• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2006년도 정기학술발표대회 논문집
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• pp.268-270
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• 2006

The purpose of this paper was to explore delay avoiding measures and strategies. The paper was based on previous work of authors on finding delay causes. Firstly, the paper has discussed about delay avoidance measures prescribed by the previous work. As the previous study identified five main causes of construction delays, various measures and strategies to overcome those delay problems have been discussed in sequence in the last sections. Major delay prevention strategies are: involving stakeholders in the project decisions, outreach program, realistic time and resource estimation, try to adjust the triple constraints of time, cost and scope, ensure fair and complete disclosure of information at an early stage of the construction project, contractor, itself should inquire about patent design errors prior to submitting its bid, owner should include in its contract with the consultant an indemnity (protection) clause etc.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.606-607
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• 2015

The traffic volume on the road shows various trends reflecting regional characteristics for monthly and hourly, and economic loss affecting users varies according to the selected period for the maintenance of road pavements. Therefore, in this study, the user cost (or delay cost) for monthly and hourly on the work zone near the Maesang Bridge Section on Poseung-Gu, Pyeongtaek-si, Gyeonggi-do was calculated using the time series models and VISSIM, and based on the result, the effect of user cost reduction according to the selection of best maintenance period was examined. The analysis result showed that the month of the lowest user cost occurred due to the maintenance of target section was January (10,293,258 KRW/Day×1km) and the month of the greatest user cost occurred was November (13,337,495 KRW/Day×1km).

• 한국통신학회논문지
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• 제19권7호
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• pp.1390-1406
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• 1994

본 논문은 로컬 엑세스 컴퓨터 네트워크를 설계할 때 발생되는 문제의 하나로 네트워크의 평균 지연 시간을 고려한 최소 비용 루프 설계 문제(DMCLP-Delay constrained Minimum Cost Loop Problem)를 다룬다. 이 문지는 종단 사용자의 트래픽 요구량을 만족시키는 링의 집합을 구하는 것으로 목적 함수는 전체라인 비용을 최소화하는 것이다. 본 논문에서는 하나의 링이 서비스할 수 있는 노드의 수가 제한되어 있으며 동시에 네트워크의 평균 지연 시간이 원하는 시간이내이어야 한다는 제약 조건하에서 이 문제에 대한 2단계-휴리스틱 알고리즘을 제안한다. 이 알고리즘은 기존의 최소 비용 루프 설계(MCLP) 알고리즘에 의한 클러스터와 본 논문에서 제안한 trade-off criterion를 이용하여 유도된다. 실제 시뮬레이션의 결과, 본 논문에서 제안한 알고리즘은 수정된 기존의 MCLP 알고리즘보다 우수한 해를 제공하며 아울러 비교적 짧은 실행 시간을 갖는다.

• 전자공학회논문지SC
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• 제41권2호
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• pp.1-8
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• 2004

본 논문은 시간지연을 갖는 2차 시스템에서 시간영역의 설계사양을 만족하는 최적 강인 LQ-PID제어기 설계방법을 제안한다. 시간지연을 갖는 2차 시스템의 LQR 해를 이용한 LQ-PID제어기 파라미터는 설계사양을 만족하는 가격함수의 가중치요소 C와 R에 의해 결정되고, Q와 R의 선정은 시간영역에서의 오버슈트와 정착시간을 조절할 수 있는 설계파라미터들 선정에 의해 결정되어진다.

• 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.

• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.15-23
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• 2008

This paper considers the problem of delay-dependent guaranteed cost controller design for uncertain neutral systems with distributed delays. The system under consideration is subject to norm-bounded time-varying parametric uncertainty appearing in all the matrices of the state-space model. By constructing appropriate Lyapunov functionals and using matrix inequality techniques, a state feedback controller is designed such that the resulting closed-loop system is not only robustly stable but also guarantees an adequate level of performance for all admissible uncertainties. Furthermore, a convex optimization problem is introduced to minimize a specified cost bound. By matrix transformation techniques, the corresponding optimal guaranteed controller can be obtained by solving a linear matrix inequality. Finally, a simulation example is presented to demonstrate the effectiveness of the proposed approach.

• 전기학회논문지
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• 제61권7호
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• pp.1019-1023
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• 2012

This paper considers a model predictive control problem of discrete-time constrained systems with time-varying delay. For this problem, a delay dependent state feedback control approach is used to achieve asymptotic stabilization of systems with input constraints. Based on Lyapunov stability theory, a new stability condition is obtained via linear matrix inequality formulation to find cost monotonicity condition of the model predictive control algorithm which guarantee the closed loop stability. Finally, the proposed method is applied to a numerical example in order to show the effectiveness of our results.

• 한국항공운항학회지
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• 제30권1호
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• pp.1-11
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• 2022

The capacity of Jeju International Airport has reached its limit due to a surge in air traffic demand such as passengers and cargo and the continuous expansion of Low Cost Carriers (LCC). Despite COVID-19 that has began in November 2019, Jeju International Airport still has continuous demand in terms of passenger and cargo transportation. As a result, it is undeniable that the delay rate also unexpectedly increased as the air traffic volume at Jeju International Airport continued to increase. In this study, the correlation between Turnaround Time and delay rates of national airlines is analyzed based on past flight data at Jeju International Airport, and the cumulative delay time trend for sampled airlines is compared with Turnaround Time. Through this study, it is expected to contribute to securing aircraft operation efficiency and on-time by analyzing delays related to Turnaround Time at Jeju International Airport.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2218-2230
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• 2012

In this paper, we propose an efficient channel delay estimation method for orthogonal frequency-division multiplexing (OFDM) systems, especially over doubly-selective fading channels which are selective in both the symbol time domain and subcarrier frequency domain. For the doubly-selective fading channels in single frequency network (SFN), long and strong echoes exist and thus the conventional discrete Fourier Transform (DFT) based channel delay estimation system often fails to produce the exact channel delay profile. Based on the analysis of the discrete-time frequency response of the channel impulse response (CIR) coefficients in the DFT-based channel delay estimation system, we develop a method to effectively extract the true CIR from the aliased signals by employing a simple narrow-band low-pass filter (NB-LPF). The performance of the proposed system is verified using the COST207 TU6 SFN channel model.

• 한국통신학회논문지
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• 제34권5A호
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• pp.355-362
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• 2009

In real-time communication services, delay constraints are among the most important QoS (Quality of Service) factors. In particular, it is difficult to guarantee the delay requirement over wireless channels, since they exhibit dynamic time-varying behavior and even severe burst-errors during periods of deep fading. Channel throughput may be increased, but at the cost of the additional delays when ARQ (Automatic Repeat Request) schemes are used. For real-time communication services, it is very essential to predict data deliverability. This paper derives the delay distribution and the successful delivery probability within a given delay budget using a priori channel model and a posteriori information from the perspective of queueing theory. The Gilbert-Elliot burst-noise channel is employed as an a Priori channel model, where a two-state Markov-modulated Bernoulli process $(MMBP_2)$ is used. for a posteriori information, the channel parameters, the queue-length and the initial channel state are assumed to be given. The numerical derivation is verified and analyzed via Monte Carlo simulations. This numerical derivation is then applied to a rate control scheme for real-time video transmission, where an optimal encoding rate is determined based on the future channel capacity and the distortion of the reconstructed pictures.