• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.119-119
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• 2010

We report strong exciton transition and exciton-phonon couplings in photoluminescence (PL) of ZnO thin films grown on MgO/sapphire (buffer/substrate) by plasma-assisted molecular beam epitaxy. The PL spectra at 10 K showed the intensity of the dominant emission, donor-bound exciton transition of front surface (top surface, the latter part in growth) is found to be about 100 times higher than that of back surface (in-depth bottom area, the initial part), while the room temperature PL spectra showed dominant contributions from the free exciton emissions and phonon-replicas of free excitons for front surface and back surface, respectively, It could be attributed to the strong contributions of exciton-phonon coupling. Time resolved PL spectra reveal that the life time of exciton recombination from the front surface are longer than those from back surface. This is most probably due to the fact that reduction of non-radiative recombination in the front surface. This investigation indicates that the existence of native defects or trap centers which can be reduced by the proper initial condition in growth and the exciton-phonon interaction couplings play an important role in optical properties and crystal quality of ZnO thin films.

• Fashion & Textile Research Journal
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• v.15 no.6
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• pp.993-999
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• 2013

This study aimed to measure the amount of sweating on 12 parts of the upper body using absorption fabric and analyze subjective sensations. The study was conducted with 9 male subjects in climate chamber controled at $30{\pm}0.5^{\circ}C$, and $55{\pm}5%$ RH. The result was that sweating amount of the upper back part was significantly more than upper front part. We assumed that forced convection flow cased by exercise decreased the sweating rate in the front. The skin temperature of upper front body rapidly decreased as soon as exercise starts and gradually increased with cessation of exercise. On the other hand, the skin temperature of palm increased with exercise and showed continuous increasing even exercise stopping all the experimental period. This is caused by thermoregulatory responses through vasodilatation on the peripheral area. Subjective sensations, such as thermal sensation, wet sensation, and thermal comfort showed the highest score at the time of exercise stop. This means the subjects felt more hot, wet, and uncomfortable after exercise stopped. Bur after wiping of sweat, subjective sensation scores were recovered rapidly. The present study has provided more detailed information on the upper body sweat distribution than previously available, which can be used in clothing design, thermo-physiological modeling, and thermal manikin design. We also think that results of the present study will play an important role in making the sweat distribution map.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1804-1809
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• 2006

The aim of this Paper is to describe the implementation of a low-power digital front-End Design (FED) that will act as the core of a stand-alone Power dissipation methodology. The design of digital integrated circuits is a large and diverse area, and we have chosen to focus on low power FED. Designs are made from synthesized logic, and we need to consider the low power digital FED including input clock, buffer, latches, voltage regulator, and capacitance-to-voltage counter which have been integrated onto hish bandwidth communication chips and system. These single- chip micro instruments, implemented in a 0.12um CMOS technology operate with a single 0.9V supply voltage, and can be used to monitor dynamic and static power dissipation, Vesture, acceleration junction temperature (Tj), etc.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.19-24
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• 2006

ZnO:Al(AZO) films prepared by rf magnetron sputtering on glass substrate and textured by post-deposition chemical etching were applied as front contact and back reflectors for ${\mu}c$-Si:H thin film solar cells. For the front transparent electrode contact, AZO films were prepared at various working pressures and substrate temperature and then were chemically etched in diluted HCl(1%). The front AZO films deposited at low working pressure(1 mTorr) and low temperature ($240^{\circ}C$) exhibited uniform and high transmittance ($\geq$80%) and excellent electrical properties. The solar cells were optimized in terms of optical and electrical properties to demonstrate a high short-circuit current.

• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.4
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• pp.196-202
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• 1977

The solidification process in a cylinder with finite thickness in studied by explicit finite difference method. The temperature distribution, the solidification front profile and the dischrged latent heat for the process are obtained. It is found that the solidification front profile is almost linear except in the vicinity of the initation of phase change. This result motivates us to use linear relations between the position of solidification and time for approximate calculations.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.1
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• pp.89-97
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• 1984

This study was carried out to investigate the effect of seasonal changes on some of the morphological and physiological characteristics, including the photosynthetic abilities and dark respiration, of young ginseng plants due to planting location under shading. The results obtained are as follows: 1. Seedlings and 2-year old plants planted in the back rows appeared to have broader leaf area, and their leaf weight greatly increased in September. Chlorophyll content was significantly reduced in September rather than in June and the plants in the back rows had more chlorophyll content than those in the front rows. 2. There was no difference in the light compensation point between the front and back rows in June, while in September the light compensation point of 2-year old ginseng leaves was much lower for plants in the back rows compared with those in the front rows. A difference in the light saturation point was not noticeable between plants in the front and back rows in June and September. But the light saturation point of 2-year old ginseng leaves at $15^{\circ}C$ was high in June, while it was high at $20^{\circ}C$ high in September. 3. Maximum photosynthetic ability was attained at $15^{\circ}C$ in June and at $20^{\circ}C$ in September. During June no significant difference in photosynthetic ability was found between plants in the front and back rows, but in September the amount of photosynthesis was significantly increased at the leaves of seedlings as well as 2-year old plants planted in the back rows. 4. The optimum temperature for maximum photosynthesis in 2-year old plants ranged from $14.0^{\circ}C$ to $14.5^{\circ}C$ in June and from $19.5^{\circ}C$ to $20.5^{\circ}C$ in September. However, the optimum temperature for maximum photosynthesis in the seedlings was from $21.2^{\circ}C$ to $21.6^{\circ}C$ in September, but a significant difference in the optimum temperature for the maximum photosynthesis in seedlings and 2-year old plants was not noticeable between the front and back rows. 5. The respiration rate was rather high in seedlings compared with 2-year old plants. During September the respiration rate in seedlings was much lower in the back rows than in the front rows. The rate of increase in the respiration of 2-year old plants was higher at September than June. The increase in respiration rate due to temperature was more significant in seedlings than 2-year old plants. 6. In September, the level of $Q_{10}$ in 2-year old plants was much lower than that found in seedlings. During June, 2-year old plants showed lower $Q_{10}$ levels at a temperature difference between $15^{\circ}C$ and $25^{\circ}C$; but in September this occurred at a temperature difference between $20^{\circ}C$ and $30^{\circ}C$.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.400-408
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• 2003

