• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.491-498
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• 2010

Humidification of PEM fuel cells is necessary for enhancing their performance and lifetime. In this study, a humidification system was designed and tested; the system includes an air-supply tube (inner diameter: 75 mm) through which a nozzle can be directly inserted and a cyclonic separator for the removal of water droplets. Three types of nozzles were employed to study the influence of injection pressure, air flow rate, and spray direction on the humidification performance. To evaluate the humidification performance, the concept of humidification efficiency was defined. In the absence of an external heat source, latent heat for evaporation will be supplied by the own enthalpies of water and air. Thus, the amount of water sprayed from the nozzle is the most critical factor affecting the humidification efficiency. Water droplets were efficiently removed by a cyclonic separator, but re-entrainment occurred at high air flow rates. The absolute humidity and humidification efficiency were $21.29\;kJ/kg_{da}$ and 86.57%, respectively, under the following conditions: nozzle type PJ24; spray direction angle $90^{\circ}$; injection pressure 1200 kPa; air flow rate 6000 Nlpm.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.62-62
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• 2018

Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).

• Journal of Digital Convergence
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• v.15 no.1
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• pp.227-238
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• 2017

Cardiac arrest is a serious intensive emergency disease that causes death within less than several minutes by depriving the body and brain of blood supply. Survival rate of cardiac arrest patients outside of hospitals is especially low. This is because pedestrians usually do not perceive the patient as a sick person, also, even if they do so, they have no medical knowledge to properly react to such emergency. The purpose of this study is to propose a solution that uses widely spread smart phones to alert pedestrians of the cardiac arrest patient, prevents cardiac arrest, and provides first-aid measures. By applying the proposed solution, cardiac arrest can be prevented in advance, pedestrians can be alerted to keep the golden time(4 minutes), and first witness can quickly proceed with CPR, ultimately enhancing the survival rate of the cardiac arrest patient.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.582-589
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• 2009

The energy generated by braking vehicle would simply be converted into waste heat by its braking resistors if no other vehicle is accelerating at exactly the same time. Up to 45% of the tractive power of vehicles capable of returning energy to the power supply can be regenerated during braking and that this energy can be used to feed vehicles which are accelerating at the same time. Such synchronized braking and accelerating can not be coordinated, the ESS(energy storage system, here after) stores the energy generated during braking and discharges it again when a vehicle accelerates. The ESS is able to store and discharge energy extremely quickly, consequently enabling a complete exchange of energy between vehicles, even if they are not braking and accelerating at precisely the same time, as is most frequently the case in everyday service. The energy saving rate is related to the headway. If the headway is long/short, the energy saving goes up/down, When the headway is short, the ESS can not save much regenerative energy. The headway of SeoulMetro line 2 as the worst case is very short in Korea urban transit system. So, the energy saving rate will be very low. If the ESSs are applied to another railway system, we can expect that the effectiveness is better than the results of SeoulMetro line 2. This paper presents effects of energy saving obtained by applying the ESS to SeoulMetro line 2.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.144-148
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• 1999

This study was conducted to test actual oxygen consumption rates of Nile tilapia (Oreochromis niloticus) at a commercial scale high density culture tank in the recirculating culture system, with a special emphasis on the oxygen consumption rate of this species with different daily feeding frequencies. Nile tilapia, an average of 400 g and a total wright of 390 kg, were stocked in a circular concrete tank of 2.9 m in diameter and 0.8 m in depth, in a recirculating culture system. The fish were fed commercial diet 1, 2, 5, and 9 times per day between 09:00 h and 19:00 h. feed was evenly supplied where the fish were fed more than once a day. Dissolved oxygen of influent and effluent water was monitored every 50 seconds by a computer with electrodes for 24 hours. The standard metabolic rate of tilapia was $39.31{\pm}4.4mg\;O_2/kg$ fish/hr in the present study. The maximum oxygen consumption was reached between 30 to 50 minutes after feeding. The maximum oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were 161.2, 123.4, 111.1 and 111.1 mg $O_2/kg$ fish/hr, respectively. While the mean oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were $79.9{\pm}21.5,\;81.3{\pm}14.8,\;84.2{\pm}9,9$ and $98,9{\pm}11.0mg\;O_2/kg$ fish/hr, respectively. These results show that oxygen consumption rates are not much different between the feeding frequencies. These results could be used to design to provide desirable oxygen supply system in the recirculating high-density tilapia culture system.

