• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.171-176
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• 2012

As langasite $A_3BC_3D_2O_{14}$ compounds with piezoelectric properties exhibit no phase transition up to the melting point of 1,400-$1,500^{\circ}C$, many high temperature applications are expected for the SAW filter, temperature sensor, pressure sensor, and so on, based on the digital transformation of wider bandwidth and higher-bit rates. It has a larger electromechanical coupling factor compared to quartz and also nearly the same temperature stability as quartz. The $La_3Ga_5SiO_{14}$ (LGS) crystal with the $Ca_3Ga_2Ge_4O_{14}$-type crystal structure was synthesized and the crystal structure was analyzed by Mill et al. It is also an important feature that the growth of the single crystal is easy. In the case of three-element compounds such as $[R_3]_A[Ga]_B[Ga_3]_C[GaSi]_DO_{14}$ (R=La, Pr and Nd), the piezoelectric constant increases with the ionic radius of R. In this study, crystal structures of four-element compounds such as $[A_3]_A[B]_B[Ga_3]_C[Si_2]_DO_{14}$ (A = Ca or Sr, B = Ta or Nb) are analyzed by a single crystal X-ray diffraction, and the mechanism and properties of the piezoelectricity depending on the species of cation was clarified based on the crystal structure.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.263-269
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• 2011

In this study, the compositions for the microwave dielectric materials were investigated to obtain the improved dielectric properties, the high temperature stability, and the sintering temperature of less than $900^{\circ}C$, which was necessary for cofiring with the internal conductor of silver. In addition, the dielectric sheets were prepared by the tape casting technique, after which the sheets were laminated and sintered. In this process, the optimum ratio of powder and binder, laminating pressure, temperature, and possibility for cofiring with the internal conductor were studied. Finally, multilayer chip treplexer filter for the 800-2,000 MHz range were fabricated, and the frequency characteristics of the triplexer filter were investigated. When the $0.6TiTe_3O_8-0.4MgTiO_3+3wt%SnO+7wt%H_3BO_3$ ceramics were sintered at $820^{\circ}C$ for 0.3 hours, the microwave dielectric properties of the dielectric constant of 29.91, quality factor of 33,000 GHz, and temperature coefficient of resonant frequency of -2.76 ppm/$^{\circ}C$ were obtained. Using the Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), the multilayer chip triplexer filter acting at the range of 800-2,000 MHz were simulated and manufactured. The manufactured triplexer filter had the excellent frequency properties in the CDAM800, GPS and PCS frequency regions, respectively.

• Nuclear Engineering and Technology
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• v.8 no.2
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• pp.81-88
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• 1976

A flash method for measuring the unknown thermal property (the density, specific heat, or thermal diffusivity could be chosen as unknown) is described. The thermal diffusivity of UO$_2$ fuel samples is obtained from room temperature (300 K) to high temperature (1400 K). The specific heat is measured using a commercially available differential scanning calorimeter from room temperature to 500 K. The thermal conductivity of UO$_2$ fuel samples is calculated from the density, thermal diffusivity, and specific heat at constant pressure. The present results are in complete agreement with the usual trends for the thermal conductivity of dielectric materials, in which impurity levels are very important at low temperatures but become relatively unimportant at high temperatures. In addition, the thermal diffusivity values at room temperature are reexamined by measuring the thermal diffusivity of several UO$_2$ fuel samples with same level of doped Gd$_2$O$_3$.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.1-11
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• 2010

The study was performed to optimize the processing conditions (alkali concentration, extraction time, and temperature) for rockfish skin gelatin based on yield using response surface methodology and comparison of the physicochemical properties with those of rockfish skin gelatin pretreated and extracted under ordinary conditions (alkali treatment concentration: 1.0 M; extraction time: 2 hr; extraction temperature: $60^{\circ}C$). Predicted maximum gelatin yield of 19.1% and gelatin content of 87.8% were obtained by extraction at $106.6^{\circ}C$ for 69.0 min after pretreatment with 1.1 M calcium hydroxide. Yield of gelatin extracted under high temperature/high pressure (G-HT/HP) was 54% higher than that extracted under ordinary temperature/time (G-OT/T). However, G-HT/HP was inferior in gel strength and gelling point to (G-OT/T), but comparable in transmission. Based on the physicochemical properties, G-HT/HP was unsuitable for use in products requiring higher physical properties, but could be useful for health-functional foods.

• Journal of Practical Agriculture & Fisheries Research
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• v.17 no.1
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• pp.93-100
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• 2015

This study was performed to examine the high temperature adaptability with CO₂ treatment for tomato under the condition of greenhouse cultivation during summer season. The indoor condition of CO₂ concentrations were controlled as control, 500 ppm, and 1,000 ppm for the greenhouse with the maximum air temperature of 44℃. With the observation of VPD (vapor pressure deficit) and CWSI (crop water stress index) by leaf-air temperature difference according to CO₂ treatment concentration, the plants with the CO₂ concentration of 1,000 ppm performed less water stress than those with the CO₂ concentrations of control and 500 ppm. The plants without CO₂ treatment performed the severest degree of water stress.

