• Wind and Structures
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• 제20권3호
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• pp.423-448
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• 2015

In this paper the unsteady fluid-structure interaction (FSI) problems with large structural displacement are solved by partitioned solution approaches in the arbitrary Lagrangian-Eulerian finite element framework. The incompressible Navier-Stokes equations are solved by the characteristic-based split (CBS) scheme. Both a rigid body and a geometrically nonlinear solid are considered as the structural models. The latter is solved by Newton-Raphson procedure. The equation governing the structural motion is advanced by Newmark-${\beta}$ method in time. The dynamic mesh is updated by using moving submesh approach that cooperates with the ortho-semi-torsional spring analogy method. A mass source term (MST) is introduced into the CBS scheme to satisfy geometric conservation law. Three partitioned coupling strategies are developed to take FSI into account, involving the explicit, implicit and semi-implicit schemes. The semi-implicit scheme is a mixture of the explicit and implicit coupling schemes due to the fluid projection splitting. In this scheme MST is renewed for interfacial elements. Fixed-point algorithm with Aitken's ${\Delta}^2$ method is carried out to couple different solvers within the implicit and semi-implicit schemes. Flow-induced vibrations of a bridge deck and a flexible cantilever behind an obstacle are analyzed to test the performance of the proposed methods. The overall numerical results agree well with the existing data, demonstrating the validity and applicability of the present approaches.

• 물과 미래
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• 제35권5호
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• pp.43-50
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• 2002

The Yellow River Basin located in the Northern part of China is well-known not only as the seriously limited water sources but the greatest sediment-carrying stream in the world. The observed annual average sediment concentration in this area is $37.6kg/\textrm{mm}^3$, and 3.1% of the water volume is occupied by sediments. Due to the reason, water development has been extremely limited and it has been appeared as one of the most difficult problems in reservoir development and management. The major obstacle to surface water uses is reservoir sedimentation so that it has been strongly requested to seek the method managing sediment by optimal fashion. To solve this problem, KOWACO (Korea Water Resources Corporation) has developed various methods on the optimal reservoir management schemes including sediment management for the Upper Fenhe Basin Reservoir System at the cooperation project with Chinese. Information Variable Dynamic Programming. which is one of them, was developed for the reservoir sediment management and a set of non-dominated solutions are generated to choose the best alternative in water supply and reservoir sediment objective problem.

• Tribology and Lubricants
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• 제29권2호
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• pp.111-116
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• 2013

This paper describes the adherence phenomenon, including the tribological characteristics, of a low-pressure fuel pump in a diesel engine for an excavator. Most fuel pumps of a diesel-engine excavator are of the fixed-quantity-gear type and have low pressure. However, the developed pumps develop problems in the pumping system owing to performance instability. Cavitation, which is the main obstacle to stable driving in the pump, occurs between an idle gear and the housing to produce a serious adherence problem. The present study not only examined how to suppress cavitation in a pump but also developed a simple method to improve pump performance through the early creation of a lubrication film with a phosphoric acid coating on the surface of the idle gear. The results showed that the coating successfully prevents breakage of the idle gear due to adherence.

• 한국중재학회지:중재연구
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• 제22권2호
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• pp.79-101
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• 2012

In 2010, the United Nations Commission on International Trade Law (UNCITRAL) initiated work on the settlement of disputes in international e-commerce through online dispute resolution (ODR). The basic goal is to use ODR to resolve disputes with low value but high volume in international e-commerce. The background is that consumers have no way to solve their legal problems in this area. An ODR system is intended to create a new way to enforce their rights. However, the legal situations of the countries in the e-commerce sector, particularly in consumer protection, are very diverse. Thus, no reasonable model for conflict resolution is available. Some countries consider this as public policy and want absolute protection of their consumers. Other countries want to encourage freer e-commerce trading. This diversity of consumer protection policy is an obstacle to ODR. However, sooner or later, reaching an agreement is feasible because each representative is making a reasonable effort to reach the goal.

• 한국게임학회 논문지
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• 제6권3호
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• pp.3-12
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• 2006

게임 인공지능 분야중 하나인 경로탐색은 좀더 사실적인 게임을 만들기 위한 중요한 요소이다. 경로탐색 시스템은 한정된 자원을 소비해야만 하는 제약사항 때문에 때때로 단순하게 처리되어 사실적이지 못한 경로를 생성하였다. 기존 연구에서는 정적인 지형과 장애물들을 이용하여 자연스럽게 회피하는 경로생성에 집중하였다. 하지만, 게임 공간에서는 다양한 종류의 움직이는 장애물들이 존재한다. 따라서 이러한 움직이는 장애물을 자연스럽게 회피하는 경로를 생성하는 시스템 이 필요하다. 본 논문에서는 네비게이션 메시(Navigation Mesh)로 공간을 표현하며 지형의 특성을 고려한 경로 탐색 방법을 적용하고, 움직이는 물체를 회피하기 위하여 지능적인 밀개와 끌개의 방법을 사용하여 경로 탐색을 수행한다. 제안된 시스템을 통하여 생성된 경로를 살펴보고 실제 게임에서의 활용성을 검증한다.

