• Journal of the Korean Wood Science and Technology
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• 제22권1호
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• pp.12-19
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• 1994

An electrically heated experimental lumber dry kiln was retrofitted with a computer-based control system to control kiln conditions more precisely and monitor and record several kiln variables. Flat-sawn 2.5cm-thick Pinus densiflora boards were dried in constant temperature process(65$^{\circ}C$ & 50~60 %RH) and continuously rising temperature process, respectively. The average drying rate in continuously rising temperature process was 5.7 %/hr, which was above 3 times faster than that in constant temperature process. But, the average rate of case-hardening and moisture difference between shells and cores of boards dried in continuously rising temperature process were 82 % and 5.5 %, respectively, which were much larger than those of boards dried in constant temperature process.

• Elastomers and Composites
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• 제44권1호
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• pp.41-46
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• 2009

천연고무의 일정하중 영구압축률에 온도와 가교시스템이 미치는 영향을 고찰하였다. 다양한 가교시스템과 가교밀도의 고무시편을 만들기 위해 여러 가지 함량의 황과 dicumyl peroxide(DCP)를 사용하여 배합하였으며, 가교된 천연고무의 일정변위 조건에서 측정된 영구압축률과 일정하중에서 측정된 영구압축률의 차이를 비교하였다. 일정하중 영구압축률은 일정변위 영구압축률에 비해 가교밀도의 변화에 따라 상대적으로 큰 차이를 보였으며, 이는 영구압축률 측정 시 공급된 변형에너지가 다르기 때문이다. 또한 일정하중 영구압축률 측정에서 황으로 가교시킨 시편의 경우 하중과 온도증가에 따라 영구압축률이 크게 증가하였고, 이에 반해 DCP로 가교시킨 시편의 경우 하중과 온도증가에 큰 영향을 받지 않았다.

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.224-227
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• 2015

Ferroelectric $Pb_2(Sc,Nb)O_6$ were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were $1350^{\circ}C$ for 25 minutes and $1400^{\circ}C$ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the $Pb_2(Sc,Nb)O_6$ compositions Pyrochlore phase showed about 2% in all $Pb_2(Sc,Nb)O_6$ specimens. It expands the growth of crystals in samples sintered at $1400^{\circ}C$ than $1350^{\circ}C$, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at $1350^{\circ}C$ and $1400^{\circ}C$ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in $Pb_2(Sc,Nb)O_6$ compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.

• 한국세라믹학회지
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• 제19권4호
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• pp.281-286
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• 1982

The composition of glasses to be suitable for crystallisation of $BaTiO_3$ by heat-treatment and the dielectric properties of the glass-ceramics were investigated. The composition of the family of glasses was defined by the formula $\chi$ $BaTiO_3 + (100-$\chi$)Al_2O_3$.$2SiO_2$ and excess BaO. Data were presented on dielectric constant and loss tangent at various frequencies. The effects of excess BaO on dielectric properties were investigated. The additions of $Na_2O$ and $Nb_2O_5$ shifted the Curite temperature of these glass-ceramics. The glass composition which was able to be melted at 145$0^{\circ}C$ and moulded as homogeneous glass phase without devitrification should contain $Al_2O_3$.$2SiO_2$ more than 30 mole %. The more the amount of additive BaO increased, the more dielectric constant increased. When the maximum heat-treatment temperature was 105$0^{\circ}C$, we obtained higher dielectric constant than that of 95$0^{\circ}C$. The dielectric constant and the dielectric loss were stable at frequencies between 5$\times$104 and 107 cycle per second. When $Na_2O$ and $Nb_2O_5$ were added, the Curie temperature, presented at 14$0^{\circ}C$ to 15$0^{\circ}C$, shifted to lower temperature. Therefore, the glass-ceramics having high dielectric constant at room temperature were obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1552-1557
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• 2004

This paper introduced about characteristics on the non-steady heat transfer of STS 304 hollow cylinder, In the non-steady state, the specific heat and conductivity are depended on the temperature variations, and these properties affect to the governing equation on heat conduction. But the most of numerical analysis on heat conduction is assumed to constant properties which is conductivity and specific heat. Assuming that conduction is assumed to constant properties which is conductivity and specific heat. Assuming that the properties are reacted sensitively, the numerical results can have the difference of between constant properties with non-constant properties. The main parameters are specific heat and conductivity. The temperature distributions of the STS 304 hollow cylinder became in steady state after 4 minutes in case of the constant properties. As the conductivity in varied with temperature, the temperature distributions became in steady state after 15 minutes. Therefore, a numerical analysis of the non steady state heat transfer will has to apply that conductivity varied with temperature.

