Association of auricular pressing and heart rate variability in pre-exam anxiety students

PubMed Central

Wu, Wocao; Chen, Junqi; Zhen, Erchuan; Huang, Huanlin; Zhang, Pei; Wang, Jiao; Ou, Yingyi; Huang, Yong

2013-01-01

A total of 30 students scoring between 12 and 20 on the Test Anxiety Scale who had been exhibiting an anxious state > 24 hours, and 30 normal control students were recruited. Indices of heart rate variability were recorded using an Actiheart electrocardiogram recorder at 10 minutes before auricular pressing, in the first half of stimulation and in the second half of stimulation. The results revealed that the standard deviation of all normal to normal intervals and the root mean square of standard deviation of normal to normal intervals were significantly increased after stimulation. The heart rate variability triangular index, very-low-frequency power, low-frequency power, and the ratio of low-frequency to high-frequency power were increased to different degrees after stimulation. Compared with normal controls, the root mean square of standard deviation of normal to normal intervals was significantly increased in anxious students following auricular pressing. These results indicated that auricular pressing can elevate heart rate variability, especially the root mean square of standard deviation of normal to normal intervals in students with pre-exam anxiety. PMID:25206734

Amplification of a high-frequency electromagnetic wave by a relativistic plasma

NASA Technical Reports Server (NTRS)

Yoon, Peter H.

1990-01-01

The amplification of a high-frequency transverse electromagnetic wave by a relativistic plasma component, via the synchrotron maser process, is studied. The background plasma that supports the transverse wave is considered to be cold, and the energetic component whose density is much smaller than that of the background component has a loss-cone feature in the perpendicular momentum space and a finite field-aligned drift speed. The ratio of the background plasma frequency squared to the electron gyrofrequency squared is taken to be sufficiently larger than unity. Such a parameter regime is relevant to many space and astrophysical situations. A detailed study of the amplification process is carried out over a wide range of physical parameters including the loss-cone index, the ratio of the electron mass energy to the temperature of the energetic component, the field-aligned drift speed, the normalized density, and the wave propagation angle.

Reduced impedance and superconductivity of SnAgCu solder alloy at high frequency

NASA Astrophysics Data System (ADS)

Yao, Wei; Basaran, Cemal

2012-10-01

Skin effect of lead-free solder joints is investigated over a wide frequency band. Contrary to common believe that `effective impedance of solder alloys increases with frequency', resistance tends to saturate when frequency reaches a critical value, 10 MHz for SAC solder alloys. Negative surface impedance growth rate is observed when employs square waveform AC current loading at high current density. Further increased frequency causes a dramatic reduction of effective resistance. At 11 MHz with current density of 106 A/cm2, effective resistance of solder alloy drops to near zero value.

Modeling and Simulation of Linear and Nonlinear MEMS Scale Electromagnetic Energy Harvesters for Random Vibration Environments

PubMed Central

Sassani, Farrokh

2014-01-01

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency. PMID:24605063

Terahertz emission from thermally-managed square intrinsic Josephson junction microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard; Davis, Andrew; Wang, Qing

We show for thin square microstrip antennas that the transverse magnetic electromagnetic cavity modes are greatly restricted in number due to the point group symmetry of a square. For the ten lowest frequency emissions, we present plots of the orthonormal wave functions and of the angular distributions of the emission power obtained from the uniform Josephson current source and from the excitation of an electromagnetic cavity mode excited in the intrinsic Josephson junctions between the layers of a highly anisotropic layered superconductor.

UHF Microstrip Antenna Array for Synthetic- Aperture Radar

NASA Technical Reports Server (NTRS)

Thomas, Robert F.; Huang, John

2003-01-01

An ultra-high-frequency microstrippatch antenna has been built for use in airborne synthetic-aperture radar (SAR). The antenna design satisfies requirements specific to the GeoSAR program, which is dedicated to the development of a terrain-mapping SAR system that can provide information on geology, seismicity, vegetation, and other terrain-related topics. One of the requirements is for ultra-wide-band performance: the antenna must be capable of operating with dual linear polarization in the frequency range of 350 plus or minus 80 MHz, with a peak gain of 10 dB at the middle frequency of 350 MHz and a gain of at least 8 dB at the upper and lower ends (270 and 430 MHz) of the band. Another requirement is compactness: the antenna must fit in the wingtip pod of a Gulfstream II airplane. The antenna includes a linear array of microstrip-patch radiating elements supported over square cavities. Each patch is square (except for small corner cuts) and has a small square hole at its center.

Modelling the dependence of contrast sensitivity on grating area and spatial frequency.

PubMed

Rovamo, J; Luntinen, O; Näsänen, R

1993-12-01

We modelled the human foveal visual system in a detection task as a simple image processor comprising (i) low-pass filtering due to the optical transfer function of the eye, (ii) high-pass filtering of neural origin, (iii) addition of internal neural noise, and (iv) detection by a local matched filter. Its detection efficiency for gratings was constant up to a critical area but then decreased with increasing area. To test the model we measured Michelson contrast sensitivity as a function of grating area at spatial frequencies of 0.125-32 c/deg for simple vertical and circular cosine gratings. In circular gratings luminance was sinusoidally modulated as a function of the radius of the grating field. In agreement with the model, contrast sensitivity at all spatial frequencies increased in proportion to the square-root of grating area at small areas. When grating area exceeded critical area, the increase saturated and contrast sensitivity became independent of area at large grating areas. Spatial integration thus obeyed Piper's law at small grating areas. The critical area of spatial integration, marking the cessation of Piper's law, was constant in solid degrees at low spatial frequencies but inversely proportional to spatial frequency squared at medium and high spatial frequencies. At low spatial frequencies the maximum contrast sensitivity obtainable by spatial integration increased in proportion to spatial frequency but at high spatial frequencies it decreased in proportion to the cube of the increasing spatial frequency. The increase was due to high-pass filtering of neural origin (lateral inhibition) and the decrease was mainly due to the optical transfer function of the eye. Our model explained 95% of the total variance of the contrast sensitivity data.

Reconfigurable Wideband Circularly Polarized Stacked Square Patch Antenna for Cognitive Radios

NASA Technical Reports Server (NTRS)

Barbosa Kortright, Miguel A.; Waldstein, Seth W.; Simons, Rainee N.

2017-01-01

An almost square patch, a square patch and a stacked square patch with corner truncation for circular polarization (CP) are researched and developed at X-band for cognitive radios. Experimental results indicate, first, that the impedance bandwidth of a CP almost square patch fed from the edge by a 50 ohm line is 1.70% and second, that of a CP square patch fed from the ground plane side by a surface launch connector is 1.87%. Third, the impedance bandwidth of a CP stacked square patch fed by a surface launch connector is 2.22%. The measured center frequency for the CP square patch fed by a surface launch connector without and with an identical stacked patch is 8.45 and 8.1017 GHz, respectively. By stacking a patch, separated by a fixed air gap of 0.254 mm, the center frequency is observed to shift by as much as 348.3 MHz. The shift in center frequency, brought about by the reconfiguring of the physical layer antenna, can be exploited in a cognitive system since it expands the usable frequency spectrum for software reconfiguration in the presence of interference. In addition, varying the fixed air gap in the stacked antenna geometry by increments of 0.254 mm further expands the usable frequency spectrum.

Joint Entropy for Space and Spatial Frequency Domains Estimated from Psychometric Functions of Achromatic Discrimination

PubMed Central

Silveira, Vladímir de Aquino; Souza, Givago da Silva; Gomes, Bruno Duarte; Rodrigues, Anderson Raiol; Silveira, Luiz Carlos de Lima

2014-01-01

We used psychometric functions to estimate the joint entropy for space discrimination and spatial frequency discrimination. Space discrimination was taken as discrimination of spatial extent. Seven subjects were tested. Gábor functions comprising unidimensionalsinusoidal gratings (0.4, 2, and 10 cpd) and bidimensionalGaussian envelopes (1°) were used as reference stimuli. The experiment comprised the comparison between reference and test stimulithat differed in grating's spatial frequency or envelope's standard deviation. We tested 21 different envelope's standard deviations around the reference standard deviation to study spatial extent discrimination and 19 different grating's spatial frequencies around the reference spatial frequency to study spatial frequency discrimination. Two series of psychometric functions were obtained for 2%, 5%, 10%, and 100% stimulus contrast. The psychometric function data points for spatial extent discrimination or spatial frequency discrimination were fitted with Gaussian functions using the least square method, and the spatial extent and spatial frequency entropies were estimated from the standard deviation of these Gaussian functions. Then, joint entropy was obtained by multiplying the square root of space extent entropy times the spatial frequency entropy. We compared our results to the theoretical minimum for unidimensional Gábor functions, 1/4π or 0.0796. At low and intermediate spatial frequencies and high contrasts, joint entropy reached levels below the theoretical minimum, suggesting non-linear interactions between two or more visual mechanisms. We concluded that non-linear interactions of visual pathways, such as the M and P pathways, could explain joint entropy values below the theoretical minimum at low and intermediate spatial frequencies and high contrasts. These non-linear interactions might be at work at intermediate and high contrasts at all spatial frequencies once there was a substantial decrease in joint entropy for these stimulus conditions when contrast was raised. PMID:24466158

Joint entropy for space and spatial frequency domains estimated from psychometric functions of achromatic discrimination.

PubMed

Silveira, Vladímir de Aquino; Souza, Givago da Silva; Gomes, Bruno Duarte; Rodrigues, Anderson Raiol; Silveira, Luiz Carlos de Lima

2014-01-01

We used psychometric functions to estimate the joint entropy for space discrimination and spatial frequency discrimination. Space discrimination was taken as discrimination of spatial extent. Seven subjects were tested. Gábor functions comprising unidimensionalsinusoidal gratings (0.4, 2, and 10 cpd) and bidimensionalGaussian envelopes (1°) were used as reference stimuli. The experiment comprised the comparison between reference and test stimulithat differed in grating's spatial frequency or envelope's standard deviation. We tested 21 different envelope's standard deviations around the reference standard deviation to study spatial extent discrimination and 19 different grating's spatial frequencies around the reference spatial frequency to study spatial frequency discrimination. Two series of psychometric functions were obtained for 2%, 5%, 10%, and 100% stimulus contrast. The psychometric function data points for spatial extent discrimination or spatial frequency discrimination were fitted with Gaussian functions using the least square method, and the spatial extent and spatial frequency entropies were estimated from the standard deviation of these Gaussian functions. Then, joint entropy was obtained by multiplying the square root of space extent entropy times the spatial frequency entropy. We compared our results to the theoretical minimum for unidimensional Gábor functions, 1/4π or 0.0796. At low and intermediate spatial frequencies and high contrasts, joint entropy reached levels below the theoretical minimum, suggesting non-linear interactions between two or more visual mechanisms. We concluded that non-linear interactions of visual pathways, such as the M and P pathways, could explain joint entropy values below the theoretical minimum at low and intermediate spatial frequencies and high contrasts. These non-linear interactions might be at work at intermediate and high contrasts at all spatial frequencies once there was a substantial decrease in joint entropy for these stimulus conditions when contrast was raised.

Multistage estimation of received carrier signal parameters under very high dynamic conditions of the receiver

NASA Technical Reports Server (NTRS)

Kumar, Rajendra (Inventor)

1991-01-01

A multistage estimator is provided for the parameters of a received carrier signal possibly phase-modulated by unknown data and experiencing very high Doppler, Doppler rate, etc., as may arise, for example, in the case of Global Positioning Systems (GPS) where the signal parameters are directly related to the position, velocity and jerk of the GPS ground-based receiver. In a two-stage embodiment of the more general multistage scheme, the first stage, selected to be a modified least squares algorithm referred to as differential least squares (DLS), operates as a coarse estimator resulting in higher rms estimation errors but with a relatively small probability of the frequency estimation error exceeding one-half of the sampling frequency, provides relatively coarse estimates of the frequency and its derivatives. The second stage of the estimator, an extended Kalman filter (EKF), operates on the error signal available from the first stage refining the overall estimates of the phase along with a more refined estimate of frequency as well and in the process also reduces the number of cycle slips.

Multistage estimation of received carrier signal parameters under very high dynamic conditions of the receiver

NASA Technical Reports Server (NTRS)

Kumar, Rajendra (Inventor)

1990-01-01

A multistage estimator is provided for the parameters of a received carrier signal possibly phase-modulated by unknown data and experiencing very high Doppler, Doppler rate, etc., as may arise, for example, in the case of Global Positioning Systems (GPS) where the signal parameters are directly related to the position, velocity and jerk of the GPS ground-based receiver. In a two-stage embodiment of the more general multistage scheme, the first stage, selected to be a modified least squares algorithm referred to as differential least squares (DLS), operates as a coarse estimator resulting in higher rms estimation errors but with a relatively small probability of the frequency estimation error exceeding one-half of the sampling frequency, provides relatively coarse estimates of the frequency and its derivatives. The second stage of the estimator, an extended Kalman filter (EKF), operates on the error signal available from the first stage refining the overall estimates of the phase along with a more refined estimate of frequency as well and in the process also reduces the number of cycle slips.

A Noise Level Prediction Method Based on Electro-Mechanical Frequency Response Function for Capacitors

PubMed Central

Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

2013-01-01

The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective. PMID:24349105

A noise level prediction method based on electro-mechanical frequency response function for capacitors.

PubMed

Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

2013-01-01

The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

Reconfigurable Wideband Circularly Polarized Stacked Square Patch Antenna for Cognitive Radios

NASA Technical Reports Server (NTRS)

Barbosa Kortright, Miguel A.; Waldstein, Seth W.; Simons, Rainee N.

2017-01-01

An almost square patch, a square patch and a stacked square patch with corner truncation for circular polarization (CP) are researched and developed at X-band for cognitive radios. Experimental results indicate, first, that the impedance bandwidth of a CP almost square patch fed from the edge by a 50 ohm line is 1.70 percent and second, that of a CP square patch fed from the ground plane side by a surface launch connector is 1.87 percent. Third, the impedance bandwidth of a CP stacked square patch fed by a surface launch connector is 2.22 percent. The measured center frequency for the CP square patch fed by a surface launch connector without and with an identical stacked patch is 8.45 and 8.1017 GHz, respectively. By stacking a patch, separated by a fixed air gap of 0.254 mm, the center frequency is observed to shift by as much as 348.3 MHz. The shift in the center frequency can be exploited to reconfigure the operating frequency by mechanically increasing the air gap. The results indicate that a tuning bandwidth of about 100 MHz can be achieved when the distance of separation between the driven patch and the stacked patch is increased from its initial setting of 0.254 to 1.016 mm.

High frequency pressure oscillator for microcryocoolers.

PubMed

Vanapalli, S; ter Brake, H J M; Jansen, H V; Zhao, Y; Holland, H J; Burger, J F; Elwenspoek, M C

2008-04-01

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm(3) when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

High frequency pressure oscillator for microcryocoolers

NASA Astrophysics Data System (ADS)

Vanapalli, S.; ter Brake, H. J. M.; Jansen, H. V.; Zhao, Y.; Holland, H. J.; Burger, J. F.; Elwenspoek, M. C.

2008-04-01

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80K, delivering a cooling power of 10mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5MPa and compression volume of about 22.6mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100V at a frequency of 1kHz. The electrical power input was 2.73W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

Real-time, high frequency QRS electrocardiograph

NASA Technical Reports Server (NTRS)

Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

2006-01-01

Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as RAZs. RAZs are displayed as go, no-go signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

Online Detection of Broken Rotor Bar Fault in Induction Motors by Combining Estimation of Signal Parameters via Min-norm Algorithm and Least Square Method

NASA Astrophysics Data System (ADS)

Wang, Pan-Pan; Yu, Qiang; Hu, Yong-Jun; Miao, Chang-Xin

2017-11-01

Current research in broken rotor bar (BRB) fault detection in induction motors is primarily focused on a high-frequency resolution analysis of the stator current. Compared with a discrete Fourier transformation, the parametric spectrum estimation technique has a higher frequency accuracy and resolution. However, the existing detection methods based on parametric spectrum estimation cannot realize online detection, owing to the large computational cost. To improve the efficiency of BRB fault detection, a new detection method based on the min-norm algorithm and least square estimation is proposed in this paper. First, the stator current is filtered using a band-pass filter and divided into short overlapped data windows. The min-norm algorithm is then applied to determine the frequencies of the fundamental and fault characteristic components with each overlapped data window. Next, based on the frequency values obtained, a model of the fault current signal is constructed. Subsequently, a linear least squares problem solved through singular value decomposition is designed to estimate the amplitudes and phases of the related components. Finally, the proposed method is applied to a simulated current and an actual motor, the results of which indicate that, not only parametric spectrum estimation technique.

Pattern masking: the importance of remote spatial frequencies and their phase alignment.

PubMed

Huang, Pi-Chun; Maehara, Goro; May, Keith A; Hess, Robert F

2012-02-16

To assess the effects of spatial frequency and phase alignment of mask components in pattern masking, target threshold vs. mask contrast (TvC) functions for a sine-wave grating (S) target were measured for five types of mask: a sine-wave grating (S), a square-wave grating (Q), a missing fundamental square-wave grating (M), harmonic complexes consisting of phase-scrambled harmonics of a square wave (Qp), and harmonic complexes consisting of phase-scrambled harmonics of a missing fundamental square wave (Mp). Target and masks had the same fundamental frequency (0.46 cpd) and the target was added in phase with the fundamental frequency component of the mask. Under monocular viewing conditions, the strength of masking depends on phase relationships among mask spatial frequencies far removed from that of the target, at least 3 times the target frequency, only when there are common target and mask spatial frequencies. Under dichoptic viewing conditions, S and Q masks produced similar masking to each other and the phase-scrambled masks (Qp and Mp) produced less masking. The results suggest that pattern masking is spatial frequency broadband in nature and sensitive to the phase alignments of spatial components.

Dual-sensitivity profilometry with defocused projection of binary fringes.

PubMed

Garnica, G; Padilla, M; Servin, M

2017-10-01

A dual-sensitivity profilometry technique based on defocused projection of binary fringes is presented. Here, two sets of fringe patterns with a sinusoidal profile are produced by applying the same analog low-pass filter (projector defocusing) to binary fringes with a high- and low-frequency spatial carrier. The high-frequency fringes have a binary square-wave profile, while the low-frequency binary fringes are produced with error-diffusion dithering. The binary nature of the binary fringes removes the need for calibration of the projector's nonlinear gamma. Working with high-frequency carrier fringes, we obtain a high-quality wrapped phase. On the other hand, working with low-frequency carrier fringes we found a lower-quality, nonwrapped phase map. The nonwrapped estimation is used as stepping stone for dual-sensitivity temporal phase unwrapping, extending the applicability of the technique to discontinuous (piecewise continuous) surfaces. We are proposing a single defocusing level for faster high- and low-frequency fringe data acquisition. The proposed technique is validated with experimental results.

