• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.69-76
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• 2000

Lots of semi-active control devices have been developed in recent years because they have the best features of passive and active system. Especially, controllable magneto-rheological(MR) fluid devices have received significant attention in these area of research. The MR fluid is the material that reversibly changes from a free-flowing, linear viscous fluid to a semisolid with a controllable yield strength in milliseconds when exposed to a magnetic field. If the magnetic field is induced by moving a permanent magnet instead of applying current to a solenoid, it is possible to design a MR damper consuming low power because the power consumption is reduced at steady state. This paper proposes valve mode MR damper using permanent magnetic circuit that has wide range of operation with low power consumption, a design parameter is adopted. The magnetic circuit, material of choke and choke type are selected experimentally with the design parameter. The behaviors of the damper are examined and torque tracking control using PID feedback controller is performed for step, ramp and sinusoidal trajectiories.

• Steel and Composite Structures
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• v.46 no.5
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• pp.673-687
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• 2023

In this study, the weight and the connections type layout of low-rise eccentrically braced frame (EBF) have been optimized based on performance-based design method. For this purpose, two objective functions were defined based on two different aspects on rigid connections, in one of which minimization and in the other one, maximization of the number of rigid connections was considered. These two objective functions seek to increase the area under the pushover curve, in addition to the reduction of the weight and selection of the optimum connections type layout. The performance of these objective functions was investigated in optimal design of a three-story eccentrically braced frame, using two meta-heuristic algorithms: Enhanced Colliding Bodies Optimization (ECBO) and Enhanced Vibrating Particles System (EVPS). Then, the reliability indices of the optimal designs for both objective functions were calculated for the story lateral drift limits using Monte-Carlo Simulation (MCS) method. Based on the reliability assessment results of the optimal designs and taking the three levels of safety into account, the final designs were selected and their specifications were compared.

• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.88-94
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• 2013

The purpose of this study is to find out the difference of foot pressure according to the firefighter's work postures for providing the basic information to prevent Musculoskeletal disorders. This study was conducted by 9 male firefighters. Work postures were selected for rescuee handling, fire hose and hydraulic rescue equipment work postures. These were divided into 3 position, "High", "Middle" and the postures of taking out and letting down hydraulic rescue equipment were analyzed as starting point and end point respectively. Foot Pressure was used to analyze contact area, peak pressure, and maximum force in terms of work postures, and compared between fire hose and hydraulic rescue equipment work postures. The results of foot pressure are as follows. According to the results of rescuee handling work postures, one person handling posture showed wide contact area and foot pressure showed the highest at right foot. Accoridng to the (High), (Middle), (Low) postures of fire hose, the results didn't show the difference among the contact area, peak pressure and maximum force. As the results of hydraulic rescue equipment work postures, (Low) postures showed the highest in terms of the right foot of contact area, peak pressure and maximum force and (High) postures showed the highest in left foot. The increase of foot pressure lead to be inconvenience of low extremity and muscle fatigue for maintaining postural control cause pain. Thus, it is necessary to design insole-equipped working shoe for reduce the impulse and effect of foot during the rescuee handling work which standing out as foot pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.7
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• pp.521-528
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• 2007

The desiccant rotor is the most essential component of desiccant cooling system, but its design relies on manufacturer's experience and principles are not yet clear in spite of a lot of theoretical/experimental work published. The mathematical modeling of desiccant rotor needs solution of coupled partial differential equations of heat and mass transfer. In this study, numerical program is developed and validated using a real desiccant rotor. The calculation results are in reasonable agreement with the experimental data and other available numerical results. Optimization of desiccant rotor on the condition of low regeneration temperature are investigated. The optimal rotor speed at which the process outlet humidity becomes minimized, shows same as that of the system optimization. Compared to high regeneration temperature, broad is the range of optimal speed of low regeneration temperature. Systematic analysis on the optimal area ratio of regeneration to dehumidification section has also been conducted.

• Research in Community and Public Health Nursing
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• v.22 no.4
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• pp.429-437
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• 2011

Purpose: The purposes of this study were to describe the prevalence of low weight and to investigate related factors contributing to low weight in community-dwelling older adults. Methods: From the database of the Fourth Korean National Health and Nutrition Examination Survey (KNHANES-IV), the researchers selected 2,964 older adults aged over 65. The original study was a population-based epidemiological survey of health and nutrition with a stratified multistage clustered probability design. Data were analyzed using ${\chi}^2$-test and multiple logistic regression with the SPSS/WIN 18.0 program. Results: The prevalence of low weight in older adults was 4.7%. The prevalence of low weight was different according to demographic characteristics. That is, the rate was higher in male elders, older ones, and rural residents. In the cases of current smoking, frequent alcohol consumption and no chronic disease, the prevalence of low weight was higher. Age, gender, area of residence, and current smoking were found to be contributing factors to low weight in community-dwelling older adults. Conclusion: The result of this study provides important insights into possible reasons for low weight in community- dwelling older adults and suggests that low weight should be considered in promoting older adults' health.

