• International Journal of Precision Engineering and Manufacturing
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• v.6 no.1
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• pp.51-58
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• 2005

The development of the high-efficiency machine-tools equipment and new cutting tool materials with high hardness, heat- and wear-resistance has opened the way to application of high-speed cutting process. The basic argument of using of high-speed cutting processes is the reduction of time and the respective increase of machining productivity. In this sense, the spindle units may be regarded as one of the most important units, directly affecting many parameters of high-speed machining efficiency. One of the possible types of spindle units for high-speed cutting is the air-bearing type. In this paper, we propose the mathematical model of the dynamic behavior of the air-bearing spindle. To provide the high-level of speed capacity and spindle rotation accuracy we need the adequate model of "spindle-bearings" system. This model should consider characteristics of the interactions between system components and environment. To find the working characteristics of spindle unit we should derive the equations of spindle axis movement under the affecting factors, and solve these equations together with equations which describe the behavior of lubricant layer in bearing (bearing stiffness equations). In this paper, the three influence coefficients are introduced, which describe the center of spindle mass displacement, angle of shaft rotation around the axes under the unit force application and that under the unit torque application. These coefficients are operated in the system of differential equations, which describes the spindle axis spatial movement. This system is solved by Runge-Kutta method. Obtained trajectories and amplitude-frequency characteristics were then compared to experimental ones. The analysis shows good agreement between theoretical and experimental results, which confirms that the proposed model of air-bearing spindle is correctis correct

• Smart Structures and Systems
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• v.20 no.2
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• pp.151-162
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• 2017

In practical engineering, the friction damper is a widely used energy dissipation device because of its large deformation capacity, stable energy dissipation capability, and cost effectiveness. While based on conventional friction dampers, the double-sliding friction damper (DSFD) being proposed is different in that it features two sliding friction forces, i.e., small and large sliding friction forces, rather than a single-sliding friction force of ordinary friction dampers. The DSFD starts to deform when the force sustained exceeds the small-sliding friction force, and stops deforming when the deformation reaches a certain value. If the force sustained exceeds the large sliding friction force, it continues to deform. Such a double-sliding behavior is expected to endow structures equipped with the DSFD better performance in both small and large earthquakes. The configuration and working mechanism of the DSFD is described and analyzed. Quasi-static loading tests and finite element analyses were conducted to investigate its hysteretic behavior. Finally, time history analysis of the single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems were performed to investigate the seismic performance of DSFD-equipped structures. For the purpose of comparison, tests on systems equipped with conventional friction dampers were also performed. The proposed DSFD can be realized perfectly, and the DSFD-equipped structures provide better performances than those equipped with conventional friction dampers in terms of interstory drift and floor acceleration. In particular, for the MDOF system, the DSFD helps the structural system to have a uniform distributed interstory drift.

• Journal of the Korean Dietetic Association
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• v.17 no.2
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• pp.142-160
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• 2011

The purpose of this study was to investigate food sanitation status in elderly welfare facilities and assess the performance of food sanitation practices. Twenty elderly welfare facilities out of 85 located in Seoul with a capacity of fewer than 50 persons participated. The food sanitation status of worktable, kitchen utensils (knives, cutting boards, ladles, spoons), and tableware and bowls were examined by ATP bioluminescence. The results found that the ATP value of knife was the highest. Those of ladles appeared relatively higher than others. Meanwhile, the tableware and bowls, although washed everyday after meals, had the lowest ATP value. This study also conducted a survey on the food sanitation practices of 32 cooking employees in the 20 facilities. Fifty-six percent were in their 40s, and 53% had graduated from high school. More than half (66%) of them had no certification of cooking. Half of the respondents had worked for at least 5 years in food service facilities, and had received food sanitation training. Among them, 31% said they applied food sanitation training while working, and 47% responded the training was very helpful. The foodservice employees demonstrated good food sanitation practices. The results show that food sanitation performance of the workers significantly differed according to their age, education level, total work experience in food service facilities, chef certification, and prior food sanitation experience.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.1-11
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• 2017

Most of the local limestone mines are developed as large-opening underground mines, while mine ventilation is heavily dependent on the natural ventilation and auxiliary systems, rather than the mechanical ventilation system using main fans. The current auxiliary ventilation system with fan and ducting requires optimization since enhanced deployment of diesel equipment demands higher airflow rate and the associated cost is expected to be too excessive for the local mine operators. This paper aims at optimizing the fan capacity for the working site ventilation through comparing the fan pressure in the mine airway and the ventilation efficiency of an axial-flow fan and a propeller fan developed in this study.

