• Journal of Biosystems Engineering
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• 제7권1호
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• pp.1-16
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• 1982

The thermal conductivies of grain are influenced by many physical factors such as' initial temperature, moisture content, composition, bulk density or porosity of grain. However, not only few researchers considered all these factors in determining thermal conductivities of grain but also many researchers considered only moisture content as a major effective factor on the thermal conductivity. This study was conducted to experimentally determine the thermal conductivities of rough rice (3 Japonica-type, 3 Indica-type) and barley(covered, naked) as a function of initial temperature, moisture content and porosity of grain, and to investigate the effect of those physical factors on the thermal conductivities of grain. The results of this study are summarized as follows; 1. The average time correction value for this experimental apparatus was 7 sec, which. was insignificant to the calculated thermal conductivity. The resulting conductivity for considering time correction value was only 4.9 percent higher than that calculated by the non-corrected equation. 2. The thermal conductivity was in the range of 0.1208~0.2058W/$m^{\circ}K$ for naked barley, 0.1138~0.1724W/$m^{\circ}K$ for covered barley, 0.0912~0.1864W/$m^{\circ}K$ for Japonica-type rice and 0.086~0.1774W/$m^{\circ}K$ for Indica-type rice. 3. The thermal conductivities of grain increased with initial temperature and moisture content of grain but decreased with porosity of grain. 4. The regression equations of the thermal conductivity of each grain were determined as a function of initial temperature, moisture content and porosity. The regression equations of the thermal conductivity of both Japonica-type and Indica-type rough rice were also determined.

• 한국표면공학회지
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• 제47권6호
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• pp.303-310
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• 2014

In this study, the average in-situ stress in metallic thin film was measured during deposition of the Cu thin films on the Si(111) wafer and then the phenomenon of stress shift by the interruption of deposition was measured using Cu thin films. We have observed the stress shift in accordance with changing amount of atom's movement between the surface and grain boundary through altering the grain size of the Cu thin film with variety of parameters. The grain size is known to be affected on the deposition rate, film thickness and deposition temperature. As a experimental results, the these parameters was not adequate to explain stress shift because these parameters affect directly on the amount of atom's movement between the surface and grain boundary as well as the grain size. Thus, we have observed the stress shift toward tensile side in accordance with the grain size changing through the interlayer deposition. From an experiment with inserting interlayer before deposit Cu, in thin film which has big grain size with high roughness, amount of stress movement is higher along direction of tensile stress after deposition that means, after deposition process, driving force of atoms moving in grain boundary and on the surface of the film is relatively higher than before.

• Journal of Biosystems Engineering
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• 제3권2호
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• pp.100-113
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• 1978

Drying grain with conventional artificial drying methods requires great quantities of petroleum fuels. Depletion of fossil fuel increases the need of the utilization of solar energy as an alternative to petroluem fuels for drying grain , an energy intensive agricultural operation. Many techniques for the utilization of solar energy in grain drying have been developed, however, there are many problems in adopting solar energy as an energy sources for drying grain. Futhermore, very little research has been done on solar grain drying in Korea. This study was conducted to evaluate the availability of solar energy for drying of rough rice in Chuncheon, Suweon, and Jinju areas based on 50year meteorological data, and to analyze experimentally the performance of a solar air collector for dying grain, and to find the effects of solar heated air compared to unheated air on the rate of drying and energy consumption required for drying of rough rice. The results of this study was may be summarized as follows ; 1. Monthly average daily total radiation on a horizontal surface in October was 260.6 ly/day for Chuncheon, 240.3 ly/day for Suweon , and 253.4 ly/day for Jinju area, respectively. 2. the ratio of monthly average daily diffuse radiation to daily total radiation on a horizontal surface was approximately 0.41 for Chuncheon, 0.45 for Suweon, and 0.44 for Jinju area, respectively. 3. Although the statistical distribution curves of daily total radiation for the three locations were not identical , the differences among them were not large and may be neglected for many practical purposes. 4. I was estimated that the optimum tilting angle of the collector in October was approximately 46 degrees for Chuncheon and Suweon and 45 degrees for Jinju. 5. The ratio of the total radiation on a optimum tilting plane to that on a horizontal plane was estimated to be 1.36 for Chuncheon, 1.31 for Suweon, and 1.27 for Jinju , respectively. 6. The collection efficiency of the solar air collector ranged from 47. 8 to 51. 5 percent at the air flow rates of 251. 1-372.96 $m^3$/hr. High efficiency remained nearly , constant during the best sunshine hours, 10 a.m. to 2 p.m. and decreased during other hours. More energy was collected as the air flow rate incresed. 7. The average temperature rise in the drying air from the solar collector for the test period varied from $6.5^\circC$ to $21.8^\circC$ above the ambient air temperature. 8. Solar-dried rough rice averaged 13.7 percent moisture (w.b.) after 130 hours of drying with the air flow rate of 1. 64 ccm/$m^3$, and rough rice dried with natural air averaged 15.1 percent moisture (w.b.) after 325 hours of drying with the same air flow rate. 9. Energy saving of 2.4 kwh per $m^3$ percentage point of moisture removed was obtained from solar heated air drYing. The solar bin used 53.3 percent less energy per percentage point of moisture removed than the natural air bin.

