• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.36-43
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• 2007

In the case of single well pumping tests the storativities are generally overestimated. To compensate these errors, the effective wellbore radius should be introduced as a distance to an imaginary observation well in the time-drawdown analysis. Effective wellbore radius can be calculated through step drawdown tests or using skin factor equation. But both are of trial-and-error methods guessing real storativity values and, therefor, are difficult to apply to the field conditions. An equation was developed to estimate effective wellbore radius from storativity values obtained from pumping well data. For this study, a total of 136 time-drawdown data set were used to derive the equation. The effective wellbore radius were estimated first by changing them till the storativity values obtained from the pumping-well data match the ones based on the observation-well data. Then the equation was regressed from the relation between effective wellbore radius and the storativity values obtained from the pumping-well data. It is believed that the equation would be useful in estimating effective wellbore radius from the single well tests.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.197-204
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• 1993

Pipe drainage is one of the effective slope protein works that can be adopted practically. As fine soil particles are suspended in percolating water, the strainer structure of under drain pipes in necessary to prevent the immediate clogging by soil suspension flow. This study deals with the effective strainer structure of under drain pipes for slope protection. The effective strainer structure of under pipes is the funneled strainer in which pore radius is enlarged toward flow direction. It is designed from the rheological properties of soil suspension flow which prevents the immediate clogging. Experimental results showed that the pipe drain discharge through the funneled strainers was larger than that through the constant pore radius strainers. This theorectial and experimental results indicate that the strainer with enlarged pore radius toward flow direction, is more effective than the strainer with constant pore radius.

• Korean Journal of Computational Design and Engineering
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• v.7 no.1
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• pp.34-41
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• 2002

Five-axis NC machining, in general, is utilized in fabricating impellers, turbine blades, marine propellers that can be machined more effectively rather than three-axis machining. There have been many researches concerning tool interference avoidance, optimization of tool orientation. The C-space or Configuration-space was originated from the robotics area, which depicts interference-free joint-values in motion planning. In the paper we propose an optimizing scheme by which the maximum effective-radius of a face-milling cutter can be achieved for each CC(cutter-contact) point. Also the concept of a C-space for a CC point, the effective-radius map for 5-axis face-milling, and some illustrative examples of marine propeller machining, are presented.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.285-300
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• 2017

Shallow coal resources are increasingly depleted, the mining has entered the deep stage. Due to "High stress, high gas, strong adsorption and low permeability" of coal seam, the gas drainage has become more difficult and the probability of coal and gas outburst accident increases. Based on the flow solid coupling theory of coal seam gas, the coupling model about stress and gas seepage of coal seam was set up by solid module and Darcy module in Comsol Multiphysics. The gas extraction effects were researched after applying hydraulic technology to increase permeability. The results showed that the effective influence radius increases with the expanded borehole radius and drainage time, decreases with initial gas pressure. The relationship between the effective influence radius and various factors presents in the form: $y=a+{\frac{b}{\left(1+{(\frac{x}{x_0})^p}\right)}}$. The effective influence radius with multiple boreholes is obviously larger than that of the single hole. According to the actual coal seam and gas geological conditions, appropriate layout way was selected to achieve the best effect. The field application results are consistent with the simulation results. It is found that the horizontal stress plays a very important role in coal seam drainage effect. The stress distribution change around the drilling hole will lead to the changes in porosity of coal seam, further resulting in permeability evolution and finally gas pressure distribution varies.

• Journal of Korean Library and Information Science Society
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• v.6
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• pp.105-140
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• 1979

This study is an attempt to present a model of the effective service area for branch library system planning in Dae Gu city as one of large urban public libraries in Korea. This model is built up through the analysis of the distribution of population and characteristics of community structure, based on the standard for the branch library system of a public library. The results are summarized as follows: 1. Under the circumstances of this country, each radius of the effective service area for branch libraries are as follows; $1{\sim}1.5km$. is adequate for the central library and major branches; 1km. for neighborhood branches; $0.5{\sim}0.8km$. for sub-branches. 2. Population within the radius of the effective service area of a given branch may range from 80,000 to 100,000 for major branches, from 50,000 to 60,000 for neighborhood branches, and from 20,000 to 30,000 for sub-branches. 3. The radius of the outer boundary for the effective service area may be between 4km. and 5km. from the heart of the city, and the inner boundary, 13.km. 4. Areas with the radius between 2km. and 3km. from the heart of the city may be selected as the most effective locations for branch libraries, and between 3km. and 4km. as the next priority. 5. The number of service areas may be 14, that is, 7 major branches(Sinam, Sinchun, Susung, Daemyung, Naedang, Dalsung, Rowon), 2 neighborhood branches (Pyungri, Nambu), and 5 sub-branches(Chimsan, Sangiuk, Bongduk, Hyomok, Dongchon)

