• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.315-315
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• 2017

In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.

• Journal of Aquaculture
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• v.16 no.3
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• pp.142-150
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• 2003

Performance of a biological filter, the rotating biological contactor (RBC), is affected by rotational speed and hydraulic residence time (HRT). A RBC with a disc diameter of 62 cm, total surface area of 48.28 $m^2$, volume of 0.34 ㎥, and submergence ratio of 35.4% was tested for the combinations of five rotational speeds (1, 2, 3, 4 & 5 rpm) and three HRT (0.5, 1.0 & 2.0 hr) to find out the maximum removal efficiencies of total ammonia nitrogen (TAN) and nitrite nitrogen of a simulated recirculating aquaculture system. Ammonia loading rate in the system was 25 g of TAN/ ㎥. day. Removal efficiencies were checked when TAN concentrations in the system stabilized for 3 days in each treatment. The concentration of TAN in the system decreased with increasing rotational speed of the RBC up to 4 rpm in all HRT (P<0.05). At the rotational speed of 5 rpm, the efficiencies decreased in all HRT (P<0.05). When the rotational speeds were 1, 2, 3, 4, and 5 rpm, TAN concentrations in the system were 1.35, 0.94, 0.69, 0.66, and 0.76 mg/L at the 0.5 hr HRT, 2.86, 1.18, 0.96, 0.87, and 1.11 mg/L at the 1.0 hr HRT, and 5.30, 2.44, 1.99, 1.77, and 2.01 mg/L at the 2.0 hr HRT, respectively. The TAN removal efficiencies of the RBC at the rotational speeds of 1, 2, 3, 4, and 5 rpm were 32.9, 49.5, 65.1, 72.9, and 62.9% in 0.5 hr HRT,33.1, 74.1, 87.1, 95.8, and 78.5% in 1.0 hr HRT, and 35.5, 76.7, 89.6, 97.0, and 85.5% in 2.0 hr HRT, respectively. TAN removal efficiency of RBC per pass increased with increasing HRT. However, TAN concentration in the system also increased. The best operating condition among the treatments was obtained at the treatment of 0.5 hr HRT and 4 rpm (P<0.05). The TAN concentration was 0.66 mg/L. Concentrations of nitrite nitrogen (NO$_2$$^{[-10]}$ -N) in the system decreased with increasing rotational speed in all HRT while that in the system increased with increasing HRT in all rotational speeds. The ranges of NO$_2$$^{[-10]}$ -N concentrations at HRT of 0.5, 1.0, and 2.0 hr in the system were 0.26~0.32, 0.31~0.56, and 0.43~l.45 mg/L, respectively. The ranges of daily removal rates of TAN in this system were 20.03~23.0 g TAN/㎥ㆍday and those of nitrite nitrogen were 19.65~30.25 g NO$_2$$^{[-10]}$ -N/㎥ㆍday.

• Journal of the Korea Convergence Society
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• v.12 no.3
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• pp.197-204
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• 2021

This study relates to a device that increases efficiency by reducing air bubbles in a hydraulic system used in hydraulic machinery. The reverse design and product production of the bubble reduction device, which is a commercial product overseas, was carried out. Overseas commercial products were set as the base model, a rotary rotor and an inclined rotor were added to increase the surface area of the fluid, and an annular equal distribution part with a slot in the lower part was additionally applied to distribute the fluid evenly. In addition, internal flow trends were analyzed and a system that evenly distributes the linear flow of fluid was selected as the first improvement model. Based on the first improvement model, a case where the angle of the inclined rotor is 45° was selected as the second improvement model. Based on this, as a result of setting the exit width of the annular equally distributed part as a variable, the bubble reduction efficiency was highest when the lower slot diameter of the annular part was 10mm. Finally, the system in which the average cross-sectional flow velocity decreased by 147% compared to the Base Model was derived as the final improved model.

