#### Sample records for linear impedance vibrator

1. Calculating impedance vibrator antennas

NASA Astrophysics Data System (ADS)

Eminov, S. I.

2017-07-01

The technique of analytical reversal of a hypersingular equation is used to solve the equation of an impedance vibrator antenna. A numerical method for solving the equation is developed, and its efficiency is demonstrated.

2. Impedance approach to designing efficient vibration energy absorbers

NASA Astrophysics Data System (ADS)

Bobrovnitskii, Y. I.; Morozov, K. D.; Tomilina, T. M.

2017-03-01

The concept introduced previously by the authors on the best sound absorber having the maximum allowable efficiency in absorbing the energy of an incident sound field has been extended to arbitrary linear elastic media and structures. Analytic relations have been found for the input impedance characteristics that the best vibrational energy absorber should have. The implementation of these relations is the basis of the proposed impedance method of designing efficient vibration and noise absorbers. We present the results of a laboratory experiment that confirms the validity of the obtained theoretical relations, and we construct the simplest best vibration absorber. We also calculate the parameters and demonstrate the efficiency of a dynamic vibration absorber as the best absorber.

3. Linearly tapered slot antenna impedance characteristics

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Lee, Richard Q.

1995-01-01

The paper presents for the first time an experimental technique to de-embed the input impedance of a LTSA from the measured reflection coefficient. The results show that the input impedance is dependent on the semi-flare angle and the length of the LTSA. The Re(Z(sub in)) is large when the electrical length of the LTSA is small and is on the order of few thousand ohms. However for an electrically large LTSA the Re(Z(sub in)) is in the range of 55 to 130 ohms. These results have potential applications in the design of broad band impedance matching networks for LTSA.

4. A fast linear reconstruction method for scanning impedance imaging.

PubMed

Liu, Hongze; Hawkins, Aaron R; Schultz, Stephen M; Oliphant, Travis E

2006-01-01

Scanning electrical impedance imaging (SII) has been developed and implemented as a novel high resolution imaging modality with the potential of imaging the electrical properties of biological tissues. In this paper, a fast linear model is derived and applied to the impedance image reconstruction of scanning impedance imaging. With the help of both the deblurring concept and the reciprocity principle, this new approach leads to a calibrated approximation of the exact impedance distribution rather than a relative one from the original simplified linear method. Additionally, the method shows much less computational cost than the more straightforward nonlinear inverse method based on the forward model. The kernel function of this new approach is described and compared to the kernel of the simplified linear method. Two-dimensional impedance images of a flower petal and cancer cells are reconstructed using this method. The images reveal details not present in the measured images.

5. Effect of External Vibration on PZT Impedance Signature.

PubMed

Yang, Yaowen; Miao, Aiwei

2008-11-01

Piezoelectric ceramic Lead Zirconate Titanate (PZT) transducers, working on the principle of electromechanical impedance (EMI), are increasingly applied for structural health monitoring (SHM) in aerospace, civil and mechanical engineering. The PZT transducers are usually surface bonded to or embedded in a structure and subjected to actuation so as to interrogate the structure at the desired frequency range. The interrogation results in the electromechanical admittance (inverse of EMI) signatures which can be used to estimate the structural health or integrity according to the changes of the signatures. In the existing EMI method, the monitored structure is only excited by the PZT transducers for the interrogating of EMI signature, while the vibration of the structure caused by the external excitations other than the PZT actuation is not considered. However, many structures work under vibrations in practice. To monitor such structures, issues related to the effects of vibration on the EMI signature need to be addressed because these effects may lead to misinterpretation of the structural health. This paper develops an EMI model for beam structures, which takes into account the effect of beam vibration caused by the external excitations. An experimental study is carried out to verify the theoretical model. A lab size specimen with different external excitations is tested and the effect of vibration on EMI signature is discussed.

6. Effect of External Vibration on PZT Impedance Signature

PubMed Central

Yang, Yaowen; Miao, Aiwei

2008-01-01

Piezoelectric ceramic Lead Zirconate Titanate (PZT) transducers, working on the principle of electromechanical impedance (EMI), are increasingly applied for structural health monitoring (SHM) in aerospace, civil and mechanical engineering. The PZT transducers are usually surface bonded to or embedded in a structure and subjected to actuation so as to interrogate the structure at the desired frequency range. The interrogation results in the electromechanical admittance (inverse of EMI) signatures which can be used to estimate the structural health or integrity according to the changes of the signatures. In the existing EMI method, the monitored structure is only excited by the PZT transducers for the interrogating of EMI signature, while the vibration of the structure caused by the external excitations other than the PZT actuation is not considered. However, many structures work under vibrations in practice. To monitor such structures, issues related to the effects of vibration on the EMI signature need to be addressed because these effects may lead to misinterpretation of the structural health. This paper develops an EMI model for beam structures, which takes into account the effect of beam vibration caused by the external excitations. An experimental study is carried out to verify the theoretical model. A lab size specimen with different external excitations is tested and the effect of vibration on EMI signature is discussed. PMID:27873903

7. Impact self-excited vibrations of linear motor

NASA Astrophysics Data System (ADS)

Zhuravlev, V. Ph.

2010-08-01

Impact self-exciting vibration modes in a linear motor of a monorail car are studied. Existence and stability conditions of self-exciting vibrations are found. Ways of avoiding the vibrations are discussed.

8. A linear parametric approach for analysis of mouse respiratory impedance.

PubMed

Hanifi, Arezoo; Goplen, Nicholas; Matin, Mohammad; Salters, Roger E; Alam, Rafeul

2012-06-01

Assessment of the lung mechanics is crucial in lung function studies. Commonly lung mechanics is achieved through measurement of the input impedance of the lung where the experimental data is ideal for the application of system identification techniques. This study proposes a new approach for investigating the severity of lung conditions and also evaluating the treatment progression. The proposed method is established based on linear parametric identification of lung input impedance in mice and is applied to normal and asthmatic models (including acute, tolerant and chronic asthma) as well as a pharmacological intervention model. Experimental findings confirm the effectiveness of the analysis technique applied here. We discuss the potential application of this method to analyses of human lung mechanics.

9. Linear lateral vibration of axisymmetric liquid briges

NASA Astrophysics Data System (ADS)

Ferrera, C.; Montanero, J. M.; Cabezas, M. G.

A liquid bridge is a mass of liquid sustained by the action of the surface tension force between two parallel supporting disks Apart from their basic scientific interest a liquid bridge can be considered as the simplest idealization of the configuration appearing in the floating zone technique used for crystal growth and purification of high melting point materials footnote Messeguer et al emph Crystal Growth Res bf 5 27 1999 This has conferred considerable interest on the study of liquid bridges not only in fluid mechanics but also in the field of material engineering The axisymmetric dynamics of an isothermal liquid bridge has been frequently analysed over the past years The studies have considered different phenomena such as free oscillations footnote Montanero emph E J Mech B Fluids bf 22 169 2003 footnote Acero and Montanero emph Phys Fluids bf 17 078105 2005 forced vibrations footnote Perales and Messeguer emph Phys Fluids A bf 4 1110 1992 g-jitter effects footnote Messeguer and Perales emph Phys Fluids A bf 3 2332 1991 extensional deformation footnote Zhang et al emph J Fluid Mech bf 329 207 1996 and breakup process footnote Espino et al emph Phys Fluids bf 14 3710 2002 among others Works considering the nonaxisymmetric dynamical behaviour of a liquid bridge has been far less common footnote Sanz and Diez emph J Fluid Mech bf 205 503 1989 In the present study the linear vibration of an axisymmetric liquid

10. Non-Linear Vibration Characteristics of Clamped Laminated Shallow Shells

NASA Astrophysics Data System (ADS)

ABE, A.; KOBAYASHI, Y.; YAMADA, G.

2000-07-01

This paper examines non-linear free vibration characteristics of first and second vibration modes of laminated shallow shells with rigidly clamped edges. Non-linear equations of motion for the shells based on the first order shear deformation and classical shell theories are derived by means of Hamilton's principle. We apply Galerkin's procedure to the equations of motion in which eigenvectors for first and second modes of linear vibration obtained by the Ritz method are employed as trial functions. Then simultaneous non-linear ordinary differential equations are derived in terms of amplitudes of the first and second vibration modes. Backbone curves for the first and second vibration modes are solved numerically by the Gauss-Legendre integration method and the shooting method respectively. The effects of lamination sequences and transverse shear deformation on the behavior are discussed. It is also shown that the motion of the first vibration mode affects the response for the second vibration mode.

11. Calculation of rotor impedance for use in design analysis of helicopter airframe vibrations

NASA Technical Reports Server (NTRS)

Nygren, Kip P.

1990-01-01

Excessive vibration is one of the most prevalent technical obstacles encountered in the development of new rotorcraft. The inability to predict these vibrations is primarily due to deficiencies in analysis and simulation tools. The Langley Rotorcraft Structural Dynamics Program was instituted in 1984 to meet long term industry needs in the area of rotorcraft vibration prediction. As a part of the Langley program, this research endeavors to develop an efficient means of coupling the rotor to the airframe for preliminary design analysis of helicopter airframe vibrations. The main effort was to modify the existing computer program for modeling the dynamic and aerodynamic behavior of rotorcraft called DYSCO (DYnamic System COupler) to calculate the rotor impedance. DYSCO was recently developed for the U.S. Army and has proven to be adaptable for the inclusion of new solution methods. The solution procedure developed to use DYSCO for the calculation of rotor impedance is presented. Verification of the procedure by comparison with a known solution for a simple wind turbine model is about 75 percent completed, and initial results are encouraging. After the wind turbine impedance is confirmed, the verification effort will continue by comparison to solutions of a more sophisticated rotorcraft model. Future work includes determination of the sensitivity of the rotorcraft airframe vibrations to helicopter flight conditions and rotor modeling assumptions. When completed, this research will ascertain the feasibility and efficiency of the impedance matching method of rotor-airframe coupling for use in the analysis of airframe vibrations during the preliminary rotorcraft design process.

12. Measurement of cantilever vibration using impedance-loaded surface acoustic wave sensor

NASA Astrophysics Data System (ADS)

Oishi, Masaki; Hamashima, Hiromitsu; Kondoh, Jun

2016-07-01

In this study, an impedance-loaded surface acoustic wave (SAW) sensor was demonstrated to monitor the vibration frequency. Commercialized pressure sensors and a variable capacitor were chosen as external sensors, which were connected to a reflector on a SAW device. As the reflection coefficient of the reflector depended on the impedance, the echo amplitude was influenced by changes in the impedance of the external sensor. The vibration frequency of the cantilever was determined by monitoring the echo amplitude of the SAW device. Moreover, the attenuation constant of an envelope was estimated. The results of our feasibility study indicate that the impedance-loaded SAW sensor can be applied as a detector for structural health monitoring.

13. Vibration analysis of cubic rotary-linear piezoelectric actuator.

PubMed

Mashimo, Tomoaki; Toyama, Shigeki

2011-04-01

Cubic design of a stator in a rotary-linear piezoelectric actuator is sophisticated and interesting, but the vibration theory of the cubic stator remains unclear when using the finite element method (FEM). In this paper, we analyze the vibration behavior of the cubic stator by applying the energy method, which distinguishes the component of mechanical energy. By changing the design of the stator (especially the length in the direction of the through-hole axis), we clarify how the vibration modes are in accordance at one equal frequency in cubic shape. The behavior of the vibration modes is discussed using conventional vibration theory of a beam and a plate. © 2011 IEEE

14. LDV measurement of bird ear vibrations to determine inner ear impedance and middle ear power flow

NASA Astrophysics Data System (ADS)

Muyshondt, Pieter G. G.; Pires, Felipe; Dirckx, Joris J. J.

2016-06-01

The mechanical behavior of the middle ear structures in birds and mammals is affected by the fluids in the inner ear (IE) that are present behind the oval window. In this study, the aim was to gather knowledge of the acoustic impedance of the IE in the ostrich, to be able to determine the effect on vibrations and power flow in the single-ossicle bird middle ear for future studies. To determine the IE impedance, vibrations of the ossicle were measured for both the quasi-static and acoustic stimulus frequencies. In the acoustic regime, vibrations were measured with a laser Doppler vibrometer and electromagnetic stimulation of the ossicle. The impedance of the inner ear could be determined by means of a simple RLC model in series, which resulted in a stiffness reactance of KIE = 0.20.1012 Pa/m3, an inertial impedance of MIE = 0.652.106 Pa s2/m3, and a resistance of RIE = 1.57.109 Pa s/m. The measured impedance is found to be considerably smaller than what is found for the human IE.

15. Radiation impedance and equivalent circuit for piezoelectric ultrasonic composite transducers of vibrational mode-conversion.

PubMed

Lin, Shuyu

2012-01-01

The piezoelectric ultrasonic composite transducer, which can be used in either gas or liquid media, is studied in this paper. The composite transducer is composed of a longitudinal sandwich piezoelectric transducer, a mechanical transformer, and a metal circular plate in flexural vibration. Acoustic radiation is produced by the flexural circular plate, which is excited by the longitudinal sandwich transducer and transformer. Based on the classic flexural theory of plates, the equivalent lumped parameters for a plate in axially symmetric flexural vibration with free boundary conditions are obtained. The radiation impedance of the plate is derived and the relationship between the radiation impedance and the frequency is analyzed. The equivalent circuits for the plate in flexural vibration and the composite transducer are given. The vibrational modes and the harmonic response of the composite piezoelectric transducer are simulated by the numerical method. Based on the theoretical and numerical analysis, two composite piezoelectric ultrasonic transducers are designed and manufactured, their admittance-frequency curves are measured, and the resonance frequency is obtained. The flexural vibrational displacement distribution of the transducer is measured with a laser scanning vibrometer. It is shown that the theoretical results are in good agreement with the measured resonance frequency and the displacement distribution.

16. Multiscale wireless sensor node for impedance-based SHM and low-frequency vibration data acquisition

SciTech Connect

Taylor, Stuart G; Farinholt, Kevin M; Park, Gyuhae; Farrar, Charles R; Todd, Michael D

2009-01-01

This paper presents recent developments in an extremely compact, wireless impedance sensor node (WID3, Wireless Impedance Device) at Los Alamos National Laboratory for use in impedance-based structural health monitoring (SHM), Sensor diagnostics and low-frequency vibrational data acquisition. The current generation WID3 is equipped with an Analog Devices AD5933 impedance chip that can resolve measurements up to 100 kHz, a frequency range ideal for many SHM applications. An integrated set of multiplexers allows the end user to monitor seven piezoelectric sensors from a single sensor node. The WID3 combines on-board processing using an Atmega1281 microcontroller, data storage using flash memory, wireless communications capabilities, and a series of internal and external triggering options into a single package to realize a truly comprehensive, self-contained wireless active-sensor node for SHM applications. Furthermore, we recently extended the capability of this device by implementing low-frequency analog to digital and digital and analog converters so that the same device can measure structural vibration data. The WID3 requires less than 70 mW of power to operate, and it can operate in various wireless network paradigms. The performance of this miniaturized and portable device is compared to our previous results and its broader capabilities are demonstrated.

17. Optimal design of linear and non-linear dynamic vibration absorbers

NASA Astrophysics Data System (ADS)

Jordanov, I. N.; Cheshankov, B. I.

1988-05-01

An efficient numerical method is applied to obtain optimal parameters for both linear and non-linear damped dynamic vibration absorbers. The minimization of the vibration response has been carried out for damped as well as undamped force excited primary systems with linear and non-linear spring characteristics. Comparison is made with the optimum absorber parameters that are determined by using Den Hartog's classical results in the linear case. Six optimization criteria by which the response is minimized over narrow and broad frequency bands are examined. Pareto optimal solutions of the multi-objective decision making problem are obtained.

18. Piezoelectric linear motor concepts based on coupling of longitudinal vibrations.

PubMed

Hemsel, T; Mracek, M; Twiefel, J; Vasiljev, P

2006-12-22

Classically, rotary motors with gears and spindle mechanisms are used to achieve translatory motion. In means of miniaturization and weight reduction piezoelectric linear motors are of interest. Several ultrasonic linear motors found in literature base on the use of two different vibration modes. Most often flexural and longitudinal modes are combined to achieve an elliptic micro-motion of surface points. This micro-motion is converted to direct linear (or translatory) motion of a driven slider. To gain high amplitudes of the micro-motion and thus having a powerful motor, the ultrasonic vibrator should be driven near the eigenfrequency of its modes. Additionally, low mechanical and electrical losses lead to increased efficiency and large amplitude magnification in resonance. This demands a geometrical design that fits the eigenfrequencies of the two different modes. A frequency-deviation of only a few percent leads to non-acceptable disturbance of the elliptical motion. Thus, the mechanical design of the vibrators has to be done very carefully. Within this contribution we discuss different motor designs based on the coupling of two the same longitudinal vibrations within one structure to generate an elliptic motion of surface points. Different concepts based on piezoelectric plates and Langevin transducers are compared. Benefits and drawbacks against the combination of longitudinal and bending modes will be discussed. Numerical results of the stator vibration as well as motor characteristics are validated by measurements on different prototypes.

19. Non-linear optical crystal vibration sensing device

DOEpatents

Kalibjian, R.

1994-08-09

A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.

20. Non-linear optical crystal vibration sensing device

DOEpatents

Kalibjian, Ralph

1994-01-11

A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).

1. Electrode impedance: an indicator of electrode-tissue contact and lesion dimensions during linear ablation.

PubMed

Zheng, X; Walcott, G P; Hall, J A; Rollins, D L; Smith, W M; Kay, G N; Ideker, R E

2000-12-01

Pre-ablation impedance was evaluated for its ability to detect electrode-tissue contact and allow creation of long uniform linear lesions with a multi-electrode ablation catheter. The study consisted of 2 parts, both of which used the in vivopig thigh muscle model. In part 1, a 7 Fr. multi-electrode catheter was held in 3 electrode-tissue contact conditions: (1) non-contact; (2) light contact with a 30g downward force; and (3) tight contact with a 90g downward force. Impedances were measured in unipolar, modified unipolar and bipolar configurations using a source with frequencies from 100Hz to 500kHz. Compared with non-contact, the impedance increased 35 +/- 22 % with 30g contact pressure and 68 +/- 40% when the contact pressure was increased to 90g across the range of frequencies studied. In part 2, the same catheter was held against the tissue with different forces. Pre-ablation impedance was measured using a 10kHz current. Phased radiofrequency energy was applied to the 5 electrodes simultaneously using 10W power at each electrode for 120s. A total of 32 linear lesions were created. The lesion dimensions correlated with pre-ablation impedance. A unipolar impedance > or = 190 Omega indicates 95% possibility to create a uniform linear lesion of at least 3mm depth with our ablation system. We conclude that pre-ablation impedance may be a useful indicator for predicting electrode-tissue contact and the ability to create a continuous and transmural linear lesion with a multi-electrode catheter.

2. Free vibration analysis of Mindlin plates with linearly varying thickness

NASA Astrophysics Data System (ADS)

Aksu, G.; Al-Kaabi, S. A.

1987-12-01

A method based on the variational principles in conjunction with the finite difference technique is applied to examine the free vibration characteristics of isotropic rectangular plates of linearly varying thickness by including the effects of transverse shear deformation and rotary inertia. The validity of the present approach is demonstrated by comparing the results with other solutions proposed for plates with uniform and linearly varying thickness. Natural frequencies and mode shapes of Mindlin plates with simply supported and clamped edges are determined for various values of relative thickness ratio and the taper thickness constant.

3. An improved statistical model for linear antenna input impedance in an electrically large cavity.

SciTech Connect

Johnson, William Arthur; Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Lee, Kelvin S. H.

2005-03-01

This report presents a modification of a previous model for the statistical distribution of linear antenna impedance. With this modification a simple formula is determined which yields accurate results for all ratios of modal spectral width to spacing. It is shown that the reactance formula approaches the known unit Lorentzian in the lossless limit.

4. Vibration and chaos control of non-linear torsional vibrating systems

NASA Astrophysics Data System (ADS)

El-Bassiouny, A. F.

2006-07-01

Vibration of a mechanical system is often an undesirable phenomenon, as it may cause damage, disturbance, discomfort and, sometimes, destruction of systems and structures. To reduce vibration, many methods can be used. The most famous method is using dynamic absorbers or dampers. In the present work, a non-linear elastomeric damper or absorber is used to control the torsional vibrations of the crankshaft in internal combustion engines, when subjected to both external and parametric excitation torques. The multiple time scale perturbation method is applied to determine the equations governing the modulation of both amplitudes and phases of the crankshaft and the absorber. These equations are used to determine the steady-state amplitudes and system stability. Numerical integration of the basic equations is applied to investigate the effects of the different parameters on system behavior. A comparison is made with the available published work. Some recommendations are given at the end of the work.

5. Non-linear analysis of vibrations of irregular plates

NASA Technical Reports Server (NTRS)

Lobitz, D. W.; Nayfeh, A. H.; Mook, D. T.

1977-01-01

A numerical perturbation method is used to investigate the forced vibrations of irregular plates. Nonlinear terms associated with the midplane stretching are retained in the analysis. The numerical part of the method involves the use of linear, finite element techniques to determine the free oscillation mode shapes and frequencies and to obtain the linear midplane stress resultants caused by the midplane stretching. Representing the solution as an expansion in terms of these linear mode shapes, these modes and the resultants are used to determine the equations governing the time-dependent coefficients of this expansion. These equations are solved by using the method of multiple scales. Specific solutions are given for the main-resonant vibrations of an elliptical plate in the presence of internal resonances. The results indicate that modes other than the driven mode can be drawn into the steady state response. Though the excitation is composed of a single harmonic, the response may not be periodic. Moreover, the particular types of responses that can occur are highly dependent on the mode being excited and are sensitive to small geometrical changes.

6. Modeling and Vibration Suppression for Fast Moving Linear Robots

NASA Astrophysics Data System (ADS)

Gattringer, H.; Kilian, F. J.; Höbarth, W.; Bremer, H.

2010-09-01

This paper deals with vibration suppression for elastic linear robots consisting of elastic beams, bearings and motor gear units. It is of vital importance to use a structured method for deriving the equations of motion for this nonlinear multi body system. The Projection Equation in subsystem form, a synthetical method for calculating the dynamical equations of motion in combination with the Ritz approximation technique, leads to highly nonlinear ordinary differential equations which can be integrated numerically. The control scheme is based on a feedforward part and a feedback loop. A Taylor expansion up to first order leading to a linear time variant system delivers the feedforward torques and a precalculation of the elastic endeffector deflections which can be compensated by a correction of the desired trajectory. Simulation and experimental results are presented.

7. [Theory study on glycine linear oligopeptide vibrational spectrum frequency shift].

PubMed

Ye, Zhi-Peng; Li, Xin; Yang, Meng-Shi; Chen, Liang; Xu, Can; Chu, Xiu-Xiang

2014-04-01

By using the density functional theory, glycine linear oligopeptide of different lengths was geometrically optimized on the 6-31G (d) basis set level, their growth processes were simulated, and the average binding energy and vibration frequency were calculated with geometry. The results showed that the average binding energies tend to change in a regular pattern and stabilize with the number of residues increasing; With the oligopeptide chain bond length analysis it was found that the chain to the radial direction there is a opposite trend for chain and radial direction, which is anisotropic. It was found by the IR spectrum analysis that red shifts and blue shifts occur respectively when the same group of peptide bond vibrate, which is anisotropic; These phenomena originate from that quasi one-dimensional nanostructures lead to the anisotropy of the bond length; the induced effects, coupling effects and hydrogen bonding etc. between the same groups lead to the vibration frequency red shifts and blue shifts. The authors conclude that the growth of glycine linear oligopeptide is conducive to stability of the structure, and the authors infer that the oligopeptide has the tendency of self-assembled growth; Through the conformation and spectrum, the authors infer that there is a size effect in physical and chemical properties. The physical and chemical properties of peptide chain end group are extremely stable and unaffected by the impact of the oligopeptide chain length The results are significant to measuring the length and the number of residue of peptide, and to manufacturing the special features oligopeptide chain.

8. Linearity of electrical impedance tomography during maximum effort breathing and forced expiration maneuvers.

PubMed

Ngo, Chuong; Leonhardt, Steffen; Zhang, Tony; Lüken, Markus; Misgeld, Berno; Vollmer, Thomas; Tenbrock, Klaus; Lehmann, Sylvia

2017-01-01

Electrical impedance tomography (EIT) provides global and regional information about ventilation by means of relative changes in electrical impedance measured with electrodes placed around the thorax. In combination with lung function tests, e.g. spirometry and body plethysmography, regional information about lung ventilation can be achieved. Impedance changes strictly correlate with lung volume during tidal breathing and mechanical ventilation. Initial studies presumed a correlation also during forced expiration maneuvers. To quantify the validity of this correlation in extreme lung volume changes during forced breathing, a measurement system was set up and applied on seven lung-healthy volunteers. Simultaneous measurements of changes in lung volume using EIT imaging and pneumotachography were obtained with different breathing patterns. Data was divided into a synchronizing phase (spontaneous breathing) and a test phase (maximum effort breathing and forced maneuvers). The EIT impedance changes correlate strictly with spirometric data during slow breathing with increasing and maximum effort ([Formula: see text]) and during forced expiration maneuvers ([Formula: see text]). Strong correlations in spirometric volume parameters [Formula: see text] ([Formula: see text]), [Formula: see text]/FVC ([Formula: see text]), and flow parameters PEF, [Formula: see text], [Formula: see text], [Formula: see text] ([Formula: see text]) were observed. According to the linearity during forced expiration maneuvers, EIT can be used during pulmonary function testing in combination with spirometry for visualisation of regional lung ventilation.

9. Simple linear models of scanning impedance imaging for fast reconstruction of relative conductivity of biological samples.

PubMed

Oliphant, Travis E; Liu, Hongze; Hawkins, Aaron R; Schultz, Stephen M

2006-11-01

Scanning impedance imaging (SH) uses a noncontacting electrical probe held at a known voltage and scanned over a thin sample on a ground plane in a conductive medium to obtain images of current. The current image is related in a nonlinear way to the conductivity of the sample. This paper develops the theory behind SII showing how the measured current relates to the desired conductivity. Also included is the development of a simplified, linear model that is effective in explaining many of the experimental results. Good agreement of the linear model with step-response data over an insulator is shown. The linear model shows that the current is a blurred version of the conductivity. Simple deblurring methods can, therefore, be applied to obtain relative conductivity images from the raw current data. Raw SII data from a flower-petal and a leaf sample are shown as well as relative conductivity images deblurred using the linear model.

10. Vibration power generator for a linear MR damper

NASA Astrophysics Data System (ADS)

Sapiński, Bogdan

2010-10-01

The paper describes the structure and the results of numerical calculations and experimental tests of a newly developed vibration power generator for a linear magnetorheological (MR) damper. The generator consists of permanent magnets and coil with foil winding. The device produces electrical energy according to Faraday's law of electromagnetic induction. This energy is applied to vary the damping characteristics of the MR damper attached to the generator by the input current produced by the device. The objective of the numerical calculations was to determine the magnetic field distribution in the generator as well as the electric potential and current density in the generator's coil during the idle run and under the load applied to the MR damper control coil. The results of the calculations were used during the design and manufacturing stages of the device. The objective of the experimental tests carried out on a dynamic testing machine was to evaluate the generator's efficiency and to compare the experimental and predicted data. The experimental results demonstrate that the engineered device enables a change in the kinetic energy of the reciprocal motion of the MR damper which leads to variations in the damping characteristics. That is why the generator may be used to build up MR damper based vibration control systems which require no external power.

11. Damping Optimization for Linear Vibrating Systems Using Dimension Reduction

NASA Astrophysics Data System (ADS)

Benner, Peter; Tomljanović, Zoran; Truhar, Ninoslav

We consider a mathematical model of a linear vibrational system described by the second-order system of differential equations Mddot{x} + Ddot{x} + Kx = 0, where M, K and D are positive definite matrices, called mass, stiffness and damping, respectively. We are interested in finding an optimal damping matrix which will damp a certain part of the undamped eigenfrequencies. For this we use a minimization criterion which minimizes the average total energy of the system. This is equivalent to the minimization of the trace of the solution of a corresponding Lyapunov equation. In this paper we consider an algorithm for the efficient optimization of the damping positions based on dimension reduction techniques. Numerical results illustrate the efficiency of our approach.

12. Validated linear dynamic model of electrically-shunted magnetostrictive transducers with application to structural vibration control

NASA Astrophysics Data System (ADS)

Scheidler, Justin J.; Asnani, Vivake M.

2017-03-01

This paper presents a linear model of the fully-coupled electromechanical behavior of a generally-shunted magnetostrictive transducer. The impedance and admittance representations of the model are reported. The model is used to derive the effect of the shunt’s electrical impedance on the storage modulus and loss factor of the transducer without neglecting the inherent resistance of the transducer’s coil. The expressions are normalized and then shown to also represent generally-shunted piezoelectric materials that have a finite leakage resistance. The generalized expressions are simplified for three shunts: resistive, series resistive-capacitive, and inductive, which are considered for shunt damping, resonant shunt damping, and stiffness tuning, respectively. For each shunt, the storage modulus and loss factor are plotted for a wide range of the normalized parameters. Then, important trends and their impact on different applications are discussed. An experimental validation of the transducer model is presented for the case of resistive and resonant shunts. The model closely predicts the measured response for a variety of operating conditions. This paper also introduces a model for the dynamic compliance of a vibrating structure that is coupled to a magnetostrictive transducer for shunt damping and resonant shunt damping applications. This compliance is normalized and then shown to be analogous to that of a structure that is coupled to a piezoelectric material. The derived analogies allow for the observations and equations in the existing literature on structural vibration control using shunted piezoelectric materials to be directly applied to the case of shunted magnetostrictive transducers.

13. Turbulence Induced Vibration: Theory and Application to the Next Linear Collider(LCC-0094)

SciTech Connect

Adiga, S.

2003-10-07

A semianalytical approach is used to estimate turbulence-induced vibration. The results are compared with the measured vibrations for three different cases, a 16-inch pipe at the NLCTA, a 10-inch pipe at the SLD and the coolant pipes around the copper structure model of the linear collider. The variation of vibrations with respect to velocity of flow is studied as well.

14. Linear unsteady aerodynamic forces on vibrating annular cascade blades

NASA Astrophysics Data System (ADS)

Nagasaki, Taketo; Yamasaki, Nobuhiko

2003-05-01

The paper presents the formulation to compute numerically the unsteady aerodynamic forces on the vibrating annular cascade blades. The formulation is based on the finite volume method. By applying the TVD scheme to the linear unsteady calculations, the precise calculation of the peak of unsteady aerodynamic forces at the shock wave location like the delta function singularity becomes possible without empirical constants. As a further feature of the present paper, results of the present numerical calculation are compared with those of the double linearization theory (DLT), which assumes small unsteady and steady disturbances but the unsteady disturbances are much smaller than the steady disturbances. Since DLT requires far less computational resources than the present numerical calculation, the validation of DLT is quite important from the engineering point of view. Under the conditions of small steady disturbances, a good agreement between these two results is observed, so that the two codes are cross-validated. The comparison also reveals the limitation on the applicability of DLT.

15. Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

SciTech Connect

Ranjbar, V.H.; Tan, C.Y.; /Fermilab

2011-08-01

The combined effect of impedance and higher order chromaticity can act on the beam in a nontrivial manner which can cause a tune shift which depends on the relative momenta with respect to the 'on momentum' particle ({Delta}p/p). Experimentally, this tune shift affects the measurement of the linear chromaticity which is traditionally measured with a change of {Delta}p/p. The theory behind this effect will be derived in this paper. Computer simulations and experimental data from the Tevatron will be used to support the theory.

16. Tissue characterization using electrical impedance spectroscopy data: a linear algebra approach.

PubMed

Laufer, Shlomi; Solomon, Stephen B; Rubinsky, Boris

2012-06-01

In this study, we use a new linear algebra manipulation on electrical impedance spectroscopy measurements to provide real-time information regarding the nature of the tissue surrounding the needle in minimal invasive procedures. Using a Comsol Multiphysics three-dimensional model, a phantom based on ex vivo animal tissue and in vivo animal data, we demonstrate how tissue inhomogeneity can be characterized without any previous knowledge of the electrical properties of the different tissues, except that they should not be linearly dependent on a certain frequency range. This method may have applications in needle biopsies, radiation seeds, or minimally invasive surgery and can reduce the number of computer tomography or magnetic resonance imaging images. We conclude by demonstrating how this mathematical approach can be useful in other applications.

17. Free vibration analysis of linear particle chain impact damper

NASA Astrophysics Data System (ADS)

Gharib, Mohamed; Ghani, Saud

2013-11-01

Impact dampers have gained much research interest over the past decades that resulted in several analytical and experimental studies being conducted in that area. The main emphasis of such research was on developing and enhancing these popular passive control devices with an objective of decreasing the three parameters of contact forces, accelerations, and noise levels. To that end, the authors of this paper have developed a novel impact damper, called the Linear Particle Chain (LPC) impact damper, which mainly consists of a linear chain of spherical balls of varying sizes. The LPC impact damper was designed utilizing the kinetic energy of the primary system through placing, in the chain arrangement, a small-sized ball between each two large-sized balls. The concept of the LPC impact damper revolves around causing the small-sized ball to collide multiple times with the larger ones upon exciting the primary system. This action is believed to lead to the dissipation of part of the kinetic energy at each collision with the large balls. This paper focuses on the outcome of studying the free vibration of a single degree freedom system that is equipped with the LPC impact damper. The proposed LPC impact damper is validated by means of comparing the responses of a single unit conventional impact damper with those resulting from the LPC impact damper. The results indicated that the latter is considerably more efficient than the former impact damper. In order to further investigate the LPC impact damper effective number of balls and efficient geometry when used in a specific available space in the primary system, a parametric study was conducted and its result is also explained herein. Single unit impact damper [14-16]. Multiunit impact damper [17,18]. Bean bag impact damper [19,20]. Particle/granular impact damper [21,23,22]. Resilient impact damper [24]. Buffered impact damper [25-27]. Multiunit impact damper consists of multiple masses instead of a single mass. This

18. The general linear theory of dynamic vibration absorbers

NASA Astrophysics Data System (ADS)

Leonov, G. A.

2017-07-01

It is shown that vibrations of an elastic platform, induced by an external force f( t ) = \\sum\\limits_{j = 0}^n {{A_j}} \\sin ( {{ω _j}t + {\\varphi _j}} ), can be suppressed using n dynamic vibration absorbers with eigenfrequencies ω j .

19. Low-impedance internal linear inductive antenna for large-area flat panel display plasma processing

SciTech Connect

Kim, K.N.; Jung, S.J.; Lee, Y.J.; Yeom, G.Y.; Lee, S.H.; Lee, J.K.

2005-03-15

An internal-type linear inductive antenna, that is, a double-comb-type antenna, was developed for a large-area plasma source having the size of 1020 mmx830 mm, and high density plasmas on the order of 2.3x10{sup 11} cm{sup -3} were obtained with 15 mTorr Ar at 5000 W of inductive power with good plasma stability. This is higher than that for the conventional serpentine-type antenna, possibly due to the low impedance, resulting in high efficiency of power transfer for the double-comb antenna type. In addition, due to the remarkable reduction of the antenna length, a plasma uniformity of less than 8% was obtained within the substrate area of 880 mmx660 mm at 5000 W without having a standing-wave effect.

20. Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

NASA Astrophysics Data System (ADS)

Song, Xizi; Xu, Yanbin; Dong, Feng

2017-04-01

Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results.

1. Minimax design of vibration absorbers for linear damped systems

NASA Astrophysics Data System (ADS)

Brown, Brandon; Singh, Tarunraj

2011-05-01

This paper addresses the issue of design of a passive vibration absorber in the presence of uncertainties in the forcing frequency. A minimax problem is formulated to determine the parameters of a vibration absorber which minimize the maximum motion of the primary mass over the domain of the forcing frequency. The limiting solutions corresponding to the forcing frequency being unrestricted and to that where the forcing frequency is known exactly, are shown to match those available in the literature. The transition of the optimal vibration absorber parameters between the extreme two cases is presented and the solutions are generalized by permitting the mass ratio of the absorber mass and the primary mass to be design parameters. For the specific case where the primary system is undamped, detailed analysis is presented to determine the transition of the optimal vibration absorber parameters between three distinct domains of solutions.

2. On the non-linear vibrations of a projectile

NASA Astrophysics Data System (ADS)

Rath, P. C.; Sharma, S. M.

1981-08-01

The Nonlinear Magnus effect on the nutational oscillations of a missile has been studied. In particular the existence of self-sustained vibrations has been proved. A numerical method is suggested to obtain the limit cycles wherever they exist.

3. Vibration Model Validation for Linear Collider Detector Platforms

SciTech Connect

Bertsche, Kirk; Amann, J.W.; Markiewicz, T.W.; Oriunno, M.; Weidemann, A.; White, G.; /SLAC

2012-05-16

The ILC and CLIC reference designs incorporate reinforced-concrete platforms underneath the detectors so that the two detectors can each be moved onto and off of the beamline in a Push-Pull configuration. These platforms could potentially amplify ground vibrations, which would reduce luminosity. In this paper we compare vibration models to experimental data on reinforced concrete structures, estimate the impact on luminosity, and summarize implications for the design of a reinforced concrete platform for the ILC or CLIC detectors.

4. The role of rotor impedance in the vibration analysis of rotorcraft, part 4

NASA Technical Reports Server (NTRS)

Hohenemser, K. H.

1978-01-01

A method for a strongly idealized case of vertical excitation and for rolling and pitching moment excitation of a four bladed hingeless rotor on an up-focussing flexible mount is developed. The aeroelastic rotor impedances are computed directly with a finite blade element method that includes aerodynamics. The rotor impedance matrix for three or more blades is determined from the root moment impedance for a single blade by a simple multiblade transformation rule. Force and moment amplitudes transferred from the rotor to support are found to be critically dependent on the support dynamics.

5. Enhancement of linear/nonlinear optical responses of molecular vibrations using metal nanoantennas

NASA Astrophysics Data System (ADS)

Morichika, Ikki; Kusa, Fumiya; Takegami, Akinobu; Ashihara, Satoshi

2017-04-01

Plasmonic enhancements of optical near-fields with metal nanostructures offer extensive potential for amplifying lightmatter interactions. We analytically formulate the enhancement of linear and nonlinear optical responses of molecular vibrations through resonant nanoantennas, based on a coupled-dipole model. We apply the formulae to evaluation of signal enhancement factors in the antenna-enhanced vibrational spectroscopy.

6. The role of rotor impedance in the vibration analysis of rotorcraft

NASA Technical Reports Server (NTRS)

Hohenemser, K. H.; Yin, S.-K.

1978-01-01

In an improved method which retains the advantage of separate treatment of rotor and airframe, the rotor impedance is used to correct the input to the airframe. This improved method is illustrated for a strongly idealized case of vertical excitation and then for rolling and pitching moment excitation of a four bladed hingeless rotor on an up-focussing flexible mount. Contrary to the usual approach that represents aeroelastic blade motions by a series of normal blade modes in vacuum, the aeroelastic rotor impedances are computed directly with a finite blade element method that includes aerodynamics. The rotor impedance matrix for three or more blades is determined from the root moment impedance for a single blade by a simple multiblade transformation rule. Force and moment amplitudes transferred from the rotor to the support are found to be critically dependent on the support dynamics.

7. Ultra-low vibration linear stirling cryogenic refrigerator for sub-nano resolution microscopy

NASA Astrophysics Data System (ADS)

Riabzev, S. V.; Veprik, A. M.; Vilenchik, H. S.; Pundak, N.; Castiel, E.

2008-04-01

Wide use of so called "dry-cooling" technology, eventually replacing the LN2 cooling approach in high-resolution instrumentation, such as Scanning Electronic Microscopes, Helium Ion Microscopes, Superconductive Quantum Interference Devices, etc., motivates further quieting of appropriate cryogenic refrigerators. Linear Stirling cryogenic refrigerators are known to be a major source of harmful vibration export compromising the overall performance of vibration-sensitive equipment. The dual-piston approach to a design of a linear compressor yields inherently low vibration export and, therefore, is widely accepted across the industry. However, the residual vibration disturbance originated even from the technological tolerances, natural wear and contamination cannot be completely eliminated. Moreover, a vibration disturbance produced by a pneumatically driven cold head is much more powerful as compared to this of a compressor. The authors successfully redesigned the existing Ricor model K535 Stirling cryogenic refrigerator for use in vibration-sensitive electronic microscopy, where the image resolution is specified in angstroms. The objective was achieved by passive mechanical counterbalancing of the expander portion of the refrigerator, in a combination with an active two-axis control of residual vibrations, relying on National Instruments CompactRIO hardware, incorporating a real-time processor and reconfigurable FPGA for reliable stand-alone embedded application, developed using LabVIEW graphical programming tools. The attainable performance of the Ultra-Low Vibration linear Stirling cryogenic refrigerator RICOR model K535-ULV was evaluated through the full-scale experimentation.

8. The direct field boundary impedance of two-dimensional periodic structures with application to high frequency vibration prediction.

PubMed

Langley, Robin S; Cotoni, Vincent

2010-04-01

Large sections of many types of engineering construction can be considered to constitute a two-dimensional periodic structure, with examples ranging from an orthogonally stiffened shell to a honeycomb sandwich panel. In this paper, a method is presented for computing the boundary (or edge) impedance of a semi-infinite two-dimensional periodic structure, a quantity which is referred to as the direct field boundary impedance matrix. This terminology arises from the fact that none of the waves generated at the boundary (the direct field) are reflected back to the boundary in a semi-infinite system. The direct field impedance matrix can be used to calculate elastic wave transmission coefficients, and also to calculate the coupling loss factors (CLFs), which are required by the statistical energy analysis (SEA) approach to predicting high frequency vibration levels in built-up systems. The calculation of the relevant CLFs enables a two-dimensional periodic region of a structure to be modeled very efficiently as a single subsystem within SEA, and also within related methods, such as a recently developed hybrid approach, which couples the finite element method with SEA. The analysis is illustrated by various numerical examples involving stiffened plate structures.

9. On Forced Vibration in the Linear Theory of Micropolar Elasticity.

DTIC Science & Technology

The present work is concerned with the problem of determining the dynamic response of a finite micropolar elastic body subject to time-dependent...properties of the general theory of micropolar elasticity. As a specific example of this theory, the forced thickness-shear vibrations of an infinite plate

10. Structural Vibration Control Using PZT Patches and Non-Linear Phenomena

NASA Astrophysics Data System (ADS)

Pai, P. F.; Wen, B.; Naser, A. S.; Schulz, M. J.

1998-08-01

We investigate non-linear saturation control, non-linear internal resonance control, and linear position-feedback control of steady-state and transient vibrations of a cantilever beam by using PZT (lead zirconate titanate) patches as actuators and sensors. The saturation control method uses the saturation phenomenon to suppress steady-state vibrations of a dynamical system with quadratic nonlinearities and 2:1 internal resonances. The internal resonance control method uses the energy exchange phenomenon due to internal resonances and added dampings to suppress transient vibrations. To test these control techniques in an efficient and systematic way, we built a digital control system that consists of SIMULINK modelling software and a dSPACE DS1102 controller in a pentium computer. Both numerical and experimental results show that the saturation control method is robust and efficient in suppression steady-state resonant vibrations. The linear position-feedback control is more robust, efficient, and convenient than the internal resonance control in suppressing transient vibrations, but it is not as robust as the saturation control in suppressing steady-state vibrations. A hybrid controller consisting of a saturation controller and a position-feedback controller is shown to be robust and efficient in controlling both transient and steady-state vibrations.

11. Linearly constrained minimum variance spatial filtering for localization of conductivity changes in electrical impedance tomography.

PubMed

Fernández-Corazza, M; von Ellenrieder, N; Muravchik, C H

2015-02-01

We localize dynamic electrical conductivity changes and reconstruct their time evolution introducing the spatial filtering technique to electrical impedance tomography (EIT). More precisely, we use the unit-noise-gain constrained variation of the distortionless-response linearly constrained minimum variance spatial filter. We address the effects of interference and the use of zero gain constraints. The approach is successfully tested in simulated and real tank phantoms. We compute the position error and resolution to compare the localization performance of the proposed method with the one-step Gauss-Newton reconstruction with Laplacian prior. We also study the effects of sensor position errors. Our results show that EIT spatial filtering is useful for localizing conductivity changes of relatively small size and for estimating their time-courses. Some potential dynamic EIT applications such as acute ischemic stroke detection and neuronal activity localization may benefit from the higher resolution of spatial filters as compared to conventional tomographic reconstruction algorithms. Copyright © 2015 John Wiley & Sons, Ltd.

12. Non-linear system identification in flow-induced vibration

SciTech Connect

Spanos, P.D.; Zeldin, B.A.; Lu, R.

1996-12-31

The paper introduces a method of identification of non-linear systems encountered in marine engineering applications. The non-linearity is accounted for by a combination of linear subsystems and known zero-memory non-linear transformations; an equivalent linear multi-input-single-output (MISO) system is developed for the identification problem. The unknown transfer functions of the MISO system are identified by assembling a system of linear equations in the frequency domain. This system is solved by performing the Cholesky decomposition of a related matrix. It is shown that the proposed identification method can be interpreted as a {open_quotes}Gram-Schmidt{close_quotes} type of orthogonal decomposition of the input-output quantities of the equivalent MISO system. A numerical example involving the identification of unknown parameters of flow (ocean wave) induced forces on offshore structures elucidates the applicability of the proposed method.

13. Force Sensor-less Workspace Virtual Impedance Control Considering Resonant Vibration for Industrial Robot

NASA Astrophysics Data System (ADS)

Tungpataratanawong, Somsawas; Ohishi, Kiyoshi; Miyazaki, Toshimasa; Katsura, Seiichiro

The motion control paradigm provides sufficient performance in many elementary industrial tasks. However, only stiff motion the robot cannot accommodate the interaction force under constrained motion. In such situation, the robot is required to perform interaction behavior with the environment. The conventional impedance control schemes require force-sensing devices to feedback force signals to the controllers. The force-sensing device is therefore indispensable and the performance of the system also depends on the quality of this device. This paper proposes a novel strategy for force sensor-less impedance control using disturbance observer and dynamic model of the robot to estimate the external force. In motion task, the robust D-PD (derivative-PD) control is used with feedforward inverse-dynamic torque compensation to ensure robustness and high-speed response with flexible joint model. When robot is in contact with environment, the proposed force sensor-less scheme impedance control with inner-loop D-PD control is utilized. D-PD control uses both position and speed as the references to implement the damping and stiffness characteristic of the virtual impedance model. In addition, the gravity and friction force-feedback compensation is computed by the same dynamic model, which is used in external force estimation. The flexible-joint robot model is utilized in both disturbance observer and motion control design. The workspace impedance control for robot interaction with human operator is implemented on the experimental setup three-degree-of-freedom (3-DOF) robot manipulator to assure the ability and performance of the proposed force sensor-less scheme for flexible-joint industrial robot.

14. Analysis of non-linear response of the human body to vertical whole-body vibration.

PubMed

Tarabini, Marco; Solbiati, Stefano; Moschioni, Giovanni; Saggin, Bortolino; Scaccabarozzi, Diego

2014-01-01

The human response to vibration is typically studied using linear estimators of the frequency response function, although different literature works evidenced the presence of non-linear effects in whole-body vibration response. This paper analyses the apparent mass of standing subjects using the conditioned response techniques in order to understand the causes of the non-linear behaviour. The conditioned apparent masses were derived considering models of increasing complexity. The multiple coherence function was used as a figure of merit for the comparison between the linear and the non-linear models. The apparent mass of eight male subjects was studied in six configurations (combinations of three vibration magnitudes and two postures). The contribution of the non-linear terms was negligible and was endorsed to the change of modal parameters during the test. Since the effect of the inter-subject variability was larger than that due to the increase in vibration magnitude, the biodynamic response should be more meaningfully modelled using a linear estimator with uncertainty rather than looking for a non-linear modelling.

15. A Novel Adaptive Structural Impedance Control Approach to Suppress Aircraft Vibration and Noise

DTIC Science & Technology

2004-10-01

damping, and effective mass. It uses stacked piezoceramic actuators to adaptively vary structural impedance at strategic locations to suppress mechanical...RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39...structures approaches using active material actuators and sensors have become an enabler that cuts across traditional boundaries in material science and

16. Linear and nonlinear energy harvesters for powering pacemakers from heart beat vibrations

NASA Astrophysics Data System (ADS)

Karami, M. Amin; Inman, Daniel J.

2011-03-01

Linear and nonlinear piezoelectric devices are introduced to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. The power requirement of the pacemakers is very low. At the same time, after about 10 years from the original implantation of the pacemakers, patients have to go through another surgical operation just to replace the batteries of their pacemakers. We investigate using vibration energy harvesters to significantly increase the battery life of the pace makers. The major source of vibrations in chest area is due to heartbeats. Linear low frequency and nonlinear mono-stable and bi-stable energy harvesters are designed according to especial signature of heart vibrations. The proposed energy harvesters are robust to variations of heart beat frequency and can meet the power requirement of the pacemakers.

17. A comparison of power output from linear and nonlinear kinetic energy harvesters using real vibration data

NASA Astrophysics Data System (ADS)

Beeby, Stephen P.; Wang, Leran; Zhu, Dibin; Weddell, Alex S.; Merrett, Geoff V.; Stark, Bernard; Szarka, Gyorgy; Al-Hashimi, Bashir M.

2013-07-01

The design of vibration energy harvesters (VEHs) is highly dependent upon the characteristics of the environmental vibrations present in the intended application. VEHs can be linear resonant systems tuned to particular frequencies or nonlinear systems with either bistable operation or a Duffing-type response. This paper provides detailed vibration data from a range of applications, which has been made freely available for download through the Energy Harvesting Network’s online data repository. In particular, this research shows that simulation is essential in designing and selecting the most suitable vibration energy harvester for particular applications. This is illustrated through C-based simulations of different types of VEHs, using real vibration data from a diesel ferry engine, a combined heat and power pump, a petrol car engine and a helicopter. The analysis shows that a bistable energy harvester only has a higher output power than a linear or Duffing-type nonlinear energy harvester with the same Q-factor when it is subjected to white noise vibration. The analysis also indicates that piezoelectric transduction mechanisms are more suitable for bistable energy harvesters than electromagnetic transduction. Furthermore, the linear energy harvester has a higher output power compared to the Duffing-type nonlinear energy harvester with the same Q factor in most cases. The Duffing-type nonlinear energy harvester can generate more power than the linear energy harvester only when it is excited at vibrations with multiple peaks and the frequencies of these peaks are within its bandwidth. Through these new observations, this paper illustrates the importance of simulation in the design of energy harvesting systems, with particular emphasis on the need to incorporate real vibration data.

