Remanufacturing through circular economy conserves energy and materials while creating economic growth and employment. Thus, it is imperative to develop better systems that optimise the use of resources, maximise the ...
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Remanufacturing through circular economy conserves energy and materials while creating economic growth and employment. Thus, it is imperative to develop better systems that optimise the use of resources, maximise the value of the product, and minimise the total cost. Towards this, we present a two-stage stochastic linear model for a make-to-order hybrid manufacturing-remanufacturing production system by integrating capacity and inventory decisions. We consider the uncertainty in demand, core returns rate and yield to impose flexibility as both operations are considered with a collective production capacity on the same assembly line. We have considered a setting where demand for new and remanufactured products does not cannibalise each other's demand (e.g. new parts for original equipment and remanufactured parts for independent aftermarket). Further, the capacity utilisation by core returns is considered in two ways: less capacity intensive case and more capacity intensive case. The developed model is solved for optimal inventory and capacity levels along with production quantities by maximising utilisation of resources and profit. We also present a closed-form solution by demand space partition to deduce the optimal policy of the firm. Based on our analysis, we have presented settings where remanufacturing can perfectly substitute manufacturing.
With the recent global energy crisis, some countries have implemented electrical rationing (ER), making it necessary for smart homes to play a pivotal role in optimizing energy consumption and contributing to sustaina...
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With the recent global energy crisis, some countries have implemented electrical rationing (ER), making it necessary for smart homes to play a pivotal role in optimizing energy consumption and contributing to sustainable practices. To effectively manage smart home consumption, a stochastic programming approach for a grid-connected smart home energy management system (SHEMS) is proposed in this paper. The system includes PV, battery, diesel, and gas-based heating/cooling systems (HCS). Additionally, a demand response program (DRP) has been employed under time-of-use tariffs in the Syrian energy market. The main objective is to minimize the day-ahead expected cost and consumer discomfort by optimizing the operation of dispatchable units and loads. To manage the risks associated with the expected cost due to potential uncertainties in PV energy generation and electrical rationing programs, the conditional value-at-risk (CVaR) approach is adopted. Two methods are proposed to model the uncertainty in PV energy generation;interval bands and interval-based scenarios. The problem is modeled as a mixed-integer non-linear programming (MINLP) model, and coded in GAMS to test different cases. Based on the results obtained, substantial reductions reached 56.2% in worst-case cost scenarios when employing concurrent DRP-risk management.
We construct an optimal investment portfolio model with deferred annuities for an individual investor saving in a retirement plan. The objective function consists of power utility in terms of consumption of all secure...
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We construct an optimal investment portfolio model with deferred annuities for an individual investor saving in a retirement plan. The objective function consists of power utility in terms of consumption of all secured retirement income from the deferred annuity purchases, as well as bequest from remaining wealth invested in equity, bond, and cash funds. The asset universe is governed by a vector autoregressive model incorporating the Nelson-Siegel term structure and equity returns. We use multi-stage stochastic programming to solve the optimization problem numerically. Deferred annuity purchases are made continuously over the working lifetime of the investor, increasing particularly in the years before retirement. The investment strategy hedges price changes in deferred annuities, and bond holding and deferred annuity purchases increase when interest rates are high. Optimal investment and deferred annuity choices depend on realized and expected values of state variables. The optimal strategy is also compared with typical retirement plan strategies such as glide paths. Our results provide support for deferred annuities as a major source of retirement income. (C) 2021 Elsevier B.V. All rights reserved.
The deepening reform of the power system has resulted in increased competition between electricity market participants. The ADP method is applied to solve the optimal self-dispatch problem of hydro-power companies und...
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This paper addresses a multi-period emergency facility location-routing problem, in which the uncertainties in material demands and transportation time, as well as dynamic inventory replenishment and carryover are inc...
