• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.2
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• pp.77-83
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• 2000

This paper deals with the design of a touch free eddy-current brake for high speed transportation systems by using 2-dimensional Finite Element Method (2-D FEM). The eddy current brake systems have to equipped with maximum braking force and deceleration at the given volume or mass, high braking force at small rate, attraction forces as small as possible and stable construction. The parameters, such as the number of pole, electric ampere-turns and slot width have influence on these braking characteristics. For the magnet to satisfy above-mentioned performance in high speed, the braking performance according to variation of the parameters are analyzed by the 2-D FEM. In addition, the magnet stack width is determined from equivalent stack width that is calculated by solution of the Field with scalar potential. From these results, the magnet of optimized configuration with maximum braking force and minimum attraction force is designed by the process of detail design.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1555-1557
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• 1998

In order to investigate the core material for over-head transmission line with non-magnetic and high strength nitrogen steel, microstructure and several basic properties of Fe-Mn-Cr-Ni-N steel have been studied. It is necessary that core material have a $\gamma$ phase to have a non-magnetic characteristics. To acquire a $\gamma$ phase, Mn, Ni and C are added as a alloying element. It was found that Fe-25Mn-16Cr-1Ni-N alloy have a stable $\gamma$ phase. The precipitate from this alloy system was $(Cr, Fe)_7C_3$. High Mn and N steel satisfies Sievert's relation that solubility of nitrogen increases with the square root of partial pressure of gas in metal-gas system and the hardness have proportional relation with nitrogen concentration.

• Journal of the Korean Institute of Gas
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• v.6 no.4 s.18
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• pp.17-22
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• 2002

LNG demand has been rapidly increasing in Korea for a variety of reasons including stable supply, non-polluting, and high combustion efficiency characteristics. One of the most important structural core element of the LNG storage tank is the membrane, consisting of stainless steel. The membrane to be applied inside of LNG storage tank is provided with corrugations to absorb thermal contraction and expansion caused by LNG temperature. Experimental studies are presented to investigate the deformation and strength of the membrane which is designed by Kogas. All experiments are conducted on the basis of RPIS, and we found the results is fully satisfied with the RPIS.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.756-759
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• 2014

DC/DC converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. The converters can be applied in the regenerative braking of DC motors to return energy back to the supply, resulting in energy savings for the systems at periodic intervals. The fundamental converter studied here consists of an IGBT (Insulated Gate Bipolar mode Transistor), an inductor, a capacitor, a diode, a PWM-IC (Pulse Width Modulation Integrated Circuit) controller with oscillator, amplifier, and comparator. The PWM-IC is a core element and delivers the switching waveform to the gate of the IGBT in a stable manner. Display of the DC/DC converter output depends on the IGBT's changes in the threshold voltage and PWM-IC's pulse width. The simulation was conducted by PSIM software, and the hardware of the DC/DC converter was also implemented. It is necessary to study the fact that the output voltage depends on the duty rate of D, and to compare the output of experimental result with the theory and the simulation.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2004.11a
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• pp.77-85
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• 2004

A significant portion (about 8% in human genome) of mammalian mRNA sequences contains AU(Adenine and Uracil) rich elements or AREs at their 3' untranslated regions (UTR). These mRNA sequences are usually stable. ARE motifs are assorted into three classes. The importance of AREs in biology is that they make certain mRNA unstable. We analyzed the occurrences of AREs and Alu, and propose a possible mechanism on how human mRNA could acquire and keep A REs at its 3' UTR originated from Alu repeats. Interspersed in the human genome, Alu repeats occupy 5% of the 3' UTR of mRNA sequences. Alu has poly-adenine (poly-A) regions at the end that lead to poly -thymine (poly-T) regions at the end of its complementary Alu. It has been discovered that AREs are present at the poly -T regions. In the all ARE's classes, 27-40% of ARE repeats were found in the poly -T region of Alu with mismatch allowed within 10% of ARE's length from the 3' UTRs of the NCBI's reference m RNA sequence database. We report that Alu, which has been reported as a junk DNA element, is a source of AREs. We found that one third of AREs were derived from the poly -T regions of the complementary Alu.

