排序方式: 共有24条查询结果,搜索用时 15 毫秒
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Hirzinger Benjamin Adam Christoph Salcher Patrick Oberguggenberger Michael 《Meccanica》2019,54(9):1385-1402
Meccanica - The scope of this paper is to evaluate the performance and computational efficiency of various stochastic simulation methods for a stochastic based reliability assessment of railway... 相似文献
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M. Oberguggenberger D. Scarpalézos 《Journal of Mathematical Analysis and Applications》2007,328(2):1321-1335
The definitions of positivity and positive definiteness are extended to generalized function algebras in coherence with the corresponding notions for distributions. Versions of Bochner's theorem for a positive definite Colombeau generalized function are given. 相似文献
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Symmetrisers and generalised solutions for strictly hyperbolic systems with singular coefficients
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This paper is devoted to strictly hyperbolic systems and equations with non‐smooth coefficients. Below a certain level of smoothness, distributional solutions may fail to exist. We construct generalised solutions in the Colombeau algebra of generalised functions. Extending earlier results on symmetric hyperbolic systems, we introduce generalised strict hyperbolicity, construct symmetrisers, prove an appropriate Gårding inequality and establish existence, uniqueness and regularity of generalised solutions. Under additional regularity assumptions on the coefficients, when a classical solution of the Cauchy problem (or of a transmission problem in the piecewise regular case) exists, the generalised solution is shown to be associated with the classical solution (or the piecewise classical solution satisfying the appropriate transmission conditions). 相似文献
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It is proved that a holomorphic generalized function in the sense of Colombeau has a representative consisting of a net of
holomorphic functions. More generally, the existence of global representatives of Colombeau solutions to elliptic partial
differential equations is proved. Further, it is shown that a generalized holomorphic function on Ω, which is equal to zero
in an open set
L ì WL\subset{\rm{\Omega}}
, is equal to zero. 相似文献
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Michael Kunzinger Michael Oberguggenberger Roland Steinbauer James A. Vickers 《Acta Appl Math》2004,80(2):221-241
Based on the concept of manifold-valued generalized functions, we initiate a study of nonlinear ordinary differential equations with singular (in particular: distributional) right-hand sides in a global setting. After establishing several existence and uniqueness results for solutions of such equations and flows of singular vector fields, we compare the solution concept employed here with the purely distributional setting. Finally, we derive criteria securing that a sequence of smooth flows corresponding to the regularization of a given singular vector field converges to a measurable limiting flow. 相似文献
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Beate Beer Birthe Schubert Anne Oberguggenberger Verena Meraner Michael Hubalek Herbert Oberacher 《Analytical and bioanalytical chemistry》2010,398(4):1791-1800
There is substantial evidence that circulating estrogens promote the proliferation of breast cancer. Consequently, adjuvant
hormonal treatment strategies targeting estrogen action have been established. Such hormonal therapies include selective estrogen
receptor modulators, such as tamoxifen, which interfere at the estrogen receptors directly, or non-steroidal aromatase inhibitors,
such as anastrozole and letrozole, which inhibit estrogen synthesis through blocking the aromatase, a key enzyme of estrogen
production. Despite considerable therapeutic success, in several cases, the use of these drugs is limited by side effects
that have been described to significantly impair the adherence of patients to endocrine treatment. However, objective data
concerning patient adherence and its clinical relevance are limited. One promising approach to check patient-reported adherence
is drug monitoring in human plasma. Therefore, a liquid chromatography–tandem mass spectrometry method to determine the plasma
concentrations of tamoxifen, anastrozole, and letrozole has been developed and fully validated according to guidelines for
clinical and forensic toxicology. The validation criteria evaluated were selectivity, linearity, accuracy and precision, limit
of quantification, recovery and matrix effects, sample stability, and carryover. The six-point calibration curves showed linearity
over the range of concentrations from 25 to 500 ng/ml for tamoxifen, 5 to 200 ng/ml for anastrozole, and 10 to 300 ng/ml for
letrozole. The intra- and inter-day precision and accuracies were always better than 15%. The validated procedure was successfully
applied to a clinical study (Patient-Reported Outcomes in Breast Cancer Patients undergoing Endocrine Therapy, PRO-BETh).
A major aim of PRO-BETh study is the comprehensive evaluation of adherence to treatment in pre- and post-menopausal women
with breast cancer. Plasma samples of 310 breast cancer patients undergoing anti-estrogen therapy were analyzed. Eight samples
did not contain a quantifiable amount of drug, strongly indicating non-adherence of the corresponding patients to adjuvant
breast cancer treatment. Furthermore, plasma concentrations at the lower end of the observed plasma level distribution might
represent a hint but not a confirmation for non-adherence in terms of non-daily and irregular intake of the prescribed drug. 相似文献
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In this paper ordinary stochastic differential equations whose coefficients depend on uncertain parameters are considered. An approach is presented how to combine both types of uncertainty (stochastic excitation and parameter uncertainty) leading to set-valued stochastic processes. The latter serve as a robust representation of solutions of the underlying stochastic differential equations. The mathematical concept is applied to a problem from earthquake engineering, where it is shown how the efficiency of Tuned Mass Dampers can be realistically assessed in the presence of uncertainty. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Gü nther Hö rmann Michael Oberguggenberger Stevan Pilipovic 《Transactions of the American Mathematical Society》2006,358(8):3363-3383
We investigate microlocal properties of partial differential operators with generalized functions as coefficients. The main result is an extension of a corresponding (microlocalized) distribution theoretic result on operators with smooth hypoelliptic symbols. Methodological novelties and technical refinements appear embedded into classical strategies of proof in order to cope with most delicate interferences by non-smooth lower order terms. We include simplified conditions which are applicable in special cases of interest.