• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.27-34
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• 2023

This paper describes the results of a pile pullout test considering the confine pressure and fines content of the ground. The Pullout tests were conducted under various ground conditions using model piles. The effect of ground confine pressure on the pullout resistance and the pullout resistance parameters of the pile were evaluated based on the experimental results. The results of pullout test showed that the maximum pullout resistance occurred at a pullout displacement of about 7mm to 9mm, regardless of the fines content and the confine pressure of the ground. The maximum pullout resistance of the pile decreased as the fines content of the ground increased, and this trend became clearer as the confine pressure increased. The pullout resistance calculated by theoretical formula was compared with the experimental results in order to ensure the reliability of the pullout test results. The comparative results showed that the experimental and theoretical values showed a tendency to decrease the pullout resistance as the fines content increased, in all confine pressure conditions. The analysis result of the pullout resistance parameters confirmed that the pullout resistance was greatly influenced by the adhesion compared to the interface friction angle, as the fines content of the ground around the pile increased.

• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.1-23
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• 1979

The use of barley seeder attached to rotary tiller in the rural area has a significant meaning not only for the solution of labor peak season, but also for the increase of land utilization efficiency. The facts that presently being used barley seeders are all based on the mechanical principles of the reverse rotation, center drive and are all using forward rotating tine, which is used to be easily and heavily worn out when it rotates reversely, raise problem of recommending them to rural area in Korea. Therefore, the main objective of the study was to develop new type of rotary tine attachable to barley seeders. To attain the objective the following approaches were applied. (1) The kinematic analysis of reverse rotating barley seeders. (2) The studies on the soil bin and artificial soil. (3) The comparative experiment on the power requirement of prototype tine. The results obtained from the studies are summarized as follow: 1. The kinematic analysis of barley seeder attached to rotary tiller: The following results were obtained from the kinematic analysis for deriving general formulae of the motion and velocity characterizing the rotary tine of barley seeders presently being used by farmers. a) The position vector (P) of edge point (P) in the rotary tine of reverse rotating, center drive was obtained by the following formula. $$P=(vt+Rcos wt)i+Rsin wt j+ \{ Rcos \theta r sin \alpha cos (wt- \beta +\theta r) +Rsin \theta r sin \alpha sin (wt-\beta + \theta r) \} lk $$ b) The velocity of edge point $(P^')$ of reverse rotating, center drive rotary tine was obtained by the following formula. $$(P^')=(V-wR sin wt)i+(w\cdot Rcoswt)j + \{ -w\cdot Rcos \theta r\cdot sin \alpha \cdot sin (wt-\beta +\theta r) + w\cdot Rsin \theta r\cdot sin \alpha \cdot cos (wt- \beta + \theta r \} k $$ c) In order to reduce the power requirement of rotary tine, the angle between holder and edge point was desired to be reduced. d) In order to reduce the power requirement, the edge point of rotary tine should be moved from the angle at the begining of cutting to center line of machine, and the additional cutting width should be also reduced. 2. The studies on the soil bin and artificial soil: In order to measure the power requirement of various cutting tines under the same physical condition of soil, the indoor experiments Viere conducted by filling soil bin with artificially made soil similar to the common paddy soil and the results were as follows: a) When the rolling frequencies$(x)$ of the artificial soil were increased, the densIty$(Y)$ was also increased as follows: $$y=1.073200 +0.070780x - 0.002263x^2 (g/cm^3)$$ b) The absolute hardness $(Y)$ of soil had following relationship with the rolling frequencies$(x)$ and were increased as the rolling frequencies were increased. $$Y=37.74 - \frac {0.64 + 0.17x-0. 0054x^2} {(3.36-0.17x + 0.0054x^2)^3} (kg/cm^3)$$ c) The density of soil had significant effect on the cohesion and angle of internal friction of soil. For instance, the soil with density of 1.6 to 1.75 had equivalent density of sandy loam soil with 29.5% of natural soil moisture content. d) The coefficient of kinetiic friction of iron plate on artificial soil was 0.31 to 0.41 and was comparable with that of the natural soil. e) When the pulling speed of soil bin was the 2nd forward speed of power tiller, the rpm of driving shaft of rotary was similar to that of power tiller, soil bin apparatus is indicating the good indoor tester. 3. The comparative experiment on the power requirement of prototype tine of reverse rotating rotary: According to the preliminary test of rotary tine developed with various degrees of angle between holder and edge pcint due to the kinematic analysis, comparative test between prototype rotary tine with $30 ^\circ $ and $10 ^\circ$ of it and presently being used rotary tine was carried out 2nd the results were as follows: a) The total cutting torque was low when the angle between holder and edge point was reduced. b) $\theta r$ (angle between holder and edge point) of rotary tine seemed to be one: of the factors maximizing the increase of torque. c) As the angle between holder and edge point ($\theta r$) of rotary tine was $30 ^\circ $ rather than $45 ^\circ $, the angle of rotation during cutting soil was reduced and the total cutting torque was accordingly reduced about 10%, and the reduction efficiency of total cutting torque was low when the angle between holder and edge point ($\theta r$) of rotary tine was $10 ^\circ $, which indicates that the proper angle between holder and edge point of rotary tine should be larger than $10 ^\circ $ and smaller than $30 ^\circ $ . From above results, it could be concluded that the use of the prototype rotary tine which reduced the angle between holder and edge point to $30 ^\circ $, insted of $45 ^\circ $, is disirable not only decreasing the power requirements, but also increasing the durabie hour of it. Also forward researches are needed, WIlich determine the optimum tilted angle of rotary brocket, and rearrangement of the rotary tine on the rotary boss.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.31-38
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• 2013

