Search

IEEE802.16 is the standard defining the Worldwide Interoperability for Microwave Access (WiMAX) for Metropolitan Area Network (MAN). WiMAX has recently being considered by Internet Service Providers (ISPs) as an attractive alternative to leasing lines from current ISPs or the deployment of new fiber networks. This is mainly the case since WiMAX is more flexible and much cheaper than other possible solutions. Our focus in this paper is on mobile WiMAX i.e. IEEE802.16e designed to provide broadband wireless access for mobile users. In this paper we have designed various scenarios using the Qualnet simulation package to evaluate the performance of WiMAX in delivering traffic under different operational conditions for a point to multi point configuration. The results showed how different factors such as load and mobility might affect the performance of WiMAX in a single cell environment. End to end delay, delay jitter and throughput were considered as the performance measures in this study. [ABSTRACT FROM AUTHOR]

This paper presents and investigates a dynamic buffer management scheme for QoS control of multimedia services in a 3.5G wireless system i.e. the High Speed Downlink Packet Access (HSDPA). HSDPA was introduced to enhance UMTS for high-speed packet switched services. With HSDPA, packet scheduling and HARQ mechanisms in the base station require data buffering at the air interface thus introducing a potential bottleneck to end-to-end communication. Hence, for multimedia services with multiplexed parallel diverse flows such as video and data in the same end-user session, buffer management schemes in the base station are essential to support end-to-end QoS provision. We propose a dynamic buffer management scheme for HSDPA multimedia sessions with aggregated real-time and non real-time flows in the paper. The end-to-end performance impact of the scheme is evaluated with an example multimedia session comprising a real-time streaming flow concurrent with TCP-based non real-time flow via extensive HSDPA simulations. Results demonstrate that the scheme can guarantee the end-to-end QoS of the real-time streaming flow, whilst simultaneously protecting non real-time flow from starvation resulting in improved end-to-end throughput performance. [ABSTRACT FROM AUTHOR]

This paper presents two simulation models for two variants of a large chipper drive used in a paper mill. If a slip ring induction motor is used, the impact of a rotor circuit rheostat with respect to starting behavior and heavy duty load impulses can be examined. Furthermore a speed controlled squirrel cage induction machine will be investigated. The modeling language for both drives is Modelica. The simulation results for both drives are compared and discussed. [ABSTRACT FROM AUTHOR]

This paper studies the modified sensitivity analysis applied into an elastic-plastic finite element analysis of a 3D blank design in sheet metal forming. Originally the sensitivity method has successfully been applied to several arbitrary shapes. In the present paper the sensitivity coefficients are not considered constant during the analysis. The presented approach computes the new coefficients from the two last iterations. This method can produce an initial blank boundary shape that has any arbitrary flange shape. A cup with uniform flange has been studied in detail and results show a faster solution convergence than the published sensitivity method. Experimental tests were conducted to compare with the numerical simulations. The optimum blank shape obtained from the numerical simulations was used during the experimental trials. The results of experimental tests for both square and optimal blank are presented here. [ABSTRACT FROM AUTHOR]

This paper presents the initial results of a study aimed at improving the method by which the vibrations produced by transport vehicles are characterised and simulated. More specifically, this paper focuses on the rigid body vibrations generated by road transport vehicles in the context of distribution of packaged goods and produce. The research uses a variety of vibration data, collected from various vehicle types and routes in Spain and Australia with high-capacity vibration recorders. Vehicles used range from small transport vehicles to large truck-trailers with both airbags and steel spring suspensions while the routes travelled include suburban streets, main roads and motorways. The paper discusses the significance and limitations of the average power spectral density (PSD) and explains why the average PSD is not always adequate as the sole descriptor of road vehicle vibrations as the process generally tends to be non-stationary and non-Gaussian. The paper adopts an alternative analysis method, based on the statistical distribution of the moving root-mean-square (RMS) vibrations, as a supplementary indicator of overall ride quality. The measured data was used to compute the statistical distribution of each vibration record, the shape of which was compared for the entire set of records. The suitability of various mathematical models, based on the Weibull and Rayleigh distributions were investigated for describing the probability distribution function (PDF) of road vehicle vibration RMS time history. The paper proposes a single mathematical model that can accurately describe the statistical character of the random vibrations generated by road vehicles in general. It shows that the model can also effectively describe the statistical parameters of the process namely the mean, median, standard deviation, skewness and kurtosis. [ABSTRACT FROM AUTHOR]

