• Korean Journal of Construction Engineering and Management
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• v.14 no.3
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• pp.134-145
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• 2013

Road construction projects are parcelled into sub-sections which are then tendered to individual contractors for construction. The type of work and equipments used are similar for each sub-section. However, such equipment are not shared on a regular basis among the contractors and only partially performed in an informal and ad hoc manner. Consequently, road construction equipment suffer from low utilization and increased leasing costs. Lean construction and Program Management approaches stress the importance of collaboration among individual participants in a way that increases the collective cost savings of the entire project. This research attempts to apply such theories with the notion that under utilization of expensive equipment can be improved by formalizing a way to enable the sharing of equipment in large, public sponsored, multi-sectioned road construction projects. A system was developed consisting of a set of criteria and processes that enables automatic allocation of equipment to multiple sites on daily basis, in a way that minimizes equipment costs and improves their individual utility. The system was then applied in allocating three different types of equipment to an actual road construction project with four sub-sections for three months. A new metric, nDPR showed that utilization improved for all equipment and also equipment related costs were decreased by 4.45%. Results also showed that increased shared opportunities of equipment correspond to an increase in utilization and cost savings.

• Journal of Power Electronics
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• v.19 no.1
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• Korean Journal of Construction Engineering and Management
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• v.13 no.4
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• pp.100-109
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• 2012

Large road construction projects are typically partitioned into sections that are then contracted individually to contractors. Each section requires using similar heavy equipment including excavators, dump trucks and pavers, which constitute the highest cost. Normally the equipment is not shared between them, as each contractor wishes to have their equipment readily available. However, such practices result in very low utilization of these equipment. The goal of this research is to develop a programmatic resource sharing system in which contractors can share equipment depending on the changing needs of a multi-sectioned road project. This paper introduces the results of a survey performed to investigate how contractors currently manage the supply and demand of equipment and the equipment that are practical for sharing across a project. More importantly, the paper describes a set of metrics (DPR, nDPR, SDI) needed to quantify the amount of supply/demand variance occurring in each section. The metrics were used on an actual road construction project, and the results show that each section suffers from an imbalance between its monthly planned and actual utilization of equipment. The results also indicate that the sharing of the equipment can lead to potentially large savings as equipment requirements can be met within a project as to short leasing from outside vendors.

• Journal of Drive and Control
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• v.19 no.3
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• pp.47-52
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• 2022

The C-ITS (Cooperative-intelligent Transport System) is a driver assistance system that prevents car accidents and enhances traffic conditions, via sharing traffic information between vehicles and roadway infrastructures. A CLAS (changing lane assistance system) for unprotected left-turn, is a C-ITS that assists a driver with safely changing lanes. This system addresses a driver's critical gap, that enables the system to express a driver's uncertainty. A driver's critical gap is a time that can be used in a threshold, to change a lane or not. Unfortunately, a driver's critical gap is difficult to use in a CLAS directly. This paper addresses a driver's critical gap, and how it can be applied in a CLAS for an unprotected left-turn.

• Journal of the Korea Society of Computer and Information
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• v.26 no.1
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• pp.135-146
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• 2021

VMP(Variable Message Protocol) is bit-based variable message processing protocol that enables the sharing situation information in real time as a tactical datalink protocol for Korean Army. System A is currently under development and will be operated as an army system when its development is completed. In system A, the VMP processing terminal is mounted and the VMP is utilized for exchanging tactical information. System A can acquire situation information from mounted situation information acquisition system and share situation information with other system A by the VMP. In this paper, we propose a method of sharing situation information with system A and speed improvement methods of sharing situation information using VMP. As speed improvement methods of sharing situation information, this paper studied 'Removing Process of Sending VMP Observation Report', 'Adopting One-time Situation Information Send Button When Sharing A System Situation Information By VMP', 'Combination of Many VMP Messages Using Repeat Function Of Application Header'. And we conducted the experiment, the result was that the transmission speed of equipment to which the research method was applied was improved by 76.8% compared to the existing equipment.

