• 한국안광학회지
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• 제1권1호
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• pp.23-28
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• 1996

실온에서 60Hz 저주파 플라즈마 CVD로 수소화된 비정질 탄소(a-C:H) 박막을 제조하였다. 이 방법으로 형성된 박막은 상용 주파수인 전원을 사용하기 때문에 종래의 다른 방법에 비하여 실험이 간단하고 저렴하게 제작되며, 적은 전력밀도(0.03~0.08 W/cm2를 사용하므로 시료의 손상이 작은 장정들을 가지고 있다. 본 연구에서 제작한 a-C:H 박막은 높은 투명도(95%), 높은 저항성(109~1011${\Omega}$-cm). 그리고 순도가 좋은 탄소를 유지하며 평탄성이 아주 좋다. 시료들은 기압비율이 1%에서 30%까지의 범위에서 메탄 (CH4)과 수소(H2)의 혼합기체의 분해에 의하여 제작되었다. 제작된 시료의 침전율 (deposition rate), 광학적 갭(optical gap), 그리고 수소 함량등은 메탄 함량의 증가에 따라 증가하였다. 반응시 플라즈마 온도(~ 6eV)와 밀도(107 cm-3)는 에탄함량에 거의 의존하지 않았다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.88-88
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• 2018

DLC(Diamond Like Carbon) 박막은 높은 열전도도, 큰 전기저항, 높은 강도 등의 다이아몬드와 유사한 특성을 가지고 있으면서 저온 저압에서도 합성이 가능하고, 합성 조건에 따라 물리 화학적 특성도 넓게 조절 할 수 있으며 상대적으로 넓은 면적에서 균일하고 평활한 박막의 합성이 가능하여 산업적 응용 면에서도 경쟁력을 갖추고 있다[1]. 이러한 DLC 박막을 합성함에 있어서 RF-PECVD(Radio Frequency Plasma Enhanced Chemical Vapor Deposition) 방법은 PECVD 방법 중 가장 보편적으로 사용되고 또 캐패시터 타입의 RF-PECVD 방법은 균일한 대면적 증착과 대량생산이 가능하다[1,2]. 본 연구에서는 우수한 특성을 갖는 DLC 박막의 증착 조건을 찾기 위해 캐패시터 타입의 RF-PECVD를 사용하여 공정 가스의 유량과 RF Power를 변화하여 박막을 증착하고, 증착된 박막의 특성을 연구하였다. DLC 박막은 ITO(Indium Tin Oxide) 유리 기판 위에 $100^{\circ}C$에서 5 min 동안 아세틸렌($C_2H_2$) 가스를 사용하여 가스 유량과 RF Power를 변화하여 증착하였다. 증착된 DLC 박막의 특성은 투과도, 평탄도, 두께를 측정하여 비교하였다. 가시광선 영역(380-780 nm)에서 투과도를 측정한 결과 ITO 유리 기판을 기준으로 한 DLC 박막의 투과도는 가시광선 영역 평균 94.8~98.8% 사이의 값으로 매우 높은 투과율을 나타내었다. 투과도는 가스 유량이 증가함에 따라 증가하는 경향을 나타내었고, RF Power의 변화에는 특정한 변화를 나타내지 않았다. 박막의 평탄도($R_a$, $R_{rms}$)와 두께는 AFM(Atomic Force Microscope)을 사용하여 측정하였다. 평탄도 $R_{rms}$는 0.8~3.3 nm, $R_a$는 0.6~2.5 nm 사이를 나타내었고 RF Power와 가스 유량의 변화에 따른 경향성을 나타내지는 않았다. 두께는 RF Power 25 W에서 55 W로 증가함에 따라 증가하는 경향을 나타내었으나 70W에서는 가스의 유량에 따라 상이한 결과를 나타내었다.

• 한국임상약학회지
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• 제29권4호
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• pp.278-285
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• 2019

Background: Rheumatoid arthritis is highly prevalent in overweight patients with type 2 diabetes mellitus and can be reduced by physical activity via altered proinflammatory parameters. However, the association between the frequency of physical activity and the prevalence of rheumatoid arthritis in prediabetic patients remains unclear and was evaluated in this study. Methods: Utilizing the Korean National Health Insurance Sharing Service database, 58,391 adults, who met the research criteria and underwent a general medical check-up between 2009 and 2013, were selected for this study. To analyze the data, a logistic regression with a proc survey logistic procedure was used. Results: The study revealed that the cumulative rheumatoid arthritis prevalence was lower in prediabetic patients compared to that in the control group (OR, 0.64; 95% CI, 0.483-0.840; p=0.001). More frequent physical activity (≥3 days/week) was significantly associated with a reduced rheumatoid arthritis prevalence in both groups (OR, 0.28; 95% CI, 0.039-0.521; p=0.044 vs. OR, 0.15; 95% CI, 0.063-0.237; p=0.007). Additionally, a 3.8-fold higher risk of rheumatoid arthritis development was observed in prediabetic adults with less frequent baseline physical activity (≤2 days/week). Overall, in prediabetes, the prevalence of rheumatoid arthritis was associated with the frequency of physical activity and not with the fasting plasma glucose levels. Conclusion: More frequent physical activity is associated with a low risk of developing rheumatoid arthritis in prediabetic patients. Thus, further studies are needed to confirm the clinical outcomes of frequent physical activity in rheumatoid arthritis prevention and control.

