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Sample records for voltage fluctuation spectrum

  1. Spectrum of Wind Power Fluctuations

    Science.gov (United States)

    Bandi, M. M.

    2017-01-01

    Wind power fluctuations for an individual turbine and plant have been widely reported to follow the Kolmogorov spectrum of atmospheric turbulence; both vary with a fluctuation time scale τ as τ2 /3. Yet, this scaling has not been explained through turbulence theory. Using turbines as probes of turbulence, we show the τ2 /3 scaling results from a large scale influence of atmospheric turbulence. Owing to this long-range influence spanning 100s of kilometers, when power from geographically distributed wind plants is summed into aggregate power at the grid, fluctuations average (geographic smoothing) and their scaling steepens from τ2 /3→τ4 /3, beyond which further smoothing is not possible. Our analysis demonstrates grids have already reached this τ4 /3 spectral limit to geographic smoothing.

  2. The Spectrum of Wind Power Fluctuations

    Science.gov (United States)

    Bandi, Mahesh

    2016-11-01

    Wind is a variable energy source whose fluctuations threaten electrical grid stability and complicate dynamical load balancing. The power generated by a wind turbine fluctuates due to the variable wind speed that blows past the turbine. Indeed, the spectrum of wind power fluctuations is widely believed to reflect the Kolmogorov spectrum; both vary with frequency f as f - 5 / 3. This variability decreases when aggregate power fluctuations from geographically distributed wind farms are averaged at the grid via a mechanism known as geographic smoothing. Neither the f - 5 / 3 wind power fluctuation spectrum nor the mechanism of geographic smoothing are understood. In this work, we explain the wind power fluctuation spectrum from the turbine through grid scales. The f - 5 / 3 wind power fluctuation spectrum results from the largest length scales of atmospheric turbulence of order 200 km influencing the small scales where individual turbines operate. This long-range influence spatially couples geographically distributed wind farms and synchronizes farm outputs over a range of frequencies and decreases with increasing inter-farm distance. Consequently, aggregate grid-scale power fluctuations remain correlated, and are smoothed until they reach a limiting f - 7 / 3 spectrum. This work was funded by the Collective Interactions Unit, OIST Graduate University, Japan.

  3. Density fluctuation spectrum in whistler turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, Dastgeer, E-mail: dastgeer.shaikh@uah.ed [Department of Physics and Center for Space Plasma and Aeronomy Research, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States)

    2010-05-31

    We develop a nonlinear two-dimensional fluid model of whistler turbulence that includes effect of electron fluid density perturbations. The latter is coupled nonlinearly with wave magnetic field. This coupling leads essentially to finite compressibility effects in whistler turbulence model. We find from our simulations that despite strong compressibility effects, the density fluctuations follow the evolution of the wave magnetic field fluctuations. In a characteristic regime where large scale whistlers are predominant, the coupled density fluctuations are found to follow a Kolmogorov-like phenomenology in the inertial range turbulence. Consequently, the turbulent energy is dominated by the large scale (compared to electron inertial length) eddies and it follows a Kolmogorov-like k{sup -7/3} spectrum, where k is a characteristic wavenumber.

  4. Voltage fluctuations in neurons: signal or noise?

    DEFF Research Database (Denmark)

    Yarom, Yosef; Hounsgaard, Jorn

    2011-01-01

    , we discuss noise-free neuronal signaling and detrimental and beneficial forms of noise in large-scale functional neural networks. Evidence that noise and variability in some cases go hand in hand with behavioral variability and increase behavioral choice, richness, and adaptability opens new avenues...... that allows and facilitates complex adaptive behavior in an unpredictable world. Here we review the growing experimental evidence that functional network activity is associated with intense fluctuations in membrane potential and spike timing. We trace origins and consequences of noise and variability. Finally...

  5. Control voltage and power fluctuations when connecting wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Berinde, Ioan, E-mail: ioan-berinde@yahoo.com; Bălan, Horia, E-mail: hbalan@mail.utcluj.ro; Oros, Teodora Susana, E-mail: teodoraoros-87@yahoo.com [Technical University of Cluj-Napoca, Romania, Faculty of Electrical Engineering, Department of Power Engineering and Management (Romania)

    2015-12-23

    Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.

  6. Propagation of disturbances as voltage fluctuations in transmission networks

    Directory of Open Access Journals (Sweden)

    Albert Hermina

    2016-08-01

    Full Text Available Significant changes occurred in the power system in Romania in recent years by reducing the power used in the system, the number of classic power sources in operation as well as by implementing renewable energy sources, have determined short circuit power reduction (node rigidity in the points where disturbing users are connected, that in the absence of adequate measures, result in disturbances above acceptable levels. The paper analyzes two power systems areas in which are connected users that cause voltage fluctuation. Disturbances as voltage fluctuations resulting in these nodes may exceed the acceptable values and can spread in the transmission network affecting power quality over large system areas. The analysis conducted reveals the influence of short circuit power in nodes where these users are connected and highlights the fact that in some cases (e.g. lines out of operation for maintenance, shutdown of classic units in the area the disturbances in the transmission network sent to the users at lower voltages may have values above those allowed. Technical Code of existing power transmission network makes no reference to voltage fluctuations, as a rule, in the electricity transmission network was considered that this phenomenon should not exist.

  7. Voltage-gated Calcium Channels and Autism Spectrum Disorders.

    Science.gov (United States)

    Breitenkamp, Alexandra F; Matthes, Jan; Herzig, Stefan

    2015-01-01

    Autism spectrum disorder is a complex-genetic disease and its etiology is unknown for the majority of cases. So far, more than one hundred different susceptibility genes were detected. Voltage-gated calcium channels are among the candidates linked to autism spectrum disorder by results of genetic studies. Mutations of nearly all pore-forming and some auxiliary subunits of voltage gated calcium channels have been revealed from investigations of autism spectrum disorder patients and populations. Though there are only few electrophysiological characterizations of voltage-gated calcium channel mutations found in autistic patients these studies suggest their functional relevance. In summary, both genetic and functional data suggest a potential role of voltage-gated calcium channels in autism spectrum disorder. Future studies require refinement of the clinical and systems biological concepts of autism spectrum disorder and an appropriate holistic approach at the molecular level, e.g. regarding all facets of calcium channel functions.

  8. A METHOD FOR DETERMINING LOCATION OF VOLTAGE FLUCTUATIONS SOURCE IN ELECTRIC GRID

    Directory of Open Access Journals (Sweden)

    G.A. Senderovich

    2016-06-01

    Full Text Available Purpose. The purpose of work is development of a method of definition of the location of a source of fluctuations of voltage. Methodology. The reasons of emergence of fluctuations of voltage at an arrangement of a source both in power lines, and in the consumer's networks, are connected with changes of consumption and active and reactive capacities. As criterion for definition of the location of a source of fluctuations of voltage we choose change of size of the active power received by reception substation on equivalent communication with system. The source of fluctuations of voltage is external for the consumer if emergence of fluctuations of voltage leads to the coordinated changes of tension and consumed in the area of active power that corresponds to a condition of the positive regulating effect of active loading on voltage (1. The source of fluctuations of voltage is internal for the consumer if emergence of fluctuations of voltage leads to counter changes of tension and consumed in the area of active power that resembles a condition of the negative regulating effect of active loading on voltage superficially (6. Results. The method of definition of the location of a source of fluctuations of voltage in an electric network which, works by the principle of an assessment of correlation of change of power and tension in a power supply network is developed. The method allows to consider shift between extrema of curves of change of voltage of U(t and power of Pload(t. Originality. The method of definition of an arrangement of a source of fluctuations of voltage is developed. Practical value. The answer to this question where the source of fluctuations of voltage (in the territory of the consumer is located or in an external network confirmed with the determined calculation, can form a basis of the expert opinion for the solution of legal disputes at an assessment of the damages caused by poor quality of electric energy.

  9. Impact of quantum entanglement on spectrum of cosmological fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Kanno, Sugumi, E-mail: sugumi.kanno@uct.ac.za [Laboratory for Quantum Gravity and Strings and Astrophysics, Cosmology and Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701 (South Africa)

    2014-07-01

    We investigate the effect of entanglement between two causally separated open charts in de Sitter space on the spectrum of vacuum fluctuations. We consider a free massive scalar field, and construct the reduced density matrix by tracing out the vacuum state for one of the open charts, as recently derived by Maldacena and Pimentel. We formulate the mean-square vacuum fluctuations by using the reduced density matrix and show that the scale invariant spectrum of massless scalar field is realized on small scales. On the other hand, we find that the quantum entanglement affects the shape of the spectrum on large scales comparable to or greater than the curvature radius.

  10. Impact of quantum entanglement on spectrum of cosmological fluctuations

    CERN Document Server

    Kanno, Sugumi

    2014-01-01

    We investigate the effect of entanglement between two causally separated open charts in de Sitter space on the spectrum of vacuum fluctuations. We consider a free massive scalar field, and construct the reduced density matrix by tracing out the vacuum state for one of the open charts, as recently derived by Maldacena and Pimentel. We formulate the mean-square vacuum fluctuations by using the reduced density matrix and show that the scale invariant spectrum of massless scalar field is realized on small scales. On the other hand, we find that the quantum entanglement affects the shape of the spectrum on large scales comparable to or greater than the curvature radius.

  11. DC-Voltage Fluctuation Elimination Through a DC-Capacitor Current Control for DFIG Converters Under Unbalanced Grid Voltage Conditions

    DEFF Research Database (Denmark)

    Liu, Changjin; Xu, Dehong; Zhu, Nan;

    2013-01-01

    Unbalanced grid voltage causes a large second-order harmonic current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor current control...... method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the dc-capacitors. In this method, a dc-capacitor current control loop, where a negative-sequence resonant controller is used to increase the loop gain, is added to the conventional GSC current control...... loop. The rejection capability to the unbalanced grid voltage and the stability of the proposed control system are discussed. The second-order harmonic current in the dc capacitor as well as dc-voltage fluctuation is very well eliminated. Hence, the dc capacitors will be more reliable under unbalanced...

  12. Measurement of the electric fluctuation spectrum of magnetohydrodynamic turbulence

    CERN Document Server

    Bale, S D; Mozer, F S; Horbury, T S; Reme, H

    2005-01-01

    Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show the spectral behavior of classical Kolmogorov fluid turbulence over an inertial subrange and departures from this at short wavelengths, where energy should be dissipated. Here we present the first measurements of the electric field fluctuation spectrum over the inertial and dissipative wavenumber ranges in a $\\beta \\gtrsim 1$ plasma. The $k^{-5/3}$ inertial subrange is observed and agrees strikingly with the magnetic fluctuation spectrum; the wave phase speed in this regime is shown to be consistent with the Alfv\\'en speed. At smaller wavelengths $k \\rho_i \\geq 1$ the electric spectrum is softer and is consistent with the expected dispersion relation of short-wavelength kinetic Alfv\\'en waves. Kinetic Alfv\\'en waves damp on the solar wind ions and electrons and may act to isotropize them. This effect may explain the fluid-like nature of the solar wind.

  13. Correlation character of ionic current fluctuations: analysis of ion current through a voltage-dependent potassium single channel.

    Science.gov (United States)

    Tong-Han, Lan; Huang, Xi; Jia-Rui, Lin

    2005-10-03

    The gating of ion channels has widely been modeled by assuming the transition between open and closed states is a memoryless process. Nevertheless, the statistical analysis of an ionic current signal recorded from voltage dependence K(+) single channel is presented. Calculating the sample auto-correlation function of the ionic current based on the digitized signals, rather than the sequence of open and closed states duration time. The results provide evidence for the existence of memory. For different voltages, the ion channel current fluctuation has different correlation attributions. The correlations in data generated by simulation of two Markov models, on one hand, auto-correlation function of the ionic current shows a weaker memory, after a delayed period of time, the attribute of memory does not exist; on the other hand, the correlation depends on the number of states in the Markov model. For V(p)=-60 mV pipette potential, spectral analysis of ion channel current was conducted, the result indicates that the spectrum is not a flat spectrum, the data set from ionic current fluctuations shows considerable variability with a broad 1/f -like spectrum, alpha=1.261+/-0.24. Thus the ion current fluctuations give information about the kinetics of the channel protein, the results suggest the correlation character of ion channel protein nonlinear kinetics regardless of whether the channel is in open or closed state.

  14. Analysis of the Vibration Spectrum Based on the Input Voltage Spectrum

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Jakobsen, Uffe; Rasmussen, Peter Omand;

    2009-01-01

    on the spectrum of the applied voltage. The measurements show that the spectral components are caused mainly by the modulation, which agrees with the results from the analytical solution. A method to determine the dominant frequency components from the radial force spectrum based on current measurements is also...

  15. CHARACTERISTICS OF CORRELATION AND SPECTRUM BETWEEN WALL FLUCTUATING PRESSURE AND FLUCTUATING VELOCITY OF IMPING-ING JET

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The correlation, the spectrum and the turbu-lent scale between wall fluctuating pressure and fluctuating ve-locity, on the bed of plunging pool under the action of single and twin impinging jet, are investigated in the paper by using 2-D LDA and the dynamic pressure scanning system of multi-ple points. It is found that the cross correlation between the horizontal fluctuating velocity and the fluctuating pressure of twin jet is bigger than that of sinlge jet, and the spectrum be-tween horizontal fluctuating velocity and fluctuating pressure obviously has approximately dominant frequency. The rela-tionship between the fluctuation pressure coefficient on wall and the turbulent intensity near the wall can be described with logarithmic curve.

  16. Analysis of temporal and spatial contact voltage fluctuation during fretting in automotive connectors

    OpenAIRE

    El Mossouess, Sofiane; Benjemâa, N; Carvou, E; El Abdi, R; Obame, H; Doublet, L; Rodari, T

    2014-01-01

    International audience; Our study is focused on contact voltage fluctuations during fretting with small amplitudes of a few tens microns which generate damage of the contact of connectors. A contact composed by a pin and a curve female part are submitted to vibration cyclic of 25µm at 100Hz and supplied with current ramp from 0.1mA to 3A in two directions. With the help of fast devices, the voltage and position data acquisition are conjointly made with the common DC contact voltage dur-ing fr...

  17. Analysis of arc emission spectra of stainless steel electric arc furnace slag affected by fluctuating arc voltage.

    Science.gov (United States)

    Aula, Matti; Mäkinen, Ari; Fabritius, Timo

    2014-01-01

    Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful.

  18. Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations.

    Science.gov (United States)

    Fernandez, Fernando R; Malerba, Paola; White, John A

    2015-04-01

    The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances.

  19. Statistics of subthreshold neuronal voltage fluctuations due to conductance-based synaptic shot noise.

    Science.gov (United States)

    Richardson, Magnus J E; Gerstner, Wulfram

    2006-06-01

    Neurons in the central nervous system, and in the cortex in particular, are subject to a barrage of pulses from their presynaptic populations. These synaptic pulses are mediated by conductance changes and therefore lead to increases or decreases of the neuronal membrane potential with amplitudes that are dependent on the voltage: synaptic noise is multiplicative. The statistics of the membrane potential are of experimental interest because the measurement of a single subthreshold voltage can be used to probe the activity occurring across the presynaptic population. Though the interpulse interval is not always significantly smaller than the characteristic decay time of the pulses, and so the fluctuations have the nature of shot noise, the majority of results available in the literature have been calculated in the diffusion limit, which is valid for high-rate pulses. Here the effects that multiplicative conductance noise and shot noise have on the voltage fluctuations are examined. It is shown that both these aspects of synaptic drive sculpt high-order features of the subthreshold voltage distribution, such as the skew. It is further shown that the diffusion approximation can only capture the effects arising from the multiplicative conductance noise, predicting a negative voltage skew for excitatory drive. Exact results for the full dynamics are derived from a master-equation approach, predicting positively skewed distributions with long tails in voltage ranges typical for action potential generation. It is argued that, although the skew is a high-order feature of subthreshold voltage distributions, the increased probability of reaching firing threshold suggests a potential role for shot noise in shaping the neuronal transfer function.

  20. A detailed procedure for measuring turbulent velocity fluctuations using constant-voltage anemometry

    Science.gov (United States)

    Mohammed-Taifour, Abdelouahab; Weiss, Julien; Sadeghi, Atabak; Vétel, Jérôme; Jondeau, Emmanuel; Comte-Bellot, Geneviève

    2015-09-01

    A detailed procedure to use a constant-voltage anemometer (CVA) for the accurate measurement of turbulent flows is proposed. The procedure is based on the usual small-perturbation analysis of hot-wire signals. It consists in three steps: (1) the calibration of internal elements, required to estimate the two main electrical parameters of the CVA circuitry that are needed in the data analysis, (2) a flow calibration to relate the CVA output voltage and the hot-wire time constant to the flow velocity, and (3) a data-processing algorithm to recover the fluctuating flow quantities from the output voltage. The procedure is tested in two classical turbulent flows: a zero-pressure-gradient boundary layer and a round jet. In both cases, the CVA results are shown to be essentially indistinguishable from the results obtained with a research-grade constant-temperature anemometer.

  1. Long-term modulation of the cosmic ray fluctuation spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Starodubtsev, S.A.; Grigoryev, A.V. [Yu.G. Shafer Inst. of Cosmophysical Research and Aeronomy, SB RAS, Yakutsk (Russian Federation); Usoskin, I.G. [Sodankylae Geophysical Observatory, Univ. of Oulu (Finland); Mursula, K. [Dept. of Physical Sciences, Univ of Oulu (Finland)

    2006-07-01

    Here we study the power level of rapid cosmic ray fluctuations in the frequency range of 10{sup -4}-1.67 . 10{sup -3} Hz (periods from 10 min to about 3h), using measurements by space-borne instruments for the period since 1974. We find that the power level of these fluctuations varies over the solar cycle, but the phase of this variation depends on the energy of cosmic ray particles. While the power level of these fluctuations in the higher energy channels (corresponding to galactic cosmic rays) changes in phase with the solar cycle, the fluctuation level for lower energy channels (predominantly of solar/interplanetary origin) is roughly in an opposite phase with the solar cycle. The results prove conclusively that these fluctuations originate in the near-Earth space, excluding their atmospheric or magnetospheric origin. We present these new results and discuss a possible scenario explaining the observed energy-dependence. (orig.)

  2. Long-term modulation of the cosmic ray fluctuation spectrum

    Directory of Open Access Journals (Sweden)

    S. A. Starodubtsev

    2006-03-01

    Full Text Available Here we study the power level of rapid cosmic ray fluctuations in the frequency range of 10-4-1.67·10-3 Hz (periods from 10 min to about 3 h, using measurements by space-borne instruments for the period since 1974. We find that the power level of these fluctuations varies over the solar cycle, but the phase of this variation depends on the energy of cosmic ray particles. While the power level of these fluctuations in the higher energy channels (corresponding to galactic cosmic rays changes in phase with the solar cycle, the fluctuation level for lower energy channels (predominantly of solar/interplanetary origin is roughly in an opposite phase with the solar cycle. The results prove conclusively that these fluctuations originate in the near-Earth space, excluding their atmospheric or magnetospheric origin. We present these new results and discuss a possible scenario explaining the observed energy-dependence.

  3. An Improved Control Strategy of Limiting the DC-Link Voltage Fluctuation for a Doubly Fed Induction Wind Generator

    DEFF Research Database (Denmark)

    Yao, J.; Li, H.; Liao, Y.;

    2008-01-01

    The paper presents to develop a new control strategy of limiting the dc-link voltage fluctuation for a back-to-back pulsewidth modulation converter in a doubly fed induction generator (DFIG) for wind turbine systems. The reasons of dc-link voltage fluctuation are analyzed. An improved control...... strategy with the instantaneous rotor power feedback is proposed to limit the fluctuation range of the dc-link voltage. An experimental rig is set up to valid the proposed strategy, and the dynamic performances of the DFIG are compared with the traditional control method under a constant grid voltage....... Furthermore, the capabilities of keeping the dc-link voltage stable are also compared in the ride-through control of DFIG during a three-phase grid fault, by using a developed 2 MW DFIG wind power system model. Both the experimental and simulation results have shown that the proposed control strategy is more...

  4. Recovery of fluctuation spectrum evolution from tomographic shear spectra

    Energy Technology Data Exchange (ETDEWEB)

    Bonometto, Silvio A.; Mezzetti, Marino, E-mail: bonometto@oats.inaf.it, E-mail: mezzetti@oats.inaf.it [Department of Physics, Astronomy Unit, Trieste University, Via Tiepolo 11, I 34143 Trieste (Italy)

    2013-05-01

    Forthcoming large angle surveys are planned to obtain high precision tomographic shear data. In principle, they will allow us to recover the spectra of matter density fluctuation, at various redshift, through the inversion of the expressions yielding shear spectra from fluctuation spectra. This was discussed in previous work, where SVD techniques for matrix inversion were also shown to be the optimal tool to this aim. Here we show the significant improvements obtainable by using a 7 bin tomography, as allowed by future Euclid data, and discuss error propagation from shear to fluctuation spectra. We find that the technique is a promising tool, namely for the analysis of baryon physics through high–l shear spectra and to test the consistency between expansion rate and fluctuation growth.

  5. Recovery of fluctuation spectrum evolution from tomographic shear spectra

    Science.gov (United States)

    Bonometto, Silvio A.; Mezzetti, Marino

    2013-05-01

    Forthcoming large angle surveys are planned to obtain high precision tomographic shear data. In principle, they will allow us to recover the spectra of matter density fluctuation, at various redshift, through the inversion of the expressions yielding shear spectra from fluctuation spectra. This was discussed in previous work, where SVD techniques for matrix inversion were also shown to be the optimal tool to this aim. Here we show the significant improvements obtainable by using a 7 bin tomography, as allowed by future Euclid data, and discuss error propagation from shear to fluctuation spectra. We find that the technique is a promising tool, namely for the analysis of baryon physics through high-l shear spectra and to test the consistency between expansion rate and fluctuation growth.

  6. Recovery of fluctuation spectrum evolution from tomographic shear spectra

    CERN Document Server

    Bonometto, Silvio A

    2013-01-01

    Forthcoming large angle surveys are planned to obtain high precision tomographic shear data. In principle, they will allow us to recover the spectra of matter density fluctuation, at various redshift, through the inversion of the expressions yielding shear from fluctuation spectra. This was discussed in previous work, where SVD techniques for matrix inversion were also shown to be the optimal tool to this aim. Here we show the significant improvements obtainable by using a 7 bin tomography, as allowed by future Euclid data, as well as the question of error propagation from shear to fluctuation spectra. We find that the technique is a promising tool, namely for the analysis of baryon physics throug high-l shear spectra and to test the consistency between expansion rate and fluctuation growth.

  7. Cosmophysical Factors in the Fluctuation Amplitude Spectrum of Brownian Motion

    Directory of Open Access Journals (Sweden)

    Kaminsky A. V.

    2010-07-01

    Full Text Available Phenomenon of the regular variability of the fine structure of the fluctuation in the am- plitude distributions (shapes of related histograms for the case of Brownian motion was investigated. We took an advantage of the dynamic light scattering method (DLS to get a stochastically fluctuated signal determined by Brownian motion. Shape of the histograms is most likely to vary, synchronous, in two proximally located independent cells containing Brownian particles. The synchronism persists in the cells distant at 2 m from each other, and positioned meridionally. With a parallel-wise positioning of the cells, high probability of the synchronous variation in the shape of the histograms by local time has been observed. This result meets the previous conclusion about the dependency of histogram shapes (“fluctuation amplitudes” of the spectra of stochastic processes upon rotation of the Earth.

  8. Cold wire constant voltage anemometry to measure temperature fluctuations and its application in a thermoacoustic system

    Science.gov (United States)

    Cleve, Sarah; Jondeau, Emmanuel; Blanc-Benon, Philippe; Comte-Bellot, Geneviève

    2017-04-01

    The knowledge of temperature fluctuations is essential for most thermoacoustic systems. In the present paper, cold wire constant-voltage anemometry (CVA) to measure temperature fluctuations is presented. Corrections for the thermal inertia and for the end losses of the wire are applied during the post-processing. The correction for the thermal inertia of the cold wire is achieved by applying a time dependent thermal lag as proposed originally for a constant-current anemometry (CCA) system. This thermal lag is measured in parallel by a hot wire. The thermal end losses of the wires to their supports are also considered and approximate corrections are proposed. The procedure for the cold wire CVA is validated in the acoustic field of an acoustic resonator with wires of different lengths. A comparison between a CVA and a CCA measurement also confirms the CVA measurement. Furthermore, the proposed measurement procedure is applied close to the stack of a thermoacoustic refrigerator. Supposing a two-dimensional flow, the simultaneous measurement of velocity and temperature fluctuations is possible. This allows a detailed examination of the acoustic field close to the stack, including the study of the correlation between temperature and velocity.

  9. A Mathematical Model to Predict Voltage Fluctuations in a Distribution System with Renewable Energy Sources

    Science.gov (United States)

    Iyer, Shivkumar Venkatraman; Wu, Bin; Li, Yunwei; Singh, Birendra

    2015-12-01

    This paper proposes a simplified mathematical model to predict the impact of connection of Distributed Generators (DGs) to the ac grid. The model allows the user to examine the fluctuations in the magnitude of voltages at different nodes in the distribution system. In order to use the model, the user does not require a commercial simulation software making it a handy tool for a practicing engineer. Analysis has been presented to describe how the detailed mathematical model of the system is reduced using elementary matrix manipulation techniques to obtain the final simplified mathematical model. Simulation results are presented to verify the mathematical model with a ring distribution system with three DGs connected to it and the results validate those attained from the mathematical model.

  10. Spectrum of turbulent-boundary-layer fluctuation pressure and response of a polyvinylidence fluoride hydrophone

    Institute of Scientific and Technical Information of China (English)

    GE Huiliang; HE Zuoyong; BAO Xuemei

    2001-01-01

    The point power spectrum density and the wavenumber frequency spectrum density of turbulent-boundary-layer fluctuation pressure were measured in water-tunnel by use of a φ8 mm hydrophone and a 20-element array, respectively. The non-dimensional representation of measured point power spectrum coincides with the measured results by Bull M. K. et. al. in wind tunnel. The convection peak can be seen clearly in the measured wavenumber frequencyspectrum and the convection velocity can be calculated from the location of the convection peak.The response spectrum of a polyvinylidence fluoride (PVDF) hydrophone, which receiving area is 100 mm × 60 mm, was also measured. By comparing it with the response spectrum of the φ8 mm hydrophone, it is shown that the PVDF hyrdophone has a strong wavenumber filtering effect on turbulent-boundary-layer pressure fluctuation.

  11. Quantum Origin of the Primordial Fluctuation Spectrum and its Statistics

    CERN Document Server

    Leon, Gabriel; Sudarsky, Daniel

    2013-01-01

    The account of the origin of cosmic structure, as provided by the standard inflationary paradigm, is not fully satisfactory, as has been argued in Perez et al 2006. The central point of that work is to point out the need to discuss and explore the physical mechanism that is capable of generating the inhomogeneity and anisotropy of our Universe, starting from an exactly homogeneous and isotropic initial state associated with the early inflationary regime. We review this issue briefly here together with the proposal to address this shortcoming in terms of a dynamical collapse of the vacuum state of the inflaton field. We also briefly indicate how this issues might be connected to other questions being faced in the study of the quantum/gravity interface, and their relevance to the investigations concerning the statistical characterization of the primordial spectrum.

  12. Harmonic Injection-Based Power Fluctuation Control of Three-Phase PV Systems under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Nian-Cheng Zhou

    2015-02-01

    Full Text Available Unbalanced voltage will inevitably cause power and DC voltage fluctuations in a three-phase PV system. The deterioration of power quality will do great harm to the PV panels and the loads, so it is necessary to suppress the power fluctuations. This paper further explores the coefficients control strategy of PV converters under unbalanced voltage conditions, aiming to suppress power fluctuations by controlling the injection of some specific orders of current harmonics into the grid. In order to achieve this, the current reference of the PV inverter has been changed by bringing in two control coefficients, and the expression of each order of the current harmonics has been deduced. Based on the standards of PV systems, the regions from which the coefficients can be selected are determined. Then, by tuning these coefficients in the feasible regions, the output parameters (power fluctuation, current THD and odd harmonics can be controlled precisely. The model of this method is built and simulated in PSCAD/EMTDC, and as a result, it is shown that the power fluctuations can be restricted according to different power quality requirements.

  13. Variable Voltage Source Inverter with controlled frequency spectrum based on Random Pulse Width Modulation

    Directory of Open Access Journals (Sweden)

    Muhammad Farrukh Yaqub

    2012-01-01

    Full Text Available This paper presents a new method for single phase variable voltage inverter based on Random Pulse Width Modulation. In Random Pulse Width Modulation based inverter, the frequency spectrum of the output current and voltage waveforms becomes continuous because of the randomization of the switching function of the devices controlling the output voltages. This paper establishes a theory that if the distributions of the random numbers generated by the random source are kept within certain limit with respect to the peak value of reference sinusoidal waveform, the frequency spectrum can be controlled. On the basis of the results, a novel drive using variable tap changing transformer (optional and adaptive random number generator, to control the ratio between the numbers generated by the random source and the reference waveform has been suggested that will guarantee a better power quality profile for a broad range of output voltages.

  14. Tension moderation and fluctuation spectrum in simulated lipid membranes under an applied electric potential

    DEFF Research Database (Denmark)

    Loubet, Bastien; Lomholt, Michael Andersen; Khandelia, Himanshu

    2013-01-01

    We investigate the effect of an applied electric potential on the mechanics of a coarse grained POPC bilayer under tension. The size and duration of our simulations allow for a detailed and accurate study of the fluctuations. Effects on the fluctuation spectrum, tension, bending rigidity, and bil......We investigate the effect of an applied electric potential on the mechanics of a coarse grained POPC bilayer under tension. The size and duration of our simulations allow for a detailed and accurate study of the fluctuations. Effects on the fluctuation spectrum, tension, bending rigidity......, and bilayer thickness are investigated in detail. In particular, the least square fitting technique is used to calculate the fluctuation spectra. The simulations confirm a recently proposed theory that the effect of an applied electric potential on the membrane will be moderated by the elastic properties...... fluctuations. The effect of the applied electric potential on the bending rigidity is non-existent within error bars. However, when the membrane is stretched there is a point where the bending rigidity is lowered due to a decrease of the thickness of the membrane. All these effects should prove important...

  15. A Microscopic Capacitor Model of Voltage Coupling in Membrane Proteins: Gating Charge Fluctuations in Ci-VSD.

    Science.gov (United States)

    Kim, Ilsoo; Warshel, Arieh

    2016-01-28

    The voltage sensitivity of membrane proteins is reflected in the response of the voltage sensing domains (VSDs) to the changes in membrane potential. This response is implicated in the displacement of positively charged residues, associated with the conformational changes of VSDs. The displaced charges generate nonlinear (i.e., voltage-dependent) capacitance current called the gating current (and its corresponding gating charge), which is a key experimental quantity that characterizes voltage activation in VSMP. However, the relevant theoretical/computational approaches, aimed to correlate the structural information on VSMP to electrophysiological measurements, have been rather limited, posing a broad challenge in computer simulations of VSMP. Concomitant with the development of our coarse-graining (CG) model of voltage coupling, we apply our theoretical framework for the treatments of voltage effects in membrane proteins to modeling the VSMP activation, taking the VSDs (Ci-VSD) derived from the Ciona intestinalis voltage sensitive phosphatase (Ci-VSP) as a model system. Our CG model reproduces the observed gating charge of Ci-VSD activation in several different perspectives. In particular, a new closed-form expression of the gating charge is evaluated in both nonequilibrium and equilibrium ways, while considering the fluctuation-dissipation relation that connects a nonequilibrium measurement of the gating charge to an equilibrium measurement of charge fluctuations (i.e., the voltage-independent linear component of membrane capacitance). In turn, the expression uncovers a novel link that connects an equilibrium measurement of the voltage-independent linear capacitance to a nonequilibrium measurement of the voltage-dependent nonlinear capacitance (whose integral over voltage is equal to the gating charge). In addition, our CG model yields capacitor-like voltage dependent free energy parabolas, resulting in the free energy difference and the free energy barrier for

  16. Anisotropic power spectrum of refractive-index fluctuation in hypersonic turbulence.

    Science.gov (United States)

    Li, Jiangting; Yang, Shaofei; Guo, Lixin; Cheng, Mingjian

    2016-11-10

    An anisotropic power spectrum of the refractive-index fluctuation in hypersonic turbulence was obtained by processing the experimental image of the hypersonic plasma sheath and transforming the generalized anisotropic von Kármán spectrum. The power spectrum suggested here can provide as good a fit to measured spectrum data for hypersonic turbulence as that recorded from the nano-planar laser scattering image. Based on the newfound anisotropic hypersonic turbulence power spectrum, Rytov approximation was employed to establish the wave structure function and the spatial coherence radius model of electromagnetic beam propagation in hypersonic turbulence. Enhancing the anisotropy characteristics of the hypersonic turbulence led to a significant improvement in the propagation performance of electromagnetic beams in hypersonic plasma sheath. The influence of hypersonic turbulence on electromagnetic beams increases with the increase of variance of the refractive-index fluctuation and the decrease of turbulence outer scale and anisotropy parameters. The spatial coherence radius was much smaller than that in atmospheric turbulence. These results are fundamental to understanding electromagnetic wave propagation in hypersonic turbulence.

  17. Kinetic Field Theory: Effects of momentum correlations on the cosmic density-fluctuation power spectrum

    CERN Document Server

    Bartelmann, Matthias; Kozlikin, Elena; Lilow, Robert; Dombrowski, Johannes; Mildenberger, Julius

    2016-01-01

    In earlier work, we have developed a Kinetic Field Theory (KFT) for cosmological structure formation and showed that the non-linear density-fluctuation power spectrum known from numerical simulations can be reproduced quite well even if particle interactions are taken into account to first order only. Besides approximating gravitational interactions, we had to truncate the initial correlation hierarchy of particle momenta at the second order. Here, we substantially simplify KFT. We show that its central object, the free generating functional, can be factorized, taking the full hierarchy of momentum correlations into account. The factors appearing in the generating functional have a universal form and can thus be tabulated for fast access in perturbation schemes. Our results show that the complete hierarchy of initial momentum correlations is responsible for a characteristic deformation in the density-fluctuation power spectrum, caused by mode transport independent of the particle interaction. At the present e...

  18. Gas Density Fluctuations in the Perseus Cluster: Clumping Factor and Velocity Power Spectrum

    CERN Document Server

    Zhuravleva, I; Arevalo, P; Schekochihin, A A; Allen, S W; Fabian, A C; Forman, W R; Sanders, J S; Simionescu, A; Sunyaev, R; Vikhlinin, A; Werner, N

    2015-01-01

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analyzed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 8 to 12 per cent on scales of ~10-30 kpc within radii of 30-160 kpc from the cluster center and from 9 to 7 per cent on scales of ~20-30 kpc in an outer, 60-220 kpc annulus. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90-140 km/s on ~20-30 kpc scales and 70-100 km/s on smaller scales ~7-10 kpc. The velocity power spectrum is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the power spectrum of the density fluctuations is low...

  19. Voltage-gated potassium channelopathy: an expanding spectrum of clinical phenotypes.

    Science.gov (United States)

    Shribman, Sam; Patani, Rickie; Deeb, Jacquie; Chaudhuri, Abhijit

    2013-01-10

    Autoimmune voltage-gated potassium channelopathies represent a wide and expanding spectrum of neurological conditions. We present a case demonstrating the phenotypic heterogeneity of antivoltage-gated potassium channels (VGKC)-associated disorders. Such cases may easily be dismissed as functional disorders at first presentation. We propose that there must remain a high index of suspicion for antiVGKC-associated disorders in cases where there are transient neurological disturbances in atypical spatial and temporal distributions.

  20. Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Zhuravleva, I.; Churazov, E.; Arevalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

    2015-05-20

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ~10–30 kpc within radii of 30–220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90–140 km s-1 on ~20–30 kpc scales and 70–100 km s-1 on smaller scales ~7–10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7–8 per cent for radii ~30–220 kpc from the centre, leading to a density bias of less than 3–4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density–velocity perturbation relation and further reduce systematic uncertainties in this analysis.

  1. Analyzing Chaos Systems and Fine Spectrum Sensing Using Detrended Fluctuation Analysis Algorithm

    Directory of Open Access Journals (Sweden)

    Javier S. González-Salas

    2016-01-01

    Full Text Available A numerical study that uses detrended fluctuation analysis (DFA algorithm of time series obtained from linear and nonlinear dynamical systems is presented. The DFA algorithm behavior toward periodic and chaotic signals is investigated and the effect of the time scale under analysis is discussed. The displayed results prove that the DFA algorithm response is invariant (stable performance to initial condition and chaotic system parameters. An initial idea of DFA algorithm implementation for fine spectrum sensing (SS is proposed under two-stage spectrum sensor approach with test statistics based on the scaling exponent value. The outcomes demonstrate a promising new SS technique that can alleviate several imperfections such as noise power uncertainty and spatial correlation between the adjacent antenna array elements.

  2. The Evolution of the Spectrum of Velocity Fluctuations in the Solar Wind

    Science.gov (United States)

    Roberts, D. Aaron

    2010-01-01

    Recent work has shown that at 1AU from the Sun the power spectrum of the solar wind magnetic field has the -5/3 spectral slope expected for Kolmogorov turbulence, but that the velocity has closer to a -3/2 spectrum. This paper traces the changes in solar wind velocity spectra from 0.3 to 5 AU using data from the Helios and Ulysses spacecraft to show that this is a transient stage in the evolution. The spectrum of the velocity is found to be flatter than that of the magnetic field for the higher frequencies examined for all cases until the slopes become equal (at -5/3) well past 1 AU when the wind is relatively nonAlfvenic. In some respects, in particular in the evolution of the frequency at which the spectrum changes from flatter at larger scales to a traditionally turbulent spectrum at smaller scales, the velocity field evolves more rapidly that the magnetic, and this is associated with the dominance of the magnetic energy over the kinetic at "inertial range" scales. The Alfvenicity of the fluctuations, not the speed of the flow, is shown to control the rate of the spectral evolution. This study shows that, for the solar wind ., the idea of a simple "inertial range" with uniform spectral properties is not realistic, and new phenomenologies will be needed to capture the true situation. In addition a flattening of the velocity spectrum persists at times for small scales, which may provide a clue to the nature of the small-scale interactions.

  3. Dynamical properties of total intensity fluctuation spectrum in two-mode Nd:YVO4 microchip laser

    Science.gov (United States)

    Zhang, Shao-Hui; Shu-Lian, Zhang; Tan, Yi-Dong; Sun, Li-Qun

    2015-12-01

    We investigate the total intensity fluctuation spectrum of the two-longitudinal- mode Nd:YVO4 microchip laser (ML). We find that low-frequency relaxation oscillation (RO) peaks still appear in the total intensity fluctuation spectrum, which is different from a previous research result that the low-frequency RO peaks exist in the spectrum of the individual mode but compensate for each other totally in the total intensity fluctuation spectrum. Taking the spatial hole-burning effect into account, one and two-mode rate equations for Nd:YVO4 ML laser are established and studied. Based on the theoretical model, we find that when the gains and losses for two longitudinal models are different, a low-frequency RO peak will appear in the total intensity fluctuation spectrum, while when they share the same gain and loss, the total spectrum will behave like that of a single mode laser. Theoretical simulation results coincide with experimental results very well. Project supported by the Beijing Higher Education Young Elite Teacher Project, China (Grant No. YETP0086), the Tsinghua University Initiative Scientific Research Programme, China (Grant No. 2012Z02166), and the Special-funded Programme on National Key Scientific Instruments and Equipment Development of China (Grant No. 2011YQ04013603).

  4. The Effect on Stellarator Neoclassical Transport of a Fluctuating Electrostatic Spectrum

    Energy Technology Data Exchange (ETDEWEB)

    H.E. Mynick; A.H. Boozer

    2004-11-23

    We study the effect on neoclassical transport of applying a fluctuating electrostatic spectrum, such as produced either by plasma turbulence, or imposed externally. For tokamaks, it is usually assumed that the neoclassical and ''anomalous'' contributions to the transport roughly superpose, D = D{sub nc} + D{sub an}, an intuition also used in modeling stellarators. An alternate intuition, however, is one where it is the collisional and anomalous scattering frequencies which superpose, {nu}{sub ef} = {nu} + {nu}{sub an}. For nonaxisymmetric systems, in regimes where {partial_derivative}D/{partial_derivative}{nu} < 0, this ''{nu}{sub ef} picture'' implies that turning on the fluctuations can decrease the total radial transport. Using numerical and analytic means, it is found that the total transport has contributions conforming to each of these intuitions, either of which can dominate. In particular, for stellarators, the {nu}{sub ef} picture is often valid, producing transport behavior differing from tokamaks.

  5. Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

    CERN Document Server

    Loi, Shyeh Tjing; Murphy, Tara; Cairns, Iver H; Bell, Martin; Hurley-Walker, Natasha; Morgan, John; Lenc, Emil; Offringa, A R; Feng, L; Hancock, P J; Kaplan, D L; Kudryavtseva, N; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Corey, B E; Deshpande, A A; Emrich, D; Gaensler, B M; Goeke, R; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Prabu, T; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Tingay, S J; Waterson, M; Wayth, R B; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2015-01-01

    Low-frequency, wide field-of-view (FoV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two datasets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the line of sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10-100 km) scales probed by the MWA, determined by the size of its FoV and the spatial density of radio sources (typically thousands in a single FoV), complement the global (100-1000 km) scales of GPS studies and local (0.01-1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of travelling ionospheric disturbances (TIDs), whi...

  6. Stochastic Dynamics of Electrical Membrane with Voltage-Dependent Ion Channel Fluctuations

    CERN Document Server

    Qian, Hong; Qian, Min

    2014-01-01

    Brownian ratchet like stochastic theory for the electrochemical membrane system of Hodgkin-Huxley (HH) is developed. The system is characterized by a continuous variable $Q_m(t)$, representing mobile membrane charge density, and a discrete variable $K_t$ representing ion channel conformational dynamics. A Nernst-Planck-Nyquist-Johnson type equilibrium is obtained when multiple conducting ions have a common reversal potential. Detailed balance yields a previously unknown relation between the channel switching rates and membrane capacitance, bypassing Eyring-type explicit treatment of gating charge kinetics. From a molecular structural standpoint, membrane charge $Q_m$ is a more natural dynamic variable than potential $V_m$; our formalism treats $Q_m$-dependent conformational transition rates $\\lambda_{ij}$ as intrinsic parameters. Therefore in principle, $\\lambda_{ij}$ vs. $V_m$ is experimental protocol dependent,e.g., different from voltage or charge clamping measurements. For constant membrane capacitance pe...

  7. Extracting sensitive spectrum bands of rapeseed using multiscale multifractal detrended fluctuation analysis

    Science.gov (United States)

    Jiang, Shan; Wang, Fang; Shen, Luming; Liao, Guiping; Wang, Lin

    2017-03-01

    Spectrum technology has been widely used in crop non-destructive testing diagnosis for crop information acquisition. Since spectrum covers a wide range of bands, it is of critical importance to extract the sensitive bands. In this paper, we propose a methodology to extract the sensitive spectrum bands of rapeseed using multiscale multifractal detrended fluctuation analysis. Our obtained sensitive bands are relatively robust in the range of 534 nm-574 nm. Further, by using the multifractal parameter (Hurst exponent) of the extracted sensitive bands, we propose a prediction model to forecast the Soil and plant analyzer development values ((SPAD), often used as a parameter to indicate the chlorophyll content) and an identification model to distinguish the different planting patterns. Three vegetation indices (VIs) based on previous work are used for comparison. Three evaluation indicators, namely, the root mean square error, the correlation coefficient, and the relative error employed in the SPAD values prediction model all demonstrate that our Hurst exponent has the best performance. Four rapeseed compound planting factors, namely, seeding method, planting density, fertilizer type, and weed control method are considered in the identification model. The Youden indices calculated by the random decision forest method and the K-nearest neighbor method show that our Hurst exponent is superior to other three Vis, and their combination for the factor of seeding method. In addition, there is no significant difference among the five features for other three planting factors. This interesting finding suggests that the transplanting and the direct seeding would make a big difference in the growth of rapeseed.

  8. A SVPWM based on fluctuate capacitor voltage in 3L-NPC back-to-back converter applied to wind energy

    DEFF Research Database (Denmark)

    Chen, Quan; Wang, Qunjing; Chen, Zhe

    2014-01-01

    Three-level Neutral-point-clamped (3L-NPC) converters are becoming a realistic alternative to the conventional converters in high-power wind-energy applications. But the unbalance in the supported capacitors' voltage of back-to-back 3L-NPC converters, including the dynamics of the capacitors...... between the fluctuate voltage of upper and lower capacitors is extracted. Based on this error factor the duty-time of every active voltage vector is calculated. In order to validate the model and the control strategy proposed in this paper, a 2MW 3L-NPC converter used in wind energy has been simulated....

  9. THE POWER SPECTRUM OF THE MILKY WAY: VELOCITY FLUCTUATIONS IN THE GALACTIC DISK

    Energy Technology Data Exchange (ETDEWEB)

    Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Bird, Jonathan C. [Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, Nashville, TN 37235 (United States); Pérez, Ana E. García; Majewski, Steven R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Nidever, David L. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48104 (United States); Zasowski, Gail, E-mail: bovy@ias.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2015-02-20

    We investigate the kinematics of stars in the mid-plane of the Milky Way (MW) on scales between 25 pc and 10 kpc with data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Radial Velocity Experiment (RAVE), and the Geneva-Copenhagen survey (GCS). Using red-clump (RC) stars in APOGEE, we determine the large-scale line-of-sight velocity field out to 5 kpc from the Sun in (0.75 kpc){sup 2} bins. The solar motion V{sub ☉} {sub –} {sub c} with respect to the circular velocity V{sub c} is the largest contribution to the power on large scales after subtracting an axisymmetric rotation field; we determine the solar motion by minimizing the large-scale power to be V{sub ☉} {sub –} {sub c} = 24 ± 1 (ran.) ± 2 (syst. [V{sub c} ]) ± 5 (syst.[large-scale]) km s{sup –1}, where the systematic uncertainty is due to (1) a conservative 20 km s{sup –1} uncertainty in V{sub c} and (2) the estimated power on unobserved larger scales. Combining the APOGEE peculiar-velocity field with RC stars in RAVE out to 2 kpc from the Sun and with local GCS stars, we determine the power spectrum of residual velocity fluctuations in the MW's disk on scales between 0.2 kpc{sup –1} ≤ k ≤ 40 kpc{sup –1}. Most of the power is contained in a broad peak between 0.2 kpc{sup –1} < k < 0.9 kpc{sup –1}. We investigate the expected power spectrum for various non-axisymmetric perturbations and demonstrate that the central bar with commonly used parameters but of relatively high mass can explain the bulk of velocity fluctuations in the plane of the Galactic disk near the Sun. Streaming motions ≈10 km s{sup –1} on ≳ 3 kpc scales in the MW are in good agreement with observations of external galaxies and directly explain why local determinations of the solar motion are inconsistent with global measurements.

  10. Life distribution of thermal fatigue crack propagation under random temperature fluctuation with wide-band spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, Michiko; Tanaka, Hiroaki [Kyoto Univ. (Japan)

    1995-05-01

    Thermal fatigue crack propagation under random temperature fluctuation is theoretically investigated from a probabilistic view point by the use of a Markov approximation method, under the condition that the temporary variation of the inner surface temperature of plate is modeled as a wide-band stationary Gaussian process. First, a crack growth equation is formulated on the basis of the Paris law under the assumption that the stress intensity factor range {Delta}K can be approximated by the local expectation of a relative maximum of the stress intensity factor K. Next it is extended to a random differential equation, where the randomness in crack propagation resistance is taken into account. The Markov approximation method is then applied to derive a residual life distribution function as well as a probability distribution function of the crack length. Finally, numerical examples are shown to examine the quantitative behavior of the residual life distribution, whose results indicate that the present model is applicable even if the spectrum of temperature is of narrow-band type. (author).

  11. Cholesterol favors the emergence of a long-range autocorrelated fluctuation pattern in voltage-induced ionic currents through lipid bilayers.

    Science.gov (United States)

    Corvalán, Natalia A; Kembro, Jackelyn M; Clop, Pedro D; Perillo, María A

    2013-08-01

    The present paper was aimed at evaluating the effect of cholesterol (CHO) on the voltage-induced lipid pore formation in bilayer membranes through a global characterization of the temporal dynamics of the fluctuation pattern of ion currents. The bilayer model used was black lipid membranes (BLMs) of palmitoyloleoylphosphatidylethanolamine and palmitoyloleoylphosphatidylcholine (POPE:POPC) at a 7:3 molar ratio in the absence (BLM0) or in the presence of 30 (BLM30), 40 (BLM40) or 50(BLM50)mol% of cholesterol with respect to total phospholipids. Electrical current intensities (I) were measured in voltage (ΔV) clamped conditions at ΔV ranging between 0 and ±200mV. The autocorrelation parameter α derived from detrended fluctuation analysis (DFA) on temporal fluctuation patterns of electrical currents allowed discriminating between non-correlated (α=0.5, white noise) and long-range correlated (0.5number of conductance states, the magnitude of conductance level, the capacitance of the bilayers and increased the tendency towards the development of long-range autocorrelated (fractal) processes (0.5<α<1) in lipid channel generation. Experiments were performed above the phase transition temperature of the lipid mixtures, but compositions used predicted a superlattice-like organization. This leads to the conclusion that structural defects other than phase coexistence may promote lipid channel formation under voltage clamped conditions. Furthermore, cholesterol controls the voltage threshold that allows the percolation of channel behavior where isolated channels become an interconnected network.

  12. Reduction of phase temporal fluctuations caused by digital voltage addressing in LC SLM "HoloEye PLUTO VIS" for holographic applications

    Science.gov (United States)

    Cheremkhin, Pavel A.; Evtikhiev, Nikolay N.; Krasnov, Vitaly V.; Rodin, Vladislav G.; Starikov, Sergey N.