Synchronized vortex shedding and sound radiation from two side-by-side rectangular cylinders of different cross-sectional aspect ratios

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

Octavianty, Ressa, E-mail: ressa-octavianty@ed.tmu.ac.jp; Asai, Masahito, E-mail: masai@tmu.ac.jp

Synchronized vortex shedding from two side-by-side cylinders and the associated sound radiation were examined experimentally at Reynolds numbers of the order of 10{sup 4} in low-Mach-number flows. In addition to a pair of square cylinders, a pair of rectangular cylinders, one with a square cross section (d × d) and the other with a rectangular cross section (d × c) having a cross-sectional aspect ratio (c/d) of 1.2–1.5, was considered. The center-to-center distance between the two cylinders L/d was 3.6, 4.5, and 6.0; these settings were within the non-biased flow regime for side-by-side square cylinders. In case of a squaremore » cylinder pair, anti-phase synchronized vortex shedding occurring for L/d = 3.6 and 4.5 generated a quadrupole-like sound source which radiated in-phase, planar-symmetric sound in the far field. Synchronized vortex shedding from the two rectangular cylinders with different c/d also occurred with almost the same frequency as the characteristic frequency of the square-cylinder wake in the case of the small center-to-center distance, L/d = 3.6, for all the cylinder pairs examined. The synchronized sound field was anti-phase and asymmetric in amplitude, unlike the case of a square cylinder pair. For larger spacing L/d = 4.5, synchronized vortex shedding and anti-phase sound still occurred, but only for close cross-sectional aspect ratios (c/d = 1.0 and 1.2), and highly modulated sound was radiated with two different frequencies due to non-synchronized vortex shedding from the two cylinders for larger differences in c/d. It was also found that when synchronized vortex shedding occurred, near-wake velocity fluctuations exhibited high spanwise-coherency, with a very sharp spectral peak compared with the single-cylinder case.« less

Microwave detector

DOEpatents

Meldner, H.W.; Cusson, R.Y.; Johnson, R.M.

1985-02-08

A microwave detector is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite produces a magnetization field flux that links a B-dot loop. The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

Numerical simulation of terahertz transmission of bilayer metallic meshes with different thickness of substrates

NASA Astrophysics Data System (ADS)

Zhang, Gaohui; Zhao, Guozhong; Zhang, Shengbo

2012-12-01

The terahertz transmission characteristics of bilayer metallic meshes are studied based on the finite difference time domain method. The bilayer well-shaped grid, the array of complementary square metallic pill and the cross wire-hole array were investigated. The results show that the bilayer well-shaped grid achieves a high-pass of filter function, while the bilayer array of complementary square metallic pill achieves a low-pass of filter function, the bilayer cross wire-hole array achieves a band-pass of filter function. Between two metallic microstructures, the medium need to be deposited. Obviously, medium thicknesses have an influence on the terahertz transmission characteristics of metallic microstructures. Simulation results show that with increasing the thicknesses of the medium the cut-off frequency of high-pass filter and low-pass filter move to low frequency. But the bilayer cross wire-hole array possesses two transmission peaks which display competition effect.

High redshift signatures in the 21 cm forest due to cosmic string wakes

NASA Astrophysics Data System (ADS)

Tashiro, Hiroyuki; Sekiguchi, Toyokazu; Silk, Joseph

2014-01-01

Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ``21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (zgtrsim10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10-7. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10-8 for the single frequency band case and 4.0 × 10-8 for the multi-frequency band case.

Dual-band frequency selective surface with large band separation and stable performance

NASA Astrophysics Data System (ADS)

Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

2012-05-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

Accumulated energy norm for full waveform inversion of marine data

NASA Astrophysics Data System (ADS)

Shin, Changsoo; Ha, Wansoo

2017-12-01

Macro-velocity models are important for imaging the subsurface structure. However, the conventional objective functions of full waveform inversion in the time and the frequency domain have a limited ability to recover the macro-velocity model because of the absence of low-frequency information. In this study, we propose new objective functions that can recover the macro-velocity model by minimizing the difference between the zero-frequency components of the square of seismic traces. Instead of the seismic trace itself, we use the square of the trace, which contains low-frequency information. We apply several time windows to the trace and obtain zero-frequency information of the squared trace for each time window. The shape of the new objective functions shows that they are suitable for local optimization methods. Since we use the acoustic wave equation in this study, this method can be used for deep-sea marine data, in which elastic effects can be ignored. We show that the zero-frequency components of the square of the seismic traces can be used to recover macro-velocities from synthetic and field data.

Magnetic vortex excitation as spin torque oscillator and its unusual trajectories

NASA Astrophysics Data System (ADS)

Natarajan, Kanimozhi; Muthuraj, Ponsudana; Rajamani, Amuda; Arumugam, Brinda

2018-05-01

We report an interesting observation of unusual trajectories of vortex core oscillations in a spin valve pillar. Micromagnetic simulation in the composite free layer spin valve nano-pillar shows magnetic vortex excitation under critical current density. When current density is slightly increased and wave vector is properly tuned, for the first time we observe a star like and square gyration. Surprisingly this star like and square gyration also leads to steady, coherent and sustained oscillations. Moreover, the frequency of gyration is also very high for this unusual trajectories. The power spectral analysis reveals that there is a marked increase in output power and frequency with less distortions. Our investigation explores the possibility of these unusual trajectories to exhibit spin torque oscillations.

Spectral L2/L1 norm: A new perspective for spectral kurtosis for characterizing non-stationary signals

NASA Astrophysics Data System (ADS)

Wang, Dong

2018-05-01

Thanks to the great efforts made by Antoni (2006), spectral kurtosis has been recognized as a milestone for characterizing non-stationary signals, especially bearing fault signals. The main idea of spectral kurtosis is to use the fourth standardized moment, namely kurtosis, as a function of spectral frequency so as to indicate how repetitive transients caused by a bearing defect vary with frequency. Moreover, spectral kurtosis is defined based on an analytic bearing fault signal constructed from either a complex filter or Hilbert transform. On the other hand, another attractive work was reported by Borghesani et al. (2014) to mathematically reveal the relationship between the kurtosis of an analytical bearing fault signal and the square of the squared envelope spectrum of the analytical bearing fault signal for explaining spectral correlation for quantification of bearing fault signals. More interestingly, it was discovered that the sum of peaks at cyclic frequencies in the square of the squared envelope spectrum corresponds to the raw 4th order moment. Inspired by the aforementioned works, in this paper, we mathematically show that: (1) spectral kurtosis can be decomposed into squared envelope and squared L2/L1 norm so that spectral kurtosis can be explained as spectral squared L2/L1 norm; (2) spectral L2/L1 norm is formally defined for characterizing bearing fault signals and its two geometrical explanations are made; (3) spectral L2/L1 norm is proportional to the square root of the sum of peaks at cyclic frequencies in the square of the squared envelope spectrum; (4) some extensions of spectral L2/L1 norm for characterizing bearing fault signals are pointed out.

High speed strain measurement of active mode locking FBG laser sensor using chirped FBG cavity

NASA Astrophysics Data System (ADS)

Kim, Gyeong Hun; Kim, Joon Young; Park, Chang Hyun; Kim, Chang-Seok; Lee, Hwi Don; Chung, Youngjoo

2017-04-01

We propose a high speed strain measurement method using an active mode locking (AML) fiber Bragg grating (FBG) laser sensor with a chirped FBG cavity. The mode-locked frequency of the AML laser depends on both the position and Bragg wavelength of the FBG. Thus, the mode-locked frequency of cascaded FBGs can be detected independently along the cavity length of cascaded FBGs. The strain across FBGs can be interrogated dynamically by monitoring the change in mode-locked frequency. In this respect, the chirped FBG critically improves the frequency sensitivity to Bragg wavelength shift as a function of increasing dispersion in the AML cavity. The strain measurement of the FBG sensor shows a highly linear response, with an R-squared value of 0.9997.

Least Squares Moving-Window Spectral Analysis.

PubMed

Lee, Young Jong

2017-08-01

Least squares regression is proposed as a moving-windows method for analysis of a series of spectra acquired as a function of external perturbation. The least squares moving-window (LSMW) method can be considered an extended form of the Savitzky-Golay differentiation for nonuniform perturbation spacing. LSMW is characterized in terms of moving-window size, perturbation spacing type, and intensity noise. Simulation results from LSMW are compared with results from other numerical differentiation methods, such as single-interval differentiation, autocorrelation moving-window, and perturbation correlation moving-window methods. It is demonstrated that this simple LSMW method can be useful for quantitative analysis of nonuniformly spaced spectral data with high frequency noise.

Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection

NASA Technical Reports Server (NTRS)

Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

2009-01-01

Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as ''RAZs''. RAZs are displayed as ''go, no-go'' signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

Ultrasound speckle tracking for radial, longitudinal and circumferential strain estimation of the carotid artery--an in vitro validation via sonomicrometry using clinical and high-frequency ultrasound.

PubMed

Larsson, Matilda; Heyde, Brecht; Kremer, Florence; Brodin, Lars-Åke; D'hooge, Jan

2015-02-01

Ultrasound speckle tracking for carotid strain assessment has in the past decade gained interest in studies of arterial stiffness and cardiovascular diseases. The aim of this study was to validate and directly contrast carotid strain assessment by speckle tracking applied on clinical and high-frequency ultrasound images in vitro. Four polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties and connected to a pump generating carotid flow profiles. Gray-scale ultrasound long- and short-axis images of the phantoms were obtained using a standard clinical ultrasound system, Vivid 7 (GE Healthcare, Horten, Norway) and a high-frequency ultrasound system, Vevo 2100 (FUJIFILM, VisualSonics, Toronto, Canada) with linear-array transducers (12L/MS250). Radial, longitudinal and circumferential strains were estimated using an in-house speckle tracking algorithm and compared with reference strain acquired by sonomicrometry. Overall, the estimated strain corresponded well with the reference strain. The correlation between estimated peak strain in clinical ultrasound images and reference strain was 0.91 (p<0.001) for radial strain, 0.73 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain and for high-frequency ultrasound images 0.95 (p<0.001) for radial strain, 0.93 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain. A significant larger bias and root mean square error was found for circumferential strain estimation on clinical ultrasound images compared to high frequency ultrasound images, but no significant difference in bias and root mean square error was found for radial and longitudinal strain when comparing estimation on clinical and high-frequency ultrasound images. The agreement between sonomicrometry and speckle tracking demonstrates that carotid strain assessment by ultrasound speckle tracking is feasible. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Latino High School Students' Perceptions of Caring: Keys to Success

ERIC Educational Resources Information Center

Garza, Rubén; Soto Huerta, Mary Esther

2014-01-01

This mixed methods investigation specifically examined Latino high school adolescents' perceptions of teacher behaviors that demonstrate caring. A chi-square test was conducted to analyze the frequency of responses, and focus group interviews were conducted to expand on the results. The data indicated that although Latino male students were as…

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

Methods for estimating the magnitude and frequency of peak streamflows at ungaged sites in and near the Oklahoma Panhandle

USGS Publications Warehouse

Smith, S. Jerrod; Lewis, Jason M.; Graves, Grant M.

2015-09-28

Generalized-least-squares multiple-linear regression analysis was used to formulate regression relations between peak-streamflow frequency statistics and basin characteristics. Contributing drainage area was the only basin characteristic determined to be statistically significant for all percentage of annual exceedance probabilities and was the only basin characteristic used in regional regression equations for estimating peak-streamflow frequency statistics on unregulated streams in and near the Oklahoma Panhandle. The regression model pseudo-coefficient of determination, converted to percent, for the Oklahoma Panhandle regional regression equations ranged from about 38 to 63 percent. The standard errors of prediction and the standard model errors for the Oklahoma Panhandle regional regression equations ranged from about 84 to 148 percent and from about 76 to 138 percent, respectively. These errors were comparable to those reported for regional peak-streamflow frequency regression equations for the High Plains areas of Texas and Colorado. The root mean square errors for the Oklahoma Panhandle regional regression equations (ranging from 3,170 to 92,000 cubic feet per second) were less than the root mean square errors for the Oklahoma statewide regression equations (ranging from 18,900 to 412,000 cubic feet per second); therefore, the Oklahoma Panhandle regional regression equations produce more accurate peak-streamflow statistic estimates for the irrigated period of record in the Oklahoma Panhandle than do the Oklahoma statewide regression equations. The regression equations developed in this report are applicable to streams that are not substantially affected by regulation, impoundment, or surface-water withdrawals. These regression equations are intended for use for stream sites with contributing drainage areas less than or equal to about 2,060 square miles, the maximum value for the independent variable used in the regression analysis.

Evaluation of adhesive-free crossed-electrode poly(vinylidene fluoride) copolymer array transducers for high frequency imaging

NASA Astrophysics Data System (ADS)

Wagle, Sanat; Decharat, Adit; Habib, Anowarul; Ahluwalia, Balpreet S.; Melandsø, Frank

2016-07-01

High frequency crossed-electrode transducers have been investigated, both as single and dual layer transducers. Prototypes of these transducers were developed for 4 crossed lines (yielding 16 square elements) on a polymer substrate, using a layer-by-layer deposition method for poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] with intermediate sputtered electrodes. The transducer was characterized using various methods [LCR analyzer, a pulse-echo experimental setup, and a numerical Finite element method (FEM) model] and evaluated in terms of uniformity of bandwidth and acoustical energy output. All 16 transducer elements produced broad-banded ultrasonic spectra with small variation in central frequency and -6 dB bandwidth. The frequency responses obtained experimentally were verified using a numerical model.

Wide Angle, Single Screen, Gridded Square-Loop Frequency Selective Surface for Diplexing Two Closely Separated Frequency Bands

NASA Technical Reports Server (NTRS)

Wu, Te-Kao (Inventor)

1996-01-01

The design and performance of a wide angle, single screen, frequency selective surface (FSS) with gridded square-loop path elements are described for diplexing closely separated signal bands, for example, X- and Ku-band signals in an Orbiting Very Long Baseline Interferometer (OVLBI) earth station reflector antenna system, as well as other applications such as military and commercial communications via satellites. Excellent agreement is obtained between the predicted and measured results of this FSS design using the gridded square-loop patch elements sandwiched between 0.0889 cm thick tetrafluoroethylene fluorocarbon polymer (PTFE) slabs. Resonant frequency drift is reduced by 1 GHz with an incidence angle from 0 deg normal to 40 deg from normal.

Treatment of late time instabilities in finite-difference EMP scattering codes

NASA Astrophysics Data System (ADS)

Simpson, L. T.; Holland, R.; Arman, S.

1982-12-01

Constraints applicable to a finite difference mesh for solution of Maxwell's equations are defined. The equations are applied in the time domain for computing electromagnetic coupling to complex structures, e.g., rectangular, cylindrical, or spherical. In a spatially varying grid, the amplitude growth of high frequency waves becomes exponential through multiple reflections from the outer boundary in cases of late-time solution. The exponential growth of the numerical noise exceeds the value of the real signal. The correction technique employs an absorbing surface and a radiating boundary, along with tailored selection of the grid mesh size. High frequency noise is removed through use of a low-pass digital filter, a linear least squares fit is made to thy low frequency filtered response, and the original, filtered, and fitted data are merged to preserve the high frequency early-time response.

Modeling and Simulation of a Parametrically Resonant Micromirror With Duty-Cycled Excitation.

PubMed

Shahid, Wajiha; Qiu, Zhen; Duan, Xiyu; Li, Haijun; Wang, Thomas D; Oldham, Kenn R

2014-12-01

High frequency large scanning angle electrostatically actuated microelectromechanical systems (MEMS) mirrors are used in a variety of applications involving fast optical scanning. A 1-D parametrically resonant torsional micromirror for use in biomedical imaging is analyzed here with respect to operation by duty-cycled square waves. Duty-cycled square wave excitation can have significant advantages for practical mirror regulation and/or control. The mirror's nonlinear dynamics under such excitation is analyzed in a Hill's equation form. This form is used to predict stability regions (the voltage-frequency relationship) of parametric resonance behavior over large scanning angles using iterative approximations for nonlinear capacitance behavior of the mirror. Numerical simulations are also performed to obtain the mirror's frequency response over several voltages for various duty cycles. Frequency sweeps, stability results, and duty cycle trends from both analytical and simulation methods are compared with experimental results. Both analytical models and simulations show good agreement with experimental results over the range of duty cycled excitations tested. This paper discusses the implications of changing amplitude and phase with duty cycle for robust open-loop operation and future closed-loop operating strategies.

Low frequency AC waveform generator

DOEpatents

Bilharz, Oscar W.

1986-01-01

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

High-precision multi-node clock network distribution.

PubMed

Chen, Xing; Cui, Yifan; Lu, Xing; Ci, Cheng; Zhang, Xuesong; Liu, Bo; Wu, Hong; Tang, Tingsong; Shi, Kebin; Zhang, Zhigang

2017-10-01

A high precision multi-node clock network for multiple users was built following the precise frequency transmission and time synchronization of 120 km fiber. The network topology adopts a simple star-shaped network structure. The clock signal of a hydrogen maser (synchronized with UTC) was recovered from a 120 km telecommunication fiber link and then was distributed to 4 sub-stations. The fractional frequency instability of all substations is in the level of 10 -15 in a second and the clock offset instability is in sub-ps in root-mean-square average.

Microwave detector

DOEpatents

Meldner, Heiner W.; Cusson, Ronald Y.; Johnson, Ray M.

1986-01-01

A microwave detector (10) is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite (26, 28) produces a magnetization field flux that links a B-dot loop (16, 20). The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means (18, 22) are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

Wave-induced fluid flow in random porous media: Attenuation and dispersion of elastic waves

NASA Astrophysics Data System (ADS)

Müller, Tobias M.; Gurevich, Boris

2005-05-01

A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. .

Frequency noise measurement of diode-pumped Nd:YAG ring lasers

NASA Technical Reports Server (NTRS)

Chen, Chien-Chung; Win, Moe Zaw

1990-01-01

The combined frequency noise spectrum of two model 120-01A nonplanar ring oscillator lasers was measured by first heterodyne detecting the IF signal and then measuring the IF frequency noise using an RF frequency discriminator. The results indicated the presence of a 1/f-squared noise component in the power-spectral density of the frequency fluctuations between 1 Hz and 1 kHz. After incorporating this 1/f-squared into the analysis of the optical phase tracking loop, the measured phase error variance closely matches the theoretical predictions.

Multi-channel unidirectional transmission of phononic crystal heterojunctions

NASA Astrophysics Data System (ADS)

Xu, Zhenlong; Tong, Jie; Wu, Fugen

2018-02-01

Two square steel columns are arranged in air to form two-dimensional square lattice phononic crystals (PNCs). Two PNCs can be combined into a non-orthogonal 45∘ heterojunction when the difference in the directional band gaps of the two PNC types is utilized. The finite element method is used to calculate the acoustic band structure, the heterogeneous junction transmission characteristics, acoustic field distribution, and many others. Results show that a non-orthogonal PNC heterojunction can produce a multi-channel unidirectional transmission of acoustic waves. With the square scatterer rotated, the heterojunction can select a frequency band for unidirectional transmission performance. This capability is particularly useful for constructing acoustic diodes with wide-bands and high-efficiency unidirectional transmission characteristics.

