外资如何提高内资企业生产效率——“己厂效应”还是企业间溢出?

外资进入是否有助于我国内资企业生产效率的提高？有关外国直接投资溢出效应的众多研究尚无一致结论，其中一个重要原因在于差异样本数据的使用以及对企业内部技术溢出效应的忽视。本文使用我国1998～2007年的微观企业数据，从企业内部和企业之间（包括行业内和行业间）两个角度检验了外资溢出效应，并进一步讨论了市场化进程对于外资溢出效应的动态影响。我们在近177万份观测样本中发现，外资参股能够显著提高参股企业的生产效率水平，“己厂效应”为正；外资进入对内资企业的前向关联效应显著为正，但是后向关联并不显著；外资对同行业内资企业的溢出作用是不确定的。进一步考察制度因素发现，在当前的市场化进程下，外国投资的正向溢出作用正在逐渐弱化。

Comparison of heavy metal removal efficiencies in four activated sludge processes

The removal efficiencies of heavy metals(As, Cr, Cu, Ni, Pb and Zn) were investigated in the 17 operating municipal wastewater treatment plants(WWTPs) and compared with those in four main activated sludge processes. Significant differences of heavy metal removal efficiencies were observed among four activated sludge processes. The removal efficiency for As(75.5%) in the oxidation ditch(OD) process is significantly higher than that in the conventional activated sludge(CAS) process(38.6%) or sequencing batch reactor(SBR) process(51.4%). The mean removal efficiencies for Cu and Ni in the OD process are 90.5% and 46.7%, respectively, while low mean removal efficiencies are observed for Cu(69.9%) and Ni(16.5%), respectively, in the SBR process. The removal efficiencies for Cu and Ni in the OD process are significantly higher than those in the anaerobic-anoxic-oxic(A2-O) process. These results highlight the differences of removal efficiencies for heavy metals in different processes and should be considered when selecting a wastewater treatment process.

Extraction of Cadmium from Sewage Sludge Using Polyepoxysuccinic Acid

Polyepoxysuccinic acid （PESA）, as an environmental benign biodegradable chelant, was used to remove heavy metals from the sewage sludge of Shanghai Taopu Wastewater Treatment Plant. The extraction of cadmium （Cd） from sewage sludge using aqueous solution of PESA was studied. It was found that PESA was capable of extracting Cd from the sludge, and the extraction efficiency was dependent on both pH and the concentration of the chelating reagent. The extraction efficiency decreased gradually with increasing of pH, whereas the dependency on pH decreased as the concentration of PESA increased. In the case of the high PESA to total metal ratio, e.g., 10：1, the extraction efficiency reached above 70% within the pH range from 1 to 7. The highest extraction efficiency obtained in tbe experiment was 78%. By comparing the contents of the heavy metals in sewage sludge before and after the extraction, it was found that the extracted Cd came mainly from the four fractions： acid-soluble, reducible, oxidizable, and water-soluble fractions.

Discussion on nitrogen and phosphorus removal process characteristics of improved oxidation ditch

In order to enhance efficiency of the nitrogen and phosphorus removal of sewage treatment plant, Taking Wu Long kou sewage treatment plant project in Zhengzhou as an example, this article introduces the structure, the working principle, the craft character, as well as the problems existed in the practical application of the improved oxidation ditch, and raises some corresponding processing countermeasures. Looked from the running situation of Wu Long kou sewage treatment plant, the improved oxidation ditch have certain advantages in city sewage treatment, such as high organic removing efficiency, good removing effect of nitrogen and phosphorus, low investing expenses and operating cost and so on. It is a craft that is worth promoting in urban sewage treatment.

Study on the Refineries＇ Energy Efficiency Based on SFA- Model

The study on the enterprise＇s energy efficiency is one of the most important fields of energy efficiency research. Most studies used DEA and aggregate data to estimate the energy efficiency of enterprises. In this study, based on Cobb-Douglas production function, we make a SFA model which takes the energy input and CO2 emission into account. By using the SFA model, we calculate the refineries＇ total-factor energy efficiency with Sinopec refineries＇ micro-data from 2004 to 2009. Meanwhile, we do empirical study on the factors which influence the energy efficiency. In the last, we put forward some advices so as to improve energy efficiency.

Research on hydraulic-powered roof supports test problems

The load-bearing characters of hydraulic-powered roof support with dual telescopic legs were analyzed. With a specific type hydraulic-powered roof support with dual telescopic legs for research object, the inside load test problems in factories was analyzed, and the correct test methods were given, which can enhance the test efficiency and make the factories away from the error design of hydraulic-powered roof supports and legs.

Electrochemical Treatment of Distillery Spent Wash Using Aluminum and Iron Electrodes

Electrochemical treatment of distillery .spentwash was carried out using different combinations of aluminum and iron electrodes in batch mode of operation. The spent wash was characterized for various parameters as per standard method of analysis and the treatment results were analyzed in terms of chemical oxygen demand （COD） removal efficiency o.f thespent.wash. The experiments were performed to s.tudy the effect of operating parameterssuch as current density, pH of the spent wash, agitation speed, electrolysis time and the distance between the elec- trodes on the COD removal efficiency of the spent wash. It was observed that aluminum electrodes were more suitable for treatment of distillery spent wash as compared to iron electrodes. The maximum COD removal effi- ciency of 81.3% was obtained with A1-A1 electrodes at the current density of 0.187 A.cm-2 and pH 3 for an elec-trolysis time of 2 h.

A planning model for multiple blending schemes

The key of production planning of refineries is to determine the production planning of units and blending schemes of blends in each period of the plan horizon,since they affect the effective utilization of components of refineries and hence profits.The optimization is difficult,because of many complicated product production–consumption relationships in production processes,which are closely related to the running modes of the units.Additionally,the blending products,such as gasoline and diesel,may use multiple blending schemes for their production that increase the complexity of the problem.This paper models the production planning problem as a mixed integer nonlinear programming.Computational experiments for a refinery show the effectiveness of the model.The optimal results give the effective utilization of the self-produced components and increase of the profit.

A flexible various-scale approach for soil-structure interaction and its application in seismic damage analysis of the underground structure of nuclear power plants

In simulations of geotechnical engineering, interface elements are versatile tools and are widely used in the modeling of the relative displacements between soils and structures. To consider the case of a local failure adjacent to a soil-structure interaction region, a partial mesh refinement should be performed. In this study, a three-dimensional(3 D) interface element with an arbitrary number of nodes is developed as a new technique to reduce the complexity and difficulty of managing the various scales between soil and structure. An asymmetric number of nodes is permissible on the two sliding surfaces. In this manner, soil and structure can be discretized independently, and the various-scale model is established conveniently and rapidly. The accuracy of the proposed method is demonstrated through numerical examples. The various-scale approach is employed in an elasto-plastic seismic damage analysis of a buried concrete drainage culvert of a nuclear power plant. The results indicate that by applying the proposed method, the number of elements decreased by 72.5%, and the computational efficiency improved by 59% with little influence on accuracy. The proposed method is powerful for local damage evolution analyses of both soil and structure and possesses great practical significance and the potential for further application, especially for nonlinear analysis of large-scale geotechnical engineering.