• 한국식품저장유통학회지
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• 제11권2호
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• pp.263-268
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• 2004

곡물냉각기를 이용하여 벼의 냉각특성을 구명하기 위하여 RPC의 원형빈에서 2회의 냉각실험을 실시하였다. 1차 냉각 실험은 하절기에 200 톤 규모의 원형빈에서, 2차 냉각실험은 수확기에 300 톤 규모의 원형빈에 저장된 벼를 대상으로 실시하였다. 그 결과를 요약하면 다음과 같다. 1차 냉각실험에서 초기곡온 23.6$^{\circ}C$, 함수율 19.3%인 벼180.3 톤을 14$^{\circ}C$까지 냉각시키는데 52.5시간이 소요되었으며, 냉각을 통해 함수율은 약 0.6% 감소하였다. 또한, 2차 냉각실험에서 초기곡온 16.1$^{\circ}C$, 함수율 19.2%인 벼 272.2 톤을 5.5$^{\circ}C$까지 냉각시키는데 78.0시간이 소요되었다. 1, 2차 냉각실험에서 냉각공기온도를 각각 8.0, 5.5$^{\circ}C$로 설정하였을 때, 곡물냉각기출구의 냉각공기온도는 각각 8.0$\pm$0.48$^{\circ}C$, 5.7$\pm$0.84$^{\circ}C$로서 정밀하게 제어되고 있음을 알 수 있었으며, 2차 냉각실험에서의 온도편차가 1차 냉각실험에서보다 높게 나타난 것은 냉각부하가 적었고, 외기조건이 급격하기 변화하여 압축기 무부하전자변, 재열기 및 증발기에 공급되는 고온고압 냉매가스량, 응축기 송풍기가 제어되었기 때문으로 판단되었다. 1차 냉각실험에서 곡물냉각기에서 냉각된 공기량은 평균77.5㎥/min인데 비해 곡물층을 통과한 냉각공기량은 42.5㎥/min에 불과해 약 45%의 냉각공기가 누설되어 이에 대한 방지책이 필요하였다. 냉각부하가 큰 하절기에 실시한 1차 냉각실험에서는 댐퍼만이 제어되었으며, 소요전력은 평균 22.1㎾를 나타낸 반면, 냉각부하가 적은 수확기에 실시한 2차 냉각실험에서는 압축기의 무부하전자변, 응축기 송풍기 등이 제어되었으며, 소요전력은 평균 17.4㎾로 나타나 하절기에 비하여 약 27%정도의 에너지가 절감된 것으로 나타났다.

