The medical waste management is of great importance due to its potential environmental hazards and public health risks. Manufacturers have to collect the medical waste and control its recovery or disposal. Medical was...
详细信息
The medical waste management is of great importance due to its potential environmental hazards and public health risks. Manufacturers have to collect the medical waste and control its recovery or disposal. Medical waste recovery, which encompasses reuse, remanufacturing and materials recycling, requires a specially structured reverse logistic network in order to collect medical waste efficiently. This paper has attempted to apply the basic theories of reverse logistics to improve the effect of medical waste management. We presents a mixed integer linear programming model of reverse logistics networks for returned medical waste. The efficiency and practicability of the proposed model is validated by an application to an illustrative example dealing with medical waste returned from some hospitals to a given medical materials producer.
Production planning for biopharmaceutical portfolios becomes more complex when products switch between fed-batch and continuous perfusion culture processes. This article describes the development of a discrete-time mi...
详细信息
Production planning for biopharmaceutical portfolios becomes more complex when products switch between fed-batch and continuous perfusion culture processes. This article describes the development of a discrete-time mixed integer linear programming (MILP) model to optimize capacity plans for multiple biopharmaceutical products, with either batch or perfusion bioprocesses, across multiple facilities to meet quarterly demands. The model comprised specific features to account for products with fed-batch or perfusion culture processes such as sequence-dependent changeover times, continuous culture constraints, and decoupled upstream and downstream operations that permit independent scheduling of each. Strategic inventory levels were accounted for by applying cost penalties when they were not met. A rolling time horizon methodology was utilized in conjunction with the MILP model and was shown to obtain solutions with greater optimality in less computational time than the full-scale model. The model was applied to an industrial case study to illustrate how the framework aids decisions regarding outsourcing capacity to third party manufacturers or building new facilities. The impact of variations on key parameters such as demand or titres on the optimal production plans and costs was captured. The analysis identified the critical ratio of in-house to contract manufacturing organization (CMO) manufacturing costs that led the optimization results to favor building a future facility over using a CMO. The tool predicted that if titres were higher than expected then the optimal solution would allocate more production to in-house facilities, where manufacturing costs were lower. Utilization graphs indicated when capacity expansion should be considered. (c) 2013 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 30:594-606, 2014
This paper presents a model for use in the problem of composite generation and transmission expansion planning considering distributed generation. Generation expansion planning is defined as the problem of determining...
详细信息
This paper presents a model for use in the problem of composite generation and transmission expansion planning considering distributed generation. Generation expansion planning is defined as the problem of determining what capacity, which, and when new generating units should be constructed over a long range planning horizon, to satisfy the expected energy demand using single nodal generation planning model. Then, the place of every planned generating units and distributed generation is determined simultaneous with transmission expansion planning considering nonuniform geographical fuel supply cost and potential of distributed generation technology. The problem is formulated as a mixed-integerlinearprogramming. By allocating the overall generation capacity among the grid nodes and determining the new transmission element additions along the planning horizon, the overall cost of the system is minimized. To assess the capabilities of the proposed approach, the Iranian Power Grid as a large scale system is considered. The effectiveness of the proposed modifications is illustrated in detail. (C) 2014 Elsevier Ltd. All rights reserved.
If railway companies ask for station capacity numbers, their underlying question is in fact one about the platformability of extra trains. Train platformability depends not only on the infrastructure, buffer times, an...
详细信息
If railway companies ask for station capacity numbers, their underlying question is in fact one about the platformability of extra trains. Train platformability depends not only on the infrastructure, buffer times, and the desired departure and arrival times of the trains, but also on route durations, which depend on train speeds and lengths, as well as on conflicts between routes at any given time. We consider all these factors in this paper. We assume a current train set and a future one, where the second is based on the expected traffic increase through the station considered. The platforming problem is about assigning a platform to each train, together with suitable in-and out-routes. Route choices lead to different route durations and imply different in-route-begin and out-route-end times. Our module platforms the maximum possible weighted sum of trains in the current and future train set. The resulting number of trains can be seen as the realistic capacity consumption of the schedule. Our goal function allows for current trains to be preferably allocated to their current platforms. Our module is able to deal with real stations and train sets in a few seconds and has been fully integrated by Infrabel, the Belgian Infrastructure Management Company, in their application called Ocapi, which is now used to platform existing and projected train sets and to determine the capacity consumption. (C) 2014 Elsevier Ltd. All rights reserved.
Counterexamples for property violations have a number of important applications like supporting the debugging of erroneous systems and verifying large systems via counterexample-guided abstraction refinement. In this ...
