• 대한조선학회지
• /
• 제27권4호
• /
• pp.27-31
• /
• 1990

양력면(揚力面)의 양력계산(揚力計算)에 흔히 쓰이고 있는 방법(方法)을 크게 나누면 Vortex Lattice 법(法)과 Mode Function법(法)이 있다. 잘 알려진 것 처럼, Vortex Lattice법(法)은 해(解)의 수렴성(收斂性)은 좋으나 계산시간(計算時間)이 많이 걸리는 문제점(問題點)이 있고, Mode Function법(法)은 계산시간(計算時間)은 짧으나 해(解)가 특이(特異)해 지는 경우가 있다. 그러므로 본(本) 논문(論文)에서는 양방법(兩方法)의 장점(長點)들을 살리도록, 양력면(揚力面)을 Span 방향(方向)으로 분할(分割)하고 각(各) Strip Mode Function을 사용하여 Vortex를 분포(分布)시켜, 양력면이론(揚力面理論)으로 양력(揚力)을 계산(計算)하였다. 우선 Horn Type의 반균형타(半均衡舵)에 본(本) 계산법(計算法)을 적용(適用)하여 타직압력(舵直壓力)을 계산(計算)하고 타(舵) 단독시험(單獨試驗)을 병행(竝行)하여 계산법(計算法)의 유용성(有用性)을 검증(檢證)하였다. 그 결과(結果), Stall과 같은 비선형적(非線形的) 유체현상(流體現象)이 일어나지 않는 한(限), 본(本) 계산법(計算法)은 유용(有用)하다는 결론(結論)을 얻었다. 끝으로, 본(本) 계산법(計算法)을 평행(平行)하게 늘어선 한척(隻)의 장방형타(長方形舵)에 적용(適用)하여 두 타(舵) 사이의 상호간섭(相互干涉)도 계산(計算)하였다.

• 한국항공우주학회지
• /
• 제32권8호
• /
• pp.47-53
• /
• 2004

타원형 날개꼴의 공력 특성에 브로잉 제트 방식과 제트 방향의 영향에 대하여 실험을 통하여 연구를 수행하였다. 본 연구는 타원형 날개꼴의 박리제어에 있어서 브로잉 제트적용에 관한 기본 데이터를 축적하는데 목적을 두었다. 본 연구에서는 날개면에서의 압력 분포, 브로잉 제트 출구에서의 유속 분포 및 공력 자료를 제공하였다. 타원형 날개꼴에 대한 실험은 레이놀즈수 $8.22{\times}10^5$에서 수행하였다. 펄스제트는 후실속각 이후에 공력 특성을 향상시키는 효과를 보여 주었다. 즉, 펄스제트는 감소된 질량유동율로 상당히 높은 양력을 발생하였다. 제트 방향도 박리제어의 주요 파라미터임을 보였다. 양의 제트각은 박리를 지연시키거나 억제하였고, 음의 제트각은 박리를 오히려 촉진시켰다.

• Journal of Microbiology and Biotechnology
• /
• 제18권8호
• /
• pp.1377-1385
• /
• 2008

The uracil-sensing domain in archaeal family B-type DNA polymerases recognizes pro-mutagenic uracils in the DNA template, leading to stalling of DNA polymerases. Here, we describe our new findings regarding the molecular, mechanism underpinning the stalling of polymerases. We observed that two successive deaminated bases were required to stall TNA1 and KOD1 DNA polymerases, whereas a single deaminated base was enough for stalling Pfu DNA polymerase, in spite of the virtually identical uracil-sensing domains. TNA1 and KOD1 DNA polymerases have a much higher extension rate than Pfu DNA polymerase; decreasing the extension rate resulted in stalling by TNA1 and KOD1 DNA polymerases at a single deaminated base. These results strongly suggest that these polymerases require two factors to stop DNA polymerization at a single deaminated base: the presence of the uracil-sensing domain and a relatively slow extension rate.

• 한국유체기계학회 논문집
• /
• 제11권5호
• /
• pp.15-21
• /
• 2008

In modem wind power system of large capacity above 1MW, horizontal axis wind turbine(HAWT) is a common type. And, the optimum design of wind turbine to guarantee excellent power performance and its reliability in structure and longevity is a key technology in wind Industry. In this study, mathematical expressions based upon the conventional BEMT(blade element momentum theory) applying to basic 1MW wind turbine blade configuration design. Power coefficient and related flow parameters, such as Prandtl's tip loss coefficient, tangential and axial flow induction factors of the wind turbine analyzed systematically. X-FOIL was used to acquire lift and drag coefficients of the 2-D airfoils and we use Viterna-Corrigan formula to interpolate the aerodynamic characteristics in post-stall region. In order to predict the performance characteristics of the blade, a performance analysis carried out by BEMT method. As a results, axial and tangential flow factors, angle of attack, power coefficient investigated in this study.

