• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3649-3654
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• 1996

A transient hydraulic flow rate computation scheme is described here so that the transient hydraulic flow rate can be determined using the dynamic pressure measurements at the ends of a straight flow line with a dynamic model of the hydraulic line. This method can be applied to determine the orifice ares of high response valve. Simulation results indicate that the method is relatively robust to realistic levels of uncertainties in the fluid properties.

• 연구논문집
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• s.30
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• pp.93-99
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• 2000

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. The electrical and rheological properties of zeolite based the ER fluids were reported. The electric field dependent yield stress are obtained from experimental investigation on the Bingham property of the ER fluid. Using ER fluids, it is possible to directly interface between electric drop and flow rate of the ER fluid was hydraulic control valve measured under application of an electric field. The purpose of the present study is pressure drop measurement of an ER valve by using strain gage. The performance characteristics of the valve system are evalusted in terms of pressrue fixed with respect to the intensity of employed electric fields and flow rates. As a result, it is esperimentally confirmed that pressure control valve using ER fluids applicable to use in hydraulic power systems.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.549-556
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• 2002

Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins and jetty). It can also be used to isolate contaminated material from harbor, detention basin dredging, and to use this unit as dikes for reclamation work. Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. The stability analysis of geotextile tube is composed geotechnical and hydrodynamic analysis. The stability check points are sliding failure, overturning, bearing capacity failure against the wave attack. In this paper presented the construction procedure and in-situ measurement(properties of filling material, effective height variation, stress variation at geotextile tube bottom) of geotextile tube at Young-Jin Bay and stability analysis by theoretical method and hydraulic model tests

• The Journal of Korea Robotics Society
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• v.14 no.4
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• pp.348-356
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• 2019

The backdrivable servovalve is a desirable component for force and interaction control of hydraulic actuation systems because it provides direct force generation mechanical impedance reduction by its own inherent backdrivability. However, high parametric uncertainty and friction effects inside the hydraulic actuation system significantly degrade its advantage. To solve this problem, this letter presents a disturbance-adaptive robust internal-loop compensator (DA-RIC) to generate ideal interactive control performance from the backdrivable-servovalve-based system. The proposed control combines a robust internal-loop compensator structure (RIC) with an explicit disturbance estimator designed for asymptotic disturbance tracking, such that the controlled system provide stable and ideal dynamic behavior for impedance control, while completely compensating the disturbance effects. With the aid of a backdrivable servovalve, we show that the proposed control structure can be implemented based on a simplified nominal model, and the controller enables implementation without accurate knowledge of the target system parameters and disturbances. The performance and properties of the proposed controller are verified by simulation and experiments.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.74-79
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• 2021

In this paper, the 3D shape of a hydraulic actuator cover was 3D printed by applying two materials, namely PLA and ABS. Subsequently, the printed shape was scanned to analyze the material properties, dimensional change characteristics, dimensions, and scan shape as a real model. To compare and analyze material-specific 3D printing dimensions, a non-contact mobile laser scanner was used to scan a portion of the printed hydraulic actuator cover and the final alignment shape of the 3D printed part was studied on the basis of the design model.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.3
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• pp.235-241
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• 2016

The soil does not only serve as a medium for plant growth but also for engineering construction purposes. It is very weak in tension, very strong in compression and fails only by shearing. The behaviour of the soil under any form of loading and the interactions of the earth materials during and after any engineering construction work has a major influence on the success, economy and the safety of the work. Soils and their management have therefore become a broad social concern. A limitless variety of soil materials are encountered in both agronomy and engineering problems, varying from hard, dense, large pieces of rock through gravel, sand, silt and clay to organic deposits of soft compressible peat. All these materials may occur over a range of physical properties, such as water contents, texture, bulk density and strength of soils. Therefore, to deal properly with soils and soil materials in any case requires knowledge and understanding of these physical properties. The desired value of bulk density varies with the degree of stability required in construction. Bulk density is also used as an indicator of problems of root penetration,soil aeration and also water infiltration. This property is also used in foundation engineering problems. While not conforming to standard test procedures, this work attempts to add to the basic information on such important soil parameters as water content, bulk density.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.99-109
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• 1999

