Science.gov

Sample records for induced vibrational cooling

  1. Vibrational Cooling of Photoassociated Homonuclear Cold Molecules

    NASA Astrophysics Data System (ADS)

    Passagem, Henry; Ventura, Paulo; Tallant, Jonathan; Marcassa, Luis

    2015-05-01

    In this work, we produce vibrationally cold homonuclear Rb molecules using spontaneous optical pumping. The vibrationally cooled molecules are produced in three steps. In the first step, we use a photoassociation laser to produce molecules in high vibrational levels of the singlet ground state. Then in a second step, a 50 W broadband laser at 1071 nm, which bandwidth is about 2 nm, is used to transfer the molecules to lower vibrational levels via optical pumping through the excited state. This process transfers the molecules from vibrational levels around ν ~= 113 to a distribution of levels below ν = 35 . The molecules can be further cooled using a broadband light source near 685 nm. In order to obtain such broadband source, we have used a 5 mW superluminescent diode, which is amplified in a tapered amplifier using a double pass configuration. After the amplification, the spectrum is properly shaped and we end up with about 90 mW distributed in the 682-689 nm range. The final vibrational distribution is probed using resonance-enhanced multiphoton ionization with a pulsed dye laser near 670 nm operating at 4KHz. The results are presented and compared with theoretical simulations. This work was supported by Fapesp and INCT-IQ.

  2. Friction induced rail vibrations

    NASA Astrophysics Data System (ADS)

    Kralov, Ivan; Sinapov, Petko; Nedelchev, Krasimir; Ignatov, Ignat

    2012-11-01

    A model of rail, considered as multiple supported beam, subjected on friction induced vibration is studied in this work using FEM. The model is presented as continuous system and the mass and elastic properties of a real object are taken into account. The friction forces are nonlinear functions of the relative velocity during slipping. The problem is solved using Matlab Simulink.

  3. Flow-Induced Vibration of a Reed in a Channel: Effect of Reed Shape on Convective Heat Transfer with Application to Electronic Cooling

    NASA Astrophysics Data System (ADS)

    Rips, Aaron; Shoele, Kourosh; Glezer, Ari; Mittal, Rajat

    2015-11-01

    Flow-induced vibration of a reed (a thin plate or flag) in a channel can improve heat transfer efficiency in forced convection applications, allowing for more heat transfer for the same fan power. Such systems have wide ranging applications in electronic and power cooling. We investigate the effect of 3D reed shape on heat transfer enhancement. To study 3D effects, we first use 2D fluid-structure interaction (FSI) simulations of an optimized reed (in terms of mass and stiffness) to generate a prescribed reed motion. We then apply that motion to a pseudo 3D reed (i.e. infinitely stiff in the spanwise direction) and study the heat transfer enhancement in a 3D channel. This method allows us to explore a large parameter space exhaustively, and using this method, we examine the effect of several parameters, such as reed planform and spanwise gap, on the heat transfer enhancements for forced convection in a channel. Simulations indicate that these geometrical feature have a significant effect on the vortex dynamics in the wake as well as the heat transfer efficiency. This work was supported by grants from AFOSR, EPRI and NSF.

  4. SHAKE OUT WORKER DUMPING COOLED MOLDS ONTO THE VIBRATING CONVEYOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SHAKE OUT WORKER DUMPING COOLED MOLDS ONTO THE VIBRATING CONVEYOR THAT TRANSPORTS SAND AND CASTINGS TO THE SEPARATION SCREEN. - Southern Ductile Casting Company, Centerville Foundry, 101 Airport Road, Centreville, Bibb County, AL

  5. Continuous Vibrational Cooling of Ground State Rb2

    NASA Astrophysics Data System (ADS)

    Tallant, Jonathan; Marcassa, Luis

    2014-05-01

    The process of photoassociation generally results in a distribution of vibrational levels in the electronic ground state that is energetically close to the dissociation limit. Several schemes have appeared that aim to transfer the population from the higher vibrational levels to lower ones, especially the ground vibrational state. We demonstrate continuous production of vibrationally cooled Rb2 using optical pumping. The vibrationally cooled molecules are produced in three steps. First, we use a dedicated photoassociation laser to produce molecules in high vibrational levels of the X1Σg+ state. Second, a broadband fiber laser at 1071 nm is used to transfer the molecules to lower vibrational levels via optical pumping through the A1Σu+ state. This process transfers the molecules from vibrational levels around ν ~= 113 to a distribution of levels where ν < 35. The molecules may then be further cooled using a broadband superluminescent diode near 685 nm that has its frequency spectrum shaped. The resulting vibrational distributions are probed using resonance-enhanced multiphoton ionization with a pulsed dye laser near 670 nm. The results are presented and compared with theoretical simulations. This work was supported by Fapesp and INCT-IQ.

  6. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current

    NASA Astrophysics Data System (ADS)

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C.

    2016-03-01

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  7. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.

    PubMed

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C

    2016-03-21

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  8. Vibration-Induced Droplet Atomization

    NASA Technical Reports Server (NTRS)

    Smith, M. K.; James, A.; Vukasinovic, B.; Glezer, A.

    1999-01-01

    Thermal management is critical to a number of technologies used in a microgravity environment and in Earth-based systems. Examples include electronic cooling, power generation systems, metal forming and extrusion, and HVAC (heating, venting, and air conditioning) systems. One technique that can deliver the large heat fluxes required for many of these technologies is two-phase heat transfer. This type of heat transfer is seen in the boiling or evaporation of a liquid and in the condensation of a vapor. Such processes provide very large heat fluxes with small temperature differences. Our research program is directed toward the development of a new, two-phase heat transfer cell for use in a microgravity environment. In this paper, we consider the main technology used in this cell, a novel technique for the atomization of a liquid called vibration-induced droplet atomization. In this process, a small liquid droplet is placed on a thin metal diaphragm that is made to vibrate by an attached piezoelectric transducer. The vibration induces capillary waves on the free surface of the droplet that grow in amplitude and then begin to eject small secondary droplets from the wave crests. In some situations, this ejection process develops so rapidly that the entire droplet seems to burst into a small cloud of atomized droplets that move away from the diaphragm at speeds of up to 50 cm/s. By incorporating this process into a heat transfer cell, the active atomization and transport of the small liquid droplets could provide a large heat flux capability for the device. Experimental results are presented that document the behavior of the diaphragm and the droplet during the course of a typical bursting event. In addition, a simple mathematical model is presented that qualitatively reproduces all of the essential features we have seen in a burst event. From these two investigations, we have shown that delayed droplet bursting results when the system passes through a resonance

  9. Vibration Induced Microfluidic Atomization

    NASA Astrophysics Data System (ADS)

    Yeo, Leslie; Qi, Aisha; Friend, James

    2008-11-01

    We demonstrate rapid generation of micron aerosol droplets in a microfluidic device in which a fluid drop is exposed to surface vibration as it sits atop a piezoelectric substrate. Little, however, is understood about the processes by which these droplets form due to the complex hydrodynamic processes that occur across widely varying length and time scales. Through experiments, scaling theory and numerical modelling, we elucidate the interfacial destabilization mechanisms that lead to droplet formation. Droplets form due to the axisymmetric break-up of cylindrical liquid jets ejected as a consequence of interfacial destabilization. Their 10 μm size correlates with the jet radius and the instability wavelength, both determined from a viscous-capillary dominant force balance and confirmed through a numerical solution. With the exception of drops that spread into thin films with thicknesses on the order of the boundary layer dimension, the free surface is always observed to vibrate at the capillary-viscous resonance frequency despite the surface vibration frequency being several orders larger. This is contrary to common assumptions used in deriving subharmonic models resulting in a Mathieu equation, which has commonly led to spurious predictions in the droplet size.

  10. Chaotic vortex induced vibrations

    SciTech Connect

    Zhao, J.; Sheridan, J.; Leontini, J. S.; Lo Jacono, D.

    2014-12-15

    This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.

  11. System and method of active vibration control for an electro-mechanically cooled device

    DOEpatents

    Lavietes, Anthony D.; Mauger, Joseph; Anderson, Eric H.

    2000-01-01

    A system and method of active vibration control of an electro-mechanically cooled device is disclosed. A cryogenic cooling system is located within an environment. The cooling system is characterized by a vibration transfer function, which requires vibration transfer function coefficients. A vibration controller generates the vibration transfer function coefficients in response to various triggering events. The environments may differ by mounting apparatus, by proximity to vibration generating devices, or by temperature. The triggering event may be powering on the cooling system, reaching an operating temperature, or a reset action. A counterbalance responds to a drive signal generated by the vibration controller, based on the vibration signal and the vibration transfer function, which adjusts vibrations. The method first places a cryogenic cooling system within a first environment and then generates a first set of vibration transfer function coefficients, for a vibration transfer function of the cooling system. Next, the cryogenic cooling system is placed within a second environment and a second set of vibration transfer function coefficients are generated. Then, a counterbalance is driven, based on the vibration transfer function, to reduce vibrations received by a vibration sensitive element.

  12. Vibrational cooling, heating, and instability in molecular conducting junctions: full counting statistics analysis.

    PubMed

    Simine, Lena; Segal, Dvira

    2012-10-28

    We study current-induced vibrational cooling, heating, and instability in a donor-acceptor rectifying molecular junction using a full counting statistics approach. In our model, electron-hole pair excitations are coupled to a given molecular vibrational mode which is either harmonic or highly anharmonic. This mode may be further coupled to a dissipative thermal environment. Adopting a master equation approach, we confirm the charge and heat exchange fluctuation theorem in the steady-state limit, for both harmonic and anharmonic models. Using simple analytical expressions, we calculate the charge current and several measures for the mode effective temperature. At low bias, we observe the effect of bias-induced cooling of the vibrational mode. At higher bias, the mode effective temperature is higher than the environmental temperature, yet the junction is stable. Beyond that, once the vibrational mode (bias-induced) excitation rate overcomes its relaxation rate, instability occurs. We identify regimes of instability as a function of voltage bias and coupling to an additional phononic thermal bath. Interestingly, we observe a reentrant behavior where an unstable junction can properly behave at a high enough bias. The mechanism for this behavior is discussed.

  13. Vibrational excitation induces double reaction.

    PubMed

    Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C

    2014-12-23

    Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics.

  14. FE design of vibration protective pads for portable cryogenically cooled infrared imagers

    NASA Astrophysics Data System (ADS)

    Azoulay, Michel; Veprik, Alexander; Babitsky, Vladimir

    2008-04-01

    Design of novel, portable and aurally undetectable cryogenically cooled infrared imagers often relies on compliant vibration protective pads for mounting the integrated dewar-detector-cooler assembly upon the imager's enclosure. Extensive analytical study and experimental effort have shown that for the best acoustic performance the visco-elastic properties of such pads need to be matched with the dynamic properties of the typically undamped enclosure, subjected to the tight limitations imposed on the low frequency cooler-induced line of sight jitter resulting from the oscillations of the gasodynamic torque and compliance of the above pads. Unfortunately, the regular approach to a design of the optimal vibration protective pad does not seem to exist. As a result, the development of the suitable vibration protective pad is widely regarded as a purely empirical process and requires a great deal of experimental trial-and-error effort. The authors are attempting to apply the regular finite element modeling approaches to an optimal design of such vibration protective pads. In doing so, they are making use of the full finite elements models of infrared imager enclosure with vibration mounted integrated dewar-detector-cooler assembly. The optimal geometry and dynamic properties of a compliant layer of vibration protective pad are evaluated using the optimisation procedure with purpose of attenuation the volume velocity of the active radiating surface. The theoretical findings are in fair agreement with the outcomes of the full-scale experimentation.

  15. Controlling vibrational cooling with zero-width resonances: An adiabatic Floquet approach

    NASA Astrophysics Data System (ADS)

    Leclerc, Arnaud; Viennot, David; Jolicard, Georges; Lefebvre, Roland; Atabek, Osman

    2016-10-01

    In molecular photodissociation, some specific combinations of laser parameters (wavelength and intensity) lead to unexpected zero-width resonances (ZWRs) with, in principle, infinite lifetimes. Their potential to induce basic quenching mechanisms has recently been devised in the laser control of vibrational cooling through filtration strategies [O. Atabek et al., Phys. Rev. A 87, 031403(R) (2013), 10.1103/PhysRevA.87.031403]. A full quantum adiabatic control theory based on the adiabatic Floquet Hamiltonian is developed to show how a laser pulse could be envelope-shaped and frequency-chirped so as to protect a given initial vibrational state against dissociation, taking advantage of its continuous transport on the corresponding ZWR all along the pulse duration. As compared with previous control scenarios that actually suffered from nonadiabatic contamination, drastically different and much more efficient filtration goals are achieved. A semiclassical analysis helps us to find and interpret a complete map of ZWRs in the laser parameter plane. In addition, the choice of a given ZWR path, among the complete series identified by the semiclassical approach, turns out to be crucial for the cooling scheme, targeting a single vibrational state population left at the end of the pulse, while all others have almost completely decayed. The illustrative example, which has the potential to be transposed to other diatomics, is Na2 prepared by photoassociation in vibrationally hot but translationally and rotationally cold states.

  16. Vibrational Relaxation of the Aqueous Proton in Acetonitrile: Ultrafast Cluster Cooling and Vibrational Predissociation.

    PubMed

    Ottosson, N; Liu, L; Bakker, H J

    2016-07-28

    We study the ultrafast O-H stretch vibrational relaxation dynamics of protonated water clusters embedded in a matrix of deuterated acetonitrile, using polarization-resolved mid-IR femtosecond spectroscopy. The clusters are produced by mixing triflic (trifluoromethanesulfonic) acid and H2O in molar ratios of 1:1, 1:2, and 1:3, thus varying the degree of hydration of the proton. At all hydration levels the excited O-H stretch vibration of the hydrated proton shows an ultrafast vibrational relaxation with a time constant T1 < 100 fs, leading to an ultrafast local heating of the protonated water cluster. This excess thermal energy, initially highly localized to the region of the excited proton, first re-distributes over the aqueous cluster and then dissipates into the surrounding acetonitrile matrix. For clusters with a triflic acid to H2O ratio of 1:3 these processes occur with time constants of 320 ± 20 fs and 1.4 ± 0.1 ps, respectively. The cooling of the clusters reveals a long-living, underlying transient absorption change with high anisotropy. We argue that this feature stems from the vibrational predissociation of a small fraction of the proton hydration structures, directly following the ultrafast infrared excitation.

  17. Thermally induced vibrations due to internal heat generation

    NASA Astrophysics Data System (ADS)

    Blandino, Joseph Robert

    Virtually all previous research on thermally induced vibrations has investigated vibrations caused by surface heating. This is the first detailed study of a thermally induced vibration caused by surface cooling. The phenomenon is shown to be driven by thermal moments. The thermal moments are caused by convection because the vibrations occur in air but not in a vacuum. A mathematical model was developed to predict the thermal-structural behavior of an internally heated beam. The convection heat transfer for a vibrating beam is complex. In most cases it is neither completely natural nor completely forced convection. The convection heat transfer is a mix of both components. The convection is further complicated by the transition of the airflow along the beam from laminar to turbulent flow. An experimental heat transfer investigation was conducted to determine expressions for the natural and forced convection as functions of both position along the beam and velocity. The results from the model were verified using experimental data for an internally heated beam undergoing thermally induced vibrations. The model was shown to predict the steady-state temperatures accurately. The model adequately predicted the steady-state displacements, although it predicted the displacement histories with some error. The analysis showed that the thermal and structural problems are coupled by the forced convection. Once initiated, the amplitude of the vibration increases until the amplitude is such that the heat removed by convection balances the internal heating. The steady-state amplitude is not affected by the initial displacement of the beam. Thermally induced vibrations of internally heated beams belong to the class of vibrations called self-sustaining oscillations.

  18. Attenuation of cryocooler induced vibration in spaceborne infrared payloads

    NASA Astrophysics Data System (ADS)

    Veprik, A.; Twitto, A.

    2014-01-01

    Recent advancement of operational responsive space programs calls for a development of compact, reliable, low power and vibration free cryogenic cooling for sophisticated infrared payloads. The refrigeration in a typical closed cycle split Stirling linear cryocooler is achieved by a cyclic compression and expansion of a gaseous working agent due to a synchronized reciprocation of electro-dynamically and pneumatically actuated compressor and expander pistons. Attenuation of the cryocooler induced vibration usually relies on the concept of actively assisted momentum cancellation. In a typical dual-piston compressor this objective is achieved by actively synchronizing the motion of oppositely moving piston assemblies; a typical single-piston expander may be counterbalanced by a motorized counter-balancer. The above approach produces complexity, weight, size, high incurred costs and affects reliability. The authors analyze the case of passive attenuation the vibration export induced by the split Stirling linear cryocooler comprised of inline mounted single-piston compressor and expander. Placement of all the moving components onto a common axis results in a single axis consolidation of vibration export and enables use of single tuned dynamic absorber and low frequency vibration mount. From theoretical analysis and full-scale testing, the performance of such vibration protection arrangement is similar to known systems of active vibration cancellation.

  19. Vibration-induced droplet atomization

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan

    The atomization of liquid drops is investigated experimentally using laser vibrometry, high-speed imaging, and particle tracking techniques. The spray is generated by a novel vibration-induced droplet atomization (VIDA) process in which a sessile drop is atomized by an underlying vibrating thin metal diaphragm, resulting in rapid ejection of small secondary droplets from the free surface of the primary drop. Under some conditions, the primary drop can be atomized extremely rapidly by a bursting-like mechanism (e.g., a 0.1 ml water drop can be atomized in 0.4 seconds). The present research has focused on four major areas: global characteristics of VIDA process, instability modes and free surface dynamics of the forced drop, mechanisms of the interface breakup, and parametric characterization of the ensuing spray. Prior to atomization, the drop free surface undergoes three transitions: from axisymmetric standing waves to azimuthal waves, to a newly-observed lattice mode, and to a disordered pre-ejection state. The droplet ejection results from localized collapse of surface troughs and initiation and ultimate breakup of momentary liquid spikes. Breakup begins with capillary pinch-off from spike tips and can be followed by additional pinching of liquid droplets. For a relatively low-viscosity liquid, e.g., water, a capillary-wave instability of the spike is observed in some cases, while for a very viscous liquid, e.g., a glycerin/water solution, the first breakup occurs near the stem of the spike, with or without subsequent breakup of the detached, elongated thread. Different mechanisms dominating the primary breakup of the spike are operative in the low- and high-viscosity ejection regimes. When ejection of the secondary droplets is triggered, the evolution and rate of atomization depend on the coupled dynamics of the primary drop and the vibrating diaphragm. Due to these dynamics, the process can be either self-intensifying or self-decaying. The resulting VIDA spray

  20. Vibration-induced liquefaction of granular suspensions.

    PubMed

    Hanotin, C; Kiesgen de Richter, S; Marchal, P; Michot, L J; Baravian, C

    2012-05-11

    We investigate the mechanical behavior of granular suspensions subjected to coupled vibrations and shear. At high shear stress, whatever the mechanical vibration energy and bead size, the system behaves like a homogeneous suspension of hard spheres. At low shear stress, in addition to a dependence on bead size, vibration energy drastically influences the viscosity of the material that can decrease by more than 2 orders of magnitude. All experiments can be rationalized by introducing a hydrodynamical Peclet number defined as the ratio between the lubrication stress induced by vibrations and granular pressure. The behavior of vibrated wet and dry granular materials can then be unified by assimilating the hookean stress in dry media to the lubrication stress in suspensions.

  1. Efficient cooling of quantized vibrations using a four-level configuration

    NASA Astrophysics Data System (ADS)

    Yan, Lei-Lei; Zhang, Jian-Qi; Zhang, Shuo; Feng, Mang

    2016-12-01

    Cooling vibrational degrees of freedom down to ground states is essential to observation of quantum properties of systems with mechanical vibration. We propose two cooling schemes employing four internal levels of the systems, which achieve the ground-state cooling in an efficient fashion by completely deleting the carrier and first-order blue-sideband transitions. The schemes, based on quantum interference and Stark-shift gates, are robust to fluctuations of laser intensity and frequency. The feasibility of the schemes is justified using current laboratory technology. In practice, our proposal readily applies to a nanodiamond nitrogen-vacancy center levitated in an optical trap or attached to a cantilever.

  2. Bellows flow-induced vibrations

    NASA Technical Reports Server (NTRS)

    Tygielski, P. J.; Smyly, H. M.; Gerlach, C. R.

    1983-01-01

    The bellows flow excitation mechanism and results of comprehensive test program are summarized. The analytical model for predicting bellows flow induced stress is refined. The model includes the effects of an upstream elbow, arbitrary geometry, and multiple piles. A refined computer code for predicting flow induced stress is described which allows life prediction if a material S-N diagram is available.

  3. Solvent and solvent isotope effects on the vibrational cooling dynamics of a DNA base derivative.

    PubMed

    Middleton, Chris T; Cohen, Boiko; Kohler, Bern

    2007-10-25

    Vibrational cooling by 9-methyladenine was studied in a series of solvents by femtosecond transient absorption spectroscopy. Signals at UV and near-UV probe wavelengths were assigned to hot ground state population created by ultrafast internal conversion following electronic excitation by a 267 nm pump pulse. A characteristic time for vibrational cooling was determined from bleach recovery signals at 250 nm. This time increases progressively in H2O (2.4 ps), D2O (4.2 ps), methanol (4.5 ps), and acetonitrile (13.1 ps), revealing a pronounced solvent effect on the dissipation of excess vibrational energy. The trend also indicates that the rate of cooling is enhanced in solvents with a dense network of hydrogen bonds. The faster rate of cooling seen in H2O vs D2O is noteworthy in view of the similar hydrogen bonding and macroscopic thermal properties of both liquids. We propose that the solvent isotope effect arises from differences in the rates of solute-solvent vibrational energy transfer. Given the similarities of the vibrational friction spectra of H2O and D2O at low frequencies, the solvent isotope effect may indicate that a considerable portion of the excess energy decays by exciting relatively high frequency (>/=700 cm-1) solvent modes.

  4. [Scalp cooling for chemotherapy-induced alopecia].

    PubMed

    Komen, Marion M C; Smorenburg, Carolien H; van den Hurk, Corina J G; Nortier, J W R Hans

    2011-01-01

    Alopecia is a very common side effect of cytostatic therapy and is considered one of the most emotionally distressing effects. To prevent alopecia scalp cooling is currently used in some indications in medical oncology in 59 hospitals in the Netherlands. The success of scalp cooling depends on various factors such as type of chemotherapy, dose, infusion time, number of treatment cycles and combinations of drugs. In general, scalp cooling is well tolerated. The reported side-effects are headache, coldness, dizziness and sometimes claustrophobia. An increase in the risk of scalp metastases has not been demonstrated. Proceeding from the South Netherlands Comprehensive Cancer Centre a national working group is put together in order to draw up a national guideline for chemotherapy-induced alopecia.

  5. Vibration-induced drop atomization and bursting

    NASA Astrophysics Data System (ADS)

    James, A. J.; Vukasinovic, B.; Smith, Marc K.; Glezer, A.

    2003-02-01

    A liquid drop placed on a vibrating diaphragm will burst into a fine spray of smaller secondary droplets if it is driven at the proper frequency and amplitude. The process begins when capillary waves appear on the free surface of the drop and then grow in amplitude and complexity as the acceleration amplitude of the diaphragm is slowly increased from zero. When the acceleration of the diaphragm rises above a well-defined critical value, small secondary droplets begin to be ejected from the free-surface wave crests. Then, quite suddenly, the entire volume of the drop is ejected from the vibrating diaphragm in the form of a spray. This event is the result of an interaction between the fluid dynamical process of droplet ejection and the vibrational dynamics of the diaphragm. During droplet ejection, the effective mass of the drop diaphragm system decreases and the resonance frequency of the system increases. If the initial forcing frequency is above the resonance frequency of the system, droplet ejection causes the system to move closer to resonance, which in turn causes more vigorous vibration and faster droplet ejection. This ultimately leads to drop bursting. In this paper, the basic phenomenon of vibration-induced drop atomization and drop bursting will be introduced, demonstrated, and characterized. Experimental results and a simple mathematical model of the process will be presented and used to explain the basic physics of the system.

  6. Vibration syndrome diagnosis using a cooling test verified by computerized photoplethysmography.

    PubMed

    Dyszkiewicz, Andrzej; Tendera, Michał

    2006-04-01

    This study addresses the problem of vibration syndrome diagnosis by means of a cooling test verified by photoplethysmography. Measurement was taken on a small area on the fingertip plexus in which many arterio-venous anastomoses are present. In the opinion of many authors, flow disorders in this area are more typical for developing vibration syndrome than changes in the micro vessels. The study group comprised 128 subjects (58 women aged 40.9 +/- 5.4 years and 70 men aged 38.7 +/- 8.8 years) exposed to vibration. The control group consisted of 41 people (20 women aged 39.6 +/- 7.3 years and 21 men aged 39.3 +/- 6.4 years) who were not exposed to vibration. The patients were examined by a questionnaire and then a vibration perception threshold test and a cooling test were performed. The cooling test was verified both visually and using the computer method. Measurement data (S1, S2 and A) for each patient were obtained from averaging three pulse graphs. We departed from an average of 60 graphs (and more), the standard established in the literature, because of the cooling test specification, which causes huge thermodynamic parameter changeability in the plexus mass of the small finger under pulse waves coming one after another. A longer measurement time will reflect the thermal drift of the tested area in a direction to compensate for the reduced temperature. In the control group, all subjects showed an increase in planimetric indicators during the cooling test verified by computerized photoplethysmography. In the study group visual verification of the cooling test was positive in eight cases (6.2%) and the vibration perception threshold test was positive in seven cases (5.5%), but in computerized photoplethysmography the planimetric indicators decreased after cooling in 87 (67.4%) cases. Computer photoplethysmography is highly specific and shows greater sensitivity in detecting preclinical forms of vascular-type vibration syndrome when compared with palesthesiometry

  7. Vortex-induced vibrations of a sphere

    NASA Astrophysics Data System (ADS)

    Govardhan, R. N.; Williamson, C. H. K.

    2005-05-01

    There are many studies on the vortex-induced vibrations of a cylindrical body, but almost none concerned with such vibrations for a sphere, despite the fact that tethered bodies are a common configuration. In this paper, we study the dynamics of an elastically mounted or tethered sphere in a steady flow, employing displacement, force and vorticity measurements. Within a particular range of flow speeds, where the oscillation frequency (f) is of the order of the static-body vortex shedding frequency (f_{vo}), there exist two modes of periodic large-amplitude oscillation, defined as modes I and II, separated by a transition regime exhibiting non-periodic vibration. The dominant wake structure for both modes is a chain of streamwise vortex loops on alternating sides of the wake. Further downstream, the heads of the vortex loops pinch off to form a sequence of vortex rings. We employ an analogy with the lift on an aircraft that is associated with its trailing vortex pair (of strength Gamma(*) and spacing b(*) ), and thereby compute the rate of change of impulse for the streamwise vortex pair, yielding the vortex force coefficient (cvortex): [ cvortex = {8}/{pi} {U^*_{v}}b^*( - Gamma^*). ] This calculation yields predicted forces in reasonable agreement with direct measurements on the sphere. This is significant because it indicates that the principal vorticity dynamics giving rise to vortex-induced vibration for a sphere are the motions of these streamwise vortex pairs. The Griffin plot, showing peak amplitudes as a function of the mass damping (m(*zeta) ), exhibits a good collapse of data, indicating a maximum response of around 0.9 diameters. Following recent studies of cylinder vortex-induced vibration, we deduce the existence of a critical mass ratio, m(*_{crit}) {≈} 0.6, below which large-amplitude vibrations are predicted to persist to infinite normalized velocities. An unexpected large-amplitude and highly periodic mode (mode III) is found at distinctly higher

  8. CFD Simulations of Vibration Induced Droplet Ejection.

    NASA Astrophysics Data System (ADS)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet ejection is a process that occurs when a liquid droplet is placed on a vibrating membrane. Above a critical value of the excitation amplitude, Faraday waves form on the surface of the drop. As the amplitude is increased secondary drops are ejected from the wave crests. A Navier-Stokes solver designed to simulate the transient fluid mechanics of the process is presented. The solver is based on a MAC method on a staggered grid. A volume of fluid method is implemented to track the free surface. The volume fraction is advected via a second-order, unsplit method that minimizes numerical diffusion of the interface. Surface tension is incorporated as a continuum surface force. This work is intended to provide a comprehensive description of the fluid dynamics involved in vibration-induced droplet ejection, with the aim of understanding the mechanism behind the ejection process. The evolution of the interface through droplet ejection will be simulated. The dependence of the ejection process on the driving parameters will be evaluated and the resonance characteristics of the drop will be determined. The results of the computations will be compared with experimental results.

  9. Laser cooling of vibrational degrees of freedom of a molecular system.

    PubMed

    Banerjee, Sumana; Gangopadhyay, Gautam

    2005-09-15

    We consider the cooling of vibrational degrees of freedom in a photoinduced excited electronic state of a model molecular system. For the various parameters of the potential surfaces of the ground and excited electronic states and depending on the excitation frequency of a single-mode laser light, the average energy or average vibrational temperature of the excited state passes through a minimum. The amount of cooling is quantified in terms of the overlap integral between the ground and excited electronic states of the molecule. We have given an approach to calculate the Franck-Condon factor for a multimode displaced-distorted-rotated oscillator surface of the molecular system. This is subsequently used to study the effect of displacement, distortion, and Duschinsky rotation on the vibrational cooling in the excited state. The absorption spectra and also the average energy or the effective temperature of the excited electronic state are studied for the above model molecular system. Considering the non-Condon effect for the symmetry-forbidden transitions, we have discussed the absorption spectra and average temperature in the excited-state vibrational manifold.

  10. Vibration Monitoring Using Fiber Optic Sensors in a Lead-Bismuth Eutectic Cooled Nuclear Fuel Assembly.

    PubMed

    De Pauw, Ben; Lamberti, Alfredo; Ertveldt, Julien; Rezayat, Ali; van Tichelen, Katrien; Vanlanduit, Steve; Berghmans, Francis

    2016-04-21

    Excessive fuel assembly vibrations in nuclear reactor cores should be avoided in order not to compromise the lifetime of the assembly and in order to prevent the occurrence of safety hazards. This issue is particularly relevant to new reactor designs that use liquid metal coolants, such as, for example, a molten lead-bismuth eutectic. The flow of molten heavy metal around and through the fuel assembly may cause the latter to vibrate and hence suffer degradation as a result of, for example, fretting wear or mechanical fatigue. In this paper, we demonstrate the use of optical fiber sensors to measure the fuel assembly vibration in a lead-bismuth eutectic cooled installation which can be used as input to assess vibration-related safety hazards. We show that the vibration characteristics of the fuel pins in the fuel assembly can be experimentally determined with minimal intrusiveness and with high precision owing to the small dimensions and properties of the sensors. In particular, we were able to record local strain level differences of about 0.2 μϵ allowing us to reliably estimate the vibration amplitudes and modal parameters of the fuel assembly based on optical fiber sensor readings during different stages of the operation of the facility, including the onset of the coolant circulation and steady-state operation.

  11. Cryogenically cooled ultra low vibration silicon mirrors for gravitational wave observatories

    NASA Astrophysics Data System (ADS)

    Shapiro, Brett; Adhikari, Rana X.; Aguiar, Odylio; Bonilla, Edgard; Fan, Danyang; Gan, Litawn; Gomez, Ian; Khandelwal, Sanditi; Lantz, Brian; MacDonald, Tim; Madden-Fong, Dakota

    2017-01-01

    Interferometric gravitational wave observatories recently launched a new field of gravitational wave astronomy with the first detections of gravitational waves in 2015. The number and quality of these detections is limited in part by thermally induced vibrations in the mirrors, which show up as noise in these interferometers. One way to reduce this thermally induced noise is to use low temperature mirrors made of high purity single-crystalline silicon. However, these low temperatures must be achieved without increasing the mechanical vibration of the mirror surface or the vibration of any surface within close proximity to the mirrors. The vibration of either surface can impose a noise inducing phase shift on the light within the interferometer or physically push the mirror through oscillating radiation pressure. This paper proposes a system for the Laser Interferometric Gravitational-wave Observatory (LIGO) to achieve the dual goals of low temperature and low vibration to reduce the thermally induced noise in silicon mirrors. Experimental results are obtained at Stanford University to prove that these dual goals can be realized simultaneously.

  12. Prediction of vibrations induced by underground railway traffic in Beijing

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Liu, W. F.; Degrande, G.; Lombaert, G.; Liu, W. N.

    2008-02-01

    This paper examines the problem of subway induced vibrations on line 4 of Beijing metro, which is currently under construction and is planned to pass in close proximity of the Physics Laboratory of Beijing University. The laboratory has a lot of equipment that is very sensitive to traffic induced vibrations and future operation of metro line 4 is a matter of concern. Hence, it is important to study the influence of subway induced vibrations inside the laboratory and to propose a viable solution to mitigate the vibrations. In this paper, the tunnel north of Chengfulu station is modelled using a coupled periodic FE-BE model and the free-field response due to moving trains is predicted. In addition, vibration measurements have been performed on the site of the Physics Laboratory to estimate the existing vibration levels due to road traffic. The predicted and measured vibrations are superimposed to assess the vibrations due to the combined effect of road and railway traffic in the vicinity of the Physics Laboratory. Apart from the numerical investigations, vibration measurements have also been performed on a similar site at line 1 of Beijing metro to substantiate the estimated results on metro line 4. Finally, it is studied how the vibrations can be controlled using a floating slab track, which is widely used as an effective measure of vibration isolation in tunnels. The efficiency of a 7.9 Hz floating slab track as a vibration countermeasure is assessed in this paper. This study demonstrates the applicability of the numerical model for the relevant assessment of subway induced vibrations and its use to study the performance of different track structures in the tunnel.

  13. An experimental investigation of airflow-induced vibrations within the multiplicity and vertex detector

    SciTech Connect

    Bernardin, J.D.; Bosze, E.; Boissevain, J.; Simon-Gillo, J.

    1997-07-01

    This report summarizes an experimental investigation of vibrations within the multiplicity and vertex detector (MVD). In particular, the maximum displacements of several MVD components were determined from accelerometer measurements of vibrations induced by an electronics air-cooling system. For an MVD inlet air volumetric flow rate of 0.022 m{sup 3}/s, maximum displacements of several MVD components including a multi-chip module, the Rohacell inlet air plenum, and an aluminum structural cross support, were found to be on the order of 1.5 {mu}m. Consequently, it was concluded that air induced vibrations will not significantly interfere with the MVD`s long-term structural integrity or operating performance. 2 refs., 3 figs., 1 tab.

  14. Application of NASTRAN to propeller-induced ship vibration

    NASA Technical Reports Server (NTRS)

    Liepins, A. A.; Conaway, J. H.

    1975-01-01

    An application of the NASTRAN program to the analysis of propeller-induced ship vibration is presented. The essentials of the model, the computational procedure, and experience are described. Desirable program enhancements are suggested.

  15. Flow-Induced Vibration of Circular Cylindrical Structures

    SciTech Connect

    Chen, Shoei-Sheng

    1985-06-01

    Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structural vibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling

  16. Crowd-induced random vibration of footbridge and vibration control using multiple tuned mass dampers

    NASA Astrophysics Data System (ADS)

    Li, Quan; Fan, Jiansheng; Nie, Jianguo; Li, Quanwang; Chen, Yu

    2010-09-01

    This paper investigates vibration characteristics of footbridge induced by crowd random walking, and presents the application of multiple tuned mass dampers (MTMD) in suppressing crowd-induced vibration. A single foot force model for the vertical component of walking-induced force is developed, avoiding the phase angle inaccessibility of the continuous walking force. Based on the single foot force model, the crowd-footbridge random vibration model, in which pedestrians are modeled as a crowd flow characterized with the average time headway, is developed to consider the worst vibration state of footbridge. In this random vibration model, an analytic formulation is developed to calculate the acceleration power spectral density in arbitrary position of footbridge with arbitrary span layout. Resonant effect is observed as the footbridge natural frequencies fall within the frequency bandwidth of crowd excitation. To suppress the excessive acceleration for human normal walking comfort, a MTMD system is used to improve the footbridge dynamic characteristics. According to the random vibration model, an optimization procedure, based on the minimization of maximum root-mean-square (rms) acceleration of footbridge, is introduced to determine the optimal design parameters of MTMD system. Numerical analysis shows that the proposed MTMD designed by random optimization procedure, is more effective than traditional MTMD design methodology in reducing dynamic response during crowd-footbridge resonance, and that the proper frequency spacing enlargement will effectively reduce the off-tuning effect of MTMD.

  17. Concorde Noise-Induced Building Vibrations, Montgomery County, Maryland

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Scholl, H. F.; Stephens, D. G.; Holliday, B. G.; Deloach, R.; Finley, T. D.; Holmes, H. K.; Lewis, R. B.; Lynch, J. W.

    1976-01-01

    A series of studies are reported to assess the noise induced building vibrations associated with Concorde operations. The levels of induced vibration and associated indoor/outdoor noise levels resulting from aircraft and nonaircraft events in selected homes, historic and other buildings near Dulles International Airport were recorded. The building response resulting from aircraft operations was found to be directly proportional to the overall sound pressure level and approximately independent of the aircraft type. The noise levels and, consequently, the response levels were observed to be higher for the Concorde operations than for the CTOL operations. Furthermore, the vibration could be closely reproduced by playing aircraft noise through a loudspeaker system located near the vibration measurement location. Nonaircraft events such as door closing were again observed to result in higher response levels than those induced by aircraft.

  18. Laser cooling of the vibrational motion of Na{sub 2} combining the effects of zero-width resonances and exceptional points

    SciTech Connect

    Lefebvre, R.; Jaouadi, A.; Dulieu, O.; Atabek, O.

    2011-10-15

    We propose various scenarios for molecular vibrational cooling combining the effects of two kinds of resonance states occurring during the photodissociation of Na{sub 2} taken as an illustrative example. Such resonances result from an appropriate sampling of laser parameters (wavelength and intensity): (a) For particular choices of intensity and wavelength, two resonance energies can be brought to complete coalescence, with their positions and widths becoming equal and leading to a so-called exceptional point (EP) in the parameter plane. Advantage can be taken from such points for very selective laser-controlled vibrational transfer strategies. (b) For specific intensities, far beyond the perturbation regime, some resonances can have a zero width (infinite lifetime). They are referred to as a zero-width resonance (ZWR) and may be used for vibrational purification purposes. We show how appropriately shaped, experimentally reachable laser pulses, encircling EPs or inducing ZWRs, may be used for a thorough and comprehensive control aiming at population transfer or purification schemes, which, starting from an initial field-free vibrational distribution, ends up in the ground vibrational level.

  19. Vibration attenuation of conductive beams by inducing eddy currents

    NASA Astrophysics Data System (ADS)

    Irazu, L.; Elejabarrieta, M. J.

    2016-09-01

    The increasing requirements for structural vibration control in many industries, require innovative attenuation techniques. In this work, the phenomenon of eddy currents is proposed to reduce the vibration of conductive and non-magnetic beam-like structures without modifying the system, neither the weight nor the stiffness. The motion of a conductive material in a stationary magnetic field induces eddy currents, which in turn generate a repulsive force and attenuate the vibration. In this study, the vibrational response of a thin aluminium beam under a partial and stationary magnetic field is analysed. The influence of the eddy currents is experimentally studied in the bandwidth from 0 to 1 kHz and a preliminary numerical model is proposed. The results show the vibration of all the length of the beam can be attenuated by inducing eddy currents, whereas the natural frequencies of the system remain unmodified. The attenuation of the vibration is more remarkable at low frequencies and when the position of the magnetic field coincides with a maximum vibration of a mode.

  20. Scalp cooling: management option for chemotherapy-induced alopecia.

    PubMed

    Roe, Helen

    Chemotherapy is increasingly being administered as a treatment for cancer and with it are a number of possible side effects. One, which has a negative impact on a patient's quality of life and their self-esteem, is that of chemotherapy-induced alopecia (CIA). A side effect of which, for some, could be prevented by the use of scalp cooling, dependent on the regimen being administered and patient choice. This article explores the issue of CIA from the patient's perspective and scalp cooling as a preventative measure, along with a review of the evidence around the risk associated with developing scalp metastases following scalp cooling. It also discusses why scalp cooling should be available for both male and female patients; along with the potential impact scalp cooling may have on clinical areas delivering chemotherapy.

  1. Picosecond Raman Study of Vibrational Cooling and Protein Dynamics in the Primary Photochemistry of Rhodopsin

    NASA Astrophysics Data System (ADS)

    Kim, Judy; Mathies, Richard

    2003-03-01

    Picosecond Stokes and anti-Stokes Raman spectra are used to probe the structural dynamics and reactive energy flow of both the chromophore and binding pocket residues in the primary cis-to-trans isomerization reaction of rhodopsin. The appearance of characteristic ethylenic, hydrogen out-of-plane (HOOP) and low-wavenumber photoproduct bands in the Stokes Raman spectra of the chromophore is instrument-response limited, consistent with a sub-picosecond product appearance time (1,2). Intense high and low-frequency anti-Stokes chromophore peaks demonstrate that the all-trans photoproduct, photorhodopsin, is produced vibrationally hot on the ground-state surface (2). Specifically, the low-frequency modes at 282, 350 and 477 cm-1 are highly vibrationally excited (T > 2000 K) immediately following isomerization, revealing that these low-frequency motions directly participate in the reactive curve-crossing process. The anti-Stokes modes are characterized by a ˜2.5 ps temporal decay that coincides with the conversion of photorhodopsin to bathorhodopsin. This correspondence shows that the photo-to-batho transition is a ground-state cooling process, and that energy storage in the primary visual photoproduct is complete on the picosecond time scale. The remarkable similarity between the room-temperature picosecond vibrational structure of photo- and bathorhodopsin and that of the low-temperature trapped primary photoproduct suggests that chromophore isomerization impulsively excites and drives changes in nearby protein residues. These amino acid changes within the binding pocket are probed by picosecond UV Raman spectroscopy of aromatic residues (3). Difference spectra reveal that at least one tryptophan (trp265) and one tyrosine (tyr191, 268 and/or 178) residue undergoes structural changes in < 5 ps, presumably due to steric interaction with the isomerizing chromophore as well as energy flow from chromophore to the binding pocket. This result indicates that the protein

  2. Scale modeling flow-induced vibrations of reactor components

    SciTech Connect

    Mulcahy, T M

    1982-06-01

    Similitude relationships currently employed in the design of flow-induced vibration scale-model tests of nuclear reactor components are reviewed. Emphasis is given to understanding the origins of the similitude parameters as a basis for discussion of the inevitable distortions which occur in design verification testing of entire reactor systems and in feature testing of individual component designs for the existence of detrimental flow-induced vibration mechanisms. Distortions of similitude parameters made in current test practice are enumerated and selected example tests are described. Also, limitations in the use of specific distortions in model designs are evaluated based on the current understanding of flow-induced vibration mechanisms and structural response.

  3. Hydrogen bond donors accelerate vibrational cooling of hot purine derivatives in heavy water.

    PubMed

    Zhang, Yuyuan; Chen, Jinquan; Kohler, Bern

    2013-08-08

    Natural nucleobases and many of their derivatives have ultrashort excited state lifetimes that make them excellent model systems for studying intermolecular energy flow from a hot solute molecule to the solvent. UV-pump/broadband-mid-IR-probe transient absorption spectra of canonical purine nucleobases and several xanthine derivatives were acquired in D2O and acetonitrile in the probe frequency range of 1500-1750 cm(-1). The spectra reveal that vibrationally hot ground state molecules created by ultrafast internal conversion return to thermal equilibrium in several picoseconds by dissipating their excess energy to solvent molecules. In acetonitrile solution, where hydrogen bonding is minimal, vibrational cooling (VC) occurs with the same time constant of 10 ± 3 ps for paraxanthine, theophylline, and caffeine within experimental uncertainty. In D2O, VC by these molecules occurs more rapidly and at different rates that are correlated with the number of N-D bonds. Hypoxanthine has a VC time constant of 3 ± 1 ps, while similar lifetimes of 2.3 ± 0.8 ps and 3.1 ± 0.3 ps are seen for 5'-adenosine monophosphate and 5'-guanosine monophosphate, respectively. All three molecules have at least two N-D bonds. Slightly slower VC time constants are measured for paraxanthine (4 ± 1 ps) and theophylline (5.1 ± 0.8 ps), dimethylated xanthines that have only one N-D bond. Caffeine, a trimethylated xanthine with no N-D bonds, has a VC time constant of 7.7 ± 0.9 ps, the longest ever observed for any nucleobase in aqueous solution. Hydrogen bond donation by solute molecules is proposed to enable rapid energy disposal to water via direct coupling of high frequency solute-solvent modes.

  4. Drop motion induced by vertical vibrations

    NASA Astrophysics Data System (ADS)

    Sartori, Paolo; Quagliati, Damiano; Varagnolo, Silvia; Pierno, Matteo; Mistura, Giampaolo; Magaletti, Francesco; Massimo Casciola, Carlo

    2015-11-01

    We have studied the motion of liquid drops on an inclined plate subject to vertical vibrations. The liquids comprised distilled water and different aqueous solutions of glycerol, ethanol and isopropanol spanning the range 1-39 mm2 s-1 in kinematic viscosities and 40-72 mN m-1 in surface tension. At sufficiently low oscillating amplitudes, the drops are always pinned to the surface. Vibrating the plate above a certain amplitude yields sliding of the drop. Further increasing the oscillating amplitude drives the drop upward against gravity. In the case of the most hydrophilic aqueous solutions, this motion is not observed and the drop only slides downward. Images taken with a fast camera show that the drop profile evolves in a different way during sliding and climbing. In particular, the climbing drop experiences a much bigger variation in its profile during an oscillating period. Complementary numerical simulations of 2D drops based on a diffuse interface approach confirm the experimental findings. The overall qualitative behavior is reproduced suggesting that the contact line pinning due to contact angle hysteresis is not necessary to explain the drop climbing.

  5. Low Head, Vortex Induced Vibrations River Energy Converter

    SciTech Connect

    Bernitsas, Michael B.; Dritz, Tad

    2006-06-30

    Vortex Induced Vibrations Aquatic Clean Energy (VIVACE) is a novel, demonstrated approach to extracting energy from water currents. This invention is based on a phenomenon called Vortex Induced Vibrations (VIV), which was first observed by Leonardo da Vinci in 1504AD. He called it ‘Aeolian Tones.’ For decades, engineers have attempted to prevent this type of vibration from damaging structures, such as offshore platforms, nuclear fuel rods, cables, buildings, and bridges. The underlying concept of the VIVACE Converter is the following: Strengthen rather than spoil vortex shedding; enhance rather than suppress VIV; harness rather than mitigate VIV energy. By maximizing and utilizing this unique phenomenon, VIVACE takes this “problem” and successfully transforms it into a valuable resource for mankind.

  6. Evaluating vehicular-induced bridge vibrations for energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Reichenbach, Matthew; Fasl, Jeremiah; Samaras, Vasilis A.; Wood, Sharon; Helwig, Todd; Lindenberg, Richard

    2012-04-01

    Highway bridges are vital links in the transportation network in the United States. Identifying possible safety problems in the approximately 600,000 bridges across the country is generally accomplished through labor-intensive, visual inspections. Ongoing research sponsored by NIST seeks to improve inspection practices by providing real-time, continuous monitoring technology for steel bridges. A wireless sensor network with a service life of ten years that is powered by an integrated energy harvester is targeted. In order to achieve the target ten-year life for the monitoring system, novel approaches to energy harvesting for use in recharging batteries are investigated. Three main sources of energy are evaluated: (a) vibrational energy, (b) solar energy, and (c) wind energy. Assessing the energy produced from vehicular-induced vibrations and converted through electromagnetic induction is the focus of this paper. The goal of the study is to process acceleration data and analyze the vibrational response of steel bridges to moving truck loads. Through spectral analysis and harvester modeling, the feasibility of vibration-based energy harvesting for longterm monitoring can be assessed. The effects of bridge conditions, ambient temperature, truck traffic patterns, and harvester position on the power content of the vibrations are investigated. With sensor nodes continually recharged, the proposed real-time monitoring system will operate off the power grid, thus reducing life cycle costs and enhancing inspection practices for state DOTs. This paper will present the results of estimating the vibration energy of a steel bridge in Texas.

  7. Non-equilibrium effects evidenced by vibrational spectra during the coil-to-globule transition in poly(N-isopropylacrylamide) subjected to an ultrafast heating-cooling cycle.

    PubMed

    Deshmukh, Sanket A; Kamath, Ganesh; Suthar, Kamlesh J; Mancini, Derrick C; Sankaranarayanan, Subramanian K R S

    2014-03-14

    Molecular dynamics simulations in conjunction with finite element calculations are used to explore the conformational dynamics of a thermo-sensitive oligomer, namely poly(N-isopropylacrylamide) (PNIPAM), subjected to an ultra-fast heating-cooling cycle. Finite element (FE) calculations were used to predict the temperature profile resulting from laser-induced heating of the polymer-aqueous system. The heating rate (∼0.6 K ps(-1)) deduced from FE calculations was used to heat an aqueous solution of PNIPAM consisting of 30 monomeric units (30-mer) from 285 K to 315 K. Non-equilibrium effects arising from the ultra-fast heating-cooling cycle results in a hysteresis during the coil-to-globule transition. The corresponding atomic scale conformations were characterized by monitoring the changes in the vibrational spectra, which provided a reliable metric to study the coil-to-globule transition in PNIPAM and vice-versa across the LCST. The vibrational spectra of bonds involving atoms from the oligomer backbone and the various side-groups (amide I, amide II, and the isopropyl group of PNIPAM) of the oligomers were analyzed to study the conformational changes in the oligomer corresponding to the observed hysteresis. The differences in the vibrational spectra calculated at various temperatures during heating and cooling cycles were used to understand the coil-to-globule and globule-to-coil transitions in the PNIPAM oligomer and identify the changes in the relative interactions between various atoms in the backbone and in the side groups of the oligomer with water. The shifts in the computed vibrational spectral peaks and the changes in the intensity of peaks for the different regions of PNIPAM, seen across the LCST during the heating cycle, are in good agreement with previous experimental studies. The changes in the radius of gyration (Rg) and vibrational spectra for amide I and amide II regions of PNIPAM suggest a clear coil-to-globule transition at ∼301 K during the

  8. Rocket Launch-Induced Vibration and Ignition Overpressure Response

    NASA Technical Reports Server (NTRS)

    Caimi, Raoul; Margasahayam, Ravi; Nayfeh, Jamal; Thompson, Karen (Technical Monitor)

    2001-01-01

    Rocket-induced vibration and ignition overpressure response environments are predicted in the low-frequency (5 to 200 hertz) range. The predictions are necessary to evaluate their impact on critical components, structures, and facilities in the immediate vicinity of the rocket launch pad.

  9. Active tuning of stroke-induced vibrations by tennis players.

    PubMed

    Chadefaux, Delphine; Rao, Guillaume; Androuet, Philippe; Berton, Eric; Vigouroux, Laurent

    2016-09-06

    This paper investigates how tennis players control stroke-induced vibration. Its aim is to characterise how a tennis player deals with entering vibration waves or how he/she has the ability to finely adjust them. A specific experimental procedure was designed, based on simultaneously collecting sets of kinematic, vibration and electromyographic data during forehand strokes using various commercial rackets and stroke intensities. Using 14 expert players, a wide range of excitations at spectral and temporal levels were investigated. Energetic and spectral descriptors of stroke-induced vibration occurring at the racket handle and at the player's wrist and elbow were computed. Results indicated that vibrational characteristics are strongly governed by grip force and to a lower extent by the racket properties. Grip force management drives the amount of energy, as well as its distribution, into the forearm. Furthermore, hand-grip can be assimilated to an adaptive filter which can significantly modify the spectral parameters propagating into the player's upper limb. A significant outcome is that these spectral characteristics are as much dependent on the player as on the racket. This contribution opens up new perspectives in equipment manufacture by underlining the need to account for player/racket interaction in the design process.

  10. A numerical investigation of flow induced vibrations in a rocket engine manifold

    NASA Astrophysics Data System (ADS)

    Peugeot, John W.

    2011-12-01

    Flow induced vibrations are common in liquid rocket engine components and have been the subject of several recent studies within the Space Shuttle and Delta launch vehicle programs. Understanding how unsteady flow phenomena develop is important when investigating failures in existing hardware and in the design of new propulsion systems. In this study, a subsonic turbulent flow in a rocket engine manifold is analyzed using a compressible form of the viscous flow equations coupled with a hybrid RANS-DES turbulence model. It is found that vortex shedding and pressure perturbations within a manifold significantly influence the stability of shear layers and flow through exit cooling tubes. By adding a chamfer to the inlet of the cooling tubes, it was demonstrated that greater shear layer stability can be obtaIned at a given pressure ratio.

  11. Vibration Monitoring Using Fiber Optic Sensors in a Lead-Bismuth Eutectic Cooled Nuclear Fuel Assembly †

    PubMed Central

    De Pauw, Ben; Lamberti, Alfredo; Ertveldt, Julien; Rezayat, Ali; van Tichelen, Katrien; Vanlanduit, Steve; Berghmans, Francis

    2016-01-01

    Excessive fuel assembly vibrations in nuclear reactor cores should be avoided in order not to compromise the lifetime of the assembly and in order to prevent the occurrence of safety hazards. This issue is particularly relevant to new reactor designs that use liquid metal coolants, such as, for example, a molten lead-bismuth eutectic. The flow of molten heavy metal around and through the fuel assembly may cause the latter to vibrate and hence suffer degradation as a result of, for example, fretting wear or mechanical fatigue. In this paper, we demonstrate the use of optical fiber sensors to measure the fuel assembly vibration in a lead-bismuth eutectic cooled installation which can be used as input to assess vibration-related safety hazards. We show that the vibration characteristics of the fuel pins in the fuel assembly can be experimentally determined with minimal intrusiveness and with high precision owing to the small dimensions and properties of the sensors. In particular, we were able to record local strain level differences of about 0.2 μϵ allowing us to reliably estimate the vibration amplitudes and modal parameters of the fuel assembly based on optical fiber sensor readings during different stages of the operation of the facility, including the onset of the coolant circulation and steady-state operation. PMID:27110782

  12. Effects of induced vibration modes on droplet sliding phenomena

    NASA Astrophysics Data System (ADS)

    Mejia, Jose Eduardo; Alvarado, Jorge; Yao, Chun-Wei; Dropwise Condensation Collaboration; Engineered Surfaces Collaboration

    2016-11-01

    An analytical and experimental investigation has been undertaken to understand the effects of induced vibration modes on droplet sliding phenomena. A mathematical model has been postulated which is capable of estimating accurately droplet sliding angles when using hydrophobic and hydrophilic surfaces. The model, which takes into account equilibrium contact angle, contact angle hysteresis, and droplet volume, has been validated using experimental data. The model has been modified to be able to estimate droplet sliding angle when different modes of vibrations are imposed on the surfaces. Experimental results to date reveal that when resonance modes of vibrations are imposed, the droplet sliding angles decrease considerably. The results also indicate that the modified model can be used effectively to relate imposed resonance frequencies to the critical sliding angle of droplets. LSAMP sponsored NSF Fellowship.

  13. Piezoelectric energy harvesting from traffic-induced bridge vibrations

    NASA Astrophysics Data System (ADS)

    Peigney, Michaël; Siegert, Dominique

    2013-09-01

    This paper focuses on energy harvesting from traffic-induced vibrations in bridges. Using a pre-stressed concrete highway bridge as a case study, in situ vibration measurements are presented and analysed. From these results, a prototype of a cantilever piezoelectric harvester is designed, tested and modelled. Even though the considered bridge vibrations are characterized by small amplitude and a low frequency (i.e. below 15 Hz), it is shown that mean power of the order of 0.03 mW can be produced, with a controlled voltage between 1.8 and 3.6 V. A simple model is proposed for theoretical prediction of the delivered power in terms of traffic intensity. This model shows good agreement with the experimental results and leads to a simple but effective design rule for piezoelectric harvesters to be used on bridges.

  14. Fluid patterns and dynamics induced by vibrations in microgravity conditions

    NASA Astrophysics Data System (ADS)

    Porter, Jeff; Tinao Perez-Miravete, Ignacio; Laverón-Simavilla, Ana

    Understanding the effects of vibrations is extremely important in microgravity environments where residual acceleration, or g-jitter, is easily generated by crew manoeuvring or machinery, and can have a significant impact on material processing systems and on-board experiments. Indeed, vibrations can dramatically affect fluid behaviour whether gravity is present or not, inducing instability in some cases while suppressing it in others. We will describe the results of investigations being conducted at the ESA affiliated Spanish User Support and Operations Centre (E-USOC) on the effect of vibrations on fluids interfaces, most notably with the forcing oriented parallel to the fluid surface. Pattern formation properties will be described in detail, and the importance of symmetry constraints and mean flows will be considered. Current exper-imental results are intriguing and have challenged existing assumptions in the field, particularly with regard to the parametric instability underlying subharmonic cross-waves. They suggest an intimate connection between Faraday waves, which are observed in vertically vibrated systems, and cross-waves, which are found in horizontally forced systems. Concurrent theoretical work, based on the analysis of reduced models, and on numerical simulations, will then be described. Finally, this research will be placed in a microgravity context and used to motivate the defini-tion of a proposed set of experiments on the International Space Station (ISS). The experiments would be in the large-aspect-ratio-limit, requiring relatively high frequency but low amplitude vibrations, where comparatively little microgravity research has been done. The interest of such a microgravity experiment will be discussed, with emphasis on fluid management and the potential of vibrations to act as a kind of artificial gravity by orienting surfaces (or density contours) perpendicular to the axis of vibration.

  15. Molecular dynamics modeling of cooling of vibrationally highly excited carbon dioxide produced in the photodissociation of organic peroxides in solution.

    PubMed

    Kandratsenka, Alexander; Schroeder, Jörg; Schwarzer, Dirk; Vikhrenko, Vyacheslav S

    2005-03-21

    Non-equilibrium (NEMD) and equilibrium (EMD) molecular dynamics simulations are performed to investigate the vibrational cooling and asymmetric stretch spectral evolution of highly excited carbon dioxide produced in the photodissociation of organic peroxides in the solvents dichloromethane, carbon tetrachloride and xenon. Due to strong Fermi resonance the symmetric stretching and bending modes of carbon dioxide in CH2Cl2 and CCl4 jointly relax on a ten and hundred picosecond timescale, respectively, which is in accordance with experiment. However, the high frequency CO2 asymmetric stretch vibration relaxes on a considerably longer time scale because of weak interaction with the other modes. The relaxation rate coefficients of (and works done by) different modes obtained from NEMD and the Landau-Teller rate coefficients calculated through equilibrium force time correlation functions are in reasonable agreement. The analysis of these results leads to the conclusion that, in contrast to xenon where the relaxation takes about 20 ns, the shorter time scales in CH2Cl2 and CCl4 are caused by efficient near resonant vibration to vibration energy transfer from carbon dioxide to solvent molecules. The results of the non-equilibrium simulations are used to monitor the quasi-stationary asymmetric stretch infrared spectra of carbon dioxide during the cooling process. Comparison of the corresponding experimental results suggests that carbon dioxide initially is produced with a broad distribution of energy disposed in its bend and symmetric stretch modes while the asymmetric stretch mode remains unexcited.

  16. Mode-specific energy absorption by solvent molecules during CO2 vibrational cooling.

    PubMed

    Kandratsenka, Alexander; Schroeder, Jörg; Schwarzer, Dirk; Vikhrenko, Vyacheslav S

    2007-04-14

    Non-equilibrium molecular dynamics (NEMD) simulations of energy transfer from vibrationally excited CO(2) to CCl(4) and CH(2)Cl(2) solvent molecules are performed to identify the efficiency of different energy pathways into the solvent bath. Studying in detail the work performed by the vibrationally excited solute on the different solvent degrees of freedom, it is shown that vibration-to-vibration (V-V) processes are strongly dominant and controlled by those accepting modes which are close in frequency to the CO(2) bend and symmetric stretch vibration.

  17. Optimal energy harvesting from vortex-induced vibrations of cables

    NASA Astrophysics Data System (ADS)

    Antoine, G. O.; de Langre, E.; Michelin, S.

    2016-11-01

    Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy towards this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with a rigid cylinder device. This results from two passive control mechanisms inherent to the cable geometry: (i) the adaptability to the flow velocity of the fundamental frequencies of cables through the flow-induced tension and (ii) the selection of successive vibration modes by the flow velocity for cables with gravity-induced tension.

  18. Optimal energy harvesting from vortex-induced vibrations of cables.

    PubMed

    Antoine, G O; de Langre, E; Michelin, S

    2016-11-01

    Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy towards this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with a rigid cylinder device. This results from two passive control mechanisms inherent to the cable geometry: (i) the adaptability to the flow velocity of the fundamental frequencies of cables through the flow-induced tension and (ii) the selection of successive vibration modes by the flow velocity for cables with gravity-induced tension.

  19. The excited-state structure, vibrations, lifetimes, and nonradiative dynamics of jet-cooled 1-methylcytosine

    NASA Astrophysics Data System (ADS)

    Trachsel, Maria A.; Wiedmer, Timo; Blaser, Susan; Frey, Hans-Martin; Li, Quansong; Ruiz-Barragan, Sergi; Blancafort, Lluís; Leutwyler, Samuel

    2016-10-01

    We have investigated the S0 → S1 UV vibronic spectrum and time-resolved S1 state dynamics of jet-cooled amino-keto 1-methylcytosine (1MCyt) using two-color resonant two-photon ionization, UV/UV holeburning and depletion spectroscopies, as well as nanosecond and picosecond time-resolved pump/delayed ionization measurements. The experimental study is complemented with spin-component-scaled second-order coupled-cluster and multistate complete active space second order perturbation ab initio calculations. Above the weak electronic origin of 1MCyt at 31 852 cm-1 about 20 intense vibronic bands are observed. These are interpreted as methyl group torsional transitions coupled to out-of-plane ring vibrations, in agreement with the methyl group rotation and out-of-plane distortions upon 1ππ∗ excitation predicted by the calculations. The methyl torsion and ν1 ' (butterfly) vibrations are strongly coupled, in the S1 state. The S0 → S1 vibronic spectrum breaks off at a vibrational excess energy Eexc ˜ 500 cm-1, indicating that a barrier in front of the ethylene-type S1⇝S0 conical intersection is exceeded, which is calculated to lie at Eexc = 366 cm-1. The S1⇝S0 internal conversion rate constant increases from kIC = 2 ṡ 109 s-1 near the S1(v = 0) level to 1 ṡ 1011 s-1 at Eexc = 516 cm-1. The 1ππ∗ state of 1MCyt also relaxes into the lower-lying triplet T1 (3ππ∗) state by intersystem crossing (ISC); the calculated spin-orbit coupling (SOC) value is 2.4 cm-1. The ISC rate constant is 10-100 times lower than kIC; it increases from kISC = 2 ṡ 108 s-1 near S1(v = 0) to kISC = 2 ṡ 109 s-1 at Eexc = 516 cm-1. The T1 state energy is determined from the onset of the time-delayed photoionization efficiency curve as 25 600 ± 500 cm-1. The T2 (3nπ∗) state lies >1500 cm-1 above S1(v = 0), so S1⇝T2 ISC cannot occur, despite the large SOC parameter of 10.6 cm-1. An upper limit to the adiabatic ionization energy of 1MCyt is determined as 8.41 ± 0.02 e

  20. DEAP-based energy harvesting using vortex-induced vibrations

    NASA Astrophysics Data System (ADS)

    Hoffstadt, Thorben; Heinze, Robert; Wahl, Tim; Kameier, Frank; Maas, Jürgen

    2014-03-01

    Generators based on dielectric electroactive polymers (DEAP) convert mechanical strain energy into electrical field energy. In order to harvest renewable energy from ambient sources adequate generator setups have to be developed. Thus, in this contribution a DEAP generator is presented which uses periodic vortex induced vibration of a circular cylinder as excitation mechanism, by which e.g. Flow energy of a wind or water current can be converted. For this purpose a novel generator design consisting of a cylinder that is elastically mounted on DEAP material is presented. Since the effect of vortex induced vibrations depends on the stiffness and damping of the utilized generator's eigenmode, a method to adapt both via the electrostatic pressure and energy conversion is proposed. After the validation of the general functionality of the novel generator design, analyses concerning the control of the overall harvester are carried out.

  1. Prediction of induced vibrations for a passenger - car ferry

    NASA Astrophysics Data System (ADS)

    Crudu, L.; Neculet, O.; Marcu, O.

    2016-08-01

    In order to evaluate the ship hull global vibrations, propeller excitation must be properly considered being mandatory to know enough accurate the magnitude of the induced hull pressure impulses. During the preliminary design stages, the pressures induced on the aft part of the ship by the operating propeller can be evaluated based on the guidelines given by the international standards or by the provisions of the Classification Societies. These approximate formulas are taking into account the wake field which, unfortunately, can be only estimated unless experimental towing tank tests are carried out. Another possibility is the numerical evaluation with different Computational Fluid Dynamics (CFD) codes. However, CFD methods are not always easy to be used requiring an accurate description of the hull forms in the aft part of the ship. The present research underlines these aspects during the preliminary prediction of propeller induced vibrations for a double-ended passenger-car ferry propelled by two azimuth fixed pitch thrusters placed at both ends of the ship. The evaluation of the global forced vibration is performed considering the 3D global Finite Element (FE) model, with NX Nastran for Windows. Based on the presented results, the paper provides reliable information to be used during the preliminary design stages.