• 동력기계공학회지
• /
• 제20권1호
• /
• pp.50-56
• /
• 2016

This paper handled an investigation on the turbulent flow characteristics of three-dimensional small-size axial fan(SSAF) according to operating loads. Also, it was carried out by unsteady-state, incompressible and three-dimensional large eddy simulation(LES). The downstream flow type of SSAF is changed from axial flow to radial flow around the beginning of stall region at the aerodynamic performance curve. Axial mean velocity component largely grows around blade tip at the operating point of A to D, but transverse and vertical mean velocity components as well as Reynolds shear stresses highly develop around blade tip at the operating point of E to H. On the other hand, the peak value of turbulent kinetic energy developed around blade tip shows the highest at the operating point of E.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.43-46
• /
• 2008

Quad-Rotor, which consists of four blades, performs a flight task by controling each rotation speed of the four blades. Quad-Rotor blade making no use of cyclic pitch or collective one is a type of fixed-wing as different from helicopter blade. Although, Quad-Rotor is simple and easy to control for those reasons, blade configuration of the fixed wing is one of the critical factors in determining the performance of Quad-Rotor. In the present study, coefficients for thrust and power of Quad-Rotor blade were derived from the data acquired by using 6-component balances. Firstly, Measurements for aerodynamic force were conducted at various pitch angles (i.e., from 0$^{\circ}$ to 90$^{\circ}$ with the interval of 10$^{\circ}$). The blade used in this experiment has aspect ratio of 6 and chord length of 35.5 mm. Secondly, assembled-blade, which was an integral blade but divided into many pieces, was used in order to test aerodynamic forces along twist angles. The curve of thrust coefficient along pitch angle indicates a parabola form. Stall which occurs during wind tunnel test to calculate lift coefficient of airfoil does not generate. When deciding the blade twist angle, structural stability of blade should be considered together with coefficients of thrust and power. Those aerodynamic force data based on experimental study will be provided as a firm basis for the design of brand-new Quad-Rotor blade.

• 한국축산시설환경학회지
• /
• 제19권2호
• /
• pp.141-148
• /
• 2013

This study was conducted to evaluate the effect of different housing systems on the performances of sows and their piglets during gestation. A total of 90 sows (Landrace ${\times}$ Yorkshire) were employed into 3 experimental farms to give 3 treatments, stall housing, group housing in either slatted floor or litter floor. Individual sow was used as an experimental unit. Group housed sows were fed with electronic sow feeder during gestation. Performance measures were taken on sows and piglets. Back-fat thickness and body condition score of sows were not affected by housing systems for pregnant sows. There was no difference of estrus interval of pregnant sows between housing systems. The lower number of still-birth was observed in group housing type. The number of wounded sows in slatted floor was remarkably increased compared with sows in litter floor. This study showed that the housing systems could fairly impact sow and piglet performances.

• 대한수의학회지
• /
• 제14권2호
• /
• pp.273-279
• /
• 1974

Studies were made on the relation of mastitis infection rate to the management and sanitations of dairy farms by examining 46 dairy herds. The results obtained were as follows: 1. The higher infection rate was observed in farms managed by employees than by owners, and in impoprted cattle than cattle horn in Korea. 2. Type of education and the period of experience of management were not correlated to the infection rate. 3. The infection rate was the highest in Summer and in cattle of 5~8 lactating age group. 4. It was observed that the amount of water supply, time of cleaning stall, frequency of disinfection, the method of using cleaning towel and the method of milking were correlated to the infection rate.