• Clean Technology
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• v.30 no.3
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• pp.239-247
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• 2024

The removal of volatile organic compounds (VOCs) from spent polypropylene (PP) sourced from the bumpers and interiors of used cars was carried out by using high-temperature supercritical carbon dioxide (scCO₂) extraction. The recycled polymers from the bumpers and interiors contained other additives beside PP such as polyethylene (PE), talc, and carbon black, which modified the properties of PP. The crystallinity of the recycled bumper and interior PP was significantly lower than that of the virgin PP pellet. The decomposition temperatures of the recycled bumper and interior PP was slightly higher than that of the virgin PP pellet, while the melting and crystallization points were slightly lower. The effect of process conditions on VOC removal was studied by varying the time (2 ~ 720 min), pressure (6.4 ~ 14 MPa), and temperature (298 ~ 473 K). Since VOC removal at 2 min produced satisfying results, times below 2 min (10 ~ 120 s) were also studied. The main goal of scCO₂ extraction was to reduce the xylene content, as the xylene content of the recycled bumpers was higher than the allowable limit. A temperature above 373 K was needed to remove the xylene from the waste PP samples. The optimum condition for VOC removal from bumper waste was determined to be 433 K, 8 MPa, and 60 s. The car interior waste had VOC content within the allowable limit, so no further treatment was needed.

• Journal of the Korean Society of Clothing and Textiles
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• v.12 no.1 s.26
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• pp.81-91
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• 1988

The purpose of this study is to investigate the physiolosical responses and subjective wear sensation to the clothes with different cellulose composition. The experimental garments were four types of cellulosic fabrics, respectively composed of $100\%$-cotton, $100\%$-Rayon, cotton/Flax 85/15, and rayon/Flax 85/15 (weft blended), were sewn in blouses with half-length sleeves. Four healthy women were chosen for this experiment. The condition of the experimental room were in two environments: Temp., $25{\pm}1^{\circ}C$, R.H. $60{\pm}3\%$ and Temp., $30{\pm}1^{\circ}C$, R.H. $70{\pm}3\%$, and air velocity was maintained at 0.25 m/sec. The results are as follows. 1) At $25^{\circ}C$, rayon blouse showed the pleasantest feeling because of its excellent humidity sensation and tactile sensation. At $30^{\circ}C$, rayon and flax blended blouse showed most comportable sensation. In both environments, blouse of $100\%$ cotton showed the least pleasant because of high vapor pressure inside the blouse and bad tactile sensation. 2) Vapor pressure inside the blouse and tactile sensation play the most impotant role in comfort. Consequantly the blouse made of $100\%$-cotton which bring low air permeability, moisture regain and water vapor permearbility showed more unpleastness than rayon blouse because it raises temperature, relative humidity and vapor pressure inside the blouse under the hot circumstances In the conditions with much sweat, rayon and flax blended blouse with high stiffness increases comfort better than $100\%$ rayon because the former prevents sticking to the skin.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.47-55
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• 1998

Steady-state and transient performance for the medium scale civil aircraft turbofan engine was analyzed. Steady-state performance was analyzed on maximum take-off condition, maximum climb condition, and cruise condition. At 90％RPM of the low pressure compressor, the partload performance was economized. The transient performance was analyzed with cases of the step increase, the ramp increase, the ramp decrease, and the step increase and ramp decrease for the input fuel flow. For the transient performance analysis, work matching between compressor and turbine was needed. Modified Euler method was used the integration of residual torque in work matching equation. At all flight condition, the overshoot of the high pressure turbine inlet temperature was appeared in the step and ramp increase case, and the surge of high pressure compressor was appeared in the step increase case and the ramp increase case within 5.5 seconds of maximum climb condition.

• Tunnel and Underground Space
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• v.17 no.6
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• pp.464-474
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• 2007

An enhancement in the performance and safety of a high-level waste repository requires a validation of its engineered barrier. An engineering-scale test (named "KENTEX") has been conducted to investigate the thermal-hydro-mechanical behaviors in the engineered barrier of the Korean reference disposal system The validation test started on May 31, 2005 and is still under operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the thermal-hydro-mechanical behaviors in the bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying-wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. Near the heater region, there was also a significant contribution of the thermal expansion of bentonite and the vapor pressure in the pores of the bentonite blocks.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.53-62
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• 2009

A set of experiments has been conducted on the performance sensitivity of the passive residual heat removal system (PRHRS) for an advanced integral type reactor, SMART, by using a high temperature and high pressure thermal-hydraulic test facility, the VISTA facility. In this paper the effects of the opening delay of the PRHRS bypass valves and the closing delay of the secondary system isolation valves, and the initial water level and the initial pressure of the compensating tank (CT) are investigated. During the reference test a stable flow occurs in a natural circulation loop that is composed of a steam generator secondary side, a secondary system, and a PRHRS; this is ascertained by a repetition test. When the PRHRS bypass valves are operated 10 seconds later than the secondary system isolation valves, the primary system is not properly cooled. When the secondary system isolation valves are operated 10 or 30 seconds later than the PRHRS bypass valves, the primary system is effectively cooled but the inventory of the PRHRS CT is drained earlier. As the initial water level of the CT is lowered to 16% of the full water level, the water is quickly drained and then nitrogen gas is introduced into the PRHRS, resulting in the deterioration of the PRHRS performance. When the initial pressure of the PRHRS is at 0.1MPa, the natural circulation is not performed properly. When the initial pressures of the PRHRS are 2.5 or 3.5 MPa, they show better performance than did the reference test.