• Journal of Korean Society of Transportation
• /
• v.17 no.5
• /
• pp.123-135
• /
• 1999

The rapid increase of Passenger cars which is caused by the discomfort of Public transit and the Preference of automobiles is the major factor of increasing traffic congestions in Seoul With the point that leading the automobilists to the Public transit can be the most important Policy to ease these traffic congestions, this study focuses on the behavioral aspects of company employees and university students and investigates factors influencing bus ridership. To be brief, by estimating bus ridership through count models, this study investigates factors which influence bus ridership and elicits Political suggestions which lead automobilists to Public transit. The Purpose in this study is the application of appropriate count data model. The count data models have been widely applied to the economic area from the middle of the 1980s and to transportation aspect mainly in the foreign countries from the latter half of the 1980s. Even though a few studies in this country employed count data model to count data. all of them were Poisson regression models without suitable tests for the importance of the model specification. In the end, as the result of statistical test, negative binomial regression model which is suitable for overdispersed data was found to be appropriate for the data of weekly bus ridership. To emphasize the importance of model specification, both of poisson regression model and negative binomial regression model were estimated and the results were compared.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.5
• /
• pp.350-355
• /
• 2013

Little information is available for emission pathway even if HFC-134a that is known as one of the major greenhouse gases has been broadly used in Korea. This paper attempts to clarify the emission characteristics of HFC-134a used for refrigerant of cold drinking vending machines (CDVMs) at the use- and disposal-phase. We measured the residual amounts in the scrap CDVMs of 47 by applying commercial recover for refrigerant. The first-order kinetic model was introduced and the emission rate would be proportional to the remaining quantity of refrigerant. The emission factor at the use-phase was determined indirectly to be $6.9{\pm}0.7$ %/yr within a confidence interval of 95%, using information on residual amount and elapsed operation time at the disposal point. Correspondingly, the annual emission rate of HFC-134a per CDVM was determined to be 11.6 g. The average residual rate of HFC-134a in scrap CDVMs was assessed to be $62.5{\pm}2.2%$, leading to a potential emission amount of 144.8 g per scrap CDVM. The chemical compositions of refrigerants from scrap passenger vehicles are quite similar to those of new refrigerants, suggesting that the refrigerants from scrap passenger vehicles could be reused. During the recovering process of refrigerant, the recovered refrigerant was contaminated by compressor lubricant that accounted for about 30% in weight. It is necessary to separate the refrigerant from the recovered material contaminated by lubricant for recycling and reuse the refrigerant.

• Environmental and Resource Economics Review
• /
• v.22 no.3
• /
• pp.411-435
• /
• 2013

Since catastrophe from explosion of Hukushima nuclear power plant, concerns over possibility of exposure to radioactive matter has been disseminating all over the world and frequent accidents of domestic nuclear power plants also has been amplifying throughout the nation. In the past, major focus was made on compensation for local residents who live nearby nuclear power plants, but focal point of this study is on wage premium of workers who are employed in R&D of nuclear power plants. It is difficult to derive socially desirable result if private sectors are responsible for compensation on workers who suffer from physical damages due to the exposure to radioactive matter. Because victims should verify the damages that occur in the working places. This study conducted a survey on which job would prefer the respondents who are engaged with the nuclear R&D projects as exposure levels to radioactive matter, security of job, location of firms, and work intensity differ. As a result, exposure to radioactive matter was the most important attribute in choosing alternative jobs followed by job security, work intensity and job location. Annual willingness to pay for reduction of exposure to radioactive matter was estimated as 7730~7770 thousand KRW depending on different econometric models. Therefore, Korean government should prepare institutional foundation in order that appropriate compensation should be made on workers who are engaged in R&D projects on nuclear power plants if they have damages from the exposure to radioactive matter.

