• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.1-7
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• 2002

In this paper, the maximum minimum strain energy density criterion was applied to the mixed mode fatigue test of A5052 H34 alloy. In this study result we can have seen that the authors stress intensity factor for the finite width specimen and method of determining testing load, based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E-647-95, is useful.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.2
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• pp.316-319
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• 2011

Biopiles which offer the potential for cost-effective treatment of contaminated soils are above-ground, engineered systems that use oxygen to stimulate the growth and reproduction of aerobic bacteria for degradation of the petroleum constituents adsorbed to soil in excavated soils. This technology involves heaping contaminated soils into piles and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Inside the biopile, microbially mediated reactions by blowing or extracting air through the pipes can enhance degradation of the organic contaminants. The influence of a aeration system on the biopile performance was investigated. Air pressure made to compare the efficiency of suction in the pipes showed that there were slightly significant difference between the two piles in the total amount of TPH biodegradation. The normalised degradation rate was, however, considerably higher in the aeration system than in the normal system without aeration, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile.

• Journal of Korean Association for Spatial Structures
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• v.13 no.3
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• pp.91-98
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• 2013

A multi-input single-output (MISO) semi-active control systems were studied by many researchers. For more improved vibration control performance, a structure requires more than one control device. In this paper, multi-input multi-output (MIMO) semi-active fuzzy controller has been proposed for vibration control of seismically excited small-scale buildings. The MIMO fuzzy controller was optimized by multi-objective genetic algorithm. For numerical simulation, five-story example building structure is used and two MR dampers are employed. For comparison purpose, a clipped-optimal control strategy based on acceleration feedback is employed for controlling MR dampers to reduce structural responses due to seismic loads. Numerical simulation results show that the MIMO fuzzy control algorithm can provide superior control performance to the clipped-optimal control algorithm.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.93-104
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• 2018

The seismic behavior of reinforced concrete (RC) short columns with limited transverse reinforcement is investigated in this paper through an experimental program. The experimental program consists of four small-scale RC columns with an aspect ratio of 1.7, which are tested to the axial failure stage. The cracking patterns, hysteretic responses, strains in reinforcing bars, displacement decomposition and cumulative energy dissipation of the tested specimens are reported in detail in the paper. The effects of column axial load are investigated to determine how this variable might influence the performance of the short columns with limited transverse reinforcement. Brittle shear failure was observed in all tested specimens. Beneficial and detrimental effects on the shear strength and drift ratio at axial failure of the test specimens due to the column axial load are found in the experimental program, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.179-185
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• 2002

Solid state deformation of PZT is effective for the micron scale displacement. Inch-worm gets large linear displacement by incrementally summing displacements of PZT actuators. Dynamic stiffness of inch-worm is generally low compared to its driving condition due to the small size and light weight of inch-worm. Mechanical vibration induced by low stiffness may degenerate the motion accuracy of the inch-worm. In this paper, dynamic characteristics of the inch-worm are modeled by using the frequency domain curve fitting based on the experimental frequency response function. SMC (sliding mode control) is examined for motion control of the inch-worm. Simulation and experimental results show that the inch-worm with SMC scheme is feasible for the precise displacement device.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.512-513
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• 2016

정보시스템은 기업에 반드시 필요하며 고품질의 정보시스템이 요구되고 있다. 하지만, 고품질의 정보시스템을 구축하는데 많은 어려움이 있다. 이에 따라 정부에서는 감리제도를 도입하여 고품질의 정보시스템 구축에 대한 문제를 해결하고자 노력하고 있지만 소규모 프로젝트의 경우에는 감리대상의 범위에 들어가지 않고 적은 비용으로 인해 프로젝트 품질 관리활동이 없이 품질 관리에 어려움을 겪고 있다. 본 연구에서는 요구분석 영역에서의 감리활동 사례를 분석하고 자주 발생하는 지적 사항을 토대로 이해당사자들이 프로젝트의 특성에 맞게 점검항목을 만들어 AHP 분석을 통하여 중요도를 산정하고 추가적인 점검사항을 더해 품질 향상을 위해 소규모 프로젝트에 적용 가능한 품질 관리 프로세스를 제안한다.

• Structural Engineering and Mechanics
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• v.28 no.3
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• pp.317-334
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• 2008

Seismic performance of coupling beams not designed for ductility is examined. Eight 1:4 scale coupling beam specimens, with seven reinforced concrete sections and one composite section, were tested under cycles of push-pull action. Characteristics of the specimens include moderate shear span ratio in the range of 2.5-3.5, high main reinforcement ratio at 3-4% and small to large stirrup spacing with 90- degree hooks. All the reinforced concrete specimens failed in a brittle manner. Displacement ductility of specimens with large stirrup spacing (${\geq}$140 mm) is in the range of 3 to 5. Seismic performance of the specimens is also examined using the ultimate drift angle and the amount of energy dissipated. Correlating the test data, an empirical relationship is proposed to estimate the ultimate drift angle of a class of coupling beams considered in the study not designed for ductility.

• Transactions on Electrical and Electronic Materials
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• v.3 no.3
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• pp.14-17
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• 2002

The HDP (High Density Plasma) CVD process consists of a simultaneous sputter etch and chemical vapor deposition. As CMOS process continues to scale down to sub- quarter micron technology, HDP process has been widely used fur the gap-fill of small geometry metal spacing in inter-metal dielectric process. However, HBP CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has been an increasingly important issue for integrated circuit process technology. In this paper, thin gate oxide charge damage caused by HDP deposition of inter-metal dielectric was studied. Multiple step HDP deposition process was demonstrated in this work to prevent plasma-induced damage by introducing an in-situ top SiH$_4$ unbiased liner deposition before conventional deposition.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1378-1389
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• 2005

This work provides the fundamental knowledge of energy transport characteristics during very short-pulse laser heating of semiconductors from a microscopic viewpoint. Based on the self-consistent hydrodynamic equations, in-situ interactions between carriers, optical phonons, and acoustic phonons are simulated to figure out energy transport mechanism during ultrafast pulse laser heating of a silicon substrate through the detailed information on the time and spatial evolutions of each temperature for carriers, longitudinal optical (LO) phonons, acoustic phonons. It is found that nonequilibrium between LO phonons and acoustic phonons should be considered for ultrafast pulse laser heating problem, two-peak structures become apparently present for the subpicosecond pulses because of the Auger heating. A substantial increase in carrier temperature is observed for lasers with a few picosecond pulse duration, whereas the temperature rise of acoustic and phonon temperatures is relatively small with decreasing laser pulse widths. A slight lagging behavior is observed due to the differences in relaxation times and heat capacities between two different phonons. Moreover, the laser fluence has a significant effect on the decaying rate of the Auger recombination.

• Journal of Power Electronics
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• v.17 no.4
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• pp.953-962
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• 2017

Momentum flywheels are widely applied for the generation of small and precise torque for the attitude control and inertial stabilization of satellites and space stations. Due to its inherited system nonlinearity, the tracking performance of the flywheel torque/speed in dynamic/plug braking operations is limited when a conventional controller is employed. To take advantage of the well-separated two-time-scale quantities of a flywheel driving system, the singular perturbation technique is adopted to improve the torque tracking performance. In addition, the composite control law, which combines slow- and fast- dynamic portions, is derived for flywheel driving systems. Furthermore, a novel control strategy for plug braking dynamics, which considers couplings between the Buck converter and the three-phase inverter load, is designed with easy implementation. Finally, experimental results are presented to demonstrate the correctness of the analysis and the superiority of the proposed methods.