h. mokhtari
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In today's dynamic and unpredictable world, the planning and management of humanitarian supply chains hold paramount importance. Efficient logistics management is crucial for effectively delivering essential aid and resources to affected areas during disasters and emergencies, ensuring timely support and relief to vulnerable populations. In this research, we addressed a novel humanitarian supply chain network design problem that considers product differentiation and demand uncertainty. Specifically, we simultaneously incorporate non-perishable, perishable, and blood products as critical components of the network. The problem is formulated as a multi-objective mixed-integer linear programming model aiming to minimize the total cost and total traveled distance of products by making location, allocation, and production decisions. To enhance realism, we account for demand uncertainty in affected areas. To tackle this challenging problem, we proposed a two-phase solution methodology. Firstly, we employed a robust optimization approach to establish a deterministic counterpart for the stochastic model. Subsequently, an efficient fuzzy programming-based approach reformulates the model into a single-objective form, effectively accommodating decision-makers' preferences. Numerical instances are solved to investigate the performance of the model and solution methodologies. The results demonstrate the effectiveness of our fuzzy approach in finding non-dominated solutions, enabling decision-makers to explore trade-offs. Also, sensitivity analyses were conducted to provide more insights. Finally, some suggestions are presented to extend the current work by feature researchers.Keywords: Relief Logistics, product differentiation, Multi-Objective Optimization, robust optimization, fuzzy programming
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Penetration of harmonics from downstream low voltage networks and resonance phenomenon has caused the level of harmonics to increase in transmission networks. Compensation of these harmonics at high voltage levels is neither recommended nor cost effective. This is due to the fact that there is no single large non-linear load which is causing these harmonics, yet filtering at low voltage non-linear load sites cannot completely compensate the harmonics and the remaining harmonic at standard levels still flow into the upstream networks. The idea of controlling harmonics at a medium/high voltage level caused by the remaining harmonics flown from low voltage networks and possibly amplified by resonance conditions with the use of series active power filters has been proposed by the authors in a published work. Since, this application of a series active filter was new, it was preferred to assign a new name for such device, i.e. harmonic power flow controller or simply HPFC. This work looks into the control strategies applicable to a HPFC in more details. The shortcomings of the previous methods are now removed resulting in better performance of a HPFC.Keywords: Harmonic Voltage Control, Current Harmonic Flow, HPFC, ZAPI, MAPI, IZAPI, IMAPI, Harmonic Power Loss control
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Scientia Iranica, Volume:30 Issue: 6, Nov-Dec 2023, PP 2183 -2202
The classical manufacturing systems assume that all of produced items are of perfect quality. They also does not consider rework process in manufacturing operations. Moreover, most of previous literature consider single stage production-inventory systems and do not consider multi stage options. However, in real world production-inventory systems, production of defective items is inevitable, and a fraction of produced items may be defective. In addition, to avoid extra costs and consider environmental issues, organizations tend to reworking activities. We propose single and multi stages production-inventory systems in manufacturing operations where the process is defective, rework is possible and a percent of items are scrapped. A main assumption, in current paper, is that the defective rate is assumed to be uncertain parameter. The grey systems theory, as a mathematical tool to address the uncertain information in real-world situations, is utilized to model the random defective rate via a grey nonlinear programming problem. The proposed issues are investigated via numerical examples to assess the impact of grey parameters on optimal solutions.
