• Title/Summary/Keyword: Speed Variation

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Stiffness effect of fitting interference for a shrunk rotor (열박음 로터에서 간섭량의 강성 효과)

  • 김영춘;박희주;박철현;김경웅
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.319-324
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    • 2003
  • In general industrial rotating machinery is operated under 3,600 rpm as rotating speed and designed to have critical speed that is above operating speed. So, there was no problem to operate rotating machine under critical speed. But nowadays, they should be operated more than the frist critical speed as usual with the trend of high speed, large scale and hish precision in industries. In case of the large rotor assembly as the trend of large scale, using fitting method of disk or cylinder on shaft is rising for the convenience of assembly and cutting down of manufacturing cost. The shrink fitting is used to assemble lamination part on shaft for manufacturing of rotor of motor or generator in many cases and also is widely used for other machinery. In rotating system, which is compose of rotor and bearing, the critical speed is determined from inertia and stiffness for the rotor and bearings. In case of fitting assembly, analysis and design of the rotor is not easy because the rotor stiffness is determined depend on a lot of factors such as shaft material/dimension, disk material/dimension and assembled interference etc. Therefore designer who makes a plan for hish-speed rotating machine should design that the critical speed is located out of operating range, as dangerous factors exist in it. In order to appropriate design, an accurate estimation of stiffness and damping is very important. The stiffness variation depend on fitting interference is a factor that changes critical speed and if it's possible to estimate it, that Is very useful to design rotor-bearing system. In this paper, the natural frequency variation of the rotor depends on fitting interference between basic shaft and cylinder is examined by experimentation. From the result, their correlation is evaluated quantitatively using numerical analysis that is introduced equivalent diameter end the calculation criteria is presented for designer who design fitting assembly to apply with ease for determination of appropriate interference.

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A Study on the Solidification and Purification of High Purity Aluminium and Silicon by Stirring Method (냉각체 회전법에 의한 고순도 알루미늄 및 규소의 응고 및 정련에 관한 연구)

  • Kim, Wook;Lee, Jong-Ki;Baik, Hong-Koo;Yoon, Woo-Young
    • Journal of Korea Foundry Society
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    • v.11 no.4
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    • pp.303-313
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    • 1991
  • The Purification mechanism of high purity aluminum was studied through the variation of stirring speed and coolant flow rate in the stirring method. In the stirring method the degree of purification was changed as the following factors;the variation of diffusion boundary layer thickness the variation of growth rate and the solute concentration of the residual melt. The concentration of Fe and Si was decreased as the stirring speed and the radial distance increased. In a high stirring speed of 2000rpm with unidirectional stirring mode, the uniformity of solutes was obtained. On the other hand, the purification of Si was done by the combinations of stirring method, fractional melting and acid leaching. In the case of Si purification, the centrifugal force developed in the melt acted as the significant purification factor. It was possible to obtain the purified 3N grade Si crystal after the complete elimination of residual aluminum by fractional melting and acid leaching.

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An Experimental Study on the Dynamic Characteristics of a Planetary Gear Train in the Low Speed Region (유성치차열의 저속영역에서의 동특성에 관한 실험적 연구)

  • Lee, J. H.;Cheon, G. J.;Kim, J. H.;Kim, C.;Han, D. C.;Myung, J. H.;Jeong, T. H.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.4
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    • pp.121-129
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    • 1997
  • Gear train system test rig of power circulating type was fabricated, and systematic experiment for measuring dynamic characteristics of the planetary gear trains in the low speed region has been carried out using the test rig. The measured parameters are fillet strains of the sun gear and ring gear, carrier displacements, torques of the input and output shafts. The results are as follows : i) Even though the loading torque is constant, torque variation has been observed on the input and output hafts, ii) The variation of the torque has two frequency components, i.e. lower one of the input shaft rotation and higher one of the two teeth meshing, iii) The variation of the fillet strains shows the same tendency as that of the torque, iv) The loci of the carrier depend on the torque and rotational speed.

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Biomechanical Analysis of Human Stability According to Running Speed: A Comparative Analysis of Lyapunov Exponent and Coefficient of Variation Methods (달리기 속도에 따른 인체 안정성의 생체역학적 분석: 리아프노프 지수와 변이계수 방법의 비교 분석)

  • Ho-Jong Gil
    • Korean Journal of Applied Biomechanics
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    • v.33 no.1
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    • pp.34-44
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    • 2023
  • Objective: The purpose of this study was to examine the effects of increasing running speed on human stability by comparing the Lyapunov Exponent (LyE) and Coefficient of Variation (CV) methods, with the goal of identifying key variables and uncovering new insights. Method: Fourteen adult males (age: 24.7 ± 6.4 yrs, height: 176.9 ± 4.6 cm, weight: 74.7 ± 10.9 kg) participated in this study. Results: In the CV method, significant differences were observed in ankle (flexion-inversion/eversion; p < .05) and hip joint (internal-external rotation; p < .05) movements, while the center of mass (COM) variable in the coronal axis movements showed a significant difference at the p < .001 level. In the LyE method, statistical differences were observed at the p < .05 level in knee (flexion-extension), hip joint (internal-external rotation) movements, and COM across all three directions (sagittal, coronal, and transverse axis). Conclusion: Our results revealed that the stability of the human body is affected at faster running speeds. The movement of the COM and ankle joint were identified as the most critical factors influencing stability. This suggests that LyE, a nonlinear time series analysis, should be actively introduced to better understand human stabilization strategies.

