• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1143-1148
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• 2005

Experimental results for heat transfer characteristic and pressure gradient of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during condensing inside horizontal double pipe heat exchangers are presented. The test sections which have one tube diameter of 12.70 mm with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than those of R-22 in 12.7 mm and 9.52 mm. This results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

• Journal of Crop Science and Biotechnology
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• 제10권3호
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• pp.141-146
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• 2007

The roots of Aristolochia elegans Mast.(Aristolochiaceae) are widely used in Mexican traditional medicine as a remedy for scorpion venom. Current experimental evidence supports its purported antidote properties. However, collection from the wilderness has lead to local extinction of natural populations. In order to contribute to species preservation, cultivation, and standardization of morphological and pharmacological properties, a micropropagation method was developed. This includes in-vitro germination of seeds to produce aseptic plantlets, induction of multiple budding, and acclimatization. The treatment with benzylamino purine(10 ${\mu}M$) induced the highest number of buds(3.1 on average) in both types of explants. On the other hand, indolebutyric acid(1.5 ${\mu}M$) caused the highest root index(11.8) per explant. One hundred percent of the micropropagated plantlets developed vigorously after the acclimatization process.

• Asian Journal of Atmospheric Environment
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• 제8권2호
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• pp.96-107
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• 2014

Extreme recovery of the thermal energy from the combustion of flue gas may bring about early gas condensation resulting in the increased formation of nitric acid vapor. The behavior of the nitric acid formed inside the stack and in the atmosphere was investigated through a computer-aided simulation in this study. Low temperatures led to high conversion rates of the nitrogen oxide to nitric acid, according to the Arrhenius relationship. Larger acid plumes could be formed with the cooled flue gas at $40^{\circ}C$ than the present exiting gas at $115^{\circ}C$. The acid vapor plume of 0.1 ppm extended to 25 m wide and 200 m high. The wind, which had a seasonal local average of 3 m/s, expanded the influencing area to 170 m along the ground level. Its tail stretched 50 m longer at $40^{\circ}C$ than at $115^{\circ}C$. The emission concentration of the acid vapor in the summer season was a little lower than in the winter. However, a warm atmosphere facilitated the Brownian motion of the discharged flue gas, finally leading to more vigorous dispersion.

• 동력기계공학회지
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• 제16권4호
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• pp.44-50
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• 2012

The present numerical study was performed to determine how the two perforated baffles( Inclined angle=$5^{\circ}$; perforation diameter=2cm) placed at a rectangular duct affect heat transfer and associated friction factors. The parametric effects of perforated baffles(3, 6 and 12 holes) and flow Reynolds number ranging from 28,900 to 61,000 on the heated target surface are explored. As for the investigation of heat transfer behaviours on the local Nusselt number with two baffles placed at $x/D_h=0.8$ and $x/D_h=0.8$ of the edge baffles, it is evident that the average Nusselt number increases with increasing number of holes, but the friction factor decreases with an increase in the hole number placed at baffles. The numerical results by commercial code CFX 10.0 are confirmed with the experimental data.

• 한국해양학회지
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• 제23권3호
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• pp.97-109
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• 1988

한국 동해의 wind stress와 wind-stress curl의 값을 수산진흥원 정선관측 바람자료를 근거로 하여 계산하였다. 바람에 의한 해수 이용을 염두에 두고 주로 지속적이고 강한 바람을 취해서 구한 월평균 wind stress 값들은 동해 전체에서 구한 기존의 값들과 거의 같았으나 wind-stress curl의 경우는 그 값이 훨씬 크게 나타났다. 이는 동해가 국지적으로 지형적인 영향을 받은 것으로 판단된다. 한편 바람에 의한 상층수의 이동으로 울릉도 부근에는 계절에 관계없이 난수괴(warm core)가 존재 하나 그 위치는 고정되어 있지 않다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.215-236
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• 2017

