• Restorative Dentistry and Endodontics
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• v.41 no.2
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• pp.106-113
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• 2016

Objectives: This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods: Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at $37^{\circ}C$, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10). Results: Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z ($4.60{\pm}1.08MPa$) and all other groups ($13.38{\pm}2.57-15.78{\pm}2.39MPa$, p < 0.05). For AA-Z, most of the adhesive remained on the bracket. Conclusions: For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.44-48
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• 2009

In this paper, two different types of natural gas liquefaction cycle with 2 staged compression were designed and simulated to develop liquefaction process which is the core technology in the Industry of natural gas liquefaction plant. These include the cascade cycle with inter-cooler which is consisted of propane, ethylene and methane cycle. One of these is that liquid-gas heat exchanger is applied to between methane and ethylene cycles, and another is that liquid-gas heat exchanger is added to between ethylene and propane on the above process. Also, these cycles are compared with two staged cascade process using an inter-cooler. The COP of process2 is shown about 14.0% higher than that of process1, respectively. Also, the yield efficiency of LNG improved comparing with process1 with 11.5% lower specific power.

• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.33-40
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• 2020

Chiller systems which have better temperature stability than Direction expansion coils are often used as condensing units in HVAC systems for offshore plants. Large capacity compressors and electronic expansion valves in chiller systems are mostly imported, and the size of a chiller system depends on heat exchangers such as evaporators and condensers which are locally produced. Due to limited space in the offshore plants, shipyards are demanding manufacturers to make equipment compact. In this paper, a shell & tube heat exchanger, which is used as an evaporator in the conventional flooded chiller system, is replaced by a newly developed compact plate & shell heat exchanger. The main development process of the plate & shell heat exchanger is introduced, and its performances were experimentally evaluated with a real flooded chiller system, and the results are presented.

• Journal of The Korea Institute of Healthcare Architecture
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• v.26 no.1
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• pp.73-84
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• 2020

Purpose: Though Korean healthcare services have been upgraded, infection and fire had been broken out in general hospitals. And higher concerns about quality assessment made it to clinical laboratory design guideline studies. So, this study investigates the facilities, equipment and personnel of laboratory medicine focusing on more than five hundred fifty bed hospital, and contributes to make guidelines for safety and efficiency in lab. Methods: Questionnaires to supervisor technologist and field surveys to medical laboratories in korean hospitals have been conducted for the data collection. 16 answers have been analysed statistically by MS Excel program. Results: Most of the sample tests such as hematology, clinical chemistry, immunology, transfusion, urinalysis, microbiology and molecular diagnosis are performed by more than 80% in large sized general hospital laboratory. In the test methods, automatic analyzers are used up to 80%, total laboratory automation up to 43% in clinical chemistry and immunology, and manual tests in all sorts of the test. There are placed in single lab or two and three labs above the ground, which are all in semi-open lab. There is some correlation with the number of specimens and the number of lab people depending on the number of hospital beds. Laboratory environment shows that work distance is good, but evacuation path width, visibility, separation of staff area from automatic analyzer, and equipment installations are needed to have more spaces and gears. Most of the infection controls are equipped with mechanical ventilation, air-conditioning, washbasin and wastewater separation, BSC installation and negative pressure lab room. Implications: Although the laboratory space area is calculated considering the number of hospital beds, type of tests and number of staff, hospital's expertise and the samples numbers per year should be taken into account in the planning of the hospital.

• Journal of Korean Society of Rural Planning
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• v.26 no.2
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• pp.117-126
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• 2020

In this study, demands of smart technology development were analyzed for rural village communities. Questionnaire items were derived by grasping the current status of information and communication technology. 49 villages in 8 regions were selected and surveys and statistical analysis were conducted. The main results of the study are as follows. First, 92% of community leaders use smartphones, search for information (38%), communicate with the Internet (36%) using smartphones, use KakaoTalk (31%), and Facebook (24%). Second, in the rural and urban exchange activities, promote support information service (51%) and promote method suggestion service (48.5%) showed that the demand for services in promote field was high. It is linked to the creation of economic opportunities. Third, in the income and production activities, demand for distribution services technology (39.3%) was high in the field of production and distribution, and cold chains that help maintain freshness until food, such as meat, fish, and vegetables are delivered to consumers when agricultural products are distributed. The constant temperature control system needs to be actively introduced. Fourth, autonomy activities showed the highest demand for air conditioning and control systems (34.2%) of community building, and the lowest demand for electronic voting (9.4%) and videoconferencing (9.4%) services. Lastly, in the general activity area of the community, the demand for technology of emergency services (37.1%) and health self-diagnosis service (35.4%), which are technologies in the welfare sector, ranked first and second respectively.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.43-53
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• 2008

