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Sample records for resonant thermal noise

  1. A second generation of low thermal noise cryogenic silicon resonators

    NASA Astrophysics Data System (ADS)

    Matei, D. G.; Legero, T.; Grebing, Ch; Häfner, S.; Lisdat, Ch; Weyrich, R.; Zhang, W.; Sonderhouse, L.; Robinson, J. M.; Riehle, F.; Ye, J.; Sterr, U.

    2016-06-01

    We have set up an improved vertically mounted silicon cavity operating at the zero-crossing temperature of the coefficient of thermal expansion (CTE) near 123 K with estimated thermal noise limited instability of 4 x 10-17 in the modified Allan deviation. Owing to the anisotropic elasticity of single-crystal silicon, the vertical acceleration sensitivity was minimized in situ by axially rotating the resonator with respect to the mounting frame. The control of the resonator temperature is greatly improved by using a combination of two thermal shields, monitoring with several temperature sensors, and employing low-thermal conductivity materials. The instability of the resonator stabilized laser was characterized by comparing with another low-noise system based on a 48 cm long room temperature cavity of PTB's strontium lattice clock, resulting in a modified Allan deviation of 7 x 10-17 at 100 s.

  2. Thermal noise induced stochastic resonance in self organizing Fe nanoparticle system

    NASA Astrophysics Data System (ADS)

    Pal, Satyendra Prakash; Sen, P.

    2014-12-01

    The natural world is replete with examples of multistable systems, known to respond to periodic modulations and produce a signal that exhibits resonance with noise amplitude. This is a concept not demonstrated in pure materials, which involve a measured physical property. In a thermoremanent magnetization experiment with a common magnetic material, Fe, in the nanoparticulate form, we establish how magnetization in a system of dilute spins during dissipation of stored magnetic energy breaks up into spontaneous oscillatory behavior. Starting at 175 K and aided by temperature (stochastic noise) the oscillation amplitude goes through a maximum reminiscent of stochastic resonance. Our observation of thermal noise induced coherent resonance is due to intrinsic self-organizing magnetic dynamics of the Fe nanoparticle system without applying any external periodic force. These results yield new possibilities in the design of magnetic materials and a platform to understand stochastic interference and phase synchronization in neural activity, as models for neural communication.

  3. Resonant activation in a colored multiplicative thermal noise driven closed system

    SciTech Connect

    Ray, Somrita; Bag, Bidhan Chandra; Mondal, Debasish

    2014-05-28

    In this paper, we have demonstrated that resonant activation (RA) is possible even in a thermodynamically closed system where the particle experiences a random force and a spatio-temporal frictional coefficient from the thermal bath. For this stochastic process, we have observed a hallmark of RA phenomena in terms of a turnover behavior of the barrier-crossing rate as a function of noise correlation time at a fixed noise variance. Variance can be fixed either by changing temperature or damping strength as a function of noise correlation time. Our another observation is that the barrier crossing rate passes through a maximum with increase in coupling strength of the multiplicative noise. If the damping strength is appreciably large, then the maximum may disappear. Finally, we compare simulation results with the analytical calculation. It shows that there is a good agreement between analytical and numerical results.

  4. Absolute measurement of thermal noise in a resonant short-range force experiment

    NASA Astrophysics Data System (ADS)

    Yan, H.; Housworth, E. A.; Meyer, H. O.; Visser, G.; Weisman, E.; Long, J. C.

    2014-10-01

    Planar, double-torsional oscillators are especially suitable for short-range macroscopic force search experiments, since they can be operated at the limit of instrumental thermal noise. As a study of this limit, we report a measurement of the noise kinetic energy of a polycrystalline tungsten oscillator in thermal equilibrium at room temperature. The fluctuations of the oscillator in a high-Q torsional mode with a resonance frequency near 1 kHz are detected with capacitive transducers coupled to a sensitive differential amplifier. The electronic processing is calibrated by means of a known electrostatic force and input from a finite-element model. The measured average kinetic energy, Eexp = (2.0 ± 0.3) × 10-21 J, is in agreement with the expected value of 1/2{{k}B}T.

  5. Uncertainty in least-squares fits to the thermal noise spectra of nanomechanical resonators with applications to the atomic force microscope

    SciTech Connect

    Sader, John E.; Yousefi, Morteza; Friend, James R.

    2014-02-15

    Thermal noise spectra of nanomechanical resonators are used widely to characterize their physical properties. These spectra typically exhibit a Lorentzian response, with additional white noise due to extraneous processes. Least-squares fits of these measurements enable extraction of key parameters of the resonator, including its resonant frequency, quality factor, and stiffness. Here, we present general formulas for the uncertainties in these fit parameters due to sampling noise inherent in all thermal noise spectra. Good agreement with Monte Carlo simulation of synthetic data and measurements of an Atomic Force Microscope (AFM) cantilever is demonstrated. These formulas enable robust interpretation of thermal noise spectra measurements commonly performed in the AFM and adaptive control of fitting procedures with specified tolerances.

  6. Optical Coating Thermal Noise Testbed

    NASA Astrophysics Data System (ADS)

    Hartman, Michael T.; Eichholz, Johannes; Tanner, David B.; Mueller, Guido

    2015-04-01

    Interferometric gravitational-wave detectors measure the length strain of a passing gravitational-wave as differential arm length changes in kilometer-long Michelson interferometers. The second-generation detectors, such as Advanced LIGO (aLIGO), will achieve strain sensitivities which are limited by Brownian thermal noise in the optical coatings of the interferometers' arm-cavity mirror test masses. Brownian coating thermal noise (CTN) is the apparent motion on the mirror surface on the order of 10-17 -10-20 m resulting from thermal fluctuations in the coating and the coating's internal friction. The result is a source of length noise in optical resonators that is a function of the coating temperature and the coating material's mechanical loss. At the University of Florida we are constructing the THermal noise Optical Resonator (THOR), a testbed for the direct measurement of CTN in the aLIGO test mass coating as well as future coating candidates. The material properties of the coating (namely mechanical loss) are temperature dependent, making cryogenic mirrors a prospect for future gravitational-wave detectors. To explore this option we are simultaneously building a cryogenic CTN testbed, CryoTHOR. This is a presentation on the status of these testbeds. This work is supported by NSF Grants PHY-0969935 and PHY-1306594.

  7. The Hannover thermal noise experiment

    NASA Astrophysics Data System (ADS)

    Leonhardt, V.; Ribichini, L.; Lück, H.; Danzmann, K.

    2004-03-01

    To analyse the thermal noise of the pendulum mode of a suspended mirror, we interferometrically detect the differential movement of two mirrors suspended as multiple-stage pendulums. We present the set-up of this experiment and the current sensitivity, and also the different steps that we took in the past to increase the sensitivity, which include an auto alignment of the laser beam into the resonator eigenmode, changes of the seismic isolation system to more damping stages and higher moments of inertia and an intensive noise hunting.

  8. Noise in nonlinear nanoelectromechanical resonators

    NASA Astrophysics Data System (ADS)

    Guerra Vidal, Diego N.

    Nano-Electro-Mechanical Systems (NEMS), due to their nanometer scale size, possess a number of desirable attributes: high sensitivity to applied forces, fast response times, high resonance frequencies and low power consumption. However, ultra small size and low power handling result in unwanted consequences: smaller signal size and higher dissipation, making the NEMS devices more susceptible to external and intrinsic noise. The simplest version of a NEMS, a suspended nanomechanical structure with two distinct excitation states, can be used as an archetypal two state system to study a plethora of fundamental phenomena such as Duffing nonlinearity, stochastic resonance, and macroscopic quantum tunneling at low temperatures. From a technical perspective, there are numerous applications such nanomechanical memory elements, microwave switches and nanomechanical computation. The control and manipulation of the mechanical response of these two state systems can be realized by exploiting a (seemingly) counterintuitive physical phenomenon, Stochastic Resonance: in a noisy nonlinear mechanical system, the presence of noise can enhance the system response to an external stimulus. This Thesis is mainly dedicated to study possible applications of Stochastic Resonance in two-state nanomechanical systems. First, on chip signal amplification by 1/falpha is observed. The effectiveness of the noise assisted amplification is observed to decrease with increasing a. Experimental evidence shows an increase in asymmetry between the two states with increasing noise color. Considering the prevalence of 1/f alpha noise in the materials in integrated circuits, the signal enhancement demonstrated here, suggests beneficial use of the otherwise detrimental noise. Finally, a nanomechanical device, operating as a reprogrammable logic gate, and performing fundamental logic functions such as AND/OR and NAND/NOR is presented. The logic function can be programmed (from AND to OR) dynamically, by

  9. Single-electron thermal noise.

    PubMed

    Nishiguchi, Katsuhiko; Ono, Yukinori; Fujiwara, Akira

    2014-07-11

    We report the observation of thermal noise in the motion of single electrons in an ultimately small dynamic random access memory (DRAM). The nanometer-scale transistors that compose the DRAM resolve the thermal noise in single-electron motion. A complete set of fundamental tests conducted on this single-electron thermal noise shows that the noise perfectly follows all the aspects predicted by statistical mechanics, which include the occupation probability, the law of equipartition, a detailed balance, and the law of kT/C. In addition, the counting statistics on the directional motion (i.e., the current) of the single-electron thermal noise indicate that the individual electron motion follows the Poisson process, as it does in shot noise. PMID:25093235

  10. Eliminating thermal violin spikes from LIGO noise

    SciTech Connect

    Santamore, D. H.; Levin, Yuri

    2001-08-15

    We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than {approx}2 x 10{sup -13} cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors.

  11. System Measures Thermal Noise In A Microphone

    NASA Technical Reports Server (NTRS)

    Zuckerwar, Allan J.; Ngo, Kim Chi T.

    1994-01-01

    Vacuum provides acoustic isolation from environment. System for measuring thermal noise of microphone and its preamplifier eliminates some sources of error found in older systems. Includes isolation vessel and exterior suspension, acting together, enables measurement of thermal noise under realistic conditions while providing superior vibrational and accoustical isolation. System yields more accurate measurements of thermal noise.

  12. Acoustic noise during functional magnetic resonance imaginga)

    PubMed Central

    Ravicz, Michael E.; Melcher, Jennifer R.; Kiang, Nelson Y.-S.

    2007-01-01

    Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 μPa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager’s permanent magnet and the room air handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions. PMID:11051496

  13. Magnetostochastic resonance under colored noise condition

    NASA Astrophysics Data System (ADS)

    Trapanese, Marco

    2012-04-01

    Stochastic resonance (SR) is an amplification of the system output in correspondence of well-defined finite values of the noise strength that is injected into the system [Gammaitoni et al., Rev. Mod. Phys. 70, 223 (1998), Grigorenko et al., IEEE Trans. Magn. 31, 2491 (1995), Mantegna et al., J. Appl. Phys. 97, 10E519 (2005)]. In order to clarify the influence of a colored noise, in this paper magnetostochastic resonance (MSR) in magnetic systems described by the dynamic Preisach model is numerically investigated in the presence of colored noise. In this paper it is shown that: a) noise spectrum affects MSR; b) white noise, 1/f and 1/f2 noise induce in magnetic systems described by the dynamic Preisach model MSR; c) the maximum level of signal-to-noise (SNR) is obtained by using white noise but 1/f noise presents a range where SNR value is higher than the case of white noise; d) maximum signal amplification is obtained for white noise.

  14. Flow noise source-resonator coupling

    SciTech Connect

    Pollack, M.L.

    1997-11-01

    This paper investigates the coupling mechanism between flow noise sources and acoustic resonators. Analytical solutions are developed for the classical cases of monopole and dipole types of flow noise sources. The effectiveness of the coupling between the acoustic resonator and the noise source is shown to be dependent on the type of noise source as well as its location on the acoustic pressure mode shape. For a monopole source, the maximum coupling occurs when the noise source is most intense near an acoustic pressure antinode (i.e., location of maximum acoustic pressure). A numerical study with the impedance method demonstrates this effect. A dipole source couples most effectively when located near an acoustic pressure node.

  15. Brownian thermal noise in multilayer coated mirrors

    NASA Astrophysics Data System (ADS)

    Hong, Ting; Yang, Huan; Gustafson, Eric K.; Adhikari, Rana X.; Chen, Yanbei

    2013-04-01

    We analyze the Brownian thermal noise of a multilayer dielectric coating used in high-precision optical measurements, including interferometric gravitational-wave detectors. We assume the coating material to be isotropic, and therefore study thermal noises arising from shear and bulk losses of the coating materials. We show that coating noise arises not only from layer thickness fluctuations, but also from fluctuations of the interface between the coating and substrate, driven by fluctuating shear stresses of the coating. Although thickness fluctuations of different layers are statistically independent, there exists a finite coherence between the layers and the substrate-coating interface. In addition, photoelastic coefficients of the thin layers (so far not accurately measured) further influence the thermal noise, although at a relatively low level. Taking into account uncertainties in material parameters, we show that significant uncertainties still exist in estimating coating Brownian noise.

  16. Thermally actuated resonant silicon crystal nanobalances

    NASA Astrophysics Data System (ADS)

    Hajjam, Arash

    As the potential emerging technology for next generation integrated resonant sensors and frequency references as well as electronic filters, micro-electro-mechanical resonators have attracted a lot of attention over the past decade. As a result, a wide variety of high frequency micro/nanoscale electromechanical resonators have recently been presented. MEMS resonators, as low-cost highly integrated and ultra-sensitive mass sensors, can potentially provide new opportunities and unprecedented capabilities in the area of mass sensing. Such devices can provide orders of magnitude higher mass sensitivity and resolution compared to Film Bulk Acoustic resonators (FBAR) or the conventional quartz and Surface Acoustic Wave (SAW) resonators due to their much smaller sizes and can be batch-fabricated and utilized in highly integrated large arrays at a very low cost. In this research, comprehensive experimental studies on the performance and durability of thermally actuated micromechanical resonant sensors with frequencies up to tens of MHz have been performed. The suitability and robustness of the devices have been demonstrated for mass sensing applications related to air-borne particles and organic gases. In addition, due to the internal thermo-electro-mechanical interactions, the active resonators can turn some of the consumed electronic power back into the mechanical structure and compensate for the mechanical losses. Therefore, such resonators can provide self-sustained-oscillation without the need for any electronic circuitry. This unique property has been deployed to demonstrate a prototype self-sustained sensor for air-borne particle monitoring. I have managed to overcome one of the obstacles for MEMS resonators, which is their relatively poor temperature stability. This is a major drawback when compared with the conventional quartz crystals. A significant decrease of the large negative TCF for the resonators has been attained by doping the devices with a high

  17. Dependence of SAW resonator 1/f noise on device size.

    PubMed

    Parker, T E

    1993-01-01

    Experiments were conducted with eight 450-MHz surface acoustic wave (SAW) resonators which demonstrate that a resonator's 1/f noise depends approximately inversely on the active acoustic area of the device. This observation is consistent with a proposed theory that 1/f noise in acoustic resonators is caused by localized velocity or dimensional fluctuations. PMID:18263254

  18. Thermal-mechanical-noise-based CMUT characterization and sensing.

    PubMed

    Gurun, Gokce; Hochman, Michael; Hasler, Paul; Degertekin, F Levent

    2012-06-01

    When capacitive micromachined ultrasonic transducers (CMUTs) are monolithically integrated with custom-designed low-noise electronics, the output noise of the system can be dominated by the CMUT thermal-mechanical noise both in air and in immersion even for devices with low capacitance. Because the thermal-mechanical noise can be related to the electrical admittance of the CMUTs, this provides an effective means of device characterization. This approach yields a novel method to test the functionality and uniformity of CMUT arrays and the integrated electronics when a direct connection to CMUT array element terminals is not available. Because these measurements can be performed in air at the wafer level, the approach is suitable for batch manufacturing and testing. We demonstrate this method on the elements of an 800-μm-diameter CMUT-on-CMOS array designed for intravascular imaging in the 10 to 20 MHz range. Noise measurements in air show the expected resonance behavior and spring softening effects. Noise measurements in immersion for the same array provide useful information on both the acoustic cross talk and radiation properties of the CMUT array elements. The good agreement between a CMUT model based on finite difference and boundary element methods and the noise measurements validates the model and indicates that the output noise is indeed dominated by thermal-mechanical noise. The measurement method can be exploited to implement CMUT-based passive sensors to measure immersion medium properties, or other parameters affecting the electro-mechanics of the CMUT structure. PMID:22718877

  19. Can intrinsic noise induce various resonant peaks?

    NASA Astrophysics Data System (ADS)

    Torres, J. J.; Marro, J.; Mejias, J. F.

    2011-05-01

    We theoretically describe how weak signals may be efficiently transmitted throughout more than one frequency range in noisy excitable media by a sort of stochastic multiresonance. This helps us to reinterpret recent experiments in neuroscience and to suggest that many other systems in nature might be able to exhibit several resonances. In fact, the observed behavior happens in our model as a result of competition between (i) changes in the transmitted signals as if the units were varying their activation threshold, and (ii) adaptive noise realized in the model as rapid activity-dependent fluctuations of the connection intensities. These two conditions are indeed known to characterize heterogeneously networked systems of excitable units, e.g. sets of neurons and synapses in the brain. Our results may find application also in the design of detector devices.

  20. Majorana Braiding with Thermal Noise.

    PubMed

    Pedrocchi, Fabio L; DiVincenzo, David P

    2015-09-18

    We investigate the self-correcting properties of a network of Majorana wires, in the form of a trijunction, in contact with a parity-preserving thermal environment. As opposed to the case where Majorana bound states are immobile, braiding Majorana bound states within a trijunction introduces dangerous error processes that we identify. Such errors prevent the lifetime of the memory from increasing with the size of the system. We confirm our predictions with Monte Carlo simulations. Our findings put a restriction on the degree of self-correction of this specific quantum computing architecture. PMID:26430973

  1. Majorana Braiding with Thermal Noise

    NASA Astrophysics Data System (ADS)

    Pedrocchi, Fabio L.; DiVincenzo, David P.

    2015-09-01

    We investigate the self-correcting properties of a network of Majorana wires, in the form of a trijunction, in contact with a parity-preserving thermal environment. As opposed to the case where Majorana bound states are immobile, braiding Majorana bound states within a trijunction introduces dangerous error processes that we identify. Such errors prevent the lifetime of the memory from increasing with the size of the system. We confirm our predictions with Monte Carlo simulations. Our findings put a restriction on the degree of self-correction of this specific quantum computing architecture.

  2. Noise control using a plate radiator and an acoustic resonator

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor)

    1996-01-01

    An active noise control subassembly for reducing noise caused by a source (such as an aircraft engine) independent of the subassembly. A noise radiating panel is bendably vibratable to generate a panel noise canceling at least a portion of the source noise. A piezoceramic actuator plate is connected to the panel. A front plate is spaced apart from the panel and the first plate, is positioned generally between the source noise and the panel, and has a sound exit port. A first pair of spaced-apart side walls each generally abut the panel and the front plate so as to generally enclose a front cavity to define a resonator.

  3. Measurement of Thermal Noise in Optical Coatings for Gravitational-Wave Detectors

    NASA Astrophysics Data System (ADS)

    Hartman, Michael; Eichholz, Johannes; Fulda, Paul; Ciani, Giacomo; Tanner, David B.; Mueller, Guido

    2014-03-01

    Interferometric gravitational-wave detectors measure the gravitational-wave-induced strain in the arms of kilometer scale Michelson interferometers. Second-generation detectors, such as Advanced LIGO, are expected to be limited by optical coating thermal noise in the most sensitive region (30-300 Hz) of the detectors' frequency bands. The direct measurement of coating thermal noise in different optical coatings is essential to both the validation of current thermal noise models as well as the research of future coating material candidates. The THermal noise Optical Resonator (THOR) is a testbed being developed at the University of Florida to directly measure the thermal noise in optical coatings on mirrors in the frequency band around 100 Hz. This is a presentation on the status of THOR. This work is supported by NSF grants PHY-0969935 and PHY-1306594.

  4. Thermal nonlinearity in silicon microcylindrical resonators

    NASA Astrophysics Data System (ADS)

    Vukovic, Natasha; Healy, Noel; Mehta, Priyanth; Day, Todd D.; Sazio, Pier J. A.; Badding, John V.; Peacock, Anna C.

    2012-04-01

    We explore the thermally induced nonlinearity in hydrogenated amorphous silicon microcylindrical resonators that are fabricated from the silicon optical fiber platform. In particular, we use a pump-probe technique to experimentally demonstrate thermally induced optical modulation and determine the response time. Through characterization of the thermal properties and the associated resonance wavelength shifts, we will show that it is possible to infer the material absorption coefficient for a range of whispering gallery mode resonators.

  5. Loss and thermal noise in plasmonic waveguides

    SciTech Connect

    Syms, R. R. A. Solymar, L.

    2014-06-07

    Rytov's theory of thermally generated radiation is used to find the noise in two-dimensional passive guides based on an arbitrary distribution of lossy isotropic dielectric. To simplify calculations, the Maxwell curl equations are approximated using difference equations that also permit a transmission-line analogy, and material losses are assumed to be low enough for modal losses to be estimated using perturbation theory. It is shown that an effective medium representation of each mode is valid for both loss and noise and, hence, that a one-dimensional model can be used to estimate the best achievable noise factor when a given mode is used in a communications link. This model only requires knowledge of the real and imaginary parts of the modal dielectric constant. The former can be found by solving the lossless eigenvalue problem, while the latter can be estimated using perturbation theory. Because of their high loss, the theory is most relevant to plasmonic waveguides, and its application is demonstrated using single interface, slab, and slot guide examples. The best noise performance is offered by the long-range plasmon supported by the slab guide.

  6. Stochastic resonance enhanced by dichotomic noise in a bistable system

    SciTech Connect

    Rozenfeld, Robert; Neiman, Alexander; Schimansky-Geier, Lutz

    2000-09-01

    We study linear responses of a stochastic bistable system driven by dichotomic noise to a weak periodic signal. We show that the effect of stochastic resonance can be greatly enhanced in comparison with the conventional case when dichotomic forcing is absent, that is, both the signal-to-noise ratio and the spectral power amplification reach much greater values than in the standard stochastic resonance setup. (c) 2000 The American Physical Society.

  7. Qubit dephasing due to photon shot noise from coherent and thermal sources

    NASA Astrophysics Data System (ADS)

    Gustavsson, S.; Yan, F.; Kamal, A.; Orlando, T. P.; Oliver, W. D.; Birenbaum, J.; Sears, A.; Hover, D.; Gudmundsen, T.; Yoder, J.

    We investigate qubit dephasing due to photon shot noise in a superconducting flux qubit transversally coupled to a coplanar microwave resonator. Due to the AC Stark effect, photon fluctuations in the resonator cause frequency shifts of the qubit, which in turn lead to dephasing. While this is universally understood, we have made the first quantitative spectroscopy of this noise for both thermal (i.e., residual photons from higher temperature stages) and coherent photons (residual photons from the readout and control pulses). We find that the bandwidth of the shot noise from thermal and coherent photons differ by approximately a factor of two, which we attribute to differences in the correlation time for the two noise sources. By comparing the results with noise spectra measured without any externally applied photons, we conclude that the qubit coherence times in our setup were limited by photon shot noise from thermal radiation, with an average resonator photon population of 0.006. Equipped with this knowledge, we improved the filtering for thermal noise and thereby improved the qubit coherence times by more than a factor of two, with T2 echo times approaching 100 us. From the measured T2 decay, we determine an upper bound on the residual photon population of 0.0004. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) via MIT LL under Air Force Contract No. FA8721-05-C-0002.

  8. Current noise of the interacting resonant level model

    NASA Astrophysics Data System (ADS)

    Suzuki, T. J.; Kennes, D. M.; Meden, V.

    2016-02-01

    We study the zero-frequency current noise of the interacting resonant level model for arbitrary bias voltages using a functional renormalization group approach. For this we extend the existing nonequilibrium scheme by deriving and solving flow equations for the current-vertex functions. On-resonance artificial divergences of the latter found in lowest-order perturbation theory in the two-particle interaction are consistently removed. Away from resonance they are shifted to higher orders. This allows us to gain a comprehensive picture of the current noise in the scaling limit. At high bias voltages, the current noise exhibits a universal power-law decay, whose exponent is, to leading order in the interaction, identical to that of the current. The effective charge on resonance is analyzed in detail, employing properties of the vertex correction. We find that it is only modified to second or higher order in the two-particle interaction.

  9. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  10. Stochastic resonance in the fractional Langevin equation driven by multiplicative noise and periodically modulated noise

    NASA Astrophysics Data System (ADS)

    Yu, Tao; Zhang, Lu; Luo, Mao-Kang

    2013-10-01

    First we study the time and frequency characteristics of fractional calculus, which reflect the memory and gain properties of fractional-order systems. Then, the fractional Langevin equation driven by multiplicative colored noise and periodically modulated noise is investigated in the over-damped case. Using the moment equation method, the exact analytical expression of the output amplitude is derived. Numerical results indicate that the output amplitude presents stochastic resonance driven by periodically modulated noise. For low frequency signal, the higher the system order is, the bigger the resonance intensity will be; while the result of high frequency signal is quite the contrary. This is consistent with the frequency characteristics of fractional calculus.

  11. Adaptive noise cancelling of multichannel magnetic resonance sounding signals

    NASA Astrophysics Data System (ADS)

    Dalgaard, E.; Auken, E.; Larsen, J. J.

    2012-10-01

    Adaptive noise cancelling of multichannel magnetic resonance sounding (MRS) signals is investigated. An analysis of the noise sources affecting MRS signals show that the applicability of adaptive noise cancelling is primarily limited to cancel powerline harmonics. The problems of handling spikes in MRS signals are discussed and an efficient algorithm for spike detection is presented. The optimum parameters for multichannel adaptive noise cancelling are identified through simulations with synthetic signals added to noise-only recordings from an MRS instrument. We discuss the design and the efficiency of different stacking methods. The results from multichannel adaptive noise cancelling are compared to time-domain multichannel Wiener filtering. Our results show that within the experimental uncertainty the two methods give identical results.

  12. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  13. Thermally affected characterization region by Barkhausen noise.

    PubMed

    Zergoug, M; Boucherrou, N; Haddad, A; Benchaala, A; Moulti, B; Tahraoui, H; Sellidj, F; Hammouda, A

    2000-07-01

    The controlling of some industrial components require the development of new and particular nondestructive testing techniques. The testing method using Barkhausen noise (BN) is a particular one which can be applied to ferromagnetic materials. It is a magnetic nondestructive evaluation method and can provide very important information about the material structure. The aim of our work is to study the material structure using this technique to characterize the region submitted to thermal processing. Samples of steel have been heated at temperatures between 650 degrees C and 1,200 degrees C with variable parameters (time processing, maintenance time, etc.). Acoustic BN processing allows an easy interpretation of results. Micrographs of samples have been obtained to confirm the results obtained by BN. PMID:10950355

  14. Robust stochastic resonance: Signal detection and adaptation in impulsive noise

    NASA Astrophysics Data System (ADS)

    Kosko, Bart; Mitaim, Sanya

    2001-11-01

    Stochastic resonance (SR) occurs when noise improves a system performance measure such as a spectral signal-to-noise ratio or a cross-correlation measure. All SR studies have assumed that the forcing noise has finite variance. Most have further assumed that the noise is Gaussian. We show that SR still occurs for the more general case of impulsive or infinite-variance noise. The SR effect fades as the noise grows more impulsive. We study this fading effect on the family of symmetric α-stable bell curves that includes the Gaussian bell curve as a special case. These bell curves have thicker tails as the parameter α falls from 2 (the Gaussian case) to 1 (the Cauchy case) to even lower values. Thicker tails create more frequent and more violent noise impulses. The main feedback and feedforward models in the SR literature show this fading SR effect for periodic forcing signals when we plot either the signal-to-noise ratio or a signal correlation measure against the dispersion of the α-stable noise. Linear regression shows that an exponential law γopt(α)=cAα describes this relation between the impulsive index α and the SR-optimal noise dispersion γopt. The results show that SR is robust against noise ``outliers.'' So SR may be more widespread in nature than previously believed. Such robustness also favors the use of SR in engineering systems. We further show that an adaptive system can learn the optimal noise dispersion for two standard SR models (the quartic bistable model and the FitzHugh-Nagumo neuron model) for the signal-to-noise ratio performance measure. This also favors practical applications of SR and suggests that evolution may have tuned the noise-sensitive parameters of biological systems.

  15. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  16. Estimation of Frequency Noise in Semiconductor Lasers Due to Mechanical Thermal Noise

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Camp, Jordan

    2012-01-01

    We evaluate mechanical thermal noise in semiconductor lasers, applying a methodology developed for fixed-spacer cavities for laser frequency stabilization. Our simple model determines an underlying fundamental limit for the frequency noise of free-running semiconductor laser, and provides a framework: where the noise may be potentially reduced with improved design.

  17. Frequency dependence of thermal noise in gram-scale cantilever flexures

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh T.-H.; Mow-Lowry, Conor M.; Slagmolen, Bram J. J.; Miller, John; Mullavey, Adam J.; Goßler, Stefan; Altin, Paul A.; Shaddock, Daniel A.; McClelland, David E.

    2015-12-01

    We present measurements of the frequency dependence of thermal noise in aluminum and niobium flexures. Our measurements cover the audio-frequency band from 10 Hz to 10 kHz, which is of particular relevance to ground-based interferometric gravitational wave detectors, and span up to an order of magnitude above and below the fundamental flexure resonances. Results from two flexures are well explained by a simple model in which both structural and thermoelastic loss play a role. The ability of such a model to explain this interplay is important for investigations of quantum-radiation-pressure noise and the standard quantum limit. Furthermore, measurements on a third flexure provide evidence that surface damage can affect the frequency dependence of thermal noise in addition to reducing the quality factor, a result which will aid the understanding of how aging effects impact on thermal noise behavior.

  18. Fundamental Limit of 1/f Frequency Noise in Semiconductor Lasers Due to Mechanical Thermal Noise

    NASA Technical Reports Server (NTRS)

    Numata, K.; Camp, J.

    2011-01-01

    So-called 1/f noise has power spectral density inversely proportional to frequency, and is observed in many physical processes. Single longitudinal-mode semiconductor lasers, used in variety of interferometric sensing applications, as well as coherent communications, exhibit 1/f frequency noise at low frequency (typically below 100kHz). Here we evaluate mechanical thermal noise due to mechanical dissipation in semiconductor laser components and give a plausible explanation for the widely-observed 1/f frequency noise, applying a methodology developed for fixed-spacer cavities for laser frequency stabilization. Semiconductor-laser's short cavity, small beam radius, and lossy components are expected to emphasize thermal-noise-limited frequency noise. Our simple model largely explains the different 1/f noise levels observed in various semiconductor lasers, and provides a framework where the noise may be reduced with proper design.

  19. Thermal Noise in Laser Interferometer Gravitational Wave Detectors

    NASA Astrophysics Data System (ADS)

    Flaminio, Raffaele

    Thermal noise is one of the major limitations to the sensitivity of present and future laser interferometers devoted to gravitational wave detection. According to the fluctuation-dissipation theorem any mechanical oscillator is affected by a motion of thermal origin directly related to its thermodynamic temperature. The mirrors and their suspensions that are used in gravitational wave detectors such as Virgo or LIGO are examples of such mechanical oscillators. As a consequence their position is affected by this thermal vibration and the sensitivity of the gravitational wave detector is thermal noise limited over a wide range of frequencies. After recalling briefly the fluctuation-dissipation theorem and its origins, this chapter describes the main types of thermal noise affecting gravitational wave detectors. In the last part of the chapter a special emphasis is given to the thermal noise due to dissipation in the mirrors optical coatings.

  20. Bimaterial Thermal Compensators for WGM Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir; Strekalov, Dmitry

    2008-01-01

    Bimaterial thermal compensators have been proposed as inexpensive means of preventing (to first order) or reducing temperature-related changes in the resonance frequencies of whispering-gallery-mode (WGM) optical resonators. A bimaterial compensator would apply, to a WGM resonator, a pressure that would slightly change the shape of the resonator and thereby change its resonance frequencies. Through suitable choice of the compensator dimensions and materials, it should be possible to make the temperature dependence of the pressure-induced frequency shift equal in magnitude and opposite in sign to the temperature dependence of the frequency shift of the uncompensated resonator so that, to first order, a change in temperature would cause zero net change in frequency.

  1. Cross-spectrum measurement of thermal-noise limited oscillators.

    PubMed

    Hati, A; Nelson, C W; Howe, D A

    2016-03-01

    Cross-spectrum analysis is a commonly used technique for the detection of phase and amplitude noise of a signal in the presence of interfering uncorrelated noise. Recently, we demonstrated that the phase-inversion (anti-correlation) effect due to amplitude noise leakage can cause complete or partial collapse of the cross-spectral function. In this paper, we discuss the newly discovered effect of anti-correlated thermal noise that originates from the common-mode power divider (splitter), an essential component in a cross-spectrum noise measurement system. We studied this effect for different power splitters and discuss its influence on the measurement of thermal-noise limited oscillators. We provide theory, simulation and experimental results. In addition, we expand this study to reveal how the presence of ferrite-isolators and amplifiers at the output ports of the power splitters can affect the oscillator noise measurements. Finally, we discuss a possible solution to overcome this problem. PMID:27036804

  2. Cross-spectrum measurement of thermal-noise limited oscillators

    NASA Astrophysics Data System (ADS)

    Hati, A.; Nelson, C. W.; Howe, D. A.

    2016-03-01

    Cross-spectrum analysis is a commonly used technique for the detection of phase and amplitude noise of a signal in the presence of interfering uncorrelated noise. Recently, we demonstrated that the phase-inversion (anti-correlation) effect due to amplitude noise leakage can cause complete or partial collapse of the cross-spectral function. In this paper, we discuss the newly discovered effect of anti-correlated thermal noise that originates from the common-mode power divider (splitter), an essential component in a cross-spectrum noise measurement system. We studied this effect for different power splitters and discuss its influence on the measurement of thermal-noise limited oscillators. We provide theory, simulation and experimental results. In addition, we expand this study to reveal how the presence of ferrite-isolators and amplifiers at the output ports of the power splitters can affect the oscillator noise measurements. Finally, we discuss a possible solution to overcome this problem.

  3. Optical Coatings and Thermal Noise in Precision Measurement

    NASA Astrophysics Data System (ADS)

    Harry, Gregory; Bodiya, Timothy P.; DeSalvo, Riccardo

    2012-01-01

    1. Theory of thermal noise in optical mirrors Y. Levin; 2. Coating technology S. Chao; 3. Compendium of thermal noises in optical mirrors V. B. Braginsky, M. L. Gorodetsky and S. P. Vyatchanin; 4. Coating thermal noise I. Martin and S. Reid; 5. Direct measurements of coating thermal noise K. Numata; 6. Methods of improving thermal noise S. Ballmer and K. Somiya; 7. Substrate thermal noise S. Rowan and I. Martin; 8. Cryogenics K. Numata and K. Yamamoto; 9. Thermo-optic noise M. Evans and G. Ogin; 10. Absorption and thermal issues P. Willems, D. Ottaway and P. Beyersdorf; 11. Optical scatter J. R. Smith and M. E. Zucker; 12. Reflectivity and thickness optimisation I. M. Pinto, M. Principe and R. DeSalvo; 13. Beam shaping A. Freise; 14. Gravitational wave detection D. Ottaway and S. D. Penn; 15. High-precision laser stabilisation via optical cavities M. J. Martin and J. Ye; 16. Quantum optomechanics G. D. Cole and M. Aspelmeyer; 17. Cavity quantum electrodynamics T. E. Northup.

  4. Asymmetric resonant exchange qubit under the influence of electrical noise

    NASA Astrophysics Data System (ADS)

    Russ, Maximilian; Burkard, Guido

    2015-06-01

    We investigate the influence of electrical charge noise on a resonant exchange (RX) qubit in a triple quantum dot. This RX qubit is a variation of the exchange-only spin qubit which responds to a narrow-band resonant frequency. Our noise model includes uncorrelated charge noise in each quantum dot giving rise to two independent (noisy) bias parameters ɛ and Δ . We calculate the energy splitting of the two qubit states as a function of these two bias detuning parameters to find "sweet spots," where the qubit is least susceptible to noise. Our investigation shows that such sweet spots exist within the low-bias regime, in which the bias detuning parameters have the same magnitude as the hopping parameters. The location of the sweet spots in the (ɛ ,Δ ) plane depends on the hopping strength and asymmetry between the quantum dots. In the regime of weak charge noise, we identify a new favorable operating regime for the RX qubit based on these sweet spots.

  5. Magnetic resonance-guided thermal surgery.

    PubMed

    Cline, H E; Schenck, J F; Watkins, R D; Hynynen, K; Jolesz, F A

    1993-07-01

    A demonstration of MR guided thermal surgery involved experiments with imaging of focused ultrasound in an MRI system, measurements of the thermal transients and a thermal analysis of the resulting images. Both the heat distribution and the creation of focused ultrasound lesions in gel phantoms, in vitro bovine muscle and in vivo rabbit muscle were monitored with magnetic resonance imaging. Thermal surgical procedures were modeled by an elongated gaussian heat source where heat flow is controlled by tissue thermal properties and tissue perfusion. Temperature profiles were measured with thermocouples or calculated from magnetic resonance imaging in agreement with the model. A 2-s T1-weighted gradient-refocused acquisition provided thermal profiles needed to localize the heat distribution produced by a 4-s focused ultrasound pulse. Thermal analysis of the images give an effective thermal diffusion coefficient of 0.0015 cm2/s in gel and 0.0033 cm2/s in muscle. The lesions were detected using a T2-weighted spin-echo or fast spin-echo pulse sequence in agreement with muscle tissue sections. Potential thermal surgery applications are in the prostate, liver, kidney, bladder, breast, eye and brain. PMID:8371680

  6. Ultralow-phase-noise oscillators based on BAW resonators.

    PubMed

    Li, Mingdong; Seok, Seonho; Rolland, Nathalie; Rolland, Paul; El Aabbaoui, Hassan; de Foucauld, Emeric; Vincent, Pierre; Giordano, Vincent

    2014-06-01

    This paper presents two 2.1-GHz low-phase noise oscillators based on BAW resonators. Both a single-ended common base structure and a differential Colpitts structure have been implemented in a 0.25-μm BiCMOS process. The detailed design methods including the realization, optimization, and test are reported. The differential Colpitts structure exhibits a phase noise 6.5 dB lower than the single-ended structure because of its good performance of power noise immunity. Comparison between the two structures is also carried out. The differential Colpitts structure shows a phase noise level of -87 dBc/Hz at 1-kHz offset frequency and a phase noise floor of -162 dBc/Hz, with an output power close to -6.5 dBm and a core consumption of 21.6 mW. Furthermore, with the proposed optimization methods, both proposed devices have achieved promising phase noise performance compared with state-of-the-art oscillators described in the literature. Finally, we briefly present the application of the proposed BAW oscillator to a micro-atomic clock. PMID:24859654

  7. Effect of thermal noise on random lasers in diffusion regime

    NASA Astrophysics Data System (ADS)

    Zarei, Mohammad Ali; Hosseini-Farzad, Mahmood; Montakhab, Afshin

    2015-09-01

    In this paper, we study the effects of thermal noise on the time evolution of a weak light pulse (probe) in the presence of a strong light pulse (pump) within a gain medium which includes random scatterer particles. Suitable thermal noise term is added to a set of four coupled equations including three diffusion equations for energy densities and a rate equation for the upper level population in a four-level gain medium. These equations have been solved simultaneously by Crank-Nicholson numerical method. The main result is that the back-scattered output probe light is increased as the thermal noise strength is increased and simultaneously, with the same rate, the amplified spontaneous emission is decreased. Therefore, the amplified response of the random laser in diffusion regime for the input probe pulse is enhanced due to effect of the thermal noise.

  8. Stochastic resonance in periodic potentials driven by colored noise

    NASA Astrophysics Data System (ADS)

    Liu, Kaihe; Jin, Yanfei

    2013-11-01

    We studied the motion of an underdamped Brownian particle in a periodic potential subject to a harmonic excitation and a colored noise. The average input energy per period and the phase lag are calculated to quantify the phenomenon of stochastic resonance (SR). The numerical results show that most of the out-of-phase trajectories make a transition to the in-phase state as the temperature increases. And the colored noise delays the transitions between these two dynamical states. The each curve of the average input energy per period and the phase lag versus the temperature exist a mono peak and SR appears in this system. Moreover, the optimal temperature where the SR occurs becomes larger and the region of SR grows wider as the correlation time of colored noise increases.

  9. Gaussian approximation and single-spin measurement in magnetic resonance force microscopy with spin noise

    SciTech Connect

    Raghunathan, Shesha; Brun, Todd A.; Goan, Hsi-Sheng

    2010-11-15

    A promising technique for measuring single electron spins is magnetic resonance force microscopy (MRFM), in which a microcantilever with a permanent magnetic tip is resonantly driven by a single oscillating spin. The most effective experimental technique is the oscillating cantilever-driven adiabatic reversals (OSCAR) protocol, in which the signal takes the form of a frequency shift. If the quality factor of the cantilever is high enough, this signal will be amplified over time to the point where it can be detected by optical or other techniques. An important requirement, however, is that this measurement process occurs on a time scale that is short compared to any noise which disturbs the orientation of the measured spin. We describe a model of spin noise for the MRFM system and show how this noise is transformed to become time dependent in going to the usual rotating frame. We simplify the description of the cantilever-spin system by approximating the cantilever wave function as a Gaussian wave packet and show that the resulting approximation closely matches the full quantum behavior. We then examine the problem of detecting the signal for a cantilever with thermal noise and spin with spin noise, deriving a condition for this to be a useful measurement.

  10. Noise-enhanced Parametric Resonance in Perturbed Galaxies

    NASA Astrophysics Data System (ADS)

    Sideris, Ioannis V.; Kandrup, Henry E.

    2004-02-01

    This paper describes how parametric resonances associated with a galactic potential subjected to relatively low-amplitude, strictly periodic time-dependent perturbations can be impacted by pseudo-random variations in the pulsation frequency, modeled as colored noise. One aim thereby is to allow for the effects of a changing oscillation frequency as the density distribution associated with a galaxy evolves during violent relaxation. Another is to mimic the possible effects of internal substructures, satellite galaxies, and/or a high-density environment. The principal conclusions are that allowing for a variable frequency does not vitiate the effects of parametric resonance, and that, in at least some cases, such variations can increase the overall importance of parametric resonance associated with systematic pulsations. In memory of Professor H. E. Kandrup, a brilliant scientist, excellent teacher, and good friend. His genius and sense of humor will be greatly missed.

  11. Physiological Noise Reduction Using Volumetric Functional Magnetic Resonance Inverse Imaging

    PubMed Central

    Lin, Fa-Hsuan; Nummenmaa, Aapo; Witzel, Thomas; Polimeni, Jonathan R.; Zeffiro, Thomas A.; Wang, Fu-Nien; Belliveau, John W.

    2013-01-01

    Physiological noise arising from a variety of sources can significantly degrade the detection of task-related activity in BOLD-contrast fMRI experiments. If whole head spatial coverage is desired, effective suppression of oscillatory physiological noise from cardiac and respiratory fluctuations is quite difficult without external monitoring, since traditional EPI acquisition methods cannot sample the signal rapidly enough to satisfy the Nyquist sampling theorem, leading to temporal aliasing of noise. Using a combination of high speed magnetic resonance inverse imaging (InI) and digital filtering, we demonstrate that it is possible to suppress cardiac and respiratory noise without auxiliary monitoring, while achieving whole head spatial coverage and reasonable spatial resolution. Our systematic study of the effects of different moving average (MA) digital filters demonstrates that a MA filter with a 2 s window can effectively reduce the variance in the hemodynamic baseline signal, thereby achieving 57-58% improvements in peak z-statistic values compared to unfiltered InI or spatially smoothed EPI data (FWHM =8.6 mm). In conclusion, the high temporal sampling rates achievable with InI permit significant reductions in physiological noise using standard temporal filtering techniques that result in significant improvements in hemodynamic response estimation. PMID:21954026

  12. Transition from double coherence resonances to single coherence resonance in a neuronal network with phase noise.

    PubMed

    Jia, Yanbing; Gu, Huaguang

    2015-12-01

    The effect of phase noise on the coherence dynamics of a neuronal network composed of FitzHugh-Nagumo (FHN) neurons is investigated. Phase noise can induce dissimilar coherence resonance (CR) effects for different coupling strength regimes. When the coupling strength is small, phase noise can induce double CRs. One corresponds to the average frequency of phase noise, and the other corresponds to the intrinsic firing frequency of the FHN neuron. When the coupling strength is large enough, phase noise can only induce single CR, and the CR corresponds to the intrinsic firing frequency of the FHN neuron. The results show a transition from double CRs to single CR with the increase in the coupling strength. The transition can be well interpreted based on the dynamics of a single neuron stimulated by both phase noise and the coupling current. When the coupling strength is small, the coupling current is weak, and phase noise mainly determines the dynamics of the neuron. Moreover, the phase-noise-induced double CRs in the neuronal network are similar to the phase-noise-induced double CRs in an isolated FHN neuron. When the coupling strength is large enough, the coupling current is strong and plays a key role in the occurrence of the single CR in the network. The results provide a novel phenomenon and may have important implications in understanding the dynamics of neuronal networks. PMID:26723163

  13. CryoTHOR: measuring thermal noise in optical coatings

    NASA Astrophysics Data System (ADS)

    Ciani, Giacomo; Eichholz, Johannes; Hartman, Michael; Mueller, Guido

    2016-03-01

    Brownian thermal noise in the optical coatings of the test mirrors is expected to be one of dominant noise sources in the most sensitive frequency band of the Advanced LIGO detectors, from a few tens to a few hundreds Hz. Together with thermo-optic noise, it is also envisioned to be one of the main obstacles to improving the sensitivity of future gravitational wave observatories, including cryogenic ones. Many groups are currently engaged in the development of advanced coatings designs with reduced noise. Expected performances of such coatings are usually calculated using independent measurements of material properties which enters in the modeling of thermal noise. However, these properties are often highly dependent on the material history and specific geometric arrangement, and their measured values affected by relatively big uncertainties. Furthermore, their temperature dependence is not always well studied. A direct measurement of the thermal noise over a wide range of temperatures is clearly the preferred way of assessing a coating design viability. We report on the design, performance and latest results of cryoTHOR, an experiment developed for the direct measurements of coating thermal noise over the entire LIGO frequency band, both at room and cryogenic temperatures.

  14. Testing resonating vector strength: Auditory system, electric fish, and noise

    NASA Astrophysics Data System (ADS)

    Leo van Hemmen, J.; Longtin, André; Vollmayr, Andreas N.

    2011-12-01

    Quite often a response to some input with a specific frequency ν○ can be described through a sequence of discrete events. Here, we study the synchrony vector, whose length stands for the vector strength, and in doing so focus on neuronal response in terms of spike times. The latter are supposed to be given by experiment. Instead of singling out the stimulus frequency ν○ we study the synchrony vector as a function of the real frequency variable ν. Its length turns out to be a resonating vector strength in that it shows clear maxima in the neighborhood of ν○ and multiples thereof, hence, allowing an easy way of determining response frequencies. We study this "resonating" vector strength for two concrete but rather different cases, viz., a specific midbrain neuron in the auditory system of cat and a primary detector neuron belonging to the electric sense of the wave-type electric fish Apteronotus leptorhynchus. We show that the resonating vector strength always performs a clear resonance correlated with the phase locking that it quantifies. We analyze the influence of noise and demonstrate how well the resonance associated with maximal vector strength indicates the dominant stimulus frequency. Furthermore, we exhibit how one can obtain a specific phase associated with, for instance, a delay in auditory analysis.

  15. Simulation of Thin-Film Damping and Thermal Mechanical Noise Spectra for Advanced Micromachined Microphone Structures

    PubMed Central

    Hall, Neal A.; Okandan, Murat; Littrell, Robert; Bicen, Baris; Degertekin, F. Levent

    2008-01-01

    In many micromachined sensors the thin (2–10 μm thick) air film between a compliant diaphragm and backplate electrode plays a dominant role in shaping both the dynamic and thermal noise characteristics of the device. Silicon microphone structures used in grating-based optical-interference microphones have recently been introduced that employ backplates with minimal area to achieve low damping and low thermal noise levels. Finite-element based modeling procedures based on 2-D discretization of the governing Reynolds equation are ideally suited for studying thin-film dynamics in such structures which utilize relatively complex backplate geometries. In this paper, the dynamic properties of both the diaphragm and thin air film are studied using a modal projection procedure in a commonly used finite element software and the results are used to simulate the dynamic frequency response of the coupled structure to internally generated electrostatic actuation pressure. The model is also extended to simulate thermal mechanical noise spectra of these advanced sensing structures. In all cases simulations are compared with measured data and show excellent agreement—demonstrating 0.8 pN/√Hz and 1.8 μPa/√Hz thermal force and thermal pressure noise levels, respectively, for the 1.5 mm diameter structures under study which have a fundamental diaphragm resonance-limited bandwidth near 20 kHz. PMID:19081811

  16. Thermal noise from optical coatings in gravitational wave detectors.

    PubMed

    Harry, Gregory M; Armandula, Helena; Black, Eric; Crooks, D R M; Cagnoli, Gianpietro; Hough, Jim; Murray, Peter; Reid, Stuart; Rowan, Sheila; Sneddon, Peter; Fejer, Martin M; Route, Roger; Penn, Steven D

    2006-03-01

    Gravitational waves are a prediction of Einstein's general theory of relativity. These waves are created by massive objects, like neutron stars or black holes, oscillating at speeds appreciable to the speed of light. The detectable effect on the Earth of these waves is extremely small, however, creating strains of the order of 10(-21). There are a number of basic physics experiments around the world designed to detect these waves by using interferometers with very long arms, up to 4 km in length. The next-generation interferometers are currently being designed, and the thermal noise in the mirrors will set the sensitivity over much of the usable bandwidth. Thermal noise arising from mechanical loss in the optical coatings put on the mirrors will be a significant source of noise. Achieving higher sensitivity through lower mechanical loss coatings, while preserving the crucial optical and thermal properties, is an area of active research right now. PMID:16539265

  17. Mirror thermal noise in interferometric gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Rao, Shanti Raja

    2003-12-01

    The LIGO (Laser Interferometer Gravitational-wave Observatory) project has begun its search for gravitational waves, and efforts are being made to improve its ability to detect these. The LIGO observatories are long, Fabry-Perot-Michelson interferometers, where the interferometer mirrors are also the gravitational wave test masses. LIGO is designed to detect the ripples in spacetime caused by cataclysmic astrophysical events, with a target gravitational wave minimum strain sensitivity of 4 × 10-22 [7] around 100 Hz. The Advanced LIGO concept [57] calls for an order of magnitude improvement in strain sensitivity, with a better signal to noise ratio to increase the rate of detection of events. Some of Advanced LIGO's major requirements are improvements over the LIGO design for thermal noise in the test mass substrates and reflective coatings [57]. Thermal noise in the interferometer mirrors is a significant challenge in LIGO's development. This thesis reviews the theory of test mass thermal noise and reports on several experiments conducted to understand this theory. Experiments to measure the thermal expansion of mirror substrates and coatings use the photothermal effect in a cross-polarized Fabry-Perot interferometer, with displacement sensitivity of 10-15m/rHz. Data are presented from 10 Hz to 4 kHz on solid aluminum, and on sapphire, BK7, and fused silica, with and without commercial TiO2/SiO2 dielectric mirror coatings. The substrate contribution to thermal expansion is compared to theories by Cerdonio et al. [32] and Braginsky, Vyatchanin, and Gorodetsky [22]. New theoretical models are presented for estimating the coating contribution to the thermal expansion. These results can also provide insight into how heat flows between coatings and substrates relevant to predicting coating thermoelastic noise [26, 108]. The Thermal Noise Interferometer (TNI) project is a interferometer built specifically to study thermal noise, and this thesis describes its

  18. Determination of the Thermal Noise Limit of Graphene Biotransistors.

    PubMed

    Crosser, Michael S; Brown, Morgan A; McEuen, Paul L; Minot, Ethan D

    2015-08-12

    To determine the thermal noise limit of graphene biotransistors, we have measured the complex impedance between the basal plane of single-layer graphene and an aqueous electrolyte. The impedance is dominated by an imaginary component but has a finite real component. Invoking the fluctuation-dissipation theorem, we determine the power spectral density of thermally driven voltage fluctuations at the graphene/electrolyte interface. The fluctuations have 1/f(p) dependence, with p = 0.75-0.85, and the magnitude of fluctuations scales inversely with area. Our results explain noise spectra previously measured in liquid-gated suspended graphene devices and provide realistic targets for future device performance. PMID:26176844

  19. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Bliss, Donald B.; Gottwald, James A.; Gustaveson, Mark B.; Burton, James R., III; Castellino, Craig

    1989-01-01

    Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselages lines with panels alternately tuned to frequencies above and below the frequency to be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cut off and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations. This program summarizes the work carried out at Duke University during the third semester of a contract supported by the Structural Acoustics Branch at NASA Langley Research Center.

  20. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Gottwald, James A.; Bliss, Donald B.

    1990-01-01

    The focus is on a noise control method which considers aircraft fuselages lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. An interior noise reduction called alternate resonance tuning (ART) is described both theoretically and experimentally. Problems dealing with tuning single paneled wall structures for optimum noise reduction using the ART methodology are presented, and three theoretical problems are analyzed. The first analysis is a three dimensional, full acoustic solution for tuning a panel wall composed of repeating sections with four different panel tunings within that section, where the panels are modeled as idealized spring-mass-damper systems. The second analysis is a two dimensional, full acoustic solution for a panel geometry influenced by the effect of a propagating external pressure field such as that which might be associated with propeller passage by a fuselage. To reduce the analysis complexity, idealized spring-mass-damper panels are again employed. The final theoretical analysis presents the general four panel problem with real panel sections, where the effect of higher structural modes is discussed. Results from an experimental program highlight real applications of the ART concept and show the effectiveness of the tuning on real structures.

  1. Receptivity to thermal noise in real airfoil configurations

    NASA Astrophysics Data System (ADS)

    Luchini, Paolo

    2014-11-01

    Thermal noise, the macroscopic manifestation of microscopic particle agitation, is present in fluid flow just as in electron flow in conductors or in other physical transport phenomena. When the flow acts as an amplifier, typically during transition to turbulence, the transition position can be influenced by the amplitude of external disturbances through the so called receptivity of the flow instabilities; internally generated thermal noise represents a thermodynamically enforced lower bound to how much disturbances can be reduced. In a previous paper (Seventh IUTAM Symposium on Laminar-Turbulent Transition, IUTAM Bookseries Volume 18, Springer, 2010, pp. 11-18), the present author showed that the maximum transition distance in a Blasius boundary layer corresponds to a Reynolds number little above 6 .106 and to an N-factor of the order of 13. Results to be exhibited at this conference show that in a real airfoil configuration the maximum transition Reynolds number imposed by thermal noise is even lower than on a flat wall, and not far from the actually observed transition position. It follows that thermal noise might actually have a role in natural transition; and that even a perfectly silenced laboratory environment cannot push the transition position much farther. Work supported by the European Community through the RECEPT grant.

  2. Stochastic resonance in a piecewise nonlinear model driven by multiplicative non-Gaussian noise and additive white noise

    NASA Astrophysics Data System (ADS)

    Guo, Yongfeng; Shen, Yajun; Tan, Jianguo

    2016-09-01

    The phenomenon of stochastic resonance (SR) in a piecewise nonlinear model driven by a periodic signal and correlated noises for the cases of a multiplicative non-Gaussian noise and an additive Gaussian white noise is investigated. Applying the path integral approach, the unified colored noise approximation and the two-state model theory, the analytical expression of the signal-to-noise ratio (SNR) is derived. It is found that conventional stochastic resonance exists in this system. From numerical computations we obtain that: (i) As a function of the non-Gaussian noise intensity, the SNR is increased when the non-Gaussian noise deviation parameter q is increased. (ii) As a function of the Gaussian noise intensity, the SNR is decreased when q is increased. This demonstrates that the effect of the non-Gaussian noise on SNR is different from that of the Gaussian noise in this system. Moreover, we further discuss the effect of the correlation time of the non-Gaussian noise, cross-correlation strength, the amplitude and frequency of the periodic signal on SR.

  3. Role of thermal noise in tripartite quantum steering

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Gong, Qihuang; Ficek, Zbigniew; He, Qiongyi

    2014-08-01

    The influence of thermal noise on bipartite and tripartite quantum steering induced by a short laser pulse in a hybrid three-mode optomechanical system is investigated. The calculation is carried out under the bad cavity limit, the adiabatic approximation of a slowly varying amplitude of the cavity mode, and with the assumption of driving the cavity mode with a blue detuned strong laser pulse. Under such conditions, explicit expressions of the bipartite and tripartite steering parameters are obtained, and the concept of collective tripartite quantum steering, recently introduced by He and Reid [Phys. Rev. Lett. 111, 250403 (2013), 10.1103/PhysRevLett.111.250403], is clearly explored. It is found that both bipartite and tripartite steering parameters are sensitive functions of the initial state of the modes and distinctly different steering behavior could be observed depending on whether the modes were initially in a thermal state or not. For the modes initially in a vacuum state, the bipartite and tripartite steering occur simultaneously over the entire interaction time. This indicates that collective tripartite steering cannot be achieved. The collective steering can be achieved for the modes initially prepared in a thermal state. We find that the initial thermal noise is more effective in destroying the bipartite rather than the tripartite steering which, on the other hand, can persist even for a large thermal noise. For the initial vacuum state of a steered mode, the tripartite steering exists over the entire interaction time even if the steering modes are in very noisy thermal states. When the steered mode is initially in a thermal state, it can be collectively steered by the other modes. There are thresholds for the average number of the thermal photons above which the existing tripartite steering appears as the collective steering. Finally, we point out that the collective steering may provide a resource in a hybrid quantum network for quantum secret sharing

  4. Thermal magnetic field noise: electron optics and decoherence.

    PubMed

    Uhlemann, Stephan; Müller, Heiko; Zach, Joachim; Haider, Max

    2015-04-01

    Thermal magnetic field noise from magnetic and non-magnetic conductive parts close to the electron beam recently has been identified as a reason for decoherence in high-resolution transmission electron microscopy (TEM). Here, we report about new experimental results from measurements for a layered structure of magnetic and non-magnetic materials. For a simplified version of this setup and other situations we derive semi-analytical models in order to predict the strength, bandwidth and spatial correlation of the noise fields. The results of the simulations are finally compared to previous and new experimental data in a quantitative manner. PMID:25499019

  5. Waterborne noise due to ocean thermal energy conversion plants

    NASA Astrophysics Data System (ADS)

    Janota, C. P.; Thompson, D. E.

    1982-06-01

    Public law reflects a United States national commitment to the rapid development of Ocean Thermal Energy Conversion (OTEC) as an alternate energy source. OTEC plants extract the stored solar energy from the world's tropical seas and in so doing pose a potential for altering the character of the ambient noise there. The sources of noise from an OTEC plant are analyzed in the context of four configurations, two of which were built and tested, and two which are concepts for future full-scale moored facilities. The analysis indicates that the noise resulting from the interaction of turbulence with the sea-water pumps is expected to dominate in the frequency range 10 Hz to 1 kHZ. Measured radiated noise data from the OTEC-I research plant, located near the island of Hawaii, are compared with the analysis. The measured data diverge from the predicted levels at frequencies above about 60 Hz because of dominant non-OTEC noise sources on this platform. However, at low frequency, the measured broadband noise is comparable to that predicted.

  6. Waterborne noise due to ocean thermal energy conversion plants

    SciTech Connect

    Janota, C.P.; Thompson, D.E.

    1983-07-01

    Public law reflects a United States national commitment to the rapid development of Ocean Thermal Energy Conversion (OTEC) as an alternate energy source. OTEC plants extract the stored solar energy from the world's tropical seas and in so doing pose a potential for altering the character of the ambient noise there. The sources of noise from an OTEC plant are analyzed in the context of four configurations, two of which were built and tested, and two which are concepts for future full-scale moored facilities. The analysis indicates that the noise resulting from the interaction of turbulence with the seawater pumps is expected to dominate in the frequency range 10 Hz to 1 kHz. Measured radiated noise data from the OTEC-I research plant, located near the island of Hawaii, are compared with the analysis. The measured data diverge from the predicted levels at frequencies above about 60 Hz because of dominant non-OTEC noise sources on this platform. However, at low frequency, the measured broadband noise is comparable to that predicted.

  7. Measurement of thermal noise in multilayer coatings with optimized layer thickness

    SciTech Connect

    Villar, Akira E.; Black, Eric D.; DeSalvo, Riccardo; Libbrecht, Kenneth G.; Michel, Christophe; Morgado, Nazario; Pinard, Laurent; Pinto, Innocenzo M.; Pierro, Vincenzo; Galdi, Vincenzo; Principe, Maria; Taurasi, Ilaria

    2010-06-15

    A standard quarter-wavelength multilayer optical coating will produce the highest reflectivity for a given number of coating layers, but in general it will not yield the lowest thermal noise for a prescribed reflectivity. Coatings with the layer thicknesses optimized to minimize thermal noise could be useful in future generation interferometric gravitational wave detectors where coating thermal noise is expected to limit the sensitivity of the instrument. We present the results of direct measurements of the thermal noise of a standard quarter-wavelength coating and a low noise optimized coating. The measurements indicate a reduction in thermal noise in line with modeling predictions.

  8. Reduction of diesel engine exhaust noise in the petroleum mining industry. [by resonator type diffuser

    NASA Technical Reports Server (NTRS)

    Marinov, T.

