• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.401-404
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• 1997

We prepared 0~20mo1% WO$_3$added ZnO composite ceramics in order to promote a CO gas sensitivity. Using SE,. we observed the microstructure of sample. The resistances of sample were measured by High Voltage Measure/source Unit in the temperature range of +5V~-5V. The measured 1000ppm CO sensitivities of pure ZnO were about 1~4.3, and the measured 1000ppm CO sensitivities of ZnO-WO$_3$composite ceramics were about 1~8.2. Therefore, the 1000ppm CO sensitivities of ZnO-WO$_3$composite ceramics were about 2 times larger than that of pure ZnO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.347-349
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• 1997

In order to investigate CO sensing property of a SnO$_2$-WO$_3$composite ceramic. we prepared pure SnO$_2$and WO$_3$added SnO$_2$compostie ceramics. Using XRD and SEM, a phase analysis and microstructure were investigated. The resistances as a function of gas atmosphere were measured by High Voltage Measure/source Unit. The measured 1000ppm CO gas sensitivity of SnO$_2$-WO$_3$composite ceramics were smaller than that of pure SnO$_2$.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.41-48
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• 2022

The purpose of this study is to evaluate seismic performances of a modular house system developed by a simple 4-clip fastening method and double metal assembly made of lightweight metals. In order to evaluate structural and non-structural seismic performances of the system. Shaking table test was carried out with full-scale modular units, and a nonlinear pushover analysis was performed to obtain suitable seismic responses for story drifts, displacements, force resistances and dynamic properties of the system. Through 3D analysis and shaking table test, the current method of lightweight modular metal unit assembly and systems with seismic performance of a 4-clip fastening type modular house were demonstrated safe and effective to seismic design.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.513-516
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• 2013

Earthmoving equipment's haul-route has a great influence on the productivity of the earth work operation. Haul-route grade is a critical factor in selecting the haul-route. The route that has low grade resistance contributes to increase machine travel speed and production. This study presents a mathematical model called "Hauling-Unit Optimal Routes Selecting system" (HUORS). The system identifies optimal path that maximize the earth-work productivity. It consists of 3 modules, i.e., (1) Module 1 which inputs site characteristic data and computes site location and elevation using GIS(Geographical Information System); (2) Module 2 which calculates haul time; (3) Module 3 which displays an optimum haul-route by considering the haul-route's gradient resistances (i.e., from the departure to the destination) and hauling time. This paper presents the system prototype in detail. A case study is presented to demonstrate the system and verifies the validity of the model.

• Tribology and Lubricants
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• v.21 no.6
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• pp.268-271
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• 2005

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15N contact force in a reciprocal sliding motion of sliding distance of 10mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji II LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.7-13
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• 2007

A Dish type solar concentrating system consists of a parabolic concentrator and a cavity receiver. In order to achieve high temperatures from solar energy, it is essential to efficiently reflect the solar rays in the concentrator and to minimize thermal losses in the cavity receiver. Improving the economical efficiency of a solar power system required the stirling unit to be operated continuously. For continuous operation of the stilting unit, the receiver must be continuously provided with thermal energy from solar as well as additional combustion heat. It is possible for a hybrid solar receiver system equipped with an additional combustion to be operated 24 hrs/day. A hybrid solar receiver was designed and manufactured for a total thermal load of 35 kW in the operating temperature range $700^{\circ}C$ to $800^{\circ}C$. The hybrid receiver system was tested in gas-only mode by gas-fired heat to investigate thermal characteristics at inclination angle varying from 0 deg to 30 deg(cavity facing down) and the aperture to cavity diameter ratios of 0(closed cavity) and 1.0(open cavity). This paper has been conducted to measure temperature distribution in cavity surface and to analyze thermal resistances, and the evaporation and condensation heat transfer coefficient in all cases(open and closed cavity).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.941-948
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• 2016

Textile composite materials have been widely applied in aerospace structures due to their various advantages such as high specific stiffnesses and strengths, better out-of-plane performances, impact and delamination resistances, and net shape fabrications. In this paper, a modified geometric model of repeating unit cell (RUC) is suggested based on the Naik's model for 2D plain weave textile composites. The RUC geometry is defined by various parameters. The proposed model considers another parameter which is a gap length between adjacent yarns. The effective stiffnesses are predicted by using the yarn slicing technique and stress averaging technique based on iso-strain assumption. And the stiffnesses of RUC are evaluated by adjusting the gap ratio and verified by comparing with Naik's model and experimental data for 2D plain weave composite specimens.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.189-196
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• 2008

The increase of system weight due to installation of cooling devices adds electrical and mechanical loads of humanoid robot, and in return, results in much heat. Therefore, the weight of cooling system is a critical issue for robot cooling. In this study, we propose non-metallic cold plates to deal with such problems. We compare thermal performances between one metallic cold plate and five different types of non-metallic cold plates. A metallic cold plate is totally made of copper. Five non-metallic PC(polycarbonate) cold plates, which are designed to reduce the overall weight of robot cooling system, are composed of a polycarbonate cover with different types of base plate. The overall heat transfer coefficients per unit mass and thermal resistances are obtained for the cold plates. The metallic cold plate shows the best thermal performance. It is interesting to note that the PC cold plate with an aluminum base plate with 18 channels shows the best overall heat transfer coefficient per unit mass. Most polycarbonate cold plates display fairly comparable thermal performance with more reduced system weight compared to the metallic cold plate.

• Journal of Korean Biological Nursing Science
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• v.20 no.1
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• pp.38-46
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• 2018

Purpose: The aim of this study was to verify the effects of daily 2% chlorhexidine gluconate (CHG) bathing on the acquisition of multidrug-resistant organisms (MDRO) and healthcare-associated infection (HAI) in a medical intensive care unit (MICU). Methods: The study was a randomized controlled group posttest only design, involving 91 patients in MICU at a tertiary hospital (47 patients in the experimental group and 44 patients in the control group). The 2% CHG bathing was performed daily according to bathing protocol to the patients in the experimental group, and traditional bath was performed every three days to those in the control group. Fisher's exact test and x2 test were used to analyze the data. Results: MDRO were found in 6 patients of the experimental group and in 15 patients of the control group. The difference was statistically significant (p= .016). HAI occurred in 2 patients of the experimental group and in 7 patients of the control group. The difference was not statistically significant (p= .084). Conclusion: The results confirmed that daily bathing with CHG was effective in reducing the incidence of MDRO acquisition. Therefore, it is expected that daily bathing with CHG will be used as an effective nursing intervention to reduce the incidence of MDRO acquisition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4117-4123
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• 2013

In the present study, coating corrosion characteristics of the heat exchanger for sea water are experimentally investigated. Coating types by a teflon, an electrodeposition and a ceramic+silicon were tested and compared with the corrosion characteristics of an aluminum. For the acceleration of corrosion by sea water, the temperature of sea water $70^{\circ}C$ and the concentration of salt 3.5% were considered. And the specimens were immersed in sea water during 9 weeks. Coating corrosion characteristics were measured by using the impedance method and SEM. Experimental results showed that polarization resistances obtained from Bode plot were related to the corrosion resistance of coating types, and the corrosion resistance of double coating were maintained during 4 weeks. From SEM photograph, we saw that blisters was generated on the interface between metal and coating.