• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.6
• /
• pp.683-690
• /
• 2006

Reducing power consumption to extend network lifetime is one of the most important challenges in designing wireless sensor networks. One promising approach to conserving system energy is to keep only a minimal number of sensors active and put others into low-powered sleep mode, while the active sensors can maintain a connected covet set for the target area. The problem of computing such minimum working sensor set is NP-hard. In this paper, a centralized Voronoi tessellation (CVT) based approximate algorithm is proposed to construct the near optimal cover set. When sensor's communication radius is at least twice of its sensing radius, the covet set is connected at the same time; In case of sensor's communication radius is smaller than twice of its sensing radius, a connection scheme is proposed to calculate the assistant nodes needed for constructing the connectivity of the cover set. Finally, the performance of the proposed algorithm is evaluated through theoretical analysis and extensive numerical experiments. Experimental results show that the proposed algorithm outperforms the greedy algorithm in terms of the runtime and the size of the constructed connected cover set.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.30 no.2
• /
• pp.67-81
• /
• 1988

The purpose of the present study is to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir and to establish a solid foundation for the automatic optimum structural design combined with finite element analysis. The major design variables are the dimensions and steel areas of each member of the structures. The construction cost which is composed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of the working stress design method. The corresponding design guides including the standard specification for concrete structures have been also employed in deraving the constraint conditions. The present nonlinear optimization problem is solved by SUMT method. The reinforced concrete intake-tower is decomposed into three major substructures. The optimization is then conducted for both the whole structure and the substructures. The following conclusions can be drawn from the present study. 1. The basis of automatic optimum design of reinforced concrete cylindrical shell structures which is combined with finite element analysis was established. 2. The efficient optimization algorithms which can execute the automatic optimum desigh of reinforced concrete intake-tower based on the working stress design method were developed. 3. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optImization algorithms developed in this study seem to be efficient and stable. 4. The difference in construction cost between the optimum designs with the substructures and with the entire structure was found to be small and thus the optimum design with the substructures,rnay conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the tensile stress insteel for salb, the minimum lonitudinal steel ratio constraints for tower body and the shearing stress in concrete, tensile stress in steel and maximum eccentricityconstraints for footing, respectively. 6. The computer program develope in the present study can be effectively used even by an unexperienced designer for the optimum design of reinforced concrete intake-tower.

• Journal of Korean Academy of Nursing
• /
• v.14 no.1
• /
• pp.21-33
• /
• 1984

The purpose of this study was to define the relationship between the leadership style of head nurses and the burnout level of nurses by taking into consideration the factors which influence the level of burnout and which show how burnout varies according to the leadership style of lead nurses. The subjects of the survey were 355 ward nurses and their 48 head nurses working in five university hospitals in Seoul. The nurses were surveyed by means of a questionnaire from Sept. 22 though Sept. 29, 1983. The Leadership Scale devised by Fleishman, and modified by Lee, and the Burnout Scale developed by Pines et al, and adapted to the Korean situation by Peek, were used as a basis of ;his survey This researcher subjected the questionnaire to a pre-test and to an internal reliability consistency test through item analysis. For the purpose of analysis of the data, the general characteristics were set at Mean and the general characteristics of head nurses in relation to the level of burnout of nurses was analysed by the Pearson Correlation Coefficient. The relation between head nurses' general characteristics 3nd leadership style, the relation between nurses' general characteristics and level of burnout and the level of burnout of nurses according to the different style of leadership of head nurses were analysed by ANOVA. A summary of the results of the study is as follows. 1. Hypothesis:“That the burnout level of the nurse will be different according to the leadership style of the head nurse”was supported. 2. Analysis of the relationship between the head nurse's general characteristics and the leadership style of the head nurse showed that the leadership style of the head nurse was not related to age and experience as head nurse. 3. Analysis of the relationship of nurses' burnout levels to general characteristics of nurses showed statistically significant differences in burnout levels according to working departments, expected working period and reasons for selecting nursing as a profession. Also, the burnout level of nurses was negatively related to the head nurse's age and experience as a head nurse.

