Hybrid time-frequency domain equalization for LED nonlinearity mitigation in OFDM-based VLC systems.

PubMed

Li, Jianfeng; Huang, Zhitong; Liu, Xiaoshuang; Ji, Yuefeng

2015-01-12

A novel hybrid time-frequency domain equalization scheme is proposed and experimentally demonstrated to mitigate the white light emitting diode (LED) nonlinearity in visible light communication (VLC) systems based on orthogonal frequency division multiplexing (OFDM). We handle the linear and nonlinear distortion separately in a nonlinear OFDM system. The linear part is equalized in frequency domain and the nonlinear part is compensated by an adaptive nonlinear time domain equalizer (N-TDE). The experimental results show that with only a small number of parameters the nonlinear equalizer can efficiently mitigate the LED nonlinearity. With the N-TDE the modulation index (MI) and BER performance can be significantly enhanced.

Periodic subsystem density-functional theory

NASA Astrophysics Data System (ADS)

Genova, Alessandro; Ceresoli, Davide; Pavanello, Michele

2014-11-01

By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn-Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn-Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.

Periodic subsystem density-functional theory.

PubMed

Genova, Alessandro; Ceresoli, Davide; Pavanello, Michele

2014-11-07

By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn-Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn-Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.

Periodic subsystem density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genova, Alessandro; Pavanello, Michele, E-mail: m.pavanello@rutgers.edu; Ceresoli, Davide

2014-11-07

By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn–Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dualmore » approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn–Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.« less

The Intimin-Like Protein FdeC Is Regulated by H-NS and Temperature in Enterohemorrhagic Escherichia coli

PubMed Central

Easton, Donna M.; Allsopp, Luke P.; Phan, Minh-Duy; Moriel, Danilo Gomes; Goh, Guan Kai; Beatson, Scott A.; Mahony, Timothy J.; Cobbold, Rowland N.

2014-01-01

Enterohemorrhagic Escherichia coli (EHEC) is a Shiga-toxigenic pathogen capable of inducing severe forms of enteritis (e.g., hemorrhagic colitis) and extraintestinal sequelae (e.g., hemolytic-uremic syndrome). The molecular basis of colonization of human and animal hosts by EHEC is not yet completely understood, and an improved understanding of EHEC mucosal adherence may lead to the development of interventions that could disrupt host colonization. FdeC, also referred to by its IHE3034 locus tag ECOK1_0290, is an intimin-like protein that was recently shown to contribute to kidney colonization in a mouse urinary tract infection model. The expression of FdeC is tightly regulated in vitro, and FdeC shows promise as a vaccine candidate against extraintestinal E. coli strains. In this study, we characterized the prevalence, regulation, and function of fdeC in EHEC. We showed that the fdeC gene is conserved in both O157 and non-O157 EHEC and encodes a protein that is expressed at the cell surface and promotes biofilm formation under continuous-flow conditions in a recombinant E. coli strain background. We also identified culture conditions under which FdeC is expressed and showed that minor alterations of these conditions, such as changes in temperature, can significantly alter the level of FdeC expression. Additionally, we demonstrated that the transcription of the fdeC gene is repressed by the global regulator H-NS. Taken together, our data suggest a role for FdeC in EHEC when it grows at temperatures above 37°C, a condition relevant to its specialized niche at the rectoanal junctions of cattle. PMID:25239893

Genetic and functional characterization of a novel meta-pathway for degradation of naringenin in Herbaspirillum seropedicae SmR1.

PubMed

Maria Marin, Anelis; de la Torre, Jésus; Ricardo Marques Oliveira, Alfredo; Barison, Andersson; Satie Chubatsu, Leda; Adele Monteiro, Rose; de Oliveira Pedrosa, Fabio; Maltempi de Souza, Emanuel; Wassem, Roseli; Duque, Estrella; Ramos, Juan-Luis

2016-12-01

In this study, a random mutant library of Herbaspirillum seropedicae SmR1 was constructed by Tn5 insertion and a mutant incapable of utilizing naringenin as a carbon source was isolated. The Tn5 transposon was found to be inserted in the fdeE gene (Hsero_1007), which encodes a monooxygenase. Two other mutant strains in fdeC (Hsero_1005) and fdeG (Hsero_1009) genes coding for a dioxygenase and a putative cyclase, respectively, were obtained by site-directed mutagenesis and then characterized. Liquid Chromatography coupled to mass spectrometry (LC-MS)/MS analyses of culture supernatant from the fdeE mutant strain revealed that naringenin remained unaltered, suggesting that the FdeE protein is involved in the initial step of naringenin degradation. LC-MS/MS analyses of culture supernatants from the wild-type (SmR1) and FdeC deficient mutant suggested that in H. seropedicae SmR1 naringenin is first mono-oxygenated by the FdeE protein, to produce 5,7,8-trihydroxy-2-(4-hydroxyphenyl)-2,3-dihydro-4H-chromen-4-one, that is subsequently dioxygenated and cleaved at the A-ring by the FdeC dioxygenase, since the latter compound accumulated in the fdeC strain. After meta-cleavage of the A-ring, the subsequent metabolic steps generate oxaloacetic acid that is metabolized via the tricarboxylic acid cycle. This bacterium can also modify naringenin by attaching a glycosyl group to the B-ring or a methoxy group to the A-ring, leading to the generation of dead-end products. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Photosynthetic and Heterotrophic Ferredoxin Isoproteins Are Colocalized in Fruit Plastids of Tomato1

PubMed Central

Aoki, Koh; Yamamoto, Miyuki; Wada, Keishiro

1998-01-01

Fruit tissues of tomato (Lycopersicon esculentum Mill.) contain both photosynthetic and heterotrophic ferredoxin (FdA and FdE, respectively) isoproteins, irrespective of their photosynthetic competence, but we did not previously determine whether these proteins were colocalized in the same plastids. In isolated fruit chloroplasts and chromoplasts, both FdA and FdE were detected by immunoblotting. Colocalization of FdA and FdE in the same plastids was demonstrated using double-staining immunofluorescence microscopy. We also found that FdA and FdE were colocalized in fruit chloroplasts and chloroamyloplasts irrespective of sink status of the plastid. Immunoelectron microscopy demonstrated that FdA and FdE were randomly distributed within the plastid stroma. To investigate the significance of the heterotrophic Fd in fruit plastids, Glucose 6-phosphate dehydrogenase (G6PDH) activity was measured in isolated fruit and leaf plastids. Fruit chloroplasts and chromoplasts showed much higher G6PDH activity than did leaf chloroplasts, suggesting that high G6PDH activity is linked with FdE to maintain nonphotosynthetic production of reducing power. This result suggested that, despite their morphological resemblance, fruit chloroplasts are functionally different from their leaf counterparts. PMID:9765529

Adaptive frequency-domain equalization in digital coherent optical receivers.

PubMed

Faruk, Md Saifuddin; Kikuchi, Kazuro

2011-06-20

We propose a novel frequency-domain adaptive equalizer in digital coherent optical receivers, which can reduce computational complexity of the conventional time-domain adaptive equalizer based on finite-impulse-response (FIR) filters. The proposed equalizer can operate on the input sequence sampled by free-running analog-to-digital converters (ADCs) at the rate of two samples per symbol; therefore, the arbitrary initial sampling phase of ADCs can be adjusted so that the best symbol-spaced sequence is produced. The equalizer can also be configured in the butterfly structure, which enables demultiplexing of polarization tributaries apart from equalization of linear transmission impairments. The performance of the proposed equalization scheme is verified by 40-Gbits/s dual-polarization quadrature phase-shift keying (QPSK) transmission experiments.

Fast convergent frequency-domain MIMO equalizer for few-mode fiber communication systems

NASA Astrophysics Data System (ADS)

He, Xuan; Weng, Yi; Wang, Junyi; Pan, Z.

2018-02-01

Space division multiplexing using few-mode fibers has been extensively explored to sustain the continuous traffic growth. In few-mode fiber optical systems, both spatial and polarization modes are exploited to transmit parallel channels, thus increasing the overall capacity. However, signals on spatial channels inevitably suffer from the intrinsic inter-modal coupling and large accumulated differential mode group delay (DMGD), which causes spatial modes de-multiplex even harder. Many research articles have demonstrated that frequency domain adaptive multi-input multi-output (MIMO) equalizer can effectively compensate the DMGD and demultiplex the spatial channels with digital signal processing (DSP). However, the large accumulated DMGD usually requires a large number of training blocks for the initial convergence of adaptive MIMO equalizers, which will decrease the overall system efficiency and even degrade the equalizer performance in fast-changing optical channels. Least mean square (LMS) algorithm is always used in MIMO equalization to dynamically demultiplex the spatial signals. We have proposed to use signal power spectral density (PSD) dependent method and noise PSD directed method to improve the convergence speed of adaptive frequency domain LMS algorithm. We also proposed frequency domain recursive least square (RLS) algorithm to further increase the convergence speed of MIMO equalizer at cost of greater hardware complexity. In this paper, we will compare the hardware complexity and convergence speed of signal PSD dependent and noise power directed algorithms against the conventional frequency domain LMS algorithm. In our numerical study of a three-mode 112 Gbit/s PDM-QPSK optical system with 3000 km transmission, the noise PSD directed and signal PSD dependent methods could improve the convergence speed by 48.3% and 36.1% respectively, at cost of 17.2% and 10.7% higher hardware complexity. We will also compare the frequency domain RLS algorithm against conventional frequency domain LMS algorithm. Our numerical study shows that, in a three-mode 224 Gbit/s PDM-16-QAM system with 3000 km transmission, the RLS algorithm could improve the convergence speed by 53.7% over conventional frequency domain LMS algorithm.

FDE-vdW: A van der Waals inclusive subsystem density-functional theory.

PubMed

Kevorkyants, Ruslan; Eshuis, Henk; Pavanello, Michele

2014-07-28

We present a formally exact van der Waals inclusive electronic structure theory, called FDE-vdW, based on the Frozen Density Embedding formulation of subsystem Density-Functional Theory. In subsystem DFT, the energy functional is composed of subsystem additive and non-additive terms. We show that an appropriate definition of the long-range correlation energy is given by the value of the non-additive correlation functional. This functional is evaluated using the fluctuation-dissipation theorem aided by a formally exact decomposition of the response functions into subsystem contributions. FDE-vdW is derived in detail and several approximate schemes are proposed, which lead to practical implementations of the method. We show that FDE-vdW is Casimir-Polder consistent, i.e., it reduces to the generalized Casimir-Polder formula for asymptotic inter-subsystems separations. Pilot calculations of binding energies of 13 weakly bound complexes singled out from the S22 set show a dramatic improvement upon semilocal subsystem DFT, provided that an appropriate exchange functional is employed. The convergence of FDE-vdW with basis set size is discussed, as well as its dependence on the choice of associated density functional approximant.

FDE-vdW: A van der Waals inclusive subsystem density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevorkyants, Ruslan; Pavanello, Michele, E-mail: m.pavanello@rutgers.edu; Eshuis, Henk

2014-07-28

We present a formally exact van der Waals inclusive electronic structure theory, called FDE-vdW, based on the Frozen Density Embedding formulation of subsystem Density-Functional Theory. In subsystem DFT, the energy functional is composed of subsystem additive and non-additive terms. We show that an appropriate definition of the long-range correlation energy is given by the value of the non-additive correlation functional. This functional is evaluated using the fluctuation–dissipation theorem aided by a formally exact decomposition of the response functions into subsystem contributions. FDE-vdW is derived in detail and several approximate schemes are proposed, which lead to practical implementations of the method.more » We show that FDE-vdW is Casimir-Polder consistent, i.e., it reduces to the generalized Casimir-Polder formula for asymptotic inter-subsystems separations. Pilot calculations of binding energies of 13 weakly bound complexes singled out from the S22 set show a dramatic improvement upon semilocal subsystem DFT, provided that an appropriate exchange functional is employed. The convergence of FDE-vdW with basis set size is discussed, as well as its dependence on the choice of associated density functional approximant.« less

Mitigation of intra-channel nonlinearities using a frequency-domain Volterra series equalizer.

PubMed

Guiomar, Fernando P; Reis, Jacklyn D; Teixeira, António L; Pinto, Armando N

2012-01-16

We address the issue of intra-channel nonlinear compensation using a Volterra series nonlinear equalizer based on an analytical closed-form solution for the 3rd order Volterra kernel in frequency-domain. The performance of the method is investigated through numerical simulations for a single-channel optical system using a 20 Gbaud NRZ-QPSK test signal propagated over 1600 km of both standard single-mode fiber and non-zero dispersion shifted fiber. We carry on performance and computational effort comparisons with the well-known backward propagation split-step Fourier (BP-SSF) method. The alias-free frequency-domain implementation of the Volterra series nonlinear equalizer makes it an attractive approach to work at low sampling rates, enabling to surpass the maximum performance of BP-SSF at 2× oversampling. Linear and nonlinear equalization can be treated independently, providing more flexibility to the equalization subsystem. The parallel structure of the algorithm is also a key advantage in terms of real-time implementation.

Conserved Features in the Structure, Mechanism, and Biogenesis of the Inverse Autotransporter Protein Family

PubMed Central

Heinz, Eva; Stubenrauch, Christopher J.; Grinter, Rhys; Croft, Nathan P.; Purcell, Anthony W.; Strugnell, Richard A.; Dougan, Gordon; Lithgow, Trevor

2016-01-01

The bacterial cell surface proteins intimin and invasin are virulence factors that share a common domain structure and bind selectively to host cell receptors in the course of bacterial pathogenesis. The β-barrel domains of intimin and invasin show significant sequence and structural similarities. Conversely, a variety of proteins with sometimes limited sequence similarity have also been annotated as “intimin-like” and “invasin” in genome datasets, while other recent work on apparently unrelated virulence-associated proteins ultimately revealed similarities to intimin and invasin. Here we characterize the sequence and structural relationships across this complex protein family. Surprisingly, intimins and invasins represent a very small minority of the sequence diversity in what has been previously the “intimin/invasin protein family”. Analysis of the assembly pathway for expression of the classic intimin, EaeA, and a characteristic example of the most prevalent members of the group, FdeC, revealed a dependence on the translocation and assembly module as a common feature for both these proteins. While the majority of the sequences in the grouping are most similar to FdeC, a further and widespread group is two-partner secretion systems that use the β-barrel domain as the delivery device for secretion of a variety of virulence factors. This comprehensive analysis supports the adoption of the “inverse autotransporter protein family” as the most accurate nomenclature for the family and, in turn, has important consequences for our overall understanding of the Type V secretion systems of bacterial pathogens. PMID:27190006

Hybrid time-frequency domain equalization based on sign-sign joint decision multimodulus algorithm for 6 × 6 mode division multiplexing system

NASA Astrophysics Data System (ADS)

Li, Jiao; Hu, Guijun; Gong, Caili; Li, Li

2018-02-01

In this paper, we propose a hybrid time-frequency domain sign-sign joint decision multimodulus algorithm (Hybrid-SJDMMA) for mode-demultiplexing in a 6 × 6 mode division multiplexing (MDM) system with high-order QAM modulation. The equalization performance of Hybrid-SJDMMA was evaluated and compared with the frequency domain multimodulus algorithm (FD-MMA) and the hybrid time-frequency domain sign-sign multimodulus algorithm (Hybrid-SMMA). Simulation results revealed that Hybrid-SJDMMA exhibits a significantly lower computational complexity than FD-MMA, and its convergence speed is similar to that of FD-MMA. Additionally, the bit-error-rate performance of Hybrid-SJDMMA was obviously better than FD-MMA and Hybrid-SMMA for 16 QAM and 64 QAM.

Neural correlates of working memory in first episode and recurrent depression: An fMRI study.

PubMed

Yüksel, Dilara; Dietsche, Bruno; Konrad, Carsten; Dannlowski, Udo; Kircher, Tilo; Krug, Axel

2018-06-08

Patients suffering from major depressive disorder (MDD) show deficits in working memory (WM) performance accompanied by bilateral fronto-parietal BOLD signal changes. It is unclear whether patients with a first depressive episode (FDE) exhibit the same signal changes as patients with recurrent depressive episodes (RDE). We investigated seventy-four MDD inpatients (48 RDE, 26 FDE) and 74 healthy control (HC) subjects performing an n-back WM task (0-back, 2-back, 3-back condition) in a 3T-fMRI. FMRI analyses revealed deviating BOLD signal in MDD in the thalamus (0-back vs. 2-back), the angular gyrus (0-back vs. 3-back), and the superior frontal gyrus (2-back vs. 3-back). Further effects were observed between RDE vs. FDE. Thus, RDE displayed differing neural activation in the middle frontal gyrus (2-back vs. 3-back), the inferior frontal gyrus, and the precentral gyrus (0-back vs. 2-back). In addition, both HC and FDE indicated a linear activation trend depending on task complexity. Although we failed to find behavioral differences between the groups, results suggest differing BOLD signal in fronto-parietal brain regions in MDD vs. HC, and in RDE vs. FDE. Moreover, both HC and FDE show similar trends in activation shapes. This indicates a link between levels of complexity-dependent activation in fronto-parietal brain regions and the stage of MDD. We therefore assume that load-dependent BOLD signal during WM is impaired in MDD, and that it is particularly affected in RDE. We also suspect neurobiological compensatory mechanisms of the reported brain regions in (working) memory functioning. Copyright © 2018 Elsevier Inc. All rights reserved.

Campylobacter jejuni inactivation in New Zealand soils.

PubMed

Ross, C M; Donnison, A M

2006-11-01

The study was undertaken to determine the inactivation rate of Campylobacter jejuni in New Zealand soils. Farm dairy effluent (FDE) inoculated at c. 10(5) ml(-1) with C. jejuni was applied to intact soil cores at a rate of 2 l m(-2). Four soils were used: Hamilton (granular); Taupo (pumice); Horotiu and Waihou (allophanic). After FDE application cores were incubated at 10 degrees C for up to 32 days. For all four soils all the FDE remained within the cores and at least 99% of C. jejuni were retained in the top 5 cm. Campylobacter jejuni had declined to the limit of detection (two C. jejuni 100 g(-1)) by 25 days in Hamilton and Taupo soils and by 32 days in Waihou soil. In contrast, in Horotiu soil the decline was only three orders of magnitude after 32 days. Simulated heavy rainfall was applied 4 and 11 days after FDE application and only about 1% of the applied C. jejuni were recovered in leachates. This study demonstrated that at least 99% of applied C. jejuni were retained in the top 5 cm of four soils where they survived for at least 25 days at 10 degrees C. Soil retention of C. jejuni is efficient at FDE application rates that prevent drainage losses. The low infectious dose of C. jejuni and its ability to survive up to 25 days have implications for stock management on dairy farms.

Some Properties of the Fractional Equation of Continuity and the Fractional Diffusion Equation

NASA Astrophysics Data System (ADS)

Fukunaga, Masataka

2006-05-01

The fractional equation of continuity (FEC) and the fractional diffusion equation (FDE) show peculiar behaviors that are in the opposite sense to those expected from the equation of continuity and the diffusion equation, respectively. The behaviors are interpreted in terms of the memory effect of the fractional time derivatives included in the equations. Some examples are given by solutions of the FDE.

Exact kinetic energy enables accurate evaluation of weak interactions by the FDE-vdW method.

PubMed

Sinha, Debalina; Pavanello, Michele

2015-08-28

The correlation energy of interaction is an elusive and sought-after interaction between molecular systems. By partitioning the response function of the system into subsystem contributions, the Frozen Density Embedding (FDE)-vdW method provides a computationally amenable nonlocal correlation functional based on the adiabatic connection fluctuation dissipation theorem applied to subsystem density functional theory. In reproducing potential energy surfaces of weakly interacting dimers, we show that FDE-vdW, either employing semilocal or exact nonadditive kinetic energy functionals, is in quantitative agreement with high-accuracy coupled cluster calculations (overall mean unsigned error of 0.5 kcal/mol). When employing the exact kinetic energy (which we term the Kohn-Sham (KS)-vdW method), the binding energies are generally closer to the benchmark, and the energy surfaces are also smoother.

Exact kinetic energy enables accurate evaluation of weak interactions by the FDE-vdW method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, Debalina; Pavanello, Michele, E-mail: m.pavanello@rutgers.edu

2015-08-28

The correlation energy of interaction is an elusive and sought-after interaction between molecular systems. By partitioning the response function of the system into subsystem contributions, the Frozen Density Embedding (FDE)-vdW method provides a computationally amenable nonlocal correlation functional based on the adiabatic connection fluctuation dissipation theorem applied to subsystem density functional theory. In reproducing potential energy surfaces of weakly interacting dimers, we show that FDE-vdW, either employing semilocal or exact nonadditive kinetic energy functionals, is in quantitative agreement with high-accuracy coupled cluster calculations (overall mean unsigned error of 0.5 kcal/mol). When employing the exact kinetic energy (which we term themore » Kohn-Sham (KS)-vdW method), the binding energies are generally closer to the benchmark, and the energy surfaces are also smoother.« less

Stressful life events and the risk of initial central nervous system demyelination.

PubMed

Saul, Alice; Ponsonby, Anne-Louise; Lucas, Robyn M; Taylor, Bruce V; Simpson, Steve; Valery, Patricia; Dwyer, Terence; Kilpatrick, Trevor J; Pender, Michael P; van der Mei, Ingrid Af

2017-06-01

There is substantial evidence that stress increases multiple sclerosis disease activity, but limited evidence on its association with the onset of multiple sclerosis. To examine the association between stressful life events and risk of first demyelinating event (FDE). This was a multicentre incident case-control study. Cases ( n = 282 with first diagnosis of central nervous system (CNS) demyelination, including n = 216 with 'classic FDE') were aged 18-59 years. Controls without CNS demyelination ( n = 558) were matched to cases on age, sex and study region. Stressful life events were assessed using a questionnaire based on the Social Readjustment Rating Scale. Those who suffered from a serious illness in the previous 12 months were more likely to have an FDE (odds ratio (OR) = 2.35 (1.36, 4.06), p = 0.002), and when we limited our reference group to those who had no stressful life events, the magnitude of effect became stronger (OR = 5.41 (1.80, 16.28)). The total stress number and stress load were not convincingly associated with the risk of an FDE. Cases were more likely to report a serious illness in the previous 12 months, which could suggest that a non-specific illness provides an additional strain to an already predisposed immune system.

Subsystem real-time time dependent density functional theory.

PubMed

Krishtal, Alisa; Ceresoli, Davide; Pavanello, Michele

2015-04-21

We present the extension of Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) to real-time Time Dependent Density Functional Theory (rt-TDDFT). FDE is a DFT-in-DFT embedding method that allows to partition a larger Kohn-Sham system into a set of smaller, coupled Kohn-Sham systems. Additional to the computational advantage, FDE provides physical insight into the properties of embedded systems and the coupling interactions between them. The extension to rt-TDDFT is done straightforwardly by evolving the Kohn-Sham subsystems in time simultaneously, while updating the embedding potential between the systems at every time step. Two main applications are presented: the explicit excitation energy transfer in real time between subsystems is demonstrated for the case of the Na4 cluster and the effect of the embedding on optical spectra of coupled chromophores. In particular, the importance of including the full dynamic response in the embedding potential is demonstrated.

Fluorescence correlation spectroscopy: the case of subdiffusion.

PubMed

Lubelski, Ariel; Klafter, Joseph

2009-03-18

The theory of fluorescence correlation spectroscopy is revisited here for the case of subdiffusing molecules. Subdiffusion is assumed to stem from a continuous-time random walk process with a fat-tailed distribution of waiting times and can therefore be formulated in terms of a fractional diffusion equation (FDE). The FDE plays the central role in developing the fluorescence correlation spectroscopy expressions, analogous to the role played by the simple diffusion equation for regular systems. Due to the nonstationary nature of the continuous-time random walk/FDE, some interesting properties emerge that are amenable to experimental verification and may help in discriminating among subdiffusion mechanisms. In particular, the current approach predicts 1), a strong dependence of correlation functions on the initial time (aging); 2), sensitivity of correlation functions to the averaging procedure, ensemble versus time averaging (ergodicity breaking); and 3), that the basic mean-squared displacement observable depends on how the mean is taken.

Demultiplexing based on frequency-domain joint decision MMA for MDM system

NASA Astrophysics Data System (ADS)

Caili, Gong; Li, Li; Guijun, Hu

2016-06-01

In this paper, we propose a demultiplexing method based on frequency-domain joint decision multi-modulus algorithm (FD-JDMMA) for mode division multiplexing (MDM) system. The performance of FD-JDMMA is compared with frequency-domain multi-modulus algorithm (FD-MMA) and frequency-domain least mean square (FD-LMS) algorithm. The simulation results show that FD-JDMMA outperforms FD-MMA in terms of BER and convergence speed in the cases of mQAM (m=4, 16 and 64) formats. And it is also demonstrated that FD-JDMMA achieves better BER performance and converges faster than FD-LMS in the cases of 16QAM and 64QAM. Furthermore, FD-JDMMA maintains similar computational complexity as the both equalization algorithms.

Antituberculosis Drug-Induced Fixed Drug Eruption: A Case Report.

PubMed

Vaghela, Jitendra H; Nimbark, Vivek; Barvaliya, Manish; Mehta, Hita; Chavada, Bhavesh

2018-05-21

Fixed drug eruption (FDE) was caused by fixed-dose combination (FDC) of antituberculosis drugs in the form of tablet Forecox ® (rifampicin [rifampin] 225 mg + isoniazid 150 mg + pyrazinamide 750 mg + ethambutol 400 mg) in a 40-year-old male patient with a history of drug allergy. The patient developed FDE after taking the third dose of tablet Forecox ® for pulmonary tuberculosis. Tablet Forecox ® was withdrawn and the patient recovered from the reaction after 15 days of treatment for FDE. As per World Health Organization-Uppsala Monitoring Centre (WHO-UMC) and Naranjo causality assessment criteria, the association between the reaction and tablet Forecox ® was possible and probable, respectively. The reaction was moderately (Level 4b) severe according to the Modified Hartwig and Siegel scale. As there is an increased risk of allergic reaction in patients with a history of drug allergy, FDCs should not be used in order to avoid complexity in identifying the culprit drug.

A Fracture Decoupling Experiment

NASA Astrophysics Data System (ADS)

Stroujkova, A. F.; Bonner, J. L.; Leidig, M.; Ferris, A. N.; Kim, W.; Carnevale, M.; Rath, T.; Lewkowicz, J.

2012-12-01

Multiple observations made at the Semipalatinsk Test Site suggest that conducting nuclear tests in the fracture zones left by previous explosions results in decreased seismic amplitudes for the second nuclear tests (or "repeat shots"). Decreased seismic amplitudes reduce both the probability of detection and the seismically estimated yield of a "repeat shot". In order to define the physical mechanism responsible for the amplitude reduction and to quantify the degree of the amplitude reduction in fractured rocks, Weston Geophysical Corp., in collaboration with Columbia University's Lamont Doherty Earth Observatory, conducted a multi-phase Fracture Decoupling Experiment (FDE) in central New Hampshire. The FDE involved conducting explosions of various yields in the damage/fracture zones of previously detonated explosions. In order to quantify rock damage after the blasts we performed well logging and seismic cross-hole tomography studies of the source region. Significant seismic velocity reduction was observed around the source regions after the initial explosions. Seismic waves produced by the explosions were recorded at near-source and local seismic networks, as well as several regional stations throughout northern New England. Our analysis confirms frequency dependent seismic amplitude reduction for the repeat shots compared to the explosions in un-fractured rocks. The amplitude reduction is caused by pore closing and/or by frictional losses within the fractured media.

Experimental demonstration of a frequency-domain Volterra series nonlinear equalizer in polarization-multiplexed transmission.

PubMed

Guiomar, Fernando P; Reis, Jacklyn D; Carena, Andrea; Bosco, Gabriella; Teixeira, António L; Pinto, Armando N

2013-01-14

Employing 100G polarization-multiplexed quaternary phase-shift keying (PM-QPSK) signals, we experimentally demonstrate a dual-polarization Volterra series nonlinear equalizer (VSNE) applied in frequency-domain, to mitigate intra-channel nonlinearities. The performance of the dual-polarization VSNE is assessed in both single-channel and in wavelength-division multiplexing (WDM) scenarios, providing direct comparisons with its single-polarization version and with the widely studied back-propagation split-step Fourier (SSF) approach. In single-channel transmission, the optimum power has been increased by about 1 dB, relatively to the single-polarization equalizers, and up to 3 dB over linear equalization, with a corresponding bit error rate (BER) reduction of up to 63% and 85%, respectively. Despite of the impact of inter-channel nonlinearities, we show that intra-channel nonlinear equalization is still able to provide approximately 1 dB improvement in the optimum power and a BER reduction of ~33%, considering a 66 GHz WDM grid. By means of simulation, we demonstrate that the performance of nonlinear equalization can be substantially enhanced if both optical and electrical filtering are optimized, enabling the VSNE technique to outperform its SSF counterpart at high input powers.

Identification of differentially expressed genes and signalling pathways in bark of Hevea brasiliensis seedlings associated with secondary laticifer differentiation using gene expression microarray.

PubMed

Loh, Swee Cheng; Thottathil, Gincy P; Othman, Ahmad Sofiman

2016-10-01

The natural rubber of Para rubber tree, Hevea brasiliensis, is the main crop involved in industrial rubber production due to its superior quality. The Hevea bark is commercially exploited to obtain latex, which is produced from the articulated secondary laticifer. The laticifer is well defined in the aspect of morphology; however, only some genes associated with its development have been reported. We successfully induced secondary laticifer in the jasmonic acid (JA)-treated and linolenic acid (LA)-treated Hevea bark but secondary laticifer is not observed in the ethephon (ET)-treated and untreated Hevea bark. In this study, we analysed 27,195 gene models using NimbleGen microarrays based on the Hevea draft genome. 491 filtered differentially expressed (FDE) transcripts that are common to both JA- and LA-treated bark samples but not ET-treated bark samples were identified. In the Eukaryotic Orthologous Group (KOG) analysis, 491 FDE transcripts belong to different functional categories that reflect the diverse processes and pathways involved in laticifer differentiation. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) and KOG analysis, the profile of the FDE transcripts suggest that JA- and LA-treated bark samples have a sufficient molecular basis for secondary laticifer differentiation, especially regarding secondary metabolites metabolism. FDE genes in this category are from the cytochrome (CYP) P450 family, ATP-binding cassette (ABC) transporter family, short-chain dehydrogenase/reductase (SDR) family, or cinnamyl alcohol dehydrogenase (CAD) family. The data includes many genes involved in cell division, cell wall synthesis, and cell differentiation. The most abundant transcript in FDE list was SDR65C, reflecting its importance in laticifer differentiation. Using the Basic Local Alignment Search Tool (BLAST) as part of annotation and functional prediction, several characterised as well as uncharacterized transcription factors and genes were found in the dataset. Hence, the further characterization of these genes is necessary to unveil their role in laticifer differentiation. This study provides a platform for the further characterization and identification of the key genes involved in secondary laticifer differentiation. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Optical fiber grating vibration sensor for vibration monitoring of hydraulic pump

NASA Astrophysics Data System (ADS)

Zhang, Zhengyi; Liu, Chuntong; Li, Hongcai; He, Zhenxin; Zhao, Xiaofeng

2017-06-01

In view of the existing electrical vibration monitoring traditional hydraulic pump vibration sensor, the high false alarm rate is susceptible to electromagnetic interference and is not easy to achieve long-term reliable monitoring, based on the design of a beam of the uniform strength structure of the fiber Bragg grating (FBG) vibration sensor. In this paper, based on the analysis of the vibration theory of the equal strength beam, the principle of FBG vibration tuning based on the equal intensity beam is derived. According to the practical application of the project, the structural dimensions of the equal strength beam are determined, and the optimization design of the vibrator is carried out. The finite element analysis of the sensor is carried out by ANSYS, and the first order resonant frequency is 94.739 Hz. The vibration test of the sensor is carried out by using the vibration frequency of 35 Hz and the vibration source of 50 Hz. The time domain and frequency domain analysis results of test data show that the sensor has good dynamic response characteristics, which can realize the accurate monitoring of the vibration frequency and meet the special requirements of vibration monitoring of hydraulic pump under specific environment.

Applying Frequency-Domain Equalization to Code-Division Multiple Access and Transform-Domain Communications Systems

DTIC Science & Technology

2008-03-01

terms the last time we spoke, I can say without a doubt that he was my favorite cousin. You are both missed, always.... I want to thank my wife for her...IEEE Communications Magazine, 50:S11–S15, September 2005. 3. Haker , M. E. Hardware Realization of a Transform Domain Communication Sys- tem. Master’s

Performance of Frozen Density Embedding for Modeling Hole Transfer Reactions.

PubMed

Ramos, Pablo; Papadakis, Markos; Pavanello, Michele

2015-06-18

We have carried out a thorough benchmark of the frozen density-embedding (FDE) method for calculating hole transfer couplings. We have considered 10 exchange-correlation functionals, 3 nonadditive kinetic energy functionals, and 3 basis sets. Overall, we conclude that with a 7% mean relative unsigned error, the PBE and PW91 functionals coupled with the PW91k nonadditive kinetic energy functional and a TZP basis set constitute the most stable and accurate levels of theory for hole transfer coupling calculations. The FDE-ET method is found to be an excellent tool for computing diabatic couplings for hole transfer reactions.

Numerical solution of distributed order fractional differential equations

NASA Astrophysics Data System (ADS)

Katsikadelis, John T.

2014-02-01

In this paper a method for the numerical solution of distributed order FDEs (fractional differential equations) of a general form is presented. The method applies to both linear and nonlinear equations. The Caputo type fractional derivative is employed. The distributed order FDE is approximated with a multi-term FDE, which is then solved by adjusting appropriately the numerical method developed for multi-term FDEs by Katsikadelis. Several example equations are solved and the response of mechanical systems described by such equations is studied. The convergence and the accuracy of the method for linear and nonlinear equations are demonstrated through well corroborated numerical results.

Combining frozen-density embedding with the conductor-like screening model using Lagrangian techniques for response properties.

PubMed

Schieschke, Nils; Di Remigio, Roberto; Frediani, Luca; Heuser, Johannes; Höfener, Sebastian

2017-07-15

We present the explicit derivation of an approach to the multiscale description of molecules in complex environments that combines frozen-density embedding (FDE) with continuum solvation models, in particular the conductor-like screening model (COSMO). FDE provides an explicit atomistic description of molecule-environment interactions at reduced computational cost, while the outer continuum layer accounts for the effect of long-range isotropic electrostatic interactions. Our treatment is based on a variational Lagrangian framework, enabling rigorous derivations of ground- and excited-state response properties. As an example of the flexibility of the theoretical framework, we derive and discuss FDE + COSMO analytical molecular gradients for excited states within the Tamm-Dancoff approximation (TDA) and for ground states within second-order Møller-Plesset perturbation theory (MP2) and a second-order approximate coupled cluster with singles and doubles (CC2). It is shown how this method can be used to describe vertical electronic excitation (VEE) energies and Stokes shifts for uracil in water and carbostyril in dimethyl sulfoxide (DMSO), respectively. In addition, VEEs for some simplified protein models are computed, illustrating the performance of this method when applied to larger systems. The interaction terms between the FDE subsystem densities and the continuum can influence excitation energies up to 0.3 eV and, thus, cannot be neglected for general applications. We find that the net influence of the continuum in presence of the first FDE shell on the excitation energy amounts to about 0.05 eV for the cases investigated. The present work is an important step toward rigorously derived ab initio multilayer and multiscale modeling approaches. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Fractional differential equations based modeling of microbial survival and growth curves: model development and experimental validation.

PubMed

Kaur, A; Takhar, P S; Smith, D M; Mann, J E; Brashears, M M

2008-10-01

A fractional differential equations (FDEs)-based theory involving 1- and 2-term equations was developed to predict the nonlinear survival and growth curves of foodborne pathogens. It is interesting to note that the solution of 1-term FDE leads to the Weibull model. Nonlinear regression (Gauss-Newton method) was performed to calculate the parameters of the 1-term and 2-term FDEs. The experimental inactivation data of Salmonella cocktail in ground turkey breast, ground turkey thigh, and pork shoulder; and cocktail of Salmonella, E. coli, and Listeria monocytogenes in ground beef exposed at isothermal cooking conditions of 50 to 66 degrees C were used for validation. To evaluate the performance of 2-term FDE in predicting the growth curves-growth of Salmonella typhimurium, Salmonella Enteritidis, and background flora in ground pork and boneless pork chops; and E. coli O157:H7 in ground beef in the temperature range of 22.2 to 4.4 degrees C were chosen. A program was written in Matlab to predict the model parameters and survival and growth curves. Two-term FDE was more successful in describing the complex shapes of microbial survival and growth curves as compared to the linear and Weibull models. Predicted curves of 2-term FDE had higher magnitudes of R(2) (0.89 to 0.99) and lower magnitudes of root mean square error (0.0182 to 0.5461) for all experimental cases in comparison to the linear and Weibull models. This model was capable of predicting the tails in survival curves, which was not possible using Weibull and linear models. The developed model can be used for other foodborne pathogens in a variety of food products to study the destruction and growth behavior.

Stereo Sound Field Controller Design Using Partial Model Matching on the Frequency Domain

NASA Astrophysics Data System (ADS)

Kumon, Makoto; Miike, Katsuhiro; Eguchi, Kazuki; Mizumoto, Ikuro; Iwai, Zenta

The objective of sound field control is to make the acoustic characteristics of a listening room close to those of the desired system. Conventional methods apply feedforward controllers, such as digital filters, to achieve this objective. However, feedback controllers are also necessary in order to attenuate noise or to compensate the uncertainty of the acoustic characteristics of the listening room. Since acoustic characteristics are well modeled on the frequency domain, it is efficient to design controllers with respect to frequency responses, but it is difficult to design a multi input multi output (MIMO) control system on a wide frequency domain. In the present study, a partial model matching method on the frequency domain was adopted because this method requires only sampled data, rather than complex mathematical models of the plant, in order to design controllers for MIMO systems. The partial model matching method was applied to design two-degree-of-freedom controllers for acoustic equalization and noise reduction. Experiments demonstrated effectiveness of the proposed method.

Naringenin degradation by the endophytic diazotroph Herbaspirillum seropedicae SmR1.

PubMed

Marin, A M; Souza, E M; Pedrosa, F O; Souza, L M; Sassaki, G L; Baura, V A; Yates, M G; Wassem, R; Monteiro, R A

2013-01-01

Several bacteria are able to degrade flavonoids either to use them as carbon sources or as a detoxification mechanism. Degradation pathways have been proposed for several bacteria, but the genes responsible are not known. We identified in the genome of the endophyte Herbaspirillum seropedicae SmR1 an operon potentially associated with the degradation of aromatic compounds. We show that this operon is involved in naringenin degradation and that its expression is induced by naringenin and chrysin, two closely related flavonoids. Mutation of fdeA, the first gene of the operon, and fdeR, its transcriptional activator, abolished the ability of H. seropedicae to degrade naringenin.

Hindbrain A2 noradrenergic neuron adenosine 5'-monophosphate-activated protein kinase activation, upstream kinase/phosphorylase protein expression, and receptivity to hormone and fuel reporters of short-term food deprivation are regulated by estradiol.

PubMed

Briski, Karen P; Alenazi, Fahaad S H; Shakya, Manita; Sylvester, Paul W

2017-07-01

Estradiol (E) mitigates acute and postacute adverse effects of 12 hr-food deprivation (FD) on energy balance. Hindbrain 5'-monophosphate-activated protein kinase (AMPK) regulates hyperphagic and hypothalamic metabolic neuropeptide and norepinephrine responses to FD in an E-dependent manner. Energy-state information from AMPK-expressing hindbrain A2 noradrenergic neurons shapes neural responses to metabolic imbalance. Here we investigate the hypothesis that FD causes divergent changes in A2 AMPK activity in E- vs. oil (O)-implanted ovariectomized female rats, alongside dissimilar adjustments in circulating metabolic fuel (glucose, free fatty acids [FFA]) and energy deficit-sensitive hormone (corticosterone, glucagon, leptin) levels. FD decreased blood glucose in oil (O)- but not E-implanted ovariectomized female rats and elevated and reduced glucagon levels in O and E, respectively. FD decreased circulating leptin in O and E, but increased corticosterone and FFA concentrations in E only. Western blot analysis of laser-microdissected A2 neurons showed that glucocorticoid receptor type II and very-long-chain acyl-CoA synthetase 3 protein profiles were amplified in FD/E vs. FD/O. A2 total AMPK protein was elevated without change in activity in FD/O, whereas FD/E exhibited increased AMPK activation along with decreased upstream phosphatase expression. The catecholamine biosynthetic enzyme dopamine-β-hydroxylase (DβH) was increased in FD/O but not FD/E A2 cells. The data show discordance between A2 AMPK activation and glycemic responses to FD; sensor activity was refractory to glucose decrements in FD/O but augmented in FD/E despite stabilized glucose and elevated FFA levels. E-dependent amplification of AMPK activity may reflect adaptive conversion to fatty acid oxidation and/or glucocorticoid stimulation. FD augmentation of A2 DβH protein profiles in FD/O but not FD/E animals suggests that FD may correspondingly regulate NE synthesis vs. metabolism/release in the absence vs. presence of E. Mechanisms underlying translation of E-contingent A2 neuron responses to FD into regulatory signaling remain to be determined. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Analytical time-domain Green’s functions for power-law media

PubMed Central

Kelly, James F.; McGough, Robert J.; Meerschaert, Mark M.

2008-01-01

Frequency-dependent loss and dispersion are typically modeled with a power-law attenuation coefficient, where the power-law exponent ranges from 0 to 2. To facilitate analytical solution, a fractional partial differential equation is derived that exactly describes power-law attenuation and the Szabo wave equation [“Time domain wave-equations for lossy media obeying a frequency power-law,” J. Acoust. Soc. Am. 96, 491–500 (1994)] is an approximation to this equation. This paper derives analytical time-domain Green’s functions in power-law media for exponents in this range. To construct solutions, stable law probability distributions are utilized. For exponents equal to 0, 1∕3, 1∕2, 2∕3, 3∕2, and 2, the Green’s function is expressed in terms of Dirac delta, exponential, Airy, hypergeometric, and Gaussian functions. For exponents strictly less than 1, the Green’s functions are expressed as Fox functions and are causal. For exponents greater than or equal than 1, the Green’s functions are expressed as Fox and Wright functions and are noncausal. However, numerical computations demonstrate that for observation points only one wavelength from the radiating source, the Green’s function is effectively causal for power-law exponents greater than or equal to 1. The analytical time-domain Green’s function is numerically verified against the material impulse response function, and the results demonstrate excellent agreement. PMID:19045774

Fancy plots for SIG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norris, J.; Daniels, B.

1986-02-01

The fancy plot package is a group of five programs which allow the user to make 2- and 3-dimensional document quality plots from the SIG data base. The fancyplot package was developed using a DEC VT100 terminal fitted with a Digital Engineering Retrographics board and the QMS Laserprinter. If a terminal emulates the VT100/Retrographic terminal the package should work. A Pericom terminal for example, works perfectly. The fancy plot package is available to provide report-ready plots without resorting to cutting and pasting. This package is contained in programs FFP, TFP, TDFD, 3DFFP and 3DTFP in directory ERD131::USER2 DISK:(HUDSON.SIG). These programsmore » may be summarized as follows: FFP - 2-Dimensional Frequency Fancy Plots with magnitude/phase option; TFP - 2-Dimensional Time Fancy Plots; TDFD - 2-Dimensional Time Domain Frequency Domain Plots; and 3DFFP - equally spaced 3-Dimensional Frequency Fancy Plots; 3DTFP - equally spaced 3-Dimensional Time Plots. 8 figs.« less

Modelling charge transfer reactions with the frozen density embedding formalism.

PubMed

Pavanello, Michele; Neugebauer, Johannes

2011-12-21

The frozen density embedding (FDE) subsystem formulation of density-functional theory is a useful tool for studying charge transfer reactions. In this work charge-localized, diabatic states are generated directly with FDE and used to calculate electronic couplings of hole transfer reactions in two π-stacked nucleobase dimers of B-DNA: 5'-GG-3' and 5'-GT-3'. The calculations rely on two assumptions: the two-state model, and a small differential overlap between donor and acceptor subsystem densities. The resulting electronic couplings agree well with benchmark values for those exchange-correlation functionals that contain a high percentage of exact exchange. Instead, when semilocal GGA functionals are used the electronic couplings are grossly overestimated.

Ursodeoxycholic acid induced generalized fixed drug eruption.

PubMed

Ozkol, Hatice Uce; Calka, Omer; Dulger, Ahmet Cumhur; Bulut, Gulay

2014-09-01

Fixed drug eruption (FDE) is a rare form of drug allergies that recur at the same cutaneous or mucosal site in every usage of drug. Single or multiple round, sharply demarcated and dusky red plaques appear soon after drug exposure. Ursodeoxycholic acid (UDCA: 3α,7β-dihydroxy-5β-cholanic acid) is used for the treatment of cholestatic liver diseases. Some side effects may be observed, such as diarrhea, dyspepsia, pruritus and headaches. We encountered only three cases of lichenoid reaction regarding the use of UDCA among previous studies. In this article, we reported a generalized FDE case related to UDCA intake in a 59-year-old male patient with cholestasis for the first time in the literature.

Laplace-Fourier-domain dispersion analysis of an average derivative optimal scheme for scalar-wave equation

NASA Astrophysics Data System (ADS)

Chen, Jing-Bo

2014-06-01

By using low-frequency components of the damped wavefield, Laplace-Fourier-domain full waveform inversion (FWI) can recover a long-wavelength velocity model from the original undamped seismic data lacking low-frequency information. Laplace-Fourier-domain modelling is an important foundation of Laplace-Fourier-domain FWI. Based on the numerical phase velocity and the numerical attenuation propagation velocity, a method for performing Laplace-Fourier-domain numerical dispersion analysis is developed in this paper. This method is applied to an average-derivative optimal scheme. The results show that within the relative error of 1 per cent, the Laplace-Fourier-domain average-derivative optimal scheme requires seven gridpoints per smallest wavelength and smallest pseudo-wavelength for both equal and unequal directional sampling intervals. In contrast, the classical five-point scheme requires 23 gridpoints per smallest wavelength and smallest pseudo-wavelength to achieve the same accuracy. Numerical experiments demonstrate the theoretical analysis.

Modelling charge transfer reactions with the frozen density embedding formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavanello, Michele; Neugebauer, Johannes

2011-12-21

The frozen density embedding (FDE) subsystem formulation of density-functional theory is a useful tool for studying charge transfer reactions. In this work charge-localized, diabatic states are generated directly with FDE and used to calculate electronic couplings of hole transfer reactions in two {pi}-stacked nucleobase dimers of B-DNA: 5{sup '}-GG-3{sup '} and 5{sup '}-GT-3{sup '}. The calculations rely on two assumptions: the two-state model, and a small differential overlap between donor and acceptor subsystem densities. The resulting electronic couplings agree well with benchmark values for those exchange-correlation functionals that contain a high percentage of exact exchange. Instead, when semilocal GGA functionalsmore » are used the electronic couplings are grossly overestimated.« less

Handwriting Examination: Moving from Art to Science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarman, Kristin H.; Hanlen, Richard C.; Manzolillo, P. A.

The scientific basis for handwriting individuality and the expertise of handwriting examiners has been questioned in several court cases and law review articles. The criticisms were originally directed at the proficiency and expertise of forensic document examiners (FDE's). However, these criticisms also illustrate the lack of empirical data to support and validate the premises and methodology of handwriting examination. As a result the admissibility and weight of FDE testimony has been called into question. These assaults on the scientific integrity of handwriting analysis have created an urgent need for the forensic document examination community to develop objective standards, measurable criteriamore » and a uniform methodology supported by properly controlled studies that evaluate and validate the significance of measurable handwriting characteristics.« less

Fatigue effect in ferroelectric crystals: Growth of the frozen domains

NASA Astrophysics Data System (ADS)

Shur, V. Ya.; Akhmatkhanov, A. R.; Baturin, I. S.

2012-06-01

The model of the fatigue effect during cyclic switching caused by growth of the frozen domain area with charged domain walls has been proposed. It was claimed on the basis of the previous experimental results that for switching in increasing field the frozen domain area started to grow at the given sub-threshold field value and stopped at the threshold field. The influence of the shape and frequency of the field pulses used for cyclic switching has been considered. The uniaxial ferroelectric stoichiometric lithium tantalate single crystals produced by vapor transport equilibration with record low value of coercive field have been chosen as a model material for experimental verification of the model. The formation of the charged domain walls as a result of cyclic switching has been revealed by analysis of the domain images obtained by optical and Raman confocal microscopy. It has been shown that the fatigue degree is equal to the fraction of the frozen domain area. The experimental dependence of the switched charge on the cycle number has been successfully fitted by modified Kolmogorov-Avrami formula. The experimentally observed frequency independence of fatigue profile for rectangular pulses and frequency dependence for triangular pulses has been explained by proposed model.

Computationally efficient algorithm for high sampling-frequency operation of active noise control

NASA Astrophysics Data System (ADS)

Rout, Nirmal Kumar; Das, Debi Prasad; Panda, Ganapati

2015-05-01

In high sampling-frequency operation of active noise control (ANC) system the length of the secondary path estimate and the ANC filter are very long. This increases the computational complexity of the conventional filtered-x least mean square (FXLMS) algorithm. To reduce the computational complexity of long order ANC system using FXLMS algorithm, frequency domain block ANC algorithms have been proposed in past. These full block frequency domain ANC algorithms are associated with some disadvantages such as large block delay, quantization error due to computation of large size transforms and implementation difficulties in existing low-end DSP hardware. To overcome these shortcomings, the partitioned block ANC algorithm is newly proposed where the long length filters in ANC are divided into a number of equal partitions and suitably assembled to perform the FXLMS algorithm in the frequency domain. The complexity of this proposed frequency domain partitioned block FXLMS (FPBFXLMS) algorithm is quite reduced compared to the conventional FXLMS algorithm. It is further reduced by merging one fast Fourier transform (FFT)-inverse fast Fourier transform (IFFT) combination to derive the reduced structure FPBFXLMS (RFPBFXLMS) algorithm. Computational complexity analysis for different orders of filter and partition size are presented. Systematic computer simulations are carried out for both the proposed partitioned block ANC algorithms to show its accuracy compared to the time domain FXLMS algorithm.

Parallel-Processing Equalizers for Multi-Gbps Communications

NASA Technical Reports Server (NTRS)

Gray, Andrew; Ghuman, Parminder; Hoy, Scott; Satorius, Edgar H.

2004-01-01

Architectures have been proposed for the design of frequency-domain least-mean-square complex equalizers that would be integral parts of parallel- processing digital receivers of multi-gigahertz radio signals and other quadrature-phase-shift-keying (QPSK) or 16-quadrature-amplitude-modulation (16-QAM) of data signals at rates of multiple gigabits per second. Equalizers as used here denotes receiver subsystems that compensate for distortions in the phase and frequency responses of the broad-band radio-frequency channels typically used to convey such signals. The proposed architectures are suitable for realization in very-large-scale integrated (VLSI) circuitry and, in particular, complementary metal oxide semiconductor (CMOS) application- specific integrated circuits (ASICs) operating at frequencies lower than modulation symbol rates. A digital receiver of the type to which the proposed architecture applies (see Figure 1) would include an analog-to-digital converter (A/D) operating at a rate, fs, of 4 samples per symbol period. To obtain the high speed necessary for sampling, the A/D and a 1:16 demultiplexer immediately following it would be constructed as GaAs integrated circuits. The parallel-processing circuitry downstream of the demultiplexer, including a demodulator followed by an equalizer, would operate at a rate of only fs/16 (in other words, at 1/4 of the symbol rate). The output from the equalizer would be four parallel streams of in-phase (I) and quadrature (Q) samples.

Method of detecting system function by measuring frequency response

DOEpatents

Morrison, John L.; Morrison, William H.

2008-07-01

Real time battery impedance spectrum is acquired using one time record, Compensated Synchronous Detection (CSD). This parallel method enables battery diagnostics. The excitation current to a test battery is a sum of equal amplitude sin waves of a few frequencies spread over range of interest. The time profile of this signal has duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known, synchronous detection processes the time record and each component, both magnitude and phase, is obtained. For compensation, the components, except the one of interest, are reassembled in the time domain. The resulting signal is subtracted from the original signal and the component of interest is synchronously detected. This process is repeated for each component.

Method of Detecting System Function by Measuring Frequency Response

NASA Technical Reports Server (NTRS)

Morrison, John L. (Inventor); Morrison, William H. (Inventor)

2008-01-01

Real time battery impedance spectrum is acquired using one time record, Compensated Synchronous Detection (CSD). This parallel method enables battery diagnostics. The excitation current to a test battery is a sum of equal amplitude sin waves of a few frequencies spread over range of interest. The time profile of this signal has duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known, synchronous detection processes the time record and each component, both magnitude and phase, is obtained. For compensation, the components, except the one of interest, are reassembled in the time domain. The resulting signal is subtracted from the original signal and the component of interest is synchronously detected. This process is repeated for each component.

Stepped frequency ground penetrating radar

DOEpatents

Vadnais, Kenneth G.; Bashforth, Michael B.; Lewallen, Tricia S.; Nammath, Sharyn R.

1994-01-01

A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

A minimax technique for time-domain design of preset digital equalizers using linear programming

NASA Technical Reports Server (NTRS)

Vaughn, G. L.; Houts, R. C.

1975-01-01

A linear programming technique is presented for the design of a preset finite-impulse response (FIR) digital filter to equalize the intersymbol interference (ISI) present in a baseband channel with known impulse response. A minimax technique is used which minimizes the maximum absolute error between the actual received waveform and a specified raised-cosine waveform. Transversal and frequency-sampling FIR digital filters are compared as to the accuracy of the approximation, the resultant ISI and the transmitted energy required. The transversal designs typically have slightly better waveform accuracy for a given distortion; however, the frequency-sampling equalizer uses fewer multipliers and requires less transmitted energy. A restricted transversal design is shown to use the least number of multipliers at the cost of a significant increase in energy and loss of waveform accuracy at the receiver.

Method of estimating pulse response using an impedance spectrum

DOEpatents

Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

2014-10-21

Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

Identification of pilot-vehicle dynamics from simulation and flight test

NASA Technical Reports Server (NTRS)

Hess, Ronald A.

1990-01-01

The paper discusses an identification problem in which a basic feedback control structure, or pilot control strategy, is hypothesized. Identification algorithms are employed to determine the particular form of pilot equalization in each feedback loop. It was found that both frequency- and time-domain identification techniques provide useful information.

Equivalence of linear canonical transform domains to fractional Fourier domains and the bicanonical width product: a generalization of the space-bandwidth product.

PubMed

Oktem, Figen S; Ozaktas, Haldun M

2010-08-01

Linear canonical transforms (LCTs) form a three-parameter family of integral transforms with wide application in optics. We show that LCT domains correspond to scaled fractional Fourier domains and thus to scaled oblique axes in the space-frequency plane. This allows LCT domains to be labeled and ordered by the corresponding fractional order parameter and provides insight into the evolution of light through an optical system modeled by LCTs. If a set of signals is highly confined to finite intervals in two arbitrary LCT domains, the space-frequency (phase space) support is a parallelogram. The number of degrees of freedom of this set of signals is given by the area of this parallelogram, which is equal to the bicanonical width product but usually smaller than the conventional space-bandwidth product. The bicanonical width product, which is a generalization of the space-bandwidth product, can provide a tighter measure of the actual number of degrees of freedom, and allows us to represent and process signals with fewer samples.

Note on zero temperature holographic superfluids

NASA Astrophysics Data System (ADS)

Guo, Minyong; Lan, Shanquan; Niu, Chao; Tian, Yu; Zhang, Hongbao

2016-06-01

In this note, we have addressed various issues on zero temperature holographic superfluids. First, inspired by our numerical evidence for the equality between the superfluid density and particle density, we provide an elegant analytic proof for this equality by a boost trick. Second, using not only the frequency domain analysis but also the time domain analysis from numerical relativity, we identify the hydrodynamic normal modes and calculate out the sound speed, which is shown to increase with the chemical potential and saturate to the value predicted by the conformal field theory in the large chemical potential limit. Third, the generic non-thermalization is demonstrated by the fully nonlinear time evolution from a non-equilibrium state for our zero temperature holographic superfluid. Furthermore, a conserved Noether charge is proposed in support of this behavior.

Ultrasonic Resonance Spectroscopy of Composite Rings for Flywheel Rotors

NASA Technical Reports Server (NTRS)

Harmon, Laura M.; Baaklini, George Y.

2001-01-01

Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The system employs a swept frequency approach and performs a fast Fourier transform on the frequency spectrum of the response signal. In addition. the system allows for equalization of the frequency spectrum, providing all frequencies with equal amounts of energy to excite higher order resonant harmonics. Interpretation of the second fast Fourier transform, along with equalization of the frequency spectrum, offers greater assurance in acquiring and analyzing the fundamental frequency, or spectrum resonance spacing. The range of frequencies swept in a pitch-catch mode was varied up to 8 MHz, depending on the material and geometry of the component. Single and multilayered material samples, with and without known defects, were evaluated to determine how the constituents of a composite material system affect the resonant frequency. Amplitude and frequency changes in the spectrum and spectrum resonance spacing domains were examined from ultrasonic responses of a flat composite coupon, thin composite rings, and thick composite rings. Also, the ultrasonic spectroscopy responses from areas with an intentional delamination and a foreign material insert, similar to defects that may occur during manufacturing malfunctions, were compared with those from defect-free areas in thin composite rings. A thick composite ring with varying thickness was tested to investigate the full-thickness resonant frequency and any possible bulk interfacial bond issues. Finally, the effect on the frequency response of naturally occurring single and clustered voids in a composite ring was established.

Linear and nonlinear frequency- and time-domain spectroscopy with multiple frequency combs.

PubMed

Bennett, Kochise; Rouxel, Jeremy R; Mukamel, Shaul

2017-09-07

Two techniques that employ equally spaced trains of optical pulses to map an optical high frequency into a low frequency modulation of the signal that can be detected in real time are compared. The development of phase-stable optical frequency combs has opened up new avenues to metrology and spectroscopy. The ability to generate a series of frequency spikes with precisely controlled separation permits a fast, highly accurate sampling of the material response. Recently, pairs of frequency combs with slightly different repetition rates have been utilized to down-convert material susceptibilities from the optical to microwave regime where they can be recorded in real time. We show how this one-dimensional dual comb technique can be extended to multiple dimensions by using several combs. We demonstrate how nonlinear susceptibilities can be quickly acquired using this technique. In a second class of techniques, sequences of ultrafast mode locked laser pulses are used to recover pathways of interactions contributing to nonlinear susceptibilities by using a photo-acoustic modulation varying along the sequences. We show that these techniques can be viewed as a time-domain analog of the multiple frequency comb scheme.

A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

NASA Astrophysics Data System (ADS)

Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

2017-02-01

We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

The Complexity of School Racial Climate: Reliability and Validity of a New Measure for Secondary Students

ERIC Educational Resources Information Center

Byrd, Christy M.

2017-01-01

Background: The conceptualization of the role of race and culture in students' experience of school has been limited. This study presents a more comprehensive and multidimensional framework than previously conceptualized and includes the two domains of (1) intergroup interactions (frequency of interaction, quality of interaction, equal status, and…

Calculating hyperfine couplings in large ionic crystals containing hundreds of QM atoms: subsystem DFT is the key.

PubMed

Kevorkyants, Ruslan; Wang, Xiqiao; Close, David M; Pavanello, Michele

2013-11-14

We present an application of the linear scaling frozen density embedding (FDE) formulation of subsystem DFT to the calculation of isotropic hyperfine coupling constants (hfcc's) of atoms belonging to a guanine radical cation embedded in a guanine hydrochloride monohydrate crystal. The model systems range from an isolated guanine to a 15,000 atom QM/MM cluster where the QM region is comprised of 36 protonated guanine cations, 36 chlorine anions, and 42 water molecules. Our calculations show that the embedding effects of the surrounding crystal cannot be reproduced by small model systems nor by a pure QM/MM procedure. Instead, a large QM region is needed to fully capture the complicated nature of the embedding effects in this system. The unprecedented system size for a relativistic all-electron isotropic hfcc calculation can be approached in this work because the local nature of the electronic structure of the organic crystals considered is fully captured by the FDE approach.

