• Journal of Wetlands Research
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• v.14 no.1
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• pp.75-87
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• 2012

Hyporheic zone is a region beneath and alongside a stream, river, or lake bed, where there is mixing of shallow groundwater and surfacewater. Hyporheic exchange controls a variety of physical, biogeochemical and thermal processes, and provides unique ecotones in a aquatic ecosystem. Field and experimental observations, and modeling studies indicate that hyporheic exchange is mainly in response to pressure gradients driven by the geomorphological features of stream beds. In the reach scale of a stream, pool-riffle structures dominate the exchange patterns. Flow over a pool-riffle sequence develops recirculation zones and stagnation points, and this flow structures make irregular pressure gradient which is driving force of the hyporheic exchange. In this study, 3 D hydro-dynamic model solves the Reynolds-averaged Navier-Stokes equations for the surface water and Darcy's Law and the continuity equation for ground water. The two sets of equations are coupled via the pressure distribution along the interface. Simulation results show that recirculation zones and stagnation points in the pool-riffle structures dominantly control the upwelling and downwelling patterns. With decrease of recirculation zones, length of donwelling zone formed in front of riffles is reduced and position of maximum downwelling point moves downward. The numerical simulation could successfully predict the behavior of hyporheic exchange and contribute the field study, river management and restoration.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.77-86
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• 2013

Laboratory pullout tests were conducted to evaluate pullout performance of steel strip reinforcements with deformed steel bars as transverse members. The steel strip reinforcement has an installation hole to assemble a deformed steel bar. Jumunjin standard sand is used to form a relative density of ground model to 80%. Frictional resistance of steel strip reinforcement without transverse member increases sharply at the initial displacement and quickly decreases with displacement. Maximum frictional resistance increases linearly as normal pressure increasing, and soil-reinforcement interaction friction angle(${\rho}_{peak}$) of a steel strip reinforcement is estimated to $14.64^{\circ}$. Passive resistance increases with displacement and converge into maximum passive resistance in most cases. Maximum passive resistance increases linearly as normal pressure increasing irrespective of shape of the steel reinforcement. Pullout force of steel strip reinforcements with installation holes or transverse members largely increases about 4 to 7 times compared to frictional resistance force of steel strip reinforcements when embedment length($L_e$) of steel strip reinforcements is 500 mm. In the case of using 2 transverse members, interference effect is observed due to the spacing of 2 transverse members and location of assembly holes and transverse members.

• Journal of the Korea Society of Computer and Information
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• v.19 no.10
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• pp.71-79
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• 2014

In this paper, the microstrip array antenna is studied to replace the parabolic antenna in the direct satellite reception. A microstrip array antenna has been used in extremely limited area, but if it is applied to practical life like a direct satellite reception antenna, we expect that it will be used in various way. First of all, if we use a microstrip array antenna for a direct satellite reception antenna, it should be guaranteed characteristics of broadband frequency. Therefore, the goal of this paper is designing technique an antenna which guarantees broadband frequency band for a direct satellite reception. In this paper, the proposed microstrip antenna is fed by orthogonal two feed lines to a rectangular patch and a sequentially rotated feeding technique is designed proposed for a good axial ratio in broadband frequency band. The rectangular patch is designed to satellite reception band, and the width and length are W=L=8.9 mm ($0.352{\lambda}o$) respectively. The antenna's ground plane has dimensions of $250{\times}250mm$. The experimental results verify that the proposed antenna had the axial ratio of above 1dB broader than that of the conventional feeding antenna. In order to verify the performance, a $8{\times}8$ array having two pairs was fabricated and tested. The maximum gain is 20.8 dB, the sidelobe level confirm less than -10 dB. It is verified by link budget calculation that C/N=6.7 dB can be obtained for domestic use if this proposed antenna is used in Koreasat reception system.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.4
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• pp.505-510
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• 2014

