International Nuclear Information System (INIS)
Vaeth, W.
1979-04-01
The correlation of signal components at different frequencies like higher harmonics cannot be detected by a normal power spectral density measurement, since this technique correlates only components at the same frequency. This paper describes a special method for measuring the correlation of two signal components at different frequencies: the CRISS power spectral density. From this new function in frequency analysis, the correlation of two components can be determined quantitatively either they stem from one signal or from two diverse signals. The principle of the method, suitable for the higher harmonics of a signal as well as for any other frequency combinations is shown for the digital frequency analysis technique. Two examples of CRISS power spectral densities demonstrates the operation of the new method. (orig.) [de
Power Spectral Density and Hilbert Transform
2016-12-01
there is 1.3 W of power. How much bandwidth does a pure sine wave require? The bandwidth of an ideal sine wave is 0 Hz. How do you represent a 1-W...the Hilbert transform. 2.3 Hilbert Transform The Hilbert transform is a math function used to convert a real function into an analytic signal...The math operation minus 2 means to move 2 steps back on the number line. For minus –2, we move 2 steps backwards from –2, which is the same as
Atmospheric turbulence profiling with unknown power spectral density
Helin, Tapio; Kindermann, Stefan; Lehtonen, Jonatan; Ramlau, Ronny
2018-04-01
Adaptive optics (AO) is a technology in modern ground-based optical telescopes to compensate for the wavefront distortions caused by atmospheric turbulence. One method that allows to retrieve information about the atmosphere from telescope data is so-called SLODAR, where the atmospheric turbulence profile is estimated based on correlation data of Shack-Hartmann wavefront measurements. This approach relies on a layered Kolmogorov turbulence model. In this article, we propose a novel extension of the SLODAR concept by including a general non-Kolmogorov turbulence layer close to the ground with an unknown power spectral density. We prove that the joint estimation problem of the turbulence profile above ground simultaneously with the unknown power spectral density at the ground is ill-posed and propose three numerical reconstruction methods. We demonstrate by numerical simulations that our methods lead to substantial improvements in the turbulence profile reconstruction compared to the standard SLODAR-type approach. Also, our methods can accurately locate local perturbations in non-Kolmogorov power spectral densities.
K-correlation power spectral density and surface scatter model
Dittman, Michael G.
2006-08-01
The K-Correlation or ABC model for surface power spectral density (PSD) and BRDF has been around for years. Eugene Church and John Stover, in particular, have published descriptions of its use in describing smooth surfaces. The model has, however, remained underused in the optical analysis community partially due to the lack of a clear summary tailored toward that application. This paper provides the K-Correlation PSD normalized to σ(λ) and BRDF normalized to TIS(σ,λ) in a format intended to be used by stray light analysts. It is hoped that this paper will promote use of the model by analysts and its incorporation as a standard tool into stray light modeling software.
Power-spectral-density relationship for retarded differential equations
Barker, L. K.
1974-01-01
The power spectral density (PSD) relationship between input and output of a set of linear differential-difference equations of the retarded type with real constant coefficients and delays is discussed. The form of the PSD relationship is identical with that applicable to unretarded equations. Since the PSD relationship is useful if and only if the system described by the equations is stable, the stability must be determined before applying the PSD relationship. Since it is sometimes difficult to determine the stability of retarded equations, such equations are often approximated by simpler forms. It is pointed out that some common approximations can lead to erroneous conclusions regarding the stability of a system and, therefore, to the possibility of obtaining PSD results which are not valid.
Power Spectral Density Evaluation of Laser Milled Surfaces
Directory of Open Access Journals (Sweden)
Raoul-Amadeus Lorbeer
2017-12-01
Full Text Available Ablating surfaces with a pulsed laser system in milling processes often leads to surface changes depending on the milling depth. Especially if a constant surface roughness and evenness is essential to the process, structural degradation may advance until the process fails. The process investigated is the generation of precise thrust by laser ablation. Here, it is essential to predict or rather control the evolution of the surfaces roughness. Laser ablative milling with a short pulse laser system in vacuum (≈1 Pa were performed over depths of several 10 µm documenting the evolution of surface roughness and unevenness with a white light interference microscope. Power spectral density analysis of the generated surface data reveals a strong influence of the crystalline structure of the solid. Furthermore, it was possible to demonstrate that this effect could be suppressed for gold.
Power Spectral Density Specification and Analysis of Large Optical Surfaces
Sidick, Erkin
2009-01-01
The 2-dimensional Power Spectral Density (PSD) can be used to characterize the mid- and the high-spatial frequency components of the surface height errors of an optical surface. We found it necessary to have a complete, easy-to-use approach for specifying and evaluating the PSD characteristics of large optical surfaces, an approach that allows one to specify the surface quality of a large optical surface based on simulated results using a PSD function and to evaluate the measured surface profile data of the same optic in comparison with those predicted by the simulations during the specification-derivation process. This paper provides a complete mathematical description of PSD error, and proposes a new approach in which a 2-dimentional (2D) PSD is converted into a 1-dimentional (1D) one by azimuthally averaging the 2D-PSD. The 1D-PSD calculated this way has the same unit and the same profile as the original PSD function, thus allows one to compare the two with each other directly.
Weld defect identification in friction stir welding using power spectral density
Das, Bipul; Pal, Sukhomay; Bag, Swarup
2018-04-01
Power spectral density estimates are powerful in extraction of useful information retained in signal. In the current research work classical periodogram and Welch periodogram algorithms are used for the estimation of power spectral density for vertical force signal and transverse force signal acquired during friction stir welding process. The estimated spectral densities reveal notable insight in identification of defects in friction stir welded samples. It was observed that higher spectral density against each process signals is a key indication in identifying the presence of possible internal defects in the welded samples. The developed methodology can offer preliminary information regarding presence of internal defects in friction stir welded samples can be best accepted as first level of safeguard in monitoring the friction stir welding process.
Effects of motor programming on the power spectral density function of finger and wrist movements
Van Galen, G P; Van Doorn, R R; Schomaker, L R
Power spectral density analysis was applied to the frequency content of the acceleration signal of pen movements in line drawing. The relative power in frequency bands between 1 and 32 Hz was measured as a function of motoric and anatomic task demands. Results showed a decrease of power at the lower
Evaluation of plasma-wave spectral density from cross-power spectra
International Nuclear Information System (INIS)
Ilic, D.B.; Harker, K.J.
1975-01-01
The plasma-wave spectral density is evaluated by performing a spatial Fourier transform on experimental cross-power spectra of ion acoustic waves. The cross-power spectra are recorded on analog magnetic tape, converted to digital form, transferred to digital magnetic tape, and Fourier transformed on a digital computer. The important effects of sampling, finite data strings, and data smoothing on the end results are discussed and illustrated. The results indicate the usefulness of the spectral density method for the study of nonlinear wave phenomena. (auth)
Road simulation for four-wheel vehicle whole input power spectral density
Wang, Jiangbo; Qiang, Baomin
2017-05-01
As the vibration of running vehicle mainly comes from road and influence vehicle ride performance. So the road roughness power spectral density simulation has great significance to analyze automobile suspension vibration system parameters and evaluate ride comfort. Firstly, this paper based on the mathematical model of road roughness power spectral density, established the integral white noise road random method. Then in the MATLAB/Simulink environment, according to the research method of automobile suspension frame from simple two degree of freedom single-wheel vehicle model to complex multiple degrees of freedom vehicle model, this paper built the simple single incentive input simulation model. Finally the spectrum matrix was used to build whole vehicle incentive input simulation model. This simulation method based on reliable and accurate mathematical theory and can be applied to the random road simulation of any specified spectral which provides pavement incentive model and foundation to vehicle ride performance research and vibration simulation.
Power spectral density measurements with 252Cf for a light water moderated research reactor
International Nuclear Information System (INIS)
King, W.T.; Mihalczo, J.T.
1979-01-01
A method of determining the reactivity of far subcritical systems from neutron noise power spectral density measurements with 252 Cf has previously been tested in fast reactor critical assemblies: a mockup of the Fast Flux Test Facility reactor and a uranium metal sphere. Calculations indicated that this measurement was feasible for a pressurized water reactor (PWR). In order to evaluate the ability to perform these measurements with moderated reactors which have long prompt neutron lifetimes, measurements were performed with a small plate-type research reactor whose neutron lifetime (57 microseconds) was about a factor of three longer than that of a PWR and approx. 50% longer than that of a boiling water reactor. The results of the first measurements of power spectral densities with 252 Cf for a water moderated reactor are presented
International Nuclear Information System (INIS)
Venancio Filho, F.; DeCarvalho Santos, S.H.; Joia, L.A.
1987-01-01
A numerical methodology to obtain Power Spectral Density Functions (PSDF) of ground accelerations, compatible with a given design response spectrum is presented. The PSDF's are derived from the statistical analysis of the amplitudes of the frequency components in a set of artificially generated time-histories matching the given spectrum. A so obtained PSDF is then used in the stochastic analysis of a NPP Reactor Building. The main results of this analysis are compared with the ones obtained by deterministic methods
International Nuclear Information System (INIS)
Venancio Filho, F.; Joia, L.A.
1987-01-01
A numerical methodology to obtain Power Spectral Density Functions (PSDF) of ground accelerations, compatible with a given design response spectrum is presented. The PSDF's are derived from the statistical analysis of the amplitudes of the frequency components in a set of artificially generated time-histories matching the given spectrum. A so obtained PSDF is then used in the stochastic analysis of a reactor building. The main results of this analysis are compared with the ones obtained by deterministic methods. (orig./HP)
Power spectral density of velocity fluctuations estimated from phase Doppler data
Jicha Miroslav; Lizal Frantisek; Jedelsky Jan
2012-01-01
Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused...
Statistical algorithm for automated signature analysis of power spectral density data
International Nuclear Information System (INIS)
Piety, K.R.
1977-01-01
A statistical algorithm has been developed and implemented on a minicomputer system for on-line, surveillance applications. Power spectral density (PSD) measurements on process signals are the performance signatures that characterize the ''health'' of the monitored equipment. Statistical methods provide a quantitative basis for automating the detection of anomalous conditions. The surveillance algorithm has been tested on signals from neutron sensors, proximeter probes, and accelerometers to determine its potential for monitoring nuclear reactors and rotating machinery
International Nuclear Information System (INIS)
Jovanovic, S.; Stormark, E.
1966-01-01
Measurements of reactor parameters the Nora reactor by Power Spectral Density (PSD) method are described. In case of critical reactor this method was applied for direct measurement of β/l ratio, β is the effective yield of delayed neutrons and l is the neutron lifetime. In case of subcritical reactor values of α+β-ρ/l were measured, ρ is the negative reactivity. Out coming PSD was measured by a filter or by ISAC. PSD was registered by ISAC as well as the auto-correlation function [sr
Beam alignment based on two-dimensional power spectral density of a near-field image.
Wang, Shenzhen; Yuan, Qiang; Zeng, Fa; Zhang, Xin; Zhao, Junpu; Li, Kehong; Zhang, Xiaolu; Xue, Qiao; Yang, Ying; Dai, Wanjun; Zhou, Wei; Wang, Yuanchen; Zheng, Kuixing; Su, Jingqin; Hu, Dongxia; Zhu, Qihua
2017-10-30
Beam alignment is crucial to high-power laser facilities and is used to adjust the laser beams quickly and accurately to meet stringent requirements of pointing and centering. In this paper, a novel alignment method is presented, which employs data processing of the two-dimensional power spectral density (2D-PSD) for a near-field image and resolves the beam pointing error relative to the spatial filter pinhole directly. Combining this with a near-field fiducial mark, the operation of beam alignment is achieved. It is experimentally demonstrated that this scheme realizes a far-field alignment precision of approximately 3% of the pinhole size. This scheme adopts only one near-field camera to construct the alignment system, which provides a simple, efficient, and low-cost way to align lasers.
2D Spatial Frequency Considerations in Comparing 1D Power Spectral Density Measurements
International Nuclear Information System (INIS)
Takacs, P.Z.; Barber, S.; Church, E.L.; Kaznatcheev, K.; McKinney, W.R.; Yashchuk, V.Y.
2010-01-01
The frequency footprint of ID and 2D profiling instruments needs to be carefully considered in comparing ID surface roughness spectrum measurements made by different instruments. Contributions from orthogonal direction frequency components can not be neglected. The use of optical profiling instruments is ubiquitous in the measurement of the roughness of optical surfaces. Their ease-of-use and non-contact measurement method found widespread use in the optics industry for measuring the quality of delicate optical surfaces. Computerized digital data acquisition with these instruments allowed for quick and easy calculation of surface roughness statistics, such as root-mean-square (RMS) roughness. The computing power of the desktop computer allowed for the rapid conversion of spatial domain data into the frequency domain, enabling the application of sophisticated signal processing techniques to be applied to the analysis of surface roughness, the most powerful of which is the power spectral density (PSP) function. Application of the PSD function to surface statistics introduced the concept of 'bandwidth-limited' roughness, where the value of the RMS roughness depends critically upon the spatial frequency response of the instrument. Different instruments with different spatial frequency response characteristics give different answers when measuring the same surface.
Power spectral density of a single Brownian trajectory: what one can and cannot learn from it
Krapf, Diego; Marinari, Enzo; Metzler, Ralf; Oshanin, Gleb; Xu, Xinran; Squarcini, Alessio
2018-02-01
The power spectral density (PSD) of any time-dependent stochastic process X t is a meaningful feature of its spectral content. In its text-book definition, the PSD is the Fourier transform of the covariance function of X t over an infinitely large observation time T, that is, it is defined as an ensemble-averaged property taken in the limit T\\to ∞ . A legitimate question is what information on the PSD can be reliably obtained from single-trajectory experiments, if one goes beyond the standard definition and analyzes the PSD of a single trajectory recorded for a finite observation time T. In quest for this answer, for a d-dimensional Brownian motion (BM) we calculate the probability density function of a single-trajectory PSD for arbitrary frequency f, finite observation time T and arbitrary number k of projections of the trajectory on different axes. We show analytically that the scaling exponent for the frequency-dependence of the PSD specific to an ensemble of BM trajectories can be already obtained from a single trajectory, while the numerical amplitude in the relation between the ensemble-averaged and single-trajectory PSDs is a fluctuating property which varies from realization to realization. The distribution of this amplitude is calculated exactly and is discussed in detail. Our results are confirmed by numerical simulations and single-particle tracking experiments, with remarkably good agreement. In addition we consider a truncated Wiener representation of BM, and the case of a discrete-time lattice random walk. We highlight some differences in the behavior of a single-trajectory PSD for BM and for the two latter situations. The framework developed herein will allow for meaningful physical analysis of experimental stochastic trajectories.
International Nuclear Information System (INIS)
Ehrhardt, J.
1979-01-01
Theoretical and experimental investigations on detection systems for small narrow-band components in noise signals were conducted. These detectionn systems are based on the continuous surveillance of the power spectral density for characteristic peaks. Detection sensitivity for auto- and cross-correlation measurements was computed for signals with normally distributed amplitudes in dependence of signal coherence. The derived detection criteria allowed the comparison of auto- and cross-power spectral density surveillance. Theoretical results were confirmed in a number of experimental parameter studies. Special theoretical investigations were done for the optimal detection of local sodium boiling in liquid-metal fast breeder reactors
Power spectral density of velocity fluctuations estimated from phase Doppler data
Jedelsky, Jan; Lizal, Frantisek; Jicha, Miroslav
2012-04-01
Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain - calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA) data in the frequency domain. Slot correlation (SC) method implemented in software program Kern by Nobach (2006) is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.
Power spectral density of velocity fluctuations estimated from phase Doppler data
Directory of Open Access Journals (Sweden)
Jicha Miroslav
2012-04-01
Full Text Available Laser Doppler Anemometry (LDA and its modifications such as PhaseDoppler Particle Anemometry (P/DPA is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA data in the frequency domain. Slot correlation (SC method implemented in software program Kern by Nobach (2006 is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.
Assessing a learning process with functional ANOVA estimators of EEG power spectral densities.
Gutiérrez, David; Ramírez-Moreno, Mauricio A
2016-04-01
We propose to assess the process of learning a task using electroencephalographic (EEG) measurements. In particular, we quantify changes in brain activity associated to the progression of the learning experience through the functional analysis-of-variances (FANOVA) estimators of the EEG power spectral density (PSD). Such functional estimators provide a sense of the effect of training in the EEG dynamics. For that purpose, we implemented an experiment to monitor the process of learning to type using the Colemak keyboard layout during a twelve-lessons training. Hence, our aim is to identify statistically significant changes in PSD of various EEG rhythms at different stages and difficulty levels of the learning process. Those changes are taken into account only when a probabilistic measure of the cognitive state ensures the high engagement of the volunteer to the training. Based on this, a series of statistical tests are performed in order to determine the personalized frequencies and sensors at which changes in PSD occur, then the FANOVA estimates are computed and analyzed. Our experimental results showed a significant decrease in the power of [Formula: see text] and [Formula: see text] rhythms for ten volunteers during the learning process, and such decrease happens regardless of the difficulty of the lesson. These results are in agreement with previous reports of changes in PSD being associated to feature binding and memory encoding.
THE X-RAY POWER SPECTRAL DENSITY FUNCTION OF THE SEYFERT ACTIVE GALACTIC NUCLEUS NGC 7469
International Nuclear Information System (INIS)
Markowitz, A.
2010-01-01
We present the broadband X-ray power spectral density (PSD) function of the X-ray-luminous Seyfert 1.2 NGC 7469, measured from Rossi X-ray Timing Explorer monitoring data and two XMM-Newton observations. We find significant evidence for a turnover in the 2-10 keV PSD at a temporal frequency of 2.0 +3.0 -0.8 x 10 -6 Hz or 1.0 +3.0 -0.6 x 10 -6 Hz, depending on the exact form of the break (sharply broken or slowly bending power law, respectively). The 'surrogate' Monte Carlo method of Press et al. was used to map out the probability distributions of PSD model parameters and obtain reliable uncertainties (68% confidence limits quoted here). The corresponding break timescale of 5.8 ± 3.5 days or 11.6 +17.5 -8.7 days, respectively, is consistent with the empirical relation between PSD break timescale, black hole mass, and bolometric luminosity of McHardy et al. Compared to the 2-10 keV PSD, the 10-20 keV PSD has a much flatter shape at high temporal frequencies, and no PSD break is significantly detected, suggesting an energy-dependent evolution not unlike that exhibited by several Galactic black hole systems.
Increased power spectral density in resting-state pain-related brain networks in fibromyalgia.
Kim, Ji-Young; Kim, Seong-Ho; Seo, Jeehye; Kim, Sang-Hyon; Han, Seung Woo; Nam, Eon Jeong; Kim, Seong-Kyu; Lee, Hui Joong; Lee, Seung-Jae; Kim, Yang-Tae; Chang, Yongmin
2013-09-01
Fibromyalgia (FM), characterized by chronic widespread pain, is known to be associated with heightened responses to painful stimuli and atypical resting-state functional connectivity among pain-related regions of the brain. Previous studies of FM using resting-state functional magnetic resonance imaging (rs-fMRI) have focused on intrinsic functional connectivity, which maps the spatial distribution of temporal correlations among spontaneous low-frequency fluctuation in functional MRI (fMRI) resting-state data. In the current study, using rs-fMRI data in the frequency domain, we investigated the possible alteration of power spectral density (PSD) of low-frequency fluctuation in brain regions associated with central pain processing in patients with FM. rsfMRI data were obtained from 19 patients with FM and 20 age-matched healthy female control subjects. For each subject, the PSDs for each brain region identified from functional connectivity maps were computed for the frequency band of 0.01 to 0.25 Hz. For each group, the average PSD was determined for each brain region and a 2-sample t test was performed to determine the difference in power between the 2 groups. According to the results, patients with FM exhibited significantly increased frequency power in the primary somatosensory cortex (S1), supplementary motor area (SMA), dorsolateral prefrontal cortex, and amygdala. In patients with FM, the increase in PSD did not show an association with depression or anxiety. Therefore, our findings of atypical increased frequency power during the resting state in pain-related brain regions may implicate the enhanced resting-state baseline neural activity in several brain regions associated with pain processing in FM. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.
Power spectral density and scaling exponent of high frequency global solar radiation sequences
Calif, Rudy; Schmitt, François G.; Huang, Yongxiang
2013-04-01
invariance: Iq(f) ~ f-?(q) , ?(q) is the scaling exponent. This allows to characterize the scaling behavior of a process: fractal or multifractal with intermittent properties. For q = 2, the Hilbert spectrum is defined. In this work, The data are collected at the University site of Guadeloupe, an island in the West Indies, located at 16°15 N latitude 60°30 W longitude. Our measurements sampled at 1 Hz were performed during one year period. The analyzed data present a power spectral density E(f) displaying a power law of the form E(f) ~ f-β with 1.6 ˜ β ˜ 2.2 for frequencies f ˜ 0.1 Hz, corresponding to time scales T × 10 s. Furthermore, global solar radiation data possesses multifractal properties. For comparison, other multifractal analysis techniques such as structure functions, MDFA, wavelet leaders are also used. This preliminary work set the basis for further investigation dedicated to simulate and forecast a sequence of solar energy fluctuation under different meteorological conditions, in the multifractal framework.
International Nuclear Information System (INIS)
Behringer, K.; Spiekerman, G.
1984-01-01
Piety (1977) proposed an automated signature analysis of power spectral density data. Eight statistical decision discriminants are introduced. For nearly all the discriminants, improved confidence statements can be made. The statistical characteristics of the last three discriminants, which are applications of non-parametric tests, are considered. (author)
Bonte, M.H.A.; de Boer, Andries; Liebregts, R.
This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the
Substructure identification for shear structures: cross-power spectral density method
International Nuclear Information System (INIS)
Zhang, Dongyu; Johnson, Erik A
2012-01-01
In this paper, a substructure identification method for shear structures is proposed. A shear structure is divided into many small substructures; utilizing the dynamic equilibrium of a one-floor substructure, an inductive identification problem is formulated, using the cross-power spectral densities between structural floor accelerations and a reference response, to estimate the parameters of that one story. Repeating this procedure, all story parameters of the shear structure are identified from top to bottom recursively. An identification error analysis is performed for the proposed substructure method, revealing how uncertain factors (e.g. measurement noise) in the identification process affect the identification accuracy. According to the error analysis, a smart reference selection rule is designed to choose the optimal reference response that further enhances the identification accuracy. Moreover, based on the identification error analysis, explicit formulae are developed to calculate the variances of the parameter identification errors. A ten-story shear structure is used to illustrate the effectiveness of the proposed substructure method. The simulation results show that the method, combined with the reference selection rule, can very accurately identify structural parameters despite large measurement noise. Furthermore, the proposed formulae provide good predictions for the variances of the parameter identification errors, which are vital for providing accurate warnings of structural damage. (paper)
International Nuclear Information System (INIS)
Zwingelstein, Gilles; Thabet, Gabriel.
1977-01-01
Control algorithms for components of nuclear power plants are currently based on external diagnostic methods. Modeling and identification techniques for autoregressive moving average models (ARMA) for stochastic processes are described. The identified models provide a means of estimating the power spectral density with improved accuracy and computer time compared with the classical methods. They are particularly will suited for on-line estimation of the power spectral density. The observable stochastic process y (t) is modeled assuming that it is the output of a linear filter driven by Gaussian while noise w (t). Two identification schemes were tested to find the orders m and n of the ARMA (m,n) models and to estimate the parameters of the recursion equation relating the input and output signals. The first scheme consists in transforming the ARMA model to an autoregressive model. The parameters of this AR model are obtained using least squares estimation techniques. The second scheme consists in finding the parameters of the ARMA by nonlinear programming techniques. The power spectral density of y(t) is instantaneously deduced from these ARMA models [fr
Bonte, M. H. A.; de Boer, A.; Liebregts, R.
2007-04-01
This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the commercial vehicle business and was implemented in combination with Finite Element software to predict and analyse fatigue failure in the frequency domain.
Directory of Open Access Journals (Sweden)
DURNEA, T. N.
2009-02-01
Full Text Available UWB-PPM systems were noted to have a power spectral density (p.s.d. consisting of a continuous portion and a line spectrum, which is composed of energy components placed at discrete frequencies. These components are the major source of interference to narrowband systems operating in the same frequency interval and deny harmless coexistence of UWB-PPM and narrowband systems. A new code denoted as Totally Flipped Code (TFC is applied to them in order to eliminate these discrete spectral components. The coded signal transports the information inside pulse position and will have the amplitude coded to generate a continuous p.s.d. We have designed the code and calculated the power spectral density of the coded signals. The power spectrum has no discrete components and its envelope is largely flat inside the bandwidth with a maximum at its center and a null at D.C. These characteristics make this code suited for implementation in the UWB systems based on PPM-type modulation as it assures a continuous spectrum and keeps PPM modulation performances.
POWER SPECTRAL DENSITY OF FLUCTUATIONS OF BULK AND THERMAL SPEEDS IN THE SOLAR WIND
International Nuclear Information System (INIS)
Šafránková, J.; Němeček, Z.; Němec, F.; Přech, L.; Chen, C. H. K.; Zastenker, G. N.
2016-01-01
This paper analyzes solar wind power spectra of bulk and thermal speed fluctuations that are computed with a time resolution of 32 ms in the frequency range of 0.001–2 Hz. The analysis uses measurements of the Bright Monitor of the Solar Wind on board the Spektr-R spacecraft that are limited to 570 km s 1 bulk speed. The statistics, based on more than 42,000 individual spectra, show that: (1) the spectra of bulk and thermal speeds can be fitted by two power-law segments; (2) despite their large variations, the parameters characterizing frequency spectrum fits computed on each particular time interval are very similar for both quantities; (3) the median slopes of the bulk and thermal speeds of the segment attributed to the MHD scale are 1.43 and 1.38, respectively, whereas they are 3.08 and 2.43 in the kinetic range; (4) the kinetic range slopes of bulk and thermal speed spectra become equal when either the ion density or magnetic field strength are high; (5) the break between MHD and kinetic scales seems to be controlled by the ion β parameter; (6) the best scaling parameter for bulk and thermal speed variations is a sum of the inertial length and proton thermal gyroradius; and (7) the above conclusions can be applied to the density variations if the background magnetic field is very low.
POWER SPECTRAL DENSITY OF FLUCTUATIONS OF BULK AND THERMAL SPEEDS IN THE SOLAR WIND
Energy Technology Data Exchange (ETDEWEB)
Šafránková, J.; Němeček, Z.; Němec, F.; Přech, L. [Charles University, Faculty of Mathematics and Physics, V Holešovičkách 2, 180 00 Prague 8 (Czech Republic); Chen, C. H. K. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Zastenker, G. N., E-mail: jana.safrankova@mff.cuni.cz [Space Research Institute of Russian Academy of Sciences, Moscow, Russia, Profsoyuznaya ul. 84/32, Moscow 117997 (Russian Federation)
2016-07-10
This paper analyzes solar wind power spectra of bulk and thermal speed fluctuations that are computed with a time resolution of 32 ms in the frequency range of 0.001–2 Hz. The analysis uses measurements of the Bright Monitor of the Solar Wind on board the Spektr-R spacecraft that are limited to 570 km s{sup 1} bulk speed. The statistics, based on more than 42,000 individual spectra, show that: (1) the spectra of bulk and thermal speeds can be fitted by two power-law segments; (2) despite their large variations, the parameters characterizing frequency spectrum fits computed on each particular time interval are very similar for both quantities; (3) the median slopes of the bulk and thermal speeds of the segment attributed to the MHD scale are 1.43 and 1.38, respectively, whereas they are 3.08 and 2.43 in the kinetic range; (4) the kinetic range slopes of bulk and thermal speed spectra become equal when either the ion density or magnetic field strength are high; (5) the break between MHD and kinetic scales seems to be controlled by the ion β parameter; (6) the best scaling parameter for bulk and thermal speed variations is a sum of the inertial length and proton thermal gyroradius; and (7) the above conclusions can be applied to the density variations if the background magnetic field is very low.
Mahmood, Faleh H.; Kadhim, Hussein T.; Resen, Ali K.; Shaban, Auday H.
2018-05-01
The failure such as air gap weirdness, rubbing, and scrapping between stator and rotor generator arise unavoidably and may cause extremely terrible results for a wind turbine. Therefore, we should pay more attention to detect and identify its cause-bearing failure in wind turbine to improve the operational reliability. The current paper tends to use of power spectral density analysis method of detecting internal race and external race bearing failure in micro wind turbine by estimation stator current signal of the generator. The failure detector method shows that it is well suited and effective for bearing failure detection.
Validation of the α-μ Model of the Power Spectral Density of GPS Ionospheric Amplitude Scintillation
Directory of Open Access Journals (Sweden)
Kelias Oliveira
2014-01-01
Full Text Available The α-μ model has become widely used in statistical analyses of radio channels, due to the flexibility provided by its two degrees of freedom. Among several applications, it has been used in the characterization of low-latitude amplitude scintillation, which frequently occurs during the nighttime of particular seasons of high solar flux years, affecting radio signals that propagate through the ionosphere. Depending on temporal and spatial distributions, ionospheric scintillation may cause availability and precision problems to users of global navigation satellite systems. The present work initially stresses the importance of the flexibility provided by α-μ model in comparison with the limitations of a single-parameter distribution for the representation of first-order statistics of amplitude scintillation. Next, it focuses on the statistical evaluation of the power spectral density of ionospheric amplitude scintillation. The formulation based on the α-μ model is developed and validated using experimental data obtained in São José dos Campos (23.1°S; 45.8°W; dip latitude 17.3°S, Brazil, located near the southern crest of the ionospheric equatorial ionization anomaly. These data were collected between December 2001 and January 2002, a period of high solar flux conditions. The results show that the proposed model fits power spectral densities estimated from field data quite well.
Xu, Chen; Tian, Hui; Reece, Charles E.; Kelley, Michael J.
2012-04-01
Microroughness is viewed as a critical issue for attaining optimum performance of superconducting radio frequency accelerator cavities. The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions derived from topography of BCP and EP with different controlled starting conditions and durations have been fitted with a combination of power law, K correlation, and shifted Gaussian models to extract characteristic parameters at different spatial harmonic scales. While the simplest characterizations of these data are not new, the systematic tracking of scale-specific roughness as a function of processing is new and offers feedback for tighter process prescriptions more knowledgably targeted at beneficial niobium topography for superconducting radio frequency applications.
International Nuclear Information System (INIS)
Reece, Charles; Tian, Hui; Kelley, Michael; Xu, Chen
2012-01-01
Microroughness is viewed as a critical issue for attaining optimum performance of superconducting radio frequency accelerator cavities. The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions derived from topography of BCP and EP with different controlled starting conditions and durations have been fitted with a combination of power law, K correlation, and shifted Gaussian models to extract characteristic parameters at different spatial harmonic scales. While the simplest characterizations of these data are not new, the systematic tracking of scale-specific roughness as a function of processing is new and offers feedback for tighter process prescriptions more knowledgably targeted at beneficial niobium topography for superconducting radio frequency applications.
Rosado-Mendez, Ivan M; Nam, Kibo; Hall, Timothy J; Zagzebski, James A
2013-07-01
Reported here is a phantom-based comparison of methods for determining the power spectral density (PSD) of ultrasound backscattered signals. Those power spectral density values are then used to estimate parameters describing α(f), the frequency dependence of the acoustic attenuation coefficient. Phantoms were scanned with a clinical system equipped with a research interface to obtain radiofrequency echo data. Attenuation, modeled as a power law α(f)= α0 f (β), was estimated using a reference phantom method. The power spectral density was estimated using the short-time Fourier transform (STFT), Welch's periodogram, and Thomson's multitaper technique, and performance was analyzed when limiting the size of the parameter-estimation region. Errors were quantified by the bias and standard deviation of the α0 and β estimates, and by the overall power-law fit error (FE). For parameter estimation regions larger than ~34 pulse lengths (~1 cm for this experiment), an overall power-law FE of 4% was achieved with all spectral estimation methods. With smaller parameter estimation regions as in parametric image formation, the bias and standard deviation of the α0 and β estimates depended on the size of the parameter estimation region. Here, the multitaper method reduced the standard deviation of the α0 and β estimates compared with those using the other techniques. The results provide guidance for choosing methods for estimating the power spectral density in quantitative ultrasound methods.
Power spectral density analysis of wind-shear turbulence for related flight simulations. M.S. Thesis
Laituri, Tony R.
1988-01-01
Meteorological phenomena known as microbursts can produce abrupt changes in wind direction and/or speed over a very short distance in the atmosphere. These changes in flow characteristics have been labelled wind shear. Because of its adverse effects on aerodynamic lift, wind shear poses its most immediate threat to flight operations at low altitudes. The number of recent commercial aircraft accidents attributed to wind shear has necessitated a better understanding of how energy is transferred to an aircraft from wind-shear turbulence. Isotropic turbulence here serves as the basis of comparison for the anisotropic turbulence which exists in the low-altitude wind shear. The related question of how isotropic turbulence scales in a wind shear is addressed from the perspective of power spectral density (psd). The role of the psd in related Monte Carlo simulations is also considered.
International Nuclear Information System (INIS)
Minato, Susumu
2000-01-01
The multiple regression analysis done for 50 sets of data of natural terrestrial gamma-ray dose rates collected from different sites of the world led to an empirical formula for the variance of the data as a function of mean value and area. The mean values and areas studied in this paper range from 10 to 100 (nGy/h) and from 10 -3 to 10 7 (km 2 ), respectively. For an isotropic field of fluctuation, a two-dimensional power spectral density (2D PSD) was derived theoretically from the above mentioned empirical formula in a form of S(k)=0.952 x 10 -3 m 2.02 k -2.36 , where k (cycles/km) and m (nGy/h) are the wave number and the mean, respectively. The validity of the estimated 2D PSD was confirmed by comparing with PSDs obtained by the following two methods. One is the spatial auto-correlation analysis for several sets of randomly distributed 2D data consisting of more than 170 samples taken through ground surveys. The other is the direct 2D Fourier transform for two sets of 100 x 100 data matrix picked up from a dose rate map produced through airborne surveys. (author)
Saroka, Kevin S; Vares, David E; Persinger, Michael A
2016-01-01
In 1954 and 1960 Koenig and his colleagues described the remarkable similarities of spectral power density profiles and patterns between the earth-ionosphere resonance and human brain activity which also share magnitudes for both electric field (mV/m) and magnetic field (pT) components. In 2006 Pobachenko and colleagues reported real time coherence between variations in the Schumann and brain activity spectra within the 6-16 Hz band for a small sample. We examined the ratios of the average potential differences (~3 μV) obtained by whole brain quantitative electroencephalography (QEEG) between rostral-caudal and left-right (hemispheric) comparisons of 238 measurements from 184 individuals over a 3.5 year period. Spectral densities for the rostral-caudal axis revealed a powerful peak at 10.25 Hz while the left-right peak was 1.95 Hz with beat-differences of ~7.5 to 8 Hz. When global cerebral measures were employed, the first (7-8 Hz), second (13-14 Hz) and third (19-20 Hz) harmonics of the Schumann resonances were discernable in averaged QEEG profiles in some but not all participants. The intensity of the endogenous Schumann resonance was related to the 'best-of-fitness' of the traditional 4-class microstate model. Additional measurements demonstrated real-time coherence for durations approximating microstates in spectral power density variations between Schumann frequencies measured in Sudbury, Canada and Cumiana, Italy with the QEEGs of local subjects. Our results confirm the measurements reported by earlier researchers that demonstrated unexpected similarities in the spectral patterns and strengths of electromagnetic fields generated by the human brain and the earth-ionospheric cavity.
Directory of Open Access Journals (Sweden)
Kevin S Saroka
Full Text Available In 1954 and 1960 Koenig and his colleagues described the remarkable similarities of spectral power density profiles and patterns between the earth-ionosphere resonance and human brain activity which also share magnitudes for both electric field (mV/m and magnetic field (pT components. In 2006 Pobachenko and colleagues reported real time coherence between variations in the Schumann and brain activity spectra within the 6-16 Hz band for a small sample. We examined the ratios of the average potential differences (~3 μV obtained by whole brain quantitative electroencephalography (QEEG between rostral-caudal and left-right (hemispheric comparisons of 238 measurements from 184 individuals over a 3.5 year period. Spectral densities for the rostral-caudal axis revealed a powerful peak at 10.25 Hz while the left-right peak was 1.95 Hz with beat-differences of ~7.5 to 8 Hz. When global cerebral measures were employed, the first (7-8 Hz, second (13-14 Hz and third (19-20 Hz harmonics of the Schumann resonances were discernable in averaged QEEG profiles in some but not all participants. The intensity of the endogenous Schumann resonance was related to the 'best-of-fitness' of the traditional 4-class microstate model. Additional measurements demonstrated real-time coherence for durations approximating microstates in spectral power density variations between Schumann frequencies measured in Sudbury, Canada and Cumiana, Italy with the QEEGs of local subjects. Our results confirm the measurements reported by earlier researchers that demonstrated unexpected similarities in the spectral patterns and strengths of electromagnetic fields generated by the human brain and the earth-ionospheric cavity.
Correlation and spectral density measurements by LDA
International Nuclear Information System (INIS)
Pfeifer, H.J.
1986-01-01
The present paper is intended to give a review on the state-of-the art in correlation and spectral density measurements by means of laser Doppler anemometry. As will be shown in detail the most important difference in performing this type of studies is the fact that laser anemometry relies on the presence of particles in the flow serving as flow velocity indicators. This means that, except in heavily seeded flows, the instantaneous velocity can only be sampled at random instants. This calls for new algorithms to calculate estimates of both correlation functions and power spectra. Various possibilities to handle the problem of random sampling have been developed in the past. They are explained from the theoretical point of view and the experimental aspects are detailed as far as they are different from conventional applications of laser anemometry
International Nuclear Information System (INIS)
Yamamoto, Toshihiro
2014-01-01
Highlights: • The cross power spectral density in ADS has correlated and uncorrelated components. • A frequency domain Monte Carlo method to calculate the uncorrelated one is developed. • The method solves the Fourier transformed transport equation. • The method uses complex-valued weights to solve the equation. • The new method reproduces well the CPSDs calculated with time domain MC method. - Abstract: In an accelerator driven system (ADS), pulsed spallation neutrons are injected at a constant frequency. The cross power spectral density (CPSD), which can be used for monitoring the subcriticality of the ADS, is composed of the correlated and uncorrelated components. The uncorrelated component is described by a series of the Dirac delta functions that occur at the integer multiples of the pulse repetition frequency. In the present paper, a Monte Carlo method to solve the Fourier transformed neutron transport equation with a periodically pulsed neutron source term has been developed to obtain the CPSD in ADSs. Since the Fourier transformed flux is a complex-valued quantity, the Monte Carlo method introduces complex-valued weights to solve the Fourier transformed equation. The Monte Carlo algorithm used in this paper is similar to the one that was developed by the author of this paper to calculate the neutron noise caused by cross section perturbations. The newly-developed Monte Carlo algorithm is benchmarked to the conventional time domain Monte Carlo simulation technique. The CPSDs are obtained both with the newly-developed frequency domain Monte Carlo method and the conventional time domain Monte Carlo method for a one-dimensional infinite slab. The CPSDs obtained with the frequency domain Monte Carlo method agree well with those with the time domain method. The higher order mode effects on the CPSD in an ADS with a periodically pulsed neutron source are discussed
International Nuclear Information System (INIS)
Markowitz, A.
2009-01-01
We present the X-ray broadband power spectral density function (PSD) of the X-ray-luminous Seyfert IC 4329a, constructed from light curves obtained via Rossi X-ray Timing Explorer monitoring and an XMM-Newton observation. Modeling the 3-10 keV PSD using a broken power-law PSD shape, a break in power-law slope is significantly detected at a temporal frequency of 2.5 +2.5 -1.7 x 10 -6 Hz, which corresponds to a PSD break timescale T b of 4.6 +10.1 -2.3 days. Using the relation between T b , black hole mass M BH , and bolometric luminosity as quantified by McHardy and coworkers, we infer a black hole mass estimate of M BH = 1.3 +1.0 -0.3 x 10 8 M sun and an accretion rate relative to Eddington of 0.21 +0.06 -0.10 for this source. Our estimate of M BH is consistent with other estimates, including that derived by the relation between M BH and stellar velocity dispersion. We also present PSDs for the 10-20 and 20-40 keV bands; they lack sufficient temporal frequency coverage to reveal a significant break, but are consistent with the same PSD shape and break frequency as in the 3-10 keV band.
Finite size scaling and spectral density studies
International Nuclear Information System (INIS)
Berg, B.A.
1991-01-01
Finite size scaling (FSS) and spectral density (SD) studies are reported for the deconfining phase transition. This talk concentrates on Monte Carlo (MC) results for pure SU(3) gauge theory, obtained in collaboration with Alves and Sanielevici, but the methods are expected to be useful for full QCD as well. (orig.)
Spectral density regression for bivariate extremes
Castro Camilo, Daniela
2016-05-11
We introduce a density regression model for the spectral density of a bivariate extreme value distribution, that allows us to assess how extremal dependence can change over a covariate. Inference is performed through a double kernel estimator, which can be seen as an extension of the Nadaraya–Watson estimator where the usual scalar responses are replaced by mean constrained densities on the unit interval. Numerical experiments with the methods illustrate their resilience in a variety of contexts of practical interest. An extreme temperature dataset is used to illustrate our methods. © 2016 Springer-Verlag Berlin Heidelberg
Gliozzi, Mario; Papadakis, Iossif E.; Eracleous, Michael; Sambruna, Rita M.; Ballantyne, David R.; Braito, Valentina; Reeves, James N.
2009-09-01
We investigate the short-term variability properties and the power spectral density (PSD) of the broad-line radio galaxy (BLRG) 3C 390.3 using observations made by XMM-Newton, RXTE, and Suzaku on several occasions between 2004 October and 2006 December. The main aim of this work is to derive model-independent constraints on the origin of the X-ray emission and on the nature of the central engine in 3C 390.3. On timescales of the order of few hours, probed by uninterrupted XMM-Newton light curves, the flux of 3C 390.3 is consistent with being constant in all energy bands. On longer timescales, probed by the 2-day RXTE and Suzaku observations, the flux variability becomes significant. The latter observation confirms that the spectral variability behavior of 3C 390.3 is consistent with the spectral evolution observed in (radio-quiet) Seyfert galaxies: the spectrum softens as the source brightens. The correlated variability between soft and hard X-rays, observed during the Suzaku exposure and between the two XMM-Newton pointings, taken 1 week apart, argues against scenarios characterized by the presence of two distinct variable components in the 0.5-10 keV X-ray band. A detailed PSD analysis carried out over five decades in frequency suggests the presence of a break at T br = 43+34 -25 days at a 92% confidence level. This is the second tentative detection of a PSD break in a radio-loud, non-jet dominated active galactic nucleus (AGN), after the BLRG 3C 120, and appears to be in general agreement with the relation between T br, M BH, and L bol, followed by Seyfert galaxies. Our results indicate that the X-ray variability properties of 3C 390.3 are broadly consistent with those of radio-quiet AGN, suggesting that the X-ray emission mechanism in 3C 390.3 is similar to that of nearby Seyfert galaxies without any significant contribution from a jet component.
International Nuclear Information System (INIS)
Gliozzi, Mario; Papadakis, Iossif E.; Eracleous, Michael; Sambruna, Rita M.; Ballantyne, David R.; Braito, Valentina; Reeves, James N.
2009-01-01
We investigate the short-term variability properties and the power spectral density (PSD) of the broad-line radio galaxy (BLRG) 3C 390.3 using observations made by XMM-Newton, RXTE, and Suzaku on several occasions between 2004 October and 2006 December. The main aim of this work is to derive model-independent constraints on the origin of the X-ray emission and on the nature of the central engine in 3C 390.3. On timescales of the order of few hours, probed by uninterrupted XMM-Newton light curves, the flux of 3C 390.3 is consistent with being constant in all energy bands. On longer timescales, probed by the 2-day RXTE and Suzaku observations, the flux variability becomes significant. The latter observation confirms that the spectral variability behavior of 3C 390.3 is consistent with the spectral evolution observed in (radio-quiet) Seyfert galaxies: the spectrum softens as the source brightens. The correlated variability between soft and hard X-rays, observed during the Suzaku exposure and between the two XMM-Newton pointings, taken 1 week apart, argues against scenarios characterized by the presence of two distinct variable components in the 0.5-10 keV X-ray band. A detailed PSD analysis carried out over five decades in frequency suggests the presence of a break at T br = 43 +34 -25 days at a 92% confidence level. This is the second tentative detection of a PSD break in a radio-loud, non-jet dominated active galactic nucleus (AGN), after the BLRG 3C 120, and appears to be in general agreement with the relation between T br , M BH , and L bol , followed by Seyfert galaxies. Our results indicate that the X-ray variability properties of 3C 390.3 are broadly consistent with those of radio-quiet AGN, suggesting that the X-ray emission mechanism in 3C 390.3 is similar to that of nearby Seyfert galaxies without any significant contribution from a jet component.
Nonparametric Collective Spectral Density Estimation and Clustering
Maadooliat, Mehdi
2017-04-12
In this paper, we develop a method for the simultaneous estimation of spectral density functions (SDFs) for a collection of stationary time series that share some common features. Due to the similarities among the SDFs, the log-SDF can be represented using a common set of basis functions. The basis shared by the collection of the log-SDFs is estimated as a low-dimensional manifold of a large space spanned by a pre-specified rich basis. A collective estimation approach pools information and borrows strength across the SDFs to achieve better estimation efficiency. Also, each estimated spectral density has a concise representation using the coefficients of the basis expansion, and these coefficients can be used for visualization, clustering, and classification purposes. The Whittle pseudo-maximum likelihood approach is used to fit the model and an alternating blockwise Newton-type algorithm is developed for the computation. A web-based shiny App found at
Nonparametric Collective Spectral Density Estimation and Clustering
Maadooliat, Mehdi; Sun, Ying; Chen, Tianbo
2017-01-01
In this paper, we develop a method for the simultaneous estimation of spectral density functions (SDFs) for a collection of stationary time series that share some common features. Due to the similarities among the SDFs, the log-SDF can be represented using a common set of basis functions. The basis shared by the collection of the log-SDFs is estimated as a low-dimensional manifold of a large space spanned by a pre-specified rich basis. A collective estimation approach pools information and borrows strength across the SDFs to achieve better estimation efficiency. Also, each estimated spectral density has a concise representation using the coefficients of the basis expansion, and these coefficients can be used for visualization, clustering, and classification purposes. The Whittle pseudo-maximum likelihood approach is used to fit the model and an alternating blockwise Newton-type algorithm is developed for the computation. A web-based shiny App found at
Anufrik, S. S.; Kurian, N. N.; Znosko, K. F.; Belkov, M. V.
2018-05-01
We have studied the intensity of the spectral lines for the main components in clay: Al I 309.4 nm, Al II 358.7 nm, Mg II 279.6 nm, Ti II 323.6 nm vs. the position of the object relative to the focus of the optical system when the samples are exposed to single laser pulses from a YAG:Nd3+ laser. We have determined the permissible ranges for positioning the object relative to the focus of the optical system (positive and negative defocusing) for which there is practically no change in the reproducibility of the intensity for the spectral lines for red and white clay samples. We show that the position of the object relative to the focus of the optical system should be within the range ΔZ ±1.5 mm for optimal laser pulse energies for the analyte spectral lines. We have calculated the radiation flux density for different laser pulse energies and different distances from the focus to the object. We have shown experimentally that reducing the radiation flux density leads to a decrease in the intensity of the analyte spectral lines.
Directory of Open Access Journals (Sweden)
Boris Jesús Goenaga
2017-01-01
Full Text Available The pavement roughness is the main variable that produces the vertical excitation in vehicles. Pavement profiles are the main determinant of (i discomfort perception on users and (ii dynamic loads generated at the tire-pavement interface, hence its evaluation constitutes an essential step on a Pavement Management System. The present document evaluates two specific techniques used to simulate pavement profiles; these are the shaping filter and the sinusoidal approach, both based on the Power Spectral Density. Pavement roughness was evaluated using the International Roughness Index (IRI, which represents the most used index to characterize longitudinal road profiles. Appropriate parameters were defined in the simulation process to obtain pavement profiles with specific ranges of IRI values using both simulation techniques. The results suggest that using a sinusoidal approach one can generate random profiles with IRI values that are representative of different road types, therefore, one could generate a profile for a paved or an unpaved road, representing all the proposed categories defined by ISO 8608 standard. On the other hand, to obtain similar results using the shaping filter approximation a modification in the simulation parameters is necessary. The new proposed values allow one to generate pavement profiles with high levels of roughness, covering a wider range of surface types. Finally, the results of the current investigation could be used to further improve our understanding on the effect of pavement roughness on tire pavement interaction. The evaluated methodologies could be used to generate random profiles with specific levels of roughness to assess its effect on dynamic loads generated at the tire-pavement interface and user’s perception of road condition.
High Spectral Density Optical Communication Technologies
Nakazawa, Masataka; Miyazaki, Tetsuya
2010-01-01
The latest hot topics of high-spectral density optical communication systems using digital coherent optical fibre communication technologies are covered by this book. History and meaning of a "renaissance" of the technology, requirements to the Peta-bit/s class "new generation network" are also covered in the first part of this book. The main topics treated are electronic and optical devices, digital signal processing including forward error correction, modulation formats as well as transmission and application systems. The book serves as a reference to researchers and engineers.
Hamiltonian indices and rational spectral densities
Byrnes, C. I.; Duncan, T. E.
1980-01-01
Several (global) topological properties of various spaces of linear systems, particularly symmetric, lossless, and Hamiltonian systems, and multivariable spectral densities of fixed McMillan degree are announced. The study is motivated by a result asserting that on a connected but not simply connected manifold, it is not possible to find a vector field having a sink as its only critical point. In the scalar case, this is illustrated by showing that only on the space of McMillan degree = /Cauchy index/ = n, scalar transfer functions can one define a globally convergent vector field. This result holds both in discrete-time and for the nonautonomous case. With these motivations in mind, theorems of Bochner and Fogarty are used in showing that spaces of transfer functions defined by symmetry conditions are, in fact, smooth algebraic manifolds.
Kascak, Daniel J.
2004-01-01
With the growing concerns of global warming, the need for pollution-free vehicles is ever increasing. Pollution-free flight is one of NASA's goals for the 21" Century. , One method of approaching that goal is hydrogen-fueled aircraft that use fuel cells or turbo- generators to develop electric power that can drive electric motors that turn the aircraft's propulsive fans or propellers. Hydrogen fuel would likely be carried as a liquid, stored in tanks at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are far too heavy (for a given horsepower) to use on aircraft. Fortunately the liquid hydrogen fuel can provide essentially free refrigeration that can be used to cool the windings of motors before the hydrogen is used for fuel. Either High Temperature Superconductors (HTS) or high purity metals such as copper or aluminum may be used in the motor windings. Superconductors have essentially zero electrical resistance to steady current. The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be l/lOO* or less of the room temperature resistance. These conductors could provide higher motor efficiency than normal room-temperature motors achieve. But much more importantly, these conductors can carry ten to a hundred times more current than copper conductors do in normal motors operating at room temperature. This is a consequence of the low electrical resistance and of good heat transfer coefficients in boiling LH2. Thus the conductors can produce higher magnetic field strengths and consequently higher motor torque and power. Designs, analysis and actual cryogenic motor tests show that such cryogenic motors could produce three or more times as much power per unit weight as turbine engines can, whereas conventional motors produce only 1/5 as much power per weight as turbine engines. This summer work has been done with Litz wire to maximize the current density. The current is limited by the amount of heat it
Ultra-High Density Spectral Storage Materials
National Research Council Canada - National Science Library
Hasan, Zameer U
2002-01-01
.... Being atomic scale storage, spectral storage has the potential of providing orders of magnitude denser memories than present day memories that depend on the hulk properties of the storage medium...
Laser line shape and spectral density of frequency noise
International Nuclear Information System (INIS)
Stephan, G.M.; Blin, S.; Besnard, P.; Tam, T.T.; Tetu, M.
2005-01-01
Published experimental results show that single-mode laser light is characterized in the microwave range by a frequency noise which essentially includes a white part and a 1/f (flicker) part. We theoretically show that the spectral density (the line shape) which is compatible with these results is a Voigt profile whose Lorentzian part or homogeneous component is linked to the white noise and the Gaussian part to the 1/f noise. We measure semiconductor laser line profiles and verify that they can be fit with Voigt functions. It is also verified that the width of the Lorentzian part varies like 1/P where P is the laser power while the width of the Gaussian part is more of a constant. Finally, we theoretically show from first principles that laser line shapes are also described by Voigt functions where the Lorentzian part is the laser Airy function and the Gaussian part originates from population noise
Spectral density regression for bivariate extremes
Castro Camilo, Daniela; de Carvalho, Miguel
2016-01-01
can be seen as an extension of the Nadaraya–Watson estimator where the usual scalar responses are replaced by mean constrained densities on the unit interval. Numerical experiments with the methods illustrate their resilience in a variety of contexts
Power spectral analysis of heart rate in hyperthyroidism.
Cacciatori, V; Bellavere, F; Pezzarossa, A; Dellera, A; Gemma, M L; Thomaseth, K; Castello, R; Moghetti, P; Muggeo, M
1996-08-01
The aim of the present study was to evaluate the impact of hyperthyroidism on the cardiovascular system by separately analyzing the sympathetic and parasympathetic influences on heart rate. Heart rate variability was evaluated by autoregressive power spectral analysis. This method allows a reliable quantification of the low frequency (LF) and high frequency (HF) components of the heart rate power spectral density; these are considered to be under mainly sympathetic and pure parasympathetic control, respectively. In 10 newly diagnosed untreated hyperthyroid patients with Graves' disease, we analyzed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. In addition, heart rate variations during deep breathing, lying and standing, and Valsalva's maneuver were analyzed. The results were compared to those obtained from 10 age-, sex-, and body mass index-matched control subjects. In 8 hyperthyroid patients, the same evaluation was repeated after the induction of stable euthyroidism by methimazole. Heart rate power spectral analysis showed a sharp reduction of HF components in hyperthyroid subjects compared to controls [lying, 13.3 +/- 4.1 vs. 32.0 +/- 5.6 normalized units (NU; P hyperthyroid subjects while both lying (11.3 +/- 4.5 vs. 3.5 +/- 1.1; P hyperthyroid patients than in controls (1.12 +/- 0.03 vs. 1.31 +/- 0.04; P activity and, thus, a relative hypersympathetic tone.
Heida, Tjitske; Wentink, E.C.; Marani, Enrico
2013-01-01
Background: Observation of the signals recorded from the extremities of Parkinson’s disease patients showing rest and/or action tremor reveal a distinct high power resonance peak in the frequency band corresponding to tremor. The aim of the study was to investigate, using quantitative measures, how
Spectral density and a family of Dirac operators
International Nuclear Information System (INIS)
Niemi, A.J.
1985-01-01
The spectral density for a class Dirac operators is investigated by relating its even and odd parts to the Riemann zeta-function and to the eta-invariant by Atiyah, Padoti and Singer. Asymptotic expansions are studied and a 'hidden' supersymmetry is revealed and used to relate the Dirac operator to a supersymmetric quantum mechanics. A general method for the computation of the odd spectral density is developed, and various applications are discussed. In particular the connection to the fermion number and a relation between the odd spectral density and some ratios of Jost functions and relative phase shifts are pointed out. Chiral symmetry breaking is investigated using methods analogous to those applied in the investigation of the fermion number, and related to supersymmetry breaking in the corresponding quantum mechanical model. (orig.)
Spectral function from Reduced Density Matrix Functional Theory
Romaniello, Pina; di Sabatino, Stefano; Berger, Jan A.; Reining, Lucia
2015-03-01
In this work we focus on the calculation of the spectral function, which determines, for example, photoemission spectra, from reduced density matrix functional theory. Starting from its definition in terms of the one-body Green's function we derive an expression for the spectral function that depends on the natural occupation numbers and on an effective energy which accounts for all the charged excitations. This effective energy depends on the two-body as well as higher-order density matrices. Various approximations to this expression are explored by using the exactly solvable Hubbard chains.
Milovanovic, Petar; Djuric, Marija; Rakocevic, Zlatko
2012-11-01
There is an increasing interest in bone nano-structure, the ultimate goal being to reveal the basis of age-related bone fragility. In this study, power spectral density (PSD) data and fractal dimensions of the mineralized bone matrix were extracted from atomic force microscope topography images of the femoral neck trabeculae. The aim was to evaluate age-dependent differences in the mineralized matrix of human bone and to consider whether these advanced nano-descriptors might be linked to decreased bone remodeling observed by some authors and age-related decline in bone mechanical competence. The investigated bone specimens belonged to a group of young adult women (n = 5, age: 20-40 years) and a group of elderly women (n = 5, age: 70-95 years) without bone diseases. PSD graphs showed the roughness density distribution in relation to spatial frequency. In all cases, there was a fairly linear decrease in magnitude of the power spectra with increasing spatial frequencies. The PSD slope was steeper in elderly individuals (-2.374 vs. -2.066), suggesting the dominance of larger surface morphological features. Fractal dimension of the mineralized bone matrix showed a significant negative trend with advanced age, declining from 2.467 in young individuals to 2.313 in the elderly (r = 0.65, P = 0.04). Higher fractal dimension in young women reflects domination of smaller mineral grains, which is compatible with the more freshly remodeled structure. In contrast, the surface patterns in elderly individuals were indicative of older tissue age. Lower roughness and reduced structural complexity (decreased fractal dimension) of the interfibrillar bone matrix in the elderly suggest a decline in bone toughness, which explains why aged bone is more brittle and prone to fractures. © 2012 The Authors Journal of Anatomy © 2012 Anatomical Society.
Robust power spectral estimation for EEG data.
Melman, Tamar; Victor, Jonathan D
2016-08-01
Typical electroencephalogram (EEG) recordings often contain substantial artifact. These artifacts, often large and intermittent, can interfere with quantification of the EEG via its power spectrum. To reduce the impact of artifact, EEG records are typically cleaned by a preprocessing stage that removes individual segments or components of the recording. However, such preprocessing can introduce bias, discard available signal, and be labor-intensive. With this motivation, we present a method that uses robust statistics to reduce dependence on preprocessing by minimizing the effect of large intermittent outliers on the spectral estimates. Using the multitaper method (Thomson, 1982) as a starting point, we replaced the final step of the standard power spectrum calculation with a quantile-based estimator, and the Jackknife approach to confidence intervals with a Bayesian approach. The method is implemented in provided MATLAB modules, which extend the widely used Chronux toolbox. Using both simulated and human data, we show that in the presence of large intermittent outliers, the robust method produces improved estimates of the power spectrum, and that the Bayesian confidence intervals yield close-to-veridical coverage factors. The robust method, as compared to the standard method, is less affected by artifact: inclusion of outliers produces fewer changes in the shape of the power spectrum as well as in the coverage factor. In the presence of large intermittent outliers, the robust method can reduce dependence on data preprocessing as compared to standard methods of spectral estimation. Copyright © 2016 Elsevier B.V. All rights reserved.
