Genetic algorithm for project time-cost optimization in fuzzy environment, A project is a combination of interrelated activities which must be executed in a certain order before the entire task is completed. The activities are interrelated in a logical sequence which is known as precedence relationship. For the analytical purpose, the activities of a project are represented in a network diagram maintaining precedence relationship to get solutions for scheduling and controlling. The longest continuous path of a project network is called critical path which determines the project duration. The most commonly used project management techniques are Gantt chart, Milestone, Critical Path Method (CPM) and Project Evaluation and Review Technique (PERT). The major objective of project scheduling is to complete the entire projectwithin budget and time constraints. Traditional project scheduling problems mainly focus on activities assuming deterministic or probabilistic time durations.Project scheduling is the conversion of a project action plan in an operating timetable. It serves as the basis for monitoring and controlling project activity. Taken together with the plan and budget, it is probably the major tool for the management of projects. The basic approach for all scheduling techniques is to form a network of activity and event relationships. Critical path of this network is an important issue for project schedulers, because it refers the duration of whole project. Project managers are highly concerned with this critical path for on time completion of a project, especially when an extension will incur a penalty (either in liquidated damages, opportunity costs and goodwill losses). When some delay have been occurred, there may be necessary to compress the critical activity by incrementing the activity resources above the normallevel. It is often the case that the performance of some or all activities can be accelerated, or the duration crashed, by allocating more resources at the expense of higher activity direct cost. This crashing of activities can be achieved by multiple shift work, extended work days, using larger and more productive equipment and increasing the size of labour crews. So, project schedule planners mainly focus on finding the most cost effective way to complete a project within a specified completion time. This class of problem is usually called time-cost trade off. In real construction projects, time and cost of activities may face significant changes due to existing uncertainties such as inflation, economical and social stresses, labour performance, execution errors of contractor, design errors, natural events such as climate changes and etc. Therefore, total time and cost of project may differ significantly because of these uncertainties.Almost all of the projects, the required information for estimation ofproject parameters are either unavailable or incomplete. In practice, the majority of construction companies do not systematically record the durations of project activities. In addition, it is commonly known that no two construction projects are alike. Also in many cases the project is done for the first time, this compels us to use expert opinion in forecasting the project parameters. Experts use their own judgment, experience and project information that is available to them. In practice, linguistic terms such as, “approximately”, “more or less”, or “about” are commonly found in the statements used by these experts. These terms clearly exhibit some sort of imprecision that naturally leads to a range of possible values, rather than a definitive estimate using a single value. So, uncertainty and project parameters are inextricable. In thesis situation, deterministic models of construction time-cost trade off are not realistic. Crisp decision making in uncertain environment causes loss of some parts of information. Use of uncertain models, whish is capable of formulating vagueness of the dynamic conditions of real world gives more stability to solve time-cost trade off problem. Some probabilistic techniques are used in many cases to meet these uncertainties to some extent. But project parameters may not be in statistical manner. That is why fuzzy set theory is appropriate to consider affecting uncertainties in activity duration, direct and indirect cost of a project.Since different alternatives of possible durations and costs for the activities can be associated with a project, the problem is arisen to search the best solution. As combinatorial optimization problems, finding optimal decisions is difficult and time consuming considering the number of possible permutations involved. Therefore, any analytical procedure may suit for small project, but it will be inefficient for large project because of exhaustive enumeration. To avoid the problem of combinatorial explosion, heuristic models can be used. It does notensure the optimality but it gives better near optimal solution without mathematical rigor.This research aimed at development of an efficient heuristic approach with fuzzy activity time and cost for project time-cost optimization incorporating the vagueness or fuzziness of the dynamic conditions of the real world.
