• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.1
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• pp.10-18
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• 2007

In this paper, we extend the multiple time scale control framework to window-based congestion control, in particular, TCP. This is performed by interfacing TCP with a large time scale control module which adjusts the aggressiveness of bandwidth consumption behavior exhibited by TCP as a function of "large time scale" network state. i.e., conformation that exceeds the horizon of the feedback loop as determined by RTT. Performance evaluation of multiple time scale TCP is facilitated by a simulation bench-mark environment which is based on physical modeling of self-similar traffic. If source traffic is not extended exceeding, when RTT is 450ms, in self similar burst environment, performance gain of TCP-SSC is up to 45% for ${\alpha}$=1.05. However, its is acquired only 20% performance gain for ${\alpha}$=1.95 relatively. Therefore we showed that by TCP-MTS at large time scale into a rate-based feedback congestion control, we are able to improve two times performance significantly.

• The KIPS Transactions:PartB
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• v.10B no.1
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• pp.33-40
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• 2003

Data mining plays an important role in a knowledge discovery process and various algorithms of data mining can be selected for the specific purpose. Most of traditional hierachical clustering methode are suitable for processing small data sets, so they difficulties in handling large data sets because of limited resources and insufficient efficiency. In this study we propose a hybrid neural networks clustering technique, called PPC for Pre-Post Clustering that can be applied to large data sets and find unknown patterns. PPC combinds an artificial intelligence method, SOM and a statistical method, hierarchical clustering technique, and clusters data through two processes. In pre-clustering process, PPC digests large data sets using SOM. Then in post-clustering, PPC measures Similarity values according to cohesive distances which show inner features, and adjacent distances which show external distances between clusters. At last PPC clusters large data sets using the simularity values. Experiment with UCI repository data showed that PPC had better cohensive values than the other clustering techniques.

• Composites Research
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• v.31 no.5
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• pp.221-226
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• 2018

The Split Hopkinson Pressure Bar(SHPB) has been the most widely used apparatus to characterize dynamic mechanical behavior of materials at high strain rates between $100s^{-1}$ and $10,000s^{-1}$. The SHPB test is based on the wave propagation theory which was developed to give the stress, strain and strain rate in the specimen using the strains measured in the incident and transmission bars. In this study, the SHPB was directly designed and fabricated for the dynamic mechanical properties of fiber reinforced plastic (FRP) composites. In addition, this apparatus was verified for the validity by comparing the strain data obtained through the high speed camera and Digital Image Correlation(DIC) during the high strain rate compression test of the self-reinforced polypropylene composite (SRPP) specimen.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.337-348
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• 2011

We examined temporal variations in and relationships among groundwater level, groundwater temperature, and electric conductivity, and estimated groundwater recharge at Jeju Island. The time lag and regulation time of groundwater level data revealed that monitoring well in Ansung (JM-AS) has the highest auto-correlation. The cross-correlations for electric conductivity-water level, precipitation-water level, and air temperature-water temperature revealed that monitoring well in Seogwi-2 (JR-SG2) (electric conductivity-water level), monitoring well in Hamo (JD-HM) (precipitation-water level), and monitoring well in Wonjongjang-2 (JT-WJJ2) (air temperature-water temperature) had the highest cross-correlations. The average groundwater recharge ratio was 39.61%, and the average groundwater recharge amount was 1,153,490,407 $m^3/yr$, which is consistent with the results of previous studies.

• Journal of Digital Convergence
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• v.18 no.8
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• pp.271-279
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• 2020

Simulation practice training is used in nursing education as an education method to improve the adaptability to the clinical field, but responds to unpredictable situations and negatively affects practice satisfaction. This study applied a team-based learning utilizing a pre-briefing inequality controls ago to investigate the effect of self-efficacy, simulation practice satisfaction and clinical performance of the nursing college in the simulation based nursing education and after quasi-experimental study. Data collection in the fourth grade and P University Nursing 72 peoples, the study period is from November 15 from October 14, 2019. As a result, the experimental group that applied team-based learning using pre-briefing showed higher self-efficacy, simulation practice satisfaction, and clinical performance than the control group. Therefore, applying team-based learning to the pre-briefing process can be an important learning strategy for simulation practice training, and suggests a follow-up study to confirm the effectiveness by standardizing the pre-briefing step later.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.162-166
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• 2012

V-I characteristics of Fe(100)/MgO(100)/Cu-phthalocyanine (CuPc)/Co hybrid magnetic tunnel junctions were investigated at different temperatures. Fe(100) and Co ferromagnetic layers were separated by an organic-inorganic hybrid barrier consisting of different thickness of CuPc thin film grown on a 2 nm thick epitaxial MgO(100) layer. As the CuPc thickness increases from 0 to 10 nm, a bistable switching behavior due to strong charging effects was observed, while a very large magenetoresistance was shown at 77 K for the junctions without the CuPc barrier. This switching behavior decreases with the increase in temperature, and finally disappears beyond 240 K. In this work, high-potential future applications of the MgO(100)/CuPc bilayer were discussed for hybrid spintronic devices as well as polymer random access memories (PoRAMs).

