• Journal of Korean Society of Forest Science
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• v.104 no.2
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• pp.221-229
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• 2015

The purpose of study was to broaden our knowledge on the productivity and cost of thinning operations which has become increasingly practiced in Korea. The thinning operations were conducted in a 40-year old larch (Larix leptolepis) stand, including chainsaw felling and processing at the stump, followed by yarding tree-length logs using a Koller K301-4 tower yarder. The logs were further processed and sorted into 1.8 m and 3.6 m log piles at the landing. We used a standard time study method to evaluate key variables that affect the productivity of thinning operations. The total stump-to-pile operational cost was $41,707won/m^3$. The highest cost activity was the yarding phase which cost $20,083won/m^3$ (48.2% of the total cost), followed by the costs of processing treelength materials into marketable log lengths ($12,143won/m^3$; 29.1%), and then by the costs of sorting/piling the processed logs ($5,039won/m^3$; 12.1%). It was interesting to see that felling and processing trees at the stump had low costs at $1,315won/m^3$ (3.2%) and $3,127won/m^3$ (7.5%), respectively. We used the detailed time study data to develop regression equations which were to predict yarding productivity. Our analysis showed that harvesting system cost was highly sensitive to the number of logs, yarding distance and lateral distance per turn, respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.2 s.302
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• pp.49-58
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• 2005

A new soft switching three-phase PWM rectifier with simple circuit configuration and high efficiency has been developed. The proposed circuit is a kind of the auxiliary resonant commutated Pole(ARCP)converter The conventional ARCP converter requires three-auxiliary reactors and six-auxiliary switches for the soft switching auxiliary circuit and for these switching elements, a gate drive circuit and a control circuit are required, resulting in high part as a disadvantage. In the main circuit proposed in this paper, the auxiliary soft switching circuit is composed of two-auxiliary reactors, two-auxiliary switches and several diodes. In addition, common use of the PWM control circuit for two-switches will make the control circuit of the auxiliary switches simple. By means of function of the soft switching auxiliary circuit, the main switching element performs zero voltage switching operation and the auxiliary switches perform the zero current switching. In this paper, the circuit configuration and the operational analysis of the proposed circuit are described at first and then, experimental results will be reported. By using a prototype with 5[kW] capacity, the conversion efficiency of maximum $98.8[\%]$ and the power factor of $99[\%]$ or higher were obtained.

• Journal of Technologic Dentistry
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• v.37 no.3
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• pp.131-144
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• 2015

Purpose: This study set out to propose plans for more efficient and effective clinical practice by investigating the current state of clinical practice in the field of dental technology and thus provide basic data to develop pre- and post-education programs for clinical practice. Methods: The subjects include dental technicians at dental technical laboratories that were appointed as the place of clinical practice by the Department of Dental Technology of G University. The survey period spanned from December 22, 2014 to January 20, 2015. Total 250 questionnaires were distributed to them, and 190(76.0%) were returned. After excluding 23 whose answers were uncertain or seemed to lack reliability, total 167(66.8%) were used in final analysis. Results: 1. The most frequent practice the student did during clinical practice was articulator attachment, which was followed by pin operation or model making, one's own task and practice, sand and crow sculpturing, burying, casting, and grinding. 2. In case of going through the entire process, porcelain had the most students at 39(23.4%), being followed by crown & bridge at 28(16.8%), clinical model at 23(13.8%), full denture at 17(10.2%), and partial denture at 17(10.2%) in the order. 3. Of the students, 59.8%(30.5% for reinforced basic practice; 29.3% for intensive practice education) said that intensive practice education should be reinforced in school; and 22.3% said that intensive theory and practice education was needed, which indicates that 82.6% voiced their opinion of reinforcing education around practice. 4. The students felt that they lacked diligence, passion, and theoretical knowledge somewhat and were relatively good at clinical adaptation and operational skills. Conclusion: The findings show that the students felt an absolute lack of practice education as the school education was focused on theory and national exams in the field of dental technology, thus raising a need to reinforce practice education. Of all the respondents, 62.9% said there was a need to improve the current education with a focus on jobs. In future, education of dental technology should work to bring up able dental technicians that can perform in clinical dental technology right after graduation by reinforcing job-based practice education.

