• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.95-105
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• 2001

A series of experiment is carried out to determine the holding power of the existing anchors used in the stationary gear in the coast of the South sea. The experiment apparatus is made of the pulling machine, the load cell, the personal computer and three water tanks the bottom of which are mud, sand and m & s respectively. The result obtained are as follows : 1. On the tension and holding power of the existing anchors, B-type of the stock anchor with two fluke shows the greatest and gets smaller on order of A-type one with a fluke. The holding power of the anchors shows the greatest in the mud and gets smaller in order of m & s, sand. And, the holding power depending upon the length of anchor rope increase as the length does up to the 4 times of depth. 2. On the holding power per fluke area of the existing anchors in case of ration of length of anchor rope to depth is 2, 3 and 4, A-type anchor shows about 310-320 kg/m supper(2), 470-480 kg/m supper(2), 590-640 kg/m supper(2) respectively, B-type one 260-265 kg/m supper(2), 390-450 kg/m supper(2), 630-700 kg/m supper(2) respectively, and C-type one 70-100 kg/m supper(2), 150-180 kg/m supper(2), 210-270 kg/m supper(2) respectively. The holding power per fluke area of the anchors increase as the length of anchor rope does. 3. On the coefficient of holding power of the existing anchors, A-type anchor shows the greatest and gets smaller in the order of B-type one, C-type one.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.347-358
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• 2012

The SWAT (Soil and Water Assessment Tool) should be calibrated and validated with observed data to secure accuracy of model prediction. Recently, the SWAT-CUP (Calibration and Uncertainty Program for SWAT) software, which can calibrate SWAT using various algorithms, were developed to help SWAT users calibrate model efficiently. In this study, three algorithms (GLUE: Generalized Likelihood Uncertainty Estimation, PARASOL: Parameter solution, SUFI-2: Sequential Uncertainty Fitting ver. 2) in the SWAT-CUP were applied for the Soyang-gang dam watershed to evaluate these algorithms. Simulated total streamflow and 0~75% percentile streamflow were compared with observed data, respectively. The NSE (Nash-Sutcliffe Efficiency) and $R^2$ (Coefficient of Determination) values were the same from three algorithms but the P-factor for confidence of calibration ranged from 0.27 to 0.81 . the PARASOL shows the lowest p-factor (0.27), SUFI-2 gives the greatest P-factor (0.81) among these three algorithms. Based on calibration results, the SUFI-2 was found to be suitable for calibration in Soyang-gang dam watershed. Although the NSE and $R^2$ values were satisfactory for total streamflow estimation, the SWAT simulated values for low flow regime were not satisfactory (negative NSE values) in this study. This is because of limitations in semi-distributed SWAT modeling structure, which cannot simulated effects of spatial locations of HRUs (Hydrologic Response Unit) within subwatersheds in SWAT. To solve this problem, a module capable of simulating groundwater/baseflow should be developed and added to the SWAT system. With this enhancement in SWAT/SWAT-CUP, the SWAT estimated streamflow values could be used in determining standard flow rate in TMDLs (Total Maximum Daily Load) application at a watershed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1349-1354
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• 2013

Sealing structure to prevent flowing hot gas into the driving device, located between the driving shaft and the liner of On-Off valve for controlling the hot gas flow path was studied. Wear occurs due to the constant movement of the driving shaft controlled by actuator on graphite as the sealing material. In this paper, the dynamic wear behavior in high temperature of graphite(HK-6) to be used as sealing material was evaluated. Reciprocating wear test was carried out for the graphite(HK-6) to the relative motion between shaft materials(W-25Re). The results of friction coefficient and specific wear rate according to contact load, sliding speed at room temperature and $485^{\circ}C$ considering the actual operating environment were evaluated. Through the SEM analysis of the worn surface, third body as lubricant films were observed and lubricant effect of third body was considered.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.238-245
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• 2010

