial pannus and joint effusion or other neighbouring structures. Within the synovial pannus, ratios (absolute signal increase) of 131.3±53.4% and 122.9±51.1% were found in T1-weighted spin-echo and in FLASH sequences respectively. The average signal increase gradient of pannus (108.2±70.6%/min) was significantly (p〈0.001) different from muscle (13.4±7.8%/min), fatty tissue (10.2±8.4%/min), bone marrow (5.5±7.1%/min), and joint effusion (14.7±7.8%/min).
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  • 24
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    European journal of pediatrics 149 (1989), S. 162-163 
    ISSN: 1432-1076
    Keywords: Antithrombin III ; l-Asparaginase ; Magnetic resonance imaging ; Osteonecrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a child with acute lymphocytic leukaemia who developed simultaneous osteonecrosis of vertebrae and cerebral thrombosis duringl-asparaginase therapy. Fibrinogen, antithrombin III and plasminogen were decreased. Fresh frozen plasma in addition to antithrombin III concentrates were used to replenish these haemostatic proteins.l-asparaginase induced coagulopathy may cause osteonecrosis.
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  • 25
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    Journal of neurology 236 (1989), S. 177-181 
    ISSN: 1432-1459
    Keywords: Cheiro-oral syndrome ; Magnetic resonance imaging ; Computed tomography ; Central gyrus ; Thalamus-Brain stem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four cases of the cheiro-oral syndrome are reported, with a review of the clinical symptoms and signs and the neuroradiological methods used to demonstrate the responsible lesion. In each case, angiography, computed tomography (CT) and magnetic resonance imaging (MRI) were performed. The lesion was found in the thalamus in three cases and in the pons in one. Infarction had occurred in three cases and haemorrhage in one. Angiography revealed normal findings in all cases. CT at the onset of the symptoms demonstrated a small haemorrhage in the thalamus in one case but was not helpful in the others, and MRI was required to identify infarction. The anatomical sites responsible for the cheirooral syndrome have been reported to be in the central gyrus, in the thalamus, and in the brain stem. The clinical symptoms and signs reported in the literature and in our four cases are reviewed to evaluate aetiological factors and clinical features according to the three different sites of lesions causing this syndrome.
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  • 26
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    Journal of neurology 236 (1989), S. 255-259 
    ISSN: 1432-1459
    Keywords: Japanese B encephalitis ; X-ray computed tomography ; Magnetic resonance imaging ; Geriatrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurological, computed tomography (CT) and magnetic resonance imaging (MRI) findings were recorded from 13 patients with Japanese encephalitis (JE) in the Kurume region diagnosed by serological criteria. The patients averaged 63 years of age, and 5 were older than 70 years. The serological data mostly indicated a primary response. Hemiplegia and tetraplegia were common, together with extrapyramidal signs. A few cases had a stroke-like onset and cerebral haemorrhage during the course of JE. CT and MRI in 7 cases revealed abnormalities in the thalamus and basal ganglia including the putamen. The CT and MRI findings from the acute stage to the convalescent stage were considered to be characteristic of JE.
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  • 27
    ISSN: 1432-1459
    Keywords: Sinus thrombosis ; Computed tomography ; Magnetic resonance imaging ; Thalamus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The case is reported of a patient with primary thrombosis of the internal cerebral veins who presented initially with unilateral and later developed bilateral thalamic lesions revealed by computed tomography. Magnetic resonance imaging and angiography confirmed the diagnosis. Upon anti-coagulation the patient recovered nearly completely.
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  • 28
    ISSN: 1432-1459
    Keywords: Multiple sclerosis ; Diagnosis ; Electrophysiological tests ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sixty multiple sclerosis (MS) patients (33 definite, 13 probale and 14 suspected were investigated by computed tomography (CT), magnetic resonance imaging (MRI), multimodality evoked potentials (EPs) and cerebrospinal fluid (CSF) electrophoresis. MRI abnormalities were found in 50 cases, while at least one abnormal evoked potential was detected in each of 52 cases. Brain-stem auditory evoked potentials were more sensitive than MRI for the detection of brainstem involvement. All the patients with oligoclonal bands had abnormal MRI and none of the patients with normal MRI had oligoclonal bands in the CSF. The number and the extent of MRI lesions were significantly correlated with the duration of disease and with the degree of disability. Our observations stress the importance of the combined use of MRI and EPs in detecting silent CNS lesions in MS patients.
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  • 29
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    Journal of neurology 236 (1989), S. 115-116 
    ISSN: 1432-1459
    Keywords: Palatal myoclonus ; Inferior olive ; Magnetic resonance imaging ; Pseudohypertrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four patients with palatal myoclonus (PM) were studied with magnetic resonance imaging (MRI). Increased signal intensity and bilateral enlargement of the inferior olives were recognized in two patients with bilateral PM, pontine haemorrhage and neuro-Behçet disease, and a similar olivary change on the contralateral side was noted in a case of pontine infarction with unilateral PM. These findings were consistent with the pathology. The changes were more obvious in proton density-weighted images than in T2-weighted images, which thus differ from the changes in common gliosis. The other patient with the syndrome of PM and progressive ataxia did not show any olivary change. These changes on MRI are considered to indicate pseudo-hypertrophy of the inferior olives, although this is not consistently shown by the imaging method.
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  • 30
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    Journal of neurology 236 (1989), S. 117-119 
    ISSN: 1432-1459
    Keywords: Cavernous angioma ; Optic tract ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A cavernous angioma of the right optic tract in a 35-year-old man is presented. The patient suffered from headaches and had a left homonymous visual field defect after subarachnoid haemorrhage and an intracerebral haematoma in the right temporomedial region, revealed by computed tomography (CT). Follow-up CT showed a small contrast-enhanced lesion in the right suprasellar and parasellar cistern. Angiography on three occasions did not reveal a vascular lesion. Magnetic resonance imaging was helpful both for diagnosis and planning surgical therapy. It showed typical signs of a cavernous angioma of the right optic tract; the diagnosis was confirmed by surgery and histological examination. This appears to be the first reported case of a cavernous angioma of the optic tract.