    2014-02-01

    Phase liquid crystal spatial light modulators (LC SLM) are widely used in optical applications such as real-time imaging of holograms and diffractive optical elements, which require high stability and linearity of phase modulation. However state of the art LC SLM with high resolution use digital voltage addressing scheme which, unfortunately, leads to phase fluctuations in time period of one frame. Fluctuations characteristics depend on SLM voltage addressing sequence used. We report results of measurement of phase characteristics of LC SLM "HoloEye PLUTO VIS". This SLM is supplied with three different addressing sequences: "18-6", "5-5" and "0-6". Dynamics of phase fluctuations were measured for all signal values (0-255) with temporal resolution of 0.5 ms in time period of one frame for available addressing sequences. Default sequence "18-6" provided phase deviation 0.24 pi. Lowest deviation 0.07 pi was achieved with sequence "0-6". Due to high periodicity of fluctuations it is possible to implement synchronization of SLM and registering camera or light source to reduce fluctuation effects. This was experimentally implemented using DVI video signal for synchronization of SLM and camera. With its application minimum phase deviation 0.013 pi was achieved with sequence "18-6" which is 5 times lower than achievable without synchronization.

  13. Power Spectrum Analysis of Heart Rate Fluctuation: A Quantitative Probe of Beat-To-Beat Cardiovascular Control

    Science.gov (United States)

    Akselrod, Solange; Gordon, David; Ubel, F. Andrew; Shannon, Daniel C.; Barger, A. Clifford; Cohen, Richard J.

    1981-07-01

    Power spectrum analysis of heart rate fluctuations provides a quantitative noninvasive means of assessing the functioning of the short-term cardiovascular control systems. We show that sympathetic and parasympathetic nervous activity make frequency-specific contributions to the heart rate power spectrum, and that renin-angiotensin system activity strongly modulates the amplitude of the spectral peak located at 0.04 hertz. Our data therefore provide evidence that the reninangiotensin system plays a significant role in short-term cardiovascular control on the time scale of seconds to minutes.

  14. Frequency Spectrum of Fluctuations Near a Rational Surface in a Toroidal Heliac

    Science.gov (United States)

    Zama, Tatsuya; Kitajima, Sumio; Takayama, Masakazu; Takeuchi, Nobunao; Watanabe, Hiroshige

    1993-03-01

    Density and space potential fluctuations have been studied in electron cyclotron resonance heating (ECRH) plasma of a helical axis stellarator TU Heliac using Langmuir probe techniques. These fluctuations are coherent and global, which can be explained by a drift instability model in cylindrical geometry. A particular fluctuation mode vanishes inside a rational surface. The ratio of this mode, n/m, corresponds to the rotational transform \\includegraphics{dummy.eps} of this rational surface, (m, n: poloidal, toroidal fluctuation modes, respectively). This phenomenon near the rational surface can also be explained by a drift instability theory.

  15. Investigation on the energy spectrums of electrons in atmospheric pressure argon plasma jets and their dependences on the applied voltage

    Science.gov (United States)

    Chen, Xinxian; Tan, Zhenyu; Liu, Yadi; Li, Xiaotong; Pan, Jie; Wang, Xiaolong

    2017-08-01

    This work presents a systematical investigation on the spatiotemporal evolution of the energy spectrum of electrons in atmospheric pressure argon plasma jets and its dependence on the applied voltage. The investigations are carried out by means of the numerical simulation based on a particle-in-cell Monte-Carlo collision model. The characteristics of the spatiotemporal evolution of the energy spectrum of electrons (ESE) in the discharge space have been presented, and especially the mechanisms of inducing these characteristics have also been revealed. The present work shows the following conclusions. In the evolution of ESE, there is a characteristic time under each applied voltage. Before the characteristic time, the peak value of ESE decreases, the peak position shifts toward high energy, and the distribution of ESE becomes wider and wider, but the reverse is true after the characteristic time. The formation of these characteristics can be mainly attributed to the transport of electrons toward a low electric field as well as a balance between the energy gained from the electric field including the effect of space charges and the energy loss due to inelastic collisions in the process of electron transport. The characteristic time decreases with the applied voltage. In addition, the average energy of electrons at the characteristic time can be increased by enhancing the applied voltage. The results presented in this work are of importance for regulating and controlling the energy of electrons in the plasma jets applied to plasma medicine.

  16. The effect of turbulent density fluctuations on wave-particle interactions and solar flare X-ray spectrum

    CERN Document Server

    Hannah, I G; Reid, H A S

    2012-01-01

    To demonstrate the effect of turbulent background density fluctuations on flare accelerated electron transport in the solar corona. Using the quasi-linear approximation, we numerically simulate the propagation of a beam of accelerated electrons from the solar corona to chromosphere, including the self-consistent response of the inhomogeneous background plasma in the form of Langmuir waves. We calculate the X-ray spectrum from these simulations using the bremsstrahlung cross-section and fit the footpoint spectrum using the collisional "thick-target" model, a standard approach adopted in observational studies. We find that the interaction of the Langmuir waves with the background electron density gradient shifts the waves to higher phase velocity where they then resonate with higher velocity electrons. The consequence is that some of the electrons are shifted to higher energies, producing more high energy X-rays than expected in the cases where the density inhomogeneity is not considered. We find that the level...

  17. Early Structure Formation from Primordial Density Fluctuations with a Blue, Tilted Power Spectrum

    Science.gov (United States)

    Hirano, Shingo; Zhu, Nick; Yoshida, Naoki; Spergel, David; Yorke, Harold W.

    2015-11-01

    While observations of large-scale structure and the cosmic microwave background (CMB) provide strong constraints on the amplitude of the primordial power spectrum (PPS) on scales larger than 10 Mpc, the amplitude of the power spectrum on sub-galactic length scales is much more poorly constrained. We study early structure formation in a cosmological model with a blue-tilted PPS. We assume that the standard scale-invariant PPS is modified at small length scales as P(k)∼ {k}{m{{s}}} with ms > 1. We run a series of cosmological hydrodynamic simulations to examine the dependence of the formation epoch and the characteristic mass of primordial stars on the tilt of the PPS. In models with ms > 1, star-forming gas clouds are formed at z > 100 when the formation of hydrogen molecules is inefficient because the intense CMB radiation destroys chemical intermediates. Without efficient coolant, the gas clouds gravitationally contract while retaining a high temperature. The protostars formed in such “hot” clouds grow very rapidly through accretion to become extremely massive stars that may leave massive black holes with a few hundred solar masses at z > 100. The shape of the PPS critically affects the properties and the formation epoch of the first generation of stars. Future experiments on CMB polarization and spectrum distortion may provide important information on the nature of the first stars and their formation epoch, and hence on the shape of the small-scale power spectrum.

  18. Energy storage system in medium-sized voltage lines for the integration of decentralized fluctuating energy sources; Energiespeicher im Niederspannungsnetz zur Integration dezentraler, fluktuierender Energiequellen

    Energy Technology Data Exchange (ETDEWEB)

    Bodach, M.

    2006-06-30

    The solar radiation fluctuates due to atmospheric and planetary influences. Concerning PV systems, the changes from dark clouds to clear sky result in fast and very deep fluctuations of the time behaviour of the power output fed into the low voltage (LV) network by DC-AC-Converters. On the example of a daily recorded global radiation curve with a very short sampling time (regular interval time 1 s) the paper shows that short-term sags of the solar radiation are possible up to 80% of the previous value as a result of sudden and intensive changes of the density of the clouds. These disturbances of the quality of the generated electric power are directly transformed into the LV grids. If the number of PV systems connected to existing LV networks rises essentially, the fluctuating photovoltaic energy generation will achieve a very high importance and therefore not only the well-known, but also a lot of new problems will occur. They have already been investigated theoretically in different papers and they have also been proven quantitatively by own simulations. Improvements of the energy quality at the point of common coupling will be possible if the grid-coupled PV power plants are supplemented with suitable intelligent storage systems bridging the short-term sags. So the influence of the fluctuating radiation on the generated power can be fundamentally reduced. The developed intelligent short-term storage system smoothes out the generated power of the PV system by means of a storage. It is based on the very high capacity of an electric double layer (UltraCap, produced by EPCOS) and includes a complex electronic control system. The UltraCap has the required storing characteristics and has been adjusted to the system voltage by a highly sophisticated microprocessor controlled DC/DC-converter system. Such an intelligent storage system can also be used for the connection of other decentralised power generation units (e.g. fuel cells, block-unit heating power plant) to the

  19. Density Fluctuation Spectrum of Solar Wind Turbulence between Ion and Electron Scales

    CERN Document Server

    Chen, C H K; Bonnell, J W; Mozer, F S; Bale, S D

    2012-01-01

    We present a measurement of the spectral index of density fluctuations between ion and electron scales in solar wind turbulence using the EFI instrument on the ARTEMIS spacecraft. The mean spectral index at 1 AU was found to be -2.75 +/- 0.06, steeper than predictions for pure whistler or kinetic Alfven wave turbulence, but consistent with previous magnetic field measurements. The steep spectra are also consistent with expectations of increased intermittency or damping of some of the turbulent energy over this range of scales. Neither the spectral index nor the flattening of the density spectra before ion scales were found to depend on the proximity to the pressure anisotropy instability thresholds, suggesting that they are features inherent to the turbulent cascade.

  20. Early structure formation from primordial density fluctuations with a blue-tilted power spectrum

    CERN Document Server

    Hirano, Shingo; Yoshida, Naoki; Spergel, David; Yorke, Harold W

    2015-01-01

    While observations of large-scale structure and the cosmic microwave background (CMB) provide strong constraints on the amplitude of the primordial power spectrum (PPS) on scales larger than 10 Mpc, the amplitude of the power spectrum on sub-galactic length scales is much more poorly constrained. We study early structure formation in a cosmological model with a blue-tilted PPS. We assume that the standard scale-invariant PPS is modified at small length scales as $P(k) \\sim k^{m_{\\rm s}}$ with $m_{\\rm s} > 1$. We run a series of cosmological hydrodynamic simulations to examine the dependence of the formation epoch and the characteristic mass of primordial stars on the tilt of the PPS. In models with $m_{\\rm s} > 1$, star-forming gas clouds are formed at $z > 100$, when formation of hydrogen molecules is inefficient because the intense CMB radiation destroys chemical intermediates. Without efficient coolant, the gas clouds gravitationally contract while keeping a high temperature. The protostars formed in such ...

  1. 光源的光通量变化随电压波动的测试分析%Testing Analysis of Light Flux Variation with Voltage Fluctuation

    Institute of Scientific and Technical Information of China (English)

    陈小龙

    2014-01-01

    Testing principle and circuit was introduced .The relationship of light flux and voltage was tested with illumination sensor ON9658, and the testing results were analyzed .The results show that the electric light quality is influenced by power supply and lighting with driver , and reasonable selection of lighting can overcome the voltage fluctuation and flicker flicker problem .%介绍了测试原理和测试电路,利用照度传感器ON9658对常用电光源的光通量与电压的关系进行测量,并对测量结果进行了分析。分析结果表明:电光源的发光品质受供电电源及灯具自带驱动器的影响,合理选择照明灯具可克服由于电压波动造成的频闪和闪烁的问题。

  2. Direct Measurement of the Phase Space Ion Fluctuation Spectrum of a Laboratory Plasma Using Two Independently Tunable Lasers

    Science.gov (United States)

    Mattingly, Sean; Berumen, Jorge; Chu, Feng; Hood, Ryan; Skiff, Fred

    2013-10-01

    A novel technique for probing velocity space correlations has been developed using laser-induced fluorescence. The experiment consists of a 3 m cylindrical plasma column of singly-charged Argon ions (Ar II) with density ~ 109 cm-3 , Te ~ 5 eV , Ti ~ . 06 eV , and a 1 kG axial magnetic field. Separate metastable lines of the Ar II ions are excited using two separate narrow bandwidth lasers. The LIF response from each laser is measured through an independently moveable periscope. These periscopes may be focused on the same localized region (~ 0 . 1 cm3) or separated to view different parts of the plasma simultaneously. By adjusting these lasers independently, one may measure a correlation function as a function of the difference in measured velocities. This measurement may be repeated for different periscope positions in the plasma to obtain a two-dimensional correlation function in space and velocity difference. This correlation is directly related to the fluctuation spectrum through a Fourier transform. Measurements of these correlations are reported and discussed. NSF DOE Grant DE-FG02-99ER54543.

  3. Static voltage fluctuation compensator for electric railway using self-commutated converters; Jireishiki denryoku henkan sochi ni yoru kidensoku denryoku yuzu hoshiki koryu denki tetsudoyo den`atsu hendo hosho sochi no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Uzuka, T.; Hase, S.; Mochida, Y. [Railway Technical Research Institute, Tokyo (Japan); Takeda, M.; Miyashita, T. [Mitsubishi Electric Corp., Tokyo (Japan); Ueda, T. [Nihon University, Tokyo (Japan)

    1995-11-20

    In this paper, authors describe a basic figure of static voltage compensator for electric railway, named RPC (Railway Static Power Conditioner), its compensating philosophy and successful result of its test using a small model of RPC. An AC electric railway is placed under a load single phase, rapidly changing. To avoid voltage fluctuations under single phase loads, electric power is received from a larger source. And at a feeding subsection, 3-phase electric power is transferred to paired directional single-phase feeding electric power. Authors already proposed a static voltage compensator for AC electric railway, called `RPC`. The RPC links a pair of feeding circuits using 2 self-commutated inverters. At the substation, the RPC accommodates an active power of the directional pair of feeding circuits to balance 3-phase power and compensate a reactive power to regulate a 3-phase voltage fluctuation. At a sectioning post, it can compensate for voltage drop using a reactive power. Also it can act as an active filter to compensate higher-harmonics. Authors have made a small model (220V, 20kVA) of RPC. And we report on the results of tests using this small model under various conditions. The results indicate that RPC can accommodate single phase loads such as transformers and thyristors, can handle an exciting rush current of transformer, can compensate higher-harmonics and so on. 11 refs., 15 figs., 2 tabs.

  4. Determination voltage applied to an X-ray tube using the spectrum; Determinacao da tensao aplicada em um tubo de raios-X usando o espectro

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, M.A.G.; David, M.G.; Almeida, Carlos Eduardo de; Magalhaes, Luis Alexandre Goncalves, E-mail: malbuqueque@hotmail.com [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Lab. de Ciencias Radiologicas; Peixoto, Guilherme [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    This work shows the methodology used to determine the voltage applied in an X-ray tube using their spectra. The measurements were made using a detector Cadmium telluride . Before the measurements are carried out detector was calibrated with a source of {sup 241}Am. After obtaining the spectra , the mean energies were calculated , the electron accelerating potential (k Vp ) of each spectrum is constructed a calibration straight for the kVp this tube. (author)

  5. Spectrum

    DEFF Research Database (Denmark)

    Høgfeldt Hansen, Leif

    2016-01-01

    The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum.......The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum....

  6. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa

    2013-01-01

    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  7. Primordial fluctuations from nonlinear couplings

    CERN Document Server

    Calzetta, E A; Calzetta, Esteban A.; Gonorazky, Sonia

    1997-01-01

    We study the spectrum of primordial fluctuations in theories where the inflaton field is coupled to massless fields and/or to itself. Conformally invariant theories generically predict a scale invariant spectrum. Scales entering the theory through infrared divergences cause logarithmic corrections to the spectrum, tiltilng it towards the blue. We discuss in some detail wether these fluctuations are quantum or classical in nature.

  8. A comparative study of two-dimensional multifractal detrended fluctuation analysis and two-dimensional multifractal detrended moving average algorithm to estimate the multifractal spectrum

    Science.gov (United States)

    Xi, Caiping; Zhang, Shunning; Xiong, Gang; Zhao, Huichang

    2016-07-01

    Multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended moving average (MFDMA) algorithm have been established as two important methods to estimate the multifractal spectrum of the one-dimensional random fractal signal. They have been generalized to deal with two-dimensional and higher-dimensional fractal signals. This paper gives a brief introduction of the two-dimensional multifractal detrended fluctuation analysis (2D-MFDFA) and two-dimensional multifractal detrended moving average (2D-MFDMA) algorithm, and a detailed description of the application of the two-dimensional fractal signal processing by using the two methods. By applying the 2D-MFDFA and 2D-MFDMA to the series generated from the two-dimensional multiplicative cascading process, we systematically do the comparative analysis to get the advantages, disadvantages and the applicabilities of the two algorithms for the first time from six aspects such as the similarities and differences of the algorithm models, the statistical accuracy, the sensitivities of the sample size, the selection of scaling range, the choice of the q-orders and the calculation amount. The results provide a valuable reference on how to choose the algorithm from 2D-MFDFA and 2D-MFDMA, and how to make the schemes of the parameter settings of the two algorithms when dealing with specific signals in practical applications.

  9. Current-oscillator correlation and Fano factor spectrum of quantum shuttle with finite bias voltage and temperature.

    Science.gov (United States)

    Lai, Wenxi; Cao, Yunshan; Ma, Zhongshui

    2012-05-01

    A general master equation is derived to describe an electromechanical single-dot transistor in the Coulomb blockade regime. In the equation, Fermi distribution functions in the two leads are taken into account, which allows one to study the system as a function of bias voltage and temperature of the leads. Furthermore, we treat the coherent interaction mechanism between electron tunneling events and the dynamics of excited vibrational modes. Stationary solutions of the equation are numerically calculated. We show that current through the oscillating island at low temperature appears to have step-like characteristics as a function of the bias voltage and the steps depend on the mean phonon number of the oscillator. At higher temperatures the current steps would disappear and this event is accompanied by the emergence of thermal noise of the charge transfer. When the system is mainly in the ground state, the zero frequency Fano factor of current manifests sub-Poissonian noise and when the system is partially driven into its excited states it exhibits super-Poissonian noise. The difference in the current noise would almost be removed for the situation in which the dissipation rate of the oscillator is much larger than the bare tunneling rates of electrons.

  10. Voltage Fluctuation Detection and Tracking Based on Adaptive Filtering Algorithm%基于自适应滤波算法的电压波动检测与跟踪

    Institute of Scientific and Technical Information of China (English)

    王伟; 张广明; 王祥华

    2011-01-01

    With the development of industry, the problem of grid voltage fluctuation has become increasingly serious, and detecting and tracking voltage fluctuation has become an important task for the electricity sectors. Based on the a-daptive filter theory, a new QR - decomposition recursive least squares algorithm is proposed. This algorithm not only improves the numerical stability, but also keeps the characteristic of the fast convergence of the traditional recursive least squares algorithm. Then, with the introduction of systolic array, Givens rotation procedure in the QR -decomposition was parallelled processing in a highly streamlined way. By this way, the efficiency and real -time applications of the algorithm was improved. Finally, the simulation of the power system voltage fluctuation detection and tracking is completed with the Matlab, and the simulation results verified the feasibility and effectiveness of the presented method.%随着工业发展电网电压波动问题变得日益严重,检测与跟踪电压波动已成为供用电部门的一项重要任务.为此,在自适应滤波理论的基础上,提出一种新的QR分解递归最小二乘算法.该算法不但提高了数值稳定性,还保持了传统递归最小二乘算法的快速收敛性.然后,引入脉动阵列以高度流水线化的方式对QR分解中的Givens旋转步骤进行并行处理,从而提高了算法的执行效率,使其具有了更好的实时性.最后,通过Matlab完成对电力系统电压波动检测与跟踪的仿真,仿真结果验证了该方法的可行性和有效性.

  11. 阔叶树材横切面构造的涨落谱分析%Fluctuation spectrum analysis on cross-section structure of hardwoods

    Institute of Scientific and Technical Information of China (English)

    龙涛; 罗建举; 孙建平

    2015-01-01

    Hardwood is widely used as interior decoration materials, mainly because that its anatomical structure is in great complication and therefore it possesses good aesthetic decorative value. To further explore the aesthetic principles of wood, thefluctuation spectrum analysis was carried out on cross-section structure of six hardwood species with typical pore distribution patterns by means of Fourier image transformation technology. The results show that all thefluctuation spectra of cross-section structure of the six hardwood species were closely similar to 1/f fluctuation spectrum, especially in the frequency bands of 8~12Hz (corresponding to the human brain's α-band) almost completely consistent with 1/ffluctuation spectrum. This result further theoretically explains the reason why hardwood is more suitable as interior decoration materials lies in that its surface structurefluctuation is close similar to 1/ffluctuation. The wood surface structurefluctuation similar to 1/ffluctuation can stimulate the human body to produce A-rhythm brain waves, and let people feel comfortable and pleasant.%阔叶树材多用作室内装饰装修材料,主要是由于其组织构造复杂多变而具有较好的美学装饰价值.为了进一步探究木材的美学原理,运用傅立叶变换图像处理技术对6种具有典型管孔分布类型的阔叶树材横切面构造进行了涨落谱分析.结果表明6种阔叶树材横切面构造的涨落谱都与1/f涨落谱相近,特别是在8-12Hz频率段(对应于人体大脑的α波段)与1/f涨落谱几乎完全一致.这一结果进一步从理论上说明阔叶树材之所以更适合于用作室内装饰装修材料,是因为其表面构造呈1/f涨落.木材表面构造上这种接近于1/f涨落现象可以刺激人体大脑产生α节律波,从而让人获得舒适愉悦的美感.

  12. Nonequilibrium mesoscopic conductance fluctuations

    Science.gov (United States)

    Ludwig, T.; Blanter, Ya. M.; Mirlin, A. D.

    2004-12-01

    We investigate the amplitude of mesoscopic fluctuations of the differential conductance of a metallic wire at arbitrary bias voltage V . For noninteracting electrons, the variance ⟨δg2⟩ increases with V . The asymptotic large- V behavior is ⟨δg2⟩˜V/Vc (where eVc=D/L2 is the Thouless energy), in agreement with the earlier prediction by Larkin and Khmelnitskii. We find, however, that this asymptotics has a very small numerical prefactor and sets in at very large V/Vc only, which strongly complicates its experimental observation. This high-voltage behavior is preceded by a crossover regime, V/Vc≲30 , where the conductance variance increases by a factor ˜3 as compared to its value in the regime of universal conductance fluctuations (i.e., at V→0 ). We further analyze the effect of dephasing due to the electron-electron scattering on ⟨δg2⟩ at high voltages. With the Coulomb interaction taken into account, the amplitude of conductance fluctuations becomes a nonmonotonic function of V . Specifically, ⟨δg2⟩ drops as 1/V for voltages V≫gVc , where g is the dimensionless conductance. In this regime, the conductance fluctuations are dominated by quantum-coherent regions of the wire adjacent to the reservoirs.

  13. Design of standalone PV inverter based on low voltage and fluctuation input%基于波动低压输入的独立光伏逆变器的设计

    Institute of Scientific and Technical Information of China (English)

    吴巍

    2013-01-01

    For lower voltages and fluctuated inputs of a standalone Photovoltaic (PV) inverter, a disturbance-rejection system with a double-closed-loop control was proposed. On the basis of the working principle of the system, the main parts of the inverter were modeled and a overall mathematical model was obtained. The inverter with an input voltage of 24 V, an output voltage of 311 V, a frequency of 50 Hz and an output power of 6 kW was illustrated as an example. In the design, the pole assignment method was used to calculate the controller parameters and the relation between fluctuation input and steady state error was described quantitatively. The simulation result indicates that the system with good stability and low steady state error can reject the disturbance. Its voltage change is 0. 03%, total Harmonic Distortion(THD) is 1. 03% ,and the highest single harmonic content is less than 3% , which meets the requirements as well. The model and design method with theoretical guidance meaning is u-niversal and can support the applications and design of high power inverters in other special fields of PV generation.%针对独立光伏逆变器输入电压较低且波动的问题,提出一种采用双闭环控制策略且抗输入电压扰动的光伏逆变器系统.在阐述其工作原理基础上,对光伏逆变器主要部件进行建模,得到总体数学模型,并举例设计了输入电压为24V、输出为311 V、输出频率为50 Hz、输出功率为6 kW的光伏逆变器.设计中采用极点配置进行控制器参数计算,定量描述了输入电压波动对逆变器跟踪误差的影响.仿真结果表明,设计的逆变器具有稳定性好、抗扰动性强和稳态误差低等特点,其电压变化率为0.03%,输出电压总谐波失真(THD)为1.03%,最高单次谐波含量小于3%,可以满足性能指标要求.所建模型和设计方法具有一定通用性和理论指导意义,可用于特殊光伏发电领域中大功率光伏逆变器的研究与设计.

  14. Deployment of low-voltage regulator considering existing voltage control in medium-voltage distribution systems

    Directory of Open Access Journals (Sweden)

    Hiroshi Kikusato

    2016-01-01

    Full Text Available Many photovoltaic (PV systems have been installed in distribution systems. This installation complicates the maintenance of all voltages within the appropriate range in all low-voltage distribution systems (LVDSs because the trends in voltage fluctuation differ in each LVDS. The installation of a low-voltage regulator (LVR that can accordingly control the voltage in each LVDS has been studied as a solution to this problem. Voltage control in a medium-voltage distribution system must be considered to study the deployment of LVRs. In this study, we installed LVRs in the LVDSs in which the existing voltage-control scheme cannot prevent voltage deviation and performed a numerical simulation by using a distribution system model with PV to evaluate the deployment of the LVRs.

  15. Calculation of the X-Ray Spectrum of a Mammography System with Various Voltages and Different Anode-Filter Combinations Using MCNP Code

    Directory of Open Access Journals (Sweden)

    Lida Gholamkar

    2016-09-01

    Full Text Available Introduction One of the best methods in the diagnosis and control of breast cancer is mammography. The importance of mammography is directly related to its value in the detection of breast cancer in the early stages, which leads to a more effective treatment. The purpose of this article was to calculate the X-ray spectrum in a mammography system with Monte Carlo codes, including MCNPX and MCNP5. Materials and Methods The device, simulated using the MCNP code, was Planmed Nuance digital mammography device (Planmed Oy, Finland, equipped with an amorphous selenium detector. Different anode/filter materials, such as molybdenum-rhodium (Mo-Rh, molybdenum-molybdenum (Mo-Mo, tungsten-tin (W-Sn, tungsten-silver (W-Ag, tungsten-palladium (W-Pd, tungsten-aluminum (W-Al, tungsten-molybdenum (W-Mo, molybdenum-aluminum (Mo-Al, tungsten-rhodium (W-Rh, rhodium-aluminum (Rh-Al, and rhodium-rhodium (Rh-Rh, were simulated in this study. The voltage range of the X-ray tube was between 24 and 34 kV with a 2 kV interval. Results The charts of changing photon flux versus energy were plotted for different types of anode-filter combinations. The comparison with the findings reported by others indicated acceptable consistency. Also, the X-ray spectra, obtained from MCNP5 and MCNPX codes for W-Ag and W-Rh combinations, were compared. We compared the present results with the reported data of MCNP4C and IPEM report No. 78 for Mo-Mo, Mo-Rh, and W-Al combinations. Conclusion The MCNPX calculation outcomes showed acceptable results in a low-energy X-ray beam range (10-35 keV. The obtained simulated spectra for different anode/filter combinations were in good conformity with the finding of previous research.

  16. Fluctuation and dissipation in liquid crystal electroconvection

    Science.gov (United States)

    Goldburg, Walter I.; Goldschmidt, Yadin Y.; Kellay, Hamid

    2002-11-01

    The power dissipation P( t) was measured in a liquid crystal (MBBA) driven by an ac voltage into the chaotic electroconvective state. In that state, the power fluctuates about its mean value . The quantity measured, and compared with the fluctuation theorem of Gallavotti and Cohen, is the dimensionless standard deviation of the fluctuations, σP/.

  17. Clustering of the Diffuse Infrared Light from the COBE DIRBE maps; 3, Power spectrum analysis and excess isotropic component of fluctuations

    CERN Document Server

    Kashlinsky, A; Odenwald, S

    1999-01-01

    The cosmic infrared background (CIB) radiation is the cosmic repository for energy release throughout the history of the universe. Using the all-sky data from the COBE DIRBE instrument at wavelengths 1.25 - 100 mic we attempt to measure the CIB fluctuations. In the near-IR, foreground emission is dominated by small scale structure due to stars in the Galaxy. There we find a strong correlation between the amplitude of the fluctuations and Galactic latitude after removing bright foreground stars. Using data outside the Galactic plane ($|b| > 20\\deg$) and away from the center ($90\\deg< l <270\\deg$) we extrapolate the amplitude of the fluctuations to cosec$|b|=0$. We find a positive intercept of $\\delta F_{\\rm rms} = 15.5^{+3.7}_{-7.0},5.9^{+1.6}_{-3.7}, 2.4^{+0.5}_{-0.9}, 2.0^{+0.25}_{-0.5}$ nW/m2/sr at 1.25, 2.2,3.5 and 4.9 mic respectively, where the errors are the range of 92% confidence limits. For color subtracted maps between band 1 and 2 we find the isotropic part of the fluctuations at $7.6^{+1.2}_...

  18. Physical interpretation of the angle-dependent magnetic helicity spectrum in the solar wind: The nature of turbulent fluctuations near the proton gyroradius scale

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Kristopher G.; Howes, Gregory G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); TenBarge, Jason M. [IREAP, University of Maryland, College Park, MD 20742 (United States); Podesta, John J., E-mail: kristopher-klein@uiowa.edu [Center for Space Plasma Physics, Space Science Institute, Boulder, CO 80301 (United States)

    2014-04-20

    Motivated by recent observations of distinct parallel and perpendicular signatures in magnetic helicity measurements segregated by wave period and angle between the local magnetic field and the solar wind velocity, this paper undertakes a comparison of three intervals of Ulysses data with synthetic time series generated from a physically motivated turbulence model. From these comparisons, it is hypothesized that the observed signatures result from a perpendicular cascade of Alfvénic fluctuations and a local, non-turbulent population of ion-cyclotron or whistler waves generated by temperature anisotropy instabilities. By constraining the model's free parameters through comparison to in situ data, it is found that, on average, ∼95% of the power near dissipative scales is contained in a perpendicular Alfvénic cascade and that the parallel fluctuations are propagating nearly unidirectionally. The effects of aliasing on magnetic helicity measurements are considered and shown to be significant near the Nyquist frequency.

  19. Physical Interpretation of the Angle Dependent Magnetic Helicity Spectrum in the Solar Wind: The Nature of Turbulent Fluctuations near the Proton Gyroradius Scale

    CERN Document Server

    Klein, Kristopher G; TenBarge, Jason M; Podesta, John J

    2014-01-01

    Motivated by recent observations of distinct parallel and perpendicular signatures in magnetic helicity measurements segregated by wave period and angle between the local magnetic field and the solar wind velocity, this paper undertakes a comparison of three intervals of \\emph{Ulysses} data with synthetic time series generated from a physically motivated turbulence model. From these comparisons, it is hypothesized that the observed signatures result from a perpendicular cascade of \\Alfvenic fluctuations and a local, non-turbulent population of ion cyclotron or whistler waves generated by temperature anisotropy instabilities. By constraining the model's free parameters through comparison to \\emph{in situ} data, it is found that, on average, $ \\sim 95\\%$ of the power near dissipative scales is contained in a perpendicular \\Alfvenic cascade and that the parallel fluctuations are propagating nearly unidirectionally. The effects of aliasing on magnetic helicity measurements are considered and shown to be significa...

  20. Astrophysical implications of the neutrino rest mass. II. The density-perturbation spectrum and small-scale fluctuations in the microwave background

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.; Zel' dovich, Y.B.; Syunyaev, R.A.; Khlopov, M.Y.

    1980-07-01

    If the neutrino has a rest mass, a scale comparable with the distance between clusters of galaxies would have been singled out in the universe. The amplitude of neutrino density perturbations on smaller scales should diminish in proportion to a high power of the perturbation wavelength. The evolution of adiabatic and entropic (isothermal) density perturbations is considered, and it is shown that the existence of a neutrino rest mass would imply smaller fine-scale fluctuations in the microwave background radiation than models in which m/sub ..nu../=0.

  1. Effect of the electromagnetic environment on current fluctuations in driven tunnel junctions

    Science.gov (United States)

    Frey, Moritz; Grabert, Hermann

    2016-07-01

    We examine current fluctuations in tunnel junctions driven by a superposition of a constant and a sinusoidal voltage source. In standard setups, the external voltage is applied to the tunneling element via an impedance providing an electromagnetic environment of the junction. The modes of this environment are excited by the time-dependent voltage and are the source of Johnson-Nyquist noise. We determine the autocorrelation function of the current flowing in the leads of the junction in the weak tunneling limit up to terms of second order in the tunneling Hamiltonian. The driven modes of the electromagnetic environment are treated exactly by means of a unitary transformation introduced recently. Particular emphasis is placed on the spectral function of the current fluctuations. The spectrum is found to comprise three contributions: a term arising from the Johnson-Nyquist noise of the environmental impedance, a part due to the shot noise of the tunneling element, and a third contribution which comes from the cross correlation between fluctuations caused by the electromagnetic environment and fluctuations of the tunneling current. All three parts of the spectral function occur already for devices under dc bias. The spectral function of ac driven tunneling elements can be determined from the result for a dc bias by means of a photoassisted tunneling relation of the Tien-Gordon type. Specific results are given for an Ohmic environment and for a junction driven through a resonator.

  2. Direct Measurements of the Spatial and Velocity Dependence of the Ion Density Fluctuation Spectrum of a Laboratory Plasma with Two Independent LIF Schemes

    Science.gov (United States)

    Mattingly, Sean; Berumen, Jorge; Chu, Feng; Hood, Ryan; Skiff, Fred

    2014-10-01

    By using two independently tunable lasers, each with its own collection optics and Ar II LIF transition scheme, we are able to investigate plasma ion density fluctuations as a function of not only spatial scales but also as a function of ion velocities as sampled on different points of a single Doppler-broadened spectral emission line. We do this by measuring the two point correlation C (x , v ,x' ,v' , τ) = t . With the current system, the two carriages determine x and x', while the velocities selected by each laser determine v and v'. Using the two lasers to make two point correlations in phase space demonstrates effects that are not fully understood. In this experiment, we explore the striking difference in correlations when, in the past, the particle orbits overlap in space versus when they do not overlap. This is performed on a small cylindrical laboratory plasma with n ~109 cm-3 , Te ~ 5 eV, Ti ~ 0 . 06 , and a 1 kG axial magnetic field. LIF is performed on ions at two locations aligned with the magnetic field line with a viewing volume comparable to the size of the Larmor radius. Results and interpretations from these experiments are presented and discussed. DOE Grant DE-FG02-99ER54543.

  3. Calculation of the X-Ray Spectrum of a Mammography System with Various Voltages and Different Anode-Filter Combinations Using MCNP Code

    OpenAIRE

    Lida Gholamkar; Mahdi Sadeghi; Ali Asghar Mowlavi; Mitra Athari

    2016-01-01

    Introduction One of the best methods in the diagnosis and control of breast cancer is mammography. The importance of mammography is directly related to its value in the detection of breast cancer in the early stages, which leads to a more effective treatment. The purpose of this article was to calculate the X-ray spectrum in a mammography system with Monte Carlo codes, including MCNPX and MCNP5. Materials and Methods The device, simulated using the MCNP code, was Planmed Nuance digital mammog...

  4. Isomerically Pure Tetramethylrhodamine Voltage Reporters.

    Science.gov (United States)

    Deal, Parker E; Kulkarni, Rishikesh U; Al-Abdullatif, Sarah H; Miller, Evan W

    2016-07-27

    We present the design, synthesis, and application of a new family of fluorescent voltage indicators based on isomerically pure tetramethylrhodamines. These new Rhodamine Voltage Reporters, or RhoVRs, use photoinduced electron transfer (PeT) as a trigger for voltage sensing, display excitation and emission profiles in the green to orange region of the visible spectrum, demonstrate high sensitivity to membrane potential changes (up to 47% ΔF/F per 100 mV), and employ a tertiary amide derived from sarcosine, which aids in membrane localization and simultaneously simplifies the synthetic route to the voltage sensors. The most sensitive of the RhoVR dyes, RhoVR 1, features a methoxy-substituted diethylaniline donor and phenylenevinylene molecular wire at the 5'-position of the rhodamine aryl ring, exhibits the highest voltage sensitivity to date for red-shifted PeT-based voltage sensors, and is compatible with simultaneous imaging alongside green fluorescent protein-based indicators. The discoveries that sarcosine-based tertiary amides in the context of molecular-wire voltage indicators prevent dye internalization and 5'-substituted voltage indicators exhibit improved voltage sensitivity should be broadly applicable to other types of PeT-based voltage-sensitive fluorophores.

  5. Effect of Perfluorane on the Amplitude-Frequency Spectrum of Fluctuations in Cerebral Blood Flow in Hemorrhagic Hypotension and During the Reperfusion Period

    Directory of Open Access Journals (Sweden)

    I. A. Ryzhkov

    2015-01-01

    Full Text Available Objective: to use laser Doppler flowmetry (LDF to investigate the effect of perfluorane on the time course of microhemocirculato ry changes in the rat pial vessels in acute blood loss and after autohemotransfusion.Material and methods. Experiments were car ried out on 31 outbred male rats weighing 300—400 g under anesthesia with intraperitoneal Nembutal 45 mg/kg. The caudal artery was catheterized to measure blood pressure (BP, to sample and reinfuse blood, and to administer infusion solutions. LDF (ЛАКК 02 device, LAZMA, Russia was used to record blood flow in the pial vessels of the left parietal region (the center coordinates were 3 mm caudal to bregma and 2 mm left of the sagittal suture. A volumefixed acute blood loss model was applied. The goal amount of blood loss was 30% of the circulating blood volume. At 10 minutes after blood sampling, the animals were administered 0.9% NaCl solution (physiologic saline (PS, n=15 or perfluorane (PF, n=16 in a dose of 3 ml/kg body weight. At 60 minutes following blood sampling, autohemotransfusion was used, after which there was a 60min reperfusion period. The investigators analyzed LDF readings and determined the following indicators: microcirculation index; the maximum amplitudes of blood flow fluctuations in the endothelial, neurogenic, and myogenic frequency ranges by a wavelet analysis. The data were statistically processed using Statistica 7.0 software.Results. Hypovolemia caused a more than 50% reduction in BP; moreover, blood flow in the pial vessels decreased by less than 20% of its baseline level (p<0.05. In the same period, there was an increase in the amplitude of flux motions mainly in the neurogenic (NA frequency. The differences in microcirculatory parameters between the PS or PF groups were in the retention of higher NA in the PS group throughout hypovolemia; at the same time the groups did not differ in the arterial blood levels of the index of perfusion (IP, рСО2, and

  6. A matter of quantum voltages.

    Science.gov (United States)

    Sellner, Bernhard; Kathmann, Shawn M

    2014-11-14

    Voltages inside matter are relevant to crystallization, materials science, biology, catalysis, and aqueous chemistry. The variation of voltages in matter can be measured by experiment, however, modern supercomputers allow the calculation of accurate quantum voltages with spatial resolutions of bulk systems well beyond what can currently be measured provided a sufficient level of theory is employed. Of particular interest is the Mean Inner Potential (V(o))--the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate V(o) from quantum calculations. Voltages are very sensitive to the distribution of electrons and provide metrics to understand interactions in condensed phases. In the present study, we find excellent agreement with measurements of V(o) for vitrified water and salt crystals and demonstrate the impact of covalent and ionic bonding as well as intermolecular/atomic interactions. Certain aspects in this regard are highlighted making use of simple model systems/approximations. Furthermore, we predict V(o) as well as the fluctuations of these voltages in aqueous NaCl electrolytes and characterize the changes in their behavior as the resolution increases below the size of atoms.

  7. Thermodynamic constraints on fluctuation phenomena

    Science.gov (United States)

    Maroney, O. J. E.

    2009-12-01

    The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.

  8. Modeling fluctuations in scattered waves

    CERN Document Server

    Jakeman, E

    2006-01-01

    Fluctuations in scattered waves limit the performance of imaging and remote sensing systems that operate on all wavelengths of the electromagnetic spectrum. To better understand these fluctuations, Modeling Fluctuations in Scattered Waves provides a practical guide to the phenomenology, mathematics, and simulation of non-Gaussian noise models and discusses how they can be used to characterize the statistics of scattered waves.Through their discussion of mathematical models, the authors demonstrate the development of new sensing techniques as well as offer intelligent choices that can be made for system analysis. Using experimental results and numerical simulation, the book illustrates the properties and applications of these models. The first two chapters introduce statistical tools and the properties of Gaussian noise, including results on phase statistics. The following chapters describe Gaussian processes and the random walk model, address multiple scattering effects and propagation through an extended med...

  9. Thermodynamic constraints on fluctuation phenomena.

    Science.gov (United States)

    Maroney, O J E

    2009-12-01

    The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.

  10. 基于混合储能电压源逆变器平抑微电网功率波动的方法研究%Research on the Method for Smoothing Power Fluctuations in Microgrid Based on Hybrid Energy Storage Voltage Source Inverter

    Institute of Scientific and Technical Information of China (English)

    周福举; 张宸宇; 郑建勇; 胡洛蠧

    2014-01-01

    为了平抑间歇性微电源引起的功率波动,研究了基于超级电容和蓄电池的混合储能电压源逆变器(VSI)控制策略,设计了混合储能系统两级能量管理方法。将超级电容作为系统一级缓冲储能优先平抑微电网功率波动。并网运行时配电网作为二级储能,通过控制联络线功率,使超级电容端电压稳定在充放电限值以内,同时维持公共连接点(PCC)母线电压在允许范围内变化;孤岛运行时蓄电池作为二级储能,通过超级电容的缓冲作用减少蓄电池充放电次数,延长蓄电池使用寿命,当超级电容达到充放电警戒值时,精确控制蓄电池以恒功率输出,调节超级电容端电压恢复到正常值。仿真结果验证了方法的有效性。%In order to smooth the power fluctuations caused by intermittent micro power source,the control strategy of hybrid energy storage based on super-capacitor and battery was researched and a two stage management method of hybrid energy storage was designed.To take full advantage of large power density and long cycle life of super-capacitor in charging and discharging,it is used as the first buffer energy storage to smooth the power fluctuations priority in this method.Distribution network is used as second energy storage when the microgrid is under grid-connected operation.The power of tie line is controlled to make the terminal voltage of super-capacitor within limits and maintain PCC bus voltage fluctuation within the permissible range.Battery is used as second energy storage when the microgrid is under island operation.The charging and discharging times of battery are reduced by the buffering effect of super-capacitor and the life of battery is prolonged.When the terminal voltage of super-capacitor reaches to alert value,battery is controlled accurately to constant power output,so the terminal voltage of super-capacitor is returned to normal value.The simulation results

  11. Accurate Switched-Voltage voltage averaging circuit

    OpenAIRE

    金光, 一幸; 松本, 寛樹

    2006-01-01

    Abstract ###This paper proposes an accurate Switched-Voltage (SV) voltage averaging circuit. It is presented ###to compensated for NMOS missmatch error at MOS differential type voltage averaging circuit. ###The proposed circuit consists of a voltage averaging and a SV sample/hold (S/H) circuit. It can ###operate using nonoverlapping three phase clocks. Performance of this circuit is verified by PSpice ###simulations.

  12. Was The Electromagnetic Spectrum A Blackbody Spectrum In The Early Universe?

    OpenAIRE

    Opher, Merav; Opher,Reuven

    1997-01-01

    It is assumed, in general, that the electromagnetic spectrum in the Primordial Universe was a blackbody spectrum in vacuum. We derive the electromagnetic spectrum, based on the Fluctuation-Dissipation Theorem that describes the electromagnetic fluctuations in a plasma. Our description includes thermal and collisional effects in a plasma. The electromagnetic spectrum obtained differs from the blackbody spectrum in vacuum at low frequencies. In particular, concentrating on the primordial nucleo...

  13. Model-based x-ray energy spectrum estimation algorithm from CT scanning data with spectrum filter

    Science.gov (United States)

    Li, Lei; Wang, Lin-Yuan; Yan, Bin

    2016-10-01

    With the development of technology, the traditional X-ray CT can't meet the modern medical and industry needs for component distinguish and identification. This is due to the inconsistency of X-ray imaging system and reconstruction algorithm. In the current CT systems, X-ray spectrum produced by X-ray source is continuous in energy range determined by tube voltage and energy filter, and the attenuation coefficient of object is varied with the X-ray energy. So the distribution of X-ray energy spectrum plays an important role for beam-hardening correction, dual energy CT image reconstruction or dose calculation. However, due to high ill-condition and ill-posed feature of system equations of transmission measurement data, statistical fluctuations of X ray quantum and noise pollution, it is very hard to get stable and accurate spectrum estimation using existing methods. In this paper, a model-based X-ray energy spectrum estimation method from CT scanning data with energy spectrum filter is proposed. First, transmission measurement data were accurately acquired by CT scan and measurement using phantoms with different energy spectrum filter. Second, a physical meaningful X-ray tube spectrum model was established with weighted gaussian functions and priori information such as continuity of bremsstrahlung and specificity of characteristic emission and estimation information of average attenuation coefficient. The parameter in model was optimized to get the best estimation result for filtered spectrum. Finally, the original energy spectrum was reconstructed from filtered spectrum estimation with filter priori information. Experimental results demonstrate that the stability and accuracy of X ray energy spectrum estimation using the proposed method are improved significantly.

  14. Temperature fluctuations in an inhomogeneous diffusive fluid

    CERN Document Server

    Haba, Z

    2014-01-01

    We discuss metric perturbations of the relativistic diffusion equation around the homogeneous Juttner equilibrium of massless particles in a homogeneous expanding universe. The metric perturbation describes matter distribution and the gravitational wave background in an inhomogeneous universe. We show that the lowest order perturbation can be treated as a variation of temperature. We derive a formula expressing temperature fluctuations in terms of the diffusion and tensor power spectrum. We discuss the multipole expansion of the fluctuations in the presence of diffusion.

  15. Shaping the spectra of the line-to-line voltage using signal injection in the common mode voltage

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Rasmussen, Peter Omand; Pedersen, John Kim

    2009-01-01

    A drawback of Pulse Width Modulation in electrical drives is the high harmonic content of the line to line voltages, which gives rise to Electro-Magnetic Interference and acoustic noise. By injection of a signal into the common mode voltage, the fundamental is not affected, but new frequency...... components are introduced in the line to line voltage spectrum. This paper introduces a new analytical method for estimation of the line to line voltage spectrum, where sinusoidal signal is injected into the common mode voltage. Based on the analytical calculations, also a new fixed carrier frequency quasi...

  16. Homeostatic fluctuations of a tissue surface

    CERN Document Server

    Risler, Thomas; Prost, Jacques

    2015-01-01

    We study the surface fluctuations of a tissue with a dynamics dictated by cell-rearrangement, cell-division and cell-death processes. Surface fluctuations are calculated in the homeostatic state, where cell division and cell death equilibrate on average. The obtained fluctuation spectrum can be mapped onto several other spectra such as those characterizing incompressible fluids, compressible Maxwell elastomers or permeable membranes in appropriate asymptotic regimes. Since cell division and cell death are out-of-equilibrium processes, detailed balance is broken, but a generalized fluctuation-response relation is satisfied in terms of appropriate observables. Our work is a first step toward the description of the out-of-equilibrium fluctuations of the surface of a thick epithelium and its dynamical response to external perturbations.

  17. Classical and quantum temperature fluctuations via holography

    Energy Technology Data Exchange (ETDEWEB)

    Balatsky, Alexander [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Institute for Materials Science, Los Alamos National Laboratory,Los Alamos, NM 87545 (United States); Gudnason, Sven Bjarke; Kedem, Yaron [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Krikun, Alexander [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Institute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation); Thorlacius, Lárus [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); University of Iceland, Science Institute,Dunhaga 3, IS-107 Reykjavik (Iceland); The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics,Stockholm University, AlbaNova University Centre, 10691 Stockholm (Sweden); Zarembo, Konstantin [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Institute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation); Department of Physics and Astronomy, Uppsala University,SE-751 08 Uppsala (Sweden)

    2015-01-07

    We study local temperature fluctuations in a 2+1 dimensional CFT on the sphere, dual to a black hole in asymptotically AdS spacetime. The fluctuation spectrum is governed by the lowest-lying hydrodynamic modes of the system whose frequency and damping rate determine whether temperature fluctuations are thermal or quantum. We calculate numerically the corresponding quasinormal frequencies and match the result with the hydrodynamics of the dual CFT at high temperature. As a by-product of our analysis we determine the appropriate boundary conditions for calculating low-lying quasinormal modes for a four-dimensional Reissner-Nordström black hole in global AdS.

  18. Transition to turbulence, intermittence, and vortex fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Bershadskii, A.G.

    1985-09-01

    A model is developed which describes the fluctuation coalescence of vortices at moderately high Reynolds numbers. The model is found to be in good agreement with experimental data on (1) flow intermittence in a boundary layer, a round jet, and a plane wake; (2) the effect of a magnetic field on the formation of a turbulent energy spectrum behind a grid and on turbulent fluctuations and friction in ducts; (3) formation of a turbulent energy spectrum in a boundary layer and in ducts. 12 references.

  19. A thermoelectric voltage effect in polyethylene oxide

    CERN Document Server

    Martin, B; Kliem, H

    2003-01-01

    The conductivity of polyethylene oxide (PEO) is described with a three-dimensional hopping model considering electrostatic interactions between the ions. Ions fluctuate over energy-barriers in a multi-well potential. To decide whether positive or negative charges are responsible for this conductivity, the thermoelectric voltage is measured. The samples are embedded between two aluminium-electrodes. The oxide on the interface between the electrodes and the PEO serves as a blocking layer. The temperature of each electrode is controlled by a Peltier element. A temperature step is applied to one electrode by changing the temperature of one of the Peltier elements. Due to this temperature gradient, the mobile charges fluctuate thermally activated from the warmer side to the colder side of the sample. The direction of the measured thermoelectric voltage indicates the type of mobile charges. It is found that positive charges are mobile. Further, it is shown that the absolute value of the thermoelectric voltage depen...