A heuristic for the inventory management of smart vending machine systems, Smart vending machines that enable sales and inventory information to be remotely monitored through the Internet using embedded online messaging devices were recently introduced. Webster et al. (1999) developed an experimental Java client-server system with a special purpose hardware interface to control a Pepsi vending machine via the Internet. Jofemar unveiled what it claims is the world’s first autonomous hydrogen-powered smart vending machine at the 2009 National Vending Machine Exposition(Fuel Cells Bulletin, 2009).Figure1 shows an example of a smart beverage vending machine operated at G20 Seoul Summit Conference in 2010.Smart vending machines are expected to resolve the problems inherent to conventional vending machines such as run-out of productsandmachine breakdowns left for a long time. Wolson (2000) insisted that smart vending machines are the future of the vending machine industry.The inventory managementof smart vending machine systems with product substitution under the replenishment point, order-up-to level policy creates a decision making problem. The problemincludesthe determination of replenishment points of products at vending machines, product allocation to vending machine storage compartments, replenishment thresholds at vending machines, and vehicle routes for inventoryreplenishments. Little work has addressed theinventory management of smart vending machine systems in the literature. Poon et al. (2010) developed an index to make replenishment decisions for smart vending machines to minimize transportation and stock-out costs. Park and Yoon (2011) proposeda two-phase solution based on a nonlinear integer mathematical model for the operation problem of conventional vending machine supply chains with stock-out based, one-stage item substitution.Among reports regarding inventory-routing problems, some are applicable for determining shipping policies in smart vending machine systems (see Archetti et al., 2007; Li et al., 2010; Moin et al., 2011). In this paper, we propose aheuristic for the inventory management of smart vendingmachine systems with product substitution under the replenishment point, order-up-to level policy and conduct computational experiments on several test problems in order to evaluate its optimality. Furthermore, a sensitivity analysis is carried out to evaluate the effect of customer service level on system profit using a computer simulation.
Low-carbon scenario analysis on urban transport of one metropolitan in China in 2020, In China, the negative environmental consequences caused by GHG emission from transport sector in metropolitan regions grow rapidly along with continuous urbanization process. Againstthe backgroundof high-speed economic development, the growing household consumption capabilityin metropolitan results in adramatic increase ofurban residential trips, which enlargescarbon emission contribution from urban passenger traffic (He & Huo, 2005). In fact, total GHG emission volume stays at a very high level, despite ofrecent achievements oftraffic and purchase restrictions upon household automobile and actions that encourages the utilizationof rail transportation. We set up baseline and relevant low-carbon scenarios to forecast total GHG emission from transport industry in one metropolitan in China, and evaluate the implemented energy conservation and emission reduction policies,such as “public transit priority”. These are of great significance to this metropolitan and even to the whole country for coming up with effective strategies to control the GHG emission and assume its commitment to emission reduction.
In reference to field study, literature review, and collectable data, the research scope of this paper is as following: firstly, only CO2is taken into account in terms of types of GHG,; for vehicle genre, only local registered vehicles are covered;and for transport modes, this research mainly involves road transport (including urban road, express highway and highway) and rail transit in This metropolitan.Our research starts with setting upcalculation modelsfor each type of fuel on roads to examinethe overall energy consumption. In accordance with terminal consumption of each energy resource, the formulas areas follows.
A new approach for an efficient human resource appraisal and selection, The aim of the paper is to provide a decision making tool for solving a multi-criteria selection problem that can accommodate the qualitative details in relations with the task requirements and candidates’ competences. Our inquiry emphasizes the use of the 2-tuple linguistic representation model as the most suitable tool to overcome the uncertain and subjective assessments. It is adapted to aggregate linguistic assessments of acquired and required competence resources generated by a group of appraisers. The resulting aggregated objective evaluations are therefore used as inputs of an extended version of the TOPSIS method. After certain customization, a candidates’ ranking based on a similarity degree between required and acquired competence components levels is provided. The quality and efficiency of the proposed approach were confirmed through a real life application from a university context. It ensures a better management of the available candidates. Moreover, it allows facing the circumstances of absenteeism, identifying the need of training, and so on.