18. Linearization of scan velocity of resonant vibrating-mirror beam deflectors

DOEpatents

Yeung, E.S.; Chen, S.L.

1991-01-15

A means and method for producing linearization of scan velocity of resonant vibrating-mirror beam deflectors in laser scanning system including presenting an elliptical convex surface to the scanning beam to reflect the scanning beam to the focal plane of the scanning line. The elliptical surface is shaped to produce linear velocity of the reflective scanning beam at the focal plane. Maximization of linearization is accomplished by considering sets of criteria for different scanning applications. 6 figures.

19. Non-linear dual-axis biodynamic response to vertical whole-body vibration

NASA Astrophysics Data System (ADS)

Nawayseh, N.; Griffin, M. J.

2003-11-01

Seated human subjects have been exposed to vertical whole-body vibration so as to investigate the non-linearity in their biodynamic responses and quantify the response in directions other than the direction of excitation. Twelve males were exposed to random vertical vibration in the frequency range 0.25-25 Hz at four vibration magnitudes (0.125, 0.25, 0.625, and 1.25 m s -2 r.m.s.). The subjects sat in four sitting postures having varying foot heights so as to produce differing thigh contact with the seat (feet hanging, feet supported with maximum thigh contact, feet supported with average thigh contact, and feet supported with minimum thigh contact). Forces were measured in the vertical, fore-and-aft, and lateral directions on the seat and in the vertical direction at the footrest. The characteristic non-linear response of the human body with reducing resonance frequency at increasing vibration magnitudes was seen in all postures, but to a lesser extent with minimum thigh contact. Appreciable forces in the fore-and-aft direction also showed non-linearity, while forces in the lateral direction were low and showed no consistent trend. Forces at the feet were non-linear with a multi-resonant behaviour and were affected by the position of the legs. The decreased non-linearity with the minimum thigh contact posture suggests the tissues of the buttocks affect the non-linearity of the body more than the tissues of the thighs. The forces in the fore-and-aft direction are consistent with the body moving in two directions when exposed to vertical vibration. The non-linear behaviour of the body, and the considerable forces in the fore-aft direction should be taken into account when optimizing vibration isolation devices.

20. Vibrational relaxation beyond the linear damping limit in two-dimensional optical spectra of molecular aggregates

NASA Astrophysics Data System (ADS)

Perlík, Václav; Šanda, František

2017-08-01

We present a computational model for the spectra of molecular aggregates with signatures of vibronic progression. Vibronic dynamics is implemented by coupling the dynamics of Frenkel excitons with underdamped vibrations. Vibrational dynamics includes linear damping resulting in the exponential decay and quadratic damping inducing subexponential or power law relaxation and increasing vibrational decoherence as demonstrated on lineshapes of the absorption spectrum. Simulations of the third-order coherent response account for bath reorganization during excitonic transport, which allows us to study the line-shape evolution of cross peaks of 2D spectra.

1. Single-Phase Drive Linear Ultrasonic Motor with Perpendicular Electrode Vibrator

NASA Astrophysics Data System (ADS)

Shih-Wei Hsiao,; Mi-Ching Tsai,

2010-02-01

Unlike most ultrasonic motor designs, in this study, we employ a pair of perpendicular electrodes to energize a piezoelectric vibrator, in which the angle between the direction of polarization and the electric field is purposely set at neither 0 nor 90° so that both the longitudinal and shear effects of the vibrator can be generated simultaneously by a single-phase voltage source. Such a vibrator can generate oblique line trajectories on the contact surface to push a slider for movement, while its moving direction can be easily controlled by switching the excitation sequence of the pair of perpendicular electrodes. In this study, the finite element analysis method was first employed to simulate the oscillatory behavior of the vibrator and then simulation results were verified by single-point, noncontact measurement on the surface of the vibrator. The newly designed linear ultrasonic motor, which can offer identical performance in both forward and backward motions, can maintain its attractive characteristics of simple structure, quiet operation, and single-phase drive. A prototype of the single-phase drive linear ultrasonic motor was fabricated to confirm the feasibility of the proposed vibrator design. The illustrated bidirectional linear ultrasonic motor is shown to be capable of generating a sliding velocity of 84.2 mm/s and a sliding force of 1.79 N.

2. Powering pacemakers from heartbeat vibrations using linear and nonlinear energy harvesters

NASA Astrophysics Data System (ADS)

Amin Karami, M.; Inman, Daniel J.

2012-01-01

Linear and nonlinear piezoelectric devices are introduced to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. The power requirement of a pacemaker is very low. However, after few years, patients require another surgical operation just to replace their pacemaker battery. Linear low frequency and nonlinear mono-stable and bi-stable energy harvesters are designed according to the especial signature of heart vibrations. The proposed energy harvesters are robust to variation of heart rate and can meet the power requirement of pacemakers.

3. H∞ optimization of dynamic vibration absorber variant for vibration control of damped linear systems

NASA Astrophysics Data System (ADS)

Chun, Semin; Lee, Youngil; Kim, Tae-Hyoung

2015-01-01

This study focuses on the H∞ optimal design of a dynamic vibration absorber (DVA) variant for suppressing high-amplitude vibrations of damped primary systems. Unlike traditional DVA configurations, the damping element in this type of DVA is connected directly to the ground instead of the primary mass. First, a thorough graphical analysis of the variations in the maximum amplitude magnification factor depending on two design parameters, natural frequency and absorber damping ratios, is performed. The results of this analysis clearly show that any fixed-points-theory-based conventional method could provide, at best, only locally but not globally optimal parameters. Second, for directly handling the H∞ optimization for its optimal design, a novel meta-heuristic search engine, called the diversity-guided cyclic-network-topology-based constrained particle swarm optimization (Div-CNT-CPSO), is developed. The variant DVA system developed using the proposed Div-CNT-CPSO scheme is compared with those reported in the literature. The results of this comparison verified that the proposed system is better than the existing methods for suppressing the steady-state vibration amplitude of a controlled primary system.

4. A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet.

PubMed

Liu, Yingxiang; Liu, Junkao; Chen, Weishan; Shi, Shengjun

2012-05-01

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).

5. Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet

SciTech Connect

Frisch, Josef; Chang, Allison; Decker, Valentin; Doyle, Eric; Eriksson, Leif; Hendrickson, Linda; Himel, Thomas; Markiewicz, Thomas; Partridge, Richard; Seryi, Andrei; /SLAC

2006-09-28

The small beam sizes at the interaction point of a X-band linear collider require mechanical stabilization of the final focus magnets at the nanometer level. While passive systems provide adequate performance at many potential sites, active mechanical stabilization is useful if the natural or cultural ground vibration is higher than expected. A mechanical model of a room temperature linear collider final focus magnet has been constructed and actively stabilized with an accelerometer based system.

6. A Simple Reduction Process for the Normal Vibrational Modes Occurring in Linear Molecules

ERIC Educational Resources Information Center

McInerny, William

2005-01-01

The students in molecular spectroscopy courses are often required to determine the permitted normal vibrations for linear molecules that belong to particular groups. The reducible group representations generated by the use of Cartesian coordinates can be reduced by the use of a simple algebraic process applied to the group representations. The…

7. A Simple Reduction Process for the Normal Vibrational Modes Occurring in Linear Molecules

ERIC Educational Resources Information Center

McInerny, William

2005-01-01

The students in molecular spectroscopy courses are often required to determine the permitted normal vibrations for linear molecules that belong to particular groups. The reducible group representations generated by the use of Cartesian coordinates can be reduced by the use of a simple algebraic process applied to the group representations. The…

8. Measurement of non-linear distortions in the vibration of acoustic transducers and acoustically driven membranes

NASA Astrophysics Data System (ADS)

Aerts, J. R. M.; Dirckx, J. J. J.; Pintelon, R.

2009-03-01

Different methods exist to quantify non-linearity, and recently a new method was proposed that uses multisines to determine output response level, noise level, and level of non-linear distortions simultaneously from one single short experiment. We used heterodyne vibrometry to measure the vibration of a membrane while it is stimulated acoustically, and to determine the non-linear distortions in its response with this new method of analysis. We demonstrate the method on an electrically driven earphone. Analysis of the sound output and optically measured vibration deliver comparable results, and clearly detect non-linear distortions. Next, we apply the method on an acoustically driven elastic membrane. At vibration amplitudes of the same magnitude as on the earphone, non-linear distortions are much smaller, as to be expected on an elastic membrane, but they can still be detected with the vibrometer. This technique can be used to investigate the non-linearity of acoustically driven systems such as the middle ear.

9. Optimization of Passive and Active Non-Linear Vibration Mounting Systems Based on Vibratory Power Transmission

NASA Astrophysics Data System (ADS)

Royston, T. J.; Singh, R.

1996-07-01

While significant non-linear behavior has been observed in many vibration mounting applications, most design studies are typically based on the concept of linear system theory in terms of force or motion transmissibility. In this paper, an improved analytical strategy is presented for the design optimization of complex, active of passive, non-linear mounting systems. This strategy is built upon the computational Galerkin method of weighted residuals, and incorporates order reduction and numerical continuation in an iterative optimization scheme. The overall dynamic characteristics of the mounting system are considered and vibratory power transmission is minimized via adjustment of mount parameters by using both passive and active means. The method is first applied through a computational example case to the optimization of basic passive and active, non-linear isolation configurations. It is found that either active control or intentionally introduced non-linearity can improve the mount's performance; but a combination of both produces the greatest benefit. Next, a novel experimental, active, non-linear isolation system is studied. The effect of non-linearity on vibratory power transmission and active control are assessed via experimental measurements and the enhanced Galerkin method. Results show how harmonic excitation can result in multiharmonic vibratory power transmission. The proposed optimization strategy offers designers some flexibility in utilizing both passive and active means in combination with linear and non-linear components for improved vibration mounts.

10. Vibration reduction of beams under successive traveling loads by means of linear and nonlinear dynamic absorbers

NASA Astrophysics Data System (ADS)

Samani, Farhad S.; Pellicano, Francesco

2012-05-01

The goal of the present work is to assess the performances of dynamic vibration absorbers (DVA) in suppressing the vibrations of a simply supported beam subjected to an infinite sequence of regularly spaced concentrated moving loads. In particular, several types of DVA are considered: linear, cubic, higher odd-order monomials and piecewise linear stiffness; linear, cubic and linear-quadratic viscous damping. The purpose is to clarify if nonlinear DVAs show improvements with respect to the classical linear devices. The dynamic scenario is deeply investigated in a wide range of operating conditions, spanning the parameter space of the DVA (damping, stiffness). Nonlinear stiffness can lead to complex dynamics such as quasi-periodic, chaotic and sub-harmonic responses; moreover, acting on the stiffness nonlinearity no improvement is found with respect to the linear DVA. A nonlinear non-symmetric dissipation in the DVA leads to a great reduction of the beam response, the reduction is larger with respect to the linear DVA.

11. Rotational-vibrational structure of a quasi-linear molecule: CH/sub 2//sup +/

SciTech Connect

Lee, J.S.; Secrest, D.

1988-04-07

A new potential energy function is obtained for the ground electronic state of CH/sub 2//sup +/ through a Simons-Parr-Finlan (SPF) type expansion of an ab initio potential surface for this molecule. The SPF type potential is found to fit the a priori potential points extremely well and has reasonable physical properties along the vibrational coordinates of the molecule. The rotation-vibration states of this molecule are calculated for J = 0, 1, 2, and 3 by using this potential function. The calculations were carried out using a linear molecule Hamiltonian. Assignments have been made to each vibrational state. It is possible to identify the (1 1 0) state through the rotational structure of the molecule. This level was assigned to (0 4 0) previously. As in the previous calculations on this molecule, the Renner-Teller effect was neglected.

12. A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot.

PubMed

Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

2010-08-01

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 V(rms).

13. Non-Linear Vibrations of a Beam on AN Elastic Foundation

NASA Astrophysics Data System (ADS)

Coskun, I.; Engin, H.

1999-06-01

The non-linear vibrations of an elastic beam resting on a non-linear tensionless Winkler foundation subjected to a concentrated load at the centre is presented in this paper. Since the foundation is assumed to be tensionless, the beam may lift off the foundation and there exists different regions namely contact and non-contact regions. Since the contact regions are not known in advance, the problem appears as a non-linear one even though there is no non-linear term in the foundation model. In this case, the calculation of the roots of a non-linear equation is needed to obtain contact lengths. The perturbation technique is used to solve the non-linear governing equation associated with the problem. Using this technique, the non-linear problem is reduced to the solution of a set of linearized partial differential equations. The lift-off points and the displacements are obtained in linear and non-linear cases, and the variation of these points with respect to various parameters are presented. It is concluded that the contact length varies with the magnitude of the load because of the non-linearity.

14. Modeling and simulation of linear and nonlinear MEMS scale electromagnetic energy harvesters for random vibration environments.

PubMed

Khan, Farid; Stoeber, Boris; Sassani, Farrokh

2014-01-01

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency.

15. Modeling and Simulation of Linear and Nonlinear MEMS Scale Electromagnetic Energy Harvesters for Random Vibration Environments

PubMed Central

Sassani, Farrokh

2014-01-01

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency. PMID:24605063

16. A rectangle-type linear ultrasonic motor using longitudinal vibration transducers with four driving feet.

PubMed

Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

2013-04-01

To make full use of the vibrational energy of a longitudinal transducer, a rectangle-type linear ultrasonic motor with four driving feet is proposed in this paper. This new motor consists of four longitudinal vibration transducers which are arranged in a rectangle and form an enclosed construction. Lead zirconate titanate ceramics are embedded into the middle of the transducer and fastened by a wedge-caulking mechanism. Each transducer includes an exponentially shaped horn located on each end. The horns of the vertical transducers intersect at the base of the horizontal transducers' horns; the tip ends of the horizontal transducers' horns are used as the driving feet. Longitudinal vibrations are superimposed in the motor and generate elliptical movements at the tip ends of the horns. The working principle of the proposed motor is analyzed. The resonance frequencies of two working modes are tuned to be close to each other by adjusting the structural parameters. Transient analysis is developed to gain the vibration characteristics of the motor. A prototype motor is fabricated and measured. The vibration test results verify the feasibility of the proposed design. Typical output of the prototype is a no-load speed of 928 mm/s and maximum thrust force of 60 N at a voltage of 200 Vrms.

17. Optimization of linear zigzag insert metastructures for low-frequency vibration attenuation using genetic algorithms

NASA Astrophysics Data System (ADS)

Abdeljaber, Osama; Avci, Onur; Kiranyaz, Serkan; Inman, Daniel J.

2017-02-01

Vibration suppression remains a crucial issue in the design of structures and machines. Recent studies have shown that with the use of metamaterial inspired structures (or metastructures), considerable vibration attenuation can be achieved. Optimization of the internal geometry of metastructures maximizes the suppression performance. Zigzag inserts have been reported to be efficient for vibration attenuation. It has also been reported that the geometric parameters of the inserts affect the vibration suppression performance in a complex manner. In an attempt to find out the most efficient parameters, an optimization study has been conducted on the linear zigzag inserts and is presented here. The research reported in this paper aims at developing an automated method for determining the geometry of zigzag inserts through optimization. This genetic algorithm based optimization process searches for optimal zigzag designs which are properly tuned to suppress vibrations when inserted in a specific host structure (cantilever beam). The inserts adopted in this study consist of a cantilever zigzag structure with a mass attached to its unsupported tip. Numerical simulations are carried out to demonstrate the efficiency of the proposed zigzag optimization approach.

18. a Normal Mode Expansion Method for the Undamped Forced Vibration of Linear Piezoelectric Solid

NASA Astrophysics Data System (ADS)

LIU, D.-C.

2000-06-01

A normal mode expansion method for the vibrational responses of non-homogeneous linear piezoelectric materials without damping is presented. It can be applied directly to arbitrary piezoelectric composites, which are widely used in vibrational and acoustic sensor/actuator/transmitter applications. In the present article it is shown that if the normal modes are given, the displacement field can be expanded as the linear superposition of normal modes, while the modal coefficients can be represented in terms of surface and volume integrals directly over the six types of distributed excitations without solving the quasi-static solution explicitly. The present treatment is a modification of an earlier work by Liu [11] using a different definition of the so-called quasi-static solution, and the damping effect has been neglected for simplicity. A simple example is given to exemplify the application of the present formulation.

19. On the linear elastic, isotropic modeling of poroelastic distributed vibration absorbers at low frequencies

NASA Astrophysics Data System (ADS)

Harne, R. L.

2013-07-01

Several past works have considered a passive vibration absorber device utilizing distributed mass and spring layers. The thickness of the poroelastic foam spring and the area density of the mass layer are modified to achieve a target natural frequency of the device while the foam itself provides adequate dissipation of energy as the mass dynamically compresses it at resonance. A model of the device earlier developed is briefly reviewed and validated by new experiments. The dependence of the absorber natural frequency and damping on the poroelastic spring thickness is observed in detail and is found to be consistent with past work on poroelastic material elastic characteristics outside of the linear dynamic regime. The results set a practical limit on the applicability of linearity assumptions in the present modeling of the distributed poroelastic vibration absorbers and thus determine a design parameter range for which the computationally efficient model is accurate.

20. Linearization of scan velocity of resonant vibrating-mirror beam deflectors

DOEpatents

Yeung, Edward S.; Chen, Shun-Le

1991-01-15

A means and method for producing linerization of scan velocity of resonant vibrating-mirror beam deflectors in laser scanning system including presenting an elliptical convex surface to the scanning beam to reflect the scanning beam to the focal plane of the scanning line. The elliptical surface is shaped to produce linear velocity of the reflective scanning beam at the focal plane. Maximization of linerization is accomplished by considering sets of criteria for different scanning applications.

1. On the nonlinear normal modes of free vibration of piecewise linear systems

NASA Astrophysics Data System (ADS)

Uspensky, B. V.; Avramov, K. V.

2014-07-01

A modification of the Shaw-Pierre nonlinear normal modes is suggested in order to analyze the vibrations of a piecewise linear mechanical systems with finite degrees of freedom. The use of this approach allows one to reduce to twice the dimension of the nonlinear algebraic equations system for nonlinear normal modes calculations in comparison with systems obtained by previous researchers. Two degrees of freedom and fifteen degrees of freedom nonlinear dynamical systems are investigated numerically by using nonlinear normal modes.

2. Development of a Non-Magnetic Inertial Sensor for Vibration Stabilization in a Linear Collider

SciTech Connect

Frisch, Josef; Decker, Valentin; Doyle, Eric; Hendrickson, Linda; Himel, Thomas; Markiewicz, Thomas; Seryi, Andrei; Chang, Allison; Partridge, Richard; /Brown U.

2006-09-01

One of the options for controlling vibration of the final focus magnets in a linear collider is to use active feedback based on accelerometers. While commercial geophysics sensors have noise performance that substantially exceeds the requirements for a linear collider, they are physically large, and cannot operate in the strong magnetic field of the detector. Conventional nonmagnetic sensors have excessive noise for this application. We report on the development of a non-magnetic inertial sensor, and on a novel commercial sensor both of which have demonstrated the required noise levels for this application.

3. Rotational and vibrational synthetic spectra of linear parent molecules in comets

NASA Astrophysics Data System (ADS)

Crovisier, J.

1987-03-01

The excitation conditions of linear parent molecules in cometary atmospheres are evaluated and modeled. The model is valid for most linear molecules without electronic angular momentum. It takes into account collisions and infrared excitation. The molecule rotational population distribution is computed as a function of distance to nucleus. The line intensities of the strongest parallel and perpendicular fundamental vibrational bands, as well as the pure rotational lines, can then be evaluated. This model is applied to several candidate parent molecules, for observing conditions corresponding to available or planned instruments, either ground-based or aboard aircrafts, satellites or space probes.

4. Vibrational spectra and non linear optical proprieties of L-histidine oxalate: DFT studies

NASA Astrophysics Data System (ADS)

Ahmed, A. Ben; Elleuch, N.; Feki, H.; Abid, Y.; Minot, C.

2011-08-01

This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a nonlinear optical material L-histidine oxalate. Due to the lack of sufficiently precise information on geometric structure in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of L-histidine oxalate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P2 12 12 1 of orthorhombic system. The FT-IR and Raman spectra of L-histidine oxalate were recorded and analyzed. The vibrational wave numbers were examined theoretical with the aid of Gaussian98 package of programs using the DFT//B3LYP/6-31G(d) level of theory. The data obtained from vibrational wave number calculations are used to assign vibrational bands obtained in IR and Raman spectroscopy of the studied compound. The geometrical parameters of the title compound are in agreement with the values of similar structures. To investigate microscopic second order non-linear optical NLO behaviour of the examined complex, the electric dipole μtot, the polarizability αtot and the hyperpolarizability βtot were computed using DFT//B3LYP/6-31G(d) method. According to our calculation, the title compound exhibits non-zero βtot value revealing microscopic second order NLO behaviour.

5. Effective suppression of pneumatic vibration isolators by using input-output linearization and time delay control

NASA Astrophysics Data System (ADS)

Chang, Pyung-hun; Ki Han, Dong; Shin, Yun-ho; Kim, Kwang-joon

2010-05-01

This paper presents a new state space representation of pneumatic vibration isolators (PVIs) and a design of a robust control, Time Delay Control (TDC), based on it. The new state space model, derived by using the input-output linearization method, is of the phase variable form with the air mass-flow as the control input. This model offers a framework that enables simultaneous suppression of both seismic vibration and direct disturbance (or payload disturbance) with an accelerometer only. Based on this model, TDC is designed and verified with experiments on a single chamber PVI with an accelerometer only. In the experiment, the PVI with TDC successfully suppresses seismic vibration and direct disturbance, both individually and simultaneously. Faced with seismic vibration, the transmissibility of the PVI with TDC has virtually no resonance peak at low frequency; under direct disturbance, the former achieves a 68 percent reduction in settling time of the latter. The final analysis of experimental result shows that TDC effectively estimates the modeling error along with other uncertainties and cancels them, while achieving desired closed-loop dynamics.

6. Small strain vibration of a continuous, linearized viscoelastic rod of expanded polymer cushion material

NASA Astrophysics Data System (ADS)

Batt, Gregory S.; Gibert, James M.; Daqaq, Mohammed

2015-08-01

In this paper, the free and forced vibration response of a linearized, distributed-parameter model of a viscoelastic rod with an applied tip-mass is investigated. A nonlinear model is developed from constitutive relations and is linearized about a static equilibrium position for analysis. A classical Maxwell-Weichert model, represented via a Prony series, is used to model the viscoelastic system. The exact solution to both the free and forced vibration problem is derived and used to study the behavior of an idealized packaging system containing Nova Chemicals' Arcel® foam. It is observed that, although three Prony series terms are deemed sufficient to fit the static test data, convergence of the dynamic response and study of the storage and loss modulii necessitate the use of additional Prony series terms. It is also shown that the model is able to predict the modal frequencies and the primary resonance response at low acceleration excitation, both with reasonable accuracy given the non-homogeneity and density variation observed in the specimens. Higher acceleration inputs result in softening nonlinear responses highlighting the need for a nonlinear elastic model that extends beyond the scope of this work. Solution analysis and experimental data indicate little material vibration energy dissipation close to the first modal frequency of the mass/rod system.

7. Quantitative non-linear ultrasonic imaging of targets with significant acoustic impedance contrast--an experimental study.

PubMed

Guillermin, Régine; Lasaygues, Philippe; Rabau, Guy; Lefebvre, Jean-Pierre

2013-08-01

This study deals with the reconstruction, from ultrasonic measured data, of the sound speed profile of a penetrable two-dimensional target of arbitrary cross-section embedded in an infinite medium. Green's theorem is used to obtain a domain integral representation of the acoustical scattered field, and a discrete formulation of the inverse problem is obtained using a moment method. An iterative non-linear algorithm minimizing the discrepancy between the measured and computed scattered fields is used to reconstruct the sound speed profile in the region of interest. The minimization process is performed using a conjugated-gradient method. An experimental study with significant acoustical impedance contrast targets immersed in water was performed. Images of the sound speed profile obtained by inversion of experimental data are presented.

8. A New Stochastic Equivalent Linearization Implementation for Prediction of Geometrically Nonlinear Vibrations

NASA Technical Reports Server (NTRS)

Muravyov, Alexander A.; Turner, Travis L.; Robinson, Jay H.; Rizzi, Stephen A.

1999-01-01

In this paper, the problem of random vibration of geometrically nonlinear MDOF structures is considered. The solutions obtained by application of two different versions of a stochastic linearization method are compared with exact (F-P-K) solutions. The formulation of a relatively new version of the stochastic linearization method (energy-based version) is generalized to the MDOF system case. Also, a new method for determination of nonlinear sti ness coefficients for MDOF structures is demonstrated. This method in combination with the equivalent linearization technique is implemented in a new computer program. Results in terms of root-mean-square (RMS) displacements obtained by using the new program and an existing in-house code are compared for two examples of beam-like structures.

9. Characteristics of 10 mm Multilayer L1-F2 Mode Vibrator and Application to a Linear Motor

NASA Astrophysics Data System (ADS)

Funakubo, Tomoki; Tomikawa, Yoshiro

2003-05-01

In the present paper we discuss a small-sized multilayer L1-F2 mode vibrator and its application to an ultrasonic linear motor. In an attempt to reduce both the size and the driving voltage of an L1-F2 mode vibrator, we constructed a multilayer L1-F2 mode vibrator whose inner electrodes are simply divided into two. Test results clarified that the multilayer L1-F2 mode vibrator exhibits two resonance modes; namely, a first longitudinal mode and a second flexural mode, and that an amplitude of vibration velocity is sufficiently large for application to a linear motor. Specific merits of our multilayer L1-F2 mode vibrator are that the driving voltage is low (5 Vrms), owing to multilayer construction, and that the vibrator is small (10 × 2.5 × 2 mm: W×H×D), owing to the simple construction of the inner electrodes. Additionally, the present study revealed that an ultrasonic linear motor using the multilayer L1-F2 mode vibrator exhibits superior performance in practical application.

10. Transverse vibrations of a linearly tapered cantilever beam with constraining springs

NASA Astrophysics Data System (ADS)

Craver, W. L., Jr.; Jampala, P.

1993-09-01

The free vibrations of a linearly tapered cantilever beam, elastically constrained at an arbitrary position along the length of the beam, have been investigated using the Bernoulli-Euler equation. The beam has a rectangular cross-section with equal taper in the horizontal and vertical planes, and the constraint is a translational spring. The characteristic determinant is derived in terms of dimensionless spring constant, and the eigenfrequencies are determined using a straight search and bisection method. The results are presented in tabular and graphical form.

11. Non-linear vibrational modes in biomolecules: A periodic orbits description

NASA Astrophysics Data System (ADS)

Kampanarakis, Alexandros; Farantos, Stavros C.; Daskalakis, Vangelis; Varotsis, Constantinos

2012-05-01

The vibrational harmonic normal modes of a molecule, which are valid at energies close to an equilibrium point (a minimum, maximum or saddle of the potential energy surface), are extended by periodic orbits to high energies where anharmonicity and coupling of the degrees of freedom are significant. In this way the assignment of the spectra, and thus the extraction of dynamics in highly excited molecules, can be obtained. New vibrational modes emanating from bifurcations of periodic orbits and long living localized trajectories signal the birth and localization of new quantum states. In this article we review and further study non-linear vibrational modes for model biomolecules such as alanine dipeptide and the active site in the oxoferryl oxidation state of the enzyme cytochrome c oxidase. We locate periodic orbits which exhibit high anhamonicity and lead to center-saddle bifurcations. These modes are associated to an isomerization process in alanine dipeptide and to frequency shifts in the oxoferryl observed by modifying the Coulomb field around the Imidazole-FeIV = O species.

12. Linear thermoelastic buckling and free vibration behavior of functionally graded truncated conical shells

NASA Astrophysics Data System (ADS)

Bhangale, Rajesh K.; Ganesan, N.; Padmanabhan, Chandramouli

2006-04-01

In recent years, structures made up of functionally graded materials (FGMs) have received considerable attention for use in high-temperature applications. In this article, a finite element formulation based on First-Order Shear Deformation Theory (FSDT) is used to study the thermal buckling and vibration behavior of truncated FGM conical shells in a high-temperature environment. A Fourier series expansion for the displacement variable in the circumferential direction is used to model the FGM conical shell. The material properties of the truncated FGM conical shells are functionally graded in the thickness direction according to a volume fraction power law distribution. Temperature-dependent material properties are considered to carry out a linear thermal buckling and free vibration analysis. The conical shell is assumed to be clamped-clamped and has a high temperature specified on the inner surface while the outer surface is at ambient temperature. The one-dimensional heat conduction equation is used across the thickness of the conical shell to determine the temperature distribution and thereby the material properties. In addition, the influence of initial stresses on the frequency behavior of FGM shells has also been investigated. Numerical studies involving the understanding of the role of power law index, r/h ratios, and semi-vertex angle on the thermal buckling temperature as well as on vibration have been carried out.

13. Decoherence of Topological Qubit in Linear Motions: Decoherence Impedance, Anti-Unruh and Information Backflow

NASA Astrophysics Data System (ADS)

Liu, Pei-Hua; Lin, Feng-Li

2017-08-01

In this work we study the decoherence of topological qubits in linear motions. The topological qubit is made of two spatially-separated Majorana zero modes which are the edge excitations of Kitaev chain [1]. In a previous work [2], it was shown by one of us and his collaborators that the decoherence of topological qubit is exactly solvable, moreover, topological qubit is robust against decoherence in the super-Ohmic environments. We extend the setup of [2] to consider the effect of motions on the decoherence of the topological qubits. Our results show the thermalization as expected by Unruh effect. Besides, we also find the so-called “anti-Unruh” phenomena which shows the rate of decoherence is anti-correlated with the acceleration in short-time scale. Moreover, we modulate the motion patterns of each Majorana modes and find information backflow and the preservation of coherence even with nonzero accelerations. This is the characteristics of the underlying non-Markovian reduced dynamics. We conclude that he topological qubit is in general more robust against decoherence than the usual qubits, and can be take into serious consideration for realistic implementation to have robust quantum computation and communication. This talk is based on our work in [3].

14. A hybrid-stress finite element approach for stress and vibration analysis in linear anisotropic elasticity

NASA Technical Reports Server (NTRS)

Oden, J. Tinsley; Fly, Gerald W.; Mahadevan, L.

1987-01-01

A hybrid stress finite element method is developed for accurate stress and vibration analysis of problems in linear anisotropic elasticity. A modified form of the Hellinger-Reissner principle is formulated for dynamic analysis and an algorithm for the determination of the anisotropic elastic and compliance constants from experimental data is developed. These schemes were implemented in a finite element program for static and dynamic analysis of linear anisotropic two dimensional elasticity problems. Specific numerical examples are considered to verify the accuracy of the hybrid stress approach and compare it with that of the standard displacement method, especially for highly anisotropic materials. It is that the hybrid stress approach gives much better results than the displacement method. Preliminary work on extensions of this method to three dimensional elasticity is discussed, and the stress shape functions necessary for this extension are included.

15. Vibrational spectra and non linear optical proprieties of L-histidine oxalate: DFT studies.

PubMed

Ben Ahmed, A; Elleuch, N; Feki, H; Abid, Y; Minot, C

2011-08-01

This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a nonlinear optical material L-histidine oxalate. Due to the lack of sufficiently precise information on geometric structure in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of L-histidine oxalate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P2(1)2(1)2(1) of orthorhombic system. The FT-IR and Raman spectra of L-histidine oxalate were recorded and analyzed. The vibrational wave numbers were examined theoretical with the aid of Gaussian98 package of programs using the DFT//B3LYP/6-31G(d) level of theory. The data obtained from vibrational wave number calculations are used to assign vibrational bands obtained in IR and Raman spectroscopy of the studied compound. The geometrical parameters of the title compound are in agreement with the values of similar structures. To investigate microscopic second order non-linear optical NLO behaviour of the examined complex, the electric dipole μ(tot), the polarizability α(tot) and the hyperpolarizability β(tot) were computed using DFT//B3LYP/6-31G(d) method. According to our calculation, the title compound exhibits non-zero β(tot) value revealing microscopic second order NLO behaviour. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

16. Crystal studies, vibrational spectra and non-linear optical properties of L-histidine chloride monohydrate.

PubMed

Ben Ahmed, A; Feki, H; Abid, Y; Boughzala, H; Minot, C

2010-01-01

This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a non-linear optical material L-histidine chloride monohydrate. Due to the lack of sufficiently precise information on geometric parameters available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of L-histidine chloride monohydrate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro-symmetric space group P2(1)2(1)2(1) of orthorhombic system. IR spectrum has been recorded in the range [400-4000 cm(-1)]. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using DFT//B3LYP/6-31G (d) method show a good agreement with the experimental data. The calculated vibrational spectra are in well agreement with the experimental one. To investigate microscopic second-order non-linear optical NLO behavior of the examined complex, the electric dipole mu, the polarizability alpha and the hyperpolarizability beta were computed using DFT//B3LYP/6-31G (d) method. The time-dependent density functional theory (TD-DFT) was employed to descript the molecular electron structure of the title compound using the B3LYP/6-31G (d) method. According to our calculations, L-histidine chloride monohydrate exhibits non-zero beta value revealing microscopic second-order NLO behavior. Copyright 2009 Elsevier B.V. All rights reserved.

17. Crystal studies, vibrational spectra and non-linear optical properties of L-histidine chloride monohydrate

NASA Astrophysics Data System (ADS)

Ahmed, A. Ben; Feki, H.; Abid, Y.; Boughzala, H.; Minot, C.

2010-01-01

This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a non-linear optical material L-histidine chloride monohydrate. Due to the lack of sufficiently precise information on geometric parameters available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of L-histidine chloride monohydrate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro-symmetric space group P2 12 12 1 of orthorhombic system. IR spectrum has been recorded in the range [400-4000 cm -1]. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using DFT//B3LYP/6-31G (d) method show a good agreement with the experimental data. The calculated vibrational spectra are in well agreement with the experimental one. To investigate microscopic second-order non-linear optical NLO behavior of the examined complex, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31G (d) method. The time-dependent density functional theory (TD-DFT) was employed to descript the molecular electron structure of the title compound using the B3LYP/6-31G (d) method. According to our calculations, L-histidine chloride monohydrate exhibits non-zero β value revealing microscopic second-order NLO behavior.

18. Linear stability of the Couette flow of a vibrationally excited gas. 2. viscous problem

NASA Astrophysics Data System (ADS)

Grigor'ev, Yu. N.; Ershov, I. V.

2016-03-01

Based on the linear theory, stability of viscous disturbances in a supersonic plane Couette flow of a vibrationally excited gas described by a system of linearized equations of two-temperature gas dynamics including shear and bulk viscosity is studied. It is demonstrated that two sets are identified in the spectrum of the problem of stability of plane waves, similar to the case of a perfect gas. One set consists of viscous acoustic modes, which asymptotically converge to even and odd inviscid acoustic modes at high Reynolds numbers. The eigenvalues from the other set have no asymptotic relationship with the inviscid problem and are characterized by large damping decrements. Two most unstable viscous acoustic modes (I and II) are identified; the limits of these modes were considered previously in the inviscid approximation. It is shown that there are domains in the space of parameters for both modes, where the presence of viscosity induces appreciable destabilization of the flow. Moreover, the growth rates of disturbances are appreciably greater than the corresponding values for the inviscid flow, while thermal excitation in the entire considered range of parameters increases the stability of the viscous flow. For a vibrationally excited gas, the critical Reynolds number as a function of the thermal nonequilibrium degree is found to be greater by 12% than for a perfect gas.

19. Development, implementation, and characterization of a standalone embedded viscosity measurement system based on the impedance spectroscopy of a vibrating wire sensor

NASA Astrophysics Data System (ADS)

Santos, José; Janeiro, Fernando M.; Ramos, Pedro M.

2015-10-01

This paper presents an embedded liquid viscosity measurement system based on a vibrating wire sensor. Although multiple viscometers based on different working principles are commercially available, there is still a market demand for a dedicated measurement system capable of performing accurate, fast measurements and requiring little or no operator training for simple systems and solution monitoring. The developed embedded system is based on a vibrating wire sensor that works by measuring the impedance response of the sensor, which depends on the viscosity and density of the liquid in which the sensor is immersed. The core of the embedded system is a digital signal processor (DSP) which controls the waveform generation and acquisitions for the measurement of the impedance frequency response. The DSP also processes the acquired waveforms and estimates the liquid viscosity. The user can interact with the measurement system through a keypad and an LCD or through a computer with a USB connection for data logging and processing. The presented system is tested on a set of viscosity standards and the estimated values are compared with the standard manufacturer specified viscosity values. A stability study of the measurement system is also performed.

20. Parallel simulations of vortex-induced vibrations in turbulent flow: Linear and nonlinear models

NASA Astrophysics Data System (ADS)

Evangelinos, Constantinos

1999-11-01

In this work unstructured spectral/hp element based direct numerical simulation (DNS) techniques are used to simulate vortex-induced vibrations (VIV) of flexible cylinders. Linear structural models are employed for tension- dominated structures (cables) and bending stiffness- dominated structures (beams). Flow-structure interactions are studied in transitional (200-300) and turbulent (1000) Reynolds numbers. Structural responses as well as hydrodynamic forces are analyzed and their relationship with the near wake flow structures is examined. The following conclusions were reached: (1)A Reynolds number effect exists for the observed oscillation amplitude. (2)The phase relationship between cross- flow displacement and coefficient of lift is correlated with both the magnitudes of lift forces and displacement. (3)Cables enhance transition to turbulent flow, while beams (and rigidly vibrating cylinders) delay it. In the transition regime beams oscillate with 70% of the amplitude of cables. (4)Oblique and parallel shedding appear to coexist in the turbulent wake of cables and beams with a traveling wave structural response. The corresponding wake structure behind a cylinder with pinned ends vibrating as a standing wave, displays lambda-type vortices similar to those seen at lower (laminar) Reynolds numbers. (5)Cables and beams at a Reynolds number of 1000 give: (a)extremely similar velocity spectra, (b)differing autocorrelation profiles and large flow structures, and (c)differing structural responses. (6)The empirical formula for the coefficient of drag due to Skop et al. (1977) is shown to be in disagreement with the experimental data; a modified formula fits the results much better. A non-linear set of equations for the finite amplitude vibrations of a string are also derived and investigated. It is combined with an Arbitrary Lagrangian-Eulerian (ALE) flow solver and applied to model simulations of low Reynolds number (100) flow past flexible cylinders with pinned ends

1. Calculation of vibrational energy of molecule using coupled cluster linear response theory in bosonic representation: convergence studies.

PubMed

Banik, Subrata; Pal, Sourav; Prasad, M Durga

2008-10-07

Vibrational excited state energies have been calculated using vibrational coupled cluster linear response theory (CCLRT). The method has been implemented on formaldehyde and water molecule. Convergence studies have been shown with varying the cluster operator from S(4) to S(6) as well as the excitation operator from four bosons to six bosons. A good agreement with full configuration interaction results has been observed with S(6) truncation at coupled-cluster method level and six bosonic excitations at CCLRT level.

2. Analytical method for steady state vibration of system with localized non-linearities using convolution integral and Galerkin method

NASA Astrophysics Data System (ADS)

Iwata, Y.; Sato, H.; Komatsuzaki, T.

2003-04-01

The analytical method using transfer function or impulse response is very effective for analyzing non-linear systems with localized non-linearities. This is because the number of non-linear equations can be reduced to that of the equations with respect to points connected with the non-linear element. In the present paper, analytical method for the steady state vibration of non-linear system including subharmonic vibration is proposed by utilizing convolution integral and the impulse response. The Galerkin method is introduced to solve the non-linear equations formulated by the convolution integral, and then the steady state vibration is obtained. An advantage of the present method is that stability or instability of the steady state vibration can be discriminated by the transient analysis from convolution integral. The three-degree-of-freedom mass-spring system is shown as a numerical example and the proposed method is verified by comparing with the result by Runge-Kutta-Gill method.

3. Design of three-element dynamic vibration absorber for damped linear structures

NASA Astrophysics Data System (ADS)

Anh, N. D.; Nguyen, N. X.; Hoa, L. T.

2013-09-01

The standard type of dynamic vibration absorber (DVA) called the Voigt DVA is a classical model and has long been investigated. In the paper, we will consider an optimization problem of another model of DVA that is called three-element type DVA for damped primary structures. Unlike the standard absorber configuration, the three-element DVA contains two spring elements in which one is connected to a dashpot in series and the other is placed in parallel. There have been some studies on the design of the three-element DVA for undamped primary structures. Those studies have shown that the three-element DVA produces better performance than the Voigt DVA does. When damping is present at the primary system, to the best knowledge of the authors, there has been no study on the three-element dynamic vibration absorber. This work presents a simple approach to determine the approximate analytical solutions for the H∞ optimization of the three-element DVA attached to the damped primary structure. The main idea of the study is based on the criteria of the equivalent linearization method in order to replace approximately the original damped structure by an equivalent undamped one. Then the approximate analytical solution of the DVA's parameters is given by using known results for the undamped structure obtained. The comparisons have been done to verify the effectiveness of the obtained results.

4. Vibration reduction of a three DOF non-linear spring pendulum

NASA Astrophysics Data System (ADS)

Eissa, M.; Sayed, M.

2008-03-01

The dynamic response of mechanical and civil structures subject to high-amplitude vibration is often dangerous and undesirable. Vibrations and dynamic chaos should be controlled or eliminated in both structures and machines. This can be employed via passive and active control methods. In this paper, a tuned absorber, in the transversally direction, is connected to an externally excited spring-pendulum system (three degree of freedom), subjected to harmonic excitation. The tuned absorber is usually designed to control one frequency at primary resonance where system damage is probable. Active control is also applied to the considered system via negative displacement feedback to change the linear frequency of the system and to shift it away from the resonating one. Also active control is applied to improve the behavior of the spring-pendulum at the primary resonance via negative velocity feedback or its square or cubic value. The multiple time scale perturbation technique is applied throughout. The stability of the system is investigated applying both frequency response function and phase-plane method. The effects of the absorber and different parameters on system behavior are studied numerically. Optimum working conditions of the system are extracted applying both passive and active control methods, to be used in the design of such systems.

5. Finite element analysis of the non-linear vibrations of moderately thick unsymmetrically laminated composite plates

NASA Astrophysics Data System (ADS)

Singh, Gajbir; Venkateswara Rao, G.; Iyengar, N. G. R.

1995-03-01

The influence of finite amplitudes on the free flexural vibration response of moderately thick laminated plates is investigated. For this purpose, a simple higher order theory involving only four unknowns and satisfying the stress free conditions at the top and bottom surface of the composite plate is proposed. The proposed theory eliminates the use of shear correction factors which are otherwise required in Mindlin's plate theory. A rectangular four-node[formula]continuous finite element is developed based on this theory. The non-linear finite element equations are reduced to two non-linear ordinary differential equations governing the response of positive and negative deflection cycles. Direct numerical integration method is then employed to obtain the periods or non-linear frequencies. The finite element developed and the direct numerical integration method employed are validated for the case of isotropic rectangular plates. It is found that unsymmetrically laminated rectangular plates with hinged-hinged edge conditions oscillate with different amplitudes in the positive and negative deflection cycles. Furthermore, such plates would oscillate with a frequency less than the fundamental frequency for finite small amplitudes of oscillation. It is shown that this behaviour is strongly influenced by the boundary conditions. Results are presented for many configurations of composite plates.

6. Modeling vibrational resonance in linear hydrocarbon chain with a mixed quantum-classical method.

PubMed

Gelman, David; Schwartz, Steven D

2009-04-07

The quantum dynamics of a vibrational excitation in a linear hydrocarbon model system is studied with a new mixed quantum-classical method. The method is suited to treat many-body systems consisting of a low dimensional quantum primary part coupled to a classical bath. The dynamics of the primary part is governed by the quantum corrected propagator, with the corrections defined in terms of matrix elements of zeroth order propagators. The corrections are taken to the classical limit by introducing the frozen Gaussian approximation for the bath degrees of freedom. The ability of the method to describe dynamics of multidimensional systems has been tested. The results obtained by the method have been compared to previous quantum simulations performed with the quasiadiabatic path integral method.

7. Equivalent Linearization Analysis of Geometrically Nonlinear Random Vibrations Using Commercial Finite Element Codes

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Muravyov, Alexander A.

2002-01-01

Two new equivalent linearization implementations for geometrically nonlinear random vibrations are presented. Both implementations are based upon a novel approach for evaluating the nonlinear stiffness within commercial finite element codes and are suitable for use with any finite element code having geometrically nonlinear static analysis capabilities. The formulation includes a traditional force-error minimization approach and a relatively new version of a potential energy-error minimization approach, which has been generalized for multiple degree-of-freedom systems. Results for a simply supported plate under random acoustic excitation are presented and comparisons of the displacement root-mean-square values and power spectral densities are made with results from a nonlinear time domain numerical simulation.

8. Modeling vibrational resonance in linear hydrocarbon chain with a mixed quantum-classical method

NASA Astrophysics Data System (ADS)

Gelman, David; Schwartz, Steven D.

2009-04-01

The quantum dynamics of a vibrational excitation in a linear hydrocarbon model system is studied with a new mixed quantum-classical method. The method is suited to treat many-body systems consisting of a low dimensional quantum primary part coupled to a classical bath. The dynamics of the primary part is governed by the quantum corrected propagator, with the corrections defined in terms of matrix elements of zeroth order propagators. The corrections are taken to the classical limit by introducing the frozen Gaussian approximation for the bath degrees of freedom. The ability of the method to describe dynamics of multidimensional systems has been tested. The results obtained by the method have been compared to previous quantum simulations performed with the quasiadiabatic path integral method.

9. A biresonant plasma source based on a gapped linear microwave vibrator

SciTech Connect

Gritsinin, S. I.; Davydov, A. M.; Kossyi, I. A.; Arapov, K. A.; Chapkevich, A. A.

2011-03-15

The operating principle of a novel microwave plasma source-a linear microwave vibrator with a gap-is discussed. The source is placed on a microwave-transparent window of a chamber filled with a plasma-forming gas (argon or methane). The device operation is based on the combination of two resonances-geometric and plasma ones. The results of experimental tests of the source are presented. For a microwave frequency of 2.45 GHz, microwave power of {<=}1 kW, and plasma-forming gas pressure in the range 5 Multiplication-Sign 10{sup -2}-10{sup -1} Torr, the source is capable of filling the reactor volume with a plasma having an electron density of about 10{sup 12} cm{sup -3} and electron temperature of a few electronvolts.

10. Orientation determination of protein helical secondary structures using linear and nonlinear vibrational spectroscopy.

PubMed

Nguyen, Khoi Tan; Le Clair, Stéphanie V; Ye, Shuji; Chen, Zhan

2009-09-10

In this paper, we systematically presented the orientation determination of protein helical secondary structures using vibrational spectroscopic methods, particularly, nonlinear sum frequency generation (SFG) vibrational spectroscopy, along with linear vibrational spectroscopic techniques such as infrared spectroscopy and Raman scattering. SFG amide I signals can be collected using different polarization combinations of the input laser beams and output signal beam to measure the second-order nonlinear optical susceptibility components of the helical amide I modes, which are related to their molecular hyperpolarizability elements through the orientation distribution of these helices. The molecular hyperpolarizability elements of amide I modes of a helix can be calculated based on the infrared transition dipole moment and Raman polarizability tensor of the helix; these quantities are determined by using the bond additivity model to sum over the individual infrared transition dipole moments and Raman polarizability tensors, respectively, of the peptide units (or the amino acid residues). The computed overall infrared transition dipole moment and Raman polarizability tensor of a helix can be validated by experimental data using polarized infrared and polarized Raman spectroscopy on samples with well-aligned helical structures. From the deduced SFG hyperpolarizability elements and measured SFG second-order nonlinear susceptibility components, orientation information regarding helical structures can be determined. Even though such orientation information can also be measured using polarized infrared or polarized Raman amide I signals, SFG has a much lower detection limit, which can be used to study the orientation of a helix when its surface coverage is much lower than a monolayer. In addition, the combination of different vibrational spectroscopic techniques, for example, SFG and attenuated total reflectance Fourier transform infrared spectroscopy, provides more

11. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states.

PubMed

Godtliebsen, Ian H; Christiansen, Ove

2015-10-07

It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.

12. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states

NASA Astrophysics Data System (ADS)

Godtliebsen, Ian H.; Christiansen, Ove

2015-10-01

It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.

13. Improved assumed-stress hybrid shell element with drilling degrees of freedom for linear stress, buckling, and free vibration analyses

NASA Technical Reports Server (NTRS)

Rengarajan, Govind; Aminpour, Mohammad A.; Knight, Norman F., Jr.

1992-01-01

An improved four-node quadrilateral assumed-stress hybrid shell element with drilling degrees of freedom is presented. The formulation is based on Hellinger-Reissner variational principle and the shape functions are formulated directly for the four-node element. The element has 12 membrane degrees of freedom and 12 bending degrees of freedom. It has nine independent stress parameters to describe the membrane stress resultant field and 13 independent stress parameters to describe the moment and transverse shear stress resultant field. The formulation encompasses linear stress, linear buckling, and linear free vibration problems. The element is validated with standard tests cases and is shown to be robust. Numerical results are presented for linear stress, buckling, and free vibration analyses.

14. Electromagnetic Wave Excitation by a Longitudinal Slot in a Broad Wall of Rectangular Waveguide in the Presence of Passive Impedance Vibrators Outside the Waveguide

NASA Astrophysics Data System (ADS)

Berdnik, S. L.; Katrich, V. A.; Nesterenko, M. V.; Penkin, Yu. M.

