• Biomass logistics A review of important-taliem-ir

    Biomass logistics: A review of important features, optimization modeling and the new trends

    تومان

    Biomass logistics comprise of inter-dependent operations related to harvesting and collection, storage, preprocessing, and transportation. Its high cost represents one of the barriers in widespread use of biomass for energy and fuel production. Therefore, improving and optimizing biomass logistics are essential in overcoming this barrier. Biomass logistics was reviewed in a previous study that aimed at categorizing logistics operations, but the inherent issues and complexities, and how they were incorporated in mathematical models were not discussed in detail. The objective of this paper is to review the important features of biomass logistics operations, discuss how they were incorporated in mathematical optimization models, and explain the new trends in biomass logistics optimization. Differences between the models dealing with forest-based and agriculture-based biomass are highlighted. Important features incorporated in logistics models include demand-driven and supplydriven collection, collection of biomass in different forms, storage at intermediate facilities, biomass quality deterioration, inter-modal distribution for long-distance transportation, operational level transportation planning, and planning the pre-processing of biomass. Recent trends in biomass logistics models include the consideration of scattered availability of biomass across supply areas, uncertainties in biomass supply, integration with GIS, emissions from logistics operations, and traffic congestion due to biomass transportation. Most of the literature on biomass logistics focused on medium-term planning, while that for short-term planning is still in its infancy. The current biomass logistics models focused mainly on economic objectives, while environmental concerns related to emissions from logistics activities received limited attention. The trade-off between environmental and economic aspects of biomass logistics operations have not been investigated. Social aspects such as increase in traffic congestion due to biomass transportation received limited attention in the literature. Most of the previous models were tested on hypothetical cases, while developing suitable models to address practical issues in real case studies would be valuable.

     

  • A DFO technique to calibrate queueing models[taliem.ir]

    A DFO technique to calibrate queueing models

    تومان

    A crucial step in the modeling of a system is to determine the values of the parameters to use in the model. In this paper we assume that we have a set of measurements collected from an operational system, and that an appropriate model of the system (e.g., based on queueing theory) has been developed  Not infrequently proper values for certain parameters of this model may be difficult to estimate from available data (because the corresponding parameters have unclear physical meaning or because they cannot be directly obtained from available measurements, etc.). Hence, we need a technique to determine the missing parameter values, i.e., to calibrate the model. As an alternative to unscalable “brute force” technique, we propose to view model calibration as a nonlinear optimization problem with constraints. The resulting method is conceptually simple  and easy to implement. Our contribution is twofold. First, we propose improved definitions of the “objective function” to quantify the “distance” between performance indices produced by the model and the values obtained from measurements. Second, we develop a customized derivative-free optimization (DFO)  technique hose original feature is the ability to allow temporary constraint violations. This technique allows us to solve this optimization problem accurately, thereby providing the “right” parameter values. We illustrate
    our method using two simple real-life case studies.

  • A model for concurrent maintenance of bridge elements[taliem.ir]

    A model for concurrent maintenance of bridge elements

    تومان

    Maintenance activities on existing bridges are important for bridge safety and management. However, maintenance activities cause traffic jams and detours, and thus increase user costs. To reduce user costs resulting from maintenance activities while maintaining bridge elements in good condition, we introduce the concept of “concurrent element maintenance.” The concurrent maintenance concept attempts to integrate maintenance timings of different elements of a bridge to reduce user costs over the bridge’s life cycle. The proposed model adopts constraint programming as the search algorithm for optimizing the maintenance strategy of any bridge .An example using real data for a reinforced  concrete highway bridge is presented. Sensitivity analysis of the discount rate investigates its influence on the life-cycle cost. The results demonstrate that the proposed model is effective for reducing the user costs as well as the total life-cycle costs.

  • A Novel Hybrid Network Architecture to Increase[taliem.ir]

    A Novel Hybrid Network Architecture to Increase DG Insertion in Electrical Distribution Systems

    تومان

    Distribution networks will experience a deep mutation concerning their planning and operation rules due to  the expected increase of distributed generation (DG) interconnection to the grid. Indeed, the opening of the electricity market or the growing global concern for environmental issues will lead to a massive development of DGs. Yet, a too large amount of DGs could raise technical problems on distribution networks which have not been planned to operate with bi-directional power flow. The existing solutions to solve marginal DG  connections could be no longer relevant. The distribution network definitely has to evolve towards a smarter and more flexible network. Two possible ways to reach this goal are through new architectures and  developing intelligent systems. This paper focuses on new architectures and operating modes. The traditional radial distribution network could accept more DGs by introducing appropriately specific loops. A new hybrid structure enabling the coexistence of the radial and meshed operation is proposed. It is equipped with  autonomous circuit-breakers and automated switches that improve its reliability. A heuristic algorithm is also proposed to build this new architecture while ensuring the equality of consumers with respect to the  continuity of service and while minimizing the global cost.

