• 한국통신학회논문지
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• 제37C권9호
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• pp.811-820
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• 2012

GNSS 신호는 구조가 개방되어 있을 뿐만 아니라 수신 신호 세기가 미약하여 전파교란에 취약하다. 이에 따라 전파교란에 대한 영향 분석 및 대응 기법에 대한 연구의 필요성이 증대되고 있다. 본 논문에서는 실제 전파교란 환경과 유사한 환경에서의 전파교란 영향 분석을 위하여 6가지 전술 환경에 대한 전파 전파 모델과 이동체의 수신환경을 고려한 동체 차단 모델을 설계 하였다. 전파전파 모델은 도심지역, 농촌지역, 수풀지역, 해안지역, 황무지, 눈/얼음 지역에 대해서 Two-ray 모델을 이용하여 설계 하였다. 동체 차단 모델은 안테나가 이동체에 의하여 받는 영향과 사용자가 직접 입력한 안테나 패턴을 이용하여 모델링하였다. 전파교란이 없는 정상 환경과 전파교란 환경에 대하여 이동체의 수신환경을 고려한 GNSS 신호 생성기의 출력은 상용수신기(NordNav)를 이용하여 검증 하였다. 정상 환경에서는 사용자의 항법 성능이 상용 H/W 신호 생성 시뮬레이터(STR4500)과 유사한 것을 확인하였다. 전파교란 환경에서는 이동체 위치에 따른 동체 차단 효과 및 전파교란 신호에 의한 GNSS 신호 획득 및 추적 손실이 정확히 반영됨을 확인 하였다.

• 한국항공우주학회지
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• 제35권12호
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• pp.1095-1100
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• 2007

도심지에서는 지형지물 및 건물 등에 의한 영향으로 가시위성 확보가 어려워지게 되며, 이는 사용자 위치결정 및 정확도에 영향을 미친다. 본 논문에서는 3D GIS 수치지도를 이용하여 서울 도심의 특정 지역을 3D 모델로 생성하는 기법에 대해 기술하고, 직선-폴리곤 충돌검사 알고리즘을 적용한 도심지에서의 가시위성 분석 기법 개발 및 필드 실험을 통한 검증을 수행하였다. 도심의 3D 모델을 이용하여 GPS/갈릴레오 단독 수신과 동시 수신의 경우에 대한 가시성을 DOP (Dilution of Precision)관점에서 분석하였다

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.488-499
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• 2016

We present a design and optical simulation of a cost-effective hybrid daylighting/LED system composed of mixing sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting. In this approach, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The proposed sunlight collector consists of a Fresnel lens array. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. The visible rays passing through the beam splitters are coupled to a stepped thickness waveguide (STW) by tilted mirrors and confined by total internal reflection (TIR). LEDs are integrated at the end of the STW to improve the lighting quality. LEDs’ light and sunlight are mixed in the waveguide and they are coupled into an optical fiber bundle for indoor illumination. An optical sensor and lighting control system are used to control the LED light flow to ensure that the total output flux for indoor lighting is a fixed value when the sunlight is inadequate. The daylighting capacity was modeled and simulated with a commercial ray tracing software (Lighttools^TM). Results show that the system can achieve 63.8% optical efficiency at geometrical concentration ratio of 630. A required accuracy of sun tracking system achieved more than ±0.5^o . Therefore, our results provide an important breakthrough for the commercialization of large scale optical fiber daylighting systems that are faced with challenges related to high costs.

• 한국도로학회논문집
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• 제3권4호
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• pp.105-116
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• 2001

본 연구는 주물고사를 이용한 아스팔트 콘크리트와 주물고사의 물리적 화학적 특성을 비교 분석하는 것이다. 주물고사의 아스팔트 콘크리트 적용성을 평가하기 위하여 XRF, SEM, 제타전위를 측정하여 주물고사의 물리 화학적 특성을 알아보았다. 주물고사 아스팔트 콘크리트의 박리저항성을 향상시키기 위하여 박리방지제(소석회(Hydrated lime), 액상박리방지제)를 사용하였다. 그리고 주물고사 아스팔트 콘크리트 혼합물의 인장특성과 내구성 향상을 위하여 LDPE를 사용하였다. 또한 주물고사 아스팔트 콘크리트의 공용성을 알아보기 위하여 간접인장강도, 수분취약성시험, 동결 융해시험, 반복주행시험을 수행하였다. 시험결과 주물고사 아스팔트 콘크리트의 역학적 특성이 일반 아스팔트 콘크리트에 비해 같거나 향상되는 것으로 나타났다. 따라서 주물고사를 아스팔트 콘크리트에 재활용할 수 있다는 결론을 얻었다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권13호
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• pp.5579-5582
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• 2015

