• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.355-361
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• 2011

The power control of the existing heating element has been using the On-Off control, phase control, and PWM control. In case of controlling power PTC heating element developed recently with the existing method, the temperature is unable to be precisely controlled or the harmful electromagnetic wave to human body is generated. In this paper, We suggest the power control of PTC heating cable using variable AC Cycles. This regards the AC cycle of N as the unit of the power control. It determines On-Off for each cycle. It is the AC power control method in which it arranges the on-cycle in N cycles in the random and it supplies the current continuously. At this time. the minimal electric power amount becomes 1/N. The maximum current amount becomes 1 and sets up the number of on cycles according to the set value and can control the electric power with the step of N consistently. In the PTC heating system, we show that proposed power control method is superior in the EMI and temperature control property using MATLAB simulation, experiments and measurements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.269-272
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• 2000

Spinel $LiMn_2O_4$ samples are prepared by heating a $LiOH{\cdot}H_2O/MnO_2$ mixture in air at $800^{\circ}C$ for 36h, and their structure and electrochemical performance are studied by using X-ray diffraction, Cyclic Voltammetry, AC Impedance, and Charge-discharge measurements. It was found that the electrochemical properties of the $LiMn_2O_4$ samples are very sensitive to substituted volume of lithium. Initial impedances of all cathode was similar. Initial resistance was $60{\sim}70{\Omega}$. Reaction peak of Cyclic voltammetry was weak by increase of substituted volume of lithium. $Li[Li_{0.08}Mn_{1.92}]O_4$ and $Li[Li_{0.1}Mn_{1.9}]O_4$ cathode materials showed the charge and discharge capacity of about 125mAh/g at first cycle, and about 95mAh/g after 70th cycle. It showed excellent property in sample revealed good structure and other electrochemical property.

• Computational Structural Engineering : An International Journal
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• v.1 no.1
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• pp.59-69
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• 2001

This study is intended to propose a systematic approach for reliability-based assessment of life cycle cost (LCC) effectiveness and economic efficiency for cost-effective seismic upgrading of existing bridges. The LCC function is expressed as the sum of the upgrading cost and all the discounted life cycle damage costs, which is formulated as a function of the Park-Ang damage index and structural damage probability. The damage costs are expressed in terms of direct damage costs such as repair/replacement costs, human losses and property damage costs, and indirect damage costs such as road user costs and indirect regional economic losses. For dealing with a variety of uncertainties associated with earthquake loads and capacities, a simulation-based reliability approach is used. The SMART-DRAIN-2DX, which is a modified version of the well-known DRAIN-2DX, is extended by incor-porating LCC analysis based on the LCC function developed in the study. Economic efficiencies for optimal seismic upgradings of the continuous PC segmental bridges are assessed using the proposed LCC functions and benefit-cost ratio.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.1
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• pp.39-50
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• 2001

Vanadium based solid solution alloys have been studied as a potential negative electrode of Ni/MH battery due to their high hydrogen storage capacity. In order to improve the kinetic property of V-Ti alloy in KOH electrolyte, the ball-milling process with Ni, which has a catalytic effect of hydrogen absorption/desorption, was carried out to modify the surface properties of V-Ti-Cr alloys with high hydrogen storage capacity. Moreover, to overcome the problem of poor cycle life, V-Ti alloy substituted by Cr, V0.68 Ti0.20 Cr0.12, has been developed showing a good cycle performance (keeping about 80 % of initial discharge capacity after 200 cycles). The cycle life of surface-modified V0.68 Ti0.20 Cr0.12 alloy was improved by suppressing the formation of TiO2 layer on the alloy surface while decreasing the amount of dissolved vanadium in the KOH electrolyte. In order to promote the effect of Ni coating on the surface property of V0.68 Ti 0.20 Cr 0.12 alloy by ball-milling, filamentary-typed Ni, which has higher surface coverage area than sphere-typed Ni was used as a surface modifier. Consequently, the surface-modified V0.68 Ti0.20 Cr0.12 alloy electrode showed a improved discharge capacity of 460 mAh/g.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.41-48
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• 2013

Several fatigue damages have recently been reported which cannot be resolved in the context of the existing fatigue design procedure, and they are suspected to be the cracks induced by the low cycle fatigue mechanism. To tackle the problem, a series of material tests together with fatigue tests have been carried out, and elasto-plastic notch strain analysis using nonlinear kinematic hardening model has been performed. The cyclic stress-strain curves are obtained and the nonlinear kinematic hardening model was calibrated based on the obtained material data. Also, the fatigue test with non-load-carrying cruciform fillet welded joint has been performed in low cycle fatigue regime. Then, the notch strain analyses have been carried out to find the precise elasto-plastic behavior of the material at the notch root of the cruciform joint. The variation of the material property from the base metal via HAZ up to the weld metal was taken into account using spatial variation of the material property. Then the detail elasto-plastic behavior of the welded joint subjected to the repeated cyclic loading has been investigated further through the comparison with the prediction with Neuber's rule. The calibration of the nonlinear kinematic hardening model and nonlinear notch strain analyses have been performed using the commercial FE program ABAQUS.

