• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1412-1413
• /
• 2011

Effects of thermal annealing on electrical characteristics of thin film transistors (TFTs) using hydrogenated zinc oxide (ZnO:H) films as active channel were extensively investigated. The ZnO:H films were deposited at room temperature by RF sputtering. The device parameters of the ZnO:H-based TFTs, such as threshold voltage ($V_{th}$), subthreshold swing (S.S.), and on-off current ratio ($I_{on}/I_{off}$), were characterized in terms of the annealing temperature as well as the gas flow ratio of $H_2$/Ar.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.12
• /
• pp.3326-3334
• /
• 1994

To theoretically predict knock occurrence in S. I. engine as a function of engine design and operating parameters, transient local temperature and pressure, mixture density of flame front in combustion period are calculated. We next determined normal combustion period and auto ignition period of end gas using the prediction method on occurrence of spark knock which we suggested. We predict knock occurrence in S. I. engine by comparing consecutively normal combustion period with the auto ignition period of end gas in combustion period. Engine design and operating parameters such as compression ratio, engine speed, spark timing, inlet temperature and pressure are taken into account in this calculations. The predicted result are well matched with the experimental results in turbocharged engine. Therefore, this method will provide the systematic guideline for designing engines in view of knocking limits.

• Journal of the Korean Ceramic Society
• /
• v.23 no.5
• /
• pp.35-40
• /
• 1986

The early hydration of tri-calcium silicate $(C_3S)$ with different cooling conditions was studied by varing water/solid ratio and atmosphere. The cooling condition and water/solid ratio affected to the second peak of heat liberation but it had no correlation to the induction period. The $Ca^{2+}$ concentration in the aqueous solution was maximized at the starting point of the second peak of heat liberation but in the $CO_2$ exsistence the $Ca^{2+}$ concentration was low and $SiO_2$ con-centration was increased. The hydration rate of $C_3S$ was so accelerated that the induction period could not appear in the $CO_2$ exsistence.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.4
• /
• pp.121-128
• /
• 1998

In this study, when tension and bending stress act on plate simultaneously, stress intensity factor is analyzed at crack tip with using BEM(Boundary Element Method). In this analysis, stress intensity factors(S.I.F) are defined for variable ligament, aspect and stress ratio($\sigma$T/$\sigma$B). Consequently, predicted that crack grow to depth direction at low aspect and ligament ratio in tension stress and to surface direction in bending stress. Tension and bending stress act on plate same time, effect of tension stress in the first stage and effect of bending stress in the after stage was to observed. The outbreak of secondary crack in backside is under the control of stress amplitude and predict that the point of outbreak is mear backside.

• Journal of Biosystems Engineering
• /
• v.17 no.2
• /
• pp.132-142
• /
• 1992

The main objective of this paper is to evaluate and modify the existing algorithms for the automatic threshold selection. Four existing algorithms were evaluated quantitatively using test images of coffee droplets and an apple. The images had the different area ratio of the object to the image size, different average gray values between the object and the background, and different S/N ratio of the Gaussian noise. The result showed that Histogram Clustering Method and Maximum Entropy Method were better than Moment Preserving Method and Simple Image Statistic Method in automatic thresholding.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.6
• /
• pp.111-119
• /
• 2019

The purpose of this study is to investigate the shear strength of reinforced concrete beam according to beam section size and shear reinforcement ratio. A total of nine specimens were tested and designed concrete compressive strength is 24 MPa. The main variables are shear reinforcement ratio and beam section size fixed with shear span to depth ratio (a/d = 2.5), the tensile reinforcement ratio (${\rho}=0.013$) and width to depth ratio (h/b = 1.5). The test specimens were divided into three series of S1 ($225{\times}338mm$), S2 ($270{\times}405mm$) and S3 ($315{\times}473mm$), respectively. The experimental results show that all specimens represent diagonal tensile failure. For $S^*-1$ specimens (d/s=0), the shear strength decreased by 33% and 46% with increasing the beam effective depth, 26% and 33% for $S^*-2$ specimens (d/s=1.5) and 16% and 20% for $S^*-3$ specimens (d/s=2.0) respectively. As the shear reinforcement ratio increases, the decrease range in shear strength decreases. In other words, this means that as the shear reinforcement ratio increases, the size effect of concrete decreases. In the S1 series, the shear strength increased by 39% and 41% as the shear reinforcement ratio increased, 54% and 76% in the S2 series and 66% and 100% in the S3 series, respectively. As the effective depth of beam increases, the increase range of shear strength increases. This means that the effect of shear reinforcement increases as the beam effective depth increases. As a result of comparing experimental values with theoretical values by standard equation and proposed equation, the ratio by Zsutty and Bazant's equation is 1.30 ~ 1.36 and the ratio by KBC1 and KBC2 is 1.55~.163, respectively. Therefore, Zsutty and Bazant's proposed equation is more likely to reflect the experimental data. The current standard for shear reinforcement ratio (i.e., $S_{max}=d/2$) is expected to be somewhat relaxed because the ratio of experimental values to theoretical values was found to be 1.01 ~ 1.44 for most specimens.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.11
• /
• pp.1038-1045
• /
• 2010