2016-09-01

Purpose: A problem of electromagnetic wave diffraction by a longitudinal slot cut in a waveguide wide wall is solved. The slot is cut in a wide wall of a rectangular waveguide and radiates in a half-space above a perfectly conducting plane where two vertical impedance monopoles with arbitrary lengths placed with their bases placed on the plane. The paper is aimed at studying the electrodynamic characteristics of vibratorwaveguide-slot structures which allow to form the emission fields as that in a Clavin element with two identical passive ideally conducting monopoles of a fixed length located on a set distance from a slot center on both sides of a narrow halfwave slot. Design/methodology/approach: The problem is solved by a generalized method of induced electromotive and magnetomotive forces in approximation of electric currents in the vibrators and equivalent magnetic current in the slot by the functions obtained by the asymptotic averaging method. Findings: The influence of geometric parameters of the structure on the directional characteristics of Clavin type element is analyzed on the assumption of simultaneous account for relative level of sidelobes in the E-plane and beamwidth differences at –3 dB level in the main planes. It is shown that the directional characteristics and energy characteristics of the radiators: radiation and reflection coefficients, antenna directivity and gain can be varied within wide limits by changing the electrical length and/or distributed surface impedances of the vibrators, providing at that a low level of radiation within a slot plane. Conclusions: The results obtained can be useful when designing both small-size and multi-element antenna arrays with Clavin elements.

15. Modeling linear vibration of cell nucleus in low intensity ultrasound field.

PubMed

Or, Meir; Kimmel, Eitan

2009-06-01

Therapeutic ultrasound of low to medium intensity is known to induce alterations in structure and functioning of cells and tissues, both in vivo and in vitro. Such effects, including excitation or inhibition of action potentials, enhanced angiogenesis rate, increased membrane permeability and changes in molecular expression, cannot be attributed in many cases to rising temperatures or the presence of gas bubbles. This study attempts to find a possible alternative explanation for the cases where neither thermal effects nor cavitation mechanisms count. We focus our attention on the complex and dense structure of cell cytoplasm, looking for periodic separating forces and relative motion between intracellular elements, such as the nucleus, and the structure in which they are embedded. It is hypothesized that relative oscillatory displacements between intracellular elements of different densities might appear in cells in response to low intensity therapeutic ultrasound (LITUS). Those displacements might induce alterations in cell structure and functioning. A linear model is constructed and solved for a spherical object, representing a typical organelle such as the nucleus, within a homogenous viscoelastic medium that vibrates uniformly. The structure in which the object is embedded is described by four different rheologic models, including viscous fluid, elastic solid, and Voigt and Maxwell viscoelastic constructs. It is found that cyclic intracellular displacements comparable with and even larger than the mean thermal fluctuations may be obtained due to LITUS irradiation in conditions where the relative motion of organelles is dominated by elastic response, or where the effective viscosity of the cytoplasm is low. Resonance frequency at which intracellular vibration of maximal amplitude is obtained is found to lie within the low LITUS frequency range, i.e., tens to hundreds of kHz. Local intracellular strain on the order of 0.5% is found for 1 microm organelle in 10

16. Vibrational energy relaxation in liquid HCl and DCl via the linearized semiclassical method: electrostriction versus quantum delocalization.

PubMed

Vázquez, Francisco X; Talapatra, Surma; Geva, Eitan

2011-09-08

The rate constant for vibrational energy relaxation of the H-Cl stretch in liquid HCl (T = 188K, ρ = 19.671 nm(-3)) is calculated within the framework of the Landau-Teller formula. The force-force correlation function is calculated via the recently introduced force-derivative-free linearized semiclassical method [Vázquez et al. J. Phys. Chem. A2010, 114, 5682]. The calculated vibrational energy relaxation rate constant is found to be in excellent agreement with experiment, and the electrostatic force is found to contribute significantly to the high frequency component of the force-force correlation function. In contrast, the corresponding classical vibrational energy relaxation rate constant is found to be 2 orders of magnitude slower than the experimental value, and the classical force-force correlation function is found to be dominated by the Lennard-Jones forces. These observations suggest that quantum delocalization, enhanced by the light mass of hydrogen, amplifies the contribution of repulsive Coulombic forces to the force-force correlation function, thereby making electrostriction an unlikely mechanism for vibrational energy relaxation in the case of hydrogen stretches. This interpretation is reinforced by the results of a similar calculation in the case of the D-Cl stretch in liquid DCl under the same conditions. In this case, the quantum enhancement of the vibrational energy relaxation rate constant is observed to be greatly diminished in comparison to HCl, thereby giving rise to a reversal of the isotope effect in comparison to that predicted by the corresponding classical treatment (i.e., whereas the classical vibrational energy relaxation rate of DCl is faster than that of HCl, the opposite trend is predicted by the linearized semiclassical treatment). It is also shown that the vibrational energy relaxation of DCl is completely dominated by the Lennard-Jones forces within either classical and semiclassical treatments, thereby suggesting that

17. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

NASA Astrophysics Data System (ADS)

Manzhelii, E. V.

2016-11-01

The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0 , are obtained. It is shown that at rvibrations frequencies, is negative. As a result, while the quasi-continuous spectrum band shifts to lower frequencies, the linear part of the temperature dependence of the heat capacity shifts to lower temperatures. The distance within only one pair of atoms is modified. It is the defect that can entail discrete states split off from the quasi-continuous spectrum band. The discrete levels with frequencies below the quasi-continuous spectrum band shift the linear part of the temperature dependence of the heat capacity to lower temperatures. The conditions for appearing of discrete frequency levels are obtained, and their characteristics are found.

18. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

NASA Astrophysics Data System (ADS)

Manzhelii, E. V.

2017-04-01

The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0, are obtained. It is shown that at rvibrations frequencies, is negative. As a result, while the quasi-continuous spectrum band shifts to lower frequencies, the linear part of the temperature dependence of the heat capacity shifts to lower temperatures. The distance within only one pair of atoms is modified. It is the defect that can entail discrete states split off from the quasi-continuous spectrum band. The discrete levels with frequencies below the quasi-continuous spectrum band shift the linear part of the temperature dependence of the heat capacity to lower temperatures. The conditions for appearing of discrete frequency levels are obtained, and their characteristics are found.

19. Elastic buckling, stability, and vibration of linear and geometrically nonlinear behavior of structures

SciTech Connect

Sabir, A.B.

1995-09-01

The present paper explores the physical and fundamental way of obtaining buckling loads of structures as well as their natural frequencies. The resulting mathematical formulations are shown, in both cases, to lead to the determination of the eigenvalues and vectors for similar transcendental equations. The analysis of a axially loaded straight member is first considered to show that when the axial load is tensile the corresponding natural frequencies are larger than when their is no applied axial load. Conversely when the axial load is compressive a decrease in the natural frequencies will take place and in the limit the natural frequencies become zero when the applied axial load is equal to the buckling load of the member. The paper will also present the results for a finite element analysis for the large deflection geometrically non-linear behavior of arches. The resulting complex relationships between load and deflection are discussed in terms of instability and snap through phenomena. The large-amplitude vibration of arches are then considered and the relationship between frequency and amplitude is discussed by inferring to the previously obtained statical loading cases.

20. Single-Phase Drive Ultrasonic Linear Motor Using a Linked Twin Square Plate Vibrator

NASA Astrophysics Data System (ADS)

Yokoyama, Keiji; Tamura, Hideki; Masuda, Kentaro; Takano, Takehiro

2013-07-01

A novel linear motion ultrasonic motor, which uses a single resonance mode driven by a single phase and has the same motor characteristics for operation in reverse directions, is developed. An in-plane breathing mode in the square plate is strongly driven by the transverse effect of a piezoelectric ceramic. A stator resonator consists of twin square plates linked by V-shaped beams. Only one side of the square plate can be excited by the resonance of the breathing mode, when the other passive side plate is electrically opened so that the effective elasticities and the resonant frequencies between both plates are different; as a result, the friction edge of the resonator vibrates in a slant locus to move a load slider. The reverse operation is easily obtained by switching the driving side of the square plates. We designed the stator resonator by FEM analysis and fabricated a prototype for our experiment. The prototype motor showed good characteristics, for example, a moving slider velocity of 100 mm/s, a thrust force of 3.5 N, and an efficiency of 30% when the preload was 10 N, the input effective voltage was 5 V, and the input power was 1.2 W.

1. Optimum vibration absorber (tuned mass damper) design for linear damped systems subjected to random loads

NASA Astrophysics Data System (ADS)

Tigli, Omer F.

2012-06-01

Optimum design of dynamic vibration absorbers (DVAs) installed on linear damped systems that are subjected to random loads is studied and closed-form design formulas are provided. Three cases are considered in the optimization process: Minimizing the variance of the displacement, velocity and acceleration of the main mass. Exact optimum design parameters for the velocity case, which to the best knowledge of the author do not exist in the literature, are derived for the first time. Exact solutions are found to be directly applicable for practical use with no simplification needed. For displacement and acceleration cases, a solution for the optimum absorber frequency ratio is obtained as a function of optimum absorber damping ratio. Numerical simulations indicate that optimum absorber damping ratio is not significantly related to the structural damping, especially when the displacement variance is minimized. Therefore, optimum damping ratio derived for undamped systems is proposed for damped systems for the displacement case. When acceleration variance is minimized, however, the optimum damping ratio derived for undamped systems is found not as accurate for damped systems. Therefore, a more accurate approximate expression is derived. Numerical comparisons with published approximate expressions at the same level of complexity indicated that proposed design formula yield more accurate estimates. Another important finding of the paper is that for specific applications where all of the response parameters are desired to be minimized simultaneously, DVAs designed per velocity criteria provide the best overall performance with the least complexity in the design equations.

2. Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an asymmetric Lanczos algorithm

NASA Astrophysics Data System (ADS)

Thomsen, Bo; Hansen, Mikkel Bo; Seidler, Peter; Christiansen, Ove

2012-03-01

We report the theory and implementation of vibrational coupled cluster (VCC) damped response functions. From the imaginary part of the damped VCC response function the absorption as function of frequency can be obtained, requiring formally the solution of the now complex VCC response equations. The absorption spectrum can in this formulation be seen as a matrix function of the characteristic VCC Jacobian response matrix. The asymmetric matrix version of the Lanczos method is used to generate a tridiagonal representation of the VCC response Jacobian. Solving the complex response equations in the relevant Lanczos space provides a method for calculating the VCC damped response functions and thereby subsequently the absorption spectra. The convergence behaviour of the algorithm is discussed theoretically and tested for different levels of completeness of the VCC expansion. Comparison is made with results from the recently reported [P. Seidler, M. B. Hansen, W. Györffy, D. Toffoli, and O. Christiansen, J. Chem. Phys. 132, 164105 (2010)] vibrational configuration interaction damped response function calculated using a symmetric Lanczos algorithm. Calculations of IR spectra of oxazole, cyclopropene, and uracil illustrate the usefulness of the new VCC based method.

3. Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an asymmetric Lanczos algorithm.

PubMed

Thomsen, Bo; Hansen, Mikkel Bo; Seidler, Peter; Christiansen, Ove

2012-03-28

We report the theory and implementation of vibrational coupled cluster (VCC) damped response functions. From the imaginary part of the damped VCC response function the absorption as function of frequency can be obtained, requiring formally the solution of the now complex VCC response equations. The absorption spectrum can in this formulation be seen as a matrix function of the characteristic VCC Jacobian response matrix. The asymmetric matrix version of the Lanczos method is used to generate a tridiagonal representation of the VCC response Jacobian. Solving the complex response equations in the relevant Lanczos space provides a method for calculating the VCC damped response functions and thereby subsequently the absorption spectra. The convergence behaviour of the algorithm is discussed theoretically and tested for different levels of completeness of the VCC expansion. Comparison is made with results from the recently reported [P. Seidler, M. B. Hansen, W. Györffy, D. Toffoli, and O. Christiansen, J. Chem. Phys. 132, 164105 (2010)] vibrational configuration interaction damped response function calculated using a symmetric Lanczos algorithm. Calculations of IR spectra of oxazole, cyclopropene, and uracil illustrate the usefulness of the new VCC based method.

4. Linear and Non-Linear Thermal Lens Signal of the Fifth C-H Vibrational Overtone of Naphthalene in Liquid Solutions of Hexane

NASA Astrophysics Data System (ADS)

Manzanares, Carlos; Diaz, Marlon; Barton, Ann; Nyaupane, Parashu R.

2017-06-01

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of naphthalene in n-hexane. The pump and probe thermal lens technique is found to be very sensitive for detecting samples of low composition (ppm) in transparent solvents. In this experiment two different probe lasers: one at 488 nm and another 568 nm were used. The C-H fifth vibrational overtone spectrum of benzene is detected at room temperature for different concentrations. A plot of normalized integrated intensity as a function of concentration of naphthalene in solution reveals a non-linear behavior at low concentrations when using the 488 nm probe and a linear behavior over the entire range of concentrations when using the 568 nm probe. The non-linearity cannot be explained assuming solvent enhancement at low concentrations. A two color absorption model that includes the simultaneous absorption of the pump and probe lasers could explain the enhanced magnitude and the non-linear behavior of the thermal lens signal. Other possible mechanisms will also be discussed.

5. Highly Accurate Quartic Force Fields, Vibrational Frequencies, and Spectroscopic Constants for Cyclic and Linear C3H3(+)

NASA Technical Reports Server (NTRS)

Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.

2011-01-01

High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.

6. Vibrational resonance and implementation of dynamic logic gate in a piecewise-linear Murali-Lakshmanan-Chua circuit

NASA Astrophysics Data System (ADS)

Venkatesh, P. R.; Venkatesan, A.

2016-10-01

We report the occurrence of vibrational resonance in piecewise-linear non-autonomous system. Especially, we show that an optimal amplitude of the high frequency second harmonic driving enhances the response of a piece-wise linear non-autonomous Murali-Lakshmanan-Chua (MLC) system to a low frequency first harmonic signal. This phenomenon is illustrated with the analytical solutions of circuit equations characterising the system and finally compared with the numerical method. Further, it has been enunciated explicitly, the implementation of the fundamental NOR/NAND gate via vibrational resonance, both by numerical and analytical solutions. In addition, these logical behaviours (AND/NAND/OR/NOR) can be decided by the amplitude of the input square waves without altering the system parameters.

7. Improved design of linear electromagnetic transducers for large-scale vibration energy harvesting

NASA Astrophysics Data System (ADS)

Tang, Xiudong; Zuo, Lei; Lin, Teng; Zhang, Peisheng

2011-03-01

This paper presents the design and optimization of tubular Linear Electromagnetic Transducers (LETs) with applications to large-scale vibration energy harvesting, such as from vehicle suspensions, tall buildings or long bridges. Four types of LETs are considered and compared, namely, single-layer configuration using axial magnets, double-layer configuration using axial magnets, single-layer configuration using both axial and radial magnets, double-layer configuration using both axial and radial magnets. In order to optimize the LETs, the parameters investigated in this paper include the thickness of the magnets in axial direction and the thickness of the coils in the radial direction. Finite element method is used to analyze the axisymmetric two-dimensional magnetic fields. Both magnetic flux densities Br [T] in the radial direction and power density [W/m3] are calculated. It is found that the parameter optimization can increase the power density of LETs to 2.7 times compared with the initial design [Zuo et al, Smart Materials and Structures, v19 n4, 2010], and the double-layer configuration with both radial and axial magnets can improve the power density to 4.7 times, approaching to the energy dissipation rate of traditional oil dampers. As a case study, we investigate its application to energy-harvesting shock absorbers. For a reasonable retrofit size, the LETs with double-layer configuration and both axial and radial NdFeB magnets can provide a damping coefficient of 1138 N.s/m while harvesting 35.5 W power on the external electric load at 0.25 m/s suspension velocity. If the LET is shorten circuit, it can dissipate energy at the rate of 142.0 W, providing of a damping coefficient of 2276 N.s/m. Practical consideration of number of coil phases is also discussed.

8. Non-linear vibrational response of Ge and SiC membranes

NASA Astrophysics Data System (ADS)

Zhou, L. Q.; Colston, G.; Pearce, M. J.; Prince, R. G.; Myronov, M.; Leadley, D. R.; Trushkevych, O.; Edwards, R. S.

2017-07-01

Characterisation of membranes produced for use as micro-electro-mechanical systems using vibrational techniques can give a measure of their behaviour and suitability for operation in different environments. Two membranes are studied here: germanium (Ge) and cubic silicon carbide (3C-SiC) on a silicon (Si) substrate. When driven at higher displacements, the membranes exhibit self-protecting behaviour. The resonant vibration amplitude is limited to a maximum value of around 10 nm, through dissipation of energy via higher harmonic vibrations. This is observed for both materials, despite their different Young's moduli and defect densities.

9. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

PubMed Central

Salvado, José; Espírito-Santo, António; Calado, Maria

2012-01-01

This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. PMID:22969364

10. An intelligent sensor array distributed system for vibration analysis and acoustic noise characterization of a linear switched reluctance actuator.

PubMed

Salvado, José; Espírito-Santo, António; Calado, Maria

2012-01-01

This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

11. Efficient algorithms for solving the non-linear vibrational coupled-cluster equations using full and decomposed tensors.

PubMed

Madsen, Niels K; Godtliebsen, Ian H; Christiansen, Ove

2017-04-07

Vibrational coupled-cluster (VCC) theory provides an accurate method for calculating vibrational spectra and properties of small to medium-sized molecules. Obtaining these properties requires the solution of the non-linear VCC equations which can in some cases be hard to converge depending on the molecule, the basis set, and the vibrational state in question. We present and compare a range of different algorithms for solving the VCC equations ranging from a full Newton-Raphson method to approximate quasi-Newton models using an array of different convergence-acceleration schemes. The convergence properties and computational cost of the algorithms are compared for the optimization of VCC states. This includes both simple ground-state problems and difficult excited states with strong non-linearities. Furthermore, the effects of using tensor-decomposed solution vectors and residuals are investigated and discussed. The results show that for standard ground-state calculations, the conjugate residual with optimal trial vectors algorithm has the shortest time-to-solution although the full Newton-Raphson method converges in fewer macro-iterations. Using decomposed tensors does not affect the observed convergence rates in our test calculations as long as the tensors are decomposed to sufficient accuracy.

12. Efficient algorithms for solving the non-linear vibrational coupled-cluster equations using full and decomposed tensors

NASA Astrophysics Data System (ADS)

Madsen, Niels K.; Godtliebsen, Ian H.; Christiansen, Ove

2017-04-01

Vibrational coupled-cluster (VCC) theory provides an accurate method for calculating vibrational spectra and properties of small to medium-sized molecules. Obtaining these properties requires the solution of the non-linear VCC equations which can in some cases be hard to converge depending on the molecule, the basis set, and the vibrational state in question. We present and compare a range of different algorithms for solving the VCC equations ranging from a full Newton-Raphson method to approximate quasi-Newton models using an array of different convergence-acceleration schemes. The convergence properties and computational cost of the algorithms are compared for the optimization of VCC states. This includes both simple ground-state problems and difficult excited states with strong non-linearities. Furthermore, the effects of using tensor-decomposed solution vectors and residuals are investigated and discussed. The results show that for standard ground-state calculations, the conjugate residual with optimal trial vectors algorithm has the shortest time-to-solution although the full Newton-Raphson method converges in fewer macro-iterations. Using decomposed tensors does not affect the observed convergence rates in our test calculations as long as the tensors are decomposed to sufficient accuracy.

13. Ab initio investigation of electronic and vibrational contributions to linear and nonlinear dielectric properties of ice

NASA Astrophysics Data System (ADS)

Casassa, S.; Baima, J.; Mahmoud, A.; Kirtman, B.

2014-06-01

Electronic and vibrational contributions to the static and dynamic (hyper)polarizability tensors of ice XI and model structures of ordinary hexagonal ice have been theoretically investigated. Calculations were carried out by the finite field nuclear relaxation method for periodic systems (FF-NR) recently implemented in the CRYSTAL code, using the coupled-perturbed Kohn-Sham approach (CPKS) for evaluating the required electronic properties. The effect of structure on the static electronic polarizabilities (dielectric constants) and second-hyperpolarizabilities is minimal. On the other hand, the vibrational contributions to the polarizabilities were found to be significant. A reliable evaluation of these (ionic) contributions allows one to discriminate amongst ice phases characterized by different degrees of proton-order, primarily through differences caused by librational motions. Transverse static and dynamic vibrational (hyper)polarizabilities were found by extrapolating calculations for slabs of increasing size, in order to eliminate substantial surface contributions.

14. Ab initio investigation of electronic and vibrational contributions to linear and nonlinear dielectric properties of ice

SciTech Connect

Casassa, S.; Baima, J.; Mahmoud, A.; Kirtman, B.

2014-06-14

Electronic and vibrational contributions to the static and dynamic (hyper)polarizability tensors of ice XI and model structures of ordinary hexagonal ice have been theoretically investigated. Calculations were carried out by the finite field nuclear relaxation method for periodic systems (FF-NR) recently implemented in the CRYSTAL code, using the coupled-perturbed Kohn-Sham approach (CPKS) for evaluating the required electronic properties. The effect of structure on the static electronic polarizabilities (dielectric constants) and second-hyperpolarizabilities is minimal. On the other hand, the vibrational contributions to the polarizabilities were found to be significant. A reliable evaluation of these (ionic) contributions allows one to discriminate amongst ice phases characterized by different degrees of proton-order, primarily through differences caused by librational motions. Transverse static and dynamic vibrational (hyper)polarizabilities were found by extrapolating calculations for slabs of increasing size, in order to eliminate substantial surface contributions.

15. Theoretical analysis of linear and nonlinear piezoelectric vibrational energy harvesters for human walking

NASA Astrophysics Data System (ADS)

Eltanany, Ali M.; Yoshimura, Takeshi; Fujimura, Norifumi; Elsayed, Nour Z.; Ebied, Mohamed R.; Ali, Mohamed G. S.

2015-10-01

The role of nonlinear stiffness in the performance of the piezoelectric vibrational energy harvester (pVEH) was discussed. Harmonic balance and numerical methods are applied to characterize the electromechanical response of pVEHs based on Duffing oscillator at a deterministic harmonic excitation of fundamental vibration characteristics (2 Hz, 1 m·s-2), which corresponds to human walking. Then, the response to a vibration with two harmonic waves, which has a fixed fundamental frequency (2 Hz, 1 m·s-2) and a frequency varied from 1.5 to 2.5 Hz. The numerical results obtained in this study indicate that nonlinearity does not have a significant advantage on the energy harvesting from human walking.

16. Controller design for delay-independent stability of linear time-invariant vibration systems with multiple delays

NASA Astrophysics Data System (ADS)

Mahmoodi Nia, Payam; Sipahi, Rifat

2013-07-01

One of the critical parameters that can deteriorate the effectiveness of active vibration control (AVC) is the delay in sensors. Especially, in remote sensing where delays are large, and in high-speed applications with even small delays, instability can be inevitable. This paper presents algebraic approaches to design controllers in order to achieve stability regardless of the amount of delays for AVC applications modeled by linear time-invariant systems with "multiple" constant delays. The approaches are based on a nonconservative framework, and can identify the regions in the controller gain space where delay-independent stability (DIS) is achievable. With these controllers, we demonstrate via simulations that vibration suppression, within certain excitation frequency bands, can be improved or be as effective as those in AVC applications without delays.

17. Natural vibration response based damage detection for an operating wind turbine via Random Coefficient Linear Parameter Varying AR modelling

NASA Astrophysics Data System (ADS)

Avendaño-Valencia, L. D.; Fassois, S. D.

2015-07-01

The problem of damage detection in an operating wind turbine under normal operating conditions is addressed. This is characterized by difficulties associated with the lack of measurable excitation(s), the vibration response non-stationary nature, and its dependence on various types of uncertainties. To overcome these difficulties a stochastic approach based on Random Coefficient (RC) Linear Parameter Varying (LPV) AutoRegressive (AR) models is postulated. These models may effectively represent the non-stationary random vibration response under healthy conditions and subsequently used for damage detection through hypothesis testing. The performance of the method for damage and fault detection in an operating wind turbine is subsequently assessed via Monte Carlo simulations using the FAST simulation package.

18. Vibrational frequencies of the HCCN molecule. A near degeneracy between bent cyanocarbene and linear allene-related geometries

SciTech Connect

Kim, K.S.; Schaefer, H.F. III; Radom, L.; Pople, J.A.; Binkley, J.S.

1983-06-29

The geometrical structure and vibrational frequencies of the ground triplet electronic state of HCCN have been examined at a wide range of levels of ab initio electronic structure theory. The potential energy surface of HCC bending is very flat for HCCN owing to a competition between linear allene OHC=C=N and bent carbene HCC=N valence structures. Evidence is presented that both the restricted Hartree-Fock (RHF) and unrestricted Hartree-Fock (UHF) methods treat this potential surface in a somewhat uneven manner. When the effects of electron correlation are included, however, RHF- and UHF-based methods converge to a similar set of structural and energetic predictions. The most reliable levels of theory suggest the HCCN is a quasi-linear molecule, with THETA/sub e/(HCC) approx. = 138/sup 0/ and a barrier to linearity of only about 2 kcal/mol.

19. Vibrational frequencies of the HCCN molecule. A near degeneracy between bent cyanocarbene and linear allene-related geometries

SciTech Connect

Kim, K.S.; Schaefer, H.F. III; Radom, L.; Pople, J.A.; Binkley, J.S.

1983-01-01

The geometrical structure and vibrational frequencies of the ground triplet electronic state of HCCN have been examined at a wide range of levels of ab initio electronic structure theory. The potential energy surface of HCC bending is very flat for HCCN owing to a competition between linear allene HC=C=N and bent carbene HCC=N valence structures. Evidence is presented that both the restricted Hartree-Fock (RHF) and unrestricted Hartree-Fock (UHF) methods treat this potential surface in a somewhat uneven manner. When the effects of electron correlation are included, however, RHF-and UHF-based methods converge to a similar set of structural and energetic predictions. The most reliable levels of theory suggest that HCCN is a quasi-linear molecule, with theta/sub e/(HCC) approx. = 138/sup 0/ and a barrier to linearity of only about 2 kcal/mol. 37 references, 2 figures, 6 tables.

20. Vibration transmissibility and damping behaviour for auxetic and conventional foams under linear and nonlinear regimes

NASA Astrophysics Data System (ADS)

Bianchi, Matteo; Scarpa, Fabrizio

2013-08-01

This work describes the vibration transmissibility behaviour in conventional and auxetic (negative Poisson’s ratio) foams under low and high amplitude vibrations. Auxetic foam pads were manufactured from conventional open cell PU-PE based blocks using an alternative manufacturing process to the one currently used in the mainstream literature. The dynamic behaviour of both conventional and auxetic porous materials was assessed within the frequency bandwidth 5-500 Hz using a base excitation technique with a calibrated seismic mass. The foam pads were subjected to white noise broadband excitation at low dynamic strain, followed by a sine sweep around the resonance of the foam-mass system. The experimental data have been used to perform an inverse identification of the nonlinear dependence of the foam permeability versus the amplitude and frequency of excitation using a single-degree-of-freedom poroelastic vibration model. The auxetic foam shows higher dynamic stiffness and enhanced viscous dissipation characteristics, in particular when subjected to nonlinear vibration loading.

1. Broadband and three-dimensional vibration energy harvesting by a non-linear magnetoelectric generator

NASA Astrophysics Data System (ADS)

Lin, Zhiming; Chen, Jun; Li, Xiaoshi; Li, Jun; Liu, Jun; Awais, Qasim; Yang, Jin

2016-12-01

Vibration, widely existing in an ambient environment with a variety of forms and wide-range of scales, recently becomes an attractive target for energy harvesting. However, its time-varying directions and frequencies render a lack of effective energy technology to scavenge it. Here, we report a rationally designed nonlinear magnetoelectric generator for broadband and multi-directional vibration energy harvesting. By using a stabilized three-dimensional (3D) magnetic interaction and spring force, the device working bandwidth was largely broadened, which was demonstrated both experimentally and theoretically. The multidirectional vibration energy harvesting was enabled by three identical suspended springs with equal intersection angles, which are all connected to a cylindrical magnet. Numerical simulations and experimental results show that the nonlinear harvester can sustain large-amplitude oscillations over a wide frequency range, and it can generate power efficiently in an arbitrary direction. Moreover, the experimental data suggest that the proposed nonlinear energy harvester has the potential to scavenge vibrational energy over a broad range of ambient frequencies in 3D space.

2. Direct determination of the non-linear connection between tension and transverse amplitude for a vibrating string

NASA Astrophysics Data System (ADS)

Pedersen, Henrik B.; Langeland Knudsen, Jeppe

2017-07-01

A vibrating stretched string is one of the most fundamental physical systems where non-linear effects play a central role. We describe results obtained with a new, dedicated experimental setup that allows unverified details of the dynamics of this classical problem to be addressed experimentally. The setup uniquely allows simultaneous registration of the transverse motion of the string as well as the longitudinal tension in the string during oscillation over extended times. The explicit non-linear connection between the string tension and the transverse oscillation amplitude is thus directly experimentally determined, allowing us to distinguish between previously reported diverging descriptions. For forced vibrations, frequency response curves for the transverse amplitudes are obtained, and found to be in good agreement with predictions from a simplified model, while the model only qualitatively reproduces the observed phases of transverse oscillation relative to the phase of the driving force. A frequency analysis of the observed string tension reveals a richer dynamics than anticipated from a simple model, and from the observed frequency response curves alone. For free oscillations, the setup is used to demonstrate the variation of the normal mode frequency with the transverse amplitudes. The reported setup is well-suited as a demonstration experiment on non-linear oscillatory phenomena, as well as a student project in either introductory or advanced mechanics teaching.

3. The influence of biodynamic factors on the mechanical impedance of the hand and arm.

PubMed

Burström, L

1997-01-01

The purpose of this study was to investigate the mechanical impedance of the human hand-arm system during exposure to random vibration under various experimental conditions and to evaluate statistically whether these experimental conditions have any influence on magnitude and phase of the mechanical impedance. A further aim was to compare the obtained results with other investigations where sinusoidal excitation has been used. The mechanical impedance was estimated in ten healthy subjects during exposure to random vibration, with a constant velocity spectrum within the frequency range 4-2000 Hz, by use of a specially designed laboratory handle. In the study, the influence of various conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), feed force (20-60 N), frequency-weighted acceleration level (3, 6, 9, 12 m/s2) and hand and arm posture (five flexions, two abductions) were studied. The outcome showed that the vibration direction and the frequency of the vibration stimuli have a strong significant influence on the impedance of the hand. An increased vibration level resulted in a significantly lower impedance for frequencies over 100 Hz. Increase grip and feed forced led on the other hand to an increased impedance for all frequencies. With regard to hand and arm posture, the results show that the flexion and abduction had a significant contribution for frequencies below 30 Hz. Furthermore, the influence of some of the studied variables had a non-linear effect on the impedance but also differed between different exposure directions. It was concluded, moreover, that the vibration response characteristics of the hand and arm differ, depending whether the signal is a discrete frequency signal or a signal consisting of several frequencies.

4. The effective ratio of acoustic impedance in predicting stress and velocity of wave propagation in viscoelastic material (standard linear solid model)

NASA Astrophysics Data System (ADS)

Musa, Abu Bakar

2013-09-01

The study is about impact of a short elastic rod(or slug) on a stationary semi-infinite viscoelastic rod. The viscoelastic materials are modeled as standard linear solid which involve three material parameters and the motion is treated as one-dimensional. We first establish the governing equations pertaining to the impact of viscoelastic materials subject to certain boundary conditions for the case when an elastic slug moving at a speed V impacts a semi-infinite stationary viscoelastic rod. The objective is to predict stresses and velocities at the interface following wave transmissions and reflections in the slug after the impact using viscoelastic discontinuity. If the stress at the interface becomes tensile and the velocity changes its sign, then the slug and the rod part company. If the stress at the interface is compressive after the impact, the slug and the rod remain in contact. In the process of predicting the stress and velocity of wave propagation using viscoelastic discontinuity, the Z-effective which is the effective ratio of acoustic impedance plays important role. It can be shown that effective ratio of acoustic impedance can help us to determine whether the slug and the rod move together or part company after the impact. After modeling the impact and solve the governing system of partial differential equations in the Laplace transform domain. We invert the Laplace transformed solution numerically to obtain the stresses and velocities at the interface for several viscosity time constants and ratios of acoustic impedances. In inverting the Laplace transformed equations, we used the complex inversion formula because there is a branch cut and infinitely many poles within the Bromwich contour. In the discontinuity analysis, we look at the moving discontinuities in stress and velocity using the impulse-momentum relation and kinematical condition of compatibility. Finally, we discussed the relationship of the stresses and velocities using numeric and the

5. Effect of flexibility on liquid-vapor coexistence and surface properties of tangent linear vibrating square well chains in two and three dimensions.

PubMed

Chapela, Gustavo A; Díaz-Herrera, Enrique; Armas-Pérez, Julio C; Quintana-H, Jacqueline

2013-06-14

The effect of flexibility on liquid-vapor and interfacial properties of tangent linear vibrating square well chains is studied. Surface tension, orthobaric densities, vapor pressures, and interfacial thicknesses are reported and analyzed using corresponding states principles. Discontinuous molecular dynamics simulations in two and three dimensions are performed on rigid tangent linear vibrating square well chains of different lengths. In the case of two dimensions, simulation results of completely flexible tangent linear vibrating square well chains are also reported. Properties are calculated for chains of 2-12 monomers. Rigidity is controlled by trapping the first and last monomer in the chain in a vibrating well at half of the distance of the whole chain. Critical property values are reported as obtained from orthobaric densities, surface tensions, and vapor pressures. For the fully flexible chains, the critical temperatures increase with chain length but the effect saturates. In contrast, the critical temperatures increase for the rigid chains until no more critical point is found.

6. Local vibrational mode of an impurity in a monatomic linear chain under open and periodic boundary conditions

NASA Astrophysics Data System (ADS)

Luo, Qiang

2016-11-01

In this paper, we revisit the lattice vibration of a one-dimensional monatomic linear chain under open and periodic boundary conditions, and give the exact conditions for the emergence of the local vibration mode when one of the atoms is replaced by an impurity. Our motivation is twofold. Firstly, in deriving the dispersion relation of the atoms, the periodic boundary condition is overwhelmingly utilized while the open boundary condition is seldom used. Therefore we manage to obtain the dispersion relation under both boundary conditions simultaneously by the Molinari formula. Secondly, in the presence of an impurity, the local vibration mode can emerge as long as the mass of the impurity m\\prime is smaller than the mass of the perfect atom m to a certain degree, which can be measured by the mass ratio δ =\\tfrac{m-m\\prime }{m}. At the periodic boundary condition, the critical mass ratio is 0 or \\tfrac{1}{N}, depending on whether the length N of the chain is even or odd. At the open boundary condition, the critical mass ratio is \\tfrac{N}{2N-1} if the impurity locates at the end of the chain, while it is \\tfrac{N}{(2{N}{{l}}+1)(2{N}{{r}}+1)} with N l and N r the number of atoms at the left- and right-hand sides of the impurity if the impurity locates at the middle.

7. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

NASA Astrophysics Data System (ADS)

Premkumar, S.; Jawahar, A.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin

2015-06-01

The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

8. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

SciTech Connect

Premkumar, S.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin; Jawahar, A.

2015-06-24

The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

9. Random vibration of nonlinear beams by the new stochastic linearization technique

NASA Technical Reports Server (NTRS)

Fang, J.

1994-01-01

In this paper, the beam under general time dependent stationary random excitation is investigated, when exact solution is unavailable. Numerical simulations are carried out to compare its results with those yielded by the conventional linearization techniques. It is found that the modified version of the stochastic linearization technique yields considerably more accurate results for the mean square displacement of the beam than the conventional equivalent linearization technique, especially in the case of large nonlinearity.

10. Vibration analysis of harmonically excited non-linear system using the method of multiple scales

NASA Astrophysics Data System (ADS)

Moon, Byung-Young; Kang, Beom-Soo

2003-05-01

An analytical method is presented for evaluation of the steady state periodic behavior of non-linear systems. This method is based on the substructure synthesis formulation and a multiple scales procedure, which is applied to the analysis of non-linear responses. A complex non-linear system is divided into substructures, of which equations are approximately transformed to modal co-ordinates including non-linear term under the reasonable procedure. Then, the equations are synthesized into the overall system and the solution of the non-linear system can be obtained. Based on the method of multiple scales, the proposed procedure reduces the size of large-degree-of-freedom problem in solving the non-linear equations. Feasibility and advantages of the proposed method are illustrated by the application of the analytic procedure to the non-linear rotating machine system as a large mechanical structure system. Results obtained are reported to be an efficient approach with respect to non-linear response prediction when compared with other conventional methods.

11. Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

NASA Technical Reports Server (NTRS)

Holliday, Ezekiel S. (Inventor)

2014-01-01

Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

12. Effect of Muscle Tension on Non-Linearities in the Apparent Masses of Seated Subjects Exposed to Vertical Whole-Body Vibration

NASA Astrophysics Data System (ADS)

MATSUMOTO, Y.; GRIFFIN, M. J.

2002-05-01

In subjects exposed to whole-body vibration, the cause of non-linear dynamic characteristics with changes in vibration magnitude is not understood. The effect of muscle tension on the non-linearity in apparent mass has been investigated in this study. Eight seated male subjects were exposed to random and sinusoidal vertical vibration at five magnitudes (0·35-1·4 m/s2 r.m.s.). The random vibration was presented for 60 s over the frequency range 2·0-20 Hz; the sinusoidal vibration was presented for 10 s at five frequencies (3·15, 4·0, 5·0, 6·3 and 8·0 Hz). Three sitting conditions were adopted such that, in two conditions, muscle tension in the buttocks and the abdomen was controlled. It was assumed that, in these two conditions, involuntary changes in muscle tension would be minimized. The force and acceleration at the seat surface were used to obtain apparent masses of subjects. With both sinusoidal and random vibration, there was statistical support for the hypothesis that non-linear characteristics were less clear when muscle tension in the buttocks and the abdomen was controlled. With increases in the magnitude of random vibration from 0·35 to 1·4 m/s2 r.m.s., the apparent mass resonance frequency decreased from 5·25 to 4·25 Hz with normal muscle tension, from 5·0 to 4·38 Hz with the buttocks muscles tensed, and from 5·13 to 4·5 Hz with the abdominal muscles tensed. Involuntary changes in muscle tension during whole-body vibration may be partly responsible for non-linear biodynamic responses.

13. First-order optimal linear and nonlinear detuning of centrifugal pendulum vibration absorbers

NASA Astrophysics Data System (ADS)

Mayet, J.; Ulbrich, H.

2015-01-01

Centrifugal pendulum vibration absorbers are used to attenuate steady-state torsional vibrations in rotating and reciprocating machines. In most practical implementations, a set of multiple absorbers is symmetrically arranged on a rotor. Typically, each absorber mass is bifilar suspended, which allows the absorber mass to be moved along a prescribed path. Previous studies have considered how to determine absorber paths in order to obtain absorbers with amplitude-independent frequency known as tautochronic absorbers. It is known that a tautochronic absorber is highly desirable if only one absorber is installed on the rotor. However, in most applications multiple interacting absorbers are installed and as a result symmetry-induced nonlinear instabilities or localization caused by relative imperfections among the absorbers may occur. An effective strategy to avoid such situations is to perturb the tautochronic tuning which has been confirmed in practice and by previous theoretical investigations. This paper presents an approach for detuning a recently developed general tautochronic absorber design. The general design makes it possible to consider a wide class of tautochronic absorbers, e.g. absorbers without bifilar suspensions. The intent of this paper is to extend the existing tautochronic design guideline to non-tautochronic designs. As a result, different absorber designs can be addressed by one uniform theoretical approach, and existing absorber designs are included as special cases. Former studies on detuning of bifilar tautochronic absorbers use a one-parameter family of curves on which the absorber mass rides. Here, however, the detuning is not restricted to a one-parameter family of curves, which makes it possible to either optimize system performance or to avoid asynchronous absorber responses. In the case of synchronously responding equal absorbers, a necessary condition for optimal performance is derived analytically. Further, it is shown that asynchronous

14. Vortex-induced vibrations of a square cylinder under linear shear flow

NASA Astrophysics Data System (ADS)

Sun, Wenjuan; Zhou, Dai; Tu, Jiahuang; Han, Zhaolong

2017-04-01

This paper investigates the numerical vortex-induced vibration (VIV) of a square cylinder which is connected to a 2-DOF mass-spring system and is immersed in the planar shear flow by employing a characteristic-based split (CBS) finite element method (FEM). The reduced mass of the square cylinder is M r = 2, while the reduced velocity, U r, is changed from 3 to 12 with an increment of ΔU r = 1. The effects of some key parameters on the cylinder dynamic responses, vibrating frequencies, the flow patterns as well as the energy transferred between the fluid and cylinder are revealed. In this study, the key parameters are selected as follows: shear ratio (k = 0, 0.05 and 0.1) and Reynolds numbers (Re = 80 and 160). Numerical results demonstrate that the X-Y trajectories of the cylinder mainly appear as a symmetrical figure ‘8’ in uniform flow (k = 0) and an unsymmetrical figure ‘8’ and ‘O’ in shear flows (k = 0.05 and 0.1). The maximum oscillation amplitudes of the square cylinder in both the inline and transverse directions have distinct characteristics compared to that of a circular cylinder. Two kinds of flow patterns, ‘2S’ and ‘P + S’, are mainly observed under the shear flow. Also, the mean values of the energy of the cylinder system increase with the reduced velocity, while the root mean square (rms) of the energy reaches its peak value at reduced velocity U r = 5.

15. Random vibration of linear and nonlinear structural systems with singular matrices: A frequency domain approach

NASA Astrophysics Data System (ADS)

Kougioumtzoglou, I. A.; Fragkoulis, V. C.; Pantelous, A. A.; Pirrotta, A.

2017-09-01

A frequency domain methodology is developed for stochastic response determination of multi-degree-of-freedom (MDOF) linear and nonlinear structural systems with singular matrices. This system modeling can arise when a greater than the minimum number of coordinates/DOFs is utilized, and can be advantageous, for instance, in cases of complex multibody systems where the explicit formulation of the equations of motion can be a nontrivial task. In such cases, the introduction of additional/redundant DOFs can facilitate the formulation of the equations of motion in a less labor intensive manner. Specifically, relying on the generalized matrix inverse theory, a Moore-Penrose (M-P) based frequency response function (FRF) is determined for a linear structural system with singular matrices. Next, relying on the M-P FRF a spectral input-output (excitation-response) relationship is derived in the frequency domain for determining the linear system response power spectrum. Further, the above methodology is extended via statistical linearization to account for nonlinear systems. This leads to an iterative determination of the system response mean vector and covariance matrix. Furthermore, to account for singular matrices, the generalization of a widely utilized formula that facilitates the application of statistical linearization is proved as well. The formula relates to the expectation of the derivatives of the system nonlinear function and is based on a Gaussian response assumption. Several linear and nonlinear MDOF structural systems with singular matrices are considered as numerical examples for demonstrating the validity and applicability of the developed frequency domain methodology.

16. Adsorption of linear alkanes on Cu(111): Temperature and chain-length dependence of the softened vibrational mode

NASA Astrophysics Data System (ADS)

Fosser, Kari A.; Kang, Joo H.; Nuzzo, Ralph G.; Wöll, Christof

2007-05-01

The vibrational spectra of linear alkanes, with lengths ranging from n-propane to n-octane, were examined on a copper surface by reflection-absorption infrared spectroscopy. The appearance and frequency of the "soft mode," a feature routinely seen in studies of saturated hydrocarbons adsorbed on metals, were examined and compared between the different adsorbates. The frequency of the mode was found to be dependent on both the number of methylene units of each alkane as well as specific aspects of the order of the monolayer phase. Studies of monolayer coverages at different temperatures provide insights into the nature of the two-dimensional (2D) melting transitions of these adlayer structures, ones that can be inferred from observed shifts in the soft vibrational modes appearing in the C-H stretching region of the infrared spectrum. These studies support recently reported hypotheses as to the origins of such soft modes: the metal-hydrogen interactions that mediate them and the dynamics that underlay their pronounced temperature dependencies. The present data strongly support a model for the 2D to one-dimensional order-order phase transition arising via a continuous rather than discrete first-order process.

17. Linear and third- and fifth-order nonlinear spectroscopies of a charge transfer system coupled to an underdamped vibration

SciTech Connect

Dijkstra, Arend G. E-mail: tanimura@kuchem.kyoto-u.ac.jp; Tanimura, Yoshitaka E-mail: tanimura@kuchem.kyoto-u.ac.jp

2015-06-07

We study hole, electron, and exciton transports in a charge transfer system in the presence of underdamped vibrational motion. We analyze the signature of these processes in the linear and third-, and fifth-order nonlinear electronic spectra. Calculations are performed with a numerically exact hierarchical equations of motion method for an underdamped Brownian oscillator spectral density. We find that combining electron, hole, and exciton transfers can lead to non-trivial spectra with more structure than with excitonic coupling alone. Traces taken during the waiting time of a two-dimensional (2D) spectrum are dominated by vibrational motion and do not reflect the electron, hole, and exciton dynamics directly. We find that the fifth-order nonlinear response is particularly sensitive to the charge transfer process. While third-order 2D spectroscopy detects the correlation between two coherences, fifth-order 2D spectroscopy (2D population spectroscopy) is here designed to detect correlations between the excited states during two different time periods.

18. A fully consistent linearized model for vibration analysis of rotating beams in the framework of geometrically exact theory

NASA Astrophysics Data System (ADS)

Invernizzi, Davide; Dozio, Lorenzo

2016-05-01

The equations of motions governing the free vibrations of prismatic slender beams rotating in a plane at constant angular velocity are derived according to a geometrically exact approach. Compared to other modeling methods, additional stiffening terms induced by pre-stress are found in the dynamic equations after fully consistent linearization about the deformed equilibrium configuration. These terms include axial, bending and torsional stiffening effects which arise when second-order generalized strains are retained. It is shown that their contribution becomes relevant at moderate to high angular speeds, where high means that the equilibrium state is subject to strains close to the limit where a physically linear constitutive law still applies. In particular, the importance of the axial stiffening is specifically investigated. The natural frequencies as a function of the angular velocity and other system parameters are computed and compared with benchmark cases available in the literature. Finally, the error on the modal characteristics of the rotating beam is evaluated when the linearization is carried out about the undeformed configuration.

19. Linear precision inertial actuator built for low-impact in-situ installation on structures with vibration problems

NASA Astrophysics Data System (ADS)

Updike, Clark A.; Greeley, Scott W.; King, James A.

1998-10-01

In the process of designing a control actuator for a vibration cancellation system demonstration on a large, precision optical testbed, it was discovered that the support struts on which the control actuators attach could not be disassembled. This led to the development of a Linear Precision ACTuator (LPACT) with a novel two piece design which could be clamped around the strut in-situ. The design requirements, LPACT characteristics, and LPACT test results are fully described and contrasted with other earlier LPACT designs. Cancellation system performance results are presented for a 3 tone disturbance case. Excellent results, on the order of 40 dB of attenuation per tone (down to the noise floor on two disturbances), are achieved using an Adaptive Neural Controller (ANC).

20. Accurate Modelling of a Flexible-Link Planar Mechanism by Means of a Linearized Model in the State-Space Form for Design of a Vibration Controller

NASA Astrophysics Data System (ADS)

GASPARETTO, A.

2001-02-01

Vibration control of flexible link mechanisms with more than two flexible links is still an open question, mainly because defining a model that is adequate for the designing of a controller is a rather difficult task. In this work, an accurate dynamic non-linear model of a flexible-link planar mechanism is presented. In order to bring the system into a form that is suitable for the design of a vibration controller, the model is then linearized about an operating point, so as to achieve a linear model of the system in the standard state-space form of system theory. The linear model obtained, which is valid for whatever planar mechanism with any number of flexible link, is then applied to a four-bar planar linkage. Extensive simulation is carried out, aimed at comparing the system dynamic evolution, both in the open- and in the closed-loop case, using the non-linear model and the linearized one. The results prove that the error made by using the linearized system instead of the non-linear one is small. Therefore, it can be concluded that the model proposed in this work can constitute an effective basis for designing and testing many types of vibration controllers for flexible planar mechanisms.

1. Thin Rotary and Linear Ultrasonic Motors Using a Double-Mode Piezoelectric Vibrator of the First Longitudinal and Second Bending Modes

NASA Astrophysics Data System (ADS)

Tomikawa, Yoshiro; Takano, Takehiro; Umeda, Hidenobu

1992-09-01

This paper deals with thin rotary and linear ultrasonic motors using a double-mode piezoelectric ceramic vibrator; a rectangular plate vibrator of the first longitudinal and second bending modes is utilized. A specific merit of the motors is that their thickness can meet the restriction of 10 mm, which is one of the practical requirements of a light load gearless motor. The rotary motor is intended for application in card forwarding, and the linear motor, in magnetic-head traveling and so on. Construction and characteristics of the motors are described herein.

2. Crystal growth, crystal structure, vibrational spectroscopy, linear and nonlinear optical properties of guanidinium phosphates

NASA Astrophysics Data System (ADS)

Němec, Ivan; Matulková, Irena; Held, Peter; Kroupa, Jan; Němec, Petr; Li, Dongxu; Bohatý, Ladislav; Becker, Petra

2017-07-01

Of the three guanidinium phosphates GuH2PO4 (space group P21/c), Gu2HPO4·H2O (space group P 4 bar 21 c) and Gu3PO4· 3/2 H2O (space group Cc) crystal structures and a vibrational spectroscopy study are presented. Large single crystals of GuH2PO4 and Gu2HPO4·H2O are grown. Refractive indices and their dispersion in the wavelength range 365 nm - 1083 nm are determined and used for the analysis of phase matching conditions for collinear SHG in the case of the non-centrosymmetric crystals of Gu2HPO4·H2O. The crystals are not phase-matchable within their transmission range. Both independent components of the SHG tensor of Gu2HPO4·H2O, determined by the Maker fringe method, are given, with d14 = 0.23 pm/V and d36 = 0.22 pm/V. In addition, the thermal stability and the anisotropy of thermal expansion of GuH2PO4 and Gu2HPO4·H2O is reported.

3. Alignment and vibration issues in TeV linear collider design

SciTech Connect

Fischer, G.E.

1989-07-01

The next generation of linear colliders will require alignment accuracies and stabilities of component placement at least one, perhaps two, orders of magnitude better than can be achieved by the conventional methods and procedures in practice today. The magnitudes of these component-placement tolerances for current designs of various linear collider subsystems are tabulated. In the micron range, long-term ground motion is sufficiently rapid that on-line reference and mechanical correction systems are called for. Some recent experiences with the upgraded SLAC laser alignment systems and examples of some conceivable solutions for the future are described. The so called ''girder'' problem is discussed in the light of ambient and vibratory disturbances. The importance of the quality of the underlying geology is stressed. The necessity and limitations of public-beam-derived placement information are mentioned. 40 refs., 4 figs., 1 tab.