• Steel and Composite Structures
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• v.48 no.1
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• pp.103-111
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• 2023

The caving property of top coal is a key factor to the success of top coal caving mining. The influence law of cyclic loading and unloading of hydraulic support on top coal caving is of great significance to improve the recovery rate of top coal. The similar simulation methods were used to study the dynamic evolution of the top coal cracks under the multi-cycle action of the support, and the parameters of top coal cracks were analyzed quantitatively in this paper. The results show that the top coal cracks can be divided into horizontal cracks and vertical cracks under the cyclic loading and unloading of the support. With the increase of the times of the support cycles loading and unloading, the load on the support decreases, the fractal dimension of the cracks increases, the number and total length of the top coal cracks increases, and the top coal caving is getting better. With the increase of the times of multi-cycle loading and unloading, the fractal dimension, total crack length and crack rate of top coal show a trend of rapid increase first and then increase slowly. Both the total length of the top coal cracks and the crack rate basically show linear growth with the change of the fractal dimension. The top coal caving can be well improved and the coal resource recovery rate increased through the multi-cycle loading and unloading.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.156-159
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• 2013

The ICT technology by using smartphone is leading the world. Apple opened the smart age with its smartphone on the first place in the world. In 2013, Samsung of Korea is spotlighted in the world, but China will run after Samsung with medium- and low-priced smartphones equipped with functionality and low and medium prices after 2014. That is, the life cycle of ICT technology gets shorter, and the volume of investment is increased. There is increasing uncertainty of enterprises and nations because the expanded volume of investment. Therefore, it is very important to predict emerging ICT technology, and investment development. Korea based on the creative economy is at the point of strengthening ICT. Therefore, this study aims to analyze intellectual property rights (patent) and the ICT market environment for the emerging ICT technology. The result of analysis will contribute to studying the intellectual property rights (patent) and the R&D matrix module in the ICT market environment for discovering and predicting national emerging ICT technology.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.4
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• pp.47-55
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• 1989

The effects of thermal cycle, aging heat treatment and Boron addition on the phase transformation characteristics and mechanical properties of the shape memory alloys of Cu-Zn-Al system, which was designed to operate about $80^{\circ}C$ by this research group, were studied. From the view point of the effects of thermal cycle on the phase transformation temperature change, it was found that up to 100 cycles Ms and Af points increased by $3-7^{\circ}C$ and Mf decreased a little bit and after that all of them were remain constant, and As point was not affected. All of the phase transformation temperatures were decreased $5-7^{\circ}C$ by aging heat treatment, at $140^{\circ}C$ for 24h however the effects of thermal cycle on aged alloys were same as on unaged alloys. As the thermal cycle increased the shape memory ability decreased a little up to 20 cycles, but above that it kept almost same ability. By Boron addition, grain size was refined from $1500{\mu}m$ to about $330{\mu}m$ and the hardness, fatigue property were improved but shape memory ability was lowered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.4
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• pp.316-322
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• 2001

Cathode materials $LiMn_{2-y}$$M_{y}$ $O_4$(M=Zn and Mg) were obtained by reacting the mixture of LiOH.$H_2O$, Mn $O_2$ and MgO ar ZnO at 80$0^{\circ}C$ for 36h in an air atmosphere. These materials showed an extended cycle life in lithium-anode cells working at room temperatue in a 3.0 to 4.3V potential window. Among these materials, LiM $n_{1.9}$M $g_{0.1}$ $O_4$ showed the best cycle performance in terms of the capacity and cycle life. The discharge capacities of the cathode for the Li/LiM $n_{1.9}$ $M_{0.1}$ $O_4$ cell at the 1st cycle and at the 70th cycle were about 120 and 105mAh/g, respectively. This cell capacity is retained by 88% after 70th cycle. In cyclic voltammetry measurement, all cells revealed tow oxidation peaks and reduction peaks. However, Li/$LiMn_{2-y}$$M_{y}$ $O_4$ cell substituted with Zn and Mg showed new reaction peak during reduction reaction.eaction.ion.ion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.387-390
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• 1999

To improve the cycle performance LiM $n_2$ $O_4$as the cathode of 4V class lithium secondary batteries, the cathode properties of the cubic spinel phases LiM $g_{x}$ /M $n_{2-x}$/ $O_4$ synthesized at 80$0^{\circ}C$ were examined. All cathode material showed spinel phase based on cubic phase in X-ray diffraction however. other peaks gradually exhibited and became intense with the increase of x value in LiM $g_{x}$ /M $n_{2-x}$/ $O_4$. The cycle performance of the LiM $g_{x}$ /M $n_{2-x}$/ $O_4$was improved by the substitution of $Mg^{2+}$ for M $n^{3+}$ in the octahedral sites. Specially LiM $g_{0.1}$/M $n_{1.9}$ / $O_4$cathode materials showed the charge and discharge capacity of about 130~125mAh/g at first cycle and about 105mAh/g after 50th cycle. It is excellent than that of pure LiM $n_{2}$/ $O_4$ which 125mAh/g at first cycle 70mAh/g at 50th. In addition cathode material prepared at 80$0^{\circ}C$ for 24hr and 42hr in the charge and discharge capapcity as well as the cycle stability.ility.y.y.