Spectral density of electron concentration fluctuations in ionospheric D region
International Nuclear Information System (INIS)
Martynenko, S.I.
1989-01-01
Expression for spectral density of electron concentration fluctuations in D-region with regard to the effect of ionization-recombination proceses and negative ions is obtained in terms of atmospheric turbulence model which obeys Kolmogorov-Obukhov 2/3 law
Spectral density of oscillator with bilinear stiffness and white noise excitation
DEFF Research Database (Denmark)
Rüdinger, Finn; Krenk, Steen
2003-01-01
The power spectral density of an oscillator with bilinear stiffness excited by Gaussian white noise is considered. A method originally proposed by Krenk and Roberts [J Appl Mech 66 (1999) 225] relying on slowly changing energy for lightly damped systems is applied. In this method an approximate...
Inference of core barrel motion from neutron noise spectral density. [PWR
Energy Technology Data Exchange (ETDEWEB)
Robinson, J.C.; Shahrokhi, F.; Kryter, R.C.
1977-03-15
A method was developed for inference of core barrel motion from the following statistical descriptors: cross-power spectral density, autopower spectral density, and amplitude probability density. To quantify the core barrel motion in a typical pressurized water reactor (PWR), a scale factor was calculated in both one- and two-dimensional geometries using forward, variational, and perturbation methods of discrete ordinates neutron transport. A procedure for selection of the proper frequency band limits for the statistical descriptors was developed. It was found that although perturbation theory is adequate for the calculation of the scale factor, two-dimensional geometric effects are important enough to rule out the use of a one-dimensional approximation for all but the crudest calculations. It was also found that contributions of gamma rays can be ignored and that the results are relatively insensitive to the cross-section set employed. The proper frequency band for the statistical descriptors is conveniently determined from the coherence and phase information from two ex-core power range neutron monitors positioned diametrically across the reactor vessel. Core barrel motion can then be quantified from the integral of the band-limited cross-power spectral density of two diametrically opposed ex-core monitors or, if the coherence between the pair is greater than or equal to 0.7, from a properly band-limited amplitude probability density function. Wide-band amplitude probability density functions were demonstrated to yield erroneous estimates for the magnitude of core barrel motion.
Breast density estimation from high spectral and spatial resolution MRI
Li, Hui; Weiss, William A.; Medved, Milica; Abe, Hiroyuki; Newstead, Gillian M.; Karczmar, Gregory S.; Giger, Maryellen L.
2016-01-01
Abstract. A three-dimensional breast density estimation method is presented for high spectral and spatial resolution (HiSS) MR imaging. Twenty-two patients were recruited (under an Institutional Review Board--approved Health Insurance Portability and Accountability Act-compliant protocol) for high-risk breast cancer screening. Each patient received standard-of-care clinical digital x-ray mammograms and MR scans, as well as HiSS scans. The algorithm for breast density estimation includes breast mask generating, breast skin removal, and breast percentage density calculation. The inter- and intra-user variabilities of the HiSS-based density estimation were determined using correlation analysis and limits of agreement. Correlation analysis was also performed between the HiSS-based density estimation and radiologists’ breast imaging-reporting and data system (BI-RADS) density ratings. A correlation coefficient of 0.91 (pdensity estimations. An interclass correlation coefficient of 0.99 (pdensity estimations. A moderate correlation coefficient of 0.55 (p=0.0076) was observed between HiSS-based breast density estimations and radiologists’ BI-RADS. In summary, an objective density estimation method using HiSS spectral data from breast MRI was developed. The high reproducibility with low inter- and low intra-user variabilities shown in this preliminary study suggest that such a HiSS-based density metric may be potentially beneficial in programs requiring breast density such as in breast cancer risk assessment and monitoring effects of therapy. PMID:28042590
Geometrical Description in Binary Composites and Spectral Density Representation
Directory of Open Access Journals (Sweden)
Enis Tuncer
2010-01-01
Full Text Available In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based on a scaled permittivity approach, ξ = (εe − εm(εi − εm−1, where the subscripts e, m and i denote the dielectric permittivities of the effective, matrix and inclusion media, respectively [Tuncer, E. J. Phys.: Condens. Matter 2005, 17, L125]. This novel representation transforms the spectral density formalism to a form similar to the distribution of relaxation times method of dielectric relaxation. Consequently, I propose that any dielectric relaxation formula, i.e., the Havriliak-Negami empirical dielectric relaxation expression, can be adopted as a scaled permittivity. The presented scaled permittivity representation has potential to be improved and implemented into the existing data analyzing routines for dielectric relaxation; however, the information to extract would be the topological/morphological description in mixtures. To arrive at the description, one needs to know the dielectric properties of the constituents and the composite prior to the spectral analysis. To illustrate the strength of the representation and confirm the proposed hypothesis, the Landau-Lifshitz/Looyenga (LLL [Looyenga, H. Physica 1965, 31, 401] expression is selected. The structural information of a mixture obeying LLL is extracted for different volume fractions of phases. Both an in-house computational tool based on the Monte Carlo method to solve inverse integral transforms and the proposed empirical scaled permittivity expression are employed to estimate the spectral density function of the LLL expression. The estimated spectral functions for mixtures with different inclusion concentration compositions show similarities; they are composed of a couple of bell
Electronic DC transformer with high power density
Pavlovský, M.
2006-01-01
This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components
Lei, Youming; Zheng, Fan
2016-12-01
Stochastic chaos induced by diffusion processes, with identical spectral density but different probability density functions (PDFs), is investigated in selected lightly damped Hamiltonian systems. The threshold amplitude of diffusion processes for the onset of chaos is derived by using the stochastic Melnikov method together with a mean-square criterion. Two quasi-Hamiltonian systems, namely, a damped single pendulum and damped Duffing oscillator perturbed by stochastic excitations, are used as illustrative examples. Four different cases of stochastic processes are taking as the driving excitations. It is shown that in such two systems the spectral density of diffusion processes completely determines the threshold amplitude for chaos, regardless of the shape of their PDFs, Gaussian or otherwise. Furthermore, the mean top Lyapunov exponent is employed to verify analytical results. The results obtained by numerical simulations are in accordance with the analytical results. This demonstrates that the stochastic Melnikov method is effective in predicting the onset of chaos in the quasi-Hamiltonian systems.
Spectral Analysis of Polynomial Nonlinearity with Applications to RF Power Amplifiers
Directory of Open Access Journals (Sweden)
G. Tong Zhou
2004-09-01
Full Text Available The majority of the nonlinearity in a communication system is attributed to the power amplifier (PA present at the final stage of the transmitter chain. In this paper, we consider Gaussian distributed input signals (such as OFDM, and PAs that can be modeled by memoryless or memory polynomials. We derive closed-form expressions of the PA output power spectral density, for an arbitrary nonlinear order, based on the so-called Leonov-Shiryaev formula. We then apply these results to answer practical questions such as the contribution of AM/PM conversion to spectral regrowth and the relationship between memory effects and spectral asymmetry.
Combat Power Analysis is Combat Power Density
2012-05-17
Lanchester equations, Weapon Effectiveness Index (WEI), Weighted Unit Value (WUV), Armored Division Equivalents (ADE), and Unit Frontages. The research...6 Lanchester Equations... Lanchester Equations ............................................................................................... 53 Appendix C: Relative Combat Power
Generation of Stationary Non-Gaussian Time Histories with a Specified Cross-spectral Density
Directory of Open Access Journals (Sweden)
David O. Smallwood
1997-01-01
Full Text Available The paper reviews several methods for the generation of stationary realizations of sampled time histories with non-Gaussian distributions and introduces a new method which can be used to control the cross-spectral density matrix and the probability density functions (pdfs of the multiple input problem. Discussed first are two methods for the specialized case of matching the auto (power spectrum, the skewness, and kurtosis using generalized shot noise and using polynomial functions. It is then shown that the skewness and kurtosis can also be controlled by the phase of a complex frequency domain description of the random process. The general case of matching a target probability density function using a zero memory nonlinear (ZMNL function is then covered. Next methods for generating vectors of random variables with a specified covariance matrix for a class of spherically invariant random vectors (SIRV are discussed. Finally the general case of matching the cross-spectral density matrix of a vector of inputs with non-Gaussian marginal distributions is presented.
High Power Density Power Electronic Converters for Large Wind Turbines
DEFF Research Database (Denmark)
Senturk, Osman Selcuk
. For these VSCs, high power density is required due to limited turbine nacelle space. Also, high reliability is required since maintenance cost of these remotely located wind turbines is quite high and these turbines operate under harsh operating conditions. In order to select a high power density and reliability......In large wind turbines (in MW and multi-MW ranges), which are extensively utilized in wind power plants, full-scale medium voltage (MV) multi-level (ML) voltage source converters (VSCs) are being more preferably employed nowadays for interfacing these wind turbines with electricity grids...... VSC solution for wind turbines, first, the VSC topology and the switch technology to be employed should be specified such that the highest possible power density and reliability are to be attained. Then, this qualitative approach should be complemented with the power density and reliability...
Achievement Motivation and EEG Spectral Power
Directory of Open Access Journals (Sweden)
Elena V. Vorobyeva
2011-01-01
Full Text Available Achievement motivation is a psychological category which implies a desire to achieve significant (powerful results in certain sphere. According to the results of psychophysiological research people who are motivated for success are very active before they are instructed by the researcher which proves that they aimed at the perception of the referent situation and the intense level of expectations. One of the vital issues today is a problem how genes influence human behaviour. Thus on the basis of contemporary researches we can conclude that such influence is regulated by brain processes.
O Electromagnetic Power Waves and Power Density Components.
Petzold, Donald Wayne
1980-12-01
On January 10, 1884 Lord Rayleigh presented a paper entitled "On the Transfer of Energy in the Electromagnetic Field" to the Royal Society of London. This paper had been authored by the late Fellow of Trinity College, Cambridge, Professor J. H. Poynting and in it he claimed that there was a general law for the transfer of electromagnetic energy. He argued that associated with each point in space is a quantity, that has since been called the Poynting vector, that is a measure of the rate of energy flow per unit area. His analysis was concerned with the integration of this power density vector at all points over an enclosing surface of a specific volume. The interpretation of this Poynting vector as a true measure of the local power density was viewed with great skepticism unless the vector was integrated over a closed surface, as the development of the concept required. However, within the last decade or so Shadowitz indicates that a number of prominent authors have argued that the criticism of the interpretation of Poynting's vector as a local power density vector is unjustified. The present paper is not concerned with these arguments but instead is concerned with a decomposition of Poynting's power density vector into two and only two components: one vector which has the same direction as Poynting's vector and which is called the forward power density vector, and another vector, directed opposite to the Poynting vector and called the reverse power density vector. These new local forward and reverse power density vectors will be shown to be dependent upon forward and reverse power wave vectors and these vectors in turn will be related to newly defined forward and reverse components of the electric and magnetic fields. The sum of these forward and reverse power density vectors, which is simply the original Poynting vector, is associated with the total electromagnetic energy traveling past the local point. Another vector which is the difference between the forward
High power density carbonate fuel cell
Energy Technology Data Exchange (ETDEWEB)
Yuh, C.; Johnsen, R.; Doyon, J.; Allen, J. [Energy Research Corp., Danbury, CT (United States)
1996-12-31
Carbonate fuel cell is a highly efficient and environmentally clean source of power generation. Many organizations worldwide are actively pursuing the development of the technology. Field demonstration of multi-MW size power plant has been initiated in 1996, a step toward commercialization before the turn of the century, Energy Research Corporation (ERC) is planning to introduce a 2.85MW commercial fuel cell power plant with an efficiency of 58%, which is quite attractive for distributed power generation. However, to further expand competitive edge over alternative systems and to achieve wider market penetration, ERC is exploring advanced carbonate fuel cells having significantly higher power densities. A more compact power plant would also stimulate interest in new markets such as ships and submarines where space limitations exist. The activities focused on reducing cell polarization and internal resistance as well as on advanced thin cell components.
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.
Non destructive defect detection by spectral density analysis.
Krejcar, Ondrej; Frischer, Robert
2011-01-01
The potential nondestructive diagnostics of solid objects is discussed in this article. The whole process is accomplished by consecutive steps involving software analysis of the vibration power spectrum (eventually acoustic emissions) created during the normal operation of the diagnosed device or under unexpected situations. Another option is to create an artificial pulse, which can help us to determine the actual state of the diagnosed device. The main idea of this method is based on the analysis of the current power spectrum density of the received signal and its postprocessing in the Matlab environment with a following sample comparison in the Statistica software environment. The last step, which is comparison of samples, is the most important, because it is possible to determine the status of the examined object at a given time. Nowadays samples are compared only visually, but this method can't produce good results. Further the presented filter can choose relevant data from a huge group of data, which originate from applying FFT (Fast Fourier Transform). On the other hand, using this approach they can be subjected to analysis with the assistance of a neural network. If correct and high-quality starting data are provided to the initial network, we are able to analyze other samples and state in which condition a certain object is. The success rate of this approximation, based on our testing of the solution, is now 85.7%. With further improvement of the filter, it could be even greater. Finally it is possible to detect defective conditions or upcoming limiting states of examined objects/materials by using only one device which contains HW and SW parts. This kind of detection can provide significant financial savings in certain cases (such as continuous casting of iron where it could save hundreds of thousands of USD).
Evaluation the complex lithologies in the oil well using spectral density instrument
International Nuclear Information System (INIS)
Zivanov, M.; Martinovic, S.; Jakovljevic, B.
1991-01-01
Spectral density instrument for logging in the oil wells, beside density, measure photo electrical cross section. The principles of logging are discussed of modern spectral density. Results of logging are used dor determining the complex lithology in the oil well. With this instrument are obtained the more accurate and reliable logging results and better lithology rate and reliable logging results and better lithology determination in the formations. (author)
Methods to enhance blanket power density
International Nuclear Information System (INIS)
Hsu, P.Y.; Miller, L.G.; Bohn, T.S.; Deis, G.A.; Longhurst, G.R.; Masson, L.S.; Wessol, D.E.; Abdou, M.A.
1982-06-01
The overall objective of this task is to investigate the extent to which the power density in the FED/INTOR breeder blanket test modules can be enhanced by artificial means. Assuming a viable approach can be developed, it will allow advanced reactor blanket modules to be tested on FED/INTOR under representative conditions
Arbitrary-order Hilbert Spectral Analysis and Intermittency in Solar Wind Density Fluctuations
Carbone, Francesco; Sorriso-Valvo, Luca; Alberti, Tommaso; Lepreti, Fabio; Chen, Christopher H. K.; Němeček, Zdenek; Šafránková, Jana
2018-05-01
The properties of inertial- and kinetic-range solar wind turbulence have been investigated with the arbitrary-order Hilbert spectral analysis method, applied to high-resolution density measurements. Due to the small sample size and to the presence of strong nonstationary behavior and large-scale structures, the classical analysis in terms of structure functions may prove to be unsuccessful in detecting the power-law behavior in the inertial range, and may underestimate the scaling exponents. However, the Hilbert spectral method provides an optimal estimation of the scaling exponents, which have been found to be close to those for velocity fluctuations in fully developed hydrodynamic turbulence. At smaller scales, below the proton gyroscale, the system loses its intermittent multiscaling properties and converges to a monofractal process. The resulting scaling exponents, obtained at small scales, are in good agreement with those of classical fractional Brownian motion, indicating a long-term memory in the process, and the absence of correlations around the spectral-break scale. These results provide important constraints on models of kinetic-range turbulence in the solar wind.
Spectral parameter power series representation for Hill's discriminant
International Nuclear Information System (INIS)
Khmelnytskaya, K.V.; Rosu, H.C.
2010-01-01
We establish a series representation of the Hill discriminant based on the spectral parameter power series (SPPS) recently introduced by Kravchenko. We also show the invariance of the Hill discriminant under a Darboux transformation and employing the Mathieu case the feasibility of this type of series for numerical calculations of the eigenspectrum.
TRIGA research reactors with higher power density
International Nuclear Information System (INIS)
Whittemore, W.L.
1994-01-01
The recent trend in new or upgraded research reactors is to higher power densities (hence higher neutron flux levels) but not necessarily to higher power levels. The TRIGA LEU fuel with burnable poison is available in small diameter fuel rods capable of high power per rod (≅48 kW/rod) with acceptable peak fuel temperatures. The performance of a 10-MW research reactor with a compact core of hexagonal TRIGA fuel clusters has been calculated in detail. With its light water coolant, beryllium and D 2 O reflector regions, this reactor can provide in-core experiments with thermal fluxes in excess of 3 x 10 14 n/cm 2 ·s and fast fluxes (>0.1 MeV) of 2 x 10 14 n/cm 2 ·s. The core centerline thermal neutron flux in the D 2 O reflector is about 2 x 10 14 n/cm 2 ·s and the average core power density is about 230 kW/liter. Using other TRIGA fuel developed for 25-MW test reactors but arranged in hexagonal arrays, power densities in excess of 300 kW/liter are readily available. A core with TRIGA fuel operating at 15-MW and generating such a power density is capable of producing thermal neutron fluxes in a D 2 O reflector of 3 x 10 14 n/cm 2 ·s. A beryllium-filled central region of the core can further enhance the core leakage and hence the neutron flux in the reflector. (author)
Single-particle spectral density of the Hubbard model
Mehlig, B.; Eskes, H.; Hayn, R.; Meinders, M.B.J.
1995-01-01
We calculate the single-particle spectral function for the Hubbard model within the framework of a projection technique equivalent to the two-pole approximation. We show that the two-pole approximation can be well understood as an average characterization of the upper and the lower Hubbard bands,
SINGLE-PARTICLE SPECTRAL DENSITY OF THE HUBBARD-MODEL
MEHLIG, B; ESKES, H; HAYN, R; MEINDERS, MBJ
1995-01-01
We calculate the single-particle spectral function for the Hubbard model within the framework of a projection technique equivalent to the two-pole approximation. We show that the two-pole approximation can be well understood as an average characterization of the upper and the lower Hubbard bands,
POWER SPECTRUM DENSITY (PSD ANALYSIS OF AUTOMOTIVE PEDAL-PAD
Directory of Open Access Journals (Sweden)
AHMED RITHAUDDEEN YUSOFF
2016-04-01
Full Text Available Vibration at the pedal-pad may contribute to discomfort of foot plantar fascia during driving. This is due to transmission of vibration to the mount, chassis, pedal, and then to the foot plantar fascia. This experimental study is conducted to determine the estimation of peak value using the power spectral density of the vertical vibration input at the foot. The power spectral density value is calculated based on the frequency range between 13 Hz to 18 Hz. This experiment was conducted using 12 subjects testing on three size of pedal-pads; small, medium and large. The result shows that peak value occurs at resonance frequency of 15 Hz. The PSD values at that resonance frequency are 0.251 (m/s2 2/Hz for small pedal-pad, followed by the medium pedal-pad is at 0.387 (m/s2 2/Hz and lastly for the large pedal-pad is at 0.483 (m/s22/Hz. The resultsindicate that during driving, the foot vibration when interact with the large pedal-pad contributed higher stimulus compared with the small and medium pedal-pad. The pedal-pad size plays an important role in the pedal element designs in terms of vibration-transfer from pedal-pads on the feet, particularly to provide comfort to the driver while driving.
International Nuclear Information System (INIS)
Ashur, S. M.
2007-01-01
In this work current voltage characteristics and voltage spectral density, in both forward and reverse bias operations were evaluated for a group of mono- crystalline silicon solar cells. The cells were tested for the sake of device quality evaluation and identification of failure modes and mechanisms. Experimental results showed transport characteristics with varying slopes. In addition, electrical noise density versus frequency response, for the constant voltage mode, showed an extremum of noise voltage spectral density at zero D.C. frequency. It decreased with increasing frequency and revealed spikes of the noise voltage density at certain frequencies. (author)
[Estimation of Hunan forest carbon density based on spectral mixture analysis of MODIS data].
Yan, En-ping; Lin, Hui; Wang, Guang-xing; Chen, Zhen-xiong
2015-11-01
With the fast development of remote sensing technology, combining forest inventory sample plot data and remotely sensed images has become a widely used method to map forest carbon density. However, the existence of mixed pixels often impedes the improvement of forest carbon density mapping, especially when low spatial resolution images such as MODIS are used. In this study, MODIS images and national forest inventory sample plot data were used to conduct the study of estimation for forest carbon density. Linear spectral mixture analysis with and without constraint, and nonlinear spectral mixture analysis were compared to derive the fractions of different land use and land cover (LULC) types. Then sequential Gaussian co-simulation algorithm with and without the fraction images from spectral mixture analyses were employed to estimate forest carbon density of Hunan Province. Results showed that 1) Linear spectral mixture analysis with constraint, leading to a mean RMSE of 0.002, more accurately estimated the fractions of LULC types than linear spectral and nonlinear spectral mixture analyses; 2) Integrating spectral mixture analysis model and sequential Gaussian co-simulation algorithm increased the estimation accuracy of forest carbon density to 81.5% from 74.1%, and decreased the RMSE to 5.18 from 7.26; and 3) The mean value of forest carbon density for the province was 30.06 t · hm(-2), ranging from 0.00 to 67.35 t · hm(-2). This implied that the spectral mixture analysis provided a great potential to increase the estimation accuracy of forest carbon density on regional and global level.
A Fiber-Optic System Generating Pulses of High Spectral Density
Abramov, A. S.; Zolotovskii, I. O.; Korobko, D. A.; Fotiadi, A. A.
2018-03-01
A cascade fiber-optic system that generates pulses of high spectral density by using the effect of nonlinear spectral compression is proposed. It is demonstrated that the shape of the pulse envelope substantially influences the degree of compression of its spectrum. In so doing, maximum compression is achieved for parabolic pulses. The cascade system includes an optical fiber exhibiting normal dispersion that decreases along the fiber length, thereby ensuring that the pulse envelope evolves toward a parabolic shape, along with diffraction gratings and a fiber spectral compressor. Based on computer simulation, we determined parameters of cascade elements leading to maximum spectral density of radiation originating from a subpicosecond laser pulse of medium energy.
Transfer equations for spectral densities of inhomogeneous MHD turbulence
International Nuclear Information System (INIS)
Tu, C.-Y.; Marsch, E.
1990-01-01
On the basis of the dynamic equations governing the evolution of magnetohydrodynamic fluctuations expressed in terms of Elsaesser variables and of their correlation functions derived by Marsch and Tu, a new set of equations is presented describing the evolutions of the energy spectrum e ± and of the residual energy spectra e R and e S of MHD turbulence in an inhomogeneous magnetofluid. The nonlinearities associated with triple correlations in these equations are analysed in detail and evaluated approximately. The resulting energy-transfer functions across wavenumber space are discussed. For e ± they are shown to be approximately energy-conserving if the gradients of the flow speed and density are weak. New cascading functions are heuristically determined by an appropriate dimensional analysis and plausible physical arguments, following the standard phenomenology of fluid turbulence. However, for e R the triple correlations do not correspond to an 'energy' conserving process, but also represent a nonlinear source term for e R . If this source term can be neglected, the spectrum equations are found to be closed. The problem of dealing with the nonlinear source terms remains to be solved in future investigations. (author)
Dijk, Derk-Jan; Brunner, Daniel P.; Beersma, Domien G.M.; Borbély, Alexander A.
1990-01-01
Human sleep electroencephalograms, recorded in four experiments, were subjected to spectral analysis. Waking prior to sleep varied from 12 to 36 h and sleep was initiated at different circadian phases. Power density of delta and theta frequencies in rapid-eye-movement (REM) sleep and non-REM (NREM)
Data depth and rank-based tests for covariance and spectral density matrices
Chau, Joris
2017-06-26
In multivariate time series analysis, objects of primary interest to study cross-dependences in the time series are the autocovariance or spectral density matrices. Non-degenerate covariance and spectral density matrices are necessarily Hermitian and positive definite, and our primary goal is to develop new methods to analyze samples of such matrices. The main contribution of this paper is the generalization of the concept of statistical data depth for collections of covariance or spectral density matrices by exploiting the geometric properties of the space of Hermitian positive definite matrices as a Riemannian manifold. This allows one to naturally characterize most central or outlying matrices, but also provides a practical framework for rank-based hypothesis testing in the context of samples of covariance or spectral density matrices. First, the desired properties of a data depth function acting on the space of Hermitian positive definite matrices are presented. Second, we propose two computationally efficient pointwise and integrated data depth functions that satisfy each of these requirements. Several applications of the developed methodology are illustrated by the analysis of collections of spectral matrices in multivariate brain signal time series datasets.
Data depth and rank-based tests for covariance and spectral density matrices
Chau, Joris; Ombao, Hernando; Sachs, Rainer von
2017-01-01
In multivariate time series analysis, objects of primary interest to study cross-dependences in the time series are the autocovariance or spectral density matrices. Non-degenerate covariance and spectral density matrices are necessarily Hermitian and positive definite, and our primary goal is to develop new methods to analyze samples of such matrices. The main contribution of this paper is the generalization of the concept of statistical data depth for collections of covariance or spectral density matrices by exploiting the geometric properties of the space of Hermitian positive definite matrices as a Riemannian manifold. This allows one to naturally characterize most central or outlying matrices, but also provides a practical framework for rank-based hypothesis testing in the context of samples of covariance or spectral density matrices. First, the desired properties of a data depth function acting on the space of Hermitian positive definite matrices are presented. Second, we propose two computationally efficient pointwise and integrated data depth functions that satisfy each of these requirements. Several applications of the developed methodology are illustrated by the analysis of collections of spectral matrices in multivariate brain signal time series datasets.
Dirac spectral density and mass anomalous dimension in 2+1 flavor QCD
Directory of Open Access Journals (Sweden)
Nakayama Katsumasa
2018-01-01
Full Text Available We compute the Dirac spectral density of QCD in a wide range of eigenvalues by using a stochastic method. We use 2+1 flavor lattice ensembles generated with Mobius domain-wall fermion at three lattice spacings (a = 0:083; 0:055; 0:044 fm to estimate the continuum limit. The discretization effect can be minimized by a generalization of the valence domain-wall fermion. The spectral density at relatively high eigenvalues can be matched with perturbation theory. We compare the lattice results with the perturbative expansion available to O(α4s.
LNG pool fire spectral data and calculation of emissive power
International Nuclear Information System (INIS)
Raj, Phani K.
2007-01-01
burning in the LNG fire. The paper discusses the procedure by which the fire spectral data are used to predict the thermal emission from large LNG fires. Unfortunately, no direct measurements of the soot density or smoke characteristics were made in the tests. These parameters have significant effect on the thermal emission from large LNG fires
Surface of Maximums of AR(2 Process Spectral Densities and its Application in Time Series Statistics
Directory of Open Access Journals (Sweden)
Alexander V. Ivanov
2017-09-01
Conclusions. The obtained formula of surface of maximums of noise spectral densities gives an opportunity to realize for which values of AR(2 process characteristic polynomial coefficients it is possible to look for greater rate of convergence to zero of the probabilities of large deviations of the considered estimates.
Mass anomalous dimension of SU(2) with Nf=8 using the spectral density method
DEFF Research Database (Denmark)
Suorsa, Joni M.; Leino, Viljami; Rantaharju, Jarno
2015-01-01
SU(2) with Nf=8 is believed to have an infrared conformal fixed point. We use the spectral density method to evaluate the coupling constant dependence of the mass anomalous dimension for massless HEX smeared, clover improved Wilson fermions with Schr\\"odinger functional boundary conditions....
International Nuclear Information System (INIS)
Assaf, J.
2009-07-01
Mathematical model for the RMS noise of JFET transistor has been realized. Fitting the model according to the experimental results gives the noise spectral densities values. Best fitting was for the model of three noise sources and real preamplifier transfer function. After gamma irradiation, an additional and important noise sources appeared and two point defects are estimated through the fitting process. (author)
Structure-property relationship in dielectric mixtures: application of the spectral density theory
International Nuclear Information System (INIS)
Tuncer, Enis
2005-01-01
This paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites. The influence of structural differences and intrinsic electrical properties of constituents on the composite's overall electrical properties is investigated. The structural differences are resolved by fitting the dielectric data with an empirical formula and by the spectral density representation approach. At low concentrations of inclusions (concentrations lower than the percolation threshold), the spectral density functions are delta-sequences, which corresponds to the predictions of the general Maxwell-Garnett (MG) mixture formula. At high concentrations of inclusions (close to the percolation threshold) systems exhibit non-Debye-type dielectric dispersions, and the spectral density functions differ from each other and that predicted by the MG expression. The analysis of the dielectric dispersions with an empirical formula also brings out the structural differences between the considered geometries, however, the information is not qualitative. The empirical formula can only be used to compare structures. The spectral representation method on the other hand is a concrete way of characterizing the structures of the dielectric mixtures. Therefore, as in other spectroscopic techniques, a look-up table might be useful to classify/characterize structures of composite materials. This can be achieved by generating dielectric data for known structures by using ab initio calculations, as presented and emphasized in this study. The numerical technique presented here is not based on any a priori assumption methods
International Nuclear Information System (INIS)
Fiebig, H. Rudolf
2002-01-01
We study various aspects of extracting spectral information from time correlation functions of lattice QCD by means of Bayesian inference with an entropic prior, the maximum entropy method (MEM). Correlator functions of a heavy-light meson-meson system serve as a repository for lattice data with diverse statistical quality. Attention is given to spectral mass density functions, inferred from the data, and their dependence on the parameters of the MEM. We propose to employ simulated annealing, or cooling, to solve the Bayesian inference problem, and discuss the practical issues of the approach
Epileptic seizure prediction based on a bivariate spectral power methodology.
Bandarabadi, Mojtaba; Teixeira, Cesar A; Direito, Bruno; Dourado, Antonio
2012-01-01
The spectral power of 5 frequently considered frequency bands (Alpha, Beta, Gamma, Theta and Delta) for 6 EEG channels is computed and then all the possible pairwise combinations among the 30 features set, are used to create a 435 dimensional feature space. Two new feature selection methods are introduced to choose the best candidate features among those and to reduce the dimensionality of this feature space. The selected features are then fed to Support Vector Machines (SVMs) that classify the cerebral state in preictal and non-preictal classes. The outputs of the SVM are regularized using a method that accounts for the classification dynamics of the preictal class, also known as "Firing Power" method. The results obtained using our feature selection approaches are compared with the ones obtained using minimum Redundancy Maximum Relevance (mRMR) feature selection method. The results in a group of 12 patients of the EPILEPSIAE database, containing 46 seizures and 787 hours multichannel recording for out-of-sample data, indicate the efficiency of the bivariate approach as well as the two new feature selection methods. The best results presented sensitivity of 76.09% (35 of 46 seizures predicted) and a false prediction rate of 0.15(-1).
On the causes of spectral enhancements in solar wind power spectra
Unti, T.; Russell, C. T.
1976-01-01
Enhancements in power spectra of the solar-wind ion flux in the frequency neighborhood of 0.5 Hz had been noted by Unti et al. (1973). It was speculated that these were due to convected small-scale density irregularities. In this paper, 54 flux spectra calculated from OGO 5 data are examined. It is seen that the few prominent spectral peaks which occur were not generated by density irregularities, but were due to several different causes, including convected discontinuities and propagating transverse waves. A superposition of many spectra, however, reveals a moderate enhancement at a frequency corresponding to convected features with a correlation length of a proton gyroradius, consistent with the results of Neugebauer (1975).
Calculation of power density with MCNP in TRIGA reactor
International Nuclear Information System (INIS)
Snoj, L.; Ravnik, M.
2006-01-01
Modern Monte Carlo codes (e.g. MCNP) allow calculation of power density distribution in 3-D geometry assuming detailed geometry without unit-cell homogenization. To normalize MCNP calculation by the steady-state thermal power of a reactor, one must use appropriate scaling factors. The description of the scaling factors is not adequately described in the MCNP manual and requires detailed knowledge of the code model. As the application of MCNP for power density calculation in TRIGA reactors has not been reported in open literature, the procedure of calculating power density with MCNP and its normalization to the power level of a reactor is described in the paper. (author)
Power density forecasting device for nuclear power plant
International Nuclear Information System (INIS)
Fukuzaki, Takaharu; Kiguchi, Takashi.
1978-01-01
Purpose: To attain effective reactor operation in a bwr type reactor by forecasting the power density of the reactor after adjustment and comparing the same with the present status of the reactor by the on-line calculation in a short time. Constitution: The present status for the reactor is estimated in a present status decision section based on a measurement signal from the reactor and it is stored in an operation result collection section. The reactor status after the forecasting is estimated in a forecasting section based on a setting signal from a forecasting condition setting section and it is compared with the result value from the operation results collection section. If the forecast value does not coincide with the result value in the above comparison, the setting value in the forecast condition setting section is changed in the control section. The above procedures are repeated so as to minimize the difference between the forecast value and the result value to thereby exactly forecast the reactor status and operate the reactor effectively. (Moriyama, K.)
Spectral density of Cooper pairs in two level quantum dot–superconductors Josephson junction
Energy Technology Data Exchange (ETDEWEB)
Dhyani, A., E-mail: archana.d2003@gmail.com [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Rawat, P.S. [Department of Nuclear Science and Technology, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Tewari, B.S., E-mail: bstewari@ddn.upes.ac.in [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India)
2016-09-15
Highlights: • The present work deals with the study of the electronic spectral density of electron pairs and its effect in charge transport in superconductor-quantum dot-superconductor junctions. • The charge transfer across such junctions can be controlled by changing the positions of the dot level. • The Josephson supercurrent can also be tuned by controlling the position of quantum dot energy levels. - Abstract: In the present paper, we report the role of quantum dot energy levels on the electronic spectral density for a two level quantum dot coupled to s-wave superconducting leads. The theoretical arguments in this work are based on the Anderson model so that it necessarily includes dot energies, single particle tunneling and superconducting order parameter for BCS superconductors. The expression for single particle spectral function is obtained by using the Green's function equation of motion technique. On the basis of numerical computation of spectral function of superconducting leads, it has been found that the charge transfer across such junctions can be controlled by the positions and availability of the dot levels.
Sum rules and spectral density flow in QCD and in superconformal theories
Directory of Open Access Journals (Sweden)
Costantini Antonio
2014-01-01
Full Text Available We discuss the signature of the anomalous breaking of the superconformal symmetry in N${\\cal N}$ = 1 super Yang Mills theory and its manifestation in the form of anomaly poles. Moreover, we describe the massive deformations of the N${\\cal N}$ = 1 theory and the spectral densities of the corresponding anomaly form factors. These are characterized by spectral densities which flow with the mass deformation and turn the continuum contributions from the two-particle cuts of the intermediate states into poles, with a single sum rule satisfied by each component. The poles can be interpreted as signaling the exchange of a composite axion/dilaton/dilatino (ADD multiplet in the effective Lagrangian. We conclude that global anomalous currents characterized by a single flow in the perturbative picture always predict the existence of composite interpolating fields.
Asymmetries in the spectral density of an interaction-quenched Luttinger liquid
Calzona, A.; Gambetta, F. M.; Carrega, M.; Cavaliere, F.; Sassetti, M.
2018-03-01
The spectral density of an interaction-quenched one-dimensional system is investigated. Both direct and inverse quench protocols are considered and it is found that the former leads to stronger effects on the spectral density with respect to the latter. Such asymmetry is directly reflected on transport properties of the system, namely the charge and energy current flowing to the system from a tunnel coupled biased probe. In particular, the injection of particles from the probe to the right-moving channel of the system is considered. The resulting fractionalization phenomena are strongly affected by the quench protocol and display asymmetries in the case of direct and inverse quench. Transport properties therefore emerge as natural probes for the observation of this quench-induced behavior.
Entanglement in random pure states: spectral density and average von Neumann entropy
Energy Technology Data Exchange (ETDEWEB)
Kumar, Santosh; Pandey, Akhilesh, E-mail: skumar.physics@gmail.com, E-mail: ap0700@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India)
2011-11-04
Quantum entanglement plays a crucial role in quantum information, quantum teleportation and quantum computation. The information about the entanglement content between subsystems of the composite system is encoded in the Schmidt eigenvalues. We derive here closed expressions for the spectral density of Schmidt eigenvalues for all three invariant classes of random matrix ensembles. We also obtain exact results for average von Neumann entropy. We find that maximum average entanglement is achieved if the system belongs to the symplectic invariant class. (paper)
Ambient RF energy scavenging: GSM and WLAN power density measurements
Visser, H.J.; Reniers, A.C.F.; Theeuwes, J.A.C.
2009-01-01
To assess the feasibility of ambient RF energy scavenging, a survey of expected power density levels distant from GSM-900 and GSM-1800 base stations has been conducted and power density measurements have been performed in a WLAN environment. It appears that for distances ranging from 25 m to 100 m
A performance analysis for MHD power cycles operating at maximum power density
International Nuclear Information System (INIS)
Sahin, Bahri; Kodal, Ali; Yavuz, Hasbi
1996-01-01
An analysis of the thermal efficiency of a magnetohydrodynamic (MHD) power cycle at maximum power density for a constant velocity type MHD generator has been carried out. The irreversibilities at the compressor and the MHD generator are taken into account. The results obtained from power density analysis were compared with those of maximum power analysis. It is shown that by using the power density criteria the MHD cycle efficiency can be increased effectively. (author)
Response of Spectral Reflectances and Vegetation Indices on Varying Juniper Cone Densities
Directory of Open Access Journals (Sweden)
Guillermo E. Ponce-Campos
2013-10-01
Full Text Available Juniper trees are widely distributed throughout the world and are common sources of allergies when microscopic pollen grains are transported by wind and inhaled. In this study, we investigated the spectral influences of pollen-discharging male juniper cones within a juniper canopy. This was done through a controlled outdoor experiment involving ASD FieldSpec Pro Spectroradiometer measurements over juniper canopies of varying cone densities. Broadband and narrowband spectral reflectance and vegetation index (VI patterns were evaluated as to their sensitivity and their ability to discriminate the presence of cones. The overall aim of this research was to assess remotely sensed phenological capabilities to detect pollen-bearing juniper trees for public health applications. A general decrease in reflectance values with increasing juniper cone density was found, particularly in the Green (545–565 nm and NIR (750–1,350 nm regions. In contrast, reflectances in the shortwave-infrared (SWIR, 2,000 nm to 2,350 nm region decreased from no cone presence to intermediate amounts (90 g/m2 and then increased from intermediate levels to the highest cone densities (200 g/m2. Reflectance patterns in the Red (620–700 nm were more complex due to shifting contrast patterns in absorptance between cones and juniper foliage, where juniper foliage is more absorbing than cones only within the intense narrowband region of maximum chlorophyll absorption near 680 nm. Overall, narrowband reflectances were more sensitive to cone density changes than the equivalent MODIS broadbands. In all VIs analyzed, there were significant relationships with cone density levels, particularly with the narrowband versions and the two-band vegetation index (TBVI based on Green and Red bands, a promising outcome for the use of phenocams in juniper phenology trait studies. These results indicate that spectral indices are sensitive to certain juniper phenologic traits that can potentially be
International Nuclear Information System (INIS)
Woo, R.; Armstrong, J.W.
1979-01-01
Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2--215 R/sub S/, and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances > or approx. =20 R/sub S/ the equivalent spacecraft-measured one-dimensional density spectrym V/sub n/e is well modeled by a single power law (f/sup -alpha/) in the frequency range 10 -4 -5 x 10 -2 Hz. The mean spectral index α is 1.65, very close to the Kolmogorov value of 5/3. Under the assumption of constant solar wind speed, V/sub n/e varies as R/sup -3.45/, where R is heliocentric distance. Within 20 R/sub S/, V/sub n/e can still be modeled by a single power law over the frequency range 10 -3 -10 1 Hz, but the spectral index becomes smaller, αapprox.1.1. The flattening of the density spectrum with 20 R/sub S/ is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind
International Nuclear Information System (INIS)
Obarski, Gregory E.; Splett, Jolene D.
2001-01-01
We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band (<5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is -110 dB/Hz, with uncertainty ≤0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by ≤0.2 dB. [copyright] 2001 Optical Society of America
Energy Technology Data Exchange (ETDEWEB)
Obarski, Gregory E.; Splett, Jolene D.
2001-06-01
We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band ({lt}5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is {minus}110 dB/Hz, with uncertainty {le}0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by {le}0.2 dB. {copyright} 2001 Optical Society of America
ICRF power limitation relation to density limit in ASDEX
International Nuclear Information System (INIS)
Ryter, F.
1992-01-01
Launching high ICRF power into ASDEX plasmas required good antenna-plasma coupling. This could be achieved by sufficient electron density in front of the antennas i.e. small antenna-plasma distance (1-2 cm) and moderate to high line-averaged electron density compared to the density window in ASDEX. These are conditions eventually close to the density limit. ICRF heated discharges terminated by plasma disruptions caused by the RF pulse limited the maximum RF power which can be injected into the plasma. The disruptions occurring in these cases have clear phenomenological similarities with those observed in density limit discharges. We show in this paper that the ICRF-power limitation by plasma disruptions in ASDEX was due to reaching the density limit. (orig.)
ICRF power limitation relation to density limit in ASDEX
International Nuclear Information System (INIS)
Ryter, F.
1992-01-01
Launching high ICRF power into ASDEX plasmas required good antenna-plasma coupling. This could be achieved by sufficient electron density in front of the antennas i.e. small antenna-plasma distance (1-2 cm) and moderate to high line-averaged electron density compared to the density window in ASDEX. These are conditions eventually close to the density limit. ICRF heated discharges terminated by plasma disruptions caused by the RF pulse limited the maximum RF power which can be injected into the plasma. The disruptions occurring in these cases have clear phenomenological similarities with those observed in density limit discharges. We show in this paper that the ICRF-power limitation by plasma disruptions in ASDEX was due to reaching the density limit. (author) 3 refs., 3 figs
Laboratory calibration of density-dependent lines in the extreme ultraviolet spectral region
Lepson, J. K.; Beiersdorfer, P.; Gu, M. F.; Desai, P.; Bitter, M.; Roquemore, L.; Reinke, M. L.
2012-05-01
We have been making spectral measurements in the extreme ultraviolet (EUV) from different laboratory sources in order to investigate the electron density dependence of various astrophysically important emission lines and to test the atomic models underlying the diagnostic line ratios. The measurement are being performed at the Livermore EBIT-I electron beam ion trap, the National Spherical Torus Experiment (NSTX) at Princeton, and the Alcator C-Mod tokamak at the Massachusetts Institute of Technology, which together span an electron density of four orders of magnitude and which allow us to test the various models at high and low density limits. Here we present measurements of Fe XXII and Ar XIV, which include new data from an ultra high resolution (λ/Δλ >4000) spectrometer at the EBIT-I facility. We found good agreement between the measurements and modeling calculations for Fe XXII, but poorer agreement for Ar XIV.
Plasma density characterization at SPARC-LAB through Stark broadening of Hydrogen spectral lines
International Nuclear Information System (INIS)
Filippi, F.; Anania, M.P.; Bellaveglia, M.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F.; Zigler, A.
2016-01-01
Plasma-based acceleration techniques are of great interest for future, compact accelerators due to their high accelerating gradient. Both particle-driven and laser-driven Plasma Wakefield Acceleration experiments are foreseen at the SPARC-LAB Test Facility (INFN National Laboratories of Frascati, Italy), with the aim to accelerate high-brightness electron beams. In order to optimize the efficiency of the acceleration in the plasma and preserve the quality of the accelerated beam, the knowledge of the plasma electron density is mandatory. The Stark broadening of the Hydrogen spectral lines is one of the candidates used to characterize plasma density. The implementation of this diagnostic for plasma-based experiments at SPARC-LAB is presented. - Highlights: • Stark broadening of Hydrogen lines has been measured to determine plasma density. • Plasma density diagnostic tool for plasma-based experiments at SPARC-LAB is presented. • Plasma density in tapered laser triggered ablative capillary discharge was measured. • Results of plasma density measurements in ablative capillaries are shown.
Plasma density characterization at SPARC-LAB through Stark broadening of Hydrogen spectral lines
Energy Technology Data Exchange (ETDEWEB)
Filippi, F., E-mail: francesco.filippi@roma1.infn.it [Dipartimento di Scienze di Base e Applicate per l' Ingegneria (SBAI), ‘Sapienza’ Università di Roma, Via A. Scarpa 14-16, 00161 Roma (Italy); INFN-Roma1, Piazzale Aldo Moro, 2 00161 Roma (Italy); Anania, M.P.; Bellaveglia, M.; Biagioni, A.; Chiadroni, E. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi, Frascati (Italy); Cianchi, A. [Dipartimento di Fisica, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Di Giovenale, D.; Di Pirro, G.; Ferrario, M. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi, Frascati (Italy); Mostacci, A.; Palumbo, L. [Dipartimento di Scienze di Base e Applicate per l' Ingegneria (SBAI), ‘Sapienza’ Università di Roma, Via A. Scarpa 14-16, 00161 Roma (Italy); INFN-Roma1, Piazzale Aldo Moro, 2 00161 Roma (Italy); Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi, Frascati (Italy); Zigler, A. [Hebrew University of Jerusalem, Jerusalem 91904 (Israel)
2016-09-01
Plasma-based acceleration techniques are of great interest for future, compact accelerators due to their high accelerating gradient. Both particle-driven and laser-driven Plasma Wakefield Acceleration experiments are foreseen at the SPARC-LAB Test Facility (INFN National Laboratories of Frascati, Italy), with the aim to accelerate high-brightness electron beams. In order to optimize the efficiency of the acceleration in the plasma and preserve the quality of the accelerated beam, the knowledge of the plasma electron density is mandatory. The Stark broadening of the Hydrogen spectral lines is one of the candidates used to characterize plasma density. The implementation of this diagnostic for plasma-based experiments at SPARC-LAB is presented. - Highlights: • Stark broadening of Hydrogen lines has been measured to determine plasma density. • Plasma density diagnostic tool for plasma-based experiments at SPARC-LAB is presented. • Plasma density in tapered laser triggered ablative capillary discharge was measured. • Results of plasma density measurements in ablative capillaries are shown.
Luczynska, Elzbieta; Niemiec, Joanna; Ambicka, Aleksandra; Adamczyk, Agnieszka; Walasek, Tomasz; Ryś, Janusz; Sas-Korczyńska, Beata
2015-09-01
Contrast-enhanced spectral mammography (CESM) is a novel technique used for detection of tumour vascularity by imaging the moment in which contrast, delivered to the lesion by blood vessels, leaks out of them, and flows out through lymphatic vessels. In our study, we included 174 women for whom spectral mammography was performed for diagnostic purposes. The relationship between enhancement in CESM and blood vessel density (BVD), lymphatic vessel density (LVD) or the percentage of fields with at least one lymphatic vessel (distribution of podoplanin-positive vessels - DPV) and other related parameters was assessed in 55 cases. BVD, LVD and DPV were assessed immunohistochemically, applying podoplanin and CD31/CD34 as markers of lymphatic and blood vessels, respectively. The sensitivity (in detection of malignant lesions) of CESM was 100%, while its specificity - 39%. We found a significant positive correlation between the intensity of enhancement in CESM and BVD (p = 0.007, r = 0.357) and a negative correlation between the intensity of enhancement in CESM and DPV (p = 0.003, r = -0.390). Lesions with the highest enhancement in CESM showed a high number of blood vessels and a low number of lymphatics. 1) CESM is a method characterized by high sensitivity and acceptable specificity; 2) the correlation between CESM results and blood/lymphatic vessel density confirms its utility in detection of tissue angiogenesis and/or lymphangiogenesis.
Institute of Scientific and Technical Information of China (English)
汤浩
2014-01-01
Objective To explore the discrepancies of individualized frequency and band power between major depressive disorder(MDD)and controls in resting state,and the association of abnormal spectral power with clinical severity of MDD.Methods Whole-head MEG recordings were collected in 19 patients with MDD and 19 non-depressed controls in eye-closed resting state.Individual spectral power of each subject was calculated based on
LENUS (Irish Health Repository)
Mahon, P
2012-02-03
BACKGROUND: In this study we analyse the behaviour, potential clinical application and optimal cortical sampling location of the spectral parameters: (i) relative alpha and beta power; (ii) spectral edge frequency 90%; and (iii) spectral entropy as monitors of moderate propofol-induced sedation. METHODS: Multi-channel EEG recorded from 12 ASA 1 (American Society of Anesthesiologists physical status 1) patients during low-dose, target effect-site controlled propofol infusion was used for this analysis. The initial target effect-site concentration was 0.5 microg ml(-1) and increased at 4 min intervals in increments of 0.5 to 2 microg ml(-1). EEG parameters were calculated for 2 s epochs in the frequency ranges 0.5-32 and 0.5-47 Hz. All parameters were calculated in the channels: P4-O2, P3-O1, F4-C4, F3-C3, F3-F4, and Fp1-Fp2. Sedation was assessed clinically using the OAA\\/S (observer\\'s assessment of alertness\\/sedation) scale. RESULTS: Relative beta power and spectral entropy increased with increasing propofol effect-site concentration in both the 0.5-47 Hz [F(18, 90) = 3.455, P<0.05 and F(18, 90) = 3.33, P<0.05, respectively] and 0.5-32 Hz frequency range. This effect was significant in each individual channel (P<0.05). No effect was seen of increasing effect-site concentration on relative power in the alpha band. Averaged across all channels, spectral entropy did not outperform relative beta power in either the 0.5-32 Hz [Pk=0.79 vs 0.814 (P>0.05)] or 0.5-47 Hz range [Pk=0.81 vs 0.82 (P>0.05)]. The best performing indicator in any single channel was spectral entropy in the frequency range 0.5-47 Hz in the frontal channel F3-F4 (Pk=0.85). CONCLUSIONS: Relative beta power and spectral entropy when considered over the propofol effect-site range studied here increase in value, and correlate well with clinical assessment of sedation.
High volumetric power density, non-enzymatic, glucose fuel cells.
Oncescu, Vlad; Erickson, David
2013-01-01
The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an "oxygen depletion design" whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm⁻²) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm⁻³). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells.
Dijk, Derk Jan; Beersma, Domien G.M.; Daan, Serge; Bloem, Gerda M.; Hoofdakker, Rutger H. van den
1987-01-01
The relation between EEG power density during slow wave sleep (SWS) deprivation and power density during subsequent sleep was investigated. Nine young male adults slept in the laboratory for 3 consecutive nights. Spectral analysis of the EEG on the 2nd (baseline) night revealed an exponential
Magnetic field power density spectra during 'scatter-free' solar particle events
Tan, L. C.; Mason, G. M.
1993-01-01
We have examined interplanetary magnetic field power spectral density during four previously identified 3He-rich flare periods when the about 1 MeV nucleon-1 particles exhibited nearly scatter-free transport from the sun to 1 AU. Since the scattering mean free path A was large, it might be expected that interplanetary turbulence was low, yet the spectral density value was low only for one of the four periods. For the other three, however, the spectral index q of the power density spectrum was near 2.0, a value at which quasi-linear theories predict an increase in the scattering mean free path. Comparing the lambda values from the energetic particles with that computed from a recent quasi-linear theory which includes helicity and the propagation direction of waves, we find lambda(QLT)/lambda(SEP) = 0.08 +/- 0.03 for the four events. Thus, the theory fits the q-dependence of lambda; however, as found for previous quasi-linear theories, the absolute value is low.
Spectral classification of medium-scale high-latitude F region plasma density irregularities
International Nuclear Information System (INIS)
Singh, M.; Rodriguez, P.; Szuszczewicz, E.P.; Sachs Freeman Associates, Bowie, MD)
1985-01-01
The high-latitude ionosphere represents a highly structured plasma. Rodriguez and Szuszczewicz (1984) reported a wide range of plasma density irregularities (150 km to 75 m) at high latitudes near 200 km. They have shown that the small-scale irregularities (7.5 km to 75 m) populated the dayside oval more often than the other phenomenological regions. It was suggested that in the lower F region the chemical recombination is fast enough to remove small-scale irregularities before convection can transport them large distances, leaving structured particle precipitation as the dominant source term for irregularities. The present paper provides the results of spectral analyses of pulsed plasma probe data collected in situ aboard the STP/S3-4 satellite during the period March-September 1978. A quantitative description of irregularity spectra in the high-latitude lower F region plasma density is given. 22 references
A numerical spectral approach to solve the dislocation density transport equation
International Nuclear Information System (INIS)
Djaka, K S; Taupin, V; Berbenni, S; Fressengeas, C
2015-01-01
A numerical spectral approach is developed to solve in a fast, stable and accurate fashion, the quasi-linear hyperbolic transport equation governing the spatio-temporal evolution of the dislocation density tensor in the mechanics of dislocation fields. The approach relies on using the Fast Fourier Transform algorithm. Low-pass spectral filters are employed to control both the high frequency Gibbs oscillations inherent to the Fourier method and the fast-growing numerical instabilities resulting from the hyperbolic nature of the transport equation. The numerical scheme is validated by comparison with an exact solution in the 1D case corresponding to dislocation dipole annihilation. The expansion and annihilation of dislocation loops in 2D and 3D settings are also produced and compared with finite element approximations. The spectral solutions are shown to be stable, more accurate for low Courant numbers and much less computation time-consuming than the finite element technique based on an explicit Galerkin-least squares scheme. (paper)
Measurements and analysis of the noise spectral density of YBCO films
International Nuclear Information System (INIS)
Taoufik, A.; Bghour, M.; Labrag, A.; Bouaaddi, A.; Abaragh, A.; Ramzi, A.; Senoussi, S.; Tirbiyine, A.
2006-01-01
We studied the voltage noise spectral density S V (f,T,H) dependence on frequency f, temperature T and applied magnetic field H in YBa 2 Cu 3 O 7-δ films. The voltage noise spectral density S V (f) as a function of frequency exhibits 1/f behavior according to a Lorentzian shape A [(1+πf/f 0 ) B ] C , where A, f 0 , B, C constants which are determined and compared for many values of H. The influence of temperature and magnetic field is clearly observed as a function of temperature, S V (T) is found to vanish at T g , the temperature of vortex glass transition, according to a (T-T g ) x law. We interpreted those results by the formation of a large distribution of glass vortex domains. Approaching T g , these domains grow in size and lifetime, while at T g those parameters diverge. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)
Uehara, Mayuko; Takagi, Nobuyuki; Muraki, Satoshi; Yanase, Yosuke; Tabuchi, Masaki; Tachibana, Kazutoshi; Miyaki, Yasuko; Ito, Toshiro; Higami, Tetsuya
2015-12-01
Transit-time flow measurement (TTFM) parameters such as mean graft flow (MGF, ml/min), pulsatility index (PI) and diastolic filling (DF, %) have been extensively researched for internal mammary arterial or saphenous vein grafts. In our experience of using the right gastroepiploic arterial (GEA) graft for right coronary artery (RCA) grafting, we observed unique GEA graft flow waveforms. We analysed the GEA graft flow waveforms for their effectiveness in determining GEA graft patency by power spectral analysis. Forty-five patients underwent off-pump coronary artery bypass using the GEA graft for RCA grafting individually. The means of intraoperative MGF, PI and DF were compared between patent and non-patent grafts, postoperatively. Furthermore, the GEA flow data were output and analysed using power spectral analysis. Forty grafts were 'patent' and five were 'non-patent'. There were no significant differences in the mean TTFM parameters between the patent and non-patent grafts (MGF: 22 vs 8 ml/min, respectively, P = 0.068; PI: 3.5 vs 6.5, respectively, P = 0.155; DF: 63 vs 53%, respectively, P = 0.237). Results of the power spectral analysis presented clear differences; the power spectral density (PSD) of patent grafts presented high peaks at frequency levels of 1, 2 and 3 Hz, and the non-patent graft PSD presented high peaks that were not limited to these frequencies. The PSD had a sensitivity and specificity of 80 and 87.5%, respectively. Power spectral analysis of the GEA graft flow is useful to distinguish between non-patent and patent grafts intraoperatively. This should be used as a fourth parameter along with MGF, PI and DF. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
Improving Power Density of Free-Piston Stirling Engines
Briggs, Maxwell H.; Prahl, Joseph M.; Loparo, Kenneth A.
2016-01-01
Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free-piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58 percent using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a piston power increase of as much as 14 percent. Analytical predictions are compared to experimental data and show close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.
Improving Free-Piston Stirling Engine Power Density
Briggs, Maxwell H.
2016-01-01
Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.
PIII Plasma Density Enhancement by a New DC Power Source
International Nuclear Information System (INIS)
Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Granda-Gutierrez, E. E.; Piedad-Beneitez, A. de la; Munoz-Castro, A. E.; Valencia A, R.; Barocio, S. R.; Mercado-Cabrera, A.; Pena-Eguiluz, R.
2006-01-01
In practical terms, those plasmas produced by a DC voltage power supply do not attain densities above the 108 to 109 cm-3 band. Here we present a power supply, controlled in current and voltage, which has been successfully designed and constructed delivering plasma densities in the orders of 109 - 1010 cm-3. Its experimental performance test was conducted within one toroidal and one cylindrical chambers capable of 29 and 35 litres, respectively, using nitrogen gas. The DC plasma was characterized by a double electric probe. Several physical phenomena present in the PIII process have been keenly investigated including plasma sheath dynamics, interaction of plasma and surface, etc. In this paper we analyze the effect of the implantation voltage, plasma density and pulse time in the PIII average heating power and fluence density
Time-variant power spectral analysis of heart-rate time series by ...
Indian Academy of Sciences (India)
Frequency domain representation of a short-term heart-rate time series (HRTS) signal is a popular method for evaluating the cardiovascular control system. The spectral parameters, viz. percentage power in low frequency band (%PLF), percentage power in high frequency band (%PHF), power ratio of low frequency to high ...
High power density yeast catalyzed microbial fuel cells
Ganguli, Rahul
Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density
Evaluation of neutron flux density and power density with SPN-detectors and micro calorimeters
International Nuclear Information System (INIS)
Gehre, G.; Rindelhardt, U.; Seidenkranz, T.; Hogel, J.; Jirousek, V.; Vazek, J.
1983-02-01
During investigations with a special equipped fuel assembly in the Rheinsberg nuclear power station the neutron flux and the power density were evaluated from measurements with SPN-detectors and micro calorimeters. The reliability of both detector types, their measurement accuracy under different physical conditions and the usefulness of the developed calculation models are discussed in detail. The thermal flux and the power density evaluated with SPND's agree well with theoretical results. The values obtained through micro calorimeter measurements are systematic lower by about 18%. This deviation is probably a result of differences in the used calculation models. (author)
Hati, Archita; Nelson, Craig W.; Pappas, David P.; Howe, David A.
