John h . cochran wrote 1928 , " the prospective resources of the country were great . the soil was deep and very rich and fertile , promising great production . 九五年启用的包括有位于侨冠超市对面的大利丰购物中心和位于李察逊市警局对面全面扩建完成的顶好商场。
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Concerned that no one coordinates the federal programs , a group of senators ? including dodd , thad cochran , r - miss . , and daniel akaka , d - hawaii ? wants to start a national foreign language coordination council 目前为止，美国军方和情治单位仍然只能彼此抢夺少数一小群合格的语言人才。印第安那大学阿拉伯语的教授约翰?沃布里吉对于阿拉伯语专家供不应求的现象感到相当忧心。
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First , this paper gives an introduction of some methods of unequal probability sampling , their estimators and variance estimators , including sampling with pps with replacement , methods of sampling without replacement suggested by brewer , durbin , sampford , des raj , murthy , rao - hartley - cochran . then , at the basis of rao and bayless ' s study , we consider that population can be splited two random subpopulations , which are respectively drawn from different infinite super - populations , and compare the stabilities of estimators of the methods that given above . we find that the minor difference between two super - populations has great effect on the efficiency of the estimators for the population with moderately large coefficient of variation ( c . v . ) 本文首先从理论上介绍了若干种不等概率抽样方法，它们的估计量、估计量的方差及其估计，其中包括有放回ppz及pps抽样，不放回不等概率抽样中的brewer 、 durbin 、 sampford 、 desraj ， murthy 、 rao - hartley - cochran等人的方法；其次，在rao和bayless两人就样本单元数n = 2的情形对上述抽样方法进行比较的基础上，将总体随机地分成两个子总体，视每个子总体取自不同的线性超总体，在文中，我们利用计算机实现随机分组，并通过画图比较各方法估计量的稳定性，结果表明，对变异系数c . v . ( x )较大的总体而言，两个超总体之间的微小差异将对估计量的稳定性产生很大的影响，从而说明rao和bayless的比较结果还不够完善。
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Two - order enhanced un - split finite volume euler method for multi - fluid flow , which combines the roe approximate riemann solver , is developed to simulate the multi - fluid interactions , such as the fluid described by polynomial eos , stiffen gas eos , jones - wilkins - lee ( jwl ) gaseous explosive eos , cochran - chan ( cc ) solid explosive eos and hom shock wave eos , etc . numerical results of the id , 2d and 3d multi - fluid interaction examples show that the high - resolution method and interface capturing equations can resolve the multi - fluid flow correctly and successfully . a simple fluid - mixture type ppm algorithm for multi - fluid flow , which is based on vof interface capturing method and resolved by langange / remap two steps , is developed to simulate the high density or high pressure ratio flow at both sides of the interface 本文提出了实用于多介质流体的增强型二阶精度有限体积欧拉数值计算方法，采用roe方法近似求解riemann问题，可以适用于多项式状态方程、 “ stiffengas ”状态方程、 jones - wilkins - lee爆轰产物状态方程、 cochran - chan固体炸药状态方程以及hom状态方程等，并对多介质流体相互作用的一维、二维、三维问题进行数值计算，数值验证了本文给出的高精度差分格式和界面捕捉方法的正确性，两种方法耦合形成的多介质流体数值计算方法是成功的。
