• 산업기술연구
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• 제23권A호
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• pp.3-7
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• 2003

Effect of nitriding on fatigue crack initiation and growth rate has been studied on SNCM. Specimens were nitrided for 15 hr at $860^{\circ}C$. The fatigue limit of nitrided specimens was superior to that of annealed($860^{\circ}C$, 15 hr) specimens. Based on detailed observations of slip band and micro crack initiation, it is concluded that the excellent fatigue limit of nitrided specimens is attributed to improved slip initiation resistance by nitriding. The characteristic of fatigue crack growth rate of nitrided specimens was investigated and compared with those of annealed specimens. It was found that by nitriding the crack growth rate was markedly decreased and the threshold stress intensity factor range was improved. It is concluded that the excellent fatigue limit of nitrided specimens is also attributed to improved fatigue crack growth rate and threshold stress intensity factor range by nitriding.

• 열처리공학회지
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• 제8권2호
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• pp.120-126
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• 1995

The effects of heating rate on the combustion temperature, the ignition temperature, the microstrurcture and the shape memory ability of products formed by combustion were investigated. The ignition temperature decreased with increasing heating rate. Combustion temperature and ${\Delta}T$(difference temperature between the ignition temperature and the combustion temperature) increased with increasing heating rate. The grain size of the product increased with increasing heating rate. Combustion synthesis did not completely occur below the heating rate of $10^{\circ}C/min$. NiTi intermetallic compound was completely formed at the heating rate of $600^{\circ}C/min$ and the product by combustion method had a good shape memory effect.

• 한국가금학회:학술대회논문집
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• 한국가금학회 2002년도 가을 학술발표논문집
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• pp.116-117
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• 2002

보존온도별(5, 25, 35$^{\circ}C$)로 정액과 희석액의 비율(1：1, 1：2, 1：3)을 달리하여 보존시간(1, 3, 6시간)에 따른 정자운동성을 조사한바, 5$^{\circ}C$ 냉장 온도에서는 희석배율에 따른 보존시간별 정자운동성은 차이가 없었으나, $25^{\circ}C$ 상온에서 6시간, 35$^{\circ}C$ 고온에서 3시간 이상 보존할 때 정액과 희석액의 비율이 1：1보다는 1：2 비율에서 정자운동성이 현저히 높게 유지되었다(P<0.05). 온도가 높을수록 1：1 배율보다는 1：2 이상 희석배율을 높여 주었을 때 정자의 운동성을 높게 유지시킬 수 있었다. Skim milk glucose액을 사용하여 닭 정액을 희석한 후 인공수정 하였을 때, 1회 주입정자수를 0.2, 0.4, 1 및 2억으로 하였을 때 각각 90.67, 94.00, 96.00 및 98.67%의 수정율을 나타냈다. 90%이상의 수정율을 얻기 위해서는 0.2억 이상의 정자 주입이 필요하며, 94%이상 안정적인 수정율을 얻기 위해서는 0.4억의 정자가 필요하다고 판단된다.

• 정보처리학회논문지C
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• 제9C권3호
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• pp.399-406
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• 2002

본 논문에서는 고정 전송율 서비스 및 가변 전송율 서비스 호들이 동적으로 네트워크에 들어와서 데이터를 전송하고, 데이터를 모두 전송하면 네트워크에서 사라지는 동적인 다중 서비스 네트워크에서, 고정 전송율 및 가변 전송율 서비스의 요구 성능을 만족하기 위한 네트워크 스위치(링크)의 성능 분석 및 설계 방법을 제안한다. 먼저 동적인 다중 서비스 네트워크의 링크를 Harkov 체인을 이용해 모델하고, QBD (Quasi-Birth-Death) 프로세스와 행렬 방정식을 이용해 가변 전송율 서비스의 호들에 할당될 전송율의 성능을 구한다. 즉, 가변 전송율 서비스의 평균 호수를 추정하고 이를 바탕으로, 호당 평균 전송율 및 평균 전송 지연 시간을 구한다. 고정 전송율 서비스의 성능은 고정 전송율 서비스 호들의 차단 확률(blocking probability)로 구해진다. 이렇게 해서 구해진 고정 전송율 및 가변 전송율 서비스의 성능을 이용해서, 고정 전송율 및 가변 전송율 서비스 호들의 요구 성능(전송율, 전송 지연 시간, 호의 차단 확률 등)을 만족하기 위한 네트워크 링크의 용량을 설계하는 방법을 제안한다. 이러한 방법을 데이터 및 음성(비디오)을 동시에 지원하는 네트워크 스위치의 성능 분석 및 용량 설계에 이용할 수 있다.