• Korean Journal of Clinical Laboratory Science
• /
• v.48 no.4
• /
• pp.401-410
• /
• 2016

Since the late 19th century, scientific logic and techniques have been used extensively in the field of clinical pathology, including many laboratory tests utilizing various apparatuses and instruments. Among the techniques to measure hemoglobin, the visual color comparison method was most popular around this time; the specific gravity method and gasometric method were not widely adopted. Instruments that use the visual color comparison method include Gowers' hemoglobinometer, von Fleischl's hemoglobinometer, Dare's hemoglobinometer, Oliver's hemoglobinometer, Haden-Hausser hemoglobinometer, and Spencer Hb meter. Initially, the visual color comparison methods were used to diluate and hemolyze blood with distilled water and then to measure its color. Later, these methods were further developed to measure hemoglobin without dilution, and improved with the formation of acid or alkaline hematin ensuring the stability of color development. Hammerschlag's method as well as the Schmaltz and Peiper's methods were based on specific gravity measurement, but they were not widely used. The gasometric method used the Van Slyke gasometer, indirectly measuring the hemoglobin concentration. This method provides the most accurate results. This survey examined the characteristics and limitations of hemoglobinometers and methods used to measure hemoglobin from the late 19th century to the early-and mid-20th century. Moreover, this study aims to improve the understanding and applicability of the current methods and emerging technologies used in measuring hemoglobin. It is also expected that this investigation is the starting point to promote awareness of the need to organize historical data for a variety of historical relics of the diagnostic laboratory tests.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.18 no.1
• /
• pp.1-10
• /
• 1982

Diffusion processes in tidal swinging coastal waters are studied by releasing one hundred liters of Rhodamine B four times. Dye patches were formed from instantaneous point sources. The patches were sampled with a pump on a tracking boat, and samples were analyzed with fluorospectro-photometer. The patterns of patches were reconstructed and their characteristics were analyzed in terms of variance of concentration, area estimation, and decrease rate of peak concentration. In all of the four experiments, the dye patches were mos시 elongated to the direction of current axis. the elongation rate was 0.34 on the average. Apparent diffusivities were 620 to 3,000 cm super(2) /sec during initial period of 90 minutes. The variance increased by exp(0.047t) on the average, and peak concentration deceased by exp(-0.044t) on the average.

• Journal of Labour Economics
• /
• v.25 no.1
• /
• pp.47-74
• /
• 2002

Since the Economic Crisis at the end of 1997, unemployment rate soared up to the record-high 8.6% (February 1999) and, for youth aged 15~29, it was 14.6% (27.8% for aged 15~19). In spite of economic recovery after the crisis, new participants in labor market at the school-to-work transition have faced with difficulties in finding their first jobs and, even further, the ratio of youth at out-of the labor force but not in school has remained at a higher level. It is important to calibrate the negative effects of nonemployment in the short-run as well as in the long-run, but there has been few study on the school-to-work transition in Korea. This study focus on the nonemployment duration to first job after formal education and comparison of its pattern before and after the crisis. A proportional hazard model, considering job prenaration before graduation (21.4% of the sample), with the semi-parametric baseline hazard is applied to the sample from the Korean Labor and Income Panel Survey(1998~2000) and its Youth Supplemental survey(2000). Interview of the Survey is conducted, by the Korea Labor Institute, to the same 5,000 household and 13,738 individual sample, guaranteeing nationwide representativeness. The Supplemental Survey consists of 3,302 young individuals aged 15 to 29 at the time of survey and 1,615 of them who are not in school and provide appropriate information is used for the analysis. The empirical results show that there exists negative duration dependence at the first three or for months at the transition period and no duration dependence since a turning point of the baseline hazard rate and that unemployment rate reflecting labor demand conditions has a positive effect on exiting the nonemployment state, which is inconsistent with a theoretical conclusion. Estimation with samples separated by the date of graduation before and after the crisis shows that the effect of unemployment rate on the hazard was negative for the pre-crisis sample but positive for the post-crisis sample.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.4
• /
• pp.117-122
• /
• 2018

A large-capacity three-phase system air conditioner recently includes an inverter circuit to reduce power consumption. The inverter circuit uses a DC voltage that comes from DC-link power capacitor with the function of rectifying, which means AC voltage to DC voltage using a diode. An electrolytic capacitor is generally used to satisfy the voltage ripple and current ripple conditions of a DC-link power capacitor used for rectifying. Reducing the capacitance of the capacitor decreases the size, weight, and cost of the circuit. This paper proposes an algorithm to reduce the input ripple current by combining the minimum point estimation phase locked loop (PLL) phase control and the average voltage d axis current control technique. When this algorithm was used, the input ripple current decreased by almost 90%. The current ripple of the DC-link capacitor decreased due to the decrease in input ripple current. The capacitor capacity can be reduced but the electrolytic capacitor has a heat generation problem and life-time limitations because of its large equivalent series resistance (ESR). This paper proposes a method to select a film capacitor considering the current ripple at DC-link stage instead of an electrolytic capacitor. The capacitance was selected considering the voltage limitation, RMS (Root Mean Square) current capacity, and RMS current frequency analysis. A $1680{\mu}F$ electrolytic capacitor can be reduced to a $20{\mu}F$ film capacitor, which has the benefit of size, weight and cost. These results were verified by motor operation.

