• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.349-362
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• 2018

A non-linear numerical simulation technique for predicting the unsteady performances of an airbreathing engine is developed. The study focuses on the simulation of integrated propulsion systems, where a closer coupling is needed between the airframe and the engine dynamics. In fact, the solution of the fully unsteady flow governing equations, rather than a lumped volume gas dynamics discretization, is essential for modeling the coupling between aero-servoelastic modes and engine dynamics in highly integrated propulsion systems. This consideration holds for any propulsion system when a full separation between the fluid dynamic time-scale and engine transient cannot be appreciated, as in the case of flow instabilities (e.g., rotating stall, surge, inlet unstart), or in case of sudden external perturbations (e.g., gas ingestion). Simulations of the coupling between external and internal flow are performed. The flow around the nacelle and inside the engine ducts (i.e., air intakes, nozzles) is solved by CFD computations, whereas the flow evolution through compressor and turbine bladings is simulated by actuator disks. Shaft work balance and rotor dynamics are deduced from the estimated torque on each turbine/compressor blade row.

• 영어영문학
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• 제56권3호
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• pp.487-500
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• 2010

In the history of colonization, how and to what extent the colonizer interacted with the local population differed according to race relations in specific periods. Generally speaking, social or sexual contact between two communities was tolerated when race relations were relatively relaxed. When the racial relationship became aggravated, however, such contact between the colonizer and the colonized was discouraged in order to forge and maintain ethnic solidarity. In Ireland, the colonizer's interaction with the colonized was not different from that of colonized countries in the Third World. Unlike those colonies, however, the settlers, that is, Protestants, simply could not be treated as the colonizer because they had lived in Ireland long enough to assert their Irishness. Joyce is keenly interested in intergender ethnic boundary crossings. In his works, two kinds of ethno-sexual interactions are presented from two totally different perspectives. As shown in the cases of the young lady in the street stall, Polly, Milkwoman, Sheila, and Cissy, Joyce describes the interaction of Irish women with Englishmen from a skeptical viewpoint. All of those cases demonstrate typical relationships epitomizing power relations in a colonial society. They reflect the turbulent time at the beginning of the century when Ireland had to fight with England to gain its independence. At such a transitional time, the ethnic relationship became aggravated and boundary crossings were discouraged. On the other hand, through the relationship between Stephen and Eileen, Girty and Reggy Wylie, Browne and Irish ladies, and Mr. & Mrs. Kernan, Joyce presents the interaction between Protestants and Catholics in terms of romantic or human relationships rather than power relations. From his description of those interactions, we can assume that Joyce, in the time of nation building, provided a blueprint for the future Irish nation, where Protestants and Catholics could build a nation and live harmoniously.

• Journal of Animal Science and Technology
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• 제52권1호
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• pp.57-64
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• 2010

This study was conducted to compare the aspects of behavior between miniature pigs and conventional sows during gestation and lactation periods. Miniature pigs and conventional sows at 3 parity were used in this experiment with 4 pigs per treatment. The behavioral patterns and stereotyped behaviors were observed on day 60 and 90 of gestation, at farrowing, and on day 10 of lactation before and after the feeding. On 60 and 90 days of pregnancy, both treatments showed the tendency of frequent lateral lying rather than other postures. On ventral lying, eating and drinking, miniature pigs spent more time than conventional pigs at day 90 of gestation (P<0.01, P=0.0539, P<0.05, respectively). The occurrence of stereotyped behaviors included bar biting and bar mouth chewing. At 90 day of pregnancy was observed, conventional pigs was higher than miniature pigs (P<0.05). At farrowing, miniature pigs spent more time on ventral lying, standing and walking than conventional sows (P<0.05), however, there were more frequency of drinking and eating. And on day 10 of lactation, there was no significant difference in stereotyped behaviors between miniature pigs and conventional sows. In conclusion, miniature pigs were generally more sensitive than conventional sows although sows were reared in stall during gestation and lactation period and the behavioral pattern during lactating period showed the similarity between miniature pigs and conventional sows for protection of nursing pigs. In consideration of the general reproductive performance of conventional sows, the high sensitivity and stress of miniature pigs did not affect the reproductive performance of miniature pigs.

