• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.161-165
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• 2015

The delay in construction is the challenge often faced in the course of executing construction projects. To the government projects, the delays become very serious. This problem directly affects the lives, social welfare of the people, and the other negative social impacts. However, the government projects have not been much interest. The questionnaire surveys in Vietnam were conducted to determine the causes of the delay and to find solutions for dealing with the delay. The average index was used to rank the delay factors and the solutions. This study identified the 5 most highly ranked delay factors and the 8 best solutions from a list of 31 delay factors and 19 solutions for the delay. The five most highly ranked delay factors were: information delays and lack of information exchange between the parties; incompetent owner; incompetent supervision consultant; incompetent contractor; and difficulties in financing project by owner. The findings of the study can help the parties involved the government construction projects and practitioners to give appropriate strategies for countering the delay in their projects.

• 한국통신학회논문지
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• 제35권6A호
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• pp.577-584
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• 2010

본 논문에서는 열악한 무선채널 환경에서 시스템 처리량을 개선시킬 수 있는 협력통신용 MAC 프로토콜을 제안하고, 컴퓨터 모의실험을 통해서 성능평가를 수행하였다. 성능평가 척도로는 시스템 처리량과 평균지연시간을 사용하였으며, 성능평가 결과를 통해서 본 논문에서 제안한 기법이 기존 rDCF 기법과 비교할 때 시스템 처리량 측면에서 24% 정도 증가함을 확인할 수 있었다. 한편 평균지연시간 측면에서는 본 논문에서 제안한 기법이 단말기 수가 상대적으로 작을 경우에는 우수하지만, 단말기 수가 상대적으로 클 경우에는 미세하지만 열악한 것을 알 수 있었다. 그 이유는 단말기 수가 상대적으로 클 경우에는 채널경쟁에 의해 시스템 성능이 좌우되며, 본 논문에서 제안한 기법의 경우는 각 노드에서 수행하는 재전송 절차 때문에 CRTS 프레임을 전송한 후 설정하는 재전송 타이머의 설정시간이 기존 방식보다 큼에 기인한다. 그러나 버퍼 내 큐잉지연시간까지 고려하면 전체적인 시스템 지연시간은 rDCF 기법에 비해 감소할 것으로 예상된다.

• 한국ITS학회 논문지
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• 제11권4호
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• pp.1-9
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• 2012

이 연구는 회전교차로의 운영효과를 다루고 있다. 연구의 목적은 보행신호 운영에 따른 회전교차로의 운영효과를 분석하는데 있다. 이를 위해 교통시뮬레이션 프로그램인 VISSIM을 사용하였다. 이 연구에서는 보행신호 운영(7개), 교차로 유형(2개), 보행교통량(8개) 및 진입교통량(15개)에 따른 1,680개의 시나리오를 분석하였다. 주요 분석 결과는 다음과 같다. 첫째, 4지 1차로 회전교차로는 유형 2, 4지 2차로 회전교차로는 유형 6이 다른 유형에 비해 운영효과가 좋은 것으로 평가되었다. 둘째, 보행신호 운영의 평균 지체가 비신호 횡단보도에 비해 낮은 것으로 분석되었다. 마지막으로, 4지 1차로는 표준 횡단보도가 2단 횡단보도에 비해 평균지체가 8.18% 감소하였다. 반면, 4지 2차로는 2단 횡단보도가 표준 횡단보도에 비해 36.53% 감소 효과가 있는 것으로 평가되었다.

• International Journal of Control, Automation, and Systems
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• 제5권5호
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• pp.492-500
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• 2007

This paper focuses on the problem of guaranteed cost control for a class of uncertain linear delay systems with actuator failures. When actuators suffer "serious failure" the never failed actuators can not stabilize the system, based on switching strategy of average dwell time method, under the condition that activation time ratio between the system without actuator failure and the system with actuator failures is not less than a specified constant, a sufficient condition for exponential stability and weighted guaranteed cost performance are developed in terms of linear matrix inequalities (LMIs). Finally, as an example, a river pollution control problem illustrates the effectiveness of the proposed approach.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.70-73
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• 1998

This paper present a new priority control mechanism which is to balance the cell loss rate by measuring, in real time, the number of discarded cells in the queuing system with a different loss priority for each class of service such that each class of service meets its cell loss rate requirements. And, to reduce the delay rates we modified existing cell scheduling scheme. Throughout the computer simulation, the existing methods and proposed scheme is compared with respect to cell loss rate and average delay time. In the result of simulation, the proposed scheme have more improved performance than the other schemes with respect to cell loss rate and average delay time.