    1974-01-01

    An important noise source in a drilling plant is Diesel engine exhaust. In order to reduce this noise, a reactive silencer of the derivative resonator type was proposed, calculated from the acoustic and design point of view and applied. As a result of applying such a silencer on the exhaust conduit of a Diesel engine the noise level dropped down to 18 db.

  9. Brownian motion at fast time scales and thermal noise imaging

    NASA Astrophysics Data System (ADS)

    Huang, Rongxin

    This dissertation presents experimental studies on Brownian motion at fast time scales, as well as our recent developments in Thermal Noise Imaging which uses thermal motions of microscopic particles for spatial imaging. As thermal motions become increasingly important in the studies of soft condensed matters, the study of Brownian motion is not only of fundamental scientific interest but also has practical applications. Optical tweezers with a fast position-sensitive detector provide high spatial and temporal resolution to study Brownian motion at fast time scales. A novel high bandwidth detector was developed with a temporal resolution of 30 ns and a spatial resolution of 1 A. With this high bandwidth detector, Brownian motion of a single particle confined in an optical trap was observed at the time scale of the ballistic regime. The hydrodynamic memory effect was fully studied with polystyrene particles of different sizes. We found that the mean square displacements of different sized polystyrene particles collapse into one master curve which is determined by the characteristic time scale of the fluid inertia effect. The particle's inertia effect was shown for particles of the same size but different densities. For the first time the velocity autocorrelation function for a single particle was shown. We found excellent agreement between our experiments and the hydrodynamic theories that take into account the fluid inertia effect. Brownian motion of a colloidal particle can be used to probe three-dimensional nano structures. This so-called thermal noise imaging (TNI) has been very successful in imaging polymer networks with a resolution of 10 nm. However, TNI is not efficient at micrometer scale scanning since a great portion of image acquisition time is wasted on large vacant volume within polymer networks. Therefore, we invented a method to improve the efficiency of large scale scanning by combining traditional point-to-point scanning to explore large vacant

  10. Speckle and thermal noise reduction techniques for SAR interferogram

    SciTech Connect

    Huang, Y.; Genderen, J.L. van

    1996-11-01

    Thermal and speckle noise is an obstacle to generating digital elevation model (DAM) from interferograms by 2-D phase unwrapping of Interferometric SAR (INSAR). Multi-look processing as a traditional method to reduce speckle noise is addressed briefly in this paper. Alternatively, we investigate the box filters in depth, as it deals with the single complex images more flexible in the complex image domain than in the frequency domain. Several Box filters are proposed and the comparison between these filters is made to illustrate the noise reduction by implementation of filtering techniques. Window size selection of the box filters is examined in details. Simulation results and raw data testing results are presented to confirm the validity of the filtering algorithms proposed in this paper.

  11. Correlated noise-based switches and stochastic resonance in a bistable genetic regulation system

    NASA Astrophysics Data System (ADS)

    Wang, Can-Jun; Yang, Ke-Li

    2016-07-01

    The correlated noise-based switches and stochastic resonance are investigated in a bistable single gene switching system driven by an additive noise (environmental fluctuations), a multiplicative noise (fluctuations of the degradation rate). The correlation between the two noise sources originates from on the lysis-lysogeny pathway system of the λ phage. The steady state probability distribution is obtained by solving the time-independent Fokker-Planck equation, and the effects of noises are analyzed. The effects of noises on the switching time between the two stable states (mean first passage time) is investigated by the numerical simulation. The stochastic resonance phenomenon is analyzed by the power amplification factor. The results show that the multiplicative noise can induce the switching from "on" → "off" of the protein production, while the additive noise and the correlation between the noise sources can induce the inverse switching "off" → "on". A nonmonotonic behaviour of the average switching time versus the multiplicative noise intensity, for different cross-correlation and additive noise intensities, is observed in the genetic system. There exist optimal values of the additive noise, multiplicative noise and cross-correlation intensities for which the weak signal can be optimal amplified.

  12. Quasi-thermal noise in space plasma: 'kappa' distributions

    SciTech Connect

    Le Chat, G.; Issautier, K.; Meyer-Vernet, N.; Maksimovic, M.; Moncuquet, M.; Zouganelis, I.

    2009-10-15

    The transport of energy in collisionless plasmas, especially in space plasmas, is far from being understood. Measuring the temperature of the electrons and their nonthermal properties can give important clues to understand the transport properties. Quasi-thermal noise (QTN) spectroscopy is a reliable tool for measuring accurately the electron density and temperature since it is less sensitive to the spacecraft perturbations than particle detectors. This work models the plasma QTN using a generalized Lorentzian ('kappa') distribution function for the electrons. This noise is produced by the quasi-thermal fluctuations of the electrons and by the Doppler-shifted thermal fluctuations of the ions. A sum of two Maxwellian functions has mainly been used for modeling the QTN of the electrons, but the observations have shown that the electrons are better fitted by a kappa distribution function. Pioneer work on QTN calculation only considered integer values of {kappa}. This paper extends these calculations to real values of {kappa} and gives the analytic expressions and numerical calculations of the QTN with a kappa distribution function. This paper shows some generic properties and gives some practical consequences for plasma wave measurements in space.

  13. Thermal noise informatics: totally secure communication via a wire, zero-power communication, and thermal noise driven computing

    NASA Astrophysics Data System (ADS)

    Kish, Laszlo B.; Mingesz, Robert; Gingl, Zoltan

    2007-06-01

    Very recently, it has been shown that Gaussian thermal noise and its artificial versions (Johnson-like noises) can be utilized as an information carrier with peculiar properties therefore it may be proper to call this topic Thermal Noise Informatics. Zero Power (Stealth) Communication, Thermal Noise Driven Computing, and Totally Secure Classical Communication are relevant examples. In this paper, while we will briefly describe the first and the second subjects, we shall focus on the third subject, the secure classical communication via wire. This way of secure telecommunication utilizes the properties of Johnson(-like) noise and those of a simple Kirchhoff's loop. The communicator is unconditionally secure at the conceptual (circuit theoretical) level and this property is (so far) unique in communication systems based on classical physics. The communicator is superior to quantum alternatives in all known aspects, except the need of using a wire. In the idealized system, the eavesdropper can extract zero bit of information without getting uncovered. The scheme is naturally protected against the man-in-the-middle attack. The communication can take place also via currently used power lines or phone (wire) lines and it is not only a point-to-point communication like quantum channels but network-ready. We report that a pair of Kirchhoff-Loop-Johnson(-like)-Noise communicators, which is able to work over variable ranges, was designed and built. Tests have been carried out on a model-line with ranges beyond the ranges of any known direct quantum communication channel and they indicate unrivalled signal fidelity and security performance. This simple device has single-wire secure key generation/sharing rates of 0.1, 1, 10, and 100 bit/second for copper wires with diameters/ranges of 21 mm / 2000 km, 7 mm / 200 km, 2.3 mm / 20 km, and 0.7 mm / 2 km, respectively and it performs with 0.02% raw-bit error rate (99.98 % fidelity). The raw-bit security of this practical system

  14. Characteristic analysis on the thermal noise of infrared CCD

    NASA Astrophysics Data System (ADS)

    Zhang, Rong-zhu; Yu, Xing; Liu, Guo-dong

    2014-09-01

    1.064 μm, 1.319 μm and 10.6 μm laser were used to irradiate silicon-based HgCdTe CCD image system. The temperature distribution of detector induced by infrared laser irradiating in the experiment above was simulated. The influence of temperature on photoelectric parameters of HgCdTe CCD was calculated. A CCD physical model of crosstalk saturation was built and the response characteristic of CCD under the influence of thermal noise was analyzed. Result indicated that the rise of temperature induced by laser irradiating little influenced imaging effect of CCD.

  15. Parameter optimization analysis to minimize the polarization error in a localized thermal tunable fiber ring resonator gyro.

    PubMed

    Bobbili, Prasada Rao; Nayak, Jagannath; Pinnoji, Prerana Dabral; Rama Koti Reddy, D V

    2016-03-10

    The accuracy of the resonant frequency servo loop is a major concern for the high-performance operation of a resonant fiber optic gyro. For instance, a bias error as large as tens or even hundreds of degrees/hour has been observed at the demodulated output of the resonant frequency servo loop. The traditional frequency servo mechanism is not an efficient tool to address this problem. In our previous work, we proposed a novel method to minimize the laser frequency noise to the level of the shot noise by refractive index modulation by a thermally tunable resonator. In this paper, we performed the parameter optimization for the resonator coil, multifunction integrated-optics chip, and couplers by the transition matrix using the Jones matrix methodology to minimize the polarization error. With the optimized parameter values, we achieved the bias value of the resonator fiber optic gyro to 1.924°/h. PMID:26974794

  16. High Resolution Viscosity Measurement by Thermal Noise Detection

    PubMed Central

    Aguilar Sandoval, Felipe; Sepúlveda, Manuel; Bellon, Ludovic; Melo, Francisco

    2015-01-01

    An interferometric method is implemented in order to accurately assess the thermal fluctuations of a micro-cantilever sensor in liquid environments. The power spectrum density (PSD) of thermal fluctuations together with Sader’s model of the cantilever allow for the indirect measurement of the liquid viscosity with good accuracy. The good quality of the deflection signal and the characteristic low noise of the instrument allow for the detection and corrections of drawbacks due to both the cantilever shape irregularities and the uncertainties on the position of the laser spot at the fluctuating end of the cantilever. Variation of viscosity below 0.03 mPa·s was detected with the alternative to achieve measurements with a volume as low as 50 μL. PMID:26540061

  17. High Resolution Viscosity Measurement by Thermal Noise Detection.

    PubMed

    Sandoval, Felipe Aguilar; Sepúlveda, Manuel; Bellon, Ludovic; Melo, Francisco

    2015-01-01

    An interferometric method is implemented in order to accurately assess the thermal fluctuations of a micro-cantilever sensor in liquid environments. The power spectrum density (PSD) of thermal fluctuations together with Sader's model of the cantilever allow for the indirect measurement of the liquid viscosity with good accuracy. The good quality of the deflection signal and the characteristic low noise of the instrument allow for the detection and corrections of drawbacks due to both the cantilever shape irregularities and the uncertainties on the position of the laser spot at the fluctuating end of the cantilever. Variation of viscosity below 0:03mPa·s was detected with the alternative to achieve measurements with a volume as low as 50 µL. PMID:26540061

  18. Thermal noise in aqueous quadrupole micro- and nano-traps.

    PubMed

    Park, Jae Hyun; Krstić, Predrag S

    2012-01-01

    Recent simulations and experiments with aqueous quadrupole micro-traps have confirmed a possibility for control and localization of motion of a charged particle in a water environment, also predicting a possibility of further reduction of the trap size to tens of nano-meters for trapping charged bio-molecules and DNA segments. We study the random thermal noise due to Brownian motion in water which significantly influences the trapping of particles in an aqueous environment. We derive the exact, closed-form expressions for the thermal fluctuations of position and velocity of a trapped particle and thoroughly examine the properties of the rms for the fluctuations as functions of the system parameters and time. The instantaneous signal transferring mechanism between the velocity and position fluctuations could not be achieved in the previous phase-average approaches. PMID:22369362

  19. Parameter-Induced Stochastic Resonance of Weak Periodic Signal Excitation with α Stable Noise

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Kou, Jie; Jiao, Shang-Bin

    In view of the nonlinear bistable system, this paper studied the parameter-induced stochastic resonance phenomenon of low-frequency weak signal excitation under α stable noise environment, and explored the action laws of the α stable noise distribution parameters α, β, μ, σ and the bistable system parameters a, b on stochastic resonance effect. The results show that in different α stable noise, adjusting the bistable system parameters can induce stochastic resonance; Moreover, when a(or b) is fixed, the intervals of b(or a) which can induce stochastic resonance are multiple and don't change with any α stable distribution parameter. Further, by combining with the parameter compensation method for researching on high-frequency weak signal, the same action laws as the low-frequency signal are got. The conclusions are significant for using parameter-induced stochastic resonance principle in weak signal detection in the abnormal diffusion dynamical system.

  20. 1/f frequency noise of 2-GHZ high-Q thin-film sapphire resonators.

    PubMed

    Ferre-Pikal, E S; Delgado Arámburo, M C; Walls, F L; Lakin, K M

    2001-03-01

    We present experimental results on intrinsic 1/f frequency modulation (FM) noise in high-overtone thin-film sapphire resonators that operate at 2 GHz. The resonators exhibit several high-Q resonant modes approximately 100 kHz apart, which repeat every 13 MHz. A loaded Q of approximately 20,000 was estimated from the phase response. The results show that the FM noise of the resonators varied between Sy (10 Hz) = -202 dB relative (rel) to 1/Hz and -210 dB rel to 1/Hz. The equivalent phase modulation (PM) noise of an oscillator using these resonators (assuming a noiseless amplifier) would range from [symbol: see text](10 Hz) = -39 to -47 dBc/Hz. PMID:11370364

  1. Noise-enhanced stability and double stochastic resonance of active Brownian motion

    NASA Astrophysics Data System (ADS)

    Zeng, Chunhua; Zhang, Chun; Zeng, Jiakui; Liu, Ruifen; Wang, Hua

    2015-08-01

    In this paper, we study the transient and resonant properties of active Brownian particles (ABPs) in the Rayleigh-Helmholtz (RH) and Schweitzer-Ebeling-Tilch (SET) models, which is driven by the simultaneous action of multiplicative and additive noise and periodic forcing. It is shown that the cross-correlation between two noises (λ) can break the symmetry of the potential to generate motion of the ABPs. In case of no correlation between two noises, the mean first passage time (MFPT) is a monotonic decrease depending on the multiplicative noise, however in case of correlation between two noises, the MFPT exhibits a maximum, depending on the multiplicative noise for both models, this maximum for MFPT identifies the noise-enhanced stability (NES) effect of the ABPs. By comparing with case of no correlation (λ =0.0 ), we find two maxima in the signal-to-noise ratio (SNR) depending on the cross-correlation intensity, i.e. the double stochastic resonance is shown in both models. For the RH model, the SNR exhibits two maxima depending on the multiplicative noise for small cross-correlation intensity, while in the SET model, it exhibits only a maximum depending on the multiplicative noise. Whether λ =0.0 or not, the MFPT is a monotonic decrease, and the SNR exhibits a maximum, depending on the additive noise in both models.

  2. Thermal design of a thermoelectrically cooled low-noise amplifier

    NASA Astrophysics Data System (ADS)

    Hyman, N. L.; Hung, H.-L.

    1981-06-01

    The development of a thermoelectrically cooled low-noise amplifier is described in terms of thermal design concepts, optimization procedures, supporting analyses, and examples of measured performance. The design objectives achieved include a compact, low-cost small overall package size (19 x 19 x 28 cm) with a heat exchanger and fan capable of maintaining at room temperature ambient the preamplifier unit of an earth station low-noise amplifier at -90 C. The size of the unit measures 1.0 x 1.8 x 8.4 cm and has a heat dissipation of 150 mW. A low system component production cost was maintained, and a high reliability from a solid-state TEHP and a gas-filled hermetically sealed container guaranteed. An inexpensive and effective insulation system was developed, based on perlite powder-krypton gas and thermal shielding, and a flexible heat conductor for strain relief was built. It is concluded that the design principles are applicable to other electronic and optical components to maintain temperatures as low as -100 C.

  3. Metallic-thin-film instability with spatially correlated thermal noise

    NASA Astrophysics Data System (ADS)

    Diez, Javier A.; González, Alejandro G.; Fernández, Roberto

    2016-01-01

    We study the effects of stochastic thermal fluctuations on the instability of the free surface of a flat liquid metallic film on a solid substrate. These fluctuations are represented by a stochastic noise term added to the deterministic equation for the film thickness within the long-wave approximation. Unlike the case of polymeric films, we find that this noise, while remaining white in time, must be colored in space, at least in some regimes. The corresponding noise term is characterized by a nonzero correlation length, ℓc, which, combined with the size of the system, leads to a dimensionless parameter β that accounts for the relative importance of the spatial correlation (β ˜ℓc-1 ). We perform the linear stability analysis (LSA) of the film both with and without the noise term and find that for ℓc larger than some critical value (depending on the system size), the wavelength of the peak of the spectrum is larger than that corresponding to the deterministic case, while for smaller ℓc this peak corresponds to smaller wavelength than the latter. Interestingly, whatever the value of ℓc, the peak always approaches the deterministic one for larger times. We compare LSA results with the numerical simulations of the complete nonlinear problem and find a good agreement in the power spectra for early times at different values of β . For late times, we find that the stochastic LSA predicts well the position of the dominant wavelength, showing that nonlinear interactions do not modify the trends of the early linear stages. Finally, we fit the theoretical spectra to experimental data from a nanometric laser-melted copper film and find that at later times, the adjustment requires smaller values of β (larger space correlations).

  4. Metallic-thin-film instability with spatially correlated thermal noise.

    PubMed

    Diez, Javier A; González, Alejandro G; Fernández, Roberto

    2016-01-01

    We study the effects of stochastic thermal fluctuations on the instability of the free surface of a flat liquid metallic film on a solid substrate. These fluctuations are represented by a stochastic noise term added to the deterministic equation for the film thickness within the long-wave approximation. Unlike the case of polymeric films, we find that this noise, while remaining white in time, must be colored in space, at least in some regimes. The corresponding noise term is characterized by a nonzero correlation length, ℓ_{c}, which, combined with the size of the system, leads to a dimensionless parameter β that accounts for the relative importance of the spatial correlation (β∼ℓ_{c}^{-1}). We perform the linear stability analysis (LSA) of the film both with and without the noise term and find that for ℓ_{c} larger than some critical value (depending on the system size), the wavelength of the peak of the spectrum is larger than that corresponding to the deterministic case, while for smaller ℓ_{c} this peak corresponds to smaller wavelength than the latter. Interestingly, whatever the value of ℓ_{c}, the peak always approaches the deterministic one for larger times. We compare LSA results with the numerical simulations of the complete nonlinear problem and find a good agreement in the power spectra for early times at different values of β. For late times, we find that the stochastic LSA predicts well the position of the dominant wavelength, showing that nonlinear interactions do not modify the trends of the early linear stages. Finally, we fit the theoretical spectra to experimental data from a nanometric laser-melted copper film and find that at later times, the adjustment requires smaller values of β (larger space correlations). PMID:26871167

  5. Quasi-thermal noise measurements on STEREO: Kinetic temperature deduction using electron shot noise model

    NASA Astrophysics Data System (ADS)

    Martinović, M. M.; Zaslavsky, A.; Maksimović, M.; Meyer-Vernet, N.; Å egan, S.; Zouganelis, I.; Salem, C.; Pulupa, M.; Bale, S. D.

    2016-01-01

    Quasi-thermal noise (QTN) spectroscopy is an accurate technique for in situ measurements of electron density and temperature in space plasmas. A QTN spectrum is determined by plasma and antenna properties. On STEREO/WAVES, since the antennas are relatively short and thick, the QTN spectrum is dominated by electron shot noise, especially at low frequencies, which reduces the accuracy of the method. Here we use the STEREO low-frequency receiver, proton density measured by Plasma and Suprathermal Ion Composition instrument, and a QTN and shot noise models to provide electron temperature data from both STEREO A and B spacecraft. This derivation is important since no reliable measurements of electron temperature exist on board these spacecraft. We compare the results of our analysis with the electron temperature provided by the Wind spacecraft during the period when Wind and STEREO B were close to each other. The comparison shows that our technique is reliable when results are integrated on a time scale of the order of 50 to 60 min.

  6. Noise-induced relaxation of a quantum oscillator interacting with a thermal bath

    NASA Astrophysics Data System (ADS)

    Efremov, G. F.; Mourokh, L. G.; Smirnov, A. Yu.

    1993-04-01

    The non-Markovian theory of quantum Brownian motion is used to analyse the relaxation of a harmonic oscillator nonlinearly coupled to a thermal bath and driven by external noise. It is shown that this nonlinearity leads to interference between additive noise and multiplicative noise and to the effect of additive noise-induced relaxation of a high frequency oscillator interacting with a low frequency thermal bath.

  7. Analysis and design of a single-resonator GaAs FET oscillator with noise degeneration

    NASA Astrophysics Data System (ADS)

    Galani, Z.; Bianchini, M. J.; Waterman, R. C., Jr.; Dibiase, R.; Laton, R. W.; Cole, J. B.

    1984-12-01

    This paper presents an analysis of a low-noise dielectric resonator GaAs FET oscillator in a frequency-locked loop (FLL), which is used for FM noise degeneration. In this circuit, one resonator serves both as the frequency-determining element of the oscillator and as the dispersive element of the discriminator. The results of the analysis are used to generate design guidelines. These guidelines were followed in an experimental realization of an X-band circuit. The measured FM noise was -120 and -142 dBc/Hz at 10- and 100-kHz offset frequencies, respectively, and corresponded closely to predicted results.

  8. Optical resonance shifts in thermal and cold Rb atomic gases

    NASA Astrophysics Data System (ADS)

    Ruostekoski, Janne; Jenkins, S. D.; Javanainen, J.; Bourgain, R.; Jennewein, S.; Sortais, Y. R. P.; Browaeys, A.; University of Southampton Collaboration; University of Connecticut Collaboration; Institut d'Optique, CNRS, Univ Paris Sud Collaboration

    2016-05-01

    We show that the resonance shifts in fluorescence of a cold gas of rubidium atoms substantially differ from those of thermal atomic ensembles that obey the standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements of the resonance shifts in light propagation.

  9. Stochastic Resonance in Ensembles of Nondynamical Elements: The Role of Internal Noise

    SciTech Connect

    Gailey, P.C.; Neiman, A.; Moss, F.; Neiman, A.; Collins, J.J.

    1997-12-01

    While many examples of noise-induced signal enhancement have been reported, the role of internal noise has received little attention. Here we study aperiodic stochastic resonance in parallel arrays of nondynamical elements with internal noise. Ensembles of both threshold and threshold-free elements are studied, and the model is applied to two-state ion channels. In finite systems where the input signal controls the probability of discrete events, we demonstrate that the internal noise is modulated by both the applied signal and the external noise. We also show that the internal noise plays a constructive role in information transfer through such systems via an increase in external noise. {copyright} {ital 1997} {ital The American Physical Society}

  10. Stochastic resonance induced by Lévy noise in a tumor growth model with periodic treatment

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Hao, Mengli; Gu, Xudong; Yang, Guidong

    2014-05-01

    In this paper, the stochastic resonance phenomenon in a tumor growth model under subthreshold periodic therapy and Lévy noise excitation is investigated. The possible reoccurrence of tumor due to stochastic resonance is discussed. The signal-to-noise ratio (SNR) is calculated numerically to measure the stochastic resonance. It is found that smaller stability index is better for avoiding tumor reappearance. Besides, the effect of the skewness parameter on the tumor regrowth is related to the stability index. Furthermore, increasing the intensity of periodic treatment does not always facilitate tumor therapy. These results are beneficial to the optimization of periodic tumor therapy.

  11. Efficient and robust analysis of complex scattering data under noise in microwave resonators

    SciTech Connect

    Probst, S.; Song, F. B.; Bushev, P. A.; Ustinov, A. V.; Weides, M.

    2015-02-15

    Superconducting microwave resonators are reliable circuits widely used for detection and as test devices for material research. A reliable determination of their external and internal quality factors is crucial for many modern applications, which either require fast measurements or operate in the single photon regime with small signal to noise ratios. Here, we use the circle fit technique with diameter correction and provide a step by step guide for implementing an algorithm for robust fitting and calibration of complex resonator scattering data in the presence of noise. The speedup and robustness of the analysis are achieved by employing an algebraic rather than an iterative fit technique for the resonance circle.

  12. An efficient technique for the reduction of wavelength noise in resonance-based integrated photonic sensors.

    PubMed

    Ghasemi, Farshid; Chamanzar, Maysamreza; Eftekhar, Ali A; Adibi, Ali

    2014-11-21

    A systematic study of the limit of detection (LOD) in resonance-based silicon photonic lab-on-chip sensors is presented. The effects of the noise, temperature fluctuations, and the fundamental thermodynamic limit of the resonator are studied. Wavelength noise is identified as the dominant source of noise, and an efficient technique for suppressing this noise is presented. A large ensemble of statistical data from the transmission measurements in a laser-scanning configuration on five silicon nitride (SiN) microrings is collected to discuss and identify the sources of noise. The experimental results show that the LOD is limited by a 3σ wavelength noise of ∼1.8 pm. We present a sub-periodic interferometric technique, relying on an inverse algorithm, to suppress this noise. Our technique reduces the wavelength noise by more than one order of magnitude to an ensemble average of 3σ = 120 fm, for a resonator quality factor (Q) of about 5 × 10(4) without any temperature stabilization or cooling. This technique is readily amenable to on-chip integration to realize highly accurate and low-cost lab-on-chip sensors. PMID:25243248

  13. Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance

    PubMed Central

    Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

    2016-01-01

    Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents. PMID:27525414

  14. Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance.

    PubMed

    Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

    2016-01-01

    Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents. PMID:27525414

  15. Trichotomous Noise Induced Resonance Behavior for a Fractional Oscillator with Random Mass

    NASA Astrophysics Data System (ADS)

    Zhong, Suchuan; Wei, Kun; Gao, Shilong; Ma, Hong

    2015-04-01

    We investigate the stochastic resonance (SR) phenomenon in a fractional oscillator with random mass under the external periodic force. The fluctuations of the mass are modeled as a trichotomous noise. Applying the Shapiro-Loginov formula and the Laplace transform technique, we obtain the exact expression of the first moment of the system. The non-monotonic behaviors of the spectral amplification (SPA) versus the driving frequency indicate that the bona fide SR appears. The necessary and sufficient conditions for the emergence of the generalized stochastic resonance phenomena on the noise flatness and on the noise intensity in the particular case of are established. Particularly, the hypersensitive response of the SPA to the noise intensity is found, which is previously reported and believed to be absent in the case of dichotomous noise.

  16. Phase Noise Improvement Techniques for Oscillator Circuit Using External Crystal Resonant Circuit

    NASA Astrophysics Data System (ADS)

    Imaike, Takeshi; Sakuta, Yukinori; Sekine, Yoshifumi

    This paper describes a new techniques of reducing phase noise in oscillator circuits. Our method uses an external crystal resonant circuit that acts as a frequency reference and is based on correlation with negative feedback control. We present the circuit configuration and the transfer function used in this method, as well as measured single sideband (SSB) phase noise characteristics. Our experiments show that phase noise can be decreased as it is a theoretical value when using LC oscillator. Furthermore, we examine application for voltage controlled crystal oscillator (VCXO). As a results, we can improve that the phase noise characteristics more than that of original VCXO without spoiling frequency tuning range of VCXO.

  17. Thermal and Quantum Mechanical Noise of a Superfluid Gyroscope

    NASA Technical Reports Server (NTRS)

    Chui, Talso; Penanen, Konstantin

    2004-01-01

    A potential application of a superfluid gyroscope is for real-time measurements of the small variations in the rotational speed of the Earth, the Moon, and Mars. Such rotational jitter, if not measured and corrected for, will be a limiting factor on the resolution potential of a GPS system. This limitation will prevent many automation concepts in navigation, construction, and biomedical examination from being realized. We present the calculation of thermal and quantum-mechanical phase noise across the Josephson junction of a superfluid gyroscope. This allows us to derive the fundamental limits on the performance of a superfluid gyroscope. We show that the fundamental limit on real-time GPS due to rotational jitter can be reduced to well below 1 millimeter/day. Other limitations and their potential mitigation will also be discussed.

  18. Logical stochastic resonance in bistable system under α-stable noise

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Song, Aiguo

    2014-05-01

    In the presence of α-stable noise, the logical stochastic resonance (LSR) phenomenon in a class of double well nonlinear system is investigated in this paper. LSR effect is obtained under α-stable noise. The probability of getting correct logic outputs is used to evaluate LSR behavior. Four main results are presented. Firstly, in the optimal band of noise intensity, Gaussian white noise is considered a better choice than heavy tailed noise to obtain clean logic operation. But at weak noise background, the success probability of getting the right logic outputs is higher when the system is subjected to heavy tailed noise. Secondly, it is shown that over the entire range of noise variance, the asymmetric noise induced LSR performs better than that induced by the symmetric noise. Furthermore, we find which side the tail skews also affects the correct probability of LSR. At last, the fractional Fokker-Planck equation is presented to show when the characteristic exponent of α-stable noise is less than 1, LSR behavior will not be obtained irrespective of the setting for other parameters.

  19. Double-maximum enhancement of signal-to-noise ratio gain via stochastic resonance and vibrational resonance.

    PubMed

    Duan, Fabing; Chapeau-Blondeau, François; Abbott, Derek

    2014-08-01

    This paper studies the signal-to-noise ratio (SNR) gain of a parallel array of nonlinear elements that transmits a common input composed of a periodic signal and external noise. Aiming to further enhance the SNR gain, each element is injected with internal noise components or high-frequency sinusoidal vibrations. We report that the SNR gain exhibits two maxima at different values of the internal noise level or of the sinusoidal vibration amplitude. For the addition of internal noise to an array of threshold-based elements, the condition for occurrence of stochastic resonance is analytically investigated in the limit of weak signals. Interestingly, when the internal noise components are replaced by high-frequency sinusoidal vibrations, the SNR gain displays the vibrational multiresonance phenomenon. In both considered cases, there are certain regions of the internal noise intensity or the sinusoidal vibration amplitude wherein the achieved maximal SNR gain can be considerably beyond unity for a weak signal buried in non-Gaussian external noise. Due to the easy implementation of sinusoidal vibration modulation, this approach is potentially useful for improving the output SNR in an array of nonlinear devices. PMID:25215715

  20. Consistent thermodynamic framework for interacting particles by neglecting thermal noise.

    PubMed

    Nobre, Fernando D; Curado, Evaldo M F; Souza, Andre M C; Andrade, Roberto F S

    2015-02-01

    An effective temperature θ, conjugated to a generalized entropy s(q), was introduced recently for a system of interacting particles. Since θ presents values much higher than those of typical room temperatures T≪θ, the thermal noise can be neglected (T/θ≃0) in these systems. Moreover, the consistency of this definition, as well as of a form analogous to the first law of thermodynamics, du=θds(q)+δW, were verified lately by means of a Carnot cycle, whose efficiency was shown to present the usual form, η=1-(θ(2)/θ(1)). Herein we explore further the heat contribution δQ=θds(q) by proposing a way for a heat exchange between two such systems, as well as its associated thermal equilibrium. As a consequence, the zeroth principle is also established. Moreover, we consolidate the first-law proposal by following the usual procedure for obtaining different potentials, i.e., applying Legendre transformations for distinct pairs of independent variables. From these potentials we derive the equation of state, Maxwell relations, and define response functions. All results presented are shown to be consistent with those of standard thermodynamics for T>0. PMID:25768486

  1. Consistent thermodynamic framework for interacting particles by neglecting thermal noise

    NASA Astrophysics Data System (ADS)

    Nobre, Fernando D.; Curado, Evaldo M. F.; Souza, Andre M. C.; Andrade, Roberto F. S.

    2015-02-01

    An effective temperature θ , conjugated to a generalized entropy sq, was introduced recently for a system of interacting particles. Since θ presents values much higher than those of typical room temperatures T ≪θ , the thermal noise can be neglected (T /θ ≃0 ) in these systems. Moreover, the consistency of this definition, as well as of a form analogous to the first law of thermodynamics, d u =θ d sq+δ W , were verified lately by means of a Carnot cycle, whose efficiency was shown to present the usual form, η =1 -(θ2/θ1) . Herein we explore further the heat contribution δ Q =θ d sq by proposing a way for a heat exchange between two such systems, as well as its associated thermal equilibrium. As a consequence, the zeroth principle is also established. Moreover, we consolidate the first-law proposal by following the usual procedure for obtaining different potentials, i.e., applying Legendre transformations for distinct pairs of independent variables. From these potentials we derive the equation of state, Maxwell relations, and define response functions. All results presented are shown to be consistent with those of standard thermodynamics for T >0 .

  2. Thermal conductivity and resonant multipole interactions.

    NASA Technical Reports Server (NTRS)

    Nyeland, C.; Mason, E. A.; Monchick, L.

    1972-01-01

    Investigation of the influence of resonant multipole interactions on exchanges of rotational energy in molecular collisions, by means of a simple two-state impact-parameter approximation. It is found that dipole-quadrupole and quadrupole-quadrupole interactions can have a significant effect for molecules with low moments of inertia.

  3. How does stochastic resonance work within the human brain? - Psychophysics of internal and external noise

    NASA Astrophysics Data System (ADS)

    Aihara, Takatsugu; Kitajo, Keiichi; Nozaki, Daichi; Yamamoto, Yoshiharu

    2010-10-01

    We review how research on stochastic resonance (SR) in neuroscience has evolved and point out that the previous studies have overlooked the interaction between internal and external noise. We propose a new psychometric function incorporating SR effects, and show that a Bayesian adaptive method applied to the function efficiently estimates the parameters of the function. Using this procedure in visual detection experiments, we provide significant insight into the relationship between internal and external noise in SR within the human brain.

  4. Laser phase noise effects on the dynamics of optomechanical resonators

    NASA Astrophysics Data System (ADS)

    Phelps, Gregory; Meystre, Pierre

    2011-05-01

    We present a theoretical analysis of the effects of laser phase noise on the sideband cooling of opto-mechanical oscillators, demonstrating how it limits the minimum occupation number of the phonon mode being cooled and how it modifies optical cooling rate and mechanical frequency shift of the mechanical element. We also comment on the effects of laser phase noise on coherent oscillations of the mechanical element in the blue detuned regime and on the back-action evasion detection method where an additional drive is used to prevent heating of one quadrature of motion of the oscillator. This work was supported by the US Office of Naval Research, the US National Science Foundation, the US Army Research Office and the DARPA ORCHID program through a grant from AFOSR.

  5. Fan Noise Control Using Herschel-quincke Resonators

    NASA Technical Reports Server (NTRS)

    Burdisso, Ricardo A.; Ng, Wing F.; Provenza, Andrew (Technical Monitor)

    2003-01-01

    The research effort proposed for this NASA NRA is mainly experimental. In addition, Virginia Tech is working in partnership with Goodrich Aerospace, Aerostructures Group for the analytical development needed to support the experimental endeavor, i.e. model development, design, and system studies. In this project, Herschel-Quincke (HQ)liner technology experiments will be performed at the NASA Glenn Active Noise Control Fan (ANCF) facility. A schematic of both inlet and aft HQ-liner systems installed in the ANCF rig as well as a picture of the Glenn facility is shown. The main goal is to simultaneously test in both the inlet and bypass duct sections. The by-pass duct will have HQ-systems in both the inner and outer duct walls. The main advantages of performing tests at the ANCF facility are that the effect of the inlet HQ-system on the by-pass HQ-system and vice versa, can be accurately determined from the in-duct modal data. Another significant advantage is that it offers the opportunity to assess (on a common basis) the proposed noise reduction concept on the ANCF rig which in the past has been used for assessing other active and passive noise reduction strategies.

  6. Fan Noise Control Using Herschel-Quincke Resonators

    NASA Astrophysics Data System (ADS)

    Burdisso, Ricardo A.; Ng, Wing F.

    2003-01-01

    The research effort proposed for this NASA NRA is mainly experimental. In addition, Virginia Tech is working in partnership with Goodrich Aerospace, Aerostructures Group for the analytical development needed to support the experimental endeavor, i.e. model development, design, and system studies. In this project, Herschel-Quincke (HQ)liner technology experiments will be performed at the NASA Glenn Active Noise Control Fan (ANCF) facility. A schematic of both inlet and aft HQ-liner systems installed in the ANCF rig as well as a picture of the Glenn facility is shown. The main goal is to simultaneously test in both the inlet and bypass duct sections. The by-pass duct will have HQ-systems in both the inner and outer duct walls. The main advantages of performing tests at the ANCF facility are that the effect of the inlet HQ-system on the by-pass HQ-system and vice versa, can be accurately determined from the in-duct modal data. Another significant advantage is that it offers the opportunity to assess (on a common basis) the proposed noise reduction concept on the ANCF rig which in the past has been used for assessing other active and passive noise reduction strategies.

  7. Improved rejection of transmitter noise: a convenient scheme with resonant crossed diodes.

    PubMed

    Sinkovits, Daniel W; Conradi, Mark S

    2004-11-01

    A method is presented for improved rejection of transmitter noise in the duplexer (transmit-receive switch). The capacitance of a set of crossed diodes forms a resonant circuit with a length of coaxial cable. The rejection of our resonant design is 60 dB, compared with only 12-15 dB for the usual method, all measured at 175 MHz. Tuning the entire duplexer to different frequencies is convenient, requiring only two new lengths of cable. The scheme is most useful with ungated linear rf power amplifiers at very high frequencies (above 100 MHz), where transmitter noise can be a severe problem. PMID:15504675

  8. Extremely low-phase-noise SAW resonators and oscillators: design and performance.

    PubMed

    Montress, G K; Parker, T E; Loboda, M J; Greer, J A

    1988-01-01

    The authors describe prototype low-noise SAW (surface acoustic wave) resonator oscillators which have demonstrated state-of-the-art phase-noise performance not only at their fundamental operating frequencies in the 400- to 600-MHz range but also after 16x frequency multiplication to X-band as well. SAW resonator designs with overmoded cavities, very wide apertures, and dual apertures, as well as modified fabrication techniques, have been used to realize an overall reduction in an oscillator's phase-noise spectrum, i.e. white phiM, flicker FM, and random-walk FM. The S resonators can typically handle incident RF power in excess of +20 dBm, a key requirement to achieving an extremely low oscillator-phase-noise floor. A novel burn-in procedure at relatively high incident-RF-power levels (>27 dBm) was used to reduce both the flicker FM and random-walk FM phase-noise levels. Using these various techniques, a 5- to 15-dB improvement in the overall phase-noise spectrum for several prototype oscillators was demonstrated. PMID:18290201

  9. Quantum noise and mode nonorthogonality in non-Hermitian PT-symmetric optical resonators

    SciTech Connect

    Yoo, Gwangsu; Sim, H.-S.; Schomerus, Henning

    2011-12-15

    PT-symmetric optical resonators combine absorbing regions with active, amplifying regions. The latter are the source of radiation generated via spontaneous and stimulated emission, which embodies quantum noise and can result in lasing. We calculate the frequency-resolved output radiation intensity of such systems and relate it to a suitable measure of excess noise and mode nonorthogonality. The line shape differs depending on whether the emission lines are isolated (as for weakly amplifying, almost-Hermitian systems) or overlapping (as for the almost-degenerate resonances in the vicinity of exceptional points associated with spontaneous PT-symmetry breaking). The calculations are carried out in the scattering input-output formalism, and are illustrated for a quasi-one-dimensional resonator setup. In our derivations, we also consider the more general case of a resonator in which the amplifying and absorbing regions are not related by symmetry.

  10. Bi-material resonant infrared thermal detector and array

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Zhang, Dacheng

    2014-10-01

    A resonant infrared thermal sensor with high sensitivity, whose sensing element is a bi-material structure with thermal expansion mismatch effect, is presented in this paper. The sensor detects infrared radiation by means of tracking the change in resonance frequency of the bi-material structure with temperature change attributed to the infrared radiation from targets. The bi-material structure can amplify the change in resonance frequency compared to a single material sensing structure. In accordance with the theory of vibration mechanics and design principle of infrared thermal detector, the bi-material resonant sensor by means of which an array can be achieved is designed. The simulation results, by ANSYS software analysis based on multi-layer shell finite element, demonstrate that the dependence of resonance frequency on temperature of the designed sensing structure achieves 1Hz/0.01°C. A microarray with 6×6 resonant infrared sensors is fabricated based on microelectronics processes being compatible with integrated circuit fabrication technology. The frequency variation corresponding to the temperature shift can be obtained by electrical measurement.

  11. Spin-noise spectroscopy under resonant optical probing conditions: Coherent and nonlinear effects

    SciTech Connect

    Horn, H.; Mueller, G. M.; Huebner, J.; Oestreich, M.; Rasel, E. M.; Santos, L.

    2011-10-15

    Highly sensitive Faraday rotation spectroscopy is used to measure the fluctuating magnetization noise of noninteracting rubidium atoms under resonant and nonresonant optical probing conditions. The spin-noise frequency spectra, in conjunction with the probe light detuning with respect to the D{sub 2} transition, reveal clear signatures of coherent coupling of the participating electronic levels. The results are explained by extended Bloch equations, including homogeneous and inhomogeneous broadening mechanisms. Our measurements further indicate that spin noise originating from excited states is governed at high intensities by collective effects.

  12. Study of noise reduction characteristics of multilayered panels and dual pane windows with Helmholtz resonators

    NASA Technical Reports Server (NTRS)

    Navaneethan, R.

    1981-01-01

    The experimental noise attenuation characteristics of flat, general aviation type, multilayered panels are discussed. Experimental results of stiffened panels, damping tape, honeycomb materials and sound absorption materials are presented. Single degree of freedom theoretical models were developed for sandwich type panels with both shear resistant and non-shear resistant core material. The concept of Helmholtz resonators used in conjunction with dual panel windows in increasing the noise reduction around a small range of frequency was tested. It is concluded that the stiffening of the panels either by stiffeners or by sandwich construction increases the low frequency noise reduction.

  13. Coherence resonance in the two-dimensional neural map driven by non-Gaussian colored noise

    NASA Astrophysics Data System (ADS)

    Li, Dongxi; Hu, Bing; Wang, Jia; Jing, Yingchuan; Hou, Fangmei

    2016-01-01

    Based on the two-dimensional (2D) neural map, we investigate the impacts of non-Gaussian colored noise on the firing activity of discrete system. Taking the coherence parameter R to measure the regularity of firing behavior, it is demonstrated that coherence parameter R has a pronounced minimum value with the noise intensity and the correlation time of non-Gaussian colored noise, which is the so-called phenomenon of coherence resonance (CR). Besides, the firing activity is not sensitive to the non-Gaussian parameter which determines the departure from the Gaussian distribution when the correlation time is large enough.

  14. Ultra-Narrow Bandwidth Optical Resonators for Integrated Low Frequency Noise Lasers

    NASA Astrophysics Data System (ADS)

    Spencer, Daryl T.

    The development of narrowband resonators has far reaching applications in integrated optics. As a precise reference of wavelength, filters can be used in sensors, metrology, nonlinear optics, microwave photonics, and laser stabilization. In this work, we develop record high quality factor (Q) Si 3N4 waveguide resonators, and utilize them to stabilize a heterogeneously integrated Si/III V laser. To increase the Q factor of waveguide resonators, particular attention is given to loss mechanisms. Propagation loss of <0.1 dB/m is demonstrated on the ultra low loss waveguide platform, a low index contrast, high aspect ratio Si3N4 waveguide geometry fabricated with high quality materials and high temperature anneals. Ideality in the directional couplers used for coupling to the resonators is studied and losses are reduced such that 81 million intrinsic Q factor is achieved. Additional results include 1x16 resonant splitters, low ? narrowband gratings, and a dual layer waveguide technology for low loss and low bend radius in separate regions of the same device layer. We then combine an ultra high Q resonator and a heterogeneous Si/III V laser in a Pound Drever Hall (PDH) frequency stabilization system to yield narrow linewidth characteristics for a stable on chip laser reference. The high frequency noise filtering is performed with Si resonant mirrors in the laser cavity. A 30 million Q factor Si3N4 resonator is used with electrical feedback to reduce close in noise and frequency walk off. The laser shows high frequency noise levels of 60x103 Hz2/Hz corresponding to 160 kHz linewidth, and the low frequency noise is suppressed 33 dB to 103 Hz2/Hz with the PDH system.

  15. Mechanism of stochastic resonance enhancement in neuronal models driven by 1/f noise

    NASA Astrophysics Data System (ADS)

    Nozaki, Daichi; Collins, James J.; Yamamoto, Yoshiharu

    1999-10-01

    Noise can assist neurons in the detection of weak signals via a mechanism known as stochastic resonance (SR). In a previous study [Phys. Lett. A 243, 281 (1998)], we showed that when colored noise with 1/fβ spectrum is added to the FitzHugh-Nagumo (FHN) neuronal model, the optimal noise variance for SR could be minimized with β~1. In this study, we investigate analytically how the noise color (β) affects the SR profile in a linearized version of the FHN model. We demonstrate that the aforementioned effect of 1/f noise is related to the dynamical characteristics of the model neuron, i.e., the refractory period, the low-pass filtering effect of the membrane capacitance, and the high-pass filtering effect of the recovery variable.

  16. 239Pu Resonance Evaluation for Thermal Benchmark System Calculations

    NASA Astrophysics Data System (ADS)

    Leal, L. C.; Noguere, G.; de Saint Jean, C.; Kahler, A. C.

    2014-04-01

    Analyses of thermal plutonium solution critical benchmark systems have indicated a deficiency in the 239Pu resonance evaluation. To investigate possible solutions to this issue, the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) Working Party for Evaluation Cooperation (WPEC) established Subgroup 34 to focus on the reevaluation of the 239Pu resolved resonance parameters. In addition, the impacts of the prompt neutron multiplicity (νbar) and the prompt neutron fission spectrum (PFNS) have been investigated. The objective of this paper is to present the results of the 239Pu resolved resonance evaluation effort.

  17. Electrical noise modulates perception of electrical pulses in humans: sensation enhancement via stochastic resonance.

    PubMed

    Iliopoulos, Fivos; Nierhaus, Till; Villringer, Arno

    2014-03-01

    Although noise is usually considered to be harmful for signal detection and information transmission, stochastic resonance (SR) describes the counterintuitive phenomenon of noise enhancing the detection and transmission of weak input signals. In mammalian sensory systems, SR-related phenomena may arise both in the peripheral and the central nervous system. Here, we investigate behavioral SR effects of subliminal electrical noise stimulation on the perception of somatosensory stimuli in humans. We compare the likelihood to detect near-threshold pulses of different intensities applied on the left index finger during presence vs. absence of subliminal noise on the same or an adjacent finger. We show that (low-pass) noise can enhance signal detection when applied on the same finger. This enhancement is strong for near-threshold pulses below the 50% detection threshold and becomes stronger when near-threshold pulses are applied as brief trains. The effect reverses at pulse intensities above threshold, especially when noise is replaced by subliminal sinusoidal stimulation, arguing for a peripheral direct current addition. Unfiltered noise applied on longer pulses enhances detection of all pulse intensities. Noise applied to an adjacent finger has two opposing effects: an inhibiting effect (presumably due to lateral inhibition) and an enhancing effect (most likely due to SR in the central nervous system). In summary, we demonstrate that subliminal noise can significantly modulate detection performance of near-threshold stimuli. Our results indicate SR effects in the peripheral and central nervous system. PMID:24353303

  18. Noise-induced transitions and resonant effects in nonlinear systems

    NASA Astrophysics Data System (ADS)

    Zaikin, Alexei

    2003-02-01

    Our every-day experience is connected with different acoustical noise or music. Usually noise plays the role of nuisance in any communication and destroys any order in a system. Similar optical effects are known: strong snowing or raining decreases quality of a vision. In contrast to these situations noisy stimuli can also play a positive constructive role, e.g. a driver can be more concentrated in a presence of quiet music. Transmission processes in neural systems are of especial interest from this point of view: excitation or information will be transmitted only in the case if a signal overcomes a threshold. Dr. Alexei Zaikin from the Potsdam University studies noise-induced phenomena in nonlinear systems from a theoretical point of view. Especially he is interested in the processes, in which noise influences the behaviour of a system twice: if the intensity of noise is over a threshold, it induces some regular structure that will be synchronized with the behaviour of neighbour elements. To obtain such a system with a threshold one needs one more noise source. Dr. Zaikin has analyzed further examples of such doubly stochastic effects and developed a concept of these new phenomena. These theoretical findings are important, because such processes can play a crucial role in neurophysics, technical communication devices and living sciences. Unsere alltägliche Erfahrung ist mit verschiedenen akustischen Einfluessen wie Lärm, aber auch Musik verbunden. Jeder weiss, wie Lärm stören kann und Kommunikation behindert oder gar unterbindet. Ähnliche optische Effekte sind bekannt: starkes Schneetreiben oder Regengüsse verschlechtern die Sicht und lassen uns Umrisse nur noch schemenhaft erkennen. Jedoch koennen ähnliche Stimuli auch sehr positive Auswirkungen haben: Autofahrer fahren bei leiser Musik konzentrierter -- die Behauptung von Schulkindern, nur bei dröhnenden Bässen die Mathehausaufgaben richtig rechnen zu können, ist allerdings nicht wissenschaftlich

  19. Resonant and time-resolved spin noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Pursley, Brennan C.; Song, X.; Sih, V.

    2015-11-01

    We demonstrate a method to extend the range of pulsed laser spin noise measurements to long spin lifetimes. We use an analog detection scheme with a bandwidth limited only by laser pulse duration. Our model uses statistics and Bloch-Torrey equations to extract the Lande g-factor, Faraday cross-section σ F , and spin lifetime τ s , while accounting for finite detector response. Varying the magnetic field with a fixed probe-probe delay yields τ s when it is longer than the laser repetition period. Varying the probe-probe delay with a fixed field produces a time-domain measurement of the correlation function.

  20. Cross correlation of thermal flux noise in layered superconductors

    SciTech Connect

    Ashkenazy, V.D.; Jung, G. |; Shapiro, B.Y. |

    1996-10-01

    Cross correlation in the magnetic flux noise due to thermally activated movements of pancake vortices in strongly anisotropic layered superconductors has been investigated theoretically. It has been shown that there exists a crossover frequency, inversely proportional to the sample thickness, below which vortices behave as rigid rods and their ends move coherently on the opposite sides of the sample. At low frequencies, the cross-correlation spectrum is identical to the spectrum measured at each side of the sample. The cross-correlation spectrum demonstrates two regimes of behavior, separated by a characteristic frequency which depends on the geometry of the flux measuring loop. At high frequencies above the crossover frequency, the excitations of the elastic lattice modes lead to exponentially vanishing oscillations of the cross-correlation spectra. Pancake movements became incoherent and the correlation function decays, accompanied by the oscillations. The oscillations are most pronounced for the separation between pickup loops smaller than the sample thickness. In a typical experimental configuration with pickup loops located on the sample surface, the oscillations constitute only small perturbations to the dominating powerlike decay of the correlation function. {copyright} {ital 1996 The American Physical Society.}

  1. Ubiquitous Crossmodal Stochastic Resonance in Humans: Auditory Noise Facilitates Tactile, Visual and Proprioceptive Sensations

    PubMed Central

    Lugo, Eduardo; Doti, Rafael; Faubert, Jocelyn

    2008-01-01

    Background Stochastic resonance is a nonlinear phenomenon whereby the addition of noise can improve the detection of weak stimuli. An optimal amount of added noise results in the maximum enhancement, whereas further increases in noise intensity only degrade detection or information content. The phenomenon does not occur in linear systems, where the addition of noise to either the system or the stimulus only degrades the signal quality. Stochastic Resonance (SR) has been extensively studied in different physical systems. It has been extended to human sensory systems where it can be classified as unimodal, central, behavioral and recently crossmodal. However what has not been explored is the extension of this crossmodal SR in humans. For instance, if under the same auditory noise conditions the crossmodal SR persists among different sensory systems. Methodology/Principal Findings Using physiological and psychophysical techniques we demonstrate that the same auditory noise can enhance the sensitivity of tactile, visual and propioceptive system responses to weak signals. Specifically, we show that the effective auditory noise significantly increased tactile sensations of the finger, decreased luminance and contrast visual thresholds and significantly changed EMG recordings of the leg muscles during posture maintenance. Conclusions/Significance We conclude that crossmodal SR is a ubiquitous phenomenon in humans that can be interpreted within an energy and frequency model of multisensory neurons spontaneous activity. Initially the energy and frequency content of the multisensory neurons' activity (supplied by the weak signals) is not enough to be detected but when the auditory noise enters the brain, it generates a general activation among multisensory neurons of different regions, modifying their original activity. The result is an integrated activation that promotes sensitivity transitions and the signals are then perceived. A physiologically plausible model for

  2. Design of thermal-noise-harnessing single-electron circuit for efficient signal propagation

    NASA Astrophysics Data System (ADS)

    Hirashima, Ryo; Oya, Takahide

    2016-06-01

    We propose a new single-electron (SE) circuit that can improve the signal propagation speed by harnessing thermal noise efficiently. Generally, an SE circuit has some weaknesses. It is very sensitive to thermal noise and it takes a long time for signal propagation. To solve these problems, we focus on a unique function at an output terminal (an axon) of a neuron that can improve the signal propagation speed because of its distinctive structure. It is expected that a new high-speed SE circuit can be realized by mimicking the structure of the neuron. Here, we indicate the possibility of improving the signal propagation speed by harnessing the thermal noise in one-dimensional neuromorphic single-electron oscillators. Moreover, we designed a two-dimensional neuromorphic single-electron oscillator as an advanced circuit and confirmed its tolerance to thermal noise. Our study will be useful for constructing novel devices that actively use noise energy in the future.

  3. Squeezing of Quantum Noise of Motion in a Micromechanical Resonator.

    PubMed

    Pirkkalainen, J-M; Damskägg, E; Brandt, M; Massel, F; Sillanpää, M A

    2015-12-11

    A pair of conjugate observables, such as the quadrature amplitudes of harmonic motion, have fundamental fluctuations that are bound by the Heisenberg uncertainty relation. However, in a squeezed quantum state, fluctuations of a quantity can be reduced below the standard quantum limit, at the cost of increased fluctuations of the conjugate variable. Here we prepare a nearly macroscopic moving body, realized as a micromechanical resonator, in a squeezed quantum state. We obtain squeezing of one quadrature amplitude 1.1±0.4  dB below the standard quantum limit, thus achieving a long-standing goal of obtaining motional squeezing in a macroscopic object. PMID:26705631

  4. Enhanced visibility of two-mode thermal squeezed states via degenerate parametric amplification and resonance

    NASA Astrophysics Data System (ADS)

    Mahboob, I.; Okamoto, H.; Yamaguchi, H.

    2016-08-01

    Two-mode squeezed states, generated via non-degenerate parametric down-conversion, are invariably revealed via their entangled vacuum or correlated thermal fluctuations. Here, two-mode thermal squeezed states, generated in an electromechanical system, are made bright by means of degenerate parametric amplification of their constituent modes to the point where they are almost perfect, even when seeded from low intensity non-degenerate parametric down-conversion. More dramatically, activating the degenerate parametric resonances of the underlying modes yields perfect correlations which can be resolved via the coordinated switching of their phase bi-stable vibrations, without recourse to monitoring their thermal fluctuations. This ability to enhance the two-mode squeezed states and to decipher them without needing to observe their intrinsic noise is supported by both analytical and numerical modelling and it suggests that the technical constraints to making this phenomenon more widely available can be dramatically relaxed.

  5. Noise effects on a birhythmic Josephson junction coupled to a resonator

    NASA Astrophysics Data System (ADS)

    Yamapi, R.; Filatrella, G.

    2014-05-01

    We study the effect of noise on a Josephson junction that, coupled to a linear RLC resonator, can oscillate at two frequencies. To establish the global stability of the attractors, we estimate the position of the separatrix, essential information to establish the stability of the attractor for this multidimensional system, from the analysis of the mean first passage time. We find that the frequency locked to the resonator is most stable at low bias and less stable at high bias, where the resonator exhibits the largest oscillations. The change in the birhythmic region is dramatic for the effective barrier changes of an order of magnitude and the corresponding lifetime of about seven decades.

  6. 1/f noise in etched groove surface acoustic wave (SAW) resonators.

    PubMed

    Parker, T E; Andres, D; Greer, J A; Montress, G K

    1994-01-01

    Measurements of 1/f (or flicker) frequency fluctuations in SAW resonators fabricated with etched groove reflectors on single crystal quartz have shown that the observed noise levels vary inversely with device size. These measurements were made on sixteen 450 MHz resonators of four different sizes. The 1/f noise levels were also evaluated on twenty-eight other SAW resonators ranging in frequency from 401 to 915 MHz. This additional data provides valuable information on the dependence of the flicker noise levels on resonator frequency. A model based an localized, independent velocity fluctuations in the quartz is proposed which correctly fits the observed size and frequency dependence of the measured 1/f noise levels. This model suggests that the velocity fluctuations originate in small regions (much less than ~5 mum in diameter) randomly distributed throughout the quartz with an average separation of about 5 mum between independent (incoherent) sources. The magnitude of the localized fractional velocity fluctuations, Deltav/v, averaged over a 5 micron cube is on the order of 1x10 (-9). PMID:18263275

  7. Role of the nature of noise in the thermal conductance of mechanical systems.

    PubMed

    Morgado, Welles A M; Duarte Queirós, Sílvio M

    2012-10-01

    Focusing on a paradigmatic small system consisting of two coupled damped oscillators, we survey the role of the Lévy-Itô nature of the noise in the thermal conductance. For white noises, we prove that the Lévy-Itô composition (Lebesgue measure) of the noise is irrelevant for the thermal conductance of a nonequilibrium linearly coupled chain, which signals the independence of mechanical and thermodynamical properties. In contrast, for the nonlinearly coupled case, the two types of properties mix and the explicit definition of the noise plays a central role. PMID:23214530

  8. Partial removal of correlated noise in thermal imagery

    SciTech Connect

    Borel, C.C.; Cooke, B.J.; Laubscher, B.E.

    1996-04-01

    Correlated noise occurs in many imaging systems such as scanners and push-broom imagers. The sources of correlated noise can be from the detectors, pre-amplifiers and sampling circuits. Correlated noise appears as streaking along the scan direction of a scanner or in the along track direction of a push-broom imager. We have developed algorithms to simulate correlated noise and pre-filter to reduce the amount of streaking while not destroying the scene content. The pre- filter in the Fourier domain consists of the product of two filters. One filter models the correlated noise spectrum, the other is a windowing function e.g. Gaussian or Hanning window with variable width to block high frequency noise away from the origin of the Fourier Transform of the image data. We have optimized the filter parameters for various scenes and find improvements of the RMS error of the original minus the pre-filtered noisy image.

  9. Finite-difference time-domain simulation of thermal noise in open cavities

    SciTech Connect

    Andreasen, Jonathan; Cao Hui; Taflove, Allen; Kumar, Prem |; Cao Changqi

    2008-02-15

    A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal radiation penetrates the cavity in the grid. The calculated amount of thermal noise in a one-dimensional dielectric cavity recovers the standard result of the quantum Langevin equation in the Markovian regime. Our FDTD simulation also demonstrates that in the non-Markovian regime the buildup of the intracavity noise field depends on the ratio of the cavity photon lifetime to the coherence time of thermal radiation. The advantage of our numerical method is that the thermal noise is introduced in the time domain without prior knowledge of cavity modes.

  10. Lévy stable noise-induced transitions: stochastic resonance, resonant activation and dynamic hysteresis

    NASA Astrophysics Data System (ADS)

    Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

    2009-05-01

    A standard approach to analysis of noise-induced effects in stochastic dynamics assumes a Gaussian character of the noise term describing interaction of the analyzed system with its complex surroundings. An additional assumption about the existence of timescale separation between the dynamics of the measured observable and the typical timescale of the noise allows external fluctuations to be modeled as temporally uncorrelated and therefore white. However, in many natural phenomena the assumptions concerning the above mentioned properties of 'Gaussianity' and 'whiteness' of the noise can be violated. In this context, in contrast to the spatiotemporal coupling characterizing general forms of non-Markovian or semi-Markovian Lévy walks, so called Lévy flights correspond to the class of Markov processes which can still be interpreted as white, but distributed according to a more general, infinitely divisible, stable and non-Gaussian law. Lévy noise-driven non-equilibrium systems are known to manifest interesting physical properties and have been addressed in various scenarios of physical transport exhibiting a superdiffusive behavior. Here we present a brief overview of our recent investigations aimed at understanding features of stochastic dynamics under the influence of Lévy white noise perturbations. We find that the archetypal phenomena of noise-induced ordering are robust and can be detected also in systems driven by memoryless, non-Gaussian, heavy-tailed fluctuations with infinite variance.

  11. Tailoring photonic metamaterial resonances for thermal radiation

    PubMed Central

    2011-01-01

    Selective solar absorbers generally have limited effectiveness in unconcentrated sunlight, because of reradiation losses over a broad range of wavelengths and angles. However, metamaterials offer the potential to limit radiation exchange to a proscribed range of angles and wavelengths, which has the potential to dramatically boost performance. After globally optimizing one particular class of such designs, we find thermal transfer efficiencies of 78% at temperatures over 1,000°C, with overall system energy conversion efficiencies of 37%, exceeding the Shockley-Quiesser efficiency limit of 31% for photovoltaic conversion under unconcentrated sunlight. This represents a 250% increase in efficiency and 94% decrease in selective emitter area compared to a standard, angular-insensitive selective absorber. PACS: 42.70.Qs; 81.05.Xj; 78.67.Pt; 42.79.Ek PMID:21978732

  12. Relationship of core exit-temperature noise to thermal-hydraulic conditions in PWRs

    SciTech Connect

    Sweeney, F.J.; Upadhyaya, B.R.

    1983-01-01

    Core exit thermocouple temperature noise and neutron detector noise measurements were performed at the Loss of Fluid Test Facility (LOFT) reactor and a Westinghouse, 1148 MW(e) PWR to relate temperature noise to core thermal-hydraulic conditions. The noise analysis results show that the RMS of the temperature noise increases linearly with increasing core ..delta..T at LOFT and the commercial PWR. Out-of-core test loop temperature noise has shown similar behavior. The phase angle between core exit temperature noise and in-core or ex-core neutron noise is directly related to the core coolant flow velocity. However, if the thermocouple response time is slow, compared to the coolant transit time between the sensors, velocities inferred from the phase angle are lower than measured coolant flow velocities.

