• Journal of Korea Foundry Society
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• v.31 no.1
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• pp.11-17
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• 2011

The effect of CaO addition to AM60B Mg alloy on tensile properties has been investigated, with focus on strength and ductility at room and elevated temperatures. The 0.25-0.65wt% CaO added AM60B Eco-Mg diecastings were prepared by high pressure die casting using Buhler 1,450-ton cold chamber machine without $SF_6$ and $SO_2$ gases. The microstructures and tensile properties of each alloy were tested. The results show that the grains of AM60B are refined and the mechanical properties increase with CaO addition at room temperature. The improvement of strength and ductility is prominent at 0.45-0.55wt% CaO addition. Also, improved mechanical properties are maintained at elevated temperature of $150^{\circ}C$. CaO addition results in $Al_2Ca$ phase formation mostly on the grain boundaries. This phase leads to the refinement of grain structures and improvement of ductility as well as strength. The suppression of ${\beta}-Mg_{17}Al_{12}$ phase as well as the decrease of fracture surface porosity and other casting defects caused by melt cleanliness also contribute to the enhancement of mechanical properties of AM60B Eco-Mg at room and elevated temperature.

• Progress in Medical Physics
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• v.15 no.4
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• pp.247-254
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• 2004

According to developing high energy linear accelerators and treatment methods, like (3 dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), many radiotherapy centers are replacing older linear accelerators with new higher technical machines. This often presents a shielding problem as the designed shield for the existing rooms is not adequate for the higher technical machines. Additional shielding in limited existing space becomes necessary. We are replacing older brachytherapy room with new higher technical linear accelerator for IMRT. This room is not adequate for the IMRT machine without additional shielding design. The logical development of optimum structural shielding designs with concrete and high density shielding blocks are presented. We obtained following results by comparison between the pre-calculating values and actual survey of completed LINAC installation. High density shielding blocks have more powerful radiation protection about 2 times.

• Journal of the Korean Institute of Educational Facilities
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• v.23 no.4
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• pp.11-20
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• 2016

Post Occupancy Evaluation(POE) has a good role to improve or adapt the design items through the survey or interview of the resident. Among buildings, the university dormitory provides the living function to support the study in the university. Therefore, it needs to find the design elements and improve the living and study condition for residents. In this paper. it aimed at conducting the POE in university women dormitory for women and providing the building and design items for the next improvement. In addition, it aimed at analyzing the relation between the building satisfaction and the affecting factors, dividing the building into 8 spatial area such as room, entrance area, toilet and etc.. For these, data are surveyed the women dormitory located in the north area of Kyungsangbuk-Do and collected the 683 samples. This study shows some results ; First, the resident evaluates living condition of the dormitory room is a little good. Second, the freshman has a good score more than any other grade, which probably affect the period of the experience and exposure in university. In addition, residents get affect from the finishings, furniture and inconvenience. Third, the resident evaluates living condition of the dormitory room is a little good. Fourth, the satisfaction degree is affected by each size more than any other components in 8 spatial areas. Especially, the number of laundry machine is important factor for satisfaction. Second, the overall satisfaction is affected by room size higher than any other factors.

• Journal of the Korean Home Economics Association
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• v.47 no.2
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• pp.39-53
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• 2009

The purpose of this study was to analyze the state of Vietnamese housing in Korea. Using ethnographic methodologies, it was examined that 22 Vietnamese households in Korea in relation to their usage of housing space. The following conclusion were established; 1). Most of households had kitchen+1 or 2 bedrooms and the majority households preferred separated kitchen and living room areas. 2). Most households had a washing machine in bathroom and they regarded bathtub as not very necessary. They all preferred the bathroom with enough space for using washing machine and hand washing both. 3). Their preferred seating style was using chairs on sleeping as like in Vietnam but they preferred eating without chairs and treated large family and guest without chairs specially. 4). All of them were took their shoes off usually and preferred designated shoes space at the entrance to the house which was not used in Vietnam. 5). A Floor material of all households was vinyl on living room and bedrooms and most of them who had been using tile only in Vietnam preferred vinyl here. 6). All of households had a modified Ondol and most of them who had never been used this before preferred and they regarded as a desirable heating system. 7). They considered the kitchen as the most important housing space and the direction of housing was the one to consider when they built or buy the house.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.74-82
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• 2004

This paper describes the speed control of the surface-mounted permanent-magent synchronous motors (SMPMSNM) for elevator drive. The elevator motor needs to be a compact and slim type. Essentially, the proposed scheme uses a vector control algorithm for a speed and torque control and Anti-windup technique is adopted to prevent a windup phenomenon. This system is implemented using a high speed 32-bit DSP (TMS320C31-50), a high-integrated logic device FPGA(EPF10K10TI144-3) to design compactly and inexpensively. The proposed scheme is verified by the results through digital simulation and experiments for a three-phase 13.3[kW] SMPMSM as a MRL(MachineRoomLess) elevator motor in the laboratory.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.193-201
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• 2006

