• 대한화학회지
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• 제4권1호
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• pp.38-43
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• 1957

Purified cellulosic materials suitable for the production of cellulose esters can be prepared from waste cotton (carding waste from textile mill). The most desirable conditions in purifying waste cotton were obtained. Waxy materials were removed by boiling in 2-3% soda ash solution for more than 30 minutes in open vessel at atmospheric pressure. As for bleaching, it is desirable to use the bleaching powder solution containing 1%, available chlorine for 60 minutes at 35 deg. C. Purified cellulosic material was acetylated to fibrous cellulose triacetate, which was fractionated in the solution of 70% monochloroacetic acid using water as a precipitant, and the degree of polymerizaion and molecular weight of each fraction were measured viscometrically, thereon, molecular weight distribution curve was drawn. Analyzing the shape of this curve, most of the polymers were concentrated on the part of higher degree of polymerization. Purified waste cotton was also analysed, the result was that this cellulosic material can be used as a raw material for cellulose esters and ethers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1762-1766
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• 2000

Estimation of reverberant time is one of important factor for the calculation of absorption ration of absorption material. In general the digital filter bank has been used for the, estimation of decay curve of the sound pressure in a reverberant room. However at low frequency, it is not easy to get a good linear decay curve for the estimation of reverberant time. Now, wavelet transform is applied to this difficult task, a good result has been obtained at low frequency. The decay curve using wavelet filter bank is better than that using digital filter bank at low frequency. At higher frequency, both curves are similar.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.711-712
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• 2015

잠수함은 운행 중 수압에 따라 자화 특성이 변하므로 자기정숙화에 어려움이 있다. 본 논문은 잠수함 운행 중 수압에 따른 압력선체의 B-H Curve 특성 변화를 측정하였다. 잠수함의 압력선체는 강자성체 재질로 모델링 하여 제작하고 비자성체인 스테인리스로 보빈을 만들어 나사를 조이는 형태로 압축응력을 모사했다. 그 결과 응력이 가해지면 투자율이 작아지고 최대 자속밀도 또한 감소하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1334-1339
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• 2003

An efficient method is developed for the shape optimization of 2-D structures. The sequential linear programming is used for minimization problems. Selected set of master nodes are employed as design variables and assigned to move towards the normal direction. After adapting the nodes on the design boundary, the B-spline curves and mesh smoothing schemes are used to maintain the finite element in good quality. Finally, a numerical implementation of optimum design of an automobile torque converter piston subjected to pressure and centrifugal loads is presented. The results shows additional weight up to 13% may be saved after the shape optimization.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1991년도 수공학논총 제33권
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• pp.221-230
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• 1991

Various Models of the moisture content-capillary pressure hysteresie based on the approach of domain concept in porous media are compared with each other, Model III-1(Mualem, 1984) is superio to others as expected. A new model based on Model III-1 is proposed of which asuumption is the linearization of P$$($\theta$) accounting for the pore blockage effect against air-entry. The feature of this model is that only one branch of boundary curve is needed to calibrate it, which is the advantage to Model III-1. The prediction of boundary drying curve from boundary wetting curve using this model is better than that using Model I-1, II-1 compared with the experimental data. This model is to simulate scanning curves, while Model I-1, II-1 is not.

• 한국농공학회논문집
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• 제48권4호
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• pp.51-57
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• 2006

This study was carried out to investigate the soil water characteristic curve and prediction of void ratio with net stress and matric suction using the linear elastic and volumetric deformation analysis method on unsaturated silty. The unsaturated soil tests were conducted using a modified oedometer cell and specimens were prepared at water content 2 times of liquid limit and required void ratio. The axis translation technique was used to create the desired matric suctions in the samples. It is shown that soil water characteristic curve and volumetric water content were affected significantly by preconsolidation pressure. As a matric suction increases, the reduction ratio of void ratio was shown to considerably small. Also, the predicted and measured void ratio for unsaturated soils using the linear elastic and volumetric deformation analysis showed good agreement as net stress and matric suction increases.

• 동력기계공학회지
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• 제11권1호
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• pp.127-133
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• 2007

SG-365 steel is an important material and used for manufacturing a pressure vessel which the gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the unloading compliance method according to the ASTM E813-97 and E1152-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the $J_{IC}$. It is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides, it improves the accuracy of toughness values, decreases a phenomenon of the tunneling and shear lip by the side groove.

• Nuclear Engineering and Technology
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• 제30권4호
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• pp.364-376
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• 1998

The statistical analysis method was applied to the evaluation of fracture toughness in the ductile-brittle transition temperature region. Because cleavage fracture in steel is of a statistical nature, fracture toughness data or values show a similar statistical trend. Using the three-parameter Weibull distribution, a fracture toughness vs. temperature curve (K-curve) was directly generated from a set of fracture toughness data at a selected temperature. Charpy V-notch impact energy was also used to obtain the K-curve by a $K_{IC}$ -CVN (Charpy V-notch energy) correlation. Furthermore, this method was applied to evaluate the neutron irradiation embrittlement of reactor pressure vessel (RPV) steel. Most of the fracture toughness data were within the 95% confidence limits. The prediction of a transition temperature shift by statistical analysis was compared with that from the experimental data.

• 한국안전학회지
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• 제16권4호
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• pp.14-21
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• 2001

SG-365 steel is an important material End used for manufacturing a pressure vessel and gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the unloading compliance method according to the ASTM E8l3-97 and E1152-97 method on the smooth and side groove In specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the $J_{IC}$. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides. it improves the accuracy of toughness values, decreases the scattering of them and crack tunneling effect and shear lip by the side groove.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.66-67
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• 2006

The master sintering curve (MSC) is derived from densification data over a range of heating rates and temperatures. To improve the accuracy, several modifications were proposed: multi-phase MSC for solid state sintering with phase changes, MSC for liquid phase sintering, and MSC with consideration of grain growth. The developed MSC models were applied to several material systems such as molybdenum, stainless steels, and tungsten heavy alloys (WHA), in order to evaluate the effect of compaction pressure, phase change, grain growth, and composition on densification, to classify regions having different sintering mechanism, and to help engineer design, optimize, and monitor sintering cycles.