两种改进的超效DEA模型

对DEA有效决策单元不能排序是传统DEA模型的一大缺点。该问题也成为DEA领域研究的热点。AP模型是最常用的区分DEA有效决策单元效率值大小的超效模型,但在实际应用中却出现了无解或解不稳定的情况。国外学者新近提出的MAJ模型、LJK模型则有效解决了这两个问题,但却存在模型区分能力不强的缺点。本文分析了这两种模型缺点产生的原因、予以改进并给出理论证明。标准数据集的实验显示改进效果显著,尤其是改进后的LJK模型表现优异。

Secondary settlement estimation in surcharge preload subject to time effect of secondary consolidation coefficient

In order to eliminate the settlement underestimation in surcharge preload engineering, a study based on Bjerrum's creep diagram and the tangent slope definition of secondary consolidation coefficient was carried out to analyze the time effect of secondary consolidation coefficient of over consolidated soil, and a time–growth model for it was formulated. As Bjerrum's creep diagram is an idealized model, oedometer tests were performed to improve the above time–growth model of secondary consolidation coefficient for the purpose of achieving a better agreement with the actual ground situations. It is found that secondary consolidation coefficient of over consolidated soil not only decreases with the ratio of historical maximum to current effective stress of soil(OCR), but also increases with the development time of secondary consolidation. No matter how large OCR is, the long-term time effect of secondary consolidation coefficient of over consolidated soil is all significant. Based on the above results, a model for settlement estimation was formulated and a case study to estimate it indicates that the settlement estimated by our method is 2–5 times larger than that estimated by the previous method. Moreover, the larger the OCR is as well as the longer the service life is, the larger the difference between our method and the previous method is. Thus, the post-construction secondary settlement in surcharge preload engineering will be underestimated when neglecting the time effect of secondary consolidation coefficient in over consolidated state.

R-Parity Violation Effects on b_1 → bχ_1~0 in Minimal SupersymmetricStandard Model

We investigate in detail the effects of R-parity lepton number violation onthe decay b_1 → bχ_1~0 in the R-parity violating minimal supersymmetric standard model (R_p-MSSM)under the present experimental constraints on R_p parameters. In our numerical calculations weconsider two cases of input parameters of the squark and slepton sectors, M_(squark) 【 M_(slepton)and M_(squark) 】 M_(slepton), for comparison. The results show that the relative R-parity violatingcorrection is not very sensitive to the mass of the lightest neutralino bχ_1~0 the degenerateR-parity violating coupling parameter λ′_2 but strongly depends on M_(squark), M_(slepton) tan βand tie degenerate R-parity violating coupling parameter λ′_1. The relative correction is about -4～ 3% and can exceed -6% in some region of parameter space. Therefore, precise experiment analyseson the decay b_1 → bχ_1~0 may provide a probe of the R-parity violation.

Measurement and Comparison of Urban Haze Governance Level and Efficiency based on the DPSIR Model:A Case Study of 31 Cities in North China

In the decisive stage of developing of a moderately prosperous society in all aspects,hazy weather has become a major obstacle to the further advancement of China.Therefore,improving the level and efficiency of haze governance has become essential.Based on the DPSIR model,this paper builds a haze governance level and efficiency index system using the entropy method and the super-efficiency data envelope-analysis(DEA)model to analyze the data for 31 cities in North China from 2007 to 2016.From the aspects of spatial differences and influence factors influencing the comparative analysis,the results are as follows.(1)During the investigation period,the level and efficiency of city haze governance in North China showed a trend of fluctuation and decline,with obvious stages in their characteristics.Haze governance efficiency is much higher than its level,and its mean value reaches the DEA level which indicates that it is effective.(2)A significant regional gradient difference occurs between these two aspects.The haze governance level presents a convex distribution pattern of"east low–middle high–west low",while the haze governance efficiency presents a concave distribution pattern of"east high–middle low–west high".(3)The regression results show that economic growth has a negative effect on both haze governance level and efficiency.By contrast,the industrial structure has a positive effect on haze governance level and efficiency,but the significance of its effect on these two is different.On this basis,policy suggestions are proposed for improving the level and efficiency of haze governance in various cities in North China.

