• Steel and Composite Structures
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• v.11 no.4
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• pp.341-358
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• 2011

This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.54-61
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• 2004

The engine-out flow is highly transient and hot, and may place tremendous thermal and inertial loads on a closed-coupled catalyst. Therefore, time-dependent and detailed flow and thermal field simulation may be crucial. The aim of this study is to develop combined chemical reaction and multi-dimensional fluid dynamic mathematical model and to study the effect of unsteady pulsating thermal and flow characteristics on thermal reliability of closed-coupled catalyst. The effect of cell density on the conversion performance under real running condition is also investigated. Unlike previous studies, the present study focuses on coupling between the problems of pulsating flow pattern and catalyst thermal response and conversion efficiency. The results are expressed in terms of temporal evolution of flow, pollutant and temperature distribution as well as transient characteristics of conversion efficiency. Fundamental understanding of the flow and thermal phenomena of closed-coupled catalyst under real running condition is presented. It is shown that instants of significantly low values of flow uniformity and conversion efficiency exist during exhaust blowdown and the temporal varaition of flow uniformity is very similar in pattern to one of conversion efficiency. It is also found that the location of hot spot in monolith is directly affected by transient flow pattern in closed-coupled catalyst.

• Journal of Institute of Convergence Technology
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• v.10 no.1
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• pp.13-17
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• 2020

Among the factors that must be taken into account when using thermal imaging cameras that are expanding their application to various fields, a basic study was conducted focusing on temperature on the effect of solar radiation on the photographed thermal image. Through all experiments, in order to use an image taken with a thermal imaging camera for an object installed or located outdoors, a separate temperature correction according to the size of solar radiation or a separate device to block the effect of solar radiation must be additionally installed. Since the temperature of the same object may vary in the thermal image taken indoors or outdoors, it is necessary to calibrate it through comparison with other temperatures as a reference point. In the case of measuring the temperature of a glossy surface such as metal indoors with a thermal imaging camera, it was confirmed that an environment that can remove the light reflection effect by the glossy surface must be constructed and photographed.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.881-890
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• 2011

In this study, thermal environment changes for a marathon course of IAAF World Championship, Daegu 2011 were modeled to provide improvements of thermal environment, so that runners could have the maximum condition and citizens pleasant streets. The three biggest size of intersections were selected for the study. Envi-met, 3G microclimate model, were used for a thermal environment analysis and three different cases - present status, planting roadside tree scenario, and roof-garden scenario - were compared. The followings are the results of the study. 1. The highest thermal distribution were shown at 1 p.m., but there was no significant difference between a thermal distribution at 1 p.m. and that at 5 p.m. since a heat flux from buildings affects thermal distributions rather than insolation does. 2. Tree planting or adding environmental friendly factors might lead a temperature drop effect, but the effect was not significant for areas covered with impermeability packing materials such as concrete or asphalt (especally, for Site case 2) 3. The combination of tree planting and adding environmental friendly factors also brought a temperature drop effect (Site 1 and 2) and this case showed even better result if green spaces (especially, parks) were closed.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.3
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• pp.249-255
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• 1999

We sdudied effect of additives on catalytic activity in thermal catalytic de-NOx process which was composed of thermal reduction, catalytic reduction and catalytic oxidation stage. Pd-Pt/${\gamma}$-$Al_2O_3$ catalysts with the addition of transition metals(Co, Cu, Fe, Ni, W, Zn, Zr) and rare earth metals(Ce, Sr) were prepared by the conventional washcoating method. Those catalysts were characterized by CO pulse chemisorption, ICP, $N_2$ adsorption, SEM and XRD. The effect of catalyst additives on NOx removal for diesel emission was studied in thermal catalytic de-NOx process at reduction temperature(350~50$0^{\circ}C$), space velocity(5,000~20,000 $hr^{-1}$) and the engine load(0~120kW). The concentraton of CO, $CO_2$, NO and $NO_2$ in the exhaust gas increased with the engine load. On the other hand the concentration of $O_2$ decreased. The de-NOx activityof all prepared catalysts increased with respect to high CO and low $O_2$ level in the thermal reduction stage of the process. Insertion of Ce to Pt-Pd/${\gamma}$-$Al_2O_3$ catalyst showed the best activity of all the catalysts under these experimental conditions. De-NOx catalysts are effective to remove CO in addition to NOx in the catalytic reduction stage.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.56-62
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• 2022

In this paper, the effect of pulse width modulation methods on thermal loadings and power losses of single-phase five-level NPC inverters for photovoltaic systems are analyzed. The pulse width modulation methods affect the power losses of the NPC inverters and thus lead to different thermal loadings of NPC inverters. To identify the reliability-critical power device with respect to thermal stress, the thermal loadings of I- and T-type NPC inverters are analyzed by applying the unipolar pulse modulation method. Then, the effect of the discontinuous pulse width modulation method on power losses and thermal loadings of power devices of I- and T-type NPC inverters are analyzed. Finally, the operation of NPC inverters applying the discontinuous pulse modulation method is confirmed by experiments. The results show that the discontinuous pulse modulation method is able to improve the reliability of NPC inverters by reducing thermal loadings of reliability-critical power devices and it is more effective for T-type NPC inverters than I-type NPC inverters.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.237-243
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• 2011

Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.8
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• pp.86-91
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• 1995

Recently, motor integrated spindle is often used in a high speed spindle system of machine tools in order to increase machining speed. The important problem in high speed motor integrated spindle is to reduce thermal effect occured by motor and ball bearings. In this study, the effect of heat transfer from motor is investigated. The experimental equipment is composed with oil-air lubrication method, air cooling system and angular contact ball bearings. The results show that the thermal effect in motor is larger than in ball bearing until DmN 8000,000 with air cooling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.209-210
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• 2009

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.16 no.2
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• pp.189-211
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• 2003

The clinical data and thermographic imaging were analyzed on the 38 cases of Bell's palsy who were treated admission in the Oriental Medicine Hospital of Wonkwang University from January 2002 to May 2003. 38 patients with Bell's palsy were within one week after the onset of the paralysis, and thermal type in the DITI were hypo or hyper generally. Nerve conduction test(ENOG and EMG) examined in two weeks after onset. We studied interaction effect between thermal type and paralysis grade on admission day. We studied each main effect ; paralysis grade on admission day - nerve conduction test, nerve conduction test - thermal type, thermal type - paralysis grade after 4 weeks, paralysis grade on admission day - paralysis grade after 4 weeks, sasang constitution - nerve conduction test. The following results were obtained that interaction effect between thermal type and paralysis grade on admission day showed no significance, each main effect ; paralysis grade on admission day - nerve conduction test, paralysis grade on admission day - paralysis grade after 4 weeks, showed significance, each main effect ; nerve conduction test - thermal type, thermal type - paralysis grade after 4 weeks, sasang constitution - nerve conduction test, showed no significance.