In this study, the anaerobic ultimate biodegradability and multiple decay rate of organic matter were evaluated according to various salt concentrations in seafood processing wastewater. The evaluation was also performed with various types of anaerobic bacteria and S/I (substrate/inoculum) ratios. After the S/I ratio was fixed at 0.9, the ultimate biodegradability values of the anaerobic digested sludge and granular sludge were became 72.0% and 92.0%, respectively. The multiple decay rate coefficients ($k_1$) coefficients of the anaerobic digested sludge and granular sludge were $0.0478{\sim}0.1252\;day^{-1}$ and $0.0667{\sim}0.1709\;day^{-1}$, respectively. The optimum S/I ratio of the seafood wastewater, which was determined based on the ultimate anaerobic biodegradability and gas production, was 0.9. The organic matter removal rate never became less than 85.0% under a 3,000 mg/L chloride concentration. The multiple decay rate coefficients ($k_1$) were $0.1603{\sim}0.1709\;day^{-1}$ under $3,000\;mgCl^-/L$, and $0.0492{\sim}0.0760\;day^{-1}$ in more than $6,000\;mgCl^-/L$. The multiple decay rate coefficients ($k_2$) were $0.0183{\sim}0.0348\;day^{-1}$ under $6,000\;mgCl^-/L$, and $0.0154\;day^{-1}$ at $9,000\;mgCl^-/L$. With increasing chloride concentrations, the reaction rate ($k_1$, $k_2$) and ratio of the rapidly degraded organic matter ($S_1$) decreased.

• YAKHAK HOEJI
• /
• v.26 no.4
• /
• pp.209-214
• /
• 1982

Acute toxicities of purified ginseng saponin (PGS) in mice, and sbacute toxicities of PGS in rats were investigated. Average lethal doses ($LD_{50}$) of PGS in male mice were 270mg/kg (i.v.), 342mg/kg (i.p.), 505mg/kg (i.m.), 950mg/kg (s.c.), and more than 5,000mg/kg (p.o.), respectively. Results of subacute toxicity of PGS was as follows. Body weight was markedly increased by administration of PGS 7.7mg/kg but side effects were shown by administration of 77mg/kg and above dose. Especially administration of PGS 240mg/kg caused a marked decrease of albumin/globulin ratio, and 28% increase of urea nitrogen in serum, as well as 33% increase of liver weight/body weight ratio.

• Tuberculosis and Respiratory Diseases
• /
• v.38 no.3
• /
• pp.262-269
• /
• 1991

The purpose of this study is to investigate the utility of the pleural fluid cholesterol level in separating the exudates from the transudates, and in differentiating tuberculous exudates from non-tuberculous exudates, 52 patients with pleural effusion were involved in this prospective study. By predefined criteria, 40 of these effusions were classified as exudates (Group I) and 12 as transudates (Group II). Group I was subdivided into tuberculous exudates (Group A) and non-tuberculous exudates (Group B). The followings are parameters used in separating the exudates from the transudates; pleural protein (P-PROT) 3.0 g/dl, pleural protein/serum protein ratio (P/S PORT) 0.5, pleural LDH (P-LDH) 200 IU, pleural LDH/serum LDH ratio (P/S LDH) 0.6, pleural cholesterol (P-CHOL) 50 mg/dl and pleural cholesterol/serum cholesterol ratio (P/S CHOL) 0.4. Mean values of the parameters in each group were compared, and then misclassified rate and the dignostic efficiency for each parameter were calculated. The results were as follows; 1) Mean P-CHOL ($94.98{\pm}73.86\;mg/dl$) in Group I was higher than that ($36.5{\pm}26.5\;mg/dl$) in Group II (p<0.05), but there was no significant difference in mean P-CHOL between Group A and Group B. 2) Mean P/S CHOL ($0.64{\pm}0.39$) in Group I was also higher than that ($0.27{\pm}0.15$) in Group II (p<0.01), but no difference was observed in mean P/S CHOL between Group A and Group B. 3) Misclassified rates for each parameter in separating the exudates from the transudates were as follows; P-PROT 1.9%. P/S PROT 3.8%. P-CHOL 9.6%, P/S CHOL 11.5%, P/S LDH 11.5%, and P-LDH 17.3%. 4) Diagnostic efficiencies for each parameter in separating the exudates from the transudates were as follows; P-PROT 98.1%, P/S PROT 96.2%. P-CHOL 90.4%. P/S CHOL 88.5%, P/S LDH 88.5%, and P-LDH 82.7%. In conclusion, we think that the pleural fluid chloesterol level could be used as a supportive parameter in separating the exudates from the transudates, but could not be used as a parameter in differentiating tuberculous exudates from non-tuberculous exudates.

• Structural Engineering and Mechanics
• /
• v.27 no.3
• /
• pp.311-331
• /
• 2007

The purpose of this paper is to study shear locking-free analysis of thick plates using Mindlin's theory and to determine the effects of the thickness/span ratio, the aspect ratio and the boundary conditions on the linear responses of thick plates subjected to uniformly distributed loads. Finite element formulation of the equations of the thick plate theory is derived by using higher order displacement shape functions. A computer program using finite element method is coded in C++ to analyze the plates clamped or simply supported along all four edges. In the analysis, 8- and 17-noded quadrilateral finite elements are used. Graphs and tables are presented that should help engineers in the design of thick plates. It is concluded that 17-noded finite element converges to exact results much faster than 8-noded finite element, and that it is better to use 17-noded finite element for shear-locking free analysis of plates. It is also concluded, in general, that the maximum displacement and bending moment increase with increasing aspect ratio, and that the results obtained in this study are better than the results given in the literature.