• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.315-319
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• 2014

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage ($V_{TH}$) under illumination with/without the gate bias, and the amount of shift in $V_{TH}$ is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in $V_{TH}$ under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.

• Wind and Structures
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• 제28권2호
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• pp.99-110
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• 2019

Vortex-Induced-Vibration (VIV) is one kind of the wind-induced vibrations, which may occur in the construction and operation period of bridges. This phenomenon can bring negative effects to the traffic safety or can cause bridge fatigue damage and should be eliminated or controlled within safe amplitudes.In the current VIV studies, one available mitigation countermeasure, the horizontal flow-isolating plate, shows satisfactory performance particularly in PI shaped bridge deck type. Details of the wind tunnel test are firstly presented to give an overall description of this appendage and its control effect. Then, the computational-fluid-dynamics(CFD) method is introduced to investigate the control mechanism, using two-dimensional Large-Eddy-Simulation to reproduce the VIV process. The Reynolds number of the cases involved in this paper ranges from $1{\times}10^5$ to $3{\times}10^5$, using the width of bridge deck as reference length. A field-filter technique and detailed analysis on wall pressure are used to give an intuitive demonstration of the changes brought by the horizontal flow-isolating plate. Results show that this aerodynamic appendage is equally effective in suppressing vertical and torsional VIV, indicating inspiring application prospect in similar PI shaped bridge decks.

• Clinical and Experimental Reproductive Medicine
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• 제46권1호
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• pp.30-35
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• 2019

Objective: Bilateral uterine artery ligation (UAL) is a fertility-preserving procedure used in women experiencing postpartum hemorrhage (PPH). However, the long-term effects of this procedure on ovarian function remain unclear. The aim of this study was to investigate whether bilateral UAL compromised ovarian reserve and ovarian blood supply. Methods: This prospective study included 49 women aged between 21 and 36 years who had undergone a cesarean section for obstetric indications. Of these, 25 underwent uterine bilateral UAL to control intractable atonic PPH. The control group consisted of 24 women who had not undergone bilateral UAL. Standard clinical parameters, the results of color Doppler screening, and ovarian reserve markers were assessed in all participants at 6 months after surgery. The clinical parameters included age, parity, cycle history, body mass index, and previous medication and/or surgery. Color Doppler screening findings included the pulsatility index (PI) and resistance index (RI) for both the uterine and ovarian arteries. The ovarian reserve markers included day 3 follicle-stimulating hormone (FSH) levels, antral follicle count, and $anti-M\ddot{u}llerian$ hormone (AMH) levels. Results: There were no significant differences in the ovarian reserve markers of day 3 FSH levels, antral follicle count, and AMH levels between the study and control groups (p> 0.05 for all). In addition, no significant differences were observed in the PI and RI indices of the uterine and ovarian arteries (p> 0.05 for all). Conclusion: In this study, we showed that bilateral UAL had no negative effects on ovarian reserve or ovarian blood supply, so this treatment should be used as a fertility preservation technique to avoid hysterectomy in patients experiencing PPH.

• Wind and Structures
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• 제22권5호
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• pp.555-571
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• 2016

A hanging-type sand-retaining wall is a very common sand-blocking fence structure used to prevent sand movement. This type of wall is widely used along the Qinghai-Tibet and Gobi desert railways in Xinjiang, Western China. To analyze the characteristics of wind-sand flow fields under the effect of such a sand fence structure, a wind tunnel test and a field test were carried out. The wind tunnel test showed the zoning characteristics of the flow fields under the effect of the hanging-type sand-retaining wall, and the field test provided the sediment transport data for effective wind-proof interval and the sand resistance data in the front and behind the sand-retaining wall. The consistency of the wind-sand flow fields with the spatial distribution characteristic of wind-carried sand motion was verified by the correspondences of the acceleration zone in the flow field and the negative elevation points of the percentage variations of the sand collection rate. The spatial distribution characteristic of the field sand collection data further showed the spatial structural characteristic of the sandy air currents under the action of the hanging-type sand-retaining wall and the sand resistance characteristic of the sand-retaining wall. This systematic study on the wind-sand flow fields under the control of the hanging-type sand-retaining wall provides a theoretical basis for the rational layout of sand control engineering systems and the efficient utilization of a hanging-type sand-retaining wall.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.777-783
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• 2000

Composting by negative aeration is a reasonable proposition to control odor generated during composting process. Cattle manure and rice hulls mixtures were composted in a bin composting system by negative aeration. Continuous(CA) and intermittent(IA) aeration methods were applied to analyze the composting characteristics. The composting temperature and the ammonia emission during composting were investigated according to the aeration methods. The main problem for the negative aeration was the generation of condensate in the suction line of blower. The quantity of condensate was significant for continuous aeration. The aeration method should be modified to escape from the cooling effect of continuous aeration at the initial stage of composting. It took a longer time to finish a composting for intermittent aeration on account of lower aeration. It was concluded that the composting by negative aeration could be accomplished by either continuous or intermittent aeration method if the flow rate would be controlled more efficiently and the water vapor in suction line of blower could be removed effectively. Ammonia emission increased up to maximum value of 675ppm for continuous aeration while 300ppm for intermittent aeration. However, the cumulative value of ammonia emission was larger for intermittent aeration than for continuous aeration.

