• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.136-138
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• 2005

무선 브로드캐스트 환경에서는 모바일 클라이언트의 제한된 배터리와 클라이언트에서 서버로의 제한된 상향 대역폭 등의 문제로 기존의 동시성 제어 기법을 그대로 사용할 수 없다. 이런 문제를 해결하고자 많은 동시성 제어 기법들이 연구되어 왔는데, 지금까지 제안된 기법들은 편향된 데이터의 접근 패턴을 반영한 브로드캐스트 환경을 고려하지 못하고 있다. 무선 브로드캐스트 환경에서 서버는 일반적으로 모바일 클라이언트의 접근 패턴을 고려하여 편향된 접근 빈도를 갖는 데이터 아이템을 브로드캐스트 한다. 본 논문에서는 무선 브로드캐스트 환경에서 편향된 데이터 접근 패턴을 고려한 동시성 제어 기법을 제안한다. 제안하는 기법은 브로드캐스트 디스크 모델에서 전체 메이저 브로드캐스트 주기마다. 모바일 트랜잭션을 위한 제어 정보를 보내는 것이 아니라 일정한 마이너 브로드캐스트 주기마다. 제어 정보를 전송한다. 이는 접근 빈도가 놓은 데이터가 갱신된 경우 갱신된 내용을 마이너 그룹마다 반영하므로 읽기 전용 트랜잭션이 접근하는 데이터가 최신 정보임을 보장할 뿐만 아니라 갱신 트랜잭션이 최종 검증을 위해서 상향 통신 대역폭을 이용하는 횟수를 줄이고, 보다. 빠른 재실행을 통해 모바일 트랜잭션의 평균 응답시간을 줄여줄 수 있다. 또한 모바일 트랜잭션의 요청이 편향된 경우, 반복적인 트랜잭션의 중단, 재실행으로 인한 성능 저하를 개선하고자 정적 백오프 기법을 이용하여 모바일 트랜잭션 간 충돌 가능성을 줄여준다. 마지막으로 시뮬레이션을 통해 기존의 기법들에 비해 평균 접근 시간, 상향 통신 대역폭 등의 사용량이 현저히 줄어드는 것을 보임으로써 제안하는 기법의 성능을 검증한다.한 평균 access time을 최소화하는 동시에 클라이언트들의 제한된 에너지 소비를 최소화하는데 목적이 있다. 제안기법에 대한 평가는 수학적 분석을 통해 HIDAF 기법과 기존의 브로드캐스트 기법의 성능을 비교 분석한다.하였으나 사료효율은 증진시켰으며, 후자(사양, 사료)와의 상호작용은 나타나지 않았다. 이상의 결과는 거세비육돈에서 1) androgen과 estrogen은 공히 자발적인 사료섭취와 등지방 침적을 억제하고 IGF-I 분비를 증가시키며, 2) 성선스테로이드호르몬의 이 같은 성장에 미치는 효과의 일부는 IGF-I을 통해 매개될 수도 있을을 시사한다. 약 $70 {\~} 90\%$의 phenoxyethanol이 유상에 존재하였다. 또한, 미생물에 대한 항균력도 phenoxyethanol이 수상에 많이 존재할수록 증가하는 경향을 나타내었다. 따라서, 제형 내 oil tomposition을 변화시킴으로써 phenoxyethanol의 사용량을 줄일 수 있을 뿐만 아니라, 피부 투과를 감소시켜 보다 피부 자극이 적은 저자극 방부시스템 개발이 가능하리라 보여 진다. 첨가하여 제조한 curd yoghurt는 저장성과 관능적인 면에서 우수한 상품적 가치가 인정되는 새로운 기능성 신제품의 개발에 기여할 수 있을 것으로 사료되었다. 여자의 경우 0.8이상이 되어서 심혈관계 질환의 위험 범위에 속하는 수준이었다. 삼두근의 두겹 두께는 남녀 각각 $20.2\pm8.58cm,\;22.2\pm4.40mm$으로 남녀간에 유의한 차이는 없었다. 조사대상자의 식습관 상태는 전체 대상자의 $84.4\%$가 대부분

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.1
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• pp.20-27
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• 2018

In this paper, the problem of a double-parked car has been investigated and a method to solve it is studied. Double parking is very common in a public parking lot with insufficient parking space. If a double-parked car blocked the way, a person needs to push the double-parked car to move it. The problem is that moving a double-parked car with hands is very hard and dangerous, especially for the old and the weak. To solve the above mentioned problem, an automatic mover for a double-parked car is proposed and developed. The basic idea is that a double-parked car can be moved by rolling its one wheel. Two rollers are designed and manufactured, which are used to roll a wheel of a double-parked car. The developed automatic mover has two rollers, two driving wheels, and four castors. It also has several ultrasonic sensors so that it can detect obstacles in the way and prevent possible collision. It is verified through several experiments that the developed automatic mover can move a double-parked car safely and easily.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.201-207
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• 2010

Recently, about 600 cases of marine accidents occur annually in Korea. According to many studies and analyses on occurrence of marine accidents, 70~80% of marine accidents were caused by human factors. Among the human factors, navigation officers' fatigue is very important factor. Although navigation officers' fatigue serves as an important role in marine accidents, there is no method to exactly examine the degree of officers' fatigue. Accordingly, this study analyzed human factors according to types of marine accidents and extracted important five factors affecting navigation officers' fatigue through the questionnaire survey by means of literatures and 5-point scale. In addition, evaluation factors of marine accident risks caused by fatigue factors were divided and structured by using ISM. Lastly, it found out the importance of each fatigue factor drawn by AHP and decided marine accidents that were most highly caused by navigation officers' fatigue in order. At the result, weights were high as sleep time 0.385, stress 0.302, health condition 0.139, rest time 0.099, alcohol and drug 0.074 in fatigue factors, and death and injury 0.328, collision 0.308, grounding 0.195, sinking 0.094, fire accident 0.075 in evaluation factors of marine accident risks. Therefore, the control plan to lower marine accident risks should be prepared on the basis of high weight factors.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.458-465
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• 2017