  13. Modulating resonance behaviors by noise recycling in bistable systems with time delay

    SciTech Connect

    Sun, Zhongkui Xu, Wei; Yang, Xiaoli; Xiao, Yuzhu

    2014-06-01

    In this paper, the impact of noise recycling on resonance behaviors is studied theoretically and numerically in a prototypical bistable system with delayed feedback. According to the interior cooperating and interacting activity of noise recycling, a theory has been proposed by reducing the non-Markovian problem into a two-state model, wherein both the master equation and the transition rates depend on not only the current state but also the earlier two states due to the recycling lag and the feedback delay. By virtue of this theory, the formulae of the power spectrum density and the linear response function have been found analytically. And the theoretical results are well verified by numerical simulations. It has been demonstrated that both the recycling lag and the feedback delay play a crucial role in the resonance behaviors. In addition, the results also suggest an alternative scheme to modulate or control the coherence or stochastic resonance in bistable systems with time delay.

  14. Living Organisms Coupling to Electromagnetic Radiation Below Thermal Noise

    NASA Astrophysics Data System (ADS)

    Stolc, Viktor; Freund, Friedemann

    2013-04-01

    Ultralow frequency (ULF) and extremely low frequency (ELF) electromagnetic (EM) radiation is part of the natural environment. Prior to major earthquakes the local ULF and global ELF radiation field is often markedly perturbed. This has detrimental effects on living organisms. We are studying the mechanism of these effects on the biochemical, cellular and organismal levels. The transfer of electrons along the Electron Transfer Chain (ETC) controls the universal reduction-oxidation reactions that are essential for fundamental biochemical processes in living cells. In order for these processes to work properly, the ETC has to maintain some form of synchronization, or coherence with all biochemical reactions in the living cells, including energy production, RNA transcription, and DNA replication. As a consequence of this synchronization, harmful chemical conflict between the reductive and the oxidative partial reactions can be minimized or avoided. At the same time we note that the synchronization allows for a transfer of energy, coherent or interfering, via coupling to the natural ambient EM field. Extremely weak high frequency EM fields, well below the thermal noise level, tuned in frequency to the electron spins of certain steps in the ETC, have already been shown to cause aberrant cell growth and disorientation among plants and animals with respect to the magnetic and gravity vectors. We investigate EM fields over a much wider frequency range, including ULF known to be generated deep in the Earth prior to major earthquakes locally, and ELF known to be fed by lightning discharges, traveling around the globe in the cavity formed between the Earth's surface and the ionosphere. This ULF/ELF radiation can control the timing of the biochemical redox cycle and thereby have a universal effect on physiology of organisms. The timing can even have a detrimental influence, via increased oxidative damage, on the DNA replication, which controls heredity.

  15. Stochastic resonance and noise delayed extinction in a model of two competing species

    NASA Astrophysics Data System (ADS)

    Valenti, D.; Fiasconaro, A.; Spagnolo, B.

    2004-01-01

    We study the role of the noise in the dynamics of two competing species. We consider generalized Lotka-Volterra equations in the presence of a multiplicative noise, which models the interaction between the species and the environment. The interaction parameter between the species is a random process which obeys a stochastic differential equation with a generalized bistable potential in the presence of a periodic driving term, which accounts for the environment temperature variation. We find noise-induced periodic oscillations of the species concentrations and stochastic resonance phenomenon. We find also a nonmonotonic behavior of the mean extinction time of one of the two competing species as a function of the additive noise intensity.

  16. Modeling Thermal Noise from Crystaline Coatings for Gravitational-Wave Detectors

    NASA Astrophysics Data System (ADS)

    Demos, Nicholas; Lovelace, Geoffrey; LSC Collaboration

    2016-03-01

    The sensitivity of current and future ground-based gravitational-wave detectors are, in part, limited in sensitivity by Brownian and thermoelastic noise in each detector's mirror substrate and coating. Crystalline mirror coatings could potentially reduce thermal noise, but thermal noise is challenging to model analytically in the case of crystalline materials. Thermal noise can be modeled using the fluctuation-dissipation theorem, which relates thermal noise to an auxiliary elastic problem. In this poster, I will present results from a new code that numerically models thermal noise by numerically solving the auxiliary elastic problem for various types of crystalline mirror coatings. The code uses a finite element method with adaptive mesh refinement to model the auxiliary elastic problem which is then related to thermal noise. I will present preliminary results for a crystal coating on a fused silica substrate of varying sizes and elastic properties. This and future work will help develop the next generation of ground-based gravitational-wave detectors.

  17. Range performance impact of noise for thermal system modeling

    NASA Astrophysics Data System (ADS)

    Fanning, Jonathan D.; Teaney, Brian P.; Reynolds, Joseph P.; Du Bosq, Todd W.

    2009-05-01

    This paper presents a comparison of the predictions of NVThermIP to human perception experiment results in the presence of large amounts of noise where the signal to noise ratio is around 1. First, the calculations used in the NVESD imager performance models that deal with sensor noise are described outlining a few errors that appear in the NVThermIP code. A perception experiment is designed to test the range performance predictions of NVThermIP with varying amounts of noise and varying frame rates. NVThermIP is found to overestimate the impact of noise, leading to pessimistic range performance predictions for noisy systems. The perception experiment results are used to find a best fit value of the constant α used to relate system noise to eye noise in the NVESD models. The perception results are also fit to an alternate eye model that handles frame rates below 30Hz and smoothly approaches an accurate prediction of the performance in the presence of static noise. The predictions using the fit data show significantly less error than the predictions from the current model.

  18. Active control of the volume acquisition noise in functional magnetic resonance imaging: Method and psychoacoustical evaluation

    NASA Astrophysics Data System (ADS)

    Chambers, John; Akeroyd, Michael A.; Summerfield, A. Quentin; Palmer, Alan R.

    2001-12-01

    Functional magnetic resonance imaging (fMRI) provides a noninvasive tool for observing correlates of neural activity in the brain while a subject listens to sound. However, intense acoustic noise is generated in the process of capturing MR images. This noise stimulates the auditory nervous system, limiting the dynamic range available for displaying stimulus-driven activity. The noise is potentially damaging to hearing and is distracting for the subject. In an active noise control (ANC) system, a reference sample of a noise is processed to form a sound which adds destructively with the noise at the listener's ear. We describe an implementation of ANC in the electromagnetically hostile and physically compact MRI scanning environment. First, a prototype system was evaluated psychoacoustically in the laboratory, using the electrical drive to a noise-generating loudspeaker as the reference. This system produced 10-20 dB of subjective noise-reduction between 250 Hz and 1 kHz, and smaller amounts at higher frequencies. The system was modified to operate in a real MR scanner where the reference was obtained by recording the acoustic scanner noise. Objective reduction by 30-40 dB of the most intense component in scanner noises was realized between 500 Hz and 3500 Hz, and subjective reduction of 12 dB and 5 dB in tests at frequencies of 600 Hz and at 1.9 kHz, respectively. Although the benefit of ANC is limited by transmission paths to the cochlea other than air-conduction routes from the auditory meatus, ANC achieves worthwhile attenuation even in the frequency range of maximum bone conduction (1.5-2 kHz). ANC should, therefore, be generally useful during auditory fMRI.

  19. Suppression of frequency locking noise in resonator fiber optic gyro by differential detection method

    NASA Astrophysics Data System (ADS)

    Feng, Lishuang; Zhi, Yinzhou; Lei, Ming; Wang, Junjie

    2014-10-01

    The performance of the resonator fiber optic gyro (RFOG) is influenced by frequency locking noise. This paper proposes a differential detection method (DDM) to suppress the frequency locking noise. First, the frequency locking noise induced by the frequency locking error is described theoretically; the description indicates that it acts as the common-mode noise in the RFOG. In the traditional signal-path detection method (SDM), there is a trade-off between suppressing the frequency locking noise and improving the gyro sensitivity. Thus, a model of the DDM is set up and analyzed. The frequency locking noise can be suppressed using the DDM by adjusting the gains of two lock-in amplifiers. Finally, the experimental setup is established, and the SDM and DDM are compared. When the tested equivalent frequency locking noise is 10.6°/h, the bias stability of the RFOG is improved from 12.9°/h to 1.1°/h by the DDM.

  20. Possible breakthrough: Significant improvement of signal to noise ratio by stochastic resonance

    SciTech Connect

    Kiss, L.B.

    1996-06-01

    The {ital simplest} {ital stochastic} {ital resonator} {ital is} {ital used}, {ital a} {ital level} {ital crossing} {ital detector} (LCD), to investigate key properties of stochastic resonance (SR). It is pointed out that successful signal processing and biological applications of SR require to work in the {ital large} {ital signal} {ital limit} (nonlinear transfer limit) which requires a completely new approach: {ital wide} {ital band} {ital input} {ital signal} and a {ital new}, {ital generalised} {ital definition} {ital of} {ital output} {ital noise}. The new way of approach is illustrated by a new arrangement. The arrangement employs a special LCD, white input noise and a special, large, subthreshold wide band signal. {ital First} {ital time} {ital in} {ital the} {ital history} {ital of} {ital SR} (for a wide band input noise), the {ital signal} {ital to} {ital noise} {ital ratio} {ital becomes} {ital much} {ital higher} {ital at} {ital the} {ital output} of a stochastic resonator than {ital at} {ital its} {ital input}. In that way, SR is proven to have a potential to improve signal transfer. Note, that the new arrangement seems to have resemblance to {ital neurone} {ital models}, therefore, it has a potential also for biological applications. {copyright} {ital 1996 American Institute of Physics.}

  1. Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy.

    PubMed

    Lübbe, Jannis; Temmen, Matthias; Rode, Sebastian; Rahe, Philipp; Kühnle, Angelika; Reichling, Michael

    2013-01-01

    The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip-surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d(z) at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d(Δ) (f) at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip-surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured d(z), we predict d(Δ) (f) for specific filter settings, a given level of detection-system noise spectral density d(z) (ds) and the cantilever-thermal-noise spectral density d(z) (th). We find an excellent agreement between the calculated and measured values for d(Δ) (f). Furthermore, we demonstrate that thermal noise in d(Δ) (f), defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth. PMID:23400758

  2. Nanophononic Metamaterial: Thermal Conductivity Reduction by Local Resonance

    NASA Astrophysics Data System (ADS)

    Davis, Bruce L.; Hussein, Mahmoud I.

    2014-02-01

    We present the concept of a locally resonant nanophononic metamaterial for thermoelectric energy conversion. Our configuration, which is based on a silicon thin film with a periodic array of pillars erected on one or two of the free surfaces, qualitatively alters the base thin-film phonon spectrum due to a hybridization mechanism between the pillar local resonances and the underlying atomic lattice dispersion. Using an experimentally fitted lattice-dynamics-based model, we conservatively predict the metamaterial thermal conductivity to be as low as 50% of the corresponding uniform thin-film value despite the fact that the pillars add more phonon modes to the spectrum.

  3. Ultra-stable, low phase noise dielectric resonator stabilized oscillators for military and commercial systems

    NASA Technical Reports Server (NTRS)

    Mizan, Muhammad; Higgins, Thomas; Sturzebecher, Dana

    1993-01-01

    EPSD has designed, fabricated and tested, ultra-stable, low phase noise microwave dielectric resonator oscillators (DRO's) at S, X, Ku, and K-bands, for potential application to high dynamic range and low radar cross section target detection radar systems. The phase noise and the temperature stability surpass commercially available DROs. Low phase noise signals are critical for CW Doppler radars, at both very close-in and large offset frequencies from the carrier. The oscillators were built without any temperature compensation techniques and exhibited a temperature stability of 25 parts per million (ppm) over an extended temperature range. The oscillators are lightweight, small and low cost compared to BAW & SAW oscillators, and can impact commercial systems such as telecommunications, built-in-test equipment, cellular phone and satellite communications systems. The key to obtaining this performance was a high Q factor resonant structure (RS) and careful circuit design techniques. The high Q RS consists of a dielectric resonator (DR) supported by a low loss spacer inside a metal cavity. The S and the X-band resonant structures demonstrated loaded Q values of 20,300 and 12,700, respectively.

  4. Clinical utility of magnetic resonance thermal imaging (MRTI) for realtime guidance of deep hyperthermia

    NASA Astrophysics Data System (ADS)

    Stauffer, P. R.; Craciunescu, Oana I.; Maccarini, P. F.; Wyatt, Cory; Arunachalam, K.; Arabe, O.; Stakhursky, V.; Soher, B.; MacFall, J. R.; Li, Z.; Joines, William T.; Rangarao, S.; Cheng, K. S.; Das, S. K.; Martins, Carlos D.; Charles, Cecil; Dewhirst, Mark W.; Wong, T.; Jones, E.; Vujaskovic, Z.

    2009-02-01

    A critical need has emerged for volumetric thermometry to visualize 3D temperature distributions in real time during deep hyperthermia treatments used as an adjuvant to radiation or chemotherapy for cancer. For the current effort, magnetic resonance thermal imaging (MRTI) is used to measure 2D temperature rise distributions in four cross sections of large extremity soft tissue sarcomas during hyperthermia treatments. Novel hardware and software techniques are described which improve the signal to noise ratio of MR images, minimize motion artifact from circulating coupling fluids, and provide accurate high resolution volumetric thermal dosimetry. For the first 10 extremity sarcoma patients, the mean difference between MRTI region of interest and adjacent interstitial point measurements during the period of steady state temperature was 0.85°C. With 1min temporal resolution of measurements in four image planes, this noninvasive MRTI approach has demonstrated its utility for accurate monitoring and realtime steering of heat into tumors at depth in the body.

  5. A study of tyre cavity resonance and noise reduction using inner trim

    NASA Astrophysics Data System (ADS)

    Mohamed, Zamri; Wang, Xu

    2015-01-01

    A study of tyre inner trim as a method for reducing tyre cavity resonance noise is presented. The tyre is modelled as a rectangular toroid where only the outside shell is flexible. A modal series solution of the sound pressure frequency response inside the tyre cavity is derived from the wave equation using modal superposition. In the solution with the rigid and flexible wall boundary condition, the effect of placing a trim layer onto the inner surface of the tyre tread plate wall is reflected by adding a damping loss term in the sound pressure frequency response function. The numerical simulation result was then compared with the result obtained from a roving impact test performed on a tyre. The results show that selective trim material may be effective for reducing the structure-borne noise magnitude resulting from the tyre cavity resonance.

  6. Calculation and observation of thermal electrostatic noise in solar wind plasma

    NASA Technical Reports Server (NTRS)

    Kellogg, P. J.

    1981-01-01

    Calculations, both approximate algebraic and numerical, have been carried out for the noise due to electrostatic waves incident on a dipole antenna. The noise is calculated both for a thermal equilibrium plasma, and one having several components at different temperatures. The results are compared with measurements from the IMP-6 satellite. In various frequency ranges, the noise power is dominated by Langmuir oscillations, by electron acoustic waves and by ion acoustic waves. The measurements are consistent with all of these, although the ion waves are not definitely observed, due to interference from shot noise.

  7. Noise-Induced Entrainment and Stochastic Resonance in Human Brain Waves

    NASA Astrophysics Data System (ADS)

    Mori, Toshio; Kai, Shoichi

    2002-05-01

    We present the first observation of stochastic resonance (SR) in the human brain's visual processing area. The novel experimental protocol is to stimulate the right eye with a subthreshold periodic optical signal and the left eye with a noisy one. The stimuli bypass sensory organs and are mixed in the visual cortex. With many noise sources present in the brain, higher brain functions, e.g., perception and cognition, may exploit SR.

  8. Strong quantum memory at resonant Fermi edges revealed by shot noise.

    PubMed

    Ubbelohde, N; Roszak, K; Hohls, F; Maire, N; Haug, R J; Novotný, T

    2012-01-01

    Studies of non-equilibrium current fluctuations enable assessing correlations involved in quantum transport through nanoscale conductors. They provide additional information to the mean current on charge statistics and the presence of coherence, dissipation, disorder, or entanglement. Shot noise, being a temporal integral of the current autocorrelation function, reveals dynamical information. In particular, it detects presence of non-Markovian dynamics, i.e., memory, within open systems, which has been subject of many current theoretical studies. We report on low-temperature shot noise measurements of electronic transport through InAs quantum dots in the Fermi-edge singularity regime and show that it exhibits strong memory effects caused by quantum correlations between the dot and fermionic reservoirs. Our work, apart from addressing noise in archetypical strongly correlated system of prime interest, discloses generic quantum dynamical mechanism occurring at interacting resonant Fermi edges. PMID:22530093

  9. Electron concentrations calculated from the lower hybrid resonance noise band observed by Ogo 3.

    NASA Technical Reports Server (NTRS)

    Burtis, W. J.

    1973-01-01

    A noise band at the lower hybrid resonance (LHR) is often detected by the VLF and ELF receivers on Ogo 3, using the electric antenna. In some cases the noise band is at the geometric mean gyrofrequency as measured by the Goddard Space Flight Center (GSFC) magnetometer, and local LHR in a dense H(+) plasma is indicated; in such cases, electron concentration can be calculated, if it is assumed that heavy ions are negligible. Observations at midlatitudes and altitudes of a few earth radii show local concentrations as low as 1.4 electrons/cu cm. In one case the concentrations obtained from the LHR noise band agree with those measured simultaneously by the GSFC ion mass spectrometer within a factor of 2. In another case the concentration is observed to fall by a factor of 2 in 150 km and then to decrease roughly as R to the minus fourth power, in agreement with whistler measurements outside the plasmapause.

  10. Vacuum-isolation vessel and method for measurement of thermal noise in microphones

    NASA Technical Reports Server (NTRS)

    Zuckerwar, Allan J. (Inventor); Ngo, Kim Chi T. (Inventor)

    1992-01-01

    The vacuum isolation vessel and method in accordance with the present invention are used to accurately measure thermal noise in microphones. The apparatus and method could be used in a microphone calibration facility or any facility used for testing microphones. Thermal noise is measured to determine the minimum detectable sound pressure by the microphone. Conventional isolation apparatus and methods have been unable to provide an acoustically quiet and substantially vibration free environment for accurately measuring thermal noise. In the present invention, an isolation vessel assembly comprises a vacuum sealed outer vessel, a vacuum sealed inner vessel, and an interior suspension assembly coupled between the outer and inner vessels for suspending the inner vessel within the outer vessel. A noise measurement system records thermal noise data from the isolation vessel assembly. A vacuum system creates a vacuum between an internal surface of the outer vessel and an external surface of the inner vessel. The present invention thus provides an acoustically quiet environment due to the vacuum created between the inner and outer vessels and a substantially vibration free environment due to the suspension assembly suspending the inner vessel within the outer vessel. The thermal noise in the microphone, effectively isolated according to the invention, can be accurately measured.

  11. Reduction and possible elimination of coating thermal noise using a rigidly controlled cavity with a quantum-nondemolition technique.

    PubMed

    Somiya, Kentaro

    2009-06-12

    Thermal noise of a mirror is one of the most important issues in high-precision measurements such as gravitational-wave detection or cold damping experiments. It has been pointed out that thermal noise of a mirror with multilayer coatings can be reduced by mechanical separation of the layers. In this Letter, we introduce a way to further reduce thermal noise by locking the mechanically separated mirrors. The reduction is limited by the standard quantum limit of control noise, but it can be overcome with a quantum-nondemolition technique, which finally raises a possibility of complete elimination of coating thermal noise. PMID:19658917

  12. Thermally tunable resonator using directly integrated metallic heater

    NASA Astrophysics Data System (ADS)

    Chen, Ruobing; Li, Xinbai; Deng, Qingzhong; Michel, Jurgen; Zhou, Zhiping

    2015-08-01

    A thermally tunable half-disk resonator (HDR) with directly-integrated metallic heater is presented. The proposed resonator is based on the structure of HDR, which allows direct electrical contacts in HDR region without causing extra loss. The metallic heater is designed to be directly integrated on the silicon devices, and single-mode operation can be retained simultaneously. Metallic heater deposited on inner side of the ring, which cannot realize before because of weakened light confinement resulting in substantial leakage and loss, guides most heat power to the waveguide. This thermal localization enhances tuning efficiency. The simulation result shows a wavelength shift of 0.855 nm under ultralow driving voltage of 0.02V, corresponding to high thermal tuning efficiency of 2.831 nm/mW. The structure possesses both the advantages of high thermal tuning efficiency and low resistance, hence requiring smaller voltage and energy to drive, desirable for optical interconnects applications. Moreover, the proposed structure also eliminates the need to use doped silicon slab for electrical contacts, as widely used in conventional directly integrated heaters. Undoped strip waveguide in HDR enables higher Q-factor and improves optical performance.

  13. Thermal magnetic noise control in the ultra-high-density read head

    NASA Astrophysics Data System (ADS)

    Zheng, Y. K.; Han, G. C.; Liu, B.

    In order to reduce the resistance of tunnel magnetoresistive (TMR) read heads, a large stripe height sensor structure was proposed. The thermal magnetic noise, called as mag-noise, in this type of TMR heads was simulated by micromagnetic modeling using the Landau-Lifshitz-Gilbert (LLG) gyro-magnetic equation. It is found that for the same hard bias strength, both the sensitivity and the mag-noise of TMR heads increase as the sensor height increases. The signal-to-noise ratio (SNR) is reduced at large stripe height. The large increase in the demagnetization field resulting from the stripe height increase causes the weakening of the effective bias field, thus increasing the mag-noise significantly. Low mag-noise and high SNR can be obtained by increasing the hard bias strength and reducing the spacer between the hard bias and the free layer. An extended hard bias structure has been proposed to further increase SNR of TMR heads.

  14. Comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging

    SciTech Connect

    O'Sullivan, Malcolm N.; Chan, Kam Wai Clifford; Boyd, Robert W.

    2010-11-15

    We present a theoretical comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging. We first calculate the signal-to-noise ratio of each process in terms of its controllable experimental conditions. We show that a key distinction is that a thermal ghost image always resides on top of a large background; the fluctuations in this background constitutes an intrinsic noise source for thermal ghost imaging. In contrast, there is a negligible intrinsic background to a quantum ghost image. However, for practical reasons involving achievable illumination levels, acquisition times for thermal ghost images are often much shorter than those for quantum ghost images. We provide quantitative predictions for the conditions under which each process provides superior performance. Our conclusion is that each process can provide useful functionality, although under complementary conditions.

  15. A review of the combined effects of thermal and noise conditions on human performance

    NASA Astrophysics Data System (ADS)

    Moscoso, Richard A.; Wang, Lily M.; Musser, Amy

    2001-05-01

    Human perception and annoyance due to background noise has been the subject of much research. A great deal of work has also been done to identify conditions that produce an acceptable thermal environment for building occupants. The experience of occupants in indoor environments, however, is much more complex than can be represented by thermal comfort or the acoustic environment in isolation. Occupants normally experience a mix of thermal, auditory, visual, and olfactory stimuli that combines to form an impression of the environment. This paper is specifically interested in how building occupants trade off between acoustic and thermal comfort. Heating, ventilation, and air-conditioning systems in buildings are often adjusted by building users to arrive at a more comfortable temperature, but this change may also produce more noise. Previous studies on the interaction effects between temperature and noise on human performance are reviewed in this presentation, followed by a discussion of the authors' current work in this area.

  16. Padé-Froissart exact signal-noise separation in nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Belkić, Dževad; Belkić, Karen

    2011-06-01

    Nuclear magnetic resonance spectroscopy is one of the key methods for studying the structure of matter on different levels (sub-nuclear, nuclear, atomic, molecular, cellular, etc). Its overall success critically depends upon reliable mathematical analysis and interpretation of the studied data. This is especially aided by parametric signal processing with the ensuing data quantification, which can yield the abundance or concentrations of the constituents in the examined matter. The sought reliability of signal processing rests upon the possibility of an accurate solution of the quantification problem alongside the unambiguous separation of true from false information in the spectrally analysed data. We presently demonstrate that the fast Padé transform (FPT), as the unique ratio of two polynomials for a given Maclaurin series, can yield exact signal-noise separation for a synthesized free induction decay curve built from 25 molecules. This is achieved by using the concept of Froissart doublets or pole-zero cancellations. Unphysical/spurious (noise or noise-like) resonances have coincident or near-coincident poles and zeros. They possess either zero- or near-zero-valued amplitudes. Such spectral structures never converge due to their instability against even the smallest perturbations. By contrast, upon convergence of the FPT, physical/genuine resonances are identified by their persistent stability against external perturbations, such as signal truncation or addition of random noise, etc. In practice, the computation is carried out by gradually and systematically increasing the common degree of the Padé numerator and denominator polynomials in the diagonal FPT. As this degree changes, the reconstructed parameters and spectra fluctuate until stabilization occurs. The polynomial degree at which this full stabilization is achieved represents the sought exact number of resonances. An illustrative set of results is reported in this work to show the exact separation of

  17. Low-noise Brillouin random fiber laser with a random grating-based resonator.

    PubMed

    Xu, Yanping; Gao, Song; Lu, Ping; Mihailov, Stephen; Chen, Liang; Bao, Xiaoyi

    2016-07-15

    A novel Brillouin random fiber laser (BRFL) with the random grating-based Fabry-Perot (FP) resonator is proposed and demonstrated. Significantly enhanced random feedback from the femtosecond laser-fabricated random grating overwhelms the Rayleigh backscattering, which leads to efficient Brillouin gain for the lasing modes and reduced lasing threshold. Compared to the intensity and frequency noises of the Rayleigh feedback resonator, those of the proposed random laser are effectively suppressed due to the reduced resonating modes and mode competition resulting from the random grating-formed filters. Using the heterodyne technique, the linewidth of the coherent random lasing spike is measured to be ∼45.8  Hz. PMID:27420494

  18. Noise effects on a birhythmic Josephson junction coupled to a resonator.

    PubMed

    Yamapi, R; Filatrella, G

    2014-05-01

    We study the effect of noise on a Josephson junction that, coupled to a linear RLC resonator, can oscillate at two frequencies. To establish the global stability of the attractors, we estimate the position of the separatrix, essential information to establish the stability of the attractor for this multidimensional system, from the analysis of the mean first passage time. We find that the frequency locked to the resonator is most stable at low bias and less stable at high bias, where the resonator exhibits the largest oscillations. The change in the birhythmic region is dramatic for the effective barrier changes of an order of magnitude and the corresponding lifetime of about seven decades. PMID:25353859

  19. Thermal noise for SBS suppression in fiber optical parametric amplifiers

    NASA Astrophysics Data System (ADS)

    Mussot, Arnaud; Le Parquier, Marc; Szriftgiser, Pascal

    2010-06-01

    We demonstrate a new and simple solution to suppress stimulated Brillouin scattering in fiber optical parametric amplifiers. Cumbersome PRBS or sinusoidal generators used to broaden the pump spectrum are replaced by a filtered microwave noise source. Stimulated Brillouin scattering threshold can be increased up to large values still keeping an excellent quality of amplification of nonreturn to zero signals. The simplicity and the performances of this setup open the way for a wide variety of applications for FOPAs.

  20. Noise

    MedlinePlus

    Noise is all around you, from televisions and radios to lawn mowers and washing machines. Normally, you ... sensitive structures of the inner ear and cause noise-induced hearing loss. More than 30 million Americans ...

  1. Stochastic resonance in an ensemble of bistable systems under stable distribution noises and nonhomogeneous coupling.

    PubMed

    Tang, Yang; Zou, Wei; Lu, Jianquan; Kurths, Jürgen

    2012-04-01

    In this paper, stochastic resonance of an ensemble of coupled bistable systems driven by noise having an α-stable distribution and nonhomogeneous coupling is investigated. The α-stable distribution considered here is characterized by four intrinsic parameters: α∈(0,2] is called the stability parameter for describing the asymptotic behavior of stable densities; β∈[-1,1] is a skewness parameter for measuring asymmetry; γ∈(0,∞) is a scale parameter for measuring the width of the distribution; and δ∈(-∞,∞) is a location parameter for representing the mean value. It is demonstrated that the resonant behavior is optimized by an intermediate value of the diversity in coupling strengths. We show that the stability parameter α and the scale parameter γ can be well selected to generate resonant effects in response to external signals. In addition, the interplay between the skewness parameter β and the location parameter δ on the resonance effects is also studied. We further show that the asymmetry of a Lévy α-stable distribution resulting from the skewness parameter β and the location parameter δ can enhance the resonance effects. Both theoretical analysis and simulation are presented to verify the results of this paper. PMID:22680556

  2. Quasi-thermal noise observed by CASSINI during the first flyby of Venus

    NASA Astrophysics Data System (ADS)

    Martinović, M.; Zaslavsky, A.; Maksimovic, M.; Šegan, S.; Svetlik, M.

    2015-12-01

    Quasi-thermal noise (QTN) spectroscopy is an accurate technique for in situ measurements of electron density and temperature in space plasmas. The QTN spectrum has a characteristic noise peak just above the plasma frequency produced by electron quasi-thermal fluctuations, which allows a very accurate measurement of the electron density. In this work, we analyze the period during the first CASSINI flyby of Venus where the thermal noise peak was visible by CASSINI/RPWS instrument. Development of the plasma parameters in the ionosphere of Venus during the closest approach (up to 284 km above the planet surface), as well as characteristics of velocity distribution function of electrons are evaluated using this method.

  3. The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

    PubMed Central

    Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

    2016-01-01

    For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation. PMID:26950936

  4. Stochastic resonance in a tumor-immune system subject to bounded noises and time delay

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Mei, Dong-Cheng

    2014-12-01

    Immunotherapy is one of the most recent approaches in cancer therapy. A mathematical model of tumor-immune interaction, subject to a periodic immunotherapy treatment (imitated by a periodic signal), correlative and bounded stochastic fluctuations and time delays, is investigated by numerical simulations for its signal power amplification (SPA). Within the tailored parameter regime, the synchronous response of tumor growth to the immunotherapy, stochastic resonance (SR), versus both the noises and delays is obtained. The details are as follows (i) the peak values of SPA versus the noise intensity (A) in the proliferation term of tumor cells decrease as the frequency of periodic signal increases, i.e. an increase of the frequency restrains the SR; (ii) an increase of the amplitude of periodic signal restrains the SR versus A, but boosts up the SR versus the noise intensity B in the immune term; (iii) there is an optimum cross-correlated degree between the two bounded noises, at which the system exhibits the strongest SR versus the delay time τα(the reaction time of tumor cell population to their surrounding environment constraints); (iv) upon increasing the delay time τα, double SR versus the delay time τβ (the time taken by both the tumor antigen identification and tumor-stimulated proliferation of effectors) emerges. These results may be helpful for an immunotherapy treatment for the sufferer.

  5. A new multiscale noise tuning stochastic resonance for enhanced fault diagnosis in wind turbine drivetrains

    NASA Astrophysics Data System (ADS)

    Hu, Bingbing; Li, Bing

    2016-02-01

    It is very difficult to detect weak fault signatures due to the large amount of noise in a wind turbine system. Multiscale noise tuning stochastic resonance (MSTSR) has proved to be an effective way to extract weak signals buried in strong noise. However, the MSTSR method originally based on discrete wavelet transform (DWT) has disadvantages such as shift variance and the aliasing effects in engineering application. In this paper, the dual-tree complex wavelet transform (DTCWT) is introduced into the MSTSR method, which makes it possible to further improve the system output signal-to-noise ratio and the accuracy of fault diagnosis by the merits of DTCWT (nearly shift invariant and reduced aliasing effects). Moreover, this method utilizes the relationship between the two dual-tree wavelet basis functions, instead of matching the single wavelet basis function to the signal being analyzed, which may speed up the signal processing and be employed in on-line engineering monitoring. The proposed method is applied to the analysis of bearing outer ring and shaft coupling vibration signals carrying fault information. The results confirm that the method performs better in extracting the fault features than the original DWT-based MSTSR, the wavelet transform with post spectral analysis, and EMD-based spectral analysis methods.

  6. The effect of magnetic resonance imaging noise on cochlear function in dogs.

    PubMed

    Venn, R E; McBrearty, A R; McKeegan, D; Penderis, J

    2014-10-01

    Noise produced by magnetic resonance imaging (MRI) scanners (which can peak at a sound pressure level of 131 dB) has been shown to cause noise-induced cochlear dysfunction in people. The aim of this study was to investigate whether noise produced during MRI had a deleterious effect on cochlear function in dogs, using distortion product otoacoustic emission (DPOAE) testing, which allows frequency specific, non-invasive assessment of cochlear function. DPOAE testing was performed before and after MRI in one or both ears under general anaesthesia at 14 frequency pairs (f2 frequency ranging from 0.84 kHz to 8.0 kHz). A control group comprised dogs undergoing anaesthesia of a similar duration for quiet procedures. Thirty-six dogs (66 ears) and 17 dogs (28 ears) were included in the MRI and control groups respectively. There was a reduction in DPOAE at all frequencies tested in the MRI group; a similar effect was not evident in the control group. This reduction in the MRI group was statistically significant in five of the 14 frequencies assessed (P < 0.05). These results demonstrate that exposure to MRI noise results in a significant reduction in frequency-specific cochlear function in dogs, although it is not known whether this is reversible or permanent. This suggests that all dogs undergoing MRI studies should be provided with ear protection as a routine precautionary measure. PMID:25155216

  7. Fast and high resolution thermal detector based on an aluminum nitride piezoelectric microelectromechanical resonator with an integrated suspended heat absorbing element

    NASA Astrophysics Data System (ADS)

    Hui, Yu; Rinaldi, Matteo

    2013-03-01

    This letter presents a miniaturized, fast, and high resolution thermal detector, in which a heat absorbing element and a temperature sensitive microelectromechanical system (MEMS) resonator are perfectly overlapped but separated by a microscale air gap. This unique design guarantees efficient and fast (˜10s μs) heat transfer from the absorbing element to the temperature sensitive device and enables high resolution thermal power detection (˜nW), thanks to the low noise performance of the high quality factor (Q = 2305) MEMS resonant thermal detector. A device prototype was fabricated, and its detection capabilities were experimentally characterized. A thermal power as low as 150 nW was experimentally measured, and a noise equivalent power of 6.5 nW/Hz1/2 was extracted. A device thermal time constant of only 350 μs was measured (smallest ever reported for MEMS resonant thermal detectors), indicating the great potential of the proposed technology for the implementation of ultra-fast and high resolution un-cooled resonant thermal detectors.

  8. Ultra-low-phase-noise cryocooled microwave dielectric-sapphire-resonator oscillators

    NASA Astrophysics Data System (ADS)

    Hartnett, John G.; Nand, Nitin R.; Lu, Chuan

    2012-04-01

    Two nominally identical ultra-stable microwave oscillators are compared. Each incorporates a sapphire resonator cooled to near 6 K in an ultra-low vibration cryostat using a pulse-tube cryocooler. The phase noise for a single oscillator is measured at -105 dBc/Hz at 1 Hz offset on the 11.2 GHz carrier. The oscillator fractional frequency stability, after subtracting a linear frequency drift of 3.5×10-14/day, is characterized by 5.3×10-16τ-1/2+9×10-17 for integration times 0.1s<τ<1000s and is limited by a flicker frequency noise floor near 1×10-16.

  9. Quantum minimax receiver for ternary coherent state signal in the presence of thermal noise

    NASA Astrophysics Data System (ADS)

    Kato, Kentaro

    2013-02-01

    This paper is concerned with the minimax strategy in quantum signal detection theory. First we show a numerical calculation method for finding a solution to the quantum minimax decision problem in the case that the average probability of decision errors is used as the quality function of a quantum communication system. To verify the numerical calculation method, ternary coherent state signal is considered in the absence of thermal noise. After that, the error probability of the quantum minimax receiver for the ternary coherent state signal in the pressure of thermal noise is computed by using this numerical calculation method.

  10. Parameter dependence of stochastic resonance in the FitzHugh-Nagumo neuron model driven by trichotomous noise

    NASA Astrophysics Data System (ADS)

    Zhang, Huiqing; Yang, Tingting; Xu, Yong; Xu, Wei

    2015-05-01

    We investigate the stochastic resonance in a FitzHugh-Nagumo neuron model driven by trichotomous noise and periodic signal, focusing on the dependence of properties of stochastic resonance (SR) on system parameters. The stochastic resonance is shown through several different measures: system response, power spectrum and signal-to-noise ratio. Firstly, it is found that whether the neuron can fire regularly depends on the cooperative effect of the signal frequency and the signal amplitude for the deterministic FHN neuron. When the forcing amplitude alone is insufficient to cause the neuron firing, the neuron can fire with the addition of trichotomous noise. Secondly, we show that power spectrum is maximized for an optimal value of the noise correlation time, which is the signature of SR. Finally, from studying SNR, the specific system parameters are found to optimize the SR phenomenon.

  11. Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation

    ERIC Educational Resources Information Center

    Blackman, Graham A.; Hall, Deborah A.

    2011-01-01

    Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

  12. Magnetic-resonance-guided directional transurethral ultrasound thermal therapy

    NASA Astrophysics Data System (ADS)

    Ross, Anthony; Diederich, Chris J.; Nau, William H.; Tyreus, Per Daniel; Gill, Harchi; Bouley, Donna; Butts, R. K.; Rieke, Viola; Daniel, Bruce; Sommer, Graham

    2003-06-01

    Two catheter-based transurethral ultrasound applicators designed for selective thermal coagulation of prostate tissue were evaluated. The first applicator utilized two 3.5 mm piezoelectric sectored tubes with the active transducer surface forming 90°. The second applicator's transducer assembly consisted of a linear array of 3.5 x 10 mm planar transducer elements. Both applicators operated at 8 MHz and were positioned on a 4 mm diameter catheter within an integrated expandable balloon (10 mm). Manual rotation of the transducer assembly within the balloon allowed for angular control and/or sweeping of the treatment volume. Ambient temperature degassed cooling water (~120 ml/min) was circulated inside the balloon to preserve the urethral mucosa. Acoustic efficiencies of 20-54% and acoustic beam distributions were measured. The thermal treatment characteristics of the applicator were investigated in vivo (canine prostate) under MRI guidance in an interventional open magnet (0.5 T). Magnetic resonance thermal imaging (MRTI) monitored the treatments (GRE phase mapping, multiple planes, 15 sec update intervals). Post-treatment imaging (T1 w/contrast) and TTC staining of the prostate were used to verify zones of thermal damage. Single sonications lasting 8-15 min produced coagulated zones of tissue extending to the outer boundary of the prostate while preserving 2-3 mm of urethral mucosa. Multiple sonications in sequence produced larger contiguous sectors of coagulated tissue (~ 3/4 of the gland). In summary, highly directional transurethral applicators under MRI guidance were able to produce selective and controllable thermal coagulation.

  13. Measurements of plasma quasi-thermal noise on STEREO spacecraft and plasma temperature deduction using antenna electron shot noise model

    NASA Astrophysics Data System (ADS)

    Martinović, M.; Zaslavsky, A.; Maksimovic, M.; Zouganelis, Y.

    2014-12-01

    Quasi-thermal noise spectroscopy is very accurate technique for in situ measurements of electron density and temperature in space plasmas. This technique uses the voltage fluctuation spectrum, which is ubiquitous in interplanetary space, obtained by an electric antenna. It is independent of antenna orientation if velocity distribution function of plasma particles is considered to be isotropic. On STEREO/WAVES antennas electron shot noise spectrum dominates because of large antenna surface area, especially at lower frequencies. This feature of antennas disables simultaneous measurements of electron density and temperature. However, technique may work accurately in high-density filamentary structures, where Debye length is small. In this paper, it has been illustrated on magnetic clouds. Obtained results have been used to recalibrate the data of PLASTIC instrument. Further on, in unperturbed solar wind, electron shot noise has been used to infer electron temperature. Electron density data, necessary in data processing, has been estimated from recalibrated PLASTIC data. For this purpose, data of both STEREO A and STEREO B spacecraft have been processed by selecting only spectra from free solar wind.

  14. Nanophononic metamaterial: Thermal conductivity reduction by dispersion-resonance hybridization

    NASA Astrophysics Data System (ADS)

    Hussein, Mahmoud I.; Honarvar, Hossein; Yang, Lina

    2015-03-01

    Engineered manipulation of phonons can yield beneficial thermal properties in semiconducting materials. One pivotal application relates to thermoelectric materials, or the concept of converting energy in the form of heat into electricity and vice-versa. The ability to use nanostructuring to reduce the thermal conductivity without negatively impacting the power factor provides a promising avenue for achieving high values of the thermoelectric energy conversion figure-of-merit, ZT. In this work, we propose a novel nanostructured material configuration that seeks to achieve this goal. Termed ``nanophononic metamaterial,'' the configuration is based on a silicon thin-film with a periodic array of pillars erected on one or two of the free surfaces. The pillars qualitatively alter the base thin-film phonon spectrum due to a hybridization mechanism between their local resonances and the underlying atomic lattice dispersion. Using lattice dynamics calculations and molecular dynamics simulations, we predict a drop in the thermal conductivity to as low as 50% of the corresponding uniform thin-film value despite the fact that the pillars add more phonon modes to the spectrum.

  15. Nanophononic metamaterial: Thermal conductivity reduction by local resonance

    NASA Astrophysics Data System (ADS)

    Davis, Bruce; Hussein, Mahmoud

    2014-03-01

    Engineered manipulation of phonons can yield beneficial thermal properties in semiconducting materials. One pivotal application relates to thermoelectric materials, or the concept of converting energy in the form of heat into electricity and vice-versa. The ability to use nanostructuring to reduce the thermal conductivity without negatively impacting the power factor provides a promising avenue for achieving high values of the thermoelectric energy conversion figure-of-merit, ZT. In this work, we propose a novel nanostructured material configuration that seeks to achieve this goal. Termed nanophononic metamaterial, the configuration is based on a silicon thin-film with a periodic array of pillars erected on one or two of the free surfaces. The pillars qualitatively alter the base thin-film phonon spectrum due to a hybridization mechanism between their local resonances and the underlying atomic lattice dispersion. Using an experimentally-fitted lattice-dynamics-based model, we conservatively predict a drop in the thermal conductivity to as low as 50% of the corresponding uniform thin-film value despite the fact that the pillars add more phonon modes to the spectrum.

  16. Ultralow-Noise SiN Trampoline Resonators for Sensing and Optomechanics

    NASA Astrophysics Data System (ADS)

    Reinhardt, Christoph; Müller, Tina; Bourassa, Alexandre; Sankey, Jack C.

    2016-04-01

    In force sensing, optomechanics, and quantum motion experiments, it is typically advantageous to create lightweight, compliant mechanical elements with the lowest possible force noise. Here, we report the fabrication and characterization of high-aspect-ratio, nanogram-scale Si3 N4 "trampolines" having quality factors above 4 ×107 and ringdown times exceeding 5 min (mHz linewidth). These devices exhibit thermally limited force noise sensitivities below 20 aN /Hz1 /2 at room temperature, which is the lowest among solid-state mechanical sensors. We also characterize the suitability of these devices for high-finesse cavity readout and optomechanics applications, finding no evidence of surface or bulk optical losses from the processed nitride in a cavity achieving finesse 40,000. These parameters provide access to a single-photon cooperativity C0˜8 in the resolved-sideband limit, wherein a variety of outstanding optomechanics goals become feasible.

  17. Coherent population trapping resonances in the presence of the frequency-phase noises of an exciting field

    SciTech Connect

    Sokolov, A V; Matveev, A N; Samokotin, A Yu; Akimov, A V; Sorokin, Vadim N; Kolachevsky, Nikolai N

    2009-05-31

    The influence of noises of the frequency and phase difference of an exciting bichromatic field on the parameters of coherent population trapping resonances is studied experimentally. When the phase difference fluctuates within a limited interval near its average value with a short correlation time, the resonance contrast decreases proportionally to exp({phi}{sup 2}{sub rms}), where {phi}{sup 2}{sub rms} is the phase dispersion (in rad{sup 2}). In this case, the spectral width of the resonance remains constant. In another limiting case, when the phase noise has a long correlation time, the resonance contour broadens, the area under the contour being invariable. Experiments were performed with the Zeeman sublevels of the ground state of {sup 87}Rb by exciting rubidium vapour in a glass cell at the resonance wavelength of 795 nm. (interaction of laser radiation with matter)

  18. Reducing the suspension thermal noise of advanced gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Hammond, G. D.; Cumming, A. V.; Hough, J.; Kumar, R.; Tokmakov, K.; Reid, S.; Rowan, S.

    2012-06-01

    The international network of gravitational wave detectors is currently undergoing sensitivity upgrades (aLIGO, aVIRGO and GEO-HF) which will lead to the first detection and subsequent observation of a rich variety of astrophysical sources. To obtain a factor of 10 improvement in the strain sensitivity at low frequencies requires the use of ultralow mechanical loss materials and monolithic fused silica suspensions, optimized mirror coatings and the development of cutting edge techniques to super-polish and figure the interferometer optics. The possibility of applying incremental upgrades to the second generation detectors can be realized by making small but significant changes to the suspensions and/or optical mirror coatings. This includes the use of longer suspensions to increase the dissipation dilution, the development of techniques to reduce the surface loss in fused silica suspensions and methods to lower the mechanical loss from the metal springs used to support the test mass. Such upgrades can potentially improve the strain sensitivity by a factor of 2.5. Looking beyond 2015, the development of techniques to further improve the sensitivity by one order of magnitude are discussed. The third generation detectors will be located underground and will be operated at cryogenic temperatures. At low temperatures, silicon is a particularly promising candidate material as it displays good thermal conductivity, high tensile strength and zero thermal expansion coefficient at 120 K, 18 K and T → 0 K.

  19. A new noise suppression algorithm for optical fiber temperature surveillance of heavy oil thermal recovery well

    NASA Astrophysics Data System (ADS)

    Wang, Jiahuai; Han, Jisheng; Pan, Yong; Zhang, Min; Zou, Qilin; Xie, Shangran

    2011-11-01

    Pure silica core optical fiber is commonly used as the sensing fiber in Raman-backscatter distributed temperature sensors (DTS) in heavy oil thermal well. However the sensing signal collected from this type of fiber statistically belongs to nonstationary random process which cannot be effectively de-noised by simply applying conventional methods. To solve this problem, we develop a novel noise suppression algorithm by combining wavelet multi-scale analysis and moving grey model GM(1,1). The algorithm first applies wavelet de-noising in spatial domain of temperature profile to remove the high frequency noise, then uses moving GM(1,1) method to remove both high frequency and low frequency nonstationary noise in time domain. Autoregressive (AR) model and least square regression are used to optimize the forecasting parameters of GM(1,1). Finally the results of both domains are reconstructed to obtain the de-noised profile. Long-term field test was proposed on the Karamay oil field F11051 steam stimulation well, Xinjiang Province, China. Field test result shows that signal to noise ratio (SNR) is improved by 11dB using the algorithm.

  20. Improvement of signal-to-noise ratio by stochastic resonance in sigmoid function threshold systems, demonstrated using a CMOS inverter

    NASA Astrophysics Data System (ADS)

    Ueda, Michihito

    2010-05-01

    Stochastic resonance (SR) has become a well-known phenomenon that can enhance weak periodic signals with the help of noise. SR is an interesting phenomenon when applied to signal processing. Although it has been proven that SR does not always improve the signal-to-noise ratio (SNR), in a strongly nonlinear system such as simple threshold system, SR does in fact improve SNR for noisy pulsed signals at appropriate noise strength. However, even in such cases, when noise is weak, the SNR is degraded. Since the noise strength cannot be known in advance, it is difficult to apply SR to real signal processing. In this paper, we focused on the shape of the threshold at which SR did not degrade the SNR when noise was weak. To achieve output change when noise was weak, we numerically analyzed a sigmoid function threshold system. When the slope around the threshold was appropriate, SNR did not degrade when noise was weak and instead was improved at suitable noise strength. We also demonstrated SNR improvement for noisy pulsed voltages using a CMOS inverter, a very common threshold device. The input-output property of a CMOS inverter resembles the sigmoid function. By inputting the noisy signal voltage to a CMOS inverter, we measured the input and output voltages and analyzed the SNRs. The results showed that SNR was effectively improved over a wide range of noise strengths.

  1. Normal metal-superconductor decoupling as a source of thermal fluctuation noise in transition-edge sensors

    NASA Astrophysics Data System (ADS)

    Kinnunen, K. M.; Palosaari, M. R. J.; Maasilta, I. J.

    2012-08-01

    We have studied the origin of excess noise in superconducting transition-edge sensors (TES) with several different detector designs. We show that most of the observed noise and complex impedance features can be explained by a thermal model consisting of three bodies. We suggest that one of the thermal blocks and the corresponding thermal fluctuation noise arise due to the high-frequency thermal decoupling of the normal and superconducting phase regions inside the TES film. Our results are also consistent with the prediction that in thin bilayer proximitized superconductors, the jump in heat capacity at the critical temperature is smaller than the universal BCS theory result.

  2. Proposed Use of Zero Bias Diode Arrays as Thermal Electric Noise Rectifiers and Non-Thermal Energy Harvesters

    NASA Astrophysics Data System (ADS)

    Valone, Thomas F.

    2009-03-01

    The well known built-in voltage potential for some select semiconductor p-n junctions and various rectifying devices is proposed to be favorable for generating DC electricity at "zero bias" (with no DC bias voltage applied) in the presence of Johnson noise or 1/f noise which originates from the quantum vacuum (Koch et al., 1982). The 1982 Koch discovery that certain solid state devices exhibit measurable quantum noise has also recently been labeled a finding of dark energy in the lab (Beck and Mackey, 2004). Tunnel diodes are a class of rectifiers that are qualified and some have been credited with conducting only because of quantum fluctuations. Microwave diodes are also good choices since many are designed for zero bias operation. A completely passive, unamplified zero bias diode converter/detector for millimeter (GHz) waves was developed by HRL Labs in 2006 under a DARPA contract, utilizing a Sb-based "backward tunnel diode" (BTD). It is reported to be a "true zero-bias diode." It was developed for a "field radiometer" to "collect thermally radiated power" (in other words, 'night vision'). The diode array mounting allows a feed from horn antenna, which functions as a passive concentrating amplifier. An important clue is the "noise equivalent power" of 1.1 pW per root hertz and the "noise equivalent temperature difference" of 10° K, which indicate sensitivity to Johnson noise (Lynch, et al., 2006). There also have been other inventions such as "single electron transistors" that also have "the highest signal to noise ratio" near zero bias. Furthermore, "ultrasensitive" devices that convert radio frequencies have been invented that operate at outer space temperatures (3 degrees above zero point: 3° K). These devices are tiny nanotech devices which are suitable for assembly in parallel circuits (such as a 2-D array) to possibly produce zero point energy direct current electricity with significant power density (Brenning et al., 2006). Photovoltaic p-n junction

  3. Thermal-noise limit in the frequency stabilization of lasers with rigid cavities.

    PubMed

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2004-12-17

    We evaluate thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/ square root Hz (0.01 Hz/ square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results. PMID:15697887

  4. Waterborne noise due to ocean thermal energy conversion plants. Technical memo

    SciTech Connect

    Janota, C.P.; Thompson, D.E.

    1982-06-17

    Public law reflects a United States national commitment to the rapid development of Ocean Thermal Energy Conversion (OTEC) as an alternate energy source. OTEC plants extract the stored solar energy from the world's tropical seas and in so doing pose a potential for altering the character of the ambient noise there. The sources of noise from an OTEC plant are analyzed in the context of four configurations, two of which were built and tested, and two which are concepts for future full-scale moored facilities. The analysis indicates that the noise resulting from the interaction of turbulence with the sea-water pumps is expected to dominate in the frequency range 10 Hz to 1 kHZ. Measured radiated noise data from the OTEC-I research plant, located near the island of Hawaii, are compared with the analysis. The measured data diverge from the predicted levels at frequencies above about 60 Hz because of dominant non-OTEC noise sources on this platform. However, at low frequency, the measured broadband noise is comparable to that predicted.

  5. Why and how to implement the quasi-thermal noise spectroscopy on a Solar Probe ?

    NASA Astrophysics Data System (ADS)

    Moncuquet, M.; Issautier, K.; Maksimovic, M.; Meyer-Vernet, N.

    Measuring in-situ the plasma charge density and more electron thermodynamic parameters onboard a close-to-the-Sun spacecraft presents a number of difficulties. Among other problems, particle analyzers have to deal with the spacecraft floating potential and with photoelectrons perturbations, especially at 4 R⊙ from the Sun. This may introduce important artifacts and, in absence of independent calibration from an other instrument, a large inaccuracy on electron parameters measurements. But on the other hand, if we may dispose of a few meters double thin wire antenna (thermal resistant), we could implement the technique of the Quasi Thermal Noise (QTN) spectroscopy, which is relatively immune (depending on its design - and thin wires fit this point) to both floating potential and photoelectrons perturbations. It also senses a large plasma volume (≳ cube of the local Debye length) while particle analyzers are usually limited by their small/directional collection area. QTN spectroscopy relies upon a fully understood theory and measurements with a simple electric dipole antenna of the quasi-thermal fluctuations of the electron population in a plasma. The quasi-thermal noise is due to the thermal motions of the particles, which produce electrostatic fluctuations. This noise is detected by any sensitive receiver at the ports of a well-designed electric antenna immersed in a plasma and can be used to measure in-situ the plasma thermodynamic parameters. The basic reason is that this noise can be formally calculated as a function of both the particle velocity distributions and the antenna geometry. Therefore, conversely, the spectroscopy of this noise reveals the local plasma properties. Theory addresses non-Maxwellian distributions (core+halo, kappa - this is why we call it "quasi-thermal" noise ), has been extended to the magnetized case and to the measure of the plasma bulk velocity. It provides, without any free parameter fit, measurements with an accuracy of

  6. Exact calculation of shot noise suppression in resonant diodes under coherent tunneling

    NASA Astrophysics Data System (ADS)

    Aleshkin, V. Ya.; Reggiani, L.

    2012-07-01

    Shot noise suppression in resonant diodes with transport controlled by coherent tunneling is investigated using the tunneling transparency D(ɛ) obtained from an exact numerical solution of the Schrödinger equation in the presence of an applied voltage. The cases of two potential barriers in GaAs/AlAs heterostructures are considered. Results show that the use of an exact dependence of D(ɛ) confirms the existence of a voltage range of values where the Fano factor γ is significantly less than 0.5, in agreement with previous findings obtained within a Lorentzian approximation and with experiments available in the literature for different heterostructures. At increasing values of the barrier width the Fano factor recovers the 0.5 value common to a transport controlled by the sequential tunneling regime.

  7. Graphene thermal transport studies via radio-frequency, cross-correlated Johnson noise thermometry

    NASA Astrophysics Data System (ADS)

    Crossno, Jesse; Liu, Xiaomeng; Wang, Ke; Harzheim, Achim; Watanabe, Kenji; Taniguchi, Takashi; Ohki, Thomas; Fong, Kin Chung; Kim, Philip

    2015-03-01

    The electronic temperature of a dissipative, mesoscale device can be determined by monitoring the Johnson noise power emitted over a wide frequency range. Using radiometry techniques, we have developed a high-frequency, wide bandwidth, cross-correlation Johnson noise thermometer operating from room temperature to cryogenic levels that is compatible with strong magnetic fields. Precisions ranging from 2 to 25 mK are demonstrated over the temperature range of 3 to 300 K with 1 second of integration time. This non-invasive thermometer has enabled us to perform sensitive electronic thermal transport studies in boron nitride encapsulated monolayer graphene over two orders of magnitude in temperature. This versatile technique also enables precision Fano factor measurements as well as studies of correlated noise phenomena, such as those found in layered Van der Waals heterostructures.

  8. Highly sensitive silicon crystal torque sensor operating at the thermal noise limit

    NASA Astrophysics Data System (ADS)

    Haiberger, L.; Weingran, M.; Schiller, S.

    2007-02-01

    We describe a sensitive torque detector, based on a silicon single-crystal double-paddle oscillator (DPO). The high Q-factor (˜105 at room temperature and in vacuum) makes DPOs well suited for the detection of weak forces. The limiting sensitivity of a sensor is given by Brownian (thermal) noise if all external disturbances are eliminated. In this case, the minimum detectable force can be decreased by measuring over a time significantly longer than the oscillator's relaxation time. We demonstrate operation in this regime, with integration times of up to 14 h. A resulting torque sensitivity of 2×10-18 N m is reached. Tests are performed to show that the sensor is only affected by thermal noise. The present sensor is well suited for measurements of extremely weak forces, e.g., of gravitational attraction between laboratory masses.

  9. Highly sensitive silicon crystal torque sensor operating at the thermal noise limit

    SciTech Connect

    Haiberger, L.; Weingran, M.; Schiller, S.

    2007-02-15

    We describe a sensitive torque detector, based on a silicon single-crystal double-paddle oscillator (DPO). The high Q-factor ({approx}10{sup 5} at room temperature and in vacuum) makes DPOs well suited for the detection of weak forces. The limiting sensitivity of a sensor is given by Brownian (thermal) noise if all external disturbances are eliminated. In this case, the minimum detectable force can be decreased by measuring over a time significantly longer than the oscillator's relaxation time. We demonstrate operation in this regime, with integration times of up to 14 h. A resulting torque sensitivity of 2x10{sup -18} N m is reached. Tests are performed to show that the sensor is only affected by thermal noise. The present sensor is well suited for measurements of extremely weak forces, e.g., of gravitational attraction between laboratory masses.

  10. Highly sensitive silicon crystal torque sensor operating at the thermal noise limit.

    PubMed

    Haiberger, L; Weingran, M; Schiller, S

    2007-02-01

    We describe a sensitive torque detector, based on a silicon single-crystal double-paddle oscillator (DPO). The high Q-factor (approximately 10(5) at room temperature and in vacuum) makes DPOs well suited for the detection of weak forces. The limiting sensitivity of a sensor is given by Brownian (thermal) noise if all external disturbances are eliminated. In this case, the minimum detectable force can be decreased by measuring over a time significantly longer than the oscillator's relaxation time. We demonstrate operation in this regime, with integration times of up to 14 h. A resulting torque sensitivity of 2 x 10(-18) N m is reached. Tests are performed to show that the sensor is only affected by thermal noise. The present sensor is well suited for measurements of extremely weak forces, e.g., of gravitational attraction between laboratory masses. PMID:17578142

  11. Spectral properties of thermal fluctuations on simple liquid surfaces below shot-noise levels.

    PubMed

    Aoki, Kenichiro; Mitsui, Takahisa

    2012-07-01

    We study the spectral properties of thermal fluctuations on simple liquid surfaces, sometimes called ripplons. Analytical properties of the spectral function are investigated and are shown to be composed of regions with simple analytic behavior with respect to the frequency or the wave number. The derived expressions are compared to spectral measurements performed orders of magnitude below shot-noise levels, which is achieved using a novel noise reduction method. The agreement between the theory of thermal surface fluctuations and the experiment is found to be excellent, elucidating the spectral properties of the surface fluctuations. The measurement method requires relatively only a small sample both spatially (few μm) and temporally (~20 s). The method also requires relatively weak light power (~0.5 mW) so that it has a broad range of applicability, including local measurements, investigations of time-dependent phenomena, and noninvasive measurements. PMID:23005425

  12. Experimental upper limit on the estimated thermal noise at low frequencies in a gravitational wave detector

    SciTech Connect

    Di Virgilio, A.; Bigotta, S.; Barsotti, L.; Braccini, S.; Bradaschia, C.; Cella, G.; Del Prete, M.; Fiori, I.; Frasconi, F.; Gennai, A.; Giazotto, A.; Passuello, D.; Raffaelli, F.; Dattilo, V.; La Penna, P.; Ferrante, I.; Fidecaro, F.; Passaquieti, R.; Losurdo, G.; Majorana, E.

    2007-12-15

    The mirror relative motion of a suspended Fabry-Perot cavity is studied in the frequency range 3-100 Hz. The experimental measurements presented in this paper have been performed at the Low Frequency Facility, a high finesse optical cavity 1 cm long suspended to a mechanical seismic isolation system like the one of the VIRGO gravitational wave antenna. Because of the radiation pressure between the two mirrors of the cavity, the dynamic behavior of the system is characterized by the optical spring stiffness. In the frequency region above 3 Hz, where seismic noise contamination is negligible, the mirror displacement noise is stationary and its statistical distribution is Gaussian. Using a simplified mechanical model of the suspended system and applying the fluctuation dissipation theorem, we show that the measured power spectrum is reproduced in the frequency region 3-90 Hz. Since the contribution coming from different sources of the system to the total noise budget turns out to be negligible, we conclude that the relative displacement power spectrum of this opto-mechanical system is compatible with a system at thermal equilibrium within its environment. In the region 3-10 Hz this measurement gives so far the best upper limit for the thermal noise of the suspension for a gravitational wave interferometer.

  13. Cryogenic measurements of mechanical loss of high-reflectivity coating and estimation of thermal noise.

    PubMed

    Granata, Massimo; Craig, Kieran; Cagnoli, Gianpietro; Carcy, Cécile; Cunningham, William; Degallaix, Jérôme; Flaminio, Raffaele; Forest, Danièle; Hart, Martin; Hennig, Jan-Simon; Hough, James; MacLaren, Ian; Martin, Iain William; Michel, Christophe; Morgado, Nazario; Otmani, Salim; Pinard, Laurent; Rowan, Sheila

    2013-12-15

    We report on low-frequency measurements of the mechanical loss of a high-quality (transmissivity T<5 ppm at λ(0)=1064 nm, absorption loss <0.5 ppm) multilayer dielectric coating of ion-beam-sputtered fused silica and titanium-doped tantala in the 10-300 K temperature range. A useful parameter for the computation of coating thermal noise on different substrates is derived as a function of temperature and frequency. PMID:24322234

  14. A digital accelerometer array utilizing suprathreshold stochastic resonance for detection of sub-Brownian noise floor accelerations.

    SciTech Connect

    Carr, Dustin Wade; Olsson, Roy H.