Progressive collapse is defined as a collapse caused by sectional destruction of a structural member which links to other surrounding structures. Currently the design guidelines for the prevention of progressive collapse is not available in Korea. So, structural engineers have a difficulty in evaluating progressive collapse. In this study, the static and dynamic analysis to evaluate the methods and procedures are conducted using commercial analysis program for RC moment resisting frames. According to the study, DCR value of RC moment resisting frame system based on code in Korea is over 2 and it shows that it can't provide alternate load paths due to the progressive collapse. And additional reinforcement should be considered for the progressive collapse resistance. As a result of vertical deflection and DCR value of linear static analysis and linear dynamic analysis, the results of dynamic analysis were underestimated more than the result of static analysis. Thus, the dynamic coefficient value of 2 provides conservative estimation.

• Journal of dental hygiene science
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• v.15 no.3
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• pp.280-286
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• 2015

The purpose of this study was to examine dental hygienist's emotional labor, burnout and turnover intention. Data were collected from 215 dental hygienists working at hospitals and dental clinics through self-administered questionnaire, and analyzed by statistical analysis using t-test, ANOVA, Pearson's correlation coefficient and multiple regression analysis. The main findings of the study are as follows: the higher the educational level of dental hygienists, and the bigger the size of dental institutions they work, and the lower the monthly income of dental hygienists, the higher the level of emotional labor of dental hygienists. Burnout was influenced on emotional labor and turnover intention. Emotion labor and turnover intention were influenced on burnout. Tenure under 5 years, five-day workweek (non), emotional burnout were found to have significant effects on the turnover intention. Dental hygienists were doing relatively high emotional labor, and it influences his burnout experience and turnover intention. It is needed to make the workplace better environment which can secure appropriate work load and rewards, and education programs etc.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.221-227
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• 2005

Aim of this study is to investigate an aerodynamic effect of a drag-reducing device on a heavy-duty truck. The vehicle experiences two different kinds of aerodynamic forces such as drag and uplifting force (or downward force) as it is traveling straight forward at constant speed. The drag force on a vehicle may cause an increase of the rate of fuel consumption and driving instability. The rolling resistance of the vehicle may be increased as result of the negative uplifting or downward force on the vehicle. A device named roof-fairing system has been applied to examine the reduction of aerodynamic drag force on a heavy-duty truck. As for a engineering design information, the drag-reducing system should be studied theoretically and experimentally for the best efficiency of the device. Four different types of roof-fairing model were considered in this study to investigate the aerodynamic effect on a model truck. The drag and downward force generated by vehicle has been obtained from numerical calculation conducted in this study. The forces produced on four fairing models considered in this study has been compared each other to evaluate the best fairing model in terms of aerodynamic performance. The result shows that the roof-fairing mounted truck has bigger negative uplifting or downward force than that of non-mounted truck in all speed ranges, and drag force on roof-fairing mounted truck has smaller than that of non-mounted truck. The drag coefficient $(C_D)$ of the roof-fairing mounted truck (Model-3) is reduced up to $41.3\%$ than that of non-mounted trucks (Model-1). A downward force generated by a roof-fairing mounted on a truck is linearly proportional to the rolling resistance force. Therefore, the negative lifting force on a heavy-duty truck is another important factor in aerodynamic design parameter and should be considered in the design of a drag-reducing device of a tractor-trailer. According to the numerical result obtained from present study, the drag force produced by the model-3 has the smallest of all in all speed ranges and has reasonable downward force. The smaller drag force on model-3 with 2/3h in height may results of smallest thickness of boundary layer generated on the topside of the container and the lowest intensity of turbulent kinetic energy occurs at the rear side of the container.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.35-41
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• 2000

