• Structural Engineering and Mechanics
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• 제82권4호
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• pp.445-458
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• 2022

Some of the control systems used in engineering structures that use sensors and decision systems have some time delay reducing efficiency of the control system or even might make it unstable. In this research, in addition to considering the effect of the time delay in vibration control process, predictive control is used to compensate the time delay. A semi-active vibration control approach with the help of magneto-rheological dampers is implemented. In addition to using fuzzy inference system to determine the appropriate control voltage for MR damper, structural behavior prediction system and specifying future responses are also used such that the time delays occurring within control process are overcome. For this purpose, determination of prediction horizon is conducted for one, five, and ten steps ahead for single degree of freedom structures with periods ranging from 0.1 to 4 seconds, subjected to twenty earthquake excitations. The amount of time delay applied to the control system is 0.1 seconds. The obtained results indicate that for 0.1 second time delay, average prediction error values compared to the case without time delay is 3.47 percent. Having 0.1 second time delay in a semi-active control system reduces its efficiency by 11.46 percent; while after providing the control system with structure behavior prediction, the difference in the results for the control system without time delay is just 1.35 percent on average; indicating a 10.11 percent performance improvement for the control system.

• 대한전자공학회논문지TC
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• 제43권5호
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• pp.162-168
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• 2006

전파 특성의 이해는 무선 통신 시스템의 설계와 서비스의 구축을 위해 매우 중요하다. 본 논문에서는 곡선형 지하철 터널환경에서 2.45GHz 주파수 대역의 전파 특성을 측정하고 분석하였다. 슬라이딩 코릴레이션 기반의 채널 측정 시스템을 구성하고 안테나의 빔 형태에 따른 특성을 비교하기 위해 5 종류의 안테나를 사용하였다. 터널내 경로손실은 자유공간에 비하여 안테나에 따라 평균 $4.38^{\sim}14.41dB$가 적고 원편파 안테나의 경로손실이 가장 적다. 또한 곡선구간에서 수신 안테나의 위치가 바깥쪽에 위치할 때 경로손실이 가장 적다. 모든 안테나의 지연성분의 90%가 20ns 이내에 존재하며, 지향성 안테나가 무지향성 안테나보다 더 넓은 코히어런스 대역폭을 갖는다. 측정결과 경로손실과 지연 특성을 고려할 때 지하철 터널에서는 원편파 안테나를 사용하는 것이 적합한 것으로 판단된다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.13-19
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• 2003

Mathematically simplified reaction scheme that simulates autoignitions of the end gases in spark ignition engines has been studied computationally. The five equation model is described, to predict the essential features of hydrocarbon oxidation. This scheme has been calibrated against autoignition delay times measured in rapid compression machines. The rate constants, activation temperatures, Ta, Arrhenius preexponential constants, A, and heats of reaction for stoichiometric n-heptane/air, iso-octane/air, and their mixtures have all been optimised. The optimisation has been guided by Morley's correlation of the ratio of chain branching to linear termination rates with octane number. Comparisons between computed and experimental autoignition delay times have validated the Present simplified reaction scheme and the influences of octane number upon autoignition delay times have been computationally investigated. It has been found that both cool flame and high temperature direct reactions can have an effect on autoignition delay times.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.362-379
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• 2015

In this study, Nuclear Power Plant (NPP) construction schedule delay risk assessment methodology is developed and the construction delay risk is assessed for turnkey international NPP projects. Three levels of delay factors were selected through literature review and discussions with nuclear industry experts. A questionnaire survey was conducted on the basis of an analytic hierarchy process (AHP) and Relative Importance Index (RII) methods and the schedule delay risk is assessed qualitatively and quantitatively by severity and frequency of occurrence of delay factors. This study assigns four main delay factors to the first level: main contractor, utility, regulatory authority, and financial and country factor. The second and the third levels are designed with 12 sub-factors and 32 sub-sub-factors, respectively. This study finds the top five most important sub-sub-factors, which are as follows: policy changes, political instability and public intervention; uncompromising regulatory criteria and licensing documents conflicting with existing regulations; robust design document review procedures; redesign due to errors in design and design changes; and worldwide shortage of qualified and experienced nuclear specific equipment manufacturers. The proposed combined AHP-RII methodology is capable of assessing delay risk effectively and efficiently. Decision makers can apply risk informed decision making to avoid unexpected construction delays of NPPs.

• 대한교통학회지
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• 제20권7호
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• pp.23-29
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• 2002

일반적으로 4지 또는 3지의 교차로가 설계·운영되고 있으나 적지 않게 5지 또는 그 이상 의 원형 신호교차로가 실질적으로 이용되고 있다. 접근로 수에 따른 교차로 형태별 분류에 의하면 5지 이상의 교차로에서의 상충지 점의 수는 4지 교차로의 그것보다 월등히 높아 설계지침에서도 4지 이하의 교차로를 설계할 것을 권하고 있으며 마찬가지로 5지 원형 신호교차로에서도 그 상충지점 수가 많다. 이러한 이유로 5지 신호 교차로의 신호 설계는 교통소통이 아닌 교통안전측면에서 신호현시 순서 및 길이가 결정되어야 할 필요가 있으며 또 그러한 현시순서는 교차로 내 원활한 교통의 흐름을 심각한 수준으로 방해하지 않을 필요가 있다. 본 연구에서는 5지 신호교차로의 안전을 고려한 현시순서설계 방안을 제시한다. 울산광역시에서 운영중인 공업탑 5지 신호교차로를 대상으로 현장자료를 수집하였으며, 신호시간 설계모형은 TRANSYT-7F를 적용했다. TRANSYT-7F에서의 최적 신호현시의 길이를 토대로 기본적으로 "한 현시에 2개 교통류의 이동" 원칙에 따라 재배열하였다. 제안된 방법으로 보정된 신호현시 순서 및 길이를 사용하여 모의실험한 결과 TRANSYT-7F에서 제시한 최적 신호현시 순서 및 길이를 적용한 것에 비하여 평균 6.2%지체도 증가가 있었으나 교차로 내 상충수를 61.5% 줄이는 결과를 도출하였다.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.76-83
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• 2002