• Journal of Korean Public Health Nursing
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• v.13 no.1
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• pp.41-62
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• 1999

Recently the request of the patients to participate in the medical courses has been expanding due to elevated sense of right on the people's health. merchandised medical treatment by mass supply, human right declaration of the patients, generalized medical informations by the mass media and the change of human relation between the medical personnels and the patients. Under these phenomena the accident by the nurses have been increasing by the area of the nurses having been expanded and their independent roles having been increased. Such nursing accidents are the important subject which the professional occupation of the nurses has been facing but legal protective capability of the nurses has been very weak. Therefore this study has examined the degree of the experience of the nursing accident that happens in the clinical nursing scenes in the general hospital to provide the basic materials for the protection and the counter measures of the nursing accidents. The following is the conclusion based by the above examination. 1) The general characters of the subjects of this study is that they are mostly single in their twenties and graduate from nursing college. Their total clinical career is above 5 years$(44.8\%)$ and their current clinical parts' career is between 1-3 years$(40.1\%)$. So these facts suggest that most hospitals has taken the working rotation policy on nurses. 2) The level of nurses' knowledge on the nursing law is accurate partially but isn't it patially. So it is suggested that nurses need the accurate information and education about the nursing law. But the nurses' attitude is very approved of the establishment of a unilateral nursing law. 3) The relation between the demographic characters of the subjects and their attitudes on the nursing law shows that there is no significant differences except the relation between the attitude 6(the sufficient level of education on nursing law in formal education course) and age. total clinical career. 4) The perception of the nurses shows that the cause of the nursing accident has been due to the heavy work$(78.2\%)$. short of professional knowledge and skill$(60.2\%)$, discordance with Doctors. patients and patients' families. They report the accident to the head nurse first$(81.8\%)$ and within 30 minute$(75.1\%)$. The hour of nursing accident frequently happened is regardless of service hour with $49.4\%$ in response rate. the highest rate. and the nursing accident happens in the night more than the daytime. Even though most nurses think that they are themselves responsible for nursing accident. it is found that the chief cause of the nursing accident is due to the nurses' heavy work$(78.2\%)$. So the causes of nursing accidents is analysed. it may be suggested that the endeavor of hospital and nursing organizations to decrease nursing accidents is very important. 5) The coping patterns of patients with nursing accidents are mostly active attitude such as a violent words$(69\%)$. sue or accusation$(36.4\%)$, monetary compensation $(35.6\%)$ except a understanding cases$(38.7\%)$. But the coping patterns of hospitals with nursing accidents are mostly to investigate the accurate cause.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.333-350
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• 1999

Today freeway is thought to be a very important transportation facility carrying tremendous traffic flow as the main corridor within the area of between the areas. However freeway is experiencing severe congestion and accidents by increased entrance ramp flow especially at peak time period. Ramp meters on the freeway entrance ramps that supply traffic to the freeway in a measured or appropriately regulated amount are needed for alleviating freeway congestion. Because ramp meters can be operated to discharge traffic at a measured or regulated rate thus maintaining more uniform speed on the mainline section maximizing the throughput to the freeway within the capacity of a downstream bottleneck and reducing the congestion related accidents. Thus the objectives in this study were to analyze the traffic characteristics on the freeway I-94 with ramp metering system before/after ITS technology in Detroit (Michigan) area compare shifts of the traffic characteristics on the freeway I-94 before/after ITS technology and finally suggest a better ramp metering strategy for the freeway system The following results were obtained: i)Flow occupancies and speeds on the mainline merge section of freeway were shown to be a big difference depending on the peak periods areas and directions based on the distribution of traffic flow characteristics on the freeway. ii)Reduced speed was shown to be more than 5 mph and ramp flow was also shown to be more than 240 vph at peak periods if there was the ramp metering system constructed on the freeway. iii)Ramp metering system was shown to be optimally operated on the freeway if ramp flow could be maximized within the range of over 900 vph and reduced occupancy could be also maximized by no more than 2 percent at peak periods. iv)The average flows on the freeway after the ITS technology were shown to be a decrease of over 20% depending on the peak periods areas and directions when compared with those flow on the freeway before the ITS technology. over 20% depending on the peak periods areas and directions when compared with those speeds on the freeway before the ITS technology. vi)The average metering rates on the freeway after the ITS technology were shown to be an increase of over 10% depending on the peak periods areas and directions when compared with those metering rates on the freeway before the ITS technology.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.1109-1117
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• 2015

