• Transactions of Materials Processing
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• v.17 no.3
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• pp.182-188
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• 2008

Crash box is one of the most important automotive parts for crash energy absorption and is equipped at the front end of the front side member. The specific characteristics of aluminum alloys offer the possibility to design cost-effective lightweight structures with high stiffness and excellent crash energy absorption potential. This study deals with crashworthiness of aluminum crash box for an auto-body with the various types of cross section. For aluminum alloys, A17003-T7 and A17003-T5, the dynamic tensile test was carried out to apply for crash analysis at the range of strain from 0.003/sec to 200/sec. The crash analysis and the crash test were carried out for three cross sections of rectangle, hexagon and octagon. The analysis results show that the octagon cross section shape with A17003-T5 has higher crashworthiness than other cross section shapes. The effect of rib shapes in the cross section is important factor in crash analysis. Finally, new configuration of crash box with high crash energy absorption was suggested.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.5
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• pp.414-420
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• 2014

In this paper, the vibration characteristics of the trapezoidal corrugated plate with axial stiffeners and lumped masses are investigated by the analytical method. The corrugated plate can be treated as an equivalent orthotropic plate as this plate has different flexure properties in two perpendicular directions; flexible in the corrugation direction and stiff in the transverse direction. The effective extensional and flexural stiffness of the equivalent plate are considered to obtain the precise solution in the analysis. The plate is stiffened by concentric stiffeners horizontally to the corrugation direction. The discrete stiffener theory is adopted to consider the position of stiffener. To demonstrate the validity of the proposed approach, the comparison is made with the results of 3D ANSYS finite element solutions. Some numerical results are presented to check the effect of the geometric properties.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.71-78
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• 2002

This paper is concerned with the design and implementation of magnetic damper system to reduce the vibration of suspension system actively. Cylindrical type electro-magnetic actuator with permanent magnet is analyzed and effective controller design is made. Magnetic force analyzed and transfer function for the total system is determined by experimental data using error minimization method. For experiments, simple suspension structure system is utilized, in which a magnetic damper composed of permanent magnet and digital controller is attached. In order to drive the system, bipolar power amplifier of voltage control type is utilized. Stable and high speed control board is used to perform digital control logic for the given system. This paper shows that the magnetic damper system using phase-lead controller excellently reduces vibration of 1-D.O.F (degree of freedom) suspension system.

• Journal of the Korean Society of Physical Medicine
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• v.1 no.1
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• pp.67-75
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• 2006

Purpose : The main purpose of this study was to investigate the effect on Balance Ability of Knee Osteoarthritis(OA) by modality. Methods : The subjects were consisted of 30 women patients with knee OA. All subjects were randomly assigned to modality group. Each group had a treatment for 45 minutes per day and three times a week during 8 weeks period. Was used to measure recovery or worse of patient's condition, muscle assessment questionnaire(MAQ) was used to measure patient's muscular strength, Endurance, coordination/balance, KWOMAC was used to pain, stiffness, and physical function, and BPM was used to measure velocity, anterior-posterior. Results : This study results in following conclusions. 1. MAQ score was significantly decreased in modality group(p<.05). 2. KWOMAC score was significantly decreased in modality group(p<.05). 3. BPM were score was significantly decreased in modality group(p<.05). Conclusions : From this result the modality treatment retrogression characteristic will be effective in treatment of patient.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.3
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• pp.21-29
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• 2011

Recently, the use of recycled fibers was increased in order to replace the virgin pulp for low production cost and forest conservation. However, the recycled fibers decreases drainage rate, papermaking efficiency and product quality by short fibers and low wettability because of hornification. To overcome the limitation of low drainage rate, the technology of organic fillers were applied. Wooden fillers gave high bulk and stiffness of paper, but they reduced the strength of paper. In order to improve strength properties 4 types of strength additives were added and analyzed. Cationic starch, branched strength additive, linear wet strength additive, and linear dry strength additive were used. The drainage rate and paper properties such as bulk, air permeability and tensile strength were measured. As results of analysis, addition of branch type of strength agent such as C-starch was effective than linear type of strength agent in the drainage rate. Nevertheless there was no effect on the drainage rate by adding the pretreated wooden fillers. By adding the pretreated wooden fillers, bulk, air permeability and tensile strength of handsheets were improved with low dosage than non-pretreated fillers.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.421-424
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• 2012

