Sharif Digital Repository

Purpose: The purpose of this paper is to present and evaluate the performance of innovation systems by considering two indicators of efficiency and effectiveness. The scope of the evaluation is globally and due to the situation of each country, the suggested strategies are proposed to maintain the status quo or move toward the desired situation for countries. Design/methodology/approach: The approach is to compare and benchmark the countries in terms of the efficiency and effectiveness of their innovation system. The Global Innovation Index report’s input-to-output ratio and the global competitiveness report are used for the assessment. Findings: The findings indicate that countries such as... 

Purpose: The purpose of this paper is to present and evaluate the performance of innovation systems by considering two indicators of efficiency and effectiveness. The scope of the evaluation is globally and due to the situation of each country, the suggested strategies are proposed to maintain the status quo or move toward the desired situation for countries. Design/methodology/approach: The approach is to compare and benchmark the countries in terms of the efficiency and effectiveness of their innovation system. The Global Innovation Index report’s input-to-output ratio and the global competitiveness report are used for the assessment. Findings: The findings indicate that countries such as... 

The sampling process in electrical devices includes non-linear distortion which needs to be compensated to boost up the system efficiency. In this paper, a blind method is suggested for non-linear distortion compensation. The core idea is to leverage the sparsity of the signal to cope with the ill-posedness of the distortion compensation task. The proposed scheme is an iterative method based on out of support energy minmization where the support information is not available. An adaptive thresholding operator is used to give a rough approximation of the support according to the estimated signal at each iteration. Various simulation scenarios have validated the capability of the suggested... 

The sampling process in electrical devices includes nonlinear distortion that needs to be compensated to boost up the system efficiency. In this brief, a blind method is suggested for nonlinear distortion compensation. The core idea is to leverage the sparsity of the signal to cope with the ill-posedness of the distortion compensation task. The proposed scheme is an iterative method based on out of support energy minimization, in which the support information is not available. An adaptive thresholding operator is used to give a rough approximation of the support according to the estimated signal at each iteration. Various simulation scenarios have validated the capability of the suggested... 

Warm-up period is considered as the most critical phase in the operation of any device that converts the energy of a fuel into heat, electricity, and other products, including power generation units since the system efficiency and environmental pollution levels are much worse than the normal operation in that phase. Considering this point, in this study, applying the zero-flow coolant strategy to reduce the warm-up period is suggested for power generation units and it is investigated in details. An internal combustion engine is selected as the case-study and implementation of the method to enhance the performance of that from both energy and environmental aspects are studied comprehensively.... 

An experimental study was conducted on a solar hybrid system to transform the waste heat of photovoltaic module (PV module) into a useful heat which could be used in a solar desalination (SD) system in order to produce freshwater (scenario 1). Then, different parameters such as the amount of the produced freshwater by condensed vapor on the glass cover and basin side walls were taken into consideration after the fabrication of the SD system. Furthermore, the effect of water depth in the tray and the effect of the presence of a fan inside the basin (scenario 3) on water yield (kg/m2hr) were evaluated. In addition, the effects of using a mirror to lead the reflected light on the PV module and... 

Presently, the urgency of creating efficient system to tackle natural hazards such as tsunamis, earthquakes, landslides and floods to cite just a few, have originated that Wireless Sensor Networks (WSNs) play an increasingly important role in the natural hazards scenario as an efficient early warning system, sometimes in synergy with satellites-GMES (Global Monitoring Earth Systems) and also with mobile robotics. Their integration into the web scenario, giving rise to the sensor-web technology, provides even more power to the intrinsic strengths of WSNs. The WSNs application in post-disaster scenarios is also an emerging challenging issue. In this paper the fundamental technology concepts of... 

In the present work, effects of height, length, and width of a single-slope basin-type solar still on its distillate production was investigated. For this purpose, a radiation model was developed which accounts for the influences of all walls on quantities of received solar radiation by the base and saline water of the still. Moreover, in this radiation model, the side walls of the still were considered as the trapezoid and the diffuse as well as beam components of solar irradiance were separately taken into account for the first time. Abilities of the present model were compared with earlier ones. Furthermore, the predictions of the current model were compared with the present experimental... 

Due to serious problems of SRAM-based caches in nano-scale technologies, researchers seek for new alternatives. Among the existing options, STT-RAMseems to be themost promising alternative.With high density and negligible leakage power, STT-RAMs open a new door to respond to future demands of multi-core systems, i.e., large on-chip caches. However, several problems in STT-RAMs should be overcome to make it applicable in on-chip caches.High probability of write error due to stochastic switching is amajor problemin STT-RAMs. Conventional Error-CorrectingCodes (ECCs) impose significant area and energy consumption overheads to protect STT-RAMcaches. These overheads in multi-core processors with... 

This research is aimed at geometric analysis of parabolic trough solar collector (PTC) in different sizes of the main components of the system. The rate of the Local Concentration Ratio (LCR) on the receiver tube and optical efficiency are two main features in geometric optimization of the parabolic trough solar collectors. In this work, parabolic trough solar collector was optimized for different sizes with three design variables: the receiver diameter, the collector aperture width and the rim angle. The method used in this research was the Monte Carlo Method (MCM) in MATLAB. The optical and geometric modeling was developed for coding in MATLAB. For the case study, a parabolic trough solar... 

