• Journal of Surface Science and Engineering
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• v.53 no.4
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• pp.138-143
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• 2020

In this study, we produced a coil of micro-pattern that can be used for electromagnetic wave absorber, heating material, wireless charging, sensor, antenna, etc. by using electrochemical additive manufacturing method. Currently, it contains research contents for manufacturing a micro pattern coil having practicality through control of process control variables such as applied voltage, distance between electrode, and nozzle injection. Circulation of the electrolyte through the nozzle injection control can significantly contribute to improving the surface characteristics of the coil because of minimizing voltage fluctuations that may occur during the additive manufacturing process. In addition, by applying the pulse method in the application of voltage, the lamination characteristics of the plated body were improved, which showed that the formation of a fine line width plays an important role in the production of a micro pattern coil. By applying the pulse signal to the voltage application, the additive manufacturing characteristics of the produced product were improved, and it was shown that the formation of a fine line width plays an important role in the production of a micro pattern coil.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.225-231
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• 2002

Severe cracks on Reinforced Concrete (RC) structures caused by structural displacement can be often one of the main reasons for the degradation of tensile and flexural rigidities of RC structures and for the deterioration of durability and serviceability of RC structures through accelerated steel corrosion. These combined factors adversely affect the performance of RC concrete, leading to shortened life time of RC structures. In consideration of these problems, we conducted 3 point bending experiments by employing three different types of concrete specimens: fiber-net reinforced concrete (FNRC), polypropylene-fiber reinforced concrete (PFRC), and plain concrete (PC). FNRC is well known for its strong corrosion resistance, light self-weight, and excellent tensile strength, while PFRC is known to be effective in crack control. FNRC was found to have the best first and final crack resistances followed by PFRC and PC, as evidenced by the highest initial crack load and the smallest final crack width, respectively. The FNRC specimens with various tensile strength of fiber net exhibited greater ultimate strengths than those for PFRC and PC. Furthermore, the crack widths of FNRC specimens were smaller than those calculated by the crack-width estimation equation of the KCI and ACI code. Therefore, we conclude that fiber net reinforcement is effective not only on crack control, but also on loading share.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.3
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• pp.40-51
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• 2008

This research presents a new active auxiliary resonant snubber with for induction heating PWM high frequency inverter solving the problem of induction heating PWM high frequency inverter circuit which is using widely in the practical application of an induction heating apparatus, the soft switching operation and power control are impossible when the lowest power supply in the active auxiliary resonant snubber with for induction heating PWM high frequency inverter. The inverter circuit which is attempted by the on-off operation of a switch has the effect of reducing the power loss due to soft switching and high frequency switching. This confirms that power regulation is possible on a continuous basis from 0.25[kW] to 2.84[kW] where the duty factor(D) changes from 0.08 to 0.3 under zero current switching which operates by an asymmetrical pulse width modulating control. The power conversion efficiency is 95[%]. Due to these results, the active auxiliary resonant snubber for an induction heating PWM high frequency inverter is considered effective as a source of induction heating.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.6
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• pp.82-91
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• 2002

This study was conducted to investigate methods to overcome serious problems in hedge making. The growth response of Enonymus japonica was investigated, using different sizes of nonwoven fabric containers. Changes of shoot length, fresh weight and chlorophyll contents were measured a period of growth in each size of container. The results of this study are as follows; 1) The maximum growth of shoot length in all treatments was observed in May and August. The significant difference was found in the smaller size of container containing a less amount of soil than the control. 2) The soil amount of rhizosphere for the production of a standardized hedge seemed to be over 2,400-3,600㎤ per plant. 3) The depth of containers had a greater influence on growth of shoot length than the width of containers. 4) The fresh weight in 40cm width containers and 30$\times$20cm containers was similar to the control, but the rest of the containers showed significant difference compared with the control. 5) A significant difference of chlorophyll content was found in A, B, C, D and G treatment but I treatment did not show significant difference at the 5% level.