Background: Sale of single cigarettes is an important factor for early experimentation, initiation and persistence of tobacco use and a vital factor in the smoking epidemic in India as it is globally. Single cigarettes also promote the sale of illicit cigarettes and neutralises the effect of pack warnings and effective taxation, making tobacco more accessible and affordable to minors. This is the first study to our knowledge which estimates the size of the single stick market in India. Materials and Methods: In February 2014, a 10 jurisdiction survey was conducted across India to estimate the sale of cigarettes in packs and sticks, by brands and price over a full business day. Results: We estimate that nearly 75% of all cigarettes are sold as single sticks annually, which translates to nearly half a billion US dollars or 30 percent of the India's excise revenues from all cigarettes. This is the price which the consumers pay but is not captured through tax and therefore pervades into an informal economy. Conclusions: Tracking the retail price of single cigarettes is an efficient way to determine the willingness to pay by cigarette smokers and is a possible method to determine the tax rates in the absence of any other rationale.

• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.343-349
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• 2012

The solar proton telescope (SPT) is considered as one of the scientific instruments to be installed in instruments for the study of space storm (ISSS) which is determined for next generation small satellite-1 (NEXTSat-1). The SPT is the instrument that acquires the information on energetic particles, especially the energy and flux of proton, according to the solar activity in the space radiation environment. We performed the simulation to determine the specification of the SPT using geometry and tracking 4 (GEANT4). The simulation was performed in the range of 0.6-1,000 MeV considering that the proton, which is to be detected, corresponds to the high energy region according to the solar activity in the space radiation environment. By using aluminum as a blocking material and adjusting the energy detection range, we determined total 7 channels (0.6~5, 5~10, 10~20, 20~35, 35~52, 52~72, and >72 MeV) for the energy range of SPT. In the SPT, the proton energy was distinguished using linear energy transfer to compare with or discriminate from relativistic electron for the channels P1-P3 which are the range of less than 20 MeV, and above those channels, the energy was determined on the basis of whether silicon semiconductor detector (SSD) signal can pass or not. To determine the optimal channel, we performed the conceptual design of payload which uses the SSD. The designed SPT will improve the understanding on the capture and decline of solar energetic particles at the radiation belt by measuring the energetic proton.

• 정보저장시스템학회논문집
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• 제1권2호
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• pp.115-120
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• 2005

As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A bluray technology using 405nm laser diode and objective lens having high NA(Numerical Aperture), 0.85, satisfies a miniaturization and a high capacity which are the requirements of the portable device. To develop SFFOP(small form factor optical pickup), it is prerequisite to minimize the number of optical components and establish evaluation and assembly method of micro optical pickup system as well as mass production method of micro optical component. To minimize optical elements of optical pickup, there have been many researches to use P-HOE(Polarized Holographic Optical Element) due to its extremely small size and versatile function. However, P-HOE is handled and assembled very accurately in SFFOP. In this paper, static error signal detection method is developed for an alignment of P-HOE in SFFOP. Using developed static error signal detection method, P-HOE can be aligned very accurately with real time result of static error signals of pickup such as FES(focusing error signal) and TES(Tracking Error Signal). The developed static error signal detection method is verified by the evaluation of commercialized DVD Pickup. And finally. developed static error signal detection method is applied for the assembly of P-HOE in SFFOP system satisfies specification of BD(Blu-ray Disk).

