Transport Properties of Inhomogeneous Fluid Mixtures

Explicit expressions for the transport coefficients of mixtures of dense, strongly inhomogeneous fluids are derived in terms of the equilibrium structure factors of such mixtures, in the framework of the nonequilibrium statistical mechanical theory suggested by the authors. Particular attention is paid to the diffusion coefficients of multicomponent inhomogeneous fluids. The case of binary diffusion in inhomogeneous fluids is considered in detail.     

High-frequency micromechanical columnar resonators

Abstract

High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10^?6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately ?173 Hz °C^{? 1}. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency.     

柱塞泵滑靴阻尼孔对滑靴/斜盘油膜的影响

根据静压支撑原理,运用计算流体力学技术,对滑靴副的流场进行仿真分析,在油膜厚度一定的情况下,选取3组不同的阻尼孔直径,对滑靴和斜盘油膜表面压力进行监控,得到底面油膜压力随着阻尼孔直径变化的压力图,讨论不同的油膜压力对滑靴副油液泄漏的影响以及对泵效率的影响。结果表明:阻尼孔直径变大,底面油膜的压力随着变大,滑靴副油液泄漏量也随着增加,而油液泄漏量又影响泵的效率。研究结果进一步揭示了滑靴阻尼孔结构对滑靴副和泵性能的影响。     

Heat Effects of Hydrogen Fluoride from Two Thermodynamic Models

We examine two published thermodynamic models for their ability to describe the excess enthalpy and heat capacity of hydrogen fluoride (HF) over a range of temperatures. Emphasis is placed on the behavior away from the saturation curve and, thus, away from the conditions used to fit the models. The first model is the association + equation of state (AEOS) treatment of Anderko, which utilizes a biased yet unconstrained association scheme. The second model is due to Kao and co-workers and treats HF as a mixture of only monomers and hexamers. Both models are found to be effective in capturing important qualitative features of the HF heat effects. The AEOS describes well the location but not the magnitude of associated-induced maxima in the vapor-phase heat capacities, while the Kao model describes the magnitude well but is slightly off in characterizing the locations of these maxima.     

影响调整井固井质量的主要因素及计算方法

油田开发已进入高含水后期，调整井数量越来越多，长期的注水开发，使地层结构遭到严重破坏，调整井固井质量受到严重影响。针对井径扩大率、钻井液性能、水泥浆密度、地层孔隙压力和孔隙流体渗流速度等影响调整井固井质量的主要因素进行了分析，并建立了地层孔隙压力和孔隙流体渗流速度的计算方法。结果表明：随着井径扩大率、钻井液密度、黏度、失水量的增大，调整井固井优质率降低；地层孔隙压力越大，孔隙流体渗流速度超过临界渗流速度时，调整井固井质量变差；建立的地层孔隙压力和孔隙流体渗流速度的计算方法能准确地预测地层孔隙压力和孔隙流体渗流速度，为提高调整井固井质量提供可靠的依据。     

Properties of polyurea greases on a synthetic base

The dependence of the properties of polyurea greases on the composition of the dispersion medium was investigated. Synthetic lubricating fluids of different chemical natures and mixtures of these fluids were used as the dispersion medium. Lubricants on a mixed base have better lubricant properties than lubricants based on the individual synthetic fluids.Translated from Tekhnologiya Topliv i Masel, No. 6, pp. 45–46, November– December, 2004     

Optimized Preparation of Elastically Soft,Highly Piezoelectric,Cellular Ferroelectrets from Nonvoided Poly(ethylene Terephthalate) Films

Electrically charged cellular polymer films can exhibit very high piezoelectric activity and are therefore more and more often employed in advanced electromechanical and electro‐acoustical transducers. In this paper, we report an optimized sequence of steps for preparing such ferroelectrets from commercial nonvoided poly(ethylene terephthalate) (PETP) films by means of foaming with CO₂, biaxial mechanical stretching, controlled void inflation, and bipolar electric charging. The nonvoided PETP films were foamed with supercritical CO₂ at a suitably high pressure and subsequently annealed for stabilization. The cellular foam structure was further optimized by means of well‐controlled biaxial stretching in a commercial stretcher and sometimes subsequent inflation in a pressure chamber. Bipolar electric charging of the internal voids was achieved through the application of high electric fields in an SF₆ atmosphere. The new optimized PETP ferroelectrets exhibit quite large piezoelectric coefficients up to almost 500 pC N^–1, for which unusually low elastic stiffnesses of only around 0.3 MPa are essential. The PETP‐foam ferroelectrets possess unclamped thickness‐extension resonance frequencies between approximately 120 and 250 kHz, and are thus highly suitable for several established as well as novel ultrasonic‐transducer applications.