Keywords: Grey Systems, Manufacturing Systems, Uncertain Systems, Multi Stage Manufacturing, rework -
Scientia Iranica, Volume:30 Issue: 3, May-June 2023, PP 1204 -1223The quality of products, maintenance operations, and transportation policies are primary concerns of managers in inventory and production planning issues. Besides that, environmental concerns and regulations are growing increasingly and attracted much attention to green production concepts such as sustainable production. Previous authors conducted a wide range of research on these problems separately. Regarding the gap of an integrated framework, we formulate a sustainable Economic Production Quantity model by considering preventive maintenance and multiple shipments of items where a portion of produced items are defective. Two different Cases are studied. In Case I, we assumed that the demand in the production period is satisfied by the produced items in the previous cycle. In another state and in Case II, simultaneous production and consumption during the production period is considered and mathematically formulated. An analytical method is presented for solving the models, and a numerical example is discussed for both Cases. Moreover, sensitivity analysis of the models is carried out, and some managerial insight is derived by changing some of the critical parameters of models. Finally, we present some directions for feature researches.Keywords: Sustainable Production, Economic production quantity, Preventive maintenance, multiple shipments, Defective items
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In many applications of the robotics, the mobile robot should be guided from a source to a specific destination. The automatic control and guidance of a mobile robot is a challenge in the context of robotics. So, in current paper, this problem is studied using various machine learning methods. Controlling a mobile robot is to help it to make the right decision about changing direction according to the information read by the sensors mounted around waist of the robot. Machine learning methods are trained using 3 large datasets read by the sensors and obtained from machine learning database of UCI. The employed methods include (i) discriminators: greedy hypercube classifier and support vector machines, (ii) parametric approaches: Naive Bayes’ classifier with and without dimensionality reduction methods, (iii) semiparametric algorithms: Expectation-Maximization algorithm (EM), C-means, K-means, agglomerative clustering, (iv) nonparametric approaches for defining the density function: histogram and kernel estimators, (v) nonparametric approaches for learning: k-nearest neighbors and decision tree and (vi) Combining Multiple Learners: Boosting and Bagging. These methods are compared based on various metrics. Computational results indicate superior performance of the implemented methods compared to the previous methods using the mentioned dataset. In general, Boosting, Bagging, Unpruned Tree and Pruned Tree (θ = 10-7) have given better results compared to the existing results. Also the efficiency of the implemented decision tree is better than the other employed methods and this method improves the classification precision, TP-rate, FP- rate and MSE of the classes by 0.1%, 0.1%, 0.001% and 0.001%.
Keywords: guidance of mobile robot, classifier, parametric approach, semiparametric approach, nonparametric approach -
Scientia Iranica, Volume:29 Issue: 4, Jul-Aug 2022, PP 2191 -2209In this paper, sustainability-related factors driving success of healthcare system management include a group of hospitals are considered. A three-pronged approach is considered based on the internal functions of the hospital, which are affecting the social responsibility as well as functions related to the service recipients from health centers. A novel comprehensive multi-period evaluation of hospitals’ performance is considered by the proposed dynamic network. This hybrid data envelopment analysis-based fuzzy multi-criteria decision-making model incorporates fuzzy DEMATEL and best-worst method provides several useful managerial insights using a realistic case study from Iran for sustainable management of the healthcare system. Obtained results indicate the importance of considering potential inter-related relations between network nodes on comprehensive performance assessment of healthcare service system.Keywords: Healthcare management, Sustainable Development, uncertainty, dynamic, Hybrid assessment method, Hospital network
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Scientia Iranica, Volume:29 Issue: 4, Jul-Aug 2022, PP 2029 -2039High penetration of Power Electronic (PE) converters in DC power grids has caused new stability challenges due to dynamic interactions among a network’s subsystems. Dynamic interactions can be avoided by the impedance coordination between the subsystems through the modification of control loops or passive elements inside a grid. Impedance coordination is a very complex and time-consuming task with no adaptations to dynamic changes in a power grid. In this paper, the concepts of dynamic interaction and passivity are explained and combined together to provide an online stability measure in terms of the DC bus impedance characteristics. A novel DC Power System Stabilizer (PSS) is proposed which is connected to a DC bus as a separate module passivizing the bus impedance at non-passive interaction frequencies. The interaction frequencies are detected through a broadband online identification process. The PSS working principle, topology, modeling, and control designs are explained in detail. Finally, the functionality and performance of the proposed stabilizer are validated by simulation results.Keywords: Dynamic Interaction, passivity, power system stabilizer, System Identification