This paper presents an approach to agent's action selection strategy called stepwise case-based reasoning (SCBR). In this paper an agent that roams in 3D synthetic world is called an SCBR agent. An SCBR agent is an entity that selects the next action based on previous interaction experience and on simulated vision. An SCBR agent's interaction experience is represented in the form of two different types of cases: plan cases and contextual cases. [ABSTRACT FROM AUTHOR]

The fatigue is the most common way of structural imperfection and, over the time, it has been a problem to the imposed requests and the type of applied load. In this paper, there is a study of the way the resistance fatigue ASTM A-36 is made among two environments: refrigerated and immerged into water at 5 atm hydrostatic pressure through bending tension fatigue tests. After that, some analyses and comparative results with the tested material were carried out. For this study, a mechanism was developed to test fatigue for bending tension to be used inside and outside hyperbaric chamber for the hydrostatic pressure simulation. This study is worth because any resistance confirmation does not exist in immerged fatigue of virgin materials; in other words, all the tests of fatigue were or have being accomplished in materials done in the air. Curves S-N were determined for each atmosphere. The methodology used for verification of resistance to the fatigue was the regression model from a data originated from accelerated life tests and it was possible to verify the environment influence in the phenomenon of the fatigue. [ABSTRACT FROM AUTHOR]

Although there are many simulations of residual stresses in quenched steel components there is little validation of these predictions particularly when the components are large. This is not surprising bearing in mind that the application of the through thickness measurement techniques (mechanical strain relief techniques) are problematic when the components exhibit high levels of residual stresses or triaxial stress state. This paper examines the application the incremental deep hole drilling technique (IDHD) to measure through thickness residual stresses in the quenched solid and hollow steel cylinders. The measured residual stresses are compared with FE predictions. [ABSTRACT FROM AUTHOR]

The paper presents a virtual reality techniques to create and to simulate a skeletal model of human upper limbs. Motions supported by the current version of the system are: arm flexion/extension, arm adduction / abduction and forearm flexion/extension. It's present the differences between VRML and Matlab. A computer system has been developed where a set of forces done by the muscles are parameterized and the limb motion animation, in real time, is achieved through biomechanics equations. [ABSTRACT FROM AUTHOR]

In this paper, we study the problem of computing tail conditional expectations (TCE) or portfolio gains at specific times (T) in the future. We present efficient algorithms to handle the following two cases: (1) we have only one option (call or put) in our portfolio, denoted as a single-stock-single-option portfolio (SSSO); (2) we have a stock and some of its options in our portfolio, denoted as a single-stock-multiple-option portfolio (SSMO). Compared with previous simulation algorithms, our algorithms compute TCE of a given portfolio more efficiently and still maintain the same degree of accuracy. In the SSSO case, we reduce the computational time complexity from the SSSO-Naïve Algorithm's O(m*n) to SSSO algorithm's O(m+n), where m is the number of possible price outcomes for an underlying stock at time T and n is the number of possible price outcomes for an underlying stock at time U (maturity) in respect to each possible price outcome for an underlying stock at time T. In the SSMO case, we provide two algorithms to compute the TCE. The computational time complexity of the SSMO-Naive Algorithm is O(q*m*n+m*log(m)), where q is the number of options. The computational time complexities of our two algorithms are O(q*(m+n)+m*log(m)), and O(q*log(q)+n+m*q+ m*q*log(q)+m*log(m)) or O(q*log(q)+n+m*q+m*q*log(m)+m* log(m)). In both cases, our experiments show that when m and n are greater than five thousand, our algorithms run thousands of times faster than the naive algorithms. [ABSTRACT FROM AUTHOR]

The continued advancement of software-defined radio (SDR) technology has been a key factor in furthering research about the implementation of most signal processing algorithms at baseband. Traditionally, most algorithms have been carried out at radio frequency (RF). With the coming of SDR, the processing can be done at baseband frequencies which are more compatible with the fast developing software radio technology. This paper looks at matched filter detection and investigates the possibility and benefits of carrying out the detection process at quadrature baseband (QBB). A simple chirp signal is considered for the analysis. The analysis is carried out using MatLab simulations at RF and QBB and the results do show the possibility of carrying out the detection process at QBB with the expected benefits as compared to carrying out the process at RF. [ABSTRACT FROM AUTHOR]