2017-11-01
The cross-spectrum noise measurement technique enables enhanced resolution of spectral measurements. However, it has disadvantages, namely, increased complexity, inability of making real-time measurements, and bias due to the "cross-spectral collapse" (CSC) effect. The CSC can occur when the spectral density of a random process under investigation approaches the thermal noise of the power splitter. This effect can severely bias results due to a differential measurement between the investigated noise and the anti-correlated (phase-inverted) noise of the power splitter. In this paper, we report an accurate measurement of the phase noise of a thermally limited electronic oscillator operating at room temperature (300 K) without significant CSC bias. We mitigated the problem by cooling the power splitter to liquid helium temperature (4 K). We quantify errors of greater than 1 dB that occur when the thermal noise of the oscillator at room temperature is measured with the power splitter at temperatures above 77 K.
International Nuclear Information System (INIS)
Rekik, Najeh
2014-01-01
Despite the considerable progress made in quantum theory and computational methods, detailed descriptions of the potential energy surfaces of hydrogen-bonded systems have not yet been achieved. In addition, the hydrogen bond (H-bond) itself is still so poorly understood at the fundamental level that it remains unclear exactly what geometry constitutes a “real” H-bond. Therefore, in order to investigate features essential for hydrogen bonded complexes, a simple, efficient, and general method for calculating matrix elements of vibrational operators capable of describing the stretching modes and the H-bond bridges of hydrogen-bonded systems is proposed. The derived matrix elements are simple and computationally easy to evaluate, which makes the method suitable for vibrational studies of multiple-well potentials. The method is illustrated by obtaining potential energy surfaces for a number of two-dimensional systems with repulsive potentials chosen to be in Gaussian form for the stretching mode and of the Morse-type for the H-bond bridge dynamics. The forms of potential energy surfaces of weak and strong hydrogen bonds are analyzed by varying the asymmetry of the Gaussian potential. Moreover, the choice and applicability of the selected potential for the stretching mode and comparison with other potentials used in the area of hydrogen bond research are discussed. The approach for the determination of spectral density has been constructed in the framework of the linear response theory for which spectral density is obtained by Fourier transform of the autocorrelation function of the dipole moment operator of the fast mode. The approach involves anharmonic coupling between the high frequency stretching vibration (double well potential) and low-frequency donor-acceptor stretching mode (Morse potential) as well as the electrical anharmonicity of the dipole moment operator of the fast mode. A direct relaxation mechanism is incorporated through a time decaying exponential
DEFF Research Database (Denmark)
Li, Qingnan; Andersen, Michael A. E.; Thomsen, Ole Cornelius
2011-01-01
Nowadays, efficiency and power density are the most important issues for Power Factor Correction (PFC) converters development. However, it is a challenge to reach both high efficiency and power density in a system at the same time. In this paper, taking a Bridgeless PFC (BPFC) as an example......, a useful compromise between efficiency and power density of the Boost inductors on 3.2kW is achieved using an optimized design procedure. The experimental verifications based on the optimized inductor are carried out from 300W to 3.2kW at 220Vac input....
Stopping power of degenerate electron liquid at metallic densities
International Nuclear Information System (INIS)
Tanaka, Shigenori; Ichimaru, Setsuo
1985-01-01
We calculate the stopping power of the degenerate electron liquid at metallic densities in the dielectric formalism. The strong Coulomb-coupling effects beyond the random-phase approximation are taken into account through the static and dynamic local-field corrections. It is shown that those strong-coupling and dynamic effects act to enhance the stopping power substantially in the low-velocity regime, leading to an improved agreement with experimental data. (author)
Effect of a pulsed power supply on the spectral and electrical characteristics of HID lamps
International Nuclear Information System (INIS)
Chammam, Abdeljelil; Elloumi, Hatem; Mrabet, Brahim; Charrada, Kamel; Stambouli, Mongi; Damelincourt, Jean Jacques
2005-01-01
Results of spectral and photometric measurements are presented for pulsed power operated high intensity discharges (HIDs). This investigation is related to the application of a pulsed power supply for pile driving of HID lamps. Specifically, we are interested in controlling the spectral response radiation of visible and ultraviolet (UV) lines for tertiary treatment of water using UV radiation. Simulations based on a physical model of the lamps were conducted. These results relate to the radial temperature, line intensity and electrical properties (voltage, power and conductivity). Good agreement has been found between the results of the simulations and the experimental findings
Spectral, spatial and temporal control of high-power diode lasers through nonlinear optical feedback
van Voorst, P.D.
2008-01-01
A high-power diode laser offers multi-Watt output power from a small and efficient device, which makes them an interesting source for numerous applications. The spatial and spectral output however, are of reduced quality which limits the applicability. This limited quality is connected to the design
High-Power-Density, High-Energy-Density Fluorinated Graphene for Primary Lithium Batteries
Directory of Open Access Journals (Sweden)
Guiming Zhong
2018-03-01
Full Text Available Li/CFx is one of the highest-energy-density primary batteries; however, poor rate capability hinders its practical applications in high-power devices. Here we report a preparation of fluorinated graphene (GFx with superior performance through a direct gas fluorination method. We find that the so-called “semi-ionic” C-F bond content in all C-F bonds presents a more critical impact on rate performance of the GFx in comparison with sp2 C content in the GFx, morphology, structure, and specific surface area of the materials. The rate capability remains excellent before the semi-ionic C-F bond proportion in the GFx decreases. Thus, by optimizing semi-ionic C-F content in our GFx, we obtain the optimal x of 0.8, with which the GF0.8 exhibits a very high energy density of 1,073 Wh kg−1 and an excellent power density of 21,460 W kg−1 at a high current density of 10 A g−1. More importantly, our approach opens a new avenue to obtain fluorinated carbon with high energy densities without compromising high power densities.
Yip, N.Y.; Vermaas, D.A.; Nijmeijer, K.; Elimelech, M.
2014-01-01
Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we
47 CFR 25.208 - Power flux density limits.
2010-10-01
... 47 Telecommunication 2 2010-10-01 2010-10-01 false Power flux density limits. 25.208 Section 25.208 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE... emissions from all co-frequency space stations of a single non-geostationary-satellite orbit (NGSO) system...
Dimmable electronic ballasts by variable power density modulation technique
Borekci, Selim; Kesler, Selami
2014-11-01
Dimming can be accomplished commonly by switching frequency and pulse density modulation techniques and a variable inductor. In this study, a variable power density modulation (VPDM) control technique is proposed for dimming applications. A fluorescent lamp is operated in several states to meet the desired lamp power in a modulation period. The proposed technique has the same advantages of magnetic dimming topologies have. In addition, a unique and flexible control technique can be achieved. A prototype dimmable electronic ballast is built and experiments related to it have been conducted. As a result, a 36WT8 fluorescent lamp can be driven for a desired lamp power from several alternatives without modulating the switching frequency.
Nonimaging optical designs for maximum-power-density remote irradiation.
Feuermann, D; Gordon, J M; Ries, H
1998-04-01
Designs for flexible, high-power-density, remote irradiation systems are presented. Applications include industrial infrared heating such as in semiconductor processing, alternatives to laser light for certain medical procedures, and general remote high-brightness lighting. The high power densities in herent to the small active radiating regions of conventional metal-halide, halogen, xenon, microwave-sulfur, and related lamps can be restored with nonimaging concentrators with little loss of power. These high fluxlevels can then be transported at high transmissivity with light channels such as optical fibers or lightpipes, and reshaped into luminaires that can deliver prescribed angular and spatial flux distributions onto desired targets. Details for nominally two- and three-dimensional systems are developed, along with estimates ofoptical performance.
High Energy Density Sciences with High Power Lasers at SACLA
Kodama, Ryosuke
2013-10-01
One of the interesting topics on high energy density sciences with high power lasers is creation of extremely high pressures in material. The pressures of more than 0.1 TPa are the energy density corresponding to the chemical bonding energy, resulting in expectation of dramatic changes in the chemical reactions. At pressures of more than TPa, most of material would be melted on the shock Hugoniot curve. However, if the temperature is less than 1eV or lower than a melting point at pressures of more than TPa, novel solid states of matter must be created through a pressured phase transition. One of the interesting materials must be carbon. At pressures of more than TPa, the diamond structure changes to BC and cubic at more than 3TPa. To create such novel states of matter, several kinds of isentropic-like compression techniques are being developed with high power lasers. To explore the ``Tera-Pascal Science,'' now we have a new tool which is an x-ray free electron laser as well as high power lasers. The XFEL will clear the details of the HED states and also efficiently create hot dense matter. We have started a new project on high energy density sciences using an XFEL (SACLA) in Japan, which is a HERMES (High Energy density Revolution of Matter in Extreme States) project.
The mass spectral density in quantitative time-of-flight mass spectrometry of polymers
Tate, Ranjeet S.; Ebeling, Dan; Smith, Lloyd M.
2001-03-01
Time-of-flight mass spectrometry (TOF-MS) is being increasingly used for the study of polymers, for example to obtain the distribution of molecular masses for polymer samples. Serious efforts have also been underway to use TOF-MS for DNA sequencing. In TOF-MS the data is obtained in the form of a time-series that represents the distribution in arrival times of ions of various m/z ratios. This time-series data is then converted to a "mass-spectrum" via a coordinate transformation from the arrival time (t) to the corresponding mass-to-charge ratio (m/z = const. t^2). In this transformation, it is important to keep in mind that spectra are distributions, or densities of weight +1, and thus do not transform as functions. To obtain the mass-spectral density, it is necessary to include a multiplicative factor of √m/z. Common commercial instruments do not take this factor into account. Dropping this factor has no effect on qualitative analysis (detection) or local quantitative measurements, since S/N or signal-to-baseline ratios are unaffected for peaks with small dispersions. However, there are serious consequences for general quantitative analyses. In DNA sequencing applications, loss of signal intensity is in part attributed to multiple charging; however, since the √m/z factor is not taken into account, this conclusion is based on an overestimate (by a factor of √z) of the relative amount of the multiply charged species. In the study of polymers, the normalized dispersion is underestimated by approximately (M_w/Mn -1)/2. In terms of M_w/Mn itself, for example, a M_w/M_n=1.5 calculated without the √m factor corresponds in fact to a M_w/M_n=1.88.
Johnson, Dexter; Brown, Gerald V.
2005-01-01
Future advanced aircraft fueled by hydrogen are being developed to use electric drive systems instead of gas turbine engines for propulsion. Current conventional electric motor power densities cannot match those of today s gas turbine aircraft engines. However, if significant technological advances could be made in high-power-density motor development, the benefits of an electric propulsion system, such as the reduction of harmful emissions, could be realized.
High power density reactors based on direct cooled particle beds
Powell, J. R.; Horn, F. L.
Reactors based on direct cooled High Temperature Gas Cooled Reactor (HTGR) type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out along the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBRs) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed.
High power density reactors based on direct cooled particle beds
International Nuclear Information System (INIS)
Powell, J.R.; Horn, F.L.
1985-01-01
Reactors based on direct cooled HTGR type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out long the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBR's) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed. 12 figs
Yip, Ngai Yin; Vermaas, David A; Nijmeijer, Kitty; Elimelech, Menachem
2014-05-06
Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we present a reversible thermodynamic model for RED and verify that the theoretical maximum extractable work in a reversible RED process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible process with maximized power density using a constant-resistance load is then examined to assess the energy conversion efficiency and power density. With equal volumes of seawater and river water, energy conversion efficiency of ∼ 33-44% can be obtained in RED, while the rest is lost through dissipation in the internal resistance of the ion-exchange membrane stack. We show that imperfections in the selectivity of typical ion exchange membranes (namely, co-ion transport, osmosis, and electro-osmosis) can detrimentally lower efficiency by up to 26%, with co-ion leakage being the dominant effect. Further inspection of the power density profile during RED revealed inherent ineffectiveness toward the end of the process. By judicious early discontinuation of the controlled mixing process, the overall power density performance can be considerably enhanced by up to 7-fold, without significant compromise to the energy efficiency. Additionally, membrane resistance was found to be an important factor in determining the power densities attainable. Lastly, the performance of an RED stack was examined for different membrane conductivities and intermembrane distances simulating high performance membranes and stack design. By thoughtful selection of the operating parameters, an efficiency of ∼ 37% and an overall gross power density of 3.5 W/m(2) represent the maximum performance that can potentially be achieved in a seawater-river water RED system with low
Active learning for noisy oracle via density power divergence.
Sogawa, Yasuhiro; Ueno, Tsuyoshi; Kawahara, Yoshinobu; Washio, Takashi
2013-10-01
The accuracy of active learning is critically influenced by the existence of noisy labels given by a noisy oracle. In this paper, we propose a novel pool-based active learning framework through robust measures based on density power divergence. By minimizing density power divergence, such as β-divergence and γ-divergence, one can estimate the model accurately even under the existence of noisy labels within data. Accordingly, we develop query selecting measures for pool-based active learning using these divergences. In addition, we propose an evaluation scheme for these measures based on asymptotic statistical analyses, which enables us to perform active learning by evaluating an estimation error directly. Experiments with benchmark datasets and real-world image datasets show that our active learning scheme performs better than several baseline methods. Copyright © 2013 Elsevier Ltd. All rights reserved.
High-field, high-density tokamak power reactor
International Nuclear Information System (INIS)
Cohn, D.R.; Cook, D.L.; Hay, R.D.; Kaplan, D.; Kreischer, K.; Lidskii, L.M.; Stephany, W.; Williams, J.E.C.; Jassby, D.L.; Okabayashi, M.
1977-11-01
A conceptual design of a compact (R 0 = 6.0 m) high power density (average P/sub f/ = 7.7 MW/m 3 ) tokamak demonstration power reactor has been developed. High magnetic field (B/sub t/ = 7.4 T) and moderate elongation (b/a = 1.6) permit operation at the high density (n(0) approximately 5 x 10 14 cm -3 ) needed for ignition in a relatively small plasma, with a spatially-averaged toroidal beta of only 4%. A unique design for the Nb 3 Sn toroidal-field magnet system reduces the stress in the high-field trunk region, and allows modularization for simpler disassembly. The modest value of toroidal beta permits a simple, modularized plasma-shaping coil system, located inside the TF coil trunk. Heating of the dense central plasma is attained by the use of ripple-assisted injection of 120-keV D 0 beams. The ripple-coil system also affords dynamic control of the plasma temperature during the burn period. A FLIBE-lithium blanket is designed especially for high-power-density operation in a high-field environment, and gives an overall tritium breeding ratio of 1.05 in the slowly pumped lithium
Efficient Spectral Power Estimation on an Arbitrary Frequency Scale
Directory of Open Access Journals (Sweden)
F. Zaplata
2015-04-01
Full Text Available The Fast Fourier Transform is a very efficient algorithm for the Fourier spectrum estimation, but has the limitation of a linear frequency scale spectrum, which may not be suitable for every system. For example, audio and speech analysis needs a logarithmic frequency scale due to the characteristic of a human’s ear. The Fast Fourier Transform algorithms are not able to efficiently give the desired results and modified techniques have to be used in this case. In the following text a simple technique using the Goertzel algorithm allowing the evaluation of the power spectra on an arbitrary frequency scale will be introduced. Due to its simplicity the algorithm suffers from imperfections which will be discussed and partially solved in this paper. The implementation into real systems and the impact of quantization errors appeared to be critical and have to be dealt with in special cases. The simple method dealing with the quantization error will also be introduced. Finally, the proposed method will be compared to other methods based on its computational demands and its potential speed.
Optimization of power and energy densities in supercapacitors
Energy Technology Data Exchange (ETDEWEB)
Robinson, David B. [Sandia National Laboratories, PO Box 969 MS 9291, Livermore, CA 94551 (United States)
2010-06-01
Supercapacitors use nanoporous electrodes to store large amounts of charge on their high surface areas, and use the ions in electrolytes to carry charge into the pores. Their high power density makes them a potentially useful complement to batteries. However, ion transport through long, narrow channels still limits power and efficiency in these devices. Proper design can mitigate this. Current collector geometry must also be considered once this is done. Here, De Levie's model for porous electrodes is applied to quantitatively predict device performance and to propose optimal device designs for given specifications. Effects unique to nanoscale pores are considered, including that pores may not have enough salt to fully charge. Supercapacitors are of value for electric vehicles, portable electronics, and power conditioning in electrical grids with distributed renewable sources, and that value will increase as new device fabrication methods are developed and proper design accommodates those improvements. Example design outlines for vehicle applications are proposed and compared. (author)
Seven, Yasin B; Mantilla, Carlos B; Zhan, Wen-Zhi; Sieck, Gary C
2013-01-15
We hypothesized that a shift in diaphragm muscle (DIAm) EMG power spectral density (PSD) to higher frequencies reflects recruitment of more fatigable fast-twitch motor units and motor unit recruitment is reflected by EMG non-stationarity. DIAm EMG was recorded in anesthetized rats during eupnea, hypoxia-hypercapnia (10% O(2)-5% CO(2)), airway occlusion, and sneezing (maximal DIAm force). Although power in all frequency bands increased progressively across motor behaviors, PSD centroid frequency increased only during sneezing (pmotor units were recruited during different motor behaviors. Motor units augmented their discharge frequencies progressively beyond the non-stationary period; yet, EMG signal became stationary. In conclusion, non-stationarity of DIAm EMG reflects the period of motor unit recruitment, while a shift in the PSD towards higher frequencies reflects recruitment of more fatigable fast-twitch motor units. Copyright © 2012 Elsevier B.V. All rights reserved.
Detection of the power lines in UAV remote sensed images using spectral-spatial methods.
Bhola, Rishav; Krishna, Nandigam Hari; Ramesh, K N; Senthilnath, J; Anand, Gautham
2018-01-15
In this paper, detection of the power lines on images acquired by Unmanned Aerial Vehicle (UAV) based remote sensing is carried out using spectral-spatial methods. Spectral clustering was performed using Kmeans and Expectation Maximization (EM) algorithm to classify the pixels into the power lines and non-power lines. The spectral clustering methods used in this study are parametric in nature, to automate the number of clusters Davies-Bouldin index (DBI) is used. The UAV remote sensed image is clustered into the number of clusters determined by DBI. The k clustered image is merged into 2 clusters (power lines and non-power lines). Further, spatial segmentation was performed using morphological and geometric operations, to eliminate the non-power line regions. In this study, UAV images acquired at different altitudes and angles were analyzed to validate the robustness of the proposed method. It was observed that the EM with spatial segmentation (EM-Seg) performed better than the Kmeans with spatial segmentation (Kmeans-Seg) on most of the UAV images. Copyright © 2017 Elsevier Ltd. All rights reserved.
Origin of the quasiparticle peak in the spectral density of Cr(001) surfaces
Peters, L.; Jacob, D.; Karolak, M.; Lichtenstein, A. I.; Katsnelson, M. I.
2017-12-01
In the spectral density of Cr(001) surfaces, a sharp resonance close to the Fermi level is observed in both experiment and theory. For the physical origin of this peak, two mechanisms were proposed: a single-particle dz2 surface state renormalized by electron-phonon coupling and an orbital Kondo effect due to the degenerate dx z/dy z states. Despite several experimental and theoretical investigations, the origin is still under debate. In this work, we address this problem by two different approaches of the dynamical mean-field theory: first, by the spin-polarized T -matrix fluctuation exchange approximation suitable for weakly and moderately correlated systems; second, by the noncrossing approximation derived in the limit of weak hybridization (i.e., for strongly correlated systems) capturing Kondo-type processes. By using recent continuous-time quantum Monte Carlo calculations as a benchmark, we find that the high-energy features, everything except the resonance, of the spectrum are captured within the spin-polarized T -matrix fluctuation exchange approximation. More precisely, the particle-particle processes provide the main contribution. For the noncrossing approximation, it appears that spin-polarized calculations suffer from spurious behavior at the Fermi level. Then, we turned to non-spin-polarized calculations to avoid this unphysical behavior. By employing two plausible starting hybridization functions, it is observed that the characteristics of the resonance are crucially dependent on the starting point. It appears that only one of these starting hybridizations could result in an orbital Kondo resonance in the presence of a strong magnetic field like in the Cr(001) surface. It is for a future investigation to first resolve the unphysical behavior within the spin-polarized noncrossing approximation and then check for an orbital Kondo resonance.
Energy Technology Data Exchange (ETDEWEB)
Hamersvelt, Robbert W. van; Schilham, Arnold M.R.; Harder, Annemarie M. den; Leiner, Tim; Jong, Pim A. de; Willemink, Martin J. [University Medical Centre Utrecht, Department of Radiology, P.O. Box 85500, Utrecht (Netherlands); Engelke, Klaus [University of Erlangen-Nuernberg, Institute of Medical Physics, Erlangen (Germany); Keizer, Bart de [University Medical Centre Utrecht, Department of Nuclear Medicine, Utrecht (Netherlands); Verhaar, Harald J. [University Medical Centre Utrecht, Department of Geriatric Medicine, Utrecht (Netherlands)
2017-10-15
To investigate the accuracy of bone mineral density (BMD) quantification using dual-layer spectral detector CT (SDCT) at various scan protocols. Two validated anthropomorphic phantoms containing inserts of 50-200 mg/cm{sup 3} calcium hydroxyapatite (HA) were scanned using a 64-slice SDCT scanner at various acquisition protocols (120 and 140 kVp, and 50, 100 and 200 mAs). Regions of interest (ROIs) were placed in each insert and mean attenuation profiles at monochromatic energy levels (90-200 keV) were constructed. These profiles were fitted to attenuation profiles of pure HA and water to calculate HA concentrations. For comparison, one phantom was scanned using dual energy X-ray absorptiometry (DXA). At both 120 and 140 kVp, excellent correlations (R = 0.97, P < 0.001) were found between true and measured HA concentrations. Mean error for all measurements at 120 kVp was -5.6 ± 5.7 mg/cm{sup 3} (-3.6 ± 3.2%) and at 140 kVp -2.4 ± 3.7 mg/cm{sup 3} (-0.8 ± 2.8%). Mean measurement errors were smaller than 6% for all acquisition protocols. Strong linear correlations (R{sup 2} ≥ 0.970, P < 0.001) with DXA were found. SDCT allows for accurate BMD quantification and potentially opens up the possibility for osteoporosis evaluation and opportunistic screening in patients undergoing SDCT for other clinical indications. However, patient studies are needed to extend and translate our findings. (orig.)
Profiles of radiation power density in WEGA stellarator
International Nuclear Information System (INIS)
Zhang, D.; Otte, M.; Giannone, L.
2005-01-01
On the WEGA stellarator, a 12 channel bolometer camera has been used to measure the radiation power losses of the plasma, which is heated by ECR at 2.45 GHz with a maximum power of 26 kW. The typical electron temperatures achieved are around 10 eV. The bolometer is of the Au resistor type and is positioned on the mid-plane, viewing the plasma from the low-field side with a spatial resolution of about 6 cm. The viewing angle is opened to poloidally (±47 o ) and covers the whole cross-section. Angular profiles of radiation power density (emissivity) can be achieved using the measured fluxes to the channels, which are given by the integrals along the sight lines. Using Abel inversion with maximum entropy regularisation, radial profiles of emissivity could be obtained. It is found that the angular profile of emissivity depends on the magnetic configuration, the working gas (Ar, He) and the heating scenario. Peaked and hollow emissivity profiles have been obtained by using different types of heating antenna. By changing the magnetic configuration, strong edge radiation has been observed. The largest emissivity values are obtained in the upper SOL range of Ar-discharges. This edge radiation can be reduced by shifting the flux surfaces inwards or by changing their shape at the antenna. The reconstruction of the radial profile of the emissivity was carried out in the case of a peaked angular profile with minimum edge radiation. The total radiation power was estimated by linear extrapolation of the integrated radiation power in the viewing region to the torus volume. It is typically less than 30% of the ECRH input power, but depending on the ECRH input power, again the magnetic configuration, the working gas as well as the absolute field strength on the magnetic axis. Maximum radiation losses have been obtained around 0.6·B0, where B 0 =87.5 mT is the resonant field strength of the ECRH. No evidence for impurities was obtained from spectroscopic measurements, and thus the
Adaptive Spectral Doppler Estimation
DEFF Research Database (Denmark)
Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt
2009-01-01
. The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to pro- vide good spectral resolution and contrast even when the ob- servation window is very short. The 2 adaptive techniques are tested......In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence...... and compared with the averaged periodogram (Welch’s method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set...
Assessment of Microbial Fuel Cell Configurations and Power Densities
Logan, Bruce E.
2015-07-30
Different microbial electrochemical technologies are being developed for a many diverse applications, including wastewater treatment, biofuel production, water desalination, remote power sources, and as biosensors. Current and energy densities will always be limited relative to batteries and chemical fuel cells, but these technologies have other advantages based on the self-sustaining nature of the microorganisms that can donate or accept electrons from an electrode, the range of fuels that can be used, and versatility in the chemicals that can be produced. The high cost of membranes will likely limit applications of microbial electrochemical technologies that might require a membrane. For microbial fuel cells, which do not need a membrane, questions remain on whether larger-scale systems can produce power densities similar to those obtained in laboratory-scale systems. It is shown here that configuration and fuel (pure chemicals in laboratory media versus actual wastewaters) remain the key factors in power production, rather than the scale of the application. Systems must be scaled up through careful consideration of electrode spacing and packing per unit volume of reactor.
Assessment of Microbial Fuel Cell Configurations and Power Densities
Logan, Bruce E.; Wallack, Maxwell J; Kim, Kyoung-Yeol; He, Weihua; Feng, Yujie; Saikaly, Pascal
2015-01-01
Different microbial electrochemical technologies are being developed for a many diverse applications, including wastewater treatment, biofuel production, water desalination, remote power sources, and as biosensors. Current and energy densities will always be limited relative to batteries and chemical fuel cells, but these technologies have other advantages based on the self-sustaining nature of the microorganisms that can donate or accept electrons from an electrode, the range of fuels that can be used, and versatility in the chemicals that can be produced. The high cost of membranes will likely limit applications of microbial electrochemical technologies that might require a membrane. For microbial fuel cells, which do not need a membrane, questions remain on whether larger-scale systems can produce power densities similar to those obtained in laboratory-scale systems. It is shown here that configuration and fuel (pure chemicals in laboratory media versus actual wastewaters) remain the key factors in power production, rather than the scale of the application. Systems must be scaled up through careful consideration of electrode spacing and packing per unit volume of reactor.
Pulsed power drivers for ICF and high energy density physics
International Nuclear Information System (INIS)
Ramirez, J.J.; Matzen, M.K.; McDaniel, D.H.
1995-01-01
Nanosecond Pulsed Power Science and Technology has its origins in the 1960s and over the past decade has matured into a flexible and robust discipline capable of addressing key physics issues of importance to ICF and high Energy Density Physics. The major leverage provided by pulsed power is its ability to generate and deliver high energy and high power at low cost and high efficiency. A low-cost, high-efficiency driver is important because of the very large capital investment required for multi-megajoule ignition-class systems. High efficiency is of additional importance for a commercially viable inertial fusion energy option. Nanosecond pulsed power has been aggressively and successfully developed at Sandia over the past twenty years. This effort has led to the development of unique multi-purpose facilities supported by highly capable diagnostic, calculational and analytic capabilities. The Sandia Particle-beam Fusion Program has evolved as part of an integrated national ICF Program. It applies the low-cost, high-efficiency leverage provided by nanosecond pulsed power systems to the longer-term goals of the national program, i.e., the Laboratory Microfusion Facility and Inertial Fusion Energy. A separate effort has led to the application of nanosecond pulsed power to the generation of intense, high-energy laboratory x-ray sources for application to x-ray laser and radiation effects science research. Saturn is the most powerful of these sources to date. It generates ∼500 kilojoules of x-rays from a magnetically driven implosion (Z-pinch). This paper describes results of x-ray physics experiments performed on Saturn, plans for a new Z-pinch drive capability for PBFA-II, and a design concept for the proposed ∼15 MJ Jupiter facility. The opportunities for ICF-relevant research using these facilities will also be discussed
Dzhebrailova, T D; Korobeĭnikova, I I; Rudneva, L P
2014-09-01
EEG spectral power was calculated in 24 students (18-21 years) with different levels of motivation and anxiety (tested by Spielberger) in two experimental conditions: during the common educational process and the examination stress. Before examination tests, in subjects with high motivation and anxiety level the relative delta activity power increased in right frontal (F4) brain areas. In students with medium motivation immediately before an examination the relative beta2-activity power increased in right frontal (F4) brain areas. It is suggested that delta oscillati- ons reflect activity of the defensive motivational system, whereas beta2 oscillations may be associated with the achievement motivation.
Galactic densities, substructure and the initial power spectrum
International Nuclear Information System (INIS)
Bullock, J.S.; Zentner, A.R.
2003-01-01
Although the currently favored cold dark matter plus cosmological constant model for structure formation assumes an n = 1 scale-invariant initial power spectrum, most inflation models produce at least mild deviations from n = 1. Because the lever arm from the CMB normalization to galaxy scales is long, even a small 'tilt' can have important implications for galactic observations. Here we calculate the COBS-normalized power spectra for several well-motivated models of inflation and compute implications for the substructure content and central densities of galaxy halos. Using an analytic model, normalized against N-body simulations, we show that while halos in the standard (n = 1) model are overdense by a factor of ∼ 6 compared to observations, several of our example inflation+LCDM models predict halo densities well within the range of observations, which prefer models with n ∼ 0.85. We go on to use a semi-analytic model (also normalized against N-body simulations) to follow the merger histories of galaxy-sized halos and track the orbital decay, disruption, and evolution of the merging substructure. Models with n ∼ 0.85 predict a factor of ∼ 3 fewer subhalos at a fixed circular velocity than the standard n 1 case. Although this level of reduction does not resolve the 'dwarf satellite problem', it does imply that the level of feedback required to match the observed number of dwarfs is sensitive to the initial power spectrum. Finally, the fraction of galaxy-halo mass that is bound up in substructure is consistent with limits imposed by multiply imaged quasars for all models considered: f sat > 0.01 even for an effective tilt of n ∼ 0.8. We conclude that, at their current level, lensing constraints of this kind do not provide an interesting probe of the primordial power spectrum
Exploring novel high power density concepts for attractive fusion systems
Energy Technology Data Exchange (ETDEWEB)
Abdou, M.A. [California State Univ., Los Angeles, CA (United States). Dept. of Mechanical Engineering; APEX Team
1999-05-01
The advanced power extraction study is aimed at exploring innovative concepts for fusion power technology (FPT) that can tremendously enhance the potential of fusion as an attractive and competitive energy source. Specifically, the study is exploring new and `revolutionary` concepts that can provide the capability to efficiently extract heat from systems with high neutron and surface heat loads while satisfying all the FPT functional requirements and maximizing reliability, maintainability, safety, and environmental requirements. The primary criteria for measuring performance of the new concepts are: (1) high power density capability with a peak neutron wall load (NWL) of {proportional_to}10 MW m{sup -2} and surface heat flux of {proportional_to}2 MW m{sup -2}; (2) high power conversion efficiency, {proportional_to}40% net; and (3) clear potential to achieve high availability; specifically low failure rate, large design margin, and short downtime for maintenance. A requirement that MTBF{>=}43 MTTR was derived as a necessary condition to achieve the required first wall/blanket availability, where MTBF is the mean time between failures and MTTR is the mean time to recover. Highlights of innovative and promising new concepts that may satisfy these criteria are provided. (orig.) 40 refs.
International Nuclear Information System (INIS)
Stahlberg, J.
1985-01-01
A method taking into account the influence of temperature and density fluctuations generated by the velocity field in stellar atmospheres on the formation of spectral lines is presented. The influenced line profile is derived by exchanging the values in a static atmosphere by a mean value and a fluctuating one. The correlations are calculated with the help of the well-know hydrodynamic eqs. It results, that in normal stellar atmospheres the visual lines are only very weakly influenced by such fluctuations due to the small values of the gradients of the pressure and density and of the velocity dispersion. (author)
Are resting state spectral power measures related to executive functions in healthy young adults?
Gordon, Shirley; Todder, Doron; Deutsch, Inbal; Garbi, Dror; Getter, Nir; Meiran, Nachshon
2018-01-08
Resting-state electroencephalogram (rsEEG) has been found to be associated with psychopathology, intelligence, problem solving, academic performance and is sometimes used as a supportive physiological indicator of enhancement in cognitive training interventions (e.g. neurofeedback, working memory training). In the current study, we measured rsEEG spectral power measures (relative power, between-band ratios and asymmetry) in one hundred sixty five young adults who were also tested on a battery of executive function (EF). We specifically focused on upper Alpha, Theta and Beta frequency bands given their putative role in EF. Our indices enabled finding correlations since they had decent-to-excellent internal and retest reliability and very little range restriction relative to a nation-wide representative large sample. Nonetheless, Bayesian statistical inference indicated support for the null hypothesis concerning lack of monotonic correlation between EF and rsEEG spectral power measures. Therefore, we conclude that, contrary to the quite common interpretation, these rsEEG spectral power measures do not indicate individual differences in the measured EF abilities. Copyright © 2017 Elsevier Ltd. All rights reserved.
Density matrix embedding in an antisymmetrized geminal power bath
International Nuclear Information System (INIS)
Tsuchimochi, Takashi; Welborn, Matthew; Van Voorhis, Troy
2015-01-01
Density matrix embedding theory (DMET) has emerged as a powerful tool for performing wave function-in-wave function embedding for strongly correlated systems. In traditional DMET, an accurate calculation is performed on a small impurity embedded in a mean field bath. Here, we extend the original DMET equations to account for correlation in the bath via an antisymmetrized geminal power (AGP) wave function. The resulting formalism has a number of advantages. First, it allows one to properly treat the weak correlation limit of independent pairs, which DMET is unable to do with a mean-field bath. Second, it associates a size extensive correlation energy with a given density matrix (for the models tested), which AGP by itself is incapable of providing. Third, it provides a reasonable description of charge redistribution in strongly correlated but non-periodic systems. Thus, AGP-DMET appears to be a good starting point for describing electron correlation in molecules, which are aperiodic and possess both strong and weak electron correlation
Ultrathin Coaxial Fiber Supercapacitors Achieving High Energy and Power Densities.
Shen, Caiwei; Xie, Yingxi; Sanghadasa, Mohan; Tang, Yong; Lu, Longsheng; Lin, Liwei
2017-11-15
Fiber-based supercapacitors have attracted significant interests because of their potential applications in wearable electronics. Although much progress has been made in recent years, the energy and power densities, mechanical strength, and flexibility of such devices are still in need of improvement for practical applications. Here, we demonstrate an ultrathin microcoaxial fiber supercapacitor (μCFSC) with high energy and power densities (2.7 mW h/cm 3 and 13 W/cm 3 ), as well as excellent mechanical properties. The prototype with the smallest reported overall diameter (∼13 μm) is fabricated by successive coating of functional layers onto a single micro-carbon-fiber via a scalable process. Combining the simulation results via the electrochemical model, we attribute the high performance to the well-controlled thin coatings that make full use of the electrode materials and minimize the ion transport path between electrodes. Moreover, the μCFSC features high bending flexibility and large tensile strength (more than 1 GPa), which make it promising as a building block for various flexible energy storage applications.
Nagy, Z.; Choi, Y.; Ossenkopf-Okada, V.; van der Tak, F. F. S.; Bergin, E. A.; Gerin, M.; Joblin, C.; Röllig, M.; Simon, R.; Stutzki, J.
2017-03-01
Context. Photon dominated regions (PDRs) are interfaces between the mainly ionized and mainly molecular material around young massive stars. Analysis of the physical and chemical structure of such regions traces the impact of far-ultraviolet radiation of young massive stars on their environment. Aims: We present results on the physical and chemical structure of the prototypical high UV-illumination edge-on Orion Bar PDR from an unbiased spectral line survey with a wide spectral coverage which includes lines of many important gas coolants such as [Cii], [Ci], and CO and other key molecules such as H2CO, H2O, HCN, HCO+, and SO. Methods: A spectral scan from 480-1250 GHz and 1410-1910 GHz at 1.1 MHz resolution was obtained by the HIFI instrument on board the Herschel Space Observatory. We obtained physical parameters for the observed molecules. For molecules with multiple transitions we used rotational diagrams to obtain excitation temperatures and column densities. For species with a single detected transition we used an optically thin LTE approximation. In the case of species with available collisional rates, we also performed a non-LTE analysis to obtain kinetic temperatures, H2 volume densities, and column densities. Results: About 120 lines corresponding to 29 molecules (including isotopologues) have been detected in the Herschel/HIFI line survey, including 11 transitions of CO, 7 transitions of 13CO, 6 transitions of C18O, 10 transitions of H2CO, and 6 transitions of H2O. The rotational temperatures are in the range between 22 and 146 K and the column densities are in the range between 1.8 × 1012 cm-2 and 4.5 × 1017 cm-2. For species with at least three detected transitions and available collisional excitation rates we derived a best fit kinetic temperature and H2 volume density. Most species trace kinetic temperatures in the range between 100 and 150 K and H2 volume densities in the range between 105 and 106 cm-3. The species with temperatures and
Moisture estimation in power transformer oil using acoustic signals and spectral kurtosis
International Nuclear Information System (INIS)
Leite, Valéria C M N; Veloso, Giscard F C; Borges da Silva, Luiz Eduardo; Lambert-Torres, Germano; Borges da Silva, Jonas G; Pinto, João Onofre Pereira
2016-01-01
The aim of this paper is to present a new technique for estimating the contamination by moisture in power transformer insulating oil based on the spectral kurtosis analysis of the acoustic signals of partial discharges (PDs). Basically, in this approach, the spectral kurtosis of the PD acoustic signal is calculated and the correlation between its maximum value and the moisture percentage is explored to find a function that calculates the moisture percentage. The function can be easily implemented in DSP, FPGA, or any other type of embedded system for online moisture monitoring. To evaluate the proposed approach, an experiment is assembled with a piezoelectric sensor attached to a tank, which is filled with insulating oil samples contaminated by different levels of moisture. A device generating electrical discharges is submerged into the oil to simulate the occurrence of PDs. Detected acoustic signals are processed using fast kurtogram algorithm to extract spectral kurtosis values. The obtained data are used to find the fitting function that relates the water contamination to the maximum value of the spectral kurtosis. Experimental results show that the proposed method is suitable for online monitoring system of power transformers. (paper)
Study on spectral entropy of two-phase flow density wave instability
International Nuclear Information System (INIS)
Zhang Zuoyi
1992-05-01
By using mathematic proof, spectral entropy calculations for simple examples and a practical two-phase flow system, it has been proved that under the same stochastic input, the output spectral entropy of a stable linear system is in maximum, while for an unstable linear system, its entropy is in relative lower level. Because the spectral entropy describes the output uncertainty of a system and the second law of thermodynamics rules the direction of natural tendency, the spontaneous process can develop only toward the direction of uncertainty increasing, and the opposite is impossible. It seems that the physical mechanism of the stability of a system can be explained as following: Any deviation from its original state of a stable system will reduce the spectral entropy and violate the natural tendency so that the system will return to original state. On the contrary, the deviation from its original state of an unstable system will increase the spectral entropy that will enhance the deviation and the system will be further away from its original state
LTCC magnetic components for high density power converter
Lebourgeois, Richard; Labouré, Eric; Lembeye, Yves; Ferrieux, Jean-Paul
2018-04-01
This paper deals with multilayer magnetic components for power electronics application and specifically for high frequency switching. New formulations based on nickel-zinc-copper spinel ferrites were developed for high power and high frequency applications. These ferrites can be sintered at low temperature (around 900°C) which makes them compatible with the LTCC (Low Temperature Co-fired Ceramics) technology. Metallic parts of silver or gold can be fully integrated inside the ferrite while guaranteeing the integrity of both the ferrite and the metal. To make inductors or transformers with the required properties, it is mandatory to have nonmagnetic parts between the turns of the winding. Then it is essential to find a dielectric material, which can be co-sintered both with the ferrite and the metal. We will present the solution we found to this problem and we will describe the results we obtained for a multilayer co-sintered transformer. We will see that these new components have good performance compared with the state of the art and are very promising for developing high density switching mode power supplies.
Sampaio, Luis Rafael L; Borges, Lucas T N; Silva, Joyse M F; de Andrade, Francisca Roselin O; Barbosa, Talita M; Oliveira, Tatiana Q; Macedo, Danielle; Lima, Ricardo F; Dantas, Leonardo P; Patrocinio, Manoel Cláudio A; do Vale, Otoni C; Vasconcelos, Silvânia M M
2018-02-01
The use of ketamine (Ket) as a pharmacological model of schizophrenia is an important tool for understanding the main mechanisms of glutamatergic regulated neural oscillations. Thus, the aim of the current study was to evaluate Ket-induced changes in the average spectral power using the hippocampal quantitative electroencephalography (QEEG). To this end, male Wistar rats were submitted to a stereotactic surgery for the implantation of an electrode in the right hippocampus. After three days, the animals were divided into four groups that were treated for 10 consecutive days with Ket (10, 50, or 100 mg/kg). Brainwaves were captured on the 1st or 10th day, respectively, to acute or repeated treatments. The administration of Ket (10, 50, or 100 mg/kg), compared with controls, induced changes in the hippocampal average spectral power of delta, theta, alpha, gamma low or high waves, after acute or repeated treatments. Therefore, based on the alterations in the average spectral power of hippocampal waves induced by Ket, our findings might provide a basis for the use of hippocampal QEEG in animal models of schizophrenia. © 2017 Société Française de Pharmacologie et de Thérapeutique.
International Nuclear Information System (INIS)
Eilek, J.A.
1989-01-01
Recent theories of magnetohydrodynamic turbulence are used to construct microphysical turbulence models, with emphasis on models of anisotropic turbulence. These models have been applied to the determination of the emergent polarization from a resolved uniform source. It is found that depolarization alone is not a unique measure of the turbulence, and that the turblence will also affect the total-intensity distributions. Fluctuations in the intensity image can thus be employed to measure turbulence strength. In the second part, it is demonstrated that a power-spectral analysis of the total and polarized intensity images can be used to obtain the power spectra of the synchrotron emission. 81 refs
Directory of Open Access Journals (Sweden)
Hua Sun
2015-11-01
Full Text Available Accurately mapping urban vegetation carbon density is challenging because of complex landscapes and mixed pixels. In this study, a novel methodology was proposed that combines a linear spectral unmixing analysis (LSUA with a linear stepwise regression (LSR, a logistic model-based stepwise regression (LMSR and k-Nearest Neighbors (kNN, to map the forest carbon density of Shenzhen City of China, using Landsat 8 imagery and sample plot data collected in 2014. The independent variables that contributed to statistically significantly improving the fit of a model to data and reducing the sum of squared errors were first selected from a total of 284 spectral variables derived from the image bands. The vegetation fraction from LSUA was then added as an independent variable. The results obtained using cross-validation showed that: (1 Compared to the methods without the vegetation information, adding the vegetation fraction increased the accuracy of mapping carbon density by 1%–9.3%; (2 As the observed values increased, the LSR and kNN residuals showed overestimates and underestimates for the smaller and larger observations, respectively, while LMSR improved the systematical over and underestimations; (3 LSR resulted in illogically negative and unreasonably large estimates, while KNN produced the greatest values of root mean square error (RMSE. The results indicate that combining the spatial modeling method LMSR and the spectral unmixing analysis LUSA, coupled with Landsat imagery, is most promising for increasing the accuracy of urban forest carbon density maps. In addition, this method has considerable potential for accurate, rapid and nondestructive prediction of urban and peri-urban forest carbon stocks with an acceptable level of error and low cost.
CENTER FOR PULSED POWER DRIVEN HIGH ENERGY DENSITY PLASMA STUDIES
Energy Technology Data Exchange (ETDEWEB)
Professor Bruce R. Kusse; Professor David A. Hammer
2007-04-18
This annual report summarizes the activities of the Cornell Center for Pulsed-Power-Driven High-Energy-Density Plasma Studies, for the 12-month period October 1, 2005-September 30, 2006. This period corresponds to the first year of the two-year extension (awarded in October, 2005) to the original 3-year NNSA/DOE Cooperative Agreement with Cornell, DE-FC03-02NA00057. As such, the period covered in this report also corresponds to the fourth year of the (now) 5-year term of the Cooperative Agreement. The participants, in addition to Cornell University, include Imperial College, London (IC), the University of Nevada, Reno (UNR), the University of Rochester (UR), the Weizmann Institute of Science (WSI), and the P.N. Lebedev Physical Institute (LPI), Moscow. A listing of all faculty, technical staff and students, both graduate and undergraduate, who participated in Center research activities during the year in question is given in Appendix A.
HEDPIN: a computer program to estimate pinwise power density
International Nuclear Information System (INIS)
Cappiello, M.W.
1976-05-01
A description is given of the digital computer program, HEDPIN. This program, modeled after a previously developed program, POWPIN, provides a means of estimating the pinwise power density distribution in fast reactor triangular pitched pin bundles. The capability also exists for computing any reaction rate of interest at the respective pin positions within an assembly. HEDPIN was developed in support of FTR fuel and test management as well as fast reactor core design and core characterization planning and analysis. The results of a test devised to check out HEDPIN's computational method are given, and the realm of application is discussed. Nearly all programming is in FORTRAN IV. Variable dimensioning is employed to make efficient use of core memory and maintain short running time for small problems. Input instructions, sample problem, and a program listing are also given
International Nuclear Information System (INIS)
Yaar, I.; Ron, E.; Modan, B.; Rinott, Y.; Yaar, M.; Modan, M.
1982-01-01
EEG tracings were compared in 44 young adults who received scalp x-radiation treatment for tinea capitis during childhood and 59 non-irradiated control subjects. The irradiated subjects were exposed, over 20 years previously, to a mean dose of 130 rads to the brain. Visual analysis of the EEG revealed an insignificant excess of abnormalities among the irradiated subjects compared to the controls. Power spectral density function analysis showed increased power values among the irradiated subjects, particularly in the beta wave frequencies. This finding provides further evidence for suspecting that x-irradiation during brain maturation may cause long-lasting damage to the brain tissue. (author)
High-power direct diode laser output by spectral beam combining
Tan, Hao; Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao
2018-03-01
We demonstrate a spectral beam combining scheme based on multiple mini-bar stacks, which have more diode laser combining elements, to increase the combined diode laser power and realize equal beam quality in both the fast and slow axes. A spectral beam combining diode laser output of 1130 W is achieved with an operating current of 75 A. When a 9.6 X de-magnifying telescope is introduced between the output mirror and the diffraction grating, to restrain cross-talk among diode laser emitters, a 710 W spectral beam combining diode laser output is achieved at the operating current of 70 A, and the beam quality on the fast and slow axes of the combined beam is about 7.5 mm mrad and 7.3 mm mrad respectively. The power reduction is caused by the existence of a couple resonator between the rear facet of the diode laser and the fast axis collimation lens, and it should be eliminated by using diode laser chips with higher front facet transmission efficiency and a fast axis collimation lens with lower residual reflectivity.
Spectral Properties, Generation Order Parameters, and Luminosities for Spin-powered X-Ray Pulsars
Wang, Wei; Zhao, Yongheng
2004-02-01
We show the spectral properties of 15 spin-powered X-ray pulsars, and the correlation between the average power-law photon index and spin-down rate. Generation order parameters (GOPs) based on polar cap models are introduced to characterize the X-ray pulsars. We calculate three definitions of generation order parameters arising from the different effects of magnetic and electric fields on photon absorption during cascade processes, and study the relations between the GOPs and spectral properties of X-ray pulsars. There exists a possible correlation between the photon index and GOP in our pulsar sample. Furthermore, we present a method stemming from the concept of GOPs to estimate the nonthermal X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated in the context of our polar cap accelerator model, which is consistent with most observed X-ray pulsar data. The ratio between the X-ray luminosity estimated by our method and the pulsar's spin-down power is consistent with the LX~10-3Lsd feature.
Chen, Xin; Cao, Jianshu; Silbey, Robert J
2013-06-14
The recent experimental discoveries about excitation energy transfer (EET) in light harvesting antenna (LHA) attract a lot of interest. As an open non-equilibrium quantum system, the EET demands more rigorous theoretical framework to understand the interaction between system and environment and therein the evolution of reduced density matrix. A phonon is often used to model the fluctuating environment and convolutes the reduced quantum system temporarily. In this paper, we propose a novel way to construct complex-valued Gaussian processes to describe thermal quantum phonon bath exactly by converting the convolution of influence functional into the time correlation of complex Gaussian random field. Based on the construction, we propose a rigorous and efficient computational method, the covariance decomposition and conditional propagation scheme, to simulate the temporarily entangled reduced system. The new method allows us to study the non-Markovian effect without perturbation under the influence of different spectral densities of the linear system-phonon coupling coefficients. Its application in the study of EET in the Fenna-Matthews-Olson model Hamiltonian under four different spectral densities is discussed. Since the scaling of our algorithm is linear due to its Monte Carlo nature, the future application of the method for large LHA systems is attractive. In addition, this method can be used to study the effect of correlated initial condition on the reduced dynamics in the future.
Vo, T D; Dwyer, G; Szeto, H H
1986-04-01
A relatively powerful and inexpensive microcomputer-based system for the spectral analysis of the EEG is presented. High resolution and speed is achieved with the use of recently available large-scale integrated circuit technology with enhanced functionality (INTEL Math co-processors 8087) which can perform transcendental functions rapidly. The versatility of the system is achieved with a hardware organization that has distributed data acquisition capability performed by the use of a microprocessor-based analog to digital converter with large resident memory (Cyborg ISAAC-2000). Compiled BASIC programs and assembly language subroutines perform on-line or off-line the fast Fourier transform and spectral analysis of the EEG which is stored as soft as well as hard copy. Some results obtained from test application of the entire system in animal studies are presented.
Energy Technology Data Exchange (ETDEWEB)
Mahi, F.Z. [Science and Technology Institute, University of Bechar, 08000 Bechar (Algeria)], E-mail: fati_zo_mahi2002@yahoo.fr; Helmaoui, A. [Science and Technology Institute, University of Bechar, 08000 Bechar (Algeria); Varani, L. [Institut d' Electronique du Sud (CNRS UMR 5214), Universite Montpellier II, 34095 Montpellier (France); Shiktorov, P.; Starikov, E.; Gruzhinskis, V. [Semiconductor Physics Institute, 01108 Vilnius (Lithuania)
2008-10-01
An analytical model for the noise spectrum of nanometric Schottky-barrier diodes (SBD) is developed. The calculated frequency dependence of the spectral density of current fluctuations exhibits resonances in the terahertz domain which are discussed and analyzed as functions of the length of the diode, free carrier concentration, length of the depletion region and applied voltage. A good agreement obtained with direct Monte Carlo simulations of GaAs SBDs operating from barrier-limited to flat-band conditions fully validates the proposed approach.
Directory of Open Access Journals (Sweden)
Jorge Alfredo Ardila-Rey
2014-02-01
Full Text Available Partial discharge (PD detection is a standardized technique to qualify electrical insulation in machines and power cables. Several techniques that analyze the waveform of the pulses have been proposed to discriminate noise from PD activity. Among them, spectral power ratio representation shows great flexibility in the separation of the sources of PD. Mapping spectral power ratios in two-dimensional plots leads to clusters of points which group pulses with similar characteristics. The position in the map depends on the nature of the partial discharge, the setup and the frequency response of the sensors. If these clusters are clearly separated, the subsequent task of identifying the source of the discharge is straightforward so the distance between clusters can be a figure of merit to suggest the best option for PD recognition. In this paper, two inductive sensors with different frequency responses to pulsed signals, a high frequency current transformer and an inductive loop sensor, are analyzed to test their performance in detecting and separating the sources of partial discharges.
Spectral and Power-Efficiency Trade-off in Fixed-Grid Optical Networks
Directory of Open Access Journals (Sweden)
Sridhar Iyer
2017-09-01
Full Text Available The improvement of spectral efficiency in the MLR networks can be obtained by the reduction of sub-band spacing, or by minimizing the spacing of the sub-bands that operate at varied data rates. However, due to the presence of physical layer impairments, minimization in sub-band spacing leads to adverse effects on the channel(s transmission reach. As a result there occurs an increase in the consumed power due to the requirement of increase in regeneration of the signal. In the current work we propose an improved DWDM grating in view of obtaining higher spectral efficiency. For a system, with and without Forward Error Correction capabilities (i for various SLR solutions, we find and compare power consumption values of the components with respect to the total traffic, and (ii for different MLR and SLR solutions, for a fixed QoT, we evaluate the minimum values of the sub-band and the channel spacing, and also evaluate and compare the power-efficiency with the distance of transmission.
Li, Zhijun; Feng, Maria Q.; Luo, Longxi; Feng, Dongming; Xu, Xiuli
2018-01-01
Uncertainty of modal parameters estimation appear in structural health monitoring (SHM) practice of civil engineering to quite some significant extent due to environmental influences and modeling errors. Reasonable methodologies are needed for processing the uncertainty. Bayesian inference can provide a promising and feasible identification solution for the purpose of SHM. However, there are relatively few researches on the application of Bayesian spectral method in the modal identification using SHM data sets. To extract modal parameters from large data sets collected by SHM system, the Bayesian spectral density algorithm was applied to address the uncertainty of mode extraction from output-only response of a long-span suspension bridge. The posterior most possible values of modal parameters and their uncertainties were estimated through Bayesian inference. A long-term variation and statistical analysis was performed using the sensor data sets collected from the SHM system of the suspension bridge over a one-year period. The t location-scale distribution was shown to be a better candidate function for frequencies of lower modes. On the other hand, the burr distribution provided the best fitting to the higher modes which are sensitive to the temperature. In addition, wind-induced variation of modal parameters was also investigated. It was observed that both the damping ratios and modal forces increased during the period of typhoon excitations. Meanwhile, the modal damping ratios exhibit significant correlation with the spectral intensities of the corresponding modal forces.
ENERGY-DEPENDENT POWER SPECTRAL STATES AND ORIGIN OF APERIODIC VARIABILITY IN BLACK HOLE BINARIES
International Nuclear Information System (INIS)
Yu Wenfei; Zhang Wenda
2013-01-01
We found that the black hole candidate MAXI J1659–152 showed distinct power spectra, i.e., power-law noise (PLN) versus band-limited noise (BLN) plus quasi-periodic oscillations (QPOs) below and above about 2 keV, respectively, in observations with Swift and the Rossi X-ray Timing Explorer during the 2010 outburst, indicating a high energy cutoff of the PLN and a low energy cutoff of the BLN and QPOs around 2 keV. The emergence of the PLN and the fading of the BLN and QPOs initially took place below 2 keV when the source entered the hard intermediate state and settled in the soft state three weeks later. The evolution was accompanied by the emergence of the disk spectral component and decreases in the amplitudes of variability in the soft and hard X-ray bands. Our results indicate that the PLN is associated with an optically thick disk in both hard and intermediate states, and the power spectral state is independent of the X-ray energy spectral state in a broadband view. We suggest that in the hard or intermediate state, the BLN and QPOs emerge from the innermost hot flow subjected to Comptonization, while the PLN originates from the optically thick disk farther out. The energy cutoffs of the PLN and the BLN or QPOs then follow the temperature of the seed photons from the inner edge of the optically thick disk, while the high frequency cutoff of the PLN follows the orbital frequency of the inner edge of the optically thick disk as well.
Reliability Study of Mechatronic Power Components Using Spectral Photon Emission Microscopy
Directory of Open Access Journals (Sweden)
N. Moultif
2016-11-01
Full Text Available In this paper, we present one of the most important failure analysis tools that permits the localizing and the identification of the failure mechanisms. It is a new spectral photon emission system, enabling to localize the failure, and quickly get the photon emission spectra that characterize the failure with high resolution. A diffraction grating is used as a spectrometer in the system. Application results on mechatronic power devices such as HEMT AlGaN/GAN and SiC MOSFETs are reported.
A Hard X-Ray Power-Law Spectral Cutoff in Centaurus X-4
DEFF Research Database (Denmark)
Chakrabarty, Deepto; Tomsick, John A.; Grefenstette, Brian W.
2015-01-01
The low-mass X-ray binary Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unkno...... behavior with PSR J1023+0038, IGR J18245-2452, and XSS J12270-4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity....
A spectral scheme for Kohn–Sham density functional theory of clusters
Energy Technology Data Exchange (ETDEWEB)
Banerjee, Amartya S., E-mail: baner041@umn.edu; Elliott, Ryan S., E-mail: relliott@umn.edu; James, Richard D., E-mail: james@umn.edu
2015-04-15
Starting from the observation that one of the most successful methods for solving the Kohn–Sham equations for periodic systems – the plane-wave method – is a spectral method based on eigenfunction expansion, we formulate a spectral method designed towards solving the Kohn–Sham equations for clusters. This allows for efficient calculation of the electronic structure of clusters (and molecules) with high accuracy and systematic convergence properties without the need for any artificial periodicity. The basis functions in this method form a complete orthonormal set and are expressible in terms of spherical harmonics and spherical Bessel functions. Computation of the occupied eigenstates of the discretized Kohn–Sham Hamiltonian is carried out using a combination of preconditioned block eigensolvers and Chebyshev polynomial filter accelerated subspace iterations. Several algorithmic and computational aspects of the method, including computation of the electrostatics terms and parallelization are discussed. We have implemented these methods and algorithms into an efficient and reliable package called ClusterES (Cluster Electronic Structure). A variety of benchmark calculations employing local and non-local pseudopotentials are carried out using our package and the results are compared to the literature. Convergence properties of the basis set are discussed through numerical examples. Computations involving large systems that contain thousands of electrons are demonstrated to highlight the efficacy of our methodology. The use of our method to study clusters with arbitrary point group symmetries is briefly discussed.
A spectral scheme for Kohn-Sham density functional theory of clusters
Banerjee, Amartya S.; Elliott, Ryan S.; James, Richard D.
2015-04-01
Starting from the observation that one of the most successful methods for solving the Kohn-Sham equations for periodic systems - the plane-wave method - is a spectral method based on eigenfunction expansion, we formulate a spectral method designed towards solving the Kohn-Sham equations for clusters. This allows for efficient calculation of the electronic structure of clusters (and molecules) with high accuracy and systematic convergence properties without the need for any artificial periodicity. The basis functions in this method form a complete orthonormal set and are expressible in terms of spherical harmonics and spherical Bessel functions. Computation of the occupied eigenstates of the discretized Kohn-Sham Hamiltonian is carried out using a combination of preconditioned block eigensolvers and Chebyshev polynomial filter accelerated subspace iterations. Several algorithmic and computational aspects of the method, including computation of the electrostatics terms and parallelization are discussed. We have implemented these methods and algorithms into an efficient and reliable package called ClusterES (Cluster Electronic Structure). A variety of benchmark calculations employing local and non-local pseudopotentials are carried out using our package and the results are compared to the literature. Convergence properties of the basis set are discussed through numerical examples. Computations involving large systems that contain thousands of electrons are demonstrated to highlight the efficacy of our methodology. The use of our method to study clusters with arbitrary point group symmetries is briefly discussed.