To respond to the fierce competition, companies have to focus on the creation of sustained competitive advantages. As performance depend more on the management of innovation and diversification, intangible resources are more likely than tangible ones to produce a competitive advantage. In such a context, human resources, with their cognitive and decision making capacities, appeared as the ‘new’ key component of the performance (Bennour & Crestani, 2007). Today, the emergence of several characteristics of the organization’s personnel, involving personnel knowledge, experience, collaborative information stemming from social network,helpsto introduce the competence concept and to stress on his importance into the realization of organization goals. This concern opens horizons for researchers to develop more adaptive and effective competence management techniques among which some have important implication on Human Resources selection and performance appraisal. Competence-based appraisal and selection problem have been recognized as a central problem. The accuracy of the resulting selection is built on both appraiser opinion and a painstaking task analysis to facilitate the definition of the appropriate selection criteria and their relative importance degree. Therefore, these criteria help the appraiser to provide his opinions about the competence level of a candidate when performing the corresponding task. Nevertheless, since the appraiser’s judgmentis inherently subjective, his opinion may lead to an unfaithful selection result. That is why it seems plausible to involve different decision-makers’ opinions. As the problem variables are vague and imprecise, the selection problem should be based on a linguistic evaluation method to represent the decision-makers’ opinions by means of linguistic variables whose values are not numbers but words or sentences in a natural or artificial language. This may help avoiding the uncertain interpretation. In the framework of the paper, we intend toprovide a decision making tool to a manager for solving a multi-criteria selection problem that can accommodate the qualitative details in relation to the task requirements and candidates’ competences. Our challenge is to ensure an improvement in human resources appraisal and selection through a more flexibility and better treatment of information with uncertainty and vagueness. Accordingly, we opt, at first, for the use of the most objective and effective evaluation method,the 2-tuple linguistic representation model, to deal with linguistic assessment information. This model proves itself by its simplicity and its robustness by overcoming the loss and the distortion of qualitative information and by providing final results always expressed in the initial linguistic domain (Herrera &Martinez, 2001). Then, we suggest carrying out one of the multi-criteria techniques, namely, TOPSIS (Technique for Order Preference by Similarity to Ideal Solution). On one hand, TOPSIS allows ranking and therefore findinga compromise solution for theselection of the best candidate to each of the predefined tasks according to the different required criteria. On the other hand, it alsoinforms on the degree of similarity between the required and acquired levels. Such informationisnot provided by the remaining multi-criteria decision making methods. Itassists the manager to make the right decision about different internal policies such as identifying individual substitution alternatives in cases of absenteeism, identifying the need of training,improving the candidate’s matching to tasks based on a detailed comparison with regard to the reference competence resources levels, etc.In the next section, a review of literature is described, including the competence evaluation and selection problem. A brief introduction of the basic definitions of the 2-tuple linguistic representation model and the TOPSIS method are presented. Then, we outline the different steps of the proposed approach based on the combination of the linguistic competence evaluation process and the TOPSIS multi-criteria decision making method. A real example from a university context is developed to illustrate each step of the proposed approach. Finally, some conclusions are pointed out in the end.
Pembangunan bendungan besar telah menyebabkan perpindahan sekitar 40 hingga 80 juta orang di seluruh dunia. Kapasitas penyimpanan agregat bendungan besar, berdasarkan desain bendungan, adalah sekitar 6000 km3. Dengan asumsi bahwa setengah dari desain penyimpanan tercapai dalam kenyataan, kapasitas penyimpanan agregat nyata dari bendungan besar secara global serupa dengan total pengambilan air tawar yang diperkirakan sekitar 3800 km3.
Diperkirakan 0,5–1% dari total kapasitas penyimpanan air tawar bendungan yang ada hilang setiap tahun akibat sedimentasi di waduk besar dan kecil di seluruh dunia. Ini berarti bahwa 25% dari kapasitas penyimpanan air tawar dunia yang ada dapat hilang dalam 25 hingga 50 tahun mendatang jika tidak ada tindakan untuk mengendalikan sedimentasi. Kehilangan ini sebagian besar terjadi di negara dan wilayah berkembang, yang memiliki tingkat sedimentasi lebih tinggi.
Dampak Ekosistem Sungai
Setidaknya 20% dari lebih dari 9000 spesies ikan air tawar dunia telah punah, terancam, atau hampir punah dalam beberapa tahun terakhir. Daerah aliran sungai di dunia adalah habitat 40% spesies ikan dunia, dan menyediakan banyak fungsi ekosistem mulai dari daur ulang nutrisi dan pemurnian air hingga pengisian kembali tanah dan pengendalian banjir.
Transformasi ekosistem tidak hanya terjadi di DAS bagian atas, bawah dan tengah, tetapi juga berdampak pada muara sungai, yang seringkali merupakan ekosistem yang kompleks. Menutup muara sungai besar, intrusi garam, kerusakan bakau dan hilangnya lahan basah adalah beberapa di antara banyak masalah yang dipertaruhkan.
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