• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1119-1125
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• 2022

The depletion of resources and waste disposal caused by the continuous development of industry have emphasized the need to reduce consumption and production, recycle and reuse, and the importance of remanufacturing has increased in recent years. The spindle part of the aging planner miller, which is currently being remanufactured, is one of the factors that has the greatest impact on the performance of the machine tool. When designing the spindle part of the spindle shaft, there are considerations such as the configuration size bearing performance of the main shaft, but the diameter of the main shaft, the dangerous speed bearing, and the arrangement that affect the machining accuracy should be basically considered. As such, various studies have been conducted on the design of machine tool spindle spindles, but research on the reverse engineering of existing aging machine tool spindle spindles is poor. Reverse engineering is designing in the direction of improving performance by extracting specifications from already finished products, and first scanning the reverse engineered object through a 3D scanner, 3D modeling is performed based on the collected data, and then the process of deriving improvement plans by reverberating to improve performance by identifying wear and damage conditions is followed. Therefore, in this study, the purpose of this study is to provide data on reverse engineering by deriving improvement plans through optimal design for the bearing position of the aging planar Miller spindle spindle using central composite programming.

• 한국소음진동공학회논문집
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• 제19권8호
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• pp.816-827
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• 2009

This paper deals with a bearing faults localization technique based on holographic approach by visualizing sound radiated from the faults. The main idea stems from the phenomenon that bearing faults in a moving vehicle generate impulsive sound. To visualize fault signal from the moving vehicle, we can use the moving frame acoustic holography [Kwon, H.-S. and Kim, Y.-H., 1998, "Moving Frame Technique for Planar Acoustic Holography," J. Acoust. Soc. Am. Vol. 103, No. 4, pp. 1734${\sim}$1741]. However, it is not easy to localize faults only by applying the method. This is because the microphone array measures noise(for example, noise from other parts of the vehicle and the wind noise) as well as the fault signal while the vehicle passes by the array. To reduce the effect of noise, we propose two ideas which utilize the characteristics of fault signal. The first one is to average holograms for several frequencies to reduce the random noise. The second one is to apply the partial field decomposition algorithm [Nam, K.-U., Kim, Y.-H., 2004, "A Partial Field Decomposition Algorithm and Its Examples for Near-field Acoustic Holography," J. of Acoust. Soc. Am. Vol. 116, No. 1, pp. 172${\sim}$185] to the moving source, which can separate the fault signal and noise. Basic theory of those methods is introduced and how they can be applied to localize bearing faults is demonstrated. Experimental results via a miniature vehicle showed how well the proposed method finds out the location of source in practice.

• 대한토목학회논문집
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• 제14권4호
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• pp.965-975
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• 1994

PHC말뚝의 선단부를 개방시켜서 사용하면 관입저항력의 감소로 인하여 관입깊이가 증가되며, 결과적으로 지지력의 증가를 가져온다. 그러나 개단 PHC말뚝의 사용을 위해서는 다음의 두가지 문제가 해결되어야 한다. 첫째는 말뚝의 선단부를 개방시킴에 따른 지지력의 변화이며, 둘째는 말뚝 내부로 유입되는 관내토에 의한 말뚝 선단부의 파괴여부이다. 따라서 본 연구에서는 개단 PHC말뚝의 실용성을 검토하기 위하여 먼저 말뚝의 선단부 형상에 따른 지지력 비교를 목적으로 두개의 폐단말뚝과 두 개의 개단말뚝을 이용하여 토조에서 모형말뚝실험을 수행하였다. 실험결과로부터 말뚝의 선단부 형상에 따른 관입저항력과 지지력의 변화 및 PHC말뚝 선단부의 파괴여부가 검토되었다. 실험결과 동일한 관입깊이에서 개단말뚝의 전체지지력은 관입깊이가 증가함에 따라 폐단말뚝의 전체지지력과 비슷해지며, PHC 말뚝의 경우 말뚝선단부로부터 말뚝내경의 0.8~1.1배되는 영역에서 균열발생의 가능성이 제시되었다.