• Resources Recycling
• /
• v.19 no.5
• /
• pp.31-43
• /
• 2010

To fabricate porous SiC candle filter for filtration facility of the IGCC system, the candle type filter preforms were fabricated by ramming and vacuum extrusion process. A commercially available ${\alpha}$-SiC powders with various particle size were used as starting raw materials, and $44\;{\mu}m$ mullite, $CaCO_3$ powder were used as non-clay based inorganic sintering additive. The candle typed preforms by ramming process and vacuum extrusion were sintered at $1400^{\circ}C$ for 2h in air atmosphere. The effect of forming method and particle size of filter matrix on porosity, density, strength (flexural and compressive strength) and microstructure of the sintered porous SiC candle tilters were investigated. The sintered porous SiC filters which were fabricated by ramming process have more higher density and strength than extruded filter in same particle size of the matrix, and its maximum density and 3-point bending strength were $2.00\;g/cm^3$ and 45 MPa, respectively. Also, corrosion test of the sintered candle filter specimens by different forming method was performed at $600^{\circ}C$ for 2400h using IGCC syngas atmosphere for estimation of long-term reliability of the candle filter matrix.

• Journal of agricultural medicine and community health
• /
• v.21 no.2
• /
• pp.231-241
• /
• 1996

The estimation of medical care status and the planning of health service program should be done according to each community resident's socio-medical background and public health service. In this point, it is most necessary to be set the exact and new socio-economic statistics data in Nepal, one of the worst countries in national health status. We surveyed 668 house, 3,425 residents in Dolka area, Nepal from January 25th to February 1st, 1995. 1. In personal characteristics, the ratio of men and women was similar, the person who were below 19 years old were 28.1% and the single were 52.4%. The illeterate person were 50.3% and the lower group in economic status which had been estimated by interviewers were 46.9%. 2. In sanitational characteristics, the person who used stream water or rainwater to drink were 42.2% and the person who always boiled water to drink were only 8.3%. The person who had not toilet in their house were 67.3% and the lower group in sanitational status which had been estimated by interviewers were 61.8%. 3. The prevalence rate of illness during the last one month were 8.6% and the chronic were 26.1% and the acute were 72.5%. The distribution of sickness symptom were headache, fever and joint pain in order and the person who took no medical treatment among the sick were 37.0%. The patterns of medical utilization were public health center, hospital and pharmacy in order. 4. Illness prevalence was significantly related to sex, age, merital status and educational experience. The residents who were women, 40 years old or more, married and had not educational experience were apt to take illness. 5. Medical utilization was significantly related to educational experience, job, distance from home to medical facilities and economic status. The person who had educational experience, were officer workers or merchants, lived near by medical facilities and had higher economic status took medical treatment very well.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.47 no.2
• /
• pp.54-64
• /
• 2010

Localization is the most important feature in the sensor network environment because it is a basic element enabling people and things to aware the circumference environment. Existing localization methods can be categorized as either range-based or range-free. While range-based is known to be not suitable because of the irregularity of radio propagation and the additional device requirement. range-free is much appropriated for the resource constrained sensor network because it can actively locate by means of the communication radio. But its location accuracy is just depended on the density of circumference nodes; it is very low in low-density sensor network environment. This paper proposes a mobile object tracking method, named DRTS(Distributed Range-hybrid Tracking Scheme), with combining range-based and range-free. It is optimally making use of the location, communication range, and received signal strength from circumference nodes. Especially, it can greatly improve the mobile tracking accuracy by adapting a new prediction method, named EGP(Estimative Gird Points) into the proposed location estimation method. The simulation results show that our method outperforms the other localization and tracking methods in the tracking accuracy point of view.