• 설비공학논문집
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• 제9권2호
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• pp.171-179
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• 1997

During the day time in summer, peak of air conditing load, and electric power management system lies under overloaded condition. The reason is the enlarged peak load value of electric power caused by increased air-cooling load in summer. To prevent load concentration during day time and overloaded condition of power management system, some energy storage methods are suggested. One of these methods is ice storage system. Water has some good properties as P.C.M.(Phase Chang Material) : Its melting point is the range of required operation temperature. It has large specific latent heat and is chemically stable compared to other organic or inorganic substances. It is cheap and easy to treat. This study represents experimental results of heat transfer characteristics of P.C.M. under the outward melting process in a vertical cylinder. We experimented with twelve combinations of conditions, i.e., three different inlet temperatures($7^{\circ}C,\;4^{\circ}C\;and\;1^{\circ}C$), two working fluid directions(upward and downward), and two aspect ratios, H/R(4 and 2). At the inlet temperature of $7^{\circ}C$ and $4^{\circ}C$, there was temperature stagnation region where the temperature of P.C.M. remains constant at $4^{\circ}C$ regardless of aspect ratio and direction of working fluid. This temperature stagnation occurs as the water, at its maximum density, flows down to the lower region. The phase change interface formed bell-shaped curve as the melting process continued. With a new set of conditions(4H/R, inlet temperature $4^{\circ}C$ and $1^{\circ}C$, downward/upwerd inlet direction), the movement of phase change interface was faster when the working flued inlet direction was downward. With the same set of conditions, melting rate and total melting energy were larger when the working fluid inlet direction was downward. The results were reversed when the other sets of conditions were applied.

• Asian-Australasian Journal of Animal Sciences
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• 제21권3호
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• pp.364-370
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• 2008

Chemical analysis and in vitro studies were conducted to investigate the nutritive value for ruminants of cell mass from lysine production (CMLP) which is a by-product of the lysine manufacturing process. Proximate analysis, protein fractionation, and in vitro protein degradation using protease from Streptomyces griseus and strained ruminal fluid were carried out to estimate ruminal protein degradability of CMLP with two reference feedstuffs-soybean meal (SBM) and fish meal (FM). Amino acid composition and pepsin-HCl degradability were also determined to evaluate postruminal availability. CMLP contained 67.8% crude protein with a major portion being soluble form (45.4% CP) which was composed of mainly ammonium nitrogen (81.8% soluble CP). The amount of nucleic acids was low (1.15% DM). The total amount of amino acids contained in CMLP was 40.60% DM, which was lower than SBM (47.69% DM) or FM (54.08% DM). CMLP was composed of mainly fraction A and fraction B2, while the protein fraction in SBM was mostly B2 and FM contained high proportions of B2 and B3 fractions. The proportion of B3 fraction, slowly degradable protein, in CP was the highest in fish meal (23.34%), followed by CMLP (7.68%) and SBM (1.46%). CMLP was degraded up to 51.40% at 18 h of incubation with Streptomyces protease, which was low compared to FM (55.23%) and SBM (83.01%). This may be due to the insoluble portion of CMLP protein being hardly degradable by the protease. The in vitro fermentation by strained ruminal fluid showed that the amount of soluble fraction was larger in CMLP (40.6%) than in SBM (17.8%). However, because the degradation rate constant of the potentially degradable fraction of CMLP (2.0%/h) was lower than that of SBM (5.8%/h), the effective ruminal protein degradability of CMLP (46.95%) was slightly lower than SBM (53.77%). Unavailable fraction in the rumen was higher in CMLP (34.0%) compared to SBM (8.8%). In vitro CP degradability of CMLP by pepsin was 80.37%, which was lower than SBM (94.42%) and FM (89.04%). The evaluation of protein degradability using different approaches indicated that soluble protein in CMLP may supply a large amount of ammonia in the rumen while insoluble protein can be by-passed from microbial attacks due to its low degradability. The results from this study suggest that CMLP can be used as a protein supplement to ruminants for supplying both non-protein nitrogen to rumen microbes and rumen undegradable protein to the host animal.

