• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.100-106
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• 2001

In this study, CT specimens were prepared from Pressure Vessel Steel which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ and in the range of stress ratio of 0.05 and 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ${\Delta}K_{th}$ in the early stage of fatigue crack growth (Region I) and stress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) was increased in proportion to descent temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN $-{\Delta}K$ in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN in proportion to descending temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.107-113
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• 2009

This paper considers the influence of floc on the sedimentation rate for the cohesive material. The effects of floc density and size changes were also taking into consideration during the experiment. The settling velocity of a discrete floc was measured in a quiescent water column. Floc diameter and density were investigated using a modified Stokes equation with some constants such as water density, viscosity, material density and the floc fractal dimension $n_f$ obtained from the relationship between the floc diameter and the floc settling. The floc diameter of quartz and alumina increased at increasing initial concentrations. The floc size of quartz with increasing NaCl concentration varied between approximately 0.8 um to $10{\mu}m$. Floc density decreased as floc size increased. The floc settling velocity and the floc diameter have a straight line relationship on a logarithm. The floc fractal dimension nf was 2.65 with increasing of initial concentration and 2.93 with increasing of NaCl. The exponent n to predict the settling velocity was proposed and varied from 1 to 1.93.

• Korean Journal of Biological Psychiatry
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• v.6 no.1
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• pp.119-124
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• 1999

This study was done to examine whether cigarette smoking improved smooth pursuit eye movement(SPEM) abnormalities in chronic schizophrenic inpatients. Fifteen schizophrenic and twelve alcoholic subjects abstained from their usual cigarette smoking for a minimum of nine hours and their baseline performances during the constant velocity smooth pursuit tasks were assessed. Then, the subjects smoked as much as they desired in a 10 minutes period and were retested immediately after smoking and 15 minutes after smoking. Electrooculographic recordings during the eye movements were converted and saved as digitized files. Power spectral density curves and natural logarithm value of signal/noise(Ln S/N) ratios were computed from them. In the schizophrenic patients, Ln S/N ratios increased significantly immediately after smoking compared to baseline. But, Ln S/N ratios showed no statistically significant changes after 15 minutes compared to baseline. In alcoholic subjects, Ln S/N ratios showed no statistically significant changes immediately after smoking and after 15 minutes compared to baseline. In conclusion, SPEM was improved in schizophrenic patients immediately after smoking and we hypothesized that nicotinic receptor dysfunction maybe a candidate mechanism for smooth pursuit eye movement abnormalities in schizophrenia.

• Journal of Nutrition and Health
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• v.29 no.1
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• pp.59-69
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• 1996

Effects of dietary calcium(Ca), protein, and phosphorus(P) intake on bone mineral density (BMD) were investigated in 129 Korean premenopausal women(age 31-54 years) without diagnosed disease. BMD was measured at the spine(vertebrae L2-4) and femur(neck, Ward's triangle and trochanter). By stepwise multiple regression analysis it was shown that protein, Ca, and P intakes affected most significantly on BMD at the vertebrae L2-4, protein and P intakes affected most significantly on BMD at the femoral neck and Ward's triangle, and body mass index(BMI) affected most significantly on BMD at the trochanteric region. When ate-matched BMD % at the vertebrae L2-4 and all femoral sites was grouped by three levels(<90%, 90-99%, >=100%), only at the vertebrae L2-4>=100% and 90-99% groups had higher Ca intakes than <90% groups. When Ca, protein and P intakes of the recommended level for Korean(RDA) were grouped by three levels (Ca or P ; <=650mg/d, 650-750mg/d, >=750mg/d, Protein ; <=55g/d, 55-60g/d, >=65g/d), only at the vertebrae L2-4>55g/d of protein intake had higher age-matched BMD % than <=55g/d intake, >=750mg/d of Ca and P intakes, age-matched BMD % than <=650mg/d. In RDA range of Ca, protein, and P intakes, age-matched BMD % of the vertebrae L2-4 and all femoral sites was greater than 90%. Correlation between Ca intake and vertebral BMD was examined closer. There was more significant linear correlation between vertebral BMD and Ca intake below 800mg/d(r=0.346, p<0.0001)than above(r=0.376, p<0.019), implying a threshold effect and vertebral BMD was better expressed as a function of the logarithm of calcium intake(r=0.3881, p<0.0001). These results suggest that Ca, protein, and P intakes greater than RDA help to maintain proper BMD in middle-aged prementopausal women. Especially dietary Ca have important role in increasing the vertebral BMD and 800mg/d of Ca intake is optimum amount.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.697-703
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• 2000