Spectral analysis of GEOS-3 altimeter data and frequency domain collocation. [to estimate gravity anomalies

NASA Technical Reports Server (NTRS)

Eren, K.

1980-01-01

The mathematical background in spectral analysis as applied to geodetic applications is summarized. The resolution (cut-off frequency) of the GEOS 3 altimeter data is examined by determining the shortest wavelength (corresponding to the cut-off frequency) recoverable. The data from some 18 profiles are used. The total power (variance) in the sea surface topography with respect to the reference ellipsoid as well as with respect to the GEM-9 surface is computed. A fast inversion algorithm for matrices of simple and block Toeplitz matrices and its application to least squares collocation is explained. This algorithm yields a considerable gain in computer time and storage in comparison with conventional least squares collocation. Frequency domain least squares collocation techniques are also introduced and applied to estimating gravity anomalies from GEOS 3 altimeter data. These techniques substantially reduce the computer time and requirements in storage associated with the conventional least squares collocation. Numerical examples given demonstrate the efficiency and speed of these techniques.

Real-time and high accuracy frequency measurements for intermediate frequency narrowband signals

NASA Astrophysics Data System (ADS)

Tian, Jing; Meng, Xiaofeng; Nie, Jing; Lin, Liwei

2018-01-01

Real-time and accurate measurements of intermediate frequency signals based on microprocessors are difficult due to the computational complexity and limited time constraints. In this paper, a fast and precise methodology based on the sigma-delta modulator is designed and implemented by first generating the twiddle factors using the designed recursive scheme. This scheme requires zero times of multiplications and only half amounts of addition operations by using the discrete Fourier transform (DFT) and the combination of the Rife algorithm and Fourier coefficient interpolation as compared with conventional methods such as DFT and Fast Fourier Transform. Experimentally, when the sampling frequency is 10 MHz, the real-time frequency measurements with intermediate frequency and narrowband signals have a measurement mean squared error of ±2.4 Hz. Furthermore, a single measurement of the whole system only requires approximately 0.3 s to achieve fast iteration, high precision, and less calculation time.

Low frequency ac waveform generator

DOEpatents

Bilharz, O.W.

1983-11-22

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Mid- to high-frequency noise from high-speed boats and its potential impacts on humpback dolphins.

PubMed

Li, Songhai; Wu, Haiping; Xu, Youhou; Peng, Chongwei; Fang, Liang; Lin, Mingli; Xing, Luru; Zhang, Peijun

2015-08-01

The impact of noise made by vessels on marine animals has come under increased concern. However, most measurements on noise from vessels have only taken into account the low-frequency components. For cetaceans operating in the mid- and high-frequencies, such as the Indo-Pacific humpback dolphin (Sousa chinensis), mid- to high-frequency noise components may be of more concern, in terms of their potential impacts. In this study, noise made by a small high-speed boat was recorded using a broadband recording system in a dolphin watching area focusing on the effects on humpback dolphins in Sanniang Bay, China. The high-speed boat produced substantial mid- to high-frequency noise components with frequencies to >100 kHz, measured at three speeds: ∼40, 30, and 15 km/h. The noise from the boat raised the ambient noise levels from ∼5 to 47 decibels (dB) root-mean-square (rms) across frequency bands ranging from 1 to 125 kHz at a distance of 20 to 85 m, with louder levels recorded at higher speeds and at closer distances. To conclude, the noise produced by the small high-speed boat could be heard by Sousa chinensis and therefore potentially had adverse effects on the dolphins.

Realisation Of Polarisation Sensitive And Frequency Selective Surfaces On Microwave Reflectors By Laser Evaporation

NASA Astrophysics Data System (ADS)

Halm, R.; Kupper, Th.; Fischer, A.

1987-01-01

Gridded reflectors are used on communication satellites antennas to provide frequency reuse in dual linear polarisation mode of operation. The polarisation sensitive surface consists of metallic strips, forming a grid with width and spacings of the order of 0.1 mm. The use of frequency-selective surface (FSS) subreflectors allows the simultaneous generation of different microwave beams with the same main reflector. Such a reflector will require a structure of conductive arrays of either dipoles, rings, squares or square loops with typical dimensions of the order of 3-6 mm. Optimisation of the electrical design leads to critical dimensioning of these structures. By direct ablation of an aluminium surface coating by means of laser evaporation, high accuracies can be achieved. The major requirements were to minimize thermal damage of the substrate material and to produce dimensionally accurate grids. Experiments were carried out using a pulsed TEA-CO2 laser and a Q-switched Alexandrite laser. Details of the experimental set-up and conditions are described.

Dietary sodium influences the effect of mental stress on heart rate variability: a randomized trial in healthy adults.

PubMed

Allen, Alexander R; Gullixson, Leah R; Wolhart, Sarah C; Kost, Susan L; Schroeder, Darrell R; Eisenach, John H

2014-02-01

Dietary sodium influences intermediate physiological traits in healthy adults independent of changes in blood pressure. The purpose of this study was to test the hypothesis that dietary sodium affects cardiac autonomic modulation during mental stress. In a prospective, randomized cross-over design separated by 1 month between diets, 70 normotensive healthy young adults (F/M: 44/26, aged 18-38 years) consumed a 5-day low (10 mmol/day), normal (150 mmol), and high (400 mmol) sodium diet followed by heart rate variability (HRV) recordings at rest and during 5-min computerized mental arithmetic. Women were studied in the low hormone phase of the menstrual cycle following each diet. Diet did not affect resting blood pressure, but heart rate (HR) (mean ± SE) was 66 ± 1, 64 ± 1, and 63 ± 1 bpm in low, normal, and high sodium conditions, respectively (analysis of variance P = 0.02). For HRV, there was a main effect of sodium on resting SD of normalized RR intervals (SDNN), square root of the mean squared difference of successive normalized RR intervals (RMSSD), high frequency, low-frequency normalized units (LFnu), and high-frequency normalized units (HFnu) (P < 0.01 for all). The response to low sodium was most marked and consistent with sympathetic activation and reduced vagal activity, with increased LFnu and decreased SDNN, RMSSD, and HFnu compared to both normal and high sodium conditions (P ≤0.05 for all). Dietary sodium-by-mental stress interactions were significant for mean NN, RMSSD, high-frequency power, LFnu, and low frequency/high frequency ratio (P < 0.05 for all). The interactions signify that sodium restriction evoked an increase in resting sympathetic activity and reduced vagal activity to the extent that mental stress caused modest additional disruptions in autonomic balance. Conversely, normal and high sodium evoked a reduction in resting sympathetic activity and incremental increase in resting vagal activity, which were disrupted to a greater extent during mental stress compared to low sodium. We conclude that autonomic control of HRV at rest and during mental stress is altered by dietary sodium in healthy normotensive young adult men and women.

Accelerometer Data Analysis and Presentation Techniques

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; Hrovat, Kenneth; McPherson, Kevin; Moskowitz, Milton E.; Reckart, Timothy

1997-01-01

The NASA Lewis Research Center's Principal Investigator Microgravity Services project analyzes Orbital Acceleration Research Experiment and Space Acceleration Measurement System data for principal investigators of microgravity experiments. Principal investigators need a thorough understanding of data analysis techniques so that they can request appropriate analyses to best interpret accelerometer data. Accelerometer data sampling and filtering is introduced along with the related topics of resolution and aliasing. Specific information about the Orbital Acceleration Research Experiment and Space Acceleration Measurement System data sampling and filtering is given. Time domain data analysis techniques are discussed and example environment interpretations are made using plots of acceleration versus time, interval average acceleration versus time, interval root-mean-square acceleration versus time, trimmean acceleration versus time, quasi-steady three dimensional histograms, and prediction of quasi-steady levels at different locations. An introduction to Fourier transform theory and windowing is provided along with specific analysis techniques and data interpretations. The frequency domain analyses discussed are power spectral density versus frequency, cumulative root-mean-square acceleration versus frequency, root-mean-square acceleration versus frequency, one-third octave band root-mean-square acceleration versus frequency, and power spectral density versus frequency versus time (spectrogram). Instructions for accessing NASA Lewis Research Center accelerometer data and related information using the internet are provided.

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

NASA Technical Reports Server (NTRS)

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

2001-01-01

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

A reconfigurable frequency-selective surface for dual-mode multi-band filtering applications

NASA Astrophysics Data System (ADS)

Majidzadeh, Maryam; Ghobadi, Changiz; Nourinia, Javad

2017-03-01

A reconfigurable single-layer frequency-selective surface (FSS) with dual-mode multi-band modes of operation is presented. The proposed structure is printed on a compact 10 × 10 mm2 FR4 substrate with the thickness of 1.6 mm. A simple square loop is printed on the front side while another one along with two defected vertical arms is deployed on the backside. To realise the reconfiguration, two pin diodes are embedded on the backside square loop. Suitable insertion of conductive elements along with pin diodes yields in dual-mode multi-band rejection of applicable in service frequency ranges. The first operating mode due to diodes' 'ON' state provides rejection of 2.4 GHz WLAN in 2-3 GHz, 5.2/5.8 GHz WLAN and X band in 5-12 GHz, and a part of Ku band in 13.9-16 GHz. In diodes 'OFF' state, the FSS blocks WLAN in 4-7.3 GHz, X band in 8-12.7 GHz as well as part of Ku band in 13.7-16.7 GHz. As well, high attenuation of incident waves is observed by a high shielding effectiveness (SE) in the blocked frequency bands. Also, a stable behaviour against different polarisations and angles of incidence is obtained. Comprehensive studies are conducted on a fabricated prototype to assess its performance from which encouraging results are obtained.

Crossover behavior of stock returns and mean square displacements of particles governed by the Langevin equation

NASA Astrophysics Data System (ADS)

Ma, Wen-Jong; Wang, Shih-Chieh; Chen, Chi-Ning; Hu, Chin-Kun

2013-06-01

It is found that the mean square log-returns calculated from the high-frequency one-day moving average of US and Taiwan stocks with the time internal τ show ballistic behavior \\theta \\tau^{\\alpha_1} with the exponent \\alpha_1 \\approx 2 for small τ and show diffusion-like behavior D \\tau^{\\alpha_2} with the exponent \\alpha_2 \\approx 1 for large τ. Such a crossover behavior can be well described by the mean square displacements of particles governed by the Langevin equation of motion. Thus, θ and D can be considered, respectively, as the temperature-like and diffusivity-like kinetic parameters of the market, and they can be used to characterize the behavior of the market.

Combined fabrication technique for high-precision aspheric optical windows

NASA Astrophysics Data System (ADS)

Hu, Hao; Song, Ci; Xie, Xuhui

2016-07-01

Specifications made on optical components are becoming more and more stringent with the performance improvement of modern optical systems. These strict requirements not only involve low spatial frequency surface accuracy, mid-and-high spatial frequency surface errors, but also surface smoothness and so on. This presentation mainly focuses on the fabrication process for square aspheric window which combines accurate grinding, magnetorheological finishing (MRF) and smoothing polishing (SP). In order to remove the low spatial frequency surface errors and subsurface defects after accurate grinding, the deterministic polishing method MRF with high convergence and stable material removal rate is applied. Then the SP technology with pseudo-random path is adopted to eliminate the mid-and-high spatial frequency surface ripples and high slope errors which is the defect for MRF. Additionally, the coordinate measurement method and interferometry are combined in different phase. Acid-etched method and ion beam figuring (IBF) are also investigated on observing and reducing the subsurface defects. Actual fabrication result indicates that the combined fabrication technique can lead to high machining efficiency on manufaturing the high-precision and high-quality optical aspheric windows.

Making High-Pass Filters For Submillimeter Waves

NASA Technical Reports Server (NTRS)

Siegel, Peter H.; Lichtenberger, John A.

1991-01-01

Micromachining-and-electroforming process makes rigid metal meshes with cells ranging in size from 0.002 in. to 0.05 in. square. Series of steps involving cutting, grinding, vapor deposition, and electroforming creates self-supporting, electrically thick mesh. Width of holes typically 1.2 times cutoff wavelength of dominant waveguide mode in hole. To obtain sharp frequency-cutoff characteristic, thickness of mesh made greater than one-half of guide wavelength of mode in hole. Meshes used as high-pass filters (dichroic plates) for submillimeter electromagnetic waves. Process not limited to square silicon wafers. Round wafers also used, with slightly more complication in grinding periphery. Grid in any pattern produced in electroforming mandrel. Any platable metal or alloy used for mesh.

On the Performance of the Martin Digital Filter for High- and Low-pass Applications

NASA Technical Reports Server (NTRS)

Mcclain, C. R.

1979-01-01

A nonrecursive numerical filter is described in which the weighting sequence is optimized by minimizing the excursion from the ideal rectangular filter in a least squares sense over the entire domain of normalized frequency. Additional corrections to the weights in order to reduce overshoot oscillations (Gibbs phenomenon) and to insure unity gain at zero frequency for the low pass filter are incorporated. The filter is characterized by a zero phase shift for all frequencies (due to a symmetric weighting sequence), a finite memory and stability, and it may readily be transformed to a high pass filter. Equations for the filter weights and the frequency response function are presented, and applications to high and low pass filtering are examined. A discussion of optimization of high pass filter parameters for a rather stringent response requirement is given in an application to the removal of aircraft low frequency oscillations superimposed on remotely sensed ocean surface profiles. Several frequency response functions are displayed, both in normalized frequency space and in period space. A comparison of the performance of the Martin filter with some other commonly used low pass digital filters is provided in an application to oceanographic data.

Non-linear Post Processing Image Enhancement

NASA Technical Reports Server (NTRS)

Hunt, Shawn; Lopez, Alex; Torres, Angel

1997-01-01

A non-linear filter for image post processing based on the feedforward Neural Network topology is presented. This study was undertaken to investigate the usefulness of "smart" filters in image post processing. The filter has shown to be useful in recovering high frequencies, such as those lost during the JPEG compression-decompression process. The filtered images have a higher signal to noise ratio, and a higher perceived image quality. Simulation studies comparing the proposed filter with the optimum mean square non-linear filter, showing examples of the high frequency recovery, and the statistical properties of the filter are given,

High-frequency seismic energy radiation from the 2003 Miyagi-Oki, JAPAN, earthquake (M7.0) as revealed from an envelope inversion analysis

NASA Astrophysics Data System (ADS)

Nakahara, H.

2003-12-01

The 2003 Miyagi-Oki earthquake (M 7.0) took place on May 26, 2003 in the subducting Pacific plate beneath northeastern Japan. The focal depth is around 70km. The focal mechanism is reverse type on a fault plane dipping to the west with a high angle. There was no fatality, fortunately. However, this earthquake caused more than 100 injures, 2000 collapsed houses, and so on. To the south of this focal area by about 50km, an interplate earthquake of M7.5, the Miyagi-Ken-Oki earthquake, is expected to occur in the near future. So the relation between this earthquake and the expected Miyagi-Ken-Oki earthquake attracts public attention. Seismic-energy distribution on earthquake fault planes estimated by envelope inversion analyses can contribute to better understanding of the earthquake source process. For moderate to large earthquakes, seismic energy in frequencies higher than 1 Hz is sometimes much larger than a level expected from the omega-squared model with source parameters estimated by lower-frequency analyses. Therefore, an accurate estimation of seismic energy in such high frequencies has significant importance on estimation of dynamic source parameters such as the seismic energy or the apparent stress. In this study, we execute an envelope inversion analysis based on the method by Nakahara et al. (1998) and clarify the spatial distribution of high-frequency seismic energy radiation on the fault plane of this earthquake. We use three-component sum of mean squared velocity seismograms multiplied by a density of earth medium, which is called envelopes here, for the envelope inversion analysis. Four frequency bands of 1-2, 2-4, 4-8, and 8-16 Hz are adopted. We use envelopes in the time window from the onset of S waves to the lapse time of 51.2 sec. Green functions of envelopes representing the energy propagation process through a scattering medium are calculated based on the radiative transfer theory, which are characterized by parameters of scattering attenuation and intrinsic absorption. We use the values obtained for the northeastern Japan (Sakurai, 1995). We assume the fault plane as follows: strike=193,a, dip=69,a, rake=87,a, length=30km, width=25km with referrence to a waveform inversion analysis in low-frequencies (e.g. Yagi, 2003). We divide this fault plane into 25 subfaults, each of which is a 5km x 5km square. Rupture velocity is assumed to be constant. Seismic energy is radiated from a point source as soon as the rupture front passes the center of each subfault. Time function of energy radiation is assumed as a box-car function. The amount of seismic energy from all the subfaults and site amplification factors for all the stations are estimated by the envelope inversion method. Rupture velocity and the duration time of a box-car function should be estimated by a grid search. Theoretical envelopes calculated with best-fit parameters generally fit to observed ones. The rupture velocity and duration time were estimated as 3.8 km/s and 1.6 sec, respectively. The high-frequency seismic energy was found to be radiated mainly from two spots on the fault plane: The first one is around the initial rupture point and the second is the northern part of the fault plane. These two spots correspond to observed two peaks on envelopes. Amount of seismic energy increases with increasing frequency in the 1-16Hz band, which contradicts an expectation from the omega-squared model. Therefore, stronger radiation of higher-frequency seismic energy is a prominent character of this earthquake. Acknowledgements: We used strong-motion seismograms recorded by the K-NET and KiK-net of NIED, JAPAN.

High-frequency profile in adolescents and its relationship with the use of personal stereo devices.

PubMed

Silvestre, Renata Almeida Araújo; Ribas, Ângela; Hammerschmidt, Rogério; de Lacerda, Adriana Bender Moreira

2016-01-01

To analyze and correlate the audiometric findings of high frequencies (9-16 kHz) in adolescents with their hearing habits and attitudes, in order to prevent noise-induced hearing loss. This was a descriptive cross-sectional study, which included 125 adolescents in a sample of normal-hearing students, at a state school. The subjects performed high-frequency audiometry testing and answered a self-administered questionnaire addressing information on sound habits concerning the use of personal stereo devices. The sample was divided according to the exposure characteristics (time, duration, intensity, etc.) and the results were compared with the observed thresholds, through the difference in proportions test, chi-squared, Student's t-test, and ANOVA, all at a significance level of 0.05. Average high-frequency thresholds were registered below 15 dB HL and no significant correlation was found between high frequency audiometric findings and the degree of exposure. The prevalence of harmful sound habits due to the use of personal stereo devices is high in the adolescent population, but there was no correlation between exposure to high sound pressure levels through personal stereos and the high-frequency thresholds in this population. Copyright © 2016 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

On the appropriateness of applying chi-square distribution based confidence intervals to spectral estimates of helicopter flyover data

NASA Technical Reports Server (NTRS)

Rutledge, Charles K.

