• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.280-289
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• 2008

This paper presents design of the quantitative feedback control system of the three axes hydraulic road simulator with respect to the dummy wheel for uncertain multiple input-output(MIMO) feedback systems. This simulator has the uncertain parameters such as fluid compressibility, fluid leakage, electrical servo components and nonlinear mechanical connections. This works have reproduced the random input signal to implement the real road vibration's data in the lab. The replaced $m^2$ MISO equivalent control systems satisfied the design specifications of the original $m^*m$ MIMO control system and developed the mathematical method using quantitative feedback theory based on schauder's fixed point theorem. This control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) having the minimum bandwidth for parameters of uncertain plant. The efficacy of the designed controller is verified through the dynamic simulation with combined hydraulic model and Adams simulator model. The Matlab simulation results to connect with Adams simulator model show that the proposed control technique works well under uncertain hydraulic plant system. The designed control system has satisfied robust performance with stability bounds, tracking bounds and disturbance. The Hydraulic road simulator consists of the specimen, hydraulic pump, servo valve, hydraulic actuator and its control equipments

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.255-258
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• 2009

Leading developed countries have studied energy self-sufficient houses such as zero or low energy buildings to reduce energy consumption for buildings since the early 1990s. Moreover, some developed countries have actually constructed self-sufficient houses and operated them for demonstration, expanding use of such houses. Korea has also established Zero Energy Solar House(ZeSH) and studied energy independence. Therefore, this study analyzed research result regarding ZeSH, self-sufficient energy house hold of Korea, found out technologies used for heating energy independence, used building interpretation program(ESP_r) to evaluate performance of each factors and analyzed energy reduction quantitatively. Results from the research are as follows: Reduction rate of actual detached house's heating load was also analyzed quantitatively depending on application of each technology. When each factor was applied step-by-step, annual reduction rate of heating load depending on increase in insulation thickness reached 6.6~22.2 %. Annual reduction rate of heating load depending on increase insulation thickness, and change in window heating performance and area ratio reached 31.5 %. Annual reduction rate of heating load through high-sealing and high-insulation depending on change in leakage rate reached 40.0~88.9 %. Annual reduction of heating load, when Mass Wall and attached sun space was applied were applied reached 28.5~39.2 %, respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.195-205
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• 2002

Most tunnel damage such as cracks or leakage which exist in tunnel liner commonly, is caused by the cavities that exist behind the tunnel liner, through the tunnel safety inspections. These cavities were analysed to check if they affect the stability of tunnels. This study is on the development of the controlled low-strength and flowable filling material which an be applied to the cavity behind the tunnel lining. The backfilling material studied here is crushed sand and stone-dust which is in cake-state and is a by-product obtained in the producing process of aggregate. Varying the compound mixing ratio, laboratory tests of compression test and chemical analyses were carried out. In addition, the material was applied to an old tunnel for the performance assessment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.53-58
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• 2001

The main noise sources in SMPS are divided into three parts: the switching devices, the rectifiers in secondary part, the output transformer and choke coil. In this paper we performed the noise analysis with respect to bobbin type and winding method, and designed an optimized transformer focusing on the transformer. For the comparison. we measured four parameters for each cases, including EMI conducted emission noise. signal from the switching devices, output ripple/noise voltage and leakage current. As the result, the transformer using a vertically-typed bobbin and a parallel, sandwich winding method showed the best performance. We confirmed that the SMPS developed in this research is satisfied with the IEC 601-1 international standard for the medical instrumentation. by testing its electrical characteristics and safety.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.551-555
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• 2004

The two-transformer full bridge (TTFB) PWM converter has two transformers which act as the output inductor as well as the main transformer, i.e. as the forward and the flyback transformer. Although the doubled leakage inductor of the TTFB makes it easier to achieve the zero-voltage switching (ZVS) of the lagging leg switch along the wide load range, it instigates a serious voltage ringing in the secondary rectifier diodes, which would require the dissipative snubber circuit, cause the serious power dissipation, and increase the voltage stress across those diodes. To overcome these problems, a, new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped on a half the output voltage $(V_o/2)$ or the output voltage $(V_o)$. Therefore, no dissipative snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. The operations, analysis and design consideration of proposed converter are presented in this paper. To verify the validity of the proposed converter, experimental results from a 425W, 385-170Vdc prototype for the plasma display panel (PDP) sustaining power module (PSPM) are presented.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1654-1663
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• 2015