Shape optimization is numerically a very demanding process, where several traditionally separate numerical processes meet together in a heterogeneous multidisciplinary environment. Typical elements involved are (1) the optimizer itself that implements the selected search strategy, (2) the parameterization procedure that provides the bidirectional mapping interface between the 3D geometric shape of the object and a limited number of parameters that control the parametric model of the geometry, (3) the simulation program that provides the results of the simulated interaction between the object and its environment (such as finite element analysis, FEA), and (4) control procedures that monitor the overall workflow and invoke mutual application calls (process flows and data flows) and handle data mining as well as acceptance or rejection of individual instances of candidate designs which are numerically generated and analyzed. In this paper, the set-up of this complex process, combined with evolutionary optimization, is developed with the objectives of numerical flexibility, computational efficiency in terms of combining sequential and parallel execution of individual applications, and low-cost implementation within an unmanaged computer cluster based on the Windows Communication Foundation, WCF. [ABSTRACT FROM AUTHOR]

Recently, the importance and necessity of engineering analysis has shown a steady growth. However, researchers working in small and medium enterprises know little about the usefulness of engineering analysis and suffer from lack of technical knowledge. Axial fan is air fluid machinery in various fields of industry such as automobile, electric appliance, and heavy machinery. It is also a time and budget consuming equipment to develop the axial fan through physical experiments. In order to overcome this problem, we have designed and developed a web-based axial fan simulator using supercomputer. In our simulator, all of processes for engineering analysis including pre-process, solving, and post-process can be performed automatically without user intervention after transferring fan model(CAD files) made by user. After executing the simulator with some parameters, user can receive report including P-Q curves. In this paper, we introduce the architecture of our easy and efficient automated axial fan simulator, related techniques and result of development. [ABSTRACT FROM AUTHOR]

Globalisation and competitive pressure force many SME organizations' to radically change business processes. Although this approach can provide significant benefits such as reducing costs or improving efficiency, there are substantial risks associated with it. Using simulation for modelling and analysis of business processes can reduce that risk and increase the chance for success. This paper exploits the potential of simulation to be used for modelling business processes and supports the case for a wider use of simulation techniques by the business community. Following a discussion on business process modelling methods and tools, the usability of simulation modelling for evaluating alternative business process strategies is explored by way of case study in the bus manufacturing domain. [ABSTRACT FROM AUTHOR]

This paper presents a physical model of a squirrel cage induction machine with rotor topology. The machine is modeled in Modelica, an object oriented multi physical modeling system. The presented machine model is used to investigate electrical rotor asymmetries in induction machines. For the case of a single broken rotor bar a simulation model is compared with measurement results. [ABSTRACT FROM AUTHOR]

Biometric recognition and authentication based on face recognitions can actually be used in many real-time applications such as surveillance, security systems, access control, and much more. For these purposes systems have to grant a fast computational speed but also robustness to illumination and facial expressions variations. In this paper we propose a very fast image pre-processing by the introduction of a linearly shaded elliptical mask centered over the faces. Simulation results, over the AR Database, show that the proposed method leads to a significant performance improvement in identification, using both eigenfaces and DCT with Nearest Neighbour and RBF Neural Network, without modifying the global computational weight. [ABSTRACT FROM AUTHOR]

This paper studies the cardiovascular response under heart failure condition supported by two types of ventricular assist devices (VADs): the positive displacement pump and the impeller pump. The cardiovascular system is modeled using the concentrated parameter method developed previously, by considering flow resistance, vessel elasticity and inertial effects of blood in individual conduit segments. The dynamic modeling of displacement and impeller pumps is represented by VAD inlet/outlet flow-rate changes. Results show that in each simulation, the diseased ventricle is effectively unloaded, and the physiological variables of arterial pressure and systemic flow are adequately maintained. The numerical model is under further development for more sophisticated studies of the interaction of the native cardiovascular system with VAD support and other cardiac prosthetic devices. [ABSTRACT FROM AUTHOR]

The emerging dominance of lean and agile techniques is resulting in a worldwide trend towards shorter product cycles, with smaller lead times and shorter production runs. Simulation is a time-consuming processes and data collection is such a major part of the time period of such a cycle. This paper introduces the circuit of observation concepts which provide a massively reduced cycle time for data collection; this makes it a much more valuable tool in a manufacturing environment and expands its uses due to its greater flexibility. The case study strongly supports the findings. [ABSTRACT FROM AUTHOR]

One of major reasons of failure of solder joints is known as the thermal fatigue. Also, The failure of the solder joints under the thermal fatigue loading is influenced by varying boundary conditions such as the material of solder joint, the materials of substrates(related the difference in CTE), the height of solder, the Distance of the solder joint from the Neutral Point (DNP), the temperature variation and the dwell time. In this paper, first, the experimental results obtained from thermal fatigue test are compared to the outcomes from theoretical thermal fatigue life equations. Second, the effects of varying boundary conditions on the failure probability of the solder joint are studied by using the probabilistic methods such as the First Order Reliability Method (FORM) and Monte Carlo Simulation (MCS). [ABSTRACT FROM AUTHOR]