  2. Impact-Ionization Cooling in Laser-Induced Plasma Filaments

    SciTech Connect

    Filin, A.; Romanov, D. A.; Compton, R.; Levis, R. J.

    2009-04-17

    The ionization rates and subsequent electron dynamics for laser-induced plasma channels are measured for the noble gas series He, Ne, Ar, Kr, and Xe at 1.0 atm. The cw fluorescence emission increases superlinearly in the series from He to Xe in agreement with Ammosov-Delone-Krainov tunnel ionization calculations. The electron temperature after laser-induced plasma formation, measured by four-wave mixing, evolves from >20 eV to <1 eV kinetic energies with time constants ranging from 1 ns for He to 100 ps for Xe in agreement with an impact-ionization cooling model.

  3. Microstructure formation mechanism and properties of AZ61 alloy processed by melt treatment with vibrating cooling slope and semisolid rolling

    NASA Astrophysics Data System (ADS)

    Zhao, Zhan Yong; Guan, Ren Guo; Wang, Xiang; Li, Yang; Dong, Lei; Lee, Chong Soo; Liu, Chun Ming

    2013-09-01

    A melt treatment with a vibrating cooling slope and a semisolid rolling process to produce an AZ61 alloy strip was proposed. The microstructure formation mechanism and the properties of the AZ61 alloy produced by the proposed process were investigated. Due to the high cooling rate and stirring action caused by the vibration cooling slope, the nucleation rate was greatly improved, which caused the formation of fine spherical or rosette primary grains. During the rolling process, the solid fraction increased from the entrance to the exit of the roll gap, and under the shearing action of the roller, the distribution of solute in the melt was homogenous, and the primary grains grew further. When the casting temperature was 680 °C, a strip with a cross section of 4 mm×160 mm was produced and a homogeneous microstructure was obtained. The ultimate tensile strength of the AZ61 alloy strip produced by the proposed method reached 242 MPa, and the corresponding elongation to failure was 4%, which were better than those achieved in previous similar studies.

  4. Excited-state structure, vibrations, and nonradiative relaxation of jet-cooled 5-fluorocytosine.

    PubMed

    Lobsiger, Simon; Trachsel, Maria A; Den, Takuya; Leutwyler, Samuel

    2014-03-20

    The S0 → S1 vibronic spectrum and S1 state nonradiative relaxation of jet-cooled keto-amino 5-fluorocytosine (5FCyt) are investigated by two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm(–1) resolution. The 0(0)(0) rotational band contour is polarized in-plane, implying that the electronic transition is (1)ππ*. The electronic transition dipole moment orientation and the changes of rotational constants agree closely with the SCS-CC2 calculated values for the (1)ππ* (S1) transition of 5FCyt. The spectral region from 0 to 300 cm(–1) is dominated by overtone and combination bands of the out-of-plane ν1′ (boat), ν2′ (butterfly), and ν3′ (HN–C6H twist) vibrations, implying that the pyrimidinone frame is distorted out-of-plane by the (1)ππ* excitation, in agreement with SCS-CC2 calculations. The number of vibronic bands rises strongly around +350 cm(–1); this is attributed to the (1)ππ* state barrier to planarity that corresponds to the central maximum of the double-minimum out-of-plane vibrational potentials along the ν1′, ν2′, and ν3′ coordinates, which gives rise to a high density of vibronic excitations. At +1200 cm(–1), rapid nonradiative relaxation (k(nr) ≥ 10(12) s(–1)) sets in, which we interpret as the height of the (1)ππ* state barrier in front of the lowest S1/S0 conical intersection. This barrier in 5FCyt is 3 times higher than that in cytosine. The lifetimes of the ν′ = 0, 2ν1′, 2ν2′, 2ν1′ + 2ν2′, 4ν2′, and 2ν1′ + 4ν2′ levels are determined from Lorentzian widths fitted to the rotational band contours and are τ ≥ 75 ps for ν′ = 0, decreasing to τ ≥ 55 ps at the 2ν1′ + 4ν2′ level at +234 cm(–1). These gas-phase lifetimes are twice those of S1 state cytosine and 10–100 times those of the other canonical nucleobases in the gas phase. On the other hand, the 5FCyt gas-phase lifetime is close to the 73 ps lifetime in room-temperature solvents. This lack of

  5. Laser-controlled vibrational heating and cooling of oriented H+2 molecules

    NASA Astrophysics Data System (ADS)

    Niederhausen, Thomas; Thumm, Uwe; Martín, Fernando

    2012-05-01

    We investigate the control of the vibrational dynamics in the hydrogen molecular ion H+2 using strong femto-second infrared control-laser pulses. For our three-dimensional calculations, we use infrared laser pulses of 800 nm wavelength, 6 fs pulse duration and a peak intensity between 1012 and 1015 W cm-2. For laser electric fields aligned along the molecular axis, we numerically solve the full vibronic Schrödinger equation and compare our results with a model calculation that only includes the nuclear motion on the two lowest coupled adiabatic Born-Oppenheimer potential curves. The initial vibrational wave packet is launched with the ionization of the parent H2 molecule in the pump pulse. Precise timing between pump- and control-laser pulses allows for the direct manipulation of the final bound vibrational-state composition and dissociation dynamics of the ion. We show that significant enhancement of the occupation of particular stationary vibrational-state contributions can be achieved for laser intensities below the onset of strong ionization (≈1014 W cm-2). In addition, we find that this vibrational selectivity strongly depends on the delay time but not on the intensity of the control pulse. The relative stationary vibrational-state contributions and the shape of the vibrating wave packet depend sensitively on the control-pulse delay time, and the overall amplitude of the final vibrational wave packet depends on the intensity of the control pulse.

  6. Sub-Tg features of glasses formed by cooling glycerol under pressure - Additional incompatibility of vibrational with configurational states in the depressurized, high density glass

    NASA Astrophysics Data System (ADS)

    Andersson, Ove; Johari, G. P.

    2016-11-01

    The vibrational state of a glass is naturally incompatible with its configurational state, which makes the glass structurally unstable. When a glass is kept at constant temperature, both the vibrational and configurational states of a glass change with time until it becomes metastable (equilibrium) liquid and the two states become compatible. The process, known as structural relaxation, occurs at a progressively higher rate during heating, and the properties of a glass change accordingly. We add to this incompatibility by depressurizing a glass that had been formed by cooling a liquid under a high pressure, p, and then investigate the effects of the added incompatibility by studying thermal conductivity, κ , and the heat capacity per unit volume ρ Cp of the depressurized glass. We use glycerol for the purpose and study first the changes in the features of κ and of ρ Cp during glass formation on cooling under a set of different p. We then partially depressurize the glass and study the effect of the p-induced instability on the features of κ and ρ Cp as the glass is isobarically heated to the liquid state. At a given low p, the glass configuration that was formed by cooling at high-p had a higher κ than the glass configuration that was formed by cooling at a low p. The difference is more when the glass is formed at a higher p and/or is depressurized to a lower p. On heating at a low p, its κ decreases before its glass-liquid transition range is reached. The effect is the opposite of the increase in κ observed on heating a glass at the same p under which it was formed. It is caused by thermally assisted loss of the added incompatibility of configurational and vibrational states of a high-p formed glass kept at low p. If a glass formed under a low-p is pressurized and then heated under high p, it would show the opposite effect, i.e., its κ would first increase to its high p value before its glass-to-liquid transition range.

  7. Experimental validation of a numerical model for subway induced vibrations

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Degrande, G.; Lombaert, G.

    2009-04-01

    This paper presents the experimental validation of a coupled periodic finite element-boundary element model for the prediction of subway induced vibrations. The model fully accounts for the dynamic interaction between the train, the track, the tunnel and the soil. The periodicity or invariance of the tunnel and the soil in the longitudinal direction is exploited using the Floquet transformation, which allows for an efficient formulation in the frequency-wavenumber domain. A general analytical formulation is used to compute the response of three-dimensional invariant or periodic media that are excited by moving loads. The numerical model is validated by means of several experiments that have been performed at a site in Regent's Park on the Bakerloo line of London Underground. Vibration measurements have been performed on the axle boxes of the train, on the rail, the tunnel invert and the tunnel wall, and in the free field, both at the surface and at a depth of 15 m. Prior to these vibration measurements, the dynamic soil characteristics and the track characteristics have been determined. The Bakerloo line tunnel of London Underground has been modelled using the coupled periodic finite element-boundary element approach and free field vibrations due to the passage of a train at different speeds have been predicted and compared to the measurements. The correspondence between the predicted and measured response in the tunnel is reasonably good, although some differences are observed in the free field. The discrepancies are explained on the basis of various uncertainties involved in the problem. The variation in the response with train speed is similar for the measurements as well as the predictions. This study demonstrates the applicability of the coupled periodic finite element-boundary element model to make realistic predictions of the vibrations from underground railways.

  8. Ionic vibration induced transparency and Autler–Townes splitting

    NASA Astrophysics Data System (ADS)

    Shao, Wenjun; Wang, Fei; Feng, Xun-Li; Oh, C. H.

    2017-04-01

    In this work, the absorption spectrum of a two-level ion in a linear Paul trap is investigated, the ion is supposed to be driven by two orthogonal laser beams, the one along the axial of the trap acts as the control light beam, the other as probe beam. When the frequency of the control laser is tuned to the first red sideband of the ionic transition, the coupling between the internal states of the ion and vibrational mode turns out to be a Jaynes–Cummings (JC) Hamiltonian, which together with the coupling between the probe beam and the two-level ion constructs a Λ -type three-level structure. In this case the transparency window may appear in the absorption spectrum of the probe light, which is induced by the ionic vibration and is very similar to the cavity induced transparency (Rice and Brecha 1996 Opt. Commun. 126 230–5). On the other hand, when the frequency of the control laser is tuned to the first blue sideband of the ionic transition, the two-level ion and vibrational mode are governed by an anti-Jaynes–Cummings (anti-JC) Hamiltonian, the total system including the probe beam forms a V-type three-level structure. And the Autler–Townes splitting in the absorption spectrum is found.

  9. Vortex-induced vibrations mitigation through a nonlinear energy sink

    NASA Astrophysics Data System (ADS)

    Dai, H. L.; Abdelkefi, A.; Wang, L.

    2017-01-01

    The passive suppression mechanism of the vortex-induced vibrations (VIV) of the cylinder by means of an essentially nonlinear element, the nonlinear energy sink (NES) is investigated. The flow-induced loads on the cylinder are modeled using a prevalent van der Pol oscillator which is experimentally validated, coupling to the structural vibrations in the presence of the NES structure. Based on the coupled nonlinear governing equations of motion, the performed analysis indicates that the mass and damping of NES have significant effects on the coupled frequency and damping of the aero-elastic system, leading to the shift of synchronization region and mitigation of vibration responses. It is demonstrated that the coupled system of flow-cylinder-NES behaves resonant interactions, showing periodic, aperiodic, and multiple stable responses which depend on the values of the NES parameters. In addition, it is found that the occurrence of multiple stable responses can enhance the nonlinear energy pumping effect, resulting in the increment of transferring energy from the flow via the cylinder to the NES, which is related to the essential nonlinearity of the sink stiffness. This results in a significant reduction in the VIV amplitudes of the primary circular cylinder for appropriate NES parameter values.

  10. Jet-Cooled Laser-Induced Fluorescence Spectroscopy of T-Butoxy

    NASA Astrophysics Data System (ADS)

    Reilly, Neil J.; Cheng, Lan; Stanton, John F.; Miller, Terry A.; Liu, Jinjun

    2015-06-01

    The vibrational structures of the tilde A ^2A_1 and tilde X ^2E states of t-butoxy were obtained in jet-cooled laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectroscopic measurements. The observed transitions are assigned based on vibrational frequencies calculated using Complete Active Space Self-Consistent Field (CASSCF) method and the predicted Franck-Condon factors. The spin-orbit (SO) splitting was measured to be 35(5) cm-1 for the lowest vibrational level of the ground (tilde X ^2E) state and increases with increasing vibrational quantum number of the CO stretch mode. Vibronic analysis of the DF spectra suggests that Jahn-Teller (JT)-active modes of the ground-state t-butoxy radical are similar to those of methoxy and would be the same if methyl groups were replaced by hydrogen atoms. Coupled-cluster calculations show that electron delocalization, introduced by the substitution of hydrogens with methyl groups, reduces the electronic contribution of the SO splittings by only around ten percent, and a calculation on the vibronic levels based on quasidiabatic model Hamiltonian clearly attributes the relatively small SO splitting of the tilde X ^2E state of t-butoxy mainly to stronger reduction of orbital angular momentum by the JT-active modes when compared to methoxy. The rotational and fine structure of the LIF transition to the first CO stretch overtone level of the tilde A^2A_1 state has been simulated using a spectroscopic model first proposed for methoxy, yielding an accurate determination of the rotational constants of both tilde A and tilde X states.

  11. Numerical Approximations of Flow Induced Vibrations of Vocal Folds

    NASA Astrophysics Data System (ADS)

    Sváček, P.; Horáček, J.

    2010-09-01

    The paper is interested in numerical modelling of incompressible channel flow interacting with elastic part of its walls simulating vocal fold oscillations. The flow in moving domain is described with the aid of the Arbitrary Lagrangian-Eulerian method, see e.g. [1], and governed by the 2D incompressible Navier-Stokes equations. The flow model is coupled with the structural motion modelled by an aeroelastic two degrees of freedom model of the oscillating vocal folds, cf. [2], [9]. The described fluid-structure interaction problem is discretized in time and space, see also [1]. The numerical results of a channel flow modelling the glottal region of the human vocal tract including the vibrating vocal folds are shown. The vibrations of the channel walls are either prescribed (1st case) or induced by the aerodynamical forces (2nd case).

  12. Laser-induced vibration of a thin soap film.

    PubMed

    Emile, Olivier; Emile, Janine

    2014-09-21

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems.

  13. Spray characterization during vibration-induced drop atomization

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2004-02-01

    Vibration-induced drop atomization is a process of rapid droplet ejection from a larger liquid drop. This occurs when a liquid drop resting on a thin diaphragm is vibrated under the appropriate forcing conditions using an attached piezoelectric actuator. The resulting spray of small droplets is characterized in this work using high-speed imaging and particle-tracking techniques. The results show that the average spatial and velocity distributions of the spray droplets are fairly axisymmetric during all stages of the atomization. The mean diameter of the droplets depends on the forcing frequency to the -2/3 power. The ejection velocity of the spray droplets depends on both the magnitude and the rate of change of the forcing amplitude. Thus, controlling the characteristics of the forcing signal may lead to strategies for controlling the spray process in specific applications.

  14. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons.

    PubMed

    Christensen, Rasmus Bjerregaard; Lü, Jing-Tao; Hedegård, Per; Brandbyge, Mads

    2016-01-01

    We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces.

  15. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    PubMed Central

    Christensen, Rasmus Bjerregaard; Lü, Jing-Tao; Hedegård, Per

    2016-01-01

    Summary We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces. PMID:26925354

  16. Experimental chaotic quantification in bistable vortex induced vibration systems

    NASA Astrophysics Data System (ADS)

    Huynh, B. H.; Tjahjowidodo, T.

    2017-02-01

    The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand. In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear

  17. Vibrational cooling dynamics of a [FeFe]-hydrogenase mimic probed by time-resolved infrared spectroscopy.

    PubMed

    Caplins, Benjamin W; Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2014-12-11

    Picosecond time-resolved infrared spectroscopy (TRIR) was performed for the first time on a dithiolate bridged binuclear iron(I) hexacarbonyl complex ([Fe₂(μ-bdt)(CO)₆], bdt = benzene-1,2-dithiolate) which is a structural mimic of the active site of the [FeFe]-hydrogenase enzyme. As these model active sites are increasingly being studied for their potential in photocatalytic systems for hydrogen production, understanding their excited and ground state dynamics is critical. In n-heptane, absorption of 400 nm light causes carbonyl loss with low quantum yield (<10%), while the majority (ca. 90%) of the parent complex is regenerated with biexponential kinetics (τ₁ = 21 ps and τ₂ = 134 ps). In order to understand the mechanism of picosecond bleach recovery, a series of UV-pump TRIR experiments were performed in different solvents. The long time decay (τ₂) of the transient spectra is seen to change substantially as a function of solvent, from 95 ps in THF to 262 ps in CCl₄. Broadband IR-pump TRIR experiments were performed for comparison. The measured vibrational lifetimes (T₁(avg)) of the carbonyl stretches were found to be in excellent correspondence to the observed τ₂ decays in the UV-pump experiments, signifying that vibrationally excited carbonyl stretches are responsible for the observed longtime decays. The fast spectral evolution (τ₁) was determined to be due to vibrational cooling of low frequency modes anharmonically coupled to the carbonyl stretches that were excited after electronic internal conversion. The results show that cooling of both low and high frequency vibrational modes on the electronic ground state give rise to the observed picosecond TRIR transient spectra of this compound, without the need to invoke electronically excited states.

  18. Flow-induced vibration and instability of some nuclear-reactor-system components. [PWR

    SciTech Connect

    Chen, S.S.

    1983-01-01

    The high-velocity coolant flowing through a reactor system component is a source of energy that can induce component vibration and instability. In fact, many reactor components have suffered from excessive vibration and/or dynamic instability. The potential for detrimental flow-induced vibration makes it necessary that design engineers give detailed considerations to the flow-induced vibration problems. Flow-induced-vibration studies have been performed in many countries. Significant progress has been made in understanding the different phenomena and development of design guidelines to avoid damaging vibration. The purpose of this paper is to present an overview of the recent progress in several selected areas, to discuss some new results and to indentify future research needs. Specifically, the following areas will be presented: examples of flow-induced-vibration problems in reactor components; excitation mechanisms and component response characteristics; instability mechanisms and stability criteria; design considerations; and future research needs.

  19. Cross flow induced vibrations in staggered arrays of cylindrical structures

    SciTech Connect

    Marn, J.

    1991-12-31

    Flow induced vibrations cause by instability is the subject of this investigation. The bulk of the work performed is theoretical in nature, the comparison with some of existing experimental data is given for each of four models described. First model encompasses the effects of prescribed motion on the cylinder. Such circumstances occur in the case of vortex shedding initiated instability. The reduced velocity within the cylinder array is low and there is no coupling between the adjacent cylinders. Second model assumes certain form of vibration and corresponding behavior of the perturbed velocity field in temporal and one of spatial coordinates thus transforming partial differential equations into ordinary differential equations and takes into account the motion of the neighboring cylinder. This corresponds to fluid elastic controlled instabilities. The resulting equations are solved analytically. The model is used for better understanding of the equations of cylinder motion as well as for quick estimates of threshold of instability. Third model relaxes an assumption about the form of vibration in spatial direction and uses the vorticity formulation of equation of fluid motion to account for fluid-solid interaction. This model analysis is of two phase (air-water mixture) flow. The void fraction distribution is found to be the single most decisive factor to determine the onset of instability for such a domain. In conclusion, two distinct mechanism were found to be responsible for flow induced vibration caused instabilities, (1) outside source controlled periodic excitation (such as vortex shedding) -- described by the first model and (2) fluid elastic forces -- described by second, third and fourth models. For the values of reduced velocity below 0.7 first model is proposed, for the values above 0.7, the rest.

  20. Complex muscle vibration patterns to induce gait-like lower-limb movements: proof of concept.

    PubMed

    Duclos, Cyril; Kemlin, Claire; Lazert, David; Gagnon, Dany; Dyer, Joseph-Omer; Forget, Robert

    2014-01-01

    Muscle vibrations can induce motor responses and illusions of complex movements. However, inducing gait-like cyclical movements and illusions requires the application of multiple fast alternating vibrations to lower-limb muscles. The objectives were (1) to test the feasibility of delivering complex vibrations in a time-organized manner and (2) to illustrate the possibility of inducing alternate gait-in-place-like movements using these vibrations. Patterns of vibration, produced by 12 vibrators applied bilaterally on the flexor and extensor muscle groups of the lower limbs, were based on normal gait kinematics. We tested 1 s and 2 s cycle patterns of vibration. Vibrator responses were assessed using auto- and crosscorrelations and frequency analyses based on accelerometry measurements, and compared between patterns. High auto- (>0.8) and crosscorrelation (>0.6) coefficients demonstrated a good response by the vibrators to the control signal. Vibrations induced cyclical, low-amplitude stepping-in-place movements that mimicked alternate walking movements with both legs, with 1 s and 2 s cycle durations, in one nondisabled participant and one participant with American Spinal Injury Association Impairment Scale B spinal cord injury standing, relaxed, with body-weight support. Electromechanical vibrators can deliver complex cyclical vibrations and trigger gait-like lower-limb movements. These results warrant the application of these vibration patterns on individuals with sensorimotor impairments to test their potential in gait rehabilitation.

  1. Expansion of radiative cooling of the laser induced plasma

    SciTech Connect

    Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph; Russo,Richard

    2006-05-05

    To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.

  2. Neck muscle vibration induces lasting recovery in spatial neglect

    PubMed Central

    Schindler, I; Kerkhoff, G; Karnath, H; Keller, I; Goldenberg, G

    2002-01-01

    See Editorial Commentary, page 357 Objectives: To evaluate whether neck muscle vibration is an effective technique for neglect rehabilitation, with lasting beneficial effects. Methods: The effects of differential treatment of visual exploration training alone or in combination with neck muscle vibration were evaluated in a crossover study of two matched groups of 10 patients suffering from left sided neglect. Each group received a sequence of 15 consecutive sessions of exploration training and combined treatment. The effects of treatment were assessed with respect to different aspects of the neglect disorder such as impaired perception of the egocentric midline, exploration deficits in visual and tactile modes, and visual size distortion. The transfer of treatment effects to activities of daily living was examined by a reading test and a questionnaire of neglect related everyday problems. All variables were measured six times: three baseline measurements, two post-treatment measurements, and one follow up after two months. Results: The results showed superior effects of combination treatment. A specific and lasting reduction in the symptoms of neglect was achieved in the visual mode, which transferred to the tactile mode with a concomitant improvement in activities of daily living. The improvement was evident two months after the completion of treatment. In contrast, isolated exploration training resulted in only minor therapeutic benefits in visual exploration without any significant transfer effects to other tasks. Conclusions: Neck muscle vibration is a decisive factor in the rehabilitation of spatial neglect and induces lasting recovery when given as a supplement to conventional exploration training. PMID:12235310

  3. Flow induced vibrations in arrays of irregularly spaced cylinders

    NASA Astrophysics Data System (ADS)

    Taub, Gordon; Michelin, Sébastien

    2014-11-01

    Historically the main industrial applications of cylinder arrays in cross flows favored regular arrangements of cylinders. For this reason, most past studies of Flow Induced Vibrations (FIV) in large cylinder arrays have focused on such arrangements. Recently there has been some interest in generating renewable energy using FIV of bluff bodies. In such applications it will likely be beneficial to enhance, rather than suppress FIV. It is not known a priori if regular or irregularly spaced arrays are most adequate for this type of application. In this study, wind tunnel experiments were conducted on one regularly spaced array and four different irregularly spaced arrays of cylinders in a cross flow. Each arrangement of cylinders was examined under eight different orientations to a cross flow ranging between 10 m/s and 17 m/s. The average amplitude of vibration of the cylinders was found to highly depend on arrangement and orientation. The typical amplitude of vibration of the rods in the irregular arrangements were found to be an order of magnitude larger than that of the regular array. A simple model was proposed in order to predict if a given arrangement was likely to produce large oscillations, and the validity of the model was examined. This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Program (Grant PIRG08-GA-2010-276762).

  4. An Experimental Investigation of Vibration Induced Droplet Atomization*

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1999-11-01

    The atomization of a millimeter-scale liquid droplet placed on a vibrating diaphragm is investigated experimentally using high-speed imaging and particle-tracking techniques. Atomization is the result of the rapid ejection of small secondary droplets from the wave crests of a hierarchy of forced surface waves on the primary droplet. The evolution and rate of ejection depend on the coupled dynamics of the primary droplet and the vibrating diaphragm. The present data indicate that secondary droplet ejection results from the collapse of surface craters formed during the evolution of capillary surface waves on the primary droplet. The collapse of the crater and the ensuing ejection of a momentary liquid jet are similar to ejection processes at free surfaces that are induced by the bursting of gas bubbles or the impingement of liquid droplets. The spray characteristics of the ejected droplets are investigated over a broad range of vibrating frequencies (up to 14 kHz) using particle-tracking velocimetry. * Supported by NASA Microgravity Res. Div., Grant NAG3-1949.

  5. An Experimental Investigation of Vibration-Induced Single Droplet Ejection.

    NASA Astrophysics Data System (ADS)

    Range, Kai; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet atomization occurs when small secondary droplets are ejected from the free surface of a larger droplet placed on a vibrating membrane. To model a single ejection event, a liquid droplet is placed on a small piston and vibrated using an electromagnetic driver. The droplet oscillates in a characteristic mode shape that depends on the driving frequency and amplitude, the properties of the liquid, and the size of the droplet. When the excitation amplitude is large enough, a small secondary droplet is ejected from the primary droplet. Observations of this process using high-speed digital video imaging show that droplet ejection occurs when a small liquid column or jet appears on the primary droplet and a secondary droplet forms on the column by a capillary-pinching mechanism. The liquid column or jet emanates from a crater in the primary droplet. As the driving frequency increases, this crater becomes smaller and the diameter of the ejected droplet decreases. We shall present results showing how the ejected droplet diameter and speed depends on the driving frequency and amplitude, the liquid properties, and the primary droplet volume.

  6. Flow induced vibrations in the SSME injector heads

    NASA Technical Reports Server (NTRS)

    Lepore, Frank A.

    1991-01-01

    A description is given of the flowfield in the Space Shuttle Main Engine (SSME) powerhead, the mechanisms which control flow-induced vibrations, and previous experimental work. An in-depth description is given of the development phase of the program , which includes the analysis, design, and fabrication of liquid oxygen (LOX) posts models used in the experimental phase, as well as test facilities, equipment, and procedures used. Also covered is the experimental data analysis, which includes overall steady state powerhead flowfield as well as the high frequency response of the LOX posts.

  7. Vortex-Induced Vibrations of Marine Cables and Structures.

    DTIC Science & Technology

    2014-09-26

    length of 130 m (425 ft) was resonantly excited by currents with magnitudes of 0.45 m/s (0.9 kt). In 1979 the jack-up rig " Offshore Mercury" was drilling ...a drill pipe deployed from the jack-up rig Ocean Monarch in the English Channel; from Every and King (8). A heli- cal strake vortex spoiler is...predict stress distributions and operational lifetimes in hostile ocean environments. This is largely because the amplitudes of vortex-induced vibration

  8. The Temporary Threshold Shift of Vibratory Sensation Induced by Hand-Arm Vibration Composed of Four One-Third Octave Band Vibrations

    NASA Astrophysics Data System (ADS)

    Nishiyama, K.; Taoda, K.; Yamashita, H.; Watanabe, S.

    1997-03-01

    The aim of the present study was to define the multiple effect hand-arm vibration composed of four equally effective one-third octave band vibrations (63 Hz, 125 Hz, 250 Hz and 500 Hz) on the temporary threshold shift in vibratory sensation.Seven healthy subjects were exposed to vibration by grasping a vibrated handle in a soundproof thermo-regulated room. The vibratory sensation threshold at 125 Hz was measured before and after vibration exposure at an exposed fingertip. At first we determined each acceleration of the component one-third octave band vibrations for each subject. These should induce the same magnitude of temporary threshold shift in vibratory sensation immediately after the vibration exposure (TTSv.0as induced by the reference one-third octave band vibration (250 Hz, 4g). We measured TTSv.tfor the exposures of the composed vibrations and the four component vibrations. TTSv.0was determined for each exposure according to the exponential recovery model stated in the previous study.The TTSv.0induced by the composite vibration was not longer than that which might have been induced by each component vibration. This result confirms our previous speculation that the component of the vibration inducing the largest TTSv.0determines TTSv.0by broadband random vibration.

  9. The temporary threshold shift of vibratory sensation induced by composite-band vibration exposure.

    PubMed

    Nishiyama, K; Taoda, K; Yamashita, H; Watanabe, S

    1996-01-01

    Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTSv,0) induced by 1/3 octave-band vibration. We then measured TTSv after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTSv,0 on the basis of the above relationship. The TTSv,0 induced by the composite vibration was not larger than the TTSv,0 induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTSv,0 determines the TTSv,0 by broad-band random vibration.

  10. Flow Induced Vibration Program at Argonne National Laboratory

    SciTech Connect

    Not Available

    1984-01-01

    Argonne National Laboratory has had a Flow Induced Vibration Program since 1967; the Program currently resides in the Laboratory's Components Technology Division. Throughout its existence, the overall objective of the program has been to develop and apply new and/or improved methods of analysis and testing for the design evaluation of nuclear reactor plant components and heat exchange equipment from the standpoint of flow induced vibration. Historically, the majority of the program activities have been funded by the US Atomic Energy Commission (AEC), Energy Research and Development Administration (ERDA), and Department of Energy (DOE). Current DOE funding is from the Breeder Mechanical Component Development Division, Office of Breeder Technology Projects; Energy Conversion and Utilization Technology (ECUT) Program, Office of Energy Systems Research; and Division of Engineering, Mathematical and Geosciences, Office of Basic Energy Sciences. Testing of Clinch River Breeder Reactor upper plenum components has been funded by the Clinch River Breeder Reactor Plant (CRBRP) Project Office. Work has also been performed under contract with Foster Wheeler, General Electric, Duke Power Company, US Nuclear Regulatory Commission, and Westinghouse.

  11. Vibrational Studies of Adsorbate-Induced Reconstruction on Molybdenum Surfaces.

    NASA Astrophysics Data System (ADS)

    Lopinski, Gregory Peter

    Adsorbate-induced rearrangement of the substrate structure strongly modifies the adsorbate-substrate and adsorbate-adsorbate interactions, leading to the complex behavior observed in many chemisorption systems. In this thesis the H/Mo(211), O/Mo(211) and Na/Mo(100) systems have been studied using high resolution electron energy loss spectroscopy (HREELS) to observe vibrations of the adsorbed atoms. The vibrational data is correlated with observations of the long-range order probed by LEED as well as the work function changes induced by adsorption. Adsorbate -induced substrate reconstruction plays an important role in all three of these systems. Studies of the coadsorption systems O+H/Mo(211) and Na+O/Mo(100) indicate how these effects can influence interactions between adsorbates. For H/Mo(211), above 1ML a (1 x 1) to (1 x 2) transition is observed and attributed to modification of the substrate periodicity. Below 1ML, H atoms are bridge bonded and induce local distortions of the substrate. The transition to the (1 x 2) phase involves the ordering of these displacements and occupation of three-fold sites partially populated by conversion of the bridge bonded species. This conversion accounts for the sawtooth-like coverage dependence of the work function. The structural model proposed for this system is also supported by the desorption parameters and partial molar entropy extracted from adsorption isobars. Oxygen adsorption on Mo(211) involves the occupation of multiple binding sites, with both the long-range order and the local geometry of the adsorbate phases strongly temperature dependent. Coadsorption of low coverages of oxygen and hydrogen leads to segregation of the two adsorbates which can be understood in terms of a substrate-mediated repulsive interaction between O and H. For Na/Mo(100), the frequency of the Na-Mo symmetric stretch mode does not shift with coverage although the mode intensity is strongly coverage dependent. The absence of a frequency shift

  12. Aircraft noise-induced building vibrations. [human annoyance responses

    NASA Technical Reports Server (NTRS)

    Stephens, D. G.; Mayes, W. H.

    1979-01-01

    The outdoor/indoor noise levels and associated vibration levels resulting from aircraft and nonaircraft events are recorded at 11 homesites, a historic building, and a school. In addition, limited subjective tests are conducted to examine the human detection/annoyance thresholds for building vibration and rattle caused by aircraft noise. Results include relationships between aircraft noise and building vibration and between vibration and human response. Comparisons of building vibration data with existing criteria for building damage and human response are also considered.

  13. Phase modulation for reduced vibration sensitivity in laser-cooled clocks in space

    NASA Technical Reports Server (NTRS)

    Klipstein, W.; Dick, G.; Jefferts, S.; Walls, F.

    2001-01-01

    The standard interrogation technique in atomic beam clocks is square-wave frequency modulation (SWFM), which suffers a first order sensitivity to vibrations as changes in the transit time of the atoms translates to perceived frequency errors. Square-wave phase modulation (SWPM) interrogation eliminates sensitivity to this noise.

  14. High Resolution Measurements of Impurity-Induced Localized Vibrational Modes in Semiconductors.

    DTIC Science & Technology

    1984-03-26

    Induced Localized Vibrational Modes in Semiconductors by William G. Spitzer Electronic Sciences Laboratory University of Southern California under Grant...neighbors (isotopic change) on the frequency of localized vibrational modes induced by impurities in a crystalline lattice. The earlier observations of...CA 90089-0241 (Received ~~1k~h~i ’~i ABSTRACT The infrared absorption due to excitation of localized vibrational modes (LVM) involving Si impurities

  15. Vibration-Induced-Emission (VIE) for imaging amyloid β fibrils.

    PubMed

    Dou, Wei-Tao; Chen, Wei; He, Xiao-Peng; Su, Jianhua; Tian, He

    2017-02-01

    This paper discusses the use of N,N'-disubstituted-dihydrodibenzo[a,c]phenazines with typical Vibration-Induced-Emission (VIE) properties for imaging amyloid β (Aβ) fibrils, which are a signature of neurological disorders such as Alzheimer's disease. A water-soluble VIEgen with a red fluorescence emission shows a pronounced, blue-shifted emission with Aβ peptide monomers and fibrils. The enhancement in blue fluorescence can be ascribed to the restriction of the molecular vibration by selectively binding to Aβ. We determine an increasing blue-to-red emission ratio of the VIEgen with both the concentration and fibrogenesis time of Aβ, thereby enabling a ratiometric detection of Aβ in its different morphological forms. Importantly, the VIEgen was proven to be suitable for the fluorescence imaging of small Aβ plaques in the hippocampus of a transgenic mouse brain (five months old), with the blue and red emissions well overlapped on the Aβ. This research offers a new rationale to design molecular VIE probes for biological applications.

  16. Ejection Dynamics in Vibration-Induced Droplet Atomization

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2001-11-01

    A primary sessile liquid drop is atomized into a fine spray of secondary droplets using vibration-induced atomization (VIDA) resulting from forced waves on a free surface of the primary drop. The mechanism of free surface breakup during the VIDA process is investigated using high-speed imaging and laser vibrometry. Secondary droplets result from a localized collapse of surface troughs and the ejection and ultimate breakup of momentary liquid spikes. The characteristic breakup time of these liquid spikes scales with the vibration period and the spike length initially varies like t0.5. The breakup begins with a capillary pinch-off from the tip of the spike that can be followed by additional pinching of liquid droplets. For relatively low-viscosity liquid (e.g., water) a capillary-wave instability of a jet is observed in some cases, while in very viscous liquid (e.g., glycerin-water solution) the first breakup occurs near the stem of the jet. The mechanisms of secondary droplet ejection and the influence of the operating parameters and fluid properties are discussed.

  17. The use of scalp cooling for chemotherapy-induced hair loss.

    PubMed

    Young, Annie; Arif, Azra

    Chemotherapy-induced hair loss is a common and distressing side effect of cancer therapy and is one of the major unmet challenges in cancer management. Scalp cooling can prevent chemotherapy-induced hair loss in some cancer patients with solid tumours receiving certain chemotherapy regimens. Recent evidence indicates that this technique does not increase the risk of scalp metastasis. A reduction in post-chemotherapy infusion duration of scalp cooling and the advancement in cool cap technology may assist clinicians in promoting scalp cooling to cancer patients. This article discusses recent research, scalp cooling guidelines, products available and implications for nurses and their organisations in providing scalp cooling. It also considers recent advancements in identifying genes associated with chemotherapy-induced hair loss and international research collaborations including a registry and a 'chemotherapy-induced hair loss action group'--all striving to improve the patient experience of chemotherapy-induced hair loss.

  18. Stall-Induced Vibrations of the AVATAR Rotor Blade

    NASA Astrophysics Data System (ADS)

    Stettner, M.; Reijerkerk, M. J.; Lünenschloß, A.; Riziotis, V.; Croce, A.; Sartori, L.; Riva, R.; Peeringa, J. M.

    2016-09-01

    In the course of the AVATAR project, partner predictions for key load components in storm/idle conditions separated in two groups. One group showed large loading due to edgewise instability, the other group damped edgewise oscillation and lower load levels. To identify the cause for this separation, the impact of structural and aerodynamic modeling options on damping of stall-induced vibrations is investigated for two simplified operating conditions of a single AVATAR blade. The choice of the dynamic stall model is found to be the primary driver, and is therefore most likely also the reason for previously observed differences in AVATAR storm load predictions. Differences in structural dynamics, mode shapes, structural and dynamic twist, as well as wake model are only secondary in terms of impact on damping. Resolution suffered from failure of system identification methods to extract reliable damping values from various non-linear response simulations.

  19. Light-induced vibration in the hearing organ.

    PubMed

    Ren, Tianying; He, Wenxuan; Li, Yizeng; Grosh, Karl; Fridberger, Anders

    2014-08-04

    The exceptional sensitivity of mammalian hearing organs is attributed to an active process, where force produced by sensory cells boost sound-induced vibrations, making soft sounds audible. This process is thought to be local, with each section of the hearing organ capable of amplifying sound-evoked movement, and nearly instantaneous, since amplification can work for sounds at frequencies up to 100 kHz in some species. To test these fundamental precepts, we developed a method for focally stimulating the living hearing organ with light. Light pulses caused intense and highly damped mechanical responses followed by traveling waves that developed with considerable delay. The delayed response was identical to movements evoked by click-like sounds. This shows that the active process is neither local nor instantaneous, but requires mechanical waves traveling from the cochlear base toward its apex. A physiologically-based mathematical model shows that such waves engage the active process, enhancing hearing sensitivity.

  20. Ultrafast Relaxation Dynamics of Photoexcited Heme Model Compounds: Observation of Multiple Electronic Spin States and Vibrational Cooling.

    PubMed

    Govind, Chinju; Karunakaran, Venugopal

    2017-04-04

    Hemin is a unique model compound of heme proteins carrying out variable biological functions. Here, the excited state relaxation dynamics of heme model compounds in the ferric form are systematically investigated by changing the axial ligand (Cl/Br), the peripheral substituent (vinyl/ethyl-meso), and the solvent (methanol/DMSO) using femtosecond pump-probe spectroscopy upon excitation at 380 nm. The relaxation time constants of these model compounds are obtained by global analysis. Excited state deactivation pathway of the model compounds comprising the decay of the porphyrin excited state (S*) to ligand to metal charge transfer state (LMCT, τ1), back electron transfer from metal to ligand (MLCT, τ2), and relaxation to the ground state through different electronic spin states of iron (τ3 and τ4) are proposed along with the vibrational cooling processes. This is based on the excited state absorption spectral evolution, similarities between the transient absorption spectra of the ferric form and steady state absorption spectra of the low-spin ferrous form, and the data analysis. The observation of an increase of all the relaxation time constants in DMSO compared to the methanol reflects the stabilization of intermediate states involved in the electronic relaxation. The transient absorption spectra of met-myoglobin are also measured for comparison. Thus, the transient absorption spectra of these model compounds reveal the involvement of multiple iron spin states in the electronic relaxation dynamics, which could be an alternative pathway to the ground state beside the vibrational cooling processes and associated with the inherent features of the heme b type.

  1. Hybrid isolation of micro vibrations induced by reaction wheels

    NASA Astrophysics Data System (ADS)

    Lee, Dae-Oen; Park, Geeyong; Han, Jae-Hung

    2016-02-01

    As the technology for precision satellite payloads continues to advance, the requirements for the pointing stability of the satellites are becoming extremely high. In many situations, even small amplitude disturbances generated by the onboard components may cause serious degradation in the performance of high precision payloads. In such situations, vibration isolators can be installed to reduce the vibration transmission. In this work, a hybrid vibration isolator comprising passive and active components is proposed to provide an effective solution to the vibration problems caused by the reaction wheel disturbances. Firstly, mathematical modeling and experimental study of a single axis vibration isolator having high damping and high roll-off rate for the high frequency region and active components that enhance isolation performance for narrow frequency bands are presented. This concept is then extended to multi-axis by forming Stewart platform and the performance is experimentally verified. The tests on a flexible testbed show effective vibration isolation by the proposed vibration isolator.

  2. The effects of pre-exercise vibration stimulation on the exercise-induced muscle damage

    PubMed Central

    Kim, Ji-Yun; Kang, Da-Haeng; Lee, Joon-Hee; O, Se-Min; Jeon, Jae-Keun

    2017-01-01

    [Purpose] To investigate the effects of pre-induced muscle damage vibration stimulation on the pressure-pain threshold and muscle-fatigue-related metabolites of exercise-induced muscle damage. [Subjects and Methods] Thirty healthy, adult male subjects were randomly assigned to the pre-induced muscle damage vibration stimulation group, post-induced muscle damage vibration stimulation group, or control group (n=10 per group). To investigate the effects of pre-induced muscle damage vibration stimulation, changes in the pressure-pain threshold (lb), creatine kinase level (U/L), and lactate dehydrogenase level (U/L) were measured and analyzed at baseline and at 24 hours, 48 hours, and 72 hours after exercise. [Results] The pressure-pain thresholds and concentrations of creatine kinase and lactate dehydrogenase varied significantly in each group and during each measurement period. There were interactions between the measurement periods and groups, and results of the post-hoc test showed that the pre-induced muscle damage vibration stimulation group had the highest efficacy among the groups. [Conclusion] Pre-induced muscle damage vibration stimulation is more effective than post-induced muscle damage vibration stimulation for preventing muscle damage. PMID:28210056

  3. Train-induced field vibration measurements of ground and over-track buildings.

    PubMed

    Zou, Chao; Wang, Yimin; Moore, James A; Sanayei, Masoud

    2017-01-01

    Transit-oriented development, such as metro depot and over-track building complexes, has expanded rapidly over the last 5years in China. Over-track building construction has the advantage of comprehensive utilization of land resources, ease of commuting to work, and provide funds for subway construction. But the high frequency of subway operations into and out of the depots can generate excessive vibrations that transmit into the over track buildings, radiate noise within the buildings, hamper the operation of vibration sensitive equipment, and adversely affect the living quality of the building occupants. Field measurements of vibration during subway operations were conducted at Shenzhen, China, a city of 10.62 million people in southern China. Considering the metro depot train testing line and throat area train lines were the main vibration sources, vibration data were captured in five measurement setups. The train-induced vibrations were obtained and compared with limitation of FTA criteria. The structure-radiated noise was calculated using measured vibration levels. The vertical vibration energy directly passed through the columns on both sides of track into the platform, amplifying vibration on the platform by up to 6dB greater than ground levels at testing line area. Vibration amplification around the natural frequency in the vertical direction of over-track building made the peak values of indoor floor vibration about 16dB greater than outdoor platform vibration. We recommend to carefully examining design of new over-track buildings within 40m on the platform over the throat area to avoid excessive vertical vibrations and noise. For both buildings, the measured vertical vibrations were less than the FTA limit. However, it is demonstrated that the traffic-induced high-frequency noise has the potential to annoy occupants on the upper floors.

  4. Vibrational predissociation and vibrationally induced isomerization of 3-aminophenol-ammonia

    SciTech Connect

    Heid, Cornelia G.; Merrill, Wyatt G.; Case, Amanda S. Crim, F. Fleming

    2015-01-07

    We investigate the vibrational predissociation dynamics of the hydrogen-bonded 3-aminophenol-ammonia cluster (3-AP-NH{sub 3}) in the OH and NH stretching regions. Vibrational excitation provides enough energy to dissociate the cluster into its constituent 3-AP and NH{sub 3} monomers, and we detect the 3-AP fragments via (1 + 1) resonance-enhanced multiphoton ionization (REMPI). The distribution of vibrational states of the 3-AP fragment suggests the presence of two distinct dissociation pathways. The first dissociation channel produces a broad, unstructured feature in the REMPI-action spectrum after excitation of any of the OH or NH stretching vibrations, pointing to a nearly statistical dissociation pathway with extensive coupling among the vibrations in the cluster during the vibrational predissociation. The second dissociation channel produces distinct, resolved features on top of the broad feature but only following excitation of the OH or symmetric NH{sub 3} stretch in the cluster. This striking mode-specificity is consistent with strong coupling of these two modes to the dissociation coordinate (the O–H⋯N bond). The presence of clearly resolved transitions to the electronic origin and to the 10a{sup 2} + 10b{sup 2} state of the cis-3-AP isomer shows that vibrational excitation is driving the isomerization of the trans-3-AP-NH{sub 3} isomer to the cis-3-AP-NH{sub 3} isomer in the course of the dissociation.

  5. Characterization of Train-Induced Vibration and its Effect on Fecal Corticosterone Metabolites in Mice

    PubMed Central

    Atanasov, Nicholas A; Sargent, Jennifer L; Parmigiani, John P; Palme, Rupert; Diggs, Helen E

    2015-01-01

    Excessive environmental vibrations can have deleterious effects on animal health and experimental results, but they remain poorly understood in the animal laboratory setting. The aims of this study were to characterize train-associated vibration in a rodent vivarium and to assess the effects of this vibration on the reproductive success and fecal corticosterone metabolite levels of mice. An instrumented cage, featuring a high-sensitivity microphone and accelerometer, was used to characterize the vibrations and sound in a vivarium that is near an active railroad. The vibrations caused by the passing trains are 3 times larger in amplitude than are the ambient facility vibrations, whereas most of the associated sound was below the audible range for mice. Mice housed in the room closest to the railroad tracks had pregnancy rates that were 50% to 60% lower than those of mice of the same strains but bred in other parts of the facility. To verify the effect of the train vibrations, we used a custom-built electromagnetic shaker to simulate the train-induced vibrations in a controlled environment. Fecal pellets were collected from male and female mice that were exposed to the simulated vibrations and from unexposed control animals. Analysis of the fecal samples revealed that vibrations similar to those produced by a passing train can increase the levels of fecal corticosterone metabolites in female mice. These increases warrant attention to the effects of vibration on mice and, consequently, on reproduction and experimental outcomes. PMID:26632783

  6. Characterization of Train-Induced Vibration and its Effect on Fecal Corticosterone Metabolites in Mice.

    PubMed

    Atanasov, Nicholas A; Sargent, Jennifer L; Parmigiani, John P; Palme, Rupert; Diggs, Helen E

    2015-11-01

    Excessive environmental vibrations can have deleterious effects on animal health and experimental results, but they remain poorly understood in the animal laboratory setting. The aims of this study were to characterize train-associated vibration in a rodent vivarium and to assess the effects of this vibration on the reproductive success and fecal corticosterone metabolite levels of mice. An instrumented cage, featuring a high-sensitivity microphone and accelerometer, was used to characterize the vibrations and sound in a vivarium that is near an active railroad. The vibrations caused by the passing trains are 3 times larger in amplitude than are the ambient facility vibrations, whereas most of the associated sound was below the audible range for mice. Mice housed in the room closest to the railroad tracks had pregnancy rates that were 50% to 60% lower than those of mice of the same strains but bred in other parts of the facility. To verify the effect of the train vibrations, we used a custom-built electromagnetic shaker to simulate the train-induced vibrations in a controlled environment. Fecal pellets were collected from male and female mice that were exposed to the simulated vibrations and from unexposed control animals. Analysis of the fecal samples revealed that vibrations similar to those produced by a passing train can increase the levels of fecal corticosterone metabolites in female mice. These increases warrant attention to the effects of vibration on mice and, consequently, on reproduction and experimental outcomes.

  7. Fretting wear behaviors of a dual-cooled nuclear fuel rod under a simulated rod vibration

    SciTech Connect

    Lee, Young-Ho; Kim, Hyung-Kyu; Kang, Heung-Seok; Yoon, Kyung-Ho; Kim, Jae-Yong; Lee, Kang-Hee

    2012-06-06

    Recently, a dual-cooled fuel (i.e., annular fuel) that is compatible with current operating PWR plants has been proposed in order to realize both a considerable amount of power uprating and an increase of safety margins. As the design concept should be compatible with current operating PWR plants, however, it shows a narrow gap between the fuel rods when compared with current solid nuclear fuel arrays and needs to modify the spacer grid shapes and their positions. In this study, fretting wear tests have been performed to evaluate the wear resistance of a dual-cooled fuel by using a proposed spring and dimple of spacer grids that have a cantilever type and hemispherical shape, respectively. As a result, the wear volume of the spring specimen gradually increases as the contact condition is changed from a certain gap, just contact to positive force. However, in the dimple specimen, just contact condition shows a large wear volume. In addition, a circular rod motion at upper region of contact surface is gradually increased and its diametric size depends on the wear depth increase. Based on the test results, the fretting wear resistance of the proposed spring and dimple is analyzed by comparing the wear measurement results and rod motion in detail.

  8. Vibration induced white-feet: Overview and field study of vibration exposure and reported symptoms in workers

    PubMed Central

    Eger, Tammy; Thompson, Aaron; Leduc, Mallorie; Krajnak, Kristine; Goggins, Katie; Godwin, Alison; House, Ron

    2015-01-01

    BACKGROUND Workers who stand on platforms or equipment that vibrate are exposed to foot-transmitted vibration (FTV). Exposure to FTV can lead to vibration white feet/toes resulting in blanching of the toes, and tingling and numbness in the feet and toes. OBJECTIVES The objectives are 1) to review the current state of knowledge of the health risks associated with foot-transmitted vibration (FTV), and 2) to identify the characteristics of FTV and discuss the associated risk of vibration-induced injury. PARTICIPANTS Workers who operated locomotives (n = 3), bolting platforms (n = 10), jumbo drills (n = 7), raise drilling platforms (n = 4), and crushers (n = 3), participated. METHODS A tri-axial accelerometer was used to measure FTV in accordance with ISO 2631-1 guidelines. Frequency-weighted root-mean-square acceleration and the dominant frequency are reported. Participants were also asked to report pain/ache/discomfort in the hands and/or feet. RESULTS Reports of pain/discomfort/ache were highest in raise platform workers and jumbo drill operators who were exposed to FTV in the 40 Hz and 28 Hz range respectively. Reports of discomfort/ache/pain were lowest in the locomotive and crusher operators who were exposed to FTV below 10 Hz. These findings are consistent with animal studies that have shown vascular and neural damage in exposed appendages occurs at frequencies above 40 Hz. CONCLUSIONS Operators exposed to FTV at 40 Hz appear to be at greater risk of experiencing vibration induced injury. Future research is required to document the characteristics of FTV and epidemiological evidence is required to link exposure with injury. PMID:24004754

  9. Simulation of scalp cooling by external devices for prevention of chemotherapy-induced alopecia.

    PubMed

    Pliskow, Bradley; Mitra, Kunal; Kaya, Mehmet

    2016-02-01

    Hypothermia of the scalp tissue during chemotherapy treatment (scalp cooling) has been shown to reduce or prevent chemotherapy-induced hair loss. In this study, numerical models are developed to investigate the interaction between different types of external scalp cooling devices and the human scalp tissue. This work focuses on improving methods of modeling scalp cooling devices as it relates specifically to the prevention of chemotherapy-induced alopecia. First, the cooling power needed for any type of device to achieve therapeutic levels of scalp hypothermia is investigated. Subsequently, two types of scalp cooling devices are simulated: a pre-cooled/frozen cap design and a liquid-cooled cap design. For an average patient, simulations show that 38.5W of heat must be extracted from the scalp tissue for this therapy in order to cool the hair follicle to 22°C. In practice, the cooling power must be greater than this amount to account for thermal losses of the device. Simulations show that pre-cooled and liquid-cooled cap designs result in different tissue temperatures over the course of the procedure. However, it is the temperature of the coolant that largely determines the resulting tissue temperature. Simulations confirm that the thermal resistance of the hair/air layer has a large impact on the resulting tissue temperatures. The results should be correlated with experimental data as an effort to determine the optimal parameter choices for this model.

  10. Substrate-borne vibrations induce behavioral responses in the leaf-dwelling cerambycid, Paraglenea fortunei.

    PubMed

    Tsubaki, Remi; Hosoda, Naoe; Kitajima, Hiroshi; Takanashi, Takuma

    2014-12-01

    Many insects utilize substrate-borne vibrations as a source of information for recognizing mates or predators. Among various substrates, plant leaves are commonly used for transmitting and receiving vibrational information. However, little is known about the utilization of vibrations by leaf-dwelling insects, especially coleopteran beetles. We conducted two experiments to examine the response of the leaf-dwelling cerambycid beetle, Paraglenea fortunei, to substrate-borne vibrations. We recorded and analyzed vibrations of host plant leaves from four different sources: wind (0.5 m/s), a beetle during landing, a walking beetle, and a beetle walking in the wind (0.5 m/s). We then measured the behavioral thresholds, the lowest amplitudes that induce behavioral responses, from beetles walking and resting on horizontal and vertical substrates with pulsed vibrations ranging from 20 Hz to 1 kHz. The vibrational characteristics of biotic and abiotic stimuli clearly differed. Beetle-generated vibrations (landing, walking, and walking in the wind) were broadly high in the low-frequency components above ∼30 Hz, while wind-generated vibrations showed a dominant peak at ∼30 Hz and a steep decrease thereafter. Among four situations, beetles walking on horizontal substrates showed lowest thresholds to vibrations of 75-500 Hz, which are characteristic of beetle-generated vibrations. Given that P. fortunei beetles are found on horizontal leaf surfaces of the host plant, vibrations transmitted though horizontal substrates may induce a strong freeze response in walking beetles to detect conspecifics or heterospecifics. Our findings provide evidence that leaf-dwelling beetles can discriminate among biotic and abiotic factors via differences in vibrational characteristics.

  11. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    SciTech Connect

    Uvan Catton; Vijay K. Dhir; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi

    2004-04-06

    Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers.

  12. Topographic analysis of the skull vibration-induced nystagmus test with piezoelectric accelerometers and force sensors.

    PubMed

    Dumas, Georges; Lion, Alexis; Perrin, Philippe; Ouedraogo, Evariste; Schmerber, Sébastien

    2016-03-23

    Vibration-induced nystagmus is elicited by skull or posterior cervical muscle stimulations in patients with vestibular diseases. Skull vibrations delivered by the skull vibration-induced nystagmus test are known to stimulate the inner ear structures directly. This study aimed to measure the vibration transfer at different cranium locations and posterior cervical regions to contribute toward stimulus topographic optimization (experiment 1) and to determine the force applied on the skull with a hand-held vibrator to study the test reproducibility and provide recommendations for good clinical practices (experiment 2). In experiment 1, a 100 Hz hand-held vibrator was applied on the skull (vertex, mastoids) and posterior cervical muscles in 11 healthy participants. Vibration transfer was measured by piezoelectric sensors. In experiment 2, the vibrator was applied 30 times by two experimenters with dominant and nondominant hands on a mannequin equipped to measure the force. Experiment 1 showed that after unilateral mastoid vibratory stimulation, the signal transfer was higher when recorded on the contralateral mastoid than on the vertex or posterior cervical muscles (P<0.001). No difference was observed between the different vibratory locations when vibration transfer was measured on vertex and posterior cervical muscles. Experiment 2 showed that the force applied to the mannequin varied according to the experimenters and the handedness, higher forces being observed with the most experienced experimenter and with the dominant hand (10.3 ± 1.0 and 7.8 ± 2.9 N, respectively). The variation ranged from 9.8 to 29.4% within the same experimenter. Bone transcranial vibration transfer is more efficient from one mastoid to the other mastoid than other anatomical sites. The mastoid is therefore the optimal site for skull vibration-induced nystagmus test in patients with unilateral vestibular lesions and enables a stronger stimulation of the healthy side. In clinical practice

  13. Light-induced basilar membrane vibrations in the sensitive cochlea

    NASA Astrophysics Data System (ADS)

    Grosh, Karl; Ren, Tianying; He, Wenxuan; Fridberger, Anders; Li, Yizeng; Nankali, Amir

    2015-12-01

    The exceptional sensitivity of mammalian hearing organ is attributed to an outer hair cell-mediated active process, where forces produced by sensory cells boost sound-induced vibrations, making soft sounds audible. This process is thought to be local, with each section of the hearing organ capable of amplifying sound-evoked movement, and nearly instantaneous, since amplification can work for sounds at frequencies up to 100 kHz in some species. To test these precepts, we developed a method for focally stimulating the living hearing organ with light. Light pulses caused intense and highly damped mechanical responses followed by traveling waves that developed with considerable delay. The delayed response was identical to movements evoked by click-like sounds. A physiologically based mathematical model shows that such waves engage the active process, enhancing hearing sensitivity. The experiments and the theoretical analysis show that the active process is neither local nor instantaneous, but requires mechanical waves traveling from the cochlear base toward its apex.

  14. Statistical analysis of vibration-induced bone and joint damages.

    PubMed

    Schenk, T

    1995-01-01

    Vibration-induced damages to bones and joints are still occupational diseases with insufficient knowledge about causing and moderating factors and resulting damages. For a better understanding of these relationships also retrospective analyses of already acknowledged occupational diseases may be used. Already recorded detailed data for 203 in 1970 to 1979 acknowledged occupational diseases in the building industry and the building material industry of the GDR are the basis for the here described investigations. The data were gathered from the original documents of the occupational diseases and scaled in cooperation of an industrial engineer and an industrial physician. For the purposes of this investigations the data are to distinguish between data which describe the conditions of the work place (e.g. material, tools and posture), the exposure parameters (e.g. beginning of exposure and latency period) and the disease (e.g. anamnestical and radiological data). These data are treated for the use with sophisticated computerized statistical methods. The following analyses were carried out. Investigation of the connections between the several characteristics, which describe the occupational disease (health damages), including the comparison of the severity of the damages at the individual joints. Investigation of the side dependence of the damages. Investigation of the influence of the age at the beginning of the exposure and the age at the acknowledgement of the occupational disease and herewith of the exposure duration. Investigation of the effect of different occupational and exposure conditions.

  15. Tangential acceleration feedback control of friction induced vibration

    NASA Astrophysics Data System (ADS)

    Nath, Jyayasi; Chatterjee, S.

    2016-09-01

    Tangential control action is studied on a phenomenological mass-on-belt model exhibiting friction-induced self-excited vibration attributed to the low-velocity drooping characteristics of friction which is also known as Stribeck effect. The friction phenomenon is modelled by the exponential model. Linear stability analysis is carried out near the equilibrium point and local stability boundary is delineated in the plane of control parameters. The system is observed to undergo a Hopf bifurcation as the eigenvalues determined from the linear stability analysis are found to cross the imaginary axis transversally from RHS s-plane to LHS s-plane or vice-versa as one varies the control parameters, namely non-dimensional belt velocity and the control gain. A nonlinear stability analysis by the method of Averaging reveals the subcritical nature of the Hopf bifurcation. Thus, a global stability boundary is constructed so that any choice of control parameters from the globally stable region leads to a stable equilibrium. Numerical simulations in a MATLAB SIMULINK model and bifurcation diagrams obtained in AUTO validate these analytically obtained results. Pole crossover design is implemented to optimize the filter parameters with an independent choice of belt velocity and control gain. The efficacy of this optimization (based on numerical results) in the delicate low velocity region is also enclosed.

  16. Harbor Seal Vibrissa Morphology Reduces Vortex-Induced Vibrations

    NASA Astrophysics Data System (ADS)

    Beem, Heather; Dahl, Jason; Triantafyllou, Michael

    2011-11-01

    Studies show that harbor seals are adept at tracking small movements in the water, such as those left in the wake of fish, by using their highly sensitive whiskers to detect fluid structures, even without auditory or visual cues. The present work investigates the intriguing claim that the unique morphology of the harbor seal whisker suppresses Vortex Induced Vibrations (VIV). This implies that the geometry is specialized to reduce the background noise caused by the whisker's own wake in the detection of the upstream target. Forces on a rigid whisker model (scale: 50x) being towed steadily down a water tank while experiencing imposed oscillations are measured. A range of frequencies and amplitudes are tested, the hydrodynamic lift coefficient in phase with velocity (CL,v) is calculated for each, and values are combined in a contour plot. The region of positive CL,v peaks at an amplitude ratio of 0.1, indicating that the whisker's undulatory, asymmetric structure considerably reduces (but does not entirely suppress) regions where the structure experiences VIV in comparison with a standard cylinder, whose peak reaches an amplitude ratio of 0.8.

  17. Regimes of flow induced vibration for tandem, tethered cylinders

    NASA Astrophysics Data System (ADS)

    Nave, Gary; Stremler, Mark

    2015-11-01

    In the wake of a bluff body, there are a number of dynamic response regimes that exist for a trailing bluff body depending on spacing, structural restoring forces, and the mass-damping parameter m* ζ . For tandem cylinders with low values of m* ζ , two such regimes of motion are Gap Flow Switching and Wake Induced Vibration. In this study, we consider the dynamics of a single degree-of-freedom rigid cylinder in the wake of another in these regimes for a variety of center-to-center cylinder spacings (3-5 diameters) and Reynolds numbers (4,000-11,000). The system consists of a trailing cylinder constrained to a circular arc around a fixed leading cylinder, which, for small angle displacements, bears a close resemblance to the transversely oscillating cylinders found more commonly in existing literature. From experiments on this system, we compare and contrast the dynamic response within these two regimes. Our results show sustained oscillations in the absence of a structural restoring force in all cases, providing experimental support for the wake stiffness assumption, which is based on the mean lift toward the center line of flow.

  18. Airways obstruction in asthmatics induced by body cooling.

    PubMed

    Chen, W Y; Horton, D J

    1978-02-01

    Pulmonary and thermoregulatory reactions to body cooling were studied in eight asthmatic and five normal subjects. The cooling was achieved by a cold shower at water temperature (T) of 15 degrees C for 1 min, followed by exposing the wet body to a high wind generated by a fan for another minute. The skin T, oral T and pulmonary functions were measured before and after cooling. After the cooling, skin T fell a mean of 7 degrees in all subjects and the oral T fell 0.5 degrees in the normals and 0.7 degrees in the asthmatics. In asthmatics, the post-cooling forced expiratory volume in 1 s (FEV1) and maximal mid-expiratory flow (MMEF) fell significantly (P less than .05) to a mean of 79% and 72%of baseline, respectively, and thoracic gas volume (TGV) and airway resistance (Raw) increased significantly to 133% and 198% of baseline, respectively. In normal subjects a small but significant increase in Raw was found. No obstruction developed in the asthmatics after a warm shower at 37 degrees or after breathing the cold shower mist. It is suggested that it is body cooling which leads first to vasoconstriction and then cooling of respiratory mucosa that initiates bronchoconstriction in asthmatics.

  19. Achilles tendon vibration-induced changes in plantar flexor corticospinal excitability.

    PubMed

    Lapole, Thomas; Temesi, John; Gimenez, Philippe; Arnal, Pierrick J; Millet, Guillaume Y; Petitjean, Michel

    2015-02-01

    Daily Achilles tendon vibration has been shown to increase muscle force, likely via corticospinal neural adaptations. The aim of the present study was to determine the extent by which corticospinal excitability is influenced during direct Achilles tendon vibration. Motor-evoked potentials (MEPs) were elicited in the soleus (SOL), gastrocnemius medialis (GM) and tibialis anterior (TA) by transcranial magnetic stimulation of the motor cortical area of the leg with and without Achilles tendon vibration at various frequencies (50, 80 and 110 Hz). Contralateral homologues were also investigated. SOL and GM MEP amplitude significantly increased by 226 ± 188 and 66 ± 39%, respectively, during Achilles tendon vibration, without any difference between the tested frequencies. No MEP changes were reported for TA or contralateral homologues. Increased SOL and GM MEP amplitude suggests increased vibration-induced corticospinal excitability independent of vibration frequency.

  20. Wind induced resonant cross flow vibrations on Norwegian offshore flare booms

    SciTech Connect

    Oppen, A.N.; Kvitrud, A.

    1995-12-31

    Vibrations and fatigue cracking have occurred, for some years, i flare boom structures on a number of platforms on the Norwegian continental shelf. In view of this, the objective of this paper is to: (1) Describe the vibrations and its characteristics on Statfjord A and Heimdal which had the largest vibrations, the vibrations can`t be predicted by vortex induced vibrations of individual members but could be caused by wake effects, local frame vibrations or global dynamic effects. (2) Review the evaluation of cracks in other flare boom structures, the work has been based on DIN 4133 and includes vibrations of both individual members and frames. (3) Review the design practice and operational experience with design parameters especially measurements of damping on individual tubular members and observed vibrations of individual members and frames. Possible limitations of the DIN standard will be discussed. (4) A promising device for reducing the vibrations is described. The problems have mainly been caused by the methods used in design, however, evidence of welding defects initiating fatigue cracks has also been found. A review of the existing methods has led to the recommendation of using the German DIN 4133 code for design purposes. This code is to a large extent similar to the proposed Eurocode-1. A design procedure based on DIN 4133 is proposed including additional parametric boundaries for avoiding resonant vibration.

  1. Study on thermally induced vibration of flexible boom in various thermal environments of vacuum chamber

    NASA Astrophysics Data System (ADS)

    Kong, Changduk; Oh, Kyung-Won; Park, Hyun-Bum; Sugiyama, Y.

    2005-02-01

    In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft such as the thin solar panel and the flexible cantilever with the attached tip mass in space, the thermally-induced vibration including thermal flutter of the flexible thin boom with the concentrated tip mass was experimentally investigated at various thermal environments using a heat lamp and both vacuum and air condition using the vacuum chamber. In this experimental study, divergence speed, natural frequency and thermal strains of the thermally-induced vibration were comparatively evaluated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the earth orbit satellite in solar radiation environment from the earth eclipse region including umbra and penumbra was simulated using the vacuum chamber and power control of the heating lamp.