    2004-12-01

    The goal of this LDRD project was to evaluate the possibilities of utilizing Stochastic resonance in micromechanical sensor systems as a means for increasing signal to noise for physical sensors. A careful study of this field reveals that in the case of a single sensing element, stochastic resonance offers no real advantage. We have, however, identified a system that can utilize very similar concepts to stochastic resonance in order to achieve an arrayed sensor system that could be superior to existing technologies in the field of inertial sensors, and could offer a very low power technique for achieving navigation grade inertial measurement units.

  15. Observations of magnetospheric ionization enhancements using upper-hybrid resonance noise band data from the RAE-1 satellite

    NASA Technical Reports Server (NTRS)

    Mosier, S. R.

    1975-01-01

    Noise bands associated with the upper-hybrid resonance were used to provide direct evidence for the existence of regions of enhanced density in the equatorial magnetosphere near L = 2. Density enhancements ranging from several percent to as high as 45 percent are observed with radial dimensions of several hundred kilometers. The enhancement characteristics strongly suggest their identification as magnetospheric whistler ducts.

  16. Joint application of a statistical optimization process and Empirical Mode Decomposition to Magnetic Resonance Sounding Noise Cancelation

    NASA Astrophysics Data System (ADS)

    Ghanati, Reza; Fallahsafari, Mahdi; Hafizi, Mohammad Kazem

    2014-12-01

    The signal quality of Magnetic Resonance Sounding (MRS) measurements is a crucial criterion. The accuracy of the estimation of the signal parameters (i.e. E0 and T2*) strongly depends on amplitude and conditions of ambient electromagnetic interferences at the site of investigation. In this paper, in order to enhance the performance in the noisy environments, a two-step noise cancelation approach based on the Empirical Mode Decomposition (EMD) and a statistical method is proposed. In the first stage, the noisy signal is adaptively decomposed into intrinsic oscillatory components called intrinsic mode functions (IMFs) by means of the EMD algorithm. Afterwards based on an automatic procedure the noisy IMFs are detected, and then the partly de-noised signal is reconstructed through the no-noise IMFs. In the second stage, the signal obtained from the initial section enters an optimization process to cancel the remnant noise, and consequently, estimate the signal parameters. The strategy is tested on a synthetic MRS signal contaminated with Gaussian noise, spiky events and harmonic noise, and on real data. By applying successively the proposed steps, we can remove the noise from the signal to a high extent and the performance indexes, particularly signal to noise ratio, will increase significantly.

  17. Thermo-optically tuned photonic resonators with concurrent electrical connection and thermal isolation

    DOEpatents

    Lentine, Anthony L.; Kekatpure, Rohan Deodatta; Zortman, William A.; Savignon, Daniel J.

    2016-06-14

    A photonic resonator system is designed to use thermal tuning to adjust the resonant wavelength of each resonator in the system, with a separate tuning circuit associated with each resonator so that individual adjustments may be made. The common electrical ground connection between the tuning circuits is particularly formed to provide thermal isolation between adjacent resonators by including a capacitor along each return path to ground, where the presence of the capacitor's dielectric material provides the thermal isolation. The use of capacitively coupling necessarily requires the use of an AC current as an input to the heater element (conductor/resistor) of each resonator, where the RMS value of the AC signal is indicative of the amount of heat that is generated along the element and the degree of wavelength tuning that is obtained.

  18. Study of thermal and acoustic noise interferences in low stiffness atomic force microscope cantilevers and characterization of their dynamic properties

    SciTech Connect

    Boudaoud, Mokrane; Haddab, Yassine; Le Gorrec, Yann; Lutz, Philippe

    2012-01-15

    The atomic force microscope (AFM) is a powerful tool for the measurement of forces at the micro/nano scale when calibrated cantilevers are used. Besides many existing calibration techniques, the thermal calibration is one of the simplest and fastest methods for the dynamic characterization of an AFM cantilever. This method is efficient provided that the Brownian motion (thermal noise) is the most important source of excitation during the calibration process. Otherwise, the value of spring constant is underestimated. This paper investigates noise interference ranges in low stiffness AFM cantilevers taking into account thermal fluctuations and acoustic pressures as two main sources of noise. As a result, a preliminary knowledge about the conditions in which thermal fluctuations and acoustic pressures have closely the same effect on the AFM cantilever (noise interference) is provided with both theoretical and experimental arguments. Consequently, beyond the noise interference range, commercial low stiffness AFM cantilevers are calibrated in two ways: using the thermal noise (in a wide temperature range) and acoustic pressures generated by a loudspeaker. We then demonstrate that acoustic noises can also be used for an efficient characterization and calibration of low stiffness AFM cantilevers. The accuracy of the acoustic characterization is evaluated by comparison with results from the thermal calibration.

  19. Experimental evidence of simultaneous multi-resonance noise reduction using an absorber with essential nonlinearity under two excitation frequencies

    NASA Astrophysics Data System (ADS)

    Côte, Renaud; Pachebat, Marc; Bellizzi, Sergio

    2014-09-01

    The addition of an essentially nonlinear membrane absorber to a linear vibroacoustic system with multiple resonances is studied experimentally, using quasiperiodic excitation. An extended experimental dataset of the system response is analyzed under steady-state excitation at two frequencies. Thresholds between low and high damping states within the system and associated noise reduction are observed and quantified thanks to frequency conversion and RMS efficiency indicators. Following previous numerical results, it is shown that the membrane NES (Nonlinear Energy Sink) acts simultaneously and efficiently on two acoustic resonances. In all cases, the introduction of energy at a second excitation frequency appears favorable to lower the frequency conversion threshold and to lower the noise within the system. In particular, a simultaneous control of two one-to-one resonances by the NES is observed. Exploration of energy conversion in the two excitation amplitudes plane advocates for a linear dependence of the frequency conversion thresholds on the two excitation amplitudes.

  20. Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids

    NASA Astrophysics Data System (ADS)

    Balderas-López, J. A.; Mandelis, A.; Garcia, J. A.

    2000-07-01

    A liquid-ambient-compatible thermal wave resonant cavity (TWRC) has been constructed for the measurement of the thermal diffusivity of liquids. The thermal diffusivities of distilled water, glycerol, ethylene glycol, and olive oil were determined at room temperature (25 °C), with four-significant-figure precision as follows: (0.1445±0.0002)×10-2 cm2/s (distilled water); (0.0922±0.0002)×10-2 cm2/s (glycerol); (0.0918±0.0002)×10-2 cm2/s (ethylene glycol); and (0.0881±0.0004)×10-2 cm2/s (olive oil). The liquid-state TWRC sensor was found to be highly sensitive to various mixtures of methanol and salt in distilled water with sensitivity limits 0.5% (v/v) and 0.03% (w/v), respectively. The use of the TWRC to measure gas evolution from liquids and its potential for environmental applications has also been demonstrated.

  1. Diurnal variations of ELF transients and background noise in the Schumann resonance band

    NASA Astrophysics Data System (ADS)

    Greenberg, Eran; Price, Colin

    2007-02-01

    Schumann resonances (SR) are resonant electromagnetic waves in the Earth-ionosphere cavity, induced primarily by lightning discharges, with a fundamental frequency of about 8 Hz and higher-order modes separated by approximately 6 Hz. The SR are made up of the background signal resulting from global lightning activity and extremely low frequency (ELF) transients resulting from particularly intense lightning discharges somewhere on the planet. Since transients within the Earth-ionosphere cavity due to lightning propagate globally in the ELF range, we can monitor and study global ELF transients from a single station. Data from our Negev Desert (Israel) ELF site are collected using two horizontal magnetic induction coils and a vertical electric field ball antenna, monitored in the 5-40 Hz range with a sampling frequency of 250 Hz. In this paper we present statistics related to the probability distribution of ELF transients and background noise in the time domain and its temporal variations during the day. Our results show that the ELF signal in the time domain follows the normal distribution very well. The σ parameter exhibits three peaks at 0800, 1400, and 2000 UT, which are related to the three main global lightning activity centers in Asia, Africa, and America, respectively. Furthermore, the occurrence of intense ELF events obeys the Poisson distribution, with such intense events occurring every ~10 s, depending on the time of the day. We found that the diurnal changes of the σ parameter are several percent of the mean, while for the number of intense events per minute, the diurnal changes are tens of percent about the mean. We also present the diurnal changes of the SR intensities in the frequency domain as observed at our station. To better understand the diurnal variability of the observations, we simulated the measured ELF background noise using space observations as input, as detected by the Optical Transient Detector (OTD). The most active center which is

  2. Electrically Isolating Thermally Coupled Device for Noise Suppression of Circuits in Deep Space

    NASA Technical Reports Server (NTRS)

    Mantooth, A.; McNutt, T.; Mojarradi, M.; Li, H.; Blalock, B.

    2001-01-01

    Mixed mode rad hard avionics Systems on a Chip (SoC) designed for deep space applications such as Europa orbiters and Europa Landers will require data isolation circuits to block noise. This paper presents the simulation performance for a novel rad hard SOI CMOS compatible thermal transducer used for on-chip data isolation in SoC. The research presented involves the use of commercially available computer aided design tools to model the transient electrothermal behavior of the transducer. Both one- and two-dimensional analyses of a prototype thermal transducer were performed. Results indicate that thermal-based data isolator technology can pass a data bit in under a microsecond and, as a measurement of feasibility, I(exp 2)C bus specifications can be met.

  3. Optimization of microelectrode design for cortical recording based on thermal noise considerations.

    PubMed

    Lempka, Scott F; Johnson, Matthew D; Barnett, David W; Moffitt, Michael A; Otto, Kevin J; Kipke, Daryl R; McIntyre, Cameron C

    2006-01-01

    Intracortical microelectrode recordings of neural activity show great promise as control signals for neuroprosthetic applications. However, faithful, consistent recording of single unit spiking activity with chronically implanted silicon-substrate microelectrode arrays has proven difficult. Many approaches seek to enhance the long-term performance of microelectrode arrays by, for example, increasing electrode biocompatibility, decreasing electrode impedance, or improving electrode interface properties through application of small voltage pulses. The purpose of this study was to use computational models to optimize the design of microelectrodes. We coupled detailed models of the neural source signal, silicon-substrate microelectrodes, and thermal noise to define the electrode contact size that maximized the signal-to-noise ratio (SNR). Model analysis combined a multi-compartment cable model of a layer V cortical pyramidal neuron with a 3D finite element model of the head and microelectrode to define the amplitude and time course of the recorded signal. A spatially-lumped impedance model was parameterized with in vitro and in vivo spectroscopy data and used to define thermal noise as a function of electrode contact size. Our results suggest that intracortical microelectrodes with a contact size of ~380 microm2 will provide an increased SNR in vivo and improve the long-term recording capabilities of silicon-substrate microelectrode arrays. PMID:17947023

  4. Feasibility study of noise analysis methods on virtual thermal reactor subcriticality monitoring

    SciTech Connect

    Kong, C.; Lee, D.; Lee, E.

    2013-07-01

    This paper presents the analysis results of Rossi-alpha, cross-correlation, Feynman-alpha, and Feynman difference methods applied to the subcriticality monitoring of nuclear reactors. A thermal spectrum Godiva model has been designed for the analysis of the four methods. This Godiva geometry consists of a spherical core containing the isotopes of H-l, U-235 and U-238, and the H{sub 2}O reflector outside the core. A Monte Carlo code, McCARD, is used in real time mode to generate virtual detector signals to analyze the feasibility of the four methods. The analysis results indicate that the four methods can be used with high accuracy for the continuous monitoring of subcriticality. In addition to that, in order to analyze the impact of the random noise contamination on the accuracy of the noise analysis, the McCARD-generated signals are contaminated with arbitrary noise. It is noticed that, even when the detector signals are contaminated, the four methods can predict the subcriticality with reasonable accuracy. Nonetheless, in order to reduce the adverse impact of the random noise, eight detector signals, rather than a single signal, are generated from the core, one signal from each equally divided eighth part of the core. The preliminary analysis with multiple virtual detector signals indicates that the approach of using many detectors is promising to improve the accuracy of criticality prediction and further study will be performed in this regard. (authors)

  5. Densely-tiled metal-insulator-metal metamaterial resonators with quasi- monochromatic thermal emission.

    PubMed

    Ito, Kota; Toshiyoshi, Hiroshi; Iizuka, Hideo

    2016-06-13

    Metal-insulator-metal metamaterial thermal emitters strongly radiate at multiple resonant wavelengths. The fundamental mode, whose wavelength is the longest among resonances, is generally utilized for selective emission. In this paper, we show that parasitic modes at shorter wavelengths are suppressed by newly employed densely-tiled resonators, and that the suppression enables quasi-monochromatic thermal emission. The second-order harmonics, which is excited at half the fundamental wavelength in conventional emitters, shifts toward shorter wavelength. The blue-shift reduces the amplitude of the second-order emission by taking a distance from the Wien wavelength. Other parasitic modes are eliminated by the small spacing between resonators. The densely-tiled resonators are fabricated, and the measured emission spectra agree well with numerical simulations. The methodology presented here for the suppression of parasitic modes adds flexibility to metamaterial thermal emitters. PMID:27410299

  6. New Performance Results for Optimum Combining in Presence of Arbitrary-Power Interferers and Thermal Noise

    NASA Astrophysics Data System (ADS)

    Wu, Yongpeng; Ding, Lv; Chen, Jiee; Gao, Xiqi

    This paper studies the optimum combining (OC) system with multiple arbitrary-power interferers and thermal noise in a flat Rayleigh fading environment. The main contribution of the paper is a concise performance analysis for the overload OC system where the number of interferers exceeds or is equal to the number of antennas elements. Simple closed-form formulas are derived for the moment generating function (m.g.f) of the output signal-to-interference-plus-noise ratio (SINR) and the symbol error rate (SER) with M-ary phase shift keying (M-PSK). These formulas are expressed as a finite sum involving polynomial, exponential and exponential integral terms. Based on the derived m.g.f, the closed-form explicit expressions for the moments of the output SINR are determined. Finally, asymptotic analysis illustrates that employing distinguished power control is an effective approach to combat the SER floor for the overload OC system.

  7. Constraints of thermal noise on the effects of weak 60-Hz magnetic fields acting on biological magnetite.

    PubMed Central

    Adair, R K

    1994-01-01

    Previous calculations of limits imposed by thermal noise on the effects of weak 60-Hz magnetic fields on biological magnetite are generalized and extended to consider multiple signals, the possibility of anomalously large magnetosome structures, and the possibility of anomalously small cytoplasm viscosities. The results indicate that the energies transmitted to the magnetite elements by fields less than 5 microT, characteristic of the electric power distribution system, will be much less than thermal noise energies. Hence, the effects of such weak fields will be masked by that noise and cannot be expected to affect biology or, therefore, the health of populations. PMID:8159681

  8. Resonance cone measurements of non-thermal plasma properties in the mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Piel, A.; Oyama, K.-I.; Thiemann, H.; Morioka, A.

    Resonance cone data obtained during the Corex experiment on January 25, 1988, were used to evaluate the electron density and temperature in the midlatitude ionosphere. The electron temperature obtained from the resonance cone measurements was found to be close to gas temperature, while the thermal electron detector results resulted in much higher temperatures, indicating that actual distribution may be characterized by two characteristic temperatures.

  9. Optical Resonance Shifts in the Fluorescence of Thermal and Cold Atomic Gases

    NASA Astrophysics Data System (ADS)

    Jenkins, S. D.; Ruostekoski, J.; Javanainen, J.; Bourgain, R.; Jennewein, S.; Sortais, Y. R. P.; Browaeys, A.

    2016-05-01

    We show that the resonance shifts in the fluorescence of a cold gas of rubidium atoms substantially differ from those of thermal atomic ensembles that obey the standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements of the resonance shifts in a steady-state response in light propagation.

  10. Estimation of neutron energy for first resonance from absorption cross section for thermal neutrons

    NASA Technical Reports Server (NTRS)

    Bogart, Donald

    1951-01-01

    Examination of published data for some 52 isotopes indicates that the neutron energy for which the first resonance occurs is related to the magnitude of the thermal absorption cross section. The empirical relation obtained is in qualitative agreement with the results of a simplified version of the resonance theory of the nucleus of Breit-Wigner.

  11. Optical Resonance Shifts in the Fluorescence of Thermal and Cold Atomic Gases.

    PubMed

    Jenkins, S D; Ruostekoski, J; Javanainen, J; Bourgain, R; Jennewein, S; Sortais, Y R P; Browaeys, A

    2016-05-01

    We show that the resonance shifts in the fluorescence of a cold gas of rubidium atoms substantially differ from those of thermal atomic ensembles that obey the standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements of the resonance shifts in a steady-state response in light propagation. PMID:27203321

  12. Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

    NASA Astrophysics Data System (ADS)

    Dillon, C. R.; Borasi, G.; Payne, A.

    2016-01-01

    For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one.

  13. Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data.

    PubMed

    Dillon, C R; Borasi, G; Payne, A

    2016-01-21

    For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one. PMID:26741344

  14. Brownian Thermal Noise in Interferometric Gravitational Wave Detectors and Single Photon Optomechanics

    NASA Astrophysics Data System (ADS)

    Hong, Ting

    The Laser Interferometric Gravitational-Wave Observatory (LIGO) is designed to detect the Gravitational Waves (GW) predicted by Albert Einstein's general theory of relativity. The advanced LIGO project is ongoing an upgrade to increase the detection sensitivity by more than a factor of 10, which will make the events detection a routine occurrence. In addition to using higher power lasers, heavier test mass, and better isolation systems, several new designs and techniques are proposed in the long-term upgrade, such as modifying the optics configuration to reduce the quantum noise, active noise cancellation of the Newtonian noise, optimizing the coating structure, and employing non-Guassian laser beams etc. In the first part of my thesis (Chapters 2 and 3), I apply statistical mechanics and elastostatics to the LIGO coated mirrors, and study the thermal fluctuations that dominate advanced LIGO's most sensitive frequency band from 40 Hz to 200 Hz. In particular, in Chapter 2, I study the so-called coating Brownian noise, fluctuations of mirrors coated with multiple layers of dielectrics due to internal friction. Assuming coating materials to be isotropic and homogeneous, I calculate the cross spectra of Brownian fluctuations in the bulk and shear strains of the coating layers, as well as fluctuations in the height of the coating-substrate interface. The additional phase shifting and back-scattering caused by photo elastic effects are also considered for the first time. In Chapter 3, I study whether it is realistic to adopt higher-order Laguerre-Gauss modes in LIGO, in order to mitigate the effect of mirror thermal noise. We investigate the effect on the detector's contrast defect caused by the mode degeneracy. With both analytical calculation and numerical simulation, we show that with this approach, the detector's susceptibility to mirror figure errors is reduced greatly compared to using the nondegenerate modes, therefore making it unacceptable for LIGO requirements

  15. Noise-induced resonance-like phenomena in InP crystals embedded in fluctuating electric fields

    NASA Astrophysics Data System (ADS)

    Persano Adorno, D.; Pizzolato, N.; Spagnolo, B.

    2016-05-01

    We explore and discuss the complex electron dynamics inside a low-doped n-type InP bulk embedded in a sub-THz electric field, fluctuating for the superimposition of an external source of Gaussian correlated noise. The results presented in this study derive from numerical simulations obtained by means of a multi-valley Monte Carlo approach to simulate the nonlinear transport of electrons inside the semiconductor crystal. The electronic noise characteristics are statistically investigated by calculating the correlation function of the velocity fluctuations, its spectral density and the integrated spectral density, i.e. the total noise power, for different values of both amplitude and frequency of the driving oscillating electric field and for different correlation times of the field fluctuations. Our results show that the nonlinear response of electrons is strongly affected by the field fluctuations. In particular, crucially depending on the relationship between the correlation times of the external Gaussian noise and the timescales of complex phenomena involved in the electron dynamical behavior: (i) electrons self-organize among different valleys, giving rise to intrinsic noise suppression; (ii) this cooperative behavior causes the appearance of a resonance-like phenomenon in the noise spectra.

  16. An improved multiscale noise tuning of stochastic resonance for identifying multiple transient faults in rolling element bearings

    NASA Astrophysics Data System (ADS)

    Wang, Jun; He, Qingbo; Kong, Fanrang

    2014-12-01

    Stochastic resonance (SR), a noise-assisted tool, has been proved to be very powerful in weak signal detection. The multiscale noise tuning SR (MSTSR), which breaks the restriction of the requirement of small parameters and white noise in classical SR, has been applied to identify the characteristic frequency of a bearing. However, the multiscale noise tuning (MST), which is originally based on discrete wavelet transform (DWT), limits the signal-to-noise ratio (SNR) improvement of SR and the performance in identifying multiple bearing faults. In this paper, the wavelet packet transform (WPT) is developed and incorporated into the MSTSR method to overcome its shortcomings and to further enhance its capability in multiple faults detection of bearings. The WPT-based MST can achieve a finer tuning of multiscale noise and aims at detecting multiple target frequencies separately. By introducing WPT into the MST of SR, this paper proposes an improved SR method particularly suited for the identification of multiple transient faults in rolling element bearings. Simulated and practical bearing signals carrying multiple characteristic frequencies are employed to validate the performance improvement of the proposed method as compared to the original DWT-based MSTSR method. The results confirm the good capability of the proposed method in multi-fault diagnosis of rolling element bearings.

  17. Self-sustained oscillation limit of tube bundle resonant noise. (Phase 1: Evaluation equation of oscillation limit)

    SciTech Connect

    Nishimura, M.; Fujita, K.; Hasegawa, N.

    1995-12-01

    Self-sustained oscillation limit of tube bundle resonant noise is studied in this paper. Excited acoustic energy and dissipating one in tube bundle are derived theoretically. In the exciting stage, the acoustic field is considered to be fed back to the flow field as the inlet flow fluctuation. And the acoustic damping is considered to induce the dissipating energy. Based on the energy balance of both and dimensional analysis, a new simple evaluation equation of self-sustained oscillation limit is proposed concerning on tube bundle resonant noise. A typical experimental results are evaluated based on this equation. The results are roughly good, but this suggests that model analysis of both exciting energy and dissipating one is necessary for more precise evaluation.

  18. Thermal effects on mass detection sensitivity of carbon nanotube resonators in nonlinear oscillation regime

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Keun; Yang, Hyun-Ik; Kim, Chang-Wan

    2015-11-01

    A mass sensor using a nano-resonator has high detection sensitivity, and mass sensitivity is higher with smaller resonators. Therefore, carbon nanotubes (CNTs) are the ultimate materials for these applications and have been actively studied. In particular, CNT-based nanomechanical devices may experience high temperatures that lead to thermal expansion and residual stress in devices, which affects the device reliability. In this letter, to demonstrate the influence of the temperature change (i.e., thermal effect) on the mass detection sensitivity of CNT-based mass sensor, dynamic analysis is carried out for a CNT resonator with thermal effects in both linear and nonlinear oscillation regimes. Based on the continuum mechanics model, the analytical solution method with an assumed deflection eigenmode is applied to solve the nonlinear differential equation which involves the von Karman nonlinear strain-displacement relation and the additional axial force associated with thermal effects. A thermal effect on the fundamental resonance behavior and resonance frequency shift due to adsorbed mas, i.e., mass detection sensitivity, is examined in high-temperature environment. Results indicate a valid improvement of fundamental resonance frequency by using nonlinear oscillation in a thermal environment. In both linear and nonlinear oscillation regimes, the mass detection sensitivity becomes worse due to the increasing of temperature in a high-temperature environment. The thermal effect on the detection sensitivity is less effective in the nonlinear oscillation regime. It is concluded that a temperature change of a mass sensor with a CNT-based resonator can be utilized to enhance the detection sensitivity depending on the CNT length, linear/nonlinear oscillation behaviors, and the thermal environment.

  19. Statistical Properties of Thermal Noise Driving the Brownian Particles in Fluids

    NASA Astrophysics Data System (ADS)

    Tóthová, Jana; Lisý, Vladimír

    2016-02-01

    In several recent works high-resolution interferometric detection allowed to study the Brownian motion of optically trapped microparticles in air and fluids. The observed positional fluctuations of the particles are well described by the generalized Langevin equation with the Boussinesq-Basset "history force" instead of the Stokes friction, which is valid only for the steady motion. Recently, also the time correlation function of the thermal random force Fth driving the Brownian particles through collisions with the surrounding molecules has been measured. In the present contribution we propose a method to describe the statistical properties of Fth in incompressible fluids. Our calculations show that the time decay of the correlator is significantly slower than that found in the literature. It is also shown how the "color" of the thermal noise can be determined from the measured positions of the Brownian particles.

  20. In-flight thermal experiments for LISA Pathfinder: Simulating temperature noise at the Inertial Sensors

    NASA Astrophysics Data System (ADS)

    Gibert, F.; Nofrarias, M.; Armano, M.; Audley, H.; Auger, G.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Bursi, A.; Caleno, M.; Cavalleri, A.; Cesarini, A.; Cruise, M.; Danzmann, K.; Diepholz, I.; Dolesi, R.; Dunbar, N.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E.; Freschi, M.; Gallegos, J.; García Marirrodriga, C.; Gerndt, R.; Gesa, Ll; Giardini, D.; Giusteri, R.; Grimani, C.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hueller, M.; Huesler, J.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C.; Lloro, I.; Maarschalkerweerd, R.; Madden, S.; Maghami, P.; Mance, D.; Martín, V.; Martin-Porqueras, F.; Mateos, I.; McNamara, P.; Mendes, J.; Mendes, L.; Moroni, A.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Prat, P.; Ragnit, U.; Ramos-Castro, J.; Reiche, J.; Romera Perez, J. A.; Robertson, D.; Rozemeijer, H.; Russano, G.; Sarra, P.; Schleicher, A.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J.; Trenkel, C.; Tu, H. B.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Waschke, S.; Wass, P.; Wealthy, D.; Wen, S.; Weber, W.; Wittchen, A.; Zanoni, C.; Ziegler, T.; Zweifel, P.

    2015-05-01

    Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations.

  1. In-flight thermal experiments for LISA Pathfinder: Simulating temperature noise at the Inertial Sensors

    NASA Astrophysics Data System (ADS)

    Armano, M.; Audley, H.; Auger, G.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Bursi, A.; Caleno, M.; Cavalleri, A.; Cesarini, A.; Cruise, M.; Danzmann, K.; Diepholz, I.; Dolesi, R.; Dunbar, N.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E.; Freschi, M.; Gallegos, J.; García Marirrodriga, C.; Gerndt, R.; Gesa, Ll; Gibert, F.; Giardini, D.; Giusteri, R.; Grimani, C.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hueller, M.; Huesler, J.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C.; Lloro, I.; Maarschalkerweerd, R.; Madden, S.; Maghami, P.; Mance, D.; Martín, V.; Martin-Porqueras, F.; Mateos, I.; McNamara, P.; Mendes, J.; Mendes, L.; Moroni, A.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Prat, P.; Ragnit, U.; Ramos-Castro, J.; Reiche, J.; Romera Perez, J. A.; Robertson, D.; Rozemeijer, H.; Russano, G.; Sarra, P.; Schleicher, A.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J.; Trenkel, C.; Tu, H. B.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Waschke, S.; Wass, P.; Wealthy, D.; Wen, S.; Weber, W.; Wittchen, A.; Zanoni, C.; Ziegler, T.; Zweifel, P.

    2015-04-01

    Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations.

  2. CFD simulation of pulsation noise in a small centrifugal compressor with volute and resonance tube

    NASA Astrophysics Data System (ADS)

    Wakaki, Daich; Sakuka, Yuta; Inokuchi, Yuzo; Ueda, Kosuke; Yamasaki, Nobuhiko; Yamagata, Akihiro

    2015-02-01

    The rotational frequency tone noise emitted from the automobile turbocharger is called the pulsation noise. The cause of the pulsation noise is not fully understood, but is considered to be due to some manufacturing errors, which is called the mistuning. The effects of the mistuning of the impeller blade on the noise field inside the flow passage of the compressor are numerically investigated. Here, the flow passage includes the volute and duct located downstream of the compressor impeller. Our numerical approach is found to successfully capture the wavelength of the pulsation noise at given rotational speeds by the comparison with the experiments. One of the significant findings is that the noise field of the pulsation noise in the duct is highly one-dimensional although the flow fields are highly three-dimensional.

  3. Effects of Thermal Noise on the Transitional Dynamics of an Inextensible Elastic Filament in Stagnation Flow

    PubMed Central

    Deng, Mingge; Grinberg, Leopold; Caswell, Bruce

    2015-01-01

    We investigate the dynamics of a single inextensible elastic filament subject to anisotropic friction in a viscous stagnation-point flow, by employing both a continuum model represented by Langevin type stochastic partial differential equations (SPDEs) and a Dissipative Particle Dynamics (DPD) method. Unlike previous works1, the filament is free to rotate and the tension along the filament is determined by the local inextensible constraint. The kinematics of the filament is recorded and studied with normal modes analysis. The results show that the filament displays an instability induced by negative tension, which is analogous to Euler buckling of a beam. Symmetry breaking of normal modes dynamics and stretch-coil transitions are observed above the threshold of the buckling instability point. Furthermore, both temporal and spatial noise are amplified resulting from the interaction of thermal fluctuations and nonlinear filament dynamics. Specifically, the spatial noise is amplified with even normal modes being excited due to symmetry breaking, while the temporal noise is amplified with increasing time correlation length and variance. PMID:26023834

  4. Effect of temperature variations and thermal noise on the static and dynamic behavior of straintronics devices

    NASA Astrophysics Data System (ADS)

    Barangi, Mahmood; Mazumder, Pinaki

    2015-11-01

    A theoretical model quantifying the effect of temperature variations on the magnetic properties and static and dynamic behavior of the straintronics magnetic tunneling junction is presented. Four common magnetostrictive materials (Nickel, Cobalt, Terfenol-D, and Galfenol) are analyzed to determine their temperature sensitivity and to provide a comprehensive database for different applications. The variations of magnetic anisotropies are studied in detail for temperature levels up to the Curie temperature. The energy barrier of the free layer and the critical voltage required for flipping the magnetization vector are inspected as important metrics that dominate the energy requirements and noise immunity when the device is incorporated into large systems. To study the dynamic thermal noise, the effect of the Langevin thermal field on the free layer's magnetization vector is incorporated into the Landau-Lifshitz-Gilbert equation. The switching energy, flipping delay, write, and hold error probabilities are studied, which are important metrics for nonvolatile memories, an important application of the straintronics magnetic tunneling junctions.

  5. Noise reduction of nuclear magnetic resonance (NMR) transversal data using improved wavelet transform and exponentially weighted moving average (EWMA)

    NASA Astrophysics Data System (ADS)

    Ge, Xinmin; Fan, Yiren; Li, Jiangtao; Wang, Yang; Deng, Shaogui

    2015-02-01

    NMR logging and core NMR signals acts as an effective way of pore structure evaluation and fluid discrimination, but it is greatly contaminated by noise for samples with low magnetic resonance intensity. Transversal relaxation time (T2) spectrum obtained by inversion of decay signals intrigued by Carr-Purcell-Meiboom-Gill (CPMG) sequence may deviate from the truth if the signal-to-noise ratio (SNR) is imperfect. A method of combing the improved wavelet thresholding with the EWMA is proposed for noise reduction of decay data. The wavelet basis function and decomposition level are optimized in consideration of information entropy and white noise estimation firstly. Then a hybrid threshold function is developed to avoid drawbacks of hard and soft threshold functions. To achieve the best thresholding values of different levels, a nonlinear objective function based on SNR and mean square error (MSE) is constructed, transforming the problem to a task of finding optimal solutions. Particle swarm optimization (PSO) is used to ensure the stability and global convergence. EWMA is carried out to eliminate unwanted peaks and sawtooths of the wavelet denoised signal. With validations of numerical simulations and experiments, it is demonstrated that the proposed approach can reduce the noise of T2 decay data perfectly.

  6. Chapter 3 Exact Signal-Noise Separation by Froissart Doublets in Fast Padé Transform for Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Belkic, Dz; Evad

    In the present study, it is demonstrated that the fast padé transform (FPT) is capable of providing the exponential convergence rate (the spectral convergence) for the exact reconstructions of all the spectral parameters from time signals equivalent to the corresponding in vivo free induction decay curves encoded by means of magnetic resonance spectroscopy with short echo times of about 20 ms at the standard clinical magnetic field strength 1.5 T from the brain of a healthy volunteer. Further, it is shown that residual spectra (the difference between the model and input spectra) are a necessary, but not a sufficient, criterion to estimate the error invoked in quantification. Full validation of the performed quantification within the FPT is possible by monitoring stabilization of all the reconstructed spectral parameters as a function of the partial signal length for a fixed bandwidth (this is equivalent to varying the total acquisition time). Moreover, all the converged fundamental frequencies and amplitudes found in this way must further be cross-validated by checking whether they also represent the joint results of both Padé variants, the FPT(+) and the FPT(-), inside and outside the unit circle, as done in the present study. The Froissart doublets (pole-zero cancellations) are used to unequivocally distinguish between genuine and spurious resonances in both noise-free and noise-corrupted time signals. This permits the exact reconstruction of all the genuine spectral parameters including the fundamental frequencies, the corresponding amplitudes, and the true number of physical resonances. The FPT is shown to be able to resolve and quantify tightly overlapped resonances that are abundantly seen in magnetic resonance spectra generated using encoded in vivo time signals. Most importantly, precisely such overlapping resonances are often of critical relevance for diagnostics in clinical oncology.

  7. Frequency-dependent hydrodynamic inductance and the determination of the thermal and quantum noise of a superfluid gyroscope

    SciTech Connect

    Chui, Talso; Penanen, Konstantin

    2005-04-01

    We reexamine mass flow in a superfluid gyroscope containing a superfluid Josephson weak link. We introduce a frequency-dependent hydrodynamic inductance to account for an oscillatory flow of the normal fluid component in the sensing loop. With this hydrodynamic inductance, we derive the thermal phase noise, and hence the thermal rotational noise of the gyroscope. We examine the thermodynamic stability of the system based on an analysis of the free energy. We derive a quantum phase noise, which is analogous to the zero-point motion of a simple harmonic oscillator. The configuration of the studied gyroscope is analogous to a conventional superconducting RF SQUID. We show that the gyroscope has very low intrinsic noise (1.9x10{sup -13} rad s{sup -1}/{radical}(Hz)), and it can potentially be applied to study general relativity, Earth science, and to improve global positioning systems (GPS)

  8. Noise analysis in fast magnetic resonance electrical impedance tomography (MREIT) based on spoiled multi gradient echo (SPMGE) pulse sequence

    NASA Astrophysics Data System (ADS)

    In Oh, Tong; Jeong, Woo Chul; Kim, Ji Eun; Sajib, Saurav Z. K.; Kim, Hyung Joong; In Kwon, Oh; Woo, Eung Je

    2014-08-01

    Magnetic resonance electrical impedance tomography (MREIT) is a promising non-invasive method to visualize a static cross-sectional conductivity and/or current density image by injecting low frequency currents. MREIT measures one component of the magnetic flux density caused by the injected current using a magnetic resonance (MR) scanner. For practical in vivo implementations of MREIT, especially for soft biological tissues where the MR signal rapidly decays, it is crucial to develop a technique for optimizing the magnetic flux density signal by the injected current while maintaining spatial-resolution and contrast. We design an MREIT pulse sequence by applying a spoiled multi-gradient-echo pulse sequence (SPMGE) to the injected current nonlinear encoding (ICNE), which fully injects the current at the end of the read-out gradient. The applied ICNE-SPMGE pulse sequence maximizes the duration of injected current almost up to a repetition time by measuring multiple magnetic flux density data. We analyze the noise level of measured magnetic flux density with respect to the pulse width of injection current and T_{2}^{*} relaxation time. In due consideration of the ICNE-SPMGE pulse sequence, using a reference information of T_{2}^{*} values in a local region of interest by a short pre-scan data, we predict the noise level of magnetic flux density to be measured for arbitrary repetition time TR. Results from phantom experiment demonstrate that the proposed method can predict the noise level of magnetic flux density for an appropriate TR = 40 ms using a reference scan for TR = 75 ms. The predicted noise level was compared with the noise level of directly measured magnetic flux density data.

  9. Effect of negative emotions evoked by light, noise and taste on trigeminal thermal sensitivity

    PubMed Central

    2014-01-01

    Background Patients with migraine often have impaired somatosensory function and experience headache attacks triggered by exogenous stimulus, such as light, sound or taste. This study aimed to assess the influence of three controlled conditioning stimuli (visual, auditory and gustatory stimuli and combined stimuli) on affective state and thermal sensitivity in healthy human participants. Methods All participants attended four experimental sessions with visual, auditory and gustatory conditioning stimuli and combination of all stimuli, in a randomized sequence. In each session, the somatosensory sensitivity was tested in the perioral region with use of thermal stimuli with and without the conditioning stimuli. Positive and Negative Affect States (PANAS) were assessed before and after the tests. Subject based ratings of the conditioning and test stimuli in addition to skin temperature and heart rate as indicators of arousal responses were collected in real time during the tests. Results The three conditioning stimuli all induced significant increases in negative PANAS scores (paired t-test, P ≤0.016). Compared with baseline, the increases were in a near dose-dependent manner during visual and auditory conditioning stimulation. No significant effects of any single conditioning stimuli were observed on trigeminal thermal sensitivity (P ≥0.051) or arousal parameters (P ≥0.057). The effects of combined conditioning stimuli on subjective ratings (P ≤0.038) and negative affect (P = 0.011) were stronger than those of single stimuli. Conclusions All three conditioning stimuli provided a simple way to evoke a negative affective state without physical arousal or influence on trigeminal thermal sensitivity. Multisensory conditioning had stronger effects but also failed to modulate thermal sensitivity, suggesting that so-called exogenous trigger stimuli e.g. bright light, noise, unpleasant taste in patients with migraine may require a predisposed or sensitized nervous

  10. Increasing the resolution and the signal-to-noise ratio of magnetic resonance sounding data using a central loop configuration

    NASA Astrophysics Data System (ADS)

    Behroozmand, Ahmad A.; Auken, Esben; Fiandaca, Gianluca; Rejkjaer, Simon

    2016-04-01

    Surface nuclear magnetic resonance technique, also called magnetic resonance sounding (MRS), is an emerging geophysical method that can detect the presence and spatial variations of the subsurface water content directly. In this paper, we introduce the MRS central loop geometry, in which the receiver loop is smaller than the transmitter loop and placed in its centre. In addition, using a shielded receiver coil we show how this configuration greatly increases signal-to-noise ratio and improves the resolution of the subsurface layers compared to the typically used coincident loop configuration. We compare sensitivity kernels for different loop configurations and describe advantages of the MRS central loop geometry in terms of superior behaviour of the sensitivity function, increased sensitivity values, reduced noise level of the shielded receiver coil, improved resolution matrix and reduced instrument dead time. With no extra time and effort in the field, central-loop MRS makes it possible to reduce measurement time and to measure data in areas with high anthropogenic noise. The results of our field example agree well with the complementary data, namely airborne electromagnetics, borehole data, and the hydrologic model of the area.

  11. Electron Paramagnetic Resonance Study of Thermally Treated Bismuth Subgallate

    PubMed Central

    Ramos, Paweł; Pilawa, Barbara

    2014-01-01

    Complex of bismuth, an anti-inflammatory drug, was studied by EPR spectroscopy. The aim of this study was to determine concentrations and properties of free radicals formed during thermal sterilization of bismuth subgallate according to pharmacopoeia norms to optimize its sterilization process. Different temperatures (160°C, 170°C, and 180°C) and times (120 minutes, 60 minutes, and 30 minutes) of sterilization were used. Interactions of bismuth subgallate with DPPH, the model free radical reference, were checked. g-Factors, amplitudes (A), integral intensities (I), and linewidths (ΔBpp) were obtained. Integral intensities were obtained by double integration of the first-derivative EPR lines. The influence of microwave power in the range of 2.2–70 mW on shape and parameters of the EPR spectra was examined. Thermal sterilization produced free radicals in bismuth subgallate in all tested cases. Strong interactions with free radicals were pointed out for all the analysed samples containing bismuth independent of sterilization conditions. Optimal conditions of thermal sterilization for bismuth subgallate with the lowest free radical formation are temperature 170°C and time of heating 60 minutes. Strong dipolar interactions exist in thermally sterilized bismuth subgallate. EPR spectroscopy is a useful method of examination of thermal sterilization conditions. PMID:25525421

  12. Electron paramagnetic resonance study of thermally treated bismuth subgallate.

    PubMed

    Ramos, Paweł; Pilawa, Barbara

    2014-01-01

    Complex of bismuth, an anti-inflammatory drug, was studied by EPR spectroscopy. The aim of this study was to determine concentrations and properties of free radicals formed during thermal sterilization of bismuth subgallate according to pharmacopoeia norms to optimize its sterilization process. Different temperatures (160°C, 170°C, and 180°C) and times (120 minutes, 60 minutes, and 30 minutes) of sterilization were used. Interactions of bismuth subgallate with DPPH, the model free radical reference, were checked. g-Factors, amplitudes (A), integral intensities (I), and linewidths (ΔB pp) were obtained. Integral intensities were obtained by double integration of the first-derivative EPR lines. The influence of microwave power in the range of 2.2-70 mW on shape and parameters of the EPR spectra was examined. Thermal sterilization produced free radicals in bismuth subgallate in all tested cases. Strong interactions with free radicals were pointed out for all the analysed samples containing bismuth independent of sterilization conditions. Optimal conditions of thermal sterilization for bismuth subgallate with the lowest free radical formation are temperature 170°C and time of heating 60 minutes. Strong dipolar interactions exist in thermally sterilized bismuth subgallate. EPR spectroscopy is a useful method of examination of thermal sterilization conditions. PMID:25525421

  13. A low noise and high precision linear power supply with thermal foldback protection

    NASA Astrophysics Data System (ADS)

    Carniti, P.; Cassina, L.; Gotti, C.; Maino, M.; Pessina, G.

    2016-05-01

    A low noise and high precision linear power supply was designed for use in rare event search experiments with macrobolometers. The circuit accepts at the input a "noisy" dual supply voltage up to ±15 V and gives at the output precise, low noise, and stable voltages that can be set between ±3.75 V and ±12.5 V in eight 1.25 V steps. Particular care in circuit design, component selection, and proper filtering results in a noise spectral density of 50 nV / √{ Hz } at 1 Hz and 20 nV / √{ Hz } white when the output is set to ±5 V. This corresponds to 125 nV RMS (0.8 μV peak to peak) between 0.1 Hz and 10 Hz, and 240 nV RMS (1.6 μV peak to peak) between 0.1 Hz and 100 Hz. The power supply rejection ratio (PSRR) of the circuit is 100 dB at low frequency, and larger than 40 dB up to high frequency, thanks to a proper compensation design. Calibration allows to reach a precision in the absolute value of the output voltage of ±70 ppm, or ±350 μV at ±5 V, and to reduce thermal drifts below ±1 ppm/∘C in the expected operating range. The maximum peak output current is about 6 A from each output. An original foldback protection scheme was developed that dynamically limits the maximum output current to keep the temperature of the output transistors within their safe operating range. An add-on card based on an ARM Cortex-M3 microcontroller is devoted to the monitoring and control of all circuit functionalities and provides remote communication via CAN bus.

  14. Case study. Health hazards of automotive repair mechanics: thermal and lighting comfort, particulate matter and noise.

    PubMed

    Loupa, G

    2013-01-01

    An indoor environmental quality survey was conducted in a small private automotive repair shop during May 2009 (hot season) and February 2010 (cold season). It was established that the detached building, which is naturally ventilated and lit, had all the advantages of the temperate local climate. It provided a satisfactory microclimatic working environment, concerning the thermal and the lighting comfort, without excessive energy consumption for air-conditioning or lighting. Indoor number concentrations of particulate matter (PM) were monitored during both seasons. Their size distributions were strongly affected by the indoor activities and the air exchange rate of the building. During working hours, the average indoor/outdoor (I/O) number concentration ratio was 31 for PM0.3-1 in the hot season and 69 for the cold season. However I/O PM1-10 number concentration ratios were similar, 33 and 32 respectively, between the two seasons. The estimated indoor mass concentration of PM10 for the two seasons was on average 0.68 mg m(-3) and 1.19 mg m(-3), i.e., 22 and 36 times higher than outdoors, during the hot and the cold seasons, respectively. This is indicative that indoor air pollution may adversely affect mechanics' health. Noise levels were highly variable and the average LEX, 8 h of 69.3 dB(A) was below the European Union exposure limit value 87db (A). Noise originated from the use of manual hammers, the revving up of engines, and the closing of car doors or hoods. Octave band analysis indicated that the prevailing noise frequencies were in the area of the maximum ear sensitivity. PMID:23984679

  15. A low noise and high precision linear power supply with thermal foldback protection.

    PubMed

    Carniti, P; Cassina, L; Gotti, C; Maino, M; Pessina, G

    2016-05-01

    A low noise and high precision linear power supply was designed for use in rare event search experiments with macrobolometers. The circuit accepts at the input a "noisy" dual supply voltage up to ±15 V and gives at the output precise, low noise, and stable voltages that can be set between ±3.75 V and ±12.5 V in eight 1.25 V steps. Particular care in circuit design, component selection, and proper filtering results in a noise spectral density of 50nV/Hz at 1 Hz and 20nV/Hz white when the output is set to ±5 V. This corresponds to 125 nV RMS (0.8 μV peak to peak) between 0.1 Hz and 10 Hz, and 240 nV RMS (1.6 μV peak to peak) between 0.1 Hz and 100 Hz. The power supply rejection ratio (PSRR) of the circuit is 100 dB at low frequency, and larger than 40 dB up to high frequency, thanks to a proper compensation design. Calibration allows to reach a precision in the absolute value of the output voltage of ±70 ppm, or ±350 μV at ±5 V, and to reduce thermal drifts below ±1 ppm/(∘)C in the expected operating range. The maximum peak output current is about 6 A from each output. An original foldback protection scheme was developed that dynamically limits the maximum output current to keep the temperature of the output transistors within their safe operating range. An add-on card based on an ARM Cortex-M3 microcontroller is devoted to the monitoring and control of all circuit functionalities and provides remote communication via CAN bus. PMID:27250450

  16. Thermal enhancement and stochastic resonance of polaron ratchets.

    PubMed

    Brizhik, L S; Eremko, A A; Piette, B M A G; Zakrzewski, W J

    2014-06-01

    We study the ratchet drift of large polarons (solitons) in molecular diatomic chains induced by unbiased time periodic electric fields at nonzero temperature below its critical value. We show that, at a nonzero temperature, the critical value of the intensity of the electric field above which the ratchet phenomenon takes place is lower than at zero temperature for the same frequency of the field. We show that there is a range of temperatures for which the polaron drift is larger than that at zero temperature. We also show that temperature decreases the value of the lowest critical period of the field. And, finally, we demonstrate that there is a stochastic resonance in a polaron ratchet, namely that there is an optimal temperature at which the polaron drift is a maximum. The values of the stochastic resonance temperature, the lowest critical values of the field intensity, and its period depend on various parameters of the system and, in particular, on the anisotropy of the chain parameters. This temperature induced decrease of the critical value of the field intensity and its period, as well as the stochastic resonance itself, may be important for practical applications of the ratchet phenomenon in systems involving conducting polymers and other low-dimensional materials. They may also be important in some biological macromolecules where the ratchet phenomenon could take place in biomotors and energy and/or charge transport. PMID:25019849

  17. Thermal enhancement and stochastic resonance of polaron ratchets

    NASA Astrophysics Data System (ADS)

    Brizhik, L. S.; Eremko, A. A.; Piette, B. M. A. G.; Zakrzewski, W. J.

    2014-06-01

    We study the ratchet drift of large polarons (solitons) in molecular diatomic chains induced by unbiased time periodic electric fields at nonzero temperature below its critical value. We show that, at a nonzero temperature, the critical value of the intensity of the electric field above which the ratchet phenomenon takes place is lower than at zero temperature for the same frequency of the field. We show that there is a range of temperatures for which the polaron drift is larger than that at zero temperature. We also show that temperature decreases the value of the lowest critical period of the field. And, finally, we demonstrate that there is a stochastic resonance in a polaron ratchet, namely that there is an optimal temperature at which the polaron drift is a maximum. The values of the stochastic resonance temperature, the lowest critical values of the field intensity, and its period depend on various parameters of the system and, in particular, on the anisotropy of the chain parameters. This temperature induced decrease of the critical value of the field intensity and its period, as well as the stochastic resonance itself, may be important for practical applications of the ratchet phenomenon in systems involving conducting polymers and other low-dimensional materials. They may also be important in some biological macromolecules where the ratchet phenomenon could take place in biomotors and energy and/or charge transport.

  18. Thermal rectification in anharmonic chains under an energy-conserving noise.

    PubMed

    Guimarães, Pedro H; Landi, Gabriel T; de Oliveira, Mário J

    2015-12-01

    Systems in which the heat flux depends on the direction of the flow are said to present thermal rectification. This effect has attracted much theoretical and experimental interest in recent years. However, in most theoretical models the effect is found to vanish in the thermodynamic limit, in disagreement with experiment. The purpose of this paper is to show that the rectification may be restored by including an energy-conserving noise which randomly flips the velocity of the particles with a certain rate λ. It is shown that as long as λ is nonzero, the rectification remains finite in the thermodynamic limit. This is illustrated in a classical harmonic chain subject to a quartic pinning potential (the Φ(4) model) and coupled to heat baths by Langevin equations. PMID:26764645

  19. Exploiting metastability and thermal noise to build a reconfigurable hardware random number generator

    NASA Astrophysics Data System (ADS)

    Lim, Daihyun; Ranasinghe, Damith C.; Devadas, Srinivas; Jamali, Behnam; Abbott, Derek; Cole, Peter H.

    2005-05-01

    While pseudo random number generators based on computational complexity are widely used for most of cryptographic applications and probabilistic simulations, the generation of true random numbers based on physical randomness is required to guarantee the advanced security of cryptographic systems. In this paper we present a method to exploit manufacturing variations, metastablity, and thermal noise in integrated circuits to generate random numbers. This metastability based physical random number generator provides a compact and low-power solution which can be fabricated using standard IC manufacturing processes. Test-chips were fabricated in TSMC 0.18um process and experimental results show that the generated random bits pass standard randomness tests successfully. The operation of the proposed scheme is robust against environmental changes since it can be re-calibrated to new environmental conditions such as temperature and power supply voltage.

  20. A low noise 500 MHz frequency source

    NASA Astrophysics Data System (ADS)

    Vulcan, A.; Bloch, M.; Tanski, W.

    A low-noise signal source providing multiple 500 MHz and 400 MHz outputs is presented whose noise characteristics approach the thermal limit at frequencies spaced greater than 1 MHz from the carrier. The unit uses bulk and surface acoustic wave resonators to insure low phase noise and spurious outputs and is totally redundant for failsafe operation. The packaging concept minimizes subassembly interconnections and provides both physical and electrical independence of two redundant generators; package shielding insures minimum conducted and radiated susceptibility.

  1. White noise response of turbine blades subjected to heat flux and thermal gradient

    SciTech Connect

    Karadag, V.; Aba, E.; Morguel, O.K.

    1997-07-01

    Design and production of the complex mechanical structures rarely result in an optimal solution. A typical example for this is a turbine blade design. Fatigue failures of the turbine blades is one of the most vexing problems of turbo-machine manufacturers, ever since the steam turbine became the main stay for power generating equipment and the gas turbines are increasingly used in air transport. Turbine blade failures due to fatigue are predominantly vibration related. The dynamic loads on the blading can arise from many different sources such as the high rotational speed, the high operating temperatures, the asymmetric aerofil tapered form of the turbine blade etc. Therefore, vibratory analysis is one of the most important stage in the designing of the turbine blades. In this study, the random response of the turbine blade to white noise excitation has been consistently calculated, including the internal damping mechanisms of the blade. Beside the damping effects, the rotational speed and the linear thermal gradient along the turbine blade are incorporated into the analysis. Pressure difference between the two surfaces of the turbine blades are modelled as white noise excitation along all over the turbine blade. The system dynamic equation of motion are derived and solved by using the combined Finite Element-Modal Analysis Method.

  2. Rician noise reduction in magnetic resonance images using adaptive non-local mean and guided image filtering

    NASA Astrophysics Data System (ADS)

    Mahmood, Muhammad Tariq; Chu, Yeon-Ho; Choi, Young-Kyu

    2016-05-01

    This paper proposes a Rician noise reduction method for magnetic resonance (MR) images. The proposed method is based on adaptive non-local mean and guided image filtering techniques. In the first phase, a guidance image is obtained from the noisy image through an adaptive non-local mean filter. Sobel operators are applied to compute the strength of edges which is further used to control the spread of the kernel in non-local mean filtering. In the second phase, the noisy and the guidance images are provided to the guided image filter as input to restore the noise-free image. The improved performance of the proposed method is investigated using the simulated and real data sets of MR images. Its performance is also compared with the previously proposed state-of-the art methods. Comparative analysis demonstrates the superiority of the proposed scheme over the existing approaches.

  3. Rician noise reduction in magnetic resonance images using adaptive non-local mean and guided image filtering

    NASA Astrophysics Data System (ADS)

    Mahmood, Muhammad Tariq; Chu, Yeon-Ho; Choi, Young-Kyu

    2016-06-01

    This paper proposes a Rician noise reduction method for magnetic resonance (MR) images. The proposed method is based on adaptive non-local mean and guided image filtering techniques. In the first phase, a guidance image is obtained from the noisy image through an adaptive non-local mean filter. Sobel operators are applied to compute the strength of edges which is further used to control the spread of the kernel in non-local mean filtering. In the second phase, the noisy and the guidance images are provided to the guided image filter as input to restore the noise-free image. The improved performance of the proposed method is investigated using the simulated and real data sets of MR images. Its performance is also compared with the previously proposed state-of-the art methods. Comparative analysis demonstrates the superiority of the proposed scheme over the existing approaches.

  4. Thermal noise limitations to force measurements with torsion pendulums: applications to the measurement of the Casimir force and its thermal correction.

    PubMed

    Lamoreaux, S K; Buttler, W T

    2005-03-01

    A general analysis of thermal noise in torsion pendulums is presented. The specific case where the torsion angle is kept fixed by electronic feedback is analyzed. This analysis is applied to a recent experiment that employed a torsion pendulum to measure the Casimir force. The ultimate limit to the distance at which the Casimir force can be measured to high accuracy is discussed, and in particular we elaborate on the prospects for measuring the thermal correction. PMID:15903495

  5. Thermal noise limitations to force measurements with torsion pendulums: Applications to the measurement of the Casimir force and its thermal correction

    SciTech Connect

    Lamoreaux, S.K.; Buttler, W.T.

    2005-03-01

    A general analysis of thermal noise in torsion pendulums is presented. The specific case where the torsion angle is kept fixed by electronic feedback is analyzed. This analysis is applied to a recent experiment that employed a torsion pendulum to measure the Casimir force. The ultimate limit to the distance at which the Casimir force can be measured to high accuracy is discussed, and in particular we elaborate on the prospects for measuring the thermal correction.

  6. Ultrasonic Resonance Spectrometry with Fourier Synthesized Pseudorandom Noise Excitation and Its Application to a Lyotropiec Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Nakamura, Haruki; Naito, Yasushi; Tsuboi, Yukitoshi; Mitaku, Shigeki; Okano, Koji

    1982-11-01

    Time domain measurement to obtain ultrasonic resonance spectra was made using Fourier Synthesized Pseudorandom Noise (FSPN) excitation in order to observe the viscoelastic property of a lyotropic liquid crystal. The FSPN with multiple frequency components was amplitude-modulated by a carrier signal with a much higher single frequency component, and a quadrature detection technique was used to obtain a shear ultrasonic resonance spectrum produced between two transducers. A reflection method was applied to observe mechanical impedance of viscous and elastic materials at about 3 MHz. The viscosities obtained for standard viscous materials agreed well with literature values, and the rigidity and viscosity of a lyotropic liquid crystal of Sodium Lauryl Sulfate with water were measured; they were ˜ 106 dyn/cm2 and ˜0.1 P, respectively.

  7. Resistance noise spectroscopy across the thermally and electrically driven metal-insulator transitions in VO2 nanobeams

    NASA Astrophysics Data System (ADS)

    Alsaqqa, Ali; Kilcoyne, Colin; Singh, Sujay; Horrocks, Gregory; Marley, Peter; Banerjee, Sarbajit; Sambandamurthy, G.

    Vanadium dioxide (VO2) is a strongly correlated material that exhibits a sharp thermally driven metal-insulator transition at Tc ~ 340 K. The transition can also be triggered by a DC voltage in the insulating phase with a threshold (Vth) behavior. The mechanisms behind these transitions are hotly discussed and resistance noise spectroscopy is a suitable tool to delineate different transport mechanisms in correlated systems. We present results from a systematic study of the low frequency (1 mHz < f < 10 Hz) noise behavior in VO2 nanobeams across the thermally and electrically driven transitions. In the thermal transition, the power spectral density (PSD) of the resistance noise is unchanged as we approach Tc from 300 K and an abrupt drop in the magnitude is seen above Tc and it remains unchanged till 400 K. However, the noise behavior in the electrically driven case is distinctly different: as the voltage is ramped from zero, the PSD gradually increases by an order of magnitude before reaching Vth and an abrupt increase is seen at Vth. The noise magnitude decreases above Vth, approaching the V = 0 value. The individual roles of percolation, Joule heating and signatures of correlated behavior will be discussed. This work is supported by NSF DMR 0847324.

  8. Nuclear magnetic resonance study of thermal oxidation of polyisoprene

    NASA Technical Reports Server (NTRS)

    Golub, M. A.; Hsu, M. S.

    1975-01-01

    An investigation was conducted concerning the microstructural changes occurring in cis- and trans-1,4-polyisoprenes during uncatalized thermal oxidation in the solid phase. The investigation made use of approaches based on proton and carbon-13 NMR spectroscopy. The oxidation of squalene and dihydromyrcene in the liquid phase was also studied. The studies provide the first NMR spectroscopic evidence for the presence of epoxy and peroxide, hydroperoxide, and alcohol groups within the oxidized polyisoprene chain.

  9. Carnot cycle for interacting particles in the absence of thermal noise.

    PubMed

    Curado, Evaldo M F; Souza, Andre M C; Nobre, Fernando D; Andrade, Roberto F S

    2014-02-01

    A thermodynamic formalism is developed for a system of interacting particles under overdamped motion, which has been recently analyzed within the framework of nonextensive statistical mechanics. It amounts to expressing the interaction energy of the system in terms of a temperature θ, conjugated to a generalized entropy s(q), with q = 2. Since θ assumes much higher values than those of typical room temperatures T ≪ θ, the thermal noise can be neglected for this system (T/θ ≃ 0). This framework is now extended by the introduction of a work term δW which, together with the formerly defined heat contribution (δ Q = θ ds(q)), allows for the statement of a proper energy conservation law that is analogous to the first law of thermodynamics. These definitions lead to the derivation of an equation of state and to the characterization of s(q) adiabatic and θ isothermic transformations. On this basis, a Carnot cycle is constructed, whose efficiency is shown to be η = 1-(θ(2)/θ(1)), where θ(1) and θ(2) are the effective temperatures of the two isothermic transformations, with θ(1)>θ(2). The results for a generalized thermodynamic description of this system open the possibility for further physical consequences, like the realization of a thermal engine based on energy exchanges gauged by the temperature θ. PMID:25353432

  10. Assessment of the Fundamental Resonance Frequency of the Sedimentary Cover in the Eskisehir Basin (Turkey) Using Noise Measuremeets

    NASA Astrophysics Data System (ADS)

    Tün, Muammer; Karabulut, Savaş; Avdan, Uǧur; Özel, Oǧuz; Güney, Yücel

    2014-05-01

    Geological observations indicate that the Eskisehir graben is related with Eskisehir Fault Zone (EFZ), one of the major active structures within the Anatolian plate. The fault zone has a considerable seismic risk for the urban area of Eskişehir. Local site conditions substantially affect the characteristics of seismic waves and generally have a direct effect on the potential of the earthquake damage. Site effects are very complex factors. The importance of site response is well known, and few would question the assertion that the motion on soil is usually greater than on rock, when all other things were being held equal. In general, site response estimation can be obtained from instrumental recordings. The purpose of this study was to estimate if there would be a relationship between the structural geology in the Eskisehir Basin and the fundamental resonance frequency. Extensive ambient noise measurements were performed in the basin of Eskisehir from June 2010 to spring 2012. In this work, we conduct microtremor surveys to investigate the 3-D basin structure of Eskisehir Basin and determine the fundamental resonance frequency of the sedimentary cover in the Eskisehir Valley area. The measurements of single-station microtremor were carried out at 318 sites in the Eskişehir Basin. We use data recorded by a broadband seismometer and digitizer CMG-6TD, Guralp seismometer. Some of the measurement locations, the CMG-6TD sensor was located into 30 cm-deep holes in the ground to avoid strongly wind-generated, long-period noise. Finally, a map showing the fundamental resonance frequency distribution in the studied area was drawn using the results obtained from applying the HVSR technique. A fundamental resonance frequency map of the Eskisehir Basin was produced from main peak in the horizontal-to-vertical component (H/V) spectral ratio.

  11. Improving the signal-to-noise ratio of thermal ghost imaging based on positive-negative intensity correlation

    NASA Astrophysics Data System (ADS)

    Song, Shu-Chun; Sun, Ming-Jie; Wu, Ling-An

    2016-05-01

    Ghost imaging with thermal light is a topic in optical imaging that has aroused great interest in recent years. However, the imaging quality must be greatly improved before the technology can be transferred from the lab to engineering applications. By means of correspondence ghost imaging (CGI) with a pseudo-thermal light source and appropriate sorting of the intensity fluctuations of the signal and reference beams, we obtain the positive and negative Hanbury Brown and Twiss intensity correlation characteristics of the optical field. Then, for ghost imaging of a transmissive binary object, we find that by subtracting the negative from the positive fluctuation frames of the presorted reference detector signals, the signal-to-noise ratio can be effectively increased, with almost all the background noise eliminated. Our results show that, compared with the generic CGI technique, the signal-to-noise ratio can be increased by nearly 60%.

