• 대한전자공학회논문지TC
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• 제46권5호
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• pp.115-121
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• 2009

공중파 방송과는 달리 통신망을 이용하는 IPTV는 사용자가 채널을 변경하면 변경된 채널 데이터를 서버로부터 받아와야 하므로 지연시간이 발생하게 되며 이러한 채널변경 지연시간의 발생은 사용자의 체감품질을 저하시킨다. 본 논문에서는 다중체인 구조를 이용한 P2P기반의 IPTV시스템에서 채널을 변경할 때 발생하는 지연시간을 감소시키는 알고리즘을 제안한다. 제안하는 방법은 인접한 채널을 함께 전송하는 방법과 새로운 채널그룹에 접속할 때 미리 구성되어 있는 테이블을 이용하여 유효한 peer로 직접 접속하는 방법으로 구성된다. 이 방법은 첫 번째 채널변경에서의 지연시간을 없애고 사용자가 채널을 계속 변경하면서 원하는 채널을 찾는 채널탐색 환경에서도 지연시간을 줄이는 장점이 있다. 수치적인 분석을 통해서 제안하는 구조의 지연시간 감소 효과가 높다는 것을 보여준다.

• 한국건축시공학회지
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• 제19권5호
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• pp.467-475
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• 2019

Delay is one of the most critical issues for construction projects and leads to huge losses in both developing and industrialized countries. The construction sector in Rwanda, a rapidly-developing nation, is no exception. Delays can be mitigated only once we have identify their primary causes, and these may not be the same in each region. This study aims to ascertain the main critical factors responsible for delays in building construction in Rwanda through an intensive literature review and questionnaire survey. A total of 40 delay causative factors were obtained from a literature review and were further classified into nine major categories. The questionnaire survey was distributed to about 80 respondents from clients, contractors, and consultants. From the list of 40 different factors, the top twelve most critical causes were identified as stoppage of work due to cash flow constraints, delay in approving design documents, confidentiality of physical plan, price fluctuations and delay in approving significant change, change orders, delay in performing inspections, Ineffective project planning, inadequate drawing details, unqualified labor, lack of materials on the market and dishonesty.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.92-96
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• 2002

This paper is concerned with properties of a Lyapunov functional of state delay systems. It is shown that if a state delay system has a pure imaginary pole for some state delay, then no Lyapunov functional satisfying a Lyapunov condition exists periodically with respect to change of the state delay. This periodic property is unique in state delay systems and has been well known in the frequency domain stability conditions. However, in the time domain stability conditions using a Lyapunov functional, the periodic property is not known explicitly.

• 한국분무공학회지
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• 제25권3호
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• pp.119-125
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• 2020

In this paper, we used Helmholtz solver based on 3D finite element method to quantitatively analyze the effects of change of gain, time delay and time delay spread, which are the main variables of flame transfer function, on combustion instability in gas turbine combustor. The effects of the variable of flame transfer function on the frequency and growth rate, which are the main results of combustion instability, were analyzed by applying the conventional heat release fluctuation model and modified one considering the time spread. The analysis results showed that the change of gain and time delay in the same resonance mode affected the frequency of the given resonance modes as well as growth rate of the feedback instability, however, the effect of time delay spread was not relatively remarkable, compared with the dominant effect of time delay.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권2호
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• pp.43-47
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• 2002

Stability conditions of time-varying discrete state delay systems are proposed. The time-varying state delay is assumed that (i) the magnitude is known to lie in a certain interval (ii) the upper bound of the rate of change is known. Under these conditions, new stability conditions are derived based on switched Lyapunov functions. Stability conditions for both fast time-varying and slowly time-varying delay are considered.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.1147-1156
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• 1993

In order to analyze lateral control in the backward maneuver of a tractor -trailer combination , a kinematic vehicle model and a human operator model with time delay were utilized for the operator/vehicle system. The analysis was carried out using the frequency domain approach. The open-loop stability of the vehicle motion was analyzed through the transfer functions. The sensitivity of the stability of the vehicle motion. to a change in the steering angle, was also analyzed. A mathematical model of the closed -loop operator/vehicle system was then formulated. The closed -loop stability of the operator /vehicle system was then analyzed. The effect of the delay time on the system was also analyzed through computer simulation.

