首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Fuzzy Approach to Prequalifying Construction Contractors   总被引:1,自引:0,他引:1  
Construction contractor prequalification (CCPQ) is a crucial decision making process to select capable potential bidders and ensure the success of construction projects. The purpose of CCPQ is to guarantee a contractor’s characteristic to meet the construction project’s requirements, which has been established worldwide as a standard practice. However, existing methods, i.e., marking method, subjective judgment method, etc., for contractor prequalification have been inadequate because it is difficult for decision makers to investigate contractor’s capabilities against inexact, vagueness, and qualitative criteria. The objective of this paper is to propose a fuzzy framework-based fuzzy number theory to solve construction contractor prequalification issues, which include decision criteria analysis, weights assessment, and decision model development. Finally, a case study for a tunnel construction project was used to demonstrate the feasibility of fuzzy approaches.  相似文献   

2.
The design–build procurement route is gaining popularity and being extensively used by many clients. Scrutinizing the capabilities of design–build “candidate” organizations (who submit proposals for prequalification/short listing), is a complex task that demands the evaluation of several quantitative and qualitative attributes. The crucial task of design–builder prequalification needs multidisciplinary expertise that often poses tough challenges to many construction clients. A Hong Kong based cross-sectional research study of various international clients’ design–builder selection approaches unveiled several selection strategies and criteria used; and benchmarked some best practices. Based on such consolidated knowledge, a structured design–builder selection model was developed. The conceptualized frameworks for design–builder prequalification are described in this paper. An overview of the development and preliminary validation of a prototype web-based decision support system for design–builder prequalification is also presented in this paper.  相似文献   

3.
Contractor selection is the process of selecting the most appropriate contractor to deliver the project as specified so that the achievement of the best value for money is ensured. Construction clients are becoming more aware of the fact that selection of a contractor based on tender price alone is quite risky and may lead to the failure of the project in terms of time delay and poor quality standards. Evaluation of contractors based on multiple criteria is, therefore, becoming more popular. Contractor selection in a multicriteria environment is, in essence, largely dependent on the uncertainty inherent in the nature of construction projects and subjective judgment of decision makers (DMs). This paper presents a systematic procedure based on fuzzy set theory to evaluate the capability of a contractor to deliver the project as per the owner’s requirements. The notion of Shapley value is used to determine the global value or relative importance of each criterion in accomplishing the overall objective of the decision-making process. The research reported upon forms part of a larger study that aims to develop a fuzzy decision model for construction contractor selection involving investigating multiple criteria selection tendencies of construction clients, relationship among decision criteria, and construction clients’ preferences of criteria in the contractor selection process. An illustration with a bid evaluation exercise is presented to demonstrate the data requirements and the application of the method in selecting the most appropriate contractor for the project under uncertainty. The proposed model is not intended to supplant the work of decision-making teams in the contractor selection process, but rather to help them make quality evaluations of the available candidate contractors. One major advantage of the proposed method is that it makes the selection process more systematic and realistic as the use of fuzzy set theory allows the DMs to express their assessment of contractors’ performance on decision criteria in linguistic terms rather than as crisp values.  相似文献   

4.
An accurate prediction of contractor potential is of vital importance during contractor selection and evaluation process. Such prediction enables identification and classification of contractor performance to ease the selection process. This paper outlines the use of clients' tender evaluation preferences for predicting a contractor performance via a logistic regression (LR) approach. A total of 31 clients’ tender evaluation criteria were selected to develop a LR model for predicting contractor performance. The proposed model was developed based on 48 of United Kingdom public and private construction projects and validated in 20 independent cases. It was found that 75% of the cases correctly and the model statistically accurate for contractor performance prediction, where the input variables consist of nominal and interval data. The paper summarized techniques and advantages of LR analysis and discussed literature findings of contractor selection and evaluation methodologies undertaken by construction researchers and commentators from the United Kingdom and Northern America.  相似文献   

5.
Contractor prequalification involves the screening of contractors by a project owner to determine their competence to complete the project on time, within budget, and to expected quality standards. The process of prequalification involves a large number of contractors, each being represented by many attributes. A neural network model was applied to aid in the prequalification process by classifying contractors into groups based on similarity in performance using the financial ratios of liquidity, activity, profitability, and leverage. Contractors are represented in this model by patterns in four-dimensional space. Patterns of similar performance tend to form clusters intercepting regions of low pattern density in between. A neuron with weights is used as a classifier to set a decision boundary between clusters. The method basically iterates the neuron weights to move the decision boundary to a place of low pattern density. Then, the statistical hypothesis testing of the mean difference of two independent samples was used to validate the classification of the parent class to the two child classes considering the four ratios separately. The method was used hierarchically to classify a group of 245 contractors into classes of small numbers. Finally, the inferred procedure of classification proves that the neural network model classified the four-dimension pattern representing contractors efficiently.  相似文献   

