中国城市公共交通行业技术效率实证研究

本文选取1999-2004年间中国城市公共交通行业的面板数据,在Cobb-Douglas函数的基础上运用随机边界法对我国城市公共交通行业的技术效率进行了考察,并从时间、地域、交通工具类型和客运规模方面,分析了该行业的效率差异及其产生原因,旨在为该行业的未来发展和管制改革提供决策依据。研究结果表明,我国城市公共交通行业技术效率情况为:近几年虽有小幅上升,但基数总体不高;东部地区技术效率偏高;客运量大和拥有轨道交通的省市的技术效率较高。     

Analytic Solution for Diffusional Filtration across Granular Beds in Low Knudsen Number Regime

The collection efficiency of aerosols in the low Knudsen number region was studied using a system of multiple spheres. Kuwabara's free vorticity model was expanded to include the effects of gas slip at the collector surface, with the collection efficiency due to diffusion obtained analytically and compared with existing experimental results. The results showed that the diffusional collection efficiency increases as the Knudsen number increases due to gas slippage at the collector surface. The obtained analytical solution converged to the existing collection efficiency of a solid sphere system with a Knudsen number of zero, and that of a bubble with an infinite Knudsen number. The comparison of the experimental results with analytic solution in this study shows that the trends agree well. Therefore, this study is a subsequent expansion of the collection efficiency in the finite Knudsen number region, and can be used for a broad range of collector sizes, pressures and temperatures.     

Improved maximum-likelihood estimation for the common shape parameter of several Weibull populations

The biasness problem of the maximum-likelihood estimate (MLE) of the common shape parameter of several Weibull populations is examined in detail. A modified MLE (MMLE) approach is proposed. In the case of complete and Type II censored data, the bias of the MLE can be substantial. This is noticeable even when the sample size is large. Such a bias increases rapidly as the degree of censorship increases and as more populations are involved. The proposed MMLE, however, is nearly unbiased and much more efficient than the MLE, irrespective of the degree of censorship, the sample sizes, and the number of populations involved. Copyright © 2007 John Wiley & Sons, Ltd.     

集值优化问题超有效解的Lagrange最优性条件

在局部凸空间中考虑约束集值优化问题（VP）在超有效解意义下的Lagrange最优性条件．在近似锥-次类凸假设下，利用择一性定理得到了（VP）取得强有效解的必要条件，利用超有效解集的性质及超有效解的定义给出了（VP）取得超有效解的充分条件，最后给出了一种与（VP）等价的无约束规划．     

函数方程求根的一种新型大范围收敛迭代法

1引言实际解函数方程f(x)=0(z∈[α,β],f(α)f(β)＜0,f(x~*)=0)时,人们常常希望选用那些仅计算函数值,具有大范围收敛性且效率较高的方法,特别对那些表示式复杂的函数以及病态函数．例如,那种仅在的某个充分小邻域内连续,而在该邻域之外光滑性很差的函数；那种在初始含根区间(α,β)上起伏多变的函数；那种|f(α)|和|f(β)|差别甚大,而x~*又十分靠近绝对值较大者一端的函数等等,这种欲望就更加强烈．     

集成光学TM模偏振器的制作

用扩钛和质子交换相结合的方法在ｘ切ｙ传ＬｉＢｎＯ３衬底上制成了ＴＭ模集成光波导偏振器。质子交换区位于扩钛波导的末端两侧。在质子交换区域Δｎｅ〉０，Δｎ０〈０，因此ＴＥ模辐射进入衬底。偏振器工作于１．３μｍ波长，消光比优于４７ｄＢ，光纤０－波导－光纤插入损耗３．５ｄＢ。     

色分离光栅镀膜减反技术研究

 根据惯性约束聚变系统技术要求，提出一种镀膜减反方案，以解决现有光栅由于元件表面反射影响衍射效率的问题。对色分离光栅镀膜减反技术进行了详细的分析，根据标量理论给出了镀膜光栅的各项技术要求，优化了光栅结构参数。模拟计算结果发现，光栅表面反射几乎完全消除，表明可以通过色分离光栅镀膜减反提高衍射效率的目的。该镀膜光栅刻槽深度的优化值为2.84μm，膜厚为等效1/4波长，即71.2nm。     

Microwave enhanced greener synthesis of indazoles via nitrenes

Non-traditional methods (grinding, water-based biphasic reactions, microwave chemistry) were used for the preparation of Schiff bases from several amines and 2-nitrobenzaldehydes. These nitro compounds were allowed to react with triethyl phosphite under microwave irradiation for the generation of nitrenes that underwent insertion reactions to form indazoles. This procedure constitutes an energy-efficient, greener chemistry version of the Cadogan reaction for nitrene-based formation of nitrogen heterocycles.     

Alternating fluorene copolymers containing isothianaphthene derivatives: A study of their aggregation properties and small band gap

Several fluorene copolymers containing isothianaphthene units ( P1 , P2 , and P3 ) or similar derivatives ( P4 and P5 ) have been synthesized by Pd‐catalyzed Suzuki polymerization. The monomers containing isothianaphthene were prepared by a ring‐closure reaction with Lawesson's reagent. Strong photoluminescence (PL) quenching in the film state was observed for P1 and P2 , which was mainly due to the enhanced quinoid character formed by introducing the isothianaphthene unit. Their energy levels of the compounds were determined using cyclic voltammetry. Among the polymers tested, the polymer containing both an isothianaphthene and a selenophene unit, P2 , showed the smallest band gap of 1.85 eV. The influence of structural variation on the band gap of the polymer chains was further investigated by optimizing the geometries of several model monomers. Our results based on the optical and electrochemical properties combined with theoretical calculations showed that polymers containing isothianaphthene have small band gaps, rigid conformations, and strong tendencies to aggregation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3573–3590, 2008     

Minimum distance estimation in linear regression with unknown error distributions

This paper discusses minimum distance (m.d.) estimators of the paramter vector in the multiple linear regression model when the distributions of errors are unknown. These estimators are defined in terms of L₂-distances involving certain weighted empirical processes. Their finite sample properties and asymptotic behavior under heteroscedastic, symmetric and asymmetric errors are discussed. Some robustness properties of these estimators are also studied.