• Advances in Traditional Medicine
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• v.5 no.4
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• pp.331-335
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• 2005

The methanolic extract of Hibiscus vitifolius flowers (HVE), was evaluated for neurophamacological activities by carrying out rota rod, locomotor activity and traction performance in mice and swim endurance activity in rats in different dosages (10, 30 and 100mg/kg body weight). HVE showed a significant effect on central nervous system by increasing the time taken for rota rod, traction performance and locomotor activity while swimming time was found to be decreased when compared to normal control animals. These results suggest that HVE possess significant anxiolytic and anti depressant activity which may be attributed to the presence of flavonoid in HVE.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.169-172
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• 2009

Multiple scale modeling has been applied to predict defect shape change during the wire rod rolling process. The size difference between bloom and defect prevent using usual FEM approaches due to the enormous number of elements required to depict the defect. The newly developed multiple scale model can visualize defect shape changes during the multi stands rolling process. The defect positioned at the top and side of bloom are smoothed out but the one at the middle evolved as folding or remained as crack. This approach can be used for defect control with roll shape design and initial bloom shape.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.402-407
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• 2014

In this paper, residual sway control of objects that are moved underwater is investigated. The fuel transfer system in a nuclear power plant transfers the nuclear fuel rods underwater. The research on the dynamics of the loads transferred in different mediums (water and air) and their control methods have not been fully developed yet. The attenuation characteristics of the fuel transfer system have been studied to minimize its residual vibration by considering the effects of hydrodynamic forces acting on the fuel rod. First, a mathematical model is derived for the underwater fuel transfer system, and then experiments have been conducted to study the dynamic behavior of the rod while it travels underwater. Lastly, the residual vibration at the end point is minimized using the input shaping technique.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.85-92
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• 2018

In order to use glued built up timber beam as a structural member for post and beam construction, it must be possible to manufacture long-span lumber. In this study, the researchers conducted a performance evaluation for longitudinal bonding of lumber (cross-section $89{\times}120mm$) made from larch. The specimens were prepared in six different forms using the longitudinal bonding method. The bonding strength of these specimens was tested through tensile strength tests and bending strength tests. The tensile strength test result of the longitudinally bonded parts was better than that of the double lap specimens. And, the tensile strength value of the scarf specimen was better than that of the hooked scarf specimen. The tensile strength of the GFRP (Glass Fiber Reinforced Plastic) rod insertion bonding specimen was 3.6 MPa, which was the highest. As for the bending strength test result of the longitudinally bonded part, the average MOR (modulus of rupture) of the specimen where a GFRP rod was inserted and bonded measured 29 MPa, while the specimens of other bonded parts showed a MOR no more than 11 MPa. Toughness destruction was observed in specimens where a GFRP rod was insertion-bonded. The rest of the specimens showed brittle destruction. The average MOR strength of the Rod + Lap specimen was 30.5 MPa, which was the highest among all longitudinally bonded specimens. The bending strength of the Rod + Lap specimens showed an effective strength that was 66% of that of the control group which were not longitudinally bonded.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.807-814
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• 2015

A control rod drive mechanism(CRDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod containing a neutron absorbing material within a reactor core to control the reactivity of the core. The top-mounted CRDM for Jordan Research and Training Reactor(JRTR) with 5 MW power has been designed and fabricated based on the HANARO's experience through KAERI and DAEWOO consortium project. This paper describes the performance qualification test results to demonstrate the operability of a prototype and four production CRDMs during the reactor lifetime. The driving performance, the drop performance and the endurance tests for CRDM are carried out at a test rig simulating the actual reactor conditions. A vibration of internal components due to the coolant flow is also measured using a laser vibrometer. As a result, the CRDMs are driven having a good driving performance without a malfunction between command and output signals for the stepping motor. Also, the pure drop time and the impact acceleration are within 0.72 s and 4.2 g to meet the design requirements, and the vibrational displacement of control rod is measured as maximum $5.2{\mu}m$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.307-316
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• 2004

