• Journal of Technologic Dentistry
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• v.16 no.1
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• pp.78-104
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• 1994

Under the fee for service schedule of Korean health insurance system, rational fee for dental laboratory products based on the cost is required to be formulated. The purpose of this study was to find actual cost of dental laboratory products in case of a University Hospital. Materials of this study were used as follows : 1. Balance sheet at Dec. 31, 1992 and profit and loss report of the year 1992 of the sample hospital 2. Performance report of dental laboratory department. 3. Purchasing and other accounting bills of dental laboratory materials. The following methods were used. 1. Actual cost finding of dental laboratory department was performed. 2. Work sampling methods were used for measuring standard working time by the process of working. 3. To porcelain fused to metal crown(non-precious), Relative value of the cost of dental laboratory products was calculated as 1.00. 4. Fee and cost of those products were compared on the basis of Relative values. The results of the study can be summarized as follow : 1. Overall, it took longs time than other items. to product denture-related items. 2. When several teeth are made in a time, average production time is much sorter than when one tooth is made in a time. 3. The relative price cost of Dicor cast crown and denture related items are higher than the criterion items. 4. The material cost occupies average 11% out of the total price cost, proportion of personnel expenses is average as 60.0%. 5. Some of the components consisting of the price cost are not reflected adequately in setting the level of the reimbursement price. 6. Relative values of dental laboratory products price cost are varied in the range from 0.05 to 2.83, overall, the reimbursement price of dental products appears not to reflect adequately the price cost. On the basis of this study results, the following ideas would be suggested : 1. Fee Schedule of dental laboratory products should be renovated in order to reflect their costs. 2. Dental laboratory product manufacturers should be enlarged for the economy of scale which may be useful for cost- containment. 3. Dental laboratory producters themselves are required to be standardiqed according to the categories of skill.

• Journal of the Korean GEO-environmental Society
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• v.19 no.11
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• pp.15-22
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• 2018

The main objective of this study was to analyse heavy metals in sediments obtained from Gwangan bridge and to evaluate pollution intensity of the sites. To evaluate pollution intensity of the sites, we used enrichment factor (EF), geoaccumulation index, potential ecological risk factor (PERF), and mean PEL quotient. Pollution intensities of these sites were evaluated by above methods, and we found most dangerous heavy metal and polluted sites. All sites showed non polluted or low risk for the heavy metals such as Cr, Cu, Ni, Pb, and Zn, but all sites were categorized as minor enrichment for Cd. G4 was evaluated as moderately polluted by Cd ($I_{geo}$) but other sites were unpolluted by heavy metals. In summary, Cd was found to be higher concentrations for all sites. For G4 and G5 sites, Pb and Zn in addition to Cd were higher than other sites.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.2
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• pp.193-207
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• 2016

This study discusses the present status of mercury emission and distribution from major anthropogenic sources in Korea and the future trend of mercury emission by activity changes and application of BATs. Atmospheric mercury emission from major anthropogenic sources based on Annex D of Minamata convention was estimated to around 4.89 tonne in 2012. Emission ratios of cement clinker production, coal-fired power plant, waste incineration and non-ferrous metal smelting were 68.68%, 24.75%, 6.29% and 0.28%, respectively. High mercury emission regions were characterized by the presence of cement clinker production facilities and coal-fired power plants. Prediction of future activities was carried out by linear regression of the previous year data. The (total) mercury emission was estimated to decrease up to 48% Under the scenario of BATs to be applied and the change of future activities. Emissions from coal-fired powerplants and cement clinkers were expected to decrease significantly.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.7
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• pp.1141-1148
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• 2017