6.
注意力缺陷多动障碍(ADHD)是儿童期最常见的精神疾病之一,在大多数情况下持续到成年期。近年来,基于功能磁共振数据的ADHD分类成为了研究热点。文献中已有的大多数分类算法均假设样本是均衡的,然而事实上,ADHD数据集通常是不平衡的。传统的学习算法会使得分类器倾向于多数类样本,从而导致性能下降。本文研究了基于不平衡神经影像数据的ADHD分类问题,即基于静息状态功能磁共振数据对ADHD进行分类。采用功能连接矩阵作为分类特征,提出了一种基于多目标支持向量机的ADHD数据分类方案。该方案将不均衡数据分类问题建模为具有三个目标的支持向量机模型,其中三个目标分别为最大化分类间隔、最小化正样本误差和最小化负样本误差,进而正负样本经验误差可以被分开处理。然后采用多目标优化的法向量边界交叉法对模型进行求解,并给出一组代表性的分类器供决策者进行选择。该方案在ADHD-200竞赛的五个数据集上进行测试评估,并与传统分类方法进行对比。实验结果表明本文提出的三个目标支持向量机分类方案比传统的分类方法效果好,可以有效的从算法层面解决数据不平衡问题。该方案不仅可用于辅助ADHD诊断,还可用于阿尔茨海默病和自闭症等疾病的辅助诊断。   相似文献   

7.
Total conceptual cost estimates and the assessment of the quality of these estimates are critical in the early stages of a building construction project. In this study, the support vector machine (SVM) model for assessing the quality of conceptual cost estimates is proposed, and the application of SVM in construction areas is investigated. The results show that the SVM model assessed the quality of conceptual cost estimates slightly more accurately than the discriminant analysis model. This shows that using the SVM has potential in construction areas. In addition, the SVM model can assist clients in their evaluation of the quality of the estimated cost and the probability of exceeding the target cost, and in their decision on whether or not it is necessary to seek a more accurate estimate in the early stages of a project.  相似文献   

8.
The construction industry has witnessed the failure of many contractors due to varying reasons such as financial problems, poor performance, or accidents arising from the lack of adequate safety consideration at worksites. All these incidents have led to the impression that the current system of awarding the contracts is inefficient in selecting the contractor capable of meeting the demands and challenges of present times and hence needs to be reviewed accordingly. Therefore, in an attempt to investigate the current situation of the Singapore construction industry a questionnaire survey was conducted for accruing the data required to identify the important contractor selection criteria (CSC) and to draw upon construction practitioners’ opinions regarding the importance of those CSC in assessing the capabilities of the candidate contractors during the selection process. The research reported upon forms part of a larger study that aims to develop a computer-interactive multicriteria decision system for contractor selection involving identification of CSC for inclusion in the system, investigation of CSC preferences of construction practitioners, and establishment of weights for those CSC from their perceived importance determined through the questionnaire survey of Singapore construction practitioners. The study highlights that there are statistically significant differences in opinions regarding the degree of importance assigned to some CSC among public clients, private clients, and contractors. Findings from the study may act as an aid in improving the Singapore construction industry by helping construction clients identify multiple CSC apart from cost which should always be considered when assessing the capability of candidate contractors during the selection process, by assisting contractors in improving their attributes in line with clients’ preferences and by facilitating Singapore construction clients and researchers to develop a contractor selection system capable of assessing multiple attributes of the candidate contractors so that the risk of the project failure due to the selection of an inappropriate contractor is minimized.  相似文献   

9.
This paper presents an approach for efficiently building analytical models for nonlinear analysis. The objective has been achieved by establishing structural component model database by collecting various structural component models addressing various structural details. A common data structure and a relational database schema for storing structural component models were proposed in this study. The proposed structural component model database can serve as a decision supporting system for building nonlinear analytical models manually. In addition, the modeling information stored in this database can be presented in XML document format to be parsed and manipulated by computer system for generating nonlinear analytical model in file automatically. A school building database is used as a case study to show the feasibility of automatic modeling for nonlinear analysis using the proposed structural component database. A semiautomatic model generation system was developed to provide an efficient modeling process, which is in the manner of form filling and option selecting on web-based user interfaces, so that the model builder can focus on making engineering decisions. The modeling details are handled automatically by the proposed system based on user selection and setting.  相似文献   