• Journal of Communications and Networks
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• 제15권6호
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• pp.559-568
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• 2013

We report on the first error-free terahertz (THz) wireless communication at 0.310 THz for data rates up to 8.2 Gbps using a 18-GHz-bandwidth GaAs/AlGaAs field-effect transistor as a detector. This result demonstrates that low-cost commercially-available plasma-wave transistors whose cut-off frequency is far below THz frequencies can be employed in THz communication. Wireless communication over 50 cm is presented at 1.4 Gbps using a uni-travelling-carrier photodiode as a source. Transistor integration is detailed, as it is essential to avoid any deleterious signals that would prevent successful communication. We observed an improvement of the bit error rate with increasing input THz power, followed by a degradation at high input power. Such a degradation appears at lower powers if the photodiode bias is smaller. Higher-data-rate communication is demonstrated using a frequency-multiplied source thanks to higher output power. Bit-error-rate measurements at data rates up to 10 Gbps are performed for different input THz powers. As expected, bit error rates degrade as data rate increases. However, degraded communication is observed at some specific data rates. This effect is probably due to deleterious cavity effects and/or impedance mismatches. Using such a system, realtime uncompressed high-definition video signal is successfully and robustly transmitted.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1657-1658
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• 2006

An external electrode fluorescent lamps (EEFLs) have the advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Studies on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter. To solve these problems of CCFL, EEFL (External Electrode Fluorescent Lamp) is introduced. Because electrode of EEFL is on the outer surface of discharge tube, the electrode is perfectly prevented from the sputtering by accelerated ions. And it is possible to drive the many CCFLs at the same time, because EEFL shows the positively resistant characteristic. But EEFL has the large non-radiative power loss in sheath. In this study the novel electrode structure was introduced in order to reduce non-radiative power loss in sheath of EEFL. The novel electrode structure comes from the idea to combine conceptually capacitive discharge with inductive discharge. Thus, this study verifies the change in the optical characteristics according to the change in electrode structure through a Maxwell's electromagnetic field simulation and examines the relationship between the change in the EEFL electrode structure and brightness by measuring the optical characteristics.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.149-149
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• 2010

The double-layer antireflection (DLAR) coatings have significant advantages over single-layer antireflection (SLAR) coatings. This is because they will be able to cover a broad range of the solar spectrum which would enhance the overall performance of solar cells. Moreover films deposited at high frequency are expected to show excellent and UV-stable passivation in the refractive index that we adopted. In this work, we present a novel DLAR coating using SiNx:H thin films with refractive indices 1.9 and 2.3 as the top and bottom layers. This approach is cost effective when compared to earlier DLAR coatings with two different materials. SiNx:H films were deposited by Plasma enhanced chemical vapor deposition (PECVD) technique using $SiH_4$, $NH_3$ and $N_2$ gases with flow rates 20~80sccm, 200sccm and 85 sccm respectively. The RF power, plasma frequency and substrate temperature for the deposition were 300W, 13.56 MHz and $450^{\circ}C$, respectively. The optimum thickness and refractive indices values for DLAR coatings were estimated theoretically using Macleod simulation software as 82.24 nm for 1.9 and 68.58 nm for 2.3 respectively. Solar cells were fabricated with SLAR and DLAR coatings of SiNx:H films and compared the cell efficacy. SiNx:H> films deposited at a substrate temperature of $450^{\circ}C$ and that at 300 W power showed best effective minority carrier lifetime around $50.8\;{\mu}s$. Average reflectance values of SLAR coatings with refractive indices 1.9, 2.05 and 2.3 were 10.1%, 9.66% and 9.33% respectively. In contrast, optimized DLAR coating showed a reflectance value as low as 8.98% in the wavelength range 300nm - 1100nm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.458-458
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• 2010

The process window for the etch selectivity of silicon nitride ($Si_3N_4$) layers to extreme ultra-violet (EUV) resist and variation of line edge roughness (LER) of EUV resist were investigated durin getching of $Si_3N_4$/EUV resist structure in a dual-frequency superimposed capacitive coupled plasma (DFS-CCP) etcher by varying the process parameters, such as the $CH_2F_2$ and $N_2$ gas flow rate in $CH_2F_2/N_2$/Ar plasma. The $CH_2F_2$ and $N_2$ flow rate was found to play a critical role in determining the process window for infinite etch selectivity of $Si_3N_4$/EUV resist, due to disproportionate changes in the degree of polymerization on $Si_3N_4$ and EUV resist surfaces. The preferential chemical reaction between hydrogen and carbon in the hydrofluorocarbon ($CH_xF_y$) polymer layer and the nitrogen and oxygen on the $Si_3N_4$, presumably leading to the formation of HCN, CO, and $CO_2$ etch by-products, results in a smaller steady-state hydrofluorocarbon thickness on $Si_3N_4$ and, in turn, in continuous $Si_3N_4$ etching due to enhanced $SiF_4$ formation, while the $CH_xF_y$ layer is deposited on the EUV resist surface. Also critical dimension (and line edge roughness) tend to decrease with increasing $N_2$ flow rate due to decreased degree of polymerization.