Spatiotemporal Differentiation and the Factors Influencing Eco-efficiency in China

Economic development,resource utilization,and environmental protection have always presented clear dilemmas for many countries at the national level.It is clear that the related concepts of eco-efficiency and the evaluation index can help in evaluating these associated issues.Thus,based on the use of undesirable output super Slacks-Based Measure models,this study evaluated the eco-efficiency of 30 Chinese provinces during the period between 2005 and 2016.This evaluation was conducted by analyzing the spatiotemporal dynamics and key factors influencing these changes using a panel regression model.The results of this analysis reveal that eco-efficiency gradually increased over the course of the study period,peaking at different levels among the regions.We used the conventional CV evolutionary method to show that inequalities in eco-efficiency gradually decreased at the national level.Indeed,our estimations of the factors affecting this variable suggest that industrial structure,degree of openness,urbanization,technical innovation,and environmental governance all exert significant positive influences,while energy consumption and traffic exert negative effects.The extent of the impacts of these factors on eco-efficiency varied between the different regions.

A Simulation for the Piston Effect in Supercritical Carbon Dioxide with the Non-flow Model

A simulation for piston effect in supercritical carbon dioxide by employing a simple model is conducted. In the first place, the thermal properties of carbon dioxide near its liquid-vapor critical point are discussed. It is calcu- lated that the heat capacity ratio and isobaric expansion coefficient of supercritical fluids are extremely high. Furthermore, the simulation for piston effect in supereritical carbon dioxide between two infinite vertical walls is presented. The numerical results prove that piston effect has a much faster speed of heat transfer than thermal conduction under mierogravity conditions. Moreover, the piston effect turns out to be stronger when closer to the critical point.

Self-trapping and Macroscopic Tunnelling of Superfluid Fermi Gases in Multi-well Potentials

We study the tunnelling dynamics of superfluid Fermi gases trapped in multi-well system along the BEC-BCS crossover. Within the hydrodynamical model and by using the multi-mode approximation, the self-trapping dynamics of superfluid Fermi gases in multi-well system are obtained numerically. We find that the self-trapping to diffusion transition strongly depends on the well number. When the well number is less than three, the self-trapped state takes place easier on the BEC side than that on the BCS side. However, when the well number is larger than three, the self-trapped state takes place easier on the BCS side instead of the BEC side. Furthermore, by considering a superfluid of 40K atoms, we obtain the zero-mode and π-mode Josephson frequencies of coherent atomic oscillations in double-well system. It is noteworthy that the Josephson mode, especially, the existence of π-mode frequency strongly depends on the atoms number on the BCS side.

Bed expansion behavior and sensitivity analysis for super-high-rate anaerobic bioreactor

Bed expansion behavior and sensitivity analysis for super-high-rate anaerobic bioreactor （SAB） were performed based on bed expansion ratio （E）, maximum bed sludge content （Vpmax）, and maximum bed contact time between sludge and liquid （Tmax）. Bed expansion behavior models were established under bed unfluidization, fluidization, and transportation states. Under unfluidization state, Ewas 0, Vprnax was 4867 ml, and rmax was 844-3800 s. Under fluidization state, E, Vpmax, and Tmax were 5.28%-255.69%, 1368-4559 ml, and 104-732 s, respectively. Under transportation state, washout of granular sludge occurred and destabilized the SAB. During stable running of SAB under fluidization state, E correlated positively with superficial gas and liquid velocities （Ug and ul）, while Vpmax and Tmax correlated negatively. For E and Vpmax, the sensitivities of ug and ul were close to each other, while for Tmax, the sensitivity of ur was greater than that of Ug. The prediction from these models was a close match to the experimental data.