Handwriting Examination: Moving from Art to Science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarman, K.H.; Hanlen, R.C.; Manzolillo, P.A.

In this document, we present a method for validating the premises and methodology of forensic handwriting examination. This method is intuitively appealing because it relies on quantitative measurements currently used qualitatively by FDE's in making comparisons, and it is scientifically rigorous because it exploits the power of multivariate statistical analysis. This approach uses measures of both central tendency and variation to construct a profile for a given individual. (Central tendency and variation are important for characterizing an individual's writing and both are currently used by FDE's in comparative analyses). Once constructed, different profiles are then compared for individuality using clustermore » analysis; they are grouped so that profiles within a group cannot be differentiated from one another based on the measured characteristics, whereas profiles between groups can. The cluster analysis procedure used here exploits the power of multivariate hypothesis testing. The result is not only a profile grouping but also an indication of statistical significance of the groups generated.« less

Analytical gradients for subsystem density functional theory within the slater-function-based amsterdam density functional program.

PubMed

Schlüns, Danny; Franchini, Mirko; Götz, Andreas W; Neugebauer, Johannes; Jacob, Christoph R; Visscher, Lucas

2017-02-05

We present a new implementation of analytical gradients for subsystem density-functional theory (sDFT) and frozen-density embedding (FDE) into the Amsterdam Density Functional program (ADF). The underlying theory and necessary expressions for the implementation are derived and discussed in detail for various FDE and sDFT setups. The parallel implementation is numerically verified and geometry optimizations with different functional combinations (LDA/TF and PW91/PW91K) are conducted and compared to reference data. Our results confirm that sDFT-LDA/TF yields good equilibrium distances for the systems studied here (mean absolute deviation: 0.09 Å) compared to reference wave-function theory results. However, sDFT-PW91/PW91k quite consistently yields smaller equilibrium distances (mean absolute deviation: 0.23 Å). The flexibility of our new implementation is demonstrated for an HCN-trimer test system, for which several different setups are applied. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

FBMC receiver for multi-user asynchronous transmission on fragmented spectrum

NASA Astrophysics Data System (ADS)

Doré, Jean-Baptiste; Berg, Vincent; Cassiau, Nicolas; Kténas, Dimitri

2014-12-01

Relaxed synchronization and access to fragmented spectrum are considered for future generations of wireless networks. Frequency division multiple access for filter bank multicarrier (FBMC) modulation provides promising performance without strict synchronization requirements contrary to conventional orthogonal frequency division multiplexing (OFDM). The architecture of a FBMC receiver suitable for this scenario is considered. Carrier frequency offset (CFO) compensation is combined with intercarrier interference (ICI) cancellation and performs well under very large frequency offsets. Channel estimation and interpolation had to be adapted and proved effective even for heavily fragmented spectrum usage. Channel equalization can sustain large delay spread. Because all the receiver baseband signal processing functionalities are proposed in the frequency domain, the overall architecture is suitable for multiuser asynchronous transmission on fragmented spectrum.

The use of linear programming techniques to design optimal digital filters for pulse shaping and channel equalization

NASA Technical Reports Server (NTRS)

Houts, R. C.; Burlage, D. W.

1972-01-01

A time domain technique is developed to design finite-duration impulse response digital filters using linear programming. Two related applications of this technique in data transmission systems are considered. The first is the design of pulse shaping digital filters to generate or detect signaling waveforms transmitted over bandlimited channels that are assumed to have ideal low pass or bandpass characteristics. The second is the design of digital filters to be used as preset equalizers in cascade with channels that have known impulse response characteristics. Example designs are presented which illustrate that excellent waveforms can be generated with frequency-sampling filters and the ease with which digital transversal filters can be designed for preset equalization.

Phase noise suppression for coherent optical block transmission systems: a unified framework.

PubMed

Yang, Chuanchuan; Yang, Feng; Wang, Ziyu

2011-08-29

A unified framework for phase noise suppression is proposed in this paper, which could be applied in any coherent optical block transmission systems, including coherent optical orthogonal frequency-division multiplexing (CO-OFDM), coherent optical single-carrier frequency-domain equalization block transmission (CO-SCFDE), etc. Based on adaptive modeling of phase noise, unified observation equations for different coherent optical block transmission systems are constructed, which lead to unified phase noise estimation and suppression. Numerical results demonstrate that the proposal is powerful in mitigating laser phase noise.

Dual-LP11 mode 4×4 MIMO-OFDM transmission over a two-mode fiber.

PubMed

Al Amin, Abdullah; Li, An; Chen, Simin; Chen, Xi; Gao, Guanjun; Shieh, William

2011-08-15

We report successful transmission of dual-LP(11) mode (LP(11a) and LP(11b)), dual polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) signals over two-mode fibers (TMF) using all-fiber mode converters. Mode converters based on mechanically induced long-period grating with better than 20 dB extinction ratios are realized and used for interfacing single-mode fiber transmitter and receivers to the TMF. We demonstrate that by using 4×4 MIMO-OFDM processing, the random coupling of the two LP(11) spatial modes can be successfully tracked and equalized with a one-tap frequency-domain equalizer. We achieve successful transmission of 35.3 Gb/s over 26-km two-mode fiber with less than 3 dB penalty. © 2011 Optical Society of America

Effect of the centrifugal force on domain chaos in Rayleigh-Bénard convection.

PubMed

Becker, Nathan; Scheel, J D; Cross, M C; Ahlers, Guenter

2006-06-01

Experiments and simulations from a variety of sample sizes indicated that the centrifugal force significantly affects the domain-chaos state observed in rotating Rayleigh-Bénard convection-patterns. In a large-aspect-ratio sample, we observed a hybrid state consisting of domain chaos close to the sample center, surrounded by an annulus of nearly stationary nearly radial rolls populated by occasional defects reminiscent of undulation chaos. Although the Coriolis force is responsible for domain chaos, by comparing experiment and simulation we show that the centrifugal force is responsible for the radial rolls. Furthermore, simulations of the Boussinesq equations for smaller aspect ratios neglecting the centrifugal force yielded a domain precession-frequency f approximately epsilon(mu) with mu approximately equal to 1 as predicted by the amplitude-equation model for domain chaos, but contradicted by previous experiment. Additionally the simulations gave a domain size that was larger than in the experiment. When the centrifugal force was included in the simulation, mu and the domain size were consistent with experiment.

Analysis performed in support of the Ad-Hoc Working Group of RTCA SC-159 on RAIM/FDE issues

DOT National Transportation Integrated Search

2002-01-01

In 1999, the FAA requested that RTCA SC-159 address one of the recommendations from the study performed by the Johns Hopkins University (JHU) Applied Physics Lab (APL) on the use of GPS and augmented GPS for aviation applications. This recommendation...

Quantitative near-infrared spectroscopy on patients with peripheral vascular disease

NASA Astrophysics Data System (ADS)

Franceschini, Maria-Angela; Fantini, Sergio; Palumbo, Renato; Pasqualini, Leonella; Vaudo, Gaetano; Franceschini, Edoardo; Gratton, Enrico; Palumbo, Barbara; Innocente, Salvatore; Mannarino, Elmo

1998-01-01

We have used near-infrared spectroscopy to measure the hemoglobin saturation at rest and during exercise on patients affected by peripheral vascular disease (PVD). The instrument used in our study is a frequency-domain tissue oximeter which employs intensity modulated (110 MHz) laser diodes. We examined 9 subjects, 3 of which were controls and 6 were patients affected by stage II PVD. The optical probe was located on the calf muscle of the subjects. The measurement protocol consisted of: (1) baseline (approximately 5 min); (2) stationary bicycle exercise (approximately 5 min); (3) recovery (approximately 15 min). The change in hemoglobin saturation during exercise ((Delta) Y) and the recovery time after exercise (trec) were significantly greater in the PVD patients ((Delta) Y equals -21 +/- 3%, trec equals 5.9 +/- 3.8 min) than in the control subjects ((Delta) Y equals 2 +/- 3%, trec equals 0.6 +/- 0.1 min).

Method of detecting system function by measuring frequency response

NASA Technical Reports Server (NTRS)

Morrison, John L. (Inventor); Morrison, William H. (Inventor); Christophersen, Jon P. (Inventor)

2012-01-01

Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

Method of detecting system function by measuring frequency response

DOEpatents

Morrison, John L [Butte, MT; Morrison, William H [Manchester, CT; Christophersen, Jon P [Idaho Falls, ID

2012-04-03

Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

Optomechanical frequency combs

NASA Astrophysics Data System (ADS)

Miri, Mohammad-Ali; D’Aguanno, Giuseppe; Alù, Andrea

2018-04-01

We study the formation of frequency combs in a single-mode optomechanical cavity. The comb is composed of equidistant spectral lines centered at the pump laser frequency and located at different harmonics of the mechanical resonator. We investigate the classical nonlinear dynamics of such system and find analytically the onset of parametric instability resulting in the breakdown of a stationary continuous wave intracavity field into a periodic train of pulses, which in the Fourier domain gives rise to a broadband frequency comb. Different dynamical regimes, including a stationary state, frequency comb generation and chaos, and their dependence on the system parameters, are studied both analytically and numerically. Interestingly, the comb generation is found to be more robust in the poor cavity limit, where optical loss is equal or larger than the mechanical resonance frequency. Our results show that optomechanical resonators open exciting opportunities for microwave photonics as compact and robust sources of frequency combs with megahertz line spacing.

Frequency dependent Lg attenuation in south-central Alaska

USGS Publications Warehouse

McNamara, D.E.

2000-01-01

The characteristics of seismic energy attenuation are determined using high frequency Lg waves from 27 crustal earthquakes, in south-central Alaska. Lg time-domain amplitudes are measured in five pass-bands and inverted to determine a frequency-dependent quality factor, Q(f), model for south-central Alaska. The inversion in this study yields the frequency-dependent quality factor, in the form of a power law: Q(f) = Q0fη = 220(±30) f0.66(±0.09) (0.75≤f≤12Hz). The results from this study are remarkably consistent with frequency dependent quality factor estimates, using local S-wave coda, in south-central Alaska. The consistency between S-coda Q(f) and Lg Q(f) enables constraints to be placed on the mechanism of crustal attenuation in south-central Alaska. For the range of frequencies considered in this study both scattering and intrinsic attenuation mechanisms likely play an equal role.

A pattern jitter free AFC scheme for mobile satellite systems

NASA Technical Reports Server (NTRS)

Yoshida, Shousei

1993-01-01

This paper describes a scheme for pattern jitter free automatic frequency control (AFC) with a wide frequency acquisition range. In this scheme, equalizing signals fed to the frequency discriminator allow pattern jitter free performance to be achieved for all roll-off factors. In order to define the acquisition range, frequency discrimination characateristics are analyzed on a newly derived frequency domain model. As a result, it is shown that a sufficiently wide acquisition range over a given system symbol rate can be achieved independent of symbol timing errors. Additionally, computer simulation demonstrates that frequency jitter performance improves in proportion to E(sub b)/N(sub 0) because pattern-dependent jitter is suppressed in the discriminator output. These results show significant promise for applciation to mobile satellite systems, which feature relatively low symbol rate transmission with an approximately 0.4-0.7 roll-off factor.

Department of Transportation Data Communications Requirements Analysis.

DTIC Science & Technology

1981-07-01

National Technical Information Service, Springfield, Virginia 22161. CJ0 us Department of Transportation FdeWAtcMk Adl*lt,. and Systems Research...General Administrative System . .. ................. 4.4 4.1.3 Coast Guard Administrative System . .. ............... 4.6 4.1.4 Transportation Automated...Office System .. .. ............ 4.6 4.1.5 OST Data Transmission Characteristics .. .. ............. 4.6 4.1.6 OST Data Communications

Rigid body mode identification of the PAH-2 helicopter using the eigensystem realization algorithm

NASA Technical Reports Server (NTRS)

Schenk, Axel; Pappa, Richard S.

1992-01-01

The rigid body modes of the PAH-2 'Tiger' helicopter were identified using the Eigensystem Realization Algorithm (ERA). This work complements ground vibration tests performed using DLR's traditional phase resonance technique and the ISSPA (Identification of Structural System Parameters) method. Rigid body modal parameters are important for ground resonance prediction. Time-domain data for ERA were obtained by inverse Fourier transformation of frequency response functions measured with stepped-sine excitation. Mode purity (based on the Phase Resonance Criterion) was generally equal to or greater than corresponding results obtained in the ground vibration tests. All identified natural frequencies and mode shapes correlate well with corresponding ground vibration test results. The modal identification approach discussed in this report has become increasingly attractive in recent years due to the steadily declining cost and increased performance of scientific computers. As illustrated in this application, modern time-domain methods can be successfully applied to data acquired using DLR's existing test equipment. Some suggestions are made for future applications of time domain modal identification in this manner.

Birth and death of protein domains: A simple model of evolution explains power law behavior

PubMed Central

Karev, Georgy P; Wolf, Yuri I; Rzhetsky, Andrey Y; Berezovskaya, Faina S; Koonin, Eugene V

2002-01-01

Background Power distributions appear in numerous biological, physical and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interactions partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution. Results A simple model of evolution of the domain composition of proteomes was developed, with the following elementary processes: i) domain birth (duplication with divergence), ii) death (inactivation and/or deletion), and iii) innovation (emergence from non-coding or non-globular sequences or acquisition via horizontal gene transfer). This formalism can be described as a birth, death and innovation model (BDIM). The formulas for equilibrium frequencies of domain families of different size and the total number of families at equilibrium are derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models are found and their appearance depending on model parameters is investigated. It is proved that the power law asymptotics appears if, and only if, the model is balanced, i.e. domain duplication and deletion rates are asymptotically equal up to the second order. It is further proved that any power asymptotic with the degree not equal to -1 can appear only if the hypothesis of independence of the duplication/deletion rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, are considered in details and the distributions of the equilibrium frequencies of domain families of different size are determined for each case. We apply the BDIM formalism to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and show an excellent fit between these empirical data and a particular form of the model, the second-order balanced linear BDIM. Calculation of the parameters of these models suggests surprisingly high innovation rates, comparable to the total domain birth (duplication) and elimination rates, particularly for prokaryotic genomes. Conclusions We show that a straightforward model of genome evolution, which does not explicitly include selection, is sufficient to explain the observed distributions of domain family sizes, in which power laws appear as asymptotic. However, for the model to be compatible with the data, there has to be a precise balance between domain birth, death and innovation rates, and this is likely to be maintained by selection. The developed approach is oriented at a mathematical description of evolution of domain composition of proteomes, but a simple reformulation could be applied to models of other evolving networks with preferential attachment. PMID:12379152

Birth and death of protein domains: a simple model of evolution explains power law behavior.

PubMed

Karev, Georgy P; Wolf, Yuri I; Rzhetsky, Andrey Y; Berezovskaya, Faina S; Koonin, Eugene V

2002-10-14

Power distributions appear in numerous biological, physical and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interactions partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution. A simple model of evolution of the domain composition of proteomes was developed, with the following elementary processes: i) domain birth (duplication with divergence), ii) death (inactivation and/or deletion), and iii) innovation (emergence from non-coding or non-globular sequences or acquisition via horizontal gene transfer). This formalism can be described as a birth, death and innovation model (BDIM). The formulas for equilibrium frequencies of domain families of different size and the total number of families at equilibrium are derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models are found and their appearance depending on model parameters is investigated. It is proved that the power law asymptotics appears if, and only if, the model is balanced, i.e. domain duplication and deletion rates are asymptotically equal up to the second order. It is further proved that any power asymptotic with the degree not equal to -1 can appear only if the hypothesis of independence of the duplication/deletion rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, are considered in details and the distributions of the equilibrium frequencies of domain families of different size are determined for each case. We apply the BDIM formalism to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and show an excellent fit between these empirical data and a particular form of the model, the second-order balanced linear BDIM. Calculation of the parameters of these models suggests surprisingly high innovation rates, comparable to the total domain birth (duplication) and elimination rates, particularly for prokaryotic genomes. We show that a straightforward model of genome evolution, which does not explicitly include selection, is sufficient to explain the observed distributions of domain family sizes, in which power laws appear as asymptotic. However, for the model to be compatible with the data, there has to be a precise balance between domain birth, death and innovation rates, and this is likely to be maintained by selection. The developed approach is oriented at a mathematical description of evolution of domain composition of proteomes, but a simple reformulation could be applied to models of other evolving networks with preferential attachment.

Research on fusion algorithm of polarization image in tetrolet domain

NASA Astrophysics Data System (ADS)

Zhang, Dexiang; Yuan, BaoHong; Zhang, Jingjing

2015-12-01

Tetrolets are Haar-type wavelets whose supports are tetrominoes which are shapes made by connecting four equal-sized squares. A fusion method for polarization images based on tetrolet transform is proposed. Firstly, the magnitude of polarization image and angle of polarization image can be decomposed into low-frequency coefficients and high-frequency coefficients with multi-scales and multi-directions using tetrolet transform. For the low-frequency coefficients, the average fusion method is used. According to edge distribution differences in high frequency sub-band images, for the directional high-frequency coefficients are used to select the better coefficients by region spectrum entropy algorithm for fusion. At last the fused image can be obtained by utilizing inverse transform for fused tetrolet coefficients. Experimental results show that the proposed method can detect image features more effectively and the fused image has better subjective visual effect

A time and frequency synchronization method for CO-OFDM based on CMA equalizers

NASA Astrophysics Data System (ADS)

Ren, Kaixuan; Li, Xiang; Huang, Tianye; Cheng, Zhuo; Chen, Bingwei; Wu, Xu; Fu, Songnian; Ping, Perry Shum

2018-06-01

In this paper, an efficient time and frequency synchronization method based on a new training symbol structure is proposed for polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The coarse timing synchronization is achieved by exploiting the correlation property of the first training symbol, and the fine timing synchronization is accomplished by using the time-domain symmetric conjugate of the second training symbol. Furthermore, based on these training symbols, a constant modulus algorithm (CMA) is proposed for carrier frequency offset (CFO) estimation. Theoretical analysis and simulation results indicate that the algorithm has the advantages of robustness to poor optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD). The frequency offset estimation range can achieve [ -Nsc/2 ΔfN , + Nsc/2 ΔfN ] GHz with the mean normalized estimation error below 12 × 10-3 even under the condition of OSNR as low as 10 dB.

Global Hopf bifurcation analysis on a BAM neural network with delays

NASA Astrophysics Data System (ADS)

Sun, Chengjun; Han, Maoan; Pang, Xiaoming

2007-01-01

A delayed differential equation that models a bidirectional associative memory (BAM) neural network with four neurons is considered. By using a global Hopf bifurcation theorem for FDE and a Bendixon's criterion for high-dimensional ODE, a group of sufficient conditions for the system to have multiple periodic solutions are obtained when the sum of delays is sufficiently large.

Method, system and computer-readable media for measuring impedance of an energy storage device

DOEpatents

Morrison, John L.; Morrison, William H.; Christophersen, Jon P.; Motloch, Chester G.

2016-01-26

Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. A time profile of this sampled signal has a duration that is a few periods of the lowest frequency. A voltage response of the battery, average deleted, is an impedance of the battery in a time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time profile by rectifying relative to sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

Diffusion-enhanced Förster resonance energy transfer and the effects of external quenchers and the donor quantum yield.

PubMed

Jacob, Maik H; Dsouza, Roy N; Ghosh, Indrajit; Norouzy, Amir; Schwarzlose, Thomas; Nau, Werner M

2013-01-10

The structural and dynamic properties of a flexible peptidic chain codetermine its biological activity. These properties are imprinted in intrachain site-to-site distances as well as in diffusion coefficients of mutual site-to-site motion. Both distance distribution and diffusion determine the extent of Förster resonance energy transfer (FRET) between two chain sites labeled with a FRET donor and acceptor. Both could be obtained from time-resolved FRET measurements if their individual contributions to the FRET efficiency could be systematically varied. Because the FRET diffusion enhancement (FDE) depends on the donor-fluorescence lifetime, it has been proposed that the FDE can be reduced by shortening the donor lifetime through an external quencher. Benefiting from the high diffusion sensitivity of short-distance FRET, we tested this concept experimentally on a (Gly-Ser)(6) segment labeled with the donor/acceptor pair naphthylalanine/2,3-diazabicyclo[2.2.2]oct-2-ene (NAla/Dbo). Surprisingly, the very effective quencher potassium iodide (KI) had no effect at all on the average donor-acceptor distance, although the donor lifetime was shortened from ca. 36 ns in the absence of KI to ca. 3 ns in the presence of 30 mM KI. We show that the proposed approach had to fail because it is not the experimentally observed but the radiative donor lifetime that controls the FDE. Because of that, any FRET ensemble measurement can easily underestimate diffusion and might be misleading even if it employs the Haas-Steinberg diffusion equation (HSE). An extension of traditional FRET analysis allowed us to evaluate HSE simulations and to corroborate as well as generalize the experimental results. We demonstrate that diffusion-enhanced FRET depends on the radiative donor lifetime as it depends on the diffusion coefficient, a useful symmetry that can directly be applied to distinguish dynamic and structural effects of viscous cosolvents on the polymer chain. We demonstrate that the effective FRET rate and the recovered donor-acceptor distance depend on the quantum yield, most strongly in the absence of diffusion, which has to be accounted for in the interpretation of distance trends monitored by FRET.

Tolerance of the frequency deviation of LO sources at a MIMO system

NASA Astrophysics Data System (ADS)

Xiao, Jiangnan; Li, Xingying; Zhang, Zirang; Xu, Yuming; Chen, Long; Yu, Jianjun

2015-11-01

We analyze and simulate the tolerance of frequency offset at a W-band optical-wireless transmission system. The transmission system adopts optical polarization division multiplexing (PDM), and multiple-input multiple-output (MIMO) reception. The transmission signal adopts optical quadrature phase shift keying (QPSK) modulation, and the generation of millimeter-wave is based on the optical heterodyning technique. After 20-km single-mode fiber-28 (SMF-28) transmission, tens of Gb/s millimeter-wave signal is delivered. At the receiver, two millimeter-wave signals are down-converted into electrical intermediate-frequency (IF) signals in the analog domain by mixing with two electrical local oscillators (LOs) with different frequencies. We investigate the different frequency LO effect on the 2×2 MIMO system performance for the first time, finding that the process during DSP of implementing frequency offset estimation (FOE) before cascaded multi-modulus-algorithm (CMMA) equalization can get rid of the inter-channel interference (ICI) and improve system bit-error-ratio (BER) performance in this type of transmission system.

Frequency-Domain Channel Estimation and Equalization for Single Carrier Underwater Acoustic Communications

DTIC Science & Technology

2007-01-01

synchronization ; vm(k) white Gaussian noise with average power σ2. If the Doppler shift f m,k is significant, then it causes the received signal ym(k) to be time ...intersymbol interference (ISI) to extend over 20-300 symbols at a data rate of 2-10 kilosymbols per second. Another obstacle is the time -varying Doppler... synchronization that employs a phase-locked loop (PLL) or delay-locked loop (DLL). However, the DFE and PLL/DLL have to interact in a nonlinear fashion

Beam-splitter switches based on zenithal bistable liquid-crystal gratings.

PubMed

Zografopoulos, Dimitrios C; Beccherelli, Romeo; Kriezis, Emmanouil E

2014-10-01

The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.

Membrane covered duct lining for high-frequency noise attenuation: prediction using a Chebyshev collocation method.

PubMed

Huang, Lixi

2008-11-01

A spectral method of Chebyshev collocation with domain decomposition is introduced for linear interaction between sound and structure in a duct lined with flexible walls backed by cavities with or without a porous material. The spectral convergence is validated by a one-dimensional problem with a closed-form analytical solution, and is then extended to the two-dimensional configuration and compared favorably against a previous method based on the Fourier-Galerkin procedure and a finite element modeling. The nonlocal, exact Dirichlet-to-Neumann boundary condition is embedded in the domain decomposition scheme without imposing extra computational burden. The scheme is applied to the problem of high-frequency sound absorption by duct lining, which is normally ineffective when the wavelength is comparable with or shorter than the duct height. When a tensioned membrane covers the lining, however, it scatters the incident plane wave into higher-order modes, which then penetrate the duct lining more easily and get dissipated. For the frequency range of f=0.3-3 studied here, f=0.5 being the first cut-on frequency of the central duct, the membrane cover is found to offer an additional 0.9 dB attenuation per unit axial distance equal to half of the duct height.

Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors

NASA Technical Reports Server (NTRS)

Erkmen, Baris I.; Barber, Zeb W.; Dahl, Jason

2014-01-01

Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramér-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal processing of the photocurrent processes at the outputs of the two detectors is to perform log-matched filtering followed by a summation and peak detection. This implies that neither difference detection, nor Fourier-domain peak detection, which are the staples of the state-of-the-art systems, is optimal when a weak local oscillator is employed.

Speech Enhancement Using Gaussian Scale Mixture Models

PubMed Central

Hao, Jiucang; Lee, Te-Won; Sejnowski, Terrence J.

2011-01-01

This paper presents a novel probabilistic approach to speech enhancement. Instead of a deterministic logarithmic relationship, we assume a probabilistic relationship between the frequency coefficients and the log-spectra. The speech model in the log-spectral domain is a Gaussian mixture model (GMM). The frequency coefficients obey a zero-mean Gaussian whose covariance equals to the exponential of the log-spectra. This results in a Gaussian scale mixture model (GSMM) for the speech signal in the frequency domain, since the log-spectra can be regarded as scaling factors. The probabilistic relation between frequency coefficients and log-spectra allows these to be treated as two random variables, both to be estimated from the noisy signals. Expectation-maximization (EM) was used to train the GSMM and Bayesian inference was used to compute the posterior signal distribution. Because exact inference of this full probabilistic model is computationally intractable, we developed two approaches to enhance the efficiency: the Laplace method and a variational approximation. The proposed methods were applied to enhance speech corrupted by Gaussian noise and speech-shaped noise (SSN). For both approximations, signals reconstructed from the estimated frequency coefficients provided higher signal-to-noise ratio (SNR) and those reconstructed from the estimated log-spectra produced lower word recognition error rate because the log-spectra fit the inputs to the recognizer better. Our algorithms effectively reduced the SSN, which algorithms based on spectral analysis were not able to suppress. PMID:21359139

[Erectile dysfunction and obstructive sleep apnea syndrome].

PubMed

Zhuravlev, V N; Frank, M A; Gomzhin, A I

2008-01-01

Of 72 patients with obstructive sleep apnea syndrome (OSAS) 32 had erectile dysfunction (ED). OSAS patients with erectile dysfunction had hypogonadism in 24 cases, in 8 men testosterone level was normal. A polysomnographic investigation with monitoring of nocturnal spontaneous erections showed that 32 patients had severe sleep fragmentation with reduced or complete absence of REM and deep sleep phases. In nocturnal penile tumescencia quantitative and qualitative characteristics were abnormal suggesting organic nature of erectile dysfunction in these patients. Eight ED and OSAS patients with normal testosterone received standard OSAS therapy with administration of FDE-5 type inhibitors. Six months later improvement of the erectile function was observed in 6 patients. OSAS patients with hypogonadism were divided into 2 groups. Group 1 (n = 5) received CPAP therapy and group 2 (n = 19) received OSAS standard therapy. Group 2 was treated with inhibitors of FDE-5 type. Three months later improvement of erectile function was seen only in 8. Group 1 received the inhibitors and testosterone replacement. Three months later all 5 patients had no ED complaints, their testosterone was normal. It is recommended to perform monitoring of nocturnal spontaneous erections in the algorithm of examination of all men with OSAS. All patients with OSAS, ED and documented hypogonadism need testosterone replacement therapy if its level persists low despite adequate therapy of OSAS.

Time-domain comparisons of power law attenuation in causal and noncausal time-fractional wave equations

PubMed Central

Zhao, Xiaofeng; McGough, Robert J.

2016-01-01

The attenuation of ultrasound propagating in human tissue follows a power law with respect to frequency that is modeled by several different causal and noncausal fractional partial differential equations. To demonstrate some of the similarities and differences that are observed in three related time-fractional partial differential equations, time-domain Green's functions are calculated numerically for the power law wave equation, the Szabo wave equation, and for the Caputo wave equation. These Green's functions are evaluated for water with a power law exponent of y = 2, breast with a power law exponent of y = 1.5, and liver with a power law exponent of y = 1.139. Simulation results show that the noncausal features of the numerically calculated time-domain response are only evident very close to the source and that these causal and noncausal time-domain Green's functions converge to the same result away from the source. When noncausal time-domain Green's functions are convolved with a short pulse, no evidence of noncausal behavior remains in the time-domain, which suggests that these causal and noncausal time-fractional models are equally effective for these numerical calculations. PMID:27250193

Comparison of techniques that use the single scattering model to compute the quality factor Q from coda waves

USGS Publications Warehouse

Novelo-Casanova, D. A.; Lee, W.H.K.

1991-01-01

Using simulated coda waves, the resolution of the single-scattering model to extract coda Q (Qc) and its power law frequency dependence was tested. The back-scattering model of Aki and Chouet (1975) and the single isotropic-scattering model of Sato (1977) were examined. The results indicate that: (1) The input Qc models are reasonably well approximated by the two methods; (2) almost equal Qc values are recovered when the techniques sample the same coda windows; (3) low Qc models are well estimated in the frequency domain from the early and late part of the coda; and (4) models with high Qc values are more accurately extracted from late code measurements. ?? 1991 Birkha??user Verlag.

United States Air Force F-35A Operational Basing Environmental Impact Statement. Volume 1

DTIC Science & Technology

2013-09-01

Evaluation (FDE) program and Weapons School (WS) beddown, the F-22 designator was used. Subsequent testing , development, and deployment resulted in...Initial F-35A Operational Basing EIS Final, September 2013 contract to develop the JSF ( designated the F-35 Lightning II). Since then, testing of F...of the aircraft even with system failures. Throughout the design and testing process, safety initiatives took previous best practices for single

A method on error analysis for large-aperture optical telescope control system

NASA Astrophysics Data System (ADS)

Su, Yanrui; Wang, Qiang; Yan, Fabao; Liu, Xiang; Huang, Yongmei

2016-10-01

For large-aperture optical telescope, compared with the performance of azimuth in the control system, arc second-level jitters exist in elevation under different speeds' working mode, especially low-speed working mode in the process of its acquisition, tracking and pointing. The jitters are closely related to the working speed of the elevation, resulting in the reduction of accuracy and low-speed stability of the telescope. By collecting a large number of measured data to the elevation, we do analysis on jitters in the time domain, frequency domain and space domain respectively. And the relation between jitter points and the leading speed of elevation and the corresponding space angle is concluded that the jitters perform as periodic disturbance in space domain and the period of the corresponding space angle of the jitter points is 79.1″ approximately. Then we did simulation, analysis and comparison to the influence of the disturbance sources, like PWM power level output disturbance, torque (acceleration) disturbance, speed feedback disturbance and position feedback disturbance on the elevation to find that the space periodic disturbance still exist in the elevation performance. It leads us to infer that the problems maybe exist in angle measurement unit. The telescope employs a 24-bit photoelectric encoder and we can calculate the encoder grating angular resolution as 79.1016'', which is as the corresponding angle value in the whole encoder system of one period of the subdivision signal. The value is approximately equal to the space frequency of the jitters. Therefore, the working elevation of the telescope is affected by subdivision errors and the period of the subdivision error is identical to the period of encoder grating angular. Through comprehensive consideration and mathematical analysis, that DC subdivision error of subdivision error sources causes the jitters is determined, which is verified in the practical engineering. The method that analyze error sources from time domain, frequency domain and space domain respectively has a very good role in guiding to find disturbance sources for large-aperture optical telescope.

Quanty for core level spectroscopy - excitons, resonances and band excitations in time and frequency domain

NASA Astrophysics Data System (ADS)

Haverkort, Maurits W.

2016-05-01

Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty, a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org.

Image alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowell, Larry Jonathan

Disclosed is a method and device for aligning at least two digital images. An embodiment may use frequency-domain transforms of small tiles created from each image to identify substantially similar, "distinguishing" features within each of the images, and then align the images together based on the location of the distinguishing features. To accomplish this, an embodiment may create equal sized tile sub-images for each image. A "key" for each tile may be created by performing a frequency-domain transform calculation on each tile. A information-distance difference between each possible pair of tiles on each image may be calculated to identify distinguishingmore » features. From analysis of the information-distance differences of the pairs of tiles, a subset of tiles with high discrimination metrics in relation to other tiles may be located for each image. The subset of distinguishing tiles for each image may then be compared to locate tiles with substantially similar keys and/or information-distance metrics to other tiles of other images. Once similar tiles are located for each image, the images may be aligned in relation to the identified similar tiles.« less

Optimized Signaling Method for High-Speed Transmission Channels with Higher Order Transfer Function

NASA Astrophysics Data System (ADS)

Ševčík, Břetislav; Brančík, Lubomír; Kubíček, Michal

2017-08-01

In this paper, the selected results from testing of optimized CMOS friendly signaling method for high-speed communications over cables and printed circuit boards (PCBs) are presented and discussed. The proposed signaling scheme uses modified concept of pulse width modulated (PWM) signal which enables to better equalize significant channel losses during data high-speed transmission. Thus, the very effective signaling method to overcome losses in transmission channels with higher order transfer function, typical for long cables and multilayer PCBs, is clearly analyzed in the time and frequency domain. Experimental results of the measurements include the performance comparison of conventional PWM scheme and clearly show the great potential of the modified signaling method for use in low power CMOS friendly equalization circuits, commonly considered in modern communication standards as PCI-Express, SATA or in Multi-gigabit SerDes interconnects.

Electromagnetic surveys to detect clay-rich sediment in the Rio Grande inner valley, Albuquerque area, New Mexico

USGS Publications Warehouse

Bartolino, James R.; Sterling, Joseph M.

2000-01-01

Information on the presence of clay-rich layers in the inner-valley alluvium is essential for quantifying the amount of water transmitted between the Rio Grande and the Santa Fe Group aquifer system. This report describes a study that used electromagnetic surveys to provide this information. In the first phase of the study, electromagnetic soundings were made using time-domain and frequency-domain electro- magnetic methods. On the basis of these initial results, the time- domain method was judged ineffective because of cultural noise in the study area, so subsequent surveys were made using the frequency-domain method. For the second phase of the study, 31 frequency-domain electromagnetic surveys were conducted along the inner valley and parallel to the Rio Grande in the Albuquerque area in the spring and summer of 1997 to determine the presence of hydrologically significant clay-rich layers buried in the inner-valley alluvium. For this report, the 31 survey sections were combined into 10 composite sections for ease of interpretation. Terrain-conductivity data from the surveys were modeled using interpretation software to produce geoelectric cross sections along the survey lines. This modeling used lithologic logs from two wells installed near the survey lines: the Bosque South and Rio Bravo 5 wells. Because of cultural interference, location of the wells and soundings, complex stratigraphy, and difficulty interpreting lithology, such interpretation was inconclusive. Instead, a decision process based on modeling results was developed using vertical and horizontal dipole 40-meter intercoil spacing terrain-conductivity values. Values larger than or equal to 20 millisiemens per meter were interpreted to contain a hydrologically significant thickness of clay-rich sediment. Thus, clay-rich sediment was interpreted to underlie seven segments of the 10 composited survey lines, totaling at least 2,660 meters of the Rio Grande inner valley. The longest of these clay-rich segments is a 940-meter reach between Bridge and Rio Bravo Boulevards.

A parallel-architecture parametric equalizer for air-coupled capacitive ultrasonic transducers.

PubMed

McSweeney, Sean G; Wright, William M D

2012-01-01

Parametric equalization is rarely applied to ultrasonic transducer systems, for which it could be used on either the transmitter or the receiver to achieve a desired response. An optimized equalizer with both bump and cut capabilities would be advantageous for ultrasonic systems in applications in which variations in the transducer performance or the properties of the propagating medium produce a less-than-desirable signal. Compensation for non-ideal transducer response could be achieved using equalization on a device-by-device basis. Additionally, calibration of ultrasonic systems in the field could be obtained by offline optimization of equalization coefficients. In this work, a parametric equalizer for ultrasonic applications has been developed using multiple bi-quadratic filter elements arranged in a novel parallel arrangement to increase the flexibility of the equalization. The equalizer was implemented on a programmable system-on-chip (PSOC) using a small number of parallel 4th-order infinite impulse response switchedcapacitor band-pass filters. Because of the interdependency of the required coefficients for the switched capacitors, particle swarm optimization (PSO) was used to determine the optimum values. The response of a through-transmission system using air-coupled capacitive ultrasonic transducers was then equalized to idealized Hamming function or brick-wall frequencydomain responses. In each case, there was excellent agreement between the equalized signals and the theoretical model, and the fidelity of the time-domain response was maintained. The bandwidth and center frequency response of the system were significantly improved. It was also shown that the equalizer could be used on either the transmitter or the receiver, and the system could compensate for the effects of transmitterreceiver misalignment. © 2012 IEEE

A joint equalization algorithm in high speed communication systems

NASA Astrophysics Data System (ADS)

Hao, Xin; Lin, Changxing; Wang, Zhaohui; Cheng, Binbin; Deng, Xianjin

2018-02-01

This paper presents a joint equalization algorithm in high speed communication systems. This algorithm takes the advantages of traditional equalization algorithms to use pre-equalization and post-equalization. The pre-equalization algorithm takes the advantage of CMA algorithm, which is not sensitive to the frequency offset. Pre-equalization is located before the carrier recovery loop in order to make the carrier recovery loop a better performance and overcome most of the frequency offset. The post-equalization takes the advantage of MMA algorithm in order to overcome the residual frequency offset. This paper analyzes the advantages and disadvantages of several equalization algorithms in the first place, and then simulates the proposed joint equalization algorithm in Matlab platform. The simulation results shows the constellation diagrams and the bit error rate curve, both these results show that the proposed joint equalization algorithm is better than the traditional algorithms. The residual frequency offset is shown directly in the constellation diagrams. When SNR is 14dB， the bit error rate of the simulated system with the proposed joint equalization algorithm is 103 times better than CMA algorithm, 77 times better than MMA equalization, and 9 times better than CMA-MMA equalization.

Dual-frequency continuous wave optical parametric oscillator

NASA Astrophysics Data System (ADS)

Sun, Bingjie; Wang, Xin; Yang, Suhui; Li, Kun

2018-01-01

This article shows a dual-frequency OPO with multi-grating (28.5-31.5 μm) periodically poled MgO:LiNbO3 (MgO:PPLN) pumped by a dual-frequency continuous wave at 1.064 μm. The wavelengths of idler and signal varying versus temperature at different periods of inverted domains were numerical simulated. It proves that as the temperature rises, or as the poling period increases, the idler wavelength shortens and signal wavelength lengthens. The pump is a 30 W dual-frequency fiber laser MOPA with beat note frequency varying from 125 MHz to 175 MHz. The pump threshold of the bow-tie ring cavity OPO was 3 W. An average dual-frequency idler output power of 2.6 W was obtained when the pump power was 17.2 W at 45 °C. The idler wavelength was 3.4 μm when the poling period was 30.5 μm. The idler wavelength could be tuned from 2.9 μm to 3.9 μm by changing the temperature and the poling period, and the beat note frequency was proved to be equal to that of the pump.

Underwater Equal-Latency Contours of a Harbor Porpoise (Phocoena phocoena) for Tonal Signals Between 0.5 and 125 kHz.

PubMed

Wensveen, Paul J; Huijser, Léonie A E; Hoek, Lean; Kastelein, Ronald A

2016-01-01

Loudness perception can be studied based on the assumption that sounds of equal loudness elicit equal reaction time (RT; or "response latency"). We measured the underwater RTs of a harbor porpoise to narrowband frequency-modulated sounds and constructed six equal-latency contours. The contours paralleled the audiogram at low sensation levels (high RTs). At high-sensation levels, contours flattened between 0.5 and 31.5 kHz but dropped substantially (RTs shortened) beyond those frequencies. This study suggests that equal-latency-based frequency weighting can emulate noise perception in porpoises for low and middle frequencies but that the RT-loudness correlation is relatively weak for very high frequencies.

Mega-Amp Opening Switch with Nested Electrodes/Pulsed Generator of Ion and Ion Cluster Beams

DTIC Science & Technology

1987-07-30

The use of a plasma focus as a mega-amp opening switch has been demonstrated by two modes of operation: (a) Single shot mode; (b) Repetitive Mode...energy level and under the same voltage and filling-pressure conditions but without field distortion elements. Misfirings of the plasma focus machine...are also virtually eliminated by using FDE at the coaxial electrode breech. The tests (based on about 10000 shots and five plasma focus machines

Systematic comparisons between PRISM version 1.0.0, BAP, and CSMIP ground-motion processing

USGS Publications Warehouse

Kalkan, Erol; Stephens, Christopher

2017-02-23

A series of benchmark tests was run by comparing results of the Processing and Review Interface for Strong Motion data (PRISM) software version 1.0.0 to Basic Strong-Motion Accelerogram Processing Software (BAP; Converse and Brady, 1992), and to California Strong Motion Instrumentation Program (CSMIP) processing (Shakal and others, 2003, 2004). These tests were performed by using the MatLAB implementation of PRISM, which is equivalent to its public release version in Java language. Systematic comparisons were made in time and frequency domains of records processed in PRISM and BAP, and in CSMIP, by using a set of representative input motions with varying resolutions, frequency content, and amplitudes. Although the details of strong-motion records vary among the processing procedures, there are only minor differences among the waveforms for each component and within the frequency passband common to these procedures. A comprehensive statistical evaluation considering more than 1,800 ground-motion components demonstrates that differences in peak amplitudes of acceleration, velocity, and displacement time series obtained from PRISM and CSMIP processing are equal to or less than 4 percent for 99 percent of the data, and equal to or less than 2 percent for 96 percent of the data. Other statistical measures, including the Euclidian distance (L2 norm) and the windowed root mean square level of processed time series, also indicate that both processing schemes produce statistically similar products.

A new principle technic for the transformation from frequency domain to time domain

NASA Astrophysics Data System (ADS)

Gao, Ben-Qing

2017-03-01

A principle technic for the transformation from frequency domain to time domain is presented. Firstly, a special type of frequency domain transcendental equation is obtained for an expected frequency domain parameter which is a rational or irrational fraction expression. Secondly, the inverse Laplace transformation is performed. When the two time-domain factors corresponding to the two frequency domain factors at two sides of frequency domain transcendental equation are known quantities, a time domain transcendental equation is reached. At last, the expected time domain parameter corresponding to the expected frequency domain parameter can be solved by the inverse convolution process. Proceeding from rational or irrational fraction expression, all solving process is provided. In the meantime, the property of time domain sequence is analyzed and the strategy for choosing the parameter values is described. Numerical examples are presented to verify the proposed theory and technic. Except for rational or irrational fraction expressions, examples of complex relative permittivity of water and plasma are used as verification method. The principle method proposed in the paper can easily solve problems which are difficult to be solved by Laplace transformation.

Coherent and phase-sensitive phenomena of ultrashort laser pulses propagating in three-level {lambda}-type systems studied with the finite-difference time-domain method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loiko, Yurii; Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Nezaleznasty Ave. 70, 220072 Minsk; Serrat, Carles

2006-06-15

Propagation of single- and two-color hyperbolic secant femtosecond laser pulses in a three-level {lambda}-type quantum system is investigated by solving the Maxwell and density matrix equations with the finite-difference time-domain and Runge-Kutta methods. As a first study of our modeling, we simulate pulse self-induced transparency (SIT) in two-level systems and see how this phenomenon can be controlled by manipulating the initial relative phase between the SIT pulse and a second control pulse, provided the ratio between both pulse frequencies obeys the relation {omega}{sub 1}/{omega}{sub 2}=3. We then examine frequency down-conversion processes that are observed with single- and two-color pulses themore » envelope area of which is equal to or a multiple of 2{pi}, for pulse frequencies close to resonance with the transitions of a three-level {lambda} medium. Also, phase-sensitive phenomena are discussed in the case of two-color {omega}-3{omega} pulses propagating resonantly in the three-level system. In particular, possibilities for such coherent control are found for frequency down-conversion processes when the ratio of the frequencies of optical transitions is {omega}{sub 13}/{omega}{sub 12}=3. The conditions for quantum control of four-wave mixing processes are also examined when the pulse frequencies of two-color {omega}-3{omega} pulses are far from any resonance of the three-level system. We demonstrate the possibility to cancel the phase sensitivity of the four-wave coupling in a {lambda}-type system by competition effects between optical transitions.« less

Remotely manageable system for stabilizing femtosecond lasers

NASA Astrophysics Data System (ADS)

Cizek, Martin; Hucl, Vaclav; Smid, Radek; Mikel, Bretislav; Lazar, Josef; Cip, Ondrej

2014-05-01

In the field of precise measurement of optical frequencies, laser spectroscopy and interferometric distance surveying the optical frequency synthesizers (femtosecond combs) are used as optical frequency references. They generate thousands of narrow-linewidth coherent optical frequencies at the same time. The spacing of generated components equals to the repetition frequency of femtosecond pulses of the laser. The position of the comb spectrum has a frequency offset that is derived from carrier to envelope frequency difference. The repetition frequency and mentioned frequency offset belong to main controlled parameters of the optical frequency comb. If these frequencies are electronically locked an ultrastable frequency standard (i.e. H-maser, Cs- or Rb- clock), its relative stability is transferred to the optical frequency domain. We present a complete digitally controlled signal processing chain for phase-locked loop (PLL) control of the offset frequency. The setup is able to overcome some dropouts caused by the femtosecond laser non-stabilities (temperature drifts, ripple noise and electricity spikes). It is designed as a two-stage control loop, where controlled offset frequency is permanently monitored by digital signal processing. In case of dropouts of PLL, the frequency-locked loop keeps the controlled frequency in the required limits. The presented work gives the possibility of long-time operation of femtosecond combs which is necessary when the optical frequency stability measurement of ultra-stable lasers is required. The detailed description of the modern solution of the PLL with remote management is presented.

A semi-blind logo watermarking scheme for color images by comparison and modification of DFT coefficients

NASA Astrophysics Data System (ADS)

Kusyk, Janusz; Eskicioglu, Ahmet M.

2005-10-01

Digital watermarking is considered to be a major technology for the protection of multimedia data. Some of the important applications are broadcast monitoring, copyright protection, and access control. In this paper, we present a semi-blind watermarking scheme for embedding a logo in color images using the DFT domain. After computing the DFT of the luminance layer of the cover image, the magnitudes of DFT coefficients are compared, and modified. A given watermark is embedded in three frequency bands: Low, middle, and high. Our experiments show that the watermarks extracted from the lower frequencies have the best visual quality for low pass filtering, adding Gaussian noise, JPEG compression, resizing, rotation, and scaling, and the watermarks extracted from the higher frequencies have the best visual quality for cropping, intensity adjustment, histogram equalization, and gamma correction. Extractions from the fragmented and translated image are identical to extractions from the unattacked watermarked image. The collusion and rewatermarking attacks do not provide the hacker with useful tools.

Frequency-Domain Streak Camera and Tomography for Ultrafast Imaging of Evolving and Channeled Plasma Accelerator Structures

NASA Astrophysics Data System (ADS)

Li, Zhengyan; Zgadzaj, Rafal; Wang, Xiaoming; Reed, Stephen; Dong, Peng; Downer, Michael C.

2010-11-01

We demonstrate a prototype Frequency Domain Streak Camera (FDSC) that can capture the picosecond time evolution of the plasma accelerator structure in a single shot. In our prototype Frequency-Domain Streak Camera, a probe pulse propagates obliquely to a sub-picosecond pump pulse that creates an evolving nonlinear index "bubble" in fused silica glass, supplementing a conventional Frequency Domain Holographic (FDH) probe-reference pair that co-propagates with the "bubble". Frequency Domain Tomography (FDT) generalizes Frequency-Domain Streak Camera by probing the "bubble" from multiple angles and reconstructing its morphology and evolution using algorithms similar to those used in medical CAT scans. Multiplexing methods (Temporal Multiplexing and Angular Multiplexing) improve data storage and processing capability, demonstrating a compact Frequency Domain Tomography system with a single spectrometer.

Automatic frequency and phase alignment of in vivo J-difference-edited MR spectra by frequency domain correlation.

PubMed

Wiegers, Evita C; Philips, Bart W J; Heerschap, Arend; van der Graaf, Marinette

2017-12-01

J-difference editing is often used to select resonances of compounds with coupled spins in 1 H-MR spectra. Accurate phase and frequency alignment prior to subtracting J-difference-edited MR spectra is important to avoid artefactual contributions to the edited resonance. In-vivo J-difference-edited MR spectra were aligned by maximizing the normalized scalar product between two spectra (i.e., the correlation over a spectral region). The performance of our correlation method was compared with alignment by spectral registration and by alignment of the highest point in two spectra. The correlation method was tested at different SNR levels and for a broad range of phase and frequency shifts. In-vivo application of the proposed correlation method showed reduced subtraction errors and increased fit reliability in difference spectra as compared with conventional peak alignment. The correlation method and the spectral registration method generally performed equally well. However, better alignment using the correlation method was obtained for spectra with a low SNR (down to ~2) and for relatively large frequency shifts. Our correlation method for simultaneously phase and frequency alignment is able to correct both small and large phase and frequency drifts and also performs well at low SNR levels.

Time and frequency domain characteristics of detrending-operation-based scaling analysis: Exact DFA and DMA frequency responses

NASA Astrophysics Data System (ADS)

Kiyono, Ken; Tsujimoto, Yutaka

2016-07-01

We develop a general framework to study the time and frequency domain characteristics of detrending-operation-based scaling analysis methods, such as detrended fluctuation analysis (DFA) and detrending moving average (DMA) analysis. In this framework, using either the time or frequency domain approach, the frequency responses of detrending operations are calculated analytically. Although the frequency domain approach based on conventional linear analysis techniques is only applicable to linear detrending operations, the time domain approach presented here is applicable to both linear and nonlinear detrending operations. Furthermore, using the relationship between the time and frequency domain representations of the frequency responses, the frequency domain characteristics of nonlinear detrending operations can be obtained. Based on the calculated frequency responses, it is possible to establish a direct connection between the root-mean-square deviation of the detrending-operation-based scaling analysis and the power spectrum for linear stochastic processes. Here, by applying our methods to DFA and DMA, including higher-order cases, exact frequency responses are calculated. In addition, we analytically investigate the cutoff frequencies of DFA and DMA detrending operations and show that these frequencies are not optimally adjusted to coincide with the corresponding time scale.

Time and frequency domain characteristics of detrending-operation-based scaling analysis: Exact DFA and DMA frequency responses.

PubMed

Kiyono, Ken; Tsujimoto, Yutaka

2016-07-01

We develop a general framework to study the time and frequency domain characteristics of detrending-operation-based scaling analysis methods, such as detrended fluctuation analysis (DFA) and detrending moving average (DMA) analysis. In this framework, using either the time or frequency domain approach, the frequency responses of detrending operations are calculated analytically. Although the frequency domain approach based on conventional linear analysis techniques is only applicable to linear detrending operations, the time domain approach presented here is applicable to both linear and nonlinear detrending operations. Furthermore, using the relationship between the time and frequency domain representations of the frequency responses, the frequency domain characteristics of nonlinear detrending operations can be obtained. Based on the calculated frequency responses, it is possible to establish a direct connection between the root-mean-square deviation of the detrending-operation-based scaling analysis and the power spectrum for linear stochastic processes. Here, by applying our methods to DFA and DMA, including higher-order cases, exact frequency responses are calculated. In addition, we analytically investigate the cutoff frequencies of DFA and DMA detrending operations and show that these frequencies are not optimally adjusted to coincide with the corresponding time scale.

Frequency-Domain Streak Camera and Tomography for Ultrafast Imaging of Evolving and Channeled Plasma Accelerator Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhengyan; Zgadzaj, Rafal; Wang Xiaoming

2010-11-04

We demonstrate a prototype Frequency Domain Streak Camera (FDSC) that can capture the picosecond time evolution of the plasma accelerator structure in a single shot. In our prototype Frequency-Domain Streak Camera, a probe pulse propagates obliquely to a sub-picosecond pump pulse that creates an evolving nonlinear index 'bubble' in fused silica glass, supplementing a conventional Frequency Domain Holographic (FDH) probe-reference pair that co-propagates with the 'bubble'. Frequency Domain Tomography (FDT) generalizes Frequency-Domain Streak Camera by probing the 'bubble' from multiple angles and reconstructing its morphology and evolution using algorithms similar to those used in medical CAT scans. Multiplexing methods (Temporalmore » Multiplexing and Angular Multiplexing) improve data storage and processing capability, demonstrating a compact Frequency Domain Tomography system with a single spectrometer.« less

Substructure coupling in the frequency domain

NASA Technical Reports Server (NTRS)

1985-01-01

Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

An Investigation of the Jetevator as a Means of Thrust Vector Control

DTIC Science & Technology

1958-02-01

actual rocket firings. Description of the Tests The cold-flow jetevator tcsts were conduc.ted in the engine test cells of the Ordnance Aerophysics...45 and 210 psia, as noted on the figures. The cel. pres- sure was adjusted to give a ratio of supply pressure to cell pressure of approximately 37...CORPORATO t. r .U and SPACE DIVISION - FDN LMSD-2630 °; •GN F.]DE NT1 .A.L`. -[, GAP DEFLECTED NOZZLE JETEVATOR FLOW 6 =220 JETEVATOR .°=60O HINGE POINT

Yield and depth Estimation of Selected NTS Nuclear and SPE Chemical Explosions Using Source Equalization by modeling Local and Regional Seismograms (Invited)

NASA Astrophysics Data System (ADS)

Saikia, C. K.; Roman-nieves, J. I.; Woods, M. T.

2013-12-01

Source parameters of nuclear and chemical explosions are often estimated by matching either the corner frequency and spectral level of a single event or the spectral ratio when spectra from two events are available with known source parameters for one. In this study, we propose an alternative method in which waveforms from two or more events can be simultaneously equalized by setting the differential of the processed seismograms at one station from any two individual events to zero. The method involves convolving the equivalent Mueller-Murphy displacement source time function (MMDSTF) of one event with the seismogram of the second event and vice-versa, and then computing their difference seismogram. MMDSTF is computed at the elastic radius including both near and far-field terms. For this method to yield accurate source parameters, an inherent assumption is that green's functions for the any paired events from the source to a receiver are same. In the frequency limit of the seismic data, this is a reasonable assumption and is concluded based on the comparison of green's functions computed for flat-earth models at various source depths ranging from 100m to 1Km. Frequency domain analysis of the initial P wave is, however, sensitive to the depth phase interaction, and if tracked meticulously can help estimating the event depth. We applied this method to the local waveforms recorded from the three SPE shots and precisely determined their yields. These high-frequency seismograms exhibit significant lateral path effects in spectrogram analysis and 3D numerical computations, but the source equalization technique is independent of any variation as long as their instrument characteristics are well preserved. We are currently estimating the uncertainty in the derived source parameters assuming the yields of the SPE shots as unknown. We also collected regional waveforms from 95 NTS explosions at regional stations ALQ, ANMO, CMB, COR, JAS LON, PAS, PFO and RSSD. We are currently employing a station based analysis using the equalization technique to estimate depth and yields of many relative to those of the announced explosions; and to develop their relationship with the Mw and Mo for the NTS explosions.

Spatial-frequency composite watermarking for digital image copyright protection

NASA Astrophysics Data System (ADS)

Su, Po-Chyi; Kuo, C.-C. Jay

2000-05-01

Digital watermarks can be classified into two categories according to the embedding and retrieval domain, i.e. spatial- and frequency-domain watermarks. Because the two watermarks have different characteristics and limitations, combination of them can have various interesting properties when applied to different applications. In this research, we examine two spatial-frequency composite watermarking schemes. In both cases, a frequency-domain watermarking technique is applied as a baseline structure in the system. The embedded frequency- domain watermark is robust against filtering and compression. A spatial-domain watermarking scheme is then built to compensate some deficiency of the frequency-domain scheme. The first composite scheme is to embed a robust watermark in images to convey copyright or author information. The frequency-domain watermark contains owner's identification number while the spatial-domain watermark is embedded for image registration to resist cropping attack. The second composite scheme is to embed fragile watermark for image authentication. The spatial-domain watermark helps in locating the tampered part of the image while the frequency-domain watermark indicates the source of the image and prevents double watermarking attack. Experimental results show that the two watermarks do not interfere with each other and different functionalities can be achieved. Watermarks in both domains are detected without resorting to the original image. Furthermore, the resulting watermarked image can still preserve high fidelity without serious visual degradation.

Effects of four kinds of electromagnetic fields (EMF) with different frequency spectrum bands on ovariectomized osteoporosis in mice.

PubMed

Lei, Tao; Li, Feijiang; Liang, Zhuowen; Tang, Chi; Xie, Kangning; Wang, Pan; Dong, Xu; Shan, Shuai; Liu, Juan; Xu, Qiaoling; Luo, Erping; Shen, Guanghao

2017-04-03

Electromagnetic fields (EMF) was considered as a non-invasive modality for treatment of osteoporosis while the effects were diverse with EMF parameters in time domain. In present study, we extended analysis of EMF characteristics from time domain to frequency domain, aiming to investigate effects of four kinds of EMF (LP (1-100 Hz), BP (100-3,000 Hz), HP (3,000-50,000 Hz) and AP (1-50,000 Hz)) on ovariectomized (OVX) osteoporosis (OP) in mice. Forty-eight 3-month-old female BALB/c mice were equally assigned to Sham, OVX, OVX + LP, OVX + BP, OVX + HP and OVX + AP groups (n = 8). After 8-week exposure (3 h/day), LP and BP significantly increased serum bone formation markers and osteogenesis-related gene expressions compared with OVX. Bedsides, LP and BP also slightly increased bone resorption activity compared with OVX, evidenced by increased RANKL/OPG ratio. HP sharply decreased serum bone formation and resporption markers and osteogenesis and osteoclastogenesis related gene expressions compared with OVX. AP had accumulative effects of LP, BP and HP, which significantly increased bone formation and decreased bone resporption activity compared with OVX. As a result, LP, BP and HP exposure did not later deterioration of bone mass, microarchitecture and mechanical strength in OVX mice with OP. However, AP stimulation attenuated OVX-induced bone loss.

Relaxation phenomena in AOT-water-decane critical and dense microemulsions

NASA Astrophysics Data System (ADS)

Letamendia, L.; Pru-Lestret, E.; Panizza, P.; Rouch, J.; Sciortino, F.; Tartaglia, P.; Hashimoto, C.; Ushiki, H.; Risso, D.

2001-11-01

We report on extensive measurements of the low and high frequencies sound velocity and sound absorption in AOT-water-decane microemulsions deduced from ultrasonic and, for the first time as far as the absorption is concerned, from Brillouin scattering experiments. New experimental results on dielectric relaxation are also reported. Our results, which include data taken for critical as well as dense microemulsions, show new interesting relaxation phenomena. The relaxation frequencies deduced from very high frequency acoustical measurements are in good agreement with new high frequency dielectric relaxation measurements. We show that along the critical isochore, sound dispersion, relaxation frequency, and static dielectric permittivity can be accurately fitted to power laws. The absolute values of the new exponents we derived from experimental data are nearly equal, and they are very close to β=0.33 characterising the shape of the coexistence curve. The exponent characterising the infinite frequency permittivity is very close to 0.04 relevant to the diverging shear viscosity. For dense microemulsions, two well defined relaxation domains have been identified and the temperature variations of the sound absorption and the zero frequency dielectric permittivity bear striking similarities. We also show that the relaxation frequency of the slow relaxation process is almost independent of temperature and volume fraction and so cannot be attributed to percolation phenomena, whereas it can more likely be attributed to an intrinsic relaxation process probably connected to membrane fluctuations.

Frequency comb swept lasers.

