Sharif Digital Repository

A novel MED-based desalination system for low-grade heat sources with a temperature between 65 °C and 90 °C has been proposed. Low-grade heat-driven desalination systems are of the most important methods for increasing energy efficiency and assisting the environment along with alleviating the water scarcity problem. The new proposed system is known as cascade multi-effect distillation (CMED). It is designed based on multi-step heat extraction from the heat source fluid (HSF). Multi-step heat absorption helps to form two arrays of MED effects and to utilize two boosters to achieve better performance. The advantage of this system is less complexity (for example, lower vapor injection), and... 

The energy efficiency of emerging nonvolatile processors equipped with FRAM-SRAM memory makes them a promising solution for energy harvesting systems. To enable correct functionality and forward progress with an unreliable power supply, the system must accumulate sufficient energy in the capacitor to execute tasks atomically, even in the worst case scenario. Due to the large gap between the average and worst case energy consumption of tasks, state-of-the-art approaches like eM-map require a large capacitor to execute tasks on the SRAM. However, the size, cost, and charging time of the capacitor are major concerns in the energy harvesting systems. In this article, we proposed CHANCE, a... 

Radiative sky cooling (RSC) systems have enjoyed a privileged position in the research community due to generating cooling energy without consuming electricity using the open atmospheric window and infrared emission to the sky. However, the system's justification occurs when it reaches a temperature below the minimum 24-hour ambient temperature. This study utilizes phase change materials (PCM) as the energy storage of a hybrid daytime photovoltaic-thermal and nighttime RSC module and investigates the nocturnal cooling energy-saving potential of the system at different phase transition temperatures. After being validated by the experimental data in the literature, the simulated model was used... 

The renewed attention paid to rammed earth materials in recent decades is related to their sustainability, high thermo-buffering capacity and relatively low cost. The energy performance of rammed earth materials can be enhanced with stabilization. However, some of thermal enhancement methods have destructive side-effects. In the current study, the effect of three different methods was investigated on thirteen different alternatives of rammed earth materials to improve energy efficiency of buildings. These methods include using phase change materials, cementitious admixtures and external insulators. Thermo-dynamic parameters such as time lag, thermal conductivity and heat flux were measured... 

Renewable hydrogen production plays a key role in transitioning to a hydrogen economy. For this, developing countries are encouraged to keep up with industrialized nations. As such, this study seeks to evaluate the potential of all capital cities of Iran in terms of solar-based hydrogen production and prioritize the nominated alternatives. This step is highly valued because finding the most suitable place for this purpose can lead to substantial outcomes and consequently avoid failure. Therefore, here a 20-kW solar power plant is simulated by PVsyst 6.7 software and meteorological data of 31 capital cities is extracted using Meteonorm 7.1 software. Considering all losses associated with... 

Reducing the renewable energy costs is necessary for the competition with the fossil energies and control strategies have great impact on the efficiency of wind machines. In the wind turbine industry, a practical approach is to maximize the energy capture of a wind machine by optimizing the power coefficient in the under-rated situations. In this paper, with the main objective of maximizing the energy capture in the second region, four different control strategies are compared in the presence of uncertainties. The proposed control methods are compared based on their power capture and robustness against probable uncertainties in the structural and environmental parameters. A two-mass... 

Efficient utilization of solar energy as the cleanest and most plentiful natural resource for drinking water is a water is as sustianble and environmental friendly approach to obviate long-standing water scarcity. Carbon-based photothermal absorbers due to broadband light absorption are very interesting in interfacial solar steam generation systems. Herein, we investigate the convenient application of reduced graphene oxide (rGO) nanosheets with carbon black (CB) nanoparticles on the cotton fabric as a flexible texture-based photothermal absorber. Polyurethane (PU) as a self-floating insulator foam was selected to manage the energy loss and preserve light converted to heat on the fabric... 

Given the various advantages of electric vehicles compared to conventional gasoline vehicles in terms of energy efficiency and environmental pollution (among others), this paper studies the factors affecting customers’ willingness to purchase electric vehicles. An integrated discrete choice and agent-based approach is applied to model the customers’ choice for the valuation of electric vehicles based on the internal reference price. The agent-based model evaluates customers’ preferences for a number of personal and vehicle attributes, according to which vehicle they chose. Data from 376 respondents are collected to estimate a random-parameter logit model where customers are asked to reveal... 

Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the... 

Energy harvesting systems powered by renewable energy sources employ hybrid volatile-nonvolatile memory to enhance energy efficiency and forward progress. These systems have unreliable power sources and energy buffers with limited capacity, so they complete long-running applications across multiple power outages. However, a power outage might cause data inconsistency, because the data in nonvolatile memories are persistent, while the data in volatile memories are unsteady. State of the art studies proposed various memory architectures and compiler-based techniques to tackle the data inconsistency in these systems. These approaches impose too many unnecessary check-points on the system to... 

Solar heater has been known as an application of the solar thermal energy that is commonly employed for water heating. Purpose of this research is to introduce a conceptual model for employing solar water heaters (SWHs) in Yazd, Iran. Moreover, structural equation modeling (SEM) is used for assessing effect(s) of the available parameters on the suggested model. Political-cultural-social issues, economic issues, financial support, geographic location, infrastructure, and interactions were assessed as the independent variables of the study. AMOS was used to implement the processes and design the research questionnaire. According to SEM, the dependent variable “interaction” via “economic... 