This research investigated growth of ginseng regard to sunshade materials and micro metrological phenomena under the sunshade material to product high quality ginseng. Followings are results of investigation of active ingredient from raw ginseng producted under the sunshade materials. The highest temperature under the sunshade material from June to August was measured from a Three-layered blue and one-layered black polyethylene net (TBOBFN) followed by a aluminium-coated polyethylene sheet (ACPS) and blue polyethylene sheet (BPS). The highest light penetration of $381.7{\mu}mol/s/m^2$ was obtained from the BPS at August, also the temperature was highest at the ginseng field. Growth of above ground part of 2~3 year old ginseng under the ACPS was the highest, followed by the ACPS and the BPS. In case of 4 year old ginseng, the ACPS and the BPS was the same, followed by the TBOBPN. Root length and diameter of 2~3 year old ginseng showed difference among treatments, but 4 year old ginseng was not showed difference. Meanwhile, the highest amount of root of 4 year old ginseng of $896g/m^2$ was obtained from ACPS. The total amount of ginsenocide of 4 year old ginseng under the ACPS was highest, followed by the BPS and the TBOBPN. Chromaticity of ginseng root under the TBOBPN was highest, followed by the ACPS and the BPS.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.71-86
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• 1999

The displacements of soil nailed wall and the nail tensile force for 11 soil nailing sites were investigated by using measurements obtained from inclinometer and strain gauge. The maximum horizontal displacement which occurred between 5% and 15% of the final excavation depth was found to be below 0.3% and 0.2% of excavation depth for well and poorly constructed sites. It was also found that the maximum horizontal displacements for 0.4%, 0.3% and 0.2% of excavation depth occurred when the ratios of nail length to final excavation depth were 0.5, 0.5~0.6 and 0.6~0.7. But the maximum horizontal displacement increased by 0.3% of excavation depth when the ratio was above 0.7. This was probably due to the shallow excavation depth and the deep soil stratum. The non-dimensional maximum tensile force of nail, K, from ground surface to $(0.6H_f)$ of the final excavation depth was less than 0.8 and decreased linearly between $(0.6H_f)$ and the final excavation depth. Also, the maximum tensile force was found to reach up to 60% of the ultimate tensile force at final excavation.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.17-32
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• 1982

The binders introduced in Korea were originally designed to be used for Japonica-type varieties which have relatively long stem and are highly resistant to shattering. In order to use it for Tongil varieties which are short and easy to be shattered, mechanical modifications are necessary to reduce a grain loss incurred during binder operation. This study was intended to investigate analytically and experimentally the major sources of grain losses caused by three kinds of binders now introduced in Korea. Actual modification for each of three binders was done and experimentally compared to see if any improvement on grain loss was achieved. The results obtained in this study are summarized as follows; 1. It was required that the power transmission of binder should have a shifting mechanism so that velocities of pick-up and traveling units could be changed independently as desired according to the Japonica-type and Tongil varieties. In other words, the desired velocity of traveling unit should be obtained by shifting the transmission and the velocity of pick-up unit should be selected by reaping clutch according to the variety independent of the velocity of traveling unit as shown in Fig. 6. 2. To reduce grain loss it was desired that the moving parts of the pick-up unit should have the lowest possible velocities in harvesting Tongil varieties, unless the reduction of the speed be hindered the conveyance of the material. Based on the study, it was concluded that the velocities of pick-up unit be reduced by about 35% of those of the existing units. 3. It was found that the lug at the upper rotating section of pick-up case gave a severe impact on the ears of rice to increase grain loss. The optimum design of pick-up case to protect the ears from the protruding part of the lug was recommended by the result of analysis of the trajectory of the end-point of lug at the position. 4. It was proved analytically and experimentally that pick-up unit at the lower-rotating part was the other important source of grain loss in pick-up and divider assembly. In order to reduce a grain loss incurred by lugs at their lower-rotating section, it was suggested to improve it by (1) widening the space between right and left lower-rotating section, (2) shortening the length of lugs, (3) enlargement of the angle between the pick-up case and ground-level, and (4) attaching guard to right and left dividers so that the rotating lug could not give a high impact to the paddy hill. 5. Pick-up and divider assembly of the original binder of three models studied was modified according to the suggestions that were given by the preliminary study. Field test showed that the modified binders were able to reduce grain losses by about 0.4-0.7 percentage points compared to those without modification.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.431-439
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• 2001