In the case of domestic general waste landfills, cumulated leachate level is often formed in the landfill due to the waste of high moisture content and it becomes important to characterize the hydraulic properties of the disposed waste. Although many hydrologic studies have been peformed for leachate barriers and pheriperal subsurface environments, few studies have been done to investigate the hydraulic property of the disposed waste and cover soils and to analyse the leachate flow behavior within landfills. In this paper, the geotechnical properties of the waste and buried cover soils are identified through the field experiment including pumping and slug tests. The results of various tests show that the field density of the cover soils is somewhat higher than the maximum laboratory density of cover soils and the vertical flow of leachate and gas in the landfill is prevented by the buried cover soils. The hydraulic conductivities of field pumping test and slug tests are well matched and stayed in the range of hydraulic conductivities of well compacted wastes in the literature.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.655-661
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• 2016

Relationships between saturated conductivity (Ks) and separate contents were evaluated from 44 soil series of arable lands: 18 for paddy fields and 26 for upland crop fields. Saturated hydraulic conductivities of A, B, and C horizons were determined with tension infiltrometer and Guelph permeameter in situ. Sand, silt, clay, and organic matter content of each horizon were analyzed. Based on correlation analysis, sand separate had a positive relationship with Ks for both paddy (r=0.27, p=0.017) and upland fields (r=0.24. p=0.030). Clay content had a negative relationship with Ks for paddy soils (r=-0.32, p=0.005) while significant correlation between them was not found for upland crop fields (r=-0.20, p=0.07). Organic matter content showed a positive relationship with Ks only for upland crop fields (r=0.33, p=0.002). Due to low correlation coefficients between separate contents and Ks, performance of pedotransfer functions was not enough to estimate Ks. It implies that hydraulic properties of arable lands were affected by other factors rather than particle characteristics. Platy structure and plow pan were suggested to limit Ks of paddy fields. Soil compaction and diversity of parent materials were proposed to influence Ks of upland crop fields. It suggests that genetic processes and artificial managements should be included in pedotransfer functions to estimate hydraulic properties appropriately.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.542-546
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• 2001

Converter slag has some compositional similarities to portland cement. But it has no hydration properties due to it's quite high concentrations of FeO(20-35%), MnO(4-6.5%). So it is needed to reduce the concentrations of iron and manganese of converter slag to use as cement additives by enhancing it's hydration properties. In this study, converter slag was modified it's composition by mixing of silica, alumina and quenched BF slag and reduced in induction furnace and quenched in running water. The hydraulic properties and structures of modified and quenched converter slag are significantly changed depend on the amount and kinds of additives. The addition of alumina up to 10% and BFQ slag up to 20% by weight on converter slag was effective to enhance the hydraulic properties of modified and quenched slag. The addition of reduced and quenched converter slag up to 20% by weight in replacement of portland cement in mixing of concrete mortar were shown higher compressive strength than 100% cement concrete mortar.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.121-131
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• 2020

In this paper, the transmissivities obtained from the pulse test, the slug test and the constant head test were compared each other to assess an applicability and a reliability of the hydrogeological test method, which are commonly used to derive the hydrogeological properties of a crystalline rock at un underground research facility. When comparing the results of the pulse test and the slug test, the transmissivities were very similar in the entire test section of the medium. However, there was a little discrepancy in the results in the areas where the permeability is relatively high. The results of the constant head test on the same section showed the lower transmissivity than the results of the pulse test and the slug test on the highly permeable section. This difference in permeability was considered to be due to the difference in the radius of the hydraulic effect applied in each hydraulic test. When the heterogenetic distribution of fracture affects the hydrogeological properties on crystalline rock, it is believed that the hydrogeological characteristics can be explained through a constant head test or a constant flow rate test with a large hydraulic effective radius, as well as a pulse and a slug test that can identify hydrogeological properties in a relatively short time.