• Structural Engineering and Mechanics
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• v.89 no.4
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• pp.411-420
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• 2024

The purpose of this research was to investigate the cyclic behavior of the D-shaped dampers (DSD). Similarly, at first, the numerical model was calibrated using the experimental sample. Then, parametric studies were conducted in order to investigate the effect of the radius and thickness of the damper on energy dissipation, effective and elastic stiffness, ultimate strength, and equivalent viscous damping ratio (EVDR). An analytical equation for the elastic stiffness of the DSD was also proposed, which showed good agreement with experimental results. Additionally, approximate equations were introduced to calculate the elastic and effective stiffness, ultimate strength, and energy dissipation. These equations were presented according to the curve fitting technique and based on numerical results. The results indicated that reducing the radius and increasing the thickness led to increased energy dissipation, effective stiffness, and ultimate strength of the damper. On the other hand, increasing the radius and thickness resulted in an increase in EVDR. Moreover, the ratio of effective stiffness to elastic stiffness also played a crucial role in increasing the EVDR. The thickness and radius of the damper were evaluated as the most effective dimensions for reducing energy dissipation and EVDR.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.5
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• pp.585-595
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• 2007

Representative impacts and effectiveness of surface meteorological observation data assimilation were examined in order to use wind resources estimation around southern coastal area of the Korean Peninsula. The data used in study are observational wind and temperature data at 5 and 41 sites of Regional Meteorological Offices and Automatical Weather Systems, respectively. Observation wind speed data tends to show small effective radius with limited area. Especially assimilation impacts of data observed at peninsula type sites like Yeosu play only around the inside of the peninsula. This limited effective radius for wind speed is caused by the strong correlation between topography and wind speed. And the efficient radius for surface air temperature is larger than that of wind. Data assimilation for observational air temperature is useful to increase the accuracy of wind energy estimation. However assimilation of wind data requires special care in its application due to high sensitivity of topographical complexity.

• Journal of Soil and Groundwater Environment
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• v.13 no.3
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• pp.15-20
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• 2008

The investigation on the previous paper(Jn. of KoSSGE vol.12, no.3), which proposed three empirical equations for the different aquifers was carried out. To draw out a single equation from the three different equations the mean value of the involution factors was adopted allowing different proportional coefficients for the different aquifers. On the other hand it was found that the square root value of storativity ratio, ${\sqrt{{S_p}/{S_o}}}$ in each well is almost equal to its wellbore radius ratio, ${r_e}/{r_w}$. From this fact, the proportional coefficients can be substituted with assumed aquifer storativity and a generalized empirical equation for the effective wellbore radius has been derived.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.72-80
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• 1995

Ultraprecision machining technology has been playing a rapidly increasing and important role in manufacturing. However, the physics of the micromachining process at very small depth of cut, which is typically 1 .mu. m or less is not well understool. Shear along the shear plane and friction at the rake face dominate in conventional machining range. But sliding along the flank face of the tool due to the elastic recovery of the workpiece material and the effects of plowing due to the large effective negative rake angle resultant from the tool edge radius may become important in micromachining range. This paper suggests an orthogonal cutting model considering the cutting edge radius and then quantifies the effect of plowing due to the large effective negative rake angle.

• Journal of Distribution Science
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• v.17 no.12
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• pp.63-70
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• 2019

Purpose: This study was to propose effective deployment of automatic external defibrillators (AEDs) installed at general supermarkets. Research design, data, and methodology : We conducted interview and data surveys on 72 large distributors in Seoul and Gyeonggi province in South Korea. The content of this survey was consisted of general status on the general supermarkets, AED deployment and management regarding public access defibrillation (PAD). G^⁎Power (v 3.1.9.4; Universität Kiel, Kiel, Germany) was also used to analyze statistical power. Radius and actual distance, radius and retrieval time were compared by t-test at α=.05. respectively. Results : Difference between the radius (102.7 meters) and the actual distance (187.8 meters) was 85.1m, it had statistically significant difference (p<.001). The actual distance was longer compared to the radius distance. Difference between the radius (114.1 seconds) and the retrieval time (208.7 seconds) was 94.6s, it had statistically significant difference (p<.001). The retrieval time took longer compared to the radius time as well. Conclusions : The finding shows that only 45.9% of the general supermarkets are satisfied with the actual AED coverage within 3 minutes. This needs to enhance AED deployment to reduce defibrillation time and AED management to boost application in South Korea.