  12. A Low-Noise, Wideband Preamplifier for a Fourier-Transform Ion Cyclotron Resonance Mass Spectrometer

    PubMed Central

    Mathur, Raman; Knepper, Ronald W.; O'Connor, Peter B.

    2009-01-01

    FTMS performance parameters such as limits of detection, dynamic range, sensitivity, and even mass accuracy and resolution can be greatly improved by enhancing its detection circuit. An extended investigation of significant design considerations for optimal signal-to-noise ratio in an FTMS detection circuit are presented. A low noise amplifier for an FTMS is developed based on the discussed design rules. The amplifier has a gain of ≈ 3500 and a bandwidth of 10 kHz - 1 MHz corresponding to m/z range of 100 Da to 10 kDa (at 7 Tesla). The performance of the amplifier was tested on a MALDI-FTMS, and has demonstrated a 25-fold reduction in noise in a mass spectrum of C60 compared to that of a commercial amplifier. PMID:18029195

  13. A non-contact, thermal noise based method for the calibration of lateral deflection sensitivity in atomic force microscopy

    SciTech Connect

    Mullin, Nic Hobbs, Jamie K.

    2014-11-15

    Calibration of lateral forces and displacements has been a long standing problem in lateral force microscopies. Recently, it was shown by Wagner et al. that the thermal noise spectrum of the first torsional mode may be used to calibrate the deflection sensitivity of the detector. This method is quick, non-destructive and may be performed in situ in air or liquid. Here we make a full quantitative comparison of the lateral inverse optical lever sensitivity obtained by the lateral thermal noise method and the shape independent method developed by Anderson et al. We find that the thermal method provides accurate results for a wide variety of rectangular cantilevers, provided that the geometry of the cantilever is suitable for torsional stiffness calibration by the torsional Sader method, in-plane bending of the cantilever may be eliminated or accounted for and that any scaling of the lateral deflection signal between the measurement of the lateral thermal noise and the measurement of the lateral deflection is eliminated or corrected for. We also demonstrate that the thermal method may be used to characterize the linearity of the detector signal as a function of position, and find a deviation of less than 8% for the instrument used.

  14. Thermal conductivity of silver loaded conductive epoxy from cryogenic to ambient temperature and its application for precision cryogenic noise measurements

    NASA Astrophysics Data System (ADS)

    Amils, Ricardo I.; Gallego, Juan Daniel; Sebastián, José Luis; Muñoz, Sagrario; Martín, Agustín; Leuther, Arnulf

    2016-06-01

    The pressure to increase the sensitivity of instrumentation has pushed the use of cryogenic Low Noise Amplifier (LNA) technology into a growing number of fields. These areas range from radio astronomy and deep space communications to fundamental physics. In this context manufacturing for cryogenic environments requires a proper thermal knowledge of the materials to be able to achieve adequate design behavior. In this work, we present experimental measurements of the thermal conductivity of a silver filled conductive epoxy (EPO-TEK H20E) which is widely used in cryogenic electronics applications. The characterization has been made using a sample preparation which mimics the practical use of this adhesive in the fabrication of cryogenic devices. We apply the data obtained to a detailed analysis of the effects of the conductive epoxy in a monolithic thermal noise source used for high accuracy cryogenic microwave noise measurements. In this application the epoxy plays a fundamental role since its limited thermal conductivity allows heating the chip with relatively low power. To our knowledge, the cryogenic thermal conductivity data of this epoxy has not been reported before in the literature in the 4-300 K temperature range. A second non-conductive epoxy (Gray Scotch-Weld 2216 B/A), also widely used in cryogenic applications, has been measured in order to validate the method by comparing with previous published data.

  15. Thermal analysis of multifacet-mirror ring resonator for XUV free-electron lasers

    SciTech Connect

    McVey, B.D.; Goldstein, J.C.; McFarland, R.D.; Newnam, B.E.

    1990-01-01

    XUV (10 nm {le} {lambda} {le} 100 nm) free-electron lasers (FELs) are potentially important light sources for advanced lithography and materials applications. The average power of an XUV FEL oscillator may be limited by thermal loading of the resonator mirrors. We analyze the requirements for the thermal performance of the mirrors of a metal, multifacet-mirror ring resonator for use at 12 nm. We use analytical methods and numerical approaches which include simulations with the 3-D FEL code FELEX. Thermal distortion of mirror surfaces leads to optical wavefront aberrations which reduce the focusability of the light beam in the gain medium (wiggler/electron beam) and limit the laser performance. 10 refs., 6 figs., 1 tab.

  16. Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

    SciTech Connect

    Chang-Hwan Kim

    2003-12-12

    Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.

  17. Improved SNR of magnetic resonance microimaging using a cooled resonance circuit at 0.3T.

    PubMed

    Nakano, Hiroshi; Nakai, Toshiharu

    2011-01-01

    Because it is noninvasive, magnetic resonance microimaging (MRMI) can be used for 3-dimensional measurement of living tissues for cell engineering. Thermal noise in the resonance circuit of the radiofrequency (RF) system of the MRMI cannot become ignored as the signal diminishes in accordance with decreasing sample size, and cooling the RF coil of the receiver circuit can effectively reduce thermal noise. We used a low temperature normal conductor circuit to reduce noise and confirmed improved signal-to-noise ratio for a conventional microimaging system at low B(0) field (0.3T) with low cost. PMID:22214912

  18. Oscillations emerging from noise-driven steady state in networks with electrical synapses and subthreshold resonance

    PubMed Central

    Tchumatchenko, Tatjana; Clopath, Claudia

    2014-01-01

    Oscillations play a critical role in cognitive phenomena and have been observed in many brain regions. Experimental evidence indicates that classes of neurons exhibit properties that could promote oscillations, such as subthreshold resonance and electrical gap junctions. Typically, these two properties are studied separately but it is not clear which is the dominant determinant of global network rhythms. Our aim is to provide an analytical understanding of how these two effects destabilize the fluctuation-driven state, in which neurons fire irregularly, and lead to an emergence of global synchronous oscillations. Here we show how the oscillation frequency is shaped by single neuron resonance, electrical and chemical synapses.The presence of both gap junctions and subthreshold resonance are necessary for the emergence of oscillations. Our results are in agreement with several experimental observations such as network responses to oscillatory inputs and offer a much-needed conceptual link connecting a collection of disparate effects observed in networks. PMID:25405458

  19. Evaluation of Silicon Neutron Resonance Parameters in the Energy Range Thermal to 1800 keV

    SciTech Connect

    Derrien, H.

    2002-09-30

    The evaluation of the neutron cross sections of the three stable isotopes of silicon in the energy range thermal to 20 MeV was performed by Hetrick et al. for ENDF/B-VI (Evaluated Nuclear Data File). Resonance parameters were obtained in the energy range thermal to 1500 keV from a SAMMY analysis of the Oak Ridge National Laboratory experimental neutron transmission data. A new measurement of the capture cross section of natural silicon in the energy range 1 to 700 keV has recently been performed at the Oak Ridge Electron Linear Accelerator. Results of this measurement were used in a SAMMY reevaluation of the resonance parameters, allowing determination of the capture width of a large number of resonances. The experimental data base is described; properties of the resonance parameters are given. For the first time the direct neutron capture component has been taken into account from the calculation by Rauscher et al. in the energy range from thermal to 1 MeV. Results of benchmark calculations are also given. The new evaluation is available in the ENDF/B-VI format.

  20. Collective behavior of globally coupled Langevin equations with colored noise in the presence of stochastic resonance

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Zhang, Xiao; Zhang, Lu; Luo, Mao-Kang

    2016-08-01

    The long-time collective behavior of globally coupled Langevin equations in a dichotomous fluctuating potential driven by a periodic source is investigated. By describing the collective behavior using the moments of the mean field and single-particle displacements, we study stochastic resonance and synchronization using the exact steady-state solutions and related stability criteria. Based on the simulation results and the criterion of the stationary regime, the notable differences between the stationary and nonstationary regimes are demonstrated. For the stationary regime, stochastic resonance with synchronization is discussed, and for the nonstationary regime, the volatility clustering phenomenon is observed.

  1. Thermal tuning of infrared resonant absorbers based on hybrid gold-VO{sub 2} nanostructures

    SciTech Connect

    Kocer, Hasan; Butun, Serkan; Aydin, Koray; Banar, Berker; Wang, Kevin; Wu, Junqiao; Tongay, Sefaatttin

    2015-04-20

    Resonant absorbers based on plasmonic materials, metamaterials, and thin films enable spectrally selective absorption filters, where absorption is maximized at the resonance wavelength. By controlling the geometrical parameters of nano/microstructures and materials' refractive indices, resonant absorbers are designed to operate at wide range of wavelengths for applications including absorption filters, thermal emitters, thermophotovoltaic devices, and sensors. However, once resonant absorbers are fabricated, it is rather challenging to control and tune the spectral absorption response. Here, we propose and demonstrate thermally tunable infrared resonant absorbers using hybrid gold-vanadium dioxide (VO{sub 2}) nanostructure arrays. Absorption intensity is tuned from 90% to 20% and 96% to 32% using hybrid gold-VO{sub 2} nanowire and nanodisc arrays, respectively, by heating up the absorbers above the phase transition temperature of VO{sub 2} (68 °C). Phase change materials such as VO{sub 2} deliver useful means of altering optical properties as a function of temperature. Absorbers with tunable spectral response can find applications in sensor and detector applications, in which external stimulus such as heat, electrical signal, or light results in a change in the absorption spectrum and intensity.

  2. Large-scale variation of electron parameters from Quasi‑Thermal Noise during WIND perigees in the Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Issautier, Karine; Ongala-Edoumou, Samuel; Moncuquet, Michel

    2016-04-01

    The quasi-thermal noise (QTN) method consists in measuring the electrostatic fluctuations produced by the thermal motion of the ambient particles. This noise is detected with a sensitive wave receiver and measured at the terminal of a passive electric antenna, which is immersed in a stable plasma. The analysis of the so-called QTN provides in situ measurements, mainly the total electron density, with a good accuracy, and thermal temperature in a large number of space media. We create a preliminary electron database to analyse the anti-correlation between electron density and temperature deduced from WIND perigees in the Earth's plasmasphere. We analyse the radio power spectra measured by the Thermal Noise Receiver (TNR), using the 100-m long dipole antenna, onboard WIND spacecraft. We develop a systematic routine to determine the electron density, core and halo temperature and the magnitude of the magnetic field based on QTN in Bernstein modes. Indeed, the spectra are weakly banded between gyroharmonics below the upper hybrid frequency, from which we derive the local electron density. From the gyrofrequency determination, we obtain an independent measure of the magnetic field magnitude, which is in close agreement with the onboard magnetometer.

  3. Low phase-noise autonomous parametric oscillator based on a 226.7 MHz AlN contour-mode resonator.

    PubMed

    Cassella, Cristian; Piazza, Gianluca

    2015-04-01

    We present the first parametric oscillator based on the use of a 226.7 MHz aluminum nitride contour-mode resonator. This topology enables an improvement in the phase noise of 16 dB at 1 kHz offset with respect to a conventional feedback-loop oscillator based on the same device. The recorded phase noise is -106 dBc/Hz at 1 kHz offset. PMID:25881340

  4. Influence of thermal deformations of resonators on propagation properties of laser annular beams through turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Peng, Yufeng; Peng, Fang; Han, Junpeng

    2013-02-01

    Based on the laser field from a positive confocal unstable resonator, considering the influence of thermal distortion of the internal resonator mirror on the annular beam, the propagation characteristics of the annular beam through turbulent atmosphere are investigated by means of the fast Fourier transform algorithm (FFT). The intensity distributions of the output laser far-field are obtained to analyze the propagation characteristics of laser annular beam through the turbulent atmosphere, which is a function about different propagation distances. The results show that the peak intensity of the laser pattern becomes depressed and the spread of the far field diagram patterns is broadened under the increasing of the transmission distance and the thermal distortion of the laser resonator. β-parameter and strehl ratio are introduced to estimate the annular beam quality characteristics. It is found that the annular beam through strong turbulence influences much less obviously than the annular beam through weak turbulence on the quality characteristics with thermal distortion. In the same atmospheric conditions with a certain distance, the greater the mirror thermal distortion is, the worse the annular beam quality characteristics is.

  5. Applying nonlinear resonant ultrasound spectroscopy to improving thermal damage assessment in concrete.

    PubMed

    Payan, C; Garnier, V; Moysan, J; Johnson, P A

    2007-04-01

    Nonlinear resonant ultrasound spectroscopy (NRUS) consists of evaluating one or more resonant frequency peak shifts while increasing excitation amplitude. NRUS exhibits high sensitivity to global damage in a large group of materials. Most studies conducted to date are aimed at interrogating the mechanical damage influence on the nonlinear response, applying bending, or longitudinal modes. The sensitivity of NRUS using longitudinal modes and the comparison of the results with a classical linear method to monitor progressive thermal damage (isotropic) of concrete are studied in this paper. In addition, feasibility and sensitivity of applying shear modes for the NRUS method are explored. PMID:17471756

  6. Synchronization and array-enhanced resonances in delayed coupled neuronal network with channel noise.

    PubMed

    Chen, Jianchun; Ding, Shaojie; Li, Hui; He, Guolong; Zhang, Xuejuan

    2014-09-01

    This paper studies the combined effect of transmission delay and channel fluctuations on population behaviors of an excitatory Erdös-Rényi neuronal network. First, it is found that the network reaches a perfect spatial temporal coherence at a suitable membrane size. Such a coherence resonance is stimulus-free and is array-enhanced. Second, the presence of transmission delay can induce intermittent changes of the population dynamics. Besides, two resonant peaks of the population firing rate are observed as delay changes: one is at τd≈7ms for all membrane areas, which reflects the resonance between the delayed interaction and the intrinsic period of channel kinetics; the other occurs when the transmission delay equals to the mean inter-spike intervals of the population firings in the absence of delay, which reflects the resonance between the delayed interaction and the firing period of the non-delayed system. Third, concerning the impact of network topology and population size, it is found that decreasing the connection probability does not change the range of transmission delay but broadens the range of synaptic coupling that supports population neurons to generate action potentials synchronously and temporally coherently. Furthermore, there exists a critical connection probability that distinguishes the population dynamics into an asynchronous and synchronous state. All the results we obtained are based on networks of size N = 500, which are shown to be robust to further increasing the population size. PMID:25273211

  7. Two-level noise and stochastic resonance in individual permalloy nanoscale magnets

    NASA Astrophysics Data System (ADS)

    Youngblood, Bern Willem

    We present the results of a study on stochastic resonance in individual magnetic random telegraph oscillators. We have fabricated sub-micron magnetic samples, which have multiple stable magnetic states. We are able to observe random telegraph switching between magnetic states and tune the energetics by varying the temperature and applied external field. If a small AC field is applied to the system, it will modulate the energy well depth for the two states and the system shows stochastic resonance near the matching condition 2fA = oD, where o D is the drive frequency and fA is the characteristic frequency of magnetic transitions. We fit our measured data for the resonance amplitude and phase of the particle as a function of temperature to a linear-response model and obtain good agreement. At low temperatures we observe a peak in the phase lag of the returned signal, which is consistent with linear-response theories. At higher temperatures, our fitted model parameters suggest that the particle has an energy surface that is not sinusoidal. This contradicts our initial approximation for the energy surface, but it is consistent with a model for magnetic energy that takes into account the magnetization dynamics near the conditions for random telegraph switching. Our work is the first clear observation of stochastic resonance in a single superparamagnetic particle where the energetics are modulated by an applied field. In addition, our work is the first physical system where stochastic resonance has been characterized with sufficient detail to allow for comparison to linear-response models.

  8. Mathematical model of thermal shields for long-term stability optical resonators.

    PubMed

    Sanjuan, Josep; Gürlebeck, Norman; Braxmaier, Claus

    2015-07-13

    Modern experiments aiming at tests of fundamental physics, like measuring gravitational waves or testing Lorentz Invariance with unprecedented accuracy, require thermal environments that are highly stable over long times. To achieve such a stability, the experiment including typically an optical resonator is nested in a thermal enclosure, which passively attenuates external temperature fluctuations to acceptable levels. These thermal shields are usually designed using tedious numerical simulations or with simple analytical models. In this paper, we propose an accurate analytical method to estimate the performance of passive thermal shields in the frequency domain, which allows for fast evaluation and optimization. The model analysis has also unveiled interesting properties of the shields, such as dips in the transfer function for some frequencies under certain combinations of materials and geometries. We validate the results by comparing them to numerical simulations performed with commercial software based on finite element methods. PMID:26191850

  9. Noise amplification in parallel whole-head ultra-low-field magnetic resonance imaging using 306 detectors.

    PubMed

    Lin, Fa-Hsuan; Vesanen, Panu T; Nieminen, Jaakko O; Hsu, Yi-Cheng; Zevenhoven, Koos C J; Dabek, Juhani; Parkkonen, Lauri T; Zhdanov, Andrey; Ilmoniemi, Risto J

    2013-08-01

    In ultra-low-field magnetic resonance imaging, arrays of up to hundreds of highly sensitive superconducting quantum interference devices (SQUIDs) can be used to detect the weak magnetic fields emitted by the precessing magnetization. Here, we investigate the noise amplification in sensitivity-encoded ultra-low-field MRI at various acceleration rates using a SQUID array consisting of 102 magnetometers, 102 gradiometers, or 306 magnetometers and gradiometers, to cover the whole head. Our results suggest that SQUID arrays consisting of 102 magnetometers and 102 gradiometers are similar in g-factor distribution. A SQUID array of 306 sensors (102 magnetometers and 204 gradiometers) only marginally improves the g-factor. Corroborating with previous studies, the g-factor in 2D sensitivity-encoded ultra-low-field MRI with 9 to 16-fold 2D accelerations using the SQUID array studied here may be acceptable. PMID:23023497

  10. Noise amplification in parallel whole-head ultra-low-field magnetic resonance imaging using 306 detectors

    PubMed Central

    Lin, Fa-Hsuan; Vesanen, Panu T.; Nieminen, Jaakko O.; Hsu, Yi-Cheng; Koos, C.J.; Ilmoniemi, åJ.

    2012-01-01

    In ultra-low-field (ULF) magnetic resonance imaging (MRI), arrays of up to hundreds of highly sensitive superconducting quantum interference devices (SQUIDs) can be used to detect the weak magnetic fields emitted by the precessing magnetization. Here we investigate the noise amplification in sensitivity encoded (SENSE) ULF MRI at various acceleration rates using a SQUID array consisting of 102 magnetometers, 102 gradiometers, or 306 magnetometers and gradiometers, to cover the whole head. Our results suggest that SQUID arrays consisting of 102 magnetometers and 102 gradiometers are similar in g-factor distribution. A SQUID array of 306 sensors (102 magnetometers and 204 gradiometers) only marginally improves the g-factor. Corroborating with previous studies, the g-factor in 2D SENSE ULF MRI with 9 to 16-fold 2D accelerations using the SQUID array studied here may be acceptable. PMID:23023497

  11. Combined action of time-delay and colored cross-associated multiplicative and additive noises on stability and stochastic resonance for a stochastic metapopulation system

    NASA Astrophysics Data System (ADS)

    Wang, Kang-Kang; Zong, De-Cai; Wang, Ya-Jun; Li, Sheng-Hong

    2016-05-01

    In this paper, the transition between the stable state of a big density and the extinction state and stochastic resonance (SR) for a time-delayed metapopulation system disturbed by colored cross-correlated noises are investigated. By applying the fast descent method, the small time-delay approximation and McNamara and Wiesenfeld's SR theory, we investigate the impacts of time-delay, the multiplicative, additive noises and colored cross-correlated noise on the SNR and the shift between the two states of the system. Numerical results show that the multiplicative, additive noises and time-delay can all speed up the transition from the stable state to the extinction state, while the correlation noise and its correlation time can slow down the extinction process of the population system. With respect to SNR, the multiplicative noise always weakens the SR effect, while noise correlation time plays a dual role in motivating the SR phenomenon. Meanwhile, time-delay mainly plays a negative role in stimulating the SR phenomenon. Conversely, it could motivate the SR effect to increase the strength of the cross-correlation noise in the SNR-β plot, while the increase of additive noise intensity will firstly excite SR, and then suppress the SR effect.

  12. Pulsed laser manipulation of an optically trapped bead: averaging thermal noise and measuring the pulsed force amplitude.

    PubMed

    Lindballe, Thue B; Kristensen, Martin V G; Berg-Sørensen, Kirstine; Keiding, Søren R; Stapelfeldt, Henrik

    2013-01-28

    An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 μm polystyrene bead, the laser pulse-bead interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our experimental method may have implications for microrheology. PMID:23389179

  13. Cooling a nanomechanical resonator using spin-dependent transport and noise interference in Andreev reflections

    NASA Astrophysics Data System (ADS)

    Stadler, Pascal; Belzig, Wolfgang; Rastelli, Gianluca

    Nanoelectromechanical systems promise to manipulate mechanical motion in the quantum regime using electron transport. For such a goal, a necessary condition is the ability of cooling the resonator into or near to its quantum ground state. A still open challenge in this field is the achievement of active cooling using purely electron transport in, for instance, suspended carbon nanotube quantum dots. We consider the quantum transport in a carbon nanotube quantum dot suspended between two electric nanocontacts. Due to the interaction between electrons and flexural mechanical modes, the electron transport results in inelastic vibration-assisted tunneling processes. These give rise to a mechanical damping and to a steady nonequilibrium phonon occupation of the resonator. We discuss these effects for two different coherent transport regimes: (i) spin-polarized current between two ferromagnets and (ii) subgap Andreev current between a superconductor and normal metal.

  14. Effect of rapid thermal annealing on the noise properties of InAs/GaAs quantum dot structures

    SciTech Connect

    Arpatzanis, N.; Tsormpatzoglou, A.; Dimitriadis, C. A.; Song, J. D.; Choi, W. J.; Lee, J. I.; Charitidis, C.

    2007-09-01

    Self-assembled InAs quantum dots (QDs) were grown by molecular beam epitaxy (MBE) on n{sup +}-GaAs substrates, capped between 0.4 {mu}m thick n-type GaAs layers with electron concentration of 1x10{sup 16} cm{sup -3}. The effect of rapid thermal annealing at 700 deg. C for 60 s on the noise properties of the structure has been investigated using Au/n-GaAs Schottky diodes as test devices. In the reference sample without containing QDs, the noise spectra show a generation-recombination (g-r) noise behavior due to a discrete energy level located about 0.51 eV below the conduction band edge. This trap is ascribed to the M4 (or EL3) trap in GaAs MBE layers, related to a chemical impurity-native defect complex. In the structure with embedded QDs, the observed g-r noise spectra are due to a midgap trap level ascribed to the EL2 trap in GaAs, which is related to the InAs QDs dissolution due to the thermal treatment.

  15. Measurement of static and vibration-induced phase noise in UHF thin-film resonator (TFR) filters.

    PubMed

    Birdsall, Steven A; Dever, Patrick B; Donovan, Joseph B; Driscoll, Michael M; Lakin, Kenneth M; Pham, Trang H

    2002-05-01

    Measurements of the static phase noise and vibration sensitivity of thin-film resonator (TFR) filters operating at 640 and 2110 MHz have been made. They show that the short-term frequency instability of the filters is small compared with that induced in the oscillator signal by the sustaining stage amplifier PM (phase modulation) noise. In-oscillator measurement of filter performance under vibration indicates that fractional frequency vibration sensitivities (deltafo/fo) are on the order of several parts in 10(-9)/g. Because the percentage bandwidth and order (number of poles) of the filters was fairly constant, so was the product of the center frequency and group delay. Thus, the fractional frequency vibration sensitivity of the filters can be expressed alternatively as carrier signal phase sensitivity to vibration. The tau-omega0 product for the filters that were tested was on the order of 300 rad, so that the equivalent phase sensitivity to vibration was approximately 1 microrad/g. PMID:12046940

  16. Thermal neutron capture and resonance integral cross sections of 45Sc

    NASA Astrophysics Data System (ADS)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim; Thi Hien, Nguyen; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Cho, Moo-Hyun; Lee, Manwoo

    2015-11-01

    The thermal neutron cross section (σ0) and resonance integral (I0) of the 45Sc(n,γ)46Sc reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (Gth) and resonance (Gepi) neutron self-shielding, the γ-ray attenuation (Fg) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the 45Sc(n,γ)46Sc reaction have been determined relative to the reference values of the 197Au(n,γ)198Au reaction, with σo,Au = 98.65 ± 0.09 barn and Io,Au = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σo,Sc = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be Io,Sc = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  17. Frequency noise and intensity noise of next-generation gravitational-wave detectors with RF/DC readout schemes

    SciTech Connect

    Somiya, K.; Chen, Y.; Kawamura, S.; Mio, N.

    2006-06-15

    The sensitivity of next-generation gravitational-wave detectors such as Advanced LIGO and LCGT should be limited mostly by quantum noise with an expected technical progress to reduce seismic noise and thermal noise. Those detectors will employ the optical configuration of resonant-sideband-extraction that can be realized with a signal-recycling mirror added to the Fabry-Perot Michelson interferometer. While this configuration can reduce quantum noise of the detector, it can possibly increase laser frequency noise and intensity noise. The analysis of laser noise in the interferometer with the conventional configuration has been done in several papers, and we shall extend the analysis to the resonant-sideband-extraction configuration with the radiation-pressure effect included. We shall also refer to laser noise in the case we employ the so-called DC readout scheme.

  18. Repulsive particles under a general external potential: Thermodynamics by neglecting thermal noise

    NASA Astrophysics Data System (ADS)

    Ribeiro, Mauricio S.; Nobre, Fernando D.

    2016-08-01

    A recent proposal of an effective temperature θ , conjugated to a generalized entropy sq, typical of nonextensive statistical mechanics, has led to a consistent thermodynamic framework in the case q =2 . The proposal was explored for repulsively interacting vortices, currently used for modeling type-II superconductors. In these systems, the variable θ presents values much higher than those of typical room temperatures T , so that the thermal noise can be neglected (T /θ ≃0 ). The whole procedure was developed for an equilibrium state obtained after a sufficiently long-time evolution, associated with a nonlinear Fokker-Planck equation and approached due to a confining external harmonic potential, ϕ (x ) =α x2/2 (α >0 ). Herein, the thermodynamic framework is extended to a quite general confining potential, namely ϕ (x ) =α|x | z/z (z >1 ). It is shown that the main results of the previous analyses hold for any z >1 : (i) The definition of the effective temperature θ conjugated to the entropy s2. (ii) The construction of a Carnot cycle, whose efficiency is shown to be η =1 -(θ2/θ1) , where θ1 and θ2 are the effective temperatures associated with two isothermal transformations, with θ1>θ2 . The special character of the Carnot cycle is indicated by analyzing another cycle that presents an efficiency depending on z . (iii) Applying Legendre transformations for a distinct pair of variables, different thermodynamic potentials are obtained, and furthermore, Maxwell relations and response functions are derived. The present approach shows a consistent thermodynamic framework, suggesting that these results should hold for a general confining potential ϕ (x ) , increasing the possibility of experimental verifications.

  19. Investigation of the MTC noise estimation with a coupled neutronic/thermal-hydraulic dedicated model - 'Closing the loop'

    SciTech Connect

    Demaziere, C.; Larsson, V.

    2012-07-01

    This paper investigates the reliability of different noise estimators aimed at determining the Moderator Temperature Coefficient (MTC) of reactivity in Pressurized Water Reactors. By monitoring the inherent fluctuations in the neutron flux and moderator temperature, an on-line monitoring of the MTC without perturbing reactor operation is possible. In order to get an accurate estimation of the MTC by noise analysis, the point-kinetic component of the neutron noise and the core-averaged moderator temperature noise have to be used. Because of the scarcity of the in-core instrumentation, the determination of these quantities is difficult, and several possibilities thus exist for estimating the MTC by noise analysis. Furthermore, the effect of feedback has to be negligible at the frequency chosen for estimating the MTC in order to get a proper determination of the MTC. By using an integrated neutronic/thermal- hydraulic model specifically developed for estimating the three-dimensional distributions of the fluctuations in neutron flux, moderator properties, and fuel temperature, different approaches for estimating the MTC by noise analysis can be tested individually. It is demonstrated that a reliable MTC estimation can only be provided if the core is equipped with a sufficient number of both neutron detectors and temperature sensors, i.e. if the core contain in-core detectors monitoring both the axial and radial distributions of the fluctuations in neutron flux and moderator temperature. It is further proven that the effect of feedback is negligible for frequencies higher than 0.1 Hz, and thus the MTC noise estimations have to be performed at higher frequencies. (authors)

  20. Measurement of macroscopic plasma parameters with a radio experiment: Interpretation of the quasi-thermal noise spectrum observed in the solar wind

    NASA Technical Reports Server (NTRS)

    Couturier, P.; Hoang, S.; Meyer-Vernet, N.; Steinberg, J. L.

    1983-01-01

    The ISEE-3 SBH radio receiver has provided the first systematic observations of the quasi-thermal (plasma waves) noise in the solar wind plasma. The theoretical interpretation of that noise involves the particle distribution function so that electric noise measurements with long antennas provide a fast and independent method of measuring plasma parameters: densities and temperatures of a two component (core and halo) electron distribution function have been obtained in that way. The polarization of that noise is frequency dependent and sensitive to the drift velocity of the electron population. Below the plasma frequency, there is evidence of a weak noise spectrum with spectral index -1 which is not yet accounted for by the theory. The theoretical treatment of the noise associated with the low energy (thermal) proton population shows that the moving electrical antenna radiates in the surrounding plasma by Carenkov emission which becomes predominant at the low frequencies, below about 0.1 F sub P.

  1. Calculation of the Thermal Footprint of Resonant Magnetic Perturbations in DIII-D

    SciTech Connect

    Joseph, I; Evans, T; Moyer, R; Fenstermacher, M; Groth, M; Kasilov, S; Lasnier, C; Porter, G; Runov, A; Schaffer, M; Schneider, R; Watkins, J

    2007-09-14

    The effect of resonant magnetic perturbations on heat transport in DIII-D H-mode plasmas has been calculated by combining the TRIP3D field-line tracing code with the E3D two-fluid transport code. Simulations show that the divertor heat flux distribution becomes non-axisymmetric because heat flux is efficiently guided to the divertor along the three-dimensional invariant manifolds of the magnetic field. Calculations demonstrate that heat flux is spread over a wider area of the divertor target, thereby reducing the peak heat flux delivered during steady-state operation. Filtered optical cameras have observed non-axisymmetric particle fluxes at the strike-point and Langmuir probes have observed non-axisymmetric floating potentials. On the other hand, the predicted magnitude of stochastic thermal transport is too large to match the pedestal plasma profiles measured by Thomson scattering and charge exchange recombination spectroscopy. The Braginskii thermal conductivity overestimates the expected heat transport in the pedestal because the mean free path is longer than estimates of the parallel thermal correlation length, and collisionless transport models are probably required for accurate description. However, even the collisionless estimates for electron thermal transport are too large by one to two orders of magnitude. Thus, it is likely that another mechanism such as rotational screening of resonant perturbations limits the stochastic region and reduces transport inside of the pedestal.

  2. Determination of Elastic Properties and Characterization of Thermal Barrier Coatings using Resonant Ultrasound Spectroscopy

    SciTech Connect

    Shyam, Amit; Lara-Curzio, Edgar

    2009-01-01

    Mechanical properties of plasma sprayed ceramic coatings are extremely important to engine design. However, the determination of these properties is often difficult because of the unique and complicated microstructure of the coatings. In this presentation the determination of the elastic constants of plasma sprayed Yttria stabilized Zirconia thermal barrier coatings using resonant ultrasound spectroscopy will be described along with an analysis that enables the determination of the elastic constants as a function of temperature and coating direction. In this work, results on the following issues will be discussed: 1) the elastic anisotropy of thermal barrier coatings, which is associated with coating failure modes; 2) sintering effects on coating compliance comparing with thermal behavior, which is important to coating performance on engineering structures, such as turbine engines; 3) coating elastic modulus at high temperatures close to the service condition, which provides insights of coating mechanical behavior in both fundamental and practical studies.

  3. A deterministic and statistical energy analysis of tyre cavity resonance noise

    NASA Astrophysics Data System (ADS)

    Mohamed, Zamri; Wang, Xu

    2016-03-01

    Tyre cavity resonance was studied using a combination of deterministic analysis and statistical energy analysis where its deterministic part was implemented using the impedance compact mobility matrix method and its statistical part was done by the statistical energy analysis method. While the impedance compact mobility matrix method can offer a deterministic solution to the cavity pressure response and the compliant wall vibration velocity response in the low frequency range, the statistical energy analysis method can offer a statistical solution of the responses in the high frequency range. In the mid frequency range, a combination of the statistical energy analysis and deterministic analysis methods can identify system coupling characteristics. Both methods have been compared to those from commercial softwares in order to validate the results. The combined analysis result has been verified by the measurement result from a tyre-cavity physical model. The analysis method developed in this study can be applied to other similar toroidal shape structural-acoustic systems.

  4. White noise of Nb-based microwave superconducting quantum interference device multiplexers with NbN coplanar resonators for readout of transition edge sensors

    NASA Astrophysics Data System (ADS)

    Kohjiro, Satoshi; Hirayama, Fuminori; Yamamori, Hirotake; Nagasawa, Shuichi; Fukuda, Daiji; Hidaka, Mutsuo

    2014-06-01

    White noise of dissipationless microwave radio frequency superconducting quantum interference device (RF-SQUID) multiplexers has been experimentally studied to evaluate their readout performance for transition edge sensor (TES) photon counters ranging from near infrared to gamma ray. The characterization has been carried out at 4 K, first to avoid the low-frequency fluctuations present at around 0.1 K, and second, for a feasibility study of readout operation at 4 K for extended applications. To increase the resonant Q at 4 K and maintain low noise SQUID operation, multiplexer chips consisting of niobium nitride (NbN)-based coplanar-waveguide resonators and niobium (Nb)-based RF-SQUIDs have been developed. This hybrid multiplexer exhibited 1 × 104 ≤ Q ≤ 2 × 104 and the square root of spectral density of current noise referred to the SQUID input √SI = 31 pA/√Hz. The former and the latter are factor-of-five and seven improvements from our previous results on Nb-based resonators, respectively. Two-directional readout on the complex plane of the transmission component of scattering matrix S21 enables us to distinguish the flux noise from noise originating from other sources, such as the cryogenic high electron mobility transistor (HEMT) amplifier. Systematic noise measurements with various microwave readout powers PMR make it possible to distinguish the contribution of noise sources within the system as follows: (1) The achieved √SI is dominated by the Nyquist noise from a resistor at 4 K in parallel to the SQUID input coil which is present to prevent microwave leakage to the TES. (2) The next dominant source is either the HEMT-amplifier noise (for small values of PMR) or the quantization noise due to the resolution of 300-K electronics (for large values of PMR). By a decrease of these noise levels to a degree that is achievable by current technology, we predict that the microwave RF-SQUID multiplexer can exhibit √SI ≤ 5 pA/√Hz, i.e., close to √SI of

  5. White noise of Nb-based microwave superconducting quantum interference device multiplexers with NbN coplanar resonators for readout of transition edge sensors

    SciTech Connect

    Kohjiro, Satoshi; Hirayama, Fuminori; Yamamori, Hirotake; Nagasawa, Shuichi; Fukuda, Daiji; Hidaka, Mutsuo

    2014-06-14

    White noise of dissipationless microwave radio frequency superconducting quantum interference device (RF-SQUID) multiplexers has been experimentally studied to evaluate their readout performance for transition edge sensor (TES) photon counters ranging from near infrared to gamma ray. The characterization has been carried out at 4 K, first to avoid the low-frequency fluctuations present at around 0.1 K, and second, for a feasibility study of readout operation at 4 K for extended applications. To increase the resonant Q at 4 K and maintain low noise SQUID operation, multiplexer chips consisting of niobium nitride (NbN)-based coplanar-waveguide resonators and niobium (Nb)-based RF-SQUIDs have been developed. This hybrid multiplexer exhibited 1 × 10{sup 4} ≤ Q ≤ 2 × 10{sup 4} and the square root of spectral density of current noise referred to the SQUID input √S{sub I} = 31 pA/√Hz. The former and the latter are factor-of-five and seven improvements from our previous results on Nb-based resonators, respectively. Two-directional readout on the complex plane of the transmission component of scattering matrix S{sub 21} enables us to distinguish the flux noise from noise originating from other sources, such as the cryogenic high electron mobility transistor (HEMT) amplifier. Systematic noise measurements with various microwave readout powers P{sub MR} make it possible to distinguish the contribution of noise sources within the system as follows: (1) The achieved √S{sub I} is dominated by the Nyquist noise from a resistor at 4 K in parallel to the SQUID input coil which is present to prevent microwave leakage to the TES. (2) The next dominant source is either the HEMT-amplifier noise (for small values of P{sub MR}) or the quantization noise due to the resolution of 300-K electronics (for large values of P{sub MR}). By a decrease of these noise levels to a degree that is achievable by current technology, we predict that the

  6. Reproducibility of magnetic resonance spectroscopy in correlation with signal-to-noise ratio.

    PubMed

    Okada, Tomohisa; Sakamoto, Setsu; Nakamoto, Yuji; Kohara, Nobuo; Senda, Michio

    2007-11-15

    An increased amount of myoinositol (mI) relative to creatine (Cr) by proton MR spectroscopy ((1)H-MRS) measurement gives a useful aid for the diagnosis of Alzheimer's disease (AD). Previous results of test-retest measurement of mI, however, have shown variability more than twice as large as for other metabolites. The aims of this study were to analyze test-retest variability of (1)H-MRS measurements in correlation with signal-to-noise ratio (SNR). Ten subjects clinically suspected of mild AD were examined twice (2-14 days apart) with (1)H-MRS measurements of voxels placed at anterior and posterior cingulate cortex. The percent differences between two measurements (%differences) of mI/Cr showed a significant linear trend to decrease as average SNR increased, but %differences of N-acetylaspartate (NAA)/Cr and choline (Cho)/Cr did not. The average of %differences was 10.5, 15.0 and 20.8 for NAA/Cr, Cho/Cr, and mI/Cr, respectively, indicating a prominent deterioration of mI/Cr measurement reproducibility, which decreased to 6.96, 15.4 and 9.87, respectively, when the analysis was limited to measurements with SNR over 25. The results indicate that MRS measurements with high SNR should be used to obtain reliable assessments of mI/Cr as accurate diagnostic indicator of AD in clinical MR examinations. PMID:17900878

  7. Identification of human activities in a thermal system with noise varied in temporal frequency

    NASA Astrophysics Data System (ADS)

    Brooks, Jason; Jacobs, Eddie; Smith, Forrest

    2011-05-01

    The ability of observers to identify human activities in noise is expected to differ from performance with static targets in noise due to the unmasking that is provided by target motion. At a minimum, the probability of identification should increase when the temporal bandwidth of the noise is less than that of the system. Results from a human activities identification experiment are presented in this paper, along with results from a moving character experiment that is intended to provide better understanding of basic motion in noise with varied temporal bandwidth. These results along with further experiments and analysis will eventually be used to improve performance predictions derived from the Targeting Task Performance (TTP) metric.

  8. Thermal imager fixed pattern noise prediction using a characterization of the infrared detector

    NASA Astrophysics Data System (ADS)

    Mariani, Paolo; Zatti, Stefano; Giunti, Claudio; Sozzi, Barbara; Guadagnoli, Emanuele; Porta, Antonio

    2014-12-01

    Cooled infrared detectors are typically characterized by well-known electro-optical parameters: responsivity, noise equivalent temperature difference, shot noise, 1/f noise, and so on. Particularly important for staring arrays is also the residual fixed pattern noise (FPN) that can be obtained after the application of the nonuniformity correction (NUC) algorithm. A direct measure of this parameter is usually hard to define because the residual FPN strongly depends, other than on the detector, on the choice of the NUC algorithm and the operative scenario. We introduce three measurable parameters: instability, nonlinearity, and a residual after a polynomial fitting of the detector response curve, and we demonstrate how they are related to the residual FPN after the application of an NUC (the relationship with three common correction algorithms is discussed). A comparison with experimental data is also presented and discussed.

  9. Fano resonance in the nonadiabatically pumped shot noise of a time-dependent quantum well in a two-dimensional electron gas and graphene

    SciTech Connect

    Zhu, Rui Dai, Jiao-Hua; Guo, Yong

    2015-04-28

    Interference between different quantum paths can generate Fano resonance. One of the examples is transport through a quasibound state driven by a time-dependent scattering potential. Previously it is found that Fano resonance occurs as a result of energy matching in one-dimensional systems. In this work, we demonstrate that when transverse motion is present, Fano resonance occurs precisely at the wavevector matching situation. Using the Floquet scattering theory, we considered the transport properties of a nonadiabatic time-dependent well both in a two-dimensional electron gas and monolayer graphene structure. Dispersion of the quasibound state of a static quantum well is obtained with transverse motion present. We found that Fano resonance occurs when the wavevector in the transport direction of one of the Floquet sidebands is exactly identical to that of the quasibound state in the well at equilibrium and follows the dispersion pattern of the latter. To observe the Fano resonance phenomenon in the transmission spectrum, we also considered the pumped shot noise properties when time and spatial symmetry secures vanishing current in the considered configuration. Prominent Fano resonance is found in the differential pumped shot noise with respect to the reservoir Fermi energy.

  10. Review of pyroelectric thermal energy harvesting and new MEMs-based resonant energy conversion techniques

    NASA Astrophysics Data System (ADS)

    Hunter, Scott R.; Lavrik, Nickolay V.; Mostafa, Salwa; Rajic, Slo; Datskos, Panos G.

    2012-06-01

    Harvesting electrical energy from thermal energy sources using pyroelectric conversion techniques has been under investigation for over 50 years, but it has not received the attention that thermoelectric energy harvesting techniques have during this time period. This lack of interest stems from early studies which found that the energy conversion efficiencies achievable using pyroelectric materials were several times less than those potentially achievable with thermoelectrics. More recent modeling and experimental studies have shown that pyroelectric techniques can be cost competitive with thermoelectrics and, using new temperature cycling techniques, has the potential to be several times as efficient as thermoelectrics under comparable operating conditions. This paper will review the recent history in this field and describe the techniques that are being developed to increase the opportunities for pyroelectric energy harvesting. The development of a new thermal energy harvester concept, based on temperature cycled pyroelectric thermal-to-electrical energy conversion, are also outlined. The approach uses a resonantly driven, pyroelectric capacitive bimorph cantilever structure that can be used to rapidly cycle the temperature in the energy harvester. The device has been modeled using a finite element multi-physics based method, where the effect of the structure material properties and system parameters on the frequency and magnitude of temperature cycling, and the efficiency of energy recycling using the proposed structure, have been modeled. Results show that thermal contact conductance and heat source temperature differences play key roles in dominating the cantilever resonant frequency and efficiency of the energy conversion technique. This paper outlines the modeling, fabrication and testing of cantilever and pyroelectric structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermal

  11. Review of pyroelectric thermal energy harvesting and new MEMs based resonant energy conversion techniques

    SciTech Connect

    Hunter, Scott Robert; Lavrik, Nickolay V; Mostafa, Salwa; Rajic, Slobodan; Datskos, Panos G

    2012-01-01

    Harvesting electrical energy from thermal energy sources using pyroelectric conversion techniques has been under investigation for over 50 years, but it has not received the attention that thermoelectric energy harvesting techniques have during this time period. This lack of interest stems from early studies which found that the energy conversion efficiencies achievable using pyroelectric materials were several times less than those potentially achievable with thermoelectrics. More recent modeling and experimental studies have shown that pyroelectric techniques can be cost competitive with thermoelectrics and, using new temperature cycling techniques, has the potential to be several times as efficient as thermoelectrics under comparable operating conditions. This paper will review the recent history in this field and describe the techniques that are being developed to increase the opportunities for pyroelectric energy harvesting. The development of a new thermal energy harvester concept, based on temperature cycled pyroelectric thermal-to-electrical energy conversion, are also outlined. The approach uses a resonantly driven, pyroelectric capacitive bimorph cantilever structure that can be used to rapidly cycle the temperature in the energy harvester. The device has been modeled using a finite element multi-physics based method, where the effect of the structure material properties and system parameters on the frequency and magnitude of temperature cycling, and the efficiency of energy recycling using the proposed structure, have been modeled. Results show that thermal contact conductance and heat source temperature differences play key roles in dominating the cantilever resonant frequency and efficiency of the energy conversion technique. This paper outlines the modeling, fabrication and testing of cantilever and pyroelectric structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermal

  12. Fiber-tip resonator excited by radiation pressure and photo-thermal effect

    NASA Astrophysics Data System (ADS)

    Ma, Cheng; Wang, Anbo

    2010-04-01

    A mechanical resonator was fabricated on the tip of a standard single mode fiber with outer diameter of 125 μm. The fabrication process involved a single-mode to a multimode fiber splicing, sputtering coating of a submicron gold nanofilm, focused ion beam (FIB) patterning and chemical wet etching. A micro-vibrating disk with suspension arms was formed on the sensing fiber tip, the resonance frequency of the vibrator is sensitive to mass loading on its surface. Vibration was excited by laser excitation via the radiation pressure and the photo-thermal effect and detected by a CW laser beam at another wavelength. The detected intensity of the fundamental and higher order harmonics can be monitored for resonance frequency determination. The excitation and detection beams were multiplexed within a single fiber link, which makes the sensor compact and versatile. The resonator maintained relatively high quality factor in air and was successfully applied to the analysis of layer-by-layer electrostatic self-assembly and immuno-sensing.

  13. Thermal Excitation of Gadolinium-Based Contrast Agents Using Spin Resonance

    PubMed Central

    Fridjhon, Peter; Rubin, David M.

    2016-01-01

    Theoretical and experimental investigations into the thermal excitation of liquid paramagnetic contrast agents using the spin resonance relaxation mechanism are presented. The electronic spin-lattice relaxation time τ1e of gadolinium-based contrast agents, which is estimated at 0.1 ns, is ten orders of magnitude faster than the relaxation time of protons in water. The shorter relaxation time is found to significantly increase the rate of thermal energy deposition. To the authors’ knowledge this is the first study of gadolinium based contrast agents in a liquid state used as thermal agents. Analysis shows that when τ1e and other experimental parameters are optimally selected, a maximum theoretical heating rate of 29.4 °C.s−1 could be achieved which would suffice for clinical thermal ablation of neoplasms. The experimental results show a statistically significant thermal response for two out of the four contrast agents tested. The results are compared to the simulated estimates via analysis of a detailed model of the system. While these experimentally determined temperature rises are small and thus of no clinical utility, their presence supports the theoretical analysis and strongly suggests that the chemical structure of the selected compounds plays an important role in this mechanism of heat deposition. There exists an opportunity for the development of alternative gadolinium-based compounds with an order of magnitude longer τ1e in a diluted form to be used as an efficient hyperthermia agent for clinical use. PMID:27341338

  14. Thermal Excitation of Gadolinium-Based Contrast Agents Using Spin Resonance.

    PubMed

    Dinger, Steven C; Fridjhon, Peter; Rubin, David M

    2016-01-01

    Theoretical and experimental investigations into the thermal excitation of liquid paramagnetic contrast agents using the spin resonance relaxation mechanism are presented. The electronic spin-lattice relaxation time τ1e of gadolinium-based contrast agents, which is estimated at 0.1 ns, is ten orders of magnitude faster than the relaxation time of protons in water. The shorter relaxation time is found to significantly increase the rate of thermal energy deposition. To the authors' knowledge this is the first study of gadolinium based contrast agents in a liquid state used as thermal agents. Analysis shows that when τ1e and other experimental parameters are optimally selected, a maximum theoretical heating rate of 29.4 °C.s-1 could be achieved which would suffice for clinical thermal ablation of neoplasms. The experimental results show a statistically significant thermal response for two out of the four contrast agents tested. The results are compared to the simulated estimates via analysis of a detailed model of the system. While these experimentally determined temperature rises are small and thus of no clinical utility, their presence supports the theoretical analysis and strongly suggests that the chemical structure of the selected compounds plays an important role in this mechanism of heat deposition. There exists an opportunity for the development of alternative gadolinium-based compounds with an order of magnitude longer τ1e in a diluted form to be used as an efficient hyperthermia agent for clinical use. PMID:27341338

  15. Resonant dipolar relaxation in poly ( ɛ -caprolactone)—A thermally stimulated depolarization current study

    NASA Astrophysics Data System (ADS)

    Patidar, M. M.; Jain, D.; Nath, R.; Ganesan, V.

    2016-07-01

    Resonant dipolar relaxation in poly( ɛ-caprolactone) (PCL) is reported using thermally stimulated discharge current spectroscopy. PCL is a bio-medically known shape memory polymer having a well defined γ, β, α, and α ' relaxations, respectively, centered around 125 K, 170 K, 220 K, and 270 K as seen by the measurements. By employing a new protocol variable poling temperature at constant freezing temperature, resonant dipolar relaxation in PCL could be induced, especially in the vicinity of α relaxation. Such a protocol is useful in de-convoluting the features in a more meaningful fashion. By an analysis of activation process, we could show a clear contrast enhancement of the dynamics of the participating dipoles by means of a minimum in the activation energies situated around the glass transition region. The relevant parameters of interest such as activation energies and relaxation times are estimated and discussed.

  16. Heat equation inversion framework for average SAR calculation from magnetic resonance thermal imaging.

    PubMed

    Alon, Leeor; Sodickson, Daniel K; Deniz, Cem M

    2016-10-01

    Deposition of radiofrequency (RF) energy can be quantified via electric field or temperature change measurements. Magnetic resonance imaging has been used as a tool to measure three dimensional small temperature changes associated with RF radiation exposure. When duration of RF exposure is long, conversion from temperature change to specific absorption rate (SAR) is nontrivial due to prominent heat-diffusion and conduction effects. In this work, we demonstrated a method for calculation of SAR via an inversion of the heat equation including heat-diffusion and conduction effects. This method utilizes high-resolution three dimensional magnetic resonance temperature images and measured thermal properties of the phantom to achieve accurate calculation of SAR. Accuracy of the proposed method was analyzed with respect to operating frequency of a dipole antenna and parameters used in heat equation inversion. Bioelectromagnetics. 37:493-503, 2016. © 2016 Wiley Periodicals, Inc. PMID:27490064

  17. An optimal design of thermal-actuated and piezoresistive-sensed CMOS-MEMS resonant sensor

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Chieh; Tsai, Chun-Yin; Chen, Tsung-Lin; Liao, Sin-Hao

    2013-11-01

    This paper proposes an optimal design of the thermal-actuated, piezoresistive-sensed resonator fabricated by a foundry-provided CMOS-MEMS process. The optimal design is achieved both by quantitatively comparing the mechanical properties of different composite films as well as by deriving an analytical model for determining the device dimensions. The analytical model includes a stress model of an asymmetric mechanical structure and a piezoresistivity model of the heavily doped, n-type polysilicon film. The analytical model predicts that the optimal length of the displacement sensor is 200 μm when the thermal actuator is 200 μm in length and the absorption plate is 100 μm in length. Additionally, the model predicts the resistivity of the polysilicon film of (6.8 ± 2.2) mΩ cm and the gauge factor of (6.8 ± 2.9) when the grain size is (250 ± 100) nm. Experimental results agree well with simulation results. Experimental data show that the resonant frequency of the device is 80.06 kHz and shifts to 79.8 kHz when a brick of Pt mass is deposited on the resonator. The mass of the Pt estimated from the frequency shift is 4.5419 × 10-12 kg, while estimated from the measured dimension is 4.4204 × 10-12 kg. Sensitivity of the resonant sensor is calculated to be 1.8 × 102 Hz ng-1. Experimental results further show that the polysilicon film used in the experiments has a grain size of (241 ± 105) nm, an average gauge factor of 5.56 and average resistivity of 5.5 mΩ cm.

  18. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2014-01-01

    An apparatus and method for thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such as Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air, and a spark. Metal is inserted continuously in a high volume of metal into a combustion chamber of the pulsejet. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tailpipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  19. Thermally tunable polarization by nanoparticle plasmonic resonance in photonic crystal fibers.

    PubMed

    Poudereux, David; Caño-García, Manuel; Algorri, José F; García-Cámara, Braulio; Sánchez-Pena, José M; Quintana, Xabier; Geday, Morten A; Otón, José M

    2015-11-01

    A photonic crystal fiber selectively filled with silver nanoparticles dispersed in polydimethylsiloxane has been numerically studied via finite elements analysis. These nanoparticles possess a localized surface plasmon resonance in the visible region which depends on the refractive index of the surrounding medium. The refractive index of polydimethylsiloxane can be thermally tuned leading to the design of polarization tunable filters. Filters found with this setup show anisotropic attenuation of the x-polarization fundamental mode around α(x) = 1200dB/cm remarkably higher than the y-polarization mode. Moreover, high fiber birefringence and birefringence reversal is observed in the spectral region of the plasmon. PMID:26561162

  20. Noise-supported actuator: Coherent resonance in the oscillations of a micrometer-sized object under a direct current-voltage

    NASA Astrophysics Data System (ADS)

    Kurimura, Tomo; Ichikawa, Masatoshi

    2016-04-01

    Noise supported regular motion in a micro-fluidic environment is studied. Recently, it was reported that an aqueous droplet in an oil phase exhibited rhythmic back-and-forth motion under stationary direct current voltage between the cone-shaped electrodes, where the oscillating water droplet moves on a limit cycle orbital. We now confirm that a combination of the limit cycle nature and white noise supports and enhances the regular motion of the object through coherent resonance. The present result will open a way to design an efficient machinery in microfluidic and micromechanical devices.

  1. Calculation of Shear Stiffness in Noise Dominated Magnetic Resonance Elastography (MRE) Data Based on Principal Frequency Estimation

    PubMed Central

    McGee, K. P.; Lake, D.; Mariappan, Y; Hubmayr, R. D.; Manduca, A.; Ansell, K.; Ehman, R. L.

    2011-01-01

    Magnetic resonance elastography (MRE) is a non invasive phase-contrast based method for quantifying the shear stiffness of biological tissues. Synchronous application of a shear wave source and motion encoding gradient waveforms within the MRE pulse sequence enable visualization of the propagating shear wave throughout the medium under investigation. Encoded shear wave induced displacements are then processed to calculate the local shear stiffness of each voxel. An important consideration in local shear stiffness estimates is that the algorithms employed typically calculate shear stiffness using relatively high signal-to-noise ratio (SNR) MRE images and have difficulties at extremely low SNR. A new method of estimating shear stiffness based on the principal spatial frequency of the shear wave displacement map is presented. Finite element simulations were performed to assess the relative insensitivity of this approach to decreases in SNR. Additionally, ex vivo experiments were conducted on normal rat lungs to assess the robustness of this approach in low SNR biological tissue. Simulation and experimental results indicate that calculation of shear stiffness by the principal frequency method is less sensitive to extremely low SNR than previously reported MRE inversion methods but at the expense of loss of spatial information within the region of interest from which the principal frequency estimate is derived. PMID:21701049

  2. Measurement of the thermal neutron capture cross section and the resonance integral of radioactive Hf182

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Bichler, M.; Wallner, A.; Kutschera, W.; Dillmann, I.; Käppeler, F.

    2008-04-01

    The neutron capture cross sections of the radioactive isotope Hf182 (t1/2=8.9×106 yr) in the thermal and epithermal energy regions have been measured by activation at the TRIGA Mark-II reactor of the Atomic Institute of the Austrian Universities in Vienna, Austria, and subsequent γ-ray spectroscopy of Hf183. High values for the thermal (kT=25 meV) cross section σ0=133±10 b and for the resonance integral I0=5850±660 b were found. Additionally, the absolute intensities of the main γ-ray transitions in the decay of Hf182 have been considerably improved.

  3. Nano-Ag on vanadium dioxide. II. Thermal tuning of surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Huang, Chun-Ming; Tazawa, Masato; Jin, Ping; Chen, De-Ming

    2008-09-01

    Thermal tuning of the localized surface plasmon resonance (LSPR) of Ag nanoparticles on a thermochromic thin film of VO2 was studied experimentally. The tuning is strongly temperature dependent and thermally reversible. The LSPR wavelength λSPR shifts to the blue with increasing temperature from 30 to 80 °C, and shifts back to the red as temperature decreases. A smart tuning is achievable on condition that the temperature is controlled in a stepwise manner. The tunable wavelength range depends on the particle size or the mass thickness of the metal nanoparticle film. Further, the tunability was found to be enhanced significantly when a layer of TiO2 was introduced to overcoat the Ag nanoparticles, yielding a marked sensitivity factor ΔλSPR/Δn, of as large as 480 nm per refractive index unit (n) at the semiconductor phase of VO2.

  4. Random telegraphic voltage noise due to thermal bi-stability in a superconducting weak link

    NASA Astrophysics Data System (ADS)

    Biswas, Sourav; Kumar, Nikhil; Winkelmann, C. B.; Courtois, Herve; Gupta, Anjan K.

    2016-05-01

    We investigated the random telegraphic voltage noise signal in the hysteretic bi-stable state of a superconducting weak link device. Fluctuation induced random switching between zero voltage state and non-zero-voltage state gives rise to a random telegraphic voltage signal in time domain. This telegraphic noise is used to find the mean lifetime of each of the two states. The mean life time in the zero voltage state is found to decrease with increasing bias current while that of resistive state increases and thus the two cross at certain bias current. We qualitatively discuss this observed switching behavior as arising from the bi-stable nature.

  5. High Q factor bonding using natural resin for reduced thermal noise of test masses

    NASA Astrophysics Data System (ADS)

    Schediwy, S. W.; Gras, S.; Ju, L.; Blair, D. G.

    2005-02-01

    We show that a low acoustic loss resin enables composite mechanical structures to be bonded with minimal Q degradation. The resin is excreted from the Australian native grass tree Xanthorrhoea. This resin has traditionally been used as an adhesive by the Australian Aborigines. It is shown that the Q factor of the resin is greater than 300 for the 5180Hz resonance, which allows a high Q factor niobium resonator to be constructed with bonded mirrors while maintaining a Q of ˜106.

  6. The accuracy and precision of two non-invasive, magnetic resonance-guided focused ultrasound-based thermal diffusivity estimation methods

    PubMed Central

    Dillon, Christopher R.; Payne, Allison; Christensen, Douglas A.; Roemer, Robert B.

    2016-01-01

    Purpose The use of correct tissue thermal diffusivity values is necessary for making accurate thermal modeling predictions during magnetic resonance-guided focused ultrasound (MRgFUS) treatment planning. This study evaluates the accuracy and precision of two non-invasive thermal diffusivity estimation methods, a Gaussian Temperature method published by Cheng and Plewes in 2002 and a Gaussian specific absorption rate (SAR) method published by Dillon et al in 2012. Materials and Methods Both methods utilize MRgFUS temperature data obtained during cooling following a short (<25s) heating pulse. The Gaussian SAR method can also use temperatures obtained during heating. Experiments were performed at low heating levels (ΔT~10°C) in ex vivo pork muscle and in vivo rabbit back muscle. The non-invasive MRgFUS thermal diffusivity estimates were compared with measurements from two standard invasive methods. Results Both non-invasive methods accurately estimate thermal diffusivity when using MR-temperature cooling data (overall ex vivo error<6%, in vivo<12%). Including heating data in the Gaussian SAR method further reduces errors (ex vivo error<2%, in vivo<3%). The significantly lower standard deviation values (p<0.03) of the Gaussian SAR method indicate that it has better precision than the Gaussian Temperature method. Conclusions With repeated sonications, either MR-based method could provide accurate thermal diffusivity values for MRgFUS therapies. Fitting to more data simultaneously likely makes the Gaussian SAR method less susceptible to noise, and using heating data helps it converge more consistently to the FUS fitting parameters and thermal diffusivity. These effects lead to the improved precision of the Gaussian SAR method. PMID:25198092

  7. Magnetic Resonance-Guided Focal Laser-Induced Interstitial Thermal Therapy in a Canine Prostate Model

    PubMed Central

    Stafford, R. Jason; Shetty, Anil; Elliott, Andrew M.; Klumpp, Sherry A.; McNichols, Roger J.; Gowda, Ashok; Hazle, John D.; Ward, John F.