• Journal of Korean society of Dental Hygiene
• /
• v.13 no.6
• /
• pp.917-923
• /
• 2013

Objectives : The purpose of this study was to investigate the level of expertise and awareness of information on toothpaste in dental hygienists and to give patients information on toothpaste. Methods : The subjects was 205 dental hygienists working at dental clinic, dental hospital or college dental hospital in Seoul and Gyeonggi-do. They filled out the questionaire from 13th to 27th April, 2013. Collected data were analyzed by SPSS 21.0 program and significant level was set at p=0.05. Results : The awareness of information on toothpaste was the highest in dental hygienists having under 3 years career and working at dental clinics(p<0.001). The level of expertise on toothpaste was the highest in those having over 5 years career and working at general hospital or college dental hospital(p<0.001). In association with the effect of toothpaste(p<0.05), experienced dental hygienists had a higher knowledge(1.68 point) that those who had no experience(2.27 point). Instruction of the oral care devices included 27.5% of dental floss, 27.1% of toothbrush and 25.4% of proxabrush, and 4.9% of toothpaste. Conclusions : The results revealed that the right choice of the toothpaste would be the best prevention of dental caries and it is necessary to educate the dental hygienists for the toothpaste information.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.75-80
• /
• 2006

ILO has contributed for seafarers to promote conditions of employment and decent work through maritime labour standards. Between 1920 and 1996, a total of 39 Conventions and 29 Recommendations concerning seafarers have been adopted, which demonstrates the import part of ILO activities devoted to seafarers' questions. But many instruments were outdated, deficient and not reflective of modern practice, many contained technical detail which discouraged ratification. the Governing Body of ILO, at its 262nd Session(March-April 1995), decided to set up a Working Party regarding the revision of maritime labour standards. This Working Party initiated its examination of maritime instruments to 273rd Session(November 1998) of the Governing Body. The review made by the Working Party has concluded that existing maritime Conventions were considered either up to date or were identified for promotion, most of which were approved by the Governing Body. Therefore, ILO started to create a single, coherent instrument embodying as far as possible all up-to-date standards of existing maritime labour convention. The Maritime Labour Convention 2006 has been adopted in February 2006. This paper aims to analyze the significance of this convention and the influence regarding to maritime labour affairs in the field of shipping industry.

• Journal of Navigation and Port Research
• /
• v.31 no.1 s.117
• /
• pp.115-119
• /
• 2007

ILO has contributed for seafarers to promote conditions of employment and decent work through maritime labour standards. Between 1920 and 1996, a total of 39 Conventions and 29 Recommendations concerning seafarers have been adopted, which demonstrates the important part of ILO activities devoted to seafarers' questions. But many instruments were outdated, deficient and not reflective of modern practice, many contained technical detail which discouraged ratification. The Governing Body of ILO, at its 262nd Session(March-April 1995), decided to set up a Working Party regarding the revision of maritime labour standards. This Working Party initiated its examination of maritime instruments to 273rd Session(November 1998) of the Governing Body. The review made by the Working Party has concluded that existing maritime Conventions were considered either up to date or were identified for promotion, most of which were approved by the Governing Body. Therefore, ILO started to create a single, coherent instrument embodying as far as possible all up-to-date standards of existing maritime labour conventions. The Maritime Labour Convention 2006 was adopted in February 2006. This paper aims to analyze the significance of this Convention and the influence regarding to maritime labour affairs in the field of shipping industry.

• Korean Journal of Materials Research
• /
• v.15 no.11
• /
• pp.705-710
• /
• 2005

NIL (nanoimprint lithography) technique has demonstrated a high potential for wafer size definition of nanometer as well as micrometer size patterns. During the replication process by NIL, the stiction between the stamp and the polymer is one of major problems. This stiction problem is moi·e important in small sized patterns. An antistiction layer prevents this stiction ana insures a clean demolding process. In this paper, we were using a TCP (transfer coupled plasma) equipment and $C_4F_8$ as a precursor to make a Teflon-like antistiction layer. This antistiction layer was deposited on a 6 inch silicon wafer to have nanometer scale thicknesses. The thickness of deposited antistiction layer was measured by ellipsometry. To optimize the process factor such as table height (TH), substrate temperature (ST), working pressure (WP) and plasma power (PP), we were using a design of experimental (DOE) method. The table of full factorial arrays was set by the 4 factors and 2 levels. Using this table, experiments were organized to achieve 2 responses such as deposition rate and non-uniformity. It was investigated that the main effects and interaction effects between parameters. Deposition rate was in proportion to table height, working pressure and plasma power. Non-uniformity was in proportion to substrate temperature and working pressure. Using a response optimization, we were able to get the optimized deposition condition at desired deposition rate and an experimental deposition rate showed similar results.