10.
Model Induction with Support Vector Machines: Introduction and Applications   总被引:9,自引:0,他引:9  
The rapid advance in information processing systems in recent decades had directed engineering research towards the development of intelligent systems that can evolve models of natural phenomena automatically—“by themselves,” so to speak. In this respect, a wide range of machine learning techniques like decision trees, artificial neural networks (ANNs), Bayesian methods, fuzzy-rule based systems, and evolutionary algorithms have been successfully applied to model different civil engineering systems. In this study, the possibility of using yet another machine learning paradigm that is firmly based on the theory of statistical learning, namely that of the support vector machine (SVM), is investigated. An interesting property of this approach is that it is an approximate implementation of a structural risk minimization (SRM) induction principle that aims at minimizing a bound on the generalization error of a model, rather than minimizing only the mean square error over the data set. In this paper, the basic ideas underlying statistical learning theory and SVM are reviewed, and the potential of the SVM for feature classification and multiple regression (modeling) problems is demonstrated by applying the method to two different cases of model induction from empirical data. The relative performance of the SVM is then analyzed by comparing its results with that of ANNs on the same data sets.  相似文献   

11.
随着我国社会发展,废旧产品的数量迅速增长,废旧铝随之大量产生。铝是优良的再生资源,传统分选技术不能将废旧铝按各自的成分牌号进行精细分类,导致很多优质铝资源被降级使用,造成巨大的浪费。研究了主成分分析(PCA)结合极限学习机(ELM)算法辅助激光诱导击穿光谱(LIBS)技术在铝合金分类识别方面的应用。选用2种系列的4个牌号铝合金作为实验样品,通过LIBS技术激发实验样品获得420组光谱数据。对原始光谱数据进行了预处理,并选取样品铝合金中5种主要差异元素(Mg、Mn、Cu、Fe和Si)的21条特征谱线构成了420×21的光谱数据矩阵,通过主成分分析对光谱数据进一步降维,使得模型输入变量从21个降至8个。选取120组光谱数据作为训练集,建立了基于极限学习机的铝合金分类模型,余下300组数据作为测试集。研究发现在主要非铝元素(Mg、Mn、Cu、Fe和Si)含量差异只有0.002 1%~3.68%的情况下,PCA-ELM分类模型的平均识别准确率达到98.01%,标准差为0.82%,建模时间为0.081s。结果表明,PCA-ELM分类模型有着很高的效率及稳定性,将其与LIBS技术结合可以适用于工业...  相似文献   

12.
Blast furnace(BF)ironmaking process has complex and nonlinear dynamic characteristics.The molten iron temperature(MIT)as well as Si,P and S contents of molten iron is difficult to be directly measured online,and large-time delay exists in offline analysis through laboratory sampling.A nonlinear multivariate intelligent modeling method was proposed for molten iron quality(MIQ)based on principal component analysis(PCA)and dynamic genetic neural network.The modeling method used the practical data processed by PCA dimension reduction as inputs of the dynamic artificial neural network(ANN).A dynamic feedback link was introduced to produce a dynamic neural network on the basis of traditional back propagation ANN.The proposed model improved the dynamic adaptability of networks and solved the strong fluctuation and resistance problem in a nonlinear dynamic system.Moreover,a new hybrid training method was presented where adaptive genetic algorithms(AGA)and ANN were integrated,which could improve network convergence speed and avoid network into local minima.The proposed method made it easier for operators to understand the inside status of blast furnace and offered real-time and reliable feedback information for realizing close-loop control for MIQ.Industrial experiments were made through the proposed model based on data collected from a practical steel company.The accuracy could meet the requirements of actual operation.  相似文献   

13.
Problems in geotechnical engineering are full of uncertain, vague, and incomplete information. In most instances, successfully solving such problems depends on experts’ knowledge and experience. The primary object of this research was to develop an evolutionary fuzzy neural inference system (EFNIS) to imitate the decision-making processes in the human brain in order to facilitate geotechnical expert decision making. First, an evolutionary fuzzy neural inference model (EFNIM) was constructed by combining the genetic algorithm (GA), fuzzy logic (FL), and neural network (NN). In the proposed model, GA is primarily concerned with optimizing parameters required in the fuzzy neural network; FL with imprecision and approximate reasoning; and NN with learning and curve fitting. This research then integrates the EFNIM with an object-oriented computer technique to develop an EFNIS. Finally, the potential to apply the proposed system to practical geotechnical decision making is validated using two real problems, namely estimating slurry wall duration and selecting retaining wall construction methods.  相似文献   

14.
Lean Management Model for Construction of High-Rise Apartment Buildings   总被引:1,自引:0,他引:1  
Execution of the finishing works in high-rise apartment buildings is made complex by the need to customize apartments to the varying requirements and designs of individual clients. The conventional construction planning practice of progressing upward from floor to floor breaks down in the face of the arbitrary sequence in which clients finalize their decisions. The results are long cycle times for delivery of completed apartments and corollary high levels of work in progress, budget and schedule overruns, and general dissatisfaction with the process on the part of the developer, contractor, subcontractors, and the clients. Application of lean construction principles to this problem has led to development of a management model that adopts pull scheduling, reduced batch sizes, and a degree of multiskilling. The main benefits expected are an enhanced ability to provide customized apartments, improved cash flow, and reduced apartment delivery cycle times. The model was first formulated in theory, then tested using a management simulation game and computer simulation, and subsequently, developed for practical application. This paper presents an analysis of conventional practice, the theoretical background to the lean approach, and the specific management changes proposed.  相似文献   