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  • 31
    ISSN: 1432-1459
    Keywords: Chronic inflammatory demyelinating polyneuropathy ; Cranial nerve lesions ; Magnetic resonance imaging ; Nerve biopsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five cases of chronic inflammatory demyelinating polyneuropathy are described in which cranial nerve involvement accompanied a more generalized neuropathy. Clinical, electrophysiological, radiological and nerve biopsy findings are presented. Cranial nerve lesions in this form of polyneuropathy may be related to lesions of the peripheral nerves or of the central nervous system, when they may be accompanied by MRI evidence of more widespread CNS demyelinating lesions. In cases of early onset, the occurrence of focal cranial nerve lesions may serve to distinguish chronic inflammatory from inherited demyelinating polyneuropathies.
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  • 32
    ISSN: 1432-1459
    Keywords: Carbon monoxide poisoning ; Midbrain syndrome ; Visual evoked potentials ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five patients (aged 19–52 years) were treated for a midbrain syndrome due to acute carbon monoxide poisoning and had clinical follow-up investigations for up to 18 months. Three patients recovered with minor neurological and neuropsychological deficits and resumed their premorbid life-style. One patient had normal findings, while the fifth remained in a permanent vegetative state. Initial CT of the brain may fail to detect low-density lesions in the globus pallidus. If present, these lesions may either have disappeared, diminished, or remained unchanged at follow-up. Long-term outcome seems to show a closer link to white matter changes, which are at present best investigated by magnetic resonance imaging. The additional value of determining visual evoked responses at repeated follow-up is suggested by the present investigation.
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  • 33
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    Child's nervous system 5 (1989), S. 172-176 
    ISSN: 1433-0350
    Keywords: Pineal cyst ; Pineal tumor ; Pineal lesion ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thirty-two cases of pineal cyst diagnosed by magnetic resonance imaging (MRI) were reviewed and are described. The pineal cyst was demonstrated to be an area with slightly less intensity than the surrounding tissue and with slightly greater intensity than the CSF on T1-weighted images. On the T2-weighted images this lesion was identified as a high-intensity area with smooth margins and was homogeneous in nature. In three cases presenting with headache, compression of the vein of Galen was identified, and compression of the quadrigeminal plate was demonstrated in five cases. No patients presented with both pineal and quadrigeminal lesions. Of the cases, 63% were not detected by CT scanning alone. There were two cases in which the cyst ruptured and collapsed spontaneously during follow-up. It is emphasized that the presence of this lesion, which was more frequent than previously expected, should be kept in mind when diagnosing pineal tumors and should not be misdiagnosed. Surgery should not be undertaken unless the lesion produces symptoms due to the compression of the quadrigeminal plate, aqueduct, or the vein of Galen.
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  • 34
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    Child's nervous system 5 (1989), S. 371-373 
    ISSN: 1433-0350
    Keywords: Temporal encephalocele ; Cerebral angiography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An unusual case of temporal encephalocele is presented in this report. A large temporal mass was detected prenatally by ultrasound and following delivery by caesarian section. It was determined to be a large temporal encephalocele with extensive invasion into the subtemporal, facial and cervical regions. This case is presented because of the unique pathology of this congenital malformation and the extensive surgery that was required. The management and the clinical and radiological features are discussed.
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  • 35
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    European archives of psychiatry and clinical neuroscience 238 (1989), S. 225-230 
    ISSN: 1433-8491
    Keywords: Magnetic resonance imaging ; Friedreich's ataxia ; Spinal cord atrophy ; MRI evaluation of the brain stem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The severity of Friedreich's ataxia was graded in ten patients by clinical examination and in five by use of posturography. These data were compared with neuroradiology findings. CT-confirmed infratentorial atrophy occured only in advanced cases of Friedreich's ataxia; the correlation with the clinical score was poor. On mid-sagittal MRI planes the diameters of fourth ventricle, brain stem at the level of the inferior olive and spinal cord at the levels of the foramen magnum and C3 were measured. Patients with Friedreich's ataxia had significant MRI-confirmed atrophy of the cranial spinal cord as compared with a normal, age-matched control group. This was also observed in patients with Friedreich's ataxia in the early stages. A reliable correlation between atrophy of the cranial spinal cord and the clinical score, however, could again not be found. MRI exploration of the cranial spinal cord may be recommended as an additional diagnostic marker in Friedreich's ataxia.
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  • 36
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    Journal of neurology 236 (1989), S. 487-488 
    ISSN: 1432-1459
    Keywords: Baló's concentric sclerosis ; Magnetic resonance imaging ; Oligoclonal CSF IgG banding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An intra vitam diagnosis of Baló's concentric sclerosis in a 39-year-old male is described. To our knowledge this is the first reported case of ante-mortem diagnosis based solely on magnetic resonance imaging (MRI) findings. MRI showed features unique to this process. After high-dose intravenous therapy with prednisone, the clinical symptoms improved, and MRI showed marked changes of the concentric lesions.
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  • 37
    ISSN: 1432-1459
    Keywords: Status epilepticus ; Computed tomography ; Magnetic resonance imaging ; Single-photon emission computed tomography ; Cerebral oedema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 35-year-old female patient suffering from epilepsy was examined during status epilepticus with simple partial and complex partial seizures by means of EEG, CT, MRI and ictal SPECT. All these examinations showed focal abnormalities with identical location due to oedema and hypervascularisation; these were, however, absent during examinations carried out before and after status epilepticus.