• Science of Emotion and Sensibility
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• v.22 no.1
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• pp.35-44
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• 2019

Individuals with problematic hypersexual behavior (PHB) evince the inability to control sexual impulses and arousal. Previous studies have identified that these characteristics are related to structural and functional changes in the brain region responsible for inhibitory functions. However, very little research has been conducted on the functional connectivity of these brain areas during the resting state in individuals with PHB. Therefore, this study used functional magnetic resonance imaging devices with the intention of identifying the deficit of the functional connectivity in the executive control network in individuals with PHB during the resting state. Magnetic resonance imaging data were obtained for 16 individuals with PHB and 19 normal controls with similar demographic characteristics. The areas related to the executive control network (LECN, RECN) were selected as the region of interest, and the correlation coefficient with time series signals between these areas was measured to identify the functional connectivity. Between groups analysis was also used. The results revealed a significant difference in the strength of the functional connectivity of the executive control network between the two groups. In other words, decreased functional connectivity was found between the superior/middle frontal gyrus and the caudate, and between the superior/middle frontal gyrus and the superior parietal gyrus/angular gyrus in individuals with PHB. In addition, these functional Connectivities related to the severity of hypersexual behavior. The findings of this study suggest that the inability to control sexual impulses and arousal in individuals with PHB might be related to the reduced functional connectivity of executive control circuits.

• Korea Information Processing Society Review
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• v.18 no.2
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• pp.59-72
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• 2011

조직의 경쟁력 확보차원에서 공공부문에 도입한 유연근무제가 제도시행 2년차에 접어들었다. 근로자들에게 일하는 시간과 장소에 있어서 유연성을 제공하게 되어 일-가족 양립이라는 현실적인 문제가 해결되었다. 그 결과 근로자의 직무만족과 사기진작으로 이어지면서 생산성 향상에 많은 기여를 하고 있는 것으로 나타났다. 유연근무제도 도입 첫 해인 2010년도 중앙 및 지방자치단체 운영현황을 분석한 결과 근무유형별로는 시차 출퇴근제가 90.5%로 가장 높은 비중을 차지하였고, 신청사유별로는 여가 자기계발, 출퇴근 편의, 효율적 업무수행, 임신 육아 순이 20%내외로 고루 분포되었다. 남녀의 비율별로는 남성이 63.3%, 여성이 36.4%로 전체공무원 남녀비율과 유사한 것으로 나타났다. 제도시행 초기인 점을 고려하여 설문을 통하여 운영현황을 점검하고 그 결과를 바탕으로 법령 제도상 문제점과 공직문화 내부 장애요인을 도출한 후 SWOT chart 분석기법을 통해 향후 활성화 방안 및 추진계획을 제시하였다. 특히, IT기술의 발달로 인한 시간과 장소에 얽매이지 않고 언제 어디서나 일할 수 있는 선진화된 근무방식인 스마트워크의 확충 필요성과 활성화 방안에 대한 구체적인 추진계획도 제시하였다.

• Proceedings of the Korean Society for Quality Management Conference
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• 2009.10a
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• pp.182-185
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• 2009

특정분야의 기술에 대한 중요도를 평가할 경우 일반적으로 해당 분야 기술의 전문가들의 의견을 델파이 방법을 이용하여 수렴하고 AHP 분석을 통해 기술의 우선순위를 결정하곤 한다. 그러나 전문가들의 직관적 판단에 의존하는 델파이 기법과 AHP 분석은 전문가 집단을 어떻게 선정하느냐에 따라 다른 결과를 초래하거나 항상 최적의 대안을 제시한다는 보장을 하지 못하므로 이에 대한 보완이 필요하다. 본 연구는 해당 기술 분야의 객관적인 자료인 특허 문서를 분석하여 델파이를 통해 도출된 전문가들의 기술 평가 결과의 타당성을 확인하도록 특허맵 분석을 활용할 것과 많은 대상 기술과 다양한 기술 평가 기준을 한꺼번에 고려하여 기술간 우선순위, 기술간 유사성, 기술군간 관련성을 쉽게 확인할 수 있는 SOM 신경망 분석을 활용할 것을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1746-1755
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• 2001

본 논문에서는 인터넷 트래픽의 자기 유사성 특성을 이용한 큐 관리 기법을 제안한다. 제안 기법은 LRD 프로세스의 특성을 이용하여 큰 타임 스케일에서 다음 혼잡 검출 주기 동안 평균 트래픽 입력율을 예측하고 이를 통해 혼잡 발생 여부를 미리 검출한다. 혼잡 검출시 입력 패킷을 확률적으로 폐기함으로써 망 내부에서 혼잡 발생을 사전에 방지한다. 제안 기법은 종단 시스템의 혼잡 제어 기법이나 각 플로우의 통신 환경에 무관하게 라우터의 평균 큐 길이와 큐 길이 변이를 작게 유지할 수 있으므로 지연과 지연 변이에 민감한 멀티미디어 서비스 제어에 적합하다. 또한 제안 기법은 입력율 예측을 통해 혼잡을 사전에 검출하기 때문에 종단간 혼잡 제어 기법을 사용하지 않는 플로우들에 의해 발생된 패킷들이 망 자원을 불평등하게 많이 사용하는 현상을 방지한다. 제안 기법은 각 플로우별 상태 정보를 관리하지 않으므로 확장성이 뛰어나며 이로 인해 소수의 PHB에 따라 각 홉별로 차등화된 서비스를 제공하는 Diffserv 구조에 적합하다. 또한 제안 기법은 기존 인터넷 구조에 변화를 주지 않고 라우터의 소프트웨어 업그레이드만으로 서비스가 가능하며, 필요한 버퍼의 양도 크지 않다는 장점을 가진다.