• Wind and Structures
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• v.27 no.4
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• pp.213-221
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• 2018

In the desert and Gobi regions with strong wind and large sediment discharge, sand transporting engineering is more effective than sand blocking and sand fixing measures in sand prevention. This study uses the discrete phase model of 3D numerical simulation to study the motion trail, motion state and distribution rule of sand particles with different grain diameters when the included angle between the main shaft of the feather-row lateral transportation sand barrier and the wind direction changes, and conducts a comparison in combination with the wind tunnel test and the flow field rule of common sand barrier. According to the comparison, when wind-sand incoming flow passes through a feather-row sand barrier, sand particles slow down and deposit within the deceleration area under the resistance of the feather-row sand barrier, move along the transportation area formed by the transportation force, and accumulate as a ridge at the tail of the engineering. With increasing wind speed, the eolian erosion of the sand particles to the ground and the feather-row sand barrier is enhanced, and the sand transporting quantity and throw-over quantity of the feather-row sand barrier are both increased. When sand particles with different grain diameters bypass the feather-row sand barrier, the particle size of the infiltrating sands will increase with the included angle between the main shaft of the feather-row sand barrier and the wind direction. The obtained result demonstrates that, at a constant wind speed, the flow field formed is most suitable for the lateral transportation of the wind-drift flow when the included angle between the main shaft of the feather-row sand barrier lateral transportation engineering and the wind speed is less than or equal to $30^{\circ}$.

• Biomolecules & Therapeutics
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• v.7 no.4
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• pp.362-370
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• 1999

Propolis, a natural resinous compound collected from honey bees, contains many biochemical constituents(wax, flavonoids, phenolic compounds, etc.) and has been used in traditional medicines as early as 300 B.C. It was been demonstrated that ethanol, acetylsalicylic acid, ischemia reperfusion, non-steroidal antiin-flammatory drugs and stress induce gastric lesions by promoting the generation of reactive oxygen metabolites. Therefore, some drugs that are capable of scavenging or inhibiting the generation of reactive oxygen radicals might be expected to prevent the gastric mucosal injury. The aim of this study was 1) to examine the antiulcer effect of propolis, 2) to investigate the mechanism of action by determining gastric acid secretion, lipid per-oxidation, mucus content and proton pump ($H^+$/$K^+$-ATPase) activity on gastric mucus in varios experimental models, and finally, 3) to isolate and identify the pure compounds that exert antiulcer activity. Step 2-1 and 2-3 sub-sub fraction shoed a significant reduction of severity of gastirc damage at the dose of 25 mg/kg in various experimental models. We isolated 4 sub-sub-sub fractions by flash column chromatography of Step 2-1 sub-sub fraction and one sub-sub-sub fraction by recrystalization of Step 2-3 sub-sub fraction. The protective effects of propolis sub-sub-sub fraction manifested sifnificant effects in HCl-ethanol induced gastric erosion model and aspirin induced gastric ulcer model. These results showed that the gastric mucosal protective effect of propolis might result from the increase of mucus secretion, free radical scavenging effect as well as the reduction of acid secretion in accordance with the reduction of $H^+$/$K^+$-ATPase activitv. Three compounds were isolated and identified from sub-sub fraction of propolis which showed antiulcer effects. Subsequently, these compounds were identified as a flavonoid, namely, 2-acetoxy-5,7,-dihydroxy-flavanone, galangin and chrysin.

• Journal of Korea Water Resources Association
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• v.44 no.8
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• pp.619-628
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• 2011

The purpose of this study is to evaluate the existing method of calculating rainfall-runoff erosivity using monthly precipitation, such as Fournier's index, modified Fournier's index, IAS (Institute of Agricultural Sciences) index, etc., and to present more reasonable regression model based on monthly rainfall data in Korea. This study introduced a new simplified method of calculating rainfall-runoff erosivity based on monthly precipitation, called by modified IAS index. It was expanded form IAS index which is the simple calculation method by summing up the rainfall amount of two months with maximum amount. Monthly precipitation and annual rainfall-runoff erosivity at 21 weather stations for over 25 years were used to analyze correlation relationship and regression model. The result shows that modified IAS index is the more reasonable parameter for estimating rainfall-runoff erosivity of the middle-western and south-western regions in Korea.

• Journal of Pharmaceutical Investigation
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• v.32 no.3
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• pp.165-172
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• 2002

Injectable gel composed of egg phosphatidylcholine (egg PC), hyaluronate (HA) and water was formulated for local drug delivery. The lamellar liquid crystalline structure of the egg PC/water system did not change by adding HA in the formulation. However, egg PC/HA/water gel was more resistant to erosion than the egg PC/water gel. The egg PC/HA/water and egg PC/water gels containing model drugs, tetracycline and sudan IV were prepared to perform in vitro and in vivo drug release experiments. In vitro release of tetracycline was sustained in the gel type formulations. The release rate of hydrophobic sudan IV was extremely slow. More than 99% of sudan IV remained inside the gel after 5 days. In vivo release of drugs from the air pouch model in Balb/c mice shows that lipophilic sudan IV remained for more than 10 days whereas tetracycline remained for 1 day in the pouch. The compatibility of the gels was also examined by histopathology. The gels did not cause any adverse inflammatory effect in the air pouch.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.377-388
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• 2014