• 한국정보전자통신기술학회논문지
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• 제10권5호
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• pp.469-475
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• 2017

소프트웨어 개발시행 과정에서 소프트웨어 신뢰성은 매우 기본적이고 필수적인 문제 중에 하나이다. 소프트웨어 고장현상을 파악하기 위하여 비동질적인 포아송 과정에서 순간 고장률인 강도함수가 고장시간에 독립적으로 일정하거나, 증가형 혹은, 감소형 추세를 가질 수 있다. 본 논문에서는 소프트웨어 설계 과정에서 강도형태가 감소패턴을 따르는 랜들리 수명분포와 증가하다가 감소하는 어랑수명 분포를 활용한 소프트웨어 신뢰속성 모형에 대하여 신뢰도 장단점에 관한 연구를 하였다. 소프트웨어 고장현상을 파악하기 위하여 모수추정은 최우추정법을 적용하였다. 따라서, 본 논문에서는 소프트웨어 고장시간 자료를 적용하여 소프트웨어 신뢰도를 비교하고, 평가하였다. 그 결과, 랜들리 모형이 어랑분포 모형보다 신뢰도가 상승하는 것으로 나타났으나, 어랑분포 모형에서는 형상모수가 높을수록 높은 신뢰도를 나타내는 추세를 보였다. 본 논문를 통하여 소프트웨어 기획 부서에서는 특정한 수명분포와 형상모수를 활용함으로서 소프트웨어 고장분석을 활용한 소프트웨어 신뢰성 모형에 대한 신뢰성 속성을 적용한 데이터 및 기본 지식을 제공함으로서 소프트웨어 설계에 실질적인 도움을 줄 수 있다.

• 한국산학기술학회논문지
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• 제18권11호
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• pp.110-117
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• 2017

다수의 고층 주거 건물을 건설하는 공동주택 프로젝트에서 마감 공종은 단위세대마다 반복적으로 시공되므로 자원이 연속적으로 투입되도록 공정관리가 이루어지면 품질을 확보하면서 공기를 단축하고 공사비를 절감할 수 있다. Bar Chart, CPM, LOB와 같은 공정관리 기법은 반복 작업에 대한 표현과 적용의 한계점으로 인하여 공동주택 마감공사에 사용하기에는 적합하지 않다. 또한 택트 기반 공정관리 기법은 반복 공종의 작업 흐름을 일정하게 유지하기 어려울 뿐만 아니라 지속적으로 필요한 자원을 할당하기 위해서는 상당한 노력과 전문 시공업체의 협조를 필요로 한다. 공동주택의 마감공사는 벽체조성공사, 마감바탕공사, 바닥미장공사, 최종마감공사 순으로 진행되고, 각 공사에는 작업 방법, 작업 공간, 자원 생산성 등과 관련하여 다양한 특성을 가지는 하위 개념의 반복 공종들이 존재한다. 이 반복 공종들의 작업이 동기화되거나 마지막 작업구역에서 수렴되도록 하면 공정관리의 목표가 유효하게 달성될 수 있다. 따라서 본 연구는 공동주택의 단위세대에서 시공되는 작업들의 순서 관계, 작업 유형 분류 및 관리 방법, 자원의 연속적인 투입을 위한 시공속도와 작업구역 등의 요소들을 고려하여 마감공사를 위한 공정 계획 프로세스를 제시하고자 한다.

• Asian-Australasian Journal of Animal Sciences
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• 제18권9호
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• pp.1273-1278
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• 2005

This study is to evaluate the effect of different levels of ensiling density on the fermentation quality of guineagrass silages during the early stage of ensiling. Guineagrass at the milky ripe stage was chopped and ensiled into a small-scale laboratory silo at two ensiling density levels (high density at 95 g/silo and low density at 75 g/silo). Three silos per level were opened after six ensiling periods (0.5, 1, 1.5, 2, 3 and 7 days of ensiling) and the fermentation qualities were analyzed. Within the initial 1.5 days of ensiling there were not significant (p>0.05) differences in the fermentation qualities between two density levels silages, and an almost constant pH and no or only small amounts of lactic acid, acetic acid and total volatile fatty acids were detected. However, the high density silage significantly (p<0.05) increased the rate and extent of fermentation after 1.5 days of ensiling, which was well reflected in significantly (p<0.05) faster and larger pH decline and lactic acid production at each elapsed time as compared with the low density silage. This resulted in significantly (p<0.05) lower finial pH and significantly (p<0.05) higher lactic acid content at the end of the experiment. Moreover, there was higher AA content relative to LA in both the H-D and L-D silages during the full fermentation course, and resulted in the AA-type silage. There were generally somewhat or significantly (p<0.05) higher acetic acid, volatile fatty acids and ammonia-N/total nitrogen in the high density silage than in the low density silage during the initial 3 days of ensiling. However, there were higher (p>0.05) ammonia-N/total nitrogen and significantly (p<0.05) higher butyric acid content in the low density silage at day 7 of ensiling. The silages of two density levels showed an initial increase in glucose between 0.5 and 1 day for the high density silage and between 1 and 1.5 days for the low density silage, respectively, thereafter showed a large decrease until the end of the experiment. There were not large differences (p>0.05) in ethanol content between the low density and high density silages that showed small amounts within initial 3 days of ensiling. However, the low density silage had a significantly (p<0.05) higher ethanol content than the high density silage at the end of experiment. From the above results it was suggested that the increase in ensiling density was an effective method to improve the fermentation quality, especially for tropical grasses.