1988-01-01

The validity of applying chi-square based confidence intervals to far-field acoustic flyover spectral estimates was investigated. Simulated data, using a Kendall series and experimental acoustic data from the NASA/McDonnell Douglas 500E acoustics test, were analyzed. Statistical significance tests to determine the equality of distributions of the simulated and experimental data relative to theoretical chi-square distributions were performed. Bias and uncertainty errors associated with the spectral estimates were easily identified from the data sets. A model relating the uncertainty and bias errors to the estimates resulted, which aided in determining the appropriateness of the chi-square distribution based confidence intervals. Such confidence intervals were appropriate for nontonally associated frequencies of the experimental data but were inappropriate for tonally associated estimate distributions. The appropriateness at the tonally associated frequencies was indicated by the presence of bias error and noncomformity of the distributions to the theoretical chi-square distribution. A technique for determining appropriate confidence intervals at the tonally associated frequencies was suggested.

Precipitation-Frequency and Discharge-Frequency Relations for Basins Less than 32 Square Miles in Kansas

USGS Publications Warehouse

Perry, Charles A.

2008-01-01

Precipitation-frequency and discharge-frequency relations for small drainage basins with areas less than 32 square miles in Kansas were evaluated to reduce the uncertainty of discharge-frequency estimates. Gaged-discharge records were used to develop discharge-frequency equations for the ratio of discharge to drainage area (Q/A) values using data from basins with variable soil permeability, channel slope, and mean annual precipitation. Soil permeability and mean annual precipitation are the dominant basin characteristics in the multiple linear regression analyses. In addition, 28 discharge measurements at ungaged sites by indirect surveying methods and by velocity meters also were used in this analysis to relate precipitation-recurrence interval to discharge-recurrence interval. Precipitation-recurrence interval for each of these discharge measurements were estimated from weather-radar estimates of precipitation and from nearby raingages. Time of concentration for each basin for each of the ungaged sites was computed and used to determine the precipitation-recurrence interval based on precipitation depth and duration. The ratio of discharge/drainage area (Q/A) value for each event was then assigned to that precipitation-recurrence interval. The relation between the ratio of discharge/drainage area (Q/A) and precipitation-recurrence interval for all 28 measured events resulted in a correlation coefficient of 0.79. Using basins less than 5.4 mi2 only, the correlation decreases to 0.74. However, when basins greater than 5.4 and less than 32 mi2 are examined the relation improves to a correlation coefficient of 0.95. There were a sufficient number of discharge and radar-measured precipitation events for both the 5-year (8 events) and the 100-year (11 events) recurrence intervals to examine the effect of basin characteristics on the Q/A values for basins less than 32 mi2. At the 5-year precipitation-/discharge-recurrence interval, channel slope was a significant predictor (r=0.99) of Q/A. Permeability (r=0.68) also had a significant effect on Q/A values for the 5-year recurrence interval. At the 100-year recurrence interval, permeability, channel slope, and mean annual precipitation did not have a significant effect on Q/A; however, time of concentration was a significant factor in determining Q/A for the 100-year events with greater times of concentration resulting in lower Q/A values. Additional high-recurrence interval (5-, 10-, 25-, 50-, and 100-year) precipitation/discharge data are needed to confirm these relations suggested above. Discharge data with attendant basin-wide precipitation data from precipitation-radar estimates provides a unique opportunity to study the effects of basin characteristics on the relation between precipitation recurrence interval and discharge-recurrence interval. Discharge-frequency values from the Q/A equations, the rational method, and the Kansas discharge-frequency equations (KFFE) were compared to 28 measured weather-radar precipitation-/discharge-frequency values. The association between precipitation frequency from weather-radar estimates and the frequency of the resulting discharge was shown in these comparisons. The measured and Q/A equation computed discharges displayed the best equality from low to high discharges of the three methods. Here the slope of the line was nearly 1:1 (y=0.9844x0.9677). Comparisons with the rational method produced a slope greater than 1:1 (y=0.0722x1.235), and the KFFE equations produced a slope less than 1:1 (y=5.9103x0.7475). The Q/A equation standard error of prediction averaged 0.1346 log units for the 5.4-to 32-square-mile group and 0.0944 log units for the less than 5.4-square mile group. The KFFE standard error averaged 0.2107 log units for the less-than-30-square-mile equations. Using the Q/A equations for determining discharge frequency values for ungaged sites thus appears to be a good alternative to the other two methods because of this s

A Cool Urban Island Change 1990 - 2014. Comparative Bioclimatic Analysis in a Desert Climate, the Case of Antofagasta City Square

NASA Astrophysics Data System (ADS)

Pérez Lancellotti, Gino; Ziede Bize, Marcela

2017-10-01

This article proposes to make a comparative bioclimatic analysis from 1990 to 2014 of the main square of Antofagasta, a coastal desert city in Chile, which was remodelled in 1995, and shows how the redesigning of green areas affects the microclimatic conditions and thermal comfort of the urban space. Ex ante measurements dating 1990 were compared with ex post results from 2014. Data were obtained in both cases in the month of September at different times of a day and in different climate conditions. The variables studied were: land surface temperature, humidity, wind speed, amount of light and square use frequency inside the square and in surrounding streets. The temperatures are not statistically different during the years 1990 and 2014 for the city of Antofagasta. The main layout of the square has not changed, and inside the square it is similar for both periods, but new species were introduced and bigger trees with shadow projection were cut down. The square had a micro-climate role in 2014 as well as in 1990. The highest frequency zone with an important surface lost it is comfort thermic condition with an increase of 1°C. Other smaller zones with less relevance for users gained in cooling with a 0.5°C reduction. The new design has been detrimental to the intensity of its micro climatic regulatory function affecting the thermic comfort of the square’s internal spaces, especially those formerly protected by shadow, which mitigate a high solar radiation. The study results suggest that bio-climatic analysis of public open spaces is a key component for the design of future projects as a heat mitigating tool in the context of climate change. Research question is: How does the redesign of the square impact a cool urban island and the thermic comfort of users? Significant differences between data in situ collected in 1990 and 2014. Thermal comfort was negatively affected by the redesign in the square. The square is still a cool island but with less strength.

Modeling and Simulation of a Parametrically Resonant Micromirror With Duty-Cycled Excitation

PubMed Central

Shahid, Wajiha; Qiu, Zhen; Duan, Xiyu; Li, Haijun; Wang, Thomas D.; Oldham, Kenn R.

2014-01-01

High frequency large scanning angle electrostatically actuated microelectromechanical systems (MEMS) mirrors are used in a variety of applications involving fast optical scanning. A 1-D parametrically resonant torsional micromirror for use in biomedical imaging is analyzed here with respect to operation by duty-cycled square waves. Duty-cycled square wave excitation can have significant advantages for practical mirror regulation and/or control. The mirror’s nonlinear dynamics under such excitation is analyzed in a Hill’s equation form. This form is used to predict stability regions (the voltage-frequency relationship) of parametric resonance behavior over large scanning angles using iterative approximations for nonlinear capacitance behavior of the mirror. Numerical simulations are also performed to obtain the mirror’s frequency response over several voltages for various duty cycles. Frequency sweeps, stability results, and duty cycle trends from both analytical and simulation methods are compared with experimental results. Both analytical models and simulations show good agreement with experimental results over the range of duty cycled excitations tested. This paper discusses the implications of changing amplitude and phase with duty cycle for robust open-loop operation and future closed-loop operating strategies. PMID:25506188

Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator

NASA Technical Reports Server (NTRS)

Mileant, A.; Simon, M.

1986-01-01

When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.

Source conductance scaling for high frequency superconducting quasiparticle receivers

NASA Technical Reports Server (NTRS)

Ke, Qing; Feldman, M. J.

1992-01-01

It has been suggested that the optimum source conductance G(sub s) for the superconductor-insulator-superconductor (SIS) quasiparticle mixer should have a l/f dependence. This would imply that the critical current density of SIS junctions used for mixing should increase as frequency squared, a stringent constraint on the design of submillimeter SIS mixers, rather than in simple proportion to frequency as previously believed. We have used Tucker's quantum theory of mixing for extensive numerical calculations to determine G(sub s) for an optimized SIS receiver. We find that G(sub s) is very roughly independent of frequency (except for the best junctions at low frequency), and discuss the implications of our results for the design of submillimeter SIS mixers.

Astronomical Verification of a Stabilized Frequency Reference Transfer System for the Square Kilometer Array

NASA Astrophysics Data System (ADS)

Gozzard, David R.; Schediwy, Sascha W.; Dodson, Richard; Rioja, María J.; Hill, Mike; Lennon, Brett; McFee, Jock; Mirtschin, Peter; Stevens, Jamie; Grainge, Keith

2017-07-01

In order to meet its cutting-edge scientific objectives, the Square Kilometre Array (SKA) telescope requires high-precision frequency references to be distributed to each of its antennas. The frequency references are distributed via fiber-optic links and must be actively stabilized to compensate for phase noise imposed on the signals by environmental perturbations on the links. SKA engineering requirements demand that any proposed frequency reference distribution system be proved in “astronomical verification” tests. We present results of the astronomical verification of a stabilized frequency reference transfer system proposed for SKA-mid. The dual-receiver architecture of the Australia Telescope Compact Array was exploited to subtract the phase noise of the sky signal from the data, allowing the phase noise of observations performed using a standard frequency reference, as well as the stabilized frequency reference transfer system transmitting over 77 km of fiber-optic cable, to be directly compared. Results are presented for the fractional frequency stability and phase drift of the stabilized frequency reference transfer system for celestial calibrator observations at 5 and 25 GHz. These observations plus additional laboratory results for the transferred signal stability over a 166 km metropolitan fiber-optic link are used to show that the stabilized transfer system under test exceeds all SKA phase-stability requirements within a broad range of observing conditions. Furthermore, we have shown that alternative reference dissemination systems that use multiple synthesizers to supply reference signals to sub-sections of an array may limit the imaging capability of the telescope.

Choice of antenna geometry for microwave power transmission from solar power satellites

NASA Technical Reports Server (NTRS)

Potter, Seth D.

1992-01-01

A comparison is made between square and circular transmitting antennas for solar power satellite microwave power transmission. It is seen that the exclusion zone around the rectenna needed to protect populations from microwaves is smaller for a circular antenna operating at 2.45 GHz than it is for a square antenna at that frequency. If the frequency is increased, the exclusion zone size remains the same for a square antenna, but becomes even smaller for a circular antenna. Peak beam intensity is the same for both antennas if the frequency and antenna area are equal. The circular antenna puts a somewhat greater amount of power in the main lobe and somewhat less in the side lobes. Since rain attenuation and atmospheric heating remain problems above 10 GHz, it is recommended that future solar power satellite work concentrate on circular transmitting antennas at frequencies of roughly 10 GHz.

RLS Channel Estimation with Adaptive Forgetting Factor for DS-CDMA Frequency-Domain Equalization

NASA Astrophysics Data System (ADS)

Kojima, Yohei; Tomeba, Hiromichi; Takeda, Kazuaki; Adachi, Fumiyuki

Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can increase the downlink bit error rate (BER) performance of DS-CDMA beyond that possible with conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a pilot-assisted channel estimation (CE) based on the MMSE criterion. Using MMSE-CE, the channel estimation accuracy is almost insensitive to the pilot chip sequence, and a good BER performance is achieved. In this paper, we propose a channel estimation scheme using one-tap recursive least square (RLS) algorithm, where the forgetting factor is adapted to the changing channel condition by the least mean square (LMS)algorithm, for DS-CDMA with FDE. We evaluate the BER performance using RLS-CE with adaptive forgetting factor in a frequency-selective fast Rayleigh fading channel by computer simulation.

Polarized point sources in the LOFAR Two-meter Sky Survey: A preliminary catalog

NASA Astrophysics Data System (ADS)

Van Eck, C. L.; Haverkorn, M.; Alves, M. I. R.; Beck, R.; Best, P.; Carretti, E.; Chyży, K. T.; Farnes, J. S.; Ferrière, K.; Hardcastle, M. J.; Heald, G.; Horellou, C.; Iacobelli, M.; Jelić, V.; Mulcahy, D. D.; O'Sullivan, S. P.; Polderman, I. M.; Reich, W.; Riseley, C. J.; Röttgering, H.; Schnitzeler, D. H. F. M.; Shimwell, T. W.; Vacca, V.; Vink, J.; White, G. J.

2018-06-01

The polarization properties of radio sources at very low frequencies (<200 MHz) have not been widely measured, but the new generation of low-frequency radio telescopes, including the Low Frequency Array (LOFAR: a Square Kilometre Array Low pathfinder), now gives us the opportunity to investigate these properties. In this paper, we report on the preliminary development of a data reduction pipeline to carry out polarization processing and Faraday tomography for data from the LOFAR Two-meter Sky Survey (LOTSS) and present the results of this pipeline from the LOTSS preliminary data release region (10h45m-15h30m right ascension, 45°-57° declination, 570 square degrees). We have produced a catalog of 92 polarized radio sources at 150 MHz at 4.'3 resolution and 1 mJy rms sensitivity, which is the largest catalog of polarized sources at such low frequencies. We estimate a lower limit to the polarized source surface density at 150 MHz, with our resolution and sensitivity, of 1 source per 6.2 square degrees. We find that our Faraday depth measurements are in agreement with previous measurements and have significantly smaller errors. Most of our sources show significant depolarization compared to 1.4 GHz, but there is a small population of sources with low depolarization indicating that their polarized emission is highly localized in Faraday depth. We predict that an extension of this work to the full LOTSS data would detect at least 3400 polarized sources using the same methods, and probably considerably more with improved data processing.

Cutoffs of Short-Term Heart Rate Variability Parameters in Brazilian Adolescents Male.

PubMed

Farah, Breno Quintella; Christofaro, Diego Giulliano Destro; Cavalcante, Bruno Remígio; Andrade-Lima, Aluísio; Germano-Soares, Antonio Henrique; Vanderlei, Luiz Carlos Marques; Lanza, Fernanda Cordoba; Ritti-Dias, Raphael Mendes

2018-05-15

A low heart rate variability (HRV) has been associated with cardiovascular risk factors in adolescents. However, no cut-off points are known for HRV parameters in this age group, making it difficult to use in clinical practice. Thus, the aims of the current study were to establish cutoffs of HRV parameters and to examine their association with cardiovascular risk in Brazilian adolescents male. For this reason, this cross-sectional study included 1152 adolescent boys (16.6 ± 1.2 years old). HRV measures of time (SD of all RR intervals, root mean square of the squared differences between adjacent normal RR intervals, and the percentage of adjacent intervals over 50 ms), frequency domains [low (LF) and high (HF) frequency], and Poincaré plot (SD1, SD2 and SD1/SD2 ratio) were assessed. Cardiovascular risk was assessed by sum of abdominal obesity, high blood pressure, overweight, and low physical activity level. The proposed cutoffs showed moderate to high sensitivity, specificity, and area under curve values (p < 0.05). HRV frequency parameters were statistically superior when compared to time-domain and Poincaré plot parameters. The binary logistic regression analysis indicated that all proposed HRV cutoffs were independently associated with a clustering of cardiovascular risk factors, with greater magnitude of HF and SD1/SD2 ratio (two or more risk factors: OR = 3.59 and 95% CI 1.76-7.34). In conclusion, proposed HRV cutoffs have moderate to high sensitivity in detecting of the cardiovascular risk factor and HRV frequency-domain were better discriminants of cardiovascular risk than time-domain and Poincaré plot parameters.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

High-frequency large-amplitude oscillations of a non-isothermal N/S boundary

NASA Astrophysics Data System (ADS)

Bezuglyj, A. I.; Shklovskij, V. A.

2016-10-01

Within the framework of a phenomenological approach based on the heat balance equation and the current dependence of the critical temperature of the superconductor, the effect of high-frequency current of large amplitude and arbitrary waveform on the non-isothermal balance of an oscillating N/S interface in a long superconductor was studied. Self-consistent average temperature field of the rapidly oscillating non-isothermal N/S boundary (heat kink) was introduced, which allowed us to go beyond the well-known concept of mean-square heating and consider the effect of the current waveform. With regard to experiments on the effects of high-power microwave radiation on the current-voltage (IV) characteristics of superconducting films, their classification was performed and the families of IV curves of inhomogeneous superconductors carrying a current containing a high-frequency component of large amplitude. Several IV curves exhibited a hysteresis of thermal nature.

Two dimensional wavefront retrieval using lateral shearing interferometry

NASA Astrophysics Data System (ADS)

Mancilla-Escobar, B.; Malacara-Hernández, Z.; Malacara-Hernández, D.

2018-06-01

A new zonal two-dimensional method for wavefront retrieval from a surface under test using lateral shearing interferometry is presented. A modified Saunders method and phase shifting techniques are combined to generate a method for wavefront reconstruction. The result is a wavefront with an error below 0.7 λ and without any global high frequency filtering. A zonal analysis over square cells along the surfaces is made, obtaining a polynomial expression for the wavefront deformations over each cell. The main advantage of this method over previously published methods is that a global filtering of high spatial frequencies is not present. Thus, a global smoothing of the wavefront deformations is avoided, allowing the detection of deformations with relatively small extensions, that is, with high spatial frequencies. Additionally, local curvature and low order aberration coefficients are obtained in each cell.

Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

NASA Technical Reports Server (NTRS)

Numata, Kenji; Kemery, Amy; Camp, Jordan

2004-01-01

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

Aerodynamic parameter estimation via Fourier modulating function techniques

NASA Technical Reports Server (NTRS)

Pearson, A. E.

1995-01-01

Parameter estimation algorithms are developed in the frequency domain for systems modeled by input/output ordinary differential equations. The approach is based on Shinbrot's method of moment functionals utilizing Fourier based modulating functions. Assuming white measurement noises for linear multivariable system models, an adaptive weighted least squares algorithm is developed which approximates a maximum likelihood estimate and cannot be biased by unknown initial or boundary conditions in the data owing to a special property attending Shinbrot-type modulating functions. Application is made to perturbation equation modeling of the longitudinal and lateral dynamics of a high performance aircraft using flight-test data. Comparative studies are included which demonstrate potential advantages of the algorithm relative to some well established techniques for parameter identification. Deterministic least squares extensions of the approach are made to the frequency transfer function identification problem for linear systems and to the parameter identification problem for a class of nonlinear-time-varying differential system models.

A Comparison Between Jerusalem Cross and Square Patch Frequency Selective Surfaces for Low Profile Antenna Applications

NASA Technical Reports Server (NTRS)

Cure, David; Weller, Thomas; Miranda, Felix A.

2011-01-01

In this paper, a comparison between Jerusalem Cross (JC) and Square Patch (SP) based Frequency Selected Surfaces (FSS) for low profile antenna applications is presented. The comparison is aimed at understanding the performance of low profile antennas backed by high impedance surfaces. In particular, an end loaded planar open sleeve dipole (ELPOSD) antenna is examined due to the various parameters within its configuration, offering significant design flexibility and a wide operating bandwidth. Measured data of the antennas demonstrate that increasing the number of unit cells improves the fractional bandwidth. The antenna bandwidth increased from 0.8% to 1.8% and from 0.8% to 2.7% for the JC and SP structures, respectively. The number of unit cells was increased from 48 to 80 for the JC-FSS and from 24 to 48 for the SP-FSS.