  • A parameter study and optimization-taliem-ir

    A parameter study and optimization of two body wave energy converters

    تومان

    This paper studies the multidisciplinary nature of two body wave energy converters by a parametric study based on the Taguchi method which helps to understand the effect of different dependent parameters on the wave energy conversion performance. Seven different parameters are analyzed and their effect on the maximum captured power, resonance frequency and bandwidth is studied. An interesting comparison between a cylindrical submerged body and a spherical one was made in terms of the system’s viscous damping and hydrodynamics. The best system parameter combinations based on the maximum output power, best resonant frequency and frequency bandwidth were identified from the outcomes of the Taguchi method and optimized to capture the maximum power to operate in the specific (Australian) sea regions where the waves’ frequencies are relatively low. This paper should provide a guideline for designers to tune their parameters based on the desired performance and sea state.

  • MIMO Capacity Improvement.[taliem.ir]

    MIMO Capacity Improvement in the Presence of Antenna Mutual Coupling

    تومان

    Applying MIMO technology in small wireless devices leads to closely spaced antennas, which results in antenna mutual coupling (MC) and highly correlated signals. In this paper, we investigate the effect of the terminal load impedance of the antennas on the MIMO capacity in the presence of the mutual coupling. We use a new concept of receiving mutual impedances to model the MC effect, which has been shown to have a much better performance than the conventional open-circuit voltage method in different applications of array  antennas. Simulation results for a 2×2 MIMO system with half-wavelength dipoles in different scattering  distribution scenarios, show that in our proposed method, an optimum value of the terminal load impedanceZL of the antennas can be obtained to maximise the capacity for all scattering distributions, whereas the conventional methods need to different ZL in different scattering scenarios.

  • Modeling of a Hybrid Power System.[taliem.ir]

    Modeling of a Hybrid Power System for Economic Analysis and Environmental Impact in HOMER

    تومان

    This paper shows the way to design the aspects of a hybrid power system that will target remote users. It emphasizes the renewable hybrid power system to obtain a reliable autonomous system with the optimization of the components size and the improvement of the capital cost. The system can provide electricity for a  remote located village. The main power of the hybrid system comes from the photovoltaic panels and wind generators, while the fuel cell and batteries are used as backup units. The optimization software used for this paper is HOMER. HOMER is a design model that determines the optimal architecture and control strategy of the hybrid system. The simulation results indicate that the proposed hybrid system would be a feasible solution for distributed generation of electric power for stand-alone applications at remote locations.

  • Multiobjective Mean-Risk Models for Optimization in Finance[taliem.ir]

    Multiobjective Mean-Risk Models for Optimization in Finance and Insurance

    تومان

    In this paper we propose some models for solving optimization problems which arise in finance and insurance. First the general framework for Mean-Risk models is introduced. Then several approaches for multiobjective programming, such as Mean-Value-at-Risk and Mean-Conditional Value-at-Risk are used for building the model Mean-Value-at-Risk-Conditional Value-at-Risk using both Value-at-Risk and Conditional Value-at-Risk  simultaneously for risk assessment. A two stage portfolio optimization model is developed, using Value-at-Risk and also Conditional Value-at-Risk measures in two stages separately.

  • Multiobjective Mean-Risk Models for Optimization in Finance[taliem.ir]

    Multiobjective Mean-Risk Models for Optimization in Finance and Insurance

    تومان

    In this paper we propose some models for solving optimization problems which arise in finance and insurance. First the general framework for Mean-Risk models is introduced. Then several approaches for multiobjective  programming, such as Mean-Value-at-Risk and Mean-Conditional Value-at-Risk are used for building the model Mean-Value-at-Risk-Conditional Value-at-Risk using both Value-at-Risk and Conditional Value-at-Risk  simultaneously for risk assessment. A two stage portfolio optimization model is developed, using Value-at-Risk and also Conditional Value-at-Risk measures in two stages separately.

  • Occurrence of Aichi Virus-taliem-ir

    Occurrence of Aichi Virus in retail shellfish in Italy

    تومان

    AiV-1 is considered an emerging human enteric pathogens and foodborne transmission has been  documented as an important source of exposure for humans, chiefly in relation to non-safe, risky  food habits. We surveyed the presence of AiV-1 in retail shellfish, including oysters and mussles,   identifying the virus in 3/170 (1.8%) of the analysed samples. The AiV-1 positive samples were of  different geographic origin. Upon sequence analysis of a portion of the 3CD junction region, two  AiV strains identified from harvesting areas in Northern Italy were characterised as genotype B and  displayed 99-100% identity at the nucleotide level to other AiV-1 strains detected in sewages in  Central Italy in 2012, suggesting that such strains are stably circulating in Italian ecosystems.  Interestingly, a strain identified from mussles harvested in Southern Italy could not be characterised  firmly, as inferred in the Bayesian analysis and by sequence comparison, indicating that different  AiV strains are also circulating in Italy. Viral contamination in retail shellfish challenges the microbiological guidelines for food control and requires the development and optimization of additional .diagnostic and prevention strategies

  • Optimal Electric Network Design for a Large[taliem.ir]