As device dimensions are lastly scaled down, impact ionization(I.I.) events are very important to analyze hot carrier transport in high energy region, and the exact model of impact ionization is demanded on device simulation. We calculate full band model by empirical pseudopotential method and the impact ionization rate is derived from modified Keldysh formula. We calculate impact ionization coefficients by full band Monte Carlo simulator to investigate temperature dependent characteristics of impact ionization for GaAs as a function of field. Resultly impact ionization coefficients are in good agreement with experimental values at look. We how energy is increasing along increasing the field, while energy is decreasing along increasing the temperature since the phonon scattering rates for emission mode are very high at high temperature. The logarithmic fitting function of impact ionization coefficients is described as a second orders function of temperature and field. The residuals of the logarithmic fitting function are mostly within 5%. We Dow, therefore, the logarithm of impact ionization coefficients has quadratic dependence on temperature, and we can save time of calculating the temperature dependent impact ionization coefncients as a function of field.

• The KIPS Transactions:PartD
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• v.11D no.1
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• pp.163-172
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• 2004

In the software development project applying object-oriented development methodology, the research on the UCP(Use Case Point) as a method to estimate development effort is being carried on. The existing research proposes the linear model calculating the development effort that multiplies an invariant on AUCP(Adjusted Use Case Point) which applied technical and environmental factors. However, the statistical model that estimates the development effort using AUCP and UUCP(Unadjusted Use Case Point) is not being studied. The irrelevant relationship of the linear regression model, whose development period is increasing tremendously as the software size increases, is confirmed. Moreover, during the UCP calculating process, there can be errors in FP by applying the TCF(Technical Complexity Factor) and EF(Environmental Factor). This paper presents a non-linear regression model, that does not consider the TCF and EF, and that estimate the development effort from UUCP directly by utilizing the exponential function. An exponential function is selected among the linear, logarithm, polynomial, power, and exponential model via statistical evaluations of the models mentioned above.

• Biomolecules & Therapeutics
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• v.19 no.3
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• pp.357-363
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• 2011

In relieving local pains, ropivacaine has been widely used. In case of their application such as ointments and creams, it is difficult to expect their effects for a significant period of time, because they are easily removed by wetting, movement and contacting. Therefore, the new formulations that have suitable bioadhesion were needed to enhance local anesthetic effects. The effect of drug concentration and temperature on drug release was studied from the prepared 1.5% Carboxymethyl cellulose (CMC) (150MC) gels using synthetic cellulose membrane at $37{\pm}0.5^{\circ}C$. As the drug concentration and temperature increased, the drug release increased. A linear relationship was observed between the logarithm of the permeability coefficient and the reciprocal temperature. The activation energy of drug permeation was 3.16 kcal/mol for a 1.5% loading dose. To increase the skin permeation of ropivacaine from CMC gel, enhancers such as saturated and unsaturated fatty acids, pyrrolidones, propylene glycol derivatives, glycerides, and non-ionic surfactants were incorporated into the ropivacaine-CMC gels. Among the enhancers used, polyoxyethylene 2-oleyl ether showed the highest enhancing effects. For the efficacy study, the anesthetic action of the formulated ropivacaine gel containing an enhancer and vasoconstrictor was evaluated with the tail-flick analgesimeter. According to the rat tail-flick test, 1.5% drug gels containing polyoxyethylene 2-oleyl ether and tetrahydrozoline showed the best prolonged local analgesic effects. In conclusion, the enhanced local anesthetic gels containing penetration enhancer and vasoconstrictor could be developed using the bioadhesive polymer.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.619-623
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• 1991