Changes of Heart Rate Variability during Methylphenidate Treatment in Attention-Deficit Hyperactivity Disorder Children: A 12-Week Prospective Study.

PubMed

Kim, Hayeon Jennifer; Yang, Jaewon; Lee, Moon Soo

2015-09-01

The aim of this study was to clarify the relationship between the autonomic nervous system and attention deficit hyperactivity disorder (ADHD) rating scales and to evaluate the usefulness of heart rate variability (HRV) as a psychophysiological biomarker for ADHD. Subjects were recruited from outpatients in the Department of Child and Adolescent Psychiatry at the Korea University Medical Center from August 2007 to December 2010. Subjects received methylphenidate. Time- and frequency-domain analyses of HRV, the Korean ADHD rating scale (K-ARS), and computerized ADHD diagnostic system were evaluated before treatment. After a 12-week period of medication administration, we repeated the HRV measurements and K-ARS rating. Eighty-six subjects were initially enrolled and 37 participants completed the 12-week treatment and HRV measurements subsequent to the treatment. Significant correlations were found between the K-ARS inattention score and some HRV parameters. All of the HRV parameters, except the standard deviations of the normal-to-normal interval, very low frequency, and low frequency to high frequency, showed a significant positive correlation between baseline and endpoint measures in completers. High frequency (HF) and the square root of the mean squared differences of successive normal-to-normal intervals (RMSSD), which are related to parasympathetic vagal tone, showed significant decreases from baseline to endpoint. The HRV test was shown to be reproducible. The decrease in HF and RMSSD suggests that parasympathetic dominance in ADHD can be altered by methylphenidate treatment. It also shows the possibility that HRV parameters can be used as psychophysiological markers in the treatment of ADHD.

Effects of spatial frequency content on classification of face gender and expression.

PubMed

Aguado, Luis; Serrano-Pedraza, Ignacio; Rodríguez, Sonia; Román, Francisco J

2010-11-01

The role of different spatial frequency bands on face gender and expression categorization was studied in three experiments. Accuracy and reaction time were measured for unfiltered, low-pass (cut-off frequency of 1 cycle/deg) and high-pass (cutoff frequency of 3 cycles/deg) filtered faces. Filtered and unfiltered faces were equated in root-mean-squared contrast. For low-pass filtered faces reaction times were higher than unfiltered and high-pass filtered faces in both categorization tasks. In the expression task, these results were obtained with expressive faces presented in isolation (Experiment 1) and also with neutral-expressive dynamic sequences where each expressive face was preceded by a briefly presented neutral version of the same face (Experiment 2). For high-pass filtered faces different effects were observed on gender and expression categorization. While both speed and accuracy of gender categorization were reduced comparing to unfiltered faces, the efficiency of expression classification remained similar. Finally, we found no differences between expressive and non expressive faces in the effects of spatial frequency filtering on gender categorization (Experiment 3). These results show a common role of information from the high spatial frequency band in the categorization of face gender and expression.

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

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

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

DOE PAGES

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.; ...

2017-03-27

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Operation of electrothermal and electrostatic MUMPs microactuators underwater

NASA Astrophysics Data System (ADS)

Sameoto, Dan; Hubbard, Ted; Kujath, Marek

2004-10-01

Surface-micromachined actuators made in multi-user MEMS processes (MUMPs) have been operated underwater without modifying the manufacturing process. Such actuators have generally been either electro-thermally or electro-statically actuated and both actuator styles are tested here for suitability underwater. This is believed to be the first time that thermal and electrostatic actuators have been compared for deflection underwater relative to air performance. A high-frequency ac square wave is used to replicate a dc-driven actuator output without the associated problem of electrolysis in water. This method of ac activation, with frequencies far above the mechanical resonance frequencies of the MEMS actuators, has been termed root mean square (RMS) operation. Both thermal and electrostatic actuators have been tested and proved to work using RMS control. Underwater performance has been evaluated by using in-air operation of these actuators as a benchmark. When comparing deflection per volt applied, thermal actuators operate between 5 and 9% of in-air deflection and electrostatic actuators show an improvement in force per volt applied of upwards of 6000%. These results agree with predictions based on the physical properties of the surrounding medium.

Effects of a Passive Online Software Application on Heart Rate Variability and Autonomic Nervous System Balance.

PubMed

Rubik, Beverly

2017-01-01

This study investigated whether short-term exposure to a passive online software application of purported subtle energy technology would affect heart rate variability (HRV) and associated autonomic nervous system measures. This was a randomized, double-blinded, sham-controlled clinical trial (RCT). The study took place in a nonprofit laboratory in Emeryville, California. Twenty healthy, nonsmoking subjects (16 females), aged 40-75 years, participated. Quantum Code Technology ™ (QCT), a purported subtle energy technology, was delivered through a passive software application (Heart+ App) on a smartphone placed <1 m from subjects who were seated and reading a catalog. HRV was measured for 5 min in triplicate for each condition via finger plethysmography using a Food and Drug Administration medically approved HRV measurement device. Measurements were made at baseline and 35 min following exposure to the software applications. The following parameters were calculated and analyzed: heart rate, total power, standard deviation node-to-node, root mean square sequential difference, low frequency to high frequency ratio (LF/HF), low frequency (LF), and high frequency (HF). Paired samples t-tests showed that for the Heart+ App, mean LF/HF decreased (p = 9.5 × 10 -4 ), while mean LF decreased in a trend (p = 0.06), indicating reduced sympathetic dominance. Root mean square sequential difference increased for the Heart+ App, showing a possible trend (p = 0.09). Post-pre differences in LF/HF for sham compared with the Heart+ App were also significant (p < 0.008) by independent t-test, indicating clinical relevance. Significant beneficial changes in mean LF/HF, along with possible trends in mean LF and root mean square sequential difference, were observed in subjects following 35 min exposure to the Heart+ App that was working in the background on an active smartphone untouched by the subjects. This may be the first RCT to show that specific frequencies of a purported non-Hertzian type of subtle energy conveyed by software applications broadcast from personal electronic devices can be bioactive and beneficially impact autonomic nervous system balance.

Process to restore obliterated serial numbers on metal surfaces

NASA Technical Reports Server (NTRS)

Young, S. G.; Parker, B.; Chisum, W. J.

1974-01-01

Metal smeared into grooves of serial numbers by grinding or filing can be cleaned out by process called cavitation. Ultrasonic vibrator generates very high frequency vibrations in water which create millions of microscopic bubbles. Cavitation bubbles impact metal surface at thousands of pounds per square inch pressure. Metal particles filling grooves are broken away.

Influence of modulation frequency in rubidium cell frequency standards

NASA Technical Reports Server (NTRS)

Audoin, C.; Viennet, J.; Cyr, N.; Vanier, J.

1983-01-01

The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.

A practical double-sided frequency selective surface for millimeter-wave applications

NASA Astrophysics Data System (ADS)

Mohyuddin, Wahab; Woo, Dong Sik; Choi, Hyun Chul; Kim, Kang Wook

2018-02-01

Analysis, design, and implementation of a practical, high-rejection frequency selective surface (FSS) are presented in this paper. An equivalent circuit model is introduced for predicting the frequency response of the FSS. The FSS consists of periodic square loop structures fabricated on both sides of the thin dielectric substrate by using the low-cost chemical etching technique. The proposed FSS possesses band-stop characteristics and is implemented to suppress the 170 GHz signal with attenuation of more than 45 dB with insensitivity to an angle of incident plane wave over 20°. Good agreement is observed among calculated, simulated, and measured results. The proposed FSS filter can be used in various millimeter-wave applications such as the protection of imaging diagnostic systems from high spurious input power.

Prospects for Future Synergies Between SKA and AtLAST

NASA Astrophysics Data System (ADS)

Wagg, Jeff

2018-01-01

The Square Kilometre Array will be the next major global radio astronomy observatory. Being built in two phases, the first phase will consist of a low frequency array in Australia and a mid to high frequency array of dishes in the Karoo of South Africa. The design of SKA1 is nearly complete with the expectation that construction should begin within the next two years. A significant fraction of the observing time on both SKA1-MID and SKA1-LOW will likely be devoted to large survey programmes covering a broad range of science objectives. Given the timeline for these SKA1 programmes to be completed, it is anticipated that they could naturally complement future high frequency surveys using AtLAST. I will highlight a few areas where such synergies should exist.

High geomagnetic intensity during the mid-Cretaceous from Thellier analyses of single plagioclase crystals.

PubMed

Tarduno, J A; Cottrell, R D; Smirnov, A V

2001-03-02

Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase crystals separated from basalts of the Rajmahal Traps (113 to 116 million years old) of India that formed during the Cretaceous Normal Polarity Superchron. These data suggest a time-averaged paleomagnetic dipole moment of 12.5 +/- 1.4 x 10(22) amperes per square meter, three times greater than mean Cenozoic and Early Cretaceous-Late Jurassic dipole moments when geomagnetic reversals were frequent. This result supports a correlation between intervals of low reversal frequency and high geomagnetic field strength.

Temporal analysis of the frequency and duration of low and high streamflow: Years of record needed to characterize streamflow variability

USGS Publications Warehouse

Huh, S.; Dickey, D.A.; Meador, M.R.; Ruhl, K.E.

2005-01-01

A temporal analysis of the number and duration of exceedences of high- and low-flow thresholds was conducted to determine the number of years required to detect a level shift using data from Virginia, North Carolina, and South Carolina. Two methods were used - ordinary least squares assuming a known error variance and generalized least squares without a known error variance. Using ordinary least squares, the mean number of years required to detect a one standard deviation level shift in measures of low-flow variability was 57.2 (28.6 on either side of the break), compared to 40.0 years for measures of high-flow variability. These means become 57.6 and 41.6 when generalized least squares is used. No significant relations between years and elevation or drainage area were detected (P>0.05). Cluster analysis did not suggest geographic patterns in years related to physiography or major hydrologic regions. Referring to the number of observations required to detect a one standard deviation shift as 'characterizing' the variability, it appears that at least 20 years of record on either side of a shift may be necessary to adequately characterize high-flow variability. A longer streamflow record (about 30 years on either side) may be required to characterize low-flow variability. ?? 2005 Elsevier B.V. All rights reserved.

Relationship between cutoff frequency and accuracy in time-interval photon statistics applied to oscillating signals

NASA Astrophysics Data System (ADS)

Rebolledo, M. A.; Martinez-Betorz, J. A.

1989-04-01

In this paper the accuracy in the determination of the period of an oscillating signal, when obtained from the photon statistics time-interval probability, is studied as a function of the precision (the inverse of the cutoff frequency of the photon counting system) with which time intervals are measured. The results are obtained by means of an experiment with a square-wave signal, where the Fourier or square-wave transforms of the time-interval probability are measured. It is found that for values of the frequency of the signal near the cutoff frequency the errors in the period are small.

Progress toward Brazilian cesium fountain second generation

NASA Astrophysics Data System (ADS)

Bueno, Caio; Rodriguez Salas, Andrés; Torres Müller, Stella; Bagnato, Vanderlei Salvador; Varela Magalhães, Daniel

2018-03-01

The operation of a Cesium fountain primary frequency standard is strongly influenced by the characteristics of two important subsystems. The first is a stable frequency reference and the second is the frequency-transfer system. A stable standard frequency reference is key factor for experiments that require high accuracy and precision. The frequency stability of this reference has a significant impact on the procedures for evaluating certain systematic biases in frequency standards. This paper presents the second generation of the Brazilian Cesium Fountain (Br-CsF) through the opto-mechanical assembly and vacuum chamber to trap atoms. We used a squared section glass profile to build the region where the atoms are trapped and colled by magneto-optical technique. The opto-mechanical system was reduced to increase stability and robustness. This newest Atomic Fountain is essential to contribute with time and frequency development in metrology systems.

Nondestructive hall coefficient measurements using ACPD techniques

NASA Astrophysics Data System (ADS)

Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled

2018-04-01

Hall coefficient measurements offer great opportunities as well as major challenges for nondestructive materials characterization. The Hall effect is produced by the magnetic Lorentz force acting on moving charge carriers in the presence of an applied magnetic field. The magnetic perturbation gives rise to a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution. Therefore, Hall coefficient measurements usually exploit the so-called transverse galvanomagnetic potential drop effect that arises when the Hall current is intercepted by the boundaries of the specimen and thereby produce a measurable potential drop. In contrast, no Hall potential is produced in a large plate in the presence of a uniform normal field at quasi-static low frequencies. In other words, conventional Hall coefficient measurements are inherently destructive since they require cutting the material under tests. This study investigated the feasibility of using alternating current potential drop (ACPD) techniques for nondestructive Hall coefficient measurements in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies, constraining the bias magnetic field can replace constraining the dimensions of the specimen, which is inherently destructive. For example, when a cylindrical permanent magnet is used to provide the bias magnetic field, the peak Hall voltage is produced when the diameter of the magnet is equal to the diagonal of the square ACPD probe. Although this method is less effective than cutting the specimen to a finite size, the loss of sensitivity is less than one order of magnitude even at very low frequencies. In contrast, at sufficiently high inspection frequencies the magnetic field of the Hall current induces a strong enough Hall electric field that produces measurable potential differences between points lying on the path followed by the Hall current even when it is not intercepted by either the edge of the specimen or the edge of the magnetic field. The induced Hall voltage increases proportionally to the square root of frequency as the current is squeezed into a shallow electromagnetic skin of decreasing depth. This approach could be exploited to measure the Hall coefficient near the surface at high frequencies without cutting the specimen.

Skyrmion-based high-frequency signal generator

NASA Astrophysics Data System (ADS)

Luo, Shijiang; Zhang, Yue; Shen, Maokang; Ou-Yang, Jun; Yan, Baiqian; Yang, Xiaofei; Chen, Shi; Zhu, Benpeng; You, Long

2017-03-01

Many concepts for skyrmion-based devices have been proposed, and most of their possible applications are based on the motion of skyrmions driven by a dc current in an area with a constricted geometry. However, skyrmion motion driven by a pulsed current has not been investigated so far. In this work, we propose a skyrmion-based high-frequency signal generator based on the pulsed-current-driven circular motion of skyrmions in a square-shaped film by micromagnetic simulation. The results indicate that skyrmions can move in a closed curve with central symmetry. The trajectory and cycle period can be adjusted by tuning the size of the film, the current density, the Dzyaloshinskii-Moriya interaction constant, and the local in-plane magnetic anisotropy. The period can be tuned from several nanoseconds to tens of nanoseconds, which offers the possibility to prepare high-frequency signal generator based on skyrmions.

High Frequency Fluctuations of Polar Motion During IGS'92 Campaign

NASA Astrophysics Data System (ADS)

Huang, Chengli; Jin, Wenjin; Liao, Dechun; Zhu, Wenyao; Wang, Jiexian

1994-09-01

During IGS'92 Campaign seven PM(Polar Motion) series provided by GPS Processing Centers are analysed in this paper. Some similar high frequency fluctuations in these PM series are detected by using spectra! analyses, least square adjustment and F-test as follows: there are short periodic fluctuations of 27.0, 16.5, 13.4, 10.4 day in X direction; and of 10.0, 20.5, 15.8 day in Y direction. And there are similar systematic deviations derived from the comparison of each series with EOP(IERS) 92 C 04. The inain cause of these systematic deviations is that the rotation between the reference frames of these series and ITRF91 exists. As for the reason, the coordinates of stations are not fixed (or partly fixed only) when solving X and Y with GPS data. The high frequency fluctuations of polar motion are explained to some extent by the excitation of atmospheric angular momentum.

Development of regional skews for selected flood durations for the Central Valley Region, California, based on data through water year 2008

USGS Publications Warehouse

Lamontagne, Jonathan R.; Stedinger, Jery R.; Berenbrock, Charles; Veilleux, Andrea G.; Ferris, Justin C.; Knifong, Donna L.

2012-01-01

Flood-frequency information is important in the Central Valley region of California because of the high risk of catastrophic flooding. Most traditional flood-frequency studies focus on peak flows, but for the assessment of the adequacy of reservoirs, levees, other flood control structures, sustained flood flow (flood duration) frequency data are needed. This study focuses on rainfall or rain-on-snow floods, rather than the annual maximum, because rain events produce the largest floods in the region. A key to estimating flood-duration frequency is determining the regional skew for such data. Of the 50 sites used in this study to determine regional skew, 28 sites were considered to have little to no significant regulated flows, and for the 22 sites considered significantly regulated, unregulated daily flow data were synthesized by using reservoir storage changes and diversion records. The unregulated, annual maximum rainfall flood flows for selected durations (1-day, 3-day, 7-day, 15-day, and 30-day) for all 50 sites were furnished by the U.S. Army Corps of Engineers. Station skew was determined by using the expected moments algorithm program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual flood-duration data. Bayesian generalized least squares regression procedures used in earlier studies were modified to address problems caused by large cross correlations among concurrent rainfall floods in California and to address the extensive censoring of low outliers at some sites, by using the new expected moments algorithm for fitting the LP3 distribution to rainfall flood-duration data. To properly account for these problems and to develop suitable regional-skew regression models and regression diagnostics, a combination of ordinary least squares, weighted least squares, and Bayesian generalized least squares regressions were adopted. This new methodology determined that a nonlinear model relating regional skew to mean basin elevation was the best model for each flood duration. The regional-skew values ranged from -0.74 for a flood duration of 1-day and a mean basin elevation less than 2,500 feet to values near 0 for a flood duration of 7-days and a mean basin elevation greater than 4,500 feet. This relation between skew and elevation reflects the interaction of snow and rain, which increases with increased elevation. The regional skews are more accurate, and the mean squared errors are less than in the Interagency Advisory Committee on Water Data's National skew map of Bulletin 17B.

Regional equations for estimation of peak-streamflow frequency for natural basins in Texas

USGS Publications Warehouse

Asquith, William H.; Slade, Raymond M.

1997-01-01

Peak-streamflow frequency for 559 Texas stations with natural (unregulated and rural or nonurbanized) basins was estimated with annual peak-streamflow data through 1993. The peak-streamflow frequency and drainage-basin characteristics for the Texas stations were used to develop 16 sets of equations to estimate peak-streamflow frequency for ungaged natural stream sites in each of 11 regions in Texas. The relation between peak-streamflow frequency and contributing drainage area for 5 of the 11 regions is curvilinear, requiring that one set of equations be developed for drainage areas less than 32 square miles and another set be developed for drainage areas greater than 32 square miles. These equations, developed through multiple-regression analysis using weighted least squares, are based on the relation between peak-streamflow frequency and basin characteristics for streamflow-gaging stations. The regions represent areas with similar flood characteristics. The use and limitations of the regression equations also are discussed. Additionally, procedures are presented to compute the 50-, 67-, and 90-percent confidence limits for any estimation from the equations. Also, supplemental peak-streamflow frequency and basin characteristics for 105 selected stations bordering Texas are included in the report. This supplemental information will aid in interpretation of flood characteristics for sites near the state borders of Texas.