A spectral scheme for Kohn–Sham density functional theory of clusters
International Nuclear Information System (INIS)
Banerjee, Amartya S.; Elliott, Ryan S.; James, Richard D.
2015-01-01
Starting from the observation that one of the most successful methods for solving the Kohn–Sham equations for periodic systems – the plane-wave method – is a spectral method based on eigenfunction expansion, we formulate a spectral method designed towards solving the Kohn–Sham equations for clusters. This allows for efficient calculation of the electronic structure of clusters (and molecules) with high accuracy and systematic convergence properties without the need for any artificial periodicity. The basis functions in this method form a complete orthonormal set and are expressible in terms of spherical harmonics and spherical Bessel functions. Computation of the occupied eigenstates of the discretized Kohn–Sham Hamiltonian is carried out using a combination of preconditioned block eigensolvers and Chebyshev polynomial filter accelerated subspace iterations. Several algorithmic and computational aspects of the method, including computation of the electrostatics terms and parallelization are discussed. We have implemented these methods and algorithms into an efficient and reliable package called ClusterES (Cluster Electronic Structure). A variety of benchmark calculations employing local and non-local pseudopotentials are carried out using our package and the results are compared to the literature. Convergence properties of the basis set are discussed through numerical examples. Computations involving large systems that contain thousands of electrons are demonstrated to highlight the efficacy of our methodology. The use of our method to study clusters with arbitrary point group symmetries is briefly discussed
Liu, Liming; Hao, Xinfeng
2008-10-01
In order to study the effect of laser pulses on arc plasma and target metal in the hybrid welding process, the spectra of the plasmas in the welding process of magnesium alloys are analysed in this paper. The acquisition system of plasma spectra is set up and the spectral lines of welding plasma are acquired. Compared with tungsten-inert gas (TIG) welding, the intensities of the spectral lines of magnesium increase sharply while those of Ar decrease for strong evaporation and ionization of magnesium alloys in low-power laser/arc hybrid welding. The electron temperature and density are estimated by the Boltzmann plot method and the Stark broadening effect. The result shows that the electron temperature of arc plasma in the hybrid welding process is much lower than that in TIG welding, especially in the laser beam-affected zone. In contrast, the electron density of the plasma is enhanced. The influences of laser parameters on electron temperature are also studied. The changes in electron temperature and density indicate that the effect of laser pulse on the target metal is the dominant factor influencing the electron temperature and density in low-power laser/arc hybrid welding.
Energy Technology Data Exchange (ETDEWEB)
Minaki, S.; Ishihara, Y.; Todaka, T.; Harada, K. [Doshisha University, Kyoto (Japan); Oshiro, T.; Nakamura, H. [Japan quality Assurance Organization, Tokyo (Japan)
1997-11-25
As to the influence of spectral solar radiation to generating power of solar cells, a study was conducted from the aspects of season, time zone, intensity of solar radiation, etc. In the study, spectral responsive variation correction coefficients were introduced as evaluation values expressing the influence of spectral solar radiation. For the spectral distribution, an all sky spectral pyranometer by wavelength was used, and data were used which were obtained in the measurement in experimental facilities of the solar techno center. Concerning solar cell relative spectral sensitivity values, used were relative spectral sensitivity values of monocrystal and amorphous standard solar cells to the short-circuit current. Spectral response variation correction coefficients are coefficients correcting variations in conversion efficiency of solar cells due to changes in the spectral distribution. The changes of spectral responsive variation correction coefficients were studied using data obtained during April 1994 and March 1996. As a result, it was found that the coefficients showed large changes in summer and small ones in winter and that amorphous solar cells indicate this trend conspicuously. 3 refs., 6 figs., 3 tabs.
Estimation of spectral kurtosis
Sutawanir
2017-03-01
Rolling bearings are the most important elements in rotating machinery. Bearing frequently fall out of service for various reasons: heavy loads, unsuitable lubrications, ineffective sealing. Bearing faults may cause a decrease in performance. Analysis of bearing vibration signals has attracted attention in the field of monitoring and fault diagnosis. Bearing vibration signals give rich information for early detection of bearing failures. Spectral kurtosis, SK, is a parameter in frequency domain indicating how the impulsiveness of a signal varies with frequency. Faults in rolling bearings give rise to a series of short impulse responses as the rolling elements strike faults, SK potentially useful for determining frequency bands dominated by bearing fault signals. SK can provide a measure of the distance of the analyzed bearings from a healthy one. SK provides additional information given by the power spectral density (psd). This paper aims to explore the estimation of spectral kurtosis using short time Fourier transform known as spectrogram. The estimation of SK is similar to the estimation of psd. The estimation falls in model-free estimation and plug-in estimator. Some numerical studies using simulations are discussed to support the methodology. Spectral kurtosis of some stationary signals are analytically obtained and used in simulation study. Kurtosis of time domain has been a popular tool for detecting non-normality. Spectral kurtosis is an extension of kurtosis in frequency domain. The relationship between time domain and frequency domain analysis is establish through power spectrum-autocovariance Fourier transform. Fourier transform is the main tool for estimation in frequency domain. The power spectral density is estimated through periodogram. In this paper, the short time Fourier transform of the spectral kurtosis is reviewed, a bearing fault (inner ring and outer ring) is simulated. The bearing response, power spectrum, and spectral kurtosis are plotted to
High-power density miniscale power generation and energy harvesting systems
Energy Technology Data Exchange (ETDEWEB)
Lyshevski, Sergey Edward [Department of Electrical and Microelectronics Engineering, Rochester Institute of Technology, Rochester, NY 14623-5603 (United States)
2011-01-15
This paper reports design, analysis, evaluations and characterization of miniscale self-sustained power generation systems. Our ultimate objective is to guarantee highly-efficient mechanical-to-electrical energy conversion, ensure premier wind- or hydro-energy harvesting capabilities, enable electric machinery and power electronics solutions, stabilize output voltage, etc. By performing the advanced scalable power generation system design, we enable miniscale energy sources and energy harvesting technologies. The proposed systems integrate: (1) turbine which rotates a radial- or axial-topology permanent-magnet synchronous generator at variable angular velocity depending on flow rate, speed and load, and, (2) power electronic module with controllable rectifier, soft-switching converter and energy storage stages. These scalable energy systems can be utilized as miniscale auxiliary and self-sustained power units in various applications, such as, aerospace, automotive, biotechnology, biomedical, and marine. The proposed systems uniquely suit various submersible and harsh environment applications. Due to operation in dynamic rapidly-changing envelopes (variable speed, load changes, etc.), sound solutions are researched, proposed and verified. We focus on enabling system organizations utilizing advanced developments for various components, such as generators, converters, and energy storage. Basic, applied and experimental findings are reported. The prototypes of integrated power generation systems were tested, characterized and evaluated. It is documented that high-power density, high efficiency, robustness and other enabling capabilities are achieved. The results and solutions are scalable from micro ({proportional_to}100 {mu}W) to medium ({proportional_to}100 kW) and heavy-duty (sub-megawatt) auxiliary and power systems. (author)
High-power density miniscale power generation and energy harvesting systems
International Nuclear Information System (INIS)
Lyshevski, Sergey Edward
2011-01-01
This paper reports design, analysis, evaluations and characterization of miniscale self-sustained power generation systems. Our ultimate objective is to guarantee highly-efficient mechanical-to-electrical energy conversion, ensure premier wind- or hydro-energy harvesting capabilities, enable electric machinery and power electronics solutions, stabilize output voltage, etc. By performing the advanced scalable power generation system design, we enable miniscale energy sources and energy harvesting technologies. The proposed systems integrate: (1) turbine which rotates a radial- or axial-topology permanent-magnet synchronous generator at variable angular velocity depending on flow rate, speed and load, and, (2) power electronic module with controllable rectifier, soft-switching converter and energy storage stages. These scalable energy systems can be utilized as miniscale auxiliary and self-sustained power units in various applications, such as, aerospace, automotive, biotechnology, biomedical, and marine. The proposed systems uniquely suit various submersible and harsh environment applications. Due to operation in dynamic rapidly-changing envelopes (variable speed, load changes, etc.), sound solutions are researched, proposed and verified. We focus on enabling system organizations utilizing advanced developments for various components, such as generators, converters, and energy storage. Basic, applied and experimental findings are reported. The prototypes of integrated power generation systems were tested, characterized and evaluated. It is documented that high-power density, high efficiency, robustness and other enabling capabilities are achieved. The results and solutions are scalable from micro (∼100 μW) to medium (∼100 kW) and heavy-duty (sub-megawatt) auxiliary and power systems.
16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers
DEFF Research Database (Denmark)
Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin
2011-01-01
output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2- values of the laser with lowest spatial coherence. The principle......Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest...... of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future....
16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers.
Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael
2011-01-17
Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2-values of the laser with lowest spatial coherence. The principle of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future.
Directory of Open Access Journals (Sweden)
Huiguo Chen
2017-01-01
Full Text Available Based on the Kanai-Tajimi power spectrum filtering method proposed by Du Xiuli et al., a genetic algorithm and a quadratic optimization identification technique are employed to improve the bimodal time-varying modified Kanai-Tajimi power spectral model and the parameter identification method proposed by Vlachos et al. Additionally, a method for modeling time-varying power spectrum parameters for ground motion is proposed. The 8244 Orion and Chi-Chi earthquake accelerograms are selected as examples for time-varying power spectral model parameter identification and ground motion simulations to verify the feasibility and effectiveness of the improved bimodal time-varying modified Kanai-Tajimi power spectral model. The results of this study provide important references for designing ground motion inputs for seismic analyses of major engineering structures.
Mundahl, John; Jianjun Meng; He, Jeffrey; Bin He
2016-08-01
Brain-computer interface (BCI) systems allow users to directly control computers and other machines by modulating their brain waves. In the present study, we investigated the effect of soft drinks on resting state (RS) EEG signals and BCI control. Eight healthy human volunteers each participated in three sessions of BCI cursor tasks and resting state EEG. During each session, the subjects drank an unlabeled soft drink with either sugar, caffeine, or neither ingredient. A comparison of resting state spectral power shows a substantial decrease in alpha and beta power after caffeine consumption relative to control. Despite attenuation of the frequency range used for the control signal, caffeine average BCI performance was the same as control. Our work provides a useful characterization of caffeine, the world's most popular stimulant, on brain signal frequencies and their effect on BCI performance.
A recommended procedure for estimating the cosmic-ray spectral parameter of a simple power law
Howell, L W
2002-01-01
A simple power law model with single spectral index alpha sub 1 is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10 sup 1 sup 3 eV. Two procedures for estimating alpha sub 1 --the method of moments and maximum likelihood (ML)--are developed and their statistical performance are compared. The ML procedure is shown to be the superior approach and is then generalized for application to real cosmic-ray data sets. Several other important results, such as the relationship between collecting power and detector energy resolution and inclusion of a non-Gaussian detector response function, are presented. These results have many practical benefits in the design phase of a cosmic-ray detector as they permit instrument developers to make important trade studies in design parameters as a function of one of the science objectives.
Effect of graphite target power density on tribological properties of graphite-like carbon films
Dong, Dan; Jiang, Bailing; Li, Hongtao; Du, Yuzhou; Yang, Chao
2018-05-01
In order to improve the tribological performance, a series of graphite-like carbon (GLC) films with different graphite target power densities were prepared by magnetron sputtering. The valence bond and microstructure of films were characterized by AFM, TEM, XPS and Raman spectra. The variation of mechanical and tribological properties with graphite target power density was analyzed. The results showed that with the increase of graphite target power density, the deposition rate and the ratio of sp2 bond increased obviously. The hardness firstly increased and then decreased with the increase of graphite target power density, whilst the friction coefficient and the specific wear rate increased slightly after a decrease with the increasing graphite target power density. The friction coefficient and the specific wear rate were the lowest when the graphite target power density was 23.3 W/cm2.
International Nuclear Information System (INIS)
Chong, Kok-Keong; Khlyabich, Petr P.; Hong, Kai-Jeat; Reyes-Martinez, Marcos; Rand, Barry P.; Loo, Yueh-Lin
2016-01-01
Highlights: • Method to analyze power-conversion efficiency under various solar irradiance. • Power-conversion efficiency at local irradiance is 5.4% higher than AM1.5G. • Diffuse local irradiance has gain of 23.7–27.9% relative to AM1.5G conditions. • Annual average energy density yield is estimated as 31.89 kW h/m 2 in Malaysia. - Abstract: The solar spectral irradiance varies significantly for different locations and time due to latitude, humidity, cosine effect of incident sunlight, etc. For convenience, the power-conversion efficiency of a solar cell is referenced to the international standard of AM1.5G spectral irradiance, which inevitably leads to varying performance of deployed solar cells under the specific local climate and insolation conditions. To predict the actual performance of solar cells under local climate conditions, we propose a methodology to compute the power-conversion efficiency of organic photovoltaic cells based upon indoor measurement with a solar simulator, the measured local solar spectrum, and making use of both optical and electrical factors. From our study, the annual average energy density yield of poly(3-hexylthiophene):phenyl-C 61 -butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction organic solar cells under the local spectral irradiance of Malaysia is estimated to be 31.89 kW h/m 2 and the power-conversion efficiency is increased by 5.4% compared to that measured under AM1.5G conditions. In addition, diffuse solar irradiance (cloudy condition) was found to be in favor of P3HT:PCBM solar cells, with gain of 23.7–27.9% relative to AM1.5G conditions.
Methods to enhance blanket power density in low-power fusion devices
International Nuclear Information System (INIS)
Hsu, P.Y.; Miller, L.G.; Bohn, T.S.; Deis, G.A.; Longhurst, G.R.; Masson, L.S.; Wessol, D.E.; Abdou, M.A.
1982-06-01
The overall objective of this task is to investigate the extent to which the power density in the FED breeder blanket test modules can be enhanced by artificial means. Assuming a viable approach can be developed, it will allow testing of advanced reactor blanket modules on INTOR at representative conditions. The tentative approach adopted for this task consists of three parts. First, the requirements for augmented heating of the test module are outlined for different applications of interest. Second, methods are identified which have potential for augmenting the heating power in a test module, and this list of methods is narrowed to those which appear to be most useful. Finally, these methods are examined in more detail to determine the practical benefits of employing each
Evaluation of abrasive waterjet produced titan surfaces topography by spectral analysis techniques
Directory of Open Access Journals (Sweden)
D. Kozak
2012-01-01
Full Text Available Experimental study of a titan grade 2 surface topography prepared by abrasive waterjet cutting is performed using methods of the spectral analysis. Topographic data are acquired by means of the optical profilometr MicroProf®FRT. Estimation of the areal power spectral density of the studied surface is carried out using the periodogram method combined with the Welch´s method. Attention is paid to a structure of the areal power spectral density, which is characterized by means of the angular power spectral density. This structure of the areal spectral density is linked to the fine texture of the surface studied.
Implementation of 252Cf-source-driven power spectrum density measurement system
International Nuclear Information System (INIS)
Ren Yong; Wei Biao; Feng Peng; Li Jiansheng; Ye Cenming
2012-01-01
The principle of 252 Cf-source-driven power spectrum density measurement method is introduced. A measurement system and platform is realized accordingly, which is a combination of hardware and software, for measuring nuclear parameters. The detection method of neutron pulses based on an ultra-high-speed data acquisition card (three channels, 1 GHz sampling rate, 1 ns synchronization) is described, and the data processing process and the power spectrum density algorithm on PC are designed. This 252 Cf-source-driven power spectrum density measurement system can effectively obtain the nuclear tag parameters of nuclear random processes, such as correlation function and power spectrum density. (authors)
High Energy Density Dielectrics for Pulsed Power Applications
National Research Council Canada - National Science Library
Wu, Richard L; Bray, Kevin R
2008-01-01
This report was developed under a SBIR contract. Aluminum oxynitride (AlON) capacitors exhibit several promising characteristics for high energy density capacitor applications in extreme environments...
You, Youbo; Bai, Lijun; Dai, Ruwei; Xue, Ting; Zhong, Chongguang; Liu, Zhenyu; Wang, Hu; Feng, Yuanyuan; Wei, Wenjuan; Tian, Jie
2012-03-01
As an ancient therapeutic technique in Traditional Chinese Medicine, acupuncture has been used increasingly in modern society to treat a range of clinical conditions as an alternative and complementary therapy. However, acupoint specificity, lying at the core of acupuncture, still faces many controversies. Considering previous neuroimaging studies on acupuncture have mainly employed functional magnetic resonance imaging, which only measures the secondary effect of neural activity on cerebral metabolism and hemodynamics, in the current study, we adopted an electrophysiological measurement technique named magnetoencephalography (MEG) to measure the direct neural activity. 28 healthy college students were recruited in this study. We filtered MEG data into 5 consecutive frequency bands (delta, theta, alpha, beta and gamma band) and grouped 140 sensors into 10 main brain regions (left/right frontal, central, temporal, parietal and occipital regions). Fast Fourier Transformation (FFT) based spectral analysis approach was further performed to explore the differential band-limited power change patterns of acupuncture at Stomach Meridian 36 (ST36) using a nearby nonacupoint (NAP) as control condition. Significantly increased delta power and decreased alpha as well as beta power in bilateral frontal ROIs were observed following stimulation at ST36. Compared with ST36, decreased alpha power in left and right central, right parietal as well as right temporal ROIs were detected in NAP group. Our research results may provide additional evidence for acupoint specificity.
An Application of Spectral Kurtosis to Separate Hybrid Power Quality Events
Directory of Open Access Journals (Sweden)
Juan José González de la Rosa
2015-09-01
Full Text Available For the development of the future smart grid, the detection of power quality events is a key issue for the power system monitoring. Voltage sags, swells, harmonics (variations and interruptions, which produce large losses for commercial and industrial consumers, are the main events to be considered due to the sensitivity of equipment to these electrical anomalies. The steady-state events are even more frequently accompanied by transients, the discrimination and localization being far more exigent and requiring advanced signal separating tools to be incorporated in the measurement equipment. This paper shows the event detection performance of the spectral kurtosis as a signal separating tool in the frequency domain. The disturbances under test are hybrid signals resulting from the coupling between amplitude defects and non-desired higher frequencies. Being a fourth-order spectrum, the kurtosis is confirmed as a noise-resistant tool that enhances impulsiveness, therefore characterizing the electrical anomalies. In the beginning of the analysis, the voltage sag is established as a reference; then, the disturbances (oscillatory transients and harmonics are coupled at the starting and ending instants of the sag, resulting in complex hybrid events. The results show that the spectral kurtosis enhances the detection Energies 2015, 8 9778 of both types of events (steady state and transients, which are outlined in a bump shape in the fourth-order frequency pattern and centered in the main carrier frequency. Indeed, while the oscillatory transients are associated with softer and lower-amplitude peaks, the harmonics correspond to crisper and higher ones. As these mixed electrical faults are very common in the actual power grid, the article postulates the higher-order spectra to be implemented in prospective online measurement instruments.
Risky, Yanuar S.; Aulia, Yogi H.; Widayani, Prima
2017-12-01
Spectral indices variations support for rapid and accurate extracting information such as built-up density. However, the exact determination of spectral waves for built-up density extraction is lacking. This study explains and compares the capabilities of 5 variations of spectral indices in spatiotemporal built-up density mapping using Landsat-7 ETM+ and Landsat-8 OLI/TIRS in Surakarta City on 2002 and 2015. The spectral indices variations used are 3 mid-infrared (MIR) based indices such as the Normalized Difference Built-up Index (NDBI), Urban Index (UI) and Built-up and 2 visible based indices such as VrNIR-BI (visible red) and VgNIR-BI (visible green). Linear regression statistics between ground value samples from Google Earth image in 2002 and 2015 and spectral indices for determining built-up land density. Ground value used amounted to 27 samples for model and 7 samples for accuracy test. The classification of built-up density mapping is divided into 9 classes: unclassified, 0-12.5%, 12.5-25%, 25-37.5%, 37.5-50%, 50-62.5%, 62.5-75%, 75-87.5% and 87.5-100 %. Accuracy of built-up land density mapping in 2002 and 2015 using VrNIR-BI (81,823% and 73.235%), VgNIR-BI (78.934% and 69.028%), NDBI (34.870% and 74.365%), UI (43.273% and 64.398%) and Built-up (59.755% and 72.664%). Based all spectral indices, Surakarta City on 2000-2015 has increased of built-up land density. VgNIR-BI has better capabilities for built-up land density mapping on Landsat-7 ETM + and Landsat-8 OLI/TIRS.
International Nuclear Information System (INIS)
Wang, RuLin; Zheng, Xiao; Kwok, YanHo; Xie, Hang; Chen, GuanHua; Yam, ChiYung
2015-01-01
Understanding electronic dynamics on material surfaces is fundamentally important for applications including nanoelectronics, inhomogeneous catalysis, and photovoltaics. Practical approaches based on time-dependent density functional theory for open systems have been developed to characterize the dissipative dynamics of electrons in bulk materials. The accuracy and reliability of such approaches depend critically on how the electronic structure and memory effects of surrounding material environment are accounted for. In this work, we develop a novel squared-Lorentzian decomposition scheme, which preserves the positive semi-definiteness of the environment spectral matrix. The resulting electronic dynamics is guaranteed to be both accurate and convergent even in the long-time limit. The long-time stability of electronic dynamics simulation is thus greatly improved within the current decomposition scheme. The validity and usefulness of our new approach are exemplified via two prototypical model systems: quasi-one-dimensional atomic chains and two-dimensional bilayer graphene
Wang, RuLin; Zheng, Xiao; Kwok, YanHo; Xie, Hang; Chen, GuanHua; Yam, ChiYung
2015-04-14
Understanding electronic dynamics on material surfaces is fundamentally important for applications including nanoelectronics, inhomogeneous catalysis, and photovoltaics. Practical approaches based on time-dependent density functional theory for open systems have been developed to characterize the dissipative dynamics of electrons in bulk materials. The accuracy and reliability of such approaches depend critically on how the electronic structure and memory effects of surrounding material environment are accounted for. In this work, we develop a novel squared-Lorentzian decomposition scheme, which preserves the positive semi-definiteness of the environment spectral matrix. The resulting electronic dynamics is guaranteed to be both accurate and convergent even in the long-time limit. The long-time stability of electronic dynamics simulation is thus greatly improved within the current decomposition scheme. The validity and usefulness of our new approach are exemplified via two prototypical model systems: quasi-one-dimensional atomic chains and two-dimensional bilayer graphene.
Three-dimensional Core Design of a Super Fast Reactor with a High Power Density
International Nuclear Information System (INIS)
Cao, Liangzhi; Oka, Yoshiaki; Ishiwatari, Yuki; Ikejiri, Satoshi; Ju, Haitao
2010-01-01
The SuperCritical Water-cooled Reactor (SCWR) pursues high power density to reduce its capital cost. The fast spectrum SCWR, called a super fast reactor, can be designed with a higher power density than thermal spectrum SCWR. The mechanism of increasing the average power density of the super fast reactor is studied theoretically and numerically. Some key parameters affecting the average power density, including fuel pin outer diameter, fuel pitch, power peaking factor, and the fraction of seed assemblies, are analyzed and optimized to achieve a more compact core. Based on those sensitivity analyses, a compact super fast reactor is successfully designed with an average power density of 294.8 W/cm 3 . The core characteristics are analyzed by using three-dimensional neutronics/thermal-hydraulics coupling method. Numerical results show that all of the design criteria and goals are satisfied
2010-07-01
... cylinders having an internal diameter of 13.0 cm and a 15.5 cm stroke length, the rounded displacement would... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Maximum engine power, displacement... Maximum engine power, displacement, power density, and maximum in-use engine speed. This section describes...
Cally, Paul S.; Xiong, Ming
2018-01-01
Fast sausage modes in solar magnetic coronal loops are only fully contained in unrealistically short dense loops. Otherwise they are leaky, losing energy to their surrounds as outgoing waves. This causes any oscillation to decay exponentially in time. Simultaneous observations of both period and decay rate therefore reveal the eigenfrequency of the observed mode, and potentially insight into the tubes’ nonuniform internal structure. In this article, a global spectral description of the oscillations is presented that results in an implicit matrix eigenvalue equation where the eigenvalues are associated predominantly with the diagonal terms of the matrix. The off-diagonal terms vanish identically if the tube is uniform. A linearized perturbation approach, applied with respect to a uniform reference model, is developed that makes the eigenvalues explicit. The implicit eigenvalue problem is easily solved numerically though, and it is shown that knowledge of the real and imaginary parts of the eigenfrequency is sufficient to determine the width and density contrast of a boundary layer over which the tubes’ enhanced internal densities drop to ambient values. Linearized density kernels are developed that show sensitivity only to the extreme outside of the loops for radial fundamental modes, especially for small density enhancements, with no sensitivity to the core. Higher radial harmonics do show some internal sensitivity, but these will be more difficult to observe. Only kink modes are sensitive to the tube centres. Variation in internal and external Alfvén speed along the loop is shown to have little effect on the fundamental dimensionless eigenfrequency, though the associated eigenfunction becomes more compact at the loop apex as stratification increases, or may even displace from the apex.
Cortical processes associated with continuous balance control as revealed by EEG spectral power.
Hülsdünker, T; Mierau, A; Neeb, C; Kleinöder, H; Strüder, H K
2015-04-10
Balance is a crucial component in numerous every day activities such as locomotion. Previous research has reported distinct changes in cortical theta activity during transient balance instability. However, there remains little understanding of the neural mechanisms underlying continuous balance control. This study aimed to investigate cortical theta activity during varying difficulties of continuous balance tasks, as well as examining the relationship between theta activity and balance performance. 37 subjects completed nine balance tasks with different levels of surface stability and base of support. Throughout the balancing task, electroencephalogram (EEG) was recorded from 32 scalp locations. ICA-based artifact rejection was applied and spectral power was analyzed in the theta frequency band. Theta power increased in the frontal, central, and parietal regions of the cortex when balance tasks became more challenging. In addition, fronto-central and centro-parietal theta power correlated with balance performance. This study demonstrates the involvement of the cerebral cortex in maintaining upright posture during continuous balance tasks. Specifically, the results emphasize the important role of frontal and parietal theta oscillations in balance control. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Estimating workload using EEG spectral power and ERPs in the n-back task
Brouwer, Anne-Marie; Hogervorst, Maarten A.; van Erp, Jan B. F.; Heffelaar, Tobias; Zimmerman, Patrick H.; Oostenveld, Robert
2012-08-01
Previous studies indicate that both electroencephalogram (EEG) spectral power (in particular the alpha and theta band) and event-related potentials (ERPs) (in particular the P300) can be used as a measure of mental work or memory load. We compare their ability to estimate workload level in a well-controlled task. In addition, we combine both types of measures in a single classification model to examine whether this results in higher classification accuracy than either one alone. Participants watched a sequence of visually presented letters and indicated whether or not the current letter was the same as the one (n instances) before. Workload was varied by varying n. We developed different classification models using ERP features, frequency power features or a combination (fusion). Training and testing of the models simulated an online workload estimation situation. All our ERP, power and fusion models provide classification accuracies between 80% and 90% when distinguishing between the highest and the lowest workload condition after 2 min. For 32 out of 35 participants, classification was significantly higher than chance level after 2.5 s (or one letter) as estimated by the fusion model. Differences between the models are rather small, though the fusion model performs better than the other models when only short data segments are available for estimating workload.
Enhancing power density of biophotovoltaics by decoupling storage and power delivery
Saar, Kadi L.; Bombelli, Paolo; Lea-Smith, David J.; Call, Toby; Aro, Eva-Mari; Müller, Thomas; Howe, Christopher J.; Knowles, Tuomas P. J.
2018-01-01
Biophotovoltaic devices (BPVs), which use photosynthetic organisms as active materials to harvest light, have a range of attractive features relative to synthetic and non-biological photovoltaics, including their environmentally friendly nature and ability to self-repair. However, efficiencies of BPVs are currently lower than those of synthetic analogues. Here, we demonstrate BPVs delivering anodic power densities of over 0.5 W m-2, a value five times that for previously described BPVs. We achieved this through the use of cyanobacterial mutants with increased electron export characteristics together with a microscale flow-based design that allowed independent optimization of the charging and power delivery processes, as well as membrane-free operation by exploiting laminar flow to separate the catholyte and anolyte streams. These results suggest that miniaturization of active elements and flow control for decoupled operation and independent optimization of the core processes involved in BPV design are effective strategies for enhancing power output and thus the potential of BPVs as viable systems for sustainable energy generation.
Institute of Scientific and Technical Information of China (English)
ZHANG JianBin; ZHANG PengYan; MA Kai; HAN Fang; CHEN GuoHua; WEI XiongHui
2008-01-01
Studies of the density and the excess molar volume of ethylene glycol (EG)-water mixtures were carried out to illustrate the hydrogen bonding interactions of EG with water at different temperatures, The re-sults suggest that a likely complex of 3 ethylene glycol molecules bonding with 4 water molecules in an ethylene glycol-water mixture (EGW) is formed at the maximal excess molar volume, which displays stronger absorption capabilities for SO2 when the concentration of SO2 reaches 400×106 (volume ratio) in the gas phase. Meanwhile, FTIR and UV spectra of EGWs were recorded at various EG concentra-tions to display the hydrogen bonding interactions of EG with water. The FTIR spectra show that the stretching vibrational band of hydroxyl in the EGWs shifts to a lower frequency and the bending vibra-tional band of water shifts to a higher frequency with increasing the EG concentration, respectively. Furthermore, the UV spectra show that the electron transferring band of the hydroxyl oxygen in EG shows red shift with increasing the EG concentration. The frequency shifts in FTIR spectra and the shifts of absorption bands in UV absorption spectra of EGWs are interpreted as the strong hydrogen bonding interactions of the hydrogen atoms in water with the hydroxyl oxygen atoms of EG.
Wang, Yuan; Bao, Shan; Du, Wenjun; Ye, Zhirui; Sayer, James R
2017-11-17
This article investigated and compared frequency domain and time domain characteristics of drivers' behaviors before and after the start of distracted driving. Data from an existing naturalistic driving study were used. Fast Fourier transform (FFT) was applied for the frequency domain analysis to explore drivers' behavior pattern changes between nondistracted (prestarting of visual-manual task) and distracted (poststarting of visual-manual task) driving periods. Average relative spectral power in a low frequency range (0-0.5 Hz) and the standard deviation in a 10-s time window of vehicle control variables (i.e., lane offset, yaw rate, and acceleration) were calculated and further compared. Sensitivity analyses were also applied to examine the reliability of the time and frequency domain analyses. Results of the mixed model analyses from the time and frequency domain analyses all showed significant degradation in lateral control performance after engaging in visual-manual tasks while driving. Results of the sensitivity analyses suggested that the frequency domain analysis was less sensitive to the frequency bandwidth, whereas the time domain analysis was more sensitive to the time intervals selected for variation calculations. Different time interval selections can result in significantly different standard deviation values, whereas average spectral power analysis on yaw rate in both low and high frequency bandwidths showed consistent results, that higher variation values were observed during distracted driving when compared to nondistracted driving. This study suggests that driver state detection needs to consider the behavior changes during the prestarting periods, instead of only focusing on periods with physical presence of distraction, such as cell phone use. Lateral control measures can be a better indicator of distraction detection than longitudinal controls. In addition, frequency domain analyses proved to be a more robust and consistent method in assessing
A HARD X-RAY POWER-LAW SPECTRAL CUTOFF IN CENTAURUS X-4
Energy Technology Data Exchange (ETDEWEB)
Chakrabarty, Deepto; Nowak, Michael A. [MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Tomsick, John A.; Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Grefenstette, Brian W.; Fürst, Felix; Harrison, Fiona A.; Rana, Vikram [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Psaltis, Dimitrios [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Bachetti, Matteo; Barret, Didier [Observatoire Midi-Pyrénées, Université de Toulouse III - Paul Sabatier, F-31400 Toulouse (France); Christensen, Finn E. [Division of Astrophysics, National Space Institute, Technical University of Denmark, DK-2800 Lyngby (Denmark); Hailey, Charles J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Kaspi, Victoria M. [Department of Physics, McGill University, Montreal, PQ H3A 2T8 (Canada); Miller, Jon M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Wik, Daniel R.; Zhang, William W. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wilms, Jörn, E-mail: deepto@mit.edu [Dr. Karl-Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Universität Erlangen-Nürnberg, D-96049 Bamberg (Germany)
2014-12-20
The low-mass X-ray binary (LMXB) Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1×10{sup 33} D{sub kpc}{sup 2} erg s{sup –1}, with ≅60% in the thermal component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. We show that thermal Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with kT{sub e} = 18 keV, which can be understood as arising either in a hot layer above the neutron star atmosphere or in a radiatively inefficient accretion flow. The power-law cutoff energy may be set by the degree of Compton cooling of the bremsstrahlung electrons by thermal seed photons from the neutron star surface. Lower thermal luminosities should lead to higher (possibly undetectable) cutoff energies. We compare Cen X-4's behavior with PSR J1023+0038, IGR J18245–2452, and XSS J12270–4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity.
New final doublets and power densities for the international linear ...
Indian Academy of Sciences (India)
Abstract. In this paper we use current and proposed final doublet magnet technologies to reoptimise the interaction region of the international linear collider and reduce the power losses. The result is a set of three new final doublet layouts with improved beam transport properties. The effect of localised power deposition and ...
Night sleep electroencephalogram power spectral analysis in excessive daytime sleepiness disorders
Directory of Open Access Journals (Sweden)
Rubens Reimão
1991-06-01
Full Text Available A group of 53 patients (40 míales, 13 females with mean age of 49 years, ranging from 30 to 70 years, was evaluated in the. following excessive daytime sleepiness (EDS disorders : obstructive sleep apnea syndrome (B4a, periodic movements in sleep (B5a, affective disorder (B2a, functional psychiatric non affective disorder (B2b. We considered all adult patients referred to the Center sequentially with no other distinctions but these three criteria: (a EDS was the main complaint; (b right handed ; (c not using psychotropic drugs for two weeks prior to the all-night polysomnography. EEG (C3/A1, C4/A2 samples from 2 to 10 minutes of each stage of the first REM cycle were chosen. The data was recorded simultaneously in magnetic tape and then fed into a computer for power spectral analysis. The percentage of power (PP in each band calculated in relation to the total EEG power was determined of subsequent sections of 20.4 s for the following frequency bands: delta, theta, alpha and beta. The PP in all EOS patients sample had a tendency to decrease progressively from the slowest to the fastest frequency bands, in every sleep stage. PP distribution in the delta range increased progressively from stage 1 to stage 4; stage REM levels were close to stage 2 levels. In an EDS patients interhemispheric coherence was high in every band and sleep stage. B4a patients sample PP had a tendency to decrease progressively from the slowest to the fastest frequency bands, in¡ every sleep stage; PP distribution in the delta range increased progressively from stage 1 to stage 4; stage REM levels were between stage 1 and stage 2 levels. B2a patients sample PP had a tendency to decrease progressively from the slowest to the fastest frequency bands, in every sleep stage; PP distribution in the delta range increased progressively from stage 1 to stage 4; stage REM levels were close to stage 2 levels. B2b patients sample PP had a tendency to decrease progressively from the
Wind power statistics and an evaluation of wind energy density
Energy Technology Data Exchange (ETDEWEB)
Jamil, M.; Parsa, S.; Majidi, M. [Materials and Energy Research Centre, Tehran (Iran, Islamic Republic of)
1995-11-01
In this paper the statistical data of fifty days` wind speed measurements at the MERC- solar site are used to find out the wind energy density and other wind characteristics with the help of the Weibull probability distribution function. It is emphasized that the Weibull and Rayleigh probability functions are useful tools for wind energy density estimation but are not quite appropriate for properly fitting the actual wind data of low mean speed, short-time records. One has to use either the actual wind data (histogram) or look for a better fit by other models of the probability function. (Author)
Frontiers in pulse-power-based high energy density plasma physics and its applications
International Nuclear Information System (INIS)
Horioka, Kazuhiko
2008-03-01
The papers in this volume of report were presented at the Symposium on Frontiers in Pulse-power-based High Energy Density Physics' held by National Institute for Fusion Science. The topics include the present status of high energy density plasma researches, extreme ultraviolet sources, intense radiation sources, high power ion beams, and R and D of related pulse power technologies. The 13 of the presented papers are indexed individually. (J.P.N.)
Frontiers of particle beam and high energy density plasma science using pulse power technology
International Nuclear Information System (INIS)
Masugata, Katsumi
2011-04-01
The papers presented at the symposium on “Frontiers of Particle Beam and High Energy Density Plasma Science using Pulse Power Technology” held in November 20-21, 2009 at National Institute for Fusion Science are collected. The papers reflect the present status and resent progress in the experiment and theoretical works on high power particle beams and high energy density plasmas produced by pulsed power technology. (author)
Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts
Dichiara, S.; Guidorzi, C.; Amati, L.; Frontera, F.; Margutti, R.
2016-05-01
Context. The origin of the gamma-ray burst (GRB) prompt emission still defies explanation, in spite of recent progress made, for example, on the occasional presence of a thermal component in the spectrum along with the ubiquitous non-thermal component that is modelled with a Band function. The combination of finite duration and aperiodic modulations make GRBs hard to characterise temporally. Although correlations between GRB luminosity and spectral hardness on one side and time variability on the other side have long been known, the loose and often arbitrary definition of the latter makes the interpretation uncertain. Aims: We characterise the temporal variability in an objective way and search for a connection with rest-frame spectral properties for a number of well-observed GRBs. Methods: We studied the individual power density spectra (PDS) of 123 long GRBs with measured redshift, rest-frame peak energy Ep,I of the time-averaged ν Fν spectrum, and well-constrained PDS slope α detected with Swift, Fermi and past spacecraft. The PDS were modelled with a power law either with or without a break adopting a Bayesian Markov chain Monte Carlo technique. Results: We find a highly significant Ep,I-α anti-correlation. The null hypothesis probability is ~10-9. Conclusions: In the framework of the internal shock synchrotron model, the Ep,I-α anti-correlation can hardly be reconciled with the predicted Ep,I ∝ Γ-2, unless either variable microphysical parameters of the shocks or continual electron acceleration are assumed. Alternatively, in the context of models based on magnetic reconnection, the PDS slope and Ep,I are linked to the ejecta magnetisation at the dissipation site, so that more magnetised outflows would produce more variable GRB light curves at short timescales (≲1 s), shallower PDS, and higher values of Ep,I. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc
LIQHYSMES – spectral power distributions of imbalances and implications for the SMES
International Nuclear Information System (INIS)
Sander, M; Gehring, R; Neumann, H
2014-01-01
LIQHYSMES, the recently proposed hybrid energy storage concept for variable renewable energies, combines the storage of LIQuid HYdrogen (LH2) with Superconducting Magnetic Energy Storage (SMES). LH2 as the bulk energy carrier is used for the large scale stationary longer-term energy storage, and the SMES cooled by the LH2 bath, provides highest power over shorter periods and at superior efficiencies. Both together contribute to the balancing of electric load or supply fluctuations from seconds to several hours, days or even weeks. Here different spectral power distributions of such imbalances between electricity supply and load reflecting different sources of fluctuations in the range between 1 sec and 15 minutes are considered. Some related implications for MgB2-based 100 MW-SMES operated at maximum fields of 2 T and 4 T, are considered for these buffering scenarios. Requirements as regards the storage capacity and correspondingly the minimum size of the LH2 storage tank are derived. The related loss contributions with a particular focus on the ramping losses are analysed.
The art of Spectral Management ; Upstream power back-off for VDSL2 - Whitepaper DSL05
Brink, R.F.M. van den
2009-01-01
Spectral Management (SpM) involves managing an access network such that different systems can co-exist with each other. In relation to DSL systems, spectral management ensures that they can co-exist within the same cable. The use of spectral signal limits (specified via mandatory access rules) is
Feedback control of plasma density and heating power for steady state operation in LHD
Energy Technology Data Exchange (ETDEWEB)
Kamio, Shuji, E-mail: kamio@nifs.ac.jp; Kasahara, Hiroshi; Seki, Tetsuo; Saito, Kenji; Seki, Ryosuke; Nomura, Goro; Mutoh, Takashi
2015-12-15
Highlights: • We upgraded a control system for steady state operation in LHD. • This system contains gas fueling system and ICRF power control system. • Automatic power boost system is also attached for stable operation. • As a result, we achieved the long pulse up to 48 min in the electron density of more than 1 × 10{sup 19} m{sup −3}. - Abstract: For steady state operation, the feedback control of plasma density and heating power system was developed in the Large Helical Device (LHD). In order to achieve a record of the long pulse discharge, stable plasma density and heating power are needed. This system contains the radio frequency (RF) heating power control, interlocks, gas fueling, automatic RF phase control, ion cyclotron range of frequency (ICRF) antenna position control, and graphical user interface (GUI). Using the density control system, the electron density was controlled to the target density and using the RF heating power control system, the RF power injection could be stable. As a result of using this system, we achieved the long pulse up to 48 min in the electron density of more than 1 × 10{sup 19} m{sup −3}. Further, the ICRF hardware experienced no critical accidents during the 17th LHD experiment campaign in 2013.
Directory of Open Access Journals (Sweden)
Ana Paula Ferreira de Carvalho
2013-05-01
Full Text Available Radiometric precision is difficult to maintain in orbital images due to several factors (atmospheric conditions, Earth-sun distance, detector calibration, illumination, and viewing angles. These unwanted effects must be removed for radiometric consistency among temporal images, leaving only land-leaving radiances, for optimum change detection. A variety of relative radiometric correction techniques were developed for the correction or rectification of images, of the same area, through use of reference targets whose reflectance do not change significantly with time, i.e., pseudo-invariant features (PIFs. This paper proposes a new technique for radiometric normalization, which uses three sequential methods for an accurate PIFs selection: spectral measures of temporal data (spectral distance and similarity, density scatter plot analysis (ridge method, and robust regression. The spectral measures used are the spectral angle (Spectral Angle Mapper, SAM, spectral correlation (Spectral Correlation Mapper, SCM, and Euclidean distance. The spectral measures between the spectra at times t1 and t2 and are calculated for each pixel. After classification using threshold values, it is possible to define points with the same spectral behavior, including PIFs. The distance and similarity measures are complementary and can be calculated together. The ridge method uses a density plot generated from images acquired on different dates for the selection of PIFs. In a density plot, the invariant pixels, together, form a high-density ridge, while variant pixels (clouds and land cover changes are spread, having low density, facilitating its exclusion. Finally, the selected PIFs are subjected to a robust regression (M-estimate between pairs of temporal bands for the detection and elimination of outliers, and to obtain the optimal linear equation for a given set of target points. The robust regression is insensitive to outliers, i.e., observation that appears to deviate
International Nuclear Information System (INIS)
Schaffer, J.P.; Shaughnessy, E.J.; Jones, P.L.
1984-01-01
A deconvolution procedure which corrects Doppler-broadened positron annihilation spectra for instrument resolution is described. The method employs fast Fourier transforms, is model independent, and does not require iteration. The mathematical difficulties associated with the incorrectly posed first order Fredholm integral equation are overcome by using power spectral analysis to select a limited number of low frequency Fourier coefficients. The FFT/power spectrum method is then demonstrated for an irradiated high purity single crystal sapphire sample. (orig.)
Radiation power profiles and density limit with a divertor in the W7-AS stellarator
International Nuclear Information System (INIS)
Giannone, L.; Burhenn, R.; McCormick, K.; Brakel, R.; Feng, Y.; Grigull, P.; Igitkhanov, Y.
2002-01-01
The addition of a divertor into the W7-AS stellarator has allowed access to a high density regime where the radiation profiles reach a steady state. In earlier limiter discharges, the plasma suffered a radiative collapse at high densities. In contrast to limiter experiments, where the impurity confinement time measured by Al laser blow-off increased with increasing line integrated density, in divertor discharges, above a density threshold, the impurity confinement time decreased with increasing line integrated density. The observation that the divertor plasma radiates mainly at the plasma edge rather than the plasma centre is a further indication that changes to the impurity transport coefficients at these high densities are the basis for the achievement of steady state discharges in the divertor configuration of W7-AS. The maximum line integrated density reached with a divertor is compared to that reached with a limiter. The previously derived scaling law for the density limit with a limiter shows that the achieved densities do not exceed those predicted when the higher deposited power is taken into account. In a divertor the radiated power is located at the plasma edge and increasing the density, cooling the plasma edge and radiating sufficient power to cause plasma detachment determines the density limit. (author)
2010-10-01
... 47 Telecommunication 2 2010-10-01 2010-10-01 false Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS. 25.223 Section 25.223 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25...
Energy Technology Data Exchange (ETDEWEB)
Martinazzo, Rocco [Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20122 Milan (Italy); Hughes, Keith H. [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Martelli, Fausto [Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20122 Milan (Italy); Departement de Chimie, Ecole Normale Superieure, 24 rue Lhomond, F-75231 Paris cedex 05 (France); Burghardt, Irene, E-mail: irene.burghardt@ens.fr [Departement de Chimie, Ecole Normale Superieure, 24 rue Lhomond, F-75231 Paris cedex 05 (France)
2010-11-25
Graphical abstract: The effect of high-dimensional environments on conical intersections can be described by hierarchies of approximate spectral densities, which translate to truncated effective-mode chains in the time domain. Abstract: A recently developed effective-mode representation is employed to characterize the influence of a multi-dimensional environment on the S{sub 2}-S{sub 1} conical intersection in pyrazine, taken as a paradigm case of high-dimensional dynamics at a conical intersection. We consider a simplified model by which four modes are strongly coupled to the electronic subsystem while a number of weakly coupled tuning modes, inducing energy gap fluctuations, are sampled from a spectral density. The latter is approximated by a series of simplified spectral densities which can be cast into a continued-fraction form, as previously demonstrated in Hughes et al. (K.H. Hughes, C.D. Christ, I. Burghardt, J. Chem. Phys. 131 (2009) 124108). In the time domain, the hierarchy of spectral densities translates to truncated effective-mode chains with a Markovian or quasi-Markovian (Rubin type) closure. A sequential deconvolution procedure is employed to generate this chain representation. The implications for the ultrafast dynamics and its representation in terms of reduced-dimensional models are discussed.
High power density superconducting motor for control applications
International Nuclear Information System (INIS)
Lopez, J; Granados, X; Lloberas, J; Torres, R; Grau, J; Maynou, R; Bosch, R
2008-01-01
A high dynamics superconducting low power motor for control applications has been considered for design. The rotor is cylindrical with machined bulks that generate the field by trapping flux in a four poles configuration. The toothless iron armature is wound by copper, acting iron only as magnetic screen. Details of the magnetic assembling, cryogenics and electrical supply conditioning will be reported. Improvements due to the use of a superconducting set are compared with performances of equivalent conventional motors
Stable formation of ultrahigh power-density 248 nm channels in Xe cluster targets
Energy Technology Data Exchange (ETDEWEB)
Borisov, Alex B.; Racz, Ervin; Khan, Shahab F.; Poopalasingam, Sankar; McCorkindale, John C.; Boguta, John; Longworth, James W.; Rhodes, Charles K. [Laboratory for X-ray Microimaging and Bioinformatics, Department of Physics, University of Illinois at Chicago, Chicago, IL 60607-7059 (United States); KFKI Research Institute for Particle and Nuclear Physics, EURATOM Association, P.O. Box 49, 1525 Budapest (Hungary)
2012-07-11
The optimization of relativistic and ponderomotive self-channeling of ultra-powerful 248 nm laser pulses launched in underdense plasmas with an appropriate longitudinal gradient in the electron density profile located at the initial stage of the self-channeling leads to (1) stable channel formation and (2) highly efficient power compression producing power densities in the 10{sup 19}-10{sup 20} W/cm{sup 3} range. The comparison of theoretical studies with experimental results involving the correlation of (a) Thomson images of the electron density with (b) x-ray images of the channel morphology demonstrates that more than 90% of the incident 248 nm power can be trapped in stable channels and that this stable propagation can be extended to power levels significantly exceeding the critical power of the self-channeling process.
Spectral analysis by correlation
International Nuclear Information System (INIS)
Fauque, J.M.; Berthier, D.; Max, J.; Bonnet, G.
1969-01-01
The spectral density of a signal, which represents its power distribution along the frequency axis, is a function which is of great importance, finding many uses in all fields concerned with the processing of the signal (process identification, vibrational analysis, etc...). Amongst all the possible methods for calculating this function, the correlation method (correlation function calculation + Fourier transformation) is the most promising, mainly because of its simplicity and of the results it yields. The study carried out here will lead to the construction of an apparatus which, coupled with a correlator, will constitute a set of equipment for spectral analysis in real time covering the frequency range 0 to 5 MHz. (author) [fr
DEFF Research Database (Denmark)
Fan, Lin; Knott, Arnold; Jørgensen, Ivan Harald Holger
2018-01-01
. This paper presents such a high voltage low power switched-capacitor DC-DC converter with an input voltage upto 380 V (compatible with rectified European mains) and an output power experimentally validated up to 21.3 W. The wideband gap semiconductor devices of GaN switches and SiC diodes are combined...... to compose the proposed power stage. Their switching and loss characteristics are analyzed with transient waveforms and thermal images. Different isolated driving circuits are compared and a compact isolated halfbridge driving circuit is proposed. The full-load efficiencies of 98.3% and 97.6% are achieved......State-of-the-art switched-capacitor DC-DC power converters mainly focus on low voltage and/or high power applications. However, at high voltage and low power levels, new designs are anticipated to emerge and a power converter that has both high efficiency and high power density is highly desirable...
Oscillating thermionic conversion for high-density space power
International Nuclear Information System (INIS)
Jacobson, D.L.; Morris, J.F.
1988-01-01
The compactness, maneuverability, and productive weight utilization of space nuclear reactors benefit from the use of thermionic converters at high temperature. Nuclear-thermionic-conversion power requirements are discussed, and the role of oscillations in thermionic energy conversion (TEC) history is examined. Proposed TEC oscillations are addressed, and the results of recent studies of TEC oscillations are reviewed. The possible use of high-frequency TEC oscillations to amplify low-frequency ones is considered. The accomplishments of various programs studying the use of high-temperature thermionic oscillators are examined. 16 references
Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios
2016-12-01
Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.
Nanomaterials Enabled High Energy and Power Density Li-ion Batteries, Phase I
National Aeronautics and Space Administration — There is a need for high energy (~ 200 Wh/kg) and high power (> 500 W/kg) density rechargeable Li-ion batteries that are safe and reliable for several space and...
Study of In-Cylinder Reactions of High Power-Density Direct Injection Diesel Engines
National Research Council Canada - National Science Library
Jansons, M
2004-01-01
Direct-injection (DI) Diesel or compression-ignition (CI) engine combustion process is investigated when new design and operational strategies are employed in order to achieve a high power-density (HPD) engine...
Efficient, High Power Density Hydrocarbon-Fueled Solid Oxide Stack System, Phase II
National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop and demonstrate an innovative high power density design for direct internal reforming of regolith off-gases...
Efficient, high power density hydrocarbon-fueled solid oxide stack system, Phase I
National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop and demonstrate an innovative high power density design for direct internal reforming of regolith off-gases...
A search for X-ray reprocessing echoes in the power spectral density functions of AGN
Czech Academy of Sciences Publication Activity Database
Emmanoulopoulos, D.; Papadakis, I.E.; Epitropakis, A.; Pecháček, Tomáš; Dovčiak, Michal; McHardy, I.M.
2016-01-01
Roč. 461, č. 2 (2016), s. 1642-1655 ISSN 0035-8711 Institutional support: RVO:67985815 Keywords : black hole physics * galaxies * X-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.961, year: 2016
Directory of Open Access Journals (Sweden)
Q. Cheng
2010-10-01
Full Text Available This contribution introduces a fractal filtering technique newly developed on the basis of a spectral energy density vs. area power-law model in the context of multifractal theory. It can be used to map anisotropic singularities of geochemical landscapes created from geochemical concentration values in various surface media such as soils, stream sediments, tills and water. A geochemical landscape can be converted into a Fourier domain in which the spectral energy density is plotted against the area (in wave number units, and the relationship between the spectrum energy density (S and the area (A enclosed by the above-threshold spectrum energy density can be fitted by power-law models. Mixed geochemical landscape patterns can be fitted with different S-A power-law models in the frequency domain. Fractal filters can be defined according to these different S-A models and used to decompose the geochemical patterns into components with different self-similarities. The fractal filtering method was applied to a geochemical dataset from 7,349 stream sediment samples collected from Gejiu mineral district, which is famous for its word-class tin and copper production. Anomalies in three different scales were decomposed from total values of the trace elements As, Sn, Cu, Zn, Pb, and Cd. These anomalies generally correspond to various geological features and geological processes such as sedimentary rocks, intrusions, fault intersections and mineralization.
A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation
Pan, Liwen; Zhang, Chengning
2015-01-01
This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge cir...
Methods for reconstruction of the density distribution of nuclear power
International Nuclear Information System (INIS)
Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S.
2015-01-01
Highlights: • Two methods for reconstruction of the pin power distribution are presented. • The ARM method uses analytical solution of the 2D diffusion equation. • The PRM method uses polynomial solution without boundary conditions. • The maximum errors in pin power reconstruction occur in the peripheral water region. • The errors are significantly less in the inner area of the core. - Abstract: In analytical reconstruction method (ARM), the two-dimensional (2D) neutron diffusion equation is analytically solved for two energy groups (2G) and homogeneous nodes with dimensions of a fuel assembly (FA). The solution employs a 2D fourth-order expansion for the axial leakage term. The Nodal Expansion Method (NEM) provides the solution average values as the four average partial currents on the surfaces of the node, the average flux in the node and the multiplying factor of the problem. The expansion coefficients for the axial leakage are determined directly from NEM method or can be determined in the reconstruction method. A new polynomial reconstruction method (PRM) is implemented based on the 2D expansion for the axial leakage term. The ARM method use the four average currents on the surfaces of the node and four average fluxes in corners of the node as boundary conditions and the average flux in the node as a consistency condition. To determine the average fluxes in corners of the node an analytical solution is employed. This analytical solution uses the average fluxes on the surfaces of the node as boundary conditions and discontinuities in corners are incorporated. The polynomial and analytical solutions to the PRM and ARM methods, respectively, represent the homogeneous flux distributions. The detailed distributions inside a FA are estimated by product of homogeneous distribution by local heterogeneous form function. Moreover, the form functions of power are used. The results show that the methods have good accuracy when compared with reference values and
Scarpace, F. L.; Voss, A. W.
1973-01-01
Dye densities of multi-layered films are determined by applying a regression analysis to the spectral response of the composite transparency. The amount of dye in each layer is determined by fitting the sum of the individual dye layer densities to the measured dye densities. From this, dye content constants are calculated. Methods of calculating equivalent exposures are discussed. Equivalent exposures are a constant amount of energy over a limited band-width that will give the same dye content constants as the real incident energy. Methods of using these equivalent exposures for analysis of photographic data are presented.
Control of plasma density distribution via wireless power transfer in an inductively coupled plasma
International Nuclear Information System (INIS)
Lee, Hee-Jin; Lee, Hyo-Chang; Kim, Young-Cheol; Chung, Chin-Wook
2013-01-01
With an enlargement of the wafer size, development of large-area plasma sources and control of plasma density distribution are required. To control the spatial distribution of the plasma density, wireless power transfer is applied to an inductively coupled plasma for the first time. An inner powered antenna and an outer resonant coil connected to a variable capacitor are placed on the top of the chamber. As the self-resonance frequency ω r of the resonant coil is adjusted, the power transfer rate from the inner powered coil to the outer resonant coil is changed and the dramatic evolution of the plasma density profile is measured. As ω r of the outer resonant coil changes from the non-resonant condition (where ω r is not the driving angular frequency ω rf ) to the resonant condition (where ω r = ω rf ), the plasma density profile evolves from a convex shape with maximal plasma density at the radial center into a concave shape with maximal plasma density in the vicinity of the resonant antenna coil. This result shows that the plasma density distribution can be successfully controlled via wireless resonance power transfer. (fast track communication)
Low-power digital ASIC for on-chip spectral analysis of low-frequency physiological signals
International Nuclear Information System (INIS)
Nie Zedong; Zhang Fengjuan; Li Jie; Wang Lei
2012-01-01
A digital ASIC chip customized for battery-operated body sensing devices is presented. The ASIC incorporates a novel hybrid-architecture fast Fourier transform (FFT) unit that is capable of scalable spectral analysis, a licensed ARM7TDMI IP hardcore and several peripheral IP blocks. Extensive experimental results suggest that the complete chip works as intended. The power consumption of the FFT unit is 0.69 mW at 1 MHz with 1.8 V power supply. The low-power and programmable features of the ASIC make it suitable for ‘on-the-fly’ low-frequency physiological signal processing. (semiconductor integrated circuits)
Atlas Pulsed Power Facility for High Energy Density Physics Experiments
International Nuclear Information System (INIS)
Miller, R.B.; Ballard, E.O.; Barr, G.W.; Bowman, D.W.; Chochrane, J.C.; Davis, H.A.; Elizondo, J.M.; Gribble, R.F.; Griego, J.R.; Hicks, R.D.; Hinckley, W.B.; Hosack, K.W.; Nielsen, K.E.; Parker, J.V.; Parsons, M.O.; Rickets, R.L.; Salazar, H.R.; Sanchez, P.G.; Scudder, D.W.; Shapiro, C.; Thompson, M.C.; Trainor, R.J.; Valdez, G.A.; Vigil, B.N.; Watt, R.G.; Wysock, F.J.
1999-01-01
The Atlas facility, now under construction at Los Alamos National Laboratory (LANL), will provide a unique capability for performing high-energy-density experiments in support of weapon-physics and basic-research programs. It is intended to be an international user facility, providing opportunities for researchers from national laboratories and academic institutions around the world. Emphasizing institutions around the world. Emphasizing hydrodynamic experiments, Atlas will provide the capability for achieving steady shock pressures exceeding 10-Mbar in a volume of several cubic centimeters. In addition, the kinetic energy associated with solid liner implosion velocities exceeding 12 km/s is sufficient to drive dense, hydrodynamic targets into the ionized regime, permitting the study of complex issues associated with strongly-coupled plasmas. The primary element of Atlas is a 23-MJ capacitor bank, comprised of 96 separate Marx generators housed in 12 separate oil-filled tanks, surrounding a central target chamber. Each tank will house two, independently-removable maintenance units, with each maintenance unit consisting of four Marx modules. Each Marx module has four capacitors that can each be charged to a maximum of 60 kilovolts. When railgap switches are triggered, the marx modules erect to a maximum of 240 kV. The parallel discharge of these 96 Marx modules will deliver a 30-MA current pulse with a 4-5-micros risetime to a cylindrical, imploding liner via 24 vertical, tri-plate, oil-insulated transmission lines. An experimental program for testing and certifying all Marx and transmission line components has been completed. A complete maintenance module and its associated transmission line (the First Article) are now under construction and testing. The current Atlas schedule calls for construction of the machine to be complete by August, 2000. Acceptance testing is scheduled to begin in November, 2000, leading to initial operations in January, 2001
Low prepulse, high power density water dielectric switching
International Nuclear Information System (INIS)
Johnson, D.L.; VanDevender, J.P.; Martin, T.H.