A study on the progressive inelastic deformation behavior of the 316 L stainless steel cylindrical structure with plate-to-shell junction under moving temperature front was carried out by structural test and analysis. The structural test intends to simulate the thermal ratcheting behavior occurring at the reactor baffle of the liquid metal reactor as free surface of hot sodium pool moves up and down under plant transients. The thermal ratchet load that heats the specimen up to 550$^{\circ}C$ was applied repeatedly and residual deformation was measured. The thermal ratcheting test was carried out with two types of cylindrical structures, one with plate to-shell junction and the other without the junction to investigate the effects of the geometric discontinuities on the global ratcheting deformation. The temperature distributions of the test specimens were measured and were used for the ratcheting analysis. The ratchet deformations were analyzed with the constitutive equation of the non-linear combined hardening model. The analysis results were in good agreement with those of the structural tests.

• KIEAE Journal
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• v.12 no.3
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• pp.53-60
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• 2012

This research is an illustrative research to verify the thermo environmental change created after introduction of indoor pond through abridged model test and simulation analysis. Especially, temperature and comfort level are analyzed by adjusting factors like size of water space, distance length, and location. Summary of the research is as follows. First, the most effective size of water space is 7% of the indoor size, from southern side. Temperature reduction effect is about $1.6^{\circ}C$(5.5%), and for the comfort level, it is found that pmv index increases 8%. Second, based on the simulation of distance length with the sphere, it is more effective as it is close to the surface. If distance length is more than 0.5m, there is no effect on reduction of temperature and comfort level of indoor environment. Lastly, for the analysis by location of the introduced water space, simulation is undertaken by dividing the water space (14% of the indoor size) with front, side, rear and center types. Temperature reduction effect is found to be : front type ($-1.53^{\circ}C$), side type ($-0.82^{\circ}C$), rear type ($-0.44^{\circ}C$), center type ($-0.28^{\circ}C$), respectively. The indoor environment change data by introduction of water space, found in this research, is at initial phase, but it is deemed to be a basic data to refer when planning actual water space.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.889-898
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• 2022

In this study, sand casting process was applied to manufacture a large aluminum turbo-type fan used for tank powerpack. To apply the sand casting method, the turbo fan was reverse engineered, and after designing three gating systems, the optimal gating system design was selected by performing casting simulation. In the case of the bottom up-gating system, there is a significant temperature loss of the molten alloy during blade filling. When the molten alloy is completely filled into the sand mold, the blade upper tip and front shroud are below the liquidus temperature. In the case of the top down-gating system, molten alloy scattering occurs, but the temperature loss while the blade is filled is smaller than that of the bottom up type. And after the inflow of molten alloy into the mold is completed, the blade upper tip and front shroud are higher than the liquidus temperature. A sand mold was manufactured with the top down-gating system and the casting process was performed. The fan was made perfectly in appearance without any unfilled parts.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.4
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• pp.398-404
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• 1985

This study was conducted to define the seasonal differences in the morphological characteristics, the photosynthetic abilities and the dark respirations of the 4-year old ginseng leaves. Chlorophyll-a content in the ginseng leaf was significantly decreased at September than at June but content of chlorophyll-b was not showed seasonal difference. At June, the amounts of chlorophyll a and b in the ginseng leaves grown in the back row were rather abundant than those grown in the front row, but no significant differencies were detected between rows at September. The estimated optimum light intensity for the photosynthesis of ginseng leaves was higher at June than at September and higher in the front row than the back row but was significantly decreased by air temperature above 25$^{\circ}C$. The light compensation point was elevated in higher temperature and at September than June. The amount of photosynthesis was significantly increased in the ginseng plant grown in the front row than the back row at June but the reverse was significant at September. The highest photosynthesis was observed in temperature range of 20 - 25$^{\circ}C$ at June and range of 15 -20$^{\circ}C$ at September. The optimum temperature range of photosynthesis was 21$^{\circ}C$ to 25$^{\circ}C$ at June and 14$^{\circ}C$ to 21$^{\circ}C$ at September, and that was higher in the back row than the front row. High temperature significantly stimulated the dark respiration of ginseng leaves and the respiratory quotients(Q$\_$10/) of the ginseng leaves showed a significant seasonal variation.