• Composites Research
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• v.14 no.3
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• pp.10-17
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• 2001

A reseach was peformed to develop composite pressure vessels in conjunction with design, fabrication, and test. Fiber pattern and angels were decided by CADFIL software and they were [$liner/15^{\circ}/15^{\circ}/90^{\circ}/18^{\circ}/90^{\circ}/21^{\circ}/21^{\circ}/90^{\circ}$]. Fabrication of bottles were done by 5-axis filament winding machine. During fabrication fiber optic sensors were embedded to measure the strain at points when internal pressure was applied by water pump. Conventional strain gage instrumentation showed the stable test results. The test results were compared to finite element analysis results and they were close each other in strain values. One can see the successful design and fabrication of single boss composite vessels.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.39-40
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• 2006

Diesel power plant(DPP) with the medium speed diesel engine is operated under the very severe condition in aspect of load and operating time as compared with the marine diesel generator set. So, minimized vibration level have to be insured for the more stable operation of engine and generator. The vibration of generator set mainly comes from the resonance between the rigid modes by resilient mount or distortion modes by structural stiffness and the excitation forces of engine. Then, avoidance of resonance with structural modification is generally well known. In this paper, the first order vibration in non-resonance range and local vibration modes were investigated by impact test, response/ODS(operational deflection shape) measurement and 3D finite element analysis for the additional reduction of vibration. The proposed countermeasures were actually applied and their final effects were verified through the in-situ measurement.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.5
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• pp.491-496
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• 2015

Electric handbike can be easily detachable to various sizes of manual wheelchair and the elderly and people with disabilities can use them easily. Therefore, connectors used for coupling between the handbike and manual wheelchair must secure structural stability for occupant safety. However, related research is rare. The aim of this study is to find the connector with highly structural stability by comparing static and dynamic mechanical characteristics among three typical connectors(a snatch lock, a slide latch, and a fastener) by computational simulations. To perform static and dynamic simulation, we referred to durability test based on Korean Standards and then calculated mechanical stresses in connectors. The results showed that the snatch lock addressed the lowest von-mises stress under the same mechanical condition. Therefore when using the combination of a handbike and a wheelchair, we concluded that the snatch lock is considered as the structurally stable connector to structural stability and usability.

• Earthquakes and Structures
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• v.18 no.5
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• pp.637-648
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• 2020

In this study, a new steel cylindrical shell configuration of the dissipative energy device is proposed to improve lateral ductility and to reduce the damage of the structures against seismic forces. Four nested-eccentric- cylindrical shells are used to constructing this device; therefore, this proposed device is named nested-eccentric-cylindrical shells damper (NECSD). The particular configuration of the nested-eccentric-cylindrical shells is applied to promote the mechanical characteristics, stability, and overall performance of the damper in cyclic loads. Shell-type components are performed as a combination of series and parallel non-linear springs into the in-plan plastic deformation. Numerical analysis with respect to dimensional variables are used to calculate the mechanical characteristics of the NECSD, and full-scale testing is conducted for verifying the numerical results. The parametric study shows the NECSD with thin shells were more flexible, while devices with thick shells were more capacious. The results from numerical and experimental studies indicate that the NECSD has a stable behavior in hysteretic loops with highly ductile performance, and can provide appropriate dissipated energy under cyclic loads.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.7 s.100
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• pp.836-842
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• 2005

Nonlinear dynamic characteristics of active piezolaminated plates are investigated with respect to the thermopiezoelastic behaviors. For largely deformed structures with small strain, the incremental total Lagrangian formulation is presented based on the virtual work principles. A multi-field layer-wise finite shell element is proposed for assuring high accuracy and non-linearity of displacement, electric and thermal fields. For dynamic consideration of thermopiezoelastic snap-through phenomena, the implicit Newmark's scheme with the Newton-Raphson iteration is implemented for the transient response of various piezolaminated models with symmetric or eccentric active layers. The bifurcate thermal buckling of symmetric structural models is first investigated and the characteristics of piezoelectric active responses are studied for finding snap-through piezoelectric potentials and the load-path tracking map. The thermoelastic stable and unstable postbuckling, thermopiezoelastic snap-through phenomena with several attractors are proved using the nonlinear time responses for various initial conditions and damping loss factors. Present results show that thermopiezoelastic snap-through phenomena can result in the difficulty of buckling and postbuckling control of intelligent structures.