  2. Effects of a Device on Mitigation of Rain/Wind-Induced Vibration

    NASA Astrophysics Data System (ADS)

    Bi, Jihong; Yin, Yuanbiao; Li, Jizhong

    2010-05-01

    Due to its complexity, the mechanism of the rain/wind-induced vibration is still unclear even now, and further studies are required on effective methods to mitigate the vibration. In this paper, based on the Den Hartog/s galloping theory, a device, which was designed to restrain larger displacement of a stayed-cable, was analyzed numerically. Parametric studies were carried out to make clear the characteristics of the dynamic behaviors of the device. Results show that the device could mitigate effectively the vibration of a stayed-cable induced by rain/wind and it could provide a choice for the bridge engineering practice.

  3. Railway ground vibrations induced by wheel and rail singular defects

    NASA Astrophysics Data System (ADS)

    Kouroussis, Georges; Connolly, David P.; Alexandrou, Georgios; Vogiatzis, Konstantinos

    2015-10-01

    Railway local irregularities are a growing source of ground-borne vibration and can cause negative environmental impacts, particularly in urban areas. Therefore, this paper analyses the effect of railway track singular defects (discontinuities) on ground vibration generation and propagation. A vehicle/track/soil numerical railway model is presented, capable of accurately predicting vibration levels. The prediction model is composed of a multibody vehicle model, a flexible track model and a finite/infinite element soil model. Firstly, analysis is undertaken to assess the ability of wheel/rail contact models to accurately simulate the force generation at the wheel/rail contact, in the presence of a singular defect. It is found that, although linear contact models are sufficient for modelling ground vibration on smooth tracks, when singular defects are present higher accuracy wheel/rail models are required. Furthermore, it is found that the variation in wheel/rail force during the singular defect contact depends on the track flexibility, and thus requires a fully coupled vehicle/track/foundation model. Next, a parametric study of ground vibrations generated by singular rail and wheel defects is undertaken. Six shapes of discontinuity are modelled, representing various defect types such as transition zones, switches, crossings, rail joints and wheel flats. The vehicle is modelled as an AM96 train set and it is found that ground vibration levels are highly sensitive to defect height, length and shape.

  4. Vibration-induced post-effects: a means to improve postural asymmetry in lower leg amputees?

    PubMed

    Duclos, C; Roll, R; Kavounoudias, A; Roll, J-P; Forget, R

    2007-10-01

    Muscle vibration has been shown to induce long-lasting and oriented alteration of standing posture in healthy individuals. The postural alterations can last several minutes following the end of vibration and are called post-effects. The goal of this study was to determine whether persons with lower leg amputation that show persistent postural asymmetry after usual rehabilitation experience these postural post-effects and if this could improve their weight bearing on the prosthesis. Centre of pressure (CP) position during stance was recorded prior to and up to 13 min after a 30s unilateral vibration applied during sitting to lateral neck (trapezius) or hip (gluteus medius) muscles in 14 individuals with unilateral lower leg amputation and 18 controls. The amputees' postural asymmetry was confirmed prior to the vibration intervention. A CP displacement, without an increase in CP velocity, was observed in both groups of participants over the 13 min post-vibration. For both the neck or hip vibration sites, the CP shifts were directed in the medio-lateral plane and were oriented either towards the vibrated side or the opposite side across subjects. This led to a decrease of postural asymmetry in half of the group of amputees. Within subject, the orientation of the post-effect was constant and changed to the opposite direction with vibration of the opposite body side. It is suggested that the post-effects are produced by a change of the postural reference consequent to the sustained proprioceptive message induced during the muscle vibration period. The orientation of the post-effects is discussed in relation to the notion of reference frame preference. All in all, because post-effect orientation is constant within subject and adaptive, future studies should investigate if individuals with lower leg amputation could benefit from postural post-effects induced by muscle vibration to improve function.

  5. Role of Kv 4.3 in vibration-induced muscle pain in the rat

    PubMed Central

    Conner, Lindsay; Alvarez, Pedro; Bogen, Oliver; Levine, Jon D.

    2015-01-01

    We hypothesized that changes in the expression of Kv4.3 contribute to the mechanical hyperalgesia induced by vibration injury, a rodent model for hand-arm vibration syndrome in humans. Here we show that the exposure of the gastrocnemius muscle to vibration injury induces muscle hyperalgesia that is accompanied by a significant down-regulation of Kv4.3 in affected sensory nerve fibers in dorsal root ganglia (DRG). We additionally demonstrate that the intrathecal administration of antisense oligonucleotides for Kv4.3 mRNA itself induces muscle hyperalgesia in the rat. Our results suggest that attenuation in the expression of Kv4.3 may contribute to neuropathic pain in people affected by hand-arm vibration syndrome. PMID:26721612

  6. Laser-induced fluorescence, dispersed fluorescence and lifetime measurements of jet-cooled chloro-substituted benzyl radicals

    NASA Astrophysics Data System (ADS)

    Hamatani, Satoshi; Tsuji, Kazuhide; Kawai, Akio; Shibuya, Kazuhiko

    2002-07-01

    We measured the laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled α-, o- and m-chlorobenzyl radicals after they were generated by the 193 nm photolysis of the corresponding parent molecules. The vibronically resolved spectra were obtained to analyze their D1-D0 transitions. The fluorescence lifetimes of α-, o-, m- and p-chlorobenzyls in the zeroth vibrational levels of the D1 states were measured to estimate the oscillator strengths of a series of benzyl derivatives. It was found that the α-substitution is inefficient to break the `accidental forbiddenness' of the D1-D0 transition of benzyl, while the ring-substitution enhances the oscillator strength by 50%.

  7. Whole-body vibration-induced muscular reflex: Is it a stretch-induced reflex?

    PubMed Central

    Cakar, Halil Ibrahim; Cidem, Muharrem; Sebik, Oguz; Yilmaz, Gizem; Karamehmetoglu, Safak Sahir; Kara, Sadik; Karacan, Ilhan; Türker, Kemal Sıtkı

    2015-01-01

    [Purpose] Whole-body vibration (WBV) can induce reflex responses in muscles. A number of studies have reported that the physiological mechanisms underlying this type of reflex activity can be explained by reference to a stretch-induced reflex. Thus, the primary objective of this study was to test whether the WBV-induced muscular reflex (WBV-IMR) can be explained as a stretch-induced reflex. [Subjects and Methods] The present study assessed 20 healthy males using surface electrodes placed on their right soleus muscle. The latency of the tendon reflex (T-reflex) as a stretch-induced reflex was compared with the reflex latency of the WBV-IMR. In addition, simulations were performed at 25, 30, 35, 40, 45, and 50 Hz to determine the stretch frequency of the muscle during WBV. [Results] WBV-IMR latency (40.5 ± 0.8 ms; 95% confidence interval [CI]: 39.0–41.9 ms) was significantly longer than T-reflex latency (34.6 ± 0.5 ms; 95% CI: 33.6–35.5 ms) and the mean difference was 6.2 ms (95% CI of the difference: 4.7–7.7 ms). The simulations performed in the present study demonstrated that the frequency of the stretch signal would be twice the frequency of the vibration. [Conclusion] These findings do not support the notion that WBV-IMR can be explained by reference to a stretch-induced reflex. PMID:26310784

  8. Nonresonant electronic transitions induced by vibrational motion in light-induced potentials.

    PubMed

    Sampedro, Pablo; Chang, Bo Y; Sola, Ignacio R

    2016-09-14

    We find a new mechanism of electronic population inversion using strong femtosecond pulses, where the transfer is mediated by vibrational motion on a light-induced potential. The process can be achieved with a single pulse tuning its frequency to the red of the Franck-Condon window. We show the determinant role that the gradient of the transition dipole moment can play on the dynamics, and extend the method to multiphoton processes with odd number of pulses. As an example, we show how the scheme can be applied to population inversion in Na2.

  9. Noise-Induced Building Vibrations Caused by Concorde and Conventional Aircraft Operations at Dulles and Kennedy International Airports

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Stephens, D. G.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.; Deloach, R.; Cawthorn, J. M.; Finley, T. D.; Lynch, J. W.

    1978-01-01

    Outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded, as were the associated vibration levels in the walls, windows, and floors at building test sites. In addition, limited subjective tests were conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise. Representative peak levels of aircraft noise-induced building vibrations are reported and comparisons are made with structural damage criteria and with vibration levels induced by common domestic events. In addition, results of a pilot study are reported which indicate the human detection threshold for noise-induced floor vibrations.

  10. Vibration-Induced Gas-Liquid Interface Breakup

    NASA Astrophysics Data System (ADS)

    O'Hern, Timothy; Torczynski, John; Romero, Ed; Shelden, Bion

    2010-11-01

    Gas-liquid interfaces can be forced to break up when subjected to vibrations within critical ranges of frequency and amplitude. This breakup mechanism was examined experimentally using deep layers of silicone oils over a range of viscosity and sinusoidal, primarily axial vibration conditions that can produce dramatic disturbances at the gas-liquid free surface. Although small-amplitude vibrations produce standing Faraday waves, large-amplitude vibrations produce liquid jets into the gas, droplets pinching off from the jets, gas cavities in the liquid from droplet impact, and bubble transport below the interface. Experiments used several different silicone oils over a range of pressures and vibration conditions. Computational simulations exhibiting similar behavior will be included in the presentation. Applications include liquid fuel rockets, inertial sensing devices, moving vehicles, mixing processes, and acoustic excitation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. Experimental investigations on flow induced vibration of an externally excited flexible plate

    NASA Astrophysics Data System (ADS)

    Purohit, Ashish; Darpe, Ashish K.; Singh, S. P.

    2016-06-01

    Flow-induced vibration of a harmonically actuated flexible plate in the wake of an upstream bluff body is experimentally investigated. The experiments are performed in an open-ended wind tunnel. A flexible plate trailing a bluff body is under fluid induced excitation due to the flowing fluid. The additional external excitation to the trailing plate is applied using an electro-magnetic exciter. The frequency and amplitude of the external harmonic excitation are selected as variable parameters in the experiments and their effect on the plate vibration and is investigated. To know the nature of acoustic pressure wave generated from the vibrating system, near-field acoustic pressure is also measured. A laser vibrometer, a pressure microphone and a high-speed camera are employed to measure the plate vibration, pressure signal, and instantaneous images of the plate motion respectively. The results obtained indicate that the dynamics of the plate is influenced by both the flow-induced excitation and external harmonic excitation. When frequency of the two excitations is close enough, a large vibration level and a high tonal sound pressure are observed. At higher amplitude of external excitation, the frequency component corresponding to the flow-induced excitation is found to reduce significantly in the frequency spectrum of the vibration signal. It is observed that, for certain range of excitation frequency, the plate vibration first reduces, reaches a minimum value and then increases with increase in the level of external excitation. A fair qualitative agreement of the experimental results with numerical simulation result of the past study has been noted. In addition to the experiments, the role of phase difference between the flow-induced excitation generated from the front obstacle and externally applied harmonic excitation is investigated through numerical simulations. The result obtained reveals that the final steady state vibration of the coupled system is

  12. Field measurements and analyses of environmental vibrations induced by high-speed Maglev.

    PubMed

    Li, Guo-Qiang; Wang, Zhi-Lu; Chen, Suwen; Xu, You-Lin

    2016-10-15

    Maglev, offers competitive journey-times compared to the railway and subway systems in markets for which distance between the stations is 100-1600km owing to its high acceleration and speed; however, such systems may have excessive vibration. Field measurements of Maglev train-induced vibrations were therefore performed on the world's first commercial Maglev line in Shanghai, China. Seven test sections along the line were selected according to the operating conditions, covering speeds from 150 to 430km/h. Acceleration responses of bridge pier and nearby ground were measured in three directions and analyzed in both the time and frequency domain. The effects of Maglev train speed on vibrations of the bridge pier and ground were studied in terms of their peak accelerations. Attenuation of ground vibration was investigated up to 30m from the track centerline. Effects of guideway configuration were also analyzed based on the measurements through two different test sections with same train speed of 300km/h. The results showed that peak accelerations exhibited a strong correlation with both train speed and distance off the track. Guideway configuration had a significant effect on transverse vibration, but a weak impact on vertical and longitudinal vibrations of both bridge pier and ground. Statistics indicated that, contrary to the commonly accepted theory and experience, vertical vibration is not always dominant: transverse and longitudinal vibrations should also be considered, particularly near turns in the track. Moreover, measurements of ground vibration induced by traditional high-speed railway train were carried out with the same testing devices in Bengbu in the Anhui Province. Results showed that the Maglev train generates significantly different vibration signatures as compared to the traditional high-speed train. The results obtained from this paper can provide good insights on the impact of Maglev system on the urban environment and the quality of human life

  13. Infrared-induced conformational isomerization and vibrational relaxation dynamics in melatonin and 5-methoxy-N-acetyl tryptophan methyl amide

    NASA Astrophysics Data System (ADS)

    Dian, Brian C.; Florio, Gina M.; Clarkson, Jasper R.; Longarte, Asier; Zwier, Timothy S.

    2004-05-01

    The conformational isomerization dynamics of melatonin and 5-methoxy N-acetyltryptophan methyl amide (5-methoxy NATMA) have been studied using the methods of IR-UV hole-filling spectroscopy and IR-induced population transfer spectroscopy. Using these techniques, single conformers of melatonin were excited via a well-defined NH stretch fundamental with an IR pump laser. This excess energy was used to drive conformational isomerization. By carrying out the infrared excitation early in a supersonic expansion, the excited molecules were re-cooled into their zero-point levels, partially re-filling the hole created in the ground state population of the excited conformer, and creating gains in population of the other conformers. These changes in population were detected using laser-induced fluorescence downstream in the expansion via an UV probe laser. The isomerization quantum yields for melatonin show some conformation specificity but no hint of vibrational mode specificity. In 5-methoxy NATMA, no isomerization was observed out of the single conformational well populated in the expansion in the absence of the infrared excitation. In order to study the dependence of the isomerization on the cooling rate, the experimental arrangement was modified so that faster cooling conditions could be studied. In this arrangement, the pump and probe lasers were overlapped in space in the high density region of the expansion, and the time dependence of the zero-point level populations of the conformers was probed following selective excitation of a single conformation. The analysis needed to extract isomerization quantum yields from the timing scans was developed and applied to the melatonin timing scans. Comparison between the frequency and time domain isomerization quantum yields under identical experimental conditions produced similar results. Under fast cooling conditions, the product quantum yields were shifted from their values under standard conditions. The results for melatonin

  14. Active Control of Panel Vibrations Induced by a Boundary Layer Flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1998-01-01

    In recent years, active and passive control of sound and vibration in aeroelastic structures have received a great deal of attention due to many potential applications to aerospace and other industries. There exists a great deal of research work done in this area. Recent advances in the control of sound and vibration can be found in the several conference proceedings. In this report we will summarize our research findings supported by the NASA grant NAG-1-1175. The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to study the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. The vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings will be presented in the next three sections. In Section II we shall describe our results on the boundary control of nonlinear panel vibration, with or without flow excitation. Section III is concerned with active control of the vibration and sound radiation from a nonlinear elastic panel. A detailed description of our work on the parametric vibrational control of nonlinear elastic panel will be presented in Section IV. This paper will be submitted to the Journal

  15. Active control of panel vibrations induced by a boundary layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1995-01-01

    The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to consider the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. Although the sound radiation has not been included, the vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings are presented in three sections. In section two we describe results on the boundary control of nonlinear panel vibration, with or without flow excitation. Sections three and four are concerned with some analytical and numerical results in the optimal control of the linear and nonlinear panel vibrations, respectively, excited by the flow pressure fluctuations. Finally, in section five, we draw some conclusions from research findings.

  16. Incorporating a disturbance observer with direct velocity feedback for control of human-induced vibrations

    NASA Astrophysics Data System (ADS)

    Nyawako, Donald; Reynolds, Paul; Hudson, Emma

    2016-04-01

    Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.

  17. Cryotherapy-Induced Persistent Vasoconstriction After Cutaneous Cooling: Hysteresis Between Skin Temperature and Blood Perfusion.

    PubMed

    Khoshnevis, Sepideh; Craik, Natalie K; Matthew Brothers, R; Diller, Kenneth R

    2016-03-01

    The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC-skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy.

  18. Cryotherapy-Induced Persistent Vasoconstriction After Cutaneous Cooling: Hysteresis Between Skin Temperature and Blood Perfusion

    PubMed Central

    Khoshnevis, Sepideh; Craik, Natalie K.; Matthew Brothers, R.; Diller, Kenneth R.

    2016-01-01

    The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC–skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy. PMID:26632263

  19. Interfacial condensation induced by sub-cooled liquid jet

    NASA Astrophysics Data System (ADS)

    Rame, Enrique; Balasubramaniam, R.

    2016-11-01

    When a sub-cooled liquid jet impinges on the free surface between a liquid and its vapor, vapor will condense at a rate dependent on the sub-cooling, the jet strength and fluid properties. In 1966 and during the examination of a different type of condensation flow, Shekriladeze found an approximate result, valid at large condensation rates, that decouples the flow in the liquid phase from that of the vapor, without putting it in the context of a formal asymptotic approximation. In this talk we will develop an asymptotic approximation that contains Shekriladze's result, and extend the calculations to the case when a non-condensable gas is present in the vapor phase.

  20. Vibration-induced jitter control in satellite optical communication

    NASA Astrophysics Data System (ADS)

    Xue, Zheng-yan; Qi, Bo; Ren, Ge

    2013-08-01

    Laser satellite communication has become especially attractive in recent years. However, because the laser beam is very narrow and there is a long distance between satellites, the laser communication channel is very sensitive to vibrations of the optical platform. These vibrations cause optical jitter, leading to the reduction of received signals and bit-error rate degradation. Consequently, optical jitter control with PAT (pointing acquisition and tracking) subsystems is a critical problem in laser satellite communication. To compensate for the platform vibration effectively in realtime, in this paper, an adaptive feedback control technique based on Youla-parameterization is presented, which can adapt to the current disturbance acting on the laser beam by adjusting its parameters in realtime to maintain optimal performance. The main idea is to use the well-known Youla parameterization formula to construct a feedback control scheme with the guaranteed closed loop stability, and the feedback controller is a function of plant coprime factors and a free parameter Q. For adaptive disturbance estimation, the free parameter Q is set to an adaptive finite impulse response (FIR) filter, the coefficients of which are updated by a recursive least-squares (RLS) algorithm in realtime. It is shown in experiment that the adaptive feedback control technique based on Youla-parameterization can reject the optical jitter caused by satellite platform vibration effectively and improve the performance of the system.

  1. Texture-induced vibrations in the forearm during tactile exploration

    PubMed Central

    Delhaye, Benoit; Hayward, Vincent; Lefèvre, Philippe; Thonnard, Jean-Louis

    2012-01-01

    Humans can detect and discriminate between fine variations of surface roughness using active touch. It is hitherto believed that roughness perception is mediated mostly by cutaneous and subcutaneous afferents located in the fingertips. However, recent findings have shown that following abolishment of cutaneous afferences resulting from trauma or pharmacological intervention, the ability of subjects to discriminate between textures roughness was not significantly altered. These findings suggest that the somatosensory system is able to collect textural information from other sources than fingertip afference. It follows that signals resulting of the interaction of a finger with a rough surface must be transmitted to stimulate receptor populations in regions far away from the contact. This transmission was characterized by measuring in the wrist vibrations originating at the fingertip and thus propagating through the finger, the hand and the wrist during active exploration of textured surfaces. The spectral analysis of the vibrations taking place in the forearm tissues revealed regularities that were correlated with the scanned surface and the speed of exploration. In the case of periodic textures, the vibration signal contained a fundamental frequency component corresponding to the finger velocity divided by the spatial period of the stimulus. This regularity was found for a wide range of textural length scales and scanning velocities. For non-periodic textures, the spectrum of the vibration did not contain obvious features that would enable discrimination between the different stimuli. However, for both periodic and non-periodic stimuli, the intensity of the vibrations could be related to the microgeometry of the scanned surfaces. PMID:22783177

  2. Light-transmission aggregometer using a vibration-induced disaggregation mechanism

    NASA Astrophysics Data System (ADS)

    Shin, S.; Jang, J. H.; Park, M. S.; Ku, Y. H.; Suh, J. S.

    2005-01-01

    The vibration-induced disaggregation technique of red blood cell (RBC) aggregates has been applied to design a new light-transmission aggregometer for measurement of aggregation index. For disaggregation of RBCs, the rotational shear flow in the Couette system is replaced with a simple low-frequency vibration in a disposable cavity slide glass. Using a vibration generator, one can disaggregate the RBC aggregates stored in the cavity slide glass. After applying the vibration for a specified duration, RBCs tend to reaggregate and instantaneous light-transmittance intensity is measured over time. A syllectogram (the transmitted light intensity versus time) consists of an initial decrease caused by the vibration-induced disaggregation, immediately followed by an increase in the light intensity due to RBC aggregation. The indices of aggregation are determined from the syllectogram using a curve-fitting program. The noble feature of this design is the vibration-induced disaggregation mechanism, which enables to incorporate disposable element that holds the blood sample.

  3. Do the Amazon and Orinoco freshwater plumes really matter for hurricane-induced ocean surface cooling?

    NASA Astrophysics Data System (ADS)

    Hernandez, O.; Jouanno, J.; Durand, F.

    2016-04-01

    Recent studies suggested that the plume of low-saline waters formed by the discharge of the Amazon and Orinoco rivers could favor Atlantic Tropical Cyclone (TC) intensification by weakening the cool wake and its impact on the hurricane growth potential. The main objective of this study is to quantify the effects of the Amazon-Orinoco river discharges in modulating the amplitude of TC-induced cooling in the western Tropical Atlantic. Our approach is based on the analysis of TC cool wake statistics obtained from an ocean regional numerical simulation with ¼º horizontal resolution over the 1998-2012 period, forced with realistic TC winds. In both model and observations, the amplitude of TC-induced cooling in plume waters (0.3-0.4ºC) is reduced significantly by around 50-60% compared to the cooling in open ocean waters out of the plume (0.6-0.7ºC). A twin simulation without river runoff shows that TC-induced cooling over the plume region (defined from the reference experiment) is almost unchanged (˜0.03ºC) despite strong differences in salinity stratification and the absence of barrier layers. This argues for a weaker than thought cooling inhibition effect of salinity stratification and barrier layers in this region. Indeed, results suggest that haline stratification and barrier layers caused by the river runoff may explain only ˜10% of the cooling difference between plume waters and open ocean waters. Instead, the analysis of the background oceanic conditions suggests that the regional distribution of the thermal stratification is the main factor controlling the amplitude of cooling in the plume region.

  4. Energy harvesting by means of flow-induced vibrations on aerospace vehicles

    NASA Astrophysics Data System (ADS)

    Li, Daochun; Wu, Yining; Da Ronch, Andrea; Xiang, Jinwu

    2016-10-01

    This paper reviews the design, implementation, and demonstration of energy harvesting devices that exploit flow-induced vibrations as the main source of energy. Starting with a presentation of various concepts of energy harvesters that are designed to benefit from a general class of flow-induced vibrations, specific attention is then given at those technologies that may offer, today or in the near future, a potential benefit to extend the operational capabilities and to monitor critical parameters of unmanned aerial vehicles. Various phenomena characterized by flow-induced vibrations are discussed, including limit cycle oscillations of plates and wing sections, vortex-induced and galloping oscillations of bluff bodies, vortex-induced vibrations of downstream structures, and atmospheric turbulence and gusts. It was found that linear or linearized modeling approaches are commonly employed to support the design phase of energy harvesters. As a result, highly nonlinear and coupled phenomena that characterize flow-induced vibrations are neglected in the design process. The Authors encourage a shift in the current design paradigm: considering coupled nonlinear phenomena, and adequate modeling tools to support their analysis, from a design limitation to a design opportunity. Special emphasis is placed on identifying designs and implementations applicable to aircraft configurations. Application fields of flow-induced vibrations-based energy harvesters are discussed including power supply for wireless sensor networks and simultaneous energy harvest and control. A large body of work on energy harvesters is included in this review journal. Whereas most of the references claim direct applications to unmanned aerial vehicles, it is apparent that, in most of the cases presented, the working principles and characteristics of the energy harvesters are incompatible with any aerospace applications. Finally, the challenges that hold back the integration of energy harvesting

  5. Tyre induced vibrations of the car-trailer system

    NASA Astrophysics Data System (ADS)

    Beregi, S.; Takács, D.; Stépán, G.

    2016-02-01

    The lateral and yaw dynamics of the car-trailer combination are analysed by means of a single track model. The equations of motion are derived rigorously by means of the Appell-Gibbs equations for constant longitudinal velocity of the vehicle. The tyres are described with the help of the so-called delayed tyre model, which is based on a brush model with pure rolling contact. The lateral forces and aligning torques of the tyre/road interaction are calculated via the instantaneous lateral deformations in the contact patches. The linear stability analysis of the rectilinear motion is performed via the analytically determined characteristic function of the system. Stability charts are constructed with respect to the vehicle longitudinal velocity and the payload position on the trailer. Self-excited lateral vibrations are detected with different vibration modes at low and at high longitudinal speeds of the vehicle. The effects of the tyre parameters are also investigated.

  6. Concorde noise-induced building vibrations John F. Kennedy International Airport

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Deloach, R.; Stephens, D. G.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.

    1978-01-01

    The outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded at six home sites along with the associated vibration levels in the walls, windows, and floors of these test homes. Limited subjective tests conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise showed that both vibration and rattle were detected subjectively in several houses for some operations of both the Concorde and subsonic aircraft. Preliminary results indicate that the relationship between window vibration and aircraft noise is: (1) linear, with vibration levels being accurately predicted from OASPL levels measured near the window; (2) consistent from flyover to flyover for a given aircraft type under approach conditions; (3) no different for Concorde than for other conventional jet transports (in the case of window vibrations induced under approach power conditions); and (4) relatively high levels of window vibration measured during Concorde operations are due more to higher OASPL levels than to unique Concorde source characteristics.

  7. Investigation into piston-slap-induced vibration for engine condition simulation and monitoring

    NASA Astrophysics Data System (ADS)

    Geng, Z.; Chen, J.

    2005-04-01

    Piston slap is a common impact phenomenon existing in the reciprocating engine. It is also a major cause of the complex transient vibration response related to the impact excitation inside the engine. In order to correlate the piston-slap impact with the slap-induced vibration and consequently find out an effective approach for the engine dynamic behaviour simulation and working condition monitoring, an in-depth investigation from theoretical modelling to experimental verification is made in this paper. Firstly, the piston-slap phenomenon inside the reciprocating engine is briefly discussed from the viewpoint of engine mechanics. Based upon this, a nonlinear model is developed to simulate the slap-induced vibration response. Using numerical integration procedure, the slap-induced vibration response and its correlation with the inner-cylinder piston-slap impact are reasonably evaluated. Guided by the simulating results and, by introducing a fast wavelet-packet decomposition and reconstruction algorithm, a specially designed experiment is made to practically measure and extract the slap-induced impact message inside the 6190Z LC diesel engine. Comparison between the simulation and practically measured and reconstructed engine vibration signals verifies the effectiveness and practicality of this approach for more detailed academic research and engineering application.

  8. Evaporative cooling over the Tibetan Plateau induced by vegetation growth.

    PubMed

    Shen, Miaogen; Piao, Shilong; Jeong, Su-Jong; Zhou, Liming; Zeng, Zhenzhong; Ciais, Philippe; Chen, Deliang; Huang, Mengtian; Jin, Chun-Sil; Li, Laurent Z X; Li, Yue; Myneni, Ranga B; Yang, Kun; Zhang, Gengxin; Zhang, Yangjian; Yao, Tandong

    2015-07-28

    In the Arctic, climate warming enhances vegetation activity by extending the length of the growing season and intensifying maximum rates of productivity. In turn, increased vegetation productivity reduces albedo, which causes a positive feedback on temperature. Over the Tibetan Plateau (TP), regional vegetation greening has also been observed in response to recent warming. Here, we show that in contrast to arctic regions, increased growing season vegetation activity over the TP may have attenuated surface warming. This negative feedback on growing season vegetation temperature is attributed to enhanced evapotranspiration (ET). The extra energy available at the surface, which results from lower albedo, is efficiently dissipated by evaporative cooling. The net effect is a decrease in daily maximum temperature and the diurnal temperature range, which is supported by statistical analyses of in situ observations and by decomposition of the surface energy budget. A daytime cooling effect from increased vegetation activity is also modeled from a set of regional weather research and forecasting (WRF) mesoscale model simulations, but with a magnitude smaller than observed, likely because the WRF model simulates a weaker ET enhancement. Our results suggest that actions to restore native grasslands in degraded areas, roughly one-third of the plateau, will both facilitate a sustainable ecological development in this region and have local climate cobenefits. More accurate simulations of the biophysical coupling between the land surface and the atmosphere are needed to help understand regional climate change over the TP, and possible larger scale feedbacks between climate in the TP and the Asian monsoon system.

  9. Experimental investigation of the flow-induced vibration of hydrofoils in cavitating flows

    NASA Astrophysics Data System (ADS)

    Wang, Guoyu; Wu, Qin; Huang, Biao; Gao, Yuan

    2015-12-01

    The objective of this paper is to investigate the correlation between fluid induced vibration and unsteady cavitation behaviours. Experimental results are presented for a modified NACA66 hydrofoil, which is fixed at α=8°. The high-speed camera is synchronized with a single point Laser Doppler Vibrometer to analyze the transient cavitating flow structures and the corresponding structural vibration characteristics. The results showed that, with the decreasing of the cavitation number, the cavitating flows in a water tunnel display several types of cavitation patterns, such as incipient cavitation, sheet cavitation and cloud cavitation. The cavity shedding frequency reduces with the decrease of the cavitation number. As for the cloud cavitation regime, the trend of the vibration velocity goes up with the growth of the attached cavity, accompanied with small amplitude fluctuations. Then the collapse and shedding of the large-scale cloud cavities leads to substantial increase of the vibration velocity fluctuations.

  10. Tactile perception of skin and skin cream by friction induced vibrations.

    PubMed

    Ding, Shuyang; Bhushan, Bharat

    2016-11-01

    Skin cream smooths, softens, and moistens skin by altering surface roughness and tribological properties of skin. Sliding generates vibrations that activate mechanoreceptors located in skin. The brain interprets tactile information to identify skin feel. Understanding the tactile sensing mechanisms of skin with and without cream treatment is important to numerous applications including cosmetics, textiles, and robotics sensors. In this study, frequency spectra of friction force and friction induced vibration signals were carried out to investigate tactile perception by an artificial finger sliding on skin. The influence of normal load, velocity, and cream treatment time were studied. Coherence between friction force and vibration signals were found. The amplitude of vibration decreased after cream treatment, leading to smoother perception. Increasing normal load or velocity between contacting surfaces generated a smoother perception with cream treatment, but rougher perception without treatment. As cream treatment time increases, skin becomes smoother. The related mechanisms are discussed.

  11. Laser induced vibration-rotation fluorescence and infrared forbidden transitions in acetylene

    NASA Astrophysics Data System (ADS)

    Jungner, Peter; Halonen, Lauri

    1997-08-01

    Laser induced fluorescence method has been used to study highly excited vibrational overtones in acetylene. A sample cell has been placed inside a Ti:Sapphire ring laser cavity and the total fluorescence collected by a parabolic mirror has been dispersed by a high-resolution FTIR spectrometer. The laser has pumped specific rotational states of the CH stretching vibrational overtone state ν1+3ν3(∑u+) and transitions to the symmetric state ν1+2ν3(∑g+) have been observed. The observations allow determining both the vibrational term value and the rotational constant of the symmetric state, which is not accessible from the ground vibrational state by one-photon absorption. The parameters obtained are in excellent agreement with simple local mode predictions.

  12. Proprioceptive control of wrist movements in Parkinson's disease. Reduced muscle vibration-induced errors.

    PubMed

    Rickards, C; Cody, F W

    1997-06-01

    The effects upon the trajectories of practised slow (approximately 9 degrees/s) voluntary wrist-extension movements of applying vibration to the tendon of an antagonist muscle (flexor carpi radialis) during the course of the movement have been studied in patients with idiopathic Parkinson's disease and age-matched healthy individuals. In both patient and control groups, flexor vibration elicited undershooting of wrist-extension movements. Wrist extensor and flexor surface EMG recordings indicated that, in patients and controls, such undershooting resulted principally from sustained reductions in extensor (prime mover) activity. Small vibration reflexes were commonly elicited in the wrist flexors which, in both Parkinson's disease and healthy subjects, were usually otherwise virtually quiescent during these slow extension movements. The amplitudes of such vibration reflexes did not differ systematically between patient and control groups and appeared inadequate to have exerted an appreciable braking action upon the extension trajectories. However, the extent of vibration-induced undershooting was, on average, significantly less in the Parkinson's disease group. In a subgroup of patients with asymmetrical parkinsonism the effects of antagonist vibration upon wrist movements of the more and less affected limb were compared. The degree of vibration-induced undershooting was significantly smaller on the more affected side. This finding suggests that disturbed proprioceptive guidance of voluntary movements in Parkinson's disease is related to the severity of clinical motor deficits. A small number Parkinson's disease patients were studied 'ON' and 'OFF' their routine anti-parkinsonian medication. A non-significant tendency was found for vibration-induced errors to be less marked in the 'OFF' state. In a separate series of experiments, under isometric conditions, vibration-induced EMG changes were recorded whilst subjects attempted to maintain a steady (15% maximum

  13. Measurement of ground and nearby building vibration and noise induced by trains in a metro depot.

    PubMed

    Zou, Chao; Wang, Yimin; Wang, Peng; Guo, Jixing

    2015-12-01

    Metro depots are where subway trains are parked and where maintenance is carried out. They usually occupy the largest ground areas in metro projects. Due to land utilization problems, Chinese cities have begun to develop over-track buildings above metro depots for people's life and work. The frequently moving trains, when going into and out of metro depots, can cause excessive vibration and noise to over-track buildings and adversely affect the living quality of the building occupants. Considering the current need of reliable experimental data for the construction of metro depots, field measurements of vibration and noise on the ground and inside a nearby 3-story building subjected to moving subway trains were conducted in a metro depot at Guangzhou, China. The amplitudes and frequency contents of velocity levels were quantified and compared. The composite A-weighted equivalent sound levels and maximum sound levels were captured. The predicted models for vibration and noise of metro depot were proposed based on existing models and verified. It was found that the vertical vibrations were significantly greater than the horizontal vibrations on the ground and inside the building near the testing line. While at the throat area, the horizontal vibrations near the curved track were remarkably greater than the vertical vibrations. The attenuation of the vibrations with frequencies above 50 Hz was larger than the ones below 50 Hz, and the frequencies of vibration transmitting to adjacent buildings were mainly within 10-50 Hz. The largest equivalent sound level generated in the throat area was smaller than the testing line one, but the instantaneous maximum sound level induced by wheels squeal, contact between wheels and rail joints as well as turnout was close to or even greater than the testing line one. The predicted models gave a first estimation for design and assessment of newly built metro depots.

  14. Whole-body vibration induces pain and lumbar spinal inflammation responses in the rat that vary with the vibration profile.

    PubMed

    Zeeman, Martha E; Kartha, Sonia; Winkelstein, Beth A

    2016-08-01

    Whole-body vibration (WBV) is linked epidemiologically to neck and back pain in humans, and to forepaw mechanical allodynia and cervical neuroinflammation in a rodent model of WBV, but the response of the low back and lumbar spine to WBV is unknown. A rat model of WBV was used to determine the effect of different WBV exposures on hind paw behavioral sensitivity and neuroinflammation in the lumbar spinal cord. Rats were exposed to 30 min of WBV at either 8 or 15 Hz on days 0 and 7, with the lumbar spinal cord assayed using immunohistochemistry at day 14. Behavioral sensitivity was measured using mechanical stimulation of the hind paws to determine the onset, persistence, and/or recovery of allodynia. Both WBV exposures induce mechanical allodynia 1 day following WBV, but only the 8 Hz WBV induces a sustained decrease in the withdrawal threshold through day 14. Similarly, increased activation of microglia, macrophages, and astrocytes in the superficial dorsal horn of the lumbar spinal cord is only evident after the painful 8 Hz WBV. Moreover, extracellular signal-regulated kinase (ERK)-phosphorylation is most robust in neurons and astrocytes of the dorsal horn, with the most ERK phosphorylation occurring in the 8 Hz group. These findings indicate that a WBV exposure that induces persistent pain also induces a host of neuroimmune cellular activation responses that are also sustained. This work indicates there is an injury-dependent response that is based on the vibration parameters, providing a potentially useful platform for studying mechanisms of painful spinal injuries. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1439-1446, 2016.

  15. Evaporative cooling over the Tibetan Plateau induced by vegetation growth

    PubMed Central

    Shen, Miaogen; Piao, Shilong; Jeong, Su-Jong; Zhou, Liming; Zeng, Zhenzhong; Ciais, Philippe; Chen, Deliang; Huang, Mengtian; Jin, Chun-Sil; Li, Laurent Z. X.; Li, Yue; Myneni, Ranga B.; Yang, Kun; Zhang, Gengxin; Zhang, Yangjian; Yao, Tandong

    2015-01-01

    In the Arctic, climate warming enhances vegetation activity by extending the length of the growing season and intensifying maximum rates of productivity. In turn, increased vegetation productivity reduces albedo, which causes a positive feedback on temperature. Over the Tibetan Plateau (TP), regional vegetation greening has also been observed in response to recent warming. Here, we show that in contrast to arctic regions, increased growing season vegetation activity over the TP may have attenuated surface warming. This negative feedback on growing season vegetation temperature is attributed to enhanced evapotranspiration (ET). The extra energy available at the surface, which results from lower albedo, is efficiently dissipated by evaporative cooling. The net effect is a decrease in daily maximum temperature and the diurnal temperature range, which is supported by statistical analyses of in situ observations and by decomposition of the surface energy budget. A daytime cooling effect from increased vegetation activity is also modeled from a set of regional weather research and forecasting (WRF) mesoscale model simulations, but with a magnitude smaller than observed, likely because the WRF model simulates a weaker ET enhancement. Our results suggest that actions to restore native grasslands in degraded areas, roughly one-third of the plateau, will both facilitate a sustainable ecological development in this region and have local climate cobenefits. More accurate simulations of the biophysical coupling between the land surface and the atmosphere are needed to help understand regional climate change over the TP, and possible larger scale feedbacks between climate in the TP and the Asian monsoon system. PMID:26170316

  16. Vibration-induced elastic deformation of Fabry-Perot cavities

    SciTech Connect

    Chen Lisheng; Hall, John L.; Ye Jun; Yang Tao; Zang Erjun; Li Tianchu

    2006-11-15

    We perform a detailed numerical analysis of Fabry-Perot cavities used for state-of-the-art laser stabilization. Elastic deformation of Fabry-Perot cavities with various shapes and mounting methods is quantitatively analyzed using finite-element analysis. We show that with a suitable choice of mounting schemes it is feasible to minimize the susceptibility of the resonator length to vibrational perturbations. This investigation offers detailed information on stable optical cavities that may benefit the development of ultrastable optical local oscillators in optical atomic clocks and precision measurements probing the fundamental laws of physics.

  17. Electronic Aharonov-Bohm effect induced by quantum vibrations.

    PubMed

    Shekhter, R I; Gorelik, L Y; Glazman, L I; Jonson, M

    2006-10-13

    Mechanical displacements of a nanoelectromechanical system shift the electron trajectories and hence perturb phase coherent charge transport through the device. We show theoretically that in the presence of a magnetic field such quantum-coherent displacements may give rise to an Aharonov-Bohm-type of effect. In particular, we demonstrate that quantum vibrations of a suspended carbon nanotube result in a positive nanotube magnetoresistance, which decreases slowly with the increase of temperature. This effect may enable one to detect quantum displacement fluctuations of a nanomechanical device.

  18. Building vibrations induced by noise from rotorcraft and propeller aircraft flyovers

    NASA Technical Reports Server (NTRS)

    Shepherd, Kevin P.; Hubbard, Harvey H.

    1992-01-01

    Noise and building vibrations were measured for a series of helicopter and propeller-driven aircraft flyovers at WFF during May 1978. The building response data are compared with similar data acquired earlier at sites near Dulles and Kennedy Airports for operation of commercial jet transports, including the Concorde supersonic transport. Results show that noise-induced vibration levels in windows and walls are directly proportional to sound pressure level and that for a given noise level, the acceleration levels induced by a helicopter or a propeller-driven aircraft flyover cannot be distinguished from the acceleration levels induced by a commercial jet transport flyover. Noise-induced building acceleration levels were found to be lower than those levels which might be expected to cause structural damage and were also lower than some acceleration levels induced by such common domestic events as closing windows and doors.

  19. Vibration serviceability of footbridges under human-induced excitation: a literature review

    NASA Astrophysics Data System (ADS)

    Živanović, S.; Pavic, A.; Reynolds, P.

    2005-01-01

    Increasing strength of new structural materials and longer spans of new footbridges, accompanied with aesthetic requirements for greater slenderness, are resulting in more lively footbridge structures. In the past few years this issue attracted great public attention. The excessive lateral sway motion caused by crowd walking across the infamous Millennium Bridge in London is the prime example of the vibration serviceability problem of footbridges. In principle, consideration of footbridge vibration serviceability requires a characterisation of the vibration source, path and receiver. This paper is the most comprehensive review published to date of about 200 references which deal with these three key issues. The literature survey identified humans as the most important source of vibration for footbridges. However, modelling of the crowd-induced dynamic force is not clearly defined yet, despite some serious attempts to tackle this issue in the last few years. The vibration path is the mass, damping and stiffness of the footbridge. Of these, damping is the most uncertain but extremely important parameter as the resonant behaviour tends to govern vibration serviceability of footbridges. A typical receiver of footbridge vibrations is a pedestrian who is quite often the source of vibrations as well. Many scales for rating the human perception of vibrations have been found in the published literature. However, few are applicable to footbridges because a receiver is not stationary but is actually moving across the vibrating structure. During footbridge vibration, especially under crowd load, it seems that some form of human-structure interaction occurs. The problem of influence of walking people on footbridge vibration properties, such as the natural frequency and damping is not well understood, let alone quantified. Finally, there is not a single national or international design guidance which covers all aspects of the problem comprehensively and some form of their

  20. Dissociative ionization of liquid water induced by vibrational overtone excitation

    SciTech Connect

    Natzle, W.C.

    1983-03-01

    Photochemistry of vibrationally activated ground electronic state liquid water to produce H/sup +/ and OH/sup -/ ions has been initiated by pulsed, single-photon excitation of overtone and combination transitions. Transient conductivity measurements were used to determine quantum yields as a function of photon energy, isotopic composition, and temperature. The equilibrium relaxation rate following perturbation by the vibrationally activated reaction was also measured as a function of temperature reaction and isotopic composition. In H/sub 2/O, the quantum yield at 283 +- 1 K varies from 2 x 10/sup -9/ to 4 x 10/sup -5/ for wave numbers between 7605 and 18140 cm/sup -1/. In D/sub 2/O, the dependence of quantum yield on wavelength has the same qualitative shape as for H/sub 2/O, but is shifted to lower quantum yields. The position of a minimum in the quantum yield versus hydrogen mole fraction curve is consistent with a lower quantum yield for excitation of HOD in D/sub 2/O than for excitation of D/sub 2/O. The ionic recombination distance of 5.8 +- 0.5 A is constant within experimental error with temperature in H/sub 2/O and with isotopic composition at 25 +- 1/sup 0/C.

  1. An Experimental Investigation of Vibration-Induced Droplet Atomization.

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1998-11-01

    The atomization process in a mm-scale liquid droplet placed on a vibrating membrane is investigated experimentally. When the wavelength of the Faraday surface waves is smaller than the characteristic dimension of the droplet, the waves grow in amplitude as the excitation amplitude increases and ultimately begin to eject small secondary droplets from the wave crests. The high membrane acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequencies (nominally 1000-6000 Hz). The evolution and rate of the droplet-ejection process depend on a coupled system dynamic between the liquid droplet and the vibrating membrane. Depending on the excitation frequency and amplitude, various types of droplet-ejection processes can occur. For example, when step forcing (with prescribed frequency and amplitude) is applied, rapid atomization occurs. This event is triggered along the circumference of the droplet near the contact line by a strong azimuthal instability. In the present experiments, the droplet-ejection process and the resulting spray characteristics are investigated using high-speed video and two-frame particle tracking velocimetry.

  2. A distributed fiber vibration sensor utilizing dispersion induced walk-off effect in a unidirectional Mach-Zehnder interferometer.

    PubMed

    Chen, Qingming; Jin, Chao; Bao, Yuan; Li, Zhaohui; Li, Jianping; Lu, Chao; Yang, Liang; Li, Guifang

    2014-02-10

    We propose and experimentally demonstrate a novel ultra-long range and sensitive distributed fiber vibration sensor. Only one unidirectional Mach-Zehnder interferometer (MZI) is employed in this scheme as the sensing element. In this sensor structure, we utilize chromatic dispersion-induced walk-off effect between the vibration signals sensed by two distributed feedback (DFB) lasers at different wavelengths to locate the vibration position. Vibration signals with frequencies up to 9 MHz can be detected and the spatial resolution of 31 m is achieved over 320 km of the standard single mode fiber. Monitoring multiple vibration sources can also be realized using this scheme.

  3. Light-induced vibration characteristics of free-standing carbon nanotube films fabricated by vacuum filtration

    SciTech Connect

    Li, Junying; Zhu, Yong Wang, Ning; Zhang, Jie; Wang, Xin

    2014-07-14

    In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 μm, 20.90 μm, 30.19 μm, and 39.98 μm respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ∼ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.

  4. Physical and numerical investigation of the flow induced vibration of the hydrofoil

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Wang, G. Y.; Huang, B.

    2016-11-01

    The objective of this paper is to investigate the flow induced vibration of a flexible hydrofoil in cavitating flows via combined experimental and numerical studies. The experiments are presented for the modified NACA66 hydrofoil made of POM Polyacetate in the closed-loop cavitation tunnel at Beijing Institute of Technology. The high-speed camera and the single point Laser Doppler Vibrometer are applied to analyze the transient flow structures and the corresponding structural vibration characteristics. The hybrid coupled fluid structure interaction model is conducted to couple the incompressible and unsteady Reynolds Averaged Navier-Stokes solver with a simplified two-degree-of-freedom structural model. The k-ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model are introduced to the present simulations. The results showed that with the decreasing of the cavitation number, the cavitating flows display incipient cavitation, sheet cavitation, cloud cavitation and supercavitation. The vibration magnitude increases dramatically for the cloud cavitation and decline for the supercavitation. The cloud cavitation development strongly affects the vibration response, which is corresponding to the periodically developing and shedding of the large-scale cloud cavity. The main frequency of the vibration amplitude is accordance with the cavity shedding frequency and other two frequencies of the vibration amplitude are corresponding to the natural frequencies of the bending and twisting modes.

  5. Poiseuille flow-induced vibrations of two tandem circular cylinders with different mass ratios

    NASA Astrophysics Data System (ADS)

    Jiang, Ren-Jie; Lin, Jian-Zhong

    2016-06-01

    Flow-induced vibrations of two tandem circular cylinders with different mass ratios confined between two parallel walls are numerically studied via a lattice Boltzmann method. With fixed Reynolds number Re = 100 and blockage ratio β = 1/4, the effects of mass ratio m* = [0.0625, 16] and streamwise separation between two cylinders S/D = [1.125, 10] on the cylinder motions and vortex wake modes are investigated. A variety of distinct cylinder motion regimes involving the symmetric periodic vibration, biased quasi-periodic vibration, beating vibration, and steady regimes, with the corresponding wake structures, e.g., two rows of alternately rotating vortices, a single row of same-sign vortices, and steady wake, are observed. For each current case, the cylinder motion type is exclusive and in the binary oscillation regime, both cylinders always vibrate at a common primary frequency. The lighter cylinder usually oscillates at a larger amplitude than the heavier one, while the heavier cylinder undergoes larger lift force than the lighter one. The lift force and cylinder displacement always behave as an out-of-phase state. In the gap-interference region, large-amplitude oscillations could be produced extensively and in the wake-interference region, the cylinder motions and fluid flows are mainly dependent on the upstream cylinder. When the separation is large enough, both cylinders behave as two isolated ones. The mechanisms for the excitations of cylinder vibrations have also been analysed.

  6. Investigation into the vibration of metro bogies induced by rail corrugation

    NASA Astrophysics Data System (ADS)

    Ling, Liang; Li, Wei; Foo, Elbert; Wu, Lei; Wen, Zefeng; Jin, Xuesong

    2017-01-01

    The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.

  7. A Numerical Study on the Screening of Blast-Induced Waves for Reducing Ground Vibration

    NASA Astrophysics Data System (ADS)

    Park, Dohyun; Jeon, Byungkyu; Jeon, Seokwon

    2009-06-01

    Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock, but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact, and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration. The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration, namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes, distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method of blast-induced waves was considerably effective under certain design conditions. The design details for field application have also been proposed.

  8. Effect of angle on flow-induced vibrations of pinniped vibrissae.

    PubMed

    Murphy, Christin T; Eberhardt, William C; Calhoun, Benton H; Mann, Kenneth A; Mann, David A

    2013-01-01

    Two types of vibrissal surface structures, undulated and smooth, exist among pinnipeds. Most Phocidae have vibrissae with undulated surfaces, while Otariidae, Odobenidae, and a few phocid species possess vibrissae with smooth surfaces. Variations in cross-sectional profile and orientation of the vibrissae also exist between pinniped species. These factors may influence the way that the vibrissae behave when exposed to water flow. This study investigated the effect that vibrissal surface structure and orientation have on flow-induced vibrations of pinniped vibrissae. Laser vibrometry was used to record vibrations along the whisker shaft from the undulated vibrissae of harbor seals (Phoca vitulina) and northern elephant seals (Mirounga angustirostris) and the smooth vibrissae of California sea lions (Zalophus californianus). Vibrations along the whisker shaft were measured in a flume tank, at three orientations (0°, 45°, 90°) to the water flow. The results show that vibration frequency and velocity ranges were similar for both undulated and smooth vibrissae. Angle of orientation, rather than surface structure, had the greatest effect on flow-induced vibrations. Vibration velocity was up to 60 times higher when the wide, flat aspect of the whisker faced into the flow (90°), compared to when the thin edge faced into the flow (0°). Vibration frequency was also dependent on angle of orientation. Peak frequencies were measured up to 270 Hz and were highest at the 0° orientation for all whiskers. Furthermore, CT scanning was used to quantify the three-dimensional structure of pinniped vibrissae that may influence flow interactions. The CT data provide evidence that all vibrissae are flattened in cross-section to some extent and that differences exist in the orientation of this profile with respect to the major curvature of the hair shaft. These data support the hypothesis that a compressed cross-sectional profile may play a key role in reducing self-noise of the

  9. Analysis & Test of Reaction Wheel Induced Micro-Vibrations

    NASA Astrophysics Data System (ADS)

    Runte, Torben; Brito, Miguel; Bourne, Duncan M.; Mariani, Marco

    2014-06-01

    Microvibrations are a major disturbance source of the pointing stability for high-precision Spacecraft. These undesirable mechanical vibrations are generated by active mechanisms and transferred via the Spacecraft structure.Throughout OHB System's design of Spacecraft platforms for Spacecraft missions with high precision pointing performance, Reaction Wheels (RWs) have been identified as the most dominant source of microvibrations in Spacecraft platforms. The RW perturbations consist of numerous harmonic components whose frequencies and amplitudes depend on the wheel speed and the ball bearing characteristics of each unit. This paper focuses on the analysis methodology used to estimate the disturbance caused by these units, its transmission via the Spacecraft structure and its verification by measurement.

  10. Regarding "A new method for predicting nonlinear structural vibrations induced by ground impact loading" [Journal of Sound and Vibration, 331/9 (2012) 2129-2140

    NASA Astrophysics Data System (ADS)

    Cartmell, Matthew P.

    2016-09-01

    The Editor wishes to make the reader aware that the paper "A new method for predicting nonlinear structural vibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140, did not contain a direct citation of the fundamental and original work in this field by Dr. Mark Svinkin. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.

  11. Vibrational relaxation and dissociative recombination of H{sub 2}{sup +} induced by slow electrons

    SciTech Connect

    Ngassam, V.; Motapon, O.; Florescu, A.; Pichl, L.; Schneider, I. F.; Suzor-Weiner, A.

    2003-09-01

    We present calculations of cross sections and rate coefficients for the dissociative recombination of H{sub 2}{sup +} ions initially in v=0-6 vibrational levels, together with rate coefficients for the competing electron-induced vibrational deexcitation. We used the multichannel quantum defect theory with a second-order treatment of the K matrix, and show that electronic interactions dominate not only the dissociative recombination but also the vibrational relaxation induced by slow electrons. Most of our rate coefficients for dissociative recombination are in good agreement with the measurements at the TSR storage ring [S. Krohn et al., Phys. Rev. A 62, 032713 (2000)]. On the contrary, our rates for vibrational deexcitation, close to former results obtained by R-matrix calculations [B. K. Sarpal and J. Tennyson, Mon. Not. R. Astron. Soc. 263, 909 (1993)], are smaller by up to one order of magnitude than the experimental values which are deduced from the time evolution of the vibrational populations, measured by the Coulomb explosion imaging method.

  12. Concorde noise-induced building vibrations for Sully Plantation, Chantilly, Virginia

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Scholl, H. F.; Stephens, D. G.; Holliday, B. G.; Deloach, R.; Holmes, H. K.; Lewis, R. B.; Lynch, J. W.

    1976-01-01

    A study to assess the noise-induced building vibrations associated with Concorde operations is presented. The approach is to record the levels of induced vibrations and associated indoor/outdoor noise levels in selected homes, historic and other buildings near Dulles and Kennedy International Airports. Presented is a small, representative sample of data recorded at Sully Plantation, Chantilly, Virginia during the period of May 20 through May 28, 1976. Recorded data provide relationships between the vibration levels of walls, floors, windows, and the noise associated with Concorde operations (2 landings and 3 takeoffs), other aircraft, nonaircraft sources, and normal household activities. Results suggest that building vibrations resulting from aircraft operations were proportional to the overall sound pressure levels and relatively insensitive to spectral differences associated with the different types of aircraft. Furthermore, the maximum levels of vibratory response resulting from Concorde operations were higher than those associated with conventional aircraft. The vibrations of nonaircraft events were observed in some cases to exceed the levels resulting from aircraft operations. These nonaircraft events are currently being analyzed in greater detail.

  13. Cryo Cooler Induced Micro-Vibration Disturbances to the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Jedrich, Nick; Zimbelman, Darrell; Turczyn, Mark; Sills, Joel; Voorhees, Carl; Clapp, Brian; Brumfield, Mark (Technical Monitor)

    2002-01-01

    This paper presents an overview of the Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cryo Cooler (MCC) system, a description of the micro-vibration characterization testing performed, and a discussion of the simulated performance. The NCC is a reverse Brayton cycle system that employs micro turbo-machinery to provide cooling to the NICMOS instrument. Extensive testing was conducted to quantify the expected on-orbit disturbances caused by the micro turbo-machinery and provide input to a flexible-body dynamic simulation to demonstrate compliance with the HST 7 milli-arcsecond root mean square jitter requirement.

  14. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

  15. Collision--induced absorption in dense atmospheres of cool stars

    SciTech Connect

    Borysow, Aleksandra; Joergensen, Uffe Graae

    1999-04-01

    In the atmosphere of the Sun the major interaction between the matter and the radiation is through light absorption by ions (predominantly the negative ion of hydrogen atoms), neutral atoms and a small amount of polar molecules. The majority of stars in the universe are, however, cooler and denser than our Sun, and for a large fraction of these, the above absorption processes are very weak. Here, collision-induced absorption (CIA) becomes the dominant opacity source. The radiation is absorbed during very short mutual passages ('collisions') of two non-polar molecules (and/or atoms), while their electric charge distributions are temporarily distorted which gives rise to a transient dipole moment. We present here a review of the present-day knowledge about the impact of collision-induced absorption processes on the structure and the spectrum of such stars.

  16. Impact of Typhoon-induced sea surface cooling on the track of next Typhoon

    NASA Astrophysics Data System (ADS)

    Ando, Y.; Horiguchi, M.; Kodera, K.; Tachibana, Y.; Yamazaki, K.

    2015-12-01

    Typhoons (TCs) MATMO, HALONG, and NAKRI (2014), which caused Japan catastrophic disaster, landed the western part of Japan. The TCs came to Japan one after another during late July to early August 2014. The tracks of these TCs were similar, i.e., the TCs followed the western edge of the subtropical northwestern Pacific high (SNPH). However, the tracks gradually reached to Japan, which were associated with weakening the westward expansion of the SNPH. It was found that the changes in westward expansion of the SNPH were associated with TC-induced sea surface cooling of previous Typhoon. It has previously been reported that TC-induced sea surface cooling is mainly caused by Ekman upwelling and vertical turbulent mixing. The TCs MATMO, HALONG, and NAKRI passed around the Philippines, and induced sea surface cooling of this area. The sea surface temperatures of this area are important for Pacific-Japan pattern, which was associated with the westward expansion of the SNPH. Consequently, previous Typhoon induced sea surface cooling around the Philippines, which weakening the westward expansion of the SNPH. Then, the tracks of next Typhoon were changed, and gradually reached to Japan.

  17. Factors influencing the effectiveness of scalp cooling in the prevention of chemotherapy-induced alopecia.

    PubMed

    Komen, Manon M C; Smorenburg, Carolien H; van den Hurk, Corina J G; Nortier, Johan W R

    2013-01-01

    The success of scalp cooling in preventing or reducing chemotherapy-induced alopecia (CIA) is highly variable between patients and chemotherapy regimens. The outcome of hair preservation is often unpredictable and depends on various factors. Methods. We performed a structured search of literature published from 1970 to February 2012 for articles that reported on factors influencing the effectiveness of scalp cooling to prevent CIA in patients with cancer. Results. The literature search identified 192 reports, of which 32 studies were considered relevant. Randomized studies on scalp cooling are scarce and there is little information on the determinants of the result. The effectiveness of scalp cooling for hair preservation depends on dose and type of chemotherapy, with less favorable results at higher doses. Temperature seems to be an important determinant. Various studies suggest that a subcutaneous scalp temperature less than 22 °C is required for hair preservation. Conclusions. The effectiveness of scalp cooling for hair preservation varies by chemotherapy type and dose, and probably by the degree and duration of cooling.

  18. Factors Influencing the Effectiveness of Scalp Cooling in the Prevention of Chemotherapy-Induced Alopecia

    PubMed Central

    Smorenburg, Carolien H.; van den Hurk, Corina J.G.; Nortier, Johan W.R.

    2013-01-01

    Introduction. The success of scalp cooling in preventing or reducing chemotherapy-induced alopecia (CIA) is highly variable between patients and chemotherapy regimens. The outcome of hair preservation is often unpredictable and depends on various factors. Methods. We performed a structured search of literature published from 1970 to February 2012 for articles that reported on factors influencing the effectiveness of scalp cooling to prevent CIA in patients with cancer. Results. The literature search identified 192 reports, of which 32 studies were considered relevant. Randomized studies on scalp cooling are scarce and there is little information on the determinants of the result. The effectiveness of scalp cooling for hair preservation depends on dose and type of chemotherapy, with less favorable results at higher doses. Temperature seems to be an important determinant. Various studies suggest that a subcutaneous scalp temperature less than 22°C is required for hair preservation. Conclusions. The effectiveness of scalp cooling for hair preservation varies by chemotherapy type and dose, and probably by the degree and duration of cooling. PMID:23650021

  19. [Vibration-induced Raynaud phenomenon caused by an electric hedge trimmer].

    PubMed

    Kákosy, T; Martin, J; Zentai, N; Székely, A

    1995-08-06

    Authors observed Raynaud's phenomenon verified by cold-provocation test and measuring finger systolic blood pressure on a man working with bush cutter equipment installed on a tractor. Vibration measurements showed acceleration superior to maximal allowable level. Other causes of a secondary Raynaud's phenomenon were excluded by means of detailed internal examination. On the ground of the exposure data and lack of other ethiological factors the authors think that the patient had vibration-induced Raynaud's phenomenon. For prevention they proposed the diminishing of the daily exposure time and periodical medical examinations. They want to draw the attention for this sort of exposure.

  20. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    NASA Astrophysics Data System (ADS)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  1. Irrigation Induced Surface Cooling in the Context of Modern and Increased Greenhouse Gas Forcing

    NASA Technical Reports Server (NTRS)

    Cook, Benjamin I.; Puma, Michael J.; Krakauer, Nir Y.

    2010-01-01

    There is evidence that expected warming trends from increased greenhouse gas (GHG) forcing have been locally masked by irrigation induced cooling, and it is uncertain how the magnitude of this irrigation masking effect will change in the future. Using an irrigation dataset integrated into a global general circulation model, we investigate the equilibrium magnitude of irrigation induced cooling under modern (Year 2000) and increased (A1B Scenario, Year 2050) GHG forcing, using modern irrigation rates in both scenarios. For the modern scenario, the cooling is largest over North America, India, the Middle East, and East Asia. Under increased GHG forcing, this cooling effect largely disappears over North America, remains relatively unchanged over India, and intensifies over parts of China and the Middle East. For North America, irrigation significantly increases precipitation under modern GHG forcing; this precipitation enhancement largely disappears under A1B forcing, reducing total latent heat fluxes and the overall irrigation cooling effect. Over India, irrigation rates are high enough to keep pace with increased evaporative demand from the increased GHG forcing and the magnitude of the cooling is maintained. Over China, GHG forcing reduces precipitation and shifts the region to a drier evaporative regime, leading to a relatively increased impact of additional water from irrigation on the surface energy balance. Irrigation enhances precipitation in the Middle East under increased GHG forcing, increasing total latent heat fluxes and enhancing the irrigation cooling effect. Ultimately, the extent to which irrigation will continue to compensate for the warming from increased GHG forcing will primarily depend on changes in the background evaporative regime, secondary irrigation effects (e.g. clouds, precipitation), and the ability of societies to maintain (or increase) current irrigation rates.

  2. Vibration-Induced Droplet Atomization --- A Theoretical Investigation.

    NASA Astrophysics Data System (ADS)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. A simple, single degree-of-freedom model of this coupled system is presented. The model is used to illustrate the effect of the excitation frequency and amplitude and the initial droplet size on the acceleration of the membrane and the droplet ejection rate. The results of the model will be compared to our experimental data on droplet ejection. Additional work is directed towards an understanding of the mechanism behind the droplet ejection process.

  3. Vibration-Induced Droplet Atomization --- An Experimental Investigation.

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. In the present experiments, the high acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequency (nominally 1000 Hz). The resonant characteristics and the acceleration during the ejection process for various droplet sizes and excitation amplitudes are investigated using a surface-mounted microfabricated accelerometer and a laboratory computer system.

  4. Vibration induced osteogenic commitment of mesenchymal stem cells is enhanced by cytoskeletal remodeling but not fluid shear.

    PubMed

    Uzer, Gunes; Pongkitwitoon, Suphannee; Ete Chan, M; Judex, Stefan

    2013-09-03

    Consistent across studies in humans, animals and cells, the application of vibrations can be anabolic and/or anti-catabolic to bone. The physical mechanisms modulating the vibration-induced response have not been identified. Recently, we developed an in vitro model in which candidate parameters including acceleration magnitude and fluid shear can be controlled independently during vibrations. Here, we hypothesized that vibration induced fluid shear does not modulate mesenchymal stem cell (MSC) proliferation and mineralization and that cell's sensitivity to vibrations can be promoted via actin stress fiber formation. Adipose derived human MSCs were subjected to vibration frequencies and acceleration magnitudes that induced fluid shear stress ranging from 0.04 Pa to 5 Pa. Vibrations were applied at magnitudes of 0.15 g, 1g, and 2g using frequencies of both 100 Hz and 30 Hz. After 14 d and under low fluid shear conditions associated with 100 Hz oscillations, mineralization was greater in all vibrated groups than in controls. Greater levels of fluid shear produced by 30 Hz vibrations enhanced mineralization only in the 2g group. Over 3d, vibrations led to the greatest increase in total cell number with the frequency/acceleration combination that induced the smallest level of fluid shear. Acute experiments showed that actin remodeling was necessary for early mechanical up-regulation of RUNX-2 mRNA levels. During osteogenic differentiation, mechanically induced up-regulation of actin remodeling genes including Wiskott-Aldrich syndrome (WAS) protein, a critical regulator of Arp2/3 complex, was related to the magnitude of the applied acceleration but not to fluid shear. These data demonstrate that fluid shear does not regulate vibration induced proliferation and mineralization and that cytoskeletal remodeling activity may play a role in MSC mechanosensitivity.

  5. Simulation of vibration-induced effect on plasma current measurement using a fiber optic current sensor.

    PubMed

    Descamps, Frédéric; Aerssens, Matthieu; Gusarov, Andrei; Mégret, Patrice; Massaut, Vincent; Wuilpart, Marc

    2014-06-16

    An accurate measurement of the plasma current is of paramount importance for controlling the plasma magnetic equilibrium in tokamaks. Fiber optic current sensor (FOCS) technology is expected to be implemented to perform this task in ITER. However, during ITER operation, the vessel and the sensing fiber will be subject to vibrations and thus to time-dependent parasitic birefringence, which may significantly compromise the FOCS performance. In this paper we investigate the effects of vibrations on the plasma current measurement accuracy under ITER-relevant conditions. The simulation results show that in the case of a FOCS reflection scheme including a spun fiber and a Faraday mirror, the error induced by the vibrations is acceptable regarding the ITER current diagnostics requirements.

