• 한국초지조사료학회지
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• 제14권1호
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• pp.27-33
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• 1994

This study was conducted to determine the nutritional value of native oriental white oak(Quercus aliena Blume) browse by Korean native goats. Oak browse were mixed with grass hay(orchardgrass 60% and red clover 40%), varing in oak browse content. Diets included 30% oak browse and 70% grass hay, 60% oak browse and 40 % grass hay, and a 100% grass hay(contro1). Oak browse diets were higher in NDF, ADF, lignin, and tannin contents, but lower in CP content than the control diet with increased oak browse levels. Gross energy levels showed no difference between the control and oak browse diets. Dry matter intake was the lowest on diet containing oak browse 60%. Digestibility for DM, cellular constituents, NDF, and ADF showed lower for oak browse diets compared to control diet(P<0.05). Oak browse diets furnished significantly lower dietary N than &d the control diet. Fecal N losses generally increased with higher levels of oak browse levels(P<0.05). Apparently digested N and retained N were lower in oak browse diets than in control diet. The higher retained N was obtained in control diet than in oak browse diets. DE and ME declined linearly as oak browse levels increased when compared to control diet(P

• Journal of Electrical Engineering and Technology
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• 제2권1호
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• pp.89-97
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• 2007

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

• 한국해양환경ㆍ에너지학회지
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• 제6권2호
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• pp.16-27
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• 2003

해상에 유출된 유류의 생물정화방법은 자연상태로 존재하고 유류분해능력이 있는 박테리아, 균류 또는 효모와 같은 토착미생물의 환경요인을 최적화하거나, 병원성 또는 유전자조작미생물을 제외한 특별한 환경정화능력을 가진 미생물을 오염된 지역에 투입하여 유류오염물질을 자연적으로 분해함으로써 오염된 환경을 원래의 상태로 회복시키는 기술이다. 현재 우리나라규정에는 해양오염사고시 생물정화제제를 사용할 수 있는 제도적인 근거가 마련되어 있지 않아 실제사용 뿐만 아니라 관련 기술개발에 있어 많은 제약이 따르고 있다. 본 연구에서는 생물정화제제의 개발과 활용을 위해 관련규정에 대한 법률적 개정방향을 제시하였고 사람의 건강과 생태계의 유해한 성분을 포함하고 있는지 혹은 발생가능성이 여부를 확인하기 위하여 4단계의 생물정화제제 성능시험방법, 검정기준 및 형식승인절차를 제시하였다. 1, 2단계의 절차를 통해 생물급성독성 및 유류분해성능을 평가하여 형식승인을 여부를 결정하고 3, 4단계 절차를 통해 현장적용 가능성을 평가하는 단계로 구분하였다.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• 대한방사선치료학회지
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• 제10권1호
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• pp.69-77
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• 1998

When a high energy photon beam is used to treat lesions located in the upper respiratory air passages or in maxillary sinus, the beams often must traverse an air cavity before it reaches the lesion. Because of this traversal of air, it is not clear that the surface layers of the lesion forming the air-tumor tissue interface will be in a state of near electronic equilibrium; if they are not, underdosing of these layers could result. Although dose corrections at large distances beyond an air cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. This problem has been investigated for 4MV and 10MV X-ray beams which are becoming widely available for radiotherapy with linear accelerator. Markus chamber was used for measurement with variouse air cavity geometries in X-ray beams. Underdosing effects occur at both the distal and proximal air cavity interface. The magnitude depended on geometry, energy, field sizes and distance from the air-tissue interfaces. As the cavity thickness increased, the central axis dose at the distal interface decreased. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Fellowing a $20{\times}2{\times}2\;cm^3$\;air\;cavity,\;4{\times}4\;cm\;field\;there\;was\;an\;11.5\%\;and\;13\%\;underdose\;at\;the\;distal\;interface,\;while\;a\;20{\times}20{\times}2\;cm^3\;air\;cavity\;yielded\;a\;24\%\;and\;29\%$ loss for the 4MV and 10MV beams, respectively. The losses were slightly larger for the 10MV beams. The measurements reported here can be used to guide the development of new calculation models under non-equilibrium conditions. This situation is of clinical concern when lesions such as larynx and maxillary carcinoma beyond air cavities are irradiated.