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  • 38
    ISSN: 1619-7089
    Keywords: Bone marrow diseases ; Radionuclide imaging ; Magnetic resonance imaging ; Lymphoma ; Plasmacytoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 63 patients with primary extramedullary malignant lymphoma or plasmacytoma, a study was performed in order to evaluate bone marrow involvement. All patients underwent a 99mTc microcolloid bone marrow whole body imaging (scintigraphy), using a gamma camera interfaced with a computer, followed by nuclear magnetic resonance bone marrow imaging (MRI), (1.5 Tesla). MR images were made of the lumbosacral region, the pelvic region, both femoral and other parts of the skeleton, according to focal lesions in the scintigraphy. A posterior iliac crest bone marrow biopsy was used as a standard reference. In the present study, both scintigraphy and MRI showed a dissiminated or focal involvement or a combination of both. In 53 of the 63 patients (84%) the results were in accordance. Pathological MR signals or pathological findings in scintigraphy did not always correspond to tumorous bone marrow involvement, and were shown to reflect reactive changes in the central part of the skeleton in combination with a periphery radionuclide extention interpreted as a periphery compensatory hematopoetic proliferation. The negative predictive value of scintigraphy and MRI was 92% and 100%, respectively. When combining the results of both examinations, the positive predictive value increased from 49% to 58%, if the bone marrow biopsy is accepted as gold standard. The results indicate that bone marrow investigation performed simultaneously using scintigraphy and MRI is superior both to the use of either of the methods alone and to the traditional iliac crest bone marrow biopsy.
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  • 39
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    Langenbeck's archives of surgery 374 (1989), S. 349-357 
    ISSN: 1435-2451
    Keywords: Magnetic resonance imaging ; Thoracic aortic surgery ; Follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Zwecks überprüfung, inwieweit die Kernspintomographie, die mit gutem Erfolg bereits in der präoperativen Diagnostik eingesetzt wird, eine sinnvolle Bereicherung des diagnostischen Instrumentariums bei der postoperativen Kontrolle thorakaler Aortenerkrankungen darstellt, haben wir zwischen dem 1. 4. 1986 und 30. 3. 1988 30 Patienten (20 männlich, 10 weiblich, mittleres Alter 53 Jahre ± 13,7 Jahre) nach Operation an der thorakalen Aorta kernspintomographisch untersucht. Es lagen 19 arteriosklerotische Aneurysmen, 10 Dissektionen sowie ein Tumor der , Aorta descendens vor. In allen 30 Patienten gelang es, kernspintomographisch postoperativ die Ergebnisse der chirurgischen Maßnahmen zu dokumentieren. Es konnten im frühen postoperativen Stadium Komplikationen ausgeschlossen bzw., wie in einem Fall eine retrograde Aortendissektion oder einem anderen ein Hämatoperikard nachgewiesen werden. In der postoperativen Verlaufskontrolle aortaler Dissektionen ließ sich eine aneurysmatische Dilatation der dissezierten Aorta distal der implantierten Prothese in allen Fällen darstellen. Wahres und falsches Lumen konnten differenziert werden. In einem Fall ließ sich die Ausbildung eines Aortenbulbusaneurysmas nachweisen. Zusammengefaßt lassen sich postoperative Komplikationen der thorakalen Aortenchirurgie mit der Kernspintomographie zuverlässig nachweisen und bildlich in 3 Ebenen darstellen. Nichtinvasibilität, das Fehlen einer ionisierenden Strahlung und das ausbleibende Risiko einer Kontrastmittelapplikation machten die Kernspintomographie zu einer idealen Methode für Folgeuntersuchungen nach Operation an der thorakalen Aorta.
    Notes: Summary Operations of the thoracic aorta for aneurysms, dissections, or congenital malformations may lead to early or late complications. Therefore, postoperative control for documentation of the surgical results, for exclusion of early changes and for comparison with later controls is mandatory. To demonstrate that magnetic resonance imaging (MRI), which we already had used with good results for preoperative studies is also able to detect postoperative abnormalities, we examined 30 patients with thoracic aortic disease (20 male, 10 female, mean age 53 ± 13.7 years) with this diagnostic tool. There were 19 arteriosclerotic aneurysms, 10 dissections, and one aortic tumor. With MRI it was possible in all patients to visualize the results of the surgical treatment postoperatively. Early postoperative complications could be excluded, or demonstrated in one case of a retrograde aortic dissection or a hematopericardium. These pathological findings could also be shown by arterial digital subtraction angiography or echocardiography. Using MRI for follow-up of aortic dissections, the development of an aneurysm of the aortic root in a Marfan-patient could be detected. In all these patients, it was possible to differentiate true and false lumen and to detect the origin of major side branches. The diagnostic advantages of MRI, which we compared with other imaging methods, as echocardiography, computed tomography or angiography are that postoperative complications of thoracic aortic aneurysm surgery can be reliably detected and visualized in 3 different planes. Non-invasiveness, the omission of ionizing radiation and no risk of contrast media application underline that magnetical resonance imaging is an ideal method for follow-up after operation of the thoracic aorta.
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  • 40
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    European archives of oto-rhino-laryngology and head & neck 246 (1989), S. 265-268 
    ISSN: 1434-4726
    Keywords: Petrous bone ; Magnetic resonance imaging ; Gadolinium ; Cholesteatoma ; Temporal bone neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twenty cases of intrapetrous lesions were studied by a 1.5 T magnetic resonance (MR) unit. In all cases, comparisons were made between MR, CT and clinical findings. Our present material included 9 cholesteatomas, 1 cholesterol cyst, 3 primary epidermoid carcinomas, 2 metastatic neoplasms, 1 glomus jugulare tumor and 4 facial neurinomas. Gadolinium was injected in 7 cases and seemed to be the best method for studying the intrapetrous tumors. MR permitted accurate topographic study and assessment of tumoral extension, as well as a ready demonstration of tumor vascularity. The present findings also showed that MR is not capable of defining small bony detail or calcifications.