• Architectural research
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• v.19 no.2
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• pp.35-43
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• 2017

In South Korea, problems such as low fertility, aging population, and income polarization have recently become more serious. In this time of social change, it is necessary to examine the current changes occurring to residences in order to improve the stability and health of residential areas. The purpose of this study is to investigate the changes of residential areas that occurred between 2000 and 2010 based on detached houses, which are the foundation of residential areas in Seoul. Changes in residential areas can be observed by examining changes in the type of housing and the characteristics of the residents. Since the type of housing and the characteristics of the residents change in the same area, it is necessary to study them together, not as individual elements. Census data is suitable for this purpose, because it can show the changes that have occurred to the housing type and the residents' characteristics within the neighborhood unit. Among the census output areas identified as residential areas based on detached houses, six sites were selected as the case study area based on the rate of change of detached houses. From the result of the case study using the census data, the study area was categorized into three regional types: (i) an urban development and redevelopment area; (ii) an area with a concentration or increasing number of detached houses; (iii) an area with an increasing number of multi-family houses based on detached houses.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.522-527
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• 2015

Decision of available soil depth based on soil physical and hydraulic properties for the $3^{rd}$ Landscape Vegetation Project in the Incheon International Airport was attempted. The soil samples were collected from the 8 sites at different depths, 0-20 and 20-60cm, for the three project fields, A, B, and C area. Physical and chemical properties including particle size distribution, organic matter content and electrical conductivity were analyzed. Hydrological properties including bulk density and water holding capacity at different water potential, -6 kPa, -10 kPa, -33 kPa, and -1500 kPa were calculated by SPAW model of Saxton and Rawls (2006), and air entry value was calculated by Campbell model (1985). Based on physical and hydrological limitation, feasibility and design criteria of soil depth for vegetation and landfill were recommended. Since the soil salinity of the soil in area A area was $19.18dS\;m^{-1}$ in top soil and $22.27dS\;m^{-1}$ in deep soil, respectively, landscape vegetation without amendment would not be possible on this area. Available soil depth required for vegetation was 2.51 m that would secure root zone water holding capacity, capillary fringe, and porosity. Available soil depth required for landscape vegetation of the B area soil was 1.51 m including capillary fringe 0.14 m and available depth for 10% porosity 1.35 m. The soils in this area were feasible for landscape vegetation. The soil in area C was feasible for bottom fill purpose only due to low water holding capacity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.395-402
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• 2007

This paper focused on fading out the factors of design innovation. Based on the previous studies, several factors were extracted to be tested by Delphi method among 15 experts in the design area. Delphi test showed a convergent result after the second round of questioning. Design mind of managers was conceived as the most important factor among those tested. On the base of importance, capability of design company was the second and industrial design demand was the third. Even though design manpower, design infrastructure and innovation network were ranked below the 4th factors, the absolute differences between high ranked factors and low ranked ones were not much wide. So. relatively low ranked factors were not negligible at all to get a desirable success in design innovation. This study provides some insights for the success of design innovation. First of all, design innovation could be achieved only when factors tested on this study upgraded simultaneously together. Desirable effect could not expected by a simple support such as logo design or kind of simple measure.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.144-151
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• 2022

In this paper, a 1.5V 256kb eFlash memory IP with low area DC-DC converter is designed for battery application. Therefore, in this paper, 5V NMOS precharging transistor is used instead of cross-coupled 5V NMOS transistor, which is a circuit that precharges the voltage of the pumping node to VIN voltage in the unit charge pump circuit for the design of a low-area DC-DC converter. A 5V cross-coupled PMOS transistor is used as a transistor that transfers the boosted voltage to the VOUT node. In addition, the gate node of the 5V NMOS precharging transistor is made to swing between VIN voltage and VIN+VDD voltage using a boost-clock generator. Furthermore, to swing the clock signal, which is one node of the pumping capacitor, to full VDD during a small ring oscillation period in the multi-stage charge pump circuit, a local inverter is added to each unit charge pump circuit. And when exiting from erase mode and program mode and staying at stand-by state, HV NMOS transistor is used to precharge to VDD voltage instead of using a circuit that precharges the boosted voltage to VDD voltage. Since the proposed circuit is applied to the DC-DC converter circuit, the layout area of the 256kb eFLASH memory IP is reduced by about 6.5% compared to the case of using the conventional DC-DC converter circuit.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.8
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• pp.47-55
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• 2010

In this paper, a timing register architecture using demultiplexer and counter is proposed to reduce the area of the high resolution SAR type analog to digital converter. The area and digital power consumption of the conventional timing register based on the shift register is drastically increased, as the resolution is increased. On the other hand, the proposed architecture results in reduction of the area and the power consumption of the error correction logic of the SAR ADC. This chip is implemented with 0.18 um CMOS process. The area is reduced by 5.4 times and the digital power consumption is minimized compared with the conventional one. The 12 bits SAR ADC shows ENOB of 11 bits, power consumption of 2 mW, and conversion speed of 1 MSPS. The die area is $1 mm{\times}1mm$.