• Journal of Power Electronics
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• v.14 no.1
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• pp.143-155
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• 2014

The stability issues of a multi-module distributed DC power system without current-sharing loop are analyzed in this study. The physical understanding of the terminal characteristics of each sub-module is focused on. All the modules are divided into two groups based on the different terminal property types, namely, impedance (Z) and admittance (Y) types. The equivalent circuits of each group are established to analyze the stability issues, and the mathematical equations of the equivalent circuits are derived. A generalized criterion for multi-module distributed systems is proposed based on the stability criterion in a cascade system. The proposed criterion is independent of the power flow direction.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.95-103
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• 2013

Protection of the electrical and electronic equipment against surges in low voltage AC power distribution systems is based on wide applications of surge protective devices(SPDs). Cascade application of SPDs located at the service entrance of a building and near sensitive equipment is intended to ensure the optimal voltage protection level and energy sharing among cascade SPDs. In this paper, when surges impinge at the service entrance of the building of interest, the protection characteristics of two-stage cascade SPD systems were investigated. The influence of the distance between the upstream and downstream SPDs on the voltage protection level and energy sharing of the two-stage cascade SPD systems were analyzed experimentally. It was found that the energy sharing of two-stage cascade SPD systems strongly depends on the distance between the two SPDs and the component of SPD. As the distance between the two SPDs increases, the energy absorbed by the upstream SPD increases while the energy absorbed by the downstream SPD decreases. Consequently, it is desirable to select the upstream and downstream SPDs having the proper energy capability with due consideration of the distance between the two SPDs.

• Journal of the Korea Safety Management & Science
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• v.19 no.1
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• pp.181-189
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• 2017

The systematic management of technology infrastructure increasingly becomes critical as it represents the driving power for creating competitive advantage of nations and enterprises. In this sense, public facility and equipment, which is one major asset of technology infrastructure, should be managed effectively, systematically and efficiently to increase its overall equipment effectiveness. However, the manual and off-line communication was the unique way to communicate between the suppliers who provide facilities in the public sector and the customers who utilize the facilities in the industrial sector. This communication way caused invisibility of available usage time and increase of idle time, thereby decreasing the equipment effectiveness. This paper presents an web-based scheduling system that enables real-time collaboration and information sharing for increasing the equipment effectiveness. The designed system performs scheduling, facility management, order management and customer relationship management in an on-line platform, and carries out the processing and storing of relevant information in an integrated database. The paper includes a development approach to identify business process models and standardized system models by using object-modeling technique. The deliverable of the present work will contribute to increasing the equipment effectiveness by enhancing visibility, transparency and predictability by means of the integration with a legacy Enterprise Resource Planning.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.153-158
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• 2005

Recently, as the feasibility study shows that trans-Korea railway and trans-continental railway are advantageous, interest in high-speed railway system is increasing. Because railway vehicle is environment-friendly and safe compared with airplane and ship, its market-sharing increases gradually. KHST(Korean High Speed Train) has been developed by KRRI (Korea Railroad Research Institute) for last 6 years to satisfy the need. An electric railway system is composed of high-tech subsystems, among which main electric equipment such as transformers and converter are critical components determining the performance of rolling stock. We developed a measurement system for on-line test and evaluation of performances of KHST. The measurement system is composed of software part and hardware part. Perfect interface between multi-users is possible. A now method to measure temperature was applied to the measurement system. By using the system, fault diagnosis and performance evaluation of electric equipment in Korean High Speed Train was conducted during test running.

• Journal of Digital Convergence
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• v.6 no.4
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• pp.35-44
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• 2008

The development of IT has contributed a lot to enhancing administrative efficiency. In particular, it enabled administrative agencies to be able to upgrade the effects and efficiency of public services by saving unnecessary time, labor, and equipment that might surely occur in delivering routine services in repetition. As the concept of governance and knowledge-based administration assumes a pivotal value in the 21 century administrative innovation, sharing information among agencies is a key to building effective governance system. However, current extent of sharing information in public agencies is below the level of expectation and thus the need exists for the steps to making information shared more widely and effectively among public agencies. This paper gives a snap shot on the extant status of information sharing among public agencies and seeks ways to facilitate it from the perspective of electrical government.