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  • 41
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    Medical & biological engineering & computing 27 (1989), S. 101-110 
    ISSN: 1741-0444
    Keywords: Electric shock ; Electrical safety ; Electrical stimulation ; Magnetic field exposure ; Magnetic resonance imaging ; Neural excitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The review evaluates thresholds of peripheral nerve stimulation by complex current waveforms. A neuroelectric model employing Frankenhaeuser-Huxley membrane nonlinearities is used to derive excitation thresholds for monophasic and biphasic pulse sequences, as well as sinusoidal stimuli. The model, along with principles of magnetic field induction, is used to derive criteria of acceptability for exposure to time-varying magnetic fields. Applications to pulsed gradient fields from magnetic resonance imaging devices are discussed.
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  • 42
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989) 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 43
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 1-15 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In order to develop a new kind of filter that makes a compromise between quasi-optical and more traditional bandpass filtering techniques at millimetre wavelengths, a theoretical modelling of grids in oversize and monomodal waveguides is performed using a variational method.
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  • 44
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 31-52 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A novel procedure for the numerical modelling of current transport in semiconductor devices is presented. The method is based on high-order trigonometric expansions (Fourier series) of the solution. The expansion coefficients are calculated in a Galerkin-type algorithm. The method offers infinite-order accuracy regardless of the number of spatial dimensions of the model. Well-conditioning and diagonal dominance of the discrete equations render the numerical procedure stable and effective. Significant advantages are expected, particularly for the solution of strongly non-linear multidimensional device models. Properties of the algorithm are demonstrated on standard semiconductor devices.
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  • 45
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 53-60 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper introduces a simple model for solving a system of first-order rate equations using the TLM numerical method. A general algorithm is developed by setting up a matrix of discrete compartments. The rate constants provide the linkage between each compartment and the neighbouring ones. The method is demonstrated by some examples in which saturation conditions are considered. The TLM solution is compared with analytical solutions and the Rung-Kutta method of solving differential equations.
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  • 46
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 75-80 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A simulation of power transformers following switching operations is presented in which each core section is represented by a non-linear inductance, the differential inductance being determined from the flux density in that section of the core. In analysing the resultant circuit model for the transformer it is shown that the circuit equations have dyadic properties which can be used to give a more efficient numerical solution.
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  • 47
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 93-102 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An approach, based on the finite element method (FEM), is used for evaluating the electromagnetic field distribution in a class of E-plane metal insert filters, operating in the Ka-band. Artificial boundary conditions are inserted directly in a functional, enabling a solution of the scalar wave equation by finite element method.The scattering parameters of the filter, the electromagnetic field and, therefore, the current distributions on the thin metal inserts are computed. Then, the power dissipated in the metallic septa, which is one of the major limitations for the maximum CW-power that can be handled by these types of filter, is evaluated using a perturbational approach. Finally, the maximum field intensity is determined, allowing an estimate of the maximum peak power that these structures can handle.
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  • 48
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 103-111 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The multigrid technique, which is mainly used in the finite difference method, is applied to the TLM (transmission-line matrix or modeling) procedure. In the multigrid TLM, the field region is covered with sets of regular transmission-line matrices of different mesh sizes. The finer grid pattern, which overlaps the coarser grid, fills the region with high field gradients. Data obtained in the coarser grid are transferred to the finer grid through an interpolation process and used as boundary conditions for the latter. The finer grid data are then transferred back to the coarser one, thus improving the coarse grid values. The method is applied to several diffusion problems and significant improvements in accuracy and efficiency are shown.
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  • 49
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 115-115 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 50
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 131-142 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Numerical quadratures encountered in solving integral equations and in finite element analysis often involve singular integrands, or integrands with very rapid local variation whose numerical stability resembles that of singularities. It is shown that specialized quadrature formulae of Gauss-Christoffel type can be generated for such integrands, using a recursive procedure based on the properties of the underlying orthogonal polynomials. Quadrature formulae of moderately high degree can be computed rapidly enough to allow them to be constructed as needed. An algorithm for generating quadrature formulae is given in detail. Singular or near -singular functions encountered in finite element analysis typically require three -point or four -point quadratures; such formulae are readily obtained, to seven -figure accuracy, in computing times short enough to regard the formulae as disposable and not worth preserving in tables.
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  • 51
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 187-188 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 52
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 189-190 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 53
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 191-201 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents an overview of the 3D transmission-line matrix method of analysis, describing the various nodes which are available to date: expanded node, asymmetrical condensed node, symmetrical condensed node. The most general scattering matrices of these nodes are given. The various techniques used to implement irregularly graded meshes are also described. A comparison of all the processes applied to the same structure is made. Conclusions on their use are then discussed.
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  • 54
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 215-225 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A new TLM-based concept analogous to the Green's function approach in classical electromagnetic theory is presented. It employs the procedure known as time domain diakoptics. The response of a TLM mesh to a unit impulse excitation at selected input points is interpreted as a discrete Green's function in the time domain, and the term ‘Johns matrix’ is proposed for this characteristic response. As in classical theory, the response of the mesh to an arbitrary excitation is found by convolving the excitation with its Johns matrix. This concept extends the generalized scattering parameter concept into the time dimension, opens unprecedented possibilities for partioning time domain problems at the field level, and permits large-scale preprocessing of substructures for computer-aided design. It also represents and elegant way of modelling broadband absorbing boundary conditions, imperfectly conducting walls and general frequency dispersive boundaries in the time domain.
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 279-279 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 56
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 249-265 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The application of the transmission-line modelling technique to the design of semiconductor lasers and optical systems is reviewed. Generalized scattering matrices are developed to allow the technique to be applied to novel devices and systems.
