• 한국항공우주학회지
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• 제40권6호
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• pp.467-474
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• 2012

무인항공기의 정찰 및 정보 수집 능력을 효율적으로 수행하기 위해 장기 체공 능력이 요구된다. 분산 추진 장치는 대형 추진 장치를 복수의 소형 추진 장치들로 대체하여 추력을 얻는 장치이다. 날개의 스팬 길이를 따라 넓게 분포하여 효율이 증가하며, 유동의 흡입을 통해 경계층을 제어하고 출구에서 분사되는 흐름이 항공기에 부착되어 흐르기 때문에 양항비가 증가한다. 본 연구에서는 전익기 융합익기와 분산 추진 장치가 장기 체공 성능을 향상시키는 점에 착안하여 연구를 수행하였다. Eppler 337 에어포일 유닛에 추진 장치의 위치 및 입 출구 가로세로비 변화에 따라 나타나는 공력특성을 분석했다. CFD를 사용하여 공력해석을 수행하였고, 빠른 해석 결과를 얻을 수 있도록 팬 영역에 작동판 이론을 적용하였다. 양항비와 모멘트 비교를 통해 추진 장치의 위치 및 형상을 결정하고자 한다.

• Asian-Australasian Journal of Animal Sciences
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• 제17권2호
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• pp.213-220
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• 2004

The purpose of this experiment was to investigate the effect of the diets supplemented with lard or prilled fat ($Carolac^{(R)}$) on lactation performance, plasma constituents and ruminal characteristics of Holstein cows under a warm climate. In trial 1, 18 Holstein cows, 14 primiparas at 43 DIM and 4 multiparas at 55 DIM, were randomly assigned into six $3{\times3}$ Latin squares, in which three dietary treatments were isoproteinous but varying in energy contents and three 21 d periods. The treatments were basal diet (Control), basal diet supplemented with 2.5% lard (LD), and basal diet supplemented with 2.5% commercial Prilled fat (PF). In trial 2, three rumen canulated pregnant nonlactating Holstein cows with 550 kg average body weight were allotted into a $3{\times}3$ Latin square design with diets same as in trial 1 were fed to the cows at the level of 1.5% body weight on dry matter (DM) basis. The results indicated that the DM intake did not differ among the treatments. Milk yield and 4% FCM yield were greater (p<0.05) in PF than in Control. LD and PF resulted in greater milk fat percentage. Protein, lactose and solid contents in milk were not different among the three dietary treatments. The concentration of nonesterified fatty acids (NEFA) in plasma was significantly greater in LD and PF than that in Control. However, the concentrations of triglycerides, urea nitrogen, and cholesterol in plasma were not significantly different among the three treatments. Although the ruminal molar percentage of isobutyrate in LD and PF was greater, no significant difference was observed in ruminal pH, NH3-N concentration and VFA production among the three treatments. Diet supplemented with fat can improve milk yield and milk fat percentage without resulting in disadvantages of ruminal characteristics in cows at early lactation and under warm climate.

• Journal of Animal Science and Technology
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• 제55권4호
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• pp.295-301
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• 2013

This study was conducted to evaluate the effects of chelated Cu and Zn on growth performance, nutrient digestibility, blood profiles, and fecal noxious gas emission in weanling pigs. A total of 90 weanling pigs with an initial body weight (BW) of $5.27{\pm}0.04kg$ were randomly allotted to two dietary treatments for 42 d. Pigs were then fed a control diet (CON) or a Zinpro diet (CON + 0.1% chelate copper and zinc). There were nine replicate-pens with five pigs in each pen. During d 0 to 14 and d 14 to 28, the ADFI decreased (p<0.05) and the G/F increased (p<0.05) in pigs fed the Zinpro diet compared with those that received the CON diet. During d 28 to 42, the ADFI increased (p<0.05) in pigs fed the Zinpro diet relative to those fed the CON diet. Additionally, the apparent total tract digestibility of DM, N, and energy increased (p<0.05) in the Zinpro group when compared to the CON group on d 14 and 28. The lymphocyte percentage was also greater (p<0.05) in the Zinpro group than in the CON group. Overall, dietary supplementation with 0.1% chelate copper and zinc improved the growth performance and nutrient digestibility in weanling pigs.

