4th Mode Research Articles

Нормативно-техническое обеспечение BIM автомобильных дорог

В мире примерно с 2010 г. начал формироваться шестой технологический уклад мировой экономики, а дорожная нормативно-техническая база всё ещё соответствует только четвёртому укладу. В статье обсуждаются шаги, необходимые для приведения процесса управления автомобильными дорогами в соответствие с требованиями уже завершенного пятого уклада (основанного на электронике, вычислительной технике, телекоммуникациях и информационных технологиях) и подготовиться к шестому (основанному на нано-, био-, IT-технологиях и их конвергенции).

Disturbance attenuation for standing wave oscillation in a water wave tank based on feedback control with a vertical-vibrating plate

This paper proposes active control system based on feedback control and an wave generating actuator with a vertical-vibrating plate, in order to attenuate standing-wave oscillation by unkown disturbance contamination in water wave tank. The validity of the system is examined by control experiments. The water wave tank is about 0.9 m in length, and has two actuators symmetrically located in the tank (one for disturbance generation and one for attenuation control) and two water-level sensors (one for control measurement and one for performance evaluation). First, the plant model is identified based on frequency response experiments, and the validity of the model is shown by a numerical analysis with the boundary element method. Secondly, the feedback controller is systematically designed by H∞ control synthesis so that the robust stability is guaranteed against plant uncertainty, and the validity of the system is shown based on the symmetry locations of actuators. Finally, control experiments are examined by using sinusoidal and random signals as unknown disturbance. It has been shown that the frequency components of resonance from the 1st to 4th modes are reduced by 20%～60%,which shows the desired performance of the proposed system to attenuate standing-wave oscillation.

Cavity piezooptomechanics: Piezoelectrically excited, optically transduced optomechanical resonators

We present a monolithic integrated aluminum nitride (AlN) optomechanical resonator in which the mechanical motion is actuated by piezoelectric force and the displacement is transduced by a high-Q optical cavity. The AlN optomechanical resonator is excited from a radio-frequency electrode via a small air gap to eliminate resonator-to-electrode loss. We observe the electrically excited mechanical motion at 47.3 MHz, 1.04 GHz, and 3.12 GHz, corresponding to the 1st, 2nd, and 4th radial-contour mode of the wheel resonator, respectively. An equivalent circuit model is developed to describe the observed Fano-like resonance spectrum.

実測データに基づく鉄骨造高層建物の構造ヘルスモニタリングと減衰特性評価

This paper describes the dynamic characteristics based on microtremor measurement data concerning a high rise steel building. The object building which was completed in October 1998 is 120 m height and rectangular plan. Microtremor measurement is continued periodically in the building. The acceleration and velocity of measurement data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 4th mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between vibration amplitude and damping ratios in free vibration waves employing manpower excitation are discussed.

Effect of local damage on the behavior of a laboratory-scale steel truss bridge

This paper presents an investigation into the performance of a steel truss bridge subjected to local damage. An experimental program with 16 damage scenarios is conducted to study the behavior of damaged truss systems. A three-dimensional numerical model is developed to predict the test results. Static and dynamic responses of the damaged trusses are compared with those of the control. Various technical aspects are studied, including damage quantification using a damage index, load rating, variation of strain energy, modal analysis, and structural safety based on simple reliability theory. Service performance of the truss bridge is significantly influenced by local damage (i.e., damage index >0.5) and the load-carrying capacity is exponentially reduced with the increased damage index. A high mode shape such as the 4th mode is of use to diagnose local damage in the truss system. The global safety index derived using deflection characteristics is an indicator to indirectly detect the presence of local damage in the system. Stress redistribution among the constituent truss members is found to be insignificant, except for those adjacent to the damage. The global safety index of the system based on deflection characteristics is an indicator to diagnose the presence of local damage. The need for developing a repair method that can address the global redundancy of a damaged truss bridge is highlighted.