PubMed

Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

2009-11-09

We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

Frequency comb swept lasers

PubMed Central

Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

2010-01-01

We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~−1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have −10dB and −5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

Full waveform inversion in the frequency domain using classified time-domain residual wavefields

NASA Astrophysics Data System (ADS)

Son, Woohyun; Koo, Nam-Hyung; Kim, Byoung-Yeop; Lee, Ho-Young; Joo, Yonghwan

2017-04-01

We perform the acoustic full waveform inversion in the frequency domain using residual wavefields that have been separated in the time domain. We sort the residual wavefields in the time domain according to the order of absolute amplitudes. Then, the residual wavefields are separated into several groups in the time domain. To analyze the characteristics of the residual wavefields, we compare the residual wavefields of conventional method with those of our residual separation method. From the residual analysis, the amplitude spectrum obtained from the trace before separation appears to have little energy at the lower frequency bands. However, the amplitude spectrum obtained from our strategy is regularized by the separation process, which means that the low-frequency components are emphasized. Therefore, our method helps to emphasize low-frequency components of residual wavefields. Then, we generate the frequency-domain residual wavefields by taking the Fourier transform of the separated time-domain residual wavefields. With these wavefields, we perform the gradient-based full waveform inversion in the frequency domain using back-propagation technique. Through a comparison of gradient directions, we confirm that our separation method can better describe the sub-salt image than the conventional approach. The proposed method is tested on the SEG/EAGE salt-dome model. The inversion results show that our algorithm is better than the conventional gradient based waveform inversion in the frequency domain, especially for deeper parts of the velocity model.

Comparison of Magnetic Characteristics of Powder Magnetic Core and Evaluation of Motor Characteristics

NASA Astrophysics Data System (ADS)

Enomoto, Yuji; Ito, Motoya; Masaki, Ryozo; Yamazaki, Katsuyuki; Asaka, Kazuo; Ishihara, Chio; Ohiwa, Syoji

A magnetic characteristic measurement, a motor characteristic forecast, and an experimental evaluation of various powder magnetic cores were performed aiming at a fixed quantity grasp when the powder magnetic core was applied to the motor core as the magnetic material. The manufacturing conditions were changed, and magnetic characteristic compares a direct current magnetization characteristic and an iron disadvantageous characteristic with the silicon steel board for a different powder magnetic core. Therefore, though some permeabilities are low, characteristics almost equal to those of a silicon steel board were obtained in the maximum saturation magnetic induction, which confirms that the powder magnetic core in disadvantageous iron in a certain frequency domain, and to confirm disadvantageous iron lowers. Moreover, it has been shown to obtain characteristics almost equal to the silicon steel board when compared in terms of motor efficiency, though some disadvantageous iron increases since the effect when applying to the motor is verified the silicon steel board and the comparison evaluation for the surface type permanent magnet motor.

Scattering Cross Section of Sound Waves by the Modal Element Method

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Kreider, Kevin L.

1994-01-01

#he modal element method has been employed to determine the scattered field from a plane acoustic wave impinging on a two dimensional body. In the modal element method, the scattering body is represented by finite elements, which are coupled to an eigenfunction expansion representing the acoustic pressure in the infinite computational domain surrounding the body. The present paper extends the previous work by developing the algorithm necessary to calculate the acoustics scattering cross section by the modal element method. The scattering cross section is the acoustical equivalent to the Radar Cross Section (RCS) in electromagnetic theory. Since the scattering cross section is evaluated at infinite distance from the body, an asymptotic approximation is used in conjunction with the standard modal element method. For validation, the scattering cross section of the rigid circular cylinder is computed for the frequency range 0.1 is less than or equal to ka is less than or equal to 100. Results show excellent agreement with the analytic solution.

Improper excess light energy dissipation in Arabidopsis results in a metabolic reprogramming

PubMed Central

Frenkel, Martin; Külheim, Carsten; Jänkänpää, Hanna Johansson; Skogström, Oskar; Dall'Osto, Luca; Ågren, Jon; Bassi, Roberto; Moritz, Thomas; Moen, Jon; Jansson, Stefan

2009-01-01

Background Plant performance is affected by the level of expression of PsbS, a key photoprotective protein involved in the process of feedback de-excitation (FDE), or the qE component of non-photochemical quenching, NPQ. Results In studies presented here, under constant laboratory conditions the metabolite profiles of leaves of wild-type Arabidopsis thaliana and plants lacking or overexpressing PsbS were very similar, but under natural conditions their differences in levels of PsbS expression were associated with major changes in metabolite profiles. Some carbohydrates and amino acids differed ten-fold in abundance between PsbS-lacking mutants and over-expressers, with wild-type plants having intermediate amounts, showing that a metabolic shift had occurred. The transcriptomes of the genotypes also varied under field conditions, and the genes induced in plants lacking PsbS were similar to those reportedly induced in plants exposed to ozone stress or treated with methyl jasmonate (MeJA). Genes involved in the biosynthesis of JA were up-regulated, and enzymes involved in this pathway accumulated. JA levels in the undamaged leaves of field-grown plants did not differ between wild-type and PsbS-lacking mutants, but they were higher in the mutants when they were exposed to herbivory. Conclusion These findings suggest that lack of FDE results in increased photooxidative stress in the chloroplasts of Arabidopsis plants grown in the field, which elicits a response at the transcriptome level, causing a redirection of metabolism from growth towards defence that resembles a MeJA/JA response. PMID:19171025

Fixed Drug Eruption Due to Selective Hypersensitivity to Naproxen with Tolerance to other Propionic Acid NSAIDs.

PubMed

Noguerado-Mellado, Blanca; Gamboa, Abdonias R; Perez-Ezquerra, Patricia R; Cabeza, Cristina M; Fernandez, Roberto P; De Barrio Fernandez, Manuel

2016-01-01

Naproxen is a non-steroidal anti-inflammatory drug (NSAID), belonging to propionic acid group, and its chemical structure is a 6-metoxi-metil-2-naftalenoacetic acid. Fixed drug eruptions (FDE) have been rarely reported. A 38-year-old woman referred that after 2 hours of taking 2 tablets of naproxen for a headache, she developed several edematous and dusky-red macules, one on right forearm and the other two in both thighs and she was diagnosed with FDE probably due to naproxen. We performed patch testing (PT) (Nonweven Patch Test Strips Curatest® Lohman & Rauscher International, Rangsdorf, Germany), with ibuprofen (5% Petrolatum), ketoprofen (2.5% Petrolatum), naproxen and nabumetone (both 10% in DMSO) on the residual lesion of the forearm with naproxen and in both thighs with ibuprofen, ketoprofen and nabumetone. Readings at day 1 (D1) and day 2 (D2) showed negative results to ibuprofen, ketoprofen and nabumetone, but were positive to naproxen in D1. A single blind oral challenge test (SBOCT) with other propionic acid derivates were performed in order to check for crossreactivity between them: ibuprofen, ketoprofen and nabumetone were administered and all drugs were well tolerated. In our patient PT confirmed the diagnosis and allowed us to study the cross-reactivity between NSAIDs of the same group, and confirmed by SBOCT. Cross-reactivity between propionic acid derivatives was studied. This is a case of hypersensitivity to naproxen with good tolerance to other propionic acids NSAIDs (ibuprofen and ketoprofen) and nabumetone, confirmed by PT and SBOCT. Some relavent patents for fixed drug eruption are discussed.

Frequency domain FIR and IIR adaptive filters

NASA Technical Reports Server (NTRS)

Lynn, D. W.

1990-01-01

A discussion of the LMS adaptive filter relating to its convergence characteristics and the problems associated with disparate eigenvalues is presented. This is used to introduce the concept of proportional convergence. An approach is used to analyze the convergence characteristics of block frequency-domain adaptive filters. This leads to a development showing how the frequency-domain FIR adaptive filter is easily modified to provide proportional convergence. These ideas are extended to a block frequency-domain IIR adaptive filter and the idea of proportional convergence is applied. Experimental results illustrating proportional convergence in both FIR and IIR frequency-domain block adaptive filters is presented.

Comparing supervised learning techniques on the task of physical activity recognition.

PubMed

Dalton, A; OLaighin, G

2013-01-01

The objective of this study was to compare the performance of base-level and meta-level classifiers on the task of physical activity recognition. Five wireless kinematic sensors were attached to each subject (n = 25) while they completed a range of basic physical activities in a controlled laboratory setting. Subjects were then asked to carry out similar self-annotated physical activities in a random order and in an unsupervised environment. A combination of time-domain and frequency-domain features were extracted from the sensor data including the first four central moments, zero-crossing rate, average magnitude, sensor cross-correlation, sensor auto-correlation, spectral entropy and dominant frequency components. A reduced feature set was generated using a wrapper subset evaluation technique with a linear forward search and this feature set was employed for classifier comparison. The meta-level classifier AdaBoostM1 with C4.5 Graft as its base-level classifier achieved an overall accuracy of 95%. Equal sized datasets of subject independent data and subject dependent data were used to train this classifier and high recognition rates could be achieved without the need for user specific training. Furthermore, it was found that an accuracy of 88% could be achieved using data from the ankle and wrist sensors only.

Relating the Hadamard Variance to MCS Kalman Filter Clock Estimation

NASA Technical Reports Server (NTRS)

Hutsell, Steven T.

1996-01-01

The Global Positioning System (GPS) Master Control Station (MCS) currently makes significant use of the Allan Variance. This two-sample variance equation has proven excellent as a handy, understandable tool, both for time domain analysis of GPS cesium frequency standards, and for fine tuning the MCS's state estimation of these atomic clocks. The Allan Variance does not explicitly converge for the nose types of alpha less than or equal to minus 3 and can be greatly affected by frequency drift. Because GPS rubidium frequency standards exhibit non-trivial aging and aging noise characteristics, the basic Allan Variance analysis must be augmented in order to (a) compensate for a dynamic frequency drift, and (b) characterize two additional noise types, specifically alpha = minus 3, and alpha = minus 4. As the GPS program progresses, we will utilize a larger percentage of rubidium frequency standards than ever before. Hence, GPS rubidium clock characterization will require more attention than ever before. The three sample variance, commonly referred to as a renormalized Hadamard Variance, is unaffected by linear frequency drift, converges for alpha is greater than minus 5, and thus has utility for modeling noise in GPS rubidium frequency standards. This paper demonstrates the potential of Hadamard Variance analysis in GPS operations, and presents an equation that relates the Hadamard Variance to the MCS's Kalman filter process noises.

Application of frequency-domain linearized Euler solutions to the prediction of aft fan tones and comparison with experimental measurements on model scale turbofan exhaust nozzles

NASA Astrophysics Data System (ADS)

Özyörük, Y.; Tester, B. J.

2011-08-01

Although it is widely accepted that aircraft noise needs to be further reduced, there is an equally important, on-going requirement to accurately predict the strengths of all the different aircraft noise sources, not only to ensure that a new aircraft is certifiable and can meet the ever more stringent local airport noise rules but also to prioritize and apply appropriate noise source reduction technologies at the design stage. As the bypass ratio of aircraft engines is increased - in order to reduce fuel consumption, emissions and jet mixing noise - the fan noise that radiates from the bypass exhaust nozzle is becoming one of the loudest engine sources, despite the large areas of acoustically absorptive treatment in the bypass duct. This paper addresses this 'aft fan' noise source, in particular the prediction of the propagation of fan noise through the bypass exhaust nozzle/jet exhaust flow and radiation out to the far-field observer. The proposed prediction method is equally applicable to fan tone and fan broadband noise (and also turbine and core noise) but here the method is validated with measured test data using simulated fan tones. The measured data had been previously acquired on two model scale turbofan engine exhausts with bypass and heated core flows typical of those found in a modern high bypass engine, but under static conditions (i.e. no flight simulation). The prediction method is based on frequency-domain solutions of the linearized Euler equations in conjunction with perfectly matched layer equations at the inlet and far-field boundaries using high-order finite differences. The discrete system of equations is inverted by the parallel sparse solver MUMPS. Far-field predictions are carried out by integrating Kirchhoff's formula in frequency domain. In addition to the acoustic modes excited and radiated, some non-acoustic waves within the cold stream-ambient shear layer are also captured by the computations at some flow and excitation frequencies. By extracting phase speed information from the near-field pressure solution, these non-acoustic waves are shown to be convective Kelvin-Helmholtz instability waves. Strouhal numbers computed along the shear layer, based on the local momentum thickness also confirm this in accordance with Michalke's instability criterion for incompressible round jets with a similar shear layer profile. Comparisons of the computed far-field results with the measured acoustic data reveal that, in general, the solver predicts the peak sound levels well when the farfield is dominated by the in-duct target mode (the target mode being the one specified to the in-duct mode generator). Calculations also show that the agreement can be considerably improved when the non-target modes are also included, despite their low in-duct levels. This is due to the fact that each duct mode has its own distinct directionality and a non-target low level mode may become dominant at angles where the higher-level target mode is directionally weak. The overall agreement between the computations and experiment strongly suggests that, at least for the range of mean flows and acoustic conditions considered, the physical aeroacoustic radiation processes are fully captured through the frequency-domain solutions to the linearized Euler equations and hence this could form the basis of a reliable aircraft noise prediction method.

Algorithms and Application of Sparse Matrix Assembly and Equation Solvers for Aeroacoustics

NASA Technical Reports Server (NTRS)

Watson, W. R.; Nguyen, D. T.; Reddy, C. J.; Vatsa, V. N.; Tang, W. H.

2001-01-01

An algorithm for symmetric sparse equation solutions on an unstructured grid is described. Efficient, sequential sparse algorithms for degree-of-freedom reordering, supernodes, symbolic/numerical factorization, and forward backward solution phases are reviewed. Three sparse algorithms for the generation and assembly of symmetric systems of matrix equations are presented. The accuracy and numerical performance of the sequential version of the sparse algorithms are evaluated over the frequency range of interest in a three-dimensional aeroacoustics application. Results show that the solver solutions are accurate using a discretization of 12 points per wavelength. Results also show that the first assembly algorithm is impractical for high-frequency noise calculations. The second and third assembly algorithms have nearly equal performance at low values of source frequencies, but at higher values of source frequencies the third algorithm saves CPU time and RAM. The CPU time and the RAM required by the second and third assembly algorithms are two orders of magnitude smaller than that required by the sparse equation solver. A sequential version of these sparse algorithms can, therefore, be conveniently incorporated into a substructuring for domain decomposition formulation to achieve parallel computation, where different substructures are handles by different parallel processors.

A Novel Range Compression Algorithm for Resolution Enhancement in GNSS-SARs.

PubMed

Zheng, Yu; Yang, Yang; Chen, Wu

2017-06-25

In this paper, a novel range compression algorithm for enhancing range resolutions of a passive Global Navigation Satellite System-based Synthetic Aperture Radar (GNSS-SAR) is proposed. In the proposed algorithm, within each azimuth bin, firstly range compression is carried out by correlating a reflected GNSS intermediate frequency (IF) signal with a synchronized direct GNSS base-band signal in the range domain. Thereafter, spectrum equalization is applied to the compressed results for suppressing side lobes to obtain a final range-compressed signal. Both theoretical analysis and simulation results have demonstrated that significant range resolution improvement in GNSS-SAR images can be achieved by the proposed range compression algorithm, compared to the conventional range compression algorithm.

76 FR 39392 - Record of Decision for the F-35 Force Development Evaluation and Weapons School Beddown, Nellis...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-06

...On June 24, 2011, the United States Air Force signed the ROD for the F-35 Force Development Evaluation (FDE) and Weapons School (WS) Beddown, Nellis AFB, Nevada. The decision was based on matters discussed in the Final Environmental Impact Statement (EIS), inputs from the public and regulatory agencies, and other relevant factors. The Final EIS was made available to the public on May 13, 2011, through a Federal Register NOA (Volume 76, Number 93, Page 28029) with a wait period that ended on June 14, 2011.

On the testing of Hardy-Weinberg proportions and equality of allele frequencies in males and females at biallelic genetic markers.

PubMed

Graffelman, Jan; Weir, Bruce S

2018-02-01

Standard statistical tests for equality of allele frequencies in males and females and tests for Hardy-Weinberg equilibrium are tightly linked by their assumptions. Tests for equality of allele frequencies assume Hardy-Weinberg equilibrium, whereas the usual chi-square or exact test for Hardy-Weinberg equilibrium assume equality of allele frequencies in the sexes. In this paper, we propose ways to break this interdependence in assumptions of the two tests by proposing an omnibus exact test that can test both hypotheses jointly, as well as a likelihood ratio approach that permits these phenomena to be tested both jointly and separately. The tests are illustrated with data from the 1000 Genomes project. © 2017 The Authors Genetic Epidemiology Published by Wiley Periodicals, Inc.

Split-mode ultrasonic transducer.

PubMed

Ostrovskii, Igor; Cremaldi, Lucien

2013-08-01

A split-mode ultrasonic transducer is investigated in both theory and experiment. This transducer is a two-dimensional structure of periodically poled domains in a ferroelectric wafer with free surfaces. The acoustic vibrations are excited by a radio frequency electric current applied along the length of the wafer, which allows the basal-plane surfaces to be free of metal coatings and thus ready for further biomedical applications. A specific physical property of this transducer consists of the multiple acousto-electric resonances, which occur due to an acoustic mode split when the acoustic half-wavelength is equal to the domain length. Possible applications include ultrasonic generation and detection at the micro-scale, intravascular sonification and visualization, ultrasound therapy of localized small areas such as the eye, biomedical applications for cell cultures, and traditional nondestructive testing including bones and tissues. A potential use of a non-metallized wafer is a therapeutic application with double action that is both ultrasound itself and an electric field over the wafer. The experimental measurements and theoretical calculations are in good agreement.

Spectral element method for elastic and acoustic waves in frequency domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Linlin; Zhou, Yuanguo; Wang, Jia-Min

Numerical techniques in time domain are widespread in seismic and acoustic modeling. In some applications, however, frequency-domain techniques can be advantageous over the time-domain approach when narrow band results are desired, especially if multiple sources can be handled more conveniently in the frequency domain. Moreover, the medium attenuation effects can be more accurately and conveniently modeled in the frequency domain. In this paper, we present a spectral-element method (SEM) in frequency domain to simulate elastic and acoustic waves in anisotropic, heterogeneous, and lossy media. The SEM is based upon the finite-element framework and has exponential convergence because of the usemore » of GLL basis functions. The anisotropic perfectly matched layer is employed to truncate the boundary for unbounded problems. Compared with the conventional finite-element method, the number of unknowns in the SEM is significantly reduced, and higher order accuracy is obtained due to its spectral accuracy. To account for the acoustic-solid interaction, the domain decomposition method (DDM) based upon the discontinuous Galerkin spectral-element method is proposed. Numerical experiments show the proposed method can be an efficient alternative for accurate calculation of elastic and acoustic waves in frequency domain.« less

[Analysis of time domain and frequency domain heart rate variability in fighter pilot before and after upright tilt].

PubMed

Wang, L; Wu, L; Ji, G; Zhang, X; Chen, T; Wang, L

1998-12-01

Effects of upright tilt on mechanism of autonomic nervous regulation of cardiovascular system and characteristics of heart rate variability (HRV) were observed in sixty healthy male pilots. Relation between time domain and frequency domain indexes of short-time HRV (5 min) were analysed before and after upright tilt. The results showed that there are significant difference in short time HRV parameters before and after upright tilt. Significant relationship was formed between time domain and frequency domain indexes of HRV. It suggests that time domain and frequency domain HRV analysis is capable of revealing certain informations embedded in a short series of R-R intervals and can help to evaluate the status of autonomic regulation of cardiovascular function in pilots.

Extracting Low-Frequency Information from Time Attenuation in Elastic Waveform Inversion

NASA Astrophysics Data System (ADS)

Guo, Xuebao; Liu, Hong; Shi, Ying; Wang, Weihong

2017-03-01

Low-frequency information is crucial for recovering background velocity, but the lack of low-frequency information in field data makes inversion impractical without accurate initial models. Laplace-Fourier domain waveform inversion can recover a smooth model from real data without low-frequency information, which can be used for subsequent inversion as an ideal starting model. In general, it also starts with low frequencies and includes higher frequencies at later inversion stages, while the difference is that its ultralow frequency information comes from the Laplace-Fourier domain. Meanwhile, a direct implementation of the Laplace-transformed wavefield using frequency domain inversion is also very convenient. However, because broad frequency bands are often used in the pure time domain waveform inversion, it is difficult to extract the wavefields dominated by low frequencies in this case. In this paper, low-frequency components are constructed by introducing time attenuation into the recorded residuals, and the rest of the method is identical to the traditional time domain inversion. Time windowing and frequency filtering are also applied to mitigate the ambiguity of the inverse problem. Therefore, we can start at low frequencies and to move to higher frequencies. The experiment shows that the proposed method can achieve a good inversion result in the presence of a linear initial model and records without low-frequency information.

Driving chiral domain walls in antiferromagnets using rotating magnetic fields

NASA Astrophysics Data System (ADS)

Pan, Keming; Xing, Lingdi; Yuan, H. Y.; Wang, Weiwei

2018-05-01

We show theoretically and numerically that an antiferromagnetic domain wall can be moved by a rotating magnetic field in the presence of Dzyaloshinskii-Moriya interaction (DMI). Two motion modes are found: rigid domain wall motion at low frequency (corresponding to the perfect frequency synchronization) and the oscillating motion at high frequency. In the full synchronized region, the steady velocity of the domain wall is universal, in the sense that it depends only on the frequency of the rotating field and the ratio between DMI strength and exchange constant. The domain wall velocity is independent of the Gilbert damping and the rotating field strength. Moreover, a rotating field in megahertz is sufficient to move the antiferromagnetic domain wall.

Frequency and time domain three-dimensional inversion of electromagnetic data for a grounded-wire source

NASA Astrophysics Data System (ADS)

Sasaki, Yutaka; Yi, Myeong-Jong; Choi, Jihyang; Son, Jeong-Sul

2015-01-01

We present frequency- and time-domain three-dimensional (3-D) inversion approaches that can be applied to transient electromagnetic (TEM) data from a grounded-wire source using a PC. In the direct time-domain approach, the forward solution and sensitivity were obtained in the frequency domain using a finite-difference technique, and the frequency response was then Fourier-transformed using a digital filter technique. In the frequency-domain approach, TEM data were Fourier-transformed using a smooth-spectrum inversion method, and the recovered frequency response was then inverted. The synthetic examples show that for the time derivative of magnetic field, frequency-domain inversion of TEM data performs almost as well as time-domain inversion, with a significant reduction in computational time. In our synthetic studies, we also compared the resolution capabilities of the ground and airborne TEM and controlled-source audio-frequency magnetotelluric (CSAMT) data resulting from a common grounded wire. An airborne TEM survey at 200-m elevation achieved a resolution for buried conductors almost comparable to that of the ground TEM method. It is also shown that the inversion of CSAMT data was able to detect a 3-D resistivity structure better than the TEM inversion, suggesting an advantage of electric-field measurements over magnetic-field-only measurements.

Cardinal and anti-cardinal points, equalities and chromatic dependence.

PubMed

Evans, Tanya; Harris, William F

2017-05-01

Cardinal points are used for ray tracing through Gaussian systems. Anti-principal and anti-nodal points (which we shall refer to as the anti-cardinal points), along with the six familiar cardinal points, belong to a much larger set of special points. The purpose of this paper is to obtain a set of relationships and resulting equalities among the cardinal and anti-cardinal points and to illustrate them using Pascal's ring. The methodology used relies on Gaussian optics and the transference T. We make use of two equations, obtained via the transference, which give the locations of the six cardinal and four anti-cardinal points with respect to the system. We obtain equalities among the cardinal and anti-cardinal points. We utilise Pascal's ring to illustrate which points depend on frequency and their displacement with change in frequency. Pascal described a memory schema in the shape of a hexagon for remembering equalities among the points and illustrating shifts in these points when an aspect of the system changes. We modify and extend Pascal's ring to include the anti-cardinal points. We make use of Pascal's ring extended to illustrate which points are dependent on the frequency of light and the direction of shift of the equalities with change in frequency. For the reduced eye the principal and nodal points are independent of frequency, but the focal points and the anti-cardinal points depend on frequency. For Le Grand's four-surface model eye all six cardinal and four anti-cardinal points depend on frequency. This has implications for definitions, particularly of chromatic aberrations of the eye, that make use of cardinal points and that themselves depend on frequency. Pascal's ring and Pascal's ring extended are novel memory schema for remembering the equalities among the cardinal and anti-cardinal points. The rings are useful for illustrating changes among the equalities and direction of shift of points when an aspect of a system changes. Care should be taken when defining concepts that rely on cardinal points that depend on frequency. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

Absolute frequency measurement of a diode laser locked on a hyperfine component of 5S1/2-5D5/2 two-photon transitions of rubidium (lambda equals 778.1 nm, nu equals 385.3 THz)

NASA Astrophysics Data System (ADS)

Zondy, Jean-Jacques; Touahri, D.; Acef, Ouali; Hilico, L.; Abed, M.; Clairon, Andre; Millerioux, Yves P.; Felder, Raymond; de Beauvoir, Beatrice; Nez, Francois; Biraben, Francois; Julien, Lucile

1995-04-01

A frequency chain, derived from the one used to measure the absolute frequency ((nu) $= 473 THz) of the He-Ne/I2 optical standard, is currently being implemented in order to measure the frequency of a diode laser stabilized on the two-photon transition of rubidium vapor. The measurement scheme is based on the comparison of the frequency of this near-IR potential secondary standard to the 13th harmonic frequency of the R(12)-CO2/OsO4 LPTF secondary standard at (nu) equals 29.096 THz. Recent results on the frequency synthesis are reported, enabling the testing of long-term stability of this Rb-locked system with respect to the IR reference standard.

Conceptual design of a 10 to the 8th power bit magnetic bubble domain mass storage unit and fabrication, test and delivery of a feasibility model

NASA Technical Reports Server (NTRS)

1972-01-01

The conceptual design of a highly reliable 10 to the 8th power-bit bubble domain memory for the space program is described. The memory has random access to blocks of closed-loop shift registers, and utilizes self-contained bubble domain chips with on-chip decoding. Trade-off studies show that the highest reliability and lowest power dissipation is obtained when the memory is organized on a bit-per-chip basis. The final design has 800 bits/register, 128 registers/chip, 16 chips/plane, and 112 planes, of which only seven are activated at a time. A word has 64 data bits +32 checkbits, used in a 16-adjacent code to provide correction of any combination of errors in one plane. 100 KHz maximum rotational frequency keeps power low (equal to or less than, 25 watts) and also allows asynchronous operation. Data rate is 6.4 megabits/sec, access time is 200 msec to an 800-word block and an additional 4 msec (average) to a word. The fabrication and operation are also described for a 64-bit bubble domain memory chip designed to test the concept of on-chip magnetic decoding. Access to one of the chip's four shift registers for the read, write, and clear functions is by means of bubble domain decoders utilizing the interaction between a conductor line and a bubble.

Thunder-induced ground motions: 1. Observations

NASA Astrophysics Data System (ADS)

Lin, Ting-L.; Langston, Charles A.

2009-04-01

Acoustic pressure from thunder and its induced ground motions were investigated using a small array consisting of five three-component short-period surface seismometers, a three-component borehole seismometer, and five infrasound microphones. We used the array to constrain wave parameters of the incident acoustic and seismic waves. The incident slowness differences between acoustic pressure and ground motions suggest that ground reverberations were first initiated somewhat away from the array. Using slowness inferred from ground motions is preferable to obtain the seismic source parameters. We propose a source equalization procedure for acoustic/seismic deconvolution to generate the time domain transfer function, a procedure similar to that of obtaining teleseismic earthquake receiver functions. The time domain transfer function removes the incident pressure time history from the seismogram. An additional vertical-to-radial ground motion transfer function was used to identify the Rayleigh wave propagation mode of induced seismic waves complementing that found using the particle motions and amplitude variations in the borehole. The initial motions obtained by the time domain transfer functions suggest a low Poisson's ratio for the near-surface layer. The acoustic-to-seismic transfer functions show a consistent reverberation series at frequencies near 5 Hz. This gives an empirical measure of site resonance that depends on the ratio of the layer velocity to layer thickness for earthquake P and S waves. The time domain transfer function approach by transferring a spectral division into the time domain provides an alternative method for studying acoustic-to-seismic coupling.

Frequency Domain Computer Programs for Prediction and Analysis of Rail Vehicle Dynamics : Volume 2. Appendixes

DOT National Transportation Integrated Search

1975-12-01

Frequency domain computer programs developed or acquired by TSC for the analysis of rail vehicle dynamics are described in two volumes. Volume 2 contains program listings including subroutines for the four TSC frequency domain programs described in V...

Loudspeaker equalization for auditory research.

PubMed

MacDonald, Justin A; Tran, Phuong K

2007-02-01

The equalization of loudspeaker frequency response is necessary to conduct many types of well-controlled auditory experiments. This article introduces a program that includes functions to measure a loudspeaker's frequency response, design equalization filters, and apply the filters to a set of stimuli to be used in an auditory experiment. The filters can compensate for both magnitude and phase distortions introduced by the loudspeaker. A MATLAB script is included in the Appendix to illustrate the details of the equalization algorithm used in the program.

The retrieval of a buried cylindrical obstacle by a constrained modified gradient method in the H-polarization case and for Maxwellian materials

NASA Astrophysics Data System (ADS)

Lambert, M.; Lesselier, D.; Kooij, B. J.

1998-10-01

The retrieval of an unknown, possibly inhomogeneous, penetrable cylindrical obstacle buried entirely in a known homogeneous half-space - the constitutive material parameters of the obstacle and of its embedding obey a Maxwell model - is considered from single- or multiple-frequency aspect-limited data collected by ideal sensors located in air above the embedding half-space, when a small number of time-harmonic transverse electric (TE)-polarized line sources - the magnetic field H is directed along the axis of the cylinder - is also placed in air. The wavefield is modelled from a rigorous H-field domain integral-differential formulation which involves the dot product of the gradients of the single component of H and of the Green function of the stratified environment times a scalar-valued contrast function which contains the obstacle parameters (the frequency-independent, position-dependent relative permittivity and conductivity). A modified gradient method is developed in order to reconstruct the maps of such parameters within a prescribed search domain from the iterative minimization of a cost functional which incorporates both the error in reproducing the data and the error on the field built inside this domain. Non-physical values are excluded and convergence reached by incorporating in the solution algorithm, from a proper choice of unknowns, the condition that the relative permittivity be larger than or equal to 1, and the conductivity be non-negative. The efficiency of the constrained method is illustrated from noiseless and noisy synthetic data acquired independently. The importance of the choice of the initial values of the sought quantities, the need for a periodic refreshment of the constitutive parameters to avoid the algorithm providing inconsistent results, and the interest of a frequency-hopping strategy to obtain finer and finer features of the obstacle when the frequency is raised, are underlined. It is also shown that though either the permittivity map or the conductivity map can be obtained for a fair variety of cases, retrieving both of them may be difficult unless further information is made available.

Nonlinear (time domain) and linearized (time and frequency domain) solutions to the compressible Euler equations in conservation law form

NASA Technical Reports Server (NTRS)

Sreenivas, Kidambi; Whitfield, David L.

1995-01-01

Two linearized solvers (time and frequency domain) based on a high resolution numerical scheme are presented. The basic approach is to linearize the flux vector by expressing it as a sum of a mean and a perturbation. This allows the governing equations to be maintained in conservation law form. A key difference between the time and frequency domain computations is that the frequency domain computations require only one grid block irrespective of the interblade phase angle for which the flow is being computed. As a result of this and due to the fact that the governing equations for this case are steady, frequency domain computations are substantially faster than the corresponding time domain computations. The linearized equations are used to compute flows in turbomachinery blade rows (cascades) arising due to blade vibrations. Numerical solutions are compared to linear theory (where available) and to numerical solutions of the nonlinear Euler equations.

Interconversion algorithm between mechanical and dielectric relaxation measurements for acetate of cis- and trans-2-phenyl-5-hydroxymethyl-1,3-dioxane.

PubMed

Garcia-Bernabé, A; Lidón-Roger, J V; Sanchis, M J; Díaz-Calleja, R; del Castillo, L F

2015-10-01

The dielectric and mechanical spectroscopies of acetate of cis- and trans-2-phenyl-5-hydroxymethyl-1,3-dioxane are reported in the frequency domain from 10(-2) to 10(6)Hz. This ester has been selected in this study for its predominant α relaxation with regard to the β relaxation, which can be neglected. This study consists of determining an interconversion algorithm between dielectric and mechanical measurements, given by using a relation between rotational and translational complex viscosities. These important viscosities were obtained from measures of the dielectric complex permittivity and by dynamic mechanical analysis, respectively. The definitions of rotational and translational viscosities were evaluated by means of fractional calculus, by using the fit parameters of the Havriliak-Negami empirical model obtained in the dielectric and mechanical characterization of the α relaxation. This interconversion algorithm is a generalization of the break of the Stokes-Einstein-Debye relationship. It uses a power law with an exponent defined as the shape factor, which modifies the translational viscosity. Two others factors are introduced for the interconversion, a shift factor, which displaces the translational viscosity in the frequency domain, and a scale factor, which makes equal values of the two viscosities. In this paper, the shape factor has been identified as the relation between the slopes of the moduli of the complex viscosities at higher frequency. This is interpreted as the degree of kinetic coupling between the molecular rotation and translational movements. Alternatively, another interconversion algorithm has been expressed by means of dielectric and mechanical moduli.

Introducing causality violation for improved DPOAE component unmixing

NASA Astrophysics Data System (ADS)

Moleti, Arturo; Sisto, Renata; Shera, Christopher A.

2018-05-01

The DPOAE response consists of the linear superposition of two components, a nonlinear distortion component generated in the overlap region, and a reflection component generated by roughness in the DP resonant region. Due to approximate scaling symmetry, the DPOAE distortion component has approximately constant phase. As the reflection component may be considered as a SFOAE generated by the forward DP traveling wave, it has rapidly rotating phase, relative to that of its source, which is also equal to the phase of the DPOAE distortion component. This different phase behavior permits effective separation of the DPOAE components (unmixing), using time-domain or time-frequency domain filtering. Departures from scaling symmetry imply fluctuations around zero delay of the distortion component, which may seriously jeopardize the accuracy of these filtering techniques. The differential phase-gradient delay of the reflection component obeys causality requirements, i.e., the delay is positive only, and the fine-structure oscillations of amplitude and phase are correlated to each other, as happens for TEOAEs and SFOAEs relative to their stimulus phase. Performing the inverse Fourier (or wavelet) transform of a modified DPOAE complex spectrum, in which a constant phase function is substituted for the measured one, the time (or time-frequency) distribution shows a peak at (exactly) zero delay and long-latency specular symmetric components, with a modified (positive and negative) delay, which is that relative to that of the distortion component in the original response. Component separation, applied to this symmetrized distribution, becomes insensitive to systematic errors associated with violation of the scaling symmetry in specific frequency ranges.

A Fundamental Relationship Between Genotype Frequencies and Fitnesses

PubMed Central

Lachance, Joseph

2008-01-01

The set of possible postselection genotype frequencies in an infinite, randomly mating population is found. Geometric mean heterozygote frequency divided by geometric mean homozygote frequency equals two times the geometric mean heterozygote fitness divided by geometric mean homozygote fitness. The ratio of genotype frequencies provides a measure of genetic variation that is independent of allele frequencies. When this ratio does not equal two, either selection or population structure is present. Within-population HapMap data show population-specific patterns, while pooled data show an excess of homozygotes. PMID:18780726

Circle-16QAM for a zero-guard-interval CO-OFDM system

NASA Astrophysics Data System (ADS)

Kong, Lingyu; Yang, Aiying; Guo, Peng; Lu, Yueming; Qiao, Yaojun

2018-01-01

In this paper, we introduce circle 16 quadrature amplitude modulation (C-16QAM) modulation format in a high spectral efficiency zero-guard-interval (ZGI) coherent optical (CO) orthogonal frequency-division multiplexing (OFDM) system. At transmitter, the C-16QAM has advantages over the conventional square 16QAM in terms of transmission distance and tolerance to laser linewidth and fiber nonlinearities. ZGI CO-OFDM enables to take away the cyclic prefix (CP), so it has the benefit of higher spectral efficiency compared with the conventional CO-OFDM system. At receiver, in order to compensate chromatic dispersion (CD) and phase noise in a single channel ZGI CO-OFDM system, we studied the overlapped frequency domain equalizer (OFDE) and two carrier phase recovery (CPR) algorithms. We simulate the above systems and the results demonstrate that with the C-16QAM, a 28GBaud ZGI CO-OFDM system can have the longer transmission distance, the higher tolerance to laser linewidth and fiber nonlinearities with contrast to the conventional square 16QAM.

Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Song, Jin Dong; Srinivasan, Kartik

2016-01-01

Optomechanical cavities have been studied for applications ranging from sensing to quantum information science. Here, we develop a platform for nanoscale cavity optomechanical circuits in which optomechanical cavities supporting co-localized 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency (RF) field through the piezo-electric effect, which produces acoustic waves that are routed and coupled to the optomechanical cavity by phononic crystal waveguides, or optically through the strong photoelastic effect. Along with mechanical state preparation and sensitive readout, we use this to demonstrate an acoustic wave interference effect, similar to atomic coherent population trapping, in which RF-driven coherent mechanical motion is cancelled by optically-driven motion. Manipulating cavity optomechanical systems with equal facility through both photonic and phononic channels enables new architectures for signal transduction between the optical, electrical, and mechanical domains. PMID:27446234

Modeling guided wave propagation in curved thick composites with ply drops and marcelling

NASA Astrophysics Data System (ADS)

Hakoda, Christopher; Choi, Gloria; Lissenden, Clifford

2018-04-01

Setting the process parameters for fabrication of thick composites having complex geometries is a challenging endeavor, with the best result being a high-quality part and less desirable results being parts that contain voids or fiber marcelling. An equal challenge is the nondestructive testing of these parts. Consider a U-shaped portion of a more complex part. The straight segments of the U-shape are approximately 10-mm thick, but a series of ply-drops reduce the thickness by one half at the center portion. Ultrasonic guided waves that have the potential to nondestructively test this part can be actuated by coupling transducers to the straight segments if and only if wave modes that are sensitive to the defects of interest can propagate through the ply drops, the curve, and the attenuation due to internal damping. A frequency domain finite element approach proposed in recent years for guided wave analysis is applied to this inhomogeneous waveguide problem in order to select modes and frequencies that are sensitive to marcelling.

Formulation of blade-flutter spectral analyses in stationary reference frame

NASA Technical Reports Server (NTRS)

Kurkov, A. P.

1984-01-01

Analytic representations are developed for the discrete blade deflection and the continuous tip static pressure fields in a stationary reference frame. Considered are the sampling rates equal to the rotational frequency, equal to blade passing frequency, and for the pressure, equal to a multiple of the blade passing frequency. For the last two rates the expressions for determining the nodal diameters from the spectra are included. A procedure is presented for transforming the complete unsteady pressure field into a rotating frame of reference. The determination of the true flutter frequency by using two sensors is described. To illustrate their use, the developed procedures are used to interpret selected experimental results.

Performance comparison between packet and continuous data transmission using two adaptive equalizers in shallow water

NASA Astrophysics Data System (ADS)

Yoon, Jong Rak; Park, Kyu-Chil; Park, Jihyun

2015-07-01

Transmitted signals are markedly affected by sea surface and bottom boundaries in shallow water. The time variant reflection signals from such boundaries characterize the channel as a frequency-selective fading channel and cause intersymbol interference (ISI) in underwater acoustic communication. A channel-estimate-based equalizer is usually adopted to compensate for the reflected signals under this kind of acoustic channel. In this study, we apply two approaches for packet and continuous data transmission of the quadrature phase shift keying (QPSK) system. One is the use of a two-dimensional (2D) rotation matrix in a non-frequency-selective channel. The other is the use of two equalizers of types — the feed forward equalizer (FFE) and decision-directed equalizer (DDE) — with a normalized least mean square (NLMS) algorithm in a frequency-selective channel. The percentage improvement of packet transmission is notably better than that of continuous transmission.

A Novel Range Compression Algorithm for Resolution Enhancement in GNSS-SARs

PubMed Central

Zheng, Yu; Yang, Yang; Chen, Wu

2017-01-01

In this paper, a novel range compression algorithm for enhancing range resolutions of a passive Global Navigation Satellite System-based Synthetic Aperture Radar (GNSS-SAR) is proposed. In the proposed algorithm, within each azimuth bin, firstly range compression is carried out by correlating a reflected GNSS intermediate frequency (IF) signal with a synchronized direct GNSS base-band signal in the range domain. Thereafter, spectrum equalization is applied to the compressed results for suppressing side lobes to obtain a final range-compressed signal. Both theoretical analysis and simulation results have demonstrated that significant range resolution improvement in GNSS-SAR images can be achieved by the proposed range compression algorithm, compared to the conventional range compression algorithm. PMID:28672830

Broader, flatter optical spectra of passively mode-locked semiconductor lasers for a wavelength-division multiplexing source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliyahu, Danny; Yariv, Amnon

1997-05-01

Using the time domain master equation for a complex electric-field pulse envelope, we find analytical results for the optical spectra of passively mode-locked semiconductor lasers. The analysis includes the effect of optical nonlinearity of semiconductor lasers, which is characterized by a slow saturable amplifier and absorber. Group velocity dispersion, bandwidth limiting, and self-phase modulation were considered as well. The FWHM of the spectrum profile was found to have a strong dependence on group velocity dispersion and self-phase modulation. For large absolute values of the chirp parameter, the optical spectra result in equispaced continuous wave frequencies, a large fraction of whichmore » have equal power. {copyright} 1997 Optical Society of America« less

Symmetry breaking in (gravitating) scalar field models describing interacting boson stars and Q-balls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brihaye, Yves; Caebergs, Thierry; Hartmann, Betti

2009-09-15

We investigate the properties of interacting Q-balls and boson stars that sit on top of each other in great detail. The model that describes these solutions is essentially a (gravitating) two-scalar field model where both scalar fields are complex. We construct interacting Q-balls or boson stars with arbitrarily small charges but finite mass. We observe that in the interacting case--where the interaction can be either due to the potential or due to gravity--two types of solutions exist for equal frequencies: one for which the two-scalar fields are equal, but also one for which the two-scalar fields differ. This constitutes amore » symmetry breaking in the model. While for Q-balls asymmetric solutions have always corresponding symmetric solutions and are thus likely unstable to decay to symmetric solutions with lower energy, there exists a parameter regime for interacting boson stars, where only asymmetric solutions exist. We present the domain of existence for two interacting nonrotating solutions as well as for solutions describing the interaction between rotating and nonrotating Q-balls and boson stars, respectively.« less

Differentiability breaking and Schwarz theorem violation in an aging material

NASA Astrophysics Data System (ADS)

Doussineau, P.; Levelut, A. L.

2002-07-01

Dielectric constant measurements are performed in the frequency range from 1 kHz to 1 MHz on a disordered material with ferroelectric properties (KTa1-xNbxO3 crystals) after isothermal aging at the plateau temperature Tpl≅10 K. They show that the derivatives of the complex capacitance with respect to temperature and time present two very peculiar behaviors. The first point is that the first and second derivatives against temperature are not equal on the two sides of Tpl; this is differentiability breaking. The second point is that the two crossed second derivatives against temperature and time are not equal (indeed they have opposite signs); this is a violation of Schwarz theorem. These results are obtained on both the real part and the imaginary part of the capacitance. A model, initially imagined for aging and memory of aging, attributes the time-dependent properties to the evolution (growth and reconformations) of the polarization domain walls. It is shown that it can also explain the observed differentiability breaking (and in particular its logarithmic increase with the plateau duration tpl) and the violation of Schwarz theorem.

A Persistent Feature of Multiple Scattering of Waves in the Time-Domain: A Tutorial

NASA Technical Reports Server (NTRS)

Lock, James A.; Mishchenko, Michael I.

2015-01-01

The equations for frequency-domain multiple scattering are derived for a scalar or electromagnetic plane wave incident on a collection of particles at known positions, and in the time-domain for a plane wave pulse incident on the same collection of particles. The calculation is carried out for five different combinations of wave types and particle types of increasing geometrical complexity. The results are used to illustrate and discuss a number of physical and mathematical characteristics of multiple scattering in the frequency- and time-domains. We argue that frequency-domain multiple scattering is a purely mathematical construct since there is no temporal sequencing information in the frequency-domain equations and since the multi-particle path information can be dispelled by writing the equations in another mathematical form. However, multiple scattering becomes a definite physical phenomenon in the time-domain when the collection of particles is illuminated by an appropriately short localized pulse.

Wavelet Analyses of F/A-18 Aeroelastic and Aeroservoelastic Flight Test Data

NASA Technical Reports Server (NTRS)

Brenner, Martin J.

1997-01-01

Time-frequency signal representations combined with subspace identification methods were used to analyze aeroelastic flight data from the F/A-18 Systems Research Aircraft (SRA) and aeroservoelastic data from the F/A-18 High Alpha Research Vehicle (HARV). The F/A-18 SRA data were produced from a wingtip excitation system that generated linear frequency chirps and logarithmic sweeps. HARV data were acquired from digital Schroeder-phased and sinc pulse excitation signals to actuator commands. Nondilated continuous Morlet wavelets implemented as a filter bank were chosen for the time-frequency analysis to eliminate phase distortion as it occurs with sliding window discrete Fourier transform techniques. Wavelet coefficients were filtered to reduce effects of noise and nonlinear distortions identically in all inputs and outputs. Cleaned reconstructed time domain signals were used to compute improved transfer functions. Time and frequency domain subspace identification methods were applied to enhanced reconstructed time domain data and improved transfer functions, respectively. Time domain subspace performed poorly, even with the enhanced data, compared with frequency domain techniques. A frequency domain subspace method is shown to produce better results with the data processed using the Morlet time-frequency technique.

Preliminary work about the reproduction of sonic boom signals for perception studies

NASA Astrophysics Data System (ADS)

Epain, N.; Herzog, P.; Rabau, G.; Friot, E.

2006-05-01

As part of a French research program, a sound restitution cabin was designed for investigating the annoyance of sonic boom signals. The first goal was to reproduce the boom spectrum and temporal waveform: this required linear generation of high pressure levels at infrasonic frequencies (110 SPL dB around 3 Hz), and response equalization over the full frequency range (1 Hz-20 kHz). At this stage the pressure inside the cabin was almost uniform around the listener, emulating an outdoor situation. A psychoacoustic study was then conducted which confirmed that the loudness (related to annoyance) of N-waves is roughly governed by the peak pressure, the rise/fall time, and the wave duration. A longer-term goal is to reproduce other aspects of an indoor situation including rattle noise, ground vibrations, and a more realistic spatial repartition of pressure. This latter point has been addressed through an Active Noise Control study aiming at monitoring the low-frequency acoustic pressure on a surface enclosing a listener. Frequency and time-domain numerical simulations of boom reproduction via ANC are given, including a sensitivity study of the coupling between a listener's head and the incident boom wave which combine into the effective sound-field to be reproduced.

Frequency domain finite-element and spectral-element acoustic wave modeling using absorbing boundaries and perfectly matched layer

NASA Astrophysics Data System (ADS)

Rahimi Dalkhani, Amin; Javaherian, Abdolrahim; Mahdavi Basir, Hadi

2018-04-01

Wave propagation modeling as a vital tool in seismology can be done via several different numerical methods among them are finite-difference, finite-element, and spectral-element methods (FDM, FEM and SEM). Some advanced applications in seismic exploration benefit the frequency domain modeling. Regarding flexibility in complex geological models and dealing with the free surface boundary condition, we studied the frequency domain acoustic wave equation using FEM and SEM. The results demonstrated that the frequency domain FEM and SEM have a good accuracy and numerical efficiency with the second order interpolation polynomials. Furthermore, we developed the second order Clayton and Engquist absorbing boundary condition (CE-ABC2) and compared it with the perfectly matched layer (PML) for the frequency domain FEM and SEM. In spite of PML method, CE-ABC2 does not add any additional computational cost to the modeling except assembling boundary matrices. As a result, considering CE-ABC2 is more efficient than PML for the frequency domain acoustic wave propagation modeling especially when computational cost is high and high-level absorbing performance is unnecessary.

A statistical package for computing time and frequency domain analysis

NASA Technical Reports Server (NTRS)

Brownlow, J.

1978-01-01

The spectrum analysis (SPA) program is a general purpose digital computer program designed to aid in data analysis. The program does time and frequency domain statistical analyses as well as some preanalysis data preparation. The capabilities of the SPA program include linear trend removal and/or digital filtering of data, plotting and/or listing of both filtered and unfiltered data, time domain statistical characterization of data, and frequency domain statistical characterization of data.

A spectral power analysis of driving behavior changes during the transition from nondistraction to distraction.

PubMed

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 driving performance compared to time domain analyses.

Evidence in Support of the Independent Channel Model Describing the Sensorimotor Control of Human Stance Using a Humanoid Robot

PubMed Central

Pasma, Jantsje H.; Assländer, Lorenz; van Kordelaar, Joost; de Kam, Digna; Mergner, Thomas; Schouten, Alfred C.

2018-01-01

The Independent Channel (IC) model is a commonly used linear balance control model in the frequency domain to analyze human balance control using system identification and parameter estimation. The IC model is a rudimentary and noise-free description of balance behavior in the frequency domain, where a stable model representation is not guaranteed. In this study, we conducted firstly time-domain simulations with added noise, and secondly robot experiments by implementing the IC model in a real-world robot (PostuRob II) to test the validity and stability of the model in the time domain and for real world situations. Balance behavior of seven healthy participants was measured during upright stance by applying pseudorandom continuous support surface rotations. System identification and parameter estimation were used to describe the balance behavior with the IC model in the frequency domain. The IC model with the estimated parameters from human experiments was implemented in Simulink for computer simulations including noise in the time domain and robot experiments using the humanoid robot PostuRob II. Again, system identification and parameter estimation were used to describe the simulated balance behavior. Time series, Frequency Response Functions, and estimated parameters from human experiments, computer simulations, and robot experiments were compared with each other. The computer simulations showed similar balance behavior and estimated control parameters compared to the human experiments, in the time and frequency domain. Also, the IC model was able to control the humanoid robot by keeping it upright, but showed small differences compared to the human experiments in the time and frequency domain, especially at high frequencies. We conclude that the IC model, a descriptive model in the frequency domain, can imitate human balance behavior also in the time domain, both in computer simulations with added noise and real world situations with a humanoid robot. This provides further evidence that the IC model is a valid description of human balance control. PMID:29615886

Evidence in Support of the Independent Channel Model Describing the Sensorimotor Control of Human Stance Using a Humanoid Robot.

PubMed

Pasma, Jantsje H; Assländer, Lorenz; van Kordelaar, Joost; de Kam, Digna; Mergner, Thomas; Schouten, Alfred C

2018-01-01

The Independent Channel (IC) model is a commonly used linear balance control model in the frequency domain to analyze human balance control using system identification and parameter estimation. The IC model is a rudimentary and noise-free description of balance behavior in the frequency domain, where a stable model representation is not guaranteed. In this study, we conducted firstly time-domain simulations with added noise, and secondly robot experiments by implementing the IC model in a real-world robot (PostuRob II) to test the validity and stability of the model in the time domain and for real world situations. Balance behavior of seven healthy participants was measured during upright stance by applying pseudorandom continuous support surface rotations. System identification and parameter estimation were used to describe the balance behavior with the IC model in the frequency domain. The IC model with the estimated parameters from human experiments was implemented in Simulink for computer simulations including noise in the time domain and robot experiments using the humanoid robot PostuRob II. Again, system identification and parameter estimation were used to describe the simulated balance behavior. Time series, Frequency Response Functions, and estimated parameters from human experiments, computer simulations, and robot experiments were compared with each other. The computer simulations showed similar balance behavior and estimated control parameters compared to the human experiments, in the time and frequency domain. Also, the IC model was able to control the humanoid robot by keeping it upright, but showed small differences compared to the human experiments in the time and frequency domain, especially at high frequencies. We conclude that the IC model, a descriptive model in the frequency domain, can imitate human balance behavior also in the time domain, both in computer simulations with added noise and real world situations with a humanoid robot. This provides further evidence that the IC model is a valid description of human balance control.

Time-domain digital pre-equalization for band-limited signals based on receiver-side adaptive equalizers.

PubMed

Zhang, Junwen; Yu, Jianjun; Chi, Nan; Chien, Hung-Chang

2014-08-25

We theoretically and experimentally investigate a time-domain digital pre-equalization (DPEQ) scheme for bandwidth-limited optical coherent communication systems, which is based on feedback of channel characteristics from the receiver-side blind and adaptive equalizers, such as least-mean-squares (LMS) algorithm and constant or multi- modulus algorithms (CMA, MMA). Based on the proposed DPEQ scheme, we theoretically and experimentally study its performance in terms of various channel conditions as well as resolutions for channel estimation, such as filtering bandwidth, taps length, and OSNR. Using a high speed 64-GSa/s DAC in cooperation with the proposed DPEQ technique, we successfully synthesized band-limited 40-Gbaud signals in modulation formats of polarization-diversion multiplexed (PDM) quadrature phase shift keying (QPSK), 8-quadrature amplitude modulation (QAM) and 16-QAM, and significant improvement in both back-to-back and transmission BER performances are also demonstrated.

Transonic streamline of symmetric wing under the influence unilateral oscillations characterized by the spectrum of two frequencies

NASA Astrophysics Data System (ADS)

Zamuraev, V. P.; Kalinina, A. P.

2017-10-01

Forced high-frequency vibrations of the airfoil surface part with the amplitude almost equal to the sound velocity can change significantly the lift force of the symmetric profile streamlined at zero angle of attack. The oscillation consists of two harmonics. The ratio of harmonics frequencies values is equal to 2. The present work shows that the aerodynamic properties depend significantly on the specific energy contribution of each frequency.

Frequency-domain multiscale quantum mechanics/electromagnetics simulation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Lingyi; Yin, Zhenyu; Yam, ChiYung, E-mail: yamcy@yangtze.hku.hk, E-mail: ghc@everest.hku.hk

A frequency-domain quantum mechanics and electromagnetics (QM/EM) method is developed. Compared with the time-domain QM/EM method [Meng et al., J. Chem. Theory Comput. 8, 1190–1199 (2012)], the newly developed frequency-domain QM/EM method could effectively capture the dynamic properties of electronic devices over a broader range of operating frequencies. The system is divided into QM and EM regions and solved in a self-consistent manner via updating the boundary conditions at the QM and EM interface. The calculated potential distributions and current densities at the interface are taken as the boundary conditions for the QM and EM calculations, respectively, which facilitate themore » information exchange between the QM and EM calculations and ensure that the potential, charge, and current distributions are continuous across the QM/EM interface. Via Fourier transformation, the dynamic admittance calculated from the time-domain and frequency-domain QM/EM methods is compared for a carbon nanotube based molecular device.« less

Robust time and frequency domain estimation methods in adaptive control

NASA Technical Reports Server (NTRS)

Lamaire, Richard Orville

1987-01-01

A robust identification method was developed for use in an adaptive control system. The type of estimator is called the robust estimator, since it is robust to the effects of both unmodeled dynamics and an unmeasurable disturbance. The development of the robust estimator was motivated by a need to provide guarantees in the identification part of an adaptive controller. To enable the design of a robust control system, a nominal model as well as a frequency-domain bounding function on the modeling uncertainty associated with this nominal model must be provided. Two estimation methods are presented for finding parameter estimates, and, hence, a nominal model. One of these methods is based on the well developed field of time-domain parameter estimation. In a second method of finding parameter estimates, a type of weighted least-squares fitting to a frequency-domain estimated model is used. The frequency-domain estimator is shown to perform better, in general, than the time-domain parameter estimator. In addition, a methodology for finding a frequency-domain bounding function on the disturbance is used to compute a frequency-domain bounding function on the additive modeling error due to the effects of the disturbance and the use of finite-length data. The performance of the robust estimator in both open-loop and closed-loop situations is examined through the use of simulations.

A comprehensive estimate of the static aerodynamic forces and moments of the 8 x 8 x 20 ft. cargo container

NASA Technical Reports Server (NTRS)

Cicolani, Luigi; Kanning, Gerd

1987-01-01

A comprehensive static aerodynamic simulation model of the 8 by 8 by 20 ft MILVAN cargo container is determined by combining the wind tunnel data from a 1972 NASA Ames Research Center study taken over the restricted domain (0 is less than or equal to phi is less than or equal to 90 degrees; 0 is less than or equal to alpha is less than or equal to 45 degrees) with extrapolation relations derived from the geometric symmetry of rectangular boxes. It is found that the aerodynamics of any attitude can be defined from the aerodynamics at an equivalent attitude in the restricted domain (0 is less than phi is less than 45 degrees; 0 is less than alpha is less than 90 degrees). However, a similar comprehensive equivalence with the domain spanned by the data is not available; in particular, about two-thirds of the domain with the absolute value of alpha is greater than 45 degrees is unrelated to the data. Nevertheless, as estimate can be defined for this region consistent with the measured or theoretical values along its boundaries and the theoretical equivalence of points within the region. These descrepancies are assumed to be due to measurement errors. Data from independent wind tunnel studies are reviewed; these are less comprehensive than the NASA Ames Research Center but show good to fair agreement with both the theory and the estimate given here.

Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane

PubMed Central

Fujiwara, Takahiro K.; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A.; Watanabe, Yusuke; Umemura, Yasuhiro M.; Murakoshi, Hideji; Suzuki, Kenichi G. N.; Nemoto, Yuri L.; Morone, Nobuhiro; Kusumi, Akihiro

2016-01-01

The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed “hop diffusion”) for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion. PMID:26864625

What can we learn about beat perception by comparing brain signals and stimulus envelopes?

PubMed

Henry, Molly J; Herrmann, Björn; Grahn, Jessica A

2017-01-01

Entrainment of neural oscillations on multiple time scales is important for the perception of speech. Musical rhythms, and in particular the perception of a regular beat in musical rhythms, is also likely to rely on entrainment of neural oscillations. One recently proposed approach to studying beat perception in the context of neural entrainment and resonance (the "frequency-tagging" approach) has received an enthusiastic response from the scientific community. A specific version of the approach involves comparing frequency-domain representations of acoustic rhythm stimuli to the frequency-domain representations of neural responses to those rhythms (measured by electroencephalography, EEG). The relative amplitudes at specific EEG frequencies are compared to the relative amplitudes at the same stimulus frequencies, and enhancements at beat-related frequencies in the EEG signal are interpreted as reflecting an internal representation of the beat. Here, we show that frequency-domain representations of rhythms are sensitive to the acoustic features of the tones making up the rhythms (tone duration, onset/offset ramp duration); in fact, relative amplitudes at beat-related frequencies can be completely reversed by manipulating tone acoustics. Crucially, we show that changes to these acoustic tone features, and in turn changes to the frequency-domain representations of rhythms, do not affect beat perception. Instead, beat perception depends on the pattern of onsets (i.e., whether a rhythm has a simple or complex metrical structure). Moreover, we show that beat perception can differ for rhythms that have numerically identical frequency-domain representations. Thus, frequency-domain representations of rhythms are dissociable from beat perception. For this reason, we suggest caution in interpreting direct comparisons of rhythms and brain signals in the frequency domain. Instead, we suggest that combining EEG measurements of neural signals with creative behavioral paradigms is of more benefit to our understanding of beat perception.

Quantitative broadband absorption and scattering spectroscopy in turbid media by combined frequency-domain and steady state methodologies

DOEpatents

Tromberg, Bruce J [Irvine, CA; Berger, Andrew J [Rochester, NY; Cerussi, Albert E [Lake Forest, CA; Bevilacqua, Frederic [Costa Mesa, CA; Jakubowski, Dorota [Irvine, CA

2008-09-23

A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.

High Accuracy Evaluation of the Finite Fourier Transform Using Sampled Data

NASA Technical Reports Server (NTRS)

Morelli, Eugene A.

1997-01-01

Many system identification and signal processing procedures can be done advantageously in the frequency domain. A required preliminary step for this approach is the transformation of sampled time domain data into the frequency domain. The analytical tool used for this transformation is the finite Fourier transform. Inaccuracy in the transformation can degrade system identification and signal processing results. This work presents a method for evaluating the finite Fourier transform using cubic interpolation of sampled time domain data for high accuracy, and the chirp Zeta-transform for arbitrary frequency resolution. The accuracy of the technique is demonstrated in example cases where the transformation can be evaluated analytically. Arbitrary frequency resolution is shown to be important for capturing details of the data in the frequency domain. The technique is demonstrated using flight test data from a longitudinal maneuver of the F-18 High Alpha Research Vehicle.

Separation of electrocardiographic from electromyographic signals using dynamic filtration.