15.
针对不同路况和运动模式下的高维、非线性、强耦合和高时变下肢加速度信号的识别问题,提出了一种基于时——频分析的步态模式自动分类方案.利用三轴加速度传感器采集运动时小腿在矢状面、冠状面和横切面的加速度信号,利用五阶Daubechies小波基对其进行特征提取,并采用线性判别式分析进行降维,最后利用决策树和支持向量机对得到的精简步态特征进行模式分类.实验结果显示两种分类器的总体分类准确率均达到90%以上,个别步态分类可达到100%,验证了特征提取和降维方法的合理性和有效性.  相似文献   

16.
D. C. Strohmer et al (see record 1983-11141-001) suggested that in the process of moving from observations to clinical judgments, the cognitive activity of the counselor can be described as a mediated stagewise decision model. The present study replicated and extended the Strohmer et al research. 20 25–49 yr old counselors were asked to make status and attributional inferences and diagnostic classification of clients. All combinations of 4 levels each of personality test, achievement, and client disability information were presented. Three theoretically derived structural equation models were tested for their ability to account for the correlations among all exogenous and endogenous variables in the parent model. Findings suggest that the clinical judgment process was stagewise mediated and that attributional inferences had little direct impact on final diagnostic classification. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

17.
Principal components analysis (PCA) is used to explore the structure of data sets containing linearly related numeric variables. Alternatively, nonlinear PCA can handle possibly nonlinearly related numeric as well as nonnumeric variables. For linear PCA, the stability of its solution can be established under the assumption of multivariate normality. For nonlinear PCA, however, standard options for establishing stability are not provided. The authors use the nonparametric bootstrap procedure to assess the stability of nonlinear PCA results, applied to empirical data. They use confidence intervals for the variable transformations and confidence ellipses for the eigenvalues, the component loadings, and the person scores. They discuss the balanced version of the bootstrap, bias estimation, and Procrustes rotation. To provide a benchmark, the same bootstrap procedure is applied to linear PCA on the same data. On the basis of the results, the authors advise using at least 1,000 bootstrap samples, using Procrustes rotation on the bootstrap results, examining the bootstrap distributions along with the confidence regions, and merging categories with small marginal frequencies to reduce the variance of the bootstrap results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

18.
19.
In construction, many owners mitigate the risk of unforeseen contractor default by accepting only bonded contractors who must endure a rigorous evaluation process by surety brokers and surety underwriters. This evaluation process includes a financial analysis and a review of work on hand and past performance, all of which have reliable structured methods for their evaluation. Additionally, a number of subjective criteria are considered that are more difficult to capture and assess objectively but which can be modeled effectively using fuzzy logic. The purpose of this paper is to illustrate how fuzzy logic and expert systems can be combined to provide a structured approach to evaluating contractors for surety underwriting purposes. Fuzzy logic is used to model both the objective and subjective factors considered in contractor evaluation using linguistic terms, and expert rules are used to capture the surety experts’ reasoning process. A fuzzy expert system, SuretyAssist, is presented that can be used to provide an initial evaluation of general contractors as well as periodic reviews to determine whether or not to accept them as clients for bonding. SuretyAssist was validated using 31 actual cases of contractor evaluation and found to be accurate in 81% of the cases.  相似文献   

20.
Delay and loss of productivity are the two main types of damage experienced by the contractor when the owner issues a change order. Courts have recognized critical path method schedule analysis as the preferred method of identifying and quantifying critical delays. As for the inefficiency damages, there is no direct way of measuring inefficiency due to its qualitative nature and the difficulty of linking the cause of the productivity loss to the damage. Most of the scholarly work published in this area was based on data supplied by the contractors; and that explains why there are discrepancies between what the contractor asks for and what the owner believes the contractor is entitled to. This study addresses the need for a statistical model to quantify the productivity loss from verifiable site data such as owner’s daily reports, change orders, drawings, and specifications, rather than rely solely on contractor surveys. A model is developed and validated to quantify the productivity loss in pipe work in roadway projects due to the change orders. The productivity loss study analyzed two sets of data that include: (1) variables that predict which of the two parties, the owner and the contractor, contributed to the productivity loss; and (2) variables that predict, from the legal viewpoint, productivity losses which only the owner is responsible for. The study showed the difference between what the contractor asked for and what he/she is actually entitled to. This model can be used by both the owner and the contractor to quantify the productivity loss due to change orders, and to offer an objective approach to reconcile their differences. This study concludes with an example to demonstrate the use of the model.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号