• Korean Parent-Child Health Journal
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• v.16 no.1
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• pp.11-16
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• 2013

Purpose: Ethiopia is one of the sub-Saharan countries most affected by high maternal and infant mortality. The government has trained health extension workers (HEWs), the community health workers, to deliver preventive and basic curative health services to community residents in Ethiopia. Very few studies have investigated on-the-job educational effects for HEWs on improvement of their knowledge and performance confidence in maternal and child health care (MCH). This study aimed at identifying the educational effects for HEWs in one health center in Tigray, Ethiopia on improvement of their knowledge in MCH. Methods: Twelve HEWs from 6 health posts participated in this study. A health center officer provided a total of 5 educational sessions on antenatal and postnatal care, family planning, and newborn care from August, 2012 to April, 2013. Ten to 12 items regarding the topics were tested before and after each education. Wilcoxon signed rank test was used to analyze the data. Results: All the HEWs were female with average 4-year working experience. Their knowledge significantly increased after education, except the first session. Their satisfaction on education was greater than 45 points out of 50. Conclusion: This study suggests a focused education for HEWs should continue to improve their capacity on MCH.

• The KIPS Transactions:PartD
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• v.12D no.4 s.100
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• pp.647-656
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• 2005

This paper proposes an adaptive resource self-management system that collects system resources, user information, and usage patterns as context information for utilization in self-configuration. This system ill ease the system maintenance burden on users by automation of large part of configuration tasks such as install, reconfiguration and update, and will also decrease cost and errors. Working from the gathered context information, this system allows users to select appropriate components and install them for user's system context. This also offers a more personalized configuration setting by using user's existing application setting and usage pattern. To avoid the overload on central server to transfer and manage related files, we employ Peer-to-Peer method. h prototype was developed to evaluate the system and a comparison study with the conventional methods of manual configuration and MS-IBM systems was conducted to validate the proposed system in terms of functional capacity, install time and etc.

• Design & Manufacturing
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• v.13 no.4
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• pp.45-50
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• 2019

The fourth industrial revolution calls for an integrated talent by improving working-level skills within the big framework of creativity and convergence. Therefore, university education focuses on solving the problem of practical ability education by improving employment ability. Based on this improvement in practical skills, this study is based on the field-based design curriculum of Capstone. Currently, the Capstone Design Course is being implemented at most universities, extending its scope to the fields of engineering, humanities, social studies and arts. However, there is a limit to the core concept of Capstone design education and capacity education developed in line with the foreign educational environment and applied directly to our nation's university education. In terms of overseas cases, the core focus is to develop practical, design, and prototype capabilities by forming a team among all grades and multidisciplinary institutions to support the capital and manpower of the industry. However, the nation's industrial linkage and curriculum have difficulties in carrying out multi-disciplinary education. In this study, students were asked to team up and solve the challenges that the industry needs based on the expertise acquired in the lower grade curriculum by applying majors and 3D printing through the first and second semester courses of the fourth grade to address these limitations. In addition, business skills for the process of creativity and leadership experience in our country through a suitable design capstone class to review the efficiency of education by applying a model. In order to achieve the purpose of Capstone design subject, the goal setting, class model composition, class model application, verification and evaluation, and final class model development procedures were carried out. Through this process, it will be used as a basic material for educating design class capstone design.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.543-555
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• 2015

At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.

• Health Policy and Management
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• v.27 no.3
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• pp.256-266
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• 2017

Background: Primary health care (PHC) plays a major role to ensure the basic right and equal distribution of the essential health care services. This study presents comparative analyses of PHC in Korea and Uzbekistan, discusses the existing scenario and the challenges, and provides recommendations. Methods: This study reviewed secondary data from Korea's National Statistical Information Service and the State Committee of the Republic of Uzbekistan on Statistic, regulatory legislation, research reports, and policy papers by research and international institutions. We focus on comparing input and outcome health data, PHC structure, and health expenditure. Results: Overall health status of the population in Korea is better than in Uzbekistan; both countries achieved more than 95% immunization coverage. The reforms implemented in both countries provide initial health care service delivery. However, there are several challenges such as the distribution of the staff between urban and rural areas and interest of the graduates on specialization rather than working in PHC system. Conclusion: PHC plays an important role in the provision of medical services to the population, addressing both health and social problems; it is the best tool for achieving universal coverage for basic health needs of the population. The community health practitioners in Korea and nurses in Uzbekistan plays main role in universal coverage through providing essential health care services. Continuous reform of the PHC system should be directed to strengthen the capacity of the PHC staff in health promotion knowledge and activities as well as to encourage population to improve their own health.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.144-152
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• 2011

The existing underground trenchless methods use reinforcing rod in steel tube to obtain structural stiffness. However, there are some problems such as inconvenience of work and expensive material fee which are resulted from limited working space and reinforcing work. To resolve these problems, a new trenchless method, namely P.S.T method (Prestressed Segment Tunnel Method), is developed which uses joint to connect the steel segment and form erection structure in underground construction. Further, installing strands for prestressing. In order to evaluate the flexural capacity of the P.S.T method structure, experiment was conducted. The parameters considered in the experiment are the span-to-depth ratio, diameter of steel tube at corner, prestressing force and welding of joint. Altogether examining the flexural behavior, the effect of deflection in structure according to different parameters has also been analysised.