• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.8
• /
• pp.102-108
• /
• 2005

In this paper, authors propose novel boost AC-DC converter of high power factor and analyze for waveform and harmonics component of input current. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of conventional converter of high power factor. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.9 no.1
• /
• pp.133-140
• /
• 2014

The purpose of this research was to identify how service composition factor impact organizational performance of long-term care facilities for elderly people. The target population was the staffs who were working at long-term care facilities for elderly people in urban areas of Seoul, Inchon and cities in Kyonggi-do as of September 2012. Independent variables, main factors for organizational performances, are leadership, educational training, compensation, initiative, and service quality. Dependent variables are selected as duty satisfaction, job performance, financial aptitude and beneficiary-oriented policy. SPSS ver18.0 statistical computer program was conducted in order to analyze the multivariate statistical data. The results are examined in detail in terms of the influence of two managing systems in the senior-care service on the organizational performance and the evaluations of the relation and difference caused by the input variables in two managing systems. In one case of the influence of two managing systems in the senior-care service on the organizational performance, the findings show 1) the influence of the service managing factor is clearly related to duty satisfaction with the result of 0.001 (F=37.429) regression data, 2) the influence of the service managing factor is clearly related to job performance with the result of 0.001 (F=55.099) regression data, 3) the influence of the service managing factor is closely related to financial aptitude with the result of 0.001 (F=56.904) regression data, and 4) the influence of the service managing factor is also clearly related to beneficiary-oriented policy with the result of 0.001 (F=61.367) regression data.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.2
• /
• pp.182-192
• /
• 2015

This study develops a digital control scheme with power factor correction for a front-end converter in an electric vehicle battery charger. The front-end converter acts as the boost-type switching-mode rectifier. The converter assumes the two roles of the battery charger, which include power factor control and robust charging performance. The proposed control scheme consists of a charging control algorithm and a grid current control algorithm. The scheme aims to obtain unity input power factor and robust performance. Based on the linear average model of the converter, a constant-current constant-voltage charging control algorithm that passes through only one proportional-integral controller and a current feed-forward path is proposed. In the current control algorithm, we utilized a second band pass filter, a single-phase phase-locked loop technique, and a duty-ratio feed-forward term to control the grid current to be in phase with the grid voltage and achieve pure sinusoidal waveform. Simulations and experiments were conducted to verify the effectiveness of the proposed control scheme, both simulations and experiments.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.30 no.11 s.158
• /
• pp.1589-1597
• /
• 2006

Nowadays, Korean consumers prefer drum-type washing machines to pulsator-type washers. Washing is a complex process involving the interaction of numerous physical and chemical influences. The main factors in the washing operations are the washing chemistry of the detergent along with the mechanical input, the wash temperature, and the time provided by the washing machine. Heavy-duty detergents that are used in drum-type washing machines contain different components from those used in vertical-axis washing machines. The bath ratio and the mechanical actions to which laundry is subjected are different between the drum-type and the vertical-axis washing machines. In this study we examined the effects of wash temperature, wash time, detergent concentration, and revolution speed on the removal of soils from artificially soiled cloths in a drum-type washing machine with heavy-duty commercial detergent. We used multiple regression analyses to find the relative importance of the factors and the optimum washing conditions. The results of these experiments showed that the washing temperature was the most important factor in the effective removal of most soils. This was followed by the washing time, the detergent concentration, and finally the revolution speed. In this study it was found that superfluous amounts of detergent did not sufficiently increase the soil removal rate. Koreans who are used to washing with cold water should increase the wash time to launder more efficiently.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.1
• /
• pp.26-33
• /
• 2007

The intake swirl motion, as one of dominant effects for an engine combustion. is very effective for turbulence enhancement during the compression process in the cylinder of 2-valve engine. Because the combustion flame speed is determined by the turbulence that is mainly generated from the mean flow of the charge air motion in intake port system. This paper describes the experimental results of swirl flow and combustion characteristics by using the oil spot method and back-scattering Laser Doppler velocimeter (LDV) in 2-valve single cylinder transparent LPG engine using the liquid phase LPG injection. For this. various intake port configurations were developed by using the flow box system and swirl ratios for different intake port configurations were determined by impulse swirl meter in a steady flow rig test. And the effects of intake swirl ratio on combustion characteristics in an LPG engine were analyzed with some analysis parameters that is swirl ratio. mean flow coefficient, swirl mean velocity fuel conversion efficiency. combustion duration and cyclic variations of indicated mean effective pressure(IMEP). As these research results, we found that the intake port configuration with swirl ratio of 2.0 that has a reasonable lean combustion stability is very suitable to an $11{\ell}$ heavy-duty LPG engine with liquid phase fuel injection system. It also has a better mean flow coefficient of 0.34 to develope a stable flame kernel and to produce high performance. This research expects to clarify major factor that effects on the design of intake port efficiently with the optimized swirl ratio for the heavy duty LPG engine.