    2014-01-01

    Purpose To evaluate a newly FDA-cleared closed-loop, magnetic resonance (MR)-guided laser-induced interstitial thermal therapy (LITT) system for targeted ablation of prostate tissue in order to assess targeting ability, lesion generation and feasibility. Materials and Methods Mongrel dogs with (n = 2) and without (n = 5) canine transmissible venereal tumors in the prostate were imaged with a 1.5-T MR imaging scanner. Real-time 3D MR imaging was used to accurately position water-cooled 980-nm laser applicators to pre-determined targets within the canine prostates. Destruction of targeted tissue was guided with MR temperature imaging in real time for precise control of thermal ablation. MR predictions of thermal damage were correlated with findings from post-treatment images and compared to histopathology. Results Template-based targeting using MR guidance allowed the laser applicator to be placed within a mean of 1.1 mm (SD = 0.7 mm) of the target location. The mean width and length of the ablation zone by MR were 13.7 mm (SD = 1.3 mm) and 19.0 mm (SD = 4.2 mm) using single and compound exposures. The thermal damage predicted by MR correlated with the thermal damage determined by post-treatment imaging with a slope near unity and excellent correlation (R2 = 0.94). Conclusions This LITT system provided rapid and localized heating of tissue with minimal collateral thermal spread or injury. Combined with real-time monitoring and template-based planning, MR-guided LITT is an attractive modality for prostate cancer focal therapy. PMID:20727549

  8. Effect of cantilever geometry on the optical lever sensitivities and thermal noise method of the atomic force microscope

    SciTech Connect

    Sader, John E.; Lu, Jianing; Mulvaney, Paul

    2014-11-15

    Calibration of the optical lever sensitivities of atomic force microscope (AFM) cantilevers is especially important for determining the force in AFM measurements. These sensitivities depend critically on the cantilever mode used and are known to differ for static and dynamic measurements. Here, we calculate the ratio of the dynamic and static sensitivities for several common AFM cantilevers, whose shapes vary considerably, and experimentally verify these results. The dynamic-to-static optical lever sensitivity ratio is found to range from 1.09 to 1.41 for the cantilevers studied – in stark contrast to the constant value of 1.09 used widely in current calibration studies. This analysis shows that accuracy of the thermal noise method for the static spring constant is strongly dependent on cantilever geometry – neglect of these dynamic-to-static factors can induce errors exceeding 100%. We also discuss a simple experimental approach to non-invasively and simultaneously determine the dynamic and static spring constants and optical lever sensitivities of cantilevers of arbitrary shape, which is applicable to all AFM platforms that have the thermal noise method for spring constant calibration.

  9. Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

    NASA Astrophysics Data System (ADS)

    Le, Kelvin; Li, Xiaosong; Figueroa, Daniel; Towner, Rheal A.; Garteiser, Philippe; Saunders, Debra; Smith, Nataliya; Liu, Hong; Hode, Tomas; Nordquist, Robert E.; Chen, Wei R.

    2011-12-01

    Laser immunotherapy (LIT) uses a synergistic approach to treat cancer systemically through local laser irradiation and immunological stimulation. Currently, LIT utilizes dye-assisted noninvasive laser irradiation to achieve selective photothermal interaction. However, LIT faces difficulties treating deeper tumors or tumors with heavily pigmented overlying skin. To circumvent these barriers, we use interstitial laser irradiation to induce the desired photothermal effects. The purpose of this study is to analyze the thermal effects of interstitial irradiation using proton resonance frequency (PRF). An 805-nm near-infrared laser with an interstitial cylindrical diffuser was used to treat rat mammary tumors. Different power settings (1.0, 1.25, and 1.5 W) were applied with an irradiation duration of 10 min. The temperature distributions of the treated tumors were measured by a 7 T magnetic resonance imager using PRF. We found that temperature distributions in tissue depended on both laser power and time settings, and that variance in tissue composition has a major influence in temperature elevation. The temperature elevations measured during interstitial laser irradiation by PRF and thermocouple were consistent, with some variations due to tissue composition and the positioning of the thermocouple's needle probes. Our results indicated that, for a tissue irradiation of 10 min, the elevation of rat tumor temperature ranged from 8 to 11°C for 1 W and 8 to 15°C for 1.5 W. This is the first time a 7 T magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. Our work provides a basic understanding of the photothermal interaction needed to control the thermal damage inside a tumor using interstitial laser treatment. Our work may lead to an optimal protocol for future cancer treatment using interstitial phototherapy in conjunction with immunotherapy.

  10. Method for Thermal Spraying of Coatings Using Resonant-Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2008-01-01

    A method has been devised for high-volume, high-velocity surface deposition of protective metallic coatings on otherwise vulnerable surfaces. Thermal spraying is used whereby the material to be deposited is heated to the melting point by passing through a flame. Rather than the usual method of deposition from the jet formed from the combustion products, this innovation uses non-steady combustion (i.e. high-frequency, periodic, confined bursts), which generates not only higher temperatures and heat transfer rates, but exceedingly high impingement velocities an order of magnitude higher than conventional thermal systems. Higher impingement rates make for better adhesion. The high heat transfer rates developed here allow the deposition material to be introduced, not as an expensive powder with high surface-area-to-volume, but in convenient rod form, which is also easier and simpler to feed into the system. The nonsteady, resonant combustion process is self-aspirating and requires no external actuation or control and no high-pressure supply of fuel or air. The innovation has been demonstrated using a commercially available resonant combustor shown in the figure. Fuel is naturally aspirated from the tank through the lower Tygon tube and into the pulsejet. Air for starting is ported through the upper Tygon tube line. Once operation commences, this air is no longer needed as additional air is naturally aspirated through the inlet. A spark plug on the device is needed for starting, but the process carries on automatically as the operational device is resonant and reignites itself with each 220-Hz pulse.

  11. Simulation of generation of dissipative soliton, dissipative soliton resonance and noise-like pulse in Yb-doped mode-locked fiber lasers.

    PubMed

    Cheng, Zhaochen; Li, Huihui; Wang, Pu

    2015-03-01

    we report three types of pulse generation in Yb-doped nonlinear polarization rotation mode-locked fiber lasers in all-normal-dispersion regime through simulation, including dissipative soliton, dissipative soliton resonance and noise-like pulse. We distinguish the different conditions of generating such different pulses by analyzing the transmission curve of saturable absorber, which plays a key role in pulse shaping. PMID:25836822

  12. Conjunction of standing wave and resonance in asymmetric nanowires: a mechanism for thermal rectification and remote energy accumulation

    PubMed Central

    Liu, Yue-Yang; Zhou, Wu-Xing; Chen, Ke-Qiu

    2015-01-01

    As an important way to control and manage heat transport, thermal rectification has become an elementary issue in the field of phononics and plays a key role in the designing of thermal devices. Here we investigate systematically the standing wave and the accompanying resonance process in asymmetric nanowires to understand the standing wave itself and its great effect on thermal rectification. Results show that the standing wave is sensitive to both the structural and thermal properties of the material, and its great effect on enhancing the thermal rectification is realized not only by the energy-localization nature of the standing wave, but also by the resonance-caused large amplitude and high energy of the standing wave. PMID:26628291

  13. Magnetic resonance-guided laser interstitial thermal therapy: report of a series of pediatric brain tumors.

    PubMed

    Tovar-Spinoza, Zulma; Choi, Hoon

    2016-06-01

    OBJECTIVE Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a novel, minimally invasive treatment that has multiple advantages in pediatric use and broad applicability for different types of lesions. Here, the authors report the preliminary results of the first series of pediatric brain tumors treated with MRgLITT at Golisano Children's Hospital in Syracuse, New York. METHODS Pediatric brain tumors treated with MRgLITT between February 2012 and August 2014 at Golisano Children's Hospital were evaluated retrospectively. Medical records, radiological findings, surgical data, complications, and results of tumor volumetric analyses were reviewed. The Visualase thermal laser system (Medtronic) was used in all MRgLITT procedures. RESULTS This series included 11 patients with 12 tumors (pilocytic astrocytoma, ependymoma, medulloblastoma, choroid plexus xanthogranuloma, subependymal giant cell astrocytoma, and ganglioglioma). A single laser and multiple overlapping ablations were used for all procedures. The mean laser dose was 10.23 W, and the mean total ablation time was 68.95 seconds. The mean initial target volume was 6.79 cm(3), and the mean immediate post-ablation volume was 7.86 cm(3). The mean hospital stay was 3.25 days, and the mean follow-up time was 24.5 months. Tumor volume decreased in the first 3 months after surgery (n = 11; p = 0.007) and continued to decrease by the 4- to 6-month followup (n = 11; mean volume 2.61 cm(3); p = 0.009). Two patients experienced post-ablation complications: transient right leg weakness in one patient, and transient hemiparesis, akinetic mutism, and eye movement disorder in the other. CONCLUSIONS Magnetic resonance-guided laser interstitial thermal therapy is an effective first- or second-line treatment for select pediatric brain tumors. Larger multiinstitutional clinical trials are necessary to evaluate its use for different types of lesions to further standardize practices. PMID:26849811

  14. Preliminary investigation into the design of thermally responsive Forster resonance energy transfer colloids

    NASA Astrophysics Data System (ADS)

    Bedford, Monte Scott

    While nuclear imaging techniques (Magnetic Resonance Imaging, Computed Tomography, and Positron Emission Tomography) have proven effective for diagnosis and treatment of disease in the human body, fluorescence-enhanced optical imaging offers additional benefits. Fluorescent imaging provides high resolution with real-time response, persistent lifetime (hours to days), cell targeting, and transdermal penetration with minimal physical encumbrance. Malignant cells can be targeted by absorbance of exogenous fluorescent nanoprobe contrast agents. Imaging is improved by fluorescent enhancement, especially by energy transfer between attached dyes. Also for use against cancer are heat-active treatments, such as hyperthermal, photothermal, and chemothermal therapies. Helpful to these treatments is the thermal response from nanoprobes, within human cells, which provide real-time feedback. The present study investigates the design and feasibility of a nanoprobe molecular device, absorbable into malignant human cells, which provides real-time tracking and thermal response, as indicated by enhanced fluorescence by energy transfer. A poly(propargyl acrylate) colloidal suspension was synthesized. The particles were modified with a triblock copolymer, previously shown to be thermally responsive, and an end-attached fluorescent dye. A second dye was modeled for attachment in subsequent work. When two fluorescent dyes are brought within sufficiently close proximity, and excitation light is supplied, energy can be transferred between dyes to give enhanced fluorescence with a large Stokes shift (increase in wavelength between excitation and emission). The dye pair was modeled for overlap of emission and absorbance wavelengths, and energy transfer was demonstrated with 23% efficiency and a 209 nm Stokes shift. The quantum yield of the donor dye was determined at 70%, and the distance for 50% energy transfer was calculated at 2.9 nm, consistent with reports for similar compounds. When

  15. Nanophononic metamaterial: Thermal conductivity reduction by full-spectrum resonance hybridizations

    NASA Astrophysics Data System (ADS)

    Hussein, Mahmoud; Honarvar, Hossein; Yang, Lina

    Engineered manipulation of phonons can yield beneficial thermal properties in semiconducting materials. One pivotal application relates to thermoelectric materials, or the concept of converting energy in the form of heat into electricity and vice-versa. The ability to use nanostructuring to reduce the thermal conductivity without negatively impacting the power factor provides a promising avenue for achieving high values of the thermoelectric energy conversion figure-of-merit, ZT. Here, we propose a novel nanostructured material configuration that seeks to achieve this goal. Termed ``nanophononic metamaterial,'' the configuration is based on a freestanding silicon membrane with a periodic array, or random forest, of nanopillars erected on the surface. The nanopillars qualitatively alter the base membrane phonon spectrum due to a hybridization mechanism between their local resonances and the underlying atomic lattice dispersion. Using equilibrium molecular dynamics simulations, we predict a factor of 10 drop in the thermal conductivity compared to the corresponding uniform membrane value despite the fact that the nanopillars add more phonon modes to the spectrum.

  16. Tailored Noise Waveform/ Collision-Induced Dissociation of Ions Stored in a Linear Ion Trap Combined with Liquid Chromatography/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    SciTech Connect

    Vilkov, Andrey N.; Bogdanov, Bogdan; Pasa-Tolic, Liljiana; Prior, David C.; Anderson, Gordon A.; Masselon, Christophe D.; Moore, Ronald J.; Smith, Richard D.

    2004-11-01

    A new collision-induced dissociation (CID) technique based on broadband tailored noise waveform (TNW) excitation of ions stored in a linear ion trap has been developed. In comparison with the conventional sustained off-resonance irradiation (SORI) CID method commonly used in Fourier transform ion cyclotron resonance mass spectrometry, this MS/MS technique increases throughput by eliminating the long pump-down delay associated with gas introduction into the high vacuum ICR cell region. In addition, the TNW-CID method speeds spectrum acquisition since it does not require Fourier transformation, calculation of resonant frequencies and generation of the excitation waveforms. We demonstrate TNW-CID coupled with on-line capillary reverse phase liquid chromatography separations for identification of peptides. The experimental results are compared with data obtained using conventional quadrupole ion trap MS/MS and SORI-CID MS/MS in an ICR cell.

  17. Blocking Phonon Transport by Structural Resonances in Alloy-Based Nanophononic Metamaterials Leads to Ultralow Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Xiong, Shiyun; Sääskilahti, Kimmo; Kosevich, Yuriy A.; Han, Haoxue; Donadio, Davide; Volz, Sebastian

    2016-07-01

    Understanding the design rules to obtain materials that enable a tight control of phonon transport over a broad range of frequencies would aid major developments in thermoelectric energy harvesting, heat management in microelectronics, and information and communication technology. Using atomistic simulations we show that the metamaterials approach relying on localized resonances is very promising to engineer heat transport at the nanoscale. Combining designed resonant structures to alloying can lead to extremely low thermal conductivity in silicon nanowires. The hybridization between resonant phonons and propagating modes greatly reduces the group velocities and the phonon mean free paths in the low frequency acoustic range below 4 THz. Concurrently, alloy scattering hinders the propagation of high frequency thermal phonons. Our calculations establish a rationale between the size, shape, and period of the resonant structures, and the thermal conductivity of the nanowire, and demonstrate that this approach is even effective to block phonon transport in wavelengths much longer than the size and period of the surface resonant structures. A further consequence of using resonant structures is that they are not expected to scatter electrons, which is beneficial for thermoelectric applications.

  18. Blocking Phonon Transport by Structural Resonances in Alloy-Based Nanophononic Metamaterials Leads to Ultralow Thermal Conductivity.

    PubMed

    Xiong, Shiyun; Sääskilahti, Kimmo; Kosevich, Yuriy A; Han, Haoxue; Donadio, Davide; Volz, Sebastian

    2016-07-01

    Understanding the design rules to obtain materials that enable a tight control of phonon transport over a broad range of frequencies would aid major developments in thermoelectric energy harvesting, heat management in microelectronics, and information and communication technology. Using atomistic simulations we show that the metamaterials approach relying on localized resonances is very promising to engineer heat transport at the nanoscale. Combining designed resonant structures to alloying can lead to extremely low thermal conductivity in silicon nanowires. The hybridization between resonant phonons and propagating modes greatly reduces the group velocities and the phonon mean free paths in the low frequency acoustic range below 4 THz. Concurrently, alloy scattering hinders the propagation of high frequency thermal phonons. Our calculations establish a rationale between the size, shape, and period of the resonant structures, and the thermal conductivity of the nanowire, and demonstrate that this approach is even effective to block phonon transport in wavelengths much longer than the size and period of the surface resonant structures. A further consequence of using resonant structures is that they are not expected to scatter electrons, which is beneficial for thermoelectric applications. PMID:27447516

  19. Andrade, Omori, and time-to-failure laws from thermal noise in material rupture.

    PubMed

    Saichev, A; Sornette, D

    2005-01-01

    Using a simple mean-field rupture model with quenched disorder in the presence of thermal fluctuations introduced by S. Ciliberto et al., we provide an analytical theory of three ubiquitous empirical observations obtained in creep (constant applied stress) experiments: the initial Andrade-like and Omori-like 1/t decay of the rate of deformation and of fiber ruptures and the 1/( tc-t) critical time-to-failure behavior of acoustic emissions just prior to the macroscopic rupture. The lifetime of the material is controlled by a thermally activated Arrhenius nucleation process, describing the crossover between these two regimes, as shown by S. Ciliberto et al. Thus tiny thermal fluctuations may actually play an essential role in macroscopic deformation and rupture processes at room temperature. We also discover a reentrant dependence of the lifetime as a function of the amount of quenched disorder. PMID:15697748

  20. Resonant Pedestal Pressure Reduction Induced by a Thermal Transport Enhancement due to Stochastic Magnetic Boundary Layers in High Temperature Plasmas

    SciTech Connect

    Schmitz, O.; Evans, T.E.; Fenstermacher, M. E.; Unterberg, E. A.; Austin, M. E.; Bray, B. D.; Brooks, N. H.; Frerichs, H.; Groth, M.; Jakubowski, M. W.; Lasnier, C. J.; Lehnen, M.; Leonard, A. W.; Mordijck, S.; Moyer, R.A.; Osborne, T. H.; Reiter, D.; Samm, U.; Schaffer, M. J.; Unterberg, B.; West, W. P.

    2009-01-01

    Good alignment of the magnetic field line pitch angle with the mode structure of an external resonant magnetic perturbation (RMP) field is shown to induce modulation of the pedestal electron pressure p(e) in high confinement high rotation plasmas at the DIII-D tokamak with a shape similar to ITER, the next step tokamak experiment. This is caused by an edge safety factor q(95) resonant enhancement of the thermal transport, while in contrast, the RMP induced particle pump out does not show a significant resonance. The measured p(e) reduction correlates to an increase in the modeled stochastic layer width during pitch angle variations matching results from resistive low rotation plasmas at the TEXTOR tokamak. These findings suggest a field line pitch angle resonant formation of a stochastic magnetic edge layer as an explanation for the q(95) resonant character of type-I edge localized mode suppression by RMPs.

  1. Resonant Pedestal Pressure Reduction Induced by a Thermal Transport Enhancement due to Stochastic Magnetic Boundary Layers in High Temperature Plasmas

    SciTech Connect

    Schmitz, O.; Frerichs, H.; Lehnen, M.; Reiter, D.; Samm, U.; Unterberg, B.; Evans, T. E.; Austin, M. E.; Bray, B. D.; Brooks, N. H.; Leonard, A. W.; Osborne, T. H.; Schaffer, M. J.; West, W. P.; Fenstermacher, M. E.; Groth, M.; Lasnier, C. J.; Unterberg, E. A.; Jakubowski, M. W.; Mordijck, S.

    2009-10-16

    Good alignment of the magnetic field line pitch angle with the mode structure of an external resonant magnetic perturbation (RMP) field is shown to induce modulation of the pedestal electron pressure p{sub e} in high confinement high rotation plasmas at the DIII-D tokamak with a shape similar to ITER, the next step tokamak experiment. This is caused by an edge safety factor q{sub 95} resonant enhancement of the thermal transport, while in contrast, the RMP induced particle pump out does not show a significant resonance. The measured p{sub e} reduction correlates to an increase in the modeled stochastic layer width during pitch angle variations matching results from resistive low rotation plasmas at the TEXTOR tokamak. These findings suggest a field line pitch angle resonant formation of a stochastic magnetic edge layer as an explanation for the q{sub 95} resonant character of type-I edge localized mode suppression by RMPs.

  2. Observation of thermal spin-transfer torque via ferromagnetic resonance in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaohui; Bai, Lihui; Chen, Xiaobin; Guo, Hong; Fan, X. L.; Xue, D. S.; Houssameddine, D.; Hu, C.-M.

    2016-08-01

    The thermal spin-transfer torque (TSTT) in magnetic tunneling junctions (MTJs) was systematically studied using electrical detection of ferromagnetic resonance (FMR). Evidence for the existence of TSTT in MTJs is observed. A temperature difference was applied across an MTJ acting as a TSTT on the free layer of the MTJ. The FMR of the free layer was then excited by a microwave current and electrically detected as a dc voltage. We found that the FMR line shape was changed by the TSTT, indicated by the ratio of dispersive and Lorentz components of the FMR spectra (D /L ). D /L increases by increasing the temperature difference. In addition, we analyze the magnetization orientation dependence of TSTT and provide solid evidence that this dependence differs from the magnetization orientation dependence of spin-transfer torque driven by a dc bias.

  3. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2010-01-01

    An apparatus and method [or thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such a Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air. and a spark. Metal is inserted continuously in a high volume of meta1 into a combustion chamber of the pulsejet. The combustion is thereafter. controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tail pipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  4. Thermal field fluctuations in a magnetic tip / implications for magnetic resonance force microscopy

    NASA Astrophysics Data System (ADS)

    Hannay, J. D.; Chantrell, R. W.; Rugar, D.

    2000-05-01

    Thermally excited magnetic fluctuations are fundamental to the behavior of small ferromagnetic particles and have practical consequences for the proposed detection of individual spins by magnetic resonance force microscopy (MRFM). In particular, fluctuating fields from a nearby magnetic tip can increase the relaxation rate of spins in a sample if there is significant spectral density of field fluctuation at the Larmor frequency of the target spin. As an initial step toward understanding this issue, magnetic field fluctuations have been simulated which emanate from a magnetic tip with dimensions 60 nm×60 nm×2 μm. It was found that the fluctuations in a cobalt magnetic tip were too strong for MRFM experiments aimed at detecting individual electron spins. However, the results obtained for a PrFeB tip fell within the tolerance required.

  5. Observations of thermally excited ferromagnetic resonance on spin torque oscillators having a perpendicularly magnetized free layer

    SciTech Connect

    Tamaru, S. Kubota, H.; Yakushiji, K.; Konoto, M.; Nozaki, T.; Fukushima, A.; Imamura, H.; Taniguchi, T.; Arai, H.; Tsunegi, S.; Yuasa, S.; Suzuki, Y.

    2014-05-07

    Measurements of thermally excited ferromagnetic resonance were performed on spin torque oscillators having a perpendicularly magnetized free layer and in-plane magnetized reference layer (abbreviated as PMF-STO in the following) for the purpose of obtaining magnetic properties in the PMF-STO structure. The measured spectra clearly showed a large main peak and multiple smaller peaks on the high frequency side. A Lorentzian fit on the main peak yielded Gilbert damping factor of 0.0041. The observed peaks moved in proportion to the out-of-plane bias field. From the slope of the main peak frequency as a function of the bias field, Lande g factor was estimated to be about 2.13. The mode intervals showed a clear dependence on the diameter of the PMF-STOs, i.e., intervals are larger for a smaller diameter. These results suggest that the observed peaks should correspond to eigenmodes of lateral spin wave resonance in the perpendicularly magnetized free layer.

  6. Observations of thermally excited ferromagnetic resonance on spin torque oscillators having a perpendicularly magnetized free layer

    NASA Astrophysics Data System (ADS)

    Tamaru, S.; Kubota, H.; Yakushiji, K.; Konoto, M.; Nozaki, T.; Fukushima, A.; Imamura, H.; Taniguchi, T.; Arai, H.; Tsunegi, S.; Yuasa, S.; Suzuki, Y.

    2014-05-01

    Measurements of thermally excited ferromagnetic resonance were performed on spin torque oscillators having a perpendicularly magnetized free layer and in-plane magnetized reference layer (abbreviated as PMF-STO in the following) for the purpose of obtaining magnetic properties in the PMF-STO structure. The measured spectra clearly showed a large main peak and multiple smaller peaks on the high frequency side. A Lorentzian fit on the main peak yielded Gilbert damping factor of 0.0041. The observed peaks moved in proportion to the out-of-plane bias field. From the slope of the main peak frequency as a function of the bias field, Lande g factor was estimated to be about 2.13. The mode intervals showed a clear dependence on the diameter of the PMF-STOs, i.e., intervals are larger for a smaller diameter. These results suggest that the observed peaks should correspond to eigenmodes of lateral spin wave resonance in the perpendicularly magnetized free layer.

  7. Resonant microwave absorption in thermally deposited au nanoparticle films near percolation coverage.

    PubMed

    Obrzut, Jan; Douglas, Jack F; Kirillov, Oleg; Sharifi, Fred; Liddle, J Alexander

    2013-07-16

    We observe a resonant transition in the microwave absorption of thin thermally deposited Au nanoparticle films near the geometrical percolation transition pc where the films exhibit a 'fractal' heterogeneous geometry. Absorption of incident microwave radiation increases sharply near pc, consistent with effective medium theory predictions. Both the theory and our experiments indicate that the hierarchical structure of these films makes their absorption insensitive to the microwave radiation wavelength λ, so that this singular absorption of microwave radiation is observed over a broad frequency range between 100 MHz and 20 GHz. The interaction of electromagnetic radiation with randomly distributed conductive scattering particles gives rise to localized resonant modes, and our measurements indicate that this adsorption process is significantly enhanced for microwaves in comparison to ordinary light. In particular, above the percolation transition a portion of the injected microwave power is stored within the film until dissipated. Finally, we find that the measured surface conductivity can be quantitatively described at all Au concentrations by generalized effective medium theory, where the fitted conductivity percolation exponents and pc itself are consistent with known two-dimensional estimates. Our results demonstrate that microwave measurements provide a powerful means of remotely measuring the electromagnetic properties of highly heterogeneous conducting films, enabling purposeful engineering of the electromagnetic properties of thin films in the microwave frequency range through fabrication of 'disordered' films of conducting particles such as metal nanoparticles or carbon nanotubes. PMID:23815370

  8. Resonant photo-thermal modification of vertical gallium arsenide nanowires studied using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Walia, Jaspreet; Boulanger, Jonathan; Dhindsa, Navneet; LaPierre, Ray; (Shirley Tang, Xiaowu; Saini, Simarjeet S.

    2016-06-01

    Gallium arsenide nanowires have shown considerable promise for use in applications in which the absorption of light is required. When the nanowires are oriented vertically, a considerable amount of light can be absorbed, leading to significant heating effects. Thus, it is important to understand the threshold power densities that vertical GaAs nanowires can support, and how the nanowire morphology is altered under these conditions. Here, resonant photo-thermal modification of vertical GaAs nanowires was studied using both Raman spectroscopy and electron microscopy techniques. Resonant waveguiding, and subsequent absorption of the excited optical mode reduces the irradiance vertical GaAs nanowires can support relative to horizontal ones, by three orders of magnitude before the onset of structural changes occur. A power density of only 20 W mm‑2 was sufficient to induce local heating in the nanowires, resulting in the formation of arsenic species. Upon further increasing the power, a hollow nanowire morphology was realized. These findings are pertinent to all optical applications and spectroscopic measurements involving vertically oriented GaAs nanowires. Understanding the optical absorption limitations, and the effects of exceeding these limitations will help improve the development of all III–V nanowire devices.

  9. Phase-dependent deterministic switching of magnetoelectric spin wave detector in the presence of thermal noise via compensation of demagnetization

    SciTech Connect

    Dutta, Sourav Naeemi, Azad; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.

    2015-11-09

    The possibility of achieving phase-dependent deterministic switching of the magnetoelectric spin wave detector in the presence of thermal noise has been discussed. The proposed idea relies on the modification of the energy landscape by partially canceling the out-of-plane demagnetizing field and the resultant change in the intrinsic magnetization dynamics to drive the nanomagnet towards a preferential final magnetization state. The remarkable increase in the probability of successful switching can be accounted for by the shift in the location of the saddle point in the energy landscape and a resultant change in the nature of the relaxation dynamics of the magnetization from a highly precessional to a fairly damped one and an increased dependence on the initial magnetization values, a crucial requirement for phase-dependent spin wave detection.

  10. Phase-dependent deterministic switching of magnetoelectric spin wave detector in the presence of thermal noise via compensation of demagnetization

    NASA Astrophysics Data System (ADS)

    Dutta, Sourav; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.; Naeemi, Azad

    2015-11-01

    The possibility of achieving phase-dependent deterministic switching of the magnetoelectric spin wave detector in the presence of thermal noise has been discussed. The proposed idea relies on the modification of the energy landscape by partially canceling the out-of-plane demagnetizing field and the resultant change in the intrinsic magnetization dynamics to drive the nanomagnet towards a preferential final magnetization state. The remarkable increase in the probability of successful switching can be accounted for by the shift in the location of the saddle point in the energy landscape and a resultant change in the nature of the relaxation dynamics of the magnetization from a highly precessional to a fairly damped one and an increased dependence on the initial magnetization values, a crucial requirement for phase-dependent spin wave detection.

  11. A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers

    NASA Astrophysics Data System (ADS)

    Paine, C. G.; Bock, J. J.; Hristov, V. V.; Lange, A. E.

    2002-05-01

    We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs˜1×10-17 W Hz-1/2. Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz-1/2 to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility.

  12. R-MATRIX RESONANCE ANALYSIS AND STATISTICAL PROPERTIES OF THE RESONANCE PARAMETERS OF 233U IN THE NEUTRON ENERGY RANGE FROM THERMAL TO 600 eV

    SciTech Connect

    Leal, L.C.

    2001-02-27

    The R-matrix resonance analysis of experimental neutron transmission and cross sections of {sup 233}U, with the Reich-Moore Bayesian code SAMMY, was extended up to the neutron energy of 600 eV by taking advantage of new high resolution neutron transmission and fission cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA). The experimental data base is described. In addition to the microscopic data (time-of-flight measurements of transmission and cross sections), some experimental and evaluated integral quantities were included in the data base. Tabulated and graphical comparisons between the experimental data and the SAMMY calculated cross sections are given. The ability of the calculated cross sections to reproduce the effective multiplication factors k{sub eff} for various thermal, intermediate, and fast systems was tested. The statistical properties of the resonance parameters were examined and recommended values of the average s-wave resonance parameters are given.

  13. Method to Produce Flexible Ceramic Thermal Protection System Resistant to High Aeroacoustic Noise

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor); Calamito, Dominic P. (Inventor); Jong, Anthony (Inventor)

    1997-01-01

    A method of producing a three dimensional angle interlock ceramic fiber which is stable to high aeroacoustic noise of about 170 decibels and to high temperatures of about 2500 F is disclosed. The method uses multiple separate strands of a ceramic fiber or ceramic tow suitable for weaving having multiple warp fibers and multiple fill fibers woven with a modified fly-shuttle loom or rapier shuttleless loom which has nip rolls, a modified fabric advancement mechanism and at least eight harnesses in connection with a Dobby pattern chain utilizing sufficient heddles for each warp fiber and a reed which accommodates at least 168 ends per inch. The method produces a multilayered top fabric, rib fabric and single-layered bottom fabric.

  14. Fuzzy epsilon filters for removal of thermal and speckle noise from gray-scale images

    NASA Astrophysics Data System (ADS)

    Bessai, H. J.

    1994-11-01

    This paper develops constructions of filters for semi-automatic enhancement of still images. It emphasizes the joint application of linear and nonlinear filtering techniques. The decision which filter type is to be activated predominantly depends on perceptual criteria. These means of judging are readily described in terms of linguistic variables, i.e., the user is relieved from the tedious task of evaluating noise statistics. The decision process itself is supported by standard fuzzy reasoning techniques and corrected updates of the crisp outputs are available on a user-defined frame-by-frame or window-by-window basis. Thus, both handling of the filter tools and the individual filtering depth (gain, bandwidth, etc.) are controlled by a common rule base. Experiments with noisy grayscale images demonstrate that compared to non-joint methods, the proposed solution results in acceptable scene interpretation and clear identification of originally concealed objects.

  15. Surface Plasmon Resonance Enhanced Polymer Solar Cells by Thermally Evaporating Au into Buffer Layer.

    PubMed

    Yao, Mengnan; Jia, Xu; Liu, Yan; Guo, Wenbin; Shen, Liang; Ruan, Shengping

    2015-08-26

    Generally, the surface plasmon resonance (SPR) effect of metal nanoparticles is widely applied on polymer solar cells (PSCs) to improve device performance by doping method into solution. Herein, a diameter-controlled thermally evaporation method was used to realize Au nanoparticles (Au NPs) doping into WO3 anode buffer layer in inverted PSCs. The surface energy differences between Au and WO3 inevitably lead to Au growing up through the process from nucleation, isolated island, aggregation of metal islands to continuous films along with the process of evaporation. The atom force microscopy (AFM) images indicate that critical thickness of Au film formation is 8 nm, which is in accordance with current density-voltage (J-V) and incident photon-to-electron conversion efficiency (IPCE) measurement results of optimal device performance. The power conversion efficiency (PCE) with 8 nm Au is dramatically improved from 4.67 ± 0.13% to 6.63 ± 0.17% compared to the one without Au. Moreover, the optical absorption enhancement is demonstrated by steady state photoluminescence (PL), which agrees well with transmission spectrum. The optical and electrical improvement all suggest that thermal evaporation is the appropriate method to further enhance device performance. PMID:26230868

  16. Electron spin resonance study of thermal instability reactions in jet fuels

    NASA Technical Reports Server (NTRS)

    Zeldes, H.; Livingston, R.

    1984-01-01

    Free radicals were studied by electron spin resonance (ESR) using model compounds that are representative of constituents of jet fuels. Radical formation was initiated with peroxides and hydroperoxides by using UV photolysis at and near room temperature and thermal initiation at higher temperatures. Both oxygen free and air saturated systems were studied. N-Dodecane was frequently used as a solvent, and a mixture of n-dodecyl radicals was made with a peroxide initiator in n-dodecane (free of oxygen) thermally at 212 C and photolytically at room temperature. Hydrogen abstraction from the 3,4,5 and 6-positions gives radicals that are sufficiently alike that their spectra are essentially superimposed. The radical formed by abstract of hydrogen from the 2-position gives a different spectrum. ESR parameters for these radicals were measured. The radical formed by abstraction of a primary hydrogen was not observed. Similar radicals are formed from n-decane. A variety of exploratory experiments were carried out with systems that give free radical spectra to which was added small amounts of 2,5-dimethylpyrrole.

  17. Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs

    PubMed Central

    Shakoor, Rana Iqtidar; Bazaz, Shafaat Ahmed; Kraft, Michael; Lai, Yongjun; Masood ul Hassan, Muhammad

    2009-01-01

    High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /°/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 × 2.6 mm2, almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has

  18. Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs.

    PubMed

    Shakoor, Rana Iqtidar; Bazaz, Shafaat Ahmed; Kraft, Michael; Lai, Yongjun; Masood Ul Hassan, Muhammad

    2009-01-01

    High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /°/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 × 2.6 mm(2), almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator

  19. Quantitative linear and nonlinear resonance inspection techniques and analysis for material characterization: application to concrete thermal damage.

    PubMed

    Payan, C; Ulrich, T J; Le Bas, P Y; Saleh, T; Guimaraes, M

    2014-08-01

    Developed in the late 1980s, Nonlinear Resonant Ultrasound Spectroscopy (NRUS) has been widely employed in the field of material characterization. Most of the studies assume the measured amplitude to be proportional to the strain amplitude which drives nonlinear phenomena. In 1D resonant bar experiments, the configuration for which NRUS was initially developed, this assumption holds. However, it is not true for samples of general shape which exhibit several resonance mode shapes. This paper proposes a methodology based on linear resonant ultrasound spectroscopy, numerical simulations and nonlinear resonant ultrasound spectroscopy to provide quantitative values of nonlinear elastic moduli taking into account the 3D nature of the samples. In the context of license renewal in the field of nuclear energy, this study aims at providing some quantitative information related to the degree of micro-cracking of concrete and cement based materials in the presence of thermal damage. The resonance based method is validated as regard with concrete microstructure evolution during thermal exposure. PMID:25096088

  20. A real-time de-noising method applied for transient and weak biomolecular interaction analysis in surface plasmon resonance biosensing

    NASA Astrophysics Data System (ADS)

    Zhan, Shuyue; Shi, Chunfei; Ou, Huichao; Song, Hong; Wang, Xiaoping

    2016-03-01

    Surface plasmon resonance (SPR) biosensing technology will likely become a type of label-free technology for transient and weak biomolecular interaction analysis (BIA); however, it needs some improvement with regard to high-speed and high-resolution measurement. We studied a type of real-time de-noising (RD) data processing method for SPR sensorgrams based on moving average; it can immediately distinguish ultra-weak signals during the process of experiment, and can display a low-noise sensorgram in real time. A flow injection analysis experiment and a CM5 sensorchip affinity experiment are designed to evaluate the characteristics of the RD method. High noise suppression ability and low signal distortion risks of the RD method have been proved. The RD method does not significantly distort signals of the sensorgram in the molecular affinity experiment, and K D values of the RD method essentially coincide with those of the raw sensorgram with a higher signal-to-noise ratio (SNR). Meanwhile, by the RD method denoising the sensorgram with an ultralow SNR that is closer to the condition of the transient and weak molecular interactions, the kinetic constant can be more accurately analyzed, whereas it cannot be realized for the raw sensorgram. The crucial function and significance of the RD method are primarily embodied in the measurement limit of SPR sensing.

  1. Resonance

    NASA Astrophysics Data System (ADS)

    Perozzi, E.; Murdin, P.

    2000-11-01

    A resonance in CELESTIAL MECHANICS occurs when some of the quantities characterizing the motion of two or more celestial bodies can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as ...

  2. Thermal noise of mechanical oscillators in steady states with a heat flux.

    PubMed

    Conti, Livia; Lazzaro, Claudia; Karapetyan, Gagik; Bonaldi, Michele; Pegoraro, Matteo; Thakur, Ram-Krishna; De Gregorio, Paolo; Rondoni, Lamberto

    2014-09-01

    We present an experimental investigation of the statistical properties of the position fluctuations of low-loss oscillators in nonequilibrium steady states. The oscillators are coupled to a heat bath, and a nonequilibrium steady state is produced by flowing a constant heat flux, setting a temperature difference across the oscillators. We investigated the distribution of the measurements of the square of the oscillator position and searched for signs of changes with respect to the equilibrium case. We found that, after normalization by the mean value, the second, third, and fourth standardized statistical moments are not modified by the underlying thermodynamic state. This differs from the behavior of the absolute, i.e., not normalized, second moment, which is strongly affected by temperature gradients and heat fluxes. We illustrate this with a numerical experiment in which we study via molecular dynamics the fluctuations of the length of a one-dimensional chain of identical particles interacting via anharmonic interparticle potentials, with the extremes thermostated at different temperatures: we use the variance of the length in correspondence to its first elastic mode of resonance to define an effective temperature which we observe to depart from the thermodynamic one in the nonequilibrium states. We investigate the effect of changing the interparticle potential and show that the qualitative behavior of the nonequilibrium excess is unchanged. Our numerical results are consistent with the chain length being Gaussian distributed in the nonequilibrium states. Our experimental investigation reveals that the position variance is the only, and crucially easily accessible, observable for distinguishing equilibrium from nonequilibrium steady states. The consequences of this fact for the design of interferometric gravitational wave detectors are discussed. PMID:25314407

  3. Resonant microphone based on laser beam deflection

    NASA Astrophysics Data System (ADS)

    Roark, Kevin; Diebold, Gerald J.

    2004-07-01

    A microphone consisting of a flexible membrane coupled to a Helmholtz resonator can be constructed to have a resonance at a specific frequency making it, unlike conventional broadband microphones, a frequency selective detector of sound. The present device uses a laser beam reflected from the membrane and directed onto a split photodiode to record the motion of the membrane. Since the microphone has a lightly damped resonance, both the thermal noise fluctuations in the displacement of the membrane from its equilibrium position and the response of the microphone to sound at the resonance frequency are large. The large amplitude of both the signal and the noise fluctuations means that effect of amplifier noise on the microphone's sensitivity is diminished relative to that in broadband microphones. Applications of the microphone include photoacoustic detection of gases employing low power lasers.

  4. Electron spin resonance study of point defects in thermal GaAs/GaAs-oxide structures

    NASA Astrophysics Data System (ADS)

    Nguyen, S.; Afanas'ev, V. V.; Stesmans, A.

    2012-12-01

    In an attempt to atomically assess interface and oxide-related point defects, a first basic multifrequency low-temperature electron spin resonance study has been carried out on semi-insulating (Fe compensated) GaAs/oxide structures, implying both powders and (100)GaAs/oxide slices, thermally grown in the range Tox=350-615 °C. Various spectra are observed: As for powders, this includes the 4-line EL2 defect spectrum centered at g~2.043 and characterized by the isotropic hyperfine constant Aiso~ 910 G, ascribed to the 75AsGa+ antisite defect. Observed in freshly crushed powder, it substantially increases in density with oxidation, in line with theoretical expectation; A maximum appears reached for at Tox~440 °C. It is not observed in the parent c-GaAs wafer. A second isotropic signal is observed at g~1.937 in powders for Tox in the range 510-615 °C, but only after additional VUV irradiation; it may correspond to As clusters. In bulk (100)GaAs, we observe the 5-branch spectrum of substitutional Fe impurities (spin S=5/2) in GaAs, with inferred crystal field constant a ≈ 360 G, well in line with previous observations. The results are discussed within the framework of advanced theoretical interface and defect models and previous experimental assessment.

  5. Properties of the solar wind electrons between 1.1 and 3.3 AU from Ulysses thermal noise measurements

    SciTech Connect

    Maksimovic, M.; Hoang, S.; Bougeret, J.-L.

    1996-07-20

    Using the distribution function f(v) of the solar wind electrons made of two Maxwellians: a core (density n{sub c}, temperature T{sub c}) and a halo (density n{sub h}, temperature T{sub h}), we determine the quasi-thermal noise (QTN) induced by the ambient electrons on the long wire dipole antenna connected to the radio receiver on the Ulysses Unified Radio and Plasma Wave (URAP) Experiment. The QTN spectroscopy yields the total electron density n{sub e}, the core temperature T{sub c}, and the core and halo kinetic pressures n{sub c}T{sub c} and n{sub h}T{sub h}. We present the results of n{sub e} and T{sub c} measured between 1.1 and 3.3 AU in the ecliptic plane, from November 1990 to June 1991. We investigate the variation of T{sub c} with the heliocentric distance. We also study this radial gradient as a function of three classes of n{sub e} normalized to 1 AU: Low, intermediate and high densities. The T{sub c} gradient is found to increase with increasing plasma density.

  6. Liquid-phase exfoliated graphene self-assembled films: Low-frequency noise and thermal-electric characterization

    NASA Astrophysics Data System (ADS)

    Tubon Usca, G.; Hernandez-Ambato, J.; Pace, C.; Caputi, L. S.; Tavolaro, A.

    2016-09-01

    In few years, graphene has become a revolutionary material, leading not only to applications in various fields such as electronics, medicine and environment, but also to the production of new types of 2D materials. In this work, Liquid Phase Exfoliation (LPE) was applied to natural graphite by brief sonication or mixer treatment in suitable solvents, in order to produce Few Layers Graphene (FLG) suspensions. Additionally, zeolite 4A (Z4A) was added during the production of FLG flakes-based inks, with the aim of aiding the exfoliation process. Conductive films were obtained by drop casting three types of suspensions over Al2O3 substrates with interdigitated electrodes, with total channel surface of 1.39 mm2. The morphology characterization resulted in the verification of the presence of thin self-assembled flakes. Raman studies gave evidence of 4 to 10 layers graphene flakes. Electrical measurements were performed to state the Low-Frequency Noise and Thermal-Electric characteristics of the samples. We observe interesting relations between sample preparation procedures and electrical properties.

  7. An analytical study on excitation of nuclear-coupled thermal-hydraulic instability due to seismically induced resonance in BWR

    SciTech Connect

    Hirano, Masashi

    1997-07-01

    This paper describes the results of a scoping study on seismically induced resonance of nuclear-coupled thermal-hydraulic instability in BWRs, which was conducted by using TRAC-BF1 within a framework of a point kinetics model. As a result of the analysis, it is shown that a reactivity insertion could occur accompanied by in-surge of coolant into the core resulted from the excitation of the nuclear-coupled instability by the external acceleration. In order to analyze this phenomenon more in detail, it is necessary to couple a thermal-hydraulic code with a three-dimensional nuclear kinetics code.

  8. 57Co (n,γ) 58Co reaction cross section: Thermal and resonance integral measurements and energy dependence

    NASA Astrophysics Data System (ADS)

    Maidana, Nora L.; Mesa, Joel; Vanin, Vito R.; Castro, Ruy M.; Dias, Mauro S.; Koskinas, Marina F.

    2004-07-01

    The 57Co (n,γ) 58Co thermal and resonance integral cross section were measured as 51 (5) b and 20.0 (19) b , respectively, by irradiating aliquots of 57Co solution sealed inside quartz bottles near the core of the IEA-R1 IPEN research reactor and counting the gamma-ray residual activity. The irradiations were monitored using Au-Al alloy foils, with and without Cd cover. The gamma-ray measurements were performed with a shielded HPGe detector. Westcott formalism was applied for the average neutron flux determination. The cross section energy dependence was evaluated using the multilevel Breit-Wigner expression considering the first two resonances and the statistical model for energies above the second resonance. Maxwellian averaged neutron capture cross section with neutron temperatures between 5 and 100 keV were also evaluated.

  9. {sup 57}Co(n,{gamma}){sup 58}Co reaction cross section: Thermal and resonance integral measurements and energy dependence

    SciTech Connect

    Maidana, Nora L.; Mesa, Joel; Vanin, Vito R.; Castro, Ruy M.; Dias, Mauro S.; Koskinas, Marina F.

    2004-07-01

    The {sup 57}Co(n,{gamma}){sup 58}Co thermal and resonance integral cross section were measured as 51(5) b and 20.0(19) b, respectively, by irradiating aliquots of {sup 57}Co solution sealed inside quartz bottles near the core of the IEA-R1 IPEN research reactor and counting the gamma-ray residual activity. The irradiations were monitored using Au-Al alloy foils, with and without Cd cover. The gamma-ray measurements were performed with a shielded HPGe detector. Westcott formalism was applied for the average neutron flux determination. The cross section energy dependence was evaluated using the multilevel Breit-Wigner expression considering the first two resonances and the statistical model for energies above the second resonance. Maxwellian averaged neutron capture cross section with neutron temperatures between 5 and 100 keV were also evaluated.

  10. A pressure gauge based on gas density measurement from analysis of the thermal noise of an atomic force microscope cantilever

    SciTech Connect

    Seo, Dongjin; Ducker, William A.; Paul, Mark R.

    2012-05-15

    We describe a gas-density gauge based on the analysis of the thermally-driven fluctuations of an atomic force microscope (AFM) cantilever. The fluctuations are modeled as a ring-down of a simple harmonic oscillator, which allows fitting of the resonance frequency and damping of the cantilever, which in turn yields the gas density. The pressure is obtained from the density using the known equation of state. In the range 10-220 kPa, the pressure readings from the cantilever gauge deviate by an average of only about 5% from pressure readings on a commercial gauge. The theoretical description we use to determine the pressure from the cantilever motion is based upon the continuum hypothesis, which sets a minimum pressure for our analysis. It is anticipated that the cantilever gauge could be extended to measure lower pressures given a molecular theoretical description. Alternatively, the gauge could be calibrated for use in the non-continuum range. Our measurement technique is similar to previous AFM cantilever measurements, but the analysis produces improved accuracy.

  11. 13C Nuclear magnetic resonance studies of kerogen from Cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations

    USGS Publications Warehouse

    Dennis, L.W.; Maciel, G.E.; Hatcher, P.G.; Simoneit, B.R.T.

    1982-01-01

    Cretaceous black shales from DSDP Leg 41, Site 368 in the Eastern Atlantic Ocean were thermally altered during the Miocene by an intrusive basalt. The sediments overlying and underlying the intrusive body were subjected to high temperatures (up to ~ 500??C) and, as a result, their kerogen was significantly altered. The extent of this alteration has been determined by examination by means of 13C nuclear magnetic resonance, using cross polarization/magic-angle spinning (CP/MAS). Results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body. Laboratory heating experiments, simulating the thermal effects of the basaltic intrusion, produced similar results on unaltered shale from the drill core. The 13C CP/MAS results appear to provide a good measure of thermal alteration. ?? 1982.

  12. Exploring single-molecule interactions through 3D optical trapping and tracking: From thermal noise to protein refolding

    NASA Astrophysics Data System (ADS)

    Wong, Wesley Philip

    The focus of this thesis is the development and application of a novel technique for investigating the structure and dynamics of weak interactions between and within single-molecules. This approach is designed to explore unusual features in bi-directional transitions near equilibrium. The basic idea is to infer molecular events by observing changes in the three-dimensional Brownian fluctuations of a functionalized microsphere held weakly near a reactive substrate. Experimentally, I have developed a unique optical tweezers system that combines an interference technique for accurate 3D tracking (˜1 nm vertically, and ˜2-3 nm laterally) with a continuous autofocus system which stabilizes the trap height to within 1-2 mn over hours. A number of different physical and biological systems were investigated with this instrument. Data interpretation was assisted by a multi-scale Brownian Dynamics simulation that I have developed. I have explored the 3D signatures of different molecular tethers, distinguishing between single and multiple attachments, as well as between stiff and soft linkages. As well, I have developed a technique for measuring the force-dependent compliance of molecular tethers from thermal noise fluctuations and demonstrated this with a short ssDNA oligomer. Another practical approach that I have developed for extracting information from fluctuation measurements is Inverse Brownian Dynamics, which yields the underlying potential of mean force and position dependent diffusion coefficient from the Brownian motion of a particle. I have also developed a new force calibration method that takes into account video motion blur, and that uses this information to measure bead dynamics. Perhaps most significantly, I have trade the first direct observations of the refolding of spectrin repeats under mechanical force, and investigated the force-dependent kinetics of this transition.

  13. Highly sensitive thermometer using a vacuum-packed Si resonator in a microfluidic chip for the thermal measurement of single cells.

    PubMed

    Inomata, Naoki; Toda, Masaya; Ono, Takahito

    2016-09-21

    A highly sensitive thermometer system for a living cell is proposed, fabricated, and evaluated. The system possesses a resonant thermal sensor surrounded by vacuum in a microfluidic chip. The measurement principle relies on resonant frequency tracking of the resonator in temperature variations due to the heat from a sample cell; the heat is conducted from the sample cell in the microfluidic channel via a heat guide connecting the resonator to a sample stage. This configuration can reduce heat loss from the resonator to the surroundings and damping in water. Two types of resonators are prepared, i.e., a cantilevered resonator and a double-supported resonator. The resonator sizes as a sensor are 30 × 50 × 1.5 μm in the cantilevered resonator, 30 × 75 × 0.40 μm in the double-supported one, respectively. The temperature and thermal resolutions of 79 μK and 1.90 nW, respectively, are achieved using the double-supported resonator. Two types of heat emissions from single brown fat cells are detected; one is continuous heat generation in the presence of chemical stimulation by a norepinephrine solution, and the other is pulsed without any stimulation. PMID:27526966

  14. Diverse output states from an all-normal dispersion ytterbium-doped fiber laser: Q-switch, dissipative soliton resonance, and noise-like pulse

    NASA Astrophysics Data System (ADS)

    Xu, Z. W.; Zhang, Z. X.

    2013-06-01

    An all-normal-dispersion ytterbium-doped fiber ring laser has been demonstrated, with different operation regimes: Q-switch, CW mode-locking and noise-like pulses, depending on the pump power and suitable orientation of the polarization controllers. As a transition between Q-switch and CW mode-locking, Q-switched mode-locking has also been observed. Moreover, our experiment shows that the CW mode-locking operation is the result of dissipative soliton resonance in the all-normal-dispersion fiber laser without external filter, which is a new way to generate high-energy pulses. This fiber laser with diverse outputs has many potential applications, and is helpful to investigate laser dynamics.

  15. Influence of skew rays on the sensitivity and signal-to-noise ratio of a fiber-optic surface-plasmon-resonance sensor: a theoretical study

    SciTech Connect

    Dwivedi, Yogendra S.; Sharma, Anuj K.; Gupta, Banshi D

    2007-07-20

    We have theoretically analyzed the influence of skew rays on the performance of a fiber-optic sensor based on surface plasmon resonance. The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for skewness dependence includes the material dispersion in fiber cores and metal layers, simultaneous excitation of skew rays, and meridional rays in the fiber core along with all guided rays launching from a collimated light source. The effect of skew rays on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the different values of design parameters such as numerical aperture, fiber core diameter, and the length of the surface-plasmon-resonance (SPR)active sensing region. This detailed analysis for the effect of skewness on the SNR and the sensitivity of the sensor leads us to achieve the best possible performance from a fiber-optic SPR sensor against the skewness in the optical fiber.

  16. Study of Thermally Induced Damage and its Recovery in ZnO Single Crystals by Elastic Resonant Ion Channeling

    NASA Astrophysics Data System (ADS)

    Dhar, S.; Pugel, D.; Hullavarad, S. S.; Vispute, R. D.; Ogale, S. B.; Venkatesan, T.

    2006-03-01

    ZnO is widely considered as the next generation wide-band gap material for optoelectronic device applications due to its excellent material properties. Although in recent years various studies on ZnO crystal have been made, very little is known about its response after thermal treatments. In this work, we studied the influence of thermal annealing on ZnO (0001) bulk single crystal in the temperature range of 30-1000 ^oC by elastic resonant ion channeling and Rutherford backscattering (RBS) techniques using a 3.05 MeV He beam. After an isochronal1 h anneal, RBS-Ion channeling analysis showed the evolution of disorder in the Zn sub-lattice of the crystal with increasing annealing temperature. The maximum disorder was observed at 200 ^oC above which it decreased. The induced disorder in the Zn sub-lattice at lower temperature (< 400 ^oC) can almost be recovered by further annealing above 800 ^oC. Elastic resonant ion channeling analysis, which monitors the oxygen in the near-surface region clearly revealed the evolution of thermally induced disorder in the oxygen sub-lattice with increasing temperature. In contrast to the disorder recovery of Zn sub-lattice, the disorder in oxygen sub-lattice did not recover completely. Possible mechanism on the disorder and its recovery will be discussed.

  17. Noise effects in two different biological systems

    NASA Astrophysics Data System (ADS)

    Spagnolo, B.; Spezia, S.; Curcio, L.; Pizzolato, N.; Fiasconaro, A.; Valenti, D.; Lo Bue, P.; Peri, E.; Colazza, S.

    2009-05-01

    We investigate the role of the colored noise in two biological systems: (i) adults of Nezara viridula (L.) (Heteroptera: Pentatomidae), and (ii) polymer translocation. In the first system we analyze, by directionality tests, the response of N. viridula individuals to subthreshold signals plus noise in their mating behaviour. The percentage of insects that react to the subthreshold signal shows a nonmonotonic behaviour, characterized by the presence of a maximum, as a function of the noise intensity. This is the signature of the non-dynamical stochastic resonance phenomenon. By using a “soft” threshold model we find that the maximum of the input-output cross correlation occurs in the same range of noise intensity values for which the behavioural activation of the insects has a maximum. Moreover this maximum value is lowered and shifted towards higher noise intensities, compared to the case of white noise. In the second biological system the noise driven translocation of short polymers in crowded solutions is analyzed. An improved version of the Rouse model for a flexible polymer is adopted to mimic the molecular dynamics by taking into account both the interactions between adjacent monomers and the effects of a Lennard-Jones potential between all beads. The polymer dynamics is simulated in a two-dimensional domain by numerically solving the Langevin equations of motion in the presence of thermal fluctuations and a colored noise source. At low temperatures or for strong colored noise intensities the translocation process of the polymer chain is delayed. At low noise intensity, as the polymer length increases, we find a nonmonotonic behaviour for the mean first translocation time of the polymer centre of inertia. We show how colored noise influences the motion of short polymers, by inducing two different regimes of translocation in the dynamics of molecule transport.

  18. A wafer-scale backplane-assisted resonating nanoantenna array SERS device created by tunable thermal dewetting nanofabrication

    NASA Astrophysics Data System (ADS)

    Chang, Te-Wei; Ranjan Gartia, Manas; Seo, Sujin; Hsiao, Austin; Logan Liu, Gang

    2014-04-01

    A tunable lithography-less nanofabrication process using a metal thin-film thermal dewetting technique has been developed to fabricate wafer-scale and uniform plasmonic substrates at low cost for optimal performance in surface enhanced Raman scattering (SERS) applications. The relationship between the tunable parameters of this process and the corresponding optical and plasmonic characteristic is investigated both experimentally and theoretically to understand the deterministic design of an optimal SERS device with a three-dimensional plasmonic nanoantenna structure. The enhancement of SERS using various nanoplasmonic particle sizes, structure lengths, lateral hot spot spacings and resonating effects are examined and demonstrated. We achieve a uniform optimal enhancement factor of 1.38 × 108 on a 4 in wafer-scale SERS substrate with a backplane-assisted resonating nanoantenna array design. Sensitive environmental nitrate sensing, vitamin detection and oligonucleotide identification are demonstrated on the high-performance SERS device.

  19. Influence of temporal noise on the skin blood flow measurements performed by cooled thermal imaging camera: limit possibilities within each physiological frequency range

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.

    2016-04-01

    This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.

  20. Local thermal resonance control of GaInP photonic crystal membrane cavities using ambient gas cooling

    SciTech Connect

    Sokolov, Sergei Lian, Jin; Yüce, Emre; Mosk, Allard P.; Combrié, Sylvain; Lehoucq, Gaelle; De Rossi, Alfredo

    2015-04-27

    We perform spatially dependent tuning of a GaInP photonic crystal cavity using a continuous wave violet laser. Local tuning is obtained by laser heating of the photonic crystal membrane. The cavity resonance shift is measured for different pump positions and for two ambient gases: He and N{sub 2}. We find that the width of the temperature profile induced in the membrane depends strongly on the thermal conductivity of the ambient gas. For He gas, a narrow spatial width of the temperature profile of 2.8 μm is predicted and verified in experiment.

  1. Quantum fluctuations of mesoscopic damped double resonance RLC circuit with mutual capacitance inductance coupling in thermal excitation state

    NASA Astrophysics Data System (ADS)

    Xu, Xing-Lei; Li, Hong-Qi; Wang, Ji-Suo

    2007-08-01

    Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics (TFD), the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.

  2. Single-crystal sapphire resonator at millikelvin temperatures: Observation of thermal bistability in high- Q factor whispering gallery modes

    NASA Astrophysics Data System (ADS)

    Creedon, Daniel L.; Tobar, Michael E.; Le Floch, Jean-Michel; Reshitnyk, Yarema; Duty, Timothy

    2010-09-01

    Resonance modes in single crystal sapphire (α-Al2O3) exhibit extremely high electrical and mechanical Q factors ( ≈109 at 4 K), which are important characteristics for electromechanical experiments at the quantum limit. We report the cool down of a bulk sapphire sample below superfluid liquid-helium temperature (1.6 K) to as low as 25 mK. The electromagnetic properties were characterized at microwave frequencies, and we report the observation of electromagnetically induced thermal bistability in whispering gallery modes due to the material T3 dependence on thermal conductivity and the ultralow dielectric loss tangent. We identify “magic temperatures” between 80 and 2100 mK, the lowest ever measured, at which the onset of bistability is suppressed and the frequency-temperature dependence is annulled. These phenomena at low temperatures make sapphire suitable for quantum metrology and ultrastable clock applications, including the possible realization of the quantum-limited sapphire clock.

  3. Measurement of the thermal neutron capture cross section and the resonance integral of radioactive {sup 182}Hf

    SciTech Connect

    Vockenhuber, C.; Bichler, M.; Wallner, A.; Kutschera, W.; Dillmann, I.; Kaeppeler, F.

    2008-04-15

    The neutron capture cross sections of the radioactive isotope {sup 182}Hf (t{sub 1/2}=8.9x10{sup 6} yr) in the thermal and epithermal energy regions have been measured by activation at the TRIGA Mark-II reactor of the Atomic Institute of the Austrian Universities in Vienna, Austria, and subsequent {gamma}-ray spectroscopy of {sup 183}Hf. High values for the thermal (kT=25 meV) cross section {sigma}{sub 0}=133{+-}10 b and for the resonance integral I{sub 0}=5850{+-}660 b were found. Additionally, the absolute intensities of the main {gamma}-ray transitions in the decay of {sup 182}Hf have been considerably improved.

  4. Making noise comfortable for people

    SciTech Connect

    Leventhall, H.G.; Wise, S.S.

    1998-10-01

    Typical HVAC noise may produce an uncomfortable environment, leading to the associated problems of general dissatisfaction and reduced productivity. It is not sufficient to have good thermal, lighting, and air cleanliness conditions if the noise is disturbing. In this paper, noise comfort is considered, with special emphasis on the developing criteria for low-frequency noise.

  5. Electron spin resonance of ultraviolet radiation induced defects in ZnO thermal control coating pigment.

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1972-01-01

    Electron spin resonance measurements on variously treated zinc oxide powders reveal that the resonance signal at g = 1.956 is due to one electron trapped oxygen ion vacancy level, at a depth of (0.31 plus or minus 0.02) eV below the conduction band. The electrons at this level are delocalized. Schottky barrier influences nearly the entire bulk of the powder sample, and the bending of the bands caused by chemisorbed oxygen puts the vacancy level above the Fermi level almost through the entire bulk.

  6. Evaluation of silicon neutron resonance parameters in the thermal to 1800 keV energy range.

    PubMed

    Derrien, H; Leal, L C; Guber, K H; Larson, N M

    2005-01-01

    Because silicon is a major constituent of concrete and soil, neutron and gamma ray information on silicon is important for reactor shielding and criticality safety calculations. Therefore, much effort was put into the ENDF/B-VI evaluation for the three stable isotopes of silicon. The neutron capture cross section of natural silicon was recently measured at the Oak Ridge Electron Linear Accelerator (ORELA) in the energy range 1-700 keV. Using the ENDF/B-VI evaluation for initial values, a new evaluation of the resonance parameters was performed by adding the results of the ORELA capture measurements to the experimental database. The computer code SAMMY was used for the analysis of the experimental data; the new version of SAMMY allows accurate calculations of the self-shielding and multiple scattering effects in the capture measurements. The accuracy of the radiative capture widths of the resonances was improved by this analysis. Accurate values of the s-, p- and d-wave neutron strength functions were also obtained. Although the resonance capture component of the present evaluation is 2-3 times smaller than that in ENDF/B-VI, the total capture cross section is much larger, at least for energies >250 keV, because the direct capture component contributes values of the same order of magnitude as the resonance component. The direct component was not taken into account in the ENDF/B-VI evaluation and was calculated for the first time in the present evaluation. PMID:16381717

  7. Optical Johnson noise thermometry

    NASA Technical Reports Server (NTRS)

    Shepard, R. L.; Blalock, T. V.; Maxey, L. C.; Roberts, M. J.; Simpson, M. L.

    1989-01-01

    A concept is being explored that an optical analog of the electrical Johnson noise may be used to measure temperature independently of emissivity. The concept is that a laser beam may be modulated on reflection from a hot surface by interaction of the laser photons with the thermally agitated conduction electrons or the lattice phonons, thereby adding noise to the reflected laser beam. If the reflectance noise can be detected and quantified in a background of other noise in the optical and signal processing systems, the reflectance noise may provide a noncontact measurement of the absolute surface temperature and may be independent of the surface's emissivity.