  20. L{sub p} norm approaches for estimating voltage flicker

    Energy Technology Data Exchange (ETDEWEB)

    Inan, Aslan [Department of Electrical Engineering, Faculty of Electrical-Electronics, Yildiz Technical University, Istanbul (Turkey); Bakroun, Maher [Antrim Crescent, Toronto, Ontario (Canada); Heydt, Gerald T. [Fulton School of Engineering, Arizona State University, Tempe, AZ (United States)

    2010-12-15

    It is important to accurately estimate instantaneous voltage flicker magnitudes and frequencies in order to correctly evaluate voltage fluctuations. Voltage flicker is a problem in electric power quality. Different approaches used to determine the magnitude of the voltage flicker have been presented: measurement methods generally use a flickermeter device. Simulation methods require a computer model of the disturbing load and the flickermeter. Calculation methods necessitate a simplified empirical formula. Estimation algorithms are based on the estimation of the voltage flicker components. In this paper, two models of voltage flicker are discussed: L{sub p} estimation algorithms utilizing L{sub 1}, L{sub 2} and L{sub {infinity}} norms are used to estimate the voltage magnitudes of the flicker signals as well as the fundamental voltage magnitude. The main result is that it is possible to design an L{sub p} estimator to identify flicker frequency and amplitude from time series measurements. (author)

  1. Thermal fluctuations in loop cosmology

    CERN Document Server

    Magueijo, J; Magueijo, Joao; Singh, Parampreet

    2007-01-01

    Quantum gravitational effects in loop quantum cosmology lead to a resolution of the initial singularity and have the potential to solve the horizon problem and generate a quasi scale-invariant spectrum of density fluctuations. We consider loop modifications to the behavior of the inverse scale factor below a critical scale in closed models and assume a purely thermal origin for the fluctuations. We show that the no-go results for scale invariance in classical thermal models can be evaded even if we just consider modifications to the background (zeroth order) gravitational dynamics. Since a complete and systematic treatment of the perturbed Einstein equations in loop cosmology is still lacking, we simply parameterize their expected modifications. These change quantitatively, but not qualitatively, our conclusions. We thus urge the community to more fully work out this complex aspect of loop cosmology, since the full picture would not only fix the free parameters of the theory, but also provide a model for a no...

  2. Algorithm refinement for fluctuating hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.

    2007-07-03

    This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.

  3. Chemical Measurement and Fluctuation Scaling.

    Science.gov (United States)

    Hanley, Quentin S

    2016-12-20

    Fluctuation scaling reports on all processes producing a data set. Some fluctuation scaling relationships, such as the Horwitz curve, follow exponential dispersion models which have useful properties. The mean-variance method applied to Poisson distributed data is a special case of these properties allowing the gain of a system to be measured. Here, a general method is described for investigating gain (G), dispersion (β), and process (α) in any system whose fluctuation scaling follows a simple exponential dispersion model, a segmented exponential dispersion model, or complex scaling following such a model locally. When gain and dispersion cannot be obtained directly, relative parameters, GR and βR, may be used. The method was demonstrated on data sets conforming to simple, segmented, and complex scaling. These included mass, fluorescence intensity, and absorbance measurements and specifications for classes of calibration weights. Changes in gain, dispersion, and process were observed in the scaling of these data sets in response to instrument parameters, photon fluxes, mathematical processing, and calibration weight class. The process parameter which limits the type of statistical process that can be invoked to explain a data set typically exhibited 0 4 possible. With two exceptions, calibration weight class definitions only affected β. Adjusting photomultiplier voltage while measuring fluorescence intensity changed all three parameters (0 < α < 0.8; 0 < βR < 3; 0 < GR < 4.1). The method provides a framework for calibrating and interpreting uncertainty in chemical measurement allowing robust comparison of specific instruments, conditions, and methods.

  4. Magnetic fluctuations in UNi4B

    DEFF Research Database (Denmark)

    Mentink, S.A.M.; Mason, T.E.; Buyers, W.J.L.;

    1997-01-01

    We investigate the magnetic fluctuation spectrum of the geometrically frustrated antiferromagnetic compound UNi4B, which partially orders below T-N = 20 K. An overdamped spin excitation is observed at the AF wave vector around 2.4 meV. Low-frequency, weakly Q-dependent inelastic scattering...

  5. Transient Voltage Recorder

    Science.gov (United States)

    Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

    2002-01-01

    A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

  6. Performance of Three-Arm Ac Automatic Voltage Regulator

    Directory of Open Access Journals (Sweden)

    T. Papinaidu

    2014-04-01

    Full Text Available In this paper the design and simulation of automatic voltage regulator (AVR is proposed. The AVR provides voltage buck and boost capability to eliminate power problems created by under voltage or over voltage fluctuations. It also protects against minor and severe spikes and surges that comprise over 80% of power problems. Over heating of components due to voltage swell is also avoided by using AVR. The switching losses are also reduced as only one arm among three arms is maintained at higher power frequencies depending on mode of operation. Moreover, there is no need to use large capacitor as a result the overall size of converter is also reduced. Hence, the output voltage of the AVR can be maintained at the specified voltage. Hence, the AVR is cost can be reduced, and the efficiency of the power convertor can be extended.

  7. Fluctuations and structure of amphiphilic films; Fluctuations et structure de films d`amphiphiles

    Energy Technology Data Exchange (ETDEWEB)

    Gourier, CH

    1996-07-01

    This thesis is divided in three parts.The first part exposes in a theoretical point of view, how the fluctuations spectrum of an amphiphilic film is governed by its properties and its bidimensional characteristics.The measurements of fluctuations spectra of an interface are accessible with the measurement of intensity that interface diffuses out of the specular angle, we present in the second chapter the principles of the X rays diffusion by a real interface and see how the diffuse diffusion experiments allow to determine the fluctuations spectrum of an amphiphilic film. The second part is devoted to the different experimental techniques that have allowed to realize the study of fluctuation as well as the structural study.The third part is devoted to experimental results concerning the measurements of fluctuations spectra and to the study of the structure of amphiphilic films. We show that it is possible by using an intense source of X rays (ESRF: European Synchrotron Radiation Facility) to measure the water and amphiphilic films fluctuations spectra until molecular scales. The last chapter is devoted to the structural study and film fluctuations made of di-acetylenic molecules. (N.C.)

  8. Simulating the spectrum of neutrons produced by a radiation beam of high voltage inside an anthropomorphic phantom; Simulacion de espectro de nuetrones producido por un haz de radioterapia de alto voltaje en el interior de un manique antropomorfico

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Soto, X.; Amgarou, K.; Langares, J. I.; Munez, J. L.; Mendez, R.; Exposito, M. R.; Gomez, F.; Domingo, C.; Sanche-Doblado, F.

    2011-07-01

    Our project aims to provide a universal method to estimate the dose deposited by neutrons in patients, using an anthropomorphic phantom. Both the detector response as relative biological effectiveness have a strong dependence on the energy spectrum of those, for this reason, a series of simulations were performed to calculate the spectrum of the neutron fluence in 16 representative points within the anthropomorphic phantom Standard for a full course of radiotherapy.

  9. Fluctuation relations for spintronics.

    Science.gov (United States)

    López, Rosa; Lim, Jong Soo; Sánchez, David

    2012-06-15

    Fluctuation relations are derived in systems where the spin degree of freedom and magnetic interactions play a crucial role. The form of the nonequilibrium fluctuation theorems relies on the assumption of a local balance condition. We demonstrate that in some cases the presence of magnetic interactions violates this condition. Nevertheless, fluctuation relations can be obtained from the microreversibility principle sustained only at equilibrium as a symmetry of the cumulant generating function for spin currents. We illustrate the spintronic fluctuation relations for a quantum dot coupled to partially polarized helical edge states.

  10. Automatic voltage imbalance detector

    Science.gov (United States)

    Bobbett, Ronald E.; McCormick, J. Byron; Kerwin, William J.

    1984-01-01

    A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

  11. Mixed voltage VLSI design

    Science.gov (United States)

    Panwar, Ramesh; Rennels, David; Alkalaj, Leon

    1993-01-01

    A technique for minimizing the power dissipated in a Very Large Scale Integration (VLSI) chip by lowering the operating voltage without any significant penalty in the chip throughput even though low voltage operation results in slower circuits. Since the overall throughput of a VLSI chip depends on the speed of the critical path(s) in the chip, it may be possible to sustain the throughput rates attained at higher voltages by operating the circuits in the critical path(s) with a high voltage while operating the other circuits with a lower voltage to minimize the power dissipation. The interface between the gates which operate at different voltages is crucial for low power dissipation since the interface may possibly have high static current dissipation thus negating the gains of the low voltage operation. The design of a voltage level translator which does the interface between the low voltage and high voltage circuits without any significant static dissipation is presented. Then, the results of the mixed voltage design using a greedy algorithm on three chips for various operating voltages are presented.

  12. Spontaneous emission of Alfvénic fluctuations

    Science.gov (United States)

    Yoon, P. H.; López, R. A.; Vafin, S.; Kim, S.; Schlickeiser, R.

    2017-09-01

    Low-frequency fluctuations are pervasively observed in the solar wind. The present paper theoretically calculates the steady state spectra of low-frequency electromagnetic (EM) fluctuations of the Alfvénic type for thermal equilibrium plasma. The analysis is based upon a recently formulated theory of spontaneously emitted EM fluctuations in magnetized thermal plasmas. It is found that the fluctuations in the magnetosonic mode branch is constant, while the kinetic Alfvénic mode spectrum is dependent on a form factor that is a function of perpendicular wave number. Potential applicability of the present work in the wider context of heliospheric research is also discussed.

  13. Adaptive Voltage Control Strategy for Variable-Speed Wind Turbine Connected to a Weak Network

    DEFF Research Database (Denmark)

    Abulanwar, Elsayed; Hu, Weihao; Chen, Zhe

    2016-01-01

    Significant voltage fluctuations and power quality issues pose considerable constraints on the efficient integration of remotely located wind turbines into weak networks. Besides, 3p oscillations arising from the wind shear and tower shadow effects induce further voltage perturbations during...... continuous operation. This study investigates and analyses the repercussions raised by integrating a doubly-fed induction generator wind turbine into an ac network of different parameters and very weak conditions. An adaptive voltage control (AVC) strategy is proposed to retain voltage constancy...

  14. Origin of density fluctuations in extended inflation

    Science.gov (United States)

    Kolb, Edward W.; Salopek, David S.; Turner, Michael S.

    1990-01-01

    The density fluctuations (both curvature and isocurvature) that arise due to quantum fluctuations in a simple model of extended inflation based upon the Jordan-Brans-Dicke theory are calculated. Curvature fluctuations arise due to quantum fluctuations in the Brans-Dicke field, in general have a nonscale-invariant spectrum, and can have an amplitude that is cosmologically acceptable and interesting without having to tune any coupling constant to a very small value. The density perturbations that arise due to the inflation field are subdominant. If there are other massless fields in the theory, e.g., an axion or an ilion, then isocurvature fluctuations arise in these fields too. Production of gravitational waves and the massless particles associated with excitations of the Brans-Dicke field are also discussed. Several attempts at more realistic models of extended inflation are also analyzed. The importance of the Einstein conformal frame in calculating curvature fluctuations is emphasized. When viewed in this frame, extended inflation closely resembles slow-rollover inflation with an exponential potential and the usual formula for the amplitude of curvature perturbations applies.

  15. CNFET Based Voltage Differencing Transconductance Amplifier

    Science.gov (United States)

    Laxya; Prasad, Dinesh; Mainuddin; Islam, S. S.

    2017-08-01

    In CMOS Technology basic Problem mainly includes dopant fluctuation, tunnelling effect and line edge roughness below 45nm technology. Carbon Nanotube based structures is better option for widen the Moore’s law due to its scalability channel electrostatics and higher mobility. In this manuscript we demonstrate an optimum design for linear property of CNTFET based VDTA at 32nm technology node. The proposed circuit consist of VDTA with CNTFET having two voltage input and two current outputs so that it works as voltage and transconductance operation to obtain the high performance. The minimum supply voltages of ±0.9V with 32nm technology mode are used. The CNTFET-VDTA performance is simulated on HSPICE. In this paper CNFET-based VDTA provides better results of DC transfer characteristics as compared with CMOS. All the simulation results are performed on HSPICE.

  16. Automatic Voltage Control (AVC) System under Uncertainty from Wind Power

    DEFF Research Database (Denmark)

    Qin, Nan; Abildgaard, Hans; Flynn, Damian

    2016-01-01

    An automatic voltage control (AVC) system maintains the voltage profile of a power system in an acceptable range and minimizes the operational cost by coordinating the regulation of controllable components. Typically, all of the parameters in the optimization problem are assumed to be certain...... and constant in the decision making process. However, for high shares of wind power, uncertainty in the decision process due to wind power variability may result in an infeasible AVC solution. This paper proposes a voltage control approach which considers the voltage uncertainty from wind power productions....... The proposed method improves the performance and the robustness of a scenario based approach by estimating the potential voltage variations due to fluctuating wind power production, and introduces a voltage margin to protect the decision against uncertainty for each scenario. The effectiveness of the proposed...

  17. DC-link Voltage Control to Compensate Voltage Deviation for PV–BESSs Integrated System in Low-Voltage (LV Networks

    Directory of Open Access Journals (Sweden)

    Lee Gyu-sub

    2016-01-01

    Full Text Available The exhaustion of fossil fuel and the greenhouse gas emission are one of the most significant energy and environmental issues, respectively. Photovoltaic (PV generators and battery energy storage systems (BESSs have been significantly increased for recent years. The BESSs are mainly used for smoothing active power fluctuation of the PV. In this paper, PV–BESSs integration of two DC/DC converters and one AC/DC converter is investigated and DC-link voltage control to compensate the AC voltage deviation is proposed for the PV‒BESS system in low-voltage (LV networks.

  18. Power and heat fluctuation theorems for electric circuits.

    Science.gov (United States)

    van Zon, R; Ciliberto, S; Cohen, E G D

    2004-04-02

    Using recent fluctuation theorems from nonequilibrium statistical mechanics, we extend the theory for voltage fluctuations in electric circuits to power and heat fluctuations. They could be of particular relevance for the functioning of small circuits. This is done for a parallel resistor and capacitor with a constant current source for which we use the analogy with a Brownian particle dragged through a fluid by a moving harmonic potential, where circuit-specific analogs are needed on top of the Brownian-Nyquist analogy. The results may also hold for other circuits as another example shows.

  19. Hadronic Correlations and Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Volker

    2008-10-09

    We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

  20. Continuous information flow fluctuations

    Science.gov (United States)

    Rosinberg, Martin Luc; Horowitz, Jordan M.

    2016-10-01

    Information plays a pivotal role in the thermodynamics of nonequilibrium processes with feedback. However, much remains to be learned about the nature of information fluctuations in small-scale devices and their relation with fluctuations in other thermodynamics quantities, like heat and work. Here we derive a series of fluctuation theorems for information flow and partial entropy production in a Brownian particle model of feedback cooling and extend them to arbitrary driven diffusion processes. We then analyze the long-time behavior of the feedback-cooling model in detail. Our results provide insights into the structure and origin of large deviations of information and thermodynamic quantities in autonomous Maxwell's demons.

  1. Quantum Fractal Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Benenti, Giuliano; Casati, Giulio; Guarneri, Italo; Terraneo, Marcello

    2001-07-02

    We numerically analyze quantum survival probability fluctuations in an open, classically chaotic system. In a quasiclassical regime and in the presence of classical mixed phase space, such fluctuations are believed to exhibit a fractal pattern, on the grounds of semiclassical arguments. In contrast, we work in a classical regime of complete chaoticity and in a deep quantum regime of strong localization. We provide evidence that fluctuations are still fractal, due to the slow, purely quantum algebraic decay in time produced by dynamical localization. Such findings considerably enlarge the scope of the existing theory.

  2. Spatial fluctuation theorem

    Science.gov (United States)

    Pérez-Espigares, Carlos; Redig, Frank; Giardinà, Cristian

    2015-08-01

    For non-equilibrium systems of interacting particles and for interacting diffusions in d-dimensions, a novel fluctuation relation is derived. The theorem establishes a quantitative relation between the probabilities of observing two current values in different spatial directions. The result is a consequence of spatial symmetries of the microscopic dynamics, generalizing in this way the Gallavotti-Cohen fluctuation theorem related to the time-reversal symmetry. This new perspective opens up the possibility of direct experimental measurements of fluctuation relations of vectorial observables.

  3. Fluctuation-Enhanced Sensing of Bacterium Odors

    CERN Document Server

    Chang, Hung-Chih; King, Maria D; Kwan, Chiman

    2009-01-01

    The goal of this paper is to explore the possibility to detect and identify bacteria by sensing their odor via fluctuation-enhanced sensing with commercial Taguchi sensors. The fluctuations of the electrical resistance during exposure to different bacterial odors, Escherichia coli and anthrax-surrogate Bacillus subtilis, have been measured and analyzed. In the present study, the simplest method, the measurement and analysis of power density spectra was used. The sensors were run in the normal heated and the sampling-and-hold working modes, respectively. The results indicate that Taguchi sensors used in these fluctuation-enhanced modes are effective tools of bacterium detection and identification even when they are utilizing only the power density spectrum of the stochastic sensor signal.

  4. Classical and quantum temperature fluctuations via holography

    Energy Technology Data Exchange (ETDEWEB)

    Balatsky, Alexander V. [KTH Royal Inst. of Technology, Stockholm (Sweden); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gudnason, Sven Bjarke [KTH Royal Inst. of Technology, Stockholm (Sweden); Thorlacius, Larus [KTH Royal Inst. of Technology, Stockholm (Sweden); University of Iceland, Reykjavik (Iceland); Zarembo, Konstantin [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Uppsala Univ. (Sweden); Krikun, Alexander [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Kedem, Yaron [KTH Royal Inst. of Technology, Stockholm (Sweden)

    2014-05-27

    We study local temperature fluctuations in a 2+1 dimensional CFT on the sphere, dual to a black hole in asymptotically AdS space-time. The fluctuation spectrum is governed by the lowest-lying hydrodynamic sound modes of the system whose frequency and damping rate determine whether temperature fluctuations are thermal or quantum. We calculate numerically the corresponding quasinormal frequencies and match the result with the hydrodynamics of the dual CFT at large temperature. As a by-product of our analysis we determine the appropriate boundary conditions for calculating low-lying quasinormal modes for a four-dimensional Reissner-Nordstrom black hole in global AdS.

  5. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D C

    2013-01-01

    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  6. Fluctuations of fragment observables

    CERN Document Server

    Gulminelli, F

    2006-01-01

    This contribution presents a review of our present theoretical as well as experimental knowledge of different fluctuation observables relevant to nuclear multifragmentation. The possible connection between the presence of a fluctuation peak and the occurrence of a phase transition or a critical phenomenon is critically analyzed. Many different phenomena can lead both to the creation and to the suppression of a fluctuation peak. In particular, the role of constraints due to conservation laws and to data sorting is shown to be essential. From the experimental point of view, a comparison of the available fragmentation data reveals that there is a good agreement between different data sets of basic fluctuation observables, if the fragmenting source is of comparable size. This compatibility suggests that the fragmentation process is largely independent of the reaction mechanism (central versus peripheral collisions, symmetric versus asymmetric systems, light ions versus heavy ion induced reactions). Configurationa...

  7. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

    2008-04-09

    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  8. High voltage engineering

    CERN Document Server

    Rizk, Farouk AM

    2014-01-01

    Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

  9. High voltage test techniques

    CERN Document Server

    Kind, Dieter

    2001-01-01

    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  10. Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

    OpenAIRE

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar; Cecati, Carlo

    2013-01-01

    Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbala...

  11. 阶梯型脉冲电压诱导连续能量质子谱数值仿真%Numerical simulation of proton generation with continuous energy spectrum by pulse voltage with discrete steps

    Institute of Scientific and Technical Information of China (English)

    石经纬; 汪志健; 巩春志; 田修波; 杨士勤

    2011-01-01

    The performance degradation of spacecraft thermal control coatings irradiated by protons is generally investigated by using protons with the same energy in ground testing while the energy of protons is in succession in space. The irradiation e-quivalence of the two kinds of protons is still not well understood. In this paper, a method of producing protons with continuous energy by plasma sheath acceleration using pulse voltage with discrete steps is proposed for better analysis of irradiation equivalence. The dose-energy distribution on the sample is numerically investigated by particle-in-cell(PIC) method. The characteristics of dose-energy distribution and the formation mechanism of protons with continuous energy are then discussed. The results show that protons with continuous energy can be realized utilizing pulse voltage with discrete steps, as the energy of protons irradiating the sample overlaps between two adjacent 1 μs periods, and the energy of protons produced is closely related to the voltage on the sample in every 1 μs period. Moreover, the number of protons irradiating the sample may decrease if the proton energy increases.%热控涂层质子辐照的地面模拟研究中采用单一能量质子替代空间能量连续分布的质子,连续能量质子谱是其等效性研究的关键.提出了采用阶梯型脉冲负偏压鞘层加速技术在一个脉冲宽度内获得连续能量质子谱的方法,并利用质点网格法对所获得质子谱的剂量-能量关系进行了数值仿真研究,分析了连续能量质子谱的剂量-能量分布特征及连续能量质子谱的形成过程.结果表明:阶梯型脉冲负偏压鞘层加速能够产生连续能量的质子谱,连续谱是每微秒区间入射到样品的质子叠加而成的,且每个区间所产生质子的能量与该区间电压值相对应,连续谱中,随着质子能量的增加,其剂量总体上呈现下降的趋势.

  12. Optical voltage sensors: principle, problem and research proposal

    Science.gov (United States)

    Li, Changsheng

    2016-10-01

    Sensing principles and main problems to be solved for optical voltage sensors are briefly reviewed. Optical effects used for voltage sensing usually include electro-optic Pockels and Kerr effects, electro-gyration effect, elasto-optical effect, and electroluminescent effects, etc. In principle, typical optical voltage sensor is based on electro-optic Pockels crystals and closed-loop signal detection scheme. Main problems to be solved for optical voltage sensors include: how to remove influence of unwanted multiple optical effects on voltage sensing performance; how to select or develop a proper voltage sensing material and element; how to keep optical phase bias to be stable under temperature fluctuation and vibration; how to achieve dc voltage sensing, etc. In order to suppress the influence of unwanted optical effects and light beam coupling-related loss on voltage sensing signals, we may pay more attention to all-fiber and waveguide voltage sensors. Voltage sensors based on electroluminescent effects are also promising in some application fields due to their compact configuration, low cost and potential long-term reliability.

  13. 1/f noise in music and speech. [Power spectrum studies

    Energy Technology Data Exchange (ETDEWEB)

    Voss, R.F.; Clarke, J.

    1975-11-27

    The power spectrum, S(f), of many fluctuating physical variables, V(t), is approximately ''1/f-like.'' Loudness fluctuations in music and speech and pitch (melody) fluctuations in music were found to exhibit 1/f power spectra. This observation has implications for stochastic music composition. 3 figures. (RWR)

  14. Voltage verification unit

    Science.gov (United States)

    Martin, Edward J.

    2008-01-15

    A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

  15. Application of VSC-HVDC with Shunt Connected SMES for Compensation of Power Fluctuation

    Science.gov (United States)

    Linn, Zarchi; Kakigano, Hiroaki; Miura, Yushi; Ise, Toshifumi

    This paper describes the application of VSC-HVDC (High Voltage DC Transmission using Voltage Source Converter) with shunt connected SMES (Superconducting Magnetic Energy Storage) for compensation of power fluctuation caused by fluctuating power source such as photovoltaics and wind turbines. The objectives of this proposed system is to smooth out fluctuating power in one terminal side of HVDC in order to avoid causing power system instability and frequency deviation by absorbing or providing power according to the system requirement while another terminal side power is fluctuated. The shunt connected SMES charges and discharges the energy to and from the dc side and it compensates required power of fluctuation to obtain constant power flow in one terminal side of VSC-HVDC system. This system configuration has ability for power system stabilization in the case of power fluctuation from natural energy source. PSCAD/EMTDC simulation is used to evaluate the performance of applied system configuration and control method.

  16. Line edge roughness induced threshold voltage variability in nano-scale FinFETs

    Science.gov (United States)

    Rathore, Rituraj Singh; Sharma, Rajneesh; Rana, Ashwani K.

    2017-03-01

    In aggressively scaled devices, the FinFET technology has become more prone to line edge roughness (LER) induced threshold voltage variability. As a result, nano scale FinFET structures face the problem of intrinsic statistical fluctuations in the threshold voltage. This paper describes the all LER induced variability of threshold voltage for 14 nm underlap FinFET using 3-D numerical simulations. It is concluded that percentage threshold voltage (VTH) fluctuations referenced with respect to rectangular FinFET can go up to 8.76%. This work has also investigated the impact of other sources of variability such as random dopant fluctuation, work function variation and oxide thickness variation on threshold voltage.

  17. DC Voltage Control Strategy for CHB-STATCOM during Capacitive-Inductive Load Transition

    Directory of Open Access Journals (Sweden)

    Bo Zhao

    2012-11-01

    Full Text Available Fluctuation of DC capacitor voltage of CHC-STATCOM(Cascaded H-Bridge Converter Based STATCOM during capacitive-inductive load transition affects the dynamic response of the equipment and, with combination of other factors like of the switching devices, can degrade the stability of the equipment. This paper illustrates the cause ofthe voltage fluctuation and proposes a novel and practical control strategy to suppress it. A simulation was conducted to testify its effectiveness.

  18. 基于双音外差的电光相位调制器半波电压自校准测量方法∗%Two-tone optical hetero dyning metho d for the self-calibrated measurement of half-wave voltage of electro optic phase mo dulator

    Institute of Scientific and Technical Information of China (English)

    王恒; 张尚剑; 邹新海; 刘俊伟; 张雅丽; 李和平; 刘永

    2015-01-01

    High speed electrooptic phase modulators play very important roles in the high-speed optical fiber communication system, microwave photonic system, and coherent optical communication system, due to their advantages of bias voltage free and linear modulation. As an intrinsic parameter, the half-wave voltage of an electrooptic phase modulator has been characterized by using an electrical spectrum method and an optical spectrum method in the last two decades. The op-tical spectrum method is generally limited by the line-width of the laser source and the resolution of the available optical spectrum analyzer, while the electrical spectrum method requires the conversion from phase modulation to intensity modulation before photodetection, since a phase modulator generates a phase modulated optical signal with constant envelope. The major difficulty in the electrical spectrum method lies in the extra calibration for the responsivity fluctu-ation in the photodetection. In this paper, a novel self-calibrated measurement of half-wave voltage of electrooptic phase modulators is carried out based on the optical heterodyning between the two-tone phase modulated sidebands and the frequency-shifted carrier. The method achieves a self-calibration measurement, and avoids the effect of the responsivity fluctuation in the photodetection by setting a specific frequency relationship between the two-tone microwave signals. Moreover, it extends the measuring frequency range to the double bandwidth of photodetection and spectrum analysis. Compared with the optical spectrum method, the proposed method achieves very high frequency resolution measure-ment, and simultaneously avoids the line-width influence of laser source by use of two-tone heterodyning. Compared with the traditional electrical spectrum method, our method works under no small-signal assumption nor photodetection calibration, and eliminates the limits of electrical driving amplitude and operating wavelength. Moreover, it

  19. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev

    2008-09-01

    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  20. The fluctuating gap model

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Xiaobin

    2011-01-15

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T{sub c} in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the

  1. Event-by-Event Fluctuations

    OpenAIRE

    2003-01-01

    In this review, we systematically examine the principles and the practices of fluctuations such as the momentum and the charge fluctuations as applied to the heavy ion collisions. Main emphases are: (i) Fluctuations as signals of phase transition (ii) Relationship between correlation functions and fluctuations (iii) Qualitative difference between fluctuations in small systems and large systems. Whenever available, theoretical results are compared with data from RHIC and SPS.

  2. Low Mach Number Fluctuating Hydrodynamics of Diffusively Mixing Fluids

    CERN Document Server

    Donev, A; Sun, Y; Fai, T; Garcia, A L; Bell, J B

    2012-01-01

    We formulate low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different density and transport coefficients. These equations eliminate the fast isentropic fluctuations in pressure associated with the propagation of sound waves by replacing the equation of state with a local thermodynamic constraint. We demonstrate that the low Mach number model preserves the spatio-temporal spectrum of the slower diffusive fluctuations. We develop a strictly conservative finite-volume spatial discretization of the low Mach number fluctuating equations in both two and three dimensions. We construct several explicit Runge-Kutta temporal integrators that strictly maintain the equation of state constraint. The resulting spatio-temporal discretization is second-order accurate deterministically and maintains fluctuation-dissipation balance in the linearized stochastic equations. We apply our algorithms to model the development of giant concentration fl...

  3. High Voltage Distribution

    Science.gov (United States)

    Norbeck, Edwin; Miller, Michael; Onel, Yasar

    2010-11-01

    For detector arrays that require 5 to 10 kV at a few microamps each for hundreds of detectors, using hundreds of HV power supplies is unreasonable. Bundles of hundreds of HV cables take up space that should be filled with detectors. A typical HV module can supply 1 ma, enough current for hundreds of detectors. It is better to use a single HV module and distribute the current as needed. We show a circuit that, for each detector, measures the current, cuts off the voltage if the current exceeds a set maximum, and allows the HV to be turned on or off from a control computer. The entire array requires a single HV cable and 2 or 3 control lines. This design provides the same voltage to all of the detectors, the voltage set by the single HV module. Some additional circuitry would allow a computer controlled voltage drop between the HV and each individual detector.

  4. Four-Switch Three-Phase PMSM Converter with Output Voltage Balance and DC-Link Voltage Offset Suppression

    Directory of Open Access Journals (Sweden)

    Fadil Hicham

    2017-01-01

    Full Text Available High power quality, efficiency, complexity, size, cost effectiveness and switching losses of the direct current to alternating current (DC–AC conversion system are crucial aspects in industrial applications. Therefore, the four-switch three-phase inverter (4S3P has been proposed as an innovative inverter design. However, this topology has been known to have many performance limitations in the low-frequency region, because of the generation of an unbalanced voltage leading to an unbalanced current due to the fluctuation and offset of the centre tap voltage of the DC-link capacitors. Those drawbacks are investigated and solved in this paper in order to provide pure sinusoidal output voltages. The generated output voltages are controlled using proportional-integral (PI controllers to follow the desired voltages. Furthermore, the DC-link capacitor voltage offset is mitigated by subtracting the direct component from the control reference voltage using low pass filters, where this direct voltage component provides the direct current component which leads to DC-link capacitor voltage divergence. A simulation model and experimental setup are used to validate the proposed concept. Many simulation and experimental results are carried out to show the effectiveness of the proposed control scheme.

  5. Quantum-gravity fluctuations and the black-hole temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

    2015-05-15

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  6. Fluctuating Asymmetry and Intelligence

    Science.gov (United States)

    Bates, Timothy C.

    2007-01-01

    The general factor of mental ability ("g") may reflect general biological fitness. If so, "g"-loaded measures such as Raven's progressive matrices should be related to morphological measures of fitness such as fluctuating asymmetry (FA: left-right asymmetry of a set of typically left-right symmetrical body traits such as finger…

  7. Diagnostics for fluctuation measurements

    NARCIS (Netherlands)

    Donne, A. J. H.

    2000-01-01

    Transport of particles and heat in magnetic confinement devices is largely attributed to the presence of microscopic instabilities. To better understand the physical mechanisms underlying plasma transport processes it is necessary to diagnose the fluctuations in the various quantities along with the

  8. Direct Measurement of Thermal Fluctuation of High-Q Pendulum

    CERN Document Server

    Agatsuma, Kazuhiro; Yamamoto, Kazuhiro; Ohashi, Masatake; Kawamura, Seiji; Miyoki, Shinji; Miyakawa, Osamu; Telada, Souichi; Kuroda, Kazuaki

    2009-01-01

    We achieved for the first time a direct measurement of the thermal fluctuation of a pendulum in an off-resonant region using a laser interferometric gravitational wave detector. These measurements have been well identified for over one decade by an agreement with a theoretical prediction, which was derived by a fluctuation-dissipation theorem. Thermal fluctuation is dominated by the contribution of resistances in coil-magnet actuator circuits. When we tuned these resistances, the noise spectrum also changed according to a theoretical prediction. The measured thermal noise level corresponds to a high quality factor on the order of 10^5 of the pendulum.

  9. Effect of voltage sags on digitally controlled line connected switched-mode power supplies

    DEFF Research Database (Denmark)

    Török, Lajos; Munk-Nielsen, Stig

    2012-01-01

    Different voltage disorders like voltage fluctuations, sags, frequency variations may occur in the power supply networks due to different fault conditions. These deviations from normal operation affects in different ways the line connected devices. Standards were developed to protect and ensure i...

  10. Range fluctuations of high energy muons passing through matter

    Science.gov (United States)

    Minorikawa, Y.; Mitsui, K.

    1985-01-01

    The information about energy spectrum of sea level muons at high energies beyond magnetic spectrographs can be obtained from the underground intensity measurements if the fluctuations problems are solved. The correction factor R for the range fluctuations of high energy muons were calculated by analytical method of Zatsepin, where most probable energy loss parameter are used. It is shown that by using the R at great depth together with the slope, lambda, of the vertical depth-intensity (D-I) curve in the form of exp(-t/lambda), the spectral index, gamma, in the power law energy spectrum of muons at sea level can be obtained.

  11. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P

    1984-01-01

    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  12. Low-voltage gyrotrons

    Science.gov (United States)

    Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S.; Nusinovich, G. S.

    2013-03-01

    For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

  13. Terrestrial Gravity Fluctuations

    Science.gov (United States)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10-23 Hz-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  14. Terrestrial Gravity Fluctuations.

    Science.gov (United States)

    Harms, Jan

    2015-01-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10(-23) Hz(-1/2) above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  15. Terrestrial Gravity Fluctuations

    Directory of Open Access Journals (Sweden)

    Jan Harms

    2015-12-01

    Full Text Available Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^–23 Hz^–1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our

  16. MPPT algorithm for voltage controlled PV inverters

    DEFF Research Database (Denmark)

    Kerekes, Tamas; Teodorescu, Remus; Liserre, Marco;

    2008-01-01

    This paper presents a novel concept for an MPPT that can be used in case of a voltage controlled grid connected PV inverters. In case of single-phase systems, the 100 Hz ripple in the AC power is also present on the DC side. Depending on the DC link capacitor, this power fluctuation can be used t...... to track the MPP of the PV array, using the information that at MPP the power oscillations are very small. In this way the algorithm can detect the fact that the current working point is at the MPP, for the current atmospheric conditions....

  17. Phase noise analysis of voltage controlled oscillator used in cesium atomic clock

    Science.gov (United States)

    Zhi, Menghui; Tang, Liang; Qiao, Donghai

    2017-03-01

    Coherent population trapping (CPT) cesium frequency standard plays a significant role in precision guidance of missile and global positioning system (GPS). Low noise 4.596 GHz voltage controlled oscillator (VCO) is an indispensable part of microwave signal source in cesium frequency standard. Low-phase noise is also the most important and difficult performance indicator of VCO. Starting from phase noise analysis method proposed by Leeson, the formulas about the relationship between phase noise of output signal of oscillator feedback model and phase fluctuation spectrum of amplifier, phase noise of oscillator are derived in this paper. Finally, the asymptote model of microwave oscillator is proposed based on the formula derivation. The experiment shows that when the reverse bias voltage of variode is 1.8 V, the designed oscillation frequency of VCO is 4.596 GHz, the power is ‑1 dBm and the DC power consumption is 19.6 mW. The tendency of phase noise simulation curve and actual test curve conform to asymptote model. The phase noise in 1 and 10 kHz is, respectively, ‑60.86 and ‑86.58 dBc/Hz. The significance of the paper lies in determining the main factors influencing oscillator phase noise and providing guiding direction for the design of low-phase noise VCO.

  18. Energy density fluctuations in inflationary cosmology

    CERN Document Server

    Müller, H F; Muller, Harald F; Schmid, Christoph

    1994-01-01

    We analyze the energy density fluctuations contributed by scalar fields \\Phi with vanishing expectation values, \\langle\\Phi\\rangle=0, which are present in addition to the inflaton field. For simplicity we take \\Phi to be non--interacting and minimally coupled to gravity. We use normal ordering to define the renormalized energy density operator \\rho, and we show that any normal ordering gives the same result for correlation functions of \\rho. We first consider massless fields and derive the energy fluctuations in a single mode \\vk, the two--point correlation function of the energy density, the power spectrum, and the variance of the smeared energy density, \\ddR. Mass effects are investigated for energy fluctuations in single modes. All quantities considered are scale invariant at the second horizon crossing (Harrison--Zel'dovich type) for massless and for unstable massive fields. The magnitude of the relative fluctuations \\de\\rho/\\rt is of order (\\Hi/\\Mp)^2 in the massless case, where \\Hi is the Hubble constan...

  19. Device for monitoring cell voltage

    Science.gov (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

    2012-08-21

    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  20. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  1. Could thermal fluctuations seed cosmic structure?

    CERN Document Server

    Magueijo, J; Magueijo, Joao; Pogosian, Levon

    2003-01-01

    We examine the possibility that thermal, rather than quantum, fluctuations are responsible for seeding the structure of our universe. We find that while the thermalization condition leads to nearly Gaussian statistics, a Harrisson-Zeldovich spectrum for the primordial fluctuations can only be achieved in very special circumstances. These depend on whether the universe gets hotter or colder in time, while the modes are leaving the horizon. In the latter case we find a no-go theorem which can only be avoided if the fundamental degrees of freedom are not particle-like, such as in string gases near the Hagedorn phase transition. The former case is less forbidding, and we suggest two potentially successful ``warming universe'' scenarios. One makes use of the Phoenix universe, the other of ``phantom'' matter.

  2. Rainbow gravity and scale-invariant fluctuations

    CERN Document Server

    Amelino-Camelia, Giovanni; Gubitosi, Giulia; Magueijo, Joao

    2013-01-01

    We re-examine a recently proposed scenario where the deformed dispersion relations associated with a flow of the spectral dimension to a UV value of 2 leads to a scale-invariant spectrum of cosmological fluctuations, without the need for inflation. In that scenario Einstein gravity was assumed. The theory displays a wavelength-dependent speed of light but by transforming to a suitable "rainbow frame" this feature can be removed, at the expense of modifying gravity. We find that the ensuing rainbow gravity theory is such that gravity switches off at high energy (or at least leads to a universal conformal coupling). This explains why the fluctuations are scale-invariant on all scales: there is no horizon scale as such. For dispersion relations that do not lead to exact scale invariance we find instead esoteric inflation in the rainbow frame. We argue that these results shed light on the behaviour of gravity under the phenomenon of dimensional reduction.

  3. Cosmic Infrared Background Fluctuations and Zodiacal Light

    CERN Document Server

    Arendt, Richard G; Moseley, S H; Mather, J

    2016-01-01

    We have performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution, or from IRAC observations of high latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS field, at low ecliptic latitude where the zodiacal light intensity varies by factors of $\\sim2$ over the range of solar elongations at which the field can be observed. We find that the white noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that ...

  4. Implementationof Single Phasing, Over Voltage, Under Voltage, Protection of Three Phase Appliances without Using Microcontroller

    Directory of Open Access Journals (Sweden)

    Girish Chandra Thakur

    2015-05-01

    Full Text Available This paper tends to develop for protection for costly appliances which require three-phase AC supply for operation. Failure of any of the phases or sudden change in voltage makes the appliance prone to erratic functioning and may even lead to failure. Hence it is of paramount importance to monitor the availability of the three-phase supply and proper voltage supply and switch off the appliance in the event of failure of one or two phases or if required voltage level is not available. The power to the appliance should resume with the availability of all phases of the supply with proper voltage level. The main advantage of this protector circuit is that it protects three-phase appliances from failure of any phase as well as from fluctuation of voltage. The concept in future can be extended to developing a mechanism to send message to the authority via SMS by interfacing GSM modem. Details description of all types of faults is given below.

  5. Fluctuations in quantum devices

    Directory of Open Access Journals (Sweden)

    H.Haken

    2004-01-01

    Full Text Available Logical gates can be formalized by Boolean algebra whose elementary operations can be realized by devices that employ the interactions of macroscopic numbers of elementary excitations such as electrons, holes, photons etc. With increasing miniaturization to the nano scale and below, quantum fluctuations become important and can no longer be ignored. Based on Heisenberg equations of motion for the creation and annihilation operators of elementary excitations, I determine the noise sources of composite quantum systems.

  6. Terrestrial Gravity Fluctuations

    CERN Document Server

    Harms, Jan

    2015-01-01

    The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.

  7. Inverse scattering problem in turbulent magnetic fluctuations

    Science.gov (United States)

    Treumann, Rudolf A.; Baumjohann, Wolfgang; Narita, Yasuhito

    2016-08-01

    We apply a particular form of the inverse scattering theory to turbulent magnetic fluctuations in a plasma. In the present note we develop the theory, formulate the magnetic fluctuation problem in terms of its electrodynamic turbulent response function, and reduce it to the solution of a special form of the famous Gelfand-Levitan-Marchenko equation of quantum mechanical scattering theory. The last of these applies to transmission and reflection in an active medium. The theory of turbulent magnetic fluctuations does not refer to such quantities. It requires a somewhat different formulation. We reduce the theory to the measurement of the low-frequency electromagnetic fluctuation spectrum, which is not the turbulent spectral energy density. The inverse theory in this form enables obtaining information about the turbulent response function of the medium. The dynamic causes of the electromagnetic fluctuations are implicit to it. Thus, it is of vital interest in low-frequency magnetic turbulence. The theory is developed until presentation of the equations in applicable form to observations of turbulent electromagnetic fluctuations as input from measurements. Solution of the final integral equation should be done by standard numerical methods based on iteration. We point to the possibility of treating power law fluctuation spectra as an example. Formulation of the problem to include observations of spectral power densities in turbulence is not attempted. This leads to severe mathematical problems and requires a reformulation of inverse scattering theory. One particular aspect of the present inverse theory of turbulent fluctuations is that its structure naturally leads to spatial information which is obtained from the temporal information that is inherent to the observation of time series. The Taylor assumption is not needed here. This is a consequence of Maxwell's equations, which couple space and time evolution. The inversion procedure takes advantage of a particular

  8. Fluctuation and Dissipation in Liquid-Crystal Electroconvection

    Science.gov (United States)

    Goldburg, Walter I.; Goldschmidt, Yadin Y.; Kellay, Hamid

    2001-12-01

    In this experiment a steady-state current is maintained through a liquid-crystal thin film. When the applied voltage is increased through a threshold, a phase transition is observed to a convective state characterized by the chaotic motion of rolls. Above the threshold, an increase in power consumption is observed that is manifested by an increase in the mean conductivity. A sharp increase in the ratio of the power fluctuations to the mean power dissipated is observed above the transition. This ratio is compared to the predictions of the fluctuation theorem of Gallavotti and Cohen using an effective temperature associated with the rolls' chaotic motion.

  9. Voltage Regulators for Photovoltaic Systems

    Science.gov (United States)

    Delombard, R.

    1986-01-01

    Two simple circuits developed to provide voltage regulation for highvoltage (i.e., is greater than 75 volts) and low-voltage (i.e., is less than 36 volts) photovoltaic/battery power systems. Use of these circuits results in voltage regulator small, low-cost, and reliable, with very low power dissipation. Simple oscillator circuit controls photovoltaic-array current to regulate system voltage and control battery charging. Circuit senses battery (and system) voltage and adjusts array current to keep battery voltage from exceeding maximum voltage.

  10. Studying Voltage Transformer Ferroresonance

    Directory of Open Access Journals (Sweden)

    Hamid Radmanesh

    2012-09-01

    Full Text Available This study studies the effect of Circuit Breaker Shunt Resistance (CBSR, Metal Oxide Vaistor (MOV and Neutral earth Resistance (NR on the control of ferroresonance in the voltage transformer. It is expected that NR can controlled ferroresonance better than MOV and CBSR. Study has been done on a one phase voltage transformer rated 100 VA, 275 kV. The simulation results reveal that considering the CBSR and MOV exhibits a great mitigating effect on ferroresonance overvoltages, but these resistances cannot control these phenomena for all range of parameters. By applying NR to the system structure, ferroresonance has been controlled and its amplitude has been damped for all parameters values.

  11. Primordial fluctuations in extended Liouville theory

    Science.gov (United States)

    Moore, Wynton E.

    2015-03-01

    Liouville gravity can be used to precisely model features of 3+1 dimensional cosmology in a simplified 1+1d setting. We study primordial fluctuations in a generally covariant extension of Liouville theory, in the context of single field inflation. The scale invariant spectrum of scalar curvature perturbations is exhibited, and their three-point correlation function is computed in the slow roll approximation. We recover Maldacena's consistency relation for the three-point function, which in this context depends on a global shift symmetry of extended Liouville theory.

  12. Primordial fluctuations in extended Liouville theory

    CERN Document Server

    Moore, Wynton E

    2014-01-01

    Liouville gravity can be used to precisely model features of 3+1 dimensional cosmology in a simplified 1+1d setting. We study primordial fluctuations in a generally covariant extension of Liouville theory, in the context of single field inflation. The scale invariant spectrum of scalar curvature perturbations is exhibited, and their three-point correlation function is computed in the slow roll approximation. We recover Maldacena's consistency relation for the three-point function, which in this context depends on a global shift symmetry of extended Liouville theory.

  13. Mesoscale wind fluctuations over Danish waters

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, C.L.

    2010-12-15

    Mesoscale wind fluctuations affect the large scale integration of wind power because they undermine the day-ahead predictability of wind speed and power production, and because they can result in large fluctuations in power generation that must be balanced using reserve power. Large fluctuations in generated power are a particular problem for offshore wind farms because the typically high concentration of turbines within a limited geographical area means that fluctuations can be correlated across large numbers of turbines. Furthermore, organised mesoscale structures that often form over water, such as convective rolls and cellular convection, have length scales of tens of kilometers, and can cause large wind fluctuations on a time scale of around an hour. This thesis is an exploration of the predictability of mesoscale wind fluctuations using observations from the world's first two large offshore wind farms - Horns Rev I in the North Sea, and Nysted in the Baltic Sea. The thesis begins with a climatological analysis of wind fluctuations on time scales of 1-10 hours at the two sites. A novel method for calculating conditional climatologies of spectral information is proposed, based on binning and averaging the time axis of the Hilbert spectrum. Results reveal clear patterns between wind fluctuations and locally observed meteorological conditions. The analysis is expanded by classifying wind fluctuations on time scales of 1-3 hours according to synoptic patterns, satellite pictures and wind classes. Results indicate that cold air outbreaks and open cellular convection are a significant contributor to mesoscale wind variability at Horns Rev. The predictability of mesoscale wind fluctuations is tested by implementing standard statistical models that relate local wind variability to parameters based on a large scale weather analysis. The models show some skill, but only achieve a 15% improvement on a persistence forecast. The possibility of explicitly modelling

  14. A Model for Lightcone Fluctuations due to Stress Tensor Fluctuations

    CERN Document Server

    Bessa, C H G; Ford, L H; Ribeiro, C C H

    2016-01-01

    We study a model for quantum lightcone fluctuations in which vacuum fluctuations of the electric field and of the squared electric field in a nonlinear dielectric material produce variations in the flight times of probe pulses. When this material has a non-zero third order polarizability, the flight time variations arise from squared electric field fluctuations, and are analogous to effects expected when the stress tensor of a quantized field drives passive spacetime geometry fluctuations. We also discuss the dependence of the squared electric field fluctuations upon the geometry of the material, which in turn determines a sampling function for averaging the squared electric field along the path of the pulse. This allows us to estimate the probability of especially large fluctuations, which is a measure of the probability distribution for quantum stress tensor fluctuations.

  15. Hydrodynamic Fluctuations in Laminar Fluid Flow. II. Fluctuating Squire Equation

    Science.gov (United States)

    Ortiz de Zárate, José M.; Sengers, Jan V.

    2013-02-01

    We use fluctuating hydrodynamics to evaluate the enhancement of thermally excited fluctuations in laminar fluid flow using plane Couette flow as a representative example. In a previous publication (J. Stat. Phys. 144:774, 2011) we derived the energy amplification arising from thermally excited wall-normal fluctuations by solving a fluctuating Orr-Sommerfeld equation. In the present paper we derive the energy amplification arising from wall-normal vorticity fluctuation by solving a fluctuating Squire equation. The thermally excited wall-normal vorticity fluctuations turn out to yield the dominant contribution to the energy amplification. In addition, we show that thermally excited streaks, even in the absence of any externally imposed perturbations, are present in laminar fluid flow.

  16. Comment on 'Hawking radiation from fluctuating black holes'

    NARCIS (Netherlands)

    Khavkine, I.

    2010-01-01

    Takahashi and Soda (2010 Class. Quantum Grav. 27 175008) have recently considered the effect (at lowest non-trivial order) of dynamical, quantized gravitational fluctuations on the spectrum of scalar Hawking radiation from a collapsing Schwarzschild black hole. However, due to an unfortunate choice

  17. Holography and the scale-invariance of density fluctuations

    CERN Document Server

    Magueijo, J; Contaldi, C R; Magueijo, Joao; Smolin, Lee; Contaldi, Carlo R.

    2006-01-01

    We study a scenario for the very early universe in which there is a fast phase transition from a non-geometric, high temperature phase to a low temperature, geometric phase described by a classical solution to the Einstein equations. In spite of the absence of a classical metric, the thermodynamics of the high temperature phase may be described by making use of the holographic principle. The thermal spectrum of fluctuations in the high temperature phase manifest themselves after the phase transition as a scale invariant spectrum of fluctuations. A simple model of the phase transition confirms that the near scale invariance of the fluctuations is natural; but the model also withstands detailed comparison with the data.

  18. Holography and the scale invariance of density fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Magueijo, Joao [Perimeter Institute for Theoretical Physics, 31 Caroline St N, Waterloo N2 L 2Y5 (Canada); Smolin, Lee [Perimeter Institute for Theoretical Physics, 31 Caroline St N, Waterloo N2 L 2Y5 (Canada); Contaldi, Carlo R [Theoretical Physics Group, Imperial College, Prince Consort Road, London SW7 2BZ (United Kingdom)

    2007-07-21

    We study a scenario for the very early universe in which there is a fast phase transition from a non-geometric, high temperature phase to a low temperature, geometric phase described by a classical solution to the Einstein equations. In spite of the absence of a classical metric, the thermodynamics of the high temperature phase may be described by making use of the holographic principle. The thermal spectrum of fluctuations in the high temperature phase manifests itself after the phase transition as a scale-invariant spectrum of fluctuations. A simple model of the phase transition confirms that the near scale invariance of the fluctuations is natural, but the model also withstands a detailed comparison with the data.