• Laser Solutions
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• v.18 no.2
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• pp.1-4
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• 2015

This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.

• Korean Journal of Plant Tissue Culture
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• v.26 no.4
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• pp.241-244
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• 1999

The effect of Milliwrap and Uniwrap attached to the lid on the growth and acclimation of lily growing in vitro was investigated. Milliwrap treatment increased the plant height 1.6 and 1.2 times higher than control in 'Dame Blanche' and '94-36', respectively, plant height of 'Dame Blanche' was 6.1㎝ and '94-36' line was 13.4 ㎝. Two treatments slightly inhibited the fresh weight in 'Dame Blanche', whereas Milliwrap and Uniwrap enhenced the fresh weight more than 30% in '94-36'. Leaf width (1.0 ㎝) of Milliwrap treatment was most wide, which was 2.5 times higher than that of control. In the fresh weight of bulblets, the fresh weight per bulblet of treatment was higher than control in '94-36', but the number of bulblets per scale were few in the treatment to control. In the air composition of culture vessel, ethylene content (0.03 ppm) was low in the Milliwrap treatment compared with the control. CO₂ content of control was higher than treatments as 0.11% and it was about 3 times to air condition of out side. The acclimation ratio of Milliwrap treatment was higher as 85.1% and control was similar with Uniwrap treatment.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.4
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• pp.526-540
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• 1992

Osteoporosis, a well known metabolic bone disease, occurs due to imbalance of bone formings and resorptions. In an attempt investigate if postmenopausal osteoporosis would have influence on the mandible, histomorphometric analysis was performed in the mandible and the femur of the albino rats. Osteoporosis was induced by bilateral oophorectomy. To determine the effect of calcitonin, calcitonin(Asahi Chemical Co., Japan) was injected in the oophorectomized rats. The results were as follows : 1. The width of cortical bone of the femur was decreased in the oophorectomized group compared to the normal control and calcitonin injected groups and the porosity of cortical bone of the femur was increased in the oophorectomized group compared to the normal control and calcitonin injected groups. 2. The osteoid tissue and resorption lacuna of the femur was increased in both oophorectormized and calcitonin injected groups than the normal control group. 3. The width of cortical bone of the mandible was decreased in the oophorectomized group compared to the normal control and calcitonin injected groups. 4. The porosity of cortical bone of the mandible was decreased in both oophorectomized and calcitonin injected groups than the normal control group. 5. The relative volume of trabecular bone of the mandible was decreased in the oophorectomized group compared to the normal control and calcitonin injected groups. 6. The osteoid tissue of the mandible was increased in the calcitonin injected group than the normal control and oophorectomized groups. 7. The resorption lacuna of the mandible was increased in both oophorectomized and calcitonin injected groups, particularly in the oophorectomized group.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.322-325
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• 2002

We describe the looper controller design for a hot strip mill. The looper is to control the strip tension which influences on the width of the strip. It is very important to control the looper control of the hot strip mill, but difficult to control the looper, because there exists on mutual interaction among strip gauge, looper angle, and strip tension. In this paper, we present the modeling for the hot strip finishing mill to control the tension of the strip and suggest a cross control method. The cross control is a very simple method that allows non-interacting control.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.129.4-129
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• 2001

The looper control of hot strip finishing mill is one of the most important control item in hot strip rolling mill process. Loopers are placed between finishing mill stands and control the mass flow of the two stands. Another important action of the looper is to control the strip tension which influences on the width of the strip. So it is very important to control both the looper angle and the strip tension simultaneously but the looper angle and the strip tension are strongly interacted by each other. There are many control schemes such as conventional, non-interactive, LQ(Linear Quadratic), Hinf and ILQ(Inverse Linear Quadratic), Adaptive(gain scheduling) control in the looper control system. In this paper, we present the modeling for the looper of a hot strip finishing mill to control the tension of the strip and suggest another control method.