This study examined the cause of the wrinkle defect which is frequently encountered in wire rod rolling of low carbon steel$(C0.08\~0.13wt.\%)$. Even a small defect on the surface of rolled bars can easily develop into fatal cracks during cold heading process of low carbon steel, and it is therefore necessary to minimize inherent defects on the surface of hot rolled bars. Hot rolling process of low carbon steel was analyzed to identify the cause of the wrinkle defect in conjunction with FE analysis. The integrated analysis revealed that the wrinkle defect initiated in the first stage of rolling, and it was at the billet edge where severe deformation and drastic temperature drop were present. To elucidate the micro-mechanical mechanism of the wrinkle defect, hot compression tests were carried out at various temperatures and strain rates using Gleeble-3800. The surface profile of the each other compressed specimens was compared, and rough surface lines were observed at relatively low temperatures. Those surface defects can develop into wrinkles during multi-pass rolling. To control the wrinkle defect in rolling, it is necessary to design an adequate caliber which can minimize the loss of ductility, and thereby prevent flow localization. To use the result of this study fur other steels, the quantitative measure of the wrinkle defect and flow localization parameter should be proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7745-7753
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• 2015

Gas springs of the television is to control the piston speed when operating under along stroke(200~300 mm, television elevation)is possible. User by this principle is capable of elevation adjustment. First carried out a flow analysis of the piston. A piston speed adjustment technique for precise pipe type cross-section was examined. The piston structure for flow rate control and elevation action is proposed. This study is the development of a gas spring of more than 50 inch television with a large television stand. Hollow piston rod for optimal control(the outer diameter 19.9 mm, the inner diameter 13.9 mm) was injected into the nitrogen gas(0.3 mm/s) in. As a result, the flow rate the pressure drop of the piston rod as the increase was increased without any change of the external force. As a result, control of the displacement via the gas spring is possible.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.6
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• pp.3-10
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• 2018

This paper described the shear strengthening effect by deviator location in pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. Three reinforced concrete beams as control beam and eight post-tensioned beams using external steel rods were tested to fail in shear. The externally post-tensioning material was a steel rod of 22 mm diameter, and it had a 655 MPa yield strength and an 805 MPa tensile strength. Specimens depend on multiple variables, such as the number of deviators, location of deviator, and load pattern. The pre-damaged loads up to about 2/3 of ultimate shear capacities were applied to specimens using displacement control and the diagonal shear crack just occurred at these loading levels. And then, the post-tensioning up to when a strain of steel rod reaches about $2000{\mu}{\varepsilon}$ was continuously applied to beam. A displacement control was changed to a load control during post-tensioning. The post-tensioning resulted in increase of load-carrying capacity and restoration of existing deflection. Also, it prevented the existing diagonal cracks from excessively growing. Two deviators effectively improved the load capacity when compared with in case of test which one deviator at mid-span installed. When deviators were located near region which the diagonal crack occurred on, the strengthening impact by post-tensioning was greater.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2397-2408
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• 1996

A numerical study was made of the control of transient oscillatory flow modes in Czochralski convection. The reduction of temperature oscillation was achieved by changing the rotation rate of crystal rod, .OMEGA.$_{S}$=.OMEG $A_{S0}$(1+ $A_{S}$sin(2.pi. $f_{S}$/ $t_{p}$t)). The temporal behavior of oscillation flow was scrutinized over broad ranges of two parameters, i.e., the rotation amplitude( $A_{S}$.leq.0.5) and the nondimensional frequency (0.9.leq. $f_{S}$.leq.1.5). The mixed convection parameter was ranged 0.225.leq.Ra/PrR $e^{2}$.leq.0.929, which encompassed the buoyancy-and forced-dominant convection regimes. Computational results revealed that the temperature oscillations could be reduced effectively by a proper adjustment of the control parameters. The uniformity of temperature distribution near the crystal rod was examined. The control of oscillatory flow modes was also made for a realistic, low value of Pr.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.638-640
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• 2002

This paper introduces the design method of a Control Rod Drive Mechanism that consists of 3 coils -lift, movable gripper and stationary gripper coil. The vertical attraction forces of the lift, movable gripper, and stationary gripper armatures are calculated by FEM, then the dynamics with full load is demonstrated.