• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.96-101
• /
• 2001

Heat transfer in linear motor driven stages for surface mounting device applications was investigated. A simple one-dimensional thermal resistance model was introduced. In order to reduce three-dimensional nature to one-dimensional, a few assumptions and simplifications were employed suitably. A good agreement with a finite element heat transfer analysis in temperature profile was obtained. For validation, the analysis was compared with the measurement with respect to motor driving power. Overall discrepancy was less than $7^{\circ}C$. The influence of two high thermal resistance parts, insulation sheet and thermal contact between the coil assembly and the mounting plate, was examined through the analysis. Additionally, the thermal resistance analysis was applied to another stage including an internal cooling-air passage, and was found available for this system as well. After validation, the cooling effect was surveyed in terms of motor power, and cooling-air flow rate.

• The Research Journal of the Costume Culture
• /
• v.2 no.2
• /
• pp.385-394
• /
• 1994

Data of the body surface is a necessary unit for the measuring of metabolism energy and activity energy. And also, these data are referring to check the degree of retaining warmth of clothes, to find the effect of heat insulation according to body surface, to calculate an average temperature of skin, and to study the several fields of clothing. In measuring of body surface, it si actually impossible to measure a subject's body surface in each experiment. As the experimental method, both gypsum method, by which the shape of body an be copied as it is, and the weighting method from which planed body surface area can be measured with consistent thickness of polyprophylene film as used. In fact, every female subject feels uncomfortable to measure her body surface as a naked body. There, it is providing a simple, accurate regressive equation with weight & height as variable factors in this study. This equation is as=117.02W+77.31H-3344.94 with average error : 0.1%, absolute average error : 2.07%.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.17 no.4
• /
• pp.518-528
• /
• 1993

The purposes of this study are to know the environmental conditions of rural houses, thermal sensation and clothing weight of rural residents and to estimate the standard clothing weight according to their indoor living temperature. In this study, the 631 rural residents of both sexes and all generations were selected from 5 rural districts of Kyunggi, Kangwon, Chungnam, Chonnam and Kyungbuk province and the surveys which include clothes, environmental conditions and thermal sensation carried out 4 times-once in each season-from July 1989 to April 1990. The results of this study are· as follows. 1. The ranges of outdoor temperature are $21{\sim}31^{\circ}C$ in summer, $7{\sim}20^{\circ}C$ in spring/autumn, $-15{\sim}5^{\circ}C$ in winter and those of indoor temperature are $24{\sim}31^{\circ}C$ in summer, $15{\sim}23^{\circ}C$ in spring/autumn, $11{\sim}17^{\circ}C$ in winter. The ranges of indoor temperature is within comfortable range in spring, summer and autumn but in winter it is below the range. 2. There is a negative relationship between indoor temperature and clothing weight(r = -0.927) and the simple regression equation is as follows. Y = -61.97X + 2048.44(Y : total clothing weight $g/m^2$, X : indoor temperature $^{\circ}C$). 3. There is no significant difference of clothing weight among the thermal sensation, so clothing insulation can not affect the thermal sensation. 4. Clothing weight of light-clothing-weight group is 70~75% of middle-clothing-weight group and clothing weight of heavy-clothing-weight group is 130% of middle-clothing-weight group. So the standard clothing weight for rural residents in their indoor living is estimated as Fig. 6.

• Journal of Bio-Environment Control
• /
• v.28 no.3
• /
• pp.273-278
• /
• 2019

The multi-layer insulating curtains used in the experiment was produced in six combinations using non-woven fabric containing aerogel and compared and analyzed by measuring heat flux and heat perfusion rates due to weight, thickness and temperature changes. Using silica aerogel, which have recently been noted as new material insulation, this study tries to produce a new combination of multi-layer insulating curtains that can complement the shortcomings of the multi-layer insulating curtains currently in use and maintain and improve its warmth, and analyze the thermal properties. The heat flux means the amount of heat passing per unit time per unit area, and the higher the value, the more heat passing through the multi-layer insulating curtain, and it can be judged that the heat retention is low. The weight and thickness of multi-layer insulation curtains were found to be highly correlated with thermal insulation. In particular, insulation curtains combined with aerogel meltblown non-woven fabric had relatively higher thermal insulation than insulation curtains with the same number of insulation materials. However, the aerogel meltblown non-woven fabric is weak in light resistance and durability, and there is a problem that the production process and aerogel are scattering. In order to solve this problems, the combination of expanded aerogel non-woven fabric and hollow fiber non-woven fabric, which are relatively simple manufacturing processes and excellent warmth, are suitable for use in real farms.