• Journal of Animal Science and Technology
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• 제45권6호
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• pp.1067-1078
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• 2003

산차가 다른 임신모돈의 임신기간 동안 스톨수용과 군사수용이 임신, 분만 및 비유기간 중 모돈의 행동패턴과 이상반복행동 및 분만성적에 미치는 영향을 조사하기 위하여 총 18두의 듀록(Duroc)종 모돈을 산차별로 1산차, 2${\sim}$3산차 및 4${\sim}$5산차 각각 3두씩 배치하여 임신초기 4주간은 스톨에 수용 후 각각 스톨과 군사돈방에 수용하였고, 분만예정일 7일전에 분만돈방으로 옮겼으며 21일간 포유로 수행하여 얻은 성적은 다음과 같다. 임신기간 동안의 모돈 행동패턴과 이상반복행동은 임신 60일과 90일 경과 시점에 24시간 동안, 분만당일 모돈 행동은 분만 2시간 전부터 후산이 배출되는 시점까지 약 6시간 동안, 비유기간 동안의 모돈 행동은 분만 10일 후, 2시간 반 동안 조사하였다. 또한 임신기간 동안 군사수용과 스톨수용 모돈의 분만성적을 비교하였다. 임신기간 동안 군사수용과 스톨수용 모돈의 행동은 옆으로 누워(ventral lying)있는 시간 비율이 양쪽 모두 가장 높았고, 산차에 따라서는 초산 모돈(71.3%)이 가장 높았다. 걷는(walking) 동작은 스톨수용 보다 군사수용이 월등히 높게 나타났고(8.68% 대 16.38%, SE=1.74; P<0.01), 산차 간에는 초산 모돈이 가장 낮았다. 마시는 (drinking) 동작으로 보낸 시간 비율은 군사수용 보다 스톨수용(0.27% 대 1.99%, SE=0.28)이 월등히 높게 나타났다(P<0.01). 임신기간 동안 나타내는 이상반복행동 발현수는 헛 씹기(vacuum chewing)가 스톨수용 임신 60일 경과시 가장 높았고, 산차와 임신일 간의 상호작용에서는 4${\sim}$5산차 임신돈의 임신 60일 경과가 높았다(P<0.05). 코로 바닥 문지르기(floor snout rubbing)는 수용형태${\times}$산차의 상호작용이 나타났으며, 군사 1산차가 가장 높게 나타났다(P<0.05). 바닥 핥기(floor licking)는 임신 90일이 높았고(P<0.01), 수용형태$\times$임신일의 상호작용에서는 군사 90일이 높게 나타났다. 머리 흔들기(head waving)은 임신 60일이 높게 나타났으며, 쇠 핥기(bar licking)는 임신 90일이 높게 나타났다(P<0.05). 총 이상행동의 발현수는 스톨수용과 군사수용 간에 차이가 나타나지 않았다. 분만돈의 행동패턴은 앉아 있는 자세와 먹는 자세로 보낸 시간 비율만 유의적인 차이를 나타내었고, 앉아 있는 자세에서는 스톨수용 1산차(3.7%)와 군사수용 2${\sim}$3산차(2.7%)가 다른 산차 보다 높게 나타났다. 먹는 자세로 보낸 시간 비율은 군사 2${\sim}$3산차 만이 낮게 나타났다. 비유모돈의 행동패턴은 임신기간 동안 군사수용 1산차 모돈의 옆으로 누워 있는(ventral lying) 시간 비율이 높았고, 마시는(drinking) 동작은 임신기간 동안 스톨 수용 모돈이 높았으며, 특히 초산 모돈이 다른 산차의 모돈에 비하여 많은 시간을 물먹는데 소비하는 것으로 나타났다. 이상의 결과를 종합해 보면, 임신기간 동안 수용형태에 따른 임신돈의 임신기간 동안의 행동패턴과 이상반복행동 발현수의 차이는 나타나지 않았으나, 비유모돈의 행동패턴과 이상반복행동 발현에 대한 결과는 군사수용 모돈이 보다 좋은 복지 상태에 있다는 것을 나타내고 있다. 또한 분만성적이 임신기간 동안 스톨수용과 군사수용 간에 차이를 나타내지 않았다. 따라서 모돈의 보다 많은 정상행동을 보장하고 복지상태를 개선하기 위해서는 임신돈의 군사수용은 스톨수용을 대체할 사양체계로서 그 가능성은 충분하며, 실제 적용을 위한 보다 진전된 연구가 필요한 것으로 사료된다.

