• ETRI Journal
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• 제19권3호
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• pp.169-185
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• 1997

This paper presents the design concepts and the system architecture of a mobile exchange for CDMA Mobile System. The paper also discusses complex subsystems in this system and design concepts of these subsystems. To evaluate the performance of the CDMA Mobile System, we have performed a computer simulation based on the framework of the mobile exchange. Simulation results are presented in terms of network traffic load (call attempts per second) and database performance requirements (transactions per second.)

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.330-335
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• 2002

To estimate the reliability of the standard electric multiple unit developed by Korea Railroad Research Institute, the vehicle system composed of 4 cars is divided into 14 subsystems. The 14 subsystems are connected in series. For each subsystem except for car body and bogie, failure rate is evaluated by an optimal failure model used in reliability engineering. For car body and bogie probabilistic structural integrity analysis is carried out. The distribution of failure rate of each part and system is assumed to be exponential. The estimated MTBF of the vehicle satisfies the planned MTBF.

• 산업기술연구
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• 제11권
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• pp.33-41
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• 1991

Using the Brayton and Tong's computer-generated Lyapunov functions, we stabilize the multilocomotive train system so that the system is globally asymptotically stable. We decompose an interconnected system into the second order subsystems. Lyapunov functions of the free subystems are constructed using the Brayton and Tong's algorithm. An aggregated test matrix is determined in terms of the qualitative properties of the free subsystems and the interconnecting structures. Stated feedback is used for stabilizing the entire system.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.869-879
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• 1995

The new field of learning control develops controllers that learn to improve their performance at executing a given task, based on experience performing this task. The simplest forms of learning control are based on the same concept as integral control, but operating in the domain of the repetitions of the task. In the previous paper, I had studied the use of such controllers in a decentralized system, such as a robot with the controller for each link acting independently. The basic result of the paper is to show that stability of the learning controllers for all subsystems when the coupling between subsystems is turned off, assures stability of the decentralized learning in the coupled system, provided that the sample time in the digital learning controller is sufficiently short. In this paper, we present two examples. The first illustrates the effect of coupling between subsystems in the system dynamics, and the second studies the application of decentralized learning control to robot problems. The latter example illustrates the application of decentralized learning control to nonlinear systems, and also studies the effect of the coupling between subsystems introduced in the input matrix by the discretization of the system equations. The conclusion is that for sufficiently small learning gain, and sufficiently small sample time, the simple learning control law based on integral control applied to each robot axis will produce zero tracking error in spite o the dynamic coupling in the robot equations. Of course, the results of this paper have much more general application than just to the robotics tracking problem. Convergence in decentralized systems is seen to depend only on the input and output matrices, provided the sample time is suffiently small.

• 한국통신학회논문지
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• 제29권4B호
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• pp.403-410
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• 2004

일반적으로 교환 시스템은 프로세서 보드, 입출력처리 보드 및 데이터 저장 장치등 그 기능별로 다수의 서브시스템들로 구성되어 있다. 또한 신뢰성을 확보하기 위하여 모든 서브 보드들은 이중화로 되어 있다. 교환시스템에서 저장 장치에는 시스템에 관련된 정보나 과금 정보등과 같은 작업 관련 데이터를 저장하며 비 휘발성 메모리에 저장해야 한다. 일반적으로 비 휘발성 저장장치를 구현할 때는 플래시메모리(flash memory) 또는 배터리 백업 메모리(battery backup memory)를 사용한다. 그러나 메모리는 단위 용량당 가격이 높고 백업(backup) 하지 않은 데이터를 손실했을 때 복구할 수 없다. 본 논문에서는 마이크로 컨트롤러를 이용하여 단위 용량당 가격이 저렴하고, 대용량의 데이터를 저장함과 동시에 이중화를 만족시키는 on-board 형태의 소형 디스크 모듈을 설계 구현하였다. 본 논문에서 구현된 이중화 저장장치는 사용 중인 엑티브(active) 디스크에 결함이 생겨 사용할 수 없을 경우에 리빌딩(rebuilding)과정을 동해 스탠바이 모듈로부터 데이터를 복구하며, 리빌딩 중에도 호스트 시스템은 스탠바이 디스크모듈을 이용하여 지속적으로 서비스를 제공할 수 있도록 설계되었다. 본 연구에서 개발된 저장장치는 교환시스템에서 플래시 메모리와 같은 값비싼 저장 장치를 대체 할 수 있을 것으로 기대된다.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.110-120
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• 2000

In order to improve the vibration characteristics of mid sized passenger car automatic transmission at idle experimental and theoretical studies have been carried out. Idle shake in "D" range occurs by various reasons such as characteristics of body bending resonance between subsystems and engine mounts etc. Using full vehicle finite element analyses and modal tests we introduce the way to reduce the idle shake in the early design stage. It shows that the exciting forces are the 2nd order torque and force of engine. A powertrain system modes in "D" range are entirely effected by the additional boundary conditions of drive line. As a result the frequencies of subsystems are arranged to be lined up at the idle frequency range in order to avoid the resonances with subsystems To reduce the idle shake mounts of radiator are tuned to act as a dynamic damper to 1st bending frequency of the body. In addition a hydraulic mount which is optimized by Phase Shift Method is applied to the rear engine mount.e rear engine mount.