1979-01-01
Prepulse voltage suppression has proven difficult in high power, high voltage accelerators employing self-breakdown water dielectric switches. A novel and cost effective water switch has been developed at Sandia Laboratories which reduces prepulse voltage by reducing the capacity across the switch. This prepulse suppression switch causes energy formerly stored in the switch capacity and dissipated in the arc to be useful output energy. The switching technique also allows the pulse forming lines to be stacked in parallel and electrically isolated from the load after the line has been discharged. The switch consists of a ground plane, with several holes, inserted between the switch electrodes. The output line switch electrodes extend through the holes and face electrodes on the pulse forming line (PFL). The capacity between the PFL and the output transmission line is reduced by about 80%. The gap spacing between the output line electrode and the hole in the ground plane is adjusted so that breakdown occurs after the main pulse and provides a crow bar between the load and the source. Performance data from the Proto II, Mite and Ripple test facilities are presented
Flexible asymmetric supercapacitors with high energy and high power density in aqueous electrolytes
Cheng, Yingwen; Zhang, Hongbo; Lu, Songtao; Varanasi, Chakrapani V.; Liu, Jie
2013-01-01
Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s-1 to 500 mV s-1. Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg-1) under high power density (7.8 kW kg-1) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required.Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of
Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries
Li, Jianlin; Du, Zhijia; Ruther, Rose E.; AN, Seong Jin; David, Lamuel Abraham; Hays, Kevin; Wood, Marissa; Phillip, Nathan D.; Sheng, Yangping; Mao, Chengyu; Kalnaus, Sergiy; Daniel, Claus; Wood, David L.
2017-09-01
Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by 70% from 2008 to 2015, the current battery pack cost (268/kWh in 2015) is still >2 times what the USABC targets (125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. This article discusses three major aspects for cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed.
Budhiraja, Rohit; Quan, Stuart F; Punjabi, Naresh M; Drake, Christopher L; Dickman, Ram; Fass, Ronnie
2010-02-01
Determine the feasibility of using power spectrum of the sleep electroencephalogram (EEG) as a more sensitive tool than sleep architecture to evaluate the relationship between gastroesophageal reflux disease (GERD) and sleep. GERD has been shown to adversely affect subjective sleep reports but not necessarily objective sleep parameters. Data were prospectively collected from symptomatic patients with heartburn. All symptomatic patients underwent upper endoscopy. Patients without erosive esophagitis underwent pH testing. Sleep was polygraphically recorded in the laboratory. Spectral analysis was performed to determine the power spectrum in 4 bandwidths: delta (0.8 to 4.0 Hz), theta (4.1 to 8.0 Hz), alpha (8.1 to 13.0 Hz), and beta (13.1 to 20.0 Hz). Eleven heartburn patients were included in the GERD group (erosive esophagitis) and 6 heartburn patients in the functional heartburn group (negative endoscopy, pH test, response to proton pump inhibitors). The GERD patients had evidence of lower average delta-power than functional heartburn patients. Patients with GERD had greater overall alpha-power in the latter half of the night (3 hours after sleep onset) than functional heartburn patients. No significant differences were noted in conventional sleep stage summaries between the 2 groups. Among heartburn patients with GERD, EEG spectral power during sleep is shifted towards higher frequencies compared with heartburn patients without GERD despite similar sleep architecture. This feasibility study demonstrated that EEG spectral power during sleep might be the preferred tool to provide an objective analysis about the effect of GERD on sleep.
Study of variations of radiofrequency power density from mobile phone base stations with distance
International Nuclear Information System (INIS)
Ayinmode, B. O.; Farai, I. P.
2013-01-01
The variations of radiofrequency (RF) radiation power density with distance around some mobile phone base stations (BTSs), in ten randomly selected locations in Ibadan, western Nigeria, were studied. Measurements were made with a calibrated hand-held spectrum analyser. The maximum Global System of Mobile (GSM) communication 1800 signal power density was 323.91 μW m -2 at 250 m radius of a BTS and that of GSM 900 was 1119.00 μW m -2 at 200 m radius of another BTS. The estimated total maximum power density was 2972.00 μW m -2 at 50 m radius of a different BTS. This study shows that the maximum carrier signal power density and the total maximum power density from a BTS may be observed averagely at 200 and 50 m of its radius, respectively. The result of this study demonstrates that exposure of people to RF radiation from phone BTSs in Ibadan city is far less than the recommended limits by International scientific bodies. (authors)
International Nuclear Information System (INIS)
Mohammadi, Kasra; Alavi, Omid; Mostafaeipour, Ali; Goudarzi, Navid; Jalilvand, Mahdi
2016-01-01
Highlights: • Effectiveness of six numerical methods is evaluated to determine wind power density. • More appropriate method for computing the daily wind power density is estimated. • Four windy stations located in the south part of Alberta, Canada namely is investigated. • The more appropriate parameters estimation method was not identical among all examined stations. - Abstract: In this study, the effectiveness of six numerical methods is evaluated to determine the shape (k) and scale (c) parameters of Weibull distribution function for the purpose of calculating the wind power density. The selected methods are graphical method (GP), empirical method of Justus (EMJ), empirical method of Lysen (EML), energy pattern factor method (EPF), maximum likelihood method (ML) and modified maximum likelihood method (MML). The purpose of this study is to identify the more appropriate method for computing the wind power density in four stations distributed in Alberta province of Canada namely Edmonton City Center Awos, Grande Prairie A, Lethbridge A and Waterton Park Gate. To provide a complete analysis, the evaluations are performed on both daily and monthly scales. The results indicate that the precision of computed wind power density values change when different parameters estimation methods are used to determine the k and c parameters. Four methods of EMJ, EML, EPF and ML present very favorable efficiency while the GP method shows weak ability for all stations. However, it is found that the more effective method is not similar among stations owing to the difference in the wind characteristics.
REJUVENATING THE MATTER POWER SPECTRUM: RESTORING INFORMATION WITH A LOGARITHMIC DENSITY MAPPING
International Nuclear Information System (INIS)
Neyrinck, Mark C.; Szalay, Alexander S.; Szapudi, Istvan
2009-01-01
We find that nonlinearities in the dark matter power spectrum are dramatically smaller if the density field first undergoes a logarithmic mapping. In the Millennium simulation, this procedure gives a power spectrum with a shape hardly departing from the linear power spectrum for k ∼ -1 at all redshifts. Also, this procedure unveils pristine Fisher information on a range of scales reaching a factor of 2-3 smaller than in the standard power spectrum, yielding 10 times more cumulative signal to noise at z = 0.
Power density effect on feasibility of water cooled thorium breeder reactor
International Nuclear Information System (INIS)
Sidik, Permana; Takaki, Naoyuki; Sekimoto, Hiroshi
2008-01-01
Breeding is made possible by the high value of neutron regeneration ratio η for 233 U in thermal energy region. The reactor is fueled by 233 U-Th oxide and it has used the light water as moderator. Some characteristics such as spectrum, η value, criticality, breeding performance and number density are evaluated. Several power densities are evaluated in order to analyze its effect to the breeding performance. The η value of fissile 233 U obtains higher value than 2 which may satisfy the breeding capability especially for thermal reactor for all investigated MFR. The increasing enrichment and decreasing conversion ratio are more significant for MFR 233 U enrichment. Number density of 233 Pa decreases significantly with decreasing power density which leads the reactor has better breeding performance because lower capture rate of 233 Pa. (author)
Power density of piezoelectric transformers improved using a contact heat transfer structure.
Shao, Wei Wei; Chen, Li Juan; Pan, Cheng Liang; Liu, Yong Bin; Feng, Zhi Hua
2012-01-01
Based on contact heat transfer, a novel method to increase power density of piezoelectric transformers is proposed. A heat transfer structure is realized by directly attaching a dissipater to the piezoelectric transformer plate. By maintaining the vibration mode of the transformer and limiting additional energy losses from the contact interface, an appropriate design can improve power density of the transformer on a large scale, resulting from effective suppression of its working temperature rise. A prototype device was fabricated from a rectangular piezoelectric transformer, a copper heat transfer sheet, a thermal grease insulation pad, and an aluminum heat radiator. The experimental results show the transformer maintains a maximum power density of 135 W/cm(3) and an efficiency of 90.8% with a temperature rise of less than 10 °C after more than 36 h, without notable changes in performance. © 2012 IEEE
Low density, microcellular, dopable, agar/gelatin foams for pulsed power experiments
Energy Technology Data Exchange (ETDEWEB)
McNamara, W.F. [Orion International Technologies, Inc., Albuquerque, NM (United States); Aubert, J.H. [Sandia National Lab., Albuquerque, NM (United States)
1997-04-01
Low-density, microcellular foams prepared from the natural polymers agar and gelatin have been developed for pulsed-power physics experiments. Numerous experiments were supported with foams having densities at or below 10 mg/cm{sup 3}. For some of the experiments, the agar/gelatin foam was uniformly doped with metallic elements using soluble salts. Depending on the method of preparation, cell sizes were typically below 10 microns and for one process were below 1.0 micron.
Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest.
Meneses, Francisco M; Queirós, Fernanda C; Montoya, Pedro; Miranda, José G V; Dubois-Mendes, Selena M; Sá, Katia N; Luz-Santos, Cleber; Baptista, Abrahão F
2016-01-01
Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F (1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F (1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F (1, 39) = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA.
Non-power law behavior of the radial profile of phase-space density of halos
International Nuclear Information System (INIS)
Popolo, A. Del
2011-01-01
We study the pseudo phase-space density, ρ(r)/σ 3 (r), of ΛCDM dark matter halos with and without baryons (baryons+DM, and pure DM), by using the model introduced in Del Popolo (2009), which takes into account the effect of dynamical friction, ordered and random angular momentum, baryons adiabatic contraction and dark matter baryons interplay. We examine the radial dependence of ρ(r)/σ 3 (r) over 9 orders of magnitude in radius for structures on galactic and cluster of galaxies scales. We find that ρ(r)/σ 3 (r) is approximately a power-law only in the range of halo radius resolved by current simulations (down to 0.1% of the virial radius) while it has a non-power law behavior below the quoted scale, with inner profiles changing with mass. The non-power-law behavior is more evident for halos constituted both of dark matter and baryons while halos constituted just of dark matter and with angular momentum chosen to reproduce a Navarro-Frenk-White (NFW) density profile, are characterized by an approximately power-law behavior. The results of the present paper lead to conclude that density profiles of the NFW type are compatible with a power-law behavior of ρ(r)/σ 3 (r), while those flattening to the halo center, like those found in Del Popolo (2009) or the Einasto profile, or the Burkert profile, cannot produce radial profile of the pseudo-phase-space density that are power-laws at all radii. The results argue against universality of the pseudo phase-space density and as a consequence argue against universality of density profiles constituted by dark matter and baryons as also discussed in Del Popolo (2009)
Dimpfel, Wilfried; Schombert, Leonie; Gericke, Nigel
2016-01-11
The endemic succulent South African plant, Sceletium tortuosum (L.) N.E. Br. (synonym Mesembryanthemum tortuosum L.), of the family Mesembryathemaceae, has an ancient oral tradition history of use by San and Khoikhoi people as an integral part of the indigenous culture and materia medica. A special standardized extract of Sceletium tortuosum (Zembrin®) has been developed and tested pre-clinically in rats, and clinically in healthy subjects. The present investigation aimed at the construction of electropharmacograms of Zembrin® in the presence of three dosages (2.5, 5.0 and 10.0 mg/kg), and comparative electropharmacograms and discriminatory analyses for other herbal extracts, citicoline and rolipram. Seventeen adult Fischer rats were each implanted with a set consisting of four bipolar concentric steel electrodes fixed by dental cement and three screws driven into the scalp. After two weeks of recovery from surgery the animals were adapted to oral administration by gavage and to experimental conditions (45 min pre-drug period and 5h of recording after a rest of 5 min for calming down). Data were transmitted wirelessly and processed using a Fast Fourier Transformation (FFT). Spectral power was evaluated for 8 frequency ranges, namely delta, theta, alpha1, alpha2, beta1a, beta1b, beta2 and gamma power. Zembrin® dose dependently attenuated all frequency ranges, to varying degrees. The most prominent was the statistically significant reduction in alpha2 and beta1a waves, correlated with activation of the dopaminergic and glutamatergic transmitter systems respectively. This feature is common to all synthetic and herbal stimulants tested to date. The second strongest effects were reduction in both the delta and the theta frequency ranges, correlated with changes in the cholinergic and norepinephrine systems respectively, a pattern seen in preparations prescribed for neurodegenerative diseases. Theta wave reduction in common with the delta, alpha2 and beta1 attenuation
NASA Glenn Research Center Program in High Power Density Motors for Aeropropulsion
Brown, Gerald V.; Kascak, Albert F.; Ebihara, Ben; Johnson, Dexter; Choi, Benjamin; Siebert, Mark; Buccieri, Carl
2005-01-01
Electric drive of transport-sized aircraft propulsors, with electric power generated by fuel cells or turbo-generators, will require electric motors with much higher power density than conventional room-temperature machines. Cryogenic cooling of the motor windings by the liquid hydrogen fuel offers a possible solution, enabling motors with higher power density than turbine engines. Some context on weights of various systems, which is required to assess the problem, is presented. This context includes a survey of turbine engine weights over a considerable size range, a correlation of gear box weights and some examples of conventional and advanced electric motor weights. The NASA Glenn Research Center program for high power density motors is outlined and some technical results to date are presented. These results include current densities of 5,000 A per square centimeter current density achieved in cryogenic coils, finite element predictions compared to measurements of torque production in a switched reluctance motor, and initial tests of a cryogenic switched reluctance motor.
Density dependence of SOL power width in ASDEX upgrade L-Mode
Directory of Open Access Journals (Sweden)
B. Sieglin
2017-08-01
A recent study [4] with an open divertor configuration found an asymmetry of the power fall-off length between inner and outer target with a smaller power fall-off length λq,i on the inner divertor target. Measurements with a closed divertor configuration find a similar asymmetry for low recycling divertor conditions. It is found, in the experiment, that the in/out asymmetry λq,i/λq,o is strongly increasing with increasing density. Most notably the heat flux density at the inner divertor target is reducing with increasing λq,i whilst the total power onto each divertor target stays constant. It is found that λq,o exhibits no significant density dependence for hydrogen and deuterium but increases with about the square root of the electron density for helium. The difference between H,D and He could be due to the different recycling behaviour in the divertor. These findings may help current modelling attempts to parametrize the density dependence of the widening of the power channel and thus allow for detailed comparison to both divertor effects like recycling or increased upstream SOL cross field transport.
Workshop on High Power ICH Antenna Designs for High Density Tokamaks
Aamodt, R. E.
1990-02-01
A workshop in high power ICH antenna designs for high density tokamaks was held to: (1) review the data base relevant to the high power heating of high density tokamaks; (2) identify the important issues which need to be addressed in order to ensure the success of the ICRF programs on CIT and Alcator C-MOD; and (3) recommend approaches for resolving the issues in a timely realistic manner. Some specific performance goals for the antenna system define a successful design effort. Simply stated these goals are: couple the specified power per antenna into the desired ion species; produce no more than an acceptable level of RF auxiliary power induced impurities; and have a mechanical structure which safely survives the thermal, mechanical and radiation stresses in the relevant environment. These goals are intimately coupled and difficult tradeoffs between scientific and engineering constraints have to be made.
Workshop on high power ICH antenna designs for high density tokamaks
International Nuclear Information System (INIS)
Aamodt, R.E.
1990-01-01
A workshop in high power ICH antenna designs for high density tokamaks was held in Boulder, Colorado on January 31 through February 2, 1990. The purposes of the workshop were to: (1) review the data base relevant to the high power heating of high density tokamaks; (2) identify the important issues which need to be addressed in order to ensure the success of the ICRF programs on CIT and Alcator C-MOD; and (3) recommend approaches for resolving the issues in a timely realistic manner. Some specific performance goals for the antenna system define a successful design effort. Simply stated these goals are: couple the specified power per antenna into the desired ion species; produce no more than an acceptable level of rf auxiliary power induced impurities; and have a mechanical structure which safely survives the thermal, mechanical and radiation stresses in the relevant environment. These goals are intimately coupled and difficult tradeoffs between scientific and engineering constraints have to be made
Maximum attainable power density and wall load in tokamaks underlying reactor relevant constraints
International Nuclear Information System (INIS)
Borrass, K.; Buende, R.
1979-09-01
The characteristic data of tokamaks optimized with respect to their power density or wall load are determined. Reactor relevant constraints are imposed, such as a fixed plant net power output, a fixed blanket thickness and the dependence of the maximum toroidal field on the geometry and conductor material. The impact of finite burn times is considered. Various scaling laws of the toroidal beta with the aspect ratio are discussed. (orig.) 891 GG/orig. 892 RDG [de
A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation
Directory of Open Access Journals (Sweden)
Liwen Pan
2015-01-01
Full Text Available This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge circuit suffers from ripple power pulsating at second-order line frequency, and a scheme of active ripple compensation circuit has been explored to solve this second-order ripple problem, in which a pair of power switches shared traction mode, a ripple energy storage capacitor, and an energy transfer inductor. Simulation results in MATLAB/Simulink validated the eligibility of the proposed topology. The integrated charger can work as a 70 kW motor drive circuit or a converter with an active ripple compensation circuit for 3 kW charging the battery. The impact of the proposed topology and control strategy on the integrated charger power losses, efficiency, power density, and thermal performance has also been analysed and simulated.
Titarchuk, Lev; Shaposhinikov, Nikolai
2007-01-01
A characteristic feature of the Fourier Power Density Spectrum (PDS) observed from black hole X-ray binaries in low/hard and intermediate spectral states is a broad band-limited noise, characterized by a constant below some frequency (a "break" frequency) and a power law above this frequency. It has been shown that the variability of this type can be produced by the inward diffusion of the local driving perturbations in a bounded configuration (accretion disk or corona). In the framework of this model, the perturbation diffusion time to is related to the phenomenological break frequency, while the PDS power-law slope above the "break" is determined by the viscosity distribution over the configuration. The perturbation diffusion scenario explains the decay of the power of X-ray variability observed in a number of compact sources (containing black hole and neutron star) during an evolution of theses sources from low/hard to high/soft states. We compare the model predictions with the subset of data from Cyg X-1 collected by the Rossi X-ray Time Explorer (RXTE). Our extensive analysis of the Cyg X-1 PDSs demonstrates that the observed integrated power P(sub x), decreases approximately as a square root of the characteristic frequency of the driving oscillations v(sub dr). The RXTE observations of Cyg X-1 allow us to infer P(sub dr), and t(sub o) as a function of v(sub dr). We also apply the basic parameters of observed PDSs, power-law index and low frequency quasiperiodic oscillations. to infer Reynolds (Re) number from the observations using the method developed in our previous paper. Our analysis shows that Re-number increases from values about 10 in low/hard state to that about 70 during the high/soft state. Subject headings: accretion, accretion disks-black hole physics-stars:individual (Cyg X-1) :radiation mechanisms: nonthermal-physical data and processes
International Nuclear Information System (INIS)
Song, Xizi; Xu, Yanbin; Dong, Feng
2017-01-01
Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results. (paper)
An asymptotically unbiased minimum density power divergence estimator for the Pareto-tail index
DEFF Research Database (Denmark)
Dierckx, Goedele; Goegebeur, Yuri; Guillou, Armelle
2013-01-01
We introduce a robust and asymptotically unbiased estimator for the tail index of Pareto-type distributions. The estimator is obtained by fitting the extended Pareto distribution to the relative excesses over a high threshold with the minimum density power divergence criterion. Consistency...
Towards High Power Density Metal Supported Solid Oxide Fuel Cell for Mobile Applications
DEFF Research Database (Denmark)
Nielsen, Jimmi; Persson, Åsa H.; Muhl, Thuy Thanh
2018-01-01
For use of metal supported solid oxide fuel cell (MS-SOFC) in mobile applications it is important to reduce the thermal mass to enable fast startup, increase stack power density in terms of weight and volume and reduce costs. In the present study, we report on the effect of reducing the Technical...
Towards High Power Density Metal Supported Solid Oxide Fuel Cell for Mobile Applications
DEFF Research Database (Denmark)
Nielsen, Jimmi; Persson, Åsa Helen; Muhl, Thuy
2017-01-01
For use of metal supported SOFC in mobile applications it is important to reduce the thermal mass to enable fast start up, increase stack power density in terms of weight and volume and reduce costs. In the present study, we report on the effect of reducing the support layer thickness of 313 μm...
Effects of SWS deprivation on subsequent EEG power density and spontaneous sleep duration
Dijk, Derk Jan; Beersma, Domien G.M.
In order to test predictions of the 2-process model of sleep regulation, the effects of slow wave sleep (SWS) deprivation by acoustic stimulation during the first part of the sleep period on EEG power density and sleep duration were investigated in 2 experiments. In the first experiment, 8 subjects
High-energy-density physics researches based on pulse power technology
International Nuclear Information System (INIS)
Horioka, Kazuhiko; Nakajima, Mitsuo; Kawamura, Tohru; Sasaki, Toru; Kondo, Kotaro; Yano, Yuuri
2006-01-01
Plasmas driven by pulse power device are of interest, concerning the researches on high-energy-density (HED) physics. Dense plasmas are produced using pulse power driven exploding discharges in water. Experimental results show that the wire plasma is tamped and stabilized by the surrounding water and it evolves through a strongly coupled plasma state. A shock-wave-heated, high temperature plasma is produced in a compact pulse power device. Experimental results show that strong shock waves can be produced in the device. In particular, at low initial pressure condition, the shock Mach number reaches 250 and this indicates that the shock heated region is dominated by radiation processes. (author)
Heavy density concrete for nuclear radiation shielding and power stations: [Part]2
International Nuclear Information System (INIS)
Singha Roy, P.K.
1987-01-01
This article is the second part of the paper entitled 'Heavy density concrete for nuclear radiation shielding and power stations'. In this part, some of the important properties of heavy density concrete are discussed. They include density, water retentivity, air content, permeability with special reference to concrete mixes used in India's nuclear power reactors. All these properties are affected to various extents by heating. Indian shield concrete is rarely subjected to temperatures above 60degC during its life, because of thermal shield protection. During placement, the maximum anticipated rise in temperature due to heat of hydration is restricted to around 45degC by chilling, if necessary to reduce shrinkage stresses and cracks. (M.G.B.)
Thulium heat source for high-endurance and high-energy density power systems
International Nuclear Information System (INIS)
Walter, C.E.; Kammeraad, J.E.; Van Konynenburg, R.; VanSant, J.H.
1991-05-01
We are studying the performance characteristics of radioisotope heat source designs for high-endurance and high-energy-density power systems that use thulium-170. Heat sources in the power range of 5--50 kW th coupled with a power conversion efficiency of ∼30%, can easily satisfy current missions for autonomous underwater vehicles. New naval missions will be possible because thulium isotope power systems have a factor of one-to-two hundred higher endurance and energy density than chemical and electrochemical systems. Thulium-170 also has several other attractive features, including the fact that it decays to stable ytterbium-170 with a half-life of four months. For terrestrial applications, refueling on that time scale should be acceptable in view of the advantage of its benign decay. The heat source designs we are studying account for the requirements of isotope production, shielding, and integration with power conversion components. These requirements are driven by environmental and safety considerations. Thulium is present in the form of thin refractory thulia disks that allow power conversion at high peak temperature. We give estimates of power system state points, performance, mass, and volume characteristics. Monte Carlo radiation analysis provides a detailed assessment of shield requirements and heat transfer under normal and distressed conditions is also considered. 11 refs., 7 figs., 4 tabs
Wei, J. Q.; Cong, Y. C.; Xiao, M. Q.
2018-05-01
As renewable energies are increasingly integrated into power systems, there is increasing interest in stochastic analysis of power systems.Better techniques should be developed to account for the uncertainty caused by penetration of renewables and consequently analyse its impacts on stochastic stability of power systems. In this paper, the Stochastic Differential Equations (SDEs) are used to represent the evolutionary behaviour of the power systems. The stationary Probability Density Function (PDF) solution to SDEs modelling power systems excited by Gaussian white noise is analysed. Subjected to such random excitation, the Joint Probability Density Function (JPDF) solution to the phase angle and angular velocity is governed by the generalized Fokker-Planck-Kolmogorov (FPK) equation. To solve this equation, the numerical method is adopted. Special measure is taken such that the generalized FPK equation is satisfied in the average sense of integration with the assumed PDF. Both weak and strong intensities of the stochastic excitations are considered in a single machine infinite bus power system. The numerical analysis has the same result as the one given by the Monte Carlo simulation. Potential studies on stochastic behaviour of multi-machine power systems with random excitations are discussed at the end.
Schillinger, Dominik
2013-07-01
The method of separation can be used as a non-parametric estimation technique, especially suitable for evolutionary spectral density functions of uniformly modulated and strongly narrow-band stochastic processes. The paper at hand provides a consistent derivation of method of separation based spectrum estimation for the general multi-variate and multi-dimensional case. The validity of the method is demonstrated by benchmark tests with uniformly modulated spectra, for which convergence to the analytical solution is demonstrated. The key advantage of the method of separation is the minimization of spectral dispersion due to optimum time- or space-frequency localization. This is illustrated by the calibration of multi-dimensional and multi-variate geometric imperfection models from strongly narrow-band measurements in I-beams and cylindrical shells. Finally, the application of the method of separation based estimates for the stochastic buckling analysis of the example structures is briefly discussed. © 2013 Elsevier Ltd.
Power-Production Diagnostic Tools for Low-Density Wind Farms with Applications to Wake Steering
Takle, E. S.; Herzmann, D.; Rajewski, D. A.; Lundquist, J. K.; Rhodes, M. E.
2016-12-01
Hansen (2011) provided guidelines for wind farm wake analysis with applications to "high density" wind farms (where average distance between turbines is less than ten times rotor diameter). For "low-density" (average distance greater than fifteen times rotor diameter) wind farms, or sections of wind farms we demonstrate simpler sorting and visualization tools that reveal wake interactions and opportunities for wind farm power prediction and wake steering. SCADA data from a segment of a large mid-continent wind farm, together with surface flux measurements and lidar data are subjected to analysis and visualization of wake interactions. A time-history animated visualization of a plan view of power level of individual turbines provides a quick analysis of wake interaction dynamics. Yaw-based sectoral histograms of enhancement/decline of wind speed and power from wind farm reference levels reveals angular width of wake interactions and identifies the turbine(s) responsible for the power reduction. Concurrent surface flux measurements within the wind farm allowed us to evaluate stability influence on wake loss. A one-season climatology is used to identify high-priority candidates for wake steering based on estimated power recovery. Typical clearing prices on the day-ahead market are used to estimate the added value of wake steering. Current research is exploring options for identifying candidate locations for wind farm "build-in" in existing low-density wind farms.
International Nuclear Information System (INIS)
Suri, Rominder P.S.; Nayak, Mohan; Devaiah, Uthappa; Helmig, Edward
2007-01-01
There are many reports documenting the adverse effects, such as feminization of fish, of estrogen hormones in the environment. One of the major sources of these compounds is from municipal wastewater effluents. The biological processes at municipal wastewater treatment plants cannot completely remove these compounds. This paper discusses the use of ultrasound to destroy estrogen compounds in water. The study examines the effect of ultrasound power density and power intensity on the destruction of various estrogen compounds which include: 17α-estradiol, 17β-estradiol, estrone, estriol, equilin, 17α-dihydroequilin, 17α-ethinyl estradiol and norgestrel. These tests were conducted in single component batch and flow through reactors using 0.6, 2 and 4 kW ultrasound sources. The sonolysis process produced 80-90% destruction of individual estrogens at initial concentration of 10 μg/L within 40-60 min of contact time. First order rate constants for the individual compounds under different conditions are presented. The estrogen degradation rates increase with increase in power intensity. However, the energy efficiency of the reactor was higher at lower power density. The 4 kW ultrasound reactor was more energy efficient compared to the 0.6 and 2 kW sonicators
Directory of Open Access Journals (Sweden)
Liu Xiping
2017-06-01
Full Text Available This paper proposes a permanent magnet (PM-assisted synchronous reluctance machine (PMASynRM using ferrite magnets with the same power density as rareearth PM synchronous motors employed in Toyota Prius 2010. A suitable rotor structure for high torque density and high power density is discussed with respect to the demagnetization of ferrite magnets, mechanical strength and torque ripple. Some electromagnetic characteristics including torque, output power, loss and efficiency are calculated by 2-D finite element analysis (FEA. The analysis results show that a high power density and high efficiency of PMASynRM are obtained by using ferrite magnets.
Non-linear behaviour of power density and exposure time of argon laser on ocular tissues
Energy Technology Data Exchange (ETDEWEB)
El-Sayed, E M; Talaat, M S; Salem, E F [Physics Department, Faculty of Science, Ain Shams University, Cairo (Egypt)
1997-12-31
In ophthalmology, the thermal effect of argon laser is the most widely used category of laser- tissue interaction. The rise in tissue temperature has to exceed a threshold value for photo coagulation of retinal blood vessels. This value mainly depends on the laser. The most suitable argon laser power P and exposure time (t) which would be more effective for thermal and electrical behaviour of chicken eye was studied. This was achieved by measuring the variations in ocular temperature in electroretinogram (ERG) records under the effect of argon experiment, while power density (P) and exposure time (t) were varied in four different ways for each dose (pt). Results indicated that for the same laser dose, the temperature distribution of the eye, using low power density and high exposure time was higher than that high power density and low exposure time, indicating non-linearity of the laser dose. This finding was confirmed by ERG records which showed similar variations in b-wave latency, amplitude and duration, for the laser exposure conditions. This indicates variations in retinal function due to laser-dependent temperature variations. 5 figs., 3 tabs.
LISA - a powerful program package for LIstmode and Spectral data Analysis
International Nuclear Information System (INIS)
Oberstedt, A.; Hambsch, F.J.
1994-01-01
LISA is a graphical program package which enables both off-line listmode and spectral data evaluation as well as on-line monitoring while multi-parameter experiments are running. It can be executed on every computer with a UNIX operating system and an X-WINDOW environment, running PV-WAVE from Visual Numerics Incorporation. This package is basically written in the language PV-WAVE CL, but integration of procedures written in the C-language and execution of UNIX shell commands lead to an additional increase of performance. (orig.)
3D Freeze-Casting of Cellular Graphene Films for Ultrahigh-Power-Density Supercapacitors.
Shao, Yuanlong; El-Kady, Maher F; Lin, Cheng-Wei; Zhu, Guanzhou; Marsh, Kristofer L; Hwang, Jee Youn; Zhang, Qinghong; Li, Yaogang; Wang, Hongzhi; Kaner, Richard B
2016-08-01
3D cellular graphene films with open porosity, high electrical conductivity, and good tensile strength, can be synthesized by a method combining freeze-casting and filtration. The resulting supercapacitors based on 3D porous reduced graphene oxide (RGO) film exhibit extremely high specific power densities and high energy densities. The fabrication process provides an effective means for controlling the pore size, electronic conductivity, and loading mass of the electrode materials, toward devices with high energy-storage performance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Yip, Ngai Yin; Elimelech, Menachem
2014-09-16
Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are emerging membrane-based technologies that can convert chemical energy in salinity gradients to useful work. The two processes have intrinsically different working principles: controlled mixing in PRO is achieved by water permeation across salt-rejecting membranes, whereas RED is driven by ion flux across charged membranes. This study compares the energy efficiency and power density performance of PRO and RED with simulated technologically available membranes for natural, anthropogenic, and engineered salinity gradients (seawater-river water, desalination brine-wastewater, and synthetic hypersaline solutions, respectively). The analysis shows that PRO can achieve both greater efficiencies (54-56%) and higher power densities (2.4-38 W/m(2)) than RED (18-38% and 0.77-1.2 W/m(2)). The superior efficiency is attributed to the ability of PRO membranes to more effectively utilize the salinity difference to drive water permeation and better suppress the detrimental leakage of salts. On the other hand, the low conductivity of currently available ion exchange membranes impedes RED ion flux and, thus, constrains the power density. Both technologies exhibit a trade-off between efficiency and power density: employing more permeable but less selective membranes can enhance the power density, but undesired entropy production due to uncontrolled mixing increases and some efficiency is sacrificed. When the concentration difference is increased (i.e., natural → anthropogenic → engineered salinity gradients), PRO osmotic pressure difference rises proportionally but not so for RED Nernst potential, which has logarithmic dependence on the solution concentration. Because of this inherently different characteristic, RED is unable to take advantage of larger salinity gradients, whereas PRO power density is considerably enhanced. Additionally, high solution concentrations suppress the Donnan exclusion effect of the
Wix-Ramos, Richard; Moreno, Xiomara; Capote, Eduardo; González, Gilbert; Uribe, Ezequiel; Eblen-Zajjur, Antonio
2014-04-01
Research of electroencephalograph (EEG) power spectrum and mean frequency has shown inconsistent results in patients with schizophrenic, schizoaffective and bipolar disorders during medication when compared to normal subjects thus; the characterization of these parameters is an important task. We applied quantitative EEG (qEEG) to investigate 38 control, 15 schizophrenic, 7 schizoaffective and 11 bipolar disorder subjects which remaine under the administration of psychotropic drugs (except control group). Absolute spectral power (ASP), mean frequency and hemispheric electrical asymmetry were measured by 19 derivation qEEG. Group mean values were compared with non parametrical Mann-Whitney test and spectral EEG maps with z-score method at p Schizoaffective patients received neuroleptic+benzodiazepine (71.4%) and for bipolar disorder patients neuroleptic+antiepileptic (81.8%). Schizophrenic (at all derivations except for Fp1, Fp2, F8 and T6) and schizoaffective (only at C3) show higher values of ASP (+57.7% and +86.1% respectively) compared to control group. ASP of bipolar disorder patients did not show differences against control group. The mean frequency was higher at Fp1 (+14.2%) and Fp2 (+17.4%) in bipolar disorder patients than control group, but no differences were found in frequencies between schizophrenic or schizoaffective patients against the control group. Majority of spectral differences were found at the left hemisphere in schizophrenic and schizoaffective but not in bipolar disorder subjects. The present report contributes to characterize quantitatively the qEEG in drug treated schizophrenic, schizoaffective or bipolar disorder patients.
Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U.
Faust, I; Delgado-Aparicio, L; Bell, R E; Tritz, K; Diallo, A; Gerhardt, S P; LeBlanc, B; Kozub, T A; Parker, R R; Stratton, B C
2014-11-01
A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.
Two-dimensional AXUV-based radiated power density diagnostics on NSTX-Ua)
Faust, I.; Delgado-Aparicio, L.; Bell, R. E.; Tritz, K.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A.; Parker, R. R.; Stratton, B. C.
2014-11-01
A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.
Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U
Energy Technology Data Exchange (ETDEWEB)
Faust, I.; Parker, R. R. [MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Delgado-Aparicio, L.; Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Tritz, K. [The Johns Hopkins University, Baltimore, Maryland 21209 (United States); Stratton, B. C. [MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)
2014-11-15
A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.
Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U
International Nuclear Information System (INIS)
Faust, I.; Parker, R. R.; Delgado-Aparicio, L.; Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A.; Tritz, K.; Stratton, B. C.
2014-01-01
A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed
Core design and fuel rod analyses of a super fast reactor with high power density
International Nuclear Information System (INIS)
Ju, Haitao; Cao, Liangzhi; Lu, Haoliang; Oka, Yoshiaki; Ikejiri, Satoshi; Ishiwatari, Yuki
2009-01-01
A Super Fast Reactor is a pressure-vessel type, fast spectrum SuperCritical Water Reactor (SCWR) that is presently researched in a Japanese project. One of the most important advantages of the Super Fast Reactor is the higher power density compared to the thermal spectrum SCWR, which reduces the capital cost. A preliminary core has an average power density of 158.8W/cc. In this paper, the principle of improving the average power density is studied and the core design is improved. After the sensitivity analyses on the fuel rod configurations, the fuel assembly configurations and the core configurations, an improved core with an average power density of 294.8W/cc is designed by 3-D neutronic/thermal-hydraulic coupled calculations. This power density is competitive with that of typical Liquid Metal Fast Breeder Reactors (LMFBR). In order to ensure the fuel rod integrity of this core design, the fuel rod behaviors on the normal operating condition are analyzed using FEMAXI-6 code. The power histories of each fuel rod are taken from the neutronics calculation results in the core design. The cladding surface temperature histories are taken from the thermal-hydraulic calculation results in the core design. Four types of the limiting fuel rods, with the Maximum Cladding Surface Temperature (MCST), Maximum Power Peak(MPP), Maximum Discharge Burnup(MDB) and Different Coolant Flow Pattern (DCFP), are chosen to cover all the fuel rods in the core. The available design range of the fuel rod design parameters, such as initial gas plenum pressure, gas plenum position, gas plenum length, grain size and gap size, are found out in order to satisfy the following design criteria: (1) Maximum fuel centerline temperature should be less than 1900degC. (2) Maximum cladding stress in circumstance direction should be less than 100MPa. (3) Pressure difference on the cladding should be less than 1/3 of buckling collapse pressure. (4) Cumulative damage faction (CDF) of the cladding should be
Teodorovich, E. V.
2018-03-01
In order to find the shape of energy spectrum within the framework of the model of stationary homogeneous isotropic turbulence, the renormalization-group equations, which reflect the Markovian nature of the mechanism of energy transfer along the wavenumber spectrum, are used in addition to the dimensional considerations and the energy balance equation. For the spectrum, the formula depends on three parameters, namely, the wavenumber, which determines the upper boundary of the range of the turbulent energy production, the spectral flux through this boundary, and the fluid kinematic viscosity.
Evaluation of population density and distribution criteria in nuclear power plant siting
International Nuclear Information System (INIS)
Young, M.
1994-06-01
The NRC has proposed revisions to 10 CFR 100 which include the codification of nuclear reactor site population density limits to 500 people per square mile, at the siting stage, averaged over any radial distance out to 30 miles, and 1,000 people per square mile within the 40-year lifetime of a nuclear plant. This study examined whether there are less restrictive alternative population density and/or distribution criteria which would provide equivalent or better protection to human health in the unlikely event of a nuclear accident. This study did not attempt to directly address the issue of actual population density limits because there are no US risk standards established for the evaluation of population density limits. Calculations were performed using source terms for both a current generation light water reactor (LWR) and an advanced light water reactor (ALWR) design. The results of this study suggest that measures which address the distribution of the population density, including emergency response conditions, could result in lower average individual risks to the public than the proposed guidelines that require controlling average population density. Studies also indicate that an exclusion zone size, determined by emergency response conditions and reactor design (power level and safety features), would better serve to protect public health than a rigid standard applied to all sites
Generation of high-power-density atmospheric pressure plasma with liquid electrodes
International Nuclear Information System (INIS)
Dong Lifang; Mao Zhiguo; Yin Zengqian; Ran Junxia
2004-01-01
We present a method for generating atmospheric pressure plasma using a dielectric barrier discharge reactor with two liquid electrodes. Four distinct kinds of discharge, including stochastic filaments, regular square pattern, glow-like discharge, and Turing stripe pattern, are observed in argon with a flow rate of 9 slm. The electrical and optical characteristics of the device are investigated. Results show that high-power-density atmospheric pressure plasma with high duty ratio in space and time can be obtained. The influence of wall charges on discharge power and duty ratio has been discussed
New directions in fusion machines: report on the MFAC Panel X on high power density options
International Nuclear Information System (INIS)
Linford, R.K.
1985-01-01
The high cost of fusion is motivating a shift in research interest toward smaller, lower-cost systems. Panel X of the Magnetic Fusion Advisory Committee (MFAC) was charged to assess the potential benefits and problems associated with small, high-power-density approaches to fusion. The Panel identified figures of merit which are useful in evaluating various approaches to reduce the development costs and capital costs of fusion systems. As a result of their deliberations, the Panel recommended that ''...increased emphasis should be given to improving the mass power density of fusion systems, aiming at a minimum target of 100 kWe/tonne'', and that ''Increased emphasis should be given to concepts that offer the potential to reduce substantially the cost of development steps in physics and technology.''
New directions in fusion machines: report on the MFAC Panel X on high power density options
Energy Technology Data Exchange (ETDEWEB)
Linford, R.K.
1985-01-01
The high cost of fusion is motivating a shift in research interest toward smaller, lower-cost systems. Panel X of the Magnetic Fusion Advisory Committee (MFAC) was charged to assess the potential benefits and problems associated with small, high-power-density approaches to fusion. The Panel identified figures of merit which are useful in evaluating various approaches to reduce the development costs and capital costs of fusion systems. As a result of their deliberations, the Panel recommended that ''...increased emphasis should be given to improving the mass power density of fusion systems, aiming at a minimum target of 100 kWe/tonne'', and that ''Increased emphasis should be given to concepts that offer the potential to reduce substantially the cost of development steps in physics and technology.''
Hydrogen consumption and power density in a co-flow planar SOFC
Energy Technology Data Exchange (ETDEWEB)
Ben Moussa, Hocine; Zitouni, Bariza [Laboratoire d' etude des systemes energetiques industriels (LESEI), Universite de Batna, Batna (Algeria); Oulmi, Kafia [Laboratoire de chimie et de chimie de l' environnement, Universite de Batna, Batna (Algeria); Mahmah, Bouziane; Belhamel, Maiouf [CDER, BP. 62 Route de l' Observatoire. Bouzareah. Alger (Algeria); Mandin, Philippe [Centre de Developpement des Energies Renouvelables (CDER), LECA, UMR 7575 CNRS-ENSCP Paris 6 (France)
2009-06-15
In the present work, power density and hydrogen consumption in a co-flow planar solid oxide fuel cell (SOFC) are studied according to the inlet functional parameters; such as the operational temperature, the operational pressure, the flow rates and the mass fractions of the species. Furthermore, the effect of the cell size is investigated. The results of a zero and a one-dimensional numerical electro-dynamic model predict the remaining quantity of the fed hydrogen at the output of the anode flow channel. The remaining hydrogen quantities and the SOFC's power density obtained are discussed as a function of the inlet functional parameters, the geometrical configuration of the cell and several operating cell voltages values. (author)
A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage
Energy Technology Data Exchange (ETDEWEB)
Wang, Ruxi [Virginia Polytechnic Institute and State University (Virginia Tech); Wang, Fei [ORNL; Boroyevich, Dushan [Virginia Polytechnic Institute and State University (Virginia Tech); Burgos, Rolando [ABB; Lai, Rixin [General Electric; Ning, Puqi [ORNL; Rajashekara, Kaushik [Rolls Royce
2011-01-01
It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.
Rijnaarts, Timon; Huerta, Elisa; van Baak, Willem; Nijmeijer, Kitty
2017-11-07
Reverse electrodialysis (RED) is a membrane-based renewable energy technology that can harvest energy from salinity gradients. The anticipated feed streams are natural river and seawater, both of which contain not only monovalent ions but also divalent ions. However, RED using feed streams containing divalent ions experiences lower power densities because of both uphill transport and increased membrane resistance. In this study, we investigate the effects of divalent cations (Mg 2+ and Ca 2+ ) on RED and demonstrate the mitigation of those effects using both novel and existing commercial cation exchange membranes (CEMs). Monovalent-selective Neosepta CMS is known to block divalent cations transport and can therefore mitigate reductions in stack voltage. The new multivalent-permeable Fuji T1 is able to transport divalent cations without a major increase in resistance. Both strategies significantly improve power densities compared to standard-grade CEMs when performing RED using streams containing divalent cations.
Xu, Zhanwei; Li, Zhi; Holt, Chris M B; Tan, Xuehai; Wang, Huanlei; Amirkhiz, Babak Shalchi; Stephenson, Tyler; Mitlin, David
2012-10-18
We employed a microwave synthesis process of cobalt phthalocyanine molecules templated by acid-functionalized multiwalled carbon nanotubes to create three-dimensional sponge-like graphene nanoarchitectures suited for ionic liquid-based electrochemical capacitor electrodes that operate at very high scan rates. The sequential "bottom-up" molecular synthesis and subsequent carbonization process took less than 20 min to complete. The 3D nanoarchitectures are able to deliver an energy density of 7.1 W·h kg(-1) even at an extra high power density of 48 000 W kg(-1). In addition, the ionic liquid supercapacitor based on this material works very well at room temperature due to its fully opened structures, which is ideal for the high-power energy application requiring more tolerance to temperature variation. Moreover, the structures are stable in both ionic liquids and 1 M H2SO4, retaining 90 and 98% capacitance after 10 000 cycles, respectively.
Power budget analysis of image-plane storage in spectral hole-burning materials
International Nuclear Information System (INIS)
Neifeld, M.A.; Randall Babbitt, W.; Krishna Mohan, R.; Craig, A.E.
2004-01-01
We analyze the power requirements of a volumetric storage system based on hole-burning materials. We consider an image-plane architecture that uses ultra-fine wavelength addressing. We perform an optimization study in which hole-depth, material thickness, and spot size are selected to minimize the system power budget. We find that a data rate of 10 Gbps and a latency of 10 μs can be achieved in a read-once system based on Eu-YSO with a total power budget of only 23 mW. The same material system designed to tolerate 1000 read cycles would require only a factor of 15 increase in power
Anderson, R. B.; Finch, N.; Clegg, S. M.; Graff, T. G.; Morris, R. V.; Laura, J.; Gaddis, L. R.
2017-12-01
Machine learning is a powerful but underutilized approach that can enable planetary scientists to derive meaningful results from the rapidly-growing quantity of available spectral data. For example, regression methods such as Partial Least Squares (PLS) and Least Absolute Shrinkage and Selection Operator (LASSO), can be used to determine chemical concentrations from ChemCam and SuperCam Laser-Induced Breakdown Spectroscopy (LIBS) data [1]. Many scientists are interested in testing different spectral data processing and machine learning methods, but few have the time or expertise to write their own software to do so. We are therefore developing a free open-source library of software called the Python Spectral Analysis Tool (PySAT) along with a flexible, user-friendly graphical interface to enable scientists to process and analyze point spectral data without requiring significant programming or machine-learning expertise. A related but separately-funded effort is working to develop a graphical interface for orbital data [2]. The PySAT point-spectra tool includes common preprocessing steps (e.g. interpolation, normalization, masking, continuum removal, dimensionality reduction), plotting capabilities, and capabilities to prepare data for machine learning such as creating stratified folds for cross validation, defining training and test sets, and applying calibration transfer so that data collected on different instruments or under different conditions can be used together. The tool leverages the scikit-learn library [3] to enable users to train and compare the results from a variety of multivariate regression methods. It also includes the ability to combine multiple "sub-models" into an overall model, a method that has been shown to improve results and is currently used for ChemCam data [4]. Although development of the PySAT point-spectra tool has focused primarily on the analysis of LIBS spectra, the relevant steps and methods are applicable to any spectral data. The
A two-parameter family of double-power-law biorthonormal potential-density expansions
Lilley, Edward J.; Sanders, Jason L.; Evans, N. Wyn
2018-05-01
We present a two-parameter family of biorthonormal double-power-law potential-density expansions. Both the potential and density are given in closed analytic form and may be rapidly computed via recurrence relations. We show that this family encompasses all the known analytic biorthonormal expansions: the Zhao expansions (themselves generalizations of ones found earlier by Hernquist & Ostriker and by Clutton-Brock) and the recently discovered Lilley et al. (2017a) expansion. Our new two-parameter family includes expansions based around many familiar spherical density profiles as zeroth-order models, including the γ models and the Jaffe model. It also contains a basis expansion that reproduces the famous Navarro-Frenk-White (NFW) profile at zeroth order. The new basis expansions have been found via a systematic methodology which has wide applications in finding other new expansions. In the process, we also uncovered a novel integral transform solution to Poisson's equation.
Sub-micrometer-thick all-solid-state supercapacitors with high power and energy densities
Energy Technology Data Exchange (ETDEWEB)
Meng, Fanhui [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, and School of Chemistry and Chemical Engineering, Shandong University, Jinan 250061 (China); Ding, Yi [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, and School of Chemistry and Chemical Engineering, Shandong University, Jinan 250061 (China); Shandong Applied Research Center for Gold Technology (Au-SDARC), Yantai 264005 (China)
2011-09-15
A sub-micrometer-thick, flexible, all-solid-state supercapacitor is fabricated. Through simultaneous realization of high dispersity of pseudocapacitance materials and quick electrode response, the hybrid nanostructures show enhanced volumetric capacitance and excellent stability, as well as very high power and energy densities. This suggests their potential as next-generation, high-performance energy conversion and storage devices for wearable electronics. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Maximization of ICRF power by SOL density tailoring with local gas injection
Czech Academy of Sciences Publication Activity Database
Jacquet, P.; Goniche, M.; Bobkov, V.; Lerche, E.; Pinsker, R.I.; Pitts, R.A.; Zhang, W.; Colas, L.; Hosea, J.; Moriyama, S.; Wang, S.-J.; Wukitch, S.; Zhang, X.; Bilato, R.; Bufferand, H.; Guimarais, L.; Faugel, H.; Hanson, G.R.; Kocan, M.; Monakhov, I.; Noterdaeme, J.-M.; Petržílka, Václav; Shaw, A.; Stepanov, I.; Sips, A.C.C.; Van Eester, D.; Wauters, T.
2016-01-01
Roč. 56, č. 4 (2016), s. 046001 ISSN 0029-5515 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : ICRF power * antenna loading * gas injection * SOL density Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016 http://iopscience.iop.org/article/10.1088/0029-5515/56/4/046001
Discrimination of neutrons and gamma quanta with the aid of their power density spectra
International Nuclear Information System (INIS)
Buchmueller, R.
1977-01-01
The paper introduces a method of using only one fission chamber to discriminate the neutron flux against the gamma flux. The gamma chamber current may be several orders of magnitude higher than the neutron chamber current. In specially dimensioned fission chambers the neutrons and gamma quanta are made to generate different current pulses. Discrimination becomes possible by recording the power density spectrum of the mixture of pulses over a broad frequency range ( [de
Effect of areal power density and relative humidity on corrosion resistant container performance
International Nuclear Information System (INIS)
Gansemer, J.D.
1994-10-01
The impact of the rewetting process on the performance of waste containers at the Yucca Mountain repository is analyzed. This paper explores the impact of the temperature-humidity relationships on pitting corrosion failure of stainless steel containers for different areal power densities (APDs)in the repository. It compares the likely performance of containers in a repository with a low APD, 55 Kw/acre, and a high APD, 110 kW/acre
Rosnik, Andreana M; Curutchet, Carles
2015-12-08
Over the past decade, both experimentalists and theorists have worked to develop methods to describe pigment-protein coupling in photosynthetic light-harvesting complexes in order to understand the molecular basis of quantum coherence effects observed in photosynthesis. Here we present an improved strategy based on the combination of quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations and excited-state calculations to predict the spectral density of electronic-vibrational coupling. We study the water-soluble chlorophyll-binding protein (WSCP) reconstituted with Chl a or Chl b pigments as the system of interest and compare our work with data obtained by Pieper and co-workers from differential fluorescence line-narrowing spectra (Pieper et al. J. Phys. Chem. B 2011, 115 (14), 4042-4052). Our results demonstrate that the use of QM/MM MD simulations where the nuclear positions are still propagated at the classical level leads to a striking improvement of the predicted spectral densities in the middle- and high-frequency regions, where they nearly reach quantitative accuracy. This demonstrates that the so-called "geometry mismatch" problem related to the use of low-quality structures in QM calculations, not the quantum features of pigments high-frequency motions, causes the failure of previous studies relying on similar protocols. Thus, this work paves the way toward quantitative predictions of pigment-protein coupling and the comprehension of quantum coherence effects in photosynthesis.
Anderson, R. B.; Finch, N.; Clegg, S. M.; Graff, T.; Morris, R. V.; Laura, J.
2018-04-01
The PySAT point spectra tool provides a flexible graphical interface, enabling scientists to apply a wide variety of preprocessing and machine learning methods to point spectral data, with an emphasis on multivariate regression.
The effects of the small-scale behaviour of dark matter power spectrum on CMB spectral distortion
Energy Technology Data Exchange (ETDEWEB)
Sarkar, Abir; Sethi, Shiv K. [Raman Research Institute, CV Raman Ave Sadashivnagar, Bengaluru, Karnataka 560080 (India); Das, Subinoy, E-mail: abir@rri.res.in, E-mail: sethi@rri.res.in, E-mail: subinoy@iiap.res.in [Indian Institute of Astrophysics, 100 Feet Rd, Madiwala, 2nd Block, Koramangala, Bengaluru, Karnataka 560034 (India)
2017-07-01
After numerous astronomical and experimental searches, the precise particle nature of dark matter is still unknown. The standard Weakly Interacting Massive Particle(WIMP) dark matter, despite successfully explaining the large-scale features of the universe, has long-standing small-scale issues. The spectral distortion in the Cosmic Microwave Background(CMB) caused by Silk damping in the pre-recombination era allows one to access information on a range of small scales 0.3 Mpc < k < 10{sup 4} Mpc{sup −1}, whose dynamics can be precisely described using linear theory. In this paper, we investigate the possibility of using the Silk damping induced CMB spectral distortion as a probe of the small-scale power. We consider four suggested alternative dark matter candidates—Warm Dark Matter (WDM), Late Forming Dark Matter (LFDM), Ultra Light Axion (ULA) dark matter and Charged Decaying Dark Matter (CHDM); the matter power in all these models deviate significantly from the ΛCDM model at small scales. We compute the spectral distortion of CMB for these alternative models and compare our results with the ΛCDM model. We show that the main impact of alternative models is to alter the sub-horizon evolution of the Newtonian potential which affects the late-time behaviour of spectral distortion of CMB. The y -parameter diminishes by a few percent as compared to the ΛCDM model for a range of parameters of these models: LFDM for formation redshift z {sub f} = 10{sup 5} (7%); WDM for mass m {sub wdm} = 1 keV (2%); CHDM for decay redshift z {sub decay} = 10{sup 5} (5%); ULA for mass m {sub a} = 10{sup −24} eV (3%). This effect from the pre-recombination era can be masked by orders of magnitude higher y -distortions generated by late-time sources, e.g. the Epoch of Reionization and tSZ from the cluster of galaxies. We also briefly discuss the detectability of this deviation in light of the upcoming CMB experiment PIXIE, which might have the sensitivity to detect this signal from
Biowaste-Derived Hierarchical Porous Carbon Nanosheets for Ultrahigh Power Density Supercapacitors.
Yu, Dengfeng; Chen, Chong; Zhao, Gongyuan; Sun, Lei; Du, Baosheng; Zhang, Hong; Li, Zhuo; Sun, Ye; Besenbacher, Flemming; Yu, Miao
2018-03-05
Low-cost activated carbons with high capacitive properties remain desirable for supercapacitor applications. Herein, a three-dimensional scaffolding framework of porous carbon nanosheets (PCNSs) has been produced from a typical biowaste, namely, ground cherry calyces, the specific composition and natural structures of which have contributed to the PCNSs having a very large specific surface area of 1612 m 2 g -1 , a hierarchical pore size distribution, a turbostratic carbon structure with a high degree graphitization, and about 10 % oxygen and nitrogen heteroatoms. A high specific capacitance of 350 F g -1 at 0.1 A g -1 has been achieved in a two-electrode system with 6 m KOH; this value is among the highest specific capacitance of biomass-derived carbon materials. More inspiringly, a high energy density of 22.8 Wh kg -1 at a power density of 198.8 W kg -1 can be obtained with 1 m aqueous solution of Li 2 SO 4 , and an ultrahigh energy density of 81.4 Wh kg -1 at a power density of 446.3 W kg -1 is realized with 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Genetic search for an optimal power flow solution from a high density cluster
Energy Technology Data Exchange (ETDEWEB)
Amarnath, R.V. [Hi-Tech College of Engineering and Technology, Hyderabad (India); Ramana, N.V. [JNTU College of Engineering, Jagityala (India)
2008-07-01
This paper proposed a novel method to solve optimal power flow (OPF) problems. The method is based on a genetic algorithm (GA) search from a High Density Cluster (GAHDC). The algorithm of the proposed method includes 3 stages, notably (1) a suboptimal solution is obtained via a conventional analytical method, (2) a high density cluster, which consists of other suboptimal data points from the first stage, is formed using a density-based cluster algorithm, and (3) a genetic algorithm based search is carried out for the exact optimal solution from a low population sized, high density cluster. The final optimal solution thoroughly satisfies the well defined fitness function. A standard IEEE 30-bus test system was considered for the simulation study. Numerical results were presented and compared with the results of other approaches. It was concluded that although there is not much difference in numerical values, the proposed method has the advantage of minimal computational effort and reduced CPU time. As such, the method would be suitable for online applications such as the present Optimal Power Flow problem. 24 refs., 2 tabs., 4 figs.
Design of robust hollow fiber membranes with high power density for osmotic energy production
Zhang, Sui; Sukitpaneenit, Panu; Chung, Neal Tai-Shung
2014-01-01
This study highlights the design strategy of highly asymmetric hollow fiber membranes that possess both characteristics of high flux and high mechanical strength to effectively reap the osmotic energy from seawater brine with an ultrahigh power density. An advanced co-extrusion technology was employed to fabricate the polyethersulfone (PES) hollow fiber supports with diversified structures from macrovoid to sponge-like. The microstructure of the supports is found critical for the stability and water permeability of the thin film composite (TFC) membranes. A high porosity in the porous layer is needed to reduce internal concentration polarization, while a thick and relatively dense skin layer underneath the TFC layer is required to maintain good mechanical stability and stress dissipation. The pore size of the supporting layer underneath the TFC layer must be small with a narrow pore size distribution to ensure the formation of a less-defective, highly permeable and mechanically stable TFC layer. The newly developed hollow fiber comprising high asymmetry, high porosity, and a thick skin layer with a small and narrow pore size distribution underneath the TFC layer produces a maximum power density of 24.3W/m2 at 20.0bar by using 1M NaCl as the concentrated brine and deionized (DI) water as the feed. The proposed design strategy for ultrahigh power density membranes clearly advances the osmotic energy production close to commercialization with a quite cost-effective and practicable approach. © 2013 Elsevier B.V.
