Pore-Level Modeling of Gas and Condensate Flow in Two- and Three-Dimensional Pore Networks: Pore Size Distribution Effects on the Relative Permeability of Gas and Condensate

We present a mechanistic model of retrograde condensation processes in two- and three-dimensional capillary tube networks under gravitational forces. Condensate filling-emptying cycles in pore segments and gas connection–isolation cycles are included. With the pore-level distribution of gas and condensate in hand, we determine their corresponding relative permeabilities. Details of pore space and displacement are subsumed in pore conductances. Solving for the pressure field in each phase, we find a single effective conductance for each phase as a function of condensate saturation. Along with the effective conductance for the saturated network, the relative permeability for each phase is calculated. Our model porous media are two- and three-dimensional regular networks of pore segments with distributed size and square cross-section. With a Monte Carlo sampling we find the optimum network size to avoid size effects and then we investigate the effect of network dimensionality and pore size distribution on the relative permeabilities of gas and condensate.     

基于改进MP-WVD算法的核电厂建设爆破振动信号处理方法

针对爆破施工产生的振动问题,结合现有信号分析方法优缺点,引入MP-WVD组合算法解决信号分析过程中交叉项干扰问题,可提高时频分辨率,满足精确提取核电爆破振动响应信号时频分布特征的需求;将HHT算法引入MP算法数据的预处理,成功降低了MP算法运算复杂度,可为大数据量分析奠定基础。运用该算法对漳州核电一期工程场地平整土石方爆破工程振动监测信号进行分析,精确提取了爆破振动信号的时频特征。     

紊动流场中悬浮颗粒分布的随机理论

通过分析固体颗粒在紊动流场中的随机运动,建立了二维流场中垂直于时均流动的方向上颗粒随机位移的概率密度分布函数所满足的方程。由该方程解出的分布函数在一定条件下即相当于颗粒浓度分布函数。运用这一方法研究了[1]、[2]中报道的壁面附近颗粒浓度降低的现象。     

圆盘离心沉降法测定固体粉末的粒度分布

本文报道用圆盘离心沉降法对几种粉末样品的粒径大小及粒度分布测定的结果,并且讨论了颗粒形状、消光系数和粉末分散状态等因素的影响。试验结果表明,在给定的条件下,利用LKY-1型微粒测定仪对粉末粒度测定的重复性好,尤其适用于测定微细粉末的粒度分布;当石墨或MoS_2粉末样品的浓度为0.5％时,选用4％鞣酸作分散剂的效果最好。作者认为,固然光密度与微粒的消光系数有关,但对于黑灰色的粉末样品而言,因其产生的光学效应非常微弱,故可近似地把消光系数视为常数而忽略它的影响。     

Statistical mechanics of temporary polymer networks I. The equilibrium theory

In part I of this work (the present article) the equilibrium state of temporary polymer networks is treated in the framework of thermodynamics and statistical mechanics. The network is described as an open system. Thereby we use a modified spring-bead model in which the beads represent junctions that decay and reform thus adding a viscous component to the assumed elastic behaviour of the permanent network. The relevant statistical equation — analogous to Liouville's equation — is solved. The grand-canonical probability density function and two of three equations of state are derived. Explicit formulae are given for several relevant probabilities. For instance the probabilityw (z)dz that a network chain connecting two junctions has a contour length betweenz andz +dz is given by the Wien type formulaw(z) =A z ³ exp {–B z} whereA andB do not depend onz.     

Concentration-dependent behaviour of the shear viscosity of coal-fuel oil suspensions