• 대한기계학회논문집B
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• 제25권1호
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• pp.18-28
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• 2001

The present study investigates flow dynamics between two dimensional compliant plates under sinusoidal flow conditions in order to understand influence of wall motion, impedance phase angle (time delay between pressure and flow waveforms), and non-Newtonian fluid on wall shear stress using computational fluid dynamics. The results showed that wall motion induced additional terms in the streamwise velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. The trend of the changes was very different depending on the impedance phase angle. As the impedance phase angle was changed to more negative values, the mean wall shear stress decreased while the amplitude of wall shear stress increased. As the phase angle was reduced from 0°to -90°under $\pm$4% wall motion, the mean wall shear stress decreased by 12% and the amplitude of wall shear stress increased by 9%. Therefore, for hypertensive patients who have large negative phase angles, the ratio of amplitude and mean of the wall shear stress is raised resulting in a more vulnerable state to atherosclerosis according to the low and oscillatory shear stress theory. We also found that non-Newtonian characteristics of the blood protect atherosclerosis by decreasing the oscillatory shear index.

• KDI Journal of Economic Policy
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• 제37권1호
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• pp.19-44
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• 2015

This paper examines the effect of the global financial crisis on corporate investment in Korea. Specifically, the crisis was considered to have possibly constrained firm-level investment as the negative shock to the credit supply dramatically unfolded. As Duchin et al. (2010) demonstrated, if a negative supply-side shock is evident during a crisis period, larger cash holdings before the crisis will lead to fewer constraints to corporate investment, or vice versa. In order to investigate the supply-side effect of the crisis, we use firm-level financial data, including firms listed on the Korean stock market as well as small and medium-sized enterprises. We find that corporate investment declined significantly after the crisis, even if we control for factors associated with the demand side, such as contemporaneous capital productivity and cash flow. More importantly, the decline is positively and significantly related to cash holdings before the crisis, implying the negative effect of a credit supply shock. Small and medium enterprises experienced relatively sharp investment declines compared to those of larger firms, and the relationship between pre-crisis cash amounts and the degree of investment decline is greater than that in large firms. Additionally, we examine whether the negative effect persists up to the present, finding evidence that the cash-investment relationship continues in small and medium-sized enterprises.

• 한국게임학회 논문지
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• 제10권5호
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• pp.75-85
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• 2010

게임 산업의 양적인 성장과 더불어 사회적 문제로 게임 중독 역시 증가되어 왔다. 게임 중독의 대응 방향으로 피로도 시스템 도입이 제시되었다. 본 연구에서는 몰입과 중독에 영향을 미치는 '자기통제력', '긍정적 기대', '관심', '경쟁심', '긍정적 자기효능감', '부정적 자기효능감' 6개의 요인이 피로도 시스템 이용 여부에 따라 '몰입'에 어떠한 영향을 미치는지 실증 분석하였다. 이를 통해 피로도 시스템을 적용하는 게임 개발 시 이용자의 몰입을 향상시키기 위하여 어떠한 전략을 개발하고 구사해야하는 가에 대한 이론적, 실무적 함의를 제공하고자 한다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.291-293
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• 2015

The experimental study on flow characteristic in various laminar coflow diffusion flame has been conducted with a particular focus on the buoyancy force exerted from gaseous hydrocarbon fuels. Methane ($CH_4$), Ethylene ($C_2H_4$) and n-Butane ($C_4H_{10}$) were used as fuels. Coflow burner and Schlieren technique were used to observe the fuel flow field near nozzle exit and flow characteristics in flames. The result showed that the vortices in n-Butane with density heavier than air were appeared near the nozzle exit with the strong negative buoyancy on the fuel stream. As Reynolds number increases by the control of velocity, the vortices were greater and the vortices tips were moved up from the nozzle exit. In addition, it can be found that the heated nozzle can affect to the flow fields of fuel stream near the nozzle exit.

• 한국식품영양과학회지
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• 제44권8호
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• pp.1105-1113
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• 2015

혈행 개선 기능성을 평가하기 위하여 8주 동안 일반식이와 고지방식이를 제공하는 그룹에 오메가-3 지방산과 복분자종자유를 일정량 제공하는 실험을 실시하였다. 실험군은 일반식이 그룹과 고지방식이 그룹으로 나누어 각 그룹 내에 음성대조군, 양성대조군(오메가-3 지방산), 복분자종자유(2 g, 4 g/2,000 kcal) 급이군으로 구성하였다. 양성대조군과 복분자종자유는 매일 경구 투여되었고 실험기간 종료 후 동물을 희생시켜 혈액과 장기를 얻어 혈중중성지방 및 콜레스테롤, 혈행 개선에 관련된 바이오마커(coagulation factor7, 12, serotonin과 TXB2)를 측정하였는데, 그 결과 복분자종자유는 혈중지질의 농도 개선을 통해 혈액의 점도를 감소시키고 혈액의 응고를 억제하여 혈행을 개선하는 기능성이 있는 것을 확인하게 되었다. 따라서 복분자종자유를 이용한 건강기능식품 개발은 혈관질환 환자들에게 혈행 개선을 통한 건강증진 효과를 보여줄 것으로 판단된다.