• 한국유체기계학회 논문집
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• 제18권6호
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• pp.63-70
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• 2015

This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

• Asian-Australasian Journal of Animal Sciences
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• 제31권5호
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• pp.748-754
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• 2018

Objective: The preference evaluation of cattle is an important factor for estimation and improvement of the grazing amounts of newly introduced or bred grasses or cultivars in barn. This study was performed to assess the grazing behavior (the amount of grazing and/or the grazing speed) of cattle as indirect method using newly bred Brachiaria ruziziensis tetraploid strain 'OKI-1'(BR) hay as treatment group and Cloris gayana 'Callide' (CG) hay as control group. It also compared the feasibility of using behavioral differences between two groups as one criteria for evaluating preference by Japanese black cattle in barn. Methods: Three experiments were carried out using 12 growing Japanese Black cattle including 6 males and 6 females. In each experiment, the four Japanese Black cattle (2 males and 2 females) were placed in separated stall and allowed to graze BR and CG in manger that was separated into two portions for about 30 min. The position and behavior of the cattle were recorded, and weighed the residual of each gay at 15 and 30 minutes after experiment start. Results: The BR was superior to CG in chemical composition such as protein, fibers and non-fibrous carbohydrate. The cattle, over all, tended to prefer BR over CG in the first half 15 minutes in terms of the time spent and amount of grazing. Additionally, growing cattle exhibited neophilia for BR bred newly. Conclusion: These findings indicated the current approach could be applied for one of criteria to evaluate the preference of hay by Japanese black cattle under indoor housing environment.

• Advances in aircraft and spacecraft science
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• 제10권4호
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• pp.303-315
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• 2023

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0° to 18° with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K- SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-kl-omega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.

• 한국항공우주학회지
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• 제50권2호
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• pp.93-101
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• 2022

실속, 결빙, 센서 이상 등으로 인해 일어나는 제어불능 또는 비정상 비행 상황은 항공기의 추락으로 이어지기 때문에 필수적으로 대비해야 한다. 이와 관련해 비정상 비행 상황에서 항공기의 동적 특성을 정확하게 파악하는 것은 매우 중요하다. 본 논문에서는 일시적인 센서 이상이 발생한 고받음각의 비정상 비행상태 항공기에 대해서 기존의 칼만 필터 기반의 시스템 식별법 대비 보다 효과적인 적응 차수 조노토픽 칼만 필터와 이동창-최소자승법을 활용한 시스템 식별법을 제시하였다. 제안한 방법을 실제 비행 데이터에 적용하고 그 성능을 기존 연구 결과와 비교하였다.

• 대한전자공학회논문지SD
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• 제37권12호
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• pp.79-90
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• 2000

본 논문에서는 고성능 수퍼스칼라 마이크로프로세서에 적합하고, IEEE 754 표준을 준수하는 고성능 부동 소수점 유닛의 구조를 설계한다. 부동 소수점 AU에서는 비정규화 수 처리를 모두 하드웨어적으로 지원하면서 추가적인 지연 시간이 생기지 않도록 점진적 언더플로우 예측 기법을 제안 구현한다. 부동 소수점 제산/제곱근기는 기존의 고정적인 길이의 몫을 구하는 방식과 달리 매 사이클마다 가변적인 길이의 몫을 구하는 구조를 채택하여 성능과 설계 복잡도 면에서 SRT 알고리즘에 의한 구현 보다 우수하도록 설계한다. 또한, 수퍼스칼라 마이크로프로세서에 이식이 용이하도록 익셉션 예측 기법을 세분화하여 적용하며, 제산 연산에서의 익셉션 예측에 필요한 스톨사이클을 제거하도록 한다. 설계된 부동 소수점 AU와 제산/제곱근기는 부동 소수점 유닛의 구성요소인 명령어 디코더, 레지스터 파일, 메모리 모델, 승산기 등과 통합되어 기능과 성능을 검증하였다.

• 대한기계학회논문집A
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• 제36권9호
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• pp.1065-1071
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• 2012

풍력발전기의 안정적인 전력생산은 정격풍속 이상에서 피치제어와 스톨제어와 같은 일정속도제어로 이루어지고 있다. 최근, 효율적인 전력생산을 위하여 정격풍속 이하의 변동풍속 조건에서 최대 출력을 얻기 위한 가변 속도제어가 적용되고 있는 추세이다. 기존의 피치제어기에서는 지글러-니콜스 계단응답법에 의한 제어기 최적화가 이루어지고 있으나, 가변 속도제어의 요구로 보다 정확한 최적화가 필요하게 되었다. 본 연구에서는 기존의 지글러-니콜스 계단응답법을 개선하기 위하여 라틴 하이퍼큐브 샘플링을 통한 신경망모델을 구축하고, 구축된 PID 제어 계수 신경망모델에 유전자 알고리즘을 적용하여 피치제어기를 최적화하였다. 유전자 알고리즘으로 구한 최적해가 지글러-니콜스 계단응답법의 초기해 보다 평균제곱근 오차가 13.4% 향상되었고, 응답특성을 나타내는 상승속도와 정착시간은 각각 15.8% 및 15.3%으로 개선되었다.