• Journal of Communications and Networks
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• v.14 no.1
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• pp.40-50
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• 2012

The Berkeley-medium access control (B-MAC) is a lightweight, configurable and asynchronous duty cycle medium access control (MAC) protocol in wireless sensor networks. This article presents an analytic modelling of single-hop B-MAC protocol under a Poisson traffic assumption.Our model considers important B-MAC parameters such as the sleep cycle, the two stage backoff mechanism, and the extended preamble. The service delay of an arriving packet and the energy consumption are calculated by an iterative method. The simulation results verify that the proposed analytic model can accurately estimate the performance of single-hop B-MAC with different operating environments.

• Wind and Structures
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• v.10 no.5
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• pp.437-462
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• 2007

A non-translating, long duration thunderstorm downburst has been simulated experimentally and numerically by modelling a spatially stationary steady flow impinging air jet. Velocity profiles were shown to compare well with an upper-bound of velocity measurements reported for full-scale microbursts. Velocity speed-up over a range of topographic features in simulated downburst flow was also tested with comparisons made to previous work in a similar flow, and also boundary layer wind tunnel experiments. It was found that the amplification measured above the crest of topographic features in simulated downburst flow was up to 35% less than that observed in boundary layer flow for all shapes tested. From the computational standpoint we conclude that the Shear Stress Transport (SST) model performs the best from amongst a range of eddy-viscosity and second moment closures tested for modelling the impinging jet flow.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1205-1207
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• 1996

The computed-torque method (CTM) shows good trajectory tracking performance in controlling robot manipulator if there is no disturbance or modelling errors. But with the increase of a payload or the disturbance of a manipulator, the tracking errors become large. So there have been many researchs to reduce the tracking error. In this paper, we propose a new control algorithm based on the CTM that decreases a tracking error by generating new reference trajectory to the controller. In this algorithm we used a fuzzy system based on the rule bases. For the numerical simulation, we used a 2-link robot manipulator. To simulate the disturbance due to a modelling uncertainty, we added errors to each elements of the inertia matrix and the nonlinear terms and assumed a payload to the end-effector. In the simulations of several cases, our method showed better trajectory tracking performance compared with the CTM.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.193-199
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• 2005

VTOL(Vertical Take-Off and Landing) aircraft is attractive due to the reason that it is not necessary to have long runway. However a rotorcraft has a definite limitation to fly at the high speed due to the stall at the tip of rotor. To solve this problem, tilt rotor, tilt wing and lift fan were researched and developed. It was verified that the tilt rotor aircraft among them was more effective in disk loading. On this basis, the tilt rotor aircraft has been made into XV-15, V-22, BA-609 and Eagle Eye. This paper shows a nonlinear simulation program for general tilt rotor aircraft that was developed in order to validate the flight characteristics of tilt rotor aircraft and verified through the simulation analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.501-506
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• 2013

This research is to develop a simulation framework to gauge the mission effectiveness of the rotorcraft system that will be a part of Korean future combat system. The rotorcraft system comprises of many subsystems that are very time-consuming and tedious to model. Each subsystem and its characteristics have been modeled using component-based modeling techniques, which enhances its reusability. The entire system is then constructed from the individually modeled component, which significantly reduces the modelling time. The mission effectiveness of the rotorcraft system is simulated using the developed models, and the output indicates that the methodology proposed in this study is useful, which will be suitable for the modeling and simulation of Korean future combat system.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.184.2-184.2
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• 2010

This study performs modelling and simulation of permanent magnetic synchronous generator wind turbine by using Matlab & Simulink. In simulation, change of wind velocity, change of load, and voltage decrease of infinite bus are performed. Through such simulation, different with wiring system that there is only existing load, this study can confirm problems and voltage changing characteristics, which can occur in distributed electric power that load and electric power is mixed and operated, especially, in interconnecting with wind power generation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.136-147
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• 2005

A theoretical design evaluation based on a hydrodynamic transport simulation of strained Si-SiGe on insulator (SSOI) type nMOSFETs is reported. Although, the net performance improvement is quite limited by the short channel effects, simulation results clearly show that the strained Si-SiGe type nMOSFETs are well-suited for gate lengths down to 20 nm. Simulation results show that the improvement in the transconductance with decreasing gate length is limited by the long-range Coulomb scattering. An influence of lateral and vertical diffusion of shallow dopants in the source/drain extension regions on the device performance (i.e., threshold voltage shift, subthreshold slope, current drivability and transconductance) is quantitatively assessed. An optimum layer thickness ($t_{si}$ of 5 and $t_{sg}$ of 10 nm) with shallow Junction depth (5-10 nm) and controlled lateral diffusion with steep doping gradient is needed to realize the sub-50 nm gate strained Si-SiGe type nMOSFETs.

• Journal of Power Electronics
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• v.10 no.6
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• pp.621-627
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• 2010

This paper presents a TSMST (Theory - Simulation - Measurement - Simulation - Theory) method for power electronics laboratory. The method successfully integrates theory, simulation and measurement, thus enabling better integration of student's knowledge and better usage of inadequate number of laboratory hours. Students are attracted with relatively simple tasks to be solved and modern, but economical laboratory equipment. A significant part of the assignments can be made at home, thus lowering the pressure on students to finish the tasks on time. The proposed method is described on three basic examples explaining characteristic phases of the TSMST method.

• Coupled systems mechanics
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• v.4 no.1
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• pp.19-36
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• 2015

Modelling and analysis of a brick masonry building involves uncertainties like modelling assumptions and properties of local material. Therefore, it is necessary to perform a calibration to evaluate the dynamic properties of the structure. The response of the finite element model is improved by predicting the parameter by performing linear dynamic analysis on experimental data by comparing the acceleration. Further, a nonlinear dynamic analysis was also performed comparing the roof acceleration and damage pattern of the structure obtained analytically with the test findings. The roof accelerations obtained analytically were in good agreement with experimental roof accelerations. The damage patterns observed analytically after every shock were almost similar to that of experimental observations. Damage pattern with amplification in roof acceleration exhibit the potentiality of earthquake resistant measures in brick masonry models.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.3
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• pp.1-9
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• 2014

The aim of this study is to develop a simulation model for analyzing 2D truss structure using Generic Agricultural System Simulator (GASS). Although the truss is simple structure, numerical methods based on matrix analysis are cumbersome and complicated. This study suggests simple and convenient methods to remove calculating steps for whole stiffness matrices. The simulation environment based on independency of object-oriented components on GASS consists of component development and component deploy stages. A component for a truss structure is implemented based on equilibrium equations at nodes. The simulator can analyze truss structures through deploying components with attributes and links. The examples using GASS show intuitive graphical results of the movements of truss nodes.