• 한국재료학회지
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• 제29권9호
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• pp.547-552
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• 2019

In the present study, the thermal conductivity of a silicon nitride($Si_3N_4$) thin-film is evaluated using the dual-wavelength pump-probe technique. A 100-nm thick $Si_3N_4$ film is deposited on a silicon (100) wafer using the radio frequency plasma enhanced chemical vapor deposition technique and film structural characteristics are observed using the X-ray reflectivity technique. The film's thermal conductivity is measured using a pump-probe setup powered by a femtosecond laser system of which pump-beam wavelength is frequency-doubled using a beta barium borate crystal. A multilayer transient heat conduction equation is numerically solved to quantify the film property. A finite difference method based on the Crank-Nicolson scheme is employed for the computation so that the experimental data can be curve-fitted. Results show that the thermal conductivity value of the film is lower than that of its bulk status by an order of magnitude. This investigation offers an effective way to evaluate thermophysical properties of nanoscale ceramic and dielectric materials with high temporal and spatial resolutions.

• Current Applied Physics
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• 제18권11호
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• pp.1381-1387
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• 2018

One dimensional (1D) grating has been fabricated (using focused ion beam) on 50 nm gold (Au) film deposited on higher refractive index Gallium phosphate (GaP) substrate. The sub-wavelength periodic metal nano structuring enable to couple photon to couple with the surface plasmons (SPs) excited by them. These grating devices provide the efficient control on the SPs which propagate on the interface of noble metal and dielectric whose frequency is dependent on the bulk electron plasma frequency of the metal. For a fixed periodicity (${\Lambda}=700 nm$) and slit width (w = 100 nm) in the grating device, the efficiency of SPP excitation is about 40% compared to the transmission in the near-field. Efficient coupling of SPs with photon in dielectric provide field localisation on sub-wavelength scale which is needed in Heat Assisted Magnetic recording (HAMR) systems. The GaP is also used to emulate Vertical Cavity Surface emitting laser (VCSEL) in order to provide cheaper alternative of light source being used in HAMR technology. In order to understand the underlying physics, far-and near-field results has been compared with the modelling results which are obtained using COMSOL RF module. Apart from this, grating devices of smaller periodicity (${\Lambda}=280nm$) and slit width (w = 22 nm) has been fabricated on GaP substrate which is photoluminescence material to observe amplified spontaneous emission of the SPs at wavelength of 805 nm when the grating device was excited with 532 nm laser light. This observation is unique and can have direct application in light emitting diodes (LEDs).

• Animal Bioscience
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• 제36권11호
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• pp.1769-1774
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• 2023

Objective: Resting comfort may influence sleep-related lying postures in cattle. This study aimed to investigate the effects of bed cleanliness on tucked (TSP) and extended (ESP) head positions in sleep-related lying postures. Methods: The study was conducted over two experimental periods. In each period, four Japanese Black fattening cattle were assigned to the cleaning treatment (CL), in which bedding material was replaced once during each experimental period. Four cattle were assigned to the control treatment (CON) with no bed cleaning. Daily duration, bout frequency, and bout length of sleep-related lying postures were measured, and bed moisture, ammonia concentration in the air, plasma cortisol, and serotonin concentration were also measured within one week before and after cleaning treatment in each period. Results: The bed moisture and ammonia concentrations decreased in CL after bed cleaning. Following bed cleaning, the duration and bout frequency of TSP in CL decreased compared to that observed in CON, whereas ESP in CL increased after bed cleaning. Total duration of sleep-related lying postures and cortisol and serotonin levels did not differ between CL and CON. Conclusion: These results suggest that cattle in sleep-related lying postures shifted from tucked head positions to extended head positions in response to improved bed cleanliness.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.442-442
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• 2008

