• 한국정보통신학회논문지
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• 제26권5호
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• pp.688-693
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• 2022

본 논문에서는 5G 이동통신에 활용되고 있는 주파수 대역인 3.7 GHz, 28 GHz에 대한 건물 복도에서 채널 전파 경로손실을 측정하고, CI (Close-In), FI (Floating-Intercept) 채널 모델과 비교·분석하였다. 전파 경로손실 측정을 위해 송신기 (Tx)로부터 수신기 (Rx)를 10 m 씩 이동시키며 측정을 수행하였다. 측정 결과 3.7 GHz, 28 GHz에서의 CI 모델의 PLE (Path Loss Exponent)값은 각각 1.5293, 1.7795이며, 표준편차는 각각 9.1606, 8.5803으로 분석되었다. FI 모델에서 α값은 각각 79.5269, 70.2012, β값은 각각 -0.6082, 1.2517이며, 표준편차는 각각 5.8113, 4.4810으로 분석되었다. CI 모델과 FI 모델을 통한 분석 결과에서 FI 모델의 표준편차가 CI 모델에 비해 적으므로 FI 모델이 실제 측정 결과와 유사함을 알 수 있었다.

• 한국통신학회논문지
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• 제39A권8호
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• pp.437-444
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• 2014

본 논문에서는 다중 안테나를 사용한 고속철도 환경의 경로 손실 모델을 제안 하였다. 기본적으로 고속 철도의 모든 특성들 사이에서, 경로 손실(path loss)는 고속 철도 통신 시스템의 설계에서 매우 중요하다. 현재까지 진행되어진 연구 중 대다수는 경로 손실 모델은 송신단과 수신단 사이이의 지리적 환경을 고려한 모델은 많았지만 다중 안테나를 사용한 시스템과 Doppler effect를 고려한 환경에서의 연구는 상대적으로 적게 고려되어 왔다. Doppler shift에 평균 residuals고려하는 모델링을 위해 사용되는 조정된 자유 공간 손실 모델(tuned free-space path loss model)은 최대 이동 속도가 340km인 ZhengZhou - Xi'an 간 전용선에서의 측정값을 활용하고 다중 안테나의 평균 residuals은 MRC 기법을 사용했을 시의 이론적 계산값을 다이버시티 이득을 활용한다. 통신 시스템상의 두 가지 요인으로 발생하는 평균 residuals을 추정하여 제안하는 모델은 다중 안테나를 사용한 시스템에서 수신 신호의 손실을 예측한다.

• 한방비만학회지
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• 제19권1호
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• pp.12-23
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• 2019

Objectives: Obesity is associated with a high mortality risk and impairment in health-related quality of life (HRQOL). The aim of this article is to examine the impact of weight loss on HRQOL and which questionnaires sensitively reflect weight loss effects on HRQOL. Methods: PubMed, Scopus, Research Information Sharing Service, and Korean Studies Information Service System were searched for the studies related to weight loss and HRQOL, published from 2009 to 2018. A total of 28 studies were eligible for inclusion. HRQOL results after weight loss from selected studies were classified and reported according to questionnaires. Results: Twenty-two studies reported statistically significant HRQOL improvements after weight loss and especially, all of studies with weight loss of more than 5% reported HRQOL improvements. HRQOL questionnaires were classified as generic, obesity-related and depression questionnaires. The most commonly used questionnaires were Short-Form health survey 36 (SF-36), Impact of Weight on Quality Life-Lite (IWQOL-Lite) and Beck Depression Inventory (BDI) respectively. SF-36 had a tendency to reflect physical health. IWQOL-Lite score was tended to be changed sensitively according to weight change. Depression questionnaires including BDI reported improvement of depression while mental aspects of SF-36 not changed in same studies. Conclusions: Improvements of HRQOL were noted in studies with weight loss of more than 5%. The main questionnaires for evaluating HRQOL were SF-36, IWQOL-Lite and BDI. It is suggested to use these questionnaires together for evaluating multiple aspects of impact of weight loss on HRQOL.

