• Journal of Communications and Networks
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• v.7 no.3
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• pp.385-393
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• 2005

In this paper, we propose a simple algorithm to adaptively adjust the value of dupthresh, the duplicate acknowledgement threshold that triggers the transmission control protocol (TCP) fast retransmission algorithm, to improve the TCP performance in a network environment with persistent packet reordering. Our algorithm uses an exponentially weighted moving average (EWMA) and the mean deviation of the lengths of the reordering events reported by a TCP receiver with the duplicate selective acknowledgement (DSACK) extension to estimate the value of dupthresh. We also apply an adaptive upper bound on dupthresh to avoid the retransmission timeout events. In addition, our algorithm includes a mechanism to exponentially reduce dupthresh when the retransmission timer expires. With these mechanisms, our algorithm is capable of converging to and staying at a near-optimal interval of dupthresh. The simulation results show that our algorithm improves the protocol performance significantly with minimal overheads, achieving a greater throughput and fewer false fast retransmissions.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.749-756
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• 1998

TiC-Ni and TiC-Ni-Mo cermet powders were produced by Self-propagating High temperature Synthesis (SHS) process. The cooling rate of synthesized powders were controlled by using the V-shaped copper jig and the carbide size decreased with increasing the cooling rate I. e decreasing the width of copper jig Round shape carbide particles were produced after SHS reaction in TiC-Ni as well as TiC-Ni-Mo powders. Local segregation of Mo rich phases was observed in SHS powder of TiC-Ni-Mo and the uneven dis-triobution of Mo promoted the faster growth rate of carbide particles during sintering compared to the same composition specimen with commercial TiC powder. Howogeneous microstructure of TiC-Ni-Mo cermet was obtained when the elemental Mo powder was mixed with the SHS powder of TiC-Ni.

• The Magazine of the IEIE
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• v.25 no.2
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• pp.48-57
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• 1998

본 기고는 시뮬레이션 기술 분류 중 Virtual Simulation, 그 중에서도 항공기 시뮬레이터 기술에 초점을 맞추고자 한다. 항공기 시뮬레이터 기술이 시뮬레이션 전체 분야에서 차지하는 비중과 현재의 위를 객관적으로 이해하기 위하여 시뮬레이션 기술이란 무엇인가 하는 원론에서부터 출발한다. Virtual, Constuctive, Live 등의 시뮬레이션 기술들을 간략히 소개하면 이들 기술의 변천을 SIMNET(SIMulator NETworking), DIS(Distributed Interative Simulation), ALSP(Aggregate Level Simulation Protocol), HLA(High Level Architecture) 등의 프로그램 등을 통하여 살펴본다. 항공기 시뮬레이터 기술은 Virtual 시뮬레이션 기술의 발원으로서 1930년대 이후로 시뮬레이션 기술 전반을 선도하여 왔는데, 그 진화과정을 간추려 언급한다. 또한, 항공기 시뮬레이터를 구현하기 위한 기술들을 간략히 살펴보고, 그 기술들을 선도하는 네덜란드 Delft 대학의 SIMONA(SImulation, MOtion and NAvigation) 프로그램과 미국 국방성, 산업체, 학계, 연구소 등을 중심 축으로 하는 NCS(National Center for Simulation)를 소개함으로써 항공기 시뮬레이터는 물론, 시뮬레이션 기술 전반의 미래를 가늠한다. 마지막으로 항공기 시뮬레이터를 중심으로 하는 국내 시뮬레이터 기술 수준과 산업 현황을 간추려 소개한다.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.142-151
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• 1995

회전체의 자동밸런싱을 위하여 고안된 자기보상 동적균형기는 홈이파인 원판에 강구와 저점성유체를 지닌 구조체이다. 유도된 운동방정식으로 부터 자기보상 동적균형기의 작동조건을 조사하기 우하여 수치해석을 통한 동 특성을 검토하였다. 수치해석의 결과에 근거하여 임계속도보다 높은 범위에서는 자기보상 동적균형기는 정상작동을 보여주었다. 임계속도에서는 회전계의 균형이 강구와 점성유체와의 감쇠계수에 의존하였으나 임계속도보다 낮은 범위에서는 어떠한 조건에 대해서도 작동하지 않음을 알 수 있었다. 자동차 및 항공기에도 응용가은한 자기보상 동적균형기의 작동조건들을 본 논문에서 예시하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.375-379
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• 1997