• Progress in Superconductivity
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• 제11권1호
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• pp.57-61
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• 2009

A superconductor flywheel energy storage(SFES) system is mainly act an electro-mechanical battery which transfers mechanical energy into electrical form and vice versa. SFES system consists of a pair of non-contacting High Temperature Superconductor (HTS) bearings with a very low frictional loss. But it is essential to design an efficient HTS bearing considering with rotor dynamic properties through correct calculation of stiffness in order to support a huge composite flywheel rotor with high energy storage density. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate HTS bearing magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measured axial / radial stiffness and found bearing stiffness can be easily changed by activated vibration direction between PM and HTS bulk. These results are used to determine the optimal design for a 10 kWh SFES.

• Asian Pacific Journal of Cancer Prevention
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• 제15권8호
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• pp.3681-3686
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• 2014

In this study, we demonstrated selenium (Se) accumulation in Bifidobacterium longum strain (B. longum) and evaluated the effect of Se-enriched B. longum (Se-B. longum) on tumor growth and immune function in tumor-bearing mice. Analysis using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) revealed that more than 99% of Se in Se-B. longum was organic, the main component of which was selenomethionine (SeMet). In the in vivo experiments, tumor-bearing mice (n=8) were orally administrated with different doses of Se-B. longum alone or combined with cyclophosphamide (CTX). The results showed that the middle and high dose of Se-B. longum significantly inhibited tumor growth. When Se-B. longum and CTX were combined, the antitumor effect was significantly enhanced and the survival time of tumor-bearing mice (n=12) was prolonged. Furthermore, compared with CTX alone, the combination of Se-B. longum and CTX stimulated the activity of natural killer (NK) cells and T lymphocytes, increasing the levels of interleukin-2 (IL-2) and tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$), and the leukocyte count of H22 tumor-bearing mice (n=12).

• Steel and Composite Structures
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• 제27권4호
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• pp.417-426
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• 2018

This paper presents the seismic behaviors and restoring force model of ring beam joints of steel tube-reinforced concrete column structure under cyclic loading. First, the main failure mode, ultimate bearing capacity, stiffness degradation and energy dissipation capacity are studied. Then, the effects of concrete grade, steel grade, reinforcement ratio and radius-to-width ratios are discussed. Finally, the restoring force model is proposed. Results show that the ring beam joints of steel tube-reinforced concrete column structure performs good seismic performances. With concrete grade increasing, the ultimate bearing capacity and energy dissipation capacity increase, while the stiffness degradation rates increases slightly. When the radius-width ratio is 2, with reinforcement ratio increasing, the ultimate bearing capacity decreases. However, when the radius-to-width ratios are 3, with reinforcement ratio increasing, the ultimate bearing capacity increases. With radius-to-width ratios increasing, the ultimate bearing capacity decreases slightly and the stiffness degradation rate increases, but the energy dissipation capacity increases slightly.

• 자원환경지질
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• 제50권6호
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• pp.435-443
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• 2017

