• The Korean Journal of Rheology
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• v.6 no.2
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• pp.104-118
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• 1994

단섬유 보강 플래스틱 재료의 사출성형 충전공정에서 금형재의 유동장이 섬유 배향 상태를 형성하는데 중요한 역할을 할 뿐만 아니라 섬유의 배향상태가 역으로 유동장에 영향 을 미친다. 충전유동과 섬유 배향의 연계해석을 위하여 단섬유에 의한 추가적인 응력을 포 함하는 Dinh과 Armstrong의 이방성 구성방정식을 충전유동의 해석에 도입하였다. 평명방향 으로의 속도구배에 의한 응력을 고려하여 새롭게 유도된 압력 지배방정식과 에너지방정식을 유한요소법과 유한차분법을 이용하여 풀고 동시에 2차배향텐서의 변화방정식을 4차 Runge-kutta 방법을 이용하여 풀었다. 절점 게이트 주변의 확장유동영역과 라인게이트를 통한 수축유동영역에서 평면방향으로의 속도구배에 의한 응력이 유동장에 미치는 영향을 고 찰하였다. 확장유동영역에서는 평면방향으로의 속도구배에 의한 영향이 추가적인 유량으로 나타나면서 주어진 유량조건하에서 평면방향으로의 속도구배에 의한 응력을 고려하지 않은 경우보다 작은 압력구배를 나타냈다. 수축유동영역에서는 위와 반대의 결과를 보였다. 이러 한 경향은 섬유의 부피분율이증가하거나 모양비가 커짐에 따라 증가한다.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.1-3
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• 2019

본 논문에서는 전차원 관측기를 이용한 유도기의 센서리스 운전에서 제정수 오차가 제어 성능에 미치는 영향을 수식적으로 분석하였다. 주파수 응답 함수를 이용해 실제 자속과 추정 자속의 관계를 운전 속도와 슬립 주파수의 함수로 나타내었다. 적응(adaptive) 법칙을 이용하여 추정 속도를 수식에서 제거하였다. 또한 각오차가 존재하는 상황에서 전류 운전점 변화를 고려하여 슬립 주파수를 토크 지령으로 변환하였다. 결과적으로 모든 운전 속도와 토크 지령에 대해서 임의의 제정수 오차가 시스템의 안정도, 속도 오차 및 토크 오차에 미치는 영향을 계산할 수 있는 수식을 구하였다. 기존의 분석 방법들이 많은 시뮬레이션과 실험을 통해 제정수의 영향을 평가했던 것과 달리, 구해진 수식에 근거하여 계산을 통해 빠르게 주어진 센서리스 운전 방법을 평가할 수 있는 방법을 제공하였다. 제안된 분석 방법은 시뮬레이션과 실험을 통해 검증되었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.33-43
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• 2005

Traffic condition monitoring system serves as the foundation for all intelligent transportation system operation. Loop detectors and Video Image Processing are the most widely common technology approach to condition monitoring in korea Highways. Lane Usage is defined as the proportion of total link volume served by each lane. In this research, the lane Usage(LU) of two lane link for one day. Interval is 56% : 44%. The LU of three lane link is 39% : 37% : 24%. The LU of four lane link is 25% : 29% : 26% : 21%. These analysis reveal that each lane distributions of link are not same. This research investigates the general concept of lane usage by using collected loop detector data and the investigated that lane distribution is different by traffic lane and lane usage is consistent by time of day.