Hydrogen was produced by water plasma excited in very high frequency inductively coupled tube reactor. Mass spectrometry was used to monitor gas phase species at various process conditions. Water dissociation rate depend on the process parameters such as ICP power, flow-rate and pressure. Water dissociation percent in ICP reactor decrease with increase of chamber pressure and $H_2O$ flow rate, while increase with increase of ICP power. In our experimental range, maximum water dissociation rate was 65.5% at the process conditions of 265 mTorr, 68 sccm, and 400 Watt. The effect of $CH_4$ addition to a water plasma on the hydrogen production has been studied in a VHF ICP reactor. With the addition of $CH_4$ gas, $H_2$ production increases to 12% until the $CH_4$ flow rate increases up to 15 sccm. But, with the flow rate of $CH_4$ more than 20 sccm, chamber wall was deposited with carbon film because of deficiency of oxygen in gas phase, hydrogen production rate decreased. The main roles of $CH_4$ gas are to reacts with O forming CO, CHO and $CO_2$ and releasing additional $H_2$ and furthermore to prevent reverse reaction for forming $H_2O$ from $H_2$ and $O_2$. But, $CH_4$ addition has negative effects such as cost increase and $CO_x$ emission, therefore process optimization is required.

• 대한지역사회영양학회지
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• 제7권6호
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• pp.749-761
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• 2002

This study investigated the anthropometric and biochemical indices, and the health and nutritional factors influencing the two indices among 194 middle-aged and elderly subjects (108 middle-aged and 86 elderly) residing in a medium sized city for more than 10 years. In the examination of their dietary habits, 8.3% of the middle-aged subjects and 14.0% of the elderly subjects had two meals a day, and more female subjects had two meals per day. Of the subjects who ate meals at regular times, 75.0% were middle-aged and 79.1% were elderly, and the degree of irregularity of meals was greater for female subjects. The study of the dietary behavior of the subjects indicated that 71.3% and 66.3% of the middle-aged and elderly, respectively responded that the amount of food in each meal was sufficient. The subjects ate alone comprised 19.7% of the middle-aged females and 31.5% of the elderly females. The prevalence of smoking among the subjects was 28.1% for the middle-aged, 18.8% for the elderly male and 7.4% for the elderly females. The percentage of the subjects who drank alcohol was 34.4% of the middle-aged males and 13.2% of the middle-aged females. Slightly less than half of the subjects exercised more than once a week, with the male subjects showing a higher rate than the female subjects. The average body mass indices (BMI) were 24.5 and 24.6 for the middle-aged male and female, respectively, and 22.6 and 24.0 for the elderly male and female, respectively. BMI assessment showed that underweight subjects (BMI ＜ 20) comprised 3.7% of the middle-aged, 14.0% of the elderly, and that 40.7% of the middle-aged and 24.4% of the elderly were overweight (25 ＜ BMI ＜ 30) , and 0.9% of the middle-aged and 1.2% of the elderly were classified as obese (BMI $\geq$ 30) . A waist/hip ratio (WHR) greater than 0.8 was found in 89.5% of the middle-aged females and 90.7% of the elderly females, showing high abdominal fat deposition in the majority of females. The average systolic blood pressure of females was 121.1 $\pm$ 17.1 mmHg for the middle-aged and 129.6 $\pm$ 21.3 mmHg for the elderly subjects. The systolic blood pressures showed a significantly difference between the two age groups. Those defined as anemic subjects based on hemoglobin values comprised 13.0% of the middled-aged group and 16.3% of the elderly group. There was a tendency for higher fasting glucose levels among the elderly subjects. An increase in total plasma cholesterol levels with age was shown. The female subjects had higher cholesterol levels than the males'The study of the correlation between the daily habits and health status showed that the amount of food eaten at each meal, the frequency of eating out, and the use of dietary supplements appeared to influence BMI, WHR, the plasma triglyceride and plasma cholesterol levels; omitting one meal had a positive correlation with the systolic blood pressure and plasma cholesterol. These results suggest that desirable dietary habits and concerns for health are contributing factors for maintaining good health, as indicated by normal blood lipid levels.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.204-205
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• 2011