Micro Polishing of Tungsten Carbide Using Magnetostrictive Vibrating Polisher

Micro structured glass lenses are highly required in new fields such as Micro channels, Fresnel lenses for solar panels and Wafer Level Cameras (WLC). The glass lenses are moulded bypress moulding with micro ceramics moulds made of tungsten carbides (WC). In this paper, a new Vibration Assisted Polishing (VAP) method is proposed and developed by using circular vibration of the magnetostrictive vibrating polisher. The polisher is composed of a magnetostrictive vibrator and a small polishing tool, and the small polishing tool is mounted on the head of the magnetostrictive vibrator. The concrete design of the magnetostrictive vibrating polisher is assisted by the finite element method (FEM) and through vibration mode analysis, the 4th mode is selected. It generates a circular vibration trace at a frequency of 9.2 kHz with a radius of 30 μm. The polisher is fixed in a 5-axis (X, Y, Z, B and C) controlled polishing system. Through some fundamental polishing experiments, the shapes of the removal function is acquired and surface roughness is reduced to 9 nm Rz (1 nm Ra).

Fabrication and Testing of Polymer Cantilevers for VOC Sensor

Abstract The mode dependences of resonance frequencies and quality factors in a PMMA (polymethyl methacrylate) cantilever and a PC (Polycarbonate) cantilever at atmospheric pressure are investigated to obtain fundamental data for polymer-based VOC (volatile organic compounds) sensors. The PMMA cantilever and the PC cantilever are fabricated using hot embossing, bonding and polishing techniques. The resonance frequencies and the quality factors are found to vary largely depending on the vibration mode. The measured resonance frequencies correlate well with the theory of undamped resonance frequency of a flexural-vibrating cantilever. The measured quality factors varied from less than 20 to more than 100 depending on the vibration mode. A higher mode tended to exhibit a higher quality factor. The highest quality factor of 100 was obtained on the 4th flexural mode in both the PMMA and PC cantilever.

440 実測データに基づく鉄骨造高層建物の構造ヘルスモニタリングと減衰特性評価

This paper describes the dynamic characteristics based on microtremor measurement data concerning a high-rise steel building. The object building which was completed in October 1998 is 120m height and rectangular plan. Microtremor measurement is continued periodically in the building. The acceleration and velocity of measurement data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 4th mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between vibration amplitude and damping ratios in free vibration waves by manpower excitation are discussed.

가속도 되먹임 제어기를 이용한 양단지지보의 능동 제어

This paper reports active control of clamped beams using acceleration feedback controllers (AF). The equations of motion of clamped beam under force and moment pairs were derived and the equations of AF controllers were formulated. The effect of the parameters - gain and damping ratio - of the AF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the AF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies. The increase of the damping ratio of the AF controller leads to decrease the magnitude of the open loop transfer function and modifies its phase characteristics to be more stable. Three AF controllers connected in parallel were then proposed. Each AF controller is tuned at the 2nd, 3rd and 4th modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 3 modes can be obtained.

Piezoelectric actuated epitaxially grown AlGaN/GaN‐resonators

AbstractIn this work we present a novel concept of piezoelectrically actuated MEMS resonators based on AlGaN/GaN‐heterostructures. The 2DEG, which is confined at the AlGaN/GaN interface, serves as back electrode for piezoelectric actuation and read‐out. Using the inverse piezoelectric effect longitudinal in‐plane mechanical oscillations could be exited by applying a RF signal to the drive contacts. Through the charges, which were generated by the direct piezoelectric effect a sensor signal could be detected at the sense contacts of the integrated resonator structure. This enables the measurement of longitudinal resonant frequencies up to the 4th mode with values from 3 to 63 MHz. The investigations were carried out in various ambient pressure conditions, which exemplarily demonstrate the sensitivity of the quality factor to environmental parameters. Thereby the AlGaN/GaN‐resonators showed the highest sensitivity in the region of viscous damping, which leads to the possibility of sensor applications concerning the property determination of gaseous or even liquid surrounding conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

11805 常時微動測定に基づく鉄骨造高層建物の構造ヘルスモニタリング(OS5 運動と制御(1),オーガナイズドセッション)

This paper describes the dynamic characteristics based on microtremor measurement data concerning a high-rise steel building. This microtremor measurement is continued periodically. The object building which was completed in October 1998 is 120m height and rectangular plan. The acceleration and velocity data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 4th mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between amplitude and damping ratios in free vibration waves by manpower excitation are discussed.

