凝析油-气在存在裂缝的双渗介质中渗流的变产量数学模型及其应用

当凝析气藏压力低于露点压力时,有凝析油析出,致使井底附近阻力变大,影响凝析气的采出量,反凝析现象带来了一些特殊的经济问题.选择合理的开发方式,提高凝析气的采收率,成为了当前工作中迫切需要解决的难题.为了控制合理的井底流压常会引起产量的改变.主要针对凝析气在存在裂缝的双渗气藏中的渗流问题,建立气井变产量生产新模型并进行求解,同时选择相关合理参数绘制了试井理论图版,根据试井理论图版利用试井测试数据进行解释,可以得到相应动态参数为气田开发预案提供相应的理论依据.     

椭圆曲线y~2=px(x~2+2)在p≡1(mod 8)时的正整数点

设p是适合p≡1(mod 8)的奇素数.运用二次和四次Diophantine方程的性质给出了椭圆曲线E:Y²=px(x2=px(x²+2)有正整数点(x,y)的判别条件,并且证明了:当p<100时,该曲线没有正整数点.     

中等收入定位与人口度量模型研究

我国正处于经济转型期和收入分配格局的重要调整期,监控收入分配格局的变化具有重大意义.首先,针对中等收入定位与人口度量模型研究,构建新的洛伦兹模型L(p)=[1-(1-p)~αe~(-βp)][1-(1-p)~γe~(ηp)],与现有的经典洛伦兹模型做比较,拟合精度最优.其次,针对收入空间法和入口空间法的缺陷,给出相应解决对策.最后,提出中等收入人群的新定义,在此基础上构建了中等人口收入效用指数模型.     

布拉德福曲线的威布尔模型

为了克服原有布拉德福曲线的模型不能描述格鲁斯段的缺陷,通过分析布拉德福数据排列的特点、分析期刊文献产生的机理、提出假设、建立微分方程、解微分方程、参数分析等一系列步骤,获得了布拉德福曲线的威布尔模型.通过实证对比分析,模型优于原有的斯马里科夫统一方程和莱姆库勒模型.     

Discussion on relationship between minimal energy and curve shapes

Energy minimization has been widely used for constructing curve and surface in the fields such as computer-aided geometric design, computer graphics. However, our testing examples show that energy minimization does not optimize the shape of the curve sometimes. This paper studies the relationship between minimizing strain energy and curve shapes, the study is carried out by constructing a cubic Hermite curve with satisfactory shape. The cubic Hermite curve interpolates the positions and tangent vectors of two given endpoints. Computer simulation technique has become one of the methods of scientific discovery, the study process is carried out by numerical computation and computer simulation technique. Our result shows that： （1） cubic Hermite curves cannot be constructed by solely minimizing the strain energy; （2） by adoption of a local minimum value of the strain energy, the shapes of cubic Hermite curves could be determined for about 60 percent of all cases, some of which have unsatisfactory shapes, however. Based on strain energy model and analysis, a new model is presented for constructing cubic Hermite curves with satisfactory shapes, which is a modification of strain energy model. The new model uses an explicit formula to compute the magnitudes of the two tangent vectors, and has the properties： （1） it is easy to compute; （2） it makes the cubic Hermite curves have satisfactory shapes while holding the good property of minimizing strain energy for some cases in curve construction. The comparison of the new model with the minimum strain energy model is included.     

随机变量函数概率密度的定点算法

利用曲线积分和曲面积分作为工具,导出计算随机变量函数的密度函数的一种定点算法,并借助实例说明相应计算公式的应用.     