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The main contribution of this paper is to present the systematic and low-complexity translation techniques betweena class of hybrid systems referred to as automaton-based DHA and piecewise affine (PWA) systems. As an startingpoint the general modeling framework of the automaton-based DHA is represented which models the controlled anduncontrolled switching phenomena between linear continuous dynamics including discrete and continuous states,inputs and outputs. The basic theoretical definitions on the state trajectories of the proposed DHA with forwardand backward evolutions which yield forward and backward piecewise affine (FPWA and BPWA) systems are given.Next, the well-posedness and equivalency properties are proposed and the sufficient conditions under which the wellposedness property is achieved with the automaton-based DHA and PWA systems are given. It is shown that thegraphical structure of the proposed automaton-based DHA makes it possible to obtain analytically the equivalent PWAsystem with a polynomial complexity in contrast to the existing numerical translation techniques via decomposedstructure of the DHA with an exponential complexity. Examples are presented to confirm the effectiveness of theproposed translation techniques.Keywords: Automaton-based discrete-time hybrid automaton, Piecewise affine (PWA) systems, Well-posedness, complexity, Equivalency, translation techniques
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Scientia Iranica, Volume:28 Issue: 6, Nov-Dec 2021, PP 3450 -3463In this paper, a single synchronous reference-frame based control method is proposed to improve the performance of AC-DC interlink converters feeding DC loads under unbalanced AC grid conditions. Unbalanced grid voltages cause undesirable double frequency (2ω0) oscillations on the DC link voltage in AC-DC converters. In the medium/high power applications, low switching frequency, and the oscillatory power of the input filter considerably degrade the functionality of the existing methods for removing 2ω0 ripples from DC link voltage. In this paper, an analytical equation for the terminal active power is derived considering the input filter inductance. Accordingly, suitable current references are proposed to eliminate the undesirable 2ω0 ripples from DC-link voltage considering low switching frequency. It is shown that the filter inductance adds a non-linear term to the active power equation which complicates the current reference calculation. Accordingly, a real-time recursive method is proposed to solve the equations and find the current references. To evaluate the performance of the proposed method, different grid unbalanced conditions, including asymmetrical short circuit faults, are applied to a test system in the PSCAD/EMTDC environment. Furthermore, the functionality of the proposed method is compared with that of the existing method for unbalanced conditions in the literature.Keywords: AC-DC power converters, DC link voltage control, interlink converter, unbalanced input voltages
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Scientia Iranica, Volume:28 Issue: 5, Sep-Oct 2021, PP 2890 -2909In classical inventory control problems, it is usually assumed that all of items are of perfect quality, and the inspection process works perfectly well. However, in practice, the order lots often contain imperfect quality items, and the inspection process, for recognition of these items, is not necessarily error-free. In this article, we extend the economic order quantity model under imperfect quality items where the inspection process involves type I and II errors. The type I error can lead to recognition of perfect quality items as defective, while the type II error can lead to delivery of imperfect quality items to customers even for several consecutive times. We present two cases depending on the length of special inspection process and determine optimal order sizes, analytically, for maximizing total profit per unit time for both cases. A numerical example is provided to compare two cases and a sensitivity analysis is discussed to assess the effect of main parameters on the total profit per unit time.Keywords: Inventory control, Imperfect Quality, Imperfect Inspection Process, Batch Replacement, Type I, II errors
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نشریه مطالعات کتابداری و سازماندهی اطلاعات، سال سی و یکم شماره 2 (پیاپی 122، تابستان 1399)، صص 38 -50هدف
تحلیل و دیداری سازی برون داد علمی فصلنامه مطالعات ملی کتابداری و سازماندهی اطلاعات از نظر شاخص های علم سنجی طی یک دهه از 1388 تا 1397.
روش شناسیبا استخراج داده های لازم از پایگاه استنادی علوم جهان اسلام و یکدست سازی اسامی و کلیدواژگان، شاخص های علم سنجی فصلنامه با کمک نرم افزارهای مختلف علم سنجی تعیین و ترسیم شد.
یافته هاالگوی نویسندگی عمدتا چندنویسندگی و شبکه هم نویسندگی حاکی از همکاری مستحکم علمی میان نویسندگان بود. هم رخدادی واژگان و خوشه بندی کلیدواژه ها نشان از تنوع موضوعی فصلنامه در راستای اهداف تخصصی آن داشت.
نتیجه گیریبا وجود ارتقای شاخص های علمی فصلنامه و توسعه مناسب در حوزه موضوعی، لازم است به افزایش استنادپذیری و رویت پذیری مقالات آن برای اثرگذاری بیشتر توجه کرد.
کلید واژگان: علم سنجی، مطالعات ملی کتابداری و سازماندهی اطلاعات، دیداری سازی علمPurposeAnalyzing and visualizing the scientific output made by the National Studies on Librarianship and Information Organization (NASTINFO) from a scientometric perspective during 2009-2018.