• 조명전기설비학회논문지
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• 제28권2호
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• pp.1-8
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• 2014

In this paper, SOA Current and Temperature Driver which consisted of LabVIEW programming part capable of current and temperature transient response pattern design, DAQ module for analog voltage in&out, and voltage to current converting chips has realized. The output current(possible to 3A) from the Driver to SOA was clearly constant without ripple and also showed no variance until 1mA unit for a long time operation. The temperature of TEC took several seconds to reach a set temperature, and were maintained stably within ${\pm}^0.1{\circ}C$ for several hours. The proposed Driver can replace the previous high cost SOA Drivers for wavelength swept lasers fully and provides the convenience of transient response design capability for current and temperature.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.286-291
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• 1998

Dielectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$, ceramics prepared by the columbite precursor method have been investigated as a function of the sintering temperature in the range of 1000∼$1250^{\circ}C$. The $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$ ceramics show typical relaxor ferroelectric behavior. As the sintering temperature increased, the dielectric constant increased and the phase transition temperature shifted to lower temperature. The TCK(temperature coefficient of dielectric constant) and VRK (variation rate of dielectric constant) increased with increasing sintering temperature. The $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$ compositions sintered at $1250^{\circ}C$ appear to be suitable for ferroelectric bolometer.

• Journal of Advanced Marine Engineering and Technology
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• 제28권7호
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• pp.1055-1062
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• 2004

As for the Production of internal combustion engines there has been further movement toward development of high Performance engines with improved fuel efficiency as well as a lightweight and a small size. These tendencies help to solve the problems in engines for example, such as thermal load. abnormal combustion and so on. In order to investigate these Problems, a thin film-type probe for measuring instantaneous temperature has been suggested. A method for manufacturing such a probe was established in this study The instantaneous surface temperature of a constant volume combustion chamber was measured by using this probe and the heat flux was obtained through Fourier analysis In order to thoroughly understand the characteristics of combustion. authors measured wall temperature of combustion chamber and calculated heat flux through a cylinder wall while varying the protrusion height of probe. For these Purposes, the instantaneous surface temperature probe was developed. thereby making possible the analysis of instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

• Tribology and Lubricants
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• 제15권1호
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• pp.8-16
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size : 18$\pm$1 ${\mu}{\textrm}{m}$) was investigated on the elevated temperature up to 10$0^{\circ}C$. For development of anhydrous ER fluids using at wide temperature range, it should be researched to how the effect of temperature on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were made from the phosphoric ester reaction of cellulose were measured. As increasing the temperature, not only the analysis of electrical properties such as dielectric constant current density and electrical conductivity but also the rheological properties of ER fluids were studied. From the experimental results, the temperature had a large influence to the ER properties of anhydrous ER fluids. The current density, conductivity and elecoorheological effect ($\tau$$_{A}$$\tau$$_{0}$) of phosphoric ester cellulose ER fluids were proportional to the temperature with power law. And the shear stress of them was closely related with the square of dielectric constant mismatch parameter ($\beta$$^2$) under constant shear rate and electric field.d.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.155-158
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• 1999

This paper discusses the validity of models to predict the compressive strength of concrete subjected to various temperature histories and the shortcomings of existing rate constant model and apparent activation energy concept. Based on the discussion, a modified rate constant model is proposed. The modified rate constant model, in which apparent activation energy is a nonlinear function of curing temperature and age, accurately estimates the development of the experimental compressive strengths by a few researches. Also, the apparent activation energy of concrete cured with high temperature decreases rapidly with age, but that cured with low temperature decreases gradually with age. Finally a generalized model to predict apparent activation energy and compressive strength is proposed, which is based on the regression results.