• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.107-120
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• 1987

This study is directed for the evolution of the rational approaches to the systematic evaluation of the load carrying capacity of bridges based on the practical and second moment reliability methods. A new approach for the evaluation of load carrying capacity of exsisting bridges is proposed in this study. The key idea behind this approach is in the fact that the load carrying capacity of an existing bridges under extreme traffic truck loadings may be measured by evaluating and classifying the reliability state of the bridge in terms of reliability index(${\beta}$). The rating formulas developed in this study are applied for the evaluation of load carrying capacity of the several actual deteriorated bridges inspected and tested for the capacity rating, and the results are compared with those calculated by using the current rating formulas. It may be concluded that the proposed rating formulas which is derived based on reliability methods, have to eventually replace the current rating formula when the basic statistical data for the resistance and load effects become available in the near future.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.483-489
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• 2007

The high availability of information security system shall be primarily studied in relation to the Next Generation Network(NGN) Information Security infrastructure, because it is very important to maintain availability at each moment as a variety of intrusions occur continuously. The high availability of the security system can be realized with the topology and configuration properly defined to fully utilize the recovery function of the security system in the thoroughly planned optimized method. The active-active high availability on the NGN information security infrastructure system in is assured by letting the failover mechanism operate upon the entire structure through the structural design and the implementation of functions. The proposed method reduces the system overload rating due to trouble packets and improves the status of connection by SNMP polling trap and the ICMP transport factor by ping packet.

• Journal of Korea Port Economic Association
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• v.32 no.2
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• pp.91-103
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• 2016

The purpose of this study is to analyze the efficiency and productivity of domestic trucking transportation companies using DEA-CCR, BCC, and Malmquist indexes. Here, we analyze the top 14 domestic trucking transportation companies, based on cargo volume. The number of freight agents, trucks, and assets are used as input variables, and cargo volumes and sales are used as output variables. The efficiency of trucking transportation companies is examined using a DEA approach, and Malmquist indexes are applied to analyze productivity. According to the DEA results, the efficiency levels of the CCR, BCC, and scales for three companies (DMU 4, 5, and 10) are 1, indicating that these companies are operated efficiently. At the same time, the Malmquist indexes show that all companies have values smaller than 1, except for the period 2012-2013, indicating that their productivity decreased. Furthermore, the TECI indexes were all larger than 1, except for the period 2012-2013, indicating that the companies are efficient. Lastly, all TCI indexes are smaller than 1, except for the period 2012-2013, indicating regressing trends.

• Journal of Korea Port Economic Association
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• v.28 no.3
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• pp.215-234
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• 2012

Since ports play a role of gateway to the sea and hinterlands, it is essential to analyse the networks of shipping and inland when evaluating the function and development of a port. The container port of Gwangyang, starting to operate its facilities in 1998, has developed itself as a hub port. Using the data of shipping schedules of Korean ports and the measurement of centrality in sociology, this study analyses the process of world-wide shipping network expansion in Gwangyang and concludes some implications including earlier development of shipping networks due to incentives to shipping companies. Although Gwangyang port also has been expanding its inland network through developing trucking, railway transport, and coastal shipping, it has weakness in inland network as in the cases of interruption in 2004, resumption in 2009 and re-interruption in 2012 at coastal shipping. In 2000s the expansion of shipping and inland networks at the newly built container ports such as Pyungtaek, Ulsan, and Gunsan has enticed the competition among Korean ports at each hinterland. Nevertheless, the operation of Gwangyang container port is considered to affect indirectly the relocation of some manufacturers including Samsung Electronics. Studies on interrelation between development of container port and geographical demography of manufacturers are needed to assess the effects of container port on regional economy.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.3
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• pp.235-240
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• 2008

In case of EU and USA, a short sea shipping and coastal shipping which are safer and environmentally better than road transportation are used widely. But a share of freight transport by a coastal transportation is extremely poor in South Korea. In this paper, we propose a Mokpo-Jeju intermodal transportation based on logistics analysis results. Firstly, we investigate a freight and passenger of a Mokpo-Jeju shipping route. And secondly, the intermodal transportations such as sea-train, sea-road, RORO ship system are investigated. Finally, we propose a coastal transportation system utilizing RORO ship system for Mokpo-Jeju shipping route and identify a technical feasibility of a coastal transportation system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.199-206
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• 1999

본 연구에서는 웹기반의 화물차량위치추적시스템의 개발과 관련된 문제를 다루고 있다. 화물위치추적 시스템이란 이동하는 화물차량으로부터 위치데이터 및 관련 정보를 수신하여 중앙관제센터에서 이 정보를 데이터베이스에 저장하여 두고 화물위치 정보를 지도 위에 표시하는 시스템으로 화주, 운송회사 등 육상물류관련 기관에서 화물위치추적, 공동수배송, 화물차량 통제 등 다양한 목적으로 사용될 수 있다. 화물차량위치추적시스템은 AVLS(Automatic Vehicle Location System)라 불리우면서 산업계에서 활용되고 있으며 위치획득 방법의 종류에 따라 다양한 유형의 AVLS모델이 등장하고 있다. 예를 들면 전통적인 GPS(Global Positioning System) 위성 수신, DGPS(Differential GPS) 기지국, PCS(Personal Communication System) Cell, 도로기반 시설에 포함되는 비콘 등의 방법에 의해 AVLS는 구현되고 있다. AVLS는 정보통신 요소 기술과 정보통신 기반 시설로 구성되는데, 정보통신 요소기술로는 위치획측의 매개체인 AVL단말기와 관제시스템 S/W. 그리고 GIS(Geographic Information System)가 있고, 정보통신 기반 시설로는 차량의 단말기와 관제시스템 사이의 데이터 중계를 담당하는 네트워크가 있다. 화물차량위치추적시스템을 구성하기 위한 구비요건으로 중계망의 안정성과 신뢰성, 획득한 위치데이터의 정확성, 관제시스템의 완성도와 AVL단말기의 사용자 인터페이스, GIS S/W개발을 위한 Map API(Application Program Interface)등을 들 수 있다. 본 연구에서는 PCS Cell 방식에 의한 위치결정방식을 채택하였는데, 이것은 PCS망을 기반으로 데이터를 주고받이며 인터넷 단말기로 확장 가능한 PCS 단말기를 사용해서 위치추적을 하는 시스템이다. 이러한 시스템을 선정하게된 배경은 단말기아 망 이용료의 가격이 저렴하여 현실적으로 트럭이 쉽게 부착할 수 있다는 장점이 있으며 나아가 인터넷 단말기를 활용하여 차량과 관제센터사이에 메시지 전송 등 부가적인 서비스가 가능하기 때문이다.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.227-234
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• 2020