• Journal of the Korean GEO-environmental Society
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• v.23 no.1
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• pp.39-49
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• 2022

Expandable steel pipe piles are installed by inserting expansion equipment to increase the cross-sectional area of steel pipes, which can improve the pile performance compared to micro-piles. In this paper, a hydraulic expansion device was developed to expand steel pipe piles in practice. A series of laboratory and field tests were conducted to verify the performance of the developed expansion device to expand steel pipes. The expansion capability and expandable range was evaluated by measuring the strain and expansion time at the maximum pressure of the hydraulic expansion device. The thinner steel pipe, the larger strain but longer expansion time required in the test. For example, the 4.0-mm-thick steel pipe showed strain reduction by 30% and a decrease in the required expansion time by 40% compared to the 2.9-mm-thick steel pipe. In addition, in-situ expansion tests were performed to verify the expandability of steel pipes under the ground, and the exhumed specimen showed clear expanded sections. The structural integrity was determined by comparing the material performance the original and expanded specimens.

• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.66-80
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• 1991

The LOFT intermediate break experiment L5-1, which simulates 12 inch diameter ECC line break in a typical PWR, has been analyzed using the reactor thermal/hydraulic analysis code RELAP5/MOD2, Cycle 36.04. The base calculation, which modeled the core with single flow channel and two heat structures without using the options of reflood and gap conductance model, has been successfully completed and compared with experimental data. Sensitivity studies were carried out to investigate the effects of nodalization at reactor vessel and core modeling on major thermal hydraulic parameters, especially on peak cladding temperature(PCT). These sensitivity items are : single flow channel and single heat structure (Case A), two flow channel and two heat structures (Case B), reflood option added (Case C) and both reflood and gap conductance options added (Case D). The code, RELAP5/MOD2 Cycle 36.04 with the base modeling, predicted the key parameters of LOFT IBLOCA Test L5-1 better than Cases A,B,C and D. Thus, it is concluded that the single flow channel modeling for core is better than the two flow channel modeling and two heat structure is also better than single heat structure modeling to predict PCT at the central fuel rods. It is, therefore, recommended to use the reflood option and not to use gap conductance option for this L5-1 type IBLOCA.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.118-124
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• 1990

The rope winder in addition to the line hauler was used for recoiling of the main line to the rope pond at the stern, however, catching the loops, evenly revoiling and arrangements of the loops were done manually by two men. The automatic loop catcher under the rope winder was consisted with the rotary lever, semicircle guide plates, transfer belt and swing rope receiver for arrangements of the loops and evenly recoiling. The obtained results are as follows: 1. The minor diameter of a loop and the diameter of the coiling pile in a lead core PP rope(ø 10mm) are about 14cm and 60cm while the rope is piled on the bottom. 2. Distribution ratio of the loops within upper or lower 10cm from the transfer belt is 93% with a lead sinker and 98% without sinker using by the smaller loop catcher. 3. The relationship between revolutions of the rotary lever N sub(1) (rpm) and the hauling pulley N sub(p) (rpm) by gear ratio 3:1 in the smaller loop catcher is as follows: N sub(p) =2.86 N sub(1) +23.74 and optimum ratio of horizontal speed of the loops by the rotary lever to hauling speed is about 70%. 4. The rope receiver is swung front and rear for the evenly recoiling and its period can be controlled by gear ratio or hydraulic circuit in accordance with the interval of the loops.

• Journal of the Korean Geotechnical Society
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• v.30 no.10
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• pp.33-44
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• 2014

The preliminary design of suction pile as the supporting system for concrete floating structures was performed for the pilot project of the southwest coast area in Korea. Prior to starting design work, site conditions of the area including ground and hydraulic conditions, and a 100-year return period external force were throughly evaluated. The suction pile for mooring of the offshore floating structures has to satisfy the lateral resistance against external force as well as the penetration ability according to the soil conditions such as soil types, shear strengths, effective stresses, and seepage forces. In the design, the required penetration depths, which were stable for lateral resistance, were evaluated with the diameters of cylindrical suction pile as the final installing ones. And the design suction pressures at each penetrating depths, at which sand boiling did not occur, were assessed through the comparison of penetration and penetrationresistance forces. As a result, it was impossible for suction piles with the diameter range of 3.0~5.0 m to penetrate into required penetration depths. On the other hand, suction piles with the diameter range of 6.0 m and 7.0 m satisfied both the horizontal stability and the penetration ability by design suction pressures at the required penetration depths of 8.5 m and 8.0 m, respectively.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.331-337
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• 2016