Compared to LC resonance, LCL resonance has distinct advantages such as a large resonant capability, low voltage and current stresses of the power device, constant voltage or current output characteristics, and fault-tolerance capability. Thus, LCL resonant compensation is employed for a movable Inductive Contactless Power Transfer (ICPT) system with a multi-load in this paper, which achieves constant current output characteristics. Peculiarly, the primary side adopts a much larger compensation inductor than the primary leakage inductor to lower the reactive power, reduce the input current ripple, generate a large current in the primary side, and realize soft-switching. Furthermore, this paper proposes an approximate resonant point for large inductor-ratio LCL resonant compensation through fundamental wave analysis. In addition, the PWM control strategy is used for this system to achieve constant current output characteristics. Finally, an experimental platform is built, whose secondary E-Type coils can ride and move on a primary rail. Simulations and experiments are conducted to verify the effectiveness and accuracy of both the theory and the design method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.57-58
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• 2006

In MIM (metal insulator metal) capacitor, Ru (ruthenium) has been suggested as new bottom electrode due to its excellent electrical performance, a low leakage of current and compatibility to the high dielectric constant materials. In this case of Ru bottom electrode, CMP (chemical mechanical planarization) process was needed m order to planarize and isolate the bottom electrode. In this study, the effect of chemical A on polishing and etching behavior was investigated as functions of chemical A concentration, abrasive particle and pressure. Chemical A was used as oxidant and etchant. The thickness of passivation layer on the treated Ru surface increased with the increase of chemical A concentration. The etch rate and removal rate of Ru were increased by the addition of chemical A. The removal rate was highest m slurry of pH 9 with the addition of 0.1 M chemical A and 2 wt% alumina at 4 psi. The maximum removal rate is about 80 nm/min.

• Journal of the Korean Vacuum Society
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• v.11 no.4
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• pp.212-217
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• 2002

A new technique for highly controllable trench corner rounding at the top and bottom of the trench using pull-back and hydrogen annealing has been developed and investigated. The pull-back process could control the trench corner rounding radius at the top comers of the trench. The silicon migration generated by hydrogen annealing at the trench coiners provided (111) and (311) crystal planes and gave a uniform gate-oxide thickness, resulting in high reliable trench DMOSFETs with highly breakdown voltages and low leakage currents. The breakdown voltage of a trench DMOSFET fabricated using hydrogen annealing was increased by 25% compared with a conventional DMOSFET. The reasonable drain current of 45.3 A was obtained when a gate voltage of 10 V was supplied. The on-resistance of the trench gate DMOSFET fabricated using the trench cell of 45,000 was about 55 m(at a gate voltage of 10 V under a drain current of 5 A.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.67-70
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• 2009

Because many research using rocket grade peroxide is studied, distillation method for domestic production of rocket grade hydrogen peroxide is required. Distillation methods are very various and divided by feeding method, distillation time, distillation pressure, and so on. Among these, vacuum distillation is a suitable method for hydrogen peroxide. This method can reduce thermal decomposition and reaction with impurities. Distillation condition is determined by Raoult's law. Low vacuum level and vacuum level control are appeared as important problems of the experiment equipment, which are solved by using less leakage vacuum chamber and metering valve.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.265-272
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• 2017

Inhibition of pitting corrosion of the copper sprinkler tubes by removing dissolved oxygen in water with sodium sulfite was studied on the wet sprinkler systems operated in 258 household sites. First, air in the sprinkler tubing was removed by vacuum pumping. The tube was then filled with sodium sulfite dissolved in water. Sodium sulfite was very effective in maintaining a very low dissolved oxygen concentration in water in the sprinkler tube for the observation period of six months. Water leakage from the copper sprinkler tube was reduced significantly by using sodium sulfite. Both pitting corrosion process and pitting corrosion inhibition mechanism were investigated by examining microscopical and structural aspects of corrosion pits formed in failed copper sprinkler tube. Pitting corrosion was caused by pressurized air as well as sediments such as sand particles in copper tubes through oxygen concentration cells. It was confirmed microscopically that growth of corrosion pits was stopped by reducing dissolved oxygen concentration to a very level by using sodium sulfite.