• 한국해양공학회지
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• 제33권6호
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• pp.526-534
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• 2019

The average coastline and the erosion control line introduced as the management coastline, and the average shoreline (MSL) was established from the observed coastline. Also, the median grain size and the wave height of 30-years return period were applied. The erosion control line (ECL) was established through the model, HaeSaBeeN. These two lines set the coastline for evaluation. Based on the observed monitoring data along the coastline, the 1-day variation according to the normal distribution was used to estimate the regional variation, and the width of the erosion was calculated by applying the median grain size (D₅₀) and the wave height of 30-years return period through the high-wave coastal erosion width model, i.e., HaeSaBeeN.

• 한국농공학회논문집
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• 제60권4호
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• pp.83-91
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• 2018

Land reclamation, coastal construction, coastline extension and port construction, all of which involve dredging, are increasingly required to meet the growing economic and societal demands in the coastal zone. During the land reclamation, a portion of landfills are lost from the desired location due to a variety of causes, and therefore prediction of sediment transport is very important for economical and efficient land reclamation management. In this study, laboratory disposal tests were performed using an open channel, and suspended sediment transport was analyzed according to flow velocity and grain size. The relationships between the average and standard deviation of the deposition distance and the flow velocity were almost linear, and the relationships between the average and standard deviation of deposition distance and the grain size were found to have high non-linearity in the form of power law. The deposition distribution of sediments was demonstrated to have log-normal distributions regardless of the flow velocity. Based on the experimental results, modeling of suspended sediment transport was performed using deep neural network, one of deep learning techniques, and the deposition distribution was reproduced through log-normal distribution.

• 한국전기전자재료학회논문지
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• 제14권11호
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• pp.879-884
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• 2001

In this paper, the structural and dielectric properties of (Sr$_{l-x}$Ca$_{x}$)TiO$_3$ (0$\leq$x$\leq$0.2) -based grain boundary layer ceramics were investigated by XRD, SEM and HP4194A. The ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 1420~152$0^{\circ}C$ and 4 hours, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca. The average grain size was increased with increase of sintering temperature. The relative density of all specimens was 96~98%. The 2nd Phase formed by the thermal diffusion of CuO from the surface leads to very excellent dielectric properties, that is, $\varepsilon$$_{r}$>50000, tan $\delta$<0.05, $\Delta$C<$\pm$10%. The appropriate Ca content was under 15 ㏖%.s under 15 ㏖%.%.

• 소성∙가공
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• 제28권5호
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• pp.247-256
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• 2019

In this study, the development of annealing textures in cold rolled and annealed tantalum sheets was analyzed using electron backscatter diffraction. At $900^{\circ}C$, the textures of the recrystallized grains in the partially and completely recrystallized microstructures displayed significant similarities. The average diameter of the recrystallized grains with ${\gamma}-fiber$ orientations exceeded that of grains with different orientations, and the average growth rates were unrelated to the orientations after an initial stage of recrystallization. Additional cold rolling and annealing was done for controlled initial microstructures and textures inherited from various processes of prior cold rolling and annealing. This second cycle of the process resulted in stronger textures with major ${\gamma}-fiber$ orientations as a result of the enhanced ${\gamma}-fiber$ orientations in the preceding textures. A coarse-grained prior microstructure resulted in a weaker annealing texture than a fine grained one regardless of the stronger previous texture, which was occasioned by the sub-structures of the minor orientations at local deformation inhomogeneities such as sharp in-grain shear bands.

• 한국세라믹학회지
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• 제24권4호
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• pp.392-396
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• 1987

Pure barium titanate was sintered at $1340^{\circ}C$ for 2, 4, 8, 16 hr to control their grain size. The measurements of breakdown strength and partial discharge characteristics were performed under rising AC voltage(60Hz). With increase of sintering time, the average grain size was increased and breakdown strength was slightly decreased. Partial discharge in pores was observed under high voltage, and a model of dielectric break down in barium titanate ceramics is proposed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.284-284
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• 2010

YBCO ceramic specimens were fabricated by added $BaTiO_3$ as donors and sintered $950^{\circ}C$/24hrs. Average grain size decreased with increased in added $BaTiO_3$. Affect to grain growth. XRD result, peak strength was lowed then crystallization not well all specimens. All specimens critical temperature about 90k.