• Journal of Communications and Networks
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• 제5권1호
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• pp.73-81
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• 2003

The controlled load service defined within the IETF's Integrated Services architecture for quality-of-service (QoS) in the Internet requires source nodes to regulate their traffic while the network, in combination with an admission control strategy, provides a guarantee of performance equivalent to that achieved in a lightly loaded network. Packets sent in violation of the traffic contract are marked so that the network may assign them a lower priority in the use of bandwidth and buffer resources. In this paper, we define the requirements of a scheduler serving packets belonging to the controlled load service and present a novel scheduler that exactly achieves these requirements. In this set of requirements, besides efficiency and throughput, we include an additional important requirement to bound the additional delay of unmarked packets caused due to the transmission of marked packets while dropping as few marked packets as possible. Without such a bound, unmarked packets that are in compliance with the traffic contract are not likely to experience delays consistent with that in al lightly loaded network. For any given desired bound ${\alpha}$ on this additional delay, we present the CL(${\alpha}$) scheduler which achieves the bound while also achieving a per-packet work complexity of O(1) with respect to the number of flows. We provide an analytical proof of these properties of the CL(${\alpha}$) scheduler, and we also verify this with simulation using real traces of video traffic. The scheduler presented here may be readily adapted for use in scheduling flows with multi-level priorities such as in some real-time video streams, as well as in other emerging service models of the Internet that mark packets to identify drop precedences.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.151-156
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• 2000

The brake system is important to stop train safely. The train is sloped by regenerative brake and pneumatic brake which are continuously blended at service brake. When service is applied to train, it is controlled by train weight and brake command. The jerk limitation function is applied for impulseless smoothing braking. All brake applications in service condition have a function of the variable load control to keep the braking effort in proportion to each car load. All of control function are performed by brake controller. Therefore, we will propose the design of brake control system in order to control efficiently

• 전기학회논문지
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• 제58권7호
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• pp.1263-1269
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• 2009

Stable and sustainable power supply means maintaining a certain level of power quality and service while securing energy resource and resolving environmental issues. Distributed generation (DG) has become an essential and indispensable element from environmental and energy security perspectives. It is known that voltage violation is the most important constraint for load variation and the maximum allowable DG. In distribution system, sending voltage from distribution substation is regulated by ULTC (Under Load Tap Changer) designed to maintain a predetermined voltage level. ULTC is controlled by LDC (Line Drop Compensation) method compensating line voltage drop for a varying load, and the sending voltage of ULTC calls for LDC parameters. The consequence is that the feasible LDC parameters considering variation of load and DG output are necessary. In this paper, we design each LDC parameters determining the sending voltage that can satisfy voltage level, decrease ULTC tap movement numbers, or increase DG introduction. Moreover, the maximum installable DG capacity based on each LDC parameters is estimated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.433-433
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• 2000

In this paper, we propose a development of internet teleoperation method applying QoS model, which has the real time control capability and the time-delay predicting capability, The QoS model gives a constant bandwidth to a specified application and makes the dynamically irregular time-delay to be predictable and fined so that it can have real-time capability.

• 전자공학회논문지S
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• 제36S권9호
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• pp.36-48
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• 1999

최근 ITU-T에서는 고속 데이터 응용을 위해 새로운 ATC (ATM Transfer Capability)로 크래딧 기반의 흐름 제어를 사용하는 CT (Controlled Transfer) 서비스가 고려되고 있다. 본 논문에서는 크래딧 기반 흐름 제어에서 단점으로 지적되는 버퍼 요구량을 줄이기 위해 적용되고 있는 동적 버퍼 할당 방식들의 성능을 분석하고, 새로운 동적 버퍼 할당 방식을 제안하였다. 그리고, 시뮬레이션을 통하여 기존의 대표적인 동적 버퍼 할당 방식인 FCVC (Flow Controlled Virtual Channels)의 동적 할당 방식과 ZQFC (Zero Queueing Flow Control) 방식 및 제안된 방식의 성능을 비교 분석하였다. 시뮬레이션 결과 제안된 동적 버퍼 할당 방식은 망의 부하 정도에 따라 할당 버퍼량의 증감량을 조절하여 빠르게 망 상황의 변화에 대처하여 VC들 사이의 대역폭 사용의 공평성, 스위치의 큐 길이 및 링크 이용 효율면에서 우수한 성능을 보임을 알 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1088-1090
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• 2001