PubMed

Christov, Ivaylo; Raikova, Rositsa; Angelova, Silvija

2018-07-01

Trunk muscle electromyographic (EMG) signals are often contaminated by the electrical activity of the heart. During low or moderate muscle force, these electrocardiographic (ECG) signals disturb the estimation of muscle activity. Butterworth high-pass filters with cut-off frequency of up to 60 Hz are often used to suppress the ECG signal. Such filters disturb the EMG signal in both frequency and time domain. A new method based on the dynamic application of Savitzky-Golay filter is proposed. EMG signals of three left trunk muscles and pure ECG signal were recorded during different motor tasks. The efficiency of the method was tested and verified both with the experimental EMG signals and with modeled signals obtained by summing the pure ECG signal with EMG signals at different levels of signal-to-noise ratio. The results were compared with those obtained by application of high-pass, 4th order Butterworth filter with cut-off frequency of 30 Hz. The suggested method is separating the EMG signal from the ECG signal without EMG signal distortion across its entire frequency range regardless of amplitudes. Butterworth filter suppresses the signals in the 0-30 Hz range thus preventing the low-frequency analysis of the EMG signal. An additional disadvantage is that it passes high-frequency ECG signal components which is apparent at equal and higher amplitudes of the ECG signal as compared to the EMG signal. The new method was also successfully verified with abnormal ECG signals. Copyright © 2018. Published by Elsevier Ltd.

How to choose a subset of frequencies in frequency-domain finite-difference migration

NASA Astrophysics Data System (ADS)

Mulder, W. A.; Plessix, R.-E.

2004-09-01

Finite-difference migration with the two-way wave equation can be accelerated by an order of magnitude if the frequency domain rather than the time domain is used. This gain is mainly accomplished by using a subset of the available frequencies. The implicit assumption is that the data have a certain amount of redundancy in the frequency domain. The choice of frequencies cannot be arbitrary. If the frequencies are chosen with a constant increment and their spacing is too large, the well-known wrap-around that occurs when transforming back to the time domain will also show up in the migration to the depth domain, albeit in a more subtle way. Because migration involves propagation in a given background velocity model and summation over shots and receivers, the effects of wrap-around may disappear even when the Nyquist theorem is not obeyed. We have studied these effects analytically for the constant-velocity case and determined sampling conditions that avoid wrap-around artefacts. The conditions depend on the velocity, depth of the migration grid and offset range. They show that the spacing between subsequent frequencies can be larger than the inverse of the time range prescribed by the Nyquist theorem. A 2-D example has been used to test the validity of these conditions for a more realistic velocity model. Finite-difference migration with the one-way wave equation shows a similar behaviour.

User's Guide for MSAP2D: A Program for Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Multistage Compressors and Turbines. 1.0

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Srivastava, R.

1996-01-01

This guide describes the input data required for using MSAP2D (Multi Stage Aeroelastic analysis Program - Two Dimensional) computer code. MSAP2D can be used for steady, unsteady aerodynamic, and aeroelastic (flutter and forced response) analysis of bladed disks arranged in multiple blade rows such as those found in compressors, turbines, counter rotating propellers or propfans. The code can also be run for single blade row. MSAP2D code is an extension of the original NPHASE code for multiblade row aerodynamic and aeroelastic analysis. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The aeroelastic equations are solved in time domain. For single blade row analysis, frequency domain analysis is also provided to obtain unsteady aerodynamic coefficients required in an eigen analysis for flutter. In this manual, sample input and output are provided for a single blade row example, two blade row example with equal and unequal number of blades in the blade rows.

Maximum likelihood method for estimating airplane stability and control parameters from flight data in frequency domain

NASA Technical Reports Server (NTRS)

Klein, V.

1980-01-01

A frequency domain maximum likelihood method is developed for the estimation of airplane stability and control parameters from measured data. The model of an airplane is represented by a discrete-type steady state Kalman filter with time variables replaced by their Fourier series expansions. The likelihood function of innovations is formulated, and by its maximization with respect to unknown parameters the estimation algorithm is obtained. This algorithm is then simplified to the output error estimation method with the data in the form of transformed time histories, frequency response curves, or spectral and cross-spectral densities. The development is followed by a discussion on the equivalence of the cost function in the time and frequency domains, and on advantages and disadvantages of the frequency domain approach. The algorithm developed is applied in four examples to the estimation of longitudinal parameters of a general aviation airplane using computer generated and measured data in turbulent and still air. The cost functions in the time and frequency domains are shown to be equivalent; therefore, both approaches are complementary and not contradictory. Despite some computational advantages of parameter estimation in the frequency domain, this approach is limited to linear equations of motion with constant coefficients.

Rapid Frequency Chirps of TAE mode due to Finite Orbit Energetic Particles

NASA Astrophysics Data System (ADS)

Berk, Herb; Wang, Ge

2013-10-01

The tip model for the TAE mode in the large aspect ratio limit, conceived by Rosenbluth et al. in the frequency domain, together with an interaction term in the frequency domain based on a map model, has been extended into the time domain. We present the formal basis for the model, starting with the Lagrangian for the particle wave interaction. We shall discuss the formal nonlinear time domain problem and the procedure that needs to obtain solutions in the adiabatic limit.

Auditory brainstem responses predict auditory nerve fiber thresholds and frequency selectivity in hearing impaired chinchillas

PubMed Central

Henry, Kenneth S.; Kale, Sushrut; Scheidt, Ryan E.; Heinz, Michael G.

2011-01-01

Non-invasive auditory brainstem responses (ABRs) are commonly used to assess cochlear pathology in both clinical and research environments. In the current study, we evaluated the relationship between ABR characteristics and more direct measures of cochlear function. We recorded ABRs and auditory nerve (AN) single-unit responses in seven chinchillas with noise induced hearing loss. ABRs were recorded for 1–8 kHz tone burst stimuli both before and several weeks after four hours of exposure to a 115 dB SPL, 50 Hz band of noise with a center frequency of 2 kHz. Shifts in ABR characteristics (threshold, wave I amplitude, and wave I latency) following hearing loss were compared to AN-fiber tuning curve properties (threshold and frequency selectivity) in the same animals. As expected, noise exposure generally resulted in an increase in ABR threshold and decrease in wave I amplitude at equal SPL. Wave I amplitude at equal sensation level (SL), however, was similar before and after noise exposure. In addition, noise exposure resulted in decreases in ABR wave I latency at equal SL and, to a lesser extent, at equal SPL. The shifts in ABR characteristics were significantly related to AN-fiber tuning curve properties in the same animal at the same frequency. Larger shifts in ABR thresholds and ABR wave I amplitude at equal SPL were associated with greater AN threshold elevation. Larger reductions in ABR wave I latency at equal SL, on the other hand, were associated with greater loss of AN frequency selectivity. This result is consistent with linear systems theory, which predicts shorter time delays for broader peripheral frequency tuning. Taken together with other studies, our results affirm that ABR thresholds and wave I amplitude provide useful estimates of cochlear sensitivity. Furthermore, comparisons of ABR wave I latency to normative data at the same SL may prove useful for detecting and characterizing loss of cochlear frequency selectivity. PMID:21699970

Time-frequency featured co-movement between the stock and prices of crude oil and gold

NASA Astrophysics Data System (ADS)

Huang, Shupei; An, Haizhong; Gao, Xiangyun; Huang, Xuan

2016-02-01

The nonlinear relationships among variables caused by the hidden frequency information complicate the time series analysis. To shed more light on this nonlinear issue, we examine their relationships in joint time-frequency domain with multivariate framework, and the analyses in the time domain and frequency domain serve as comparisons. The daily Brent oil prices, London gold fixing price and Shanghai Composite index from January 1991 to September 2014 are adopted as example. First, they have long-term cointegration relationship in time domain from holistic perspective. Second, the Granger causality tests in different frequency bands are heterogeneous. Finally, the comparison between results from wavelet coherence and multiple wavelet coherence in the joint time-frequency domain indicates that in the high (1-14 days) and medium frequency (14-128 days) bands, the combination of Brent and gold prices has stronger correlation with the stock. In the low frequency band (256-512 days), year 2003 is the structure broken point before which Brent and oil are ideal choice for hedging the risk of the stock market. Thus, this paper offers more details between the Chinese stock market and the commodities markets of crude oil and gold, which suggests that the decisions for different time and frequencies should consider the corresponding benchmark information.

A frequency-domain estimator for use in adaptive control systems

NASA Technical Reports Server (NTRS)

Lamaire, Richard O.; Valavani, Lena; Athans, Michael; Stein, Gunter

1991-01-01

This paper presents a frequency-domain estimator that can identify both a parametrized nominal model of a plant as well as a frequency-domain bounding function on the modeling error associated with this nominal model. This estimator, which we call a robust estimator, can be used in conjunction with a robust control-law redesign algorithm to form a robust adaptive controller.

Disgust sensitivity is primarily associated with purity-based moral judgments.

PubMed

Wagemans, Fieke M A; Brandt, Mark J; Zeelenberg, Marcel

2018-03-01

Individual differences in disgust sensitivity are associated with a range of judgments and attitudes related to the moral domain. Some perspectives suggest that the association between disgust sensitivity and moral judgments will be equally strong across all moral domains (i.e., purity, authority, loyalty, care, fairness, and liberty). Other perspectives predict that disgust sensitivity is primarily associated with judgments of specific moral domains (e.g., primarily purity). However, no study has systematically tested if disgust sensitivity is associated with moral judgments of the purity domain specifically, more generally to moral judgments of the binding moral domains, or to moral judgments of all of the moral domains equally. Across 5 studies (total N = 1,104), we find consistent evidence for the notion that disgust sensitivity relates more strongly to moral condemnation of purity-based transgressions (meta-analytic r = .40) than to moral condemnation of transgressions of any of the other domains (range meta-analytic rs: .07-.27). Our findings are in line with predictions from Moral Foundations Theory, which predicts that personality characteristics like disgust sensitivity make people more sensitive to a certain set of moral issues. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Real-Time Classification of Exercise Exertion Levels Using Discriminant Analysis of HRV Data.

PubMed

Jeong, In Cheol; Finkelstein, Joseph

2015-01-01

Heart rate variability (HRV) was shown to reflect activation of sympathetic nervous system however it is not clear which set of HRV parameters is optimal for real-time classification of exercise exertion levels. There is no studies that compared potential of two types of HRV parameters (time-domain and frequency-domain) in predicting exercise exertion level using discriminant analysis. The main goal of this study was to compare potential of HRV time-domain parameters versus HRV frequency-domain parameters in classifying exercise exertion level. Rest, exercise, and recovery categories were used in classification models. Overall 79.5% classification agreement by the time-domain parameters as compared to overall 52.8% classification agreement by frequency-domain parameters demonstrated that the time-domain parameters had higher potential in classifying exercise exertion levels.

Frequency- and Time-Domain Methods in Soil-Structure Interaction Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolisetti, Chandrakanth; Whittaker, Andrew S.; Coleman, Justin L.

2015-06-01

Soil-structure interaction (SSI) analysis in the nuclear industry is currently performed using linear codes that function in the frequency domain. There is a consensus that these frequency-domain codes give reasonably accurate results for low-intensity ground motions that result in almost linear response. For higher intensity ground motions, which may result in nonlinear response in the soil, structure or at the vicinity of the foundation, the adequacy of frequency-domain codes is unproven. Nonlinear analysis, which is only possible in the time domain, is theoretically more appropriate in such cases. These methods are available but are rarely used due to the largemore » computational requirements and a lack of experience with analysts and regulators. This paper presents an assessment of the linear frequency-domain code, SASSI, which is widely used in the nuclear industry, and the time-domain commercial finite-element code, LS-DYNA, for SSI analysis. The assessment involves benchmarking the SSI analysis procedure in LS-DYNA against SASSI for linearly elastic models. After affirming that SASSI and LS-DYNA result in almost identical responses for these models, they are used to perform nonlinear SSI analyses of two structures founded on soft soil. An examination of the results shows that, in spite of using identical material properties, the predictions of frequency- and time-domain codes are significantly different in the presence of nonlinear behavior such as gapping and sliding of the foundation.« less

Multiple point least squares equalization in a room

NASA Technical Reports Server (NTRS)

Elliott, S. J.; Nelson, P. A.

1988-01-01

Equalization filters designed to minimize the mean square error between a delayed version of the original electrical signal and the equalized response at a point in a room have previously been investigated. In general, such a strategy degrades the response at positions in a room away from the equalization point. A method is presented for designing an equalization filter by adjusting the filter coefficients to minimize the sum of the squares of the errors between the equalized responses at multiple points in the room and delayed versions of the original, electrical signal. Such an equalization filter can give a more uniform frequency response over a greater volume of the enclosure than can the single point equalizer above. Computer simulation results are presented of equalizing the frequency responses from a loudspeaker to various typical ear positions, in a room with dimensions and acoustic damping typical of a car interior, using the two approaches outlined above. Adaptive filter algorithms, which can automatically adjust the coefficients of a digital equalization filter to achieve this minimization, will also be discussed.

Time-Delay Interferometry for Space-based Gravitational Wave Searches

NASA Technical Reports Server (NTRS)

Armstrong, J.; Estabrook, F.; Tinto, M.

1999-01-01

Ground-based, equal-arm-length laser interferometers are being built to measure high-frequency astrophysical graviatational waves. Because of the arm-length equality, laser light experiences the same delay in each arm and thus phase or frequency noise from the laser itself precisely cancels at the photodetector.

Time-Domain Impedance Boundary Conditions for Computational Aeroacoustics

NASA Technical Reports Server (NTRS)

Tam, Christopher K. W.; Auriault, Laurent

1996-01-01

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

Measurement of high-degree solar oscillation frequencies

NASA Technical Reports Server (NTRS)

Bachmann, K. T.; Duvall, T. L., Jr.; Harvey, J. W.; Hill, F.

1995-01-01

We present m-averaged solar p- and f-mode oscillation frequencies over the frequency range nu greater than 1.8 and less than 5.0 mHz and the spherical harmonic degree range l greater than or equal to 100 and less than or equal to 1200 from full-disk, 1000 x 1024 pixel, Ca II intensity images collected 1993 June 22-25 with a temporal cadence of 60 s. We itemize the sources and magnitudes of statistical and systematic uncertainties and of small frequency corrections, and we show that our frequencies represent an improvement in accuracy and coverage over previous measurements. Our frequencies agree at the 2 micro Hz level with Mount Wilson frequencies determined for l less than or equal to 600 from full-disk images, and we find systematic offsets of 10-20 micro Hz with respect to frequencies measured from Big Bear and La Palma observations. We give evidence that these latter offsets are indicative of spatial scaling uncertainties associated with the analysis of partial-disk images. In comparison with theory, our p-mode frequencies agree within 10 micro Hz of frequencies predicted by the Los Alamos model but are as much as 100 micro Hz smaller than frequencies predicted by the Denmark and Yale models at degrees near 1000. We also find systematic differences between our n = 0 frequencies and the frequencies closely agreed upon by all three models.

Assessment of Sensorimotor Abilities of Severely Retarded Children and Adolescents.

ERIC Educational Resources Information Center

Hupp, Susan C.; And Others

1984-01-01

An investigation of the order of acquisition of domains by severely retarded children and adolescents indicated that object permanence performance always equaled or exceeded means-ends, which in turn always equaled or exceeded causality for 23 of 25 subjects. (Author/CL)

Self Consistent Ambipolar Transport and High Frequency Oscillatory Transient in Graphene Electronics

DTIC Science & Technology

2015-08-17

study showed that in the presence of an ac field, THz oscillations exhibit soft resonances at a frequency roughly equal to half of the inverse of the ...exhibit soft resonances at a frequency roughly equal to half of the inverse of the carrier transit time to the LO phonon energy. It also showed that in...carriers in graphene undergo an anomalous parametric resonance. Such resonance occurs at about half the frequency ωF = 2πeF/~ωOP , where 2π/ωF is the time

Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy

PubMed Central

Vogel, Manuel; Quint, Wolfgang; Nörtershäuser, Wilfried

2010-01-01

The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state life-times. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below μeV in the microwave domain to beyond MeV in the X-ray domain. PMID:22294921

Cerebral autoregulation in the preterm newborn using near-infrared spectroscopy: a comparison of time-domain and frequency-domain analyses

NASA Astrophysics Data System (ADS)

Eriksen, Vibeke R.; Hahn, Gitte H.; Greisen, Gorm

2015-03-01

The aim was to compare two conventional methods used to describe cerebral autoregulation (CA): frequency-domain analysis and time-domain analysis. We measured cerebral oxygenation (as a surrogate for cerebral blood flow) and mean arterial blood pressure (MAP) in 60 preterm infants. In the frequency domain, outcome variables were coherence and gain, whereas the cerebral oximetry index (COx) and the regression coefficient were the outcome variables in the time domain. Correlation between coherence and COx was poor. The disagreement between the two methods was due to the MAP and cerebral oxygenation signals being in counterphase in three cases. High gain and high coherence may arise spuriously when cerebral oxygenation decreases as MAP increases; hence, time-domain analysis appears to be a more robust-and simpler-method to describe CA.

Multi-scale Slip Inversion Based on Simultaneous Spatial and Temporal Domain Wavelet Transform

NASA Astrophysics Data System (ADS)

Liu, W.; Yao, H.; Yang, H. Y.

2017-12-01

Finite fault inversion is a widely used method to study earthquake rupture processes. Some previous studies have proposed different methods to implement finite fault inversion, including time-domain, frequency-domain, and wavelet-domain methods. Many previous studies have found that different frequency bands show different characteristics of the seismic rupture (e.g., Wang and Mori, 2011; Yao et al., 2011, 2013; Uchide et al., 2013; Yin et al., 2017). Generally, lower frequency waveforms correspond to larger-scale rupture characteristics while higher frequency data are representative of smaller-scale ones. Therefore, multi-scale analysis can help us understand the earthquake rupture process thoroughly from larger scale to smaller scale. By the use of wavelet transform, the wavelet-domain methods can analyze both the time and frequency information of signals in different scales. Traditional wavelet-domain methods (e.g., Ji et al., 2002) implement finite fault inversion with both lower and higher frequency signals together to recover larger-scale and smaller-scale characteristics of the rupture process simultaneously. Here we propose an alternative strategy with a two-step procedure, i.e., firstly constraining the larger-scale characteristics with lower frequency signals, and then resolving the smaller-scale ones with higher frequency signals. We have designed some synthetic tests to testify our strategy and compare it with the traditional one. We also have applied our strategy to study the 2015 Gorkha Nepal earthquake using tele-seismic waveforms. Both the traditional method and our two-step strategy only analyze the data in different temporal scales (i.e., different frequency bands), while the spatial distribution of model parameters also shows multi-scale characteristics. A more sophisticated strategy is to transfer the slip model into different spatial scales, and then analyze the smooth slip distribution (larger scales) with lower frequency data firstly and more detailed slip distribution (smaller scales) with higher frequency data subsequently. We are now implementing the slip inversion using both spatial and temporal domain wavelets. This multi-scale analysis can help us better understand frequency-dependent rupture characteristics of large earthquakes.

Comparison of Frequency-Domain Array Methods for Studying Earthquake Rupture Process

NASA Astrophysics Data System (ADS)

Sheng, Y.; Yin, J.; Yao, H.

2014-12-01

Seismic array methods, in both time- and frequency- domains, have been widely used to study the rupture process and energy radiation of earthquakes. With better spatial resolution, the high-resolution frequency-domain methods, such as Multiple Signal Classification (MUSIC) (Schimdt, 1986; Meng et al., 2011) and the recently developed Compressive Sensing (CS) technique (Yao et al., 2011, 2013), are revealing new features of earthquake rupture processes. We have performed various tests on the methods of MUSIC, CS, minimum-variance distortionless response (MVDR) Beamforming and conventional Beamforming in order to better understand the advantages and features of these methods for studying earthquake rupture processes. We use the ricker wavelet to synthesize seismograms and use these frequency-domain techniques to relocate the synthetic sources we set, for instance, two sources separated in space but, their waveforms completely overlapping in the time domain. We also test the effects of the sliding window scheme on the recovery of a series of input sources, in particular, some artifacts that are caused by the sliding window scheme. Based on our tests, we find that CS, which is developed from the theory of sparsity inversion, has relatively high spatial resolution than the other frequency-domain methods and has better performance at lower frequencies. In high-frequency bands, MUSIC, as well as MVDR Beamforming, is more stable, especially in the multi-source situation. Meanwhile, CS tends to produce more artifacts when data have poor signal-to-noise ratio. Although these techniques can distinctly improve the spatial resolution, they still produce some artifacts along with the sliding of the time window. Furthermore, we propose a new method, which combines both the time-domain and frequency-domain techniques, to suppress these artifacts and obtain more reliable earthquake rupture images. Finally, we apply this new technique to study the 2013 Okhotsk deep mega earthquake in order to better capture the rupture characteristics (e.g., rupture area and velocity) of this earthquake.

Multiple Input Design for Real-Time Parameter Estimation in the Frequency Domain

NASA Technical Reports Server (NTRS)

Morelli, Eugene

2003-01-01

A method for designing multiple inputs for real-time dynamic system identification in the frequency domain was developed and demonstrated. The designed inputs are mutually orthogonal in both the time and frequency domains, with reduced peak factors to provide good information content for relatively small amplitude excursions. The inputs are designed for selected frequency ranges, and therefore do not require a priori models. The experiment design approach was applied to identify linear dynamic models for the F-15 ACTIVE aircraft, which has multiple control effectors.

Frequency-domain method for discrete frequency noise prediction of rotors in arbitrary steady motion

NASA Astrophysics Data System (ADS)

Gennaretti, M.; Testa, C.; Bernardini, G.

2012-12-01

A novel frequency-domain formulation for the prediction of the tonal noise emitted by rotors in arbitrary steady motion is presented. It is derived from Farassat's 'Formulation 1A', that is a time-domain boundary integral representation for the solution of the Ffowcs-Williams and Hawkings equation, and represents noise as harmonic response to body kinematics and aerodynamic loads via frequency-response-function matrices. The proposed frequency-domain solver is applicable to rotor configurations for which sound pressure levels of discrete tones are much higher than those of broadband noise. The numerical investigation concerns the analysis of noise produced by an advancing helicopter rotor in blade-vortex interaction conditions, as well as the examination of pressure disturbances radiated by the interaction of a marine propeller with a non-uniform inflow.

Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

PubMed Central

Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

2016-01-01

Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

Wavelet transformation to determine impedance spectra of lithium-ion rechargeable battery

NASA Astrophysics Data System (ADS)

Hoshi, Yoshinao; Yakabe, Natsuki; Isobe, Koichiro; Saito, Toshiki; Shitanda, Isao; Itagaki, Masayuki

2016-05-01

A new analytical method is proposed to determine the electrochemical impedance of lithium-ion rechargeable batteries (LIRB) from time domain data by wavelet transformation (WT). The WT is a waveform analysis method that can transform data in the time domain to the frequency domain while retaining time information. In this transformation, the frequency domain data are obtained by the convolution integral of a mother wavelet and original time domain data. A complex Morlet mother wavelet (CMMW) is used to obtain the complex number data in the frequency domain. The CMMW is expressed by combining a Gaussian function and sinusoidal term. The theory to select a set of suitable conditions for variables and constants related to the CMMW, i.e., band, scale, and time parameters, is established by determining impedance spectra from wavelet coefficients using input voltage to the equivalent circuit and the output current. The impedance spectrum of LIRB determined by WT agrees well with that measured using a frequency response analyzer.

Ajustement automatique des parametres de coupe pour l'obtention de stabilite dynamique en usinage

NASA Astrophysics Data System (ADS)

Tabet, Ricardo

High speed machining has as principal limitation the dynamic stability of the cutting action which can generate premature wear of the machine spindle and the cutting tool, tool breakage and dimensional errors on the machined part. This phenomenon is known in the literature as chatter and is defined as being self-excited vibrations. This master thesis presents an approach applicable to manufacturing environments that allows eliminating chatter in real time during machining of aerospace aluminum alloys before the damaging effect can occur. A control algorithm is developed in order to detect chatter using a microphone and by analyzing the audio signal in the frequency domain. The analysis allows determining precisely the frequency at which the chatter occurs and therefore, the spindle speed is adjusted in order to make the tooth passing frequency equal to the detected chatter frequency. Also, a new feedrate is determined by keeping a constant chip load and within the physical limits of the cutting tool. The new cutting parameters are then sent out to the machine controller as a command using a communication interface between an external computer and the controller. Multiples experimental tests were conducted to validate the effectiveness to detect and suppress chatter. High speed machining tests, between 15 000 and 33 000 RPM, were performed in order to reflect real conditions for aerospace components manufacturing.

Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting

PubMed Central

Yun, S. H.; Tearney, G. J.; de Boer, J. F.; Bouma, B. E.

2009-01-01

A novel technique using an acousto-optic frequency shifter in optical frequency domain imaging (OFDI) is presented. The frequency shift eliminates the ambiguity between positive and negative differential delays, effectively doubling the interferometric ranging depth while avoiding image cross-talk. A signal processing algorithm is demonstrated to accommodate nonlinearity in the tuning slope of the wavelength-swept OFDI laser source. PMID:19484034

Computer-Aided Design/Manufacturing (CAD/M) for High-Speed Interconnect.

DTIC Science & Technology

1981-10-01

are frequency sensitive and hence lend themselves to frequency domain ananlysis . Most of the classical microwave analysis is handled in the frequency ...capability integrated into a time-domain analysis program. This approach allows determination of frequency -dependent transmission line (interconnect...the items to consider in any interconnect study is that of the frequency range of interest. This determines whether the interconnections must be treated

Iterated intracochlear reflection shapes the envelopes of basilar-membrane click responses

PubMed Central

Shera, Christopher A.

2015-01-01

Multiple internal reflection of cochlear traveling waves has been argued to provide a plausible explanation for the waxing and waning and other temporal structures often exhibited by the envelopes of basilar-membrane (BM) and auditory-nerve responses to acoustic clicks. However, a recent theoretical analysis of a BM click response measured in chinchilla concludes that the waveform cannot have arisen via any equal, repetitive process, such as iterated intracochlear reflection [Wit and Bell (2015), J. Acoust. Soc. Am. 138, 94–96]. Reanalysis of the waveform contradicts this conclusion. The measured BM click response is used to derive the frequency-domain transfer function characterizing every iteration of the loop. The selfsame transfer function that yields waxing and waning of the BM click response also captures the spectral features of ear-canal stimulus-frequency otoacoustic emissions measured in the same animal, consistent with the predictions of multiple internal reflection. Small shifts in transfer-function phase simulate results at different measurement locations and reproduce the heterogeneity of BM click response envelopes observed experimentally. PMID:26723327

An analysis of scatter decomposition

NASA Technical Reports Server (NTRS)

Nicol, David M.; Saltz, Joel H.

1990-01-01

A formal analysis of a powerful mapping technique known as scatter decomposition is presented. Scatter decomposition divides an irregular computational domain into a large number of equal sized pieces, and distributes them modularly among processors. A probabilistic model of workload in one dimension is used to formally explain why, and when scatter decomposition works. The first result is that if correlation in workload is a convex function of distance, then scattering a more finely decomposed domain yields a lower average processor workload variance. The second result shows that if the workload process is stationary Gaussian and the correlation function decreases linearly in distance until becoming zero and then remains zero, scattering a more finely decomposed domain yields a lower expected maximum processor workload. Finally it is shown that if the correlation function decreases linearly across the entire domain, then among all mappings that assign an equal number of domain pieces to each processor, scatter decomposition minimizes the average processor workload variance. The dependence of these results on the assumption of decreasing correlation is illustrated with situations where a coarser granularity actually achieves better load balance.

Holographic imaging based on time-domain data of natural-fiber-containing materials

DOEpatents

Bunch, Kyle J.; McMakin, Douglas L.

2012-09-04

Methods and apparatuses for imaging material properties in natural-fiber-containing materials can utilize time-domain data. In particular, images can be constructed that provide quantified measures of localized moisture content. For example, one or more antennas and at least one transceiver can be configured to collect time-domain data from radiation interacting with the natural-fiber-containing materials. The antennas and the transceivers are configured to transmit and receive electromagnetic radiation at one or more frequencies, which are between 50 MHz and 1 THz, according to a time-domain impulse function. A computing device is configured to transform the time-domain data to frequency-domain data, to apply a synthetic imaging algorithm for constructing a three-dimensional image of the natural-fiber-containing materials, and to provide a quantified measure of localized moisture content based on a pre-determined correlation of moisture content to frequency-domain data.

EDDIE Seismology: Introductory spectral analysis for undergraduates

NASA Astrophysics Data System (ADS)

Soule, D. C.; Gougis, R.; O'Reilly, C.

2016-12-01

We present a spectral seismology lesson in which students use spectral analysis to describe the frequency of seismic arrivals based on a conceptual presentation of waveforms and filters. The goal is for students to surpass basic waveform terminology and relate a time domain signals to their conjugates in the frequency domain. Although seismology instruction commonly engages students in analysis of authentic seismological data, this is less true for lower-level undergraduate seismology instruction due to coding barriers to many seismological analysis tasks. To address this, our module uses Seismic Canvas (Kroeger, 2015; https://seiscode.iris.washington.edu/projects/seismiccanvas), a graphically interactive application for accessing, viewing and analyzing waveform data, which we use to plot earthquake data in the time domain. Once students are familiarized with the general components of the waveform (i.e. frequency, wavelength, amplitude and period), they use Seismic Canvas to transform the data into the frequency domain. Bypassing the mathematics of Fourier Series allows focus on conceptual understanding by plotting and manipulating seismic data in both time and frequency domains. Pre/post-tests showed significant improvements in students' use of seismograms and spectrograms to estimate the frequency content of the primary wave, which demonstrated students' understanding of frequency and how data on the spectrogram and seismogram are related. Students were also able to identify the time and frequency of the largest amplitude arrival, indicating understanding of amplitude and use of a spectrogram as an analysis tool. Students were also asked to compare plots of raw data and the same data filtered with a high-pass filter, and identify the filter used to create the second plot. Students demonstrated an improved understanding of how frequency content can be removed from a signal in the spectral domain.

On the role of density and attenuation in 3D multi-parameter visco-acoustic VTI frequency-domain FWI: an OBC case study from the North Sea

NASA Astrophysics Data System (ADS)

Operto, S.; Miniussi, A.

2018-03-01

Three-dimensional frequency-domain full waveform inversion (FWI) is applied on North Sea wide-azimuth ocean-bottom cable data at low frequencies (≤ 10 Hz) to jointly update vertical wavespeed, density and quality factor Q in the visco-acoustic VTI approximation. We assess whether density and Q should be viewed as proxy to absorb artefacts resulting from approximate wave physics or are valuable for interpretation in presence of saturated sediments and gas. FWI is performed in the frequency domain to account for attenuation easily. Multi-parameter frequency-domain FWI is efficiently performed with a few discrete frequencies following a multi-scale frequency continuation. However, grouping a few frequencies during each multi-scale step is necessary to mitigate acquisition footprint and match dispersive shallow guided waves. Q and density absorb a significant part of the acquisition footprint hence cleaning the velocity model from this pollution. Low Q perturbations correlate with low velocity zones associated with soft sediments and gas cloud. However, the amplitudes of the Q perturbations show significant variations when the inversion tuning is modified. This dispersion in the Q reconstructions is however not passed on the velocity parameter suggesting that cross-talks between first-order kinematic and second-order dynamic parameters are limited. The density model shows a good match with a well log at shallow depths. Moreover, the impedance built a posteriori from the FWI velocity and density models shows a well-focused image with however local differences with the velocity model near the sea bed where density might have absorbed elastic effects. The FWI models are finally assessed against time-domain synthetic seismogram modelling performed with the same frequency-domain modelling engine used for FWI.

On the role of density and attenuation in three-dimensional multiparameter viscoacoustic VTI frequency-domain FWI: an OBC case study from the North Sea

NASA Astrophysics Data System (ADS)

Operto, S.; Miniussi, A.

2018-06-01

3-D frequency-domain full waveform inversion (FWI) is applied on North Sea wide-azimuth ocean-bottom cable data at low frequencies (≤10 Hz) to jointly update vertical wave speed, density and quality factor Q in the viscoacoustic VTI approximation. We assess whether density and Q should be viewed as proxy to absorb artefacts resulting from approximate wave physics or are valuable for interpretation in the presence of soft sediments and gas cloud. FWI is performed in the frequency domain to account for attenuation easily. Multiparameter frequency-domain FWI is efficiently performed with a few discrete frequencies following a multiscale frequency continuation. However, grouping a few frequencies during each multiscale step is necessary to mitigate acquisition footprint and match dispersive shallow guided waves. Q and density absorb a significant part of the acquisition footprint hence cleaning the velocity model from this pollution. Low Q perturbations correlate with low-velocity zones associated with soft sediments and gas cloud. However, the amplitudes of the Q perturbations show significant variations when the inversion tuning is modified. This dispersion in the Q reconstructions is however not passed on the velocity parameter suggesting that cross-talks between first-order kinematic and second-order dynamic parameters are limited. The density model shows a good match with a well log at shallow depths. Moreover, the impedance built a posteriori from the FWI velocity and density models shows a well-focused image with however local differences with the velocity model near the sea bed where density might have absorbed elastic effects. The FWI models are finally assessed against time-domain synthetic seismogram modelling performed with the same frequency-domain modelling engine used for FWI.

Frequency domain kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics

NASA Astrophysics Data System (ADS)

Fl'unt, Orest; Klym, Halyna; Ingram, Adam

2018-03-01

In this work, the kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics sintered at different temperatures (1100, 1200 and 1400 °C) has been calculated and analyzed in a frequency domain. The spectra of real (in-phase) and imaginary (quadrature) components of positron-electron annihilation kinetic have been obtained numerically from usual temporal characteristics using integral Fourier transform. The numerical calculations were carried out using cubic spline interpolation of the pulse characteristics of MgO-Al2O3 ceramics in time domain with following analytical calculations of integrals. The obtained spectra as real so imaginary part of MgO-Al2O3 ceramics in frequency domain almost good obey a Debye law denying correlation between elementary positron annihilation processes. Complex diagrams of frequency domain responses of as-prepared samples have a shape of semicircles with close characteristic frequencies. Some deviation on low-frequency side of the semicircles is observed confirming an availability of longer time kinetic processes. Sintering temperature dependencies of the relaxation times and characteristic frequencies of positron-electron annihilation processes have been obtained. It is shown that position of large maxima on the frequency dependencies of imaginary part corresponds to fast average relaxation lifetime representing the most intensive interaction process of positrons with small cavity traps in solids.

Coulomb couplings in solubilised light harvesting complex II (LHCII): challenging the ideal dipole approximation from TDDFT calculations.

PubMed

López-Tarifa, P; Liguori, Nicoletta; van den Heuvel, Naudin; Croce, Roberta; Visscher, Lucas

2017-07-19

The light harvesting complex II (LHCII), is a pigment-protein complex responsible for most of the light harvesting in plants. LHCII harvests sunlight and transfers excitation energy to the reaction centre of the photo-system, where the water oxidation process takes place. The energetics of LHCII can be modulated by means of conformational changes allowing a switch from a harvesting to a quenched state. In this state, the excitation energy is no longer transferred but converted into thermal energy to prevent photooxidation. Based on molecular dynamics simulations at the microsecond time scale, we have recently proposed that the switch between different fluorescent states can be probed by correlating shifts in the chromophore-chromophore Coulomb interactions to particular protein movements. However, these findings are based upon calculations in the ideal point dipole approximation (IDA) where the Coulomb couplings are simplified as first order dipole-dipole interactions, also assuming that the chromophore transition dipole moments lay in particular directions of space with constant moduli (FIX-IDA). In this work, we challenge this approximation using the time-dependent density functional theory (TDDFT) combined with the frozen density embedding (FDE) approach. Our aim is to establish up to which limit FIX-IDA can be applied and which chromophore types are better described under this approximation. For that purpose, we use the classical trajectories of solubilised light harvesting complex II (LHCII) we have recently reported [Liguori et al., Sci. Rep., 2015, 5, 15661] and selected three pairs of chromophores containing chlorophyll and carotenoids (Chl and Car): Chla611-Chla612, Chlb606-Chlb607 and Chla612-Lut620. Using the FDE in the Tamm-Dancoff approximation (FDEc-TDA), we show that IDA is accurate enough for predicting Chl-Chl Coulomb couplings. However, the FIX-IDA largely overestimates Chl-Car interactions mainly because the transition dipole for the Cars is not trivially oriented on the polyene chain.

Plasma focus sources: Supplement to the Neutron Resonance Radiography Workshop proceedings

NASA Astrophysics Data System (ADS)

Nardi, Vittorio; Brzosko, Jan

1989-01-01

Since their discovery, plasma focus discharges have been recognized as very intense pulsed sources of deuterium-deuterium (D-D) or deuterium-tritium (D-T) fusion-reaction neutrons, with outstanding capabilities. Specifically, the total neutron emission/shot, Y (sub n), and the rate of neutron emission, Y (sub n), of an optimized plasma focus (PF) are higher than the corresponding quantities observed in any other type of pinched discharge at the same level of powering energy W (sub 0). Recent developments have led to the concept and experimental demonstration of an Advanced Plasma Focus System (APF) that consists of a Mather-geometry plasma focus in which field distortion elements (FDEs) are inserted in the inter-electrode gap for increasing the neutron yield/shot, Y (sub n). The FDE-induced redistribution of the plasma current increases Y (sub n) by a factor approximate to or greater than 5 to 10 above the value obtained without FDEs under otherwise identical conditions of operation of the plasma focus. For example, an APF that is fed by a fast capacitor bank with an energy, W (sub 0) = 6 kJ, and voltage, V (sub 0) = 16.5 kV provides Y (sub n) congruent to 4 x 10 to the 9th D-D neutrons/shot (pure D2 filling) and Y (sub n) = 4 x 10 to the 11th D-T neutrons/shot (filling is 50 pct deuterium and 50 pct tritium). The FDE-induced increase of Y (sub n) for fixed values of (W sub 0, V sub 0), the observed scaling law Y (sub n) proportional to W (sub 0) squared for optimized plasma focus systems, and our experience with neutron scattering in bulk objects lead us to the conclusion that we can use an APF as a source of high-intensity neutron pulses (10 to the 14th n/pulse) in the field off neutron radiography (surface and bulk) with a nanosecond or millisecond time resolution.

Beatquency domain and machine learning improve prediction of cardiovascular death after acute coronary syndrome.

PubMed

Liu, Yun; Scirica, Benjamin M; Stultz, Collin M; Guttag, John V

2016-10-06

Frequency domain measures of heart rate variability (HRV) are associated with adverse events after a myocardial infarction. However, patterns in the traditional frequency domain (measured in Hz, or cycles per second) may capture different cardiac phenomena at different heart rates. An alternative is to consider frequency with respect to heartbeats, or beatquency. We compared the use of frequency and beatquency domains to predict patient risk after an acute coronary syndrome. We then determined whether machine learning could further improve the predictive performance. We first evaluated the use of pre-defined frequency and beatquency bands in a clinical trial dataset (N = 2302) for the HRV risk measure LF/HF (the ratio of low frequency to high frequency power). Relative to frequency, beatquency improved the ability of LF/HF to predict cardiovascular death within one year (Area Under the Curve, or AUC, of 0.730 vs. 0.704, p < 0.001). Next, we used machine learning to learn frequency and beatquency bands with optimal predictive power, which further improved the AUC for beatquency to 0.753 (p < 0.001), but not for frequency. Results in additional validation datasets (N = 2255 and N = 765) were similar. Our results suggest that beatquency and machine learning provide valuable tools in physiological studies of HRV.

Finding the Secret of Image Saliency in the Frequency Domain.

PubMed

Li, Jia; Duan, Ling-Yu; Chen, Xiaowu; Huang, Tiejun; Tian, Yonghong

2015-12-01

There are two sides to every story of visual saliency modeling in the frequency domain. On the one hand, image saliency can be effectively estimated by applying simple operations to the frequency spectrum. On the other hand, it is still unclear which part of the frequency spectrum contributes the most to popping-out targets and suppressing distractors. Toward this end, this paper tentatively explores the secret of image saliency in the frequency domain. From the results obtained in several qualitative and quantitative experiments, we find that the secret of visual saliency may mainly hide in the phases of intermediate frequencies. To explain this finding, we reinterpret the concept of discrete Fourier transform from the perspective of template-based contrast computation and thus develop several principles for designing the saliency detector in the frequency domain. Following these principles, we propose a novel approach to design the saliency detector under the assistance of prior knowledge obtained through both unsupervised and supervised learning processes. Experimental results on a public image benchmark show that the learned saliency detector outperforms 18 state-of-the-art approaches in predicting human fixations.

Volterra equalization of complex modulation utilizing frequency chirp in directly modulated lasers

NASA Astrophysics Data System (ADS)

Hu, Shaohua; Yi, Xingwen; Zhang, Jing; Song, Yang; Zhu, Mingyue; Qiu, Kun

2018-02-01

We apply Volterra-based equalization for complex modulated optical signals utilizing the frequency chirp in DMLs. We experimentally demonstrate that the higher order Volterra filter is necessary in the higher speed transmissions. For further study, we isolate the adiabatic chirp by injection locking and realize the optical PM transmission. We make a comparison among IM, FM and PM with Volterra equalization, finding that PM and FM are more power insensitive and suitable for high speed, power limited fiber transmission. The performance can be further improved by exploiting the diversity gain.

VISAR Analysis in the Frequency Domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolan, D. H.; Specht, P.

2017-05-18

VISAR measurements are typically analyzed in the time domain, where velocity is approximately proportional to fringe shift. Moving to the frequency domain clarifies the limitations of this approximation and suggests several improvements. For example, optical dispersion preserves high-frequency information, so a zero-dispersion (air delay) interferometer does not provide optimal time resolution. Combined VISAR measurements can also improve time resolution. With adequate bandwidth and reasonable noise levels, it is quite possible to achieve better resolution than the VISAR approximation allows.

Determining XV-15 aeroelastic modes from flight data with frequency-domain methods

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.; Tischler, Mark B.

1993-01-01

The XV-15 tilt-rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier transformed). All spectral data were computed using chirp z-transforms. Modal frequencies and damping were determined by fitting curves to frequency-response magnitude and phase data. The results given in this report are for the XV-15 with its original metal rotor blades. Also, frequency and damping values are compared with theoretical predictions made using two different programs, CAMRAD and ASAP. The frequency-domain data-analysis method proved to be very reliable and adequate for tracking aeroelastic modes during flight-envelope expansion. This approach required less flight-test time and yielded mode estimations that were more repeatable, compared with the exponential-decay method previously used.

Time Domain Stability Margin Assessment Method

NASA Technical Reports Server (NTRS)

Clements, Keith

2017-01-01

The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.

Time-Domain Stability Margin Assessment

NASA Technical Reports Server (NTRS)

Clements, Keith

2016-01-01

The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.

Quality of life improvement after pressure equalization tube placement in Down syndrome: A prospective study.

PubMed

Labby, Alex; Mace, Jess C; Buncke, Michelle; MacArthur, Carol J

2016-09-01

To evaluate quality-of-life changes after bilateral pressure equalization tube placement with or without adenoidectomy for the treatment of chronic otitis media with effusion or recurrent acute otitis media in a pediatric Down syndrome population compared to controls. Prospective case-control observational study. The OM Outcome Survey (OMO-22) was administered to both patients with Down syndrome and controls before bilateral tube placement with or without adenoidectomy and at an average of 6-7 months postoperatively. Thirty-one patients with Down syndrome and 34 controls were recruited. Both pre-operative and post-operative between-group and within-group score comparisons were conducted for the Physical, Hearing/Balance, Speech, Emotional, and Social domains of the OMO-22. Both groups experienced improvement of mean symptom scores post-operatively. Patients with Down syndrome reported significant post-operative improvement in mean Physical and Hearing domain item scores while control patients reported significant improvement in Physical, Hearing, and Emotional domain item scores. All four symptom scores in the Speech domain, both pre-operatively and post-operatively, were significantly worse for Down syndrome patients compared to controls (p ≤ 0.008). Surgical placement of pressure equalizing tubes results in significant quality of life improvements in patients with Down syndrome and controls. Problems related to speech and balance are reported at a higher rate and persist despite intervention in the Down syndrome population. It is possible that longer follow up periods and/or more sensitive tools are required to measure speech improvements in the Down syndrome population after pressure equalizing tube placement ± adenoidectomy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Time Domain and Frequency Domain Deterministic Channel Modeling for Tunnel/Mining Environments.

PubMed

Zhou, Chenming; Jacksha, Ronald; Yan, Lincan; Reyes, Miguel; Kovalchik, Peter

2017-01-01

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

Time Domain and Frequency Domain Deterministic Channel Modeling for Tunnel/Mining Environments

PubMed Central

Zhou, Chenming; Jacksha, Ronald; Yan, Lincan; Reyes, Miguel; Kovalchik, Peter

2018-01-01

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments — one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.† PMID:29457801

A developed nearly analytic discrete method for forward modeling in the frequency domain

NASA Astrophysics Data System (ADS)

Liu, Shaolin; Lang, Chao; Yang, Hui; Wang, Wenshuai

2018-02-01

High-efficiency forward modeling methods play a fundamental role in full waveform inversion (FWI). In this paper, the developed nearly analytic discrete (DNAD) method is proposed to accelerate frequency-domain forward modeling processes. We first derive the discretization of frequency-domain wave equations via numerical schemes based on the nearly analytic discrete (NAD) method to obtain a linear system. The coefficients of numerical stencils are optimized to make the linear system easier to solve and to minimize computing time. Wavefield simulation and numerical dispersion analysis are performed to compare the numerical behavior of DNAD method with that of the conventional NAD method. The results demonstrate the superiority of our proposed method. Finally, the DNAD method is implemented in frequency-domain FWI, and high-resolution inverse results are obtained.

Frequency Domain Analysis of Multiwavelength Photoacoustic Signals for Differentiating Tissue Components

NASA Astrophysics Data System (ADS)

Jian, X. H.; Dong, F. L.; Xu, J.; Li, Z. J.; Jiao, Y.; Cui, Y. Y.

2018-05-01

The feasibility of differentiating tissue components by performing frequency domain analysis of photoacoustic images acquired at different wavelengths was studied in this paper. Firstly, according to the basic theory of photoacoustic imaging, a brief theoretical model for frequency domain analysis of multiwavelength photoacoustic signal was deduced. The experiment results proved that the performance of different targets in frequency domain is quite different. Especially, the acoustic spectrum characteristic peaks of different targets are unique, which are 2.93 MHz, 5.37 MHz, 6.83 MHz, and 8.78 MHz for PDMS phantom, while 13.20 MHz, 16.60 MHz, 26.86 MHz, and 29.30 MHz for pork fat. The results indicated that the acoustic spectrum of photoacoustic imaging signals is possible to be utilized for tissue composition characterization.

Wavelet-based 3-D inversion for frequency-domain airborne EM data

NASA Astrophysics Data System (ADS)

Liu, Yunhe; Farquharson, Colin G.; Yin, Changchun; Baranwal, Vikas C.

2018-04-01

In this paper, we propose a new wavelet-based 3-D inversion method for frequency-domain airborne electromagnetic (FDAEM) data. Instead of inverting the model in the space domain using a smoothing constraint, this new method recovers the model in the wavelet domain based on a sparsity constraint. In the wavelet domain, the model is represented by two types of coefficients, which contain both large- and fine-scale informations of the model, meaning the wavelet-domain inversion has inherent multiresolution. In order to accomplish a sparsity constraint, we minimize an L1-norm measure in the wavelet domain that mostly gives a sparse solution. The final inversion system is solved by an iteratively reweighted least-squares method. We investigate different orders of Daubechies wavelets to accomplish our inversion algorithm, and test them on synthetic frequency-domain AEM data set. The results show that higher order wavelets having larger vanishing moments and regularity can deliver a more stable inversion process and give better local resolution, while the lower order wavelets are simpler and less smooth, and thus capable of recovering sharp discontinuities if the model is simple. At last, we test this new inversion algorithm on a frequency-domain helicopter EM (HEM) field data set acquired in Byneset, Norway. Wavelet-based 3-D inversion of HEM data is compared to L2-norm-based 3-D inversion's result to further investigate the features of the new method.

Overview of multi-input frequency domain modal testing methods with an emphasis on sine testing

NASA Technical Reports Server (NTRS)

Rost, Robert W.; Brown, David L.

1988-01-01

An overview of the current state of the art multiple-input, multiple-output modal testing technology is discussed. A very brief review of the current time domain methods is given. A detailed review of frequency and spatial domain methods is presented with an emphasis on sine testing.

Band-selective shaped pulse for high fidelity quantum control in diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Yan-Chun; Xing, Jian; Liu, Gang-Qin

High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host {sup 14}N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevelsmore » (e.g., of a nearby {sup 13}C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.« less

Multidimensional signal modulation and/or demodulation for data communications

DOEpatents

Smith, Stephen F [London, TN; Dress, William B [Camas, WA

2008-03-04

Systems and methods are described for multidimensional signal modulation and/or demodulation for data communications. A method includes modulating a carrier signal in a first domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; modulating the carrier signal in a second domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; and modulating the carrier signal in a third domain selected from the group consisting of phase, frequency, amplitude, polarization and spread.

Within-trait heterogeneity in age group differences in personality domains and facets: implications for the development and coherence of personality traits.

PubMed

Mõttus, René; Realo, Anu; Allik, Jüri; Esko, Tõnu; Metspalu, Andres; Johnson, Wendy

2015-01-01

The study investigated differences in the Five-Factor Model (FFM) domains and facets across adulthood. The main questions were whether personality scales reflected coherent units of trait development and thereby coherent personality traits more generally. These questions were addressed by testing if the components of the trait scales (items for facet scales and facets for domain scales) showed consistent age group differences. For this, measurement invariance (MI) framework was used. In a sample of 2,711 Estonians who had completed the NEO Personality Inventory 3 (NEO PI-3), more than half of the facet scales and one domain scale did not meet the criterion for weak MI (factor loading equality) across 12 age groups spanning ages from 18 to 91 years. Furthermore, none of the facet and domain scales met the criterion for strong MI (intercept equality), suggesting that items of the same facets and facets of the same domains varied in age group differences. When items were residualized for their respective facets, 46% of them had significant (p < 0.0002) residual age-correlations. When facets were residualized for their domain scores, a majority had significant (p < 0.002) residual age-correlations. For each domain, a series of latent factors were specified using random quarters of their items: scores of such latent factors varied notably (within domains) in correlations with age. We argue that manifestations of aetiologically coherent traits should show similar age group differences. Given this, the FFM domains and facets as embodied in the NEO PI-3 do not reflect aetiologically coherent traits.

Within-Trait Heterogeneity in Age Group Differences in Personality Domains and Facets: Implications for the Development and Coherence of Personality Traits

PubMed Central

Mõttus, René; Realo, Anu; Allik, Jüri; Esko, Tõnu; Metspalu, Andres; Johnson, Wendy

2015-01-01

The study investigated differences in the Five-Factor Model (FFM) domains and facets across adulthood. The main questions were whether personality scales reflected coherent units of trait development and thereby coherent personality traits more generally. These questions were addressed by testing if the components of the trait scales (items for facet scales and facets for domain scales) showed consistent age group differences. For this, measurement invariance (MI) framework was used. In a sample of 2,711 Estonians who had completed the NEO Personality Inventory 3 (NEO PI-3), more than half of the facet scales and one domain scale did not meet the criterion for weak MI (factor loading equality) across 12 age groups spanning ages from 18 to 91 years. Furthermore, none of the facet and domain scales met the criterion for strong MI (intercept equality), suggesting that items of the same facets and facets of the same domains varied in age group differences. When items were residualized for their respective facets, 46% of them had significant (p < 0.0002) residual age-correlations. When facets were residualized for their domain scores, a majority had significant (p < 0.002) residual age-correlations. For each domain, a series of latent factors were specified using random quarters of their items: scores of such latent factors varied notably (within domains) in correlations with age. We argue that manifestations of aetiologically coherent traits should show similar age group differences. Given this, the FFM domains and facets as embodied in the NEO PI-3 do not reflect aetiologically coherent traits. PMID:25751273

Volterra-type Lyapunov functions for fractional-order epidemic systems

NASA Astrophysics Data System (ADS)

Vargas-De-León, Cruz

2015-07-01

In this paper we prove an elementary lemma which estimates fractional derivatives of Volterra-type Lyapunov functions in the sense Caputo when α ∈ (0, 1) . Moreover, by using this result, we study the uniform asymptotic stability of some Caputo-type epidemic systems with a pair of fractional-order differential equations. These epidemic systems are the Susceptible-Infected-Susceptible (SIS), Susceptible-Infected-Recovered (SIR) and Susceptible-Infected-Recovered-Susceptible (SIRS) models and Ross-Macdonald model for vector-borne diseases. We show that the unique endemic equilibrium is uniformly asymptotically stable if the basic reproductive number is greater than one. We illustrate our theoretical results with numerical simulations using the Adams-Bashforth-Moulton scheme implemented in the fde12 Matlab function.

The importance of quadrupole sources in prediction of transonic tip speed propeller noise

NASA Technical Reports Server (NTRS)

Hanson, D. B.; Fink, M. R.

1978-01-01

A theoretical analysis is presented for the harmonic noise of high speed, open rotors. Far field acoustic radiation equations based on the Ffowcs-Williams/Hawkings theory are derived for a static rotor with thin blades and zero lift. Near the plane of rotation, the dominant sources are the volume displacement and the rho U(2) quadrupole, where u is the disturbance velocity component in the direction blade motion. These sources are compared in both the time domain and the frequency domain using two dimensional airfoil theories valid in the subsonic, transonic, and supersonic speed ranges. For nonlifting parabolic arc blades, the two sources are equally important at speeds between the section critical Mach number and a Mach number of one. However, for moderately subsonic or fully supersonic flow over thin blade sections, the quadrupole term is negligible. It is concluded for thin blades that significant quadrupole noise radiation is strictly a transonic phenomenon and that it can be suppressed with blade sweep. Noise calculations are presented for two rotors, one simulating a helicopter main rotor and the other a model propeller. For the latter, agreement with test data was substantially improved by including the quadrupole source term.

Time Domain Stability Margin Assessment of the NASA Space Launch System GN&C Design for Exploration Mission One

NASA Technical Reports Server (NTRS)

Clements, Keith; Wall, John

2017-01-01

The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.

Time Domain Stability Margin Assessment of the NS Space Launch System GN&C Design for Exploration Mission One

NASA Technical Reports Server (NTRS)

Clements, Keith; Wall, John

2017-01-01

The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.

Time-frequency domain SNR estimation and its application in seismic data processing

NASA Astrophysics Data System (ADS)

Zhao, Yan; Liu, Yang; Li, Xuxuan; Jiang, Nansen

2014-08-01

Based on an approach estimating frequency domain signal-to-noise ratio (FSNR), we propose a method to evaluate time-frequency domain signal-to-noise ratio (TFSNR). This method adopts short-time Fourier transform (STFT) to estimate instantaneous power spectrum of signal and noise, and thus uses their ratio to compute TFSNR. Unlike FSNR describing the variation of SNR with frequency only, TFSNR depicts the variation of SNR with time and frequency, and thus better handles non-stationary seismic data. By considering TFSNR, we develop methods to improve the effects of inverse Q filtering and high frequency noise attenuation in seismic data processing. Inverse Q filtering considering TFSNR can better solve the problem of amplitude amplification of noise. The high frequency noise attenuation method considering TFSNR, different from other de-noising methods, distinguishes and suppresses noise using an explicit criterion. Examples of synthetic and real seismic data illustrate the correctness and effectiveness of the proposed methods.

Analysis of automobile engine cylinder pressure and rotation speed from engine body vibration signal

NASA Astrophysics Data System (ADS)

Wang, Yuhua; Cheng, Xiang; Tan, Haishu

2016-01-01

In order to improve the engine vibration signal process method for the engine cylinder pressure and engine revolution speed measurement instrument, the engine cylinder pressure varying with the engine working cycle process has been regarded as the main exciting force for the engine block forced vibration. The forced vibration caused by the engine cylinder pressure presents as a low frequency waveform which varies with the cylinder pressure synchronously and steadily in time domain and presents as low frequency high energy discrete humorous spectrum lines in frequency domain. The engine cylinder pressure and the rotation speed can been extract form the measured engine block vibration signal by low-pass filtering analysis in time domain or by FFT analysis in frequency domain, the low-pass filtering analysis in time domain is not only suitable for the engine in uniform revolution condition but also suitable for the engine in uneven revolution condition. That provides a practical and convenient way to design motor revolution rate and cylinder pressure measurement instrument.

Testing for Granger Causality in the Frequency Domain: A Phase Resampling Method.

PubMed

Liu, Siwei; Molenaar, Peter

2016-01-01

This article introduces phase resampling, an existing but rarely used surrogate data method for making statistical inferences of Granger causality in frequency domain time series analysis. Granger causality testing is essential for establishing causal relations among variables in multivariate dynamic processes. However, testing for Granger causality in the frequency domain is challenging due to the nonlinear relation between frequency domain measures (e.g., partial directed coherence, generalized partial directed coherence) and time domain data. Through a simulation study, we demonstrate that phase resampling is a general and robust method for making statistical inferences even with short time series. With Gaussian data, phase resampling yields satisfactory type I and type II error rates in all but one condition we examine: when a small effect size is combined with an insufficient number of data points. Violations of normality lead to slightly higher error rates but are mostly within acceptable ranges. We illustrate the utility of phase resampling with two empirical examples involving multivariate electroencephalography (EEG) and skin conductance data.

Further development of the dynamic gas temperature measurement system. Volume 2: Computer program user's manual

NASA Technical Reports Server (NTRS)

Stocks, Dana R.

1986-01-01

The Dynamic Gas Temperature Measurement System compensation software accepts digitized data from two different diameter thermocouples and computes a compensated frequency response spectrum for one of the thermocouples. Detailed discussions of the physical system, analytical model, and computer software are presented in this volume and in Volume 1 of this report under Task 3. Computer program software restrictions and test cases are also presented. Compensated and uncompensated data may be presented in either the time or frequency domain. Time domain data are presented as instantaneous temperature vs time. Frequency domain data may be presented in several forms such as power spectral density vs frequency.

A Modified Normalization Technique for Frequency-Domain Full Waveform Inversion

NASA Astrophysics Data System (ADS)

Hwang, J.; Jeong, G.; Min, D. J.; KIM, S.; Heo, J. Y.

2016-12-01

Full waveform inversion (FWI) is a technique to estimate subsurface material properties minimizing the misfit function built with residuals between field and modeled data. To achieve computational efficiency, FWI has been performed in the frequency domain by carrying out modeling in the frequency domain, whereas observed data (time-series data) are Fourier-transformed.One of the main drawbacks of seismic FWI is that it easily gets stuck in local minima because of lacking of low-frequency data. To compensate for this limitation, damped wavefields are used, as in the Laplace-domain waveform inversion. Using damped wavefield in FWI plays a role in generating low-frequency components and help recover long-wavelength structures. With these newly generated low-frequency components, we propose a modified frequency-normalization technique, which has an effect of boosting contribution of low-frequency components to model parameter update.In this study, we introduce the modified frequency-normalization technique which effectively amplifies low-frequency components of damped wavefields. Our method is demonstrated for synthetic data for the SEG/EAGE salt model. AcknowledgementsThis work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20168510030830) and by the Dual Use Technology Program, granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea.

Tunable radio-frequency photonic filter based on an actively mode-locked fiber laser.

PubMed

Ortigosa-Blanch, A; Mora, J; Capmany, J; Ortega, B; Pastor, D

2006-03-15

We propose the use of an actively mode-locked fiber laser as a multitap optical source for a microwave photonic filter. The fiber laser provides multiple optical taps with an optical frequency separation equal to the external driving radio-frequency signal of the laser that governs its repetition rate. All the optical taps show equal polarization and an overall Gaussian apodization, which reduces the sidelobes. We demonstrate continuous tunability of the filter by changing the external driving radio-frequency signal of the laser, which shows good fine tunability in the operating range of the laser from 5 to 10 GHz.

HRV Analysis to Identify Stages of Home-based Telerehabilitation Exercise.

PubMed

Jeong, In Cheol; Finkelstein, Joseph

2014-01-01

Spectral analysis of heart rate variability (HRV) has been widely used to investigate activity of autonomous nervous system. Previous studies demonstrated potential of analysis of short-term sequences of heart rate data in a time domain for continuous monitoring of levels of physiological stress however the value of HRV parameters in frequency domain for monitoring cycling exercise has not been established. The goal of this study was to assess whether HRV parameters in frequency domain differ depending on a stage of cycling exercise. We compared major HRV parameters in high, low and very low frequency ranges during rest, height of exercise, and recovery during cycling exercise. Our results indicated responsiveness of frequency-domain indices to different phases of cycling exercise program and their potential in monitoring autonomic balance and stress levels as a part of a tailored home-based telerehabilitation program.