• Journal of Astronomy and Space Sciences
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• 제38권2호
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• pp.135-143
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• 2021

We report, for the first time, the afternoon (i.e., from noon to sunset time) observations of the northern mid-latitude E-region field-aligned irregularities (FAIs) made by the very high frequency (VHF) coherent backscatter radar operated continuously since 29 December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea. We present the statistical characteristics of the mid-latitude afternoon E-region FAIs based on the continuous radar observations. Echo signal-to-noise ratio (SNR) of the afternoon E-region FAIs is found to be as high as 35 dB, mostly occurring around 100-135 km altitudes. Most spectral widths of the afternoon echoes are close to zero, indicating that the irregularities during the afternoon time are not related to turbulent plasma motions. The occurrence of afternoon E-regional FAI is observed with significant seasonal variation, with a maximum in summer and a minimum in winter. Furthermore, to investigate the afternoon E-region FAIs-Sporadic E (E_s) relationship, the FAIs have also been compared with E_s parameters based on observations made from an ionosonde located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of Daejeon. The virtual height of E_s (h'E_s) is mainly in the height range of 105 km to 110 km, which is 5 km to 10 km greater than the bottom of the FAI. There is no relationship between the FAI SNR and the highest frequencies (f_tE_s) (or blanket frequencies (f_bE_s)). SNR of FAIs, however, is found to be related well with (f_tE_s-f_bE_s).

• 한국식품영양과학회지
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• 제27권6호
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• pp.1244-1252
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• 1998

The purpose of this study is to evaluate the nutritional status of vitamin and minerals in the patients with alcoholic liver disease and to obtain the materials for nutritional education for alcoholics. The subjects consist of 80 patients with alcoholic liver cirrhosis(ALC) and 12 patients with alcoholic fatty liver(AFL). The control group included 57 alcoholics without liver disease(A), 32 patients with viral liver cirrhosis(VLC) and 194 normal men(NL). Biochemical evaluation of nutritional status was investigated by the analysis of blood samples. The frequency of vitamin B1 deficiency in the ALC, AFL and A groups as indicated by the erythrocyte transketolase activity coefficient were 46.0%, 66.7% and 57.9% respectively. The frequency of vitamin B2 deficiency in the ALC, AFL and A groups as indicated by the erythrocyte glutathione reductase activity coefficient were 9.8%, 8.3% and 38.6% respectively. Vitamin A deficiency was not detected in the alcoholic subjects. The frequency of vi tamin E deficiency in ALC, AFL and A were 96.3%, 66.7% and 86.0% respectively. The levels of plasma lipid peroxidation products were significantly higher in the alcoholic subjects than in the normal subjects. The frequency of subjects below normal range of hemoglobin were 85.0% in ALC, 50.0% in AFL and 31.6% in A. The frequency of copper deficiency in the ALC, AFL and A groups were 48.4%, 16.7% and 17.5% respectively. The frequency of zinc deficiency in the ALC, AFL and A groups were 83.8%, 41.7% and 66.7% respectively. Overall, the vitamin and minerals status of the alcoholic subjects in this study was evaluated to be very poor on the basis of biochemical assessments. The results suggest that alcohol abuse and poor dietary intake could cause malnutrition and may be important risk factors in causing alcoholic liver disease in alcoholics. In addition, vitamin B1, vitamin B2, Cu, Fe and antioxidant supplementation may be effective in nutritional therapy for chronic alcoholics.

• 한국수산과학회지
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• 제56권5호
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• pp.734-740
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• 2023

The effect of feeding frequency on growth performance, body nutrient composition, and hematological parameters of juvenile chum salmon Oncorhynchus keta was investigated. The juveniles (10.9±0.3 g) were fed commercial feed for 30 days with feeding frequencies of 1, 2, 3, 4, or 5 meal (s)/day (n=2 tanks per treatment) in a recirculating aquaculture system (RAS). Fish were fed to satiation at each of the feeding frequencies. At the end of the feeding trial, final body weight, weight gain, and specific growth rate of fish fed 2 meals/day were significantly higher than those of fish fed 1 meal/day(P<0.05); however, no difference was detected among the other feeding frequencies. Daily feed intake significantly increased with increasing feeding frequency, whereas feed and protein utilization efficiencies continuously decreased with increase in the feeding frequency. Among the treatments, fish fed 1 meal/day showed the lowest value in whole-body lipid content and total protein concentration in plasma. Taken together, the optimal feeding frequency for growth performance and feed utilization efficiency in chum salmon juveniles reared in the RAS was determined to be 2 meals/day.