• Journal of Environmental Health Sciences
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• v.34 no.3
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• pp.188-198
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• 2008

Since 2003, the National Institute of Environmental Research (NIER) of Korea has been conducting "The monitoring study on exposure level and biomarkers of environmental pollutants" in the Ulsan industrial complex with the goals to establish a surveillance system for residents, to evaluate the health effects associated with chronic exposure to environmental pollutants and to develop the environmental health indicators in Ulsan industrial complex. This program consists of three phases an initial or foundation phase in which the program is developed, made operational and extended to the community, followed by an evaluation and accountability assessment of the surveillance system and finally an improvement in the quality of life and the maintenance of good health for Ulsan residents. In the period 2003 to 2008, the study program developed the surveillance system which will be used for the full-length survey. All participants in this study were contacted at a presentation meeting for residents, introduced to the objectives and protocols of the survey, and asked to participate. Informed consent was obtained from each participant. The study is now underway and includes questionnaires, health examinations and the analysis/collection/banking of bio-sample such as blood and urine. To date 828 subjects have participated and already 588 subjects have been followed up. We are committed to complete health examinations and to arrange storage of biosample for all participants. During the current year, we will analyze metals (Pb in blood and Cd, inorganic As and Hg in urine) in 1,972 samples and VOCs (11 species) and PARs (18 species) in 300 samples (blood sample). Moreover, the summary of the first step and the further preparation of the second step are currently underway. In this article, we introduce the study and its protocols and the distribution and size of the study participants. In conclusion, this survey will be continuously conducted on the established cohort and will enable the identification of relationship between environmental pollutant exposures and the health status of residents in Ulsan industrial complex.

• Spatial Information Research
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• v.22 no.3
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• pp.79-87
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• 2014

In order to foster rapid disaster response and public life protection, National Emergency Management Agency has been trying to spread 'Emergency Rescue Standard System' on a national scale since 2006. The agency has also intensified management of firefighter's safety on disaster site by implementing danger predication training, specialized training and education and safety procedure check as a part of safety management officer duties. Nevertheless, there are limitations for effective fire fighting steps, such as damage spreading and life damage due to unawareness of illegal converted structure, structure transformation by high temperature and nearby hazardous material storage as well as extemporary situation handling endangered firefighter's life. In order to eliminate these limitations there is a need for an effort and technology application to minimize human errors such as inaccurate situational awareness, wrong decision built on experience and judgment of field commander and firefighters. The purpose of this study is to propose a new disaster response model which is applied with geospatial information. we executed spatial contextual awareness map analysis using fire-fighting vulnerable zone model to propose the new disaster response model and also examined a case study for Dalseo-gu in Daegu Metropolitan City. Finally, we also suggested operational concept of new proposed model on a national scale.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.159-165
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• 1987

This study proposes an operational method of typhoon risk assessments in Korea, using Statistical analysis and probabilistic description of typhoon at a site. Two alternative simulation and fitting methods are discussed to predict the probabilistic typhoon wind speeds by indirect methods. A Commonly used indirect method is Russell's procedure, which generates about 1,000 Simulation data for typhoon winds, statistically evaluate the base-line distribution, and then fits the results to the Weibull distribution based on probabilistic description of climatological Characteristics and Wind field model of typhoon at a site. However, an alternative procedure proposed in this Paper simulates extreme typhoon wind data of about 150~200 years and directly fits the generated data to the Weibull distribution. The computational results show that the proposed simulation method is more economical and reasonable for typhoon risk-assessment based on the indirect method. And using the proposed indirect method, the probabilistic design wind speed for transmission towers in typhoon-prone region along the South-Western coast is investigated.