  19. FUNDAMENTALS OF TRANSMISSION FLUCTUATION SPECTROMETRY WITH VARIABLE SPATIAL AVERAGING

    Institute of Scientific and Technical Information of China (English)

    Jianqi Shen; Ulrich Riebel; Marcus Breitenstein; Udo Kr(a)uter

    2003-01-01

    Transmission signal of radiation in suspension of particles performed with a high spatial and temporal resolution shows significant fluctuations, which are related to the physical properties of the particles and the process of spatial and temporal averaging. Exploiting this connection, it is possible to calculate the parti cie size distribution (PSD)and particle concentration. This paper provides an approach of transmission fluctuation spectrometry (TFS) with variable spatial averaging. The transmission fluctuations are expressed in terms of the expectancy of transmission square (ETS)and are obtained as a spectrum, which is a function of the variable beam diameter. The reversal point and the depth of the spectrum contain the information of particle size and particle concentration, respectively.

  20. VOLTAGE REGULATORS ASYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available A promising is currently the use of asynchronous generators with capacitive excitation as a source of electricity in stand-alone power systems. Drive asynchronous generators may exercise as a thermal engine and wind wheel wind power plant or turbines of small hydropower plants. The article discusses the structural and schematics of voltage stabilizers and frequency of asynchronous generators with improved operational and technical specifications. Technical novelty of design solutions of the magnetic system and stabilizers asynchronous generator of electricity parameters confirmed by the patents for the invention of the Russian Federation. The proposed technical solution voltage stabilizer asynchronous generators, can reduce the weight of the block capacitors excitation and reactive power compensation, as well as to simplify the control system power circuit which has less power electronic devices. For wind power plants it is an important issue not only to stabilize the voltage of the generator, but also the frequency of the current. Recommend functionality stabilizer schemes parameters of electric power made for direct frequency converters with artificial and natural switching power electronic devices. It is also proposed as part of stabilization systems use single-phase voltage, three-phase transformers with rotating magnetic field, reduce the level of electromagnetic interference generated by power electronic devices for switching, enhance the efficiency and reliability of the stabilizer.

  1. Geomagnetism and Induced Voltage

    Science.gov (United States)

    Abdul-Razzaq, W.; Biller, R. D.

    2010-01-01

    Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it…

  2. High-voltage picoamperemeter

    Energy Technology Data Exchange (ETDEWEB)

    Bugl, Andrea; Ball, Markus; Boehmer, Michael; Doerheim, Sverre; Hoenle, Andreas; Konorov, Igor [Technische Universitaet Muenchen, Garching (Germany); Ketzer, Bernhard [Technische Universitaet Muenchen, Garching (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2014-07-01

    Current measurements in the nano- and picoampere region on high voltage are an important tool to understand charge transfer processes in micropattern gas detectors like the Gas Electron Multiplier (GEM). They are currently used to e.g. optimize the field configuration in a multi-GEM stack to be used in the ALICE TPC after the upgrade of the experiment during the 2nd long shutdown of the LHC. Devices which allow measurements down to 1pA at high voltage up to 6 kV have been developed at TU Muenchen. They are based on analog current measurements via the voltage drop over a switchable shunt. A microcontroller collects 128 digital ADC values and calculates their mean and standard deviation. This information is sent with a wireless transmitting unit to a computer and stored in a root file. A nearly unlimited number of devices can be operated simultaneously and read out by a single receiver. The results can also be displayed on a LCD directly at the device. Battery operation and the wireless readout are important to protect the user from any contact to high voltage. The principle of the device is explained, and systematic studies of their properties are shown.

  3. Technical Conditions of Microgenerator Connection to a Low Voltage Network Taking Into Account Valid Rules and Practices Applied in Europe and Poland

    Directory of Open Access Journals (Sweden)

    Marian Sobierajski

    2014-12-01

    Full Text Available Connection of microgenerators to a low voltage network affects the electrical energy quality. In the paper, the basic relationships have been set out to compute voltage deviations and fluctuations. The basic criteria of microgeneration connection to a low voltage network have been given. The valid rules and practices applied in Europe and Poland have been described.

  4. Voltage-controlled nanoscale reconfigurable magnonic crystal

    Science.gov (United States)

    Wang, Qi; Chumak, Andrii V.; Jin, Lichuan; Zhang, Huaiwu; Hillebrands, Burkard; Zhong, Zhiyong

    2017-04-01

    A nanoscale reconfigurable magnonic crystal is designed using voltage-controlled perpendicular magnetic anisotropy (PMA) in ferromagnetic-dielectric heterostructures. A periodic array of gate metallic strips is placed on top of a MgO/Co structure in order to apply a periodic electric field and to modify the PMA in Co. It is numerically demonstrated that the introduction of PMA, which can be realized experimentally via applying a voltage, modifies the spin-wave propagation and leads to the formation of band gaps in the spin-wave spectrum. The band gaps can be controlled, i.e., it is possible to switch band gaps on and off within a few tens of nanoseconds. The width and the center frequency of the band gaps are defined by the applied voltage. Finally, it is shown that the introduction of PMA to selected, rather than to all gate strips allows for a predefined modification of the band-gap spectra. The proposed voltage-controlled reconfigurable magnonic crystal opens a way to low power consumption magnonic applications.

  5. A Novel Neutral Point Voltage Control Strategy for Three-Level NPC APF Based on SVPWM

    Directory of Open Access Journals (Sweden)

    Yao Xiaolong

    2015-01-01

    Full Text Available The unbalance of the neutral point voltage is an inherent problem of three-level neutral-point-clamped (NPC Active Power Filter (APF; this paper analyzes the causes of unbalanced neutral point voltage and studies the reason of the unbalance of the neutral point voltage. A novel neutral point voltage control strategy using Space Vector Pulse Width Modulation (SVPWM is proposed. The proposed strategy is based on the traditional SVPWM, by controlling the effect time of small vector, which can change the state of the midpoint voltage fluctuation, and the neutral point voltage can be maintained balance. The influence of the vector on neutral point balance is investigated in depth. Simulation results show the neutral point voltage balancing control strategy based on SPWM is effective.

  6. Self-Averaging Fluctuations in the Chaoticity of Simple Fluids

    Science.gov (United States)

    Das, Moupriya; Green, Jason R.

    2017-09-01

    Bulk properties of equilibrium liquids are a manifestation of intermolecular forces. Here, we show how these forces imprint on dynamical fluctuations in the Lyapunov exponents for simple fluids with and without attractive forces. While the bulk of the spectrum is strongly self-averaging, the first Lyapunov exponent self-averages only weakly and at a rate that depends on the length scale of the intermolecular forces; short-range repulsive forces quantitatively dominate longer-range attractive forces, which act as a weak perturbation that slows the convergence to the thermodynamic limit. Regardless of intermolecular forces, the fluctuations in the Kolmogorov-Sinai entropy rate diverge, as one expects for an extensive quantity, and the spontaneous fluctuations of these dynamical observables obey fluctuation-dissipation-like relationships. Together, these results are a representation of the van der Waals picture of fluids and another lens through which we can view the liquid state.

  7. Wall effects on density fluctuations in the GBL thermal lattice gas automaton

    Science.gov (United States)

    Hoekstra, A. G.; Sloot, P. M. A.

    2001-12-01

    We measure density fluctuations in a 19-bits thermal lattice gas automaton, in the presence of solid walls. The walls have a prominent effect on the dynamic structure factor. Fluctuating hydrodynamics predicts extra peaks in the spectrum. These extra features are indeed observed in the simulated dynamic structure factor.

  8. Fermionic influence (action) on inflationary fluctuations

    CERN Document Server

    Boyanovsky, Daniel

    2016-01-01

    Motivated by apparent persistent large scale anomalies in the CMB we study the influence of fermionic degrees of freedom on the dynamics of inflaton fluctuations as a possible source of violations of (nearly) scale invariance on cosmological scales. We obtain the non-equilibrium effective action of an inflaton-like scalar field with Yukawa interactions ($Y_{D,M}$) to light \\emph{fermionic} degrees of freedom both for Dirac and Majorana fields in de Sitter space-time. The effective action leads to Langevin equations of motion for the fluctuations of the inflaton-like field, with self-energy corrections and a stochastic gaussian noise. We solve the Langevin equation in the super-Hubble limit implementing a dynamical renormalization group resummation. For a nearly massless inflaton its power spectrum of super Hubble fluctuations is \\emph{enhanced}, $\\mathcal{P}(k;\\eta) = (\\frac{H}{2\\pi})^2\\,e^{\\gamma_t[-k\\eta] }$ with $\\gamma_t[-k\\eta] = \\frac{1}{6\\pi^2} \\Big[\\sum_{i=1}^{N_D}{Y^2_{i,D}}+2\\sum_{j=1}^{N_M}{Y^2_{j,...

  9. Voltage Stability Improvement of Grid Connected Wind Driven Induction Generator Using Svc

    Directory of Open Access Journals (Sweden)

    Ruchi Aggarwal

    2014-05-01

    Full Text Available Voltage stability is one of the major problem associated with wind power generating system which may be due to fluctuating nature of wind, heavy load, fault occurrence or insufficient reactive power supply. The wind power generating system most commonly employed with squirrel cage induction generator(SCIG that needs the support of an external device such as capacitor bank, FACTS devices etc. to support reactive power in order to remain connected with the grid during voltage dips. The voltage stability of a wind driven induction generator can be improved by using FACTS devices such as SVC, STATCOM.In this paper svc is used for voltage stability improvement.

  10. Wind Power Plant Voltage Control Optimization with Embedded Application of Wind Turbines and Statcom

    DEFF Research Database (Denmark)

    Wu, Qiuwei; Solanas, Jose Ignacio Busca; Zhao, Haoran

    2017-01-01

    Increasing wind power penetration and the size of wind power plants (WPPs) brings challenges to the operation and control of power systems. Most of WPPs are located far from load centers and the short circuit ratio at the point of common coupling (PCC) is low. The fluctuations of wind power...... will cause voltage variations. An optimal voltage control scheme for WPPs with STATCOMs is presented in the paper. It ensures that the voltages within the WPPs and at the high voltage side of the WPPs are within the limits and maximizes the dynamic Var reserve of the WPPs. Case studies were conducted...

  11. Analyzing of Dynamic Voltage Restorer in Series Compensation Voltage

    Directory of Open Access Journals (Sweden)

    Naser Parhizgar

    2012-02-01

    Full Text Available The Dynamic Voltage Restorer (DVR is a series-connected compensator to generate a controllable voltage to against the short-term voltage disturbances. The technique of DVR is an effective and cost competitive approach to improve voltage quality at the load side. This study presents a single-phase and threephase DVR system with reduced switch-count topology to protect the sensitive load against abnormal voltage conditions. Most basic function, the DVR configuration consist of a two level Voltage Source Converter (VSC, a dc energy storage device, a coupling transformer Connected in shunt with the ac system This study presents the application of Dynamic Voltage Restorer (DVR on power distribution systems for mitigation of voltage sag at critical loads. DVR is one of the compensating types of custom power devices. The DVR, which is based on forced-commutated Voltage Source Converter (VSC has been proved suitable for the task of compensating voltage sags/swells. Simulation results are presented to illustrate and understand the performances of DVR in supporting load voltages under voltage sags/swells conditions.

  12. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  13. Quantifying economic fluctuations

    Science.gov (United States)

    Stanley, H. Eugene; Nunes Amaral, Luis A.; Gabaix, Xavier; Gopikrishnan, Parameswaran; Plerou, Vasiliki

    2001-12-01

    This manuscript is a brief summary of a talk designed to address the question of whether two of the pillars of the field of phase transitions and critical phenomena-scale invariance and universality-can be useful in guiding research on interpreting empirical data on economic fluctuations. Using this conceptual framework as a guide, we empirically quantify the relation between trading activity-measured by the number of transactions N-and the price change G( t) for a given stock, over a time interval [ t, t+Δ t]. We relate the time-dependent standard deviation of price changes-volatility-to two microscopic quantities: the number of transactions N( t) in Δ t and the variance W2( t) of the price changes for all transactions in Δ t. We find that the long-ranged volatility correlations are largely due to those of N. We then argue that the tail-exponent of the distribution of N is insufficient to account for the tail-exponent of P{ G> x}. Since N and W display only weak inter-dependency, our results show that the fat tails of the distribution P{ G> x} arises from W. Finally, we review recent work on quantifying collective behavior among stocks by applying the conceptual framework of random matrix theory (RMT). RMT makes predictions for “universal” properties that do not depend on the interactions between the elements comprising the system, and deviations from RMT provide clues regarding system-specific properties. We compare the statistics of the cross-correlation matrix C-whose elements Cij are the correlation coefficients of price fluctuations of stock i and j-against a random matrix having the same symmetry properties. It is found that RMT methods can distinguish random and non-random parts of C. The non-random part of C which deviates from RMT results, provides information regarding genuine collective behavior among stocks. We also discuss results that are reminiscent of phase transitions in spin systems, where the divergent behavior of the response function at

  14. Increased voltage photovoltaic cell

    Science.gov (United States)

    Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

    1985-01-01

    A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

  15. High Voltage Seismic Generator

    Science.gov (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  16. Primordial Fluctuations within Teleparallelism

    CERN Document Server

    Wu, Yi-Peng

    2011-01-01

    To study the primordial fluctuations for gravity within teleparallelism, we perform a 3+1 decomposition of the vierbein field which makes the metric tensor identical to the ADM formulation. The torsion scalar is differ by a total divergence from the Ricci scalar under this representation as a consistent result. Using the unitary gauge of the scalar field, we obtain the same quadratic actions for both scalar and tensor perturbations as the standard ones in the minimal torsion scalar coupling. When the same scenario is applied to the higher-order action, $f(T)$ gravity, we find that the scalar-tensor coupling in the Einstein frame becomes a total divergence. Consequently, the cosmological perturbations are the same for $f(T)$ and $f(R)$ gravity theories in the earlier universe although the behaviors of the late time cosmic acceleration are apparently different.

  17. Fluctuating multicomponent lattice Boltzmann model.

    Science.gov (United States)

    Belardinelli, D; Sbragaglia, M; Biferale, L; Gross, M; Varnik, F

    2015-02-01

    Current implementations of fluctuating lattice Boltzmann equations (FLBEs) describe single component fluids. In this paper, a model based on the continuum kinetic Boltzmann equation for describing multicomponent fluids is extended to incorporate the effects of thermal fluctuations. The thus obtained fluctuating Boltzmann equation is first linearized to apply the theory of linear fluctuations, and expressions for the noise covariances are determined by invoking the fluctuation-dissipation theorem directly at the kinetic level. Crucial for our analysis is the projection of the Boltzmann equation onto the orthonormal Hermite basis. By integrating in space and time the fluctuating Boltzmann equation with a discrete number of velocities, the FLBE is obtained for both ideal and nonideal multicomponent fluids. Numerical simulations are specialized to the case where mean-field interactions are introduced on the lattice, indicating a proper thermalization of the system.

  18. Classification and Identification of Over-voltage Based on HHT and SVM

    Institute of Scientific and Technical Information of China (English)

    WANG Jing; YANG Qing; CHEN Lin; SIMA Wenxia

    2012-01-01

    This paper proposes an effective method for over-voltage classification based on the Hilbert-Huang transform(HHT) method.Hilbert-Huang transform method is composed of empirical mode decomposition(EMD) and Hilbert transform.Nine kinds of common power system over-voltages are calculated and analyzed by HHT.Based on the instantaneous amplitude spectrum,Hilbert marginal spectrum and Hilbert time-frequency spectrum,three kinds of over-voltage characteristic quantities are obtained.A hierarchical classification system is built based on HHT and support vector machine(SVM).This classification system is tested by 106 field over-voltage signals,and the average classification rate is 94.3%.This research shows that HHT is an effective time-frequency analysis algorithms in the application of over-voltage classification and identification.

  19. Transport generated by dichotomous fluctuations

    Science.gov (United States)

    Kula, J.; Czernik, T.; łuczka, J.

    1996-02-01

    Overdamped motion of Brownian particles in spatially periodic potentials and subjected to fluctuations modeled by asymmetric exponentially correlated two-state noise of zero mean value is considered. The probability current is presented in a closed form and analyzed in asymptotic regimes of very long and very short correlation times of the fluctuations. Explicit results are obtained for a piecewise linear potential. The role of correlations and temporal asymmetry of fluctuations is elucidated.

  20. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar;

    2013-01-01

    problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0....

  1. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    . An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...

  2. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  3. Theory of slightly fluctuating ratchets

    Science.gov (United States)

    Rozenbaum, V. M.; Shapochkina, I. V.; Lin, S. H.; Trakhtenberg, L. I.

    2017-04-01

    We consider a Brownian particle moving in a slightly fluctuating potential. Using the perturbation theory on small potential fluctuations, we derive a general analytical expression for the average particle velocity valid for both flashing and rocking ratchets with arbitrary, stochastic or deterministic, time dependence of potential energy fluctuations. The result is determined by the Green's function for diffusion in the time-independent part of the potential and by the features of correlations in the fluctuating part of the potential. The generality of the result allows describing complex ratchet systems with competing characteristic times; these systems are exemplified by the model of a Brownian photomotor with relaxation processes of finite duration.

  4. Prospective medium voltage and low voltage control systems. Functions and IT implementation in the environment of smart grids; Zukuenftige Mittelspannungs- und Niederspannungsleitsysteme. Funktionen und IT Umsetzung im Smart Grid Umfeld

    Energy Technology Data Exchange (ETDEWEB)

    Luhmann, T.; Guo, X.; Meister, J.; Meister, K.; Walther, R.; Stadler, M. [BTC AG, Oldenburg (Germany)

    2011-07-01

    The integration of decentralized and fluctuating production in the power supply is a challenge for network control systems for medium voltage and low voltage level. The contribution under consideration outlines emerging issues and offers potential future contributions to the solution from the information technology.

  5. Turbulent magnetic fluctuations in laboratory reconnection

    Science.gov (United States)

    Von Stechow, Adrian; Grulke, Olaf; Klinger, Thomas

    2016-07-01

    The role of fluctuations and turbulence is an important question in astrophysics. While direct observations in space are rare and difficult dedicated laboratory experiments provide a versatile environment for the investigation of magnetic reconnection due to their good diagnostic access and wide range of accessible plasma parameters. As such, they also provide an ideal chance for the validation of space plasma reconnection theories and numerical simulation results. In particular, we studied magnetic fluctuations within reconnecting current sheets for various reconnection parameters such as the reconnection rate, guide field, as well as plasma density and temperature. These fluctuations have been previously interpreted as signatures of current sheet plasma instabilities in space and laboratory systems. Especially in low collisionality plasmas these may provide a source of anomalous resistivity and thereby contribute a significant fraction of the reconnection rate. We present fluctuation measurements from two complementary reconnection experiments and compare them to numerical simulation results. VINETA.II (Greifswald, Germany) is a cylindrical, high guide field reconnection experiment with an open field line geometry. The reconnecting current sheet has a three-dimensional structure that is predominantly set by the magnetic pitch angle which results from the superposition of the guide field and the in-plane reconnecting field. Within this current sheet, high frequency magnetic fluctuations are observed that correlate well with the local current density and show a power law spectrum with a spectral break at the lower hybrid frequency. Their correlation lengths are found to be extremely short, but propagation is nonetheless observed with high phase velocities that match the Whistler dispersion. To date, the experiment has been run with an external driving field at frequencies higher than the ion cyclotron frequency f_{ci}, which implies that the EMHD framework applies

  6. Transient voltage sharing in series-coupled high voltage switches

    Directory of Open Access Journals (Sweden)

    Editorial Office

    1992-07-01

    Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

  7. Fluctuations When Driving Between Nonequilibrium Steady States

    Science.gov (United States)

    Riechers, Paul M.; Crutchfield, James P.

    2017-08-01

    Maintained by environmental fluxes, biological systems are thermodynamic processes that operate far from equilibrium without detailed-balanced dynamics. Yet, they often exhibit well defined nonequilibrium steady states (NESSs). More importantly, critical thermodynamic functionality arises directly from transitions among their NESSs, driven by environmental switching. Here, we identify the constraints on excess heat and dissipated work necessary to control a system that is kept far from equilibrium by background, uncontrolled "housekeeping" forces. We do this by extending the Crooks fluctuation theorem to transitions among NESSs, without invoking an unphysical dual dynamics. This and corresponding integral fluctuation theorems determine how much work must be expended when controlling systems maintained far from equilibrium. This generalizes thermodynamic feedback control theory, showing that Maxwellian Demons can leverage mesoscopic-state information to take advantage of the excess energetics in NESS transitions. We also generalize an approach recently used to determine the work dissipated when driving between functionally relevant configurations of an active energy-consuming complex system. Altogether, these results highlight universal thermodynamic laws that apply to the accessible degrees of freedom within the effective dynamic at any emergent level of hierarchical organization. By way of illustration, we analyze a voltage-gated sodium ion channel whose molecular conformational dynamics play a critical functional role in propagating action potentials in mammalian neuronal membranes.

  8. Monte Carlo analysis of a low power domino gate under parameter fluctuation

    Institute of Scientific and Technical Information of China (English)

    Wang Jinhui; Wu Wuchen; Gong Na; Hou Ligang; Peng Xiaohong; Gao Daming

    2009-01-01

    Using the multiple-parameter Monte Carlo method, the effectiveness of the dual threshold voltage technique (DTV) in low power domino logic design is analyzed. Simulation results indicate that under significant temperature and process fluctuations, DTV is still highly effective in reducing the total leakage and active power consumption for domino gates with speed loss. Also, regarding power and delay characteristics, different structure domino gates with DTV have different robustness against temperature and process fluctuation.

  9. Monte Carlo analysis of a low power domino gate under parameter fluctuation

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jinhui; Wu Wuchen; Hou Ligang; Peng Xiaohong; Gao Daming [VLSI and System Laboratory, Beijing University of Technology, Beijing 100124 (China); Gong Na, E-mail: wangjinhui888@emails.bjut.edu.c [Department of Computer Science and Engineering, State University of New York at Buffalo, Buffalo 14260, NY (United States)

    2009-12-15

    Using the multiple-parameter Monte Carlo method, the effectiveness of the dual threshold voltage technique (DTV) in low power domino logic design is analyzed. Simulation results indicate that under significant temperature and process fluctuations, DTV is still highly effective in reducing the total leakage and active power consumption for domino gates with speed loss. Also, regarding power and delay characteristics, different structure domino gates with DTV have different robustness against temperature and process fluctuation. (semiconductor integrated circuits)

  10. Stochastic Heisenberg limit: optimal estimation of a fluctuating phase.

    Science.gov (United States)

    Berry, Dominic W; Hall, Michael J W; Wiseman, Howard M

    2013-09-13

    The ultimate limits to estimating a fluctuating phase imposed on an optical beam can be found using the recently derived continuous quantum Cramér-Rao bound. For Gaussian stationary statistics, and a phase spectrum scaling asymptotically as ω(-p) with p>1, the minimum mean-square error in any (single-time) phase estimate scales as N(-2(p-1)/(p+1)), where N is the photon flux. This gives the usual Heisenberg limit for a constant phase (as the limit p→∞) and provides a stochastic Heisenberg limit for fluctuating phases. For p=2 (Brownian motion), this limit can be attained by phase tracking.

  11. No-Voltage Meter

    Science.gov (United States)

    1976-02-01

    VW- IKft, 1/4 H4 -Wv- IK!1, I/4W INTERNAL VOLTAGE NOTE ALL TRANSISTORS ARE 2N43A OR EQUIVALENT GERMANIUM ALLOY PNP AA ALKALINE BATTERY...D-,, regardless of polarity. This signal is then full-wave rectified by the diode-connected Germanium transistor bridge, T,, T-,, T3, and T4... Transistor T5 acts as a second current limiter. Resistor R2 was selected to give 90 f# of full-scale meter deflection with an input signal of 115 volts

  12. Five-Level Converter with Low Switching Frequency Applied as DC Voltage Supply

    DEFF Research Database (Denmark)

    Rasmussen, Tonny Wederberg

    1999-01-01

    This paper describes the use of a multi-level converter as a DC supply. Equations for the converter will be deduced in the nondissipative case. The equations provide solutions to DC voltage and the angle of converter voltage. In addition the spectrum for the harmonics after the elimination...

  13. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...... to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution...

  14. Quantum Fluctuation Theorem in an Interacting Setup: Point Contacts in Fractional Quantum Hall Edge State Devices

    Science.gov (United States)

    Komnik, A.; Saleur, H.

    2011-09-01

    We verify the validity of the Cohen-Gallavotti fluctuation theorem for the strongly correlated problem of charge transfer through an impurity in a chiral Luttinger liquid, which is realizable experimentally as a quantum point contact in a fractional quantum Hall edge state device. This is accomplished via the development of an analytical method to calculate the full counting statistics of the problem in all the parameter regimes involving the temperature, the Hall voltage, and the gate voltage.

  15. Fluctuating Selection in the Moran

    Science.gov (United States)

    Dean, Antony M.; Lehman, Clarence; Yi, Xiao

    2017-01-01

    Contrary to classical population genetics theory, experiments demonstrate that fluctuating selection can protect a haploid polymorphism in the absence of frequency dependent effects on fitness. Using forward simulations with the Moran model, we confirm our analytical results showing that a fluctuating selection regime, with a mean selection coefficient of zero, promotes polymorphism. We find that increases in heterozygosity over neutral expectations are especially pronounced when fluctuations are rapid, mutation is weak, the population size is large, and the variance in selection is big. Lowering the frequency of fluctuations makes selection more directional, and so heterozygosity declines. We also show that fluctuating selection raises dn/ds ratios for polymorphism, not only by sweeping selected alleles into the population, but also by purging the neutral variants of selected alleles as they undergo repeated bottlenecks. Our analysis shows that randomly fluctuating selection increases the rate of evolution by increasing the probability of fixation. The impact is especially noticeable when the selection is strong and mutation is weak. Simulations show the increase in the rate of evolution declines as the rate of new mutations entering the population increases, an effect attributable to clonal interference. Intriguingly, fluctuating selection increases the dn/ds ratios for divergence more than for polymorphism, a pattern commonly seen in comparative genomics. Our model, which extends the classical neutral model of molecular evolution by incorporating random fluctuations in selection, accommodates a wide variety of observations, both neutral and selected, with economy. PMID:28108586

  16. Fluctuation Relations for Molecular Motors

    Science.gov (United States)

    Lacoste, David; Mallick, Kirone

    This review is focused on the application of specific fluctuation relations, such as the Gallavotti-Cohen relation, to ratchet models of a molecular motor. A special emphasis is placed on two-state models such as the flashing ratchet model. We derive the Gallavotti-Cohen fluctuation relation for these models and we discuss some of its implications.

  17. Fluctuations as stochastic deformation

    Science.gov (United States)

    Kazinski, P. O.

    2008-04-01

    A notion of stochastic deformation is introduced and the corresponding algebraic deformation procedure is developed. This procedure is analogous to the deformation of an algebra of observables like deformation quantization, but for an imaginary deformation parameter (the Planck constant). This method is demonstrated on diverse relativistic and nonrelativistic models with finite and infinite degrees of freedom. It is shown that under stochastic deformation the model of a nonrelativistic particle interacting with the electromagnetic field on a curved background passes into the stochastic model described by the Fokker-Planck equation with the diffusion tensor being the inverse metric tensor. The first stochastic correction to the Newton equations for this system is found. The Klein-Kramers equation is also derived as the stochastic deformation of a certain classical model. Relativistic generalizations of the Fokker-Planck and Klein-Kramers equations are obtained by applying the procedure of stochastic deformation to appropriate relativistic classical models. The analog of the Fokker-Planck equation associated with the stochastic Lorentz-Dirac equation is derived too. The stochastic deformation of the models of a free scalar field and an electromagnetic field is investigated. It turns out that in the latter case the obtained stochastic model describes a fluctuating electromagnetic field in a transparent medium.

  18. Extension of the coherence function to quadratic models. [applied to plasma density and potential fluctuations

    Science.gov (United States)

    Kim, Y. C.; Wong, W. F.; Powers, E. J.; Roth, J. R.

    1979-01-01

    It is shown how the use of higher coherence functions can recover some of the lost coherence due to nonlinear relationship between two fluctuating quantities whose degree of mutual coherence is being measured. The relationship between the two processes is modeled with the aid of a linear term and a quadratic term. As a specific example, the relationship between plasma density and potential fluctuations in a plasma is considered. The fraction of power in the auto-power spectrum of the potential fluctuations due to a linear relationship and to a quadratic relationship between the density and potential fluctuations is estimated.

  19. Density Fluctuation Measurements Using FIR Interferometer on HL-2A Tokamak

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yan; PENG Bei-Bin; YANG Qing-wei; DUAN Xu-Ru; DING Xuan-Tong; LI Lian-Cai; LI Yong-Gao; JIAO Yi-Ming; DENG Zhong-Chao; YI Jiang; LIU Yi; ZHAO Kai-Jun; JI Xiao-Quan

    2008-01-01

    Denity fluctuations were first measured in the core region of HL-2A tokamak plasma using a newly developed multi-channel FIR interferometer system. In divertor ohmic discharges, we measured the radial density fluctuation levels of 5%, which increase to 10-20% during the appearance of MHD activity. Most of the power density in the density fluctuation spectrum is directly associated with m=2 tearing modes. The fluctuation levels reduce to 1/3 and plasma confinement is improved during off-axis electron-cyclotron-resonance heating (ECRH).Supported by the National Natural Science Foundation of China under Grant Nos 10575030 and 10675043.

  20. Nonequilibrium fluctuations in a resistor.

    Science.gov (United States)

    Garnier, N; Ciliberto, S

    2005-06-01

    In small systems where relevant energies are comparable to thermal agitation, fluctuations are of the order of average values. In systems in thermodynamical equilibrium, the variance of these fluctuations can be related to the dissipation constant in the system, exploiting the fluctuation-dissipation theorem. In nonequilibrium steady systems, fluctuations theorems (FT) additionally describe symmetry properties of the probability density functions (PDFs) of the fluctuations of injected and dissipated energies. We experimentally probe a model system: an electrical dipole driven out of equilibrium by a small constant current I, and show that FT are experimentally accessible and valid. Furthermore, we stress that FT can be used to measure the dissipated power P = R I2 in the system by just studying the PDFs' symmetries.

  1. Fluctuation of the Download Network

    Institute of Scientific and Technical Information of China (English)

    HAN Ding-Ding; LIV Jin-Gao; MA Yu-Gang

    2008-01-01

    The scaling behaviour of fluctuation for a download network we investigated a few years ago based upon Zhang's Econophysics web page is presented.A power law scaling,namely σ~α exists between the dispersion σ and average flux of the download rates.The fluctuation exponent α is neither 1/2 nor 1,which were claimed as two universal fluctuation classes in previous publication,while it varies from 1/2 to 1 with the time window in which the download data are accumulated.The crossover behaviour of fluctuation exponents can be qualitatively understood by the external driving fluctuation model for a small-size system or a network traffic model which suggests congestion as the origin.

  2. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  3. Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

    Directory of Open Access Journals (Sweden)

    William J.B. Heffernan

    2014-12-01

    Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

  4. Spontaneous magnetic fluctuations in ultrathin magnetic films at zero field

    Science.gov (United States)

    Balk, Andrew; Unguris, John

    2014-03-01

    We use magneto optical Kerr effect (MOKE) microscopy to observe room temperature, zero field magnetic fluctuations in perpendicularly magnetized cobalt films at thicknesses near the in-plane to out-of-plane spin reorientation transition. The magnetic behavior of our films resembles that of collections of superparamagnetic particles, in that globally they exhibit zero net moment, while local areas continually undergo thermal magnetic fluctuations between saturated states of the maze-like domain structure. Unlike superparamagnetic particles, the fluctuations are not constrained by particle boundaries and thus are subject to both exchange and magnetostatic interactions. Due to this we can observe temporal and spatial correlations in the fluctuations. Furthermore, we observe that the fluctuations obey dynamics distinct from field-driven Barkhausen jumps. We also determine scaling exponents of the fluctuations, finding their areas follow a power law distribution (t =1.5), and their temporal noise power spectrum is close to 1/f (a = 1.04). Based on these observations, we discuss these films as possible candidates for exhibiting magnetic self-organized criticality.

  5. Density Spectrums from Kinetic Inflations

    CERN Document Server

    Hwang, J

    1996-01-01

    The pole-like accelerated expansion stages purely driven by the coupling between the gravity and the dilaton field without referring to the potential term can be realized in a class of generalized gravity theories. We consider three such scenarios based on the scalar-tensor gravity, the induced gravity and the string theory. Quantum fluctuations during the expansion stages (including more general situations) can be derived in exact analytic forms. Assuming that the pole-like acceleration stage provides a viable inflation scenario in the early universe we derive the generated classical density spectrums. The generated classical density field shows a generic tilted spectrum with $n \\simeq 4$ which differs from the observed spectrum supporting $n \\simeq 1$.

  6. Voltage Swells Improvement in Low Voltage Network Using Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    R. Omar

    2011-01-01

    Full Text Available Problem statement: Voltage disturbances are the most common power quality problem due to the increased use of a large numbers of sophisticated electronic equipment in industrial distribution system. The voltage disturbances such as voltage sags, swells, harmonics, unbalance and flickers. High quality in the power supply is needed, since failures due to such disturbances usually have a high impact on production cost. There are many different solutions to compensate voltage disturbances but the use of a DVR is considered to be the most cost effective method. The objective of this study is to propose a new topology of a DVR in order to mitigate voltage swells using a powerful power custom device namely the Dynamic Voltage Restorer (DVR. Approach: New configuration of a DVR with an improvement of a controller based on direct-quadrature-zero method has been introduced to compensate voltage swells in the network. Results: The effectiveness of the DVR with its controller were verify using Matlab/Simulinks SimPower Toolbox and then implemented using 5KVA DVR experimental setup. Simulations and experimental results demonstrate the effective dynamic performance of the proposed configuration. Conclusion: The implimentation of the proposed DVR validate the capabilities in mitigating of voltage swells effectiveness.During voltage swells, the DVR injects an appropriate voltage to maintain the load voltage at its nominal value.

  7. Zellweger Spectrum

    Science.gov (United States)

    ... severe defect, resulting in essentially nonfunctional peroxisomes. This phenomenon produces the range of severity of the disorders. How is the Zellweger Spectrum Diagnosed? The distinctive shape of the head and face of a child born with one of the diseases of the ...

  8. Conductance fluctuations in high mobility monolayer graphene: Nonergodicity, lack of determinism and chaotic behavior

    Science.gov (United States)

    da Cunha, C. R.; Mineharu, M.; Matsunaga, M.; Matsumoto, N.; Chuang, C.; Ochiai, Y.; Kim, G.-H.; Watanabe, K.; Taniguchi, T.; Ferry, D. K.; Aoki, N.

    2016-09-01

    We have fabricated a high mobility device, composed of a monolayer graphene flake sandwiched between two sheets of hexagonal boron nitride. Conductance fluctuations as functions of a back gate voltage and magnetic field were obtained to check for ergodicity. Non-linear dynamics concepts were used to study the nature of these fluctuations. The distribution of eigenvalues was estimated from the conductance fluctuations with Gaussian kernels and it indicates that the carrier motion is chaotic at low temperatures. We argue that a two-phase dynamical fluid model best describes the transport in this system and can be used to explain the violation of the so-called ergodic hypothesis found in graphene.

  9. Density fluctuations in traffic flow

    CERN Document Server

    Yukawa, S

    1996-01-01

    Density fluctuations in traffic current are studied by computer simulations using the deterministic coupled map lattice model on a closed single-lane circuit. By calculating a power spectral density of temporal density fluctuations at a local section, we find a power-law behavior, \\sim 1/f^{1.8}, on the frequency f, in non-congested flow phase. The distribution of the headway distance h also shows the power law like \\sim 1/h^{3.0} at the same time. The power law fluctuations are destroyed by the occurence of the traffic jam.

  10. Mesoscopic Fluctuations in Stochastic Spacetime

    CERN Document Server

    Shiokawa, K

    2000-01-01

    Mesoscopic effects associated with wave propagation in spacetime with metric stochasticity are studied. We show that the scalar and spinor waves in a stochastic spacetime behave similarly to the electrons in a disordered system. Viewing this as the quantum transport problem, mesoscopic fluctuations in such a spacetime are discussed. The conductance and its fluctuations are expressed in terms of a nonlinear sigma model in the closed time path formalism. We show that the conductance fluctuations are universal, independent of the volume of the stochastic region and the amount of stochasticity.

  11. Understanding experimentally-observed fluctuations

    CERN Document Server

    Kitazawa, Masakiyo

    2016-01-01

    We discuss two topics on the experimental measurements of fluctuation observables in relativistic heavy-ion collisions. First, we discuss the effects of the thermal blurring, i.e. the blurring effect arising from the experimental measurement of fluctuations in momentum space as a proxy of the thermal fluctuations defined in coordinate space, on higher order cumulants. Second, we discuss the effect of imperfect efficiency of detectors on the measurement of higher order cumulants. We derive effective formulas which can carry out the correction of this effect for higher order cumulants based on the binomial model.

  12. Fluctuation theorem: A critical review

    Science.gov (United States)

    Malek Mansour, M.; Baras, F.

    2017-10-01

    Fluctuation theorem for entropy production is revisited in the framework of stochastic processes. The applicability of the fluctuation theorem to physico-chemical systems and the resulting stochastic thermodynamics were analyzed. Some unexpected limitations are highlighted in the context of jump Markov processes. We have shown that these limitations handicap the ability of the resulting stochastic thermodynamics to correctly describe the state of non-equilibrium systems in terms of the thermodynamic properties of individual processes therein. Finally, we considered the case of diffusion processes and proved that the fluctuation theorem for entropy production becomes irrelevant at the stationary state in the case of one variable systems.

  13. Structure and fluctuations of a single floating lipid bilayer.

    Science.gov (United States)

    Daillant, J; Bellet-Amalric, E; Braslau, A; Charitat, T; Fragneto, G; Graner, F; Mora, S; Rieutord, F; Stidder, B

    2005-08-16

    A single lipid molecular bilayer of 17 or 18 carbon chain phosphocholines, floating in water near a flat wall, is prepared in the bilayer gel phase and then heated to the fluid phase. Its structure (electron density profile) and height fluctuations are determined by using x-ray reflectivity and non-specular scattering. By fitting the off-specular signal to that calculated for a two-dimensional membrane using a Helfrich Hamiltonian, we determine the three main physical quantities that govern the bilayer height fluctuations: The wall attraction potential is unexpectedly low; the surface tension, roughly independent on chain length and temperature, is moderate (approximately 5 x 10(-4) J.m(-2)) but large enough to dominate the intermediate range of the fluctuation spectrum; and the bending modulus abruptly decreases by an order-of-magnitude from 10(-18) J to 10(-19) J at the bilayer gel-to-fluid transition.

  14. Near-Milne realization of scale-invariant fluctuations

    CERN Document Server

    Magueijo, Joao

    2007-01-01

    A near-Milne Universe produces a very red spectrum of vacuum quantum fluctuations, but has the potential to produce near-scale invariant {\\it thermal} fluctuations. This happens if the energy and entropy are mildly sub-extensive, for example if there is a Casimir contribution. Therefore, one does not need to invoke corrections to Einstein gravity (as in loop quantum cosmology) for a thermal scenario to be viable. Neither do we need the energy to scale like the area, as in scenarios where the thermal fluctuations are subject to a phase transition in the early Universe. Some odd features of this model are pointed out: whether they are fatal or merely unusual should be the subject of future investigations.

  15. Fluorescence fluctuation spectroscopy and its artifacts: simulations and tests

    Institute of Scientific and Technical Information of China (English)

    MENG; Fanbo; CHEN; Bo; LIU; Guang; DING; Jianying

    2005-01-01

    Fluorescence fluctuation spectroscopy (FFS) technique is capable of monitoring changes in concentration, mass, size and structure of fluorescent-labeled bio-molecules in microscopic volume and is suitable for measuring biological interactions in living cells. FFS data may be affected by many experimental factors in complicated biological systems. Using a Monte Carlo approach, we generate fluorescence fluctuation data for different experimental systems. This approach helps to separate the contributions by different experimental factors in a complicated fluorescence fluctuation spectrum. It also helps to validate new theoretical models and new fitting formulations. We describe the algorithm of the simulation program and tests on its statistical performance. The program is then used successfully to study the effects of several experimental factors on FFS detection.

  16. Vacuum fluctuations in theories with deformed dispersion relations

    CERN Document Server

    Arzano, Michele; Magueijo, Joao; Amelino-Camelia, Giovanni

    2015-01-01

    We examine vacuum fluctuations in theories with modified dispersion relations which represent dimensional reduction at high energies. By changing units of energy and momentum we can obtain a description rendering the dispersion relations undeformed and transferring all the non-trivial effects to the integration measure in momentum space. Using this description we propose a general quantization procedure, which should be applicable whether or not the theory explicitly introduces a preferred frame. Based on this scheme we evaluate the power spectrum of quantum vacuum fluctuations. We find that in {\\it all} theories which run to 2 dimensions in the ultraviolet the vacuum fluctuations, in the ultraviolet regime, are scale-invariant. This is true in flat space but also for "inside the horizon" modes in an expanding universe. We spell out the conditions upon the gravity theory for this scale-invariance to be preserved as the modes are frozen-in outside the horizon. We also digress on the meaning of dimensionality (...

  17. Almost Periodically Correlated Time Series in Business Fluctuations Analysis

    CERN Document Server

    Lenart, Lukasz

    2012-01-01

    We propose a non-standard subsampling procedure to make formal statistical inference about the business cycle, one of the most important unobserved feature characterising fluctuations of economic growth. We show that some characteristics of business cycle can be modelled in a non-parametric way by discrete spectrum of the Almost Periodically Correlated (APC) time series. On the basis of estimated characteristics of this spectrum business cycle is extracted by filtering. As an illustration we characterise the man properties of business cycles in industrial production index for Polish economy.

  18. Amplitude of primeval fluctuations from cosmological mass density reconstructions

    Science.gov (United States)

    Seljak, Uros; Bertschinger, Edmund

    1994-01-01

    We use the POTENT reconstruction of the mass density field in the nearby universe to estimate the amplitude of the density fluctuation power spectrum for various cosmological models. We find that sigma(sub 8) Omega(sub m sup 0.6) = 1.3(sub -0.3 sup +0.4), almost independently of the power spectrum. This value agrees well with the Cosmic Background Explorer (COBE) normalization for the standard cold dark matter model, while alternative models predict an excessive amplitude compared with COBE. Flat, low Omega(sub m) models and tilted models with spectral index n less than 0.8 are particularly discordant.

  19. Kinetic Scale Density Fluctuations in the Solar Wind

    CERN Document Server

    Chen, C H K; Bonnell, J W; Mozer, F S; Klein, K G; Bale, S D

    2013-01-01

    We motivate the importance of studying kinetic scale turbulence for understanding the macroscopic properties of the heliosphere, such as the heating of the solar wind. We then discuss the technique by which kinetic scale density fluctuations can be measured using the spacecraft potential, including a calculation of the timescale for the spacecraft potential to react to the density changes. Finally, we compare the shape of the density spectrum at ion scales to theoretical predictions based on a cascade model for kinetic turbulence. We conclude that the shape of the spectrum, including the ion scale flattening, can be captured by the sum of passive density fluctuations at large scales and kinetic Alfven wave turbulence at small scales.

  20. Non-standard primordial fluctuations and nongaussianity in string inflation

    CERN Document Server

    Burgess, C P; Gomez-Reino, M; Quevedo, F; Tasinato, G; Zavala, I

    2010-01-01

    Inflationary scenarios in string theory often involve a large number of light scalar fields, whose presence can enrich the post-inflationary evolution of primordial fluctuations generated during the inflationary epoch. We provide a simple example of such post-inflationary processing within an explicit string-inflationary construction, using a Kahler modulus as the inflaton within the framework of LARGE Volume Type-IIB string flux compactifications. We argue that inflationary models within this broad category often have a selection of scalars that are light enough to be cosmologically relevant, whose contributions to the primordial fluctuation spectrum can compete with those generated in the standard way by the inflaton. These models consequently often predict nongaussianity at a level, f_NL ~ O(10), potentially observable by the Planck satellite, with a bi-spectrum maximized by triangles with squeezed shape in a string realisation of the curvaton scenario. We argue that the observation of such a signal would ...

  1. Introduction to multifractal detrended fluctuation analysis in matlab.

    Science.gov (United States)

    Ihlen, Espen A F

    2012-01-01

    Fractal structures are found in biomedical time series from a wide range of physiological phenomena. The multifractal spectrum identifies the deviations in fractal structure within time periods with large and small fluctuations. The present tutorial is an introduction to multifractal detrended fluctuation analysis (MFDFA) that estimates the multifractal spectrum of biomedical time series. The tutorial presents MFDFA step-by-step in an interactive Matlab session. All Matlab tools needed are available in Introduction to MFDFA folder at the website www.ntnu.edu/inm/geri/software. MFDFA are introduced in Matlab code boxes where the reader can employ pieces of, or the entire MFDFA to example time series. After introducing MFDFA, the tutorial discusses the best practice of MFDFA in biomedical signal processing. The main aim of the tutorial is to give the reader a simple self-sustained guide to the implementation of MFDFA and interpretation of the resulting multifractal spectra.

  2. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  3. A fluidized granular medium as an instance of the Fluctuation theorem

    Science.gov (United States)

    Menon, Narayanan; Feitosa, Klebert

    2003-03-01

    Recent theoretical work by Gallavotti and Cohen has led to a theorem on the spectrum of fluctuations in the entropy production rate of a driven nonequilibrium steady state. This fluctuation theorem has been difficult to experimentally illustrate in a macroscopic system because the fluctuations are typically too small to apply strong tests of the results of the theorem. We apply the theorem's result to a particulate system where fluctuations are quite large. The experimental quantities we study are the fluctuations in the flux of power and momentum into a small volume of a 2D vibration-fluidized granular medium. We find that the ratio of the probabilities of a positive and a negative fluctuation of a given amplitude is approximately exponential in that amplitude. We acknowledge support from NSF DMR-9874833.

  4. Localized Spectral Analysis of Fluctuating Power Generation from Solar Energy Systems

    Directory of Open Access Journals (Sweden)

    Johan Nijs

    2007-01-01

    Full Text Available Fluctuations in solar irradiance are a serious obstacle for the future large-scale application of photovoltaics. Occurring regularly with the passage of clouds, they can cause unexpected power variations and introduce voltage dips to the power distribution system. This paper proposes the treatment of such fluctuating time series as realizations of a stochastic, locally stationary, wavelet process. Its local spectral density can be estimated from empirical data by means of wavelet periodograms. The wavelet approach allows the analysis of the amplitude of fluctuations per characteristic scale, hence, persistence of the fluctuation. Furthermore, conclusions can be drawn on the frequency of occurrence of fluctuations of different scale. This localized spectral analysis was applied to empirical data of two successive years. The approach is especially useful for network planning and load management of power distribution systems containing a high density of photovoltaic generation units.

  5. Fluctuations in diffusion processes in microgravity.

    Science.gov (United States)

    Mazzoni, Stefano; Cerbino, Roberto; Vailati, Alberto; Giglio, Marzio

    2006-09-01

    It has been shown recently that diffusion processes exhibit giant nonequilibrium fluctuations (NEFs). That is, the diffusing fronts display corrugations whose length scale ranges from the molecular to the macroscopic one. The amplitude of the NEF diverges following a power law behavior proportional to q(-4) (where q is the wave vector). However, fluctuations of wave number smaller than a critical "rolloff" wave vector are quenched by the presence of gravity. It is therefore expected that in microgravity conditions, the amplitude of the NEF should be boosted by the absence of the buoyancy-driven restoring force. This may affect any diffusion process performed in microgravity, such as the crystallization of a protein solution induced by the diffusion of a salt buffer. The aim of GRADFLEX (GRAdient-Driven FLuctuation EXperiment), a joint project of ESA and NASA, is to investigate the presence of NEFs arising in a diffusion process under microgravity conditions. The project consists of two experiments. One is carried out by UNIMI (University of Milan) and INFM (Istituto Nazionale per la Fisica della Materia) and is focused on NEF in a concentration diffusion process. The other experiment is performed by UCSB (University of California at Santa Barbara) concerning temperature NEF in a simple fluid. In the UNIMI part of the GRADFLEX experimental setup, NEFs are induced in a binary mixture by means of the Soret effect. The diagnostic method is an all-optical quantitative shadowgraph technique. The power spectrum of the induced NEFs is obtained by the processing of the shadowgraph images. A detailed description of the experimental apparatus as well as the ground-based experimental results is presented here for the UNIMI-INFM experiment. The GRADFLEX payload is scheduled to fly on the FOTON M3 capsule in April 2007.

  6. Cosmic Infrared Background Fluctuations and Zodiacal Light

    Science.gov (United States)

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

    2017-01-01

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR (near-infrared)background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC (Infrared Array Camera) observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS (Cosmic Evolution Survey) field at low ecliptic latitude where the zodiacal light intensity varies by factors of approximately 2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (greater than or approximately equal to 100 arcseconds) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

  7. Spin fluctuations in 3d paramagnetic metals

    Science.gov (United States)

    Wysocki, Aleksander; Kutepov, Andrey; Antropov, Vladimir

    Spin fluctuations (SFs) in 3d paramagnetic metals were investigated using the linear response formalism within the time dependent density functional theory. An efficient scheme of frequency integration using the Matsubara technique has been implemented and tested. The SFs spectrum in 3d paramagnets is analyzed in real and reciprocal spaces as a function of frequency and temperature. For all materials the SFs are characterized by the coexistence of low and high energy branches which originate from different regions of the Brillouin zone. The low-energy ones can be measured by neutron scattering experiments while the high-energy SFs appear to be more localized. Further, we studied the nature of square of fluctuating magnetic moment in these materials. This work was supported, in part, by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy (DOE), and by the Office of Basic Energy Science, Division of Materials Science and Engineering. The research was performed at Ames Laboratory, which is operated for the U.S. DOE by Iowa State University under contract # DE-AC02-07CH11358.

