• Journal of Welding and Joining
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• 제17권1호
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• pp.55-61
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• 1999

The effect of S content in welding wires on the arc stability was investigated, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing S content, average arcing time and average short circuit time were decreased. Therefore, droplet transfer frequency was increased, due to the reduction of arcing time and peak current at the moment of arc-reiginition was decreased, due to the decrease of short circuit time. In the region of spray transfer, the fluctuation degree of arc current and arc voltage became more stable, with increasing S content.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.329-336
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• 2004

The lock-up position of the floating ring seal affects the leakage flowrate and the stability. And it is changed depending on the operating and geometry condition. In this paper, the leakage flowrate and stability with change of the height and length were investigated by theoretical analysis and experiment. The parameter of the height and length is expressed to the b and L. The decreasing of the b resulted in the increasing of equivalent whirl frequency ratio in the experimental result at the low speed and high pressure not such as theoretical analysis. As the L increased the leakage flowrate decreased and stiffness and direct damping coefficient increased in the experimental result. That was similar to the theoretical analysis.

• Earthquakes and Structures
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• 제9권6호
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• pp.1181-1192
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• 2015

In this paper, an analytical method is proposed to study the effect of crack and axial load on vibration behavior and stability of the cracked columns. Using the local flexibility model, the crack has been simulated by a torsional spring with connecting two segments of column in crack location. By solving governing eigenvalue equation, the effects of crack parameters and axial load on the natural frequencies and buckling load as well as buckling load are investigated. The results show that the presents of crack cause to reduction in natural frequencies and buckling load whereas this reduction is affected by the location and depth of the crack. Furthermore, the tensile and compressive axial load increase and decrease the natural frequencies, respectively. In addition, as the compression load approaches to certain value, the fundamental natural frequency reaches zero and instability occurs. The accuracy of the model is validated through the experimental data reported in the literature.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.611-616
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• 2011

본 논문은 산업 전반에 걸쳐 널리 사용되는 교반기에서 기계동력을 교반에너지로 바꾸어 주는 임펠러에 대해 연구이다. 기존 제품과 새로 제안한 두 가지 형상의 모델에 대한 구조해석 및 고유진동수, 진동 조화 해석을 수행함으로써 임펠러의 형상에 따라 국부적 응력 집중되는 취약부위에 대한 분석과 설계를 확인함으로써 임펠러의 형상에 따른 구조적 안정성을 평가하였다.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2002년도 11월 학술대회지
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• pp.93-96
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• 2002

This research studied the correlation of word frequency effect in Korean corpus. Experiment 1 showed that word frequency of each other corpus was significant correlated. Experiment 2 showed significant correlation between word frequency of each corpus and lexical decision time of participants. These results support that 4 corpus in this research should have stability to word frequency effect of participants

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.279-282
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• 1999

Frequency divider selects the channel of the frequency synthesizer. General programmable divider has many flip-flops to realize all integer division value and stability problem by using dual modules prescaler. In this paper, a new architecture of programmable divider is proposed and designed to improve these problems. The proposed programmable divider has only thirteen flip-flops. The programmable divider is designed by 0.65${\mu}{\textrm}{m}$ CMOS technology and HSPICE. Operating frequency of the programmable divider is 200MHz with a 3V supply voltage.

• The Journal of Korean Physical Therapy
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• 제26권3호
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• pp.156-162
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• 2014

Purpose: The purpose of this study was to investigate muscle activation related to postural stability depending on different head positions with whole body vibration (WBV) in standing. Methods: Eighteen healthy subjects voluntarily participated in this single-group, repeated-measures study in which the surface electromyography (EMG) data from upper trapezius, rectus abdominis, external oblique abdominis, erector spinae, gluteus maximus, rectus femoris, semitendinosus, medial gastrocnemius were collected over 3 different frequencies (0-10-20Hz) and 4 different head positions (neutral, flexion, extension, chin tuck) for each subject on WBV while standing. Results: The results of this study demonstrated that the EMG activity of all recorded muscles shows significant difference between three different frequencies and four head positions of WBV while standing (p<0.05). In the multiple comparison, significant differences could be observed for most of different frequency conditions except 0-10Hz of RA, 10-20Hz of ST. In contrast, no significant difference showed the comparison of the EMG activity depending on different head positions (p<0.05). Conclusion: These findings suggest that different head positions on WBV do not activate muscles related to postural stability. However, higher frequency on WBV is highly effective to activate whole body muscles included postural muscles regardless of different head positions.

• 한국연소학회지
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• 제3권1호
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• pp.71-78
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• 1998

The flame stabilization and the combustion characteristics of diffusion flame formed in the wake of a cylindrical bluff body with fuel injection are studied. With the turbulence generator, the flame stability limits and ion currents were measured and analyzed. The results from this experimental study are summarized as follows. The region with highest average value of ion currents in the middle of flame is moved to the upstream side by the turbulent components of main stream. The flame mass with partially active reaction is moved fast for uniform flow and turbulence generator G3, but the flame mass with relatively slow reaction is moved slowly for turbulence generator G1. If the turbulence generator with strong turbulent component is installed, the turbulent time scale is increased with movement from main stream side to recirculation zone as well as the flame stability limits is deteriorated. Though the special dominant frequency is not appeared in the eddy which exists in flame, high frequency characteristics are appeared in uniform flow and turbulence generator G3, and low frequency characteristics are appeared in uniform flow, turbulence generator G3 and G1.

• 대한기계학회논문집
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• 제19권3호
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• pp.639-646
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• 1995

The objective of this study is to minimize the weight of a damped anisotropic roto-bearing system considering whirl natural frequency and stability. The system is modeled as an assemblage of rigid disks, flexible shafts and discrete bearings. The system design variables are the crosssectional areas of shaft elements and the properties of bearings. To analyze the system, the polynomial method which is derived by rearranging the calculations performed by a transfer matrix method is adopted. For the optimization, the optimization software IDOL (Integrated Design Optimization Library) which is based on the Augmented Lagrange Multiplier (ALM) method is employed. Also, an analytical design sensitivity analysis of the system is used for high accuracy and efficiency. To demonstrate the usefulness of the proposed optimal design program incorporating analysis, design sensitivity analysis, and optimization modules, a damped anisotropic rotor-bearing system is optimized to obtain 34$ weight reduction.

• 전기학회논문지
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• 제56권2호
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• pp.233-239
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• 2007

As the Kyoto Protocol, which aims at reducing greenhouse gases in accordance to the UNFCCC, came into force, research on environment friendly energy resources has been a matter of concern worldwide. As a general power generation system, among renewable energy resources, that is interconnected and operated with power system, the wind turbine is emerging as an effective alternative. Since power capacity of the wind turbine has been steadily increasing and its relative importance is also increasing in total facility capacity, we cannot ignore its effect. Because controlling generation output in the wind turbine is not as easy as in the synchronous machine due to its facility characteristics and it generates irregular output fluctuations when interconnected with power system, system interconnection was difficult. But the effect of large capacity wind turbine on isolated power system like Jeju island is serious problem on the frequency stability. Accordingly, it is necessary to analyze the effects of wind turbine on system interconnection and assess the optimum capacity of wind turbine that satisfies the most important principle of stable power supply. This paper have analyzed the effects of wind turbine capacity increases on the system and suggested the method of the capacity to achieve its steady operation. And It is applied to the Jeju island.