MethodologyBy extracting needed data from ISC and unifying names and keywords, the scientometric indicators of NASTINFO were determined and made visualized by applying some scientometric software packages.
FindingsNASTINFO had a multi-authored authorship pattern and its co-authorship network showed a significant collaboration among its authors. Co-word occurrence and keyword clustering networks revealed that NASTINFO considered its vast variety of related topics.
ConclusionIn spite of its progression in the scientific indicators and appropriate development in its special field, NASTINFO needs to increase its citability and visibility for its more influence.
Keywords: Scientometrics, National Studies on Librarianship, Information Organization (NASTINFO), Visualization of Science -
برنامه ریزی ظرفیت تولید و زمانبندی تولید جزئی از فرآیند تصمیم گیری در زنجیره تامین بسیاری از صنایع ساخت و خدماتی محسوب می شوند که نقش مهمی را در برآورده سازی نیازهای مشتریان و ارتقای سطح خدمت دهی به مشتریان ایفا می نمایند. از آنجائیکه این دو فرآیند در دو سطح متفاوت از زنجیره تامین عمل می نمایند (برنامه ریزی ظرفیت در سطح تاکتیکی و زمانبندی تولید در سطح عملیاتی)، لذا معمولا تصمیمات مربوط به این دو حیطه نیز مستقلا و جدای از هم اتخاذ می شود. در چنین شرائطی شدنی بودن تخصیص ظرفیت انجام شده در سطح تاکتیکی، زمانیکه برنامه بصورت عملیاتی وارد کارگاه می شود، به عنوان یکی از چالش های اصلی این رویکرد تصمیم گیری مجزا، مطرح است. لذا در این تحقیق، پس از مدلسازی یکپارچه مساله برنامه ریزی ظرفیت تولید و مساله زمانبندی تولید دو ماشینه، به ارائه یک رویکرد حل تحلیلی مبتنی بر تجزیه مساله پرداخته شده است. در راستای کمینه سازی حداکثر زمان تکمیل سفارشات، مفهومی تحت عنوان «زوج سفارش» تعریف، و الگوریتمی جهت تعیین زوج سفارشات بهینه بر مبنای مساله تخصیص متقارن ارائه می شود. سپس در راستای تعیین توالی بهینه ی زوج سفارشات، الگوریتم شاخه و کرانی بر مبنای سه کران پائین پیشنهادی و همچنین دو استراتژی جستجوی عمق اول و سطح اول، طراحی و در راستای افزایش کارآیی آن تعدادی ویژگی ریاضی اثبات، و بر اساس آن ها تعدادی قائده چیرگی جهت مساله استخراج شده است. همچنین جهت تعیین مقادیر تخصیص ظرفیت به عملیات، یک الگوریتم جستجوی همسایگی طراحی و بر اساس ویژگی های ساختاری مساله بهبود داده شد.
کلید واژگان: برنامه ریزی ظرفیت، زمانبندی سفارشات، الگوریتم شاخه و کران، کران پائین، استراتژی جستجوInternational Journal of Industrial Engineering & Production Management, Volume:24 Issue: 2, 2013, PP 117 -139Production capacity planning and scheduling are parts of decision process in supply chain of many manufacturing and service industries, which have important role in satisfying customer requirements and enhancing customer service level. Since these two processes performs in two different levels of supply chain (capacity planning in tactical level and scheduling in operational one), usually their decision are made independently. In such circumstances, the feasibility of capacity decisions in tactical level, when plan imports into the shop floor, is one of the critical challenges in this decision making approach. Hence in this paper, after formulating the capacity planning and two-machine scheduling problems integrately, an analytical solution approach will be presented. In order to minimize the maximum completion time of orders, concept of order pairs is defined and the optimal orders pairs are established based on the optimal solution of symmetric assignment problem. Afterwards, to determine the optimal sequence of order pairs, a branch and bound procedure is designed which is based on three proposed lower bounds, depth first and best first strategies. To improve the efficiency of algorithm, some mathematical properties are proved and some corresponding dominance rules are derived. Furthermore, to delineate the quantity of resource allocation to the operations, a neighborhood search algorithm is designed and improved based on some structural properties of problem.
Keywords: Capacity Planning, Order Scheduling, Branch, Bound Algorithm, Lower Bound, Search Strategy
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