Sharif Digital Repository

In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. An approach to compare the solutions for different conditions used in air dehumidifier has been investigated according to the previous published studies. Comparing the simulated results with the published actual values of an experimental work substantiates the validity of model. The model accuracy with respect to the key... 

This paper presents anti-synchronization of chaos between two different chaotic systems using active control method. The proposed technique is applied to achieve chaos antisynchronization for the Lu and Rössler dynamical systems. Numerical simulations are implemented to verify the results. COPYRIGHT © ENFORMATIKA  

This paper presents a simulation-based environment to study fault effects in message missing failures in CAN-based systems. A CAN controller is modeled by VHDL at behavioral level and is exploited to set up a network composed of several nodes. A total of 27,000 transient faults of seven types are injected into five critical portions of the system including the bus and four portions of the CAN controller. The experimental results show that the faults affect the message sending in which more than 20% of faults cause the failure. Besides, with a heavy workload, faults that are occurred into the CAN controller and on the bus cause about 90% and 10% of all failures, respectively  

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating hydrofoils.Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile's motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is... 

In this paper we present a novel planar structure of a snake-like robot. This structure enables passive locomotion in snake-like robots through an auxiliary link in joint and a torsional spring. Dynamic equations are derived, using Gibbs-Appell method. Kinematic model of the robot include numerous non-holonomic constraints, which can be omitted at the beginning by choosing proper coordinates to describe the model in Gibbs-Appell framework. In such a case, dynamic equations will be significantly simplified, resulting in significant reduction of simulation time. Simulation results show that, by proper selecting initial conditions, joint angles operate in a limit cycle and robot can locomote... 

The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. The current work presents a state of the art design for the blade tip injection. This is characterized by a high pressure fluid injecting means for delivery of a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by some 30% of the tip chord both in the upstream and downstream directions. Using an injected mass flow of around 2.4% of the annulus flow, the present design can improve stall margin by up to 7% by... 

The budding yeast Saccharomyces cerevisiae is the first eukaryote whose genome has been completely sequenced. It is also the first eukaryotic cell whose proteome (the set of all proteins) and interactome (the network of all mutual interactions between proteins) has been analyzed. In this paper we study the structure of the yeast protein complex network in which weighted edges between complexes represent the number of shared proteins. It is found that the network of protein complexes is a small world network with scale free behavior for many of its distributions. However we find that there are no strong correlations between the weights and degrees of neighboring complexes. To reveal... 

An analytic method to predict the oscillation amplitude and supply current values of a differential CMOS oscillator is presented. A simplified model to predict the phase noise performance for this type of oscillator is developed. Using this method, it becomes possible to design an optimised oscillator in terms of a minimum phase noise and low power consumption. The validity of the method has been verified by designing a LC CMOS oscillator using 0.25 μm CMOS technology. The predictions are in good agreement with simulation results over a wide range of the supply voltage  

The non-linear bubble dynamics equations in a compressible liquid have been modified by considering the effects of compressibility of both the liquid and the gas at the bubble interface. A new bubble boundary equation has been derived, which includes a new term resulting from the liquid bulk viscosity effect. The influence of this term has been numerically investigated by considering the effects of water vapour and chemical reactions inside the bubble. The results clearly indicate that the new term has an important damping role at the collapse, so that its consideration dramatically decreases the amplitude of the bubble rebounds after the collapse. This damping feature is more remarkable for... 

This paper introduces an analytical method for approximating the fraction of jobs that miss their deadlines in a real-time system when earliest-deadline-first scheduling policy (EDF) is used. In the system, jobs either all have deadlines until the beginning of service or deadlines until the end of service. In the former case, EDF is known to be optimal and, in the latter case, it will be optimal if preemption is allowed. In both cases, the system is modeled by an M/M/1/EDF+M queue, i.e., a single server queue with Poisson arrival, and service times and customer impatience, which are exponentially distributed. The optimality property of EDF is used for the estimation of a key parameter, γn... 

