• Journal of Advanced Navigation Technology
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• v.5 no.2
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• pp.149-157
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• 2001

A high speed data link capability is one of the critical factors in determining the performance of the spaceborne SAR system with high resolution. It is due to the strict requirement for the real-time data transmission from a series of massive raw image data of spaceborne SAR to the ground station in a limited time of mission. In this paper, based on the data link model characterized by the spaceborne small SAR system, the high rate multi-channel data link module is designed including link storage, link processor, transmitter, and wide-angle antenna. The design results are presented with the performance analysis on the data link budget as well as the multi-mode data rate in association with the SAR imaging mode of operation from high resolution to the wide swath.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.39-47
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• 2000

This paper is to propose an efficient and reliable control procedure of Base Station Controller of mobile communication system for bulk input messages which was delivered instantaneously. We divided the input messages that are processed by the base station controller of the mobile communication system into two things ; they are messages related to call connection and o&m(operation and maintenance). In addition, we analyzed the properties of the input messages and then performed computer simulation on each input message by using M/M/1/K queueing model in term of the following viewpoints : the loss probability of input messages, the average queue length, the utilization of process controller(server),the average waiting time in queue. And we compared the performance of the two input messages in the overload controlling which was caused by the congested input messages.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1091-1101
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• 2015

Cache mechanism, which has been a research subject for a significant period of time in computer science, has become realized in the form of web caching in network practice. Web caching has various advantages, such as saving of network resources and response time reduction, depends its performance on cache replacement policy, therefore, analysis and consideration of the environment in which a web cache operates is essential for designing better replacement policies. Thus, in the current web environment where is rapidly changing relative to the past, a new cache replacement policy is necessary to reflect those changes. In this paper we stipulate some characteristics of the web at present, propose a new cache replacement policy, and evaluate it.

• Annual Conference of KIPS
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• 2003.05b
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• pp.1181-1184
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• 2003

인터넷의 급속한 성장과 더불어 네트워크 관련 기술은 발달하였고 이에 따라 사용자는 시간과 공간적 제약을 벗어나 인터넷을 활용하고 있다. 급증하는 사용자와 함께 인터넷 트래픽도 급격히 증가하였고 이에 따라 국가 간, ISP 간 증설되는 회선의 비용과 관리의 비용 부담의 문제가 중요한 문제로 부각되었다. 공정한 요금의 부담을 위해서는 인터넷 사용량에 근거한 상호 과금 분담 체계를 이용해야하지만 현재까지의 시스템으로는 트래픽의 정확한 측정과 평가를 위한 과금 시스템과 과금 분담에 대한 표준화 둥이 존재하지 않는다. 따라서 본 논문에서는 이러한 불공정한 인터넷 사용환경을 개선할 수 있는 트래픽 측정 시스템에 대해서 연구하였으며 트래픽 측정 에이전트간의 역할 분담 및 에이전트가 수집하고 평가해야할 트래픽을 분류하였다. 그리고 장애가 발생하여 자신의 임무를 수행할 수 없는 에이전트를 대신하여 임무를 대행할 수 있는 임무 대체기법에 대해서도 연구하였으며 효율적인 트래픽 수집 과정을 위하여 적응형 순환 큐를 적용시켜 트래픽 수집에이전트의 효율적인 메모리 관리 방법을 제시함으로써 트래픽 측정 에이전트의 운용 효율성을 개선하였다.

• Annual Conference of KIPS
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• 2003.11a
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• pp.389-392
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• 2003

인터넷상의 생물학 자원들을 이용하는 에이전트 시스템들에는 몇 가지 특징들이 있는데, 그중 하나가 바로 사용자 에이전트와 공개 데이터베이스들을 대신하는 에이전트들간의 자원 이용과정에서 발생하는 정보를 효율적으로 중계하고 조정하는 역할을 하는 기능이 존재해야 한다는 것이다. 공개 데이터베이스 자원들을 이용하는 경우 서로 다른 데이터 양식과 용어 체계, 제공하는 정보의 양과 정보를 제공하는데 걸리는 시간 등의 차이점이 존재하며, 또한 하나의 UI 에이전트로부터 복수 개의 질의를 수행하는 경우나 복수 개의 UI 에이전트들로부터 복수 개의 질의가 이루어지는 경우, 다양한 형태와 제공 정보로 인해 발생하는 자원들의 특성이 존재하게 된다. 이를 해결하기 위해서는 자원들의 다양성에 대한 고려, 메시지 트랜잭션의 관리와 더불어 다양한 플랫폼들에서 운용이 가능한 메시지 형식을 띠고 있어야 한다. 본 논문에서는 현재 개발중인 단백질 구조예측 연구를 지원하는 APSS 시스템 내에서의 사용자 에이전트와 여러 분석 및 자원 에이전트들 간의 효율적인 메시지 중재 및 조정기능을 갖는 CODY 에이전트를 설계하였고 이에 관하여 기술하고자 한다.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.78-83
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• 2010

On the paved track, the ballast is used as aggregate for the filling layer using the pre-packed concrete technique. The most important condition of aggregate is adhesive strength with mortar. To satisfy this condition, surface of aggregate should be cleaned by water or others. In a paved-track method to be introduced domestically, an environment-friendly dry-washing technology which will replace the water-washing method has been developed. A dry-washing method was designed to blast the crushed weight material with a diameter of 0.3~0.5mm at high pressure to peel the surface of the aggregate. The study was intended to enhance the washing efficiency of dry-blasting technology and to that end, the tests including blasting material, content of fine aggregate depending on time elapsed, content of chloride, LA abrasion rate and compressive strength were conducted to recommend the efficient washing material and the process.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1160-1165
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• 2011

This study is focused on the structural dynamic responses, i.e., vibration analysis results of the high-accuracy observation multi-axial camera, which is installed and operated for the UAV (Unmanned Aerial Vehicle) and helicopter etc. And, the authors newly suggest a modeling technology of the ball bearing applied to the camera by using three-axis spring elements. The vibration analysis results well agreed to the randum vibration test results. Also, the vibration responses characteristics of the multi-axial camera through the time history analysis of the random vibration were analyzed and evaluated. The above results can be applied to the FE-modeling of the ball bearings used for the space cameras.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.29-36
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• 2017

In this study, a numerical analysis is made of the fluid flow and heat transfer characteristics in the solar arrays of HALE (High Altitude Lond Endurance) UAV. In the stratosphere where UAV operates, high level solar radiation is induced, heat transfer decreases due to natural convection and forced convection is dominated by ambient flow. In order to predict the solar array temperature range in this environment condition, the conjugate heat transfer analysis was carried out for the solar arrays on the main wing. The investigation focused on the temperature distribution of solar array and heat transfer characteristics according to influence of solar energy, flight condition as vehicle speed, air density, temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.223-224
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• 2009

This study was performed to development 80MPa high strength concrete using local raw material of Busan and to estimate field application ability. As the result of three types of mixture, fresh and hardened properties were satisfied with target requirement properties. Hydration temperature was revealed mean 75$\sim$85$\circ$C. Additionally, in case of compressive strength, core specimen's strength is six times higher than field curing specimen by very high hydration heat.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.213-221
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• 2012

In this paper, a dynamic power management system is proposed to reduce energy consumption for multiple clients in cloud computing environments. The proposed system monitors both keyboard and mouse input from the user, available memory, and CPU usage in the virtual machine. If the system detects no keyboard and mouse input for a certain amount of time and both available memory and CPU usage reach predefined threshold value, the manager in the virtual machine orders the client to shutdown the client machine, which results in significant power save. The developed system is applied to the real university computer lab and the performance of the system is evaluated.