Lu, Yonghui; Xu, Shangcheng; He, Mindi; Chen, Chunhai; Zhang, Lei; Liu, Chuan; Chu, Fang; Yu, Zhengping; Zhou, Zhou; Zhong, Min
2012-07-16
Extensive evidence indicates that glucose administration attenuates memory deficits in rodents and humans, and cognitive impairment has been associated with reduced glucose metabolism and uptake in certain brain regions including the hippocampus. In the present study, we investigated whether glucose treatment attenuated memory deficits caused by chronic low-power-density microwave (MW) exposure, and the effect of MW exposure on hippocampal glucose uptake. We exposed Wistar rats to 2.45 GHz pulsed MW irradiation at a power density of 1 mW/cm(2) for 3 h/day, for up to 30 days. MW exposure induced spatial learning and memory impairments in rats. Hippocampal glucose uptake was also reduced by MW exposure in the absence or presence of insulin, but the levels of blood glucose and insulin were not affected. However, these spatial memory deficits were reversed by systemic glucose treatment. Our results indicate that glucose administration attenuates the spatial memory deficits induced by chronic low-power-density MW exposure, and reduced hippocampal glucose uptake may be associated with cognitive impairment caused by MW exposure. Copyright © 2012 Elsevier Inc. All rights reserved.
Graphene-based in-plane micro-supercapacitors with high power and energy densities
Wu, Zhong–Shuai; Parvez, Khaled; Feng, Xinliang; Müllen, Klaus
2013-01-01
Micro-supercapacitors are important on-chip micro-power sources for miniaturized electronic devices. Although the performance of micro-supercapacitors has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures, their power or energy densities remain far from those of electrolytic capacitors or lithium thin-film batteries. Here we demonstrate graphene-based in-plane interdigital micro-supercapacitors on arbitrary substrates. The resulting micro-supercapacitors deliver an area capacitance of 80.7 μF cm−2 and a stack capacitance of 17.9 F cm−3. Further, they show a power density of 495 W cm−3 that is higher than electrolytic capacitors, and an energy density of 2.5 mWh cm−3 that is comparable to lithium thin-film batteries, in association with superior cycling stability. Such microdevices allow for operations at ultrahigh rate up to 1,000 V s−1, three orders of magnitude higher than that of conventional supercapacitors. Micro-supercapacitors with an in-plane geometry have great promise for numerous miniaturized or flexible electronic applications. PMID:24042088
Graphene-based in-plane micro-supercapacitors with high power and energy densities.
Wu, Zhong-Shuai; Parvez, Khaled; Feng, Xinliang; Müllen, Klaus
2013-01-01
Micro-supercapacitors are important on-chip micro-power sources for miniaturized electronic devices. Although the performance of micro-supercapacitors has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures, their power or energy densities remain far from those of electrolytic capacitors or lithium thin-film batteries. Here we demonstrate graphene-based in-plane interdigital micro-supercapacitors on arbitrary substrates. The resulting micro-supercapacitors deliver an area capacitance of 80.7 μF cm⁻² and a stack capacitance of 17.9 F cm⁻³. Further, they show a power density of 495 W cm⁻³ that is higher than electrolytic capacitors, and an energy density of 2.5 mWh cm⁻³ that is comparable to lithium thin-film batteries, in association with superior cycling stability. Such microdevices allow for operations at ultrahigh rate up to 1,000 V s⁻¹, three orders of magnitude higher than that of conventional supercapacitors. Micro-supercapacitors with an in-plane geometry have great promise for numerous miniaturized or flexible electronic applications.
Design of robust hollow fiber membranes with high power density for osmotic energy production
Zhang, Sui
2014-04-01
This study highlights the design strategy of highly asymmetric hollow fiber membranes that possess both characteristics of high flux and high mechanical strength to effectively reap the osmotic energy from seawater brine with an ultrahigh power density. An advanced co-extrusion technology was employed to fabricate the polyethersulfone (PES) hollow fiber supports with diversified structures from macrovoid to sponge-like. The microstructure of the supports is found critical for the stability and water permeability of the thin film composite (TFC) membranes. A high porosity in the porous layer is needed to reduce internal concentration polarization, while a thick and relatively dense skin layer underneath the TFC layer is required to maintain good mechanical stability and stress dissipation. The pore size of the supporting layer underneath the TFC layer must be small with a narrow pore size distribution to ensure the formation of a less-defective, highly permeable and mechanically stable TFC layer. The newly developed hollow fiber comprising high asymmetry, high porosity, and a thick skin layer with a small and narrow pore size distribution underneath the TFC layer produces a maximum power density of 24.3W/m2 at 20.0bar by using 1M NaCl as the concentrated brine and deionized (DI) water as the feed. The proposed design strategy for ultrahigh power density membranes clearly advances the osmotic energy production close to commercialization with a quite cost-effective and practicable approach. © 2013 Elsevier B.V.
Nominal power density analysis of thermoelectric pins with non-constant cross sections
International Nuclear Information System (INIS)
Shi, Yaoguang; Mei, Deqing; Yao, Zhehe; Wang, Yancheng; Liu, Haiyan; Chen, Zichen
2015-01-01
Highlights: • Nominal power density of TEGs with non-constant cross sections pins is analyzed. • An analytical model of nominal power density (NPD) is developed. • Influences of shape parameter on NPD for different geometric pins are investigated. • Effects of dimensionless efficiency and the temperature ratio on NPD are examined. - Abstract: The investigation of the geometric structure of TEG (thermoelectric generator) pins is essential, as their geometry determines the performance of devices. In this study, nominal power density (NPD) is used to find a better geometric structure of thermoelectric pins of TEGs, since a comparison of maximum dimensionless efficiencies for different geometric pins cannot be used to identify the optimum geometry. The influence of shape parameter on NPD for TEG pins in linear, quadratic and exponential cross-sectional functions is studied. The NPD decreases when the shape parameter increases for different geometric pins, while the maximum values of NPD are the same. Then, the effects of dimensionless efficiency and the temperature ratio on the NPD are analyzed. The NPD decreases with the increase in dimensionless efficiency and temperature ratio. Pins with linear variation in cross section have the highest NPD among the three geometries of pins evaluated
Flexible Aqueous Li-Ion Battery with High Energy and Power Densities.
Yang, Chongyin; Ji, Xiao; Fan, Xiulin; Gao, Tao; Suo, Liumin; Wang, Fei; Sun, Wei; Chen, Ji; Chen, Long; Han, Fudong; Miao, Ling; Xu, Kang; Gerasopoulos, Konstantinos; Wang, Chunsheng
2017-11-01
A flexible and wearable aqueous symmetrical lithium-ion battery is developed using a single LiVPO 4 F material as both cathode and anode in a "water-in-salt" gel polymer electrolyte. The symmetric lithium-ion chemistry exhibits high energy and power density and long cycle life, due to the formation of a robust solid electrolyte interphase consisting of Li 2 CO 3 -LiF, which enables fast Li-ion transport. Energy densities of 141 Wh kg -1 , power densities of 20 600 W kg -1 , and output voltage of 2.4 V can be delivered during >4000 cycles, which is far superior to reported aqueous energy storage devices at the same power level. Moreover, the full cell shows unprecedented tolerance to mechanical stress such as bending and cutting, where it not only does not catastrophically fail, as most nonaqueous cells would, but also maintains cell performance and continues to operate in ambient environment, a unique feature apparently derived from the high stability of the "water-in-salt" gel polymer electrolyte. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material
Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.
1999-01-01
A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.
Hotfiel, Thilo; Swoboda, Bernd; Krinner, Sebastian; Grim, Casper; Engelhardt, Martin; Uder, Michael; Heiss, Rafael U
2017-04-01
Hotfiel, T, Swoboda, B, Krinner, S, Grim, C, Engelhardt, M, Uder, M, and Heiss, R. Acute effects of lateral thigh foam rolling on arterial tissue perfusion determined by spectral Doppler and power Doppler ultrasound. J Strength Cond Res 31(4): 893-900, 2017-Foam rolling has been developed as a popular intervention in training and rehabilitation. However, evidence on its effects on the cellular and physiological level is lacking. The aim of this study was to assess the effect of foam rolling on arterial blood flow of the lateral thigh. Twenty-one healthy participants (age, 25 ± 2 years; height, 177 ± 9 cm; body weight, 74 ± 9 kg) were recruited from the medical and sports faculty. Arterial tissue perfusion was determined by spectral Doppler and power Doppler ultrasound, represented as peak flow (Vmax), time average velocity maximum (TAMx), time average velocity mean (TAMn), and resistive index (RI), and with semiquantitative grading that was assessed by 4 blindfolded investigators. Measurement values were assessed under resting conditions and twice after foam rolling exercises of the lateral thigh (0 and 30 minutes after intervention). The trochanteric region, mid portion, and distal tibial insertion of the lateral thigh were representative for data analysis. Arterial blood flow of the lateral thigh increased significantly after foam rolling exercises compared with baseline (p ≤ 0.05). We detected a relative increase in Vmax of 73.6% (0 minutes) and 52.7% (30 minutes) (p power Doppler scores at all portions revealed increased average grading of 1.96 after intervention and 2.04 after 30 minutes compared with 0.75 at baseline. Our results may contribute to the understanding of local physiological reactions to self-myofascial release.
Cognitive strategies in the mental rotation task revealed by EEG spectral power.
Gardony, Aaron L; Eddy, Marianna D; Brunyé, Tad T; Taylor, Holly A
2017-11-01
The classic mental rotation task (MRT; Shepard & Metzler, 1971) is commonly thought to measure mental rotation, a cognitive process involving covert simulation of motor rotation. Yet much research suggests that the MRT recruits both motor simulation and other analytic cognitive strategies that depend on visuospatial representation and visual working memory (WM). In the present study, we investigated cognitive strategies in the MRT using time-frequency analysis of EEG and independent component analysis. We scrutinized sensorimotor mu (µ) power reduction, associated with motor simulation, parietal alpha (pα) power reduction, associated with visuospatial representation, and frontal midline theta (fmθ) power enhancement, associated with WM maintenance and manipulation. µ power increased concomitant with increasing task difficulty, suggesting reduced use of motor simulation, while pα decreased and fmθ power increased, suggesting heightened use of visuospatial representation processing and WM, respectively. These findings suggest that MRT performance involves flexibly trading off between cognitive strategies, namely a motor simulation-based mental rotation strategy and WM-intensive analytic strategies based on task difficulty. Flexible cognitive strategy use may be a domain-general cognitive principle that underlies aptitude and spatial intelligence in a variety of cognitive domains. We close with discussion of the present study's implications as well as future directions. Published by Elsevier Inc.
International Nuclear Information System (INIS)
Yuan, Liq-Ji
1987-01-01
This work described the investigations of reactor core power peaking and three dimensional power density distribution of present core configuration of Tsing Hua Open-pool reactor (THOR). An experimental program, based on non-destructive fuel gamma scanning of 91 Sr activities, provides the data of fission density distribution for individual fuel pin of four-rod TRIGA-LEU cluster or for MTR-type fuel assembly. The informations are essentially important for the safety of reactor operation and for fuel management especially for the mixed loading with three different types of fuel at present. The relative power peaking values and the power density distribution for present core are discussed. (author)
High-resolution Tangential AXUV Arrays for Radiated Power Density Measurements on NSTX-U
Energy Technology Data Exchange (ETDEWEB)
Delgado-Aparicio, L [PPPL; Bell, R E [PPPL; Faust, I [MIT; Tritz, K [The Johns Hopkins University, Baltimore, MD, 21209, USA; Diallo, A [PPPL; Gerhardt, S P [PPPL; Kozub, T A [PPPL; LeBlanc, B P [PPPL; Stratton, B C [PPPL
2014-07-01
Precise measurements of the local radiated power density and total radiated power are a matter of the uttermost importance for understanding the onset of impurity-induced instabilities and the study of particle and heat transport. Accounting of power balance is also needed for the understanding the physics of various divertor con gurations for present and future high-power fusion devices. Poloidal asymmetries in the impurity density can result from high Mach numbers and can impact the assessment of their flux-surface-average and hence vary the estimates of P[sub]rad (r, t) and (Z[sub]eff); the latter is used in the calculation of the neoclassical conductivity and the interpretation of non-inductive and inductive current fractions. To this end, the bolometric diagnostic in NSTX-U will be upgraded, enhancing the midplane coverage and radial resolution with two tangential views, and adding a new set of poloidally-viewing arrays to measure the 2D radiation distribution. These systems are designed to contribute to the near- and long-term highest priority research goals for NSTX-U which will integrate non-inductive operation at reduced collisionality, with high-pressure, long energy-confinement-times and a divertor solution with metal walls.
Heavy density concrete for nuclear radiation shielding and power stations: [Part]3
International Nuclear Information System (INIS)
Singha Roy, P.K.
1987-01-01
This article is the third part of the paper entitled 'Heavy density concrete for nuclear radiation shielding and power stations'. Specific considerations relevant to natural but manufactured heavy aggregates like haematite used in India are briefly discussed. They include water-cement ratio, strength versus water-cement ratio, mix design strength and aggregate grading. Some typical mix proportions in haematite concretes used in India are given. Equipment for heavy density concrete is mentioned. Quality control methods and tests for heavy density concrete are described under the heading: type and chemical composition of the rock, specific gravity and surface absorption of the aggregates, grading of aggregates, cement, batching, mixing, compressive strength, and density. Construction aspects such as form work, placement, vibration, finishing, and temperature control are discussed. Finally it is pointed out that for optimising the design and economy of heavy density concrete, it is necessary to carry out country-wide survey of suitable materials, to study their properties, suitability and effectiveness in shielding radiation. (M.G.B.)
The effects of the small-scale behaviour of dark matter power spectrum on CMB spectral distortion
Sarkar, Abir; Sethi, Shiv. K.; Das, Subinoy
2017-07-01
After numerous astronomical and experimental searches, the precise particle nature of dark matter is still unknown. The standard Weakly Interacting Massive Particle(WIMP) dark matter, despite successfully explaining the large-scale features of the universe, has long-standing small-scale issues. The spectral distortion in the Cosmic Microwave Background(CMB) caused by Silk damping in the pre-recombination era allows one to access information on a range of small scales 0.3 Mpc Light Axion (ULA) dark matter and Charged Decaying Dark Matter (CHDM); the matter power in all these models deviate significantly from the ΛCDM model at small scales. We compute the spectral distortion of CMB for these alternative models and compare our results with the ΛCDM model. We show that the main impact of alternative models is to alter the sub-horizon evolution of the Newtonian potential which affects the late-time behaviour of spectral distortion of CMB. The y-parameter diminishes by a few percent as compared to the ΛCDM model for a range of parameters of these models: LFDM for formation redshift zf = 105 (7%); WDM for mass mwdm = 1 keV (2%); CHDM for decay redshift zdecay = 105 (5%); ULA for mass ma = 10-24 eV (3%). This effect from the pre-recombination era can be masked by orders of magnitude higher y-distortions generated by late-time sources, e.g. the Epoch of Reionization and tSZ from the cluster of galaxies. We also briefly discuss the detectability of this deviation in light of the upcoming CMB experiment PIXIE, which might have the sensitivity to detect this signal from the pre-recombination phase.
DEFF Research Database (Denmark)
Zubov, F. I.; Zhukov, A. E.; Shernyakov, Yu M.
2015-01-01
It is demonstrated that the use of asymmetric barrier layers in a waveguide of a diode laser suppress non-linearity of light-current characteristic and thus improve its power characteristics under high current injection. The results are presented for 850-nm AlGaAs/GaAs broad-area lasers with Ga...
Smit, D.J.A.; Boomsma, D.I.; Schnack, H.G.; Hulshoff Pol, H.E.; de Geus, E.J.C.
2012-01-01
The human electroencephalogram (EEG) consists of oscillations that reflect the summation of postsynaptic potentials at the dendritic tree of cortical neurons. The strength of the oscillations (EEG power) is a highly genetic trait that has been related to individual differences in many phenotypes,
A geographical model of radio-frequency power density around mobile phone masts
International Nuclear Information System (INIS)
Briggs, David; Beale, Linda; Bennett, James; Toledano, Mireille B.; Hoogh, Kees de
2012-01-01
Public concern about possible health effects of EMF radiation from mobile phone masts has led to an increase of epidemiological studies and health risk assessments which, in turn, require adequate methods of exposure estimation. Difficulties in exposure modelling are exacerbated both by the complexity of the propagation processes, and the need to obtain estimates for large study populations in order to provide sufficient statistical power to detect or exclude the small relative risks that might exist. Use of geographical information system (GIS) techniques offers the means to make such computations efficiently. This paper describes the development and field validation of a GIS-based exposure model (Geomorf). The model uses a modified Gaussian formulation to represent spatial variations in power densities around mobile phone masts, on the basis of power output, antenna height, tilt and the surrounding propagation environment. Obstruction by topography is allowed for, through use of a visibility function. Model calibration was done using field data from 151 measurement sites (1510 antenna-specific measurements) around a group of masts in a rural location, and 50 measurement sites (658 antenna-specific measurements) in an urban area. Different parameter settings were found to be necessary in urban and rural areas to obtain optimum results. The calibrated models were then validated against independent sets of data gathered from measurement surveys in rural and urban areas, and model performance was compared with that of two commonly used path-loss models (the COST-231 adaptations of the Hata and Walfisch–Ikegami models). Model performance was found to vary somewhat between the rural and urban areas, and at different measurement levels (antenna-specific power density, total power density), but overall gave good estimates (R 2 = 0.641 and 0.615, RMSE = 10.7 and 6.7 dB m at the antenna and site-level respectively). Performance was considerably better than that of both
Directory of Open Access Journals (Sweden)
Weifang Sun
2017-08-01
Full Text Available Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.
Sun, Weifang; Yao, Bin; He, Yuchao; Chen, Binqiang; Zeng, Nianyin; He, Wangpeng
2017-08-09
Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.
von Hansen, Yann; Mehlich, Alexander; Pelz, Benjamin; Rief, Matthias; Netz, Roland R
2012-09-01
The thermal fluctuations of micron-sized beads in dual trap optical tweezer experiments contain complete dynamic information about the viscoelastic properties of the embedding medium and-if present-macromolecular constructs connecting the two beads. To quantitatively interpret the spectral properties of the measured signals, a detailed understanding of the instrumental characteristics is required. To this end, we present a theoretical description of the signal processing in a typical dual trap optical tweezer experiment accounting for polarization crosstalk and instrumental noise and discuss the effect of finite statistics. To infer the unknown parameters from experimental data, a maximum likelihood method based on the statistical properties of the stochastic signals is derived. In a first step, the method can be used for calibration purposes: We propose a scheme involving three consecutive measurements (both traps empty, first one occupied and second empty, and vice versa), by which all instrumental and physical parameters of the setup are determined. We test our approach for a simple model system, namely a pair of unconnected, but hydrodynamically interacting spheres. The comparison to theoretical predictions based on instantaneous as well as retarded hydrodynamics emphasizes the importance of hydrodynamic retardation effects due to vorticity diffusion in the fluid. For more complex experimental scenarios, where macromolecular constructs are tethered between the two beads, the same maximum likelihood method in conjunction with dynamic deconvolution theory will in a second step allow one to determine the viscoelastic properties of the tethered element connecting the two beads.
Vidyadharan, Baiju; Aziz, Radhiyah Abd; Misnon, Izan Izwan; Anil Kumar, Gopinathan M.; Ismail, Jamil; Yusoff, Mashitah M.; Jose, Rajan
2014-12-01
Electrochemical materials are under rigorous search for building advanced energy storage devices. Herein, supercapacitive properties of highly crystalline and ultrathin cobalt oxide (Co3O4) nanowires (diameter ∼30-60 nm) synthesized using an aqueous polymeric solution based electrospinning process are reported. These nanowire electrodes show a specific capacitance (CS) of ∼1110 F g-1 in 6 M KOH at a current density of 1 A g-1 with coulombic efficiency ∼100%. Asymmetric supercapacitors (ASCs) (CS ∼175 F g-1 at 2 A g-1 galvanostatic cycling) are fabricated using the Co3O4 as anode and commercial activated carbon (AC) as cathode and compared their performance with symmetric electrochemical double layer capacitors (EDLCs) fabricated using AC (CS ∼31 F g-1 at 2 A g-1 galvanostatic cycling). The Co3O4//AC ASCs deliver specific energy densities (ES) of 47.6, 35.4, 20 and 8 Wh kg-1 at specific power densities (PS) 1392, 3500, 7000 and 7400 W kg-1, respectively. The performance of ASCs is much superior to the control EDLCs, which deliver ES of 9.2, 8.9, 8.4 and 6.8 Wh kg-1 at PS 358, 695, 1400 and 3500 W kg-1, respectively. The ASCs show nearly six times higher energy density (∼47.6 Wh kg-1) than EDLC (8.4 Wh kg-1) without compromising its power density (∼1400 W kg-1) at similar galvanostatic cycling conditions (2 A g-1).
Interaction of a high-power laser pulse with supercritical-density porous materials
International Nuclear Information System (INIS)
Gus'kov, Sergei Yu; Rozanov, Vladislav B; Caruso, A; Strangio, C
2000-01-01
The properties of a nonequilibrium plasma produced by high-power laser pulses with intensities I L ∼ 10 14 -10 15 W cm -2 irradiating plane targets made of a porous material are investigated. The mean density of matter in targets was substantially higher than the critical plasma density corresponding to a plasma resonance. The density of porous material was ρ a ∼ 1 - 20 mg cm -3 , whereas the critical density at the wavelength of incident radiation was ρ cr ∼ 3 mg cm -3 . An anomalously high absorption (no less than 80%) of laser radiation inside a target was observed. Within the first 3 - 4 ns of interaction, the plasma flow through the irradiated target surface in the direction opposite of the direction of the laser beam was noticeably suppressed. Only about 5% of absorbed laser energy was transformed into the energy of particles in this flow during the laser pulse. Absorbed energy was stored as the internal plasma energy at this stage (the greenhouse effect). Then, this energy was transformed, similar to a strong explosion, into the energy of a powerful hydrodynamic flow of matter surrounding the absorption region. The specific features of the formation and evolution of a nonequilibrium laser-produced plasma in porous media are theoretically analysed. This study allows the results of experiments to be explained. In particular, we investigated absorption of laser radiation in the bulk of a target, volume evaporation of porous material, the expansion of a laser-produced plasma inside the pores, stochastic collisions of plasma flows, and hydrothermal energy dissipation. These processes give rise to long-lived oscillations of plasma density and lead to the formation of an internal region where laser radiation is absorbed. (invited paper)
International Nuclear Information System (INIS)
Wang, P.-Y.; Hou, S.-S.
2005-01-01
In this paper, performance analysis and comparison based on the maximum power and maximum power density conditions have been conducted for an Atkinson cycle coupled to variable temperature heat reservoirs. The Atkinson cycle is internally reversible but externally irreversible, since there is external irreversibility of heat transfer during the processes of constant volume heat addition and constant pressure heat rejection. This study is based purely on classical thermodynamic analysis methodology. It should be especially emphasized that all the results and conclusions are based on classical thermodynamics. The power density, defined as the ratio of power output to maximum specific volume in the cycle, is taken as the optimization objective because it considers the effects of engine size as related to investment cost. The results show that an engine design based on maximum power density with constant effectiveness of the hot and cold side heat exchangers or constant inlet temperature ratio of the heat reservoirs will have smaller size but higher efficiency, compression ratio, expansion ratio and maximum temperature than one based on maximum power. From the view points of engine size and thermal efficiency, an engine design based on maximum power density is better than one based on maximum power conditions. However, due to the higher compression ratio and maximum temperature in the cycle, an engine design based on maximum power density conditions requires tougher materials for engine construction than one based on maximum power conditions
Zhai, Teng; Lu, Xihong; Wang, Hanyu; Wang, Gongming; Mathis, Tyler; Liu, Tianyu; Li, Cheng; Tong, Yexiang; Li, Yat
2015-05-13
Electrochemical capacitors represent a new class of charge storage devices that can simultaneously achieve high energy density and high power density. Previous reports have been primarily focused on the development of high performance capacitor electrodes. Although these electrodes have achieved excellent specific capacitance based on per unit mass of active materials, the gravimetric energy densities calculated based on the weight of entire capacitor device were fairly small. This is mainly due to the large mass ratio between current collector and active material. We aimed to address this issue by a 2-fold approach of minimizing the mass of current collector and increasing the electrode performance. Here we report an electrochemical capacitor using 3D graphene hollow structure as current collector, vanadium sulfide and manganese oxide as anode and cathode materials, respectively. 3D graphene hollow structure provides a lightweight and highly conductive scaffold for deposition of pseudocapacitive materials. The device achieves an excellent active material ratio of 24%. Significantly, it delivers a remarkable energy density of 7.4 Wh/kg (based on the weight of entire device) at the average power density of 3000 W/kg. This is the highest gravimetric energy density reported for asymmetric electrochemical capacitors at such a high power density.
International Nuclear Information System (INIS)
Wang, Yue-Sheng; Tsai, Dah-Shyang; Chung, Wen-Hung; Syu, Yong-Sin; Huang, Ying-Sheng
2012-01-01
Highlights: ► Mo-doping (15 mol%) enhances capacitance and diminishes oxide resistance. ► Influences of Mo-doped MnO 2 are analyzed at the level of capacitor power and energy. ► Polarization loss of the asymmetric capacitor is more than that of the symmetric one. ► Pseudocapacitance benefit on energy is evaluated with power and current densities. - Abstract: Ultracapacitors of asymmetric configuration have been prepared with activated carbon (AC) and undoped or Mo-doped manganese oxide (MnO 2 ) in 1.0 M Na 2 SO 4 electrolyte. Phase analysis shows the AC powder, 1–15 μm in size, contains both disordered and graphitic structures, and the undoped and Mo-doped oxide powder, 0.05–0.20 μm in particle size, mainly involves amorphous MnO 2 and MoO 2 . CV results indicate the single electrode of AC plus 10 wt% Mo-doped MnO 2 (A9O M 1) is superior to the electrode with undoped MnO 2 or high content of doped MnO 2 , exhibiting features of double layer capacitance at high scan rate and pseudocapacitance characteristics at low scan rate. When assembled with a negative electrode of AC, the capacitor of positive A9O M 1 electrode demonstrates the least power loss among three asymmetric capacitors. This asymmetric capacitor also shows a higher capacitance than the symmetric AC capacitor when the current density is less than 8.0 A g −1 in 1.8 V potential window. But a higher electrode resistance of A9O M 1, in contrast with AC, compromises its capacitance plus. When the energy density of A9O M 1 asymmetric capacitor is compared with that of symmetric AC capacitor at the same power level, the capacitance benefit on energy density is restricted to current density ≤ 3.0 A g −1 .
Measurements of soft X-ray power and spectral features on Angara-5-1
International Nuclear Information System (INIS)
Branitskij, A.V.; Olejnik, G.M.
1996-01-01
In many tasks related to high temperature plasmas and ICF is it important to investigate the power and spectrum features of radiation with nanosecond resolution. Measurement methods and signal processing methods are presented. The methods were applied in experiments at the ''Angara-5-1'' facility in the 0.1-2 keV band. The time resolution was 0.5 ns. (author). 1 tab., 2 figs., 8 refs
Measurements of soft X-ray power and spectral features on Angara-5-1
Energy Technology Data Exchange (ETDEWEB)
Branitskij, A V; Olejnik, G M [Troitsk Inst. of Innovative and Fusion Research (Russian Federation)
1997-12-31
In many tasks related to high temperature plasmas and ICF is it important to investigate the power and spectrum features of radiation with nanosecond resolution. Measurement methods and signal processing methods are presented. The methods were applied in experiments at the ``Angara-5-1`` facility in the 0.1-2 keV band. The time resolution was 0.5 ns. (author). 1 tab., 2 figs., 8 refs.
3D macroporous graphene frameworks for supercapacitors with high energy and power densities.
Choi, Bong Gill; Yang, Minho; Hong, Won Hi; Choi, Jang Wook; Huh, Yun Suk
2012-05-22
In order to develop energy storage devices with high power and energy densities, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) macroporous structure that consists of chemically modified graphene (CMG). These 3D macroporous electrodes, namely, embossed-CMG (e-CMG) films, were fabricated by using polystyrene colloidal particles as a sacrificial template. Furthermore, for further capacitance boost, a thin layer of MnO(2) was additionally deposited onto e-CMG. The porous graphene structure with a large surface area facilitates fast ionic transport within the electrode while preserving decent electronic conductivity and thus endows MnO(2)/e-CMG composite electrodes with excellent electrochemical properties such as a specific capacitance of 389 F/g at 1 A/g and 97.7% capacitance retention upon a current increase to 35 A/g. Moreover, when the MnO(2)/e-CMG composite electrode was asymmetrically assembled with an e-CMG electrode, the assembled full cell shows remarkable cell performance: energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life.
Lee, Jae Ah; Shin, Min Kyoon; Kim, Shi Hyeong; Kim, Seon Jeong; Spinks, Geoffrey M; Wallace, Gordon G; Ovalle-Robles, Raquel; Lima, Márcio D; Kozlov, Mikhail E; Baughman, Ray H
2012-01-24
We report mechanically robust, electrically conductive, free-standing, and transparent hybrid nanomembranes made of densified carbon nanotube sheets that were coated with poly(3,4-ethylenedioxythiophene) using vapor phase polymerization and their performance as supercapacitors. The hybrid nanomembranes with thickness of ~66 nm and low areal density of ~15 μg/cm(2)exhibited high mechanical strength and modulus of 135 MPa and 12.6 GPa, respectively. They also had remarkable shape recovery ability in liquid and at the liquid/air interface unlike previous carbon nanotube sheets. The hybrid nanomembrane attached on a current collector had volumetric capacitance of ~40 F/cm(3) at 100 V s(-1) (~40 and ~80 times larger than that of onion-like carbon measured at 100 V s(-1) and activated carbon measured at 20 V s(-1), respectively), and it showed rectangular shapes of cyclic voltammograms up to ~5 V s(-1). High mechanical strength and flexibility of the hybrid nanomembrane enabled twisting it into microsupercapacitor yarns with diameters of ~30 μm. The yarn supercapacitor showed stable cycling performance without a metal current collector, and its capacitance decrease was only ~6% after 5000 cycles. Volumetric energy and power density of the hybrid nanomembrane was ~70 mWh cm(-3) and ~7910 W cm(-3), and the yarn possessed the energy and power density of ~47 mWh cm(-3) and ~538 W cm(-3). © 2011 American Chemical Society
Chen, Ying-Chu; Lin, Yan-Gu; Hsu, Yu-Kuei; Yen, Shi-Chern; Chen, Kuei-Hsien; Chen, Li-Chyong
2014-09-24
A simple one-step electroplating route is proposed for the synthesis of novel iron oxyhydroxide lepidocrocite (γ-FeOOH) nanosheet anodes with distinct layered channels, and the microstructural influence on the pseudocapacitive performance of the obtained γ-FeOOH nanosheets is investigated via in situ X-ray absorption spectroscopy (XAS) and electrochemical measurement. The in situ XAS results regarding charge storage mechanisms of electrodeposited γ-FeOOH nanosheets show that a Li(+) can reversibly insert/desert into/from the 2D channels between the [FeO6 ] octahedral subunits depending on the applied potential. This process charge compensates the Fe(2+) /Fe(3+) redox transition upon charging-discharging and thus contributes to an ideal pseudocapacitive behavior of the γ-FeOOH electrode. Electrochemical results indicate that the γ-FeOOH nanosheet shows the outstanding pseudocapacitive performance, which achieves the extraordinary power density of 9000 W kg(-1) with good rate performance. Most importantly, the asymmetric supercapacitors with excellent electrochemical performance are further realized by using 2D MnO2 and γ-FeOOH nanosheets as cathode and anode materials, respectively. The obtained device can be cycled reversibly at a maximum cell voltage of 1.85 V in a mild aqueous electrolyte, further delivering a maximum power density of 16 000 W kg(-1) at an energy density of 37.4 Wh kg(-1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Biopolymer-nanocarbon composite electrodes for use as high-energy high-power density electrodes
Karakaya, Mehmet; Roberts, Mark; Arcilla-Velez, Margarita; Zhu, Jingyi; Podila, Ramakrishna; Rao, Apparao
2014-03-01
Supercapacitors (SCs) address our current energy storage and delivery needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Although activated carbon is extensively used as a supercapacitor electrode due to its inexpensive nature, its low specific capacitance (100-120 F/g) fundamentally limits the energy density of SCs. We demonstrate that a nano-carbon based mechanically robust, electrically conducting, free-standing buckypaper electrode modified with an inexpensive biorenewable polymer, viz., lignin increases the electrode's specific capacitance (~ 600-700 F/g) while maintaining rapid discharge rates. In these systems, the carbon nanomaterials provide the high surface area, electrical conductivity and porosity, while the redox polymers provide a mechanism for charge storage through Faradaic charge transfer. The design of redox polymers and their incorporation into nanomaterial electrodes will be discussed with a focus on enabling high power and high energy density electrodes. Research supported by US NSF CMMI Grant 1246800.
Wind farm density and harvested power in very large wind farms: A low-order model
Cortina, G.; Sharma, V.; Calaf, M.
2017-07-01
In this work we create new understanding of wind turbine wakes recovery process as a function of wind farm density using large-eddy simulations of an atmospheric boundary layer diurnal cycle. Simulations are forced with a constant geostrophic wind and a time varying surface temperature extracted from a selected period of the Cooperative Atmospheric Surface Exchange Study field experiment. Wind turbines are represented using the actuator disk model with rotation and yaw alignment. A control volume analysis around each turbine has been used to evaluate wind turbine wake recovery and corresponding harvested power. Results confirm the existence of two dominant recovery mechanisms, advection and flux of mean kinetic energy, which are modulated by the background thermal stratification. For the low-density arrangements advection dominates, while for the highly loaded wind farms the mean kinetic energy recovers through fluxes of mean kinetic energy. For those cases in between, a smooth balance of both mechanisms exists. From the results, a low-order model for the wind farms' harvested power as a function of thermal stratification and wind farm density has been developed, which has the potential to be used as an order-of-magnitude assessment tool.
Effect of low-power density laser radiation on heatling of open skin wounds in rats
Energy Technology Data Exchange (ETDEWEB)
Kana, J.S.; Hutschenreiter, G.; Haina, D.; Waidelich, W.
1981-03-01
Researchers performed a study to determine whether laser radation of low-power density would affect the healing of open skin wounds in rats. The wounds were irradiated daily with a helium-neon laser and an argon laser at a constant power density of 45 mW/sq cm. The rate of wound closure was followed by photographing the wounds in a standardized way. The collagen hydroxyproline concentration in the scar tissue was determined on the 18th postoperative day. Helium-neon laser radiation had a statistically significant stimulating effect on collagen synthesis in the wound, with a maximum effect at an energy density of 4 joules/sq cm. The rate of wound closure was enhanced significantly between the third and 12th postoperative days. The argon laser exposure produced a significant increase in collagen concentration both in irradiated and nonirradiated contralateral wounds. However, an acceleration of the healing rate was not registered in this case. The wound contraction up to the fourth day of the experiment was inhibited under helium-neon and argon laser exposure to 20 joules/sq cm. The described effects were not specific for the laser light. There may be a wavelength-selective influence of coherent light on the metabolic and proliferation processes in wound healing, with the associated problem of the possible carcinogenic effects of laser radiation.
Timing A Pulsed Thin Film Pyroelectric Generator For Maximum Power Density
International Nuclear Information System (INIS)
Smith, A.N.; Hanrahan, B.M.; Neville, C.J.; Jankowski, N.R
2016-01-01
Pyroelectric thermal-to-electric energy conversion is accomplished by a cyclic process of thermally-inducing polarization changes in the material under an applied electric field. The pyroelectric MEMS device investigated consisted of a thin film PZT capacitor with platinum bottom and iridium oxide top electrodes. Electric fields between 1-20 kV/cm with a 30% duty cycle and frequencies from 0.1 - 100 Hz were tested with a modulated continuous wave IR laser with a duty cycle of 20% creating temperature swings from 0.15 - 26 °C on the pyroelectric receiver. The net output power of the device was highly sensitive to the phase delay between the laser power and the applied electric field. A thermal model was developed to predict and explain the power loss associated with finite charge and discharge times. Excellent agreement was achieved between the theoretical model and the experiment results for the measured power density versus phase delay. Limitations on the charging and discharging rates result in reduced power and lower efficiency due to a reduced net work per cycle. (paper)
Power probability density function control and performance assessment of a nuclear research reactor
International Nuclear Information System (INIS)
Abharian, Amir Esmaeili; Fadaei, Amir Hosein
2014-01-01
Highlights: • In this paper, the performance assessment of static PDF control system is discussed. • The reactor PDF model is set up based on the B-spline functions. • Acquaints of Nu, and Th-h. equations solve concurrently by reformed Hansen’s method. • A principle of performance assessment is put forward for the PDF of the NR control. - Abstract: One of the main issues in controlling a system is to keep track of the conditions of the system function. The performance condition of the system should be inspected continuously, to keep the system in reliable working condition. In this study, the nuclear reactor is considered as a complicated system and a principle of performance assessment is used for analyzing the performance of the power probability density function (PDF) of the nuclear research reactor control. First, the model of the power PDF is set up, then the controller is designed to make the power PDF for tracing the given shape, that make the reactor to be a closed-loop system. The operating data of the closed-loop reactor are used to assess the control performance with the performance assessment criteria. The modeling, controller design and the performance assessment of the power PDF are all applied to the control of Tehran Research Reactor (TRR) power in a nuclear process. In this paper, the performance assessment of the static PDF control system is discussed, the efficacy and efficiency of the proposed method are investigated, and finally its reliability is proven
Carbon loaded Teflon (CLT): a power density meter for biological experiments using millimeter waves.
Allen, Stewart J; Ross, James A
2007-01-01
The standard technique for measurement of millimeter wave fields utilizes an open-ended waveguide attached to a HP power meter. The alignment of the waveguide with the propagation (K) vector is critical to making accurate measurements. Using this technique, it is difficult and time consuming to make a detailed map of average incident power density over areas of biological interest and the spatial resolution of this instrument does not allow accurate measurements in non-uniform fields. For biological experiments, it is important to know the center field average incident power density and the distribution over the exposed area. Two 4 ft x 4 ft x 1/32 inch sheets of carbon loaded Teflon (CLT) (one 15% carbon and one 25% carbon) were procured and a series of tests to determine the usefulness of CLT in defining fields in the millimeter wavelength range was initiated. Since the CLT was to be used both in the laboratory, where the environment was well controlled, and in the field, where the environment could not be controlled, tests were made to determine effects of change in environmental conditions on ability to use CLT as a millimeter wave dosimeter. The empirical results of this study indicate CLT to be an effective dosimeter for biological experiments both in the laboratory and in the field.
Wind Characteristics and an Evaluation of Wind Power Density at Three Sites in Egypt
International Nuclear Information System (INIS)
Etman, S.M.
2008-01-01
This paper presents the results of the analysis of wind speed data for one calendar year (2005) at three stations (El-Tor, El-Nonzha, and El-Notron) in Egypt along with the wind energy potential of each site. The wind power density at 25 m height was obtained by extrapolation of data at 10 m using a Power-law expression. The frequency distribution of observed hourly wind speeds occurring at each station is examined, particularly for wind speeds greater than or equal to 3 and 5 m/s (cut-in wind speeds for most wind turbines). The study reveals that the wind turbine can be operated at the sites El-Tor, El-Nouzha, and El-Notron with an annual availability factor of about 89.9 %, 76.2 %, and 67.9 % if the cut-in wind speed is 3 m/s and 67.2 %,51.8 %, and 17.1 % if the cut-in wind speed is 5 m/s, respectively. The total available wind power density ( kWh/m 2 /yr) Was estimated at the selected sites; El-Tor, El-Nouzha and El-Notron and was found to be: 3838.4, 825.5 and 284 kWh/m 2 /yr for case 3m/s and 2276.2, 489,5 and 71 kWh/m 2 /yr for case 5 m/s, respectively
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.
Govindasamy, P.; Gunasekaran, S.; Ramkumaar, G. R.
2014-09-01
The Fourier transform infrared (FT-IR) and FT-Raman spectra of N-(4-hydroxy phenyl) acetamide (N4HPA) of painkiller agent were recorded in the region 4000-450 cm-1 and 4000-50 cm-1 respectively. Density functional theory (DFT) has been used to calculate the optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations at DFT/B3LYP level with 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p) and 6-311++G(d,p) basis sets. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes calculated using Vibrational energy distribution analysis (VEDA 4) program. The oscillator’s strength calculated by TD-DFT and N4HPA is approach complement with the experimental findings. The NMR chemical shifts 13C and 1H were recorded and calculated using the gauge independent atomic orbital (GIAO) method. The molecular electrostatic potential (MESP) and electron density surfaces of the molecule were constructed. The Natural charges and intermolecular contacts have been interpreted using Natural Bond orbital (NBO) analysis the HOMO-LUMO energy gap has been calculated. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated.
Boriskina, Svetlana; Kraemer, Daniel; McEnaney, Kenneth; Weinstein, Lee A.; Chen, Gang
2018-03-13
Solar power conversion system. The system includes a cavity formed within an enclosure having highly specularly reflecting in the IR spectrum inside walls, the enclosure having an opening to receive solar radiation. An absorber is positioned within the cavity for receiving the solar radiation resulting in heating of the absorber structure. In a preferred embodiment, the system further contains an energy conversion and storage devices thermally-linked to the absorber by heat conduction, convection, far-field or near-field thermal radiation.
New directions in fusion machines: Report on the MFAC panel X on high power density options
International Nuclear Information System (INIS)
Linford, R.K.
1986-01-01
The high cost of fusion is motivating a shift in research interest toward smaller, lower-cost systems. Panel X of the Magnetic Fusion Advisory Committee (MFAC) was charged to assess the potential benefits and problems associated with small, highpower-density approaches to fusion. The Panel identified figures of merit which are useful in evaluating various approaches to reduce the development costs and capital costs of fusion systems. As a result of their deliberations, the Panel recommended that ''...increased emphasis should be given to improving the mass power density of fusion systems, aiming at a minimum target of 100 kWe/tonne'', and that ''Increased emphasis should be given to concepts that offer the potential to reduce4 substantially the cost of development steps in physics and technology.''
DEFF Research Database (Denmark)
Hu, Hao; Pu, Minhao; Yvind, Kresten
2017-01-01
We experimentally demonstrated 10 GHz frequency comb spectral broadening with a 30-dB bandwidth of 238 nm in an 11-mm long AlGaAsOI nano-waveguide. The 10-GHz 230-fs pump pulse has an average power of only 12 mW.......We experimentally demonstrated 10 GHz frequency comb spectral broadening with a 30-dB bandwidth of 238 nm in an 11-mm long AlGaAsOI nano-waveguide. The 10-GHz 230-fs pump pulse has an average power of only 12 mW....
Wörman, A.; Bottacin-Busolin, A.; Zmijewski, N.; Riml, J.
2017-08-01
Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power.
Impact of laser power density on tribological properties of Pulsed Laser Deposited DLC films
Gayathri, S.; Kumar, N.; Krishnan, R.; AmirthaPandian, S.; Ravindran, T. R.; Dash, S.; Tyagi, A. K.; Sridharan, M.
2013-12-01
Fabrication of wear resistant and low friction carbon films on the engineered substrates is considered as a challenging task for expanding the applications of diamond-like carbon (DLC) films. In this paper, pulsed laser deposition (PLD) technique is used to deposit DLC films on two different types of technologically important class of substrates such as silicon and AISI 304 stainless steel. Laser power density is one of the important parameter used to tailor the fraction of sp2 bonded amorphous carbon (a-C) and tetrahedral amorphous carbon (ta-C) made by sp3 domain in the DLC film. The I(D)/I(G) ratio decreases with the increasing laser power density which is associated with decrease in fraction of a-C/ta-C ratio. The fraction of these chemical components is quantitatively analyzed by EELS which is well supported to the data obtained from the Raman spectroscopy. Tribological properties of the DLC are associated with chemical structure of the film. However, the super low value of friction coefficient 0.003 is obtained when the film is predominantly constituted by a-C and sp2 fraction which is embedded within the clusters of ta-C. Such a particular film with super low friction coefficient is measured while it was deposited on steel at low laser power density of 2 GW/cm2. The super low friction mechanism is explained by low sliding resistance of a-C/sp2 and ta-C clusters. Combination of excellent physical and mechanical properties of wear resistance and super low friction coefficient of DLC films is desirable for engineering applications. Moreover, the high friction coefficient of DLC films deposited at 9GW/cm2 is related to widening of the intergrain distance caused by transformation from sp2 to sp3 hybridized structure.
International Nuclear Information System (INIS)
Wang Haobin; Thoss, Michael
2010-01-01
Graphical abstract: □□□ - Abstract: The dynamics of the spin-boson model at zero temperature is studied for a bath characterized by a sub-Ohmic spectral density. Using the numerically exact multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method, the population dynamics of the two-level subsystem has been investigated in a broad range of parameter space. The results show the transition of the dynamics from weakly damped coherent motion to localization upon increase of the system-bath coupling strength. Comparison of the exact ML-MCTDH simulations with the non-interacting blip approximation (NIBA) shows that the latter performs rather poorly in the weak coupling regime with small Kondo parameters. However, NIBA improves significantly upon increase in the coupling strength and is quantitatively correct in the strong coupling, nonadiabatic limit. The transition from coherent motion to localization as a function of the different parameters of the model is analyzed in some detail.
Kanagathara, N.; Marchewka, M. K.; Drozd, M.; Renganathan, N. G.; Gunasekaran, S.; Anbalagan, G.
2013-10-01
An organic-organic salt, bis (4-nitrophenol) 2,4,6-triamino 1,3,5-triazine monohydrate (BNPM) has been prepared by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in triclinic system with centrosymmetric space group P-1. IR and Raman spectra of BNPM have been recorded and analyzed. The study has been extended to confocal Raman spectral analysis. Band assignments have been made for the melamine and p-nitrophenol molecules. Vibrational spectra have also been discussed on the basis of quantum chemical density functional theory calculations using Firefly (PC GAMESS) Version 7.1 G. Vibrational frequencies are calculated and scaled values are compared with the experimental one. The Mulliken charges, HOMO-LUMO orbital energies are calculated and analyzed. The chemical structure of the compound was established by 1H NMR and 13C NMR spectra.
Sensitivity analysis for reactivity and power density investigations in nuclear reactors
International Nuclear Information System (INIS)
Naguib, K.; Morcos, H.N.; Sallam, O.H.; Abdelsamei, SH.
1993-01-01
Sensitivity analysis theory based on the variational functional approaches was applied to evaluate sensitivities of eigenvalues and power densities due to variation of the absorber concentration in the reactor core. The practical usefulness of this method is illustrated by considering test cases. The result indicates that this method is as accurate as those obtained from direct calculations, yet it provides an economical means in saving computational time since it requires fewer calculations. The SARC-1/2 code have been written in Fortran-77 to solve this problem.3 tab. 1 fig
Singh, Rajendra; Houser, Donald R.
1993-01-01
This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.
High power density supercapacitor electrodes of carbon nanotube films by electrophoretic deposition
International Nuclear Information System (INIS)
Du Chunsheng; Pan Ning
2006-01-01
Carbon nanotube thin films have been successfully fabricated by the electrophoretic deposition technique. The supercapacitors built from such thin film electrodes have a very small equivalent series resistance, and a high specific power density over 20 kW kg -1 was thus obtained. More importantly, the supercapacitors showed superior frequency response. Our study also demonstrated that these carbon nanotube thin films can serve as coating layers over ordinary current collectors to drastically enhance the electrode performance, indicating a huge potential in supercapacitor and battery manufacturing
Directory of Open Access Journals (Sweden)
Allen L. Garner
2016-03-01
Full Text Available Calculations indicate that selectively heating the extracellular media induces membrane temperature gradients that combine with electric fields and a temperature-induced reduction in the electropermeabilization threshold to potentially facilitate exogenous molecular delivery. Experiments by a wide-field, pulsed femtosecond laser with peak power density far below typical single cell optical delivery systems confirmed this hypothesis. Operating this laser in continuous wave mode at the same average power permeabilized many fewer cells, suggesting that bulk heating alone is insufficient and temperature gradients are crucial for permeabilization. This work suggests promising opportunities for a high throughput, low cost, contactless method for laser mediated exogenous molecule delivery without the complex optics of typical single cell optoinjection, for potential integration into microscope imaging and microfluidic systems.
Analytical method for reconstruction pin to pin of the nuclear power density distribution
Energy Technology Data Exchange (ETDEWEB)
Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S., E-mail: ppessoa@con.ufrj.br, E-mail: fernando@con.ufrj.br, E-mail: aquilino@imp.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)
2013-07-01
An accurate and efficient method for reconstructing pin to pin of the nuclear power density distribution, involving the analytical solution of the diffusion equation for two-dimensional neutron energy groups in homogeneous nodes, is presented. The boundary conditions used for analytic as solution are the four currents or fluxes on the surface of the node, which are obtained by Nodal Expansion Method (known as NEM) and four fluxes at the vertices of a node calculated using the finite difference method. The analytical solution found is the homogeneous distribution of neutron flux. Detailed distributions pin to pin inside a fuel assembly are estimated by the product of homogeneous flux distribution by local heterogeneous form function. Furthermore, the form functions of flux and power are used. The results obtained with this method have a good accuracy when compared with reference values. (author)
Analytical method for reconstruction pin to pin of the nuclear power density distribution
International Nuclear Information System (INIS)
Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S.
2013-01-01
An accurate and efficient method for reconstructing pin to pin of the nuclear power density distribution, involving the analytical solution of the diffusion equation for two-dimensional neutron energy groups in homogeneous nodes, is presented. The boundary conditions used for analytic as solution are the four currents or fluxes on the surface of the node, which are obtained by Nodal Expansion Method (known as NEM) and four fluxes at the vertices of a node calculated using the finite difference method. The analytical solution found is the homogeneous distribution of neutron flux. Detailed distributions pin to pin inside a fuel assembly are estimated by the product of homogeneous flux distribution by local heterogeneous form function. Furthermore, the form functions of flux and power are used. The results obtained with this method have a good accuracy when compared with reference values. (author)
Improving the peak power density estimation for the DNBR trip signal
International Nuclear Information System (INIS)
Moreira, Joao M. L.; Souza, Rose Mary G.P.
2002-01-01
The departure from nucleate boiling (DNB) core protection in PWR reactors is usually carried out through the over temperature trip or the instantaneous minimum DNB ratio (DNBR) trip. The protection is obtained through specialized correlations or fast digital computer simulators that infer the core power level, and local coolant thermal and flow conditions out of process variables furnished by the instrumentation. The power density distribution information is usually expressed in terms of F q , the power peak factor, and its location. F q , in its turn, can be determined through the control rod position or, more often, through the power axial offset (AO) F q =f (AO, control rod positions). The AO, defined as the difference between upper and lower long ion chambers signals, is supplied for each channel by separate sets of out-of-core detectors positioned 90 or 120 degrees apart in plan. The AO is given by AO=(S t -S b )/(S t +S b ) where S t and S b are the out-of-core signals from the top and the bottom sections, respectively. In current PWRs a large penalty is imposed to the result of the first equation, because of the difficult of inferring with good accuracy the peak factor from the AO obtained from the out-of-core instrumentation. This ends up reducing the plant capacity factor. In this work, the f function in the first equation, which correlates the power peak factor with the axial offset yielded by out-of-core detectors and control rod positions, is obtained through a combination of specific experiments in the IPEN/MB-01 zero-power reactor and calculation results. For improving the peak factor estimation, it is necessary to consider accurately the response of the out-of-core detectors to different power density distribution in the core. This task is not easily accomplished through calculation due to the difficulties involved in the necessary neutron transport treatment for the out-of-core detector responses
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Objective: The functional relationship between calculated alpha band spectral power and inter-/intra-hemispheric coherence during a three-level working memory task of patients with mild cognitive impairment (MCI) was investigated. Methods:Subjects included 35 MCI patients according to the DSM-Ⅳ criteria (mean age: 62.3, SD: 6.5) and 34 healthy controls (mean age:57.4, SD: 4.0) were selected from the community at large. All subjects performed a simple calculation and recall task with three levels of working memory load while electroencephalograph (EEG) signal was recorded. The spectral EEG power was computed over alphal (8.0～10.0 Hz) and alpha2 (10.5～13.0 Hz) frequency bands and was compared between rest stage and working memory processing stage by two-way ANOVA. Post hoc testing analyzed the differences between each two levels of working memory load during task processing. The inter-hemisphere EEG coherence of frontal (F3-F4), central (C3-C4), parietal (P3-P4), temporal (T5-T6) as well as occipital (O1-O2) was compared between MCI patients and normal controls. The EEG signals from F3-C3,F4-C4, C3-P3, C4-P4, P3-O1, P4-O2, T5-C3, T6-C4, T5-P3 and T6-P4 electrode pairs resulted from the intra-hemispheric action for alphal and alpha2 frequency bands. Result: There was significantly higher EEG power from MCI patients than from normal controls both at rest and during working memory processing. Significant differences existed between rest condition and three-level working memory tasks (P＜0.001). The inter- and intra-hemispheric coherence during working memory tasks showed a "drop to rise" tendency compared to that at rest condition. There was significantly higher coherence in MCI patients than in the controls.When task difficulties increased, the cortical connectivity of intra-hemispheric diminished while the inter-hemispheric connectivity dominantly maintained the cognitive processing in MCI patients. Conclusion: The results of the present study indicate that the
High power density thin film SOFCs with YSZ/GDC bilayer electrolyte
International Nuclear Information System (INIS)
Cho, Sungmee; Kim, YoungNam; Kim, Jung-Hyun; Manthiram, Arumugam; Wang Haiyan
2011-01-01
Graphical abstract: . A: Cross-sectional TEM images show a GDC single layer and YSZ/GDC bilayer electrolyte structures. As clearly observed from TEM images, the YSZ interlayer thickness varies from ∼330 nm to ∼1 μm. B: The cell with the bilayer electrolyte (YSZ ∼330 nm) doubles the overall power output at 750 deg. C compared to that achieved in the GDC single layer cell. Display Omitted Highlights: → YSZ/ GDC bilayer thin film electrolytes were deposited by a pulsed laser deposition (PLD) technique. → Thin YSZ film as a blocking layer effectively suppresses the cell voltage drop without reducing the ionic conductivity of the electrolyte layer. → The YSZ/ GDC bilayer structure presents a feasible architecture for enhancing the overall power density and enabling chemical, mechanical, and structural stability in the cells. - Abstract: Bilayer electrolytes composed of a gadolinium-doped CeO 2 (GDC) layer (∼6 μm thickness) and an yttria-stabilized ZrO 2 (YSZ) layer with various thicknesses (∼330 nm, ∼440 nm, and ∼1 μm) were deposited by a pulsed laser deposition (PLD) technique for thin film solid oxide fuel cells (TFSOFCs). The bilayer electrolytes were prepared between a NiO-YSZ (60:40 wt.% with 7.5 wt.% carbon) anode and La 0.5 Sr 0.5 CoO 3 -Ce 0.9 Gd 0.1 O 1.95 (50:50 wt.%) composite cathode for anode-supported single cells. Significantly enhanced maximum power density was achieved, i.e., a maximum power density of 188, 430, and 587 mW cm -2 was measured in a bilayer electrolyte single cell with ∼330 nm thin YSZ at 650, 700, and 750 deg. C, respectively. The cell with the bilayer electrolyte (YSZ ∼330 nm) doubles the overall power output at 750 deg. C compared to that achieved in the GDC single layer cell. This signifies that the YSZ thin film serves as a blocking layer for preventing electrical current leakage in the GDC layer and also provides chemical, mechanical, and structural integrity in the cell, which leads to the overall enhanced
International Nuclear Information System (INIS)
Zhang, Yanliang; Cleary, Martin; Wang, Xiaowei; Kempf, Nicholas; Schoensee, Luke; Yang, Jian; Joshi, Giri; Meda, Lakshmikanth
2015-01-01
Highlights: • A thermoelectric generator (TEG) is fabricated using nanostructured half-Heusler materials. • The TE unicouple devices produce superior power density above 5 W/cm"2. • A TEG system with over 1 kW power output is demonstrated by recovering automotive waste heat. - Abstract: Given increasing energy use as well as decreasing fossil fuel sources worldwide, it is no surprise that interest in promoting energy efficiency through waste heat recovery is also increasing. Thermoelectric generators (TEGs) are one of the most promising pathways for waste heat recovery. Despite recent thermoelectric efficiency improvement in nanostructured materials, a variety of challenges have nevertheless resulted in few demonstrations of these materials for large-scale waste heat recovery. Here we demonstrate a high-performance TEG by combining high-efficiency nanostructured bulk materials with a novel direct metal brazing process to increase the device operating temperature. A unicouple device generates a high power density of 5.26 W cm"−"2 with a 500 °C temperature difference between hot and cold sides. A 1 kW TEG system is experimentally demonstrated by recovering the exhaust waste heat from an automotive diesel engine. The TEG system operated with a 2.1% heat-to-electricity efficiency under the average temperature difference of 339 °C between the TEG hot- and cold-side surfaces at a 550 °C exhaust temperature. The high-performance TEG reported here open up opportunities to use TEGs for energy harvesting and power generation applications.
International Nuclear Information System (INIS)
Gardet, G.
1995-01-01
A systematic study of small lithium clusters (with size less than 19), within the Density Functional Theory (DFT) formalism is presented. We examine structural properties of the so called local level of approximation. For clusters with size smaller than 8, the conformations are well known from ab initio calculations and are found here at much lower computational cost, with only small differences. For bigger clusters, two growth pattern have been used, based upon the increase of the number of pentagonal subunits in the clusters by absorption of one or two Li atoms. Several new stable structures are proposed. Then DFT gradient-corrected functionals have been used for relative stability determination of these clusters. Ionisation potentials and binding energies are also investigated in regard to clusters size and geometry. Calculations of excited states of lithium clusters (with size less than 9) have been performed within two different approaches. Using a set of Kohn-Sham orbitals to construct wave functions, oscillator strengths calculation of the electric dipole transitions is performed. Transition energies, oscillator strengths and optical absorption presented here are generally in reasonable agreement with the experimental data and the Configuration Interaction calculations. (author)
Institute of Scientific and Technical Information of China (English)
2008-01-01
Studies of the density and the excess molar volume of ethylene glycol (EG)-water mixtures were carried out to illustrate the hydrogen bonding interactions of EG with water at different temperatures. The re-sults suggest that a likely complex of 3 ethylene glycol molecules bonding with 4 water molecules in an ethylene glycol-water mixture (EGW) is formed at the maximal excess molar volume,which displays stronger absorption capabilities for SO2 when the concentration of SO2 reaches 400×10?6 (volume ratio) in the gas phase. Meanwhile,FTIR and UV spectra of EGWs were recorded at various EG concentra-tions to display the hydrogen bonding interactions of EG with water. The FTIR spectra show that the stretching vibrational band of hydroxyl in the EGWs shifts to a lower frequency and the bending vibra-tional band of water shifts to a higher frequency with increasing the EG concentration,respectively. Furthermore,the UV spectra show that the electron transferring band of the hydroxyl oxygen in EG shows red shift with increasing the EG concentration. The frequency shifts in FTIR spectra and the shifts of absorption bands in UV absorption spectra of EGWs are interpreted as the strong hydrogen bonding interactions of the hydrogen atoms in water with the hydroxyl oxygen atoms of EG.