Frequency-domain-independent vector analysis for mode-division multiplexed transmission

NASA Astrophysics Data System (ADS)

Liu, Yunhe; Hu, Guijun; Li, Jiao

2018-04-01

In this paper, we propose a demultiplexing method based on frequency-domain independent vector analysis (FD-IVA) algorithm for mode-division multiplexing (MDM) system. FD-IVA extends frequency-domain independent component analysis (FD-ICA) from unitary variable to multivariate variables, and provides an efficient method to eliminate the permutation ambiguity. In order to verify the performance of FD-IVA algorithm, a 6 ×6 MDM system is simulated. The simulation results show that the FD-IVA algorithm has basically the same bit-error-rate(BER) performance with the FD-ICA algorithm and frequency-domain least mean squares (FD-LMS) algorithm. Meanwhile, the convergence speed of FD-IVA algorithm is the same as that of FD-ICA. However, compared with the FD-ICA and the FD-LMS, the FD-IVA has an obviously lower computational complexity.

Velocity measurement using frequency domain interferometer and chirped pulse laser

NASA Astrophysics Data System (ADS)

Ishii, K.; Nishimura, Y.; Mori, Y.; Hanayama, R.; Kitagawa, Y.; Sekine, T.; Sato, N.; Kurita, T.; Kawashima, T.; Sunahara, A.; Sentoku, Y.; Miura, E.; Iwamoto, A.; Sakagami, H.

2017-02-01

An ultra-intense short pulse laser induces a shock wave in material. The pressure of shock compression is stronger than a few tens GPa. To characterize shock waves, time-resolved velocity measurement in nano- or pico-second time scale is needed. Frequency domain interferometer and chirped pulse laser provide single-shot time-resolved measurement. We have developed a laser-driven shock compression system and frequency domain interferometer with CPA laser. In this paper, we show the principle of velocity measurement using a frequency domain interferometer and a chirped pulse laser. Next, we numerically calculated spectral interferograms and show the time-resolved velocity measurement can be done from the phase analysis of spectral interferograms. Moreover we conduct the laser driven shock generation and shock velocity measurement. From the spectral fringes, we analyze the velocities of the sample and shockwaves.

Turbulence excited frequency domain damping measurement and truncation effects

NASA Technical Reports Server (NTRS)

Soovere, J.

1976-01-01

Existing frequency domain modal frequency and damping analysis methods are discussed. The effects of truncation in the Laplace and Fourier transform data analysis methods are described. Methods for eliminating truncation errors from measured damping are presented. Implications of truncation effects in fast Fourier transform analysis are discussed. Limited comparison with test data is presented.

Frequency domain modeling and dynamic characteristics evaluation of existing wind turbine systems

NASA Astrophysics Data System (ADS)

Chiang, Chih-Hung; Yu, Chih-Peng

2016-04-01

It is quite well accepted that frequency domain procedures are suitable for the design and dynamic analysis of wind turbine structures, especially for floating offshore wind turbines, since random wind loads and wave induced motions are most likely simulated in the frequency domain. This paper presents specific applications of an effective frequency domain scheme to the linear analysis of wind turbine structures in which a 1-D spectral element was developed based on the axially-loaded member. The solution schemes are summarized for the spectral analyses of the tower, the blades, and the combined system with selected frequency-dependent coupling effect from foundation-structure interactions. Numerical examples demonstrate that the modal frequencies obtained using spectral-element models are in good agreement with those found in the literature. A 5-element mono-pile model results in less than 0.3% deviation from an existing 160-element model. It is preliminarily concluded that the proposed scheme is relatively efficient in performing quick verification for test data obtained from the on-site vibration measurement using the microwave interferometer.

Wide tracking range, auto ranging, low jitter phase lock loop for swept and fixed frequency systems

DOEpatents

Kerner, Thomas M.

2001-01-01

The present invention provides a wide tracking range phase locked loop (PLL) circuit that achieves minimal jitter in a recovered clock signal, regardless of the source of the jitter (i.e. whether it is in the source or the transmission media). The present invention PLL has automatic harmonic lockout detection circuitry via a novel lock and seek control logic in electrical communication with a programmable frequency discriminator and a code balance detector. (The frequency discriminator enables preset of a frequency window of upper and lower frequency limits to derive a programmable range within which signal acquisition is effected. The discriminator works in combination with the code balance detector circuit to minimize the sensitivity of the PLL circuit to random data in the data stream). In addition, the combination of a differential loop integrator with the lock and seek control logic obviates a code preamble and guarantees signal acquisition without harmonic lockup. An adaptive cable equalizer is desirably used in combination with the present invention PLL to recover encoded transmissions containing a clock and/or data. The equalizer automatically adapts to equalize short haul cable lengths of coaxial and twisted pair cables or wires and provides superior jitter performance itself. The combination of the equalizer with the present invention PLL is desirable in that such combination permits the use of short haul wires without significant jitter.

Quasi-optical reflective polarimeter for wide millimeter-wave band

NASA Astrophysics Data System (ADS)

Shinnaga, Hiroko; Tsuboi, Masato; Kasuga, Takashi

1998-11-01

We constructed a new reflective-type polarimeter system at 35 - 250 GHz for the 45 m telescope at Nobeyama Radio Observatory (NRO). Using the system, we can measure both linear polarization and circular polarization for our needs. The new system has two key points. First is that we can tune the center frequency of the polarimeter in the available frequency range, second is that insertion loss is low (0.15 plus or minus 0.03 dB at 86 GHz). These characteristics extended achievable scientific aims. In this paper, we present the design and the performance of the system. Using the system, we measured linear polarizations of some astronomical objects at 86 GHz, with SiO (nu) equals 0,1 and 2 at J equals 2 - 1 and 29SiO (nu) equals 0 J equals 2 - 1 simultaneously. As a result, the observation revealed SiO (nu) equals 0 J equals 2 - 1 of VY Canis Majoris is highly linearly polarized, the degree of linear polarization is up to 64%, in spite of SiO J equals 2 - 1 (nu) equals 1 is not highly linearly polarized. The highly linearly polarized feature is a strong evidence that 28SiO J equals 2 - 1 transition at the ground vibrational state originate through maser action. This is the first detection of the cosmic maser emission of SiO (nu) equals 0 J equals 2 - 1 transition.

CAPN1, CAST, and DGAT1 genetic effects on preweaning performance, carcass quality traits, and residual variance of tenderness in a beef cattle population selected for haplotype and allele equalization

USDA-ARS?s Scientific Manuscript database

Genetic marker effects and type of inheritance are estimated with poor precision when minor marker allele frequencies are low. A stable composite population (MARC III) was subjected to marker assisted selection for multiple years to equalize specific marker frequencies to 1) estimate effect size an...

PLATSIM: A Simulation and Analysis Package for Large-Order Flexible Systems. Version 2.0

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Kenny, Sean P.; Giesy, Daniel P.

1997-01-01

The software package PLATSIM provides efficient time and frequency domain analysis of large-order generic space platforms. PLATSIM can perform open-loop analysis or closed-loop analysis with linear or nonlinear control system models. PLATSIM exploits the particular form of sparsity of the plant matrices for very efficient linear and nonlinear time domain analysis, as well as frequency domain analysis. A new, original algorithm for the efficient computation of open-loop and closed-loop frequency response functions for large-order systems has been developed and is implemented within the package. Furthermore, a novel and efficient jitter analysis routine which determines jitter and stability values from time simulations in a very efficient manner has been developed and is incorporated in the PLATSIM package. In the time domain analysis, PLATSIM simulates the response of the space platform to disturbances and calculates the jitter and stability values from the response time histories. In the frequency domain analysis, PLATSIM calculates frequency response function matrices and provides the corresponding Bode plots. The PLATSIM software package is written in MATLAB script language. A graphical user interface is developed in the package to provide convenient access to its various features.

Superfluid Boson-Fermion Mixture: Structure Formation and Collective Periodic Motion

NASA Astrophysics Data System (ADS)

Mitra, A.

2018-01-01

Multiple periodic domain formation due to a modulation instability in a boson-fermion mixture superfluid in the unitary regime has been studied. The periodicity of the structure evolves with time. At the early stage of evolution, bosonic domains show the periodic nature, whereas the periodicity in the fermionic (Cooper pair) domains appears at the late stage of evolution. The nature of interatomic interspecies interactions affects the domain formation. In a harmonic trap, the mixture executes an undamped oscillation. The frequency of the oscillation depends on the relative coupling strength between boson-fermion and fermion-fermion. The repulsive boson-fermion interaction reduces the oscillation frequency, whereas the attractive interaction enhances the frequency significantly.

Differential associations between domains of sibling conflict and adolescent emotional adjustment.

PubMed

Campione-Barr, Nicole; Greer, Kelly Bassett; Kruse, Anna

2013-01-01

Issues of equality and fairness and invasion of the personal domain, 2 previously identified topic areas of adolescent sibling conflict (N. Campione-Barr & J. G. Smetana, 2010), were examined in 145 dyads (Mfirst-born = 14.97, SD = 1.69 years; Msecond-born = 12.20, SD = 1.90 years) for their differential effects on youths' emotional adjustment over 1 year. The impact of internalizing symptoms on later sibling conflicts also was tested. Invasion of the personal domain conflicts were associated with higher levels of anxiety and lower self-esteem 1 year later, whereas Equality and Fairness issues were associated with greater depressed mood. Conversely, greater internalizing symptomatology and lower self-esteem predicted more of both types of conflict. Moderating influences of gender and ordinal position were also examined. © 2012 The Authors. Child Development © 2012 Society for Research in Child Development, Inc.

Fundamentals of dielectric properties measurements and agricultural applications.

PubMed

Nelson, Stuart O

2010-01-01

Dielectrics and dielectric properties are defined generally and dielectric measurement methods and equipment are described for various frequency ranges from audio frequencies through microwave frequencies. These include impedance and admittance bridges, resonant frequency, transmission-line, and free-space methods in the frequency domain and time-domain and broadband techniques. Many references are cited describing methods in detail and giving sources of dielectric properties data. Finally a few applications for such data are presented and sources of tabulated and dielectric properties data bases are identified.

Binary neutron star merger simulations with different initial orbital frequency and equation of state

NASA Astrophysics Data System (ADS)

Maione, F.; De Pietri, R.; Feo, A.; Löffler, F.

2016-09-01

We present results from three-dimensional general relativistic simulations of binary neutron star coalescences and mergers using public codes. We considered equal mass models where the baryon mass of the two neutron stars is 1.4{M}⊙ , described by four different equations of state (EOS) for the cold nuclear matter (APR4, SLy, H4, and MS1; all parametrized as piecewise polytropes). We started the simulations from four different initial interbinary distances (40,44.3,50, and 60 km), including up to the last 16 orbits before merger. That allows us to show the effects on the gravitational wave (GW) phase evolution, radiated energy and angular momentum due to: the use of different EOS, the orbital eccentricity present in the initial data and the initial separation (in the simulation) between the two stars. Our results show that eccentricity has a major role in the discrepancy between numerical and analytical waveforms until the very last few orbits, where ‘tidal’ effects and missing high-order post-Newtonian coefficients also play a significant role. We test different methods for extrapolating the GW signal extracted at finite radii to null infinity. We show that an effective procedure for integrating the Newman-Penrose {\\psi }4 signal to obtain the GW strain h is to apply a simple high-pass digital filter to h after a time domain integration, where only the two physical motivated integration constants are introduced. That should be preferred to the more common procedures of introducing additional integration constants, integrating in the frequency domain or filtering {\\psi }4 before integration.

A Review and Framework for Categorizing Current Research and Development in Health Related Geographical Information Systems (GIS) Studies.

PubMed

Lyseen, A K; Nøhr, C; Sørensen, E M; Gudes, O; Geraghty, E M; Shaw, N T; Bivona-Tellez, C

2014-08-15

The application of GIS in health science has increased over the last decade and new innovative application areas have emerged. This study reviews the literature and builds a framework to provide a conceptual overview of the domain, and to promote strategic planning for further research of GIS in health. The framework is based on literature from the library databases Scopus and Web of Science. The articles were identified based on keywords and initially selected for further study based on titles and abstracts. A grounded theory-inspired method was applied to categorize the selected articles in main focus areas. Subsequent frequency analysis was performed on the identified articles in areas of infectious and non-infectious diseases and continent of origin. A total of 865 articles were included. Four conceptual domains within GIS in health sciences comprise the framework: spatial analysis of disease, spatial analysis of health service planning, public health, health technologies and tools. Frequency analysis by disease status and location show that malaria and schistosomiasis are the most commonly analyzed infectious diseases where cancer and asthma are the most frequently analyzed non-infectious diseases. Across categories, articles from North America predominate, and in the category of spatial analysis of diseases an equal number of studies concern Asia. Spatial analysis of diseases and health service planning are well-established research areas. The development of future technologies and new application areas for GIS and data-gathering technologies such as GPS, smartphones, remote sensing etc. will be nudging the research in GIS and health.

A Review and Framework for Categorizing Current Research and Development in Health Related Geographical Information Systems (GIS) Studies

PubMed Central

Nøhr, C.; Sørensen, E. M.; Gudes, O.; Geraghty, E. M.; Shaw, N. T.; Bivona-Tellez, C.

2014-01-01

Summary Objectives The application of GIS in health science has increased over the last decade and new innovative application areas have emerged. This study reviews the literature and builds a framework to provide a conceptual overview of the domain, and to promote strategic planning for further research of GIS in health. Method The framework is based on literature from the library databases Scopus and Web of Science. The articles were identified based on keywords and initially selected for further study based on titles and abstracts. A grounded theory-inspired method was applied to categorize the selected articles in main focus areas. Subsequent frequency analysis was performed on the identified articles in areas of infectious and non-infectious diseases and continent of origin. Results A total of 865 articles were included. Four conceptual domains within GIS in health sciences comprise the framework: spatial analysis of disease, spatial analysis of health service planning, public health, health technologies and tools. Frequency analysis by disease status and location show that malaria and schistosomiasis are the most commonly analyzed infectious diseases where cancer and asthma are the most frequently analyzed non-infectious diseases. Across categories, articles from North America predominate, and in the category of spatial analysis of diseases an equal number of studies concern Asia. Conclusion Spatial analysis of diseases and health service planning are well-established research areas. The development of future technologies and new application areas for GIS and data-gathering technologies such as GPS, smartphones, remote sensing etc. will be nudging the research in GIS and health. PMID:25123730

A Computer Model of a Phase Lock Loop

NASA Technical Reports Server (NTRS)

Shelton, Ralph Paul

1973-01-01

A computer model is reported of a PLL (phase-lock loop), preceded by a bandpass filter, which is valid when the bandwidth of the bandpass filter is of the same order of magnitude as the natural frequency of the PLL. New results for the PLL natural frequency equal to the bandpass filter bandwidth are presented for a second order PLL operating with carrier plus noise as the input. However, it is shown that extensions to higher order loops, and to the case of a modulated carrier are straightforward. The new results presented give the cycle skipping rate of the PLL as a function of the input carrier to noise ratio when the PLL natural frequency is equal to the bandpass filter bandwidth. Preliminary results showing the variation of the output noise power and cycle skipping rates of the PLL as a function of the loop damping ratio for the PLL natural frequency equal to the bandpass filter bandwidth are also included.

Recent progress in synchrotron-based frequency-domain Fourier-transform THz-EPR.

PubMed

Nehrkorn, Joscha; Holldack, Karsten; Bittl, Robert; Schnegg, Alexander

2017-07-01

We describe frequency-domain Fourier-transform THz-EPR as a method to assign spin-coupling parameters of high-spin (S>1/2) systems with very large zero-field splittings. The instrumental foundations of synchrotron-based FD-FT THz-EPR are presented, alongside with a discussion of frequency-domain EPR simulation routines. The capabilities of this approach is demonstrated for selected mono- and multinuclear HS systems. Finally, we discuss remaining challenges and give an outlook on the future prospects of the technique. Copyright © 2017 Elsevier Inc. All rights reserved.

Gastric Emptying Assessment in Frequency and Time Domain Using Bio-impedance: Preliminary Results

NASA Astrophysics Data System (ADS)

Huerta-Franco, R.; Vargas-Luna, M.; Hernández, E.; Córdova, T.; Sosa, M.; Gutiérrez, G.; Reyes, P.; Mendiola, C.

2006-09-01

The impedance assessment to measure gastric emptying and in general gastric activity has been reported since 1985. The physiological interpretation of these measurements, is still under research. This technique usually uses a single frequency, and the conductivity parameter. The frequency domain and the Fourier analysis of the time domain behavior of the gastric impedance in different gastric conditions (fasting state, and after food administration) has not been explored in detail. This work presents some insights of the potentiality of these alternative methodologies to measure gastric activity.

Negative refraction in metamaterials based on dielectric spherical particles

NASA Astrophysics Data System (ADS)

Huang, T. C.; Wang, B. X.; Zhao, C. Y.

2018-07-01

Negative refraction (NR) metamaterials are featured with unique physical properties and potential to realize full control of electromagnetic waves, which have attracted much attention since the last decade. However, few researches focus on the realization of three-dimensional dielectric NR metamaterials in optic frequency, and the current design methods need further development. In this paper, a three-dimensional all-dielectric NR metamaterial with two NR bands has been realized based on proper excitation of electric and magnetic multipoles. It is also predicted that the coupling of magnetic dipole and electric dipole can lead to the NR bands in near-infrared frequencies, and NR in the visible frequencies can be achieved by the coupling of magnetic quadrupole and electric dipole. Band structures and equal-frequency surfaces of proposed metamaterial arranged in the periodic cubic lattice are solved by adopting the plane wave expansion method, and then the results verify the existence of these two NR frequency bands in periodic metamaterials. In this way, the characteristic parameters such as transmission and absorption of light in two NR bands are also analyzed. In the meantime, the finite-deference time-domain method is used to intuitively display the phenomenon of NR and investigate the effects of disorder in particle arrangement. Besides, it is found that the proposed metamaterials have fine robustness to the disorder in particle arrangement, and these two NR bands can be tuned by adjusting volume fraction. In brief, this work provides means for preliminary designing, profound analysis and intuitively exhibition of NR metamaterials based on dielectric particles.

Thermal characteristics of time-periodic electroosmotic flow in a circular microchannel

NASA Astrophysics Data System (ADS)

Moghadam, Ali Jabari

2015-10-01

A theoretical analysis is performed to explore the thermal characteristics of electroosmotic flow in a circular microchannel under an alternating electric field. An analytical approach is presented to solve energy equation, and then, the exact solution of temperature profiles is obtained by using the Green's function method. This study reveals that the temperature field repeats itself for each half-period. Frequency has a strong influence on the thermal behavior of the flow field. For small values of the dimensionless frequency (small channel size, large kinematic viscosity, or small frequency), the advection mechanism is dominant in the whole domain and the resultant heating (Joule heating and wall heat flux) can be transferred by the complete flow field in the axial direction; while, the middle portion of the flow field at high dimensionless frequencies does not have sufficient time to transfer heat by advection, and the bulk fluid temperature, especially in heating, may consequently become greater than the wall temperature. In a particular instance of cooling mode, a constant surface temperature case is temporarily occurred in which the axial temperature gradient will be zero. For relatively high frequencies, the unsteady bulk fluid temperature in some radial positions at some moments may be equal to the wall temperature; hence instantaneous cylindrical surfaces with zero radial heat flux may occur over a period of time. Depending on the value and sign of the thermal scale ratio, the quasi-steady-state Nusselt number (time-averaged at one period) approaches a specific value as the electrokinetic radius becomes infinity.

Spectral analysis of heart rate dynamics in elderly persons with postprandial hypotension

NASA Technical Reports Server (NTRS)

Ryan, S. M.; Goldberger, A. L.; Ruthazer, R.; Mietus, J.; Lipsitz, L. A.

1992-01-01

Prior studies suggest that postprandial hypotension in elderly persons may be due to defective sympathetic nervous system activation. We examined autonomic control of heart rate (HR) after a meal using spectral analysis of HR data in 13 old (89 +/- 6 years) and 7 young (24 +/- 4 years) subjects. Total spectral power, an index of overall HR variability, was calculated for the frequency band between 0.01 and 0.40 Hz. Relatively low-frequency power, associated with sympathetic nervous system and baroreflex activation, was calculated for the 0.01 to 0.15 Hz band. High-frequency power, representing parasympathetic influences on HR, was calculated for the 0.15 to 0.40 Hz band. Mean arterial blood pressure declined 27 +/- 8 mm Hg by 60 minutes after the meal in elderly subjects, compared with 9 +/- 8 mm Hg in young subjects (p less than or equal to 0.0001, young vs old). The mean change in low-frequency HR power from 30 to 50 minutes after the meal was +19.4 +/- 25.3 U in young subjects versus -0.1 +/- 1.5 U in old subjects (p less than or equal to 0.02). Mean change in total power was also greater in young (19.0 +/- 26.6 U) subjects compared with old subjects (0.0 +/- 1.6 U, p greater than or equal to 0.02). Mean ratio of low:high-frequency power increased 3.1 +/- 3.3 U in young subjects vs 0.5 +/- 2.7 U in old subjects (p less than or equal to 0.01). The increase in low-frequency HR power and in the low:high frequency band ratio in young subjects is consistent with sympathetic activation in the postprandial period.(ABSTRACT TRUNCATED AT 250 WORDS).

Cone pigment polymorphism in New World monkeys: are all pigments created equal?

PubMed

Rowe, Mickey P; Jacobs, Gerald H

2004-01-01

Most platyrrhine monkeys have a triallelic M/L opsin gene polymorphism that underlies significant individual variations in color vision. A survey of the frequencies of these polymorphic genes suggests that the three alleles occur with equal frequency among squirrel monkeys (subfamily Cebinae), but are not equally frequent in a number of species from the subfamily Callitrichinae. This departure from equal frequency in the Callitrichids should slightly increase the ratio of dichromats to trichromats in the population and significantly alter the relative representation of the three possible dichromatic and trichromatic phenotypes. A particular feature of the inequality is that it leads to a relative increase in the number of trichromats whose M/L pigments have the largest possible spectral separation. To assess whether these trichromatic phenotypes are equally well equipped to make relevant visual discriminations, psychophysical experiments were run on human observers. A technique involving the functional substitution of photopigments was used to simulate the discrimination between fruits among a background of leaves. The goal of the simulation was to reproduce in the cones of human observers excitations equivalent to those produced in monkey cones as the animals view fruit. Three different viewing conditions were examined involving variations in the relative luminances of fruit and leaves and the spectrum of the illuminant. In all cases, performance was best for simulated trichromacies including M/L pigments with the largest spectral separation. Thus, the inequality of opsin gene frequency in Callitrichid monkeys may reflect adaptive pressures.

Time-domain wavefield reconstruction inversion

NASA Astrophysics Data System (ADS)

Li, Zhen-Chun; Lin, Yu-Zhao; Zhang, Kai; Li, Yuan-Yuan; Yu, Zhen-Nan

2017-12-01

Wavefield reconstruction inversion (WRI) is an improved full waveform inversion theory that has been proposed in recent years. WRI method expands the searching space by introducing the wave equation into the objective function and reconstructing the wavefield to update model parameters, thereby improving the computing efficiency and mitigating the influence of the local minimum. However, frequency-domain WRI is difficult to apply to real seismic data because of the high computational memory demand and requirement of time-frequency transformation with additional computational costs. In this paper, wavefield reconstruction inversion theory is extended into the time domain, the augmented wave equation of WRI is derived in the time domain, and the model gradient is modified according to the numerical test with anomalies. The examples of synthetic data illustrate the accuracy of time-domain WRI and the low dependency of WRI on low-frequency information.

Broadband CARS spectral phase retrieval using a time-domain Kramers–Kronig transform

PubMed Central

Liu, Yuexin; Lee, Young Jong; Cicerone, Marcus T.

2014-01-01

We describe a closed-form approach for performing a Kramers–Kronig (KK) transform that can be used to rapidly and reliably retrieve the phase, and thus the resonant imaginary component, from a broadband coherent anti-Stokes Raman scattering (CARS) spectrum with a nonflat background. In this approach we transform the frequency-domain data to the time domain, perform an operation that ensures a causality criterion is met, then transform back to the frequency domain. The fact that this method handles causality in the time domain allows us to conveniently account for spectrally varying nonresonant background from CARS as a response function with a finite rise time. A phase error accompanies KK transform of data with finite frequency range. In examples shown here, that phase error leads to small (<1%) errors in the retrieved resonant spectra. PMID:19412273

Pipelined digital SAR azimuth correlator using hybrid FFT-transversal filter

NASA Technical Reports Server (NTRS)

Wu, C.; Liu, K. Y. (Inventor)

1984-01-01

A synthetic aperture radar system (SAR) having a range correlator is provided with a hybrid azimuth correlator which utilizes a block-pipe-lined fast Fourier transform (FFT). The correlator has a predetermined FFT transform size with delay elements for delaying SAR range correlated data so as to embed in the Fourier transform operation a corner-turning function as the range correlated SAR data is converted from the time domain to a frequency domain. The azimuth correlator is comprised of a transversal filter to receive the SAR data in the frequency domain, a generator for range migration compensation and azimuth reference functions, and an azimuth reference multiplier for correlation of the SAR data. Following the transversal filter is a block-pipelined inverse FFT used to restore azimuth correlated data in the frequency domain to the time domain for imaging.

Application of Cross-Correlation Greens Function Along With FDTD for Fast Computation of Envelope Correlation Coefficient Over Wideband for MIMO Antennas

NASA Astrophysics Data System (ADS)

Sarkar, Debdeep; Srivastava, Kumar Vaibhav

2017-02-01

In this paper, the concept of cross-correlation Green's functions (CGF) is used in conjunction with the finite difference time domain (FDTD) technique for calculation of envelope correlation coefficient (ECC) of any arbitrary MIMO antenna system over wide frequency band. Both frequency-domain (FD) and time-domain (TD) post-processing techniques are proposed for possible application with this FDTD-CGF scheme. The FDTD-CGF time-domain (FDTD-CGF-TD) scheme utilizes time-domain signal processing methods and exhibits significant reduction in ECC computation time as compared to the FDTD-CGF frequency domain (FDTD-CGF-FD) scheme, for high frequency-resolution requirements. The proposed FDTD-CGF based schemes can be applied for accurate and fast prediction of wideband ECC response, instead of the conventional scattering parameter based techniques which have several limitations. Numerical examples of the proposed FDTD-CGF techniques are provided for two-element MIMO systems involving thin-wire half-wavelength dipoles in parallel side-by-side as well as orthogonal arrangements. The results obtained from the FDTD-CGF techniques are compared with results from commercial electromagnetic solver Ansys HFSS, to verify the validity of proposed approach.

Estimation of spectral kurtosis

NASA Astrophysics Data System (ADS)

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 visualize the pattern of each fault. Keywords: frequency domain Fourier transform, spectral kurtosis, bearing fault

Prediction of lamb carcass composition by impedance spectroscopy.

PubMed

Altmann, M; Pliquett, U; Suess, R; von Borell, E

2004-03-01

The objective of this study was to compare impedance spectroscopy with resistance measurements at a single frequency (50 kHz) for the prediction of lamb carcass composition. The impedance spectrum is usually recorded by measuring the complex impedance at various frequencies (frequency domain); however, in this study, we also applied the faster and simpler measurement in the time domain (application of a current step and measurement of the voltage response). The study was carried out on 24 male, German Black-headed Mutton lambs with an average BW of 45 kg. Frequency- and time domain-based impedance measurements were collected at 20 min and 24 h postmortem with different electrode placements. Real and imaginary parts at various frequencies were calculated from the locus diagram. Left sides were dissected into lean, fat, and bone, and right sides were ground to determine actual carcass composition. Crude fat, crude protein, and moisture were chemically analyzed on ground samples. Frequency- and time domain-based measurements did not provide the same absolute impedance values; however, the high correlations (P < 0.001) between these methods for the "real parts" showed that they ranked individuals in the same order. Most of the time domain data correlated higher to carcass composition than did the frequency domain data. The real parts of impedance showed correlations between -0.37 (P > 0.05) and -0.74 (P < 0.001) to water, crude fat, lean, and fatty tissue, whereas the relations to CP were much lower (from 0.00 to -0.47, P < 0.05). Electrode placements at different locations did not substantially improve the correlations with carcass composition. The "imaginary parts" of impedance were not suitable for the prediction of carcass composition. The highest accuracy (R2 = 0.66) was reached for the estimation of crude fat percentage by a regression equation with the time domain-based impedance measured at 24 h postmortem. Furthermore, there was not a clear superiority of measurements in a wide frequency range over a single frequency measurement at 50 kHz for the prediction of carcass composition. Even though we calculated the impedance at 50 kHz based on the locus diagram, which allowed for a high precision for predicting this impedance trait, single-frequency impedance devices typically used in practice cannot record the locus diagram and, therefore, exhibit a greater amount of uncertainty.

Frequency domain analysis of noise in simple gene circuits

NASA Astrophysics Data System (ADS)

Cox, Chris D.; McCollum, James M.; Austin, Derek W.; Allen, Michael S.; Dar, Roy D.; Simpson, Michael L.

2006-06-01

Recent advances in single cell methods have spurred progress in quantifying and analyzing stochastic fluctuations, or noise, in genetic networks. Many of these studies have focused on identifying the sources of noise and quantifying its magnitude, and at the same time, paying less attention to the frequency content of the noise. We have developed a frequency domain approach to extract the information contained in the frequency content of the noise. In this article we review our work in this area and extend it to explicitly consider sources of extrinsic and intrinsic noise. First we review applications of the frequency domain approach to several simple circuits, including a constitutively expressed gene, a gene regulated by transitions in its operator state, and a negatively autoregulated gene. We then review our recent experimental study, in which time-lapse microscopy was used to measure noise in the expression of green fluorescent protein in individual cells. The results demonstrate how changes in rate constants within the gene circuit are reflected in the spectral content of the noise in a manner consistent with the predictions derived through frequency domain analysis. The experimental results confirm our earlier theoretical prediction that negative autoregulation not only reduces the magnitude of the noise but shifts its content out to higher frequency. Finally, we develop a frequency domain model of gene expression that explicitly accounts for extrinsic noise at the transcriptional and translational levels. We apply the model to interpret a shift in the autocorrelation function of green fluorescent protein induced by perturbations of the translational process as a shift in the frequency spectrum of extrinsic noise and a decrease in its weighting relative to intrinsic noise.

Four-channel magnetic resonance imaging receiver using frequency domain multiplexing.

PubMed

He, Wang; Qin, Xu; Jiejing, Ren; Gengying, Li

2007-01-01

An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3 T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60 dB, the phase fluctuations were about 1 degrees , and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.

Strategies of Raising the Quality of Higher Education and Attaining Equality of Educational Opportunities

ERIC Educational Resources Information Center

Petrovskiy, Igor V.; Agapova, Elena N.

2016-01-01

The aim of the research is to develop the policy and strategy recommendations to increase the quality of higher education in Russian Federation. The study examines the significance of equal educational opportunities and the influence of this factor on the educational systems of developing countries. Transformational processes in the domain of…

Bi-Directional Theta Modulation between the Septo-Hippocampal System and the Mammillary Area in Free-Moving Rats

PubMed Central

Ruan, Ming; Young, Calvin K.; McNaughton, Neil

2017-01-01

Hippocampal (HPC) theta oscillations have long been linked to various functions of the brain. Many cortical and subcortical areas that also exhibit theta oscillations have been linked to functional circuits with the hippocampus on the basis of coupled activities at theta frequencies. We examine, in freely moving rats, the characteristics of diencephalic theta local field potentials (LFPs) recorded in the supramammillary/mammillary (SuM/MM) areas that are bi-directionally connected to the HPC through the septal complex. Using partial directed coherence (PDC), we find support for previous suggestions that SuM modulates HPC theta at higher frequencies. We find weak separation of SuM and MM by dominant theta frequency recorded locally. Contrary to oscillatory cell activities under anesthesia where SuM is insensitive, but MM is sensitive to medial septal (MS) inactivation, theta LFPs persisted and became indistinguishable after MS-inactivation. However, MS-inactivation attenuated SuM/MM theta power, while increasing the frequency of SuM/MM theta. MS-inactivation also reduced root mean squared power in both HPC and SuM/MM equally, but reduced theta power differentially in the time domain. We provide converging evidence that SuM is preferentially involved in coding HPC theta at higher frequencies, and that the MS-HPC circuit normally imposes a frequency-limiting modulation over the SuM/MM area as suggested by cell-based recordings in anesthetized animals. In addition, we provide evidence that the postulated SuM-MS-HPC-MM circuit is under complex bi-directional control, rather than SuM and MM having roles as unidirectional relays in the network. PMID:28955209

Time-Domain Computation Of Electromagnetic Fields In MMICs

NASA Technical Reports Server (NTRS)

Lansing, Faiza S.; Rascoe, Daniel L.

1995-01-01

Maxwell's equations solved on three-dimensional, conformed orthogonal grids by finite-difference techniques. Method of computing frequency-dependent electrical parameters of monolithic microwave integrated circuit (MMIC) involves time-domain computation of propagation of electromagnetic field in response to excitation by single pulse at input terminal, followed by computation of Fourier transforms to obtain frequency-domain response from time-domain response. Parameters computed include electric and magnetic fields, voltages, currents, impedances, scattering parameters, and effective dielectric constants. Powerful and efficient means for analyzing performance of even complicated MMIC.

Power spectral ensity of markov texture fields

NASA Technical Reports Server (NTRS)

Shanmugan, K. S.; Holtzman, J. C.

1984-01-01

Texture is an important image characteristic. A variety of spatial domain techniques were proposed for extracting and utilizing textural features for segmenting and classifying images. for the most part, these spatial domain techniques are ad hos in nature. A markov random field model for image texture is discussed. A frequency domain description of image texture is derived in terms of the power spectral density. This model is used for designing optimum frequency domain filters for enhancing, restoring and segmenting images based on their textural properties.

Using Receiver Operating Characteristic Curve to Define the Cutoff Points of Voice Handicap Index Applied to Young Adult Male Smokers.

PubMed

Tafiadis, Dionysios; Chronopoulos, Spyridon K; Kosma, Evangelia I; Voniati, Louiza; Raptis, Vasilis; Siafaka, Vasiliki; Ziavra, Nausica

2017-07-11

Voice performance is an inextricable key factor of everyday life. Obviously, the deterioration of voice quality can cause various problems to human communication and can therefore reduce the performance of social skills (relevant to voice). The deterioration could be originated from changes inside the system of the vocal tract and larynx. Various prognostic methods exist, and among them is the Voice Handicap Index (VHI). This tool includes self-reported questionnaires, used for determining the cutoff points of total score and of its three domains relevant to young male Greek smokers. The interpretation of the calculated cutoff points can serve as a strong indicator of imminent or future evaluation by a clinician. Consistent with previous calculation, the VHI can also act as a feedback for smokers' voice condition and as monitoring procedure toward smoking cessation. Specifically, the sample consisted of 130 male nondysphonic smokers (aged 18-33 years) who all participated in the VHI test procedure. The test results (through receiver operating characteristic analysis) concluded to a total cutoff point score of 19.50 (sensitivity: 0.838, 1-specificity: 0). Also, in terms of constructs, the Functional domain was equal to 7.50 (sensitivity: 0.676, 1-specificity: 0.032), the Physical domain was equal to 7.50 (sensitivity: 0.706, 1-specificity: 0.032), and the Emotional domain was equal to 6.50 (sensitivity: 0.809, 1-specificity: 0.048). Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Poincare inequalities, uniform domains and extension properties for Newton-Sobolev functions in metric spaces

NASA Astrophysics Data System (ADS)

Bjorn, Jana; Shanmugalingam, Nageswari

2007-08-01

In the setting of metric measure spaces equipped with a doubling measure supporting a weak p-Poincare inequality with 1[less-than-or-equals, slant]p<[infinity], we show that any uniform domain [Omega] is an extension domain for the Newtonian space N1,p([Omega]) and that [Omega], together with the metric and the measure inherited from X, supports a weak p-Poincare inequality. For p>1, we obtain a near characterization of N1,p-extension domains with local estimates for the extension operator.

The application of the Routh approximation method to turbofan engine models

NASA Technical Reports Server (NTRS)

Merrill, W. C.

1977-01-01

The Routh approximation technique is applied in the frequency domain to a 16th order state variable turbofan engine model. The results obtained motivate the extension of the frequency domain formulation of the Routh method to the time domain to handle the state variable formulation directly. The time domain formulation is derived, and a characterization, which specifies all possible Routh similarity transformations, is given. The characterization is computed by the solution of two eigenvalue eigenvector problems. The application of the time domain Routh technique to the state variable engine model is described, and some results are given.

Time- and frequency-domain parameters of heart rate variability and sympathetic skin response in Parkinson's disease.

PubMed

Maetzler, Walter; Karam, Marie; Berger, Monika Fruhmann; Heger, Tanja; Maetzler, Corina; Ruediger, Heinz; Bronzova, Juliana; Lobo, Patricia Pita; Ferreira, Joaquim J; Ziemssen, Tjalf; Berg, Daniela

2015-03-01

The autonomic nervous system (ANS) is regularly affected in Parkinson's disease (PD). Information on autonomic dysfunction can be derived from e.g. altered heart rate variability (HRV) and sympathetic skin response (SSR). Such parameters can be quantified easily and measured repeatedly which might be helpful for evaluating disease progression and therapeutic outcome. In this 2-center study, HRV and SSR of 45 PD patients and 26 controls were recorded. HRV was measured during supine metronomic breathing and analyzed in time- and frequency-domains. SSR was evoked by repetitive auditory stimulation. Various ANS parameters were compared (1) between patients and healthy controls, (2) to clinical scales (Unified Parkinson's disease rating scale, Mini-Mental State Examination, Becks Depression Inventory), and (3) to disease duration. Root mean square of successive differences (RMSSD) and low frequency/high frequency (LF/HF) ratio differed significantly between PD and controls. Both, HRV and SSR parameters showed low or no association with clinical scores. Time-domain parameters tended to be affected already at early PD stages but did not consistently change with longer disease duration. In contrast, frequency-domain parameters were not altered in early PD phases but tended to be lower (LF, LF/HF ratio), respectively higher (HF) with increasing disease duration. This report confirms previous results of altered ANS parameters in PD. In addition, it suggests that (1) these ANS parameters are not relevantly associated with motor, behavioral, and cognitive changes in PD, (2) time-domain parameters are useful for the assessment of early PD, and (3) frequency-domain parameters are more closely associated with disease duration.

Progress Report for a New Cryogenic Sapphire Oscillator

NASA Technical Reports Server (NTRS)

Wang, Rabi T.; Dick, G. J.; Tjoelker, R. L.

2006-01-01

We present design progress and subsystem test results for a new short-term frequency standard, the Voltage Controlled Sapphire Oscillator (VCSO). Included are sapphire resonator and coupling design, cryocooler environmental sensitivity tests, Q measurement results, and turnover temperature results. A previous report presented history of the design related to resonator frequency and frequency compensation [1]. Performance goals are a frequency stability of 1x10(exp -14) (1 second less than or equal to (tau) less than or equal to 100 seconds) and two years or more continuous operation. Long-term operation and small size are facilitated by use of a small Stirling cryo-cooler (160W wall power) with an expected 5 year life.

Time-domain damping models in structural acoustics using digital filtering

NASA Astrophysics Data System (ADS)

Parret-Fréaud, Augustin; Cotté, Benjamin; Chaigne, Antoine

2016-02-01

This paper describes a new approach in order to formulate well-posed time-domain damping models able to represent various frequency domain profiles of damping properties. The novelty of this approach is to represent the behavior law of a given material directly in a discrete-time framework as a digital filter, which is synthesized for each material from a discrete set of frequency-domain data such as complex modulus through an optimization process. A key point is the addition of specific constraints to this process in order to guarantee stability, causality and verification of thermodynamics second law when transposing the resulting discrete-time behavior law into the time domain. Thus, this method offers a framework which is particularly suitable for time-domain simulations in structural dynamics and acoustics for a wide range of materials (polymers, wood, foam, etc.), allowing to control and even reduce the distortion effects induced by time-discretization schemes on the frequency response of continuous-time behavior laws.

Accelerated pharmacokinetic map determination for dynamic contrast enhanced MRI using frequency-domain based Tofts model.

PubMed

Vajuvalli, Nithin N; Nayak, Krupa N; Geethanath, Sairam

2014-01-01

Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI) is widely used in the diagnosis of cancer and is also a promising tool for monitoring tumor response to treatment. The Tofts model has become a standard for the analysis of DCE-MRI. The process of curve fitting employed in the Tofts equation to obtain the pharmacokinetic (PK) parameters is time-consuming for high resolution scans. Current work demonstrates a frequency-domain approach applied to the standard Tofts equation to speed-up the process of curve-fitting in order to obtain the pharmacokinetic parameters. The results obtained show that using the frequency domain approach, the process of curve fitting is computationally more efficient compared to the time-domain approach.

A cost-efficient frequency-domain photoacoustic imaging system

PubMed Central

LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

2013-01-01

Photoacoustic (PA) imaging techniques have recently attracted much attention and can be used for noninvasive imaging of biological tissues. Most PA imaging systems in research laboratories use the time domain method with expensive nanosecond pulsed lasers that are not affordable for most educational laboratories. Using an intensity modulated light source to excite PA signals is an alternative technique, known as the frequency domain method, with a much lower cost. In this paper, we describe a simple frequency domain PA system and demonstrate its imaging capability. The system provides opportunities not only to observe PA signals in tissue phantoms, but also to acquire hands-on skills in PA signal detection. It also provides opportunities to explore the underlying mechanisms of the PA effect. PMID:24659823

Distributed fiber strain and vibration sensor based on Brillouin optical time-domain reflectometry and polarization optical time-domain reflectometry.

PubMed

Wang, Feng; Zhang, Xuping; Wang, Xiangchuan; Chen, Haisheng

2013-07-15

A distributed fiber strain and vibration sensor which effectively combines Brillouin optical time-domain reflectometry and polarization optical time-domain reflectometry is proposed. Two reference beams with orthogonal polarization states are, respectively, used to perform the measurement. By using the signal obtained from either reference beam, the vibration of fiber can be measured from the polarization effect. After combining the signals obtained by both reference beams, the strain can be measured from the Brillouin effect. In the experiment, 10 m spatial resolution, 0.6 kHz frequency measurement range, 2.5 Hz frequency resolution, and 0.2 MHz uncertainty of Brillouin frequency measurement are realized for a 4 km sensing distance.

A cost-efficient frequency-domain photoacoustic imaging system.

PubMed

Leboulluec, Peter; Liu, Hanli; Yuan, Baohong

2013-09-01

Photoacoustic (PA) imaging techniques have recently attracted much attention and can be used for noninvasive imaging of biological tissues. Most PA imaging systems in research laboratories use the time domain method with expensive nanosecond pulsed lasers that are not affordable for most educational laboratories. Using an intensity modulated light source to excite PA signals is an alternative technique, known as the frequency domain method, with a much lower cost. In this paper, we describe a simple frequency domain PA system and demonstrate its imaging capability. The system provides opportunities not only to observe PA signals in tissue phantoms, but also to acquire hands-on skills in PA signal detection. It also provides opportunities to explore the underlying mechanisms of the PA effect.

SPA- STATISTICAL PACKAGE FOR TIME AND FREQUENCY DOMAIN ANALYSIS

NASA Technical Reports Server (NTRS)

Brownlow, J. D.

1994-01-01

The need for statistical analysis often arises when data is in the form of a time series. This type of data is usually a collection of numerical observations made at specified time intervals. Two kinds of analysis may be performed on the data. First, the time series may be treated as a set of independent observations using a time domain analysis to derive the usual statistical properties including the mean, variance, and distribution form. Secondly, the order and time intervals of the observations may be used in a frequency domain analysis to examine the time series for periodicities. In almost all practical applications, the collected data is actually a mixture of the desired signal and a noise signal which is collected over a finite time period with a finite precision. Therefore, any statistical calculations and analyses are actually estimates. The Spectrum Analysis (SPA) program was developed to perform a wide range of statistical estimation functions. SPA can provide the data analyst with a rigorous tool for performing time and frequency domain studies. In a time domain statistical analysis the SPA program will compute the mean variance, standard deviation, mean square, and root mean square. It also lists the data maximum, data minimum, and the number of observations included in the sample. In addition, a histogram of the time domain data is generated, a normal curve is fit to the histogram, and a goodness-of-fit test is performed. These time domain calculations may be performed on both raw and filtered data. For a frequency domain statistical analysis the SPA program computes the power spectrum, cross spectrum, coherence, phase angle, amplitude ratio, and transfer function. The estimates of the frequency domain parameters may be smoothed with the use of Hann-Tukey, Hamming, Barlett, or moving average windows. Various digital filters are available to isolate data frequency components. Frequency components with periods longer than the data collection interval are removed by least-squares detrending. As many as ten channels of data may be analyzed at one time. Both tabular and plotted output may be generated by the SPA program. This program is written in FORTRAN IV and has been implemented on a CDC 6000 series computer with a central memory requirement of approximately 142K (octal) of 60 bit words. This core requirement can be reduced by segmentation of the program. The SPA program was developed in 1978.

A frequency domain analysis of respiratory variations in the seismocardiogram signal.

PubMed

Pandia, Keya; Inan, Omer T; Kovacs, Gregory T A

2013-01-01

The seismocardiogram (SCG) signal traditionally measured using a chest-mounted accelerometer contains low-frequency (0-100 Hz) cardiac vibrations that can be used to derive diagnostically relevant information about cardiovascular and cardiopulmonary health. This work is aimed at investigating the effects of respiration on the frequency domain characteristics of SCG signals measured from 18 healthy subjects. Toward this end, the 0-100 Hz SCG signal bandwidth of interest was sub-divided into 5 Hz and 10 Hz frequency bins to compare the spectral energy in corresponding frequency bins of the SCG signal measured during three key conditions of respiration--inspiration, expiration, and apnea. Statistically significant differences were observed between the power in ensemble averaged inspiratory and expiratory SCG beats and between ensemble averaged inspiratory and apneaic beats across the 18 subjects for multiple frequency bins in the 10-40 Hz frequency range. Accordingly, the spectral analysis methods described in this paper could provide complementary and improved classification of respiratory modulations in the SCG signal over and above time-domain SCG analysis methods.

Early Breast Cancer Diagnosis Using Microwave Imaging via Space-Frequency Algorithm

NASA Astrophysics Data System (ADS)

Vemulapalli, Spandana

The conventional breast cancer detection methods have limitations ranging from ionizing radiations, low specificity to high cost. These limitations make way for a suitable alternative called Microwave Imaging, as a screening technique in the detection of breast cancer. The discernible differences between the benign, malignant and healthy breast tissues and the ability to overcome the harmful effects of ionizing radiations make microwave imaging, a feasible breast cancer detection technique. Earlier studies have shown the variation of electrical properties of healthy and malignant tissues as a function of frequency and hence stimulates high bandwidth requirement. A Ultrawideband, Wideband and Narrowband arrays have been designed, simulated and optimized for high (44%), medium (33%) and low (7%) bandwidths respectively, using the EM (electromagnetic software) called FEKO. These arrays are then used to illuminate the breast model (phantom) and the received backscattered signals are obtained in the near field for each case. The Microwave Imaging via Space-Time (MIST) beamforming algorithm in the frequency domain, is next applied to these near field backscattered monostatic frequency response signals for the image reconstruction of the breast model. The main purpose of this investigation is to access the impact of bandwidth and implement a novel imaging technique for use in the early detection of breast cancer. Earlier studies show the implementation of the MIST imaging algorithm on the time domain signals via a frequency domain beamformer. The performance evaluation of the imaging algorithm on the frequency response signals has been carried out in the frequency domain. The energy profile of the breast in the spatial domain is created via the frequency domain Parseval's theorem. The beamformer weights calculated using these the MIST algorithm (not including the effect of the skin) has been calculated for Ultrawideband, Wideband and Narrowband arrays, respectively. Quality metrics such as dynamic range, radiometric resolution etc. are also evaluated for all the three types of arrays.

Unsteady transonic flows - Introduction, current trends, applications

NASA Technical Reports Server (NTRS)

Yates, E. C., Jr.

1985-01-01

The computational treatment of unsteady transonic flows is discussed, reviewing the historical development and current techniques. The fundamental physical principles are outlined; the governing equations are introduced; three-dimensional linearized and two-dimensional linear-perturbation theories in frequency domain are described in detail; and consideration is given to frequency-domain FEMs and time-domain finite-difference and integral-equation methods. Extensive graphs and diagrams are included.

Using frequency-domain methods to identify XV-15 aeroelastic modes

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.; Tischler, Mark B.

1987-01-01

The XV-15 Tilt-Rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier transformed) with cross spectral and transfer function methods. Modal frequencies and damping were determined by performing curve fits to transfer function magnitude and phase data and to cross spectral magnitude data. Results are given for the XV-15 with its original metal rotor blades. Frequency and damping values are also compared with earlier predictions.

Non-contact fluid characterization in containers using ultrasonic waves

DOEpatents

Sinha, Dipen N [Los Alamos, NM

2012-05-15

Apparatus and method for non-contact (stand-off) ultrasonic determination of certain characteristics of fluids in containers or pipes are described. A combination of swept frequency acoustic interferometry (SFAI), wide-bandwidth, air-coupled acoustic transducers, narrowband frequency data acquisition, and data conversion from the frequency domain to the time domain, if required, permits meaningful information to be extracted from such fluids.

Digital techniques for ULF wave polarization analysis

NASA Technical Reports Server (NTRS)

Arthur, C. W.

1979-01-01

Digital power spectral and wave polarization analysis are powerful techniques for studying ULF waves in the earth's magnetosphere. Four different techniques for using the spectral matrix to perform such an analysis have been presented in the literature. Three of these techniques are similar in that they require transformation of the spectral matrix to the principal axis system prior to performing the polarization analysis. The differences in the three techniques lie in the manner in which determine this transformation. A comparative study of these three techniques using both simulated and real data has shown them to be approximately equal in quality of performance. The fourth technique does not require transformation of the spectral matrix. Rather, it uses the measured spectral matrix and state vectors for a desired wave type to design a polarization detector function in the frequency domain. The design of various detector functions and their application to both simulated and real data will be presented.

Surface plasmon polaritons generated by radial polarized laser beam on silver nano-ring

NASA Astrophysics Data System (ADS)

Kozlova, Elena S.; Kotlyar, Victor V.

2017-04-01

In this work the single surface plasmon-polariton was obtained by using frequency-dependent finite difference time domain method for the radial polarized and vortex beams at 532 nm, which were propagating through the silver nanoring on substrate from silica glass, placed in an aqueous medium. The height and width of device were equal to 20 nm and 215 nm respectively. The intensity of surface plasmon-polariton was four times higher and three times higher the intensity of the incident radiation for case of conventional and vortex beams respectively. The full width at half maximum of the nanojet was near 160 nm for each cases. The presented design can be used for manufacturing of highly integrated optical devices and circuits used in high-speed communication applications. The results also can be used to design devices that allow capturing and moving the particles in water or other biofluidics.

Evaluation of piezoceramic actuators for control of aircraft interior noise

NASA Technical Reports Server (NTRS)

Silcox, Richard J.; Lefebvre, Sylvie; Metcalf, Vern L.; Beyer, Todd B.; Fuller, Chris R.

1992-01-01

Results of an experiment to evaluate piezoceramic actuators as the control actuator for active control of interior noise in a large-scale fuselage model are presented. Control was demonstrated for tonal excitation using a time domain least mean squares algorithm. A maximum of four actuator channels and six error signals were used. The actuators were employed for control of noise at frequencies where interior cavity modes were the dominant response and for driven acoustic responses where a structure resonance was dominant. Global reductions of 9 to 12 dB were obtained for the cases examined. The most effective configuration of skin-mounted actuators was found to be a pure in-plane forcing function as opposed to a bending excitation. The frame-mounted actuators were found to be equally effective as the skin-mounted actuators. However, both configurations resulted in local regions of unacceptably high vibration response in the structure.

The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

PubMed Central

Yankiwski, Victor; Noonan, James P; Neff, Norma F

2001-01-01

Background Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10) or PML (promyelocytic leukemia) nuclear bodies, where it associates with TOPIIIα, and to the nucleolus. Results This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities. Conclusion The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies. PMID:11472631

Illusion optics via one-dimensional ultratransparent photonic crystals with shifted spatial dispersions.

PubMed

Yao, Zhongqi; Luo, Jie; Lai, Yun

2017-12-11

In this work, we propose that one-dimensional ultratransparent dielectric photonic crystals with wide-angle impedance matching and shifted elliptical equal frequency contours are promising candidate materials for illusion optics. The shift of the equal frequency contour does not affect the refractive behaviors, but enables a new degree of freedom in phase modulation. With such ultratransparent photonic crystals, we demonstrate some applications in illusion optics, including creating illusions of a different-sized scatterer and a shifted source with opposite phase. Such ultratransparent dielectric photonic crystals may establish a feasible platform for illusion optics devices at optical frequencies.

Corrosion of Type 7075-T73 Aluminum in a 10% HNO3 + Fe2(SO4)3 Deoxidizer Solution

NASA Astrophysics Data System (ADS)

Savas, Terence P.; Earthman, James C.

2009-03-01

Localized corrosion damage in Type 7075-T73 aluminum was investigated for a HNO3 + Fe2(SO4)3 deoxidizer solution which is frequently used for surface pretreatment prior to anodizing. The corrosion damage was quantified in the time domain using the electrochemical noise resistance ( Rn) and in the frequency domain using the spectral noise impedance ( Rsn). The Rsn was derived from an equivalent electrical circuit model that represented the corrosion cell implemented in the present study. These data are correlated to scanning electron microscopy (SEM) examinations and corresponding statistical analysis based on digital image analysis of the corroded surfaces. Other data used to better understand the corrosion mechanisms include the open circuit potential (OCP) and coupling-current time records. Based on statistical analysis of the pit structures for 600 and 1200 s exposures, the best fit was achieved with a 3-paramater lognormal distribution. It was observed for the 1200 s exposure that a small population of pits continued to grow beyond a threshold critical size of 10 μm. In addition, significant grain boundary attack was observed after 1200 s exposure. These data are in good agreement with the electrochemical data. Specifically, the Rn was computed to be 295 and 96 Ω-cm2 for 600 and 1200 s exposures, respectively. The calculated value of Rsn, theoretically shown to be equal to Rn in the low frequency limit, was higher than Rn for a 1200 s exposure period. However, better agreement between the Rn and Rsn was found for frequencies above 0.01 Hz. Experimental results on the measurement performance for potassium chloride (KCl) saturated double-junction Ag/AgCl and single-junction Hg/Hg2Cl2 reference electrodes in the low-pH deoxidizer solution are also compared.

Solution to the indexing problem of frequency domain simulation experiments

NASA Technical Reports Server (NTRS)

Mitra, Mousumi; Park, Stephen K.

1991-01-01

A frequency domain simulation experiment is one in which selected system parameters are oscillated sinusoidally to induce oscillations in one or more system statistics of interest. A spectral (Fourier) analysis of these induced oscillations is then performed. To perform this spectral analysis, all oscillation frequencies must be referenced to a common, independent variable - an oscillation index. In a discrete-event simulation, the global simulation clock is the most natural choice for the oscillation index. However, past efforts to reference all frequencies to the simulation clock generally yielded unsatisfactory results. The reason for these unsatisfactory results is explained in this paper and a new methodology which uses the simulation clock as the oscillation index is presented. Techniques for implementing this new methodology are demonstrated by performing a frequency domain simulation experiment for a network of queues.

Pitch expertise is not created equal: Cross-domain effects of musicianship and tone language experience on neural and behavioural discrimination of speech and music.

PubMed

Hutka, Stefanie; Bidelman, Gavin M; Moreno, Sylvain

2015-05-01

Psychophysiological evidence supports a music-language association, such that experience in one domain can impact processing required in the other domain. We investigated the bidirectionality of this association by measuring event-related potentials (ERPs) in native English-speaking musicians, native tone language (Cantonese) nonmusicians, and native English-speaking nonmusician controls. We tested the degree to which pitch expertise stemming from musicianship or tone language experience similarly enhances the neural encoding of auditory information necessary for speech and music processing. Early cortical discriminatory processing for music and speech sounds was characterized using the mismatch negativity (MMN). Stimuli included 'large deviant' and 'small deviant' pairs of sounds that differed minimally in pitch (fundamental frequency, F0; contrastive musical tones) or timbre (first formant, F1; contrastive speech vowels). Behavioural F0 and F1 difference limen tasks probed listeners' perceptual acuity for these same acoustic features. Musicians and Cantonese speakers performed comparably in pitch discrimination; only musicians showed an additional advantage on timbre discrimination performance and an enhanced MMN responses to both music and speech. Cantonese language experience was not associated with enhancements on neural measures, despite enhanced behavioural pitch acuity. These data suggest that while both musicianship and tone language experience enhance some aspects of auditory acuity (behavioural pitch discrimination), musicianship confers farther-reaching enhancements to auditory function, tuning both pitch and timbre-related brain processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of complaints and singing style in singers voice handicap.

PubMed

Moreti, Felipe; Ávila, Maria Emília Barros de; Rocha, Clara; Borrego, Maria Cristina de Menezes; Oliveira, Gisele; Behlau, Mara

2012-01-01

The aim of this research was to verify whether the difference of singing styles and the presence of vocal complaints influence the perception of voice handicap of singers. One hundred eighteen singing voice handicap self-assessment protocols were selected: 17 popular singers with vocal complaints, 42 popular singers without complaints, 17 classic singers with complaints, and 42 classic singers without complaints. The groups were similar regarding age, gender and voice types. Both protocols used--Modern Singing Handicap Index (MSHI) and Classical Singing Handicap Index (CSHI)--have specific questions to their respective singing styles, and consist of 30 items equally divided into three subscales: disability (functional domain), handicap (emotional domain) and impairment (organic domain), answered according to the frequency of occurrence. Each subscale has a maximum of 40 points, and the total score is 120 points. The higher the score, the higher the singing voice handicap perceived. For statistical analysis, we used the ANOVA test, with 5% of significance. Classical and popular singers referred higher impairment, followed by disability and handicap. However, the degree of this perception varied according to the singing style and the presence of vocal complaints. The classical singers with vocal complaints showed higher voice handicap than popular singers with vocal complaints, while the classic singers without complaints reported lower handicap than popular singers without complaints. This evidences that classical singers have higher perception of their own voice, and that vocal disturbances in this group may cause greater voice handicap when compared to popular singers.

[Visualizing Research Lines in Public Health: An analysis Based on Bibliometric Maps Applied to the Revista Española de Salud Pública (2006-2015)].

PubMed

Gálvez, Carmen

2016-12-01

Identifying research lines is essential to understand the knowledge structure of a scientific domain. The aim of this study was to identify the main research topics of within the domain of public health, in the Revista Española de Saslud Pública during 2006-2015. Original articles included in the Social Sciences Citation Index (SSCI) database, available online through the Web of Science (WoS), were selected. The analysis units used were the keywords, KeyWords Plus (KW+), extracted automatically by SSCI. With KW+ obtained bibliometric, maps were created using a methodology based on the combination of co-word analysis, co-word analysis, clustering techniques and visualization techniques. We analyzed 512 documents, of which 176 KW+ were obtained with a frequency greater than or equal to 3. The results were bidimensional bibliometric maps with thematic groupings of KW+, representing the main research fronts: i) epidemiology, risk control programs disease and, in general, service organization and health policies; ii) infectious diseases, principally HIV; iii) a progressive increase in several lines interrelated with cardiovascular diseases (CVD); iv) a line multidimensional dedicated to different aspects associated to the quality of life related to health (HRQoL); and v) an emerging line linked to binge drinking. For the multidisciplinary and multidimensional nature of public health, the construction of bibliometric maps is an appropriate methodology to understand the knowledge structure of this scientific domain.

Is 50 Hz high enough ECG sampling frequency for accurate HRV analysis?