Research for Optimal Operation of Switched Reluctance Motors (스위치드 릴럭턴스 전동기 최적운전을 위한 연구)

  • Sungin Jeong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.23 no.4
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    • pp.143-148
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    • 2023
  • Among the characteristics of SRM, due to nonlinearity, it is difficult to properly operate to form maximum torque and minimum torque pulsation. In addition, in the case of fixed switching angle control, torque formation according to speed variation is unstable, thereby reducing efficiency. Therefore, active switching angle control according to speed variation is required. Therefore, active switching angle control according to speed variation is required. In this paper, a method for improving driving performance by reducing torque ripple by automatic control of the advance angle and increasing output torque was sought from the problem caused by the nonlinearity of the SRM. In addition, the optimal operation of SRM due to the switching variable according to the performance of the hysteretic current controller was examined.

Wafer TTV Measurement and Variable Effect Analysis According to Settling Time (Settling Time에 따른 웨이퍼 TTV 측정 및 변수 영향 분석)

  • Hyeong Won Kim;Anmok Jeong;Taeho Kim;Hak Jun Lee
    • Journal of the Semiconductor & Display Technology
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    • v.22 no.3
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    • pp.8-13
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    • 2023
  • High bandwidth memory a core technology of the future memory semiconductor industry, is attracting attention. Temporary bonding and debonding process technology, which plays an important role in high bandwidth memory process technology, is also being studied. In this process, total thickness variation is a major factor determining wafer performance. In this study, the reliability of the equipment measuring total thickness variation is identified, and the servo motor settling, and wafer total thickness variation measurement accuracy are analyzed. As for the experimental variables, vacuum, acceleration time, and speed are changed to find the most efficient value by comparing the stabilization time. The smaller the vacuum and the larger the radius, the longer the settling time. If the radius is small, high-speed rotation performance is good, and if the radius is large, low-speed rotation performance is good. In the future, we plan to conduct an experiment to measure the entire of the wafer.

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Numerical Study of Reduction of External Pressure Variation and Micro-Pressure Wave for high-speed train in tunnel (고속열차의 터널 주행시 실외 압력 변화 및 미기압파 저감을 위한 수치해석적 연구)

  • Lee, Jung-Uk;Yun, Su-Hwan;Kwak, Min-Ho;Lee, Dong-Ho;Kwon, Hyeok-Bin
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.158-164
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    • 2011
  • When a train passes a conventiaonl tunnel at high speed, external pressure variation problem arises. It is known that this issue can be reduced by control the tunnel length. We studied the variances of external pressure variation within the tunnel, by altering length of the dummy tunnel duct. We also studies the variances of micro-pressure waves at the exit of tunnel, by altering surface area of dummy tunnel duct. For analyzing this train-tunnel relation problem, axisymmetric steady compressible flow solver was used.

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The Dynamic Characteristics Analysis Between Pantograph and Catenary System Using Block Pulse Function (블럭펄스함수를 이용한 판토그래프와 가선시스템사이의 동특성 해석)

  • Shin, Seung-Kwon;Song, Yong-Soo;Eum, Ju-Hwan;Eum, Ki-Young
    • Proceedings of the KIEE Conference
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    • 2004.11c
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    • pp.748-750
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    • 2004
  • The pantograph should supply the electrification equipments of a train with the current from the overhead catenary system over a broad range of speeds. For a high-speed electrical train, the dynamic interaction between the pantograph and the overhead catenary system causes the variation of the contact force. As the operational speed increases, the variation of the contact force increases. The contact force variation can cause contact losses, arcing and sparking. If the spark happens between the pantograph and the overhead catenary system, the EMI(electro magnetic interface) and noises may occur. After all, the quality of current collection is deteriorated. This paper deals with the dynamic characteristics analysis between pantograph and catenary system using block pulse function.

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Development of Feed-forward AGC using Adaptive Control Algorithm (적응기법을 이용한 Feed-forward AGC 기술 개발)

  • 홍성철;이영교
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.168-171
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    • 2003
  • Generally RF AGC (Roll Force Automatic Gauge Control) controls the roll gap using the variation of rolling force caused by the roll eccentricity and the entry thickness of material, but RE AGC takes the bad effect of the roll eccentricity. The Feed-forward (FF) AGC method, which controls the next stand roll gap by the estimation of the thickness variation due to skid mark is needed to supplement the shortage of RF AGC. In this paper, an adaptive filtering method which takes account of the kind of material, the final objective thickness and the rolling speed is proposed to predict skid mark thickness variation. In addition, an improved estimation method of control point using a speedometer and looper angle is suggested. Via on line test, the performance improvement of the suggested FF AGC method is verified.

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Stability Analysis of High-speed Driveshafts under the Variation of the Support Conditions (초고속 구동축의 지지 조건에 따른 안정성 분석)

  • Shin, Eung-Su
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.1
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    • pp.40-46
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    • 2011
  • This paper is to investigate the effects of the asymmetrical support stiffness on the stability of a supercritical driveshaft with asymmetrical shaft stiffness and anisotropic bearings. The equations of motion is derived for a system including a rigid disk, a massless flexible asymmetric shaft, anisotropic bearings and a support beam. The Floquet theory is applied to perform the stability analysis with the variation of the support stiffness, the shaft asymmetry, the shaft damping and the shaft speed. The results show that the asymmetric support stiffness is closely related to the stability caused by primary resonance as well as the supercritical operation. First, the stiffness variation can stabilize the system around primary resonance by weakening the parametric resonance from the shaft asymmetry. Second, it also improve the stability characteristics at a supercritical operation when the support stiffness is not so high relative to the shaft stiffness.