  8. Cosmic Infrared Background Fluctuations and Zodiacal Light

    Science.gov (United States)

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

    2017-01-01

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR (near-infrared)background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC (Infrared Array Camera) observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS (Cosmic Evolution Survey) field at low ecliptic latitude where the zodiacal light intensity varies by factors of approximately 2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (greater than or approximately equal to 100 arcseconds) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

  9. How to observe fluctuating temperature?

    CERN Document Server

    Utyuzh, O V; Wlodarczyk, Z

    2001-01-01

    We provide arguments that event-by-event (EBE) analysis of multiparticle production data are ideal place to search for the possible fluctuation of temperature characterizing hadronizing source in thermodynamical approach.

  10. Local fluctuations in solution mixtures

    Science.gov (United States)

    Ploetz, Elizabeth A.; Smith, Paul E.

    2011-01-01

    An extension of the traditional Kirkwood-Buff (KB) theory of solutions is outlined which provides additional fluctuating quantities that can be used to characterize and probe the behavior of solution mixtures. Particle-energy and energy-energy fluctuations for local regions of any multicomponent solution are expressed in terms of experimentally obtainable quantities, thereby supplementing the usual particle-particle fluctuations provided by the established KB inversion approach. The expressions are then used to analyze experimental data for pure water over a range of temperatures and pressures, a variety of pure liquids, and three binary solution mixtures – methanol and water, benzene and methanol, and aqueous sodium chloride. In addition to providing information on local properties of solutions it is argued that the particle-energy and energy-energy fluctuations can also be used to test and refine solute and solvent force fields for use in computer simulation studies. PMID:21806137

  11. Fluctuating attention in Parkinson's disease

    DEFF Research Database (Denmark)

    Starrfelt, Randi; Aarsland, Dag; Janvin, Carmen

    2001-01-01

    great variability in performance in reactiontime tasks. Aiming to investigate fluctuation of attention in PD, we re- analysed data from a cue-target reactiontime task, specifically searching for differences in variability between patients and controls. The subjects included were a representative group...... a significant difference (pattention might be fluctuating on a moment to moment basis in PD. Some of the PD patients have also been tested with a choice reaction time...... task, shown by Walker et al. (2000) to be sensi- tive to fluctuation of cognition in DLB patients. Preliminary data-analysis indicate that PD patients also show considerable intra-individual variation in performance on this test. These findings suggest that fluctuating attention and cogni- tion...

  12. Decoherence induced by fluctuating boundaries

    CERN Document Server

    De Lorenci, V A

    2012-01-01

    The effects of fluctuating boundaries on a superposition state of a quantum particle in a box is studied. We consider a model in one space dimension in which the initial state is a coherent superposition of two energy eigenstates. The locations of the walls of the box are assumed to undergo small fluctuation with a Gaussian probability distribution. The spatial probability density of the particle contains an interference term, which is found to decay in time due to the boundary fluctuations. At late times, this term vanishes and the quantum coherence is lost. The system is now described by a density matrix rather than a pure quantum state.This model gives a simple illustration of how environment-induced decoherence can take place in quantum systems. It can also serve as an analog model for the effects of spacetime geometry fluctuations on quantum systems.

  13. Gaussian fluctuations in chaotic eigenstates

    CERN Document Server

    Srednicki, M A; Srednicki, Mark; Stiernelof, Frank

    1996-01-01

    We study the fluctuations that are predicted in the autocorrelation function of an energy eigenstate of a chaotic, two-dimensional billiard by the conjecture (due to Berry) that the eigenfunction is a gaussian random variable. We find an explicit formula for the root-mean-square amplitude of the expected fluctuations in the autocorrelation function. These fluctuations turn out to be O(\\hbar^{1/2}) in the small \\hbar (high energy) limit. For comparison, any corrections due to scars from isolated periodic orbits would also be O(\\hbar^{1/2}). The fluctuations take on a particularly simple form if the autocorrelation function is averaged over the direction of the separation vector. We compare our various predictions with recent numerical computations of Li and Robnik for the Robnik billiard, and find good agreement. We indicate how our results generalize to higher dimensions.

  14. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  15. Buck supplies output voltage ripple reduction using fuzzy control

    Directory of Open Access Journals (Sweden)

    Nicu BIZON

    2007-12-01

    Full Text Available Using the PWM control for switching power supplies the peaks EMI noise appear at the switching frequency and its harmonics. Using randomize or chaotic PWM control techniques in these systems the power spectrum is spread out in all frequencies band spectral emissions, but with a bigger ripple in the output voltage. The proposed nonlinear feedback control method, which induces chaos, is based by fuzzy rules that minimize the output voltage ripple. The feasibility and effectiveness of this relative simple method is shown by simulation. A comparison with the previous control method is included, too.

  16. Principle of minimal work fluctuations.

    Science.gov (United States)

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality 〈e-βW〉=e-βΔF, a change in the fluctuations of e-βW may impact how rapidly the statistical average of e-βW converges towards the theoretical value e-βΔF, where W is the work, β is the inverse temperature, and ΔF is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-βW. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-βW, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-βW. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014)].

  17. Turbulence in nearly incompressible fluids: density spectrum, flows, correlations and implication to the interstellar medium

    Directory of Open Access Journals (Sweden)

    S. Dastgeer

    2005-01-01

    Full Text Available Interstellar scintillation and angular radio wave broadening measurements show that interstellar and solar wind (electron density fluctuations exhibit a Kolmogorov-like k-5/3 power spectrum extending over many decades in wavenumber space. The ubiquity of the Kolmogorov-like interstellar medium (ISM density spectrum led to an explanation based on coupling incompressible magnetohydrodynamic (MHD fluctuations to density fluctuations through a 'pseudosound' relation within the context of 'nearly incompressible' (NI hydrodynamics (HD and MHD models. The NI theory provides a fundamentally different explanation for the observed ISM density spectrum in that the density fluctuations can be a consequence of passive scalar convection due to background incompressible fluctuations. The theory further predicts generation of long-scale structures and various correlations between the density, temperature and the (magneto acoustic as well as convective pressure fluctuations in the compressible ISM fluids in different thermal regimes that are determined purely by the thermal fluctuation level. In this paper, we present the results of our two dimensional nonlinear fluid simulations, exploring various nonlinear aspects that lead to inertial range ISM turbulence within the context of a NI hydrodymanics model. In qualitative agreement with the NI predictions and the in-situ observations, we find that i the density fluctuations exhibit a Kolmogorov-like spectrum via a passive convection in the field of the background incompressible fluctuations, ii the compressible ISM fluctuations form long scale flows and structures, and iii the density and the temperature fluctuations are anti-correlated.

  18. Fluctuations in classical sum rules.

    Science.gov (United States)

    Elton, John R; Lakshminarayan, Arul; Tomsovic, Steven

    2010-10-01

    Classical sum rules arise in a wide variety of physical contexts. Asymptotic expressions have been derived for many of these sum rules in the limit of long orbital period (or large action). Although sum-rule convergence may well be exponentially rapid for chaotic systems in a global phase-space sense with time, individual contributions to the sums may fluctuate with a width which diverges in time. Our interest is in the global convergence of sum rules as well as their local fluctuations. It turns out that a simple version of a lazy baker map gives an ideal system in which classical sum rules, their corrections, and their fluctuations can be worked out analytically. This is worked out in detail for the Hannay-Ozorio sum rule. In this particular case the rate of convergence of the sum rule is found to be governed by the Pollicott-Ruelle resonances, and both local and global boundaries for which the sum rule may converge are given. In addition, the width of the fluctuations is considered and worked out analytically, and it is shown to have an interesting dependence on the location of the region over which the sum rule is applied. It is also found that as the region of application is decreased in size the fluctuations grow. This suggests a way of controlling the length scale of the fluctuations by considering a time dependent phase-space volume, which for the lazy baker map decreases exponentially rapidly with time.

  19. Transient demonstration of exciton behaviours in solid state cathodoluminescence under different driving voltage

    Institute of Scientific and Technical Information of China (English)

    Zhang Fu-Jun; Zhao Su-Ling; Xu Zheng; Huang Jin-Zhao; Xu Xu-Rong

    2007-01-01

    In the solid state cathodoluminescence (SSCL), organic materials were excited by hot electrons accelerated in silicon oxide (SiO2) layer under alternating current (AC). In this paper exciton behaviours were analysed by using transient spectra under different driving voltages. The threshold voltages of SSCL and exciton ionization were obtained from the transient spectra. The recombination radiation occurred when the driving voltage went beyond the threshold voltage of exciton ionization. Prom the transient spectrum of two kinds of luminescence (exciton emission and recombination radiation), it was demonstrated that recombination radiation should benefit from the exciton ionization.

  20. SVPWM Technique with Varying DC-Link Voltage for Common Mode Voltage Reduction in a Matrix Converter and Analytical Estimation of its Output Voltage Distortion

    Science.gov (United States)

    Padhee, Varsha

    Common Mode Voltage (CMV) in any power converter has been the major contributor to premature motor failures, bearing deterioration, shaft voltage build up and electromagnetic interference. Intelligent control methods like Space Vector Pulse Width Modulation (SVPWM) techniques provide immense potential and flexibility to reduce CMV, thereby targeting all the afore mentioned problems. Other solutions like passive filters, shielded cables and EMI filters add to the volume and cost metrics of the entire system. Smart SVPWM techniques therefore, come with a very important advantage of being an economical solution. This thesis discusses a modified space vector technique applied to an Indirect Matrix Converter (IMC) which results in the reduction of common mode voltages and other advanced features. The conventional indirect space vector pulse-width modulation (SVPWM) method of controlling matrix converters involves the usage of two adjacent active vectors and one zero vector for both rectifying and inverting stages of the converter. By suitable selection of space vectors, the rectifying stage of the matrix converter can generate different levels of virtual DC-link voltage. This capability can be exploited for operation of the converter in different ranges of modulation indices for varying machine speeds. This results in lower common mode voltage and improves the harmonic spectrum of the output voltage, without increasing the number of switching transitions as compared to conventional modulation. To summarize it can be said that the responsibility of formulating output voltages with a particular magnitude and frequency has been transferred solely to the rectifying stage of the IMC. Estimation of degree of distortion in the three phase output voltage is another facet discussed in this thesis. An understanding of the SVPWM technique and the switching sequence of the space vectors in detail gives the potential to estimate the RMS value of the switched output voltage of any

  1. Probing Reionization through Near-Infrared Background Fluctuations with CIBER

    Science.gov (United States)

    Sullivan, Ian S.

    2010-01-01

    The Cosmic Infrared Background Experiment (CIBER) is a NASA sounding rocket payload that was first launched in February 2009. CIBER consists of four co-aligned instruments designed with foreground subtraction and control of systematics in mind. In addition, the platform of a sounding rocket enables observations of the NIRB outside of narrow atmospheric windows that are uncontaminated by airglow. We will present preliminary results from the first flight. CIBER seeks to measure the absolute brightness spectrum of the extragalactic NIRB, and has two spectrometers dedicated to that purpose. One, a high-resolution Fabry-Perot spectometer, is tuned to the 8545 nm Ca II line of the solar spectrum, and is designed to measure the absolute brightness of the Zodiacal Light directly, which is the source of greatest uncertainty in the NIRB spectrum. The second spectrometer measures the NIRB spectrum from 700nm to 1800nm, which spans the wavelength range where a Lyman cutoff feature from Reionization could appear. CIBER also houses two Infrared imaging telescopes, which have identical optics that give 2º x 2º field of views with 7 arcsec pixels, but have different band defining filters. The first imager has a wide band centered at 1600nm, and images the background at the expected peak of the spectrum. The imagers’ wide field of view allows them to measure the distinctive power spectrum peaking at 10 arcminutes. The second imager has a wide band centered at 1000nm that is intended to image at wavelengths shorter than the Lyman cutoff, and provides a powerful systematic test for any detection made at 1600 nm. First-light fluctuations should have a distinctive spatial power spectrum with very red 1600nm / 1000nm color, distinctly redder than the approximately solar color of any residual fluctuations arising from Zodiacal light, Galactic starlight, or low-redshift galaxies.

  2. Order by virtual crystal field fluctuations in pyrochlore XY antiferromagnets

    Science.gov (United States)

    Rau, Jeffrey G.; Petit, Sylvain; Gingras, Michel J. P.

    2016-05-01

    Conclusive evidence of order by disorder is scarce in real materials. Perhaps one of the strongest cases presented has been for the pyrochlore XY antiferromagnet Er2Ti2O7 , with the ground state selection proceeding by order by disorder induced through the effects of quantum fluctuations. This identification assumes the smallness of the effect of virtual crystal field fluctuations that could provide an alternative route to picking the ground state. Here we show that this order by virtual crystal field fluctuations is not only significant, but competitive with the effects of quantum fluctuations. Further, we argue that higher-multipolar interactions that are generically present in rare-earth magnets can dramatically enhance this effect. From a simplified bilinear-biquadratic model of these multipolar interactions, we show how the virtual crystal field fluctuations manifest in Er2Ti2O7 using a combination of strong-coupling perturbation theory and the random-phase approximation. We find that the experimentally observed ψ2 state is indeed selected and the experimentally measured excitation gap can be reproduced when the bilinear and biquadratic couplings are comparable while maintaining agreement with the entire experimental spin-wave excitation spectrum. Finally, we comment on possible tests of this scenario and discuss implications for other order-by-disorder candidates in rare-earth magnets.

  3. Charge density fluctuation of low frequency in a dusty plasma

    Institute of Scientific and Technical Information of China (English)

    李芳; 吕保维; O.Havnes

    1997-01-01

    The charge density fluctuation of low frequency in a dusty plasma, which is derived from the longitudinal dielectric permittivity of the dusty plasma, has been studied by kinetic theory. The results show that the P value, which describes the relative charge density on the dust in the plasma, and the charging frequency of a dust particle Ωc, which describes the ratio of charge changing of the dust particles, determine the character of the charge density fluctuation of low frequency. For a dusty plasma of P<<1, when the charging frequency Ωc is much smaller than the dusty plasma frequency wd, there is a strong charge density fluctuation which is of character of dust acoustic eigen wave. For a dusty plasma of P>>1, when the frequency Ωc, is much larger than wd there are weaker fluctuations with a wide spectrum. The results have been applied to the ionosphere and the range of radius and density of dust particles is found, where a strong charge density fluctuation of low frequency should exist.

  4. Spatial fluctuation of forest fires and their regional behaviors

    Institute of Scientific and Technical Information of China (English)

    Mingyu WANG; Long SUN; Lifu SHU; Xiaorui TIAN

    2008-01-01

    Historical forest fire records from Alaska State (1950-2000),California State (1895-2001), USA and Heilongjiang Province (1980-1999), China were used to calculate the longitude and latitude of the annual burned area's centroids for these regions. Fluctuation phenomena by year were analyzed using spectrum analysis. The results show that centroids of burned areas in these three regions are in a fluctuating condition that encircles the distribution center. The distribution centers are 151.11°W, 64.96°N in Alaska State, 120.02°W, 37.11°N in California State and 127.07°E, 49.59°N in Heilongjiang Province, respectively. The fluctuation of the burned area's centroids in Alaska State and California State in longitude has obvious periodicity,and the periodicities are 4.2 years,6.25 years in Alaska State and 6.24 years, 106 years in California State. The fluctuation of the burned area's centroids in Heilongjiang Province has a periodicity both in longitude and latitude, and the periodicities are both 3.3 years, 6.67 years. Fluctuation of the burned area's centroids in Alaska State and California State in latitude does not have periodicity, and big forest fires with low frequencies predominate.

  5. Study of fluctuation and turbulance of JFT-2M

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, Hiroshi; Hanada, Kazuaki; Yamagishi, Kenichi [Tokyo Univ. (Japan)] [and others

    1998-01-01

    In many improved containment modes, it is said that E x B shear flow formed by shear of radial electric field acts as a mechanism of fluctuation control. In order to understand the mechanism of these improved containment modes, it is necessary to investigate a cause and result relation between controls of fluctuation on formation of sheared flow and fluctuating magnetic wave by using geometrical optics approximation. In this study, the following articles were conducted: (1) to improve a reflectometer with fixed 1-ch frequency using at last fiscal year to one with 2-ch variable frequency to test density fluctuation ranging 0.98 to 3.1 x 10(exp 19)m(sup-3) in density, (2) to examine a relationship between runaway phase and scattering, to propose and application of complex spectrum for usable analytical method even to runaway phase, (3) to study density fluctuation at L-H transition by using this analytical method, and (4) to research cause and result relation of the L-H transition by measuring various plasma parameters by inserting a triple probe array into main plasma. (G.K.)

  6. Electron temperature fluctuation in the HT-7 tokamak plasma observed by electron cyclotron emission imaging

    Institute of Scientific and Technical Information of China (English)

    Xu Xiao-Yuan; Wang Jun; Yu Yi; Wen Yi-Zhi; Yu Chang-Xuan; Liu Wan-Dong; Wan Bao-Nian; Gao Xiang; N. C. Luhmann; C. W. Domier; Jian Wang; Z. G. Xia; Zuowei Shen

    2009-01-01

    The fluctuation of the electron temperature has been measured by using the electron cyclotron emission imaging in the Hefei Tokamak-7 (HT-7) plasma. The electron temperature fluctuation with a broadband spectrum shows that it propagates in the electron diamagnetic drift direction, and the mean poloidal wave-number kg is calculated to be about 1.58 cm-1, or keps ≈0.34. It indicates that the fluctuation should come from the electron drift wave turbulence. The linear global scaling of the electron temperature fluctuation with the gradient of electron temperature is consistent with the mixing length scale qualitatively. Evolution of spectrum of the fluctuation during the sawtooth oscillation phases is investigated, and the fluctuation is found to increase with the gradient of electron temperature increasing during most phases of the sawtooth oscillation. The results indicate that the electron temperature gradient is probably the driver of the fluctuation enhancement. The steady heat flux driven by electron temperature fluctuation is estimated and compared with the results from power balance estimation.

  7. Primordial fluctuations from deformed quantum algebras

    Energy Technology Data Exchange (ETDEWEB)

    Day, Andrew C. [Department of Applied Mathematics, University of Western Ontario London, ON, Canada N6A 5B7 (Canada); Brown, Iain A. [Institute of Theoretical Astrophysics, University of Oslo P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Seahra, Sanjeev S., E-mail: aday46@uwo.ca, E-mail: ibrown@astro.uio.no, E-mail: sseahra@unb.ca [Department of Mathematics and Statistics, University of New Brunswick Fredericton, NB, Canada E3B 5A3 (Canada)

    2014-03-01

    We study the implications of deformed quantum algebras for the generation of primordial perturbations from slow-roll inflation. Specifically, we assume that the quantum commutator of the inflaton's amplitude and momentum in Fourier space gets modified at energies above some threshold M{sub *}. We show that when the commutator is modified to be a function of the momentum only, the problem of solving for the post-inflationary spectrum of fluctuations is formally equivalent to solving a one-dimensional Schr and quot;odinger equation with a time dependent potential. Depending on the class of modification, we find results either close to or significantly different from nearly scale invariant spectra. For the former case, the power spectrum is characterized by step-like behaviour at some pivot scale, where the magnitude of the jump is O(H{sup 2}/M{sub *}{sup 2}). (H is the inflationary Hubble parameter.) We use our calculated power spectra to generate predictions for the cosmic microwave background and baryon acoustic oscillations, hence demonstrating that certain types of deformations are incompatible with current observations.

  8. Primordial fluctuations from deformed quantum algebras

    CERN Document Server

    Day, Andrew C; Seahra, Sanjeev S

    2013-01-01

    We study the implications of deformed quantum algebras for the generation of primordial perturbations from slow-roll inflation. Specifically, we assume that the quantum commutator of the inflaton's amplitude and momentum in Fourier space gets modified at energies above some threshold $M_{\\star}$. We show that when the commutator is modified to be a function of the momentum only, the problem of solving for the post-inflationary spectrum of fluctuations is formally equivalent to solving a one-dimensional Schr\\"odinger equation with a time dependent potential. Depending on the class of modification, we find results either close to or significantly different from nearly scale invariant spectra. For the former case, the power spectrum is characterized by step-like behaviour at some pivot scale, where the magnitude of the jump is $\\mathcal{O}(H^{2}/M_{\\star}^{2})$. ($H$ is the inflationary Hubble parameter.) We use our calculated power spectra to generate predictions for the cosmic microwave background and baryon a...

  9. Fluctuation Analyses for Pattern Classification in Nondestructive Materials Inspection

    Directory of Open Access Journals (Sweden)

    A. P. Vieira

    2010-01-01

    Full Text Available We review recent work on the application of fluctuation analyses of time series for pattern classification in nondestructive materials inspection. These analyses are based on the evaluation of time-series fluctuations across time intervals of increasing size, and were originally introduced in the study of fractals. A number of examples indicate that this approach yields relevant features allowing the successful classification of patterns such as (i microstructure signatures in cast irons, as probed by backscattered ultrasonic signals; (ii welding defects in metals, as probed by TOFD ultrasonic signals; (iii gear faults, based on vibration signals; (iv weld-transfer modes, as probed by voltage and current time series; (v microstructural composition in stainless steel, as probed by magnetic Barkhausen noise and magnetic flux signals.

  10. Spectrum analysis of hydrogen plasma in spherically convergent beam fusion

    Energy Technology Data Exchange (ETDEWEB)

    Ogasawara, Kazuki; Yamauchi, Kunihito; Watanabe, Masato; Sunaga, Yoshitaka; Hotta, Eiki [Tokyo Institute of Technology, Dept. of Energy Sciences, Yokohama, Kanagawa (Japan); Okino, Akitoshi [Tokyo Institute of Technology, Dept. of Electrical and Electronic Engineering, Tokyo (Japan)

    2001-09-01

    Spectroscopic analysis of spherical glow discharge fusion device was carried out using hydrogen gas. Effects of the discharge current and cathode voltage on spectrum profiles of hydrogen Balmar lines were measured. The profiles of all hydrogen lines were broadened with the cathode voltage. From the relationship between the maximum broadening width and the cathode voltage, it was indicated that the broadening was caused by the Doppler effect. From the spatial distribution of emission intensity, it was found that plasma core size became larger with discharge current and smaller with cathode voltage. (author)

  11. Enhanced stochastic fluctuations to measure steep adhesive energy landscapes.

    Science.gov (United States)

    Haider, Ahmad; Potter, Daniel; Sulchek, Todd A

    2016-12-13

    Free-energy landscapes govern the behavior of all interactions in the presence of thermal fluctuations in the fields of physical chemistry, materials sciences, and the biological sciences. From the energy landscape, critical information about an interaction, such as the reaction kinetic rates, bond lifetimes, and the presence of intermediate states, can be determined. Despite the importance of energy landscapes to understanding reaction mechanisms, most experiments do not directly measure energy landscapes, particularly for interactions with steep force gradients that lead to premature jump to contact of the probe and insufficient sampling of transition regions. Here we present an atomic force microscopy (AFM) approach for measuring energy landscapes that increases sampling of strongly adhesive interactions by using white-noise excitation to enhance the cantilever's thermal fluctuations. The enhanced fluctuations enable the recording of subtle deviations from a harmonic potential to accurately reconstruct interfacial energy landscapes with steep gradients. Comparing the measured energy landscape with adhesive force measurements reveals the existence of an optimal excitation voltage that enables the cantilever fluctuations to fully sample the shape and depth of the energy surface.

  12. Wide Operational Range Processor Power Delivery Design for Both Super-Threshold Voltage and Near-Threshold Voltage Computing

    Institute of Scientific and Technical Information of China (English)

    Xin He; Gui-Hai Yan; Yin-He Han; Xiao-Wei Li

    2016-01-01

    The load power range of modern processors is greatly enlarged because many advanced power management techniques are employed, such as dynamic voltage frequency scaling, Turbo Boosting, and near-threshold voltage (NTV) technologies. However, because the efficiency of power delivery varies greatly with different load conditions, conventional power delivery designs cannot maintain high efficiency over the entire voltage spectrum, and the gained power saving may be offset by power loss in power delivery. We propose SuperRange, a wide operational range power delivery unit. SuperRange complements the power delivery capability of on-chip voltage regulator and off-chip voltage regulator. On top of SuperRange, we analyze its power conversion characteristics and propose a voltage regulator (VR) aware power management algorithm. Moreover, as more and more cores have been integrated on a singe chip, multiple SuperRange units can serve as basic building blocks to build, in a highly scalable way, more powerful power delivery subsystem with larger power capacity. Experimental results show SuperRange unit offers 1x and 1.3x higher power conversion efficiency (PCE) than other two conventional power delivery schemes at NTV region and exhibits an average 70%PCE over entire operational range. It also exhibits superior resilience to power-constrained systems.

  13. Sectoral Shifts and Cyclical Fluctuations Sectoral Shifts and Cyclical Fluctuations

    Directory of Open Access Journals (Sweden)

    Richard Rogerson

    1991-03-01

    Full Text Available Sectoral Shifts and Cyclical Fluctuations This paper studies a two sector real business cycle model in which the sectors experience different trend rates of growth and labor mobility is costly. Predictions are derived concerning the correlation between sectoral reallocation of workers and the cycle. This correlation may be positive or negative depending upon whether the growing sector displays larger or smaller fluctuations than the shrinking sector. The post- World War II period has witnessed two major patterns of sectoral change in industrialized countries: movement out of agriculture and movement out of the industrial sector. The model's basic prediction is shown to be consistent with the observed pattern of reallocation.

  14. Fission Spectrum

    Science.gov (United States)

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  15. Comparison of control strategies for DFIG under symmetrical grid voltage dips

    DEFF Research Database (Denmark)

    Chen, Wenjie; Xu, Dehong; Chen, Min;

    2013-01-01

    This paper presents a series of current control strategies for the DFIG under symmetrical grid voltage dips. The controllable range, the damping time constant of the stator natural flux and the torque fluctuations of six control strategies are analyzed and compared. The control strategies which...

  16. Kerr black hole thermodynamical fluctuations

    Science.gov (United States)

    Pavon, D.; Rubi, J. M.

    1985-04-01

    The near-equilibrium thermodynamical (TD) fluctuations of a massive rotating uncharged Kerr black hole immersed in a uniformly corotating radiation bath at its temperature are investigated theoretically, generalizing Schwarzschild-black-hole analysis of Pavon and Rubi(1983), based on Einstein fluctuation theory. The correlations for the energy and angular moment fluctuations and the second moments of the other TD parameters are obtained, and the generalized second law of black-hole TD and the Bekenstein (1975) interpretation of black-hole entropy are seen as functioning well in this case. A local-stability criterion and relation for TD equilibrium between the Kerr hole and its own radiation in the flat-space-time limit are derived, and a restriction between C and Lambda is deduced.

  17. Fluctuation theorems for quantum processes

    CERN Document Server

    Albash, Tameem; Marvian, Milad; Zanardi, Paolo

    2013-01-01

    We present fluctuation theorems and moment generating function equalities for generalized thermodynamic observables and quantum dynamics described by completely positive trace preserving (CPTP) maps, with and without feedback control. Our results include the quantum Jarzynski equality and Crooks fluctuation theorem, and clarify the special role played by the thermodynamic work and thermal equilibrium states in previous studies. We show that unitality replaces micro-reversibility as the condition for the physicality of the reverse process in our fluctuation theorems. We present an experimental application of our theory to the problem of extracting the system-bath coupling magnitude, which we do for a system of pairs of coupled superconducting flux qubits undergoing quantum annealing.

  18. Kaon fluctuations from lattice QCD

    CERN Document Server

    Noronha-Hostler, Jacquelyn; Gunther, Jana; Parotto, Paolo; Pasztor, Attila; Vazquez, Israel Portillo; Ratti, Claudia

    2016-01-01

    We show that it is possible to isolate a set of kaon fluctuations in lattice QCD. By means of the Hadron Resonance Gas (HRG) model, we calculate the actual kaon second-to-first fluctuation ratio, which receives contribution from primordial kaons and resonance decays, and show that it is very close to the one obtained for primordial kaons in the Boltzmann approximation. The latter only involves the strangeness and electric charge chemical potentials, which are functions of $T$ and $\\mu_B$ due to the experimental constraint on strangeness and electric charge, and can therefore be calculated on the lattice. This provides an unambiguous method to extract the kaon freeze-out temperature, by comparing the lattice results to the experimental values for the corresponding fluctuations.

  19. Fluctuations in Relativistic Causal Hydrodynamics

    CERN Document Server

    Kumar, Avdhesh; Mishra, Ananta P

    2013-01-01

    The formalism to calculate the hydrodynamics fluctuation using the quasi-stationary fluctuation theory of Onsager to the relativistic Navier-Stokes hydrodynamics is already known. In this work we calculate hydrodynamic fluctuations in relativistic causal theory of Muller, Israel and Stewart and other related causal hydrodynamic theories. We show that expressions for the Onsager coefficients and the correlation functions have form similar to the ones obtained by using Navier-Stokes equation. However, temporal evolution of the correlation functions obtained using MIS and the other causal theories can be significantly different than the correlation functions obtained using the Navier-Stokes equation. Finally, as an illustrative example, we explicitly plot the correlation functions obtained using the causal-hydrodynamics theories and compare them with correlation functions obtained by earlier authors using the expanding boost-invariant (Bjorken) flows.

  20. Quantum fluctuations in mesoscopic systems

    Science.gov (United States)

    Benatti, F.; Carollo, F.; Floreanini, R.; Narnhofer, H.

    2017-10-01

    Recent experimental results point to the existence of coherent quantum phenomena in systems made of a large number of particles, despite the fact that for many-body systems the presence of decoherence is hardly negligible and emerging classicality is expected. This behaviour hinges on collective observables, named quantum fluctuations, that retain a quantum character even in the thermodynamic limit: they provide useful tools for studying properties of many-body systems at the mesoscopic level, in-between the quantum microscopic scale and the classical macroscopic one. We herein present the general theory of quantum fluctuations in mesoscopic systems, and study their dynamics in a quantum open system setting, taking into account the unavoidable effects of dissipation and noise induced by the external environment. As in the case of microscopic systems, decoherence is not always the only dominating effect at the mesoscopic scale: certain types of environment can provide means for entangling collective fluctuations through a purely noisy mechanism.

  1. Fluctuation scaling in point processes

    CERN Document Server

    Koyama, Shinsuke

    2014-01-01

    Fluctuation scaling has universally been observed in a wide variety of phenomena. For time series describing sequences of events, it can be expressed as power function relationship between the variance and the mean of either the inter-event interval or counting statistics, depending on the measurement variables. In this article, fluctuation scaling for series of events is formulated for the first time, in which the scaling exponents in the inter-event interval and counting statistics are related. It is also shown that a simple mechanism consisting of first-passage time to a threshold for Ornstein-Uhlenbeck processes explains fluctuation scaling with various exponents depending on the subthreshold dynamics. A possible implication of the results is discussed in terms of characterizing `intrinsic' variability of neuronal discharges.

  2. Voltage Sensors Monitor Harmful Static

    Science.gov (United States)

    2009-01-01

    A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

  3. A New Transformerless Single-Phase Buck-Boost AC Voltage Regulator

    Directory of Open Access Journals (Sweden)

    YALCIN, F.

    2016-05-01

    Full Text Available Voltage regulation is one of the important goals for electrical sources and consumers. In this paper a new transformerless single-phase AC voltage regulator based on buck-boost converter topology is presented. The regulator circuit has a simple structure using only two bidirectional active switches, one inductor and one capacitor. A closed loop control system is implemented for the proposed regulator operation. A control law depending on the instantaneous values of the regulator's real input and desired output voltage is obtained and supports the PI controller. The control law allows the controller to obtain efficient pulse width modulation (PWM switching duty ratio for the desired output voltage when the input voltage has surges or fluctuations and the output load is changed. An experimental laboratory setup has been implemented for the proposed AC voltage regulator. The obtained results demonstrate that the proposed topology is capable of and efficient for both bucking and boosting the input AC voltage to a high quality output voltage with a low total harmonic distortion (THD for different input voltage and load conditions.

  4. Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere

    Science.gov (United States)

    Podglajen, Aurélien; Hertzog, Albert; Plougonven, Riwal; Legras, Bernard

    2016-04-01

    Wave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum.

  5. Warm inflation with coupled thermal quantum fluctuations a new semiclassical approach

    CERN Document Server

    Bellini, M

    2000-01-01

    I consider a new semiclassical expansion for the inflaton field in theframework of warm inflation scenario. The fluctuations of the matter field areconsidered as coupled with the particles of the thermal bath. This couplingparameter depends with the temperature of the bath. The power spectrum remainsinvariant under this new semiclassical expansion for the inflaton. However, Ifind that the amplitude for the matter field fluctuations could be stronglydependent with the coupling for temperatures $T_r \\sim 10^{15}$ GeV.

  6. Calculations of Turbulent Boundary Layer (TBL) Pressure Fluctuations Transmitted into a Viscoelastic Layer

    Science.gov (United States)

    2016-06-07

    turbulent boundary layer pressure fluctuation transmitted into a layer of viscoelastic material. The theoretical model used here is a plane elastomer...Spring 1985. The objective of this paper is to develop a model for calculating the turbulent boundary layer pressure fluctuation transmitted into a...the noise level calculated in terms of decibels. FIGURE 4 (CORCOS MODEL ) This is a model cross-spectrum of turbulent wall pressure , frequently

  7. Poloidal correlation reflectometry at W7-X: radial electric field and coherent fluctuations

    Science.gov (United States)

    Windisch, T.; Krämer-Flecken, A.; Velasco, JL; Könies, A.; Nührenberg, C.; Grulke, O.; Klinger, T.; the W7-X Team

    2017-10-01

    Poloidal correlation reflectometry measurements during the first plasma campaign of the optimized stellarator Wendelstein-7X are presented. The radial electric field is determined and a comparison with neoclassical calculations and shows good qualitative agreement. The measured density fluctuation spectrum exhibits coherent low- and high-frequency modes. Magneto-hydrodynamic (MHD) modeling results suggest that the coherent fluctuations are caused by stable MHD-modes and Alfvén waves.

  8. Merits and qualms of work fluctuations in classical fluctuation theorems

    Science.gov (United States)

    Deng, Jiawen; Tan, Alvis Mazon; Hänggi, Peter; Gong, Jiangbin

    2017-01-01

    Work is one of the most basic notions in statistical mechanics, with work fluctuation theorems being one central topic in nanoscale thermodynamics. With Hamiltonian chaos commonly thought to provide a foundation for classical statistical mechanics, here we present general salient results regarding how (classical) Hamiltonian chaos generically impacts on nonequilibrium work fluctuations. For isolated chaotic systems prepared with a microcanonical distribution, work fluctuations are minimized and vanish altogether in adiabatic work protocols. For isolated chaotic systems prepared at an initial canonical distribution at inverse temperature β , work fluctuations depicted by the variance of e-β W are also minimized by adiabatic work protocols. This general result indicates that, if the variance of e-β W diverges for an adiabatic work protocol, it diverges for all nonadiabatic work protocols sharing the same initial and final Hamiltonians. Such divergence is hence not an isolated event and thus greatly impacts on the efficiency of using Jarzynski's equality to simulate free-energy differences. Theoretical results are illustrated in a Sinai model. Our general insights shall boost studies in nanoscale thermodynamics and are of fundamental importance in designing useful work protocols.

  9. Turbulent fluctuations around Bjorken flow

    CERN Document Server

    Floerchinger, Stefan

    2011-01-01

    We study the evolution of local event-by-event deviations from smooth average fluid dynamic fields, as they can arise in heavy ion collisions from the propagation of fluctuating initial conditions. Local fluctuations around Bjorken flow are found to be governed by non-linear equations whose solutions can be characterized qualitatively in terms of Reynolds numbers. Perturbations at different rapidities decouple quickly, and satisfy (after suitable coordinate transformations) an effectively two-dimensional Navier-Stokes equation of non-relativistic form. We discuss the conditions under which non-linearities in these equations cannot be neglected and turbulent behavior is expected to set in.

  10. Einstein equations with fluctuating volume

    Science.gov (United States)

    Dzhunushaliev, Vladimir; Quevedo, Hernando

    2017-07-01

    We develop a simple model to study classical fields on the background of a fluctuating spacetime volume. It is applied to formulate the stochastic Einstein equations with a perfect-fluid source. We investigate the particular case of a stochastic Friedmann-Lema\\^itre-Robertson-Walker cosmology, and show that the resulting field equations can lead to solutions which avoid the initial big bang singularity. By interpreting the fluctuations as the result of the presence of a quantum spacetime, we conclude that classical singularities can be avoided even within a stochastic model that include quantum effects in a very simple manner.

  11. Neutron fluctuation measurements on TFTR

    Science.gov (United States)

    Heidbrink, W. W.

    1986-08-01

    Measurements of fluctuations in the neutron yield are made on the tokamak fusion test reactor (TFTR) with plastic scintillators. Light from the scintillators is coupled through acrylic rods or fiber-optic cables to photomultipliers operated in current mode. Discrimination against hard x rays is accomplished through comparison with the signal from a ZnS(6Li) scintillator. These measurements are useful in studies of deuterium pellet deposition, of the acceleration of beam ions during major radial compression, and of MHD instabilities. Techniques for measuring the neutral beam density profile and Qequivdt using neutron fluctuation measurements during pellet injection also have been proposed.

  12. Fluctuation Analysis of Human Electroencephalogram

    CERN Document Server

    Hwa, R C; Hwa, Rudolph C.; Ferree, Thomas C.

    2001-01-01

    The scaling behaviors of the human electroencephalogram (EEG) time series are studied using detrended fluctuation analysis. Two scaling regions are found in nearly every channel for all subjects examined. The scatter plot of the scaling exponents for all channels (up to 129) reveals the complicated structure of a subject's brain activity. Moment analyses are performed to extract the gross features of all the scaling exponents, and another universal scaling behavior is identified. A one-parameter description is found to characterize the fluctuation properties of the nonlinear behaviors of the brain dynamics.

  13. Consistency of detrended fluctuation analysis

    CERN Document Server

    Løvsletten, Ola

    2016-01-01

    The scaling function $F(s)$ in detrended fluctuation analysis (DFA) scales as $F(s)\\sim s^{H}$ for stochastic processes with Hurst exponents $H$. We prove this scaling law for both stationary stochastic processes with $01$. As a final application of the new theory, we present an estimator $\\hat F(s)$ that can handle missing data in regularly sampled time series without the need for interpolation schemes. Under mild regularity conditions, $\\hat F(s)$ is equal in expectation to the fluctuation function $F(s)$ in the gap-free case.

  14. Low Voltage Power Supply Incorporating Ceramic Transformer

    CERN Document Server

    Imori, M

    2007-01-01

    A low voltage power supply provides the regulated output voltage of 1 V from the supply voltage around 48 V. The low voltage power supply incorporates a ceramic transformer which utilizes piezoelectric effect to convert voltage. The ceramic transformer isolates the secondary from the primary, thus providing the ground isolation between the supply and the output voltages. The ceramic transformer takes the place of the conventional magnetic transformer. The ceramic transformer is constructed from a ceramic bar and does not include any magnetic material. So the low voltage power supply can operate under a magnetic field. The output voltage is stabilized by feedback. A feedback loop consists of an error amplifier, a voltage controlled oscillator and a driver circuit. The amplitude ratio of the transformer has dependence on the frequency, which is utilized to stabilize the output voltage. The low voltage power supply is investigated on the analogy of the high voltage power supply similarly incorporating the cerami...

  15. Modular High Voltage Power Supply

    Energy Technology Data Exchange (ETDEWEB)

    Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-18

    The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

  16. Nonequilibrium fluctuations from a nematic under a thermal gradient and a gravity field*. II. Rayleigh scattering

    Science.gov (United States)

    Camacho, Jorge F.; Rodríguez, Rosalío F.

    2017-02-01

    The fluctuating hydrodynamic treatment developed in the previous article for a nematic liquid crystal under the influence of a thermal gradient α and a uniform gravity field g, is used to calculate its Rayleigh light scattering spectrum. We find that the dissipative thermal gradient force enhances the Rayleigh-line intensity which varies as k -4 with the fluctuations of the wave number k. The Rayleigh line consists of three central Lorentzians, two of which are determined by the visco-heat modes coupling the entropy and director fluctuations, which is a pure non-equilibrium effect. The third Lorentzian is due only to director fluctuations. We find that the former peaks contain the Rayleigh wings owing to the orientational fluctuations of the aniosotropic molecules. It is also shown that the obtained spectrum reduces to the known equilibrium spectrum of a nematic and to that of a simple fluid. For the particular case in which the decay rates are diffusive, we calculate and plot the amplitudes of non-equilibrium fluctuations of the dynamic structure factor as a function of | α|2/ k 4, and also, the intermediate function in the equilibrium and non-equilibrium states.

  17. Reliability criteria for voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Carson W.; Silverstein, Brian L. [Bonneville Power Administration, Portland, OR (United States)

    1994-12-31

    In face of costs pressures, there is need to allocate scare resources more effectively in order to achieve voltage stability. This naturally leads to development of probabilistic criteria and notions of rick management. In this paper it is presented a discussion about criteria for long term voltage stability limited to the case in which the time frames are topically several minutes. (author) 14 refs., 1 fig.

  18. A Voltage Quality Detection Method

    DEFF Research Database (Denmark)

    Chen, Zhe; Wei, Mu

    2008-01-01

    This paper presents a voltage quality detection method based on a phase-locked loop (PLL) technique. The technique can detect the voltage magnitude and phase angle of each individual phase under both normal and fault power system conditions. The proposed method has the potential to evaluate vario...... power quality disturbances, such as interruptions, sags and imbalances. Simulation studies have been performed. The effectiveness of the proposed method has been demonstrated under the simulated typical power disturbances....

  19. Voltage sensitivity based reactive power control on VSC-HVDC in a wind farm connected hybrid multi-infeed HVDC system

    DEFF Research Database (Denmark)

    Liu, Yan; Chen, Zhe

    2013-01-01

    With increasing application of both Line Commutated Converter based High Voltage Direct Current (LCC-HVDC) systems and Voltage Source Converter based HVDC (VSC-HVDC) links, a new type of system structure named Hybrid Multi-Infeed HVDC (HMIDC) system is formed in the modern power systems. This paper...... presents the operation and control method of the wind farm connected HMIDC system. The wind power fluctuation takes large influence to the system voltages. In order to reduce the voltage fluctuation of LCC-HVDC infeed bus caused by the wind power variation, a voltage sensitivity-based reactive power...... control method is proposed in the paper. According to the calculated sensitivity factors, a reactive power increment is added in the control loop of VSC-HVDC so as to regulate the voltage of the target bus. Dynamic simulations in PSCAD/EMTDC and MATLAB are presented to assess the performance...

  20. Firm default and aggregate fluctuations

    NARCIS (Netherlands)

    Jacobson, Tor; Linde, Jesper; Roszbach, Kasper

    2013-01-01

    This paper studies the relationship between macroeconomic fluctuations and corporate defaults while conditioning on industry affiliation and an extensive set of firm-specific factors. By using a panel data set for virtually all incorporated Swedish businesses over 1990-2009, a period which includes

  1. Fluctuations in Overlapping Generations Economies

    DEFF Research Database (Denmark)

    Tvede, Mich

    . The approach to existence of endogenous fluctuations is basic in the sense that the prime ingredients are the implicit function theorem and linear algebra. Moreover the approach is applied to show that for an open and dense set of utility functions there exist endowment vectors such that sunspot equilibria...

  2. Chaotic dynamics, fluctuations, nonequilibrium ensembles.

    Science.gov (United States)

    Gallavotti, Giovanni

    1998-06-01

    The ideas and the conceptual steps leading from the ergodic hypothesis for equilibrium statistical mechanics to the chaotic hypothesis for equilibrium and nonequilibrium statistical mechanics are illustrated. The fluctuation theorem linear law and universal slope prediction for reversible systems is briefly derived. Applications to fluids are briefly alluded to. (c) 1998 American Institute of Physics.

  3. $1/f$ fluctuations in spinning-particle motions around Schwarzschild black hole

    CERN Document Server

    Koyama, H; Konishi, T; Kiuchi, Kenta; Konishi, Tetsuro; Koyama, Hiroko

    2007-01-01

    We study the properties of chaos in spinning-particle motions in Schwarzschild spacetime. We characterize the chaos in the motions using the power spectrum. We discover that the power spectrum shows not only white noise but also $1/f$-type fluctuation, depending on the value of the spin and the angular momentum of the test particle. We obtain the phase diagram for the properties of the chaos. Furthermore, we suggest that the origin of the $1/f$ fluctuations is the ``stagnant motions,'' itinerating among regular orbits (tori).

  4. VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK

    African Journals Online (AJOL)

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF RUMUOLA DISTRIBUTION NETWORK. ... The artificial neural networks controller engaged to controlling the dynamic voltage ... Article Metrics.

  5. Suppression of tunneling rate fluctuations in tunnel field-effect transistors by enhancing tunneling probability

    Science.gov (United States)

    Mori, Takahiro; Migita, Shinji; Fukuda, Koichi; Asai, Hidehiro; Morita, Yukinori; Mizubayashi, Wataru; Liu, Yongxun; O’uchi, Shin-ichi; Fuketa, Hiroshi; Otsuka, Shintaro; Yasuda, Tetsuji; Masahara, Meishoku; Ota, Hiroyuki; Matsukawa, Takashi

    2017-04-01

    This paper discusses the impact of the tunneling probability on the variability of tunnel field-effect transistors (TFETs). Isoelectronic trap (IET) technology, which enhances the tunneling current in TFETs, is used to suppress the variability of the ON current and threshold voltage. The simulation results show that suppressing the tunneling rate fluctuations results in suppression of the variability. In addition, a formula describing the relationship between the tunneling rate fluctuations and the electric field strength is derived based on Kane’s band-to-band tunneling model. This formula indicates that the magnitude of the tunneling rate fluctuations is proportional to the magnitude of the fluctuations in the electric field strength and a higher tunneling probability results in a lower variability. The derived relationship is universally valid for any technologies that exploit enhancement of the tunneling probability, including IET technology, channel material engineering, heterojunctions, strain engineering, etc.

  6. Floquet Scattering Matrix Theory of Heat Fluctuations in Dynamical Quantum Conductors

    Science.gov (United States)

    Moskalets, Michael

    2014-05-01

    I present the Floquet scattering matrix theory of low-frequency heat fluctuations in driven quantum-coherent conductors in the linear response regime and beyond. The Floquet theory elucidates the use of the Callen-Welton fluctuation-dissipation theorem for a description of heat fluctuations in a multiterminal case. The intrinsic fluctuations of energy of dynamically excited electrons are identified as the fundamental source of heat noise not revealed by the electrical noise. The role of backscattering in the increase of heat noise above the level defined by the Callen-Welton theorem is highlighted. The exception is the case when a conductor is driven by a Lorentzian voltage pulse with quantized flux. The heat noise in this case falls down to the level pertaining to a linear response regime.

  7. Universal Axial Fluctuations in Optical Tweezers

    CERN Document Server

    Ribezzi-Crivellari, Marco; Ritort, Felix

    2015-01-01

    Optical tweezers allow the measurement of fluctuations at the nano-scale, in particular fluctuations in the end-to-end distance in single molecules. Fluctuation spectra can yield valuable information, but they can easily be contaminated by instrumental effects. We identify axial fluctuations, i.e. fluctuations of the trapped beads in the direction of light propagation, as one of these instrumental effects. Remarkably, axial fluctuations occur on a characteristic timescale similar to that of conformational (folding) transitions, which may lead to misinterpretation of the experimental results. We show that a precise measurement of the effect of force on both axial and conformational fluctuations is crucial to disentangle them. Our results on axial fluctuations are captured by a simple and general formula valid for all optical tweezers setups and provide experimentalists with a general strategy to distinguish axial fluctuations from conformational transitions.

  8. Anodic Bubble Behavior and Voltage Drop in a Laboratory Transparent Aluminum Electrolytic Cell

    Science.gov (United States)

    Zhao, Zhibin; Wang, Zhaowen; Gao, Bingliang; Feng, Yuqing; Shi, Zhongning; Hu, Xianwei

    2016-06-01

    The anodic bubbles generated in aluminum electrolytic cells play a complex role to bath flow, alumina mixing, cell voltage, heat transfer, etc., and eventually affect cell performance. In this paper, the bubble dynamics beneath the anode were observed for the first time from bottom view directly in a similar industrial electrolytic environment, using a laboratory-scale transparent aluminum electrolytic cell. The corresponding cell voltage was measured simultaneously for quantitatively investigating its relevance to bubble dynamics. It was found that the bubbles generated in many spots that increased in number with the increase of current density; the bubbles grew through gas diffusion and various types of coalescences; when bubbles grew to a certain size with their surface reaching to the anode edge, they escaped from the anode bottom suddenly; with the increase of current density, the release frequency increases, and the size of these bubbles decreases. The cell voltage was very consistent with bubble coverage, with a high bubble coverage corresponding to a higher cell voltage. At low current density, the curves of voltage and coverage fluctuated in a regularly periodical pattern, while the curves became more irregular at high current density. The magnitude of voltage fluctuation increased with current density first and reached a maximum value at current density of 0.9 A/cm2, and decreased when the current density was further increased. The extra resistance induced by bubbles was found to increase with the bubble coverage, showing a similar trend with published equations.

  9. Monte Carlo study of the frame, fluctuation and internal tensions of fluctuating membranes with fixed area

    Science.gov (United States)

    Shiba, Hayato; Noguchi, Hiroshi; Fournier, Jean-Baptiste

    Three types of surface tensions can be defined for lipid membranes: the internal tension, $\\sigma$, conjugated to the real membrane area in the Hamiltonian, the mechanical frame tension, $\\tau$, conjugated to the projected area, and the "fluctuation tension", $r$, obtained from the fluctuation spectrum of the membrane height. We investigate these surface tensions by means of a Monge gauge lattice Monte Carlo simulation involving the exact, nonlinear, Helfrich Hamiltonian and a measure correction for excess entropy of the Monge gauge. Our results for the relation between $\\sigma$ and $\\tau$ agrees well with the theoretical prediction of [J.-B. Fournier and C. Barbetta, Phys. Rev. Lett., 2008, 100, 078103] based on a Gaussian approximation. This provides a valuable knowledge of~$\\tau$ in the standard Gaussian models where the tension is controlled by $\\sigma$. However, contrary to the conjecture in the above paper, we find that $r$ exhibits no significant difference from $\\tau$ over more than five decades of tension. Our results appear to be valid in the thermodynamic limit and are robust to changing the ensemble in which the membrane area is controlled.