하내광상은 경상계 하양층군의 진동층 퇴적암내의 열극을 충진하여 발달한 함 동 열수 석영 맥상광상이다. 초기 맥상 석영과 함께 자류철석-황철석의 산출로 시작된 금속 광화작용은 자류철석-황철석 $\rightarrow$ 황철석-황동석-섬아연석(${\pm}$함비스무스 텔루라이드) 광화작용 $\rightarrow$ 함 은(Ag) 텔루라이드 광화작용 $\rightarrow$ 2차 광물 광화작용의 공생관계를 보이며 진행되었다. 유체포유물 가열실험 결과 하내 함 동 열수광화작용은 약 $400^{\circ}C$ 내지 $200^{\circ}C$ 온도조건의 열수계에서 진행되었다. 맥상 광물의 생성조합과 공생관계 및 유체포유물 가열실험 결과를 이용한 열역학적 해석결과, 하내 함 동 열수광체의 주된 함 동 광물인 황동석 주 광화시기 초기의 온도인 $350^{\circ}C$의 경우 $10^{-9.2}bar$의 황 분압조건에서 광화작용이 시작되었으며, $10^{-8.7}bar$에 이르는 황 분압조건과 ${\approx}10^{-32.1}bar$에서 ${\approx}10^{-29.8}bar$에 이르는 산소 분압조건에서 진행되었다. 주 광화시기 후기의 온도조건인 $250^{\circ}C$의 경우 ${\approx}10^{-13.5}bar$에서 ${\approx}10^{-13.2}bar$에 이르는 황 분압조건과 ${\approx}10^{-38.4}bar$에서 ${\approx}10^{-37.6}bar$에 이르는 산소 분압조건에서 시작되어 ${\approx}10^{-11.7}bar$ 및 ${\approx}10^{-35.2}bar$에 이르는 황 분압 및 산소 분압 각각의 점증에 의하여 진행되었다. 하내 열수계 최후기(${\geq}200^{\circ}C$) 텔루라이드 광화작용과 관련된 Te의 최소 분압조건은 ${\approx}10^{-18}bar$이며, 황 분압 조건은 ${\approx}10^{-14.0}bar$ 에서 ${\approx}10^{-10.9}bar$이었다.

• 콘크리트학회논문집
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• 제21권3호
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• pp.291-302
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• 2009

현행 기준식에 따르면 초고강도콘크리트에서는 철근 인장이음길이보다 압축이음길이가 더 길어지는 현상이 발생된다. 초고강도콘크리트의 경제적 실용화를 위해 합리적인 압축이음강도의 평가가 필요하다. 이를 위해 압축이음의 거동 특성을 분석하고 영향인자를 도출하였으며, 설계강도 40, 60 MPa 콘크리트에 대한 압축이음 실험을 수행하였다. 압축이음강도는 부착과 지압으로 구성되고, 부착과 지압의 복합 거동에 의해 발현되므로, 압축이음 거동특성 및 강도평가를 위해서는 부착과 지압이 함께 존재하는 상태에서의 연구가 수행되어야한다. 인장이음과 달리 압축이음은 이음길이가 짧고 지압의 존재로 인해 콘크리트 강도의 영향이 크다. 실험결과 압축이음강도는 콘크리트의 제곱근에 비례하는 것으로 평가되었다. 부착과 지압 모두 주변 콘크리트의 응력상태에 따라 결정되는데, 콘크리트의 축방향 응력이 높기 때문에 철근 순간격 증가에 따른 이음강도 증가는 거의 없다. 지압강도는 이음길이와 철근 순간격에 무관하며, 콘크리트 강도의 제곱근의 함수로 표현할 수 있다. 파괴양상이 측면파열파괴와 유사하므로 지압강도는 앵커의 측면파열파괴 강도식을 활용하여 평가가 가능하다. 부착에 의해 발현되는 강도는 인장이음의 경우와 유사하므로, 인장이음강도에 비해 향상된 압축이음강도는 단부 지압효과로 설명될 수 있다.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1583-1593
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• 2002

This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller. The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.151-156
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• 2001

Experimental frictional and wear characteristics of silicon graphite materials is studied in this paper. Those specimens are lubricated with high temperature and highly pressurized water to simulate the same operating condition for the journal bearing and the thrust bearing on the main coolant pump bearing in the newly developing nuclear reactor named SMART(System-integrated Modular Advanced ReacTor). Operating condition of the bearings is realized by the tribometer and the autoclave. Friction coefficient and wear loss are analyzed to choose the best silicon graphite material. Pin on plate test specimens are used and coned disk springs are used to control the applied force on the specimens. Wear loss ana wear width are measured by a precision balance and a micrometer. The friction force is measured by the strain gauge which can be used under high temperature and high pressure. Three kinds of silicon graphite materials are examined and compared with each other, and each material shows similar but different results on frictional and wear characteristics.