• 동력기계공학회지
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• 제12권2호
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• pp.5-11
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• 2008

An analytical study was performed to have temperature and thermal stress distribution on a piston with the change of the 2nd land length of a piston and the existence of knocking in a cylinder. The result showed that the temperature on the skirt region was about $4\sim10^{\circ}C$ higher than that on the pin region. However the thermal stress on the skirt region was about 4MPa lower than on the pin region. It may be due to the higher heat release rate on the pin boss than on the skirt. The result regarding the variation of the 2nd land length of the piston showed that the temperature distribution on the piston was getting lower and the thermal stress distribution was getting higher as the 2nd land length of the piston was shorter.

• 한국대기환경학회지
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• 제24권2호
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• pp.259-270
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• 2008

The regional air movement in a coastal area is generated by the different heat capacities of sea and land sides, which is called sea/land breeze. In the west coast area, the local air quality is significantly influenced by this sea/land breeze. In this study, the mathematical model is proposed to estimate the effective area of sea/land breeze. A commercial air model, that is suggested as an alternative air model by USEPA, is introduced to simulate the mechanism of sea/land breeze generation. From this study, it is confirmed that the numerical approach proposed in this study is reliable to predict the effective area of sea breeze in a coastal area. It implies that the current application of common air model needs to be carefully reviewed especially when dealing with a coastal air quality issue. It is also found that the sea breeze in Incheon area has the impact in the range of approximately 24 km in-land side, so-called penetration length.

• 한국환경농학회지
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• 제39권3호
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• pp.204-213
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• 2020

BACKGROUND: Since the number of crops cultivated in reclaimed land is huge, it is very difficult to quantify the total crop production. Therefore, a non-destructive method for predicting crop production is needed. Salt tolerant root vegetables such as red beets and sugar beet are suitable for cultivation in reclaimed land. If their underground biomass can be predicted, it helps to estimate crop productivity. Objectives of this study are to investigate maximum leaf length and weight of red beet, sugar beet, and turnips grown in reclaimed land, and to determine optimal model with regression analysis for linear and allometric growth models. METHODS AND RESULTS: Maximum leaf length, width, and root fresh weight of red beets, sugar beets, and turnips were measured. Ten linear models and six allometric growth models were selected for estimation of root fresh weight and non-linear regression analysis was conducted. The allometric growth model, which have a variable multiplied by square of maximum leaf length and maximum leaf width, showed highest R² values of 0.67, 0.70, and 0.49 for red beets, sugar beets, and turnips, respectively. Validation results of the models for red beets and sugar beets showed the R² values of 0.63 and 0.65, respectively. However, the model for turnips showed the R² value of 0.48. The allometric growth model was suitable for estimating the root fresh weight of red beets and sugar beets, but the accuracy for turnips was relatively low. CONCLUSION: The regression models established in this study may be useful to estimate the total production of root vegetables cultivated in reclaimed land, and it will be used as a non-destructive method for prediction of crop information.

• 한국농공학회지
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• 제45권6호
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• pp.83-95
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• 2003

In this study, a new concept in a paddy consolidation project is introduced in that curved parallel terracing with contour-lined layout is adopted in sloping areas instead of conventional rectangular terracing. The contoured layout reduces earth-moving considerably compared to rectangular methods in consolidation projects. The objective of the paper is to develop a combinatorial optimization model using the network theory for the design of contour-lined plots which minimizes the volume of earth moving. The results showed that as the length of short side of plot is longer or the land slope is steeper, the volume of earth moving for land leveling increases. The developed optimization model is applied for three consolidated districts and the resulting optimal earth moving is compared with the volume of earth from the conventional method. The shorter is the minimum length of short side of a polt with increases the number of plots, the less is the volume of earth. As the minimum length of short side is 20 m for efficient field works by farm machinery, the volume of earth moving of optimal plot is less by 21.0∼27.1 % than that of the conventional consolidated plots.

• 한국패류학회지
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• 제23권1호
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• pp.59-63
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• 2007

The chromosome numbers and karyotype of Euphaedusa fusaniana, a kind of Korean land snail are investigated here. From E. fusaniana, chromosome numbers of 28 (n) and 56 (2n) were counted. Euphaedusa fusaniana has 15 pairs of metacentric chromosomes and 13 pairs of submetacentric chromosomes. The mean total length of all chromosomes was $128.7\;{\pm}\;9.93\;{\mu}m$. The maximum length of chromosomes No. 1 was $9.6\;{\pm}\;0.21\;{\mu}m$.

