2nd Mode Research Articles

Low Amplitude High Frequency Atomic Force Microscopy

Heterodyne laser Doppler interferometry was used to implement a high frequency atomic force microscope (AFM) that can accommodate a cantilever with a natural frequency of up to 200 MHz. Since Doppler interferometry measures velocity, the signal level increases proportionally with frequency for a given amplitude of oscillation, or the noise floor in terms of displacement decreases with 1/f. A noise level of 0.5 fm/√Hz was attained around 2 MHz, giving a large signal to noise margin for high frequency cantilevers and higher vibration mode detection. We have so far confirmed the following: (i) atomic resolution of Si(111) 7×7 with an amplitude of drive as low as 0.03 nm at 1.6 MHz, (ii) true atomic resolution dynamic lateral force microscopy, (iii) lateral force gradient detection at the atomic level, (iv) manipulation of Si atoms at room temperature, (v) vibration measurement of Si nanowires, tungsten oxide whiskers and graphene cantilevers above 100 MHz, (vi) atomic resolution imaging with the 2nd and 3rd mode of deflection and (v) true atomic resolution imaging in water using deflection or torsion with a few 10 pm amplitude of drive.

3202 扇形圧電振動子を用いた薄型マイクロ超音波モータの駆動特性の解析と評価(J22-1 次世代アクチュエータシステム(1),ジョイントセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

A low-profile micro ultrasonic motor has been designed and fabricated. This motor has two sector shaped vibrators. The vibrators generate elliptical motion by the 1st longitudinal mode and the 2nd bending mode. They are supported by planar elastic structure that combined with preload mechanism. Three types of pre-load systems were designed and evaluated. The diameter and thickness of one type was 9.8[mm] and 0.6[mm]. These vibrators have been oscillated around 340 [kHz]. The maximum rotation speed was 1.2 x 10^3 [rpm] and the maximum starting torque was 98.8[μNm] when the applied voltage was 20[V_<p-p>].

Factors Affecting the Wintering Habitat of Major Fishery Resources in Southwestern Korean Waters

We investigated the temperature and salinity effects on the major fish species in the wintering grounds based on trawl surveys and oceanographic observations in the southwestern waters of Korea during March-early April in 2002-2003. The influence area of warm Kuroshio water was limited to the southwestern area of Korea in 2003 with a range of 7.7-16.3°C, 32.54-34.70 of salinity, wider than that of 2002. The number of fish species and density of major fish species in 2003 were higher than in 2002. Geographical estimation showed high proportions of species number and catches in the areas around Jeju Islands, southwestern waters and the southeastern coast of Korea. Five species; silver pomfret (Pampus echinogaster), hairtail (Trichiurus lepturus), anchovy (Engraulis japonicus), small yellow croaker (Larimichthys polyactis) and yellow goosefish (Lophius litulon) were most abundant, composing above 60% of the total catch in 2002 and 2003. More than 50% of catch in the major fish species were mostly distributed in the range of 9.5-11.0°C of temperature and 33.1-33.9 of salinity. Non-parametric estimation for the major species showed the 1st mode around 10°C and the 2nd mode at 8-9°C in 2002 and 11-14°C in 2003. A m o n g major fish species, hairtail was principally composed of juveniles, and larger individuals were caught in southeastern waters. These results are considered to be helpful for the areabased fishery management strategy for the wintering grounds of the Yellow Sea and coastal waters of Korea.

A Q-value Measurement for Damping Evaluation and Rotational Test of Over-Hung Rotor Supported by AMBs

In recent years, Active Magnetic Bearings (AMBs) characterized by non-contact support without mechanical loss have been applied in industrial rotors. The purpose of this research is to develop a flexible, overhanging rotor supported by AMBs to pass smoothly the 2nd bending mode critical speed. This paper deals with the following topics : (1) Controller design based on the phase adjustment method and the evaluation of the designs using sensitivity functions, (2) Evaluation of the designs using a new method, called Q-value function, and (3) Application of modal balancing method to pass the 2nd bending mode critical speed.

