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排序方式: 共有102条查询结果,搜索用时 15 毫秒
1.
The availability is determined for the following kind of system. When the system is operational (up), it can fail in either one of two modes. However, the system operator does not always diagnose the failure mode correctly. Given that one failure mode has occurred, the authors correctly diagnose the failure mode with a given probability η and misdiagnose it with probability 1-η, where η may vary with failure mode. The problem is modeled by a partially observable Markov process. Numerical results indicate that a high probability of misdiagnosis produces appreciably high system-downtime 相似文献
2.
在常温常压下,以Cu-Zn—Al合金为基体经过简单的化学处理,在基体上成功地合成了直径为几十纳米,长度在微米量级的Si-维纳米结构。利用TEM,HREM,EDS等测试手段对Si-维纳米结构的形貌和微观结构进行了表征。观察到Cu-Zn-Al合金中存在着运动的“非线性振荡胞区”,并且发现Si-维纳米结构的生长和形貌与这些胞区的运动有着密切的关系。另外,对于Si-维纳米结构生长机制进行了初步探讨。 相似文献
3.
Topology optimization of a cantilevered piezoelectric energy harvester using stress norm constraints
Fabian Wein Manfred Kaltenbacher Michael Stingl 《Structural and Multidisciplinary Optimization》2013,48(1):173-185
Vibrational piezoelectric energy harvesters are devices which convert ambient vibrational energy into electric energy. Here we focus on the common cantilever type in which an elastic beam is sandwiched between two piezoelectric plates. In order to maximize the electric power for a given sinusoidal vibrational excitation, we perform topology optimization of the elastic beam and tip mass by means of the SIMP approach, leaving the piezoelectric plates solid. We are interested in the first and especially second resonance mode. Homogenizing the piezoelectric strain distribution is a common indirect approach increasing the electric performance. The large design space of the topology optimization approach and the linear physical model also allows the maximization of electric performance by maximizing peak bending, resulting in practically infeasible designs. To avoid such problems, we formulate dynamic piezoelectric stress constraints. The obtained result is based on a mechanism which differs significantly from the common designs reported in literature. 相似文献
4.
Abstract. We consider two fundamental problems in dynamic scheduling: scheduling to meet deadlines in a preemptive multiprocessor setting,
and scheduling to provide good response time in a number of scheduling environments. When viewed from the perspective of traditional
worst-case analysis, no good on-line algorithms exist for these problems, and for some variants no good off-line algorithms
exist unless P = NP .
We study these problems using a relaxed notion of competitive analysis, introduced by Kalyanasundaram and Pruhs, in which
the on-line algorithm is allowed more resources than the optimal off-line algorithm to which it is compared. Using this approach,
we establish that several well-known on-line algorithms, that have poor performance from an absolute worst-case perspective,
are optimal for the problems in question when allowed moderately more resources. For optimization of average flow time, these
are the first results of any sort, for any NP -hard version of the problem, that indicate that it might be possible to design good approximation algorithms. 相似文献
5.
Perry Fizzano David Karger Clifford Stein Joel Wein 《Journal of Parallel and Distributed Computing》1997,45(2):531
We give a distributed approximation algorithm for job scheduling in a ring architecture. In contrast to many other parallel scheduling models, the model we consider captures the influence of the underlying communications network by specifying that task migration from one processor to another takes time proportional to the distance between those two processors in the network. As a result, our algorithm must balance computational load and communication time. The algorithm is simple, requires no global control, and yields schedules of length at most 4.22 times optimal. We also give a lower bound on the performance of any distributed algorithm and the results of simulation experiments which suggest better performance than does our worst-case analysis. 相似文献
6.
Ondřej Wein 《International Journal of Heat and Mass Transfer》2010,53(9-10):1874-1881
Voltage-step transient problem, useful in electrodiffusion diagnostics of the near-to-wall flow kinematics, is solved for microdispersion liquids that manifest non-linear velocity profile close to the wall. The known solution of this problem for circular probes in a diffusion-layer approximation (DLA), assuming a power-law representation of the velocity profiles, Wein and Kovalevskaya [11], is corrected on the edge effects, important at low Peclet number, i.e. for the small probes and slow flows. A model of the transient process, controlled by convective diffusion at finite Peclet number, is developed here as a generalization of the approach by Wein et al. [9]. The model is applied for treating primary voltage-step transient data of several aqueous high-molecular polysaccharide solutions, displaying strongly non-linear velocity profiles close to the wall. 相似文献
7.
8.
Diclofenac antiserum was previously developed and used to detect protein adducts of metabolites of dichlofenac in livers of mice and rats. In this study, the antibody has been used to facilitate the purification of a major 51 kDa microsomal adduct of diclofenac from the liver microsomes of male rats that were treated with diclofenac. The adduct was identified as male-specific cytochrome P4502C11 based on its N-terminal amino acid sequence, reaction with a cytochrome P4502C11 antibody, and by its absence from liver microsomes of diclofenac-treated female rats. When diclofenac was incubated with liver microsomes of control rats in the presence of NADPH, only the 51 kDa adduct was produced. The formation of the adduct was inhibited by a cytochrome P4502C11 monoclonal antibody, but not by reduced glutathione or N-alpha-acetyl-L-lysine. No adduct was detected when diclofenac was incubated with liver microsomes from female rats. Moreover, adduct formation in vivo appeared to lead to a 72% decrease in the activity of cytochrome P4502C11. The results indicate that cytochrome P4502C11 metabolizes diclofenac into a highly reactive product that covalently binds to this enzyme before it can diffuse away and react with other proteins. 相似文献
9.
O. Wein 《Journal of Applied Electrochemistry》1991,21(12):1091-1094
The ohmic potential drop between the working and reference electrodes plays an important role in the early stage of the voltage-step transient process. The non-linear effect of the ohmic drop on the transient currents is calculated for large voltage steps, assuming reversible behaviour (negligible surface overpotential) of the redox couple O+ne=R.This paper was presented at the Workshop on Electrodiffusion Flow Diagnostics, CHISA, Prague, August 1990. 相似文献
10.
Dr. Mélissa Degardin Dr. Sharon Wein Dr. Jean‐Frédéric Duckert Marjorie Maynadier Dr. Alexandre Guy Dr. Thierry Durand Prof. Roger Escale Dr. Henri Vial Dr. Yen Vo‐Hoang 《ChemMedChem》2014,9(2):300-304
Plasmodium falciparum is responsible of the most severe form of malaria, and new targets and novel chemotherapeutic scaffolds are needed to fight emerging multidrug‐resistant strains of this parasite. Bis‐alkylguanidines have been designed to mimic choline, resulting in the inhibition of plasmodial de novo phosphatidylcholine biosynthesis. Despite potent in vitro antiplasmodial and in vivo antimalarial activities, a major drawback of these compounds for further clinical development is their low oral bioavailability. To solve this issue, various modulations were performed on bis‐alkylguanidines. The introduction of N‐disubstituents on the guanidino motif improved both in vitro and in vivo activities. On the other hand, in vivo pharmacological evaluation in a mouse model showed that the N‐hydroxylated derivatives constitute the first oral bioprecursors in bis‐alkylguanidine series. This study paves the way for bis‐alkylguanidine‐based oral antimalarial agents targeting plasmodial phospholipid metabolism. 相似文献