• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.664-669
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• 2005

In this note, we present a different asymptotes from the standard approximate lines of the Bode magnitude plot. Wherein the pseudo break frequency is defined in terms of coefficients of denominator and numerator polynomials of the transfer function instead of its poles and zeros. Several comparative examples are given. This result can be used for the characteristic ratio assignment(CRA) [1], [2] with frequency response requirements, which is a method of designing linear controller in parameter space.

• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.248-253
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• 2009

This paper presents a numerical study for unsteady flows in a high-pressure steam turbine with a partial admission stage. Compressible Navier-Stokes equations are solved by the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. The SST-model is also solved for evaluating the eddy-viscosity. The unsteady two-dimensional flows through whole nozzle-rotor cascade channels considering a partial admission are numerically investigated. 108 nozzle passages with two blockages and 60 rotor passages are simultaneously calculated. The influence of the flange in the nozzle box to the lift of rotors is predicted. Also the efficiency of the partial admission stage changing the number of blockages and the number of nozzles is parametrically predicted.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.1
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• pp.29-36
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• 2009

Power supply noise is fundamentally caused by large current peaks. Since large current peaks are induced by simultaneous switching of many circuit elements, power supply noise can be minimized by deliberate clock scheduling which utilizes nonzero clock skew. In this paper, nonzero skew clock scheduling is used to avoid the large peak current and consequently reduce power supply noise. While previous approaches require extra characterization efforts to acquire current waveform of a circuit, we approximate it only with existing cell library information to be easily adapted to conventional design flow. A simulated annealing based algorithm is performed, and the peak current values are estimated for feasible clock schedules found by the algorithm. The clock schedule with the minimum peak current is selected for a solution. Experimental results on ISCAS89 benchmark circuits show that the proposed method can effectively reduce the peak current.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.3
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• pp.372-384
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• 1993

The inverted pendulum system has interesting and challenging problems related to robotics and rocket attitude control view of both control theory and applications. Generally approximately linearized plant models are employed to control the system. In this paper a recently developed control theory based on differentiable manifold theory is used to control the inverted pendulum system which is typically nonlinear. First, the nonlinear model is transformed into the approximate feedback linearized system by nonlinear state feedback. Secondly, the linear controller is designed using the pole-placement method for the approximate feedback linearized plant model, the output of which are finally inverse-transformed to yield the control input to the actual system of the inverted pendulum. The proposed method is evaluated by the computer simulation to compare with the 3rd order linearization model.

• Spatial Information Research
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• v.21 no.2
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• pp.1-9
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• 2013

Recently many researches have focused on indoor navigation system. An optimal indoor navigation method can help people to find a path in large and complex buildings easily. However, some indoor navigation algorithms only calculate approximate routes based on spatial topology analysis, while others only use indoor road networks. However, both of them use only one of the spatial topology or network information. In this paper, we present a navigation method based on topology analysis and room internal networks for indoor navigation path. FT-Indoornavi (Flexible Topology Analysis Indoornavi) calculate internal routes based on spatial topology and internal path networks to support length-dependent and running-time optimal routing, which adapt to complex indoor environment and can achieve a better performance in comparison of Elastic algorithm and iNav.

• Structural Engineering and Mechanics
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• v.28 no.4
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• pp.479-489
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• 2008

In this study an approximate method based on the continuum approach and transfer matrix method for static and dynamic analyses of stiffened multi-bay coupled shear walls is presented. In this method the whole structure is idealized as a sandwich beam. Initially the differential equation of this equivalent sandwich beam is written then shape functions for each storey is obtained by the solution of differential equations. By using boundary conditions and storey transfer matrices which are obtained by these shape functions, system modes and periods can be calculated. Reliability of the study is shown with a few examples. A computer program has been developed in MATLAB and numerical samples have been solved for demonstration of the reliability of this method. The results of the samples show the agreement between the present method and the other methods given in literature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.71-76
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• 2001

This paper describes a research work of developing system for conceptual die design system for Fine blanking. The method of approaching to the system is based on the knowledge-based rules. Knowledge for the system is formulated from experimental results and the empirical knowledge of field experts. This system has been written in VisualLISP on the AutoCAD using a personal computer and in Microsoft Visual Basic ver.6.0. Transference of data is accomplished by DXF (Drawing Exchange Format) method. This system consists of six modules, which are cognition of a drawing, cognition of shear length, calculation of shear force, materials properties database, determination of degree of difficulty of the product, determination of approximate life of punch and die modules. Results carried out in each module will provide efficiency to the designer and the manufacturer of die for Fine blanking. But the main focus of this system is the design of die for Fine blanking in the level of general concept. In order to use powerful tool in this field, developed system will be studied continuously.