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  • 57
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    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 2 (1989), S. 280-280 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 58
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 169-183 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The dynamic behaviour of marine vehicles in extreme sea states is a matter of great concern following some recent and dramatic mishaps. The complex problem of its prediction can be approached from the study, yet of broader scope, of non-linear dynamic systems subjected to stochastic excitations. However, a general non-linear stochastic dynamic theory is not yet available.A new technique, the so-called linearize-and-match method, for predicting the response statistics of non-linear systems, is presented. Essentially, the technique involves the construction of an infinite series of linear systems aimed at the prediction of the response statistical moments of a given order.The linear systems are successively defined by linearizing the original, non-linear system and matching the Volterra functional model response statistics to the desired order. The linear system for predicting second order statistics is shown to coincide with the one obtained using the method of equivalent linearization.Response probability distributions can be constructed from the knowledge of such statistics. Particular attention is devoted to the distribution of maximum entropy and its justification in such underdetermined moment problems.Finally, applications to the roll motion of ships serve to exemplify as well as to assess the accuracy and the versatility of the overall method. Response distributions of maxima so predicted compare very well with digital simulation estimates.
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  • 59
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 215-230 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper a mathematical model is presented, based on the application of an averaging technique, in which the equations governing the behaviour of saturated porous media are integrated (averaged) over the smallest dimension of the domain of the problem (thickness). This results in a two dimensional model, in which the three dimensional nature of the problem is accounted for. In fact, the solution is sought in terms of the mean values over the thickness of the field variables and of the transverse displacement components. For the solution of the resulting governing equations a partitioned procedure is employed, which improves the efficiency of the method. The proposed model is very useful in solving problems in which the spatial nature prevents the applications of two dimensional models.Examples are presented, which illustrate the validity of this approach.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 233-255 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite element analysis was used to study the fracture toughening of a ceramic by a stress induced dilatant transformation of second phase particles. The finite element method was based on a continuum theory which modelled the composite as subcritical material. Transient crack growth was simulated in the finite element mesh by a nodal release technique. The crack's remote tensile opening load was adjusted to maintain the near-tip energy release rate at the level necessary for crack advance. The transformation zone surrounding the crack developed as the crack propagated through the composite. Resistance curves were computed from the analysis; and the results show that during crack advance maximum toughness is achieved before a steady state is reached.The toughening effect of a crack-bridging ductile phase in a brittle material may be predicted if ligament deformation is characterized. A plastically deforming ligament constrained by surrounding elastic matrix material is modelled using finite elements and the relevant toughness enhancement information extracted. Comparison is made to model experiments as well as to toughness measured for technologically important materials. The results suggest that debonding along the interface between the ligament and the matrix may enhance the toughening effect of a ductile phase.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 323-341 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A closed form approach to the assessment of the fatigue life of graphite/epoxy laminates under cyclic tension-compression loading has been developed. The model is mechanistic and uses cyclic energy release rates for prediction of delamination growth and of critical delamination sizes which induce buckling and the final failure of the laminates. Tests performed with graphite/epoxy specimens of stacking order [0n, φm]s with severed central plies [φ], and of stacking order [02, +45, 02, -45, 0, 90]s with a central unloaded hole, indicate good correlation between estimated values and observed delamination growth, critical buckling strength of separated plies and load cycles to failure.
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  • 62
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 429-436 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents a formulation in the frequency domain for the viscoelastic material behaviour of structural elements. This approach is equally valid for deterministic forces, but also in the case of probabilistic descriptions of those forces. The method takes advantage of readily available experimental data and shows how to introduce them in e.g. finite element formulations.
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  • 63
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 449-452 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 64
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 483-499 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Chebyshev acceleration for a symmetrizable basic iterative method u(n+1) = Gu(n) + k; requires estimates of the extreme eigenvalues m(G) and M(G) of the iteration matrix G. Adaptive procedures are often used in order to obtain good estimates for m(G) and M(G). Some existing adaptive procedures are able to give an estimate of either m(G) or M(G) but not both on any given iteration. In this paper we present an adaptive procedure which can estimate both m(G) and M(G) at the same time and which has other useful properties. Numerical results are given which show the new procedure usually requires fewer iterations than previous procedures.