Image Noise Reduction Using Vibration Mode Shaping for Scanning Electron Microscope

This paper addresses Scanning Electron Microscope (SEM). There is the quality problem that the image noise caused by the acoustic noise disturbs observation for correct shape of the specimen. Thus, SEM be less influenced by the acoustic noise is expected.This paper approaches to this image noise problem from the mode shapes of the base plate, and the transmission path of the acoustic noise and vibration. Firstly, the mode shapes of the base plate with conventional rib are compared to those of the plain base plate, and no remarkable increase in natural frequencies and no change in mode shapes are shown. Secondary, new base plate, which has two twisting mode as 1st and 2nd mode by arranging position of the rib, is developed. In those two twisting modes, vibration amplitude around the center of the base plate is smaller than that in bending modes. Thus, less vibration is transmitted to the specimen chamber and to the specimen in twisting modes than bending ones. Finally, the developed base plate is assembled to SEM, and remarkable reduction of the image noise under the condition of the acoustic noise below 250Hz is shown. This base plate has already applied to the products on the market.

223 FEMによる浮屋根式タンクのスロッシングシミュレーション

The 2003 Tokachi-Oki earthquake caused severe damage of oil storage tanks due to long-period ground motions. After that, the technical standards of the Fire Service Act regarding the sloshing with floating roof tanks were revised. The influences of non-linearity of liquid behavior and 2nd mode sloshing were taken into consideration using FEM(Finite Element Method) at this time. However, it is not enough that sufficient description about FEM model such as contact definition, time steps, number of element division, hourglass control and seal model. In this paper, the authors present the suitable model of sloshing simulation for floating roof in oil storage tanks using FEM.

Analysis of two dimensional and three dimensional supersonic turbulence flow around tandem cavities

The supersonic flows around tandem cavities were investigated by two-dimensional and three-dimensional numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) equation with thek-ω turbulence model. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves, and the acoustic effect transmitted from wake flow to upstream. The upwind TVD scheme based on the flux vector split with van Leer’s limiter was used as the numerical method. Numerical calculations were performed by the parallel processing with time discretizations carried out by the 4th-order Runge-Kutta method. The aspect ratios of cavities are 3 for the first cavity and 1 for the second cavity. The ratio of cavity interval to depth is 1. The ratio of cavity width to depth is 1 in the case of three dimensional flow. The Mach number and the Reynolds number were 1.5 and 4.5 × 105, respectively. The characteristics of the dominant frequency between twodimensional and three-dimensional flows were compared, and the characteristics of the second cavity flow due to the first cavity flow was analyzed. Both two dimensional and three dimensional flow oscillations were in the ‘shear layer mode’, which is based on the feedback mechanism of Rossiter’s formula. However, three dimensional flow was much less turbulent than two dimensional flow, depending on whether it could inflow and outflow laterally. The dominant frequencies of the two dimensional flow and three dimensional flows coincided with Rossiter’s 2nd mode frequency. The another dominant frequency of the three dimensional flow corresponded to Rossiter’s 1st mode frequency.

Vibration damping properties of gradient polyurethane/vinyl ester resin interpenetrating polymer network

In this paper, the vibration damping properties were measured by cantilever method with steel beams as substrate, gradient PU/VER (BMA) IPN as coatings and when used, polysulfide rubber modified epoxy resin without fillers and with common inorganic fillers and whisker crystals as constrained layer. The effects of the thickness ratio of damping layer and steel beam and the sequence of gradient coating on loss factor ( η) of extensional damping structure were studied. The effects of the thickness ratio and the time interval of coating (the time difference between coating a layer and another layer) between constrained layer and damping layer on damping properties of constrained damping structure were detected. Modulus of constrained layer was further increased by adding common fillers and inorganic whisker crystals in order to increase η of overall structure. The results show that damping properties of the extensional damping structure with the thickness ratio of 2:1 and the sequence of 70:30–60:40–50:50 (on the steel beam, the first layer is IPN with the component ratio of 70:30, the second layer is 60:40 IPN and the third layer is 50:50 IPN), are better compared with the others. When the thickness of constrained layer and damping layer is respectively 1 mm and the time interval of coating is 3 h, the η of optimized constrained damping structure with 10% aluminum borate (Al 18B 4O 33) whisker crystal in the constrained layer at 2nd mode are higher than 0.14 from −20 to 55 °C and its η at 2nd mode is 0.32 at −20 °C. The binding condition between constrained layer and damping layer was observed by SEM.

The Evaluation of the Damping Characteristics of a Hard Coating on Titanium

Engine failures due to fatigue have cost the Air Force an estimated &amp;dollar;400 million dollars per year over the past two decades. Damping treatments capable of reducing the internal stresses of fan and turbine blades to levels where fatigue is less likely to occur have the potential for reducing cost while enhancing reliability. This research evaluates the damping characteristics of magnesium aluminate spinel, MgO+Al2O3, (mag spinel) on titanium plates from an experimental point of view. The material and aspect ratio were chosen to approximate the low aspect ratio blades found in military gas turbine fans. In the past, work has generally been performed on cantilever supported beams, and thus the two‐dimensional features of damping were lost. In this study plates were tested with a cantilevered boundary condition, using electrodynamic shaker excitation. The effective test area of each specimen was 4.5 in × 4.5 in. The nominal plate thickness was 0.125 in. Mag spinel was applied to both sides of the plate, at a thickness of 0.01 in, and damping tests were run at room temperature. The effect of the coating was evaluated at the 2nd bending mode (mode 3) and the chord wise bending mode (mode 4). A scanning laser vibrometer revealed the frequency and shape of each mode for the plates. Sine sweeps were used to characterize the damping of the coated and uncoated specimens for the modes tested. The coating increased damping nonlinearly for both modes tested in which the general outcome was similar to that found in beams.

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.

Acoustic resonance in a staggered tube array: Tube response and the effect of baffles

An experimental laboratory study was performed to measure the effect of acoustic noise on the magnitude of tube vibrations in a staggered tube array and to measure the effectiveness of baffles on suppressing transverse duct modes. The acoustically induced tube vibration was experimentally determined for a flexible tube in three different transverse locations in the tube array. It was found that a tube located in the center of the duct, where a nodal point of the acoustic pressure resided, was most influenced by the transverse mode. On the other hand, a tube located near the duct side wall, where the acoustic pressure oscillation was highest, was not affected by the acoustic standing wave since it produced almost imperceptible vibration. It is shown that the acoustic pressure gradient across a tube is the cause of the tube vibration. Experiments were also performed to determine the effect of baffles for reducing the noise of acoustic resonance. The results showed that a single baffle substantially reduced the first mode resonance, as long as it was located close to the center of the bundle. The insertion of two baffles, in various locations, effectively eliminated acoustic resonance in the 1st and 2nd transverse duct modes. It is seen that the third acoustic mode is not significantly affected by either one or two baffles.

Enhancement of oxygen transfer in hollow fiber membrane by the vibration method

The purpose of this study was to assess and quantify the beneficial effects of gas exchange according to the various frequencies of the sinusoidal wave that are excited by a PZT actuator, on patients suffering from acute respiratory distress syndrome (ARDS). In this study, an experimental method for the flow hydrodynamics was developed through a bundle of sinusoidally vibrated hollow fibers to observe how well vibrations might enhance the performance of the VIVLAD. We measured the effect of the various excitation frequencies of the PZT actuator on the gas transfer rates and hemolysis from the maximum gas transfer rate. As a result, the maximum oxygen transfer rate was reached at the maximum amplitude and through the transfer of vibrations to the hollow fiber membranes. The device was maximum excited by a frequency band of 7 Hz at various water flow rates, as this frequency was the 2nd mode resonance frequency of the flexible beam. 675 hollow fiber membranes were also bundled, within the blood flow, into the device.

The Multimode LC Alignment on the Substrates Obliquely Treated with a Plasma Flux

ABSTRACT We describe a variety of liquid crystal (LC) alignment modes on the aligning substrates obliquely treated with a flux of accelerated plasma from the anode layer thruster (ALT). The discharge area has a form of race track so that the generated flux contained two sheets of plasma corresponding to linear parts of the discharge. Within each “sheet” the intensity of flow (ion current density) is uniform in the direction parallel to the linear part of discharge. Across the “sheet”, the intensity of flow has the Gaussian distribution. The alignment of LC with positive and negative dielectric anisotropy, Δϵ, was tested on the substrates of organic (polymers) and inorganic (glass and DLC) origin treated in static and dynamic regime (unidirectional translation perpendicularly to plasma “sheet”). In the dynamic regime of irradiation, with the substrate moving with respect to the plasma beam, for LC with Δϵ > 0 we observed two aligning modes, with the easy axis confined to the plane of plasma incidence (mode 1) or perpendicular to this plane (mode 2). In the 1st aligning mode the LC pretilt angle is non-zero and can be varied with the incidence angle of plasma beam and the irradiation dose. With the increase of irradiation dose, the alignment transition from the 1st to the 2nd mode occurs. For LC with Δϵ < 0 only the 1st alignment mode uniform over all substrate was observed. In the static regime of irradiation, characterized by smooth distribution of the particle's flow across the sheet, two modes are clearly observed simultaneously; 2nd mode alignment occurs in central, most intensive part of flow, while the periphery part shows the 1st mode. The areas of the 1st and the 2nd mode are separated with the narrow transition area showing multidomain (two-fold degenerate) LC alignment. The easy axis in these domains is turned by about ±45° with respect to the alignment direction in the 1st mode area. This sequence of the alignment transitions is observed in both LC with Δϵ > 0 and Δϵ < 0. We also describe a high-tilt alignment (87°–90°) in the 1st mode realized on the hydrophobic polymers at the extremely low doses of plasma irradiation. The origin of the observed alignment effects is discussed.

Four-arm 2nd- mode slot spiral antenna with simple single-port feed

The design and performance of a novel 4-arm equiangular slot spiral antenna operating in the 2nd mode are discussed in this letter. A straightforward feeding method consisting of a single vertical coaxial probe and no underlying mode forming network is proposed. Along with inherent simplicity, this feed enables design flexibility with respect to the slot-to-metal ratio, growth rate, and other spiral parameters. Numerical tools including an in-house finite element-boundary integral (FE-BI) code and Ansoft HFSS are used in designing the antenna. Good performance over an octave bandwidth is achieved, with axial ratio and WoW less than 3 dB, nominal gain of 3 dBic, and VSWR less than 1.6. Performance is verified with measurements. A method for increasing the bandwidth up to 3 : 1, which is the theoretical value determined by the excitation of the first higher order mode, is demonstrated computationally.

Low-profile broadband dual-mode four-arm slot spiral antenna with dual Dyson balun feed

The authors propose a low profile 4-arm slot spiral for broadband commercial applications. The antenna is designed for circularly polarised dual-mode, 1st (normal) mode and 2nd (split-beam) mode, operation from 1.4–3.5 GHz and 2.5–6 GHz, respectively. Phase progressions at arm ports are realised through the odd and even coplanar waveguide (CPW) excitations, a dual Dyson balun, and a single broadband 180° hybrid. A finite-element boundary-integral (FE-BI) based numerical tool is extensively used to study effects of various antenna parameters, including slot width, resistive taper etc. The designed antenna has return loss better than 10 dB, nominal gain of 3 dBic, wobble on wave less than 3 dB and axial ratio lower than 4 dB over realised bandwidth for both modes. When compared with classical printed 4-arm spirals, the proposed antenna has only two access ports and is about five times shallower. Thus, a much simpler mode-forming network is needed and significant reduction in the cost can be achieved. Measured and simulated results are presented and, generally, a very good agreement between the two is obtained.

Experimental Consideration of Acceleration Sensor Utilizing Resonance Frequency Change of Flexural Vibrator

In this paper, the characteristics of the acceleration sensor utilizing the resonance frequency change in the flexural vibrator are examined experimentally. The sensor sample was produced using stainless steel. It was confirmed that the relationship between the applied acceleration and the resonance frequency change becomes linear and almost coincides with the theoretical value by the finite element analysis. The sensor sensitivities of approximately 2800 ppm/G and 2150 ppm/G are measured in the cases of using the 1st and 2nd modes, respectively. It was clarified experimentally that the spurious vibrations do not appear in the vicinity of the resonance frequency f0. Moreover, it is shown that this sensor can also be used as an inclination angle sensor.