  10. Spectrum Trading for Efficient Spectrum Utilization

    Directory of Open Access Journals (Sweden)

    Cong Xiong

    2014-04-01

    Full Text Available The conventional command and control based spectrum management has led to substantial underutilization of some spectrum bands while severely crowding others due to the uneven and dynamic needs that vary over time and at different locations. Spectrum trading has emerged as a promising management approach to substantially improve spectrum utilization and user experience in wireless communications by taking advantage of market-based mechanisms. This article presents an overview of spectrum trading, including the fundamental characteristics of spectrum trading markets, the state-of-the-art techniques for modeling and resolving various spectrum trading issues, and trading based dynamic spectrum sharing and access. Moreover, some open issues in spectrum trading are identified for future research in this area.

  11. Redistribution of phase fluctuations in a periodically driven cuprate superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hoeppner, Robert; Zhu, Beilei; Rexin, Tobias [Zentrum fuer Optische Quantentechnologien und Institut fuer Laserphysik, Hamburg (Germany); Mathey, Ludwig [Zentrum fuer Optische Quantentechnologien und Institut fuer Laserphysik, Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Hamburg (Germany); Cavalleri, Andrea [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, Oxford (United Kingdom)

    2015-07-01

    We study the thermally fluctuating state of a bi-layer cuprate superconductor under the periodic action of a staggered field oscillating at optical frequencies. This analysis distills essential elements of the recently discovered phenomenon of light enhanced coherence in YBCO, which was achieved by periodically driving infrared active apical oxygen distortions. The effect of a staggered periodic perturbation is studied using a Langevin description of driven, coupled Josephson junctions, which represent two neighboring pairs of layers and their two plasmons. We demonstrate that the external driving leads to a suppression of phase fluctuations of the low-energy plasmon, an effect which is amplified via the resonance of the high energy plasmon, with a striking suppression of the low-energy fluctuations, as visible in the power spectrum. We also find that this effect acts onto the in-plane fluctuations, which are reduced on long length scales and we discuss the behavior of vortices in the ab-planes and across the weakly coupled junctions.

  12. Improved Power Control Using Optimal Adjustable Coefficients for Three-Phase Photovoltaic Inverter under Unbalanced Grid Voltage

    Science.gov (United States)

    Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

    2014-01-01

    Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software. PMID:25243215

  13. Improved Power Control Using Optimal Adjustable Coefficients for Three-Phase Photovoltaic Inverter under Unbalanced Grid Voltage

    Directory of Open Access Journals (Sweden)

    Qianggang Wang

    2014-01-01

    Full Text Available Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation. Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software.

  14. Improved power control using optimal adjustable coefficients for three-phase photovoltaic inverter under unbalanced grid voltage.

    Science.gov (United States)

    Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

    2014-01-01

    Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software.

  15. Electrode voltage fall and total voltage of a transient arc

    Science.gov (United States)

    Valensi, F.; Ratovoson, L.; Razafinimanana, M.; Masquère, M.; Freton, P.; Gleizes, A.

    2016-06-01

    This paper deals with an experimental study of the components of a transient arc total voltage with duration of a few tens of ms and a current peak close to 1000 A. The cathode tip is made of graphite whereas the flat anode is made either of copper or of graphite; the electrodes gap is a few mm. The analysis of the electrical parameters is supported and validated by fast imaging and by two models: the first one is a 2D physical model of the arc allowing to calculate both the plasma temperature field and the arc voltage; the second model is able to estimate the transient heating of the graphite electrode. The main aim of the study was to detect the possible change of the cathode voltage fall (CVF) during the first instants of the arc. Indeed it is expected that during the first ms the graphite cathode is rather cool and the main mechanism of the electron emission should be the field effect emission, whereas after several tens of ms the cathode is strongly heated and thermionic emission should be predominant. We have observed some change in the apparent CVF but we have shown that this apparent change can be attributed to the variation of the solid cathode resistance. On the other hand, the possible change of CVF corresponding to the transition between a ‘cold’ and a ‘hot’ cathode should be weak and could not be characterized considering our measurement uncertainty of about 2 V. The arc column voltage (ACV) was estimated by subtracting the electrode voltage fall from the total arc voltage. The experimental transient evolution of the ACV is in very good agreement with the theoretical variation predicted by the model, showing the good ability of the model to study this kind of transient arc.

  16. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  17. Automated Voltage Control in LHCb

    CERN Document Server

    Granado Cardoso, L; Jacobsson, R

    2011-01-01

    LHCb is one of the 4 LHC experiments. In order to ensure the safety of the detector and to maximize efficiency, LHCb needs to coordinate its own operations, in particular the voltage configuration of the different subdetectors, according to the accelerator status. A control software has been developed for this purpose, based on the Finite State Machine toolkit and the SCADA system used for control throughout LHCb (and the other LHC experiments). This software permits to efficiently drive both the Low Voltage (LV) and High Voltage (HV) systems of the 10 different sub-detectors that constitute LHCb, setting each sub-system to the required voltage (easily configurable at run-time) based on the accelerator state. The control software is also responsible for monitoring the state of the Sub-detector voltages and adding it to the event data in the form of status-bits. Safe and yet flexible operation of the LHCb detector has been obtained and automatic actions, triggered by the state changes of the ...

  18. Characterization of (100)-orientated diamond film grown by HFCVD method with a positive DC bias voltage

    Institute of Scientific and Technical Information of China (English)

    MA Ying; WANG Lin-jun; LIU Jian-min; SU Qing-feng; XU Run; PENG Hong-yan; SHI Wei-min; XIA Yi-ben

    2006-01-01

    The (100)-orientated diamond film was deposited by hot-filament chemical vapor deposition (HFCVD) technology with a positive DC bias voltage. The morphology,X-ray diffraction (XRD),RAMAN spectrum and dark current versus applied voltage characteristics analysis show that the positive dc bias can increase the nucleation density and (100)-orientated growth,making the growth of the high quality diamond film easier and cheaper than using other methods.

  19. Intrinsic Fluctuations and Driven Response of Insect Swarms

    Science.gov (United States)

    Ni, Rui; Puckett, James G.; Dufresne, Eric R.; Ouellette, Nicholas T.

    2015-09-01

    Animals of all sizes form groups, as acting together can convey advantages over acting alone; thus, collective animal behavior has been identified as a promising template for designing engineered systems. However, models and observations have focused predominantly on characterizing the overall group morphology, and often focus on highly ordered groups such as bird flocks. We instead study a disorganized aggregation (an insect mating swarm), and compare its natural fluctuations with the group-level response to an external stimulus. We quantify the swarm's frequency-dependent linear response and its spectrum of intrinsic fluctuations, and show that the ratio of these two quantities has a simple scaling with frequency. Our results provide a new way of comparing models of collective behavior with experimental data.

  20. Study of erythrocyte membrane fluctuation using light scattering analysis

    Science.gov (United States)

    Lee, Hoyoon; Lee, Sangyun; Park, YongKeun; Shin, Sehyun

    2016-03-01

    It is commonly known that alteration of erythrocyte deformability lead to serious microcirculatory diseases such as retinopathy, nephropathy, etc. Various methods and technologies have been developed to diagnose such membrane properties of erythrocytes. In this study, we developed an innovative method to measure hemorheological characteristics of the erythrocyte membrane using a light scattering analysis with simplified optic setting and multi-cell analysis as well. Light scattering intensity through multiple erythrocytes and its power density spectrum were obtained. The results of light scattering analyses were compared in healthy control and artificially hardened sample which was treated with glutaraldehyde. These results were further compared with conventional assays to measure deformable property in hemorheology. We found that light scattering information would reflect the disturbance of membrane fluctuation in artificially damaged erythrocytes. Therefore, measuring fluctuation of erythrocyte membrane using light scattering signal could facilitate simple and precise diagnose of pathological state on erythrocyte as well as related complications.

  1. Effects of quantum fluctuations of metric on the universe

    Science.gov (United States)

    Yang, Rongjia

    2016-09-01

    We consider a model of modified gravity from the nonperturbative quantization of a metric. We obtain the modified gravitational field equations and the modified conservational equations. We apply it to the FLRW spacetime and find that due to the quantum fluctuations a bounce universe can be obtained and a decelerated expansion can also possibly be obtained in a dark energy dominated epoch. We also discuss the effects of quantum fluctuations on inflation parameters (such as slow-roll parameters, spectral index, and the spectrum of the primordial curvature perturbation) and find values of parameters in the comparing the predictions of inflation can also work to drive the current epoch of acceleration. We obtain the constraints on the parameter of the theory from the observation of the big bang nucleosynthesis.

  2. Cosmic Microwave Background and Density Fluctuations from Strings plus Inflation

    CERN Document Server

    Contaldi, C; Magueijo, J; Contaldi, Carlo; Hindmarsh, Mark; Magueijo, Joao

    1999-01-01

    In cosmological models where local cosmic strings are formed at the end of a period of inflation, the perturbations are seeded both by the defects and by the quantum fluctuations. In a subset of these models, for example those based on $D$-term inflation, the amplitudes are similar. Using our recent calculations of structure formation with cosmic strings, we point out that in a flat cosmology with zero cosmological constant and 5% baryonic component, strings plus inflation fits the observational data much better than each component individually. The large-angle CMB spectrum is mildly tilted, for Harrison-Zeldovich inflationary fluctuations. It then rises to a thick Doppler bump, covering $\\ell=200-600$, modulated by soft secondary undulations. The standard CDM anti-biasing problem is cured, giving place to a slightly biased scenario of galaxy formation.

  3. Dissipative Dynamics of Quantum Fluctuations

    CERN Document Server

    Benatti, F; Floreanini, R

    2015-01-01

    One way to look for complex behaviours in many-body quantum systems is to let the number $N$ of degrees of freedom become large and focus upon collective observables. Mean-field quantities scaling as $1/N$ tend to commute, whence complexity at the quantum level can only be inherited from complexity at the classical level. Instead, fluctuations of microscopic observables scale as $1/\\sqrt{N}$ and exhibit collective Bosonic features, typical of a mesoscopic regime half-way between the quantum one at the microscopic level and the classical one at the level of macroscopic averages. Here, we consider the mesoscopic behaviour emerging from an infinite quantum spin chain undergoing a microscopic dissipative, irreversible dynamics and from global states without long-range correlations and invariant under lattice translations and dynamics. We show that, from the fluctuations of one site spin observables whose linear span is mapped into itself by the dynamics, there emerge bosonic operators obeying a mesoscopic dissipa...

  4. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    OpenAIRE

    Arash Toudeshki; Norman Mariun; Hashim Hizam; Noor Izzri Abdul Wahab

    2014-01-01

    For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  5. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  6. Simple buck/boost voltage regulator

    Science.gov (United States)

    Paulkovich, J.; Rodriguez, G. E.

    1980-01-01

    Circuit corrects low or high supply voltage, produces regulated output voltage. Circuit has fewer components because inductory/transformer combination and pulse-width modulator serve double duty. Regulator handles input voltage variation from as low as one half output voltage to as high as input transistor rating. Solar arrays, fuel cells, and thermionic generators might use this regulator.

  7. 30 CFR 18.47 - Voltage limitation.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Voltage limitation. 18.47 Section 18.47 Mineral... § 18.47 Voltage limitation. (a) A tool or switch held in the operator's hand or supported against his... particular voltage(s) are provided in the design and construction of the equipment, its wiring,...

  8. Cyclical Fluctuations in Workplace Accidents

    OpenAIRE

    Boone, J.; J. C. VAN OURS

    2002-01-01

    This Paper presents a theory and an empirical investigation on cyclical fluctuations in workplace accidents. The theory is based on the idea that reporting an accident dents the reputation of a worker and raises the probability that he is fired. Therefore a country with a high or an increasing unemployment rate has a low (reported) workplace accident rate. The empirical investigation concerns workplace accidents in OECD countries. The analysis confirms that workplace accident rates are invers...

  9. Molecular fluctuation in living cells

    Institute of Scientific and Technical Information of China (English)

    唐孝威

    1997-01-01

    The concept of molecular fluctuation in living cells is introduced. Many apparently different experi-mental facts in living cells, including the velocity non-uniformity of organelle movement, the saltatory movement of transport vesicles in axoplasmic transport, the chromosome oscillation during metaphase in mitosis and the pauses in the chromosome movement during anaphase are explained using a unified viewpoint. A method of determination of average number of the attached motor protein molecules from the experimental data is also proposed.

  10. Random numbers from vacuum fluctuations

    Science.gov (United States)

    Shi, Yicheng; Chng, Brenda; Kurtsiefer, Christian

    2016-07-01

    We implement a quantum random number generator based on a balanced homodyne measurement of vacuum fluctuations of the electromagnetic field. The digitized signal is directly processed with a fast randomness extraction scheme based on a linear feedback shift register. The random bit stream is continuously read in a computer at a rate of about 480 Mbit/s and passes an extended test suite for random numbers.

  11. Cavity Voltage Phase Modulation MD

    CERN Document Server

    Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

  12. Portable High Voltage Impulse Generator

    Directory of Open Access Journals (Sweden)

    S. Gómez

    2011-07-01

    Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

  13. Fluctuating hydrodynamics for ionic liquids

    Science.gov (United States)

    Lazaridis, Konstantinos; Wickham, Logan; Voulgarakis, Nikolaos

    2017-04-01

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau-Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids.

  14. Consistency of detrended fluctuation analysis

    Science.gov (United States)

    Løvsletten, O.

    2017-07-01

    The scaling function F (s ) in detrended fluctuation analysis (DFA) scales as F (s ) ˜sH for stochastic processes with Hurst exponent H . This scaling law is proven for stationary stochastic processes with 0 law) autocorrelation function (ACF) scales as ˜s1 /2 . It is also demonstrated that the fluctuation function in DFA is equal in expectation to (i) a weighted sum of the ACF and (ii) a weighted sum of the second-order structure function. These results enable us to compute the exact finite-size bias for signals that are scaling and to employ DFA in a meaningful sense for signals that do not exhibit power-law statistics. The usefulness is illustrated by examples where it is demonstrated that a previous suggested modified DFA will increase the bias for signals with Hurst exponents 1 fluctuation function F (s ) in the gap-free case.

  15. Classical enhancement of quantum vacuum fluctuations

    CERN Document Server

    De Lorenci, V A

    2016-01-01

    We propose a mechanism for the enhancement of vacuum fluctuations by means of a classical field. The basic idea is that if an observable quantity depends quadratically upon a quantum field, such as the electric field, then the application of a classical field produces a cross term between the classical and quantum fields. This cross term may be significantly larger than the purely quantum part, but also undergoes fluctuations driven by the quantum field. We illustrate this effect in a model for lightcone fluctuations involving pulses in a nonlinear dielectric. Vacuum electric field fluctuations produce fluctuations in the speed of a probe pulse, and form an analog model for quantum gravity effects. If the material has a nonzero third-order susceptibility, then the fractional light speed fluctuations are proportional to the square of the fluctuating electric field. Hence the application of a classical electric field can enhance the speed fluctuations. We give an example where this enhancement can be an increas...

  16. Correlated interaction fluctuations in photosynthetic complexes

    CERN Document Server

    Vlaming, Sebastiaan M

    2011-01-01

    The functioning and efficiency of natural photosynthetic complexes is strongly influenced by their embedding in a noisy protein environment, which can even serve to enhance the transport efficiency. Interactions with the environment induce fluctuations of the transition energies of and interactions between the chlorophyll molecules, and due to the fact that different fluctuations will partially be caused by the same environmental factors, correlations between the various fluctuations will occur. We argue that fluctuations of the interactions should in general not be neglected, as these have a considerable impact on population transfer rates, decoherence rates and the efficiency of photosynthetic complexes. Furthermore, while correlations between transition energy fluctuations have been studied, we provide the first quantitative study of the effect of correlations between interaction fluctuations and transition energy fluctuations, and of correlations between the various interaction fluctuations. It is shown t...

  17. Predicting growth fluctuation in network economy

    CERN Document Server

    Maeno, Yoshiharu

    2011-01-01

    This study presents a method to predict the growth fluctuation of firms interdependent in a network economy. The risk of downward growth fluctuation of firms is calculated from the statistics on Japanese industry.

  18. Determination of neutron energy spectrum at KAMINI shielding experiment location.

    Science.gov (United States)

    Sen, Sujoy; Bagchi, Subhrojit; Prasad, R R; Venkatasubramanian, D; Mohanakrishnan, P; Keshavamurty, R S; Haridas, Adish; Arul, A John; Puthiyavinayagam, P

    2016-09-01

    The neutron spectrum at KAMINI reactor south beam tube end has been determined using multifoil activation method. This beam tube is being used for characterizing neutron attenuation of novel shield materials. Starting from a computed guess spectrum, the spectrum adjustment/unfolding procedure makes use of minimization of a modified constraint function representing (a) least squared deviations between the measured and calculated reaction rates, (b) a measure of sharp fluctuations in the adjusted spectrum and (c) the square of the deviation of adjusted spectrum from the guess spectrum. The adjusted/unfolded spectrum predicts the reaction rates accurately. The results of this new procedure are compared with those of widely used SAND-II code.

  19. A low voltage CMOS low drop-out voltage regulator

    Science.gov (United States)

    Bakr, Salma Ali; Abbasi, Tanvir Ahmad; Abbasi, Mohammas Suhaib; Aldessouky, Mohamed Samir; Abbasi, Mohammad Usaid

    2009-05-01

    A low voltage implementation of a CMOS Low Drop-Out voltage regulator (LDO) is presented. The requirement of low voltage devices is crucial for portable devices that require extensive computations in a low power environment. The LDO is implemented in 90nm generic CMOS technology. It generates a fixed 0.8V from a 2.5V supply which on discharging goes to 1V. The buffer stage used is unity gain configured unbuffered OpAmp with rail-to-rail swing input stage. The simulation result shows that the implemented circuit provides load regulation of 0.004%/mA and line regulation of -11.09mV/V. The LDO provides full load transient response with a settling time of 5.2μs. Further, the dropout voltage is 200mV and the quiescent current through the pass transistor (Iload=0) is 20μA. The total power consumption of this LDO (excluding bandgap reference) is only 80μW.

  20. Implementation of Dynamic Voltage Restorer for Mitigation of Voltage Sag

    Directory of Open Access Journals (Sweden)

    K.Vinod Kumar

    2013-07-01

    Full Text Available Power quality is one of major concerns in the present. It has become important, especially with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. The dynamic voltage restorer (DVR is one of the modern devices used in distribution systems to improve the power quality. In this paper, emergency control in distribution systems is discussed by using the proposed multifunctional DVR control strategy.Also, themultiloop controller using the Posicast and P+Resonant controllers is proposed in order to improve the transient response and eliminate the steady state error in DVR response,respectively.The proposed process is applied to some riots in load voltage effected by induction motors starting, and a three-phase short circuit fault. The three-phase short circuits, and the large induction motors are suddenly started then voltage sags areoccurred.The innovation here is that by using the Multifunctional Dynamic Voltage Restorer, improve the power quality in distribution side. Simulation results show the capability of the DVR to control the emergency conditions of the distribution systems by using MATLAB/Simulink software.

  1. The high voltage homopolar generator

    Science.gov (United States)

    Price, J. H.; Gully, J. H.; Driga, M. D.

    1986-11-01

    System and component design features of proposed high voltage homopolar generator (HVHPG) are described. The system is to have an open circuit voltage of 500 V, a peak output current of 500 kA, 3.25 MJ of stored inertial energy and possess an average magnetic-flux density of 5 T. Stator assembly components are discussed, including the stator, mount structure, hydrostatic bearings, main and motoring brushgears and rotor. Planned operational procedures such as monitoring the rotor to full speed and operation with a superconducting field coil are delineated.

  2. Pressure Fluctuations in Turbulent Wall Layers

    Science.gov (United States)

    Panton, Ronald; Lee, Myoungkyu; Moser, Robert

    2016-11-01

    Pressure fluctuation profile data from the channel flow DNS of Lee and Moser extend to Reτ 5200 . In the outer region, with Y = y / h , the overlap layer pressure correlates very well by a log law; limY -> 0 + (1 / η) lnY +Do . The constant η = - 0 . 380 is remarkable like the von Kármán value. In the inner region, the defect variable P (y+) ≡ + - + |y=0 absorbs the Reτ dependence. The inner overlap equation is; limy + -> ∞ P (1 / η) lny+ +Di . Together, the overlap laws imply that the wall pressure relation is +|y=0 (- 1 / η) lnReτ +Di -Do . A completely equivalent expression, which is finite as Reτ -> ∞ , is obtained by rescaling the pressure variable; #|y=0 ≡ (uτ /Uo) + | y = 0 =C1 +C2 (uτ /Uo) . Here, the constants are related to η ,D0 , and Di . Additionally, it was found that the wavenumber spectrum Epp {kx / h } does not have a k-1 region. However, the trends do not rule out this at higher Re. This work was supported by NSF (OCI-0749223 and PRAC Grant 0832634), and computation resources were provided by the Argonne Leadership Computing Facility through the Early Science, INCITE 2013 and Directors Discretionary Programs.

  3. Voltage Flicker Mitigation in Electric Arc Furnace using D-STATCOM

    Directory of Open Access Journals (Sweden)

    Deepthisree Madathil

    2014-10-01

    Full Text Available The major power quality issue of voltage flicker has resulted as a serious concern for the customers and heavy power companies. Voltage flicker is an impression of unsteadiness of visual sensation induced by a light source whose luminance fluctuates with time. This phenomenon is experienced when an Electric Arc Furnace (EAF as load is connected to the power system. Flexible AC transmission devices (FACTS devices were gradually utilized for voltage flicker reduction. In this paper the FACTS device of Distribution Static Synchronous Compensator (D-STATCOM is used to serve the purpose of mitigating voltage flickering caused by electric arc furnace load, which is efficiently controlled by Icosɸ control algorithm. The model of electric arc furnace is considered as a current source controlled by a non linear resistance, which had been simulated and performance was analyzed using MATLAB/SIMULINK Software.

  4. High-voltage thin-absorber photovoltaic device structures for efficient energy harvesting

    Science.gov (United States)

    Welser, Roger E.; Pethuraja, Gopal G.; Zeller, John W.; Sood, Ashok K.; Sablon, Kimberly A.; Dhar, Nibir K.

    2014-06-01

    Efficient photovoltaic energy harvesting requires device structures capable of absorbing a wide spectrum of incident radiation and extracting the photogenerated carriers at high voltages. In this paper, we review the impact of active layer thickness on the voltage performance of GaAs-based photovoltaic device structures. We observe that thin absorber structures can be leveraged to increase the operating voltage of energy harvesting devices. Thin absorbers in combination with advanced light trapping structures provide an exciting pathway for enhancing the performance of flexible, lightweight photovoltaic modules suitable for mobile and portable power applications.

  5. Simulation of characteristic variation in 16 nm gate FinFET devices due to intrinsic parameter fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Li Yiming; Hwang, Chih-Hong; Han, Ming-Hung, E-mail: ymli@faculty.nctu.edu.tw [Institute of Communication Engineering, National Chiao-Tung University, Hsinchu 300, Taiwan (China)

    2010-03-05

    High-{kappa}/metal-gate and vertical channel transistors are well-known solutions to continue the device scaling. This work extensively explores the physics and mechanism of the intrinsic parameter fluctuations in nanoscale fin-type field-effect transistors by using an experimentally validated three-dimensional quantum-corrected device simulation. The dominance fluctuation sources in threshold voltage, gate capacitance and cutoff frequency have been found. The emerging fluctuation source, workfunction fluctuation, shows significant impacts on DC characteristics; however, its impact is reduced in AC characteristics due to the screening effect of the inversion layer. Additionally, the channel discrete dopant may enhance the electric field and therefore make the averaged cutoff frequency of fluctuated devices larger than the nominal value of cutoff frequency.

  6. Incommensurate Magnetic Fluctuations in the Underdoped Copper Oxide Materials

    Institute of Scientific and Technical Information of China (English)

    YUAN Feng; FENG Shi-Ping; CHEN Wei-Yeu

    2001-01-01

    The doping dependence of magnetic fluctuations in the underdoped copper oxide materials are studied within the t-J model. It is shown that away from the half-filling, the magnetic Bragg peaks from the dynamical spin structure factor spectrum S(k, ω) are incommensurate with the lattice. Although the incommensurability δ(x) is almost energy-independent, the dynamical spin susceptibility x〃(k,ω) at the incommensurate wave vectors is changed dramatically with energies, which is consistent with the experiments.``

  7. Producing small scale temperature fluctuations in an airstream.

    Science.gov (United States)

    Schacher, G E; Fairall, C W

    1978-10-01

    A 4.5-microm ''hot'' wire is used to heat a low-speed airstream at frequencies from dc to 400 Hz. For dc excitation the thermal noise spectrum produced was white to a frequency of 2 kHz. ac heating of the wire up to a frequency of 400 Hz (800 Hz thermal fluctuation of the airstream) yielded a good thermal signal as far as 2 cm from the hot wire. Calculation shows excellent heat transfer between the wire and airstream. The technique is very useful for calibrating the frequency response of temperature sensors and for investigating turbulent heat transfer for various flow configurations.

  8. A fluctuating quantum model of the CO vibration in carboxyhemoglobin.

    Science.gov (United States)

    Falvo, Cyril; Meier, Christoph

    2011-06-07

    In this paper, we present a theoretical approach to construct a fluctuating quantum model of the CO vibration in heme-CO proteins and its interaction with external laser fields. The methodology consists of mixed quantum-classical calculations for a restricted number of snapshots, which are then used to construct a parametrized quantum model. As an example, we calculate the infrared absorption spectrum of carboxy-hemoglobin, based on a simplified protein model, and found the absorption linewidth in good agreement with the experimental results.

  9. Micromechanical Disk Array for Enhanced Frequency Stability Against Bias Voltage Fluctuations

    Science.gov (United States)

    2014-11-20

    sense of humor . I would also like to thank Professor Liwei Lin for reading this research report. His course ME219 (Parametric and Optimal Design of...work provides designers with needed visual cues that enable them to more intelligently choose device topologies to maximize the performance of

  10. Voltage Fluctuation in a Supercapacitor During a High-g Impact

    Science.gov (United States)

    Dai, Keren; Wang, Xiaofeng; Yin, Yajiang; Hao, Chenglong; You, Zheng

    2016-12-01

    Supercapacitors (SCs) are a type of energy storage device with high power density and long lifecycles. They have widespread applications, such as powering electric vehicles and micro scale devices. Working stability is one of the most important properties of SCs, and it is of significant importance to investigate the operational characteristics of SCs working under extreme conditions, particularly during high-g acceleration. In this paper, the failure mechanism of SCs upon high-g impact is thoroughly studied. Through an analysis of the intrinsic reaction mechanism during the high-g impact, a multi-faceted physics model is established. Additionally, a multi-field coupled kinetics simulation of the SC failure during a high-g impact is presented. Experimental tests are conducted that confirm the validity of the proposed model. The key factors of failure, such as discharge currents and discharging levels, are analyzed and discussed. Finally, a possible design is proposed to avoid the failure of SCs upon high-g impact.

  11. The power spectrum of IRAS galaxies

    CERN Document Server

    Tadros, H; Tadros, Helen; Efstathiou, George

    1995-01-01

    We estimate the three-dimensional power spectrum of IRAS galaxies from the QDOT and 1.2Jy redshift surveys. We use identical estimators for both surveys and show how the results depend on the weights assigned to the galaxies. The power spectrum for the QDOT survey is steeper and has a higher amplitude at wavenumbers k \\sim 0.05\\; h {\\rm Mpc}^{-1} (where h is Hubble's constant in units of 100 \\kmsmpc) than the power spectrum derived from the 1.2Jy sample. However, the QDOT power spectrum is sensitive to a small number of galaxies in the Hercules supercluster, in agreement with a recent analysis of galaxy counts in cells in these surveys. We argue that the QDOT results are an upward fluctuation. We combine the two surveys to derive our best estimate of the power spectrum of IRAS galaxies. This is shallower and has a lower amplitude on scales \\simlt 0.1 h {\\rm Mpc}^{-1} than the power spectrum derived by Feldman \\et (1994) from the QDOT survey alone. The power spectrum of the combined surveys is well described b...

  12. VOLTAGE REGULATORS OF SYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available Synchronous generators are the primary source of electrical power autonomous electrosupply systems, including backup systems. They are also used in a structure of rotating electricity converters and are widely used in renewable energy as part of wind power plants of small, mini and micro hydroelectric plants. Increasing the speed and the accuracy of the system of the voltage regulation of synchronous generators is possible due to the development of combined systems containing more stabilizers. The article illustrates the functional schemes of circuit voltage stabilizers and frequency synchronous generators (with electromagnetic excitation and permanent magnet excitation and describes the features of their work, including two and three-aggregate rotating converters of electricity used in uninterruptible power supply systems. To improve the technical characteristics of the system of stabilization we have proposed functional solutions for stabilizers of synchronous generators made on the base of direct frequency converters and using a transformer with a rotating magnetic field. To improve the reliability of and to improve the operational characteristics of the autonomous independent sources of electricity we suggest creating the main functional blocks and the elements of the stabilization system in a modular way. The functional circuit solutions of voltage regulators of synchronous generators and the characteristics of their work considered in the article, are able to improve the efficiency of pre-design work in the development of new technical solutions for stabilizing the voltage and the frequency in synchronous generators of electrosupply autonomous systems

  13. Frequency-controlled voltage regulator

    Science.gov (United States)

    Mclyman, W. T.

    1980-01-01

    Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

  14. The timescale of phenotypic plasticity and its impact on competition in fluctuating environments

    NARCIS (Netherlands)

    Stomp, M.; Dijk, van M.A.; Overzee, van H.M.J.; Wortel, M.T.; Sigon, C.A.M.; Egas, M.; Hoogveld, H.; Gons, H.J.; Huisman, J.

    2008-01-01

    Although phenotypic plasticity can be advantageous in fluctuating environments, it may come too late if the environment changes fast. Complementary chromatic adaptation is a colorful form of phenotypic plasticity, where cyanobacteria tune their pigmentation to the prevailing light spectrum. Here, we

  15. Band tailing in heavily doped semiconductors. Scattering and impurity-concentration-fluctuation effects

    Science.gov (United States)

    Serre, J.; Ghazali, A.; Hugon, P. Leroux

    1981-02-01

    Using a self-consistent multiple-scattering method, we estimate the relative importance of both effects of scattering and of impurity-concentration fluctuations on band states in heavily doped semiconductors and thus we account for band tailing. We apply this formalism to the estimate of the interband absorption spectrum in a typical case, in satisfactory agreement with experiment.

  16. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H+ for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens. PMID:23798303

  17. Next generation KATRIN high precision voltage divider for voltages up to 65kV

    CERN Document Server

    Bauer, S; Hochschulz, F; Ortjohann, H -W; Rosendahl, S; Thümmler, T; Schmidt, M; Weinheimer, C

    2013-01-01

    The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to determine the mass of the electron antineutrino with a sensitivity of 200meV by precisely measuring the electron spectrum of the tritium beta decay. This will be done by the use of a retarding spectrometer of the MAC-E-Filter type. To achieve the desired sensitivity the stability of the retarding potential of -18.6kV has to be monitored with a precision of 3ppm over at least two months. Since this is not feasible with commercial devices, two ppm-class high voltage dividers were developed, following the concept of the standard divider for DC voltages of up to 100kV of the Physikalisch-Technische Bundesanstalt (PTB). In order to reach such high accuracies different effects have to be considered. The two most important ones are the temperature dependence of resistance and leakage currents, caused by insulators or corona discharges. For the second divider improvements were made concerning the high-precision resistors and the thermal design of the divider....

  18. Asymmetrical solutions and role of thermal fluctuations in dc current driven extended Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Artemov, A.N., E-mail: artemov@fti.dn.ua [Donetsk Physical and Technology Institute, Donetsk 83114 (Ukraine)

    2012-10-01

    Extended Josephson junction driven by dc bias current is studied numerically. Two types of solutions, symmetrical and asymmetrical, are found. The current–voltage characteristic (IVC) is calculated. The symmetrical solutions form main hysteretic IVC and asymmetrical ones create an additional branch. Depending on the bias current value periodic, quasiperiodic and chaotic modes of the junction motion was observed. Dynamics of the junction affected by thermal fluctuations was analyzed. Stability of different states of the junction is discussed. -- Highlights: ► Symmetrical and asymmetrical solutions of dc driven sine-Gordon equation are found. ► Current–voltage characteristic of extended in-line Josephson junction was calculated. ► Periodic, quasiperiodic and chaotic modes of the junction motion was observed. ► Stability of dynamical junction states under thermal fluctuations is discussed.

  19. Fluctuations of the unruh temperature

    CERN Document Server

    Demers, J G

    1994-01-01

    Using the influence functional formalism, the problem of an accelerating detector in the presence of a scalar field in its ground state is considered in Minkowski space. As is known since the work of Unruh, to a quantum mechanical detector following a definite, classical acceleration, the field appears to be thermally excited. We relax the requirement of perfect classicality for the trajectory and substitute it with one of {\\it derived} classicality through the criteria of decoherence. The ensuing fluctuations in temperature are then related with the time and the amplitude of excitation in the detector's internal degree of freedom.

  20. Fluctuations in some climate parameters

    CERN Document Server

    Erlykin, A D; Wolfendale, A W; 10.1016/j.jastp.2011.01.021

    2011-01-01

    There is argument as to the extent to which there has been an increase over the past few decades in the frequency of the extremes of climatic parameters, such as temperature, storminess, precipitation, etc, an obvious point being that Global Warming might be responsible. Here we report results on those parameters of which we have had experience during the last few years: Global surface temperature, Cloud Cover and the MODIS Liquid Cloud Fraction. In no case we have found indications that fluctuations of these parameters have increased with time.

  1. Simulation of nanoscale density fluctuations

    Science.gov (United States)

    Reiss, Howard; Bowles, Richard K.

    2000-11-01

    Problems associated with the simulation of density fluctuations of limited breadth in a small cell are exposed and studied. The fluctuations are viewed as "physical clusters" of the type that might appear in nucleation processes and related phenomena. One of the most important features of the study stems from the fact that the simulation of a small heterogeneity in a macroscopic system presents problems that do not occur in the simulation of a bulk homogeneous property of the system. For example, once having simulated the probability of appearance of the fluctuation in a small cell, how is that result to be "mapped" onto the macrosystem in order to specify the equilibrium number of such fluctuations in that system? This problem is closely associated with the proper separation of the translational and internal degrees of freedom of the system, and has arisen in a number of fields, including the theory of nucleation. There are other problems associated with exponential dependence of cluster probability on the work of formation of the cluster, and also with rareness of some important clusters. In the latter case, simulative "umbrella sampling" does not always solve the entire problem. The present study is confined to clusters that appear in rarefied gases. Such systems are important in a number of scenarios, including nucleation processes. Several cluster models are considered including those consisting of molecules confined to a "container" of fixed volume and those constructed on the center of mass of the cluster. Connections between them are derived and rigorous solutions to the mapping problem are derived. Quantitative measures for the accuracy of approximate solutions, applied to cases in which the cluster is compact, are provided and exact solutions are provided even for the noncompact case. Some surprising results emerge from the study, among which is the fact that a cluster whose location is determined by one of its molecules, does not always have a

  2. Fluctuation modes of nanoconfined DNA.

    Science.gov (United States)

    Karpusenko, Alena; Carpenter, Joshua H; Zhou, Chunda; Lim, Shuang Fang; Pan, Junhan; Riehn, Robert

    2012-01-15

    We report an experimental investigation of the magnitude of length and density fluctuations in DNA that has been stretched in nanofluidic channels. We find that the experimental data can be described using a one-dimensional overdamped oscillator chain with nonzero equilibrium spring length and that a chain of discrete oscillators yields a better description than a continuous chain. We speculate that the scale of these discrete oscillators coincides with the scale at which the finite extensibility of the polymer manifests itself. We discuss how the measurement process influences the apparent measured dynamic properties, and outline requirements for the recovery of true physical quantities.

  3. Critical swelling of fluctuating capsules

    Science.gov (United States)

    Diamant, Haim; Haleva, Emir

    2009-03-01

    In many natural transport processes the solute molecules to be transported are encapsulated in semipermeable, flexible membrane vesicles of micron size. We study the swelling of such fluctuating capsules, as the number of encapsulated particles is increased, or the concentration of the outer solution is decreased. The approach to the maximum volume-to-area ratio and the associated buildup of membrane tension involve a continuous phase transition and follow universal scaling laws. The criticality and its features are model-independent, arising solely from the interplay between volume and surface degrees of freedom.ootnotetextE. Haleva and H. Diamant, Phys. Rev. Lett. 101, 078104 (2008).

  4. An objective fluctuation score for Parkinson's disease.

    Directory of Open Access Journals (Sweden)

    Malcolm K Horne

    Full Text Available Establishing the presence and severity of fluctuations is important in managing Parkinson's Disease yet there is no reliable, objective means of doing this. In this study we have evaluated a Fluctuation Score derived from variations in dyskinesia and bradykinesia scores produced by an accelerometry based system.The Fluctuation Score was produced by summing the interquartile range of bradykinesia scores and dyskinesia scores produced every 2 minutes between 0900-1800 for at least 6 days by the accelerometry based system and expressing it as an algorithm.This Score could distinguish between fluctuating and non-fluctuating patients with high sensitivity and selectivity and was significant lower following activation of deep brain stimulators. The scores following deep brain stimulation lay in a band just above the score separating fluctuators from non-fluctuators, suggesting a range representing adequate motor control. When compared with control subjects the score of newly diagnosed patients show a loss of fluctuation with onset of PD. The score was calculated in subjects whose duration of disease was known and this showed that newly diagnosed patients soon develop higher scores which either fall under or within the range representing adequate motor control or instead go on to develop more severe fluctuations.The Fluctuation Score described here promises to be a useful tool for identifying patients whose fluctuations are progressing and may require therapeutic changes. It also shows promise as a useful research tool. Further studies are required to more accurately identify therapeutic targets and ranges.

  5. Statistics of Multiscale Fluctuations in Macromolecular Systems

    CERN Document Server

    Yukalov, V I

    2012-01-01

    An approach is suggested for treating multiscale fluctuations in macromolecular systems. The emphasis is on the statistical properties of such fluctuations. The approach is illustrated by a macromolecular system with mesoscopic fluctuations between the states of atomic orbitals. Strong-orbital and weak-orbital couplings fluctuationally arise, being multiscale in space and time. Statistical properties of the system are obtained by averaging over the multiscale fluctuations. The existence of such multiscale fluctuations causes phase transitions between strong-coupling and weak-coupling states. These transitions are connected with structure and size transformations of macromolecules. An approach for treating density and size multiscale fluctuations by means of classical statistical mechanics is also advanced.

  6. Quantum Fluctuations Of The Stress Tensor

    CERN Document Server

    Wu, C

    2002-01-01

    Quantum fluctuations of the stress tensor are important in many branches of physics, including the study of the validity of semiclassical gravity and the backreaction problem in stochastic semiclassical gravity. The geometry fluctuations induced by stress tensor fluctuations are important to understand quantum gravity and the problem of lightcone fluctuations. Stress tensor fluctuations also hold the key to understand fundamental physical effects like quantum fluctuations of radiation pressure, and that is crucial to the sensitivity of interferometers and the limitations on the detection of gravitational waves. Even the wave-particle duality of light can be better understood by the study of quantum fluctuations of thermal radiation. It is well known in quantum field theory that the expectation value of the energy density, which contains quadratic field operators (e.g. E2 and B2 in the electromagnatic field case), is divergent and can be renormalized simply by normal ordering, which is subtracting out the vac...

  7. On multifractality of high-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    Z. Vörös

    Full Text Available In order to contribute to the understanding of solar wind-magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic fluctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so defined intermittent field ε, a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic fluctuations locally in time by means of singularity exponents α, which represent a generalization of the local degree of differentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic fluctuations is insured by the spectrum of exponents f(α which represents a rate function quantifying the deviations of the observed singularities α from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and different types of f(α spectra describe the fluctuations in direct dissipation or loading-unloading regimes of the solar wind-magnetosphere interaction. On the time scale of substorms and storms the multi-fractal structure of the loading-unloading mode fluctuations seems to be analogous to the simple multiplicative P-model, while the f(α spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative

  8. The Signatures of Large-scale Temperature Fluctuations in the Lyman-alpha Forest

    CERN Document Server

    McQuinn, Matthew; Lidz, Adam; Zaldarriaga, Matias

    2010-01-01

    It appears inevitable that reionization processes would have produced large-scale temperature fluctuations in the intergalactic medium. Using toy temperature models and detailed heating histories in cosmological simulations of HeII reionization, we study the consequences of inhomogeneous heating for the Ly-alpha forest. The impact of temperature fluctuations in physically well-motivated models can be surprisingly subtle. In fact, we show that temperature fluctuations at the level predicted by our reionization simulations do not give rise to detectable signatures in the types of statistics that have been employed previously. However, because of the aliasing of small-scale density power to larger scale modes in the line-of-sight Ly-alpha forest power spectrum, earlier analyses were not sensitive to 3D modes with >~ 30 comoving Mpc wavelengths -- scales where temperature fluctuations are likely to be relatively largest. The ongoing Baryon Oscillation Spectroscopic Survey (BOSS) aims to measure the 3D power spect...

  9. Fluctuations of the initial color fields in high energy heavy ion collisions

    CERN Document Server

    Epelbaum, Thomas

    2013-01-01

    In the Color Glass Condensate approach to the description of high energy heavy ion collisions, one needs to superimpose small random Gaussian distributed fluctuations to the classical background field, in order to resum the leading secular terms that result from the Weibel instability, that would otherwise lead to pathological results beyond leading order. In practical numerical simulations, one needs to know this spectrum of fluctuations at a proper time $\\tau \\ll Q_s^{-1}$ shortly after the collision, in the Fock-Schwinger gauge $\\ma{A}^\\tau=0$. In this paper, we derive these fluctuations from first principles, by solving the Yang-Mills equations linearized around the classical background, with plane wave initial conditions in the remote past. We perform the intermediate steps in light-cone gauge, and we convert the results to the Fock-Schwinger gauge at the end. We obtain simple and explicit formulas for the fluctuation modes.

  10. Reversible Diffusion by Thermal Fluctuations

    Science.gov (United States)

    Donev, Aleksandar; Fai, Thomas G.; vanden-Eijnden, Eric

    A model for diffusion in liquids that couples the dynamics of tracer particles to a fluctuating Stokes equation for the fluid is investigated in the limit of large Schmidt number. In this limit, the concentration of tracers is shown to satisfy a closed-form stochastic advection-diffusion equation that is used to investigate the collective diffusion of hydrodynamically-correlated tracers through a combination of Eulerian and Lagrangian numerical methods. This analysis indicates that transport in liquids is quite distinct from the traditional Fickian picture of diffusion. While the ensemble-averaged concentration follows Fick's law with a diffusion coefficient that obeys the Stokes-Einstein relation, each instance of the diffusive mixing process exhibits long-ranged giant fluctuations around its average behavior. We construct a class of mesoscopic models for diffusion in liquids at different observation scales in which the renormalized diffusion coefficient depends on this scale. This indicates that the Fickian diffusion coefficient in liquids is not a material constant, but rather, changes with the scale at which experimental measurements are performed.

  11. Currency speculation and dollar fluctuations

    Directory of Open Access Journals (Sweden)

    S. SCHULMEISTER

    2013-12-01

    Full Text Available In this study the reasons behind the wide fluctuations of the dollar exchange rate following the breakdown of the Bretton Woods system, for the most part unexplained by the prevailing exchange rate theories, are explored. The author investigates the exchange rate between the two most traded currencies, the dollar and the deutschemark, from 1973 to 1988. In the first part, the pattern of the daily exchange rate movements is examined to show that a sequence of upward and downward trends interrupted by non-directional movements is typical of exchange rate dynamics in the short run. This pattern is systemically exploited through currency speculation, particularly through the use of “technical analysis”. In the second part, the author focuses on the medium-term, arguing that fluctuations can be explained as the result of interacting disequilibria in the goods and asset markets. Although currency speculation has been systemically profitable for most currencies, it should be considered to be destabilising since the sequence of price runs caused large and persistent deviations of exchange rates from their equilibrium values (purchasing power parity.  

  12. Currency speculation and dollar fluctuations

    Directory of Open Access Journals (Sweden)

    Stephan Schulmeister

    1988-12-01

    Full Text Available In this study the reasons behind the wide fluctuations of the dollar exchange rate following the breakdown of the Bretton Woods system, for the most part unexplained by the prevailing exchange rate theories, are explored. To do so, the author investigates the exchange rate between the two most traded currencies, the dollar and the deutschemark, from 1973 to 1988. In the first part, the pattern of the daily exchange rate movements is examined to show that a sequence of upward and downward trends interrupted by non-directional movements is typical of exchange rate dynamics in the short run. Moreover, this pattern is systemically exploited through currency speculation, particularly through the use of “technical analysis”. In the second part, the author focuses on the medium-term, arguing that fluctuations can be explained as the result of interacting disequilibria in the goods and asset markets. Although currency speculation has been systemically profitable for most currencies, it should be considered to be destabilizing since the sequence of price runs caused large and persistent deviations of exchange rates from their equilibrium values (purchasing power parity.

  13. Analysis of Fluctuations in a Combustion-Driven Open-Cycle MHD Generator.

    Science.gov (United States)

    Skorska, Malgorzata Bozena

    Fluctuations present in MHD generators may cause significant degradation in the generated power. The fluctuations may result from three sources. First, the mass flow rates of the components' input to the combustor vary. Second, the combustor initiates its own variations which are functions of the combustor geometry and injection techniques. Third, the generator action, i.e., flow of plasma in a magnetic field, introduces variations in the plasma variables. The purpose of the study is to investigate the fluctuations of MHD output signals, which may either arise from the combustor fluctuations propagating into a conducting channel, or are inherent in the generator dynamics. The analysis of fluctuations is based on the analytical and empirical models. Both models assume that stochastic processes take place within the MHD plasma, and both models yield results in the form of autocorrelation, crosscorrelation, and power spectral density functions of the system variables. The study showed that fluctuations, whose frequencies exceed 200 Hz, in the plasma density, velocity, pressure, current and voltage variables are acoustic in nature, and are caused by longitudinal standing waves present in the generator. The analysis proved that Hall generators develop fluctuations mainly in the range 700 Hz to 2000 Hz, whereas Faraday and DCW generators are favorable for the low frequency fluctuations. Parametric study of the plasma disclosed that stronger magnetic fields and larger Hall parameters increase the frequency range of fluctuations. Changes in plasma specific heat ratio or in inlet steady-state parameters may increase or decrease the intensities of some odd harmonics of the standing waves. The fluctuations that originate in the combustion chamber also affect the plasma variables. A white noise character of these fluctuations guarantees a fairly uniform distribution of energy in the fluctuations of the plasma variables in the frequency range up to 200 Hz. Future research in

  14. Over-voltage protection system and method

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Song; Dong, Dong; Lai, Rixin

    2017-05-02

    An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device. A plurality of self-powered gate drive circuits are connected to the plurality of semiconductor devices, wherein the plurality of self-powered gate drive circuits receive over-voltage triggering pulses from the optocoupler during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit.

  15. Giant enhancement of fluctuation in small biological systems under external fields

    Science.gov (United States)

    Hayashi, Kumiko; Hasegawa, Shin; Tsunoda, Satoshi P.

    2016-05-01

    The giant enhancement (GE) of fluctuation under an external field is a universal phenomenon predicted by the theoretical analysis given in (Reimann et al 2001 Phys. Rev. Lett.). Here, we propose the application of the theory of the GE of fluctuation to estimate the energy barrier of a biomolecule that exhibits its function subject to thermal noise. The rotary motor protein F1 was used as a model, which is a component of FoF1 adenosine triphosphate (ATP)-synthase. In the single-molecule experiment on F1, the diffusion coefficients of a rotary probe attached to F1, which characterised the fluctuation of the system, were measured under the influence of an electro-rotary field. These diffusion coefficients were then used to estimate a high-energy barrier of the rotary potential of F1 based on the theory of the GE of fluctuation. Furthermore, the ion channel protein channelrhodopsin (ChR) was used as another research model. The current fluctuations of ions moving through ChR were numerically investigated using a simulation model of the protein in the presence of an external voltage. The energy barrier for ion conduction is discussed based on the current fluctuations.

  16. Symmetries in fluctuations far from equilibrium.

    Science.gov (United States)

    Hurtado, Pablo I; Pérez-Espigares, Carlos; del Pozo, Jesús J; Garrido, Pedro L

    2011-05-10

    Fluctuations arise universally in nature as a reflection of the discrete microscopic world at the macroscopic level. Despite their apparent noisy origin, fluctuations encode fundamental aspects of the physics of the system at hand, crucial to understand irreversibility and nonequilibrium behavior. To sustain a given fluctuation, a system traverses a precise optimal path in phase space. Here we show that by demanding invariance of optimal paths under symmetry transformations, new and general fluctuation relations valid arbitrarily far from equilibrium are unveiled. This opens an unexplored route toward a deeper understanding of nonequilibrium physics by bringing symmetry principles to the realm of fluctuations. We illustrate this concept studying symmetries of the current distribution out of equilibrium. In particular we derive an isometric fluctuation relation that links in a strikingly simple manner the probabilities of any pair of isometric current fluctuations. This relation, which results from the time-reversibility of the dynamics, includes as a particular instance the Gallavotti-Cohen fluctuation theorem in this context but adds a completely new perspective on the high level of symmetry imposed by time-reversibility on the statistics of nonequilibrium fluctuations. The new symmetry implies remarkable hierarchies of equations for the current cumulants and the nonlinear response coefficients, going far beyond Onsager's reciprocity relations and Green-Kubo formulas. We confirm the validity of the new symmetry relation in extensive numerical simulations, and suggest that the idea of symmetry in fluctuations as invariance of optimal paths has far-reaching consequences in diverse fields.

  17. Advances in high voltage engineering

    CERN Document Server

    Haddad, A

    2005-01-01

    This book addresses the very latest research and development issues in high voltage technology and is intended as a reference source for researchers and students in the field, specifically covering developments throughout the past decade. This unique blend of expert authors and comprehensive subject coverage means that this book is ideally suited as a reference source for engineers and academics in the field for years to come.