Radial collector wells (RCWs) have been managed by Korea Rural Community Corporation (KRC) since 1983, installing 98 wells for agriculture in rural area over the country. Among them, 20 wells were installed upstream of 5 subsurface dams and the remaining were installed regardless of the subsurface dam. Most of RCWs have been developed in 1980s and 1990s, and 83 wells have been passed more than 20 years after construction. The number of horizontal arms for RCWs varies from 9 to 28, with length and diameter being 10~30 m and 65 mm, respectively. The central caisson with an inner diameter of 3.5 m was commonly constructed to a depth of 10 m. The maximum pumping rates in RCWs, which are located at distances of 10 to 1,200 m from the river, are 2,000~10,000 m³/day. RCW has a fundamental problem that reduced pumping capacity and degraded well efficiency, due to the physical and chemical clogging. From the feasibility test for improving RCW performance, specific capacity increased to 67% after rehabilitation. TV logging for RCW horizontal arm shows that near the caisson is more severe clogging. From the results of this study, KRC has established the guidebook for monitoring and improving well efficiency through physical/chemical treatment, well logging, and hydraulic tests and managed RCWs periodically with its rehabilitation methods.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.430-437
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• 2012

In order to obtain information on the design parameters of the horizontal laterals in floodplain filtration, laboratory-scale sand-box experiments were performed where the head distributions on the laterals and the groundwater profiles were measured according to the change in parameters including lateral diameter, hydraulic conductivity of the sand, water level at the well and raw-water supply rate. Measured data were analyzed using a numerical code in order to identify the discharge intensity distribution along the laterals. It was observed from the result that the lowering of the water level at the well had minimal adverse effect on the performance of the floodplain filtration. Results also elucidated that the low conveyance of the laterals to transmit the filtrate was compensated and supplemented by a natural augmentation in horizontal conveyance through the aquifer when the raw-water supply rate exceeded the adequate recovery rate. With this mechanism, the water quality is expected to improve further since the travel distance through the aquifer is amplified. Based on these findings it can be suggested that the diameter of the lateral used in the floodplain filtration may be smaller than those in riverbank/bed filtration. It was also found that the ratio between the head loss occurring in a lateral and the total head loss in the floodplain filtration was proportional to the exit velocities of the laterals, which may be used to design and/or evaluate the lateral in floodplain filtration.

• Journal of Soil and Groundwater Environment
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• v.22 no.6
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• pp.112-119
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• 2017

In this study, the availability of cow manure as raw material for solid fuel production was investigated. Since the water content of the cow manure was too high, it was dewatered using a laboratory hydraulic compressure ($11.3kg/cm^2$). The moisture content of the cow manure decreased from 82.01% to 73.36 wt.%. The dewatered cow manure was homogenized by the experimental apparatus and then put into the rotating cylindrical apparatus. From the consecutive processes, the cow ball-shaped pellet which size ranged from 3.0 to 25.0 mm was produced. The major factor for making palletized fuel from cow manure was the moisture content. Based on the experimental data, the moisture content of cow manure for pelletizing cow manure was identified as 65~75 wt.%. When the moisture content of the cow manure was lower than 30 wt.%, the diameter of the pellets maded from cow manure was smaller than 3 mm. On the other hand, when the water content of the cow manure was higher than 75 wt/%, the diameter of the processed pellets tended to be larger than 25 mm. The characteristics of the processed cow manure pellets was analyzed to be in accordance with the livestock solid fuel quality standard. The pyrolysis characteristic of the pellet was analyzed by raising the heating temperature of the experimental equipment from 200 to $900^{\circ}C$. The mass change between of 20 and $130^{\circ}C$ corresponds to the amount of moisture contained in the cow manure. The amount of moisture was about 15% of the total weight of cow manure samples. The cow manure pellet was thermally stable up to $280^{\circ}C$. It can be interpreted that combustion of cow manure pellet does not occur until the surface temperature reaches $280^{\circ}C$. The mass change of pellet between of 280 and $450^{\circ}C$ was considered to be due to the vaporization of volatile organic compounds (VOCs) present in the cow manure pellet. The maximum production of VOCs was showed near $330^{\circ}C$.