Design of a reconfigurable front‐end for a multistandard receiver for the frequency range of 800 MHz to 2.5 GHz

In this paper, a reconfigurable receiver front‐end for the frequency range of 800 MHz to 2.5 GHz is presented. The radio frequency front‐end is realized in wideband form with reconfigurable baseband filter. The proposed front‐end targets the GSM, WLAN, WCDMA, and GPS standards residing in the aimed frequency range. The necessary specifications for each individual standard have been revisited and recalculated. The interaction of the different standards and their interoperability has been thoroughly investigated and extra specifications derived for the multistandard receiver. The multistandard receiver has been designed, layouted, and simulated in RFCMOS 0.18‐μm process.     

An efficient method for combining adaptive echo and noise canceller in hands‐free systems

Acoustic interferences severely degrade the quality and the intelligibility of the desired speech signal, thus posing a severe problem for many speech applications. Several acoustic echo cancellation (AEC) techniques have been proposed with a view to solving this problem. There are, however, few reports of AEC methods working under real noisy conditions. In this paper, we investigate the maximum positive synergies of the combination of acoustic echo canceller with a new adaptive beamformer. The proposed system achieves both the AEC and noise reduction of speech in an actual environment with real noise sources. Since the AEC is located behind the fixed beamformer of the new adaptive beamformer only one AEC is required for an arbitrary number of array elements, and the AEC does not feel any repercussions from the new adaptive beamformer. The proposed system was implemented in a real environment using National Instruments NI‐PXI‐1042Q controller system and data acquisition card PXI‐4472. Experimental results show that the proposed system has successfully improved the performance of hands‐free systems. Copyright © 2008 John Wiley & Sons, Ltd.     

Data envelopment analysis and robust optimization: A review

This paper reviews the milestone approaches for handling uncertainty in data envelopment analysis (DEA). This paper presents the detailed classifications of robust data envelopment analysis (RDEA). RDEA is appropriate for measuring the efficiencies of decision-making units in the presence of the data and distributional uncertainties. This paper reviews scenario-based and uncertainty set of DEA models. It covers 73 studies from 2008 to 2019. The paper concludes with suggestions about the guidelines for future researches in the field of RDEA.     

Proposed soil classification based on the experiences of soft-ground tunneling in Iran

Bulletin of Engineering Geology and the Environment - An essential step in successful mechanized and conventional tunneling operations is a thorough characterization of ground conditions and...     

Application of modified complementary reservoir approach in analysis of water distribution networks under pressure-deficient conditions

Hydraulic simulation models which simulate water distribution systems in different operating conditions are essential tools to evaluate network reliability. Simulation models found in most commercial software are not effectively capable of analyzing demand nodes under critical conditions such as fire-fighting demand or network pipe breakage. In the current study, a combination of hydraulic model and complementary reservoir solution (CRS) method is used for solving network's problems in critical conditions for both series-looped networks and a part of water network in Ilam city (Iran). Obtained results show that CRS provide more than actual need on the demand node for some reservoir total pressure heads. Thus, two modified versions of CRS method are proposed to deal with failures of CRS in such cases. Obtained results demonstrate improved efficiency in the combined model for analyzing networks in abnormal conditions.     

Developing a conceptual model for the environmental management of power plant wastes

Despite the vital role of electricity in human life, the energy supply process produces all kinds of pollutants such as solid wastes. Unfortunately, due to the lack of specific charge of administration, lack of legal and statutory criteria for effective control, and lack of supervising organizations, in Iran the industrial wastes couldn’t be managed well. The quantity and quality of waste of power plants have been investigated, and then a questionnaire was sent to all stations. The results showed that the use of Mazut fuel and gas oil will increase the rate of wastes. In thermal-gas power plants, due to the consumption of natural gas and lack of water consumption in the production cycle, less wastes have been produced than the other thermal power plants. To determine and explain the factors affecting the production of waste in power plants, an interview was held in the presence of 40 experts in the field of power plant wastes, and after determining the factors affecting the rate of wastes in power plants, Analytical Hierarchy Processes (AHPs) were used for the weighing and prioritization of each of these factors. In the next step, according to the collected data, the conceptual model for the environmental management of power plants was provided. The most important factors in the production of wastes based on the type of fuel type are the type of power plant and the quality of water. Generally, power plant wastes are divided into three categories: ordinary, industrial, and hazardous. Ordinary wastes could be buried in the landfill of urban wastes. However, in the case of industrial and hazardous wastes, location for the landfill is necessary. Also, some wastes like clarifier sediments and combustion wastes could be reused in other industries in order to reduce the volume of these wastes and in some cases reduces the risk of as well.     

Test System for Detailed Model of Transformers for Transient Analysis Using the Electromagnetic Transient Program (EMTP)

This paper describes a detailed model of a transformer designed to evaluate the ability of winding insulation to withstand transients. The time domain electromagnetic transient program (EMTP) was used to develop a model of the transient characteristics of the winding. It is difficult for students to use EMTP and understand simulation results. This paper contains all the data needed to develop a detailed model for transient analysis and presents basic case studies and alternative design/operating configurations.     

Developing a multi-objective, multi-item inventory model and three algorithms for its solution

We develop a multi-objective model in a multi-product inventory system.The proposed model is a joint replenishment problem (JRP) that has two objective functions.The first one is minimization of total ...     

An accurate model for prediction of gas hydrate formation conditions in mixtures of aqueous electrolyte solutions and alcohol

A new thermodynamic model for calculating the hydrate formation temperature of different hydrate formers in aqueous solutions of both electrolytes and a single alcohol has been presented. This method uses a generalization of the Aasberg‐Petersen model for water activity. For calculation of water activity in the presence of electrolytes, the effect of alcohols was taken into account without using any new fitting parameters. The results are in good agreement with published experimental data. Calculated values of the hydrate formation temperature in the presence of alcohols and electrolytes are compared with those obtained by other existing models. The average absolute error of hydrate formation temperature for 524 available experimental data points is about 0.87 K.