To investigate nisin production and resistance of Lactococcus lactis ssp. tactis ML (L. lactis $ML_8$, effects of medium, pH of culture broth, and cell growth on the nisin activity, and effect of nisin with or without $Ca^[2+}$ ion on the growth of L. lactzs were analyzed. In the bio-assay of nisin by the agar diffusion method, inhibition-zone diameter of Micrococcus Javus was propotional to the logarithm of nisin concentration ranged 0.5~20 unitlml (12.5~500 ng/mf). Nisin activity of the pasteurized culture filtrates of L. lactis MLs was high at pH 2!3 but was inactivated completely at pH over 6.0. Nisin production of the L. lactis $ML_8$ cultured on LTB broth increased at late logarithmic phase and reached 10.5 unitlml after 16 hr. The cell growth of L. lactis LM 0230, a plasmid free and nisin sensitive strain, was inhibited on agar medium containing 7 unitlrnl of nisin, while L. lactis $ML_8$ showed high survival ability at 20 unitld of nisin. When 40 mM $Ca^[2+}$ ion was added to Elliker broth with 8 unitlml of nisin, the growth pattern of L. lactis $ML_8$ was similiar to that on control medium which did not contain nisin and $Ca^[2+}$ ion, and this suggested that $Ca^[2+}$ increased the nisin resistance of the L. lactis.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.33-38
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• 2006

This work was conducted to find the operating characteristics of an efficient wet grinding system designed to obtain fine rice husk ash powder. Once the rice husk was combusted and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement. Grinding time (15, 30, 45 min), impeller speed (250, 500, 750 rpm), and mixed ratio (6.7, 8.4, 11.l, 20.9) were three operating factors examined for the performance of a wet-type stirred ball mill grinding system. For the operating conditions employed, mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of $2.83{\sim}9.58{\mu}m,\;0.5{\sim}6.73kWh/kg,\;and\;0.51{\sim}3.27m^2/Wh$, respectively. With the wet-type stirred ball mill grinding system used in this study, the grinding energy efficiency decreased with the increase in total grinding time, impeller speed, and mixed ratio. The difference in specific surface area of powder linearly increased with logarithm in total number of impeller revolution and the grinding energy efficiency linearly decreased. Grinding time of 45 min, impeller speed of 500 rpm, and mixed ratio of 6.7 were chosen as the best operating condition. At this condition, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughput, and specific energy input were $2.84{\mu}m,\;2.28m^2/Wh,\;0.17kg/h$, and 2.03kWh/kg, respectively. Wet fine grinding which generates no fly dust causing pollution and makes continuous operation easy, is appeared to be a promising solution to the automatization of rice husk ash grinding process.

• The Journal of Industrial Distribution & Business
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• v.10 no.12
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• pp.35-42
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• 2019

Purpose : This study examines The impact of human resource investment in internal control on stock price crash risk. Effective internal control ensures that information provided is complete and accurate, financial statements are reliable. By overseeing management, internal control systems can reduce agency costs between management and outside parties. In Korea, firms have to disclose information about internal control systems. The working experience of human resources in internal control systems is also provided for interested parties. If a firm hires more experienced internal control personnel, it can better facilitate the disclosure of information. Prior studies reported that information asymmetry between managers and investors increases future stock price crash risk. Therefore, the longer working experience internal control personnel have, the lower probability stock crashes have. Research design, data and methodology : This study analyzed the association between the working experience of internal control personnel and crash risk using regression analysis on KOSPI listed companies for fiscal years 2016 through 2017. The sample consists of 1,034 firm-years of non-financial firms whose fiscal year end on December 31. Career spanning data of internal control personnel was collected from internal control reports. The professionalism(IC_EXP) was measured as the logarithm of the average working experience of internal control personnel in months. Negative conditional skewness(NSKEW) and down-to-up volatility (DUVOL) are used to measure firm-specific crash risk. Both measures are based on firm-specific weekly returns derived from the expanded market model. Results : We find that work experience in internal control environment is negatively related to stock price crashes. Specifically, skewness(NSKEW) and volatility (DUVOL) are reduced when firms have longer tenure of human resources in internal control division. The results imply that firms with experienced internal control personnel are less likely to experience stock price crashes. Conclusions : Stock price crashes occur when investors realize that stock prices have been inflated due to information asymmetry. There is a learning effect when internal control processes are done repetitively. Thus, firms with more experienced internal control personnel could manage their internal control more effectively. The results of this study suggest that firms could decrease information asymmetry by investing in human resources for their internal control system.