Characterization of hollow fiber membranes in a permeator using binary gas mixtures

We have studied the CO₂/CH₄ mixed gas permeation through hollow fiber membranes in a permeator. An approach to characterize the true separation performance of hollow fiber membranes for binary gas mixtures was provided based on experiments and simulations. Experiments were carried out to measure the retentate and permeate flow rates and compositions at each outlet. The influences of pressure drop within the hollow fibers, non-ideal gas behavior in the mixture and concentration polarization were taken into consideration in the mathematics model. The calculation results indicate that the net influence of the non-ideal gas behavior, competitive sorption and plasticization yields the calculated CO₂ permeance in a mixed gas permeator close to that obtained in pure gas tests. Whereas the CH₄ permeance is higher in the mixed gas tests than that in the pure gas tests, as the plasticization caused by CO₂ dominates the permeation process. As a result, the CO₂/CH₄ mixed gas selectivity is smaller than those obtained in pure gas tests at equivalent pressures.The calculated membrane performance shows little changes with stage cut if the effect of concentration polarization is accounted for in the calculation. The integration method developed in this study could provide more accurate characterizations of mixed gas permeance of hollow membranes than other estimation methods, as our model considers the roles of non-ideal gas behavior and concentration polarization properly.     

Use of Explosives on The Moon

The utilization of explosives for excavation on the lunar surface is under serious consideration as a part of the design for construction of temporary and permanent bases. An excavation research program has shown that small‐scale explosives blasting in a lunar‐soil simulant will greatly reduce the digging forces required for scoop and dragline excavators. Some crater‐blasting parameters were determined for the lunar soil simulant at one Earth gravity and at 10 Earth gravities using a centrifuge. The size of the craters produced at 10 Earth gs matched those formed at one earth g by scaling according to the weight of the explosive. These data can be applied to explosive‐excavation problems such as habitat construction, burial of nuclear power sources, and the rapid construction of shelters remote from the main base to shield against solar‐flare activity.     

换热网络数值模拟稳定性分析

换热网络的数值模拟在换热网络的定量分析中起着重要作用。但在模拟计算中,有时表现出数值稳定性差。提高数值稳定性的方法,目前多通过改善算法来实现。本文通过对换热网络数值模拟的误差分析,提出了误差放大因子的概念,并依此选择迭代变量。通过对迭代变量的选择,达到提高换热网络数值模拟稳定性的目的。     

A generalized gamma distribution with application to drought data

Gamma distributions are some of the most popular models for hydrological processes. In this paper, a very flexible family which contains the gamma distribution as a particular case is introduced. Evidence of flexibility is shown by examining the shape of its probability density function (pdf). A treatment of the mathematical properties is provided by deriving expressions for the n th moment. Estimation and simulation issues are also considered. Finally, a detailed application to drought data from the State of Nebraska is illustrated.     

Simulation of Temperature Distribution in Stored Wheat without Aeration

A neural-deterministic simulation model applied for calculating distributions of temperatures and moisture content in a bed of wheat stored in a steel silo without aeration is presented in the article. The model consists of differential equations of heat and moisture transfer, initial and boundary conditions, and three artificial neural networks used during simulated ambient air conditions. Experiments and computer simulations were carried out in order to determine temperature fields in wheat grain stored in a steel silo for two months. The computer simulations were carried using MATLAB and FEMLAB software. The difference between measured and simulated temperature in grain near the silo wall at a height of 2.5 m from the bottom was less than 3.0°C. On the basis of the analysis performed it was concluded that the temperature distributions obtained with the model were consistent with the measured results obtained for grain stored in a steel silo without aeration.     

低压铸造流动与传热耦合计算的研究

根据低压铸造充型流动的特点 ,利用计算机数值模拟技术 ,对低压铸造充型阶段的流动怀传热过程进行了耦合计算 ,从而保证了模拟结果的准确性和可靠性。在此基础上开发出了模拟软件 ,并对实际低压铸件进行了模拟分析 ,结果与实际生产情况吻合很好     

运输包装件振动特性的计算机仿真

应用有限元法对计算机主机在运输过程中的振动特性进行了计算机仿真。首先利用Pro/E建立几何模型，然后基于ANSYS进行有限元动力分析，求出了包装件的固有频率与固有振型，以及频域／时域的动态响应。     

77K MOSFET计算机模拟增量限制方法

对低温器件计算机模拟方法作了具体的考虑。从求解变量和半导体物理意义出发，数值计算结果事先有一个定性范围，如果每一次循环的迭代初值都修正到这个数值范围内，那么选代过程将以更快的速度接近真解。提出了适用于低温半导体器件计算机模拟的增量限制方法，并且将该方法插入ＭＩＮＩＭＯＳ４．０进行了数值实验。结果表明，设置增量限制能保证低温半导体器件模拟的数值收敛性，并巨有较快的收敛速度。     

带FPGA的PCI接口应用

文章介绍了一种带FPGA的PCI接口的应用及设计方法。该方法将PCI接口和PCI用户逻辑集成在一片FPGA里，可以对整个逻辑进行仿真测试，大大缩短了开发周期，提高了系统集成度和性能。文章重点叙述了Quicklogic公司提供的32wug TARGET接口芯片QL5030的原理和结构，分析了时序设计要点，给出了典型应用的逻辑框图和注意事项。     

一种快速的海面特征SAR成像仿真技术

水下物体运动引起扰动，会在海面产生尾迹。这种尾迹特征同运动物体的参数和下潜的深度以及海况有关。研究这种尾迹特征及其合成孔径雷达(SAR)成像，就有可能利用SAR来检测这个水下运动物体。本文给出了一种水下运动物体的伴流尾迹的快速模拟方法及其合成孔径雷达(SAR)成像仿真方法，并对模拟仿真的结果进行了讨论。