After debris flow caused damage during recent years, many scholars and engineers have thrown their effort into analyzing risk from debris flow in Korea. But it is hard to predict damage by debris flow taken place in wide area. Recently, SINMAP program is widely well used to estimate the amount of debris flow and its' range. In order to make frequent use of it, the most important thing is selection of accurate input parameters. In-situ experiments, which are avaliable in the mountain, is to be suggested to get dependable input parameters for SINMAP. Those are permeability, cohesion, density, friction angle and thickness in SINMAP. To get those, test pit, block sampling, in-situ density test, auger boring, permeability test on ground surface, borehole shear test and dynamic cone test and so forth were selected. In addition, the reliability of the results will be increased through comparing with those by laboratory tests. Hence, the experiments are hard to enter the sites without temporary road and, if possible, licensing and many times are needed, too. Small size experiments are indeed necessary to get accurate parameters.

• Journal of the Korean Geotechnical Society
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• v.35 no.6
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• pp.39-48
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• 2019

This study investigated the lateral behavior of monopile embedded in the dry sand through cyclic lateral loading test using a centrifuge test. The sand sample for the experiment was the dry Jumunjin standard sand at 80% relative density and the friction angle of $38^{\circ}$. In the experimental procedure, firstly, it was determined the static lateral bearing capacity by performing the static lateral loading test to decide the cyclic load. This derived static lateral bearing capacity values of 30%, 50%, 80%, 120% were determined as the cyclic lateral load, and the number of cycle was performed 100 times. Through the results, the experiment cyclic p-y curve was calculated, and the cyclic p-y backbone curve by depth was derived using the derived maximum soil resistance point by the load. The initial slope at the same depth was underestimated than API (1987) p-y curves, and the ultimate soil resistance was overestimated than API (1987) p-y curves. In addition, the result of the comparison with the suggested dynamic p-y curve was that the suggested dynamic p-y curve was overestimated than the cyclic p-y backbone curve on the initial slope and soil resistance at the same depth. It is considered that the p-y curve should be applied differently depending on the loading conditions of the pile.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.216-225
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• 2023

This paper describes the finite element analysis and die design change of cold heading punching process to increase the cold forging tool life and reduce the tool wear and stress concentration. Through this study, the optimization of punch tool design has been studied by an analysis of tool stress and wear distribution to improve the tool life. Plastic deformation analysis was carried out in order to understand the cold heading process between tool and workpiece stress distribution. Cold heading punch die design was set up to each process with different four types analysis progressing, the cold heading punch dies shapes with combination of point angle and punch edge corner radius shapes of cold forging dies, punch die material properties and frictional coefficient. The design parameters of point angle and corner radius of punch die geometry, die material properties and frictional coefficient were selected to apply optimization with the DoE (design of experiment) and Taguchi method. DoE and Taguchi method was performed to optimize the cold heading punch die design parameters optimization for bolt head cold forging process, it was possible to expect an reduce the cold heading punch die wear to the 37 % compared with current using cold heading punch in the shop floor.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.4
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• pp.373-379
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• 1988