Kishimoto, Junichi; Ohta, Yasutoshi; Kitao, Shinichiro; Watanabe, Tomomi; Ogawa, Toshihide
2018-04-01
Single-source dual-energy CT (ssDECT) allows the reconstruction of iodine density images (IDIs) from projection based computing. We hypothesized that adding adaptive statistical iterative reconstruction (ASiR) could improve image quality. The aim of our study was to evaluate the effect and determine the optimal blend percentages of ASiR for IDI of myocardial late iodine enhancement (LIE) in the evaluation of chronic myocardial infarction using ssDECT. A total of 28 patients underwent cardiac LIE using a ssDECT scanner. IDIs between 0 and 100% of ASiR contributions in 10% increments were reconstructed. The signal-to-noise ratio (SNR) of remote myocardia and the contrast-to-noise ratio (CNR) of infarcted myocardia were measured. Transmural extent of infarction was graded using a 5-point scale. The SNR, CNR, and transmural extent were assessed for each ASiR contribution ratio. The transmural extents were compared with MRI as a reference standard. Compared to 0% ASiR, the use of 20-100% ASiR resulted in a reduction of image noise (p ASiR images, reconstruction with 100% ASiR image showed the highest improvement in SNR (229%; p ASiR above 80% showed the highest ratio (73.7%) of accurate transmural extent classification. In conclusion, ASiR intensity of 80-100% in IDIs can improve image quality without changes in signal and maximizes the accuracy of transmural extent in infarcted myocardium.
Bustomi, A.; Wijaya, S. K.; Prawito
2017-07-01
Rehabilitation of motoric dysfunction from the body becomes the main objective of developing Brain Computer Interface (BCI) technique, especially in the field of medical rehabilitation technology. BCI technology based on electrical activity of the brain, allow patient to be able to restore motoric disfunction of the body and help them to overcome the shortcomings mobility. In this study, EEG signal phenomenon was obtained from EMOTIV EPOC+, the signals were generated from the imagery of lifting arm, and look for any correlation between the imagery of motoric muscle movement against the recorded signals. The signals processing were done in the time-frequency domain, using Wavelet relative power (WRP) as feature extraction, and Support vector machine (SVM) as the classifier. In this study, it was obtained the result of maximum accuracy of 81.3 % using 8 channel (AF3, F7, F3, FC5, FC6, F4, F8, and AF4), 6 channel remaining on EMOTIV EPOC + does not contribute to the improvement of the accuracy of the classification system
Power spectrum constraints from spectral distortions in the cosmic microwave background
Hu, Wayne; Scott, Douglas; Silk, Joseph
1994-01-01
Using recent experimental limits on chemical potential distortions from Cosmic Background Explorer (COBE) Far Infrared Astronomy Satellite (FIRAS), and the large lever-arm spanning the damping of sub-Jeans scale fluctuations to the COBE DMR fluctuations, we set a constraint on the slope of the primordial power spectrum n. It is possible to analytically calculate the contribution over the full range of scales and redshifts, correctly taking into account fluctuation growth and damping as well as thermalization processes. Assuming conservatively that mu is less than 1.76 x 10(exp -4), we find that the 95% upper limit on n is only weakly dependent on other cosmological parameters, e.g., n is less than 1.60 (h=0.5) and n is less than 1.63 (h=1.0) for Omega(sub 0) = 1, with marginally weaker constraints for Omega(sub 0) is less than 1 in a flat model with a cosmological constant.
Fatigue-associated alterations of cognitive function and electroencephalographic power densities.
Directory of Open Access Journals (Sweden)
Masaaki Tanaka
Full Text Available Fatigue is a common problem in modern society. We attempted to identify moderate- to long-term fatigue-related alterations in the central nervous system using cognitive tasks and electroencephalography (EEG measures. The study group consisted of 17 healthy male participants. After saliva samples were collected to measure copy number of human herpesvirus (HHV-6 DNA to assess the level of moderate- to long-term fatigue, subjects were evaluated using EEG, with their eyes open for 2 min, then closed for 1 min sitting quietly. Thereafter, they completed cognitive task trials to evaluate simple selective attention for 3 min (Task 1 and conflict-controlling selective attention for 6 min (Task 2, which included Stroop trials. The percent error of Task 2 for Stroop trials was positively associated with the copy number of saliva HHV-6 DNA, although the simple selective attention measures in Task 1 did not differ significantly. EEG power densities (especially the alpha power density during the eye-closed condition were negatively associated with the saliva HHV-6 DNA level. Impaired high-level information processing such as that required for conflict-controlling selective attention in the central nervous system may be a characteristic feature of moderate- to long-term fatigue.
Determination of power density in VVER-1000 Mock-Up in LR-0 reactor
Directory of Open Access Journals (Sweden)
Košál Michal
2017-01-01
Full Text Available The pin power density is an important quantity which has to be monitored during the reactor operation, for two main reasons. Firstly, it is part of the limits and conditions of safe operation and, secondly, it is source term in neutron transport calculations used for the adequate assessing of the state of core structures and pressure vessel material. It is often calculated using deterministic codes which may have problems with an adequate definition of boundary conditions in subcritical regions. This may lead to overestimation of real situation, and therefore the validation of the utility codes contributes not only to better fuel utilization, but also to more precise description of radiation situation in structural components of core. Current paper presents methods developed at LR-0 reactor, as well as selected results for pin power density measurement in peripheral regions of VVER-1000 mock-up. The presented data show that the results of a utility diffusion code at core boundary overestimate the measurement. This situation, however satisfactory safe, may lead to unduly conservative approach in the determination of radiation damage of core structures.
National Aeronautics and Space Administration — FastCAP proposes to develop an ultra-high power density and high frequency ultracapacitor capable of surviving over the wide temperature range of -60C to 130C and...
International Nuclear Information System (INIS)
Takamatsu, Kuniyoshi; Shimakawa, Satoshi; Nojiri, Naoki; Fujimoto, Nozomu
2003-10-01
In the case of evaluations for the highest temperature of the fuels in the HTTR, it is very important to expect the power density distributions accurately; therefore, it is necessary to improve the analytical model with the neutron diffusion and the burn-up theory. The power density distributions are analyzed in terms of two models, the one mixing the fuels and the burnable poisons homogeneously and the other modeling them heterogeneously. Moreover these analytical power density distributions are compared with the ones derived from the gross gamma-ray measurements and the Monte Carlo calculational code with continuous energy. As a result the homogeneous mixed model isn't enough to expect the power density distributions of the core in the axial direction; on the other hand, the heterogeneous model improves the accuracy. (author)
Kahveci, E. E.; Taymaz, I.
2018-03-01
In this study it was experimentally investigated the effect of mass flow rates of reactant gases which is one of the most important operational parameters of polymer electrolyte membrane (PEM) fuel cell on power density. The channel type is serpentine and single PEM fuel cell has an active area of 25 cm2. Design-Expert 8.0 (trial version) was used with four variables to investigate the effect of variables on the response using. Cell temperature, hydrogen mass flow rate, oxygen mass flow rate and humidification temperature were selected as independent variables. In addition, the power density was used as response to determine the combined effects of these variables. It was kept constant cell and humidification temperatures while changing mass flow rates of reactant gases. From the results an increase occurred in power density with increasing the hydrogen flow rates. But oxygen flow rate does not have a significant effect on power density within determined mass flow rates.
The reversed-field pinch as a poloidal-field-dominated, compact, high-power-density fusion system
International Nuclear Information System (INIS)
Krakowski, R.A.
1988-01-01
This paper discusses the feasibility of reversed-field pinch devices as future thermonuclear reactors. Safety, cost, ion temperatures, Lawson numbers, and power densities are reviewed for these types of devices. 12 refs., 2 figs., 1 tab
ADX: a high field, high power density, Advanced Divertor test eXperiment
Vieira, R.; Labombard, B.; Marmar, E.; Irby, J.; Shiraiwa, S.; Terry, J.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; ADX Team
2014-10-01
The MIT PSFC and collaborators are proposing an advanced divertor experiment (ADX) - a tokamak specifically designed to address critical gaps in the world fusion research program on the pathway to FNSF/DEMO. This high field (6.5 tesla, 1.5 MA), high power density (P/S ~ 1.5 MW/m2) facility would utilize Alcator magnet technology to test innovative divertor concepts for next-step DT fusion devices (FNSF, DEMO) at reactor-level boundary plasma pressures and parallel heat flux densities while producing high performance core plasma conditions. The experimental platform would also test advanced lower hybrid current drive (LHCD) and ion-cyclotron range of frequency (ICRF) actuators and wave physics at the plasma densities and magnetic field strengths of a DEMO, with the unique ability to deploy launcher structures both on the low-magnetic-field side and the high-field side - a location where energetic plasma-material interactions can be controlled and wave physics is most favorable for efficient current drive, heating and flow drive. This innovative experiment would perform plasma science and technology R&D necessary to inform the conceptual development and accelerate the readiness-for-deployment of FNSF/DEMO - in a timely manner, on a cost-effective research platform. Supported by DE-FC02-99ER54512.
International Nuclear Information System (INIS)
Ahmed, S. A.; Peter, J. K.; Semmler, W.; Shultis, J. K.
2007-01-01
By measuring neutron fluxes at different locations throughout a core, it's possible to derive the power-density profile P k (W cm - 3), at an axial depth z of fuel rod k. Micro-pocket fission detectors (MPFD) have been fabricated to perform such in-core neutron flux measurements. The purpose of this study is to develop a mathematical model to obtain axial power density distributions in the fuel rods from the in-core responses of the MPFDs
Yao, Kui; Chen, Shuting; Rahimabady, Mojtaba; Mirshekarloo, Meysam Sharifzadeh; Yu, Shuhui; Tay, Francis Eng Hock; Sritharan, Thirumany; Lu, Li
2011-09-01
Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.
Czech Academy of Sciences Publication Activity Database
Fagard, R.H.; Stolarz, K.; Kuznetsova, T.; Seidlerová, J.; Tikhonoff, V.; Grodzicki, T.; Nikitin, Y.; Filipovský, J.; Peleška, Jan; Casiglia, E.; Thijs, L.; Staessen, J.A.; Kawecka-Jaszcz, K.
2007-01-01
Roč. 25, č. 11 (2007), s. 2280-2285 ISSN 0263-6352 Institutional research plan: CEZ:AV0Z10300504 Keywords : heart rate variability * masked hypertension * power spectral analysis * sympathetic activity * white-coat hypertension Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 4.364, year: 2007
A Cryogenic High-Power-Density Bearingless Motor for Future Electric Propulsion
Choi, Benjamin; Siebert, Mark
2008-01-01
The NASA Glenn Research Center (GRC) is developing a high-power-density switched-reluctance cryogenic motor for all-electric and pollution-free flight. However, cryogenic operation at higher rotational speeds markedly shortens the life of mechanical rolling element bearings. Thus, to demonstrate the practical feasibility of using this motor for future flights, a non-contact rotor-bearing system is a crucial technology to circumvent poor bearing life that ordinarily accompanies cryogenic operation. In this paper, a bearingless motor control technology for a 12-8 (12 poles in the stator and 8 poles in the rotor) switched-reluctance motor operating in liquid nitrogen (boiling point, 77 K (-196 C or -321 F)) was presented. We pushed previous disciplinary limits of electromagnetic controller technique by extending the state-of-the-art bearingless motor operating at liquid nitrogen for high-specific-power applications. The motor was levitated even in its nonlinear region of magnetic saturation, which is believed to be a world first for the motor type. Also we used only motoring coils to generate motoring torque and levitation force, which is an important feature for developing a high specific power motor.
Exceptional power density and stability at intermediate temperatures in protonic ceramic fuel cells
Choi, Sihyuk; Kucharczyk, Chris J.; Liang, Yangang; Zhang, Xiaohang; Takeuchi, Ichiro; Ji, Ho-Il; Haile, Sossina M.
2018-03-01
Over the past several years, important strides have been made in demonstrating protonic ceramic fuel cells (PCFCs). Such fuel cells offer the potential of environmentally sustainable and cost-effective electric power generation. However, their power outputs have lagged behind predictions based on their high electrolyte conductivities. Here we overcome PCFC performance and stability challenges by employing a high-activity cathode, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), in combination with a chemically stable electrolyte, BaZr0.4Ce0.4Y0.1Yb0.1O3 (BZCYYb4411). We deposit a thin dense interlayer film of the cathode material onto the electrolyte surface to mitigate contact resistance, an approach which is made possible by the proton permeability of PBSCF. The peak power densities of the resulting fuel cells exceed 500 mW cm-2 at 500 °C, while also offering exceptional, long-term stability under CO2.
International Nuclear Information System (INIS)
Jafferis, Noah T; Lok, Mario; Wei, Gu-Yeon; Wood, Robert J; Winey, Nastasia
2016-01-01
In previous work we presented design and manufacturing rules for optimizing the energy density of piezoelectric bimorph actuators through the use of laser-induced melting, insulating edge coating, and features for rigid ground attachments to maximize force output, as well as a pre-stacked technique to enable mass customization. Here we adapt these techniques to bending actuators with four active layers, which utilize thinner material layers. This allows the use of lower operating voltages, which is important for overall power usage optimization, as typical small-scale power supplies are low-voltage and the efficiency of boost-converter and drive circuitry increases with decreasing output voltage. We show that this optimization results in a 24%–47% reduction in the weight of the required power supply (depending on the type of drive circuit used). We also present scaling arguments to determine when multi-layer actuator are preferable to thinner actuators, and show that our techniques are capable of scaling down to sub-mg weight actuators. (paper)
Radial power density distribution of MOX fuel rods in the IFA-651
Energy Technology Data Exchange (ETDEWEB)
Lee, Byung Ho; Koo, Yang Hyun; Joo, Hyung Kook; Cheon, Jin Sik; Oh, Je Yong; Sohn, Dong Seong [Korea Atomic Energy Research Institute, Taejeon (Korea)
2002-04-01
Two MOX fuel rods, which were fabricated in the Paul Scherrer Institute (PSI), Switzerland in cooperation with Korea Atomic Energy Research Institute, have been irradiated in the HBWR from June, 2000 in the framework of OECD-HRP together with a reference MOX fuel rod supplied by the BNFL. Since fuel temperature, which is influenced by radial power distribution, is basic in analyzing fuel behavior, it is required to consider radial power distribution in the HBWR. A subroutine FACTOR{sub H}BWR that calculates radial power density distribution for three MOX fuel rods has been developed based on neutron physics results and DEPRESS program. The developed subroutine FACTOR{sub H}BWR gives good agreement with the physics calculation except slight under-prediction at the outer part of the pellet above the burnup of 20 MWd/kgHM. The subroutine will be incorporated into a computer code COSMOS and used to analyze the in-reactor behavior of the three MOX fuel rods during the Halden irradiation test. 24 figs., 4 tabs. (Author)
Radial power density distribution of MOX fuel rods in the HBWR
International Nuclear Information System (INIS)
Koo, Yang Hyun; Joo, Hyung Kook; Lee, Byung Ho; Sohn, Dong Seong
1999-07-01
Two MOX fuel rods, which ar being fabricated in the Paul Scherrer Institute (PSI), Switzerland in cooperation with the Korea Atomic Energy Research Institute (KAERI), are going to be irradiated in the HBWR (Halden Boiling Water Reactor) from the beginning of 2000 in the framework of OECD Halden Reactor Programme (HRP) together with a reference MOX fuel rod supplied by the BNFL. Since fuel temperature, which is influenced by radial power distribution, is a basic property in analyzing fuel behavior, it is required to consider radial power distribution in the HBWR. A subroutine FACTOR H BWR that calculates radial power density distribution for three MOX fuel rods have been developed subroutine FACTOR H BWR gives good agreement with the physics calculation except slight underprediction in the central part and a little overprediction at the outer part of the pellet. The subroutine will be incorporated into a computer code COSMOS and used to analyze the in-reactor behavior of the three MOX fuel rods during the Halden irradiation test. (author). 5 refs., 3 tabs., 24 figs
Durability of Low Platinum Fuel Cells Operating at High Power Density
Energy Technology Data Exchange (ETDEWEB)
Polevaya, Olga [Nuvera Fuel Cells Inc.; Blanchet, Scott [Nuvera Fuel Cells Inc.; Ahluwalia, Rajesh [Argonne National Lab; Borup, Rod [Los-Alamos National Lab; Mukundan, Rangachary [Los-Alamos National Lab
2014-03-19
Understanding and improving the durability of cost-competitive fuel cell stacks is imperative to successful deployment of the technology. Stacks will need to operate well beyond today’s state-of-the-art rated power density with very low platinum loading in order to achieve the cost targets set forth by DOE ($15/kW) and ultimately be competitive with incumbent technologies. An accelerated cost-reduction path presented by Nuvera focused on substantially increasing power density to address non-PGM material costs as well as platinum. The study developed a practical understanding of the degradation mechanisms impacting durability of fuel cells with low platinum loading (≤0.2mg/cm2) operating at high power density (≥1.0W/cm2) and worked out approaches for improving the durability of low-loaded, high-power stack designs. Of specific interest is the impact of combining low platinum loading with high power density operation, as this offers the best chance of achieving long-term cost targets. A design-of-experiments approach was utilized to reveal and quantify the sensitivity of durability-critical material properties to high current density at two levels of platinum loading (the more conventional 0.45 mgPt.cm–1 and the much lower 0.2 mgPt.cm–2) across several cell architectures. We studied the relevance of selected component accelerated stress tests (AST) to fuel cell operation in power producing mode. New stress tests (NST) were designed to investigate the sensitivity to the addition of electrical current on the ASTs, along with combined humidity and load cycles and, eventually, relate to the combined city/highway drive cycle. Changes in the cathode electrochemical surface area (ECSA) and average oxygen partial pressure on the catalyst layer with aging under AST and NST protocols were compared based on the number of completed cycles. Studies showed elevated sensitivity of Pt growth to the potential limits and the initial particle size distribution. The ECSA loss
Spectral Analysis of Vector Magnetic Field Profiles
Parker, Robert L.; OBrien, Michael S.
1997-01-01
We investigate the power spectra and cross spectra derived from the three components of the vector magnetic field measured on a straight horizontal path above a statistically stationary source. All of these spectra, which can be estimated from the recorded time series, are related to a single two-dimensional power spectral density via integrals that run in the across-track direction in the wavenumber domain. Thus the measured spectra must obey a number of strong constraints: for example, the sum of the two power spectral densities of the two horizontal field components equals the power spectral density of the vertical component at every wavenumber and the phase spectrum between the vertical and along-track components is always pi/2. These constraints provide powerful checks on the quality of the measured data; if they are violated, measurement or environmental noise should be suspected. The noise due to errors of orientation has a clear characteristic; both the power and phase spectra of the components differ from those of crustal signals, which makes orientation noise easy to detect and to quantify. The spectra of the crustal signals can be inverted to obtain information about the cross-track structure of the field. We illustrate these ideas using a high-altitude Project Magnet profile flown in the southeastern Pacific Ocean.
Energy Technology Data Exchange (ETDEWEB)
Perret, G.; Pattupara, R. M. [Paul Scherrer Inst., 5232 Villigen (Switzerland); Girardin, G. [Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Chawla, R. [Paul Scherrer Inst., 5232 Villigen (Switzerland); Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)
2012-07-01
The gas-cooled fast reactor (GCFR) concept was investigated experimentally in the PROTEUS zero power facility at the Paul Scherrer Inst. during the 1970's. The experimental program was aimed at neutronics studies specific to the GCFR and at the validation of nuclear data in fast spectra. A significant part of the program used thorium oxide and thorium metal fuel either distributed quasi-homogeneously in the reference PuO{sub 2}/UO{sub 2} lattice or introduced in the form of radial and axial blanket zones. Experimental results obtained at the time are still of high relevance in view of the current consideration of the Gas-cooled Fast Reactor (GFR) as a Generation-IV nuclear system, as also of the renewed interest in the thorium cycle. In this context, some of the experiments have been modeled with modern Monte Carlo codes to better account for the complex PROTEUS whole-reactor geometry and to allow validating recent continuous neutron cross-section libraries. As a first step, the MCNPX model was used to test the JEFF-3.1, JEFF-3.1.1, ENDF/B-VII.0 and JENDL-3.3 libraries against spectral indices, notably involving fission and capture of {sup 232}Th and {sup 237}Np, measured in GFR-like lattices. (authors)
Directory of Open Access Journals (Sweden)
Catur Apriono
2015-08-01
Full Text Available A terahertz system uses dielectric lens antennas for focusing and collimating beams of terahertz wave radiation. Linearly polarized terahertz wave radiation has been widely applied in the terahertz system. Therefore, an accurate method for analyzing the power flow density in the dielectric lens antenna irradiated with the linearly polarized terahertz wave radiation is important to design the terahertz systems. In optics, ray-tracing method has been used to calculate the power flow density by a number density of rays. In this study, we propose a method of ray-tracing combined with Fresnel’s transmission, including transmittance and polarization of the terahertz wave radiation to calculate power flow density in a Silicon lens antenna. We compare power flow density calculated by the proposed method with the regular ray-tracing method. When the Silicon lens antenna is irradiated with linearly polarized terahertz wave radiation, the proposed method calculates the power flow density more accurately than the regular ray-tracing.
Thermal-Hydraulic Performance of Cross-Shaped Spiral Fuel in High-Power-Density BWRs
International Nuclear Information System (INIS)
Conboy, Thomas; Hejzlar, Pavel
2006-01-01
Power up-rating of existing nuclear reactors promises to be an area of great study for years to come. One of the major approaches to efficiently increasing power density is by way of advanced fuel design, and cross-shaped spiral-fuel has shown such potential in previous studies. Our work aims to model the thermal-hydraulic consequences of filling a BWR core with these spiral-shaped pins. The helically-wound pins have a cross-section resembling a 4-petaled flower. They fill an assembly in a tight bundle, their dimensions chosen carefully such that the petals of neighboring pins contact each other at their outer-most extent in a self-supporting lattice, absent of grid spacers. Potential advantages of this design raise much optimism from a thermal-hydraulic perspective. These spiral rods possess about 40% larger surface area than traditional rods, resulting in increased cooling and a proportional reduction in average surface heat flux. The thin petal-like extensions help by lowering thermal resistance between the hot central region of the pin and the bulk coolant flow, decreasing the maximum fuel temperature by 200 deg. C according to Finite Element (COSMOS) models. However, COSMOS models also predict a potential problem area at the 'elbow' region of two adjoining petals, where heat flux peaking is twice that along the extensions. Preliminary VIPRE models, which account only for the surface area increase, predict a 22% increase in critical power. It is also anticipated that the spiral twist would provide the flowing coolant with an additional radial velocity component, and likely promote turbulence and mixing within an assembly. These factors are expected to provide further margin for increased power density, and are currently being incorporated into the VIPRE model. The reduction in pressure drop inherent in any core without grid-spacers is also expected to be significant in aiding core stability, though this has not yet been quantified. Spiral-fuel seems to be a
Soft-solution route to ZnO nanowall array with low threshold power density
Jang, Eue-Soon; Chen, Xiaoyuan; Won, Jung-Hee; Chung, Jae-Hun; Jang, Du-Jeon; Kim, Young-Woon; Choy, Jin-Ho
2010-07-01
ZnO nanowall array (ZNWA) has been directionally grown on the buffer layer of ZnO nanoparticles dip-coated on Si-wafer under a soft solution process. Nanowalls on substrate are in most suitable shape and orientation not only as an optical trap but also as an optical waveguide due to their unique growth habit, V[011¯0]≫V[0001]≈V[0001¯]. Consequently, the stimulated emission at 384 nm through nanowalls is generated by the threshold power density of only 25 kW/cm2. Such UV lasing properties are superior to those of previously reported ZnO nanorod arrays. Moreover, there is no green (defect) emission due to the mild procedure to synthesize ZNWA.
Statistical measurement of power spectrum density of large aperture optical component
International Nuclear Information System (INIS)
Xu Jiancheng; Xu Qiao; Chai Liqun
2010-01-01
According to the requirement of ICF, a method based on statistical theory has been proposed to measure the power spectrum density (PSD) of large aperture optical components. The method breaks the large-aperture wavefront into small regions, and obtains the PSD of the large-aperture wavefront by weighted averaging of the PSDs of the regions, where the weight factor is each region's area. Simulation and experiment demonstrate the effectiveness of the proposed method. They also show that, the obtained PSDs of the large-aperture wavefront by statistical method and sub-aperture stitching method fit well, when the number of small regions is no less than 8 x 8. The statistical method is not sensitive to translation stage's errors and environment instabilities, thus it is appropriate for PSD measurement during the process of optical fabrication. (authors)
Development of an Axial Flux MEMS BLDC Micromotor with Increased Efficiency and Power Density
Directory of Open Access Journals (Sweden)
Xiaofeng Ding
2015-06-01
Full Text Available This paper presents a rigorous design and optimization of an axial flux microelectromechanical systems (MEMS brushless dc (BLDC micromotor with dual rotor improving both efficiency and power density with an external diameter of only around 10 mm. The stator is made of two layers of windings by MEMS technology. The rotor is developed by film permanent magnets assembled over the rotor yoke. The characteristics of the MEMS micromotor are analyzed and modeled through a 3-D magnetic equivalent circuit (MEC taking the leakage flux and fringing effect into account. Such a model yields a relatively accurate prediction of the flux in the air gap, back electromotive force (EMF and electromagnetic torque, whilst being computationally efficient. Based on 3-D MEC model the multi-objective firefly algorithm (MOFA is developed for the optimal design of this special machine. Both 3-D finite element (FE simulation and experiments are employed to validate the MEC model and MOFA optimization design.
Kimble, Michael C.; White, Ralph E.
1991-01-01
A mathematical model of a hydrogen/oxygen alkaline fuel cell is presented that can be used to predict the polarization behavior under various power loads. The major limitations to achieving high power densities are indicated and methods to increase the maximum attainable power density are suggested. The alkaline fuel cell model describes the phenomena occurring in the solid, liquid, and gaseous phases of the anode, separator, and cathode regions based on porous electrode theory applied to three phases. Fundamental equations of chemical engineering that describe conservation of mass and charge, species transport, and kinetic phenomena are used to develop the model by treating all phases as a homogeneous continuum.
Erkaya, Yunus
system variables so that any PV module can be emulated as the design requires. A non-synchronous buck converter is proposed for the emulation of a single, high-power PV module using traditional silicon devices. With the proof-of-concept working and improvements in efficiency, power density and steady-state errors made, dynamic tests were performed using an inverter connected to the PV emulator. In order to improve the dynamic characteristics, a synchronous buck converter topology is proposed along with the use of advanced GaNFET devices which resulted in very high power efficiency and improved dynamic response characteristics when emulating PV modules.
Jones, Stephanie G; Riedner, Brady A; Smith, Richard F; Ferrarelli, Fabio; Tononi, Giulio; Davidson, Richard J; Benca, Ruth M
2014-02-01
Obstructive sleep apnea (OSA) is associated with significant alterations in neuronal integrity resulting from either hypoxemia and/or sleep loss. A large body of imaging research supports reductions in gray matter volume, alterations in white matter integrity and resting state activity, and functional abnormalities in response to cognitive challenge in various brain regions in patients with OSA. In this study, we used high-density electroencephalography (hdEEG), a functional imaging tool that could potentially be used during routine clinical care, to examine the regional distribution of neural activity in a non-clinical sample of untreated men and women with moderate/severe OSA. Sleep was recorded with 256-channel EEG in relatively healthy subjects with apnea-hypopnea index (AHI) > 10, as well as age-, sex-, and body mass index-matched controls selected from a research population initially recruited for a study on sleep and meditation. Sleep laboratory. Nine subjects with AHI > 10 and nine matched controls. N/A. Topographic analysis of hdEEG data revealed a broadband reduction in EEG power in a circumscribed region overlying the parietal cortex in OSA subjects. This parietal reduction in neural activity was present, to some extent, across all frequency bands in all stages and episodes of nonrapid eye movement sleep. This investigation suggests that regional deficits in electroencephalography (EEG) power generation may be a useful clinical marker for neural disruption in obstructive sleep apnea, and that high-density EEG may have the sensitivity to detect pathological cortical changes early in the disease process.
Finite difference applied to the reconstruction method of the nuclear power density distribution
International Nuclear Information System (INIS)
Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S.
2016-01-01
Highlights: • A method for reconstruction of the power density distribution is presented. • The method uses discretization by finite differences of 2D neutrons diffusion equation. • The discretization is performed homogeneous meshes with dimensions of a fuel cell. • The discretization is combined with flux distributions on the four node surfaces. • The maximum errors in reconstruction occur in the peripheral water region. - Abstract: In this reconstruction method the two-dimensional (2D) neutron diffusion equation is discretized by finite differences, employed to two energy groups (2G) and meshes with fuel-pin cell dimensions. The Nodal Expansion Method (NEM) makes use of surface discontinuity factors of the node and provides for reconstruction method the effective multiplication factor of the problem and the four surface average fluxes in homogeneous nodes with size of a fuel assembly (FA). The reconstruction process combines the discretized 2D diffusion equation by finite differences with fluxes distribution on four surfaces of the nodes. These distributions are obtained for each surfaces from a fourth order one-dimensional (1D) polynomial expansion with five coefficients to be determined. The conditions necessary for coefficients determination are three average fluxes on consecutive surfaces of the three nodes and two fluxes in corners between these three surface fluxes. Corner fluxes of the node are determined using a third order 1D polynomial expansion with four coefficients. This reconstruction method uses heterogeneous nuclear parameters directly providing the heterogeneous neutron flux distribution and the detailed nuclear power density distribution within the FAs. The results obtained with this method has good accuracy and efficiency when compared with reference values.
Development of Optimized Core Design and Analysis Methods for High Power Density BWRs
Shirvan, Koroush
Increasing the economic competitiveness of nuclear energy is vital to its future. Improving the economics of BWRs is the main goal of this work, focusing on designing cores with higher power density, to reduce the BWR capital cost. Generally, the core power density in BWRs is limited by the thermal Critical Power of its assemblies, below which heat removal can be accomplished with low fuel and cladding temperatures. The present study investigates both increases in the heat transfer area between ~he fuel and coolant and changes in operating parameters to achieve higher power levels while meeting the appropriate thermal as well as materials and neutronic constraints. A scoping study is conducted under the constraints of using fuel with cylindrical geometry, traditional materials and enrichments below 5% to enhance its licensability. The reactor vessel diameter is limited to the largest proposed thus far. The BWR with High power Density (BWR-HD) is found to have a power level of 5000 MWth, equivalent to 26% uprated ABWR, resulting into 20% cheaper O&M and Capital costs. This is achieved by utilizing the same number of assemblies, but with wider 16x16 assemblies and 50% shorter active fuel than that of the ABWR. The fuel rod diameter and pitch are reduced to just over 45% of the ABWR values. Traditional cruciform form control rods are used, which restricts the assembly span to less than 1.2 times the current GE14 design due to limitation on shutdown margin. Thus, it is possible to increase the power density and specific power by 65%, while maintaining the nominal ABWR Minimum Critical Power Ratio (MCPR) margin. The plant systems outside the vessel are assumed to be the same as the ABWR-Il design, utilizing a combination of active and passive safety systems. Safety analyses applied a void reactivity coefficient calculated by SIMULA TE-3 for an equilibrium cycle core that showed a 15% less negative coefficient for the BWR-HD compared to the ABWR. The feedwater
Jung, SungHoon; Myung, Yusik; Kim, Bit Na; Kim, In Gyoo; You, In-Kyu; Kim, TaeYoung
2018-01-30
Here, we present a facile and low-cost method to produce hierarchically porous graphene-based carbons from a biomass source. Three-dimensional (3D) graphene-based carbons were produced through continuous sequential steps such as the formation and transformation of glucose-based polymers into 3D foam-like structures and their subsequent carbonization to form the corresponding macroporous carbons with thin graphene-based carbon walls of macropores and intersectional carbon skeletons. Physical and chemical activation was then performed on this carbon to create micro- and meso-pores, thereby producing hierarchically porous biomass-derived graphene-based carbons with a high Brunauer-Emmett-Teller specific surface area of 3,657 m 2 g -1 . Owing to its exceptionally high surface area, interconnected hierarchical pore networks, and a high degree of graphitization, this carbon exhibited a high specific capacitance of 175 F g -1 in ionic liquid electrolyte. A supercapacitor constructed with this carbon yielded a maximum energy density of 74 Wh kg -1 and a maximum power density of 408 kW kg -1 , based on the total mass of electrodes, which is comparable to those of the state-of-the-art graphene-based carbons. This approach holds promise for the low-cost and readily scalable production of high performance electrode materials for supercapacitors.
International Nuclear Information System (INIS)
Lawson, K.; Peacock, N.; Gianella, R.
1998-12-01
The derivation of elemental components of radiated powers and impurity concentrations in bulk tokamak plasmas is complex, often requiring a full description of the impurity transport. A novel, empirical method, the Line Intensity Normalization Technique (LINT) has been developed on the JET (Joint European Torus) tokamak to provide routine information about the impurity content of the plasma and elemental components of radiated power (P rad ). The technique employs a few VUV and XUV resonance line intensities to represent the intrinsic impurity elements in the plasma. From a data base comprising these spectral features, the total bolometric measurement of the radiated power and the Z eff measured by visible spectroscopy, separate elemental components of P rad and Z eff are derived. The method, which converts local spectroscopic signals into global plasma parameters, has the advantage of simplicity, allowing large numbers of pulses to be processed, and, in many operational modes of JET, is found to be both reliable and accurate. It relies on normalizing the line intensities to the absolute calibration of the bolometers and visible spectrometers, using coefficients independent of density and temperature. Accuracies of the order of ± 15% can be achieved for the elemental P rad components of the most significant impurities and the impurity concentrations can be determined to within ±30%. Trace elements can be monitored, although with reduced accuracy. The present paper deals with limiter discharges, which have been the main application to date. As a check on the technique and to demonstrate the value of the LINT results, they have been applied to the transport modelling of intrinsic impurities carried out with the SANCO transport code, which uses atomic data from ADAS. The simulations provide independent confirmation of the concentrations empirically derived using the LINT technique. For this analysis, the simple case of the L-mode regime is considered, the chosen
Engineering and physics of high-power-density, compact, reversed-field-pinch fusion reactors
International Nuclear Information System (INIS)
Najmabadi, F.; Conn, R.W.; Krakowski, R.A.; Schultz, K.R.; Steiner, D.
1989-01-01
The technical feasibility and key developmental issues of compact, high-power-density Reversed-Field-Pinch (RFP) reactors are the primary results of the TITAN RFP reactor study. Two design approaches emerged, TITAN-I and TITAN-II, both of which are steady-state, DT-burning, circa 1000 MWe power reactors. The TITAN designs are physically compact and have a high neutron wall loading of 18 MW m 2 . Detailed analyses indicate that: a) each design is technically feasible; b) attractive features of compact RFP reactors can be realized without sacrificing the safety and environmental potential of fusion; and c) major features of this particular embodiment of the RFP reactor are retained in a design window of neutron wall loading ranging from 10 to 20 MW/m 2 . A major product of the TITAN study is the identification and quantification of major engineering and physics requirements for this class of RFP reactors. These findings are the focus of this paper. (author). 26 refs.; 4 figs.; 1 tab
APEX and ALPS, high power density technology programs in the U.S
International Nuclear Information System (INIS)
Wong, C.P.C.; Berk, S.; Abdou, M.; Mattas, R.
1999-02-01
In fiscal year (FY) 1998 two new fusion technology programs were initiated in the US, with the goal of making marked progress in the scientific understanding of technologies and materials required to withstand high plasma heat flux and neutron wall loads. APEX is exploring new and revolutionary concepts that can provide the capability to extract heat efficiently from a system with high neutron and surface heat loads while satisfying all the fusion power technology requirements and achieving maximum reliability, maintainability, safety, and environmental acceptability. ALPS program is evaluating advanced concepts including liquid surface limiters and divertors on the basis of such factors as their compatibility with fusion plasma, high power density handling capabilities, engineering feasibility, lifetime, safety and R and D requirements. The APEX and ALPS are three-year programs to specify requirements and evaluate criteria for revolutionary approaches in first wall, blanket and high heat flux component applications. Conceptual design and analysis of candidate concepts are being performed with the goal of selecting the most promising first wall, blanket and high heat flux component designs that will provide the technical basis for the initiation of a significant R and D effort beginning in FY2001. These programs are also considering opportunities for international collaborations
ADX: a high field, high power density, advanced divertor and RF tokamak
LaBombard, B.; Marmar, E.; Irby, J.; Terry, J. L.; Vieira, R.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; Baek, S.; Beck, W.; Bonoli, P.; Brunner, D.; Doody, J.; Ellis, R.; Ernst, D.; Fiore, C.; Freidberg, J. P.; Golfinopoulos, T.; Granetz, R.; Greenwald, M.; Hartwig, Z. S.; Hubbard, A.; Hughes, J. W.; Hutchinson, I. H.; Kessel, C.; Kotschenreuther, M.; Leccacorvi, R.; Lin, Y.; Lipschultz, B.; Mahajan, S.; Minervini, J.; Mumgaard, R.; Nygren, R.; Parker, R.; Poli, F.; Porkolab, M.; Reinke, M. L.; Rice, J.; Rognlien, T.; Rowan, W.; Shiraiwa, S.; Terry, D.; Theiler, C.; Titus, P.; Umansky, M.; Valanju, P.; Walk, J.; White, A.; Wilson, J. R.; Wright, G.; Zweben, S. J.
2015-05-01
The MIT Plasma Science and Fusion Center and collaborators are proposing a high-performance Advanced Divertor and RF tokamak eXperiment (ADX)—a tokamak specifically designed to address critical gaps in the world fusion research programme on the pathway to next-step devices: fusion nuclear science facility (FNSF), fusion pilot plant (FPP) and/or demonstration power plant (DEMO). This high-field (⩾6.5 T, 1.5 MA), high power density facility (P/S ˜ 1.5 MW m-2) will test innovative divertor ideas, including an ‘X-point target divertor’ concept, at the required performance parameters—reactor-level boundary plasma pressures, magnetic field strengths and parallel heat flux densities entering into the divertor region—while simultaneously producing high-performance core plasma conditions that are prototypical of a reactor: equilibrated and strongly coupled electrons and ions, regimes with low or no torque, and no fuelling from external heating and current drive systems. Equally important, the experimental platform will test innovative concepts for lower hybrid current drive and ion cyclotron range of frequency actuators with the unprecedented ability to deploy launch structures both on the low-magnetic-field side and the high-magnetic-field side—the latter being a location where energetic plasma-material interactions can be controlled and favourable RF wave physics leads to efficient current drive, current profile control, heating and flow drive. This triple combination—advanced divertors, advanced RF actuators, reactor-prototypical core plasma conditions—will enable ADX to explore enhanced core confinement physics, such as made possible by reversed central shear, using only the types of external drive systems that are considered viable for a fusion power plant. Such an integrated demonstration of high-performance core-divertor operation with steady-state sustainment would pave the way towards an attractive pilot plant, as envisioned in the ARC concept
International Nuclear Information System (INIS)
Krizova, Hana; Zidek, Lukas; Stone, Martin J.; Novotny, Milos V.; Sklenar, Vladimir
2004-01-01
Backbone dynamics of mouse major urinary protein I (MUP-I) was studied by 15 N NMR relaxation. Data were collected at multiple temperatures for a complex of MUP-I with its natural pheromonal ligand, 2-sec-4,5-dihydrothiazole, and for the free protein. The measured relaxation rates were analyzed using the reduced spectral density mapping. Graphical analysis of the spectral density values provided an unbiased qualitative picture of the internal motions. Varying temperature greatly increased the range of analyzed spectral density values and therefore improved reliability of the analysis. Quantitative parameters describing the dynamics on picosecond to nanosecond time scale were obtained using a novel method of simultaneous data fitting at multiple temperatures. Both methods showed that the backbone flexibility on the fast time scale is slightly increased upon pheromone binding, in accordance with the previously reported results. Zero-frequency spectral density values revealed conformational changes on the microsecond to millisecond time scale. Measurements at different temperatures allowed to monitor temperature depencence of the motional parameters
International Nuclear Information System (INIS)
Meilleurat, Michele
1973-07-01
The application of harmonic analysis to the brain spontaneous electrical activity has been studied theoretically and practically in 30 adult rabbits chronically implanted with electrodes. Theoretically, an accurate energetic study of the signal can only be achieved by the calculation of the autocorrelation function and its Fourier transform, the power density spectrum. Secondly, a comparative study has been made of the analogical methods using analogic or hybrid devices and the digital method with an analysis and computing program (the sampling rate, the delay, the period of integration and the problems raised by the amplification of the biological signals and sampling). Data handling is discussed, the method mainly retaining the study of variance, the calculation of the total energy carried by the signal and the energies carried along the frequency bandwidth ΔF, their percentage as related to the total energy, the relationships of these various values for various electroencephalographic states. Experimentally, the general aspect of the spontaneous electric activity of the dorsal hippocampus and the visual cortex during vigilance variations is accurately described by the calculation of the variance and the study of the position of the maximum values of the peaks of the power density spectra on the frequency axis as well as by the calculation of the energies carried in various frequency bands, 0-4, 4-8, 8-12 Hz. With the same theoretical bases, both the analogical and digital methods lead to similar results, the former being easier to operate, the latter more accurate. (author) [fr
International Nuclear Information System (INIS)
Han, Deming; Zhang, Gang; Cai, Hongxing; Zhang, Xihe; Zhao, Lihui
2013-01-01
We report a quantum-chemistry study of electronic structures and spectral properties of four Ir(III) complexes Ir[2-(2,4-di-X-phenyl)pyridine] 2 (picolinate), where X=–CH 3 (1), –H (2), –CN (3), –NO 2 (4). The absorption and emission spectra were calculated based on the optimized ground state and excited state geometries, respectively, by means of the time-dependent density functional theory (TDDFT). The effect from the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption, and phosphorescent properties has been investigated. The absorption and emission properties can be altered by the different electron-withdrawing and electron-donating groups. Besides, ionization potential (IP), electron affinities (EA) and reorganization energy (λ hole/electron ) were obtained to evaluate the charge transfer and balance properties between hole and electron. The calculated results show that the different substitute groups affect the charge transfer rate and balance. It can be anticipated that the complexes 3 and 4 have good charge transport rates and balance between the hole and electron. -- Highlights: ► Four Ir(III) complexes have been theoretically investigated. ► The different substituents affect the charge transfer rate and balance. ► We design two candidate materials for OLEDs
Energy Technology Data Exchange (ETDEWEB)
Han, Deming [International Joint Research Center for Nanophotonics and Biophotonics, School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China); Zhang, Gang [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China); Cai, Hongxing; Zhang, Xihe [International Joint Research Center for Nanophotonics and Biophotonics, School of Science, Changchun University of Science and Technology, Changchun 130022 (China); Zhao, Lihui, E-mail: zhaolihui@yahoo.com [International Joint Research Center for Nanophotonics and Biophotonics, School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China)
2013-06-15
We report a quantum-chemistry study of electronic structures and spectral properties of four Ir(III) complexes Ir[2-(2,4-di-X-phenyl)pyridine]{sub 2}(picolinate), where X=–CH{sub 3} (1), –H (2), –CN (3), –NO{sub 2} (4). The absorption and emission spectra were calculated based on the optimized ground state and excited state geometries, respectively, by means of the time-dependent density functional theory (TDDFT). The effect from the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption, and phosphorescent properties has been investigated. The absorption and emission properties can be altered by the different electron-withdrawing and electron-donating groups. Besides, ionization potential (IP), electron affinities (EA) and reorganization energy (λ{sub hole/electron}) were obtained to evaluate the charge transfer and balance properties between hole and electron. The calculated results show that the different substitute groups affect the charge transfer rate and balance. It can be anticipated that the complexes 3 and 4 have good charge transport rates and balance between the hole and electron. -- Highlights: ► Four Ir(III) complexes have been theoretically investigated. ► The different substituents affect the charge transfer rate and balance. ► We design two candidate materials for OLEDs.
Huang, Jian; Wei, Kai; Jin, Kai; Li, Min; Zhang, YuDong
2018-06-01
The Sodium laser guide star (LGS) plays a key role in modern astronomical Adaptive Optics Systems (AOSs). The spot size and photon return of the Sodium LGS depend strongly on the laser power density distribution at the Sodium layer and thus affect the performance of the AOS. The power density distribution is degraded by turbulence in the uplink path, launch system aberrations, the beam quality of the laser, and so forth. Even without any aberrations, the TE00 Gaussian type is still not the optimal power density distribution to obtain the best balance between the measurement error and temporal error. To optimize and control the LGS power density distribution at the Sodium layer to an expected distribution type, a method that combines pre-correction and beam-shaping is proposed. A typical result shows that under strong turbulence (Fried parameter (r0) of 5 cm) and for a quasi-continuous wave Sodium laser (power (P) of 15 W), in the best case, our method can effectively optimize the distribution from the Gaussian type to the "top-hat" type and enhance the photon return flux of the Sodium LGS; at the same time, the total error of the AOS is decreased by 36% with our technique for a high power laser and poor seeing.
Energy Technology Data Exchange (ETDEWEB)
Yamagami, Y.; Tani, T. [Science University of Tokyo, Tokyo (Japan)
1997-11-25
A method was proposed for estimating the spectral distribution using air mass, precipitable water, and clear indexes which are generally obtainable, and a comparative study was made between the spectral distribution obtained by this method and the measured data using output power of PV modules, etc. as indexes. When solar light comes into the atmosphere, it dissipates receiving scattering/absorption by various gases and aerosols. Direct light component and scattered light component which arrive at the earth surface become functions of air mass and precipitable water. The wavelength distribution of scattered light in cloudy sky is not dependent upon air mass, but affected strongly by absorption band by steam of clouds. By relational equations considered of these, output power and short-circuit current of PV modules are obtained to make a comparison with the measured data. As a result, it was found that this method estimated the spectral distribution with accuracy. Further, seasonal changes in the spectral distribution were well reproduced. The simulation of the module output in Sapporo and Okinawa brought a result that the output in Okinawa is 1.93% larger than in Okinawa. 5 refs., 5 figs., 6 tabs.
Spectral properties of 441 radio pulsars
Jankowski, F.; van Straten, W.; Keane, E. F.; Bailes, M.; Barr, E. D.; Johnston, S.; Kerr, M.
2018-02-01
We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100 MHz. The observations at 728 and 3100 MHz were conducted simultaneously using the dual-band 10-50 cm receiver. These high-sensitivity, multifrequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory, we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low- or high-frequency cut-off and log-parabolic spectrum. While about 79 per cent of the pulsars that could be classified have simple power-law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power-law spectra is -1.60 ± 0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.
Machado, Calixto; Estévez, Mario; Leisman, Gerry; Melillo, Robert; Rodríguez, Rafael; DeFina, Phillip; Hernández, Adrián; Pérez-Nellar, Jesús; Naranjo, Rolando; Chinchilla, Mauricio; Garófalo, Nicolás; Vargas, José; Beltrán, Carlos
2015-01-01
We studied autistics by quantitative EEG spectral and coherence analysis during three experimental conditions: basal, watching a cartoon with audio (V-A), and with muted audio band (VwA). Significant reductions were found for the absolute power spectral density (PSD) in the central region for delta and theta, and in the posterior region for sigma…
Spectral distribution of radiation on plane and axial channeling of ultrarelativistic electrons
International Nuclear Information System (INIS)
Bazylev, V.A.; Glebov, V.I.; Zhevago, N.K.
1980-01-01
The spectral angular and polarization charactristics of the radiation from channeled ultrarelativistic electrons are calculated. Analytic expressions for the spectral-angular power density of the radiation are obtained for some realistic models of the continuous potential of the crystal planes and axes. A critical analysis is also presented of some existent results of the theory of radiation on channeling
Pervasive randomness in physics: an introduction to its modelling and spectral characterisation
Howard, Roy
2017-10-01
An introduction to the modelling and spectral characterisation of random phenomena is detailed at a level consistent with a first exposure to the subject at an undergraduate level. A signal framework for defining a random process is provided and this underpins an introduction to common random processes including the Poisson point process, the random walk, the random telegraph signal, shot noise, information signalling random processes, jittered pulse trains, birth-death random processes and Markov chains. An introduction to the spectral characterisation of signals and random processes, via either an energy spectral density or a power spectral density, is detailed. The important case of defining a white noise random process concludes the paper.
Optimization of fusion power density in the two-energy-component tokamak reactor
International Nuclear Information System (INIS)
Jassby, D.L.
1974-10-01
The optimal plasma conditions for maximizing fusion power density P/sub f/ in a beam-driven D--T tokamak reactor (TCT) are considered. Given T/sub e/ = T/sub i/ and fixed total plasma pressure, there is an optimal n/sub e/tau/sub E/ for maximizing P/sub f/, viz. n/sub e/tau/sub E/ = 4 x 10 12 to 2 x 10 13 cm -3 sec for T/sub e/ = 3--15 keV and 200-keV D beams. The corresponding anti GAMMA equals (beam pressure/bulk-plasma pressure) is 0.96 to 0.70. P/sub fmax/ increases as T/sub e/ is reduced and can be an order of magnitude larger than the maximum P/sub f/ of a thermal reactor of the same beta, at any temperature. A lower practical limit to T/sub e/ may be set by requiring a minimum beam power multiplication Q/sub b/. For the purpose of fissile breeding, the minimum Q/sub b/ approximately 0.6, requiring T/sub e/ greater than or equal to 3 keV if Z = 1. The optimal operating conditions of a TCT for obtaining P/sub fmax/ are considerably different from those for enhancing Q/sub b/. Maximizing P/sub f/ requires restricting both T/sub e/ and n/sub e/tau/sub E/, maintaining a bulk plasma markedly enriched in tritium, and spoiling confinement of fusion alphas. Considerable impurity content can be tolerated without seriously degrading P/sub fmax/, and high-Z impurity radiation may be useful for regulating tau/sub E/. (auth)
High-density fluid-perturbation theory based on an inverse 12th-power hard-sphere reference system
International Nuclear Information System (INIS)
Ross, M.
1979-01-01
A variational theory is developed that is accurate at normal liquid densities and densities up to 4 times that of the argon triple point. This theory uses the inverse 12th-power potential as a reference system. The properties of this reference system are expressed in terms of hard-sphere packing fractions by using a modified form of hard-space variational theory. As a result of this ''bootstrapping,'' a variational procedure may be followed that employs the inverse 12th-power system as a reference but uses the hard-sphere packing fraction as the scaling parameter with which to minimize the Helmholtz free energy
Lu, Hui; Rihko-Struckmann, Liisa; Sundmacher, Kai
2011-10-28
The spontaneous oscillations of the cell voltage and output power density of a PEMFC (with PtRu/C anode) using CO-containing H(2) streams as anodic fuels have been observed during galvanostatic operating. It is ascribed to the dynamic coupling of the CO adsorption (poisoning) and the electrochemical CO oxidation (reactivating) processes in the anode chamber of the single PEMFC. Accompanying the cell voltage and power density oscillations, the discrete CO concentration oscillations at the anode outlet of the PEMFC were also detected, which directly confirms the electrochemical CO oxidation taking place in the anode chamber during galvanostatic operating. This journal is © the Owner Societies 2011
The use of surface power for characterisation of structure-borne sound sources of low modal density
DEFF Research Database (Denmark)
Ohlrich, Mogens
1996-01-01
The use of the surface power methods for source characterisaiton of vibrating machinery of low modal density is investigated in this paper. It was demonstrated by Ohlrich and Larsen that this relatively simple, but very useful measurement technique for quantifying the vibratory strength of machin......The use of the surface power methods for source characterisaiton of vibrating machinery of low modal density is investigated in this paper. It was demonstrated by Ohlrich and Larsen that this relatively simple, but very useful measurement technique for quantifying the vibratory strength...
Converter Power Density Increase using Low Inductive Integrated DC-link Capacitor/Bus
DEFF Research Database (Denmark)
Trintis, Ionut; Franke, Toke; Rannested, Bjørn
2015-01-01
The power losses in switching devices have a direct effect on the maximum converter power. For a voltage source converter, the DC-link bus has a major influence on the power loss and safe operating area of the power devices. The Power Ring Film CapacitorTM integrated with an optimized bus structu...
High power density superconducting rotating machines—development status and technology roadmap
Haran, Kiruba S.; Kalsi, Swarn; Arndt, Tabea; Karmaker, Haran; Badcock, Rod; Buckley, Bob; Haugan, Timothy; Izumi, Mitsuru; Loder, David; Bray, James W.; Masson, Philippe; Stautner, Ernst Wolfgang
2017-12-01
Superconducting technology applications in electric machines have long been pursued due to their significant advantages of higher efficiency and power density over conventional technology. However, in spite of many successful technology demonstrations, commercial adoption has been slow, presumably because the threshold for value versus cost and technology risk has not yet been crossed. One likely path for disruptive superconducting technology in commercial products could be in applications where its advantages become key enablers for systems which are not practical with conventional technology. To help systems engineers assess the viability of such future solutions, we present a technology roadmap for superconducting machines. The timeline considered was ten years to attain a Technology Readiness Level of 6+, with systems demonstrated in a relevant environment. Future projections, by definition, are based on the judgment of specialists, and can be subjective. Attempts have been made to obtain input from a broad set of organizations for an inclusive opinion. This document was generated through a series of teleconferences and in-person meetings, including meetings at the 2015 IEEE PES General meeting in Denver, CO, the 2015 ECCE in Montreal, Canada, and a final workshop in April 2016 at the University of Illinois, Urbana-Champaign that brought together a broad group of technical experts spanning the industry, government and academia.
A New CDS Structure for High Density FPA with Low Power
Directory of Open Access Journals (Sweden)
Xiao Wang
2015-01-01
Full Text Available Being an essential part of infrared readout integrated circuit, correlated double sampling (CDS circuits play important roles in both depressing reset noise and conditioning integration signals. To adapt applications for focal planes of large format and high density, a new structure of CDS circuit occupying small layout area is proposed, whose power dissipation has been optimized by using MOSFETs in operation of subthreshold region, which leads to 720 nW. Then the noise calculation model is established, based on which the noise analysis has been carried out by the approaches of transfer function and numerical simulations using SIMULINK and Verilog-A. The results are in good agreement, demonstrating the validity of the present noise calculation model. Thermal noise plays a dominant role in the long wave situation while 1/f noise is the majority in the medium wave situation. The total noise of long wave is smaller than medium wave, both of which increase with the integration capacitor and integration time increasing.
New structures of power density spectra for four Kepler active galactic nuclei
Dobrotka, A.; Antonuccio-Delogu, V.; Bajčičáková, I.
2017-09-01
Many nearby active galactic nuclei display a significant short-term variability. In this work, we reanalyse photometric data of four active galactic nuclei observed by Kepler in order to study the flickering activity, with our main goal to search for multiple components in the power density spectra. We find that all four objects have similar characteristics, with two break frequencies at approximately log( f /Hz) = -5.2 and -4.7. We consider some physical phenomena whose characteristic time-scales are consistent with those observed, in particular mass accretion fluctuations in the inner geometrically thick disc (hot X-ray corona) and unstable relativistic Rayleigh-Taylor modes. The former is supported by detection of the same break frequencies in the Swift X-ray data of ZW229-15. We also discuss rms-flux relations, and we detect a possible typical linear trend at lower flux levels. Our findings support the hypothesis of a multiplicative character of variability, in agreement with the propagating accretion fluctuation model.
ADX: A high Power Density, Advanced RF-Driven Divertor Test Tokamak for PMI studies
Whyte, Dennis; ADX Team
2015-11-01
The MIT PSFC and collaborators are proposing an advanced divertor experiment, ADX; a divertor test tokamak dedicated to address critical gaps in plasma-material interactions (PMI) science, and the world fusion research program, on the pathway to FNSF/DEMO. Basic ADX design features are motivated and discussed. In order to assess the widest range of advanced divertor concepts, a large fraction (>50%) of the toroidal field volume is purpose-built with innovative magnetic topology control and flexibility for assessing different surfaces, including liquids. ADX features high B-field (>6 Tesla) and high global power density (P/S ~ 1.5 MW/m2) in order to access the full range of parallel heat flux and divertor plasma pressures foreseen for reactors, while simultaneously assessing the effect of highly dissipative divertors on core plasma/pedestal. Various options for efficiently achieving high field are being assessed including the use of Alcator technology (cryogenic cooled copper) and high-temperature superconductors. The experimental platform would also explore advanced lower hybrid current drive and ion-cyclotron range of frequency actuators located at the high-field side; a location which is predicted to greatly reduce the PMI effects on the launcher while minimally perturbing the core plasma. The synergistic effects of high-field launchers with high total B on current and flow drive can thus be studied in reactor-relevant boundary plasmas.
Lin, Sheng-Chi; Lu, Yi-Ting; Chien, Yu-An; Wang, Jeng-An; You, Ting-Hsuan; Wang, Yu-Sheng; Lin, Chih-Wen; Ma, Chen-Chi M.; Hu, Chi-Chang
2017-09-01
Carbon nanofibers modified with carboxyl groups (CNF-COOH) possessing good wettability and high porosity are homogeneously deposited with amorphous manganese dioxide (amorphous MnO2) by potentiodynamic deposition for asymmetric super-capacitors (ASCs). The potential-cycling in 1 M H2SO4 successfully enhances the hydrophilicity of carbonized polymer nanofibers and facilitates the access of electrolytes within the CNF-COOH matrix. This modification favors the deposition of amorphous MnO2 and improves its electrochemical utilization. In this composite, MnO2 homogeneously dispersed onto CNF-COOH provides desirable pseudocapacitance and the CNF-COOH network works as the electron conductor. The composite of CNF-COOH@MnO2-20 shows a high specific capacitance of 415 F g-1 at 5 mV s-1. The capacitance retention of this composite is 94% in a 10,000-cycle test. An ASC cell consisting of this composite and activated carbon as positive and negative electrodes can be reversibly charged/discharged to a cell voltage of 2.0 V in 1 M Na2SO4 and 4 mM NaHCO3 with specific energy and power of 36.7 Wh kg-1 and 354.9 W kg-1, respectively. This ASC also shows excellent cell capacitance retention (8% decay) in the 2V, 10,000-cycle stability test, revealing superior performance.