• 한국통신학회논문지
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• 제21권10호
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• pp.2620-2633
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• 1996

In this paper, a new high-speed local area network using a dual mode switching access (DMSA) protocol implemented on a dual unidirectional bus is described. By utilizing the implicit positionalordering of stations on a unidirectional bus, the proposed system switches between random access mode and the token access model withoug unnecessary delay. Therefore, unlike other hybrid systems such as Buzz-net and Z-net, DMSA does not show a rapid degradation in performance as the load increases. We obtain the average channel utilization and the average access delay by using a simplified analytic model. The numerical results obtained via analysis are compared to the simulation resuls for a partial validation of the approximate model. The performance characteristics of DMSA are superior delay-throughput characteristics at light and medium loads, compared to compared to other LAN systems, and the capability of providing a single active station with full capabity of the channel.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2002년도 제41회 학술발표회논문집
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• pp.143-159
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• 2002

The performance of two single-barrier three-phase actuated control systems at diamond interchanges was evaluated for various traffic conditions. To emulate the actuated signal control, hardware-in-the-loop system combined with CORSIM simulation program was used. Two performance measures, average delay and total stops, were used for the evaluation process. Results showed that the two three-phase systems gave similar performance in terms of average delay, but not stops. The delay performance of each phasing system was generally dependent on the traffic pattern and ramp spacing. The total stops decreased as the spacing increased, and it was the most sensitive variable that can differentiate between the two three-phase systems. It was also shown that the hardware-in-the-loop control could provide a good method to overcome the limitations of current simulation technology.

• 한국ITS학회 논문지
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• 제17권5호
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• pp.29-38
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• 2018

본 연구에서는 버스사고 발생 시 교통카드자료를 이용한 운행지연비용을 추정하는 방법을 제안하였다. 12개 버스회사를 대상으로 설문조사를 통하여 사고 시 평균 운행지연시간을 조사하였고, 실제 교통사고자료와 교통카드자료를 기반으로 운행지연비용을 추정하였다. 조사결과 버스사고시 운행지연으로 평균 45분의 손실시간이 발생하는 것으로 파악되었다. 교통카드자료 분석결과 사고가 발생한 노선의 재차인원의 총 합은 659명으로 추정되었고, 이에 따른 손실 시간은 총 494.25시간으로 계산되었다. 본 방법론으로 추정된 운행지연 비용은 약 186.9천원/건이며, 이는 사회적기관비용의 6.37%에 해당하는 값으로 나타나 운행지연비용이 도로교통사고 비용에 유의한 영항을 미치는 것으로 평가되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.185-201
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• 2023

Grant-free random access (GFRA) can reduce the access delay and signaling cost, and satisfy the short transmission packet and strict delay constraints requirement in internet of things (IoT). IoT is a major trend in the future, which is characterized by the variety of applications and devices. However, most existing studies on GFRA only consider a single type of device and omit the effect of access delay. In this paper, we study GFRA in multicell massive multipleinput multiple-output (MIMO) systems where different types of devices with various configurations and requirements co-exist. By introducing the backoff mechanism, each device is randomly activated according to the backoff parameter, and active devices randomly select an orthogonal pilot sequence from a predefined pilot pool. An analytical approximation of the average spectral efficiency for each type of device is derived. Based on it, we obtain the optimal backoff parameter for each type of devices under their delay constraints. It is found that the optimal backoff parameters are closely related to the device number and delay constraint. In general, devices that have larger quantity should have more backoff time before they are allowed to access. However, as the delay constraint become stricter, the required backoff time reduces gradually, and the device with larger quantity may have less backoff time than that with smaller quantity when its delay constraint is extremely strict. When the pilot length is short, the effect of delay constraints mentioned above works more obviously.

• 전기학회논문지P
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• 제64권4호
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• pp.321-326
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• 2015

Smart metering is one of the most implementable internet-of-thing service. In order to implement the smart metering, a wireless communication network should be newly designed and evaluated so as to satisfy quality-of-service of smart metering. In this paper, we consider a wireless network for the smart metering implemented with multi-purpose wireless chips and channel coding-functioned micro controllers. Especially, channel coding is newly adopted to improve successful frame transmission probability. Based on the successful frame transmission probability, average transmission delay and delay violation probability are analyzed. Using the analytical results, service coverage expansion is evaluated. Through the delay analysis, service feasibility can be verified. According to our results, channel coding needs not to be utilized to improve the delay performance if the smart metering service coverage is several tens of meters. However, if more coverage is required, chanel coding adoption definitely reduces the delay time and improve the service feasibility.