• Title/Summary/Keyword: Helical mode

Search Result 64, Processing Time 0.02 seconds

Dynamic Behavior Analysis of a Helical Coil Spring Using Space Curve Vector (공간곡선 벡터에 의한 원통 코일 스프링의 동적 거동 해석)

  • 김대원;김종수
    • Journal of KSNVE
    • /
    • v.8 no.6
    • /
    • pp.1015-1022
    • /
    • 1998
  • This paper addresses the results of an experimental and analytical research of a helical coil spring subjected to dynamic behavior using space curve vector after considering elongation rate. Vibrations in helical coil spring can be divided into 3 modes such as vibrations of coil spring center axis' vertical direction. axis' horizontal direction, direction about center axis. However. these 3 modes are dependent one another and are characterized as coupled. The dependency was proved through both theoretically and experimentally analyzing the results of dynamic characteristics of coil spring center axis' vertical direction vibration by transfer matrix method using the governing equation of static equilibrium. Also this paper shows that pitch angle and active coils in coil spring affect the dynamic spring characteristics of the above 3 modes and are especially sensitive to the mode for vibration of axis' horizontal direction which most affects especially on dynamo stability of helical coil spring.

  • PDF

Vibro-acoustic Characteristics of a Cylindrical Shell Type Gearbox Models by Helical Gear Excitation (헬리컬기어 가진에 의한 원통형 기어박스 모델의 진동음향 특성)

  • Park, Chan IL
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.27 no.1
    • /
    • pp.36-42
    • /
    • 2017
  • Helical gear excitation is transmitted to a gearbox through the shafts and bearings and the vibration of the gearbox radiates the noise in the air. Therefore gearbox modeling is essential to evaluate the gear noise. This work deals with vibration and acoustic analysis of a cylindrical shell-type gearbox with/without holes excited by helical gears and focuses on the development of the simple gearbox model. To do so, helical gears and bearing forces are calculated. Gearbox with/without holes is modeled by the aluminum end plates and PMMA cylindrical shell body. The vibration mode and the forced harmonic response were calculated by the commercial FE software and the end plate of the gearbox is more contributed to vibration than the body. Acoustic analysis was also conducted by the commercial acoustic software and a cylindrical shell type gearbox with/without holes has the similar vibro-acoustic characteristics.

Fretting-wear Characteristics of Steam Generator Helical Tubes (증기발생기 나선형 전열관의 프레팅 마모 특성)

  • Jong Chull Jo;Woong Sik Kim;Hho Jung Kim;Tae Hyung Kim;Myung Jo Jhung
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.14 no.4
    • /
    • pp.327-335
    • /
    • 2004
  • This study investigates the safety assessment of the potential for fretting-wear damages caused by foreign object in operating nuclear power plants. To get the natural frequency, corresponding mode shape and participation factor, modal analyses are performed for the helical type tubes with various conditions. The wear rate of helical type tube caused by foreign object is calculated using the Archard formula and the remaining life of the tube is predicted, and discussed in this study is the effect of the vibration of the tube on the remaining life of the tube. In addition, addressed is the effect of the external pressure on the vibration and fretting-wear characteristics of the tube.

The design of bent monopole antenna for 400MHz ISM band applications (400MHz ISM대역용 굴곡형 모노폴 안테나의 설계)

  • Lee, Young-Soon
    • Journal of Advanced Navigation Technology
    • /
    • v.15 no.2
    • /
    • pp.189-196
    • /
    • 2011
  • In order to subsitute for the normal mode helical wire antenna, bent monopole antenna combined with a helical structure is proposed as a kind of printed antenna. The antenna which can be operated at 418MHz has been simulated and designed by use of a commercial EM simulator Microwave Studio(MWS). It has been observed that the proposed antenna has good agreements between simulated results and measured results such as the return loss and the radiation pattern. The proposed antenna has been applied practically to the wireless remote controller operationg at 418MHz. It has been observed that the use of the proposed antenna result in similar antenna performance from view point of radiation power when compared with the use of the previous normal mode helical antenna.

Binding Interactions of TMAP to Triple- and Double Helical DNA

  • Kim, Nan-Jung;Yoo, Sang-Heon;Huh, Sung-Ho
    • Journal of the Korean Magnetic Resonance Society
    • /
    • v.10 no.2
    • /
    • pp.175-187
    • /
    • 2006
  • Binding interactions between a positively charged porphyrin derivative TMAP(meso-tetra(p-trimethylanilinium-4-yl)porphyrin) and triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, as well as double helical $(dA)_{12}{\cdot}(dT)_{12}$ have been studied with NMR, UV and CD spectroscopy to obtain the detailed information about the binding mode and binding site. UV melting studies showed both DNA duplex and triple helix represented very similar UV absorption patterns upon binding TMAP, but the presence of third strand of triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, inhibited improvement in thermal stability in terms of melting temperature, $T_m$. In addition, the TMAP molecule is thought to bind to the major groove, according to CD and NMR data. But absence of the clear isosbestic point in UV absorption spectra represented that binding of TMAP to DNA duplex as well as DNA triplex did not show a single binding mode, rather complex binding modes.

