• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.483-489
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• 2005

For the raw materials of 3CaO$\cdot$3Al$_{2}$O$_{3}$ $\cdot$CaSO$_{4}$(CSA) clinker manufacturing, the applications of industrial wastes such as waste shell, spent oil-refining catalyst and desulfurized gypsum were examined. The c1inkerbility of the raw mix and the behaviour of formation of clinker minerals were studied and then some hydraulic properties of cements containing the clinker were also investigated. By virtue of the high reactivity of thermally decomposed raw materials, CSA clinkers were obtained at relatively low temperature of 1250$^{\circ}C$ and thus oil-refining catalysts were more desirable than aluminium hydroxide as an aluminous raw material. The expansive cement samples showed somewhat lower flow value than that of OPC, but their compressive strengths were developed earlier and higher than that of OPC due to formation of ettringite in the early hydration time, which indicated the possibility of practical use of low-cost CSA clinker using industrial wastes only.

• Journal of Drive and Control
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• v.15 no.1
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• pp.38-49
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• 2018

This research describes the development model and testing of a hybrid damper which can be applicable to a vehicle suspension. The hybrid damper is devised to improve the performance of a conventional passive oil damper using a magneto-rheological (MR) accumulator which consists of a gas accumulator and a MR device. The level of damping is continuously variable by the means of control in the applied current in a MR device fitted to a floating piston which separates the gas and the oil chamber. A simple MR device is used to resist the movement of floating piston. At first a mathematical model which describes all flows within the conventional oil damper is formulated, and then a small MR device is also devised and adopted to a mathematical model to characterize the performance of the device.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.927-935
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• 2016

A gerotor is suitable for miniature manufacturing because it has a high discharge per cycle and a simple structure, while also being widely used as lubrication oil of engines and the hydraulic source of automatic transmission. In the automobile industry, it has been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor design. In this study, to obtain an optimal gerotor with an ellipse-elliptical involute-ellipse combined lobe shape, an automatic program was developed for calculating performance parameters and drawing a gerotor profile. An oil pump was assembled with the optimal gerotor together with the port used at the actual field and CFD analysis was performed on this assembly using Ansys-CFX. A performance test for the oil pump was carried out and showed good agreement with the results obtained from the theoretical analysis and the CFD analysis.

• Analytical Science and Technology
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• v.18 no.5
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• pp.410-418
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• 2005

PCBs had numerous uses such as hydraulic fluid, heat exchange fluid, sealant, lubricant, and carbonless copy paper. They are most likely found in electric utilities, power stations, industrial facilities, electronic manufacturing plants, petrochemical plants, railroad systems, electric equipment repair facilities, mining sites (active or abandoned), and military camps. Due to its outstanding chemical and thermal stabilities and electrical insulation properties, the commercial and industrial products of PCBs, such as Aroclors, Kaneclors, Clophens, Phenaclors etc., had been widely used as thermal oil and transformer oil from 1930s until the 1970s. The transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. Qualitative estimation of oil extracts as carried out with Aroclor 1242, 1248, 1254, 1260. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. Also, commercial screening kit of 20 ppm and 50 ppm were applied to the transformer oil samples.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.37-50
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• 2001

Through the modeting study on the groundwater now system around the underground stockpile site of crude oil near Seoul, we carried out the research on the influence of the groundwater yield near the site, the effect of the water curtain construction in order to reduce the influence of water yield, and the realized case study by measuring the water level change after the construction of the water curtain. For the simu1ation of the water yield and the water curtain, the nwnerical analysis code, MODFLOW has been utilized. Groundwater levels of the observation wells which were established to observe the hydraulic head around underground oil storage cavern of the study area have been changed in the range of from EL.+30 to +60 meter, while the simulation study revealed that groundwater levels changed in the range of from EL.+20 to +5Om. The hydrogeological condition of the underground oil storage cavern becomes stable by injection water to maintain the groundwater level around the cavern. The result shows the proper input of the hydrogeological factors helps the management to be effective for the oil stockpile site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.548-553
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• 2013

EHPS(Electro-Hydraulic Power Steering) is a system to generate the steering operation force from the electric motor connected directly to the oil pump. To optimize the manufacturing cost and efficiency of the performance of the steering system is very important. Until now, the development of the hydraulic system is implemented by the field test which needs a significant time and cost. In this paper, flow measurement of an external gear pump is performed. Then using the experimental results, an approximate model expressed by flow rate characteristics is proposed to calculate the discharge flow rate. Proposed approximate model is verified by comparing with the experimental data and AMESim results. As the experimental data and AMESim results agree well, the approximate model data can be used as an alternative to highly cost experimental procedure.

