Sharif Digital Repository

Optimizing highway alignment requires a versatile set of cost functions and an efficient search method to achieve the best design. Because of numerous highway design considerations, this issue is classified as a constrained problem. Moreover, because of the infinite number of possible solutions for the problem and the continuous search space, highway alignment optimization is a complex problem. In this study, a customized particle swarm optimization algorithm was used to search for a near-optimal highway alignment, which is a compound of several tangents, consisting of circular (for horizontal design) and parabolic (for vertical alignment) curves. The selected highway alignment should meet... 

Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

This paper analytically investigates the effects of system and controller parameters and operating conditions on the dynamic and transient behavior of wind turbines (WTs) with doubly-fed induction generators (DFIGs) under voltage dips and wind speed fluctuations. Also, it deals with the design considerations regarding rotor and speed controllers. The poorly damped electrical and mechanical modes of the system are identified, and the effects of system parameters, and speed/rotor controllers on these modes are investigated by modal and sensitivity analyses. The results of theoretical studies are verified by time domain simulations. It is found that the dynamic behavior of the DFIG-based WT... 

This research studies multi-objective master production schedule (MPS) and advanced order commitment (AOC) in two-stage supply chains. Simulation-based experimental analysis evaluates the impact of environmental and MPS design factors on schedule cost and instability. The results provide insight into multi-objective MPS design considerations through rolling schedule policies. The study reveals that the manufacturers production smoothness utility coefficient and its interaction with other experimental factors considerably impact on the systems performance. In addition, it introduces a simulation framework with embedded mixed integer programming models that could be used as a framework for... 

In this paper, a thorough design procedure for concurrent design of integrated antiparallel Schottky-diode-based limiter and low noise amplifier (LNA) is presented. The optimum number of limiter branches, the size and number of diodes in each branch, width of the transmission line loaded by diode branches, and design considerations for input transistor of the LNA are discussed in detail. To improve power handling of the limiter with a minimum impact on overall noise figure (NF), a novel limiter structure is proposed where transistors are utilized in a limiter topology. A design procedure is also introduced for the transistor-based limiter-LNA. Developed methodologies are employed to design... 

To propose a conceptual arrangement of reverse osmosis desalination plants, four comprehensive decision algorithms and a software are developed. Typically, commercial software predict the performance of the reverse osmosis membranes based on their pre-determined configuration; however, the developed decision algorithms and the developed software in this study have the capability of introducing the conceptual arrangement of pretreatment units, reverse osmosis membranes, and energy recovery devices for both seawater and brackish water reverse osmosis plants. To perform a comprehensive study, alongside the developed software and the decision algorithms, both design considerations of the... 

The developed wireless multi-channel PPG system comprises tiered communication subsystem with two sensor modules and a single base module. The sensor modules process the input signals simultaneously into 16-bit samples and wirelessly transfer them to base module using Bluetooth technology. In base module, the samples are combined using time division multiplexing into composite stream and serially forwarded to the host computer. The string buffer is implemented in the sensor module firmware to increase the transfer time, transfer samples in chunks and eliminate the wireless transmission latency. The wireless network is established between modules. The newly implemented firmware results in... 

This paper presents an RF Front-END for an 860-960thinspaceMHz passive RFID Reader. The direct conversion receiver architecture with the feedback structure in the RF front-end circuit is used to give good immunity against the large transmitter leakage and to suppress leakage. The system design considerations for receiver on NF and IIP3 have been discussed in detail. The RF Front-END contains a power amplifier (PA) in transmit chain and receive front-end with low-noise amplifier, up/down mixer, LP filter and variable-gain amplifier. In the transmitter, a differential PA with a new power combiner is designed and fabricated in a 0.18-μm technology. The chip area is 2.65 mm × 1.35 mm including... 

Multi-turn resolvers are consisted of two individual resolvers in one housing. Due to use of both single speed and multi-speed resolvers in one frame, multi-turn resolvers are supposed to provide the benefits of higher accuracy and absolute position measurement, simultaneously. In this paper, after presenting different configurations of wound-rotor (WR), multi-turn resolvers, their design considerations are discussed. Winding function (WF) method is used for finding appropriate slot-pole combinations, and winding configurations. Then time stepping finite element analysis is applied to evaluate the performance of the designed resolvers. Finally, experimental measurements validate the... 

A systematic procedure of simulating charge pump based delay locked loops (DLLs) represents in this paper. The presented procedure is based on the systematic modeling of the DLL components in Matlab Simulink simulator. The system has been designed for 1Hz input clock signal that by changing the whole system scale, it can be used for every other input frequencies. The simulation results in Matlab and design considerations for DLL based frequency multiplier are presented  

This paper represents a systematic procedure of simulating charge pump based delay locked loops (DLLs). The presented procedure is based on the systematic modelling of the DLL components in Matlab simulink simulator. The system has been designed for 1Hz input clock signal that by changing the whole system scale, it can be used for every other input frequencies. The simulation results in Matlab and design considerations for DLL based frequency multiplier are presented  

Substation Automation Systems (SAS) offer powerful, fast, and viable ways to design, automate, and implement substation protection, control, and monitoring functions in modern transmission and distribution grids. Today's SAS -more than ever- rely on the adoption of IEC61850 as a worldwide standard for interoperability and dependable peer-to-peer and substation communications. Being based on the Ethernet computer networking technology, the reliability issues associated with latency in 61850-enabled SAS is of a design consideration. Unpredictability is the most important challenge for latency assessment. This paper discusses the background framework for latency evaluations in SAS by... 

Aseptic loosening is one of the main reasons for the revision of a total knee replacement (TKR). The design of the key component of a TKR, the femoral component, is particularly problematic because its failure can be the result of different causes. This makes the development of new biomaterials for use in the femoral component a challenging task. This paper focuses on the engineering design aspects in order to understand the limitationsof current materials and design deficiencies. The paper describes the introduction of a new biomaterial for a femoral component and justifies the recommendation to use multi-functional materials as a possible solution to aseptic loosening. The potential... 

A large number of generators failed due to stator winding problems, mainly insulation deterioration. Insulation degradation assessment plays vital role in the asset life management. Electro thermal analysis is the main characteristic for simulation of generator behavior and to improve the design of stator slot's insulation. Dielectric parameters such as insulation thickness, spacing, material types, geometry of winding and slot are major design consideration. A very powerful method available to analyze electro thermal performance is Finite Element Method (FEM) which is used in this paper. The analysis of various stator coil and slot configurations are used to design the better dielectric...