新世纪中国建筑产业竞争力形成机理动态演进规律研究——兼论加入GPA后的发展策略

中国即将加入政府采购协议,面对大量优质外资企业的进入,中国建筑市场将面临更为激烈的竞争。为此,探索中国建筑产业竞争力形成机理动态演进规律、分析目前竞争力在发展过程中存在的不足,科学引导、合理调控建筑产业的健康发展,具有重要的现实意义。基于此,本研究构建出中国建筑产业竞争力评价指标体系,并采用多指标系统评估指数法构建建筑产业竞争力评价模型,分析出2005~2008年间中国建筑产业各竞争要素重要程度的变化趋势,以描绘建筑产业竞争力形成机理动态演进规律。研究发现,中国建筑产业依旧处于劳动密集型与资金密集型的发展初级阶段、产业整体素质低、注重规模忽视效率;生产要素的简单追加投入是当前提高产业竞争能力最为有效的途径,且这种状况逐步加强。最后,剖析了中国建筑产业竞争力不强的主要原因,并有针对性地提出改善措施。     

高等学校化工安全管理课程案例教学法初探

以高等学校培养工科类专业学生为背景,探讨案例教学法在化工安全管理课程中的必要性和可行性,采用具体案例说明教学过程,并根据调查问卷的结果对案例教学法的实施效果进行评价,对不尽人意之处提出改进措施。     

Application of hydrocolloids as baking improvers

Hydrocolloids (or gums) belong to a group of biopolymers widely used in food technology. In the bakery industry, these compounds help to improve food texture and moisture retention, to retard starch retrogradation, and, finally, to enlarge the overall quality of the products during storage. Since recently, some hydrocolloids are being used due to their polymeric structure as fat replacers to obtain low calorie products and to substitute gluten in the formulation of gluten-free breads. This study describes the applications of some hydrocolloids in the bakery industry. Technological effects of these substances for different types of bakery products are also discussed.     

Sequential injection analysis (SIA) and response surface methodology: A versatile small volume approach for optimization of photo-Fenton processes

Optimization of photo-Fenton degradation of copper phthalocyanine blue was achieved by response surface methodology (RSM) constructed with the aid of a sequential injection analysis (SIA) system coupled to a homemade photo-reactor. Highest degradation percentage was obtained at the following conditions [H₂O₂]/[phthalocyanine] = 7, [H₂O₂]/[FeSO₄] = 10, pH = 2.5, and stopped flow time in the photo reactor = 30 s. The SIA system was designed to prepare a monosegment containing the reagents and sample, to pump it toward the photo-reactor for the specified time and send the products to a flow-through spectrophotometer for monitoring the color reduction of the dye. Changes in parameters such as reagent molar ratios, residence time and pH were made by modifications in the software commanding the SI system, without the need for physical reconfiguration of reagents around the selection valve. The proposed procedure and system fed the statistical program with degradation data for fast construction of response surface plots. After optimization, 97% of the dye was degraded.     

Uranium and fluorine cycles in the nuclear industry

In the nuclear fuel cycle, fluorine is currently not recycled. In this paper, we have examined the possible routes to implement such a cycle. Because UF₆ deconversion requires an excess of water, aqueous HF is produced. Two alternatives are then possible: either separate HF from H₂O or recycle the HF-H₂O in the deconversion process. Alternative UF₆ deconversion could also be implemented to resorb the high UF₆ inventory.     

浊点萃取技术的应用

浊点萃取是近年发展起来的一种新兴的萃取技术。重点阐述了浊点萃取在环境样品、生物样品和食品工业分析中的应用,总结了浊点萃取技术的优点,指出了存在的问题,探讨了该技术的发展前景。     

Urban rapid transit network design: accelerated Benders decomposition

This paper presents an urban rapid transit network design model, which consists of the location of train alignments and stations in an urban traffic context. The design attempts to maximize the public transportation demand using the new infrastructure, considering a limited budget and number of transit lines. The location problem also incorporates the fact that users can choose their transportation mode and trips. In real cases, this problem is complex to solve because it has thousands of binary variables and constraints, and cannot be solved efficiently by Branch and Bound. For this reason, some algorithms based on Benders decomposition have been defined in order to solve it. These algorithms have been compared in test networks. The project has been supported by the research project 70029/T05, from the Spanish “Ministerio de Fomento” and the research project TRA2005-09068-C03-01, from the Spanish “Ministerio de Educación y Ciencia”.     

货运列车编组调度问题的模型与算法研究

从双向编组站运输生产实际情况出发,以最大化车站发出车数和最小化车辆在站平均停留时间(中时)为目标,综合考虑解体、编组调机能力限制、到发列车车流接续、车流在站停留时间约束的影响,建立了车站货运列车编组调度问题的多目标非线性混合整数规划模型,结合该优化模型难以求解的特点,将编组调度问题分解为配流、待解车列解体和待编车列编组三个子问题,进而设计了求解该问题的分层启发式算法,对正常和特殊运输组织条件下的列车编组调度问题进行了求解.     

First passage time for multivariate jump‐diffusion processes in finance and other areas of applications

The first passage time (FPT) problem is an important problem with a wide range of applications in science, engineering, economics, and industry. Mathematically, such a problem can be reduced to estimating the probability of a stochastic process first to reach a boundary level. In most important applications in the financial industry, the FPT problem does not have an analytical solution and the development of efficient numerical methods becomes the only practical avenue for its solution. Most of our examples in this contribution are centered around the evaluation of default correlations in credit risk analysis, where we are concerned with the joint defaults of several correlated firms, the task that is reducible to a FPT problem. This task represents a great challenge for jump‐diffusion processes (JDP). In this contribution, we develop further our previous fast Monte Carlo method in the case of multivariate (and correlated) JDP. This generalization allows us, among other things, to evaluate the default events of several correlated assets based on a set of empirical data. The developed technique is an efficient tool for a number of financial, economic, and business applications, such as credit analysis, barrier option pricing, macroeconomic dynamics, and the evaluation of risk, as well as for a number of other areas of applications in science and engineering, where the FPT problem arises. Copyright © 2008 John Wiley & Sons, Ltd.     

Modelling and forecasting vehicle stocks using the trends of stochastic Gompertz diffusion models: The case of Spain

In the present study, we treat the stochastic homogeneous Gompertz diffusion process (SHGDP) by the approach of the Kolmogorov equation. Firstly, using a transformation in diffusion processes, we show that the probability transition density function of this process has a lognormal time‐dependent distribution, from which the trend and conditional trend functions and the stationary distribution are obtained. Second, the maximum likelihood approach is adapted to the problem of parameters estimation in the drift and the diffusion coefficient using discrete sampling of the process, then the approximated asymptotic confidence intervals of the parameter are obtained. Later, we obtain the corresponding inference of the stochastic homogeneous lognormal diffusion process as limit from the inference of SHGDP when the deceleration factor tends to zero. A statistical methodology, based on the above results, is proposed for trend analysis. Such a methodology is applied to modelling and forecasting vehicle stocks. Finally, an application is given to illustrate the methodology presented using real data, concretely the total vehicle stocks in Spain. Copyright © 2008 John Wiley & Sons, Ltd.