Sharif Digital Repository

Spin-Transfer Torque Random Access Memories (STT-RAMs) are a promising alternative to SRAMs in on-chip caches. STT-RAMs face with a high error rate in write operations due to stochastic switching. To alleviate this problem, Error-Correcting Codes (ECCs) are commonly used, which results in a significant area and energy consumption overhead. This paper proposes an efficient technique, so-called Adaptive Way Allocation for Reconfigurable ECCs (AWARE), to correct write errors in STT-RAM caches. AWARE exploits the asymmetric error rate in cell switching directions, which leads to data-dependent write error rates, to reduce the ECC overheads without compromising the reliability of the cache. To... 

For the purposes of lowering environmental emission cost and increasing economic profit, energy efficient combined heat and power (CHP) units can be integrated with conventional separate heat and power production units to meet heat and power demands. The goal of this study is to develop and examine a novel heuristic and deterministic optimization algorithm for solving the profit-based unit commitment (PBUC) problem for a generation company with integrated CHP-thermal-heat only system for (i) satisfying demands for heat and power, (ii) selling spinning reserve for power, (iii) reducing environmental CO2 emission cost, and (iv) accounting for valve-point effects for steam turbines. For... 

Crosstalk faults occurring in wires of Networks on Chip (NoCs) can seriously threaten the reliability of data transfer. One efficient way to tackle crosstalk faults is numeral-based Crosstalk Avoidance Codes (CACs). Numeral-based CACs reduce crosstalk faults by preventing specific transition patterns to occur. One-Lambda Codes (OLCs) are the most efficient types of CACs. However, the codec of OLCs imposes overheads including power consumption, critical path and area occupation to the routers of NoCs. To find overhead-efficient OLCs, this paper proposes an Algorithm for Generating OLC Numeral systems (AGON). AGON provides a tradeoff for designers in selecting overhead-efficient OLCs. Using... 

Regarding the increasing number of electrical devices in the smart homes that leads to increase in total electricity consumption and cost, it is essential to use energy management methods to reduce the electricity cost. However, this can cause resident's dissatisfaction. Hence, it is important to define a method in which cost and dissatisfaction be optimized simultaneously. Among different services, an electric vehicle is the one that can be used as an energy storage system, so it can reduce the daily cost despite of increasing the total energy consumption. In this paper, we study the effect of the EV on the cost and dissatisfaction in our proposed method. © 2018 IEEE  

There are a vast number of cloud service providers, which offer virtual machines (VMs) with different configurations. From the companies perspective, an appropriate selection of VMs is an important issue, as the proper service selection leads to improved productivity, higher efficiency, and lower cost. An effective service selection cannot be done without a systematic approach due to the modularity of requests, the conflicts between requirements, and the impact of network parameters. In this paper, we introduce an innovative framework, called PCA, to solve service selection problem in the hybrid environment of peer-assisted, public, and private clouds. PCA detects the conflicts between the... 

Series of experimental tests were conducted on a section of a 660 kW wind turbine blade to measure the pressure distribution of this model oscillating in plunging motion. In order to minimize the amount of data required to predict aerodynamic loads of the airfoil, a General Regression Neural Network, GRNN, was trained using the measured experimental data. The network once proved to be accurate enough, was used to predict the flow behavior of the airfoil for the desired conditions. Results showed that with using a few of the acquired data, the trained neural network was able to predict accurate results with minimal errors when compared with the corresponding measured values. Therefore with... 

Motivated by applications of sensor networks, there has been growing interest in monitoring large scale distributed systems. In these applications, we usually wish to monitor a global system condition defined as a function of local network elements parameters. In this paper, we study Reactive Monitoring in sensor networks, which has the benefit of operating in a decentralized manner. Our primary concern in adopting such a monitoring paradigm is reducing the communication cost which is the dominant factor of energy drain in wireless sensor networks. In this study, we address the reactive aggregate monitoring problem by casting the underlying threshold assignment as an optimization problem.... 

Sectionalizing switches are the main components of any restoration scheme in fault situations of power distribution systems. In this paper, customer outage costs reduction is aimed through the optimal simultaneous placement of manual and remote-controlled switches (RCSs). Network reconfigurations are constrained such that operational considerations like statutory ranges for voltage levels, lines' thermal capacities, and necessity of radial configuration be conserved. Total cost reduction is mathematically modeled in a mixed-integer linear programming (MILP) model that makes the global optimal solution accessible. The validity of the proposed model is evaluated on the IEEE 33-bus network. In... 

Spin-Transfer Torque Random Access Memories (STT-RAMs) are a promising alternative to SRAMs in on-chip caches. STT-RAMs face with a high error rate in write operations due to stochastic switching. To alleviate this problem, Error-Correcting Codes (ECCs) are commonly used, which results in a significant area and energy consumption overhead. This paper proposes an efficient technique, so-called Adaptive Way Allocation for Reconfigurable ECCs (AWARE), to correct write errors in STT-RAM caches. AWARE exploits the asymmetric error rate in cell switching directions, which leads to data-dependent write error rates, to reduce the ECC overheads without compromising the reliability of the cache. To... 

This paper finds near equilibrium prices for electricity markets with non-convexities due to binary variables, in order to reduce the market participants’ opportunity costs, such as generators’ unrecovered costs. The opportunity cost is defined as the difference between the profit when the instructions of the market operator are followed and when the market participants can freely make their own decisions based on the market prices. We use the minimum complementarity approximation to the minimum total opportunity cost model, from previous research, with tests on a much more realistic unit commitment model than in previous research, including features such as reserve requirements, ramping... 