• Resources Recycling
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• v.25 no.4
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• pp.60-67
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• 2016

This study was conducted to establish the adsorption-desorption mechanism and the optimum condition of chromatographic operation for separations of heavy rare earth elements (Gd, Tb, Dy) using a p507-containing resin. By employing Langmuir and Freundlich isotherm together with pseudo first and second order kinetics, absorption-desorption reaction mechanism was investigated. Langmuir and Freundlich isotherm was applied under assumption that adsorption reaction occurs in form of monolayer, and because the result was identical to the assumption, now we know adsorption of heavy rare earth elements occurs in form of monolayer. Concerning the pseudo first and second order kinetic, the pseudo second order seemed to be more suitable to represent heavy rare earth element adsorption mechanism. By using the extraction chromatography to separate heavy rare earth elements, ${\alpha}^{Tb}_{Gd}=1.24$, and ${\alpha}^{Dy}_{Tb}=1.03$ were confirmed in eluent HCl 0.25 M which indicates almost perfect separations of three elements. Furthermore, as concentrations of eluent became higher, the resolution value decreased and the elution area got shortened.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.4
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• pp.329-339
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• 1995

To clarify the surface drift velocity in gravity waves. experimental data measured in a two-dimensional wave flume were compared with theoretical values predicted by the Stokes 2nd- and 5th- order theories as well as by the conduction solution or Longuet-Hinggins (1953). Relative water depth and wave height ranged 0.040.13. For a closed flume condition, Stokes 2nd-order theory gives lower values than the experimental data, and the differences increase as both relative water depth and wave height increase. Based on the observed data of the surface drift velocities, a modified Parabolic model of the return current velocity Profile has been suggested, which is Proved to fit better to the existing experimental data of mass transport velocity profiles in a closed wave flume than the models of Longuet-Hinggins (1953) and Stokes wave theories do.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.839-846
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• 2008

The flocculation characteristics of polyacrylamide base flocculants were estimated to reduce the moisture content of the dehydrated cakes. The dewaterability for sewage sludge was found to have a marked effect depending on the flocculant type, agitating speed and time, kind of dissolution water, etc. The optimal agitating speed and time were 700 rpm and 3 sec, respectively, in this experimental condition. and the dewaterability was proportion to the agitating speed upto 700rpm. When recycle water as the dissolution water was used, the solution viscosity of all kind of flocculants was decreased. However, the change of its viscosity are not proportioned to the dewaterabilities for each flocculant. Flocculation system of combinations of the first and sencond flocculation using single flocculant was investigated. Effects of the ratio of first and second dosage for dual flocculation on the dewaterability were also investigated. The optimum conditions of dual flocculation system are 75% and 50% as first dosages for low and high viscous flocculant for total dosage of common flocculation, respectively. Based on the results, an overall mechanism of dual flocculation system is proposed and it is envisaged that optimization of flocculation processes in this way can result in considerable savings in cost.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.682-690
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• 2014

In order to improve the thermal stability of wood plastic composites (WPC), thermal degradation behavior of WPC in this study was investigated by the addition of wood flour and fire retardant after hybridization of wood flour and ammonium polyphosphate (APP) into polypropylene (PP) matrix. Thermal degradation behavior of all formulations was analyzed with thermogravimetric analyzer under nitrogen environment at heating rate of $10^{\circ}C/min$. As the thermal degradation temperature of wood flour is lower than that of PP, char layer formed by the wood flour decreases the speed of heat transfer to PP. In addition, the char layer increases the 2nd thermal degradation temperature and decreases the 2nd thermal degradation speed. The WPC treated with APP increases the 1st and 2nd degradation temperatures. In the case of WPC with high loading level of wood flour, the 1st thermal degradation temperature and 2nd thermal degradation rate were increased by the addition of APP, and then the amount of remnants at high temperature was increased by the increase of the APP loading level. In the case of WPC treated with APP, the amount of the remnants at high temperature was increased with the increase of wood flour content from 10 wt% to 50 wt%, indicating that char formation of the APP and wood flour occurred at the same time, resulting in high thermal stability effect by the increase of wood flour content.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.578-584
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• 2009