• Korean Journal of Occupational Health Nursing
• /
• v.27 no.4
• /
• pp.224-234
• /
• 2018

Purpose: In this study, we attempted to analyze the occupational accident experience rate by working life cycle of Korean workers considering entrance and turnover in their jobs. The specific goal of this study was to calculate the accident experience rate according to workers' turnover history and previous accident experience. Methods: We constructed a cumulative data set of 90,338 cases of workers' accident experiences in their jobs from the Fourth Korean Working Conditions Survey. The accident experience rates according to workers' turnover and previous accident experiences were analyzed using descriptive statistics and analysis of variance. Results: In this study, the cumulative accident experience rate of Korean workers was found to be 5.2%. It was confirmed that the accident experience rate of workers increased as the turnover frequencies increased. In addition, we analyzed only the data of the workers who had experienced turnover and found that the accident experience rate after turnover increased about 7.5 times when workers had experienced accidents in the past. Conclusion: To prevent occupational accidents in workers, safety strategies should consider a worker's previous job history and injury experiences. It will also be necessary to focus preventive efforts on new and young workers through ongoing monitoring and on-the-job training.

• Journal of the Korean Society of Safety
• /
• v.37 no.6
• /
• pp.102-107
• /
• 2022

South Korea will soon be a super-aged society, as more than 20.6% of its population will be 65 years and older by 2025. As of 2022, 17.5% of the total population in South Korea is 65 years and older, which exceeds the set threshold for an aged society, where more than 14% of the population is 65 years and older. The proportion of older subway construction workers has increased. Aging workers and their work stress negatively impact their workability. A previous study demonstrated that the stress index measured using the uBioMacpa measurement device (Macpa stress index) had a significant correlation with work stress in South Korea. The device tests vascular health and measures stress levels via Macpa signal analysis. In this study, the pulse waves of subway construction workers were measured using uBioMacpa to identify their stress levels. The stress levels were analyzed by age, years of service, job position, employment type, and work type. Herein, these statistics could not be easily represented by a normal distribution; therefore, the Kruskal-Wallis test, a nonparametric statistical method, was used for the analysis of data. The results showed that age, job position, employment type, and working type affected the Macpa stress index and the stress levels of workers increased with age. In terms of job position, technical engineers were more stressed than other workers because of their poor working environment. In terms of employment type, daily-wage workers were more stressed than other workers. In terms of working type, tunneling, waterproofing, and construction scored the highest Macpa stress indexes without any significant difference, whereas earthworks scored the lowest. Based on the analysis of Macpa stress index, safety and health management plans were proposed to reduce the stress levels of workers. Moreover, a manual for efficient stress management must be developed for subway construction workers.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.33 no.3
• /
• pp.291-297
• /
• 2023

Objectives: An epidemiological investigation was requested for a worker who developed COPD and IPF after long-term molding and firing at a domestic tile manufacturing site. We would like to share the results of the exposure assessment and the estimation of past work. Methods: The content of crystalline silica in four raw materials was analyzed, and the respirable fraction of crystalline silica and dust generated in the air from molding and firing workers and other processes were measured. The measurement and analysis method referred to the NIOSH method. Results: The crystalline silica content of the raw material was 24~47%. The concentration of crystalline silica in the molding and firing process workers and the surrounding area was at the level of the exposure standards set by the Ministry of Employment and Labor and ACGIH, and the respirable and total dust exposure levels were generally low. The crystalline silica concentration of the area samples measured to estimate past work was about twice as high as the exposure standard of the Ministry of Employment and Labor (0.05 mg/m3), and the exposure levels of respirable dust were also quite high at 0.903 and 1.332 mg/m3. Conclusions: It was confirmed that tile molding and firing workers are currently exposed to a fairly high level of crystalline silica, and a high level is also confirmed in area samples to estimate past work. In the past, it is judged that the level of exposure would have been much higher due to differences in production volume, working method, presence/absence of local ventilation facilities, and process layout. When working in such a working environment for a long time, respiratory diseases such as lung cancer, COPD, and IPF can occur.