• 설비공학논문집
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• 제16권7호
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• pp.639-644
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• 2004

This paper deals with the heat transfer characteristics of R-1270 (Propylene), R-600a (Iso-butane) and R-290 (Propane) as an environment friendly refrigerant and R-22 for condensing. The experimental apparatus has been set-up as a conventional vapor compression type heat pump system. The test section is a horizontal double pipe heat exchanger. A tube diameter of 12.70 mm with 1.32 mm wall thickness is used for this investigation. The test results showed that the local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average condensing heat transfer coefficient was obtained with the maximum value in R-1270 and the minimum one in R-22. Comparing the heat transfer coefficient of experimental results with that of other correlations, the presented results had a good agreement with the Cavallini-Zecchin's correlation. It reveals that the natural refrigerants can be used as substitute for R-22.

• 동력기계공학회지
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• 제18권5호
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• pp.42-47
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• 2014

In this paper, the cycle performance analysis for the COP of supercritical heat pump using various refrigerants is presented to offer the basic design data for the operating parameters of the system. The working fluids are R134a, R22, R32, R290, R600, R600a, R1270 and R744. The operating parameters considered in this study include superheating degree of evaporator, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature in the supercritical heat pump system. The main results were summarized as follows : Superheating degree, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature of supercritical heat pump system have an effect on the COP of this system. With a thorough grasp of these effect, it is necessary to design the supercritical heat pump using R134a. And, in comparison of COP of supercritical heat pump using various refrigerants, R32 and R600 is the highest, and R744 is the lowest among other refrigerants. From these results, it is confirmed that the COP of supercritical heat pump using R744 is higher than that using freon refrigerants such as R32 and R134a.

• 대한방사선기술학회지:방사선기술과학
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• 제41권5호
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• pp.445-450
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• 2018

We aim to evaluate safety of radiation by measuring leakage dose and patient(phantom) incident dose of ZEN-PX II dental portable equipment developed by G company. Measurement for leakage dose of equipment is conducted on the top, at the bottom, on the left, on the right and at the back. Dose measurement incident on the subject with the area dosimeter when using the phantom and measurement the leakage dose of equipment when using the phantom are evaluated. Comparing the right with the highest leakage dose as a 0 cm, 25 cm, 50 cm, 75 cm and 100 cm dose measurement at the measurement height of 100 cm, 64.2 uR was reduced to 47.3 uR in the senser mode 0.32sec. Even in film mode it was measured at 414.4 uR and about 27% lower at 162.6 uR. As the result of this study, when the irradiation time is 2 sec the right side dose is 290.5 uR and sensor mode is 0.32 sec the right side dose is 64.2 uR.

• 설비공학논문집
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• 제19권10호
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• pp.726-734
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• 2007

In this study, lower flammability limits (LFLs) of three hydrocarbon refrigerants (R600a, R290, R1270) and two hydrofluorocarbon refrigerants (R152a, R32) and DME (RE170) are measured by the method proposed by ASTM E681-04 Standard. Flammability tests are carried out at three temperatures of $23^{\circ}C,\;60^{\circ}C\;and\;100^{\circ}C$ and relative humidity 50%. Test results show that the present data for isobutane and propane obtained at $23^{\circ}C$ are similar to those found in the literature, confirming indirectly the reliability of the present test method and facility. For propylene, R152a, and R32, LFLs found in the literature differ considerably. Especially, the deviation of LFL of propylene is more than 30% among the literature data. The present data for propylene, R152a, and R32 agree with either of the data sets available. As the temperature increases from $23^{\circ}C\;to\;100^{\circ}C$, LFLs of all refrigerants tested decrease. LFLs of most refrigerants tested in this study at $60^{\circ}C$ decrease by $0.1{\sim}0.3%$ as compared to those at $23^{\circ}C$. Also LFLs of most refrigerants tested in this study at $100^{\circ}C$ decrease by $0.1{\sim}0.3%$ as compared to those at $60^{\circ}C$.