Carbon Fiber reinforced composite material can be designed for the optimized performances of structural member that have achieve appropriate mechanical properties with cross-sectional shape, fiber direction, stacking sequence and thickness. So there are needed extensive databases each optimal design of CFRP structural member by impact through the preparation of different shape, interface number, thickness and stacking angle. When pressure is applied to structural member, compression, bending and torsion is shown on the corresponding member. For the effective utilization of fiber reinforced composite material as main structural member, optimized design technology should be established to maximize mechanical properties for compression, bending and torsion. In this paper, CFRP prepreg sheet with different stacking angle is manufactured in CFRP and hybrid(Al+CFRP) with circular cross-section. Strength and stiffness is gotten respectively by flexure test. CFRP structure and hybrid structure can be compared with each other. The best design guideline can be analyzed by use of this study result.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.968-975
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• 2012

ABS(Anti-skid Brake System) had been developed on purpose of most effect at breaking in limited runway. An aircraft has a large amount of kinetic energy on landing. When the brakes are applied, the kinetic energy of the aircraft is dissipated as heat energy in the brake disks between the tire and the ground. The optimum value of the slip during braking is the value at the maximum coefficient of friction. An anti-skid system should maintain the brake torque at a level corresponding to this optimum value of slip. This system is electric control system for brake control valve at effective control to prevent slip and wheel speed or speed ratio. In this study we measured the thickness of the carbon disk before and after to find its wear and it shows that carbon disk brake has higher stiffness and strength than metal disk at high temperature. In addition, thermal structural stability and appropriate frictional coefficient of the carbon disk brake prove its possible substitution of metal disk brake.

• Journal of the Korean Wood Science and Technology
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• v.26 no.3
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• pp.9-15
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• 1998

The strength and stiffness of structures would be weakened by thermal degradation of wood members which are exposed to a variety of heat including a fire. For this reason, thermal degraded wood members can't pertinently support the load. However, it is easy to repair or rehabilitate wood structures. So, the degraded wood members which can't support the load can be replaced with new members. For the sake of this advantage, there is a need for nondestructive evaluation(NDE) technique, which is very effective to assess wood members in service. In this paper, it was considered whether the stress wave method is adequate to estimate static bending MOE of thermal degraded wood. As the result, the relationship between static bending MOE and MOEsw in elevated temperature was found out significant. Therefore, the application of stress wave method for estimating static bending MOE of thermal degraded zzwood would be possible. However, it is thought that further research for the effects of exposure temperature, time, and thermal degradation on the relationship between static bending MOEb and MOEsw would be needed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.6
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• pp.50-55
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• 2014

An oxidized starch was modified for surface sizing via etherification and esterification. Propylene oxide (PO), sodium monochloroacetate (SMCA), and acrylonitrile (AN) were used as etherification, and vinyl acetate monomer (VAM), maleic anhydride (MA), fumaric acid (FA), and itaconic acid (ITA) were used for esterification. Esterification and etherification of starch decreased both Brookfield viscosity and Brabender viscosity substantially even though the solids level was increased by 2% from 14 to 16%. Surface sizing performance of starches in tensile strength, stiffness and compressive strength was improved by esterification and etherification of the oxidized starch. Especially, SMCA etherification was found to be the most effective modification method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1338-1346
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• 2009

We present a one-dimensional annular plate element with which the in-plane vibration of full disks can be analyzed efficiently and accurately by using the FEM. Its elementary mass matrix and stiffness matrix are derived, respectively, from the virtual work by effective forces and the virtual strain energy. The static deformation modes obtained from an integration of the differential equilibrium equations of the annular plate are used as interpolation functions of the one-dimensional annular plate element. The in-plane natural vibration characteristics of a 2-step full disk and a uniform full disk are analysed. Its results are compared with the results obtained by utilizing two-dimensional 8-node quadrilateral plane elements and cyclic symmetry of the disk. And also, by comparing with the theoretical results of previous researchers, the efficiency and accuracy of the presented element are verified.