A function correlating the relative viscosity of a suspension of solid particles in liquids to their concentration is derived here theoretically using only general thermodynamic ideas, with out any consideration of microscopic hydrodynamic models. This function ( _r = exp (1/2B ^* C ²)) has a great advantage over the many different functions proposed in literature, for it depends on a single parameter,B ^*, and is therefore concise. To test the validity of this function, a least-squares regression analysis was undertaken of available data on the viscosity and concentration of suspensions of coal particles in fuel oil, which promise to be a useful alternative to fuel oil in the near future. The proposed function was found to accurately describe the concentration-dependent behaviour of the relative viscosity of these suspensions. Furthermore, an attempt was made to obtain information about the factors affecting the value ofB ^*, however the results were only qualitative because of, among other things, the inaccuracy of the viscosity measurements in such highly viscous fluids. shear viscosity of the suspension - ₀ shear viscosity of the Newtonian suspending medium - _r = /₀ relative viscosity - solid volume concentration - c solid weight concentration - _m maximum attainable volume concentration of solids - solid volume concentration at which the relative viscosity of the suspension becomes infinite - c _m maximum attainable solid weight concentration - _s density of the solid phase - _l density of the liquid phase - _m density of the suspension - k _n coefficients of theø-power series expansion of _r - { _j } sets of parameters specifying the thermodynamic state of the solid phase of a suspension - T absolute temperature (K) - f (c, T, _j) formal expression for the relative variation of the viscosity with concentration = [1 / (/c)] _T,j - d median size of the granulometric distribution - _B plastic or Bingham viscosity - K consistency factor - n flow index - g ([c _m –c],T, _j ) function including an asymptotic divergence asc tends toc _m , formally describing the concentration dependent behaviour of the shear viscosity of a suspension - A (T, _j) regression analysis parameters - B (T, _j) regression analysis parameters - B ^* (T, _j ) regression analysis parameters     

土壤内水分流动及温度分布计算——耦合型模型

本文目的在于发展一个计算土壤内水分输送及能量交換的物理模型——耦合型模型,驱动该模型的大气条件是由实测而得的,引用对蒸发的土壤表面阻抗关联了在大气中水汽通量与从地表的蒸发,由于这种阻抗引入,计算模拟的结果与实测值达到了较好的吻合。     

Impact of average photon-energy coefficient of solar spectrum on the short circuit current of photovoltaic modules

The output energy of photovoltaic (PV) modules is influenced by the spectral irradiance distribution of the solar spectrum under outdoor conditions. To rate the precise output energy of PV modules, the correction of short circuit current (I_SC) based on actual environmental conditions is needed, because I_SC significantly depends on the shape of the spectral irradiance distribution. The average photon energy (APE) is a zero-dimensional index for spectral irradiance distribution, and APE value uniquely describes the shape of a solar spectrum. Thus, APE has an impact on I_SC of PV modules. In this contribution, the relationship between APE coefficient and I_SC of the multi-crystalline silicon, single-crystalline silicon, heterojunction intrinsic thin-layer, back contact, copper indium selenide and cadmium telluride PV modules has explored. It is revealed that APE value changes the I_SC of PV modules which appeared to have immense possibilities of I_SC correction using APE coefficient. This new approach can be very effective for precise rating the output energy of PV modules under actual outdoor conditions.     

The oblique chiral nematic phase in calamitic bimesogens

ABSTRACT

The discovery of the oblique chiral (or, the twist-bend, N_TB) nematic phase predicted for bent-core mesogens has engendered much interest due to its unique structure and physical properties, and the possibility of use in the next generation of fast electro-optic technology. Bimesogenic calamitic as well as bent-core mesogens are found to form the N_TB phase. Here, we report direct measurements of the temperature dependence of the conical tilt and the evidence of volcano-like orientational distribution of molecules in the N_TB phase. Optical and x-ray scattering investigations of two single-component calamitic bimesogens and their mixtures show that, while the Maier–Saupe orientational distribution function (ODF) is valid for the higher temperature nematic phase, a generalised expansion in terms of even Legendre functions is needed for the N_TB phase. Temperature dependence of the ODFs and the order parameters 〈P₂(cosβ)〉, 〈P₄(cosβ)〉, and 〈P₆(cosβ)〉 has been measured in both phases. The parameters 〈P₂(cosβ)〉 and 〈P₄(cosβ)〉 increase/decrease in the N/N_TB phase with decreasing temperature, while 〈P₆(cosβ)〉 remains vanishingly small for all samples. The value of 〈P₄(cosβ)〉 becomes negative in the N_TB phase confirming a conical distribution of molecules as they follow a helical trajectory keeping the local director tilted at an angle α wrt the macroscopic director. The heliconical tilt calculated from ODFs, exhibits a power law behaviour with temperature, vanishing at the transition to the N phase.