• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.521-531
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• 2018

This paper presents a procedure for field measurements which provides a generalized Narrowband Power Line Communications (NB-PLC) channel model for low voltage (LV) access network in order to deploy advanced metering infrastructure (AMI) within Lahore, Pakistan. The measurements of allocated sites were performed in the residential (urban and rural), industrial and commercial electricity consumers for the NB-PLC channel modeling of overhead transmission lines (TLs). On the basis of extensive field measurement results, the average attenuation profile and transfer functions are presented. The results obtained from field measurements are validated by comparing them with a proposed Simulink model. A close agreement in the measured and simulated transfer function (TF) results is observed. The proposed Simulink model is an effort to model the NB-PLC channels in an effective way, especially in South Asian countries.

• 한국의류학회지
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• 제43권4호
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• pp.592-604
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• 2019

This study examines the stealth function of sputtered fabric with an infrared thermal imaging camera in terms of the thermal and infrared (IR) transmittance characteristics. Various base fabrics were selected, infrared imaging was performed, and infrared transmittance was measured. By infrared camera experiment it was found that the sample was concealed because it had a similar color to the surroundings when the aluminum layer was directed toward the outside. In addition, a comparison of the infrared thermographic image of the untreated sample and the sputtered sample in the laboratory showed that the difference in ${\Delta}E$ value ranged from 31 to 90.4 and demonstrated effective concealment. However, concealment was not observed in the case of the 3-layer (Nylon-Al-Nylon) model when a sputtered aluminum layer existed between two nylon layers. The direction of the sputtering layer did not affect the infrared transmittance in the infrared transmittance experiment. Therefore, it seems better to interpret the concealing effect in the infrared thermographic images by using thermal transfer theory rather than infrared transmittance theory. We believe that the results of this study will be applicable to developing high performance smart clothing and military uniforms.

• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.65-70
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• 2006

Transient heat transfer caused by an impulsive heating in subcooled liquid nitrogen is investigated experimentally. This study is part of out ongoing efforts directed to a stable cryogenic cooling system lot superconducting fault current limiters (SFCL). A thin heater attached by epoxy on one surface of a GFRP plate is immersed in liquid-nitrogen bath at temperatures between 77 K and 55 K. A strong heat flux up to $150W/cm^2$ is generated lot 100 ms, and the temperature of the heater sulfate is measured as a function of time. The behavior of bubbles on the heating surface can be explained by comparing the measured temperature history for vertical and two horizontal (up and down) orientations. It is concluded that the subcooling of liquid nitrogen below 70 K is very effective in suppressing bubbles, resulting in better thermal protection and faster recovery from an impulsive heat.

• 한국방사선학회논문지
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• 제11권5호
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• pp.353-359
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• 2017

대표적인 저강도 초음파 자극 기술인 음파영동은 초음파의 물리적 진동과 온열 효과를 이용하여 약물을 인체 표피 내부로 전달시키는 기법이다. 음파영동법은 치료 약물 전달의 효율을 높일 수 있으며, 인슐린이나 지질 등 분자 크기가 비교적 큰 약물의 전달에도 효과적이라는 장점을 갖는다. 본 연구에서는 효율적인 음파영동 치료를 위하여 대면적 단일 진동소자와 치료 부위에 약물 이송 기능을 갖는 복합 구조 초음파 변환기 어셈블리를 제안하였다. 또한, 치료 부위의 온도를 상승 및 유지시킬 수 있는 변환기 어셈블리 구조를 제안하고 유효성을 평가하였다. 본 연구에서 제안된 변환기 어셈블리는 지속적으로 정량의 약물을 제공하고, 가온을 통하여 약물 전달을 보조함으로써 초음파를 이용한 음파영동 시술의 효율을 향상시킬 수 있을 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1443-1451
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• 2020