• 한국산학기술학회논문지
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• 제17권7호
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• pp.86-91
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• 2016

가공배전선에 의하여 통신선에 유도되는 전압을 계산하는데에 있어서 기존의 중성선 차폐계수를 단일의 값으로 사용함으로 인한 과다 오차 발생 문제를 해결하기 위하여 실제 배전 구간의 전주 접지 마다 발생하는 누설전류에 의한 대지귀로전류의 영향이 반영된 일반식이 개발된 바 있다. 각 전주 접지에서 발생하는 누설전류의 근원은 중성선에 유입되는 불평형전류이다. 그러므로 누설전류와 그 합인 대지귀로전류는 이 불평형전류에 대한 각 전주 위치에서의 누설율들의 합성적 인수 관계로 표현이 가능하다. 본 논문에서는 결국 원래의 일반식을 누설율의 관점에서 전개하여 좀더 실용적인 의미를 갖도록 하였다. 이렇게 하면 유도의 원천 전류인 중성선 불평형전류에 대한 누설전류 요율만의 합성 인수로 대체된 중성선 차폐계수 계산식이 도출된다. 이 계산식의 의미는 전 배전 구간에서 중성선에 의한 차폐 효과가 일정한 것이 아니라 유도 구간의 위치에 따라서 원래 유도를 발생시키는 전류인 중성선 불평형전류의 양이 달라지는 요율을 말한다는 것이다. 이와 같은 방식으로 계산하였을 때 기존 방식에 비하여 과소 예측에 대하여는 14% 증진율을, 과다 예측에 대하여는 평균 1/10 수준으로의 감소 효과를 기대할 수 있다.

• 한국토양환경학회지
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• 제1권2호
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• pp.73-81
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• 1996

실험실 내에서 부피비로 약 50%내외의 수분함량을 가진 3개의 서로 다른 깊이의 토양에서 염소와 중수의 확산계수는 4.8$\times$ $10${-7}$ 부터 7.2$\times$ $10${-7}$ $\textrm{cm}^2$/sec와 5.5 $\times$ $10${-5}$ 부터 1.6$\times$ $10${-4}$ $\textrm{cm}^2$//sec였다. 한편, 물과 물질의 이동성에 대한 연구는 중간사로 구성된 토양층 위에 위치하는 점토로부터 미사질 양토에 속하는 약 70cm깊이의 토양에서 실시되었고, 87일간의 실험기간동안 리터당 15.2$m\ell$의 염소와 0.6bq의 중수로 처리된 물을 일정한 유량(2cm/일)으로 관개하였다. 토양의 깊이와 시간에 따른 염소와 중수의 변동위치는 suction probe에 채취된 토양수를 가지고 측정하였는데 실험지 안에서 서로 다른 깊이 또는 동일 위치에서 염소와 중수가 발견되었다. 이러한 실험의 결과로부터 추정컨대 토양수의 유속과 표면확산 계수가 염소와 중수의 분포에 직접적인 영향을 미쳤고 24개의 suction probe에서의 결과는 실질적 물질과 토양의 상호작용의 효과를 나타내는 순수치의 25% 내외에서 평가치를 추정할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제14권5호
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• pp.249-254
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• 2014

본 논문에서는 포물선 엣지 형태의 평면 모노폴 안테나의 스케일링 기법을 통한 소형화를 제안하였다. 매칭스텝과 불연속 CPW 구조를 사용해서 효과적인 임피던스 매칭을 시도하였다. 안테나 제작 시 유전상수가 4.4인 FR4 유전체 기판을 사용하였다. 기판의 규격은 $26mm{\times}31mm{\times}1.6mm$이다. 불연속 CPW로 급전한 안테나의 실제 측정 결과 2.37~10.52GHz (8.15GHz)로 10dB 이상의 반사손실 값을 얻었다. 복사패턴은 모든 주파수에서 다이폴 안테나의 복사 패턴과 비슷한 결과를 보였다. 더불어 급전부를 제외한 안테나 구성 요소를 동일한 비율로 축소하여 안테나의 크기를 줄이고 광대역 특성은 유지되도록 했다. 이를 통해 안테나의 self-complementary 특성을 확인하였다. 스케일링을 통해 소형화한 안테나 중에 UWB 대역을 만족하면서 가장 작은 크기를 갖는 경우는 스케일이 0.6이었을 때이다. 이 때 안테나의 크기는 $15.6mm{\times}18.6mm$이다. 측정된 10dB 대역은 3.07~12.59GHz (9.52GHz)이다.