The sustainable design of the waste-management system is of crucial importance for cities like Tehran, capital of Iran. Tehran’s municipal solid-waste management has adopted modern practices and technologies very slowly. This study proposes the optimum pathway to reach maximum environmental benefits as well as the most cost-effective technologies according to the financial limits. The hybrid life cycle assessment (LCA)–emergy approach is applied to utilize the life cycle emissions as an inventory database to estimate the ecosystem services provided by the natural ecosystem to dilute the emissions and compensate raw material consumption. Among organic waste-treatment options, composting is... 

Using zero liquid discharge systems is one of the efficient methods to reduce the negative environmental impact of the brines of the desalination systems and also to recycle the industrial wastewaters for reuse. Due to the simple fabrication process, low maintenance cost, intensive to inlet water quality, and the ability to use renewable and low-grade-heat, modified humidification-dehumidification systems may be a proper choice for the zero liquid discharge applications. Thus, in the present study, the energy, exergy, exergoeconomic, and exergoenvironmental assessment of three advanced brine recycle humidification-dehumidification systems for zero liquid discharge operation are... 

Supplying sustainable energy is of a critical prominence nowadays. A main outcome of the galloping development in energy generation technologies is the ability to integrate multi-carrier energy systems that facilitates meeting the fast growth of energy demand. Energy hub is one of the main infrastructures making the incorporation of multi-carrier systems smoother. In this paper, the optimal scheduling problem of an energy hub structure equipped with combined heat and power, boiler, power-to-gas storage, thermal energy storage and electrical energy storage in order to supply power, heat and gas demands is presented. Power to gas is regarded as a new technology that creates a connection... 

Hybrid Multi-Level Cache Architectures (HCAs) are promising solutions for the growing need of high-performance and cost-efficient data storage systems. HCAs employ a high endurable memory as the first-level cache and a Solid-State Drive (SSD) as the second-level cache. Spin-Transfer Torque Magnetic RAM (STT-MRAM) is one of the most promising candidates for the first-level cache of HCAs because of its high endurance and DRAM-comparable performance along with non-volatility. However, STT-MRAM faces with three major reliability challenges named Read Disturbance, Write Failure, and Retention Failure. To provide a reliable HCA, the reliability challenges of STT-MRAM should be carefully addressed.... 

This article presents a mixed-integer linear stochastic model for the optimal expansion planning of electricity distribution networks and distributed generation (DG) units. In the proposed framework, autonomous DG units are aggregated and modeled using the well-known energy hub concept. In this model, the uncertainties of heat and electricity demand as well as renewable generation are represented using various scenarios. Although this is a standard technique to capture the uncertainties, it drastically increases the dimensions of this optimization problem and makes it practically intractable. In order to address this issue, a novel iterative method is developed in this article to enhance the... 

In directional drilling, the most important thing that leads to pulling out the drill string is end of mud motor working life. Considering the working conditions of down hole mud motors; increasing the mechanical properties of their stator’s elastomer is crucial. Some attempts were done to increase the motor performance through geometrical changes but lack of material improvement is significant in previous studies. In this study, NBR/nanoclay composite samples were prepared through melt intercalation in an internal mixer and tested with regard to the temperature and drilling mud of down hole. Hardness, tear, fatigue and tensile test results of neat NBR elastomer and nanocomposite of NBR and... 

This paper introduces a cyber-physical system for building automation and control that is developed based on a distributed model predictive control. The implemented distributed method significantly reduces computation overhead with respect to the centralized methods. However, continuous data transfer between subsystems, which are often far from each other, is required when using this method. Information transmission between subsystems is very often subject to the limitations of transmission bandwidth and/or short communication range resulting in significant communication overhead. This causes significant time latency between making measurements and applying control commands, which adversely... 

All costs within the life cycle of a building are known as its life cycle cost (LCC). In the design process of a building, the use of a lower initial cost index to select an option among others with similar performance may not lead to an economically optimal alternative during the life cycle. Hence, today, building designers and investors require a tool to estimate life cycle cost at the conceptual design stage to select an economically efficient option. Resilient solutions generally lead to a higher level of complexity and upfront costs and carry additional embodied environmental impact as well. This study aims to support the design of resilient buildings using a sound LCC methodology in... 

Finite element analysis of huge and/or complicated structures often requires long times and large computational expenses. Superelements are huge elements that exploit the deformation theory of a specific problem to provide the capability of discretizing the problem with minimum number of elements. They are employed to reduce the computational cost while retaining the accuracy of results in FEM analysis of engineering problems. In this research, a new shell superelement is presented to study linear/nonlinear static and free vibration analysis of spherical structures with partial or full spherical geometries that exist in many industrial applications. Furthermore, this study investigates the... 

Direct steam generation (DSG) in parabolic trough collectors causes an increase to competitiveness of solar thermal power plants (STPP) by substitution of oil with direct steam generation that results in lower investment and operating costs. In this study the integrated solar combined cycle system with DSG technology is introduced and techno-economic assessment of this plant is reported compared with two conventional cases. Three considered cases are: an integrated solar combined cycle system with DSG technology (ISCCS-DSG), a solar electric generating system (SEGS), and an integrated solar combined cycle system with HTF (heat transfer fluid) technology (ISCCS-HTF).This study shows that...