• Journal of Korea Port Economic Association
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• v.35 no.3
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• pp.19-40
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• 2019

Ports have been facing the adverse impacts of the global recession. In terms of imports, with a vast consumption hinterland, the Incheon Port has developed as the metropolitan's gateway. Additionally, the port's exports to China has been increasing due to a consistent increase in the demand of cold chain foods in the country. Considering the short distance between the Incheon Port and the ports in Northern China, the Incheon Port can serve as a logistics hub and a distribution center for exporting processed foodstuffs to China. The establishment of a cold chain logistics system at the Incheon Port will prove to be a robust strategy. After reviewing studies and interviews from various departments, this study suggested strengths, weaknesses, opportunities, and threats (SWOT) facing the Incheon Port, based on a SWOT analysis; it also recommended competitive strategies for the port. Additionally, the study used the analytic hierarchy process (AHP) to identify important factors such as the infrastructural, operational, cost, and technology factors. This study identified the infrastructural factor to be highly critical to the activation of the Incheon Port's cold chain system. Based on the results, the study proposed policies and strategy directions.

• The Journal of Sustainable Design and Educational Environment Research
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• v.17 no.2
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• pp.11-21
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• 2018

This study suggests desirable disaster safety education curriculum through analyzing the operational status of the school disaster safety management training course and demand survey of school staff. First, the problem of the disaster safety training course of the school is not connected with the lack of law and system and the school disaster safety job. Second, improvement of law and system and variety of training should be made to acquire professional knowledge. Third, it is necessary to divide curriculum into the following four categories, according to educational needs of public officials ; Educational administration officers course focused on facility safety, maintenance and disaster countermeasure. Educational officials in technical post course addressing approval and permission of school facility projects, seismic reinforcement of school building, etc. Educational supervisors course covering roles and responsibilities of the school safety supervisors in the event of disaster. Teaching staffs course focused on safety instructions for students. Fourth, it is found that lectures and experiential learning methods are the most desirable methods of teaching and learning, and the major ranks are earthquake disaster, fire, gas, typhoon, school road, and electrical safety.

• Survey Research
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• v.8 no.2
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• pp.67-89
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• 2007

The Korea National Health and Nutrition Examination Survey(KNHANES) consists of Health Interview Survey, Health Behaviour Survey, Nutrition Survey, and Health Examination, and is designed to produce a broad range of descriptive health and nutritional statistics for sex and age subdomains of the population. These data can be used to measure and monitor the health and nutritional status of the population of Korea. The survey has been conducted three times from 1998. The Korea Centers for Disease Control and Prevention(KCDC) is preparing for the 4th survey which is to be conducted from 2007 through 2009. This study is to design a sample for the 4th survey. The main new feature of the sampling design is using a rolling sampling design method. Since KCDC has imposed some operational requirements, e,g., the needs of producing the annual national statistics and of year-round data collection by some regular staffs, a rolling sampling design method is introduced. This is the first time in history of applying a rolling sampling design for a national-wide large scale survey in Korea. Bringing in the rolling sampling, measurement variation due to different data collectors may be minimized.

• Korea journal of population studies
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• v.29 no.3
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• pp.89-109
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• 2006

The 'Joongsancheung(JSC)', a unique term for the middle class in Korea, is defined as a stratum sharing common lifestyles and a certain level of life chances. It involves non-economic factors such as life chance, educational attainment, occupational groups as well as economic factor. Such objective measures as the occupational status of the main breadwinner, family income, and the educational level of respondent, and subjective measures of class identification are used for the operational definition of the JSC. Data from a national survey of 1,515 respondents is analyzed to investigate the change of the JSC in size and the major determinants of class identification. The results show that while there is no strong evidence of any significant change of the JSC by the objective measures during the recent decade, there seems to be a slight decrease in the subjective class identification. In addition, binary logistical regression analysis reveals that self-identification of JSC is heavily influenced by house ownership, along with subjective evaluation of one's own income and property ownership. This study demonstrates that the apparent class polarization in Korean society reflects not so much objective conditions but subjective perception of respondent of his or her circumstance. It is suggested that problems of housing and relative derivation people have as regards income and property should be resolved to alleviate such class polarization in Korean society.