  18. High Voltage Pulse Testing Survey.

    Science.gov (United States)

    1985-10-01

    Cryogenic 23 E. Liquids 26 F. Solids 28 1. Polyethylene 28 2. Cross-Linked Polyethylene ( XLPE ) 29 3. Polyimide and Polyvenylchloride (PVC) 31 VI Benefits 35 A...Strength of XLPE Cables 29 vii * 4" I PROGRAM OBJECTIVES The Pulse Test Survey summarizes government, industry, and technical reports on high voltage pulse...system of silicone oil on a XLPE (cross-linked polyethylene) spacer tends to lower the impulse breakdown by approximately 10 percent. The negative impulse

  19. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    Science.gov (United States)

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  20. Static versus dynamic analysis of the influence of gravity on concentration non-equilibrium fluctuations.

    Science.gov (United States)

    Croccolo, Fabrizio; Bataller, Henri; Scheffold, Frank

    2014-11-01

    In a binary fluid mixture subject to gravity and a stabilizing concentration gradient, concentration non-equilibrium fluctuations are long-ranged. While the gradient leads to an enhancement of the respective equilibrium fluctuations, the effect of gravity is a damping of fluctuations larger than a "characteristic" size. This damping is visible both in the fluctuation power spectrum probed by static and the temporal correlation function probed by dynamic light scattering. One aspect of the "characteristic" size can be appreciated by the dynamic analysis; in fact at the corresponding "characteristic" wave vector q* one can observe a maximum of the fluctuation time constant indicating the more persistent fluctuation of the system. Also in the static analysis a "characteristic" size can be extracted from the crossover wave vector. According to common theoretical concepts, the result should be the same in both cases. In the present work we provide evidence for a systematic difference in the experimentally observed "characteristic" size as obtained by static and dynamic measurements. Our observation thus points out the need for a more refined theory of non-equilibrium concentration fluctuations.

  1. X-Ray surface brightness and gas density fluctuations in the Coma cluster

    CERN Document Server

    Churazov, E; Zhuravleva, I; Schekochihin, A; Parrish, I; Sunyaev, R; Forman, W; Boehringer, H; Randall, S

    2011-01-01

    X-ray surface brightness fluctuations in the core ($650 \\times 650$ kpc) region of the Coma cluster observed with XMM-Newton and Chandra are analyzed using a 2D power spectrum approach. The resulting 2D spectra are converted to 3D power spectra of gas density fluctuations. The characteristic amplitude of the volume filling density fluctuations relative to the smooth underlying density distribution varies from 7-10% on scales of $\\sim$500 kpc down to $\\sim$5% at scales $\\sim$ 30 kpc. On smaller spatial scales, projection effects smear the density fluctuations by a large factor, precluding strong limits on the fluctuations in 3D. On the largest scales probed (hundreds of kpc), the dominant contributions to the observed fluctuations most likely arise from perturbations of the gravitational potential by the two most massive galaxies in Coma, NGC4874 and NGC4889, and the low entropy gas brought to the cluster by an infalling group. Other plausible sources of density fluctuations are discussed, including turbulence...

  2. Investigation of multifractal nature of floating potential fluctuations obtained from a dc glow discharge magnetized plasma

    Science.gov (United States)

    Shaw, Pankaj Kumar; Saha, Debajyoti; Ghosh, Sabuj; Janaki, M. S.; Iyengar, A. N. Sekar

    2017-03-01

    In this paper, multifractal detrended fluctuation analysis (MF-DFA) has been used to analyze the floating potential fluctuations obtained with a Langmuir probe from a dc glow discharge magnetized plasma device. The generalized Hurst exponents (h(q)) , local fluctuation function (Fq(s)) , the Rényi exponents (τ(q)) and the multifractal spectrum F(α) have been calculated by applying the MF-DFA method. The result of the MF-DFA shows the multifractal nature of these fluctuations. We have investigated the influence of magnetic field on the multifractal nature of the fluctuations and it is seen that degree of multifractality is reduced with the increase in the magnetic field strength. The values of h(q) have been restricted between 0.7 and 1 for the magnetized fluctuations. This result is evidence of the existence of long-range correlations in the fluctuations. Furthermore, we employed shuffle and surrogate approaches to analyze the origins of multifractality. Comparing the MF-DFA results for the data set to those for shuffled and surrogate series, we have found that its multifractal nature is due to the existence of significant long-term correlation.

  3. OH* imager response to turbulence-induced temperature fluctuations

    Science.gov (United States)

    Gardner, Chester S.; Vargas, Fabio A.

    2016-12-01

    The layer of the excited state hydroxyl radical (OH*) is formed in the mesopause region by the reaction of ozone (O3) and atomic hydrogen (H). We derive the theoretical expressions for the OH* brightness and rotational temperature (T*) responses to high-frequency atmospheric temperature perturbations. The theory is used to calculate the 1-D and 2-D horizontal wave number spectra of the OH* and T* image fluctuations induced by atmospheric turbulence. By applying the theory to images of a breaking gravity wave packet, acquired by the Utah State University Advanced Mesospheric Temperature Mapper, we show that existing infrared OH* imager technology can observe the evolution of gravity wave breakdown and characterize the resulting turbulent eddies in the source region and in the inertial subrange of the turbulence spectrum. For the example presented here, the RMS OH* brightness fluctuations induced by the gravity wave packet was 2.90% and by the associated turbulence was 1.07%. Unfortunately, the T* fluctuations induced by turbulence are usually too small to be observed in the OH* rotational temperature maps.

  4. Phenomenology with fluctuating quantum geometries in loop quantum cosmology

    Science.gov (United States)

    Agullo, Ivan; Ashtekar, Abhay; Gupt, Brajesh

    2017-04-01

    The goal of this paper is to probe phenomenological implications of large fluctuations of quantum geometry in the Planck era, using cosmology of the early universe. For the background (Friedmann, Lemaître, Robertson, Walker) quantum geometry, we allow ‘widely spread’ states in which the relative dispersions are as large as 168 % in the Planck regime. By introducing suitable methods to overcome the ensuing conceptual and computational issues, we calculate the power spectrum {{P}R}(k) and the spectral index n s (k) of primordial curvature perturbations. These results generalize the previous work in loop quantum cosmology which focused on those states which were known to remain sharply peaked throughout the Planck regime. Surprisingly, even though the fluctuations we now consider are large, their presence does not add new features to the final {{P}R}(k) and n s (k): within observational error bars, their effect is degenerate with a different freedom in the theory, namely the number of pre-inflationary e-folds {{N}\\text{B\\star}} between the bounce and the onset of inflation. Therefore, with regard to observational consequences, one can simulate the freedom in the choice of states with large fluctuations in the Planck era using the simpler, sharply peaked states, simply by allowing for different values of {{N}\\text{B \\star}} .

  5. Nonlinear density fluctuation field theory for large scale structure

    Institute of Scientific and Technical Information of China (English)

    Yang Zhang; Hai-Xing Miao

    2009-01-01

    We develop an effective field theory of density fluctuations for a Newtonian self-gravitating N-body system in quasi-equilibrium and apply it to a homogeneous uni-verse with small density fluctuations. Keeping the density fluctuations up to second or-der, we obtain the nonlinear field equation of 2-pt correlation ξ(r), which contains 3-pt correlation and formal ultra-violet divergences. By the Groth-Peebles hierarchical ansatz and mass renormalization, the equation becomes closed with two new terms beyond the Gaussian approximation, and their coefficients are taken as parameters. The analytic solu-tion is obtained in terms of the hypergeometric functions, which is checked numerically.With one single set of two fixed parameters, the correlation ξ(r) and the corresponding power spectrum P(k) simultaneously match the results from all the major surveys, such as APM, SDSS, 2dfGRS, and REFLEX. The model gives a unifying understanding of several seemingly unrelated features of large scale structure from a field-theoretical per-spective. The theory is worth extending to study the evolution effects in an expanding universe.

  6. Thermal fluctuations and bending rigidity of bilayer membranes.

    Science.gov (United States)

    Tarazona, Pedro; Chacón, Enrique; Bresme, Fernando

    2013-09-07

    We present a new scheme to estimate the elastic properties of biological membranes in computer simulations. The method analyzes the thermal fluctuations in terms of a coupled undulatory mode, which disentangle the mixing of the mesoscopic undulations and the high-q protrusions. This approach makes possible the accurate estimation of the bending modulus both for membranes under stress and in tensionless conditions; it also extends the applicability of the fluctuation analysis to the small membrane areas normally used in atomistic simulations. Also we clarify the difference between the surface tension imposed in simulations through a pressure coupling barostat, and the surface tension that can be extracted from the analysis of the low wave vector dependence of the coupled undulatory fluctuation spectrum. The physical analysis of the peristaltic mode is also refined, by separating the bulk and protrusions contributions. We illustrate the procedure by analyzing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayers. The bending moduli obtained from our analysis, shows good agreement with available experiments.

  7. Multifractal analysis of low-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2009-02-01

    Full Text Available The technique of large deviation multifractal spectrum has shown that the high-latitude (77.5° N, 69.2° W geomagnetic fluctuations can be described from direct dissipation process or loading-unloading regimes of the solar wind-magnetosphere coupling. In this paper, we analyze the H-component of low-latitude (22.4° S, 43.6° W geomagnetic field variability observed during the month of July 2000 at the Geomagnetic Observatory, Vassouras, RJ, Brazil. The variability pattern during this period is a mixture of quiet and disturbed days including the Bastille Day intense geomagnetic storm on 15 July. Due to the complexity of this data, we pursue a detailed analysis of the geomagnetic fluctuations in different time scales including a multifractal approach using the singular power spectrum deviations obtained from the wavelet transform modulus maxima (WTMM. The results suggest, as observed from high-latitude data, the occurrence of low-latitude multifractal processes driving the intermittent coupling between the solar wind-magnetosphere and geomagnetic field variations. On finer scales possible physical mechanisms in the context of nonlinear magnetosphere response are discussed.

  8. Non-standard primordial fluctuations and nongaussianity in string inflation

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, C.P. [McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronomy; Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Cicoli, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Gomez-Reino, M. [CERN, Geneve (Switzerland). Theory Div.; Oviedo Univ. (Spain). Dept. of Physics; Quevedo, F. [Cambridge Univ. (United Kingdom). DAMTP/CMS; Abdus Salam ICTP, Trieste (Italy); Tasinato, G. [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Zavala, I. [Bonn Univ. (Germany). Bethe Center for Theoretical Physics and Physikalisches Inst.

    2010-05-15

    Inflationary scenarios in string theory often involve a large number of light scalar fields, whose presence can enrich the post-inflationary evolution of primordial fluctuations generated during the inflationary epoch. We provide a simple example of such post-inflationary processing within an explicit string-inflationary construction, using a Kaehler modulus as the inflaton within the framework of LARGE Volume Type-IIB string flux compactifications. We argue that inflationary models within this broad category often have a selection of scalars that are light enough to be cosmologically relevant, whose contributions to the primordial fluctuation spectrum can compete with those generated in the standard way by the inflaton. These models consequently often predict nongaussianity at a level, f{sub NL}{approx_equal}O(10), potentially observable by the Planck satellite, with a bi-spectrum maximized by triangles with squeezed shape in a string realization of the curvaton scenario. We argue that the observation of such a signal would robustly prefer string cosmologies such as these that predict a multi-field dynamics during the very early universe. (orig.)

  9. Pull-in voltage of microswitch rough plates in the presence of electromagnetic and acoustic Casimir forces

    NARCIS (Netherlands)

    Palasantzas, George

    2007-01-01

    In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence

  10. Pull-in voltage of microswitch rough plates in the presence of electromagnetic and acoustic Casimir forces

    NARCIS (Netherlands)

    Palasantzas, George

    2007-01-01

    In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence

  11. Low voltage electron beam accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Masafumi [Iwasaki Electric Co., Ltd., Tokyo (Japan)

    2003-02-01

    Widely used electron accelerators in industries are the electron beams with acceleration voltage at 300 kV or less. The typical examples are shown on manufactures in Japan, equipment configuration, operation, determination of process parameters, and basic maintenance requirement of the electron beam processors. New electron beam processors with acceleration voltage around 100 kV were introduced maintaining the relatively high dose speed capability of around 10,000 kGy x mpm at production by ESI (Energy Science Inc. USA, Iwasaki Electric Group). The application field like printing and coating for packaging requires treating thickness of 30 micron or less. It does not require high voltage over 110 kV. Also recently developed is a miniature bulb type electron beam tube with energy less than 60 kV. The new application area for this new electron beam tube is being searched. The drive force of this technology to spread in the industries would be further development of new application, process and market as well as the price reduction of the equipment, upon which further acknowledgement and acceptance of the technology to societies and industries would entirely depend. (Y. Tanaka)

  12. Equilibrium & Nonequilibrium Fluctuation Effects in Biopolymer Networks

    Science.gov (United States)

    Kachan, Devin Michael

    speculate that cells take advantage of this equilibrium effect by tuning near the transition point, where small changes in free cross-linker density will affect large structural rearrangements between free filament networks and networks of bundles. Cells are naturally found far from equilibrium, where the active influx of energy from ATP consumption controls the dynamics. Motor proteins actively generate forces within biopolymer networks, and one may ask how these differ from the random stresses characteristic of equilibrium fluctuations. Besides the trivial observation that the magnitude is independent of temperature, I find that the processive nature of the motors creates a temporally correlated, or colored, noise spectrum. I model the network with a nonlinear scalar elastic theory in the presence of active driving, and study the long distance and large scale properties of the system with renormalization group techniques. I find that there is a new critical point associated with diverging correlation time, and that the colored noise produces novel frequency dependence in the renormalized transport coefficients. Finally, I study marginally elastic solids which have vanishing shear modulus due to the presence of soft modes, modes with zero deformation cost. Although network coordination is a useful metric for determining the mechanical response of random spring networks in mechanical equilibrium, it is insufficient for describing networks under external stress. In particular, under-constrained networks which are fluid-like at zero load will dynamically stiffen at a critical strain, as observed in numerical simulations and experimentally in many biopolymer networks. Drawing upon analogies to the stress induced unjamming of emulsions, I develop a kinetic theory to explain the rigidity transition in spring and filament networks. Describing the dynamic evolution of non-affine deformation via a simple mechanistic picture, I recover the emergent nonlinear strain

  13. Carbon nanotube based sensors and fluctuation enhanced sensing

    Energy Technology Data Exchange (ETDEWEB)

    Kukovecz, Akos; Konya, Zoltan; Haspel, Henrik; Mohl, Melinda; Sapi, Andras; Kiricsi, Imre [Department of Applied and Environmental Chemistry, University of Szeged (Hungary); Molnar, Daniel; Heszler, Peter [Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged (Hungary); Kordas, Krisztian; Maeklin, Jani; Halonen, Niina; Toth, Geza [Microelectronics and Materials Physics Laboratories, and EMPART Research Group of Infotech Oulu, University of Oulu (Finland); Gingl, Zoltan; Mingesz, Robert [Department of Experimental Physics, University of Szeged (Hungary); Moilanen, Hannu [Laserprobe LP Ltd., Oulu (Finland); Roth, Siegmar [Max Planck Institute for Solid State Research, Stuttgart (Germany); Vajtai, Robert; Ajayan, Pulickel M. [Department of Mechanical Engineering and Materials Science, Rice University, Houston, TX (United States); Pouillon, Yann; Rubio, Angel [Nano-Bio Spectroscopy Group y ETSF Scientific Development Centre, Dpto. Fisica de Materiales, Universidad del Pais Vasco, Centro de Fisica de Materiales CSIC-UPV/EHU-MPC y DIPC, San Sebastian (Spain)

    2010-04-15

    Drop-cast thin films of multi-walled carbon nanotubes are used as gas sensors in a four-probe measurement setup. The novelty of the approach is that the sensor information is extracted from the noise of the dc resistance data using Fluctuation Enhanced Sensing (FES). We investigate the effects of measurement duration, gate voltage and frequency window on the chemical selectivity of the MWCNT-FES sensor. The selectivity of the device is superior to those of conventional gas sensors, and preliminary experiments indicate that it may also be possible to extract quantitative information from the noise. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Piezo Voltage Controlled Planar Hall Effect Devices

    OpenAIRE

    Bao Zhang; Kang-Kang Meng; Mei-Yin Yang; Edmonds, K. W.; Hao Zhang; Kai-Ming Cai; Yu Sheng; Nan Zhang; Yang Ji; Jian-Hua Zhao; Hou-Zhi Zheng; Kai-You Wang

    2015-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the pie...

  15. Modelling the TSZ power spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Suman [Los Alamos National Laboratory; Shaw, Laurie D [YALE; Nagai, Daisuke [YALE

    2010-01-01

    The structure formation in university is a hierarchical process. As universe evolves, tiny density fluctuations that existed in the early universe grows under gravitational instability to form massive large scale structures. The galaxy clusters are the massive viralized objects that forms by accreting smaller clumps of mass until they collapse under their self-gravity. As such galaxy clusters are the youngest objects in the universe which makes their abundance as a function of mass and redshift, very sensitive to dark energy. Galaxy clusters can be detected by measuring the richness in optical waveband, by measuring the X-ray flux, and in the microwave sky using Sunyaev-Zel'dovich (SZ) effect. The Sunyaev-Zel'dovich (SZ) effect has long been recognized as a powerful tool for detecting clusters and probing the physics of the intra-cluster medium. Ongoing and future experiments like Atacama Cosmology Telescope, the South Pole Telescope and Planck survey are currently surveying the microwave sky to develop large catalogs of galaxy clusters that are uniformly selected by the SZ flux. However one major systematic uncertainties that cluster abundance is prone to is the connection between the cluster mass and the SZ flux. As shown by several simulation studies, the scatter and bias in the SZ flux-mass relation can be a potential source of systematic error to using clusters as a cosmology probe. In this study they take a semi-analytic approach for modeling the intra-cluster medium in order to predict the tSZ power spectrum. The advantage of this approach is, being analytic, one can vary the parameters describing gas physics and cosmology simultaneously. The model can be calibrated against X-ray observations of massive, low-z clusters, and using the SZ power spectrum which is sourced by high-z lower mass galaxy groups. This approach allows us to include the uncertainty in gas physics, as dictated by the current observational uncertainties, while measuring the

  16. Fluctuations and interactions in microemulsions

    Energy Technology Data Exchange (ETDEWEB)

    Menes, R.; Safran, S.A. [Weizmann Institute, Rehovot (Israel); Strey, R. [Max Planck Institute, Gottingen (Germany)

    1995-12-01

    We review the properties of microemulsions as described by an interfacial model which focuses upon the deformations of the surfactant monolayer separating mesoscopic water and oil domains. In some cases, the interfacial shape is well defined, resulting in a globular phase, while in others, the interface is strongly affected by thermal fluctuations, resulting in a random, sponge-like structure. In the globular phase, interactions between globules can result in phase coexistence comparable to those observed in polymeric systems. Recent experiments indicate that these interactions can result in closed-loop coexistence regions in the isothermal, concentration phase diagram. We propose a mechanism for this reentrant phase separation based on the combined effects of a shape transition and attractive interactions. Long cylindrical globules can phase separate at relatively low interglobular attractions. A transformation from elongated globules to compact spherical drops alters the balance between the entropy and the effective interglobule interactions, leading to the remixing of the globular system.

  17. Characterizing flow fluctuations with moments

    Energy Technology Data Exchange (ETDEWEB)

    Bhalerao, Rajeev S. [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Ollitrault, Jean-Yves, E-mail: jean-yves.ollitrault@cea.fr [CNRS, URA2306, IPhT, Institut de physique théorique de Saclay, F-91191 Gif-sur-Yvette (France); Pal, Subrata [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005 (India)

    2015-03-06

    We present a complete set of multiparticle correlation observables for ultrarelativistic heavy-ion collisions. These include moments of the distribution of the anisotropic flow in a single harmonic and also mixed moments, which contain the information on correlations between event planes of different harmonics. We explain how all these moments can be measured using just two symmetric subevents separated by a rapidity gap. This presents a multi-pronged probe of the physics of flow fluctuations. For instance, it allows to test the hypothesis that event-plane correlations are generated by non-linear hydrodynamic response. We illustrate the method with simulations of events in A MultiPhase Transport (AMPT) model.

  18. Characterizing flow fluctuations with moments

    Directory of Open Access Journals (Sweden)

    Rajeev S. Bhalerao

    2015-03-01

    Full Text Available We present a complete set of multiparticle correlation observables for ultrarelativistic heavy-ion collisions. These include moments of the distribution of the anisotropic flow in a single harmonic and also mixed moments, which contain the information on correlations between event planes of different harmonics. We explain how all these moments can be measured using just two symmetric subevents separated by a rapidity gap. This presents a multi-pronged probe of the physics of flow fluctuations. For instance, it allows to test the hypothesis that event-plane correlations are generated by non-linear hydrodynamic response. We illustrate the method with simulations of events in A MultiPhase Transport (AMPT model.

  19. Characterizing price index behavior through fluctuation dynamics

    CERN Document Server

    Panigrahi, Prasanta K; Banerjee, Arjun; Bahadur, Jainendra; Manimaran, P

    2012-01-01

    We study the nature of fluctuations in variety of price indices involving companies listed on the New York Stock Exchange. The fluctuations at multiple scales are extracted through the use of wavelets belonging to Daubechies basis. The fact that these basis sets satisfy vanishing moments conditions makes them ideal to extract local polynomial trends, through the low pass or `average coefficients'. Subtracting the trends from the original time series yields the fluctuations, at different scales, depending on the level of low-pass coefficients used for finding the `average behavior'. The fluctuations are then studied using wavelet based multifractal detrended fluctuation analysis to analyze their self-similar and non-statistical properties. Due to the multifractality of such time series, they deviate from Gaussian behavior in different frequency regimes. Their departure from random matrix theory predictions in such regimes is also analyzed. These deviations and non-statistical properties of the fluctuations can...

  20. Vacuum Lightcone Fluctuations in a Dielectric

    CERN Document Server

    Bessa, C H G; Ford, L H; Svaiter, N F

    2014-01-01

    A model for observable effects of electromagnetic vacuum fluctuations is presented. The model involves a probe pulse which traverses a slab of nonlinear optical material with a nonzero second order polarizability. We argue that the pulse interacts with the ambient vacuum fluctuations of other modes of the quantized electric field, and these vacuum fluctuations cause variations in the flight time of the pulse through the material. The geometry of the slab of material defines a sampling function for the quantized electric field, which in turn determines that vacuum modes whose wavelengths are of the order of the thickness of the slab give the dominant contribution. Some numerical estimates are made, which indicate that fractional fluctuations in flight time of the order of $10^{-9}$ are possible in realistic situations. The model presented here is both an illustration of a physical effect of vacuum fluctuations, and an analog model for the lightcone fluctuations predicted by quantum gravity.

  1. 49 CFR 234.221 - Lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lamp voltage. 234.221 Section 234.221 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION..., Inspection, and Testing Maintenance Standards § 234.221 Lamp voltage. The voltage at each lamp shall...

  2. Bootstrapped Low-Voltage Analog Switches

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1999-01-01

    Novel low-voltage constant-impedance analog switch circuits are proposed. The switch element is a single MOSFET, and constant-impedance operation is obtained using simple circuits to adjust the gate and bulk voltages relative to the switched signal. Low-voltage (1-volt) operation is made feasible...

  3. Nonlocally of plasma fluctuations and transport in magnetically confined plasmas theoretical background of nonlocality in fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, Sanae-I.; Yagi, Masatoshi [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    2002-09-01

    Nonlocal properties of fluctuations in confined plasmas are briefly surveyed. Contributions to understanding the bifurcation phenomena, improved confinement, and transient transport problem are explained. The theoretical progress in this aspect is addressed: Namely, the fluctuations are not excited by linear instabilities but are dressed with other turbulent fluctuations or fluctuations of meso-scale. Nonlinear interactions of fluctuations with different scale lengths are essential in dictating the dynamics of turbulence and turbulent transport. There are activators and suppressers in global inhomogeneities for evolution of turbulence. Turbulent fluctuations, on the other hand, induce or destroy these global inhomogeneities. Finally, statistical nature of turbulence is addressed. (author)

  4. Power Spectrum Analysis and Missing Level Statistics of Microwave Graphs with Violated Time Reversal Invariance

    Science.gov (United States)

    Białous, Małgorzata; Yunko, Vitalii; Bauch, Szymon; Ławniczak, Michał; Dietz, Barbara; Sirko, Leszek

    2016-09-01

    We present experimental studies of the power spectrum and other fluctuation properties in the spectra of microwave networks simulating chaotic quantum graphs with violated time reversal invariance. On the basis of our data sets, we demonstrate that the power spectrum in combination with other long-range and also short-range spectral fluctuations provides a powerful tool for the identification of the symmetries and the determination of the fraction of missing levels. Such a procedure is indispensable for the evaluation of the fluctuation properties in the spectra of real physical systems like, e.g., nuclei or molecules, where one has to deal with the problem of missing levels.

  5. Rapidity fluctuations in the initial state

    CERN Document Server

    Broniowski, Wojciech

    2016-01-01

    We analyze two-particle pseudorapidity correlations in a simple model, where strings of fluctuating length are attached to wounded nucleons.The obtained straightforward formulas allow us to understand the anatomy of the correlations, i.e., to identify the component due to the fluctuation of the number of wounded nucleons and the contribution from the string length fluctuations. Our results reproduce qualitatively and semiquantitatively the basic features of the recent correlation measurements at the LHC.

  6. Quantum fluctuations of geometry in hot Universe

    CERN Document Server

    Bialynicki-Birula, Iwo

    2015-01-01

    The fluctuations of spacetime geometries at finite temperature are evaluated within the linearized theory of gravity. These fluctuations are described by the probability distribution of various configurations of the gravitational field. The field configurations are described by the linearized Riemann-Weyl tensor. The probability distribution has a foam-like structure; prevailing configurations are those with the large changes of geometry at nearby points. Striking differences are found between the fluctuations of the electromagnetic field and the gravitational field.

  7. The North Ecliptic Pole Extragalactic Background LIght Fluctuations Survey

    Science.gov (United States)

    Bock, James; Zemcov, Michael; Cooray, Asantha; Smidt, Joseph; Serjeant, Stephen; Malkan, Matt; Matsuhara, Hideo; Matsumoto, Toshia; Matsuura, Shuji; Clements, David; Pearson, Chris; Im, Myung Shin

    2013-10-01

    We propose to image 6 deg^2 in the North Ecliptic Pole (NEP) with IRAC to determine the origin of Extragalactic Background Light (EBL) fluctuations. These Spitzer images will be combined with CIBER data at 1.1 and 1.6 um, and Akari data at 2.4, 3.2, and 4.1 um, to probe the spectrum and band-to-band correlations of the fluctuations. The fluctuations have been reported by Spitzer and Akari, and are now positively detected in new and CIBER data, but their origin is controversial. This multi-wavelength analysis will allow us to determine if EBL fluctuations arise from epoch of reionization galaxies or diffuse intra-halo light emission both by measuring their spectral energy distribution (SED) from 1.0 to 4.5 um, and by measuring the cross-correlation between different bands. The analysis uses multiple field combinations in Spitzer, CIBER and Akari data to carry out a robust measurement with multiple data combinations for internal consistency tests. In addition, the proposed survey will be used in conjunction with Akari and Herschel data in the NEP survey that has the most comprehensive multi-band infrared coverage of any degree-scale field on the sky and the best available constraints on dust phases (e.g. PAH, silicate absorption, AGN dust tori, GMCs) in galaxies. We will use this multi-wavelength coverage to cross-identify IRAC counterparts to Herschel and Akari sources and obtain SEDs of dusty, star bursting galaxies at z ~ 1 to 3 from the UV to radio, and obtain accurate PAH luminosities of Akari 7.7 um-rest detected galaxies and AGNs.

  8. Local Multiplicity Fluctuations in Z decay

    OpenAIRE

    Chekanov, S. V.

    1996-01-01

    Local multiplicity fluctuations of hadrons produced in the decay of $Z^0$ were studied on the basis of L3 data. In addition to the normalized-factorial-moment method, the fluctuations were studied for the first time by the use of bunching parameters. A strong multifractal structure was observed inside jets. JETSET 7.4 PS describes the fluctuations in the azimuthal angle defined with respect to the beam axis reasonably well. For the fluctuations in rapidity, defined with respect to the thrust ...

  9. Resetting of fluctuating interfaces at power-law times

    Science.gov (United States)

    Gupta, Shamik; Nagar, Apoorva

    2016-11-01

    What happens when the time evolution of a fluctuating interface is interrupted by resetting to a given initial configuration after random time intervals τ distributed as a power-law ∼ {τ }-(1+α ); α \\gt 0? For an interface of length L in one dimension, and an initial flat configuration, we show that depending on α, the dynamics in the limit L\\to ∞ exhibit a spectrum of rich long-time behavior. It is known that without resetting, the interface width grows unbounded with time as {t}β in this limit, where β is the so-called growth exponent characteristic of the universality class for a given interface dynamics. We show that introducing resetting leads to fluctuations that are bounded at large times for α \\gt 1. Corresponding to such a reset-induced stationary state is a distribution of fluctuations that is strongly non-Gaussian, with tails decaying as a power-law. The distribution exhibits a distinctive cuspy behavior for a small argument, implying that the stationary state is out of equilibrium. For α \\lt 1, on the contrary, resetting to the flat configuration is unable to counter the otherwise unbounded growth of fluctuations in time, so that the distribution of fluctuations remains time dependent with an ever-increasing width, even at long times. Although stationary for α \\gt 1, the width of the interface grows forever with time as a power-law for 1\\lt α \\lt {α }({{w})}, and converges to a finite constant only for larger α, thereby exhibiting a crossover at {α }({{w})}=1 + 2β . The time-dependent distribution of fluctuations exhibits for α \\lt 1 and for small arguments further interesting crossover behavior from cusp to divergence across {α }({{d})}=1-β . We demonstrate these results by exact analytical results for the paradigmatic Edwards–Wilkinson (EW) dynamical evolution of the interface, and further corroborate our findings by extensive numerical simulations of interface models in the EW and Kardar–Parisi–Zhang universality

  10. Measurement of laser quantum frequency fluctuations using a Pound-Drever stabilization system

    Science.gov (United States)

    Cheng, Yuh-Jen; Mussche, Paul L.; Siegman, Anthony E.

    1994-06-01

    We describe a method for measuring the frequency fluctuation spectrum of a laser oscillator, especially the weak noise contributions in the wings of the spectrum, and apply this method to confirm the existence of large excess quantum frequency fluctuations in a laser oscillator using an unstable optical resonator. Our measurement apparatus uses the Pound-Drever technique, which employs an RF phase modulator and a Fabry-Perot cavity to produce a sensitive high-speed frequency discrimination signal. We show that this signal can also be used to measure the quantum noise contributions to the frequency spectrum of a laser oscillator. Experimental measurements on a miniature diode-pumped Nd:YAG laser using a stable optical cavity closely match the predictions of the usual Schawlow-Townes theory, while the frequency fluctuations in a nearly identical laser employing an unstable optical resonator are approximately 1300 times larger. These much larger fluctuations arise in part from the larger output coupling and cavity bandwidth of the unstable cavity, but they also appear to confirm a predicted excess spontaneous emission factor (Petermann excess noise factor) of approximately = 180 times arising from the nonorthogonal transverse mode properties of the unstable cavity.

  11. Chaotic dynamic characteristics of pressure fluctuation signals in hydro-turbine

    Energy Technology Data Exchange (ETDEWEB)

    Su, Wen Tao; An, Shi [School of Management, Harbin Institute of Technology, Harbin (China); Li, Xiao Bin; Lan, Chao Feng; Li, Feng Chen [School of Energy Science and Engineering, Harbin Institute of Technology, Harbin (China); Wang, Jian Sheng [Ministry of Education of China, Tianjin (China)

    2016-11-15

    The pressure fluctuation characteristics in a Francis hydro-turbine running at partial flow conditions were studied based on the chaotic dynamic methods. Firstly, the experimental data of pressure fluctuations in the draft tube at various flow conditions was de-noised using lifting wavelet transformation, then, for the de-noised signals, their spectrum distribution on the frequency domain, the energy variation and the energy partition accounting for the total energy was calculated. Hereby, for the flow conditions ranging from no cavitation to severe cavitation, the chaos dynamic features of fluctuation signals were analyzed, including the temporal-frequency distribution, phase trajectory, Lyapunov exponent and Poincaré map etc. It is revealed that, the main energy of pressure fluctuations in the draft tube locates at low-frequency region. As the cavitation grows, the amplitude of power spectrum at frequency domain becomes larger. For all the flow conditions, all the maximal Lyapunov exponents are larger than zero, and they increase with the cavitation level. Therefore, it is believed that there indeed exist the chaotic attractors in the pressure fluctuation signals for a hydro-turbine.

  12. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    DEFF Research Database (Denmark)

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis...

  13. Estimating Voltage Asymmetry Making by One Phase Micro-generator in Low Voltage Network

    Directory of Open Access Journals (Sweden)

    Marian Sobierajski

    2014-12-01

    Full Text Available Connection of one phase micro-generator to the low voltage network increases voltage asymmetry. The voltage asymmetry is defined as the quotient of negative and positive voltage components. The mathematical background of exact and rough computation of the asymmetry quotient is presented in the paper. Considerations are illustrated by simple examples.

  14. 76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop

    Science.gov (United States)

    2011-11-15

    ... Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice that the Federal Energy Regulatory Commission will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011 from 9 a.m. to 4:30 p.m. This staff-led workshop will be...

  15. Spectral fluctuations of quantum graphs

    Energy Technology Data Exchange (ETDEWEB)

    Pluhař, Z. [Faculty of Mathematics and Physics, Charles University, 180 00 Praha 8 (Czech Republic); Weidenmüller, H. A. [Max-Planck-Institut für Kernphysik, 69029 Heidelberg (Germany)

    2014-10-15

    We prove the Bohigas-Giannoni-Schmit conjecture in its most general form for completely connected simple graphs with incommensurate bond lengths. We show that for graphs that are classically mixing (i.e., graphs for which the spectrum of the classical Perron-Frobenius operator possesses a finite gap), the generating functions for all (P,Q) correlation functions for both closed and open graphs coincide (in the limit of infinite graph size) with the corresponding expressions of random-matrix theory, both for orthogonal and for unitary symmetry.

  16. Improving transition voltage spectroscopy of molecular junctions

    DEFF Research Database (Denmark)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian Sommer

    2011-01-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin...... is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln...

  17. Piezo Voltage Controlled Planar Hall Effect Devices

    Science.gov (United States)

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-06-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

  18. Piezo Voltage Controlled Planar Hall Effect Devices.

    Science.gov (United States)

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-06-22

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

  19. Capacitor Voltages Measurement and Balancing in Flying Capacitor Multilevel Converters Utilizing a Single Voltage Sensor

    DEFF Research Database (Denmark)

    Farivar, Glen; Ghias, Amer M. Y. M.; Hredzak, Branislav

    2017-01-01

    This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac...... side of the phase leg. The proposed method is subsequently used to balance the capacitor voltages using only the measured ac voltage. The operation of the proposed measurement and balancing method is independent of the number of the converter levels. Experimental results presented for a five-level FC...

  20. Voltage-Sensitive Load Controllers for Voltage Regulation and Increased Load Factor in Distribution Systems

    DEFF Research Database (Denmark)

    Douglass, Philip James; Garcia-Valle, Rodrigo; Østergaard, Jacob

    2014-01-01

    consumption which can be mapped to temperature setpoint offsets of thermostat controlled loads. In networks where a lower voltage level corresponds to high system load (and vice versa), this controller acts to regulate voltage and increase the load factor. Simulations are conducted on low- and medium-voltage......This paper presents a novel controller design for controlling appliances based on local measurements of voltage. The controller finds the normalized voltage deviation accounting for the sensitivity of voltage measurements to appliance state. The controller produces a signal indicating desired power...... distribution systems with residential loads including voltage-sensitive water heaters. In low-voltage systems, the results of the simulations show the controller to be effective at reducing the extremes of voltage and increasing the load factor while respecting end-use temperature constraints. In medium-voltage...

  1. Voltage-controlled photonic oscillator.

    Science.gov (United States)

    Savchenkov, A A; Ilchenko, V S; Liang, W; Eliyahu, D; Matsko, A B; Seidel, D; Maleki, L

    2010-05-15

    We report the development and demonstration of an X-band voltage-controlled photonic oscillator based on a whispering gallery mode resonator made of an electro-optic crystalline material. The oscillator has good spectral purity and wide, agile, linear tunability. We have modified the existing theoretical model of the opto-electronic oscillator to describe the performance of our tunable oscillator and have found a good agreement between the theoretical predictions and the measurement results. We show that the device is promising for higher-frequency applications where high-performance tunable oscillators with wide tunability do not exist.

  2. Pinch-off voltage modeling for CMOS image pixels with a pinned photodiode structure

    Science.gov (United States)

    Chen, Cao; Bing, Zhang; Longsheng, Wu; Xin, Li; Junfeng, Wang

    2014-07-01

    A novel analytical model of pinch-off voltage for CMOS image pixels with a pinned photodiode structure is proposed. The derived model takes account of the gradient doping distributions in the N buried layer due to the impurity compensation formed by manufacturing processes; the impurity distribution characteristics of two boundary PN junctions located in the region for particular spectrum response of a pinned photodiode are quantitative analyzed. By solving Poisson's equation in vertical barrier regions, the relationships between the pinch-off voltage and the corresponding process parameters such as peak doping concentration, N type width and doping concentration gradient of the N buried layer are established. Test results have shown that the derived model features the variations of the pinch-off voltage versus the process implant conditions more accurately than the traditional model. The research conclusions in this paper provide theoretical evidence for evaluating the pinch-off voltage design.

  3. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    OpenAIRE

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia; Han, Xue

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis. The load profiles are characterized by using single phase measurement data on voltages, currents and active powers with a 10 minutes resolution. Different scenarios are considered: no tap action, th...

  4. Multifractal Detrended Fluctuation Analysis of Interevent Time Series in a Modified OFC Model

    Institute of Scientific and Technical Information of China (English)

    LIN Min; YAN Shuang-Xi; ZHAO Gang; WANG Gang

    2013-01-01

    We use multifractal detrended fluctuation analysis (MF-DFA) method to investigate the multifractal behavior of the interevent time series in a modified Olami-Feder-Christensen (OFC) earthquake model on assortative scale-free networks.We determine generalized Hurst exponent and singularity spectrum and find that these fluctuations have multifractal nature.Comparing the MF-DFA results for the original interevent time series with those for shuffled and surrogate series,we conclude that the origin of multifractality is due to both the broadness of probability density function and long-range correlation.

  5. Edge Electrostatic Fluctuation Characteristics in the Sino-United Spherical Tokamak

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-Hao; HE Ye-Xi; GAO Zhe; ZENG Li; ZHANG Guo-Ping; XIE Li-Feng; FENG Chun-Hua; XIAO Qiong; LI Xiao-Yan

    2004-01-01

    @@ Edge plasma parameters, including electron temperature Te, density ne, plasma potential φp, radial electric field Er and the corresponding fluctuations in the Sino- United Spherical Tokamak, have been systematically measured with Langmuir probe arrays. Wavenumber spectrum analyses show that edge fluctuations have a radial propagation character of the drift wave turbulence, with a characteristic radial phase velocity νphr ~ 0.7 km.s-1in the scrape-off layer and vphr ~ 0.9-1.4km's-1 in the plasma edge.

  6. Comparison of the Sachs-Wolfe Effect for Gaussian and Non-Gaussian Fluctuations

    CERN Document Server

    Kung, J H

    1993-01-01

    A consequence of non-Gaussian perturbations on the Sachs-Wolfe effect is studied. For a particular power spectrum, predicted Sachs-Wolfe effects are calculated for two cases: Gaussian (random phase) configuration, and a specific kind of non-Gaussian configuration. We obtain a result that the Sachs-Wolfe effect for the latter case is smaller when each temperature fluctuation is properly normalized with respect to the corresponding mass fluctuation ${\\delta M\\over M}(R)$. The physical explanation and the generality of the result are discussed.

  7. Thermal SZ fluctuations in the ICM: probing turbulence and thermodynamics in Coma cluster with Planck

    Science.gov (United States)

    Khatri, Rishi; Gaspari, Massimo

    2016-11-01

    We report the detection of thermal Sunyaev-Zeldovich (SZ) effect fluctuations in the intracluster medium (ICM) of Coma cluster observed with Planck. The SZ data links the maximum observable X-ray scale to the large Mpc scale, extending our knowledge of the power spectrum of ICM fluctuations. Deprojecting the 2D SZ perturbations into 3D pressure fluctuations, we find an amplitude spectrum which peaks at δP/P = 33 ± 12 and 74 ± 19 per cent in the 15 and 40 arcmin radius region, respectively. We perform tests to ensure fluctuations are intrinsic to the cluster and not due to noise contamination. By using high-resolution hydrodynamical models, we improve the ICM turbulence constraints in Coma, finding 3D Mach number Ma3d = 0.8 ± 0.3 (15 arcmin region), increasing to supersonic values at larger radii (40 arcmin) and an injection scale Linj ≈ 500 kpc. Such properties are consistent with driving due to mergers, in particular tied to internal galaxy groups. The large pressure fluctuations show that Coma is in adiabatic mode (mediated by sound waves), rather than isobaric mode (mediated by buoyancy waves). As predicted by turbulence models, the distribution of SZ fluctuations is lognormal with mild non-Gaussianities (heavy tails). The substantial non-thermal pressure support implies hydrostatic mass bias bM = -15 to -45 per cent from the core to the outskirt region, respectively. While total SZ power probes the thermal energy content, the SZ fluctuations constrain the non-thermal deviations important for precision cosmology. The proposed, novel approach can be exploited by multifrequency observations using ground-based interferometers and future space cosmic microwave background missions.

  8. Global Fluctuation Spectra in Big Crunch/Big Bang String Vacua

    CERN Document Server

    Craps, B; Craps, Ben; Ovrut, Burt A.

    2004-01-01

    We study Big Crunch/Big Bang cosmologies that correspond to exact world-sheet superconformal field theories of type II strings. The string theory spacetime contains a Big Crunch and a Big Bang cosmology, as well as additional ``whisker'' asymptotic and intermediate regions. Within the context of free string theory, we compute, unambiguously, the scalar fluctuation spectrum in all regions of spacetime. Generically, the Big Crunch fluctuation spectrum is altered while passing through the bounce singularity. The change in the spectrum is characterized by a function $\\Delta$, which is momentum and time-dependent. We compute $\\Delta$ explicitly and demonstrate that it arises from the whisker regions. The whiskers are also shown to lead to ``entanglement'' entropy in the Big Bang region. Finally, in the Milne orbifold limit of our superconformal vacua, we show that $\\Delta\\to 1$ and, hence, the fluctuation spectrum is unaltered by the Big Crunch/Big Bang singularity. We comment on, but do not attempt to resolve, su...

  9. Diagnosis of stator faults in induction motor based on zero sequence voltage after switch-off

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To improve the accuracy of the stator winding fault diagnosis in induction motor, a new diagnostic method based on the Hilbert-Huang transform (HHT) was proposed. The ratio of fundamental zero sequence voltage to positive sequence voltage after switch-offwas selected as the stator fault characteristic, which could effectively avoid the influence of the supply unbalance and the load fluctuation, and directly represent the asymmetry in the stator. Using the empirical mode decomposition (EMD) based on HHT, the zero sequence voltage after switch-off was decomposed and the fundamental component was extracted. Then, the fault characteristic can be acquired. Experimental results on a 4-kW induction motor demonstrate the feasibility and effectiveness of this method.

  10. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The

  11. Inverse scattering problem in turbulent magnetic fluctuations

    CERN Document Server

    Treumann, R A; Narita, Y

    2016-01-01

    We apply a particular form of the inverse scattering theory to turbulent magnetic fluctuations in a plasma. In the present note we develop the theory, formulate the magnetic fluctuation problem in terms of its electrodynamic turbulent response function, and reduce it to the solution of a special form of the famous Gel$'$fand-Levitan-Marchenko equation of quantum mechanical scattering theory.

  12. Charge conservation effects for high order fluctuations

    CERN Document Server

    Begun, Viktor

    2016-01-01

    The exact charge conservation significantly impacts multiplicity fluctuations. The result depends strongly on the part of the system charge carried by the particles of interest. Along with the expected suppression of fluctuations for large systems, charge conservation may lead to negative skewness or kurtosis for small systems.

  13. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    1997-01-01

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The e

  14. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    1997-01-01

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The e

  15. Wave Beam Propagation Through Density Fluctuations

    NARCIS (Netherlands)

    Balakin, A. A.; Bertelli, N.; Westerhof, E.

    2011-01-01

    Perturbations induced by edge density fluctuations on electron cyclotron wave beams propagating in fusion plasmas are studied by means of a quasi-optical code. The effects of such fluctuations are illustrated here by showing the beam propagation in the case of single harmonic perturbations to the wa

  16. Computer simulations of phospholipid - membrane thermodynamic fluctuations

    DEFF Research Database (Denmark)

    Pedersen, U.R.; Peters, Günther H.j.; Schröder, T.B.

    2008-01-01

    This paper reports all-atom computer simulations of five phospholipid membranes, DMPC, DPPC, DMPG, DMPS, and DMPSH, with a focus on the thermal equilibrium fluctuations of volume, energy, area, thickness, and order parameter. For the slow fluctuations at constant temperature and pressure (defined...

  17. Measuring shape fluctuations in biological membranes

    Science.gov (United States)

    Monzel, C.; Sengupta, K.

    2016-06-01

    Shape fluctuations of lipid membranes have intrigued cell biologists and physicists alike. In the cellular context, their origin—thermal or active—and their physiological significance are open questions. These small incessant displacements, also called membrane undulations, have mostly been studied in model membranes and membranes of simple cells like erythrocytes. Thermal fluctuations of such membranes have been very well described both theoretically and experimentally; active fluctuations are a topic of current interest. Experimentally, membrane fluctuations are not easy to measure, the main challenge being to develop techniques which are capable of measuring very small displacements at very high speed, and preferably over a large area and long time. Scattering techniques have given access to fluctuations in membrane stacks and a variety of optical microscopy based techniques have been devised to study membrane fluctuations of unilamellar vesicles, erythrocytes and other cells. Among them are flicker spectroscopy, dynamic light scattering, diffraction phase microscopy and reflection interference contrast microscopy. Each of these techniques has its advantages and limitations. Here we review the basic principles of the major experimental techniques used to measure bending or shape fluctuations of biomembranes. We report seminal results obtained with each technique and highlight how these studies furthered our understanding of physical properties of membranes and their interactions. We also discuss suggested role of membrane fluctuations in different biological processes.

  18. Fluctuating brane in a dilatonic bulk

    CERN Document Server

    Brax, P; Rodríguez-Martinez, M; Brax, Philippe; Langlois, David; Rodriguez-Martinez, Maria

    2003-01-01

    We consider a cosmological brane moving in a static five-dimensional bulk spacetime endowed with a scalar field whose potential is exponential. After studying various cosmological behaviours for the homogeneous background, we investigate the fluctuations of the brane that leave spacetime unaffected. A single mode embodies these fluctuations and obeys a wave equation which we study for bouncing and ever-expanding branes.

  19. Dynamic magnetization switching and spin wave excitations by voltage-induced torque

    Science.gov (United States)

    Shiota, Yoichi

    2013-03-01

    The effect of electric fields on ultrathin ferromagnetic metal layer is one of the promising approaches for manipulating the spin direction with low-energy consumption, localization, and coherent behavior. Several experimental approaches to realize it have been investigated using ferromagnetic semiconductors, magnetostriction together with piezo-electric materials, multiferroic materials, and ultrathin ferromagnetic layer. In this talk, we will present a dynamic control of spins by voltage-induced torque. We used the magnetic tunnel junctions with ultrathin ferromagnetic layer, which shows voltage-induced perpendicular magnetic anisotropy change. By applying the voltage to the junction, the magnetic easy-axis in the ultrathin ferromagnetic layer changes from in-plane to out-of-plane, which causes a precession of the spins. This precession resulted in a two-way toggle switching by determining an appropriate pulse length. On the other hand, an application of rf-voltage causes an excitation of a uniform spin-wave. Since the precession of spin associates with an oscillation in the resistance of the junction, the applied rf-signal is rectified and produces a dc-voltage. From the spectrum of the dc-voltage as a function of frequency, we could estimate the voltage-induced torque. This research was supported by CREST-JST, G-COE program, and JSPS for the fellowship. Collaborators include T. Nozaki, S. Miwa, F. Bonell, N. Mizuochi, T. Shinjo, and Y. Suzuki.

  20. Measurements of radio frequent cavity volt ages by X-ray spectrum measurements

    Directory of Open Access Journals (Sweden)

    Toprek Dragan

    2005-01-01

    Full Text Available This paper deals with X-ray spectrum measurement as a method for the measurement of radio frequent cavity voltage and the theory of X-ray spectrum calculation. Experimental results at 72 MHz for three different values of the radio frequent power of ACCEL K250 super conducting cyclotron are being presented.

  1. Low voltage electrodeposition of diamond like carbon (DLC)

    Science.gov (United States)

    Sreejith, K.; Nuwad, J.; Pillai, C. G. S.

    2005-10-01

    Attempt has been made to deposit diamond like carbon (DLC) films from ethanol through electrodeposition at low voltages (80-300 V) at 1 mm interelectrode separation. The films were characterized by atomic force microscopy (AFM), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and Auger electron Spectroscopy (AES). AFM investigations revealed the grain sizes are of tens of nanometers. The films were found to be continuous, smooth and close packed. Presence of peaks at 2958, 2929 and 2869 cm -1 in FTIR spectrum indicates the bonding states to be of predominantly sp 3 type (C-H). Raman spectroscopy analysis revealed two broad bands at ˜1350 and ˜1570 cm -1. The downshift of the G-band of graphite is indicative of presence of DLC. Analysis of the Raman spectra for the samples revealed an improvement in the film quality with increase in the voltage. Micro Raman investigations indicate the formation of diamond phase at the deposition potential of 80 V. The sp 2 contents the films calculated from Auger electron spectra were calculated and were found to be 31, 19 and 7.8% for the samples prepared at 80, 150 and 300 V, respectively. A tentative mechanism for the formation of DLC has been proposed. These results indicate the possibility of deposition of DLC at low voltage.