Mathematically and chemically simplified reaction scheme for n(heptane that simulates autoignitions of the end gases in spark ignition engines has been developed and studied computationally. The five(equation model is described, to predict the essential features of hydrocarbon oxidation. This scheme has been calibrated against autoignition delay times measured in rapid compression machines. The rate constants, activation temperatures, Ta, Arrhenius pre-exponential constants, A, and heats of reaction for stoichiometric nheptane/air has all been optimized. Comparisons between computed and experimental autoignition delay times have validated the present simplified reaction scheme. The influences of heat loss and concentration of chain carrier at the beginning of compression upon autoignition delay times have been computationally investigated.

• 한국통신학회논문지
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• 제13권2호
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• pp.171-181
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• 1988

본 논문에서는 packet-switched network에서 음성을 서비스하는데 있어서 고려해야 할 여러가지 점들을 살펴보고, 실제로 음성과 데이터를 동시에 서비스하는 packet voice/data terminal을 구현하였으며 그 성능 분석을 시도하였다. PVDT의 software는 OSI 7 layer architecture에 맞추어 설계하였으며 음성과 데이터를 link level부터 구별하여 서비스하였다. 또한 음성 packet의 전송 delay를 작게 하기 위해 데이터보다 음성을 우선적으로 서비스하도록 하였으며 간략화된 protocol로 재전송에 의한 overhead를 없앴다. PVDT의 hardware의 구성은 기능별로 master control module, speech processing module, speech activity detection module, telelphone interface module, input/output inteface module로 나누어진다. Packet음성통신망에 대한 해석으로는 음성 packet의 전송 delay의 variance에 의한 영향을 줄이기 위한 최적 재생지연시간을 전송 delay의 분포를 통해 계산하였다.

• 동의생리병리학회지
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• 제20권2호
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• pp.494-497
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• 2006

A child with five delay, five ankylosis, five weakening needs to take herbal medicine for a long term. So safety, efficacy inspection for the long term usage of herbal medicine and mixed dose is needed because other medication or functional health foods, etc could be taken during this process. Operated liver function test before and after dosing herbal medicine to one hundred and sixty children who aided private oriental medicine located in Seoul, and measured the efficacy by comparing sleeping hours, morbidity, stamina, sanguineness, personality, digestion with the state before taking herbal medicine based on questionnaire done by the parents. Every children were under the limits, and there were no differences between boys and girls, and no notable differences according to family histories. There were positive results in efficacy inspection ordered as improvement in personality, stamina, sanguineness, decrease in morbidity, increase in appetite, digestion. No signs of disorder in liver function has been found during the dose of herbal medicine or simultaneous medicine, and shown promotion of health.

• 복식
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• 제45권
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• pp.71-84
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• 1999

This study was to identify the dimensions of consumer's purchasing motives and purchasing delay reasons toward casual hanbok. Other objective was to examine relationship between these variables and future purchasing intention. Th 22 purchasing motive questions and 19 purchasing delay reasons were selected through the result of self-questionnaire analysis. 302 purchaser and 297 consumers who delay for particular reasons in Pusan responsed to the second questionnaire of purchasing motives and purchasing delay reasons toward casual Hanbok. The results as follows: 1. For factor analysis 22 purchasing motive questions were subjected to the principle component analysis with orthogonal rotation after extraction of 6 major factors. Six dimensions are consciousness of nation goodness of design conformity with fashion charming apperance relaxation fo body and mind nation goodness of design conformity with fashion charming appearance relaxation of body and mind and pursuit of individuality. These factors explained 62.0% of total variables. 2. Consumer's purchasing motives such as consciousness of nation goodness of design charming appearance and relaxation of body and mind has predicting power to the re-purchasing intention of casual hanbok 3. For factor analysis 19 delay reason question were subjected to the principle component analysis with orthogonal rotation after extraction of 5 major factors. Five dimensions are non-fitness for occasion and body shape unsatisfaction with design unsatisfaction with price need of information search for better product and preference for traditional hangok. These factors explained 60.4% of total variables. 4. Delay reasons of unsatisfaction with design and price were positively related to the future purchasing intention. This delay reason is caused by forces external to the consumer and the consumer has engaged in information search. This result explained this type of consumer has the strong future purchasing intention.

• 전자공학회논문지A
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• 제33A권3호
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• pp.82-88
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• 1996

A simpel formular is proposed for the analysis of gate delay of CMOS gate in the low V$_{GS}-V_{TH}$ scaling. The effects of magnitude of V$_{GS}-V_{TH}$ on gate delay can be readily found through the formula so that it can be used ot design the device parameters in the low V$_{DD}$ CMOS circuits. The measured sresutls confirm the usability of the proposed formula and quantifies the improtance of V$_{TH}$ effects on gate delay under low voltae operation. Applying the formula to the prototype NMOSFET devices representing the five generations of technology, the impacts of the V$_{GS}-V_{TH}$ on the various aspects of the circuit and device characteristics are investigated in a consistent manner.