• Architectural research
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• 제10권1호
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• pp.41-48
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• 2008

Construction projects have frequently exceeded their schedule despite reliable estimates at the start of a project. This problem was attributed to unpredictable causes at the beginning and to shortage of proper tools to accurately predict project completion date. To supplement this difficulty, project managers need a comprehensive system that can be employed to monitor the progress of an ongoing project and to evaluate potential delay for achieving the goal on time. This paper proposed a progressive-based expert system for quantitative assessments of project delay at the early stages of the execution. Furthermore, the system is used to inspect the change of the uncertainty on completion date and its magnitude. The proposed expert system is helpful for furnishing project managers a warning signal as a project is going behind schedule and for tracking the changed uncertainty at a desired confidence level. The main objectives of this paper are to offer a new system to overcome the difficulties of conventional forecasting tools and to apply a construction project into the system to illustrate its effectiveness. This paper focuses on construction phase of project development and is intended for the use by project managers.

• 한국과학교육학회지
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• 제24권2호
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• pp.408-415
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• 2004

이 연구는 인지갈등전략을 사용한 중학생들의 작용과 반작용에 관한 수업에서 인지갈등 해소 지연에 따른 학생들의 개념변화의 차이를 알아보았다. 인지갈등이 일어나고 있는 동안 학습자는 의식적 무의식적으로 인지갈등을 해소하기 위해 여러 정신 과정과 육체적인 활동이 이루어지리라 생각할 수 있다. 그러나 아직까지 이에 대한 연구는 별로 이루어진 바가 없었다. 이 연구에서는 인지갈등을 유발한 후 어느 정도의 시간이 경과한 다음 인지갈등을 해소하는 것이 개념변화에 효과적인가를 알아보기 위해 연구대상을 즉시해소 집단, 2일지연해소 집단, 7일지연해소 집단으로 나누었다. 세 집단에 대해서 작용과 반작용에 관한 문항으로 사전개념검사와 해소직전개념검사, 사후개념검사, 지연개념검사를 실시하였으며, 설문조사를 통해 지연해소 집단의 학생들이 인지갈등 해소를 지연하는 기간 동안 인지갈등 해소를 위해 어떠한 활동을 하였는지 알아보았다. 연구결과는 다음과 같다. 첫째, 즉시해소 집단이 지연해소 집단보다 개념변화 정도가 유의미하게 큰 것으로 나타났다. 즉, 즉시해소 집단이 2일지연해소 집단과 7일지연해소 집단보다 사전개념검사에서 오개념을 가졌던 학생들이 지연개념검사에서 과학적 개념으로 더 많이 바뀌었다. 둘째, 지연해소 집단의 학생들은 인지갈등 해소를 위해 동료와의 상호작용을 통한 방법을 가장 많이 사용하였다. 셋째, 지연해소 집단 내에서 인지갈등 해소를 위해 시간을 소모한 학생이 그렇지 않은 학생보다 개념변화가 유의미하게 큰 것으로 냐타났다. 위의 연구결과를 볼 때, 인지갈등전략을 사용한 중학생의 과학수업에서 인지갈등 해소를 지연시키는 것보다 불일치 상황을 인지하고 있는 상태에서 즉시 해소기키려고 하는 것이 개념변화에 더 효과적임을 알 수 있다.

• 화약ㆍ발파
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• 제23권3호
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• pp.11-18
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• 2005

MS 지발 전기뇌관을 사용하는 발파형태에 있어 파형은 거리와 주파수 정도에 따라 인접 단차 간 간섭의 정도가 상이하다. 이 간섭의 정도는 계측지점에서 발파진동의 크기에 영향을 미친다. 본 연구에서는 40ms 간격으로 분리되어 기폭되는 MS 지발 발파의 협동장약 특성을 고찰하고 MS지발 발파에서 발파진동의 협력을 최소화 할 수 있는 주파수에 따른 시차 설계 방법을 제시하였다.

• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.70-78
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• 2007

We prove that TCP Vegas globally converges to its equilibrium point in finite time assuming no feedback information delay. We analyze a continuous-time TCP Vegas model with discontinuity and high nonlinearity. Using the upper right-hand derivative and applying the comparison lemma, we cope with the discontinuous signum function in the TCP Vegas model; using a change of state variables, we deal with the high nonlinearity. Although we ignore feedback information delay in analyzing the model of TCP Vegas, the simulation results illustrate that TCP Vegas in the presence of feedback information delay shows very similar dynamic trends to TCP Vegas without feedback information delay. Consequently, dynamic properties of TCP Vegas without feedback information delay can be used to estimate those of TCP Vegas in the presence of feedback information delay.