4. Alighment and Vibration Issues in TeV Linear Collider Design

SciTech Connect

Fischer, G.E.; /SLAC

2005-08-12

The next generation of linear colliders will require alignment accuracies and stabilities of component placement at least one, perhaps two, orders of magnitude better than can be achieved by the conventional methods and procedures in practice today. The magnitudes of these component-placement tolerances for current designs of various linear collider subsystems are tabulated. In the micron range, long-term ground motion is sufficiently rapid that on-line reference and mechanical correction systems are called for. Some recent experiences with the upgraded SLAC laser alignment systems and examples of some conceivable solutions for the future are described. The so called ''girder'' problem is discussed in the light of ambient and vibratory disturbances. The importance of the quality of the underlying geology is stressed. The necessity and limitations of particle-beam-derived placement information are mentioned.

5. VIBRA: An interactive computer program for steady-state vibration response analysis of linear damped structures

NASA Technical Reports Server (NTRS)

Bowman, L. M.

1984-01-01

An interactive steady state frequency response computer program with graphics is documented. Single or multiple forces may be applied to the structure using a modal superposition approach to calculate response. The method can be reapplied to linear, proportionally damped structures in which the damping may be viscous or structural. The theoretical approach and program organization are described. Example problems, user instructions, and a sample interactive session are given to demonstate the program's capability in solving a variety of problems.

6. Nucleic acid vibrational circular dichroism, absorption, and linear dichroism spectra. I. A DeVoe theory approach.

PubMed Central

Self, B D; Moore, D S

1997-01-01

Infrared (IR) vibrational circular dichroism (VCD), absorption, and linear dichroism (LD) spectra of four homopolyribonucleotides, poly(rA), poly(rG), poly(rC), and poly(rU), have been calculated, in the 1750-1550 cm-1 spectral region, using the DeVoe polarizability theory. A newly derived algorithm, which approximates the Hilbert transform of imaginaries to reals, was used in the calculations to obtain real parts of oscillator polarizabilities associated with each normal mode. The calculated spectra of the polynucleotides were compared with previously measured solution spectra. The good agreement between calculated and measured polynucleotide spectra indicates, for the first time, that the DeVoe theory is a useful means of calculating the VCD and IR absorption spectra of polynucleotides. For the first time, calculated DeVoe theory VCD and IR absorption spectra of oriented polynucleotides are presented. The calculated VCD spectra for the oriented polynucleotides are used to predict the spectra for such measurements made in the future. The calculated IR spectra for the oriented polynucleotides are useful in interpreting the linear dichroism of the polynucleotides. PMID:9199798

7. Self-assembly of kagome lattices, entangled webs and linear fibers with vibrating patchy particles in two dimensions.

PubMed

Chapela, Gustavo A; Guzmán, Orlando; Martínez-González, José Adrián; Díaz-Leyva, Pedro; Quintana-H, Jacqueline

2014-12-07

A vibrating version of patchy particles in two dimensions is introduced to study self-assembly of kagome lattices, disordered networks of looping structures, and linear arrays. Discontinuous molecular dynamics simulations in the canonical ensemble are used to characterize the molecular architectures and thermodynamic conditions that result in each of those morphologies, as well as the time evolution of lattice formation. Several versions of the new model are tested and analysed in terms of their ability to produce kagome lattices. Due to molecular flexibility, particles with just attractive sites adopt a polarized-like configuration and assemble into linear arrays. Particles with additional repulsive sites are able to form kagome lattices, but at low temperature connect as entangled webs. Abundance of hexagonal motifs, required for the kagome lattice, is promoted even for very small repulsive sites but hindered when the attractive range is large. Differences in behavior between the new flexible model and previous ones based on rigid bodies offer opportunities to test and develop theories about the relative stability, kinetics of formation and mechanical response of the observed morphologies.

8. Electron Impedances

SciTech Connect

P Cameron

2011-12-31

It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

9. Displacement detection with a vibrating rf superconducting interference device: beating the standard linear limit.

PubMed

Buks, Eyal; Zaitsev, Stav; Segev, Eran; Abdo, Baleegh; Blencowe, M P

2007-08-01

We study a configuration for displacement detection consisting of a nanomechanical resonator coupled to both a radio frequency superconducting interference device and to a superconducting stripline resonator. We employ an adiabatic approximation and rotating wave approximation and calculate the displacement sensitivity. We study the performance of such a displacement detector when the stripline resonator is driven into a region of nonlinear oscillations. In this region the system exhibits noise squeezing in the output signal when homodyne detection is employed for readout. We show that displacement sensitivity of the device in this region may exceed the upper bound imposed upon the sensitivity when operating in the linear region. On the other hand, we find that the high displacement sensitivity is accompanied by a slowing down of the response of the system, resulting in a limited bandwidth.

10. A non-linear 3D printed electromagnetic vibration energy harvester

NASA Astrophysics Data System (ADS)

Constantinou, P.; Roy, S.

2015-12-01

This paper describes a novel electromagnetic energy harvester that exploits the low flexural modulus of ABS and comprises of a nonlinear mechanism to enhance the generated power and bandwidth. The device is printed using desktop additive manufacturing techniques (3D printing) that use thermoplastics. It has a ‘V’ spring topology and exhibits a softening spring non-linearity introduced through the magnetic arrangement, which introduces a monostable potential well. A model is presented and measurements correspond favourably. The produced prototype generates a peak power of approximately 2.5mW at a frame acceleration of 1g and has a power bandwidth of approximately 1.2→1.5Hz and 3.5→3.9Hz during up and down sweeps respectively. The device has a power density of 0.4mW/cm3 at a frame acceleration of 1g and a density of 0.04mW/cm3 from a generated power of 25μW at 0.1g.

11. Linear- and nonlinear-electromyographic analysis of supracutaneous vibration stimuli of the forearm using diverse frequencies and considering skin physiological properties.

PubMed

Ko, Chang-Yong; Chang, Yunhee; Kim, Sol-Bi; Kim, Shinki; Kim, Gyoosuk; Ryu, Jeicheong; Mun, Musung

2014-01-01

Numerous studies have reported the efficacy of vibration in sensory feedback or substitution devices for users of myoelectric hand prostheses. Although most myoelectric hand prostheses are presently manipulated by a surface electromyogram (sEMG), only a few studies have been conducted on the effect of vibration on an sEMG. This study aimed to determine whether vibration stimulation affects the linear and nonlinear properties of surface electromyography (sEMG) considering the skin properties. The vibration stimuli, with frequencies ranging from 37 to 258 Hz, were applied to the proximal part of the arms of the eight female and seven male subjects. The skinfold thickness, hardness, and vibration threshold at the stimuli loci were measured. The root mean square (rms) and fractal dimension (DF) of the sEMG were measured at a distance of 1 cm in the upward direction from the stimuli loci. Above 223 Hz there were no differences between the rms of the genders in between the vibration stimuli (p > 0.05). Moreover, no differences were observed between the DF of the genders for any frequency (p > 0.05). Above 149 Hz, there were correlations between the rms and the skin hardness in the females. Otherwise, no correlations were observed between the rms and DF and the skin properties in both genders for most of the frequencies (all p > 0.05). These results suggest that vibration stimuli affect the linear properties of the sEMG, but not the nonlinear properties.

12. Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm.

PubMed

Ming, Yang; Hanson, Ben; Levesley, Martin C; Walker, Peter G; Watterson, Kevin G

2006-12-01

In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).

13. Vibrational energy relaxation rates via the linearized semiclassical approximation: applications to neat diatomic liquids and atomic-diatomic liquid mixtures.

PubMed

Ka, Being J; Shi, Qiang; Geva, Eitan

2005-06-30

We report the results obtained from the application of our previously proposed linearized semiclassical method for computing vibrational energy relaxation (VER) rates (J. Phys. Chem. A 2003, 107, 9059, 9070) to neat liquid oxygen, neat liquid nitrogen, and liquid mixtures of oxygen and argon. Our calculations are based on a semiclassical approximation for the quantum-mechanical force-force correlation function, which puts it in terms of the Wigner transforms of the force and the product of the Boltzmann operator and the force. The calculation of the multidimensional Wigner integrals is made feasible by the introduction of a local harmonic approximation. A systematic analysis has been performed of the temperature and mole-fraction dependences of the VER rate constant, as well as the relative contributions of centrifugal and potential forces, and of different types of quantum effects. The results were found to be in very good quantitative agreement with experiment, and they suggest that this semiclassical approximation can capture the quantum enhancement, by many orders of magnitude, of the experimentally observed VER rate constants over the corresponding classical predictions.

14. Note: high frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method.

PubMed

Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

2013-08-01

In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot.

15. OH Vibrational Prompt Emission and Water Hot-Band Fluorescent Emission in C/2000 WM1 (LINEAR)

NASA Astrophysics Data System (ADS)

Bonev, B. P.; Mumma, M. J.; Dello Russo, N.; DiSanti, M. A.; Gibb, E. L.; Magee-Sauer, K.; Weaver, H. A.; Chin, G.

2004-11-01

Two methods for deriving cometary water production rates from ground-based high-resolution near-infrared spectra have now been developed. The water molecule can be directly sampled through "hot-band" fluorescent emission near 2.0, 2.9, 4.6, and 5.0 μ m [1]. Knowledge of the H2O rotational temperature and ortho-to-para ratio is needed to fully constrain its production rate via this method. More recently, vibrational prompt emission from OH has also been used as a proxy for water production. This method depends on the accuracy of the OH emission efficiencies derived from simultaneous observations of H2O and OH in comets C/1999 H1 (Lee) and C/2001 A2 (Linear) [2]. We report water production rates for a third comet (C/2000 WM1) based on independent analyses of H2O hot-band lines near 2.9 μ m and of OH prompt emission lines near 3046 cm-1, observed with NIRSPEC at the W. M. Keck Observatory. This comparison further reveals the capabilities and potential limitations of the two methods, while placing a special emphasis on the newer OH-based method. This work was supported by grants to M. J. Mumma (RTOP 344-32-30-07) and to H. A. Weaver and G. Chin (NAG5-12230) under NASA's Planetary Astronomy Program, and to N. Dello Russo (NAG5-10795) under NASA's Planetary Atmospheres Program. [1] Dello Russo et al. 2002, JGR, 107 (E11) 5095. [2] Bonev et al. 2004, ApJ, in press.

16. [A vertical vibration model of human body in supine position].

PubMed

Sun, Jing-gong; Niu, Fu; Qi, Jian-cheng; Li, Ruo-xin

2002-12-01

Objective. To establish the models of head, abdomen, and chest of supine human body respectively under vertical vibration. Method. The mechanical impedance of 12 healthy volunteers aged 24-56 was measured under vertical white noise stimulus in the frequency range of 2-35 Hz. To explain these findings, the model of head was proposed, the models of abdomen and chest were computed by way of an optimization procedure. Result. The models of abdomen and chest are three-degree-of-freedom and the head is rigid. Conclusion. The mechanical impedance of the supine human body is linear and sole. The established models of head, abdomen and chest of supine human body when subjected to vertical vibration are useful for calculating and evaluating the comfort of supine human body under whole-body vibration.

17. Impeded Dark Matter

SciTech Connect

Kopp, Joachim; Liu, Jia; Slatyer, Tracy; Wang, Xiao-Ping; Xue, Wei

2016-12-12

Here, we consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario \\Impeded Dark Matter". We also demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. Furthermore, for positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.

18. Impeded Dark Matter

DOE PAGES

Kopp, Joachim; Liu, Jia; Slatyer, Tracy; ...

2016-12-12

Here, we consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario \\Impeded Dark Matter". We also demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may evenmore » be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. Furthermore, for positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.« less

19. Impeded Dark Matter

NASA Astrophysics Data System (ADS)

Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei

2016-12-01

We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario "Impeded Dark Matter". We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.

20. Transducers in medical ultrasound: Part Two. Vibration modes, matching layers and grating lobes.

PubMed

de Jong, N; Souquet, J; Faber, G; Bom, N

1985-07-01

The performance of transducers used for medical diagnosis depends to a great extent on matching layer, backing impedance and geometry of the active surface. In this paper special attention is given to the element vibrational modes, the optimum matching, the grating lobe and change of the real acoustic impedance into an imaginary impedance as a function of the product of the width and wavelength. Grating lobes on the echo image and the effect of a mismatch of the matching layer are illustrated. Suggestions are made for the design of linear and phased array transducers considering the above-mentioned aspects.

1. LQR-Based least-squares output feedback control of rotor vibrations using the complex mode and balanced realization methods. [Linear-Quadratic-Regulator

SciTech Connect

Fan, G.W. ); Nelson, H.D. ); Crouch, P.E.; Mignolet, M.P. )

1993-04-01

The complex mode and balanced realization methods are used separately to obtain reduced-order models for general linear asymmetric rotor systems. The methods are outlined and then applied to a typical rotor system represented by a 52 degree-or-freedom finite element model. The accuracy of the two methods is compared for this model and the complex model method is found to be more accurate than the balanced realization method for the desired frequency bandwidth and for models of the same reduced order. However, with some limitations, it is also shown that the balanced realization method can be applied to the reduced-order complex mode model to obtain further order reduction without loss of model accuracy. A Linear-Quadratic-Regulator-based least-squares output feedback control procedure is developed for the vibration control of rotor systems. This output feedback procedure eliminates the requirement of an observer for the use of an LQ regulator, and provides the advantage that the rotor vibration can be effectively controlled by monitoring only one single location along the rotor shaft while maintaining an acceptable performance. The procedures presented are quite general and may be applied to a large class of vibration problems including rotordynamics.

2. Non-Linear Thermal Lens Signal of the (Δυ = 6) C-H Vibrational Overtone of Benzene in Liquid Solutions of Hexane

NASA Astrophysics Data System (ADS)

Nyaupane, Parashu R.; Manzanares, Carlos

2016-06-01

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of benzene. The pump and probe thermal lens technique has been found to be very sensitive for detecting samples of low concentration in transparent solvents. The C-H fifth vibrational (Δυ = 6) overtone spectrum of benzene is detected at room temperature for compositions per volume in the range (1 to 1× 10-4) using n-C_6H14 as the solvent. By detecting the absorption band in a 100 ppm solution, the peak absorption of the signal is approximately (2.2 ± 0.3)× 10-7 cm-1. The parameters that determine the magnitude of the thermal lens signal such as the pump laser power and the thermodynamic properties of the solvent and solute are discussed. A plot of normalized integrated intensity as a function of composition of benzene in solution reveals a non-linear behavior. The non-linearity cannot be explained assuming solvent enhancement at low concentrations. A two color absorption model that includes the simultaneous absorption of the pump and probe lasers could explain the enhanced magnitude and the non-linear behavior of the thermal lens signal for solutions of composition below 0.01.

3. Non-linear dual-axis biodynamic response to fore-and-aft whole-body vibration

NASA Astrophysics Data System (ADS)

Nawayseh, N.; Griffin, M. J.

2005-04-01

Seated subjects have participated in two experiments with fore-and-aft whole-body vibration to investigate dynamic responses at the seat and footrest in the direction of vibration and in other directions. In the first experiment, 12 males were exposed to fore-and-aft random vibration (0.25-20 Hz) at four magnitudes (0.125, 0.25, 0.625, and 1.25 m s -2 rms) while sitting on a seat with no backrest in four postures with varying foot heights to produce differing thigh contact with the seat (feet hanging, feet supported with maximum thigh contact, feet supported with average thigh contact, and feet supported with minimum thigh contact). In the second experiment, six subjects were exposed to three vibration magnitudes (0.125, 0.25, 0.625 m s -2 rms) in the average thigh contact posture, both with and without a rigid backrest. Forces were measured in the vertical, fore-and-aft, and lateral directions on the supporting seat surface (in the first experiment) and in the fore-and-aft and vertical directions at the footrest (in the second experiment). On the seat, there were three vibration modes in the fore-and-aft apparent mass on the seat at frequencies below 10 Hz in all postures (around 1 Hz, between 1 and 3 Hz, and between 3 and 5 Hz); large vertical forces were dependent on foot support while lateral forces were relatively small. At the feet, the fore-and-aft apparent mass showed a resonance between 3 and 5 Hz, which increased in frequency and magnitude when a backrest was used. The fore-and-aft vibration produced high vertical forces at the footrest. At frequencies below resonance, the backrest reduced vertical and fore-and-aft forces at the footrest. On the seat and the footrest, the forces showed a nonlinear characteristic that varied between postures. The presence of appreciable vertical forces indicate that during fore-and-aft excitation the body moved in two dimensions. It is concluded that forces in directions other than the direction of excitation should be

4. NEW REACTOR DESIGN AND ANALYSIS OF NON LINEAR VIBRATIONS OF DOUBLY CURVED SHALLOW SHELL UNDER A THERMAL GRADIENT

SciTech Connect

Chanda, S.

2004-10-06

The present study concerns with the effects of material orthotropy,curvature, shear ratio and circumferential modulus under the influence of a temperature distribution throughout the shell structure. Here analysis is restricted to the study of nonlinear vibration of a doubly curved shell structure considering the periodic response of a simple bending mode due to curtailment of pages. Solutions of the problems with suitable illustrations are also presented.

5. Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study.

PubMed

Suresh Kumar, V R; Binoy, J; Dawn Dharma Roy, S; Marchewka, M K; Jayakumar, V S

2015-01-01

Bis(melaminium) sulphate dihydrate (BMSD), an interesting melaminium derivative for nonlinear optical activity, has been subjected to vibrational spectral analysis using FT IR and FT Raman spectra. The analysis has been aided by the Potential Energy Distribution (PED) of vibrational spectral bands, derived using density functional theory (DFT) at B3LYP/6-31G(d) level. The geometry is found to correlate well with the XRD structure and the band profiles for certain vibrations in the finger print region have been theoretically explained using Evans hole. The detailed Natural Bond Orbital (NBO) analysis of the hydrogen bonding in BMSD has also been carried out to understand the correlation between the stabilization energy of hyperconjugation of the lone pair of donor with the σ(∗) orbital of hydrogen-acceptor bond and the strength of hydrogen bond. The theoretical calculation shows that BMSD has NLO efficiency, 2.66 times that of urea. The frontier molecular orbital analysis points to a charge transfer, which contributes to NLO activity, through N-H…O intermolecular hydrogen bonding between the melaminium ring and the sulphate. The molecular electrostatic potential (MEP) mapping has also been performed for the detailed analysis of the mutual interactions between melaminium ring and sulphate ion.

6. A differential quadrature analysis of vibration and buckling of an SS-C-SS-C rectangular plate loaded by linearly varying in-plane stresses

NASA Astrophysics Data System (ADS)

Wang, Xinwei; Gan, Lifei; Wang, Yongliang

2006-11-01

Thin rectangular plates having two opposite edges simply supported, with those edges subjected to linearly varying in-plane stresses, and the other two edges clamped, are encountered in engineering practice. Recently, Leissa and Kang used the classical power series method and obtained the first known exact vibration and some buckling solutions. The classical plate theory based on the Kirchhoff hypothesis is employed in the analysis. The relatively wild character of the convergence is observed, however, and 20 or 30 more terms of the series are needed to obtain reasonably accurate results. The differential quadrature (DQ) method has proved an accurate and computationally efficient numerical method. Thus, the DQ method is used to study the vibration and buckling of an SS-C-SS-C rectangular plate loaded by linearly varying in-plane stresses. Convergence study shows that DQ method with 15×15 or more non-uniform grid points can yield very accurate results for cases considered. Exactly the same, accurate results as of Leissa and Kang are easy to reproduce.

7. Every Nucleus, When Created, Will Exhibit No Motion or Linear, Rotational and/or Vibrational Motion Which May Later Become Modified By Outside Forces

NASA Astrophysics Data System (ADS)

Brekke, Stewart

2012-10-01

Due to the excess energy of creation a newly created nucleus may exhibit linear, rotational and/or vibrational motion. For example, in nuclear decay mPc^2 + 1/2mPvP^2 + 1/2IPφP^2 + 1/2kPxP^2 = mDc^2 + 1/2mDvD^2 + 1/2IDφD^2 + 1/2kDxD^2 + (particle mass-energy equivalence, linear, rotational and vibrational energies). In another nuclear reaction m1c^2 + 1/2I1φ1^2 + 1/2k1x1^2 + m2c^2 + 1/2m2v2^2 + 1/2I2φ2^2 + 1/2k2x2^2 = m3c^2 + 1/2m3v3^2 + 1/2k3x3^2 +...+mnc^2 + 1/2mnvn^2 + 1/2Inφn^2 + 1/2knxn^2.

8. A wavelet-based method for the forced vibration analysis of piecewise linear single- and multi-DOF systems with application to cracked beam dynamics

NASA Astrophysics Data System (ADS)

Joglekar, D. M.; Mitra, M.

2015-12-01

The present investigation outlines a method based on the wavelet transform to analyze the vibration response of discrete piecewise linear oscillators, representative of beams with breathing cracks. The displacement and force variables in the governing differential equation are approximated using Daubechies compactly supported wavelets. An iterative scheme is developed to arrive at the optimum transform coefficients, which are back-transformed to obtain the time-domain response. A time-integration scheme, solving a linear complementarity problem at every time step, is devised to validate the proposed wavelet-based method. Applicability of the proposed solution technique is demonstrated by considering several test cases involving a cracked cantilever beam modeled as a bilinear SDOF system subjected to a harmonic excitation. In particular, the presence of higher-order harmonics, originating from the piecewise linear behavior, is confirmed in all the test cases. Parametric study involving the variations in the crack depth, and crack location is performed to bring out their effect on the relative strengths of higher-order harmonics. Versatility of the method is demonstrated by considering the cases such as mixed-frequency excitation and an MDOF oscillator with multiple bilinear springs. In addition to purporting the wavelet-based method as a viable alternative to analyze the response of piecewise linear oscillators, the proposed method can be easily extended to solve inverse problems unlike the other direct time integration schemes.

9. Non-linear control logics for vibrations suppression: a comparison between model-based and non-model-based techniques

NASA Astrophysics Data System (ADS)

Ripamonti, Francesco; Orsini, Lorenzo; Resta, Ferruccio

2015-04-01

Non-linear behavior is present in many mechanical system operating conditions. In these cases, a common engineering practice is to linearize the equation of motion around a particular operating point, and to design a linear controller. The main disadvantage is that the stability properties and validity of the controller are local. In order to improve the controller performance, non-linear control techniques represent a very attractive solution for many smart structures. The aim of this paper is to compare non-linear model-based and non-model-based control techniques. In particular the model-based sliding-mode-control (SMC) technique is considered because of its easy implementation and the strong robustness of the controller even under heavy model uncertainties. Among the non-model-based control techniques, the fuzzy control (FC), allowing designing the controller according to if-then rules, has been considered. It defines the controller without a system reference model, offering many advantages such as an intrinsic robustness. These techniques have been tested on the pendulum nonlinear system.

10. Generalized Vibrational Perturbation Theory for Rotovibrational Energies of Linear, Symmetric and Asymmetric Tops: Theory, Approximations, and Automated Approaches to Deal with Medium-to-Large Molecular Systems.

PubMed

Piccardo, Matteo; Bloino, Julien; Barone, Vincenzo

2015-08-05

Models going beyond the rigid-rotor and the harmonic oscillator levels are mandatory for providing accurate theoretical predictions for several spectroscopic properties. Different strategies have been devised for this purpose. Among them, the treatment by perturbation theory of the molecular Hamiltonian after its expansion in power series of products of vibrational and rotational operators, also referred to as vibrational perturbation theory (VPT), is particularly appealing for its computational efficiency to treat medium-to-large systems. Moreover, generalized (GVPT) strategies combining the use of perturbative and variational formalisms can be adopted to further improve the accuracy of the results, with the first approach used for weakly coupled terms, and the second one to handle tightly coupled ones. In this context, the GVPT formulation for asymmetric, symmetric, and linear tops is revisited and fully generalized to both minima and first-order saddle points of the molecular potential energy surface. The computational strategies and approximations that can be adopted in dealing with GVPT computations are pointed out, with a particular attention devoted to the treatment of symmetry and degeneracies. A number of tests and applications are discussed, to show the possibilities of the developments, as regards both the variety of treatable systems and eligible methods.

11. Generalized Vibrational Perturbation Theory for Rotovibrational Energies of Linear, Symmetric and Asymmetric Tops: Theory, Approximations, and Automated Approaches to Deal with Medium-to-Large Molecular Systems

PubMed Central

Piccardo, Matteo; Bloino, Julien; Barone, Vincenzo

2015-01-01

Models going beyond the rigid-rotor and the harmonic oscillator levels are mandatory for providing accurate theoretical predictions for several spectroscopic properties. Different strategies have been devised for this purpose. Among them, the treatment by perturbation theory of the molecular Hamiltonian after its expansion in power series of products of vibrational and rotational operators, also referred to as vibrational perturbation theory (VPT), is particularly appealing for its computational efficiency to treat medium-to-large systems. Moreover, generalized (GVPT) strategies combining the use of perturbative and variational formalisms can be adopted to further improve the accuracy of the results, with the first approach used for weakly coupled terms, and the second one to handle tightly coupled ones. In this context, the GVPT formulation for asymmetric, symmetric, and linear tops is revisited and fully generalized to both minima and first-order saddle points of the molecular potential energy surface. The computational strategies and approximations that can be adopted in dealing with GVPT computations are pointed out, with a particular attention devoted to the treatment of symmetry and degeneracies. A number of tests and applications are discussed, to show the possibilities of the developments, as regards both the variety of treatable systems and eligible methods. © 2015 Wiley Periodicals, Inc. PMID:26345131

12. Inertial Linear Actuators

NASA Technical Reports Server (NTRS)

Laughlin, Darren

1995-01-01

Inertial linear actuators developed to suppress residual accelerations of nominally stationary or steadily moving platforms. Function like long-stroke version of voice coil in conventional loudspeaker, with superimposed linear variable-differential transformer. Basic concept also applicable to suppression of vibrations of terrestrial platforms. For example, laboratory table equipped with such actuators plus suitable vibration sensors and control circuits made to vibrate much less in presence of seismic, vehicular, and other environmental vibrational disturbances.

13. ADVANCES IN IMPEDANCE THEORY

SciTech Connect

Stupakov, G.; /SLAC

2009-06-05

We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

14. Optimal virtual mechanical impedances for the vibroacoustic active control of a thin plate.

PubMed

Michau, M; Berry, A; Micheau, Ph; Herzog, Ph

2015-01-01

In order to reduce the acoustic power radiated by a flexible panel, dual colocated actuator / sensor pairs are used to modify its vibration. The control strategy implemented for harmonic disturbances leads to locally impose a virtual mechanical impedance to the structure, using the linear relation between the actuator input and the control output of each pair. This virtual mechanical impedance is computed in order to minimize the radiated acoustic power. The proposed approach consists in two steps: (1) the matrix of optimal virtual mechanical impedance is calculated by measuring the primary disturbance and the transfer functions between actuators and structural/acoustic sensors and (2) the virtual mechanical impedance objective is achieved using a real-time integral controller. It is shown that such an optimal control approach leads to better sound power reduction than a classical active damping strategy where the virtual mechanical impedance is defined as real positive. Theoretical and experimental results are compared, also showing that the method proposed here is robust regarding variations of the primary disturbance.

15. Transient Vibration Prediction for Rotors on Ball Bearings Using Load-dependent Non-linear Bearing Stiffness

NASA Technical Reports Server (NTRS)

Fleming, David P.; Poplawski, J. V.

2002-01-01

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for non-linear speed and load dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis - Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running 5 degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller beatings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.

16. Biodynamic response of the human body in the sitting position when subjected to vertical vibration

NASA Astrophysics Data System (ADS)

Donati, P. M.; Bonthoux, C.

1983-10-01

Previous studies of the location of those areas in which the sensation of vibration is perceived under whole body vertical vibration have underlined the predominance of the relative movement between thorax and pelvis. Experiments were designed to explore systematically the transmissibility between the pelvis and thorax. These were supplemented by measurements of mechanical impedance of the body and absorbed power. To determine the body impedance, a procedure was developed to remove the effect of the load platform itself. Fifteen subjects were presented first with a swept sinusoidal vibration, and then with a broad band random vibration, to see how the wave form of the motion might affect the mechanical response of the body. The results obtained for the seat to thorax transmissibility suggest that within the range of vertical vibration investigated (1-10 Hz, 1·6 m/s 2 r.m.s.) the human body in the sitting position can be modelled by a linear system with one or two degrees of freedom according to the subject. Data from the impedance function, which is a more complete description of the response of the body as a mechanical system, lead to systems with one further degree of freedom.

17. The frequency dependent impedance of an HVdc converter

SciTech Connect

Wood, A.R.; Arrillaga, J.

1995-07-01

A linear and direct method of determining the frequency dependent impedance of a 12 pulse HVdc converter is presented. Terms are developed for both the dc and ac side impedances of the converter, including the effect of the firing angle control system, the commutation period, and the variability of the commutation period. The impedance predictions are verified by dynamic simulation.

18. Biodynamic response of the seated human body to single-axis and dual-axis vibration: effect of backrest and non-linearity.

PubMed

Qiu, Yi; Griffin, Michael J

2012-01-01

The biodynamic responses to the human body give an understanding of why human responses to vibration (changes in health, comfort, and performance) vary with the frequency and direction of vibration. Studies have shown that biodynamic responses also vary with the magnitude of vibration and that the backrests of seats influence the transmission of vibration to the seated human body. There has been little study of the nonlinearity in the biodynamic responses of the body to dual-axis excitation and no study of the influence of backrests during dual-axis excitation. This study investigated the apparent mass and cross-axis apparent mass of the human body exposed to random vibration (0.2 to 20 Hz) in all 15 possible combinations of four magnitudes (0, 0.25, 0.5 and 1.0 ms(-2) r.m.s.) of fore-and-aft vibration and the same four magnitudes of vertical vibration. Nonlinearity was evident, with the body softening with increasing magnitude of vibration when using a fixed magnitude of vibration in one direction and varying the magnitude of vibration in the other direction. The fore-and-aft apparent mass on the seat was greater without a backrest at the lower frequencies but greater with a backrest at the higher frequencies. The vertical apparent mass on the seat was decreased by the backrest at low frequencies. Cross-axis coupling was evident, with excitation in one axis producing a response in the other axis. It is concluded that the nonlinearity of the body evident during single-axis and multi-axis vibration, and the influence of backrests, should be taken into account when determining frequency weightings for predicting human responses to vibration and when optimising the dynamics of seating to minimise exposure to vibration.

19. Non-Gaussian statistics of amide I mode frequency fluctuation of N-methylacetamide in methanol solution: linear and nonlinear vibrational spectra.

PubMed

Kwac, Kijeong; Lee, Hochan; Cho, Minhaeng

2004-01-15

By carrying out molecular dynamics simulations of an N-methylacetamide (NMA) in methanol solution, the amide I mode frequency fluctuation and hydrogen bonding dynamics were theoretically investigated. Combining an extrapolation formula developed from systematic ab initio calculation studies of NMA-(CH3OH)n clusters with a classical molecular dynamics simulation method, we were able to quantitatively describe the solvatochromic vibrational frequency shift induced by the hydrogen-bonding interaction between NMA and solvent methanol. It was found that the fluctuating amide I mode frequency distribution is notably non-Gaussian and it can be decomposed into two Gaussian peaks that are associated with two distinctively different solvation structures. The ensemble-average-calculated linear response function associated with the IR absorption is found to be oscillating, which is in turn related to the doublet amide I band shape. Numerically calculated infrared absorption spectra are directly compared with experiment and the agreement was found to be excellent. By using the Onsager's regression hypothesis, the rate constants of the interconversion process between the two solvation structures were obtained. Then, the nonlinear response functions associated with two-dimensional infrared pump-probe spectroscopy were simulated. The physics behind the two-dimensional line shape and origin of the cross peaks in the time-resolved pump-probe spectra is explained and the result is compared with 2D spectra experimentally measured recently by Woutersen et al.

20. Determination of in vivo mechanical properties of long bones from their impedance response curves

NASA Technical Reports Server (NTRS)

Borders, S. G.

1981-01-01

A mathematical model consisting of a uniform, linear, visco-elastic, Euler-Bernoulli beam to represent the ulna or tibia of the vibrating forearm or leg system is developed. The skin and tissue compressed between the probe and bone is represented by a spring in series with the beam. The remaining skin and tissue surrounding the bone is represented by a visco-elastic foundation with mass. An extensive parametric study is carried out to determine the effect of each parameter of the mathematical model on its impedance response. A system identification algorithm is developed and programmed on a digital computer to determine the parametric values of the model which best simulate the data obtained from an impedance test.

1. Mechanical Impedance of the Human Body in the Horizontal Direction

NASA Astrophysics Data System (ADS)

Holmlund, P.; Lundström, R.

1998-08-01

The mechanical impedance of the seated human body in horizontal directions (fore-and-aft and lateral) was measured during different experimental conditions, such as vibration level (0·25-1·4 m/s2r.m.s.), frequency (1·13-80 Hz), body weight (54-93 kg), upper body posture (relaxed and erect) and gender. The outcome showed that impedance, normalized by the sitting weight, varies with direction, level, posture and gender. Generally the impedance spectra show one peak for the fore-and-aft (X) direction while two peaks are found in the lateral (Y) direction. Males showed a lower normalized impedance than females. Increasing fore-and-aft vibration decreases the frequency at which maximum impedance occurs but also reduces the overall magnitude. For the lateral direction a more complex pattern was found. The frequency of impedance peaks are constant with increasing vibration level. The magnitude of the second peak decreases when changing posture from erect to relaxed. Males showed a higher impedance magnitude than females and a greater dip between the two peaks. The impedance spectra for the two horizontal directions have different shapes. This supports the idea of treating them differently; such as with respect to risk assessments and development of preventative measures.

2. Systematic studies of molecular vibrational anharmonicity and vibration-rotation interaction by self-consistent-field higher derivative methods: Applications to asymmetric and symmetric top and linear polyatomic molecules

SciTech Connect

Clabo, D.A. Jr.

1987-04-01

Inclusion of the anharmonicity normal mode vibrations (i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface) is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules.

3. Compact Vibration Damper

NASA Technical Reports Server (NTRS)

Ivanco, Thomas G. (Inventor)

2014-01-01

A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

4. Electrochemical Impedance Spectroscopy

NASA Astrophysics Data System (ADS)

Retter, Utz; Lohse, Heinz

Non-steady-state measuring techniques are known to be extremely suitable for the investigation of the electrode kinetics of more complex electrochemical systems. Perturbation of the electrochemical system leads to a shift of the steady state. The rate at which it proceeds to a new steady state depends on characteristic parameters (reaction rate constants, diffusion coefficients, charge transfer resistance, double-layer capacity). Due to non-linearities caused by the electron transfer, low-amplitude perturbation signals are necessary. The small perturbation of the electrode state has the advantage that the solutions of relevant mathematical equations used are transformed in limiting forms that are normally linear. Impedance spectroscopy represents a powerful method for investigation of electrical properties of materials and interfaces of conducting electrodes. Relevant fields of application are the kinetics of charges in bulk or interfacial regions, the charge transfer of ionic or mixed ionic-ionic conductors, semiconducting electrodes, the corrosion inhibition of electrode processes, investigation of coatings on metals, characterisation of materials and solid electrolyte as well as solid-state devices.

5. Impedance match for Stirling type cryocoolers

NASA Astrophysics Data System (ADS)

Dai, Wei; Luo, Ercang; Wang, Xiaotao; Wu, Zhanghua

Impedance match in Stirling type cryocoolers is important for the compressor efficiency and available acoustic power. This paper generalizes the basic principles concerning the efficiency and acoustic power output of the linear compressor. Starting from basic governing equations and mainly from the viewpoint of energy balance, the physical mechanisms behind the principles are clearly shown. Specially, this paper focuses on the impedance match for an existing compressor, where the current limit and displacement limit should also be taken into consideration when selecting a suitable impedance. Some case studies based on a commercial compressor are also provided for a deep understanding.

6. An Accurate Method for Free Vibration Analysis of Structures with Application to Plates

NASA Astrophysics Data System (ADS)

KEVORKIAN, S.; PASCAL, M.

2001-10-01

In this work, the continuous element method which has been used as an alternative to the finite element method of vibration analysis of frames is applied to more general structures like 3-D continuum and rectangular plates. The method is based on the concept of the so-called impedance matrix giving in the frequency domain, the linear relation between the generalized displacements of the boundaries and the generalized forces exerted on these boundaries. For a 3-D continuum, the concept of impedance matrix is introduced assuming a particular kind of boundary conditions. For rectangular plates, this new development leads to the solution of vibration problems for boundary conditions other than the simply supported ones.

7. Change in resonance parameters of a linear molecule as it bends: Evidence in electron-impact vibrational transitions of hot COS and CO2 molecules*

NASA Astrophysics Data System (ADS)

Hoshino, Masamitsu; Ishijima, Yohei; Kato, Hidetoshi; Mogi, Daisuke; Takahashi, Yoshinao; Fukae, Katsuya; Limão-Vieira, Paulo; Tanaka, Hiroshi; Shimamura, Isao

2016-04-01

Inelastic and superelastic electron-impact vibrational excitation functions of hot carbonyl sulphide COS (and hot CO2) are measured for electron energies from 0.5 to 3.0 eV (1.5 to 6.0 eV) and at a scattering angle of 90°. Based on the vibrational populations and the principle of detailed balance, these excitation functions are decomposed into contributions from state-to-state vibrational transitions involving up to the second bending overtone (030) in the electronically ground state. Both the 2Π resonance for COS around 1.2 eV and the 2Πu resonance for CO2 around 3.8 eV are shifted to lower energies as the initial vibrational state is excited in the bending mode. The width of the resonance hump for COS changes only little as the molecule bends, whereas that of the overall boomerang resonance for CO2 becomes narrower. The angular distribution of the electrons resonantly scattered by hot COS and hot CO2 is also measured. The different shapes depending on the vibrational transitions and gas temperatures are discussed in terms of the symmetry of the vibrational wave functions. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

8. On the vibrational linear and nonlinear optical properties of compounds involving noble gas atoms: HXeOXeH, HXeOXeF, and FXeOXeF.

PubMed

Avramopoulos, Aggelos; Reis, Heribert; Luis, Josep M; Papadopoulos, Manthos G

2013-06-30

The vibrational (hyper)polarizabilities of some selected Xe derivatives are studied in the context of Bishop-Kirtman perturbation theory (BKPT) and numerical finite field methodology. It was found that for this set of rare gas compounds, the static vibrational properties are quite large, in comparison to the corresponding electronic ones, especially those of the second hyperpolarizability. This also holds for the dc-Pockels β(-ω;ω,0), Kerr γ(-ω;ω,0,0) and electric field second harmonic generation γ (-2ω;ω,ω,0) effects, although the computed nuclear relaxation (nr) vibrational contributions are smaller in magnitude than the static ones. HXeOXeH was used to study the effects of electron correlation, basis set, and geometry. Geometry effects were found to lead to noticeable changes of the vibrational and electronic second hyperpolarizability. A limited study of the effect of Xe insertion to the nr vibrational properties is also reported. Assessment of the results revealed that Xe insertion has a remarkable effect on the nr (hyper)polarizabilities. In terms of the BKPT, this is associated with a remarkable increase of the electrical and mechanical anharmonicity terms. The latter is consistent with the anharmonic character of several vibrational modes reported for rare gas compounds.

9. Anisotropic Artificial Impedance Surfaces

NASA Astrophysics Data System (ADS)

Quarfoth, Ryan Gordon

Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.

10. Robust impedance shaping telemanipulation

SciTech Connect

Colgate, J.E.

1993-08-01

When a human operator performs a task via a bilateral manipulator, the feel of the task is embodied in the mechanical impedance of the manipulator. Traditionally, a bilateral manipulator is designed for transparency; i.e., so that the impedance reflected through the manipulator closely approximates that of the task. Impedance shaping bilateral control, introduced here, differs in that it treats the bilateral manipulator as a means of constructively altering the impedance of a task. This concept is particularly valuable if the characteristic dimensions (e.g., force, length, time) of the task impedance are very different from those of the human limb. It is shown that a general form of impedance shaping control consists of a conventional power-scaling bilateral controller augmented with a real-time interactive task simulation (i.e., a virtual environment). An approach to impedance shaping based on kinematic similarity between tasks of different scale is introduced and illustrated with an example. It is shown that an important consideration in impedance shaping controller design is robustness; i.e., guaranteeing the stability of the operator/manipulator/task system. A general condition for the robustness of a bilateral manipulator is derived. This condition is based on the structured singular value ({mu}). An example of robust impedance shaping bilateral control is presented and discussed.

11. Vibration manual

NASA Technical Reports Server (NTRS)

Green, C.

1971-01-01

Guidelines of the methods and applications used in vibration technology at the MSFC are presented. The purpose of the guidelines is to provide a practical tool for coordination and understanding between industry and government groups concerned with vibration of systems and equipments. Topics covered include measuring, reducing, analyzing, and methods for obtaining simulated environments and formulating vibration specifications. Methods for vibration and shock testing, theoretical aspects of data processing, vibration response analysis, and techniques of designing for vibration are also presented.

12. Perspective on quantifying electron localization/delocalization, non-linear optical response and vibrational analysis of 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline

NASA Astrophysics Data System (ADS)

Arun Sasi, B. S.; Jebin, R. P.; Suthan, T.; James, C.

2017-10-01

An organic nonlinear optical material 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline (DMBDNA) has been grown by slow evaporation technique. Vibrational spectral analysis has been carried out using FT Raman, FT-IR and UV-Vis spectroscopic techniques. The influence of intramolecular charge transfer within the molecule has been studied on the basis of NBO analysis. Vibrational frequencies have been calculated and scaled, which has been compared with the experimental FT-IR and FT Raman spectra. The effect of electronic localization and delocalization within the molecule is conceded on the basis of electron density partitioning paradigm.

13. Impedance-matched Marx generators

NASA Astrophysics Data System (ADS)

Stygar, W. A.; LeChien, K. R.; Mazarakis, M. G.; Savage, M. E.; Stoltzfus, B. S.; Austin, K. N.; Breden, E. W.; Cuneo, M. E.; Hutsel, B. T.; Lewis, S. A.; McKee, G. R.; Moore, J. K.; Mulville, T. D.; Muron, D. J.; Reisman, D. B.; Sceiford, M. E.; Wisher, M. L.

2017-04-01

We have conceived a new class of prime-power sources for pulsed-power accelerators: impedance-matched Marx generators (IMGs). The fundamental building block of an IMG is a brick, which consists of two capacitors connected electrically in series with a single switch. An IMG comprises a single stage or several stages distributed axially and connected in series. Each stage is powered by a single brick or several bricks distributed azimuthally within the stage and connected in parallel. The stages of a multistage IMG drive an impedance-matched coaxial transmission line with a conical center conductor. When the stages are triggered sequentially to launch a coherent traveling wave along the coaxial line, the IMG achieves electromagnetic-power amplification by triggered emission of radiation. Hence a multistage IMG is a pulsed-power analogue of a laser. To illustrate the IMG approach to prime power, we have developed conceptual designs of two ten-stage IMGs with L C time constants on the order of 100 ns. One design includes 20 bricks per stage, and delivers a peak electrical power of 1.05 TW to a matched-impedance 1.22 -Ω load. The design generates 113 kV per stage and has a maximum energy efficiency of 89%. The other design includes a single brick per stage, delivers 68 GW to a matched-impedance 19 -Ω load, generates 113 kV per stage, and has a maximum energy efficiency of 90%. For a given electrical-power-output time history, an IMG is less expensive and slightly more efficient than a linear transformer driver, since an IMG does not use ferromagnetic cores.

14. Overview Of Impedance Sensors

NASA Astrophysics Data System (ADS)

Abele, John E.

1989-08-01

Electrical impedance has been one of the many "tools of great promise" that physicians have employed in their quest to measure and/or monitor body function or physiologic events. So far, the expectations for its success have always exceeded its performance. In simplistic terms, physiologic impedance is a measure of the resistance in the volume between electrodes which changes as a function of changes in that volume, the relative impedance of that volume, or a combination of these two. The history and principles of electrical impedance are very nicely reviewed by Geddes and Baker in their textbook "Principles of Applied Biomedical Instrumentation". It is humbling, however, to note that Cremer recorded variations in electrical impedance in frog hearts as early as 1907. The list of potential applications includes the measurement of thyroid function, estrogen activity, galvanic skin reflex, respiration, blood flow by conductivity dilution, nervous activity and eye movement. Commercial devices employing impedance have been and are being used to measure respiration (pneumographs and apneamonitors), pulse volume (impedance phlebographs) and even noninvasive cardiac output.

15. Vibration control in accelerators

SciTech Connect

Montag, C.

2011-01-01

In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

16. Microfabricated AC impedance sensor

DOEpatents

Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

2002-01-01

A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

17. Energy-storage of a prescribed impedance

NASA Technical Reports Server (NTRS)

Smith, W. E.

1969-01-01

General mathematical expression found for energy storage shows that for linear, passive networks there is a minimum possible energy storage corresponding to a prescribed impedance. The electromagnetic energy storage is determined at different excitation frequencies through analysis of the networks terminal and reactance characteristics.

18. On Impedance Spectroscopy of Supercapacitors

NASA Astrophysics Data System (ADS)

Uchaikin, V. V.; Sibatov, R. T.; Ambrozevich, A. S.

2016-10-01

Supercapacitors are often characterized by responses measured by methods of impedance spectroscopy. In the frequency domain these responses have the form of power-law functions or their linear combinations. The inverse Fourier transform leads to relaxation equations with integro-differential operators of fractional order under assumption that the frequency response is independent of the working voltage. To compare long-term relaxation kinetics predicted by these equations with the observed one, charging-discharging of supercapacitors (with nominal capacitances of 0.22, 0.47, and 1.0 F) have been studied by means of registration of the current response to a step voltage signal. It is established that the reaction of devices under study to variations of the charging regime disagrees with the model of a homogeneous linear response. It is demonstrated that relaxation is well described by a fractional stretched exponent.

19. vapor phase lubrication of SiO2 surfaces via adsorption of short chain linear alcohols & a sum frequency generation vibration spectroscopy study of crystalline cellulose in biomass

NASA Astrophysics Data System (ADS)

Barnette, Anna Lorraine

The use of silicon oxide with its native oxide layer for the fabrication of microelectromechanical systems (MEMS) with contacting sliding parts requires the need for innovative lubrication methods to extend device lifetimes. The most promising method to date involves the equilibrium vapor phase lubrication (VPL) of MEMS using short chain linear alcohols in ambient conditions. Still, some questions remain regarding the effectiveness of this lubrication method, these include (1) whether or not the adsorbed n-alcohol molecules are the primary lubricant and (2) is this lubrication method effective in humid environments. This study investigates the vapor phase lubrication of SiO2 surfaces using short chain linear alcohols, more specifically n-propanol and n-pentanol. Macro-scale ball-on-flat tribometer tests are used to evaluate the lubriciousness of n-pentanol vapor under a series of contact loads/ pressures. Wear reduction of the SiO2 surfaces is achieved when there is complete coverage of the SiO2 surfaces with the adsorbed n-pentanol molecules. This occurs when the partial pressure relative to the saturation pressure (P/Psat) of n-pentanol was kept above 20% P/Psat which corresponds to approximately monolayer coverage of the SiO2 surface. In contrast to the lubricious effect of n-pentanol vapor, water vapor proves to enhance wear of the SiO2 surfaces when compared to dry (low moisture) conditions. This study also demonstrates that the primary lubrication method of the SiO 2 surfaces is most likely the adsorbed n-pentanol molecules and not the tribochemical reaction species produced during the sliding contact. Although this reaction species is always present within the wear tested regions, the production of the tribochemical reaction species is enhanced when more severe wear is observed. So, the adsorbed n-pentanol molecules are the primary method of lubrication. The effectiveness of the lubrication method in environments containing water vapor is also investigated

20. Surface Roughness Impedance

SciTech Connect

Stupakov, Gennady

2000-12-21

The next generation of linac-based free electron lasers will use very short bunches with a large peak current. For such beams, the impedance caused by submicron imperfections in the vacuum beam tube may generate an additional energy spread within the bunch. A review of two mechanisms of the roughness impedance is given with the emphasis on the importance of the high-aspect ratio property of the real surface roughness.

1. Aircraft panel with sensorless active sound power reduction capabilities through virtual mechanical impedances

NASA Astrophysics Data System (ADS)

Boulandet, R.; Michau, M.; Micheau, P.; Berry, A.

2016-01-01

This paper deals with an active structural acoustic control approach to reduce the transmission of tonal noise in aircraft cabins. The focus is on the practical implementation of the virtual mechanical impedances method by using sensoriactuators instead of conventional control units composed of separate sensors and actuators. The experimental setup includes two sensoriactuators developed from the electrodynamic inertial exciter and distributed over an aircraft trim panel which is subject to a time-harmonic diffuse sound field. The target mechanical impedances are first defined by solving a linear optimization problem from sound power measurements before being applied to the test panel using a complex envelope controller. Measured data are compared to results obtained with sensor-actuator pairs consisting of an accelerometer and an inertial exciter, particularly as regards sound power reduction. It is shown that the two types of control unit provide similar performance, and that here virtual impedance control stands apart from conventional active damping. In particular, it is clear from this study that extra vibrational energy must be provided by the actuators for optimal sound power reduction, mainly due to the high structural damping in the aircraft trim panel. Concluding remarks on the benefits of using these electrodynamic sensoriactuators to control tonal disturbances are also provided.

2. Vibration interaction in a multiple flywheel system

NASA Astrophysics Data System (ADS)

Firth, Jordan; Black, Jonathan

2012-03-01

This paper investigates vibration interaction in a multiple flywheel system. Flywheels can be used for kinetic energy storage in a satellite Integrated Power and Attitude Control System (IPACS). One hitherto unstudied problem with IPACS is vibration interaction between multiple unbalanced wheels. This paper uses a linear state-space dynamics model to study the impact of vibration interaction. Specifically, imbalance-induced vibration inputs in one flywheel rotor are used to cause a resonant whirling vibration in another rotor. Extra-synchronous resonant vibrations are shown to exist, but with damping modeled the effect is minimal. Vibration is most severe when both rotors are spinning in the same direction.

3. Time-Domain Impedance Boundary Conditions for Computational Aeroacoustics

NASA Technical Reports Server (NTRS)

Tam, Christopher K. W.; Auriault, Laurent

1996-01-01

It is an accepted practice in aeroacoustics to characterize the properties of an acoustically treated surface by a quantity known as impedance. Impedance is a complex quantity. As such, it is designed primarily for frequency-domain analysis. Time-domain boundary conditions that are the equivalent of the frequency-domain impedance boundary condition are proposed. Both single frequency and model broadband time-domain impedance boundary conditions are provided. It is shown that the proposed boundary conditions, together with the linearized Euler equations, form well-posed initial boundary value problems. Unlike ill-posed problems, they are free from spurious instabilities that would render time-marching computational solutions impossible.

4. Network asymptotics for high contrast impedance tomography

SciTech Connect

Borcea, L.; Papanicolaou, G.C.; Berryman, J.G.

1996-05-01

Fluid contaminant plumes underground are often electrically conducting and, therefore, can be imaged using electrical impedance tomography. The authors introduce an output least-squares method for impedance tomography problems that have regions of high conductivity surrounded by regions of lower conductivity. The high conductivity is modeled on network approximation results from an asymptotic analysis and its recovery is based on this model. The smoothly varying part of the conductivity is recovered by a linearization process as is usual. The authors present the results of several numerical experiments that illustrate the performance of the method.

5. Coal storage hopper with vibrating screen agitator

SciTech Connect

Daw, C.S.; Lackey, M.E.; Sy, R.L.

1984-09-11

The present invention is directed to a vibrating screen agitator in a coal storage hopper for assuring the uniform feed of coal having sufficient moisture content to effect agglomeration and bridging thereof in the coal hopper from the latter onto a conveyor mechanism. The vibrating screen agitator is provided by a plurality of transversely oriented and vertically spaced apart screens in the storage hopper with a plurality of vertically oriented rods attached to the screens. The rods are vibrated to effect the vibration of the screens and the breaking up of agglomerates in the coal which might impede the uniform flow of the coal from the hopper onto a conveyer.

6. Coal storage hopper with vibrating screen agitator

DOEpatents

Daw, Charles S.; Lackey, Mack E.; Sy, Ronald L.

1984-01-01

The present invention is directed to a vibrating screen agitator in a coal storage hopper for assuring the uniform feed of coal having sufficient moisture content to effect agglomeration and bridging thereof in the coal hopper from the latter onto a conveyor mechanism. The vibrating screen agitator is provided by a plurality of transversely oriented and vertically spaced apart screens in the storage hopper with a plurality of vertically oriented rods attached to the screens. The rods are vibrated to effect the vibration of the screens and the breaking up of agglomerates in the coal which might impede the uniform flow of the coal from the hopper onto a conveyer.

7. Force Limited Vibration Testing

NASA Technical Reports Server (NTRS)

Scharton, Terry; Chang, Kurng Y.

2005-01-01

This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test

8. Refocusing vibrating targets in SAR images

NASA Astrophysics Data System (ADS)

Wang, Qi; Santhanam, Balu; Pepin, Matthew; Atwood, Tom; Hayat, Majeed M.

2012-06-01

In synthetic-aperture radar (SAR) returned signals, ground-target vibrations introduce a phase modulation that is linearly proportional to the vibration displacement. Such modulation, termed the micro-Doppler effect, introduces ghost targets along the azimuth direction in reconstructed SAR images that prevents SAR from forming focused images of the vibrating targets. Recently, a discrete fractional Fourier transform (DFrFT) based method was developed to estimate the vibration frequencies and instantaneous vibration accelerations of the vibrating targets from SAR returned signals. In this paper, a demodulation-based algorithm is proposed to reconstruct focused SAR images of vibrating targets by exploiting the estimation results of the DFrFT-based vibration estimation method. For a single-component harmonic vibration, the history of the vibration displacement is first estimated from the estimated vibration frequency and the instantaneous vibration accelerations. Then a reference signal whose phase is modulated by the estimated vibration displacement with a delay of 180 degree is constructed. After that, the SAR phase history from the vibration target is multiplied by the reference signal and the vibration-induced phase modulation is canceled. Finally, the SAR image containing the re-focused vibration target is obtained by applying the 2-D Fourier transform to the demodulated SAR phase history. This algorithm is applied to simulated SAR data and successfully reconstructs the SAR image containing the re-focused vibrating target.

9. Superconducting active impedance converter

DOEpatents

Ginley, D.S.; Hietala, V.M.; Martens, J.S.

1993-11-16

A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductors allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology. 12 figures.

10. Superconducting active impedance converter

DOEpatents

Ginley, David S.; Hietala, Vincent M.; Martens, Jon S.

1993-01-01

A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductor allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology.

11. Smart mug to measure hand's geometrical mechanical impedance.

PubMed

Hondori, Hossein Mousavi; Tech, Ang Wei

2011-01-01

A novel device, which looks like a mug, has been proposed for measuring the impedance of human hand. The device is designed to have convenient size and light weight similar to an ordinary coffee mug. It contains a 2-axis inertia sensor to monitor vibration and a small motor to carry an eccentric mass (m=100 gr, r=2 cm, rpm=600). The centrifugal force due to the rotating mass applies a dynamic force to the hand that holds the mug. Correlation of the acceleration signals with the perturbing force gives the geometrical mechanical impedance. Experimental results on a healthy subject shows that impedance is posture dependant while it changes with the direction of the applied perturbing force. For nine postures the geometrical impedance is obtained all of which have elliptical shapes. The method can be used for assessment of spasticity and monitoring stability in patients with stroke or similar problems.

12. Theoretical investigation on the non-linear optical properties, vibrational spectroscopy and frontier molecular orbital of (E)-2-cyano-3-(3-hydroxyphenyl)acrylamide molecule.

PubMed

Xiao-Hong, Li; Hong-Ling, Cui; Rui-Zhou, Zhang; Xian-Zhou, Zhang

2015-02-25

The vibrational frequencies of (E)-2-cyano-3-(3-hydroxyphenyl)acrylamide (HB-CA) in the ground state have been calculated using density functional method (B3LYP) with B3LYP/6-311++G(d,p) basis set. The analysis of natural bond orbital was also performed. The IR spectra were obtained and interpreted by means of potential energies distributions (PEDs) using MOLVIB program. In addition, the results show that there exists C-H⋯O hydrogen bond in the title compound, which is confirmed by the natural bond orbital analysis. The predicted NLO properties show that the title compound is a good candidate as nonlinear optical material. The analysis of frontier molecular orbitals shows that HB-CA has high excitation energies, good stability and high chemical hardness. The analysis of MEP map shows the negative and the positive potential sites.

13. Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

NASA Astrophysics Data System (ADS)

Asami, Takuya; Tamada, Yosuke; Higuchi, Yusuke; Miura, Hikaru

2017-07-01

Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

14. Longitudinal impedance of RHIC

SciTech Connect

Blaskiewicz, M.; Brennan, J. M.; Mernick, K.

2015-05-03

The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.

15. Impedances of Tevatron separators

SciTech Connect

K. Y. Ng

2003-05-28

The impedances of the Tevatron separators are revisited and are found to be negligibly small in the few hundred MHz region, except for resonances at 22.5 MHz. The later are contributions from the power cables which may drive head-tail instabilities if the bunch is long enough.

16. Implantable Impedance Plethysmography

PubMed Central

Theodor, Michael; Ruh, Dominic; Ocker, Martin; Spether, Dominik; Förster, Katharina; Heilmann, Claudia; Beyersdorf, Friedhelm; Manoli, Yiannos; Zappe, Hans; Seifert, Andreas

2014-01-01

We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term. PMID:25123467

17. Ground Vibration Measurements at LHC Point 4

SciTech Connect

Bertsche, Kirk; Gaddi, Andrea; /CERN

2012-09-17

Ground vibration was measured at Large Hadron Collider (LHC) Point 4 during the winter shutdown in February 2012. This report contains the results, including power and coherence spectra. We plan to collect and analyze vibration data from representative collider halls to inform specifications for future linear colliders, such as ILC and CLIC. We are especially interested in vibration correlations between final focus lens locations.

18. Recycler short kicker beam impedance

SciTech Connect

Crisp, Jim; Fellenz, Brian; /Fermilab

2009-07-01

Measured longitudinal and calculated transverse beam impedance is presented for the short kicker magnets being installed in the Fermilab Recycler. Fermi drawing number ME-457159. The longitudinal impedance was measured with a stretched wire and the Panofsky equation was used to estimate the transverse impedance. The impedance of 3319 meters (the Recycler circumference) of stainless vacuum pipe is provided for comparison. Although measurements where done to 3GHz, impedance was negligible above 30MHz. The beam power lost to the kicker impedance is shown for a range of bunch lengths. The measurements are for one kicker assuming a rotation frequency of 90KHz. Seven of these kickers are being installed.

19. Experiences with active damping and impedance-matching compensators

NASA Astrophysics Data System (ADS)

Betros, Robert S.; Alvarez, Oscar S.; Bronowicki, Allen J.

1993-09-01

TRW has been implementing active damping compensators on smart structures for the past five years. Since that time there have been numerous publications on the use of impedance matching techniques for structural damping augmentation. The idea of impedance matching compensators came about by considering the flow of power in a structure undergoing vibration. The goal of these compensators is to electronically dissipate as much of this flowing power as possible. This paper shows the performance of impedance matching compensators used in smart structures to be comparable to that of active damping compensators. Theoretical comparisons between active damping and impedance matching methods are made using PZT actuators and sensors. The effects of these collocated and non-collocated PZT sensors and actuators on the types of signals they sense and actuate are investigated. A method for automatically synthesizing impedance matching compensators is presented. Problems with implementing broad band active damping and impedance matching compensators on standard Digital Signal Processing (DSP) chips are discussed. Simulations and measurements that compare the performance of active damping and impedance matching techniques for a lightly damped cantilevered beam are shown.

20. Non-Linear Dynamics and Stability of Circular Cylindrical Shells Containing Flowing Fluid. Part Iv: Large-Amplitude Vibrations with Flow

NASA Astrophysics Data System (ADS)

AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.

2000-11-01

The response of a shell conveying fluid to harmonic excitation, in the spectral neighbourhood of one of the lowest natural frequencies, is investigated for different flow velocities. The theoretical model has already been presented in Part I of the present study. Non-linearities due to moderately large-amplitude shell motion are considered by using Donnell's non-linear shallow-shell theory. Linear potential flow theory is applied to describe the fluid-structure interaction by using the model proposed by Paı̈doussis and Denise. For different amplitudes and frequencies of the excitation and for different flow velocities, the following are investigated numerically: (1) periodic response of the system; (2) unsteady and stochastic motion; (3) loss of stability by jumps to bifurcated branches. The effect of the flow velocity on the non-linear periodic response of the system has also been investigated. Poincaré maps and bifurcation diagrams are used to study the unsteady and stochastic dynamics of the system. Amplitude modulated motions, multi-periodic solutions, chaotic responses, cascades of bifurcations as the route to chaos and the so-called “blue sky catastrophe” phenomenon have all been observed for different values of the system parameters; the latter two have been predicted here probably for the first time for the dynamics of circular cylindrical shells.

1. Monoclinic and triclinic polymorphs of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene}malononitrile-solid-state linear-polarized IR-spectroscopy, DFT calculations and vibrational analysis.

PubMed

Koleva, Bojidarka B; Kolev, Tsonko

2008-12-01

The linear-dichroic infrared (IR-LD) spectroscopy of oriented solid samples as suspension in nematic liquid crystal have been carried out for experimental IR-band assignment and structural information of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene} malononitrile polymorphs. The last data have been compared with known crystallographic ones, thus determining the validity of IR-LD spectral conclusions as well as its possibility to determination of Davydov's splitting effect and separation of pairs of maxima corresponding to non-equivalent molecules included in the unit cell of given compound. The experimental structural and spectroscopic data in our case are supported with theoretical DFT ones, obtaining both the electronic structure and vibrational frequencies in gas phase.

2. The Physics of Vibration

NASA Astrophysics Data System (ADS)

Pippard, A. B.

1989-11-01

The study of vibration in physical systems is an important part of almost all fields in physics and engineering. This work, originally published in two volumes, examines the classical aspects in Part I and the quantum oscillator in Part II. The classical linear vibrator is treated first and the underlying unity of all linear oscillations in electrical, mechanical and acoustic systems is emphasized. Following this the book turns to the treatment of nonlinear vibrations, a field with which engineers and physicists are generally less familiar. In Part II the emphasis turns to quantum systems, that is those systems which can only be adequately described by quantum mechanics. The treatment concentrates on vibrations in atoms and molecules and their interaction with electromagnetic radiation. The similarities of classical and quantum methods are stressed and the limits of the classical treatment are examined. Throughout the book, each phenomenon discussed is illustrated with many examples and theory and experiment are compared. Although the reader may find that the physics discussed is demanding and the concepts are subtle in places, all mathematics used is familiar to both engineers and experimental scientists. Although not a textbook this is a useful introduction to the more advanced mathematical treatment of vibrations as it bridges the gap between the basic principles and more specialized concepts. It will be of great interest to advanced undergraduates and postgraduates as well as applied mathematicians, physicists and engineers in university and industry.

3. Chemical synthesis, crystal structure, vibrational spectroscopy, non-linear optical properties and DFT calculation of bis (2,6-diaminopyridinium) sulfate monohydrate

NASA Astrophysics Data System (ADS)

Ben Hassen, Chaouki; Dammak, Thameur; Chniba-Boudjada, Nassira; Mhiri, Tahar; Boujelbene, Mohamed

2017-01-01

Single crystals of a new organic inorganic hybrid compound "bis (2,6-diaminopyridinium) sulfate monohydrate [C5H8N3]2SO4·H2O ([2,6-HDAP]2SO4·H2O)" was synthesized by slow evaporation method at room temperature and characterized by X-ray single crystal diffraction, infrared spectroscopy and DFT calculation. The new hybrid compound crystallizes in the orthorhombic system with the non-centro symmetric space group Pna21 and the following parameters a = 14.759(2) Å, b = 7.076 (2) Å and c = 28.159 (2) Å. The atomic arrangement can be described as inorganic chains following the b axis connected with the organic groups by means of Nsbnd H⋯O hydrogen bonds to form 3D network. Antiparallelly π-π stacked 2,6-HDAP cations form molecular columns in the spaces between the chains. The optimized molecular structure, vibrational spectra and the optical properties were calculated by the density functional theory (DFT) method using the B3LYP function with the LanL2DV basis set. The wavenumber calculated are in good agreement with the observed frequency values. The calculated hyperpolarizability βtot is about 4.5 times more than that of the reference crystal KDP. Hence, the large β value shows that the title compound is an attractive object for future studies of nonlinear optical properties.

4. Computational study of the vibrational spectroscopic studies, natural bond orbital, frontier molecular orbital and second-order non-linear optical properties of acetophenone thiosemicarbazone molecule.

PubMed

Li, Xiao-Hong; Mei, Zheng; Zhang, Xian-Zhou

2014-01-24

The vibrational frequencies of acetophenone thiosemicarbazone in the ground state have been calculated using density functional method (B3LYP) with 6-31G(d), 6-31G(d,p) and 6-311++G(d,p) basis sets. The analysis of natural bond orbital was also performed. The IR spectra were obtained and interpreted by means of potential energies distributions (PEDs) using MOLVIB program. In addition, the results show that there exist N-H…N and N-H…S hydrogen bonds in the title compound, which play a major role in stabilizing the molecule and are confirmed by the natural bond orbital analysis. The predicted NLO properties show that the title compound is a good candidate as second-order NLO material. In addition, the frontier molecular orbitals were analyzed and the crystal structure obtained by molecular mechanics belongs to the Pbca space group, with lattice parameters Z=8, a=16.0735 Å, b=7.1719 Å, c=7.8725 Å, ρ=0.808 g/cm(3).

5. Impedance calculation for ferrite inserts

SciTech Connect

Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

2005-01-01

Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

6. Non-Linear Dynamics and Stability of Circular Cylindrical Shells Containing Flowing Fluid, Part II: Large-Amplitude Vibrations Without Flow

NASA Astrophysics Data System (ADS)

AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.

1999-12-01

The non-linear response of empty and fluid-filled circular cylindrical shells to harmonic excitations is investigated. Both modal and point excitations have been considered. The model is suitable to study simply supported shells with and without axial constraints. Donnell's non-linear shallow-shell theory is used. The boundary conditions on radial displacement and the continuity of circumferential displacement are exactly satisfied. The radial deflection of the shell is expanded by using a basis of seven linear modes. The effect of internal quiescent, incompressible and inviscid fluid is investigated. The equations of motion, obtained in Part I of this study, are studied by using a code based on the collocation method. The validation of the present model is obtained by comparison with other authoritative results. The effect of the number of axisymmetric modes used in the expansion on the response of the shell is investigated, clarifying questions open for a long time. The results show the occurrence of travelling wave response in the proximity of the resonance frequency, the fundamental role of the first and third axisymmetric modes in the expansion of the radial deflection with one longitudinal half-wave, and limit cycle responses. Modes with two longitudinal half-waves are also investigated.

7. Impedance Measurement Box

ScienceCinema

Christophersen, Jon

2016-07-12

Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

8. Impedance Measurement Box

SciTech Connect

Christophersen, Jon

2011-01-01

Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

9. Impedance Measurement Box

SciTech Connect

Morrison, William

2014-11-20

The IMB 50V software provides functionality for design of impedance measurement tests or sequences of tests, execution of these tests or sequences, processing measured responses and displaying and saving of the results. The software consists of a Graphical User Interface that allows configuration of measurement parameters and test sequencing, a core engine that controls test sequencing, execution of measurements, processing and storage of results and a hardware/software data acquisition interface with the IMB hardware system.

10. Acoustic ground impedance meter

NASA Astrophysics Data System (ADS)

Zuckerwar, A. J.

1981-12-01

A compact, portable instrument was developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is a variable up to a maximum 3600 rpm. The sound pressure at the test surface is measured by means of a microphone flush-mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. Measurements using a 5-lobed cam can be made up to 300 Hz. Detailed design criteria and results on a soil sample are presented.

11. Acoustic ground impedance meter

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J.

1983-01-01

A compact, portable instrument was developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholtz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is a variable up to a maximum 3600 rpm. The sound pressure at the test surface is measured by means of a microphone flush-mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. Measurements using a 5-lobed cam can be made up to 300 Hz. Detailed design criteria and results on a soil sample are presented. Previously announced in STAR as N82-17476

12. High input impedance amplifier

NASA Technical Reports Server (NTRS)

Kleinberg, Leonard L.

1995-01-01

High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provide an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude. These amplifiers, while generally useful, are very useful as sensor buffer amplifiers that may eliminate significant sources of error.

13. Acoustic ground impedance meter

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J.

1981-01-01

A compact, portable instrument was developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is a variable up to a maximum 3600 rpm. The sound pressure at the test surface is measured by means of a microphone flush-mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. Measurements using a 5-lobed cam can be made up to 300 Hz. Detailed design criteria and results on a soil sample are presented.

14. Gynecologic electrical impedance tomograph

NASA Astrophysics Data System (ADS)

Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.

2010-04-01

Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.

15. VIBRATION COMPACTION

DOEpatents

Hauth, J.J.

1962-07-01

A method of compacting a powder in a metal container is described including the steps of vibrating the container at above and below the resonant frequency and also sweeping the frequency of vibration across the resonant frequency several times thereby following the change in resonant frequency caused by compaction of the powder. (AEC)

16. Vibration isolation

NASA Technical Reports Server (NTRS)

Bastin, Paul

1990-01-01

Viewgraphs on vibration isolation are presented. Techniques to control and isolate centrifuge disturbances were identified. Topics covered include: disturbance sources in the microgravity environment; microgravity assessment criteria; life sciences centrifuge; flight support equipment for launch; active vibration isolation system; active balancing system; and fuzzy logic control.

17. RF impedance measurement calibration

SciTech Connect

Matthews, P.J.; Song, J.J.

1993-02-12

The intent of this note is not to explain all of the available calibration methods in detail. Instead, we will focus on the calibration methods of interest for RF impedance coupling measurements and attempt to explain: (1). The standards and measurements necessary for the various calibration techniques. (2). The advantages and disadvantages of each technique. (3). The mathematical manipulations that need to be applied to the measured standards and devices. (4). An outline of the steps needed for writing a calibration routine that operated from a remote computer. For further details of the various techniques presented in this note, the reader should consult the references.

18. Introduction to Electrochemical Impedance

DTIC Science & Technology

1994-02-24

in polar coordinates and Z’ and Z" in Cartesian coordinates. Algebra has a special way of expressing "two-component numbers" as complex numbers. This...test is a small batch file that invokes a BASICA program and loads P STAT.BAS program in it. By replacing test with atwill, the program at-will will be...SYSTEM. This will end the BASICA program, return the computer to DOS and consequently, return to Z-PLOT. Petr Vantsek Introduction to impedance 55 23

19. Acoustic input impedance of the avian inner ear measured in ostrich (Struthio camelus).

PubMed

Muyshondt, Pieter G G; Aerts, Peter; Dirckx, Joris J J

2016-09-01

In both mammals and birds, the mechanical behavior of the middle ear structures is affected by the mechanical impedance of the inner ear. In this study, the aim was to quantify the acoustic impedance of the avian inner ear in the ostrich, which allows us to determine the effect on columellar vibrations and middle ear power flow in future studies. To determine the inner ear impedance, vibrations of the columella were measured for both the quasi-static and acoustic stimulus frequencies. In the frequency range of 0.3-4 kHz, we used electromagnetic stimulation of the ossicle and a laser Doppler vibrometer to measure the vibration response. At low frequencies, harmonic displacements were imposed on the columella using piezo stimulation and the resulting force response was measured with a force sensor. From these measurement data, the acoustic impedance of the inner ear could be determined. A simple RLC model in series of the impedance measurements resulted in a stiffness reactance of KIE = 0.20·10(12) Pa/m³, an inertial impedance of MIE = 0.652·10(6) Pa s(2)/m³, and a resistance of RIE = 1.57·10(9) Pa s/m. We found that values of the inner ear impedance in the ostrich are one to two orders in magnitude smaller than what is found in mammal ears.

20. Theoretical explanation of the low-lying ν(6) vibrational fundamental of the FSO3 radical by the linear vibronic coupling approach.

PubMed

Uhlíková, Tereza; Urban, Štěpán

2013-06-21

The first attempt for a theoretical explanation of the ν6 fundamental energy levels of the fluorosulfate radical (FSO3) electronic ground state has been made. The vibronic interaction of the two lowest electronic states of the radical (X̃ (2)A2 and Ã (2)E) has been taken into consideration in the basis of the linear vibronic coupling (LVC) approximation. The strengths of the intrastate and interstate vibronic couplings have been calculated within the framework of the Köppel, Domcke, and Cederbaum (KDC) model Hamiltonian. Already this simple KDC-LVC model provides the ν6 fundamental energy, which is in very good agreement with the experimental results. From the inclusion of vibronic interactions such as the pseudo-Jahn-Teller and Jahn-Teller effects into the calculation of the fundamental energy of the ν6 mode, it can be said that mainly the interstate coupling with the electronic excited state E causes the unexpectedly low fundamental energy ν6 of the FSO3 radical.

1. Outdoor ground impedance models.

PubMed

Attenborough, Keith; Bashir, Imran; Taherzadeh, Shahram

2011-05-01

Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.

2. Impedance-based damage assessment using piezoelectric sensors

NASA Astrophysics Data System (ADS)

Rim, Mi-Sun; Yoo, Seung-Jae; Lee, In; Song, Jae-Hoon; Yang, Jae-Won

2011-04-01

Recently structural health monitoring (SHM) systems are being focused because they make it possible to assess the health of structures at real-time in many application fields such as aircraft, aerospace, civil and so on. Piezoelectric materials are widely used for sensors of SHM system to monitor damage of critical parts such as bolted joints. Bolted joints could be loosened by vibration, thermal cycling, shock, corrosion, and they cause serious mechanical failures. In this paper, impedance-based method using piezoelectric sensors was applied for real-time SHM. A steel beam specimen fastened by bolts was tested, and polymer type piezoelectric materials, PVDFs were used for sensors to monitor the condition of bolted joint connections. When structure has some damage, for example loose bolts, the impedance of PVDF sensors showed different tendency with normal structure which has no loose bolts. In the case of loose bolts, impedance values are decreased and admittance values are increased.

3. Polyatomic molecule vibrations

NASA Technical Reports Server (NTRS)

1976-01-01

Polyatomic molecule vibrations are analyzed as harmonic vibrations along normal coordinates. The energy eigenvalues are found for linear and nonlinear symmetric triatomic molecules for valence bond models of the potential function with arbitrary coupling coefficients; such models can usually be fitted to observed energy levels with reasonably good accuracy. Approximate normal coordinates for the H2O molecule are discussed. Degenerate vibrational modes such as occur in CO2 are analyzed and expressions for Fermi resonance between close-lying states of the same symmetry are developed. The bending modes of linear triatomic molecules are expressed in terms of Laguerre polynomials in cylindrical coordinates as well as in terms of Hermite polynomials in Cartesian coordinates. The effects of large-amplitude bending such as occur in the C3 molecule are analyzed, along with anharmonic effects, which split the usually degenerate bending mode energy levels. Finally, the vibrational frequencies, degeneracies, and symmetry properties of XY3, X2Y2, and XY4 type molecules are discussed.

4. Impedance Study for BEPC Separator

NASA Astrophysics Data System (ADS)

Zhou, Feng; Tang, Chuanxiang

1997-05-01

This paper focuses on the impedance studies for the separator. The impedance measurement results show that the shunt impedances of trapped modes in the separator are very small, and find that the load connected to the plates can damp some modes. The field distributions of these modes are also presented. Its wake is also calculated by using 3-D MAFIA. The relations between its wake with separator length, separator width, and etc are studied in detail.

5. Ionospheric effects to antenna impedance

NASA Technical Reports Server (NTRS)

Bethke, K. H.

1986-01-01

The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

6. Design of an active vibration dummy of sitting man.

PubMed

Cullmann, A; Wölfel, H P

2001-01-01

The determination of vibration transmission through vehicle seats today is still performed with small groups of test subjects. This method suffers from several severe disadvantages, in particular poor repeatability and objectivity due to varying test conditions and limited group sizes. Replacing test persons with a vibration dummy helps to solve this problem. The active vibration dummy simulates the dynamic behaviour of sitting man expressed in terms of the driving point impedance for arbitrary body masses and excitation signals. The dummy is realized as a mechatronic system basing on a single degree of freedom setup. A real-time control loop of mass accelerations (and thus acting forces) fits the active dummy to the desired driving point impedance data set. Model and controller parameters are determined by a parameter-identification technique giving meaningful results for arbitrary impedance data sets. The prototype shows excellent agreement with the target data under laboratory conditions. Body mass and excitation level can be varied over the full range of car seat test requirements. The determination of vibration transmission through vehicle seats should be possible without human experiments. An active vibration dummy with adjustable vibration behaviour expressed by the vertical driving point impedance covering the entire scope of car seat tests (masses/excitation intensities) is presented. With the dummy, improved seat test procedures could be established, leading to design improvements and therefore to prevention of whole-body vibration injuries.

7. Optically stimulated differential impedance spectroscopy

DOEpatents

Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P

2014-02-18

Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.

8. Vibration-Response Analysis

NASA Technical Reports Server (NTRS)

Bowman, L. M.

1986-01-01

Dynamic behaviors of structures analyzed interactively. Interactive steadystate vibration-response program, VIBRA, developed. Frequency-response analyses commonly used in evaluating dynamic behaviors of structures subjected to cyclic external forces. VIBRA calculates frequency response using modalsuperposition approach. Method applicable to single or multiple forces applied to linear, proportionally damped structure in which damping is viscous or structural. VIBRA written in FORTRAN 77 for interactive execution.

9. Impedance matching at arterial bifurcations.

PubMed

Brown, N

1993-01-01

Reflections of pulse waves will occur in arterial bifurcations unless the impedance is matched continuously through changing geometric and elastic properties. A theoretical model is presented which minimizes pulse wave reflection through bifurcations. The model accounts for the observed linear changes in area within the bifurcation, generalizes the theory to asymmetrical bifurcations, characterizes changes in elastic properties from parent to daughter arteries, and assesses the effect of branch angle on the mechanical properties of daughter vessels. In contradistinction to previous models, reflections cannot be minimized without changes in elastic properties through bifurcations. The theoretical model predicts that in bifurcations with area ratios (beta) less than 1.0 Young's moduli of daughter vessels may be less than that in the parent vessel if the Womersley parameter alpha in the parent vessel is less than 5. Larger area ratios in bifurcations are accompanied by greater increases in Young's moduli of branches. For an idealized symmetric aortic bifurcation (alpha = 10) with branching angles theta = 30 degrees (opening angle 60 degrees) Young's modulus of common iliac arteries relative to that of the distal abdominal aorta has an increase of 1.05, 1.68 and 2.25 for area ratio of 0.8, 1.0 and 1.15, respectively. These predictions are consistent with the observed increases in Young's moduli of peripheral vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

10. Monolithically compatible impedance measurement

DOEpatents

Ericson, Milton Nance; Holcomb, David Eugene

2002-01-01

A monolithic sensor includes a reference channel and at least one sensing channel. Each sensing channel has an oscillator and a counter driven by the oscillator. The reference channel and the at least one sensing channel being formed integrally with a substrate and intimately nested with one another on the substrate. Thus, the oscillator and the counter have matched component values and temperature coefficients. A frequency determining component of the sensing oscillator is formed integrally with the substrate and has an impedance parameter which varies with an environmental parameter to be measured by the sensor. A gating control is responsive to an output signal generated by the reference channel, for terminating counting in the at least one sensing channel at an output count, whereby the output count is indicative of the environmental parameter, and successive ones of the output counts are indicative of changes in the environmental parameter.

11. Development on electromagnetic impedance function modeling and its estimation

SciTech Connect

Sutarno, D.

2015-09-30

Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition

12. Vibrational Diver

NASA Astrophysics Data System (ADS)

Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef

2014-10-01

The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

13. Impedance spectroscopy for the detection and identification of unknown toxins

NASA Astrophysics Data System (ADS)

Riggs, B. C.; Plopper, G. E.; Paluh, J. L.; Phamduy, T. B.; Corr, D. T.; Chrisey, D. B.

2012-06-01

Advancements in biological and chemical warfare has allowed for the creation of novel toxins necessitating a universal, real-time sensor. We have used a function-based biosensor employing impedance spectroscopy using a low current density AC signal over a range of frequencies (62.5 Hz-64 kHz) to measure the electrical impedance of a confluent epithelial cell monolayer at 120 sec intervals. Madin Darby canine kidney (MDCK) epithelial cells were grown to confluence on thin film interdigitated gold electrodes. A stable impedance measurement of 2200 Ω was found after 24 hrs of growth. After exposure to cytotoxins anthrax lethal toxin and etoposide, the impedance decreased in a linear fashion resulting in a 50% drop in impedance over 50hrs showing significant difference from the control sample (~20% decrease). Immunofluorescent imaging showed that apoptosis was induced through the addition of toxins. Similarities of the impedance signal shows that the mechanism of cellular death was the same between ALT and etoposide. A revised equivalent circuit model was employed in order to quantify morphological changes in the cell monolayer such as tight junction integrity and cell surface area coverage. This model showed a faster response to cytotoxin (2 hrs) compared to raw measurements (20 hrs). We demonstrate that herein that impedance spectroscopy of epithelial monolayers serves as a real-time non-destructive sensor for unknown pathogens.

14. Chatter suppression through variable impedance and smart fluids

SciTech Connect

Segalman, D.; Redmond, J.

1996-02-01

A novel approach to mitigating chatter vibrations in machine tools is presented. Encountered in many types of metal removal processes, chatter is a dangerous condition which results from the interaction of the cutting dynamics with the modal characteristics of the machine-workpiece assembly. Tool vibrations are recored on the surface of the workpiece during metal removal, imposing a waviness which alters the chip thickness during subsequent cutting passes. Deviations from the nominal chip thickness effect changes in the cutting force which, under certain conditions, can further excite vibrations. The chatter mitigation strategy presented is based on periodically altering the impedance of the cutting tool assembly. A cyclic electric (or magnetic) field is applied to the spindle quill which contains an electro-rheological (or magneto-rheological) fluid. The variable yield stress in the fluid affects the coupling of the spindle to the machine tool structure, changing the natural frequency of oscillation. Altering the modal characteristics in this fashion disrupts the modulation of current tool vibrations with previous tool vibrations recorded on the workpiece surface. Results from a simulated milling process reveal that significant reductions in vibration amplitude can be achieved through proper selection of fluid and excitation frequency.

15. Ultra-wideband impedance sensor

DOEpatents

McEwan, T.E.

1999-03-16

The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks. 2 figs.

16. Ultra-wideband impedance sensor

DOEpatents

McEwan, Thomas E.

1999-01-01

The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks.

17. Impedance in School Screening Programs.

ERIC Educational Resources Information Center

Robarts, John T.

1985-01-01

This paper examines the controversy over use of impedance screening in public schools to identify students with hearing problems, including otitis media, a common ear condition in infants and young children. It cites research that questions the value of pure tone screening as a single test and raises critics' objections to the use of impedance,…

18. Impedance in School Screening Programs.

ERIC Educational Resources Information Center

Robarts, John T.

1985-01-01

This paper examines the controversy over use of impedance screening in public schools to identify students with hearing problems, including otitis media, a common ear condition in infants and young children. It cites research that questions the value of pure tone screening as a single test and raises critics' objections to the use of impedance,…

19. Experimental verification of the feasibility of the cardiovascular impedance simulator.

PubMed

Gwak, Kwan-Woong; Paden, Brad E; Antaki, James F; Ahn, Ihn-Seok

2010-05-01

Mock circulatory systems (MCS) are often used for the development of cardiovascular devices and for the study of the dynamics of blood flow through the cardiovascular system. However, conventional MCS suffer from the repeatability, flexibility, and precision problems because they are typically built up with passive and linear fluidic elements such as compliance chamber, manual valve, and tube. To solve these limitations, we have developed an impedance simulator, comprised of a feedback-controlled positive displacement pump that is capable of generating analogous dynamic characteristics as the conventional fluidic elements would generate, thereby replacing the conventional passive fluidic elements that often cause problems. The impedance simulator is experimentally proven to reproduce the impedance of the various discrete elements, such as resistance and compliance of the cardiovascular system model, as well as the combined impedances of them.

20. Electromagnetic scattering by impedance structures

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Griesser, Timothy

1987-01-01

The scattering of electromagnetic waves from impedance structures is investigated, and current work on antenna pattern calculation is presented. A general algorithm for determining radiation patterns from antennas mounted near or on polygonal plates is presented. These plates are assumed to be of a material which satisfies the Leontovich (or surface impedance) boundary condition. Calculated patterns including reflection and diffraction terms are presented for numerious geometries, and refinements are included for antennas mounted directly on impedance surfaces. For the case of a monopole mounted on a surface impedance ground plane, computed patterns are compared with experimental measurements. This work in antenna pattern prediction forms the basis of understanding of the complex scattering mechanisms from impedance surfaces. It provides the foundation for the analysis of backscattering patterns which, in general, are more problematic than calculation of antenna patterns. Further proposed study of related topics, including surface waves, corner diffractions, and multiple diffractions, is outlined.

1. Random Vibrations

NASA Technical Reports Server (NTRS)

Messaro. Semma; Harrison, Phillip

2010-01-01

Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

2. Coupling between plate vibration and acoustic radiation

NASA Technical Reports Server (NTRS)

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1992-01-01

A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far-field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far-field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

3. Coupling between plate vibration and acoustic radiation

NASA Technical Reports Server (NTRS)

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1993-01-01

A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

4. Acoustic impedance testing for aeroacoustic applications

NASA Astrophysics Data System (ADS)

Schultz, Todd

Accurate acoustic propagation models are required to characterize and subsequently reduce aircraft engine noise. These models ultimately rely on acoustic impedance measurements of candidate materials used in sound-absorbing liners. The standard two-microphone method (TMM) is widely used to estimate acoustic impedance but is limited in frequency range and does not provide uncertainty estimates, which are essential for data quality assessment and model validation. This dissertation presents a systematic framework to estimate uncertainty and extend the frequency range of acoustic impedance testing. Uncertainty estimation for acoustic impedance data using the TMM is made via two methods. The first employs a standard analytical technique based on linear perturbations and provides useful scaling information. The second uses a Monte Carlo technique that permits the propagation of arbitrarily large uncertainties. Both methods are applied to the TMM for simulated data representative of sound-hard and sound-soft acoustic materials. The results indicate that the analytical technique can lead to false conclusions about the magnitude and importance of specific error sources. Furthermore, the uncertainty in acoustic impedance is strongly dependent on the frequency and the uncertainty in the microphone locations. Next, an increased frequency range of acoustic impedance testing is investigated via two methods. The first method reduces the size of the test specimen (from 25.4 mm square to 8.5 mm square) and uses the standard TMM. This method has issues concerning specimen nonuniformity because the small specimens may not be representative of the material. The second method increases the duct cross section and, hence, the required complexity of the sound field propagation model. A comparison among all three methods is conducted for each of the three specimens: two different ceramic tubular specimens and a single degree-of-freedom liner. The results show good agreement between the

5. Tunable sound transmission at an impedance-mismatched fluidic interface assisted by a composite waveguide

NASA Astrophysics Data System (ADS)

Zhang, Hui; Wei, Zhi; Fan, Li; Qu, Jianmin; Zhang, Shu-Yi

2016-10-01

We report a composite waveguide fabricated by attaching a coupling aperture to a waveguide. The acoustic impedance of the composite waveguide can be regulated by merely controlling its coupling vibrations, depending on its structure size. By changing the size to adjust the acoustic impedance of the composite waveguide at an impedance-mismatched fluidic interface, tunable sound transmission at the desired frequencies is achieved. The reported composite waveguide provides a new method for sound regulation at a mismatched fluidic interface and has extensive frequency hopping and frequency agility applications in air-water sound communication.

6. Tunable sound transmission at an impedance-mismatched fluidic interface assisted by a composite waveguide

PubMed Central

Zhang, Hui; Wei, Zhi; Fan, Li; Qu, Jianmin; Zhang, Shu-yi

2016-01-01

We report a composite waveguide fabricated by attaching a coupling aperture to a waveguide. The acoustic impedance of the composite waveguide can be regulated by merely controlling its coupling vibrations, depending on its structure size. By changing the size to adjust the acoustic impedance of the composite waveguide at an impedance-mismatched fluidic interface, tunable sound transmission at the desired frequencies is achieved. The reported composite waveguide provides a new method for sound regulation at a mismatched fluidic interface and has extensive frequency hopping and frequency agility applications in air-water sound communication. PMID:27698379

7. Vibrational energy relaxation of large-amplitude vibrations in liquids.

PubMed

Zhang, Baofeng; Stratt, Richard M

2012-07-14

Given the limited intermolecular spaces available in dense liquids, the large amplitudes of highly excited, low frequency vibrational modes pose an interesting dilemma for large molecules in solution. We carry out molecular dynamics calculations of the lowest frequency ("warping") mode of perylene dissolved in liquid argon, and demonstrate that vibrational excitation of this mode should cause identifiable changes in local solvation shell structure. But while the same kinds of solvent structural rearrangements can cause the non-equilibrium relaxation dynamics of highly excited diatomic rotors in liquids to differ substantially from equilibrium dynamics, our simulations also indicate that the non-equilibrium vibrational energy relaxation of large-amplitude vibrational overtones in liquids should show no such deviations from linear response. This observation seems to be a generic feature of large-moment-arm vibrational degrees of freedom and is therefore probably not specific to our choice of model system: The lowest frequency (largest amplitude) cases probably dissipate energy too quickly and the higher frequency (more slowly relaxing) cases most likely have solvent displacements too small to generate significant nonlinearities in simple nonpolar solvents. Vibrational kinetic energy relaxation, in particular, seems to be especially and surprisingly linear.

8. Detection of complex formation and determination of intermolecular geometry through electrical anharmonic coupling of molecular vibrations using electron-vibration-vibration two-dimensional infrared spectroscopy.

PubMed

Guo, Rui; Fournier, Frederic; Donaldson, Paul M; Gardner, Elizabeth M; Gould, Ian R; Klug, David R

2009-10-14

Electrical interactions between molecular vibrations can be non-linear and thereby produce intermolecular coupling even in the absence of a chemical bond. We use this fact to detect the formation of an intermolecular complex using electron-vibration-vibration two-dimensional infrared spectroscopy (EVV 2DIR) and also to determine the distance and angle between the two molecular species.

9. The transmission of vertical vibration through seats: Influence of the characteristics of the human body

NASA Astrophysics Data System (ADS)

Toward, Martin G. R.; Griffin, Michael J.

2011-12-01

The transmission of vibration through a seat depends on the impedance of the seat and the apparent mass of the seat occupant. This study was designed to determine how factors affecting the apparent mass of the body (age, gender, physical characteristics, backrest contact, and magnitude of vibration) affect seat transmissibility. The transmission of vertical vibration through a car seat was measured with 80 adults (41 males and 39 females aged 18-65) at frequencies between 0.6 and 20 Hz with two backrest conditions (no backrest and backrest), and with three magnitudes of random vibration (0.5, 1.0, and 1.5 m s -2 rms). Linear regression models were used to study the effects of subject physical characteristics (age, gender, and anthropometry) and features of their apparent mass (resonance frequency, apparent mass at resonance and at 12 Hz) on the measured seat transmissibility. The strongest predictor of both the frequency of the principal resonance in seat transmissibility and the seat transmissibility at resonance was subject age, with other factors having only marginal effects. The transmissibility of the seat at 12 Hz depended on subject age, body mass index, and gender. Although subject weight was strongly associated with apparent mass, weight was not strongly associated with seat transmissibility. The resonance frequency of the seat decreased with increases in the magnitude of the vibration excitation and increased when subjects made contact with the backrest. Inter-subject variability in the resonance frequency and transmissibility at resonance was less with greater vibration excitation, but was largely unaffected by backrest contact. A lumped parameter seat-person model showed that changes in seat transmissibility with age can be predicted from changes in apparent mass with age, and that the dynamic stiffness of the seat appeared to increase with increased loading so as to compensate for increases in subject apparent mass associated with increased sitting

10. Coal storage hopper with vibrating-screen agitator

DOEpatents

Daw, C.S.; Lackey, M.E.; Sy, R.L.

1982-04-27

The present invention is directed to a vibrating screen agitator in a coal storage hopper for assuring the uniform feed of coal having sufficient moisture content to effect agglomeration and bridging thereof in the coal hopper from the latter onto a conveyer mechanism. The vibrating scrren agitator is provided by a plurality of transversely oriented and vertically spaced apart screens in the storage hopper with a plurality of vertically oriented rods attached to the screens. The rods are vibrated to effect the vibration of the screens and the breaking up of agglomerates in the coal which might impede the uniform flow of the coal from the hopper onto a conveyer.

11. Impedance-estimation methods, modeling methods, articles of manufacture, impedance-modeling devices, and estimated-impedance monitoring systems

SciTech Connect

Richardson, John G

2009-11-17

An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.

12. I/O impedance controller

DOEpatents

Ruesch, Rodney; Jenkins, Philip N.; Ma, Nan

2004-03-09

There is disclosed apparatus and apparatus for impedance control to provide for controlling the impedance of a communication circuit using an all-digital impedance control circuit wherein one or more control bits are used to tune the output impedance. In one example embodiment, the impedance control circuit is fabricated using circuit components found in a standard macro library of a computer aided design system. According to another example embodiment, there is provided a control for an output driver on an integrated circuit ("IC") device to provide for forming a resistor divider network with the output driver and a resistor off the IC device so that the divider network produces an output voltage, comparing the output voltage of the divider network with a reference voltage, and adjusting the output impedance of the output driver to attempt to match the output voltage of the divider network and the reference voltage. Also disclosed is over-sampling the divider network voltage, storing the results of the over sampling, repeating the over-sampling and storing, averaging the results of multiple over sampling operations, controlling the impedance with a plurality of bits forming a word, and updating the value of the word by only one least significant bit at a time.

13. Active vibration control in Duffing mechanical systems using dynamic vibration absorbers

NASA Astrophysics Data System (ADS)

Beltrán-Carbajal, F.; Silva-Navarro, G.

2014-07-01

This paper deals with the multi-frequency harmonic vibration suppression problem in forced Duffing mechanical systems using passive and active linear mass-spring-damper dynamic vibration absorbers. An active vibration absorption scheme is proposed to extend the vibrating energy dissipation capability of a passive dynamic vibration absorber for multiple excitation frequencies and, simultaneously, to perform reference position trajectory tracking tasks planned for the nonlinear primary system. A differential flatness-based disturbance estimation scheme is also described to estimate the unknown multiple time-varying frequency disturbance signal affecting the differentially flat nonlinear vibrating mechanical system dynamics. Some numerical simulation results are provided to show the efficient performance of the proposed active vibration absorption scheme and the fast estimation of the vibration disturbance signal.

14. Scattering patterns of dihedral corner reflectors with impedance surface impedances

NASA Astrophysics Data System (ADS)

Balanis, Constantine A.; Griesser, Timothy; Liu, Kefeng

The radar cross section patterns of lossy dihedral corner reflectors are calculated using a uniform geometrical theory of diffraction for impedance surfaces. All terms of up to third order reflections are considered for patterns in the principal plane. The surface waves are included whenever they exist for reactive surface impedances. The dihedral corner reflectors examined have right, obtuse, and acute interior angles, and patterns over the entire 360 deg azimuthal plane are calculated. The surface impedances can be different on the four faces of the dihedral corner reflector; however, the surface impedance must be uniform over each face. Computed cross sections are compared with a moment method technique for a dielectric/ferrite absorber coating on a metallic corner reflector. The analysis of the dihedral corner reflector is important because it demonstrates many of the important scattering contributors of complex targets including both interior and exterior wedge diffraction, half-plane diffraction, and dominant multiple reflections and diffractions.

15. Scattering patterns of dihedral corner reflectors with impedance surface impedances

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Griesser, Timothy; Liu, Kefeng

1988-01-01

The radar cross section patterns of lossy dihedral corner reflectors are calculated using a uniform geometrical theory of diffraction for impedance surfaces. All terms of up to third order reflections are considered for patterns in the principal plane. The surface waves are included whenever they exist for reactive surface impedances. The dihedral corner reflectors examined have right, obtuse, and acute interior angles, and patterns over the entire 360 deg azimuthal plane are calculated. The surface impedances can be different on the four faces of the dihedral corner reflector; however, the surface impedance must be uniform over each face. Computed cross sections are compared with a moment method technique for a dielectric/ferrite absorber coating on a metallic corner reflector. The analysis of the dihedral corner reflector is important because it demonstrates many of the important scattering contributors of complex targets including both interior and exterior wedge diffraction, half-plane diffraction, and dominant multiple reflections and diffractions.

16. Reactanceless synthesized impedance bandpass amplifier

NASA Technical Reports Server (NTRS)

Kleinberg, L. L. (Inventor)

1985-01-01

An active R bandpass filter network is formed by four operational amplifier stages interconnected by discrete resistances. One pair of stages synthesize an equivalent input impedance of an inductance (L sub eq) in parallel with a discrete resistance (R sub o) while the second pair of stages synthesizes an equivalent input impedance of a capacitance (C sub eq) serially coupled to another discrete resistance (R sub i) coupled in parallel with the first two stages. The equivalent input impedances aggregately define a tuned resonant bandpass filter in the roll-off regions of the operational amplifiers.

17. IMPEDANCE ALARM SYSTEM

DOEpatents

Cowen, R.G.

1959-09-29

A description is given of electric protective systems and burglar alarm systems of the capacitance type in which the approach of an intruder at a place to be protected varies the capacitance in an electric circuit and the change is thereafter communicated to a remote point to actuate an alarm. According to the invention, an astable transitor multi-vibrator has the amplitude at its output voltage controlled by a change in the sensing capacitance. The sensing capacitance is effectively connected between collector and base of one stage of the multivibrator circuit through the detector-to-monitor line. The output of the detector is a small d-c voltage across the detector-to-monitor line. This d- c voltage is amplified and monitored at the other end of the line, where an appropriate alarm is actuated if a sudden change in the voltage occurs. The present system has a high degree of sensitivity and is very difficult to defeat by known techniques.

18. Efficient Simultaneous Reconstruction of Time-Varying Images and Electrode Contact Impedances in Electrical Impedance Tomography

PubMed Central

Boverman, Gregory; Isaacson, David; Newell, Jonathan C.; Saulnier, Gary J.; Kao, Tzu-Jen; Amm, Bruce C.; Wang, Xin; Davenport, David M.; Chong, David H.; Sahni, Rakesh; Ashe, Jeffrey M.

2016-01-01

In Electrical Impedance Tomography (EIT), we apply patterns of currents on a set of electrodes at the external boundary of an object, measure the resulting potentials at the electrodes, and, given the aggregate data set, reconstruct the complex conductivity and permittivity within the object. It is possible to maximize sensitivity to internal conductivity changes by simultaneously applying currents and measuring potentials on all electrodes but this approach also maximizes sensitivity to changes in impedance at the interface. We have therefore developed algorithms to assess contact impedance changes at the interface as well as to efficiently and simultaneously reconstruct internal conductivity/permittivity changes within the body. We use simple linear algebraic manipulations, the generalized SVD, and a dual-mesh finite-element-based framework to reconstruct images in real time. We are also able to efficiently compute the linearized reconstruction for a wide range of regularization parameters and to compute both the Generalized Cross-Validation (GCV) parameter as well as the L-curve, objective approaches to determining the optimal regularization parameter, in a similarly efficient manner. Results are shown using data from a normal subject and from a clinical ICU patient, both acquired with the GE GENESIS prototype EIT system, demonstrating significantly reduced boundary artifacts due to electrode drift and motion artifact. PMID:27295649

19. Vibrational spectroscopy

Treesearch

Umesh P. Agarwal; Rajai Atalla

2010-01-01

Vibrational spectroscopy is an important tool in modern chemistry. In the past two decades, thanks to significant improvements in instrumentation and the development of new interpretive tools, it has become increasingly important for studies of lignin. This chapter presents the three important instrumental methods-Raman spectroscopy, infrared (IR) spectroscopy, and...

20. Impedance Control for Robotic Rehabilitation: A Robust Markovian Approach

PubMed Central

Jutinico, Andres L.; Jaimes, Jonathan C.; Escalante, Felix M.; Perez-Ibarra, Juan C.; Terra, Marco H.; Siqueira, Adriano A. G.

2017-01-01

The human-robot interaction has played an important role in rehabilitation robotics and impedance control has been used in the regulation of interaction forces between the robot actuator and human limbs. Series elastic actuators (SEAs) have been an efficient solution in the design of this kind of robotic application. Standard implementations of impedance control with SEAs require an internal force control loop for guaranteeing the desired impedance output. However, nonlinearities and uncertainties hamper such a guarantee of an accurate force level in this human-robot interaction. This paper addresses the dependence of the impedance control performance on the force control and proposes a control approach that improves the force control robustness. A unified model of the human-robot system that considers the ankle impedance by a second-order dynamics subject to uncertainties in the stiffness, damping, and inertia parameters has been developed. Fixed, resistive, and passive operation modes of the robotics system were defined, where transition probabilities among the modes were modeled through a Markov chain. A robust regulator for Markovian jump linear systems was used in the design of the force control. Experimental results show the approach improves the impedance control performance. For comparison purposes, a standard H∞ force controller based on the fixed operation mode has also been designed. The Markovian control approach outperformed the H∞ control when all operation modes were taken into account. PMID:28883790

1. Uncertainty Analysis of the Grazing Flow Impedance Tube

NASA Technical Reports Server (NTRS)

Brown, Martha C.; Jones, Michael G.; Watson, Willie R.

2012-01-01

This paper outlines a methodology to identify the measurement uncertainty of NASA Langley s Grazing Flow Impedance Tube (GFIT) over its operating range, and to identify the parameters that most significantly contribute to the acoustic impedance prediction. Two acoustic liners are used for this study. The first is a single-layer, perforate-over-honeycomb liner that is nonlinear with respect to sound pressure level. The second consists of a wire-mesh facesheet and a honeycomb core, and is linear with respect to sound pressure level. These liners allow for evaluation of the effects of measurement uncertainty on impedances educed with linear and nonlinear liners. In general, the measurement uncertainty is observed to be larger for the nonlinear liners, with the largest uncertainty occurring near anti-resonance. A sensitivity analysis of the aerodynamic parameters (Mach number, static temperature, and static pressure) used in the impedance eduction process is also conducted using a Monte-Carlo approach. This sensitivity analysis demonstrates that the impedance eduction process is virtually insensitive to each of these parameters.

2. Linear Motor With Air Slide

NASA Technical Reports Server (NTRS)

Johnson, Bruce G.; Gerver, Michael J.; Hawkey, Timothy J.; Fenn, Ralph C.

1993-01-01

Improved linear actuator comprises air slide and linear electric motor. Unit exhibits low friction, low backlash, and more nearly even acceleration. Used in machinery in which positions, velocities, and accelerations must be carefully controlled and/or vibrations must be suppressed.

3. Linear Motor With Air Slide

NASA Technical Reports Server (NTRS)

Johnson, Bruce G.; Gerver, Michael J.; Hawkey, Timothy J.; Fenn, Ralph C.

1993-01-01

Improved linear actuator comprises air slide and linear electric motor. Unit exhibits low friction, low backlash, and more nearly even acceleration. Used in machinery in which positions, velocities, and accelerations must be carefully controlled and/or vibrations must be suppressed.

4. Plasma Impedance Spectrum Analyzer (PISA): an advanced impedance probe for measuring plasma density and other parameters

NASA Astrophysics Data System (ADS)

Rowland, D. E.; Pfaff, R. F.; Uribe, P.; Burchill, J.

2006-12-01

as close as possible to the plasma potential, collapsing the ion sheath and minimizing sheath-induced errors in the measurement of the temperature-dependent series resonance frequency. In addition, by stepping the bias voltage through a range of values, we can measure the sheath capacitance as a function of voltage and get an independent measure of the Debye length. 3) Drive voltage amplitude stepping which allows the diagnosis of sheath rectification and non-linear effects that may drive harmonics of the plasma / upper hybrid frequency. By stepping the amplitude through a range, we can also find the optimal drive voltage which provides a reasonable SNR while minimizing the impedance probe's impact on other instruments, such as high frequency electric field probes. We present flight data from representative souding rocket flights of the Goddard Impedance Probe and discuss the instrument performance, error bars, and future improvements.

5. Vibration Control of Large Structures.

DTIC Science & Technology

1987-09-01

Vibration Control of a Beam with a Proof-Mass Actuator," AIAA Guidance, Navigation and Control Conference, Monterey, CA, August, 19S7. Haviland , J. K...Conference, Monterey, CA, August, 1987. Haviland , J. K., Politansky, H., Lim, T. W., and Pilkey, W. D., "The Control of Linear Proof-Mass Dampers," Sixth

6. Vibrational soliton: an experimental overview

SciTech Connect

Bigio, I.J.

1986-03-08

To date the most convincing evidence of vibrational solitons in biopolymers has been found in two very disparate systems: Davydov-like excitations in hydrogen-bonded linear chains (acetanilide and N-methylacetamide) which are not biopolymers but plausible structural paradigms for biopolymers, and longitudinal accoustic modes of possibly nonlinear character in biologically viable DNA. 17 refs., 4 figs.

7. Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators

PubMed Central

Kim, Pil-Jong; Kim, Hong-Gee

2015-01-01

Objectives The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC. PMID:25984472

8. Good Vibrations

NASA Technical Reports Server (NTRS)

2001-01-01

A Small Business Innovation Research (SBIR) sponsorship from NASA's Dryden Flight Research Center, assisted MetroLaser, of Irvine, California, in the development of a self-aligned laser vibrometer system. VibroMet, capable of measuring surface vibrations in a variety of industries, provides information on the structural integrity and acoustical characteristics of manufactured products. This low-cost, easy-to-use sensor performs vibration measurement from distances of up to three meters without the need for adjustment. The laser beam is simply pointed at the target and the system then uses a compact laser diode to illuminate the surface and to subsequently analyze the reflected light. The motion of the surface results in a Doppler shift that is measured with very high precision. VibroMet is considered one of the many behind-the-scenes tools that can be relied on to assure the quality, reliability and safety of everything from airplane panels to disk brakes

9. Study of molecular vibration by coupled cluster method: Bosonic approach

NASA Astrophysics Data System (ADS)

Banik, Subrata; Pal, Sourav; Prasad, M. Durga

2015-01-01

The vibrational coupled cluster method in bosonic representation is formulated to describe the molecular anharmonic vibrational spectra. The vibrational coupled cluster formalism is based on Watson Hamiltonian in normal coordinates. The vibrational excited states are described using coupled cluster linear response theory (CCLRT). The quality of the coupled cluster wave function is analyzed. Specifically, the mean displacement values of the normal coordinates and expectation values of the square of the normal coordinates of different vibrational states are calculated. A good agreement between the converged full CI results and coupled cluster results is found for the lower lying vibrational states.

10. Biomolecular Imaging with Coherent Nonlinear Vibrational Microscopy

PubMed Central

Chung, Chao-Yu; Boik, John; Potma, Eric O.

2014-01-01

Optical imaging with spectroscopic vibrational contrast is a label-free solution for visualizing, identifying, and quantifying a wide range of biomolecular compounds in biological materials. Both linear and nonlinear vibrational microscopy techniques derive their imaging contrast from infrared active or Raman allowed molecular transitions, which provide a rich palette for interrogating chemical and structural details of the sample. Yet nonlinear optical methods, which include both second-order sum-frequency generation (SFG) and third-order coherent Raman scattering (CRS) techniques, offer several improved imaging capabilities over their linear precursors. Nonlinear vibrational microscopy features unprecedented vibrational imaging speeds, provides strategies for higher spatial resolution, and gives access to additional molecular parameters. These advances have turned vibrational microscopy into a premier tool for chemically dissecting live cells and tissues. This review discusses the molecular contrast of SFG and CRS microscopy and highlights several of the advanced imaging capabilities that have impacted biological and biomedical research. PMID:23245525

11. Impedance studies - Part 4: The APS impedance budget

SciTech Connect

1988-07-01

This note will wrap up the numerical results that were obtained in our calculations of the wake potentials, the loss factors, and the impedances for a variety of structures in the APS storage ring. It consists of five sections and one appendix. Section 1 is an introduction. Section 2 summarizes the hand calculations. The computer calculations are the subject 1 of Section 3. Section 4 discusses several tests in our numerical methods. Section 5 presents the APS impedance budget, along with some discussion. The appendix contains the figures of the structures, the longitudinal/transverse wake potentials and the real/imaginary part of the impedances of various sorts of geometries that have been included in the budget.

12. Vibration syndrome

PubMed Central

Stewart, Alice M.; Goda, D. F

1970-01-01

Stewart, Alice M., and Goda, D. F. (1970).Brit. J. industr. Med.,27, 19-27. Vibration syndrome. Raynaud's phenomenon, or the finger blanching of men who work with vibrating tools, is undoubtedly due to vasospasm. Nevertheless the abnormal element in the situation is not a series of traumatized nerve endings but a deposition of callus under the palmar surfaces of fingers and thumbs. This deposition is a late consequence of the most distinctive, but not necessarily the most painful, of the numerous effects incurred as a result of the tool speed being completely out of the control of the operator and of the tool/component rebound being only partially under his control. The replacement of soft finger pads by rigid callus is also the only consequence of hard manual work to show how necessary it is for a structure like a finger–which is largely composed of bones, joints, tendons, and skin–to have a reservoir, the equivalent of a blood-filled sponge, between every joint to accommodate any sudden reduction in blood volume, or indeed any sudden increase in the volume of blood held in the arteries and veins relative to the amount held in the capillaries. It is still a moot point whether users of vibrating tools have more arm complaints of a serious nature than other manual workers. They do, however, have a multiplicity of aches and pains, ascribable to various causes including tool speed and tool/component rebound, which are in toto very sensitive to such things as blunt impacts, hard components, heavy tools, awkward jobs, and inept handling of tools, whether the ineptness be due to inexperience or to advancing age. Users of vibrating tools have more pain in the hands and wrists than in the elbows and shoulders, but the pain tends to persist longer in the latter sites than in the former sites. PMID:5418915

13. [Monitoring cervical dilatation by impedance].

PubMed

Salvat, J; Lassen, M; Sauze, C; Baud, S; Salvat, F

1992-01-01

Several different physics procedures have been tried to mechanize the recording of partograms. Can a measure of impedance of tissue Z using potential difference V, according to Ohm's law V = Z1, and 1 is a constant, be correlated with a measure of cervical dilatation using vaginal examination? This was our hypothesis. The tissue impedance meter was made to our design and applied according to a bipolar procedure. Our work was carried out on 28 patients. 10 patients were registered before labour started in order to test the apparatus and to record the impedance variations without labour taking place, and 18 patients were registered in labour to see whether there was any correlation. The level of impedance in the cervix without labour was 302.7 Ohms with a deviation of 8.2. Using student's t tests it was found that there was a significant correlation (p less than 0.001) in four measurements between the impedance measure and measures obtained by extrapolating the degrees of dilatation calculated from vaginal examination. This is a preliminary study in which we have defined the conditions that are necessary to confirm these first results and to further develop the method.

14. Mathematical simulation of sound propagation in a flow channel with impedance walls

NASA Astrophysics Data System (ADS)

Osipov, A. A.; Reent, K. S.

2012-07-01

The paper considers the specifics of calculating tonal sound propagating in a flow channel with an installed sound-absorbing device. The calculation is performed on the basis of numerical integrating on linearized nonstationary Euler equations using a code developed by the authors based on the so-called discontinuous Galerkin method. Using the linear theory of small perturbations, the effect of the sound-absorbing lining of the channel walls is described with the modified value of acoustic impedance proposed by the authors, for which, under flow channel conditions, the traditional classification of the active and reactive types of lining in terms of the real and imaginary impedance values, respectively, remains valid. To stabilize the computation process, a generalized impedance boundary condition is proposed in which, in addition to the impedance value itself, some additional parameters are introduced characterizing certain fictitious properties of inertia and elasticity of the impedance surface.

15. Symmetry impedes symmetry discrimination.

PubMed

Tjan, Bosco S; Liu, Zili

2005-12-16

Objects in the world, natural and artificial alike, are often bilaterally symmetric. The visual system is likely to take advantage of this regularity to encode shapes for efficient object recognition. The nature of encoding a symmetric shape, and of encoding any departure from it, is therefore an important matter in visual perception. We addressed this issue of shape encoding empirically, noting that a particular encoding scheme necessarily leads to a specific profile of sensitivity in perceptual discriminations. We studied symmetry discrimination using human faces and random dots. Each face stimulus was a frontal view of a three-dimensional (3-D) face model. The 3-D face model was a linearly weighted average (a morph) between the model of an original face and that of the corresponding mirror face. Using this morphing technique to vary the degree of asymmetry, we found that, for faces and analogously generated random-dot patterns alike, symmetry discrimination was worst when the stimuli were nearly symmetric, in apparent opposition to almost all studies in the literature. We analyzed the previous work and reconciled the old and new results using a generic model with a simple nonlinearity. By defining asymmetry as the minimal difference between the left and right halves of an object, we found that the visual system was disproportionately more sensitive to larger departures from symmetry than to smaller ones. We further demonstrated that our empirical and modeling results were consistent with Weber-Fechner's and Stevens's laws.

16. Uncertainties in Transfer Impedance Calculations

NASA Astrophysics Data System (ADS)

Schippers, H.; Verpoorte, J.

2016-05-01

The shielding effectiveness of metal braids of cables is governed by the geometry and the materials of the braid. The shielding effectiveness can be characterised by the transfer impedance of the metal braid. Analytical models for the transfer impedance contain in general two components, one representing diffusion of electromagnetic energy through the metal braid, and a second part representing leakage of magnetic fields through the braid. Possible sources of uncertainties in the modelling are inaccurate input data (for instance, the exact size of the braid diameter or wire diameter are not known) and imperfections in the computational model. The aim of the present paper is to estimate effects of variations of input data on the calculated transfer impedance.

17. Wide operation frequency band magnetostrictive vibration power generator using nonlinear spring constant by permanent magnet

NASA Astrophysics Data System (ADS)

Furumachi, S.; Ueno, T.

2016-04-01

We study magnetostrictive vibration based power generator using iron-gallium alloy (Galfenol). The generator is advantages over conventional, such as piezoelectric material in the point of high efficiency highly robust and low electrical impedance. Generally, the generator exhibits maximum power when its resonant frequency matches the frequency of ambient vibration. In other words, the mismatch of these frequencies results in significant decrease of the output. One solution is making the spring characteristics nonlinear using magnetic force, which distorts the resonant peak toward higher or lower frequency side. In this paper, vibrational generator consisting of Galfenol plate of 6 by 0.5 by 13 mm wound with coil and U shape-frame accompanied with plates and pair of permanent magnets was investigated. The experimental results show that lean of resonant peak appears attributed on the non-linear spring characteristics, and half bandwidth with magnets is 1.2 times larger than that without. It was also demonstrated that the addition of proof mass is effective to increase the sensitivity but also the bandwidth. The generator with generating power of sub mW order is useful for power source of wireless heath monitoring for bridge and factory machine.

18. Biomechanical models for vibration feedthrough to hands and head for a semisupine pilot.

PubMed

Jex, H R; Magdaleno, R E

1978-01-01

A series of tracking experiments under vibration has been carried out on the AMRL/BBV shaker facilities covering three axes of vibration with sinusoidal and random waveforms and different control stick configurations. Based on this and other data, a lumped-parameter biomechanical model has been evolved to suit the needs of aircraft control system designers for the new generation of low-altitude, high-speed bombers and highly maneuverable fighters. This paper shows that measured vibration feedthrough to hands and head can be adequately described by this model when linearized about the appropriate configuration of display, posture, and control. The model includes effects of: semisupine torso; sliding hip, plus rocking chest supported on a compliant buttocks/seat; head bobbing on an articulated neck; upper arm and forearm links plus grip-interface compliance, driven by an active neuromuscular system; elbow rest (optional); and stick "feel system" dynamics. Examples are given of the model's application to predict effects of: a 65 degrees semisupine seat, apparent impedance increase of a control stick under pilot control, and a sliding arm rest.

19. Active impedance metasurface with full 360° reflection phase tuning

PubMed Central

Zhu, Bo O.; Zhao, Junming; Feng, Yijun

2013-01-01

Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas. PMID:24162366

20. Microfabricated thin film impedance sensor & AC impedance measurements.

PubMed

Yu, Jinsong; Liu, Chung-Chiun

2010-01-01

Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (∼3 μm) and sand (∼300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness.

1. Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements

PubMed Central

Yu, Jinsong; Liu, Chung-Chiun

2010-01-01

Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (∼3 μm) and sand (∼300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. PMID:22219690

2. Radial vibrations of BPS skyrmions

NASA Astrophysics Data System (ADS)

Adam, C.; Haberichter, M.; Romanczukiewicz, T.; Wereszczynski, A.

2016-11-01

We study radial vibrations of spherically symmetric Skyrmions in the Bogomol'nyi-Prasad-Sommerfield Skyrme model. Concretely, we numerically solve the linearized field equations for small fluctuations in a Skyrmion background, both for linearly stable oscillations and for (unstable) resonances. This is complemented by numerical solutions of the full nonlinear system, which confirm all the results of the linear analysis. In all cases, the resulting fundamental excitation provides a rather accurate value for the Roper resonance, supporting the hypothesis that the Bogomol'nyi-Prasad-Sommerfield Skyrme model already gives a reasonable approximate description of this resonance. Furthermore, for many potentials additional higher resonances appear, again in agreement with known experimental results.

3. AC impedance analysis of polypyrrole thin films

NASA Technical Reports Server (NTRS)

Penner, Reginald M.; Martin, Charles R.

1987-01-01

The AC impedance spectra of thin polypyrrole films were obtained at open circuit potentials from -0.4 to 0.4 V vs SCE. Two limiting cases are discussed for which simplified equivalent circuits are applicable. At very positive potentials, the predominantly nonfaradaic AC impedance of polypyrrole is very similar to that observed previously for finite porous metallic films. Modeling of the data with the appropriate equivalent circuit permits effective pore diameter and pore number densities of the oxidized film to be estimated. At potentials from -0.4 to -0.3 V, the polypyrrole film is essentially nonelectronically conductive and diffusion of polymer oxidized sites with their associated counterions can be assumed to be linear from the film/substrate electrode interface. The equivalent circuit for the polypyrrole film at these potentials is that previously described for metal oxide, lithium intercalation thin films. Using this model, counterion diffusion coefficients are determined for both semi-infinite and finite diffusion domains. In addition, the limiting low frequency resistance and capacitance of the polypyrrole thin fims was determined and compared to that obtained previously for thicker films of the polymer. The origin of the observed potential dependence of these low frequency circuit components is discussed.

4. Nonlinear feature identification of impedance-based structural health monitoring

SciTech Connect

Rutherford, A. C.; Park, G. H.; Sohn, H.; Farrar, C. R.

2004-01-01

The impedance-based structural health monitoring technique, which utilizes electromechanical coupling properties of piezoelectric materials, has shown feasibility for use in a variety of structural health monitoring applications. Relying on high frequency local excitations (typically > 30 kHz), this technique is very sensitive to minor changes in structural integrity in the near field of piezoelectric sensors. Several damage sensitive features have been identified and used coupled with the impedance methods. Most of these methods are, however, limited to linearity assumptions of a structure. This paper presents the use of experimentally identified nonlinear features, combined with impedance methods, for structural health monitoring. Their applicability to damage detection in various frequency ranges is demonstrated using actual impedance signals measured from a portal frame structure. The performance of the nonlinear feature is compared with those of conventional impedance methods. This paper reinforces the utility of nonlinear features in structural health monitoring and suggests that their varying sensitivity in different frequency ranges may be leveraged for certain applications.

5. High Power Low Impedance Therapeutic Intracavitary Phased Array

NASA Astrophysics Data System (ADS)

Kukic, Aleksandra; Hynynen, Kullervo

2010-03-01

Ultrasound phased arrays can be used for noninvasive surgical applications, and are ideal for intracavitary applications, where their properties of dynamic focusing and beam steering compensate for the spatial constraints. Phase shifting without grating lobes requires small elements, which results in low width-thickness ratios and thus high electrical impedance. This study demonstrates, for the first time, a method of lateral coupling for the purposes of reduction of electrical impedance of linear phased arrays. Fabrication procedure for a lateral coupled array for therapeutic purposes is demonstrated. Impedance analysis of a thickness mode driven phased array is compared to a lateral coupling mode array. For a 1.5 MHz resonant frequency, impedance drop of 33 times is seen at antiresonance, and 6 times at resonance. Thickness mode phase peak is never higher than -41.3°, whereas it reaches to 42.3° in the lateral coupling mode. This allows for a phase crossing of 0° for lateral mode transducer, where the impedance is 111Ω, eliminating the need for matching circuits. Scanning laser vibrometer measurements of surface displacements show that a lateral mode element can achieve intensity levels greater than 20 W/cm2, when an unmatched element is tested.

6. Sensing Estrogen with Electrochemical Impedance Spectroscopy

PubMed Central

Li, Jing; Kim, Byung Kun; Im, Ji-Eun; Choi, Han Nim; Kim, Dong-Hwan; Cho, Seong In

2016-01-01

This study demonstrates the application feasibility of electrochemical impedance spectroscopy (EIS) in measuring estrogen (17β-estradiol) in gas phase. The present biosensor gives a linear response (R2 = 0.999) for 17β-estradiol vapor concentration from 3.7 ng/L to 3.7 × 10−4 ng/L with a limit of detection (3.7 × 10−4 ng/L). The results show that the fabricated biosensor demonstrates better detection limit of 17β-estradiol in gas phase than the previous report with GC-MS method. This estrogen biosensor has many potential applications for on-site detection of a variety of endocrine disrupting compounds (EDCs) in the gas phase. PMID:27803838

7. Algorithmic Error Correction of Impedance Measuring Sensors

PubMed Central

Starostenko, Oleg; Alarcon-Aquino, Vicente; Hernandez, Wilmar; Sergiyenko, Oleg; Tyrsa, Vira

2009-01-01

This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance. PMID:22303177

8. Rotorcraft Smoothing Via Linear Time Periodic Methods

DTIC Science & Technology

2007-07-01

Optimal Control Methodology for Rotor Vibration Smoothing . . 30 vii Page IV. Mathematic Foundations of Linear Time Periodic Systems . . . . 33 4.1 The...62 6.3 The Maximum Likelihood Estimator . . . . . . . . . . . 63 6.4 The Cramer-Rao Inequality . . . . . . . . . . . . . . . . 66 6.4.1 Statistical ...adjustments for vibration reduction. 2.2.2.4 1980’s to late 1990’s. Rotor vibrational reduction methods during the 1980’s began to adopt a mathematical

9. Motion of liquid drops on surfaces induced by asymmetric vibration: role of contact angle hysteresis.

PubMed

Mettu, Srinivas; Chaudhury, Manoj K

2011-08-16

Hysteresis of wetting, like the Coulombic friction at solid/solid interface, impedes the motion of a liquid drop on a surface when subjected to an external field. Here, we present a counterintuitive example, where some amount of hysteresis enables a drop to move on a surface when it is subjected to a periodic but asymmetric vibration. Experiments show that a surface either with a negligible or high hysteresis is not conducive to any drop motion. Some finite hysteresis of contact angle is needed to break the periodic symmetry of the forcing function for the drift to occur. These experimental results are consistent with simulations, in which a drop is approximated as a linear harmonic oscillator. The experiment also sheds light on the effect of the drop size on flow reversal, where drops of different sizes move in opposite directions due to the difference in the phase of the oscillation of their center of mass.

10. Acoustic Ground-Impedance Meter

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J.

1983-01-01

Helmoltz resonator used in compact, portable meter measures acoustic impedance of ground or other surfaces. Earth's surface is subject of increasing acoustical investigations because of its importance in aircraft noise prediction and measurment. Meter offers several advantages. Is compact and portable and set up at any test site, irrespective of landscape features, weather or other environmental condition.

11. The Aberdeen Impedance Imaging System.

PubMed

Kulkarni, V; Hutchison, J M; Mallard, J R

1989-01-01

The Aberdeen Impedance Imaging System is designed to reconstruct 2 dimensional images of the average distribution of the amplitude and phase of the complex impedance within a 3 dimensional region. The system uses the four electrode technique in a 16 electrode split-array. The system hardware consists of task-orientated electronic modules for: driving a constant current, multiplexing the current drive, demultiplexing peripheral voltages, differential amplification, phase sensitive detection and low-pass filtration, digitisation with a 14 bit analog to digital converter (ADC), and -control logic for the ADC and multiplexors. A BBC microprocessor (Master series), initiates a controlled sequence for the collection of a number of data sets which are averaged and stored on disk. Image reconstruction is by a process of convolution-backprojection similar to the fan-beam reconstruction of computerised tomography and is also known as Equipotential Backprojection. In imaging impedance changes associated with fracture healing the changes may be large enough to allow retrieval of both the amplitude and phase of the complex impedance. Sequential imaging of these changes would necessitate monitoring electronic and electrode drift by imaging an equivalent region of the contralateral limb. Differential images could be retrieved when the image of the normal limb is the image template. Better characterisation of tissues would necessitate a cleaner retrieval of the quadrature signal.

12. Characteristic impedance of microstrip lines

NASA Technical Reports Server (NTRS)

Bailey, M. C.; Deshpande, M. D.

1989-01-01

The dyadic Green's function for a current embedded in a grounded dielectric slab is used to analyze microstrip lines at millimeter wave frequencies. The dyadic Green's function accounts accurately for fringing fields and dielectric cover over the microstrip line. Using Rumsey's reaction concept, an expression for the characteristic impedance is obtained. The numerical results are compared with other reported results.

13. Calibration of electrical impedance tomography

SciTech Connect

Daily, W; Ramirez, A

2000-05-01

Over the past 10 years we have developed methods for imaging the electrical resistivity of soil and rock formations. These technologies have been called electrical resistance tomography of ERT (e.g. Daily and Owen, 1991). Recently we have been striving to extend this capability to include images of electric impedance--with a new nomenclature of electrical impedance tomography or EIT (Ramirez et al., 1999). Electrical impedance is simply a generalization of resistance. Whereas resistance is the zero frequency ratio of voltage and current, impedance includes both the magnitude and phase relationship between voltage and current at frequency. This phase and its frequency behavior is closely related to what in geophysics is called induced polarization or (Sumner, 1976). Why is this phase or IP important? IP is known to be related to many physical phenomena of importance so that image of IP will be maps of such things as mineralization and cation exchange IP (Marshall and Madden, 1959). Also, it is likely that IP, used in conjunction with resistivity, will yield information about the subsurface that can not be obtained by either piece of information separately. In order to define the accuracy of our technologies to image impedance we have constructed a physical model of known impedance that can be used as a calibration standard. It consists of 616 resistors, along with some capacitors to provide the reactive response, arranged in a three dimensional structure as in figure 1. Figure 2 shows the construction of the network and defines the coordinate system used to describe it. This network of components is a bounded and discrete version of the unbounded and continuous medium with which we normally work (the subsurface). The network has several desirable qualities: (1) The impedance values are known (to the accuracy of the component values). (2) The component values and their 3D distribution is easily controlled. (3) Error associated with electrode noise is eliminated. (4

14. DOWNHOLE VIBRATION MONITORING AND CONTROL SYSTEM

SciTech Connect

Martin E. Cobern

2003-02-01

The purpose of this program is to develop the Drilling Vibration Monitoring & Control System (DVMCS) to both record and reduce drilling vibrations in a ''smart'' drill string. It is composed of two main elements. The first is a multi-axis active vibration damper to minimize harmful axial, lateral and torsional vibrations, and thereby increase both rate of penetration (ROP) and bit life, as well that the life of other drillstring components. The hydraulic impedance (hardness) of this damper will be continuously adjusted using unique technology that is robust, fast-acting and reliable. The second component is a real-time system to monitor 3-axis drillstring vibration, and related parameters including weight- and torque-on-bit (TOB) and temperature. This monitor will determine the current vibration environment and adjust the damper accordingly. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. Phase I of this program addresses an evaluation of the environment in which the DVMCS will operate; modeling of a drillstring response including the active damper; a top-level design of the mechanical and electronic systems; analyzing the anticipated performance of the damper by modeling and laboratory testing of small prototypes; and doing preliminary economic, market, environmental and financing analyses. This phase is scheduled to last fourteen months, until November 30, 2003. During this first quarter, significant progress was achieved on the first two objectives, and work was begun on several others. Initial designs of the DVMCS are underway.

15. Enhancement of the vibration stability of a microdiffraction goniometer.

SciTech Connect

Lee, S. H.; Preissner, C.; Lai, B.; Cai, Z.; Shu, D.

2002-07-02

High-precision instrumentation, such as that for x-ray diffraction, electron microscopy, scanning probe microscopy, and other optical micropositioning systems, requires the stability that comes from vibration-isolated support structures. Structure-born vibrations impede the acquisition of accurate experimental data through such high-precision instruments. At the Advanced Photon Source, a multiaxis goniometer is installed in the 2-ID-D station for synchrotron microdiffraction investigations. However, ground vibration can excite the kinematic movements of the goniometer linkages, resulting in critically contaminated experimental data. In this paper, the vibration behavior of the goniometer has been considered. Experimental vibration measurements were conducted to define the present vibration levels and determine the threshold sensitivity of the equipment. In addition, experimental modal tests were conducted and used to guide an analytical finite element analysis. Both results were used for finding the best way to reduce the vibration levels and to develop a vibration damping/isolation structure for the 2-ID-D goniometer. The device that was designed and tested could be used to reduce local vibration levels for the vibration isolation of similar high-precision instruments.

16. Incorporating finite element techniques to simplify the impedance modeling of active structures

NASA Astrophysics Data System (ADS)

Fairweather, James A.; Craig, Kevin C.

1998-07-01

An impedance model is formulated for the prediction of the response of structures to induced-strain actuation. The approach utilizes finite element analysis (FEA) to determine the host- structure mechanical impedance. The method couples the numerically obtained impedance to an analytical vibration solution of the induced-strain actuator to determine the dynamic response of the active structure. The methodology is demonstrated in the computation of the dynamic response of a beam structure to induced-strain actuation. This system has been extensively explored by the active structures community. Comparisons of the predicted dynamic response of this structure are made to the predictions of models previously documented in the literature. Experiments are conducted for the purpose of model validation, and an excellent agreement is demonstrated between the predictions of the FEA-based impedance model and measurements made on physical systems. It is anticipated that the formulation extends the FEA-based impedance modeling approach to a broader class of active structures, those for which closed-form expressions of host-structure mechanical impedance are non- existent. Use of the FEA-based impedance approach is suggested when modeling generic distributed structures possessing material anisotropy, mass loading, and non-uniform boundary conditions.

17. Analysis of a disk-type piezoelectric ultrasonic motor using impedance matrices.

PubMed

Kim, Young H; Ha, Sung K

2003-12-01

The dynamic behavior and the performance characteristics of the disk-type traveling wave piezoelectric ultrasonic motors (USM) are analyzed using impedance matrices. The stator is divided into three coupled subsystems: an inner metal disk, a piezoelectric annular actuator with segmented electrodes, and an outer metal disk with teeth. The effects of both shear deformation and rotary inertia are taken into account in deriving an impedance matrix for the piezoelectric actuator. The impedance matrices for each subsystem then are combined into a global impedance matrix using continuity conditions at the interfaces. A comparison is made between the impedance matrix model and the three-dimensional finite element model of the piezoelectric stator, obtaining the resonance and antiresonance frequencies and the effective electromechanical coupling factors versus circumferential mode numbers. Using the calculated resonance frequency and the vibration modes for the stator and a brush model with the Coulomb friction for the stator and rotor contact, stall torque, and no-load speed versus excitation frequencies are calculated at different preloads. Performance characteristics such as speed-torque curve and the output efficiency of the USM also are estimated using the current impedance matrix and the contact model. The present impedance model can be shown to be very effective in the design of the USM.

18. Vibrational dynamics of DNA. I. Vibrational basis modes and couplings

NASA Astrophysics Data System (ADS)

Lee, Chewook; Park, Kwang-Hee; Cho, Minhaeng

2006-09-01

Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400to1800cm-1. These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs.

19. On Kinetics Modeling of Vibrational Energy Transfer

NASA Technical Reports Server (NTRS)

Gilmore, John O.; Sharma, Surendra P.; Cavolowsky, John A. (Technical Monitor)

1996-01-01

Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.

20. On Kinetics Modeling of Vibrational Energy Transfer

NASA Technical Reports Server (NTRS)

Gilmore, John O.; Sharma, Surendra P.; Cavolowsky, John A. (Technical Monitor)

1996-01-01

Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.

1. Smart Multi-Frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications.

PubMed

Harder, Rene; Diedrich, Andre; Whitfield, Jonathan S; Buchowski, Macie S; Pietsch, John B; Baudenbacher, Franz J

2016-08-01

Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3 kHz to 150 kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r(2)=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment.

2. Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes.

PubMed

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Seligman, Peter; Cowan, Robert; Shepherd, Robert

2011-06-01

Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Z(t)) and access resistance (R(a)) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between R(a) and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation, suggesting that the level of stimulation applied was creating localized changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation.

3. Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes

PubMed Central

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Seligman, Peter; Cowan, Robert; Shepherd, Robert

2011-01-01

Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Zt) and access resistance (Ra) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between Ra and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation suggesting that the level of stimulation applied was creating localised changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation. PMID:21572219

4. Smart Multi-frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications

PubMed Central

Harder, Rene; Diedrich, André; Whitfield, Jonathan; Buchowski, Maciej S.; Pietsch, John B.; Baudenbacher, Franz

2016-01-01

Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3kHz to 150kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r2=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment. PMID:26863670

5. Signatures of vibronic coupling in two-dimensional electronic-vibrational and vibrational-electronic spectroscopies.

PubMed

Gaynor, James D; Khalil, Munira

2017-09-07

Two-Dimensional Electronic-Vibrational (2D EV) spectroscopy and Two-Dimensional Vibrational-Electronic (2D VE) spectroscopy are new coherent four-wave mixing spectroscopies that utilize both electronically resonant and vibrationally resonant field-matter interactions to elucidate couplings between electronic and vibrational degrees of freedom. A system Hamiltonian is developed here to lay a foundation for interpreting the 2D EV and 2D VE signals that arise from a vibronically coupled molecular system in the condensed phase. A molecular system consisting of one anharmonic vibration and two electronic states is modeled. Equilibrium displacement of the vibrational coordinate and vibrational frequency shifts upon excitation to the first electronic excited state are included in our Hamiltonian through linear and quadratic vibronic coupling terms. We explicitly consider the nuclear dependence of the electronic transition dipole moment and demonstrate that these spectroscopies are sensitive to non-Condon effects. A series of simulations of 2D EV and 2D VE spectra obtained by varying parameters of the system, system-bath, and interaction Hamiltonians demonstrate that one of the following conditions must be met to observe signals: (1) non-zero linear and/or quadratic vibronic coupling in the electronic excited state, (2) vibrational-coordinate dependence of the electronic transition dipole moment, or (3) electronic-state-dependent vibrational dephasing dynamics. We explore how these vibronic interactions are manifested in the positions, amplitudes, and line shapes of the peaks in 2D EV and 2D VE spectroscopies.

6. Signatures of vibronic coupling in two-dimensional electronic-vibrational and vibrational-electronic spectroscopies

NASA Astrophysics Data System (ADS)

Gaynor, James D.; Khalil, Munira

2017-09-01

Two-Dimensional Electronic-Vibrational (2D EV) spectroscopy and Two-Dimensional Vibrational-Electronic (2D VE) spectroscopy are new coherent four-wave mixing spectroscopies that utilize both electronically resonant and vibrationally resonant field-matter interactions to elucidate couplings between electronic and vibrational degrees of freedom. A system Hamiltonian is developed here to lay a foundation for interpreting the 2D EV and 2D VE signals that arise from a vibronically coupled molecular system in the condensed phase. A molecular system consisting of one anharmonic vibration and two electronic states is modeled. Equilibrium displacement of the vibrational coordinate and vibrational frequency shifts upon excitation to the first electronic excited state are included in our Hamiltonian through linear and quadratic vibronic coupling terms. We explicitly consider the nuclear dependence of the electronic transition dipole moment and demonstrate that these spectroscopies are sensitive to non-Condon effects. A series of simulations of 2D EV and 2D VE spectra obtained by varying parameters of the system, system-bath, and interaction Hamiltonians demonstrate that one of the following conditions must be met to observe signals: (1) non-zero linear and/or quadratic vibronic coupling in the electronic excited state, (2) vibrational-coordinate dependence of the electronic transition dipole moment, or (3) electronic-state-dependent vibrational dephasing dynamics. We explore how these vibronic interactions are manifested in the positions, amplitudes, and line shapes of the peaks in 2D EV and 2D VE spectroscopies.

7. Modular Wideband Active Vibration Absorber

NASA Technical Reports Server (NTRS)

Smith, David R.; Zewari, Wahid; Lee, Kenneth Y.

1999-01-01

A comparison of space experiments with previous missions shows a common theme. Some of the recent experiments are based on the scientific fundamentals of instruments of prior years. However, the main distinguishing characteristic is the embodiment of advances in engineering and manufacturing in order to extract clearer and sharper images and extend the limits of measurement. One area of importance to future missions is providing vibration free observation platforms at acceptable costs. It has been shown by researchers that vibration problems cannot be eliminated by passive isolation techniques alone. Therefore, various organizations have conducted research in the area of combining active and passive vibration control techniques. The essence of this paper is to present progress in what is believed to be a new concept in this arena. It is based on the notion that if one active element in a vibration transmission path can provide a reasonable vibration attenuation, two active elements in series may provide more control options and better results. The paper presents the functions of a modular split shaft linear actuator developed by NASA's Goddard Space Flight Center and University of Massachusetts Lowell. It discusses some of the control possibilities facilitated by the device. Some preliminary findings and problems are also discussed.

8. Impact of bolus volume on small intestinal intra-luminal impedance in healthy subjects

PubMed Central

Nguyen, Nam Q; Bryant, Laura K; Burgstad, Carly M; Fraser, Robert J; Sifrim, Daniel; Holloway, Richard H

2010-01-01

AIM: To assess the impact of bolus volume on the characteristics of small intestinal (SI) impedance signals. METHODS: Concurrent SI manometry-impedance measurements were performed on 12 healthy volunteers to assess the pattern of proximal jejunal fluid bolus movement over a 14 cm-segment. Each subject was given 34 boluses of normal saline (volume from 1 to 30 mL) via the feeding tube placed immediately above the proximal margin of the studied segment. A bolus-induced impedance event occurred if there was > 12% impedance drop from baseline, over ≥ 3 consecutive segments within 10 s of bolus injection. A minor or major impedance event was defined as a duration of impedance drop < 60 s or ≥ 60 s, respectively. RESULTS: The minimum volume required for a detectable SI impedance event was 2 mL. A direct linear relationship between the SI bolus volume and the occurrence of impedance events was noted until SI bolus volume reached 10 mL, a volume which always produced an impedance flow event. There was a moderate correlation between the bolus volume and the duration of impedance drop (r = 0.63, P < 0.0001) and the number of propagated channels (r = 0.50, P < 0.0001). High volume boluses were associated with more major impedance events (≥ 10 mL boluses = 63%, 3 mL boluses = 17%, and < 3 mL boluses = 0%, P = 0.02). CONCLUSION: Bolus volume had an impact on the type and length of propagation of SI impedance events and a threshold of 2 mL is required to produce an event. PMID:20440856

9. Scattering by an impedance sphere coated with a chiral layer

NASA Technical Reports Server (NTRS)

Uslenghi, Piergiorgio L. E.

1990-01-01

The scattering of a plane, linearly polarized electromagnetic wave by a sphere on whose surface an impedance boundary condition holds, and that is covered with a concentric layer of chiral material, is considered. Exact, explicit expressions are derived for the scattered field coefficients. The co-polarized and cross-polarized components of the far backscattered field are determined and discussed. The value of this canonical problem as a benchmark for computer codes is pointed out.

10. Development of noise and vibration ride comfort criteria

NASA Technical Reports Server (NTRS)

Dempsey, T. K.; Leatherwood, J. D.; Clevenson, S. A.

1979-01-01

A laboratory investigation was directed at the development of criteria for the prediction of ride quality in a noise-vibration environment. The stimuli for the study consisted of octave bands of noise centered at 500 and 2000 Hz and vertical floor vibrations composed of either 5 Hz sinusoidal vibrations, or random vibrations centered at 5 Hz and with a 5 Hz bandwidth. Results indicated that the total subjective discomfort response could be divided into two subjective components. One component consisted of subjective discomfort to vibration and was found to be a linear function of vibration acceleration level. The other component consisted of discomfort due to noise which varied logarithmically with noise level (power relationship). A model of subjective discomfort that accounted for the interdependence of noise and vibration was developed. The model was then used to develop a set of criteria (constant discomfort) curves that illustrate the basic design tradeoffs available between noise and vibration.

11. Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.

PubMed

Kim, Hyeoungwoo; Priya, Shashank; Stephanou, Harry; Uchino, Kenji

2007-09-01

This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 x 10(-3) V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit approximately 40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to a lower output load. The converter was optimized such that it required less than 5 mW for operation.

12. Coupled rotor-body vibrations with inplane degrees of freedom

NASA Technical Reports Server (NTRS)

Ming-Sheng, H.; Peters, D. A.

1985-01-01

In an effort to understand the vibration mechanisms of helicopters, the following basic studies are considered. A coupled rotor-fuselage vibration analysis including inplane degrees of freedom of both rotor and airframe is performed by matching of rotor and fuselage impedances at the hub. A rigid blade model including hub motion is used to set up the rotor flaplag equations. For the airframe, 9 degrees of freedom and hub offsets are used. The equations are solved by harmonic balance. For a 4-bladed rotor, the coupled responses and hub loads are calculated for various parameters in forward flight. The results show that the addition of inplane degrees of freedom does not significantly affect the vertical vibrations for the cases considered, and that inplane vibrations have similar resonance trends as do flapping vibrations.

13. Active Vibration Damping of Solar Arrays

NASA Astrophysics Data System (ADS)

Reinicke, Gunar; Baier, Horst; Grillebeck, Anton; Scharfeld, Frank; Hunger, Joseph; Abou-El-Ela, A.; Lohberg, Andreas

2012-07-01

Current generations of large solar array panels are lightweight and flexible constructions to reduce net masses. They undergo strong vibrations during launch. The active vibration damping is one convenient option to reduce vibration responses and limit stresses in facesheets. In this study, two actuator concepts are used for vibration damping. A stack interface actuator replaces a panel hold down and is decoupled from bending moments and shear forces. Piezoelectric patch actuators are used as an alternative, where the number, position and size of actuators are mainly driven by controllability analyses. Linear Quadratic Gaussian control is used to attenuate vibrations of selected mode shapes with both actuators. Simulations as well as modal and acoustic tests show the feasibility of selected actuator concepts.

14. Tapping mode microwave impedance microscopy

SciTech Connect

Lai, K.

2010-02-24

We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results.

15. Impedance analysis of acupuncture points and pathways

NASA Astrophysics Data System (ADS)

Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena

2011-12-01

Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.

16. 21 CFR 870.2770 - Impedance plethysmograph.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral blood...

17. 21 CFR 870.2770 - Impedance plethysmograph.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral blood...

18. 21 CFR 870.2750 - Impedance phlebograph.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of the...

19. 21 CFR 870.2770 - Impedance plethysmograph.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral blood...

20. 21 CFR 870.2770 - Impedance plethysmograph.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral blood...

1. 21 CFR 870.2770 - Impedance plethysmograph.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral blood...

2. 21 CFR 870.2750 - Impedance phlebograph.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of the...

3. 21 CFR 870.2750 - Impedance phlebograph.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of the...

4. 21 CFR 870.2750 - Impedance phlebograph.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of the...

5. 21 CFR 870.2750 - Impedance phlebograph.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of the...

6. Impedance modeling of electromagnetic energy harvesting system using full-wave bridge rectifier

NASA Astrophysics Data System (ADS)

Liang, Junrui; Ge, Cong; Shu, Yi-Chung

2017-04-01

In the conventional model of general vibration energy harvesters, the harvesting effect was regarded as only the electrically induced damping. Such intuition has overlooked the detailed dynamic contribution of practical power conditioning circuits. This paper presents an improved impedance model for the electromagnetic energy harvesting (EMEH) system considering the detailed dynamic components, which are introduced by the most extensively used full-wave bridge rectifier. The operation of the power electronics is studied under harmonic excitation. The waveforms, energy cycles, and impedance picture are illustrated for showing more information about the EMEH system. The theoretical prediction on harvesting power can properly describe the changing trend of the experimental result.

7. Active Inertial Vibration Isolators And Dampers

NASA Technical Reports Server (NTRS)

Laughlin, Darren; Blackburn, John; Smith, Dennis

1994-01-01

Report describes development of active inertial vibration isolators and dampers in which actuators electromagnet coils moving linearly within permanent magnetic fields in housings, somewhat as though massive, low-frequency voice coils in loudspeakers. Discusses principle of operation, electrical and mechanical considerations in design of actuators, characteristics of accelerometers, and frequency responses of control systems. Describes design and performance of one- and three-degree-of-freedom vibration-suppressing system based on concept.

8. Noncontact Electromagnetic Vibration Source

NASA Technical Reports Server (NTRS)

Namkung, Min; Fulton, James P.; Wincheski, Buzz A.

1994-01-01

Metal aircraft skins scanned rapidly in vibration tests. Relatively simple combination of permanent magnets and electromagnet serves as noncontact vibration source for nondestructive testing of metal aircraft skins. In test, source excites vibrations, and vibration waveforms measured, then analyzed for changes in resonances signifying cracks and other flaws.

9. Investigation of the effect of vibration amplitude on vibration measurements of polarimetric fiber sensors embedded in composite beams

NASA Astrophysics Data System (ADS)

Ramakrishnan, Manjusha; Rajan, Ginu; Semenova, Yuliya; Callaghan, Dean; Farrell, Gerald

2014-04-01

Glass fiber reinforced composite material beams embedded with two types of polarimetric sensors are fabricated by the hand layup method and characterized. Two types of polarimetric sensors, a high strain sensitive Panda type fiber and a low strain sensitive polarization maintaining photonic crystal fiber (PM-PCF), are compared for low frequency vibration measurements from 0 to 100 Hz. Different lengths of glass fiber reinforced composite samples with embedded polarimetric sensors are fabricated and compared for different vibration amplitudes and vibration frequencies. The influence of the vibration amplitude of the composite beams on the accuracy of vibration measurements using the two types of polarimetric sensors is investigated. At high amplitude vibrations the low strain sensitive PM-PCF polarimetric sensors offer a wider linear range and thus reproduce the vibration frequency and vibration amplitude accurately. However for high amplitude vibrations the high sensitivity and low dynamic strain range of Panda type fibers result in a multiple-peak intensity pattern within one vibration cycle which leads to inaccurate vibration frequency and vibration amplitude measurements. The experimental results show that the strain sensitivity of polarimetric sensors limits the vibration measurements to a certain range of vibration amplitudes. The vibration amplitude range over which the polarimetric sensors provide accurate information about the vibration frequency is experimentally investigated and the results are presented. Also, for a composite beam undergoing deflections in the ‘simply-simply supported’ configuration, a theoretical method to predict the allowable maximum measurable vibration amplitude for any type of polarimetric sensor, is derived in this paper. It is envisaged that the results from the studies will provide significant information, which can be used in composite material applications such as marine and aerospace for selecting an appropriate type and

10. Flow-induced vibration

SciTech Connect

Blevins, R.D.

1990-01-01

This book reports on dimensional analysis; ideal fluid models; vortex-induced vibration; galloping and flutter; instability of tube and cylinder arrays; vibrations induced by oscillating flow; vibration induced by turbulence and sound; damping of structures; sound induced by vortex shedding; vibrations of a pipe containing a fluid flow; indices. It covers the analysis of the vibrations of structures exposed to fluid flows; explores applications for offshore platforms and piping; wind-induced vibration of buildings, bridges, and towers; and acoustic and mechanical vibration of heat exchangers, power lines, and process ducting.

11. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

NASA Technical Reports Server (NTRS)

Anderson, Karl F. (Inventor)

1994-01-01

A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

12. A magnetically sprung vibration harvester

NASA Astrophysics Data System (ADS)

Constantinou, P.; Mellor, P. H.; Wilcox, P. D.

2010-04-01

The use of energy harvesting systems is becoming a more prominent research topic in supplying energy to wireless sensor nodes. The paper will present an analytical 'toolbox' for designing and modeling a vibration energy harvester where the moving mass is suspended magnetically. Calculations from the presented model and measurements from a prototype are compared, and the presence of system non-linearities is shown and discussed. The use of the magnetic suspension and its equivalent hardening spring suspension leads to the system's non-linearity, demonstrating a broad band response and 'jump' phenomenon characteristic. The benefits of these are discussed and the system's performance is compared with those from literature, showing similarity.

13. Investigating the sources of variability in the dynamic response of built-up structures through a linear analytical model

NASA Astrophysics Data System (ADS)

Abolfathi, Ali; O'Boy, Dan J.; Walsh, Stephen J.; Fisher, Stephen A.

2017-01-01

It is well established that the dynamic response of a number of nominally identical built-up structures are often different and the variability increases with increasing complexity of the structure. Furthermore, the effects of the different parameters, for example the variation in joint locations or the range of the Young's modulus, on the dynamic response of the system are not the same. In this paper, the effects of different material and geometric parameters on the variability of a vibration transfer function are compared using an analytical model of a simple linear built-up structure that consist of two plates connected by a single mount. Similar results can be obtained if multiple mounts are used. The scope of this paper is limited to a low and medium frequency range where usually deterministic models are used for vibrational analysis. The effect of the mount position and also the global variation in the properties of the plate, such as modulus of elasticity or thickness, is higher on the variability of vibration transfer function than the effect of the mount properties. It is shown that the vibration transfer function between the plates is independent of the mount property if a stiff enough mount with a small mass is implemented. For a soft mount, there is a direct relationship between the mount impedance and the variation in the vibration transfer function. Furthermore, there are a range of mount stiffnesses between these two extreme cases at which the vibration transfer function is more sensitive to changes in the stiffness of the mount than when compared to a soft mount. It is found that the effect of variation in the mount damping and the mount mass on the variability is negligible. Similarly, the effect of the plate damping on the variability is not significant.