• 한국가금학회지
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• 제49권1호
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• pp.9-14
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• 2022

This study was conducted to investigate the effects of dietary inclusion of phytase on the growth performance, organ weight, and tibia ash of broilers. A total of 1008 one-day-old Ross 308 broiler chicks (mixed gender) with body weight 42 ± 0.90 g (mean ± SD) were used in a trial for 32 d. Chicks were assigned to one of the two treatment diets. Each treatment consisted of 28 replicate cages, with 18 birds per cage. The dietary treatments were as follows: CON, basal diet; TRT1, basal diet + phytase 1,500 Fan Terminal Unit (FTU)/kg diet. Dietary inclusion of 1,500 FTU/kg phytase supplementation in broilers showed only slight improvements in daily feed intake (P=0.086) and feed conversion ratio (P=0.065) on day 9 compared with that in the control group. However, organ weights of the breast muscle, liver, spleen, kidney, and bursa of Fabricius were not affected by the dietary treatments. In addition, the dietary inclusion of 1,500 FTU/kg phytase supplementation in the broiler diet had no effect on tibia ash. The addition of 1,500 FTU/kg phytase in the basal diet of broilers did not have any adverse effect on growth performance, organ weight, and tibia ash, suggesting that phytase supplementation in broiler diets will exhibit comparable effects as that of corn-soybean meal-based diet.

• Asian-Australasian Journal of Animal Sciences
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• 제29권6호
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• pp.901-907
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• 2016

The present study investigated stocking density and genetic lines, factors that may alter the severity and incidence of angel wing (AW), in White Roman geese. Geese (n = 384) from two genetically selected lines (normal- winged line, NL, and angel-winged line, AL, respectively) and one commercial line (CL) were raised in four pens. Following common commercial practice, low-stocking-density (LD), medium-stocking-density, and high-stocking-density treatments were respectively administered to 24, 32, and 40 geese per pen at 0 to 3 weeks ($1.92m^2/pen$) and 4 to 6 weeks ($13.2m^2/pen$) of age and to 24, 30, and 36 geese at 7 to 14 weeks ($20.0m^2/pen$) of age. The results revealed that stocking density mainly affected body weight gain in geese younger than 4 weeks, and that geese subjected to LD had a high body weight at 2 weeks of age. However, the effect of stocking density on the severity score of AW (SSAW) and incidence of AW (IAW) did not differ significantly among the treatments. Differences were observed among the genetic stocks; that is, SSAW and IAW were significantly higher in AL than in NL and CL. Genetic selection generally aggravates AW, complicating its elimination. To effectively reduce IAW, stocking density, a suspected causal factor, should be lower than that presently applied commercially.

• 설비공학논문집
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• 제1권2호
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• pp.116-127
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• 1989

Research on reheating cooling cycle and its practical application have been made to prevent unequalized distribution of temperature and humidity of room due to lack of supply air volume and dewdrops on supply diffusers to be taken place as a result of lower temperature of supply air than that of dew point of room air in cooling cycle of constant air volume, single duct, single zone and draw-through fan type. In view of the fact that human body is insensitive to humidity, it is possible not only to construct the complete non-reheating cooling cycle by increasing the humidity point allowable with the deduction of occupant's sense of pleasantness minimizing, but also to get cooling cycle decreasing the reheating quantity if the humidity exceeds the point allowable. In addition, it is possible to save maximum 8% in electric energy for cooling in cooling system by constructing non-reheating cooling cycle instead of reheating cooling cycle and by increasing the relative humidity of room from 50% to 65% in case efficiency and air pressure of cooling system are low. It is also possible to get an optimum cooling cycle by determining the room humidity in consideration of pleasantness of occupants and conservation rate of electric energy if the cooling capacity, efficiency and total pressure of cooling equipment are fixed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.883-888
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• 2008