  6. Preventing chemotherapy-induced alopecia in cancer patients: is scalp cooling worthwhile?

    PubMed

    Tierney, A J

    1987-05-01

    Alopecia (hair loss) is often singled out as the most distressing side-effect of cancer chemotherapy treatment. This paper provides a comprehensive and critical review of the research literature on scalp cooling, a procedure introduced to prevent chemotherapy-induced alopecia. In spite of a considerable amount of research (both nursing and medical) over a 15-year period, the evidence on scalp cooling is inconclusive. Although concerned with a specialist issue, this paper may interest the general reader as it illustrates the value of a literature review in raising questions about current practice and in identifying issues for future research.

  7. Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer.

    PubMed

    Loh, Byoung-Gook; Hyun, Sinjae; Ro, Paul I; Kleinstreuer, Clement

    2002-02-01

    Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.

  8. Vibration amplitude and induced temperature limitation of high power air-borne ultrasonic transducers.

    PubMed

    Saffar, Saber; Abdullah, Amir

    2014-01-01

    The acoustic impedances of matching layers, their internal loss and vibration amplitude are the most important and influential parameters in the performance of high power airborne ultrasonic transducers. In this paper, the optimum acoustic impedances of the transducer matching layers were determined by using a genetic algorithm, the powerful tool for optimizating domain. The analytical results showed that the vibration amplitude increases significantly for low acoustic impedance matching layers. This enhancement is maximum and approximately 200 times higher for the last matching layer where it has the same interface with the air than the vibration amplitude of the source, lead zirconate titanate-pizo electric while transferring the 1 kW is desirable. This large amplitude increases both mechanical failure and temperature of the matching layers due to the internal loss of the matching layers. It has analytically shown that the temperature in last matching layer with having the maximum vibration amplitude is high enough to melt or burn the matching layers. To verify suggested approach, the effect of the amplitude of vibration on the induced temperature has been investigated experimentally. The experimental results displayed good agreement with the theoretical predictions.

  9. Venus pancake dome formation: Morphologic effects of a cooling-induced variable viscosity during emplacement

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Zuber, M. T.

    1993-01-01

    The distinctive steep-sided 'pancake' domes discovered in the Magellan images of Venus have morphologies that suggest formation by a single continuous emplacement of a high viscosity magma. A resemblance of the venusian domes to much smaller terrestrial rhyolite and dacite volcanic domes has prompted some authors to suggest that the domes on Venus also have high silica compositions and thus, high viscosities. However, viscosity is a function of crystallinity as well as silica content in a magma, and thus increases as a result of magmatic cooling. To investigate the effect of a cooling-induced viscosity increase on dome morphology, we have modeled the domes as radial viscous gravity currents that cool during emplacement. Various aspects of the investigation are discussed.

  10. Laser-induced cooling of a Yb:YAG crystal in air at atmospheric pressure.

    PubMed

    Soares de Lima Filho, Elton; Nemova, Galina; Loranger, Sébastien; Kashyap, Raman

    2013-10-21

    We report for the first time the experimental demonstration of optical cooling of a bulk crystal at atmospheric pressure. The use of a fiber Bragg grating (FBG) sensor to measure laser-induced cooling in real time is also demonstrated for the first time. A temperature drop of 8.8 K from the chamber temperature was observed in a Yb:YAG crystal in air when pumped with 4.2 W at 1029 nm. A background absorption of 2.9 × 10⁻⁴ cm⁻¹ was estimated with a pump wavelength at 1550 nm. Simulations predict further cooling if the pump power is optimized for the sample's dimensions.

  11. Development of Design Criteria for Fluid Induced Structural Vibration in Steam Generators and Heat Exchangers

    SciTech Connect

    Catton, Ivan; Dhir, Vijay K.; Alquaddoomi, O.S.; Mitra, Deepanjan; Adinolfi, Pierangelo

    2004-03-26

    OAK-B135 Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The research is divided between two primary experimental efforts, the first conducted using water alone (single phase) and the second using a mixture of air or steam and water as the working fluid (two phase). The outline of this report is as follows: After the introduction to fluid-elastic instability, the experimental apparatus constructed to conduct the experiments is described in Chapter 2 along with the measurement procedures. Chapter 3 presents results obtained on the tube array and the flow loop, as well as techniques used in data processing. The project performance is described and evaluated in Chapter 4 followed by

  12. Low frequency vibration induced streaming in a Hele-Shaw cell

    SciTech Connect

    Costalonga, M.; Brunet, P.; Peerhossaini, H.

    2015-01-15

    When an acoustic wave propagates in a fluid, it can generate a second order flow whose characteristic time is much longer than the period of the wave. Within a range of frequency between ten and several hundred Hz, a relatively simple and versatile way to generate streaming flow is to put a vibrating object in the fluid. The flow develops vortices in the viscous boundary layer located in the vicinity of the source of vibrations, leading in turn to an outer irrotational streaming called Rayleigh streaming. Because the flow originates from non-linear time-irreversible terms of the Navier-Stokes equation, this phenomenon can be used to generate efficient mixing at low Reynolds number, for instance in confined geometries. Here, we report on an experimental study of such streaming flow induced by a vibrating beam in a Hele-Shaw cell of 2 mm span using long exposure flow visualization and particle-image velocimetry measurements. Our study focuses especially on the effects of forcing frequency and amplitude on flow dynamics. It is shown that some features of this flow can be predicted by simple scaling arguments and that this vibration-induced streaming facilitates the generation of vortices.

  13. Concorde noise-induced building vibrations, Sully Plantation - Report no. 2, Chantilly, Virginia

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Noise-induced building vibrations associated with Concorde operations were studied. The approach is to record the levels of induced vibrations and associated indoor/outdoor noise levels in selected homes, historic and other buildings near Dulles International Airport. Representative data are presented which were recorded at Sully Plantation, Chantilly, Virginia during the periods of May 20 through May 28, 1976, and June 14 through June 17, 1976. Recorded data provide relationships between the vibration levels of windows, walls, floors, and the noise associated with Concorde operations, other aircraft, and nonaircraft events. The results presented are drawn from the combined May-June data base which is considerably larger than the May data base covered. The levels of window, wall and floor vibratory response resulting from Concorde operations are higher than the vibratory levels associated with conventional aircraft. Furthermore, the vibratory responses of the windows are considerably higher than those of the walls and floors. The window response is higher for aircraft than recorded nonaircraft events and exhibits a linear response relationship with the overall sound pressure level. For a given sound pressure level, the Concorde may cause more vibration than a conventional aircraft due to spectral or other differences. However, the responses associated with Concorde appear to be much more dependent upon sound pressure level than spectral or other characteristics of the noise.

  14. Flow-induced vibration testing of replacement thermowell designs

    NASA Astrophysics Data System (ADS)

    Haslinger, K. H.

    2003-09-01

    Inconel 600 Primary Water Stress Corrosion Cracking (PWSCC) in Nuclear Pressurized Water Reactors (PWRs) has necessitated the repair/replacement of various small bore nozzles. These repairs/replacements must be designed to avoid unwanted vibrations. So, to this end, new RTD-Thermowell-Nozzle replacement designs were developed and subjected to flow testing over a velocity range from 9.14 to 33.53m/s (30-110ft/s), and temperatures ranging from 121°C to 316°C (250-600°F). The replacement nozzles are welded on the pipe OD, rather than on the pipe ID. A split, tapered ferrule is used to support the nozzle tip inside the pipe bore. This maintains high thermowell tip-resonance frequencies with the objective of avoiding self-excitation from vortex shedding that is believed to have caused failures in an earlier design during initial, precritical plant startup testing. The flow testing was complicated by the small size of the thermowell tips (5.08mm or 0.2in ID), which necessitated use of a complement of low temperature and high temperature instrumentation. Since the high temperature device had an internal resonance (750Hz) within the frequency range of interest (0-2500Hz), adequate sensor correlations had to be derived from low temperature tests. The current nozzle/thermowell design was tested concurrently with two slight variations of the replacement design. The acceleration signals were acquired during incremental and continuous flow sweeps, nominally at 5kHz sampling rates and for time domain processing as high as 25kHz. Whereas vortex-shedding frequencies were predicted to prevail between 400 and 1500Hz, no such response was observed at these frequencies. Rather, the thermowell tips responded due to turbulent buffeting with a peak response that was related directly to flow velocity. Lift direction response was always larger than drag direction response. The thermowell tips also responded at their natural tip frequencies in a narrow band random fashion. At the higher

  15. The effect of end conditions on the vortex-induced vibration of cylinders

    NASA Astrophysics Data System (ADS)

    Morse, T. L.; Govardhan, R. N.; Williamson, C. H. K.

    2008-11-01

    In the present investigation we study the effect of end conditions on the vortex-induced vibration of an elastically mounted rigid cylinder. This work was triggered by some initial controlled vibration experiments which showed that spanwise end conditions can have a large effect on measured fluid forces on a cylinder, and this suggested that some of the disparity amongst previous free vibration studies may possibly be attributed to differences in end conditions. In the principal experiments here, we are concerned with a vertical cylinder piercing the clean free surface of a water channel, and attached to a carriage system mounted atop the channel. The upper end of the submerged cylinder is thus the free surface, while the lower end is manipulated to yield three different conditions, namely: an attached endplate; an unattached endplate fixed to the channel floor (with a variable gap between cylinder and plate); and a condition of no endplate at all. Interestingly, we find that the free vibration response for the attached and unattached endplate cases were nearly identical. One expectation was that the case without an endplate would lead to a flow around the end of the body, modifying the vortex dynamics, and thereby reducing the correlation of the induced fluid forces on the body. Surprisingly, over the entire response plot, the vibration amplitude is markedly higher in the absence of an endplate, with the exception of the peak amplitude, which remains nearly unchanged. Unexpectedly, the vibrations become much more steady at flow velocities in the vicinity of the peak response, if the endplate is removed. In a further set of experiments, we undertake controlled vibration, where we vary the gap between cylinder and endplate. We discover a large discontinuous jump in the magnitude of fluid excitation, when the gap exceeds 15% of a diameter. For larger gaps, the fluid excitation becomes independent of the gap size, effectively equivalent to having no plate at all. This

  16. Ice water submersion for rapid cooling in severe drug-induced hyperthermia

    PubMed Central

    Laskowski, Larissa K.; Landry, Adaira; Vassallo, Susi U.; Hoffman, Robert S.

    2015-01-01

    Context The optimal method of cooling hyperthermic patients is controversial. Although controlled data support ice water submersion, many authorities recommend a mist and fan technique. We report two patients with drug-induced hyperthermia, to demonstrate the rapid cooing rates of ice water submersion. Case details Case 1. A 27-year-old man presented with a sympathomimetic toxic syndrome and a core temperature of 41.4°C after ingesting 4-fluoroamphetamine. He was submerged in ice water and his core temperature fell to 38°C within 18 minutes (a mean cooling rate of 0.18°C/min). His vital signs stabilized, his mental status improved and he left on hospital day 2. Case 2. A 32-year-old man with a sympathomimetic toxic syndrome after cocaine use was transported in a body bag and arrived with a core temperature of 44.4°C. He was intubated, sedated with IV benzodiazepines, and submerged in ice water. After 20 minutes his temperature fell to 38.8°C (a cooling rate of 0.28°C/min). He was extubated the following day, and discharged on day 10. Discussion In these two cases, cooling rates exceeded those reported for mist and fan technique. Since the priority in hyperthermia is rapid cooling, clinical data need to be collected to reaffirm the optimal approach. PMID:25695144

  17. Soft Computing Approach to Evaluate and Predict Blast-Induced Ground Vibration

    NASA Astrophysics Data System (ADS)

    Khandelwal, Manoj

    2010-05-01

    Drilling and blasting is still one of the major economical operations to excavate a rock mass. The consumption of explosive has been increased many folds in recent years. These explosives are mainly used for the exploitation of minerals in mining industry or the removal of undesirable rockmass for community development. The amount of chemical energy converted into mechanical energy to fragment and displace the rockmass is minimal. Only 20 to 30% of this explosive energy is utilized for the actual fragmentation and displacement of rockmass and rest of the energy is wasted in undesirable ill effects, like, ground vibration, air over pressure, fly rock, back break, noise, etc. Ground vibration induced due to blasting is very crucial and critical as compared to other ill effects due to involvement of public residing in the close vicinity of mining sites, regulating and ground vibration standards setting agencies together with mine owners and environmentalists and ecologists. Also, with the emphasis shifting towards eco-friendly, sustainable and geo-environmental activities, the field of ground vibration have now become an important and imperative parameter for safe and smooth running of any mining and civil project. The ground vibration is a wave motion, spreading outward from the blast like ripples spreading outwards due to impact of a stone dropped into a pond of water. As the vibration passes through the surface structures, it induces vibrations in those structures also. Sometimes, due to high ground vibration level, dwellings may get damaged and there is always confrontation between mine management and the people residing in the surroundings of the mine area. There is number of vibration predictors available suggested by different researchers. All the predictors estimate the PPV based on mainly two parameters (maximum charge used per delay and distance between blast face to monitoring point). However, few predictors considered attenuation/damping factor too. For

  18. Sensor-controlled scalp cooling to prevent chemotherapy-induced alopecia in female cancer patients

    PubMed Central

    Fehr, M.K.; Welter, J.; Sell, W.; Jung, R.; Felberbaum, R.

    2016-01-01

    Background Scalp cooling has been used since the 1970s to prevent chemotherapy-induced alopecia, one of the most common and psychologically troubling side effects of chemotherapy. Currently available scalp cooling systems demonstrate varying results in terms of effectiveness and tolerability. Methods For the present prospective study, 55 women receiving neoadjuvant, adjuvant, or palliative chemotherapy were enrolled. The aim was to assess the effectiveness of a sensor-controlled scalp cooling system (DigniCap: Sysmex Europe GmbH, Norderstedt, Germany) to prevent chemotherapy-induced alopecia in breast or gynecologic cancer patients receiving 1 of 7 regimens. Clinical assessments, satisfaction questionnaires, and alopecia evaluations [World Health Organization (who) grading for toxicity] were completed at baseline, at each cycle, and at completion of chemotherapy. Results Of the 55 patients, 78% underwent scalp cooling until completion of chemotherapy. In multivariate analysis, younger women and those receiving paclitaxel weekly or paclitaxel–carboplatin experienced less alopecia. The compound successful outcome (“no head covering” plus “who grade 0/1”) was observed in all patients 50 years of age and younger receiving 4 cycles of docetaxel–cyclophosphamide or 6 cycles of paclitaxel–carboplatin. Conversely, alopecia was experienced by all women receiving triplet polychemotherapy (6 cycles of docetaxel–doxorubicin–cyclophosphamide). For women receiving sequential polychemotherapy regimens (3 cycles of fluorouracil–epirubicin–cyclophosphamide followed by 3 cycles of docetaxel or 4 cycles of doxorubicin–cyclophosphamide followed by 4 cycles of docetaxel), the subgroup 50 years of age and younger experienced a 43% success rate compared with a 10% rate for the subgroup pf older women receiving the same regimens. Conclusions The ability of scalp cooling to prevent chemotherapy-induced alopecia varies with the chemotherapy regimen and the age of the

  19. Acute exposure to vibration is an apoptosis-inducing stimulus in the vocal fold epithelium.

    PubMed

    Novaleski, Carolyn K; Kimball, Emily E; Mizuta, Masanobu; Rousseau, Bernard

    2016-10-01

    Clinical voice disorders pose significant communication-related challenges to patients. The purpose of this study was to quantify the rate of apoptosis and tumor necrosis factor-alpha (TNF-α) signaling in vocal fold epithelial cells in response to increasing time-doses and cycle-doses of vibration. 20 New Zealand white breeder rabbits were randomized to three groups of time-doses of vibration exposure (30, 60, 120min) or a control group (120min of vocal fold adduction and abduction). Estimated cycle-doses of vocal fold vibration were extrapolated based on mean fundamental frequency. Laryngeal tissue specimens were evaluated for apoptosis and gene transcript and protein levels of TNF-α. Results revealed that terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was significantly higher after 120min of vibration compared to the control. Transmission electron microscopy (TEM) revealed no significant effect of time-dose on the mean area of epithelial cell nuclei. Extrapolated cycle-doses of vibration exposure were closely related to experimental time-dose conditions, although no significant correlations were observed with TUNEL staining or mean area of epithelial cell nuclei. TUNEL staining was positively correlated with TNF-α protein expression. Our findings suggest that apoptosis can be induced in the vocal fold epithelium after 120min of modal intensity phonation. In contrast, shorter durations of vibration exposure do not result in apoptosis signaling. However, morphological features of apoptosis are not observed using TEM. Future studies are necessary to examine the contribution of abnormal apoptosis to vocal fold diseases.

  20. Cooling and Laser-Induced Fluorescence of Electronically-Excited He2 in a Supersonic Microcavity Plasma Jet

    NASA Astrophysics Data System (ADS)

    Su, Rui; Mironov, Andrey; Houlahan, Thomas, Jr.; Eden, J. Gary; LaboratoryOptical Physics; Engineering Team

    2016-09-01

    Laser-induced fluorescence (LIF) resulting from transitions between different electronic states of helium dimers generated within a microcavity plasma jet was studied with rotational resolution. In particular, the d3Σu+ , e3Πg and f3Σu+ states, all having electronic energies above 24 eV, are populated by a microplasma in 4 bar of helium gas and rotationally cooled through supersonic expansion. Analysis of two dimensional maps (spectrograms) of dimer emission spectra as a function of distance from the nozzle orifice indicates collisional coupling during the expansion between the lowest rotational levels of the e3Πg , f3Σu+ states and high rotational levels (around N=11) of the d3Σu+ state (all of which are in the v = 0 vibrational state). In an attempt to verify the coupling, a scanning dye laser (centered near 596 nm) pumps the b3Πg -> f3Σu+ transition of the molecule several hundred micrometers downstream of the nozzle. As a result, the emission intensities of relevant rotational lines are observed to be enhanced. This research shows the potential of utilizing microcavity plasma jets as a tool to study and manipulate the collisional dynamics of highly-excited diatomic molecules.

  1. Determination of the effects of wind-induced vibration on cylindrical beams

    NASA Technical Reports Server (NTRS)

    Artusa, E. A.

    1991-01-01

    The objective of the analysis was to determine the critical length to diameter ratio (L/Do) of a hollow, cylindrical beam subjected to wind-induced vibration. The sizes of beams ranged from 4 to 24 inches and were composed of ASTM grade A and grade B and American Petroleum Institute grade X42 steels. Calculations used maximum steady-state wind speeds of 130 mph associated with hurricane conditions possible at the Kennedy Space Center. The study examined the effect that different end support and load conditions have on the natural frequencies of the beams. Finally, methods of changing the frequency of the wind-induced vibration were examined. The conclusions drawn were that the greatest possible L/Do is achieved using welded supports and limiting the maximum applied axial and bending loads to less than 50 percent.

  2. Hybrid predictions of railway induced ground vibration using a combination of experimental measurements and numerical modelling

    NASA Astrophysics Data System (ADS)

    Kuo, K. A.; Verbraken, H.; Degrande, G.; Lombaert, G.

    2016-07-01

    Along with the rapid expansion of urban rail networks comes the need for accurate predictions of railway induced vibration levels at grade and in buildings. Current computational methods for making predictions of railway induced ground vibration rely on simplifying modelling assumptions and require detailed parameter inputs, which lead to high levels of uncertainty. It is possible to mitigate against these issues using a combination of field measurements and state-of-the-art numerical methods, known as a hybrid model. In this paper, two hybrid models are developed, based on the use of separate source and propagation terms that are quantified using in situ measurements or modelling results. These models are implemented using term definitions proposed by the Federal Railroad Administration and assessed using the specific illustration of a surface railway. It is shown that the limitations of numerical and empirical methods can be addressed in a hybrid procedure without compromising prediction accuracy.

  3. Increased efficiency of rf-induced evaporative cooling by utilizing gravity

    NASA Astrophysics Data System (ADS)

    Klinner, Julian; Wolke, Matthias; Hemmerich, Andreas

    2010-04-01

    We report on an efficient rf-induced forced evaporative cooling of an ensemble of Rb87 atoms in state |F=2,mF=2> magnetically trapped in a quadrupole-Ioffe configuration trap. The cigar-shaped trap is oriented with its weak confining axis along the direction of gravity leading to, first, a significant separation of the trapping positions for low-field-seeking atoms with different mF value and, second, a reduced resonance volume for rf-induced evaporation confined to a small region around the lower tip of the cigar-shaped ensemble. This results in an enhancement of the evaporation efficiency α≡dlnT/(dlnN) due to either reduced or completely vanishing scattering events between cooled and evaporated atoms. We present data illustrating this effect.

  4. 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.

  5. Stance- and locomotion-dependent processing of vibration-induced proprioceptive inflow from multiple muscles in humans.

    PubMed

    Courtine, Grégoire; De Nunzio, Alessandro Marco; Schmid, Micaela; Beretta, Maria Vittoria; Schieppati, Marco

    2007-01-01

    We performed a whole-body mapping study of the effect of unilateral muscle vibration, eliciting spindle Ia firing, on the control of standing and walking in humans. During quiet stance, vibration applied to various muscles of the trunk-neck system and of the lower limb elicited a significant tilt in whole body postural orientation. The direction of vibration-induced postural tilt was consistent with a response compensatory for the illusory lengthening of the stimulated muscles. During walking, trunk-neck muscle vibration induced ample deviations of the locomotor trajectory toward the side opposite to the stimulation site. In contrast, no significant modifications of the locomotor trajectory could be detected when vibrating various muscles of the lower as well as upper limb. The absence of correlation between the effects of muscle vibration during walking and standing dismisses the possibility that vibration-induced postural changes can account for the observed deviations of the locomotor trajectory during walking. We conclude that the dissimilar effects of trunk-neck and lower limb muscle vibration during walking and standing reflect a general sensory-motor plan, whereby muscle Ia input is processed according to both the performed task and the body segment from which the sensory inflow arises.

  6. System for measurement of small vibrations at material interfaces induced by electrostrictive forces

    SciTech Connect

    Ali, J.S.; Joines, W.T.

    1985-10-01

    The mechanisms of interaction of ELF and ELF-modulated RF fields with biological systems is presently an active area of research. Some models propose that field-induced forces may influence certain observed biological effects such as RF hearing and calcium ion efflux. To investigate the validity of the field-induced force model for the calcium-ion efflux effect, a system is needed which is capable of exposing samples to ELF fields or to ELF-modulated RF fields. At the same time the induced vibration caused by the forces of electrostriction must be monitored preferably by a noncontacting method. A microwave phase-sensitive receiver was designed to sense the small vibrations. Limitations on the receiver sensitivity imposed by phase noise is discussed. Phase noise measurement systems were designed and used to characterize the key receiver components. A limiting amplifier in the IF section of the receiver eliminates the need for knowledge of the reflection coefficient of the object of interest for quantitative vibration measurements.

  7. Tactile Perception and Friction-Induced Vibrations: Discrimination of Similarly Patterned Wood-Like Surfaces.

    PubMed

    Dacleu Ndengue, Jessica; Cesini, B Ilaria; Faucheu, C Jenny; Chatelet, D Eric; Zahouani, E Hassan; Delafosse, F David; Massi, G Francesco

    2016-12-22

    The tactile perception of a surface texture is mediated by factors such as material, topography and vibrations induced by the sliding contact. In this paper, sensory characterizations are developed together with topographical and tribo-tactile characterizations to relate perceived features with objective measurements of tribological and dynamic signals. Two sets of surface samples are used in this study: the first set is made of a commercial floor covering tiles that aim at counter-typing natural wood flooring, with both a visual and a tactile texture mimicking wood. A second set is custom-made by replicating the first set using a plain purple polyurethane resin. The comparison between tribo-tactile signals and sensory analysis allowed the identification of objective indices for textures with slight topographical differences. Even though the topography of the replicated samples is the same as their corresponding commercial products, the fact that the material is different, induces differences in the contact and vibrational parameters. This in turn modifies the discrimination performances during the sensory experiment. Tactile characteristics collected during sensory procedures are found to be in agreement with objective indices such as friction coefficients and induced vibrations.

  8. Long-term daily vibration exposure alters current perception threshold (CPT) sensitivity and myelinated axons in a rat-tail model of vibration-induced injury.

    PubMed

    Krajnak, Kristine; Raju, Sandya G; Miller, G Roger; Johnson, Claud; Waugh, Stacey; Kashon, Michael L; Riley, Danny A

    2016-01-01

    Repeated exposure to hand-transmitted vibration through the use of powered hand tools may result in pain and progressive reductions in tactile sensitivity. The goal of the present study was to use an established animal model of vibration-induced injury to characterize changes in sensory nerve function and cellular mechanisms associated with these alterations. Sensory nerve function was assessed weekly using the current perception threshold test and tail-flick analgesia test in male Sprague-Dawley rats exposed to 28 d of tail vibration. After 28 d of exposure, Aβ fiber sensitivity was reduced. This reduction in sensitivity was partly attributed to structural disruption of myelin. In addition, the decrease in sensitivity was also associated with a reduction in myelin basic protein and 2',3'- cyclic nucleotide phosphodiasterase (CNPase) staining in tail nerves, and an increase in circulating calcitonin gene-related peptide (CGRP) concentrations. Changes in Aβ fiber sensitivity and CGRP concentrations may serve as early markers of vibration-induced injury in peripheral nerves. It is conceivable that these markers may be utilized to monitor sensorineural alterations in workers exposed to vibration to potentially prevent additional injury.

  9. Scalp cooling by cold air for the prevention of chemotherapy-induced alopecia.

    PubMed

    Hillen, H F; Breed, W P; Botman, C J

    1990-12-01

    A new system is described for cooling the scalp with cold air in order to prevent chemotherapy-induced alopecia. Compressed air was cooled by means of a vortex tube built into a hair-drier cap. This system reduced the blood flow in the scalp to 35%, the surface temperature to 14.2 degrees C and the intradermal temperature at hair follicle level to 29.2 degrees C. The low temperature could be kept constant for at least one hour of cooling. By means of comparison, with cryogel packs the lowest epidermal temperature attained was 17.9 degrees C; moreover, once this was reached after 10 min, it rapidly rose again to 20.6 degrees C after 40 min. Forty-eight patients receiving cytostatic treatment for breast cancer were subjected to scalp cooling with the cold air system, starting 15 min before chemotherapy and lasting for 90 min. With the system set at an air temperature of -12 degrees C, the treatment was well tolerated. Of the 13 patients treated with 40 mg/m2 doxorubicin in combination with other cytostatics, 6 had hair loss less than WHO grade 3, in contrast to 1 of 4 patients given cryogel packs. However, patients treated with epirubicin at 75 mg/m2 all showed grade 3 hair loss in spite of air cooling. In view of the possibility of achieving and maintaining low scalp temperatures, the cold air system is to be preferred to cryogel packs. Whether better clinical results may be obtained with cooling for longer periods and/or to lower temperatures remains to be determined.

  10. Active control of panel vibrations induced by boundary-layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1991-01-01

    Some problems in active control of panel vibration excited by a boundary layer flow over a flat plate are studied. In the first phase of the study, the optimal control problem of vibrating elastic panel induced by a fluid dynamical loading was studied. For a simply supported rectangular plate, the vibration control problem can be analyzed by a modal analysis. The control objective is to minimize the total cost functional, which is the sum of a vibrational energy and the control cost. By means of the modal expansion, the dynamical equation for the plate and the cost functional are reduced to a system of ordinary differential equations and the cost functions for the modes. For the linear elastic plate, the modes become uncoupled. The control of each modal amplitude reduces to the so-called linear regulator problem in control theory. Such problems can then be solved by the method of adjoint state. The optimality system of equations was solved numerically by a shooting method. The results are summarized.

  11. Novel magnetically induced membrane vibration (MMV) for fouling control in membrane bioreactors.

    PubMed

    Bilad, Muhammad R; Mezohegyi, Gergo; Declerck, Priscilla; Vankelecom, Ivo F J

    2012-01-01

    Conventional submerged membrane bioreactors (MBRs) rely on the coarse bubbles aeration to generate shear at the liquid-membrane interface to limit membrane fouling. Unfortunately, it is a very energy consuming method, still often resulting in a rapid decrease of membrane permeability and consequently in higher expenses. In this paper, the feasibility of a novel magnetically induced membrane vibration (MMV) system was studied in a lab-scale MBR treating synthetic wastewater. The effects on membrane fouling of applied electrical power of different operation strategies, of membrane flux and of the presence of multiple membranes on one vibrating engine on membrane fouling were investigated. The filtration performance was evaluated by determining the filtration resistance profiles and critical flux. The results showed clear advantages of the vibrating system over conventional MBR processes by ensuring higher fluxes at lower fouling rates. Intermittent vibration was found a promising strategy for both efficient fouling control and significant energy saving. The optimised MMV system is presumed to lead to significant energy and cost reduction in up-scaled MBR operations.

  12. Influence of subglottic stenosis on the flow-induced vibration of a computational vocal fold model

    PubMed Central

    Smith, Simeon L.; Thomson, Scott L.

    2012-01-01

    The effect of subglottic stenosis on vocal fold vibration is investigated. An idealized stenosis is defined, parameterized, and incorporated into a two-dimensional, fully-coupled finite element model of the vocal folds and laryngeal airway. Flow-induced responses of the vocal fold model to varying severities of stenosis are compared. The model vibration was not appreciably affected by stenosis severities of up to 60% occlusion. Model vibration was altered by stenosis severities of 90% or greater, evidenced by decreased superior model displacement, glottal width amplitude, and flow rate amplitude. Predictions of vibration frequency and maximum flow declination rate were also altered by high stenosis severities. The observed changes became more pronounced with increasing stenosis severity and inlet pressure, and the trends correlated well with flow resistance calculations. Flow visualization was used to characterize subglottal flow patterns in the space between the stenosis and the vocal folds. Underlying mechanisms for the observed changes, possible implications for human voice production, and suggestions for future work are discussed. PMID:23503699

  13. Vortex-induced vibrations of a flexible cylinder at large inclination angle.

    PubMed

    Bourguet, Rémi; Triantafyllou, Michael S

    2015-01-28

    The free vibrations of a flexible circular cylinder inclined at 80° within a uniform current are investigated by means of direct numerical simulation, at Reynolds number 500 based on the body diameter and inflow velocity. In spite of the large inclination angle, the cylinder exhibits regular in-line and cross-flow vibrations excited by the flow through the lock-in mechanism, i.e. synchronization of body motion and vortex formation. A profound reconfiguration of the wake is observed compared with the stationary body case. The vortex-induced vibrations are found to occur under parallel, but also oblique vortex shedding where the spanwise wavenumbers of the wake and structural response coincide. The shedding angle and frequency increase with the spanwise wavenumber. The cylinder vibrations and fluid forces present a persistent spanwise asymmetry which relates to the asymmetry of the local current relative to the body axis, owing to its in-line bending. In particular, the asymmetrical trend of flow-body energy transfer results in a monotonic orientation of the structural waves. Clockwise and counter-clockwise figure eight orbits of the body alternate along the span, but the latter are found to be more favourable to structure excitation. Additional simulations at normal incidence highlight a dramatic deviation from the independence principle, which states that the system behaviour is essentially driven by the normal component of the inflow velocity.

  14. Predictions of experimentally observed stochastic ground vibrations induced by blasting.

    PubMed

    Kostić, Srđan; Perc, Matjaž; Vasović, Nebojša; Trajković, Slobodan

    2013-01-01

    In the present paper, we investigate the blast induced ground motion recorded at the limestone quarry "Suva Vrela" near Kosjerić, which is located in the western part of Serbia. We examine the recorded signals by means of surrogate data methods and a determinism test, in order to determine whether the recorded ground velocity is stochastic or deterministic in nature. Longitudinal, transversal and the vertical ground motion component are analyzed at three monitoring points that are located at different distances from the blasting source. The analysis reveals that the recordings belong to a class of stationary linear stochastic processes with Gaussian inputs, which could be distorted by a monotonic, instantaneous, time-independent nonlinear function. Low determinism factors obtained with the determinism test further confirm the stochastic nature of the recordings. Guided by the outcome of time series analysis, we propose an improved prediction model for the peak particle velocity based on a neural network. We show that, while conventional predictors fail to provide acceptable prediction accuracy, the neural network model with four main blast parameters as input, namely total charge, maximum charge per delay, distance from the blasting source to the measuring point, and hole depth, delivers significantly more accurate predictions that may be applicable on site. We also perform a sensitivity analysis, which reveals that the distance from the blasting source has the strongest influence on the final value of the peak particle velocity. This is in full agreement with previous observations and theory, thus additionally validating our methodology and main conclusions.

  15. Tracking Ultrafast Vibrational Cooling during Excited-State Proton Transfer Reaction with Anti-Stokes and Stokes Femtosecond Stimulated Raman Spectroscopy.

    PubMed

    Liu, Weimin; Tang, Longteng; Oscar, Breland G; Wang, Yanli; Chen, Cheng; Fang, Chong

    2017-03-02

    Energy dissipation following photoexcitation is foundational to photophysics and chemistry. Consequently, understanding such processes on molecular time scales holds paramount importance. Femtosecond stimulated Raman spectroscopy (FSRS) has been used to study the molecular structure-function relationships but usually on the Stokes side. Here, we perform both Stokes and anti-Stokes FSRS to track energy dissipation and excited-state proton transfer (ESPT) for the photoacid pyranine in aqueous solution. We reveal biphasic vibrational cooling on fs-ps time scales during ESPT. Characteristic low-frequency motions (<800 cm(-1)) exhibit initial energy dissipation (∼2 ps) that correlates with functional events of forming contact ion pairs via H-bonds between photoacid and water, which lengthens to ∼9 ps in methanol where ESPT is inhibited. The interplay between photoinduced dissipative and reactive channels is implied. Thermal cooling to bulk solvent occurs on the ∼50 ps time scale. These results demonstrate the combined Stokes and anti-Stokes FSRS as a powerful toolset to elucidate structural dynamics.

  16. Predictions of Experimentally Observed Stochastic Ground Vibrations Induced by Blasting

    PubMed Central

    Kostić, Srđan; Perc, Matjaž; Vasović, Nebojša; Trajković, Slobodan

    2013-01-01

    In the present paper, we investigate the blast induced ground motion recorded at the limestone quarry “Suva Vrela” near Kosjerić, which is located in the western part of Serbia. We examine the recorded signals by means of surrogate data methods and a determinism test, in order to determine whether the recorded ground velocity is stochastic or deterministic in nature. Longitudinal, transversal and the vertical ground motion component are analyzed at three monitoring points that are located at different distances from the blasting source. The analysis reveals that the recordings belong to a class of stationary linear stochastic processes with Gaussian inputs, which could be distorted by a monotonic, instantaneous, time-independent nonlinear function. Low determinism factors obtained with the determinism test further confirm the stochastic nature of the recordings. Guided by the outcome of time series analysis, we propose an improved prediction model for the peak particle velocity based on a neural network. We show that, while conventional predictors fail to provide acceptable prediction accuracy, the neural network model with four main blast parameters as input, namely total charge, maximum charge per delay, distance from the blasting source to the measuring point, and hole depth, delivers significantly more accurate predictions that may be applicable on site. We also perform a sensitivity analysis, which reveals that the distance from the blasting source has the strongest influence on the final value of the peak particle velocity. This is in full agreement with previous observations and theory, thus additionally validating our methodology and main conclusions. PMID:24358140

  17. Collision-induced vibrational absorption in molecular hydrogens

    SciTech Connect

    Reddy, S.P.

    1993-05-01

    Collision induced absorption (CIA) spectra of the first overtone bands of H{sub 2}, D{sub 2}, and HD have been recorded for gas densities up to 500 amagat at 77-300 K. Analyses of these spectra reveal that (1) contrary to the observations in the fundamental bands, the contribution of the isotropic overlap interaction to the first overtone bands is negligible, (2) the squares of the matrix elements B{sub 32}(R)/ea{sub o} [= {lambda}{sub 32} exp(-(R-{sigma})/{rho}{sub 32}) + 3 (R/a{sub o}){sup -4}] where the subscripts 3 and 2 represent L and {lambda}, respectively, account for the absorption intensity of the bands and (3) the mixed term, 2,3 {lambda}{sub 32} exp (-(R-{sigma})/{rho}{sub 32}) <{vert_bar}Q{vert_bar}> <{alpha}> (R/a){sup -4}, gives a negative contribution. In the CIA spectra of H{sub 2} in its second overtone region recorded at 77, 201 and 298 K for gas densities up to 1000 amagat, a dip in the Q branch with characteristic Q{sub p} and Q{sub R} components has been observed. The analysis of the absorption profiles reveals, in addition to the previously known effects, the occurrence of the triple-collision transitions of H{sub 2} of the type Q{sub 1}(J) + Q{sub 1}(J) + Q{sub 1}(J) for the first time. From the profile analysis the absorption coefficient of these transitions is obtained.

  18. Ameliorative effect of Phytocee™ Cool against carbon tetrachloride-induced oxidative stress

    PubMed Central

    Joseph, Joshua Allan; Ayyappan, Usha Parackal Thachappully; Sasidharan, Suja Rani; Mutyala, Sridhar; Goudar, Krishnagouda Shankargouda; Agarwal, Amit

    2014-01-01

    Background: Antioxidants from natural sources have a major role in reversing the effects of oxidative stress and promoting health, growth and productivity in animals. Objective: This study was undertaken to investigate the possible antioxidant activity and hepatoprotective effects of Phytocee™ Cool on carbon tetrachloride (CCl4) induced oxidative stress and liver damage in rats. Materials and Methods: Animals were pretreated with Phytocee™ Cool for 10 days and were challenged with CCl4 (1:1 v/v) in olive oil on the 10th day. After 24 h of CCl4 administration blood was collected and markers of hepatocellular damage aspartate aminotransferase (AST), alanine aminotransferase (ALT) were evaluated. Rats were sacrificed and oxidative stress in liver was estimated using malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase. Results: CCl4 caused a significant increase in serum AST, ALT, hepatic MDA and GSH levels, whereas the SOD and catalase activities were decreased. Phytocee™ Cool pretreatment attenuated the MDA, AST ALT levels and increased the activities of SOD and catalase. Conclusion: Phytocee™ Cool demonstrated antioxidant potential and hepatoprotective effects and plausibly be used in the amelioration of oxidative stress. PMID:25276070

  19. Response of upper ocean and impact of barrier layer on Sidr cyclone induced sea surface cooling

    NASA Astrophysics Data System (ADS)

    Vissa, Naresh Krishna; Satyanarayana, A. N. V.; Kumar, B. Prasad

    2013-09-01

    In the present study an attempt has been made to investigate the impact of salinity stratification on the SST during the tropical cyclone (TC) passage. In this context, a severe post monsoon cyclone, Sidr, (Category 4) that developed over the south-eastern Bay of Bengal (BoB) during 11-16 November, 2007 was chosen as a case study. Pre-existence of a thick barrier layer (BL), temperature inversions and a higher effective oceanic layer for cyclogenesis (EOLC) were noticed along the path of the Sidr cyclone. The analysis of available Argo floats along the Sidr cyclone track also revealed less cooling during as well as after its passage as was reported from satellite derived SST. The role of BL on Sidr induced sea surface cooling was investigated using a diagnostic mixed layer model. Model results also depict the reduced sea surface cooling during the passage of Sidr. This is attributed to the presence of BL which results in the inhibition of the entrainment of cool thermocline water into the shallow mixed layer. Climatological as well as in situ observations of tropical cyclone heat potential (TCHP) and EOLC shows that the Sidr cyclone propagated towards the regions of higher EOLC.

  20. Dorsal neck muscle vibration induces upward shifts in the endpoints of memory-guided saccades in monkeys.

    PubMed

    Corneil, Brian D; Andersen, Richard A

    2004-07-01

    Producing a movement in response to a sensory stimulus requires knowledge of the body's current configuration, and spindle organs embedded within muscles are a primary source of such kinesthetic information. Here, we sought to develop an animal model of kinesthetic illusions induced by mechanically vibrating muscles as a first step toward a mechanistic understanding of how kinesthesia is integrated into neural plans for action. We elected to examine the effects of mechanical vibration of dorsal neck muscles in head-restrained monkeys performing memory-guided saccades requiring them to look to the remembered location of a flashed target only after an imposed delay. During the delay on one-half of all trials, mechanical vibration (usually 1,500 ms in duration, 200 microm in amplitude, 100 Hz in frequency) was applied to the dorsal aspect on one side of the monkey's neck. We compared the metrics of such vibration saccades to control saccades without vibration during the delay interval. Relative to control saccades, the endpoints of vibration saccades were shifted consistently upward, even though the variability in saccadic endpoints was unaltered. Although the stability of the eye was compromised during the delay interval of vibration trials, as evidenced by an increased incidence of upward drifts and downward microsaccades, vibration saccades displayed different metrics than control saccades, including an upwardly deviated radial direction and increased vertical amplitude. The influence of variations in the duration (500-2,500 ms), amplitude (100-300 microm), or frequency (75-125 Hz) of vibration scaled well with the presumed change in spindle activity entrained by vibration. Comparisons of the profile of these results are made to the human literature. We conclude that neck muscle vibration induces alterations in oculomotor performance in monkeys consistent with a central interpretation of illusory neck flexion and downward gaze deviation due to increased activation

  1. Nonlinear characteristics analysis of vortex-induced vibration for a three-dimensional flexible tube

    NASA Astrophysics Data System (ADS)

    Feng, Zhipeng; Jiang, Naibin; Zang, Fenggang; Zhang, Yixiong; Huang, Xuan; Wu, Wanjun

    2016-05-01

    Vortex-induced vibration of a three-dimensional flexible tube is one of the key problems to be considered in many engineering situations. This paper aims to investigate the nonlinear dynamic behaviors and response characteristics of a three-dimensional tube under turbulent flow. The three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model are solved with the finite volume approach, and the dynamic equilibrium equations are discretized by the finite element theory. A three-dimensional fully coupled numerical model for vortex-induced vibration of flexible tube is proposed. The model realized the fluid-structure interaction with solving the fluid flow and the structure vibration simultaneously. Based on this model, Response regimes, trajectory, phase difference, fluid force coefficient and vortex shedding frequency are obtained. The nonlinear phenomena of lock-in, phase-switch are captured successfully. Meanwhile, the limit cycle, bifurcation of lift coefficient and displacement are analyzed using phase portrait and Poincare section. The results reveal that, a quasi-upper branch occurs in the present fluid-flexible tube coupling system with high mass-damping and low mass ratio. There is no bifurcation of lift coefficient and lateral displacement occurred in the three-dimensional flexible tube submitted to uniform turbulent flow.

  2. Structural coloration of metallic surfaces with micro/nano-structures induced by elliptical vibration texturing

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Pan, Yayue; Guo, Ping

    2017-04-01

    Creating orderly periodic micro/nano-structures on metallic surfaces, or structural coloration, for control of surface apparent color and optical reflectivity has been an exciting research topic over the years. The direct applications of structural coloration include color marking, display devices, and invisibility cloak. This paper presents an efficient method to colorize metallic surfaces with periodic micro/nano-gratings using elliptical vibration texturing. When the tool vibration is coupled with a constant cutting velocity, controlled periodic ripples can be generated due to the overlapping tool trajectory. These periodic ripples with a wavelength near visible spectrum can act as micro-gratings to introduce iridescent colors. The proposed technique also provides a flexible method for color marking of metallic surfaces with arbitrary patterns and images by precise control of the spacing distance and orientation of induced micro/nano-ripples. Theoretical analysis and experimental results are given to demonstrate structural coloration of metals by a direct mechanical machining technique.

  3. Chemical reactions of water molecules on Ru(0001) induced by selective excitation of vibrational modes

    SciTech Connect

    Mugarza, Aitor; Shimizu, Tomoko K.; Ogletree, D. Frank; Salmeron, Miquel

    2009-05-07

    Tunneling electrons in a scanning tunneling microscope were used to excite specific vibrational quantum states of adsorbed water and hydroxyl molecules on a Ru(0 0 0 1) surface. The excited molecules relaxed by transfer of energy to lower energy modes, resulting in diffusion, dissociation, desorption, and surface-tip transfer processes. Diffusion of H{sub 2}O molecules could be induced by excitation of the O-H stretch vibration mode at 445 meV. Isolated molecules required excitation of one single quantum while molecules bonded to a C atom required at least two quanta. Dissociation of single H{sub 2}O molecules into H and OH required electron energies of 1 eV or higher while dissociation of OH required at least 2 eV electrons. In contrast, water molecules forming part of a cluster could be dissociated with electron energies of 0.5 eV.

  4. Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow.

    PubMed

    Matsusaka, Shuji; Kobayakawa, Murino; Mizutani, Megumi; Imran, Mohd; Yasuda, Masatoshi

    2013-01-01

    We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system.

  5. Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow

    NASA Astrophysics Data System (ADS)

    Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu

    2016-06-01

    In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.

  6. Low Mass-Damping Vortex-Induced Vibrations of a Single Cylinder at Moderate Reynolds Number.

    PubMed

    Jus, Y; Longatte, E; Chassaing, J-C; Sagaut, P

    2014-10-01

    The feasibility and accuracy of large eddy simulation is investigated for the case of three-dimensional unsteady flows past an elastically mounted cylinder at moderate Reynolds number. Although these flow problems are unconfined, complex wake flow patterns may be observed depending on the elastic properties of the structure. An iterative procedure is used to solve the structural dynamic equation to be coupled with the Navier-Stokes system formulated in a pseudo-Eulerian way. A moving mesh method is involved to deform the computational domain according to the motion of the fluid structure interface. Numerical simulations of vortex-induced vibrations are performed for a freely vibrating cylinder at Reynolds number 3900 in the subcritical regime under two low mass-damping conditions. A detailed physical analysis is provided for a wide range of reduced velocities, and the typical three-branch response of the amplitude behavior usually reported in the experiments is exhibited and reproduced by numerical simulation.

  7. Review of leakage-flow-induced vibrations of reactor components. [LMFBR

    SciTech Connect

    Mulcahy, T.M.

    1983-05-01

    The primary-coolant flow paths of a reactor system are usually subject to close scrutiny in a design review to identify potential flow-induced vibration sources. However, secondary-flow paths through narrow gaps in component supports, which parallel the primary-flow path, occasionally are the excitation source for significant vibrations even though the secondary-flow rates are orders of magnitude smaller than the primary-flow rate. These so-called leakage flow problems are reviewed here to identify design features and excitation sources that should be avoided. Also, design rules of thumb are formulated that can be employed to guide a design, but quantitative prediction of component response is found to require scale-model testing.

  8. On the Computation of Structural Vibrations Induced by a Low-speed Turbulent Flow

    NASA Technical Reports Server (NTRS)

    Hwang, Y. F.

    1985-01-01

    A method for numerical evaluation of the vibrations of a cylindrical shell structure induced by a low speed external turbulent flow is discussed. The direction of flow is along the axis of revolution of the shell, and the source of excitation is the pressure fluctuations in the turbulent boundary layer. For the investigation of vibration and noise problems it is usually more desirable to utilize the modal expansion approach. The axisymmetric shell structure can be modeled by the assemblage of conical-shell finite-elements. This modeling allows the eigenfunction psi sub mn (x,theta) to be represented in a rectangular product of a longitudinal modal function f sub mn (x) and a circular harmonic function cos m theta (or sin m theta).

  9. Numerical and experimental investigation of natural flow-induced vibrations of flexible hydrofoils

    NASA Astrophysics Data System (ADS)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Lelong, Alexandra; Astolfi, Jacques Andre; Young, Yin Lu

    2016-07-01

    The objective of this work is to present combined numerical and experimental studies of natural flow-induced vibrations of flexible hydrofoils. The focus is on identifying the dependence of the foil's vibration frequencies and damping characteristics on the inflow velocity, angle of attack, and solid-to-fluid added mass ratio. Experimental results are shown for a cantilevered polyacetate (POM) hydrofoil tested in the cavitation tunnel at the French Naval Academy Research Institute (IRENav). The foil is observed to primarily behave as a chordwise rigid body and undergoes spanwise bending and twisting deformations, and the flow is observed to be effectively two-dimensional (2D) because of the strong lift retention at the free tip caused by a small gap with a thickness less than the wall boundary layer. Hence, the viscous fluid-structure interaction (FSI) model is formulated by coupling a 2D unsteady Reynolds-averaged Navier-Stokes (URANS) model with a two degree-of-freedom (2-DOF) model representing the spanwise tip bending and twisting deformations. Good agreements were observed between viscous FSI predictions and experimental measurements of natural flow-induced vibrations in fully turbulent and attached flow conditions. The foil vibrations were found to be dominated by the natural frequencies in absence of large scale vortex shedding due to flow separation. The natural frequencies and fluid damping coefficients were found to vary with velocity, angle of attack, and solid-to-fluid added mass ratio. In addition, the numerical results showed that the in-water to in-air natural frequency ratios decreased rapidly, and the fluid damping coefficients increased rapidly, as the solid-to-fluid added mass ratio decreases. Uncoupled mode (UM) linear potential theory was found to significantly over-predict the fluid damping for cases of lightweight flexible hydrofoils, and this over-prediction increased with higher velocity and lower solid-to-fluid added mass ratio.

  10. Suppression of vortex-induced vibration using the rotary oscillation of a cylinder

    NASA Astrophysics Data System (ADS)

    Du, Lin; Sun, Xiaofeng

    2015-02-01

    An active control method for suppressing the response of an elastically mounted cylinder by forcing rotary oscillation is presented. Vortex-induced vibration (VIV) of structures is related to the interaction between body and shedding vortex. In the synchronization/lock-in regime, when the vortex shedding frequency fs matches the natural frequency fN of the spring-mass system, large displacement amplitude in the transverse direction is observed. The effect of rotary oscillation on unsteady laminar flow past a freely vibrating cylinder has been investigated. In this study, the cylinder has two degrees of freedom: forced rotary oscillation and vortex induced vibration. The investigation is based on the solutions of flow equations by using the immersed boundary method at moderate Reynolds number. The present computational results indicate the rotary oscillation control can be implemented to suppress the response amplitude of VIV by locking the vortex shedding frequency fs at the forcing frequency fr in the "lock-on" region. The "lock-on" phenomenon occurs in the wake of a rotationally oscillating cylinder, which is free to vibrate in the transverse direction. The essence of the present active control method is to change the frequency of the vortex shedding, rather than suppress it. The response of an elastically mounted cylinder is drastically suppressed to less than 1% of the cylinder diameter, when proper frequency ratio fr/fN and rotational velocity are imposed. Detailed analyses of aerodynamic performance are given to interpret the mechanism of the suppression of response caused by forced rotary oscillation. The effects of mass ratio and velocity rate of rotary oscillation are also found to play an important role in the spring-mass system. The efficiency of the present method increases with Reynolds number.

  11. Cold-induced vasoconstriction may persist long after cooling ends: an evaluation of multiple cryotherapy units

    PubMed Central

    Khoshnevis, Sepideh; Craik, Natalie K.

    2015-01-01

    Purpose Localized cooling is widely used in treating soft tissue injuries by modulating swelling, pain, and inflammation. One of the primary outcomes of localized cooling is vasoconstriction within the underlying skin. It is thought that in some instances, cryotherapy may be causative of tissue necrosis and neuropathy via cold-induced ischaemia leading to nonfreezing cold injury (NFCI). The purpose of this study is to quantify the magnitude and persistence of vasoconstriction associated with cryotherapy. Methods Data are presented from testing with four different FDA approved cryotherapy devices. Blood perfusion and skin temperature were measured at multiple anatomical sites during baseline, active cooling, and passive rewarming periods. Results Local cutaneous blood perfusion was depressed in response to cooling the skin surface with all devices, including the DonJoy (DJO, p = 2.6 × 10−8), Polar Care 300 (PC300, p = 1.1 × 10−3), Polar Care 500 Lite (PC500L, p = 0.010), and DeRoyal T505 (DR505, p = 0.016). During the rewarming period, parasitic heat gain from the underlying tissues and the environment resulted in increased temperatures of the skin and pad for all devices, but blood perfusion did not change significantly, DJO (n.s.), PC300 (n.s.), PC500L (n.s.), and DR505 (n.s.). Conclusions The results demonstrate that cryotherapy can create a deep state of vasoconstriction in the local area of treatment. In the absence of independent stimulation, the condition of reduced blood flow persists long after cooling is stopped and local temperatures have rewarmed towards the normal range, indicating that the maintenance of vasoconstriction is not directly dependent on the continuing existence of a cold state. The depressed blood flow may dispose tissue to NFCI. PMID:24562697

  12. Raynaud's phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure.

    PubMed

    Pettersson, Hans; Burström, Lage; Nilsson, Tohr

    2014-01-01

    Raynaud's phenomenon is characterized by constriction in blood supply to the fingers causing finger blanching, of white fingers (WF) and is triggered by cold. Earlier studies found that workers using vibrating hand-held tools and who had vibration-induced white fingers (VWF) had an increased risk for hearing loss compared with workers without VWF. This study examined the occurrence of Raynaud's phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure. All 342 participants had a confirmed noise-induced hearing loss medico legally accepted as work-related by AFA Insurance. Each subject answered a questionnaire concerning their health status and the kinds of exposures they had at the time when their hearing loss was first discovered. The questionnaire covered types of exposures, discomforts in the hands or fingers, diseases and medications affecting the blood circulation, the use of alcohol and tobacco and for women, the use of hormones and whether they had been pregnant. The participation rate was 41% (n = 133) with 38% (n = 94) for men and 50% (n = 39) for women. 84 men and 36 women specified if they had Raynaud's phenomenon and also if they had used hand-held vibrating machines. Nearly 41% of them had used hand-held vibrating machines and 18% had used vibrating machines at least 2 h each workday. There were 23 men/6 women with Raynaud's phenomenon. 37% reported WF among those participants who were exposed to hand-arm vibration (HAV) and 15% among those not exposed to HAV. Among the participants with hearing loss with daily use of vibrating hand-held tools more than twice as many reports WF compared with participants that did not use vibrating hand-held tools. This could be interpreted as Raynaud's phenomenon could be associated with an increased risk for noise-induced hearing loss. However, the low participation rate limits the generalization of the results from this study.

  13. Physiologic and Perceptual Responses to Cold-Shower Cooling After Exercise-Induced Hyperthermia

    PubMed Central

    Butts, Cory L.; McDermott, Brendon P.; Buening, Brian J.; Bonacci, Jeffrey A.; Ganio, Matthew S.; Adams, J. D.; Tucker, Matthew A.; Kavouras, Stavros A.

    2016-01-01

    Context:  Exercise conducted in hot, humid environments increases the risk for exertional heat stroke (EHS). The current recommended treatment of EHS is cold-water immersion; however, limitations may require the use of alternative resources such as a cold shower (CS) or dousing with a hose to cool EHS patients. Objective:  To investigate the cooling effectiveness of a CS after exercise-induced hyperthermia. Design:  Randomized, crossover controlled study. Setting:  Environmental chamber (temperature = 33.4°C ± 2.1°C; relative humidity = 27.1% ± 1.4%). Patients or Other Participants:  Seventeen participants (10 male, 7 female; height = 1.75 ± 0.07 m, body mass = 70.4 ± 8.7 kg, body surface area = 1.85 ± 0.13 m2, age range = 19–35 years) volunteered. Intervention(s):  On 2 occasions, participants completed matched-intensity volitional exercise on an ergometer or treadmill to elevate rectal temperature to ≥39°C or until participant fatigue prevented continuation (reaching at least 38.5°C). They were then either treated with a CS (20.8°C ± 0.80°C) or seated in the chamber (control [CON] condition) for 15 minutes. Main Outcome Measure(s):  Rectal temperature, calculated cooling rate, heart rate, and perceptual measures (thermal sensation and perceived muscle pain). Results:  The rectal temperature (P = .98), heart rate (P = .85), thermal sensation (P = .69), and muscle pain (P = .31) were not different during exercise for the CS and CON trials (P > .05). Overall, the cooling rate was faster during CS (0.07°C/min ± 0.03°C/min) than during CON (0.04°C/min ± 0.03°C/min; t16 = 2.77, P = .01). Heart-rate changes were greater during CS (45 ± 20 beats per minute) compared with CON (27 ± 10 beats per minute; t16 = 3.32, P = .004). Thermal sensation was reduced to a greater extent with CS than with CON (F3,45 = 41.12, P < .001). Conclusions:  Although the CS facilitated cooling rates faster than no treatment, clinicians should continue

  14. Localized cooling of stems induces latewood formation and cambial dormancy during seasons of active cambium in conifers

    PubMed Central

    Begum, Shahanara; Kudo, Kayo; Matsuoka, Yugo; Nakaba, Satoshi; Yamagishi, Yusuke; Nabeshima, Eri; Rahman, Md Hasnat; Nugroho, Widyanto Dwi; Oribe, Yuichiro; Jin, Hyun-O; Funada, Ryo

    2016-01-01

    Background and Aims In temperate regions, trees undergo annual cycles of cambial growth, with periods of cambial activity and dormancy. Environmental factors might regulate the cambial growth, as well as the development of cambial derivatives. We investigated the effects of low temperature by localized cooling on cambial activity and latewood formation in two conifers, Chamaecyparis obtusa and Cryptomeria japonica. Methods A plastic rubber tube that contained cooled water was wrapped around a 30-cm-wide portion of the main stem of Chamaecyparis obtusa and Cryptomeria japonica trees during seasons of active cambium. Small blocks were collected from both cooled and non-cooled control portions of the stems for sequential observations of cambial activity and for anatomical measurements of cell morphology by light microscopy and image analysis. Key Results The effect of localized cooling was first observed on differentiating tracheids. Tracheids narrow in diameter and with significantly decreased cambial activity were evident 5 weeks after the start of cooling in these stems. Eight weeks after the start of cooling, tracheids with clearly diminished diameters and thickened cell walls were observed in these stems. Thus, localized low temperature induced narrow diameters and obvious thickening of secondary cell walls of tracheids, which were identified as latewood tracheids. Two months after the cessation of cooling, a false annual ring was observed and cambium became active again and produced new tracheids. In Cryptomeria japonica, cambial activity ceased earlier in locally cooled portions of stems than in non-cooled stems, indicating that the cambium had entered dormancy sooner in the cooled stems. Conclusions Artificial cooling of stems induced latewood formation and cessation of cambial activity, indicating that cambium and its derivatives can respond directly to changes in temperature. A decrease in the temperature of the stem is a critical factor in the control of

  15. Measurement of pump-induced transient lensing in a cryogenically-cooled high average power Ti:sapphire amplifier.

    PubMed

    Planchon, Thomas A; Amir, Wafa; Childress, Colby; Squier, Jeff A; Durfee, Charles G

    2008-11-10

    The transient thermal lensing in a liquid-nitrogren cooled kilohertz multipass amplifier is quantitatively measured with spatially-resolved Fourier transform spectral interferometry. A pump-probe arrangement allows the observation of a polarization-dependent non-thermal component following the fluorescence timescale: additional cooling would not suppress this residual lensing. We also observe a time-dependent thermal component that has a timescale sufficiently fast to indicate that there is cooling between shots even at a repetition rate of 1 kHz. The value of pump-induced lensing would be underestimated when performing time-averaged measurements of pump-induced phase shifts.

  16. Role of Vibration-Induced Streaming in Float-Zone Crystal Growth

    NASA Technical Reports Server (NTRS)

    Anilkumar, A. V.; Grugel, R. N.; Lee, C. P.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    This presentation will examine in detail the role of vibration-induced streaming flow in the context of float-zone crystal growth. It is very well known that during float-zone materials processing, the naturally occurring temperature gradients along the zone surface impose a thermocapillary flow in the zone. Under certain processing conditions, the thermocapillary flow can also become nonsteady (oscillatory). The presence of thermocapillary flow is detrimental to crystal quality, for it can promote non-uniform dopant distribution and crystal striations. To null this effect we have imposed a counter streaming flow in the zone, via end-wall vibration. This technique has been adapted to float-zone processing of Sodium Nitrate-Barium Nitrate eutectic alloys, under both steady and nonsteady thermocapillary flow conditions. The beneficial effects of counter streaming flow have been clearly brought out through the before and after comparisons of the crystal microstructure. In addition, we are also examining the theoretical underpinnings of the balancing of thermocapillary flows with vibration-driven counter flows in float-zones.

  17. Role of Vibration-Induced Streaming in Float-Zone Crystal Growth

    NASA Technical Reports Server (NTRS)

    Anikumar, A. V.; Grugel, R. N.; Lee, C. P.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    This presentation will examine in detail the role of vibration-induced streaming flow in the context of float-zone crystal growth. It is very well known that during float-zone materials processing, the naturally occurring temperature gradients along the zone surface impose a thermocapillary flow in the zone. Under certain processing conditions, the thermocapillary flow can also become nonsteady (oscillatory). The presence of thermocapillary flow is detrimental to crystal quality, for it can promote non-uniform dopant distribution and crystal striations. To null this effect we have imposed a counter streaming flow in the zone, via end-wall vibration. This technique has been adapted to float-zone processing of Sodium Nitrate-Barium Nitrate eutectic alloys, under both steady and nonsteady thermocapillary flow conditions. The beneficial effects of counter streaming flow have been clearly brought out through the before and after comparisons of the crystal microstructure. In addition, we are also examining the theoretical underpinnings of the balancing of thermocapillary flows with vibration-driven counter flows in float-zones.

  18. Wind tunnel balance system for determination of wind-induced vibrations of a rigid shuttle model in the launch configuration

    NASA Technical Reports Server (NTRS)

    1971-01-01

    A wind tunnel balance system was designed to determine the wind-induced vibrations of a space shuttle model. The balance utilizes a flexible sting mounting in conjunction with a geometrically scaled rigid model. Bending and torsional displacements are determined through strain-gauge-instrumented spring bar mechanisms. The natural frequency of the string-model system can be varied continuously throughout the expected scaled frequency range of the shuttle vehicle while a test is in progress by the use of moveable riders on the spring bar mechanism. Through the use of a frequency analyzer, the output can be used to determine troublesome vibrational frequencies. A dimensional analysis of the wind-induced vibration problem is also presented which suggests a test procedure. In addition a computer program for analytical studies of the forced vibration problem is presented.

  19. Electron-induced excitation of vibrations of Ce atoms inside a C80 cage

    NASA Astrophysics Data System (ADS)

    Stróżecka, A.; Muthukumar, K.; Larsson, J. A.; Dybek, A.; Dennis, T. J. S.; Mysliveček, J.; Voigtländer, B.

    2011-04-01

    Inelastic electron tunneling spectroscopy of Ce2@C80 dimetallofullerenes reveals a low-energy inelastic excitation that is interpreted using ab initio calculations and associated with the movements of encapsulated Ce atoms inside the C80 cage. The electron-vibration interaction in Ce2@C80 is unusually high, inducing a pronounced zero-bias anomaly in differential conductance of Ce2@C80. Our observations show that the atoms encapsulated in fullerene cages can actively participate in determining the properties of molecular junctions.

  20. Comparative assessment of different treatment modalities in miners with vibration- and noise-induced disease

    SciTech Connect

    Velskaya, M.L.; Nekhorosheva, M.A.; Konovalova, S.I.; Kukhtina, G.V.; Gonchar, I.G.; Terentyeva, D.P.; Grishchenko, L.A.; Soboleva, N.P.; Kharitonov, S.A.; Priklonskiy, I.V.

    1985-02-01

    A group of 71 miners with vibration sickness and noise-induced pathology were managed either by standard methods, or in combination with acupuncture and/or hyperbaric oxygenation for a comparative assessment of the effectiveness of the different therapeutic approaches. Analysis of subjective factors as well as standard physiological parameters (EKG, rheoencephalography, peripheral rheography, EEG, neuropsychological tests) demonstrate that both acupuncture and hyperbaric oxygenation are effective modalities in the majority of the subjects. Nevertheless, the lack of improvement in certain criteria, or even what could be regarded as adverse sequelae, suggest that the use of hyperbaric oxygenation in the management of such disorders be approached with considerable care.

  1. Vibration-induced Kondo tunneling through metal-organic complexes with even electron occupation number.

    PubMed

    Kikoin, K; Kiselev, M N; Wegewijs, M R

    2006-05-05

    We investigate transport through a mononuclear transition-metal complex with strong tunnel coupling to two electrodes. The ground state of this molecule is a singlet, while the first excited state is a triplet. We show that a modulation of the tunnel-barrier due to a molecular distortion which couples to the tunneling induces a Kondo-effect, provided the discrete vibrational energy compensates the singlet-triplet gap. We discuss the single-phonon and two-phonon-assisted cotunneling and possible experimental realization of the theory.

  2. The influence of source-receiver interaction on the numerical prediction of railway induced vibrations

    NASA Astrophysics Data System (ADS)

    Coulier, P.; Lombaert, G.; Degrande, G.