14. Finite element simulation of non-linear acoustic generation in a horn loudspeaker

NASA Astrophysics Data System (ADS)

Tsuchiya, T.; Kagawa, Y.; Doi, M.; Tsuji, T.

2003-10-01

The loudspeaker is an electro-acoustic device for sound reproduction which requires the distortion as small as possible. The distortion may arise from the magnetic non-linearity of the york, the uneven magnetic field distribution, the mechanical non-linearity at the diaphragm suspension and the acoustic non-linearity due to the high sound pressure and velocity in the duct-radiation system. A horn is sometimes provided in front of the vibrating diaphragm radiator, which plays an important role to increase the efficiency by matching the acoustic impedance between the radiator and the ambient medium. The horn is in many cases folded twice or three times to shorten the length, which further degrades the reproduction quality. The sound intensity and velocity are apt to attain very high in the small cross-sectional area in the throat and in the folded regions, which may cause the distortion due to the non-linear effect of the medium. The present paper is to investigate the frequency characteristics of the loudspeaker numerically evaluating the generation of the harmonics and sub-harmonics. An axisymmetric folded horn is considered for which the wave equation with the non-linear term retained is solved by the finite element method. The solution is made in time domain in which the sound pressure calculated at the opening end of the horn is Fourier-transformed to the frequency domain to evaluate the distortion, while the wave marching in the horn is visualized.

15. Tunable nanogap devices for ultra-sensitive electrochemical impedance biosensing.

PubMed

Lu, Yong; Guo, Zheng; Song, Jing-Jing; Huang, Qin-An; Zhu, Si-Wei; Huang, Xing-Jiu; Wei, Yan

2016-01-28

A wealth of research has been available discussing nanogap devices for detecting very small quantities of biomolecules by observing their electrical behavior generally performed in dry conditions. We report that a gold nanogapped electrode with tunable gap length for ultra-sensitive detection of streptavidin based on electrochemical impedance technique. The gold nanogap is fabricated using simple monolayer film deposition and in-situ growth of gold nanoparticles in a traditional interdigitated array (IDA) microelectrode. The electrochemical impedance biosensor with a 25-nm nanogap is found to be ultra-sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin hinder the electron transfer between two electrodes, resulting in a large increase in electron-transfer resistance (Ret) for operating the impedance. A linear relation between the relative Ret and the logarithmic value of streptavidin concentration is observed in the concentration range from 1 pM (picomolar) to 100 nM (nanomolar). The lowest detectable concentration actually measured reaches 1 pM. We believe that such an electrochemical impedance nanogap biosensor provides a useful approach towards biomolecular detection that could be extended to a number of other systems. Copyright © 2015 Elsevier B.V. All rights reserved.

16. Multivariable Dynamic Ankle Mechanical Impedance With Active Muscles

PubMed Central

Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

2015-01-01

Multivariable dynamic ankle mechanical impedance in two coupled degrees-of-freedom (DOFs) was quantified when muscles were active. Measurements were performed at five different target activation levels of tibialis anterior and soleus, from 10% to 30% of maximum voluntary contraction (MVC) with increments of 5% MVC. Interestingly, several ankle behaviors characterized in our previous study of the relaxed ankle were observed with muscles active: ankle mechanical impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness; stiffness was greater in the sagittal plane than in the frontal plane at all activation conditions for all subjects; and the coupling between dorsiflexion–plantarflexion and inversion–eversion was small—the two DOF measurements were well explained by a strictly diagonal impedance matrix. In general, ankle stiffness increased linearly with muscle activation in all directions in the 2-D space formed by the sagittal and frontal planes, but more in the sagittal than in the frontal plane, resulting in an accentuated “peanut shape.” This characterization of young healthy subjects’ ankle mechanical impedance with active muscles will serve as a baseline to investigate pathophysiological ankle behaviors of biomechanically and/or neurologically impaired patients. PMID:25203497

17. Three-dimensional electrical impedance tomography: a topology optimization approach.

PubMed

Mello, Luís Augusto Motta; de Lima, Cícero Ribeiro; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez; Silva, Emílio Carlos Nelli

2008-02-01

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.

18. Wave impedance selection for passivity-based bilateral teleoperation

NASA Astrophysics Data System (ADS)

D'Amore, Nicholas John

When a task must be executed in a remote or dangerous environment, teleoperation systems may be employed to extend the influence of the human operator. In the case of manipulation tasks, haptic feedback of the forces experienced by the remote (slave) system is often highly useful in improving an operator's ability to perform effectively. In many of these cases (especially teleoperation over the internet and ground-to-space teleoperation), substantial communication latency exists in the control loop and has the strong tendency to cause instability of the system. The first viable solution to this problem in the literature was based on a scattering/wave transformation from transmission line theory. This wave transformation requires the designer to select a wave impedance parameter appropriate to the teleoperation system. It is widely recognized that a small value of wave impedance is well suited to free motion and a large value is preferable for contact tasks. Beyond this basic observation, however, very little guidance exists in the literature regarding the selection of an appropriate value. Moreover, prior research on impedance selection generally fails to account for the fact that in any realistic contact task there will simultaneously exist contact considerations (perpendicular to the surface of contact) and quasi-free-motion considerations (parallel to the surface of contact). The primary contribution of the present work is to introduce an approximate linearized optimum for the choice of wave impedance and to apply this quasi-optimal choice to the Cartesian reality of such a contact task, in which it cannot be expected that a given joint will be either perfectly normal to or perfectly parallel to the motion constraint. The proposed scheme selects a wave impedance matrix that is appropriate to the conditions encountered by the manipulator. This choice may be implemented as a static wave impedance value or as a time-varying choice updated according to the

19. Impedance adaptation methods of the piezoelectric energy harvesting

NASA Astrophysics Data System (ADS)

Kim, Hyeoungwoo

In this study, the important issues of energy recovery were addressed and a comprehensive investigation was performed on harvesting electrical power from an ambient mechanical vibration source. Also discussed are the impedance matching methods used to increase the efficiency of energy transfer from the environment to the application. Initially, the mechanical impedance matching method was investigated to increase mechanical energy transferred to the transducer from the environment. This was done by reducing the mechanical impedance such as damping factor and energy reflection ratio. The vibration source and the transducer were modeled by a two-degree-of-freedom dynamic system with mass, spring constant, and damper. The transmissibility employed to show how much mechanical energy that was transferred in this system was affected by the damping ratio and the stiffness of elastic materials. The mechanical impedance of the system was described by electrical system using analogy between the two systems in order to simply the total mechanical impedance. Secondly, the transduction rate of mechanical energy to electrical energy was improved by using a PZT material which has a high figure of merit and a high electromechanical coupling factor for electrical power generation, and a piezoelectric transducer which has a high transduction rate was designed and fabricated. The high g material (g33 = 40 [10-3Vm/N]) was developed to improve the figure of merit of the PZT ceramics. The cymbal composite transducer has been found as a promising structure for piezoelectric energy harvesting under high force at cyclic conditions (10--200 Hz), because it has almost 40 times higher effective strain coefficient than PZT ceramics. The endcap of cymbal also enhances the endurance of the ceramic to sustain ac load along with stress amplification. In addition, a macro fiber composite (MFC) was employed as a strain component because of its flexibility and the high electromechanical coupling

20. Sensing fluid viscosity and density through mechanical impedance measurement using a whisker transducer

NASA Astrophysics Data System (ADS)

Ju, Feng; Ling, Shih-Fu

2013-05-01

This paper presents a new technique for fluid viscosity and density sensing through measuring the mechanical impedance of the fluid load applied on a sphere. A piezoelectric whisker transducer (WT) is proposed which acts simultaneously as both the actuator to excite the sphere tip to oscillate in the fluid and the sensor to measure the force, velocity and mechanical impedance. The relationship between mechanical impedance of the fluid load and electrical impedance of the WT is derived based on a transduction matrix model which characterizes the electro-mechanical transduction process of the WT in both directions. The mechanical impedance is further related to the fluid viscosity and density using a theoretical model. The establishment of this fluid-mechanical-electrical relationship allows the WT to extract the fluid viscosity and density conveniently and accurately just from its electrical impedance. Experimental studies are carried out to calibrate the WT and test its performance using glycerol-water mixtures. It is concluded that the WT is capable of providing results comparable to those of standard viscometers within a wide measurement range due to its low working frequency and large vibration amplitude. Its unique self-actuation-and-sensing feature makes it a suitable solution for online fluid sensing.

1. Impedance of pistons on a two-layer medium in a planar infinite rigid baffle.

PubMed

Hassan, Scott E

2007-07-01

An integral transform technique is used to develop a general solution for the impedance of rigid pistons acting on a two-layer medium. The medium consists of a semi-infinite acoustic fluid on a viscoelastic thick plate in a rigid infinite baffle. The stresses acting on the planar baffle, as a result of piston motion, are determined using theory of linear elasticity and are therefore unrestricted in terms of applicable frequency range. The special case of a circular piston is considered and expressions for the self-and mutual impedances are developed and evaluated numerically. Numerical results are compared with classical piston impedance functions and finite-element model results. At low frequencies (k(0)a<1), the self-impedances vary significantly from the classical piston impedance functions due to the shear properties of the viscoelastic medium. In the midfrequency range (1impedances vary from the classical piston impedance functions for moderate viscoelastic layer thicknesses (0.5impedances associated with pistons on a two-layer medium generally exhibit an increased decay, as a function of separation distance, over the classical results.

2. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

SciTech Connect

Maximillian J. Kieba

2004-02-01

This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

3. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

SciTech Connect

Maximillian J. Kieba; Christopher J. Ziolkowski

2004-06-30

This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

4. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

SciTech Connect

Maximillian J. Kieba; Christopher J. Ziolkowski

2005-01-17

This project aimed at developing a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GTI. GTI proposed to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment

5. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

SciTech Connect

Maximillian J. Kieba

2002-08-30

This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD

6. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

SciTech Connect

Maximillian J. Kieba

2003-10-01

This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

7. Bilateral Impedance Control For Telemanipulators

NASA Technical Reports Server (NTRS)

Moore, Christopher L.

1993-01-01

Telemanipulator system includes master robot manipulated by human operator, and slave robot performing tasks at remote location. Two robots electronically coupled so slave robot moves in response to commands from master robot. Teleoperation greatly enhanced if forces acting on slave robot fed back to operator, giving operator feeling he or she manipulates remote environment directly. Main advantage of bilateral impedance control: enables arbitrary specification of desired performance characteristics for telemanipulator system. Relationship between force and position modulated at both ends of system to suit requirements of task.

8. Impedance spectroscopy of food mycotoxins

NASA Astrophysics Data System (ADS)

Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.

2012-01-01

A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.

9. Input gate circuit converted for use as linear amplifier

NASA Technical Reports Server (NTRS)

Harper, T. P.

1968-01-01

Commercially available integrated circuit that is marketed as a digital computer input gate circuit was converted to a linear amplifier in a microphone circuit that has high input impedance, low output impedance, low cost, and is small enough to fit on a standard printed circuit card.

10. Journal bearing impedance descriptions for rotordynamic applications

NASA Technical Reports Server (NTRS)

Childs, D.; Moes, H.; Van Leeuwen, H.

1976-01-01

The paper deals with the development of analytic descriptions for plain circumferentially-symmetric fluid journal bearings, which are suitable for use in rotor dynamic analysis. The bearing impedance vector is introduced, which defines the bearing reaction force components as a function of the bearing motion. Impedances are derived directly for the Ocvirk (short) and Sommerfeld (long) bearings, and the relationships between the impedance vector and the more familiar mobility vector are developed and used to derive analytic impedance for finite-length bearings. The static correctness of the finite-length cavitating impedance is verified. Analytic stiffness and damping coefficient definitions are derived in terms of an impedance vector for small motion around an equilibrium position and demonstrated for the finite-length cavitating impedance. Nonlinear transient rotordynamic simulations are presented for the short pi and 2-pi impedances and the finite-length cavitating impedance. It is shown that finite-length impedance yields more accurate results for substantially less computer time than the short-bearing numerical-pressure-integration approach.

11. MEMS-based adaptive impedance matching network

NASA Astrophysics Data System (ADS)

Srivastava, Ashok

2003-07-01

The architecture level design of an impedance matching network is presented for the global system for mobile communication radio frequency (GSM RF) power amplifier module used in a typical cellular handset. Designs for the low and high output impedance of the power amplifier and 50 Ω antenna impedance are considered. Impedance matching network design is presented for a typical low output impedance (Z = 2-j*0.4 Ω) of the power amplifier and 50 Ω antenna impedance and is made adaptive for high output impedance (Z = 7+j*2 Ω). It is shown that the network can be made adaptive to varying output requirements of the power amplifier by tuning the network capacitance toward the antenna end. The architecture level design of a 25 Ω antenna impedance is also presented and shown that that the impedance matching network can be made adaptive, which would require the use of MEMS switches. The adaptive impedance matching networks can be implemented in a passive integration technology with post-processing for MEMS components.

12. Noninvasive measurement of transdermal drug delivery by impedance spectroscopy

PubMed Central

Arpaia, Pasquale; Cesaro, Umberto; Moccaldi, Nicola

2017-01-01

The effectiveness in transdermal delivery of skin permeation strategies (e.g., chemical enhancers, vesicular carrier systems, sonophoresis, iontophoresis, and electroporation) is poorly investigated outside of laboratory. In therapeutic application, the lack of recognized techniques for measuring the actually-released drug affects the scientific concept itself of dosage for topically- and transdermally-delivered drugs. Here we prove the suitability of impedance measurement for assessing the amount of drug penetrated into the skin after transdermal delivery. In particular, the measured amount of drug depends linearly on the impedance magnitude variation normalized to the pre-treated value. Three experimental campaigns, based on the electrical analysis of the biological tissue behavior due to the drug delivery, are reported: (i) laboratory emulation on eggplants, (ii) ex-vivo tests on pig ears, and finally (iii) in-vivo tests on human volunteers. Results point out that the amount of delivered drug can be assessed by reasonable metrological performance through a unique measurement of the impedance magnitude at one single frequency. In particular, in-vivo results point out sensitivity of 23 ml−1, repeatability of 0.3%, non-linearity of 3.3%, and accuracy of 5.7%. Finally, the measurement resolution of 0.20 ml is compatible with clinical administration standards. PMID:28338008

13. ONERA-NASA Cooperative Effort on Liner Impedance Eduction

NASA Technical Reports Server (NTRS)

Primus, Julien; Piot, Estelle; Simon, Frank; Jones, Michael G.; Watson, Willie R

2013-01-01

As part of a cooperation between ONERA and NASA, the liner impedance eduction methods developed by the two research centers are compared. The NASA technique relies on an objective function built on acoustic pressure measurements located on the wall opposite the test liner, and the propagation code solves the convected Helmholtz equation in uniform ow using a finite element method that implements a continuous Galerkin discretization. The ONERA method uses an objective function based either on wall acoustic pressure or on acoustic velocity acquired above the liner by Laser Doppler Anemometry, and the propagation code solves the linearized Euler equations by a discontinuous Galerkin discretization. Two acoustic liners are tested in both ONERA and NASA ow ducts and the measured data are treated with the corresponding impedance eduction method. The first liner is a wire mesh facesheet mounted onto a honeycomb core, designed to be linear with respect to incident sound pressure level and to grazing ow velocity. The second one is a conventional, nonlinear, perforate-over-honeycomb single layer liner. Configurations without and with ow are considered. For the nonlinear liner, the comparison of liner impedance educed by NASA and ONERA shows a sensitivity to the experimental conditions, namely to the nature of the source and to the sample width.

14. Hybrid active vibration control of rotorbearing systems using piezoelectric actuators

NASA Technical Reports Server (NTRS)

Palazzolo, A. B.; Jagannathan, S.; Kascak, A. F.; Montague, G. T.; Kiraly, L. J.

1993-01-01

The vibrations of a flexible rotor are controlled using piezoelectric actuators. The controller includes active analog components and a hybrid interface with a digital computer. The computer utilizes a grid search algorithm to select feedback gains that minimize a vibration norm at a specific operating speed. These gains are then downloaded as active stillnesses and dampings with a linear fit throughout the operating speed range to obtain a very effective vibration control.

15. Soil amplification with a strong impedance contrast: Boston, Massachusetts

USGS Publications Warehouse

Baise, Laurie G.; Kaklamanos, James; Berry, Bradford M; Thompson, Eric

2016-01-01

In this study, we evaluate the effect of strong sediment/bedrock impedance contrasts on soil amplification in Boston, Massachusetts, for typical sites along the Charles and Mystic Rivers. These sites can be characterized by artificial fill overlying marine sediments overlying glacial till and bedrock, where the depth to bedrock ranges from 20 to 80 m. The marine sediments generally consist of organic silts, sand, and Boston Blue Clay. We chose these sites because they represent typical foundation conditions in the city of Boston, and the soil conditions are similar to other high impedance contrast environments. The sediment/bedrock interface in this region results in an impedance ratio on the order of ten, which in turn results in a significant amplification of the ground motion. Using stratigraphic information derived from numerous boreholes across the region paired with geologic and geomorphologic constraints, we develop a depth-to-bedrock model for the greater Boston region. Using shear-wave velocity profiles from 30 locations, we develop average velocity profiles for sites mapped as artificial fill, glaciofluvial deposits, and bedrock. By pairing the depth-to-bedrock model with the surficial geology and the average shear-wave velocity profiles, we can predict soil amplification in Boston. We compare linear and equivalent-linear site response predictions for a soil layer of varying thickness over bedrock, and assess the effects of varying the bedrock shear-wave velocity (VSb) and quality factor (Q). In a moderate seismicity region like Boston, many earthquakes will result in ground motions that can be modeled with linear site response methods. We also assess the effect of bedrock depth on soil amplification for a generic soil profile in artificial fill, using both linear and equivalent-linear site response models. Finally, we assess the accuracy of the model results by comparing the predicted (linear site response) and observed site response at the Northeastern

16. Vibration characterisation of cymbal transducers for power ultrasonic applications

NASA Astrophysics Data System (ADS)

Bejarano, F.; Feeney, A.; Lucas, M.

2012-08-01

A Class V cymbal flextensional transducer is composed of a piezoceramic disc or ring sandwiched between two cymbal-shaped shell end-caps. These end-caps act as mechanical transformers to convert high impedance, low radial displacement of the piezoceramic into low impedance, large axial motion of the end-cap. The cymbal transducer was developed in the early 1990's at Penn State University, and is an improvement of the moonie transducer which has been in use since the 1980's. Despite the fact that cymbal transducers have been used in many fields, both as sensors and actuators, due to its physical limitations its use has been mainly at low power intensities. It is only very recently that its suitability for high amplitude and high power applications has been studied, and consequently implementation in this area of research remains undeveloped. This paper employs experimental modal analysis (EMA), vibration response measurements and electrical impedance measurements to characterise two variations of the cymbal transducer design, both aimed at incorporation in ultrasonic cutting devices. The transducers are fabricated using the commercial Eccobond 45LV epoxy adhesive as the bonding agent. The first cymbal transducer is of the classic design where the piezoceramic disc is bonded directly to the end-caps. The second cymbal transducer includes a metal ring bonded to the outer edge of the piezoceramic disc. The reason for the inclusion of this metal ring is to improve the mechanical coupling with the end-caps. This would therefore make this design particularly suitable for power ultrasonic applications, reducing the possibility of debonding at the higher ultrasonic amplitudes. The experimental results demonstrate that the second cymbal design is a significant improvement on the more classic design, allowing the transducer to operate at higher voltages and higher amplitudes, exhibiting a linear response over a practical power ultrasonic device driving voltage range. The

17. Model Parameterization and P-wave AVA Direct Inversion for Young's Impedance

NASA Astrophysics Data System (ADS)

Zong, Zhaoyun; Yin, Xingyao

2017-05-01

AVA inversion is an important tool for elastic parameters estimation to guide the lithology prediction and "sweet spot" identification of hydrocarbon reservoirs. The product of the Young's modulus and density (named as Young's impedance in this study) is known as an effective lithology and brittleness indicator of unconventional hydrocarbon reservoirs. Density is difficult to predict from seismic data, which renders the estimation of the Young's impedance inaccurate in conventional approaches. In this study, a pragmatic seismic AVA inversion approach with only P-wave pre-stack seismic data is proposed to estimate the Young's impedance to avoid the uncertainty brought by density. First, based on the linearized P-wave approximate reflectivity equation in terms of P-wave and S-wave moduli, the P-wave approximate reflectivity equation in terms of the Young's impedance is derived according to the relationship between P-wave modulus, S-wave modulus, Young's modulus and Poisson ratio. This equation is further compared to the exact Zoeppritz equation and the linearized P-wave approximate reflectivity equation in terms of P- and S-wave velocities and density, which illustrates that this equation is accurate enough to be used for AVA inversion when the incident angle is within the critical angle. Parameter sensitivity analysis illustrates that the high correlation between the Young's impedance and density render the estimation of the Young's impedance difficult. Therefore, a de-correlation scheme is used in the pragmatic AVA inversion with Bayesian inference to estimate Young's impedance only with pre-stack P-wave seismic data. Synthetic examples demonstrate that the proposed approach is able to predict the Young's impedance stably even with moderate noise and the field data examples verify the effectiveness of the proposed approach in Young's impedance estimation and "sweet spots" evaluation.

18. Model Parameterization and P-wave AVA Direct Inversion for Young's Impedance

NASA Astrophysics Data System (ADS)

Zong, Zhaoyun; Yin, Xingyao

2017-03-01

AVA inversion is an important tool for elastic parameters estimation to guide the lithology prediction and "sweet spot" identification of hydrocarbon reservoirs. The product of the Young's modulus and density (named as Young's impedance in this study) is known as an effective lithology and brittleness indicator of unconventional hydrocarbon reservoirs. Density is difficult to predict from seismic data, which renders the estimation of the Young's impedance inaccurate in conventional approaches. In this study, a pragmatic seismic AVA inversion approach with only P-wave pre-stack seismic data is proposed to estimate the Young's impedance to avoid the uncertainty brought by density. First, based on the linearized P-wave approximate reflectivity equation in terms of P-wave and S-wave moduli, the P-wave approximate reflectivity equation in terms of the Young's impedance is derived according to the relationship between P-wave modulus, S-wave modulus, Young's modulus and Poisson ratio. This equation is further compared to the exact Zoeppritz equation and the linearized P-wave approximate reflectivity equation in terms of P- and S-wave velocities and density, which illustrates that this equation is accurate enough to be used for AVA inversion when the incident angle is within the critical angle. Parameter sensitivity analysis illustrates that the high correlation between the Young's impedance and density render the estimation of the Young's impedance difficult. Therefore, a de-correlation scheme is used in the pragmatic AVA inversion with Bayesian inference to estimate Young's impedance only with pre-stack P-wave seismic data. Synthetic examples demonstrate that the proposed approach is able to predict the Young's impedance stably even with moderate noise and the field data examples verify the effectiveness of the proposed approach in Young's impedance estimation and "sweet spots" evaluation.

19. Linear Accelerators

NASA Astrophysics Data System (ADS)

Sidorin, Anatoly

2010-01-01

In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

20. Linear Accelerators

SciTech Connect

Sidorin, Anatoly

2010-01-05

In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

1. Development of an innovative device for ultrasonic elliptical vibration cutting.

PubMed

Zhou, Ming; Hu, Linhua

2015-07-01

An innovative ultrasonic elliptical vibration cutting (UEVC) device with 1st resonant mode of longitudinal vibration and 3rd resonant mode of bending vibration was proposed in this paper, which can deliver higher output power compared to previous UEVC devices. Using finite element method (FEM), resonance frequencies of the longitudinal and bending vibrations were tuned to be as close as possible in order to excite these two vibrations using two-phase driving voltages at a single frequency, while wave nodes of the longitudinal and bending vibrations were also adjusted to be as coincident as possible for mounting the device at a single fixed point. Based on the simulation analysis results a prototype device was fabricated, then its vibration characteristics were evaluated by an impedance analyzer and a laser displacement sensor. With two-phase sinusoidal driving voltages both of 480 V(p-p) at an ultrasonic frequency of 20.1 kHz, the developed prototype device achieved an elliptical vibration with a longitudinal amplitude of 8.9 μm and a bending amplitude of 11.3 μm. The performance of the developed UEVC device is assessed by the cutting tests of hardened steel using single crystal diamond tools. Experimental results indicate that compared to ordinary cutting process, the tool wear is reduced significantly by using the proposed device.

2. Application of short linear transformers in multifrequency matching

NASA Astrophysics Data System (ADS)

Fox, Joshua A.

In microwave circuits the source and load impedance must match for maximum power transfer. This can be achieved using an impedance matching network utilizing several different techniques. The short linear transformer (SLT) is a method which uses transmission lines of alternating impedances with calculated lengths for the desired frequency. This method has been expanded for multi-band applications of up to four frequencies. These designs are demonstrated in this project. The SLT proves to be shorter than comparable methods with a preferred response. Also, the design only requires transmission lines of the same impedance as the source and load.

3. Appraisal of broadband acoustic impedances from first principles and band-limited seismic reflection data

NASA Astrophysics Data System (ADS)

Mandal, A.; Ghosh, S. K.

2015-12-01

Seismic derived acoustic impedance is an essential output for the quantitative interpretation of seismic data. However, the band limitation of seismic data leads to a nonunique estimate of the acoustic impedance profile. The prevalent methods counter the nonuniqueness either by stabilizing the answer with respect to an initial model or by resorting to an assumption of certain criterion such as sparsity of the reflection coefficients. Making a nominal assumption of a homogeneous layered earth model, we formulate a set of linear equations where the reflection coefficients are the unknowns and the recursively integrated seismic trace constitutes the data. The approach makes a frontal assault on the problem of reconstructing reflection coefficients from band-limited data and stems from first principles, i.e., Zöppritz's equation in this case. Nonuniqueness is countered in part by the layercake assumption, and in part by the adoption of the singular value decomposition (SVD) method of finding an optimal solution to the set of linear equations, provided the objective is to reconstruct a smoothed version of the impedance profile that includes only its coarser structures. The efficacy of the method has been tested with synthetic data added with significant noise and generated from rudimentary earth models as well as from measured logs of acoustic impedance. Emergence of consistent estimates of impedance from synthetic data generated for several frequency bands increases the confidence in the method. The study also proves the successfulness of the method for (a) an accurate estimate of the impedance mean, (b) an accurate reconstruction of the direct-current (dc) frequency of the reflectivity, and (c) an acceptable reconstruction of the broad trend of the original impedance profile. All these outputs can serve as significant constraints for either more refined inversions or geological interpretations. (Keywords: Reflection data, Acoustic impedance, Broadband, Linear

4. Electrical Impedance Tomography of Breast Cancer

DTIC Science & Technology

2005-06-01

SUBJECT TERMS Diagnosis of Metastatic Cancer, Magnetic Resonance Imaging, Electrical Impedance Imaging, Electrical Impedance Scanning, MRI current...1) To develop and optimize the necessary hardware and software for Magnetic Resonance Electrical Impedance Tomography (MREIT) and interface it with...of Magnetic Resonance in Medicine (ISMRM) conference and included in the appendix for reference. 2.2.2. Second Year: A series of new phantom studies

5. Impedance signature of pharyngeal gaseous reflux.

PubMed

Kawamura, Osamu; Bajaj, Shailesh; Aslam, Muhammad; Hofmann, Candy; Rittmann, Tanya; Shaker, Reza

2007-01-01

Pharyngeal impedance changes induced by various pharyngeal reflux events have not been characterized. To characterize pharyngeal impedance changes induced by participant-perceived belching events. We systematically evaluated pharyngeal impedance and pH changes related to 453 belch events in 11 gastroesophageal reflux disease, 10 reflux attributed-laryngitis patients and 16 controls. Of 453 belch events, 362 were analyzable. Of these, 72% occurred within 10 s, 93% within 20 s, 99% within 30 s and 100% within 40 s of the time that participants marked a belch event. In 15% impedance changes in the pharynx preceded, in 12% they were simultaneous and in 73% they occurred after the start of the impedance change in the proximal esophagus. Time interval between the two events ranged between 0.4+/-0.03 and 0.7+/-0.1 s. In all, there were three types of belch-induced impedance changes: (a) impedance increase, (b) impedance decrease and (c) multiphasic. Twenty percent of impedance events associated with belching had less than 50% change from baseline, whereas in 51% changes exceeded or were equal to 50%. Among events with a drop in pharyngeal impedance, only two satisfied the criteria for the liquid reflux event. Pharyngeal ventilation of gastric gaseous content seems to have a unique impedance signature. During pharyngeal gas reflux events, impedance changes may start before or after proximal esophageal changes. Belching may induce negative pharyngeal changes that do not meet the criteria for liquid reflux. These findings need to be taken into consideration in the analysis of pharyngeal reflux events.

6. Research and development of energy harvesting from vibrations and human motions (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liao, Wei-Hsin

2017-04-01

Most of the ambient energy, which was regarded useless in the past, now is under the spotlight. With the rapid developments on low power electronics, future personal mobile devices and remote sensing systems might become self-powered by scavenging energy in different forms from their surroundings. Kinetic energy is one of the promising energy forms in our living environment, e.g., human motions and vibrations. We have proposed an energy flow to clarify the functions of piezoelectric energy harvesting, dissipation, and their effects on the structural damping of vibrating structures. Impedance modeling and analysis were performed. We have designed an improved self-powered switching interface for piezoelectric energy harvesting circuits. With electromagnetic transduction, we also proposed a knee-mounted energy harvester that could convert the mechanical power from knee joints into electricity during walking. On the other hand, we have developed magnetorheological (MR) fluid devices with multiple functions, including rotary actuators and linear dampers. Multifunctional rotary actuator was designed to integrate motor/generator part and MR fluids into a single device. The actuator could function as motor, generator, clutch and brake, with compact size and good energy efficiency. In addition, novel self-sensing MR dampers with power generation, so as to integrate the dynamic sensing, controllable damping and power generation functions, were developed and investigated. Prototypes were fabricated and tested. The developed actuators were promising for various applications. In this paper, related research in energy harvesting done at The Chinese University of Hong Kong and key results will be presented.

7. Random Vibrations: Assessment of the State of the Art

SciTech Connect

Paez, T.L.

1999-02-23

Random vibration is the phenomenon wherein random excitation applied to a mechanical system induces random response. We summarize the state of the art in random vibration analysis and testing, commenting on history, linear and nonlinear analysis, the analysis of large-scale systems, and probabilistic structural testing.

8. Function generator for synthesizing complex vibration mode patterns

NASA Technical Reports Server (NTRS)

Naumann, E. C.; Hagood, G. J., Jr. (Inventor)

1973-01-01

A simple highly flexible device for synthesizing complex vibration mode patterns is described. These mode patterns can be used to identify vibration mode data. This device sums selected sine and cosine functions and then plots the sum against a linear function.

9. Portable vibration exciter

NASA Technical Reports Server (NTRS)

Beecher, L. C.; Williams, F. T.

1970-01-01

Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

10. Control System Damps Vibrations

NASA Technical Reports Server (NTRS)

Kopf, E. H., Jr.; Brown, T. K.; Marsh, E. L.

1983-01-01

New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.

11. Research on autotransformer short-circuit impedance

NASA Astrophysics Data System (ADS)

Wang, Huan; Li, Yan

2017-04-01

Short-circuit impedance is an important technical parameters of power transformers, which will affect the efficiency, cost, mechanical strength of transformer. In this paper, the conventional winding arrangement of the high-impedance autotransformer is improved, and the short-circuit impedance of the new-type autotransformer is calculated and analyzed by the engineering leakage flux method and the finite element method respectively, and compared with the measured value. The results show that the impedance value that calculated by finite element method is closer to the measured value.

12. Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

NASA Technical Reports Server (NTRS)

Watson, W. R.; Jones, M. G.

2012-01-01

The accuracy of the Ingard-Myers boundary condition and a recently proposed modified Ingard-Myers boundary condition is evaluated for use in impedance eduction under the assumption of uniform mean flow. The evaluation is performed at three centerline Mach numbers, using data acquired in a grazing flow impedance tube, using both upstream and downstream propagating sound sources, and on a database of test liners for which the expected behavior of the impedance spectra is known. The test liners are a hard-wall insert consisting of 12.6 mm thick aluminum, a linear liner without a facesheet consisting of a number of small diameter but long cylindrical channels embedded in a ceramic material, and two conventional nonlinear liners consisting of a perforated facesheet bonded to a honeycomb core. The study is restricted to a frequency range for which only plane waves are cut on in the hard-wall sections of the flow impedance tube. The metrics used to evaluate each boundary condition are 1) how well it educes the same impedance for upstream and downstream propagating sources, and 2) how well it predicts the expected behavior of the impedance spectra over the Mach number range. The primary conclusions of the study are that the same impedance is educed for upstream and downstream propagating sources except at the highest Mach number, that an effective impedance based on both the upstream and downstream measurements is more accurate than an impedance based on the upstream or downstream data alone, and that the Ingard-Myers boundary condition with an effective impedance produces results similar to that achieved with the modified Ingard-Myers boundary condition.

13. Low impedance printed circuit radiating element

NASA Technical Reports Server (NTRS)

Rahm, James K. (Inventor); Frankievich, Robert H. (Inventor); Martinko, John D. (Inventor)

1993-01-01

A printed circuit radiating element comprises a geometrically symmetric planar area of a conducting material separated from a ground plane by a dielectric medium. The driving point of the radiating element is at the base of a notch in one side thereof so that the driving impedance is reduced from that obtained when the element is driven at its edge. Symmetrically disposed on opposite sides of an axis of symmetry of the element along which the driving point lies are two notches which restore the electrical symmetry of the radiating element thereby to suppress higher order modes. The suppression of these higher order modes results in a radiation pattern with minimal cross-polarized energy in the principal planes and high port-to-port isolation which could not be achieved with an asymmetrical element. Two driving points may be employed with the radiating element to produce a dual linearly polarized antenna and a reactive combiner or hybrid may be employed to obtain circularly-polarized radiations. The shape of the radiating element may be square, rectangular or circular, for example, in accordance with the desired characteristics. A plurality of radiating elements may be interconnected via appropriate transmission paths to form an antenna array.

14. Motion and force controlled vibration testing. [of aerospace hardware

NASA Technical Reports Server (NTRS)

Scharton, Terry D.; Boatman, David J.; Kern, Dennis L.

1990-01-01

A technique for controlling both the input acceleration and force in vibration tests is proposed to alleviate the overtesting risks and the problems associated with response limiting in conventional vibration tests of aerospace hardware. Previous research on impedance and force controlled vibration tests is reviewed and a simple equation governing the dual control of acceleration and force is derived. A practical method for implementing the dual control technique in random vibration tests has been demonstrated in JPL's environmental test facility using a conventional digital controller operating in the extremal mode. The dual control technique provides appropriate real-time notching of the input acceleration and a corresponding reduction of the test item response at resonances. Issues concerning the need for force and acceleration phase information, the adequacy of specifying the blocked force, and the derivation of the total force for multipoint supports are discussed.

15. Active Suppression Of Vibrations On Elastic Beams

NASA Technical Reports Server (NTRS)

Silcox, Richard J.; Fuller, Chris R.; Gibbs, Gary P.

1993-01-01

Pairs of colocated piezoelectric transducers, independently controlled by multichannel adaptive controller, employed as actuators and sensors to achieve simultaneous attenuation of both extensional and flexural motion. Single pair used to provide simultaneous control of flexural and extensional waves, or two pairs used to control torsional motion also. Capability due to nature of piezoelectric transducers, when bonded to surfaces of structures and activated by oscillating voltages, generate corresponding oscillating distributions of stresses in structures. Phases and amplitudes of actuator voltages adjusted by controller to impede flow of vibrational energy simultaneously, in waves of various forms, beyond locations of actuators. Concept applies equally to harmonic or random response of structure and to multiple responses of structure to transverse bending, torsion, and compression within structural element. System has potential for many situations in which predominant vibration transmission path through framelike structure.

16. Active Suppression Of Vibrations On Elastic Beams

NASA Technical Reports Server (NTRS)

Silcox, Richard J.; Fuller, Chris R.; Gibbs, Gary P.

1993-01-01

Pairs of colocated piezoelectric transducers, independently controlled by multichannel adaptive controller, employed as actuators and sensors to achieve simultaneous attenuation of both extensional and flexural motion. Single pair used to provide simultaneous control of flexural and extensional waves, or two pairs used to control torsional motion also. Capability due to nature of piezoelectric transducers, when bonded to surfaces of structures and activated by oscillating voltages, generate corresponding oscillating distributions of stresses in structures. Phases and amplitudes of actuator voltages adjusted by controller to impede flow of vibrational energy simultaneously, in waves of various forms, beyond locations of actuators. Concept applies equally to harmonic or random response of structure and to multiple responses of structure to transverse bending, torsion, and compression within structural element. System has potential for many situations in which predominant vibration transmission path through framelike structure.

17. Insect sound production: transduction mechanisms and impedance matching.

PubMed

Bennet-Clark, H C

1995-01-01

The chain of sound production in insects can be summarised as: (1) muscle power-->(2) mechanical vibration of the sound-producing structure-->(3) acoustic loading of this source-->(4) sound radiation. At each link (-->) optimal impedance matching is desirable but, to meet other acoustic requirements, each stage has special properties. The properties of sound waves are discussed in the context of impedance matching between sources of different sizes or configurations and the surrounding fluid medium. Muscles produce high pressures over small areas, but sound sources produce low pressures over large areas. Link 1-->2 requires a change in the force: area ratio between the muscle and the sound source. Because the source size is necessarily small, sounds tend to be produced at a higher frequency than that of the driving muscle contraction, so link 1-->2 may involve a frequency multiplication mechanism. This can also be regarded as a mechanism of impedance matching between the aqueous muscle and the structure from which the insect produces sound. Stage 2 typically involves a resonant structure that determines the song frequency and is excited by link 1-->2. If link 2-->3 provides good impedance matching, the mechanical resonance is likely to be damped, with loss of song purity. So it is desirable for the stage 2 resonance to be sustained by coherent excitation and for the acoustic loading (link 2-->3) to maintain the dominant frequency between stages 2 and 4. Examples where this occurs are cricket wings and cicadas. At stage 3, the source size or configuration should allow impedance matching between the sound source (3) and its load (4). A variety of acoustic devices are exploited, leading to loud, efficient sound production. Examples that use resonant loads, tuned to the insects' song frequency, are the burrows of mole crickets and the abdomens of cicadas. Overall, the mechanisms of sound production of many insects are capable of producing songs of high species

18. Electrical Impedance Tomography of Electrolysis

PubMed Central

Meir, Arie; Rubinsky, Boris

2015-01-01

The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations. PMID:26039686

19. Impedance Spectroscopy of Human Blood

NASA Astrophysics Data System (ADS)

Mesa, Francisco; Bernal, José J.; Sosa, Modesto A.; Villagómez, Julio C.; Palomares, Pascual

2004-09-01

The blood is one of the corporal fluids more used with analytical purposes. When the blood is extracted, immediately it is affected by agents that act on it, producing transformations in its elements. Among the effects of these transformations the hemolysis phenomenon stands out, which consists of the membrane rupture and possible death of the red blood cells. The main purpose of this investigation was the quantification of this phenomenon. A Solartron SI-1260 Impedance Spectrometer was used, which covers a frequency range of work from 1 μHz to 10 MHz, and its accuracy has been tested in the accomplishment of several applications. Measurements were performed on 3 mL human blood samples, from healthy donors. Reactive strips for sugar test of 2 μL, from Bayer, were used as electrodes, which allow gathering a portion of the sample, to be analyzed by the spectrometer. Preliminary results of these measurements are presented.

20. Electrical impedance tomography of electrolysis.

PubMed

Meir, Arie; Rubinsky, Boris

2015-01-01

The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.

1. Hermetically sealed vibration damper

NASA Technical Reports Server (NTRS)

Wheatley, D. G.

1969-01-01

Simple fluidic vibration damper for installation at each pivotal mounting between gimbals isolates inertial measuring units from external vibration and other disruptive forces. Installation between each of the three gimbal axes can dampen vibration and shock in any direction while permitting free rotation of the gimbals.

2. Tunable Passive Vibration Suppressor

NASA Technical Reports Server (NTRS)

Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)

2016-01-01

An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.

3. C-130J Human Vibration

DTIC Science & Technology

2005-08-01

Organisation DSTO-TR-1756 ABSTRACT Human exposure to whole - body vibration (WBV) has been associated with a variety of changes in health...1.2.1 Whole - body Vibration (WBV) ................................................................... 3 1.2.2 Local vibration ...amplitude transmissibility VDV vibration dose value VWF vibration -induced white finger WBV whole body vibration DSTO-TR-1756 1 1. Introduction

4. Full dimensional Franck-Condon factors for the acetylene Ã (1)A(u)-X̃ (1)Σ(g)(+) transition. I. Method for calculating polyatomic linear-bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene.

PubMed

Park, G Barratt

2014-10-07

Franck-Condon vibrational overlap integrals for the Ã Au1-X̃ 1Σg+ transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ν4(″), is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ν5(″), is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated Ã-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene Ã Au1-X̃ 1Σg+ transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)].

5. Wave based optimization of distributed vibration absorbers

NASA Astrophysics Data System (ADS)

Johnson, Marty; Batton, Brad

2005-09-01

The concept of distributed vibration absorbers or DVAs has been investigated in recent years as a method of vibration control and sound radiation control for large flexible structures. These devices are comprised of a distributed compliant layer with a distributed mass layer. When such a device is placed onto a structure it forms a sandwich panel configuration with a very soft core. With this configuration the main effect of the DVA is to create forces normal to the surface of the structure and can be used at low frequencies to either add damping, where constrain layer damper treatments are not very effective, or to pin the structure over a narrow frequency bandwidth (i.e., large input impedance/vibration absorber approach). This paper analyses the behavior of these devices using a wave based approach and finds an optimal damping level for the control of broadband disturbances in panels. The optimal design is calculated by solving the differential equations for waves propagating in coupled plates. It is shown that the optimal damping calculated using the infinite case acts as a good rule of thumb'' for designing DVAs to control the vibration of finite panels. This is bourn out in both numerical simulations and experiments.

6. Acoustic vibrations of single suspended gold nanostructures

NASA Astrophysics Data System (ADS)

Major, Todd A.

The acoustic vibrations for single gold nanowires and gold plates were studied using time-resolved ultrafast transient absorption. The objective of this work was to remove the contribution of the supporting substrate from the damping of the acoustic vibrations of the metal nano-objects. This was achieved by suspending the nano-objects across trenches created by photolithography and reactive ion etching. Transient absorption measurements for single suspended gold nanowires were initially completed in air and water environments. The acoustic vibrations for gold nanowires over the trench in air last typically for several nanoseconds, whereas gold nanowires in water are damped more quickly. Continuum mechanics models suggest that the acoustic impedance mismatch between air and water dominates the damping rate. Later transient absorption studies on single suspended gold nanowires were completed in glycerol and ethylene glycol environments. However, our continuum mechanical model suggests nearly complete damping in glycerol due to its high viscosity, but similar damping rates are seen between the two liquids. The continuum mechanics model thus incorrectly addresses high viscosity effects on the lifetimes of the acoustic vibrations, and more complicated viscoelastic interactions occur for the higher viscosity liquids. (Abstract shortened by UMI.).

7. Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges

NASA Technical Reports Server (NTRS)

Kraft, R. E.; Yu, J.; Kwan, H. W.

1999-01-01

The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.

8. Beam impedance of a split cylinder

SciTech Connect

Lambertson, G.

1990-04-01

A common geometry for position electrodes at moderately low frequencies is the capacitive pickup consisting of a diagonally- divided cylinder that encloses the beam trajectory. For the simplified system here, a relatively direct approach will given the longitudinal and transverse beam impedances (Z{parallel}and Z{perpendicular}) at low frequencies. This paper discusses the determination of this impedance.

9. Possibilities of electrical impedance tomography in gynecology

NASA Astrophysics Data System (ADS)

V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.

2013-04-01

The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.

10. Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls.

PubMed

Ravi, Karthik; Katzka, David A

2016-09-01

The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology.

11. FDTD modeling of thin impedance sheets

NASA Technical Reports Server (NTRS)

Luebbers, Raymond J.; Kunz, Karl S.

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

12. Transverse impedance localization using intensity dependent optics

SciTech Connect

Calaga,R.; Arduini, G.; Metral, E.; Papotti, G.; Quatraro, D.; Rumolo, G.; Salvant, B.; Tomas, R.

2009-05-04

Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed.

13. Behind the (impedance) baseline in children.

PubMed

Salvatore, S; Salvatoni, A; Van Steen, K; Ummarino, D; Hauser, B; Vandenplas, Y

2014-01-01

Impedance baseline is a new parameter recently related to esophageal integrity. The aim of this study was to assess the effect of different factors on impedance baseline in pediatric patients. We analyzed the impedance baseline of 800 children with symptoms of gastroesophageal reflux. Mean impedance baseline was automatically calculated throughout 24-hour tracings. The presence of different age groups and of esophagitis was evaluated. Unpaired t-test, Spearman rank correlation, polynomial, and regression plot were used for statistical analysis. Age-related percentile curves were created. We considered a P-value<0.05 as statistically significant. Impedance baseline was significantly (P<0.001) lower in younger compared to older children up to 48 months. The mean increase of baseline per month was much higher in the first 36 months of life (47.5 vs. 2.9 Ohm in Channel 1 and 29.9 vs. 2.3 Ohm in Channel 6, respectively) than in older ages. Patients with esophagitis showed significantly decreased impedance baseline (P<0.05). Infants (especially in the first months of life) and young children present a significantly lower impedance baseline compared to older children both in proximal and distal esophagus. The presence of esophagitis may also determine a decreased impedance baseline regardless of the age of the patients.

14. Active impedance matching of complex structural systems

NASA Technical Reports Server (NTRS)

Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.

1991-01-01

Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.

15. LHC Kicker Beam-Impedance Calculation

SciTech Connect

Lambertson, G.R.

1998-10-01

Longitudinal and transverse beam impedances are calculated for the injection kickers designed for use in the CERN large hadron col- Iider. These combine the contributions of a ceramic beam tube with conducting stripes and a traveling-wave kicker magnet. The results show peak impedances of 1300 ohm longitudinal and 8 Mfl/m trans- verse for four units per ring.

16. Feedforward control of bending waves in frequency domain at structural junctions using an impedance formulation

NASA Astrophysics Data System (ADS)

Svensson, Jonas L.; Andersson, Patrik B. U.; Scheuren, Joachim; Kropp, Wolfgang

2009-06-01

This paper presents an active impedance-matching technique for vibrating structures described by Euler-Bernoulli theory. Full 2×2 impedance matrices are included in the derivation of the reflection matrix of an arbitrary structural junction. This implies that the effects of both bending waves and bending near-fields are included. An active impedance load is introduced in order to match a discontinuity at the junction, i.e. to force the reflection matrix to zero. The impedance-matching technique is applied to two theoretical examples. First, maximum power transfer at a free end is investigated under the condition of incident bending wave and bending near-field; second, the approach is used to match the junction between an Euler-Bernoulli beam and a sandwich composite for an incident bending wave. The latter example proposes an active-passive damping configuration which employs active control to enclose all incident wave power in a dissipative sandwich-type structure. Results show that for this configuration, the active impedance load is responsible for the main part of the power absorption over a broad frequency range.

17. Anti-vibration gloves?

PubMed

Hewitt, Sue; Dong, Ren G; Welcome, Daniel E; McDowell, Thomas W

2015-03-01

For exposure to hand-transmitted vibration (HTV), personal protective equipment is sold in the form of anti-vibration (AV) gloves, but it remains unclear how much these gloves actually reduce vibration exposure or prevent the development of hand-arm vibration syndrome in the workplace. This commentary describes some of the issues that surround the classification of AV gloves, the assessment of their effectiveness and their applicability in the workplace. The available information shows that AV gloves are unreliable as devices for controlling HTV exposures. Other means of vibration control, such as using alternative production techniques, low-vibration machinery, routine preventative maintenance regimes, and controlling exposure durations are far more likely to deliver effective vibration reductions and should be implemented. Furthermore, AV gloves may introduce some adverse effects such as increasing grip force and reducing manual dexterity. Therefore, one should balance the benefits of AV gloves and their potential adverse effects if their use is considered.

18. Structural health monitoring using piezoelectric impedance measurements.

PubMed

Park, Gyuhae; Inman, Daniel J

2007-02-15

This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in turn can indicate that damage has occurred. An experimental study is presented to demonstrate how this technique can be used to detect structural damage in real time. Signal processing methods that address damage classifications and data compression issues associated with the use of the impedance methods are also summarized. Finally, a modified frequency-domain autoregressive model with exogenous inputs (ARX) is described. The frequency-domain ARX model, constructed by measured impedance data, is used to diagnose structural damage with levels of statistical confidence.

19. Design of a nonlinear torsional vibration absorber

NASA Astrophysics Data System (ADS)

Tahir, Ammaar Bin

Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

20. PREFACE: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT)

NASA Astrophysics Data System (ADS)

Pliquett, Uwe

2013-04-01

. Structures down to sub-micrometer range and complex impedance measurements tools integrated at single chips are now affordable. Moreover, the introduction of alternative signals and data processing algorithms focuses on very fast and parallel electrical characterization which in turn pushes this technique to new applications and markets. Electrical impedance tomography today yields pictures in real time with a resolution that was impossible 10 years ago. The XVth International Conference on Electrical Bio-Impedance in conjunction with the XIVth Electrical Impedance Tomography ICEBI/EIT 2013 organized by the Institute for Bioprocessing and Analytical Measurement Techniques, Heilbad Heiligenstadt, Germany, together with the EIT-group at the University of Göttingen, Germany, brings world leading scientists in these fields together. It is a platform to present the latest developments in instrumentation and signal processing but also points to new applications, especially in the field of biosensors and non-linear phenomena. Two Keynote lectures will extend the view of the participants above the mainstream of bio-impedance measurement. Friederich Kremer (University of Leipzig) delivers the plenary lecture on broad bandwidth dielectric spectroscopy. New achievements in the research of ligand gated ionic channels will be presented by Klaus Benndorf (University of Jena). Leading scientists in the field of bio-impedance measurement, such as, Sverre Grimnes, Orjan Martinsen, Andrea Robitzki, Richard Bayford, Jan Gimsa and Mart Min will give lectures for students but also more experienced scientists in a pre-conference tutorial which is a good opportunity to learn or refresh the basics. List of committees Conference Chair Dr Uwe Pliquett Professor Dieter Beckmann Institut für Bioprozess- und Analysenmesstechnik eV, Rosenhof, Heilbad Heiligenstadt, Germany Technical Program Chair Maik Hiller Conventus Congressmanagement & Marketing GmbH, Carl-Pulfrich-Str. 1 - 07745 Jena Pre

1. Prediction of the acoustic impedance of duct liners

NASA Technical Reports Server (NTRS)

Zorumski, W. E.; Tester, B. J.