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  • 65
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 523-546 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The storage requirements and performance consequences of a few different data parallel implementations of the finite element method for domains discretized by three-dimensional brick elements are reviewed. Letting a processor represent a nodal point per unassembled finite element yields a concurrency that may be one to two orders of magnitude higher for common elements than if a processor represents an unassembled finite element. The former representation also allows for higher order elements with a limited amount of storage per processor. A totally parallel stiffness matrix generation algorithm is presented. The equilibrium equations are solved by a conjugate gradient method with diagonal scaling. The results from several simulations designed to show the dependence of the number of iterations to convergence upon the Poisson ratio, the finite element discretization and the element order are reported. The domain was discretized by three-dimensional Lagrange elements in all cases. The number of iterations to convergence increases with the Poisson ratio. Increasing the number of elements in one special dimension increases the number of iterations to convergence, linearly. Increasing the element order p in one spatial dimension increases the number of iterations to convergence as pα, where α is 1·4-1·5 for the model problems.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 559-570 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A matrix relationship connecting the Jacobi and the Symmetric Successive Overrelaxation (SSOR) matrices associated with a k-cyclic consistently ordered matrix A is presented. Next the equivalence of the SSOR method and a certain monoparametric k-step one for the solution of the linear algebraic system Ax = b is established. The aforementioned equivalence can be exploited to derive regions of convergence, optimum parameters involved, etc. of the two iterative methods above. This is done by studying the simplest of the two methods that is the monoparametric k-step one. To show how the idea works the case k = 2 is very briefly discussed.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 637-654 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The standard implementations of iterative solvers for finite element and finite difference methods frequently use a diagonal (Jacobi) preconditioner, particularly for element-by-element schemes. However, for such methods the actual order of the condition number with respect to mesh size is not reduced by the preconditioner. In the present paper we describe an iterative method where, in addition, the condition number is reduced by an order of magnitude. Moreover, the scheme may also be implemented as an element-by-element method. The method uses a generalized SSOR preconditioner and a wave front or multi-frontal ordering of the mesh nodes. For a general irregular finite element mesh a striped irregular wave front ordering may be used. The performance of the method as well as various iterative acceleration techniques for a parallel computer are examined in the numerical studies.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. ii 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 69
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 43-73 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a geometrically non-linear formulation (GNL) for the three dimensional curved beam elements using the total Lagrangian approach. The element geometry is constructed using co-ordinates of the nodes on the centroidal or reference axis and the orthogonal nodal vectors representing the principal bending directions. The element displacement field is described using three translations at the element nodes and three rotations about the local axesThe element displacement field has also been described in the literature using Euler parameters, Milenkovic parameters, or Rodriges parameters representing the effects of large rotations.. The GNL three dimensional beam element formulations based on these element approximations are restricted to small nodal rotations between two successive load increments. The element formulation presented here removes such restrictions. This is accomplished by retaining non-linear nodal terms in the definition of the element displacement field, and the consistent derivation of the element properties. The formulation presented here is very general and yet can be made specific by selecting proper non-linear functions representing the effects of nodal rotations. The details of the element properties are presented and discussed. Numerical examples are also presented to demonstrate the behaviour and the accuracy of the elements. A comparison of the results obtained from the present formulation with those available in the literature using a linearized element approximation clearly demonstrate the superiority of the formulation in terms of large load steps, large rotations between two load steps and extremely good convergence characteristics during equilibrium iterations. The displacement approximation of these elements is fully compatible with the isoparametric curved shell elements (with large rotations), and since the elements possess offset capability, these elements can also serve as stiffeners for the curved shells.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 75-93 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The alternative to quadrature, as a procedure for dealing with the integrations required in the direct boundary element method (DBEM), is to carry out the integration analytically and code the results directly. The potential benefits are efficient computer programs; the avoidance of numerical instability; and generally, better accuracy. The technique is developed in this paper.Serious problems arise when Gauss quadrature is employed for the integration of functions which contain, or are close to singularities. A numerical integration approach may fail at the first stage of the analysis, that is, during the assembly of the discrete equations; or it may fail at the subsequent stage of computing domain points near the boundary. The severity of the problem is dependent both on the strength of the singularity, and on geometry. These points are illustrated with examples.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 127-144 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The successive quadratic programming (SQP) method is used with the finite element method (FEM) to solve frictionless geometrically non-linear contact problems involving large deformations of the elastica in the presence of flat rigid walls. To formulate the SQP problems, the potential energy (PE) is expanded in a Taylor series of second order in displacement increments about a configuration near a contact solution. The SQP problems consist of minimizing the Taylor expansion of the PE subject to the inequality constraints which represent contact. The quadratic programming (QP) method is made part of a Newton-Raphson (NR) search in which the QP corrections are made when a NR step does not satisfy the constraints. A revised simplex method developed by Rusin is used to solve the QP problems. The elastica is modelled with a total Lagrangian FEM developed by Fried. Solutions are obtained for the end loaded buckled elastica in point contact with a rigid wall and for a uniformly loaded elastica in regional contact with a rigid wall. The problems are also solved using a penalty method. The results obtained for the point contact problem are compared to an analytical solution. Calculations were made to obtain numerical information on maximum load step size and the number of inverse operations required for each load step. Cases in which the elastica stiffened substantially as a result of the initiation of contact are also discussed.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 261-277 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The basic concept, formulation and numerical application of a fully automatic version of the finite difference method (FDM) on a two-dimensional manifold embedded in three-dimensional Euclidean space are presented. This version of the FDM was developed in order to enable automatic solution of problems formulated in arbitrary curvilinear co-ordinate systems in terms of covariant derivatives (e.g. shell equations).In the classical version of the FDM all operations in the curvilinear co-ordinates (the derivation of base vectors, curvature tensors and so on) have to be performed manually. The goal of the present work was to transfer this job to a computer, in order to minimize the user's effort during the numerical formulation of the physical problem. The relevant version of the fully automatized program FIDAMF, based on the FDM on arbitrary irregular grids,1,2 has been worked out. This code performs automatically all stages of the numerical analysis, starting from the mesh generation and approximation of the shape of the manifold, through computation of necessary objects on this manifold, to the solution of linear or non-linear problems formulated in terms of covariant derivatives.The method has been extended to the analysis of problems in which the co-ordinate system changes during the computation (e.g. the analysis of large deformations in the convectional description). This version of the curvilinear FDM was applied to the analysis of large deformations of hyperelastic membrane shells.The approach and the numerical routines, although used here with the FDM, can be combined with any other approximation method, in particular the finite element method.