A Census of Southern Pulsars at 185 MHz

NASA Astrophysics Data System (ADS)

Xue, Mengyao; Bhat, N. D. R.; Tremblay, S. E.; Ord, S. M.; Sobey, C.; Swainston, N. A.; Kaplan, D. L.; Johnston, Simon; Meyers, B. W.; McSweeney, S. J.

2017-12-01

The Murchison Widefield Array, and its recently developed Voltage Capture System, facilitates extending the low-frequency range of pulsar observations at high-time and -frequency resolution in the Southern Hemisphere, providing further information about pulsars and the ISM. We present the results of an initial time-resolved census of known pulsars using the Murchison Widefield Array. To significantly reduce the processing load, we incoherently sum the detected powers from the 128 Murchison Widefield Array tiles, which yields 10% of the attainable sensitivity of the coherent sum. This preserves the large field-of-view ( 450 deg2 at 185 MHz), allowing multiple pulsars to be observed simultaneously. We developed a WIde-field Pulsar Pipeline that processes the data from each observation and automatically folds every known pulsar located within the beam. We have detected 50 pulsars to date, 6 of which are millisecond pulsars. This is consistent with our expectation, given the telescope sensitivity and the sky coverage of the processed data ( 17 000 deg2). For 10 pulsars, we present the lowest frequency detections published. For a subset of the pulsars, we present multi-frequency pulse profiles by combining our data with published profiles from other telescopes. Since the Murchison Widefield Array is a low-frequency precursor to the Square Kilometre Array, we use our census results to forecast that a survey using the low-frequency component of the Square Kilometre Array Phase 1 can potentially detect around 9 400 pulsars.

Comparison of athletic training professional preparation to the prevalence of injury occurrence in the collegiate setting

NASA Astrophysics Data System (ADS)

Westerman, Beverly Jean

1999-10-01

This study investigated the relationship between the frequency of injuries that occur to certain body areas in National Collegiate Athletic Association (NCAA) athletes and the percentage of time teaching about the same subject areas in Athletic Training Education Programs (ATEP). Directors of Commission of Accreditation of Allied Health Education Programs (CAAHEP) accredited and National Athletic Trainers' Association (NATA) approved programs were surveyed. Randomly selected ATEP directors were interviewed by telephone to collect information on estimated teaching time, the strengths and weaknesses of their programs, and preferred teaching methods. Data were collected from the NCAA Injury Surveillance System to calculate the frequency of injury. Chi-square 'goodness-of-fit' tests were used to determine if a 'good fit' existed between injury frequency and teaching time in two categories: general body areas (head and face, upper extremity, lower extremity, spine, and abdomen and thorax) and specific body areas (head, face, upper arm and shoulder, elbow and forearm, wrist and hand, hip and pelvis, thigh, knee, lower leg, ankle and foot, cervical spine, thoracic spine, lumbar spine, abdomen, and thorax). Standardized residuals were used to assist in determining the location of statistical significance within the same two categories. The chi-square values calculated for both the general and specific body areas were greater than the critical value set at a significance level of .05 with 4 and 14 degrees of freedom respectively. Therefore, it was found that a 'good fit' does not exist between injury frequency and teaching time. The standardized residuals were calculated for each variable within the categories. One out of five general body areas and 10 out of 15 specific body areas were less than 2.00 in absolute value and were found not to contribute to the high chi-square value. Although the chi-square values showed a lack of fit between injury frequency and teaching time in the general and specific body areas, the standardized residuals indicated a relationship exists between some variables (body areas) within each category. In other words, the percentage of teaching time may correspond with injury frequency in some general and specific body areas. The responses from the program directors indicated they thought their academic programs were spending the appropriate amount of time teaching about the general and specific body areas. However, the percentages of teaching time reported for each of the body areas varied greatly among the responders. Further study is indicated to examine the relationship between teaching time/content and injury frequency.

MgB2 Thin-Film Bolometer for Applications in Far-Infrared Instruments on Future Planetary Missions

NASA Technical Reports Server (NTRS)

Lakew, B.; Aslam, S.; Brasunas, J.; Cao, N.; Costen, N.; La, A.; Stevenson, T.; Waczynski, A.

2012-01-01

A SiN membrane based MgB2 thin-film bolometer, with a non-optimized absorber, has been fabricated that shows an electrical noise equivalent power of 256 fW/square root Hz operating at 30 Hz in the 8.5 - 12.35 micron spectral bandpass. This value corresponds to an electrical specific detectivity of 7.6 x 10(exp 10) cm square root Hz/W. The bolometer shows a measured blackbody (optical) specific detectivity of 8.8 x 10(exp 9) cm square root Hz/W, with a responsivity of 701.5 kV/W and a first-order time constant of 5.2 ms. It is predicted that with the inclusion of a gold black absorber that a blackbody specific detectivity of 6.4 x 10(exp 10) cm/square root Hz/W at an operational frequency of 10 Hz, can be realized for integration into future planetary exploration instrumentation where high sensitivity is required in the 17 - 250 micron spectral wavelength range.

Square-Wave Ocular Oscillation and Ataxia in an Anti-GAD-Positive Individual With Hypothyroidism.

PubMed

Brokalaki, Chrysoula; Kararizou, Evangelia; Dimitrakopoulos, Antonis; Evdokimidis, Ioannis; Anagnostou, Evangelos

2015-12-01

Cerebellar ataxia is an uncommon manifestation of hypothyroidism with unknown pathomechanism. The few descriptions of the clinical phenotype range from limb, gait, and trunk ataxia to various ocular motor abnormalities. We evaluated a 62-year-old woman with previously undetected severe hypothyroidism who presented with prominent saccadic intrusions and gait ataxia. She had high titers of antithyroid autoantibodies and anti-glutamic acid decarboxylase (anti-GAD) antibodies. Horizontal eye movement recordings revealed a series of nearly continuous pseudoharmonic square wave jerks (SWJs) constituting a square wave oscillation. Amplitudes reached maximum values of about 4, and wave frequency approached 100 cycles per minute. Thyroxine substitution and corticosteroid administration had little effect on SWJ parameters. The square wave oscillation nearly completely resolved after a single treatment session with intravenous immunoglobulin suggesting a causal link between an autoimmune process and the cerebellar dysfunction. Current concepts of the genesis of saccadic intrusions favor a role for anti-GAD antibodies in the etiology of SWJs.

High-speed spatial frequency domain imaging of rat cortex detects dynamic optical and physiological properties following cardiac arrest and resuscitation.

PubMed

Wilson, Robert H; Crouzet, Christian; Torabzadeh, Mohammad; Bazrafkan, Afsheen; Farahabadi, Maryam H; Jamasian, Babak; Donga, Dishant; Alcocer, Juan; Zaher, Shuhab M; Choi, Bernard; Akbari, Yama; Tromberg, Bruce J

2017-10-01

Quantifying rapidly varying perturbations in cerebral tissue absorption and scattering can potentially help to characterize changes in brain function caused by ischemic trauma. We have developed a platform for rapid intrinsic signal brain optical imaging using macroscopically structured light. The device performs fast, multispectral, spatial frequency domain imaging (SFDI), detecting backscattered light from three-phase binary square-wave projected patterns, which have a much higher refresh rate than sinusoidal patterns used in conventional SFDI. Although not as fast as "single-snapshot" spatial frequency methods that do not require three-phase projection, square-wave patterns allow accurate image demodulation in applications such as small animal imaging where the limited field of view does not allow single-phase demodulation. By using 655, 730, and 850 nm light-emitting diodes, two spatial frequencies ([Formula: see text] and [Formula: see text]), three spatial phases (120 deg, 240 deg, and 360 deg), and an overall camera acquisition rate of 167 Hz, we map changes in tissue absorption and reduced scattering parameters ([Formula: see text] and [Formula: see text]) and oxy- and deoxyhemoglobin concentration at [Formula: see text]. We apply this method to a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) to quantify hemodynamics and scattering on temporal scales ([Formula: see text]) ranging from tens of milliseconds to minutes. We observe rapid concurrent spatiotemporal changes in tissue oxygenation and scattering during CA and following CPR, even when the cerebral electrical signal is absent. We conclude that square-wave SFDI provides an effective technical strategy for assessing cortical optical and physiological properties by balancing competing performance demands for fast signal acquisition, small fields of view, and quantitative information content.

Experimental demonstrations in audible frequency range of band gap tunability and negative refraction in two-dimensional sonic crystal.

PubMed

Pichard, Hélène; Richoux, Olivier; Groby, Jean-Philippe

2012-10-01

The propagation of audible acoustic waves in two-dimensional square lattice tunable sonic crystals (SC) made of square cross-section infinitely rigid rods embedded in air is investigated experimentally. The band structure is calculated with the plane wave expansion (PWE) method and compared with experimental measurements carried out on a finite extend structure of 200 cm width, 70 cm depth and 15 cm height. The structure is made of square inclusions of 5 cm side with a periodicity of L = 7.5 cm placed inbetween two rigid plates. The existence of tunable complete band gaps in the audible frequency range is demonstrated experimentally by rotating the scatterers around their vertical axis. Negative refraction is then analyzed by use of the anisotropy of the equi-frequency surface (EFS) in the first band and of a finite difference time domain (FDTD) method. Experimental results finally show negative refraction in the audible frequency range.

Age-related macular degeneration changes the processing of visual scenes in the brain.

PubMed

Ramanoël, Stephen; Chokron, Sylvie; Hera, Ruxandra; Kauffmann, Louise; Chiquet, Christophe; Krainik, Alexandre; Peyrin, Carole

2018-01-01

In age-related macular degeneration (AMD), the processing of fine details in a visual scene, based on a high spatial frequency processing, is impaired, while the processing of global shapes, based on a low spatial frequency processing, is relatively well preserved. The present fMRI study aimed to investigate the residual abilities and functional brain changes of spatial frequency processing in visual scenes in AMD patients. AMD patients and normally sighted elderly participants performed a categorization task using large black and white photographs of scenes (indoors vs. outdoors) filtered in low and high spatial frequencies, and nonfiltered. The study also explored the effect of luminance contrast on the processing of high spatial frequencies. The contrast across scenes was either unmodified or equalized using a root-mean-square contrast normalization in order to increase contrast in high-pass filtered scenes. Performance was lower for high-pass filtered scenes than for low-pass and nonfiltered scenes, for both AMD patients and controls. The deficit for processing high spatial frequencies was more pronounced in AMD patients than in controls and was associated with lower activity for patients than controls not only in the occipital areas dedicated to central and peripheral visual fields but also in a distant cerebral region specialized for scene perception, the parahippocampal place area. Increasing the contrast improved the processing of high spatial frequency content and spurred activation of the occipital cortex for AMD patients. These findings may lead to new perspectives for rehabilitation procedures for AMD patients.

Volume conductor model of transcutaneous electrical stimulation with kilohertz signals

PubMed Central

Medina, Leonel E.; Grill, Warren M.

2014-01-01

Objective Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequencies beyond those typically used in neural stimulation. Approach We implemented a multilayer volume conductor model including dispersion and capacitive effects, coupled to a cable model of a nerve fiber. We simulated voltage- and current-controlled transcutaneous stimulation, and quantified the effects of frequency on the distribution of potentials and fiber excitation. We also quantified the effects of a novel transdermal amplitude modulated signal (TAMS) consisting of a non-zero offset sinusoidal carrier modulated by a square-pulse train. Main results The model revealed that high-frequency signals generated larger potentials at depth than did low frequencies, but this did not translate into lower stimulation thresholds. Both TAMS and conventional rectangular pulses activated more superficial fibers in addition to the deeper, target fibers, and at no frequency did we observe an inversion of the strength-distance relationship. Current regulated stimulation was more strongly influenced by fiber depth, whereas voltage regulated stimulation was more strongly influenced by skin thickness. Finally, our model reproduced the threshold-frequency relationship of experimentally measured motor thresholds. Significance The model may be used for prediction of motor thresholds in TES, and contributes to the understanding of high-frequency TES. PMID:25380254

Volume conductor model of transcutaneous electrical stimulation with kilohertz signals

NASA Astrophysics Data System (ADS)

Medina, Leonel E.; Grill, Warren M.

2014-12-01

Objective. Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequencies beyond those typically used in neural stimulation. Approach. We implemented a multilayer volume conductor model including dispersion and capacitive effects, coupled to a cable model of a nerve fiber. We simulated voltage- and current-controlled transcutaneous stimulation, and quantified the effects of frequency on the distribution of potentials and fiber excitation. We also quantified the effects of a novel transdermal amplitude modulated signal (TAMS) consisting of a non-zero offset sinusoidal carrier modulated by a square-pulse train. Main results. The model revealed that high-frequency signals generated larger potentials at depth than did low frequencies, but this did not translate into lower stimulation thresholds. Both TAMS and conventional rectangular pulses activated more superficial fibers in addition to the deeper, target fibers, and at no frequency did we observe an inversion of the strength-distance relationship. Current regulated stimulation was more strongly influenced by fiber depth, whereas voltage regulated stimulation was more strongly influenced by skin thickness. Finally, our model reproduced the threshold-frequency relationship of experimentally measured motor thresholds. Significance. The model may be used for prediction of motor thresholds in TES, and contributes to the understanding of high-frequency TES.

Sound diffraction at wall impedance discontinuities in a circular cylinder, investigated using Wiener-Hopf technique

NASA Technical Reports Server (NTRS)

Cho, Y. C.

1983-01-01

Rigorous solutions are presented for sound diffraction in a circular cylinder with axial discontinuities of the wall admittance (or impedance). Analytical expressions are derived for the reflection and the transmission coefficients for duct modes. The results are discussed quantitatively in the limits of small admittance shifts (delta) and of low frequencies (ka). One of the results is the low frequency behavior of the reflection coefficient R(o) sub 00 of the fundamental mode. For the mode of a hardwall duct reflected from the junction with a softwall duct, (R(o) sub oo yields - (1-square root of (ka) square root of (2/i delta)); this result is in contrast to the frequency dependence of the reflection from the open end of a hardwall duct, for which R(o) sub oo yields - 1-(ka) squared/2 .

Modal characterization of the ASCIE segmented optics testbed: New algorithms and experimental results

NASA Technical Reports Server (NTRS)

Carrier, Alain C.; Aubrun, Jean-Noel

1993-01-01

New frequency response measurement procedures, on-line modal tuning techniques, and off-line modal identification algorithms are developed and applied to the modal identification of the Advanced Structures/Controls Integrated Experiment (ASCIE), a generic segmented optics telescope test-bed representative of future complex space structures. The frequency response measurement procedure uses all the actuators simultaneously to excite the structure and all the sensors to measure the structural response so that all the transfer functions are measured simultaneously. Structural responses to sinusoidal excitations are measured and analyzed to calculate spectral responses. The spectral responses in turn are analyzed as the spectral data become available and, which is new, the results are used to maintain high quality measurements. Data acquisition, processing, and checking procedures are fully automated. As the acquisition of the frequency response progresses, an on-line algorithm keeps track of the actuator force distribution that maximizes the structural response to automatically tune to a structural mode when approaching a resonant frequency. This tuning is insensitive to delays, ill-conditioning, and nonproportional damping. Experimental results show that is useful for modal surveys even in high modal density regions. For thorough modeling, a constructive procedure is proposed to identify the dynamics of a complex system from its frequency response with the minimization of a least-squares cost function as a desirable objective. This procedure relies on off-line modal separation algorithms to extract modal information and on least-squares parameter subset optimization to combine the modal results and globally fit the modal parameters to the measured data. The modal separation algorithms resolved modal density of 5 modes/Hz in the ASCIE experiment. They promise to be useful in many challenging applications.

Analysis on the time and frequency domains of the acceleration in front crawl stroke.

PubMed

Gil, Joaquín Madera; Moreno, Luis-Millán González; Mahiques, Juan Benavent; Muñoz, Víctor Tella

2012-05-01

The swimming involves accelerations and decelerations in the swimmer's body. Thus, the main objective of this study is to make a temporal and frequency analysis of the acceleration in front crawl swimming, regarding the gender and the performance. The sample was composed by 31 male swimmers (15 of high-level and 16 of low-level) and 20 female swimmers (11 of high-level and 9 of low-level). The acceleration was registered from the third complete cycle during eight seconds in a 25 meters maximum velocity test. A position transducer (200Hz) was used to collect the data, and it was synchronized to an aquatic camera (25Hz). The acceleration in the temporal (root mean square, minimum and maximum of the acceleration) and frequency (power peak, power peak frequency and spectral area) domains was calculated with Fourier analysis, as well as the velocity and the spectrums distribution in function to present one or more main peaks (type 1 and type 2). A one-way ANOVA was used to establish differences between gender and performance. Results show differences between genders in all the temporal domain variables (p<0.05) and only the Spectral Area (SA) in the frequency domain (p<0.05). Between gender and performance, only the Root Mean Square (RMS) showed differences in the performance of the male swimmers (p<0.05) and in the higher level swimmers, the Maximum (Max) and the Power Peak (PP) of the acceleration showed differences between both genders (p<0.05). These results confirms the importance of knowing the RMS to determine the efficiency of the swimmers regarding gender and performance level.

Enhanced Microwave Absorption Properties of Carbon Black/Silicone Rubber Coating by Frequency-Selective Surface

NASA Astrophysics Data System (ADS)

Yang, Zhaoning; Luo, Fa; Gao, Lu; Qing, Yuchang; Zhou, Wancheng; Zhu, Dongmei

2016-10-01

A square frequency-selective surface (FSS) design has been employed to improve the microwave absorption properties of carbon black/silicone rubber (CBSR) composite coating. The FSS is placed on the surface of the CBSR coating. The effects of FSS design parameters on the microwave absorption properties of the CBSR coating have been investigated, including the size and period of the FSS design, and the thickness and permittivity of the coating. Simulation results indicate that the absorption peak for the CBSR coating alone is related to its thickness and electromagnetic parameters, while the combination of the CBSR coating with a FSS can exhibit a new absorption peak in the reflection curve; the frequency of the new absorption peak is determined by the resonance of the square FSS design and tightly depends on the size of the squares, with larger squares in the FSS design leading to a lower frequency of the new absorption peak. The enhancement of the absorption performance depends on achievement of a new absorption peak using a suitable size and period of the FSS design. In addition, the FSS design has a stable frequency response for both transverse electromagnetic (TE) and transverse magnetic (TM) polarizations as the incident angle varies from 0° to 40°. The optimized results indicate that the bandwidth with reflection loss below -5 dB can encompass the whole frequency range from 8 GHz to 18 GHz for thickness of the CBSR coating of only 1.8 mm. The simulation results are confirmed by experiments.