Correlating Low-energy Impact Damage with Changes in Modal Parameters: A Preliminary Study on Composite Beams

This article is an experimental study of the effects of multi-site damage on the vibration response of a composite beam damaged by low-energy impact. The variation of the modal parameters with different levels of impact energy and density of impact is studied. Specimens are impacted symmetrically in order to induce a global rate of damage. A damage detection tool Damage Index is introduced in order to verify the estimation of damping ratios. Design of Experiments is used to establish the sensitivity of both energy of impact and density of damage. The DOE analysis results (using natural frequency only) indicate that impact energy for 2nd, 3rd, and 4th bending modes is the most significant factor contributing to the changes in the modal parameters for this kind of symmetrical dynamic test.

454 常時微動測定に基づ<鉄骨造高層建物の構造ヘルスモニタリングと振動特性評価

This paper describes the dynamic characteristics based on microtremor measurement data concerning a high-rise steel building. The object building which was completed in October 1998 is 120m height and rectangular plan. Microtremor measurement is continued periodically in the building. The acceleration and velocity of measurement data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 4th mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between amplitude and damping ratios in free vibration waves by manpower excitation are discussed.

EBG-Embedded Multiple-Mode Resonator for UWB Bandpass Filter With Improved Upper-Stopband Performance

An electromagnetic bandgap (EBG) embedded multiple-mode resonator (MMR) is proposed to constitute an upper-stopband-improved and size-miniaturized ultra-wideband (UWB) bandpass filter (BPF). This EBG-embedded MMR is studied to relocate its first three resonant modes within the 3.1-10.6GHz passband, whereas placing its 4th resonant mode at the coupling transmission zero of interdigital coupled-lines that drive this MMR at two sides. Meanwhile, the fifth resonant mode is rejected by virtue of the bandstop behavior of the EBG itself. Thus, a modified UWB BPF with widened upper-stopband, sharpened upper rejection skirt and lowered loss in the passband is finally constituted, designed and fabricated. The measured results demonstrate that the insertion loss is lower than 1.0 dB in the passband (4.0-10.6GHz) and higher than 15.0dB in the upper-stopband (12.0 to 20.0GHz) while the group delay variation in the passband is less than 0.2ns

Prediction of acoustic resonance phenomena for weapon bays using detached eddy simulation

AbstractIt is argued that acoustic resonance phenomena in open cavities such as weapons bays cannot be adequately predicted through numerical solution of Reynolds averaged Navier-Stokes (RANS) equations. The requirement to resolve the growth of the shear layer instability from the lip of the cavity inevitably implies that turbulence further downstream is resolved while also being modelled thus making RANS over dissipative. Large eddy simulation (LES) models only unresolved scales and a hybrid method combining RANS near walls with LES in the cavity appears a practical alternative to pure RANS. This paper compares computations of the M219 cavity configuration made with unsteady RANS and with the hybrid method known as detached eddy simulation (DES). It is shown that whilst unsteady RANS and DES give very similar predictions for the 1st and 3rd modes of the acoustic resonance the 2nd mode (which is dominant near the centre of the cavity) is absent in the RANS results but well predicted by DES. The 2nd mode is thought to arise from an interaction with vortical structures in the shear layer which are suppressed in the highly dissipative RANS method. The 4th mode, which is much weaker than the other three modes, is over-predicted by DES and under-predicted by a smaller amount in RANS.

Effect of Ni substitution on the dielectric properties and lattice vibration of Ba(Mg 1/3Ta 2/3)O 3

Far infrared reflectivity spectra for Ba(Mg 1/3,Ta 2/3)O 3 and Ba([Mg 1− x Ni x ] 1/3,Ta 2/3)O 3 ceramics were measured and eigenfrequencies and damping constants of transverse optical modes were estimated in order to investigate the variations in the dielectric properties with Ni substitution. These ceramics were prepared by the conventional solid phase reaction method using high purity chemicals. The observed reflectivity spectra were fitted as a function of the vibration frequencies and the damping constants. The permittivity and Qf value decreased with Ni substitution. The decrease in permittivity is due to the decrease in the damping constant of 4th vibration mode of the oxygen layer vibration. The decrease in Qf value is due to the increase in the damping constant of 5th vibration mode of the oxygen layer vibration. It was inferred that the increase in the Qf value might be due to the substitution of the Ni ion for the Ta ion in the Ta layer in the BMT.

