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排序方式: 共有773条查询结果,搜索用时 53 毫秒
41.
Dynamic response of deformable structures subjected to shock load and cavitation reload 总被引:1,自引:0,他引:1
The dynamic response of deformable structures subjected to shock load and cavitation reload has been simulated using a multiphase
model, which consists of an interface capturing method and a one-fluid cavitation model. Fluid–structure interaction (FSI)
is captured via a modified ghost fluid method (Liu et al. in J Comput Phys 190: 651–681, 2003), where the structure is assumed
to be a hydro-elasto-plastic material if subjected to a strong shock load. Bulk cavitation near the structural surface is
captured using an isentropic model (Liu et al. in J Comput Phys 201:80–108, 2004). The integrated multiphase model is validated
by comparing numerical predictions with 1D analytical solutions, and with numerical solutions calculated using the cavitation
acoustic finite element (CAFé) method (Sprague and Geers in Shocks vib 7:105–122, 2001). To assess the ability of the multiphase
model for multi- dimensions, underwater explosions (UNDEX) near structures are computed. The importance of cavitation reloading
and FSI is investigated. Comparisons of the predicted pressure time histories with different explosion center are shown, and
the effect on the structure is discussed. 相似文献
42.
The auto-charge pump is a self-starting and self-sustaining circuit used to generate a floating voltage supply for the high side circuitry of half-bridge inverters. The switching output of the half-bridge replaces the dedicated pump oscillator thus simplifying the circuit. A model is derived which is then verified experimentally 相似文献
43.
In this work, we deal with the 1D compressible fluid coupled with elastic solid in an Eulerian-Lagrangian system. To facilitate
the analysis, the Naviers equation for elastic solid is cast into a 2×2 system similar to the Euler equation but in Lagrangian
coordinate. The modified Ghost Fluid Method is employed to treat the fluid-elastic solid coupling, where an Eulerian-Lagrangian
Riemann problem is defined and a nonlinear characteristic from the fluid and a Riemann invariant from the solid are used to
predict and define the ghost fluid states. Theoretical analysis shows that the present approach is accurate in the sense of
approximating the solution of the Riemann problem at the interface. Numerical validation of this approach is also accomplished
by extensive comparison to 1D problems (both water-solid and gas-solid) with their respective analytical solutions.
T.G. Liu’s current address: Department of Mathematics, Beijing University of Aeronautics and Astronautics, Beijing 100083.
email: liutg@buaa.edu.cn. 相似文献
44.
Methods for assessing treatment effects of longitudinal randomized intervention are considered. The focus is on modeling the nonlinear relationship between treatment effects and baseline often observed in prevention programs designed for at-risk populations. Piecewise linear growth modeling was used to study treatment effects during the different periods of development. A multistep multiple-group analysis procedure is proposed for assessing treatment effects in the presence of nonlinear treatment-baseline interactions. Standard errors of the estimates from this multistep procedure were obtained using a bootstrap approach. The methods are illustrated using data from the Johns Hopkins Prevention Research Center involving an intervention aimed at improving classroom behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Tsuen-Hsi Liu Iam-Choon Khoo 《Quantum Electronics, IEEE Journal of》1987,23(11):2020-2027
The theory of probe beam amplification via degenerate optical wave mixing in a Kerr medium is presented. This theory includes consideration of the self-phase modulation, two-wave mixing, and multiwave mixing terms in the coupled-wave equations. Both analytical solutions, under the assumptions of a nondepleted pump beam and a transparent Kerr medium, and numerical solutions with these assumptions removed are presented. Our solutions show that under certain conditions, phase matching can be satisfied and a high probe beam gain is possible, even for a zero phase shift between the refractive index and the intensity gratings. 相似文献
46.
H Kashiwagi AD Spigelman IC Talbot HS Debinski AB McKie NR Lemoine RK Phillips 《Canadian Metallurgical Quarterly》1997,84(6):826-829
BACKGROUND: The genetic alterations in patients with familial adenomatous polyposis (FAP) and duodenal adenomas are poorly characterized when compared with data relating to colorectal tumorigenesis in the same patients. METHODS: Point mutation of the K-ras oncogene and point mutation and overexpression of the TP53 tumour suppressor gene were investigated in 32 duodenal polyps (seven without mucosal pathology, 23 with mildly dysplastic adenomas and two with moderately dysplastic adenomas) from 21 patients with FAP. RESULTS: K-ras mutation, TP53 mutation or positive p53 staining were not found in duodenal polyps without histological abnormality. Of 25 duodenal adenomas, K-ras mutation was found in three (two mildly dysplastic, one moderately dysplastic), 20 showed positive p53 immunostaining, and mutation of the TP53 gene was found in one moderately dysplastic adenoma. p53 protein overexpression in duodenal adenomas was significantly more frequent than mutation of either K-ras or TP53 (P < 0.01). CONCLUSION: p53 dysfunction is a hallmark of duodenal adenomas in patients with FAP. Overexpression may indicate DNA damage and thus an early step in tumorigenesis. 相似文献
47.
A fusion protein was constructed between the porcine alpha2A-adrenoceptor and a pertussis toxin-insensitive (Cys351Gly) form of the alpha subunit of the G protein Gi1. Addition of agonist ligands to membranes of COS-7 cells transiently transfected to express this construct, and treated with pertussis toxin prior to cell harvest, resulted in stimulation of both high affinity GTPase activity and enhanced binding of [35S]GTPgammaS. By considering the fusion protein as an agonist-activated enzyme and measuring Vmax of GTP hydrolysis a range of agonist ligands displayed varying efficacy in their capacity to activate the receptor-associated G protein with adrenaline = noradrenaline = alpha-methylnoradrenaline > UK14304 > BHT933 > or = xylazine = clonidine. A similar rank order was observed following independent co-expression of the alpha2A-adrenoceptor and Cys351Gly-Gi1alpha. These data demonstrate the utility and applicability of using a receptor-G protein fusion protein approach, in which the stoichiometry of receptor and G protein is fixed at 1:1, to measure and further understand the nature of agonist efficacy. 相似文献
48.
49.
Sally Cole Johnson 《集成电路应用》2008,(8):36-37
正如2007版国际半导体技术蓝图(ITRS)所提到的,自动测试设备(ATE)所面临的最紧迫的技术挑战便是“促进良率提高的测试”,特别是对于90、65、45nm和未来工艺节点上的晶圆工艺和器件良率学习。 相似文献
50.
Computing the Percentage Points of the Run-Length Distributions of Multivariate CUSUM Control Charts
Multivariate CUSUM control charts are often used instead of the standard Hotelling's control charts in many practical problems when detection of small shifts in the process mean is important. However, design of multivariate CUSUM control charts are usually based on the average run length (ARL). In this work, we will compute the percentage points of the run-length distributions of two multivariate CUSUM control charts. It will be shown that interpretations based on ARL can be misleading since the in-control run-length distribution of a multivariate CUSUM is highly skewed. On the other hand, the percentage points of the run-length distribution provide additional information such as the median run length, early false out-of-control signals, and the skewness of the run-length distribution for a particular scheme. These extra information might provide quality control engineers further knowledge of a particular multivariate CUSUM control chart scheme. 相似文献