Because the torque control method, which is also caled the clamping method in domestic construction sites, is affected by a variation of the torque coefficient, quality control of the torque coefficient is essential. This study was focused to evaluate the effects of several environmental factors and errors when installing bolts while tightening high-strength bolts. Conditioning environmental parameters include wet, rusty and exposure-to-air-only conditions. In addition, because of errors in workability such as instalation of two washers, upset washers are selected. During the tests, torque, torque coefficient, tension and angle of nut rotation were obtained using a bolt testing machine. Test specimens of four types of bolts (High-Strength Hexagon bolt on KS B 1010, Torque Shear Bolt on KS B 2819, High-Strength Hexagon bolt coated with zinc, and ASTM 490 bolt) were recomended. Based on test results, the tightening characteristics subjected to environmental parameters were investigated and compared with the results in normal condition.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.185-191
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• 1999

An air-conditioning system based on the chemical heat storage principle was considered. $H_2O$ was chosen as the reaction gas and the working fluid as well. Na$_2$S, CaCl$_2$, MnCl$_2$, BaCl$_2$, MgCl$_2$, Fe$_2$(SO$_4$)$_3$ and MnSO$_4$ were tested as the solid reactants by using Cahn pressure balance. Na$_2$S was superior to other salts in respect of high capability of absorption of water gas, 5 moles of $H_2O$ per unit mole of Na$_2$S, and adequate temperature of adsorption, $65^{\circ}C$ at 7torr, and of desorption, 13$0^{\circ}C$ at 76torr. Clausius-Clapeyron diagram of Na$_2$S was obtained via adsorption experiments at several vapor pressures of water gas. To enhance heat and mass transfer characteristics, usually below 1W/m K, of the reactor bed of general adsorption systems, expanded graphite block was adapted as the support of Na$_2$S salt. Expanded graphite blocks had thermal conductivity values of 20~80W/mK with respect to 100~400kg/㎥ of block bulk density. Permeability values of expanded graphite blocks were 10$^{-13}$ ~ 10$^{-14}$ $m^2$ with respect to 100~300kg/㎥ of block bulk density showing highly decreasing values of permeability, below 10$^{-l4}$$m^2$, in the range of above 150kg/㎥ of block bulk density.y.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2195-2201
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• 2009

This paper considers the influence of suction-line heat exchangers on the efficiency of a refrigeration cycle using hydrocarbon refrigerants such as R290, R600a and R1270. These suction-line heat exchangers can, in some cases, yield improved system performance while in other cases they degrade system performance. A steady state mathematical model is used to analyze the performance characteristics of refrigeration cycle with suction-line heat exchanger. The influence of operating conditions, such as the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, to the performance of the cycle is also analyzed in the paper. Results showed that the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, and effectiveness have an effect on the cooling capacity, compressor work and RCI(Relative Capacity Index) of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle of hydrocarbon refrigerants using suction-line heat exchanger.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.38-42
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• 2012

A scroll compressor used in the air conditioning in automobile consists of the fixed scroll and the orbiting scroll. Temperature gradient in the scroll compressor during the operation induces the thermal expansion of two scrolls. Therefore, the gap between scrolls in the initial stage is regarded as an important variable in structural design of the scroll compressor. The coupled thermal-stress analysis was carried out for the scrolls of a scroll compressor. The temperatures of major points of two scrolls in the steady states were referred by the literature of C. Lin. The sequentially coupled thermal-stress analysis is utilized to the heat transfer analysis and the thermal expansion analysis. In the thermal expansion analysis, the contact analysis was considered between the fixed and the orbiting scrolls in order to obtain the penetration distance and the contact pressure between two scrolls. The range of deformation was from 44 to $76{\mu}m$ according to the height of the scroll. The maximum penetration distance of $60{\mu}m$ occurred at the top surface of the fixed scroll in the center of the scroll parts.

• Journal of Korean Society of Forest Science
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• v.95 no.5
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• pp.591-594
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• 2006

To have better urban forests in future we are focusing on two major issues like other countries. How we could have more urban forest-quantitative approach-against the expanding of urbanization, and how we could produce better urban forest-qualitative approach-to give a chance in contact with better nature for urban people. Prime surveys on urban forests have been carried out in 6 major cities since 1991, and the city of Daegu which is located on the east southern area of Korea have been case studied for qualitative approaches during last 3 years. Major species of the remnant forests were Pinus densiflora, Pinus rigida, Pinus thunbergii and Robinia pseudoacacia. Approximately 20% of the surveyed forests were lost their structure as forests caused by illegal farming, facilities and as the bare ground by excessive visitors. Generally speaking the condition of forests for biotope was very poor in overall. From two years data of monitoring of birds, we found that wooded parkways and woodland squares had more species than street tree areas. Nests were found mainly on the branch of Zelkova serrata, Pinus densiflora and Quercus myrsinaefolia. The size of urban forests mainly determined the species richness of birds. According to the oxygen output and carbon input by photosynthesis measurement, the capability was in order of Platanus occidentalis, Zelkova serrata and Ginko biloba. Air conditioning effects of trees through transpiration measurement was found and the quality of forests also related to the reducing of urban heat-island.