• 한국가스학회지
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• 제14권4호
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• pp.6-11
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• 2010

연구실험실 사고 방지를 위하여 2005년 연구실 안전환경조성에 관한 법률이 법제화되어 국내 대학 또는 국공립출연연구소나 기업부설 연구소 실험실에서는 안전관리시스템을 구축하고, 안전점검과 정밀안전진단을 실시하고 있음에도 불구하고 폭발, 화재 등 각종 대형 사고가 지속적으로 발생하여 연구 활동 종사자의 인명 피해와 재산 손실이 상당한 수준에 이르고 있다. 또한 연구실험실에서 발생하는 사고는 유사한 내용으로 반복적으로 발생되고 있으므로 이러한 사고의 원인분석과 재발 방지를 위한 안전관리 대책이 시급하다. 따라서 본 논문에서는 국내 해외 대학 또는 국공립출연 연구소나 기업 부설 연구소 실험실에서 발생한 사건 사고에 대해 Root Cause Analysis 기법을 이용하여 사고원인 조사 결과를 보여주고, 이에 따른 실험실 사고원인 조사 분류 Map과 개선사항을 제시하여 연구실험실의 안전관리를 향상시키고자 한다.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.1029-1035
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• 2020

The detector suffers from pulse pileup by overlapping of the signals when it was used in high radiation fields. The pulse pileup deteriorates the energy spectrum and causes count losses due to random co-incidences, which might not resolve within the resolving time of the detection system. In this study, it is aimed to propose a new pulse pileup correction method. The proposed method is to correct the start point of the pileup pulse. The parameters are obtained from the fitted exponential curve using the peak point of the previous pulse and the start point of the pileup pulse. The amplitude at the corrected start point of the pileup pulse can be estimated by the peak time of the pileup pulse. The system is composed of a NaI (Tl) scintillation crystal, a photomultiplier tube, and an oscilloscope. A 61 μCi ¹³⁷Cs check-source was placed at a distance of 3 cm, 5 cm, and 10 cm, respectively. The gamma energy spectra for the radioisotope of ¹³⁷Cs were obtained to verify the proposed method. As a result, the correction of the pulse pileup through the proposed method shows a remarkable improvement of FWHM at 662 keV by 29, 39, and 7%, respectively.

• Journal of Animal Science and Technology
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• 제63권1호
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• pp.1-15
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• 2021

As a result of intensive breeding, litter size has considerably increased in pig production over the last three decades. This has resulted in an increase in farrowing complications. Prolonged farrowing will shorten the window for suckling colostrum and reduce the chances for high-quality colostrum intake. Studies also agree that increasing litter sizes concomitantly resulted in decreased piglet birth weight and increased within-litter birth weight variations. Birth weight, however, is one of the critical factors affecting the prognosis of colostrum intake, and piglet growth, welfare, and survival. Litters of uneven birth weight distribution will suffer and lead to increased piglet mortality before weaning. The proper management is key to handle the situation. Feeding strategies before farrowing, management routines during parturition (e.g., drying and moving piglets to the udder and cross-fostering) and feeding an energy source to piglets after birth may be beneficial management tools with large litters. Insulin-like growth factor 1 (IGF-1)-driven recovery from energy losses during lactation appears critical for supporting follicle development, the viability of oocytes and embryos, and, eventually, litter uniformity. This paper explores certain management routines for neonatal piglets that can lead to the optimization of their colostrum intake and thereby their survival in large litters. In addition, this paper reviews the evidence concerning nutritional factors, particularly lactation feeding that may reduce the loss of sow body reserves, affecting the growth of the next oocyte generation. In conclusion, decreasing birth weight and compromised immunity are subjects warranting investigation in the search for novel management tools. Furthermore, to increase litter uniformity, more focus should be placed on nutritional factors that affect IGF-1-driven follicle development before ovulation.