The frequency dependence of the pyroelectric characteristics of $LiTaO_3$ have been investigated by using the dynamic method. In the frequency range between 2 and 1000 Hz, they are measured in both the regimes of pyroelectric current ($R_L=1M{\Omega}$) and pyrelectric voltage ($R_L=17.3G{\Omega}$), which can be selected by adjusting the value of the load resistance. Pyroelectric coefficient depending on the voltage response in the regime of pyroelectric current shows the maximum value of $1.56{\times}10^{-8}C/cm^2{\cdot}K$ at 40 Hz. The maximum values of figures of merits for the voltage response and for the detectivity are measured as $10.8{\times}10^{-11}C{\cdot}cm/J$ and $13{\times}10^{-7}C{\cdot}cm/J$, respectively. The voltage responsivity depending on the voltage response in the regime of pyroelectrci voltage shows the maximum value of 488 V/W at 2 Hz. Noise equivalent power and detectivity shows the minimum value of $3.95{\times}10^{-10}W/{\sqrt}Hz$ and maximum value of $5.6{\times}10^8cm{\cdot}{\sqrt}Hz/W$ at 40 Hz, respectively.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.127-137
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• 2001

Polychlorinated biphenyls(PCBs) are halogenated aromatic compounds with the empirical formula $C_{12}$ $H_{10-n}$C $l_{n}$(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors and transformers, plasticizers, lubricant inks and paint addirives. Once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their persistence in the environment, PCBs in ecological food chains undergo biomagnification because of their high degree of lipophilicity. In 1970s, the worldwide production of PCBs was ceased and the import of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seems to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs in the serum samples of 112 women by GC/MSD and GC/ECD. The main results of this study were as follows. 1. PCBs were detected in all samples. The mean $\pm$SD levels of PCBs in the serum were 3.613$\pm$0.759 ppb, and median were 3.828 ppb. 2. The correlation coefficients of the concentrations of 13 PCB congeners were from minimum, 0.7913 to maximum, 0.9985, and all was significant(p=0.0001). The correlation coefficient between the concentrations of PCBs and p,p'-DDE was 0.9641(p=0.0001). 3. There was a positive association between age and PCBs' concentrations (simple linear regression ; $R^2$=0.86, $\beta$=0.08023, p<0.001). 4. There was a positive association between total lipids in the serum and PCBs' concentrations (simple linear regression ; $R^2$=0.7058, $\beta$=0.00486, p<0.001). 5. For possible predictors of PCBs and p,p' -DDE levels in the serum, age adjusted model (Y=$\beta$$_{0}$+$\beta$$_1$age+ $B_2$X) was applied. For BMI, major residential area, wether to eat caught fish by angling, where to eat caught fish by angling(by parents in the past), fish consumption, meat consumption, meat consumption, and dairy consumption, there was no association. For total conception frequency and lactation frequency and lactation period, there was negative association.ion.

• Journal of Korea Water Resources Association
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• v.53 no.8
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• pp.605-616
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• 2020

The purpose of this study is to assess the future hydrological and water quality change of Man-gyeong river basin (1,602 ㎢) based on future extreme climate change scenarios and reduction of inter-basin water transfer amount using SWAT (Soil and Water Assessment Tool). The SWAT was calibrated (2012~2014) and validated (2016~2018) at 2 water level observation stations (DC, JJ) and 2 water quality observation stations (SR, GJ) considering inter-basin water transfer amount, stream water withdrawal, and point source data. For the streamflow, the coefficient of determination (R²) was 0.70 and the average Nash-Sutcliffe efficiency (NSE) was 0.51 respectively. For the water quality of SS, T-N, and T-P, the R² was 0.72, 0.80 and 0.72 respectively. The future average streamflow under climate change scenarios increased up to 459 mm/yr, and average SS, T-N and T-P yields also increased up to 19,548 ton/yr, 68,748 kg/yr, and 13,728 kg/yr respectively. When the amount of inter basin water transfer decreased, the streamflow especially decreased in spring and winter periods, and the future water quality yields increased under the influence of precipitation. In order to solve the deterioration of water quality due to decrease in the flow rate and an increase in the load, the amount of inter basin water transfer should be maintained to a certain level.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.