PubMed

Mahdiani, Shadi; Jeyhani, Vala; Peltokangas, Mikko; Vehkaoja, Antti

2015-01-01

With the worldwide growth of mobile wireless technologies, healthcare services can be provided at anytime and anywhere. Usage of wearable wireless physiological monitoring system has been extensively increasing during the last decade. These mobile devices can continuously measure e.g. the heart activity and wirelessly transfer the data to the mobile phone of the patient. One of the significant restrictions for these devices is usage of energy, which leads to requiring low sampling rate. This article is presented in order to investigate the lowest adequate sampling frequency of ECG signal, for achieving accurate enough time domain heart rate variability (HRV) parameters. For this purpose the ECG signals originally measured with high 5 kHz sampling rate were down-sampled to simulate the measurement with lower sampling rate. Down-sampling loses information, decreases temporal accuracy, which was then restored by interpolating the signals to their original sampling rates. The HRV parameters obtained from the ECG signals with lower sampling rates were compared. The results represent that even when the sampling rate of ECG signal is equal to 50 Hz, the HRV parameters are almost accurate with a reasonable error.

Modulation format identification enabled by the digital frequency-offset loading technique for hitless coherent transceiver.

PubMed

Fu, Songnian; Xu, Zuying; Lu, Jianing; Jiang, Hexun; Wu, Qiong; Hu, Zhouyi; Tang, Ming; Liu, Deming; Chan, Calvin Chun-Kit

2018-03-19

We propose a blind and fast modulation format identification (MFI) enabled by the digital frequency-offset (FO) loading technique for hitless coherent transceiver. Since modulation format information is encoded to the FO distribution during digital signal processing (DSP) at the transmitter side (Tx), we can use the fast Fourier transformation based FO estimation (FFT-FOE) method to obtain the FO distribution of individual data block after constant modulus algorithm (CMA) pre-equalization at the receiver side, in order to realize non-data-aided (NDA) and fast MFI. The obtained FO can be also used for subsequent FO compensation (FOC), without additional complexity. We numerically investigate and experimentally verify the proposed MFI with high accuracy and fast format switching among 28 Gbaud dual-polarization (DP)-4/8/16/64QAM, time domain hybrid-4/16QAM, and set partitioning (SP)-128QAM. In particular, the proposed MFI brings no performance degradation, in term of tolerance of amplified spontaneous emission (ASE) noise, laser linewidth, and fiber nonlinearity. Finally, a hitless coherent transceiver enabled by the proposed MFI with switching-block of only 2048 symbols is demonstrated over 1500 km standard single mode fiber (SSMF) transmission.

Interaction between moving tandem wheels and an infinite rail with periodic supports - Green's matrices of the track method in stationary reference frame

NASA Astrophysics Data System (ADS)

Mazilu, Traian

2017-08-01

This paper approaches the issue of the interaction between moving tandem wheels and an infinite periodically supported rail and points out at the basic characteristics in the steady-state interaction behaviour and in the interaction in the presence of the rail random irregularity. The rail is modelled as an infinite Timoshenko beam resting on supports which are discretely modelling the inertia of the sleepers and ballast and also the viscoelastic features of the rail pads, the ballast and the subgrade. Green‧s matrices of the track method in stationary reference frame were applied so as to conduct the time-domain analysis. This method allows to consider the nonlinearities of the wheel/rail contact and the Doppler effect. The study highlights certain aspects regarding the influence of the wheel base on the wheels/rail contact forces, particularly at the parametric resonance, due to the coincidence between the wheel/rail natural frequency and the passing frequency and also when the rail surface exhibits random irregularity. It has been shown that the wheel/rail dynamic behaviour is less intense when the wheel base equals integer multiple of the sleeper bay.

Carpet cloak with graded dielectric metasurface (Presentation Recording)

NASA Astrophysics Data System (ADS)

Hsu, LiYi; Lepetit, Thomas; Kante, Boubacar

2015-09-01

We demonstrate a method to hide a Gaussian-shaped bump on a ground plane from an incoming plane wave. In essence, we use a graded metasurface to shape the wavefronts like those of a flat ground plane[1,2].The metasurface provides additional phase to the electromagnetic field to control the reflection angle. To mimic a flat ground plane, the reflection angle is chosen to be equal to the incident angle. The desired phase distribution is calculated based on generalized Snell's laws[3]. We design our metasurface in the microwave range using sub-wavelength dielectric resonators. We verify the design by full-wave time-domain simulations and show that the result matches our theory well. This approach can be applied to hide any object on a ground plane not only at microwave frequencies but also at higher frequencies up to the infrared. 1. Jensen Li and J. B. Pendry, Hiding under the Carpet: A New Strategy for Cloaking. Phys. Rev. Lett. 101, 203901 (2008) 2. Andrea Alu, Mantle cloak: Invisibility induced by a surface. Phys. Rev. B 80, 245115 (2009) 3. Yu N, et al. Light propagation with phase discontinuities: Generalized laws of reflection and refraction. Science 334(6054):333-337 (2011)

An operational modal analysis method in frequency and spatial domain

NASA Astrophysics Data System (ADS)

Wang, Tong; Zhang, Lingmi; Tamura, Yukio

2005-12-01

A frequency and spatial domain decomposition method (FSDD) for operational modal analysis (OMA) is presented in this paper, which is an extension of the complex mode indicator function (CMIF) method for experimental modal analysis (EMA). The theoretical background of the FSDD method is clarified. Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density (PSD) is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.

Time-domain SFG spectroscopy using mid-IR pulse shaping: practical and intrinsic advantages.

PubMed

Laaser, Jennifer E; Xiong, Wei; Zanni, Martin T

2011-03-24

Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra. © 2011 American Chemical Society

Assessment of resting-state blood flow through anterior cerebral arteries using trans-cranial doppler recordings.

PubMed

Huang, Hanrui; Sejdić, Ervin

2013-12-01

Trans-cranial Doppler (TCD) recordings are used to monitor cerebral blood flow in the main cerebral arteries. The resting state is usually characterized by the mean velocity or the maximum Doppler shift frequency (an envelope signal) by insonating the middle cerebral arteries. In this study, we characterized cerebral blood flow in the anterior cerebral arteries. We analyzed both envelope signals and raw signals obtained from bilateral insonation. We recruited 20 healthy patients and conducted the data acquisition for 15 min. Features were extracted from the time domain, the frequency domain and the time-frequency domain. The results indicate that a gender-based statistical difference exists in the frequency and time-frequency domains. However, no handedness effect was found. In the time domain, information-theoretic features indicated that mutual dependence is higher in raw signals than in envelope signals. Finally, we concluded that insonation of the anterior cerebral arteries serves as a complement to middle cerebral artery studies. Additionally, investigation of the raw signals provided us with additional information that is not otherwise available from envelope signals. Use of direct trans-cranial Doppler raw data is therefore validated as a valuable method for characterizing the resting state. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Advance in ERG Analysis: From Peak Time and Amplitude to Frequency, Power, and Energy

PubMed Central

Lina, Jean-Marc; Lachapelle, Pierre

2014-01-01

Purpose. To compare time domain (TD: peak time and amplitude) analysis of the human photopic electroretinogram (ERG) with measures obtained in the frequency domain (Fourier analysis: FA) and in the time-frequency domain (continuous (CWT) and discrete (DWT) wavelet transforms). Methods. Normal ERGs (n = 40) were analyzed using traditional peak time and amplitude measurements of the a- and b-waves in the TD and descriptors extracted from FA, CWT, and DWT. Selected descriptors were also compared in their ability to monitor the long-term consequences of disease process. Results. Each method extracted relevant information but had distinct limitations (i.e., temporal and frequency resolutions). The DWT offered the best compromise by allowing us to extract more relevant descriptors of the ERG signal at the cost of lesser temporal and frequency resolutions. Follow-ups of disease progression were more prolonged with the DWT (max 29 years compared to 13 with TD). Conclusions. Standardized time domain analysis of retinal function should be complemented with advanced DWT descriptors of the ERG. This method should allow more sensitive/specific quantifications of ERG responses, facilitate follow-up of disease progression, and identify diagnostically significant changes of ERG waveforms that are not resolved when the analysis is only limited to time domain measurements. PMID:25061605

OFDM inspired waveforms for 5G

DOE PAGES

Farhang-Boroujeny, Behrouz; Moradi, Hussein

2016-05-12

As the standardization activities are being formed to lay the foundation of 5G wireless networks, there is a common consensus on the need to replace the celebrated OFDM by a more effective air interface that better serves the challenging needs of 5G. The main reason that has made OFDM popular in the past is related to the fact that information symbols are carried over a number of pure tones/sinusoidal signals. Moreover, with the use of cyclic prefix (CP), it is assured that the information carrying tones are only affected by the channel (complex) gains at the respective frequencies. Accordingly, themore » channel effect can be trivially compensated for (equalized) in the frequency domain through a single complex tap per subcarrier. However, as network air interfaces become more complex and the demand for multiuser services grows, OFDM is found to be incapable of handling the inevitable loss of synchronization among users. In the recent past, two novel waveforms (namely, GFDM and C-FBMC) have been discussed in the literature to overcome this and other drawbacks of OFDM. Interestingly, and at the same time not surprising, these methods share a common fundamental property with OFDM: each data packet is made up of a number of tones that are modulated by information symbols. In this tutorial article, we build a common framework based on the said OFDM principle and derive GFDM and C-FBMC waveforms from this point of view. This derivation provides a new prospective that facilitates straightforward understanding of channel equalization and the application of these new waveforms to MIMO channels. As a result, it also facilitates derivation of new structures for more efficient synthesis/analysis of these waveforms than those that have been reported in the literature.« less

A Population-based Study Evaluating the Association between Surgery in Early Life and Child Development at Primary School Entry.

PubMed

O'Leary, James D; Janus, Magdalena; Duku, Eric; Wijeysundera, Duminda N; To, Teresa; Li, Ping; Maynes, Jason T; Crawford, Mark W

2016-08-01

It is unclear whether exposure to surgery in early life has long-term adverse effects on child development. The authors aimed to investigate whether surgery in early childhood is associated with adverse effects on child development measured at primary school entry. The authors conducted a population-based cohort study in Ontario, Canada, by linking provincial health administrative databases to children's developmental outcomes measured by the Early Development Instrument (EDI). From a cohort of 188,557 children, 28,366 children who underwent surgery before EDI completion (age 5 to 6 yr) were matched to 55,910 unexposed children. The primary outcome was early developmental vulnerability, defined as any domain of the EDI in the lowest tenth percentile of the population. Subgroup analyses were performed based on age at first surgery (less than 2 and greater than or equal to 2 yr) and frequency of surgery. Early developmental vulnerability was increased in the exposed group (7,259/28,366; 25.6%) compared with the unexposed group (13,957/55,910; 25.0%), adjusted odds ratio, 1.05; 95% CI, 1.01 to 1.08. Children aged greater than or equal to 2 yr at the time of first surgery had increased odds of early developmental vulnerability compared with unexposed children (odds ratio, 1.05; 95% CI, 1.01 to 1.10), but children aged less than 2 yr at the time of first exposure were not at increased risk (odds ratio, 1.04; 95% CI, 0.98 to 1.10). There was no increase in odds of early developmental vulnerability with increasing frequency of exposure. Children who undergo surgery before primary school age are at increased risk of early developmental vulnerability, but the magnitude of the difference between exposed and unexposed children is small.

An improved adaptive interpolation clock recovery loop based on phase splitting algorithm for coherent optical communication system

NASA Astrophysics Data System (ADS)

Liu, Xuan; Liu, Bo; Zhang, Li-jia; Xin, Xiang-jun; Zhang, Qi; Wang, Yong-jun; Tian, Qing-hua; Tian, Feng; Mao, Ya-ya

2018-01-01

Traditional clock recovery scheme achieves timing adjustment by digital interpolation, thus recovering the sampling sequence. Based on this, an improved clock recovery architecture joint channel equalization for coherent optical communication system is presented in this paper. The loop is different from the traditional clock recovery. In order to reduce the interpolation error caused by the distortion in the frequency domain of the interpolator and to suppress the spectral mirroring generated by the sampling rate change, the proposed algorithm joint equalization, improves the original interpolator in the loop, along with adaptive filtering, and makes error compensation for the original signals according to the balanced pre-filtering signals. Then the signals are adaptive interpolated through the feedback loop. Furthermore, the phase splitting timing recovery algorithm is adopted in this paper. The time error is calculated according to the improved algorithm when there is no transition between the adjacent symbols, making calculated timing error more accurate. Meanwhile, Carrier coarse synchronization module is placed before the beginning of timing recovery to eliminate the larger frequency offset interference, which effectively adjust the sampling clock phase. In this paper, the simulation results show that the timing error is greatly reduced after the loop is changed. Based on the phase splitting algorithm, the BER and MSE are better than those in the unvaried architecture. In the fiber channel, using MQAM modulation format, after 100 km-transmission of single-mode fiber, especially when ROF(roll-off factor) values tends to 0, the algorithm shows a better clock performance under different ROFs. When SNR values are less than 8, the BER could achieve 10-2 to 10-1 magnitude. Furthermore, the proposed timing recovery is more suitable for the situation with low SNR values.

Morphological Simulation of Phase Separation Coupled Oscillation Shear and Varying Temperature Fields

NASA Astrophysics Data System (ADS)

Wang, Heping; Li, Xiaoguang; Lin, Kejun; Geng, Xingguo

2018-05-01

This paper explores the effect of the shear frequency and Prandtl number ( Pr) on the procedure and pattern formation of phase separation in symmetric and asymmetric systems. For the symmetric system, the periodic shear significantly prolongs the spinodal decomposition stage and enlarges the separated domain in domain growth stage. By adjusting the Pr and shear frequency, the number and orientation of separated steady layer structures can be controlled during domain stretch stage. The numerical results indicate that the increase in Pr and decrease in the shear frequency can significantly increase in the layer number of the lamellar structure, which relates to the decrease in domain size. Furthermore, the lamellar orientation parallel to the shear direction is altered into that perpendicular to the shear direction by further increasing the shear frequency, and also similar results for larger systems. For asymmetric system, the quantitative analysis shows that the decrease in the shear frequency enlarges the size of separated minority phases. These numerical results provide guidance for setting the optimum condition for the phase separation under periodic shear and slow cooling.

Comparison of frequency-domain and time-domain rotorcraft vibration control methods

NASA Technical Reports Server (NTRS)

Gupta, N. K.

1984-01-01

Active control of rotor-induced vibration in rotorcraft has received significant attention recently. Two classes of techniques have been proposed. The more developed approach works with harmonic analysis of measured time histories and is called the frequency-domain approach. The more recent approach computes the control input directly using the measured time history data and is called the time-domain approach. The report summarizes the results of a theoretical investigation to compare the two approaches. Five specific areas were addressed: (1) techniques to derive models needed for control design (system identification methods), (2) robustness with respect to errors, (3) transient response, (4) susceptibility to noise, and (5) implementation difficulties. The system identification methods are more difficult for the time-domain models. The time-domain approach is more robust (e.g., has higher gain and phase margins) than the frequency-domain approach. It might thus be possible to avoid doing real-time system identification in the time-domain approach by storing models at a number of flight conditions. The most significant error source is the variation in open-loop vibrations caused by pilot inputs, maneuvers or gusts. The implementation requirements are similar except that the time-domain approach can be much simpler to implement if real-time system identification were not necessary.

Marginal instability threshold condition of the aperiodic ordinary mode in equal-mass plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vafin, S.; Schlickeiser, R.; Yoon, P. H.

The purely growing ordinary (O) mode instability for counter-streaming bi-Maxwellian plasma particle distribution functions has recently received renewed attention due to its importance for the solar wind plasma. Here, the analytical marginal instability condition is derived for magnetized plasmas consisting of equal-mass charged particles, distributed in counter-streams with equal temperatures. The equal-mass composition assumption enormously facilitates the theoretical analysis due to the equality of the values of the electron and positron (positive and negative ion) plasma and gyrofrequencies. The existence of a new instability domain of the O-mode at small plasma beta values is confirmed, when the parallel counter-stream freemore » energy exceeds the perpendicular bi-Maxwellian free energy.« less

Spectral behavior of a terahertz quantum-cascade laser.

PubMed

Hensley, J M; Montoya, Juan; Allen, M G; Xu, J; Mahler, L; Tredicucci, A; Beere, H E; Ritchie, D A

2009-10-26

In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.

Allan deviation computations of a linear frequency synthesizer system using frequency domain techniques

NASA Technical Reports Server (NTRS)

Wu, Andy

1995-01-01

Allan Deviation computations of linear frequency synthesizer systems have been reported previously using real-time simulations. Even though it takes less time compared with the actual measurement, it is still very time consuming to compute the Allan Deviation for long sample times with the desired confidence level. Also noises, such as flicker phase noise and flicker frequency noise, can not be simulated precisely. The use of frequency domain techniques can overcome these drawbacks. In this paper the system error model of a fictitious linear frequency synthesizer is developed and its performance using a Cesium (Cs) atomic frequency standard (AFS) as a reference is evaluated using frequency domain techniques. For a linear timing system, the power spectral density at the system output can be computed with known system transfer functions and known power spectral densities from the input noise sources. The resulting power spectral density can then be used to compute the Allan Variance at the system output. Sensitivities of the Allan Variance at the system output to each of its independent input noises are obtained, and they are valuable for design trade-off and trouble-shooting.

Scaled nonuniform Fourier transform for image reconstruction in swept source optical coherence tomography

NASA Astrophysics Data System (ADS)

Mezgebo, Biniyam; Nagib, Karim; Fernando, Namal; Kordi, Behzad; Sherif, Sherif

2018-02-01

Swept Source optical coherence tomography (SS-OCT) is an important imaging modality for both medical and industrial diagnostic applications. A cross-sectional SS-OCT image is obtained by applying an inverse discrete Fourier transform (DFT) to axial interferograms measured in the frequency domain (k-space). This inverse DFT is typically implemented as a fast Fourier transform (FFT) that requires the data samples to be equidistant in k-space. As the frequency of light produced by a typical wavelength-swept laser is nonlinear in time, the recorded interferogram samples will not be uniformly spaced in k-space. Many image reconstruction methods have been proposed to overcome this problem. Most such methods rely on oversampling the measured interferogram then use either hardware, e.g., Mach-Zhender interferometer as a frequency clock module, or software, e.g., interpolation in k-space, to obtain equally spaced samples that are suitable for the FFT. To overcome the problem of nonuniform sampling in k-space without any need for interferogram oversampling, an earlier method demonstrated the use of the nonuniform discrete Fourier transform (NDFT) for image reconstruction in SS-OCT. In this paper, we present a more accurate method for SS-OCT image reconstruction from nonuniform samples in k-space using a scaled nonuniform Fourier transform. The result is demonstrated using SS-OCT images of Axolotl salamander eggs.

Blunted autonomic response in cluster headache patients.

PubMed

Barloese, Mads; Brinth, Louise; Mehlsen, Jesper; Jennum, Poul; Lundberg, Helena Inez Sofia; Jensen, Rigmor

2015-12-01

Cluster headache (CH) is a disabling headache disorder with chronobiological features. The posterior hypothalamus is involved in CH pathophysiology and is a hub for autonomic control. We studied autonomic response to the head-up tilt table test (HUT) including heart rate variability (HRV) in CH patients and compared results to healthy controls. Twenty-seven episodic and chronic CH patients and an equal number of age-, sex- and BMI-matched controls were included. We analyzed responses to HUT in the time and frequency domain and by non-linear analysis. CH patients have normal cardiovascular responses compared to controls but increased blood pressure. In the frequency analysis CH patients had a smaller change in the normalized low- (LF) (2.89 vs. 13.38, p < 0.05) and high-frequency (HF) (-2.86 vs. -13.38, p < 0.05) components as well as the LF/HF ratio (0.81 vs. 2.62, p < 0.05) in response to tilt. In the Poincaré plot, the change in ratio between long- and short-term variation was lower in patients (SD1/SD2, -0.05 vs. -0.17, p < 0.05). CH patients show decreased autonomic response to HUT compared to healthy controls. This can be interpreted as dysregulation in the posterior hypothalamus and supports a theory of central autonomic mechanisms involvement in CH. © International Headache Society 2015.

The Stability of Periodic Orbits.

DTIC Science & Technology

1981-01-21

first class, the new stable orbit has a fundamental frequency equal to half that of the original orbit. Thesebifurcations (for which one real...eigenvalue of the Poincare map passes out through the unit circle at -1 : see Appendix 1) 9,10 are observed and are referred to as subharmonic or period...doubling bifurcations. At such a bifurcation componenns of x(t) with a frequency -8- equal to half that of the original longitudinal motion grow

A two-dimensional time domain near zone to far zone transformation

NASA Technical Reports Server (NTRS)

Luebbers, Raymond J.; Ryan, Deirdre; Beggs, John H.; Kunz, Karl S.

1991-01-01

A time domain transformation useful for extrapolating three dimensional near zone finite difference time domain (FDTD) results to the far zone was presented. Here, the corresponding two dimensional transform is outlined. While the three dimensional transformation produced a physically observable far zone time domain field, this is not convenient to do directly in two dimensions, since a convolution would be required. However, a representative two dimensional far zone time domain result can be obtained directly. This result can then be transformed to the frequency domain using a Fast Fourier Transform, corrected with a simple multiplicative factor, and used, for example, to calculate the complex wideband scattering width of a target. If an actual time domain far zone result is required, it can be obtained by inverse Fourier transform of the final frequency domain result.

A two-dimensional time domain near zone to far zone transformation

NASA Technical Reports Server (NTRS)

Luebbers, Raymond J.; Ryan, Deirdre; Beggs, John H.; Kunz, Karl S.

1991-01-01

In a previous paper, a time domain transformation useful for extrapolating 3-D near zone finite difference time domain (FDTD) results to the far zone was presented. In this paper, the corresponding 2-D transform is outlined. While the 3-D transformation produced a physically observable far zone time domain field, this is not convenient to do directly in 2-D, since a convolution would be required. However, a representative 2-D far zone time domain result can be obtained directly. This result can then be transformed to the frequency domain using a Fast Fourier Transform, corrected with a simple multiplicative factor, and used, for example, to calculate the complex wideband scattering width of a target. If an actual time domain far zone result is required it can be obtained by inverse Fourier transform of the final frequency domain result.

Software Library for Bruker TopSpin NMR Data Files

DOE Office of Scientific and Technical Information (OSTI.GOV)

A software library for parsing and manipulating frequency-domain data files that have been processed using the Bruker TopSpin NMR software package. In the context of NMR, the term "processed" indicates that the end-user of the Bruker TopSpin NMR software package has (a) Fourier transformed the raw, time-domain data (the Free Induction Decay) into the frequency-domain and (b) has extracted the list of NMR peaks.

Ultrasonic Phased Array Compressive Imaging in Time and Frequency Domain: Simulation, Experimental Verification and Real Application

PubMed Central

Bai, Zhiliang; Chen, Shili; Jia, Lecheng; Zeng, Zhoumo

2018-01-01

Embracing the fact that one can recover certain signals and images from far fewer measurements than traditional methods use, compressive sensing (CS) provides solutions to huge amounts of data collection in phased array-based material characterization. This article describes how a CS framework can be utilized to effectively compress ultrasonic phased array images in time and frequency domains. By projecting the image onto its Discrete Cosine transform domain, a novel scheme was implemented to verify the potentiality of CS for data reduction, as well as to explore its reconstruction accuracy. The results from CIVA simulations indicate that both time and frequency domain CS can accurately reconstruct array images using samples less than the minimum requirements of the Nyquist theorem. For experimental verification of three types of artificial flaws, although a considerable data reduction can be achieved with defects clearly preserved, it is currently impossible to break Nyquist limitation in the time domain. Fortunately, qualified recovery in the frequency domain makes it happen, meaning a real breakthrough for phased array image reconstruction. As a case study, the proposed CS procedure is applied to the inspection of an engine cylinder cavity containing different pit defects and the results show that orthogonal matching pursuit (OMP)-based CS guarantees the performance for real application. PMID:29738452

Direct Numerical Simulation of Automobile Cavity Tones

NASA Technical Reports Server (NTRS)

Kurbatskii, Konstantin; Tam, Christopher K. W.

2000-01-01

The Navier Stokes equation is solved computationally by the Dispersion-Relation-Preserving (DRP) scheme for the flow and acoustic fields associated with a laminar boundary layer flow over an automobile door cavity. In this work, the flow Reynolds number is restricted to R(sub delta*) < 3400; the range of Reynolds number for which laminar flow may be maintained. This investigation focuses on two aspects of the problem, namely, the effect of boundary layer thickness on the cavity tone frequency and intensity and the effect of the size of the computation domain on the accuracy of the numerical simulation. It is found that the tone frequency decreases with an increase in boundary layer thickness. When the boundary layer is thicker than a certain critical value, depending on the flow speed, no tone is emitted by the cavity. Computationally, solutions of aeroacoustics problems are known to be sensitive to the size of the computation domain. Numerical experiments indicate that the use of a small domain could result in normal mode type acoustic oscillations in the entire computation domain leading to an increase in tone frequency and intensity. When the computation domain is expanded so that the boundaries are at least one wavelength away from the noise source, the computed tone frequency and intensity are found to be computation domain size independent.

On the Domain Specificity of Cognitive Complexity: An Alternative Approach.

ERIC Educational Resources Information Center

Cohen, Harvey S.; Feldman, Jack M.

This study attempts to assess differences in the three aspects of cognitive complexity--differentiation, discrimination, and integration--as functions of information about and interest in the relevant domain. The two groups of subjects consisted of 20 members of a local sports car club and an equal number from a local garden club. Each group had…

A TAD Closer to Understanding Dosage Compensation.

PubMed

Wood, Andrew J; Bickmore, Wendy A

2015-06-08

Eukaryotic chromosomes are organized into topological domains, but how these are established and maintained is poorly understood. Writing in Nature, Crane et al. (2015) show that a specialized condensin complex enforces the domain boundaries along the C. elegans X chromosome to equalize transcription from the X between males and hermaphrodites. Copyright © 2015 Elsevier Inc. All rights reserved.

A frequency domain linearized Navier-Stokes equations approach to acoustic propagation in flow ducts with sharp edges.

PubMed

Kierkegaard, Axel; Boij, Susann; Efraimsson, Gunilla

2010-02-01

Acoustic wave propagation in flow ducts is commonly modeled with time-domain non-linear Navier-Stokes equation methodologies. To reduce computational effort, investigations of a linearized approach in frequency domain are carried out. Calculations of sound wave propagation in a straight duct are presented with an orifice plate and a mean flow present. Results of transmission and reflections at the orifice are presented on a two-port scattering matrix form and are compared to measurements with good agreement. The wave propagation is modeled with a frequency domain linearized Navier-Stokes equation methodology. This methodology is found to be efficient for cases where the acoustic field does not alter the mean flow field, i.e., when whistling does not occur.

Frequency-Domain Multiplexing Readout with a Self-Trigger System for Pulse Signals from Kinetic Inductance Detectors

NASA Astrophysics Data System (ADS)

Yamada, Y.; Ishino, H.; Kibayashi, A.; Kida, Y.; Hidehira, N.; Komatsu, K.; Hazumi, M.; Sato, N.; Sakai, K.; Yamamori, H.; Hirayama, F.; Kohjiro, S.

2018-04-01

We present the development of a frequency-domain multiplexing readout of kinetic inductance detectors (KIDs) for pulse signals with a self-trigger system. The KIDs consist of an array of superconducting resonators that have different resonant frequencies individually, allowing us to read out multiple channels in the frequency domain with a single wire using a microwave-frequency comb. The energy deposited to the resonators break Cooper pairs, changing the kinetic inductance and, hence, the amplitude and the phase of the probing microwaves. For some applications such as X-ray detections, the deposited energy is detected as a pulse signal shaped by the time constants of the quasiparticle lifetime, the resonator quality factor, and the ballistic phonon lifetime in the substrate, ranging from microseconds to milliseconds. A readout system commonly used converts the frequency-domain data to the time-domain data. For the short pulse signals, the data rate may exceed the data transfer bandwidth, as the short time constant pulses require us to have a high sampling rate. In order to overcome this circumstance, we have developed a KID readout system that contains a self-trigger system to extract relevant signal data and reduces the total data rate with a commercial off-the-shelf FPGA board. We have demonstrated that the system can read out pulse signals of 15 resonators simultaneously with about 10 Hz event rate by irradiating α particles from ^{241} Am to the silicon substrate on whose surface aluminum KID resonators are formed.

Interior noise reduction by alternate resonance tuning

NASA Technical Reports Server (NTRS)

Bliss, Donald B.; Gottwald, James A.; Bryce, Jeffrey W.

1987-01-01

Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at low frequencies, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is studied which considers aircraft fuselages lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. Adjacent panel would oscillate at equal amplitude, to give equal acoustic source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to be cut off, and therefore be nonpropagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is being investigated theoretically and experimentally. Progress to date is discussed.

Investigation of advanced pre- and post-equalization schemes in high-order CAP modulation based high-speed indoor VLC transmission system

NASA Astrophysics Data System (ADS)

Wang, Yiguang; Chi, Nan

2016-10-01

Light emitting diodes (LEDs) based visible light communication (VLC) has been considered as a promising technology for indoor high-speed wireless access, due to its unique advantages, such as low cost, license free and high security. To achieve high-speed VLC transmission, carrierless amplitude and phase (CAP) modulation has been utilized for its lower complexity and high spectral efficiency. Moreover, to compensate the linear and nonlinear distortions such as frequency attenuation, sampling time offset, LED nonlinearity etc., series of pre- and post-equalization schemes should be employed in high-speed VLC systems. In this paper, we make an investigation on several advanced pre- and postequalization schemes for high-order CAP modulation based VLC systems. We propose to use a weighted preequalization technique to compensate the LED frequency attenuation. In post-equalization, a hybrid post equalizer is proposed, which consists of a linear equalizer, a Volterra series based nonlinear equalizer, and a decision-directed least mean square (DD-LMS) equalizer. Modified cascaded multi-modulus algorithm (M-CMMA) is employed to update the weights of the linear and the nonlinear equalizer, while DD-LMS can further improve the performance after the preconvergence. Based on high-order CAP modulation and these equalization schemes, we have experimentally demonstrated a 1.35-Gb/s, a 4.5-Gb/s and a 8-Gb/s high-speed indoor VLC transmission systems. The results show the benefit and feasibility of the proposed equalization schemes for high-speed VLC systems.

Stochastic Gabor reflectivity and acoustic impedance inversion

NASA Astrophysics Data System (ADS)

Hariri Naghadeh, Diako; Morley, Christopher Keith; Ferguson, Angus John

2018-02-01

To delineate subsurface lithology to estimate petrophysical properties of a reservoir, it is possible to use acoustic impedance (AI) which is the result of seismic inversion. To change amplitude to AI, removal of wavelet effects from the seismic signal in order to get a reflection series, and subsequently transforming those reflections to AI, is vital. To carry out seismic inversion correctly it is important to not assume that the seismic signal is stationary. However, all stationary deconvolution methods are designed following that assumption. To increase temporal resolution and interpretation ability, amplitude compensation and phase correction are inevitable. Those are pitfalls of stationary reflectivity inversion. Although stationary reflectivity inversion methods are trying to estimate reflectivity series, because of incorrect assumptions their estimations will not be correct, but may be useful. Trying to convert those reflection series to AI, also merging with the low frequency initial model, can help us. The aim of this study was to apply non-stationary deconvolution to eliminate time variant wavelet effects from the signal and to convert the estimated reflection series to the absolute AI by getting bias from well logs. To carry out this aim, stochastic Gabor inversion in the time domain was used. The Gabor transform derived the signal’s time-frequency analysis and estimated wavelet properties from different windows. Dealing with different time windows gave an ability to create a time-variant kernel matrix, which was used to remove matrix effects from seismic data. The result was a reflection series that does not follow the stationary assumption. The subsequent step was to convert those reflections to AI using well information. Synthetic and real data sets were used to show the ability of the introduced method. The results highlight that the time cost to get seismic inversion is negligible related to general Gabor inversion in the frequency domain. Also, obtaining bias could help the method to estimate reliable AI. To justify the effect of random noise on deterministic and stochastic inversion results, a stationary noisy trace with signal-to-noise ratio equal to 2 was used. The results highlight the inability of deterministic inversion in dealing with a noisy data set even using a high number of regularization parameters. Also, despite the low level of signal, stochastic Gabor inversion not only can estimate correctly the wavelet’s properties but also, because of bias from well logs, the inversion result is very close to the real AI. Comparing deterministic and introduced inversion results on a real data set shows that low resolution results, especially in the deeper parts of seismic sections using deterministic inversion, creates significant reliability problems for seismic prospects, but this pitfall is solved completely using stochastic Gabor inversion. The estimated AI using Gabor inversion in the time domain is much better and faster than general Gabor inversion in the frequency domain. This is due to the extra number of windows required to analyze the time-frequency information and also the amount of temporal increment between windows. In contrast, stochastic Gabor inversion can estimate trustable physical properties close to the real characteristics. Applying to a real data set could give an ability to detect the direction of volcanic intrusion and the ability of lithology distribution delineation along the fan. Comparing the inversion results highlights the efficiency of stochastic Gabor inversion to delineate lateral lithology changes because of the improved frequency content and zero phasing of the final inversion volume.

Frequency Domain Computer Programs for Prediction and Analysis of Rail Vehicle Dynamics : Volume 1. Technical Report

DOT National Transportation Integrated Search

1975-12-01

Frequency domain computer programs developed or acquired by TSC for the analysis of rail vehicle dynamics are described in two volumes. Volume I defines the general analytical capabilities required for computer programs applicable to single rail vehi...

A frequency domain radar interferometric imaging (FII) technique based on high-resolution methods

NASA Astrophysics Data System (ADS)

Luce, H.; Yamamoto, M.; Fukao, S.; Helal, D.; Crochet, M.

2001-01-01

In the present work, we propose a frequency-domain interferometric imaging (FII) technique for a better knowledge of the vertical distribution of the atmospheric scatterers detected by MST radars. This is an extension of the dual frequency-domain interferometry (FDI) technique to multiple frequencies. Its objective is to reduce the ambiguity (resulting from the use of only two adjacent frequencies), inherent with the FDI technique. Different methods, commonly used in antenna array processing, are first described within the context of application to the FII technique. These methods are the Fourier-based imaging, the Capon's and the singular value decomposition method used with the MUSIC algorithm. Some preliminary simulations and tests performed on data collected with the middle and upper atmosphere (MU) radar (Shigaraki, Japan) are also presented. This work is a first step in the developments of the FII technique which seems to be very promising.

A Note on a Sampling Theorem for Functions over GF(q)n Domain

NASA Astrophysics Data System (ADS)

Ukita, Yoshifumi; Saito, Tomohiko; Matsushima, Toshiyasu; Hirasawa, Shigeichi

In digital signal processing, the sampling theorem states that any real valued function ƒ can be reconstructed from a sequence of values of ƒ that are discretely sampled with a frequency at least twice as high as the maximum frequency of the spectrum of ƒ. This theorem can also be applied to functions over finite domain. Then, the range of frequencies of ƒ can be expressed in more detail by using a bounded set instead of the maximum frequency. A function whose range of frequencies is confined to a bounded set is referred to as bandlimited function. And a sampling theorem for bandlimited functions over Boolean domain has been obtained. Here, it is important to obtain a sampling theorem for bandlimited functions not only over Boolean domain (GF(q)n domain) but also over GF(q)n domain, where q is a prime power and GF(q) is Galois field of order q. For example, in experimental designs, although the model can be expressed as a linear combination of the Fourier basis functions and the levels of each factor can be represented by GF(q)n, the number of levels often take a value greater than two. However, the sampling theorem for bandlimited functions over GF(q)n domain has not been obtained. On the other hand, the sampling points are closely related to the codewords of a linear code. However, the relation between the parity check matrix of a linear code and any distinct error vectors has not been obtained, although it is necessary for understanding the meaning of the sampling theorem for bandlimited functions. In this paper, we generalize the sampling theorem for bandlimited functions over Boolean domain to a sampling theorem for bandlimited functions over GF(q)n domain. We also present a theorem for the relation between the parity check matrix of a linear code and any distinct error vectors. Lastly, we clarify the relation between the sampling theorem for functions over GF(q)n domain and linear codes.

Comment on ``Experimental Free Energy Reconstruction From Single-Molecule Force Spectroscopy Using Jarzynski's Equality''

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friddle, R W

2008-01-14

Harris, Song and Kiang [1] (HSK) describe their results on reconstructing the free energy profiles for both the stretch of the titin polymer, and the unfolding of an individual I27 domain. The new finding reported in [1] is the measurement of the free energy barrier (or activation energy) to unfolding the I27 domain. Due to a misinterpretation of the mechanics involved, the free energy surface (and thus the energy barrier) to unfolding the I27 domain was not measured.

Fast-Running Aeroelastic Code Based on Unsteady Linearized Aerodynamic Solver Developed

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Bakhle, Milind A.; Keith, T., Jr.

2003-01-01

The NASA Glenn Research Center has been developing aeroelastic analyses for turbomachines for use by NASA and industry. An aeroelastic analysis consists of a structural dynamic model, an unsteady aerodynamic model, and a procedure to couple the two models. The structural models are well developed. Hence, most of the development for the aeroelastic analysis of turbomachines has involved adapting and using unsteady aerodynamic models. Two methods are used in developing unsteady aerodynamic analysis procedures for the flutter and forced response of turbomachines: (1) the time domain method and (2) the frequency domain method. Codes based on time domain methods require considerable computational time and, hence, cannot be used during the design process. Frequency domain methods eliminate the time dependence by assuming harmonic motion and, hence, require less computational time. Early frequency domain analyses methods neglected the important physics of steady loading on the analyses for simplicity. A fast-running unsteady aerodynamic code, LINFLUX, which includes steady loading and is based on the frequency domain method, has been modified for flutter and response calculations. LINFLUX, solves unsteady linearized Euler equations for calculating the unsteady aerodynamic forces on the blades, starting from a steady nonlinear aerodynamic solution. First, we obtained a steady aerodynamic solution for a given flow condition using the nonlinear unsteady aerodynamic code TURBO. A blade vibration analysis was done to determine the frequencies and mode shapes of the vibrating blades, and an interface code was used to convert the steady aerodynamic solution to a form required by LINFLUX. A preprocessor was used to interpolate the mode shapes from the structural dynamic mesh onto the computational dynamics mesh. Then, we used LINFLUX to calculate the unsteady aerodynamic forces for a given mode, frequency, and phase angle. A postprocessor read these unsteady pressures and calculated the generalized aerodynamic forces, eigenvalues, and response amplitudes. The eigenvalues determine the flutter frequency and damping. As a test case, the flutter of a helical fan was calculated with LINFLUX and compared with calculations from TURBO-AE, a nonlinear time domain code, and from ASTROP2, a code based on linear unsteady aerodynamics.

Device and method for generating a beam of acoustic energy from a borehole, and applications thereof

DOEpatents

Vu, Cung Khac; Sinha, Dipen N; Pantea, Cristian; Nihei, Kurt T; Schmitt, Denis P; Skelt, Christopher

2013-10-01

In some aspects of the invention, a method of generating a beam of acoustic energy in a borehole is disclosed. The method includes generating a first broad-band acoustic pulse at a first broad-band frequency range having a first central frequency and a first bandwidth spread; generating a second broad-band acoustic pulse at a second broad-band frequency range different than the first frequency range having a second central frequency and a second bandwidth spread, wherein the first acoustic pulse and second acoustic pulse are generated by at least one transducer arranged on a tool located within the borehole; and transmitting the first and the second broad-band acoustic pulses into an acoustically non-linear medium, wherein the composition of the non-linear medium produces a collimated pulse by a non-linear mixing of the first and second acoustic pulses, wherein the collimated pulse has a frequency equal to the difference in frequencies between the first central frequency and the second central frequency and a bandwidth spread equal to the sum of the first bandwidth spread and the second bandwidth spread.

Coherent frequency combs produced by self frequency modulation in quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khurgin, J. B.; Dikmelik, Y.; Hugi, A.

2014-02-24

One salient characteristic of Quantum Cascade Laser (QCL) is its very short τ ∼ 1 ps gain recovery time that so far thwarted the attempts to achieve self-mode locking of the device into a train of single pulses. We show theoretically that four wave mixing, combined with the short gain recovery time causes QCL to operate in the self-frequency-modulated regime characterized by a constant power in time domain and stable coherent comb in the frequency domain. Coherent frequency comb may enable many potential applications of QCL's in sensing and measurement.

Simultaneous storage of medical images in the spatial and frequency domain: a comparative study.

PubMed

Nayak, Jagadish; Bhat, P Subbanna; Acharya U, Rajendra; Uc, Niranjan

2004-06-05

Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads. The patient information is encrypted before interleaving with images to ensure greater security. The bio-signals are compressed and subsequently interleaved with the image. This interleaving is carried out in the spatial domain and Frequency domain. The performance of interleaving in the spatial, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) coefficients is studied. Differential pulse code modulation (DPCM) is employed for data compression as well as encryption and results are tabulated for a specific example. It can be seen from results, the process does not affect the picture quality. This is attributed to the fact that the change in LSB of a pixel changes its brightness by 1 part in 256. Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain. The Results show that spatial domain the interleaving, the %NRMSE was less than 0.25% for 8-bit encoded pixel intensity. Among the frequency domain interleaving methods, DFT was found to be very efficient.

PLATSIM: An efficient linear simulation and analysis package for large-order flexible systems

NASA Technical Reports Server (NTRS)

Maghami, Periman; Kenny, Sean P.; Giesy, Daniel P.

1995-01-01

PLATSIM is a software package designed to provide efficient time and frequency domain analysis of large-order generic space platforms implemented with any linear time-invariant control system. Time domain analysis provides simulations of the overall spacecraft response levels due to either onboard or external disturbances. The time domain results can then be processed by the jitter analysis module to assess the spacecraft's pointing performance in a computationally efficient manner. The resulting jitter analysis algorithms have produced an increase in speed of several orders of magnitude over the brute force approach of sweeping minima and maxima. Frequency domain analysis produces frequency response functions for uncontrolled and controlled platform configurations. The latter represents an enabling technology for large-order flexible systems. PLATSIM uses a sparse matrix formulation for the spacecraft dynamics model which makes both the time and frequency domain operations quite efficient, particularly when a large number of modes are required to capture the true dynamics of the spacecraft. The package is written in MATLAB script language. A graphical user interface (GUI) is included in the PLATSIM software package. This GUI uses MATLAB's Handle graphics to provide a convenient way for setting simulation and analysis parameters.

Decay-ratio calculation in the frequency domain with the LAPUR code using 1D-kinetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munoz-Cobo, J. L.; Escriva, A.; Garcia, C.

This paper deals with the problem of computing the Decay Ratio in the frequency domain codes as the LAPUR code. First, it is explained how to calculate the feedback reactivity in the frequency domain using slab-geometry i.e. 1D kinetics, also we show how to perform the coupling of the 1D kinetics with the thermal-hydraulic part of the LAPUR code in order to obtain the reactivity feedback coefficients for the different channels. In addition, we show how to obtain the reactivity variation in the complex domain by solving the eigenvalue equation in the frequency domain and we compare this result withmore » the reactivity variation obtained in first order perturbation theory using the 1D neutron fluxes of the base case. Because LAPUR works in the linear regime, it is assumed that in general the perturbations are small. There is also a section devoted to the reactivity weighting factors used to couple the reactivity contribution from the different channels to the reactivity of the entire reactor core in point kinetics and 1D kinetics. Finally we analyze the effects of the different approaches on the DR value. (authors)« less

Speech Enhancement, Gain, and Noise Spectrum Adaptation Using Approximate Bayesian Estimation

PubMed Central

Hao, Jiucang; Attias, Hagai; Nagarajan, Srikantan; Lee, Te-Won; Sejnowski, Terrence J.

2010-01-01

This paper presents a new approximate Bayesian estimator for enhancing a noisy speech signal. The speech model is assumed to be a Gaussian mixture model (GMM) in the log-spectral domain. This is in contrast to most current models in frequency domain. Exact signal estimation is a computationally intractable problem. We derive three approximations to enhance the efficiency of signal estimation. The Gaussian approximation transforms the log-spectral domain GMM into the frequency domain using minimal Kullback–Leiber (KL)-divergency criterion. The frequency domain Laplace method computes the maximum a posteriori (MAP) estimator for the spectral amplitude. Correspondingly, the log-spectral domain Laplace method computes the MAP estimator for the log-spectral amplitude. Further, the gain and noise spectrum adaptation are implemented using the expectation–maximization (EM) algorithm within the GMM under Gaussian approximation. The proposed algorithms are evaluated by applying them to enhance the speeches corrupted by the speech-shaped noise (SSN). The experimental results demonstrate that the proposed algorithms offer improved signal-to-noise ratio, lower word recognition error rate, and less spectral distortion. PMID:20428253

On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain

NASA Astrophysics Data System (ADS)

Østerberg, Frederik Westergaard; Rizzi, Giovanni; Hansen, Mikkel Fougt

2013-06-01

We present and demonstrate a new method for on-chip Brownian relaxation measurements on magnetic nanobeads in the time domain using magnetoresistive sensors. The beads are being magnetized by the sensor self-field arising from the bias current passed through the sensors and thus no external magnetic fields are needed. First, the method is demonstrated on Brownian relaxation measurements of beads with nominal sizes of 40, 80, 130, and 250 nm. The results are found to compare well to those obtained by an already established measurement technique in the frequency domain. Next, we demonstrate the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s, which is about six times faster than in the frequency domain. This substantial reduction of the measurement time allows for continuous monitoring of the bead dynamics vs. time and opens for time-resolved studies, e.g., of binding kinetics.

Magnetic properties of cylindrical diameter modulated Ni80Fe20 nanowires: interaction and coercive fields

NASA Astrophysics Data System (ADS)

Salem, Mohamed Shaker; Sergelius, Philip; Corona, Rosa M.; Escrig, Juan; Görlitz, Detlef; Nielsch, Kornelius

2013-04-01

Magnetic properties of cylindrical Ni80Fe20 nanowires with modulated diameters are investigated theoretically as a function of their geometrical parameters and compared with those produced inside the pores of anodic alumina membranes by pulsed electrodeposition. We observe that the Ni80Fe20 nanowires with modulated diameters reverse their magnetization via the nucleation and propagation of a vortex domain wall. The system begins generating vortex domains in the nanowire ends and in the transition region between the two segments to minimize magnetostatic energy generated by surfaces perpendicular to the initial magnetization of the sample. Besides, we observed an increase of the coercivity for the sample with equal volumes in relation to the sample with equal lengths. Finally, the interaction field is stronger in the case of constant volume segments. These structures could be used to control the motions of magnetic domain walls. In this way, these nanowires with modulated diameters can be an alternative to store information or even perform logic functions.

Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain

NASA Astrophysics Data System (ADS)

De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.

1991-06-01

PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.

Quantifying the Extremity of Windstorms for Regions Featuring Infrequent Events

NASA Astrophysics Data System (ADS)

Walz, M. A.; Leckebusch, G. C.; Kruschke, T.; Rust, H.; Ulbrich, U.

2017-12-01

This paper introduces the Distribution-Independent Storm Severity Index (DI-SSI). The DI-SSI represents an approach to quantify the severity of exceptional surface wind speeds of large scale windstorms that is complementary to the Storm Severity Index (SSI) introduced by Leckebusch et al. (2008). While the SSI approaches the extremeness of a storm from a meteorological and potential loss (impact) perspective, the DI-SSI defines the severity in a more climatological perspective. The idea is to assign equal index values to wind speeds of the same singularity (e.g. the 99th percentile) under consideration of the shape of the tail of the local wind speed climatology. Especially in regions at the edge of the classical storm track the DI-SSI shows more equitable severity estimates, e.g. for the extra-tropical cyclone Klaus. Here were compare the integral severity indices for several prominent windstorm in the European domain and discuss the advantages and disadvantages of the respective index. In order to compare the indices, their relation with the North Atlantic Oscillation (NAO) is studied, which is one of the main large scale drivers for the intensity of European windstorms. Additionally we can identify a significant relationship between the frequency and intensity of windstorms for large parts of the European domain.

Effect of application of dairy manure, effluent and inorganic fertilizer on nitrogen leaching in clayey fluvo-aquic soil: A lysimeter study.

PubMed

Fan, Jianling; Xiao, Jiao; Liu, Deyan; Ye, Guiping; Luo, Jiafa; Houlbrooke, David; Laurenson, Seth; Yan, Jing; Chen, Lvjun; Tian, Jinping; Ding, Weixin

2017-08-15

Dairy farm manure and effluent are applied to cropland in China to provide a source of plant nutrients, but there are concerns over its effect on nitrogen (N) leaching loss and groundwater quality. To investigate the effects of land application of dairy manure and effluent on potential N leaching loss, two lysimeter trials were set up in clayey fluvo-aquic soil in a winter wheat-summer maize rotation cropping system on the North China Plain. The solid dairy manure trial included control without N fertilization (CK), inorganic N fertilizer (SNPK), and fresh (RAW) and composted (COM) dairy manure. The liquid dairy effluent trial consisted of control without N fertilization (CF), inorganic N fertilizer (ENPK), and fresh (FDE) and stored (SDE) dairy effluent. The N application rate was 225kgNha -1 for inorganic N fertilizer, dairy manure, and effluent treatments in both seasons. Annual N leaching loss (ANLL) was highest in SNPK (53.02 and 16.21kgNha -1 in 2013/2014 and 2014/2015, respectively), which were 1.65- and 2.04-fold that of COM, and 1.59- and 1.26-fold that of RAW. In the effluent trial (2014/2015), ANLL for ENPK and SDE (16.22 and 16.86kgNha -1 , respectively) were significantly higher than CF and FDE (6.3 and 13.21kgNha -1 , respectively). NO 3 - contributed the most (34-92%) to total N leaching loss among all treatments, followed by dissolved organic N (14-57%). COM showed the lowest N leaching loss due to a reduction in NO 3 - loss. Yield-scaled N leaching in COM (0.35kgNMg -1 silage) was significantly (P<0.05) lower than that in the other fertilization treatments. Therefore, the use of composted dairy manure should be increased and that of inorganic fertilizer decreased to reduce N leaching loss while ensuring high crop yield in the North China Plain. Copyright © 2017 Elsevier B.V. All rights reserved.

Novel object recognition ability in female mice following exposure to nanoparticle-rich diesel exhaust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Win-Shwe, Tin-Tin, E-mail: tin.tin.win.shwe@nies.go.jp; Fujimaki, Hidekazu; Fujitani, Yuji

2012-08-01

Recently, our laboratory reported that exposure to nanoparticle-rich diesel exhaust (NRDE) for 3 months impaired hippocampus-dependent spatial learning ability and up-regulated the expressions of memory function-related genes in the hippocampus of female mice. However, whether NRDE affects the hippocampus-dependent non-spatial learning ability and the mechanism of NRDE-induced neurotoxicity was unknown. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE, 47 μg/m{sup 3}), high-dose NRDE (H-NRDE, 129 μg/m{sup 3}), or filtered H-NRDE (F-DE) for 3 months. We then investigated the effect of NRDE exposure on non-spatial learning ability and the expression of genes related to glutamate neurotransmission using amore » novel object recognition test and a real-time RT-PCR analysis, respectively. We also examined microglia marker Iba1 immunoreactivity in the hippocampus using immunohistochemical analyses. Mice exposed to H-NRDE or F-DE could not discriminate between familiar and novel objects. The control and M-NRDE-exposed groups showed a significantly increased discrimination index, compared to the H-NRDE-exposed group. Although no significant changes in the expression levels of the NMDA receptor subunits were observed, the expression of glutamate transporter EAAT4 was decreased and that of glutamic acid decarboxylase GAD65 was increased in the hippocampus of H-NRDE-exposed mice, compared with the expression levels in control mice. We also found that microglia activation was prominent in the hippocampal area of the H-NRDE-exposed mice, compared with the other groups. These results indicated that exposure to NRDE for 3 months impaired the novel object recognition ability. The present study suggests that genes related to glutamate metabolism may be involved in the NRDE-induced neurotoxicity observed in the present mouse model. -- Highlights: ► The effects of nanoparticle-induced neurotoxicity remain unclear. ► We investigated the effect of exposure to nanoparticles on learning behavior. ► We found that exposure to nanoparticles impaired novel object recognition ability.« less

Comparison of filtering methods for extracellular gastric slow wave recordings.

PubMed

Paskaranandavadivel, Niranchan; O'Grady, Gregory; Du, Peng; Cheng, Leo K

2013-01-01

Extracellular recordings are used to define gastric slow wave propagation. Signal filtering is a key step in the analysis and interpretation of extracellular slow wave data; however, there is controversy and uncertainty regarding the appropriate filtering settings. This study investigated the effect of various standard filters on the morphology and measurement of extracellular gastric slow waves. Experimental extracellular gastric slow waves were recorded from the serosal surface of the stomach from pigs and humans. Four digital filters: finite impulse response filter (0.05-1 Hz); Savitzky-Golay filter (0-1.98 Hz); Bessel filter (2-100 Hz); and Butterworth filter (5-100 Hz); were applied on extracellular gastric slow wave signals to compare the changes temporally (morphology of the signal) and spectrally (signals in the frequency domain). The extracellular slow wave activity is represented in the frequency domain by a dominant frequency and its associated harmonics in diminishing power. Optimal filters apply cutoff frequencies consistent with the dominant slow wave frequency (3-5 cpm) and main harmonics (up to ≈ 2 Hz). Applying filters with cutoff frequencies above or below the dominant and harmonic frequencies was found to distort or eliminate slow wave signal content. Investigators must be cognizant of these optimal filtering practices when detecting, analyzing, and interpreting extracellular slow wave recordings. The use of frequency domain analysis is important for identifying the dominant and harmonics of the signal of interest. Capturing the dominant frequency and major harmonics of slow wave is crucial for accurate representation of slow wave activity in the time domain. Standardized filter settings should be determined. © 2012 Blackwell Publishing Ltd.

Method for enhancing signals transmitted over optical fibers

DOEpatents

Ogle, James W.; Lyons, Peter B.

1983-01-01

A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

Determination of magnetic domain state of carbon coated iron nanoparticles via 57Fe zero-external-field NMR

NASA Astrophysics Data System (ADS)

Manjunatha, M.; Kumar, Rajeev; Sahoo, Balaram; Damle, Ramakrishna; Ramesh, K. P.

2018-05-01

The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57Fe-IFNMR.

Frequency doubling technique perimetry and spectral domain optical coherence tomography in patients with early glaucoma.

PubMed

Horn, F K; Mardin, C Y; Bendschneider, D; Jünemann, A G; Adler, W; Tornow, R P

2011-01-01

To assess the combined diagnostic power of frequency-doubling technique (FDT)-perimetry and retinal nerve fibre layer (RNFL) thickness measurements with spectral domain optical coherence tomography (SDOCT). The study included 330 experienced participants in five age-related groups: 77 'preperimetric' open-angle glaucoma (OAG) patients, 52 'early' OAG, 50 'moderate' OAG, 54 ocular hypertensive patients, and 97 healthy subjects. For glaucoma assessment in all subjects conventional perimetry, evaluation of fundus photographs, FDT-perimetry and RNFL thickness measurement with SDOCT was done. Glaucomatous visual field defects were classified using the Glaucoma Staging System. FDT evaluation used a published method with casewise calculation of an 'FDT-score', including all missed localized probability levels. SDOCT evaluation used mean RNFL thickness and a new individual SDOCT-score considering normal confidence limits in 32 sectors of a peripapillary circular scan. To examine the joined value of both methods a combined score was introduced. Significance of the difference between Receiver-operating-characteristic (ROC) curves was calculated for a specificity of 96%. Sensitivity in the preperimetric glaucoma group was 44% for SDOCT-score, 25% for FDT-score, and 44% for combined score, in the early glaucoma group 83, 81, and 89%, respectively, and in the moderate glaucoma group 94, 94, and 98%, respectively, all at a specificity of 96%. ROC performance of the newly developed combined score is significantly above single ROC curves of FDT-score in preperimetric and early OAG and above RNFL thickness in moderate OAG. Combination of function and morphology by using the FDT-score and the SDOCT-score performs equal or even better than each single method alone.

Frequency doubling technique perimetry and spectral domain optical coherence tomography in patients with early glaucoma

PubMed Central

Horn, F K; Mardin, C Y; Bendschneider, D; Jünemann, A G; Adler, W; Tornow, R P

2011-01-01

Purpose To assess the combined diagnostic power of frequency-doubling technique (FDT)-perimetry and retinal nerve fibre layer (RNFL) thickness measurements with spectral domain optical coherence tomography (SDOCT). Methods The study included 330 experienced participants in five age-related groups: 77 ‘preperimetric' open-angle glaucoma (OAG) patients, 52 ‘early' OAG, 50 ‘moderate' OAG, 54 ocular hypertensivepatients, and 97 healthy subjects. For glaucoma assessment in all subjects conventional perimetry, evaluation of fundus photographs, FDT-perimetry and RNFL thickness measurement with SDOCT was done. Glaucomatous visual field defects were classified using the Glaucoma Staging System. FDT evaluation used a published method with casewise calculation of an ‘FDT-score', including all missed localized probability levels. SDOCT evaluation used mean RNFL thickness and a new individual SDOCT-score considering normal confidence limits in 32 sectors of a peripapillary circular scan. To examine the joined value of both methods a combined score was introduced. Significance of the difference between Receiver-operating-characteristic (ROC) curves was calculated for a specificity of 96%. Results Sensitivity in the preperimetric glaucoma group was 44% for SDOCT-score, 25% for FDT-score, and 44% for combined score, in the early glaucoma group 83, 81, and 89%, respectively, and in the moderate glaucoma group 94, 94, and 98%, respectively, all at a specificity of 96%. ROC performance of the newly developed combined score is significantly above single ROC curves of FDT-score in preperimetric and early OAG and above RNFL thickness in moderate OAG. Conclusion Combination of function and morphology by using the FDT-score and the SDOCT-score performs equal or even better than each single method alone. PMID:21102494

Numerical simulation of the induction heating of hybrid semi-finished materials into the semi-solid state

NASA Astrophysics Data System (ADS)

Seyboldt, Christoph; Liewald, Mathias

2017-10-01

Current research activities at the Institute for Metal Forming Technology (IFU) of the University of Stuttgart are focusing on the manufacturing of hybrid components using semi-solid forming strategies. As part of the research project "Hybrid interaction during and after thixoforging of multi-material systems", which is founded by the German Research Foundation (DFG), a thixoforging process for producing hybrid components with cohesive metal-to-metal connections is developed. In this context, this paper deals with the numerical simulation of the inductive heating process of hybrid semi-finished materials, consisting of two different aluminium alloys. By reason of the skin effect that leads to inhomogeneous temperature distributions during inductive heating processes, the aluminium alloy with the higher melting point is thereby assembled in the outer side and the alloy with the lower melting point is assembled in the core of the semi-finished material. In this way, the graded heat distribution can be adapted to the used materialś flow properties that are heavily heat dependent. Without this graded heat distribution a proper forming process in the semi-solid state will not be possible. For numerically modelling the inductive heating system of the institute, a coupling of the magnetostatic and the thermal solver was realized by using Ansys Workbench. While the electromagnetic field and its associated heat production rate were solved in a frequency domain, the temperature development was solved in the time based domain. The numerical analysis showed that because of the high thermal conductivity of the aluminium, which leads to a rapid temperature equalization in the semi-finished material, the heating process has to be fast and with a high frequency for produce most heat in the outer region of the material. Finally, the obtained numerical results were validated with experimental heating tests.

Chiral interface at the finite temperature transition point of QCD

NASA Technical Reports Server (NTRS)

Frei, Z.; Patkos, A.

1990-01-01

The domain wall between coexisting chirally symmetric and broken symmetry regions is studied in a saddle point approximation to the effective three-flavor sigma model. In the chiral limit the surface tension varies in the range ((40 to -50)MeV)(exp 3). The width of the domain wall is estimated to be approximately or equal to 4.5 fm.

Differential Associations between Domains of Sibling Conflict and Adolescent Emotional Adjustment

ERIC Educational Resources Information Center

Campione-Barr, Nicole; Greer, Kelly Bassett; Kruse, Anna

2013-01-01

Issues of equality and fairness and invasion of the personal domain, 2 previously identified topic areas of adolescent sibling conflict (N. Campione-Barr & J. G. Smetana, 2010), were examined in 145 dyads ("M" [subscript first-born] = 14.97, "SD" = 1.69 years; "M" [subscript second-born] = 12.20,…

Recovering an unknown source in a fractional diffusion problem

NASA Astrophysics Data System (ADS)

Rundell, William; Zhang, Zhidong

2018-09-01

A standard inverse problem is to determine a source which is supported in an unknown domain D from external boundary measurements. Here we consider the case of a time-independent situation where the source is equal to unity in an unknown subdomain D of a larger given domain Ω and the boundary of D has the star-like shape, i.e.