• Journal of Communications and Networks
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• v.5 no.3
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• pp.249-257
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• 2003

Ring networks are very commonly exploited among local area and metropolitan area networks (LAN/MAN), whereas cells or small fixed-size packets are widely used in synchronized ring networks. In this paper, we present an analytical method for evaluating the delay-throughput performance of a MAC protocol with multiple self-tokens in a slotted ring network under uniform traffic. In our analysis, we introduce the stationary probability, which indicates the number of packets in a node. Also, it is assumed that each node has a sufficiently large amount of self-tokens, and a slotted ring has the symmetry. The analytical results with respect to delay-throughput performance have similar values to computer simulated ones. Furthermore, in order to achieve fair access under non-uniform traffic, we propose an adaptive MAC protocol, where the number of self-tokens in a node dynamically varies, based on the number of packets transmitted within a specified period. In the proposed protocol, when the number of packets transmitted by a node within a specified period is larger than a specified threshold, the node decreases the number of self-tokens in a per-node distributed method. That results in creating free slots in the ring, thus all nodes can obtain an equal opportunity to transmit into the ring. Performance results obtained by computer simulation show that our proposed protocol can maintain throughput fairness under non-uniform traffic.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.125-128
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• 2004

최근 이동 통신 기술의 급속한 발달로 인해 휴대폰, PDA 등과 같은 휴대용 단말기의 사용이 보편화 되고 있다. 따라서 이동 객체의 시간에 따른 공간적인 위치정보를 활용하여 다양한 서비스를 제공하는 위치 기반 서비스(Location-Based Service)에 관한 많은 연구가 진행되고 있다. 위치 기반 서비스의 효율적 제공을 위하여 시간에 따라 지속적으로 변하는 이동 객체의 대용량 시공간 정보를 신속하게 저장, 관리, 검색할 수 있는 인덱싱 및 질의 처리 기술이 수반되어야 한다. 본 논문에서는 대용량 이동 객체 데이터베이스를 대상으로 한 효율적인 인덱스 구축을 위한 데이터 압축 표현 방식에 대하여 논한다. 이를 위해 본 논문에서는 기존의 주요 연구에서 2 차원 공간 좌표 (X, Y)로 표현되던 이동 객체의 공간 정보를 계층적 구조를 갖는 행정구역에 기반하여 1 차원의 공간 정보로 압축 표현하는 방식을 제안한다. 이를 이용하여 대용량의 공간정보를 저장하고 있는 이동 객체 데이터베이스의 인덱스 크기의 감소 및 질의 처리 시간의 향상 효과를 얻을 수 있다. 또한, 제안된 방식은 2 차원 공간 좌표를 1 차원의 행정구역 기반의 위치정보로 표현하기 때문에 이로 인한 데이터 손실이 발생할 수 있으나, 일정 공간 내의 객체분포를 필요로 하는 교통 상황 파악, 근사적(approximate) 공간 정보를 필요로 하는 사람${\cdot}$차량 위치 추적 서비스와 같은 위치 기반 서비스를 신속하게 처리하는데 유용하게 사용될 수 있다.

• Journal of the Korea Society for Simulation
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• v.3 no.2
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• pp.57-67
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• 1994

For many practical and industrial optimization problems where some or all of the system components are stochastic, the objective functions cannot be represented analytically. Therefore, modeling by computer simulation is one of the most effective means of studying such complex systems. In this paper, with discussion of simulation optimization techniques, a case study in machining process for application of simulation optimization is presented. Most of optimization techniques can be classified as single-or multiple-response techniques. The optimization of single-response category, these strategies are gradient based search methods, stochastic approximate method, response surface method, and heuristic search methods. In the multiple-response category, there are basically five distinct strategies for treating the responses and finding the optimum solution. These strategies are graphical method, direct search method, constrained optimization, unconstrained optimization, and goal programming methods. The choice of the procedure to employ in simulation optimization depends on the analyst and the problem to be solved.