• 소성∙가공
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• 제10권4호
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• pp.302-310
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• 2001

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.447-452
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• 2002

An honeycomb/smooth land seal alternating with the honeycomb seal is suggested for structural enhancement in high pressure turbomachinery. Governing equations are derived for an honeycomb/smooth land annular gas seal based on Hirs' lubrication theory and Moody's friction factor model for smooth land and empirical friction factor model for honeycomb land. By using a perturbation analysis and a numerical integration method, the governing equations are solved to yield leakage and the corresponding dynamic coefficients developed by the seal. Theoretical results show that leakage is increasing and rotordynamic stability is decreasing as increasing the length of smooth land part in the honeycomb/smooth land seal.

• 한국유체기계학회 논문집
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• 제5권4호
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• pp.40-46
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• 2002

An honeycomb/smooth land seal alternating with the honeycomb seal is suggested for structural enhancement in high pressure turbomachinery. Governing equations are derived for an honeycomb/smooth land annular gas seal based on Hirs' lubrication theory and Moody's friction factor model for smooth land and empirical friction factor model for honeycomb land. By using a perturbation analysis and a numerical integration method, the governing equations are solved to yield leakage and the corresponding dynamic coefficients developed by the seal. Theoretical results show that the leakage increases and rotordynamic stability decreases as increasing the length of smooth land part in the honeycomb/smooth land seal.

• 환경영향평가
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• 제15권1호
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• pp.1-12
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• 2006

Changes in the soil physical property and the topographic condition derived from agricultural activities like as farming activities, land clearance and cutting down resulted in environmental and economic problems including the outflow of nutrient from farms and the water pollution. Several theories on the soil conservation have been developed and reviewed to protect soil erosion in the regions having a high risk of erosion. This study was done using the USLE model developed by Wischmeier and Smith (1978), and model for the slope length and steepness made by Desmet and Govers (1996), and Nearing (1997) to evaluate the potential of the soil erodibility. Therefore, several results were obtained as follows. First, factors affecting the soil erosion based on the USLE could be extracted to examine the erosion potential in farms. Soil erodibility (K), slope length (L), and slope steepness (S) were used as main factors in the USLE in consideration of the soil, not by the land use or land cover. Second, the soil erodibility increased in paddy soils where it is low in soil content, and the very fine sandy loam exists. Analysis of the slope length showed that the value of a flat ground was 1, and the maximum value was 9.17 appearing on the steep mountain. Soil erodibility showed positive relationship to a slope. Third, the potential soil erodibility index (PSEI) showed that it is high in the PSEI of the areas of steep upland and orchard on the slope of mountainous region around Dokjigol mountain, Dunji mountain, and Deummit mountain. And the PSEI in the same land cover was different depending on the slope rather than on the physical properties in soil. Forth, the analysis of land suitability in soil erosion explained that study area had 3,672.35ha showing the suitable land, 390.88ha for the proper land, and 216.54ha for the unsuitable land. For unsuitable land, 8.71ha and 6.29ha were shown in fallow uplands and single cropping uplands, respectively.

• 소성∙가공
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• 제18권2호
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• pp.156-159
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• 2009

Slot coating has been wide spread in photo-resist coating on the glass for liquid crystal display. Die in slot coater consists of manifold and land. Material comes in inlet of the die and flow into the manifold and then flow out through the land. The coating thickness variations along the die length depend upon inside of die design such as manifold and die land. However the coating thickness variations along the moving direction(coating direction) of the coater depend upon the operational conditions of coater as well as die lip design. The coating behaviors including atmospheric air have been investigated in this study. Die geometries considered in this study were nozzle gap and length of the die lip. Coating gap and coating speed were the variables fur coating operational conditions. When the nozzle gap and length of die lip increased climbing effect of PR on the downstream die lip was reduced. Subsequently uniformity of coating thickness improved. Uniformity of coating thickness also enhanced as coating gap and coater speed increased. The uniformity of coating gap was related to the velocity vector distributions on the coating surface.