    Optimal Electric Network Design for a Large Offshore Wind Farm Based on a Modified Genetic Algorithm Approach

    تومان

    The increasing development of large-scale offshore wind farms around the world has caused many new  technical and economic challenges to emerge. The capital cost of the electrical network that supports a large offshore wind farm constitutes a significant proportion of the total cost of the wind farm. Thus, finding the optimal design of this electrical network is an important task, a task that is addressed in this paper. A cost model has been developed that includes a more realistic treatment of the cost of transformers, transformer substations, and cables. These improvements make this cost model more detailed than others that are currently in use. A novel solution algorithm is used. This algorithm is based on an improved genetic algorithm and includes a specific algorithm that considers different cable cross sections when designing the radial arrays. The proposed approach is tested with a large offshore wind farm; this testing has shown that the proposed algorithm produces valid optimal electrical network designs.

  • Optimal Roadside Units Placement in Urban Areas for Vehicular Networks[taliem.ir]

    Optimal Roadside Units Placement in Urban Areas for Vehicular Networks

    تومان

    The most important component of a vehicular ad hoc network (VANET), besides VANET-enabled vehicles, is roadside units (RSUs). The effectiveness of a VANET largely depends on the density and location of these RSUs. During the initial stages of VANET, it will not be possible to deploy a large number of RSUs either due to the low market penetration of VANET-enabled vehicles or due to the deployment cost of RSUs. There is, therefore, a need to optimally place a limited number of RSUs in a given region in order to achieve maximum performance. In this paper, we present two different optimization methods for placement of a limited number of RSUs in an urban region: an analytical Binary Integer Programming (BIP) method and a novel Balloon Expansion Heuristic (BEH) method. BIP method utilizes branch and bound approach to find an optimal analytical solution whereas BEH method uses balloon expansion analogy to find an optimal or near optimal solution. Our evaluations show that both methods perform optimally or near optimally compared with the exhaustive method. Further, BEH method is more versatile and performs better than BIP method in terms of
    computational cost and scalability.

  • Optimization of Manufacturing System through World Class Manufacturing[taliem.ir]

    Optimization of Manufacturing System through World Class Manufacturing

    تومان

    Each company struggles with the same question: How can I provide – at the lowest possible costs and with an acceptable delivery time – products or services that add maximum value for my customers? Firms must develop strategic objectives which result in a competitive advantage in the market place. There are many different methods which address this problem: Lean (the value adding organization), Six Sigma (the perfect organization), TOC (the unlimited organization), TPM (the smooth organization), RCM (the reliable  organization) and QRM (the cellular organization). In addition, combinations of these methods exist, like Lean Six Sigma (value adding and perfect organization) and World Class (value adding and perfect and smooth organization). The aim of this work is to present establishments of the basic model of WCM for the logistics system in the automotive industry in order to improve the work standards. The result of this research was to develop principles on strategic objectives, performance measurement systems and performance  measurement system linkages for improved organizational coordination.

  • Optimization of processing parameters of a ball mill refiner[taliem.ir]

    Optimization of processing parameters of a ball mill refiner for chocolate

    تومان

    The aim of this work was to optimize the ball mill based refining process of chocolate, in terms of refining time and energy consumption. Experiments were planned following a central composite design (CCD), considering refining time (rt) and agitator shaft speed (as) as factors. The experimental variables measured were chosen  from the main characteristics that describe unmoulded chocolate. A complete second-order model was fitted  to the experimental data. The most significant coefficients were that of energy consumption, iron content and particle size. Optimization consists in a bound minimization of refining time using the desirability function.  Before experiments, working conditions were 70 rpm for as and 55 min for rt. The optimum conditions  calculated by optimization were as follows: 58 rpm for as and 38.5 min for rt. The new working conditions identified for the ball mill considered enabled to rise output from 109 kg/h to 156 kg/h, with a 43% increase in productivity. A control experiment carried out in the optimized conditions to corroborate the results obtained, confirmed calculated expectations of response variables.

  • Optimized Design Considering the Mass Influence of an Axial[taliem.ir]

    Optimized Design Considering the Mass Influence of an Axial Flux Permanent-Magnet Synchronous Generator With Concentrated Pole Windings

    تومان

    In this paper, the efficiency optimization of an axial flux permanent-magnet synchronous generator with  concentrated pole windings is examined for a 3.6 kW/2000 rpm combined heat and power application.  Because the efficiency of the machine is important, specific measures are taken in order to reduce losses in the machine: thin laminated grain oriented material in the teeth, concentrated pole windings, and segmented magnets. A study of the influence of a limited set of geometry parameters on the efficiency of this type of  machine is done, using both analytical and finite-element methods. In the analytical as well as in the finite- element model, the inherent 3-D geometry of the axial flux machine is approximated by multiple 2-D models at different radii in circumferential direction. Afterwards, the influence of mass on the optimal values of the geometry parameters and the efficiency is considered, and it is found that mass can be seriously decreased with only a small reduction in efficiency. Finally, the results of both methods are compared with  measurements on a prototype to evaluate their validity.