  8. Magnetic Resonance-Guided Laser Induced Thermal Therapy for Glioblastoma Multiforme: A Review

    PubMed Central

    Norred, Sarah E.; Johnson, Jacqueline Anne

    2014-01-01

    Magnetic resonance-guided laser induced thermotherapy (MRgLITT) has become an increasingly relevant therapy for tumor ablation due to its minimally invasive approach and broad applicability across many tissue types. The current state of the art applies laser irradiation via cooled optical fiber applicators in order to generate ablative heat and necrosis in tumor tissue. Magnetic resonance temperature imaging (MRTI) is used concurrently with this therapy to plan treatments and visualize tumor necrosis. Though application in neurosurgery remains in its infancy, MRgLITT has been found to be a promising therapy for many types of brain tumors. This review examines the current use of MRgLITT with regard to the special clinical challenge of glioblastoma multiforme and examines the potential applications of next-generation nanotherapy specific to the treatment of glioblastoma. PMID:24527455

  9. A micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications

    NASA Astrophysics Data System (ADS)

    Wingqvist, G.; Arapan, L.; Yantchev, V.; Katardjiev, I.

    2009-03-01

    Micromachined thin film plate acoustic wave resonators (FPARs) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2 µm thick aluminium nitride (AlN) membranes have been successfully demonstrated (Yantchev and Katardjiev 2007 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54 87-95). The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900 MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is the non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm K-1 to -25 ppm K-1. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.

  10. Assessment of heavy metals exposure, noise and thermal safety in the ambiance of a vacuum metallurgy separation system for recycling heavy metals from crushed e-wastes.

    PubMed

    Zhan, Lu; Xu, Zhenming

    2014-12-01

    Vacuum metallurgy separation (VMS) is a technically feasible method to recover Pb, Cd and other heavy metals from crushed e-wastes. To further determine the environmental impacts and safety of this method, heavy metals exposure, noise and thermal safety in the ambiance of a vacuum metallurgy separation system are evaluated in this article. The mass concentrations of total suspended particulate (TSP) and PM10 are 0.1503 and 0.0973 mg m(-3) near the facilities. The concentrations of Pb, Cd and Sn in TSP samples are 0.0104, 0.1283 and 0.0961 μg m(-3), respectively. Health risk assessments show that the hazard index of Pb is 3.25 × 10(-1) and that of Cd is 1.09 × 10(-1). Carcinogenic risk of Cd through inhalation is 1.08 × 10(-5). The values of the hazard index and risk indicate that Pb and Cd will not cause non-cancerous effects or carcinogenic risk on workers. The noise sources are mainly the mechanical vacuum pump and the water cooling pump. Both of them have the noise levels below 80 dB (A). The thermal safety assessment shows that the temperatures of the vacuum metallurgy separation system surface are all below 303 K after adopting the circulated water cooling and heat insulation measures. This study provides the environmental information of the vacuum metallurgy separation system, which is of assistance to promote the industrialisation of vacuum metallurgy separation for recovering heavy metals from e-wastes. PMID:25391553

  11. Nonlinear mechanical resonators for ultra-sensitive mass detection

    SciTech Connect

    Datskos, Panos G; Lavrik, Nickolay V

    2014-01-01

    The fundamental sensitivity limit of an appropriately scaled down mechanical resonator can approach one atomic mass unit when only thermal noise is present in the system. However, operation of such nanoscale mechanical resonators is very challenging due to minuteness of their oscillation amplitudes and presence of multiple noise sources in real experimental environments. In order to surmount these challenges, we use microscale cantilever resonators driven to large amplitudes, far beyond their nonlinear instability onset. Our experiments show that such a nonlinear cantilever resonator, described analytically as a Duffing oscillator, has mass sensing performance comparable to that of much smaller resonators operating in a linear regime. We demonstrate femtogram level mass sensing that relies on a bifurcation point tracking that does not require any complex readout means. Our approaches enable straightforward detection of mass changes that are near the fundamental limit imposed by thermo-mechanical fluctuations.

  12. Reconfigurable optical add-drop multiplexer based on thermally tunable micro-ring resonators

    NASA Astrophysics Data System (ADS)

    Wu, Danning; Wu, Yuanda; Wang, Yue; An, Junming; Hu, Xiongwei

    2016-05-01

    We report on an eight-channel reconfigurable optical add-drop multiplexer (ROADM) based on micro-ring resonators (MRRs). The effective footprint of the device is about 1000×760 μm2. The free spectral range (FSR) is about 18 nm. The adjacent channel crosstalk ranges from -19.02 dB to -8.29 dB. With the help of the multi-wire structure heaters, compact footprint and high tuning efficiency are achieved simultaneously. Therefore, the minimum average tuning efficiency is 2.723 mW/nm.

  13. Neutron Capture by Cadmium: Thermal Cross Sections and Resonance Integrals of ^106,108,110,112,114,116Cd

    NASA Astrophysics Data System (ADS)

    Gicking, Allison M.; Krane, Kenneth S.

    2011-10-01

    The neutron capture cross sections of the stable, even-mass Cd isotopes (A = 106, 108, 110, 112, 114, and 116) have been previously measured in sources of natural abundance or low enrichment, often making the results uncertain owing to the large absorption cross section of naturally occurring ^113Cd. Ambiguities in values of the isomeric branching ratios have also contributed to uncertainties in previous results. We have remeasured the Cd neutron capture cross sections using samples of greater than 90% isotopic enrichment irradiated in the OSU TRIGA reactor. Gamma-ray emission spectra were analyzed to determine the effective resonance integrals and thermal cross sections leading to eight radioactive ground and isomeric states in the Cd isotopes.

  14. High-power and high-quality, green-beam generation by employing a thermally near-unstable resonator design.

    PubMed

    Bo, Yong; Geng, Aicong; Bi, Yong; Sun, Zhipei; Yang, Xiaodong; Peng, Qinjun; Li, Huiqing; Li, Ruining; Cui, Dafu; Xu, Zuyan

    2006-04-10

    We have obtained green-beam quality of M2 = 6.2 at an average output power of 120 W by intracavity frequency doubling of a diode-side-pumped, Q-switched Nd:YAG rod laser with a repetition rate of 10 kHz and an optical-to-optical conversion efficiency of 15.2%. To achieve high-beam quality at high average power, the laser employs a thermally near-unstable resonator design with two-rod birefringence compensation in an L-shaped flat-flat cavity. The output power fluctuation of the green laser remains less than 0.9% in 4 h. PMID:16623247

  15. Magnetic Resonance Imaging-Guided Focused Laser Interstitial Thermal Therapy for Intracranial Lesions: Single-Institution Series

    PubMed Central

    Hawasli, Ammar H.; Bagade, Swapnil; Shimony, Joshua S.; Miller-Thomas, Michelle

    2013-01-01

    BACKGROUND: Surgical treatments for deep-seated intracranial lesions have been limited by morbidities associated with resection. Real-time magnetic resonance imaging–guided focused laser interstitial thermal therapy (LITT) offers a minimally invasive surgical treatment option for such lesions. OBJECTIVE: To review treatments and results of patients treated with LITT for intracranial lesions at Washington University School of Medicine. METHODS: In a review of 17 prospectively recruited LITT patients (34-78 years of age; mean, 59 years), we report demographics, treatment details, postoperative imaging characteristics, and peri- and postoperative clinical courses. RESULTS: Targets included 11 gliomas, 5 brain metastases, and 1 epilepsy focus. Lesions were lobar (n = 8), thalamic/basal ganglia (n = 5), insular (n = 3), and corpus callosum (n = 1). Mean target volume was 11.6 cm3, and LITT produced 93% target ablation. Patients with superficial lesions had shorter intensive care unit stays. Ten patients experienced no perioperative morbidities. Morbidities included transient aphasia, hemiparesis, hyponatremia, deep venous thrombosis, and fatal meningitis. Postoperative magnetic resonance imaging showed blood products within the lesion surrounded by new thin uniform rim of contrast enhancement and diffusion restriction. In conjunction with other therapies, LITT targets often showed stable or reduced local disease. Epilepsy focus LITT produced seizure freedom at 8 months. Preliminary overall median progression-free survival and survival from LITT in tumor patients were 7.6 and 10.9 months, respectively. However, this small cohort has not been followed for a sufficient length of time, necessitating future outcomes studies. CONCLUSION: Early peri- and postoperative clinical data demonstrate that LITT is a safe and viable ablative treatment option for intracranial lesions, and may be considered for select patients. ABBREVIATION: LITT, laser interstitial thermal therapy

  16. The effects of boron on the electron paramagnetic resonance spectra of alanine irradiated with thermal neutrons

    SciTech Connect

    Ciesielski, B.; Wielopolski, L.

    1995-10-01

    The effects of boric acid admixture on the intensity and line structure of EPR spectra of free radicals produced in alanine by thermal neutrons are presented. The EPR signal enhancement, up to a factor of 40 depending on the boron concentration, is related to additional energy deposition in alanine crystals by the disintegration products resulting from the capture of a thermal neutron by boron, {sup 10}B(n,{alpha}){sup 7}Li. The changes in the shape of the EPR spectra observed by changing the microwave power are due to the differences in the microwave power saturation of the free radicals produced by a low-LET radiation and those produced by the high-LET components of the radiation after the neutron capture reaction. 27 refs., 4 figs., 2 tabs.

  17. Accuracy of Young's Modulus of Thermal Barrier Coating Layer Determined by Bending Resonance of a Multilayered Specimen

    NASA Astrophysics Data System (ADS)

    Waki, Hiroyuki; Takizawa, Kensuke; Kato, Masahiko; Takahashi, Satoru

    2016-04-01

    The Young's modulus of individual layer in thermal barrier coating (TBC) system is an important mechanical property because it allows determining the parameters of materials mechanics in the TBC system. In this study, we investigated the accuracy of the evaluation method for the Young's modulus of a TBC layer according to the first bending resonance of a multilayered specimen comprising a substrate, bond coating, and TBC. First, we derived a closed-form solution for the Young's modulus of the TBC layer using the equation of motion for the bending vibration of a composite beam. The solution for the three-layered model provided the Young's modulus of the TBC layer according to the measured resonance frequency and the known values for the dimensions, mass, and Young's moduli of all the other layers. Next, we analyzed the sensitivity of these input errors to the evaluated Young's modulus and revealed the important inputs for accurate evaluation. Finally, we experimentally confirmed that the Young's modulus of the TBC layer was obtained accurately by the developed method.

  18. Near-infrared tailored thermal emission from wafer-scale continuous-film resonators.

    PubMed

    Roberts, Alexander S; Chirumamilla, Manohar; Thilsing-Hansen, Kasper; Pedersen, Kjeld; Bozhevolnyi, Sergey I

    2015-09-21

    We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-film Fabry-Perot-type resonators, consisting only of unstructured dielectric and metallic films. We show that the proposed configuration is suitable for realization of narrowband emitters, tunable in ranges from mid- to near-infrared, and demonstrate emission centered at the wavelength of 1.7 μm, which corresponds to the band gap energy of GaSb-based photodetectors. The emission is measured at 748 K and follows well the emissivity as predicted from reflection measurements and Kirchhoff's reciprocity. The considered emitter configuration is spectrally highly tunable and, consisting of only few unstructured layers, is amenable to wafer-scale fabrication at low cost by use of standard deposition procedures. PMID:26406741

  19. Single-crystal sapphire resonator at millikelvin temperatures: Observation of thermal bistability in high-Q factor whispering gallery modes

    SciTech Connect

    Creedon, Daniel L.; Tobar, Michael E.; Le Floch, Jean-Michel; Reshitnyk, Yarema; Duty, Timothy

    2010-09-01

    Resonance modes in single crystal sapphire ({alpha}-Al{sub 2}O{sub 3}) exhibit extremely high electrical and mechanical Q factors ({approx_equal}10{sup 9} at 4 K), which are important characteristics for electromechanical experiments at the quantum limit. We report the cool down of a bulk sapphire sample below superfluid liquid-helium temperature (1.6 K) to as low as 25 mK. The electromagnetic properties were characterized at microwave frequencies, and we report the observation of electromagnetically induced thermal bistability in whispering gallery modes due to the material T{sup 3} dependence on thermal conductivity and the ultralow dielectric loss tangent. We identify ''magic temperatures'' between 80 and 2100 mK, the lowest ever measured, at which the onset of bistability is suppressed and the frequency-temperature dependence is annulled. These phenomena at low temperatures make sapphire suitable for quantum metrology and ultrastable clock applications, including the possible realization of the quantum-limited sapphire clock.

  20. High-sensitivity optical monitoring of a micromechanical resonator with a quantum-limited optomechanical sensor.

    PubMed

    Arcizet, O; Cohadon, P-F; Briant, T; Pinard, M; Heidmann, A; Mackowski, J-M; Michel, C; Pinard, L; Français, O; Rousseau, L

    2006-09-29

    We experimentally demonstrate the high-sensitivity optical monitoring of a micromechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30 000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10(-19) m/sqrt[Hz] level, and cooled the resonator down to 5 K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator. PMID:17026032

  1. The low-frequency continuum as observed in the solar wind from ISEE 3 - Thermal electrostatic noise

    NASA Technical Reports Server (NTRS)

    Hoang, S.; Steinberg, J.-L.; Epstein, G.; Tilloles, P.; Fainberg, J.; Stone, R. G.

    1980-01-01

    The low frequency continuum (LFC) noise between 30 and 200 kHz has been investigated from the ISEE 3 spacecraft in the solar wind by means of a radio astronomy experiment more sensitive than previously available. It is demonstrated that the LFC radiation observed in the solar wind is in the form of longitudinal plasma waves rather than transverse electromagnetic waves. The observed spectral characteristics are found to be a function of antenna length. In addition, both the absence of antenna spin modulation and the fact that these plasma waves do not propagate to large distances imply a local origin for the LFC.

  2. Measurement of the Fundamental Thermal Noise Limit in a Cryogenic Sapphire Frequency Standard Using Bimodal Maser Oscillations

    SciTech Connect

    Benmessai, Karim; Kersale, Yann; Giordano, Vincent; Creedon, Daniel Lloyd; Tobar, Michael Edmund; Bourgeois, Pierre-Yves

    2008-06-13

    We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10{sup -14}{tau}{sup -1/2} with only 0.5 pW of output power.

  3. Magnetic Resonance-Guided Thermal Therapy for Localized and Recurrent Prostate Cancer.

    PubMed

    Woodrum, David A; Kawashima, Akira; Gorny, Krzysztof R; Mynderse, Lance A

    2015-11-01

    The advent of focal therapies theoretically offers new treatment options for patients with localized prostate cancer. The goal of prostate cancer treatment is effective long-term cure with minimal impact on health-related quality of life. Multiparametric MR imaging of the prostate is being increasingly used for diagnosis, image-guided targeted biopsy, guidance for targeted focal and regional therapy, and monitoring the effectiveness of treatments for prostate cancer of all stages. In this article, the use of prostate MRI in the burgeoning domain of thermal ablative therapy for localized and recurrent prostate cancer is reviewed. PMID:26499278

  4. Correction of Birefringence and Thermal Lensing in Nonreciprocal Resonators by use of a Dynamic Imaging Mirror

    NASA Astrophysics Data System (ADS)

    Moshe, Inon; Jackel, Steven

    2000-08-01

    Enhanced correction of thermally induced birefringence in the presence of strong single-pass, azimuthally dependent bipolar focusing was achieved in single-rod laser oscillators by use of an adaptive optic rear mirror with image relay and aberration correction capabilities. Together with a Faraday rotator, the imaging variable radius mirror was successfully tested in stable and unstable Nd:Cr:GSGG power oscillators under variable pump power conditions from 0 to 800 W. Birefringence correction in the absence of ray retracing was achieved.

  5. Correction of birefringence and thermal lensing in nonreciprocal resonators by use of a dynamic imaging mirror.

    PubMed

    Moshe, I; Jackel, S

    2000-08-20

    Enhanced correction of thermally induced birefringence in the presence of strong single-pass, azimuthally dependent bipolar focusing was achieved in single-rod laser oscillators by use of an adaptive optic rear mirror with image relay and aberration correction capabilities. Together with a Faraday rotator, the imaging variable radius mirror was successfully tested in stable and unstable Nd:Cr:GSGG power oscillators under variable pump power conditions from 0 to 800 W. Birefringence correction in the absence of ray retracing was achieved. PMID:18350015

  6. Effect of interference between two colored noises on the stationary states of a Brownian particle.

    PubMed

    Mondal, Shrabani; Bag, Bidhan Chandra

    2015-04-01

    In this paper we present properties of an external colored cross-correlated noise-driven Brownian system which is coupled to a thermal bath. Multiplicative cross-correlated noises can stabilize the transition state. Thus by monitoring the interference between the noises one can understand the mechanism of a chemical reaction. At the same time, we have investigated how the interference affects the barrier-crossing dynamics. In its presence breakdown of the Arrhenius result occurs. The breakdown becomes prominent if the multiplicative noises become additive in nature. We have also investigated how the power law behavior of the rate constant as a function of damping strength is affected by the properties of external colored noises. Furthermore, we have observed that multiplicative colored cross-correlated noises can induce the resonant activation phenomenon. PMID:25974476

  7. Effect of interference between two colored noises on the stationary states of a Brownian particle

    NASA Astrophysics Data System (ADS)

    Mondal, Shrabani; Bag, Bidhan Chandra

    2015-04-01

    In this paper we present properties of an external colored cross-correlated noise-driven Brownian system which is coupled to a thermal bath. Multiplicative cross-correlated noises can stabilize the transition state. Thus by monitoring the interference between the noises one can understand the mechanism of a chemical reaction. At the same time, we have investigated how the interference affects the barrier-crossing dynamics. In its presence breakdown of the Arrhenius result occurs. The breakdown becomes prominent if the multiplicative noises become additive in nature. We have also investigated how the power law behavior of the rate constant as a function of damping strength is affected by the properties of external colored noises. Furthermore, we have observed that multiplicative colored cross-correlated noises can induce the resonant activation phenomenon.

  8. Ovenized microelectromechanical system (MEMS) resonator

    SciTech Connect

    Olsson, Roy H; Wojciechowski, Kenneth; Kim, Bongsang

    2014-03-11

    An ovenized micro-electro-mechanical system (MEMS) resonator including: a substantially thermally isolated mechanical resonator cavity; a mechanical oscillator coupled to the mechanical resonator cavity; and a heating element formed on the mechanical resonator cavity.

  9. Plasmomechanical Resonators Based on Dimer Nanoantennas.

    PubMed

    Thijssen, Rutger; Kippenberg, Tobias J; Polman, Albert; Verhagen, Ewold

    2015-06-10

    Nanomechanical resonators are highly suitable as sensors of minute forces, displacements, or masses. We realize a single plasmonic dimer antenna of subwavelength size, integrated with silicon nitride nanobeams. The sensitive dependence of the antenna response on the beam displacement creates a plasmomechanical system of deeply subwavelength size in all dimensions. We use it to demonstrate transduction of thermal vibrations to scattered light fields and discuss the noise properties and achievable coupling strengths in these systems. PMID:25938170

  10. The influence of thermal and free carrier dispersion effects on all-optical wavelength conversion in a silicon racetrack-shaped microring resonator

    NASA Astrophysics Data System (ADS)

    Wang, Zhaolu; Liu, Hongjun; Sun, Qibing; Huang, Nan; Li, Shaopeng; Han, Jing

    2016-07-01

    We experimentally demonstrate ultra-low pump power wavelength conversion based on four-wave mixing in a silicon racetrack-shaped microring resonator. When the pump and signal are located at the resonance wavelengths, wavelength conversion with a pump power of only 1 mW can be realized in this microring resonator because of the resonant enhancement of the device. However, saturation of the conversion efficiency occurs because of the shift of the resonance peak, which is caused by the change of the effective refractive index induced by a combination of thermal and free carrier dispersion effects, and it is demonstrated that the thermal effect is the leading-order factor for the change of the refractive index. The maximum conversion efficiency of  ‑21 dB is obtained when the pump power is less than 12 mW. This ultra-low-power on-chip wavelength convertor based on a silicon microring resonator can find important potential applications in highly integrated optical circuits for all-optical signal processing.

  11. Measurement of thermal neutron cross section and resonance integral for the {sup 170}Er(n,{gamma}){sup 171}Er reaction by using a {sup 55}Mn monitor

    SciTech Connect

    Yuecel, Haluk; Budak, M. Gueray; Karadag, Mustafa

    2007-09-15

    The thermal neutron cross section and the resonance integral of the reaction {sup 170}Er(n,{gamma}){sup 171}Er were measured by the Cd-ratio method using a {sup 55}Mn monitor as single comparator. Analytical grade MnO{sub 2} and Er{sub 2}O{sub 3} powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three {sup 241}Am-Be neutron sources. The induced activities in the samples were measured with a 120.8% relative efficiency p-type HPGe detector. The correction factors for gamma-ray attenuation (F{sub g}), thermal neutron self-shielding (G{sub th}), and resonance neutron self-shielding (G{sub epi}) effects, and the epithermal neutron spectrum shape factor ({alpha}) were taken into account. The thermal neutron cross section for the (n,{gamma}) reaction in {sup 170}Er has been determined to be 8.00 {+-} 0.56 b, relative to that of the {sup 55}Mn monitor. However, some previously reported experimental results compared to the present result show a large discrepancy ranging from 8.3 to 86%. The present result is, in general, in good agreement with the recently measured values by 9%. According to the definition of Cd cut-off energy at 0.55 eV, the resonance integral obtained is 44.5 {+-} 4.0 b, which is determined relative to the reference integral value of the {sup 55}Mn monitor by using cadmium ratios. The existing experimental data for the resonance integral are distributed between 18 and 43 b. The present resonance integral value agrees only with the measurement of 43 {+-} 5 b by Gillette [Thermal Cross Section and Resonance Integral Studies, ORNL-4155, 15 (1967)] within uncertainty limits.

  12. The effect of blood flow on magnetic resonance imaging of non thermal irreversible electroporation.

    PubMed

    Hjouj, Mohammad; Lavee, Jacob; Last, David; Guez, David; Daniels, Dianne; Sharabi, Shirley; Rubinsky, Boris; Mardor, Yael

    2013-01-01

    To generate an understanding of the physiological significance of MR images of Non-Thermal Irreversible Electroporation (NTIRE) we compared the following MR imaging sequences: T1W, T2W, PD, GE, and T2 SPAIR acquired after NTIRE treatment in a rodent liver model. The parameters that were studied included the presence or absence of a Gd-based contrast agent, and in vivo and ex-vivo NTIRE treatments in the same liver. NTIRE is a new minimally invasive tissue ablation modality in which pulsed electric fields cause molecularly selective cell death while, the extracellular matrix and large blood vessels remain patent. This attribute of NTIRE is of major clinical importance as it allows treatment of undesirable tissues near critical blood vessels. The presented study results suggest that MR images acquired following NTIRE treatment are all directly related to the unique pattern of blood flow after NTIRE treatment and are not produced in the absence of blood flow. PMID:24169528

  13. The Effect of Blood Flow on Magnetic Resonance Imaging of Non Thermal Irreversible Electroporation

    NASA Astrophysics Data System (ADS)

    Hjouj, Mohammad; Lavee, Jacob; Last, David; Guez, David; Daniels, Dianne; Sharabi, Shirley; Rubinsky, Boris; Mardor, Yael

    2013-10-01

    To generate an understanding of the physiological significance of MR images of Non-Thermal Irreversible Electroporation (NTIRE) we compared the following MR imaging sequences: T1W, T2W, PD, GE, and T2 SPAIR acquired after NTIRE treatment in a rodent liver model. The parameters that were studied included the presence or absence of a Gd-based contrast agent, and in vivo and ex-vivo NTIRE treatments in the same liver. NTIRE is a new minimally invasive tissue ablation modality in which pulsed electric fields cause molecularly selective cell death while, the extracellular matrix and large blood vessels remain patent. This attribute of NTIRE is of major clinical importance as it allows treatment of undesirable tissues near critical blood vessels. The presented study results suggest that MR images acquired following NTIRE treatment are all directly related to the unique pattern of blood flow after NTIRE treatment and are not produced in the absence of blood flow.

  14. Electron thermal effects on electron acceleration and energy cascades in geomagnetic field line resonances

    NASA Astrophysics Data System (ADS)

    Damiano, P. A.; Johnson, J.; Wright, A. N.

    2010-12-01

    Some of the most intense electron precipitation and largest ion outflows are found in regions of intense, Alfvenic waves. Recent analysis of auroral turbulence suggests that large-scale waves couple energy to smaller scale lengths on the order of the electron inertial, ion-acoustic or ion-gyroradius. In this presentation, we examine the effects of electron temperature on the characteristics of electron acceleration and cross-scale energy coupling of wave energy using a hybrid MHD-kinetic electron simulation of Field Line Resonances in a dipolar coordinate system. The simulations describe a cascade of energy from a large-scale global driver to kinetic scales principally in the auroral acceleration region where electron inertial effects dominate and electron acceleration occurs. However, the fine scale transverse structuring of the upward current associated with this cascade appears to depend on the temperature of the ambient electron population suggesting that the ion acoustic scale length (which is dominant at higher altitudes) can influence the characteristics of the current fragmentation. Additionally, although the majority of the electron acceleration remains in the auroral acceleration region, the higher temperature cases appear to require a more extended (along the field line) source of electrons in order to carry the parallel current. We also consider the possible mechanisms by which coupling of large and small perpendicular scale lengths occurs and what effects the addition of ion gyro-radius physics may have on the characteristics of the acceleration and cascade.

  15. Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy

    SciTech Connect

    Tan, Yang; Shyam, Amit; Choi, Wanhuk Brian; Lara-Curzio, Edgar; Sampath, Sanjay

    2010-01-01

    The determination of elastic properties of plasma-sprayed ceramic and metallic coatings is difficult due to their complex microstructure, which involves a myriad array of pores, interfaces and other defects. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. In this paper, we report on the anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy (RUS). This approach along with the analysis presented enables, for the first time, the determination of elastic properties as a function of direction and temperature for these complex systems with concomitant implications for design. The coating systems investigated included plasma-sprayed yttria-stabilized zirconia (YSZ) and nickel. An additional nickel coating deposited by high-velocity oxygen-fuel process was investigated and its elastic properties were compared to those of plasma-sprayed nickel. Average Young s moduli of the coatings were independently measured by using the instrumented indentation method. The elastic properties determined from the RUS and indentation methodologies allowed description of the microstructure elastic property relationships in the coatings.

  16. Thermal behavior of resonant waveguide-grating mirrors in Yb:YAG thin-disk lasers.

    PubMed

    Rumpel, Martin; Dannecker, Benjamin; Voss, Andreas; Moeller, Michael; Moormann, Christian; Graf, Thomas; Ahmed, Marwan Abdou

    2013-11-15

    We present the experimental investigations of different designs of resonant waveguide-grating (RWG) mirrors, used as intracavity folding mirrors in an Yb:YAG thin-disk laser (TDL). The investigation was focused on the rise of the surface temperature due to the coupling of the incident radiation to a waveguide mode as well as on laser efficiency, polarization, and wavelength selectivity. It was found that the damage threshold and efficiency can be increased significantly with a proper design of the structure in comparison to the simplest design with a single waveguide layer. So far, the presented RWG allow the generation of linear polarization with a narrow spectral linewidth down to 25 pm FWHM in a fundamental mode Yb:YAG TDL. Damage thresholds of 60 kW/cm(2) have been reached where only 63 K of surface temperature increase was observed. This showed that the improved mirrors are suitable for the generation of kW-class narrow linewidth, linearly polarized Yb:YAG TDL. PMID:24322127

  17. Realization of the thermal equilibrium in inhomogeneous magnetic systems by the Landau-Lifshitz-Gilbert equation with stochastic noise, and its dynamical aspects

    NASA Astrophysics Data System (ADS)

    Nishino, Masamichi; Miyashita, Seiji

    2015-04-01

    It is crucially important to investigate the effects of temperature on magnetic properties such as critical phenomena, nucleation, pinning, domain wall motion, and coercivity. The Landau-Lifshitz-Gilbert (LLG) equation has been applied extensively to study dynamics of magnetic properties. Approaches of Langevin noises have been developed to introduce the temperature effect into the LLG equation. To have the thermal equilibrium state (canonical distribution) as the steady state, the system parameters must satisfy some condition known as the fluctuation-dissipation relation. In inhomogeneous magnetic systems in which spin magnitudes are different at sites, the condition requires that the ratio between the amplitude of the random noise and the damping parameter depend on the magnitude of the magnetic moment at each site. Focused on inhomogeneous magnetic systems, we systematically showed agreement between the stationary state of the stochastic LLG equation and the corresponding equilibrium state obtained by Monte Carlo simulations in various magnetic systems including dipole-dipole interactions. We demonstrated how violations of the condition result in deviations from the true equilibrium state. We also studied the characteristic features of the dynamics depending on the choice of the parameter set. All the parameter sets satisfying the condition realize the same stationary state (equilibrium state). In contrast, different choices of parameter set cause seriously different relaxation processes. We show two relaxation types, i.e., magnetization reversals with uniform rotation and with nucleation.

  18. Pseudomorphic InGaAs/AlGaAs modulation-doped FET's with reduced low-frequency noise and thermally stable performance

    NASA Technical Reports Server (NTRS)

    Liu, Shih-Ming; Das, M. B.; Peng, C. K.; Klem, J.; Henderson, T.

    1987-01-01

    A high-performance MODFET structure grown by MBE with the incorporation of a single quantum well In(0.15)Ga(0.85)As layer for the transport of two-dimensional electron gas has been critically examined for its thermal stability at 80 K and low-frequency noise form 0.01 to 10 to the 8th Hz. Experimental results indicate that the behavior of this device in both these respects is much superior when compared with the same behavior of conventional MODFETs. A maximum low-field carrier mobility of 29,000 sq cm/s at 80 K and an average carrier saturation velocity of 2 x 10 to the 7th cm/s at 300 K in a 1-micron gate device clearly indicate that the quality of the pseudomorphic quantum well (InGaAs) layer is either comparable or better than that of the usual GaAs buffer layer. The deep level spectra, obtained through photo-FET measurements, and the low-frequency noise spectra at different temperatures obtained for the new pseudomorphic and conventional MODFET's have clearly indicated that contributions from various deep levels present in the new structure are significantly reduced.

  19. Dispersive Thermometry with a Josephson Junction Coupled to a Resonator

    NASA Astrophysics Data System (ADS)

    Saira, O.-P.; Zgirski, M.; Viisanen, K. L.; Golubev, D. S.; Pekola, J. P.

    2016-08-01

    We embed a small Josephson junction in a microwave resonator that allows simultaneous dc biasing and dispersive readout. Thermal fluctuations drive the junction into phase diffusion and induce a temperature-dependent shift in the resonance frequency. By sensing the thermal noise of a remote resistor in this manner, we demonstrate primary thermometry in the range of 300 mK to below 100 mK, and high-bandwidth (7.5 MHz) operation with a noise-equivalent temperature of better than 10 μ K /√{Hz } . At a finite bias voltage close to a Fiske resonance, amplification of the microwave probe signal is observed. We develop an accurate theoretical model of our device based on the theory of dynamical Coulomb blockade.

  20. Rotorcraft noise

    NASA Technical Reports Server (NTRS)

    Huston, R. J. (Compiler)

    1982-01-01

    The establishment of a realistic plan for NASA and the U.S. helicopter industry to develop a design-for-noise methodology, including plans for the identification and development of promising noise reduction technology was discussed. Topics included: noise reduction techniques, scaling laws, empirical noise prediction, psychoacoustics, and methods of developing and validing noise prediction methods.

  1. Heterogeneous Superconducting Low-Noise Sensing Coils

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Penanen, Konstantin I.; Ho Eom, Byeong

    2008-01-01

    A heterogeneous material construction has been devised for sensing coils of superconducting quantum interference device (SQUID) magnetometers that are subject to a combination of requirements peculiar to some advanced applications, notably including low-field magnetic resonance imaging for medical diagnosis. The requirements in question are the following: The sensing coils must be large enough (in some cases having dimensions of as much as tens of centimeters) to afford adequate sensitivity; The sensing coils must be made electrically superconductive to eliminate Johnson noise (thermally induced noise proportional to electrical resistance); and Although the sensing coils must be cooled to below their superconducting- transition temperatures with sufficient cooling power to overcome moderate ambient radiative heat leakage, they must not be immersed in cryogenic liquid baths. For a given superconducting sensing coil, this combination of requirements can be satisfied by providing a sufficiently thermally conductive link between the coil and a cold source. However, the superconducting coil material is not suitable as such a link because electrically superconductive materials are typically poor thermal conductors. The heterogeneous material construction makes it possible to solve both the electrical- and thermal-conductivity problems. The basic idea is to construct the coil as a skeleton made of a highly thermally conductive material (typically, annealed copper), then coat the skeleton with an electrically superconductive alloy (typically, a lead-tin solder) [see figure]. In operation, the copper skeleton provides the required thermally conductive connection to the cold source, while the electrically superconductive coating material shields against Johnson noise that originates in the copper skeleton.

  2. Correcting Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) High Altitude (40 - 65 km) Temperature Retrievals for Instrumental Correlated Noise and Biases

    NASA Astrophysics Data System (ADS)

    McConnochie, T. H.; Smith, M. D.

    2011-12-01

    Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) nadir-soundings have been used to derive atmospheric temperatures up to roughly 40 km [Conrath et al., JGR 105 2000, Smith et al., JGR 106, 2001], and MGS-TES limb soundings have been used to extend the atmospheric temperature data set to > 60 km in altitude [Smith et al., JGR 106, 2001]. The ~40 - ~65 km altitude range probed by the MGS-TES limb sounding is particularly important for capturing key dynamical features such as the warm winter polar mesosphere [e.g., Smith et al., JGR 106, 2001; McCleese et al., Nature Geoscience 1, 2008], and the response of thermal tides to dust opacity [e.g. Wilson and Hamilton, J. Atmos. Sci. 53, 1996]. Thus accurate and precise temperature profiles at these altitudes are particularly important for constraining global circulation models. They are also critical for interpreting observations of mesospheric condensate aerosols [e.g., Määttänen et al., Icarus 209, 2010; McConnochie et al., Icarus 210, 2010)]. We have indentified correlated noise components in the MGS-TES limb sounding radiances that propagate into very large uncertainties in the retrieved temperatures. We have also identified a slowly varying radiance bias in the limb sounding radiances. Note that the nadir-sounding-based MGS-TES atmospheric temperatures currently available from the Planetary Data System are not affected by either of these issues. These two issues affect the existing MGS-TES limb sounding temperature data set are as follows: Considering, for example, the 1.5 Pascal pressure level (which typically falls between 50 and 60 km altitude), correlated-noise induced standard errors for individual limb-sounding temperature retrievals were 3 - 5 K in Mars Year 24, rising to 5 - 15 K in Mars Year 25 and 10 - 15 K in Mars Year 26 and 27. The radiance bias, although consistent on ~10-sol time scales, is highly variable over the course of the MGS-TES mission. It results in temperatures (at the 1

  3. Noise Pollution

    MedlinePlus

    ... here: EPA Home Air and Radiation Noise Pollution Noise Pollution This page has moved. You should be ... epa.gov/clean-air-act-overview/title-iv-noise-pollution Local Navigation Air & Radiation Home Basic Information ...

  4. Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode

    PubMed Central

    Baldacci, Lorenzo; Pitanti, Alessandro; Masini, Luca; Arcangeli, Andrea; Colangelo, Francesco; Navarro-Urrios, Daniel; Tredicucci, Alessandro

    2016-01-01

    We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 104 at 8.3 · 10−3 mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale. PMID:27538586

  5. Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode.

    PubMed

    Baldacci, Lorenzo; Pitanti, Alessandro; Masini, Luca; Arcangeli, Andrea; Colangelo, Francesco; Navarro-Urrios, Daniel; Tredicucci, Alessandro

    2016-01-01

    We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 10(4) at 8.3 · 10(-3) mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale. PMID:27538586

  6. Temperature and velocity determination of shock-heated flows with non-resonant heterodyne laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Förster, F. J.; Baab, S.; Lamanna, G.; Weigand, B.

    2015-12-01

    Non-resonant laser-induced thermal acoustics (LITA), a four-wave mixing technique, was applied to post-shock flows within a shock tube. Simultaneous single-shot determination of temperature, speed of sound and flow velocity behind incident and reflected shock waves at different pressure and temperature levels are presented. Measurements were performed non-intrusively and without any seeding. The paper describes the technique and outlines its advantages compared to more established laser-based methods with respect to the challenges of shock tube experiments. The experiments include argon and nitrogen as test gas at temperatures of up to 1000 K and pressures of up to 43 bar. The experimental data are compared to calculated values based on inviscid one-dimensional shock wave theory. The single-shot uncertainty of the technique is investigated for worst-case test conditions resulting in relative standard deviations of 1, 1.7 and 3.4 % for Mach number, speed of sound and temperature, respectively. For all further experimental conditions, calculated values stay well within the 95 % confidence intervals of the LITA measurement.

  7. Giant Dipole Resonance in the hot and thermalized 132Ce nucleus: damping of collective modes at finite temperature

    SciTech Connect

    Wieland, O; Bracco, A; Camera, F; Benzoni, G; Blasi, N; Brambilla, S; Crespi, F; Giussani, A; Leoni, S; Million, B; Moroni, A; Barlini, S; Kravchuk, V L; Gramegna, F; Lanchais, A; Mastinu, P; Maj, A; Brekiesz, M; Kmiecik, M; Bruno, M; Geraci, E; Vannini, G; Casini, G; Chiari, M; Nannini, A; Ordine, A; Ormand, W E

    2006-06-16

    The {gamma} decay of the Giant Dipole Resonance in the {sup 132}Ce compound nucleus with temperature up to {approx} 4 MeV has been measured. The symmetric {sup 64}Ni + {sup 68}Zn at E{sub beam} = 300, 400, 500 MeV and the asymmetric reaction {sup 16}O + {sup 116}Sn at E{sub beam} = 130, 250 MeV have been investigated. Light charged particles and {gamma} rays have been detected in coincidence with the recoiling compound system. In the case of the mass symmetric {sup 64}Ni induced reaction the {gamma} and charged particle spectral shapes are found to be consistent with the emission from a fully equilibrated compound nuclei and the GDR parameters are extracted from the data using a statistical model analysis. The GDR width is found to increase almost linear with temperature. This increase is rather well reproduced within a model which includes both the thermal fluctuation of the nuclear shape and the lifetime of the compound nucleus.

  8. Dramatic enhancement of fullerene anion formation in polymer solar cells by thermal annealing: Direct observation by electron spin resonance

    SciTech Connect

    Liu, Dong; Nagamori, Tatsuya; Yabusaki, Masaki; Yasuda, Takeshi; Han, Liyuan; Marumoto, Kazuhiro

    2014-06-16

    Using electron spin resonance (ESR), we clarified the origin of the efficiency degradation of polymer solar cells containing a lithium-fluoride (LiF) buffer layer created by a thermal annealing process after the deposition of an Al electrode (post-annealing). The device structure was indium-tin-oxide/ poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/poly (3-hexylthiophene):phenyl-C{sub 61}-butyric acid methyl ester (P3HT:PCBM)/LiF/Al. Three samples consisting of quartz/P3HT:PCBM/LiF/Al, quartz/P3HT:PCBM/Al, and quartz/PCBM/LiF/Al were investigated and compared. A clear ESR signal from radical anions on the PCBM was observed after LiF/Al was deposited onto a P3HT:PCBM layer because of charge transfer at the interface between the PCBM and the LiF/Al, which indicated the formation of PCBM{sup −}Li{sup +} complexes. The number of radical anions on the PCBM was enhanced remarkably by the post-annealing process; this enhancement was caused by the surface segregation of PCBM and by the dissociation of LiF at the Al interface by the post-annealing process. The formation of a greater number of anions enhanced the electron scattering, decreased the electron-transport properties of the PCBM molecules, and caused an energy-level shift at the interface. These effects led to degradation in the device performance.

  9. Observation of the fundamental Nyquist noise limit in an ultra-high Q-factor cryogenic bulk acoustic wave cavity

    SciTech Connect

    Goryachev, Maxim Ivanov, Eugene N.; Tobar, Michael E.; Kann, Frank van; Galliou, Serge

    2014-10-13

    Thermal Nyquist noise fluctuations of high-Q bulk acoustic wave cavities have been observed at cryogenic temperatures with a DC superconducting quantum interference device amplifier. High Q modes with bandwidths of few tens of milliHz produce thermal fluctuations with a signal-to-noise ratio of up to 23 dB. The estimated effective temperature from the Nyquist noise is in good agreement with the physical temperature of the device, confirming the validity of the equivalent circuit model and the non-existence of any excess resonator self-noise. The measurements also confirm that the quality factor remains extremely high (Q > 10{sup 8} at low order overtones) for very weak (thermal) system motion at low temperatures, when compared to values measured with relatively strong external excitation. This result represents an enabling step towards operating such a high-Q acoustic device at the standard quantum limit.

  10. An Inexpensive Resonance Demonstration

    ERIC Educational Resources Information Center

    Dukes, Phillip

    2005-01-01

    The phenomenon of resonance is applicable to almost every branch of physics. Without resonance, there wouldn't be televisions or stereos, or even swings on the playground. However, resonance also has undesirable side effects such as irritating noises in the car and the catastrophic events such as helicopters flying apart. In this article, the…

  11. Impact of Plant Noise on BWR Stability Analyses

    SciTech Connect

    Andersen, J.G.M.; Pearson, G.; Chung, A.K.; Heck, C.L.; Vedovi, J.

    2007-07-01

    A small amount of thermal-hydraulic noise is present in a boiling water reactor (BWR). The noise originates primarily from minor fluctuations in fluid flow and pressure distribution in the recirculation system of the BWR and manifests itself as a small fluctuation on the order of 1-2% for the average power range monitors (APRM) during normal operation. A larger noise level is observed for single-loop operation than for two-loop operation. This noise has an impact on the stability performance of the BWR. This is particularly the case when the noise contains a significant component at the resonant frequency for BWR instabilities, which is typically on the order of 0.5 Hz. For a pump trip event that can lead to instability, the noise will impact the growth rate of the reactor instability. The initial magnitude of the oscillations will be larger as the decay ratio increases above unity. For operation at low flow, such as for minimum pump speed or single loop operation where the decay ratio is larger, the impact of noise could lead to small oscillations at the resonant frequency for the APRM signals. The impact of noise on BWR instabilities is analyzed with the TRACG code. TRACG consists of a multi dimensional two-fluid thermal hydraulics model and the three-dimensional kinetics model consistent with the GE 3D core simulator, PANACEA. TRACG models the reactor primary system and has been extensively qualified against test data and BWR plant data. Thermal hydraulic instability test data, as well as data from BWR instability events and tests, have been used extensively in this qualification. This paper demonstrates the impact of noise on BWR stability response for events leading to instability, such as pump trip events, as well as operation at low core flow due to single loop operation. The impact is illustrated through sensitivity studies with the TRACG code and by comparison to plant data. The impact of reactor noise on the performance of the instability detection system

  12. Noise prevention

    NASA Astrophysics Data System (ADS)

    Methods for noise abatement are discussed. Noise nuisance, types of noise (continuous, fluctuating, intermittent, pulsed), and types of noise abatement (absorption, vibration damping, isolation) are defined. Rockwool panels, industrial ceiling panels, baffles, acoustic foam panels, vibration dampers, acoustic mats, sandwich panels, isolating cabins and walls, ear protectors, and curtains are presented.

  13. Noise spectroscopy of an optical microresonator

    SciTech Connect

    Kozlov, G. G.

    2013-05-15

    The noise spectrum is calculated for the intensity of light transmitted through an optical microresonator whose thickness experiences thermal oscillations. The noise spectrum reveals a maximum at the frequency of an acoustic mode localized in the optical microresonator and depends on the size of the illuminated region. The noise intensity estimates show that it can be detected by the modern noise spectroscopy technique.

  14. Photoluminescence, thermally stimulated luminescence and electron paramagnetic resonance investigations of Tb{sup 3+} doped SrBPO{sub 5}

    SciTech Connect

    Kumar, Mithlesh; Seshagiri, T.K.; Kadam, R.M.; Godbole, S.V.

    2011-09-15

    Graphical abstract: EPR spectra of BOHC's in 2 kGy {gamma}-irradiated SrBPO{sub 5}:Tb sample using Receiver Gain RG = 4 x 10{sup 4}, Modulation Amplitude MA = 0.25 G, Microwave power setting 6.3 mW: (A) un-annealed sample recorded at 300 K, (B) un-annealed sample recorded at 100 K and (C) sample annealed at 550 K for 10 min and recorded at 100 K. Highlights: {yields} PL studies on Tb doped SrBPO{sub 5} phosphor have shown emission due to Tb{sup 3+} associated with {sup 5}D{sub 3} {yields} {sup 7}F{sub J} and {sup 5}D{sub 4} {yields} {sup 7}F{sub J} (J = 3, 4, 5 and 6) transitions. {yields} The EPR studies on {gamma}-irradiated samples revealed formation of three types of boron oxygen hole trapped centres viz., BOHC{sub 1}, BOHC{sub 2} and BOHC{sub 3} and an electron trapped centre. {yields} The TSL peak at 475 K was associated with the thermal destruction of BOHC{sub 2}. -- Abstract: Trap level spectroscopic studies were carried out on {gamma}-irradiated Tb (1 mole%) doped SrBPO{sub 5} were carried out using photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) techniques. The incorporation of Tb in the 3+ oxidation state was ascertained from PL studies. Life time for Tb{sup 3+} emission corresponding to the intense transition {sup 5}D{sub 4} {yields} {sup 7}F{sub 5} at 543 nm was determined. The spectral characteristics of the TSL glows have shown that Tb{sup 3+} ions act as the emission center for the glow peak at 475 K. The trap parameters of the glow peak were determined. EPR investigations at room temperature/77 K revealed the stabilization of three boron oxygen hole trapped centers (BOHC's) and oxygen centered radicals such as O{sup -} and O{sub 2}{sup -} and trapped electrons in room temperature {gamma}-irradiated samples. TSL glow peak at 475 K was found to be associated with recombination of electron released from trapped electron center and the BOHC{sub 2} center.

  15. Combustion noise

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.

    1977-01-01

    A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

  16. Airport noise

    NASA Technical Reports Server (NTRS)

    Pendley, R. E.

    1982-01-01

    The problem of airport noise at several airports and air bases is detailed. Community reactions to the noise, steps taken to reduce jet engine noise, and the effect of airport use restrictions and curfews on air transportation are discussed. The adverse effect of changes in allowable operational noise on airport safety and altenative means for reducing noise pollution are considered. Community-airport relations and public relations are discussed.

  17. Engineered Theranostic Magnetic Nanostructures: Role of Composition and Surface Coating on Magnetic Resonance Imaging Contrast and Thermal Activation.

    PubMed

    Nandwana, Vikas; Ryoo, Soo-Ryoon; Kanthala, Shanthi; De, Mrinmoy; Chou, Stanley S; Prasad, Pottumarthi V; Dravid, Vinayak P

    2016-03-23

    Magnetic nanostructures (MNS) have emerged as promising functional probes for simultaneous diagnostics and therapeutics (theranostic) applications due to their ability to enhance localized contrast in magnetic resonance imaging (MRI) and heat under external radio frequency (RF) field, respectively. We show that the "theranostic" potential of the MNS can be significantly enhanced by tuning their core composition and architecture of surface coating. Metal ferrite (e.g., MFe2O4) nanoparticles of ∼8 nm size and nitrodopamine conjugated polyethylene glycol (NDOPA-PEG) were used as the core and surface coating of the MNS, respectively. The composition was controlled by tuning the stoichiometry of MFe2O4 nanoparticles (M = Fe, Mn, Zn, ZnxMn1-x) while the architecture of surface coating was tuned by changing the molecular weight of PEG, such that larger weight is expected to result in longer length extended away from the MNS surface. Our results suggest that both core as well as surface coating are important factors to take into consideration during the design of MNS as theranostic agents which is illustrated by relaxivity and thermal activation plots of MNS with different core composition and surface coating thickness. After optimization of these parameters, the r2 relaxivity and specific absorption rate (SAR) up to 552 mM(-1) s(-1) and 385 W/g were obtained, respectively, which are among the highest values reported for MNS with core magnetic nanoparticles of size below 10 nm. In addition, NDOPA-PEG coated MFe2O4 nanostructures showed enhanced biocompatibility (up to [Fe] = 200 μg/mL) and reduced nonspecific uptake in macrophage cells in comparison to other well established FDA approved Fe based MR contrast agents. PMID:26936392

  18. Shot noise effect on noise source and noise parameter of 10-nm-scale quasi-ballistic n-/p-type MOS devices

    NASA Astrophysics Data System (ADS)

    Jeon, Jongwook; Kang, Myounggon

    2016-05-01

    In this work, we investigated the noise source and noise parameters of a quasi-ballistic MOSFET at the high-frequency regime. We presented the shot noise properties in the measured drain current noise and its impact on the induced gate noise and the noise parameters of 10-nm-scale n-/p-type MOS (N/PMOS) devices for the first time. The measured noise sources and noise parameters were carefully analyzed with the shot and thermal noise models in all operation regions. On the basis of the results, new noise parameter models are proposed and the noise performance improvement in the quasi-ballistic regime is shown.

  19. Analysis of a Precambrian resonance-stabilized day length

    NASA Astrophysics Data System (ADS)

    Bartlett, Benjamin C.; Stevenson, David J.

    2016-06-01

    During the Precambrian era, Earth's decelerating rotation would have passed a 21 h period that would have been resonant with the semidiurnal atmospheric thermal tide. Near this point, the atmospheric torque would have been maximized, being comparable in magnitude but opposite in direction to the lunar torque, halting Earth's rotational deceleration, maintaining a constant day length, as detailed by Zahnle and Walker (1987). We develop a computational model to determine necessary conditions for formation and breakage of this resonant effect. Our simulations show the resonance to be resilient to atmospheric thermal noise but suggest a sudden atmospheric temperature increase like the deglaciation period following a possible "snowball Earth" near the end of the Precambrian would break this resonance; the Marinoan and Sturtian glaciations seem the most likely candidates for this event. Our model provides a simulated day length over time that resembles existing paleorotational data, though further data are needed to verify this hypothesis.

  20. Control of noise in magnetic multilayers by spin torque

    NASA Astrophysics Data System (ADS)

    Rebei, Adnan

    2012-02-01

    In this work we show that the stability of magnetic nanostructures can be enhanced by time-dependent spin momentum transfer. Building reliable magnetic devices at smaller scales need to address the issue of thermal noise. Using two commonly studied magnetic systems with multiple stable states at zero temperature as examples, we show that periodic spin torques can enhance the stability of the system and hence suppress the noise due to interwell transitions. In the case of weak periodic spin torques, stochastic resonance which is usually associated with ac magnetic fields is also manifested for non-conservative torques. In more complex systems with a relatively low energy barrier, it is shown that high frequency spin torques can inhibit interwell transitions and in effect suppress the telegraph noise due to the switching between neigboring states.

  1. Three mode interaction noise in laser interferometer gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Ju, Li; Zhao, Chunnong; Ma, Yiqiu; Blair, David; Danilishin, Stefan L.; Gras, Slawek

    2014-07-01

    Triply resonant three mode interactions in long optical cavities have been shown to lead to enhanced scattering of carrier light by the ultrasonic acoustic modes of the test mass mirrors. At high optical power, this can lead to parametric instability (parametric gain R>1) for a few acoustic modes with strong spectral and spatial overlap. Numerous \\sim {{10}^{3}} acoustic modes of the test masses are predicted to have R>{{10}^{-2}}. Experimental studies have shown that such modes also strongly scatter the carrier light, enabling very sensitive readout of the acoustic modes. The three-mode scattering from the thermal fluctuation of large population of ultrasonic modes would causes random changes in occupation number of the carrier light and cavity transverse optical modes. Because the thermal fluctuation time scale (set by the acoustic mode relaxation times) is typically a few seconds, the noise spectrum from thermally induced photon number fluctuations is strongly peaked at low frequency. The noise level depends on the acoustic mode structure and acoustic losses of the test masses, the transverse optical mode spectrum of the optical cavities and on the test mass temperature. We theoretically investigate the possible effect of this noise and show that in advanced detectors under construction three mode interaction noise is below the standard quantum limit, but could set limits on future low frequency detectors that aim to exceed the free mass standard quantum limit.

  2. Jet Noise Suppression

    NASA Technical Reports Server (NTRS)

    Gliebe, P. R.; Brausch, J. F.; Majjigi, R. K.; Lee, R.

    1991-01-01

    The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

  3. Noise powered nonlinear energy harvesting

    NASA Astrophysics Data System (ADS)

    Gammaitoni, Luca; Neri, Igor; Vocca, Helios

    2011-04-01

    The powering of small-scale electronic mobile devices has been in recent years the subject of a great number of research efforts aimed primarily at finding an alternative solution to standard batteries. The harvesting of kinetic energy present in the form of random vibrations (from non-equilibrium thermal noise up to machine vibrations) is an interesting option due to the almost universal presence of some kind of motion. Present working solutions for vibration energy harvesting are based on oscillating mechanical elements that convert kinetic energy via capacitive, inductive or piezoelectric methods. These oscillators are usually designed to be resonantly tuned to the ambient dominant frequency. However, in most cases the ambient random vibrations have their energy distributed over a wide spectrum of frequencies, especially at low frequency, and frequency tuning is not always possible due to geometrical/dynamical constraints. We present a new approach to the powering of small autonomous sensors based on vibration energy harvesting by the exploitation of nonlinear stochastic dynamics. Such a method is shown to outperform standard linear approaches based on the use of resonant oscillators and to overcome some of the most severe limitations of present strategies, like narrow bandwidth, need for continuous frequency tuning and low power efficiency. We demonstrate the superior performances of this method by applying it to piezoelectric energy harvesting from ambient vibration.

  4. Noise-induced transitions in optomechanical synchronization

    NASA Astrophysics Data System (ADS)

    Weiss, Talitha; Kronwald, Andreas; Marquardt, Florian

    2016-01-01

    We study how quantum and thermal noise affects synchronization of two optomechanical limit-cycle oscillators. Classically, in the absence of noise, optomechanical systems tend to synchronize either in-phase or anti-phase. Taking into account the fundamental quantum noise, we find a regime where fluctuations drive transitions between these classical synchronization states. We investigate how this ‘mixed’ synchronization regime emerges from the noiseless system by studying the classical-to-quantum crossover and we show how the time scales of the transitions vary with the effective noise strength. In addition, we compare the effects of thermal noise to the effects of quantum noise.

  5. Community noise

    NASA Technical Reports Server (NTRS)

    Bragdon, C. R.

    1982-01-01

    Airport and community land use planning as they relate to airport noise reduction are discussed. Legislation, community relations, and the physiological effect of airport noise are considered. Noise at the Logan, Los Angeles, and Minneapolis/St. Paul airports is discussed.

  6. Spin noise spectroscopy of ZnO

    SciTech Connect

    Horn, H.; Berski, F.; Hübner, J.; Oestreich, M.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.

    2013-12-04

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  7. Measuring Excess Noise in SDL's

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.; Kowitz, H. R.; Rowland, C. W.; Shull, T. A.; Ruggles, S. L.; Matthews, L. F.

    1983-01-01

    New instrument gives quantitive information on "excess noise" in semiconductor-diode laser (SDL's). By proper selection of detector, instrument tests any SDL from visible wavelengths through thermal infrared. Lasers determine excess noise in SKL source by measuring photocurrent generated in photodetector exposed first to reference laser then to SKL under test.

  8. Electrical Characterization of Microelectromechanical Silicon Carbide Resonators

    PubMed Central

    Chang, Wen-Teng; Zorman, Christian

    2008-01-01

    This manuscript describes the findings of a study to investigate the performance of SiC MEMS resonators with respect to resonant frequency and quality factor under a variety of testing conditions, including various ambient pressures, AC drive voltages, bias potentials and temperatures. The sample set included both single-crystal and polycrystalline 3C-SiC lateral resonators. The experimental results show that operation at reduced pressures increases the resonant frequency as damping due to the gas-rarefaction effect becomes significant. Both DC bias and AC drive voltages result in nonlinearities, but the AC drive voltage is more sensitive to noise. The AC voltage has a voltage coefficient of 1∼4ppm/V at a DC bias of 40V. The coefficient of DC bias is about -11ppm/V to - 21ppm/V for poly-SiC, which is more than a factor of two better than a similarly designed polysilicon resonator (-54 ppm/V). The effective stiffness of the resonator decreases (softens) as the bias potential is increased, but increases (hardens) as drive voltage increase when scan is from low to high frequency. The resonant frequency decreases slightly with increasing temperature, exhibiting a temperature coefficient of -22 ppm/°C, between 22°C and 60°C. The thermal expansion mismatch between the SiC device and the Si substrate could be a reason that thermal coefficient for these SiC resonators is about twofold higher than similar polysilicon resonators. However, the Qs appear to exhibit no temperature dependence in this range.

  9. Rotor noise

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.

    1991-01-01

    The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.

  10. A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    SciTech Connect

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-15

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m{sup −1}(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  11. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

    PubMed

    Lockerbie, N A; Tokmakov, K V

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm. PMID:25430131

  12. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    NASA Astrophysics Data System (ADS)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m-1(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  13. Optical motion sensor for resonant-bar gravitational wave antennas.

    PubMed

    Richard, J P; Pang, Y; Hamilton, J J

    1992-04-01

    An experiment is described in which an optical method was used to measure fluctuations in the separation between two mirrors of a Fabry-Perot sensor cavity. Noise measurements were made to determine the sensitivity of this device to vibration amplitudes in the frequency range 1.1-2.1 kHz, which is of interestfor resonant-bar gravitational wave antennas. The rms spectral noise density for length fluctuations inthis range was 3.7 x 10(15-) m/Hz((1/2)) and can be related to electronic noise of the circuitry plus vibrationalnoise from the environment. The cavity finesse was relatively low at 117, and the power dissipated in the mirrors was estimated to be 1.9 muW. On a multimode gravitational wave detector, the sensor cavity would be formed by one reference mirror and by one mirror mounted on the last resonator. For a 1200-kg bar, 1.2-g last resonator system operating at 1600 Hz, the sensor described here would exhibit a noise temperature of 18 muK; the resolution in h in the case of negligible thermal noise from the mechanical system would be 3.7 x 10(-18)/Hz((1/2)). Improvements in the sensitivity in a quiet antenna-like environment should be possible with higher finesse mirrors. PMID:20720800

  14. Environmental Fluctuations and Stochastic Resonance in Protein Folding.

    PubMed

    Dave, Kapil; Davtyan, Aram; Papoian, Garegin A; Gruebele, Martin; Platkov, Max

    2016-05-01

    Stochastic resonance is a mechanism whereby a weak signal becomes detectable through the addition of noise. It is common in many macroscopic biological phenomena, but here we ask whether it can be observed in a microscopic biological phenomenon, protein folding. We investigate the folding kinetics of the protein VlsE, with a folding relaxation time of about 0.7 seconds at 38 °C in vitro. First we show that the VlsE unfolding/refolding reaction can be driven by a periodic thermal excitation above the reaction threshold. We detect the reaction by fluorescence from FRET labels on VlSE and show that accurate rate coefficients and activation barriers can be obtained from modulated kinetics. Then we weaken the periodic temperature modulation below the reaction threshold, and show that addition of artificial thermal noise speeds up the reaction from an undetectable to a detectable rate. We observe a maximum in the recovered signal as a function of thermal noise, a stochastic resonance. Simulation of a small model-protein, analysis in an accompanying theory paper, and our experimental result here all show that correlated noise is a physically and chemically plausible mechanism by which cells could modulate biomolecular dynamics during threshold processes such as signaling. PMID:26711088

  15. A microrod-resonator Brillouin laser with 240 Hz absolute linewidth

    NASA Astrophysics Data System (ADS)

    Loh, William; Becker, Joe; Cole, Daniel C.; Coillet, Aurelien; Baynes, Fred N.; Papp, Scott B.; Diddams, Scott A.

    2016-04-01

    We demonstrate an ultralow-noise microrod-resonator based laser that oscillates on the gain supplied by the stimulated Brillouin scattering optical nonlinearity. Microresonator Brillouin lasers are known to offer an outstanding frequency noise floor, which is limited by fundamental thermal fluctuations. Here, we show experimental evidence that thermal effects also dominate the close-to-carrier frequency fluctuations. The 6 mm diameter microrod resonator used in our experiments has a large optical mode area of ∼100 μm2, and hence its 10 ms thermal time constant filters the close-to-carrier optical frequency noise. The result is an absolute laser linewidth of 240 Hz with a corresponding white-frequency noise floor of 0.1 Hz2 Hz‑1. We explain the steady-state performance of this laser by measurements of its operation state and of its mode detuning and lineshape. Our results highlight a mechanism for noise that is common to many microresonator devices due to the inherent coupling between intracavity power and mode frequency. We demonstrate the ability to reduce this noise through a feedback loop that stabilizes the intracavity power.

  16. Dependence of electrically detected magnetic resonance signal shape from iron-contaminated silicon wafers on the thermal treatment of the samples

    NASA Astrophysics Data System (ADS)

    Mchedlidze, T.; Matsumoto, K.; Lin, T.-C.; Suezawa, M.