Recently, import supply of glass eels from Philippines has been increased in South Korea, and the species distinction was very important to import traders and Anguilla marmorata and A. bicolor pacifica are major species at Philippines. In this study, the species distinction and the rate were researched targeting imported glass eels from the estuaries of North Luzon and the South Mindanao in May and July, 2014. Dorsal fin position and pigmentation pattern at caudal fin are the trait standard for species distinction. The results about morphological identification were coincide with the result of the genetic identification, and the regional distribution of A. marmorata rate was over 90% at North Ruzon in May. However, the rates of A. bicolor pacifica and A. mamorata were 63.3% and 36.7% in May, and were 53.3% and 46.7% in July respectively at South Mindanao.

• Plant Journal
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• v.13 no.2
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• pp.46-51
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• 2017

In this study, the boiler efficiency and the change of boiler combustion state with the burner operation of the uppermost layer of 870MW opposite fired coal boiler were measured. Test results showed that the boiler efficiency was high in the order of the uppermost layer simultaneous operation of the front and rear burners, the front burner, and the rear burner operation. When the front and rear burners were operated simultaneously, the heat absorption rate of water walls in the boiler furnace was uniform at four side, and the temperature deviation of the left and right steam on the convection front surface decreased. As the heat absorption rate of the boiler improved, the loss of boiler exhaust gas decreased and the coal supply amount decreased by 8 tons/hour compared to the operation of the rear burner. This will contribute not only to the reduction of fuel cost but also to the reduction of greenhouse gas emissions.

• Journal of Preventive Medicine and Public Health
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• v.27 no.3 s.47
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• pp.609-626
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• 1994

This study was conducted to investigate whether variations in hospital services utilization across small geographic areas in Korea existed, and if so, what factors are responsible for the variation. The claims data of the fiscal year 1992 obtained from the regional health insurance societies were used for the study. Main findings of the research can be summarized as follows: 1 Extremal Quotients (EQ) of hospital expenditure per capita and hospital days per capita were 2.69 and 2.73, and Coefficient of Variation (CV) were 0.14, both, respectively. The EQ and the CV of admission rate were also 2.71, 0.15. The EQ and the CV of expenditure per admission were 1.73, 0.10 and those of hospital days per admission were 1.29, 0.06. All these statistics were statistically significant and this result provides strong evidence for the existence of small area variations. 2. Comparing patterns of variation among areas, the area which showed higher utilization amounts is Chansungp'o. Koje area, whereas the areas which showed lower utilization amounts are Yongju, Changhung, Miryang, Mokp'o, Koch'ang area. 3. Multivariate analytic methods were used to examine factors related to the variation across areas. In terms of the health resource availability variables, beds per capita or physicians per capita were positively associated with all utilization indices. As for the health service market structure variables, the proportion of health care institutions operating for less than f years was positively related to the expenditure per capita, hospital days per capita and expenditure per admission. In addition the proportion of the private health care institutions also had a negative relationship with total utilization amount and admission rate and the proportion of physicians under age 40 was negatively associated with expenditure per capita and expenditure per admission. With regard to the socio-demographic characteristics, proportion of medicaid population was positively related to hospital days per capita, and percentage of paved road was positively related to hospital days per admission. As a conclusion, wide variations existed across small areas in Korea and supply factors were found to be important in explaining the variation.