• 한국경영과학회지
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• 제20권2호
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• pp.159-178
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• 1995

Supervisory control is an approach based on formal language. it is used to model and control discrete event systems in which each discrete event process is represented as an automation. A supervisor is a generator that switches control patterns in such a way that a given discrete evenet process behaves in obedience to various constraints. A flexible manufacturing cell (FMC) is one of discrete evenet systems. Functions necessary for the operation of an FMC are characterized by operational components and informational compoments. The operational components can be modeled using the finite state machines and the informational components can be modeled using the abstract formalism which describes supporting operations of the cell controller. In this paper, we addressed function required for FMC control specification, software engineering aspects on FMC control based on supervisory control, a concept of event queue for resolving synchronization problem, and complexity reduction. Based on the mathematical model of an FMC. we synthesized the controller by integrating a supervisor for FMC with control specification that specifies event-driven operation of the cell controller. The proposed control scheme is stable mathematically so that the system always behaves on a controlled way even under the existence of uncontrollable events. Furthermore, using an event queue concept, we can solve a synchronization problem caused by the violation of instantaneity assumption of supervisory control theory in real life situation. And also, we can propotype a control software rapidly due to the modularity of the proposed control scheme.

• 한국통신학회논문지
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• 제22권8호
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• pp.1765-1773
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• 1997

PLL을 사용하는 통신 시스템에서는 선로 잡음에 의해서 사이클 슬립 현상이 발생 할 수 있다. 이 사이클 슬립 현상이 동기식 스트림 암호 통신 시스템에 발생하면 난수 동기 이탈 현상을 발생시켜 통신을 할 수 없게 된다. 이러한 난수 동기 이탈의 위험성을 줄이기 위하여 연속 재동기 방식을 사용하지만 이에 따른 문제점이 있다. 본 논문에서는 수신 클럭 복원시에 사용되는 수신 클럭 보상 알고리즘을 연속 재동기 방식에 적용하여 기존의 연속 재동기 방식의 문제점을 해결하는 방법을 제안하였다. 즉, 정해진 기준 시간 동안에 실제 수신 클럭 펄스 수를 계수하여 얻은 계수치와 동일 시간 동안에 사이클 슬립이 발생하지 않은 정상 상태에서의 수신 클럭 펄스 수인 정상치가 일치하지 않으면 사이클 슬럽이 발생된 것으로 판단하여 훼손된 수신 클럭을 사이클 스립의 발생 형태에 따라 클럭 펄스를 더해주거나 빼주는 방법을 연속 재동기 방식과 같이 사용하였다. 제안된 방법을 절대 클럭 동기를 요구하는 동기식 스트림 암호 통신 시스템에서 시험한 결과 기존의 연속 재동기 방법에 비하여 재동기 시간을 최대 20배까지 단축시켰는데 그것은 전송 데이터 량을 17.8% 감축하는 효과와 동일하다.

• 산업경영시스템학회지
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• 제41권4호
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• pp.22-33
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• 2018

Recently domestic manufacturing companies have been experiencing worsening profitability and stunted growth due to the long-term economic recession and the rapid rise of developing countries such as China and Southeast Asia. These difficulties force many companies to concentrate their core competencies on new value creation and innovation in order to gain momentum for new growth. Enterprise Resource Planning (ERP) has been considered as one of viable solutions. Among the various modules in ERP, shop floor control function in the production management module is rather limited. In order to overcome this problem, Manufacturing Execution System (MES) has been used as a subsystem which has a strong information gathering power and flexibility. Both systems interact closely with each other. In particular, ERP requires fast, accurate shop floor information at MES. This paper describes how to synchronize relevant information between ERP and MES with theory of constraints (TOC). The processing time information transmitted from the MES workplace is received at the ERP workplace. In the process, the received processing time is causing information distortion in ERP, when the information gathering standard of MES is different from the ERP information interpretation standard. The Drum-Buffer-Rope theory of TOC was applied to resolve this problem, therefore, information synchronization between both systems was made. As a precondition, the standard time of the upper ERP system was rearranged according to the capacity constraints resource. As a result, standard time restructuring has affected changes in labor costs. Standard labor costs have come close to actual ones, and information synchronization of MES transmission data has improved the reliability of standard product costs, such that it enabled various company-wide restructuring actions to be much more effective.