The railway signaling system, which controls the course of trains and the distance between trains, is a safety critical system of the railway system because derailment or collision of trains can occur if unsafe failure is generated by any fault. The international standards of reliability, availability, maintainability, and safety of railway applications require that the safety of functions be guaranteed in safety critical systems; system reliability and safety are quantitatively estimated and demonstrated by the failure rates of devices. The development of technology has accelerated the development of railway signaling systems. Existing devices, which have already been verified as to their safety, are applied with special user requirements to reflect the new operation scenario. It is found that the reliability and safety of the devices are different depending on individual application. Therefore, the reliability of the railway signaling system must be considered while complying with the international standards; this requires that the initial failure rate be estimated and demonstrated using fault data gathered over several years. This paper shows a method for demonstrating the initial estimated failure rate and suggests a fault data collection method and an overall process that is based on probability.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.673-683
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• 2016

In recent years, frequent terror or military attack by explosion, impact, fire accidents have occurred. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. Also, nuclear power plant incident on Mar. 11 of 2011. These attacks and incidents were raised public concerns and anxiety of potential terrorist attacks on major infrastructures and structures. Therefore, the extreme loading researches were performed of prestressed concrete (PSC) member, which widely used for nuclear containment vessel and gas tank. In this paper, to evaluate the blast resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, blast tests were carried out on $1,400{\times}1,000{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by the detonation of 55 lbs ANFO explosive charge at 1.0 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included displacement, acceleration, and strains at steel, concrete, PS tendon. The results can be used as basic research references for related research areas, which include protective design and blast simulation under blast loading.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.36-41
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• 2017

As the space debris in the satellite orbit increases, the risk of collision between the currently operating satellites and the space debris is continuously increasing. Therefore, in this study, we designed one-degree-of-freedom capture device using simple deployment mechanism. The capture device consists of four link groups connected with net. To increase the reliability, each link group is connected to one driving part so that the total degree of freedom is 1. In addition, the links were stowed on each side of the satellites so that they would not affect the janitor satellite mission. Finally, to confirm the possibility of deployment in the space environment, we carried out deployment experiments in water similar to the microgravity environment, and confirmed the deployment of capture device and the possibility of capturing target satellite.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.841-850
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• 2019

The Korean government has designated speed-limit zones and speed limits in 19 ports and 3 routes to ensure safe navigation and transportation. However, the speed limit differs from port to port, no practical means of management exist. This often leads to violation of the speed limit. Additionally, ship collisions due to human error continue to occur. First, the study analyzed marine accidents that occurred at trade ports and fairways. The result of the analysis revealed the occurrence of 1344 accidents (average 269 cases per year) from 2014 to 2018. Five hundred sixty three accidents involved fishing boats, whereas, merchant vessels were involved in 508 cases. Second, the efficacy of the application of voice and message warnings to GPS plotters and electronic chart display and information system (ECDIS) was reviewed, and these were proposed as measures to inform vessel operators of the hazards of speed limit violation. Third, experts' opinions from relevant agencies and navigation system manufacturers were consulted and it was found that the proposed warning function was technically implementable. The findings are expected to help reduce human error among ship operators and establish a Korean e-navigation system.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.445-450
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• 2017

It is necessary to set a route to reflect the traffic flow for the safety of the traffic vessels. This ongoing analysis is needed to ensure that the vessels comply with a route. The purpose of this study is to discover the problems of the recommended route vicinity for Wando Harbor and suggest an improvement plan. We used a support vector machine based on the ship's trajectory to establish an efficient route center line. Since the vessels should navigate to the starboard side, with reference to the center line of the recommended route, the trajectories of the vessels were divided into two clusters. The support vector machine is being used in many fields such as pattern recognition, and it is effective for this binary classification. As a result of this study, about 79.5 % of the merchant eastbound ships in a 2.4 NM distance to Jangjuk Sudo did not observe the recommended route, so the risk of collision always existed. The contraflow traffic rate of the route of the eastbound ships decreased from 79.5 % to 30.9 % when the recommended route was reset about 300 meters to the north, from its present position. The support vector machine applied in this study is expected to be applicable, to effectively set the route center line because the ship trajectories can be classified into two clusters.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.823-830
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• 2002

Enterprise security management system proposed to properly manage heterogeneous security products is the security management infrastructure designed to avoid needless duplications of management tasks and inter-operate those security products effectively. In this paper, we propose the model of generalized security policies. It is designed to help security management build invulnerable security policies that can unify various existing management infrastructures of security policies. Its goal is not only to improve security strength and increase the management efficiency and convenience but also to make it possible to include different security management infrastructures while building security policies. In the generalization process of security policies. we first diagnose the security status of monitored networks by analyzing security goals, requirements, and security-related information that security agents collect. Next, we decide the security mechanisms and objects for security policies, and then evaluate the properness of them on the basis of security goals, requirements and a policy list. With the generalization process, it is possible to integrate heterogeneous security policies and guarantee the integrity of them by avoiding conflicts or duplications among security policies. And further, it provides convenience to manage many security products existing in large networks.