Various effluents generated in cooking processes contribute a great deal to indoor air pollution among many other indoor pollutants such as dusts from outdoor and carbon dioxide from human body. Kitchen exhaust hoods are not believed to exhaust indoor contaminants properly in many cases, while generating too much noise. Instead of focusing on individual products of kitchen hoods, we should address the problem by attacking the ventilation system as a whole including vertical shafts and building air-tightness. In this study, it is intended to investigate the pressure distribution along the vertical shaft depending on various system parameters, such as shaft size, concurrent hood usage rate, roof fan, inlet pressure loss, and outdoor temperature. The maximum static pressure in the vertical shaft has been obtained using the method of design of experiments and analyzed by the analysis of variance. The results can be used for the design of kitchen exhaust systems by analyzing the pressure distributions in vertical shafts.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.271.1-271.1
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• 2013

Titania is usually used in sun-screens, tooth paste, and other daily used objects as a pigment. However, scientists have focused on titania as photocatalyst due to its excellent activities. By fabricating vanadium doped TiO2 and CuOx co-catalyzed TiO2 nano-size filter, the degradation level of the volatile organic compound (VOC) concentration was tested using 365nm UV LED as light source in a closed chamber. Main purpose for this test is to evaluate the activities of various catalysts for degrading the VOCs which are detrimental to human body and toluene and p-xylene were chosen in the VOC removal test. Target gas materials were injected into the test chamber with dry air as carrier gas which was flowed into the gas washer bottle filled with liquid form of VOC substance. When the VOC gas flows into the chamber, it is circulated by 200 mm fan in order to contact with the set-up filter on the aluminum holder. Target gas concentration in the chamber was monitored using VOC detector (miniRae3000, Raesystems) which was also placed inside the chamber. With the measured concentration, the VOC degradation efficiency and the degradation rate were evaluated and used to compare the catalytic activities.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권4호
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• pp.286-290
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• 2021

Objectives: The use of fat grafts in maxillofacial sculpturing is currently a common technique. Unlike fillers, autologous fats unite with facial tissues, but long-term results may still be unsatisfactory. Sharing long-term follow-ups can be helpful in making outcomes more predictable. Materials and Methods: The data from patients who were admitted from 2014 to 2016 for fat augmentation were collected. In all cases, fat grafts were injected by blunt cannula using a tunneling technique in different planes. A fan shape order for the malar, periorbital, nasolabial fold, mandibular angle and body, and perioral area was established. Results: Autologous fat was used for different sites of the maxillofacial regions. Of 15 patients, two patients were not satisfied due to fat graft resorption. For this, further injections were performed six months after the first injection using preserved fat grafts. One patient continued to be dissatisfied. There were no other complications related to fat transplants. Conclusion: Fat transplantation is a safe, reliable, and non-invasive method for facial contour and facial soft tissue defect restoration. Additional methods such as mesenchymal stem cells along with fat injection increase the survival rate of transferred fat.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1655-1666
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• 2003

It is experimentally well-known that high anisotropies of the turbulent flow field are dominant inside the tip leakage vortex, which is attributable to a substantial proportion of the total loss and constitutes one of the dominant mechanisms of the noise generation. This anisotropic nature of turbulence invalidates the use of the conventional isotropic eddy viscosity turbulence models based on the Boussinesq assumption. In this study, to check whether an anisotropic turbulence model is superior to the isotropic ones or not, the results obtained from the steady-state Reynolds averaged Navier-Stokes simulations based on the RNG k-$\varepsilon$ model and the Reynolds stress model (RSM) are compared with experimental data for two test cases: a linear compressor cascade and a forward-swept axial-flow fan. Through this comparative study of turbulence models, it is clearly shown that the RSM, which can express the production term and body-force term induced by system rotation without introducing any modeling, should be used to predict quantitatively the complex tip leakage flow, especially in the rotating environment.