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 359-368 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A direct-search optimization strategy, involving pattern-searches, pattern-moves and a simplex algorithm, has been applied to a number of frequency-domain circuit problems. We show that an approximate minimax result can be obtained with our simple approach, which includes using a modified minimax error function. In the examples attempted, the method comes quite close to the accuracy, if not the efficiency, of true minimax optimizers, and yields an accuracy as good as or better than a least-pth (p = 10) gradient optimizer. The method is broadly appropriate wherever it is difficult or inconvenient to calculate the gradients required for conventional minimax optimization.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 431-443 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The formulation of the recently presented hybrid-Trefftz (HT) p-version elements1 has thus far been restricted to straight-sided polygonal elements. The present paper removes this limitation. Two alternative formulations are studied. In the first one any curvilinear geometry is represented accurately but the rigid body modes are recovered only in the limit as the p-refinement level is increased. In contrast, the second formulation represents the rigid modes exactly while the actual curvilinear geometry is approached with increasing accuracy as the p-refinement level is increased. The practical efficiency of the two alternative approaches is studied and assessed on pertinent examples of thin plates in bending.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 477-478 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 483-487 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 533-560 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper deals with the formulation and the evaluation of a new three node, nine d.o.f. triangular plate bending element valid for the analysis of thick to thin plates. The formulation is based on a generalization of the discrete Kirchhoff technique to include the transverse shear effects. The element, called DST (Discrete Shear Triangle), has a proper rank and is free of shear locking. It coincides with the DKT (Discrete Kirchhoff Triangle) element if the transverse shear effects are not significant. However, an incompatibility of the rotation of the normal appears due to shear effects. A detailed numerical evaluation of the characteristics and of the behaviour of the element has been performed including patch tests for thin and thick plates, convergence tests for clamped and simply supported plates under uniform loading and evaluation of stress resultants. The overall performance of the DST element is found to be very satisfactory.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 593-607 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The introduction of composite materials is having a profound effect on the design process. Because these materials permit the designer to tailor material properties to improve structural, aerodynamic and acoustic performance, they require a more integrated multidisciplinary design process. Because of the complexity of the design process numerical optimization methods are required.The present paper is focused on a major difficulty associated with the multidisciplinary design optimization process - its enormous computational cost. We consider two approaches for reducing this computational burden: (i)development of efficient methods for cross-sensitivity calculation using perturbation methods; and (ii) the use of approximate numerical optimization procedures. Our efforts are concentrated upon combined aerodynamic-structural optimization. Results are presented for the integrated design of a sailplane wing. The impact of our computational procedures on the computational costs of integrated designs is discussed.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 645-666 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical strategy for the simulation of structural modifications by virtual distortions is proposed. Two cases of structural modification are considered: the first concerns modifications of material distribution, and the second modifications of local constitutive relations (e.g. unilateral constraints for stresses or deformations). A formaulation of the fundamental equations of the simulation method is presented. These equations are applicable to the general structural modification problem of a truss-like structure. Then numerical algorithms which refer to particular applications, such as progressive collapse analysis or the analysis of structures with gaps, are discussed.The versatility of the method is illustrated with a number of examples, and the computational advantages of structural modification by the virtual distortion method are discussed.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 725-726 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 733-752 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An adjoint approach is presented for the design sensitivity analysis of transient conduction problems. Variations of a general design functional are expressed in explicit form with respect to all design quantities, i.e. material properties, shape, applied thermal loads including convection, and initial conditions. The methodology incorporates the mutual energy between the real and adjoint thermal problems and a geometric mapping to describe shape variations. Finite element implementation of the method is discussed and an example is provided. Some potential difficulties that might be encountered when using the adjoint method with the finite element method are addressed. These involve the application of impulse loadings and Dirac temperature fields in the adjoint loadings.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 801-815 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper we compare direct and preconditioned iterative methods for the solution of nonsymmetric, sparse systems of linear algebraic equations. These problems occur in finite difference and finite element simulations of semiconductor devices, and fluid flow problems.We consider five iterative methods that appear to be the most promising for this class of problems: the biconjugate gradient method, the conjugate gradient squared method, the generalized minimal residual method, the generalized conjugate residual method and the method of orthogonal minimization. Each of these methods was tested using similar preconditioning (incomplete LU factorization) on a set of large, sparse matrices arising from finite element simulation of semiconductor devices. Results are shown where we compare the computation time and memory requirements for each of these methods against one another, as well as against a direct method that uses LU factorization to solve these problems.The results of our numerical experiments show that preconditioned iterative methods are a practical alternative to direct methods in the solution of large, sparse systems of equations, and can offer significant savings in storage and CPU time.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 861-877 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The results of a numerical study of swirling and non-swirling combustor flows with and without density variations are presented. Constant-density arguments are used to justify closure assumptions invoked for the transport equations for turbulent momentum and scalar fluxes, which are written in terms of density-weighted variables. Comparisons are carried out with measurements obtained from three different axisymmetric model combustors. The three experiments cover recirculating flow, swirling flow and variable-density, swirling flow inside model combustors. Together, they offer wide ranging flow conditions to test the validity of the models. Results show that the Reynolds stress/flux models do a credible job of predicting constant-density, swirling and non-swirling combustor flows with passive scalar transport. However, their improvements over algebraic stress/flux models are marginal. The extension of the constant-density models to variable-density flow calculations shows that the models are equally valid for such flows. Therefore, the present results argue well for the adoption of constant-density models for variable-density flows until a successfully validated variable-density model is available.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 37-55 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: With a boundary-fitted curvilinear co-ordinate system, the parabolic approximation is applied to the mildslope equation to describe the wave propagation. Both refraction and diffraction are included in the numerical model. Because the shoreline coincides with one of the curvilinear co-ordinates, the numerical model can be used to compute wave propagations near an irregular shoreline.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 103-112 