Hyperdimensional (HD) computing is a lightweight machine learning method widely used in Internet of Things applications for classification tasks. Although many hardware accelerators are proposed to improve the performance of HD, they suffer from low flexibility that makes them not practical in most real-life scenarios. To improve the flexibility, an open-source instruction set architecture (ISA) called RISC-V has been employed and extended for a specific application such as machine learning. This article aims to improve the efficiency and flexibility of HD computing for resource-constrained applications. To this end, we extend a RISC-V core (RI5CY) for HD computing called RISC-HD. First, to... 

A new strategy for enhancing the efficiency of TiO2 dye-sensitized solar cells (DSSCs) by design of a new double-layer film doped with Zn ions, with various morphologies and phase compositions, is reported. X-ray photoelectron spectroscopy (XPS) revealed that Zn2+ (in the range 0.25-0.1 at.%) was successfully incorporated into the TiO2 lattice without forming secondary phases. X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) analyses showed that the synthesized nanoparticles had nanometer grains with different phase compositions and average crystallite sizes in the range of 8-48 nm, depending upon Zn atomic percentage. UV-vis absorption verified that Zn... 

In advanced combined-cycle power plants, significant improvements in the thermodynamic performance are mainly achieved by the development of more efficient gas-turbine systems. This paper evaluates the effect of selected decision variables in the steam system for optimization of Thermal Combined Cycle Gas Turbine (TCCGT) power plant using an iterative exergoeconomic. The design variables were the thermodynamic parameters that establish the configuration both of the steam and gas systems. The design data of an existing plant (Damavand power plant in Tehran-Iran) is used. Two different objective functions are proposed: one minimizes the total cost of production per unit of output, and the... 

The emerging multimedia applications of Wireless Sensor Network (WSNs) impose new challenges in design of algorithms and communication protocols for such networks. In the view of these challenges, error control is an important mechanism that enables us to provide robust multimedia communication and maintain Quality of Service (QoS). Despite the existence of some good research works on error control analysis in WSNs, none of them provides a thorough study of error control schemes for multimedia delivery. In this paper, a comprehensive performance evaluation of Automatic Repeat Request (ARQ), Forward Error Correction (FEC), Erasure Coding (EC), link-layer hybrid FEC/ARQ, and cross-layer hybrid... 

The objective of this research is geometrical optimization of half toroidal Continuously Variable Transmission (CVT) in order to achieve high power transmission efficiency. The dynamic analysis of CVT is implemented and contact between the disk and the roller is modeled viaelastohydrodynamic (EHL) lubrication principles. Computer model is created using geometrical, thermal and kinetic parameters to determine the efficiency of CVT. Results are compared by other models to confirm the model validity. Geometrical parameters are obtained by means of Particle Swarm Optimization (PSO) algorithm, while the optimization objective is to maximize the power transmission efficiency. Optimization was... 

Enzymatic decolorization of reactive blue 221 (RB221) using laccase was investigated in a dual-chamber microbial fuel cell (MFC). Suspended laccase was used in the cathode chamber in the absence of any mediators in order to decolorize RB221 and also improve oxygen reduction reaction in the cathode. Molasses was utilized as low cost and high strength energy source in the anode chamber. The capability of MFC for simultaneous molasses and dye removal was investigated. A decolorization efficiency of 87% was achieved in the cathode chamber and 84% COD removal for molasses was observed in the anode chamber. Laccase could catalyze the removal of RB221 and had positive effect on MFC performance as... 

Wireless networks with the shared media require Medium Access Control (MAC) protocol that provides contention resolution mechanism. The design of MAC protocol in underwater sensor networks is a challenging issue because of limited energy source and high propagation delay. The most important goal of the MAC design for underwater sensor networks is to resolve data packet collision efficiently with respect to energy consumption. So, selection of MAC protocol is an important task because it has significant impact on the system efficiency. A suitable MAC protocol must consider some factors such as fairness, energy consumption, latency and throughput based on various applications. The bandwidth in... 

In this paper, we present two energy-efficient full adders (FAs) which are a crucial building block of nano arithmetic logic units (nano-ALUs) with the Cell Design Methodology (CDM). Since the most suitable design configuration for CNT-based ICs is pass transistor configuration (PTL), CDM which properly benefits from PTL advantages is utilized. So the designs herewith take full advantages of simplicity, fewer transistors and better immunity against threshold voltage fluctuations of the PTL than the CCMOS configuration. CDM also resolves two problems of PTL by employing elegant mechanisms which are threshold voltage drop and loss of gain. Using the amend mechanisms and SEA sizing algorithm... 

An optimal soft multiple-input multiple-output (MIMO) detector is proposed with linear complexity for a general spatial multiplexing system with two transmitting symbols and NR 2 receiving antennas. The computational complexity of the proposed scheme is independent of the operating signal-to-noise ratio and grows linearly with the constellation order. It provides the soft maximum-likelihood solution using an efficient log-likelihood ratio calculation method, avoiding the exhaustive search on all the candidate nodes. Moreover, an efficient pipelined hardware implementation of the detection algorithm is proposed, which is fabricated and fully tested in a 130-nm CMOS technology. Operating at...