优化双圆弧拟合

本文提出一种优化双圆弧拟合的新算法，它采用的方法是用改变双圆弧联结点的切线使双圆弧与样条曲线间的法向误差达到最小（或小于允许误差），与其他双圆弧拟合方法相比较，该算法计算简单，线性，并可消除拟合曲线的不稳定性，拟合效果快速，良好。可直接应用于雕塑曲面的ＣＮＣ加工中。     

Finite Element Analysis of a Moving Boundary Value Problem

A finite element formulation and the solution of a set of nonlinear coupled heat and mass transfer equations for a two-phase system with a moving evaporation interface is presented. The interface condition takes into account the moisture transfer balance at the moving boundary. The finite element results were compared with existing results for a single phase system for model validation. In the two-phase system, the movement of evaporation front has an appreciable effect on the temperature and moisture distribution inside the porous medium during drying. The effect of the nondimensional heat of vapourization parameter γ on the evaporation front, temperature and moisture distribution in porous medium was studied. The higher the value of γ, the slower is the movement of the evaporation front. The temperature decreased and the moisture content increased as the nondimensional vapourization parameter γ increased. This model has potential applications in studying the heat and mass transfer characteristics in food and biomaterials.     

大型储罐的罐壁设计

根据十万立方米浮顶油罐罐壁板应力测试的实测结果，运用应力分析程序，对罐壁板应力分布情况进行了分析和比较，通过调整罐壁板的厚度，使新设计储罐的罐壁板应力分布更加均匀、合理。     

等距码的对偶距离分布及其性质

本文主要讨论了等距码的对偶距离分布及其性质，然后利用这些性质将［１］中的某些结果推广到ｑ元等距码情形，并得到了其对偶距离分布的递推关系式，最后，本文给出了ｑ元等距码的码字数目的一个上界。     

分子结构对增塑聚氯乙烯性能的影响

研究了聚合度、分子量分布和支化结构对增塑聚氯乙烯加工流变性能和物理力学性能的影响。结果表明，增塑ＰＶＣ的加工流变性能随聚合度的增加而恶化；拓宽分子量分布和引入支化结构均有利于加工流变性能的提高；增塑ＰＶＣ的拉伸强度随聚合度的增加而提高，而压缩永久变形却随之减小；分子量分布对物理力学性能的影响不大；支化ＰＶＣ的拉伸强度略有下降。     

A method for multi-parameter PDF estimation of random variables

The probability distribution function (PDF) of a random variable Z is approximated with c·e^Q(z), where Q(z) is a polynomial function and c is normalizing constant. Based upon the weighted residual method, general linear algebraic equations have been derived for the evaluation of the unknown parameters in the polynomial. Numerical examples are presented and the results show that the PDFs obtained using the proposed method converge to those obtained from Monte Carlo simulation as the number of parameters in the approximate PDF increases.     

柱形颗粒群直径分布的激光衍射测量技术

提出了用激光衍射功率谱方法测量柱形颗粒群直径分布的技术方法，解决了长颗粒随机排列时的功率谱探测，及数据快速优化方法等技术难题。此技术已地应用于由羊毛和化纤截成的柱形颗粒群直径分布的测量，实现结果证明了此技术的可行性和实用性。     

Workload Distribution in Fault Simulation

Simulation at the gate level is computationally very expensive.Parallel processing is one technique to reduce simulation time.Possessing knowledge of the distribution of computational activity insimulation can aid in parallelizing it efficiently. We present a newcharacterization of the distribution of the computational workload infault simulation. An empirical analysis shows that the workloaddistribution is circuit specific, and is largely independent of thevector set being simulated. An inexpensive method to predict theworkload distribution is also discussed.     

Air Filtration and Radon Decay Product Mitigation

Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased.