The application of inerter in tuned mass absorber

In this paper we investigate the dynamics of tuned mass absorber with additional viscous damper and inerter attached to the pendulum. The devices are used to damp out oscillations of non-linear Duffing oscillator. Analysis of how these devices influence the dynamics of tuned mass absorber and its damping properties is shown. We calculate the detailed bifurcation diagrams and show how by changing the parameters of damper and inerter one can eliminate dangerous dynamic instabilities from the systems. Finally, in the last section we present an optimization of TMA׳s parameters in order to achieve best efficiency in damping of the main body vibrations.     

掠入射真空紫外摄谱仪的强度校准

为了使E-580型真空紫外摄谱仪能够运用在等离子体诊断实验中,我们用Okazaki等的实验方法,以角向箍缩等离子体为光源,对它作了强度校准。 真空紫外摄谱仪及等离子体光源的情况见文献[2,3],仪器布置同文献[1],本实验选用9对谱线,见表1。 图1是OⅥ150和OⅥ3811的示波图(第二半周內波形),全屏扫描时间约12μs。在信号     

Photon-Counting Phase-Modulation Fluorometer

We propose a phase-modulation fluorometer that is applicable to a very weak fluorescence intensity level. In order to counter the single-photon event situation, we have introduced a combination of a time-to-amplitude converter and a pulse height analyzer (PHA) to the fluorometer, the combination of which is usually used in the single-photon correlation method to measure fluorescence decay waveforms with pulsed excitation. In the proposed fluorometer, a sinusoidal response waveform that is shifted in phase over the reference one is obtained statistically as a histogram in the PHA memory, and then the fluorescence lifetime can be calculated by the same procedure as the conventional analog phase-modulation method. The excitation light source used was a current-modulated ultraviolet light-emitting diode, whose center wavelength was 370 nm and whose spectral bandwidth was 10 nm. Fluorescence lifetimes of 17.5 ns and 5.7 ns obtained for 10 ppb quinine sulfate in 0.1 N H₂SO₄ and for 10 ppb rhodamine 6G in ethanol, respectively, agreed well with those reported in the literature. In passing, we report that the fluorescence lifetime of benzo[a]pyrene in dichloromethane is 14.6 ns, which is known as one of the carcinogenic, environmental-pollution materials.This paper was originally presented at the 2001 International Conference (2nd Joint OSJ-SPIE Conference) on Optical Engineering for Sensing and Nanotechnology, ICOSN 2001 which was held June 6#x2013;8, 2001 at the Pacifico-Yokohama Conference Center, Yokohama, Japan.     

双色激光场中极端远紫外超连续谱相干辐射产生

通过脉宽为周期量级的超快强场激光脉冲与惰性气体原子的极端非线性相互作用,能够产生单个的阿秒量级的极端远紫外光脉冲。然而,现有的周期量级的激光脉冲的最短脉宽仍在两个光周期左右,尚不足以支持产生脉宽短于100as的单个极端远紫外脉冲。文章作者首次提出通过在一个周期量级(如6fs)激光脉冲上再叠加一个强度较弱但相对位相精确控制的二倍频激光,能够直接实现单个的65as光脉冲。如进一步经过位相补偿,将有望产生一个脉宽仅为23as的单脉冲,从而将阿秒光脉冲的时间宽度推进到短于一个原子时间单位。     

Measurements of selected NI multiplet strength ratios and comparison with recent calculations

Results of recent calculations of multiplet strengths of atomic nitrogen (NI) are compared with arc emission measurements. Intensities of eleven infrared multiplets are measured and transformed into multiplet strength values applying the determined arc temperature values. Properly defined seven multiplet strength ratios are selected for comparison with results of calculations and previously obtained experimental data. Our measured multiplet strength ratios are in a very good agreement with the recent Breit-Pauli results of Tachiev and Froese Fischer.     

Measurement of OH spatially resolved spectrum in a wire-plate pulsed streamer discharge

In this study, spatially resolved measurements of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperature of N₂ (C) have been performed during a positive pulsed streamer discharge with a wire-plate electrode configuration at atmospheric pressure. The effects of pulse peak voltage, pulse repetition rate and the added O₂ flow rate on the spatial distributions of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperatures of N₂ (C) perpendicular to the wire in the direction towards the plate (in the radial direction) are investigated. It has been found that the emission intensity of OH (A²Σ↦X²Π, 0-0) increases with increasing pulse peak voltage and pulse repetition rate and decreases with increasing the distance from the wire electrode. When the different oxygen flows are added in N₂ and H₂O mixture gas, the emission intensity of OH (A²Σ↦X²Π, 0-0) decreases with increasing the flow rate of oxygen. The vibrational temperature of N₂ (C) is nearly independent of pulsed peak voltage and pulsed repetition rate, but increases with increasing the added O₂ flow rate and keeps almost constant in the radial direction under the present experimental conditions. This measurement plays a crucial role in understanding the discharge characters of pulsed streamer discharge and establishing the molecule reaction dynamics model of pulsed streamer discharge.     

Suppressing Flow-Induced Vibrations by Parametric Excitation

The possibility of suppressing self-excited vibrations of mechanicalsystems using parametric excitation is discussed. We consider a two-masssystem of which the main mass is excited by a flow-induced, self excitedforce. A single mass which acts as a dynamic absorber is attached to themain mass and, by varying the stiffness between the main mass and theabsorber mass, represents a parametric excitation. It turns out that forcertain parameter ranges full vibration cancellation is possible. Usingthe averaging method the fully non-linear system is investigatedproducing as non-trivial solutions stable periodic solutions and tori.In the case of a small absorber mass we have to carry out a second-ordercalculation.     

Growth Dynamics Study of Silver Nanoparticles Obtained by Green Synthesis using Salvia officinalis Extract

ABSTRACT

Silver nanoparticles were synthesized by the bottom-up approach using Salvia officinalis extract, and their growth process was correlated with changes in their ultraviolet–visible spectra. Experiments were performed at different initial mixing ratios of silver nitrate to plant extract and at pH values to outline a pattern concerning the growth of silver nanoparticles obtained by this synthesis procedure. Relative areas calculated from the spectra from 350 to 600?nm were used as a comparison for the growth dynamics of silver nanoparticles synthesized in mixtures with different compositions. The graphical representation of relative areas vs. time presents four stages of nanoparticle growth with each linear portion corresponding to a different process rate.     

Gas phase detection of explosives such as 2,4,6-trinitrotoluene by molecularly imprinted polymers

Fast, reliable and inexpensive analytical techniques for trace detection of explosive components are in high demand. Our approach is to develop specific sensor coating materials based on molecularly imprinted polymers (MIPs). Despite the known inhibition of radical polymerisations by nitro groups and the known shrinkage of the polymer lattice during/after drying we were able to synthesize particulate MIPs by suspension polymerisation as well as thin MIP coatings by direct surface polymerisation on quartz crystal microbalances (QCM). The best method to purify the porous beads was Soxhlet extraction followed by supercritical carbon dioxide extraction (SFE with sc-CO₂) at mild conditions (150 bar, 50 °C). At least a removal of >99.7% of the template was achieved. Performance tests of TNT imprinted polymer beads showed that acrylamide (AA) and more pronounced also methacrylic acid (MAA) possessed an enhanced adsorption tendency for gaseous TNT. An adsorption of 2,4-DNT, dinitrotoluene, by these MIPs was not detected. Using 2,4-DNT as template and methacrylamide, MAAM, a positive imprint effect for gaseous 2,4-DNT was achieved with no measurable cross-sensitivity for 2,4,6-TNT.The thin MIP coatings directly synthesized on the QCMs showed thicknesses of 20 to up to 500 nm. Preliminary screening experiments were performed for five different monomers and three different solvents (acetonitrile, chloroform and dimethylformamide). Best adsorption properties for TNT vapour until now showed a PAA-MIP synthesized with chloroform. Direct measurements of the mass attachment, respectively frequency decrease of the coated QCMs during vapour treatment showed a TNT-uptake of about 150 pg per μg MIP per hour. Results look worthy for further studies.     

In situ diagnostics of the decomposition of silacyclobutane on a hot filament by vacuum ultraviolet laser ionization mass spectrometry

The gas-phase reaction products of silacyclobutane (SCB) and 1, 1-dideuterio-silacyclobutane (SCB-d(2)) from a hot-wire chemical vapor deposition (HWCVD) chamber were diagnosed in situ using vacuum ultraviolet (VUV) laser single-photon ionization (SPI) coupled with time-of-flight (TOF) mass spectrometry. The SCB molecule was found to decompose at a filament temperature as low as 900 degrees C. Both Si- (silylene, methylsilylene, and silene) and C-containing (ethene and propene) species were produced from the SCB decomposition on the filament. Ethene and propene were detected by the mass spectrometer. It is demonstrated that the formation of ethene is favored over that of propene. The experimental study of hot-wire decomposition of SCB-d(2) shows that propene is most likely produced by a process that is initiated by a 1,2-H(D) migration to form n-propylsilylene, followed by an equilibration with silacyclopropane, which then decomposes to propene. The detection of ethene in our experiment indicates that a competitive route of fragmentation exists for SCB decomposition on the filament. It has been shown that this competitive route occurs without H/D scrambling. The highly reactive silylene, silene, and methylsilylene species produced from SCB decomposition underwent either insertion reactions into the Si-H bonds of the parent molecule or pi-type addition reaction across the double and triple CC bonds. The dimerization product of silene, 1,3-disilacyclobutane, at m/z = 88 was also observed.