• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.76-81
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• 2003

The purpose of this study is to analyze the collapse characteristics of widely used spot welded section members coated damping material Y1000 and to develop an analysis method for acquiring exact collapse loads and energy absorption ratio. Hat-shaped thin-walled members have the biggest energy absorbing capacity in a front-end collision. The sections were tested on quasi-static and impact loads. Specimens with two type thickness, width ratio and spot weld pitch on the flange have been tested in impact velocities(6.73n0sec and 7.54n1sec) which imitate a real-life car collision. As a result, it was developed the system for acquiring impact energy absorbing characteristics of structure united thin-walled member and damping materials.

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.195-208
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• 2000

To confirm the theory and static defect energy (SDE) equations proposed in the first part, extensive numerical simulation studies are performed in this portion. Stiffness method is applied to calculate the components of the stresses and strains from which the energy components and finally, the SDE are obtained. Examples are designed to cover almost all kinds of possibilities. Variables include structural type, material, cross-section, support constraint, loading type, magnitude and position. The SDE diagram is unique in the way of presenting damage information: two different energy constants are separated by a sharp vertical drop right at the damage location. Simulation results are successfully implemented for both methods in all the cases.

• Journal of Sensor Science and Technology
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• v.21 no.3
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• pp.172-179
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• 2012

This paper presents the design and analysis of a vibration-driven electromagnetic energy harvester that uses a multi-pole magnet. The physical backgrounds of the vibration electromagnetic energy harvester are reported, and an ANSYS finite element analysis simulation has been used to determine the different alignments of the magnetic pole array with their flux lines and density. The basic working principles for a single and multi-pole magnet are illustrated and the proposed harvester has been presented in a schematic diagram. Mechanical parameters such as input frequency, maximum displacement, number of coil turns, and load resistance have been analyzed to obtain an optimized output power for the harvester through theoretical study. The paper reports a maximum of 1.005 mW of power with a load resistance of $1.9k{\Omega}$ for 5 magnets with 450 coil turns.

• The Journal of Korean Institute for Practical Engineering Education
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• v.2 no.2
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• pp.42-48
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• 2010

For a basic engineering education Problem-Based Learning (PBL) method was adopted in order to pursuit the learner acquisition of critical knowledge, problem solving proficiency, and self-directed learning strategies by measurements of various physical and biological units, by calculation of errors in experimental data, by leraning energy conservation law and equation of motion, and, by analysis ability on data patterns through Elliptical Trainer(ET) exercise. The results show the ET may be a good experimental tool for understanding the PBL method. A sample syllabus was provided for one semester use, and by use of data obtained by self-directed and creative learning, the results of three groups for the PBL problems proposed by using ET were (1) the slope of angle was 23.5o in the diagram of energy exhaustion against velocity (GROUP A), (2) the angle range between the maximal and minimal energy exhaustion against weight loss was 15.0o ~ 26.5o (GROUP B), and finally (3) the angle was varied by 51.0o in the diagram of weight loss against distance (GROUP C).

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.160-170
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• 1997

The objective of this study is to investigate the atomization characteristics and the performance characteristics of a C. I. engine by using the changes of the injection nozzle type and the ultrasonic-energy-added system. In order to evaluate the effect of ultrasonic energy and of change of injection nozzle type in the performance characte- ristics of a diesel engine, measurements of droplet size of diesel fuel were carried out by using Malvern system. In all types of injection nozzles, SMD of the ultrasonic- energy -added diesel fuel was smaller than that of the conventional diesel fuel and the more injection pressure increased, the more SMD decreased. There was a small increase in SMD with the distance from injection nozzle under all conditions of the injection nozzle types. The minimum SMD was found in the injection nozzle of B type. In the diesel engine test, there were three results about the engine performance. Compared with the injection nozzle of A type, B type had excellent effects in the engine performance. The most excellent effects about the engine performance were obtained in the case of ultrasonic-energy-added diesel fuel. In addition, the torque diagram in the case of ultrasonic-energy-added diesel fuel was more stable and periodical than others.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.636-640
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• 2012

We modify ZnO nanorods with Zn-porphyrin to obtain the improved characteristics of energy transfer, which is further investigated for the applicability to photovoltaic devices. A nitrogen heterocyclic ligand containing a thiol group is covalently grafted onto the surface of finely structured ZnO nanorods with a length of 50-250 nm and a diameter of 15-20 nm. Zn-porphyrin is then attached to the ligand molecules by the mechanism of metalligand axial coordination. The resulting energy band diagram suggests that the porphyrin-modified ZnO nanorods might provide an efficient pathway for energy transfer upon being applied to photovoltaic devices.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.135-142
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• 2002

This paper introduces the technologies related to seismic resistance assessment of nuclear power plant structures by seismic fragility analysis(SFA). The inelastic energy absorption factor is considered in SFA to represent the effects due to the nonlinear behavior of structures and has a significant effect on the seismic fragility that is a probability of failure of structures by earthquake. Several practical methods to evaluate the inelastic energy absorption capacity of structures are investigated. The capacities determined by those methods are compared with each other. And an improved method that uses the inelastic demand capacity diagram is presented. Conclusively, some comments on each method for practical application are made.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.339-346
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• 2003

Molecular dynamic simulations of nano indentation on single-crystal silicon (100) surface were performed using diamond indentor. Silicon substrate and diamond indentor were modeled diamond structure with Tersoff potential model. Phase transformation of silicon, incipient plastic deformation, change of incident temperature distribution are investigated through the change of potential energy distribution, displacement-load diagram, the change of kinetic energy distribution and displacements of silicon atoms. Phase transformation is highly localized and consists of a high-density region surrounding the tip. Axial load linearly increased according to the indenting depth. Number of atoms with high kinetic energy increased at the interface between substrate and indentor tip.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.3-12
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• 1999

This research concentrates on the influence of non-linearities associated with impact for the nonlinear rocking behavior of rigid block subjected to one dimensional sinusoidal excitation of horizontal direction. The transition of two governing rocking equations, the abrupt reduction in the kinetic energy associated with impact, and sliding motion of block. In this study, two type of rocking vibration system are considered. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation and sliding motion. The response analysis using non-dimensional rocking equation is carried out for the change of excitation parameters and friction coefficient. The chaos responses were discovered in the wide response region, particularly, for the case of high excitation amplitude and their chaos characteristics were examined by the time history, Poincare map, power spectra and Lyapunov Exponent of rocking responses. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. The bifurcation diagram and Poincare map were shown to be effective in order to understand chaos of rocking system.