• Tunnel and Underground Space
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• v.28 no.3
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• pp.258-276
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• 2018

The accurate and quantitative ground information on the hydraulic conductivity characteristics of rock mass is one of the key factors for evaluation of the hydro-geological behaviour of rock mass around an excavated opening under high water pressure. For tunnel and rock structures in seabed, where the sea acts as an infinite source of water, its importance become greater with increasing construction depth below sea level. In this study, to improve the problems related with poor system configuration and incorrect data acquisition of previous hydraulic packer testing equipment, we newly developed an integrated main frame and 30 bar level waterproof downhole sonde apparatus, which were optimized for deep hydraulic packer test in seabed rock mass. Integration of individual test equipment into one frame allows safe and efficient field testing work on a narrow offshore drilling platform. For the integrated type main frame, it is possible to make precise stepwise control of downhole net injection pressure at intervals of $2.0kg_f/cm^2$ or less with dual hydraulic oil volume controller. To ensure the system performance and the operational stability of the prototype mainframe and downhole sonde apparatus, the field feasibility tests were completed in two research boreholes, and using the developed apparatus, the REV(Representative Elementary Volume) scale deep hydraulic packer tests were successfully carried out at a borehole located in the basalt region, Jeju. In this paper, the characteristics of the new testing apparatus are briefly introduced and also some results from the laboratory and in-situ performance tests are shown.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.822-829
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• 2015

In this paper, the piezoelectric-hydraulic pump with a piezostack actuator as a driving source has been designed, fabricated, and evaluated for its application to UAV's brake system. The performance requirements of the piezoelectric-hydraulic pump were decided based on the requirements analysis of the target aircraft brake system. The geometric design of the piezoelectric-hydraulic pump to meet the performance requirements of the pump was conducted, and all components of the pump including the spring sheet type check valves were machined with close tolerance. By constructing a test apparatus for the performance check of the piezoelectric-hydraulic pump, the performance characteristics of the pump, such as the outlet flow rate for load-free condition and the outlet oil pressure for closed loop condition, have been evaluated. It has been found by the performance test result that the developed piezoelectric-hydraulic pump satisfies the design requirements effectively.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.1-7
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• 2003

A modified model was developed for solute transport in porous media that can consider the movement of an LNAPL above the water table. From the results of sensitivity analyses with and without considering LNAPL movement, there are some differences according to the hydraulic gradient, the quantity of oil leakage and dispersivity. The mean deviation between the model in this study and a conventional model without LNAPL movement increases as the hydraulic gradient decreases and the quantity of oil leakage increases. Variation of dispersivity has no influence on the magnitude of the mean deviation. However, the spatial distribution of the deviation between the two models is wider as dispersivity increases. Furthermore, groundwater is at high risk of contamination in the vertical direction in the case that transverse dispersion value is large. A conventional model underestimates the concentration of solute in an aquifer where the movement of an LNAPL cannot be negligible: Based on the study results, it is important to understand how fast the LNAPL moves on the water table for realistic prediction of solute transport in an aquifer with the movable LNAPL on the water table.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.409-417
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• 2016

The shale gas is emerging as one of the oil and gas resources which can replace the traditional oil and gas resources. As the shale layer where the shale gas is deposited has low permeability, the hydrofracturing method is required to improve the productivity. This study is designed to conduct the laboratory hydrofracturing test on the samples which are modeled after the drilling hole having the general drilling hole and spiral groove. And compare the initial fracturing pressure and fluid contact between them in order to the result of the hydrofracturing depending on the shape of the drilling hole. In addition, the results were compared with the numerical modeling values from 3DEC and they were also compared with the data from the advance researches. It was found from the study that rather than the contact area of the high pressures water, the force concentration depending on the form of guide hole was more effective in the hydrofracturing.