• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.161-165
• /
• 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.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6A
• /
• pp.577-584
• /
• 2010

In this paper, a cooperative MAC protocol that is reliable over bad wireless channel environments and thus can enhance the system performance much more is proposed. Its performance is evaluated with the computer simulation. The system throughput and average waiting delay are used as performance measures. According to numerical results, the proposed MAC protocol provides better system throughput by 24% than the traditional rDCF scheme. From the average waiting delay point of view, when the number of terminals is small, the proposed MAC protocol has the better performance in an average view-point than the rDCF scheme. However, when the number of terminals is large, the proposed MAC protocol provides a little worse performance than the rDCF scheme. That is because, when the number of terminals is large, the dominant factor affecting the system performance is channel contention procedure, which results in lots of collisions. However, if the queuing delays in the waiting buffers are included for calculating the average waiting delay, then the total system delay will be smaller than the rDCF scheme.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.4
• /
• pp.1-9
• /
• 2012

This study deals with the operation effectiveness of roundabout. The objective of this study was to analyze the operational effectiveness of roundabout based on the operation of pedestrian signal. For pursuing the above, VISSIM was as a traffic simulation program. this study gives particular attention to analyzing the 1,680 scenarios by operation of Pedestrian Signal(7 cases), roundabout type(2 cases), pedestrian volume(8 cases) and entering volume(15 cases). The main results analyzed are as follows. First, the operational effectiveness analyzed by 2 type of 4-legged 1-lane roundabout and 6 type of 4-legged 2-lane were evaluated to be better than that by the others type. Second, the average delay time analyzed by operation of pedestrian signal were evaluated to be less than that by unsignalized pedestrian crossing. Finally, the average delay time analyzed by pedestrian crossing were decreased 8.18% than that by staggered pedestrian crossing in 4-legged 1-lane. However, the average delay time analyzed by staggered pedestrian crossing were evaluated to be decreased 36.53% than that by pedestrian crossing in 4-legged 2-lane.

• International Journal of Control, Automation, and Systems
• /
• v.5 no.5
• /
• pp.492-500
• /
• 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.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.70-73
• /
• 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.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.10
• /
• pp.2620-2633
• /
• 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.

• Proceedings of the KOR-KST Conference
• /
• 2002.02a
• /
• pp.143-159
• /
• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.17 no.5
• /
• pp.29-38
• /
• 2018

This study aims to propose a method for the estimation of operational delay cost using transportation card data in bus accidents. Average operational delay time from bus accidents was surveyed among 12 bus companies through an interview method. Then, the operational delay cost was estimated using actual traffic accident data and transportation card data. Results showed that average loss time per bus accident was found to be 45 minutes. In addition, total occupancy of 659 was estimated for the accidents investigated using transportation card data, resulting a total loss time of 494.25 hours. An estimated operational delay cost was 186.9 thousand won per accident, which was 6.37% of social agency cost. The magnitude of this number implied that operational delay cost may have a significant impact on traffic accident cost if included.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.17 no.1
• /
• pp.185-201
• /
• 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.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.64 no.4
• /
• pp.321-326
• /
• 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.