• The Journal of Korean Academy of Prosthodontics
• /
• v.39 no.6
• /
• pp.709-734
• /
• 2001

The aims of this experiment were to investigate the strain and temperature changes simultaneously within autopolymerzing acrylic resin specimens. A computerized data acquisition system with an electrical resistance strain gauge and a thermocouple was used over time periods up to 180 minutes. The overall strain kinetics, the effects of stress relaxation and additional heat supply during the polymerization were evaluated. Stone mold replicas with an inner butt-joint rectangular cavity ($40.0{\times}25.0mm$, 5.0mm in depth) were duplicated from a brass master mold. A strain gauge (AE-11-S50N-120-EC, CAS Inc., Korea) and a thermocouple were installed within the cavity, which had been connected to a personal computer and a precision signal conditioning amplifier (DA1600 Dynamic Strain Amplifier, CAS Inc., Korea) so that real-time recordings of both polymerization-induced strain and temperature changes were performed. After each of fresh resin mixture was poured into the mold replica, data recording was done up to 180 minutes with three-second interval. Each of two poly(methyl methacrylate) products (Duralay, Vertex) and a vinyl ethyl methacrylate product (Snap) was examined repeatedly ten times. Additionally, removal procedures were done after 15, 30 and 60 minutes from the start of mixing to evaluate the effect of stress relaxation after deflasking. Six specimens for each of nine conditions were examined. After removal from the mold, the specimen continued bench-curing up to 180 minutes. Using a waterbath (Hanau Junior Curing Unit, Model No.76-0, Teledyne Hanau, New York, U.S.A.) with its temperature control maintained at $50^{\circ}C$, heat-soaking procedures with two different durations (15 and 45 minutes) were done to evaluate the effect of additional heat supply on the strain and temperature changes within the specimen during the polymerization. Five specimens for each of six conditions were examined. Within the parameters of this study the following results were drawn: 1. The mean shrinkage strains reached $-3095{\mu}{\epsilon},\;-1796{\mu}{\epsilon}$ and $-2959{\mu}{\epsilon}$ for Duralay, Snap and Vertex, respectively. The mean maximum temperature rise reached $56.7^{\circ}C,\;41.3^{\circ}C$ and $56.1^{\circ}C$ for Duralay, Snap, and Vertex, respectively. A vinyl ethyl methacrylate product (Snap) showed significantly less polymerization shrinkage strain (p<0.01) and significantly lower maximum temperature rise (p<0.01) than the other two poly(methyl methacrylate) products (Duralay, Vertex). 2. Mean maximum shrinkage rate for each resin was calculated to $-31.8{\mu}{\epsilon}/sec,\;-15.9{\mu}{\epsilon}/sec$ and $-31.8{\mu}{\epsilon}/sec$ for Duralay, Snap and Vertex, respectively. Snap showed significantly lower maximum shrinkage rate than Duralay and Vertex (p<0.01). 3. From the second experiment, some expansion was observed immediately after removal of specimen from the mold, and the amount of expansion increased as the removal time was delayed. For each removal time, Snap showed significantly less strain changes than the other two poly(methyl methacrylate) products (p<0.05). 4. During the external heat supply for the resins, higher maximum temperature rises were found. Meanwhile, the maximum shrinkage rates were not different from those of room temperature polymerizations. 5. From the third experiment, the external heat supply for the resins during polymerization could temporarily decrease or even reverse shrinkage strains of each material. But, shrinkage re-occurred in the linear nature after completion of heat supply. 6. Linear thermal expansion coefficients obtained from the end of heat supply continuing for an additional 5 minutes, showed that Snap exhibited significantly lower values than the other two poly(methyl methacrylate) products (p<0.01). Moreover, little difference was found between the mean linear thermal expansion coefficients obtained from two different heating durations (p>0.05).

• Journal of the Korean Society of Food Culture
• /
• v.5 no.1
• /
• pp.59-75
• /
• 1990

The tzeam is the one of steaming cook that boiled the main material of poultry. meat and the sub-material of vegetables. It is always setted on the main-table in above seven chup ban sang and also kyoja sang. In this thesis, according to the kinds of tzeam in the main material of poultry, meat was to analysis reference frequency to them the materials, the measuring unit of materials, the terms of cooking and kitchen utensil by 47 books published in Korea from 1420 to 1987. 1. It was 37 kinds of tzeam in the main material of poultry, meat. 2. Materials were classified into the main-material, sub-materials, seasioning and decorations. 3. There were 43 kinds of measuring units, of them 18 kinds were for volume, 12 kinds were for quantity, 4 kinds were for length and the rest measuring units were 9 kinds. 4. There were 26 kinds of kitchen utensil for cooking. They were mainly used a hab 1 rice ball with lids, and castles (cast iron castle). 5. There were 27 kinds of cooking terms. The terms of them, 11 kinds were for heating methods, 16 terms of them were for the cutting process.