Effects of smoking cessation on heart rate variability among long-term male smokers.

PubMed

Harte, Christopher B; Meston, Cindy M

2014-04-01

Cigarette smoking has been shown to adversely affect heart rate variability (HRV), suggesting dysregulation of cardiac autonomic function. Conversely, smoking cessation is posited to improve cardiac regulation. The aim of the present study was to examine the effects of smoking cessation on HRV among a community sample of chronic smokers. Sixty-two healthy male smokers enrolled in an 8-week smoking cessation program involving a nicotine transdermal patch treatment. Participants were assessed at baseline (while smoking regularly), at mid-treatment (while using a high-dose patch), and at follow-up, 4 weeks after patch discontinuation. Both time-domain (standard deviation of normal-to-normal (NN) intervals (SDNN), square root of the mean squared difference of successive NN intervals (RMSSD), and percent of NN intervals for which successive heartbeat intervals differed by at least 50 ms (pNN50)) and frequency-domain (low frequency (LF), high frequency (HF), LF/HF ratio) parameters of HRV were assessed at each visit. Successful quitters (n = 20), compared to those who relapsed (n = 42), displayed significantly higher SDNN, RMSSD, pNN50, LF, and HF at follow-up, when both nicotine and smoke free. Smoking cessation significantly enhances HRV in chronic male smokers, indicating improved autonomic modulation of the heart. Results suggest that these findings may be primarily attributable to nicotine discontinuation rather than tobacco smoke discontinuation alone.

Tire-road friction coefficient estimation based on the resonance frequency of in-wheel motor drive system

NASA Astrophysics Data System (ADS)

Chen, Long; Bian, Mingyuan; Luo, Yugong; Qin, Zhaobo; Li, Keqiang

2016-01-01

In this paper, a resonance frequency-based tire-road friction coefficient (TRFC) estimation method is proposed by considering the dynamics performance of the in-wheel motor drive system under small slip ratio conditions. A frequency response function (FRF) is deduced for the drive system that is composed of a dynamic tire model and a simplified motor model. A linear relationship between the squared system resonance frequency and the TFRC is described with the FRF. Furthermore, the resonance frequency is identified by the Auto-Regressive eXogenous model using the information of the motor torque and the wheel speed, and the TRFC is estimated thereafter by a recursive least squares filter with the identified resonance frequency. Finally, the effectiveness of the proposed approach is demonstrated through simulations and experimental tests on different road surfaces.

Anti-aliasing Wiener filtering for wave-front reconstruction in the spatial-frequency domain for high-order astronomical adaptive-optics systems.

PubMed

Correia, Carlos M; Teixeira, Joel

2014-12-01

Computationally efficient wave-front reconstruction techniques for astronomical adaptive-optics (AO) systems have seen great development in the past decade. Algorithms developed in the spatial-frequency (Fourier) domain have gathered much attention, especially for high-contrast imaging systems. In this paper we present the Wiener filter (resulting in the maximization of the Strehl ratio) and further develop formulae for the anti-aliasing (AA) Wiener filter that optimally takes into account high-order wave-front terms folded in-band during the sensing (i.e., discrete sampling) process. We employ a continuous spatial-frequency representation for the forward measurement operators and derive the Wiener filter when aliasing is explicitly taken into account. We further investigate and compare to classical estimates using least-squares filters the reconstructed wave-front, measurement noise, and aliasing propagation coefficients as a function of the system order. Regarding high-contrast systems, we provide achievable performance results as a function of an ensemble of forward models for the Shack-Hartmann wave-front sensor (using sparse and nonsparse representations) and compute point-spread-function raw intensities. We find that for a 32×32 single-conjugated AOs system the aliasing propagation coefficient is roughly 60% of the least-squares filters, whereas the noise propagation is around 80%. Contrast improvements of factors of up to 2 are achievable across the field in the H band. For current and next-generation high-contrast imagers, despite better aliasing mitigation, AA Wiener filtering cannot be used as a standalone method and must therefore be used in combination with optical spatial filters deployed before image formation actually takes place.

Operating principles of an electrothermal vibrometer for optical switching applications

NASA Astrophysics Data System (ADS)

Pai, Min-fan; Tien, Norman C.

1999-09-01

A compact polysilicon surface-micromachined microactuator designed for optical switching applications is described. This actuator is fabricated using the foundry MUMPs process provided by Cronos Integrated Microsystems Inc. Actuated electrothermally, the microactuator allows fast switching speeds and can be operated with a low voltage square-wave signal. The design, operation mechanisms for this long-range and high frequency thermal actuation are described. A vertical micromirror integrated with this actuator can be operated with a 10.5 V, 20 kHz 15% duty-cycle pulse signal, achieving a lateral moving speed higher than 15.6 mm/sec. The optical switch has been operated to frequencies as high as 30 kHz.

Dynamic magnetic hysteresis properties of two-dimensional ferrimagnetic structures containing high-spin (S = 5/2) and low-spin (S = 1/2)

NASA Astrophysics Data System (ADS)

Batı, Mehmet; Ertaş, Mehmet

2017-09-01

The dynamic hysteresis behaviors of a containing high spin-5/2 and low spin-1/2 Ising ferrimagnetic system on a square lattice are studied by using the dynamic mean-field approximation. The influences of the temperature, the single-ion anisotropy and the frequency on dynamic hysteresis behaviors are investigated in detail. Somewhat characteristic behaviors are found, such as the presence of triple hysteresis loop for appropriate values of the crystal field or temperature. Besides, we observed that, hysteresis loop area and phase transition points are very sensitive to changes in frequency and thus have profound importance in device application.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard A.; Davis, Andrew E.; Wang, Qing X.; Yamamoto, Takashi; Cerkoney, Daniel P.; Reid, Candy; Koopman, Maximiliaan L.; Minami, Hidetoshi; Kashiwagi, Takanari; Rain, Joseph R.; Doty, Constance M.; Sedlack, Michael A.; Morales, Manuel A.; Watanabe, Chiharu; Tsujimoto, Manabu; Delfanazari, Kaveh; Kadowaki, Kazuo

2017-12-01

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C ∞v , C 4v , and C 3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

l/f Noise in the Superconducting Transition of a MgB2 Thin Film

NASA Technical Reports Server (NTRS)

Lakew, B.; Aslam, S.; Jones, H.; Stevenson, T.; Cao, N.

2010-01-01

The noise voltage spectral density in the superconducting transition of a MgB2 thin film on a SiN-coated Si thick substrate was measured over the frequency range 1 Hz-to-1 KHz. Using established bolometer noise theory the theoretical noise components due to Johnson, 1/f(excess) and phonon noise are modeled to the measured data. It is shown that for the case of a MgB2 thin film in the vicinity of the mid-point of transition, coupled to a heat sink via a fairly high thermal conductance (approximately equal to 10(sup -1) W/K)) that the measured noise voltage spectrum is 1/f limited and exhibits lit dependence with a varying between 0.3 and 0.5 in the measured frequency range. At a video frame rate frequency of 30 Hz the measured noise voltage density in the film is approximately equal to 61 nV /the square root of HZ, using this value an upper limit of electrical NEP approximately equal to 0.67pW / the square root of Hz is implied for a practical MgB2 bolometer operating at 36.1 K.

Metafitting: Weight optimization for least-squares fitting of PTTI data

NASA Technical Reports Server (NTRS)

Douglas, Rob J.; Boulanger, J.-S.

1995-01-01

For precise time intercomparisons between a master frequency standard and a slave time scale, we have found it useful to quantitatively compare different fitting strategies by examining the standard uncertainty in time or average frequency. It is particularly useful when designing procedures which use intermittent intercomparisons, with some parameterized fit used to interpolate or extrapolate from the calibrating intercomparisons. We use the term 'metafitting' for the choices that are made before a fitting procedure is operationally adopted. We present methods for calculating the standard uncertainty for general, weighted least-squares fits and a method for optimizing these weights for a general noise model suitable for many PTTI applications. We present the results of the metafitting of procedures for the use of a regular schedule of (hypothetical) high-accuracy frequency calibration of a maser time scale. We have identified a cumulative series of improvements that give a significant reduction of the expected standard uncertainty, compared to the simplest procedure of resetting the maser synthesizer after each calibration. The metafitting improvements presented include the optimum choice of weights for the calibration runs, optimized over a period of a week or 10 days.

A revisit to contingency table and tests of independence: bootstrap is preferred to Chi-square approximations as well as Fisher's exact test.

PubMed

Lin, Jyh-Jiuan; Chang, Ching-Hui; Pal, Nabendu

2015-01-01

To test the mutual independence of two qualitative variables (or attributes), it is a common practice to follow the Chi-square tests (Pearson's as well as likelihood ratio test) based on data in the form of a contingency table. However, it should be noted that these popular Chi-square tests are asymptotic in nature and are useful when the cell frequencies are "not too small." In this article, we explore the accuracy of the Chi-square tests through an extensive simulation study and then propose their bootstrap versions that appear to work better than the asymptotic Chi-square tests. The bootstrap tests are useful even for small-cell frequencies as they maintain the nominal level quite accurately. Also, the proposed bootstrap tests are more convenient than the Fisher's exact test which is often criticized for being too conservative. Finally, all test methods are applied to a few real-life datasets for demonstration purposes.

The influence of a time-varying least squares parametric model when estimating SFOAEs evoked with swept-frequency tones

NASA Astrophysics Data System (ADS)

Hajicek, Joshua J.; Selesnick, Ivan W.; Henin, Simon; Talmadge, Carrick L.; Long, Glenis R.

2018-05-01

Stimulus frequency otoacoustic emissions (SFOAEs) were evoked and estimated using swept-frequency tones with and without the use of swept suppressor tones. SFOAEs were estimated using a least-squares fitting procedure. The estimated SFOAEs for the two paradigms (with- and without-suppression) were similar in amplitude and phase. The fitting procedure minimizes the square error between a parametric model of total ear-canal pressure (with unknown amplitudes and phases) and ear-canal pressure acquired during each paradigm. Modifying the parametric model to allow SFOAE amplitude and phase to vary over time revealed additional amplitude and phase fine structure in the without-suppressor, but not the with-suppressor paradigm. The use of a time-varying parametric model to estimate SFOAEs without-suppression may provide additional information about cochlear mechanics not available when using a with-suppressor paradigm.

Multivariable frequency domain identification via 2-norm minimization

NASA Technical Reports Server (NTRS)

Bayard, David S.

1992-01-01

The author develops a computational approach to multivariable frequency domain identification, based on 2-norm minimization. In particular, a Gauss-Newton (GN) iteration is developed to minimize the 2-norm of the error between frequency domain data and a matrix fraction transfer function estimate. To improve the global performance of the optimization algorithm, the GN iteration is initialized using the solution to a particular sequentially reweighted least squares problem, denoted as the SK iteration. The least squares problems which arise from both the SK and GN iterations are shown to involve sparse matrices with identical block structure. A sparse matrix QR factorization method is developed to exploit the special block structure, and to efficiently compute the least squares solution. A numerical example involving the identification of a multiple-input multiple-output (MIMO) plant having 286 unknown parameters is given to illustrate the effectiveness of the algorithm.

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.

Efficient block processing of long duration biotelemetric brain data for health care monitoring

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

Soumya, I.; Zia Ur Rahman, M., E-mail: mdzr-5@ieee.org; Rama Koti Reddy, D. V.

In real time clinical environment, the brain signals which doctor need to analyze are usually very long. Such a scenario can be made simple by partitioning the input signal into several blocks and applying signal conditioning. This paper presents various block based adaptive filter structures for obtaining high resolution electroencephalogram (EEG) signals, which estimate the deterministic components of the EEG signal by removing noise. To process these long duration signals, we propose Time domain Block Least Mean Square (TDBLMS) algorithm for brain signal enhancement. In order to improve filtering capability, we introduce normalization in the weight update recursion of TDBLMS,more » which results TD-B-normalized-least mean square (LMS). To increase accuracy and resolution in the proposed noise cancelers, we implement the time domain cancelers in frequency domain which results frequency domain TDBLMS and FD-B-Normalized-LMS. Finally, we have applied these algorithms on real EEG signals obtained from human using Emotive Epoc EEG recorder and compared their performance with the conventional LMS algorithm. The results show that the performance of the block based algorithms is superior to the LMS counter-parts in terms of signal to noise ratio, convergence rate, excess mean square error, misadjustment, and coherence.« less

Generation and evolution of mode-locked noise-like square-wave pulses in a large-anomalous-dispersion Er-doped ring fiber laser.

PubMed

Liu, Jun; Chen, Yu; Tang, Pinghua; Xu, Changwen; Zhao, Chujun; Zhang, Han; Wen, Shuangchun

2015-03-09

In a passively mode-locked Erbium-doped fiber laser with large anomalous-dispersion, we experimentally demonstrate the formation of noise-like square-wave pulse, which shows quite different features from conventional dissipative soliton resonance (DSR). The corresponding temporal and spectral characteristics of a variety of operation states, including Q-switched mode-locking, continuous-wave mode-locking and Raman-induced noise-like pulse near the lasing threshold, are also investigated. Stable noise-like square-wave mode-locked pulses can be obtained at a fundamental repetition frequency of 195 kHz, with pulse packet duration tunable from 15 ns to 306 ns and per-pulse energy up to 200 nJ. By reducing the linear cavity loss, stable higher-order harmonic mode-locking had also been observed, with pulse duration ranging from 37 ns at the 21st order harmonic wave to 320 ns at the fundamental order. After propagating along a piece of long telecom fiber, the generated square-wave pulses do not show any obvious change, indicating that the generated noise-like square-wave pulse can be considered as high-energy pulse packet for some promising applications. These experimental results should shed some light on the further understanding of the mechanism and characteristics of noise-like square-wave pulses.

Spatial noise and threshold contrasts in LCD displays

NASA Astrophysics Data System (ADS)

Roehrig, Hans; Krupinski, Elizabeth A.; Chawla, Amarpreet S.; Fan, Jiahua; Gandhi, Kunal

2003-05-01

This paper presents the results of initial physical and psycho-physical evaluations of the noise of high resolution LCDs. 5 LCDs were involved, having 4 different pixel structures. Spatial as well as temporal noise was physically measured with the aid of a high-performance CCD camera. Human contrast sensitivity in the presence of spatial noise was determined psycho-physically using periodic stimuli (square-wave patterns) as well as aperiodic stimuli (squares). For the measurements of the human contrast sensitivity, all LCDs were calibrated to the DICOM 14 Grayscale Standard Display Function (GSDF). The results demonstrate that spatial noise is the dominant noise in all LCDs, while temporal noise is insignificant and plays only a minor part. The magnitude of spatial noise of LCDs is in the range between that of CRTs with a P104 and that of CRTs with a P45. Of particular importance with respect to LCD noise is the contribution of the pixel structure to the Noise Power Spectrum, which shows up as sharp spikes at spatial frequencies beyond the LCDs" Nyquist frequency. The paper does not offer any clues about the importance of these spikes on the human contrast sensitivity.

1- and 2-particle Microrheology of Hyaluronic Acid

NASA Astrophysics Data System (ADS)

Sagan, Austin; Kearns, Sarah; Ross, David; Das, Moumita; Thurston, George; Franklin, Scott

2015-03-01

Hyaluronic acid (also called HA or Hyaluronan) is a high molecular weight polysaccaride ubiquitous in the extracellular matrix of soft tissue such as cartilage, skin, the eye's vitreous gel and synovial fluid. It has been shown to play an important role in mechanotransduction, cell migration and proliferation, and in tissue morphodynamics. We present a confocal microrheology study of hyaluronic acid of varying concentrations. The mean squared displacement (MSD) of sub-micron colloidal tracer particles is tracked in two dimensions and shows a transition from diffusive motion at low concentrations to small-time trapping by the protein network as the concentration increases. Correlations between particle motion can be used to determine an effective mean-squared displacement which deviates from the single-particle MSD as the fluid becomes less homogeneous. The real and effective mean-squared displacements are used to probe the local and space-averaged frequency dependent rheological properties of the fluid as the concentration changes.

Aerodynamic coefficient identification package dynamic data accuracy determinations: Lessons learned

NASA Technical Reports Server (NTRS)

Heck, M. L.; Findlay, J. T.; Compton, H. R.

1983-01-01

The errors in the dynamic data output from the Aerodynamic Coefficient Identification Packages (ACIP) flown on Shuttle flights 1, 3, 4, and 5 were determined using the output from the Inertial Measurement Units (IMU). A weighted least-squares batch algorithm was empolyed. Using an averaging technique, signal detection was enhanced; this allowed improved calibration solutions. Global errors as large as 0.04 deg/sec for the ACIP gyros, 30 mg for linear accelerometers, and 0.5 deg/sec squared in the angular accelerometer channels were detected and removed with a combination is bias, scale factor, misalignment, and g-sensitive calibration constants. No attempt was made to minimize local ACIP dynamic data deviations representing sensed high-frequency vibration or instrument noise. Resulting 1sigma calibrated ACIP global accuracies were within 0.003 eg/sec, 1.0 mg, and 0.05 deg/sec squared for the gyros, linear accelerometers, and angular accelerometers, respectively.

Artificial Aurora and Ionospheric Heating by HAARP

NASA Astrophysics Data System (ADS)

Hadavandkhani, S.; Nikouravan, Bijan; Ghazimaghrebi, F.

2016-08-01

A recent experiment was achieved at HAARP to study the scaling of the ionospherically generated ELF signal with power transmitted from the high frequency (HF) array. The results were in excellent agreement with computer simulations. The outcomes approving that the ELF power increases with the square of the incident HF power. This paper present a review on the situation of the ionized particles in Ionospheric layer when stimulated by artificial an ELF and VLF external high energy radio waves.

Resonant ultrasound spectrometer

DOEpatents

Migliori, Albert; Visscher, William M.; Fisk, Zachary

1990-01-01

An ultrasound resonant spectrometer determines the resonant frequency spectrum of a rectangular parallelepiped sample of a high dissipation material over an expected resonant response frequency range. A sample holder structure grips corners of the sample between piezoelectric drive and receive transducers. Each transducer is mounted on a membrane for only weakly coupling the transducer to the holder structure and operatively contacts a material effective to remove system resonant responses at the transducer from the expected response range. i.e., either a material such as diamond to move the response frequencies above the range or a damping powder to preclude response within the range. A square-law detector amplifier receives the response signal and retransmits the signal on an isolated shield of connecting cabling to remove cabling capacitive effects. The amplifier also provides a substantially frequency independently voltage divider with the receive transducer. The spectrometer is extremely sensitive to enable low amplitude resonance to be detected for use in calculating the elastic constants of the high dissipation sample.

Compact CPW-fed spiral-patch monopole antenna with tuneable frequency for multiband applications

NASA Astrophysics Data System (ADS)

Beigi, P.; Nourinia, J.; Zehforoosh, Y.