We investigated acid hydrolysis characteristics of yellow poplar woodmeal with concentrated sulfuric acid for high concentration of monosaccharides production. Woodmeal to 72% sulfuric acid ratio (w/w), $2^{nd}$ hydrolysis temperature and time were main variables for finding optimum reaction condition. Optimum woodmeal to 72% sulfuric acid ratio was 1 : 2.61 (w/w) and $2^{nd}$ hydrolysis temperature and time was $105^{\circ}C$ and 40 min as 44.8 g/L of glucose and 25.2 g/L of xylose in hydrolysis solution. In this acid hydrolysis solution, furfural, 5-HMF, low molecular weight phenolic compounds were identified. Furfural and 5-HMF concentration were increased as increasing $2^{nd}$ hydrolysis time. More than 40 min of $2^{nd}$ hydrolysis at $110^{\circ}C$, xylose concentration was decreased but glucose concentration was leveled out because xylose to furfural reaction was faster than xylan to xylose, but cellulose to glucose reaction was similar rate with glucose to 5-HMF at that $2^{nd}$ hydrolysis reaction condition.

• Korean Journal of Poultry Science
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• v.17 no.3
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• pp.141-156
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• 1990

The experiments were conducted to investigate the possibility of improving the effectiveness of the existing method to estimate the edible meat weight in the live broiler chicken. A total of 360 birds, five male and female chicks from each line were sacrificed at Trial 1 (body weight 900-1, 000g), Trial 2 (body weight 1.200-1, 400g), Trial 3(body weight 1, 600-1, 700), and Trial 4(body weight 2, 000g) in order to measure the body weight, edible meat weight of breast, thigh and drumsticks, and various components of body weight. Each line was reared at the Poultry Breeding Farm, Seoul National University from the second of july, 1987 to the thirteenth of September, 1987. The results obtained from this study were summarized as follows ： 1. The average body weights of each line( H. T, M, A) were $2150.5\pm$34.9, $2133.0\pm$26.2, $1960.0\pm$23.1, and $2319.3\pm$27.9, respectively. at 7 weeks of age. The feed to body weight eain ratio for each line chicks was 2.55, 2.13, 2.08, and 2.03, respectively, for 0 to 7 weeks of age. The viability of each line was 99.7. 99.7, 100.0, and 100.0%, respectively, for 0 to 7 weeks of age.01 was noticed that A Line chicks grow significantly heavier than did T, H, M line chic ks from 0 to 7 weeks of age. The regression coefficients of growth curves from each line chicks were bA＝1.015, bH＝0.265, bM＝0.950 and bT＝0.242, respectively. 2. Among the body weight components, the feather. abdominal fat, breast, and thigh and drumsticks increased in their weight percentage as the birds grew older, while neck. head, giblets and inedible viscera decreased. No difference wat apparent in shank, wings and hack. 3. The weight percentages of breast in edible part for each line thicks were 19.2, 19.0, 19.9 and 19.0% at Trial 4, respectively. The weight percentages of thigh and drumsticks in edible part for each line chicks were 23.1, 23.3, 22.8, and 23.0% at Trial 4. respective1y. 4. The values for the percentage meat yield from breast were 77.2. 78.9 73.5 and 74.8% at Trial 4 in H, T, M and A Line chicks. respectively. For thigh and drumstick, the values of 80.3, 78.4. 79.7 and 80.2% were obtained. These data indicate that the percentage meat yield increase as the birds grow older. 5. The correlation coefficients between body weight and blood. head, shanks. breast. thigh-drumstick were high. The degree if correlation between abdominal fat(%) and percentage of edible meat were extremely low at all times, but those between abdominal fat (%) and inedible viscera were significantly high.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.87-93
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• 2001

Velocity anisotropy of unconsolidated sediments in the Ulleung Basin, East Sea were studied by using 22 piston cores. Velocity anisotropy shows about 0.4 and 1.2％ in the Plain and Slope sediments, respectively. Horizontal velocity is greater than vertical velocity. It is resulted in positive anisotropy. Thus, bedding must be regarded as the principal cause of acoustic anisotropy in the Ulleung Basin sediments. The differences of the value are different from 5 m/s to 18 m/s in the Plain and Slope area, respectively. The relationships between physical properties and velocity anisotropy are clearly grouped. This result suggests that the slope sediments are probably affected by sedimentological (esp. physical properties) changes resulting from diagenesis.