1976-01-01

Recent research which contributes to the prediction of the acoustic impedance of duct liners is reviewed. This review includes the linear and nonlinear properties of sheet and bulk type materials and methods for the measurement of these properties. It also includes the effect of grazing flow on the acoustic properties of materials. Methods for predicting the properties of single or multilayered, point reacting or extended reaction, and flat or curved liners are discussed. Based on this review, methods for predicting the properties of the duct liners which are typically used in aircraft engines are recommended. Some areas of needed research are discussed briefly.

2. Linear Collider Diagnostics

SciTech Connect

Ross, Marc

2000-05-17

Each major step toward higher energy particle accelerators relies on new technology. Linear colliders require beams of unprecedented brightness and stability. Instrumentation and control technology is the single most critical tool that enables linear colliders to extend the energy reach. In this paper the authors focus on the most challenging aspects of linear collider instrumentation systems. In the Next Linear Collider (NLC), high brightness multibunch e{sup +}/e{sup {minus}} beams, with I{sub {+-}} = 10{sup 12} particles/pulse and sigma{sub x,y} {approximately} 50 x 5 mu-m, originate in damping rings and are subsequently accelerated to several hundred GeV in 2 X-band 11,424 MHz linacs from which they emerge with typical sigma{sub x,y} {approximately} 7 x 1 mu-m. Following a high power collimation section the e{sup +}/e{sup {minus}} beams are focused to sigma{sub x,y} {approximately} 300 x 5 nm at the interaction point. In this paper they review the beam intensity, position and profile monitors (x,y,z), mechanical vibration sensing and stabilization systems, long baseline RF distribution systems and beam collimation hardware.

3. Electric impedance microflow cytometry for characterization of cell disease states.

PubMed

Du, E; Ha, Sungjae; Diez-Silva, Monica; Dao, Ming; Suresh, Subra; Chandrakasan, Anantha P

2013-10-07

The electrical properties of biological cells have connections to their pathological states. Here we present an electric impedance microflow cytometry (EIMC) platform for the characterization of disease states of single cells. This platform entails a microfluidic device for a label-free and non-invasive cell-counting assay through electric impedance sensing. We identified a dimensionless offset parameter δ obtained as a linear combination of a normalized phase shift and a normalized magnitude shift in electric impedance to differentiate cells on the basis of their pathological states. This paper discusses a representative case study on red blood cells (RBCs) invaded by the malaria parasite Plasmodium falciparum. Invasion by P. falciparum induces physical and biochemical changes on the host cells throughout a 48-h multi-stage life cycle within the RBC. As a consequence, it also induces progressive changes in electrical properties of the host cells. We demonstrate that the EIMC system in combination with data analysis involving the new offset parameter allows differentiation of P. falciparum infected RBCs from uninfected RBCs as well as among different P. falciparum intraerythrocytic asexual stages including the ring stage. The representative results provided here also point to the potential of the proposed experimental and analysis platform as a valuable tool for non-invasive diagnostics of a wide variety of disease states and for cell separation.

4. Acoustic Impedance Inversion of Seismic Data Using Genetic Algorithm

NASA Astrophysics Data System (ADS)

Eladj, Said; Djarfour, Noureddine; Ferahtia, Djalal; Ouadfeul, Sid-Ali

2013-04-01

The inversion of seismic data can be used to constrain estimates of the Earth's acoustic impedance structure. This kind of problem is usually known to be non-linear, high-dimensional, with a complex search space which may be riddled with many local minima, and results in irregular objective functions. We investigate here the performance and the application of a genetic algorithm, in the inversion of seismic data. The proposed algorithm has the advantage of being easily implemented without getting stuck in local minima. The effects of population size, Elitism strategy, uniform cross-over and lower mutation are examined. The optimum solution parameters and performance were decided as a function of the testing error convergence with respect to the generation number. To calculate the fitness function, we used L2 norm of the sample-to-sample difference between the reference and the inverted trace. The cross-over probability is of 0.9-0.95 and mutation has been tested at 0.01 probability. The application of such a genetic algorithm to synthetic data shows that the inverted acoustic impedance section was efficient. Keywords: Seismic, Inversion, acoustic impedance, genetic algorithm, fitness functions, cross-over, mutation.

5. Electric Impedance Microflow Cytometry for Characterization of Cell Disease States†

PubMed Central

Diez-Silva, Monica; Dao, Ming; Suresh, Subra; Chandrakasan, Anantha P.

2013-01-01

The electrical properties of biological cells have connections to their pathological states. Here we present an electric impedance microflow cytometry (EIMC) platform for the characterization of disease states of single cells. This platform entails a microfluidic device for a label-free and non-invasive cell-counting assay through electric impedance sensing. We identified a dimensionless offset parameter δ obtained as a linear combination of a normalized phase shift and a normalized magnitude shift in electric impedance to differentiate cells on the basis of their pathological states. This paper discusses a representative case study on red blood cells (RBCs) invaded by Plasmodium falciparum malaria parasites. Invasion of P. falciparum induces physical and biochemical changes on the host cells throughout a 48-h multi-stage life cycle within the RBC. As a consequence, it also induces progressive changes in electrical properties of the host cells .We demonstrate that the EIMC system in combination with data analysis involving the new offset parameter allows differentiation of Pf–invaded RBCs from uninfected RBCs as well as among different P. falciparum intraerythrocytic asexual stages including the ring stage. The representative results provided here also point to the potential of the proposed experimental and analysis platform as a valuable tool for non-invasive diagnostics of a wide variety of disease states and for cell separation. PMID:23925122

6. Eggshell Cutter Using Ultrasonic Vibration

NASA Astrophysics Data System (ADS)

Miura, Hikaru

2003-05-01

An eggshell cutting apparatus which utilizes ultrasonic vibration was developed, replacing the conventional apparatus which uses an air cutter, to cut eggshells at the blunt end of eggs. Two ultrasonic vibration sources were used: one with longitudinal vibration only and the other with torsional vibration plus longitudinal vibration. Eggshell cutting experiments using these vibration sources were conducted. The eggshell cutting time sharply decreased with increasing longitudinal vibration amplitude as well as increasing input power. When the source with torsional vibration plus longitudinal vibration was used and the amplitude of longitudinal vibration was 12 μm or less, the torsional vibration was effective for cutting eggshells. Furthermore, at the same input power, the eggshell cutting time by the source with longitudinal vibration only was shorter than that by the source with torsional vibration plus longitudinal vibration. When an egg was cut using the apparatus, there was essentially no cutting noise and the cut surface was smooth.

7. Vibration Control via Stiffness Switching of Magnetostrictive Transducers

NASA Technical Reports Server (NTRS)

Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

2016-01-01

This paper presents a computational study of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magnetomechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.25; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping.

8. Spectral modulation observed in artificial photosynthetic complexes by real-time vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Du, Juan; Yuan, Wei; Xing, Xin; Miyatake, Tomohiro; Tamiaki, Hitoshi; Kobayashi, Takayoshi; Leng, Yuxin

2017-09-01

By real-time vibrational spectroscopy using 6.8 fs pulses, real-time vibronic coupling in stair-like zinc chlorin aggregates was studied. Besides the observed fast excitonic relaxation, amplitudes of coherent molecular vibrations are found to be linearly dispersed from the resonant peak as a function of their own vibrational frequencies. In addition, the initial phases of the molecular vibrations exhibiting clear π phase jump have been observed. All these results indicate that coherent vibrations in the artificial chlorosome intermediate energy exchange between the laser fields around the resonant peak and those separated from it by photon energy equal to the vibrational frequencies.

9. Vibration and noise analysis of a gear transmission system

NASA Technical Reports Server (NTRS)

Choy, F. K.; Qian, W.; Zakrajsek, J. J.; Oswald, F. B.

1993-01-01

This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig.

10. Passive, wireless transduction of electrochemical impedance across thin-film microfabricated coils using reflected impedance.

PubMed

Baldwin, Alex; Yu, Lawrence; Pratt, Madelina; Scholten, Kee; Meng, Ellis

2017-09-25

A new method of wirelessly transducing electrochemical impedance without integrated circuits or discrete electrical components was developed and characterized. The resonant frequency and impedance magnitude at resonance of a planar inductive coil is affected by the load on a secondary coil terminating in sensing electrodes exposed to solution (reflected impedance), allowing the transduction of the high-frequency electrochemical impedance between the two electrodes. Biocompatible, flexible secondary coils with sensing electrodes made from gold and Parylene C were microfabricated and the reflected impedance in response to phosphate-buffered saline solutions of varying concentrations was characterized. Both the resonant frequency and impedance at resonance were highly sensitive to changes in solution conductivity at the secondary electrodes, and the effects of vertical separation, lateral misalignment, and temperature changes were also characterized. Two applications of reflected impedance in biomedical sensors for hydrocephalus shunts and glucose sensing are discussed.

11. Comparison of a Convected Helmholtz and Euler Model for Impedance Eduction in Flow

NASA Technical Reports Server (NTRS)

Watson, Willie R.; Jones, Michael G.

2006-01-01

Impedances educed from a well-tested convected Helmholtz model are compared to that of a recently developed linearized Euler model using two ceramic test liners under the assumed conditions or uniform flow and a plane wave source. The convected Helmholtz model is restricted to uniform mean flow whereas the linearized Euler model can account for the effect or the shear layer. Test data to educe the impedance is acquired from measurements obtained in the NASA Langley Research Center Grazing Incidence Tube for mean flow Mach numbers ranging from 0.0 to 0.5 and source frequencies ranging from 0.5 kHz to 3.0 kHz. The unknown impedance of the liner b educed by judiciously chooingth e impedance via an optimization method to match the measured acoustic pressure on the wall opposite the test liner. Results are presented on four spatial grids using three different optimization methods (contour deformation, Davidon-Fletcher Powell, and the Genetic Algorithm). All three optimization methods converge to the same impedance when used with the same model and to nearly identical impedances when used on different models. h anomaly was observed only at 0.5 kHz for high mean flow speeds. The anomaly is likely due to the use of measured data in a flow regime where shear layer effects are important but are neglected in the math models. Consistency between the impedances educed using the two models provides confidence that the linearized Euler model is ready For application to more realistic flows, such as those containing shear layers.

12. Understanding Artifacts in Impedance Spectroscopy

DOE PAGES

Veal, B. W.; Baldo, P. M.; Paulikas, A. P.; ...

2014-11-22

Four-terminal measurements of impedance spectra have long been troubled by the presence of high frequency artifacts that typically indicate unphysically large inductive behavior. In this paper, we follow up on the observation of Fleig et al., that voltage and current are necessarily measured in different locations of the potentiostat circuit, and that, typically, the electrometer input is a virtual ground. In this case, the capacitance of coaxial cables that connect sample electrodes to the potentiostat provides a high frequency conduction path to ground, so that some of the current that passes through the sample bypasses the electrometer. In four-electrode measurements,more » this mechanism produces the observed inductive artifacts. We examine a variety of simulated samples, with calculations compared to measurements of relevant circuits, to quantitatively investigate the nature of the artifacts. Model results agree with measurements when the leakage capacitances are properly included in the circuit analyses. With understanding of the origin of the inductive artifacts, the four-electrode method can be effectively utilized, enabling a combination of two-, three- and four-electrode measurements to be used to best advantage. Finally, using this combination of electrode configurations, temperature dependent measurements of SrTiO3, Y2O3-stabilized ZrO2, and In2O3 films deposited on YSZ substrates are presented.« less

13. Understanding Artifacts in Impedance Spectroscopy

SciTech Connect

Veal, B. W.; Baldo, P. M.; Paulikas, A. P.; Eastman, J. A.

2014-11-22

Four-terminal measurements of impedance spectra have long been troubled by the presence of high frequency artifacts that typically indicate unphysically large inductive behavior. In this paper, we follow up on the observation of Fleig et al., that voltage and current are necessarily measured in different locations of the potentiostat circuit, and that, typically, the electrometer input is a virtual ground. In this case, the capacitance of coaxial cables that connect sample electrodes to the potentiostat provides a high frequency conduction path to ground, so that some of the current that passes through the sample bypasses the electrometer. In four-electrode measurements, this mechanism produces the observed inductive artifacts. We examine a variety of simulated samples, with calculations compared to measurements of relevant circuits, to quantitatively investigate the nature of the artifacts. Model results agree with measurements when the leakage capacitances are properly included in the circuit analyses. With understanding of the origin of the inductive artifacts, the four-electrode method can be effectively utilized, enabling a combination of two-, three- and four-electrode measurements to be used to best advantage. Finally, using this combination of electrode configurations, temperature dependent measurements of SrTiO3, Y2O3-stabilized ZrO2, and In2O3 films deposited on YSZ substrates are presented.

14. Vibrationally-resolved polyatomic photoelectron spectroscopy: Mode-specific behavior

NASA Astrophysics Data System (ADS)

Rathbone, G. J.; Poliakoff, E. D.; Bozek, J. D.; Lucchese, R. R.

2002-05-01

We report the first vibrationally-resolved photoelectron spectra for polyatomic molecules performed over a broad spectral range. Such studies elucidate vibrationally mode-specific aspects of the photoelectron scattering dynamics. Three linear triatomic systems (CO_2, N_2O, and CS_2) are studied, and the results exhibit striking differences for alternative modes. For CO_2^+(C^2Σ_g^+), a continuum resonance results in a 15 eV wide dip for the symmetric stretch branching ratio, while strong peaks are observed for vibrational branching ratios associated with the two symmetry forbidden modes. For CS_2^+(B^2Σ_u^+), mode-specific behavior is displayed, as resonance enhancement of a single quantum excitation is weak for the symmetric stretch, but strong for the bending vibration. For N_2O^+(A^2Σ^+), many vibrational excitations are observed and families of vibrational branching ratio spectra emerge.

15. Design of a non-traditional dynamic vibration absorber.

PubMed

Cheung, Y L; Wong, W O

2009-08-01

A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. Optimum parameters of the proposed absorber are derived based on the fixed-point theory for minimizing the maximum vibration velocity response of a single-degree-of-freedom system under harmonic excitation. The extent of reduction in maximum vibration velocity response of the primary system when using the traditional dynamic absorber is compared with that using the proposed one. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a greater reduction in maximum vibration velocity response of the primary system than the traditional absorber.

16. Thermal Vibrational Convection

NASA Astrophysics Data System (ADS)

Gershuni, G. Z.; Lyubimov, D. V.

1998-08-01

Recent increasing awareness of the ways in which vibrational effects can affect low-gravity experiments have renewed interest in the study of thermal vibrational convection across a wide range of fields. For example, in applications where vibrational effects are used to provide active control of heat and mass transfer, such as in heat exchangers, stirrers, mineral separators and crystal growth, a sound understanding of the fundamental theory is required. In Thermal Vibrational Convection, the authors present the theory of vibrational effects caused by a static gravity field, and of fluid flows which appear under vibration in fluid-filled cavities. The first part of the book discusses fluid-filled cavities where the fluid motion only appears in the presence of temperature non-uniformities, while the second considers those situations where the vibrational effects are caused by a non-uniform field. Throughout, the authors concentrate on consideration of high frequency vibrations, where averaging methods can be successfully applied in the study of the phenomena. Written by two of the pioneers in this field, Thermal Vibrational Convection will be of great interest to scientists and engineers working in the many areas that are concerned with vibration, and its effect on heat and mass transfer. These include hydrodynamics, hydro-mechanics, low gravity physics and mechanics, and geophysics. The rigorous approach adopted in presenting the theory of this fascinating and highly topical area will facilitate a greater understanding of the phenomena involved, and will lead to the development of more and better-designed experiments.

17. Modeling and analysis of circular flexural-vibration-mode piezoelectric transformer.

PubMed

Huang, Yihua; Huang, Wei

2010-12-01

We propose a circular flexural-vibration-mode piezoelectric transformer and perform a theoretical analysis of the transformer. An equivalent circuit is derived from the equations of piezoelectricity and the Hamilton's principle. With this equivalent circuit, the voltage gain ratio, input impedance, and the efficiency of the circular flexural-vibration-mode piezoelectric transformer can be determined. The basic behavior of the transformer is shown by numerical results.

18. Tracking of electrochemical impedance of batteries

NASA Astrophysics Data System (ADS)

Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.

2016-04-01

This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.

19. Estimates of Acausal Joint Impedance Models

PubMed Central

Perreault, Eric J.

2013-01-01

Estimates of joint or limb impedance are commonly used in the study of how the nervous system controls posture and movement, and how that control is altered by injury to the neural or musculoskeletal systems. Impedance characterizes the dynamic relationship between an imposed perturbation of joint position and the torques generated in response. While there are many practical reasons for estimating impedance rather than its inverse, admittance, it is an acausal representation of the limb mechanics that can lead to difficulties in interpretation or use. The purpose of this study was to explore the acausal nature of nonparametric estimates of joint impedance representations to determine how they are influenced by common experimental and computational choices. This was accomplished by deriving discrete-time realizations of first-and second-order derivatives to illustrate two key difficulties in the physical interpretation of impedance impulse response functions. These illustrations were provided using both simulated and experimental data. It was found that the shape of the impedance impulse response depends critically on the selected sampling rate, and on the bandwidth and noise characteristics of the position perturbation used during the estimation process. These results provide important guidelines for designing experiments in which nonparametric estimates of impedance will be obtained, especially when those estimates are to be used in a multistep identification process. PMID:22907963

20. Prediction of Ground Vibration from Freight Trains

NASA Astrophysics Data System (ADS)

Jones, C. J. C.; Block, J. R.

1996-05-01

Heavy freight trains emit ground vibration with predominant frequency components in the range 4-30 Hz. If the amplitude is sufficient, this may be felt by lineside residents, giving rise to disturbance and concern over possible damage to their property. In order to establish the influence of parameters of the track and rolling stock and thereby enable the design of a low vibration railway, a theoretical model of both the generation and propagation of vibration is required. The vibration is generated as a combination of the effects of dynamic forces, due to the unevenness of the track, and the effects of the track deformation under successive axle loads. A prediction scheme, which combines these effects, has been produced. A vehicle model is used to predict the dynamic forces at the wheels. This includes the non-linear effects of friction damped suspensions. The loaded track profile is measured by using a track recording coach. The dynamic loading and the effects of the moving axles are combined in a track response model. The predicted track vibration is compared to measurements. The transfer functions from the track to a point in the ground can be calculated by using a coupled track and a three-dimensional layered ground model. The propagation effects of the ground layers are important but the computation of the transfer function from each sleeper, which would be required for a phase coherent summation of the vibration in the ground, would be prohibitive. A compromise summation is used and results are compared with measurements.

1. Directional motion of liquid under mechanical vibrations

NASA Astrophysics Data System (ADS)

Costalonga, Maxime; Brunet, Philippe; Peerhossaini, Hassan

2014-11-01

When a liquid is submitted to mechanical vibrations, steady flows or motion can be generated by non-linear effects. One example is the steady acoustic streaming one can observe when an acoustic wave propagates in a fluid. At the scale of a droplet, steady motion of the whole amount of liquid can arise from zero-mean periodic forcing. As It has been observed by Brunet et al. (PRL 2007), a drop can climb an inclined surface when submitted to vertical vibrations above a threshold in acceleration. Later, Noblin et al. (PRL 2009) showed the velocity and the direction of motion of a sessile drop submitted to both horizontal and vertical vibrations can be tuned by the phase shift between these two excitations. Here we present an experimental study of the mean motion of a sessile drop under slanted vibrations, focusing on the effects of drop properties, as well as the inclination angle of the axis of vibrations. It is shown that the volume and viscosity strongly affect the drop mean velocity, and can even change the direction of its motion. In the case of a low viscous drop, gravity can become significant and be modulated by the inclination of the axis of vibrations. Contact line dynamic during the drop oscillations is also investigated.

2. Laser vibrometry measurements of rotating blade vibrations

SciTech Connect

Reinhardt, A.K.; Kadambi, J.R.; Quinn, R.D.

1995-07-01

One of the most important design factors in modern turbomachinery is the vibration of turbomachinery blading. There is a need for developing an in-service, noncontacting, noninterfering method for the measurement and monitoring of gas turbine, jet engine, and steam turbine blade vibrations and stresses. Such a technique would also be useful for monitoring rotating helicopter blades. In the power generation industry, blade failures can result in millions of dollars of downtime. The measurement of blade vibrations and dynamic stresses is an important guide for preventive maintenance, which can be a major contributor to the availability of steam turbine, gas turbine, and helicopter operations. An experiment is designed to verify the feasibility of such a vibration monitoring system using the reference beam on-axis laser-Doppler technique. The experimental setup consists of two flat, cantilever blades mounted on a hub attached to the shaft of a dc motor. The motor rests on a linear bearing permitting motion only in the direction of the motor shaft. The motor and blade assembly is then excited via an electrodynamic shaker at the first natural frequency of the blades. The resulting blade vibration is then detected using a laser vibrometer. The vibration frequencies and amplitudes of the two rotating blades are successfully measured.

3. Vibrational nonequilibrium effects on diatomic dissociation rates

NASA Technical Reports Server (NTRS)

Hansen, C. F.

1993-01-01

The collision-induced dissociation rate of diatomic molecules from a ladder of rotational and anharmonic vibrational states is developed, and the correction for vibrational nonequilibrium is considered. The result is similar to an analytic correction derived by Hammerling et al. (1959) for harmonic oscillators. An empirical correction algorithm suggested by Park (1987, 1990) gives similar results when vibrational temperature is comparable to kinetic temperature but underestimates the dissociation rate when vibrational temperature is small compared with the kinetic temperature. This algorithm uses an effective temperature in the experimentally determined Arrhenius expression for the rate coefficient, which is a weighted average of the vibrational and kinetic temperature, whereas theory indicates that kinetic temperature should appear only in the exponential term of the Arrhenius expression. Nevertheless, an effective temperature can always be found that will numerically duplicate the proper rate coefficient at any given condition, but a constant weighting factor cannot be expected to provide this. However, the algorithm can he adjusted to give reasonable results over a range of conditions if the geometric weighting factor is taken to be a simple linear function of the ratio of vibrational to kinetic temperature in the gas.

4. Quantum Monte Carlo for vibrating molecules

SciTech Connect

Brown, W.R. |

1996-08-01

Quantum Monte Carlo (QMC) has successfully computed the total electronic energies of atoms and molecules. The main goal of this work is to use correlation function quantum Monte Carlo (CFQMC) to compute the vibrational state energies of molecules given a potential energy surface (PES). In CFQMC, an ensemble of random walkers simulate the diffusion and branching processes of the imaginary-time time dependent Schroedinger equation in order to evaluate the matrix elements. The program QMCVIB was written to perform multi-state VMC and CFQMC calculations and employed for several calculations of the H{sub 2}O and C{sub 3} vibrational states, using 7 PESs, 3 trial wavefunction forms, two methods of non-linear basis function parameter optimization, and on both serial and parallel computers. In order to construct accurate trial wavefunctions different wavefunctions forms were required for H{sub 2}O and C{sub 3}. In order to construct accurate trial wavefunctions for C{sub 3}, the non-linear parameters were optimized with respect to the sum of the energies of several low-lying vibrational states. In order to stabilize the statistical error estimates for C{sub 3} the Monte Carlo data was collected into blocks. Accurate vibrational state energies were computed using both serial and parallel QMCVIB programs. Comparison of vibrational state energies computed from the three C{sub 3} PESs suggested that a non-linear equilibrium geometry PES is the most accurate and that discrete potential representations may be used to conveniently determine vibrational state energies.

5. Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air: 2: Measurement of ground impedance

NASA Technical Reports Server (NTRS)

Meredith, R. W.; Becher, J.

1981-01-01

Parts were fabricated for the acoustic ground impedance meter and the instrument was tested. A rubber hose was used to connect the resonator neck to the chamber in order to suppress vibration from the volume velocity source which caused chatter. An analog to digital converter was successfully hardwired to the computer detection system. The cooling system for the resonant tube was modified to use liquid nitrogen cooling. This produced the required temperature for the tube, but the temperature gradients within each of the four tube sections reached unacceptable levels. Final measurements of the deexcitation of nitrogen by water vapor indicate that the responsible physical process is not the direct vibration-translation energy transfer, but is a vibration-vibration energy transfer.

6. Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air: 2: Measurement of ground impedance

NASA Astrophysics Data System (ADS)

Meredith, R. W.; Becher, J.

1981-09-01

Parts were fabricated for the acoustic ground impedance meter and the instrument was tested. A rubber hose was used to connect the resonator neck to the chamber in order to suppress vibration from the volume velocity source which caused chatter. An analog to digital converter was successfully hardwired to the computer detection system. The cooling system for the resonant tube was modified to use liquid nitrogen cooling. This produced the required temperature for the tube, but the temperature gradients within each of the four tube sections reached unacceptable levels. Final measurements of the deexcitation of nitrogen by water vapor indicate that the responsible physical process is not the direct vibration-translation energy transfer, but is a vibration-vibration energy transfer.

7. FDTD modeling of thin impedance sheets

NASA Technical Reports Server (NTRS)

Luebbers, Raymond; Kunz, Karl

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

8. RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE.

SciTech Connect

HAHN,H.; DAVINO,D.

2002-06-02

Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without external resistive damping, such as the RHIC abort kicker, would benefit.

9. Summary of the impedance working group

SciTech Connect

Chao, A.W.

1995-05-01

The impedance working group concentrated on the LHC design during the workshop. They look at the impedance contributions of liner, beam position monitors, shielded bellows, experimental chambers, superconducting cavities, recombination chambers, space charge, kickers, and the resistive wall. The group concluded that the impedance budgeting and the conceptual designs of the vacuum chamber components looked basically sound. It also noted, not surprisingly, that a large amount of studies are to be carried out further, and it ventured to give a partial list of these studies.

10. Wearable impedance monitoring system for dialysis patients.

PubMed

Bonnet, S; Bourgerette, A; Gharbi, S; Rubeck, C; Arkouche, W; Massot, B; McAdams, E; Montalibet, A; Jallon, P

2016-08-01

This paper describes the development and the validation of a prototype wearable miniaturized impedance monitoring system for remote monitoring in home-based dialysis patients. This device is intended to assess the hydration status of dialysis patients using calf impedance measurements. The system is based on the low-power AD8302 component. The impedance calibration procedure is described together with the Cole parameter estimation and the hydric volume estimation. Results are given on a test cell to validate the design and on preliminary calf measurements showing Cole parameter variations during hemodialysis.

11. LINEAR ACCELERATOR

DOEpatents

Christofilos, N.C.; Polk, I.J.

1959-02-17

Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

12. Vibrating fuel grapple. [LMFBR

DOEpatents

Chertock, A.J.; Fox, J.N.; Weissinger, R.B.

A reactor refueling method is described which utilizes a vibrating fuel grapple for removing spent fuel assemblies from a reactor core. It incorporates a pneumatic vibrator in the grapple head which allows additional withdrawal capability without exceeding the allowable axial force limit. The only moving part in the vibrator is a steel ball, pneumatically driven by a gas, such as argon, around a track, with centrifugal force created by the ball being transmitted through the grapple to the assembly handling socket.

13. Vibrating fuel grapple

DOEpatents

Chertock, deceased, Alan J.; Fox, Jack N.; Weissinger, Robert B.

1982-01-01

A reactor refueling method utilizing a vibrating fuel grapple for removing spent fuel assemblies from a reactor core which incorporates a pneumatic vibrator in the grapple head, enabling additional withdrawal capability without exceeding the allowable axial force limit. The only moving part in the vibrator is a steel ball, pneumatically driven by a gas, such as argon, around a track, with centrifugal force created by the ball being transmitted through the grapple to the assembly handling socket.

14. System characterization in nonlinear random vibration

SciTech Connect

Paez, T.L.; Gregory, D.L.

1986-01-01

Linear structural models are frequently used for structural system characterization and analysis. In most situations they can provide satisfactory results, but under some circumstances they are insufficient for system definition. The present investigation proposes a model for nonlinear structure characterization, and demonstrates how the functions describing the model can be identified using a random vibration experiment. Further, it is shown that the model is sufficient to completely characterize the stationary random vibration response of a structure that has a harmonic frequency generating form of nonlinearity. An analytical example is presented to demonstrate the plausibility of the model.

15. Adaptive vibration energy harvesting

NASA Astrophysics Data System (ADS)

Behrens, Sam; Ward, John; Davidson, Josh

2007-04-01

By scavenging energy from their local environment, portable electronic devices such as mobile phones, radios and wireless sensors can achieve greater run-times with potentially lower weight. Vibration energy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy, through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as wind, seismic forces and traffic. Existing approaches to vibration energy harvesting typically utilise a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibration energy harvesting, including adaption to non-periodic vibrations so as to extract the maximum amount of vibration energy available. Experimental results of an experimental apparatus using off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27 - 34%. However, simulations of a more electro-mechanical efficient and lightly damped transducer show conversion efficiencies in excess of 80%.

16. Spatial feature tracking impedence sensor using multiple electric fields

DOEpatents

Novak, James L.

1998-01-01

Linear and other features on a workpiece are tracked by measuring the fields generated between electrodes arrayed in pairs. One electrode in each pair operates as a transmitter and the other as a receiver, and both electrodes in a pair are arrayed on a carrier. By combining and subtracting fields between electrodes in one pair and between a transmitting electrode in one pair and a receiving electrode in another pair, information describing the location and orientation of the sensor relative to the workpiece in up to six degrees of freedom may be obtained. Typical applications will measure capacitance, but other impedance components may be measured as well. The sensor is designed to track a linear feature axis or a protrusion or pocket in a workpiece. Seams and ridges can be tracked by this non-contact sensor. The sensor output is useful for robotic applications.

17. Spatial feature tracking impedence sensor using multiple electric fields

DOEpatents

Novak, J.L.

1998-08-11

Linear and other features on a workpiece are tracked by measuring the fields generated between electrodes arrayed in pairs. One electrode in each pair operates as a transmitter and the other as a receiver, and both electrodes in a pair are arrayed on a carrier. By combining and subtracting fields between electrodes in one pair and between a transmitting electrode in one pair and a receiving electrode in another pair, information describing the location and orientation of the sensor relative to the workpiece in up to six degrees of freedom may be obtained. Typical applications will measure capacitance, but other impedance components may be measured as well. The sensor is designed to track a linear feature axis or a protrusion or pocket in a workpiece. Seams and ridges can be tracked by this non-contact sensor. The sensor output is useful for robotic applications. 10 figs.

18. On Ultrafast Time-Domain TeraHertz Spectroscopy in the Condensed Phase: Linear Spectroscopic Measurements of Hydrogen-Bond Dynamics of Astrochemical Ice Analogs and Nonlinear TeraHertz Kerr Effect Measurements of Vibrational Quantum Beats

NASA Astrophysics Data System (ADS)

Allodi, Marco A.

. We tentatively observe a new feature in both amorphous solid water and crystalline water at 33 wavenumbers (1 THz). In addition, our studies of mixed and layered ices show how it is possible to identify the location of carbon dioxide as it segregates within the ice by observing its effect on the THz spectrum of water ice. The THz spectra of mixed and layered ices are further analyzed by fitting their spectra features to those of pure amorphous solid water and crystalline water ice to quantify the effects of temperature changes on structure. From the results of this work, it appears that THz spectroscopy is potentially well suited to study thermal transformations within the ice. To advance the study of liquids with THz spectroscopy, we developed a new ultrafast nonlinear THz spectroscopic technique: heterodyne-detected, ultrafast THz Kerr effect (TKE) spectroscopy. We implemented a heterodyne-detection scheme into a TKE spectrometer that uses a stilbazoium-based THz emitter, 4-N,N-dimethylamino-4-N-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS), and high numerical aperture optics which generates THz electric field in excess of 300 kV/cm, in the sample. This allows us to report the first measurement of quantum beats at terahertz (THz) frequencies that result from vibrational coherences initiated by the nonlinear, dipolar interaction of a broadband, high-energy, (sub)picosecond THz pulse with the sample. Our instrument improves on both the frequency coverage, and sensitivity previously reported; it also ensures a backgroundless measurement of the THz Kerr effect in pure liquids. For liquid diiodomethane, we observe a quantum beat at 3.66 THz (122 wavenumbers), in exact agreement with the fundamental transition frequency of the lowest energy vibration of the molecule. This result provides new insight into dipolar vs. Raman selection rules at terahertz frequencies. To conclude we discuss future directions for the nonlinear THz spectroscopy in the Blake lab

19. Transverse impedances of cavities and collimators

SciTech Connect

Kheifets, S.A.; Bane, K.L.F.; Bizek, H.

1987-03-01

Field matching has been used to compute the transverse impedance of simple, cylindrically symmetric, perfectly conducting structures, the subregions of which are separated by radial cuts. The method is briefly described, and some early results are presented. (LEW)

20. Adaptive impedance control of redundant manipulators

NASA Technical Reports Server (NTRS)

Colbaugh, R.; Glass, K.; Seraji, H.

1990-01-01

A scheme for controlling the mechanical impedance of the end-effector of a kinematically redundant manipulator is presented. The proposed control system consists of two subsystems: an adaptive impedance controller which generates the Cartesian-space control input F (is a member of Rm) required to provide the desired end-effector impedance characteristics, and an algorithm that maps this control input to the joint torque T (is a member of Rn). The F to T map is constructed so that the robot redundancy is utilized to improve either the kinematic or dynamic performance of the robot. The impedance controller does not require knowledge of the complex robot dynamic model or parameter values for the robot, the payload, or the environment, and is implemented without calculation of the robot inverse kinematic transformation. As a result, the scheme is very general and is computationally efficient for on-line implementation.

1. Antenna pattern control using impedance surfaces

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Liu, Kefeng; Tirkas, Panayiotis A.

1993-01-01

During the period of this research project, a comprehensive study of pyramidal horn antennas was conducted. Full-wave analytical and numerical techniques were developed to analyze horn antennas with or without impedance surfaces. Based on these full-wave analytic techniques, research was conducted on the use of impedance surfaces on the walls of the horn antennas to control the antenna radiation patterns without a substantial loss of antenna gain. It was found that the use of impedance surfaces could modify the antenna radiation patterns. In addition to the analytical and numerical models, experimental models were also constructed and they were used to validate the predictions. Excellent agreement between theoretical predictions and the measured data was obtained for pyramidal horns with perfectly conducting surfaces. Very good comparisons between numerical and experimental models were also obtained for horns with impedance surfaces.

2. Characterizing an improved broad band impedance

SciTech Connect

Chao, A.

2000-03-06

A phenomenological model of broadband impedance containing two free parameters has been recently proposed. This paper attempts to assign physical characterizations to these free parameters by relating them to the geometric dimensions of a stand-alone cavity structure.

3. Surface impedance of transversely moving microwave ferrite

NASA Astrophysics Data System (ADS)

Mueller, R. S.

1990-01-01

A theoretical study was made of the surface impedance Z for an electromagnetic transverse magnetic wave from free space on a magnetized ferrite surface moving normal to the plane of incidence. It was found convenient to decompose the surface impedance into two transfer impedances, Z1 and Z2, which relate the hybrid reflected amplitudes to the amplitude of the incident wave. The surface impedance does not vary much with respect to the angle of incidence, so only the case of normal incidence (θi = 0°) was evaluated. Resonant poles at ƒc, [ƒc(ƒc + ƒm)]1/2, and ƒc + ƒm dominate the frequency characteristics of Z1 and Z2. The frequencies ƒc andƒm are the precessional frequency and magnetization frequency, respectively.

4. Closed-loop stimulation using intracardiac impedance as a sensor principle: correlation of right ventricular dP/dtmax and intracardiac impedance during dobutamine stress test.

PubMed

Osswald, S; Cron, T; Grädel, C; Hilti, P; Lippert, M; Ströbel, J; Schaldach, M; Buser, P; Pfisterer, M

2000-10-01

Changes of the unipolar right ventricular impedance during the cardiac cycle are related to the changing content of blood (low impedance) and tissue (high impedance) around the tip of the pacing electrode. During myocardial contraction, the impedance continuously increases reaching its maximum in late systole. This impedance increase is thought to correlate with right ventricular contractility, and thus, with the inotropic state of the heart. In the new Inos2 DDDR pacemaker, integrated information from the changing ventricular impedance (VIMP) is used for closed-loop regulation of the rate response. The aim of this study was to analyze the effect of increasing dobutamine challenge on RV contractility and the measured impedance signals. In 12 patients (10 men, 68 +/- 12 years) undergoing implantation of an Inos2 DDDR pacemaker (Biotronik), a right ventricular pigtail catheter was inserted for continuous measurements of RV-dP/dtmax and simultaneous VIMP signals during intrinsic and ventricular paced rhythm. Then, a stress test with a stepwise increase of intravenous dobutamine (5-20 micrograms/kg per min) was performed. To assess the relationship between RV contractility and measured sensor signals, normalized values of dP/dtmax and VIMP were compared by linear regression. There was a strong and highly significant correlation between dP/dtmax and VIMP for ventricular paced (r2 = 0.93) and intrinsic rhythm (r2 = 0.92), although the morphologies of the original impedance curves differed quite substantially between paced and intrinsic rhythm in the same patient. Furthermore, VIMP correlated well with sinus rate (r2 = 0.82), although there were at least four patients with documented chronotropic incompetence. We conclude, that for intrinsic and ventricular paced rhythms sensor signals derived from right ventricular unipolar impedance curves closely correlate with dP/dtmax, and thus, with a surrogate of right ventricular contractility during dobutamine stress testing. Our

5. Scattering from coated structures and antenna pattern control using impedance surfaces, part A/B

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polka, Lesley A.; Liu, Kefeng

1990-01-01

The scattering from coated, conducting structures, specifically the coated dihedral corner reflector configuration and the coated strip/plate configuration is examined. The formulation uses impedance-wedge Uniform Theory of Diffraction scattering coefficients to calculate the diffracted fields. A finite-thickness coating is approximated using the impedance boundary condition to arrive at an equivalent impedance for the coating. The formulation of the impedance wedge coefficients is outlined. Far-field, perfectly conducting approximations are discussed. Problems with the present dihedral corner reflector model for certain angles of incidence and observation are discussed along with a potentially rectifying modification. Also, the capacity to measure the electromagnetic properties of lossy materials was developed. The effects of using multiple material coatings on the radiation pattern of the horn antenna were studied. Numerous computations were devoted toward the inverse problem of synthesizing desired radiation patterns using the impedance surfaces. Stabilizing the equivalent sheet impedance using the linear control condition was attempted, and it was found to be a very difficult task.

6. An impedance device for study of multisegment hemodynamic changes during orthostatic stress

NASA Astrophysics Data System (ADS)

Montgomery, L. D.; Hanish, H. M.; Marker, R. A.

1989-11-01

Definition of multisegment hemodynamic changes that take place in the body would provide a more complete understanding of the physiologic responses to various orthostatic stress techniques. A self-contained impedance device is described which may be used to measure the electrical transmission characteristics produced by blood flow and volume changes in six segments of the human body during head-up tilt, bed rest, and lower body negative pressure. The device consists of a module that contains the electronics for the impedance system, a separate controller/multiplexer, a personal computer interface/analog to digital conversion/power supply system, and the associated computer control softwave. The instrument is linear over a range of 0 to 200 ohms; provides analog outputs of base impedance, phase angle, pulsatile impedance change, and the first derivative of the pulsatile impedance changes; and can be used to automatically record basal impedance values into spread-sheet format with cycle times between 12 s and 1 h. Typical results are presented to illustrate its application in aerospace research.

7. Effect of shear on duct wall impedance.

NASA Technical Reports Server (NTRS)

Goldstein, M.; Rice, E.

1973-01-01

The solution to the equation governing the propagation of sound in a uniform shear layer is expressed in terms of parabolic cylinder functions. This result is used to develop a closed-form solution for acoustic wall impedance which accounts for both the duct liner and the presence of a boundary layer in the duct. The effective wall impedance can then be used as the boundary condition for the much simpler problem of sound propagation in uniform flow.

8. Electrical Impedance Tomography of Breast Cancer

DTIC Science & Technology

2004-06-01

Resonance Research Systems, Guildford, UK) that has broadband RF transmit and receive channels. A 16 leg, quadrature, high-pass birdcage coil with 10...metastatic cancer, magnetic resonance imaging, 43 electrical impedance imaging, electrical impedance scanning, MRI 16. PRICE CODE current density imaging...tissue with high spatial resolution, by using it in conjunction with Magnetic Resonance Imaging (MRI) to improve diagnostic accuracy of screening. For

9. Acoustic Impedance Measurement for Underground Surfaces.

NASA Astrophysics Data System (ADS)

Cockcroft, Paul William

Available from UMI in association with The British Library. Requires signed TDF. This thesis investigates the measurement of acoustic impedance for surfaces likely to be found in underground coal mines. By introducing the concepts of industrial noise, the effects of noise on the ear and relevant legislation the need for the protection of workers can be appreciated. Representative acoustic impedance values are vital as input for existing computer models that predict sound levels in various underground environments. These enable the mining engineer to predict the noise level at any point within a mine in the vicinity of noisy machinery. The concepts of acoustic intensity and acoustic impedance are investigated and different acoustic impedance measurement techniques are detailed. The possible use of either an impedance tube or an intensity meter for these kinds of measurements are suggested. The problems with acoustic intensity and acoustic impedance measurements are discussed with reference to the restraints that an underground environment imposes on any measurement technique. The impedance tube method for work in an acoustics laboratory is shown and the theory explained, accompanied by a few representative results. The use of a Metravib intensity meter in a soundproof chamber to gain impedance values is explained in detail. The accompanying software for the analysis of the two measured pressure signals is shown as well as the actual results for a variety of test surfaces. The use of a Nagra IV-SJ tape recorder is investigated to determine the effect of recording on the measurement and subsequent analysis of the input signals, particularly with reference to the phase difference introduced between the two simultaneous pressure signals. The subsequent use of a Norwegian Electronic intensity meter, including a proposal for underground work, is shown along with results for tests completed with this piece of equipment. Finally, recommendations are made on how to link up

10. Inversion of elastic impedance for unconsolidated sediments

USGS Publications Warehouse

Lee, Myung W.

2006-01-01

Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.

11. Acoustic impedance measurements of pulse tube refrigerators

NASA Astrophysics Data System (ADS)

Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

2010-02-01

Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

12. CSR Impedance for Non-Ultrarelativistic Beams

SciTech Connect

Li, Rui; Tsai, Cheng Y.

2015-09-01

For the analysis of the coherent synchrotron radiation (CSR)-induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.

13. Impedance Analysis of Surface-Bound Biomembranes

DTIC Science & Technology

1990-06-08

and identify by block numb (i FIELD GROUP SUB-GROLm--- AC Impedance, Biomembranes, Lipid, Electrod\\) ’CBiosensor - O ( S. &-’te ,,• J ABSTRACT...Instit-ute 57 Union St., Worcester, MA 01608 ABSTRACTElcchria isThe impedance of different electrode substratesElcharacteriz l biomemance atnactuses fomed ...T10 2), indium/tin oxide (ITO) and platinum electrodes that have been "primed" by covalent attachment of long-chained alkyl groups . The electroes were

14. Use of a small overpotential approximation to analyze Geobacter sulfurreducens biofilm impedance

NASA Astrophysics Data System (ADS)

Babauta, Jerome T.; Beyenal, Haluk

2017-07-01

The electrochemical impedance of Geobacter sulfurreducens biofilms reflects the extracellular electron transfer mechanisms determining the rate of current output. Binned into two characteristic parameters, conductance and capacitance, biofilm impedance has received significant attention. The goal of this study was to evaluate a small overpotential approximation for extracellular electron transfer in G. sulfurreducens biofilms. Our motivation was to determine whether conductance over biofilm growth behaved linearly with respect to limiting current. Biofilm impedance was tracked during growth using electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (eQCM). We showed that normalization of the biofilm impedance is useful for characterizing the changes during growth. When the conductance and capacitance were compared to the biofilm current, we found that: 1) conductance had a linear response and 2) constant phase elements (CPE) had a saturating response that coincided with the limiting current. We provided a framework using a simple iV relationship that predicted the conductance-current slope to be 9.57 V-1. CPEs showed more variability across biofilm replicates than conductance values. Although G. sulfurreducens biofilms were used here, other electrochemically active biofilms exhibiting catalytic waves could be studied using the same methods.

15. Antenna impedance matching with neural networks.

PubMed

Hemminger, Thomas L

2005-10-01

Impedance matching between transmission lines and antennas is an important and fundamental concept in electromagnetic theory. One definition of antenna impedance is the resistance and reactance seen at the antenna terminals or the ratio of electric to magnetic fields at the input. The primary intent of this paper is real-time compensation for changes in the driving point impedance of an antenna due to frequency deviations. In general, the driving point impedance of an antenna or antenna array is computed by numerical methods such as the method of moments or similar techniques. Some configurations do lend themselves to analytical solutions, which will be the primary focus of this work. This paper employs a neural control system to match antenna feed lines to two common antennas during frequency sweeps. In practice, impedance matching is performed off-line with Smith charts or relatively complex formulas but they rarely perform optimally over a large bandwidth. There have been very few attempts to compensate for matching errors while the transmission system is in operation and most techniques have been targeted to a relatively small range of frequencies. The approach proposed here employs three small neural networks to perform real-time impedance matching over a broad range of frequencies during transmitter operation. Double stub tuners are being explored in this paper but the approach can certainly be applied to other methodologies. The ultimate purpose of this work is the development of an inexpensive microcontroller-based system.

16. Effects of ultrasonic vibrations in micro-groove turning.

PubMed

Zhang, Chen; Guo, Ping; Ehmann, Kornel F; Li, Yingguang

2016-04-01

Ultrasonic vibration cutting is an efficient cutting process for mechanical micro-machining. This process can generate intricate surface textures with different geometric characteristics. Micro-grooves/micro-channels are among the most frequently encountered micro-structures and, as such, are the focus of this paper. The effectiveness of both the linear and ultrasonic elliptical vibration-assisted machining technique in micro-groove turning is analyzed and discussed in the paper. The paper first investigates the mechanisms of micro-groove generation induced by the linear and elliptical vibration modes. A simplified cutting force analysis method is given to compare the effectiveness of the two modes in micro-groove turning. The surface roughness of the generated micro-grooves is analyzed next and theoretical expressions are given for the two cases. Finally, micro-groove turning experiments are conducted to compare the influences of the two vibration modes on the cutting forces and the surface roughness. The experimental results show that linear vibration-assisted micro-groove turning leads to better surface roughness as compared to the elliptical vibration-assisted case, while elliptical vibration-assisted micro-groove turning shows advantages in terms of decreasing the cutting forces.

17. Vibration characteristics of pipe organ reed tongues and the effect of the shallot, resonator, and reed curvature.

PubMed

Plitnik, G R

2000-06-01

Pipe organ reed pipes sound when a fixed-free curved brass reed mounted on a shallot connected to a resonator is forced to vibrate by an impressed static air pressure. Five sets of experiments were performed in order to investigate the influence of the most important parameters which could affect the tone of a reed pipe. First, the phase difference between the pressure variation in the shallot and the boot, and its relationship to the motion of the reed tongue were analyzed to compare their phases and their spectra. Next, the frequency dependence of the reed on three basic parameters (reed thickness, its vibrating length, and the imposed static air pressure) was investigated in an attempt to determine an empirical equation for the frequency. For each trial, two of the variables were kept constant while the third was altered in order to construct an equation giving frequency as a function of the three variables. Third, experiments were conducted using three different types of shallots: the American (or English) style, the French style, and the German style. The results show that for each shallot, the frequency increases linearly with thickness and linearly with air pressure (over the normal operating range of the reed). For each of the shallots, frequency varies inversely with length when the other variables are held constant. The effect on the reed spectrum of using the three different types of shallot was also investigated, as was the effect of reducing the interior volume of each type. Progressively filling the shallot interior generally decreases the frequency of the vibrating reed. The effect of the resonators on frequency and spectrum was studied because the resonator is an integral part of the resulting tone; virtually every reed stop has some type of resonator. The resonator tends to raise the Q of the impedance peaks and reduce the fundamental frequency. Finally, the influence of the type and degree of curvature on reed vibration was briefly examined

18. Vibrational Schroedinger Cats

NASA Technical Reports Server (NTRS)

Kis, Z.; Janszky, J.; Vinogradov, An. V.; Kobayashi, T.

1996-01-01

The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture.

19. Multiple direction vibration fixture

DOEpatents

Cericola, Fred; Doggett, James W.; Ernest, Terry L.; Priddy, Tommy G.

1991-01-01

An apparatus for simulating a rocket launch environment on a test item undergoing centrifuge testing by subjecting the item simultaneously or separately to vibration along an axis of centripetal force and along an axis perpendicular to the centripetal force axis. The apparatus includes a shaker motor supported by centrifuge arms and a right angle fixture pivotally connected to one of the shaker motor mounts. When the shaker motor vibrates along the centripetal force axis, the vibrations are imparted to a first side of the right angle fixture. The vibrations are transmitted 90 degrees around the pivot and are directed to a second side of the right angle fixture which imparts vibrations perpendicular to the centripetal force axis. The test item is in contact with a third side of the right angle fixture and receives both centripetal-force-axis vibrations and perpendicular axis vibrations simultaneously. A test item can be attached to the third side near the flexible coupling or near the air bag to obtain vibrations along the centripetal force axis or transverse to the centripetal force axis.

20. [Vibration on agricultural tractors].

PubMed

Peretti, Alessandro; Delvecchio, Simone; Bonomini, Francesco; di Bisceglie, Anita Pasqua; Colosio, Claudio

2013-01-01

In the article, details related to the diffusion of agricultural tractors in Italy are given and considerations about the effects of vibration on operators, the sources of vibration and suggestions to reduce them are presented. The acceleration values observed in Italy amongst 244 tractors and levels of worker exposure are shown by means of histograms. The relevant data variability is discussed.