详细信息
Counterexamples for property violations have a number of important applications like supporting the debugging of erroneous systems and verifying large systems via counterexample-guided abstraction refinement. In this paper, we propose the usage of minimal critical subsystems of discrete-time Markov chains and Markov decision processes as counterexamples for violated omega-regular properties. Minimality can thereby be defined in terms of the number of states or transitions. This problem is known to be NP-complete for Markov decision processes. We show how to compute such subsystems using mixed integer linear programming and evaluate the practical applicability in a number of experiments. They show that our method yields substantially smaller counterexample than using existing techniques. (C) 2014 Elsevier B.V. All rights reserved.
Selecting an optimal vertical alignment while satisfying safety and design constraints is an important task during road construction. The amount of earthwork operations depends on the design of the vertical alignment,...
详细信息
Selecting an optimal vertical alignment while satisfying safety and design constraints is an important task during road construction. The amount of earthwork operations depends on the design of the vertical alignment, so a good vertical alignment can have a profound impact on final construction costs. In this research, we improve the performance of a previous mixed-integerlinearprogramming model, and we propose a new quasi-network flow model. Both models use a piecewise quadratic curve to compute the minimum cost vertical alignment and take earthwork operations into account. The models consider several features such as side-slopes, and physical blocks in the terrain. In addition to improving the precision, we propose several techniques that speed up the search for a solution, so that it is possible to make interactive design tools. We report numerical tests that validate the accuracy of the models, and reduce the calculation time. (C) 2013 Elsevier Ltd. All rights reserved.
A method of real-time path planning for unmanned air vehicles in a radar-guided surface-to-air missile (SAM) netting environment was proposed. First, a simplified threat netting model is established based on the proba...
详细信息
A method of real-time path planning for unmanned air vehicles in a radar-guided surface-to-air missile (SAM) netting environment was proposed. First, a simplified threat netting model is established based on the probability of an UAV being detected by threats;then, the model of threat netting is integrated with models of SAMs. The first step in the path planning algorithm based on MPC is to construct a UAV state-space model. In the threat netting situation, a SAM may receive target information from other SAMs via a communication network. The completeness of transmitted information depends on the connective probability of the communication network, which depends on the network topology and capacity. The path planning problem is formulated as a model predictive control problem. Simulation results and the present analysis indicate that the presented threat netting model and path planning algorithm can compensate for the increase in the lethality of a particular threat.
In this paper we deal with the problem of efficiently optimizing microgrid operations while satisfying a time-varying request and operation constraints. Microgrids are subsystems of the distribution grid comprising su...
详细信息
In this paper we deal with the problem of efficiently optimizing microgrid operations while satisfying a time-varying request and operation constraints. Microgrids are subsystems of the distribution grid comprising sufficient generating resources to operate in isolation from the main grid, in a deliberate and controlled way. The Model Predictive Control (MPC) approach is applied for achieving economic efficiency in microgrid operation management. The method is thus applied to an experimental microgrid located in Athens, Greece: experimental results show the feasibility and the effectiveness of the proposed approach. (C) 2013 Elsevier Ltd. All rights reserved.
Agile methods for software development promote iterative design and implementation. Most of them divide a project into functionalities, called user stories;at each iteration, often called a sprint, a subset of user st...
详细信息
Agile methods for software development promote iterative design and implementation. Most of them divide a project into functionalities, called user stories;at each iteration, often called a sprint, a subset of user stories are developed. The sprint planning phase is critical to ensure the project success, but it is also a difficult problem because several factors impact on the optimality of a sprint plan, e.g., the estimated complexity, business value, and affinity of the user stories to be included in each sprint. In this paper we present an approach for sprint planning based on an integerlinearprogramming model. Given the estimates made by the project team and a set of development constraints, the optimal solution of the model is a sprint plan that maximizes the business value perceived by users. Solving to optimality the model by a general-purpose MIP solver, such as IBM llog Cplex, takes time and for some instances even finding a feasible solution requires too large computing times for an operational use. For this reason we propose an effective Lagrangian heuristic based on a relaxation of the proposed model and some greedy and exchange algorithms. Computational results on both real and synthetic projects show the effectiveness of the proposed approach. (C) 2013 Elsevier Ltd. All rights reserved.
This paper studies the scheduling of lots (jobs) of different product types (job family) on parallel machines, where not all machines are able to process all job families (non-identical machines). A special time const...
详细信息
This paper studies the scheduling of lots (jobs) of different product types (job family) on parallel machines, where not all machines are able to process all job families (non-identical machines). A special time constraint, associated to each job family, should be satisfied for a machine to remain qualified for processing a job family. This constraint imposes that the time between the executions of two consecutive jobs of the same family on a qualified machine must not exceed the time threshold of the family. Otherwise, the machine becomes disqualified. This problem comes from semiconductor manufacturing, when Advanced Process Control constraints are considered in scheduling problems. To solve this problem, two mixed integer linear programming models are proposed that use different types of variables. Numerical experiments show that the second model is much more effective, and that there is a trade-off between optimizing the scheduling objective and maximizing the number of machines that remain qualified for the job families. Two heuristics are also presented and studied in the numerical experiments.
暂无评论