• 한국세라믹학회지
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• 제47권4호
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• pp.329-332
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• 2010

In order to investigate the effect of tail state on the electrical and the optical properties in amorphous IGZO(a-IGZO), a-IGZO films were deposited at room temperature on fused silica substrats using pulsed laser deposition method. The laser pulse energy was used as the processing parameter. In-situ post annealing was carried out at $150^{\circ}C$ right after the film deposition. The $O_2$ partial pressure during the deposition and the post annealing was fixed to 10mTorr. The carrier mobility of the a-IGZO films had a range from 2 to $18\;cm^2/Vs$ at carrier concentrations greater than $10^{18}\;cm^{-3}$. As the laser energy density increased, the Hall mobility increased. And post annealing improved the Hall mobility, as well. The optical property was examined using the ultraviolet-visible spectroscopy. The a-IGZO films that have low Hall mobility exhibited stronger and broader absorption tails in >3.0 eV region. Post annealing reduced the intensity of the tail-like absorption. The absorption tail in a-IGZO films is an important factor which affects the electrical and the optical properties.

• 한국지반공학회논문집
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• 제27권3호
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• pp.55-61
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• 2011

일반적으로 하천제방 배수통문은 다양한 원인에 의하여 붕괴가 발생하며, 특히 연약지반 상에 말뚝기초를 이용하여 설치된 경우 1) 주변 지반(외부토체)/말뚝기초 처리된 암거 상단(내부토체)의 상대적 침하 차에 의한 배수통문 암거 측벽부의 다짐도 약화, 2) 하이드로릭 플랙처링에 의한 홍수 시 침투수압의 지속적 반복에 의한 측벽부 교란 등에 의해 붕괴가 발생한다. 특히 측벽부는 시공여건상 다짐장비의 접근이 어려운 다짐 취약부이고, 이질재료에 의한 마찰력 감소로 전단저항력이 일반 흙의 전단강도에 비해 1/3 이상 감소하여 발현된다. 이에 본 연구에서는 주변 지반에 인위적인 변형을 발생시키는 방법으로 침하를 모사한 실내 모형실험을 통하여 연약지반 상 말뚝 기초된 배수통문 암거의 상대적 침하에 따른 외부토체/내부토체 발현 메카니즘과 저판확폭에 따른 배수통문 암거 측벽부 다짐도 향상 효과를 비교 분석함으로써 배수통문 저판 확폭을 통한 주변지반 공동 확장 억제기법을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1968-1970
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• 1996

We investigate a surface-micromachined polysilicon microgyroscope, whose resonant frequencies are electrostatically-tunable after fabrication. The microgyroscope with two oscillation nudes has been designed so that the resonant frequency in the sensing mode is higher than that in the actuating mode. The microgyroscope has been fabricated by a 4-mask surface-micrormachining process, including the deep RIE of a $6{\mu}m$-thick LPCVD polycrystalline silicon layer. The resonant frequency in the sensing mode has been lowered to that in actuating mode through the adjustment of an inter-plate bias voltage; thereby achieving a frequency matching at 5.8kHz under the bias voltage of 2V in a reduced pressure of 0.1torr. For an input angular rate of $50^{\circ}/sec$, an output signal of 20mV has been measured from the tuned microgyroscope under an AC drive voltage of 2V with a DC bias voltage of 3V.

• Smart Structures and Systems
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• 제26권2호
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• pp.175-184
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• 2020

Conventional Monte Carlo simulation-based methods for seismic risk assessment of water networks often require excessive computational time costs due to the hydraulic analysis. In this study, an Artificial Neural Network-based surrogate model was proposed to efficiently evaluate the flow-based system reliability of water distribution networks. The surrogate model was constructed with appropriate training parameters through trial-and-error procedures. Furthermore, a deep neural network with hidden layers and neurons was composed for the high-dimensional network. For network training, the input of the neural network was defined as the damage states of the k-dimensional network facilities, and the output was defined as the network system performance. To generate training data, random sampling was performed between earthquake magnitudes of 5.0 and 7.5, and hydraulic analyses were conducted to evaluate network performance. For a hydraulic simulation, EPANET-based MATLAB code was developed, and a pressure-driven analysis approach was adopted to represent an unsteady-state network. To demonstrate the constructed surrogate model, the actual water distribution network of A-city, South Korea, was adopted, and the network map was reconstructed from the geographic information system data. The surrogate model was able to predict network performance within a 3% relative error at trained epicenters in drastically reduced time. In addition, the accuracy of the surrogate model was estimated to within 3% relative error (5% for network performance lower than 0.2) at different epicenters to verify the robustness of the epicenter location. Therefore, it is concluded that ANN-based surrogate model can be utilized as an alternative model for efficient seismic risk assessment to within 5% of relative error.