Far-infrared reflection and microwave properties of Ba([Mg 1− xZn x] 1/3,Ta 2/3)O 3 ceramics

Far-infrared reflectivity spectra for Ba(Mg 1/3,Ta 2/3)O 3 and Ba([Mg 1− x Zn x ] 1/3,Ta 2/3)O 3 ceramics were measured and eigen frequencies and damping constants of lattice vibration were calculated. In this paper, decrease of Qf value by Zn substitution was analyzed using the vibration parameters. These ceramics were prepared by conventional solid phase reaction using high purity reagents. The observed reflectivity spectra were fitted by 16 IR active modes predicted by factor group analysis in order to estimate the vibration eigen frequencies and damping constants. A slight change of reflectivity appeared in the low frequency region, and it was found that there was certain correlation between the changes of dielectric loss and damping constants in lattice vibration in 4th and 5th modes. The decrease of Qf value might be caused by the correlation in this system.

Dielectric loss and damping constants of lattice vibrations in Ba(Mg1/3,Ta2/3)O3 ceramics

Far-infrared reflectivity spectra for Ba(Mg1/3,Ta2/3)O3 ceramics (prepared from high quality oxide reagents) sintered at 1600 °C for 4 and 50 h were measured at room temperature, to determine eigen frequencies and damping constants of lattice vibration in order to understand why the Q·f value at microwave frequency was improved by sintering time. The observed reflectivity spectra were fitted to 16 IR active modes predicted by factor group analysis in order to estimate the fitting parameters. Differences in reflectivity and damping constants were confirmed between the two samples by observation of the measurement spectra and their spectrum fitting. The fitting parameters were used to simulate dielectric loss at low frequency. Results of the simulation suggested a contribution of 3rd, 4th and 5th vibration modes to dielectric loss at low frequency.

Nonlinear effects in an asymmetrical vibrating wire

The asymmetries of a vibrating harpsichord wire which yield different free vibrational frequencies along two characteristic orthogonal transverse axes were described previously [Hanson et al., J. Acoust Soc. Am. 106, 2141 (1999)]. This splitting of the fundamental vibrational frequency is of the order of 0.3%. Its value depends upon the particular wire sample and the tension, with lower tensions yielding larger absolute splittings. For the 2nd, 3rd and 4th vibrational modes, splittings differ greatly from integral multiples of the splitting of the fundamental. If the wire is driven sinusoidally there can be large nonlinear generation of motion in a direction (P) perpendicular to the driving direction (D) and of higher harmonics of the driving frequency. These nonlinear effects are, however, very sensitive to the frequency splitting and the relation of the driving direction to the characteristic axes. Theory indicates that P/D∼1, independent of the vibrational amplitude. However, with a small splitting of 0.11 Hz out of 77 Hz, it was found that to obtain P/D∼1 an amplitude at the antinode of about 0.15% of the wire length was necessary. The driving frequency region for generation of higher harmonics is sharply dependent on the higher free-vibration mode frequencies.

Coupling of velocity dispersion curves of leaky Lamb waves on a fluid-loaded plate

The coupling of velocity dispersion curves of leaky Lamb waves is studied based on analytical calculations to clarify the problem of repulsion and crossing of the curves. Two curves, corresponding to the 4th and 5th modes, are closely observed while artificially varying the properties of virtual materials, in the combination of piezoelectric ceramic and glass. The imaginary part of the Lamb-wave velocity is essential for distinguishing the coupling phenomena. The behaviors of the velocity values as functions of two variables, material property and the product of frequency and thickness of the plate, are analogous to the Riemann sphere defined by a mathematical function of ω=z(1/2) (both z and ω are complex) inside the domain containing the point z=0 on the complex plane.