In this paper, the a-Diamond films were synthesized using filtered vacuum arc source (FVAS), FVAS was composed of a torus structure with bending angle of 60 degree. The radius of torus was 266 mm, the radius of plasma duct was 80 mm and the total length was 600 mm. The magnet parts were composed of one permanent magnet and five solenoid magnets. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The baffles inside plasma duct were installed in order to prevent the recoil effect of macro-particles. Cathode was made of graphite with 80 mm in diameter. The effects of solenoid magnet on plasma extraction were investigated by computer simulation and experiment using Taguchi's methode. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with low value of the source magnet current and high value of the filtering magnet current. The beam current density was 3.2 mA/$\textrm{cm}^2$ and average deposition rate was 5 $\AA$/sec when the currents of arc discharge, source, extraction, bending, deflection and outlet magnet were 30 A, 1 A, 3 A, 5 A, 5 A, and 5 A, respectively. The beam current density and the efficiency of beam transportation were increased with the positive bias voltage of the plasma duct.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.172-180
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• 2007

A new diagnostics of plasma electron temperature and plasma density is introduced with the observation of the light emission along the tube of external electrode fluorescent lamps. With two different methods operating an external electrode fluorescent lamp of outer diameter 4.0 mm and length 860 mm for the back-light source of 37-inch LCD-TVs, the lighting modes and the plasma properties are investigated. In the center balance operation, the light-emission propagates simultaneously from both sides of the high voltage electrodes to the center of the lamp, while in conventional operation the light-emission propagates from the one end of a high voltage to the other ground electrode. In the operation value of luminance $10,000{\sim}15,000cd/m^2$, the electron plasma thermal energy $(kT_e)$ is about $1.3{\sim}2.7eV$ with the electron density $(n_e)$ is about $(1.6{\sim}3.6){\times}10^{16}m^{-3}$.

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.1
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• pp.47-56
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• 2003

Recently with the conclusion of fisheries agreements between Korea and Japan, and between Korea and China, trawlers in korea must operate in smaller fishing ground than before. As a result of this, the possibilities of collisionin increases gradually between trawlers under operation in this area. Authors performed a series of experiments on board to give the information of collision avoiding action to navigators of trawlers. The obtained results are summerized as follows : 1. The greater the rudder angle, the smaller the value of T, but there is no big diffierence in K due to rudder angle. 2. The greatest distance is to be kept by the give way vessel to avoid collision when the crossing course angle is $70^{\circ}{\sim}90^{\circ}$. In this case the safety minimum approaching distance must be more than 5 times of her own length. 3. Risk of collision in crossing is more greater in obtuse situation than in acute one. 4. The navigator of the give way vessel must take an action to avoid collisions outside of the minimum safety approaching distance.

• Journal of the Korea Convergence Society
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• v.8 no.8
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• pp.191-196
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• 2017

This study was conducted to investigate the effect of fine bubble water treatment on the growth of ginseng seedlings. The growth of ginseng seedlings which were treated with general water and fine bubble water was investigated. The above ground part, the growth of leaf was increased by about 10% and the growth of the stem was about 6%, as the ginseng seedlings which were treated with fine bubble water comparing to the ginseng seedlings treated with general water. Root length was increased about 5%, root width was increased about 8%, roots weight was increased about 9%, and dry weight was increased about 7%. This is not because the whole root growth was increased, but the main root growth was increased about 7%. These results suggested that the physical properties of the fine bubble water stimulated the growth of ginseng seedlings. These results are initial study in the case of ginseng seedlings. Therefore, it can be applicable to the 3-5 years old ginseng plants. Further research will be needed to find out the optimal cultivation condition by controlling the dissolved oxygen amount according to the soil condition and the research applied to the ginseng seedlings.