Sharif Digital Repository

One of the main requisites for multi agent researchers is a multi-purpose infrastructure that enables them to create, test and evaluate protocols, methods and algorithms. RoboCupRescue simulation environment is a flexible and configurable environment that can fill this gap. With changes in its configuration files, it will gain different features, so different methods can be designed, implemented, and tested. This environment is actually suitable for most multi-agent research issues such as cooperation, coordination, agent communication languages, and agent micro level issues. Sensible roles and tasks in the system motivate more research and make this environment a suitable infrastructure for... 

Purpose - In this paper, the polygonal-FEM technique is presented in modeling large deformation - large sliding contact on non-conformal meshes. The purpose of this paper is to present a new technique in modeling arbitrary interfaces and discontinuities for non-linear contact problems by capturing discontinuous deformations in elements cut by the contact surface in uniform non-conformal meshes. Design/methodology/approach - The geometry of contact surface is used to produce various polygonal elements at the intersection of the interface with the regular FE mesh, in which the extra degrees-of-freedom are defined along the interface. The contact constraints are imposed between polygonal... 

Purpose: Safety and productivity are key concerns in the construction projects. While safety looks to the construction workers need to work in a safe environment, productivity affects the project’s profitability and is of a paramount importance from the project owner’s view. The different perspective to the safety and productivity from these two major players in construction projects poses a potential for the conflict between the two. This problem can be fundamentally addressed by methods concurrently improving project safety and productivity. The paper aims to discuss this issue. Design/methodology/approach: To this aim, a discrete event simulation (DES) based framework applicable was... 

A wind turbine transformer resonance can occur due to high frequency transients at its terminal i.e.; under its energization through a length of cable. Occurrence of resonance can be addressed by a sophisticated transformer design procedure. The goal is to obtain an optimum design capable of controlling the frequency response of the winding in such a way to avoid occurrence of any resonance under transient conditions. Three insulation clearances parameters which are employed for the wind turbine transformer winding design have been investigated in design of a (800 kVA, 690/20,000 V) wind turbine transformer to determine effect of their variation on its frequency response. It is shown that... 

Purpose: The purpose of this study is to use correlation analysis to understand how knowledge structure, task structure and collaboration affect collective knowledge (CK) by the mediating mechanism of communication. Design/methodology/approach: Drawing on an existing gap in the literature related to CK, a research model with five hypotheses is proposed. The hypotheses were analyzed based on data collected from 114 work-team practitioners using structural equation modeling. Findings: The results indicate that communication, knowledge structure, task structure and collaboration significantly contribute to CK and that communication partially mediates the impact of these constructs on CK.... 

The ODYSSEY design methodology is an object-oriented design methodology which models a system in terms of its constituting objects and their corresponding method calls. Some of these method calls are implemented in hardware functional units, while others are simply executed by a general-purpose processor. There is a communication overhead because functional units must communicate with each other and with the processor core. In this paper we utilize the custom instructions capability of Nios II processor to enhance the performance of our ASIP. Since these instructions are in the processor itself, there will be no communication overhead for using them. We analyze the performance of the... 

Purpose: This paper aims to propose a novel matrix-based systematic approach for vulnerability assessment. Design/methodology/approach: The proposed method consists of two major steps. First, the power network is modeled as a topological combination of edges (transmission lines, transformers, etc.) and nodes (buses, substations, etc.). The second step is to use an axiomatic design-based index for topology analysis. This index is based on the systematic counting of possible routes from the start (generators) to destination (loads), considering load importance, before and after a disruption. Findings: The effectiveness of the proposed method is demonstrated through an illustrative example and... 

Purpose - The purpose of this paper is to investigate the effect of power on pulsed plasma thruster (PPT) discharge current with respect to its peak, duration, and behavior while the power elevates in a low power range. Design/methodology/approach - A rectangular parallel-plate breech-fed PPT has been developed with a self-inductor coupling element connecting the PPT cathode to the ignitor plug cathode. The PPT has been operated in vacuum chamber at 10-6mbar and its discharge current has been recorded using a Rogowski coil while input power has been changed by means of varying the capacitor voltage at given capacitance and frequency. Findings - The analysis leads to elucidate the effects of... 

Purpose - The purpose of this paper is to study a two-dimensional steady convective flow of a micropolar fluid over a stretching sheet in the presence of radiation with constant temperature. Design/methodology/approach - The corresponding momentum, microrotation and energy equations are analytically solved using homotopy analysis method (HAM). Findings - To validate the method, investigate the accuracy and convergence of the results, a comparison with existing numerical and experimental results is done for several cases. Finally, by using the obtained analytical solution, for the skin-friction coefficient and the local Nusselt number as well as the temperature, velocity and angular velocity,... 

In this paper, we report on the design and analysis of filters and lenses realized by an array of metallic posts integrated in a parallel-plate waveguide (PPWG). The design methodology of these components is inferred from the modal analysis of a spoof surface plasmonic waveguide composed of metallic posts arranged in a 1D periodic structure inside PPWG. Samples of the proposed devices are analyzed using a full-wave analysis method and their performance is assessed. We show that the mentioned structure can be used to realize all-metallic band-pass filters and lenses for mm-wave and terahertz applications  

Purpose - The purpose of the study is to present a simplified model to replace the complicated foaming simulations for investigating the liquid polyurethane behavior just before solidification. Design/methodology/approach - This model is inspired from the traveling heater method of crystallization because of the low injection velocity. Besides, the heat generated during the reaction is considered as a heat source function in the energy equation. Findings - Various distributions of the heat generation function inside the geometry have been studied to choose the most realistic one. Effect of parameters such as the soil material and porosity on the temperature distribution and flow field are... 

