Modeling and solving a multi-objective supplier quota allocation problem considering transaction costs

Suppliers’ evaluation is a subject, which has attracted the attention of many researchers. The performance of potential suppliers is evaluated against multiple criteria rather than considering a single factor such as cost or quality. One of the major objectives of suppliers’ evaluation is to determine the optimal quota assigned to each supplier while needing to replenish an order. This problem has been studied by many researchers as a multi-objective problem. The usual objectives are minimizing the purchasing cost, rejected units, and late delivered units. However, in a few researches maximizing the evaluation scores of the selected suppliers is considered as fourth objective. In this paper, we present a model with five objectives including minimizing the transaction costs of purchasing from suppliers as well as the four addressed objectives. We convert the model to a single objective one using the well-known weighting method, solve it utilizing two meta-heuristic algorithms, and analyze the efficiency of the heuristics. The reason why we utilize the meta-heuristic algorithms is that the problem is proved to be an NP-hard one.     

A memetic algorithm for bi-objective integrated forward/reverse logistics network design

Logistics network design is a major strategic issue due to its impact on the efficiency and responsiveness of the supply chain. This paper proposes a model for integrated logistics network design to avoid the sub-optimality caused by a separate, sequential design of forward and reverse logistics networks. First, a bi-objective mixed integer programming formulation is developed to minimize the total costs and maximize the responsiveness of a logistics network. To find the set of non-dominated solutions, an efficient multi-objective memetic algorithm is developed. The proposed solution algorithm uses a new dynamic search strategy by employing three different local searches. To assess the quality of the novel solution approach, the quality of its Pareto-optimal solutions is compared to those generated by an existing powerful multi-objective genetic algorithm from the recent literature and to exact solutions obtained by a commercial solver.     

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.     

Unilateral digital clubbing in a hemodialysis patient

We present an unusual case of a chronic hemodialysis patient with moderate diffuse acrocyanosis and prominent unilateral clubbing of his right hand fingers, with classic physical features of hypertrophic osteoarthropathy. The patient's left hand, which had a functioning arteriovenous fistula, did not show any evidence of clubbing. We briefly discuss the different theories in regards to the pathogenesis of clubbing, and the potential role of arteriovenous fistula in preventing its occurrence.     

Comments on “Second-order sliding mode control with experimental application”

In this paper, some points to the stability analysis of the paper [Eker I, Second-order sliding mode control with experimental application, ISA Trans 2010;50:394–405] are presented. It is illustrated that the way the author in [1] proves stability, suffers lack of correct justification. A modification to the stability analysis is presented and the stability conditions are restated. Moreover, some other flaws in the original paper are addressed.     

Novel Binary Solvents-Dispersive Liquid—Liquid Microextraction (BS-DLLME) Method for Determination of Patulin in Apple Juice Using High-Performance Liquid Chromatography

A simple and rapid binary solvents-based dispersive liquid–liquid microextraction (BS-DLLME) method has been developed for determination of patulin (PAT) in apple juice followed by high-performance liquid chromatography. This method involves the use of an appropriate mixture of miscible binary extraction solvents and disperser solvent to form fine droplets of extractant in a sample solution. Parameters affecting extraction efficiency such as the type and volume of high-density extraction solvent, the volume of ethyl acetate, the kind and volume of disperser solvent, and salt addition were investigated and optimized. The detection and quantification limits were 2.0 and 10.0 μg L^?1, respectively. The relative standard deviation for five measurements of 25 μg L^?1 of PAT was 3.8 %. The relative recoveries of PAT from apple juice samples at spiking levels of 25, 50, and 75 ng mL^?1 were in the range of 91.3–95.2 %.     

Trading pollutant discharge permits in rivers using fuzzy nonlinear cost functions

Transferable Discharge Permit (TDP) programs in water quality management produce environmental benefit, which closely achieves the same benefit through a command-and-control approach, with comparatively lower costs. Estimating abatement cost functions is one of the greatest challenges in these trading programs. According to the fact that water flows to the lowest level uni-directionally, the Trading Ratio System (TRS) is utilized for water quality management in river systems. TRS considers the river assimilative capacity and provides the optimum trading pattern. TRS has been designed for a single water quality variable and the existing uncertainties are not incorporated. In this study, an extended version of TRS is utilized which considers the uncertainties in treatment cost functions and can be used for BOD/DO management in rivers. Then, by combining the extended TRS and a fuzzy nonlinear regression, a novel model is proposed to configure a permit trading structure and provide decision maker with a wealth of cost-effective management strategies. The proposed model has been used for trading water pollutant discharge permits in the Zarjub river in northern part of Iran. The results show that trading discharge permit in this river system is a cost-effective strategy. It is also shown that the uncertainty in the wastewater treatment cost functions can be easily considered using the fuzzy set theory.