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991.
根据定向井注水泥环空流变学的若干特性,设计并建立了定向井环空流变学模拟试验装置,可完成在不同并斜角、偏心度、流体粘度和流量下对定向井环空顶替流变特性的模拟试验研究。运用压降分析法间接探讨了这些参数对定向井注水泥顶替效果的影响。由模拟试验结果得出了定向并注水泥顶替效果随这些参数变化的规律。 相似文献
992.
993.
Drift‐flux analyses are a common way of estimating the phase fractions and fluxes in vertical multiphase flows. However their use has had scant impact on the flotation and foam fractionation communities despite the publication of a number of such analyses over the past two decades. By recognizing that the physics that underpin the hydrodynamics of the froth are dissimilar to those that pertain to the bubbly liquid beneath, we present a drift‐flux analysis with two characteristic curves. A method for obtaining the characteristic curve for the froth from experimental data for the drainage of stationary foams is presented. 相似文献
994.
Barry A. Bell 《Journal of research of the National Institute of Standards and Technology》1990,95(4):377-405
Over the last decade the use of digital synthesis and sampling techniques for generating and measuring electrical waveforms has increased dramatically with the availability of improved digital-to-analog (D/A) and analog-to-digital (A/D) converters and related devices. With this evolution has come the need for physical laboratory standards and test methods to support the performance specifications of digital devices and the instruments in which they are used. This article describes the research and development at NIST of several laboratory standards and test systems that utilize “digital technology” for characterizing data converters and for implementing various waveform synthesis and sampling instruments. 相似文献
995.
Alan I. Nakatani Hongdoo Kim Charles C. Han 《Journal of research of the National Institute of Standards and Technology》1990,95(1):7-14
The design and construction of an apparatus for studying the simultaneous small angle neutron scattering (SANS) and steady shear viscosity behavior of polymer melts and concentrated solutions is discussed. Successful operation of the device is demonstrated on a blend of 20 weight percent deuterated polystyrene and 80 weight percent poly(vinylmethylether). The effects of shear on the critical behavior of the blend are observed in the SANS behavior as a function of temperature and shear rate and indicate shear induced mixing behavior for the range of shear rates examined. The steady shear viscosity results alone are insufficient for detecting the transition from one to two phases. The examination of shear effects in polymer blends is important for understanding the critical behavior of binary systems. Technologically, knowledge of the phase behavior of polymer blends under shear are important for the design and improvement of commercial blend processing. 相似文献
996.
本文建立的螺纹中径当量全微分优化逼近模型,考虑了螺距偏差,螺距累积偏差和半角偏差本身及其相互间对中径的综合影响,并用理想螺纹在径向和轴向二维逼近实际螺纹,计算机计算表明,本文提出了全微分优化逼近算法优于常用算法及三点接触式算法,经计算机图形仿真显示算法是正确的。 相似文献
997.
An experimental system has been commissioned which allows the collection of time-resolved simultaneous two-dimensional small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS) and stress-strain data with a temporal resolution of 40 ms during the drawing of synthetic polymers. X-ray data collection is achieved via two CCD-based area detectors which are positioned in order to maximize the amount of scattering that can be observed from a particular sample. True stress-strain measurements are obtained from video extensometer and load cell measurements. The system was used at the Daresbury SRS to study the structural changes which occur in a sample of isotropic high-density polyethylene when subjected to an overall strain rate of ≈ 3 s−1. It is shown that the onset of both a partial stress-induced crystal phase change and micro-voiding in the sample can be directly correlated to the point of yield in the true stress-strain curve. © 1997 Elsevier Science Ltd. 相似文献
998.
井巷光面爆破不偶合系数研究 总被引:1,自引:1,他引:0
从理论上研究了井巷光面爆破轴向不偶合装药缓冲作用原理的成缝机理,提出了轴向不偶合系数的计算方法,得出了轴向不偶合系数在不同条件下的取值范围,并在工程实践中得到了验证。 相似文献
999.
We have studied structural properties of amorphous hydrogenated silicon usingab initio molecular dynamics simulations. A sample was generated by simulated annealing using periodic boundary conditions with a supercell
containing 64 silicon and 8 hydrogen atoms. The radial pair distribution functions for Si-Si, Si-H and H-H have been studied
at 300 K and are found to be in good agreement with experimental data. Our results show that hydrogen saturates the dangling
bonds and reduces bond strain. We also report existence of Si-H-Si bridge sites which are likely to play an important role
in understanding the light induced metastability in this material. 相似文献
1000.