This experiment was carried out to investigate the effects of long-term applications of rice straw and compost on the physical and mechanical properties of paddy fields and the yearly variation of rice yield in Fluvio-Marine plain of Jeonbug series. Amounts of rice straw and compost applied in this experiment were 500kg/10a, 1,000kg/10a respectively, and the nitrogen levels were 0, 15 and 20kg/10a. This experiment were continued for 9 years from 1979 to 1987. The results are summarized as follows: 1. Clay and silt ratios were decreased but versa in sand ratio, by the long-term application of rice straw and compost. 2. Bulk density in the long-term application of organic matter was lower in surface soil of non-application than nitrogen application (15kg/10a) and in rice straw than compost. 3. Solid ratio went down, but liquid and gaseous ratio went up especially, by organic matter application liquid ratio were increased by compost and gaseous ratio were increased by in rice straw. 4. Aggregates of bigger than 2mm were increased by long-term application of organic matter, and the effects was better in rice straw than compost. Accumulative aggregate of 2mm was 66.5% in nitrogen of 15kg/ 10a with rice straw, which showed the increase of 9.1% in comparison with the non-application of nitrogen and organic matter. 5. Liquid limit, plastic limit and plastic index were high in order of rice straw, compost and control, and liquid index was lower in compost than in rice straw. 6. Cole value was higher in vertical than horizontal and highest in the application of rice straw with nitrogen of 15kg/10a. Cone and shearing resistance were lowest in the application of rice straw with nitrogen. In total vertical pressure friction was higher in the long-term application of organic matter than control. 7. The change of yield index was higher in the long-term application of compost than rice straw in non-nitrogen and it showed the yearly competitive variation between the long-term application of compost and rice straw in nitrogen of 10kg/10a. In nitrogen application of 20kg/10a, it was increased from 6th year by rice straw application.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.515-527
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• 2014

This study conducted experiment for understanding engineering characteristics of domestic sands by examining standard sand and sand from Yokji Island and Nakdong River in terms of confining pressure, $K_0$, over consolidation and relative density factors through triaxial compression test. The test showed that deviator stress by strain positively changed as confining pressure and relative density grow while $K_0$ and over consolidation factors do not directly correlated with it. Angle of internal friction decreases as confining pressure increases which strengthens contact force between particles, and declines as relative density drops, whereas $K_0$ and over consolidation factors hardly affect the results. When it comes to volumetric strain, volume expansion decreases as confining pressure increase due to crushability and rearrangement of particles while $K_0$ and over consolidation shows same movement unconditionally, and relative density appears compressed as it grows at the beginning however it expands as axial strain increases. Modulus of elasticity ($E_{sec}$) by strain has tendency into convergence resulting in initial secant modulus of elasticity ($E_{ini}$) > secant modulus of elasticity($E_{sec}$) > tangent modulus of elasticity ($E_{tan}$). On the other hand, it grows as confining pressure and relative density increase while indicating similar modulus of elasticity ($E_{sec}$) regarding on $K_0$ and over consolidation. Slope of critical line (M) tended to decrease as confining pressure increases, follow same line according to $K_0$, confining pressure and relative density, and increase as relative density grows.

• The korean journal of orthodontics
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• v.36 no.2 s.115
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• pp.125-135
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• 2006

