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991.
The use of commercially available bubble detectors for gamma and neutron detection has been reported by several groups. We have carried out systematic investigations to study the response of gamma bubble detector as a function of energy, the effect of waiting time on sensitivity of BD-100R neutron bubble detector and the effect of shelf life on both types of bubble detectors. Our results show that the response of the gamma bubble detector is energy dependent. Waiting time of up to 260 hours for BD-100R neutron detector has no significant effect. Both the detectors have a limited shelf life. These factors must be taken into account while using these detectors. 相似文献
992.
Seung‐Jin Yang Choonkeun Lee Wonbong Jang Jinuk Kwon Saimani Sundar Haksoo Han 《Journal of Polymer Science.Polymer Physics》2004,42(23):4293-4302
Poly(epoxy imide)s were prepared by a reaction between a hydroxyl‐group‐containing soluble copolyimide and commercial epoxy resins at 220 °C for 2 h. Poly(epoxy imide) thin films exhibited higher thermal stability and lower dielectric constants than a commercial flip‐chip package material (U300). The thermal stabilities of the poly(epoxy imide)s were 1.4–2.0 times higher than that of U300. The thermal stability increased with increasing crosslink density and with decreasing bulky CF3 groups (which were easily decomposable). The dielectric constants of the poly(epoxy imide)s were 1.1–1.3 times lower than that of U300, and this is highly desirable for the microelectronic packaging industry. The dielectric constant dramatically decreased when bulky CF3 groups were added and when the functionalities of epoxy resins decreased. The residual stresses, slopes in the cooling curves, and glass‐transition temperatures of the poly(epoxy imide)s were measured with a thin‐film stress analyzer. Low residual stresses and slopes in the cooling curves were achieved with a higher crosslink density. However, in the presence of bulky CF3 groups, the copolyimide backbone structure did not affect the residual stress values. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4293–4302, 2004 相似文献
993.
The computational efficiency of three numerical schemes has been examined for the solution of a linearized system of equations resulting from the finite element discretization of a viscoelastic fluid flow problem. The first scheme is a modified frontal solver, which solves the linear system of equations directly. The other two, one based on a biconjugate gradient stabilized (BiCGStab) method and another based on a generalized minimal residual (GMRES) method, are iterative schemes. The stick-slip problem and the four-to-one contraction problem were analyzed and the viscoelastic fluid was assumed to obey the Oldroyd-B model. The two iterative schemes are superior to the direct scheme in terms of CPU time consumed and the BiCGStab scheme is even faster than the GMRES scheme. The range of convergence for both iterative schemes is compatible with that of the direct scheme. 相似文献
994.
Moshe Shaked Nozer D. Singpurwalla 《Annals of the Institute of Statistical Mathematics》1990,42(1):1-19
In this paper we propose a Bayesian approach for the estimation of a potency curve which is assumed to be nondecreasing and concave or convex. This is done by assigning the Dirichlet as a prior distribution for transformations of some unknown parameters. We motivate our choice of the prior and investigate several aspects of the problem, including the numerical implementation of the suggested scheme. An approach for estimating the quantiles is also given. By casting the problem in a more general context, we argue that distributions which are IHR or IHRA can also be estimated via the suggested procedure. A problem from a government laboratory serves as an example to illustrate the use of our procedure in a realistic scenario. 相似文献
995.
996.
997.
Q235A钢用新型耐磨覆层材料的残余应力计算 总被引:1,自引:0,他引:1
计算了Q2 35A钢用新型耐磨金属陶瓷覆层材料的残余应力分布 ,通过对残余应力的计算发现覆层材料中的残余应力随覆层与基体厚度比的变化而变化。由于此种新型覆层材料的覆层厚度可不受限制 ,据此本文提出了可以对覆层材料的厚度进行优化 ,从而得到有利的残余应力分布的设计方案 相似文献
998.
Average life of oxygen vacancies of quartz in sediments is estimated by using the ESR(electron spin resonance) signals of E' centers from the thermal activation technique. The experi-mental results show that the second-order kinetics equation is more applicable to the life estima-tion compared with the first order equation. The average life of oxygen vacancies of quartz from4895 to 4908 deep sediments in the Tarim Basin is about 10~(18) a at 27℃. 相似文献
999.
回归系数的主相关估计及其优良性 总被引:6,自引:0,他引:6
本文在回归系数的主成分估计的基础上,提出一种新的降维估计-主相关估计,讨论了它的优良性,并用实例说明主相关估计对主成分估计的改进效果。 相似文献
1000.
For some lattice systems with an infinite number of ground states, it is shown that the pressure and the coexistence surfaces of several phases admit asymptotic expansions aroundT=0. In particular, it follows that the coexistence surfaces are differentiable atT=0, and at low temperatures the stable states are those with maximal residual entropy. The results are applied to construct the phase diagrams for several spin-1 models. 相似文献