    2014-06-01

    The numerical prediction of vibrations in buildings due to railway traffic is a complicated problem where wave propagation in the soil couples the source (railway tunnel or track) and the receiver (building). This through-soil coupling is often neglected in state-of-the-art numerical models in order to reduce the computational cost. In this paper, the effect of this simplifying assumption on the accuracy of numerical predictions is investigated. A coupled finite element-boundary element methodology is employed to analyze the interaction between a building and a railway tunnel at depth or a ballasted track at the surface of a homogeneous halfspace, respectively. Three different soil types are considered. It is demonstrated that the dynamic axle loads can be calculated with reasonable accuracy using an uncoupled strategy in which through-soil coupling is disregarded. If the transfer functions from source to receiver are considered, however, large local variations in terms of vibration insertion gain are induced by source-receiver interaction, reaching up to 10 dB and higher, although the overall wave field is only moderately affected. A global quantification of the significance of through-soil coupling is made, based on the mean vibrational energy entering a building. This approach allows assessing the common assumption in seismic engineering that source-receiver interaction can be neglected if the distance between source and receiver is sufficiently large compared to the wavelength of waves in the soil. It is observed that the interaction between a source at depth and a receiver mainly affects the power flow distribution if the distance between source and receiver is smaller than the dilatational wavelength in the soil. Interaction effects for a railway track at grade are observed if the source-receiver distance is smaller than six Rayleigh wavelengths. A similar trend is revealed if the passage of a freight train is considered. The overall influence of dynamic

  3. Atom-membrane cooling and entanglement using cavity electromagnetically induced transparency

    SciTech Connect

    Genes, Claudiu; Ritsch, Helmut; Drewsen, Michael; Dantan, Aurelien

    2011-11-15

    We investigate a hybrid optomechanical system composed of a micromechanical oscillator as a movable membrane and an atomic three-level ensemble within an optical cavity. We show that a suitably tailored cavity field response via electromagnetically induced transparency (EIT) in the atomic medium allows for strong coupling of the membrane's mechanical oscillations to the collective atomic ground-state spin. This facilitates ground-state cooling of the membrane motion, quantum state mapping, and robust atom-membrane entanglement even for cavity widths larger than the mechanical resonance frequency.

  4. Empirical evidence for a recent slowdown in irrigation-induced cooling

    SciTech Connect

    Bonfils, C; Lobell, D

    2007-01-19

    Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (-0.15 to -0.25 C.decade{sup -1}), which corresponds to a cooling estimated at -2.0 - -3.3 C since the introduction of irrigation practice. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (-0.06 to -0.19 C.decade{sup -1}). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for most irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broadscale temperatures, but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide roughly 40% of global food production.

  5. Effects of cooling on histamine-induced contractions of human umbilical artery: the role of ion channels.

    PubMed

    Atalik, K E; Kiliç, M; Nurullahoğlu, Z U; Doğan, N

    2007-11-01

    The effects of cooling (to 28 degrees C) on histamine (10(-9) - 3 x 10(-4) M)-induced contractions and the role of calcium (Ca(2+)), potassium (K(Ca) (2+)) and sodium (Na(+)) channel blockers in the cooling-induced responses were investigated in the endothelium-denuded human umbilical artery. Concentration-response curves to histamine were isometrically recorded at 37 and 28 degrees C (control). The same procedure was repeated at 28 degrees C in the presence of tetraethylammonium (TEA, 10(-3) M), pilsicainide (10(-6) M), ouabain (10(-6) M), caffeine (3 x 10(-4) M), verapamil (10(-6) M) and also in Ca(2+)-free medium with ethylene glycol bis-(beta-aminoethyl ether) N,N,N(1),N(1)-tetraacetic acid (EGTA). During cooling, the sensitivity, but not the maximal response, was significantly higher than 37 degrees C. Cooling to 28 degrees C after treatment with verapamil or pilsicainide decreased the sensitivity, whereas treatment with TEA and ouabain significantly increased sensitivity. Treatment with caffeine did not modify the effect of cooling. Furthermore, cooling to 28 degrees C after incubation in Ca(2+)-free solution with EGTA decreased the sensitivity to histamine. The results of this study suggest the role of Ca(2+), K(Ca) (2+) and Na(+)-ion channels in the cooling-induced changes of human umbilical arteries treated with histamine.

  6. [Occupational therapy for work-related damage induced by mechanical vibration].

    PubMed

    Foti, C; Ciocchetti, E; Antignani, E; Pitruzzella, M; Laurini, A

    2010-01-01

    Vibrations are defined as repeated oscillatory movements of a body; they can be transmitted by contact to humans. From the point of view of physics, vibrations can be differentiated on the basis of frequency, wavelength, amplitude of the oscillation, velocity and acceleration. As far as concerns occupational hazards, two risk factors have been identified: the first involves low frequency vibrations (vehicle drivers), while the second involves high frequency vibrations (manual percussion tools). The transmission of vibration energy can be localized or generalized. Tertiary prevention of exposure to vibrations is based on the use of anti-vibration gloves (for vibrations of the hand and arm) and on anti-vibration shoes (for vibrations of the whole body). The damage caused by vibrations is due to reduced blood circulation and mechanical stimulation in the joints exposed.

  7. Strain-induced vibration and temperature sensing BOTDA system combined frequency sweeping and slope-assisted techniques.

    PubMed

    Hu, Junhui; Xia, Lan; Yang, Li; Quan, Wenwen; Zhang, Xuping

    2016-06-13

    A BOTDA sensing scheme combined frequency sweeping and slope-assisted techniques is proposed and experimentally demonstrated for simultaneously temperature and strain-induced vibration sensing. In this scheme, during sweeping Brillouin gain spectrum (BGS) for temperature measurement, we simultaneously perform FFT to the time-domain traces whose probe-pump frequency difference (PPFD) is within the FWHM of the BGS at each position of fiber, and the location and the frequency of the strain-induced vibration event can be acquired based on SA-BOTDA technique. In this way, the vibration can be continuously measured at each selected working frequency point during the BGS scanning process and multiple measurements of vibration event can be completed in one whole BGS scanning process. Meanwhile, double sidebands probe method is employed to reduce the nonlocal effects. In our experiment, a temperature event and two vibration events with the frequency of 7.00Hz or 10.00Hz are simultaneously measured near the end of 10.6km long sensing fiber in a traditional BOTDA system. The system shows 1.2°C temperature accuracy and 0.67Hz frequency resolution, as well as a 3m spatial resolution. The proposed method may find some potential applications where both the strain-induced vibration frequency and temperature are the diagnostic objects.

  8. Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior.

    PubMed

    Van Nimmen, Katrien; Lombaert, Geert; De Roeck, Guido; Van den Broeck, Peter

    2016-04-13

    For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

  9. The Skull Vibration-Induced Nystagmus Test of Vestibular Function—A Review

    PubMed Central

    Dumas, Georges; Curthoys, Ian S.; Lion, Alexis; Perrin, Philippe; Schmerber, Sébastien

    2017-01-01

    A 100-Hz bone-conducted vibration applied to either mastoid induces instantaneously a predominantly horizontal nystagmus, with quick phases beating away from the affected side in patients with a unilateral vestibular loss (UVL). The same stimulus in healthy asymptomatic subjects has little or no effect. This is skull vibration-induced nystagmus (SVIN), and it is a useful, simple, non-invasive, robust indicator of asymmetry of vestibular function and the side of the vestibular loss. The nystagmus is precisely stimulus-locked: it starts with stimulation onset and stops at stimulation offset, with no post-stimulation reversal. It is sustained during long stimulus durations; it is reproducible; it beats in the same direction irrespective of which mastoid is stimulated; it shows little or no habituation; and it is permanent—even well-compensated UVL patients show SVIN. A SVIN is observed under Frenzel goggles or videonystagmoscopy and recorded under videonystagmography in absence of visual-fixation and strong sedative drugs. Stimulus frequency, location, and intensity modify the results, and a large variability in skull morphology between people can modify the stimulus. SVIN to 100 Hz mastoid stimulation is a robust response. We describe the optimum method of stimulation on the basis of the literature data and testing more than 18,500 patients. Recent neural evidence clarifies which vestibular receptors are stimulated, how they cause the nystagmus, and why the same vibration in patients with semicircular canal dehiscence (SCD) causes a nystagmus beating toward the affected ear. This review focuses not only on the optimal parameters of the stimulus and response of UVL and SCD patients but also shows how other vestibular dysfunctions affect SVIN. We conclude that the presence of SVIN is a useful indicator of the asymmetry of vestibular function between the two ears, but in order to identify which is the affected ear, other information and careful clinical judgment are

  10. Laser Induced Fluorescence Spectroscopy of Jet Cooled SiCN : Rotational Analysis of the Hot Bands

    NASA Astrophysics Data System (ADS)

    Fukushima, Masaru; Ishiwata, Takashi

    2013-06-01

    We have generated SiCN in supersonic free jet expansions, and observed the laser induced fluorescence ( LIF ) of the vibrationally hot bands of the ˜{A} ^2Δ - ˜{X} ^2Π transition. We have measured dispersed fluorescence ( DF ) spectra from the single vibronic levels ( SVL's ), ˜{A} (01^10) ^2Φ and ^2Π, and rotationally resolved LIF excitation spectra of the two hot bands, ˜{A} (01^10) ^2Φ - ˜{X} (01^10) ^2Δ and ˜{A} (01^10) ^2Π - ˜{X} (01^10) ^2Σ^{(-)}. The rotational energy levels were reasonably analyzed as those of the ^2K' - ^2K'' transitions, but their line intensities calculated from the Hönl-London factors derived in the intermediate case between Hund's case (a) and (b) could not reproduce the observed spectra. The Hönl-London factors derived in the ^2Λ' - ^2Λ'' ( ^2Δ - ^2Π ) transition reasonably reproduced the spectra. It indicates that coupling between the electronic orbital and vibrational angular momenta is weak in the SiCN ^2Δ - ^2Π system, and a basis set of |Λ v_2 l Σ; J P M_Jrangle, so-called ''l-basis", better describes the system than that of |Λ v_2 K Σ; J P M_Jrangle.

  11. Quantitative probing of tip-induced local cooling with a resistive nanoheater/thermometer

    NASA Astrophysics Data System (ADS)

    Hamian, Sina; Yun, Jeonghoon; Park, Inkyu; Park, Keunhan

    2016-12-01

    This article reports the investigation of tip-induced local cooling when an atomic force microscope (AFM) cantilever tip scans over a joule-heated Pt nanowire. We fabricated four-point-probe Pt resistive nanothermometers having a sensing area of 250 nm × 350 nm by combining electron-beam lithography and photolithography. The electrical resistance of a fabricated nanothermometer is ˜27.8 Ω at room temperature and is linearly proportional to the temperature increase up to 350 K. The equivalent temperature coefficient of resistance is estimated to be (7.0 ±0.1 )×10-4 K-1. We also joule-heated a nanothermometer to increase its sensing area temperature up to 338.5 ± 0.2 K, demonstrating that the same device can be used as a nanoheater. An AFM probe tip scanning over a heated nanoheater/thermometer's sensing area induces local cooling due to heat conduction through solid-solid contact, water meniscus, and surrounding air. The effective contact thermal conductance is 32.5 ± 0.8 nW/K. These results contribute to the better understanding of tip-substrate thermal interactions, which is the fundamental subject in tip-based thermal engineering applications.

  12. Vortex-Induced Vibration of a Circular Cylinder Fitted with a Single Spanwise Tripwire

    NASA Astrophysics Data System (ADS)

    Vaziri, Ehsan; Ekmekci, Alis

    2016-11-01

    A spanwise tripwire can be used to alter the coherence and strength of the vortex shedding from cylindrical structures. While this has been well-documented for cylinders in stationary state, there exists a lack of understanding regarding the control induced by spanwise tripwires for cylinders undergoing vortex-induced vibration (VIV). The current experimental research investigates the consequences of spanwise tripping on VIV of a cylinder. Experiments are conducted in a recirculating water tunnel at a Reynolds number of 10,000. The test setup allows the rigid test cylinder to have one-degree-of-freedom vibration in the cross-flow direction as a result of fluid forcing. To measure the cylinder motion, a high-resolution laser displacement sensor is used. The tripwire diameter to cylinder diameter ratio is fixed at 6.1%. Various angular positions of tripwire are studied ranging from 40 to 90 degrees. It is shown that the tripwire location controls the pattern, amplitude, frequency, and mid-position of oscillations significantly. Different oscillation modes are classified based on the observed oscillation pattern, amplitude and frequency. Oscillation amplitude can be reduced by 61% with respect to the amplitude of a clean cylinder undergoing VIV under the same flow condition.

  13. Suppression of vortex-induced vibration of a circular cylinder using thermal effects

    NASA Astrophysics Data System (ADS)

    Wan, Hui; Patnaik, Soumya S.

    2016-12-01

    Transverse vortex-induced vibration (VIV) of a cylinder with various body-to-fluid density ratio and stiffness is studied. The cylinder is elastically mounted and heated, and the flow direction is aligned with the direction of the thermal induced buoyancy force. Amplitude of VIV can be reduced as the thermal control parameter Richardson number (Ri) increases, or even be fully suppressed when Ri is above a critical value. This critical Richardson number depends on both body-to-fluid density and structural stiffness. A higher critical Richardson is required to fully suppress the VIV of a structure with smaller density ratio. With the same density or mass, a structure with intermediate stiffness vibrating in lock-in regime needs higher critical Ri to suppress VIV than either rigid or flexible structures. Drag experienced by the body is also studied. It is found that for a flexible body, drag gradually increases with the Richardson number. For a body with intermediate stiffness, both drag and amplitude of VIV can be reduced until the Richardson number reaches the critical value, after which drag builds up if the Richardson number is further increased. A drag reduction of 30%-40% can be obtained at the critical Richardson number.

  14. Friction-induced whirl vibration: root cause of squeaking in total hip arthroplasty.

    PubMed

    Weiss, Cornelius; Hothan, Arne; Huber, Gerd; Morlock, Michael M; Hoffmann, Norbert P

    2012-01-10

    Squeaking is reported for ceramic-on-ceramic hip arthroplasty, and risk factors leading to this phenomenon have been investigated empirically in the past, this way giving hints to when this phenomenon occurs. The aim of this study is to present an experimentally validated explanation for the dynamical mechanism underlying the squeak, i.e. a description of what happens when noise is generated. First the kinematics of the ceramic bearing couple in relative motion are reconsidered. The relative motion at the contact zone can be understood as superposition of relative rotation and translation. The relative weight of both components depends substantially on the instantaneous load vector, which primarily determines the position of the contact area, and the instantaneous relative rotation vector. For the investigated gait scenarios, both load vector and rotation axis vary strongly during the gait cycle. Second, experimental vibration analysis during squeak is performed. A pronounced micrometer scale elliptical motion of the ball inside the liner is found. It is shown that the rotational component of the relative kinematics during gait indeed leads to friction induced vibrations. We show that a generic whirl type friction induced flutter instability, also known from similar (non bio-) mechanical systems, is the root cause of the emitted squeaking noise. Based on the identified mechanism, the role of THA system parameters (materials, design), patient risk factors, as well as the role of the gait cycle, will have to be reconsidered and linked in the future to develop effective measures against squeaking.

  15. Hydrodynamic mechanism behind the suppression of vortex-induced vibration with permeable meshes

    NASA Astrophysics Data System (ADS)

    Assi, Gustavo R. S.; Cicolin, Murilo M.; Freire, Cesar M.

    2016-11-01

    Vortex-induced vibration (VIV) induces resonant vibrations on elastic bluff bodies when exposed to a flow. A VIV suppressor called "ventilated trousers" (VT) - consisting of a flexible net with tens of bobbins fitted every other node - has been developed as a commercial solution. Only a few experiments in the literature have evaluated the effectiveness of the VT, but very little is know about the underlying mechanism behind the suppression. Experiments have been carried out in a water channel with models of circular cylinders fitted with three different permeable meshes. VIV response and drag were obtained for models free to oscillate in the cross-flow direction with low mass and damping (Re = 5 , 000 to 25,000). All meshes achieved an average 50% reduction of the peak amplitude and reduced the mean drag when compared to that of a bare cylinder. PIV visualization of the wake revealed that the VT produced a much longer vortex-formation length, thus explaining its enhanced efficiency in suppressing VIV and reducing drag. The geometry and distribution of the bobbins proved to be important parameters. PIV also revealed the rich three-dimensional flow structures created by the bobbins that disrupt the formation of a coherent vortex wake. FAPESP 11/00205-6, 14/50279-4; CNPq 306917/2015-7.

  16. Vortex-induced vibrations of a neutrally buoyant circular cylinder near a plane wall

    NASA Astrophysics Data System (ADS)

    Wang, X. K.; Hao, Z.; Tan, S. K.

    2013-05-01

    This paper presents an experimental study of the motions, drag force and vortex shedding patterns of an elastically mounted circular cylinder, which is held at various heights above a plane wall and is subject to vortex-induced vibration (VIV) in the transverse direction. The cylinder is neutrally buoyant with a mass ratio m=1.0 and has a low damping ratio ζ=0.0173. Effects of the gap ratio (S/D) ranged from 0.05 to 2.5 and the free-stream velocity (U) ranged from 0.15 to 0.65m/s (corresponding to 3000≤Re≤13 000, and 1.53≤U≤6.62) are examined. The flow around the cylinder has been measured using particle image velocimetry (PIV), in conjunction with direct measurements of the dynamic drag force on the cylinder using a piezoelectric load cell. Results of the vibrating cylinder under unbounded (or free-standing) condition, as well as those of a near-wall stationary cylinder at the same gap ratios, are also provided. For the free-standing cylinder, the transition from the initial branch to the upper branch is characterized by a switch of vortex pattern from the classical 2S mode to the newly-discovered 2PO mode by Morse and Williamson (2009). The nearby wall not only affects the amplitude and frequency of vibration, but also leads to non-linearities in the cylinder response as evidenced by the presence of super-harmonics in the drag force spectrum. In contrast to the case of a stationary cylinder that vortex shedding is suppressed below a critical gap ratio (S/D≈0.3), the elastically mounted cylinder always vibrates even at the smallest gap ratio S/D=0.05. Due to the proximity of the plane wall, the vortices shed from the vibrating cylinder that would otherwise be in a double-sided vortex street pattern (either 2S or 2PO mode) under free-standing condition are arranged into a single-sided pattern.

  17. Use of in vitro human keratinocyte models to study the effect of cooling on chemotherapy drug-induced cytotoxicity.

    PubMed

    Al-Tameemi, Wafaa; Dunnill, Christopher; Hussain, Omar; Komen, Manon M; van den Hurk, Corina J; Collett, Andrew; Georgopoulos, Nikolaos T

    2014-12-01

    A highly distressing side-effect of cancer chemotherapy is chemotherapy-induced alopecia (CIA). Scalp cooling remains the only treatment for CIA, yet there is no experimental evidence to support the cytoprotective capacity of cooling. We have established a series of in vitro models for the culture of human keratinocytes under conditions where they adopt a basal, highly-proliferative phenotype thus resembling the rapidly-dividing sub-population of native hair-matrix keratinocytes. Using a panel of chemotherapy drugs routinely used clinically (docetaxel, doxorubicin and the active metabolite of cyclophosphamide 4-OH-CP), we demonstrate that although these drugs are highly-cytotoxic, cooling can markedly reduce or completely inhibit drug cytotoxicity, in agreement with clinical observations. By contrast, we show that cytotoxicity caused by specific combinatorial drug treatments cannot be adequately attenuated by cooling, supporting data showing that such treatments do not always respond well to cooling clinically. Importantly, we provide evidence that the choice of temperature may be critical in determining the efficacy of cooling in rescuing cells from drug-mediated toxicity. Therefore, despite their reductive nature, these in vitro models have provided experimental evidence for the clinically-reported cytoprotective role of cooling and represent useful tools for future studies on the molecular mechanisms of cooling-mediated cytoprotection.

  18. Vibration mitigation for wind-induced jitter for the Giant Magellan Telescope

    NASA Astrophysics Data System (ADS)

    Glaese, Roger M.; Sheehan, Michael

    2012-09-01

    The Giant Magellan Telescope (GMT) is a planned large terrestrial telescope with a segmented primary mirror with a 24.5 meter overall diameter. Like most terrestrial telescopes, the GMT resides within an enclosure designed to protect the telescope from the elements and to reduce the effects of wind on the optical performance of the telescope. Wind impingement on the telescope causes static deformation and vibration in the telescope structure that affects the alignment and image jitter performance of the telescope. Actively controlled primary mirror segments and a secondary mirror can correct for the static and low frequency portions of the wind effects, but typically the actuators do not have the bandwidth to address higher frequency components of the wind environment. Preliminary analyses on the GMT indicate that the image jitter associated with wind effects meets budgeted allowances but without much margin. Preliminary models show that the bulk of the residual jitter arises from excitation of a small number of modes in the 9 to 12 Hz range. Therefore, as a risk mitigation effort to increase the margin on the wind induced jitter, passive and active vibration mitigation approaches have been examined for the GMT, which will be the focus of this paper. Using a finite element model of the GMT along with wind loading load cases, several passive and active vibration mitigation approaches were analyzed. These approaches include passive approaches such as tuned mass dampers targeting the worst offending modes, and constrained layer damping targeting all of the modes within the troublesome frequency range. Active approaches evaluated include two active damping approaches, one using several reaction mass actuators and the other using active strut type actuators. The results of the study show that although all approaches are successful in reducing the jitter, the active damping approach using reaction mass actuators offers the lightest weight, least implementation impact

  19. Empirical evidence for a recent slowdown in irrigation-induced cooling

    PubMed Central

    Bonfils, Céline; Lobell, David

    2007-01-01

    Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (−0.14°C to −0.25°C per decade), which corresponds to an estimated cooling of −1.8°C to −3.2°C since the introduction of irrigation practices. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (−0.06°C to −0.19°C per decade). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for many irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broad-scale temperatures, but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide ≈40% of global food production. PMID:17698963

  20. Development and modelisation of a hydro-power conversion system based on vortex induced vibration

    NASA Astrophysics Data System (ADS)

    Lefebure, David; Dellinger, Nicolas; François, Pierre; Mosé, Robert

    2016-11-01

    The Vortex Induced Vibration (VIV) phenomenon leads to mechanical issues concerning bluff bodies immerged in fluid flows and have therefore been studied by numerous authors. Moreover, an increasing demand for energy implies the development of alternative, complementary and renewable energy solutions. The main idea of EauVIV project consists in the use of VIV rather than its deletion. When rounded objects are immerged in a fluid flow, vortices are formed and shed on their downstream side, creating a pressure imbalance resulting in an oscillatory lift. A convertor modulus consists of an elastically mounted, rigid cylinder on end-springs, undergoing flow- induced motion when exposed to transverse fluid-flow. These vortices induce cyclic lift forces in opposite directions on the circular bar and cause the cylinder to vibrate up and down. An experimental prototype was developed and tested in a free-surface water channel and is already able to recover energy from free-stream velocity between 0.5 and 1 m.s -1. However, the large number of parameters (stiffness, damping coefficient, velocity of fluid flow, etc.) associated with its performances requires optimization and we choose to develop a complete tridimensionnal numerical model solution. A 3D numerical model has been developed in order to represent the real system behavior and improve it through, for example, the addition of parallel cylinders. The numerical model build up was carried out in three phases. The first phase consists in establishing a 2D model to choose the turbulence model and quantify the dependence of the oscillations amplitudes on the mesh size. The second corresponds to a 3D simulation with cylinder at rest in first time and with vertical oscillation in a second time. The third and final phase consists in a comparison between the experimental system dynamic behavior and its numerical model.

  1. Current-Induced Cooling Phenomenon in a Two-Dimensional Electron Gas Under a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Hirayama, Naomi; Endo, Akira; Fujita, Kazuhiro; Hasegawa, Yasuhiro; Hatano, Naomichi; Nakamura, Hiroaki; Shirasaki, Ryōen; Yonemitsu, Kenji

    2013-07-01

    We investigate the spatial distribution of temperature induced by a dc current in a two-dimensional electron gas (2DEG) subjected to a perpendicular magnetic field. We numerically calculate the distributions of the electrostatic potential ϕ and the temperature T in a 2DEG enclosed in a square area surrounded by insulated-adiabatic (top and bottom) and isopotential-isothermal (left and right) boundaries (with ϕ left< ϕ right and T left= T right), using a pair of nonlinear Poisson equations (for ϕ and T) that fully take into account thermoelectric and thermomagnetic phenomena, including the Hall, Nernst, Ettingshausen, and Righi-Leduc effects. We find that, in the vicinity of the left-bottom corner, the temperature becomes lower than the fixed boundary temperature, contrary to the naive expectation that the temperature is raised by the prevalent Joule heating effect. The cooling is attributed to the Ettingshausen effect at the bottom adiabatic boundary, which pumps up the heat away from the bottom boundary. In order to keep the adiabatic condition, downward temperature gradient, hence the cooled area, is developed near the boundary, with the resulting thermal diffusion compensating the upward heat current due to the Ettingshausen effect.

  2. Use of a laser-induced fluorescence thermal imaging system for film cooling heat transfer measurement

    SciTech Connect

    Chyu, M.K.

    1996-04-01

    This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:Eu{sup +3}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.

  3. Use of a laser-induced fluorescence thermal imaging system for film cooling heat transfer measurement

    SciTech Connect

    Chyu, M.K.

    1995-10-01

    This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:EU{sup 3+}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.

  4. Spin-orbit-coupling-induced backaction cooling in cavity optomechanics with a Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Yasir, Kashif Ammar; Zhuang, Lin; Liu, Wu-Ming

    2017-01-01

    We report a spin-orbit-coupling-induced backaction cooling in an optomechanical system, composed of a spin-orbit-coupled Bose-Einstein condensate trapped in an optical cavity with one movable end mirror, by suppressing heating effects of quantum noises. The collective density excitations of the spin-orbit-coupling-mediated hyperfine states—serving as atomic oscillators equally coupled to the cavity field—trigger strongly driven atomic backaction. We find that the backaction not only revamps low-temperature dynamics of its own but also provides an opportunity to cool the mechanical mirror to its quantum-mechanical ground state. Further, we demonstrate that the strength of spin-orbit coupling also superintends dynamic structure factor and squeezes nonlinear quantum noises, like thermomechanical and photon shot noise, which enhances optomechanical features of the hybrid cavity beyond previous investigations. Our findings are testable in a realistic setup and enhance the functionality of cavity optomechanics with spin-orbit-coupled hyperfine states in the field of quantum optics and quantum computation.

  5. Wall-Thickness Dependence of Cooling-Induced Deformation of Polystyrene Spherical Shells

    SciTech Connect

    Endo, T.; Kobayashi, N.; Goto, K.; Yasuda, M.; Fujima, Y.

    2003-05-15

    Experiments on the wall-thickness dependence of the cooling-induced deformation (CID) of polystyrene (PS) spherical shells were carried out. For the experiments, the PS shells were fabricated by the density-matched emulsion method using the hand-shaken microencapsulation technique. The number-averaged and weight-averaged molecular weights of the PS were M{sub n} 1.1 x 10{sup 5} and M{sub w} = 4.0 x 10{sup 5}, respectively. The diameter of the PS shells was {approx}400-550 {mu}m. To investigate the wall-thickness dependence of the CID, the wall thickness of the PS shells was varied between 5 and 60 {mu}m. In the experiments, the PS shells were cooled by using liquid nitrogen, and their images were captured at 0 and -190 deg. C. For the investigation of the CID, two shapes of each shell that were measured at 0 and -190 deg. C were compared. The thinner PS shells showed larger CID. The maximum deformation was almost 1% of the outer radius when the shell aspect ratio (outer radius)/(wall thickness) was higher than 20. The repeatability of the CID was studied, and the results implied that residual stress in the PS shells had an influence on the CID.

  6. Artificial piezoelectric grass for energy harvesting from turbulence-induced vibration

    NASA Astrophysics Data System (ADS)

    Hobeck, J. D.; Inman, D. J.

    2012-10-01

    The primary objective of this research is to develop a deploy-and-forget energy harvesting device for use in low-velocity, highly turbulent fluid flow environments i.e. streams or ventilation systems. The work presented here focuses on a novel, lightweight, highly robust, energy harvester design referred to as piezoelectric grass. This biologically inspired design consists of an array of cantilevers, each constructed with piezoelectric material. When exposed to proper turbulent flow conditions, these cantilevers experience vigorous vibrations. Preliminary results have shown that a small array of piezoelectric grass was able to produce up to 1.0 mW per cantilever in high-intensity turbulent flow having a mean velocity of 11.5 m s-1. According to the literature, this is among the highest output achieved using similar harvesting methods. A distributed parameter model for energy harvesting from turbulence-induced vibration will be introduced and experimentally validated. This model is generalized for the case of a single cantilever in turbulent cross-flow. Two high-sensitivity pressure probes were needed to perform spectral measurements within various turbulent flows. The design and performance of these probes along with calibration and measurement techniques will be discussed.

  7. Solvent induced conformational fluctuation of alanine dipeptide studied by using vibrational probes

    NASA Astrophysics Data System (ADS)

    Cai, Kaicong; Du, Fenfen; Liu, Jia; Su, Tingting

    2015-02-01

    The solvation effect on the three dimensional structure and the vibrational feature of alanine dipeptide (ALAD) was evaluated by applying the implicit solvents from polarizable continuum solvent model (PCM) through ab initio calculations, by using molecular dynamic (MD) simulations with explicit solvents, and by combining these two approaches. The implicit solvent induced potential energy fluctuations of ALAD in CHCl3, DMSO and H2O are revealed by means of ab initio calculations, and a global view of conformational and solvation environmental dependence of amide I frequencies is achieved. The results from MD simulations with explicit solvents show that ALAD trends to form PPII, αL, αR, and C5 in water, PPII and C5 in DMSO, and C5 in CHCl3, ordered by population, and the demonstration of the solvated structure, the solute-solvent interaction and hydrogen bonding is therefore enhanced. Representative ALAD-solvent clusters were sampled from MD trajectories and undergone ab initio calculations. The explicit solvents reveal the hydrogen bonding between ALAD and solvents, and the correlation between amide I frequencies and the Cdbnd O bond length is built. The implicit solvents applied to the ALAD-solvent clusters further compensate the solvation effect from the bulk, and thus enlarge the degree of structural distortion and the amide I frequency red shift. The combination of explicit solvent in the first hydration shell and implicit solvent in the bulk is helpful for our understanding about the conformational fluctuation of solvated polypeptides through vibrational probes.

  8. Electronic, structural and vibrational induced effects upon ionization of 2-quinolinone

    NASA Astrophysics Data System (ADS)

    Bellili, A.; Pan, Y.; Al Mogren, M. M.; Lau, K. C.; Hochlaf, M.

    2016-07-01

    Using first principle methodologies, we characterize the lowest electronic states of 2-quinolinone+ cation. The ground state of this ion is of X˜2A″ nature. We deduce the adiabatic ionization energy of 2-quinolinone to be equal 8.249 eV using the explicitly correlated coupled cluster level and where zero point vibrational energy, core-valence and scalar relativistic effects are taken into account. We examine also the ionization induced structural changes and vibrational shifts and analyze the electron density differences between the neutral and ionic species. These data show that the formation of 2-quinolinone+X˜2A″ from 2-quinolinone affects strongly the HNCO group, whereas the carbon skeletal is perturbed when the upper electronic cationic states are populated. The comparison to 2-pyridone allows the elucidation of the effect of benzene ring fused with this heterocyclic ring. Since quinolones and pyridones are both model systems of DNA bases, these findings might help in understanding the charge redistribution in these biological entities upon ionization.

  9. Frequency weighting for vibration-induced white finger compatible with exposure-response models.

    PubMed

    Brammer, Anthony J; Pitts, Paul M

    2012-01-01

    An analysis has been performed to derive a frequency weighting for the development of vibration-induced white finger (VWF). It employs a model to compare health risks for pairs of population groups that are selected to have similar health outcomes from operating power tools or machines with markedly different acceleration spectra (rock drills, chain saws, pavement breakers and motorcycles). The model defines the Relative Risk, RR(f(trial)), which is constructed from the ratio of daily exposures and includes a trial frequency weighting that is applied to the acceleration spectra. The trial frequency weighting consists of a frequency-independent primary frequency range, and subordinate frequency ranges in which the response to vibration diminishes, with cut-off frequencies that are changed to influence the magnitude of RR(f(trial)). The frequency weighting so derived when RR(f(trial)) = 1 is similar to those obtained by other methods (W(hf), W(hT)). It consists of a frequency independent range from about 25 Hz to 500 Hz (-3 dB frequencies), with an amplitude cut-off rate of 12 dB/octave below 25 Hz and above 500 Hz. The range is compatible with studies of vasoconstriction in persons with VWF. The results provide further evidence that the ISO frequency weighting may be inappropriate for assessing the risk of developing VWF.

  10. Hummingbird feather sounds are produced by aeroelastic flutter, not vortex-induced vibration.

    PubMed

    Clark, Christopher J; Elias, Damian O; Prum, Richard O

    2013-09-15

    Males in the 'bee' hummingbird clade produce distinctive, species-specific sounds with fluttering tail feathers during courtship displays. Flutter may be the result of vortex shedding or aeroelastic interactions. We investigated the underlying mechanics of flutter and sound production of a series of different feathers in a wind tunnel. All feathers tested were capable of fluttering at frequencies varying from 0.3 to 10 kHz. At low airspeeds (Uair) feather flutter was highly damped, but at a threshold airspeed (U*) the feathers abruptly entered a limit-cycle vibration and produced sound. Loudness increased with airspeed in most but not all feathers. Reduced frequency of flutter varied by an order of magnitude, and declined with increasing Uair in all feathers. This, along with the presence of strong harmonics, multiple modes of flutter and several other non-linear effects indicates that flutter is not simply a vortex-induced vibration, and that the accompanying sounds are not vortex whistles. Flutter is instead aeroelastic, in which structural (inertial/elastic) properties of the feather interact variably with aerodynamic forces, producing diverse acoustic results.

  11. Wake reconfiguration downstream of an inclined flexible cylinder at the onset of vortex-induced vibrations

    NASA Astrophysics Data System (ADS)

    Bourguet, Remi; Triantafyllou, Michael

    2016-11-01

    Slender flexible cylinders immersed in flow are common in nature (e.g. plants and trees in wind) and in engineering applications, for example in the domain of offshore engineering, where risers and mooring lines are exposed to ocean currents. Vortex-induced vibrations (VIV) naturally develop when the cylinder is placed at normal incidence but they also appear when the body is inclined in the current, including at large angles. In a previous work concerning a flexible cylinder inclined at 80 degrees, we found that the occurrence of VIV is associated with a profound alteration of the flow dynamics: the wake exhibits a slanted vortex shedding pattern in the absence of vibration, while the vortices are shed parallel to the body once the large-amplitude VIV regime is reached. The present study aims at bridging the gap between these two extreme configurations. On the basis of direct numerical simulations, we explore the intermediate states of the flow-structure system. We identify two dominant components of the flow: a high-frequency component that relates to the stationary body wake and a low-frequency component synchronized with body motion. We show that the scenario of flow reconfiguration is driven by the opposite trends of these two component contributions.

  12. Solvent induced conformational fluctuation of alanine dipeptide studied by using vibrational probes.

    PubMed

    Cai, Kaicong; Du, Fenfen; Liu, Jia; Su, Tingting

    2015-02-25

    The solvation effect on the three dimensional structure and the vibrational feature of alanine dipeptide (ALAD) was evaluated by applying the implicit solvents from polarizable continuum solvent model (PCM) through ab initio calculations, by using molecular dynamic (MD) simulations with explicit solvents, and by combining these two approaches. The implicit solvent induced potential energy fluctuations of ALAD in CHCl3, DMSO and H2O are revealed by means of ab initio calculations, and a global view of conformational and solvation environmental dependence of amide I frequencies is achieved. The results from MD simulations with explicit solvents show that ALAD trends to form PPII, αL, αR, and C5 in water, PPII and C5 in DMSO, and C5 in CHCl3, ordered by population, and the demonstration of the solvated structure, the solute-solvent interaction and hydrogen bonding is therefore enhanced. Representative ALAD-solvent clusters were sampled from MD trajectories and undergone ab initio calculations. The explicit solvents reveal the hydrogen bonding between ALAD and solvents, and the correlation between amide I frequencies and the CO bond length is built. The implicit solvents applied to the ALAD-solvent clusters further compensate the solvation effect from the bulk, and thus enlarge the degree of structural distortion and the amide I frequency red shift. The combination of explicit solvent in the first hydration shell and implicit solvent in the bulk is helpful for our understanding about the conformational fluctuation of solvated polypeptides through vibrational probes.

  13. SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars

    NASA Astrophysics Data System (ADS)

    Aringer, B.; Höfner, S.; Wiedemann, G.; Hron, J.; Jørgensen, U. G.; Käufl, H. U.; Windsteig, W.

    1999-02-01

    The first overtone rotation-vibration transitions of SiO give rise to prominent bandheads in the wavelength range between 4.0 and 4.5 mu m. In order to study the behaviour of these features in AGB stars we observed the 3.94 to 4.12 mu m spectra for a sample of 23 oxygen-rich late-type variables. In contrast to the SRb objects, the Miras show a very large scatter of the equivalent widths of the SiO bands. Despite their cool temperatures some of them have only weak or no SiO absorption, which seems to be related to their strong pulsations producing a large variability of the features. When comparing the band intensities with photometric data, we found a general decrease with bluer IRAS (12-25) colors. However, this trend may only reflect the different behaviour of the Miras and SRb stars in our sample. We did not discover any correlation of the equivalent widths with the effective temperatures derived from (J-K), or with the (K-12) color and the IRAS-LRS class, both of which can be regarded as a rough measure for the thickness of the circumstellar shell. In Paper I of this series (Aringer et al. \\cite{siop}) we have shown that synthetic spectra calculated from hydrostatic MARCS atmospheres are successful in reproducing the observed band intensities of giants with spectral types earlier than about M5 III and M2 II\\@. However, they generally predict too strong features for very cool and extended objects, as they are discussed in this work. And they fail completely when it comes to Miras with weak or no SiO absorption. These stars are dominated by dynamical phenomena and, not surprisingly, they can therefore not be described by hydrostatic structures. Thus, we have also computed synthetic spectra based on experimental dynamical models. Although they still have some shortcomings, we demonstrate that, in principle, they are able to explain the whole range of equivalent widths of the observed SiO bandheads and their variations. Based on observations made at the European

  14. Fast optical cooling of nanomechanical cantilever with the dynamical Zeeman effect.

    PubMed

    Zhang, Jian-Qi; Zhang, Shuo; Zou, Jin-Hua; Chen, Liang; Yang, Wen; Li, Yong; Feng, Mang

    2013-12-02

    We propose an efficient optical electromagnetically induced transparency (EIT) cooling scheme for a cantilever with a nitrogen-vacancy center attached in a non-uniform magnetic field using dynamical Zeeman effect. In our scheme, the Zeeman effect combined with the quantum interference effect enhances the desired cooling transition and suppresses the undesired heating transitions. As a result, the cantilever can be cooled down to nearly the vibrational ground state under realistic experimental conditions within a short time. This efficient optical EIT cooling scheme can be reduced to the typical EIT cooling scheme under special conditions.

  15. The role of angular momentum in collision-induced vibration-rotation relaxation in polyatomics.

    PubMed

    McCaffery, Anthony J; Osborne, Mark A; Marsh, Richard J; Lawrance, Warren D; Waclawik, Eric R

    2004-07-01

    Vibrational relaxation of the 6(1) level of S(1)((1)B(2u)) benzene is analyzed using the angular momentum model of inelastic processes. Momentum-(rotational) angular momentum diagrams illustrate energetic and angular momentum constraints on the disposal of released energy and the effect of collision partner on resultant benzene rotational excitation. A kinematic "equivalent rotor" model is introduced that allows quantitative prediction of rotational distributions from inelastic collisions in polyatomic molecules. The method was tested by predicting K-state distributions in glyoxal-Ne as well as J-state distributions in rotationally inelastic acetylene-He collisions before being used to predict J and K distributions from vibrational relaxation of 6(1) benzene by H(2), D(2), and CH(4). Diagrammatic methods and calculations illustrate changes resulting from simultaneous collision partner excitation, a particularly effective mechanism in p-H(2) where some 70% of the available 6(1)-->0(0) energy may be disposed into 0-->2 rotation. These results support the explanation for branching ratios in 6(1)-->0(0) relaxation given by Waclawik and Lawrance and the absence of this pathway for monatomic partners. Collision-induced vibrational relaxation in molecules represents competition between the magnitude of the energy gap of a potential transition and the ability of the colliding species to generate the angular momentum (rotational and orbital) needed for the transition to proceed. Transition probability falls rapidly as DeltaJ increases and for a given molecule-collision partner pair will provide a limit to the gap that may be bridged. Energy constraints increase as collision partner mass increases, an effect that is amplified when J(i)>0. Large energy gaps are most effectively bridged using light collision partners. For efficient vibrational relaxation in polyatomics an additional requirement is that the molecular motion of the mode must be capable of generating molecular

  16. 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

  17. Modelling the Source of Blasting for the Numerical Simulation of Blast-Induced Ground Vibrations: A Review

    NASA Astrophysics Data System (ADS)

    Ainalis, Daniel; Kaufmann, Olivier; Tshibangu, Jean-Pierre; Verlinden, Olivier; Kouroussis, Georges

    2017-01-01

    The mining and construction industries have long been faced with considerable attention and criticism in regard to the effects of blasting. The generation of ground vibrations is one of the most significant factors associated with blasting and is becoming increasingly important as mining sites are now regularly located near urban areas. This is of concern to not only the operators of the mine but also residents. Mining sites are subjected to an inevitable compromise: a production blast is designed to fragment the utmost amount of rock possible; however, any increase in the blast can generate ground vibrations which can propagate great distances and cause structural damage or discomfort to residents in surrounding urban areas. To accurately predict the propagation of ground vibrations near these sensitive areas, the blasting process and surrounding environment must be characterised and understood. As an initial step, an accurate model of the source of blast-induced vibrations is required. This paper presents a comprehensive review of the approaches to model the blasting source in order to critically evaluate developments in the field. An overview of the blasting process and description of the various factors which influence the blast performance and subsequent ground vibrations are also presented. Several approaches to analytically model explosives are discussed. Ground vibration prediction methods focused on seed waveform and charge weight scaling techniques are presented. Finally, numerical simulations of the blasting source are discussed, including methods to estimate blasthole wall pressure time-history, and hydrodynamic codes.

  18. Effects of tension on vortex-induced vibration (VIV) responses of a long tensioned cylinder in uniform flows

    NASA Astrophysics Data System (ADS)

    Kang, Ling; Ge, Fei; Wu, Xiaodong; Hong, Youshi

    2017-02-01

    The effects of tension on vortex-induced vibration (VIV) responses for a tension-dominated long cylinder with an aspect ratio of 550 in uniform flows are experimentally investigated in this paper. The results show that elevated tension suppresses fluctuations of maximum displacement with respect to flow velocity and makes chaotic VIV more likely to appear. With respect to periodic VIV, if elevated tension is applied, the dominant vibration frequency in the in-line (IL) direction will switch from a fundamental vibration frequency to twice the value of the fundamental vibration frequency, which results in a ratio of the dominant vibration frequency in the IL direction to that in the cross-flow direction of 2.0. The suppression of the elevated tension in the fluctuation of the maximum displacement causes the axial tension to become an active control parameter for the VIV maximum displacement of a tension-dominated long riser or tether of an engineering structure in deep oceans. However, the axial tension must be optimized before being used since the high dominant vibration frequency due to the elevated tension may unfavorably affect the fatigue life of the riser or tether.

  19. Thermally induced vibrations of smart solar panel in a low-orbit satellite

    NASA Astrophysics Data System (ADS)

    Azadi, E.; Fazelzadeh, S. Ahmad; Azadi, M.

    2017-03-01

    In this paper, a smart flexible satellite moving in a circular orbit with two flexible panels are studied. The panels have been modeled as clamped-free-free-free rectangular plates with attached piezoelectric actuators. It is assumed that the satellite has a pitch angle rotation maneuver. Rapid temperature changes at day-night transitions in orbit generate time dependent bending moments. Satellite maneuver and temperature varying induce vibrations in the appendages. So, to simulate the system, heat radiation effects on the appendages have been considered. The nonlinear equations of motion and the heat transfer equations are coupled and solved simultaneously. So, the governing equations of motion are nonlinear and very complicated ones. Finally, the whole system is simulated and the effects of the heat radiation, radius of the orbit, piezoelectric voltages, and piezoelectric locations on the response of the system are studied.

  20. Orientation of bluff body for designing efficient energy harvesters from vortex-induced vibrations

    SciTech Connect

    Dai, H. L.; Abdelkefi, A.; Yang, Y.; Wang, L.

    2016-02-01

    The characteristics and performances of four distinct vortex-induced vibrations (VIVs) piezoelectric energy harvesters are experimentally investigated and compared. The difference between these VIV energy harvesters is the installation of the cylindrical bluff body at the tip of cantilever beam with different orientations (bottom, top, horizontal, and vertical). Experiments show that the synchronization regions of the bottom, top, and horizontal configurations are almost the same at low wind speeds (around 1.5 m/s). The vertical configuration has the highest wind speed for synchronization (around 3.5 m/s) with the largest harvested power, which is explained by its highest natural frequency and the smallest coupled damping. The results lead to the conclusion that to design efficient VIV energy harvesters, the bluff body should be aligned with the beam for low wind speeds (<2 m/s) and perpendicular to the beam at high wind speeds (>2 m/s)

  1. Research and design of underwater flow-induced vibration energy harvester based on Karman vortex street

    NASA Astrophysics Data System (ADS)

    Yao, Gang; Wang, Hai; Yang, Chunlai; Wen, Li

    2017-03-01

    With the increasing development of wireless sensor network (WSN), power supply for WSN nodes had attracted increasing attention, and the energy harvesting system based on Karman vortex street has been widely used in underwater WSN. But the research of the influences of affecting factors towards the energy harvesting system is yet to be completed. So, in this paper, an underwater flow-induced vibration energy harvesting system based on Karman vortex street was proposed and tested. The influence of bluff body geometry and flow velocity towards the performance of the energy harvesting has been researched. The results showed that the output voltage increased as the diameter of bluff body and the water velocity increase. The power generation efficiency was the best when the shape of bluff body was circular.

  2. A global strategy for the stability analysis of friction induced vibration problem with parameter variations

    NASA Astrophysics Data System (ADS)

    Do, H. Q.; Massa, F.; Tison, T.; Lallemand, B.

    2017-02-01

    This paper presents a numerical strategy to reanalyze the modified frequency stability analysis of friction induced vibration problem. The stability analysis of a mechanical system relies on several coupling steps, namely a non-linear static analysis followed by linear and complex eigenvalue problems. We thus propose a numerical strategy to perform more rapidly multiple complex eigenvalue analyses. This strategy couples three methods namely, Fuzzy Logic Controllers to manage frictional contact problem, homotopy developments and projection techniques to reanalyze the projection matrices and component mode synthesis to calculate the modified eigensolutions. A numerical application is performed to highlight the efficiency of the strategy and a discussion is proposed in terms of precision and computational time.

  3. Analysis of vibration induced error in turbulence velocity measurements from an aircraft wing tip boom

    NASA Technical Reports Server (NTRS)

    Akkari, S. H.; Frost, W.

    1982-01-01

    The effect of rolling motion of a wing on the magnitude of error induced due to the wing vibration when measuring atmospheric turbulence with a wind probe mounted on the wing tip was investigated. The wing considered had characteristics similar to that of a B-57 Cambera aircraft, and Von Karman's cross spectrum function was used to estimate the cross-correlation of atmospheric turbulence. Although the error calculated was found to be less than that calculated when only elastic bendings and vertical motions of the wing are considered, it is still relatively large in the frequency's range close to the natural frequencies of the wing. Therefore, it is concluded that accelerometers mounted on the wing tip are needed to correct for this error, or the atmospheric velocity data must be appropriately filtered.

  4. CFD simulation of flow-induced vibration of an elastically supported airfoil

    NASA Astrophysics Data System (ADS)

    Šidlof, Petr

    2016-03-01

    Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge) coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.

  5. Harvesting microalgal biomass using a magnetically induced membrane vibration (MMV) system: filtration performance and energy consumption.

    PubMed

    Bilad, M R; Discart, V; Vandamme, D; Foubert, I; Muylaert, K; Vankelecom, Ivo F J

    2013-06-01

    This study was performed to investigate the effectiveness of submerged microfiltration to harvest both a marine diatom Phaeodactylum tricornutum and a Chlorella vulgaris in a recently developed magnetically induced membrane vibrating (MMV) system. We assess the filtration performance by conducting the improved flux step method (IFM), fed-batch concentration filtrations and membrane fouling autopsy using two lab-made membranes with different porosity. The full-scale energy consumption was also estimated. Overall results suggest that the MMV offers a good fouling control and the process was proven to be economically attractive. By combining the membrane filtration (15× concentration) with centrifugation to reach a final concentration of 25% w/v, the energy consumption to harvest P. tricornutum and C. vulgaris was, respectively, as low as 0.84 and 0.77kWh/m(3), corresponding to 1.46 and 1.39 kWh/kg of the harvested biomass.

  6. Suppression of two-dimensional vortex-induced vibration with active velocity feedback controller

    NASA Astrophysics Data System (ADS)

    Ma, B.; Srinil, N.

    2016-09-01

    Vortex-induced vibrations (VIV) establish key design parameters for offshore and subsea structures subject to current flows. Understanding and predicting VIV phenomena have been improved in recent years. Further, there is a need to determine how to effectively and economically mitigate VIV effects. In this study, linear and nonlinear velocity feedback controllers are applied to actively suppress the combined cross-flow and in-line VIV of an elastically-mounted rigid circular cylinder. The strongly coupled fluid-structure interactions are numerically modelled and investigated using a calibrated reduced-order wake oscillator derived from the vortex strength concept. The importance of structural geometrical nonlinearities is studied which highlights the model ability in matching experimental results. The effectiveness of linear vs nonlinear controllers are analysed with regard to the control direction, gain and power. Parametric studies are carried out which allow us to choose the linear vs nonlinear control, depending on the target controlled amplitudes and associated power requirements.

  7. A study on the relationship between subjective unpleasantness and body surface vibrations induced by high-level low-frequency pure tones.

    PubMed

    Takahashi, Yukio; Kanada, Kazuo; Yonekawa, Yoshiharu; Harada, Noriaki

    2005-07-01

    Human body surface vibrations induced by high-level low-frequency pure tones were measured at the chest and the abdomen. At the same time, the subject rated the unpleasantness that he had just perceived during the exposure to low-frequency noise stimulus. Examining the relationship between the measured vibration and the rating score of the unpleasantness revealed that the unpleasantness was in close correlation with the vibration acceleration level (VAL) of the vibration measured. Taking previous results into account, this finding suggests that noise-induced vibrations primarily induce vibratory sensations and through the vibratory sensation or together with some other factors, secondarily contribute to the unpleasantness. The present results suggest that in evaluating high-level low-frequency noise, the effect of vibration should be taken into account.

  8. A distributed parameter electromechanical and statistical model for energy harvesting from turbulence-induced vibration

    NASA Astrophysics Data System (ADS)

    Hobeck, J. D.; Inman, D. J.

    2014-11-01

    Extensive research has been done on the topics of both turbulence-induced vibration and vibration based energy harvesting; however, little effort has been put into bringing these two topics together. Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. This research could serve to benefit applications such as powering remote, self-sustained sensors in small rivers or air ventilation systems where turbulent fluid flow is a primary source of ambient energy. A novel solution for harvesting energy in these unpredictable fluid flow environments was explored by the authors in previous work, and a harvester prototype was developed. This prototype, called piezoelectric grass, has been the focus of many experimental studies. In this paper the authors present a theoretical analysis of the piezoelectric grass harvester modeled as a single unimorph cantilever beam exposed to turbulent cross-flow. This distributed parameter model was developed using a combination of both analytical and statistical techniques. The analytical portion uses a Rayleigh-Ritz approximation method to describe the beam dynamics, and utilizes piezoelectric constitutive relationships to define the electromechanical coupling effects. The statistical portion of the model defines the turbulence-induced forcing function distributed across the beam surface. The model presented in this paper was validated using results from several experimental case studies. Preliminary results show that the model agrees quite well with experimental data. A parameter optimization study was performed with the proposed model. This study demonstrated how a new harvester could be designed to achieve maximum power output in a given turbulent fluid flow environment.

  9. Pulsed UV Laser-Induced Stationary Capillary Vibration for Highly Sensitive and Direct Detection of Capillary Electrophoresis.

    PubMed

    Odake, T; Kitamori, T; Sawada, T

    1997-07-01

    A stationary wave of the capillary vibration effect was successfully induced by a series of short laser pulses. This wave could be applied to highly sensitive detection of capillary electrophoresis as well as the already reported capillary vibration induced by an intensity-modulated CW laser (CVL effect). Generally, pulses with much shorter width than the period of the natural frequency of the vibrating system cannot induce a standing vibration. However, utilizing the time constant of CVL determined by heat dissipation time, we found conditions which could induce a stable stationary wave of the capillary by a series of nanosecond light pulses. We used the KrF excimer laser operated at 248 nm with a pulse width of 60 ns and output of ∼10 μJ/pulse as the CVL excitation source and applied it to highly sensitive detection of nonderivatized amino acids at the femtomole level. The sensitivity was at least 2 orders of magnitude superior to that of a commercially available UV absorbance detector. This technique extends the CVL's spectral regions. For example, in the UV region, where many biological materials have significant absorption bands, this technique will extend analytical applications in capillary electrophoresis by eliminating the need for a derivatization process.

  10. Oximetry: a new non-invasive method to detect metabolic effects induced by a local application of mechanical vibration

    NASA Astrophysics Data System (ADS)

    Felici, A.; Trombetta, C.; Abundo, P.; Foti, C.; Rosato, N.

    2012-10-01

    Mechanical vibrations application is increasingly common in clinical practice due to the effectiveness induced by these stimuli on the human body. Local vibration (LV) application allows to apply and act only where needed, focusing the treatment on the selected body segment. An experimental device for LV application was used to generate the vibrations. The aim of this study was to detect and analyze the metabolic effects induced by LV on the brachial bicep muscle by means of an oximeter. This device monitors tissue and muscle oxygenation using NIRS (Near Infrared Spectroscopy) and is able to determine the concentration of haemoglobin and oxygen saturation in the tissue. In a preliminary stage we also investigated the effects induced by LV application, by measuring blood pressure, heart rate, oxygen saturation and temperature. These data confirmed that the effects induced by LV application are actually localized. The results of the measurements obtained using the oximeter during the vibration application, have shown a variation of the concentrations. In particular an increase of oxygenate haemoglobin was shown, probably caused by an increased muscle activity and/or a rise in local temperature detected during the application.

  11. An Intensity-Based Demodulation Approach for the Measurement of Strains Induced by Structural Vibrations using Bragg Gratings

    DTIC Science & Technology

    2011-02-01

    gratings for response measurement. DSTO’s involvement in this program is to develop the distributed Bragg grating in- terrogation system and conduct... Calibration 29 E System Operation Documentation 30 E.1 Configuration Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 E.2 Scan Screen...challenges associated with this type of distributed response measurement using Bragg gratings is that the strains induced by structural vibrations tend

  12. Regional atmospheric cooling and wetting effect of permafrost thaw-induced boreal forest loss.

    PubMed

    Helbig, Manuel; Wischnewski, Karoline; Kljun, Natascha; Chasmer, Laura E; Quinton, William L; Detto, Matteo; Sonnentag, Oliver

    2016-12-01

    In the sporadic permafrost zone of North America, thaw-induced boreal forest loss is leading to permafrost-free wetland expansion. These land cover changes alter landscape-scale surface properties with potentially large, however, still unknown impacts on regional climates. In this study, we combine nested eddy covariance flux tower measurements with satellite remote sensing to characterize the impacts of boreal forest loss on albedo, eco-physiological and aerodynamic surface properties, and turbulent energy fluxes of a lowland boreal forest region in the Northwest Territories, Canada. Planetary boundary layer modelling is used to estimate the potential forest loss impact on regional air temperature and atmospheric moisture. We show that thaw-induced conversion of forests to wetlands increases albedo: and bulk surface conductance for water vapour and decreases aerodynamic surface temperature. At the same time, heat transfer efficiency is reduced. These shifts in land surface properties increase latent at the expense of sensible heat fluxes, thus, drastically reducing Bowen ratios. Due to the lower albedo of forests and their masking effect of highly reflective snow, available energy is lower in wetlands, especially in late winter. Modelling results demonstrate that a conversion of a present-day boreal forest-wetland to a hypothetical homogeneous wetland landscape could induce a near-surface cooling effect on regional air temperatures of up to 3-4 °C in late winter and 1-2 °C in summer. An atmospheric wetting effect in summer is indicated by a maximum increase in water vapour mixing ratios of 2 mmol mol(-1) . At the same time, maximum boundary layer heights are reduced by about a third of the original height. In fall, simulated air temperature and atmospheric moisture between the two scenarios do not differ. Therefore, permafrost thaw-induced boreal forest loss may modify regional precipitation patterns and slow down regional warming trends.

  13. Concorde noise-induced building vibrations: John F. Kennedy International Airport

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Stephens, D. G.; Deloach, R.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.; Miller, W. T.

    1978-01-01

    Outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded at eight homesites and a school along with the associated vibration levels in the walls, windows, and floors at these test sites. Limited subjective tests were conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise. Both vibration and rattle were detected subjectively in several houses for some operations of both the Concorde and subsonic aircraft. Seated subjects more readily detected floor vibrations than wall or window vibrations. Aircraft noise generally caused more window vibrations than common nonaircraft events such as walking and closing doors. Nonaircraft events and aircraft flyovers resulted in comparable wall vibration levels, while floor vibrations were generally greater for nonaircraft events than for aircraft flyovers. The relationship between structural vibration and aircraft noise is linear, with vibration levels being accurately predicted from overall sound pressure levels (OASPL) measured near the structure. Relatively high levels of structural vibration measured during Concorde operations are due more to higher OASPL levels than to unique Concorde-source characteristics.

  14. Oral cooling (cryotherapy), an effective treatment for the prevention of 5-fluorouracil-induced stomatitis.

    PubMed

    Cascinu, S; Fedeli, A; Fedeli, S L; Catalano, G

    1994-07-01

    Recently, a randomised study demonstrated the utility of oral cooling (cryotherapy) in the prevention of 5-fluorouracil (5FU)-induced stomatitis. In order to verify these results a confirmatory study, using identical treatment regimen, was initiated. 84 patients treated with a 5-FU-containing regimen were randomised to a control arm or to receive oral cryotherapy. End point evaluation was obtained by a global assessment of the physician's judgement and patients' description of mucositis severity graded 0-4. Mucositis was significantly reduced by cryotherapy considering both the first cycle of therapy (the mean toxicity score for cryotherapy was 0.59 and it was 1.1 for the control group, P < or = 0.05) and all the chemotherapeutic courses (the mean toxicity score for cryotherapy was 0.36 when it was 0.69 for the control group, P < or = 0.05). In conclusion, the present study confirms that cryotherapy can decrease 5FU-induced stomatitis and should be recommended for patients receiving bolus 5FU-containing regimens.

  15. A Massive, Cooling-Flow-Induced Starburst in the Core of a Highly Luminous Galaxy Cluster

    NASA Technical Reports Server (NTRS)

    McDonald, M.; Bayliss, M.; Benson, B. A.; Foley, R. J.; Ruel, J.; Sullivan, P.; Veilleux, S.; Aird, K. A.; Ashby, M. L. N.; Bautz, M.; Bazin, G.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Clocchiatti, A.; Crawford, T. M.; Crites, A. T.; deHaan, T.; Desai, S.; Dobbs, M. A.; Dudley, J. P.; Egami, E.; Joy, M.

    2012-01-01

    In the cores of some galaxy clusters the hot intracluster plasma is dense enough that it should cool radiatively in the cluster s lifetime, leading to continuous "cooling flows" of gas sinking towards the cluster center, yet no such cooling flow has been observed. The low observed star formation rates and cool gas masses for these "cool core" clusters suggest that much of the cooling must be offset by astrophysical feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical, and infrared observations of the galaxy cluster SPT-CLJ2344-4243 at z = 0.596. These observations reveal an exceptionally luminous (L(sub 2-10 keV) = 8.2 10(exp 45) erg/s) galaxy cluster which hosts an extremely strong cooling flow (M(sub cool) = 3820 +/- 530 Stellar Mass/yr). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (740 +/- 160 Stellar Mass/ yr), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form via accretion of the intracluster medium, rather than the current picture of central galaxies assembling entirely via mergers.

  16. Local cooling, plasma reheating and thermal pinching induced by single aerosol droplets injected into an inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Chan, George C.-Y.; Hieftje, Gary M.

    2016-07-01

    The injection of a single micrometer-sized droplet into an analytical inductively coupled plasma (ICP) perturbs the plasma and involves three sequential effects: local cooling, thermal pinching and plasma reheating. Time-resolved two-dimensional monochromatic imaging of the load-coil region of an ICP was used to monitor this sequence of plasma perturbations. When a microdroplet enters the plasma, it acts as a local heat sink and cools the nearby plasma region. The cooling effect is considered local, although the cooling volume can be large and extends 6 mm from the physical location of the vaporizing droplet. The liberated hydrogen, from decomposition of water, causes a thermal pinch effect by increasing the thermal conductivity of the bulk plasma and accelerating heat loss at the plasma periphery. As a response to the heat loss, the plasma shrinks in size, which increases its power density. Plasma shrinkage starts around the same time when the microdroplet enters the plasma and lasts at least 2 ms after the droplet leaves the load-coil region. Once the vaporizing droplet passes through a particular plasma volume, that volume is reheated to an even higher temperature than under steady-state conditions. Because of the opposing effects of plasma cooling and reheating, the plasma conditions are different upstream (downward) and downstream (upward) from a vaporizing droplet - cooling dominates the downstream region whereas reheating controls in the upstream domain. The boundary between the local cooling and reheating zones is sharp and is only ~ 1 mm thick. The reheating effect persists a relatively long time in the plasma, at least up to 4 ms after the droplet moves out of the load-coil region. The restoration of plasma equilibrium after the perturbation induced by microdroplet injection is slow. Microdroplet injection also induces a momentary change in plasma impedance, and the impedance change was found to correlate qualitatively with the different stages of plasma

  17. 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.

  18. Flow-induced vein-wall vibration in an arteriovenous graft

    NASA Astrophysics Data System (ADS)

    Lee, S.-W.; Fischer, P. F.; Loth, F.; Royston, T. J.; Grogan, J. K.; Bassiouny, H. S.

    2005-08-01

    The hemodynamic environment of an arteriovenous (AV) graft differs from that of arterial grafts because mean flow rates are typically 10 times greater. This increased flow rate can create a weakly turbulent state, which alters the biomechanical environment greatly and may play a role in AV graft failure. A canine animal study was conducted to simulate the hemodynamic environment of a human AV graft. In vivo measurements were obtained for vein-wall vibration (VWV), graft geometry, and blood flow rate. In order to investigate the complex flow structure at the venous anastomosis of an AV graft, which is thought to induce these vibrations, a computational fluid dynamics study was conducted by direct numerical simulation under pulsatile flow and geometry conditions based on the animal study. The simulation technique employs the spectral element method, which is a high-order discretization ideally suited to the simulation of transitional flows in complex domains. The minimum and maximum Reynolds numbers entering the graft, based on average velocities, were 875 and 1235, respectively. While velocity and pressure fluctuations are clearly present in the numerical simulations, their magnitude and frequency do not correlate well with the in vivo VWV measurements. Potential reasons for this discrepancy are threefold. First, a quiescent inflow condition was used in the present computations; a more realistic inflow condition might alter the velocity fluctuations significantly. Second, simulations were conducted with a rigid geometry; compliance may play an important role in flow stability within an AV graft. Third, the flow split between the graft and vein inlet may also play an important role in the stability of the flow structures.

  19. An excitation spectrum criterion for the vibration-induced fatigue of small bore pipes

    NASA Astrophysics Data System (ADS)

    Moussou, P.

    2003-09-01

    The purpose of the study is to determine an easy-to-use criterion to evaluate the risk of vibration-induced fatigue of small bore pipes. The failure mechanism considered is the resonant amplification of a stationary broadband excitation by the main pipe, leading to bending stresses above the fatigue limit of the steel. Based on the Euler beam theory, a simple model is built up for the natural mode shapes of the small bore pipe close to its root. It is shown that the velocity spectrum at the root of the small bore pipe is equal to the r.m.s. value of the bending stress multiplied by a function of the natural frequency, the damping coefficient, the speed of elastic waves in the steel, Young's modulus and a nondimensional factor weakly depending on the geometry of the small bore pipe. A maximum velocity spectrum can then be deduced, assuming that a small bore pipe vibrates mainly on its natural mode shapes. The maximum excitation spectrum is defined for each frequency f as the one which would generate a maximum bending stress equal to the endurance limit of the steel, would the small bore pipe have a natural frequency equal to f. Using envelope values of the nondimensional factor, the stress intensification factor, the peak factor and the endurance limit of the steel, one obtains the following maximum velocity spectrum for the stainless steel: v<6mm/s/sqrt(f), and the following maximum velocity spectrum for the ferritic steel: v<2.7mm/s/sqrt(f). The velocity spectrum criterion appears less penalizing than the 12mm/s criterion and more conservative than the strict enforcement of the ANSI-OM3 standard. Comparisons with former plant studies show that the velocity spectrum criterion leads to the correct fatigue diagnosis.

  20. Laser-induced fluorescence and dispersed fluorescence spectroscopy of jet-cooled 1-phenylpropargyl radical

    NASA Astrophysics Data System (ADS)

    Reilly, Neil J.; Nakajima, Masakazu; Gibson, Bligh A.; Schmidt, Timothy W.; Kable, Scott H.