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is a most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. For best performance of thin film silicon solar cell, the dopant profiles at p/i and i/n interfaces need to be as sharp as possible. The sharpness of dopant profiles can easily achieved when using multi-chamber PECVD equipment, in which each layer is deposited in separate chamber. However, in a single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of a single-chamber PECVD system in spite of the advantage of lower initial investment cost for the equipment. In order to resolve the cross-contamination problem in single-chamber PECVD systems, flushing method of the chamber with NH3 gas or water vapor after doped layer deposition process has been used. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. A single-chamber VHF-PECVD system was used for superstrate type p-i-n a-Si:H solar cell manufacturing on Asahi-type U FTO glass. A 80 MHz and 20 watts of pulsed RF power was applied to the parallel plate RF cathode at the frequency of 10 kHz and 80% duty ratio. A mixture gas of Ar, H2 and SiH4 was used for i-layer deposition and the deposition pressure was 0.4 Torr. For p and n layer deposition, B2H6 and PH3 was used as doping gas, respectively. The deposition temperature was $250^{\circ}C$ and the total p-i-n layer thickness was about $3500{\AA}$. In order to remove the deposited B inside of the vacuum chamber during p-layer deposition, a high pulsed RF power of about 80 W was applied right after p-layer deposition without SiH4 gas, which is followed by i-layer and n-layer deposition. Finally, Ag was deposited as top electrode. The best initial solar cell efficiency of 9.5 % for test cell area of 0.2 $cm^2$ could be achieved by applying the in-situ plasma cleaning method. The dependence on RF power and treatment time was investigated along with the SIMS analysis of the p-i interface for boron profiles.

• Journal of Nutrition and Health
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• 제56권2호
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• pp.168-183
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• 2023

본 연구는 20-30대 성인을 대상으로 심혈관계 질환 예측인자인 AIP가 어떤 요인들과 상관성이 있는지를 밝혀 중년 이후 심혈관계질환의 발병을 조기에 예방할 수 있도록 하는 근거를 제공하고자 수행이 되었다. 연구대상자는 2013-2015년 국민건강영양조사에 참여한 20-39세 성인 3,040명으로 AIP에 따라 5분위수로 나누어서 일반사항, 건강지표, 식습관, 영양섭취상태를 비교하였다. 남성과 여성 대상자 모두 나이가 많을수록, 비만할수록, 흡연할수록 AIP 평균이 높았고, 교육수준의 경우 남성은 교육수준이 높을수록 여성은 교육 수준이 낮을수록 AIP 평균이 높았다. 남성은 음주 정도에 따라 AIP 평균에 차이가 있었고, 운동을 하지 않는 남성이 운동을 하는 남성보다 AIP 평균이 높았다. 건강지표는 남녀 모두 AIP가 높은 분위로 갈수록 수축기 혈압, 이완기 혈압, 공복혈당, 인슐린, 총 콜레스테롤, 중성지방, LDL 콜레스테롤이 유의하게 증가하는 경향이 나타났다. 남성의 경우 당화혈색소 수치도 AIP가 높아질수록 유의하게 증가하는 경향이 나타났지만, 여성에서는 유의적인 차이는 없었고, HDL 콜레스테롤의 경우 남녀 모두 AIP가 높아질수록 수치가 유의하게 낮아지는 경향이 있었다. 식습관은 여성에서 AIP가 높은 분위수로 갈수록 아침식사를 먹지 않는 비율이 높았고, 음료의 섭취량이 높았으며 커피의 섭취량은 낮았다. AIP에 따른 영양소 섭취량은 남녀 모두 차이가 없었다. 본 연구 결과를 통해 20-30대 성인에서도 나이가 많을수록 비만할수록 흡연을 할수록 운동을 안 할수록 동맥경화의 위험도가 높아짐을 확인하였고, AIP는 젊은 성인에서도 수축기 혈압, 이완기 혈압, 공복혈당, 인슐린, 총 콜레스테롤, 중성지방, LDL 콜레스테롤, HDL 콜레스테롤 등의 건강지표와 상관성이 있었다. 또한 여성에서 음료의 섭취가 많고 커피의 섭취가 적을수록 AIP가 증가하여서 탄산음료와 가당 음료의 섭취를 줄이는 것이 바람직함을 확인하였다. 따라서 20-30대 젊은 성인도 체중조절과 바람직한 생활습관을 통해 심혈관질환 예방을 위한 노력이 필요함을 확인하였다.