This study was performed to investigate employee exposures to waste anesthetic gases, such as enflurane and sevoflurane in operating rooms of general surgical, children's and dental clinics of a large hospital located in Seoul and to analyze factors affecting the concentrations of waste anesthetic gases. The results of the study are summarized below. 1. Based on results of personal and area samples for airborne enflurane, all of the employees investigated in this study were exposed to airborne enflurane concentrations below the ACGIH-threshold limit value (TLV) of 75 ppm. 2. However, based on results of personal samples for sevoflurane, employees of two (2) out of eleven (11) operating rooms were exposed to sevoflurane concentrations in excess of the NIOSH recommended exposure limit (REL) of 2 ppm. A similar trend was found in the area samples. 3. To investigate the source of sevoflurane emissions, airborne sevoflurane concentrations were measured on an anesthesia machine, a drug cabinet and a desk. It was indicated that the geometric means were 0.93 ppm, 0.83 ppm and 0.72 ppm, respectively. 4. Factors affecting waste anesthetic gas concentrations were the age of anesthesia machine, the volume of operating room and the extent of ventilation (p<0.05). 5. It is recommended that the use of anesthesia equipments be properly controlled, the operating room be well ventilated, and the airborne concentrations of anesthetic gases be continuously monitored.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.974-981
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• 2007

Seoul Metro has operated the air cooling equipment established in a machine room of a station building to improve our services focused on our customers who use Seoul Metro during the summer season. However, a new set of problems has arisen with the cooling tower to support a heat exchange of cooling water. One of them is loss of efficiency in the air conditioner. The leading cause of this problem is that we use an underground type of the cooling tower. As the machine room of a station building is located in the underground of inner city because of the nature of the subway, it is difficult to establish the cooling tower on the ground. The underground structure of the No. $1{\sim}4$ subway line is unsuitable for the location requirements of the underground type of the one because it has a limited space to set up the air cooling equipment, for example, the cooling tower and a ventilating opening. As a result of such an unfavorable condition, the cooling tower doesn't work efficiently and the warmth of cooling water because of insufficiency of a heat exchange and a refrigerator's technical obstacle such as a high-temperature and a high-pressure has arisen. Accordingly, the efficiency of the air conditioning is getting lower and lower. Another problem is too wasteful with water. Each station uses the water over 30 tons every day with waterworks to replenish the cooling tower such as a evaporation, a scattering and a distribution of water. Nevertheless, the more an air conditioner increase, the more the use of water supply increase. For this reason, we can't help wasting an enormous amount of water and discharging the congelation of a low temperature(about $15^{\circ}C$) occurred in a heat exchanger inside an air conditioner. The purpose of this study is to analyze the utility of congealing water to improve efficiency of the air cooling equipment and save energy as a supplementary water for the cooling tower.

• Journal of Biosystems Engineering
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• v.28 no.5
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• pp.411-420
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• 2003

Physical and cultural properties were investigated on the rice-seed pellets made by the pelleting machine(Yu, 2003) as the changes with mixing ratios of soil to rice seed of 6 : 1, 7 : 1, and 8 : I, and rotating speeds of forming rolls of 7, 10, and 13 rpm. Average weight, average diameter, and average sphericity of the pellets were 1.70 g, 12.0 ㎜, and 99.1 ％, respectively. Average number of seeds per pellet was more than 3, and almost all pellets had more than 3 seeds in the cases of mixing ratios of 6 : 1, and 7 : 1 at the forming rolls' speed of 7 rpm. Gradual drying was needed because rapid drying caused cracks on surface of the pellets. Compression strength of the pellets dried in shady room was in the range of 132 ∼ 152 N, which was enough for handling. Comparing with the previous pellets(Park, 2002), average number of seeds per pellet, ratio of pellets including more than 3 seeds, and compression strength increased due to the effects of pressure feed of pellet materials, and improvements of the forming rolls. Emergence ratio of the pellets made at the mixing ratio of 6 : 1 and the forming rolls' speed of 7 rpm, was 100 % on dry paddy and was 97 % on flooded paddy surface. Good growth characteristics, and yield except number of seedling stand and ratio of missing plant were shown in planting of the pellets made at the mixing ratio of 7 : 1 and the forming rolls' speed of 7 rpm on flooded paddy surface field. Considering the cultural results, the mixing ratio of 6 : 1, and the forming rolls' speed of 7 rpm seems to be optimum operating condition for the improved pelleting machine.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.331-337
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• 2015

By comparing and evaluating the neutron dose when running cyclotron in fixed type measuring machine and portable type measuring machine, we performed this study to see if there is any difference between the doses in both measuring devices. We performed correction 3 times for the portable type during the experiment. We measured the values 12 times for each correction, so total 36 times by using the fixed type and portable type once every 2 weeks from June 2012 to February 2014. The statistics for the portable type and fixed type for each experiment showed 0.186, 0.511, and 0.057, which are not statistically significant. Therefore, we have come to the conclusion that unless there is deviation based on the correction period of the portable type, correction of fixed type wouldn't be necessary. Also, reduction of social costs may be achieved if we install an alarm meter, which is relatively low priced compared to the high cost neutron measuring machine, when detecting higher level than the interested standard level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.488-492
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• 2007

Since Equipment-Noises occurring in machine room penetrate wall-body and travel to the adjacent room in the form of air-borne sound and structure-borne sound, it is appearing as the main factor that injures a peaceful residential environment, and due to this, such noise-damage is currently increasing rapidly. Consequently, despite the measures for sound-insulation and soundproof against the equipment-noise penetrated wall-body is urgently required, but as the subjective evaluation considered for psychological response about the equipment-noise was not practiced, many dissatisfactions are still raising even after some measure was taken. On such point of view, this Research, at the spot, has actually measured the equipment-noise that had permeated various wall-bodies, and examined its physical characteristics, thence based upon this, has conducted Psycho-Acoustics Experiment and investigated the interrelation between the physical evaluation value and psychological reaction value. It is considered that such study result could be utilized as the useful material at the time of establishment of the Grading Standard for the insulation performance against the Architectural Plumbing Noise, in the future.