The purpose of this study was to measure and compare the level of frictional resistance generated from three currently used ceramic brackets; 1, Crystaline $V^{(R)}$, Tomy International Inc., Tokyo, Japan; 2, $Clarity^{(R)}$, 3M Unitek, Monrovia, CA, USA; 3, $Inspire^{(R)}$, Ormco, Orange, CA, USA; with composite resin brackets, Spirit, Ormco, Orange, CA, USA; and conventional stainless steel brackets, Kosaka, Tomy International Inc., Tokyo, Japan used as controls. In this experiment, the resistance to sliding was studied as a function of four angulations $(0^{\circ},\;5^{\circ},\;10^{\circ}\;and\;15^{\circ})$ using 2 different orthodontic wire alloys: stainless steel (stainless steel, SDS Ormco, Orange, CA, USA), and beta-titanium (TMA, SDS Ormco, Orange, CA, USA). After mounting the 22 mil brackets to the fixture and $.019{\times}.025$ wires ligated with elastic ligatures, the arch wires were slid through the brackets at 5mm/min in the dry state at $34^{\circ}C$. Silica-insert ceramic brackets generated a significantly lower frictional force than did other ceramic brackets, similar to that of stainless steel brackets. Beta-titanium archwires had higher frictional resistance than did stainless steel, and all the brackets showed higher static and kinetic frictional force as the angulation increased. When the angulation exceeded $5^{\circ}$, the active configuration emerged and frictional force quickly increased by 2.5 to 4.5-fold. The order of frictional force of the different wire-bracket couples transposed as the angle increased. The silica-insert ceramic bracket is a valuable alternative to conventional stainless steel brackets for patients with esthetic demands.

• Korean Journal of Agricultural Science
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• v.5 no.2
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• pp.127-135
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• 1978

For improvement and new design of tillage equipments, indoor test is very useful and more desirable than outdoor because the experiment of outdoor is very difficult and its cost is expensive. This study was carried out to determine the physical properties of artificial soil suitable for the indoor test with the soil bin manufactured at the workshop of the Dept. of Agricultural Machinery Engineering. The artificial soil being studied was made with very similarity to the natural soil of the experimental plots of Chungnam National University, and it consist of 39.35 percent, by weight of bentonite and 48.10 percent of sand with 12.55 percent of SAE 10W oil. The results are summarized as follows: 1. Bulk density increased with increasing number of rolling, and its relationship could be expressed. $y=1.073200+0.070780x-0.002263x^2$ where, y=bulk density ($g/cm^3$), x=number of rolling. These results could be explained that the effect of rolling velocity on the bulk density was not singnificant in the range of 4.5~10.4 em/sec. 2. The absolute soil hardness depended directly upon number of rolling, and their relationship could be expressed by the equation. $y=37.74(0.64 +0.17x-0.0054x^2)/(3.36-0.17x-0.0054x^2)^3$. where, y=absolute soil hardness($kg/cm^3$), x=number of rolling. 3. Relationship between the bulk density and absolute soil hardness could be expressed by the equation; $y=37.74(2.46x-2.02)/(6.02-2.46x)^3$. where, y=absolute soil hardness, x=bulk density. 4. The cohesion and the angle of internal friction of artificial soil were increased with increasing its bulk density. According to the cohesion and angle of internal friction, at the range of 1.60~1.75 ($g/cm^3$) of bulk density, this artificial soil was similar with sandy loam of 29.5% moisture content of natural soil. 5. Sliding-fricfion coefficient of steel plate on the artificial soil was 0.3~0.4 and rubber plate on it is 0.64~0.72. Those values were very similar with those of natural soil being studies by many others.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.4
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• pp.21-31
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• 2001

When an oil-spilling accident occurs at sea, it is of the primary importance to predict the amount of oil leakage for the swift response and decision-making. The simplest method of oil-leakage estimation is based on the hydrostatic pressure balance between oil inside the tank and seawater outside of leakage hole, that is the so-called Torricelli equilibrium relation. However, there exists discrepancy between the reality and the Torricelli relation, since the latter is obtained from the quasi-steady treatment of Bernoulli equation ignoring viscous friction. A preliminary experiment has been performed to find out the oil-leaking speed and shape. Soy-bean oil inside the inner tank was ejected into water of the outer tank through four different leakage holes to record the amount of oil leakage. Furthermore, a CFD (Computational Fluid Dynamics) method was utilized to simulate the experimental situation. The Wavier-Stokes equations were solved for two-density flow of oil and water. VOF method was employed to capture the shape of their interface. It is found that the oil-leaking speed varies due to the frictional resistance of the leakage hole passage dependent on its aspect ratio. The Torricelli factor relating the speed predicted by using the hydrostatic balance and the real leakage speed is assessed. For the present experimental setup, Torricelli factors were in the range of 35%~55% depending on the aspect ratio of leakage holes. On the other hand, CFD results predicted that Torricelli factor could be 52% regardless of the aspect ratio of the leakage holes, when the frictional resistance of leakage hole passage was neglected.