Thermal drift of the machine tool spindle due to temperature increase dominates the major source of the machine tool error. To compensate the thermal errors, software based error correction methods could be implemented. In th~s case, we need model to map the relationship between temperature and thermal distortion. Traditionally, two or three different methods have been trled: step increase of spindle speed, constant, random. The latter two methods are described in the document of ISOlDIS230-3. In this research, three different methods were verified through the experiments from the viewpoint of compensation of thermal distortion. Constant spindle speed turned out good enough for monitoring the behavior of the thermal drift and modeling the relationship between temperature and thermal distortion.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.1-8
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• 1998

In this paper, the radiation characteristics of a bar-type tranceiver are analyzed by using FDTD method and the effectiveness of the analysis method is verified by comparing the calculated data with experimental data. The effects of human head and hand on the radiation characteristics of fold-type transceiver are analyzed. In order to observe the effects of human head and hand on the input impedance and far-field radiation pattern, a fold-type transceiver with .lambda./4 monopole antenna wrapped by human hand operating in the proximity of hea dis modeled an analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.745-748
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• 1990

MMS (Manufacturing Message Specification) is a communications standard of MAP (Manufacturing Automation Protocol), which is a Network Protocol for Industrial Automation. In the environment of Mini-MAP, MMS is situated in the application layer and on the LLC (Logical Link Control) layer. In this paper, MMS software is implemented on the basis of ISO DIS 9506. The implemented software was tested with Token Passing Bus Network Interface Unit, which was designed in our laboratory and performs the actions of layer 1 and 2.

• Journal of the Korean Society of Safety
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• v.10 no.4
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• pp.22-35
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• 1995

In this paper, an electronic control unit is developed using 16bit microcomputer for automobile engine. This system incorporate AFS(Air Flow Sensor) of Hot Wire type, DIS(Direct Ignition System), ISC(Idle Speed Control) system, CAS(Cranke Angle Sensor) and other peripheral device. This system includes hardware and software to facilitate precision control of both fuel injection and ignition timing. Especially, this controller consists of position signal(180 teeth) and 4 REF signals. Present system has maximum $720^{\circ}CA$ delay. But this system has maximum $180^{\circ}CA$. Thus, this system is able to precision control both fuel injection and ignition timing.

• Journal of the Korean Society of Costume
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• v.22
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• pp.177-192
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• 1994

The purpose of this study lies in giving help to the rational life of clothing of costmer and presenting some measures for solving problems of the fashion merchandising policy of children's ready-made clothes and the searching of feasibility of the children's ready-made clothes market in the wave of market liberalization. data for this study were obtained from interviews with managers in children's apparel company. The results are as follows : the most important change of children's ready-made clothes market is the increase in national brand license brand direct import brand and the variety of the channel of distri-bution. The most children's apparel companies showed double-edged viewpoints for these tendencies in the wave of market libera-lization. In therms of positive aspect it would give stimulus to improve product quality of fashion merchandise which were the most dis-advantageous factors in competing with oversea's brand. In terms of negative aspect it would bring the oversupply and the foreign product's penetration in domestic market. In order to improve the present condition the companies should try to establish strat-government should try to support to the small and medium sized apparel firms.

• 한국약용작물학회:학술대회논문집
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• 2006.04a
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• pp.75-90
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• 2006

Both synthetic and endogenous $A{\beta}$ are degraded by peptidase G. Both $A{\beta}40$ and 42 are cleaved by peptidase G. Peptidase G cleaves $A{\beta}40$ into small fragments ($A{\beta}18$) which lacks aggregation property and are not toxic to neuron. Peptidase G seems to degrade multimeric $A{\beta}$ more efficiently than monomeric $A{\beta}$. Peptidase G protects neurons from toxicity induced by $A{\beta}$ by cleaving it into smaller fragments. Thus, dis-regulation of peptidase G could contribute amyloid deposit found in AD brain.