• 한국전산유체공학회지
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• 제18권3호
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• pp.8-13
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• 2013

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1050-1056
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• 2010

디젤기관은 공기만을 흡입 압축한 후에 연료를 분사하여 연소하기 때문에 높은 압축비가 가능하다. 높은 압축비에 의한 고효율의 장점과 연료의 직접분사에 의한 매연미립자의 배출 및 질소산화물의 배출이 많은 단점을 갖고 있다. 이러한 문제점을 해결하기 위하여 많은 연구들이 진행되었으며 수소를 흡기중에 공급하는 기술도 연구되고 있다. 본 논문에서는 미량의 수소를 연소실에 공급하여 엔진성능에 미치는 영향을 평가하였다. 토크와 엔진속도를 100%, 75%, 50%, 25%, 0%와 700rpm, 1000rpm, 1500rpm, 2000rpm로 구분하여 실험하였다. 실험결과 질소산화물이 약간 증가하였지만 연료소비율, 스모크와 일산화탄소 배출은 감소하였다. 수소의 첨가는 저부하 영역에서는 효과가 거의 없었지만 고부하 영역에서 큰 효과가 있었다.

• 대한한의학회지
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• 제23권4호
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• pp.64-72
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• 2002

Objective: Ramulus mori (RM) has been known to be effective for the treatment of obesity. To show the effectiveness of RM in a more scientific way, RM extract was prepared and evaluated in high fat diet rats by measuring the changes of body weight and lipid metabolism as described briefly below. Methods: 200 g of crushed RM was extracted withmethyl alcohol. The extract was evaporated under reduced pressure to give 33.4 g. For 10 weeks, control group rats were fed a high fat diet, while the test group rats were fed with the same diet plus RM extract. The normal group was fed with a normal diet. 150 mg of RM extract per 1 kg of body weight was added to the diet in the test group rats. Results: The control group rats on the high fat diet gained weight significantly, whereas the test group rats on the high fat diet plus RM extract gamed less weight. The significant increase of liver weight caused by the high fat diet was also inhibited by the RM extract treatment. Total lipid, triglyceride and total cholesterol levels of serum in the high fat diet rats were remarkably increased, whereastheir levels on the high fat diet plus RM extract were less increased. While serum HDL-cholesterol levels were remarkably decreased in the high fat diet, its level was less decreased in the high fat diet plus RM extract. Furthermore, we observed that the activities of hepatic acetyl-CoA carboxylase and fatty acid synthetase increased under the high fat diet, while their activities under the high fat diet plus RM extract were getting back nearly to the normal levels of the normal diet rats. Conclusions: These result show that the obesity caused by a high fat diet was effectively inhibited by an RM extract. Our results also showed that the abnormal lipid metabolism caused by a high fat diet was effectively cured by adding RM extract.

• Nutrition Research and Practice
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• 제8권4호
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• pp.469-475
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• 2014

