Using the von thunen model the author analyzes the mechanism for the rise in urban commercial house price and draw the following conclusions : when the urban commercial house price difference between central area and peripheral area is equal to or more than the cost to reside in peripheral area , rational buyers tend to buy commercial houses in peripheral area ; with the reduction of the cost to reside in peripheral area , the urban commercial house price level in central area tends to be close to that in peripheral area ; given that the cost to reside in peripheral area is fixed , the urban commercial house price level in peripheral area is restricted by the price level in central area 摘要借鉴冯?杜能模型分析城市商品房价格上涨机理，可得出以下结论：当购买城市周边区商品房相比购买中心区商品房少支付的房价大于等于居住周边区所需多支付的居住成本时，理性购买者会作出购买周边区商品房的决策；随着周边区相比居住周边区居住成本的降低，周边商品房价格水平会趋近于中心区商品房价格水平；当周边区居住成本相对稳定时，周边区商品房价格水平受制于中心区商品房价格水平。
In this paper . flow properties of multistage fluidized - bed bioreactor with external circulation at a pilot scale is studied . according to characteristic analysis , the model of completely mixing reactor in series is introduced to characterize real reactor as a theoretical model . on the basis of analog computing analysis and discussion of theoretical model . by means of pulse tracer method , experiments on residence time distribution ( rtd ) have been done in different conditions including the change of tracer level , feeding flow rate and circulation flow rate . the result shows when the ratio of circulation flow rate and feeding flow rate amounts to at least 4 , the flow properties of multistage fluidized - bed bioreactor with external circulation at a pilot scale is very close to the model of completely mixing reactor in series . an amendatory model has been established by the regression method 作者首先在对反应器进行特征分析的基础上，建立了描述中试规模多级外循环流化床生物反应器流动特性的串级全混流模型，并对理论模型进行了模拟计算分析和讨论，在此基础上，作者分别在无循环和有循环(改变示踪剂用量、流加流量和循环流量)的条件下，利用脉冲示踪法对一到五级串联外循环流化床反应器进行了停留时间分布实验，结果表明，在循环流量与流加流量的比值达到大于等于4时，中试规模多级外循环流化床反应器的流动特性接近串级全混流模型，通过数据回归拟合的方法，建立了中试规模一到五级串联外循环流化床反应器的流动模型。
( 3 ) inbreeding population to the population that the inbreeding coefficient is f , the population information entropy is a increase function when reach equilibrium in random matting system , that is when fix the f , the population have the largest information entropy ; population information entropy large or equal to the gene distribution entropy , less or equal the two time of gene distribution entropy ( 3 )近亲繁殖群体证明了近交系数为f的群体在随机交配下达到平衡的群体信息熵是f的增函数，即f固定时，其值最大；群体信息熵大于等于基因库信息熵，小于等于基因库信息熵的两倍。
The maximum entropy principle were used to follow population : ( 1 ) mutiallel population in all population that have the given gene distribution , the equilibrium population entropy reach it ' s maximum , the maximum entropy more than 0 , and less than 2 nk ( k is the number of the allel ) , and maximum entropy equal two times of the same locus gene entropy ( 1 )复等位基因群体对具有同一基因库的复等位基因位点，用最大熵证明了该位点所对应的所有群体中，平衡群体的基因型熵最大，其数值大于等于0 ，小于等于21nk (这里k为该位点等位基因数目) ，且等于该位点基因库熵的两倍。