• 정보보호학회논문지
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• 제19권2호
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• pp.93-103
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• 2009

본 논문에서는 3GPP 네트워크에서 USIM 기반의 사용자 인증 기법을 제안한다. 제안 기법은 기존의 3GPP 네트워크 접속을 위한 인증 방식에서 발생 가능한 Sequence Number 동기 문제, 인증 데이터 Overhead 문제, 네트워크 간 시그널링 Overhead 문제 등을 개선한다. 제안 기법은 기존의 USIM 기반의 AKA 인증 프로토콜을 기본 모델로 사용하고 단말과 SN이 공유한 SK와 Time Stamp를 통해서 AKA 인증 절차를 수행하도록 한다. 이렇게 함으로써 인증 벡터의 Sequence Number의 동기 여부를 확인할 필요 없이 Time Stamp 값으로 인증 벡터의 맵핑을 수행하여 Sequence Number 동기 문제를 해결할 수 있다. 뿐만 아니라 하나의 인증 벡터만을 관리하여 사용하기 때문에 SN에서의 인증 데이터 Overhead문제를 해결하고, SN과 HN 사이의 시그널링 Overhead 문제를 개선할 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(3)
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• pp.181-184
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• 2001

In recent, a morphological analyzer be used for indexing system in information retrieval system. A morphological analyzer as a indexing system must have multiprocessing ability to deal with multiple users and documents. To meet the needs of these, we propose a morphological analyzer with multi-threads method. To use multi-threads method, we consider memory allocation problem, threads synchronization problem, code optimization and so on. In this paper, first, we report several manners for multi-threads. And next, to evaluate our proposed system, we make a comparison test between proposed system and existing system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1858-1862
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• 2005

Stepping motor normally operates without feedback and may loss the synchronization. This problem can be prevented by using positional feedback. This paper introduces one method for closed loop control of stepping motor and a method for combining full-step control and micro-step control. This combination controlling apparatus can perform position control with high accuracy in a high speed, so that it will not suffer from vibration (or hunting) problem when stopping motor. Controlling apparatus contains a position counter block for detecting rotor position of stepping motor, a driving block for supplying current to windings of stepping motor, a control block for comparing output signal of position counter block with command position (desired position) and outputting current command signal based on deviation between current position and command position of rotor. To output current command signal, the control block refers to a sine wave data table. This table contains value of duty cycle of Pulse Width Modulation signal. As the second object of this paper, the process of building this data table is also presented.

• Journal of information and communication convergence engineering
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• 제5권4호
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• pp.346-350
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• 2007

Almost all network systems provide an authentication mechanism based on user ID and password. In such system, it is easy to obtain the user password using a sniffer program with illegal eavesdropping. The one-time password and challenge-response method are useful authentication schemes that protect the user passwords against eavesdropping. In client/server environments, the one-time password scheme using time is especially useful because it solves the synchronization problem. It is the stability that is based on Square Root Problem, and we would like to suggest PBSI(Password Based Secure Identification), enhancing the stability, for all of the well-known attacks by now including Off-line dictionary attack, password file compromise, Server and so on. The PBSI is also excellent in the aspect of the performance.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.537-541
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• 2003

The synchronization of production-delivery artivities is one of crucial factors to get competitive collaboration benefits between the manufacturer and the retailor(s). There were several researches to study on He optimal delivery policy to minimize the total cost of integrated system of both manufacturer and retailor(s). In this research, we investigate the joint optimal shipment policy in case that a manufacturer produces multiple products sharing a single production facility in the manufacturer side and retailor(s) deploys JIT delivery pattern with equal-size shipment policy. We formulate this problem as a form of 'Common Cycle Approach' in classical ELSP (Economic Lot Scheduling Problem) and provide simple optimal solution procedure.

• Journal of information and communication convergence engineering
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• 제3권4호
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• pp.213-216
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• 2005

Almost all network systems provide an authentication mechanism based on user ID and password. In such system, it is easy to obtain the user password using a sniffer program with illegal eavesdropping. The one-time password and challenge-response method are useful authentication schemes that protect the user passwords against eavesdropping. In client/server environments, the one-time password scheme using time is especially useful because it solves the synchronization problem. It is the stability that is based on Square Root Problem, and we would like to suggest PBI(password Based Identification), enhancing the stability, for all of the well-known attacks by now including Off-line dictionary attack, password file compromise, Server and so on. The PBI is also excellent in the aspect of the performance.

• 전기학회논문지
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• 제67권8호
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• pp.987-993
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• 2018

In the existing distribution automation system, the database is managed by each distribution office. But there is a high possibility to happened a problem during a fault processing because the representation of the connection switches between distribution offices are complicated. In addition, if a distribution office will be going to collapse due to disaster, for example, a big fire or earthquake, its own database may be lost. In order to solve this problem, it is necessary to have a structure of an integrated database management from an integration center to under the distribution office. To do this, the integration center must store and manage it as the database using the own office code.