• Journal of the Mineralogical Society of Korea
• /
• v.6 no.1
• /
• pp.1-16
• /
• 1993

The chemical and optical absorption spectroscopic characters of pink and colorless tourmalines from San Diego mine in California, U.S.A., blue/green tourmalines from anonymous mine, Brazil, and brownis black tourmalines from Uncheon and Haksan mines in Korea have been studied using X-ray diffractometer, electron microprobe, optical absorption spectroscopy, and heat treatment. Least-squares refinements give unit cell diminsions : a = 15.96-16.01 ${\AA}$, c = 7.15-7.16 ${\AA}$ for the brownish black tourmalines, a = 15.82 - 15.87 ${\AA}$, c = 7.09 - 7.10 ${\AA}$ for pink tourmalines, and a = 15.88 - 15.94 ${\AA}$, c = 7.12 - 7.15 ${\AA}$ for blue green tourmalines. The colors of tourmalines are responsible for the transition elements. The pink color is attributed to the $Mn^{3+}$ ions, the blue-green to $Fe^{2+}$ and $Mn^{2+}$, bluish green to $Cu^{2+}$, and the brownish black to $Fe^{2+}$, $Fe^{2+}$ - $Fe^{3+}$, and $Fe^{2+}$ - $Ti^{4+}$. The $Mn^{3+}$ ions of pink color tourmalines are stabilized in the Y sites compressed along the O(1)H-O(3)H axis by Jahn-Teller distortion. Heating removes the pink or red component from tourmalines, producing the colorless stones from the pink and red ones. The bluish green samples change into the greenish blue ones and a certain yellowish green samples change into the light green ones by heat treatment. In the elbaite-schorl series, the concentration of Fe and Mn are variable depending on the color zones. The green zone is characterrized by the high content of Fe and Mn are variable depending on the color zones. The green zone is characterized by the high content of Fe, whereas the pink zone by the high content of Mn. Mn increases in deep yellow zone compared with yellow or colorless zones.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.4
• /
• pp.341-348
• /
• 2010

The basic principle of fry drying process of sludge lies in the rapid pressure change of sludge material caused by the change of temperature between oil and moisture due to the difference of specific heat. Therefore, the rapid increase of pressure in drying sludge induces the efficient moisture escape through sludge pores toward heating oil media. The object of this study is to carry out a systematic investigation of the influence of various parameters associated with the sludge fry drying processes on the drying efficiency. To this end, a series of parametric experimental investigation has been made together with the numerical calculation in order to obtain typical drying curves as function of important parameters such as drying temperature, sludge diameter, oil type and sludge type. In the aspect of frying temperature, especially it is found that the operation higher than $140^{\circ}C$ was favorable in drying efficiency regardless of type of waste oil employed in this study. The same result was also noted consistently in the investigation of numerical calculation, that is, in that the sludge particle drying was efficiently made over $140^{\circ}C$ irrespective of the change of particle diameter. As expected, in general, the decrease of diameter in sludge was found efficient both experiment and numerical calculation in drying due to the increased surface area per unit volume. In the investigation of oil type and property, the effect of the viscosity of waste oil was found to be more influential in drying performance. In particular, when the oil with high viscosity, a visible time delay was noticed in moisture evaporation especially in the early stage of drying. However, the effect of high viscosity decreased significantly over the temperature of $140^{\circ}C$. There was no visible difference observed in the study of sludge type but the sewage sludge with a slightly better efficiency. The numerical study is considered to be a quite useful tool to assist in experiment with more detailed empirical modeling as further work.

• Journal of Bio-Environment Control
• /
• v.31 no.3
• /
• pp.246-254
• /
• 2022

Domestic facility agriculture grows rapidly, such as modernization and large-scale. And the production scale increases significantly compared to the area, accounting for about 60% of the total agricultural production. Greenhouses require energy input to create an appropriate environment for stable mass production throughout the year, but the energy load per unit area is large because of low insulation properties. Through the rooftop greenhouse, one of the types of urban agriculture, energy that is not discarded or utilized in the building can be used in the rooftop greenhouse. And the cooling and heating load of the building can be reduced through optimal greenhouse operation. Dynamic energy analysis for various environmental conditions should be preceded for efficient operation of rooftop greenhouses, and about 40% of the solar energy introduced in the greenhouse is energy exchange for crops, so it should be considered essential. A major analysis is needed for each sensible heat and latent heat load by leaf surface temperature and evapotranspiration, dominant in energy flow. Therefore, an experiment was conducted in a rooftop greenhouse located at the Korea Institute of Machinery and Materials to analyze the energy exchange according to the growth stage of crops. A micro-meteorological and nutrient solution environment and growth survey were conducted around the crops. Finally, a regression model of leaf temperature and evapotranspiration according to the growth stage of leafy vegetables was developed, and using this, the dynamic energy model of the rooftop greenhouse considering heat transfer between crops and the surrounding air can be analyzed.