Purpose - The purpose of this paper is to propose a new guidance algorithm for launching a satellite using an expendable rocket from an equatorial site to an equatorial low-Earth orbit. Design/methodology/approach - Guidance during endoatmospheric portion is based on a nominal trajectory computed prior to take-off. A set of updating computations begins anew at the time instant tg of transition from endoatmosphere to exoatmosphere. The updating computations determine a guidance trajectory and an associated control law for the remainder of path by taking into account the rocket state at time tg. Thus, the overall guidance involves both initial and midcourse operations, and it has both open-... 

Purpose: The purpose of this paper is to present a new efficient method for the tolerance–reliability analysis and quality control of complex nonlinear assemblies where explicit assembly functions are difficult or impossible to extract based on Bayesian modeling. Design/methodology/approach: In the proposed method, first, tolerances are modelled as the random uncertain variables. Then, based on the assembly data, the explicit assembly function can be expressed by the Bayesian model in terms of manufacturing and assembly tolerances. According to the obtained assembly tolerance, reliability of the mechanical assembly to meet the assembly requirement can be estimated by a proper first-order... 

Purpose: Many construction projects are implemented in open-environment job sites and can be significantly affected by various weather conditions. Evaluating the overall impacts of the weather conditions on a project can assist project managers to prepare effectively. Nevertheless, methods measuring the overall adverse impacts of the job sites’ weather condition on the project performance are still missing. This study aims to address this gap. Design/methodology/approach: In this investigation, a survey-based method was proposed to evaluate the overall impacts of the weather conditions on the construction project resources through a new indicator called job site weather index (JWI). The... 

Organ-on-chip devices have provided the pharmaceutical and tissue engineering worlds much hope since they arrived and began to grow in sophistication. However, limitations for their applicability were soon realized as they lacked real-time monitoring and sensing capabilities. The users of these devices relied solely on endpoint analysis for the results of their tests, which created a chasm in the understanding of life between the lab the natural world. However, this gap is being bridged with sensors that are integrated into organ-on-chip devices. This review goes in-depth on different sensing methods, giving examples for various research on mechanical, electrical resistance, and bead-based... 

Purpose: The purpose of this study is to present a comprehensive hydrothermal analysis on an inclined mini-channel using numerical and experimental techniques. The fin array acts as heat source within the channel, and a wavy wall located at the top of the channel is heat sink. The side walls are insulated with curved profiles. Also, the channel is inclined with four known inclination angles. To solve the governing equations, the dual-multi-relaxation-time lattice Boltzmann method with D2Q9 and D2Q5 lattice models for flow and temperature fields is used, respectively. Also, the channel is filled with SiO2-glycol nanofluid. Design/methodology/approach: Identifying the behavior of a thermal... 

In this article, a design methodology is presented to realize integrated class-F high-power amplifiers (HPAs). A harmonic-control network (HCN) is proposed to present short- and open-circuit impedances to each transistor employed in the output stage of the HPA at {2}f {0} and {3}f {0} frequencies. The HCN absorbs the parasitic capacitance of the transistor and lends itself to be absorbed in the matching and power combiner networks, reducing the die area of the HPA. A proof-of-concept 9.7-10.3-GHz class-F HPA was designed and implemented in a 0.25- μ ext{m} GaAs pHEMT technology with V {DD} of 6 V. The designed HPA consists of two amplifying stages, and its output stage includes 16... 

In this article, a design methodology is presented to realize integrated class-F high-power amplifiers (HPAs). A harmonic-control network (HCN) is proposed to present short- and open-circuit impedances to each transistor employed in the output stage of the HPA at {2}f {0} and {3}f {0} frequencies. The HCN absorbs the parasitic capacitance of the transistor and lends itself to be absorbed in the matching and power combiner networks, reducing the die area of the HPA. A proof-of-concept 9.7-10.3-GHz class-F HPA was designed and implemented in a 0.25- μ ext{m} GaAs pHEMT technology with V {DD} of 6 V. The designed HPA consists of two amplifying stages, and its output stage includes 16... 

Purpose: Motivated by the high cost of material movements in road construction projects, past studies have used analytical methods to optimize materials logistics plans. A key shortcoming of these methods is their inability to capture the uncertain, dynamic and complex characteristics of the road construction material logistics. Failure to incorporate these characteristics can lead to sub-optimal results. The purpose of this study is to propose the use of discrete event simulation (DES) to address the existing shortfall. Design/methodology/approach: Despite the powerful capabilities of DES models in capturing the operational complexities of construction projects, they have not been... 

Purpose: Dams require high-volume of construction materials and operations over the life cycle. This paper aims to select a proper type of dam structure that can significantly contribute to the sustainability of dam projects. Design/methodology/approach: This research proposes a complementary fuel consumption and carbon dioxide (CO2) emission assessment method for the alternate dam structure types to assist decision-makers in selecting sustainable choices. Related equations are developed for two common earthen and rock-fill dam structures types in Iran. These equations are then successfully applied to two real dam project cases where the significance of the achieved results are assessed and...