Apparent Mass Nonlinearity for Paired Oscillating Plates

NASA Astrophysics Data System (ADS)

Granlund, Kenneth; Ol, Michael

2014-11-01

The classical potential-flow problem of a plate oscillating sinusoidally at small amplitude, in a direction normal to its plane, has a well-known analytical solution of a fluid ``mass,'' multiplied by plate acceleration, being equal to the force on the plate. This so-called apparent-mass is analytically equal to that of a cylinder of fluid, with diameter equal to plate chord. The force is directly proportional to frequency squared. Here we consider experimentally a generalization, where two coplanar plates of equal chord are placed at some lateral distance apart. For spacing of ~0.5 chord and larger between the two plates, the analytical solution for a single plate can simply be doubled. Zero spacing means a plate of twice the chord and therefore a heuristic cylinder of fluid of twice the cross-sectional area. This limit is approached for plate spacing <0.5c. For a spacing of 0.1-0.2c, the force due to apparent mass was found to increase with frequency, when normalized by frequency squared; this is a nonlinearity and a departure from the classical theory. Flow visualization in a water-tank suggests that such departure can be imputed to vortex shedding from the plates' edges inside the inter-plate gap.

On the Inequalities of Babu\\vska-Aziz, Friedrichs and Horgan-Payne

NASA Astrophysics Data System (ADS)

Costabel, Martin; Dauge, Monique

2015-09-01

The equivalence between the inequalities of Babu\\vska-Aziz and Friedrichs for sufficiently smooth bounded domains in the plane was shown by Horgan and Payne 30 years ago. We prove that this equivalence, and the equality between the associated constants, is true without any regularity condition on the domain. For the Horgan-Payne inequality, which is an upper bound of the Friedrichs constant for plane star-shaped domains in terms of a geometric quantity known as the Horgan-Payne angle, we show that it is true for some classes of domains, but not for all bounded star-shaped domains. We prove a weaker inequality that is true in all cases.

Biometric identification based on novel frequency domain facial asymmetry measures

NASA Astrophysics Data System (ADS)

Mitra, Sinjini; Savvides, Marios; Vijaya Kumar, B. V. K.

2005-03-01

In the modern world, the ever-growing need to ensure a system's security has spurred the growth of the newly emerging technology of biometric identification. The present paper introduces a novel set of facial biometrics based on quantified facial asymmetry measures in the frequency domain. In particular, we show that these biometrics work well for face images showing expression variations and have the potential to do so in presence of illumination variations as well. A comparison of the recognition rates with those obtained from spatial domain asymmetry measures based on raw intensity values suggests that the frequency domain representation is more robust to intra-personal distortions and is a novel approach for performing biometric identification. In addition, some feature analysis based on statistical methods comparing the asymmetry measures across different individuals and across different expressions is presented.

Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for the Convective Wave Equation

NASA Technical Reports Server (NTRS)

Baumeister, K. J.; Kreider, K. L.

1996-01-01

An explicit finite difference iteration scheme is developed to study harmonic sound propagation in ducts. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for Aircraft Acoustic Nacelle Design

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Kreider, Kevin L.

1996-01-01

An explicit finite difference iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Properties of an improved Gabor wavelet transform and its applications to seismic signal processing and interpretation

NASA Astrophysics Data System (ADS)

Ji, Zhan-Huai; Yan, Sheng-Gang

2017-12-01

This paper presents an analytical study of the complete transform of improved Gabor wavelets (IGWs), and discusses its application to the processing and interpretation of seismic signals. The complete Gabor wavelet transform has the following properties. First, unlike the conventional transform, the improved Gabor wavelet transform (IGWT) maps time domain signals to the time-frequency domain instead of the time-scale domain. Second, the IGW's dominant frequency is fixed, so the transform can perform signal frequency division, where the dominant frequency components of the extracted sub-band signal carry essentially the same information as the corresponding components of the original signal, and the subband signal bandwidth can be regulated effectively by the transform's resolution factor. Third, a time-frequency filter consisting of an IGWT and its inverse transform can accurately locate target areas in the time-frequency field and perform filtering in a given time-frequency range. The complete IGW transform's properties are investigated using simulation experiments and test cases, showing positive results for seismic signal processing and interpretation, such as enhancing seismic signal resolution, permitting signal frequency division, and allowing small faults to be identified.

Characterization of Errors Inherent in System EMP Vulnerability Assessment Programs,

DTIC Science & Technology

1980-10-01

Patriot system. * B-i aircraft. * E-3A airborne warning and control system aircraft. * PRC-77 radio. * Lance missile system. * Safeguard ABM system...carefully or the offset will create large frequency domain error. Frequency-tying, too, can improve f-domain data. Of the various recording sytems studied

Factors That Influence the Difficulty of Science Words

ERIC Educational Resources Information Center

Cervetti, Gina N.; Hiebert, Elfrieda H.; Pearson, P. David; McClung, Nicola A.

2015-01-01

This study examines, within the domain of science, the characteristics of words that predict word knowledge and word learning. The authors identified a set of word characteristics--length, part of speech, polysemy, frequency, morphological frequency, domain specificity, and concreteness--that, based on earlier research, were prime candidates to…

Optimization of spatial frequency domain imaging technique for estimating optical properties of food and biological materials

USDA-ARS?s Scientific Manuscript database

Spatial frequency domain imaging technique has recently been developed for determination of the optical properties of food and biological materials. However, accurate estimation of the optical property parameters by the technique is challenging due to measurement errors associated with signal acquis...

Frequency-Domain Green's Functions for Radar Waves in Heterogeneous 2.5D Media

EPA Science Inventory

Green’s functions for radar waves propagating in heterogeneous media may be calculated in the frequency domain using a hybrid of two numerical methods. The model is defined in the Cartesian coordinate system, and its electromagnetic properties may vary in the x and z directions, ...

Belief in luck or in skill: which locks people into gambling?

PubMed

Zhou, Kun; Tang, Hui; Sun, Yue; Huang, Gui-Hai; Rao, Li-Lin; Liang, Zhu-Yuan; Li, Shu

2012-09-01

According to the social axioms framework, people's beliefs about how the world functions (i.e., internal or external locus of control) are related to their social behaviors. Previous researchers have attempted to relate locus of control to gambling behavior, but the results have not been clear-cut. The present study speculated that the effects of perceived control (i.e., belief in luck and belief in skill) on gambling behavior are domain-specific and vary with the type of gambling. A total of 306 adult Macau residents ranging in age from 18 to 65 with casino gambling experience were recruited by going door to door. Empirical data on gambling frequency and perceived control relating to 13 types of gambling were collected. Our results demonstrated that the effects of belief in luck or skill on gambling behavior varied across different gambling categories. Specifically, for football lottery, Chinese lottery, and baccarat, it was not belief in skill but rather belief in luck that was a positive significant predictor of gambling frequency. Only for slot machines and stud poker did belief in skill significantly predict gambling frequency. For the remaining eight gambling categories, neither belief in luck nor belief in skill could predict gambling frequency. Our findings indicate that neither internal nor external locus of control can consistently explain people's gambling behaviors. Instead, which factor plays a greater role in a person's gambling behavior is dependent on the gambling type. Therefore, the finding that not all gambles are created equal might be a promising avenue for further research and treatment approaches.

A hybrid modelling approach for predicting ground vibration from trains

NASA Astrophysics Data System (ADS)

Triepaischajonsak, N.; Thompson, D. J.

2015-01-01

The prediction of ground vibration from trains presents a number of difficulties. The ground is effectively an infinite medium, often with a layered structure and with properties that may vary greatly from one location to another. The vibration from a passing train forms a transient event, which limits the usefulness of steady-state frequency domain models. Moreover, there is often a need to consider vehicle/track interaction in more detail than is commonly used in frequency domain models, such as the 2.5D approach, while maintaining the computational efficiency of the latter. However, full time-domain approaches involve large computation times, particularly where three-dimensional ground models are required. Here, a hybrid modelling approach is introduced. The vehicle/track interaction is calculated in the time domain in order to be able t account directly for effects such as the discrete sleeper spacing. Forces acting on the ground are extracted from this first model and used in a second model to predict the ground response at arbitrary locations. In the present case the second model is a layered ground model operating in the frequency domain. Validation of the approach is provided by comparison with an existing frequency domain model. The hybrid model is then used to study the sleeper-passing effect, which is shown to be less significant than excitation due to track unevenness in all the cases considered.

Acoustic Treatment Design Scaling Methods. Volume 4; Numerical Simulation of the Nonlinear Acoustic Impedance of a Perforated Plate Single-Degree-of-Freedom Resonator Using a Time-Domain Finite Difference Method

NASA Technical Reports Server (NTRS)

Kraft, R. E.

1999-01-01

Single-degree-of-freedom resonators consisting of honeycomb cells covered by perforated facesheets are widely used as acoustic noise suppression liners in aircraft engine ducts. The acoustic resistance and mass reactance of such liners are known to vary with the intensity of the sound incident upon the panel. Since the pressure drop across a perforated liner facesheet increases quadratically with the flow velocity through the facesheet, this is known as the nonlinear resistance effect. In the past, two different empirical frequency domain models have been used to predict the Sound Pressure Level effect of the incident wave on the perforated liner impedance, one that uses the incident particle velocity in isolated narrowbands, and one that models the particle velocity as the overall velocity. In the absence of grazing flow, neither frequency domain model is entirely accurate in predicting the nonlinear effect that is measured for typical perforated sheets. The time domain model is developed in an attempt to understand and improve the model for the effect of spectral shape and amplitude of multi-frequency incident sound pressure on the liner impedance. A computer code for the time-domain finite difference model is developed and predictions using the models are compared to current frequency-domain models.

The anti-counterfeiting hologram of encryption processing in frequency domain

NASA Astrophysics Data System (ADS)

Bao, Nai K.; Chen, Zhongyu Y.

2004-09-01

This paper proposed a new encryption method using Computer Generated Fourier Hologram in frequency domain. When the main frequency spectrum, i.e. brand and an encrypted information frequency spectrum are mixed, it will not recognized and copied. We will use the methods of Dot Matrix (Digital) Hologram Modulation and the filter to get real signal. One new multi-modulated dot matrix hologram is introduced. It is encoded using several gratings. These gratings have different angles of inclination and different periods in same dot, to enable us in obtaining more information.

Simulative research on generating UWB signals by all-optical BPF

NASA Astrophysics Data System (ADS)

Yang, Chunyong; Hou, Rui; Chen, Shaoping

2007-11-01

The simulating technique is used to investigate generating and distributing Ultra-Wide-Band signals depend on fiber transmission. Numerical result for the system about the frequency response shows that the characteristics of band-pass filter is presented, and the shorter the wavelength is, the bandwidth of lower frequency is wider. Transmission performance simulation for 12.5Gb/s psudo-random sequence also shows that Gaussian pulse signal after transported in fiber is similar to UWB wave pattern mask of FCC in time domain and frequency spectrum specification of FCC in frequency domain .

Spin-wave-driven high-speed domain-wall motions in soft magnetic nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jaehak; Yoo, Myoung-Woo; Kim, Sang-Koog, E-mail: sangkoog@snu.ac.kr

We report on a micromagnetic simulation study of interactions between propagating spin waves and a head-to-head domain wall in geometrically confined magnetic nanotubes. We found that incident spin waves of specific frequencies can lead to sufficiently high-speed (on the order of a few hundreds of m/s or higher) domain-wall motions in the same direction as that of the incident spin-waves. The domain-wall motions and their speed vary remarkably with the frequency and the amplitude of the incident spin-waves. High-speed domain-wall motions originate from the transfer torque of spin waves' linear momentum to the domain wall, through the partial or completemore » reflection of the incident spin waves from the domain wall. This work provides a fundamental understanding of the interaction of the spin waves with a domain wall in the magnetic nanotubes as well as a route to all-magnetic control of domain-wall motions in the magnetic nanoelements.« less

Miscellaneous methods for measuring matric or water potential

USGS Publications Warehouse

Scanlon, Bridget R.; Andraski, Brian J.; Bilskie, Jim; Dane, Jacob H.; Topp, G. Clarke

2002-01-01

A variety of techniques to measure matric potential or water potential in the laboratory and in the field are described in this section. The techniques described herein require equilibration of some medium whose matric or water potential can be determined from previous calibration or can be measured directly. Under equilibrium conditions the matric or water potential of the medium is equal to that of the soil. The techniques can be divided into: (i) those that measure matric potential and (ii) those that measure water potential (sum of matric and osmotic potentials). Matric potential is determined when the sensor matrix is in direct contact with the soil, so salts are free to diffuse in or out of the sensor matrix, and the equilibrium measurement therefore reflects matric forces acting on the water. Water potential is determined when the sensor is separated from the soil by a vapor gap, so salts are not free to move in or out of the sensor, and the equilibrium measurement reflects the sum of the matric and osmotic forces acting on the water.Seven different techniques are described in this section. Those that measure matric potential include (i) heat dissipation sensors, (ii) electrical resistance sensors, (iii) frequency domain and time domain sensors, and (iv) electro-optical switches. A method that can be used to measure matric potential or water potential is the (v) filter paper method. Techniques that measure water potential include (vi) the Dew Point Potentiameter (Decagon Devices, Inc., Pullman, WA1) (water activity meter) and (vii) vapor equilibration.The first four techniques are electronically based methods for measuring matric potential. Heat dissipation sensors and electrical resistance sensors infer matric potential from previously determined calibration relations between sensor heat dissipation or electrical resistance and matric potential. Frequency-domain and timedomain matric potential sensors measure water content, which is related to matric potential of the sensor through calibration. Electro-optical switches measure changes in light transmission through thin, nylon filters as they absorb or desorb water in response to changes in matric potential. Heat dissipation sensors and electrical resistance sensors are used primarily in the field to provide information on matric potential. Frequency domain matric potential sensors are new and have not been widely used. Time domain matric potential sensors and electro-optical switches are new and have not been commercialized. For the fifth technique, filter paper is used as the standard matrix. The filter paper technique measures matric potential when the filter paper is in direct contact with soil or water potential when separated from soil by a vapor gap. The Dew Point Potentiameter calculates water potential from the measured dew point and sample temperature. The vapor equilibration technique involves equilibration of soil samples with salt solutions of known osmotic potential. The filter paper, Dew Point Potentiameter, and vapor equilibration techniques are generally used in the laboratory to measure water potential of disturbed field samples or to measure water potential for water retention functions.

Single mode CO2 laser frequency modulation up to 350 MHz

NASA Technical Reports Server (NTRS)

Leeb, W. R.; Peruso, C. J.

1977-01-01

Experiments on internal frequency modulation (FM) of a CO2 laser showed no limitation of FM by the linewidth. However, distortions in the form of strong enhancement of sideband amplitude arise for frequencies equal to the cavity resonant frequencies, most pronounced if the modulator is positioned near a cavity mirror.

Study of Frequency Transfer via Optical Fiber in the Microwave Domain

DTIC Science & Technology

2009-11-01

DOMAIN M. Amemiya, M. Imae, Y. Fujii, T. Suzuyama, K. Watabe, T. Ikegami , and H. Tsuchida* National Metrology Institute of Japan (NMIJ...Yanagimachi, A. Takamizawa, K. Watabe, T. Ikegami , M. Imae, Y. Fujii, M. Amemiya, K. Nakagawa, K. Ueda, and H. Katori, 2009, “Measuring the frequency of a...Shimazaki, T. Ikegami and S. Ohshima, 2006, “Short term frequency stability tests of two cryogenic sapphire oscillators,” Japanese Journal of

High-resolution wave-theory-based ultrasound reflection imaging using the split-step fourier and globally optimized fourier finite-difference methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lianjie

Methods for enhancing ultrasonic reflection imaging are taught utilizing a split-step Fourier propagator in which the reconstruction is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wave number domains. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wave number domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the tissue being imaged (e.g., breast tissue). Resultsmore » from various data input to the method indicate significant improvements are provided in both image quality and resolution.« less

Interpreting Popov criteria in Lure´ systems with complex scaling stability analysis

NASA Astrophysics Data System (ADS)

Zhou, J.

2018-06-01

The paper presents a novel frequency-domain interpretation of Popov criteria for absolute stability in Lure´ systems by means of what we call complex scaling stability analysis. The complex scaling technique is developed for exponential/asymptotic stability in LTI feedback systems, which dispenses open-loop poles distribution, contour/locus orientation and prior frequency sweeping. Exploiting the technique for alternatively revealing positive realness of transfer functions, re-interpreting Popov criteria is explicated. More specifically, the suggested frequency-domain stability conditions are conformable both in scalar and multivariable cases, and can be implemented either graphically with locus plotting or numerically without; in particular, the latter is suitable as a design tool with auxiliary parameter freedom. The interpretation also reveals further frequency-domain facts about Lure´ systems. Numerical examples are included to illustrate the main results.

Adaptive precompensators for flexible-link manipulator control

NASA Technical Reports Server (NTRS)

Tzes, Anthony P.; Yurkovich, Stephen

1989-01-01

The application of input precompensators to flexible manipulators is considered. Frequency domain compensators color the input around the flexible mode locations, resulting in a bandstop or notch filter in cascade with the system. Time domain compensators apply a sequence of impulses at prespecified times related to the modal frequencies. The resulting control corresponds to a feedforward term that convolves in real-time the desired reference input with a sequence of impulses and produces a vibration-free output. An adaptive precompensator can be implemented by combining a frequency domain identification scheme which is used to estimate online the modal frequencies and subsequently update the bandstop interval or the spacing between the impulses. The combined adaptive input preshaping scheme provides the most rapid slew that results in a vibration-free output. Experimental results are presented to verify the results.

Carbon financial markets: A time-frequency analysis of CO2 prices

NASA Astrophysics Data System (ADS)

Sousa, Rita; Aguiar-Conraria, Luís; Soares, Maria Joana

2014-11-01

We characterize the interrelation of CO2 prices with energy prices (electricity, gas and coal), and with economic activity. Previous studies have relied on time-domain techniques, such as Vector Auto-Regressions. In this study, we use multivariate wavelet analysis, which operates in the time-frequency domain. Wavelet analysis provides convenient tools to distinguish relations at particular frequencies and at particular time horizons. Our empirical approach has the potential to identify relations getting stronger and then disappearing over specific time intervals and frequencies. We are able to examine the coherency of these variables and lead-lag relations at different frequencies for the time periods in focus.

Single-sideband modulator for frequency domain multiplexing of superconducting qubit readout

NASA Astrophysics Data System (ADS)

Chapman, Benjamin J.; Rosenthal, Eric I.; Kerckhoff, Joseph; Vale, Leila R.; Hilton, Gene C.; Lehnert, K. W.

2017-04-01

We introduce and experimentally characterize a superconducting single-sideband modulator compatible with cryogenic microwave circuits and propose its use for frequency domain multiplexing of superconducting qubit readout. The monolithic double-balanced modulators that comprise the device are formed with purely reactive elements (capacitors and Josephson junction inductors) and require no microwave-frequency control tones. Microwave signals in the 4 to 8 GHz band, with power up to -85 dBm, are converted up or down in frequency by as much as 120 MHz. Spurious harmonics in the device can be suppressed by up to 25 dB for select probe and modulation frequencies.

A spherical model for orientation and spatial-frequency tuning in a cortical hypercolumn.

PubMed Central

Bressloff, Paul C; Cowan, Jack D

2003-01-01

A theory is presented of the way in which the hypercolumns in primary visual cortex (V1) are organized to detect important features of visual images, namely local orientation and spatial-frequency. Given the existence in V1 of dual maps for these features, both organized around orientation pinwheels, we constructed a model of a hypercolumn in which orientation and spatial-frequency preferences are represented by the two angular coordinates of a sphere. The two poles of this sphere are taken to correspond, respectively, to high and low spatial-frequency preferences. In Part I of the paper, we use mean-field methods to derive exact solutions for localized activity states on the sphere. We show how cortical amplification through recurrent interactions generates a sharply tuned, contrast-invariant population response to both local orientation and local spatial frequency, even in the case of a weakly biased input from the lateral geniculate nucleus (LGN). A major prediction of our model is that this response is non-separable with respect to the local orientation and spatial frequency of a stimulus. That is, orientation tuning is weaker around the pinwheels, and there is a shift in spatial-frequency tuning towards that of the closest pinwheel at non-optimal orientations. In Part II of the paper, we demonstrate that a simple feed-forward model of spatial-frequency preference, unlike that for orientation preference, does not generate a faithful representation when amplified by recurrent interactions in V1. We then introduce the idea that cortico-geniculate feedback modulates LGN activity to generate a faithful representation, thus providing a new functional interpretation of the role of this feedback pathway. Using linear filter theory, we show that if the feedback from a cortical cell is taken to be approximately equal to the reciprocal of the corresponding feed-forward receptive field (in the two-dimensional Fourier domain), then the mismatch between the feed-forward and cortical frequency representations is eliminated. We therefore predict that cortico-geniculate feedback connections innervate the LGN in a pattern determined by the orientation and spatial-frequency biases of feed-forward receptive fields. Finally, we show how recurrent cortical interactions can generate cross-orientation suppression. PMID:14561324

Reducing injection loss in drill strings

DOEpatents

Drumheller, Douglas S.

2004-09-14

A system and method for transferring wave energy into or out of a periodic structure having a characteristic wave impedance profile at a prime frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, comprising: locating one or more energy transfer elements each having a wave impedance at the prime frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with the imaginary portion approximately equaling zero; and employing the one or more energy transfer elements to transfer wave energy into or out of the periodic structure. The energy transfer may be repeaters. Quarter-wave transformers can be provided at one or more points on the periodic structure with the imaginary portion approximately equaling zero to transmit waves across one or more discontinuities. A terminator can be employed for cancellation of waves. The invention substantially eliminates reflections of the wave energy at the prime frequency by joints between sections of the periodic structure.

Flight testing and frequency domain analysis for rotorcraft handling qualities characteristics

NASA Technical Reports Server (NTRS)

Ham, Johnnie A.; Gardner, Charles K.; Tischler, Mark B.

1993-01-01

A demonstration of frequency domain flight testing techniques and analyses was performed on a U.S. Army OH-58D helicopter in support of the OH-58D Airworthiness and Flight Characteristics Evaluation and the Army's development and ongoing review of Aeronautical Design Standard 33C, Handling Qualities Requirements for Military Rotorcraft. Hover and forward flight (60 knots) tests were conducted in 1 flight hour by Army experimental test pilots. Further processing of the hover data generated a complete database of velocity, angular rate, and acceleration frequency responses to control inputs. A joint effort was then undertaken by the Airworthiness Qualification Test Directorate (AQTD) and the U.S. Army Aeroflightdynamics Directorate (AFDD) to derive handling qualities information from the frequency response database. A significant amount of information could be extracted from the frequency domain database using a variety of approaches. This report documents numerous results that have been obtained from the simple frequency domain tests; in many areas, these results provide more insight into the aircraft dynamics that affect handling qualities than to traditional flight tests. The handling qualities results include ADS-33C bandwidth and phase delay calculations, vibration spectral determinations, transfer function models to examine single axis results, and a six degree of freedom fully coupled state space model. The ability of this model to accurately predict aircraft responses was verified using data from pulse inputs. This report also documents the frequency-sweep flight test technique and data analysis used to support the tests.

Gapped fermionic spectrum from a domain wall in seven dimension

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Subir; Rai, Nishal

2018-05-01

We obtain a domain wall solution in maximally gauged seven dimensional supergravity, which interpolates between two AdS spaces and spontaneously breaks a U (1) symmetry. We analyse frequency dependence of conductivity and find power law behaviour at low frequency. We consider certain fermions of supergravity in the background of this domain wall and compute holographic spectral function of the operators in the dual six dimensional theory. We find fermionic operators involving bosons with non-zero expectation value lead to gapped spectrum.

Metastability in the formation of Condon domains

NASA Astrophysics Data System (ADS)

Bakaleinikov, L. A.; Gordon, A.

2018-05-01

Metastability effects in the formation of Condon non-spin magnetic domains are considered. A possibility for the first-order phase transition occurrence in a three-dimensional electron gas is described in the case of two-frequency de-Haas-van Alphen magnetization oscillations originating from two extremal cross sections of the Fermi surface. The appearance of two additional domains is shown in the metastable region in aluminum. The phase diagram temperature-magnetic field exhibits the presence of second-order and first- order phase transitions in the two-frequency case.

New optical frequency domain differential mode delay measurement method for a multimode optical fiber.

PubMed

Ahn, T; Moon, S; Youk, Y; Jung, Y; Oh, K; Kim, D

2005-05-30

A novel mode analysis method and differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.

Applying the Scientific Method & Phylogenetics to Understand the Transition from Kingdoms to Domains: Does One Plus One Equal Five, Six, or Three?

ERIC Educational Resources Information Center

Davis, Sandra L.

2012-01-01

The progression of the taxonomic organization of life from Linnaeus's original two kingdoms to the traditional five-kingdom system to today's widely accepted three-domain system is explored in a group-learning activity. Working with a set of organisms, students organize them into each system. Discussion after each step focuses on viewing…

A Graphical Presentation to Teach the Concept of the Fourier Transform

ERIC Educational Resources Information Center

Besalu, E.

2006-01-01

A study was conducted to visualize the reason why the Fourier transform technique is useful to detect the originating frequencies of a complicated superposition of waves. The findings reveal that students respond well when instructors adapt pictorial presentation to show how the time-domain function is transformed into the frequency domain.

Measurement techniques for the characterization in the frequency domain of regulated energy-storage DC-to-DC converters. M.S. Thesis

NASA Technical Reports Server (NTRS)

Bahler, D. D.

1978-01-01

Procedures are presented for obtaining valid frequency-domain transfer functions of regulated reactor energy-storage dc-to-dc converters. These procedures are for measuring loop gain, closed loop gain, output impedance, and audio susceptibility. The applications of these measurements are discussed.

Infrared maritime target detection using a probabilistic single Gaussian model of sea clutter in Fourier domain

NASA Astrophysics Data System (ADS)

Zhou, Anran; Xie, Weixin; Pei, Jihong; Chen, Yapei

2018-02-01

For ship targets detection in cluttered infrared image sequences, a robust detection method, based on the probabilistic single Gaussian model of sea background in Fourier domain, is put forward. The amplitude spectrum sequences at each frequency point of the pure seawater images in Fourier domain, being more stable than the gray value sequences of each background pixel in the spatial domain, are regarded as a Gaussian model. Next, a probability weighted matrix is built based on the stability of the pure seawater's total energy spectrum in the row direction, to make the Gaussian model more accurate. Then, the foreground frequency points are separated from the background frequency points by the model. Finally, the false-alarm points are removed utilizing ships' shape features. The performance of the proposed method is tested by visual and quantitative comparisons with others.

Efficient Power Network Analysis with Modeling of Inductive Effects

NASA Astrophysics Data System (ADS)

Zeng, Shan; Yu, Wenjian; Hong, Xianlong; Cheng, Chung-Kuan

In this paper, an efficient method is proposed to accurately analyze large-scale power/ground (P/G) networks, where inductive parasitics are modeled with the partial reluctance. The method is based on frequency-domain circuit analysis and the technique of vector fitting [14], and obtains the time-domain voltage response at given P/G nodes. The frequency-domain circuit equation including partial reluctances is derived, and then solved with the GMRES algorithm with rescaling, preconditioning and recycling techniques. With the merit of sparsified reluctance matrix and iterative solving techniques for the frequency-domain circuit equations, the proposed method is able to handle large-scale P/G networks with complete inductive modeling. Numerical results show that the proposed method is orders of magnitude faster than HSPICE, several times faster than INDUCTWISE [4], and capable of handling the inductive P/G structures with more than 100, 000 wire segments.

Frequency-domain coherent multidimensional spectroscopy when dephasing rivals pulsewidth: Disentangling material and instrument response

DOE PAGES

Kohler, Daniel D.; Thompson, Blaise J.; Wright, John C.

2017-08-31

Ultrafast spectroscopy is often collected in the mixed frequency/time domain, where pulse durations are similar to system dephasing times. In these experiments, expectations derived from the familiar driven and impulsive limits are not valid. This work simulates the mixed-domain four-wave mixing response of a model system to develop expectations for this more complex field-matter interaction. We also explore frequency and delay axes. We show that these line shapes are exquisitely sensitive to excitation pulse widths and delays. Near pulse overlap, the excitation pulses induce correlations that resemble signatures of dynamic inhomogeneity. We describe these line shapes using an intuitive picturemore » that connects to familiar field-matter expressions. We develop strategies for distinguishing pulse-induced correlations from true system inhomogeneity. Our simulations provide a foundation for interpretation of ultrafast experiments in the mixed domain.« less

Real time recognition of explosophorous group and explosive material using laser induced photoacoustic spectroscopy associated with novel algorithm for time and frequency domain analysis.

PubMed

El-Sharkawy, Yasser H; Elbasuney, Sherif

2018-06-07

Energy-rich bonds such as nitrates (NO 3 - ) and percholorates (ClO 4 - ) have an explosive nature; they are frequently encountered in high energy materials. These bonds encompass two highly electronegative atoms competing for electrons. Common explosive materials including urea nitrate, ammonium nitrate, and ammonium percholorates were subjected to photoacoustic spectroscopy. The captured signal was processed using novel digital algorithm designed for time and frequency domain analysis. Frequency domain analysis offered not only characteristic frequencies for NO 3 - and ClO 4 - groups; but also characteristic fingerprint spectra (based on thermal, acoustical, and optical properties) for different materials. The main outcome of this study is that phase-shift domain analysis offered an outstanding signature for each explosive material, with novel discrimination between explosive and similar non-explosive material. Photoacoustic spectroscopy offered different characteristic signatures that can be employed for real time detection with stand-off capabilities. There is no two materials could have the same optical, thermal, and acoustical properties. Copyright © 2018 Elsevier B.V. All rights reserved.

Simultaneous storage of medical images in the spatial and frequency domain: A comparative study

PubMed Central

Nayak, Jagadish; Bhat, P Subbanna; Acharya U, Rajendra; UC, Niranjan

2004-01-01

Background Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads. Methods The patient information is encrypted before interleaving with images to ensure greater security. The bio-signals are compressed and subsequently interleaved with the image. This interleaving is carried out in the spatial domain and Frequency domain. The performance of interleaving in the spatial, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) coefficients is studied. Differential pulse code modulation (DPCM) is employed for data compression as well as encryption and results are tabulated for a specific example. Results It can be seen from results, the process does not affect the picture quality. This is attributed to the fact that the change in LSB of a pixel changes its brightness by 1 part in 256. Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain. Conclusion The Results show that spatial domain the interleaving, the %NRMSE was less than 0.25% for 8-bit encoded pixel intensity. Among the frequency domain interleaving methods, DFT was found to be very efficient. PMID:15180899

The Noisiness of Low Frequency Bands of Noise

NASA Technical Reports Server (NTRS)

Lawton, B. W.

1975-01-01

The relative noisiness of low frequency 1/3-octave bands of noise was examined. The frequency range investigated was bounded by the bands centered at 25 and 200 Hz, with intensities ranging from 50 to 95 db (SPL). Thirty-two subjects used a method of adjustment technique, producing comparison band intensities as noisy as 100 and 200 Hz standard bands at 60 and 72 db. The work resulted in contours of equal noisiness for 1/3-octave bands, ranging in intensity from approximately 58 to 86 db (SPL). These contours were compared with the standard equal noisiness contours; in the region of overlap, between 50 and 200 Hz, the agreement was good.

Frequency domain measurement systems

NASA Technical Reports Server (NTRS)

Eischer, M. C.

1978-01-01

Stable frequency sources and signal processing blocks were characterized by their noise spectra, both discrete and random, in the frequency domain. Conventional measures are outlined, and systems for performing the measurements are described. Broad coverage of system configurations which were found useful is given. Their functioning and areas of application are discussed briefly. Particular attention is given to some of the potential error sources in the measurement procedures, system configurations, double-balanced-mixer-phase-detectors, and application of measuring instruments.

Flight-testing and frequency-domain analysis for rotorcraft handling qualities

NASA Technical Reports Server (NTRS)

Ham, Johnnie A.; Gardner, Charles K.; Tischler, Mark B.

1995-01-01

A demonstration of frequency-domain flight-testing techniques and analysis was performed on a U.S. Army OH-58D helicopter in support of the OH-58D Airworthiness and Flight Characteristics Evaluation and of the Army's development and ongoing review of Aeronautical Design Standard 33C, Handling Qualities Requirements for Military Rotorcraft. Hover and forward flight (60 kn) tests were conducted in 1 flight hour by Army experimental test pilots. Further processing of the hover data generated a complete database of velocity, angular-rate, and acceleration-frequency responses to control inputs. A joint effort was then undertaken by the Airworthiness Qualification Test Dirtectorate and the U.S. Army Aeroflightdynamics Directorate to derive handling-quality information from the frequency-domain database using a variety of approaches. This report documents numerous results that have been obtained from the simple frequency-domain tests; in many areas, these results provide more insight into the aircraft dynmamics that affect handling qualities than do traditional flight tests. The handling-quality results include ADS-33C bandwidth and phase-delay calculations, vibration spectral determinations, transfer-function models to examine single-axis results, and a six-degree-of-freedom fully coupled state-space model. The ability of this model to accurately predict responses was verified using data from pulse inputs. This report also documents the frequency-sweep flight-test technique and data analysis used to support the tests.

[Optimization of the pseudorandom input signals used for the forced oscillation technique].

PubMed

Liu, Xiaoli; Zhang, Nan; Liang, Hong; Zhang, Zhengbo; Li, Deyu; Wang, Weidong

2017-10-01

The forced oscillation technique (FOT) is an active pulmonary function measurement technique that was applied to identify the mechanical properties of the respiratory system using external excitation signals. FOT commonly includes single frequency sine, pseudorandom and periodic impulse excitation signals. Aiming at preventing the time-domain amplitude overshoot that might exist in the acquisition of combined multi sinusoidal pseudorandom signals, this paper studied the phase optimization of pseudorandom signals. We tried two methods including the random phase combination and time-frequency domain swapping algorithm to solve this problem, and used the crest factor to estimate the effect of optimization. Furthermore, in order to make the pseudorandom signals met the requirement of the respiratory system identification in 4-40 Hz, we compensated the input signals' amplitudes at the low frequency band (4-18 Hz) according to the frequency-response curve of the oscillation unit. Resuts showed that time-frequency domain swapping algorithm could effectively optimize the phase combination of pseudorandom signals. Moreover, when the amplitudes at low frequencies were compensated, the expected stimulus signals which met the performance requirements were obtained eventually.

Multivariate frequency domain analysis of protein dynamics

NASA Astrophysics Data System (ADS)

Matsunaga, Yasuhiro; Fuchigami, Sotaro; Kidera, Akinori

2009-03-01

Multivariate frequency domain analysis (MFDA) is proposed to characterize collective vibrational dynamics of protein obtained by a molecular dynamics (MD) simulation. MFDA performs principal component analysis (PCA) for a bandpass filtered multivariate time series using the multitaper method of spectral estimation. By applying MFDA to MD trajectories of bovine pancreatic trypsin inhibitor, we determined the collective vibrational modes in the frequency domain, which were identified by their vibrational frequencies and eigenvectors. At near zero temperature, the vibrational modes determined by MFDA agreed well with those calculated by normal mode analysis. At 300 K, the vibrational modes exhibited characteristic features that were considerably different from the principal modes of the static distribution given by the standard PCA. The influences of aqueous environments were discussed based on two different sets of vibrational modes, one derived from a MD simulation in water and the other from a simulation in vacuum. Using the varimax rotation, an algorithm of the multivariate statistical analysis, the representative orthogonal set of eigenmodes was determined at each vibrational frequency.

Application of Time-Frequency Domain Transform to Three-Dimensional Interpolation of Medical Images.

PubMed

Lv, Shengqing; Chen, Yimin; Li, Zeyu; Lu, Jiahui; Gao, Mingke; Lu, Rongrong

2017-11-01

Medical image three-dimensional (3D) interpolation is an important means to improve the image effect in 3D reconstruction. In image processing, the time-frequency domain transform is an efficient method. In this article, several time-frequency domain transform methods are applied and compared in 3D interpolation. And a Sobel edge detection and 3D matching interpolation method based on wavelet transform is proposed. We combine wavelet transform, traditional matching interpolation methods, and Sobel edge detection together in our algorithm. What is more, the characteristics of wavelet transform and Sobel operator are used. They deal with the sub-images of wavelet decomposition separately. Sobel edge detection 3D matching interpolation method is used in low-frequency sub-images under the circumstances of ensuring high frequency undistorted. Through wavelet reconstruction, it can get the target interpolation image. In this article, we make 3D interpolation of the real computed tomography (CT) images. Compared with other interpolation methods, our proposed method is verified to be effective and superior.

Extraction of repetitive transients with frequency domain multipoint kurtosis for bearing fault diagnosis

NASA Astrophysics Data System (ADS)

Liao, Yuhe; Sun, Peng; Wang, Baoxiang; Qu, Lei

2018-05-01

The appearance of repetitive transients in a vibration signal is one typical feature of faulty rolling element bearings. However, accurate extraction of these fault-related characteristic components has always been a challenging task, especially when there is interference from large amplitude impulsive noises. A frequency domain multipoint kurtosis (FDMK)-based fault diagnosis method is proposed in this paper. The multipoint kurtosis is redefined in the frequency domain and the computational accuracy is improved. An envelope autocorrelation function is also presented to estimate the fault characteristic frequency, which is used to set the frequency hunting zone of the FDMK. Then, the FDMK, instead of kurtosis, is utilized to generate a fast kurtogram and only the optimal band with maximum FDMK value is selected for envelope analysis. Negative interference from both large amplitude impulsive noise and shaft rotational speed related harmonic components are therefore greatly reduced. The analysis results of simulation and experimental data verify the capability and feasibility of this FDMK-based method

A numerical exercise in musical scales

NASA Astrophysics Data System (ADS)

Hartmann, George C.

1987-03-01

This paper investigates why the 12-note scale, having equal intervals, seems to be the best representation of scales constructed from purely harmonic intervals. Is it possible that other equal temperament scales with more or less than 12 notes would serve just as well? The investigation is done by displaying the difference between a set of harmonic notes and scales with equal intervals having n notes per octave. The difference is small when n is equal to 12, but also when n equals 19 and 29. The number density of notes per unit frequency intervals is also investigated.

Method for enhancing signals transmitted over optical fibers

DOEpatents

Ogle, J.W.; Lyons, P.B.

1981-02-11

A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber is disclosed. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

Pharmacist provision of primary health care: a modified Delphi validation of pharmacists' competencies.

PubMed

Kennie-Kaulbach, Natalie; Farrell, Barbara; Ward, Natalie; Johnston, Sharon; Gubbels, Ashley; Eguale, Tewodros; Dolovich, Lisa; Jorgenson, Derek; Waite, Nancy; Winslade, Nancy

2012-03-28

Pharmacists have expanded their roles and responsibilities as a result of primary health care reform. There is currently no consensus on the core competencies for pharmacists working in these evolving practices. The aim of this study was to develop and validate competencies for pharmacists' effective performance in these roles, and in so doing, document the perceived contribution of pharmacists providing collaborative primary health care services. Using a modified Delphi process including assessing perception of the frequency and criticality of performing tasks, we validated competencies important to primary health care pharmacists practising across Canada. Ten key informants contributed to competency drafting; thirty-three expert pharmacists replied to a second round survey. The final primary health care pharmacist competencies consisted of 34 elements and 153 sub-elements organized in seven CanMeds-based domains. Highest importance rankings were allocated to the domains of care provider and professional, followed by communicator and collaborator, with the lower importance rankings relatively equally distributed across the manager, advocate and scholar domains. Expert pharmacists working in primary health care estimated their most important responsibilities to be related to direct patient care. Competencies that underlie and are required for successful fulfillment of these patient care responsibilities, such as those related to communication, collaboration and professionalism were also highly ranked. These ranked competencies can be used to help pharmacists understand their potential roles in these evolving practices, to help other health care professionals learn about pharmacists' contributions to primary health care, to establish standards and performance indicators, and to prioritize supports and education to maximize effectiveness in this role.

Silicon as a model ion trap: Time domain measurements of donor Rydberg states

PubMed Central

Vinh, N. Q.; Greenland, P. T.; Litvinenko, K.; Redlich, B.; van der Meer, A. F. G.; Lynch, S. A.; Warner, M.; Stoneham, A. M.; Aeppli, G.; Paul, D. J.; Pidgeon, C. R.; Murdin, B. N.

2008-01-01

One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr–Sommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. Manipulation of Rydberg states in free atoms and ions by single and multiphoton processes has been tremendously productive since the development of pulsed visible laser spectroscopy. The analogous manipulations have not been conducted for donor impurities in silicon. Here, we use the FELIX pulsed free electron laser to perform time-domain measurements of the Rydberg state dynamics in phosphorus- and arsenic-doped silicon and we have obtained lifetimes consistent with frequency domain linewidths for isotopically purified silicon. This implies that the dominant decoherence mechanism for excited Rydberg states is lifetime broadening, just as for atoms in ion traps. The experiments are important because they represent a step toward coherent control and manipulation of atomic-like quantum levels in the most common semiconductor and complement magnetic resonance experiments in the literature, which show extraordinarily long spin lattice relaxation times—key to many well known schemes for quantum computing qubits—for the same impurities. Our results, taken together with the magnetic resonance data and progress in precise placement of single impurities, suggest that doped silicon, the basis for modern microelectronics, is also a model ion trap.

Pharmacist provision of primary health care: a modified Delphi validation of pharmacists' competencies

PubMed Central

2012-01-01

Background Pharmacists have expanded their roles and responsibilities as a result of primary health care reform. There is currently no consensus on the core competencies for pharmacists working in these evolving practices. The aim of this study was to develop and validate competencies for pharmacists' effective performance in these roles, and in so doing, document the perceived contribution of pharmacists providing collaborative primary health care services. Methods Using a modified Delphi process including assessing perception of the frequency and criticality of performing tasks, we validated competencies important to primary health care pharmacists practising across Canada. Results Ten key informants contributed to competency drafting; thirty-three expert pharmacists replied to a second round survey. The final primary health care pharmacist competencies consisted of 34 elements and 153 sub-elements organized in seven CanMeds-based domains. Highest importance rankings were allocated to the domains of care provider and professional, followed by communicator and collaborator, with the lower importance rankings relatively equally distributed across the manager, advocate and scholar domains. Conclusions Expert pharmacists working in primary health care estimated their most important responsibilities to be related to direct patient care. Competencies that underlie and are required for successful fulfillment of these patient care responsibilities, such as those related to communication, collaboration and professionalism were also highly ranked. These ranked competencies can be used to help pharmacists understand their potential roles in these evolving practices, to help other health care professionals learn about pharmacists' contributions to primary health care, to establish standards and performance indicators, and to prioritize supports and education to maximize effectiveness in this role. PMID:22455482

High frequency resolution terahertz time-domain spectroscopy

NASA Astrophysics Data System (ADS)

Sangala, Bagvanth Reddy

2013-12-01

A new method for the high frequency resolution terahertz time-domain spectroscopy is developed based on the characteristic matrix method. This method is useful for studying planar samples or stack of planar samples. The terahertz radiation was generated by optical rectification in a ZnTe crystal and detected by another ZnTe crystal via electro-optic sampling method. In this new characteristic matrix based method, the spectra of the sample and reference waveforms will be modeled by using characteristic matrices. We applied this new method to measure the optical constants of air. The terahertz transmission through the layered systems air-Teflon-air-Quartz-air and Nitrogen gas-Teflon-Nitrogen gas-Quartz-Nitrogen gas was modeled by the characteristic matrix method. A transmission coefficient is derived from these models which was optimized to fit the experimental transmission coefficient to extract the optical constants of air. The optimization of an error function involving the experimental complex transmission coefficient and the theoretical transmission coefficient was performed using patternsearch algorithm of MATLAB. Since this method takes account of the echo waveforms due to reflections in the layered samples, this method allows analysis of longer time-domain waveforms giving rise to very high frequency resolution in the frequency-domain. We have presented the high frequency resolution terahertz time-domain spectroscopy of air and compared the results with the literature values. We have also fitted the complex susceptibility of air to the Lorentzian and Gaussian functions to extract the linewidths.

Autonomic nervous functions in fetal type Minamata disease patients: assessment of heart rate variability.

PubMed

Oka, Tomoko; Matsukura, Makoto; Okamoto, Miwako; Harada, Noriaki; Kitano, Takao; Miike, Teruhisa; Futatsuka, Makoto

2002-12-01

In order to assess the cardiovascular autonomic nervous functions in patients with fetal type Minamata disease (FMD), we investigated blood pressure (BP), and conducted time and frequency domain analysis of heart rate variability (HRV). Subjects were 9 patients in Meisuien recognized as FMD, and 13 healthy age matched control subjects. HRV and BP were assessed after subjects rested in a supine position for 10 minutes. Electrocardiographic (ECG) data were collected for 3 minutes during natural breathing. Time domain analysis (the average of R-R intervals [Mean RR], standard deviation of R-R intervals [SD RR], coefficient of variation [CV]), and frequency domain analysis by fast Fourier transformation (FFT) (power of low frequency [LF] and high frequency [HF] component, expressed in normalized units[nu]) were then conducted. In the time domain analysis, the mean RR of the FMD group was significantly lower than that of the control group. Neither SD RR nor CV showed significant differences between the two groups, but both tended to be lower in the FMD group. In the frequency domain analysis, the HF component of the FMD group was significantly lower than that of the control group. Pulse pressure (PP) was significantly lower in the FMD subjects. These findings suggest that parasympathetic nervous dysfunction might exist in FMD patients, who were exposed to high doses of methylmercury (MeHg) during the prenatal period. Decrease of PP might be due to degenerative changes of blood vessels driven by exposure to high doses of MeHg.

A Multi-Epoch Timing and Spectral Study of the Ultraluminous X-Ray NGC 5408 X-1 with XMM-Newton

NASA Technical Reports Server (NTRS)

Dheeraj, Pasham; Strohmayer, Tod E.

2012-01-01

We present results of new XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the few ULXs to show quasi-periodic oscillations (QPOs). We detect QPOs in each of four new (approximately equal to 100 ks) pointings, expanding the range of frequencies observed from 10 to 40 mHz. We compare our results with the timing and spectral correlations seen in stellar-mass black hole systems, and find that the qualitative nature of the timing and spectral behavior of NGC 5408 X-1 is similar to systems in the steep power-law state exhibiting Type-C QPOs. However, in order for this analogy to quantitatively hold we must only be seeing the so-called saturated portion of the QPO frequency-photon index (or disk flux) relation. Assuming this to be the case, we place a lower limit on the mass of NGC 5408 X-1 of greater than or equal to 800 solar mass. Alternatively, the QPO frequency is largely independent of the spectral parameters, in which case a close analogy with the Type-C QPOs in stellar system is problematic. Measurement of the source's timing properties over a wider range of energy spectral index is needed to definitively resolve this ambiguity. We searched all the available data for both a broad Fe emission line as well as high-frequency QPO analogs (0.1- 1 Hz), but detected neither. We place upper limits on the equivalent width of any Fe emission feature in the 6-7 keV band and of the amplitude (rms) of a high-frequency QPO analog of approximately equal to 10 eV and approximately equal to 4%, respectively.

Estimating the frequency interval of a regularly spaced multicomponent harmonic line signal in colored noise

NASA Astrophysics Data System (ADS)

Frazer, Gordon J.; Anderson, Stuart J.

1997-10-01

The radar returns from some classes of time-varying point targets can be represented by the discrete-time signal plus noise model: xt equals st plus [vt plus (eta) t] equals (summation)i equals o P minus 1 Aiej2(pi f(i)/f(s)t) plus vt plus (eta) t, t (epsilon) 0, . . ., N minus 1, fi equals kfI plus fo where the received signal xt corresponds to the radar return from the target of interest from one azimuth-range cell. The signal has an unknown number of components, P, unknown complex amplitudes Ai and frequencies fi. The frequency parameters fo and fI are unknown, although constrained such that fo less than fI/2 and parameter k (epsilon) {minus u, . . ., minus 2, minus 1, 0, 1, 2, . . ., v} is constrained such that the component frequencies fi are bound by (minus fs/2, fs/2). The noise term vt, is typically colored, and represents clutter, interference and various noise sources. It is unknown, except that (summation)tvt2 less than infinity; in general, vt is not well modelled as an auto-regressive process of known order. The additional noise term (eta) t represents time-invariant point targets in the same azimuth-range cell. An important characteristic of the target is the unknown parameter, fI, representing the frequency interval between harmonic lines. It is desired to determine an estimate of fI from N samples of xt. We propose an algorithm to estimate fI based on Thomson's harmonic line F-Test, which is part of the multi-window spectrum estimation method and demonstrate the proposed estimator applied to target echo time series collected using an experimental HF skywave radar.

Regional Attenuation at PIDC Stations and the Transportability of the S/P Discriminant

DTIC Science & Technology

1998-03-31

amplitude ratios using a variety of frequency bands subject to the constraint that the P-wave frequency is greater than or equal to the 5 - wave frequency... the 5 - wave frequency. First, we discuss our distance and source corrections and show that we were able to remove these dependencies in the data

A kind of graded sub-pixel motion estimation algorithm combining time-domain characteristics with frequency-domain phase correlation

NASA Astrophysics Data System (ADS)

Xie, Bing; Duan, Zhemin; Chen, Yu

2017-11-01

The mode of navigation based on scene match can assist UAV to achieve autonomous navigation and other missions. However, aerial multi-frame images of the UAV in the complex flight environment easily be affected by the jitter, noise and exposure, which will lead to image blur, deformation and other issues, and result in the decline of detection rate of the interested regional target. Aiming at this problem, we proposed a kind of Graded sub-pixel motion estimation algorithm combining time-domain characteristics with frequency-domain phase correlation. Experimental results prove the validity and accuracy of the proposed algorithm.

Method and apparatus for wavefront sensing

DOEpatents

Bahk, Seung-Whan

2016-08-23

A method of measuring characteristics of a wavefront of an incident beam includes obtaining an interferogram associated with the incident beam passing through a transmission mask and Fourier transforming the interferogram to provide a frequency domain interferogram. The method also includes selecting a subset of harmonics from the frequency domain interferogram, individually inverse Fourier transforming each of the subset of harmonics to provide a set of spatial domain harmonics, and extracting a phase profile from each of the set of spatial domain harmonics. The method further includes removing phase discontinuities in the phase profile, rotating the phase profile, and reconstructing a phase front of the wavefront of the incident beam.

Enhancement of frequency domain indices of heart rate variability by cholinergic stimulation with pyridostigmine bromide.

PubMed

Zarei, Ali Asghar; Foroutan, Seyyed Abbas; Foroutan, Seyyed Mohsen; Erfanian Omidvar, Abbas

2011-01-01

Pyridostigmine bromide (PB) is a reversible cholinesterase inhibitor. The aim of this study was to determine the effect of orally administration of single dose sustained-released tablet of pyridostigmine bromide (PBSR) on the frequency domain indices of heart rate variability (HRV). Thirty-two healthy young men were participated in this study. They were divided into 2 groups; the pyridostigmine group (n = 22) and the placebo group (n = 10). Electrocardiogram (ECG) was recorded at 10, 30, 60, 90, 120, 150, 180, 210, 240, 300 and 420 min after PBSR administration. At each time, simultaneously, a blood sample was prepared and PB plasma concentration was measured by high-performance liquid chromatography (HPLC) method. Statistical analysis showed that in different indices of HRV, there is a significant increase in low frequency (LF) band at 300 min, but no difference in high frequency band (HF). It also showed significant decreases in normalized high frequency band (Hfnu), normalized low frequency band (Lfnu) and LF/HF ratio at 120, 240 and 300 min after PBSR administration. Maximum plasma concentration of PB was 150 min after the administration. In conclusion, administration of a single dose PBSR can enhance the frequency domains indices of HRV and improvesympathovagal balance.

ProteinAC: a frequency domain technique for analyzing protein dynamics

NASA Astrophysics Data System (ADS)

Bozkurt Varolgunes, Yasemin; Demir, Alper

2018-03-01

It is widely believed that the interactions of proteins with ligands and other proteins are determined by their dynamic characteristics as opposed to only static, time-invariant processes. We propose a novel computational technique, called ProteinAC (PAC), that can be used to analyze small scale functional protein motions as well as interactions with ligands directly in the frequency domain. PAC was inspired by a frequency domain analysis technique that is widely used in electronic circuit design, and can be applied to both coarse-grained and all-atom models. It can be considered as a generalization of previously proposed static perturbation-response methods, where the frequency of the perturbation becomes the key. We discuss the precise relationship of PAC to static perturbation-response schemes. We show that the frequency of the perturbation may be an important factor in protein dynamics. Perturbations at different frequencies may result in completely different response behavior while magnitude and direction are kept constant. Furthermore, we introduce several novel frequency dependent metrics that can be computed via PAC in order to characterize response behavior. We present results for the ferric binding protein that demonstrate the potential utility of the proposed techniques.

A Joint Method of Envelope Inversion Combined with Hybrid-domain Full Waveform Inversion

NASA Astrophysics Data System (ADS)

CUI, C.; Hou, W.

2017-12-01

Full waveform inversion (FWI) aims to construct high-precision subsurface models by fully using the information in seismic records, including amplitude, travel time, phase and so on. However, high non-linearity and the absence of low frequency information in seismic data lead to the well-known cycle skipping problem and make inversion easily fall into local minima. In addition, those 3D inversion methods that are based on acoustic approximation ignore the elastic effects in real seismic field, and make inversion harder. As a result, the accuracy of final inversion results highly relies on the quality of initial model. In order to improve stability and quality of inversion results, multi-scale inversion that reconstructs subsurface model from low to high frequency are applied. But, the absence of very low frequencies (< 3Hz) in field data is still bottleneck in the FWI. By extracting ultra low-frequency data from field data, envelope inversion is able to recover low wavenumber model with a demodulation operator (envelope operator), though the low frequency data does not really exist in field data. To improve the efficiency and viability of the inversion, in this study, we proposed a joint method of envelope inversion combined with hybrid-domain FWI. First, we developed 3D elastic envelope inversion, and the misfit function and the corresponding gradient operator were derived. Then we performed hybrid-domain FWI with envelope inversion result as initial model which provides low wavenumber component of model. Here, forward modeling is implemented in the time domain and inversion in the frequency domain. To accelerate the inversion, we adopt CPU/GPU heterogeneous computing techniques. There were two levels of parallelism. In the first level, the inversion tasks are decomposed and assigned to each computation node by shot number. In the second level, GPU multithreaded programming is used for the computation tasks in each node, including forward modeling, envelope extraction, DFT (discrete Fourier transform) calculation and gradients calculation. Numerical tests demonstrated that the combined envelope inversion + hybrid-domain FWI could obtain much faithful and accurate result than conventional hybrid-domain FWI. The CPU/GPU heterogeneous parallel computation could improve the performance speed.

Asymmetry of plasma membrane lipid order in Madin-Darby Canine Kidney cells.

PubMed

Le Grimellec, C; Friedlander, G; Giocondi, M C

1988-07-01

Fluorescence anisotropy experiments have been done to estimate, in situ, the lipid order of the plasma membrane of polarized Madin-Darby Canine Kidney cells (MDCK) grown on glass cover slips and labeled by 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), a specific marker of the plasma membrane of living cells. Fluorescence microscopy, back-exchange, and quenching experiments indicated that TMA-DPH labeled the highly ordered (r greater than or equal to 0.32, 37 degrees C) apical domain of the plasma membrane of confluent monolayers. Opening of tight junctions or addition of the probe to cell suspensions resulted in a homogeneous distribution of TMA-DPH over the cell surface and in a marked decrease in anisotropy (0.27 less than or equal to r less than or equal to 0.29) that was due neither to a direct effect of Ca2+ on the probe nor to a change in fluorescence lifetime. Our data indicate that the apical domain, likely the external leaflet, of the plasma membrane of polarized MDCK cells is much more ordered than its basolateral counterpart.

Determination of medium electrical properties through full-wave modelling of frequency domain reflectrometry data

NASA Astrophysics Data System (ADS)

André, Frédéric; Lambot, Sébastien

2015-04-01

Accurate knowledge of the shallow soil properties is of prime importance in agricultural, hydrological and environmental engineering. During the last decade, numerous geophysical techniques, either invasive or resorting to proximal or remote sensing, have been developed and applied for quantitative characterization of soil properties. Amongst them, time domain reflectrometry (TDR) and frequency domain reflectometry (FDR) are recognized as standard techniques for the determination of soil dielectric permittivity and electrical conductivity, based on the reflected electromagnetic waves from a probe inserted into the soil. TDR data were first commonly analyzed in the time domain using methods considering only a part of the waveform information. Later, advancements have led to the possibility of analyzing the TDR signal through full-wave inverse modeling either in the time or the frequency domains. A major advantage of FDR compared to TDR is the possibility to increase the bandwidth, thereby increasing the information content of the data and providing more detailed characterization of the medium. Amongst the recent works in this field, Minet et al. (2010) developed a modeling procedure for processing FDR data based on an exact solution of Maxwell's equations for wave propagation in one-dimensional multilayered media. In this approach, the probe head is decoupled from the medium and is fully described by characteristic transfer functions. The authors successfully validated the method for homogeneous sand subject to a range of water contents. In the present study, we further validated the modelling approach using reference liquids with well-characterized frequency-dependent electrical properties. In addition, the FDR model was coupled with a dielectric mixing model to investigate the ability of retrieving water content, pore water electrical conductivity and sand porosity from inversion of FDR data acquired in sand subject to different water content levels. Finally, the possibility of reconstructing the vertical profile of the properties by inversion of FDR data collected during progressive insertion of the probe into a vertically heterogeneous medium was also investigated. Index Terms: Frequency domain reflectrometry (FDR), frequency dependence, dielectric permittivity, electrical conductivity Reference: Minet J., Lambot S., Delaide G., Huisman J.A., Vereecken H., Vanclooster M., 2010. A generalized frequency domain reflectometry modeling technique for soil electrical properties determination. Vadose Zone Journal, 9: 1063-1072.

Time-domain measurement of terahertz frequency magnetoplasmon resonances in a two-dimensional electron system by the direct injection of picosecond pulsed currents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jingbo; Mayorov, Alexander S.; Wood, Christopher D.

2016-02-29

We have investigated terahertz (THz) frequency magnetoplasmon resonances in a two-dimensional electron system through the direct injection of picosecond duration current pulses. The evolution of the time-domain signals was measured as a function of magnetic field, and the results were found to be in agreement with calculations using a mode-matching approach for four modes observed in the frequency range above 0.1 THz. This introduces a generic technique suitable for sampling ultrafast carrier dynamics in low-dimensional semiconductor nanostructures at THz frequencies.

Assessing co-regulation of directly linked genes in biological networks using microarray time series analysis.

PubMed

Del Sorbo, Maria Rosaria; Balzano, Walter; Donato, Michele; Draghici, Sorin

2013-11-01

Differential expression of genes detected with the analysis of high throughput genomic experiments is a commonly used intermediate step for the identification of signaling pathways involved in the response to different biological conditions. The impact analysis was the first approach for the analysis of signaling pathways involved in a certain biological process that was able to take into account not only the magnitude of the expression change of the genes but also the topology of signaling pathways including the type of each interactions between the genes. In the impact analysis, signaling pathways are represented as weighted directed graphs with genes as nodes and the interactions between genes as edges. Edges weights are represented by a β factor, the regulatory efficiency, which is assumed to be equal to 1 in inductive interactions between genes and equal to -1 in repressive interactions. This study presents a similarity analysis between gene expression time series aimed to find correspondences with the regulatory efficiency, i.e. the β factor as found in a widely used pathway database. Here, we focused on correlations among genes directly connected in signaling pathways, assuming that the expression variations of upstream genes impact immediately downstream genes in a short time interval and without significant influences by the interactions with other genes. Time series were processed using three different similarity metrics. The first metric is based on the bit string matching; the second one is a specific application of the Dynamic Time Warping to detect similarities even in presence of stretching and delays; the third one is a quantitative comparative analysis resulting by an evaluation of frequency domain representation of time series: the similarity metric is the correlation between dominant spectral components. These three approaches are tested on real data and pathways, and a comparison is performed using Information Retrieval benchmark tools, indicating the frequency approach as the best similarity metric among the three, for its ability to detect the correlation based on the correspondence of the most significant frequency components. Copyright © 2013. Published by Elsevier Ireland Ltd.