• 대한지역사회영양학회지
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• 제25권6호
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• pp.485-501
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• 2020

Objectives: The purpose of this study was to examine the biochemical characteristics and dietary intake of adolescents aged 12 to 18 years according to the frequency of milk consumption. Methods: Data from the 2010~2011 Korea National Health and Nutrition Examination Survey was used for the study. The study examined adolescents' (12~18 years) demographic characteristics (house income level, residence region, skipping or not-skipping of breakfast/lunch/dinner, eating-out frequency), anthropometric characteristics (height, weight, weight status), biochemical characteristics (fasting plasma glucose, blood urea nitrogen, creatine, triglycerides, cholesterol, HDL-cholesterol, hemoglobin, hematocrit) and nutrient intakes through quantitative and qualitative evaluation using the Korean Dietary Reference Intakes (KDRI), index of nutrition quality (INQ), nutrition adequacy ratio (NAR) of 3 groups (< 1/week, 1~6/week, ≥ 1/day) according to the frequency of milk consumption. Results: There were significant differences in gender and income levels among the 3 groups. There were no differences in height, weight, and weight status among groups. There were differences in biochemical characteristics and nutrient intake. In boys, there were differences in the mean of BUN and HDL-cholesterol, in quantitative intakes of riboflavin, calcium, phosphorus, potassium by KDRI levels, in qualitative intakes of riboflavin, calcium, phosphorus by INQ and riboflavin, calcium, phosphorus by NAR among 3 groups. In girls, there were differences in the mean of blood urea nitrogen, creatine, HDL-cholesterol, in quantitative intakes of protein, riboflavin, calcium, phosphorus by KDRI levels, in qualitative intakes of riboflavin, calcium, phosphorus by INQ and riboflavin, calcium, phosphorus by NAR among the 3 groups. Conclusions: In Korean adolescents, boys had a higher frequency of milk consumption than girls, and higher the income level, higher the frequency of milk consumption. Consumption of milk appeared to have a positive association with triglycerides, HDL-cholesterol, and indices related to muscle mass. Regular consumption of milk is an important factor in enhancing the intake of riboflavin, calcium, and phosphorus, which adolescents lack. The results of the study indicate a need to prepare an environment and education program to increase milk consumption in adolescents at home and school.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권1호
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• pp.84-93
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• 2001

An electromagnetic micro x-y stage for probe-based data storage (PDS) has been fabricated. The x-y stage consists of a silicon body inside which planar copper coils are embedded, a glass substrate bonded to the silicon body, and eight permanent magnets. The dimensions of flexures and copper coils were determined to yield $100{\;}\mu\textrm{m}$ in x and y directions under 50 mA of supplied current and to have 440 Hz of natural frequency. For the application to PDS devices, electromagnetic stage should have flat top surface for the prevention of its interference with multi-probe array, and have coils with low resistance for low power consumption. In order to satisfy these design criteria, conducting planar copper coils have been electroplated within silicon trenches which have high aspect ratio ($5{\;}\mu\textrm{m}$in width and $30{\;}\mu\textrm{m}$in depth). Silicon flexures with a height of $250{\;}\mu\textrm{m}$ were fabricated by using inductively coupled plasma reactive ion etching (ICP-RIE). The characteristics of a fabricated electromagnetic stage were measured by using laser doppler vibrometer (LDV) and dynamic signal analyzer (DSA). The DC gain was $0.16{\;}\mu\textrm{m}/mA$ and the maximum displacement was $42{\;}\mu\textrm{m}$ at a current of 180 mA. The measured natural frequency of the lowest mode was 325 Hz. Compared with the designed values, the lower natural frequency and DC gain of the fabricated device are due to the reverse-tapered ICP-RIE process and the incomplete assembly of the upper-sided permanent magnets for LDV measurements.

• 한국항행학회논문지
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• 제8권1호
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• pp.10-18
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• 2004

하향 링크에서 고품질의 멀티미디어 서비스를 위한 기술로 직교 시공간 블록 부호를 이용한 전송 다이버시티 기법이 제안 되었지만 3개 이상의 송신 안테나를 사용하는 경우 대역효율이 저하되기 때문에 송신 안테나의 수가 증가하는 만큼의 다이버시티 효과를 얻을 수 없다. 따라서, 이를 개선하기 위한 연구로 송신 안테나의 수가 증가하더라도 추가적 대역을 필요로 하지 않는 준직교 시공간 블록부호가 제안되었다. 그러나 시공간 블록부호를 이용한 전송 다이버시티 기법은 준정지, 주파수 비선택적 채널을 가정하여 성능을 검증하였기 때문에 본 논문에서는 주파수 선택적 채널이 비선택적 채널로 등가화되는 OFDM 시스템에 준직교 시공간 블록부호를 적용함으로써 기존의 직교 시공간 블록 부호화된 OFDM 시스템과 성능을 비교, 분석하였다.