    2009-04-01

    The D1(A2″)-D0(A2″) electronic transition of the resonance-stabilized 1-phenylpropargyl radicalooled discharge of 3-phenyl-1-propyne, has been investigated in detail by laser-induced fluorescence excitation and dispersed single vibronic level fluorescence (SVLF) spectroscopy. The transition is dominated by the origin band at 21 007 cm-1, with weaker Franck-Condon activity observed in a' fundamentals and even overtones and combinations of a″ symmetry. Ab initio and density functional theory calculations of the D0 and D1 geometries and frequencies were performed to support and guide the experimental assignments throughout. Analysis of SVLF spectra from 16 D1 vibronic levels has led to the assignment of 15 fundamental frequencies in the excited state and 19 fundamental frequencies in the ground state; assignments for many more normal modes not probed directly by fluorescence spectroscopy are also suggested. Duschinsky mixing, in which the excited state normal modes are rotated with respect to the ground state modes, is prevalent throughout, in vibrations of both a' and a″ symmetry.

  1. "Beating speckles" via electrically-induced vibrations of Au nanorods embedded in sol-gel.

    PubMed

    Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

    2014-01-13

    Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative "speckle beats" induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of "beats", for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged.

  2. Modeling and simulation of vortex induced vibration on the subsea riser/pipeline (GRP pipe)

    NASA Astrophysics Data System (ADS)

    Raja Adli, Raja Nor Fauziah bt; Ibrahim, Idris

    2012-06-01

    This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline.

  3. A massive, cooling-flow-induced starburst in the core of a luminous cluster of galaxies.

    PubMed

    McDonald, M; Bayliss, M; Benson, B A; Foley, R J; Ruel, J; Sullivan, P; Veilleux, S; Aird, K A; Ashby, M L N; Bautz, M; Bazin, G; Bleem, L E; Brodwin, M; Carlstrom, J E; Chang, C L; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; de Haan, T; Desai, S; Dobbs, M A; Dudley, J P; Egami, E; Forman, W R; Garmire, G P; George, E M; Gladders, M D; Gonzalez, A H; Halverson, N W; Harrington, N L; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Jones, C; Joy, M; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Mantz, A; Marrone, D P; McMahon, J J; Mehl, J; Meyer, S S; Miller, E D; Mocanu, L; Mohr, J J; Montroy, T E; Murray, S S; Natoli, T; Padin, S; Plagge, T; Pryke, C; Rawle, T D; Reichardt, C L; Rest, A; Rex, M; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Shaw, L; Shirokoff, E; Simcoe, R; Song, J; Spieler, H G; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; Suhada, R; van Engelen, A; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zahn, O; Zenteno, A

    2012-08-16

    In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.

  4. Ground-state cooling of a suspended nanowire through inelastic macroscopic quantum tunneling in a current-biased Josephson junction.

    PubMed

    Sonne, Gustav; Gorelik, Leonid Y

    2011-04-22

    We demonstrate that a suspended nanowire forming a weak link between two superconductors can be cooled to its motional ground state by a supercurrent flow. The predicted cooling mechanism has its origins in magnetic field induced inelastic tunneling of the macroscopic superconducting phase associated with the junction. Furthermore, we show that the voltage drop over the junction is proportional to the average population of the vibrational modes in the stationary regime, a phenomenon which can be used to probe the level of cooling.

  5. Concorde noise-induced building vibrations, John F. Kennedy International Airport

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Deloach, R.; Stephens, D. G.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Miller, W. T.; Ward, D. W.

    1978-01-01

    The outdoor/indoor noise levels and associated vibration levels resulting from aircraft and nonaircraft events were recorded at eight homesites and a school. In addition, limited subjective tests were conducted to examine the human detection/annoyance thresholds for building vibration and rattle caused by aircraft noise. Presented herein are the majority of the window and wall vibration data recorded during Concorde and subsonic aircraft overflights.

  6. Evaluation of human response to structural vibrations induced by sonic booms

    NASA Technical Reports Server (NTRS)

    Sutherland, Louis C.; Czech, J.

    1992-01-01

    The topic is addressed of building vibration response to sonic boom and the evaluation of the associated human response to this vibration. An attempt is made to reexamine some of the issues addressed previously and to offer fresh insight that may assist in reassessing the potential impact of sonic boom over populated areas. Human response to vibration is reviewed first and a new human vibration response criterion curve is developed as a function of frequency. The difference between response to steady state versus impulsive vibration is addressed and a 'vibration exposure' or 'vibration energy' descriptor is suggested as one possible way to evaluate duration effects on response to transient vibration from sonic booms. New data on the acoustic signature of rattling objects are presented along with a review of existing data on the occurrence of rattle. Structural response to sonic boom is reviewed and a new descriptor, 'Acceleration Exposure Level' is suggested which can be easily determined from the Fourier Spectrum of a sonic boom. A preliminary assessment of potential impact from sonic booms is provided in terms of human response to vibration and detection of rattle based on a synthesis of the preceding material.

  7. Prevention of chemotherapy-induced alopecia using an effective scalp cooling system.

    PubMed

    Katsimbri, P; Bamias, A; Pavlidis, N

    2000-04-01

    Alopecia is a distressing side-effect of cancer treatment. Taxanes (TX), anthracyclines (ANR) and etoposide (ET) have been consistently associated with significant alopecia. We studied an effective scalp cooling system, the Penguin Cold Cap system, for the prevention of chemotherapy-induced alopecia in 70 patients receiving chemotherapy, including one of the following major alopecia-causing agents: Group A, TX-based regimes (without ANR); Group B, TX+ANR; Group C, ANR-based regimes (without TX); Group D, ET-based regimes. Protection from hair loss was achieved by maintaining scalp temperatures below 15 degrees C before, during and after chemotherapy by frequent changing of the caps. Assessment was carried out using a grading system from 0 to 4. Grades 0-2 were considered as satisfactory hair protection, whilst Grades 3-4 were considered failures. 57 patients were evaluable for assessment. An overall 81% protection was achieved. In groups C and D 11 of 12 patients (92%) had no alopecia, whilst 30 of 34 patients (88%) treated with taxanes had adequate hair protection. In Group B, 4 of 11 patients (36%) had adequate hair protection. The system was well tolerated and is a very effective method for protection from hair loss caused by TX, ANR and ET. Our results are comparable with and, in most cases, better than those reported in other studies using various alopecia preventive methods.

  8. Laser Induced Fluorescence Spectroscopy of Jet-Cooled CaOCa

    NASA Astrophysics Data System (ADS)

    Sullivan, Michael N.; Frohman, Daniel J.; Heaven, Michael; Fawzy, Wafaa M.

    2016-06-01

    The group IIA metals have stable hypermetallic oxides of the general form MOM. Theoretical interest in these species is associated with the multi-reference character of the ground states. It is now established that the ground states can be formally assigned to the M+O^{2-M+} configuration, which leaves two electrons in orbitals that are primarily metal-centered ns orbitals. Hence the MOM species are diradicals with very small energy spacings between the lowest energy singlet and triplet states. Previously, we have characterized the lowest energy singlet transition (1Σ^{+u← X1Σ+g}) of BeOBe. In this study we obtained the first electronic spectrum of CaOCa. Jet-cooled laser induced fluorescence spectra were recorded for multiple bands that occured within the 14,800 - 15,900 cm-1 region. Most of the bands exhibited simple P/R branch rotational line patterns that were blue-shaded. Only even rotational levels were observed, consistent with the expected X 1Σ^{+g} symmetry of the ground state (40Ca has zero nuclear spin). A progression of excited bending modes was evident in the spectrum, indicating that the transition is to an upper state that has a bent equilibrium geometry. Molecular constants were extracted from the rovibronic bands using PGOPHER. The experimental results and interpretation of the spectrum, which was guided by the predictions of electronic structure calculation, will be presented.

  9. Discussion of "A new method for predicting nonlinear structural vibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140

    NASA Astrophysics Data System (ADS)

    Svinkin, Mark R.

    2016-12-01

    The authors suggested a hybrid method for modeling the time history of structural vibrations triggered by impact dynamic loads from construction equipment and blasting, and they stated, "In this work, a hybrid method has been proposed to calculate the theoretical seismograms of structural vibrations. The word "hybrid" denotes a combination of field measurements and computer simulations. Then, based on nonlinear system theory, a novel method is proposed to predict the signal induced by impact loading".

  10. Investigation on flow and mixing characteristics of supersonic mixing layer induced by forced vibration of cantilever

    NASA Astrophysics Data System (ADS)

    Zhang, Dongdong; Tan, Jianguo; Lv, Liang

    2015-12-01

    The mixing process has been an important issue for the design of supersonic combustion ramjet engine, and the mixing efficiency plays a crucial role in the improvement of the combustion efficiency. In the present study, nanoparticle-based planar laser scattering (NPLS), particle image velocimetry (PIV) and large eddy simulation (LES) are employed to investigate the flow and mixing characteristics of supersonic mixing layer under different forced vibration conditions. The indexes of fractal dimension, mixing layer thickness, momentum thickness and scalar mixing level are applied to describe the mixing process. Results show that different from the development and evolution of supersonic mixing layer without vibration, the flow under forced vibration is more likely to present the characteristics of three-dimensionality. The laminar flow region of mixing layer under forced vibration is greatly shortened and the scales of rolled up Kelvin-Helmholtz vortices become larger, which promote the mixing process remarkably. The fractal dimension distribution reveals that comparing with the flow without vibration, the turbulent fluctuation of supersonic mixing layer under forced vibration is more intense. Besides, the distribution of mixing layer thickness, momentum thickness and scalar mixing level are strongly influenced by forced vibration. Especially, when the forcing frequency is 4000 Hz, the mixing layer thickness and momentum thickness are 0.0391 m and 0.0222 m at the far field of 0.16 m, 83% and 131% higher than that without vibration at the same position, respectively.

  11. Stress wave propagation analysis on vortex-induced vibration of marine risers

    NASA Astrophysics Data System (ADS)

    Li, Hua-jun; Wang, Chao; Liu, Fu-shun; Hu, Sau-Lon James

    2017-03-01

    To analyze the stress wave propagation associated with the vortex-induced vibration (VIV) of a marine riser, this paper employed a multi-signal complex exponential method. This method is an extension of the classical Prony's method which decomposes a complicated signal into a number of complex exponential components. Because the proposed method processes multiple signals simultaneously, it can estimate the "global" dominating frequencies (poles) shared by those signals. The complex amplitude (residues) corresponding to the estimated frequencies for those signals is also obtained in the process. As the signals were collected at different locations along the axial direction of a marine riser, the phenomena of the stress wave propagation could be analyzed through the obtained residues of those signals. The Norwegian Deepwater Program (NDP) high mode test data were utilized in the numerical studies, including data sets in both the in-line (IL) and cross-flow (CF) directions. It was found that the most dominant component in the IL direction has its stress wave propagation along the riser being dominated by a standing wave, while that in the CF direction dominated by a traveling wave.

  12. Experimental investigation on vortex-induced vibration of steel catenary riser

    NASA Astrophysics Data System (ADS)

    Fan, Yu-ting; Mao, Hai-ying; Guo, Hai-yan; Liu, Qing-hai; Li, Xiao-min

    2015-10-01

    Steel catenary riser (SCR) is the transmission device between the seabed and the floating production facilities. As developments move into deeper water, the fatigue life of the riser can become critical to the whole production system, especially due to the vortex-induced vibration (VIV), which is the key factor to operational longevity. As a result, experimental investigation about VIV of the riser was performed in a large plane pool which is 60 m long, 36 m wide and 6.5 m deep. Experiments were developed to study the influence of current speed and seabed on VIV of SCR. The results show that amplitudes of strain and response frequencies increase with the current speed both in cross-flow (CF) and in-line (IL). When the current speed is high, multi-mode response is observed in the VIV motion. The amplitudes of strain in IL direction are not much smaller than those in CF direction. The seabed has influence on the response frequencies of riser and the positions of damage for riser.

  13. Vortex-Induced Vibrations of a Flexibly-Mounted Cyber-Physical Rectangular Plate

    NASA Astrophysics Data System (ADS)

    Onoue, Kyohei; Strom, Benjamin; Song, Arnold; Breuer, Kenneth

    2013-11-01

    We have developed a cyber-physical system to explore the vortex-induced vibration (VIV) behavior of a flat plate mounted on a virtual spring damper support. The plate is allowed to oscillate about its mid-chord and the measured angular position, velocity, and torque are used as inputs to a feedback control system that provides a restoring torque and can simulate a wide range of structural dynamic behavior. A series of experiments were carried out using different sized plates, and over a range of freestream velocities, equilibrium angles of attack, and simulated stiffness and damping. We observe a synchronization phenomenon over a wide range of parameter space, wherein the plate oscillates at moderate to large amplitude with a frequency dictated by the natural structural frequency of the system. Additionally, the existence of bistable states is reflected in the hysteretic response of the system. The cyber-physical damping extracts energy from the flow and the efficiency of this harvesting mechanism is characterized over a range of dimensionless stiffness and damping parameters. This research is funded by the Air Force Office of Scientific Research (AFOSR).

  14. Dynamic characteristics of an inclined flexible cylinder undergoing vortex-induced vibrations

    NASA Astrophysics Data System (ADS)

    Han, Qinghua; Ma, Yexuan; Xu, Wanhai; Lu, Yan; Cheng, Ankang

    2017-04-01

    A series of experimental tests were conducted on vortex-induced vibrations (VIV) of a flexible inclined cylinder with a yaw angle equals 45° for investigating the response characteristics in a towing tank. The flexible cylinder model was 5.6 m in length and 16 mm in diameter with an aspect ratio of 350 and a mass ratio of 1.9. The Reynolds numbers ranged from about 800 to 16,000.The strain responses were measured directly in both cross-flow (CF) and in-line (IL) directions and corresponding displacements were obtained using a modal approach. The dynamic response characteristics of the inclined flexible cylinder excited by vortex shedding was examined from the aspect of strain response, displacement amplitudes, dominant modes, response frequencies and drag force coefficients. The experimental results indicated that the CF response amplitude could be up to a value of 3.0D and the IL one more than 1.1D. The dominant modes were from 1 to 3 in CF direction and 1 to 5 in IL direction. And it was found that dominant frequencies increased linearly with the reduced velocity. The multi-modal response of the flexible inclined cylinder model excited by VIV was observed and analyzed. Moreover, the values of drag coefficients were in the range of 0.9-2.6.

  15. Examination of hydrodynamic force acting on a circular cylinder in vortex-induced vibrations in synchronization

    NASA Astrophysics Data System (ADS)

    Shen, Linwei; Chan, Eng-Soon; Sun, Zhilin

    2017-04-01

    An immersed boundary method is employed to simulate vortex-induced vibrations (VIV) of a circular cylinder in two dimensions. The Reynolds number is 150, and the cylinder mass ratios of 2 and 10 are considered. The synchronization regions for these two mass ratios are determined by the simulations. It is found that the cycle-averaged added mass is about zero at the reduced velocity of 6.1. The instantaneous frequency, which is obtained by Hilbert transformation of the cylinder oscillating displacement, exhibits an important feature whereby the cylinder oscillation in the VIV synchronization region is modulated with a frequency twice the displacement prevailing frequency. The cylinder displacement could still be well approximated by a sine function with a constant frequency and amplitude. However, the lift force acting on the cylinder cannot be estimated in the same manner. In fact, both the lift force amplitude and frequency are modulated. The suggested expression provides a better approximation of the lift force. Moreover, it reveals that the presence of the higher harmonics in the lift force is the result of the amplitude and frequency modulation.

  16. Tension and drag forces of flexible risers undergoing vortex-induced vibration

    NASA Astrophysics Data System (ADS)

    Song, Lei-jian; Fu, Shi-xiao; Li, Man; Gao, Yun; Ma, Lei-xin

    2017-03-01

    This paper presents the results of an experimental investigation on the variation in the tension and the distribution of drag force coefficients along flexible risers under vortex-induced vibration (VIV) in a uniform flow for Reynolds numbers ( Re) up to 2.2×105. The results show that the mean tension is proportional to the square of the incoming current speed, and the tension coefficient of a flexible riser undergoing VIV can be up to 12. The mean drag force is uniformly and symmetrically distributed along the axes of the risers undergoing VIV. The corresponding drag coefficient can vary between 1.6 and 2.4 but is not a constant value of 1.2, as it is for a fixed cylinder in the absence of VIV. These experimental results are used to develop a new empirical prediction model to estimate the drag force coefficient for flexible risers undergoing VIV for Reynolds number on the order of 105, which accounts for the effects of the incoming current speed, the VIV dominant modal number and the frequency.

  17. Reconfiguration and the reduction of vortex-induced vibrations in broad leaves.

    PubMed

    Miller, Laura A; Santhanakrishnan, Arvind; Jones, Shannon; Hamlet, Christina; Mertens, Keith; Zhu, Luoding

    2012-08-01

    Flexible plants, fungi and sessile animals reconfigure in wind and water to reduce the drag acting upon them. In strong winds and flood waters, for example, leaves roll up into cone shapes that reduce drag compared with rigid objects of similar surface area. Less understood is how a leaf attached to a flexible leaf stalk will roll up stably in an unsteady flow. Previous mathematical and physical models have only considered the case of a flexible sheet attached to a rigid tether in steady flow. In this paper, the dynamics of the flow around the leaf of the wild ginger Hexastylis arifolia and the wild violet Viola papilionacea are described using particle image velocimetry. The flows around the leaves are compared with those of simplified physical and numerical models of flexible sheets attached to both rigid and flexible beams. In the actual leaf, a stable recirculation zone is formed within the wake of the reconfigured cone. In the physical model, a similar recirculation zone is observed within sheets constructed to roll up into cones with both rigid and flexible tethers. Numerical simulations and experiments show that flexible rectangular sheets that reconfigure into U-shapes, however, are less stable when attached to flexible tethers. In these cases, larger forces and oscillations due to strong vortex shedding are measured. These results suggest that the three-dimensional cone structure in addition to flexibility is significant to both the reduction of vortex-induced vibrations and the forces experienced by the leaf.

  18. Dynamic characteristics of a cable-stayed bridge measured from traffic-induced vibrations

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Che; Chen, Chern-Hwa

    2012-09-01

    This paper studies the dynamic characteristics of the Kao-Ping-Hsi cable-stayed bridge under daily traffic conditions. Experimental data were measured from a structural monitoring system, and system-identification techniques, such as the random decrement (RD) technique and Ibrahim time-domain (ITD) method, were adopted. The first five modes of the bridge were identified for their natural frequencies and damping ratios under different traffic loading conditions, in terms of root-mean-square (RMS) deck velocities. The magnitude of the torsion mode of the Kao-Ping-Hsi cable-stayed bridge is found to be one order-of-magnitude less than the transfer mode, and two orders-of-magnitude less than the vertical modes. Out results indicated that vibrations induced by traffic flow can be used as an indicator to monitor the health of the bridge due to their insensitivity to the natural frequencies of the cable-stayed bridge. Furthermore, the damping ratios may be used as a more sensitive indicator to describe the condition of the bridge.

  19. Study on optical attenuation performance of special stock power optical cable based on a wind induced vibration environment in laboratory

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhao, Ziyuan

    2010-08-01

    For the purpose of 10G communication system upgrade for Guangdong Power Grid, laboratory simulation tests on dynamic and temperature cycle are performed for the reserved cables (stock optical cables) of existing 2.5G special optical cable lines that have operated for ten years, in order to verify the possibility of optical cable to be upgraded to a 10G transmission level and evaluate the degradation level of optical cables. This paper points out the necessity of laboratory test on attenuation performance in a wind-induced vibration environment, describes the test methods thereof, summarizes and analyzes a variety of optical attenuation performance data, and finds that the attenuation performance of current OPGW, ADSS, ADL optical fiber lines in wind-induced vibration environment meets the industry standards.

  20. Understanding the vibrational mode-specific polarization effects in femtosecond Raman-induced Kerr-effect spectroscopy.

    PubMed

    McAnally, Michael O; Guo, Yinsheng; Balakrishnan, Gurusamy; Schatz, George C; Van Duyne, Richard P

    2016-11-15

    Optically heterodyne-detected femtosecond Raman-induced Kerr-effect spectroscopy (OHD-FRIKES) was observed in neat cyclohexane. In this Letter, an examination of the effect of the Raman pump ellipticity on the multiplex OHD-FRIKES spectra is discussed. The Raman pump ellipticity scanned OHD-FRIKES results reproduce anomalous observables from previous OHD-FRIKES experiments and suggest new methods of tracking transient vibrational mode polarization in complex systems.

  1. Experimental Study on the Vortex-Induced Vibration of Towed Pipes

    NASA Astrophysics Data System (ADS)

    HONG, S.; CHOI, Y. R.; PARK, J.-B.; PARK, Y.-K.; KIM, Y.-H.

    2002-01-01

    We experimentally attempted to understand the vibration characteristics of a flexible pipe excited by vortex shedding. This has been extensively studied in the previous decades (for example, see Sarpkaya 1979 Journal of Applied Mechanics46, 241-258; Price et al. 1989 Eighth International Conference on Offshore Mechanics and Arctic Engineering, The Hague-March 19 -23, 447-454; Yoerger et al. 1991 Journal of Offshore Mechanics and Arctic Engineering, Transaction of Engineers113, 117-127; Grosenbaugh et al. 1991Journal of Offshore Mechanics and Arctic Engineering, Transaction of Engineers113 , 199-204; Brika and Laneville 1992 Journal of Fluid Mechanics250, 481-508; Chakrabarti et al. 1993 Ocean Engineering20, 135-162; Jong 1983 Ph.D. Dissertation, Department of Ocean Engineering, M. I. T.; Kimet al. 1986 Journal of Energy Resources Technology, Transactions of American Society of Mechanical Engineers108, 77-83). However, there are still areas that need more study. One of them is the relation between spatial characteristics of a flow-induced vibrating pipe, such as its length, the distribution of wave number, and frequency responses. A non-linear mechanism between the responses of in-line and cross-flow directions is also an area of interest, if the pipe is relatively long so that structural modal density is reasonably high. In order to investigate such areas, two kinds of instrumented pipe were designed. The instrumented pipes, of which the lengths are equally 6 m, are wound with rubber and silicon tape in different ways, having different vortex-shedding conditions. One has uniform cross-section of diameter of 26·7 mm, and the other has equally spaced four sub-sections, which are composed of different diameters of 75·9, 61·1, 45·6 and 26·7 mm. Both pipes are towed in a water tank (200 m×16 m×7 m) so that they experienced different vortex-shedding excitations. Various measures were obtained from the towing experiment, including frequency responses, the time

  2. Embedding human annoyance rate models in wireless smart sensors for assessing the influence of subway train-induced ambient vibration

    NASA Astrophysics Data System (ADS)

    Sun, Ke; Zhang, Wei; Ding, Huaping; Kim, Robin E.; Spencer, Billie F., Jr.

    2016-10-01

    The operation of subway trains induces ambient vibrations, which may cause annoyance and other adverse effects on humans, eventually leading to physical, physiological, and psychological problems. In this paper, the human annoyance rate (HAR) models, used to assess the human comfort under the subway train-induced ambient vibrations, were deduced and the calibration curves for 5 typical use circumstances were addressed. An autonomous measurement system, based on the Imote2, wireless smart sensor (WSS) platform, plus the SHM-H, high-sensitivity accelerometer board, was developed for the HAR assessment. The calibration curves were digitized and embedded in the computational core of the WSS unit. Experimental validation was conducted, using the developed system on a large underground reinforced concrete frame structure adjoining the subway station. The ambient acceleration of both basement floors was measured; the embedded computation was implemented and the HAR assessment results were wirelessly transmitted to the central server, all by the WSS unit. The HAR distributions of the testing areas were identified, and the extent to which both basements will be influenced by the close-up subway-train’s operation, in term of the 5 typical use circumstances, were quantitatively assessed. The potential of the WSS-based autonomous system for the fast environment impact assessment of the subway train-induced ambient vibration was well demonstrated.

  3. The Modeling of Vibration Damping in SMA Wires

    SciTech Connect

    Reynolds, D R; Kloucek, P; Seidman, T I

    2003-09-16

    Through a mathematical and computational model of the physical behavior of shape memory alloy wires, this study shows that localized heating and cooling of such materials provides an effective means of damping vibrational energy. The thermally induced pseudo-elastic behavior of a shape memory wire is modeled using a continuum thermodynamic model and solved computationally as described by the authors in [23]. Computational experiments confirm that up to 80% of an initial shock of vibrational energy can be eliminated at the onset of a thermally-induced phase transformation through the use of spatially-distributed transformation regions along the length of a shape memory alloy wire.

  4. Interaction dynamics of gap flow with vortex-induced vibration in side-by-side cylinder arrangement

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Jaiman, Rajeev K.

    2016-12-01

    A numerical investigation of the vortex-induced vibration (VIV) in a side-by-side circular cylinder arrangement has been performed in a two-dimensional laminar flow environment. One of the cylinders is elastically mounted and only vibrates in the transverse direction, while its counterpart remains stationary in a uniform flow stream. When the gap ratio is sufficiently small, the flip-flopping phenomenon of the gap flow can be an additional time-dependent interference to the flow field. This phenomenon was reported in the experimental work of Bearman and Wadcock ["The interaction between a pair of circular cylinders normal to a stream," J. Fluid Mech. 61(3), 499-511 (1973)] in a side-by-side circular cylinder arrangement, in which the gap flow deflects toward one of the cylinders and switched its sides intermittently. Albeit one of the two cylinders is free to vibrate, the flip-flop of a gap flow during VIV dynamics can still be observed outside the lock-in region. The exact moments of the flip-flop phenomenon due to spontaneous symmetry breaking are observed in this numerical study. The significant characteristic vortex modes in the near-wake region are extracted via dynamic modal analysis and the interference between the gap flow and VIV is found to be mutual. In a vibrating side-by-side arrangement, the lock-in region with respect to reduced velocity becomes narrower due to the interference from its stationary counterpart. The frequency lock-in occurs and ends earlier than that of an isolated vibrating circular cylinder subjected to an identical flow environment. Similar to a tandem cylinder arrangement, in the post-lock-in region, the maximum vibration amplitudes are escalated compared with those of an isolated circular cylinder configuration. On the other hand, subjected to the influence from VIV, the biased gap flow deflects toward the vibrating cylinder quasi-stably during the frequency lock-in process. This behavior is different from the reported bi

  5. Development of the magnetic force-induced dual vibration energy harvester using a unimorph cantilever

    NASA Astrophysics Data System (ADS)

    Umaba, M.; Nakamachi, E.; Morita, Y.

    2015-12-01

    In this study, a high frequency piezoelectric energy harvester converted from the human low vibrated motion energy was newly developed. This hybrid energy harvester consists of the unimorph piezoelectric cantilever, the pendulum and a pair of permanent magnets. One magnet was attached at the edge of cantilever, and the counterpart magnet at the edge of pendulum. The mechanical energy provided through the human walking motion, which is a typical ubiquitous existence of vibration, is converted to the electric energy via the piezoelectric unimorph cantilever vibration. At first, we studied the energy convert mechanism and analyze the performance of novel energy harvester, where the resonance free vibration of unimorph piezoelectric cantilever generated a high electric power. Next, we equipped the counterpart permanent magnet at the edge of pendulum, which vibrates with a very low frequency caused by the human walking. Then the counterpart magnet was set at the edge of unimorph piezoelectric cantilever, which vibrated with a high frequency. This low-to-high frequency convert "dual vibration system" can be characterized as an enhanced energy harvester. We examined and obtained average values of voltage and power in this system, as 8.31 mV and 0.33 μW. Those results show the possibility to apply for the energy harvester in the portable and implantable Bio-MEMS devices.

  6. Impact of blast induced transitory vibration and air-overpressure/noise on human brain--an experimental study.

    PubMed

    Raina, A K; Baheti, M; Haldar, A; Ramulu, M; Chakraborty, A K; Sahu, P B; Bandopadhayay, C

    2004-04-01

    Human response to blast induced ground vibration and air-overpressure/noise is a major concern of current mining activity. This is because the fact that mines are fast transgressing the habitats and people are getting educated. Consequently the response of humans is changing and expectedly will increase in days to come with no viable and economic alternative to blasting--an essential component of mining. The response of humans can be purely physiological or psychological in nature or combination of both depending upon the situation and conditions of mining. Where physiological response is documented in terms of effects on ears and lungs there is a meager amount or no literature available regarding effects of blasting on the brain. Moreover, the studies on transitory phenomenon like the effects of blasting on humans are rare in comparison to the whole body vibration studies. This study was designed to address the issues as a precursor to a major initiative. The preliminary investigations conducted with the monitoring of EEG responses of humans to vibration and air-overpressure/noise due to blasting revealed that there is no major response of the brain to transitory vibrations and noise.

  7. Time-resolved imaging of laser-induced vibrational wave packets in neutral and ionic states of iodomethane

    NASA Astrophysics Data System (ADS)

    Malakar, Y.; Kaderiya, B.; Zohrabi, M.; Pearson, W. L.; Ziaee, F.; Kananka Raju, P.; Ben-Itzhak, I.; Rolles, D.; Rudenko, A.

    2016-05-01

    Light-driven vibrational wave packets play an important role in molecular imaging and coherent control applications. Here we present the results of a pump-probe experiment characterizing laser-induced vibrational wave packets in both, neutral and ionic states of CH3 I (iodomethane), one of the prototypical polyatomic systems. Measuring yields and kinetic energies of all ionic fragments as a function of the time delay between two 25 fs, 800 nm pump and probe pulses, we map vibrational motion of the molecule, and identify the states involved by channel-resolved Fourier spectroscopy. In the Coulomb explosion channels we observe features with ~ 130 fs periodicity resulting from C-I symmetric stretch (ν3 mode) of the electronically excited cationic state. However the Fourier transform of the low-energy I+ ion yield produced by the dissociative ionization of CH3 I reveals the signatures of the same vibrational mode in the ground electronic states of both, neutral and cation, reflected in 65-70 fs oscillations. We observe the degeneration of the oscillatory structures from the cationic states within ~ 2 ps and discuss most likely reasons for this behavior. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. DOE. K. R. P. and W. L. P. supported by NSF Award No. IIA-143049.

  8. Low Frequency Vibrations Induce Malformations in Two Aquatic Species in a Frequency-, Waveform-, and Direction-Specific Manner

    PubMed Central

    Vandenberg, Laura N.; Stevenson, Claire; Levin, Michael

    2012-01-01

    Environmental toxicants such as industrial wastes, air particulates from machinery and transportation vehicles, and pesticide run-offs, as well as many chemicals, have been widely studied for their effects on human and wildlife populations. Yet other potentially harmful environmental pollutants such as electromagnetic pulses, noise and vibrations have remained incompletely understood. Because developing embryos undergo complex morphological changes that can be affected detrimentally by alterations in physical forces, they may be particularly susceptible to exposure to these types of pollutants. We investigated the effects of low frequency vibrations on early embryonic development of two aquatic species, Xenopus laevis (frogs) and Danio rerio (zebrafish), specifically focusing on the effects of varying frequencies, waveforms, and applied direction. We observed treatment-specific effects on the incidence of neural tube defects, left-right patterning defects and abnormal tail morphogenesis in Xenopus tadpoles. Additionally, we found that low frequency vibrations altered left-right patterning and tail morphogenesis, but did not induce neural tube defects, in zebrafish. The results of this study support the conclusion that low frequency vibrations are toxic to aquatic vertebrates, with detrimental effects observed in two important model species with very different embryonic architectures. PMID:23251546

  9. A new mathematical model to simulate AVA cold-induced vasodilation reaction to local cooling.

    PubMed

    Rida, Mohamad; Karaki, Wafaa; Ghaddar, Nesreen; Ghali, Kamel; Hoballah, Jamal

    2014-11-01

    The purpose of this work was to integrate a new mathematical model with a bioheat model, based on physiology and first principles, to predict thermoregulatory arterio-venous anastomoses (AVA) and cold-induced vasodilation (CIVD) reaction to local cooling. The transient energy balance equations of body segments constrained by thermoregulatory controls were solved numerically to predict segmental core and skin temperatures, and arterial blood flow for given metabolic rate and environmental conditions. Two similar AVA-CIVD mechanisms were incorporated. The first was activated during drop in local skin temperature (<32 °C). The second mechanism was activated at a minimum finger skin temperature, T(CIVD, min), where the AVA flow is dilated and constricted once the skin temperature reached a maximum value. The value of T(CIVD,min) was determined empirically from values reported in literature for hand immersions in cold fluid. When compared with published data, the model predicted accurately the onset time of CIVD at 25 min and T(CIVD,min) at 10 °C for hand exposure to still air at 0 °C. Good agreement was also obtained between predicted finger skin temperature and experimentally published values for repeated immersion in cold water at environmental conditions of 30, 25, and 20 °C. The CIVD thermal response was found related to core body temperature, finger skin temperature, and initial finger sensible heat loss rate upon exposure to cold fluid. The model captured central and local stimulations of the CIVD and accommodated observed variability reported in literature of onset time of CIVD reaction and T(CIVD,min).

  10. [Development of vibration-induced intrahepatic cholestasis in pilots and new ways of correcting these disorders].

    PubMed

    Preobrazhenskiĭ, V N; Vasilenko, V V; Taianovskiĭ, V Iu

    1999-01-01

    Data of analysis of the role of vibration in the development of hepatobiliary pathology in helicopter pilots are reported. Vibration was found to drastically deteriorate colloid-osmotic qualities of the bile and increase the lithogenesis risk. Exposure to vibration over 10 and more years of the flying career may instigate cholelithiasis. Dynamic USI with functional testing for early diagnostics and correction with ursodeoxycholic acid (ursosan) of disorders in the colloid-osmotic properties of the bile and can be proposed as one of the methods to prevent cholelithiasis.

  11. Postponement of incipient collapse due to work-induced heat stress by limited cooling

    NASA Technical Reports Server (NTRS)

    Blockley, W. V.

    1973-01-01

    Four subjects completed five treadmill training sessions under comfortable to cool conditions and were calibrated to find an optimum combination of speed and grade on the treadmill which would produce a metabolic rate of 2000 Btu-hr. Dressed in an Apollo liquid cooling garment, each man underwent a total of four experiments in which the rate of heat extraction from the liquid cooling garment was adjusted to an amount which would cause a storage within the body of 1000 Btu/hr. Physiological measurements included skin temperature at 9 locations, rectal and ear canal probes, and heart rate. The increases in tolerance time for the various subjects and the various methods of emergency cooling, ranged from a low of six minutes to a high of 48 minutes, or from 8 to 102% of the baseline tolerance times. The largest gains were achieved in a subject whose tolerance endpoint was atypical, and whose baseline heat tolerance was unsually low.

  12. Vibration-induced muscle injury. An experimental model and preliminary findings.

    PubMed

    Necking, L E; Dahlin, L B; Fridén, J; Lundborg, G; Lundström, R; Thornell, L E

    1992-06-01

    The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.

  13. Disk/Shaft Vibration Induced by Bearing Clearance Effects: Analysis and Experiment

    NASA Technical Reports Server (NTRS)

    Flowers, George T.; Wu, Fangsheng

    1996-01-01

    This study presents an investigation of the dynamics of a rotor system with bearing clearance. Of particular interest is the influence of such effects on coupled disk/shaft vibration. Experimental results for a rotor system with a flexible disk are presented and compared to predictions from a simulation model. Some insights and conclusions are obtained with regard to the conditions under which such vibration may be significant.

  14. What is wrong with the 30-year-old practice of scalp cooling for the prevention of chemotherapy-induced hair loss?

    PubMed

    Breed, Wim P M

    2004-01-01

    Since about 1970 scalp cooling has been used to prevent chemotherapy-induced hair loss, one of the most common and emotionally distressing side effects of cancer therapy. Generally accepted opinions, uncertainty and controversy, topics to study and recommendations for improving the results of scalp cooling are the subjects of this article which was also presented at the MASCC Symposium, June 2003, Berlin.

  15. The rate parameters for coupled vibration-dissociation in a generalized SSH approximation. [Schwarz, Slawsky, and Herzfeld

    NASA Technical Reports Server (NTRS)

    Sharma, Surendra P.; Huo, Winifred M.; Park, Chul

    1988-01-01

    A theoretical study of vibrational excitations and dissociations of nitrogen undergoing a nonequilibrium relaxation process upon heating and cooling is reported. The rate coefficients for collisional induced vibrational transitions and transitions from a bound vibrational state into a dissociative state have been calculated using an extension of the theory originally proposed by Schwarz (SSH) et al. (1952). High-lying vibrational states and dissociative states were explicitly included but rotational energy transfer was neglected. The transition probabilities calculated from the SSH theory were fed into the master equation, which was integrated numerically to determine the population distribution of the vibrational states as well as bulk thermodynamic properties. The results show that: (1) the transition rates have a minimum near the middle of the bound vibrational levels, causing a bottleneck in the vibrational relaxation and dissociation rates; (2) high vibrational states are always in equilibrium with the dissociative state; (3) for the heating case, only the low vibrational states relax according to the Landau-Teller theory; (4) for the cooling case, vibrational relaxation cannot be described by a rate equation; (5) Park's (1985, 1988) two-temperature model is approximately valid; and (6) the average vibrational energy removed in dissociation is about 30 percent of the dissociation energy.

  16. Vortex-induced vibration effect on fatigue life estimate of turbine blades

    NASA Astrophysics Data System (ADS)

    Lau, Y. L.; Leung, R. C. K.; So, R. M. C.

    2007-11-01

    An analysis of a turbine blade fatigue life that includes the physics of fluid-structure interaction on the high cycle fatigue (HCF) life estimate of turbine blades is carried out. The rotor wake excitation is modeled by rows of Karman vortices superimposed on an inviscid uniform flow. The vortex-induced vibration problem is modeled by a linear cascade composed of five turbine blades and the coupled Euler and structural dynamics equations are numerically solved using a time-marching boundary element technique. The analysis can be applied to any blade geometries; it is not limited to the blade geometry considered here. Two major design parameters have been identified; the ratio of blade spacing to blade chord length s/ c of the stator, and the normalized frequency parameter c/ d which is related to the wake passing frequency of the rotor. For a rigid cascade, it is found that aerodynamic resonance prevails at the resonant c/ d values corresponding to an isolated blade while s/ c is responsible for the level of the aerodynamic response. If the central blades were elastic, the parameter s/ c plays a different role in the fluid-structure interaction problem. With a c/ d that could lead to structural resonance for an isolated blade, changing s/ c would stabilize the aerodynamic and structural response of the elastic blade in a cascade. On the contrary, an improper choice of s/ c might turn the elastic blade response into structural resonance even though the oncoming c/ d is non-resonant. The results of the nonlinear effects of c/ d and s/ c could be used together with the Campbell diagram to obtain an improved HCF design of rotor-stator pair.

  17. Mechanisms of free-surface breakup in vibration-induced liquid atomization

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2007-01-01

    The mechanisms of droplet formation that take place during vibration-induced drop atomization are investigated experimentally. Droplet ejection results from the breakup of transient liquid spikes that form following the localized collapse of free-surface waves. Breakup typically begins with capillary pinch-off of a droplet from the tip of the spike and can be followed by additional pinch-offs of satellite droplets if the corresponding capillary number is sufficiently small (e.g., in low-viscosity liquids). If the capillary number is increased (e.g., in viscous liquids), breakup first occurs near the base of the spike, with or without subsequent breakup of the detached, thread-like spike. The formation of these detached threads is governed by a breakup mechanism that is separated from the tip-dominated capillary pinch-off mechanism by an order of magnitude in terms of dimensionless driving frequency f*. The dependence of breakup time and unbroken spike length on fluid and driving parameters is established over a broad range of dimensionless driving frequencies (10-3

  18. Influence of light-induced conical intersection on the photodissociation dynamics of D2(+) starting from individual vibrational levels.

    PubMed

    Halász, Gábor J; Csehi, András; Vibók, Ágnes; Cederbaum, Lorenz S

    2014-12-26

    Previous works have shown that dressing of diatomic molecules by standing or by running laser waves gives rise to the appearance of so-called light-induced conical intersections (LICIs). Because of the strong nonadiabatic couplings, the existence of such LICIs may significantly change the dynamical properties of a molecular system. In our former paper (J. Phys. Chem. A 2013, 117, 8528), the photodissociation dynamics of the D(2)(+) molecule were studied in the LICI framework starting the initial vibrational nuclear wave packet from the superposition of all the vibrational states initially produced by ionizing D(2). The present work complements our previous investigation by letting the initial nuclear wave packets start from different individual vibrational levels of D(2)(+), in particular, above the energy of the LICI. The kinetic energy release spectra, the total dissociation probabilities, and the angular distributions of the photofragments are calculated and discussed. An interesting phenomenon has been found in the spectra of the photofragments. Applying the light-induced adiabatic picture supported by LICI, explanations are given for the unexpected structure of the spectra.

  19. Extension of the prognostic model of sea surface temperature to rain-induced cool and fresh lenses

    NASA Astrophysics Data System (ADS)

    Bellenger, Hugo; Drushka, Kyla; Asher, William; Reverdin, Gilles; Katsumata, Masaki; Watanabe, Michio

    2017-01-01

    The Zeng and Beljaars (2005) sea surface temperature prognostic scheme, developed to represent diurnal warming, is extended to represent rain-induced freshening and cooling. Effects of rain on salinity and temperature in the molecular skin layer (first few hundred micrometers) and the near-surface turbulent layer (first few meters) are separately parameterized by taking into account rain-induced fluxes of sensible heat and freshwater, surface stress, and mixing induced by droplets penetrating the water surface. Numerical results from this scheme are compared to observational data from two field studies of near-surface ocean stratifications caused by rain, to surface drifter observations and to previous computations with an idealized ocean mixed layer model, demonstrating that the scheme produces temperature variations consistent with in situ observations and model results. It reproduces the dependency of salinity on wind and rainfall rate and the lifetime of fresh lenses. In addition, the scheme reproduces the observed lag between temperature and salinity minimum at low wind speed and is sensitive to the peak rain rate for a given amount of rain. Finally, a first assessment of the impact of these fresh lenses on ocean surface variability is given for the near-equatorial western Pacific. In particular, the variability due to the mean rain-induced cooling is comparable to the variability due to the diurnal warming so that they both impact large-scale horizontal surface temperature gradients. The present parameterization can be used in a variety of models to study the impact of rain-induced fresh and cool lenses at different spatial and temporal scales.

  20. Resonance forever: existence of a critical mass and an infinite regime of resonance in vortex-induced vibration

    NASA Astrophysics Data System (ADS)

    Govardhan, R.; Williamson, C. H. K.

    2002-12-01

    In this paper, we study the transverse vortex-induced vibrations of a cylinder with no structural restoring force (k = 0). In terms of the conventionally used normalized flow velocity, U*, the present experiments correspond to an infinite value (where U* = U/fND, fN = natural frequency, D = diameter). A reduction of mass ratios m* (mass/displaced mass) from the classically studied values of order m* = 100, down to m* = 1, yields negligible oscillations. However, a further reduction in mass exhibits a surprising result: large-amplitude vigorous vibrations suddenly appear for values of mass less than a critical mass ratio, m*crit = 0.54. The classical assumption, since the work of den Hartog (1934), has been that resonant large-amplitude oscillations exist only over a narrow range of velocities, around U*[similar]5, where the vortex shedding frequency is comparable with the natural frequency. However, in the present study, we demonstrate that, so long as the body’s mass is below this critical value, the regime of normalized velocities (U*) for resonant oscillations is infinitely wide, beginning at around U*[similar]5 and extending to U*[rightward arrow][infty infinity]. This result is in precise accordance with the predictions put forward by Govardhan & Williamson (2000), based on elastically mounted vibration studies (where k > 0). We deduce a condition under which this unusual concept of an infinitely wide regime of resonance will occur in any generic vortex-induced vibration system.

  1. Jet-cooled laser-induced dispersed fluorescence spectroscopy of TaN: Observation of a3Δ and A1Δ states

    NASA Astrophysics Data System (ADS)

    Mukund, Sheo; Bhattacharyya, Soumen; Nakhate, S. G.

    2016-07-01

    Laser-induced dispersed fluorescence spectra of TaN molecules, produced in a free-jet apparatus, have been studied. Two spin components of the lowest-lying a3Δ state along with their vibrational structure have been observed. The A1Δ state, which was predicted earlier by ab initio calculation has also been observed. The X1Σ+ ground state vibrational progression up to v = 9 has been recorded. The experimentally determined term energies and vibrational constants at equilibrium for the ground and a3Δ states are in fairly good agreement with the ab initio values reported earlier.

  2. Experimental study on cross-flow induced vibrations in heat exchanger tube bundle

    NASA Astrophysics Data System (ADS)

    Khushnood, Shahab; Nizam, Luqman Ahmad

    2017-03-01

    Vibration in heat exchangers is one of the main problems that the industry has faced over last few decades. Vibration phenomenon in heat exchangers is of major concern for designers and process engineers since it can lead to the tube damage, tube leakage, baffle damage, tube collision damage, fatigue, creep etc. In the present study, vibration response is analyzed on single tube located in the centre of the tube bundle having parallel triangular arrangement (60°) with P/ D ratio of 1.44. The experiment is performed for two different flow conditions. This kind of experiment has not been reported in the literature. Under the first condition, the tube vibration response is analyzed when there is no internal flow in the tube and under the second condition, the response is analyzed when the internal tube flow is maintained at a constant value of 0.1 m/s. The free stream shell side velocity ranges from 0.8 m/s to 1.3 m/s, the reduced gap velocity varies from 1.80 to 2.66 and the Reynolds number varies from 44500 to 66000. It is observed that the internal tube flow results in larger vibration amplitudes for the tube than that without internal tube flow. It is also established that over the current range of shell side flow velocity, the turbulence is the dominant excitation mechanism for producing vibration in the tube since the amplitude varies directly with the increase in the shell side velocity. Damping has no significant effect on the vibration behavior of the tube for the current velocity range.

  3. The Acute Effect of Local Vibration As a Recovery Modality from Exercise-Induced Increased Muscle Stiffness

    PubMed Central

    Pournot, Hervé; Tindel, Jérémy; Testa, Rodolphe; Mathevon, Laure; Lapole, Thomas

    2016-01-01

    Exercise involving eccentric muscle contractions is known to decrease range of motion and increase passive muscle stiffness. This study aimed at using ultrasound shear wave elastography to investigate acute changes in biceps brachii passive stiffness following intense barbell curl exercise involving both concentric and eccentric contractions. The effect of local vibration (LV) as a recovery modality from exercise-induced increased stiffness was further investigated. Eleven subjects performed 4 bouts of 10 bilateral barbell curl movements at 70% of the one-rep maximal flexion force. An arm-to-arm comparison model was then used with one arm randomly assigned to the passive recovery condition and the other arm assigned to the LV recovery condition (10 min of 55-Hz vibration frequency and 0.9-mm amplitude). Biceps brachii shear elastic modulus measurements were performed prior to exercise (PRE), immediately after exercise (POST-EX) and 5 min after the recovery period (POST-REC). Biceps brachii shear elastic modulus was significantly increased at POST-EX (+53 ± 48%; p < 0.001) and POST-REC (+31 ± 46%; p = 0.025) when compared to PRE. No differences were found between passive and LV recovery (p = 0.210). LV as a recovery strategy from exercise-induced increased muscle stiffness was not beneficial, probably due to an insufficient mechanical action of vibrations. Key points Bouts of barbell curl exercise induce an immediate increased passive stiffness of the biceps brachii muscle, as evidenced by greater shear elastic modulus measured by supersonic shear imaging. The administration of a vibratory massage did not reduce this acute exercise-induced increased stiffness. PMID:26957937

  4. Satellites of Xe transitions induced by infrared active vibrational modes of CF4 and C2F6 molecules.

    PubMed

    Alekseev, Vadim A; Schwentner, Nikolaus

    2011-07-28

    Absorption and luminescence excitation spectra of Xe/CF(4) mixtures were studied in the vacuum UV region at high resolution using tunable synchrotron radiation. Pressure-broadened resonance bands and bands associated with dipole-forbidden states of the Xe atom due to collision-induced breakdown of the optical selection rules are reported. The spectra display in addition numerous satellite bands corresponding to transitions to vibrationally excited states of a Xe-CF(4) collisional complex. These satellites are located at energies of Xe atom transition increased by one quantum energy in the IR active v(3) vibrational mode of CF(4) (v(3) = 1281 cm(-1)). Satellites of both resonance and dipole-forbidden transitions were observed. Satellites of low lying resonance states are spectrally broad bands closely resembling in shape their parent pressure-broadened resonance bands. In contrast, satellites of dipole-forbidden states and of high lying resonance states are spectrally narrow bands (FWHM ∼10 cm(-1)). The satellites of dipole-forbidden states are orders of magnitude stronger than transitions to their parent states due to collision-induced breakdown of the optical selection rules. These satellites are attributed to a coupling of dipole-forbidden and resonance states induced by the electric field of the transient CF(4) (v(3) = 0 ↔ v(3) = 1) dipole. Similar satellites are present in spectra of Xe/C(2)F(6) mixtures where these bands are induced by the IR active v(10) mode of C(2)F(6). Transitions to vibrationally excited states of Xe-CF(4)(C(2)F(6)) collision pairs were also observed in two-photon LIF spectra.

  5. Transport-Coefficient Dependence of Current-Induced Cooling Effect in a Two-Dimensional Electron Gas

    NASA Astrophysics Data System (ADS)

    Hirayama, Naomi; Endo, Akira; Fujita, Kazuhiro; Hasegawa, Yasuhiro; Hatano, Naomichi; Nakamura, Hiroaki; Shirasaki, Ryōen; Yonemitsu, Kenji

    2012-06-01

    The dependence of the current-induced cooling effect on the electron mobility μ e is explored for a two-dimensional electron gas (2DEG) subjected to a perpendicular magnetic field. We calculate the distributions of the electrochemical potentials and the temperatures under a magnetic field, fully taking account of thermoelectric and thermomagnetic phenomena. Whereas the electrochemical potential and the electric current remain qualitatively unchanged, the temperature distribution exhibits drastic mobility dependence. The lower-mobility system has cold and hot areas at opposite corners, which results from the heat current brought about by the Ettingshausen effect in the vicinity of the adiabatic boundaries. The cooling effect is intensified by an increase in μ e. Intriguingly, the cold and hot areas change places with each other as the mobility μ e is further increased. This is because the heating current on the adiabatic edges due to the Righi-Leduc effect exceeds that due to the Ettingshausen effect in the opposite direction.

  6. Oxygen isotopes in western Australian coral reveal Pinatubo aerosol-induced cooling in the Western Pacific Warm Pool

    SciTech Connect

    Gagan, M.K.; Chivas, A.R.

    1995-05-01

    The authors report a 12 year record study of oxygen 18 isotope signals in a coral (Ningaloo Reef), which is situated so as to give an ideal measure of the sea-surface temperature variation of the local Leeuwin Current. This record consists of nearly weekly readings from 1981 to 1993, and brackets the period following the June 1991 eruption of Mt. Pinatubo. Extended study shows a strong correlation of sea-surface temperature on this coral with changes in the Western Pacific Warm Pool (WPWP), with a lag of 2.5 years. A distinct cooling signal was seen in the inferred sea-surface temperatures from coral measurements, in 1992 and 1993, which suggests the WPWP was cooled roughly 0.5{degrees}C by aerosol induced effects.

  7. Scanning LDV for vibration measurement of filiform hairs in crickets in response to induced airflow

    NASA Astrophysics Data System (ADS)

    Santulli, C.; Finn, T. J.; Seidel, R.; Jeronimidis, G.

    2006-06-01

    Cercal hairs represent in cricket a wind sensitive escape system, able to detect the airflow generated from predating species. These sensors have been studied as a biomimetic concept to allow the development of MEMS for biomedical use. In particular, the behaviour of the hairs, including airflow response, resonant frequency and damping, has been investigated up to a frequency of 20 kHz. The microscopic nature of the hairs, the complex vibrations of excited hairs and the high damping of the system suggested that the use of Laser Doppler vibrometry could possibly improve the test performance. Two types of tests were performed: in the first case the hairs were indirectly excited using the signal obtained from a vibrating aluminium plate, whilst in the second case the hairs were directly excited using a white noise chirp. The results from the first experiment indicated that the hairs move in-phase with the exciting signal up to frequencies in the order of 10 kHz, responding to the vibration modes of the plate with a signal attenuation of 12 to 20 dB. The chirp experiment revealed the presence of rotational resonant modes at 6850 and 11300 Hz. No clear effect of hair length was perceivable on the vibration response of the filiform sensors. The obtained results proved promising to support the mechanical and vibration characterisation of the hairs and suggest that scanning Laser vibrometry can be used extensively on highly dampened biological materials.

  8. Characterization of Turbulence and Cavitation Induced Pipe Vibrations Due to Flow thru Baffle Plates

    NASA Astrophysics Data System (ADS)

    Holt, Gavin; Maynes, Daniel; Blotter, Jonathan

    2010-11-01

    We report experimental results characterizing pipe vibrations caused by turbulent flow and cavitation due to water flow through baffle plates mounted in a 10.2 cm diameter schedule 40 PVC pipe test section of a closed water flow loop. The baffle plates contained varying hole sizes that ranged from 0.159 cm to 2.54 cm, with the total through area, or openness, of each baffle plate ranging between 11% and 60%. Pipe wall acceleration data was collected for a range of Reynolds numbers from 5-85 x 10^4. Acceleration measurements were acquired at locations along the pipe from 3-110 diameters downstream of the baffle plate. The measurements show that vibration levels at a given streamwise position increase with larger holes size, a decrease in openness, and increased flow rate. The incipient point of cavitation was observed to occur at decreasing flow rate with increasing hole size and decreasing openness. Vibration levels decreased asymptotically with increased distance downstream of the baffle plate for all scenarios and the streamwise distance at which the vibration level was attenuated increased as the hole size increased, openness decreased, and flow rate increased. The downstream vibration level also increased with these parameters.

  9. A framework for advanced methods of control of human-induced vibrations

    NASA Astrophysics Data System (ADS)

    Reynolds, Paul

    2012-04-01

    The vibration serviceability of civil engineering structures under human dynamic excitation is becoming ever more critical with the design and redevelopment of structures with reduced mass, stiffness and damping. A large number of problems have been reported in floors, footbridges, sports stadia, staircases and other structures. Unfortunately, the range of options available to fix such problems are very limited and are primarily limited to structural modification or the implementation of passive vibration control measures, such as tuned mass dampers. This paper presents the initial development of a new framework for advanced methods of control of humaninduced vibrations in civil engineering structures. This framework includes both existing passive methods of vibration control and more advanced active, semi-active and hybrid control techniques, which may be further developed as practical solutions for these problems. Through the use of this framework, rational decisions as to the most appropriate technologies for particular human vibration problems may be made and pursued further. This framework is also intended to be used in the design of new civil engineering structures, where advanced control technologies may be used both to increase the achievable slenderness and to reduce the amount of construction materials used and hence their embodied energy. This will be an ever more important consideration with the current drive for structures with reduced environmental impact.

  10. A non-resonant, frequency up-converted electromagnetic energy harvester from human-body-induced vibration for hand-held smart system applications

    NASA Astrophysics Data System (ADS)

    Halim, Miah A.; Park, Jae Y.

    2014-03-01

    We present a non-resonant, frequency up-converted electromagnetic energy harvester that generates significant power from human-body-induced vibration, e.g., hand-shaking. Upon excitation, a freely movable non-magnetic ball within a cylinder periodically hits two magnets suspended on two helical compression springs located at either ends of the cylinder, allowing those to vibrate with higher frequencies. The device parameters have been designed based on the characteristics of human hand-shaking vibration. A prototype has been developed and tested both by vibration exciter (for non-resonance test) and by manual hand-shaking. The fabricated device generated 110 μW average power with 15.4 μW cm-3 average power density, while the energy harvester was mounted on a smart phone and was hand-shaken, indicating its ability in powering portable hand-held smart devices from low frequency (<5 Hz) vibrations.

  11. Radiofrequency catheter ablation: different cooled and noncooled electrode systems induce specific lesion geometries and adverse effects profiles.

    PubMed

    Dorwarth, Uwe; Fiek, Michael; Remp, Thomas; Reithmann, Cristopher; Dugas, Martin; Steinbeck, Gerhard; Hoffmann, Ellen

    2003-07-01

    The success and safety of standard catheter radiofrequency ablation may be limited for ablation of atrial fibrillation and ventricular tachycardia. The aim of this study was to characterize and compare different cooled and noncooled catheter systems in terms of their specific lesion geometry, incidence of impedance rise, and crater and coagulum formation to facilitate appropriate catheter selection for special indications. The study investigated myocardial lesion generation of three cooled catheter systems (7 Fr, 4-mm tip): two saline irrigation catheters with a showerhead-type electrode tip (sprinkler) and a porous metal tip and an internally cooled catheter. Noncooled catheters (7 Fr) had a large tip electrode (8 mm) and a standard tip electrode (4 mm). RF energy was delivered on isolated porcine myocardium superfused with heparinized pig blood (37 degrees C) at power settings of 10-40 W. Both irrigated systems were characterized by a large lesion depth (8.1 +/- 1.6 mm) and a large lesion diameter (13.8 +/- 1.6 mm). In comparison, internally cooled lesions showed a similar lesion depth (8.0 +/- 1.0 mm), but a significantly smaller lesion diameter (12.3 +/- 1.2 mm,P = 0.04). Large tip lesions had a similar lesion diameter (14.5 +/- 1.6 mm), but a significantly smaller lesion depth (6.3 +/- 1.0 mm,P = 0.002) compared to irrigated lesions. However, lesion volume was not significantly different between the three cooled and the large tip catheter. To induce maximum lesion size, power requirements were three times higher for the irrigation systems and two times higher for the internally cooled and the large tip catheter compared to the standard catheter. Impedance rise was rarest with irrigated and large tip ablation. In case of impedance rise crater formation was a frequent observation (61-93%). Irrigated catheters prevented coagulum formation most effectively. Irrigated rather than internally cooled ablation appears to be most adequate for the induction of deep and

  12. A Dimensional Analysis Approach to Study Blast-Induced Ground Vibration

    NASA Astrophysics Data System (ADS)

    Khandelwal, Manoj; Saadat, Mahdi

    2015-03-01

    The prediction of ground vibration is of great importance in the alleviation of the detrimental effects of blasting. Therefore, a vibration control study to minimize the harm of ground vibration and its influence on nearby structures can play an important role in the mining industry. In this paper, a dimensional analysis (DA) technique has been performed on various blast design parameters to propose a new formula for the prediction of the peak particle velocity (PPV). After obtaining the DA formula, 105 data sets were used to determine the unknown coefficients of the DA equation, as well as site constants of different conventional predictor equations. Then, 12 new blast data sets were used to compare the capability of the DA formula with conventional predictor equations. The results were compared based on the coefficient of determination and mean absolute error between measured and predicted values of the PPV.

  13. Dynamic effect of metro-induced vibration on the rammed earth base of the Bell Tower.

    PubMed

    Lai, Jinxing; Niu, Fangyuan; Wang, Ke; Chen, Jianxun; Qiu, Junling; Fan, Haobo; Hu, Zhinan

    2016-01-01

    Xi'an Bell Tower (the Bell Tower) is a state-level ancient relic in China. The vibration caused by metro will exert adverse effect on the Bell Tower. This paper aims at presenting 3D-FEM models to predict the peak period velocity (PPV) of rammed earth base when the metro passing through the Bell Tower. The calculation results are compared with those of field test. Both results were found to be in good agreement. Furthermore, the results indicated that the effect of shock absorption measures is significant. The shock absorption tracks can obviously decrease the vibration of the Bell Tower, and the maximum decrease of PPV of the rammed earth base is 78.91 %. The proposed prediction has the potential to be developed as a decision and management tool for the evaluation of the risk associated with the influence of vibration caused by metro on buildings in urban areas.

  14. Electron–vibration coupling induced renormalization in the photoemission spectrum of diamondoids

    PubMed Central

    Gali, Adam; Demján, Tamás; Vörös, Márton; Thiering, Gergő; Cannuccia, Elena; Marini, Andrea

    2016-01-01

    The development of theories and methods devoted to the accurate calculation of the electronic quasi-particle states and levels of molecules, clusters and solids is of prime importance to interpret the experimental data. These quantum systems are often modelled by using the Born–Oppenheimer approximation where the coupling between the electrons and vibrational modes is not fully taken into account, and the electrons are treated as pure quasi-particles. Here, we show that in small diamond cages, called diamondoids, the electron–vibration coupling leads to the breakdown of the electron quasi-particle picture. More importantly, we demonstrate that the strong electron–vibration coupling is essential to properly describe the overall lineshape of the experimental photoemission spectrum. This cannot be obtained by methods within Born–Oppenheimer approximation. Moreover, we deduce a link between the vibronic states found by our many-body perturbation theory approach and the well-known Jahn–Teller effect. PMID:27103340

  15. Experimental evidence for quantum interference and vibrationally induced decoherence in single-molecule junctions.

    PubMed

    Ballmann, Stefan; Härtle, Rainer; Coto, Pedro B; Elbing, Mark; Mayor, Marcel; Bryce, Martin R; Thoss, Michael; Weber, Heiko B

    2012-08-03

    We analyze quantum interference and decoherence effects in single-molecule junctions both experimentally and theoretically by means of the mechanically controlled break junction technique and density-functional theory. We consider the case where interference is provided by overlapping quasidegenerate states. Decoherence mechanisms arising from electronic-vibrational coupling strongly affect the electrical current flowing through a single-molecule contact and can be controlled by temperature variation. Our findings underline the universal relevance of vibrations for understanding charge transport through molecular junctions.

  16. Vibration-induced coherence enhancement of the performance of a biological quantum heat engine

    NASA Astrophysics Data System (ADS)

    Chen, Hong-Bin; Chiu, Pin-Yi; Chen, Yueh-Nan

    2016-11-01

    Photosynthesis has been a long-standing research interest due to its fundamental importance. Recently, studies on photosynthesis processes also have inspired attention from a thermodynamical aspect when considering photosynthetic apparatuses as biological quantum heat engines. Quantum coherence is shown to play a crucial role in enhancing the performance of these quantum heat engines. Based on the experimentally reported structure, we propose a quantum heat engine model with a non-Markovian vibrational mode. We show that one can obtain a performance enhancement easily for a wide range of parameters in the presence of the vibrational mode. Our results provide insights into the photosynthetic processes and a design principle mimicking natural organisms.

  17. Experiments on reduction of propeller induced interior noise by active control of cylinder vibration

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Jones, J. D.

    1987-01-01

    The feasibility of reducing interior noise caused by advanced turbo propellers by controlling the vibration of aircraft fuselages was investigated by performing experiments in an anechoic chamber with an aircraft model test rig and apparatus. It was found that active vibration control provides reasonable global attenuation of interior noise levels for the cases of resonant (at 576 Hz) and forced (at 708 Hz) system response. The controlling mechanism behind the effect is structural-acoustic coupling between the shell and the contained field, termed interface modal filtering.

  18. Cooling-induced SUMOylation of EXOSC10 down-regulates ribosome biogenesis.

    PubMed

    Knight, John R P; Bastide, Amandine; Peretti, Diego; Roobol, Anne; Roobol, Jo; Mallucci, Giovanna R; Smales, C Mark; Willis, Anne E

    2016-04-01

    The RNA exosome is essential for 3' processing of functional RNA species and degradation of aberrant RNAs in eukaryotic cells. Recent reports have defined the substrates of the exosome catalytic domains and solved the multimeric structure of the exosome complex. However, regulation of exosome activity remains poorly characterized, especially in response to physiological stress. Following the observation that cooling of mammalian cells results in a reduction in 40S:60S ribosomal subunit ratio, we uncover regulation of the nuclear exosome as a result of reduced temperature. Using human cells and an in vivo model system allowing whole-body cooling, we observe reduced EXOSC10 (hRrp6, Pm/Scl-100) expression in the cold. In parallel, both models of cooling increase global SUMOylation, leading to the identification of specific conjugation of SUMO1 to EXOSC10, a process that is increased by cooling. Furthermore, we define the major SUMOylation sites in EXOSC10 by mutagenesis and show that overexpression of SUMO1 alone is sufficient to suppress EXOSC10 abundance. Reducing EXOSC10 expression by RNAi in human cells correlates with the 3' preribosomal RNA processing defects seen in the cold as well as reducing the 40S:60S ratio, a previously uncharacterized consequence of EXOSC10 suppression. Together, this work illustrates that EXOSC10 can be modified by SUMOylation and identifies a physiological stress where this regulation is prevalent both in vitro and in vivo.

  19. Cooling-induced SUMOylation of EXOSC10 down-regulates ribosome biogenesis

    PubMed Central

    Bastide, Amandine; Peretti, Diego; Roobol, Anne; Roobol, Jo; Mallucci, Giovanna R.; Smales, C. Mark; Willis, Anne E.