The objective of this study is to design a robust power control system for a small pressurized water reactor (PWR) to achieve stable power operations under conditions of external disturbances and internal model uncertainties. For this purpose, the multiple-input multiple-output transfer function models of the reactor core at five power levels are derived from point reactor kinetics equations and the Mann's thermodynamic model. Using the transfer function models, five local reactor power controllers are designed using an H infinity (H_∞) mixed sensitivity method to minimize the core power disturbance under various uncertainties at the five power levels, respectively. Then a multimodel approach with triangular membership functions is employed to integrate the five local controllers into a multimodel robust control system that is applicable for the entire power range. The performance of the robust power system is assessed against 10% of full power (FP) step load increase transients with coolant inlet temperature disturbances at different power levels and large-scope, rapid ramp load change transient. The simulation results show that the robust control system could maintain satisfactory control performance and good robustness of the reactor under external disturbances and internal model uncertainties, demonstrating the effective of the robust power control design.

• 한국음향학회지
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• 제30권5호
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• pp.255-264
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• 2011

3차원 공간에서 음원으로부터 사람의 귀로 음향적인 전달 과정을 표현하는 머리전달함수는 사람이 음원의 위치를 판단할 수 있는 중요한 정보를 포함하고 있으며, 이를 이용하여 실질적으로는 존재하지 않는 음원을 근사적으로 생성할 수 있다. 그러나 각 청자에 특화되지 않는 머리전달함수를 사용함으로 인해 전후 방향이나 상하 방향의 혼동이 발생하게 되어 음상정위 성능이 저하된다. 이 논문에서는 머리전달함수를 통해 생성된 입체음향을 인간의 청각 특성을 사용하여 개선하는 알고리즘을 제안한다. 머리전달함수가 적용된 사운드 신호의 전역 마스킹 값을 계산한 후, 청자에게 크게 영향을 미치는 주파수 대역만을 추출하여 이를 강조함으로서 각 방향에 해당하는 인지 특성을 부각시키는 방법을 제안하였으며, 제안된 방법의 성능을 청감테스트를 통해 증명하였다.

• International Journal of Computer Science & Network Security
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• 제23권9호
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• pp.8-16
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• 2023

In Japan, high-speed ground transportation service using linear motors at speeds of 500 km/h is scheduled to begin in 2027. To accommodate 5G services in trains, a subcarrier spacing frequency of 30 kHz will be used instead of the typical 15 kHz subcarrier spacing to mitigate Doppler effects in such high-speed transport. Furthermore, to increase the cell size of the 5G mobile system, multiple base station antennas will transmit identical downlink (DL) signals to form an expanded cell size along the train rails. In this situation, the forward and backward antenna signals are Doppler-shifted in opposite directions, respectively, so the receiver in the train may suffer from estimating the exact Channel Transfer Function (CTF) for demodulation. In a previously published paper, we proposed a channel estimator based on Delay and Doppler Profiler (DDP) in a 5G SISO (Single Input Single Output) environment and successfully implemented it in a signal processing simulation system. In this paper, we extend it to 2×2 MIMO (Multiple Input Multiple Output) with spatial multiplexing environment and confirm that the delay and DDP based channel estimator is also effective in 2×2 MIMO environment. Its simulation performance is compared with that of a conventional time-domain linear interpolation estimator. The simulation results show that in a 2×2 MIMO environment, the conventional channel estimator can barely achieve QPSK modulation at speeds below 100 km/h and has poor CNR performance versus SISO. The performance degradation of CNR against DDP SISO is only 6dB to 7dB. And even under severe channel conditions such as 500km/h and 8-path inverse Doppler shift environment, the error rate can be reduced by combining the error with LDPC to reduce the error rate and improve the performance in 2×2 MIMO. QPSK modulation scheme in 2×2 MIMO can be used under severe channel conditions such as 500 km/h and 8-path inverse Doppler shift environment.