Study on the propagation of coupling shock waves with phase transition under combined tension-torsion impact loading

Phase transition can strongly change the stress wave propagation features. In this paper, the characteristic wave propagation under combined tension and torsion impact loading was studied with a simplified constitutive model of phase transition considering both pressure and shear stress. The results showed that for loading from the austenitic phase to the mixed phase, the wave propagation was similar to that in the elasto-plastic materials. However, for an instantaneous loading from the austenitic phase or mixed phase directly to the martensitic phase, a coupling shock wave (CSHW) with phase transition was predicted due to the second phase strengthening effect, which has barely been studied before. Through analysis of the constitutive equations with phase transition and the discontinuity conditions of shock waves, the control equations of the generalized Hugoniot curve was obtained and the CSHW problem with phase transition was solved analytically. An independent numerical simulation of step loading along a NiTi thin walled tube suffering a combined tension-torsion impact loading was given to prove the existence of CSHW. The simulation discloses the formation mechanism of CSHW and the adjusting process of the stress state ahead of CSHW, which reflects the intrinsic characteristic of materials with strong nonlinear constitutive behavior.     

Two queues with non-stochastic arrivals

This article presents a paradigm where no stochastic assumptions are made on a queue’s arrival process. To this end, we study two queueing systems which exhibit a form of stability under an arbitrary arrival process. The first queueing system applies Blackwell’s Approachability Theorem and the second analyzes the Vacuum Cleaner Problem.     

Quantitative analysis of essential oils in perfume using multivariate curve resolution combined with comprehensive two-dimensional gas chromatography

The use of multivariate curve resolution (MCR) to build multivariate quantitative models using data obtained from comprehensive two-dimensional gas chromatography with flame ionization detection (GC × GC-FID) is presented and evaluated. The MCR algorithm presents some important features, such as second order advantage and the recovery of the instrumental response for each pure component after optimization by an alternating least squares (ALS) procedure. A model to quantify the essential oil of rosemary was built using a calibration set containing only known concentrations of the essential oil and cereal alcohol as solvent. A calibration curve correlating the concentration of the essential oil of rosemary and the instrumental response obtained from the MCR-ALS algorithm was obtained, and this calibration model was applied to predict the concentration of the oil in complex samples (mixtures of the essential oil, pineapple essence and commercial perfume). The values of the root mean square error of prediction (RMSEP) and of the root mean square error of the percentage deviation (RMSPD) obtained were 0.4% (v/v) and 7.2%, respectively. Additionally, a second model was built and used to evaluate the accuracy of the method. A model to quantify the essential oil of lemon grass was built and its concentration was predicted in the validation set and real perfume samples. The RMSEP and RMSPD obtained were 0.5% (v/v) and 6.9%, respectively, and the concentration of the essential oil of lemon grass in perfume agreed to the value informed by the manufacturer. The result indicates that the MCR algorithm is adequate to resolve the target chromatogram from the complex sample and to build multivariate models of GC × GC-FID data.     

Phase Behavior of Poly(Oxyethylene)–Poly(Oxypropylene)–Poly(Oxyethylene) Block Copolymer in Water and Water–C12EO5 Systems

Abstract

The binary phase diagram of a triblock copolymer poly(oxyethylene) (PEO) poly(oxypropylene) (PPO) poly(oxyethylene) (PEO), (PEO)₃₇(PPO)₅₈(PEO)₃₇ or P105 in water and the ternary system of P105, water, and pentaoxyethylene dodecyl ether (C₁₂EO₅) has been studied to understand the miscibility of a small amphiphile, C₁₂EO₅ and a copolymer, as well as the mixing effect on the formed liquid crystalline structures. Phase diagrams, small angle x‐ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize these systems. The phase diagram of the binary system is presented together with the characteristic parameters for founded phases, namely, cubic, hexagonal, and lamellar phases. In the ternary system it was found that the small amphiphile and the block copolymer, despite having very different chain lengths are essentially miscible forming single phases. A large amount of C₁₂EO₅ can be solubilized in the P105 aggregates whereas P105 is most difficult to dissolve in the C₁₂EO₅ aggregates because of the difference in the molecular size. The copolymer is practically insoluble in the lamellar phase of C₁₂EO₅ due to the packing constraint. Hence, two lamellar phases coexist in a surfactant‐rich region, at W _s  = 0.66, where W _s is the weight fraction of the total amphiphile in the system. This indicates that the thickness of the lipophilic part of the C₁₂EO₅ lamellar phase is too small to allocate the large lipophilic chain of the P105 triblock copolymer.