Generally, a thermistor made by sintering a metal oxide is widely used to measure the ambient temperature. This thermistor is widely used not only for industrial use but also for medical use because of its excellent sensitivity, durability, temperature change characteristics and low cost. In particular, the normal body temperature is 36.9 degrees relative to the armpit temperature, and it is most closely related to the circulating blood flow. Previous studies have shown that body temperature changes during biomechanical changes and body temperature changes by anomalous signs or illnesses. Therefore, in this study, we propose a Lock-In-Amp design to detect minute temperature changes of clothing and thermistor wired by a preacher as a method to regularly measure body temperature in daily life. Especially, it is designed to measure the minute resistance change of the thermistor according to body temperature change even in a low-cost microprocessor environment by using a micro-processor-based Lock-In-Amp, and a jacquard and the thermistor is arranged so as to be close to the side, so that the reference body temperature can be easily measured. The temperature was measured and stored in real time using short-range wireless communication for non - restraint temperature monitoring. A baby vest was made to verify its performance through temperature experiments for infants. The measurement of infant body temperature through the existing skin sensor or thermometer has limitations in monitoring infant body temperature for a long time without restriction. However, it can be overcome by using the embroidery fabric based micro temperature monitoring wireless monitoring device proposed in this study.

• Restorative Dentistry and Endodontics
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• v.40 no.3
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• pp.229-235
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• 2015

Objectives: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at $135^{\circ}$ vertical angle, subjected to thermo-mechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. Conclusions: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.74-77
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• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for AC power system of railroad vehicles. Metal oxide surge arrester for most electric power system applications, electric train and must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of ZnO elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock. pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion. The main research works are focused on the structure design by finite element method, pressure relief of module, and studies of performance of surge arrester for electric railway vehicle.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.400-406
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• 1999

Piezoresistive flow sensors with four different types of microbeam structures were fabricated using (100), n/$n^+$/n three-layer silicon wafer and their characteristics were investigated. Piezoresistors were formed through boron diffusion and its values were about $1\;k{\Omega}$. Three-dimensional silicon microbeams were constructed by porous silicon micromachining and curled microbeams were fabricated by the difference in the thermal expansion coefficient between silicon and metal. The output response of the fabricated sensor was evaluated through half- bridge. The output voltage increased with increasing length of microbeam at the same flow velocity, while the detectable measurement range extended with decreasing length of microbeam. The output voltage of the fabricated sensors were increased with quotient of 3.2 of the flow rate since the stress of the beam versus the gas flow showed non-linear characteristics.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.109-113
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• 2002

A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.4
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• pp.181-185
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• 2013

This paper deals with the electromagnetic loss characteristics of enclosures for a 24kV high voltage switchgear by using a finite element method (FEM). A study on the electromagnetic characteristics of enclosures for a high voltage switchgear should be conducted to minimize the size and the temperature rising of a switchgear. Generally, the enclosures made by stainless steel are used to minimize the eddy current loss caused by the transporting current in Bus bars due to its non-magnetic characteristics although the price of stainless steel is expensive compared with other metal for enclosures. Therefore, a switchgear made by stainless steel enclosures could be fabricated as a small size and are applied to a switchgear in urban substations. On the contrary, the switchgear enclosures made by steel could be fabricated with relatively cheap manufacturing price. However, the temperature easily rises due to the transporting current in Bus bars because steel is a ferromagnetic material. Therefore, the size of a switchgear made by steel enclosures is relatively massive and installed in rural substations. In this paper, the electromagnetic losses in the enclosures of a switchgear according to various enclosure thicknesses are calculated and compared with each other. Especially, we proposed a hybrid type enclosures for a switchgear made by stainless steel (top and bottom enclosure) and steel (left and right enclosure). It is concluded that the cost electromagnetic performance of applying the hybrid type enclosure is favorable to develop a high voltage switchgear.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.05a
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• pp.57-61
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• 2005

In this study, the machine vision system for inspection using color recognition method have been designed and developed to automatically sort out a specified material such as Cu scraps or other non-ferrous metal scraps mixed in Fe scraps. The system consists of a CCD camera, light sources, a frame grabber, conveying devices and an air nozzled ejector, and is program-controlled by a image processing algorithm. The ejector is designed to be operated by an I/O interface communication with a hardware controller. The sorting examination results show that the efficiency of separating Cu scraps from the Fe scraps mixed with Cu scraps is around 90 % at the conveying speed of 15 m/min. and the system is proven to be excellent in terms of its efficiency. Therefore, it is expected that the system can be commercialized in shredder firms, if the high-speed automated sorting system will be realized.