• Asian-Australasian Journal of Animal Sciences
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• 제26권10호
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• pp.1424-1436
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• 2013

The objective of this study was to investigate the effect of banana flower powder (BAFLOP) supplementation on gas production kinetics and rumen fermentation efficiency in in vitro incubation with different ratios of roughage to concentrate in swamp buffalo and cattle rumen fluid. Two male, rumen fistulated dairy steers and swamp buffaloes were used as rumen fluid donors. The treatments were arranged according to a $2{\times}2{\times}3$ factorial arrangement in a Completely randomized design by using two ratios of roughage to concentrate (R:C; 75:25 and 25:75) and 3 levels of BAFLOP supplementation (0, 2 and 4% of dietary substrate) into two different kinds of rumen fluid (beef cattle and swamp buffalo). Under this investigation, the results revealed that the rumen ecology was affected by R:C ratio. The pH declined as a result of using high concentrate ratio; however, supplementation of BAFLOP could buffer the pH which led to an improvement of ruminal efficiency. BAFLOP supplementation affected acetic acid (C2) when the proportion of concentrate was increased. However, there were no effect on total volatile fatty acid (TVFA) and butyric acid (C4) by BAFLOP supplementation. The microbial community was affected by BAFLOP supplementation, especially the bacterial population. As revealed by real-time PCR, the populations of F. succinogenes and R. albus were reduced by the high concentrate treatments while that of R. flavafaciens were increased. The populations of three dominant cellulolytic bacteria were enhanced by BAFLOP supplementation, especially on high concentrate diet. BAFLOP supplementation did not influence the ammonia nitrogen ($NH_3$-N) concentration, while R:C did. In addition, the in vitro digestibility was improved by either R:C or BAFLOP supplementation. The BAFLOP supplementation showed an effect on gas production kinetics, except for the gas production rate constant for the insoluble fraction (c), while treatments with high concentrate ratio resulted in the highest values. In addition, BAFLOP tended to increase gas production. Based on this study, it could be concluded that R:C had an effect on rumen ecology both in buffalo and cattle rumen fluid and hence, BAFLOP could be used as a rumen buffering agent for enhancing rumen ecology fed on high concentrate diet. It is recommended that level of BAFLOP supplementation should be at 2 to 4% of total dry matter of substrate. However, in vivo trials should be subsequently conducted to investigate the effect of BAFLOP in high concentrate diets on rumen ecology as well as ruminant production.

• Environmental Analysis Health and Toxicology
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• 제19권1호
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• pp.33-40
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• 2004

Benzoyl peroxide is a High Production Volume Chemical, which is produced about 1,371 tons/year in Korea as of 2001 survey. The substance is mainly used as initiators in polymerization, catalysts in the plastics industry, bleaching agents for flour and medication for acne vulgaris. In this study, Quantitative Structure-Activity Relationships (QSAR) are used for getting adequate information on the physical -chemical properties of this chemical. And hydrolysis in water, acute toxicity to aquatic and terrestrial organisms for benzoyl peroxide were studied. The physical -chemical properties of benzoyl peroxide were estimated as followed; vapor pressure=0.00929 Pa, Log $K_{ow}$ = 3.43, Henry's Law constant=3.54${\times}$10$^{-6}$ atm-㎥/mole at $25^{\circ}C$, the half-life of photodegradation=3 days and bioconcentration factor (BCF)=92. Hydrolysis half-life of benzoyl peroxide in water was 5.2 hr at pH 7 at $25^{\circ}C$ and according to the structure of this substance hydrolysis product was expected to benzoic acid. Benzoyl peroxide has toxic effects on the aquatic organisms. 72 hr-Er $C_{50}$ (growth rate) for algae was 0.44 mg/1.,48 hr-E $C_{50}$ for daphnia was 0.07mg/L and the 96hr-L $C_{50}$ of acute toxicity to fish was 0.24mg/L. Acute toxicity to terrestrial organisms (earth worm) of benzoyl peroxide was low (14 day-L $C_{50}$ = > 1,000 mg/kg). Although benzoyl peroxide is high toxic to aquatic organisms, the substance if not bioaccumulated because of the rapid removal by hydrolysis (half-life=5.2 hr at pH 7 at $25^{\circ}C$) and biodegradation (83% by BOD after 21 days). The toxicity observed is assumed to be due to benzoyl peroxide rather than benzoic acid, which shows much lower toxicity to aquatic organisms. One can assume that effects occur before hydrolysis takes place. From the acute toxicity value of algae, daphnia and fish, an assessment factor of 100 was used to determine the predicted no effect concentration (PNEC). The PNEC was calculated to be 0.7$\mu\textrm{g}$/L based on the 48 hr-E $C_{50}$ daphnia (0.07 mg/L). The substance shows high acute toxicity to aquatic organisms and some information indicates wide-dispersive ore of this substance. So this substance is, a candidate for further work, even if it hydrolysis rapidly and has a low bioaccumulation potential. This could lead to local concern for the aquatic environment and therefore environmental exposure assessment is recommended.