Several statistical tools and most recently Functional Networks (FN) have been used to solve nonlinear regression problems. One of the tasks associated with all of these methodologies consists of discovering the functional form of the contribution of the explanatory variables to the response variable. In this paper, we tackle this problem using functional network models (FNs). Since these models usually involve from a moderate to high number of parameters, a genetic algorithm (GA) for model selection is proposed. After an introduction of FNs and GAs, the performance of the proposed methodology is assessed using a simulation study as well as a real-life data set. [ABSTRACT FROM AUTHOR]

This paper presents the work carried out by CALPE team on the development of a mathematical model used in the study and simulation of the pantograph-catenarydynamic interaction in high speed railways considering two independent spans of catenary where the transition spans are overlapped. According to the developedmathematical model, a non lineal system of differential equations with variableconstraint depending on the pantograph position has been obtained. In order to verify the correctness of the model, a numerical integration algorithm based on an explicit method of the central differentials has been implemented. The procedure that has been designed allows us to study the more appropiate contact wire configuration, in order to make smoth transition of the pantograph between sets of spans. This procedure can be generalized considering the case of several pantographs, obtaining very realistic simulations. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study for evaluting the decision support value if queueing network (QN) based simulation models for information system design performance. For illustration, queueing network simulation models have been extracted corresponding to three annotated design alternatives of a selected case study. The design alternatives are produced using logical requirements of the selected system. The performance of each alternative is then predicted using quantifiable parameters considering the dynamics of the system such as service time, waiting time and number of entities waiting in the system. In particular, results have shown that the first alternative performs better than the other two in terms of the selected parameters. In general, the case study revealed that QN-based simulation models alternatives in terms of selected parameters and under given assumptions. This is also means that the use of simulation may lead ti better designed information systems. [ABSTRACT FROM AUTHOR]

Clock jitter and its effects on signal-to-noise ratio (SNR) were widely investigated in the published literatures. However, most of the issues mainly focused on white-Gaussian-noise-only clock jitter, based on the scenario (assumption) of ideal interference-free clock circuit design which never existed in reality. This paper presents a realistic analog to digital converter (ADC) performance analysis model based on better realistic circuit noise conditions, particularly investigated on the clock jitter error with the combination of Gaussian noise and circuit noise (interference). An analytical expression for the A/D conversion with such combined clock jitter error is developed. The computer simulations are presented, which showed excellent agreement with the developed expression. Also, a real experiment is carried out to bring forth a comprehensive evaluation in A/D system design. [ABSTRACT FROM AUTHOR]

The verification of the system performances becomes of prime importance and notably with the emergence of the soc, in which, the spurious couplings between the functional circuits can be critical. the needs in terms of system simulation tools become thus very important. This paper is divided into two parts, the first part presents a method to implement the volterra and nonlinear impulse response models in matlab/simulink environment. The second part presents a co-simulation interface between Matlab/Simulink and Goldengate (Agilent Technologie) circuit simulator. [ABSTRACT FROM AUTHOR]

The development of the transformer insulation failure undergoes three stages: insulation aging, incipient faults and a short circuit. This paper presents a complete scheme to simulate single-phase transformers with insulation deterioration and arcing phenomena i.e. in the first two stages. The approach incorporates Transmission Line Methods (TLM), Jiles-Atherton Hysteretic Model, Composite Cassie-Mayr Arcing Model and Dielectric Model. A small 25kVA 11kV/220V power transformer with aging and incipient faults is taken as example for simulation. [ABSTRACT FROM AUTHOR]

Staff attrition is a problem often faced by software development organizations. We used process modeling and simulation to estimate the effect of different staffing policies on the project cost. A simulation technique has been used for analyzing the effect of the policies pertaining to replacement for engineers who leave the project, and also overstaffing in the beginning of the project. This paper presents the simulation technique for optimizing the cost of staffing by analyzing replenishment level and replenishment strength with respect to attrition. [ABSTRACT FROM AUTHOR]

This paper deals with the identification of best and optimized test cases in program components and software artifacts. Our purpose is to simulate the model on a sample software program component and evaluate the efficacy and correctness of the code through set of test cases. [ABSTRACT FROM AUTHOR]