• 한국음향학회지
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• 제37권1호
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• pp.1-11
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• 2018

천해 환경에서 음파 전달은 경계면에 의해 구형 분산에서 원통형 분산으로 음파 전달 조건이 전환되는데, 이 지점을 음파 전달 조건의 변환점 (transition point)이라고 정의한다. 이론적으로 거리에 따른 전달손실을 이용하여 음파 전달 조건의 변환점을 계산할 수가 있으며, 본 논문에서는 포물선 방정식 기반 음향모델을 이용하여 Pekeris 도파관에서 송 수신기가 수층의 중심에 위치한 경우 전달손실을 모의한 후 변환점을 도출하였다. 계산된 변환점은 수층과 퇴적층의 음속비로 계산된 임계각으로 추정한 임계거리와 비교, 분석되었으며, 동일한 환경에서 수층에 음향채널이 존재하는 경우와 음원 수심 변화에 따른 변환점 변동성을 확인하였다. 최종적으로 2015년 5월, 제주도 서남쪽으로 약 65 km 떨어진 SAVEX15(Shallow Water Acoustic Variability EXperiment 2015) 실험에서 획득한 천해 환경에서의 거리에 따른 저 중주파수 음파 전달 실험의 전달손실 자료를 이용하여 실험 해역에서의 음파 전달 조건 변환점을 도출하였으며, 이를 실험해역의 해양환경과 비교를 통하여 음전달 특성을 파악하였다.

• 한국항행학회논문지
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• 제23권6호
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• pp.542-547
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• 2019

열차 자율주행은 제한된 열차 선로의 용량을 증가시키기 위한 미래 철도 기술이며, 무선통신의 안정성은 열차간 간격 감소에 있어서 핵심적인 역할을 한다. 본 논문에서는 자율주행열차 통신을 위한 혼잡 환경에서의 전송 기법을 제안하였다. 제안하는 분산 UORA (uplink OFDMA (orthogonal frequency division multiple access) random access) 기법은 최신 6세대 무선랜 표준인 IEEE 802.11ax의 TUA (triggered uplink access) 기법과 UORA 기법을 분산적으로 적용하여 혼잡도가 매우 높은 승강장 진입 환경에서, 승강장 및 차량의 센서가 효율적으로 차량 및 승강장의 수집 장치에게 전달할 수 있도록 한다. 본 논문의 실험 결과에 따르면, 제안하는 기법은 기존 EDCA (enhanced distributed channel access) 방식 대비 혼잡 상황에서 효과적으로 전송 성공률을 향상 시키는 것으로 나타났다.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1551-1558
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• 2001

Recently, a number of underground pipelines have been drastically increased. The integrity of these buried pipelines, especially gas transmitting pipelines, is of importance due to an explosive characteristic of natural gas. The third party damage is known as one of the most critical factor which causes fatal accidents. For this reason, a number of systems detecting third party damage are under development. The major concern in the development of third party damage detection system is to transmit vibration signals out of accelerometer to signal conditioner and data acquisition system without any interference caused by noise. The objective of this paper is to develope a fiber optic accelerometer applicable to third party damage detection system. A fiber optic accelerometer was developed by use of combining principles of one degree of freedom vibration model and an extrinsic Fabry-Perot interferometer. The developed fiber optic accelerometer was designed to perform with a sensitivity of 0.06mVg, a frequency range of less than 6kHz and an amplitude range of -200g to 200g. The developed, accelerometer was compared with a piezoelectric accelerometer and calibrated. In order to verify the developed accelerometer, the field experiment was performed. From the field experiment, vibration signals and the location of impact were successfully detected. The developed accelerometer is expected to be used for the third party damage detection system which requires long distance transmission of signals.

• Archives of Plastic Surgery
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• 제42권3호
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• pp.309-315
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• 2015

Background Breast projection is a critical element of breast reconstruction aesthetics, but little has been published regarding breast projection as the firm expander is changed to a softer implant. Quantitative data representing this loss in projection may enhance patient education and improve our management of patient expectations. Methods Female patients who were undergoing immediate tissue-expander breast reconstruction with the senior author were enrolled in this prospective study. Three-dimensional camera software was used for all patient photographs and data analysis. Projection was calculated as the distance between the chest wall and the point of maximal projection of the breast form. Values were calculated for final tissue expander expansion and at varying intervals 3, 6, and 12 months after implant placement. Results Fourteen breasts from 12 patients were included in the final analysis. Twelve of the 14 breasts had a loss of projection at three months following the implant placement or beyond. The percentage of projection lost in these 12 breasts ranged from 6.30% to 43.4%, with an average loss of projection of 21.05%. Conclusions This study is the first prospective quantitative analysis of temporal changes in breast projection after expander-implant reconstruction. By prospectively capturing projection data with three-dimensional photographic software, we reveal a loss of projection in this population by three months post-implant exchange. These findings will not only aid in managing patient expectations, but our methodology provides a foundation for future objective studies of the breast form.