• 센서학회지
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• 제32권5호
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• pp.290-294
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• 2023

Among various types of harmful gases, hydrogen sulfide is a strong toxic gas that is mainly generated during spillage and wastewater treatment at industrial sites. Hydrogen sulfide can irritate the conjunctiva even at low concentrations of less than 10 ppm, cause coughing, paralysis of smell and respiratory failure at a concentration of 100 ppm, and coma and permanent brain loss at concentrations above 1000 ppm. Therefore, rapid detection of hydrogen sulfide among harmful gases is extremely important for our safety, health, and comfortable living environment. Most hydrogen sulfide gas sensors that have been reported are electrical resistive metal oxide-based semiconductor gas sensors that are easy to manufacture and mass-produce and have the advantage of high sensitivity; however, they have low gas selectivity. In contrast, the electrochemical sensor measures the concentration of hydrogen sulfide using an electrochemical reaction between hydrogen sulfide, an electrode, and an electrolyte. Electrochemical sensors have various advantages, including sensitivity, selectivity, fast response time, and the ability to measure room temperature. However, most electrochemical hydrogen sulfide gas sensors depend on imports. Although domestic technologies and products exist, more research is required on their long-term stability and reliability. Therefore, this study includes the processes from electrode material synthesis to sensor fabrication and characteristic evaluation, and introduces the sensor structure design and material selection to improve the sensitivity and selectivity of the sensor. A sensor case was fabricated using a 3D printer, and an Ag reference electrode, and a Pt counter electrode were deposited and applied to a Polytetrafluoroethylene (PTFE) filter using PVD. The working electrode was also deposited on a PTFE filter using vacuum filtration, and an electrochemical hydrogen sulfide gas sensor capable of measuring concentrations as low as 0.6 ppm was developed.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1957-1963
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• 2005

In this study, external condensation heat transfer coefficients (HTCs) of six flammable refrigerants of propylene (RI270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of $39^{\circ}C$ on a 1023 fpm low fin and Turbo-C tubes. All data were taken under the heat flux of $32\~116\;and\;42\~142kW/m^2$ for the low fin and Turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to $30\%$ higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of $7.3\%$. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.534-541
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• 2008

This paper deals with the heat transfer characteristics of R-290 (Propane), R-600a (Iso-butane) and R-1270 (Propylene) as an environment friendly refrigerant and R-22 as a HCFC's refrigerant for evaporating. The experimental apparatus has been set-up as conventional vapor compression type refrigeration and air-conditioning system. The test section is a horizontal double pipe heat exchanger. Evaporating heat transfer measurements were performed for smooth tube with the outer diameters of 12.70, 9.52 and 6.35 mm and micro-fin tube 12.70 mm, respectively. For the smooth and micro-fin tubes measured in this study, the evaporating heat transfer coefficient was enhanced according to the increase of the mass flux and decrease of the tube diameter. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were superior to those of R-22 and the maximum increasing rate of heat transfer coefficient was found in R-1270. The average evaporating heat transfer coefficients in hydrocarbon refrigerants showed 20 to 28% higher values than those of R-22. Also, the evaporating heat transfer coefficients of R-22 in the tube diameter of the 12.70 mm smooth and micro-fin tube were compared. Generally, the local heat transfer coefficients for both types of tubes increased with an increase of the mass flux. The heat transfer enhancement factor (EF) between smooth and micro-fin tube varied from 1.9 to 2.7 in all experimental conditions.

• 여성건강간호학회지
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• 제13권4호
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• pp.290-298
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• 2007

Purpose: This study was to measure the quality of life(QOL) and to identify the related factors in gynecological cancer patients during chemotherapy. Method: The subjects of this study were the patients who had undergone a hysterectomy and were admitted for chemotherapy at S university hospital between November 2006 and April 2007. Data was collected from 106 gynecological cancer patients with the use of a structured questionnaire which measured the QOL(FACT-G), body image, the presence of anxiety & depression, uncertainty, and family support. The data was analyzed by the SPSS win 12.0 program. Results: The mean FACT-total score was 62.1$({\pm}16.7)$ (range; 26-107). Positive correlations were found between QOL and body image(r= .67, p= .00), and QOL and family support(r= .32, p= .00), whereas there were negative correlations between QOL and anxiety(r= -.54, p= .00), QOL and depression(r= -.70, p= .00), and QOL and uncertainty(r= -.59, p= .00). Fifty seven pre cent of the variance in subjective overall QOL can be explained by depression, body image, and uncertainty(Adj $R^2$= .57, F=47.00, p= .00). Conclusion: Our patients had a relatively low QOL score. Factors significantly affecting quality of life were depression, body image and uncertainty. Nursing interventions, therefore, should be focused on improving QOL in gynecological cancer patients during chemotherapy, particularly so in patients with depression, uncertainty or poor body image.