• Progress in Superconductivity and Cryogenics
• /
• v.16 no.1
• /
• pp.14-18
• /
• 2014

The mechanical, electrical and thermal characteristics of insulating materials may significantly affect the performance and reliability of electrical devices using superconductors. General method to provide insulating layer between coated conductors is wrapping coated conductor with Kapton tape. But uniform and compact wrapping without failure or delamination in whole coverage for long length conductor is not a simple task and need careful control. Coating of insulating layer directly on coated conductor is desirable for providing compact insulating layer rather than wrapping insulating layers around conductor. Ceramic added polymer has been widely used as an insulating material for electric machine because of its good electrical insulating properties as well as excellent heat resistance and fairy good mechanical properties. The insulating layer of coated conductor should have high breakdown voltage and possesses suitable mechanical strength and maintain adhesiveness at the cryogenic temperature where it is used and withstand stress from thermal cycling. The insulating and mechanical properties of polymer can be improved by adding functional filler. In this study, insulating layer has been made by adding ceramic particles such as $SiO_2$ to a polymer resin. The size, amount and morphology of added ceramic powder was controlled and their effect on dielectric property of the final composite was measured and discussed for optimum composite fabrication.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.12
• /
• pp.61-67
• /
• 2023

Heat pipes located underground in urban areas and operated under high temperature and pressure conditions can cause large-scale human and economic damage if damaged. In order to predict damage in advance, damage and construction information of heat pipe are analyzed to derive independent variables that have a correlation with frequency of damage, and a simple regression analysis modified model using each variable is applied to the field. However, as the correlation between independent variables applied to the model increases, the independence between variables is harmed and the reliability of the model decreases. In this study, the independence of the pipe diameter, burial depth, insulation level of monitoring system, and disconnection or short circuit of the detection line, which are judged to be interrelated, was tested to derive a method for combining variables and setting categories necessary to apply to the frequency of damage estimation model. For the test of independence, the continuous variables pipe diameter and burial depth were each converted into three categories, insulation level of monitoring system was converted into two categories, and the categorical variable disconnection or short circuit of the detection line status was kept as two categories. As a result of the test of independence, p-value between pipe diameter and burial depth, level of monitoring system and disconnection or short circuit of the detection line was lower than the significance level (α = 0.05), indicating a large correlation between them. Therefore, the pipe diameter and burial depth were combined into one variable, and the categories of the combined variable were set to 9 considering the previously set categories. The insulation level of monitoring system and the disconnection or short circuit of the detection line were also combined into one variable. Since the insulation level is unreliable when the detection line status is disconnection or short circuit, the categories of the combined variable were set to 3.

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.254-262
• /
• 2003

In this study, the results of applying cold weather concreting mixed with Accelerator for Freeze Protection(AFP) to full scale structures are presented. Since the determination of W/C and amount of AFP significantly have an effect on strength gain and protection of frost damage in early, a full investigation is needed to determine these values at stage of nux design. The flowability of fresh cold weather concreting with AFP was similar to the same W/C. Lower loss of workability and initial slump flow of concrete using superplasticizer of polycarboxylic ester than that of melamine sulphonate showed that polycarboxylic ester was more effective on elapsed time. Temperature histories of specimens located in insulation boxes at the site was similar to that of structures. Thus, it is cleared that simple adiabatic curing method is effective for evaluating in-place concrete strength than specimens cured by sealing method. The investigation results of development of compressive strength of cold weather concreting included AFP with curing methods by logistic curves indicated that AFP can be effective to gain strength at lower temperature than normal curing temperature. In field testing, vinyl sheets were placed over the concrete sections and AFP enabled concrete to gain $5N/{mm}^2$ to protect frost damage in early ages and specified compressive strength of concrete at 28 days under average temperature of $-2^{\circ}C$ (lowest temperature was $-12^{\circ}C$) during site application.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.669-672
• /
• 2008