• 한국컴퓨터정보학회논문지
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• 제29권2호
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• pp.1-12
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• 2024

경로 손실(Path Loss)을 예측하는 것은 셀룰러 네트워크(Cellular Network)에서 기지국(Base Station) 의 설치 위치 선정 등 무선망 설계에 중요한 요인 중 하나다. 기존에는 기지국의 최적 설치 위치를 결정하기 위해 수많은 현장 테스트(Field Tests)를 통해 경로 손실 값을 측정했다. 따라서 측정에 많은 시간이 소요된다는 단점이 있었다. 이러한 문제를 해결하기 위해 본 연구에서는 머신러닝(Machine Learning, ML) 기반의 경로 손실 예측 방법을 제안한다. 특히, 경로 손실 예측 성능을 향상시키기 위해서 앙상블 학습(Ensemble Learning) 접근법을 적용하였다. 부트스트랩 데이터 세트(Bootstrap Dataset)을 활용하여 서로 다른 하이퍼파라미터(Hyperparameter) 구성을 갖는 모델들을 얻고, 이 모델들을 앙상블하여 최종 모델을 구축했다. 인터넷상에 공개된 경로 손실 데이터 세트를 활용하여 제안하는 앙상블 기반 경로 손실 예측 방법과 다양한 ML 기반 방법들의 성능을 평가 및 비교했다. 실험 결과, 제안하는 방법이 기존 방법들보다 우수한 성능을 달성하였으며, 경로 손실 값을 가장 정확하게 예측할 수 있다는 것을 입증하였다.

• Journal of applied mathematics & informatics
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• 제2권1호
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• pp.33-40
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• 1995

Entropy loss is derived by the scale parameter of Rayleigh distribution. Under this entropy loss we obtain the best invariant estimators and the Bayes estimators of the scale parameter. Also we compare MLE with the proposed estimators.

• Korean Journal of Mathematics
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• 제11권1호
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• pp.35-43
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• 2003

We study the weak convergence to Fractional Brownian motion and some examples with applications to traffic modeling. Finally, we get loss probability for queue-length distribution related to self-similar process.

• Journal of Power Electronics
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• 제18권4호
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• pp.1099-1110
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• 2018

In this paper, a loss minimization control method for interior permanent magnet synchronous motors is presented with considering self-saturation and cross saturation. According to variation of the d-axis and q-axis inductances by different values of the d-axis and q-axis components of currents, it is necessary to consider self-saturation and cross saturation in the loss minimization control method. In addition, the iron loss resistance variation due to frequency variation is considered in the condition of loss minimization. Furthermore, the loss minimization control method is compared with maximum torque per ampere (MTPA), unity power factor (UPF) and $i_d=0$ control methods. Experimental results verify the performance and proper dynamic response of the loss minimization control method with considering self-saturation and cross saturation.

• 한국멀티미디어학회논문지
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• 제20권7호
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• pp.1030-1037
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• 2017

Traffic flows of real-time multimedia services such as Internet phone and IPTV are bounded on the end-to-end delay. Packets violating their delay limits will be dropped at a router because of not useful anymore. Service providers promise the quality of their providing services in terms of SLA(Service Level Agreement), and they, especially, have to guarantee the packet loss rates listed in the SLA. This paper is about a method to guarantee the required packet loss rate of each traffic flow keeping the high network resource utilization as well. In details, it assures the required loss rate by adjusting adaptively the timestamps of packets of the flow according to the difference between the required and measured loss rates in the lossy Weighted Fair Queuing(WFQ) scheduler. The proposed method is expected to be highly applicable because of assuring the packet loss rates regardless of the fluctuations of offered traffic load in terms of quality of services and statistical characteristics.

• International Journal of Advanced Culture Technology
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• 제10권4호
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• pp.555-560
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• 2022

In this study, the insertion loss and phase delay according to the multi-layer structure radome parameters were analyzed using the boundary value solution approach, and the multi-layer structure and hexa mesh structures with low-loss electrical characteristics for the Ku-band transmission/reception frequency of 10.7 ~ 14.5 GHz were designed and manufactured. A hexa mesh was applied to minimize radio wave transmission and scattering, which lowered the transmittance refractive index according to the radio incident angle and minimized dielectric loss through high-density foam. Similar to the simulation result, the transmission loss obtained the gain in a specific receiving frequency band, and in the transmission frequency band, an excellent low loss characteristic was obtained with an insertion loss of 0.8dB or less. The results of this study can be used in radio transmission radomes of low-weight, low-cost end-system protection devices.

• Journal of the Korean Data and Information Science Society
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• 제9권2호
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• pp.211-218
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• 1998

This paper deals with the problem of obtaining some Bayes estimators of exponential reliability in a time censored sampling with incomplete information. Some Bayes estimators are proposed and studied under squared error loss and Harris loss.