The main purpose of this work is to improve the efficiency and performance of a primitive finite volume element method which provides superior capability on a single platform. This method is suitably extended in order to use the advantages of parallel computing on multiprocessors or multicomputers. The method is fully implicit which renders huge sparse linear algebraic kernels. Nevertheless, the attention is focused on solving the sparse system rather than constructing it. The current method is a cell-centered scheme. Since the grid is unstructured, each non-boundary node engages with nodes on three or more surrounding elements around that node. Depending on global node numbering, the... 

There are many reported researches considering movement behavior of vehicles. In these studies the two basic types of movement of a vehicle are longitudinal movement, car following, and lateral movement, lane changing. Dependency between car following and lane changing models and the fact that many of drivers does not consider driving lanes, necessitate developing of models that combine the car following and lane changing without considering the driving lanes. Utilizing computer simulation, the work can also be applied to conditions where lane disciplines are strictly observed. Microscopic simulation models considering the movement of individual vehicles in a traffic stream can be... 

A simplified four-layer recurrent neural network (RNN) based architecture is introduced to generate prosodic information for improving naturalness in Persian text-to-speech (TTS) systems. The proposed RNN uses the first two layers at word level and the last two layers at syllable level to provide the TTS system with major prosodic parameters, including: pitch contour, energy contour, length of syllables, length and onset time of vowels, and duration of pauses. The experimental results show improvement of accuracy in prediction of prosodic parameters, as compared to similar prosody generation systems of higher complexity  

Modified two-phase latch and flip-flop are introduced to implement a linear phase-detector (LPD) for 1/N-rate clock recovery applications. This technique greatly simplifies the required circuitry of the LPD and makes it suitable for higher speed applications while consuming less power compared to the conventional techniques  

An investigation into the dynamics of vehicle-occupant-structure-induced vibration of bridges traversed by moving vehicles is presented. The vehicle including the driver and passengers is modelled as a half-car planar model with six degrees-of-freedom, and the bridge is assumed to obey the Euler-Bernoulli beam theory with arbitrary conventional boundary conditions. Due to the continuously moving location of the variable loads on the bridge, the governing differential equations become rather complicated. The numerical simulations presented here are for the case of vehicle travelling at a constant speed on a uniform bridge with simply supported end conditions. The relationship between the... 

The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on... 

In the last decade, the intelligent control community has paid great attention to the topic of intelligent control systems for nuclear plants (core, steam generator). Papers mostly used approximate and simple mathematical SISO (single-input-single-output) model of nuclear plants for testing and/or tuning of the control systems. They also tried to generalize theses models to a real MIMO (multi-input-multi-output) plant, while nuclear plants are typically of complex nonlinear and multivariable nature with high interactions between their state variables and therefore, many of these proposed intelligent control systems are not appropriate for real cases. In this paper, we designed an on-line... 

A methodology for analysis and synthesis of lowpass sigma-delta (∑Δ) converters is presented in this paper. This method permits the synthesis of ∑Δ modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of a continuous-time model and using a discrete simulator, which is more efficient than an analog simulator. In our analysis approach, the influence of the sample and hold block and non-idealities of the feedback DAC can be systematically modeled by discrete-time systems. Finally, a realistic design of a second-order ∑Δ modulator with a compensation of the non-ideal behavior of the DAC is given. Moreover, simulation... 

This article describes an automatic reactor power control system for VVER-1000 reactor and reports simulation analysis results for a typical daily load follow operation. The associated reactor control algorithm is called `mode G' that uses a heavy-worth bank (H-bank) dedicated to axial power shape control and the light-gray banks (G-banks) for reactor power change and reactivity compensation. The simulation results for daily load follow operation in three burnup states of first cycle illustrate that the load follow capability of VVER-1000 reactors using this algorithm will be improved  

A manipulator mounted on a moving vehicle is called a mobile manipulator. A mobile manipulator with an appropriate suspension system can pass over uneven surfaces, thus having an infinite workspace. If the manipulator could operate while the vehicle is traveling, the efficiency concerning with the time and energy used for stopping and starting will be increased. This paper presents the kinematic and dynamic modeling of a one degree of freedom manipulator attached to a vehicle with a two degrees of freedom suspension system. The vehicle is considered to move with a constant linear speed over an uneven surface while the end effector tracks a desired trajectory in a fixed reference frame. In...