• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.85-87
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• 1994

Feeding biological cells one by one is the key point in the manipulation of cells. The conventional valve systems have many difficulties in feeding cells one by one, because they shut the whole flow of fluids when they are closed and have possibilities of breaking the fragile cells. They need some other equipments for continuous supply of suspension and to protect the cells. We design a check valve for feeding biological cells one by one using polyimide all the silicon substrate. The cells are fed by hydraulic pressure through the isotropically etched cavity. When the suspension flows continuously along the channel the valve is bent by hydraulic pressure and a cell is fed to the outlet. We have studied a cell fusion device fabricated with polyimide and electroplating. If the designed check valve is located in front of the cell fusion device it is helpful to fuse two different kinds of cells.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.199-200
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• 2006

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.718-723
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• 1992

A hydraulic gun/turret servo system requires fast and robust controller performance because of severe operating condition and precise target tracking objective. Digital controllers are able to satisfy this requirement due to high speed electronic device. The purpose of this study is to compare with pre-EPU with new-designed optimal, adaptive controllers by simulating nonlinear hydraulic simulation program. The designed digital controller shows good tracking performance and robustness to disturbance.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1998.12a
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• pp.422-428
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• 1998

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1080-1084
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• 2011

Urban maglev should have such characteristics as not only environmentally friendliness and excellent driving capability but also curve negotiation performance because its routes have many sharp curves. Due to normal mechanism of urban maglev its relative displacements of secondary spring are bigger than conventional railway vehicle and the centering force of levitation magnet is smaller than wheel-on-rail system. These features of maglev affect the curving negotiation and so the additional steering device is to be required on Urban maglev to improve the running performance at sharp curve of less than about R50m. Some developed urban maglev had the passive steering device which consists of mechanical linkage or hydraulic cylinder and closed-route piping. But it has drawback as complexity of layout of understructure of vehicle and functional limitation of passive mechanism regarding transient curve. These demerits could be solved by using active steering system. But it has a weak point that an active device should have actuators and additional inverter or hydraulic power source. In this paper, the semi-active steering system for urban maglev is to be introduced.

• Design & Manufacturing
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• v.15 no.1
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• pp.8-13
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• 2021

Excavators are construction machines used for digging soil, transporting soil, dismantling buildings and clearing the ground at construction sites. There are various attachments attached to the arm end of the excavator and used for various operations. There are the most common types of buckets attached for excavation and other types of attachments used for foresting, road cleaning, snow removal, and waste disposal. When multiple types of work are done at the same time, several attachments must be replaced and a device called a quick coupler is used to reduce replacement time. Although a quick coupler reduces the replacement time of the Attachment, it is necessary to attach safety devices to prevent unintentional detachment of attached attachments during the operation. To prevent the attachment from leaving or falling regardless of the operator's intention, support is installed in the hook of the bucket pin and controlled through a separate hydraulic cylinder to ensure safety. When attaching an attachment, it shall be attached without any action. This study is intended to verify the design validity of safety devices to prevent falls of attachments occurring at construction sites.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.292-301
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• 2014

This paper describes development of distributed type independent electro-hydraulic ballast valve remote control system with diagnostic function based on fuzzy inference using redundant Modbus communication and ethernet Modbus TCP/IP. Diagnostic function estimate degradation of system components and diagnose system faults, which results in shortage of fault maintenance time and improvement of system safety. Slave devices which control each valve and master device which command, monitor and diagnose slave system are developed. Slave devices are connected to master device with redundant Modbus networks and master device is connected to ship's integrated control system with Modbus TCP/IP. Also this paper describes development of simulator to test and confirm whether developed system can be integrated with ship's integrated control and monitoring system.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.153-163
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• 2020

Laboratory experiments were conducted with two different soil conditions to investigate rainfall infiltration characteristics. The soil layer materials that were tested were weathered granite soil and weathered gneiss soil. Artificial rainfall of 80 mm/hr was reproduced through the use of a rainfall device, and the volumetric water content and matric suction were measured. In the case of the granite soil, the saturation velocity and the moving direction of the wetting front were fast and upward, respectively, whereas in the case of the weathered gneiss soil, the velocity and direction were slow and downward, respectively. Rainfall penetrated and saturated from the bottom to the top as the hydraulic conductivity of the granite soil was higher than the infiltration capacity of the artificial rainfall. In contrast, as the hydraulic conductivity of the gneiss soil was lower than the infiltration capacity of the rainfall, ponding occurred on the surface: part of the rainfall first infiltrated, with the remaining rainfall subsequently flowing out. The unsaturated hydraulic conductivity function of weathered soils was determined and analyzed with matric suction and the effective degree of saturation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1705-1709
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• 2005

The hydraulic LSD which uses the principle of gear pump is packed with viscous oil in tight container. When a slip occurs on one wheel, the hydraulic LSD generates torque caused by high oil pressure in the container. In this study, two dimensional(2-D) side pinion gear model was developed for hydraulic LSD. Using that model the flow analysis was conducted to preestimate pressure distributions of the side pinion gear according to the variations in the design factors such as oil viscosity, gear gap and rpm. Then, applying the obtained pressure distributions on the side pinion gear, finite element analysis was conducted to evaluate the torque characteristics. From the analysis results, the torque characteristics according to the design factor variations were evaluated.

• Tunnel and Underground Space
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• v.5 no.3
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• pp.251-265
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• 1995

One of the most important matters in stress measurement by hydraulic fracturing technique is the determination of the breakdown pressure, reopening pressure, and shut-in pressure, since these values are the basic input data for the calculation of the in-situ stress. The control of the fracture propagation is also important when the hydraulic fracturing technique is applied to the development of groundwater system, geothermal energy, oil, and natural gas. In this study, a laboratory scale hydraulic fracturing device was built and a series of model tests were conducted with cube blocks of Machon gabbro. A new method called 'flatjack method' was adopted to determine shut-in pressure. The initial stress calculated from the shut-in pressure measured by flatjack method showed much higher accuracy than the stress determined by the conventional method. The dependency of the direction of fracture propagation on the state of the initial stresses was measured by introducin g artificial slots in the borehole made by water jet system. Numerical modeling by BEM was also performed to simulate the fracture propagation process. Both results form numerical and laboratory tests showed good agreement. From this study which provides the extensive results on the determination of shut-in pressure and the control of fracture propagation which are the critical issue in the recent hydraulic fracturing, it is conclued that in-situ stress measurement and the control of fracture propagation could be achived more accurately.