Effects of model-mimic frequency on insect visitation and plant reproduction in a self-mimicry pollination system

PubMed Central

Oleques, Suiane Santos; Marciniak, Brisa; Ribeiro, José Ricardo I

2017-01-01

Abstract The proportion of mimics and models is a key parameter in mimetic systems. In monoecious plants with self-mimicry pollination systems, the mimic-model ratio is determined by the floral sex ratio. While an equal sex ratio (1:1) could provide the perfect balance between pollen donors and stigma surfaces able to receive the pollen, an unequal ratio could increase pollination by production of a greater number of rewarding, model flowers. The aim of the present study is to test the differences in visitation frequency and reproductive rates of different mimic and model flower arrays in order to assess the efficacy of the mimetic system in a Begonia cucullata population. The frequencies of visitors to groups of flowers with three distinctive sex ratio arrays (male-biased, female-biased and equal ratio) were compared using a Bayesian approach. The reproductive outcomes were compared in order to detect advantages of particular sex ratios. Low visitation frequency was recorded in all arrays. Pollinators showed similar behaviour regardless of sex ratio; they tended to avoid female, rewardless flowers. Pollination quality was highest in the equal sex ratio array. The current study shows that sex ratio plays a critical role in the pollination of B. cucullata and that the efficacy of the self-mimicry system appears to be doubtful. Visitation frequency may be associated with visual or chemical cues that allow pollinators to recognize models and mimics, regardless of their frequency in the population. PMID:29255587

Effects of model-mimic frequency on insect visitation and plant reproduction in a self-mimicry pollination system.

PubMed

de Avila, Rubem Samuel; Oleques, Suiane Santos; Marciniak, Brisa; Ribeiro, José Ricardo I

2017-11-01

The proportion of mimics and models is a key parameter in mimetic systems. In monoecious plants with self-mimicry pollination systems, the mimic-model ratio is determined by the floral sex ratio. While an equal sex ratio (1:1) could provide the perfect balance between pollen donors and stigma surfaces able to receive the pollen, an unequal ratio could increase pollination by production of a greater number of rewarding, model flowers. The aim of the present study is to test the differences in visitation frequency and reproductive rates of different mimic and model flower arrays in order to assess the efficacy of the mimetic system in a Begonia cucullata population. The frequencies of visitors to groups of flowers with three distinctive sex ratio arrays (male-biased, female-biased and equal ratio) were compared using a Bayesian approach. The reproductive outcomes were compared in order to detect advantages of particular sex ratios. Low visitation frequency was recorded in all arrays. Pollinators showed similar behaviour regardless of sex ratio; they tended to avoid female, rewardless flowers. Pollination quality was highest in the equal sex ratio array. The current study shows that sex ratio plays a critical role in the pollination of B. cucullata and that the efficacy of the self-mimicry system appears to be doubtful. Visitation frequency may be associated with visual or chemical cues that allow pollinators to recognize models and mimics, regardless of their frequency in the population.

A new unequal-weighted triple-frequency first order ionosphere correction algorithm and its application in COMPASS

NASA Astrophysics Data System (ADS)

Liu, WenXiang; Mou, WeiHua; Wang, FeiXue

2012-03-01

As the introduction of triple-frequency signals in GNSS, the multi-frequency ionosphere correction technology has been fast developing. References indicate that the triple-frequency second order ionosphere correction is worse than the dual-frequency first order ionosphere correction because of the larger noise amplification factor. On the assumption that the variances of three frequency pseudoranges were equal, other references presented the triple-frequency first order ionosphere correction, which proved worse or better than the dual-frequency first order correction in different situations. In practice, the PN code rate, carrier-to-noise ratio, parameters of DLL and multipath effect of each frequency are not the same, so three frequency pseudorange variances are unequal. Under this consideration, a new unequal-weighted triple-frequency first order ionosphere correction algorithm, which minimizes the variance of the pseudorange ionosphere-free combination, is proposed in this paper. It is found that conventional dual-frequency first-order correction algorithms and the equal-weighted triple-frequency first order correction algorithm are special cases of the new algorithm. A new pseudorange variance estimation method based on the three carrier combination is also introduced. Theoretical analysis shows that the new algorithm is optimal. The experiment with COMPASS G3 satellite observations demonstrates that the ionosphere-free pseudorange combination variance of the new algorithm is smaller than traditional multi-frequency correction algorithms.

TDR method for determine IC's parameters

NASA Astrophysics Data System (ADS)

Timoshenkov, V.; Rodionov, D.; Khlybov, A.

2016-12-01

Frequency domain simulation is a widely used approach for determine integrated circuits parameters. This approach can be found in most of software tools used in IC industry. Time domain simulation approach shows intensive usage last years due to some advantages. In particular it applicable for analysis of nonlinear and nonstationary systems where frequency domain is inapplicable. Resolution of time domain systems allow see heterogeneities on distance 1mm, determine it parameters and properties. Authors used approach based on detecting reflected signals from heterogeneities - time domain reflectometry (TDR). Field effect transistor technology scaling up to 30-60nm gate length and 10nm gate dielectric, heterojunction bi-polar transistors with 10-30nm base width allows fabricate digital IC's with 20GHz clock frequency and RF-IC's with tens GHz bandwidth. Such devices and operation speed suppose transit signal by use microwave lines. There are local heterogeneities can be found inside of the signal path due to connections between different parts of signal lines (stripe line-RF-connector pin, stripe line - IC package pin). These heterogeneities distort signals that cause bandwidth decrease for RF-devices. Time domain research methods of transmission and reflected signals give the opportunities to determine heterogeneities, it properties, parameters and built up equivalent circuits. Experimental results are provided and show possibility for inductance and capacitance measurement up to 25GHz. Measurements contains result of signal path research on IC and printed circuit board (PCB) used for 12GHz RF chips. Also dielectric constant versus frequency was measured up to 35GHz.

Numerical Investigation of Three-dimensional Instability of Standing Waves

NASA Astrophysics Data System (ADS)

Zhu, Qiang; Liu, Yuming; Yue, Dick K. P.

2002-11-01

We study the three-dimensional instability of finite-amplitude standing waves under the influence of gravity using the transition matrix method. For accurate calculation of the transition matrices, we apply an efficient high-order spectral element method for nonlinear wave dynamics in complex domain. We consider two types of standing waves: (a) plane standing waves; and (b) standing waves in a circular tank. For the former, in addition to the confirmation of the side-band-like instability, we find a new three-dimensional instability for arbitrary base standing waves. The dominant component of the unstable disturbance is an oblique standing wave, with an arbitrary angle relative to the base flow, whose frequency is approximately equal to that of the base standing wave. Based on direct simulations, we confirm such a three-dimensional instability and show the occurrence of the Fermi-Pasta-Ulam recurrence phenomenon during nonlinear evolution. For the latter, we find that beyond a threshold wave steepness, the standing wave with frequency Ω becomes unstable to a small three-dimensional disturbance, which contains two dominant standing-wave components with frequencies ω1 and ω_2, provided that 2Ω ω1 + ω_2. The threshold wave steepness is found to decrease/increase as the radial/azimuthal wavenumber of the base standing wave increases. We show that the instability of standing waves in rectangular and circular tanks is caused by third-order quartet resonances between base flow and disturbance.

Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

PubMed Central

Bore, Thierry; Wagner, Norman; Delepine Lesoille, Sylvie; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

2016-01-01

Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

2.5-D frequency-domain viscoelastic wave modelling using finite-element method

NASA Astrophysics Data System (ADS)

Zhao, Jian-guo; Huang, Xing-xing; Liu, Wei-fang; Zhao, Wei-jun; Song, Jian-yong; Xiong, Bin; Wang, Shang-xu

2017-10-01

2-D seismic modelling has notable dynamic information discrepancies with field data because of the implicit line-source assumption, whereas 3-D modelling suffers from a huge computational burden. The 2.5-D approach is able to overcome both of the aforementioned limitations. In general, the earth model is treated as an elastic material, but the real media is viscous. In this study, we develop an accurate and efficient frequency-domain finite-element method (FEM) for modelling 2.5-D viscoelastic wave propagation. To perform the 2.5-D approach, we assume that the 2-D viscoelastic media are based on the Kelvin-Voigt rheological model and a 3-D point source. The viscoelastic wave equation is temporally and spatially Fourier transformed into the frequency-wavenumber domain. Then, we systematically derive the weak form and its spatial discretization of 2.5-D viscoelastic wave equations in the frequency-wavenumber domain through the Galerkin weighted residual method for FEM. Fixing a frequency, the 2-D problem for each wavenumber is solved by FEM. Subsequently, a composite Simpson formula is adopted to estimate the inverse Fourier integration to obtain the 3-D wavefield. We implement the stiffness reduction method (SRM) to suppress artificial boundary reflections. The results show that this absorbing boundary condition is valid and efficient in the frequency-wavenumber domain. Finally, three numerical models, an unbounded homogeneous medium, a half-space layered medium and an undulating topography medium, are established. Numerical results validate the accuracy and stability of 2.5-D solutions and present the adaptability of finite-element method to complicated geographic conditions. The proposed 2.5-D modelling strategy has the potential to address modelling studies on wave propagation in real earth media in an accurate and efficient way.

Metrology for terahertz time-domain spectrometers

NASA Astrophysics Data System (ADS)

Molloy, John F.; Naftaly, Mira

2015-12-01

In recent years the terahertz time-domain spectrometer (THz TDS) [1] has emerged as a key measurement device for spectroscopic investigations in the frequency range of 0.1-5 THz. To date, almost every type of material has been studied using THz TDS, including semiconductors, ceramics, polymers, metal films, liquid crystals, glasses, pharmaceuticals, DNA molecules, proteins, gases, composites, foams, oils, and many others. Measurements with a TDS are made in the time domain; conversion from the time domain data to a frequency spectrum is achieved by applying the Fourier Transform, calculated numerically using the Fast Fourier Transform (FFT) algorithm. As in many other types of spectrometer, THz TDS requires that the sample data be referenced to similarly acquired data with no sample present. Unlike frequency-domain spectrometers which detect light intensity and measure absorption spectra, a TDS records both amplitude and phase information, and therefore yields both the absorption coefficient and the refractive index of the sample material. The analysis of the data from THz TDS relies on the assumptions that: a) the frequency scale is accurate; b) the measurement of THz field amplitude is linear; and c) that the presence of the sample does not affect the performance characteristics of the instrument. The frequency scale of a THz TDS is derived from the displacement of the delay line; via FFT, positioning errors may give rise to frequency errors that are difficult to quantify. The measurement of the field amplitude in a THz TDS is required to be linear with a dynamic range of the order of 10 000. And attention must be given to the sample positioning and handling in order to avoid sample-related errors.

Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

PubMed

Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

2016-04-18

Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

Terahertz photonic crystals

NASA Astrophysics Data System (ADS)

Jian, Zhongping

This thesis describes the study of two-dimensional photonic crystals slabs with terahertz time domain spectroscopy. In our study we first demonstrate the realization of planar photonic components to manipulate terahertz waves, and then characterize photonic crystals using terahertz pulses. Photonic crystal slabs at the scale of micrometers are first designed and fabricated free of defects. Terahertz time domain spectrometer generates and detects the electric fields of single-cycle terahertz pulses. By putting photonic crystals into waveguide geometry, we successfully demonstrate planar photonic components such as transmission filters, reflection frequency-selective filters, defects modes as well as superprisms. In the characterization study of out-of-plane properties of photonic crystal slabs, we observe very strong dispersion at low frequencies, guided resonance modes at middle frequencies, and a group velocity anomaly at high frequencies. We employ Finite Element Method and Finite-Difference Time-Domain method to simulate the photonic crystals, and excellent agreement is achieved between simulation results and experimental results.

Frequency dependent polarisation switching in h-ErMnO3

NASA Astrophysics Data System (ADS)

Ruff, Alexander; Li, Ziyu; Loidl, Alois; Schaab, Jakob; Fiebig, Manfred; Cano, Andres; Yan, Zewu; Bourret, Edith; Glaum, Julia; Meier, Dennis; Krohns, Stephan

2018-04-01

We report an electric-field poling study of the geometrically-driven improper ferroelectric h-ErMnO3. From a detailed dielectric analysis, we deduce the temperature and the frequency dependent range for which single-crystalline h-ErMnO3 exhibits purely intrinsic dielectric behaviour, i.e., free from the extrinsic so-called Maxwell-Wagner polarisations that arise, for example, from surface barrier layers. In this regime, ferroelectric hysteresis loops as a function of frequency, temperature, and applied electric fields are measured, revealing the theoretically predicted saturation polarisation on the order of 5-6 μC/cm2. Special emphasis is put on frequency dependent polarisation switching, which is explained in terms of domain-wall movement similar to proper ferroelectrics. Controlling the domain walls via electric fields brings us an important step closer to their utilization in domain-wall-based electronics.

Two dimensional microcirculation mapping with real time spatial frequency domain imaging

NASA Astrophysics Data System (ADS)

Zheng, Yang; Chen, Xinlin; Lin, Weihao; Cao, Zili; Zhu, Xiuwei; Zeng, Bixin; Xu, M.

2018-02-01

We present a spatial frequency domain imaging (SFDI) study of local hemodynamics in the human finger cuticle of healthy volunteers performing paced breathing and the forearm of healthy young adults performing normal breathing with our recently developed Real Time Single Snapshot Multiple Frequency Demodulation - Spatial Frequency Domain Imaging (SSMD-SFDI) system. A two-layer model was used to map the concentrations of deoxy-, oxy-hemoglobin, melanin, epidermal thickness and scattering properties at the subsurface of the forearm and the finger cuticle. The oscillations of the concentrations of deoxy- and oxy-hemoglobin at the subsurface of the finger cuticle and forearm induced by paced breathing and normal breathing, respectively, were found to be close to out-of-phase, attributed to the dominance of the blood flow modulation by paced breathing or heartbeat. Our results suggest that the real time SFDI platform may serve as one effective imaging modality for microcirculation monitoring.

Simulation and analysis on ultrasonic testing for the cement grouting defects of the corrugated pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qingbang, Han; Ling, Chen; Changping, Zhu

2014-02-18

The defects exist in the cement grouting process of prestressed corrugated pipe may directly impair the bridge safety. In this paper, sound fields propagation in concrete structures with corrugated pipes and the influence of various different defects are simulated and analyzed using finite element method. The simulation results demonstrate a much complex propagation characteristic due to multiple reflection, refraction and scattering, where the scattering signals caused by metal are very strong, while the signals scattered by an air bubble are weaker. The influence of defect both in time and frequency domain are found through deconvolution treatment. In the time domain,more » the deconvolution signals correspond to larger defect display a larger head wave amplitude and shorter arrive time than those of smaller defects; in the frequency domain, larger defect also shows a stronger amplitude, lower center frequency and lower cutoff frequency.« less

Use of the Morlet mother wavelet in the frequency-scale domain decomposition technique for the modal identification of ambient vibration responses

NASA Astrophysics Data System (ADS)

Le, Thien-Phu

2017-10-01

The frequency-scale domain decomposition technique has recently been proposed for operational modal analysis. The technique is based on the Cauchy mother wavelet. In this paper, the approach is extended to the Morlet mother wavelet, which is very popular in signal processing due to its superior time-frequency localization. Based on the regressive form and an appropriate norm of the Morlet mother wavelet, the continuous wavelet transform of the power spectral density of ambient responses enables modes in the frequency-scale domain to be highlighted. Analytical developments first demonstrate the link between modal parameters and the local maxima of the continuous wavelet transform modulus. The link formula is then used as the foundation of the proposed modal identification method. Its practical procedure, combined with the singular value decomposition algorithm, is presented step by step. The proposition is finally verified using numerical examples and a laboratory test.

Vagus nerve stimulation for 6- to 12-year-old children with refractory epilepsy: Impact on seizure frequency and parenting stress index.

PubMed

Fan, Hueng-Chuen; Hsu, Ting-Rong; Chang, Kai-Ping; Chen, Shyi-Jou; Tsai, Jeng-Dau

2018-06-01

Refractory epilepsy (RE) is frequently associated with neuropsychological impairment in children and may disrupt their social development. Vagus nerve stimulation (VNS) had been reported to have beneficial effects on behavioral outcomes. The aim of this study was to compare Parenting Stress Index (PSI) scores before and after VNS device implantation in children with RE, especially those who experienced seizure frequency reduction. We conducted a one-group pretest-posttest study in school age children with RE. Seizure frequency and PSI were recorded at 12months after VNS device implantation. Treatment with VNS was significantly associated with reduced seizure frequency and parental stress as measured by PSI. Factors contributing to seizure frequency included idiopathic/cryptogenic etiology and neurobehavioral comorbidities. In children with reduced seizure frequency, statistically significant improvements in the child domain of the PSI on the subscales of mood and reinforces parent were found. In the parent domain, the scores for social isolation were reduced. Treatment with VNS was significantly associated with reduced seizure frequency and improved PSI scores, especially within the child domain on the mood and reinforces parent subscales. These findings suggest that VNS reduced not only seizure frequency but also the psychological burden on children with RE. Copyright © 2017 Elsevier Inc. All rights reserved.

The Derivation of Simple Poles in a Transfer Function from Real Frequency Information. Part 3. Object Classification and Identification,

DTIC Science & Technology

1977-01-10

This report is the third in a series of three that evaluate a technique (frequency-domain Prony) for obtaining the poles of a transfer function. The...main objective was to assess the feasibility of classifying or identifying ship-like targets by using pole sets derived from frequency-domain data. A...predictor-correlator procedure for using spectral data and library pole sets for this purpose was developed. Also studied was an iterative method for

Universal Frequency Domain Baseband Receiver Structure for Future Military Software Defined Radios

DTIC Science & Technology

2010-09-01

selective channels, i.e., it may have a poor performance at good conditions [4]. Military systems may require a direct sequence ( DS ) component for...frequency bins using a spreading code. This is called the MC- CDMA signal. Note that spreading does not need to cover all the subcarriers but just a few, like...preambles with appropriate frequency domain properties. A DS component can be added as usually. The FDP block then includes this code as a reference

Equal vibrotactile sense thresholds of the fingers and its diagnostic significance for hand-arm vibration syndrome.

PubMed

Cheng, H; Zhang, X C; Duan, L; Ma, Y; Wang, J X

1995-01-01

The vibrotactile sense thresholds (VSTs) of the middle fingers of 60 healthy persons and 97 patients with Hand-Arm Vibration Syndrome (HAVS) or subclinical HAVS were measured quantitatively. Intermittent vibratory irritations were adopted, with vibration stimulus frequencies at 8, 16, 31.5, 63, 125, 250, and 500 Hz. The equal VST contours of the fingers were mapped. Results showed that the VSTs of the normal group were not correlated with sex or handedness. From 8 Hz to 250 Hz the equal VST contours of the normal group were relatively flat; at more than 250 Hz the contours began an abrupt ascent. The VST values had a logarithmic rising tendency with the increasing age of subjects. In the equal VST contours the frequency of the most sensitive threshold value was 125 Hz in the normal group and 8 Hz in the HAVS group. The patients' VST values were higher than that of the healthy persons. The vibrotactilegram showed that the VST values of the patient groups first shifted at high frequencies and VST loss displayed a "V"-type hollow at 125 Hz and 250 Hz. The quantitative test method of VST was a valuable auxiliary detection method for HAVS. The "V"-type hollow of VST was an early clinical manifestation of HAVS.

Cardiac Frequency and Caloric Cost of Aerobic Dancing in Young Women.

ERIC Educational Resources Information Center

Nelson, Deborah J.; And Others

1988-01-01

A study of cardiac frequency during aerobic dancing indicated that it can sustain an elevated cardiac frequency in most cases. The caloric cost of aerobic dancing is approximately 50 percent greater than an equal duration of barre and center-floor exercise by elite ballet dancers. (JD)

[Analysis of characteristics shown in self introduction letter and professor's recommendation letter].

PubMed

Kim, Sang Hyun

2013-09-01

The purpose of this study was to investigate applicants' behavioral characteristics based on the evaluation of cognitive, affective and social domain shown in self introduction letter and professor's recommendation letter. Self introduction letters and professor's recommendation letters of 109 applicants students who applied to medical school were collected. Frequency analysis and simple correlation were done in self introduction letter and professor's recommendation letter. Frequency analysis showed affective characteristics were most often mentioned in self introduction letter, and cognitive characteristics were most frequently described in professor's recommendation letter. There was a strong correlation between cognitive domains of self introduction letter and cognitive domain of professor's recommendation letter. There was a strong correlation between affective domain of self introduction letter and cognitive domain professor's recommendation letter. It is very important to make full use of self introduction letter and professor's recommendation letter for selecting medical students. Through the frequency analysis and simple correlation, more specific guidelines need to be suggested in order to secure fairness and objectivity in the evaluation of self-introduction letter and professor's recommendation letter.

Mechanical logic switches based on DNA-inspired acoustic metamaterials with ultrabroad low-frequency band gaps

NASA Astrophysics Data System (ADS)

Zheng, Bowen; Xu, Jun

2017-11-01

Mechanical information processing and control has attracted great attention in recent years. A challenging pursuit is to achieve broad functioning frequency ranges, especially at low-frequency domain. Here, we propose a design of mechanical logic switches based on DNA-inspired chiral acoustic metamaterials, which are capable of having ultrabroad band gaps at low-frequency domain. Logic operations can be easily performed by applying constraints at different locations and the functioning frequency ranges are able to be low, broad and tunable. This work may have an impact on the development of mechanical information processing, programmable materials, stress wave manipulation, as well as the isolation of noise and harmful vibration.

System and method for detection of dispersed broadband signals

DOEpatents

Qian, S.; Dunham, M.E.

1999-06-08

A system and method for detecting the presence of dispersed broadband signals in real time are disclosed. The present invention utilizes a bank of matched filters for detecting the received dispersed broadband signals. Each matched filter uses a respective robust time template that has been designed to approximate the dispersed broadband signals of interest, and each time template varies across a spectrum of possible dispersed broadband signal time templates. The received dispersed broadband signal x(t) is received by each of the matched filters, and if one or more matches occurs, then the received data is determined to have signal data of interest. This signal data can then be analyzed and/or transmitted to Earth for analysis, as desired. The system and method of the present invention will prove extremely useful in many fields, including satellite communications, plasma physics, and interstellar research. The varying time templates used in the bank of matched filters are determined as follows. The robust time domain template is assumed to take the form w(t)=A(t)cos[l brace]2[phi](t)[r brace]. Since the instantaneous frequency f(t) is known to be equal to the derivative of the phase [phi](t), the trajectory of a joint time-frequency representation of x(t) is used as an approximation of [phi][prime](t). 10 figs.

System and method for detection of dispersed broadband signals

DOEpatents

Qian, Shie; Dunham, Mark E.

1999-06-08

A system and method for detecting the presence of dispersed broadband signals in real time. The present invention utilizes a bank of matched filters for detecting the received dispersed broadband signals. Each matched filter uses a respective robust time template that has been designed to approximate the dispersed broadband signals of interest, and each time template varies across a spectrum of possible dispersed broadband signal time templates. The received dispersed broadband signal x(t) is received by each of the matched filters, and if one or more matches occurs, then the received data is determined to have signal data of interest. This signal data can then be analyzed and/or transmitted to Earth for analysis, as desired. The system and method of the present invention will prove extremely useful in many fields, including satellite communications, plasma physics, and interstellar research. The varying time templates used in the bank of matched filters are determined as follows. The robust time domain template is assumed to take the form w(t)=A(t)cos{2.phi.(t)}. Since the instantaneous frequency f(t) is known to be equal to the derivative of the phase .phi.(t), the trajectory of a joint time-frequency representation of x(t) is used as an approximation of .phi.'(t).

Quantification of MDL-induced signal degradation in MIMO-OFDM mode-division multiplexing systems.

PubMed

Tian, Yu; Li, Juhao; Zhu, Paikun; Wu, Zhongying; Chen, Yuanxiang; He, Yongqi; Chen, Zhangyuan

2016-08-22

Mode-division multiplexing (MDM) transmission over few-mode optical fiber has emerged as a promising technology to enhance transmission capacity, in which multiple-input-multiple-output (MIMO) digital signal processing (DSP) after coherent detection is used to demultiplex the signals. Compared with conventional single-mode systems, MIMO-MDM systems suffer non-recoverable signal degradation induced by mode-dependent loss (MDL). In this paper, the MDL-induced signal degradation in orthogonal-frequency-division-multiplexing (OFDM) MDM systems is theoretically quantified in terms of mode-average error vector magnitude (EVM) through frequency domain norm analysis. A novel scalar MDL metric is proposed considering the probability distribution of the practical MDM input signals, and a closed-form expression for EVM measured after zero-force (ZF) MIMO equalization is derived. Simulation results show that the EVM estimations utilizing the novel MDL metric remain unbiased for unrepeated links. For a 6 × 100 km 20-mode MDM transmission system, the estimation accuracy is improved by more than 90% compared with that utilizing traditional condition number (CN) based MDL metric. The proposed MDL metric can be used to predict the MDL-induced SNR penalty in a theoretical manner, which will be beneficial for the design of practical MIMO-MDM systems.

Terahertz plasmon-induced transparency based on asymmetric dual-disk resonators coupled to a semiconductor InSb waveguide and its biosensor application

NASA Astrophysics Data System (ADS)

Shahamat, Yadollah; Vahedi, Mohammad

2017-06-01

An ultracompact double eight-shaped plasmonic structure for the realization of plasmon-induced transparency (PIT) in the terahertz (THz) region has been studied. The device consists of a semiconductor-insulator-semiconductor bus waveguide coupled to the dual-disk resonators. Indium antimonide is employed to excite SPP in the THz region. The transmission characteristics of the proposed device are simulated numerically by the finite-difference time-domain method. In addition, a theoretical analysis based on the coupled-mode theory for transmission features is presented and compared with the numerical results. Results are in good agreement. Also, the dependence of PIT frequency characteristics on the radius of the outer disk is discussed in detail. In addition, by removing one of the outer disk resonators, double-PIT peaks can be observed in the transmission spectrum, and the physical mechanism of the appeared peaks is investigated. Finally, an application of the proposed structure for distinguishing different states of DNA molecules is discussed. Results show that the maximum sensitivity with 654 GHz/RIU-1 could be obtained for a single PIT structure. The frequency shifts equal to 37 and 99 GHz could be observed for the denatured and the hybridized DNA states, respectively.

Gender differences in public and private drinking contexts: a multi-level GENACIS analysis.

PubMed

Bond, Jason C; Roberts, Sarah C M; Greenfield, Thomas K; Korcha, Rachael; Ye, Yu; Nayak, Madhabika B

2010-05-01

This multi-national study hypothesized that higher levels of country-level gender equality would predict smaller differences in the frequency of women's compared to men's drinking in public (like bars and restaurants) settings and possibly private (home or party) settings. GENACIS project survey data with drinking contexts included 22 countries in Europe (8); the Americas (7); Asia (3); Australasia (2), and Africa (2), analyzed using hierarchical linear models (individuals nested within country). Age, gender and marital status were individual predictors; country-level gender equality as well as equality in economic participation, education, and political participation, and reproductive autonomy and context of violence against women measures were country-level variables. In separate models, more reproductive autonomy, economic participation, and educational attainment and less violence against women predicted smaller differences in drinking in public settings. Once controlling for country-level economic status, only equality in economic participation predicted the size of the gender difference. Most country-level variables did not explain the gender difference in frequency of drinking in private settings. Where gender equality predicted this difference, the direction of the findings was opposite from the direction in public settings, with more equality predicting a larger gender difference, although this relationship was no longer significant after controlling for country-level economic status. Findings suggest that country-level gender equality may influence gender differences in drinking. However, the effects of gender equality on drinking may depend on the specific alcohol measure, in this case drinking context, as well as on the aspect of gender equality considered. Similar studies that use only global measures of gender equality may miss key relationships. We consider potential implications for alcohol related consequences, policy and public health.

Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

NASA Astrophysics Data System (ADS)

Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

1995-03-01

We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

Determining mode excitations of vacuum electronics devices via three-dimensional simulations using the SOS code

NASA Technical Reports Server (NTRS)

Warren, Gary

1988-01-01

The SOS code is used to compute the resonance modes (frequency-domain information) of sample devices and separately to compute the transient behavior of the same devices. A code, DOT, is created to compute appropriate dot products of the time-domain and frequency-domain results. The transient behavior of individual modes in the device is then plotted. Modes in a coupled-cavity traveling-wave tube (CCTWT) section excited beam in separate simulations are analyzed. Mode energy vs. time and mode phase vs. time are computed and it is determined whether the transient waves are forward or backward waves for each case. Finally, the hot-test mode frequencies of the CCTWT section are computed.

Strain induced parametric pumping of a domain wall and its depinning from a notch

NASA Astrophysics Data System (ADS)

Nepal, Rabindra; Gungordu, Utkan; Kovalev, Alexey

Using Thiele's method and detailed micromagnetic simulations, we study resonant oscillation of a domain wall in a notch of a ferromagnetic nanowire due to the modulation of magnetic anisotropy by external AC strain. Such resonant oscillation results from the parametric pumping of domain wall by AC strain at frequency about double the free domain wall oscillation frequency, which is mainly determined by the perpendicular anisotropy and notch geometry. This effect leads to a substantial reduction in depinning field or current required to depin a domain wall from the notch, and offers a mechanism for efficient domain wall motion in a notched nanowire. Our theoretical model accounts for the pinning potential due to a notch by explicitly calculating ferromagnetic energy as a function of notch geometry parameters. We also find similar resonant domain wall oscillations and reduction in the domain wall depinning field or current due to surface acoustic wave in soft ferromagnetic nanowire without uniaxial anisotropy that energetically favors an in-plane domain wall. DOE Early Career Award DE-SC0014189 and DMR- 1420645.

Sound reflection by a resonator array in a multimode cylindrical waveguide

NASA Astrophysics Data System (ADS)

Lapin, A. D.

2012-09-01

The paper considers the problem of scattering of the mth symmetric mode by an array of Q rings of identical, closely located Helmholtz resonators joined by necks to the walls of a wide circular pipe. The distance between rings is equal to half the wavelength of this mode at frequency ω, equal or close to the eigen-frequency of the resonator ring with allowance for the connected mass and interaction of neighboring rings via inhomogeneous modes. The coefficient of reflection of the mth mode from this grating array is calculated.

Equality between gravitational and electromagnetic absorption cross sections of extreme Reissner-Nordstroem black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, Ednilton S.; Crispino, Luis C. B.; Higuchi, Atsushi

2011-10-15

The absorption cross section of Reissner-Nordstroem black holes for the gravitational field is computed numerically, taking into account the coupling of the electromagnetic and gravitational perturbations. Our results are in excellent agreement with low- and high-frequency approximations. We find equality between gravitational and electromagnetic absorption cross sections of extreme Reissner-Nordstroem black holes for all frequencies, which we explain analytically. This gives the first example of objects in general relativity in four dimensions that absorb the electromagnetic and gravitational waves in exactly the same way.

Digitally synthesized beat frequency-multiplexed fluorescence lifetime spectroscopy

PubMed Central

Chan, Jacky C. K.; Diebold, Eric D.; Buckley, Brandon W.; Mao, Sien; Akbari, Najva; Jalali, Bahram

2014-01-01

Frequency domain fluorescence lifetime imaging is a powerful technique that enables the observation of subtle changes in the molecular environment of a fluorescent probe. This technique works by measuring the phase delay between the optical emission and excitation of fluorophores as a function of modulation frequency. However, high-resolution measurements are time consuming, as the excitation modulation frequency must be swept, and faster low-resolution measurements at a single frequency are prone to large errors. Here, we present a low cost optical system for applications in real-time confocal lifetime imaging, which measures the phase vs. frequency spectrum without sweeping. Deemed Lifetime Imaging using Frequency-multiplexed Excitation (LIFE), this technique uses a digitally-synthesized radio frequency comb to drive an acousto-optic deflector, operated in a cat’s-eye configuration, to produce a single laser excitation beam modulated at multiple beat frequencies. We demonstrate simultaneous fluorescence lifetime measurements at 10 frequencies over a bandwidth of 48 MHz, enabling high speed frequency domain lifetime analysis of single- and multi-component sample mixtures. PMID:25574449

Instantaneous frequency based newborn EEG seizure characterisation

NASA Astrophysics Data System (ADS)

Mesbah, Mostefa; O'Toole, John M.; Colditz, Paul B.; Boashash, Boualem

2012-12-01

The electroencephalogram (EEG), used to noninvasively monitor brain activity, remains the most reliable tool in the diagnosis of neonatal seizures. Due to their nonstationary and multi-component nature, newborn EEG seizures are better represented in the joint time-frequency domain than in either the time domain or the frequency domain. Characterising newborn EEG seizure nonstationarities helps to better understand their time-varying nature and, therefore, allow developing efficient signal processing methods for both modelling and seizure detection and classification. In this article, we used the instantaneous frequency (IF) extracted from a time-frequency distribution to characterise newborn EEG seizures. We fitted four frequency modulated (FM) models to the extracted IFs, namely a linear FM, a piecewise-linear FM, a sinusoidal FM, and a hyperbolic FM. Using a database of 30-s EEG seizure epochs acquired from 35 newborns, we were able to show that, depending on EEG channel, the sinusoidal and piecewise-linear FM models best fitted 80-98% of seizure epochs. To further characterise the EEG seizures, we calculated the mean frequency and frequency span of the extracted IFs. We showed that in the majority of the cases (>95%), the mean frequency resides in the 0.6-3 Hz band with a frequency span of 0.2-1 Hz. In terms of the frequency of occurrence of the four seizure models, the statistical analysis showed that there is no significant difference( p = 0.332) between the two hemispheres. The results also indicate that there is no significant differences between the two hemispheres in terms of the mean frequency ( p = 0.186) and the frequency span ( p = 0.302).

Early Indications of Delayed Cognitive Development in Preschool Children Born Very Preterm: Evidence from Domain-General and Domain-Specific Tasks

ERIC Educational Resources Information Center

Pitchford, Nicola; Johnson, Samantha; Scerif, Gaia; Marlow, Neil

2011-01-01

Cognitive impairment often follows preterm birth but its early underlying nature is not well understood. We used a novel approach by investigating the development of colour cognition in 54 very preterm children born less than or equal to 30 weeks gestational age without severe neurosensory impairment and 37 age-matched term-born controls, aged 2-5…

All-fiber dynamic gain equalizer based on a twisted long-period grating written by high-frequency CO2 laser pulses.

PubMed

Zhu, T; Rao, Y J; Wang, J L

2007-01-20

A novel dynamic gain equalizer for flattening Er-doped fiber amplifiers based on a twisted long-period fiber grating (LPFG) induced by high-frequency CO(2) laser pulses is reported for the first time to our knowledge. Experimental results show that its transverse-load sensitivity is up to 0.34 dB/(g.mm(-1)), while the twist ratio of the twisted LPFG is approximately 20 rad/m, which is 7 times higher than that of a torsion-free LPFG. In addition, it is found that the strong orientation dependence of the transverse-load sensitivity of the torsion-free LPFG reported previously has been weakened considerably. Therefore such a dynamic gain equalizer based on the unique transverse-load characteristics of the twisted LPFG provides a much larger adjustable range and makes packaging of the gain equalizer much easier. A demonstration has been carried out to flatten an Er-doped fiber amplifier to +/-0.5 dB over a 32 nm bandwidth.

Spectral identification of topological domains

PubMed Central

Chen, Jie; Hero, Alfred O.; Rajapakse, Indika

2016-01-01

Motivation: Topological domains have been proposed as the backbone of interphase chromosome structure. They are regions of high local contact frequency separated by sharp boundaries. Genes within a domain often have correlated transcription. In this paper, we present a computational efficient spectral algorithm to identify topological domains from chromosome conformation data (Hi-C data). We consider the genome as a weighted graph with vertices defined by loci on a chromosome and the edge weights given by interaction frequency between two loci. Laplacian-based graph segmentation is then applied iteratively to obtain the domains at the given compactness level. Comparison with algorithms in the literature shows the advantage of the proposed strategy. Results: An efficient algorithm is presented to identify topological domains from the Hi-C matrix. Availability and Implementation: The Matlab source code and illustrative examples are available at http://bionetworks.ccmb.med.umich.edu/ Contact: indikar@med.umich.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27153657

The spatial unmasking of speech: evidence for within-channel processing of interaural time delay.

PubMed

Edmonds, Barrie A; Culling, John F

2005-05-01

Across-frequency processing by common interaural time delay (ITD) in spatial unmasking was investigated by measuring speech reception thresholds (SRTs) for high- and low-frequency bands of target speech presented against concurrent speech or a noise masker. Experiment 1 indicated that presenting one of these target bands with an ITD of +500 micros and the other with zero ITD (like the masker) provided some release from masking, but full binaural advantage was only measured when both target bands were given an ITD of + 500 micros. Experiment 2 showed that full binaural advantage could also be achieved when the high- and low-frequency bands were presented with ITDs of equal but opposite magnitude (+/- 500 micros). In experiment 3, the masker was also split into high- and low-frequency bands with ITDs of equal but opposite magnitude (+/-500 micros). The ITD of the low-frequency target band matched that of the high-frequency masking band and vice versa. SRTs indicated that, as long as the target and masker differed in ITD within each frequency band, full binaural advantage could be achieved. These results suggest that the mechanism underlying spatial unmasking exploits differences in ITD independently within each frequency channel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majetich, Sara

In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magneticmore » order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500 MHz), and high frequency (up to 20 GHz) regimes. Our results will demonstrate whether a DC dipolar ferromagnet shows collective frequency-dependent reponse similar to that of an exchange-based ferromagnet, and will provide data for comparison of optimal nanocomposite properties with those of ferrites used in high frequency applications. Both the magnetic and electronic response of the composites will be examined in order to determine the frequency range where hopping conductivity leads to significant eddy current power losses. In the high frequency regime we will look for evidence of spin wave quantization and the resulting decrease in non-linear spin wave processes that could affect the performance of high frequency magnetic devices.« less

On optimization of energy harvesting from base-excited vibration

NASA Astrophysics Data System (ADS)

Tai, Wei-Che; Zuo, Lei

2017-12-01

This paper re-examines and clarifies the long-believed optimization conditions of electromagnetic and piezoelectric energy harvesting from base-excited vibration. In terms of electromagnetic energy harvesting, it is typically believed that the maximum power is achieved when the excitation frequency and electrical damping equal the natural frequency and mechanical damping of the mechanical system respectively. We will show that this optimization condition is only valid when the acceleration amplitude of base excitation is constant and an approximation for small mechanical damping when the excitation displacement amplitude is constant. To this end, a two-variable optimization analysis, involving the normalized excitation frequency and electrical damping ratio, is performed to derive the exact optimization condition of each case. When the excitation displacement amplitude is constant, we analytically show that, in contrast to the long-believed optimization condition, the optimal excitation frequency and electrical damping are always larger than the natural frequency and mechanical damping ratio respectively. In particular, when the mechanical damping ratio exceeds a critical value, the optimization condition is no longer valid. Instead, the average power generally increases as the excitation frequency and electrical damping ratio increase. Furthermore, the optimization analysis is extended to consider parasitic electrical losses, which also shows different results when compared with existing literature. When the excitation acceleration amplitude is constant, on the other hand, the exact optimization condition is identical to the long-believed one. In terms of piezoelectric energy harvesting, it is commonly believed that the optimal power efficiency is achieved when the excitation and the short or open circuit frequency of the harvester are equal. Via a similar two-variable optimization analysis, we analytically show that the optimal excitation frequency depends on the mechanical damping ratio and does not equal the short or open circuit frequency. Finally, the optimal excitation frequencies and resistive loads are derived in closed-form.

Respiratory-phase domain analysis of heart rate variability can accurately estimate cardiac vagal activity during a mental arithmetic task.

PubMed

Kotani, Kiyoshi; Takamasu, Kiyoshi; Tachibana, Makoto

2007-01-01

The objectives of this paper were to present a method to extract the amplitude of RSA in the respiratory-phase domain, to compare that with subjective or objective indices of the MWL (mental workload), and to compare that with a conventional frequency analysis in terms of its accuracy during a mental arithmetic task. HRV (heart rate variability), ILV (instantaneous lung volume), and motion of the throat were measured under a mental arithmetic experiment and subjective and objective indices were also obtained. The amplitude of RSA was extracted in the respiratory-phase domain, and its correlation with the load level was compared with the results of the frequency domain analysis, which is the standard analysis of the HRV. The subjective and objective indices decreased as the load level increased, showing that the experimental protocol was appropriate. Then, the amplitude of RSA in the respiratory-phase domain also decreased with the increase in the load level. The results of the correlation analysis showed that the respiratory-phase domain analysis has higher negative correlations, -0.84 and -0.82, with the load level as determined by simple correlation and rank correlation, respectively, than does frequency analysis, for which the correlations were found to be -0.54 and -0.63, respectively. In addition, it was demonstrated that the proposed method could be applied to the short-term extraction of RSA amplitude. We proposed a simple and effective method to extract the amplitude of the respiratory sinus arrhythmia (RSA) in the respiratory-phase domain and the results show that this method can estimate cardiac vagal activity more accurately than frequency analysis.

Field-scale comparison of frequency- and time-domain spectral induced polarization

NASA Astrophysics Data System (ADS)

Maurya, P. K.; Fiandaca, G.; Christiansen, A. V.; Auken, E.

2018-05-01

In this paper we present a comparison study of the time-domain (TD) and frequency-domain (FD) spectral induced polarization (IP) methods in terms of acquisition time, data quality, and spectral information retrieved from inversion. We collected TDIP and FDIP surface measurements on three profiles with identical electrode setups, at two different field sites with different lithology. In addition, TDIP data were collected in two boreholes using the El-Log drilling technique, in which apparent formation resistivity and chargeability values are measured during drilling using electrodes integrated within the stem auger.

High-resolution frequency domain second harmonic optical coherence tomography

NASA Astrophysics Data System (ADS)

Su, Jianping; Tomov, I. V.; Jiang, Yi; Chen, Zhongping

2007-02-01

We used continuum generated in an 8.5 cm long fiber by a femtosecond Yb fiber laser to improve threefold the axial resolution of frequency domain SH-OCT to 12μm. The acquisition time was shortened by more than two orders of magnitude compared to time domain SH-OCT. The system was applied to image biological tissue of fish scales, pig leg tendon and rabbit eye sclera. Highly organized collagen fibrils can be visualized in the recorded images. Polarization dependence on second harmonic has been used to obtain polarization resolved images.

Extended-bandwidth frequency sweeps of a distributed feedback laser using combined injection current and temperature modulation

NASA Astrophysics Data System (ADS)

Hefferman, Gerald; Chen, Zhen; Wei, Tao

2017-07-01

This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.26 GHz. A digital optical phase lock loop is used to lock the frequency sweep speed during current modulation, resulting in a linear frequency chirp. In the second step, the temperature of the DFB laser is modulated, resulting in a shifted starting laser output frequency. A laser frequency chirp is again generated beginning at this shifted starting frequency, resulting in a frequency-shifted spectrum relative to the first recorded data. This process is then repeated across a range of starting temperatures, resulting in a series of partially overlapping, frequency-shifted spectra. These spectra are then aligned using cross-correlation and combined using averaging to form a single, broadband spectrum with a total bandwidth of 510.9 GHz. In order to investigate the utility of this technique, experimental testing was performed in which the approach was used as the swept-frequency source of a coherent optical frequency domain reflectometry system. This system was used to interrogate an optical fiber containing a 20 point, 1-mm pitch length fiber Bragg grating, corresponding to a period of 100 GHz. Using this technique, both the periodicity of the grating in the frequency domain and the individual reflector elements of the structure in the time domain were resolved, demonstrating the technique's potential as a method of extending the sweeping bandwidth of semiconductor lasers for frequency-based sensing applications.

Extended-bandwidth frequency sweeps of a distributed feedback laser using combined injection current and temperature modulation.

PubMed

Hefferman, Gerald; Chen, Zhen; Wei, Tao

2017-07-01

This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.26 GHz. A digital optical phase lock loop is used to lock the frequency sweep speed during current modulation, resulting in a linear frequency chirp. In the second step, the temperature of the DFB laser is modulated, resulting in a shifted starting laser output frequency. A laser frequency chirp is again generated beginning at this shifted starting frequency, resulting in a frequency-shifted spectrum relative to the first recorded data. This process is then repeated across a range of starting temperatures, resulting in a series of partially overlapping, frequency-shifted spectra. These spectra are then aligned using cross-correlation and combined using averaging to form a single, broadband spectrum with a total bandwidth of 510.9 GHz. In order to investigate the utility of this technique, experimental testing was performed in which the approach was used as the swept-frequency source of a coherent optical frequency domain reflectometry system. This system was used to interrogate an optical fiber containing a 20 point, 1-mm pitch length fiber Bragg grating, corresponding to a period of 100 GHz. Using this technique, both the periodicity of the grating in the frequency domain and the individual reflector elements of the structure in the time domain were resolved, demonstrating the technique's potential as a method of extending the sweeping bandwidth of semiconductor lasers for frequency-based sensing applications.

Phase-space topography characterization of nonlinear ultrasound waveforms.

PubMed

Dehghan-Niri, Ehsan; Al-Beer, Helem

2018-03-01

Fundamental understanding of ultrasound interaction with material discontinuities having closed interfaces has many engineering applications such as nondestructive evaluation of defects like kissing bonds and cracks in critical structural and mechanical components. In this paper, to analyze the acoustic field nonlinearities due to defects with closed interfaces, the use of a common technique in nonlinear physics, based on a phase-space topography construction of ultrasound waveform, is proposed. The central idea is to complement the "time" and "frequency" domain analyses with the "phase-space" domain analysis of nonlinear ultrasound waveforms. A nonlinear time series method known as pseudo phase-space topography construction is used to construct equivalent phase-space portrait of measured ultrasound waveforms. Several nonlinear models are considered to numerically simulate nonlinear ultrasound waveforms. The phase-space response of the simulated waveforms is shown to provide different topographic information, while the frequency domain shows similar spectral behavior. Thus, model classification can be substantially enhanced in the phase-space domain. Experimental results on high strength aluminum samples show that the phase-space transformation provides a unique detection and classification capabilities. The Poincaré map of the phase-space domain is also used to better understand the nonlinear behavior of ultrasound waveforms. It is shown that the analysis of ultrasound nonlinearities is more convenient and informative in the phase-space domain than in the frequency domain. Copyright © 2017 Elsevier B.V. All rights reserved.

Study on the description method of upper limb's muscle force levels during simulated in-orbit operations

NASA Astrophysics Data System (ADS)

Zhao, Yan; Li, DongXu; Liu, ZhiZhen; Liu, Liang

2013-03-01

The dexterous upper limb serves as the most important tool for astronauts to implement in-orbit experiments and operations. This study developed a simulated weightlessness experiment and invented new measuring equipment to quantitatively evaluate the muscle ability of the upper limb. Isometric maximum voluntary contractions (MVCs) and surface electromyography (sEMG) signals of right-handed pushing at the three positions were measured for eleven subjects. In order to enhance the comprehensiveness and accuracy of muscle force assessment, the study focused on signal processing techniques. We applied a combination method, which consists of time-, frequency-, and bi-frequency-domain analyses. Time- and frequency-domain analyses estimated the root mean square (RMS) and median frequency (MDF) of sEMG signals, respectively. Higher order spectra (HOS) of bi-frequency domain evaluated the maximum bispectrum amplitude ( B max), Gaussianity level (Sg) and linearity level (S l ) of sEMG signals. Results showed that B max, S l , and RMS values all increased as force increased. MDF and Sg values both declined as force increased. The research demonstrated that the combination method is superior to the conventional time- and frequency-domain analyses. The method not only described sEMG signal amplitude and power spectrum, but also deeper characterized phase coupling information and non-Gaussianity and non-linearity levels of sEMG, compared to two conventional analyses. The finding from the study can aid ergonomist to estimate astronaut muscle performance, so as to optimize in-orbit operation efficacy and minimize musculoskeletal injuries.

Magnetoresistance and noise properties of chevron stretcher detectors for field access bubble domain devices

NASA Technical Reports Server (NTRS)

George, P. K.; Oeffinger, T. R.; Chen, T. T.

1976-01-01

Experiments were devised to study the angular variation of the resistance and noise properties of one- and two-level chevron stretcher magnetoresistive detectors for use in field access bubble memory devices. All measurements, made with an electronic system, were performed on glass or garnet samples upon which 1 micron of SiO2 was sputter-deposited, followed by 4000 A of Permalloy for the 28-micron-period devices and 0.8 microns of SiO2, followed by 3000 A of Permalloy for the 20-micron-period devices. The geometrical and drive-state dependence of the zero-state noise were studied, as was its frequency dependence. It is found that both types of detectors operate primarily in the amplitude-shift mode for drive fields of interest and that the presence of a bubble in a detector causes a magnetoresistance change equal to that produced by increasing the in-plane drive field about 8 Oe in the absence of a bubble.

Tuning subwavelength-structured focus in the hyperbolic metamaterials

NASA Astrophysics Data System (ADS)

Pan, Rong; Tang, Zhixiang; Pan, Jin; Peng, Runwu

2016-10-01

In this paper, we have systematically investigated light propagating in the hyperbolic metamaterials (HMMs) covered by a subwavelength grating. Based on the equal-frequency contour analyses, light in the HMM is predicted to propagate along a defined direction because of its hyperbolic dispersion, which is similar to the self-collimating effects in photonic crystals. By using the finite-difference time-domain, numerical simulations demonstrate a subwavelength bright spot at the intersection of the adjacent directional beams. Different from the images in homogeneous media, the magnetic fields and electric fields at the spot are layered, especially for the electric fields Ez that is polarized to the propagating direction, i.e., the layer normal direction. Moreover, the Ez is hollow in the layer plane and is stronger than the other electric field component Ex. Therefore, the whole electric field is structured and its pattern can be tuned by the HMM's effective anisotropic electromagnetic parameters. Our results may be useful for generating subwavelength structured light.

Experimental demonstration of non-iterative interpolation-based partial ICI compensation in100G RGI-DP-CO-OFDM transport systems.

PubMed

Mousa-Pasandi, Mohammad E; Zhuge, Qunbi; Xu, Xian; Osman, Mohamed M; El-Sahn, Ziad A; Chagnon, Mathieu; Plant, David V

2012-07-02

We experimentally investigate the performance of a low-complexity non-iterative phase noise induced inter-carrier interference (ICI) compensation algorithm in reduced-guard-interval dual-polarization coherent-optical orthogonal-frequency-division-multiplexing (RGI-DP-CO-OFDM) transport systems. This interpolation-based ICI compensator estimates the time-domain phase noise samples by a linear interpolation between the CPE estimates of the consecutive OFDM symbols. We experimentally study the performance of this scheme for a 28 Gbaud QPSK RGI-DP-CO-OFDM employing a low cost distributed feedback (DFB) laser. Experimental results using a DFB laser with the linewidth of 2.6 MHz demonstrate 24% and 13% improvement in transmission reach with respect to the conventional equalizer (CE) in presence of weak and strong dispersion-enhanced-phase-noise (DEPN), respectively. A brief analysis of the computational complexity of this scheme in terms of the number of required complex multiplications is provided. This practical approach does not suffer from error propagation while enjoying low computational complexity.

Discrete Walsh Hadamard transform based visible watermarking technique for digital color images

NASA Astrophysics Data System (ADS)

Santhi, V.; Thangavelu, Arunkumar

2011-10-01

As the size of the Internet is growing enormously the illegal manipulation of digital multimedia data become very easy with the advancement in technology tools. In order to protect those multimedia data from unauthorized access the digital watermarking system is used. In this paper a new Discrete walsh Hadamard Transform based visible watermarking system is proposed. As the watermark is embedded in transform domain, the system is robust to many signal processing attacks. Moreover in this proposed method the watermark is embedded in tiling manner in all the range of frequencies to make it robust to compression and cropping attack. The robustness of the algorithm is tested against noise addition, cropping, compression, Histogram equalization and resizing attacks. The experimental results show that the algorithm is robust to common signal processing attacks and the observed peak signal to noise ratio (PSNR) of watermarked image is varying from 20 to 30 db depends on the size of the watermark.

Uniqueness of boundary blow-up solutions on exterior domain of RN

NASA Astrophysics Data System (ADS)

Dong, Wei; Pang, Changci

2007-06-01

In this paper, we consider the existence and uniqueness of positive solutions of the degenerate logistic type elliptic equation where N[greater-or-equal, slanted]2, D[subset of]RN is a bounded domain with smooth boundary and a(x), b(x) are continuous functions on RN with b(x)[greater-or-equal, slanted]0, b(x)[not identical with]0. We show that under rather general conditions on a(x) and b(x) for large x, there exists a unique positive solution. Our results improve the corresponding ones in [W. Dong, Y. Du, Unbounded principal eigenfunctions and the logistic equation on RN, Bull. Austral. Math. Soc. 67 (2003) 413-427] and [Y. Du, L. Ma, Logistic type equations on RN by a squeezing method involving boundary blow-up solutions, J. London Math. Soc. (2) 64 (2001) 107-124].

Equalizer design techniques for dispersive cables with application to the SPS wideband kicker

NASA Astrophysics Data System (ADS)

Platt, Jason; Hofle, Wolfgang; Pollock, Kristin; Fox, John

2017-10-01

A wide-band vertical instability feedback control system in development at CERN requires 1-1.5 GHz of bandwidth for the entire processing chain, from the beam pickups through the feedback signal digital processing to the back-end power amplifiers and kicker structures. Dispersive effects in cables, amplifiers, pickup and kicker elements can result in distortions in the time domain signal as it proceeds through the processing system, and deviations from linear phase response reduce the allowable bandwidth for the closed-loop feedback system. We have developed an equalizer analog circuit that compensates for these dispersive effects. Here we present a design technique for the construction of an analog equalizer that incorporates the effect of parasitic circuit elements in the equalizer to increase the fidelity of the implemented equalizer. Finally, we show results from the measurement of an assembled backend equalizer that corrects for dispersive elements in the cables over a bandwidth of 10-1000 MHz.

Quantified Energy Dissipation Rates in the Terrestrial Bow Shock. 2; Waves and Dissipation

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Sibeck, D. G.; Breneman, A. W.; Le Contel, O.; Cully, C.; Turner, D. L.; Angelopoulos, V.; Malaspina, D. M.

2014-01-01

We present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collision-less bow shock using data from the Time History of Events and Macro-Scale Interactions during Sub-Storms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collision-less shocks. In every bow shock crossing examined, we observed both low-frequency (less than 10 hertz) and high-frequency (approximately or greater than10 hertz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding delta B approximately equal to 10 nanoteslas and delta E approximately equal to 300 millivolts per meter, though more typical values were delta B approximately equal to 0.1-1.0 nanoteslas and delta E approximately equal to 10-50 millivolts per meter (2) Poynting fluxes in excess of 2000 microWm(sup -2) (micro-waves per square meter) (typical values were approximately 1-10 microWm(sup -2) (micro-waves per square meter); (3) resistivities greater than 9000 omega meters; and (4) associated energy dissipation rates greater than 10 microWm(sup -3) (micro-waves per cubic meter). The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for approximately 90 percent of the wave burst durations. For approximately 22 percent of these times, the wave-particle interactions needed to only be less than or equal to 0.1 percent efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collision-less shocks.

The Importance of the Cathode Plume and Its Interactions with the Ion Beam in Numerical Simulations of Hall Thrusters

NASA Technical Reports Server (NTRS)

Lopez Ortega, Alejandro; Mikellides, Ioannis G.

2015-01-01

Hall2De is a first-principles, 2-D axisymmetric code that solves the equations of motion for ions, electrons, and neutrals on a magnetic-field-aligned grid. The computational domain downstream of the acceleration channel exit plane is large enough to include self-consistently the cathode boundary. In this paper, we present results from numerical simulations of the H6 laboratory thruster with an internally mounted cathode, with the aim of highlighting the importance of properly accounting for the interactions between the ion beam and cathode plume. The anomalous transport of electrons across magnetic field lines in Hall2De is modelled using an anomalous collision frequency, ?anom, yielding ?anom approximately equal to omega ce (i.e., the electron cyclotron frequency) in the plume. We first show that restricting the anomalous collision frequency to only regions where the current density of ions is large does not alter the plasma discharge in the Hall thruster as long as the interaction between the ion beam and the cathode plume is captured properly in the computational domain. This implies that the boundary conditions must be placed sufficiently far as to not interfere with the electron transport in this region. These simulation results suggest that electron transport across magnetic field lines occurs largely inside the beam and may be driven by the interactions between beam ions and electrons. A second finding that puts in relevance the importance of including the cathode plume in numerical simulations is on the significance of accounting for the ion acoustic turbulence (IAT), now known to occur in the vicinity of the cathode exit. We have included in the Hall2De simulations a model of the IAT-driven anomalous collision frequency based on Sagdeev's model for saturation of the ion-acoustic instability. This implementation has allowed us to achieve excellent agreement with experimental measurements in the near plume obtained during the operation of the H6 thruster at nominal conditions (300V, 20A) and chamber background pressure of approximately 1.5 x 10(exp -5) Torr. In addition, the numerical results obtained with the latter approach exhibit less sensitivity to background pressure than previous attempts at explaining the features of the plasma properties in the near plume.

Postural Analysis in Time and Frequency Domains in Patients with Ehlers-Danlos Syndrome

ERIC Educational Resources Information Center

Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo

2011-01-01

The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30 s in two conditions: open eyes (OE) and closed…

Aircraft interior noise reduction by alternate resonance tuning

NASA Technical Reports Server (NTRS)

Bliss, Donald B.; Gottwald, James A.; Srinivasan, Ramakrishna; Gustaveson, Mark B.

1990-01-01

Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower frequencies, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselage lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cutoff, and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations.

Frequency Domain Beamforming for a Deep Space Network Downlink Array

NASA Technical Reports Server (NTRS)

Navarro, Robert

2012-01-01

This paper describes a frequency domain beamformer to array up to 8 antennas of NASA's Deep Space Network currently in development. The objective of this array is to replace and enhance the capability of the DSN 70m antennas with multiple 34m antennas for telemetry, navigation and radio science use. The array will coherently combine the entire 500 MHz of usable bandwidth available to DSN receivers. A frequency domain beamforming architecture was chosen over a time domain based architecture to handle the large signal bandwidth and efficiently perform delay and phase calibration. The antennas of the DSN are spaced far enough apart that random atmospheric and phase variations between antennas need to be calibrated out on an ongoing basis in real-time. The calibration is done using measurements obtained from a correlator. This DSN Downlink Array expands upon a proof of concept breadboard array built previously to develop the technology and will become an operational asset of the Deep Space Network. Design parameters for frequency channelization, array calibration and delay corrections will be presented as well a method to efficiently calibrate the array for both wide and narrow bandwidth telemetry.

Visualization of evolving laser-generated structures by frequency domain tomography

NASA Astrophysics Data System (ADS)

Chang, Yenyu; Li, Zhengyan; Wang, Xiaoming; Zgadzaj, Rafal; Downer, Michael

2011-10-01

We introduce frequency domain tomography (FDT) for single-shot visualization of time-evolving refractive index structures (e.g. laser wakefields, nonlinear index structures) moving at light-speed. Previous researchers demonstrated single-shot frequency domain holography (FDH), in which a probe-reference pulse pair co- propagates with the laser-generated structure, to obtain snapshot-like images. However, in FDH, information about the structure's evolution is averaged. To visualize an evolving structure, we use several frequency domain streak cameras (FDSCs), in each of which a probe-reference pulse pair propagates at an angle to the propagation direction of the laser-generated structure. The combination of several FDSCs constitutes the FDT system. We will present experimental results for a 4-probe FDT system that has imaged the whole-beam self-focusing of a pump pulse propagating through glass in a single laser shot. Combining temporal and angle multiplexing methods, we successfully processed data from four probe pulses in one spectrometer in a single-shot. The output of data processing is a multi-frame movie of the self- focusing pulse. Our results promise the possibility of visualizing evolving laser wakefield structures that underlie laser-plasma accelerators used for multi-GeV electron acceleration.