• 한국가금학회지
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• 제11권2호
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• pp.99-108
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• 1984

본 시험의 기초사료의 에너지수준을 고정하고 단백질수준을 10%에서 30%까지 달리하여 rapid bioassay 방법과 true metabolizable energy(TME) bioassay 방법을 통해 옥수수와 대두백의 apparent metabolizable energy of Farrell (AM $E_{F}$ ), Corrected AM $E_{F}$ (AM $E_{FC}$ )와 AME, TME 가 AME, TME가 측정시 미치는 영향을 검토하기 위하여 실시한 결과 다음의 성적을 얻었다. 1. 기초사료의 AM $E_{F}$ 치는 각 처리간 현저한 유의차가 인정되었으나( P＜0.05) 옥수수와 대두박의 AM $E_{F}$ 치는 전처리간 유의차가 없었다(P＞0.05). 기초사료의 AM $E_{FC}$ 치는 처리간 유의성이 인정된( P＜0.05) 반면 옥수수는 유의차가 없었고(P＞0.05) 대두박은 20% crude protein(CP), 30% CP 처리는 타 처리와 비교시 현저히 낮았다( P＜0.05). 2. AM $E_{F}$ 와 AM $E_{FC}$ 측정시 섭취량은 일정치 못하여 단백섭취량도 처리간 뚜렷한 차가 없었다. 3. 기초사료 및 옥수수, 대두박의 AME가는 전처리간 현저한 차가 없었던(P＞0.05). 반면 TME가는 처리간 일정한 경향없이 유의차가 있었는데 (P＜0.05) 이는 metabolic fecal energy＋endogenous urinary energy(FEm＋UEe) 손실량이 개체마다 급이한 사료에 따라 차가 있었는데 기인한 것이었다. 4. 채분시간별 (24시간 이 30시간) 기초사료의 AME, TME치는 10, 15, 20% CP 수준에선 유의차(P＜0.05)가 인정되었지만 옥수수와 대두백의 AME, TME 치는 채분시간에 따라 영향 받지 않았다. 이는 단백수준에 상관없이 채분시간은 24시간으로 충분하다고 생각된다.

• 대한토목학회논문집
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• 제37권2호
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• pp.311-324
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• 2017

과부하 맨홀에서의 에너지 손실은 도심지의 침수피해를 가중시키는 요인이 된다. 그러므로 과부하 4방향 합류맨홀에서 에너지 손실의 저감을 위한 흐름특성 분석이 필요하다. 본 연구에서는 현황조사 결과를 고려하여 수리실험 장치를 제작하였으며, 사각형 맨홀 및 연결관은 하수도시설 기준을 준용하여 1/5로 축소 제작하였다. 또한 과부하 4방향 사각형 합류맨홀에서 에너지 손실을 저감 시킬 수 있는 인버트 형상 조건을 도출하기 위하여 Fluent 6.3모형으로 수치모의를 실시하였다. 선정된 수리실험 조건인 유출유량($Q_{out}$)에 대한 측면 유입유량($Q_{lar}$)의 비($Q_{lat}/Q_{out}$)와 유출유량(2.0, 3.0, 4.0, 4.8 l/sec) 및 인버트 형상 변화 조건(십자형, 개선형)을 변화시키며 수리실험을 실시하였다. 십자형 인버트는 과부하 4방향 합류 맨홀의 배수능력 향상에 영향이 미미한 것으로 분석되었다. 그러나 개선된 직사각 개거형 인버트와 정사각 개거형 인버트는 각각 평균적으로 약 7%, 28%의 손실계수가 감소하여 배수능력을 개선하는 것으로 분석되었다. 따라서 도시 관거 시설의 배수능력을 증대시키기 위하여 본 연구에서 제시된 개선형 인버트의 설치 및 활용이 가능할 것으로 판단된다.