• 대한방사선기술학회지:방사선기술과학
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• 제42권6호
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• pp.429-434
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• 2019

The gonads are directly affected by radiation exposure during radiography of the pelvis, abdomen, and spine. Exposure of the gonads to radiation can cause genetic mutations and can result in the occurrence of malignant tumors. In this study, we created three types of shielding material shapes for shielding of the ovaries, which are the gonads of female during radiography of the pelvis, and comparative evaluations using shadow shielding methods. The source surface distance(SSD) was 100 cm and the field size was 42 cm × 43 cm. The three types of shielding material shapes(type 1, 2 and 3) were assessed and the entrance surface dose in the ovaries were measured. The thickness of the shielding material was expanded from 0.3 mm to 2.4 mm and after five repetitions, radiation values were measured and mean values were calculated. The mean dose were 3.09 mGy for type 1, 3.54 mGy for type 2, and 3.19 mGy for type 3, indicating that the measurements were the lowest for type 1. When an additional filter of 0.2 Cu + 1 Al was used, the dose were 3.72 mGy for type 1, 5.43 mGy for type 2, and 4.05 mGy for type 3, indicating that the measurements were the lowest for type 1. The results show that, even if the shielding material is not thick, in other words, even with a thickness of 2.94 mGy for the SN 3(0.9 mm) of type 1, shielding can be achieved, with a patient dose lower than the diagnostic reference level(3.42 mGy). Additionally, among the three types of shielding material, the type 1 appeared to be the most appropriate shielding material. It is thought that the use of shielding material could reduce the risk factors for stochastic effects or critical effects of ionizing radiation during pelvic or lumbar radiography.

• Progress in Superconductivity
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• 제8권1호
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• pp.71-74
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• 2006

High $J_c$ over 1 $MA/cm^2$ YBCO film has been successfully prepared using nitrate precursors by spray pyrolysis method. Aerosol drolpets generated using a concentric spray nozzle were directly sprayed on a $LaAlO_3$(100) single crystal substrate. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:1.35. The distance between nozzle and substrate was 15 cm. Deposition temperature was ranging from $750^{\circ}C\;to\;800^{\circ}C$. Deposition pressure was 100 Torr, and oxygen partial pressure was varied from 10 Torr to 50 Torr. The microstructure, phase formation, texture development and superconducting properties of deposited films were largely changed with oxygen partial pressure. Deposited films showed a texture with(001) planes parallel to substrate plane. High quality film was obtained when film was deposited at $760^{\circ}C$ with an oxygen partial pressure of 30 Torr. The critical current density($J_c$) of the YBCO film was 1.75 $MA/cm^2$ at 77 K and self-field.

• 한국물환경학회지
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• 제23권6호
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• pp.913-919
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• 2007

This study was conducted to develop a model equation to estimate the delivered point and nonpoint pollutant loads, which are critical factor to determine the water quality of watersheds. The model equation was developed by considering various factors such as biological removal and delivered distance of pollutants, basin shape and geomorphic runoff condition. The parameters for the model equation were estimated in 3 periods, which are October to March, April to June, and July to September. As a parameter, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$, a and b for $BOD_5$-delivered pollutant loads were estimated to be 0.010~0.0155, 0.051, -0.033, 0.018~0.050 and 0.93, respectively. For T-N, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$ a and b were estimated to be 0.0060~0.0140, 0.014, -0.02, 0.044~0.079 and 0.93, respectively. The same parameters for T-P were estimated to be 0.0160, 0.014, -0.0250, 0.015 and 1.21, respectively. The relationship, $E^2$ (Model efficiency), between observed and calculated delivered pollutant loads showed 0.65 for $BOD_5$, 0.81 for T-N, and 0.66 for T-P, respectively. Consequently, the model equation is effective to estimate delivered pollutant loads for TMDL.