To analyze possibility for high performance concrete that massively displaces blast furnace slag, this study analyzed the characteristics of concrete by blast furnace slag displacement rate changes, and the results are summarized as follows. Firstly, as for fresh concrete characteristics, flow tended to increase and air amount decreased with increase in blast furnace slag displacement rate, and settling time was shown delayed. As for hardened concrete characteristics, in conditions where blast furnace slag displacement rate increased up to 50%, the compressive strength decreased below OPC at early age, however at age 28 days, its level was no less than that of OPC, and as for temperature rise by simple insulation, it decreased as displacement rate increased at early stage of hydration, but in the latter stage, hydration progress slowed down and hydration heat increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.5
• /
• pp.307-312
• /
• 2018

Liquid phases in ZnO varistors cause more complex phase development and microstructure, which makes the control of electrical properties and reliability more difficult. Therefore, we have investigated 2 mol% $CaCO_3$ doped $ZnO-Co_3O_4-Cr_2O_3-La_2O_3$ (ZCCLCa) bulk ceramics as one of the compositions without liquid phase sintering additive. The results were as follows: when $CaCO_3$ is added to ZCCLCa ($644{\Omega}cm$) acting as a simple ohmic resistor, CaO does not form a secondary phase with ZnO but is mostly distributed in the grain boundary and has excellent varistor characteristics (high nonlinear coefficient ${\alpha}=78$, low leakage current of $0.06{\mu}A/cm^2$, and high insulation resistance of $1{\times}10^{11}{\Omega}cm$). The main defects $Zn_i^{{\cdot}{\cdot}}$ (AS: 0.16 eV, IS & MS: 0.20 eV) and $V_o^{\bullet}$ (AS: 0.29 eV, IS & MS: 0.37 eV) were found, and the grain boundaries had 1.1 eV with electrically single grain boundary. The resistance of each defect and grain boundary decreases exponentially with increasing the measurement temperature. However, the capacitance (0.2 nF) of the grain boundary was ~1/10 lower than that of the two defects (~3.8 nF, ~2.2 nF) and showed a tendency to decrease as the measurement temperature increased. Therefore, ZCCLCa varistors have high sintering temperature of $1,200^{\circ}C$ due to lack of liquid phase additives, but excellent varistor characteristics are exhibited, which means ZCCLCa is a good candidate for realizing chip type or disc type commercial varistor products with excellent performance.

• Journal of Bio-Environment Control
• /
• v.14 no.2
• /
• pp.95-105
• /
• 2005

This study was carried out to file up using effect and requirement of energy for environmental design data of Pleurotus eryngii growing houses. Heating and cooling Degree-Hour (D-H) were calculated and compared for. some Pleurotus eryngii growing houses of sandwich-panel (permanent) o. arch-roofed(simple) type structures modified and suggested through field survey and analysis. Also thermal resistance (R-value) was calculated for the heat insulating and covering materials of the permanent and simple-type, which were made of polyurethane or polystyrene panel and $7\~8$ layers heat conservation cover wall. The variations of heating and cooling D-H simulated for Jinju area was nearly linearly proportional to the setting inside temperatures. The variations of cooling D-H was much more sensitive than those of heating D-H. Therefore, it was expected that the variations of required energy in accordance with setting temperature or actual temperature maintained inside of the cultivation house could be estimated and also the estimated results of heating and cooling D-H could be effectively used far the verification of environmental simulation as well as for the calculation of required energy amounts. When the cultivation floor areas are all equal, panel type houses to be constructed by various combinations of materials were found to by far more effective than simple type pipe house in the aspect of energy conservation maintenance except some additional cost invested initially. And also the energy effectiveness of multi-span house compared to single span together with the prediction of energy requirement depending on the level insulated for the wall and roof area could be estimated. Additionally, structural as well as environmental optimizations are expected to be possible by calculating periodical and/or seasonal energy requirements for those various combinations of insulation level and different climate conditions, etc.