International Nuclear Information System (INIS)
Huang Desuo; Wu Yican
2004-01-01
The impact of the engineering energy gain and the fusion-power-core (FPC) mass power density (MPD) on the generation cost of fusion power plant are analyzed based on the economic elasticity approach in this paper. From the functions describing the relationship of the generation cost with the engineering energy gain and the MPD, the elasticity coefficients of the generation cost with the engineering energy gain and the MPD have been derived respectively to analyze their sensitivity to the generation cost and the MPD to the generation cost decreases with increasing the engineering energy gain or the MPD. (authors)
Directory of Open Access Journals (Sweden)
Ram Sewak SINGH
2017-12-01
Full Text Available Power spectral analysis of short-term heart rate variability (HRV can provide instant valuable information to understand the functioning of autonomic control over the cardiovascular system. In this study, an adaptive continuous Morlet wavelet transform (ACMWT method has been used to describe the time-frequency characteristics of the HRV using band power spectra and the median value of interquartile range. Adaptation of the method was based on the measurement of maximum energy concentration. The ACMWT has been validated on synthetic signals (i.e. stationary, non-stationary as slow varying and fast changing frequency with time modeled as closest to dynamic changes in HRV signals. This method has been also tested in the presence of additive white Gaussian noise (AWGN to show its robustness towards the noise. From the results of testing on synthetic signals, the ACMWT was found to be an enhanced energy concentration estimator for assessment of power spectral of short-term HRV time series compared to adaptive Stockwell transform (AST, adaptive modified Stockwell transform (AMST, standard continuous Morlet wavelet transform (CMWT and Stockwell transform (ST estimators at statistical significance level of 5%. Further, the ACMWT was applied to real HRV data from Fantasia and MIT-BIH databases, grouped as healthy young group (HYG, healthy elderly group (HEG, arrhythmia controlled medication group (ARCMG, and supraventricular tachycardia group (SVTG subjects. The global results demonstrate that spectral indices of low frequency power (LFp and high frequency power (HFp of HRV were decreased in HEG compared to HYG subjects (p<0.0001. While LFp and HFp indices were increased in ARCMG compared to HEG (p<0.00001. The LFp and HFp components of HRV obtained from SVTG were reduced compared to other group subjects (p<0.00001.
International Nuclear Information System (INIS)
Gonca, Guven; Sahin, Bahri; Ust, Yasin; Parlak, Adnan
2015-01-01
This paper presents comprehensive performance analyses and comparisons for air-standard irreversible thermodynamic cycle engines (TCE) based on the power output, power density, thermal efficiency, maximum dimensionless power output (MP), maximum dimensionless power density (MPD) and maximum thermal efficiency (MEF) criteria. Internal irreversibility of the cycles occurred during the irreversible-adiabatic processes is considered by using isentropic efficiencies of compression and expansion processes. The performances of the cycles are obtained by using engine design parameters such as isentropic temperature ratio of the compression process, pressure ratio, stroke ratio, cut-off ratio, Miller cycle ratio, exhaust temperature ratio, cycle temperature ratio and cycle pressure ratio. The effects of engine design parameters on the maximum and optimal performances are investigated. - Highlights: • Performance analyses are conducted for irreversible thermodynamic cycle engines. • Comprehensive computations are performed. • Maximum and optimum performances of the engines are shown. • The effects of design parameters on performance and power density are examined. • The results obtained may be guidelines to the engine designers
On the impact of low power density microwaves in some living tissues
Energy Technology Data Exchange (ETDEWEB)
Creanga, M.; Tufescu, D.E. [Univ. Al. I. Cuza, Faculty of Physics, Iasi (Romania)
2006-07-01
The biomedical and ecological interest for the microwave impact on the Earth biosphere is continuously increased since the industrial, military and communication activities strongly contribute to the electromagnetic stress of living bodies. In the next the authors present some of the main results obtained regarding the microwave exposure of various types of biological material: bacteria, fungi, young plant seedlings, dry seeds, animal tissues. The electromagnetic exposure was carried out in open space in well controlled environmental conditions by using 10.75 GHz/1 m W cm{sup -2} microwaves. Biochemical assays and cytogenetic tests have been carried out to reveal the changes induced post irradiation. The response of some pathogen bacteria, have been emphasized by means of turbidimetric measurements - the stimulatory effect being noticed at the level of the microbial population density (the stimulation of the human body microbial flora seems to be one of the side effects of microwave exposures). The behavior of some fungus species was investigated by spectrophotometric assay of various enzyme systems: either inhibitor y or stimulatory effects have been revealed, depending on the species and enzyme peculiarities (certain biotechnological tools could be developed based on fungi exposure to microwaves). The genetic effects of seed exposure have been studied by applying cytogenetic tests to meristem tissues provided by freshly germinated cereal plantlets. Significant rate of chromosomal aberrations has been observed following the microwave exposure as well as stimulatory influence on the proliferation rate (the possibility of plant growth stimulation is suggested). The vegetal tissue cultures (in vitro micro propagated pharmaceutical plants) exposed to low power density microwaves presented increased levels of assimilatory pigments (the controlled development of technical plants for medical uses is proposed). The chlorophyll ratio in young tree seedlings after
On the impact of low power density microwaves in some living tissues
International Nuclear Information System (INIS)
Creanga, M.; Tufescu, D.E.
2006-01-01
The biomedical and ecological interest for the microwave impact on the Earth biosphere is continuously increased since the industrial, military and communication activities strongly contribute to the electromagnetic stress of living bodies. In the next the authors present some of the main results obtained regarding the microwave exposure of various types of biological material: bacteria, fungi, young plant seedlings, dry seeds, animal tissues. The electromagnetic exposure was carried out in open space in well controlled environmental conditions by using 10.75 GHz/1 m W cm -2 microwaves. Biochemical assays and cytogenetic tests have been carried out to reveal the changes induced post irradiation. The response of some pathogen bacteria, have been emphasized by means of turbidimetric measurements - the stimulatory effect being noticed at the level of the microbial population density (the stimulation of the human body microbial flora seems to be one of the side effects of microwave exposures). The behavior of some fungus species was investigated by spectrophotometric assay of various enzyme systems: either inhibitor y or stimulatory effects have been revealed, depending on the species and enzyme peculiarities (certain biotechnological tools could be developed based on fungi exposure to microwaves). The genetic effects of seed exposure have been studied by applying cytogenetic tests to meristem tissues provided by freshly germinated cereal plantlets. Significant rate of chromosomal aberrations has been observed following the microwave exposure as well as stimulatory influence on the proliferation rate (the possibility of plant growth stimulation is suggested). The vegetal tissue cultures (in vitro micro propagated pharmaceutical plants) exposed to low power density microwaves presented increased levels of assimilatory pigments (the controlled development of technical plants for medical uses is proposed). The chlorophyll ratio in young tree seedlings after
Changes in EEG power density of non-REM sleep in depressed patients during treatment with trazodone
Bemmel, Alex L. van; Beersma, Domien G.M.; Hoofdakker, Rutger H. van den
1995-01-01
Recently, it was hypothesized that acute or cumulative suppression of non-REM sleep intensity might be related to the therapeutic effects of antidepressants. This intensity has been proposed to be expressed in the EEG power density in non-REM sleep. In the present study, the relationship was
Chen, Yanxin; Bellini, Marco; Bevilacqua, Manuela; Fornasiero, Paolo; Lavacchi, Alessandro; Miller, Hamish A; Wang, Lianqin; Vizza, Francesco
2015-02-01
A 2 μm thick layer of TiO2 nanotube arrays was prepared on the surface of the Ti fibers of a nonwoven web electrode. After it was doped with Pd nanoparticles (1.5 mgPd cm(-2) ), this anode was employed in a direct alcohol fuel cell. Peak power densities of 210, 170, and 160 mW cm(-2) at 80 °C were produced if the cell was fed with 10 wt % aqueous solutions of ethanol, ethylene glycol, and glycerol, respectively, in 2 M aqueous KOH. The Pd loading of the anode was increased to 6 mg cm(-2) by combining four single electrodes to produce a maximum peak power density with ethanol at 80 °C of 335 mW cm(-2) . Such high power densities result from a combination of the open 3 D structure of the anode electrode and the high electrochemically active surface area of the Pd catalyst, which promote very fast kinetics for alcohol electro-oxidation. The peak power and current densities obtained with ethanol at 80 °C approach the output of H2 -fed proton exchange membrane fuel cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Takubo, Chikako; Yasuda, Genta; Murayama, Ryosuke; Ogura, Yukari; Tonegawa, Motoka; Kurokawa, Hiroyasu; Miyazaki, Masashi
2010-08-01
We used ultrasonic measurements to monitor the influence of power density and primer application on the polymerization reaction of dual-cured resin cements. The ultrasonic equipment comprised a pulser-receiver, transducers, and an oscilloscope. Resin cements were mixed and inserted into a transparent mould, and specimens were placed on the sample stage, onto which the primer, if used, was also applied. Power densities of 0 (no irradiation), 200, or 600 mW cm(-2) were used for curing. The transit time through the cement disk was divided by the specimen thickness to obtain the longitudinal sound velocity. When resin cements were light-irradiated, each curve displayed an initial plateau of approximately 1,500 m s(-1), which rapidly increased to a second plateau of 2,300-2,900 m s(-1). The rate of sound velocity increase was retarded when the cements were light-irradiated at lower power densities, and increased when the primer was applied. The polymerization behaviour of dual-cured resin cements was therefore shown to be affected by the power density of the curing unit and the application of self-etching primer. (c) 2010 The Authors. Journal compilation (c) 2010 Eur J Oral Sci.
International Nuclear Information System (INIS)
Brik, A.
2009-01-01
In the first decade of June 2008, during the power commissioning of the reactor at the Mochovce NPP unit 1, the experiment with reducing the thermal power of core almost to the balance-of-plant (BOP) needs was performed. After the reactor has operated for seven hours at low power (about 200 220 MW (thermal)), its power was increased (at a rate of about 0.25% of N nom /min) to the initial level, close to 107% (1471 MW). During the experiment, core parameters, which were subsequently used for comparing the measured data with the results of experiment simulation calculations, were recorded in the reactor in-core monitoring system database. Calculated and measured levels of critical concentrations of boric acid were compared, along with power density distributions by fuel elements and assemblies obtained both by the KRUIZ in-core monitoring system and on the basis of calculations simulating reactor operation in accordance with the given core power variation schedule. The final stage consisted of assessing the methodical component of power density micro- and macro-fields calculation error in the core of Mochovce-1 reactor operating with varying load. (author)
International Nuclear Information System (INIS)
Brik, A.
2009-01-01
In the first decade of June 2008, during the power commissioning of the reactor at Mochovce NPP unit 1, the experiment with reducing the thermal power of core almost to the balance-of-plant needs was performed. After the reactor has operated for seven hours at low power (about 200 220 MW (thermal)), its power was increased (at a rate of about 0.25% of N nom /min) to the initial level, close to 107% (1471 MW). During the experiment, core parameters, which were subsequently used for comparing the measured data with the results of experiment simulation calculations, were recorded in the reactor in-core monitoring system's database. Calculated and measured levels of critical concentrations of boric acid were compared, along with power density distributions by fuel elements and assemblies obtained both by the KRUIZ in-core monitoring system and on the basis of calculations simulating reactor operation in accordance with the given core power variation schedule. The final stage consisted of assessing the methodical component of power density micro- and macro-fields' calculation error in the core of Mochovce-1 reactor operating with varying load. (Authors)
Multi-phase Turbulence Density Power Spectra in the Perseus Molecular Cloud
Pingel, N. M.; Lee, Min-Young; Burkhart, Blakesley; Stanimirović, Snežana
2018-04-01
We derive two-dimensional spatial power spectra of four distinct interstellar medium tracers, H I, 12CO(J = 1–0), 13CO(J = 1–0), and dust, in the Perseus molecular cloud, covering linear scales ranging from ∼0.1 pc to ∼90 pc. Among the four tracers, we find the steepest slopes of ‑3.23 ± 0.05 and ‑3.22 ± 0.05 for the uncorrected and opacity-corrected H I column density images. This result suggests that the H I in and around Perseus traces a non-gravitating, transonic medium on average, with a negligible effect from opacity. On the other hand, we measure the shallowest slope of ‑2.72 ± 0.12 for the 2MASS dust extinction data and interpret this as the signature of a self-gravitating, supersonic medium. Possible variations in the dust-to-gas ratio likely do not alter our conclusion. Finally, we derive slopes of ‑3.08 ± 0.08 and ‑2.88 ± 0.07 for the 12CO(1–0) and 13CO(1–0) integrated intensity images. Based on theoretical predictions for an optically thick medium, we interpret these slopes of roughly ‑3 as implying that both CO lines are susceptible to the opacity effect. While simple tests for the impact of CO formation and depletion indicate that the measured slopes of 12CO(1–0) and 13CO(1–0) are not likely affected by these chemical effects, our results generally suggest that chemically more complex and/or fully optically thick media may not be a reliable observational tracer for characterizing turbulence.
Digital Repository Service at National Institute of Oceanography (India)
Chakraborty, B.; Saran, A.K.; Kuncolienker, D.S.; Sreepada, R.A.; Haris, K.; Fernandes, W.A
based on the assumption of combinations of normal / Gaussian distributions indicate well fitted multimodal curves generated using MATLAB (Math Works Inc 2005) programs. Out of the twenty three clicks, four clicks (two clicks of 16 and 18cm male... Society of America 115: 2331-2333. Malamud BD, Turcotte DL. 1999. Self affine time series: measures of weak and strong persistence. Journal of Statistical Planning and Inference 80:173-196. MATLAB, Curve Fitting toolbox, Math Works Inc 2005. Available...
Effects of laser power density and initial grain size in laser shock punching of pure copper foil
Zheng, Chao; Zhang, Xiu; Zhang, Yiliang; Ji, Zhong; Luan, Yiguo; Song, Libin
2018-06-01
The effects of laser power density and initial grain size on forming quality of holes in laser shock punching process were investigated in the present study. Three different initial grain sizes as well as three levels of laser power densities were provided, and then laser shock punching experiments of T2 copper foil were conducted. Based upon the experimental results, the characteristics of shape accuracy, fracture surface morphology and microstructures of punched holes were examined. It is revealed that the initial grain size has a noticeable effect on forming quality of holes punched by laser shock. The shape accuracy of punched holes degrades with the increase of grain size. As the laser power density is enhanced, the shape accuracy can be improved except for the case in which the ratio of foil thickness to initial grain size is approximately equal to 1. Compared with the fracture surface morphology in the quasistatic loading conditions, the fracture surface after laser shock can be divided into three zones including rollover, shearing and burr. The distribution of the above three zones strongly relates with the initial grain size. When the laser power density is enhanced, the shearing depth is not increased, but even diminishes in some cases. There is no obvious change of microstructures with the enhancement of laser power density. However, while the initial grain size is close to the foil thickness, single-crystal shear deformation may occur, suggesting that the ratio of foil thickness to initial grain size has an important impact on deformation behavior of metal foil in laser shock punching process.
Tonegawa, Motoka; Yasuda, Genta; Chikako, Takubo; Tamura, Yukie; Yoshida, Takeshi; Kurokawa, Hiroyasu; Miyazaki, Masashi
2009-07-01
To monitor the influence of the power density of the curing unit on the setting behaviour of light-cured glass-ionomer cements (LCGICs) using ultrasound measurements. The ultrasound equipment comprised a pulser-receiver, transducers and an oscilloscope. The LCGICs used were Fuji II LC, Fuji II LC EM and Fuji Filling LC. The cements were mixed according to the manufacturer's instructions and then inserted into a transparent mould. The specimens were placed on the sample stage and cured with power densities of 0 (no irradiation), 200 or 600 mW/cm(2). The transit time through the cement disk was divided by the specimen thickness and then the longitudinal ultrasound velocity (V) within the material was obtained. Analysis of variance and Tukey's Honestly Significantly Different test were used to compare the V values between the set cements. When the LCGICs were light-irradiated, each curve displayed an initial plateau at approximately 1500 m/s and then rapidly increased to a second plateau at approximately 2600 m/s. The rate of increase of V was retarded when the cements were light-irradiated with a power density of 200 mW/cm(2) than with a power density of 600 mW/cm(2). Although sonic echoes were detected from the beginning of the measurements, the rates of increase of the sonic velocity were relatively slow when the cement was not light-irradiated. The ultrasound device monitored the setting processes of LCGICs accurately based on the longitudinal V. The polymerization behaviour of LCGICs was shown to be affected by the power density of the curing unit.
International Nuclear Information System (INIS)
Sahu, G K; Baruah, S; Thakur, K B
2012-01-01
Electron beam is preferably used for large scale evaporation of refractory materials. Material evaporation from a long and narrow source providing a well collimated wedge shaped atomic beam has applications in isotopic purification of metals relevant to nuclear industry. The electron beam from an electron gun with strip type filament provides a linear heating source. However, the high power density of the electron beam can lead to turbulence of the melt pool and undesirable splashing of molten metal. For obtaining quiet surface evaporation, the linear electron beam is generally scanned along its length. To further reduce the power density to maintain quiet evaporation the width of the vapour source can be controlled by rotating the electron gun on its plane, thereby scanning an inclined beam over the molten pool. The rotation of gun has further advantages. When multiple strip type electron guns are used for scaling up evaporation length, a dark zone appears between two beams due to physical separation of adjacent guns. This dark zone can be reduced by rotating the gun and thereby bringing two adjacent beams closer. The paper presented here provides the simulation results of the electron beam trajectory and incident power density originating from two strip electron guns by using in-house developed code. The effect of electron gun rotation on the electron beam trajectory and power density is studied. The simulation result is experimentally verified with the image of molten pool and heat affected zone taken after experiment. This technique can be gainfully utilized in controlling the time averaged power density of the electron beam and obtaining quiet evaporation from the metal molten pool.
International Nuclear Information System (INIS)
Okamoto, T.; Hotta, A.; Ama, T.
2008-01-01
The hyper ABWR (Advanced Boiling Water Reactor) project aims to develop an advanced BWR concept that is competitive in the global market with both highly economic and safety features. Expecting plant construction within the coming ten years, a research program for substantiating the basic design of a high core power density ABWR was conducted. By inheriting the conventional ABWR design, it is possible to reduce construction costs. In order to achieve the rated core power of over 1650MWe which is almost equivalent to that of the EPR (European Pressurized Water Reactor), the core power density of ABWR will be up-rated by at least 25%. Three key subjects linked to this target were recognized. They are, (1) fuel design applicable to the high power density core, (2) improvement of the evaluation method for the coupled neutronic and thermal-hydraulic instability under a wider power-flow operating range, and (3) improvement of the steam separator performance under high quality conditions. In this paper, the second subject has been focused on. In the second subject, the uncertainty approach was introduced in the instability analysis where the best-estimate plant simulator was combined with a direct prediction of boiling transition by the sub-channel code. By employing the CSAU like method, a safety evaluation system that enables to include influences of uncertainties has been developed. Based on the correlation between the time margin for reaching the boiling transition under power oscillations and the decay ratio in the power-flow operation map, an automatic power oscillation suppressing system was designed. The set-point for activating suppression mechanisms (i.e. scram or SRI) could be determined based on this correlation. It was proposed that the present conservative acceptance criterion of the deterministic decay ratio can be replaced with a more rational one of the time margin with including uncertainties. (author)
Power density investigations for the large wind turbines' grid-side press-pack IGBT 3L-NPC-VSCs
DEFF Research Database (Denmark)
Senturk, Osman Selcuk; Helle, Lars; Munk-Nielsen, Stig
2012-01-01
-thermal models are required to be derived, implemented, and utilized. In this study, employed as a grid-side medium voltage full-scale voltage source converters (VSCs) in a multi-MW wind turbine, press-pack IGBT three-level neutral-point-clamped VSC (3L-NPC-VSC), 3L active NPC-VSC (3L-ANPC-VSC), and 3L neutral......Power density is the important design criterion in wind turbine converter design provided that satisfactory converter performance is guaranteed. In order to assess a converter in terms of power density, which is dependent on converter electrical and thermal behaviors, converter electro......-point-piloted VSC (3L-NPP-VSC) are characterized in terms of converter operating principles, physical structure, power loss, and DC bus capacitor size for establishing the basis for converter electro-thermal modeling. Via the practical implementations of the converter electro-thermal models in a computation...
Power density investigation on the press-pack IGBT 3L-HB-VSCs applied to large wind turbine
DEFF Research Database (Denmark)
Senturk, Osman Selcuk; Munk-Nielsen, Stig; Teodorescu, Remus
2011-01-01
capabilities, DC capacitor sizes, converter cabinet volumes of the three 3LHB- VSCs utilizing press-pack IGBTs are investigated in order to quantify and compare the power densities of the 3L-HB-VSCs employed as grid-side converters. Also, the suitable transformer types for the 3L-HB-VSCs are determined......With three different DC-side and AC-side connections, the three-level H-bridge voltage source converters (3L-HB-VSCs) are alternatives to 3L neutral-point-clamped VSCs (3L-NPC-VSCs) for interfacing large wind turbines with electricity grids. In order to assess their feasibility for large wind...... turbines, they should be investigated in terms of power density, which is one of the most important design criteria for wind turbine converters due to turbine nacelle space limitation. In this study, by means of the converter electro-thermal models based on the converter characteristics, the power...
DEFF Research Database (Denmark)
Johansen, Per; Roemer, Daniel Beck; Andersen, Torben O.
2015-01-01
-stroke displacement simulations are used as basis for the parametric analysis. From the parametric analysis a change, in the minimum film thickness as function of piston and cylinder density, is shown for certain operating modes of the digital fluid power displacement motor. This indicate a need for careful....... In this paper the influence of the inertia term on the lubrication gaps of a radial piston motor are studied by a parametric analysis of the piston and cylinder density in a multibody tribodynamic simulation model. The motor is modeled as a digital fluid power displacement machine and a series of full...... assessment of the applicability, of the force balance condition, if it is used in multibody tribodynamic simulations of radial piston digital fluid power displacement motors....
International Nuclear Information System (INIS)
Camparo, James; Fathi, Gilda
2009-01-01
Atomic clocks that fly on global-navigation satellites such as global positioning system (GPS) and Galileo employ light from low-temperature, inductively coupled plasmas (ICPs) for atomic signal generation and detection (i.e., alkali/noble-gas rf-discharge lamps). In this application, the performance of the atomic clock and the capabilities of the navigation system depend sensitively on the stability of the ICP's optical emission. In order to better understand the mechanisms that might lead to instability in these rf-discharge lamps, and hence the satellite atomic clocks, we studied the optical emission from a Rb/Xe ICP as a function of the rf power driving the plasma. Surprisingly, we found that the electron density in the plasma was essentially independent of increases in rf power above its nominal value (i.e., 'rf-power gain') and that the electron temperature was only a slowly varying function of rf-power gain. The primary effect of rf power was to increase the temperature of the neutrals in the plasma, which was manifested by an increase in Rb vapor density. Interestingly, we also found evidence for electron temperature fluctuations (i.e., fluctuations in the plasma's high-energy electron content). The variance of these fluctuations scaled inversely with the plasma's mean electron temperature and was consistent with a simple model that assumed that the total electron density in the discharge was independent of rf power. Taken as a whole, our results indicate that the electrons in alkali/noble-gas ICPs are little affected by slight changes in rf power and that the primary effect of such changes is to heat the plasma's neutral species.
Achieving High-Energy-High-Power Density in a Flexible Quasi-Solid-State Sodium Ion Capacitor.
Li, Hongsen; Peng, Lele; Zhu, Yue; Zhang, Xiaogang; Yu, Guihua
2016-09-14
Simultaneous integration of high-energy output with high-power delivery is a major challenge for electrochemical energy storage systems, limiting dual fine attributes on a device. We introduce a quasi-solid-state sodium ion capacitor (NIC) based on a battery type urchin-like Na2Ti3O7 anode and a capacitor type peanut shell derived carbon cathode, using a sodium ion conducting gel polymer as electrolyte, achieving high-energy-high-power characteristics in solid state. Energy densities can reach 111.2 Wh kg(-1) at power density of 800 W kg(-1), and 33.2 Wh kg(-1) at power density of 11200 W kg(-1), which are among the best reported state-of-the-art NICs. The designed device also exhibits long-term cycling stability over 3000 cycles with capacity retention ∼86%. Furthermore, we demonstrate the assembly of a highly flexible quasi-solid-state NIC and it shows no obvious capacity loss under different bending conditions.
Duffy, Kirsten P.
2016-01-01
NASA Glenn Research Center is investigating hybrid electric and turboelectric propulsion concepts for future aircraft to reduce fuel burn, emissions, and noise. Systems studies show that the weight and efficiency of the electric system components need to be improved for this concept to be feasible. This effort aims to identify design parameters that affect power density and efficiency for a double-Halbach array permanent-magnet ironless axial flux motor configuration. These parameters include both geometrical and higher-order parameters, including pole count, rotor speed, current density, and geometries of the magnets, windings, and air gap.
International Nuclear Information System (INIS)
Hocquet, St.
2009-11-01
This research thesis deals with the problem of phase modulations in power lasers (such as the MegaJoule laser which is developed in France) and their impact of different physical phenomena like the suppression of the stimulated Brillouin scattering (which is necessary to avoid optics damage) and the optical smoothing which allows a spatial homogenisation of focal stains. The author deeply discusses the phase modulation counterparts, and more particularly the FM-AM conversion which is the source of unwanted intensity modulation and of energy loss. He reports the development of a comprehensive modelling of phenomena generating FM-AM conversion on a power laser chain. He theoretically and experimentally studies two methods allowing the FM-AM conversion to be reduced to a given spectral distortion: the compensation of transfer functions and the modification of the phase modulation signal to make it less sensitive to spectral distortion effects. For this last method, he determines the ideal spectrum shape for the phase modulation, and proposes a method to approach it. He shows the feasibility of such a method and reports experiments showing to which extent these solutions may improve performance of power lasers. Finally, he proposed optimised solutions for the MegaJoule Laser
Foffani, Guglielmo; Bianchi, Anna M.; Priori, Alberto; Baselli, Giuseppe
2004-09-01
We propose a method that combines adaptive autoregressive (AAR) identification and spectral power decomposition for the study of movement-related spectral changes in scalp EEG signals and basal ganglia local field potentials (LFPs). This approach introduces the concept of movement-related poles, allowing one to study not only the classical event-related desynchronizations (ERD) and synchronizations (ERS), which correspond to modulations of power, but also event-related modulations of frequency. We applied the method to analyze movement-related EEG signals and LFPs contemporarily recorded from the sensorimotor cortex, the globus pallidus internus (GPi) and the subthalamic nucleus (STN) in a patient with Parkinson's disease who underwent stereotactic neurosurgery for the implant of deep brain stimulation (DBS) electrodes. In the AAR identification we compared the whale and the exponential forgetting factors, showing that the whale forgetting provides a better disturbance rejection and it is therefore more suitable to investigate movement-related brain activity. Movement-related power modulations were consistent with previous studies. In addition, movement-related frequency modulations were observed from both scalp EEG signals and basal ganglia LFPs. The method therefore represents an effective approach to the study of movement-related brain activity.
Kais, A.; Lo, J.; Thérèse, L.; Guillot, Ph.
2018-01-01
To control the temperature during a plasma treatment, an understanding of the link between the plasma parameters and the fundamental process responsible for the heating is required. In this work, the power supplied by the plasma onto the surface of a glass substrate is measured using the calorimetric method. It has been shown that the powers deposited by ions and electrons, and their recombination at the surface are the main contributions to the heating power. Each contribution is estimated according to the theory commonly used in the literature. Using the corona balance, the Modified Boltzmann Plot (MBP) is employed to determine the electron temperature. A correlation between the power deposited by the plasma and the results of the MBP has been established. This correlation has been used to estimate the electron number density independent of the Langmuir probe in considered conditions.
Directory of Open Access Journals (Sweden)
Bahri Prebreza
2018-03-01
Full Text Available In this paper is presented the protection of transmission power lines of the Kosovo Power System from atmospheric discharges, with the use of surge arresters. Atmospheric discharges represent one of the main causes of interruptions for the Kosovo Power System. In addition, the ground flash density for Kosovo is given. The transmission lines with the worst performance regarding atmospheric discharges are discussed in more detail and are presented recommendations about the surge arresters used to protect the system from these overvoltages. The data provided by the localized lightning system in Kosovo enable us to provide a detailed correlation of the reported outages of the Kosovo Power System and corresponding atmospheric discharges. Recommendations for protection in terms of surge arresters are given followed by subsequent dynamic simulations using MATLAB software.
Energy Technology Data Exchange (ETDEWEB)
Mueller, Martin; /SLAC
2010-12-16
The study of the power density spectrum (PDS) of fluctuations in the X-ray flux from active galactic nuclei (AGN) complements spectral studies in giving us a view into the processes operating in accreting compact objects. An important line of investigation is the comparison of the PDS from AGN with those from galactic black hole binaries; a related area of focus is the scaling relation between time scales for the variability and the black hole mass. The PDS of AGN is traditionally modeled using segments of power laws joined together at so-called break frequencies; associations of the break time scales, i.e., the inverses of the break frequencies, with time scales of physical processes thought to operate in these sources are then sought. I analyze the Method of Light Curve Simulations that is commonly used to characterize the PDS in AGN with a view to making the method as sensitive as possible to the shape of the PDS. I identify several weaknesses in the current implementation of the method and propose alternatives that can substitute for some of the key steps in the method. I focus on the complications introduced by uneven sampling in the light curve, the development of a fit statistic that is better matched to the distributions of power in the PDS, and the statistical evaluation of the fit between the observed data and the model for the PDS. Using archival data on one AGN, NGC 3516, I validate my changes against previously reported results. I also report new results on the PDS in NGC 4945, a Seyfert 2 galaxy with a well-determined black hole mass. This source provides an opportunity to investigate whether the PDS of Seyfert 1 and Seyfert 2 galaxies differ. It is also an attractive object for placement on the black hole mass-break time scale relation. Unfortunately, with the available data on NGC 4945, significant uncertainties on the break frequency in its PDS remain.
Chaplin, Vernon H; Bellan, Paul M
2015-07-01
An electrically floating radiofrequency (RF) pre-ionization plasma source has been developed to enable neutral gas breakdown at lower pressures and to access new experimental regimes in the Caltech laboratory astrophysics experiments. The source uses a customized 13.56 MHz class D RF power amplifier that is powered by AA batteries, allowing it to safely float at 3-6 kV with the electrodes of the high voltage pulsed power experiments. The amplifier, which is capable of 3 kW output power in pulsed (<1 ms) operation, couples electrical energy to the plasma through an antenna external to the 1.1 cm radius discharge tube. By comparing the predictions of a global equilibrium discharge model with the measured scalings of plasma density with RF power input and axial magnetic field strength, we demonstrate that inductive coupling (rather than capacitive coupling or wave damping) is the dominant energy transfer mechanism. Peak ion densities exceeding 5 × 10(19) m(-3) in argon gas at 30 mTorr have been achieved with and without a background field. Installation of the pre-ionization source on a magnetohydrodynamically driven jet experiment reduced the breakdown time and jitter and allowed for the creation of hotter, faster argon plasma jets than was previously possible.
Third-Order Density Perturbation and One-Loop Power Spectrum in Dark-Energy-Dominated Universe
Takahashi, Ryuichi
2008-01-01
We investigate the third-order density perturbation and the one-loop correction to the linear power spectrum in the dark-energy cosmological model. Our main interest is to understand the dark-energy effect on baryon acoustic oscillations in a quasi-nonlinear regime ($k \\approx 0.1h$/Mpc). Analytical solutions and simple fitting formulae are presented for the dark-energy model with the general time-varying equation of state $w(a)$. It turns out that the power spectrum coincides with the approx...
Simulation study of a high power density rectenna array for biomedical implantable devices
Day, John; Yoon, Hargsoon; Kim, Jaehwan; Choi, Sang H.; Song, Kyo D.
2016-04-01
The integration of wireless power transmission devices using microwaves into the biomedical field is close to a practical reality. Implanted biomedical devices need a long lasting power source or continuous power supply. Recent development of high efficiency rectenna technology enables continuous power supply to these implanted devices. Due to the size limit of most of medical devices, it is imperative to minimize the rectenna as well. The research reported in this paper reviews the effects of close packing the rectenna elements which show the potential of directly empowering the implanted devices, especially within a confined area. The rectenna array is tested in the X band frequency range.
International Nuclear Information System (INIS)
Bhatnagar, V.P.; Taroni, A.; Ellis, J.J.; Jacquinot, J.; Stuart, D.F.
1989-01-01
In this paper, we compare experimental results of electron and ion-heating in discharges that feature monster sawtooth with those in pellet-produced peaked-density profile discharges which were heated with ICRF. Also we carry out a comprehensive analysis of ICRF-heated peaked-density profile discharges by a transport code to simulate the evolution of JET discharges and to provide an insight into the improved heating and confinement found in these discharges. In this analysis, the ICRF power-deposition profile in the minority-heating scenario is computed by the ray-tracing code BRAYCO that self-consistently takes the finite antenna geometry, its radiation spectrum and the hot-plasma damping into account. The power delivered to ions and electrons is calculated based on Stix model. (author) 10 refs., 5 figs
Hanafusa, Hiroaki; Nakashima, Ryosuke; Nakano, Wataru; Higashi, Seiichiro
2018-06-01
In this study, the effect of N2 addition to an atmospheric-pressure Ar thermal plasma jet (TPJ) on ultrarapid heating was investigated. With increasing N2 flow rate, a boost of arc voltage to ∼36 V was observed, which significantly improved heating characteristics. As a result, a drastic power density increase from 10 to 125 kW/cm2 was achieved with the addition of 2.0 L/min N2 to 3.0 L/min Ar. The results of optical emission analysis and heating characteristics evaluation implied that dissociation and recombination of N2 molecules and the high thermal transport property of nitrogen gas play important roles in the increase in TPJ power density. Furthermore, we obtained TPJ extension with N2 addition that reached 300 mm, and it showed spatial enhancement of heat transport characteristics.
Curvature Effect and the Spectral Softening Phenomenon Detected ...
Indian Academy of Sciences (India)
soft spectral evolution, indicating that this spectral softening is not a rare phenomenon .... of time, there exists a temporal steep decay phase accompanied by spectral softening. (d) In most cases, the temporal power law index α and the spectral.
Dunn, H. J.
1981-01-01
A computer program for performing frequency analysis of time history data is presented. The program uses circular convolution and the fast Fourier transform to calculate power density spectrum (PDS) of time history data. The program interfaces with the advanced continuous simulation language (ACSL) so that a frequency analysis may be performed on ACSL generated simulation variables. An example of the calculation of the PDS of a Van de Pol oscillator is presented.
Henault, M.; Wattieaux, G.; Lecas, T.; Renouard, J. P.; Boufendi, L.
2016-02-01
Nanoparticles growing or injected in a low pressure cold plasma generated by a radiofrequency capacitively coupled capacitive discharge induce strong modifications in the electrical parameters of both plasma and discharge. In this paper, a non-intrusive method, based on the measurement of the plasma impedance, is used to determine the volume averaged electron density and effective coupled power to the plasma bulk. Good agreements are found when the results are compared to those given by other well-known and established methods.
Design and Performance Test of Axial Halbach Brushless DC Motor with Power Density 1.5 Kw/Kg
Directory of Open Access Journals (Sweden)
Kevin Dwi Prasetio
2017-01-01
Full Text Available Progress of technology on electric vehicle component sector is one reason the emergence of electric vehicles at the moment. Starting from battery which has a great current density up to the automatic control systems on electric vehicles. But there are still some shortcomings of this electric vehicle components, one of which is the low value of power density of existing electric motor in the market today.On vehicles such as electric cars when Race Car Contest, energy saving problems about power density of the driving motor is very vital. This is because the total weight of the vehicle has a huge influence on the vehicle efficiency is against it. The issue is one of the reasons of the research task. In this final task is done making the design, simulation, and architecture of the Axial Halbach Brushless DC Motor. Use of system configuration on the halbach magnet to avoid the use of iron as a material cantilever rotor. By changing the material of the cantilever rotor with lighter materials such as aluminum or even carbon fibre, the value of power density electric motors can be increased. Then using the litz wire on coil stator to reduce loss-power loss due to the barriers on the coil. Coreless stator on the system and to avoid the phenomenon of cogging at the time due to low rpm style attraction magnet with iron in the core material. While the creation process begins by determining the specifications of the Axial Halbach Brushless DC motors. Then go into the design phase of the mechanical and electrical design. Who then conducted simulations to help determine other parameters such as air gap, slot turn, and magnetic orientation. The process of making a component of stator and rotor after the simulation is completed. After all the components of the rotor and stator on assembly, mounting the hall sensor is carried out to the right to position obtained by reading the signals. After the motor can spin with good motor performance, testing can be done
Yost, Dillon C.; Yao, Yi; Kanai, Yosuke
2017-09-01
In ion irradiation processes, electronic stopping power describes the energy transfer rate from the irradiating ion to the target material's electrons. Due to the scarcity and significant uncertainties in experimental electronic stopping power data for materials beyond simple solids, there has been growing interest in the use of first-principles theory for calculating electronic stopping power. In recent years, advances in high-performance computing have opened the door to fully first-principles nonequilibrium simulations based on real-time time-dependent density functional theory (RT-TDDFT). While it has been demonstrated that the RT-TDDFT approach is capable of predicting electronic stopping power for a wide range of condensed matter systems, there has yet to be an exhaustive examination of the physical and numerical approximations involved and their effects on the calculated stopping power. We discuss the results of such a study for crystalline silicon with protons as irradiating ions. We examine the influences of key approximations in RT-TDDFT nonequilibrium simulations on the calculated electronic stopping power, including approximations related to basis sets, finite size effects, exchange-correlation approximation, pseudopotentials, and more. Finally, we propose a simple and efficient correction scheme to account for the contribution from core-electron excitations to the stopping power, as it was found to be significant for large proton velocities.
Energy Technology Data Exchange (ETDEWEB)
Savander, V. I.; Shumskiy, B. E., E-mail: borisshumskij@yandex.ru [National Research Nuclear University MEPhI (Russian Federation); Pinegin, A. A. [National Research Center Kurchatov Institute (Russian Federation)
2016-12-15
The possibility of decreasing the vapor fraction at the VVER-1200 fuel assembly outlet by shaping the axial power density field is considered. The power density field was shaped by axial redistribution of the concentration of the burnable gadolinium poison in the Gd-containing fuel rods. The mathematical modeling of the VVER-1200 core was performed using the NOSTRA computer code.
Power Burst Facility: power oscillation problem
International Nuclear Information System (INIS)
Lussie, W.G.; Wadkins, R.P.; Wells, R.A.
1975-01-01
In late 1973 PBF achieved a power level of 15 MW. During this period of operation fluctuations in reactor power were observed. Many possible causes of these fluctuations were considered and a number of nuclear and non-nuclear tests were conducted. Initial instrumentation installed in the core showed coolant outlet temperature variations of 10 0 F for several fuel cannisters and approximately 10 percent power variations at 15 MW. Power spectral density analysis showed a predominant frequency of 0.05 to 0.06 HZ. The testing program to determine the cause of the power oscillations is described
Directory of Open Access Journals (Sweden)
Y. Wang
2017-10-01
Full Text Available In order to promote the development of the passive DOAS technique the Multi Axis DOAS – Comparison campaign for Aerosols and Trace gases (MAD-CAT was held at the Max Planck Institute for Chemistry in Mainz, Germany, from June to October 2013. Here, we systematically compare the differential slant column densities (dSCDs of nitrous acid (HONO derived from measurements of seven different instruments. We also compare the tropospheric difference of SCDs (delta SCD of HONO, namely the difference of the SCDs for the non-zenith observations and the zenith observation of the same elevation sequence. Different research groups analysed the spectra from their own instruments using their individual fit software. All the fit errors of HONO dSCDs from the instruments with cooled large-size detectors are mostly in the range of 0.1 to 0.3 × 1015 molecules cm−2 for an integration time of 1 min. The fit error for the mini MAX-DOAS is around 0.7 × 1015 molecules cm−2. Although the HONO delta SCDs are normally smaller than 6 × 1015 molecules cm−2, consistent time series of HONO delta SCDs are retrieved from the measurements of different instruments. Both fits with a sequential Fraunhofer reference spectrum (FRS and a daily noon FRS lead to similar consistency. Apart from the mini-MAX-DOAS, the systematic absolute differences of HONO delta SCDs between the instruments are smaller than 0.63 × 1015 molecules cm−2. The correlation coefficients are higher than 0.7 and the slopes of linear regressions deviate from unity by less than 16 % for the elevation angle of 1°. The correlations decrease with an increase in elevation angle. All the participants also analysed synthetic spectra using the same baseline DOAS settings to evaluate the systematic errors of HONO results from their respective fit programs. In general the errors are smaller than 0.3 × 1015 molecules cm−2, which is
Cho, Chahee Peter
1995-01-01
Until recently, brush dc motors have been the dominant drive system because they provide easily controlled motor speed over a wide range, rapid acceleration and deceleration, convenient control of position, and lower product cost. Despite these capabilities, the brush dc motor configuration does not satisfy the design requirements for the U.S. Navy's underwater propulsion applications. Technical advances in rare-earth permanent magnet materials, in high-power semiconductor transistor technology, and in various rotor position-sensing devices have made using brushless permanent magnet motors a viable alternative. This research investigates brushless permanent magnet motor technology, studying the merits of dual-air gap, axial -field, brushless, permanent magnet motor configuration in terms of power density, efficiency, and noise/vibration levels. Because the design objectives for underwater motor applications include high-power density, high-performance, and low-noise/vibration, the traditional, simplified equivalent circuit analysis methods to assist in meeting these goals were inadequate. This study presents the development and verification of detailed finite element analysis (FEA) models and lumped parameter circuit models that can calculate back electromotive force waveforms, inductance, cogging torque, energized torque, and eddy current power losses. It is the first thorough quantification of dual air-gap, axial -field, brushless, permanent magnet motor parameters and performance characteristics. The new methodology introduced in this research not only facilitates the design process of an axial field, brushless, permanent magnet motor but reinforces the idea that the high-power density, high-efficiency, and low-noise/vibration motor is attainable.
Troussel, Ph; Villette, B; Emprin, B; Oudot, G; Tassin, V; Bridou, F; Delmotte, F; Krumrey, M
2014-01-01
CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.
Energy Technology Data Exchange (ETDEWEB)
Ishida, Yoshio; Fukuoka, Shuji; Shimotsu, Yoriko; Sasaki, Tatsuya; Kamakura, Shiro; Yasumura, Yoshio; Miyatake, Kunio; Shimomura, Katsuro [National Cardiovascular Center, Suita, Osaka (Japan); Tani, Akihiro
1997-04-01
The significance of power spectral analysis of heart rate variability and of MIBG myocardial imaging to see the sympathetic nervous function was evaluated in patients with congestive heart failure due to dilated cardiomyopathy. Subjects were 10 normal volunteers and 8 patients with severity NYHA II; 10 normals and 25 patients with NYHA II and III; and 17 patients treated with a beta-blocker (metoprolol 5-40 mg). ECG was recorded with a portable ECG recorder for measuring RR intervals for 24 hr, which were applied for power spectral analysis. Early and delayed imagings with 111 MBq of {sup 123}I-MIBG were performed at 15 min and 4 hr, respectively, after its intravenous administration for acquisition of anterior planar and SPECT images. Myocardial blood flow SPECT was also done with 111 MBq of {sup 201}Tl given intravenously, and difference of total defect scores between MIBG and Tl images was computed. MIBG myocardial sympathetic nerve imaging in those patients was found useful to assess the severity of heart failure, to predict the risk patients for beta-blocker treatment and to assess the risk in complicated ventricular tachycardia. (K.H.)
Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs
Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi
2014-01-01
Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10-7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.
Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs.
Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi
2014-01-22
Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10(-7) in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.
Directory of Open Access Journals (Sweden)
Kazunori Hirasawa
2017-09-01
Full Text Available AIM: To evaluate the influence of corneal power on circumpapillary retinal nerve fiber layer (cpRNFL and optic nerve head (ONH measurements by spectral-domain optical coherence tomography (SD-OCT. METHODS: Twenty-five eyes of 25 healthy participants (mean age 23.6±3.6y were imaged by SD-OCT using horizontal raster scans. Disposable soft contact lenses of different powers (from −11 to +5 diopters including 0 diopter were worn to induce 2-diopter changes in corneal power. Differences in the cpRNFL and ONH measurements per diopter of change in corneal power were analyzed. RESULTS: As corneal power increased by 1 diopter, total and quadrant cpRNFL thicknesses, except for the nasal sector, decreased by −0.19 to −0.32 μm (P<0.01. Furthermore, the disc, cup, and rim areas decreased by −0.017, −0.007, and −0.015 mm2, respectively (P<0.001; the cup and rim volumes decreased by −0.0013 and −0.006 mm3, respectively (P<0.01; and the vertical and horizontal disc diameters decreased by −0.006 and −0.007 mm, respectively (P<0.001. CONCLUSION: For more precise OCT imaging, the ocular magnification should be corrected by considering both the axial length and corneal power. However, the effect of corneal power changes on cpRNFL thickness and ONH topography are small when compare with those of the axial length.
Zhi, Mingjia; Manivannan, Ayyakkannu; Meng, Fanke; Wu, Nianqiang
2012-06-01
This paper presents highly conductive carbon nanofiber/MnO2 coaxial cables in which individual electrospun carbon nanofibers are coated with an ultrathin hierarchical MnO2 layer. In the hierarchical MnO2 structure, an around 4 nm thick sheath surrounds the carbon nanofiber (CNF) in a diameter of 200 nm, and nano-whiskers grow radically outward from the sheath in view of the cross-section of the coaxial cables, giving a high specific surface area of MnO2. The CNFs are synthesized by electrospinning a precursor containing iron acetylacetonate (AAI). The addition of AAI not only enlarges the specific surface area of the CNF but also greatly enhances their electronic conductivity, which leads to a dramatic improvement in the specific capacitance and the rate capability of the CNF/MnO2 electrode. The AAI-CNF/MnO2 electrode shows a specific capacitance of 311 F g-1 for the whole electrode and 900 F g-1 for the MnO2 shell at a scan rate of 2 mV s-1. Good cycling stability, high energy density (80.2 Wh kg-1) and high power density (57.7 kW kg-1) are achieved. This work indicates that high electronic conductivity of the electrode material is crucial to achieving high power and energy density for pseudo-supercapacitors.
Nuclear data uncertainties for local power densities in the Martin-Hoogenboom benchmark
International Nuclear Information System (INIS)
Van der Marck, S.C.; Rochman, D.A.
2013-01-01
The recently developed method of fast Total Monte Carlo to propagate nuclear data uncertainties was applied to the Martin-Hoogenboom benchmark. This Martin- Hoogenboom benchmark prescribes that one calculates local pin powers (of light water cooled reactor) with a statistical uncertainty lower than 1% everywhere. Here we report, for the first time, an estimate of the nuclear data uncertainties for these local pin powers. For each of the more than 6 million local power tallies, the uncertainty due to nuclear data uncertainties was calculated, based on random variation of data for 235 U, 238 U, 239 Pu and H in H 2 O thermal scattering. In the center of the core region, the nuclear data uncertainty is 0.9%. Towards the edges of the core, this uncertainty increases to roughly 3%. The nuclear data uncertainties have been shown to be larger than the statistical uncertainties that the benchmark prescribes
International Nuclear Information System (INIS)
Wang, Kun-lun; Ren, Xiao-dong; Huang, Xian-bin; Zhang, Si-qun; Zhou, Shao-tong; Dan, Jia-kun; Li, Jing; Xu, Qiang; Ouyang, Kai; Cai, Hong-chun; Wei, Bing; Ji, Ce; Feng, Shu-ping; Wang, Meng; Xie, Wei-ping; Deng, Jian-jun
2015-01-01
Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter to yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%
Energy Technology Data Exchange (ETDEWEB)
Li, Shou-lin; Ikeda, Jun; Takita, Tamotsu; Sekiguchi, Yohei; Demachi, Jun; Chikama, Hisao; Goto, Atsushi; Shirato, Kunio [Tohoku Univ., Sendai (Japan). School of Medicine
1998-11-01
The relationship between the myocardial uptake of iodine-123 metaiodobenzylguanidine ({sup 123}I-MIBG) and heart rate variability parameters has not been determined. This study determined the relationship between the change in myocardial uptake of {sup 123}I-MIBG and improvement in left ventricular function after treatment, to determine the usefulness of {sup 123}I-MIBG imaging to assess the effect of therapy on heart failure due to dilated cardiomyopathy (DCM). {sup 123}I-MIBG imaging and power spectral analysis of heart rate variability were performed before and after treatment in 17 patients with heart failure due to DCM. The following parameters were compared before and after treatment: New York Heart Association (NYHA) functional class, radiographic cardiothoracic ratio (CTR), blood pressure, echocardiographic data (left ventricular end-systolic (LVDs) and end-diastolic (LVDd) diameters, left ventricular ejection fraction (LVEF)), plasma concentrations of norepinephrine and epinephrine, heart rate variability power spectral analysis data (mean low frequency (MLF) and high frequency power (MHF)) and the myocardium to mediastinum activity ratio (MYO/M) obtained in early and late images, and washout rate calculated by anterior planar imaging of {sup 123}I-MIBG. The NYHA functional class, LVEF, LVDs, CTR, MLF and MHF improved after treatment. Early MYO/M and late MYO/M improved after treatment. The rate of increase in late MYO/M was positively correlated with the rate of improvement of LVEF after treatment. Furthermore, the late MYO/M was negatively correlated with MLF. Washout rate revealed no correlation with hemodynamic parameters. These findings suggest that late MYO/M is more useful than washout rate to assess the effect of treatment on heart failure due to DCM. Furthermore, the {sup 123}I-MIBG imaging and heart rate variability parameters are useful to assess the autonomic tone in DCM with heart failure. (author)
International Nuclear Information System (INIS)
Li, Shou-lin; Ikeda, Jun; Takita, Tamotsu; Sekiguchi, Yohei; Demachi, Jun; Chikama, Hisao; Goto, Atsushi; Shirato, Kunio
1998-01-01
The relationship between the myocardial uptake of iodine-123 metaiodobenzylguanidine ( 123 I-MIBG) and heart rate variability parameters has not been determined. This study determined the relationship between the change in myocardial uptake of 123 I-MIBG and improvement in left ventricular function after treatment, to determine the usefulness of 123 I-MIBG imaging to assess the effect of therapy on heart failure due to dilated cardiomyopathy (DCM). 123 I-MIBG imaging and power spectral analysis of heart rate variability were performed before and after treatment in 17 patients with heart failure due to DCM. The following parameters were compared before and after treatment: New York Heart Association (NYHA) functional class, radiographic cardiothoracic ratio (CTR), blood pressure, echocardiographic data (left ventricular end-systolic (LVDs) and end-diastolic (LVDd) diameters, left ventricular ejection fraction (LVEF)), plasma concentrations of norepinephrine and epinephrine, heart rate variability power spectral analysis data (mean low frequency (MLF) and high frequency power (MHF)) and the myocardium to mediastinum activity ratio (MYO/M) obtained in early and late images, and washout rate calculated by anterior planar imaging of 123 I-MIBG. The NYHA functional class, LVEF, LVDs, CTR, MLF and MHF improved after treatment. Early MYO/M and late MYO/M improved after treatment. The rate of increase in late MYO/M was positively correlated with the rate of improvement of LVEF after treatment. Furthermore, the late MYO/M was negatively correlated with MLF. Washout rate revealed no correlation with hemodynamic parameters. These findings suggest that late MYO/M is more useful than washout rate to assess the effect of treatment on heart failure due to DCM. Furthermore, the 123 I-MIBG imaging and heart rate variability parameters are useful to assess the autonomic tone in DCM with heart failure. (author)
Covariant density functional theory: predictive power and first attempts of a microscopic derivation
Ring, Peter
2018-05-01
We discuss systematic global investigations with modern covariant density functionals. The number of their phenomenological parameters can be reduced considerable by using microscopic input from ab-initio calculations in nuclear matter. The size of the tensor force is still an open problem. Therefore we use the first full relativistic Brueckner-Hartree-Fock calculations in finite nuclear systems in order to study properties of such functionals, which cannot be obtained from nuclear matter calculations.
Cooling of high-density and power electronics by means of heat pipes
International Nuclear Information System (INIS)
Hubbeling, L.
1980-06-01
This report describes how heat pipes can be used for cooling modern electronic equipment, with numerous advantages over air-cooled systems. A brief review of heat-pipe properties is given, with a detailed description of a functioning prototype. This is a single-width CAMAC unit containing high-density electronic circuits cooled by three heat pipes, and allowing a dissipation of over 120 W instead of the normal maximum of 20 W. (orig.)
Covariant density functional theory: predictive power and first attempts of a microscopic derivation
Directory of Open Access Journals (Sweden)
Ring Peter
2018-01-01
Full Text Available We discuss systematic global investigations with modern covariant density functionals. The number of their phenomenological parameters can be reduced considerable by using microscopic input from ab-initio calculations in nuclear matter. The size of the tensor force is still an open problem. Therefore we use the first full relativistic Brueckner-Hartree-Fock calculations in finite nuclear systems in order to study properties of such functionals, which cannot be obtained from nuclear matter calculations.
Razali, Akhtar; Rahman, Fadhlur; Azlan, Syaiful; Razali Hanipah, Mohd; Azri Hizami, Mohd
2018-04-01
Cogging is an attraction of magnetism between permanent magnets and soft ironcore lamination in a conventional electric ironcore generator. The presence of cog in the generator is seen somehow restricted the application of the generator in an application where low rotational torque is required. Cog torque requires an additional input power to overcome, hence became one of the power loss sources. With the increasing of power output, the cogging is also proportionally increased. This leads to the increasing of the supplied power of the driver motor to overcome the cog. Therefore, this research is embarked to study fundamentally about the possibility of removing ironcore lamination in an electric generator. This research deals with removal of ironcore lamination in electric generator to eliminate cog torque. A confinement technique is proposed to confine and focus magnetic flux by introducing opposing permanent magnets arrangement. The concept is then fabricated and experimentally validated to qualify its no-load characteristics. The rotational torque and power output are measured and efficiency is then analyzed. Results indicated that the generator produced RMS voltage of 416VAC at rotational speed of 1762 RPM. Torque required to rotate the generator was at 2Nm for various rotational speed. The generator has shown 30% lesser rotational torque compared to the conventional ironcore type generator due to the absent of cogging torque in the system. Lesser rotational torque required to rotate has made this type of generator has a potential to be used for low wind density wind turbine application.
International Nuclear Information System (INIS)
Casper, T A; Burrell, K H; Doyle, E J; Gohil, P; Lasnier, C J; Leonard, A W; Moller, J M; Osborne, T H; Snyder, P B; Thomas, D M; Weiland, J; West, W P
2006-01-01
Quiescent double barrier (QDB) conditions often form when an internal transport barrier is created with high-power neutral-beam injection into a quiescent H-mode (QH) plasma. These QH-modes offer an attractive, high-performance operating scenario for burning plasma experiments due to their quasi-stationarity and lack of edge localized modes. Our initial experiments and modelling using ECH/ECCD in QDB shots were designed to control the current profile and, indeed, we have observed a strong dependence on the q-profile when EC-power is used inside the core transport barrier region. While strong electron heating is observed with EC power injection, we also observe a drop in the other core parameters, namely ion temperature and rotation, electron density and impurity concentration. At onset and termination of the EC pulse, dynamically changing conditions are induced that provide a rapid evolution of T e /T i profiles accessible with 0.3 e /T i ) axis e /T i ratio as the ion temperature and density profiles flatten with this change in transport. The change in transport is consistent with a destabilization of ITG turbulence as inferred from the reduction of the stability threshold due to the change in T e /T i
International Nuclear Information System (INIS)
Sorini, D.
2017-01-01
Measuring the clustering of galaxies from surveys allows us to estimate the power spectrum of matter density fluctuations, thus constraining cosmological models. This requires careful modelling of observational effects to avoid misinterpretation of data. In particular, signals coming from different distances encode information from different epochs. This is known as ''light-cone effect'' and is going to have a higher impact as upcoming galaxy surveys probe larger redshift ranges. Generalising the method by Feldman, Kaiser and Peacock (1994) [1], I define a minimum-variance estimator of the linear power spectrum at a fixed time, properly taking into account the light-cone effect. An analytic expression for the estimator is provided, and that is consistent with the findings of previous works in the literature. I test the method within the context of the Halofit model, assuming Planck 2014 cosmological parameters [2]. I show that the estimator presented recovers the fiducial linear power spectrum at present time within 5% accuracy up to k ∼ 0.80 h Mpc −1 and within 10% up to k ∼ 0.94 h Mpc −1 , well into the non-linear regime of the growth of density perturbations. As such, the method could be useful in the analysis of the data from future large-scale surveys, like Euclid.
Zhao, Quan-Liang; He, Guang-Ping; Di, Jie-Jian; Song, Wei-Li; Hou, Zhi-Ling; Tan, Pei-Pei; Wang, Da-Wei; Cao, Mao-Sheng
2017-07-26
A flexible semitransparent energy harvester is assembled based on laterally aligned Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) single-crystal nanowires (NWs). Such a harvester presents the highest open-circuit voltage and a stable area power density of up to 10 V and 0.27 μW/cm 2 , respectively. A high pressure sensitivity of 0.14 V/kPa is obtained in the dynamic pressure sensing, much larger than the values reported in other energy harvesters based on piezoelectric single-crystal NWs. Furthermore, theoretical and finite element analyses also confirm that the piezoelectric voltage constant g 33 of PZT NWs is competitive to the lead-based bulk single crystals and ceramics, and the enhanced pressure sensitivity and power density are substantially linked to the flexible structure with laterally aligned PZT NWs. The energy harvester in this work holds great potential in flexible and transparent sensing and self-powered systems.
Transport dynamics of a high-power-density matrix-type hydrogen-oxygen fuel cell
Prokopius, P. R.; Hagedorn, N. H.
1974-01-01
Experimental transport dynamics tests were made on a space power fuel cell of current design. Various operating transients were introduced and transport-related response data were recorded with fluidic humidity sensing instruments. Also, sampled data techniques were developed for measuring the cathode-side electrolyte concentration during transient operation.