• 대한교통학회지
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• 제26권3호
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• pp.41-51
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• 2008

본고에서는 노선별 카드자료와 정산자료를 바탕으로 시내버스 운행계통 및 운행실태를 여러 가지 통계기법을 이용하여 분석함으로서 시내버스 노선개편 이후의 시내버스 노선체계 특성을 밝히고 있다. 운행거리와 운행시간과의 관계는 운행속도에 영향을 많이 받는 것으로 나타났고, 배차간격을 10분 이내로 하기 위해서는 단위시간당 운행대수가 0.1013대/분이상이 되어야 하며, 운행시간의 경우는 오전시간대보다 오후시간대가 더 많이 소요되는 것으로 나타났다. 이용승객 규모에 따른 운행계통 비교에서는 운행거리, 배차간격, 운행시간, 운행속도 모든 부문에서 이용승객이 적은 노선의 편차가 이용승객이 많은 노선보다 크게 나타났다. 한편, 카드건수, 평균수입, 환승률간의 분석 결과, 카드건수와 평균수입의 관계는 일반노선이 선형함수 관계, 좌석 및 급행노선은 지수함수 관계로 설명될 수 있다. 또한 일반노선, 좌석 및 급행노선의 환승률 1% 증가를 카드건수로 환산하면 각각 6.3건/대/일, 4.9건/대/일의 감소에 해당하는 것으로 분석되었다. 마지막으로 흑자노선과 적자노선의 분석 결과인데, 흑자노선과 적자노선을 판별하는데 유효한 4가지 변수를 판별력의 크기순으로 나열하면 km당 운행대수, 외곽경유 유무, 지하철 경유수, 종합대학 경유수순이 된다. 향후 마을버스 환승요금제 시행 시에는 수입증가를 위하여 상기 유효변수들을 잘 고려한 시내버스 노선조정과 대중교통우선정책이 필요하며, 비용절감을 위하여 시내버스와 마을버스의 위계를 보다 명확히 한 노선운영이 필요할 것으로 판단된다.

• Archives of Reconstructive Microsurgery
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• 제9권1호
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• pp.56-61
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• 2000

Recommendable reconstructive surgery in the patient with thumb amputation through base of the first metacarpal bone is pollicization. Some patients who do not agree with harvest sound finger as a new thumb, we can consider other options as toe transplantation or osteoplastic thumb reconstruction for creating thumb. Toe transplantation to the thumb is effective procedure in the amputation of distal to metacarpal shaft, it is rarely indicated in the cases of proximal to base of the first metacarpal bone. We performed three cases of modified osteoplastic thumb reconstruction with free vascularized rib that combined with scapular free flap or radial forearm flap. The length of transplanted rib ranged from 7~11cm, the donor vessels are posterior intercostal artery and vein which anastomosed to radial artery. The grafted rib wrapped with additional free flap for creating new thumb. Result of that procedure was not much encouraging, aesthetic appearance and mobility of thumb were not so satisfactory but reconstructed thumb gave improvement of the hand function without sacrificing toe or other digit. That gave reasonable stability for powerful side pinch and three pod pinch and opposable thumb with normal carpo-metacarpal joint motion that can give much function to the thumb absent hand. In spite of those disadvantages, thumb reconstruction with rib transfer can be useful for patients who do not want to lose another part of the body for creating thumb in basal amputation of the thumb metacarpal.

• 대한전자공학회논문지SD
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• 제38권9호
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• pp.616-623
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• 2001

회절격자의 인접한 반주기 길이 사이에 음의 상관관계가 있는 반주기 길이의 랜덤 변이가 QWS-DFB 레이저의 주모드 파장 분포에 미치는 영향을 유효 굴절률 전달 매트릭스 방법으로 알아보았다. 주모드 파장 분포를 쉽게 파악할 수 있도록 주모드 파장 분포를 회절격자 반주기의 정규화된 표준편차 σΛ와 인접 반주기 랜덤 변이 사이의 상관계수 γ 의 해석적인 근사식으로 나타내었다. 이 확률 밀도 함수는 가우스 분포 함수이며, 그 표준편차는 σΛ가 커질수록 커지고 γ가 -1로 갈수록 작아진다.