In general, Power SCR(Silicon Controlled Rectifier) is most widely used in Power Plant as well as Industrial field. It has been controlled and operated according to its own control method. Especially, in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control unit is described, it gets over the past analog control system limit, uses DSP(Digital signal processor) had high speed response, controls SCR gate firing angle for 3 phase current balance.

• 대한산업공학회지
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• 제34권2호
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• pp.140-150
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• 2008

Point Coordination Function (PCF) of the IEEE 802.11 protocol providing a centrally-controlled polling-based multiple access to a wireless channel is very efficient in high load conditions. However, its performance degrades with increasing the number of terminals and decreasing the load, because of wastes related to unsuccessful polling attempts. To solve the problem, we propose and study analytically the generic dynamic polling policy using backoff concept. For this aim, we develop Markov models describing the network queues changes, what allows us to estimate such performance measures as the average MAC service time and the average MAC sojourn time, to show the dynamic polling efficiency and to tune optimally the backoff rule.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.53-56
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• 2002

In this paper, we study the network structure that can guarantee the end-to-end quality of service in the Explicit multicast network. In order to guarantee the end-to-end quality of service, we adopt the end-to-end measurement based admission control (EMBAC) scheme. For the effective measurement of the network state and minimum influence on the current data traffic, the queue structure, which the drop precedence in assured forwarding (AF) Per hop behavior (PHB) of the differentiated service (Diffserv) is applied to, is proposed. Through a simulation, we show that EMBAC can make tile controlled load service in tile AF PHB applied Xcast network, and the qualify of the admitted traffic is guaranteed. In addition, the performance of the EMBAC is changing according to the selling parameter of AF PHB.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.98-105
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• 2018

철근 콘크리트 부재에서 균열은 구조적 요인 뿐만 아니라 재료적 인자에 의해서도 발생한다. 이러한 균열의 크기와 발생 위치를 파악하는 것은 매우 어렵다. 도로교설계기준(한계상태설계법)과 콘크리트구조기준(2012)에서는 균열을 제어하기 위해 직접균열제어 방법과 간접균열제어 방법을 제시하였다. 콘크리트구조기준 본문에서는 사용하중 하에서 철근 간격을 사용하여 간접적으로 균열을 제어한다. 이에 반해, 콘크리트구조기준 부록에서는 지속하중 하에서 균열폭을 통해 직접적으로 균열을 제어한다. 즉, 균열 제어를 위해 고려하는 하중 상태가 상이하다. 그러나 도로교설계기준에서는 사용하중조합에서 균열을 제어하고, 유효탄성계수를 사용하고 있다. 따라서 이 연구에서는 고정 하중과 활하중의 비율을 반영할 수 있는 유효탄성계수를 적용한 설계 균열폭으로부터 최대철근간격을 산정하였다. 그리고 변수 해석을 수행하여 합리적인 균열 검증 방법에 대하여 모색하였다. 해석 결과 콘크리트구조기준으로부터 유도된 철근 간격은 도로교설계기준으로부터 유도된 값보다 작아 보수적인 설계를 유도하였다. 또한, 이 연구에서 제시한 최대철근간격은 직접균열제어와 간접균열제어 사이의 차이를 제거하여 해석의 일관성을 확보할 수 있는 것으로 판단된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1091-1093
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• 2001

The power semiconductor is widely used in the power plant or industrial field because of genealization and enlargement. It has been controlled and operated according to its own control method. Especially in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control algorithm is described. it gets over the past analog control system limit, controls SCR gate firing angle for 3 phase current balance.