In recent years, a great deal of attention has been paid to multi-energy systems that improve energy efficiency and reliability. In this respect, this paper examines the issue of energy flow of these systems in a probabilistic context in the presence of energy responsive programs. Responsive energy programs are provided by system operator of multi-carrier energy to manage these networks where energy customers can participate in it. The probabilistic method used is 2m + 1 point estimation method, which has high speed and high accuracy. The presented numerical results show the impact of each responsive energy program on the cost of operating a multi-carrier system. © 2019 IEEE  

Gravity drainage is known as the controlling mechanism of oil recovery in naturally fractured reservoirs. The efficiency of this mechanism is controlled by block-to-block interactions through capillary continuity and/or reinfiltration processes. In this study, at first, several free-fall gravity drainage experiments were conducted on a well-designed three-block apparatus and the role of tilt angle, spacers’ permeability, wettability and effective contact area (representing a different status of the block-to-block interactions between matrix blocks) on the recovery efficiency were investigated. Then, an experimental-based numerical model of free-fall gravity drainage process was developed,... 

In this paper, a common energy harvester is investigated which uses a specimen of magnetic shape memory alloy (MSMA). The aim of this study is to improve system performance and to evaluate the magneto-mechanical loading on the MSMA material. Since demagnetization effect is not included in the employed original MSMA model, a method to incorporate this effect is proposed which has a good performance for the specific magneto-mechanical loading of this problem. In order to decrease the need for bias magnetic field and increase system efficiency, a new return mechanism for the MSMA specimen is proposed. The results indicate that the maximum harvested power from the improved system is obtained at... 

Distributed generation (DG) corresponds to the application of small generating units which are the set up in distribution systems or near load centers. Utilization of DG influences various operational indices of the distribution feeders such as feeder loading, electrical losses and voltage profile. In addition, use of DG in its appropriate size is an essential tool to attain the DG maximum potential advantages. In this paper, an optimization method is proposed to determine the optimal size of DG in the distribution system. This method considers the system technical factors such as losses, voltage profile and loading of the primary distribution system feeders. The optimization process is... 

In the present study, enhancing the heat transfer is experimentally investigated by the electro-hydrodynamics (EHD) through a single-pass air-cooled PV/T (Photovoltaic/Thermal System). The corona wind increases the heat transfer coefficient by producing a secondary flow and vortex, and consequently, increases the PV/T system efficiency. The effects of the corona wind are studied by changing the voltage values and the flow rates in the air channel. The results show that the corona wind is effective on enhancing the system performance; so that the heat transfer coefficient increases by 65% in natural flow regime by applying 11 kV voltage in the pilot setup. Totally, the thermal efficiency of... 

Global warming escalation has extended average temperature of earth beyond its safe limit. To avert this environmental-threat, solar energy has acquired substantial attention of remarkable researchers in this century. To effectively utilize solar energy by transforming into thermal and electrical energy, the involvement of nanofluids having intensified thermal, optical and magnetic properties, has become very popular. The foremost objective of this article is to provide a comprehensive review on the applications of nanofluids in solar energy systems like solar collectors, photovoltaic cells, solar stills, and thermal energy storage, which are thoroughly discussed in this paper. The effect of... 

In this paper, a common energy harvester is investigated which uses a specimen of magnetic shape memory alloy (MSMA). The aim of this study is to improve system performance and to evaluate the magneto-mechanical loading on the MSMA material. Since demagnetization effect is not included in the employed original MSMA model, a method to incorporate this effect is proposed which has a good performance for the specific magneto-mechanical loading of this problem. In order to decrease the need for bias magnetic field and increase system efficiency, a new return mechanism for the MSMA specimen is proposed. The results indicate that the maximum harvested power from the improved system is obtained at... 

The efficient catalytic systems were investigated for the oxidation of various sulfide by manganese(III)-oxazoline complexes, [Mn(phox)2(MeOH)2]ClO4 and Mn(phox)3 (Hphox = 2-(2′-hydroxyphenyl)oxazoline). These complexes were found efficient catalysts for the oxidation of sulfides with urea hydrogen peroxide (UHP) in short reaction times (5 min) and under mild condition. Sulfoxides were obtained as the main products together with variable amounts of sulfones. The efficiency of the catalytic system was strongly influenced by the nature of solvents and axial ligands so the best yields were achieved in a mixture of methanol: dichloromethane and in the presence of imidazole as co-catalyst. © 2008... 

In the realization of adaptive beamforming algorithms, the least-mean-squares (LMS) algorithm had been the most popular scheme used for Smart Antenna systems. This Paper proposes an alternate scheme in the form of the Normalized LMS (NLMS) algorithm with active tap detection for WCDMA systems. By taking advantage of spatial filtering, the proposed scheme promises to reduce the bandwidth required for transmitting data by improving convergence rate. The performance of the Frequency Domain NLMS algorithm in the presence of multipath effects and multiple users is analyzed using simulations. This analysis is compared to that of LMS algorithm and suggests improvement in the convergence rate and...