• Animal Bioscience
• /
• 제37권6호
• /
• pp.1110-1120
• /
• 2024

Objective: This study was conducted to evaluate the effect of offering (OSF) or not (NSF) supplemental feed at milking on temperament (TS), udder hygiene (UHS) and body condition (BCS) scores, and milk yield per milking (MYM), milk quality traits, and profitability of primiparous Anatolian buffalo cows at 90 days of lactation confined in closed-tied (CB) or semi-open free-stall (OB) barns. Methods: In Experiment I, 108 cows were selected to encompass four treatments (OBOSF, OB-NSF, CB-OSF, and CB-NSF) of 27 cows, considering barn type (OB and CB) and supplementary feed (OSF and NSF) at milking. In Experiment II, 60 OB cows were selected to encompass one of five groups of 12 cows each: i) no supplemental feed (CON), ii) commercial concentrate (CC), iii) CC + corn silage (CCS), iv) CCS + alfalfa hay (CSA), or v) CC + ryegrass silage (CRS) at milking. Results: The TS and UHS of the OB and OSF cows were lower (better) than those of the CB and NSF cows, respectively. The OSF increased milk protein, lactose, and solids-not-fat but decreased milk freezing point and electrical conductivity compared with the NSF. The MYM and milk fat of the OB-OSF cows were higher than those of the OB-NSF and CBNSF cows. The TS and UHS of the cows negatively correlated with MYM and some milk chemicals (fat, protein, and solids-not-fat), but BCS correlated positively. The TS and milk electrical conductivity of the CCS, CSA, and CRS cows were lower than those of the CON and CC cows, but BCS, MYM, and milk fat were higher. Partial budget analysis identified a higher net profit for supplemental feed-offered groups (OB-OSF, CCS, CSA, and CRS). Conclusion: Offering roughage with concentrates at milking for indoor primiparous buffalo cows is more conducive to well-being, milk yield, milk quality, and economy.

• 한국가축번식학회지
• /
• 제26권3호
• /
• pp.291-298
• /
• 2002

본 연구는 경상북도 영주지역의 한우 사육농가를 대상으로 사육규모와 형태, 사양관리 방법 등 번식우의 사양관리 형태와 번식우의 번식장애 발생률을 조사하였으며, 번식장애우에 대하여 proge-sterone제재인 control internal drug releasing for cattle(CIDR)를 처리하여 치료효과를 구명하기 위하여 수행하였다 번식장애우에 대한 CIDR 처리는 7일간 질내에 삽입하였으며, 제거 하루 전에 PGF$_2$$\alpha$를 투여하여 황체를 퇴행 발정을 유기하고 발정 확인 후 10시간 간격으로 인공수정을 실시 임신의 유무로 치료 판정한 결과는 다음과 같다. 1. 경북 영주지방의 127호의 한우 사육농가에서 사육하는 총 1,061두의 번식우의 번식상황을 조사한 결과 번식장애우는 209두로서 발생률은 19.7%이었다. 사육규모별 번식장애 발생율은 10두 이하, 10~20두 및 20두 이상 농가에서 각각 37.5, 14.7 및 13.6%로서 사육규모가 커질수록 발생률이 유의적으로(P<0.05) 낮아지는 경 향이 었다. 2. 번식우의 농가 사육형태별 번식장애 발생률은 계류사육이 30.4%로서 군사의 14.7%보다 유의 적으로(P<0.05) 발생률이 높았으며, 군사의 경우 두당 사육면적이 넓을수록 번식장애 발생률이 낮아지는 경향이었다. 3. 번식장애우의 산차별 분포를 보면 미경산우가 50.7%로 가장 많았으며 산차가 증가할수록 번식장애우에서 차지하는 비율이 감소하는 경향이었다. 4. 번식장애우의 요인별 분포는 무발정이 65.1%, 미약발정 29.2%, 난소낭종 4.3% 그리고 기타1.4%의 순으로 많이 분포되었다. 5. 209두의 번식장애우에 CIDR를 처리하고 인공 수정한 결과 157두가 임신되어 75.1%의 치료효과를 얻었다. 번식장애우의 신체충실 지수별 치료효과는 신체충실 지수가 1, 2 및 3인 경우 수태 율이 각각 85.7, 84.9 및 86.8%로서 유의 적으로(P<0.05) 높았으며, 전체적으로 다소 야윈 경우가 과비된 경우에 비하여 치료 효과가 좋았다. 본 연구결과를 종합하면, 한우 사육농가의 번식장애 발생률은 19.7%로서 사육규모가 커서 농가의 관심도가 높을수록 또한 계류보다는 넓은 면적에서 군사하는 경우가 번식장애 발생률이 낮았으며, 요인별로는 발정과 관련된 장애가 많았다. 이러한 번식장애우도 농가에서 손쉽게 이용할 수 있는 progesterone 제재인 CIDR를 처리함으로서 75.1%를 치료할 수 있으며 치료 효과를 높이기 위해서는 신체충실지수를 1, 2 및 3으로 유지하기 위한 적정 사양관리가 필요하다고 사료된다.