大跨度双向BOX管钢桁架施工技术

大跨度钢桁架的吊装施工通常需要大型吊装设备的支持,文章依托实际工程实例,针对场地狭小、工况复杂等不利条件的大跨度双向BOX管钢桁架的吊装工程,提出以支撑架为作业承重平台的多段施工方案,并对该方案的具体施工方案及安全性进行了阐述、分析。     

300MW及以下机组汽机发电机定子吊装方法的选择

文章阐述了汽机发电机定子吊装方法,并根据吊装能力和本单位传统吊装方法介绍了如何确定定子的吊装方法,即汽机房主要设备的吊装方案应根据机组的容量、布置形式、设备重量、行车提升能力、行车台数、施工单位所拥有的机具及习惯性成熟的施工方案来确定,只有这样才能保证定子吊装工作能够达到尽可能地快速、高效、安全。     

大型多跨桁架整体吊装施工技术应用

以普光气田某多跨桁架为实例,阐述了在山区复杂自然地理环境下,场地狭小跨越工程困难,施工设备到达现场困难的情况下,通过对桁架施工方案的选择,最终选择使用大型吊装设备进行吊装,并对方案进行验算,确保了桁架整体吊装施工技术的成功,取得了较好的效益,解决了山区场地狭小的施工难题。     

浅谈MDSOLIDS软件在吊装方案编制过程中的应用

在大型电力建设工程项目规划和施工过程中,大型设备吊装工程起到举足轻重的作用。吊装方案的编制直接影响到吊装工程成本,吊装工程的安全施工。随着信息技术的不断发展,计算机软件越来越多的应用到吊装方案编制及其计算过程,不仅能够提高吊装计算准确度,而且能够大大节省方案编制时间。     

1280立方高炉主吊设备技术选型初探

文章就中大型高炉主体及设备吊装过程的共性问题进行了总结,对正确选取吊装设备、制定合理的吊装方案,主要吊装步骤、吊装准备工作以及吊装安全技术措施等进行了探讨.     

上跨营运线门式墩钢盖梁吊装施工技术

本文依托安九铁路安庆北特大桥46#-52#墩上跨高铁营运线门式墩钢盖梁吊装施工案例，详细介绍了钢盖梁吊装设备选型、设备运行场地处理、起吊点设置与验算、吊装工艺、钢梁与墩柱定位技术及施工安全管控措施。明确上跨高铁营运线门式墩钢盖梁吊装施工关键技术技术参数，为高精度安全吊装、施工质量控制及施工安全管控奠定了基础，为类似上跨营运线工程提供一定的参考。     

300MW火电机组锅炉汽包吊装方案

在电力工程火力发电厂的施工建设中大型起重机械贯穿整个施工过程的的始末,对于大件设备如锅炉汽包、锅炉大板梁、发电机定子等等设备的吊装就位更是需要制定合理的吊装方案,其中吊装机具的选择将直接影响着施工作业的安全、质量、进度和成本.一般来说大容量锅炉的汽包设计采用采用滑轮组和卷扬机或采用液压提升装置来提升,但是作为300MW火电机组的锅炉汽包的吊装就位无论从经济成本还是从工期的方面来考虑,采用卷扬机和滑轮组的方法都是首选.     

除尘器吊装方案研究

电袋除尘器多采用塔式起重机吊装方案进行施工,施工工序比较系统规范。文章通过研究除尘器吊装方案分别用塔式起重机和履带吊的不同方案,在吊装灰斗、壳体板、喇叭口等方式上的不同,分析了两种方案的优缺点,并以10t塔式起重机吊装和70t履带吊吊装为例作比较研究。     

韩城第二发电厂锅炉汽包吊装

在火电施工中,锅炉汽包吊装一直是一项很重要的施工项目,如何利用炉顶结构和选择合理的吊装机具,实现汽包安全快速吊装就位是我国大多数电力安装施工企业都会遇到的问题。文章主要介绍了韩城第二发电厂新建工程锅炉安装时汽包吊装方案制定过程、存在的问题及对策,对类似汽包吊装有借鉴作用。     

大跨度钢管桁架分块吊装施工技术

大跨度钢桁架结构在施工中具有跨度大、单构件重量重、拼装精度要求高等特点,其施工方法选择的正确与否显得尤为重要。本文结合工程实例,全面阐述大跨度钢桁架吊装方法、过程控制、分块组合方案及重难点控制,通过优化吊装工序的施工工艺,详细的制定出了安全可靠、施工简单有效,且经济实用的大跨度钢桁架施工技术方案,保证了吊装质量,提高了施工速度,同时在一定程度上降低了钢桁架施工安全和成本风险。     

Optimality results on orthogonal arrays plus <Emphasis Type="Italic">p</Emphasis> runs for <Emphasis Type="Italic">s</Emphasis><Superscript><Emphasis Type="Italic">m</Emphasis></Superscript> factorial experiments

The optimality of designs obtained by adding p runs to an orthogonal array is studied for experiments involving m factors each at s levels. The optimality criterion used here, is the Type 1 criterion due to Cheng (1978) which is an extension of Kiefer (1975) universal optimality criterion. Unlike what happens with orthogonal array plus one run designs, the behavior of designs obtained via augmentation of an orthogonal array by p runs depends on the particular runs added.     