One of the most important operational goals in container terminals is to maximize the quay side productivity by minimizing the turnaround times of the vessels, for which the operations of the quay cranes (QC) to load/unload containers onto/from the vessels should be conducted efficiently without delays. This paper suggests using a policy-based dispatching method for YTs (Yard Tractor) that deliver containers between QCs and the storage yard. The goal of using such a dispatching policy is to maximize the efficiency of the YT operation and accordingly to minimize the QC delays because of late arrivals of the YTs. In particular, in this paper, we modified the previously proposed policy for its application to real container terminal and verified the effect through simulation experiments using real terminal data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1523-1531
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• 2011

Multi-axle driving vehicle are favored for military use in off road operations because of their high mobility on extreme terrains and obstacles. Especially, Military Vehicle needs an ability to driving on hills of 60% angle slope. This paper presents the improvement of the ability of hill climbing for 6WD/6WS vehicle through the optimal tire force distribution method. From the driver's commands, the desired longitudinal force, the desired lateral force, and the desired yaw moment were obtained for the hill climbing of vehicle using optimal tire force distribution method. These three values were distributed to each wheel as the torque based on optimal tire force distribution method using friction circle and cost function. To verify the performance of the proposed algorithm, the simulation is executed using TruckSim software. Two vehicles, the one the proposed algorithm is implemented and the another the tire's forces are equivalently distributed, are compared. At the hill slop, the ability to driving on hills is improved by using the optimum tire force distribution method.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.171-173
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• 2016

일반적으로 대형 버스 및 트럭 등 같은 경우, 부하가 아주 크다. 또한 내리막길이나 장거리 운행 시에 잦은 제동으로 인하여 마찰을 이용한 기존 방식의 브레이크들은 브레이크 파열 및 페이드 현상 때문에 제동 안전성에 문제가 있다. 이러한 제동 부담을 분담하기 위해 현재 보조브레이크(리타더)가 필수적이며, 엔진 계통의 보조브레이크가 아닌 비접촉식 브레이크 같은 친환경 보조브레이크가 요구되고 있다. 그리고 차량 제동시 발생하는 기계에너지를 전기에너지로 회생하여 에너지효율을 향상시키려는 연구가 현재 활발히 진행되고 있다. 본 논문에서는 와전류를 이용한 전자기형 리타더에서 발생되는 전기에너지를 회수하기 위한 전압 제어 방법을 다룰 것이다. 리타더의 제동에너지를 전기에너지로 회생하기 위해 L-C 공진회로로 구성하였다. 리타더를 자여자 유도발전기(Self-Excited Induction Generator)로 모델링 하였고 이를 토대로 시뮬레이션 및 실험을 진행하였다. 자여자 유도발전기의 구동 조건에 대해서 언급하고 이를 파라미터에 따라 3-D map으로 만들었다. 또 회로 중의 FET 게이트에 전압을 인가하는 제어장치의 구동펄스에 따라 바뀌는 공진회로의 전압을 분석하였으며, 이 전압을 제어하기 위하여 PI 제어기를 이용한 알고리즘을 제안하였다. 이 전압을 3상 AC/DC컨버터를 통과한 후 DC/DC컨버터를 통하여 차량 내부의 배터리에 충전되는데 제어를 위해 3상 AC/DC에서의 전압 리플을 MA(Moving Average) 방식의 필터를 사용하여 DC/DC컨버터의 입력에 맞도록 제어하였다. 이와 같이 전자기형 리타더에서 유도되는 전압을 제어기의 제어 펄스에 따라 제어할 수 있으며 Matlab Simulink를 이용하여 리타더의 모델과 그 제어기의 타당성을 보였다. 또 실제 M-G Set 실험을 통하여 그 연관성을 확인하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.165-174
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• 2010

In this paper, a two-phase structural health monitoring system using acceleration response signatures are presented to firstly alarm the change in structural condition and to secondly detect the changed location for full-scale concrete girder bridges. Firstly, Mihocheon Bridge which is a two-span continuous concrete girder bridge is selected as the target structure. The dynamic response features of Mihocheon Bridge are extracted by forced vibration test using bowling ball. Secondly, the damage alarming occurrence and the damage localization techniques are selected to design two-phase structural health monitoring system for Mihocheon Bridge. As the damage alarming techniques, auto-regressive model using time-domain signatures, correlation coefficient of frequency response function and frequency response ratio assurance criterion are selected. As the damage localization technique, modal strain energy-based damage index method is selected. Finally, the feasibility of two-phase structural health monitoring systems is evaluated from static loading tests using a dump truck.