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This paper addresses a multi-period emergency facility location-routing problem, in which the uncertainties in material demands and transportation time, as well as dynamic inventory replenishment and carryover are incorporated in the design of multi-level emergency logistics networks. To measure the risks stemming from uncertain transportation time, mean-CVaR method is used. Then, a risk-averse stochastic programming model for the presented problem is formulated to minimize the total rescue time of the network. Moreover, a genetic algorithm is developed to solve the proposed model. Extensive numerical experiments including the randomly generated instances and a case study on the Wenchuan earthquake in China are conducted to verify the effectiveness of the presented model and algorithm. Experimental results show that the genetic algorithm significantly performs better than the Gurobi solver in terms of both solution quality and solution time.
Emergency medical supplies are crucial for the successful disaster response of healthcare coalitions. In practice, a healthcare coalition can obtain emergency medical supplies from three channels, i.e., supply pre-pos...
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Emergency medical supplies are crucial for the successful disaster response of healthcare coalitions. In practice, a healthcare coalition can obtain emergency medical supplies from three channels, i.e., supply pre-positioning, contracted reserve and emergency procurement, which, however, are not planned integrally in the literature. To fill the research gap, this study proposes a two-stage stochastic programming model for integrated emergency medical supply planning considering multiple supply channels in healthcare coalitions. In the first stage before disasters, decisions on emergency medical supply pre-positioning and signing of two types of medical supply procurement contracts are determined. In the second stage after disasters, decisions of emergency supply procurement, contract implementation, and supply transshipment are optimized based on the first-stage decisions and the realized uncertain disaster impacts. To show the effectiveness of our model and obtain managerial insight, we develop four comparison models and conduct a case study on the healthcare coalition of West China Hospital in China. This study highlights the great benefits of supplementing the pre-positioning of emergency medical supplies with multi-type contracted reserve in healthcare coalitions and emphasizes the importance of strengthening cooperation with suppliers and encouraging all member hospitals to implement the contracted reserve.
With the construction and development of new-type power system with a gradually increasing proportion of new energies, large-scale distributed generations are widely integrated, electric energy substitution is gradual...
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The resilience of the Texas power grid has been tested by winter storms and the attendant cold on multiple occasions. Notable events include the United States cold wave of December 1989, the Groundhog Day Blizzard of ...
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This paper presents a bi-level approach to support retailers in making investment decisions in renewable -based systems to provide clean electricity. The proposed model captures the strategic nature of the problem and...
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This paper presents a bi-level approach to support retailers in making investment decisions in renewable -based systems to provide clean electricity. The proposed model captures the strategic nature of the problem and combines capacity sizing decisions for installed technologies with pricing decisions regarding the electricity tariffs to offer to a reference end -user, representative of a class of residential prosumers. The interaction between retailer and end -user is modeled using the Stackelberg game framework, with the former acting as a leader and the latter as follower. The reaction of the follower to the electricity tariff affects the retailer's profit, which is calculated as the difference between the revenue generated from selling electricity and the total investment, operation and management costs. To account for uncertainty in wholesale electricity prices, renewable resource availability and electricity request, the upper -level problem is formulated as a two -stage stochastic programming model. First -stage decisions refer to the sizing of installed technologies and electricity tariffs, whereas second -stage decisions refer to the operation and management of the designed system. The model also incorporates a safety measure to control the average profit that can be achieved in a given percentage of worst -case situations, thus providing a contingency against unforeseen changes. At the lower level, the follower reacts to the offered tariffs by defining the procurement plan in terms of energy to purchase from the retailer or potential competitors, with the final aim of minimizing the expected value of the electricity bill. A tailored approach that exploits the specific problem structure is designed to solve the proposed formulation and extensively tested on a realistic case study. The numerical results demonstrate the efficiency of the proposed approach and validate the significance of explicitly dealing with the uncertainty and the importance of incorporat
We consider a multistage inventory model. At each stage, a company determines order quantities of several products to satisfy a demand. The demand is described by a discrete random process. If the demand on a product ...
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