• Asian Journal of Atmospheric Environment
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• 제2권2호
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• pp.116-124
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• 2008

In this study, the Tier 2 method recommended by the Intergovernmental Panel on Climate Change (IPCC) was used to predict the methane generation rate at two landfill sites, designated as Y and C for purposes of this study, in South Korea. Factors such as the average annual waste disposal, methane emissions ($L_0$) and methane gas generation rate constant (k) were estimated by analyses of waste and the historical data for the landfills. The value of k was estimated by field experiments and then the changes in the methane generation rate were predicted through the year 2050, based on the value of k. The Y landfill site, which was in operation until the year 2008, will generate a total of 17, 198.7 tons by the end of 2018, according to our estimations. At the C landfill site, which will not be closed until the end of 2011, the amount of methane gas generated in 2011 will be 3,316 tons and the total amount of gas generated by 2029 will be 61,200 tons. The total production rate of methane gas at the C landfill is higher than that of the Y landfill. This indicates that the capacity of a landfill site affects the production rate of methane gas. However, the interrelation between the generation rate of methane and the value of k is weak. In addition, the generation of methane gas does not cease even when the operations at a landfill site come to a close and the methane gas production rate is at its highest at end of the operating life of a landfill site.

• 한국재료학회지
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• 제12권10호
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• pp.825-830
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• 2002

The growth rate of solid grains in TiC-XC-2vol% and TiC-XC-30vo1% Ni cermets, where X=Zr, W or Mo, was fitted to an equation of the form $d^3$-$do^3$=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with addition of $Mo_2$C or WC and increased with addition of ZrC. The contiguity ratio was greater in the alloys with smaller growth rate constant and decreased with increasing Ni content in the $TiC-Mo_2$C-Ni cermet. The grain growth mechanism could be explained by the effect of contiguous grain boundaries in restricting the overall grain growth.

• Korea-Australia Rheology Journal
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• 제12권3_4호
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• pp.175-179
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• 2000

Rheological properties of chitosan solutions were investigated as a function of polymer concentration. The viscosity curves for chitosan solutions consisted of two distinct viscosity regions, the Newtonian zero-shear viscosity (η$_{0}$) region and the shear rate dependent apparent viscosity (η$_{app}$) region. The shear rate dependence of viscosity was more clearly observed at higher chitosan concentrations. The critical coil overlap parameter (C＊〔η〕) was determined to be approximately 3.2 from a plot of zero-shear specific viscosity η$_{sp,0}$ vs coil overlap parameter (C〔η〕), which was lower than C〔η〕4.0 reported for other random coil polysaccharides. It was also found that the slope of η$_{sp,0}$ vs C〔η〕 was 3.9 at concentrated C〔η〕>C＊〔η〕domain, while 1.2 at dilute C〔η〕$_{0}$ ${\gamma}$/${\gamma}$$_{0.8}$ relation.ion.n.n.

• 한국분말재료학회지
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• 제16권3호
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• pp.167-172
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• 2009

This study has been carried out to investigate the non-isothermal behaviors and kinetic parameter of calcium carbonate by different thermal analysis methods. At the heating rate of $10^{\circ}C$/min, the onset calcination temperature, the peak and final temperatures of calcium carbonate were $612^{\circ}C$, $748^{\circ}C$, and $890^{\circ}C$ respectively. As the heating rate of the calcium carbonate increased from $5^{\circ}C$/min to $20^{\circ}C$/min, the peak temperature increased from $719^{\circ}C$ to $782^{\circ}C$. The activation energies of the calcium carbonate calculated by the methods of Kissinger and Freeman-Carroll were 40.15 kcal/mol and 43.47 kcal/mol, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.170-171
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• 2006

The chemical shift of SiOC film was observed according to the flow rate ratio. SiOC film has the broad main band of $880{\sim}1190cm^{-1}$ and the sharp Si-$CH_3$ bond at $1252cm^{-1}$, and the infrared spectra in the Si-O-C bond moved to low frequency according to the increasing of an oxygen flow rate. The chemical shift affected the carbon content in the SiOC film, and the decreasing of carbon atoms elongated the C-H bonding length, relatively. The main bond without the sharp Si-$CH_3$ bond at $1252cm^{-1}$ consisted of Si-C, C-O and Si-O bonds, and became the bonding structure of the Si-O-C bond.

• 한국해양공학회지
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• 제1권2호
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• pp.83-92
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• 1987

Inorder ot estimate the running life of turbine rotors, fatigue crack propagation low, da/dN = C(${\DELTA}K)^m$, proposed by paris et al. has been widely applied. In this study, fatigue crack propagation rates for 16 samples of 1% Cr-Mo-V rotor steel were measured and statistical characteristics of m and C values in above equation were reviewed. The results are summarized as follows. 1. C and m follow a log-normal distribution and normal distribution, respectively. And the relation of C and shows a strong negative correlation. 2. Fatigue crack propagation equation can be expressed as da/dN=$4.11{\times}10^{-4}({\Delta}K/153.8)^m$, introducing the ralationship C=$C_oK_o^{-m}$. In this case, contribution of $C_o$ distribution to the distribution of log C shows very small compared to degrees of contribution by m.