• 한국국방경영분석학회지
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• 제1권1호
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• pp.131-135
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• 1975

One of the pending issues of the Ministry of Defense is the efficient management of space parts for the weapon systems. It has been known that more than 000 million dollars are needed for spare parts for the weapon systems annually. Though the problem demands a serious consideration, there has not been any systematic study on the problem as far as the author knows. One way to approach the problem is through an investigation of the system reliability under constraints. A measure of how well a system performs or meets its design objectives is provided by the concept of system reliability. If successful operation is desired for a specified period of time, reliability is defined as the probability that the system will perform satisfactorily for the required time period. This interpretation of reliability is normally applied to devices which are subject to random failures such as electrical or mechanical systems. It has been found necessary to express system reliability in terms of the reliability of the components or subsystems which comprise the system. The major subsystems of an aircraft, for example, include the electronics, powerplant, airframe and armament subsystems. Therefore, the optimal spare part kit can be found by maximizing the system reliability subject to cost or other constraints.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2028-2038
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• 2003

High-speed feed drive systems have been widely used in the manufacturing and semiconductor industries. Specifications for high-speed systems require more advanced capabilities than conventional feed drive systems. It is necessary to devise special design concepts to achieve the level of performance for high-speed feed drive systems. In this paper, an integrated design method is proposed for high-speed feed drive systems in which the interactions between mechanical and electrical subsystems ought to be considered simultaneously during the design process. Based on the integrated design method, a nonlinear optimal design procedure of mechanical subsystems considering the Abbe and radius errors is accomplished through the design process of electrical subsystems satisfying the control stability and the saturation condition of actuators as well as the relative stability. Both mechanical and electrical parameters are considered as design variables. Simulations and numerical case studies show that the integrated design method of high-speed feed drive systems creates results satisfying the desired performances of mechatronic systems.

• 천문학회보
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• 제42권1호
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• pp.49.1-49.1
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• 2017

In order to investigate the origin of multiple stellar populations in the halo and bulge of the Milky Way, we have constructed chemical evolution models for the low-mass proto-Galactic subsystems such as globular clusters (GCs). Unlike previous studies, we assume that supernova blast waves undergo blowout without expelling the pre-enriched gas, while relatively slow winds of massive stars, together with the winds and ejecta from low and intermediate mass asymptotic giant branch stars, are all locally retained in these less massive systems. We first applied these models to investigate the origin of super-helium-rich red clump stars in the metal-rich bulge as recently suggested by Lee et al. (2015). We find that chemical enrichments by the winds of massive stars can naturally reproduce the required helium enhancement (dY/dZ = 6) for the second generation stars. Disruption of these "building blocks" in a hierarchical merging paradigm would have provided helium enhanced stars to the bulge field. Interestingly, we also find that the observed Na-O anticorrelation in metal-poor GCs can be reproduced, when multiple episodes of starbursts are allowed to continue in these subsystems. Specific star formation history with decreasing time intervals between the stellar generations, however, is required to obtain this result, as would be expected from the orbital evolution of these subsystems in a proto-Galaxy. The "mass budget problem" is also much alleviated by our models without ad-hoc assumptions on star formation efficiency and initial mass function.

• 디자인학연구
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• 제16권1호
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• pp.209-218
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• 2003

인간의 모든 주제는 목표와 절차와 수단을 갖고 있다. 이러한 점에서 사회에서의 하위체계는 이데올로기, 제도와 규범 그리고 기술과 경제로 구분하며 문화에서는 가치적 문화, 규범적 문화 그리고 용구적 문화로 구분된다. 기술과 경제, 그리고 용구 문화에 직접 연관되어 있는 디자인의 경우, 앞의 세 가지 사항과 관련하여 상징적 가치, 미적 형식 그리고 기능성의 측면을 지니게 된다. 산업 사회의 틀을 벗어나고 있는 지금, 사회는 엄청난 변화의 와중에 있으며 디자인 또한 과거의 물질적 개념을 벗어나 새로운 영역으로 확대되어 가고 있는 상황이다. 그러나 이러한 변화는 디자인 자체의 변화라기보다는 디자인의 상위 개념 즉 문화와 사회가 변화하기 때문에 비롯되는 것이라고 볼 수 있다. 이런 점에 주목하여 본 논문에서는 사회 변화와 디자인 변화를 연계시켜 디자인 교육의 미래 방향에 대해서 연구하였다.