    1999-12-01

    The shape of the electrically detected magnetic resonance (EDMR) signal from iron-contaminated Czochralski-grown silicon (CZ-Si) samples strongly depends on the thermal treatments applied to the samples before and after the contamination procedure, although the average g-value of the spectra apparently does not vary. A signal from an iron-contaminated float-zone grown silicon (FZ-Si) sample was detected employing an EDMR signal detection unit with enhanced sensitivity. For similar contamination levels, the signal from the FZ-Si sample has amplitude about {1}/{45} that of the CZ-Si signal and has specific shape. Further study of the EDMR signals from iron-contaminated Si samples will be useful for the investigation of gettering and recombination processes in Si wafers. Besides that, dependence of the EDMR spectrum shape on the thermal processes employed can help to pinpoint the process responsible for wafer contamination during semiconductor device fabrication.

  17. AsGa+ antisites identified by electron spin resonance as a main interface defect system in thermal GaAs/native oxide structures

    NASA Astrophysics Data System (ADS)

    Stesmans, A.; Nguyen, S.; Afanas'ev, V. V.

    2013-10-01

    Aiming to assess the atomic-structural identity of inherently generated interfacial point defects during thermal oxidation, a conventional low-temperature electron spin resonance study has been carried out on (100)GaAs/native oxide structures thermally grown in the range of 350-615 °C on both powders and slices of semi-insulating (100)GaAs. This compellingly reveals substantial generation (density ˜ 1 × 1013 cm-2) of interfacial 75AsGa+ antisites in registry with the GaAs substrate layer, thus providing solid independent evidence of substantial interfacial As enrichment, appearing as endemic to oxidation of GaAs, and at the same time, providing an answer of how a major part of excess As gets interfacially incorporated. Given the known electrical deep double donor attribute of AsGa, direct identification is thus established of a major system of detrimental interface traps.

  18. THERMAL RESPONSE OF A HUMAN IN THE NEAR-ZONE OF A RESONANT THIN-WIRE ANTENNA

    EPA Science Inventory

    The thermal response of a human in the near-zone of an antenna was determined by numerical procedures. The approach taken was to modify the heat transfer equations for man in air to account for thermal loading due to the energy absorbed from the radiating antenna. The loading due...

  19. Airframe noise

    NASA Astrophysics Data System (ADS)

    Crighton, David G.

    1991-08-01

    Current understanding of airframe noise was reviewed as represented by experiment at model and full scale, by theoretical modeling, and by empirical correlation models. The principal component sources are associated with the trailing edges of wing and tail, deflected trailing edge flaps, flap side edges, leading edge flaps or slats, undercarriage gear elements, gear wheel wells, fuselage and wing boundary layers, and panel vibration, together with many minor protrusions like radio antennas and air conditioning intakes which may contribute significantly to perceived noise. There are also possibilities for interactions between the various mechanisms. With current engine technology, the principal airframe noise mechanisms dominate only at low frequencies, typically less than 1 kHz and often much lower, but further reduction of turbomachinery noise in particular may make airframe noise the principal element of approach noise at frequencies in the sensitive range.

  20. Generation of micro-domains in AT-cut quartz by thermal processing and the effect on resonator modes

    SciTech Connect

    Weisenback, L.; Martin, S.J.; Frye, G.C.; Bohuszewicz, T.V.; Doughty, D.H.

    1994-08-01

    The fabrication of acoustic sensors with sol-gel selective coatings requires the deposition of thin films on quartz resonators using solution chemistry techniques. Oxide films are spin-cast, then heat treated. A variety of film compositions are deposited, requiring a variety of firing schedules. Network analysis of the untreated AT-cut quartz devices revealed a resonant frequency of 5.0 MHz, corresponding to a pure thickness-shear mode resonance. For devices that were rapidly fired to 400C and rapidly air cooled, network analysis showed the shear-mode response at 5.0 MHz disappeared, while a predominantly compressional mode response at 7.3 MHz emerged. Structural analysis explored the crystal structure changes induced by processing which resulted in this new mode.

  1. Interior Noise

    NASA Technical Reports Server (NTRS)

    Mixson, John S.; Wilby, John F.

    1991-01-01

    The generation and control of flight vehicle interior noise is discussed. Emphasis is placed on the mechanisms of transmission through airborne and structure-borne paths and the control of cabin noise by path modification. Techniques for identifying the relative contributions of the various source-path combinations are also discussed along with methods for the prediction of aircraft interior noise such as those based on the general modal theory and statistical energy analysis.

  2. Noise Protection

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Environmental Health Systems puts forth an increasing effort in the U.S. to develop ways of controlling noise, particularly in industrial environments due to Federal and State laws, labor union insistence and new findings relative to noise pollution impact on human health. NASA's Apollo guidance control system aided in the development of a noise protection product, SMART. The basis of all SMART products is SMART compound a liquid plastic mixture with exceptional energy/sound absorbing qualities. The basic compound was later refined for noise protection use.

  3. Ideal current patterns yielding optimal signal-to-noise ratio and specific absorption rate in magnetic resonance imaging: computational methods and physical insights.

    PubMed

    Lattanzi, Riccardo; Sodickson, Daniel K

    2012-07-01

    At high and ultra-high magnetic field strengths, understanding interactions between tissues and the electromagnetic fields generated by radiofrequency coils becomes crucial for safe and effective coil design as well as for insight into limits of performance. In this work, we present a rigorous electrodynamic modeling framework, using dyadic Green's functions, to derive the electromagnetic field in homogeneous spherical and cylindrical samples resulting from arbitrary surface currents in the presence or absence of a surrounding radiofrequency shield. We show how to calculate ideal current patterns that result in the highest possible signal-to-noise ratio (ultimate intrinsic signal-to-noise ratio) or the lowest possible radiofrequency power deposition (ultimate intrinsic specific absorption rate) compatible with electrodynamic principles. We identify familiar coil designs within optimal current patterns at low to moderate field strength, thereby establishing and explaining graphically the near-optimality of traditional surface and volume quadrature designs. We also document the emergence of less familiar patterns, e.g., involving substantial electric--as well as magnetic-dipole contributions, at high field strength. Performance comparisons with particular coil array configurations demonstrate that optimal performance may be approached with finite arrays if ideal current patterns are used as a guide for coil design. PMID:22127735

  4. Fully vectorial laser resonator modeling of continuous-wave solid-state lasers including rate equations, thermal lensing and stress-induced birefringence.

    PubMed

    Asoubar, Daniel; Wyrowski, Frank

    2015-07-27

    The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator. PMID:26367545

  5. The cavity resonance mode of Bi2Sr2CaCu2O8 mesa terahertz sources as probed by scanning laser thermal microscopy

    NASA Astrophysics Data System (ADS)

    Benseman, Timothy; Koshelev, Alexei; Vlasko-Vlasov, Vitalii; Welp, Ulrich; Kwok, Wai-Kwong; Hao, Yang; Gross, Boris; Lange, Matthias; Koelle, Dieter; Kleiner, Reinhold; Kadowaki, Kazuo

    Stacked Intrinsic Josephson Junctions (IJJs) in the extremely anisotropic high-Tc superconductor Bi2Sr2CaCu2O8 are a promising solid-state source of coherent terahertz radiation in the so-called ``THz gap'' range. In these devices, a geometric resonant mode of a stack of IJJs of typical dimensions 300 x 60 x 1 microns3 acts to synchronize the individual junctions, resulting in coherent far-field THz emission. This resonance can be probed by scanning thermal laser microscopy, in which a modulated optical laser beam is rastered across the top surface of a stack. The resulting thermal perturbation to the stack's cavity mode can thus be mapped via the resulting xy-dependent modulation of the stack's electrical resistance. Here we discuss the experimentally measured scanning laser pattern of such a THz cavity mode, and the implications of its symmetry for the mechanism of IJJ synchronization in these devices. This research was supported by the Department of Energy, Office of Basic Energy Sciences, under Contract No. De-AC02-06CH11357.

  6. Overall mechanical transfer function calculated for a spherical resonant gravitational waves antenna

    NASA Astrophysics Data System (ADS)

    Melo, José L.; Velloso, Walter F.; Aguiar, Odylio D.

    2004-06-01

    In this article, we describe the vibrational isolation system, the thermal link and the transducer mechanical structure, for the Schenberg resonant gravitational wave detector, which has been conceived modeled and analyzed using the finite element method. The dynamical equations corresponding to the structure have been solved using the MSC/NASTRAN software. In order to study the overall system behavior and the noise influence on it, we have carried out the analysis considering simultaneously all mechanical systems: vibrational isolation, thermal linking (between the dilution refrigerator and the suspension), and transducer-resonant mass mechanical coupling. Our calculation shows that a 300 dB attenuation level could be obtained.

  7. Application of Electron Paramagnetic Resonance Spectroscopy to Comparative Examination of Different Groups of Free Radicals in Thermal Injuries Treated with Propolis and Silver Sulphadiazine

    PubMed Central

    Olczyk, Pawel; Ramos, Pawel; Bernas, Marcin; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

    2013-01-01

    Different groups of free radicals expressed in burn wounds treated with propolis and silver sulphadiazine were examined. The thermal effect forms major types of free radicals in a wound because of the breaking of chemical bonds. Free radicals, located in the heated skin, were tested after 21 days of treating by these two substances. The aim of this work was to find the method for determination of types and concentrations of different groups of free radicals in wound after high temperature impact during burning. The effects of the therapy by propolis and silver sulphadiazine on free radicals were studied. Since the chemical methods of free radicals studies are destructive, the usefulness of the electron paramagnetic resonance spectroscopy was tested in this work. The electron paramagnetic resonance spectra measured with the microwave power of 2.2 mW were numerically fitted by theoretical curves of Gaussian and Lorentzian shapes. The experimental electron paramagnetic resonance spectra of tissue samples are best fitted by the sum of one Gauss and two Lorentz lines. An innovatory numerical procedure of spectroscopic skin analysis was presented. It is very useful in the alternative medicine studies. PMID:23762162

  8. Thermal Microphotonic Focal Plane Array (TM-FPA).

    SciTech Connect

    McCormick, Frederick Bossert; Lentine, Anthony L.; Wright, Jeremy Benjamin; Watts, Michael R.; Shaw, Michael J.; Rakich, Peter T.; Nielson, Gregory N.; Peters, David William; Zortman, William A.

    2009-10-01

    The advent of high quality factor (Q) microphotonic-resonators has led to the demonstration of high-fidelity optical sensors of many physical phenomena (e.g. mechanical, chemical, and biological sensing) often with far better sensitivity than traditional techniques. Microphotonic-resonators also offer potential advantages as uncooled thermal detectors including significantly better noise performance, smaller pixel size, and faster response times than current thermal detectors. In particular, microphotonic thermal detectors do not suffer from Johnson noise in the sensor, offer far greater responsivity, and greater thermal isolation as they do not require metallic leads to the sensing element. Such advantages make the prospect of a microphotonic thermal imager highly attractive. Here, we introduce the microphotonic thermal detection technique, present the theoretical basis for the approach, discuss our progress on the development of this technology and consider future directions for thermal microphotonic imaging. Already we have demonstrated viability of device fabrication with the successful demonstration of a 20{micro}m pixel, and a scalable readout technique. Further, to date, we have achieved internal noise performance (NEP{sub Internal} < 1pW/{radical}Hz) in a 20{micro}m pixel thereby exceeding the noise performance of the best microbolometers while simultaneously demonstrating a thermal time constant ({tau} = 2ms) that is five times faster. In all, this results in an internal detectivity of D*{sub internal} = 2 x 10{sup 9}cm {center_dot} {radical}Hz/W, while roughly a factor of four better than the best uncooled commercial microbolometers, future demonstrations should enable another order of magnitude in sensitivity. While much work remains to achieve the level of maturity required for a deployable technology, already, microphotonic thermal detection has demonstrated considerable potential.

  9. An analytical formulation for phase noise in MEMS oscillators.

    PubMed

    Agrawal, Deepak; Seshia, Ashwin

    2014-12-01

    In recent years, there has been much interest in the design of low-noise MEMS oscillators. This paper presents a new analytical formulation for noise in a MEMS oscillator encompassing essential resonator and amplifier nonlinearities. The analytical expression for oscillator noise is derived by solving a second-order nonlinear stochastic differential equation. This approach is applied to noise modeling of an electrostatically addressed MEMS resonator-based square-wave oscillator in which the resonator and oscillator circuit nonlinearities are integrated into a single modeling framework. By considering the resulting amplitude and phase relations, we derive additional noise terms resulting from resonator nonlinearities. The phase diffusion of an oscillator is studied and the phase diffusion coefficient is proposed as a metric for noise optimization. The proposed nonlinear phase noise model provides analytical insight into the underlying physics and a pathway toward the design optimization for low-noise MEMS oscillators. PMID:25474770

  10. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    SciTech Connect

    Barhoumi, A. Guermazi, S.; Leroy, G.; Gest, J.; Carru, J. C.; Yang, L.; Boughzala, H.; Duponchel, B.

    2014-05-28

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures T{sub s}. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with T{sub s} which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, R{sub sh} and [αμ]{sub eff} increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  11. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    NASA Astrophysics Data System (ADS)

    Barhoumi, A.; Leroy, G.; Yang, L.; Gest, J.; Boughzala, H.; Duponchel, B.; Guermazi, S.; Carru, J. C.

    2014-05-01

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures Ts. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with Ts which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, Rsh and [αμ]eff increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  12. High level white noise generator

    DOEpatents

    Borkowski, Casimer J.; Blalock, Theron V.

    1979-01-01

    A wide band, stable, random noise source with a high and well-defined output power spectral density is provided which may be used for accurate calibration of Johnson Noise Power Thermometers (JNPT) and other applications requiring a stable, wide band, well-defined noise power spectral density. The noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of a special inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise or a 100 ohm resistor at a temperature of approximately 64,000 Kelvins. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 db) in the frequency range of from 1 KHz to 100 KHz which brackets typical passbands of the signal-processing channels of JNPT's. Two embodiments, one of higher accuracy that is suitable for use as a standards instrument and another that is particularly adapted for ambient temperature operation, are illustrated in this application.

  13. Aircraft Noise

    NASA Astrophysics Data System (ADS)

    Michel, Ulf; Dobrzynski, Werner; Splettstoesser, Wolf; Delfs, Jan; Isermann, Ullrich; Obermeier, Frank

    Aircraft industry is exposed to increasing public pressure aiming at a continuing reduction of aircraft noise levels. This is necessary to both compensate for the detrimental effect on noise of the expected increase in air traffic and improve the quality of living in residential areas around airports.

  14. Environmental Noise

    NASA Astrophysics Data System (ADS)

    Rumberg, Martin

    Environmental noise may be defined as unwanted sound that is caused by emissions from traffic (roads, air traffic corridors, and railways), industrial sites and recreational infrastructures, which may cause both annoyance and damage to health. Noise in the environment or community seriously affects people, interfering with daily activities at school, work and home and during leisure time.

  15. Natural radio noise - A mini-review

    NASA Technical Reports Server (NTRS)

    Flock, W. L.; Smith, E. K.

    1984-01-01

    Natural radio noise in telecommunication systems can be accounted for by the contribution which it makes to antenna noise temperature. Attenuation due to water vapor and oxygen, clouds, and precipitation is accompanied by thermal noise which further degrades the applicable signal-to-noise ratio. Extraterrestrial noise may be of thermal or nonthermal origin and may cover a continuum of frequencies or occur at discrete frequencies. The spectral index n (the exponent giving the variation of noise power density with wavelength) is -2 for a black body and between 0 and -2 for thermal emission in general. The mechanism responsible for much of the extensive nonthermal extraterrestrial noise is synchrotron radiation, characterized by a positive spectral index.

  16. Low-noise fan exit guide vanes

    NASA Technical Reports Server (NTRS)

    Jones, Michael G. (Inventor); Parrott, Tony L. (Inventor); Heidelberg, Laurence J. (Inventor); Envia, Edmane (Inventor)

    2008-01-01

    Low-noise fan exit guide vanes are disclosed. According to the present invention a fan exit guide vane has an outer shell substantially shaped as an airfoil and defining an interior cavity. A porous portion of the outer shell allows communication between the fluctuations in the air passing over the guide vane and the interior cavity. At least one acoustically resonant chamber is located within the interior cavity. The resonant chamber is in communication with the porous portion of the outer perimeter. The resonant chamber is configured to reduce the noise generated at a predetermined frequency. In various preferred embodiments, there is a plurality of acoustically resonant chambers located within the interior cavity. The resonant chambers can be separated by one or more partitions within the interior cavity. In these embodiments, the resonant chambers can be configured to reduce the noise generated over a range of predetermined frequencies.

  17. Squeezed light from a silicon micromechanical resonator.

    PubMed

    Safavi-Naeini, Amir H; Gröblacher, Simon; Hill, Jeff T; Chan, Jasper; Aspelmeyer, Markus; Painter, Oskar

    2013-08-01

    Monitoring a mechanical object's motion, even with the gentle touch of light, fundamentally alters its dynamics. The experimental manifestation of this basic principle of quantum mechanics, its link to the quantum nature of light and the extension of quantum measurement to the macroscopic realm have all received extensive attention over the past half-century. The use of squeezed light, with quantum fluctuations below that of the vacuum field, was proposed nearly three decades ago as a means of reducing the optical read-out noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror's position with light may itself give rise to squeezed light. Such squeezed-light generation has recently been demonstrated in a system of ultracold gas-phase atoms whose centre-of-mass motion is analogous to the motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity. Laser light sent into the cavity is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the mechanical resonator's highly excited thermal state (10(4) phonons), we observe, through homodyne detection, squeezing of the reflected light's fluctuation spectrum at a level 4.5 ± 0.2 per cent below that of vacuum noise over a bandwidth of a few megahertz around the mechanical resonance frequency of 28 megahertz. With further device improvements, on-chip squeezing at significant levels should be possible, making such integrated microscale devices well suited for precision metrology applications. PMID:23925241

  18. Thermal Cross Sections and Resonance Integrals for Ag{sup 109}(n,{gamma})Ag{sup 110m} and Several Other Reactions

    SciTech Connect

    Williams, J.G.

    2011-07-01

    In this paper measurements reported from the Rikkyo Research Reactor are reanalysed using a least squares adjustment procedure in which the adjustable parameters were the thermal and epithermal neutron fluences, the epithermal shape parameter and the thermal neutron cross sections and resonance integrals of all the dosimeters, including the gold and cobalt standards. The methodology and the results are described. Nuclear data including cross sections, recommended in ASTM Standard Test Method E 481, for the {sup 59}Co(n,{gamma}){sup 60}Co and Ag{sup 109}(n,{gamma})Ag{sup 110m} reactions were changed in a recent revision of the standard. The change for the silver thermal neutron cross section was very large compared to the previously cited uncertainties. The reference cited in the standard is the only new measurement that has been reported in many years. The value reported there for the 2200 m/s cross section is 4.12 {+-} 0.10 barn. This reevaluation adjusts that value to 3.87 {+-} 0.08 barn. The value in the previous edition of E481, however, was 4.7 barns {+-} 4%. Such a large change greatly affects the neutron fluence values that will be calculated. (author)

  19. Dual surface plasmon resonances in Zn nanoparticles in SiO(2): an experimental study based on optical absorption and thermal stability.

    PubMed

    Amekura, H; Umeda, N; Kono, K; Takeda, Y; Kishimoto, N; Buchal, Ch; Mantl, S

    2007-10-01

    Metallic zinc nanoparticles (NPs) of 5-15 nm in diameter, formed in silica glass (SiO(2)) by Zn ion implantation of 60 keV, showed a strong ultraviolet absorption peak at around 4.8 eV, which has been assigned as the surface plasmon resonance (SPR) of Zn NPs, and another small peak at 1.2 eV, which has never been reported before. To identify the origin of the 1.2 eV peak, the correlations of thermal stability between the two peaks and Zn NPs were evaluated under annealing both in a vacuum (pure thermal stability) and in oxygen gas (thermal oxidation stability). The well-correlated stability between the 1.2 eV peak, the 4.8 eV peak and Zn NPs indicates that the 1.2 eV peak is not ascribed to radiation-induced defects but to the Zn NPs. The 1.2 eV peak can be ascribed to an SPR of Zn NPs in SiO(2), because the peak satisfies the criterion of the SPR of metallic NPs. Since the 4.8 eV peak is also expected to satisfy the criterion, Zn NPs in SiO(2) have two SPRs at 1.2 and 4.8 eV. PMID:21730432

  20. Ambient resonance of rock arches

    NASA Astrophysics Data System (ADS)

    Starr, Alison Margaret

    Resonant frequencies of structural elements are related to fundamental material properties of mass and stiffness, and monitoring over time can thus serve as an indirect indictor of internal mechanical change. Until now, however, this methodology has not been applied to natural rock structures such as arches and towers. We evaluated the resonance characteristics of four rock arches in southeastern Utah, combining in-situ ambient vibration measurements with numerical modal analysis. At each location, we measured the spectral and polarization attributes of ambient vibrations using up to two broadband seismometers. Ambient vibration spectra measured on the arches showed clear peaks at distinct frequencies (typically between 1-10 Hz), which we interpret as resonant frequencies, as opposed to the relatively flat spectra recorded on nearby bedrock. Polarization analysis helped us identify the orientations of vibration and explore resonant mode shapes. We then verified the measured resonant frequencies through 3D finite-element numerical modal analysis, and in most cases we were able to match the fundamental along with several higher-order modes. Repeat occupation and short-term continuous ambient vibration monitoring were aimed at assessing daily and seasonal changes in resonant frequencies, which in turn may provide evidence of internal mechanical change; Mesa Arch in Canyonlands National Park served as the main focus for our repeat measurements. Results revealed that minor, reversible changes in resonant frequencies can be created by thermal effects, i.e., changes in bulk material stiffness as the arch expands and contracts on daily and seasonal time scales. No irreversible change in the resonant frequency of Mesa Arch was detected over the period of this study. Our research provides the first step towards monitoring the long-term structural health of natural rock arches as they change through time or in the wake of a damaging event. We have shown that the resonance

  1. Squeezed light spin noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Lucivero, Vito Giovanni; Jiménez-Martínez, Ricardo; Kong, Jia; Mitchell, Morgan

    2016-05-01

    Spin noise spectroscopy (SNS) has recently emerged as a powerful technique for determining physical properties of an unperturbed spin system from its power noise spectrum both in atomic and solid state physics. In the presence of a transverse magnetic field, we detect spontaneous spin fluctuations of a dense Rb vapor via Faraday rotation of an off-resonance probe beam, resulting in the excess of spectral noise at the Larmor frequency over a white photon shot-noise background. We report quantum enhancement of the signal-to-noise ratio via polarization squeezing of the probe beam up to 3dB over the full density range up to n = 1013 atoms cm-3, covering practical conditions used in optimized SNS experiments. Furthermore, we show that squeezing improves the trade-off between statistical sensitivity and systematic errors due to line broadening, a previously unobserved quantum advantage.

  2. Low-frequency noise in hot-carrier detectors

    NASA Astrophysics Data System (ADS)

    Ivanov, N. I.; Petko, G. V.

    1981-01-01

    The low-frequency noise of hot-carrier detectors has been studied theoretically and experimentallyywith reference to the contributions of each of the following noise sources: thermal noise, shot effect, flicker noise, and noise generated in the input waveguide which is converted to thermoelectromotive force during detection. It is shown that hot-carrier detectors can be used for low-noise detection of electromagnetic radiation in the centimeter and millimeter ranges for various radioelectronic and measurements applications.

  3. Near-interfacial thermal donor generation during processing of (100)Si/low-κ Si-oxycarbide insulator structures revealed by electron spin resonance

    NASA Astrophysics Data System (ADS)

    Stesmans, A.; Iacovo, S.; Nguyen, S.; Afanas'ev, V. V.; Baklanov, M. R.; Urbanowicz, A. M.

    2014-09-01

    A low-temperature multifrequency electron spin resonance (ESR) study has been carried out on Cz-(110)Si/insulator structures with organosilicate films of low dielectric constant κ grown at 300 °C using the plasma-enhanced chemical vapor deposition method (PECVD). After subjection to a short-term UV-irradiation-assisted thermal curing treatment at 430 °C to remove the organic component from the low-κ film and obtain optimal porosity, the NL8 ESR spectrum of C2v symmetry is observed, characterized by g1 (//[100] = 1.999 83(8), g2(//[011] = 1.992 74(8), g3 = (//[1\\bar{1}0]) = 2.001 15(8). Based on previous insight, this reveals the generation in the c-Si substrate of singly ionized thermal double donor (TDD) defects with a core containing oxygen atoms. Remarkably, the generation is found to be highly nonuniform, and the defect density depth profile shows an exponential-like decay (decay length ˜3.8 μm) from the oxide/Si interface inward the Si substrate, thus exposing the defect formation as an interface-administered effect. Upon analysis, the strain induced by interfacial stress in the c-Si beneath the interface is suggested as the major driving component in the enhancement of TDD formation during thermal treatment, suggesting that substantial stress is involved with PECVD organosilicate low-κ glasses. The result represents a different and affirmative illustration of the influence of strain on TDD formation. Based on the principal g values, the observed TDD is closest to the NL81 type, the one formed first in bulk c-Si through oxygen agglomeration during short-term thermal treatment.

  4. Periodic and stochastic thermal modulation of protein folding kinetics.

    PubMed

    Platkov, Max; Gruebele, Martin

    2014-07-21

    Chemical reactions are usually observed either by relaxation of a bulk sample after applying a sudden external perturbation, or by intrinsic fluctuations of a few molecules. Here we show that the two ideas can be combined to measure protein folding kinetics, either by periodic thermal modulation, or by creating artificial thermal noise that greatly exceeds natural thermal fluctuations. We study the folding reaction of the enzyme phosphoglycerate kinase driven by periodic temperature waveforms. As the temperature waveform unfolds and refolds the protein, its fluorescence color changes due to FRET (Förster resonant Energy Transfer) of two donor/acceptor fluorophores labeling the protein. We adapt a simple model of periodically driven kinetics that nicely fits the data at all temperatures and driving frequencies: The phase shifts of the periodic donor and acceptor fluorescence signals as a function of driving frequency reveal reaction rates. We also drive the reaction with stochastic temperature waveforms that produce thermal fluctuations much greater than natural fluctuations in the bulk. Such artificial thermal noise allows the recovery of weak underlying signals due to protein folding kinetics. This opens up the possibility for future detection of a stochastic resonance for protein folding subject to noise with controllable amplitude. PMID:25053342

  5. Periodic and stochastic thermal modulation of protein folding kinetics

    PubMed Central

    Platkov, Max; Gruebele, Martin

    2014-01-01

    Chemical reactions are usually observed either by relaxation of a bulk sample after applying a sudden external perturbation, or by intrinsic fluctuations of a few molecules. Here we show that the two ideas can be combined to measure protein folding kinetics, either by periodic thermal modulation, or by creating artificial thermal noise that greatly exceeds natural thermal fluctuations. We study the folding reaction of the enzyme phosphoglycerate kinase driven by periodic temperature waveforms. As the temperature waveform unfolds and refolds the protein, its fluorescence color changes due to FRET (Förster resonant Energy Transfer) of two donor/acceptor fluorophores labeling the protein. We adapt a simple model of periodically driven kinetics that nicely fits the data at all temperatures and driving frequencies: The phase shifts of the periodic donor and acceptor fluorescence signals as a function of driving frequency reveal reaction rates. We also drive the reaction with stochastic temperature waveforms that produce thermal fluctuations much greater than natural fluctuations in the bulk. Such artificial thermal noise allows the recovery of weak underlying signals due to protein folding kinetics. This opens up the possibility for future detection of a stochastic resonance for protein folding subject to noise with controllable amplitude. PMID:25053342

  6. Periodic and stochastic thermal modulation of protein folding kinetics

    SciTech Connect

    Platkov, Max; Gruebele, Martin

    2014-07-21

    Chemical reactions are usually observed either by relaxation of a bulk sample after applying a sudden external perturbation, or by intrinsic fluctuations of a few molecules. Here we show that the two ideas can be combined to measure protein folding kinetics, either by periodic thermal modulation, or by creating artificial thermal noise that greatly exceeds natural thermal fluctuations. We study the folding reaction of the enzyme phosphoglycerate kinase driven by periodic temperature waveforms. As the temperature waveform unfolds and refolds the protein, its fluorescence color changes due to FRET (Förster resonant Energy Transfer) of two donor/acceptor fluorophores labeling the protein. We adapt a simple model of periodically driven kinetics that nicely fits the data at all temperatures and driving frequencies: The phase shifts of the periodic donor and acceptor fluorescence signals as a function of driving frequency reveal reaction rates. We also drive the reaction with stochastic temperature waveforms that produce thermal fluctuations much greater than natural fluctuations in the bulk. Such artificial thermal noise allows the recovery of weak underlying signals due to protein folding kinetics. This opens up the possibility for future detection of a stochastic resonance for protein folding subject to noise with controllable amplitude.

  7. Periodic and stochastic thermal modulation of protein folding kinetics

    NASA Astrophysics Data System (ADS)

    Platkov, Max; Gruebele, Martin

    2014-07-01

    Chemical reactions are usually observed either by relaxation of a bulk sample after applying a sudden external perturbation, or by intrinsic fluctuations of a few molecules. Here we show that the two ideas can be combined to measure protein folding kinetics, either by periodic thermal modulation, or by creating artificial thermal noise that greatly exceeds natural thermal fluctuations. We study the folding reaction of the enzyme phosphoglycerate kinase driven by periodic temperature waveforms. As the temperature waveform unfolds and refolds the protein, its fluorescence color changes due to FRET (Förster resonant Energy Transfer) of two donor/acceptor fluorophores labeling the protein. We adapt a simple model of periodically driven kinetics that nicely fits the data at all temperatures and driving frequencies: The phase shifts of the periodic donor and acceptor fluorescence signals as a function of driving frequency reveal reaction rates. We also drive the reaction with stochastic temperature waveforms that produce thermal fluctuations much greater than natural fluctuations in the bulk. Such artificial thermal noise allows the recovery of weak underlying signals due to protein folding kinetics. This opens up the possibility for future detection of a stochastic resonance for protein folding subject to noise with controllable amplitude.

  8. Noise temperature and noise figure concepts: DC to light

    NASA Technical Reports Server (NTRS)

    Stelzried, C. T.

    1982-01-01

    The Deep Space Network is investigating the use of higher operational frequencies for improved performance. Noise temperature and noise figure concepts are used to describe the noise performance of these receiving systems. It is proposed to modify present noise temperature definitions for linear amplifiers so they will be valid over the range (hf/kT) 1 (hf/kT). This is important for systems operating at high frequencies and low noise temperatures, or systems requiring very accurate calibrations. The suggested definitions are such that for an ideal amplifier, T sub e = (hg/k) = T sub q and F = 1. These definitions revert to the present definition for (hf/kT) 1. Noise temperature calibrations are illustrated with a detailed example. These concepts are applied to system signal-to-noise analysis. The fundamental limit to a receiving system sensitivity is determined by the thermal noise of the source and the quantum noise limit of the receiver. The sensitivity of a receiving system consisting of an ideal linear amplifier with a 2.7 K source, degrades significantly at higher frequencies.

  9. Noise temperature and noise figure concepts: DC to light

    NASA Astrophysics Data System (ADS)

    Stelzried, C. T.

    1982-02-01

    The Deep Space Network is investigating the use of higher operational frequencies for improved performance. Noise temperature and noise figure concepts are used to describe the noise performance of these receiving systems. It is proposed to modify present noise temperature definitions for linear amplifiers so they will be valid over the range (hf/kT) 1 (hf/kT). This is important for systems operating at high frequencies and low noise temperatures, or systems requiring very accurate calibrations. The suggested definitions are such that for an ideal amplifier, T sub e = (hg/k) = T sub q and F = 1. These definitions revert to the present definition for (hf/kT) 1. Noise temperature calibrations are illustrated with a detailed example. These concepts are applied to system signal-to-noise analysis. The fundamental limit to a receiving system sensitivity is determined by the thermal noise of the source and the quantum noise limit of the receiver. The sensitivity of a receiving system consisting of an ideal linear amplifier with a 2.7 K source, degrades significantly at higher frequencies.

  10. Ultrapure Blue Thermally Activated Delayed Fluorescence Molecules: Efficient HOMO-LUMO Separation by the Multiple Resonance Effect.

    PubMed

    Hatakeyama, Takuji; Shiren, Kazushi; Nakajima, Kiichi; Nomura, Shintaro; Nakatsuka, Soichiro; Kinoshita, Keisuke; Ni, Jingping; Ono, Yohei; Ikuta, Toshiaki

    2016-04-01

    Ultrapure blue-fluorescent molecules based on thermally activated delayed fluorescence are developed. Organic light-emitting diode (OLED) devices employing the new emitters exhibit a deep blue emission at 467 nm with a full-width at half-maximum of 28 nm, CIE coordinates of (0.12, 0.13), and an internal quantum efficiency of ≈100%, which represent record-setting performance for blue OLED devices. PMID:26865384

  11. CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?

    PubMed Central

    Samaras, Theodoros; Yarmolenko, Pavel S.; Dewhirst, Mark W.; Neufeld, Esra; Kuster, Niels

    2013-01-01

    Objective To define thresholds of safe local temperature increases for MR equipment that exposes patients to radiofrequency fields of high intensities for long duration. These MR systems induce heterogeneous energy absorption patterns inside the body and can create localised hotspots with a risk of overheating. Methods The MRI + EUREKA research consortium organised a “Thermal Workshop on RF Hotspots”. The available literature on thresholds for thermal damage and the validity of the thermal dose (TD) model were discussed. Results/Conclusions The following global TD threshold guidelines for safe use of MR are proposed: All persons: maximum local temperature of any tissue limited to 39 °CPersons with compromised thermoregulation AND Uncontrolled conditions: maximum local temperature limited to 39 °CControlled conditions: TD<2 CEM43°CPersons with uncompromised thermoregulation AND Uncontrolled conditions: TD<2 CEM43°CControlled conditions: TD<9 CEM43°C The following definitions are applied: Controlled conditions A medical doctor or a dedicated trained person can respond instantly to heat-induced physiological stress Compromised thermoregulation All persons with impaired systemic or reduced local thermoregulation PMID:23553588

  12. Treatment of a supratentorial primitive neuroectodermal tumor using magnetic resonance-guided laser-induced thermal therapy.

    PubMed

    Jethwa, Pinakin R; Lee, Jason H; Assina, Rachid; Keller, Irwin A; Danish, Shabbar F

    2011-11-01

    Supratentorial primitive neuroectodermal tumors (PNETs) are rare tumors that carry a poorer prognosis than those arising from the infratentorial compartment (such as medulloblastoma). The overall prognosis for these patients depends on several factors including the extent of resection, age at diagnosis, CSF dissemination, and site in the supratentorial space. The authors present the first case of a patient with a newly diagnosed supratentorial PNET in which cytoreduction was achieved with MR-guided laser-induced thermal therapy. A 10-year-old girl presented with left-sided facial weakness and a large right thalamic mass extending into the right midbrain. The diagnosis of supratentorial PNET was made after stereotactic biopsy. Therapeutic options for this lesion were limited because of the risks of postoperative neurological deficits with resection. The patient underwent MR-guided laser-induced thermal ablation of her tumor. Under real-time MR thermometry, thermal energy was delivered to the tumor at a core temperature of 90°C for a total of 960 seconds. The patient underwent follow-up MR imaging at regular intervals to evaluate the tumor response to the thermal ablation procedure. Initial postoperative scans showed an increase in the size of the lesion as well as the amount of the associated edema. Both the size of the lesion and the edema stabilized by 1 week and then decreased below preablation levels at the 3-month postsurgical follow-up. There was a slight increase in the size of the lesion and associated edema at the 6-month follow-up scan, presumably due to concomitant radiation she received as part of her postoperative care. The patient tolerated the procedure well and has had resolution of her symptoms since surgery. Further study is needed to assess the role of laser-induced thermal therapy for the treatment of intracranial tumors. As such, it is a promising tool in the neurosurgical armamentarium. Postoperative imaging has shown no evidence of definitive

  13. Mechanical monolithic horizontal sensor for low frequency seismic noise measurement.

    PubMed

    Acernese, Fausto; Giordano, Gerardo; Romano, Rocco; De Rosa, Rosario; Barone, Fabrizio

    2008-07-01

    This paper describes a mechanical monolithic horizontal sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric discharge machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. The monolithic mechanical design and the introduction of laser interferometric techniques for the readout implementation makes it a very compact instrument, very sensitive in the low frequency seismic noise band, with a very good immunity to environmental noises. Many changes have been produced since last version (2007), mainly aimed to the improvement of the mechanics and of the optical readout of the instrument. In fact, we have developed and tested a prototype with elliptical hinges and mechanical tuning of the resonance frequency together with a laser optical lever and a new laser interferometer readout system. The theoretical sensitivity curve for both laser optical lever and laser interferometric readouts, evaluated on the basis of suitable theoretical models, shows a very good agreement with the experimental measurements. Very interesting scientific result is the measured natural resonance frequency of the instrument of 70 mHz with a Q=140 in air without thermal stabilization. This result demonstrates the feasibility of a monolithic folded pendulum sensor with a natural resonance frequency of the order of millihertz with a more refined mechanical tuning. PMID:18681722

  14. Exploration of Adiabatic Resonance Crossing Through Neutron Activator Design for Thermal and Epithermal Neutron Formation in (99)Mo Production and BNCT Applications.

    PubMed

    Khorshidi, Abdollah

    2015-10-01

    A feasibility study was performed to design thermal and epithermal neutron sources for radioisotope production and boron neutron capture therapy (BNCT) by moderating fast neutrons. The neutrons were emitted from the reaction between (9)Be, (181)Ta, and (184)W targets and 30 MeV protons accelerated by a small cyclotron at 300 μA. In this study, the adiabatic resonance crossing (ARC) method was investigated by means of (207)Pb and (208)Pb moderators, graphite reflector, and boron absorber around the moderator region. Thermal/epithermal flux, energy, and cross section of accumulated neutrons in the activator were examined through diverse thicknesses of the specified regions. Simulation results revealed that the (181)Ta target had the highest neutron yield, and also tungsten was found to have the highest values in both surface and volumetric flux ratio. Transmutation in the (98)Mo sample through radiative capture was investigated for the natural lead moderator. When the sample radial distance from the target was increased inside the graphite region, the production yield had the greatest value of activity. The potential of the ARC method is a replacement or complements the current reactor-based supply sources of BNCT purposes. PMID:26397967

  15. Investigation on thermal behavior of resonant waveguide-grating mirrors in an Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Rumpel, Martin; Dannecker, Benjamin; Voss, Andreas; Möller, Michael; Moormann, Christian; Graf, Thomas; Abdou Ahmed, Marwan

    2014-05-01

    We present the experimental investigations of different designs of resonant waveguide-grating mirrors (RWG) which are used as intracavity folding mirror in an Yb:YAG thin-disk laser. The studied mirrors combine structured fused silica substrates, a thin-layer waveguide (Ta2O5), a buffer layer (SiO2) and partial reflectors. The grating period was chosen to be 510 nm to allow resonances at an angle of incidence of ~10° for TE polarization. The waveguide layer has a thickness of 236 nm. It is followed by the buffer layer with a thickness of 580 nm and the subsequent alternating Ta2O5/SiO2 layers. The exact coating sequence depends on the two design approaches which were investigated in this work: either introducing different partial reflectors, i.e. stacks of quarter-wave layers on top of the waveguide while keeping the groove depth of the grating constant, or increasing the grating depth, while keeping an identical partial reflector. The investigation was focused on the rise of the surface temperature due to the coupling of the incident radiation to a waveguide mode, as well as on the laser efficiency, polarization and wavelength selectivity. It is found that, when compared to the simplest RWG design which consists of only a single Ta2O5 waveguide layer, damage threshold as well as laser efficiency can be significantly increased, while the laser performances in terms of polarization- and wavelength selectivity are maintained. So far, the presented RWG allow the generation of linear polarization with a narrow spectral linewidth down to 25 pm FWHM in a fundamental mode Yb:YAG thin-disk laser. Damage thresholds of 60kW/cm2 have been reached where only 63K of surface temperature increase was observed. This shows that the improved mirrors are suitable for the generation of kW-class narrow linewidth, linearly polarized Yb:YAG thin-disk lasers.

  16. Demonstration of a cavity coupler based on a resonant waveguide grating.

    PubMed

    Brückner, Frank; Friedrich, Daniel; Clausnitzer, Tina; Burmeister, Oliver; Britzger, Michael; Kley, Ernst-Bernhard; Danzmann, Karsten; Tünnermann, Andreas; Schnabel, Roman

    2009-01-01

    Thermal noise in multilayer optical coatings may not only limit the sensitivity of future gravitational wave detectors in their most sensitive frequency band but is also a major impediment for experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. Here, we present the experimental realization and characterization of a cavity coupler, which is based on a surface relief guided ode resonant grating. Since the required thickness of the dielectric coating is dramatically decreased compared to conventional mirrors, it is expected to provide low mechanical loss and, thus, low thermal noise. The cavity coupler was incorporated into a Fabry-Perot resonator together with a conventional high quality mirror. The finesse of this cavity was measured to be F = 657, which corresponds to a coupler reflectivity of R = 99.08 %. PMID:19129884

  17. Chain reconfiguration in active noise

    NASA Astrophysics Data System (ADS)

    Samanta, Nairhita; Chakrabarti, Rajarshi

    2016-05-01

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow.

  18. Superparamagnetic Fe3O4 Nanoparticles: Synthesis by Thermal Decomposition of Iron(III) Glucuronate and Application in Magnetic Resonance Imaging.

    PubMed

    Patsula, Vitalii; Kosinová, Lucie; Lovrić, Marija; Ferhatovic Hamzić, Lejla; Rabyk, Mariia; Konefal, Rafal; Paruzel, Aleksandra; Šlouf, Miroslav; Herynek, Vít; Gajović, Srećko; Horák, Daniel

    2016-03-23

    Monodisperse superparamagnetic Fe3O4 nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe3O4 nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis(ethane-2,1-diyl)phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG-P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG-P&Fe3O4 nanoparticles were tested on rat mesenchymal stem cells to determine the particle toxicity and their ability to label the cells. MR relaxometry confirmed that the PMG-P&Fe3O4 nanoparticles had high relaxivity but rather low cellular uptake. Nevertheless, the labeled cells still provided visible contrast enhancement in the magnetic resonance image. In addition, the cell viability was not compromised by the nanoparticles. Therefore, the PMG-P&Fe3O4 nanoparticles have the potential to be used in biomedical applications, especially as contrast agents for magnetic resonance imaging. PMID:26928653

  19. Stochastic resonance in an ion channel following the non-Arrhenius gating rate

    NASA Astrophysics Data System (ADS)

    Parc, Yong Woon; Koh, Duk-Su; Sung, Wokyung

    2009-05-01

    Stochastic resonance (SR) is a novel cooperative phenomenon occurring in nonlinear systems due to coupling of an ambient noise and an external signal. Biological systems may use SR mechanism to detect the signal efficiently from an external environment. A number of studies have addressed the SR in artificial ion channels considering external voltages as noises. More important than these external noises is the internal, thermal noise which changes the channel conformations essential for biological functions. In this work, we consider that the channel gating rates follow a non-Arrhenius temperature dependence derived from experimental data of a real biological channel. Using the Monte-Carlo simulations, we find that in this channel SR occurs near a physiological temperature in a very distinctive manner compared with that for the Arrhenius gating model.

  20. Solid state nuclear magnetic resonance spectroscopy in the evaluation of soil organic matter changes following thermal variations

    NASA Astrophysics Data System (ADS)

    de Pasquale, C.; Berns, A. E.; Kucerik, J.; Conte, P.; Alonzo, G.

    2009-04-01

    Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving force in environmental global change as it acts as both a source and sink of atmospheric carbon. However, SOM is subjected to rapid changes due to environmental transformations such as massive deforestations, fires, intensive land uses, temperature increases and so on. In the present work, a characterization of humic substances was done in order to obtain information about the transformation occurring to SOM as affected by temperature increases. For the first time variable temperature cross polarization magic angle spinning (CPMAS) 13C NMR spectroscopy was applied in combination with thermal analyses (TG and DSC) on environmentally relevant soil organic matter. The results show that the conformational changes occurring in humic substances as temperature is raised can be associated to melting of alkyl components connected with sublimation of some organic compounds. The simultaneous application of solid phase micro extraction GC-MS also allowed the identification of the components which were released by sublimation processes.

  1. Monolithic Cylindrical Fused Silica Resonators with High Q Factors.

    PubMed

    Pan, Yao; Wang, Dongya; Wang, Yanyan; Liu, Jianping; Wu, Suyong; Qu, Tianliang; Yang, Kaiyong; Luo, Hui

    2016-01-01

    The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is determined by the Q factor and frequency mismatch of the cylindrical resonator. Enhancing the Q factor is crucial for improving the rate sensitivity and noise performance of the CRG. In this paper, for the first time, a monolithic cylindrical fused silica resonator with a Q factor approaching 8 × 10⁵ (ring-down time over 1 min) is reported. The resonator is made of fused silica with low internal friction and high isotropy, with a diameter of 25 mm and a center frequency of 3974.35 Hz. The structure of the resonator is first briefly introduced, and then the experimental non-contact characterization method is presented. In addition, the post-fabrication experimental procedure of Q factor improvement, including chemical and thermal treatment, is demonstrated. The Q factor improvement by both treatments is compared and the primary loss mechanism is analyzed. To the best of our knowledge, the work presented in this paper represents the highest reported Q factor for a cylindrical resonator. The proposed monolithic cylindrical fused silica resonator may enable high performance inertial sensing with standard manufacturing process and simple post-fabrication treatment. PMID:27483263

  2. SU-F-BRE-12: Optical Resonator Water Calorimeter

    SciTech Connect

    Abraham, J; DeMarco, J; Low, D

    2014-06-15

    Purpose: Water calorimetry based on resistance thermometry has matured as a primary standard. Developing an optical technique hold the promise to push the boundaries of what is currently achievable with dosimetry. We will present a feasibility study and the current progress of construction of a Fabry-Perot resonator for dose to water measurement. Additionally, estimations of the theoretical limits resonator sensitivity and potential sources of noise for the system are described. Methods: A temperature change from the dose to water would be measured by the change in the index of refraction from the water in the cavity. Calculations are presented of the expected signal from the resonator for dose to water. The Fabry-Perot resonator constructed from optical quality narrowband mirrors is described. A water cell will be inserted into the cavity gap to provide the medium swept cavity length technique is explored as a specific implementation of this technique. Results: Calculations indicate that a dose to water on the order of a Gray is measureable with a reasonably implementable system. A resonator is currently under construction and progress towards a proof of principle measurement will be presented. The primary sources of noise, in order of importance, are expected to be; optical absorption by the medium, mechanical perturbations of the cavity length and thermal expansion of the optical mounts. Estimations of these noise sources and mitigation techniques will be discussed. Conclusion: A Fabry-Perot resonator is a promising technique for measuring the absorbed dose to water from a radiotherapy beam. This technique has the potential to serve as a check on the current primary standard for dose to water measurements. As well, i0074 may be the foundation for a new class of optical property based dosimetry measurement.

  3. Thermal-noise suppression in nano-scale Si field-effect transistors by feedback control based on single-electron detection

    SciTech Connect

    Chida, Kensaku Nishiguchi, Katsuhiko; Yamahata, Gento; Tanaka, Hirotaka; Fujiwara, Akira

    2015-08-17

    We perform feedback (FB) control for suppressing thermal fluctuation in the number of electrons in a silicon single-electron (SE) device composed of a small transistor and capacitor. SEs enter and leave the capacitor via the transistor randomly at thermal equilibrium, which is monitored in real time using a high-charge-sensitivity detector. In order to suppress such random motion or thermal fluctuation of the electrons, SEs are injected and removed using the transistor according to the monitored change in the number of electrons in the capacitor, which is exactly the FB control. As a result, thermal fluctuation in the number of electrons in a SE device is suppressed by 60%, which corresponds to the so-called FB cooling from 300 to 110 K. Moreover, a thermodynamics analysis of this FB cooling reveals that entropy in the capacitor is reduced and the device is at non-equilibrium; i.e., the free energy of the device increases. Since this entropy reduction originates from information about the electrons' motion monitored by the detector, our results by the FB control represent one type of information-to-energy conversion.

  4. Techniques for noise removal and registration of TIMS data

    USGS Publications Warehouse

    Hummer-Miller, S.

    1990-01-01

    Extracting subtle differences from highly correlated thermal infrared aircraft data is possible with appropriate noise filters, constructed and applied in the spatial frequency domain. This paper discusses a heuristic approach to designing noise filters for removing high- and low-spatial frequency striping and banding. Techniques for registering thermal infrared aircraft data to a topographic base using Thematic Mapper data are presented. The noise removal and registration techniques are applied to TIMS thermal infrared aircraft data. -Author

  5. The Fluctuation-Dissipation Theorem of Colloidal Particle's energy on 2D Periodic Substrates: A Monte Carlo Study of thermal noise-like fluctuation and diffusion like Brownian motion

    NASA Astrophysics Data System (ADS)

    Najafi, Amin

    2014-05-01

    Using the Monte Carlo simulations, we have calculated mean-square fluctuations in statistical mechanics, such as those for colloids energy configuration are set on square 2D periodic substrates interacting via a long range screened Coulomb potential on any specific and fixed substrate. Random fluctuations with small deviations from the state of thermodynamic equilibrium arise from the granular structure of them and appear as thermal diffusion with Gaussian distribution structure as well. The variations are showing linear form of the Fluctuation-Dissipation Theorem on the energy of particles constitutive a canonical ensemble with continuous diffusion process of colloidal particle systems. The noise-like variation of the energy per particle and the order parameter versus the Brownian displacement of sum of large number of random steps of particles at low temperatures phase are presenting a markovian process on colloidal particles configuration, too.

  6. Community noise sources and noise control issues

    NASA Technical Reports Server (NTRS)

    Nihart, Gene L.

    1992-01-01

    The topics covered include the following: community noise sources and noise control issues; noise components for turbine bypass turbojet engine (TBE) turbojet; engine cycle selection and noise; nozzle development schedule; NACA nozzle design; NACA nozzle test results; nearly fully mixed (NFM) nozzle design; noise versus aspiration rate; peak noise test results; nozzle test in the Low Speed Aeroacoustic Facility (LSAF); and Schlieren pictures of NACA nozzle.

  7. Listen to the Noise: Noise Is Beneficial for Cognitive Performance in ADHD

    ERIC Educational Resources Information Center

    Soderlund, Goran; Sikstrom, Sverker; Smart, Andrew

    2007-01-01

    Background: Noise is typically conceived of as being detrimental to cognitive performance. However, given the mechanism of stochastic resonance, a certain amount of noise can benefit performance. We investigate cognitive performance in noisy environments in relation to a neurocomputational model of attention deficit hyperactivity disorder (ADHD)…

  8. Kramers' rate for systems with multiplicative noise

    NASA Astrophysics Data System (ADS)

    Rosas, Alexandre; Pinto, Italo'Ivo Lima Dias; Lindenberg, Katja

    2016-07-01

    Kramers' rate for the passage of trajectories X (t ) over an energy barrier due to thermal or other fluctuations is usually associated with additive noise. We present a generalization of Kramers' rate for systems with multiplicative noise. We show that the expression commonly used in the literature for multiplicative noise is not correct, and we present results of numerical integrations of the Langevin equation for d X (t )/d t evolving in a quartic bistable potential which corroborate our claim.

  9. Kramers' rate for systems with multiplicative noise.

    PubMed

    Rosas, Alexandre; Pinto, Italo'Ivo Lima Dias; Lindenberg, Katja

    2016-07-01

    Kramers' rate for the passage of trajectories X(t) over an energy barrier due to thermal or other fluctuations is usually associated with additive noise. We present a generalization of Kramers' rate for systems with multiplicative noise. We show that the expression commonly used in the literature for multiplicative noise is not correct, and we present results of numerical integrations of the Langevin equation for dX(t)/dt evolving in a quartic bistable potential which corroborate our claim. PMID:27575071

  10. Hyphenation of Thermal Analysis to Ultrahigh-Resolution Mass Spectrometry (Fourier Transform Ion Cyclotron Resonance Mass Spectrometry) Using Atmospheric Pressure Chemical Ionization For Studying Composition and Thermal Degradation of Complex Materials.

    PubMed

    Rüger, Christopher P; Miersch, Toni; Schwemer, Theo; Sklorz, Martin; Zimmermann, Ralf

    2015-07-01

    In this study, the hyphenation of a thermobalance to an ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometer (UHR FTICR MS) is presented. Atmospheric pressure chemical ionization (APCI) is used for efficient ionization. The evolved gas analysis (EGA), using high-resolution mass spectrometry allows the time-resolved molecular characterization of thermally induced processes in complex materials or mixtures, such as biomass or crude oil. The most crucial part of the setup is the hyphenation between the thermobalance and the APCI source. Evolved gases are forced to enter the atmospheric pressure ionization interface of the MS by applying a slight overpressure at the thermobalance side of the hyphenation. Using the FTICR exact mass data, detailed chemical information is gained by calculation of elemental compositions from the organic species, enabling a time and temperature resolved, highly selective detection of the evolved species. An additional selectivity is gained by the APCI ionization, which is particularly sensitive toward polar compounds. This selectivity on the one hand misses bulk components of petroleum samples such as alkanes and does not deliver a comprehensive view but on the other hand focuses particularly on typical evolved components from biomass samples. As proof of principle, the thermal behavior of different fossil fuels: heavy fuel oil, light fuel oil, and a crude oil, and different lignocellulosic biomass, namely, beech, birch, spruce, ash, oak, and pine as well as commercial available softwood and birch-bark pellets were investigated. The results clearly show the capability to distinguish between certain wood types through their molecular patterns and compound classes. Additionally, typical literature known pyrolysis biomass marker were confirmed by their elemental composition, such as coniferyl aldehyde (C10H10O3), sinapyl aldehyde (C11H12O4), retene (C18H18), and abietic acid (C20H30O2). PMID:26024433

  11. Analysis of the Thermal Degradation of the Individual Anthocyanin Compounds of Black Carrot (Daucus carota L.): A New Approach Using High-Resolution Proton Nuclear Magnetic Resonance Spectroscopy.

    PubMed

    Iliopoulou, Ioanna; Thaeron, Delphine; Baker, Ashley; Jones, Anita; Robertson, Neil

    2015-08-12

    The black carrot dye is a mixture of cyanidin molecules, the nuclear magnetic resonance (NMR) spectrum of which shows a highly overlapped aromatic region. In this study, the (1)H NMR (800 MHz) aromatic chemical shifts of the mixture were fully assigned by overlaying them with the characterized (1)H NMR chemical shifts of the separated compounds. The latter were isolated using reverse-phase high-performance liquid chromatography (RP-HPLC), and their chemical shifts were identified using (1)H and two-dimensional (2D) correlation spectroscopy (COSY) NMR spectroscopy. The stability of the black carrot mixture to heat exposure was investigated at pH 3.6, 6.8, and 8.0 by heat-treating aqueous solutions at 100 °C and the powdered material at 180 °C. From integration of high-resolution (1)H NMR spectra, it was possible to follow the relative degradation of each compound, offering advantages over the commonly used ultraviolet/visible (UV/vis) and HPLC approaches. UV/vis spectroscopy and CIE color measurements were used to determine thermally induced color changes, under normal cooking conditions. PMID:26160425

  12. Nanomechanical detection of nuclear magnetic resonance using a silicon nanowire oscillator

    NASA Astrophysics Data System (ADS)

    Nichol, John M.; Hemesath, Eric R.; Lauhon, Lincoln J.; Budakian, Raffi

    2012-02-01

    The authors report the use of a radio frequency (rf) silicon nanowire mechanical oscillator as a low-temperature nuclear magnetic resonance force sensor to detect the statistical polarization of 1H spins in polystyrene. To couple the 1H spins to the nanowire oscillator, a magnetic resonance force detection protocol was developed that utilizes a nanoscale current-carrying wire to produce large time-dependent magnetic field gradients as well as the rf magnetic field. Under operating conditions, the nanowire experienced negligible surface-induced dissipation and exhibited an ultralow force noise near the thermal limit of the oscillator.

  13. Control of Environmental Noise

    ERIC Educational Resources Information Center

    Jensen, Paul

    1973-01-01

    Discusses the physical properties, sources, physiological effects, and legislation pertaining to noise, especially noise characteristics in the community. Indicates that noise reduction steps can be taken more intelligently after determination of the true noise sources and paths. (CC)

  14. Silicon single-crystal cryogenic optical resonator.

    PubMed

    Wiens, Eugen; Chen, Qun-Feng; Ernsting, Ingo; Luckmann, Heiko; Rosowski, Ulrich; Nevsky, Alexander; Schiller, Stephan

    2014-06-01

    We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 h. This stability allowed sensitive measurements of the resonator thermal expansion coefficient (α). We found that α=4.6×10(-13)  K(-1) at 1.6 K. At 16.8 K α vanishes, with a derivative equal to -6×10(-10)  K(-2). The temperature of the resonator was stabilized to a level below 10 μK for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-10(-17) level. PMID:24876023

  15. Optical Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Chevalier, Paul; Bouchon, Patrick; Haïdar, Riad; Pardo, Fabrice

    2014-08-01

    Helmholtz resonators are widely used acoustic components able to select a single frequency. Here, based on an analogy between acoustics and electromagnetism wave equations, we present an electromagnetic 2D Helmholtz resonator made of a metallic slit-box structure. At the resonance, the light is funneled in the λ/800 apertures, and is subsequently absorbed in the cavity. As in acoustics, there is no higher order of resonance, which is an appealing feature for applications such as photodetection or thermal emission. Eventually, we demonstrate that the slit is of capacitive nature while the box behaves inductively. We derive an analytical formula for the resonance wavelength, which does not rely on wave propagation and therefore does not depend on the permittivity of the material filling the box. Besides, in contrast with half-wavelength resonators, the resonance wavelength can be engineered by both the slit aspect ratio and the box area.

  16. Quantum Squeezing of Motion in a Mechanical Resonator

    NASA Astrophysics Data System (ADS)

    Wollman, Emma E.

    Quantum mechanics places limits on the minimum energy of a harmonic oscillator via the ever-present "zero-point" fluctuations of the quantum ground state. Through squeezing, however, it is possible to decrease the noise of a single motional quadrature below the zero-point level as long as noise is added to the orthogonal quadrature. While squeezing below the quantum noise level was achieved decades ago with light, quantum squeezing of the motion of a mechanical resonator is a more difficult prospect due to the large thermal occupations of megahertz-frequency mechanical devices even at typical dilution refrigerator temperatures of ~ 10 mK. Kronwald, Marquardt, and Clerk (2013) propose a method of squeezing a single quadrature of mechanical motion below the level of its zero-point fluctuations, even when the mechanics starts out with a large thermal occupation. The scheme operates under the framework of cavity optomechanics, where an optical or microwave cavity is coupled to the mechanics in order to control and read out the mechanical state. In the proposal, two pump tones are applied to the cavity, each detuned from the cavity resonance by the mechanical frequency. The pump tones establish and couple the mechanics to a squeezed reservoir, producing arbitrarily-large, steady-state squeezing of the mechanical motion. In this dissertation, I describe two experiments related to the implementation of this proposal in an electromechanical system. I also expand on the theory presented in Kronwald et. al. to include the effects of squeezing in the presence of classical microwave noise, and without assumptions of perfect alignment of the pump frequencies. In the first experiment, we produce a squeezed thermal state using the method of Kronwald et. al. We perform back-action evading measurements of the mechanical squeezed state in order to probe the noise in both quadratures of the mechanics. Using this method, we detect single-quadrature fluctuations at the level of 1

  17. An experimental investigation of noise attenuating techniques for space-shuttle canisters

    NASA Technical Reports Server (NTRS)

    Mirandy, L.; On, F. J.; Scott, J.

    1980-01-01

    A model of the space shuttle thermal canister was acoustically tested to determine the amount of noise attenuation which could be derived using a simple, single-wall canister construction having rectangular shape. Acoustic testing was performed on the basic canister and with noise-attenuating design modifications. The basic canister experienced noise amplifications at 56 and 80 Hz, which are attributed to the fundamental canister acoustic mode and local panel structural resonances, respectively. The standing wave response at 56 Hz was effectively suppressed by the incorporation of a cardboard baffle midway between the canister end-caps (an additional overall noise reduction of 4 dB). The canister was next tested with 14%, 22.5% and 31% sound absorptive coverages on the interior walls. The coverage was effective between 400-3000 Hz; the maximum benefit (9 dB) occurring at 1600 Hz. Viscoelastic damping strips bonded to the canister exterior provided an additional 4 to 5 dB attenuation over much of the frequency range and has an overall reduction of about 10 dB as compared to 4.4 dB without damping. A significant reduction of the resonant effect at 80 Hz was noted.

  18. Aircraft noise problems

    NASA Astrophysics Data System (ADS)

    1981-01-01

    The problems related to aircraft noise were studied. Physical origin (sound), human reaction (noise), quantization of noise and sound sources of aircraft noise are discussed. Noise abatement at the source, technical, fleet-political and air traffic measures are explained. The measurements and future developments are also discussed. The position of Lufthansa as regards aircraft noise problems is depicted.

  19. Noise pollution resources compendium

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Abstracts of reports concerning noise pollution are presented. The abstracts are grouped in the following areas of activity: (1) sources of noise, (2) noise detection and measurement, (3) noise abatement and control, (4) physical effects of noise and (5) social effects of noise.

  20. Noise Abatement

    NASA Technical Reports Server (NTRS)

    1983-01-01

    SMART, Sound Modification and Regulated Temperature compound, is a liquid plastic mixture with exceptional energy and sound absorbing qualities. It is derived from a very elastic plastic which was an effective noise abatement material in the Apollo Guidance System. Discovered by a NASA employee, it is marketed by Environmental Health Systems, Inc. (EHS). The product has been successfully employed by a diaper company with noisy dryers and a sugar company with noisy blowers. The company also manufactures an audiometric test booth and acoustical office partitions.