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2019년도 추계학술발표대회
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• pp.1019-1022
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• 2019

최근의 영상 처리 분야는 딥러닝 기법들의 성능이 입증됨에 따라 다양한 분야에서 이와 같은 기법들을 활용해 영상에 대한 분류, 분석, 검출 등을 수행하려는 시도가 활발하다. 그중에서도 의료 진단 보조 역할을 할 수 있는 의료 영상 분석 소프트웨어에 대한 기대가 증가하고 있는데, 본 연구에서는 캡슐내시경 영상에 주목하였다. 캡슐내시경은 주로 소장 촬영을 목표로 하며 식도부터 대장까지 약 8~10시간 동안 촬영된다. 이로 인해 CT, MR, X-ray와 같은 다른 의료 영상과 다르게 하나의 데이터 셋이 10~15만 장의 이미지를 갖는다. 일반적으로 캡슐내시경 영상을 판독하는 순서는 위장관 교차점(Z-Line, 유문판, 회맹판)을 기준으로 위장관 랜드마크(식도, 위, 소장, 대장)를 구분한 뒤, 각 랜드마크 별로 병변 정보를 찾아내는 방식이다. 그러나 워낙 방대한 영상 데이터를 가지기 때문에 의사 혹은 의료 전문가가 영상을 판독하는데 많은 시간과 노력이 소모되고 있다. 본 논문의 목적은 캡슐내시경 영상의 판독에서 모든 환자에 대해 공통으로 수행되고, 판독하는 데 많은 시간을 차지하는 위장관 랜드마크를 찾는 것에 있다. 이를 위해, 위장관 랜드마크를 식별할 수 있는 CNN 학습 모델을 설계하였으며, 더욱 효과적인 학습을 위해 전처리 과정으로 학습에 방해가 되는 학습 노이즈 영상들을 제거하고 위장관 랜드마크 별 특징 분석을 진행하였다. 총 8명의 환자 데이터를 가지고 학습된 모델에 대해 평가 및 검증을 진행하였는데, 무작위로 환자 데이터를 샘플링하여 학습한 모델을 평가한 결과, 평균 정확도가 95% 가 확인되었으며 개별 환자별로 교차 검증 방식을 진행한 결과 평균 정확도 67% 가 확인되었다.

• Metals and materials international
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• 제24권6호
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• pp.1359-1368
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• 2018

The mechanical properties and microstructure evolution of Mg-8Li-3Al-1Y alloy undergoing different rolling processes were systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electron microscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testing was employed to characterize the mechanical properties. After hot rolling, the $MgLi_2Al$ precipitated in ${\beta}-Li$ matrix due to the transformation reaction: ${\beta}-Li{\rightarrow}{\beta}-Li+MgLi_2Al+{\alpha}-Mg$. As for the alloy subjected to annealed hot rolling, ${\beta}-Li$ phase was clearly recrystallized while recrystallization rarely occurred in ${\alpha}-Mg$ phase. With regard to the microstructure undergoing cold rolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjected to annealed cold rolling revealed the formation of new fresh ${\alpha}-Mg$ grains in ${\beta}-Li$ phase due to the precipitation reaction. The mechanical properties and fracture modes of Mg-8Li-3Al-1Y alloys can be effectively tuned by different rolling processes.

• Journal of Ginseng Research
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• 제47권2호
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• pp.210-217
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• 2023

Background: Effects of the major ginsenoside Rg1 on mammalian longevity and physical vitality are rarely reported. Purpose: To examine longevity, tumor, and spontaneous locomotor activity in rats consuming Rg1. Methods: A total of 138 Wistar rats were randomized into 2 groups: control (N = 69) and Rg1 (N = 69). Rg1 (0.1 mg/kg per day) were orally supplemented from 6 months of age until natural death. Spontaneous mobility was measured by video-tracking together with body composition (dual energy x-ray absorptiometry) and inflammation markers at 5, 14, 21, and 28 months of age. Results: No significant differences in longevity (control: 706 days; Rg1: 651 days, p = 0.77) and tumor incidence (control: 19%; Rg1: 12%, p = 0.24) were observed between the two groups. Movement distance in the control group declined significantly by ~60% at 21 months of age, together with decreased TNF-α (p = 0.01) and increased IL-10 (p = 0.02). However, the movement distance in the Rg1 group was maintained ~50% above the control groups (p = 0.01) at 21 months of age with greater magnitudes of TNF-α decreases and IL-10 increases. Glucose, insulin, and body composition (bone, muscle and fat percentages) were similar for both groups during the entire observation period. Conclusion: The results of the study suggest a delay age-dependent decline in physical vitality during late life by lifelong Rg1 consumption. This improvement is associated with inflammatory modulation. Significant effects of Rg1 on longevity and tumorigenesis were not observed.