• 한국컴퓨터정보학회논문지
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• 제20권5호
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• pp.99-106
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• 2015

본 논문에서는 비디오 콘텐츠 검색 및 관리를 위하여 OTT 디바이스 내부의 DB 개발과 이와 연동하여 비디오 질의 검색 서비스를 탑재할 인터페이스(리모콘 스마트폰) 어플리케이션에서 필수적인 요소인 검색 알고리즘의 개발 방법을 제안한다. 디지털 방송이 시작되고 각 가정에 보급이 됨으로써 사용자들이 선택하여 시청하는 채널 및 프로그램의 수와 종류는 공중파 환경과 비교하여 폭발적으로 증가하였다. 채널의 수가 수십에서 수백 개로 늘어남에 따라 사용자는 자신이 원하는 프로그램을 찾기가 점점 어려워지게 되었고 이 문제를 해결하기 위해 콘텐츠 공급자는 소비자의 취향에 맞는 프로그램을 추천해줄 방법이 필요하게 되었다. 시청자의 시청 패턴을 분석하여 사용자의 취향을 분석하여 적합한 프로그램을 추천해줄 수 있는 방법이 필요하다. 이러한 문제를 해결하기 위하여 시청자의 시청 패턴을 분석하여 시청자의 취향에 적합한 프로그램을 추천해줄 수 있는 방법이 필요하다. 본 연구는 개인의 시청 패턴과 히스토리를 바탕으로 OTT 프로그램의 콘텐츠를 추천하는 알고리즘을 구현하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.197-197
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• 2011

In this study, in contrast with cases in which Scanning Tunneling Microscopy (STM) tip-induced reactions were instigated by the tunneling electrons, the local electric field, or the mechanical force between a tip and a surface, we found that the tungsten oxide (WO3) covered tungsten (W) tip of a STM acted as a chemical catalyst for the S-H dissociative adsorption of phenylthiol and 1-octanethiol onto a Ge(100) surface. By varying the distance between the tip and the surface, the degree of the tip-catalyzed adsorption could be controlled. We have found that the thiol head-group is the critical functional group for this catalysis and the catalytic material is the WO3 layer of the tip. After removing the WO3 layer by field emission treatment, the catalytic activity of the tip has been lost. 3-mercapto isobutyric acid is a chiral bi-functional molecule which has two functional groups, carboxylic acid group and thiol group, at each end. 3-Mercapto Isobutyric Acid adsorbs at Ge(100) surface only through carboxylic acid group at room temperature and this adsorption was enhanced by the tunneling electrons between a STM tip and the surface. Using this enhancement, it is possible to make thiol group-terminated surface where we desire. On the other hand, surprisingly, the WO3 covered W tip of STM was found to act as a chemical catalyst to catalyze the adsorption of 3-mercapto isobutyric acid through thiol group at Ge(100) surface. Using this catalysis, it is possible to make carboxylic acid group-terminated surface where we want. This functional group-selective adsorption of bi-functional molecule using the catalysis may be used in positive lithographic methods to produce semiconductor substrate which is terminated by desired functional groups.

• 대한치과보철학회지
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• 제44권4호
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• pp.374-382
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• 2006

Purpose: This study was designed to investigate the present conditions of illumination techniques in dental clinics in order to contribute improvement of operating environment. This study also aimed exploring qualitative and quantitative luminous intensity required for color temperature in dental clinic illumination, which was a critical part of esthetic dentistry. Materials and methods: A total of forty-eight local dental clinics were selected for sampling a) luminous intensity, and b) color temperature. The author measured the luminous intensity and the color temperature with lux meter and color meter respectively between 12pm and 2pm. The dental unit chair placed in the general operation positions were kept the distance 60 cm then all dental units were measured three times and averaged. The author measured the luminous intensity and color temperature with both common dental operating light and then without operating light in different office environments. The study was conducted under three conditions: 1 artificial illumination in clear day light 2. artificial illumination in cloudy day light, and 3. artificial illumination alone. Results : The results obtained were as follows. 1. The average luminous intensity in dental clinic lighting was 425 lux which was not sufficient to produce the optimal shade of the patient's teeth. Furthermore, the average luminous intensity even in full operating lighting was 9532 lux which fell short of the required level of 10,000 lux. 2. The average color temperature of all dental clinics surveyed was 5169 K which met the optimal range. However, only 33.3% fell in the correct region between 5,000-5,500 K as 25% were over 5,500 K and 41.6% were below 5,000 K. As a result, 66.7% were under insufficient color temperature conditions. 3. The dental unit chair placed next to a window, hence exposure to natural lighting, had significantly higher luminous intensity and color temperature compared to the dental unit chair which didn't have a window or natural lighting. 4. The data analysis revealed that only 6.3% of the dental clinic were met the standard of the average luminous intensity and color temperature.