• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.332-337
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• 2001

The objective of research is to clarify the interaction between dislocations and precipitates during high temperature creep deformation behaviors of high Mn austenitic steels. After measuring the internal stress in minimum creep rate at 873K, a transmission electron microscope (TEM) observation was performed to investigate the interaction between dislocations and precipitates during high temperature creep deformation. The band width of effective stress and internal stress increased when the nitride precipitates distribute more densely. Fine nitrides disturbed the dislocation movement with pinning the dislocations and perfect dislocations were separated into Shockley partial dislocations by fine nitrides. Coarse nitrides disturbed the dislocation movement with climb mechanism.

• Journal of Information Technology Applications and Management
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• 제14권3호
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• pp.169-178
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• 2007

The next generation mobile multimedia network is expected to provide higher-rate multimedia communication services to versatile mobile terminals moving in even higher speed. For achieving more efficient reusability of scarce radio resources and thereby accommodating more user population in this network, the smaller cell such as micro or pico cell structure is used. More efficient and faster hand-over schemes are necessary to prevent the degradation of QoS of multimedia services caused by hand-over processing delay and packet loss during frequent hand-over. This paper proposes a faster and more effective hand-over scheme for high-rate multimedia services in the future mobile multimedia networks. by utilizing the GPS information on the position of the mobile terminal and its estimated moving directions. The simulation results show that our proposed method provides a better performance than the conventional method.

• 한국생산제조학회지
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• 제21권1호
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• pp.156-160
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• 2012

Recently WCDMA signal transmission technology by large output microwave antenna have showed reduction of human resources and operating expense. But the existing antenna brackets cost is very expensive also its structure and functions are complicated. Unit brackets, suspending some sensors, subjected to acceleration loads, often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using tests or analysis techniques. The objective of this study is to develop the component test specifications, which are applicable to predict fatigue life at initial product design step, for unit brackets using vibration fatigue technique. So its application is limited to installation and management. In this project, we studied about more convenient bracket for microwave antennas through improvement on the existing antenna bracket's shortcoming and could develop an improved universal antenna bracket system for simple installation and application.

• ETRI Journal
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• 제26권1호
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• pp.48-52
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• 2004

In this letter, we consider a new packet scheduling algorithm for an orthogonal frequency division multiplexing access/frequency division duplex (OFDMA/FDD)-based system, e.g., mobile broadband wireless access or high-speed portable internet systems, in which the radio resources of both time and frequency slots are dynamically shared by all users under a proper scheduling policy. Our design objective is to increase the number of non-realtime service (e.g., WWW) users that can be supported in the system, especially when the minimum bit rate requirement is imposed on them. The simulation results show that our proposed algorithm can provide a significant improvement in the average outage probability performance for the NRT service, i.e., significantly increasing the number of NRT users without much compromising of the cell throughput.

• 디지털콘텐츠학회 논문지
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• 제8권4호
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• pp.425-430
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• 2007

본 논문에서는 주파수 자원의 고갈로 인하여 차세대 무선 정보통신으로 사용의 가능성이 예상되는 가시광 소자를 조명, 신호기, 전광표시, 표시 등에 이용하여, 발광효율의 가시 광 반도체가 조명이나 표시에 이용되어지는 경향이 있고 거기다 고속으로 점멸 가능한 능력을 갖는 것이나 이을 이용한 가시광 통신의 무선 통신에의 응용과 표준화 기술에 대하여 알아보고자한다.

• Journal of the Optical Society of Korea
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• 제8권4호
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• pp.188-191
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• 2004

A new laser Doppler velocimeter employing a $CO_2$ laser has been developed by using its photoacoustic effect. A change in the pressure of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, is employed to detect the Doppler frequency shift. We found that a Doppler frequency shift as small as 50 kHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

• 한국산업정보학회논문지
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• 제11권2호
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• pp.1-8
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• 2006

본 논문은 이동망에서 위치등록 방식에 따른 성능평가에 관한 것이다. 먼저 거리기반 위치등록 방식을 제안하고, 이를 이동망 모델에 적용하여 성능을 평가하였다. 제안한 방식과 기존의 지역기반 위치등록 방식과의 성능을 비교, 평가한 결과, 거리기반 위치등록 방식은 지역기반 위치등록 방식과 위치 등록에 따른 부하는 대동소이하나 주어진 지역내에서 모든 셀들이 고르게 분포하여 주파수 자원이 효율적으로 사용됨을 알 수 있다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2012년도 추계학술발표대회
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• pp.712-714
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• 2012

D2D(Device-to-Device) 통신은 이동통신망을 기반으로 동작할 경우 이동통신망의 자원을 재사용함으로써 주파수 자원사용의 효율성을 높일 수 있다. 그러나 D2D 통신 단말(DUE; D2D user equipment)이 이동통신망의 자원을 재사용하는 경우 동일자원을 사용하는 이동통신개체와 DUE 간 및 D2D 통신 쌍 간에 신호 간섭이 발생할 수 있어 이를 고려한 자원할당기법에 대한 연구가 필요하다. 본 논문에서는 다수의 DUE가 이동통신망의 상향링크 자원을 다중으로 재사용할 때 이동통신개체 및 DUE가 달성가능 한 주파수 효율을 고려하여 DUE에게 자원을 할당함으로써 셀 수율을 향상시킬 수 있는 자원할당 기법을 제안한다.

• 전자통신동향분석
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• 제34권3호
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• pp.106-113
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• 2019

Mobile traffic is one of the most important indexes of the growth of the mobile communications market, and it has a close relationship with subscribers' service usage patterns, frequency demand and supply, network management, and information communication policy. The purpose of this paper is to understand mobile data usage in Korea and to suggest the optimal steps for establishing the frequency supply and demand system by researching the traffic trends that reflect the characteristics of radio resources in the mobile communications field. To achieve this goal, attempts were made to increase the possibility of policy use by analyzing and forecasting mobile traffic trends, and to improve the accuracy of the research through the verification of the existing prediction results. The paper ends with a discussion of the necessity of a frequency management system based on data science.

• 전자통신동향분석
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• 제37권6호
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• pp.74-83
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• 2022

Shannon and Weaver's semantic communication has been actively studied in recent years as a new communication method to provide intelligent mobile services without requiring more capacity, infrastructure, and energy, even with limited radio resources. Considered a breakthrough beyond the Shannon paradigm, semantic communication aims at successfully transmitting semantic information conveyed by a source rather than accurately receiving each symbol or bit, regardless of meaning. Thus, semantic communication can lead to knowledgeable systems that significantly reduce data traffic because the transmitter only transmits the necessary information related to a specific task. This study describes essential differences between existing and semantic communication, research trends related to semantic communication principles and theory, performance metrics of semantic communication, semantic communication system framework, and future research and development issues.