Purpose: Determining the spatial structure of data is important in understanding within-field variability for site-specific crop management. An understanding of the spatial structures present in the data may help illuminate interrelationships that are important in subsequent explanatory analyses, especially when site variables are correlated or are a combined response to multiple causative factors. Methods: In this study, correlation, principal component analysis, and single and nested variogram models were applied to soil electrical conductivity and chemical property data of two fields in central Missouri, USA. Results: Some variables that were highly correlated, or were strongly expressed in the same principal component, exhibited similar spatial ranges when fitted with a single variogram model. However, single variogram results were dependent on the active lag distance used, with short distances (30 m) required to fit short-range variability. Longer active lag distances only revealed long-range spatial components. Nested models generally yielded a better fit than single models for sensor-based conductivity data, where multiple scales of spatial structure were apparent. Gaussian-spherical nested models fit well to the data at both short (30 m) and long (300 m) active lag distances, generally capturing both short-range and long-range spatial components. As soil conductivity relates strongly to profile texture, we hypothesize that the short-range components may relate to the scale of erosion processes, while the long-range components are indicative of the scale of landscape morphology. Conclusion: In this study, we investigated the effect of changing active lag distance on the calculation of the range parameter. Future work investigating scale effects on other variogram parameters, including nugget and sill variances, may lead to better model selection and interpretation. Once this is achieved, separation of nested spatial components by factorial kriging may help to better define the correlations existing between spatial datasets.

• Journal of Korea Water Resources Association
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• v.43 no.10
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• pp.921-932
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• 2010

In this study, the adjustment processes of the disturbed channels by sand or gravel mining were investigated by a two dimensional numerical model in the generalized coordinate system. As a numerical scheme, the CIP (cubic interpolated pseudoparticle method) method was used to calculate the advection term in the flow field and central difference method was used to the diffusion term in it. The pit of the channel was partially filled with sediment at the toe of the pit upstream. As time increased, the headcut erosion upstream in the pit was decreased due to the sediment inflow. The almost inflow sediment upstream was trapped into the pit and the sediment deposit wedge migrated downstream in the pit with the steep submerged angle of repose. The numerical model was reproduced well the evolution processes of the channel. The mining pit migrated with speed as the channel was steep, and the numerical results were in overall agreement with the experimental results.

• Journal of Korean Society of Transportation
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• v.23 no.5 s.83
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• pp.93-104
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• 2005

Transit-Oriented Development Model, which is recently proposed to activate transit use, is suitable for solving environmental erosion problems of sprawl cities with low urban density. Accordingly this model is inadequate to apply to Muti-Nucleated City with high urban density like Seoul. With this background. this study proposes ways to effectively implement changes from automobile-oriented Seoul to transit-oriented city through comparative analysis of the urban design policy of Station Impact Zone (SIZ) of Seoul and Transit-Oriented Development Policy of Singapore and Tokyo. First, the study suggests that the implementation strategies for Transit-Oriented Development in the job-oriented SIZ and the neighborhood-oriented SIZ should be made separately. In addition, the job-oriented SIZ should be designated as 'Strategic Centers' in Seoul Comprehensive Plan in order to make Transit-Oriented Centers. Lastly, the SIZ should be designated as 'the Empowerment Zones' in order to make the blighted areas around stations viable for redevelopment and new incentive system should be applied to activate setting up transit-transfer facilities.

• Tunnel and Underground Space
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• v.17 no.5
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• pp.360-371
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• 2007

This paper presents an application of drainage control and slope stability by GIS-based hydrological modeling to control the surface water from an operational point of view. This study was carried out on a region of Pasir open-pit coal mine, Indonesia. A detailed topographical survey was performed at the study area to generate a reliable DEM (Digital Elevation Model). Hydrology tools implemented in ArcGIS 9.1 were used to extract the characteristics of drainage system such as flow direction, flow accumulation and catchment area from DEM. The results of hydrological modeling and spatial analysis showed that current arrangement of pumping facility is not suitable and some vulnerable places to erosion exist on the bench face due to concentrated surface runoff. Finally, some practical measures were suggested to optimize the design of drainage system and to monitor the slope stability by the surface water management at the study region during heavy rainfall.

• Journal of Ocean Engineering and Technology
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• v.24 no.2
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• pp.18-24
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• 2010

Submerged rubble structures include artificial reef and the mound part of the rubble mound breakwater. Artificial reef is a type of the submerged wave absorbing structure installed in a coastal zone to prevent beach erosion and designed to initially reduce the energy of incoming waves so that its run-up height and overtopping quantity can be decreased. In order to ascertain the stability of such submerged rubble structures, minimum weight of the rubble has to be calculated first from the incoming wave height using Hudson's formula or Brebner-Donnelly formula. Based on the calculated minimum weight, a model is built for use in a hydraulic model test carried out to check its stability. The foregoing two formulas used to calculate the minimum weight are empirically derived formulas based on the result of the tests on the rubble mound breakwater and it is, therefore, difficult for us to apply them directly in the calculation of the minimum weight of the submerged structures. Accordingly, this study comes up with a numerical simulation method capable of deformation analysis for rubble structures. This study also tries to identify the deformation mechanism of the submerged rubble structures using the numerical simulation. The method researched through this study will be sufficient for use for usual preparations of the design guidelines for submerged rubble structures.

• Journal of the Korean Geographical Society
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• v.39 no.5 s.104
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• pp.722-734
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• 2004

Longitudinal profiles of bedrock rivers play a fundamental role in landscape history by setting the boundary conditions for landform evolution. Longitudinal profiles are changed with climatic conditions, lithology and tectonic movements. Tectonic movement is an important factor controlling longitudinal profiles, especially in tectonically active area where uplift rates are regarded as a major factor controlling channel gradient. However study on bedrock channel has made little progress, because controls over bedrock river incision are yet to be clarified. Previous numerical simulations have used a simple diffusion model, which links together the overall processes of bedrock channel erosion as in other landform evolution models. In this study, previous bedrock incision models based on physical processes (especially abrasion) are reviewed and new modifications are introduced. Using newly formulated numerical model, the role of spatial pattern and intensity of tectonic uplift on changes in river longitudinal profile was simulated and discussed.