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排序方式: 共有6417条查询结果,搜索用时 8 毫秒
1.
中原油田岩石可钻性与声波时差关系研究 总被引:3,自引:0,他引:3
选取中原油田的大量岩心,采用常规岩石力学测试方法测定了岩石的可钻性、声波测试方法测定了岩石和岩屑声波时差,通过对测得的岩石可钻性级值和声波时差进行回归拟合,得出了中原油田岩石可钻性与声波时差的关系式。现场应用表明,该关系式较好地反映了中原油田地层岩石可钻性与声波时差的关系,可以在优选钻头时作为参考或直接应用。 相似文献
2.
Jui-Ting Weng Jiunn Ru Lai Wanjiun Liao 《Wireless Communications, IEEE Transactions on》2006,5(7):1676-1684
In this paper, we analyze node mobility for reliable packet delivery in mobile IP networks. In mobile IP, packets destined to roaming nodes are intercepted by their home agents and delivered via tunneling to their care of addresses (CoA). A mobile node may roam across multiple subnets. At each boundary crossing, a handoff is initiated such that the CoA is updated and a new tunnel is established. We consider both basic mobile IP handoff and smooth handoff. We find that reliable packet delivery in mobile IP networks can be modeled as a renewal process, because the retransmission over a new tunnel after each boundary crossing is independent of the previous history. We then derive the probability distribution of boundary crossings for each successful packet, based on which the packet reliable delivery time can be obtained. Our analytical model is derived based on a general distribution of residence time in a subnet and a general distribution of successful retransmission attempts in each subnet. The results can be readily applied to any distributions for both items. We also provide numerical examples to calculate the probability distribution of boundary crossings, and conduct simulations to validate our analytical results 相似文献
3.
Initial geopolymeric reaction processes governing dissolution of solid aluminosilicate particles in alkali solutions have
been investigated using conventional experimental techniques, and the data analysed by speciation predictions of the partial
charge model (PCM). For metakaolin powders activated with 5.0 M NaOH, solid-state nuclear magnetic resonance (NMR) spectra
disclose the existence of monomeric [Al(OH)4]− species after two hours of dissolution, consistent with PCM predictions. However, no equivalent monomeric silicate species
were observed for 5.0–10.0 M NaOH activator solutions characteristic of systems with nominal Si/Al ≤ 1. The apparent absence
of monomeric silicate species suggest rapid condensation of silicate units with [Al(OH)4]− to generate aluminosilicate species, as indicated by the evolution of the shoulder at around −87 ppm in the 29Si NMR spectra. Of the two possible stable silicate species [SiO2(OH)2]2− and [SiO(OH)3]−, the latter appears most likely to condense with [Al(OH)4]− to produce aluminosilicate oligomers, from which larger oligomers subsequently form through further condensation with [Al(OH)4]− leading to a gradual build up of aluminosilicate networks and a lowering of system alkalinity. This dissolution and hydrolysis
sequence at the early stages of synthesis suggests a reaction path wholly consistent with predictions of the partial charge
model. 相似文献
4.
Examined the theory that chronic migraine headaches can lead to permanent changes in brain function in 71 female college students. Ss were 20 classic migraineurs, 27 common migraineurs, and 24 controls. No significant group differences were found on the Halstead Reitan Neuropsychological Test Battery and additional memory tests. Classic migraineurs had significantly higher scores than common migraineurs on the Hysteria and Paranoia scales of the Minnesota Multiphasic Personality Inventory (MMPI) and significantly higher scores than the controls on Hypochondriasis and Hysteria scales. Explanations for the lack of cognitive deficits in this group are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
We give a parametrized family of rational interval maps of degree two, each ergodic, exact and preserving a measure equivalent to a Lebesgue measure. The family includes the unique quadratic Chebyshev polynomial as its only polynomial map. We extend the family to other settings on the circle and real line. We also give numerical approximations to the entropy of the equivalent invariant measure and the Hausdorff dimension of the singular measure of maximal entropy. 相似文献
6.
Qing-Huo Liu Anderson B. Weng Cho Chew 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(3):494-498
The authors formulate and implement a numerical mode-matching (NMM) method to model electrode-type resistivity tools in invaded thin beds. The authors derive the low-frequency approximation of the Maxwell's equations to obtain the partial differential equation for the potential field. The new NMM program is validated by comparing the numerical results with those obtained from other dc programs. It is found that this new program is much faster than the program using the finite-element method (FEM), and hence is useful for routine interpretation of resistivity logs and for inversion 相似文献
7.
Snell-Johns Jessica; Mendez Julia L.; Smith Bradley H. 《Canadian Metallurgical Quarterly》2004,18(1):19
Various definitions exist for what constitutes family therapy. In this article, we consider family therapy to encompass any intervention that targets family interactions and conceptualizes problems as existing beyond individual clients. Numerous individual studies and several quantitative reviews have established family therapy as an effective treatment modality and the treatment of choice for many disorders. However, critiques of existing service provision highlight the unfortunate fact that numerous barriers to treatment exist at multiple levels of the broader ecology, preventing many families from benefiting from these services. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Sigal Gottlieb Julia S. Mullen Steven J. Ruuth 《Journal of scientific computing》2006,27(1-3):271-287
The weighted essentially non-oscillatory (WENO) method is an excellent spatial discretization for hyperbolic partial differential equations with discontinuous solutions. However, the time-step restriction associated with explicit methods may pose severe limitations on their use in applications requiring large scale computations. An efficient implicit WENO method is necessary. In this paper, we propose a prototype flux-implicit WENO (iWENO) method. Numerical tests on classical scalar equations show that this is a viable and stable method, which requires appropriate time-stepping methods. Future study will include the examination of such methods as well as extension of iWENO to systems and higher dimensional problems.Sigal Gottlieb - The work of this author supported by NSF grant DMS-0106743.Steven J. Ruuth - The work of this author was partially supported by a grant from NSERC Canada. 相似文献
9.
10.
纺织信息的网上检索方法 总被引:2,自引:0,他引:2
主要介绍在网上检索纺织信息的几种方法和处理技术,为人们检索纺织信息提供了方便快捷的途径。 相似文献