Obtaining accurate location information is important in practical applications of wireless sensor networks (WSNs). The distance vector hop (DV-Hop) is a frequently-used range-free localization algorithm in WSNs, but it has low localization accuracy. Moreover, despite various improvements to DV-Hop-based localization algorithms, maintaining a balance between high localization accuracy and good stability and convergence is still a challenge. To overcome these shortcomings, we proposed an improved DV-Hop localization algorithm based on the bat algorithm (IBDV-Hop) for WSNs. The IBDV-Hop algorithm incorporates optimization methods that enhance the accuracy of the average hop distance and fitness function. We also introduce a nonlinear dynamic inertial weight strategy to extend the global search scope and increase the local search accuracy. Moreover, we develop an updated solutions strategy that avoids premature convergence by the IBDV-Hop algorithm. Both theoretical analysis and simulation results show that the IBDV-Hop algorithm achieves higher localization accuracy than the original DV-Hop algorithm and other improved algorithms. The IBDV-Hop algorithm also exhibits good stability, search capability and convergence, and it requires little additional time complexity and energy consumption.

• 대한기계학회논문집
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• 제13권1호
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• pp.153-160
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• 1989

본 연구는 수평전도관과 수평원통 사이의 환상공간에 수직격판이 부착된 경우와 수평직판이 부착된 경우에 Rayleigh수와 무차원 관열전도율을 변수로하여 수직해석과 Mach-Mehnder 간섭계를 이용한 실험으로 자연대류 열전달특성을 연구 하였다.

• Archives of Reconstructive Microsurgery
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• 제11권2호
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• pp.179-185
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• 2002

The wrist and forearm are a frequently damaged area in high tension electrical injury as an input or output of the current. Electrical burns affecting the wrist and forearm may produce full thickness necrosis of the skin and damage deep vital structures beneath the eschar, affecting the local tendons, nerves, even bones and joints which result in serious dysfunction of the hand. From January 1997 to December 2001, we had treated 20 patients with high tension electrical burn in the wrist and forearm using anterolateral thigh free flap. Average follow up period were 24 months and we get satisfactory results both in functional and aesthetic aspects. This flap is considered useful in one-stage reconstruction of wide and large soft tissue defect combined with arterial injuries.

• 한국정밀공학회지
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• 제24권4호
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• pp.57-67
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• 2007

Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance fur mold parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface hardening for the case of SKD61 steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. From the results of the experiments, it has been shown that the maximum average hardness is approximatly 780 Hv when the power, focal position and the travel of laser are 1,095 W, 0mm and 0.3 m/min, respectively. In samples treated with lower scanning speeds, some small carbide particles appear in the interdendritic regions. This region contains fine martensite and carbide in proportions which depend on the local thermal cycle.

• Archives of Plastic Surgery
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• 제36권6호
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• pp.685-690
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• 2009

Purpose: Autologous fat graft is a widely accepted technique used for soft tissue augmentation. Nonetheless, the use of fat graft is limited by unpredictable survival rates and repeated grafting. To avoid repeated grafting, cryopreserved fat graft technique has recently been widely used. On the other hand, the number of patients with chronic infection(who received cryopreserved fat injection) has currently been increasing. Therefore, this study was focused on the safety of cryopreserved fat injection from the infection. Methods: We collected 150 samples from local aesthetic clinics to examine the safety of cryopreserved autologous fat. To test for microbacterial contaminations of the cryopreserved fat specimens, microbacterial cultures & antibiotics sensitivity tests were performed. Then, we examined possible correlation between the preservation period and donor sites, focused on the results of microbacterial culture. Results: Cultures were positive for Staphylococcus epidermidis in 5 samples(methicillin - resistant Staphylococcus epidermidis in 4 samples), Micrococcus species in 3 samples. An average duration of preservation was 191 days and there was no significant correlation between the duration of preservation and microbacterial growth. Conclusion: Staphylococcus epidermidis was the leading cause of cryopreserved fat contamination, and the resistance to methicillin is common. Based on the above results, aseptic handling of fat during harvesting and preservation appeared to be most important.