    2016-01-01

    The RNA exosome is essential for 3′ processing of functional RNA species and degradation of aberrant RNAs in eukaryotic cells. Recent reports have defined the substrates of the exosome catalytic domains and solved the multimeric structure of the exosome complex. However, regulation of exosome activity remains poorly characterized, especially in response to physiological stress. Following the observation that cooling of mammalian cells results in a reduction in 40S:60S ribosomal subunit ratio, we uncover regulation of the nuclear exosome as a result of reduced temperature. Using human cells and an in vivo model system allowing whole-body cooling, we observe reduced EXOSC10 (hRrp6, Pm/Scl-100) expression in the cold. In parallel, both models of cooling increase global SUMOylation, leading to the identification of specific conjugation of SUMO1 to EXOSC10, a process that is increased by cooling. Furthermore, we define the major SUMOylation sites in EXOSC10 by mutagenesis and show that overexpression of SUMO1 alone is sufficient to suppress EXOSC10 abundance. Reducing EXOSC10 expression by RNAi in human cells correlates with the 3′ preribosomal RNA processing defects seen in the cold as well as reducing the 40S:60S ratio, a previously uncharacterized consequence of EXOSC10 suppression. Together, this work illustrates that EXOSC10 can be modified by SUMOylation and identifies a physiological stress where this regulation is prevalent both in vitro and in vivo. PMID:26857222

  20. Vortex-induced vibrations of a flexibly-mounted inclined cylinder

    NASA Astrophysics Data System (ADS)

    Jain, Anil; Modarres-Sadeghi, Yahya

    2013-11-01

    The majority of studies on vortex-induced vibrations of a flexibly-mounted rigid cylinder are for the cases where the flow direction is perpendicular to the long axis of the structure. However, in many engineering applications, such as cable stays in bridges and mooring lines of floating offshore wind turbines, the flow direction may not be perpendicular to the structure. To understand the vortex shedding behind a fixed inclined cylinder, the Independence Principle (IP) has been used. The IP assumes that an inclined cylinder behaves similarly to a normal-incidence case, if only the component of the free stream velocity normal to the cylinder axis is considered. The IP neglects the effect of the axial component of the flow, which seems reasonable for small angles of inclination, but not for large angles. In the present study, a series of experiments have been conducted on a flexibly-mounted rigid cylinder placed inclined to the oncoming flow with various angles of inclination (0°<θ<75°) in a range of Reynolds numbers from 500 to 4000 to investigate how the angle of inclination affects VIV. A rigid cylinder was mounted on springs, and air bearings were used to reduce the structural damping of the system. The system was placed in the test-section of a recirculating water tunnel and the crossflow displacements were measured at each flow velocity. Even at high angles of inclination, large-amplitude oscillations were observed. As the angle of inclination was increased, the lock-in range (the range of reduced flow velocities for which the cylinder oscillates with a large amplitude) started at a higher reduced velocity. When only the normal component of the oncoming flow was considered, the onset of lock-in was observed to be at the same normalized flow velocity for all angles of inclination except for 75°. However, the width of the lock-in region, its pattern, the maximum amplitude of oscillations and its corresponding normalized reduced velocity were not following

  1. On the Proper Estimation of the Confidence Interval for the Design Formula of Blast-Induced Vibrations with Site Records

    NASA Astrophysics Data System (ADS)

    Yan, W. M.; Yuen, Ka-Veng

    2015-01-01

    Blast-induced ground vibration has received much engineering and public attention. The vibration is often represented by the peak particle velocity (PPV) and the empirical approach is employed to describe the relationship between the PPV and the scaled distance. Different statistical methods are often used to obtain the confidence level of the prediction. With a known scaled distance, the amount of explosives in a planned blast can then be determined by a blast engineer when the PPV limit and the confidence level of the vibration magnitude are specified. This paper shows that these current approaches do not incorporate the posterior uncertainty of the fitting coefficients. In order to resolve this problem, a Bayesian method is proposed to derive the site-specific fitting coefficients based on a small amount of data collected at an early stage of a blasting project. More importantly, uncertainty of both the fitting coefficients and the design formula can be quantified. Data collected from a site formation project in Hong Kong is used to illustrate the performance of the proposed method. It is shown that the proposed method resolves the underestimation problem in one of the conventional approaches. The proposed approach can be easily conducted using spreadsheet calculation without the need for any additional tools, so it will be particularly welcome by practicing engineers.

  2. Vibration-induced drop atomization and the numerical simulation of low-frequency single-droplet ejection

    NASA Astrophysics Data System (ADS)

    James, Ashley J.; Smith, Marc K.; Glezer, Ari

    2003-02-01

    Vibration-induced droplet ejection is a novel way to create a spray. In this method, a liquid drop is placed on a vertically vibrating solid surface. The vibration leads to the formation of waves on the free surface. Secondary droplets break off from the wave crests when the forcing amplitude is above a critical value. When the forcing frequency is small, only low-order axisymmetric wave modes are excited, and a single secondary droplet is ejected from the tip of the primary drop. When the forcing frequency is high, many high-order non-axisymmetric modes are excited, the motion is chaotic, and numerous small secondary droplets are ejected simultaneously from across the surface of the primary drop. In both frequency regimes a crater may form that collapses to create a liquid spike from which droplet ejection occurs. An axisymmetric, incompressible, Navier Stokes solver was developed to simulate the low-frequency ejection process. A volume-of-fluid method was used to track the free surface, with surface tension incorporated using the continuum-surface-force method. A time sequence of the simulated interface shape compared favourably with an experimental sequence. The dynamics of the droplet ejection process was investigated, and the conditions under which ejection occurs and the effect of the system parameters on the process were determined.

  3. Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

    NASA Astrophysics Data System (ADS)

    Justino, Licínia L. G.; Reva, Igor; Fausto, Rui

    2016-07-01

    Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N2, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

  4. Influence of numerical model decisions on the flow-induced vibration of a computational vocal fold model

    PubMed Central

    Shurtz, Timothy E.; Thomson, Scott L.

    2012-01-01

    Computational vocal fold models are often used to study the physics of voice production. In this paper the sensitivity of predicted vocal fold flow-induced vibration and resulting airflow patterns to several modeling selections is explored. The location of contact lines used to prevent mesh collapse and assumptions of symmetry were found to influence airflow patterns. However, these variables had relatively little effect on the vibratory response of the vocal fold model itself. Model motion was very sensitive to Poisson’s ratio. The importance of these parameter sensitivities in the context of vocal fold modeling is discussed. PMID:23794762

  5. Thermally Induced Vibrations of the Hubble Space Telescope's Solar Array 3 in a Test Simulated Space Environment

    NASA Technical Reports Server (NTRS)

    Early, Derrick A.; Haile, William B.; Turczyn, Mark T.; Griffin, Thomas J. (Technical Monitor)

    2001-01-01

    NASA Goddard Space Flight Center and the European Space Agency (ESA) conducted a disturbance verification test on a flight Solar Array 3 (SA3) for the Hubble Space Telescope using the ESA Large Space Simulator (LSS) in Noordwijk, the Netherlands. The LSS cyclically illuminated the SA3 to simulate orbital temperature changes in a vacuum environment. Data acquisition systems measured signals from force transducers and accelerometers resulting from thermally induced vibrations of the SAI The LSS with its seismic mass boundary provided an excellent background environment for this test. This paper discusses the analysis performed on the measured transient SA3 responses and provides a summary of the results.

  6. Coupling system dynamics and contact behaviour: Modelling bearings subjected to environmental induced vibrations and ‘false brinelling’ degradation

    NASA Astrophysics Data System (ADS)

    Massi, Francesco; Rocchi, J.; Culla, A.; Berthier, Y.

    2010-05-01

    During the last decades the increase in power of mechanical systems and the demand for increasing service life leads mechanical components of a system to work in extreme conditions. Moreover, actual mechanical systems include surfaces in sliding contact that are subjected to wear if exposed to high vibration. In fact, the vibration of components in contact results in large oscillations of the local contact stresses, due to the local deformation of the components at the contact interfaces. To approach correctly tribological problems, the coupling between the scale of the mechanism (system dynamics) and the scale of the contact needs to be accounted for. This paper presents an analysis concerning the influence of the vibrations induced by aircraft engines on the contact stresses of rolling bearings of the bleed system valves. To study the wear, resulting from false brinelling at the contact surfaces between balls and races of the bearings, it is then necessary to determine the forces due to the system vibrations and acting at the bearing connections with the structure. In order to perform a numerical transient analysis of the system dynamics a nonlinear simplified model of the valve (mechanism scale) is developed. The model is validated by comparing the numerical results with experimental tests. The time behaviour of the global forces on the bearings, and the respective displacements between the contact surfaces, are then used as inputs for a finite element model of the bearings (contact scale). The model is used to calculate and analyze the behaviour in time of the local contact constraints between race and balls. This analysis, developed in the framework of a European project, is an example of the proposed general approach to contact problems, by coupling the analysis of the mechanism and contact scales.

  7. Calculation of vibrational branching ratios and hyperfine structure of 24Mg19F and its suitability for laser cooling and magneto-optical trapping

    NASA Astrophysics Data System (ADS)

    Xu, Liang; Yin, Yanning; Wei, Bin; Xia, Yong; Yin, Jianping

    2016-01-01

    More recently, laser cooling of the diatomic radical magnesium monofluoride (24Mg19F ) is being experimentally preformed [Appl. Phys. Express 8, 092701 (2015), 10.7567/APEX.8.092701 and Opt. Express 22, 28645 (2014), 10.1364/OE.22.028645] and was also studied theoretically [Phys. Rev. A 91, 042511 (2015), 10.1103/PhysRevA.91.042511]. However, some important problems still remain unsolved, so, in our paper, we perform further theoretical study for the feasibility of laser cooling and trapping the 24Mg19F molecule. At first, the highly diagonal Franck-Condon factors of the main transitions are verified by the closed-form approximation, Morse approximation, and Rydberg-Klein-Rees inversion methods, respectively. Afterwards, we investigate the lower X 2Σ1/2 + hyperfine manifolds using a quantum effective Hamiltonian approach and obtain the zero-field hyperfine spectrum with an accuracy of less than 30 kHz ˜5 μ K compared with the experimental results, and then find out that one cooling beam and one or two repumping beams with their first-order sidebands are enough to implement an efficient laser slowing and cooling of 24Mg19F . Meanwhile, we also calculate the accurate hyperfine structure magnetic g factors of the rotational state (X 2Σ1/2 +,N =1 ) and briefly discuss the influence of the external fields on the hyperfine structure of 24Mg19F as well as its possibility of preparing three-dimensional magneto-optical trapping. Finally we give an explanation for the difference between the Stark and Zeeman effects from the perspective of parity and time reversal symmetry. Our study shows that, besides appropriate excitation wavelengths, the short lifetime for the first excited state A 2Π1 /2 , and lighter mass, the 24Mg19F radical could be a good candidate molecule amenable to laser cooling and magneto-optical trapping.

  8. 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.

  9. Prevention of doxorubicin-induced alopecia by scalp cooling in patients with advanced breast cancer.

    PubMed Central

    Anderson, J E; Hunt, J M; Smith, I E

    1981-01-01

    Scalp cooling with gel packs was used to try to prevent alopecia in 31 patients being treated with doxorubicin (Adriamycin), 29 for advanced breast carcinoma and two for carcinoid tumour. Twenty-eight of the 31 patients tolerated the procedure well, and 22 of these had either no hair loss or only slight loss which remained acceptable and did not require a wig. The main factor limiting success was biochemical impairment of liver function, which occurred in nine patients; of these, six had severe or total alopecia despite scalp cooling. Conversely, the technique was successful in all 19 patients with normal liver function. Carried out properly, this simple and effective technique greatly diminishes socially unacceptable alopecia associated with doxorubicin, and merits wider use. PMID:6780057

  10. Prevention of doxorubicin-induced alopecia by scalp cooling in patients with advanced breast cancer.

    PubMed

    Anderson, J E; Hunt, J M; Smith, I E

    1981-02-07

    Scalp cooling with gel packs was used to try to prevent alopecia in 31 patients being treated with doxorubicin (Adriamycin), 29 for advanced breast carcinoma and two for carcinoid tumour. Twenty-eight of the 31 patients tolerated the procedure well, and 22 of these had either no hair loss or only slight loss which remained acceptable and did not require a wig. The main factor limiting success was biochemical impairment of liver function, which occurred in nine patients; of these, six had severe or total alopecia despite scalp cooling. Conversely, the technique was successful in all 19 patients with normal liver function. Carried out properly, this simple and effective technique greatly diminishes socially unacceptable alopecia associated with doxorubicin, and merits wider use.

  11. Determination of the most effective cooling temperature for the prevention of chemotherapy-induced alopecia

    PubMed Central

    EKWALL, EVA M.; NYGREN, LISA M.L.; GUSTAFSSON, ANDERS O.; SORBE, BENGT G.

    2013-01-01

    Computer-controlled scalp cooling to prevent alopecia is currently available for patients undergoing chemo-therapy. Previous studies have suggested that the temperature should be <22°C at a depth of 1–2 mm in the scalp to prevent alopecia. However, the optimal pre-set temperature of the coolant medium to achieve this temperature requires further investigation. A pre-study was conducted to investigate which pre-set coolant temperature of 3 and 8°C was the most effective in achieving a scalp temperature of <22°C. The temperature variations at different sites of the scalp and variations within and among the participants at baseline and during the cooling procedure were also evaluated. A randomized main study was then performed to compare the efficacy and side effects of the two temperature levels during paclitaxel/carboplatin chemotherapy. A group of 5 healthy female volunteers participated in a series of scalp temperature measurements during cooling with 3 and 8°C of the coolant medium. In the randomized main study, a total of 47 patients were included, of whom 43 were evaluable after the first cycle. A pre-set temperature of 3°C tended to be the most efficient in achieving a hair follicle temperature of <22°C. The top of the head was less responsive to scalp cooling. There were no significant differences in the prevention of alopecia between the two temperatures in the main study. However, headache and a feeling of coldness were more common in the 3°C group. A coolant temperature of 3°C was more effective in achieving a subcutaneous temperature of <22°C. However, this finding was not reflected by a significant difference in the prevention of alopecia in this study, although a higher incidence of side effects was associated with a lower temperature level. PMID:24649294

  12. Determination of the most effective cooling temperature for the prevention of chemotherapy-induced alopecia.

    PubMed

    Ekwall, Eva M; Nygren, Lisa M L; Gustafsson, Anders O; Sorbe, Bengt G

    2013-11-01

    Computer-controlled scalp cooling to prevent alopecia is currently available for patients undergoing chemo-therapy. Previous studies have suggested that the temperature should be <22°C at a depth of 1-2 mm in the scalp to prevent alopecia. However, the optimal pre-set temperature of the coolant medium to achieve this temperature requires further investigation. A pre-study was conducted to investigate which pre-set coolant temperature of 3 and 8°C was the most effective in achieving a scalp temperature of <22°C. The temperature variations at different sites of the scalp and variations within and among the participants at baseline and during the cooling procedure were also evaluated. A randomized main study was then performed to compare the efficacy and side effects of the two temperature levels during paclitaxel/carboplatin chemotherapy. A group of 5 healthy female volunteers participated in a series of scalp temperature measurements during cooling with 3 and 8°C of the coolant medium. In the randomized main study, a total of 47 patients were included, of whom 43 were evaluable after the first cycle. A pre-set temperature of 3°C tended to be the most efficient in achieving a hair follicle temperature of <22°C. The top of the head was less responsive to scalp cooling. There were no significant differences in the prevention of alopecia between the two temperatures in the main study. However, headache and a feeling of coldness were more common in the 3°C group. A coolant temperature of 3°C was more effective in achieving a subcutaneous temperature of <22°C. However, this finding was not reflected by a significant difference in the prevention of alopecia in this study, although a higher incidence of side effects was associated with a lower temperature level.

  13. Convection induced by radiative cooling of a layer of participating medium

    SciTech Connect

    Prasanna, Swaminathan; Venkateshan, S. P.

    2014-05-15

    Simulations and experiments have been conducted to study the effect of radiative cooling on natural convection in a horizontal layer of a participating medium enclosed between isothermal opaque wall and radiatively transparent wall and exposed to a cold background. The study is of relevance to a nocturnal boundary layer under clear and calm conditions. The focus of the study is to capture the onset of convection caused by radiative cooling. The experiments have been designed to mimic the atmospheric radiative boundary conditions, and hence decoupling convection and radiation boundary conditions. Planck number Pl and optical thickness of the layer τ{sub H} are the two important parameters that govern the interaction between radiation and convection. The radiation-convection coupling is a strong function of length scale. Convection sets up within first few seconds for all the experiments. Strong plume like convection is observed for the experimental conditions used in the present study. Both simulations and experiments confirm that radiative cooling increases substantially with decrease in emissivity of the bottom wall. Radiative cooling is strongly influenced by the nongray nature of the participating medium, especially when strong emission from the medium escapes to space, in the window region of the atmosphere. Accurate representation of radiative properties is critical. Linear stability analysis of onset of convection indicates that radiation stabilizes convection as Pl decreases. The observations are similar to the case of Rayleigh Bénard convection in a radiating gas. However, for both experimental and numerical conditions, the observed Rayleigh numbers are much greater than the critical Rayleigh number. To conclude, the role of radiation is to drive and sustain convection in the unstable layer.

  14. Jet-cooled laser-induced fluorescence spectroscopy of cyclohexoxy: rotational and fine structure of molecules in nearly degenerate electronic States.

    PubMed

    Liu, Jinjun; Miller, Terry A

    2014-12-26

    The rotational structure of the previously observed B̃(2)A' ← X̃(2)A″ and B̃(2)A' ← Ã(2)A' laser-induced fluorescence spectra of jet-cooled cyclohexoxy radical (c-C6H11O) [ Zu, L.; Liu, J.; Tarczay, G.; Dupré, P; Miller, T. A. Jet-cooled laser spectroscopy of the cyclohexoxy radical. J. Chem. Phys. 2004 , 120 , 10579 ] has been analyzed and simulated using a spectroscopic model that includes the coupling between the nearly degenerate X̃ and à states separated by ΔE. The rotational and fine structure of these two states is reproduced by a 2-fold model using one set of molecular constants including rotational constants, spin-rotation constants (ε's), the Coriolis constant (Aζt), the quenched spin-orbit constant (aζed), and the vibronic energy separation between the two states (ΔE0). The energy level structure of both states can also be reproduced using an isolated-state asymmetric top model with rotational constants and effective spin-rotation constants (ε's) and without involving Coriolis and spin-orbit constants. However, the spin-orbit interaction introduces transitions that have no intensity using the isolated-state model but appear in the observed spectra. The line intensities are well simulated using the 2-fold model with an out-of-plane (b-) transition dipole moment for the B̃ ← X̃ transitions and in-plane (a and c) transition dipole moment for the B̃ ← à transitions, requiring the symmetry for the X̃ (Ã) state to be A″ (A'), which is consistent with a previous determination and opposite to that of isopropoxy, the smallest secondary alkoxy radical. The experimentally determined Ã-X̃ separation and the energy level ordering of these two states with different (A' and A″) symmetries are consistent with quantum chemical calculations. The 2-fold model also enables the independent determination of the two contributions to the Ã-X̃ separation: the relativistic spin-orbit interaction (magnetic effect) and the nonrelativistic

  15. MEMS Device Being Developed for Active Cooling and Temperature Control

    NASA Technical Reports Server (NTRS)

    Moran, Matthew E.

    2001-01-01

    High-capacity cooling options remain limited for many small-scale applications such as microelectronic components, miniature sensors, and microsystems. A microelectromechanical system (MEMS) is currently under development at the NASA Glenn Research Center to meet this need. It uses a thermodynamic cycle to provide cooling or heating directly to a thermally loaded surface. The device can be used strictly in the cooling mode, or it can be switched between cooling and heating modes in milliseconds for precise temperature control. Fabrication and assembly are accomplished by wet etching and wafer bonding techniques routinely used in the semiconductor processing industry. Benefits of the MEMS cooler include scalability to fractions of a millimeter, modularity for increased capacity and staging to low temperatures, simple interfaces and limited failure modes, and minimal induced vibration.

  16. Vortex-induced vibrations of two cylinders in tandem arrangement in the proximity-wake interference region.

    PubMed

    Borazjani, Iman; Sotiropoulos, Fotis

    2009-01-01

    We investigate numerically vortex-induced vibrations (VIV) of two identical two-dimensional elastically mounted cylinders in tandem in the proximity-wake interference regime at Reynolds number Re = 200 for systems having both one (transverse vibrations) and two (transverse and in-line) degrees of freedom (1-DOF and 2-DOF, respectively). For the 1-DOF system the computed results are in good qualitative agreement with available experiments at higher Reynolds numbers. Similar to these experiments our simulations reveal: (1) larger amplitudes of motion and a wider lock-in region for the tandem arrangement when compared with an isolated cylinder; (2) that at low reduced velocities the vibration amplitude of the front cylinder exceeds that of the rear cylinder; and (3) that above a threshold reduced velocity, large-amplitude VIV are excited for the rear cylinder with amplitudes significantly larger than those of the front cylinder. By analysing the simulated flow patterns we identify the VIV excitation mechanisms that lead to such complex responses and elucidate the near-wake vorticity dynamics and vortex-shedding modes excited in each case. We show that at low reduced velocities vortex shedding provides the initial excitation mechanism, which gives rise to a vertical separation between the two cylinders. When this vertical separation exceeds one cylinder diameter, however, a significant portion of the incoming flow is able to pass through the gap between the two cylinders and the gap-flow mechanism starts to dominate the VIV dynamics. The gap flow is able to periodically force either the top or the bottom shear layer of the front cylinder into the gap region, setting off a series of very complex vortex-to-vortex and vortex-to-cylinder interactions, which induces pressure gradients that result in a large oscillatory force in phase with the vortex shedding and lead to the experimentally observed larger vibration amplitudes. When the vortex shedding is the dominant

  17. Vibration damping method and apparatus

    DOEpatents

    Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.

    1999-01-01

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.

  18. Vibration damping method and apparatus

    DOEpatents

    Redmond, J.M.; Barney, P.S.; Parker, G.G.; Smith, D.A.

    1999-06-22

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof. 38 figs.

  19. A study on the contribution of body vibrations to the vibratory sensation induced by high-level, complex low-frequency noise.

    PubMed

    Takahashi, Yukio

    2011-01-01

    To investigate the contribution of body vibrations to the vibratory sensation induced by high-level, complex low-frequency noise, we conducted two experiments. In Experiment 1, eight male subjects were exposed to seven types of low-frequency noise stimuli: two pure tones [a 31.5-Hz, 100-dB(SPL) tone and a 50-Hz, 100-dB(SPL) tone] and five complex noises composed of the pure tones. For the complex noise stimuli, the sound pressure level of one tonal component was 100 dB(SPL) and that of another one was either 90, 95, or 100 dB(SPL). Vibration induced on the body surface was measured at five locations, and the correlation with the subjective rating of the vibratory sensation at each site of measurement was examined. In Experiment 2, the correlation between the body surface vibration and the vibratory sensation was similarly examined using seven types of noise stimuli composed of a 25-Hz tone and a 50-Hz tone. In both the experiments, we found that at the chest and the abdomen, the rating of the vibratory sensation was in close correlation with the vibration acceleration level (VAL) of the body surface vibration measured at each corresponding location. This was consistent with our previous results and suggested that at the trunk of the body (the chest and the abdomen), the mechanoreception of body vibrations plays an important role in the experience of the vibratory sensation in persons exposed to high-level low-frequency noise. At the head, however, no close correlation was found between the rating of the vibratory sensation and the VAL of body surface vibration. This suggested that at the head, the perceptual mechanisms of vibration induced by high-level low-frequency noise were different from those in the trunk of the body.

  20. Asymmetric airflow and vibration induced by the Coanda effect in a symmetric model of the vocal folds.

    PubMed

    Tao, Chao; Zhang, Yu; Hottinger, Daniel G; Jiang, Jack J

    2007-10-01

    A model constructed from Navier-Stokes equations and a two-mass vocal fold description is proposed in this study. The composite model not only has the capability to describe the aerodynamics in a vibratory glottis but also can be used to study the vocal fold vibration under the driving of the complex airflow in the glottis. Numerical simulations show that this model can predict self-oscillations of the coupled glottal aerodynamics and vocal fold system. The Coanda effect could occur in the vibratory glottis even though the vocal folds have left-right symmetric prephonatory shape and tissue properties. The Coanda effect causes the asymmetric flow in the glottis and the difference in the driving force on the left and right vocal folds. The different pressures applied to the left and right vocal folds induce their displacement asymmetry. By using various lung pressures (0.6-2.0 kPa) to drive the composite model, it was found that the asymmetry of the vocal fold displacement is increased from 1.87% to 11.2%. These simulation results provide numerical evidence for the presence of asymmetric flow in the vibratory glottis; moreover, they indicate that glottal aerodynamics is an important factor in inducing the asymmetric vibration of the vocal folds.

  1. Real-time 1-D/2-D transient elastography on a standard ultrasound scanner using mechanically induced vibration.

    PubMed

    Azar, Reza Zahiri; Dickie, Kris; Pelissier, Laurent

    2012-10-01

    Transient elastography has been well established in the literature as a means of assessing the elasticity of soft tissue. In this technique, tissue elasticity is estimated from the study of the propagation of the transient shear waves induced by an external or internal source of vibration. Previous studies have focused mainly on custom single-element transducers and ultrafast scanners which are not available in a typical clinical setup. In this work, we report the design and implementation of a transient elastography system on a standard ultrasound scanner that enables quantitative assessment of tissue elasticity in real-time. Two new custom imaging modes are introduced that enable the system to image the axial component of the transient shear wave, in response to an externally induced vibration, in both 1-D and 2-D. Elasticity reconstruction algorithms that estimate the tissue elasticity from these transient waves are also presented. Simulation results are provided to show the advantages and limitations of the proposed system. The performance of the system is also validated experimentally using a commercial elasticity phantom.

  2. Ultrafast excited-state dynamics and vibrational cooling of 8-oxo-7,8-dihydro-2'-deoxyguanosine in D2O.

    PubMed

    Zhang, Yuyuan; Dood, Jordan; Beckstead, Ashley; Chen, Jinquan; Li, Xi-Bo; Burrows, Cynthia J; Lu, Zhen; Matsika, Spiridoula; Kohler, Bern

    2013-12-05

    Nguyen and Burrows recently demonstrated that UV-B irradiation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a signature product of oxidatively damaged DNA, can repair cyclobutane pyrimidine dimers in double-stranded DNA (J. Am. Chem. Soc. 2011, 133, 14586 - 14589). In order to test the hypothesis that repair occurs by photoinduced electron transfer, it is critical to determine basic photophysical parameters of 8-oxodG including the excited-state lifetime. Here, femtosecond transient absorption spectroscopy was used to study the ultrafast excited-state dynamics of 8-oxodG with excitation in the UV and probing at visible and mid-IR wavelengths. The excited-state lifetimes of both neutral and basic forms of 8-oxodG in D2O are reported for the first time by monitoring the disappearance of excited-state absorption at 570 nm. The lifetime of the first excited state of the neutral form is 0.9 ± 0.1 ps, or nearly twice as long as that of 2'-deoxyguanosine. The basic form of 8-oxodG exhibits a much longer excited-state lifetime of 43 ± 3 ps. Following ultrafast internal conversion by neutral 8-oxodG, a vibrationally hot ground state is created that dissipates its excess vibrational energy to the solvent on a time scale of 2.4 ± 0.4 ps. Femtosecond time-resolved IR experiments provide additional insights into excited-state dynamics and the vibrational relaxation of several modes in the fingerprint region.

  3. Shunted piezoelectrics for passive control of turbomachine blading flow-induced vibrations

    NASA Astrophysics Data System (ADS)

    Cross, Charles J.; Fleeter, Sanford

    2002-04-01

    The application of shunted piezoelectric elements to provide passive structural damping is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. An array of piezoelectric elements is bonded to an airfoil in the stator row. This airfoil is excited in a chordwise bending mode by the wakes generated by an upstream rotor. As the wakes drive the airfoil vibrations, the piezoelectrics experience a strain and in response produce an electric field. Tuned electrical circuits connected to the piezoelectrics as shunts dissipate this electrical energy, with multiple shunting techniques utilized. This electrical energy dissipation and the corresponding reduction in the airfoil mechanical energy result in a reduction in the magnitude of the resonant vibrations.

  4. Low-frequency vibration treatment of bone marrow stromal cells induces bone repair in vivo

    PubMed Central

    He, Shengwei; Zhao, Wenzhi; Zhang, Lu; Mi, Lidong; Du, Guangyu; Sun, Chuanxiu; Sun, Xuegang

    2017-01-01

    Objective(s): To study the effect of low-frequency vibration on bone marrow stromal cell differentiation and potential bone repair in vivo. Materials and Methods: Forty New Zealand rabbits were randomly divided into five groups with eight rabbits in each group. For each group, bone defects were generated in the left humerus of four rabbits, and in the right humerus of the other four rabbits. To test differentiation, bones were isolated and demineralized, supplemented with bone marrow stromal cells, and implanted into humerus bone defects. Varying frequencies of vibration (0, 12.5, 25, 50, and 100 Hz) were applied to each group for 30 min each day for four weeks. When the bone defects integrated, they were then removed for histological examination. mRNA transcript levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligan, and pre-collagen type 1 α were measured. Results: Humeri implanted with bone marrow stromal cells displayed elevated callus levels and wider, more prevalent, and denser trabeculae following treatment at 25 and 50 Hz. The mRNA levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligand, and pre-collagen type 1 α were also markedly higher following 25 and 50 Hz treatment. Conclusion: Low frequency (25–50 Hz) vibration in vivo can promote bone marrow stromal cell differentiation and repair bone injury. PMID:28133520

  5. Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae).

    PubMed

    Timerman, David; Greene, David F; Urzay, Javier; Ackerman, Josef D

    2014-12-06

    In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind-stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems.

  6. Reduction of EEG artefacts induced by vibration in the MR-environment.

    PubMed

    Rothlübbers, Sven; Relvas, Vânia; Leal, Alberto; Figueiredo, Patrícia

    2013-01-01

    The EEG acquired simultaneously with functional magnetic resonance imaging (fMRI) is distorted by a number of artefacts related to the presence of strong magnetic fields. In order to allow for a useful interpretation of the EEG data, it is necessary to reduce these artefacts. For the two most prominent artefacts, associated with magnetic field gradient switching and the heart beat, reduction methods have been developed and applied successfully. Due to their repetitive nature, such artefacts can be reduced by subtraction of the respective template retrieved by averaging across cycles. In this paper, we investigate additional artefacts related to the MR environment and propose a method for the reduction of the vibration artefact caused by the cryo-cooler compression pumps system. Data were collected from the EEG cap placed on an MR head phantom, in order to characterise the MR environment related artefacts. Since the vibration artefact was found to be repetitive, a template subtraction method was developed for its reduction, and this was then adjusted to meet the specific requirements of patient data. The developed methodology successfully reduced the vibration artefact by about 90% in five EEG-fMRI datasets collected from two epilepsy patients.

  7. Conformational Changes of Trialanine in Water Induced by Vibrational Relaxation of the Amide I Mode.

    PubMed

    Bastida, Adolfo; Zúñiga, José; Requena, Alberto; Miguel, Beatriz; Candela, María Emilia; Soler, Miguel Angel

    2016-01-21

    Most of the protein-based diseases are caused by anomalies in the functionality and stability of these molecules. Experimental and theoretical studies of the conformational dynamics of proteins are becoming in this respect essential to understand the origin of these anomalies. However, a description of the conformational dynamics of proteins based on mechano-energetic principles still remains elusive because of the intrinsic high flexibility of the peptide chains, the participation of weak noncovalent interactions, and the role of the ubiquitous water solvent. In this work, the conformational dynamics of trialanine dissolved in water (D2O) is investigated through Molecular Dynamics (MD) simulations combined with instantaneous normal modes (INMs) analysis both at equilibrium and after the vibrational excitation of the C-terminal amide I mode. The conformational equilibrium between α and pPII conformers is found to be altered by the intramolecular relaxation of the amide I mode as a consequence of the different relaxation pathways of each conformer which modify the amount of vibrational energy stored in the torsional motions of the tripeptide, so the α → pPII and pPII → α conversion rates are increased differently. The selectivity of the process comes from the shifts of the vibrational frequencies with the conformational changes that modify the resonance conditions driving the intramolecular energy flows.

  8. Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae)

    PubMed Central

    Timerman, David; Greene, David F.; Urzay, Javier; Ackerman, Josef D.

    2014-01-01

    In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind–stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems. PMID:25297315

  9. Flow-induced vibrations of the SSME LOX inlet tee vanes

    NASA Technical Reports Server (NTRS)

    O'Connor, G. M.; Jones, J.

    1988-01-01

    This paper describes the results of a program initiated to identify the cause and the mechanism of 4-kHz vibrations of the Space Shuttle main engine's (SSME's) LOX inlet tee, which were revealed in 17 percent of the SSMEs during ground tests. The results of the engines' inspection, structural analyses, computational fluid dynamics studies, literature reviews, expert consultations, and laboratory testings identified the probable cause of the 4-kHz vibrations being related to the fact that the walls of some tees were thinner than in the mojority of tees, resulting in less stiff structures. The mechanism of the vibrations was identified as vortex shedding in combination with a structural coupling with the thrust cone, which increased the vane mobility, which, in turn, aggravated the fluid coupling with the thrust cone. As a result, the vane mobility was increased, aggravating the fluid coupling with the vanes. An internal modification was developed and was successfully demonstrated on an engine that had previously exhibited a 4-kHz problem.

  10. Granular core phenomenon induced by convection in a vertically vibrated cylindrical container

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Liu, Chuanping; Wu, Ping; Xie, Zi-Ang; Hu, Kaiwei; Wang, Li

    2016-09-01

    A mixture of 13X molecular sieve (13XMS) particles and glass particles with identical diameters is placed in a cylindrical container. Under vertical vibration, heavier glass particles tend to cluster and are wrapped inside the convection of 13XMS particles, resulting in the granular core phenomenon. The vibration frequency f strongly influences particle convection and particle cluster modes. By contrast, the effect of the dimensionless acceleration amplitude Γ can be neglected. For different f ranges, the granular core is classified as center-type and ring-type cores. For the center-type core, heavy particles are distributed as an approximate zeroth-order Bessel function of the first kind in the radial direction and an exponential function in the height direction. For the ring-type core, the concentration of heavy particles follows the power-series function in the radial direction. A granular transport model is then established based on heavy-particle movements under steady state to analyze the effect of vibration parameters and granular convection on density segregation.

  11. Postexercise cooling interventions and the effects on exercise-induced heat stress in a temperate environment.

    PubMed

    Hausswirth, Christophe; Duffield, Rob; Pournot, Hervé; Bieuzen, François; Louis, Julien; Brisswalter, Jeanick; Castagna, Olivier

    2012-10-01

    The aim of this study was to examine the effects of cool water immersion (20 °C; CWI) while wearing a cooling jacket (Cryovest;V) and a passive control (PAS) as recovery methods on physiological and thermoregulatory responses between 2 exercise bouts in temperate conditions. Nine well-trained male cyclists performed 2 successive bouts of 45 min of endurance cycling exercise in a temperate environment (20 °C) separated by 25 min of the respective recovery interventions. Capillary blood samples were obtained to measure lactate (La⁻), sodium (Na⁺), bicarbonate (HCO₃⁻) concentrations and pH, whilst body mass loss (BML), core temperature (T(core)), skin temperature (T(skin)), heart rate (HR), oxygen uptake , and minute ventilation were measured before (Pre), immediately after the first exercise bout (Ex1), the recovery (R), and after the second exercise bout (Ex2). V and CWI both resulted in a reduction of T(skin) at R (-2.1 ± 0.01 °C and -11.6 ± 0.01 °C, respectively, p < 0.01). Despite no difference in final values post-Ex2 (p > 0.05), V attenuated the rise in HR, minute ventilation, and oxygen uptake from Ex1 to Ex2, while T(core) and T(skin) were significantly lower following the second session (p < 0.05). Further, CWI was also beneficial in lowering T(core), T(skin), and BML, while a rise in Na⁺ was observed following Ex2 (p < 0.05). Overall results indicate that cooling interventions (V and CWI) following exercise in a temperate environment provide a reduction in thermal strain during ensuing exercise bouts.

  12. Universal response spectrum procedure for predicting walking-induced floor vibration

    NASA Astrophysics Data System (ADS)

    Brownjohn, James; Racic, Vitomir; Chen, Jun

    2016-03-01

    Floor vibrations caused by people walking are an important serviceability problem both for human occupants and vibration-sensitive equipment. Present design methodologies available for prediction of vibration response due to footfall loading are complex and suffer from division between low and high frequency floors. In order to simplify the design process and to avoid the problem of floor classification, this paper presents a methodology for predicting vibration response metrics due to pedestrian footfalls for any floor type having natural frequency in the range 1-20 Hz. Using a response spectrum approach, a database of 852 weight-normalised vertical ground reaction force (GRF) time histories recorded for more than 60 individuals walking on an instrumented treadmill was used to calculate response metrics. Chosen metrics were peak values of 1 s peak root-mean-square (RMS) acceleration and peak envelope one-third octave velocities. These were evaluated by weight-normalising the GRFs and applying to unit-mass single degree of freedom oscillators having natural frequencies in the range 1-20 Hz and damping ratios in the range 0.5-5%. Moreover, to account for effect of mode shape and duration of crossing (i.e. duration of dynamic loading), the recorded GRFs were applied for three most typical mode shapes and floor spans from 5 m to 40 m. The resulting peak values as functions of frequency i.e. spectra are condensed to statistical representations for chosen probability of being exceeded over a wide range of applications. RMS (acceleration) spectra show strong peaks corresponding to the first harmonic of pacing rate followed by clear minima at approximately 3.5 Hz, a second much smaller peak corresponding to the second harmonic and a steady decline with increasing frequency beginning around 5 Hz. One-third octave spectra show asymptotic trends with frequency, span and damping. A comprehensive validation exercise focusing on the acceleration RMS spectra was based on a

  13. Vortex-induced vibration of a cylinder with two degrees of freedom

    NASA Astrophysics Data System (ADS)

    Jauvtis, N.; Williamson, C. H. K.

    2003-06-01

    In this work, we study the response of an elastically mounted cylinder, which is free to move in two degrees of freedom in a fluid flow, and which has low mass and damping. There has been a great deal of work concerned with bodies restrained to move in the direction transverse to the free stream, but very few studies which comprise motion in both the transverse (/Y) and in-line (/X) directions. In such cases, it has generally been assumed that in-line response would dramatically change the character of the wake vortex dynamics as well as the transverse body response. We find in the present work that, surprisingly, the freedom to move in two directions has very little effect on the transverse response, the modes of vibration, or the vortex wake dynamics (for a body of similar low mass ratio (relative density) in the range m*=5-25). For low values of normalised velocity (U*~2-4) below the classical synchronisation regime for transverse response, we find two in-line vibration modes, which are associated with symmetric and antisymmetric vortex wake modes, corresponding well with the modes discovered by Wooton et al. and by King for a flexible cantilever. Coupled with a parallel effort by D.O. Rockwell's group at Lehigh, these experiments form the first such studies in which both the oscillating mass and the natural frequency are precisely the same in the /X and /Y directions. A principal conclusion from this investigation is that it demonstrates the validity, for bodies in two degrees of freedom, of employing the existing comprehensive results for bodies restrained to vibrate only in the transverse Y-direction, even down to low mass ratios of m*=5.

  14. Investigating Premature Ignition of Thruster Pressure Cartridges by Vibration-Induced Electrostatic Discharge

    NASA Technical Reports Server (NTRS)

    Woods, Stephen S.; Saulsberry, Regor

    2010-01-01

    Pyrotechnic thruster pressure cartridges (TPCs) are used for aeroshell separation on a new NASA crew launch vehicle. Nondestructive evaluation (NDE) during TPC acceptance testing indicated that internal assemblies moved during shock and vibration testing due to an internal bond anomaly. This caused concerns that the launch environment might produce the same movement and release propellant grains that might be prematurely ignited through impact or through electrostatic discharge (ESD) as grains vibrated against internal surfaces. Since a new lot could not be fabricated in time, a determination had to be made as to whether the lot was acceptable to fly. This paper discusses the ESD evaluation and a separate paper addresses the impact problem. A challenge to straight forward assessment existed due to the unavailability of triboelectric data characterizing the static charging characteristics of the propellants within the TPC. The approach examined the physical limitations for charge buildup within the TPC system geometry and evaluated it for discharge under simulated vibrations used to qualify components for launch. A facsimile TPC was fabricated using SS 301 for the case and surrogate worst case materials for the propellants based on triboelectric data. System discharge behavior was evaluated by applying high voltage to the point of discharge in air and by placing worst case charge accumulations within the facsimile TPC and forcing discharge. The facsimile TPC contained simulated propellant grains and lycopodium, a well characterized indicator for static discharge in dust explosions, and was subjected to accelerations equivalent to the maximum accelerations possible during launch. The magnitude of charge generated within the facsimile TPC system was demonstrated to lie in a range of 100 to 10,000 times smaller than the spark energies measured to ignite propellant grains in industry standard discharge tests. The test apparatus, methodology, and results are described in

  15. Glutamine and Asparagine Side Chain Hyperconjugation-Induced Structurally Sensitive Vibrations.

    PubMed

    Punihaole, David; Hong, Zhenmin; Jakubek, Ryan S; Dahlburg, Elizabeth M; Geib, Steven; Asher, Sanford A

    2015-10-15

    We identified vibrational spectral marker bands that sensitively report on the side chain structures of glutamine (Gln) and asparagine (Asn). Density functional theory (DFT) calculations indicate that the Amide III(P) (AmIII(P)) vibrations of Gln and Asn depend cosinusoidally on their side chain OCCC dihedral angles (the χ3 and χ2 angles of Gln and Asn, respectively). We use UV resonance Raman (UVRR) and visible Raman spectroscopy to experimentally correlate the AmIII(P) Raman band frequency to the primary amide OCCC dihedral angle. The AmIII(P) structural sensitivity derives from the Gln (Asn) Cβ-Cγ (Cα-Cβ) stretching component of the vibration. The Cβ-Cγ (Cα-Cβ) bond length inversely correlates with the AmIII(P) band frequency. As the Cβ-Cγ (Cα-Cβ) bond length decreases, its stretching force constant increases, which results in an upshift in the AmIII(P) frequency. The Cβ-Cγ (Cα-Cβ) bond length dependence on the χ3 (χ2) dihedral angle results from hyperconjugation between the Cδ═Oϵ (Cγ═Oδ) π* and Cβ-Cγ (Cα-Cβ) σ orbitals. Using a Protein Data Bank library, we show that the χ3 and χ2 dihedral angles of Gln and Asn depend on the peptide backbone Ramachandran angles. We demonstrate that the inhomogeneously broadened AmIII(P) band line shapes can be used to calculate the χ3 and χ2 angle distributions of peptides. The spectral correlations determined in this study enable important new insights into protein structure in solution, and in Gln- and Asn-rich amyloid-like fibrils and prions.

  16. Flow Induced Vibration and Glottal Aerodynamics in a Three-Dimensional Laryngeal Model

    NASA Astrophysics Data System (ADS)

    Zheng, Xudong; Xue, Qian; Mittal, Rajat; Bielamowicz, Steven

    2009-11-01

    Three-dimensional effects associated with phonation remain unclear due to the lack of capability of simulating 3D fluid-tissue interaction in the past. To advance the state-of-the-art in this arena, an immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed to conduct high-fidelity direct-numerical simulations of phonation in a 3D model of the human larynx. Three-dimensional vibration patterns are captured along with turbulence effects and three-dimensional vortex structures in the glottal jet. Results from these simulations are presented.

  17. Observation of sound-induced corneal vibrational modes by optical coherence tomography.

    PubMed

    Akca, B Imran; Chang, Ernest W; Kling, Sabine; Ramier, Antoine; Scarcelli, Giuliano; Marcos, Susana; Yun, Seok H

    2015-09-01

    The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 µm at a sound pressure level of 100 dB (2 Pa). Vibrography allows the visualization of the radially symmetric profiles of the resonance modes. A dynamic finite-element analysis supports our observation.

  18. Observation of sound-induced corneal vibrational modes by optical coherence tomography

    PubMed Central

    Akca, B. Imran; Chang, Ernest W.; Kling, Sabine; Ramier, Antoine; Scarcelli, Giuliano; Marcos, Susana; Yun, Seok H.

    2015-01-01

    The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 µm at a sound pressure level of 100 dB (2 Pa). Vibrography allows the visualization of the radially symmetric profiles of the resonance modes. A dynamic finite-element analysis supports our observation. PMID:26417503

  19. Sulfate-induced cooling in the southeastern U.S.: An observational assessment

    NASA Astrophysics Data System (ADS)

    Saxena, V. K.; Menon, Surabi

    The effect of sulfates on cloud microphysical and optical properties have been studied using data from a rural mountaintop location in the Mt. Mitchell State Park, North Carolina. Although the amended Clean Air Act has limited the sulfur emissions beginning 1990, we found the sulfate concentrations greater during 1993-97 compared to that during 1986-89. Cloud albedo inferred from satellite data and calculated from surface observations does not indicate a monotonic increase with increasing sulfates. The direct and indirect (cloud-mediated) sulfate forcing are assessed to be 4.8 and -4 W m-2. These values exceed current model predictions as evaluated by other investigators. Surface temperature records of the region during 1949-94 indicate a cooling trend tacitly supporting our assessment.

  20. Dark matter merging induced turbulence as an efficient engine for gas cooling

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Jimenez, Raul; Martí, Jose

    2012-02-01

    We have performed a cosmological numerical simulation of primordial baryonic gas collapsing on to a 3 × 107 M⊙ dark matter (DM) halo. We show that the large scale baryonic accretion process and the merger of few ˜ 106 M⊙ DM haloes, triggered by the gravitational potential of the biggest halo, are enough to create supersonic (?) shocks and develop a turbulent environment. In this scenario, the post-shocked regions are able to produce both H2 and deuterated H2 molecules very efficiently, reaching maximum abundances of ? and nHD˜ few × 10-6 nH, enough to cool the gas below 100 K in some regions. The kinetic energy spectrum of the turbulent primordial gas is close to a Burgers spectrum, ?, which could favour the formation of low-mass primordial stars. The solenoidal-to-total kinetic energy ratio is 0.65 ≲Rk≲ 0.7 for a wide range of wavenumbers; this value is close to the Rk≈ 2/3 natural equipartition energy value of a random turbulent flow. In this way, turbulence and molecular cooling seem to work together in order to produce potential star formation regions of cold dense gas in primordial environments. We conclude that both the mergers and the collapse process on to the main DM halo provide enough energy to develop supersonic turbulence which favours the molecular coolant formation: this mechanism, which could be universal and the main route towards the formation of the first galaxies, is able to create potential star-forming regions at high redshift.

  1. Cooling dissociates glucose-induced insulin release from electrical activity and cation fluxes in rodent pancreatic islets.

    PubMed Central

    Atwater, I; Goncalves, A; Herchuelz, A; Lebrun, P; Malaisse, W J; Rojas, E; Scott, A

    1984-01-01

    Insulin release and beta-cell membrane potentials in response to glucose at 37 and 27 degrees C have been measured simultaneously in single, micro-dissected, perifused islets of Langerhans from normal mice. Insulin release and 45Ca outflow in response to glucose at 37 and 27 degrees C have been measured simultaneously from perfused islets isolated by collagenase digestion from normal rats. The effect of cooling on beta-cell membrane potassium permeability was assessed by changes in measured membrane potential and input resistance (in the mouse) and by changes in 86Rb outflow (in the rat). Resting and active beta-cell membrane parameters (i.e. membrane potential, spike frequency, input resistance, 45Ca outflow and 86Rb outflow), in both mouse and rat islets, were affected only slightly by cooling to 27 degrees C, with temperature coefficients of 2 or lower. At 27 degrees C glucose-stimulated insulin release was inhibited completely in mouse islets and almost completely in rat islets. The temperature coefficients in both preparations were greater than 5. It is concluded that beta-cell electrical activity and changes in membrane permeability induced by glucose are not consequences of insulin release. PMID:6371219

  2. Performance of a reduced-order FSI model for flow-induced vocal fold vibration

    NASA Astrophysics Data System (ADS)

    Chang, Siyuan; Luo, Haoxiang; Luo's lab Team

    2016-11-01

    Vocal fold vibration during speech production involves a three-dimensional unsteady glottal jet flow and three-dimensional nonlinear tissue mechanics. A full 3D fluid-structure interaction (FSI) model is computationally expensive even though it provides most accurate information about the system. On the other hand, an efficient reduced-order FSI model is useful for fast simulation and analysis of the vocal fold dynamics, which is often needed in procedures such as optimization and parameter estimation. In this work, we study the performance of a reduced-order model as compared with the corresponding full 3D model in terms of its accuracy in predicting the vibration frequency and deformation mode. In the reduced-order model, we use a 1D flow model coupled with a 3D tissue model. Two different hyperelastic tissue behaviors are assumed. In addition, the vocal fold thickness and subglottal pressure are varied for systematic comparison. The result shows that the reduced-order model provides consistent predictions as the full 3D model across different tissue material assumptions and subglottal pressures. However, the vocal fold thickness has most effect on the model accuracy, especially when the vocal fold is thin. Supported by the NSF.

  3. Numerical simulation of vibration of horizontal cylinder induced by progressive waves

    NASA Astrophysics Data System (ADS)

    Chern, Ming-Jyh; Odhiambo, E. A.; Horng, Tzyy-Leng; Borthwick, A. G. L.

    2016-02-01

    Maritime structures often comprise cylinders of small diameter relative to the prevailing wave length. This paper describes the direct forcing immersed boundary simulation of the hydroelastic behaviour of a rigid, horizontal circular cylinder in regular progressive waves. Fluid motions are numerically solved by the full Navier-Stokes equations, and the free surface by the volume-of-fluid method. The Reynolds number Re = 110, Keulegan-Carpenter number KC = 10, Froude number Fr = 0.69 and Ursell number U rs ≈ 12. A single-degree-of-freedom model is used for the elastically mounted cylinder. Velocity profiles for the stationary cylinder case have been successfully validated using experimental results. The frequency response for reduced velocities 4.5\\lt {U}R*\\lt 5.3 have been compared with theoretical data. Three transverse vibration regimes are identified: lower beating (4\\lt {U}R*\\lt 4.5); lock-in (4.7\\lt {U}R*\\lt 4.8); and upper beating (5\\lt {U}R*\\lt 10) modes. The lower and upper beating regimes exhibit varying amplitude response. The lock-in mode represents the region of fixed and maximum response. The lower beating and lock-in modes have peaks at a common vibration to wave frequency ratio {f}{{w}}* = 2. For the upper beating mode, {f}{{w}}* = 1, except for {U}R*=10 when {f}{{w}}* = 2.

  4. Cooling-induced contraction of the rat gastric fundus: mediation via transient receptor potential (TRP) cation channel TRPM8 receptor and Rho-kinase activation.

    PubMed

    Mustafa, S; Oriowo, Ma

    2005-10-01

    1. Cooling has been shown to induce contractions of several smooth muscles in vitro. However, the mechanism involved in the response is not yet known. In the present study, we investigated the possible involvement of transient receptor potential (TRP) cation channel TRPM8 receptors and the Rho-kinase pathway in cooling-induced contraction of the rat fundus. 2. Cooling-induced contractions were inversely proportional to temperature. Contractions were significantly reduced (by 65.6 +/- 2.4%; P < 0.05) in a Ca2+-free (1 mmol/L EGTA) medium, but were not significantly inhibited by nifedipine (10(-6) mol/L). 3. Capsazepine (3 x 10(-6) and 3 x 10(-5) mol/L), a TRPM8 receptor antagonist, inhibited cooling-induced contraction of the rat gastric fundus. 4. The Rho-kinase inhibitor Y-27632 concentration-dependently inhibited cooling-induced contraction of the gastric fundus, producing approximately 90% inhibition at a concentration of 10(-5) mol/L. Contractions were also inhibited by genistein (3 x 10(-5) mol/L), a tyrosine kinase inhibitor, but not by GF 109203X (10(-7) mol/L), a protein kinase C inhibitor. 5. Using reverse transcription-polymerase chain reaction techniques, it was observed that the mRNA for the TRPM8 receptor and Rho-kinase were expressed in the rat gastric fundus. 6. These results would suggest that cooling-induced contraction of the rat fundus is mediated by activation of TRPM8 receptors via a mechanism involving activation of Rho-kinase.

  5. 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.

  6. Coupling of Vibrational Modes of Adsorbates: Application to Field Induced Shifts for CO and CN on Cu(100).

    DTIC Science & Technology

    1987-11-01

    lengths and vibrational frequencies for both chemisorbed CO and CN as a Stark effect. Chemical changes are shown to be small. Keywords: Chemisorption, Vibrational modes , Potential energy surface, Electrochemistry.

  7. Assessing the potential for tropical cyclone induced sea surface cooling to reduce thermal stress on the world's coral reefs

    NASA Astrophysics Data System (ADS)

    Carrigan, A. D.; Puotinen, M. L.

    2011-12-01

    Coral reefs face an uncertain future as rising sea surface temperature (SST) continues to lead to increasingly frequent and intense mass bleaching. At broad spatial scales, tropical cyclone (TC) induced cooling of the upper ocean (SST drops up to 6° C persisting for weeks) reduces thermal stress and accelerates recovery of bleached corals - yet the global prevalence and spatial distribution of this effect remains undocumented and unquantified. A global dataset (1985-2009) of TC wind exposure was constructed and examined against existing thermal stress data to address this. Significant correlations were found between TC activity and the severity of thermal stress at various spatial scales, particularly for Caribbean reefs. From this, it is apparent that TCs play a role in bleaching dynamics at a global scale. However, the prevalence and distribution of this interaction varies by region and requires further examination at finer spatial and temporal scales using actual SST data.

  8. Medical Devices; General and Plastic Surgery Devices; Classification of the Scalp Cooling System To Reduce the Likelihood of Chemotherapy-Induced Alopecia. Final order.

    PubMed

    2016-02-12

    The Food and Drug Administration (FDA) is classifying the scalp cooling system to reduce the likelihood of chemotherapy-induced alopecia into class II (special controls). The special controls that will apply to the device are identified in this order and will be part of the codified language for the scalp cooling system to reduce the likelihood of chemotherapy-induced alopecia's classification. The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

  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. Ultrafast cooling and heating scenarios for the laser-induced phase transition in CuO

    NASA Astrophysics Data System (ADS)

    Hellsvik, Johan; Mentink, Johan H.; Lorenzana, José

    2016-10-01

    The multiferroic compound CuO exhibits low-temperature magnetic properties similar to antiferromagnetic iron oxides, while the electronic properties have much more in common with the high-Tc cuprate superconductors. This suggests novel possibilities for the ultrafast optical excitation of magnetism. On the basis of atomistic spin dynamics simulations, we study the effect of phonon-assisted multimagnon absorption and photodoping on the spin dynamics in the vicinity of the first-order phase transition from collinear to spin-spiral magnetic order. Similar as in recent experiments, we find that for both excitations the phase transition can proceed on the picosecond timescale. Interestingly, however, these excitation mechanisms display very distinct dynamics. Following photodoping, the spin system first cools down on subpicosecond time scales, which we explain as an ultrafast magnetocaloric effect. Opposed to this, following phonon-assisted multimagnon excitation, the spin systems rapidly heats up and subsequently evolves to the noncollinear phase even under the influence of isotropic exchange interactions alone.

  11. 2.5D Finite/infinite Element Approach for Simulating Train-Induced Ground Vibrations

    NASA Astrophysics Data System (ADS)

    Yang, Y. B.; Hung, H. H.; Kao, J. C.

    2010-05-01

    The 2.5D finite/infinite element approach for simulating the ground vibrations by surface or underground moving trains will be briefly summarized in this paper. By assuming the soils to be uniform along the direction of the railway, only a two-dimensional profile of the soil perpendicular to the railway need be considered in the modeling. Besides the two in-plane degrees of freedom (DOFs) per node conventionally used for plane strain elements, an extra DOF is introduced to account for the out-of-plane wave transmission. The profile of the half-space is divided into a near field and a semi-infinite far field. The near field containing the train loads and irregular structures is simulated by the finite elements, while the far field covering the soils with infinite boundary by the infinite elements, by which due account is taken of the radiation effects for the moving loads. Enhanced by the automated mesh expansion procedure proposed previously by the writers, the far field impedances for all the lower frequencies are generated repetitively from the mesh created for the highest frequency considered. Finally, incorporated with a proposed load generation mechanism that takes the rail irregularity and dynamic properties of trains into account, an illustrative case study was performed. This paper investigates the vibration isolation effect of the elastic foundation that separates the concrete slab track from the underlying soil or tunnel structure. In addition, the advantage of the 2.5D approach was clearly demonstrated in that the three-dimensional wave propagation effect can be virtually captured using a two-dimensional finite/infinite element mesh. Compared with the conventional 3D approach, the present approach appears to be simple, efficient and generally accurate.

  12. Explosion-induced stress changes estimated from vibrating-wire stressmeter measurements near the Mighty Epic event, Nevada Test Site

    USGS Publications Warehouse

    Ellis, William L.; Kibler, J.D.

    1983-01-01

    Explosion-induced compressive stress increases near an underground nuclear explosion are believed to contribute significantly to the containment of high-pressure gases within the explosion-produced cavity. These induced compressive stresses are predicted by computer calculations, but have never been adequately confirmed by field measurements, owing primarily to the unique difficulties of obtaining such field data. Vibrating-wire stressmeter measurements made near the Mighty Epic nuclear detonation, however, qualitatively indicate that within 150 meters of the working point, permanent compressive stress increases of several megapascals were present 15 weeks after the event. Additionally, stress-change magnitudes interpreted from the stressmeter data between the 75- and 260-meter range from the working point compare favorably with calculational predictions of the stress changes believed to be present shortly after detonation of the event. The measurements and calculations differ, however, with regard to the pattern of stress change radial and transverse to the explosion source. For the range of the field measurements from the working point, computer models predict the largest compressive-stress increase to be radial to the explosion source, while the field data indicate the transverse component of. stress change to be the most compressive. The significance of time-dependent modification of the initial explosion-induced stress distribution is, however, uncertain with regard to the comparison of the field measurements and theoretical predictions.

  13. Exaggerated haemodynamic and neural responses to involuntary contractions induced by whole-body vibration in normotensive obese versus lean women.

    PubMed

    Dipla, Konstantina; Kousoula, Dimitra; Zafeiridis, Andreas; Karatrantou, Konstantina; Nikolaidis, Michalis G; Kyparos, Antonios; Gerodimos, Vassilis; Vrabas, Ioannis S

    2016-06-01

    What is the central question of this study? In obesity, the exaggerated blood pressure response to voluntary exercise is linked to hypertension, yet the mechanisms are not fully elucidated. We examined whether involuntary contractions elicit greater haemodynamic responses and altered neural control of blood pressure in normotensive obese versus lean women. What is the main finding and its importance? During involuntary contractions induced by whole-body vibration, there were augmented blood pressure and spontaneous baroreflex responses in obese compared with lean women. This finding is suggestive of an overactive mechanoreflex in the exercise-induced hypertensive response in obesity. Passive contractions did not elicit differential heart rate responses in obese compared with lean women, implying other mechanisms for the blunted heart rate response reported during voluntary exercise in obesity. In obesity, the exaggerated blood pressure (BP) response to exercise is linked to hypertension, yet the mechanisms are not fully elucidated. In this study, we examined whether involuntary mechanical oscillations, induced by whole-body vibration (WBV), elicit greater haemodynamic responses and altered neural control of BP in obese versus lean women. Twenty-two normotensive, premenopausal women (12 lean and 10 obese) randomly underwent a passive WBV (25 Hz) and a control protocol (similar posture without WVB). Beat-by-beat BP, heart rate, stroke volume, systemic vascular resistance, cardiac output, parasympathetic output (evaluated by heart rate variability) and spontaneous baroreceptor sensitivity (sBRS) were assessed. We found that during WBV, obese women exhibited an augmented systolic BP response compared with lean women that was correlated with body fat percentage (r = 0.77; P < 0.05). The exaggerated BP rise was driven mainly by the greater increase in cardiac output index in obese versus lean women, associated with a greater stroke volume index in obese women

  14. Crystallization kinetics of alkali feldspars in cooling and decompression-induced crystallization experiments in trachytic melt

    NASA Astrophysics Data System (ADS)

    Arzilli, Fabio; Carroll, Michael R.

    2013-10-01

    Cooling and decompression experiments have been carried out on trachytic melts in order to investigate crystallization kinetics of alkali feldspar, the effect of the degree of undercooling ( ΔT = T liquidus - T experimental) and time on nucleation and crystal growth process. This experimental work gives us new data about crystallization kinetics of trachytic melts, and it that will be useful to better understand the natural system of Campi Flegrei volcanoes. Experiments have been conducted using cold seal pressure vessel apparatus, at pressure between 30 and 200 MPa, temperature between 750 and 855 °C, time between 7,200 and 57,600 s and redox condition close to the NNO +0.8 buffer. These conditions are ideal to reproducing pre- and syn-eruptive conditions of the Campi Flegrei volcanoes, where the "conditions" pertain to the complete range of pressures, temperatures and time at which the experiments were performed. Alkali feldspar is the main phase present in this trachyte, and its abundance can strongly vary with small changes in pressure, temperature and water content in the melt, implying appreciable variations in the textures and in the crystallization kinetics. The obtained results show that crystallization kinetics are strictly related to ΔT, time, final pressure, superheating (- ΔT) and water content in the melt. ΔT is the driving force of the crystallization, and it has a strong influence on nucleation and growth processes. In fact, the growth process dominates crystallization at small ΔT, whereas the nucleation dominates crystallization at large ΔT. Time also is an important variable during crystallization process, because long experiment durations involve more nucleation events of alkali feldspar than short experiment durations. This is an important aspect to understand magma evolution in the magma chamber and in the conduit, which in turn has strong effects on magma rheology.

  15. Identification of warm day and cool night conditions induced flowering-related genes in a Phalaenopsis orchid hybrid by suppression subtractive hybridization.

    PubMed

    Li, D M; Lü, F B; Zhu, G F; Sun, Y B; Xu, Y C; Jiang, M D; Liu, J W; Wang, Z

    2014-02-14

    The influence of warm day and cool night conditions on induction of spikes in Phalaenopsis orchids has been studied with respect to photosynthetic efficiency, metabolic cycles and physiology. However, molecular events involved in spike emergence induced by warm day and cool night conditions are not clearly understood. We examined gene expression induced by warm day and cool night conditions in the Phalaenopsis hybrid Fortune Saltzman through suppression subtractive hybridization, which allowed identification of flowering-related genes in warm day and cool night conditions in spikes and leaves at vegetative phase grown under warm daily temperatures. In total, 450 presumably regulated expressed sequence tags (ESTs) were identified and classified into functional categories, including metabolism, development, transcription factor, signal transduction, transportation, cell defense, and stress. Furthermore, database comparisons revealed a notable number of Phalaenopsis hybrid Fortune Saltzman ESTs that matched genes with unknown function. The expression profiles of 24 genes (from different functional categories) have been confirmed by quantitative real-time PCR in induced spikes and juvenile apical leaves. The results of the real-time PCR showed that, compared to the vegetative apical leaves, the transcripts of genes encoding flowering locus T, AP1, AP2, KNOX1, knotted1-like homeobox protein, R2R3-like MYB, adenosine kinase 2, S-adenosylmethionine synthetase, dihydroflavonol 4-reductase, and naringenin 3-dioxygenase accumulated significantly higher levels, and genes encoding FCA, retrotransposon protein Ty3 and C3HC4-type RING finger protein accumulated remarkably lower levels in spikes of early developmental stages. These results suggested that the genes of two expression changing trends may play positive and negative roles in the early floral transition of Phalaenopsis orchids. In conclusion, spikes induced by warm day and cool night conditions were complex in

  16. Smoothing HCCI heat release with vaporization-cooling-induced thermal stratification using ethanol.

    SciTech Connect

    Dec, John E.; Sjoberg, Carl-Magnus G.

    2010-12-01

    Ethanol and ethanol/gasoline blends are being widely considered as alternative fuels for light-duty automotive applications. At the same time, HCCI combustion has the potential to provide high efficiency and ultra-low exhaust emissions. However, the application of HCCI is typically limited to low and moderate loads because of unacceptably high heat-release rates (HRR) at higher fueling rates. This work investigates the potential of lowering the HCCI HRR at high loads by using partial fuel stratification to increase the in-cylinder thermal stratification. This strategy is based on ethanol's high heat of vaporization combined with its true single-stage ignition characteristics. Using partial fuel stratification, the strong fuel-vaporization cooling produces thermal stratification due to variations in the amount of fuel vaporization in different parts of the combustion chamber. The low sensitivity of the autoignition reactions to variations of the local fuel concentration allows the temperature variations to govern the combustion event. This results in a sequential autoignition event from leaner and hotter zones to richer and colder zones, lowering the overall combustion rate compared to operation with a uniform fuel/air mixture. The amount of partial fuel stratification was varied by adjusting the fraction of fuel injected late to produce stratification, and also by changing the timing of the late injection. The experiments show that a combination of 60-70% premixed charge and injection of 30-40 % of the fuel at 80{sup o}CA before TDC is effective for smoothing the HRR. With CA50 held fixed, this increases the burn duration by 55% and reduces the maximum pressure-rise rate by 40%. Combustion stability remains high but engine-out NO{sub x} has to be monitored carefully. For operation with strong reduction of the peak HRR, ISNO{sub x} rises to around 0.20 g/kWh for an IMEP{sub g} of 440 kPa. The single-cylinder HCCI research engine was operated naturally aspirated

  17. Numerical investigation of two-degree-of-freedom vortex-induced vibration of a circular cylinder in oscillatory flow

    NASA Astrophysics Data System (ADS)

    Zhao, Ming

    2013-05-01

    Two-degree-of-freedom (2dof) vortex-induced vibration (VIV) of a circular cylinder in oscillatory flow is investigated numerically. The direction of the oscillatory flow is perpendicular to the spanwise direction of the circular cylinder. Simulations are carried out for the Keulegan-Carpenter (KC) numbers of 10, 20 and 40 and the Reynolds numbers ranging from 308 to 9240. The ratio of the Reynolds number to the reduced velocity is 308. At KC=10, the amplitude of the primary frequency component is much larger than those of other frequency components. Most vibrations for KC=20 and 40 have multiple frequencies. The primary frequency of the response in the cross-flow direction decreases with the increasing reduced velocity, except when the reduced velocity is very small. Because the calculated primary frequencies of the response in the cross-flow direction are multiple of the oscillatory flow frequency in most of the calculated cases, the responses are classified into single-frequency mode, double-frequency mode, triple frequency mode, etc. If the reduced velocity is in the range where the VIV is transiting from one mode to another, the vibration is very irregular.For each KC number the range of the reduced velocity can be divided into a cross-flow-in-phase regime (low Vr), where the response and the hydrodynamic force in the cross-flow direction synchronize, and a cross-flow-anti-phase regime (high Vr), where the response and the hydrodynamic force in the cross-flow direction are in anti-phase with each other. The boundary values of Vr between the cross-flow-in-phase and the cross-flow-anti-phase regimes are 7, 9 and 11 for KC=10, 20 and 40, respectively. For KC=20, another cross-flow-anti-phase regime is found between 15≤Vr≤19. Similarly the in-line-in-phase and the in-line-anti-phase regimes are also identified for the response in the in-line direction. It is found that the boundary value of Vr between the in-line-in-phase and the in-line-anti-phase regimes is

  18. Triaxial modulation of the acceleration induced in the lower extremity during whole-body vibration training: a pilot study.