• 대한치과기공학회지
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• 제42권3호
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• pp.290-297
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• 2020

Purpose: This study aimed at exploring the impacts of organizational conflict and job satisfaction on the turnover intention among dental technicians. Methods: This study utilized a descriptive research design. A structured questionnaire was administered to 159 dental technicians. Of the collected questionnaires, data from 127 valid questionnaires were analyzed using t-tests, analysis of variance, Pearson's correlation coefficient, and hierarchical multiple regression using the IBM SPSS 20.0 statistical package. Results: A positive correlation was identified between organizational conflict and turnover intention (r=0.46, p<0.001); however, a negative correlation was shown between job satisfaction and turnover intention (r=-0.50, p<0.001). A hierarchical multiple-regression model was employed to analyze working hours, unfair treatment from dentists and dental hygienists, organizational conflict, and job satisfaction, which contributed to providing an explanation to 39% of the turnover intention of dental technicians (F=14.16, p<0.001). Furthermore, organizational conflict (β=0.32, p<0.001), job satisfaction (β=-0.31, p=0.003), and working hours (β=0.21, p=0.010) were all shown to affect turnover intention. Conclusion: The impact of the negative consequences of organizational conflict and working hours on the turnover intention should be considered within core strategies for increasing the turnover periods for dental technicians.

• 대한수의학회지
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• 제32권4호
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• pp.511-521
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• 1992

The distribution of the hepatic arteries within the liver in 30 Korean native cattle were observed. Vinylite solution was injected into the hepatic arteries of 10 livers for cast preparation. The angiography was prepared in 20 livers by injected 30% barium sulfate solution into the hepatic arteries and then radiographed on X-ray apparatus. The results were summarized as follow ; 1. The hepatic arteries were divided into the Ramus (R.) sinister, R. dexter and R. intermedius. The intrahepatic arteries were derived from the R. sinister and R. dexter. The R. intermedius divided into the Arteria(A.) gastrica dextra, A. gastroduodenalis and A. cystica. 2. The right branch (ramus dexter) of the hepatic artery supplies the right lobe and caudate process. It consisted of the A. dorsalis lobi dextri, A. ventralis lobi dextri and A. lobi caudati. They formed one common trunk with three arteries(6 cases, 20%), and two arteries formed common trunk with the A. ventralis lobi dextri and A. lobi caudati (16 cases, 52.8%), or with A. dorsalis lobi dextri and A. lobi caudati (5 cases, 16.5%). The three arteries arose from the A. hepatia independently(3 cases, 10%). 3. The left branch (ramus sinister), larger than the right and often double (6 cases, 20%), supplies the caudate, quadrate and left lobes, and often gives origin to the A. gastrica dextra. 4. The branches of hepatic artery in the left lobe were derived from A. dorsalis lobi sinistri, A. ventralis lobi sinistri and A. intermedius lobi sinistri. The A. intermedius lobi sinistri were absent in some cases (3 cases, 10%). They almostly originated a single branch and often two branches. 5. The A. cystica arose from the R. intermedius(27 cases, 90%) and A. hepaica(3 cases, 10%). 6. The Rami processus papillarum arose from dorsal border of the Pars transversa of the left branch(19 cases, 62.7%), the left branch and right branch (9 cases, 30%) or A. hepatica(2 cases, 6.6%). 7. The A. lobi quadrata arose from either the Pars transversa of left branch (12 cases, 40%) or A. hepatica(4 cases, 13.2%). It also arose from both Pars transversa of left branch and A. ventralis lobi sinistri (3 cases, 10%). 8. The anastomosis on the branches of A. hepatica was observed in intrahepatic and cystic arteries. The left and right branches ramified several secondary radiating branches within the liver. 9. The hepatic arteries formed a very short common trunk of the right branch ($18.75{\pm}11.89$ : 2.20~44.8mm) and a long Pars transversa of the left branch($72.85{\pm}20.04$ : 28.2~104.1mm). 10. The ramified angles at the A. dorsalis lobi dextri, A. ventralis lobi dextri, A. lobi sinistri, A. ventralis lobi sinistri, A. lobi quadrata, A. cystica and Rami processus papillarum were 50-80, 270-300, 340-20, 120-160, 160-290, 200-230, 250~290, 230~280 and 80~120 degrees, respectively.