• The Korean Journal of Community Living Science
• /
• v.20 no.2
• /
• pp.263-274
• /
• 2009

The objective of this study is to verify work satisfaction of school food-service employee, of their job characteristics. Subjects were comprised 9 elementary schools, 11 middle schools, and 3 high schools in Ansan city. Data were analyzed 203 questionnaires for frequency, means, one-way ANOVA, $Scheff{\acute{e}}$ test, t-test, and Pearson correlation using SPSS PC Package. Most of the respondents were high school graduate(91.1%), under one million won salary(41.9%), and non license holder(60.6%). Working conditions were part-time job(41.9%), unlimited contractors(51.2%), and 3-5 years of working experience(21.7%). Measure of overall job satisfaction by Likert-type 5 scale, satisfaction of work operation attitude was 3.55 points and work characteristic duty of 4.32 points. The certificate qualified and elementary school's working posture were more satisfied their work attitude than other groups(p<0.05). Salary satisfaction score showed 2.64 points, but the work esteem satisfaction showed 3.34 points. The factor of working circumstance and potentiality satisfaction was only 2.61 points, but interpersonal connection and communication satisfaction was 3.50 points. Between job satisfactions factors, they were highly correlated with each other. The pride and characteristic duty of the work showed the strongest correlated(p<0.001). The satisfaction score of work operation attitude were significantly correlated with characteristic duty(p<0.001), work esteem, interpersonal relationships and communication(p<0.01). With this results, work satisfaction of food service employees showed a relatively high to perform a job task characteristics and work attitudes. However, the working environment and growth in salaries satisfaction were low. A set of duties must be paid according to the labor intensity. As removing the disturbing factors, the improvement in the quality of the feed will be able to expect substantial effects.

• Korean Journal of Materials Research
• /
• v.25 no.11
• /
• pp.616-621
• /
• 2015

Atmospheric pressure plasma is used in the biological and medical fields. Miniaturization and safety are important in the application of apply atmospheric plasma to bio devices. In this study, we made a small, pocket-sized inverter for the discharge of atmospheric plasma. We used pulse power to control the neutral gas temperature at which the, when plasma was discharged. We used direct current of 5 V of bias(voltage). The output voltage is about 1 to 2 kilo volts the frequency is about 80 kilo hertz. We analyzsed the characteristics of the atmospheric plasma using OES(Optical emission spectroscopy) and the Current-Voltage characteristic of pulse power. By calculating of the current voltage characteristics, we were able to determine that, when the duty ratio increased, the power that actually effects the plasma discharge also increased. To apply atmospheric plasma to human organisms, the temperature is the most important factor, we were able to control the temperature by modulating the pulse power duty ratio. This means we can use atmospheric plasma on the human body or in other areas of the medical field.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.1
• /
• pp.68-78
• /
• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Journal of Korean Society for Atmospheric Environment
• /
• v.11 no.4
• /
• pp.323-329
• /
• 1995

The number of motor vehicles in Korea has increased to about 4 million, and the exhaust gases of these vehicles have become a more threatening factor to public health. Traffic policemen are one of the highest health risk groups since they work on roadsides where they are exposed to high levels of air pollutants. The health effects on them due to air pollution were determined by measuring personal carbon monoxide(CO) exposure and carboxyhemoglobin(COHb) level in blood. Thirty-one traffic policemen in Seoul volunteered to be subjects of the study. In October 1992, personal CO exposure was measured by a CO passive sampler. The subjects wore the CO passive sampler for 8 hours while on duty. The exposed samples were analyzed by gas chromatography. Blood samples from each subject were collected just after the exposure sampling, and were analyzed within 3 hours of blood collection by a CO-oximeter. The activities of the subjects were recorded by the subject in 30 minute intervals using an activity log sheet containing location and time spent. Personal CO exposure were ranged between 0.1 and 14.5ppm, eith an average of 5.9ppm. Carboxyhemoglobin levels ranged from 1.1% to 6.9%, with an average of 3.6%. policemen on duty outdoors had significantly higher CO exposures and COHb levels than policemen on duty indoors(p<0.01). Personal CO exposure and COHb were positively correlated, although the coefficient was not significant. The relationship between CO level and COHb level was confounded by smoking status. Among smokers, COHb level was significantly higher as CO exposure and hours worked outdoors increased.

• Journal of agricultural medicine and community health
• /
• v.31 no.2
• /
• pp.165-176
• /
• 2006

Objectives: This study aimed to evaluate job satisfaction and its related factors among radiological technologists. Methods: The subjects were 302 persons in various hospitals and the data were collected from 22 May to 17 July, 2005 using a structured questionnaire. It was composed of socio-demographic characteristics, job-related factors, and job satisfaction with the duty inner factors, the duty outside factors, and the organizational factors. Results: Men were more satisfied than women in their employment(p<0.05). Job satisfaction level of university hospital workers were higher than the general hospital, the hospital, and medical clinics. Job satisfaction level of the general radiological technologists showed lower than the chief radiological technologists (p<0.05). In monthly average grant, the more gained, the higher the satisfaction level(p<0.05). By multiple linear regression analysis, the related factors of job satisfaction level were medical field and duty position (p<0.05). Conclusions: The research shows that job satisfactions levels of the radiological technologists are determined by the health and safety of the work environment. Therefore more improvements must be made for radiological technologists to be more satisfied in their jobs.