    PubMed

    Cook, David P; Mileva, Katya N; James, Darren C; Zaidell, Lisa N; Goss, Victor G; Bowtell, Joanna L

    2011-02-01

    The purpose of the present study was to quantify vibration transmissibility through the lower extremity during exercise on a whole-body vibration (WBV) platform. Six healthy adults completed 20 trials of 30-second static squat exercise at 30 or 40 degrees of knee flexion angle on a WBV platform working at combinations of 5 frequencies (VF: 20, 25, 30, 35, 40 Hz) and 2 amplitudes (VA: low, 1.5 mm or high, 3 mm). Accelerations induced by the platform were recorded simultaneously at the shank and the thigh using triaxial accelerometers positioned at the segmental center of mass. Root-mean-square (RMS) acceleration amplitude and transmission ratios between the platform and the leg segments were calculated and compared between the experimental conditions. An alpha level of 0.05 was set to establish significance. Shank vertical acceleration was greatest at the lower VF (p = 0.028), higher VA (p = 0.028), and deeper squat (p = 0.048). Thigh vertical acceleration was not affected by depth of squat (p = 0.25), but it was greatest at higher VA (p = 0.046) and lower VF (p = 0.028). Medial-lateral shank acceleration was greatest at higher VF and deeper squat (both p = 0.046) and at higher VA (p = 0.028). Medial-lateral thigh acceleration was positively related to both VF (p = 0.046) and VA (p = 0.028) but was not affected by knee angle (p = 0.46). Anterior-posterior shank acceleration was higher at deeper squat (p = 0.046) and at lower VF and higher VA (both p = 0.028). Anterior-posterior thigh acceleration was related positively to the VA (p = 0.028), inversely to the VF (p = 0.028), and not dependent on knee angle (p = 0.75). Identification of specific vibration parameters and posture, which underpin WBV training efficacy, will enable coaches and athletes to design WBV training programs to specifically target shank or thigh muscles for enhanced performance.

  19. Investigation of Vibration Induced Artifact in Clinical Diffusion-Weighted Imaging of Pediatric Subjects

    PubMed Central

    Berl, Madison M.; Walker, Lindsay; Modi, Pooja; Irfanoglu, M. Okan; Sarlls, Joelle; Nayak, Amritha; Pierpaoli, Carlo

    2015-01-01

    It has been reported that mechanical vibrations of the MRI scanner could produce spurious signal dropouts in diffusion-weighted images resulting in artifactual anisotropy in certain regions of the brain with red appearance in the Directionally Encoded Color maps. We performed a review of the frequency of this artifact across pediatric studies, noting differences by scanner manufacturer, acquisition protocol, as well as weight and position of the subject. We also evaluated the ability of automated and quantitative methods to detect this artifact. We found that the artifact may be present in over 50% of data in certain protocols and is not limited to one scanner manufacturer. While a specific scanner had the highest incidence, low body weight and positioning were also associated with appearance of the artifact for both scanner types evaluated, making children potentially more susceptible than adults. Visual inspection remains the best method for artifact identification. Software for automated detection showed very low sensitivity (10%). The artifact may present inconsistently in longitudinal studies. We discuss a published case report that has been widely cited and used as evidence to set policy about diagnostic criteria for determining vegetative state. That report attributed longitudinal changes in anisotropy to white matter plasticity without considering the possibility that the changes were caused by this artifact. Our study underscores the need to check for the presence of this artifact in clinical studies, analyzes circumstances for when it may be more likely to occur, and suggests simple strategies to identify and potentially avoid its effects. PMID:26350492

  20. Investigation of vibration-induced artifact in clinical diffusion-weighted imaging of pediatric subjects.

    PubMed

    Berl, Madison M; Walker, Lindsay; Modi, Pooja; Irfanoglu, M Okan; Sarlls, Joelle E; Nayak, Amritha; Pierpaoli, Carlo

    2015-12-01

    It has been reported that mechanical vibrations of the magnetic resonance imaging scanner could produce spurious signal dropouts in diffusion-weighted images resulting in artifactual anisotropy in certain regions of the brain with red appearance in the Directionally Encoded Color maps. We performed a review of the frequency of this artifact across pediatric studies, noting differences by scanner manufacturer, acquisition protocol, as well as weight and position of the subject. We also evaluated the ability of automated and quantitative methods to detect this artifact. We found that the artifact may be present in over 50% of data in certain protocols and is not limited to one scanner manufacturer. While a specific scanner had the highest incidence, low body weight and positioning were also associated with appearance of the artifact for both scanner types evaluated, making children potentially more susceptible than adults. Visual inspection remains the best method for artifact identification. Software for automated detection showed very low sensitivity (10%). The artifact may present inconsistently in longitudinal studies. We discuss a published case report that has been widely cited and used as evidence to set policy about diagnostic criteria for determining vegetative state. That report attributed longitudinal changes in anisotropy to white matter plasticity without considering the possibility that the changes were caused by this artifact. Our study underscores the need to check for the presence of this artifact in clinical studies, analyzes circumstances for when it may be more likely to occur, and suggests simple strategies to identify and potentially avoid its effects.

  1. Defect-Induced Vibration Modes of Ar+ -Irradiated MoS2

    NASA Astrophysics Data System (ADS)

    Bae, Soungmin; Sugiyama, Natsuki; Matsuo, Takatoshi; Raebiger, Hannes; Shudo, Ken-ichi; Ohno, Koichi

    2017-02-01

    The Ar+ -irradiated molybdenum-disulfide (MoS2 ) surface is studied by means of Raman spectroscopy and first-principles calculation. This experimental study reveals that Ar+ irradiation gives rise to satellite peaks at the lower-frequency side of the Raman-active E2g 1 and A1 g modes of MoS2 and a new peak at approximately 450 cm-1 . We calculate the phonon modes and Raman spectra of defective MoS2 systems from first principles, and show that Mo and S vacancies give rise to such satellite peaks. These satellite peaks are a modulation of the E2g 1 and A1 g modes, described in terms of localization and scattering of vibration modes. The new peak at 450 cm-1 , however, is a unique signature of the S vacancy. At low irradiation doses, the S vacancy is the dominant defect, whereas for large irradiation doses, the satellite peaks overshadow the MoS2 peaks, which we show to be typical for the Mo vacancy and MoS6 vacancy cluster. We thus show that Raman spectroscopy can be used not only to observe defects in two-dimensional materials, but also to identify the type of the defects.

  2. Nonlinear vibration and radiation from a panel with transition to chaos induced by acoustic waves

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Frendi, Abdelkader; Brown, Donald E.

    1992-01-01

    The dynamic response of an aircraft panel forced at resonance and off-resonance by plane acoustic waves at normal incidence is investigated experimentally and numerically. Linear, nonlinear (period doubling) and chaotic responses are obtained by increasing the sound pressure level of the excitation. The response time history is sensitive to the input level and to the frequency of excitation. The change in response behavior is due to a change in input conditions, triggered either naturally or by modulation of the bandwidth of the incident waves. Off-resonance, bifurcation is diffused and difficult to maintain, thus the panel response drifts into a linear behavior. The acoustic pressure emanated by the panel is either linear or nonlinear as is the vibration response. The nonlinear effects accumulate during the propagation with distance. Results are also obtained on the control of the panel response using damping tape on aluminum panel and using a graphite epoxy panel having the same size and weight. Good agreement is obtained between the experimental and numerical results.

  3. Prediction of flow induced sound and vibration of periodically stiffened plates.

    PubMed

    Maxit, Laurent; Denis, Vivien

    2013-01-01

    Stiffened structures excited by the turbulent boundary layer (TBL) occur very frequently in engineering applications; for instance, in the wings of airplanes or the pressure hulls of submarines. To improve knowledge of the interaction between stiffened structures and TBL, this paper deals with the modeling of infinite periodically stiffened plates excited by TBL. The mathematical formulation of the problem is well-established in the literature. The originality of the present work relies on the use of a wavenumber-point reciprocity technique for evaluating the response of the plate to convected harmonic pressure waves. It follows a methodology for estimating the vibro-acoustic response of the plate excited by the TBL from the wall pressure spectrum and its displacements in the wavenumber space due to point excitations located at the receiving positions. The computing process can be reduced to the numerical integration of an analytical expression in the case of a periodically stiffened plate. An application to a naval test case highlights the effect of Bloch-Floquet waves on the vibrations of the plate and its radiated pressure in the fluid.

  4. Dynamics and flow structures in the turbulent wake of rigid and flexible cylinders subject to vortex-induced vibrations

    NASA Astrophysics Data System (ADS)

    Evangelinos, Constantinos; Karniadakis, George Em

    1999-12-01

    We present simulation results of vortex-induced vibrations of an infinitely long flexible cylinder at Reynolds number Re = 1000, corresponding to a ‘young’ turbulent wake (i.e. exhibiting a small inertial subrange). The simulations are based on a new class of spectral methods suitable for unstructured and hybrid grids. To obtain different responses of the coupled flow structure system we vary the structure's bending stiffness to model the behaviour of a vibrating inflexible (rigid) cylinder, a cable, and a beam. We have found that unlike the laminar flow previously studied, the amplitude of the cross-flow oscillation is about one diameter for the cable and the beam, close to experimental measurements, but is lower for the rigid cylinder. We have also found that for the latter case the flow response corresponds to parallel shedding, but for the beam and cable with free endpoints a mixed response consisting of oblique and parallel shedding is obtained, caused by the modulated travelling wave motion of the structure. This mixed shedding pattern which alternates periodically along the span can be directly related to periodic spatial variation of the lift force. In the case of structures with pinned endpoints a standing wave response is obtained for the cylinder; lace-like flow structures are observed similar to the ones seen in the laminar regime. Examination of the frequency spectra in the near wake shows that at Re = 1000 all cases follow a [minus sign]5/3 law in the inertial range, which extends about half a decade in wavenumber. However, these spectra are different in all three cases both in low and high frequencies, with the exception of the beam and cable, for which the high-frequency portion is identical despite the differences in the displacement time history and the large-scale features of the corresponding flow.

  5. A simplified approach for the calculation of acoustic emission in the case of friction-induced noise and vibration

    NASA Astrophysics Data System (ADS)

    Soobbarayen, K.; Besset, S.; Sinou, J.-. J.

    2015-01-01

    The acoustic response associated with squeal noise radiations is a hard issue due to the need to consider non-linearities of contact and friction, to solve the associated nonlinear dynamic problem and to calculate the noise emissions due to self-excited vibrations. In this work, the focus is on the calculation of the sound pressure in free space generated during squeal events. The calculation of the sound pressure can be performed by the Boundary Element Method (BEM). The inputs of this method are a boundary element model, a field of normal velocity characterized by a unique frequency. However, the field of velocity associated with friction-induced vibrations is composed of several harmonic components. So, the BEM equation has to be solved for each frequency and in most cases, the number of harmonic components is significant. Therefore, the computation time can be prohibitive. The reduction of the number of harmonic component is a key point for the quick estimation of the squeal noise. The proposed approach is based on the detection and the selection of the predominant harmonic components in the mean square velocity. It is applied on two cases of squeal and allows us to consider only few frequencies. In this study, a new method will be proposed in order to quickly well estimate the noise emission in free space. This approach will be based on an approximated acoustic power of brake system which is assumed to be a punctual source, an interpolated directivity and the decrease of the acoustic power levels. This method is applied on two classical cases of squeal with one and two unstable modes. It allows us to well reconstruct the acoustic power levels map. Several error estimators are introduced and show that the reconstructed field is close to the reference calculated with a complete BEM.

  6. Nonlinear vibration induced by the water-film whirl and whip in a sliding bearing rotor system

    NASA Astrophysics Data System (ADS)

    Zhai, Liming; Luo, Yongyao; Wang, Zhengwei; Kitauchi, Seishiro; Miyagawa, Kazuyoshi

    2016-03-01

    Many industrial applications and experiments have shown that sliding bearings often experience fluid film whip due to nonlinear fluid film forces which can cause rotor-stator rub-impact failures. The oil-film whips have attracted many studies while the water-film whips in the water lubricated sliding bearing have been little researched with the mechanism still an open problem. The dynamic fluid film forces in a water sliding bearing are investigated numerically with rotational, whirling and squeezing motions of the journal using a nonlinear model to identify the relationships between the three motions. Rotor speed-up and slow-down experiments are then conducted with the rotor system supported by a water lubricated sliding bearing to induce the water-film whirl/whip and verify the relationship. The experimental results show that the vibrations of the journal alternated between increasing and decreasing rather than continuously increasing as the rotational speed increased to twice the first critical speed, which can be explained well by the nonlinear model. The radial growth rate of the whirl motion greatly affects the whirl frequency of the journal and is responsible for the frequency lock in the water-film whip. Further analysis shows that increasing the lubricating water flow rate changes the water-film whirl/whip characteristics, reduces the first critical speed, advances the time when significant water-film whirling motion occurs, and also increases the vibration amplitude at the bearing center which may lead to the rotor-stator rub-impact. The study gives the insight into the water-film whirl and whip in the water lubricated sliding bearing.

  7. Performance enhancement of a rotational energy harvester utilizing wind-induced vibration of an inclined stay cable

    NASA Astrophysics Data System (ADS)

    Kim, In-Ho; Jang, Seon-Jun; Jung, Hyung-Jo

    2013-07-01

    In this paper, an innovative strategy for improving the performance of a recently developed rotational energy harvester is proposed. Its performance can be considerably enhanced by replacing the electromagnetic induction part, consisting of moving permanent magnets and a fixed solenoid coil, with a moving mass and a rotational generator (i.e., an electric motor). The proposed system is easily tuned to the natural frequency of a target structure using the position change of a proof mass. Owing to the high efficiency of the rotational generator, the device can more effectively harness electrical energy from the wind-induced vibration of a stay cable. Also, this new configuration makes the device more compact and geometrically tunable. In order to validate the effectiveness of the new configuration, a series of laboratory and field tests are carried out with the prototype of the proposed device, which is designed and fabricated based on the dynamic characteristics of the vibration of a stay cable installed in an in-service cable-stayed bridge. From the field test, it is observed that the normalized output power of the proposed system is 35.67 mW (m s-2)-2, while that of the original device is just 5.47 mW (m s-2)-2. These results show that the proposed device generates much more electrical energy than the original device. Moreover, it is verified that the proposed device can generate sufficient electricity to power a wireless sensor node placed on a cable under gentle-moderate wind conditions.

  8. Passive containment cooling system

    DOEpatents

    Conway, Lawrence E.; Stewart, William A.

    1991-01-01

    A containment cooling system utilizes a naturally induced air flow and a gravity flow of water over the containment shell which encloses a reactor core to cool reactor core decay heat in two stages. When core decay heat is greatest, the water and air flow combine to provide adequate evaporative cooling as heat from within the containment is transferred to the water flowing over the same. The water is heated by heat transfer and then evaporated and removed by the air flow. After an initial period of about three to four days when core decay heat is greatest, air flow alone is sufficient to cool the containment.

  9. Stochastic Cooling

    SciTech Connect

    Blaskiewicz, M.

    2011-01-01

    Stochastic Cooling was invented by Simon van der Meer and was demonstrated at the CERN ISR and ICE (Initial Cooling Experiment). Operational systems were developed at Fermilab and CERN. A complete theory of cooling of unbunched beams was developed, and was applied at CERN and Fermilab. Several new and existing rings employ coasting beam cooling. Bunched beam cooling was demonstrated in ICE and has been observed in several rings designed for coasting beam cooling. High energy bunched beams have proven more difficult. Signal suppression was achieved in the Tevatron, though operational cooling was not pursued at Fermilab. Longitudinal cooling was achieved in the RHIC collider. More recently a vertical cooling system in RHIC cooled both transverse dimensions via betatron coupling.

  10. An attempt at a product vibrational analysis of a photo-induced chemical reaction by means of time-resolved (e, 2e) electron momentum spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamazaki, M.; Nakazawa, H.; Zhu, C. Y.; Takahashi, M.

    2015-09-01

    We report on a new attempt at an analysis of the vibrational state distributions in the products of a photo-induced chemical reaction. The experiment was performed by using time- resolved electron momentum spectroscopy (TR-EMS) for the products produced by the three- body photodissociation dynamics of the deuterated acetone molecule at 195 nm. It has been found from a comparison between the experiment and associated theoretical calculations that future TR-EMS measurements with improved statistics could be useful for the vibrational analysis of reaction products, in cases when effects of molecular vibration on their electron momentum densities are large enough so as to be noticeable in the binding energy spectra.

  11. Polarization-Resolved Raman Study of Bulk-like and Davydov-Induced Vibrational Modes of Exfoliated Black Phosphorus.

    PubMed

    Phaneuf-L'Heureux, Anne-Laurence; Favron, Alexandre; Germain, Jean-Francis; Lavoie, Patrick; Desjardins, Patrick; Leonelli, Richard; Martel, Richard; Francoeur, Sebastien

    2016-12-14

    Owing to its crystallographic structure, black phosphorus is one of the few 2D materials expressing strongly anisotropic optical, transport, and mechanical properties. We report on the anisotropy of electron-phonon interactions through a polarization-resolved Raman study of the four vibrational modes of atomically thin black phosphorus (2D phosphane): the three bulk-like modes Ag(1), B2g, and Ag(2) and the Davydov-induced mode labeled Ag(B2u). The complex Raman tensor elements reveal that the relative variation in permittivity of all Ag modes is irrespective of the atomic motion involved lowest along the zigzag direction, the basal anisotropy of these variations is most pronounced for Ag(2) and Ag(B2u), and interlayer interactions in multilayer samples lead to reduced anisotropy. The bulk-forbidden Ag(B2u) mode appears for n ≥ 2 and quickly subsides in thicker layers. It is assigned to a Davydov-induced IR to Raman conversion of the bulk IR mode B2u and exhibits characteristics similar to Ag(2). Although this mode is expected to be weak, an electronic resonance significantly enhances its Raman efficiency such that it becomes a dominant mode in the spectrum of bilayer 2D phosphane.

  12. Dimethyl Sulfoxide Induced Destabilization and Disassembly of Various Structural Variants of Insulin Fibrils Monitored by Vibrational Circular Dichroism.

    PubMed

    Zhang, Ge; Babenko, Viktoria; Dzwolak, Wojciech; Keiderling, Timothy A

    2015-12-15

    Dimethyl sulfoxide (DMSO) induced destabilization of insulin fibrils has been previously studied by Fourier transform infrared spectroscopy and interpreted in terms of secondary structural changes. The variation of this process for fibrils with different types of higher-order morphological structures remained unclear. Here, we utilize vibrational circular dichroism (VCD), which has been reported to provide a useful biophysical probe of the supramolecular chirality of amyloid fibrils, to characterize changes in the macroscopic chirality following DMSO-induced disassembly for two types of insulin fibrils formed under different conditions, at different reduced pH values with and without added salt and agitation. We confirm that very high concentrations of DMSO can disaggregate both types of insulin fibrils, which initially maintained a β-sheet conformation and eventually changed their secondary structure to a disordered form. The two types responded to varying concentrations of DMSO, and disaggregation followed different mechanisms. Interconversion of specific insulin fibril morphological types also occurred during the destabilization process as monitored by VCD. With transmission electron microscopy, we were able to correlate the changes in VCD sign patterns to alteration of morphology of the insulin fibrils.

  13. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

    NASA Astrophysics Data System (ADS)

    Fujihashi, Yuta; Fleming, Graham R.; Ishizaki, Akihito

    2015-06-01

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

  14. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

    SciTech Connect

    Fujihashi, Yuta; Ishizaki, Akihito; Fleming, Graham R.

    2015-06-07

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

  15. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra.

    PubMed

    Fujihashi, Yuta; Fleming, Graham R; Ishizaki, Akihito

    2015-06-07

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

  16. Laser-induced fluorescence studies of jet-cooled S2O: Axis-switching and predissociation effects

    NASA Astrophysics Data System (ADS)

    Zhang, Qingguo; Dupré, Patrick; Grzybowski, Bartosz; Vaccaro, Patrick H.

    1995-07-01

    Laser-induced fluorescence spectroscopy has been used to probe the intense C˜ 1A'-X˜ 1A' (π*←π) electronic system of S2O (315-340 nm) under supersonic free-jet conditions that yield effective rotational temperatures of roughly 1 K. Least-squares analysis of high-resolution scans performed on the 2v0(v=0-5) progression, where ν2 corresponds to the S-S stretching mode, not only furnish refined band origins and rotational constants, but also provide evidence for an axis-switching effect in this asymmetric triatomic species. Based on the limited set of vibronic bands examined in the present study, the harmonic frequency and anharmonicity for S-S stretching motion in the C˜ state are determined to be ω2=415.2(4) cm-1 and x22=-2.10(6) cm-1, respectively. Predissociation of the C˜ 1A' potential energy surface is found to become more pronounced with increasing excitation of the ν2 mode. Collision-free lifetime data, obtained either directly from time-resolved fluorescence decay profiles or indirectly from measurements of broadened spectral linewidths, permit formulation of a simple, one-dimensional tunneling model which predicts the excited state predissociation barrier to be located in the vicinity of the 26 vibrational level. These results, as well as possible candidates for the electronic manifold responsible for the predissociation process, are discussed in light of preliminary ab initio calculations.

  17. Vortex-induced vibration for an isolated circular cylinder under the wake interference of an oscillating airfoil: Part II. Single degree of freedom

    NASA Astrophysics Data System (ADS)

    Zhang, G. Q.; Ji, L. C.; Hu, X.

    2017-04-01

    The vortex-induced vibration behind an isolated cylinder under the wake interference of an oscillating airfoil at different oscillating frequencies and amplitudes have been studied numerically. Our previous research [11] mainly focused on the two degree of freedom vibration problem, several types of the phase portraits of the displacement have been newly found, including the "half -8″ and "cone-net" types as reduced velocity increases. At present, we have continued the research to the single degree of freedom vibration, the corresponding results had been found that under the wake of the free steady flow, as the reduced velocity increases, the phase portraits displacements of the single degree of freedom vibrating cylinder will begin to rotate counterclockwise from the first and third quadrants to the second and fourth quadrants in a Cartesian coordinate system. Under the wake of the oscillating airfoil, the single bending curve and the single closed orbit (double ;8-shape; like) of the displacements are newly found in the drag and thrust producing cases respectively. Except this, the two triplets of vortices have also been newly found in the pair and single plus pair wakes at each cycle. The vorticity dynamics behind the vibrating cylinder together with the corresponding force variations have also been obtained computationally and analyzed in details.

  18. Extensive Measurements of Vibration-Induced Permanent Electric Dipole Moments of Methane

    NASA Astrophysics Data System (ADS)

    Okuda, Shoko; Sasada, Hiroyuki

    2016-06-01

    A methane molecule (CH_4) has a permanent electric dipole moment (PEDM) in the excited state of the triply-degenerate vibrational modes. The rotational dependence of the PEDM was reported in the 2νb{3} band. However, in the νb{3} band, it was only determined on the P(7) E transition which fortunately lies in the tunable range of a 3.4 μm He-Ne laser. We have developed a mid-infrared broadband sub-Doppler resolution spectrometer consisting of a difference-frequency-generation source and an optical frequency comb linked to International Atomic Time. This spectrometer enables us to measure the Stark effects of 20 transitions in the νb{3} band of methane from 87.7 to 92.8 THz (2927˜3095 wn). The observed linewidth is 0.5 MHz, and the frequency scale is absolutely calibrated. The figure depicts the Stark modulation spectrum of the P(4) E transition. The applied DC electric field was 3.5 kV/cm. We determined Stark coefficients with a relative uncertainty of 1 %. Our goal is to reveal the rotational dependence of the PEDM. For this end, we yield molecular constants which reproduce the transition frequencies by a least-square method and determine the mixing of the wave functions. M. Mizushima and P. Venkateswarlu, J. Chem. Phys. 21, 705 (1953) K. Uehara, K. Sakurai and K. Shimoda, J. Phys. Soc. Jpn. 26, 1018 (1969) H. Sasada, K. Suzumura and C. Ishibashi, J. Chem. Phys. 105, 9027 (1996)

  19. Nonlinear analysis of wind-induced vibration of high-speed railway catenary and its influence on pantograph-catenary interaction

    NASA Astrophysics Data System (ADS)

    Song, Yang; Liu, Zhigang; Wang, Hongrui; Lu, Xiaobing; Zhang, Jing

    2016-06-01

    The wind-induced vibration of the high-speed catenary and the dynamic behaviour of the pantograph-catenary under stochastic wind field are firstly analysed. The catenary model is established based on nonlinear cable and truss elements, which can fully describe the nonlinearity of each wire and the initial configuration. The model of the aerodynamic forces acting on the messenger/contact wire is deduced by considering the effect of the vertical and horizontal fluctuating winds. The vertical and horizontal fluctuating winds are simulated by employing the Davenport and Panofsky spectrums, respectively. The aerodynamic coefficients of the contact/messenger wire are calculated through computational fluid dynamics. The wind-induced vibration response of catenary is analysed with different wind speeds and angles. Its frequency-domain characteristics are discussed using Auto Regression model. Finally, a pantograph model is introduced and the contact force of the pantograph-catenary under stochastic wind is studied. The results show that both the wind speed and the attack angle exert a significant effect on the wind-induced vibration. The existence of the groove on the contact wire cross-section leads to a significant change of the aerodynamic coefficient, which affects largely the aerodynamic forces applied on the catenary wires, as well as the vibration response. The vibration frequency with high spectral power mainly concentrates on the predominant frequency of the fluctuating wind and the natural frequency of catenary. The increase in the wind speed results in a significant deterioration of the current collection. The numerical example shows that a relatively stable current collection can be ensured when the wind flows at the relatively horizontal direction.

  20. Effect of experimentally reduced distal sensation on postural response to hip abductor/ankle evertor muscle vibration.

    PubMed

    Glasser, S; Collings, R; Paton, J; Marsden, J

    2015-07-01

    This study assessed whether postural responses induced by vibratory perturbations of the hip abductors and ankle evertors, were modified when distal tactile sensation was experimentally reduced through cooling. Sixteen healthy subjects were investigated pre and post cooling. Subjects stood with their eyes closed with a stance width of 4 cm. A 2s vibratory stimulus was applied to the left or right hip abductor or ankle evertor muscle. The order of the site and side of the stimulation was randomised. The postural response to hip abductor and ankle evertor vibration was recorded using 3D motion analysis (Codamotion, Leicestershire). Medio-lateral centre of pressure motion was simultaneously recorded during quiet standing via a force plate (Kistler, UK). Pre-cooling people responded to unilateral ankle vibration with an ipsilateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. People responded to unilateral hip vibration with a contralateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. Following an experimental reduction in distal tactile sensation there was a significant reduction in the amplitude of pelvic tilt in response to ankle vibration (F(6.2)=P<0.05) and a significant increase in amplitude of pelvic tilt in response to hip vibration (F(5.2)=P<0.05). This suggests that the sensitivity to artificial stimulation of hip proprioception increases with distal cooling, possibly indicating a change in the gain/weighting placed upon sensory information from the hips.

  1. Stress-anneal-induced magnetic anisotropy in highly textured Fe-Ga and Fe-Al magnetostrictive strips for bending-mode vibrational energy harvesters

    NASA Astrophysics Data System (ADS)

    Park, Jung Jin; Na, Suok-Min; Raghunath, Ganesh; Flatau, Alison B.

    2016-05-01

    Magnetostrictive Fe-Ga and Fe-Al alloys are promising materials for use in bending-mode vibrational energy harvesters. For this study, 50.8 mm × 5.0 mm × 0.5 mm strips of Fe-Ga and Fe-Al were cut from 0.50-mm thick rolled sheet. An atmospheric anneal was used to develop a Goss texture through an abnormal grain growth process. The anneal lead to large (011) grains that covered over 90% of sample surface area. The resulting highly-textured Fe-Ga and Fe-Al strips exhibited saturation magnetostriction values (λsat = λ∥ - λ⊥) of ˜280 ppm and ˜130 ppm, respectively. To maximize 90° rotation of magnetic moments during bending of the strips, we employed compressive stress annealing (SA). Samples were heated to 500°C, and a 100-150 MPa compressive stress was applied while at 500°C for 30 minutes and while being cooled. The effectiveness of the SA on magnetic moment rotation was inferred by comparing post-SA magnetostriction with the maximum possible yield of rotated magnetic moments, which is achieved when λ∥ = λsat and λ⊥ = 0. The uniformity of the SA along the sample length and the impact of the SA on sensing/energy harvesting performance were then assessed by comparing pre- and post-SA bending-stress-induced changes in magnetization at five different locations along the samples. The SA process with a 150 MPa compressive load improved Fe-Ga actuation along the sample length from 170 to 225 ppm (from ˜60% to within ˜80% of λsat). The corresponding sensing/energy harvesting performance improved by as much as a factor of eight in the best sample, however the improvement was not at all uniform along the sample length. The SA process with a 100 MPa compressive load improved Fe-Al actuation along the sample length from 60 to 73 ppm (from ˜46% to ˜56% of λsat, indicating only a marginally effective SA and suggesting the need for modification of the SA protocol. In spite of this, the SA was effective at improving the sensing/energy harvesting

  2. Selective excitation of vibrational states by shaping of light-induced potentials

    PubMed

    Sola; Chang; Santamaria; Malinovsky; Krause

    2000-11-13

    In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays. As an example, selective population transfer is demonstrated for a three-state model of the sodium dimer.

  3. Shape and 3D acoustically induced vibrations of the human eardrum characterized by digital holography

    NASA Astrophysics Data System (ADS)

    Khaleghi, Morteza; Furlong, Cosme; Cheng, Jeffrey Tao; Rosowski, John J.

    2014-07-01

    The eardrum or Tympanic Membrane (TM) transfers acoustic energy from the ear canal (at the external ear) into mechanical motions of the ossicles (at the middle ear). The acousto-mechanical-transformer behavior of the TM is determined by its shape and mechanical properties. For a better understanding of hearing mysteries, full-field-of-view techniques are required to quantify shape, nanometer-scale sound-induced displacement, and mechanical properties of the TM in 3D. In this paper, full-field-of-view, three-dimensional shape and sound-induced displacement of the surface of the TM are obtained by the methods of multiple wavelengths and multiple sensitivity vectors with lensless digital holography. Using our developed digital holographic systems, unique 3D information such as, shape (with micrometer resolution), 3D acoustically-induced displacement (with nanometer resolution), full strain tensor (with nano-strain resolution), 3D phase of motion, and 3D directional cosines of the displacement vectors can be obtained in full-field-ofview with a spatial resolution of about 3 million points on the surface of the TM and a temporal resolution of 15 Hz.

  4. Dissociation pathways of a single dimethyl disulfide on Cu(111): Reaction induced by simultaneous excitation of two vibrational modes

    SciTech Connect

    Motobayashi, Kenta; Kim, Yousoo; Arafune, Ryuichi; Ohara, Michiaki; Ueba, Hiromu; Kawai, Maki

    2014-05-21

    We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH{sub 3}S){sub 2}) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.

  5. Electron beam exposure mechanisms in hydrogen silsesquioxane investigated by vibrational spectroscopy and in-situ electron beam induced desorption

    SciTech Connect

    Olynick, D.L.; Cord, B.; Schipotinin, A.; Ogletree, D.F.; Schuck, P.J.

    2009-11-13

    Hydrogen Silsesquioxane (HSQ) is used as a high-resolution resist with resolution down below 10nm half-pitch. This material or materials with related functionalities could have widespread impact in nanolithography and nanoscience applications if the exposure mechanism was understood and instabilities controlled. Here we have directly investigated the exposure mechanism using vibrational spectroscopy (both Raman and Fourier transform Infrared) and electron beam desorption spectrocscopy (EBDS). In the non-networked HSQ system, silicon atoms sit at the corners of a cubic structure. Each silicon is bonded to a hydrogen atom and bridges 3 oxygen atoms (formula: HSiO3/2). For the first time, we have shown, via changes in the Si-H2 peak at ~;;2200 cm -1 in the Raman spectra and the release of SiHx products in EBID, that electron-bam exposed materials crosslinks via a redistribution reaction. In addition, we observe the release of significantly more H2 than SiH2 during EBID, which is indicative of additional reaction mechanisms. Additionally, we compare the behavior of HSQ in response to both thermal and electron-beam induced reactions.

  6. Computational study of vortex-induced vibration of a sprung rigid circular cylinder with a strongly nonlinear internal attachment

    NASA Astrophysics Data System (ADS)

    Tumkur, Ravi Kumar R.; Calderer, Ramon; Masud, Arif; Pearlstein, Arne J.; Bergman, Lawrence A.; Vakakis, Alexander F.

    2013-07-01

    For a Reynolds number (Re) based on cylinder diameter of 100, and a ratio of cylinder density to fluid density of 10, we investigate the effect of a strongly nonlinear internal attachment on the vortex-induced vibration (VIV) of a rigid circular cylinder restrained by a linear spring, and constrained to move perpendicularly to the mean flow. The variational multiscale residual-based stabilized finite-element method used to compute approximate solutions of the incompressible Navier-Stokes equations about the moving cylinder is coupled to a simple model of a "nonlinear energy sink" (NES), an essentially nonlinear oscillator consisting of a mass, a linear damper, and a strongly nonlinear spring. The NES promotes nearly one-way transfer of energy to itself from the primary structure (the cylinder), resulting in reduction of the amplitude of the limit-cycle oscillation by as much as 75%, depending on the parameters characterizing the NES. Various mechanisms of nonlinear interaction of the NES with the cylinder undergoing VIV are discussed. Although no optimization of the NES is performed in this work, we demonstrate capacity for passive suppression of VIV and compare the performance of the NES to the tuned linear absorber of equal mass.

  7. A theoretical study of the coupling between a vortex-induced vibration cylindrical resonator and an electromagnetic energy harvester

    NASA Astrophysics Data System (ADS)

    Xu-Xu, J.; Barrero-Gil, A.; Velazquez, A.

    2015-11-01

    This paper presents a theoretical study of the coupling between a vortex-induced vibration (VIV) cylindrical resonator and its associated linear electromagnetic generator. The two-equation mathematical model is based on a dual-mass formulation in which the dominant masses are the stator and translator masses of the generator. The fluid-structure interaction implemented in the model equations follows the so-called ‘advanced forcing model’ whose closure relies on experimental data. The rationale to carry out the study is the fact that in these types of configurations there is a two-way interaction between the moving parts in such a way that their motions influence each other simultaneously, thereby affecting the energy actually harvested. It is believed that instead of mainly resorting to complementary numerical simulations, a theoretical model can shed some light on the nature of the interaction and, at the same time, provide scaling laws that can be used for practical design and optimization purposes. It has been found that the proposed configuration has a maximum hydrodynamic to mechanical to electrical conversion efficiency (based on the VIV resonator oscillation amplitude) of 8%. For a cylindrical resonator 10 cm long with a 2 cm diameter, this translates into an output power of 20 to 160 mW for water stream velocities in the range from 0.5 to 1 m s-1.

  8. Dissociation pathways of a single dimethyl disulfide on Cu(111): reaction induced by simultaneous excitation of two vibrational modes.

    PubMed

    Motobayashi, Kenta; Kim, Yousoo; Arafune, Ryuichi; Ohara, Michiaki; Ueba, Hiromu; Kawai, Maki

    2014-05-21

    We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH3S)2) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.

  9. Theoretical analysis of transurethral laser-induced thermo-therapy for treatment of benign prostatic hyperplasia. Evaluation of a water-cooled applicator

    NASA Astrophysics Data System (ADS)

    Sturesson, C.; Andersson-Engels, S.

    1996-03-01

    A mathematical model for predicting the temperature rise in transurethral laser-induced thermo-therapy for benign prostatic hyperplasia was developed. In the model an optical line source emitting light from an Nd:YAG laser isotropically was placed in the urethra. Water cooling of the urethral epithelium was modelled using a two-tube system. The relationship between the difference in outlet and inlet water temperatures and the highest tissue temperature level reached was theoretically investigated. It was found that the water temperature difference was linearly dependent on the steady-state maximum tissue temperature. The theoretical calculations suggest that the water-cooled applicator can be used to measure the maximum tissue temperature. With temperature control, the prostatic tissue temperature can be prevented from exceeding the boiling point of water, excluding tissue carbonization. The model was also used to evaluate the influence of a number of different parameters on the damaged tissue volume. Increasing the urethral lumen radius by a factor of two by means of inserting different sized tubes was found to augment the tissue volume raised to therapeutic temperatures by up to 50%. The calculations showed that cooling of the urethral epithelium can result in an increase in the damaged volume by 80% as compared to not applying any cooling. The temperature of the cooling water was found to influence the tissue temperature only to a small extent.

  10. A comparison between intravascular and traditional cooling for inducing and maintaining temperature control in patients following cardiac arrest.

    PubMed

    Rosman, Jérémy; Hentzien, Maxime; Dramé, Moustapha; Roussel, Vincent; Just, Bernard; Jolly, Damien; Mateu, Philippe

    2016-11-29

    Therapeutic temperature control has been widely used during the last decade to improve clinical outcomes. We conducted this retrospective observational study to compare traditional cooling with endovascular cooling in post-cardiac arrest comatose survivors and to compare results with current guidelines.

  11. Impact of storm-induced cooling of sea surface temperature on large turbulent eddies and vertical turbulent transport in the atmospheric boundary layer of Hurricane Isaac

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Wang, Yuting; Chen, Shuyi S.; Curcic, Milan; Gao, Cen

    2016-01-01

    Roll vortices in the atmospheric boundary layer (ABL) are important to oil operation and oil spill transport. This study investigates the impact of storm-induced sea surface temperature (SST) cooling on the roll vortices generated by the convective and dynamic instability in the ABL of Hurricane Isaac (2012) and the roll induced transport using hindcasting large eddy simulations (LESs) configured from the multiply nested Weather Research & Forecasting model. Two experiments are performed: one forced by the Unified Wave INterface - Coupled Model and the other with the SST replaced by the NCEP FNL analysis that does not include the storm-induced SST cooling. The simulations show that the roll vortices are the prevalent eddy circulations in the ABL of Isaac. The storm-induced SST cooling causes the ABL stability falls in a range that satisfies the empirical criterion of roll generation by dynamic instability, whereas the ABL stability without considering the storm-induced SST cooling meets the criterion of roll generation by convective instability. The ABL roll is skewed and the increase of convective instability enhances the skewness. Large convective instability leads to large vertical transport of heat and moisture; whereas the dominant dynamic instability results in large turbulent kinetic energy but relatively weak heat and moisture transport. This study suggests that failure to consider roll vortices or incorrect initiation of dynamic and convective instability of rolls in simulations may substantially affect the transport of momentum, energy, and pollutants in the ABL and the dispersion/advection of oil spill fume at the ocean surface.

  12. Simulation of vortex-induced vibrations of a cylinder using ANSYS CFX rigid body solver

    NASA Astrophysics Data System (ADS)

    Izhar, Abubakar; Qureshi, Arshad Hussain; Khushnood, Shahab

    2017-03-01

    This article simulates the vortex-induced oscillations of a rigid circular cylinder with elastic support using the new ANSYS CFX rigid body solver. This solver requires no solid mesh to setup FSI (Fluid Structure Interaction) simulation. The two-way case was setup in CFX only. Specific mass of the cylinder and flow conditions were similar to previous experimental data with mass damping parameter equal to 0.04, specific mass of 1 and Reynolds number of 3800. Two dimensional simulations were setup. Both one-degree-of-freedom and two-degree-of-freedom cases were run and results were obtained for both cases with reasonable accuracy as compared with experimental results. Eight-figure XY trajectory and lock-in behavior were clearly captured. The obtained results were satisfactory.

  13. Thermal Wick Cooling for Vibroacoustic Transducers

    DTIC Science & Technology

    2009-09-25

    affecting vibrational characteristics of the transducer . (2) Description of the Prior Art [0004] Vibroacoustic transducers , such as piezoceramic tonpilz ...Distribution is unlimited 20091013084 Attorney Docket No. 84708 THERMAL WICK COOLING FOR VIBROACOUSTIC TRANSDUCERS STATEMENT OF GOVERNMENT INTEREST...INVENTION (1) Field of the Invention [0003] The present invention provides a device for cooling a vibroacoustic transducer without adversely

  14. Vibrations in MagAO: resonance sources identification and first approaches for modeling and control

    NASA Astrophysics Data System (ADS)

    Garcés, Javier; Zúñiga, Sebastián.; Close, Laird; Males, Jared; Morzinski, Katie; Escárate, Pedro; Castro, Mario; Marchioni, José; Rojas, Diego

    2016-07-01

    The Magellan Telescope Adaptive Optics System (MagAO) is subject to resonance effects induced by elements within the system instrumentation, such as fans and cooling pumps. Normalized PSDs are obtained through frequency-based analysis of closed-loop on-sky data, detecting and measuring vibration effects. Subsequently, a space-state model for the AO loop is obtained, using a standard AO loop scheme with an integrator-based controller and including the vibration effects as disturbances. Finally, a new control alternative is proposed, focusing on residual phase variance minimization through the design and simulation of an optimal LQG control approach.

  15. Active vibration control of structures undergoing bending vibrations

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)

    1995-01-01

    An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.

  16. A vibrational study of the hydrogen induced reconstructions on Cu(110)

    NASA Astrophysics Data System (ADS)

    Hayden, B. E.; Lackey, D.; Schott, J.

    1990-12-01

    Hydrogen adsorbed at 100 K on Cu(110) induces a (1 × 3) surface reconstruction observable in LEED in the coverage region 0.2 > φ H > 0.8. Two loss peaks associated with the hydrogen adsorbed in this phase are observed in HREELS at 620 and 505 cm -1. These features persist throughout the coverage range 0.0 < φ H < 1.0. Additional losses associated with hydrogen on a (1 × 2) reconstructed surface appear at φ H > 0.8 where a conversion of the (1 × 3) to the (1 × 2) phase is evident in LEED. Hydrogen adsorption at 300 K leads directly to the (1 × 2) reconstructed phase observable in LEED over the coverage range 0.1 < φ H < 1.0 and exhibits associated HREELS losses at 765, 950 and 1150 cm -1. Heating the (1 × 3) phase formed at 100 K irreversibly produces the (1 × 2) reconstruction in the temperature range 140-190 K. We assign the modes observed in the (1 × 3) phase to hydrogen in a pseudo four-fold hollow site on a buckled reconstructed surface. The modes on the (1 × 2) phase are associated with hydrogen in a tilted trigonal site on a missing row reconstructed surface. The hydrogen site transition from (1 × 3) to (1 × 2) on Cu(110) is analogous to the behaviour in metal hydrides where a conversion from octahedral to tetrahedral hydrogen coordination occurs for increasing hydrogen concentrations.

  17. [Dynamics of vegetative indicators induced by low-frequency magnetotherapy and EHF-puncture in hypertensive workers exposed to vibration].

    PubMed

    Drobyshev, V A; Efremov, A V; Loseva, M I; Sukharevskaia, T M; Michurin, A I

    2002-01-01

    Low-frequency magnetic fields and EHF-therapy have been used in correction of autonomic homeostasis in workers exposed to vibration for different periods of time. The workers suffered from early arterial hypertension. Vegetative status and central hemodynamics improved best in workers exposed to vibration for less than 5 years. If the exposure was 6-15 years, a positive trend occurred in the tension of regulatory mechanisms. Workers with long exposure to vibration suffering from vagotonia showed an inadequate response of the autonomic parameters to treatment. This necessitates enhancement of therapeutic measures with medicines.

  18. 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.

  19. Vibrational Stability of NLC Linac accelerating structure

    SciTech Connect

    Le Pimpec, Frederic

    2002-09-25

    The vibration of components of the NLC linac, such as accelerating structures and girders, is being studied both experimentally and analytically. Various effects are being considered including structural resonances and vibration caused by cooling water in the accelerating structure. This paper reports the status of ongoing work.

  20. Sorption cooling: a valid extension to passive cooling

    NASA Astrophysics Data System (ADS)

    Doornink, Jan; Burger, Johannes; ter Brake, Marcel

    2007-10-01

    Passive cooling has shown to be a very dependable cryogenic cooling method for space missions. Several missions employ passive radiators to cool down their delicate sensor systems for many years, without consuming power, without exporting vibrations or producing electromagnetic interference. So for a number of applications, passive cooling is a good choice. At lower temperatures, the passive coolers run into limitations that prohibit accommodation on a spacecraft. The approach to this issue has been to find a technology able to supplement passive cooling for lower temperatures, which maintains as much as possible of the advantages of passive coolers. Sorption cooling employs a closed cycle Joule-Thomson expansion process to achieve the cooling effect. Sorption cells perform the compression phase in this cycle. At a low temperature and pressure, these cells adsorb the working fluid. At a higher temperature they desorb the fluid and thus produce a high-pressure flow to the restriction in the cold stage. The sorption process selected for this application is of the physical type, which is completely reversible. It does not suffer from degradation as is the case with chemical sorption of e.g. hydrogen in metal hydrides. Sorption coolers include no moving parts except for some check valves, they export neither mechanical vibrations nor electromagnetic interference, and are potentially very dependable due to their simplicity. The required cooling temperature determines the type of working fluid to be applied. Sorption coolers can be used in conjunction with passive cooling for heat rejection at different levels. This paper starts with a brief discussion on applications of passive coolers in different types of orbits and the limitations on passive cooling at low cooling temperatures. Next, the working principle of sorption cooling is summarized. The DARWIN mission is chosen as an example application of sorption and passive cooling and special attention is paid to the

  1. Sorption cooling: A valid extension to passive cooling

    NASA Astrophysics Data System (ADS)

    Doornink, D. J.; Burger, J. F.; ter Brake, H. J. M.

    2008-05-01

    Passive cooling has shown to be a very dependable cryogenic cooling method for space missions. Several missions employ passive radiators to cool down their delicate sensor systems for many years, without consuming power, without exporting vibrations or producing electromagnetic interference. So for a number of applications, passive cooling is a good choice. At lower temperatures, the passive coolers run into limitations that prohibit accommodation on a spacecraft. The approach to this issue has been to find a technology able to supplement passive cooling for lower temperatures, which maintains as much as possible of the advantages of passive coolers. Sorption cooling employs a closed cycle Joule-Thomson expansion process to achieve the cooling effect. Sorption cells perform the compression phase in this cycle. At a low temperature and pressure, these cells adsorb the working fluid. At a higher temperature they desorb the fluid and thus produce a high-pressure flow to the expander in the cold stage. The sorption process selected for this application is of the physical type, which is completely reversible. It does not suffer from degradation as is the case with chemical sorption of, e.g., hydrogen in metal hydrides. Sorption coolers include no moving parts except for some check valves, they export neither mechanical vibrations nor electromagnetic interference, and are potentially very dependable due to their simplicity. The required cooling temperature determines the type of working fluid to be applied. Sorption coolers can be used in conjunction with passive cooling for heat rejection at different levels. This paper starts with a brief discussion on applications of passive coolers in different types of orbits and on the limitations of passive cooling for lower cooling temperatures. Next, the working principle of sorption cooling is summarized. The DARWIN mission is chosen as an example application of sorption and passive cooling and special attention is paid to the

  2. Time resolved measurements of vortex-induced vibrations of a positively buoyant tethered sphere in uniform water flow

    NASA Astrophysics Data System (ADS)

    Eshbal, L.; Krakovich, A.; van Hout, R.

    2012-11-01

    Vortex-induced vibrations (VIV) of a positively buoyant (light) tethered sphere in uniform flow as well as its wake characteristics were measured in a closed loop water channel. Experiments were performed at free stream velocities ranging between 0.048 and 0.22 m/s, corresponding to sphere Reynolds numbers ranging from ReD=430 to 1925. The measurements were done using high-speed sphere tracking as well as time resolved particle image velocimetry in a horizontal plane located at the sphere's center. Until the Hopf bifurcation, the sphere remained stationary and the wake was characterized by a train of hairpin vortices exhibiting near-symmetry in the vertical plane similar to stationary sphere visualization results. For our limited parameter range, the amplitude response of two different data sets (same sphere and free stream velocity but different water viscosity) collapsed better when plotted versus ReD than when plotted versus the reduced velocity, U*. The amplitude response beyond the first bifurcation displayed continuously increasing rms amplitudes in agreement with the sphere's small mass parameter (

  3. The influence of higher harmonic flow forces on the response of a curved circular cylinder undergoing vortex-induced vibration

    NASA Astrophysics Data System (ADS)

    Seyed-Aghazadeh, Banafsheh; Budz, Collin; Modarres-Sadeghi, Yahya

    2015-09-01

    Vortex-induced vibration (VIV) of a curved circular cylinder (a quarter of a ring, with no extension added to either end) free to oscillate in the crossflow direction was studied experimentally. Both the concave and the convex orientations (with respect to the oncoming flow direction) were considered. As expected, the amplitude of oscillations in both configurations was decreased compared to a vertical cylinder with the same mass ratio. Flow visualizations showed that the vortices were shed in parallel to the curved cylinder, when the cylinder was free to oscillate. The sudden jump in the phase difference between the flow forces and the cylinder displacement observed in the VIV of vertical cylinders was not observed in the curved cylinders. Higher harmonic force components at frequencies twice and three times the frequency of oscillations were observed in flow forces acting on the vertical cylinder, as well as the curved cylinder. Asymmetry in the wake was responsible for the 2nd harmonic force component and the relative velocity of the structure with respect to the oncoming flow was responsible for the 3rd harmonic force component. The lock-in occurred over the same range of reduced velocities for the curved cylinder in the convex orientation as for a vertical cylinder, but it was extended to higher reduced velocities for a curved cylinder in the concave orientation. Higher harmonic force components were found to be responsible for the extended lock-in range in the concave orientation. Within this range, the higher harmonic forces were even larger than the first harmonic force and the structure was being excited mainly by these higher harmonic forces.

  4. Active control of vortex-induced vibrations of a circular cylinder using windward-suction- leeward-blowing actuation

    NASA Astrophysics Data System (ADS)

    Wang, Chenglei; Tang, Hui; Yu, Simon C. M.; Duan, Fei

    2016-05-01

    This paper studies the control of two-dimensional vortex-induced vibrations (VIVs) of a single circular cylinder at a Reynolds number of 100 using a novel windward-suction-leeward-blowing (WSLB) concept. A lattice Boltzmann method based numerical framework is adopted for this study. Both open-loop and closed-loop controls are implemented. In the open-loop control, three types of actuation arrangements, including the pure suction on the windward side of the cylinder, the pure blowing on the leeward side, and the general WSLB on both sides, are implemented and compared. It is found that the general WSLB is the most effective, whereas the pure suction is the least effective. In the closed-loop control, the proportional (P), integral (I), and proportional-integral (PI) control schemes are applied to adjust the WSLB velocities according to the flow information obtained from a sensor. The effects of four key control parameters including the proportional gain constant, the integral gain constant, the length of data history used for the feedback, and the location of the sensor are investigated. It is found that the use of only P control fails to completely suppress the VIV, the use of only I control can achieve the complete suppression, and the PI control performs the best in terms of both the control effectiveness and efficiency. In the PI control, there exists an optimal length of data history for the feedback, at which the VIV control is the most efficient. There also exist the minimum required WSLB velocities for the VIV suppression, independent of the control schemes. Moreover, it is found that the VIV control is independent of the sensor location.

  5. Probabilistic analysis of mean-response along-wind induced vibrations on wind turbine towers using wireless network data sensors

    NASA Astrophysics Data System (ADS)

    Velazquez, Antonio; Swartz, Raymond A.

    2011-04-01

    Wind turbine systems are attracting considerable attention due to concerns regarding global energy consumption as well as sustainability. Advances in wind turbine technology promote the tendency to improve efficiency in the structure that support and produce this renewable power source, tending toward more slender and larger towers, larger gear boxes, and larger, lighter blades. The structural design optimization process must account for uncertainties and nonlinear effects (such as wind-induced vibrations, unmeasured disturbances, and material and geometric variabilities). In this study, a probabilistic monitoring approach is developed that measures the response of the turbine tower to stochastic loading, estimates peak demand, and structural resistance (in terms of serviceability). The proposed monitoring system can provide a real-time estimate of the probability of exceedance of design serviceability conditions based on data collected in-situ. Special attention is paid to wind and aerodynamic characteristics that are intrinsically present (although sometimes neglected in health monitoring analysis) and derived from observations or experiments. In particular, little attention has been devoted to buffeting, usually non-catastrophic but directly impacting the serviceability of the operating wind turbine. As a result, modal-based analysis methods for the study and derivation of flutter instability, and buffeting response, have been successfully applied to the assessment of the susceptibility of high-rise slender structures, including wind turbine towers. A detailed finite element model has been developed to generate data (calibrated to published experimental and analytical results). Risk assessment is performed for the effects of along wind forces in a framework of quantitative risk analysis. Both structural resistance and wind load demands were considered probabilistic with the latter assessed by dynamic analyses.

  6. Changes in illusory ankle movements induced by tendon vibrations during the delayed recovery phase of stretch-shortening cycle fatigue: an indirect study of muscle spindle sensitivity modifications.

    PubMed

    Regueme, S C; Barthèlemy, J; Gauthier, G M; Nicol, C

    2007-12-14

    This study examined the perceived movement velocity induced by tendon vibrations during the delayed recovery phase of a stretch-shortening cycle (SSC)-type exercise characterized by 2 to 4 days of neuromuscular and proprioceptive impairments. Seven subjects performed until exhaustion series of unilateral rebounds involving mostly the triceps surae muscle group. Fatigue effects were quantified for the exercised and non-exercised legs through muscle soreness and maximal voluntary plantarflexion test (MVC) performed immediately before (PRE) and after the SSC exercise, and repeated 2 days later (D2). At PRE and D2, mechanical vibrations at 40, 60, 80, 100, and 120 Hz were applied to distal tendons of the exercised ankle. For each vibration, the subjects had to reproduce the perceived movement velocity with the non-exercised ankle. According to previous studies, the sole exercised leg was characterized by a D2 peak of muscle soreness associated, in the MVC test, with significant decreases in maximal force and mean soleus muscle activity. As compared to the PRE test and in all subjects, the vibrations applied at D2 to the tendon of the fatigued ankle extensor muscles led to significant decreases in the perceived movement velocity at 80 and 100 Hz, but to an increased one at 40 Hz. In contrast, vibrations applied to the tendon of the non-fatigued ankle flexor muscle did not result in any significant change. These results suggest that the delayed recovery phase of SSC fatigue is characterized by changes in muscle proprioception, which may partly result from a decreased sensitivity of the primary endings.

  7. A novel calibration and task guidance framework for motor imagery BCI via a tendon vibration induced sensation with kinesthesia illusion

    NASA Astrophysics Data System (ADS)

    Yao, Lin; Meng, Jianjun; Sheng, Xinjun; Zhang, Dingguo; Zhu, Xiangyang

    2015-02-01

    Objective. Lack of efficient calibration and task guidance in motor imagery (MI) based brain-computer interface (BCI) would result in the failure of communication or control, especially in patients, such as a stroke with motor impairment and intact sensation, locked-in state amyotrophic lateral sclerosis, in which the sources of data for calibration may worsen the subsequent decoding. In addition, enhancing the proprioceptive experience in MI might improve the BCI performance. Approach. In this work, we propose a new calibrating and task guidance methodology to further improve the MI BCI, exploiting the afferent nerve system through tendon vibration stimulation to induce a sensation with kinesthesia illusion. A total of 30 subjects’ experiments were carried out, and randomly divided into a control group (control-group) and calibration and task guidance group (CTG-group). Main results. Online experiments have shown that MI could be decoded by classifier calibrated solely using sensation data, with 8 of the 15 subjects in the CTG-Group above 80%, 3 above 95% and all above 65%. Offline chronological cross-validation analysis shows that it has reached a comparable performance with the traditional calibration method (F(1,14)=0.14,P=0.7176). In addition, the discrimination accuracy of MI in the CTG-Group is significantly 12.17% higher on average than that in the control-group (unpaired-T test, P = 0.0086), and illusory sensation indicates no significant difference (unpaired-T test, p = 0.3412). The finding of the existed similarity of the discriminative brain patterns and grand averaged ERD/ERS between imagined movement (actively induced) and illusory movement (passively evoked) also validates the proposed calibration and task guidance framework. Significance. The cognitive complexity of the illusory sensation task is much lower and more objective than that of MI. In addition, subjects’ kinesthetic experience mentally simulated during the MI task might be enhanced by

  8. Cool & Connected

    EPA Pesticide Factsheets

    The Cool & Connected planning assistance program helps communities develop strategies and an action plan for using broadband to promote environmentally and economically sustainable community development.

  9. Cooling wall

    SciTech Connect

    Nosenko, V.I.

    1995-07-01

    Protecting the shells of blast furnaces is being resolved by installing cast iron cooling plates. The cooling plates become non-operational in three to five years. The problem is that defects occur in manufacturing the cooling plates. With increased volume and intensity of work placed on blast furnaces, heat on the cast iron cooling plates reduces their reliability that limits the interim repair period of blast furnaces. Scientists and engineers from the Ukraine studied this problem for several years, developing a new method of cooling the blast furnace shaft called the cooling wall. Traditional cast iron plates were replaced by a screen of steel tubes, with the area between the tubes filled with fireproof concrete. Before placing the newly developed furnace shaft into operation, considerable work was completed such as theoretical calculations, design, research of temperature fields and tension. Continual testing over many years confirms the value of this research in operating blast furnaces. The cooling wall works with water cooling as well as vapor cooling and is operating in 14 blast furnaces in the Ukraine and two in Russia, and has operated for as long as 14 years.

  10. Jet-cooled laser-induced dispersed fluorescence spectroscopy of NiC: Observation of low-lying Ω = 0+ state

    NASA Astrophysics Data System (ADS)

    Mukund, Sheo; Yarlagadda, Suresh; Bhattacharyya, Soumen; Nakhate, S. G.

    2014-01-01

    Laser-induced dispersed fluorescence spectra of 58Ni12C molecules, produced in a free-jet apparatus, have been studied. A new low-lying Ω = 0+ state has been observed at Te = 5178 (6) cm-1. Based on previous ab initio calculations this state is plausibly assigned as 0+ spin-orbit component of the first excited 3 Π state. The term energies of vibrational levels up to v = 10 for X1Σ+ ground and v = 3 for Ω = 0+ states have been determined. The harmonic and anharmonic wavenumbers respectively equal to 833 (4) and 6.7 (13) cm-1 for Ω = 0+ state have been measured.

  11. Solvent-induced infrared frequency shifts in aromatic nitriles are quantitatively described by the vibrational Stark effect.

    PubMed

    Levinson, Nicholas M; Fried, Stephen D; Boxer, Steven G

    2012-09-06

    The physical properties of solvents strongly affect the spectra of dissolved solutes, and this phenomenon can be exploited to gain insight into the solvent-solute interaction. The large solvatochromic shifts observed for many dye molecules in polar solvents are due to variations in the solvent reaction field, and these shifts are widely used to estimate the change in the dye's dipole moment upon photoexcitation, which is typically on the order of ∼1-10 D. In contrast, the change in dipole moment for vibrational transitions is approximately 2 orders of magnitude smaller. Nonetheless, vibrational chromophores display significant solvatochromism, and the relative contributions of specific chemical interactions and electrostatic interactions are debated, complicating the interpretation of vibrational frequency shifts in complex systems such as proteins. Here we present a series of substituted benzonitriles that display widely varying degrees of vibrational solvatochromism. In most cases, this variation can be quantitatively described by the experimentally determined Stark tuning rate, coupled with a simple Onsager-like model of solvation, reinforcing the view that vibrational frequency shifts are largely caused by electrostatic interactions. In addition, we discuss specific cases where continuum solvation models fail to predict solvatochromic shifts, revealing the necessity for more advanced theoretical models that capture local aspects of solute-solvent interactions.

  12. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  13. Cool Shelter

    ERIC Educational Resources Information Center

    Praeger, Charles E.

    2005-01-01

    Amid climbing energy costs and tightening budgets, administrators at school districts, colleges and universities are looking for all avenues of potential savings while promoting sustainable communities. Cool metal roofing can save schools money and promote sustainable design at the same time. Cool metal roofing keeps the sun's heat from collecting…

  14. Analysis of Thermally Induced Changes in Fractured Rock Permeability during Eight Years of Heating and Cooling at the Yucca Mountain Drift Scale Test

    SciTech Connect

    Rutqvist, J.; Freifeld, B.; Min, K.-B.; Elsworth, D.; Tsang, Y.

    2008-06-01

    We analyzed a data set of thermally induced changes in fractured rock permeability during a four-year heating (up to 200 C) and subsequent four-year cooling of a large volume, partially saturated and highly fractured volcanic tuff at the Yucca Mountain Drift Scale Test, in Nevada, USA. Permeability estimates were derived from about 700 pneumatic (air-injection) tests, taken periodically at 44 packed-off borehole intervals during the heating and cooling cycle from November 1997 through November 2005. We analyzed air-permeability data by numerical modeling of thermally induced stress and moisture movements and their impact on air permeability within the highly fractured rock. Our analysis shows that changes in air permeability during the initial four-year heating period, which were limited to about one order of magnitude, were caused by the combined effects of thermal-mechanically-induced stress on fracture aperture and thermal-hydrologically-induced changes in fracture moisture content. At the end of the subsequent four-year cooling period, air-permeability decreases (to as low as 0.2 of initial) and increases (to as high as 1.8 of initial) were observed. By comparison to the calculated thermo-hydro-elastic model results, we identified these remaining increases or decreases in air permeability as irreversible changes in intrinsic fracture permeability, consistent with either inelastic fracture shear dilation (where permeability increased) or inelastic fracture surface asperity shortening (where permeability decreased). In this paper, we discuss the possibility that such fracture asperity shortening and associated decrease in fracture permeability might be enhanced by dissolution of highly stressed surface asperities over years of elevated stress and temperature.

  15. Experimental investigation of vibration-induced bulk solids transport and segregation. Quarterly report ending March 31, 1996

    SciTech Connect

    Rosato, A.D.; Dave, R.N.

    1996-09-01

    An experimental investigation of the motion of a single large sphere in a bed of dry granular material subjected to vertical vibration is presented. We have studied the rise time of the sphere as a function of vibration parameters, frequency and amplitude. While previous results report a decreasing rise time with increasing relative acceleration, we evidence the existence of a critical frequency where the rise time jumps to greater values before decreasing again. We also show that the rise time scales with the velocity amplitude of vibration and the transition corresponds approximately to a doubling of rise time. The results reported are over a rather narrow range of input accelerations, and generally involve gross phenomena of heaping and fluidization. Observations of the dynamic trajectory of the rising particle are also reported through the use of a novel non-intrusive particle tracking system. 16 refs., 7 figs.

  16. Phase coherence in vibration-induced responses of tactile fibres associated with Pacinian corpuscle receptors in the cat.

    PubMed Central

    Greenstein, J; Kavanagh, P; Rowe, M J

    1987-01-01

    1. In pentobarbitone-anaesthetized cats, responses were recorded in peripheral nerves or cervical dorsal columns from sensory fibres associated with Pacinian corpuscle (P.c.) receptors in the forelimb footpads. Factors affecting the phase of response to cutaneous vibration in individual P.c. fibres, and the extent of phase coherence in the responses of different P.c. fibres were examined when sinusoidal vibratory stimuli at 100-400 Hz were delivered using a 1 mm diameter probe. 2. Increases in vibration amplitude from the absolute to the 1:1 threshold for the P.c. fibre led to phase advances in the response, often of about 60 deg, in over 85% of fibres tested at 200 and 300 Hz, but further increases had little effect. 3. Variations in stimulus position within the receptive field led to unpredictable changes in the response phase that ranged from minimal change to shifts of 180 deg. As the response phase was unrelated to the distance from the point of peak sensitivity it is likely that at high vibration frequencies (greater than or equal to 100 Hz) the recruited population of P.c. fibres will respond over the whole range of phase angles. 4. The calculated phase of spike initiation in different pairs of P.c. fibres that shared coincident points of best sensitivity on the skin ranged from near synchrony to maximum asynchrony indicating that there is little phase coherence even in the subpopulation of somatotopically related P.c. fibres recruited by high-frequency cutaneous vibration. 5. Paired recordings from P.c. fibres within the cervical dorsal columns revealed a broad range of phase discrepancies in the responses of P.c. fibres to vibration at 200 and 300 Hz. 6. Several hypotheses are considered to explain the known presence of phase-locked responses to high-frequency (greater than or equal to 100 Hz) vibration in the central neurones of dorsal column nuclei. PMID:3681709

  17. Vibrational relaxation of anharmonic oscillators in expanding flows

    NASA Technical Reports Server (NTRS)

    Ruffin, Stephen M.; Park, Chul

    1992-01-01

    Although the Landau-Teller vibrational model accurately predicts vibrational excitation process in post-shock and compressing flows, it under-predicts the rate of de-