  2. Low voltage electrodeposition of diamond like carbon (DLC)

    Energy Technology Data Exchange (ETDEWEB)

    Sreejith, K. [Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Nuwad, J. [Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Pillai, C.G.S. [Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)]. E-mail: cgspil@apsara.barc.ernet.in

    2005-10-15

    Attempt has been made to deposit diamond like carbon (DLC) films from ethanol through electrodeposition at low voltages (80-300 V) at 1 mm interelectrode separation. The films were characterized by atomic force microscopy (AFM), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and Auger electron Spectroscopy (AES). AFM investigations revealed the grain sizes are of tens of nanometers. The films were found to be continuous, smooth and close packed. Presence of peaks at 2958, 2929 and 2869 cm{sup -1} in FTIR spectrum indicates the bonding states to be of predominantly sp{sup 3} type (C-H). Raman spectroscopy analysis revealed two broad bands at {approx}1350 and {approx}1570 cm{sup -1}. The downshift of the G-band of graphite is indicative of presence of DLC. Analysis of the Raman spectra for the samples revealed an improvement in the film quality with increase in the voltage. Micro Raman investigations indicate the formation of diamond phase at the deposition potential of 80 V. The sp{sup 2} contents the films calculated from Auger electron spectra were calculated and were found to be 31, 19 and 7.8% for the samples prepared at 80, 150 and 300 V, respectively. A tentative mechanism for the formation of DLC has been proposed. These results indicate the possibility of deposition of DLC at low voltage.

  3. Solar wind thermally induced magnetic fluctuations.

    Science.gov (United States)

    Navarro, R E; Moya, P S; Muñoz, V; Araneda, J A; F-Viñas, A; Valdivia, J A

    2014-06-20

    A kinetic description of Alfvén-cyclotron magnetic fluctuations for anisotropic electron-proton quasistable plasmas is studied. An analytical treatment, based on the fluctuation-dissipation theorem, consistently shows that spontaneous fluctuations in plasmas with stable distributions significantly contribute to the observed magnetic fluctuations in the solar wind, as seen, for example, in [S. D. Bale et al., Phys. Rev. Lett. 103, 211101 (2009)], even far below from the instability thresholds. Furthermore, these results, which do not require any adjustable parameters or wave excitations, are consistent with the results provided by hybrid simulations. It is expected that this analysis contributes to our understanding of the nature of magnetic fluctuations in the solar wind.

  4. Correlated fluctuations near the QCD critical point

    CERN Document Server

    Jiang, Lijia; Song, Huichao

    2015-01-01

    In this paper, we introduce a freeze-out scheme for the dynamical models near the QCD critical point through coupling the decoupled classical particles with the order parameter field. With a modified distribution function that satisfies specific static fluctuations, we calculate the correlated fluctuations of net protons on the hydrodynamic freeze-out surface. A comparison with recent STAR data shows that our model calculations could roughly reproduce energy dependent cumulant $C_4$ and $\\kappa \\sigma^2$ of net protons through tuning the related parameters. However, the calculated $C_2$ and $C_3$ with both Poisson and Binomial baselines are always above the experimental data due to the positive contributions from the static critical fluctuations. In order to qualitatively and quantitatively describe the experimental data, the dynamical critical fluctuations and more realistic non-critical fluctuation baselines should be investigated in the near future.

  5. Net Charge Fluctuation and String Fragmentation

    Institute of Scientific and Technical Information of China (English)

    SABen-Hao; CAIXu; TAIAn; ZHOUDai-Mei

    2004-01-01

    We present the simulation results of the net charge fluctuation in Au+Au collisions at √Snn=130 GeV from a dynamic model, JPCIAE, and its revisions. The simulations are done for the quark-gluon matter, the directly produced pions, the pion matter, and the hadron matter. The simulated net charge fluctuation of the quark-gluon matter is close to the thermal model prediction for the quark-gluon gas. However, the discrepancy exists comparing the simulated net charge fluctuation for directly produced pions and the pion matter with the thermal model prediction for pion gas and the resonance pion gas, respectively. The net charge fluctuation of hadron matter from default JPCIAE simulations is nearly 3.5 times larger than quark-gluon matter. A discussion is given for the net charge fluctuation as an evidence of QGP phase transition.

  6. Fluctuations in lipid bilayers: Are they understood?

    CERN Document Server

    Schmid, Friederike

    2013-01-01

    We review recent computer simulation studies of undulating lipid bilayers. Theoretical interpretations of such fluctuating membranes are most commonly based on generalized Helfrich-type elastic models, with additional contributions of local "protrusions" and/or density fluctuations. Such models provide an excellent basis for describing the fluctuations of tensionless bilayers in the fluid phase at a quantitative level. However, this description is found to fail for membranes in the gel phase and for membranes subject to high tensions. The fluctuations of tilted gel membranes show a signature of the modulated ripple structure, which is a nearby phase observed in the pretransition regime between the fluid and tilted gel state. This complicates a quantitative analysis on mesoscopic length scales. In the case of fluid membranes under tension, the large-wavelength fluctuation modes are found to be significantly softer than predicted by theory. In the latter context, we also address the general problem of the relat...

  7. Spacetime Conformal Fluctuations and Quantum Dephasing

    CERN Document Server

    Bonifacio, Paolo M

    Any quantum system interacting with a complex environment undergoes decoherence. Empty space is filled with vacuum energy due to matter fields in their ground state and represents an underlying environment that any quantum particle has to cope with. In particular quantum gravity vacuum fluctuations should represent a universal source of decoherence. To study this problem we employ a stochastic approach that models spacetime fluctuations close to the Planck scale by means of a classical, randomly fluctuating metric (random gravity framework). We enrich the classical scheme for metric perturbations over a curved background by also including matter fields and metric conformal fluctuations. We show in general that a conformally modulated metric induces dephasing as a result of an effective nonlinear newtonian potential obtained in the appropriate nonrelativistic limit of a minimally coupled Klein-Gordon field. The special case of vacuum fluctuations is considered and a quantitative estimate of the expected effect...

  8. Coupled Quantum Fluctuations and Quantum Annealing

    Science.gov (United States)

    Hormozi, Layla; Kerman, Jamie

    We study the relative effectiveness of coupled quantum fluctuations, compared to single spin fluctuations, in the performance of quantum annealing. We focus on problem Hamiltonians resembling the the Sherrington-Kirkpatrick model of Ising spin glass and compare the effectiveness of different types of fluctuations by numerically calculating the relative success probabilities and residual energies in fully-connected spin systems. We find that for a small class of instances coupled fluctuations can provide improvement over single spin fluctuations and analyze the properties of the corresponding class. Disclaimer: This research was funded by ODNI, IARPA via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  9. Correlated fluctuations near the QCD critical point

    Science.gov (United States)

    Jiang, Lijia; Li, Pengfei; Song, Huichao

    2016-08-01

    In this article, we introduce a freeze-out scheme for the dynamical models near the QCD critical point through coupling the decoupled classical particles with the order parameter field. With a modified distribution function that satisfies specific static fluctuations, we calculate the correlated fluctuations of net protons on the hydrodynamic freeze-out surface. A comparison with recent STAR data shows that our model calculations could roughly reproduce energy-dependent cumulant C4 and κ σ2 of net protons through tuning the related parameters. However, the calculated C2 and C3 with both Poisson and binomial baselines are always above the experimental data due to the positive contributions from the static critical fluctuations. To qualitatively and quantitatively describe all the related experimental data, the dynamical critical fluctuations and more realistic noncritical fluctuation baselines should be investigated in the near future.

  10. Fluctuation theorem for constrained equilibrium systems

    Science.gov (United States)

    Gilbert, Thomas; Dorfman, J. Robert

    2006-02-01

    We discuss the fluctuation properties of equilibrium chaotic systems with constraints such as isokinetic and Nosé-Hoover thermostats. Although the dynamics of these systems does not typically preserve phase-space volumes, the average phase-space contraction rate vanishes, so that the stationary states are smooth. Nevertheless, finite-time averages of the phase-space contraction rate have nontrivial fluctuations which we show satisfy a simple version of the Gallavotti-Cohen fluctuation theorem, complementary to the usual fluctuation theorem for nonequilibrium stationary states and appropriate to constrained equilibrium states. Moreover, we show that these fluctuations are distributed according to a Gaussian curve for long enough times. Three different systems are considered here: namely, (i) a fluid composed of particles interacting with Lennard-Jones potentials, (ii) a harmonic oscillator with Nosé-Hoover thermostatting, and (iii) a simple hyperbolic two-dimensional map.

  11. 49 CFR 236.551 - Power supply voltage; requirement.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Power supply voltage; requirement. 236.551 Section... supply voltage; requirement. The voltage of power supply shall be maintained within 10 percent of rated voltage....

  12. Numerical Investigation of Pressure Fluctuation Characteristics in a Centrifugal Pump with Variable Axial Clearance

    Directory of Open Access Journals (Sweden)

    Lei Cao

    2016-01-01

    Full Text Available Clearance flows in the sidewall gaps of centrifugal pumps are unsteady as well as main flows in the volute casing and impeller, which may cause vibration and noise, and the corresponding pressure fluctuations are related to the axial clearance size. In this paper, unsteady numerical simulations were conducted to predict the unsteady flows within the entire flow passage of a centrifugal pump operating in the design condition. Pressure fluctuation characteristics in the volute casing, impeller, and sidewall gaps were investigated with three axial clearance sizes. Results show that an axial clearance variation affects the pressure fluctuation characteristics in each flow domain by different degree. The greatest pressure fluctuation occurs at the blade pressure surface and is almost not influenced by the axial clearance variation which has a certainly effect on the pressure fluctuation characteristics around the tongue. The maximum pressure fluctuation amplitude in the sidewall gaps is larger than that in the volute casing, and different spectrum characteristics show up in the three models due to the interaction between the clearance flow and the main flow as well as the rotor-stator interaction. Therefore, clearance flow should be taken into consideration in the hydraulic design of centrifugal pumps.

  13. Development of the W-band density profile and fluctuation reflectometer on EAST

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.M.; Gao, X., E-mail: xgao@ipp.ac.cn; Ling, B.L.; Zhang, S.B.; Zhang, T.; Han, X.; Liu, S.C.; Liu, Z.X.; Liu, Y.; Ti, A.

    2013-11-15

    Highlights: • A X-mode W-band reflectometer is designed and installed on Experimental Advanced Superconducting Tokamak (EAST) for the first time. • Both density profile and fluctuations can be measured by the newly developed reflectometer. • The core density profile has been measured in high magnetic field condition together with V-band reflectometer. • Sawtooth precursor has been measured by fluctuation reflectometer in the low magnetic field condition. -- Abstract: A X-mode polarized W-band reflectometer for plasma density profile and fluctuation measurement is designed and installed on EAST. In measuring the density profile, a voltage controlled oscillator (VCO) is used as the source, allowing a high temporal resolution measurement. The density profile in a plasma with high magnetic field (3.0 T) has been measured by combination of V- and W-band reflectometers. For fluctuation measurements, a frequency synthesizer is used instead of the VCO as a microwave source. The core density fluctuations during sawtooth activity are measured and analyzed.

  14. Current fluctuation of electron and hole carriers in multilayer WSe{sub 2} field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho-Kyun; Jin, Jun Eon; Kim, Gyu-Tae, E-mail: gtkim@korea.ac.kr [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); Kim, Yong Jin; Kim, Young Keun [Department of Materials Science and Engineering, Korea University, Seoul 02481 (Korea, Republic of); Shin, Minju [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); IMEP-LAHC, Grenoble INP-MINATEC, 3 Parvis Louis Neel, 38016 Grenoble (France)

    2015-12-14

    Two-dimensional materials have outstanding scalability due to their structural and electrical properties for the logic devices. Here, we report the current fluctuation in multilayer WSe{sub 2} field effect transistors (FETs). In order to demonstrate the impact on carrier types, n-type and p-type WSe{sub 2} FETs are fabricated with different work function metals. Each device has similar electrical characteristics except for the threshold voltage. In the low frequency noise analysis, drain current power spectral density (S{sub I}) is inversely proportional to frequency, indicating typical 1/f noise behaviors. The curves of the normalized drain current power spectral density (NS{sub I}) as a function of drain current at the 10 Hz of frequency indicate that our devices follow the carrier number fluctuation with correlated mobility fluctuation model. This means that current fluctuation depends on the trapping-detrapping motion of the charge carriers near the channel interface. No significant difference is observed in the current fluctuation according to the charge carrier type, electrons and holes that occurred in the junction and channel region.

  15. Gravitational Wave Spectrums from Pole-like Inflations based on Generalized Gravity Theories

    CERN Document Server

    Hwang, J

    1998-01-01

    We present a general and unified formulation which can handle the classical evolution and quantum generation processes of the cosmological gravitational wave in a broad class of generalized gravity theories. Applications are made in several inflation models based on the scalar-tensor theory, the induced gravity, and the low energy effective action of string theory. The gravitational wave power spectrums based on the vacuum expectation value of the quantized fluctuating metric during the pole-like inflation stages are derived in analytic forms. Assuming that the gravity theory transits to Einstein one while the relevant scales remain in the superhorizon scale, we derive the consequent power spectrums and the directional fluctuations of the relic radiation produced by the gravitational wave. The spectrums seeded by the vacuum fluctuations in the pole-like inflation models based on the generalized gravity show a distinguished common feature which differs from the scale invariant spectrum generated in an exponent...

  16. Method of estimating pulse response using an impedance spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

    2014-10-21

    Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

  17. Voltage Unbalance Compensation with Smart Three-phase Loads

    DEFF Research Database (Denmark)

    Douglass, Philip; Trintis, Ionut; Munk-Nielsen, Stig

    2016-01-01

    voltage, but it does not reduce the negative sequence voltage. The controller that uses phase-phase voltage as input eliminates negative sequence voltage, and reduces voltage deviations from the average to approximately half their initial value. Current unbalance is reduced when the voltage unbalance...... is caused by asymmetrical loads. These results suggest that the optimal algorithm to reduce system unbalance depends on which system parameter is most important: phase-neutral voltage unbalance, phase-phase voltage unbalance, or current unbalance....

  18. Power conditioning using dynamic voltage restorers under different voltage sag types

    Directory of Open Access Journals (Sweden)

    Ahmed M. Saeed

    2016-01-01

    Full Text Available Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs. By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  19. Power conditioning using dynamic voltage restorers under different voltage sag types.

    Science.gov (United States)

    Saeed, Ahmed M; Abdel Aleem, Shady H E; Ibrahim, Ahmed M; Balci, Murat E; El-Zahab, Essam E A

    2016-01-01

    Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  20. Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8).

    Science.gov (United States)

    Raddatz, Natalia; Castillo, Juan P; Gonzalez, Carlos; Alvarez, Osvaldo; Latorre, Ramon

    2014-12-19

    Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca(2+)-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol(-1). The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening.

  1. Comparison of Harmony Search Algorithm and Particle Swarm Optimization for Distributed Generation Allocation to Improve Steady State Voltage Stability of Distribution Networks

    Directory of Open Access Journals (Sweden)

    Hamed Piarehzadeh

    2012-08-01

    Full Text Available In this study is tried to optimal distributed generation allocation for stability improvement in radial distribution systems. Voltage instability implies an uncontrolled decrease in voltage triggered by a disturbance, leading to voltage collapse and is primarily caused by dynamics connected with the load. The instability is divided into steady state and transient voltage instability Based on the time spectrum of the incident of the phenomena. The analysis is accomplished using a steady state voltage stability index which can be evaluated at each node of the distribution system. Several optimal capacities and locations are used to check these results. The location of DG has the main effect voltage stability on the system. Effects of location and capacity on incrementing steady state voltage stability in radial distribution systems are examined through Harmony Search Algorithm (HSA and finally the results are compared to Particle Swarm Optimization (PSO on the terms of speed, convergence and accuracy.

  2. Image processing for non-ratiometric measurement of membrane voltage using fluorescent reporters and pulsed laser illumination.

    Science.gov (United States)

    Silve, Aude; Rocke, Sarah; Frey, Wolfgang

    2015-06-01

    The measurement of transmembrane voltages induced by pulsed electric field exposure can be achieved by using fluorescent dyes like ANNINE-6. Such approach requires a quantitative determination of the fluorescence intensity along the cell's membrane by image processing. When high temporal resolution is required, the illumination source is frequently a dye-laser which causes high fluctuations in the intensity of illumination which in turn affects the fluorescence intensity and thus the quality of the results. We propose an image processing technique that allows to overcome the fluctuations and to produce quantitative data. It uses the optical background noise as a correcting factor. Standard deviation in the fluctuations is thus efficiently reduced by at least a factor of 2.5. Additionally we draw attention to the fact that the parasitic component of the laser radiation (ASE) can also suppress fluctuations although it deteriorates wavelength precision.

  3. Levy Stability Index from Multifractal Spectrum

    CERN Document Server

    Yuan, H B; Lian Shou Liu; Yuan, Hu; Meiling, Yu; Lianshou, Liu

    1999-01-01

    A method for extracting the Levy stability index $\\mu$ from the multi-fractal spectrum $f(\\alpha)$ in high energy multiparticle production is proposed. This index is an important parameter, characterizing the non-linear behaviour of dynamical fluctuations in high energy collisions. Using the random cascading that this method, basing on a linear fit, is consistent with and more accurate than the usual method of fitting the ratio of $q$th to 2nd order multi-fractal (Rényi) dimensions to the Peschanski formula.

  4. Observation of Phillips's spectrum in Faraday waves

    Science.gov (United States)

    Castillo, Gustavo; Falcon, Claudio

    2016-11-01

    We consider the problem of wave turbulence generated by singularities from an experimental point of view. We study a system of Faraday waves interacting with waves generated by a wave-maker driven with a random forcing. We measure the temporal fluctuations of the surface wave amplitude at a given location and we show that for a wide range of forcing parameters the surface height displays a power-law spectra that greatly differs from the one predicted by the WT theory. In the capillary region the power spectrum turns out to be proportional to f-5, which we believe is due to singularities moving across the system. Proyecto Postdoctorado Fondecyt Nro 3160032.

  5. High voltage load resistor array

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, Monty Ray [Smithfield, VA

    2005-01-18

    A high voltage resistor comprising an array of a plurality of parallel electrically connected resistor elements each containing a resistive solution, attached at each end thereof to an end plate, and about the circumference of each of the end plates, a corona reduction ring. Each of the resistor elements comprises an insulating tube having an electrode inserted into each end thereof and held in position by one or more hose clamps about the outer periphery of the insulating tube. According to a preferred embodiment, the electrode is fabricated from stainless steel and has a mushroom shape at one end, that inserted into the tube, and a flat end for engagement with the end plates that provides connection of the resistor array and with a load.

  6. Experimental study on oscillating grid turbulence and free surface fluctuation

    Science.gov (United States)

    Chiapponi, Luca; Longo, Sandro; Tonelli, Mara

    2012-11-01

    This paper analyses the interaction between the turbulence and free surface. The phenomenon takes place in many natural flows and industrial processes. In the present experiments, turbulence is generated by a vertically oscillating grid moving beneath the free surface. Fluid velocity has been measured through a hot-film anemometer, and the free surface elevation has been measured by an ultrasonic sensor. Integral length scales and several turbulence estimators have been computed. In order to detect the generation of turbulence near the free surface, the correlation between free surface elevation and the underneath flow velocity has been studied, as well as the time lag between turbulence and free surface. The free surface dynamics has been characterized by a velocity scale and a length scale. The kinetic energy associated with the free surface fluctuations increases with the Reynolds number at a rate depending on the frequency of the grid movement. For Reynolds number larger than ≈1000, however, the relationships collapse to a single curve characterized by a lower rate. The present experiments do not achieve the inertial sub-range in the vertical velocity fluctuations, and the estimated spectrum decays with an exponent smaller than -3, which is the typical value for the two-dimensional turbulence in the inertial sub-range. The macro length scale, estimated by using the Taylor's frozen turbulence hypothesis, experiences a decay away from the grid, which follows reasonably well the profile of Thompson and Turner (J Fluid Mechanics 67: 349-368, 1975). The micro length scale reduces immediately beneath the free surface, which can be interpreted by the increase of dissipation rate in the subsurface layer. The classification diagram by Brocchini and Peregrine (J Fluid Mech 449: 225-254, 2001) indicates that most tests fall in the weak turbulence domain, but some tests fall in the wavy domain. The vertical velocity fluctuations and the free surface level show a

  7. Impact of Precipitation Fluctuation on Desert-Grassland ANPP

    Directory of Open Access Journals (Sweden)

    Liangxu Liu

    2016-11-01

    Full Text Available Precipitation change has significantly influenced annual net primary productivity (ANPP at either annual or seasonal scales in desert steppes in arid and semi-arid regions. In order to reveal the process of precipitation driving ANPP at different time scales, responses of different ANPP levels to the inter-annual and intra-annual precipitation fluctuations were analyzed. ANPP was reversed by building a ground reflectance spectrum model, from 2000 to 2015, using the normalized differential vegetation index of the Moderate-Resolution Imaging Spectroradiometer (MODIS-NDVI data at 250 m × 250 m spatial resolution. Since the description of the differently expressing forms of precipitation are not sufficient in former studies in order to overcome the deficiency of former studies, in this study, intra-annual precipitation fluctuations were analyzed not only with precipitation of May–August, June–August, July–August, and August, respectively, which have direct influence on vegetation productivity within the year, but quantitative description, vector precipitation (R, concentration ratio (Cd, and concentration period (D, were also used to describe the overall characteristics of intra-annual precipitation fluctuations. The concentration ratio and the maximum precipitation period of the intra-annual precipitation were represented by using monthly precipitation. The results showed that: (1 in the period from 1971 to 2015, the maximum annual precipitation is 3.76 times that of the minimum in the Urat desert steppe; (2 vector precipitation is more significantly related to ANPP (r = 0.7724, p = 0.000 compared to meteorological annual precipitation and real annual precipitation influence; and (3 annual precipitation is almost concentrated in 5–8 months and monthly precipitation accumulation has significantly effected ANPP, especially in the period of June–August, since the vegetation composition in the study area was mainly sub-shrubs and perennial

  8. Voltage-Controlled Floating Resistor Using DDCC

    Directory of Open Access Journals (Sweden)

    M. Kumngern

    2011-04-01

    Full Text Available This paper presents a new simple configuration to realize the voltage-controlled floating resistor, which is suitable for integrated circuit implementation. The proposed resistor is composed of three main components: MOS transistor operating in the non-saturation region, DDCC, and MOS voltage divider. The MOS transistor operating in the non-saturation region is used to configure a floating linear resistor. The DDCC and the MOS transistor voltage divider are used for canceling the nonlinear component term of MOS transistor in the non-saturation region to obtain a linear current/voltage relationship. The DDCC is employed to provide a simple summer of the circuit. This circuit offers an ease for realizing the voltage divider circuit and the temperature effect that includes in term of threshold voltage can be compensated. The proposed configuration employs only 16 MOS transistors. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.

  9. Fluctuating Asymmetry of Human Populations: A Review

    Directory of Open Access Journals (Sweden)

    John H. Graham

    2016-12-01

    Full Text Available Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA. Both environmental (diet, climate, toxins and genetic (aneuploidy, heterozygosity, inbreeding stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1 fluctuating asymmetry is a weak signal in a sea of noise; and (2 studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination, inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible to compare results across traits, and across studies.

  10. ZnO films deposited by optimized PLD technique with bias voltages

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Hiroyuki; Shitara, Tamae; Komiyama, Takao; Chonan, Yasunori; Aoyama, Takashi [Department of Electronics and Information Systems, Akita Prefectural University, 84-4 Tsuchiya Ebinokuchi, 015-0055 Yuri-Honjo (Japan)

    2010-02-15

    The pulsed laser deposition (PLD) technique with bias voltage application for formation of high quality ZnO films was investigated. Oxygen ambient in the PLD chamber significantly decreased the photoluminescence (PL) intensity of near band edge (NBE) emission. Then, instead of using oxygen ambient, the PLD technique with bias voltage application was optimized to attain the stoichiometric composition of the ZnO films. As the deposition temperature was increased, the X-ray spectrum width diffracted from the (0002) planes was decreased and it showed a minimum value at 700 C. The PL intensity of the NBE emission also had its maximum value for the film deposited at 700 C. For the ZnO films deposited at 700 C, the X-ray spectrum width showed the minimum value under a bias voltage of -50 V. The PL intensity of the NBE emission also had a maximum value under the same bias voltage. Thus, ZnO films deposited under a bias voltage of -50 V at 700 C had strong NBE emission intensities. These results could be explained not only by attaining the stoichiometric composition of the ZnO film but also by decreasing the number of high energy O{sup 2-} ions which caused non-radiative recombination centers in the film. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Programable Driver for Voltage-Controlled Oscillators

    Science.gov (United States)

    Fowler, L. E.; Mcneil, J. A.

    1985-01-01

    Electronically programable read-only memory (EPROM) and digital-to-analog converter provide customized time-varying voltage for frequency modulation. Voltage used to modulate IMPATT oscillator that serves as microwave pump for solid-state maser in low-noise amplifier. EPROM simple to tailor voltage waveform to suit characteristics of given maser. Digital information for waveform programed into EPROM chip; digital-to-analog converter reads information and produces corresponding analog wave. Principle readily adapted to other applications.

  12. Generator of ultrashort megavolt voltage pulses

    CERN Document Server

    Zheltov, K A; Shalimanov, V F

    2002-01-01

    Paper describes approx 3 ns duration and > 1 MW amplitude voltage pulse generator under high-ohmic (approx 450 Ohm) load. Generator comprises pulse transformer with magnetized core, as well as, resonance tuned circuit of high-voltage solenoid and accumulating spaces of a shaping line containing, moreover, spark gap to switch charge in transmitting line. Paper contains the results of voltage measuring in generator basic units

  13. Investigation of pulsed voltage limiters characteristics

    Directory of Open Access Journals (Sweden)

    Karimov A. V.

    2012-06-01

    Full Text Available A new method for measuring the voltage limit is offered. It has been designed to measure high-power pulsed current of voltage limiters. The error of this method is half as much as the error of the known method of direct measurement. The investigation of dependence of power capability of single-crystal and double-crystal voltage limiters and of the pulsed operation time on pulse duration.

  14. Temporal step fluctuations on a conductor surface: electromigration force, surface resistivity and low-frequency noise

    Science.gov (United States)

    Williams, E. D.; Bondarchuk, O.; Tao, C. G.; Yan, W.; Cullen, W. G.; Rous, P. J.; Bole, T.

    2007-10-01

    Scattering of charge carriers from surface structures will become an increasing factor in the resistivity as the structure decreases in size to the nanoscale. The effects of scattering at the most basic surface defect, a kink in a step edge, are here analyzed using the continuum step model. Using a Langevin analysis, it has been shown that the electromigration force on the atoms at the step edge causes changes in the temporal evolution of the step-edge. For an electromigration force acting perpendicular to the average step edge and mass-transport dominated by step-edge diffusion, significant deviations from the usual t1/4 scaling of the displacement correlation function occur dependent on a critical time τ and the direction of the force relative to the step edge (i.e. uphill or downhill). Experimental observations of step fluctuations on Ag(111) show the predicted changes among step fluctuations without current, and with current in the up- and down-hill directions for a current density of order 105 A cm-2. The results yield the magnitude of the electromigration force acting on kinked sites at the step-edge. This in turn yields the contribution of the fluctuating steps to the surface resistivity, which exceeds 1% of the bulk resistivity as wire diameters decrease below 10s of nanometres. The temporal fluctuations of kink density can thus also be related to resistivity noise. Relating the known fluctuation spectrum of the step displacements to fluctuations in their lengths, the corresponding resistivity noise is predicted to show spectral signatures of ~f-1/2 for step fluctuations governed by random attachment/detachment, and ~f-3/4 for step fluctuations governed by step-edge diffusion.

  15. Low-Voltage Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Bidari, E.; Keskin, M.; Maloberti, F.

    1999-01-01

    Switched-capacitor stages are described which can function with very low (typically 1 V) supply voltages, without using voltage boosting or switched op-amps. Simulations indicate that high performance may be achieved using these circuits in filter or data converter applications.......Switched-capacitor stages are described which can function with very low (typically 1 V) supply voltages, without using voltage boosting or switched op-amps. Simulations indicate that high performance may be achieved using these circuits in filter or data converter applications....

  16. Characterisation of the VELO High Voltage System

    CERN Document Server

    Rakotomiaramanana, B; Eklund, L

    2008-01-01

    The high voltage system supplies the bias voltage to the 88 silicon sensors which comprise the LHCb Vertex Locator (VELO). This note describes the results of the tests which have been performed on the hardware of the high voltage system of the VELO. Each individual test detailed in this note corresponds to a specific requirement of the system. These requirements arise primarily from ensuring the safety of the silicon sensors and the quality of the data taken from the VELO modules. The tests performed are in four categories: normal operation of the high voltage system; vercation of its stability under operation; discussion of its behaviour in failure modes; and details of operation at low voltage. Noteworthy issues, identified through the tests, include the behaviour of the high voltage modules at voltages below 9V, the current limit that can be applied during ramping of the voltage, and the speed with which the voltage is cut during failures of the system. The results of these tests provide high confidence th...

  17. Characterisation of the VELO High Voltage System

    CERN Document Server

    Rakotomiaramanana, B; Parkes, C; Eklund, L

    2008-01-01

    The high voltage system supplies the bias voltage to the 88 silicon sensors which comprise the LHCb Vertex Locator (VELO). This note describes the results of the tests which have been performed on the hardware of the high voltage system of the VELO. Each individual test detailed in this note corresponds to a specific requirement of the system. These requirements arise primarily from ensuring the safety of the silicon sensors and the quality of the data taken from the VELO modules. The tests performed are in four categories: normal operation of the high voltage system; verification of its stability under operation; discussion of its behaviour in failure modes; and details of operation at low voltage. Noteworthy issues, identified through the tests, include the behaviour of the high voltage modules at voltages below 9V, the current limit that can be applied during ramping of the voltage, and the speed with which the voltage is cut during failures of the system. The results of these tests provide high confidence...

  18. Microprocessor-controlled, programmable ramp voltage generator

    Energy Technology Data Exchange (ETDEWEB)

    Hopwood, J.

    1978-11-01

    A special-purpose voltage generator has been developed for driving the quadrupole mass filter of a residual gas analyzer. The generator is microprocessor-controlled with desired ramping parameters programmed by setting front-panel digital thumb switches. The start voltage, stop voltage, and time of each excursion are selectable. A maximum of five start-stop levels may be pre-selected for each program. The ramp voltage is 0 to 10 volts with sweep times from 0.1 to 999.99 seconds.

  19. Magnetoelectric voltage coefficients of magnetoelectric composites

    Institute of Scientific and Technical Information of China (English)

    WAN Yong-ping; ZHONG Zheng; QIU Jin-hao

    2006-01-01

    The magnetoelectric(ME) effect of the particulate magnetostrictive/piezoelectric composite was theoretically studied. The dependence of the ME voltage coefficients on the material properties of the magnetostrictive phase was discussed. The permittivity,permeability and the elastic modulus of the magnetostrictive phase generally have obvious influences on the ME voltage coefficients. The magnetostrictive phase with a large permittivity,large permeability or stiffer modulus will respectively contribute to the higher ME voltage coefficients. For a certain kind of piezoelectric matrix,the ME voltage coefficients can be improved to some extent by choosing those magnetostrictive materials with large permittivity,permeability or high elastic modulus.

  20. Maximum permissible voltage of YBCO coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z. [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Hong, Z., E-mail: zhiyong.hong@sjtu.edu.cn [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Wang, D.; Zhou, H.; Shen, X.; Shen, C. [Qingpu Power Supply Company, State Grid Shanghai Municipal Electric Power Company, Shanghai (China)

    2014-06-15

    Highlights: • We examine three kinds of tapes’ maximum permissible voltage. • We examine the relationship between quenching duration and maximum permissible voltage. • Continuous I{sub c} degradations under repetitive quenching where tapes reaching maximum permissible voltage. • The relationship between maximum permissible voltage and resistance, temperature. - Abstract: Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (I{sub c}) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the I{sub c} degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

  1. Inductive voltage divider modeling in Matlab

    Science.gov (United States)

    Andreev, S. A.; Kim, V. L.

    2017-01-01

    Inductive voltage dividers have the most appropriate metrological characteristics on alternative current and are widely used for converting physical signals. The model of a double-decade inductive voltage divider was designed with the help of Matlab/Simulink. The first decade is an inductive voltage divider with balanced winding, the second decade is a single-stage inductive voltage divider. In the paper, a new transfer function algorithm was given. The study shows errors and differences that appeared between the third degree reduced model and a twenty degree unreduced model. The obtained results of amplitude error differ no more than by 7 % between the reduced and unreduced model.

  2. Development of a voltage scanner of chopper

    CERN Document Server

    Shen Guan Ren; LiShengLi; WangQuanXing; Wu Long Cheng

    2001-01-01

    Development of voltage sweeper of chopper with CPNG are introduced. Voltage sweeper is one of important key parts of chopper. Two years working prove that it is stable and reliable. Its main technology performance save: sine wave frequency: 750 kHz +- 20 Hz; total distortion: 65 Db; output voltage (V-V): 0->=4000 V; the error7 W; voltage supply: 220V AC +-10%, 50 +- 1 Hz; total power supply: <100W; Work temperature range: 0 - 40 degree; Stability in long time <=1%

  3. Effects of plasma collisionality on power balance and magnetic fluctuations in the T1 reversed-field pinch

    Science.gov (United States)

    Hedin, G.; Brzozowski, J. H.; Hörling, P.; Mazur, S.; Nordlund, P.; Drake, J. R.

    1996-05-01

    The effects of plasma collisionality on power balance and magnetic fluctuations have been studied on the Extrap T1 reversed-field pinch. A characteristic minimum in loop voltage is observed as the plasma collisionality decreases. The minimum is caused by an increase in the anomalous input power and coincides with a change of scaling of the magnetic fluctuations and a rapid increase of the electron mean free path. However, the increase of anomalous input power in the low collisional regime appears to have little influence on the total amount of energy stored in the plasma.

  4. Population Genetics with Fluctuating Population Sizes

    CERN Document Server

    Chotibut, Thiparat

    2016-01-01

    Standard neutral population genetics theory with a strictly fixed population size has important limitations. An alternative model that allows independently fluctuating population sizes and reproduces the standard neutral evolution is reviewed. We then study a situation such that the competing species are neutral at the equilibrium population size but population size fluctuations nevertheless favor fixation of one species over the other. In this case, a separation of timescales emerges naturally and allows adiabatic elimination of a fast population size variable to deduce the fluctuations-induced selection dynamics near the equilibrium population size. The results highlight the incompleteness of the standard population genetics with a strictly fixed population size.

  5. Elasticity and Fluctuations of Frustrated Nanoribbons

    Science.gov (United States)

    Grossman, Doron; Sharon, Eran; Diamant, Haim

    2016-06-01

    We derive a reduced quasi-one-dimensional theory of geometrically frustrated elastic ribbons. Expressed in terms of geometric properties alone, it applies to ribbons over a wide range of scales, allowing the study of their elastic equilibrium, as well as thermal fluctuations. We use the theory to account for the twisted-to-helical transition of ribbons with spontaneous negative curvature and the effect of fluctuations on the corresponding critical exponents. The persistence length of such ribbons changes nonmonotonically with the ribbon's width, dropping to zero at the transition. This and other statistical properties qualitatively differ from those of nonfrustrated fluctuating filaments.

  6. Population Genetics with Fluctuating Population Sizes

    Science.gov (United States)

    Chotibut, Thiparat; Nelson, David R.

    2017-05-01

    Standard neutral population genetics theory with a strictly fixed population size has important limitations. An alternative model that allows independently fluctuating population sizes and reproduces the standard neutral evolution is reviewed. We then study a situation such that the competing species are neutral at the equilibrium population size but population size fluctuations nevertheless favor fixation of one species over the other. In this case, a separation of timescales emerges naturally and allows adiabatic elimination of a fast population size variable to deduce the fluctuation-induced selection dynamics near the equilibrium population size. The results highlight the incompleteness of the standard population genetics with a strictly fixed population size.

  7. Fluctuation in nonextensive reaction-diffusion systems

    Energy Technology Data Exchange (ETDEWEB)

    Wu Junlin; Chen Huaijun [Department of Physics, Shaanxi Normal University, Xian 710062 (China)

    2007-05-15

    The density fluctuation in a nonextensive reaction-diffusion system is investigated, where the nonequilibrium stationary-state distribution is described by the generalized Maxwell-Boltzmann distribution in the framework of Tsallis statistics (or nonextensive statistics). By using the density operator technique, the nonextensive pressure effect is introduced into the master equation and thus the generalized master equation is derived for the system. As an example, we take the{sup 3}He reaction-diffusion model inside stars to analyse the nonextensive effect on the density fluctuation and we find that the nonextensive parameter q different from one plays a very important role in determining the characteristics of the fluctuation waves.

  8. Diffusive transport by thermal velocity fluctuations.

    Science.gov (United States)

    Donev, Aleksandar; Bell, John B; de la Fuente, Anton; Garcia, Alejandro L

    2011-05-20

    We study the contribution of advection by thermal velocity fluctuations to the effective diffusion coefficient in a mixture of two identical fluids. We find good agreement between a simple fluctuating hydrodynamics theory and particle and finite-volume simulations. The enhancement of the diffusive transport depends on the system size L and grows as ln(L/L₀) in quasi-two-dimensional systems, while in three dimensions it scales as L₀⁻¹ - L⁻¹, where L₀ is a reference length. Our results demonstrate that fluctuations play an important role in the hydrodynamics of small-scale systems.

  9. CHIPS: The Cosmological HI Power Spectrum Estimator

    CERN Document Server

    Trott, Cathryn M; Procopio, Pietro; Wayth, Randall B; Mitchell, Daniel A; McKinley, Benjamin; Tingay, Steven J; Barry, N; Beardsley, A P; Bernardi, G; Bowman, Judd D; Briggs, F; Cappallo, R J; Carroll, P; de Oliveira-Costa, A; Dillon, Joshua S; Ewall-Wice, A; Feng, L; Greenhill, L J; Hazelton, B J; Hewitt, J N; Hurley-Walker, N; Johnston-Hollitt, M; Jacobs, Daniel C; Kaplan, D L; Kim, HS; Lenc, E; Line, J; Loeb, A; Lonsdale, C J; Morales, M F; Morgan, E; Neben, A R; Thyagarajan, Nithyanandan; Oberoi, D; Offringa, A R; Ord, S M; Paul, S; Pober, J C; Prabu, T; Riding, J; Shankar, N Udaya; Sethi, Shiv K; Srivani, K S; Subrahmanyan, R; Sullivan, I S; Tegmark, M; Webster, R L; Williams, A; Williams, C L; Wu, C; Wyithe, J S B

    2016-01-01

    Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization, and estimation of its basic physical parameters, is the principal scientific aim of many current low-frequency radio telescopes. Here we describe the Cosmological HI Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array (MWA), to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximising the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation ("foreground suppression"). We describe the motivation for the algorithm, implementation, application to ...

  10. Control of mean and fluctuating forces on a circular cylinder at high Reynolds numbers

    Institute of Scientific and Technical Information of China (English)

    Chuanping Shao; Jianming Wang

    2007-01-01

    A narrow strip is used to control mean and fluctuating forces on a circular cylinder at Reynolds numbers from 2.0 x 104 to 1.0 x 105. The axes of the strip and cylinder are parallel. The control parameters are strip width ratio and strip position characterized by angle of attack and distance from the cylinder. Wind tunnel tests show that the vortex shedding from both sides of the cylinder can be suppressed, and mean drag and fluctuating lift on the cylinder can be reduced if the strip is installed in an effective zone downstream of the cylinder. A phenomenon of mono-side vortex shedding is found. The strip-induced local changes of velocity profiles in the near wake of the cylinder are measured, and the relation between base suction and peak value in the power spectrum of fluctuating lift is studied. The control mechanism is then discussed from different points of view.

  11. Probing multifractality in depth-resolved refractive index fluctuations in biological tissues using backscattering spectral interferometry

    Science.gov (United States)

    Das, Nandan Kumar; Dey, Rajib; Chakraborty, Semanti; Panigrahi, P. K.; Ghosh, Nirmalya

    2016-12-01

    Fourier domain low coherence interferometry is a promising method for quantification of the depth distribution of the refractive index in a layered scattering medium such as biological tissue. Here, we have explored backscattering spectral interferometric measurement in combination with multifractal detrended fluctuation analysis to probe and quantify multifractality in depth distribution of the refractive index in tissue. The depth resolution of the experimental system was validated on model systems comprising of polystyrene microspheres and mica sheet, and was initially tested on turbid collagen layer, the main building blocks of the connective tissue. Following successful evaluation, the method was applied on ex vivo tissues of human cervix. The derived multifractal parameters of depth-resolved index fluctuations of tissue, namely, the generalized Hurst exponent and the width of the singularity spectrum showed interesting differences between tissues having different grades of precancers. The depth-resolved index fluctuations exhibited stronger multifractality with increasing pathological grades, demonstrating its promise as a potential biomarker for precancer detection.

  12. Low-frequency 1/f fluctuations in hydrodynamic and magnetohydrodynamic turbulence.

    Science.gov (United States)

    Dmitruk, Pablo; Matthaeus, W H

    2007-09-01

    We investigate the occurrence of 1/f spectra of low-frequency fluctuations in numerical simulations of three-dimensional hydrodynamic and magnetohydrodynamic turbulence driven by a random forcing with a controlled correlation time. A range of one decade of 1/f spectrum is observed when a strong background magnetic field is present. The frequency spectra of individual Fourier modes is also analyzed and it is observed that the 1/f range is present in the largest available wavelength mode for the magnetohydrodynamic simulations with and without a background magnetic field and it is not observed (or is less clear) for the hydrodynamic case. The presence of 1/f spectra of low-frequency fluctuations is also analyzed for two-dimensional magnetohydrodynamic and hydrodynamic turbulence simulations and it is observed in both cases. The origin of these long period fluctuations is discussed.

  13. The impact of temperature fluctuations on the large scale clustering of the Ly$\\alpha$ forest

    CERN Document Server

    Greig, Bradley; Wyithe, J Stuart B

    2014-01-01

    We develop a semi-analytic method for assessing the impact of the large scale IGM temperature fluctuations expected following He${\\rm\\,{\\scriptstyle II}}$ reionization on three dimensional clustering measurements of the Ly$\\alpha$ forest. Our methodology builds upon the existing large volume, mock Ly$\\alpha$ forest survey simulations presented by Greig et al. (2011) by including a prescription for a spatially inhomogeneous ionising background, temperature fluctuations induced by patchy He${\\rm\\,{\\scriptstyle II}}$ photo-heating and the clustering of quasars. This approach enables us to achieve a dynamic range within our semi-analytic model substantially larger than currently feasible with computationally expensive, fully numerical simulations. The results agree well with existing numerical simulations, with large scale temperature fluctuations introducing a scale dependent increase in the spherically averaged 3D Ly$\\alpha$ forest power spectrum of up to 20-30 per cent at wavenumbers $k\\sim0.02$ Mpc$^{-1}$. Al...

  14. Fluctuations around Periodic BPS-Density Waves in the Calogero Model

    CERN Document Server

    Bardek, V; Meljanac, S

    2010-01-01

    The collective field formulation of the Calogero model supports periodic density waves. An important set of such density waves is a two-parameter family of BPS solutions of the equations of motion of the collective field theory. One of these parameters is essentially the average particle density, which determines the period, while the other parameter determines the amplitude. These BPS solutions are sometimes referred to as "small amplitude waves" since they undulate around their mean density, but never vanish. We present complete analysis of quadratic fluctuations around these BPS solutions. The corresponding fluctuation hamiltonian (i.e., the stability operator) is diagonalized in terms of bosonic creation and annihilation operators which correspond to the complete orthogonal set of Bloch-Floquet eigenstates of a related periodic Schr\\"odinger hamiltonian, which we derive explicitly. Remarkably, the fluctuation spectrum is independent of the parameter which determines the density wave's amplitude. As a cons...

  15. Magnetic fluctuations in anisotropic space plasmas: The effect of the plasma environment

    Science.gov (United States)

    Valdivia, J. A.; Toledo, B. A.; Gallo, N.; Muñoz, V.; Rogan, J.; Stepanova, M.; Moya, P. S.; Navarro, R. E.; Viñas, A. F.; Araneda, J.; López, R. A.; Díaz, M.

    2016-11-01

    The observations in the solar wind, which are usually organized in a beta-anisotropy diagram, seem to be constrained by linear instability thresholds. Unexpectedly, under these quasi-stable conditions, there is a finite level of electromagnetic fluctuations. A relevant component of these fluctuations can be understood in terms of the electromagnetic fields produced by the thermal motion of the charged particles. For the simple case of parallel propagating fields in an electron-proton plasma, we study the effect of the parameter ωpp /Ωc that characterizes the different space physics environments, and can affect the continuum spectrum produced by these fluctuations, which in turn may be used to understand the relevance of these processes occurring in a specific plasma environment.

  16. Stochastic Faraday rotation induced by the electric current fluctuations in nanosystems

    Science.gov (United States)

    Smirnov, D. S.; Glazov, M. M.

    2017-01-01

    We demonstrate theoretically that in gyrotropic semiconductors and semiconductor nanosystems the Brownian motion of electrons results in temporal fluctuations of the polarization plane of light passing through or reflected from the structure, i.e., in stochastic Faraday or Kerr rotation effects. The theory of the effects is developed for a number of prominent gyrotropic systems such as bulk tellurium, ensembles of chiral carbon nanotubes, and GaAs-based quantum wells of different crystallographic orientations. We show that the power spectrum of these fluctuations in thermal equilibrium is proportional to the a c conductivity of the system. We evaluate contributions resulting from the fluctuations of the electric current, as well as of spin, valley polarization, and the spin current to the noise of the Faraday/Kerr rotation. Hence all-optical measurements of the Faraday and Kerr rotation noise provide an access to the transport properties of the semiconductor systems.

  17. Plasma density fluctuations observed during Space Shuttle Orbiter water releases

    Science.gov (United States)

    Pickett, J. S.; D'Angelo, N.; Kurth, W. S.

    1989-01-01

    Observations by the Langmuir probe on the Plasma Diagnostics Package flown as part of the Spacelab 2 mission in the summer of 1985 show a strong increase in the level of turbulence near the Shuttle Orbiter during operations in which liquid water is released. The spectrum of the plasma density fluctuations peaks at the lowest frequencies measured (a few Hz) and extends up to a few kHz, near the lower hybrid frequency. Two potential mechanisms for generating the plasma turbulence are suggested which are both based on the production of water ions as a result of charge exchange with the ambient oxygen ions in the ionosphere. The first mechanism proposed is the ion-plasma instability which arises from the drift of the contaminant with respect to the ambient oxygen ions. The other mechanism proposed is the Ott-Farley instability, which is a result of the ring distribution formed by the 'pick-up' water ions.

  18. Multifractal detrended fluctuation analysis of analog random multiplicative processes

    Energy Technology Data Exchange (ETDEWEB)

    Silva, L.B.M.; Vermelho, M.V.D. [Instituto de Fisica, Universidade Federal de Alagoas, Maceio - AL, 57072-970 (Brazil); Lyra, M.L. [Instituto de Fisica, Universidade Federal de Alagoas, Maceio - AL, 57072-970 (Brazil)], E-mail: marcelo@if.ufal.br; Viswanathan, G.M. [Instituto de Fisica, Universidade Federal de Alagoas, Maceio - AL, 57072-970 (Brazil)

    2009-09-15

    We investigate non-Gaussian statistical properties of stationary stochastic signals generated by an analog circuit that simulates a random multiplicative process with weak additive noise. The random noises are originated by thermal shot noise and avalanche processes, while the multiplicative process is generated by a fully analog circuit. The resulting signal describes stochastic time series of current interest in several areas such as turbulence, finance, biology and environment, which exhibit power-law distributions. Specifically, we study the correlation properties of the signal by employing a detrended fluctuation analysis and explore its multifractal nature. The singularity spectrum is obtained and analyzed as a function of the control circuit parameter that tunes the asymptotic power-law form of the probability distribution function.

  19. Quantum fluctuations in planar domain wall space-times: A possible origin of primordial preferred direction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chih-Hung, E-mail: chwang@phy.ncu.edu.tw [Department of Physics, Tamkang University, Taipei 25137, Taiwan (China); Department of Physics, National Central University, Chungli 320, Taiwan (China); Wu, Yu-Huei, E-mail: yhwu@phy.ncu.edu.tw [Center for Mathematics and Theoretical Physics, National Central University, Chungli 320, Taiwan (China); Department of Physics, National Central University, Chungli 320, Taiwan (China); Hsu, Stephen D.H., E-mail: hsu@uoregon.edu [Institute of Theoretical Science, University of Oregon, Eugene, OR 97403 (United States)

    2012-06-18

    We study the gravitational effects of a planar domain wall on quantum fluctuations of a massless scalar field during inflation. By obtaining an exact solution of the scalar field equation in de-Sitter space, we show that the gravitational effects of the domain wall break the rotational invariance of the primordial power spectrum without affecting the translational invariance. The strength of rotational violation is determined by one dimensionless parameter {beta}, which is a function of two physical parameters, the domain wall surface tension {sigma} and cosmological constant {Lambda}. In the limit of small {beta}, the leading effect of rotational violation of the primordial power spectrum is scale-invariant.

  20. AKARI near-infrared background fluctuations arise from normal galaxy populations

    CERN Document Server

    Helgason, Kári

    2016-01-01

    We show that measurements of the fluctuations in the near-infrared background (NIRB) from the AKARI satellite can be explained by faint galaxy populations at low redshifts. We demonstrate this using reconstructed images from deep galaxy catalogs (HUGS/S-CANDELS) and two independent galaxy population models. In all cases, we find that the NIRB fluctuations measured by AKARI are consistent with faint galaxies and there is no need for a contribution from unknown populations. We find no evidence for a steep Rayleigh-Jeans spectrum for the underlying sources as previously reported. The apparent Rayleigh-Jeans spectrum at large angular scales is likely a consequence of galaxies being removed systematically to deeper levels in the longer wavelength channels.