Measuring process capability index <Emphasis Type="Italic">C</Emphasis><Subscript><Emphasis Type="Italic">pm</Emphasis></Subscript> with fuzzy data

The process capability index C _pm , which considers the process variance and departure of the process mean from the target value, is important in the manufacturing industry to measure process potential and performance. This paper extends its applications to calculate the process capability index [(C)\tilde]_pm{\tilde {C}_{pm} } of fuzzy numbers. In this paper, the α-cuts of fuzzy observations are first derived based on various values of α. The membership function of fuzzy process capability index [(C)\tilde]_pm{\tilde {C}_{pm} } is then constructed based on the α-cuts of fuzzy observations. An example is presented to demonstrate how the fuzzy process capability index [(C)\tilde]_pm{\tilde {C}_{pm} } is interpreted. When the quality characteristic cannot be precisely determined, the proposed method provides the most possible value and spread of fuzzy process capability index [(C)\tilde]_pm{\tilde {C}_{pm} }. With crisp data, the proposed method reduces to the classical method of process capability index C _pm .     

Maximal Rank Minimum Aberration Foldover Plans for 2<Superscript><Emphasis Type="Italic">m</Emphasis>-<Emphasis Type="Italic">k</Emphasis></Superscript> Fractional Factorial Designs

Two level regular fractional factorial designs are often used in industry as screening designs to help identify early on in an experimental process those experimental or system variables which have significant effects on the process being studied. In a recent paper, Li and Lin (2003) suggested a strategy for constructing optimal follow up designs using the well known foldover technique and the minimum aberration criterion. In this paper, we extend the results of Li and Lin (2003) by giving an alternate technique for constructing optimal follow up designs using the foldover technique in conjunction with the maximal rank–minimum aberration criterion suggested in Jacroux (2003).     

Top-<Emphasis Type="Italic">k</Emphasis>-lists

Top-k-lists are introduced as sequences of k-dimensional random vectors with ordered components being k largest observations from a sequence of independent identically distributed random variables. Such lists changing in time are natural stochastic models of ranking tables which appear in many situations in real life, when one wants to keep a track of several best results in a given field. Here we study basic properties of top-k-lists as joint distributions, conditional structures, representations, driving examples of top-k-lists from exponential and uniform distributions, asymptotics and a relation to generalized order statistics.     

¿Está adoptando Asia la «flexiseguridad»?

Incitados por la competencia mundial, muchos países están adaptando la reglamentación laboral al principio de la «flexiseguridad>>, que da a las empresas más flexibilidad para contratar y despedir a los trabajadores, al tiempo que ampara a éstos cuando deben pasar de un empleo a otro. El presente estudio de seis países asiáticos indica que China y República de Corea han promulgado reformas de este género; Singapur y Malasia han implantado algunos elementos de «flexiseguridad>>, pero no un seguro de desempleo, y la India y Sri Lanka han hecho pocas reformas y mantienen un modelo anticuado en el que la protección depende de la empresa. Para prestar apoyo a los trabajadores del sector informal, China, India y Sri Lanka se valen de obras públicas y de programas de fomento del trabajo por cuenta propia y de formación profesional.     

Inference by the <Emphasis Type="Italic">m</Emphasis> out of <Emphasis Type="Italic">n</Emphasis> bootstrap in nonparametric frontier models

It is well-known that the naive bootstrap yields inconsistent inference in the context of data envelopment analysis (DEA) or free disposal hull (FDH) estimators in nonparametric frontier models. For inference about efficiency of a single, fixed point, drawing bootstrap pseudo-samples of size m < n provides consistent inference, although coverages are quite sensitive to the choice of subsample size m. We provide a probabilistic framework in which these methods are shown to valid for statistics comprised of functions of DEA or FDH estimators. We examine a simple, data-based rule for selecting m suggested by Politis et al. (Stat Sin 11:1105–1124, 2001), and provide Monte Carlo evidence on the size and power of our tests. Our methods (i) allow for heterogeneity in the inefficiency process, and unlike previous methods, (ii) do not require multivariate kernel smoothing, and (iii) avoid the need for solutions of intermediate linear programs.     

Two-stage DEA: <Emphasis Type="Italic">caveat emptor</Emphasis>

This paper examines the wide-spread practice where data envelopment analysis (DEA) efficiency estimates are regressed on some environmental variables in a second-stage analysis. In the literature, only two statistical models have been proposed in which second-stage regressions are well-defined and meaningful. In the model considered by Simar and Wilson (J Prod Anal 13:49–78, 2007), truncated regression provides consistent estimation in the second stage, where as in the model proposed by Banker and Natarajan (Oper Res 56: 48–58, 2008a), ordinary least squares (OLS) provides consistent estimation. This paper examines, compares, and contrasts the very different assumptions underlying these two models, and makes clear that second-stage OLS estimation is consistent only under very peculiar and unusual assumptions on the data-generating process that limit its applicability. In addition, we show that in either case, bootstrap methods provide the only feasible means for inference in the second stage. We also comment on ad hoc specifications of second-stage regression equations that ignore the part of the data-generating process that yields data used to obtain the initial DEA estimates.     

Bayesian estimation of log odds ratios from R × C and 2 × 2 × K contingency tables

In this paper, Bayesian estimation of log odds ratios over R × C and 2 × 2 × K contingency tables is considered, which is practically reasonable in the presence of prior information. Likelihood functions for log odds ratios are derived for each table structure. A prior specification strategy is proposed. Posterior inferences are drawn using Gibbs sampling and Metropolis–Hastings algorithm. Two numerical examples are given to illustrate the matters argued.