• 한국인터넷방송통신학회논문지
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• 제13권2호
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• pp.165-170
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• 2013

본 논문은 기능 축약화 스크립트를 이용한 로봇 시뮬레이션을 제작하는 방법을 제안한다. 일반적인 로봇 시뮬레이션 저작 도구들은 이를 사용하기 위한 전문적인 개발 언어와 이와 연동되는 API등에 대한 전문적인 지식을 요구하고 있으며, 이러한 사전지식들은 로봇 시뮬레이션을 환경을 구현하는 데 매우 큰 장애 요인이 되고 있다. 이러한 문제를 해결하기 위해서 본 논문은 시뮬레이션 환경을 구성하기위해 기능 축약화 스크립트를 설계하였으며, 축약화된 스크립트는 단순화된 서비스 명령들과 최소의 옵션들로 구성된다. 실험에서는 개발된 저작 도구를 고등학교 학생과 선생님들에게 교육하였으며, 초보자들이 본 저작도구 하루의 교육과정 이수를 통해 로봇 시뮬레이션 환경을 구성하고 시뮬레이션 환경의 로봇을 제어할 수 있음을 검증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1168-1173
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• 2007

The Seoul Subway is one of the most heavily used Subway System in the world. It provides reliable transportation services, conveys nearly 4 million Passengers across 117 subway stations with a length of 134.9 Km. Over the years the safety for the Subway has been a major concern, trains going off the track, equipment failure, careless operation, Signal failure are increasing day by day. In a Recent Public opinion 40% said the causes to above facts are Vehicle breakdown because of Operators, Old rail defect, Quality of material. 20% of the opinion said the obstacles were because of Operation, crew carelessness, negligence in signal operation. In case of any accident the crew members cannot resolve the issue on site (Aid insufficiency), because of lack of knowledge and carelessness. The main obstacles for Subway are vehicle breakdown, Electric equipment failure, Signal Equipment failure, and Crew carelessness. This paper aims to provide major problems which are needed to be solved as quickly as possible for citizen's safety for a comfortable subway system making a comfortable ride and providing better service gradually.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.2309-2318
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• 2010

It is a plan the government increases a railroad section SOC investment, and to activate railroad construction while a railroad wins the spotlight with green transportation. But an error of the demand forecast that is a base of a railroad investment evaluation follows in occurring big, there is it with an operation with an obstacle of a railroad investment. Case of the Incheon International Airport Railroad which went into operation recently, While a present transportation demand showed about 10% than a demand forecasted in a past conference, it was magnified in a social problem. A lot of research was gone on in road project about traffic demand forecast and error, a study to find out the error cause is an insufficient situation although errors of a railroad occurs big. So, this study looked for errors and causes about trip generation model and modes sharing model of railroad demand forecast but it was defined causes so that it can occur similar problems in the future. Especially it investigated causes after comparing rate of development plan for the realization and O/D size in trip generation model and after comparing rate of modes sharing of past and current and conducting a survey for airport users. In conclusion, it suggested method to reduce errors of railroad demand forecasting in the future.

• Journal of Communications and Networks
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• 제9권1호
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• pp.56-66
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• 2007

Mobile ad-hoc networks (MANETs) have attracted great research interest in recent years. Among many issues, lack of motivation for participating nodes to collaborate forms a major obstacle to the adoption of MANETs. Many contemporary collaboration enforcement techniques employ reputation mechanisms for nodes to avoid and penalize malicious participants. Reputation information is propagated among participants and updated based on complicated trust relationships to thwart false accusation of benign nodes. The aforementioned strategy suffers from low scalability and is likely to be exploited by adversaries. In this paper, we propose a novel approach to address these problems. With the proposed technique, no reputation information is propagated in the network and malicious nodes cannot cause false penalty to benign hosts. Nodes classify their one-hop neighbors through direct observation and misbehaving nodes are penalized within their localities. Data packets are dynamically rerouted to circumvent selfish nodes. As a result, overall network performance is greatly enhanced. This approach significantly simplifies the collaboration enforcement process, incurs low overhead, and is robust against various malicious behaviors. Simulation results based on different system configurations indicate that the proposed technique can significantly improve network performance with very low communication cost.

• 약학회지
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• 제53권6호
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• pp.368-376
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• 2009

DUR (Drug Utilization Review) originally referred to the evaluation of drug usage details: however DUR refers to the system used to support the services of prescribing and dispensing through linking from Health Insurance Review and Assessment (HIRA) Service in Korea. HIRA is going to begin the DUR enforcement for extending to nationwide coverage after pilot test. Objectives: The aims for this study were to evaluate and clarify the current opinions of the pharmacists for the recognition and acceptance rates before nationwide coverage concerning DUR system. Methods: A 16-question-questionnaire was developed and pilot tested. For 40 days of survey by both on-line and fax paper, it was carried out on 80 pharmacists working at community pharmacy in Goyang-si, Gyeonggi-do. Results: Most of answers were broadly positive and interested in begining the DUR system and kept in mind that the goal of DUR is safety guarantee for people. On the other hand, most of answerers worry that delay of patient waiting time and inharmonious communication with doctors in DUR processing can be a major obstacle to begin the DUR system. Conclusion: To solve several problems, the most important things are to make good reciprocal relationships between doctors and pharmacists, investigate intervention tool to shorten patient waiting time, and activate educational program of inspecting items for the pharmacists.