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非定常方形波 펄즈 加熱에 의한 세라믹 誘電體의 熱物性値 測定에 관한 硏究
차경옥 대한기계학회 1988 대한기계학회논문집 Vol.12 No.1
본 연구에서는 열물성치 측정시 여러가지 어려운 수고를 가급적 줄이고 측정시간도 짧도록 하기 위해서 방평파 펄즈상가열법을 채용하여 이론적 검토와 고온에 유한원형인 시료로 부터 복사열손실을 최소화할 수 있는 방법을 고려하였다. 물론 시료는 전지회로의 용량소자, 콘텐서(condenser) 또는 전기절연이 주용도이며 유전율이 서로 다른 5종류의 세라믹 유전체에 관해서도 상온으로부터 약 1300k 까지 열물성치를 계측하였다. 특히 세라믹 유도체에는 유전율 및 기공율에 의한 열물성치가 가 다르기 때문에 그들사이의 관계에 대해서도 검토하였다. In recent years, attention has been paid to the ceramic material next to metals and plastics due to its inherent characteristics, i.e., good hardness, resistance to heat and corrosion. Recently, various kinds of ceramic dielectrics have been developed for application in industry. It is of prime importance to know the thermophysical properties for wider use of these new materials. However, no extensive effort has been made for systematic measurement of the properties. In this paper, the dielectric constant of five different kinds of ceramic dielectrics ware measured. We call these samples as MgO.SiO$_{2}$, MgTiO$_{3}$, TiO$_{2}$, CaTiO$_{3}$, and BaTiO$_{3}$. Which are currently in commercial sue. The values of thermal dirrusivities, specific heats, and thermal conductivities of these ceramic dielectrics sere measured as a function of temperature ranging from room temperature to about 1300k.
한경,이민호,이준서,이해철,차경옥 明知大學校 産業技術硏究所 1999 産業技術硏究所論文集 Vol.18 No.-
There are various noises generated by friction. Among the rest, eliminating squeal noise generated during braking is an important task for the improvement of vehicle passenger's comport. The parameters affecting brake squeal noise are the material properties of the braking pad, the dynamic properties of the brake parts and the dimensions of the brake assembly etc. Also, the squeal noise changes its inherent form(i.e. its sound pressure level and its frequency) with the normal load and sliding speed. In this study, the characteristics of brake squeal noise generated by friction is analyzed experimentally. The experiment focused on the analysis of friction self-excited vibration and squeal noise level. Friction self-excited vibration is caused by the dry friction between pads and rotor, and occurs as a function of their relative sliding speeds. and Friction self-excited vibration is raised the brake squeal noise.
吳栗權,張熙碩,吳炯俊,車京玉 明知大學校 産業技術硏究所 1988 産業技術硏究所論文集 Vol.7 No.-
The theoretical analysis of the exhaust noise of an internal combustion entwine contains various difficult factors. The exhaust system is closely related with these problems, that is, the resistance of tile exhaust system is a factor governing the fuel economy and dynamic performance of an internal combustion engine, while exhaust noise and radiated noise from the system are one of the main factor affecting the quietness of an internal combustion engine and also one of the main sources of external noise of all internal combustion engine. Reducing tile resistance and lowering the exhaust and radiated noise are contracdictory requirements and it has been considered difficult to satisfy these requirements simultaneously. Almost all the studies on the attenuation characteristics of a muffler are an analysis based on the assumption that the time of intake-exhaust valve opening - closing is deadpoint. This paper introduces a practical exhaust system for internal combustion engine newly developed as the result of studies on the reduction of the exhaust system, pulsating noise and draft noise.
차경옥,김재근,Kim, J. G. 대한기계학회 1995 대한기계학회논문집 Vol.19 No.10
Two phase flow phenomena are observed in many industrial facilities and make much importance of optimum design for nuclear power plant and various heat exchangers. This experimental study has been investigated the classification of the flow pattern, the local void distribution and convective heat transfer in swirl and non-swirl two phase flow under the isothermal and nonisothermal conditions. The convective heat transfer coefficients in the single phase water flow were measured and compared with the calculated results from the Sieder-Tate correlation. These coefficients were used for comparisons with the two-phase heat transfer coefficients in the flow orientations. The experimental results indicate, that the void probe signal and probability density function of void distribution can used into classify the flow patterns, no significant difference in voidage distribution was observed between isothermal and non-isothermal condition in non-swirl flow, the values of two phase heat transfer coefficients increase when superficial air velocities increase, and the enhancement of the values is observed to be most pronounced at the highest superficial water velocity in non-swirl flow. Also two phase heat transfer coefficients in swirl flow are increased when the twist ratios are decreased.
방형파펄즈가열법에 의한 세라믹스의 열물성 측정에 관한 연구
차경옥,이경희,임굉,Cha, K.O.,Lee, K.H.,Yim, Going 한국결정성장학회 1999 韓國結晶成長學會誌 Vol.9 No.6
본 연구에서는 방형파 펄즈 가열법을 이용하여 세라믹 고유전체 열물성치의 측정에 활용하는 것에 대한 가능성을 검토하였다. 여기서 측정의 이론을 설정하고 측정의 자동화를 시도함으로써 매우 짧은 시간내 시료의 열확산계수, 비열 및 열전도율을 얻을 수 있었다. 또한 시료는 실온으로부터 약 1300 K 온도 범위까지 측정하였다. Thermophysical properties of the high-dielectric ceramics were measured by a single rectangular pulse heating method. The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature ranging from room temperature to 1300 K.
機關 排氣系에서 非正常 가스流動의 壓力波豫測에 關한 硏究
李珉湖,梁振承,車京玉 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-
This paper describes a theoretical and experimental investigation of the pressure-time histories of some basic internal combustion engine exhaust systems. The program package is utilized the method of characteristics to solve the general equations of one-dimensional unsteady gas flow. This analysis is then combined with boundary models, based on quasi-steady flow approach, to give a complete treatment of the flow behavior in the exhaust system. Using a rotary valve simulator, experimental pressure-time were obtained. The predictions are compared with measured results and show a high degree of correlation in amplitude and phasing.
非定常熱源인 펄즈狀加熱法에 의한 强誘電體 Ceramic의 熱物性 測定
車京玉 明知大學校 産業技術硏究所 1992 産業技術硏究所論文集 Vol.11 No.-
The square wave pulse heating method of measuring thermophysical properties has been developed. The cylindrical of a specimen in the ferroelectricity ceramincs are heated square wave for a few second by a film heater which is placed between the plates. The resulting temperature history of the opposite surface is attached to make it hove high thermal and conductivites, is measured by pressing seperated C-A thermocouple wires against the surface. From a compassion between the measured and theoretical temperature histories, the thermal diffusivity, the specific heat and t conductivity of the specimen can be deformined automatically in a few minuted by a computer. The values of thermophysical properties were measured as a function of temperature ranging from room temperature to 1000℃ Thus, the effects of dielectricity upon themophysical properties were analyzied in detail.
이해철,차경옥 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-
Setting the channel-switching phase of automobile control mufflers in low-speed region is effective measures to improve low-speed torque. A muffler sensing exhaust-gas pressure has been developed to solve this problem. This muffler reduces exhaust noise in a pair of tailpipes by generating interference through a reverse-phasing process. This reduces exhaust noise makes it possible to set the muffler's channel-switching phase in the low-speed region.