  • PDF

Vibration from a Shaft-Bearing-Plate System Due to an Axial Excitation of Helical Gears

  • Park, Chan-Il
    • Journal of Mechanical Science and Technology
    • /
    • v.20 no.12
    • /
    • pp.2105-2114
    • /
    • 2006
  • In this paper, a simplified model is studied to predict analytically the vibration from the helical gear system due to an axial excitation of helical gears. The simplified model describes gear, shaft, bearing, and housing. In order to obtain the axial force of helical gears, the mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer matrices for the rod and bearing are used, using a spectral method with four pole parameters. The model is validated by finite element analysis. Using the model, parameter studies are carried out. As a result, the linearized dynamic shaft force due to the gear excitation in the frequency domain was proposed. Out-of-plan displacement from the forced vibrating circular plate and the renewed mode normalization constant of the circular plate were also proposed. In order to control the axial vibration of the helical gear system, the plate was more important than the shaft and the bearing. Finally, the effect of the dominant design parameters for the gear system can be investigated by this model.

Instability of High-Speed Impinging Jets(II) (고속 충돌제트의 불안정 특성)

  • Gwon, Yeong-Pil;Im, Jeong-Bin
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.22 no.4
    • /
    • pp.450-467
    • /
    • 1998
  • The characteristics of the unstable impinging circular jet is investigated based on the frequency characteristics and the sound field of the impinging-tones. Two symmetric modes S1 and S2, associated with low frequency and high frequency respectively, and one helical mode H have been observed. At low speed the S2 mode is dominant and switched by the S1 mode as the speed increases. When the jet speed is high the S1 mode is very active over the impinging distance from half the nozzle diameter to its ten times, while the S2 mode occurs at shorter distance corresponding to stage 2 and 3. The helical mode H seems unstable, likely to be influenced much by the experimental environment, and occurs at relatively high speed with almost the same frequency characteristics as the S2 mode. By estimating the convection speed of the unstable jet, it is found that the ratio of the convection speed to the jet speed decreases with both Strouhal number and Reynolds number and the speed of S2 mode is faster than the Si mode. When the present experimental results are compared with the previous investigations performed for the hole tone and the impinging tone with a small plate, the S1 mode is found to be associated with the ring vortex of large diameter with low speed, but the S2 mode with the vortex of small diameter with high speed. In addition, the frequency is found to be influenced by the nozzle configuration but the characteristics is almost the same. From the impinging distance and frequency range, it can be deduced that S1 mode is related with the jet column mode and S2 mode with the shear mode.

Design of Tx/Rx Broadband Antenna on LTCC at K/Ka Band (LTCC 공정을 이용한 K/Ka 대역 송수신 겸용 이중 급전 안테나)

  • 천영민;김성남;오민석;최재익;표철식;이종문;천창율
    • The Transactions of the Korean Institute of Electrical Engineers C
    • /
    • v.53 no.9
    • /
    • pp.481-487
    • /
    • 2004
  • The Ku band that has been using for the satellite communication and broadcasting would be changed to K/Ka bands. The satellite system requires the antenna structure to fabricate low loss and small antenna that is able to be integrated with other Rf circuits for both Rx and Tx. So we should design it with dual feed antennas at K/Ka bands, high isolation between two different feeds and broadband circular polarization. This paper proposes the LTCC(Low Temperature Co-fired Ceramic) process for integration with other Rf circuits and the Axial mode of the helical antenna to satisfy those requirements.

Instabilities of High-speed Impinging Circular Jets (고속 원형충돌제트의 불안정 특성)

  • 임정빈;권영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 1997.10a
    • /
    • pp.256-262
    • /
    • 1997
  • The characteristics of the unstable impinging circular jet were investigated based on the frequency characteristics and the sound field of the impinging-tones. Two symmetric modes Si and S2, associated with low frequency and high frequency respectively, and one helical mode H have been observed by measuring frequency and phase-distribution around the jet. Radiation characteristics of impinging-tone were studied by measuring axial directivity. It was founded that the radiation patterns of symmetric and helical mode are different and it is toward the plate as the impinging distance increased. By estimating the convection velocity of the unstable jet, it was founded that the convection speed decreases with the frequency and its decreasing pattern varies with unstable modes S1, S2 and H, respectively.

  • PDF