BACKGROUND/OBJECTIVE: The goal of the present study was to investigate the effects of moderate caloric restriction on ${\beta}$-cell function and insulin sensitivity in middle-aged obese Korean women. SUBJECTS/METHODS: Fifty-seven obese pre-menopausal Korean women participated in a 12-week calorie restriction program. Data on total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglycerides (TG), and fasting serum levels of glucose, insulin, C-peptide, blood pressure, leptin and anthropometrics were collected. A dietary intake assessment was based on three days of food recording. Additionally, ${\beta}$-cell function [homeostasis model assessment of ${\beta}$-cell (HOMA-${\beta}$), insulinogenic index (ISI), C-peptide:glucose ratio, and area under curve insulin/glucose ($AUC_{ins/glu}$)] and insulin sensitivity [homeostasis model assessment for insulin resistance (HOMA-IR), Quantitative insulin-sensitivity check index (QUICKI) and Matsuda index (MI)] were recorded. RESULTS: When calories were reduced by an average of 422 kcal/day for 12 weeks, BMI (-2.7%), body fat mass (-10.2%), and waist circumference (-5%) all decreased significantly (P < 0.05). After calorie restriction, weight, body fat percentage, hip circumference, BP, TC, HDL-C, LDL-C, plasma glucose at fasting, insulin at fasting and 120 min, $AUC_{glu}$ and the insulin area under the curve all decreased significantly (all P < 0.05), while insulin sensitivity (HOMA-IR, QUICKI and Matsuda index) measured by OGTT improved significantly (P < 0.01). CONCLUSIONS: Moderate weight loss due to caloric restriction with reduction in insulin resistance improves glucose tolerance and insulin sensitivity in middle-aged obese women and thereby may help prevent the development of type 2 diabetes mellitus.

• Preventive Nutrition and Food Science
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• 제9권2호
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• pp.156-160
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• 2004

This study aims to investigate the changes in the lipid composition and angiotensin-converting enzyme activity in serum of rats exposed to microwave radiation, and to examine improving effects of green tea catechin to the lipid composition. The microwave-exposed rats received the normal and one of 3 diets: catechin free (MW-0C), 0.25% catechin (MW-0.25C) or 0.5% catechin (MW-0.5C). Rats were sacrificed 6th day after microwave radiation (2.45 ㎓, 15 min). The concentration of serum triglyceridein MW-0C group was increased by 85%, compared with the normal group, but that of MW-0.25C group with 0.25% catechin supplementation was to 17% lower, compared with the MW-0C group. There was no significant difference between normal group and MW-0.5C group. Total-cholesterol and LDL-cholesterol concentrations were increased by 21.4% and 38.6%, respectively, by microwave irradiation. The concentration of HDL-cholesterol in MW-0C group was lower to 29.3%, but it was maintained at the normal level by catechin supplementation. There was no significant difference among four groups in HLD-cholesterol/LDL-cholesterol. Atherogenic index in MW-0C group was increased by 56%, compared with the normal group. Angiotensin-converting enzyme (ACE) activity in lung tissue of MW-0C group was increased by 59 %, while that of MW -0.25C and MW -0.5C group were maintained at the normal level. ACE activity of MW-0C group in serum was increased by 122.8%, compared with the normal group. Catechin supplementation group was significantly reduced, compared with the MW-0C group ACE activity. In conclusion, microwave irradiation increased the serum triglyceride and cholesterol concentrations and ACE activity which are considered as the blood pressure increasing agents. However, catechin supplementation decreased the level of triglyceride, total cholesterol, LDL cholesterol, and ACE activity, which maybe consider catechin as being agent of lowering effect for blood lipid profile for athero-genesis.

• 한국식품영양과학회지
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• 제17권1호
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• pp.1-5
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• 1988

한국재래식(韓國在來式) 고추장의 효소숙성과정중(酵素熟成過程中), 향기성분생성(香氣成分生成)에 주(主)로 관여(關與)하는 Saccharomyces 속(屬) 1 주(株) Bacillus 속(屬) 3 주(株)를 각각(各各) 접종(接種)하여 담근, 고추장의 향기성분(香氣成分)을 동정(同定)한 결과(結果)를 요약(要約)하면 다음과 같다. Saccharomyces sp. 는 tetrahydro geroniol, methoxy acecoptenone 및 myrtanal의 생성(生咸)에 주(主)로 관여(關與)하며 Bacillus sp. B-1과 Bacillus sp. B-2는 furfuryl-n-butyrate, 그리고 Bacillus sp. B-3는 n-propylbenzene 의 생성(生成)에 주(主)로 관여(關與)하는것으로 밝혀 졌다.