ヘッドサスペンションの制振機構の研究(S62-2 機構・制御(2),S62 情報機器コンピュータメカニクス)

We investigated an optimal design method of a head suspension with dynamic absorber that can suppress the flow induced vibration of suspension. We call this new suspension Dynamic Absorber Suspension (DAS), and numerically studied the effect of the dynamic absorber to suppress the flow-induced sway mode and 2nd torsion mode vibrations of a head suspension by FEM. As a result, we proposed a proper dynamic absorber design for suppressing the sway mode and 2nd torsion mode, and showed the suppressing effect of the sway and 2nd torsion modes. From frequency response function of DAS, we found that magnification factor of sway mode can be reduced 25dB, and that of 2^<nd> torsion mode is less than OdB by means of the additional mass of about 5% of suspension main body.

高次共振同相アクチュエータ設計に関する研究(情報機器コンピュータメカニクス2 -機構・制御,IIP2004 情報・知能・精密機器部門講演会)

This research shows the new design concept of an actuator in hard disk drives. The actuator which has several higher-order mechanical resonance determines the stability and mechanical noise suppression ability of the servo control system. We presented the new design concept that higher resonance are made in-phase to the first major resonance. In this concept, all the resonance with high gain are in-phase but the outphase resonance's gain are reduced. This mechanical characteristic can be achieved by the carriage arm shape design which pay its attention to 1st and 2nd arm sway mode. In the actuator based on this concept, the higher resonance can be compensated only by the compensator which is designed for the first major resonance.

Diblock copolymer adsorption from the aqueous micellar phase to solid surfaces: real time monitoring by ATR spectroscopy in the mid‐infrared

AbstractAttenuated Total Reflectance (ATR) in the mid‐infrared is employed to monitor the adsorption of poly(tert‐butyl styrene ‐ b ‐ styrene sulfonate), PtBS‐PSS, copolymers with a small hydrophobic head as well as of an analogous poly(styrene sulfonate), PSS, homopolymer on germanium and Au‐plated germanium surfaces from aqueous NaCl solutions. The surface density of the adsorbed polyelectrolyte is monitored via the growth of characteristic infrared absorptions of the sulfonated ring at 1036‐ and 1008 cm−1 in the 2nd derivative mode. These probe bands do not exhibit shifts or changes in bandshape over very prolongued adsorption experiments. Pronounced differences in the kinetics of adsorption are observed between the PSS homopolymer and the PtBS‐PSS copolymers in agreement to previous investigations by phase‐modulated ellipsometry on similar systems. Adsorption of the diblocks above the critical micelle concentration is found to involve a sequence of diffusion, micellar relaxation and brush‐limited processes.

BAT Model Lateral Parameters Characterization Using Finite Element Model

Abstract The bushing analogy tire (BAT) model has been shown to be capable of modeling tire dynamics in vehicle dynamic simulations. In a recent paper, the tire and vehicle data have been used to demonstrate that the BAT model yields reasonable predictions of the vehicle vertical suspension dynamic responses up to the tire 2nd vertical mode (∼90 Hz). This paper studies the modeling of the tire dynamics in the lateral direction as the next step toward completion of the BAT model as a consistent 3-dimensional tire dynamics model. Finite element (FE) analysis is an advanced analytical method for engineering analysis and has been accepted as the standard analytical tool for tires in the automotive industry. The tire data generated with FE models are also repeatable, without the data noise contained in physically measured laboratory tire data. FE models are also ideal for tire modeling studies because they enable the analysts to precisely control the modeling parameters. A tire FE model is, therefore, used here to generate the needed tire data, including mass, static forces and dynamic vibration modes for BAT model characterization. The BAT model parameters, including the tire lateral stiffnesses and the tire/wheel mass and inertia, are extracted from the FE analysis results. The analytically predicted lateral vibration modal frequencies of the BAT model are then compared with the corresponding lateral vibration modes of the same FE model. It is shown that the resulting BAT model is a good approximation for the FE model in the lateral direction up to the third lateral (including rotational) vibration mode (∼70 Hz).