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 129-144 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A global three dimensional model for numerical weather prediction is described. It uses spheric harmonic basis functions with triangular truncation in the horizontal and a finite element discretization for the vertical. Model experiments are used to compare this model with another version, which uses a finite difference scheme for vertical discretization.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 185-193 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The paper deals with non-Fickian dispersion of inert solutes in random permeability fields. Attention is focused critically on the statistical characterization of the porous medium which affects pollutant dispersion in groundwater. After a brief account of recent results of stochastic theories of transport in porous media and of the fundamental indications of large-scale field experiments, it is inferred from numerical studies that the particular choice of an analytical form of covariance of log-conductivity has a poor influence on the overall dispersion process. In fact, different covariance structures with the same macroscale (a measure of the distance between two points beyond which the permeability ceases to be correlated) yield very similar dispersion processes. The result has a noteworthy bearing on field studies of pollutant dispersion in groundwater because it underlines the reliability of exponential correlation structures yielding analytical expression for time-varying macrodispersion coefficients.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 231-231 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1803-1812 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A consistent tangent stiffness matrix for the analysis of non-linear contact problems is presented. The associated element has three or four nodes and establishes contact between three-dimensional structures like solids and shells. It accounts for the non-linear kinematics of large deformation analysis and guarantees a quadratic convergence rate. Two formulations, the penalty method and the Lagrange multiplier method, are investigated.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1855-1874 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Two domain-by-domain algorithms, suitable for coarse-grained parallel processing analysis of the transient structural dynamics equation, are investigated for accuracy. The application under specific consideration is the analysis of three-dimensional framed structures subjected to time-varying loading. The domain-by-domain approaches attempt to include the advantageous aspects of both conditionally stable explicit algorithms, which require no simultaneous solution of equations and employ simple communication, and unconditionally stable implicit algorithms, which permit large time steps. The alternating group explicit algorithm is developed for finite element analysis, and its accuracy is investigated for a linear formulation. The group implicit algorithm is extended to non-linear finite element analysis, and its accuracy is investigated for the frame dynamics application. Both algorithms are shown to provide inadequate accuracy for practical time step sizes.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1929-1949 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper we propose an original numerical method to get upper and lower bounds for the eigenfrequencies of an elastic structure.This method is based on a ‘static’ formulation for eigenvalue problems built up from a new quotient Rs which is defined on a load space. From Rs properties, upper and lower bounds for the exact eigenfrequencies are proved. The application of the method requires the solution of an eigenvalue problem of finite dimension and the computation of a constant which is characteristic of the discretization subspace. Results of numerical tests are given for the vibration problem of an elastic clamped membrane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 92
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 1965-1967 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 93
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 1971-1975 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 94
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2041-2058 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The primary goal of this paper is to show how second derivative information can be used in an effective way in structural optimization problems. The basic idea is to generate such an information at the expense of only one more ‘virtual load case’ in the sensitivity analysis part of the finite element code. To achieve this goal a primal-dual approach is employed, that can also be interpreted as a sequential quadratic programming method.Another objective is to relate the proposed method to the well known family of approximation concepts techniques, where the primary optimization problem is transformed into a sequence of non-linear explicit subproblems. When restricted to diagonal second derivatives, the new approach can be viewed as a recursive convex programming method, similar to the ‘Convex Linearization’ method (CONLIN), and to its recent generalization, the ‘Method of Moving Asymptotes’ (MMA).This new method has been successfully tested on simple problems that can be solved in closed form, as well as on sizing optimization of trusses. In all cases the method converges faster than CONLIN, MMA or other approximation techniques based on reciprocal variables.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 95
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2203-2218 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The aim is to build up and test a numerical method to calculate the velocity of stationary two-dimensional flows. Both inviscid and viscous fluids are considered. They act in the unbounded domain surrounding a given profile and a stream function is introduced. A variational procedure, adapted to unbounded domains, reduces the problem to solving a finite sequence of hormonic equations, posed in bounded domains. Some profiles are tested using a finite element method.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 96
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2223-2238 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, a Mindlin plate element is formulated based on the Hellinger-Reissner principle and the γ-technique. The stiffness consists of a constant stress (one-point quadrature) matrix and a stabilization matrix. The stabilization matrix is compared with those previously proposed. In addition, the element uses a projection to modify the nodal displacements so that the patch test is satisfied. The projection matrix is based on a mode decomposition. Several numerical cases are presented, and it is shown that the mode decomposition projection is necessary both for satisfaction of the patch test and convergence.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 97
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2307-2321 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method for the time domain identification of modal parameters of a vibrating structure using Z-transformation sequences is presented in this paper.This identification proceeds using the Z-transfer function of a vibrating structure from which an auto-regressive and moving-average (ARMA) model of the vibrating structure is derived. From this ARMA model and time domain data, the modal parameters can be identified. The time domain data can be obtained from single point or multiple shaker excitation modal testing. To demonstrate the application and efficiency of the method, a test on a simulated cantilever beam is presented.
    Additional Material: 2 Tab.
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  • 98
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2361-2381 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The dynamic behaviour of a saggy suspension cable under a moving load was investigated. First of all, the updated Lagrangian formulation and the finite element method were used to derive the property matrices of a saggy suspension cable in order to define the discretized equations of motion. Then, the Jacobi method was applied to the determination of the natural frequencies and the mode shapes of the suspended cable. The moving-load-induced dynamic responses of the saggy suspended cable were obtained by using the Newmark direct integration method incorporated with the Newton-Raphson iteration technique. The influence of some pertinent factors, such as speed of moving load, ratio of axial rigidity to total cable weight (AE/0m̄g0L) and ratio of moving load mass to total cable mass, is the key point of the dynamic analysis.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 99
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 211-236 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An a posteriori error estimator is presented which allows a good pointwise evaluation of the error in predicted stresses and can easily be implemented in existing FE codes. Although this estimator has especially been developed for and tested on p-version Hybrid-Trefftz (HT) elements, it is anticipated that it can also be applied to conventional conforming p-version elements. The practical efficiency of the estimator is illustrated through the solution of various plate bending problems by using the HT p-version Kirchhoff plate elements.2
    Additional Material: 13 Ill.
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  • 100
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 245-260 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical model is developed for computing two-dimensional circulation in coastal regions dominated by large tidal flat motion. This model is based on the shallow water momentum and continuity equations being operated upon by the Galerkin finite element method. The particular advantage of the model lies in its ability to accommodate a changing domain boundary. This is accomplished by adopting finite elements that change shape so as to consistently move with the water's edge. Application of the model to the Kuwait Bay is described, and the associated results on circulation are given.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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