2018-04-01

A frequency reconfigurable monopole antenna with coplanar waveguide-fed with four switchable for multiband application is reported. The monopole antenna includes square-spiral patch and two L-shaped elements. The number of frequency resonances are increased by adding square spiral. In the reported antenna, two PIN diodes are used to achieve the multiband operation. PIN diodes embedded on the spiral patch can control the frequency resonance when they are forward-biased or in those off-state. The final designed antenna, with compact size of 20 × 20 ×1 mm3, has been fabricated on an inexpensive FR4 substrate. All experimental and simulation results are acceptable suggesting that the reported antenna is a good candidate for multiband applications.

Assessment of environmental and nondestructive earthquake effects on modal parameters of an office building based on long-term vibration measurements

NASA Astrophysics Data System (ADS)

Wu, Wen-Hwa; Wang, Sheng-Wei; Chen, Chien-Chou; Lai, Gwolong

2017-05-01

Identification for the modal parameters of an instrumented office building using ambient vibration measurements is conducted in this study based on a recently developed stochastic subspace identification methodology equipped with an alternative stabilization diagram and a hierarchical sifting process. The identified results are then deliberately examined to recognize the dynamic features for quite a few dominant modes of this building structure including three pairs of closely-spaced modes. Making use of the collected three-month data including three seismic events, the analyzed results show that the root-mean-square vibration response is directly related to the wind speed and indirectly related to the air temperature under a specific condition. More importantly, it is discovered that the root-mean-square response is the dominant factor to induce the variation of modal parameters. Except for the torsional modes, all the other modal frequencies are highly correlated with the root-mean-square acceleration in a negative manner and the corresponding damping ratios also clearly display a positive correlation. Another crucial observation from this assessment is that the percentages of frequency variation in three months for most of the identified modes go beyond 10%. The effects of three nondestructive earthquakes are further traced to observe the tendencies of reducing the modal frequencies and raising the damping ratios, both with a variation level possibly increasing with the seismic intensity. But different from the effects of environmental factors, the changes in modal parameters caused by nondestructive earthquakes will vanish right after the seismic events.

Use of a torsional pendulum as a high-pressure gage and determination of viscosity of helium gas at high pressures

NASA Technical Reports Server (NTRS)

Maisel, J. E.; Webeler, R. W. H.; Grimes, H. H.

1973-01-01

Three torsional crystal parameters were examined for suitability in sensing pressure in gases up to 131 million newtons per square meter. The best parameters were found to be the change in crystal decrement at resonance and the change in crystal electrical resistance at resonance. The change in crystal resonant frequency did not appear to be a reliable pressure measuring parameter. Pure argon and pure helium gases were studied for use as working fluids. Helium functioned better over a wider pressure range. Calibration of the gage also provided a measure of the viscosity-density product of the gas as a function of pressure. These data, together with known extrapolated density data, permitted the determination of the viscosity of helium to 131 million N/square meter.

Navy Applications of High-Frequency Acoustics

NASA Astrophysics Data System (ADS)

Cox, Henry

2004-11-01

Although the emphasis in underwater acoustics for the last few decades has been in low-frequency acoustics, motivated by long range detection of submarines, there has been a continuing use of high-frequency acoustics in traditional specialized applications such as bottom mapping, mine hunting, torpedo homing and under ice navigation. The attractive characteristics of high-frequency sonar, high spatial resolution, wide bandwidth, small size and relatively low cost must be balanced against the severe range limitation imposed by attenuation that increases approximately as frequency-squared. Many commercial applications of acoustics are ideally served by high-frequency active systems. The small size and low cost, coupled with the revolution in small powerful signal processing hardware has led to the consideration of more sophisticated systems. Driven by commercial applications, there are currently available several commercial-off-the-shelf products including acoustic modems for underwater communication, multi-beam fathometers, side scan sonars for bottom mapping, and even synthetic aperture side scan sonar. Much of the work in high frequency sonar today continues to be focused on specialized applications in which the application is emphasized over the underlying acoustics. Today's vision for the Navy of the future involves Autonomous Undersea Vehicles (AUVs) and off-board ASW sensors. High-frequency acoustics will play a central role in the fulfillment of this vision as a means of communication and as a sensor. The acoustic communication problems for moving AUVs and deep sensors are discussed. Explicit relationships are derived between the communication theoretic description of channel parameters in terms of time and Doppler spreads and ocean acoustic parameters, group velocities, phase velocities and horizontal wavenumbers. Finally the application of synthetic aperture sonar to the mine hunting problems is described.

A symmetrical method to obtain shear moduli from microrheology.

PubMed

Nishi, Kengo; Kilfoil, Maria L; Schmidt, Christoph F; MacKintosh, F C

2018-05-16

Passive microrheology typically deduces shear elastic loss and storage moduli from displacement time series or mean-squared displacements (MSD) of thermally fluctuating probe particles in equilibrium materials. Common data analysis methods use either Kramers-Kronig (KK) transformation or functional fitting to calculate frequency-dependent loss and storage moduli. We propose a new analysis method for passive microrheology that avoids the limitations of both of these approaches. In this method, we determine both real and imaginary components of the complex, frequency-dependent response function χ(ω) = χ'(ω) + iχ''(ω) as direct integral transforms of the MSD of thermal particle motion. This procedure significantly improves the high-frequency fidelity of χ(ω) relative to the use of KK transformation, which has been shown to lead to artifacts in χ'(ω). We test our method on both model and experimental data. Experiments were performed on solutions of worm-like micelles and dilute collagen solutions. While the present method agrees well with established KK-based methods at low frequencies, we demonstrate significant improvement at high frequencies using our symmetric analysis method, up to almost the fundamental Nyquist limit.

Transmit beamforming for optimal second-harmonic generation.

PubMed

Hoilund-Kaupang, Halvard; Masoy, Svein-Erik

2011-08-01

A simulation study of transmit ultrasound beams from several transducer configurations is conducted to compare second-harmonic imaging at 3.5 MHz and 11 MHz. Second- harmonic generation and the ability to suppress near field echoes are compared. Each transducer configuration is defined by a chosen f-number and focal depth, and the transmit pressure is estimated to not exceed a mechanical index of 1.2. The medium resembles homogeneous muscle tissue with nonlinear elasticity and power-law attenuation. To improve computational efficiency, the KZK equation is utilized, and all transducers are circular-symmetric. Previous literature shows that second-harmonic generation is proportional to the square of the transmit pressure, and that transducer configurations with different transmit frequencies, but equal aperture and focal depth in terms of wavelengths, generate identical second-harmonic fields in terms of shape. Results verify this for a medium with attenuation f1. For attenuation f1.1, deviations are found, and the high frequency subsequently performs worse than the low frequency. The results suggest that high frequencies are less able to suppress near-field echoes in the presence of a heterogeneous body wall than low frequencies.

Multivariate analysis of correlation between electrophysiological and hemodynamic responses during cognitive processing

PubMed Central

Kujala, Jan; Sudre, Gustavo; Vartiainen, Johanna; Liljeström, Mia; Mitchell, Tom; Salmelin, Riitta

2014-01-01

Animal and human studies have frequently shown that in primary sensory and motor regions the BOLD signal correlates positively with high-frequency and negatively with low-frequency neuronal activity. However, recent evidence suggests that this relationship may also vary across cortical areas. Detailed knowledge of the possible spectral diversity between electrophysiological and hemodynamic responses across the human cortex would be essential for neural-level interpretation of fMRI data and for informative multimodal combination of electromagnetic and hemodynamic imaging data, especially in cognitive tasks. We applied multivariate partial least squares correlation analysis to MEG–fMRI data recorded in a reading paradigm to determine the correlation patterns between the data types, at once, across the cortex. Our results revealed heterogeneous patterns of high-frequency correlation between MEG and fMRI responses, with marked dissociation between lower and higher order cortical regions. The low-frequency range showed substantial variance, with negative and positive correlations manifesting at different frequencies across cortical regions. These findings demonstrate the complexity of the neurophysiological counterparts of hemodynamic fluctuations in cognitive processing. PMID:24518260

Asymptotics for metamaterials and photonic crystals

PubMed Central

Antonakakis, T.; Craster, R. V.; Guenneau, S.

2013-01-01

Metamaterial and photonic crystal structures are central to modern optics and are typically created from multiple elementary repeating cells. We demonstrate how one replaces such structures asymptotically by a continuum, and therefore by a set of equations, that captures the behaviour of potentially high-frequency waves propagating through a periodic medium. The high-frequency homogenization that we use recovers the classical homogenization coefficients in the low-frequency long-wavelength limit. The theory is specifically developed in electromagnetics for two-dimensional square lattices where every cell contains an arbitrary hole with Neumann boundary conditions at its surface and implemented numerically for cylinders and split-ring resonators. Illustrative numerical examples include lensing via all-angle negative refraction, as well as omni-directive antenna, endoscope and cloaking effects. We also highlight the importance of choosing the correct Brillouin zone and the potential of missing interesting physical effects depending upon the path chosen. PMID:23633908

Wavelength dependence of the Brillouin spectral width of boron doped germanosilicate optical fibers.

PubMed

Law, Pi-Cheng; Dragic, Peter D

2010-08-30

Boron co-doped germanosilicate fibers are investigated via the Brillouin light scattering technique using two wavelengths, 1534 nm and 1064 nm. Several fibers are investigated, including four drawn from the same preform but at different draw temperatures. The Stokes' shifts and the Brillouin spectral widths are found to increase with increasing fiber draw temperature. A frequency-squared law has adequately described the wavelength dependence of the Brillouin spectral width of conventional Ge-doped fibers. However, it is found that unlike conventional Ge-doped fibers these fibers do not follow the frequency-squared law. This is explained through a frequency-dependent dynamic viscosity that modifies this law.

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications

PubMed Central

Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J.; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-01-01

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications. PMID:27147324

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.

PubMed

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-05-01

High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.

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

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew, E-mail: andrew.karellas@umassmed.edu

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixelmore » pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.« less

Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads.

PubMed

Padulo, Johnny; Di Giminiani, Riccardo; Dello Iacono, Antonio; Zagatto, Alessandro M; Migliaccio, Gian M; Grgantov, Zoran; Ardigò, Luca P

2016-01-01

We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P < 0.05), with the exception of flexor carpi radialis (at low acceleration load, P > 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P < 0.05), with the exception of flexor digitorum superficialis (P > 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads.

Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads

PubMed Central

Padulo, Johnny; Di Giminiani, Riccardo; Dello Iacono, Antonio; Zagatto, Alessandro M.; Migliaccio, Gian M.; Grgantov, Zoran; Ardigò, Luca P.

2016-01-01

We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P < 0.05), with the exception of flexor carpi radialis (at low acceleration load, P > 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P < 0.05), with the exception of flexor digitorum superficialis (P > 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads. PMID:27378948

Note: An inexpensive square waveform ion funnel driver

NASA Astrophysics Data System (ADS)

Hoffman, Nathan M.; Opačić, Bojana; Reilly, Peter T. A.

2017-01-01

An inexpensive frequency variable square waveform generator (WFG) was developed to use with existing sinusoidal waveform driven ion funnels. The developed WFG was constructed using readily available low voltage DC power supplies and discrete components placed in printed circuit boards. As applied to ion funnels, this WFG represents considerable cost savings over commercially available products without sacrificing performance. Operation of the constructed pulse generator has been demonstrated for a 1 nF ion funnel at an operating frequency of 1 MHz while switching 48 Vp-p.

Note: An inexpensive square waveform ion funnel driver.

PubMed

Hoffman, Nathan M; Opačić, Bojana; Reilly, Peter T A

2017-01-01

An inexpensive frequency variable square waveform generator (WFG) was developed to use with existing sinusoidal waveform driven ion funnels. The developed WFG was constructed using readily available low voltage DC power supplies and discrete components placed in printed circuit boards. As applied to ion funnels, this WFG represents considerable cost savings over commercially available products without sacrificing performance. Operation of the constructed pulse generator has been demonstrated for a 1 nF ion funnel at an operating frequency of 1 MHz while switching 48 V p-p .

An Implantable Neuroprosthetic Device to Normalize Bladder Function after SCI

DTIC Science & Technology

2013-10-01

we now used 2 separate cuff electrodes (one bipolar and one tripolar , i.e., the electrode #1 and #2 in Fig.1A) to deliver the low and high...Stim. A in Fig.1B) Page 5 and a high frequency (5-20 kHz, 0-11 V) biphasic square waveform (see Fig.1B) to the tripolar cuff electrodes #2 and...sacral spine. Two tripolar cuff electrodes were implanted bilaterally on the pudendal nerves in addition to one bipolar cuff electrode that was

Allele frequency distribution of 1691G >A F5 (which confers Factor V Leiden) across Europe, including Slavic populations.

PubMed

Clark, Jeremy S C; Adler, Grażyna; Salkic, Nermin N; Ciechanowicz, Andrzej

2013-11-01

The allele 1691A F5, conferring Factor V Leiden, is a common risk factor in venous thromboembolism. The frequency distribution for this allele in Western Europe has been well documented; but here data from Central, Eastern and South-Eastern Europe has been included. In order to assess the significance of the collated data, a chi-squared test was applied, and Tukey tests and z-tests with Bonferroni correction were compared. A distribution with a North-Southeast band of high frequency of the 1691A F5 allele was discovered with a pocket including some Southern Slavic populations with low frequency. European countries/regions can be arbitrarily delimited into low (group 1, <2.8 %, mean 1.9 % 1691A F5 allele) or high (group 2, ≥2.8 %, mean 4.0 %) frequency groups, with many significant differences between groups, but only one intra-group difference (the Tukey test is suggested to be superior to the z-tests). In Europe a North-Southeast band of 1691A F5 high frequency has been found, clarified by inclusion of data from Central, Eastern and South-Eastern Europe, which surrounds a pocket of low frequency in the Balkans which could possibly be explained by Slavic migration. There seem to be no indications of variation in environmental selection due to geographical location.

Effects of cold water immersion and active recovery on post-exercise heart rate variability.

PubMed

Bastos, F N; Vanderlei, L C M; Nakamura, F Y; Bertollo, M; Godoy, M F; Hoshi, R A; Junior, J N; Pastre, C M

2012-11-01

The aim of the present study was to investigate the potential benefits of cold water immersion (CWI) and active recovery (AR) on blood lactate concentration ([Lac]) and heart rate variability (HRV) indices following high-intensity exercise. 20 male subjects were recruited. On the first visit, an incremental test was performed to determine maximal oxygen consumption and the associated speed (MAS). The remaining 3 visits for the performance of constant velocity exhaustive tests at MAS and different recovery methods (6 min) were separated by 7-day intervals [randomized: CWI, AR or passive recovery (PR)]. The CWI and AR lowered [Lac] (p<0.05) at 11, 13 and 15 min after exercise cessation in comparison to PR. There was a 'time' and 'recovery mode' interaction for 2 HRV indices: standard deviation of normal R-R intervals (SDNN) (partial eta squared=0.114) and natural log of low-frequency power density (lnLF) (partial eta squared=0.090). CWI presented significantly higher SDNN compared to PR at 15 min of recovery (p<0.05). In addition, greater SDNN values were found in CWI vs. AR during the application of recovery interventions, and at 30 and 75 min post-exercise (p<0.05 for all differences). The lnLF during the recovery interventions and at 75 min post-exercise was greater using CWI compared with AR (p<0.05). For square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) and natural log of high-frequency power density (lnHF), a moderate effect size was found between CWI and PR during the recovery interventions and at 15 min post-exercise. Our findings show that AR and CWI offer benefits regarding the removal of [Lac] following high-intensity exercise. While limited, CWI results in some improvement in post-exercise cardiac autonomic regulation compared to AR and PR. Further, AR is not recommended if the aim is to accelerate the parasympathetic reactivation. © Georg Thieme Verlag KG Stuttgart · New York.

A resolution-enhancing image reconstruction method for few-view differential phase-contrast tomography

NASA Astrophysics Data System (ADS)

Guan, Huifeng; Anastasio, Mark A.

2017-03-01

It is well-known that properly designed image reconstruction methods can facilitate reductions in imaging doses and data-acquisition times in tomographic imaging. The ability to do so is particularly important for emerging modalities such as differential X-ray phase-contrast tomography (D-XPCT), which are currently limited by these factors. An important application of D-XPCT is high-resolution imaging of biomedical samples. However, reconstructing high-resolution images from few-view tomographic measurements remains a challenging task. In this work, a two-step sub-space reconstruction strategy is proposed and investigated for use in few-view D-XPCT image reconstruction. It is demonstrated that the resulting iterative algorithm can mitigate the high-frequency information loss caused by data incompleteness and produce images that have better preserved high spatial frequency content than those produced by use of a conventional penalized least squares (PLS) estimator.

Note: Low phase noise programmable phase-locked loop with high temperature stability.

PubMed

Michálek, Vojtěch; Procházka, Ivan

2017-03-01

The design and construction of low jitter programmable phase-locked loop with low temperature coefficient of phase are presented. It has been designed for demanding high precision timing applications, especially as a clock source for event timer with subpicosecond precision. The phase-locked loop itself has a jitter of few hundreds of femtoseconds. It produces square wave with programmable output frequency from 100 MHz to 500 MHz and programmable amplitude of 0.25 V to 1.2 V peak-to-peak, which is locked to 5 MHz or 10 MHz reference frequency common for disciplined oscillators and highly stable clocks such as hydrogen maser. Moreover, it comprises an on-board temperature compensated crystal oscillator for stand-alone usage. The device provides temperature coefficient of the phase lock of 0.9 ps/K near room temperature.

Tunable all-angle negative refraction and photonic band gaps in two-dimensional plasma photonic crystals with square-like Archimedean lattices

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

Zhang, Hai-Feng, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Nanjing Artillery Academy, Nanjing 211132; Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn

In this paper, the tunable all-angle negative refraction and photonic band gaps (PBGs) in two types of two-dimensional (2D) plasma photonic crystals (PPCs) composed of homogeneous plasma and dielectric (GaAs) with square-like Archimedean lattices (ladybug and bathroom lattices) for TM wave are theoretically investigated based on a modified plane wave expansion method. The type-1 structure is dielectric rods immersed in the plasma background, and the complementary structure is named as type-2 PPCs. Theoretical simulations demonstrate that the both types of PPCs with square-like Archimedean lattices have some advantages in obtaining the higher cut-off frequency, the larger PBGs, more number ofmore » PBGs, and the relative bandwidths compared to the conventional square lattices as the filling factor or radius of inserted rods is same. The influences of plasma frequency and radius of inserted rod on the properties of PBGs for both types of PPCs also are discussed in detail. The calculated results show that PBGs can be manipulated by the parameters as mentioned above. The possibilities of all-angle negative refraction in such two types of PPCs at low bands also are discussed. Our calculations reveal that the all-angle negative phenomena can be observed in the first two TM bands, and the frequency range of all-angle negative refraction can be tuned by changing plasma frequency. Those properties can be used to design the optical switching and sensor.« less

An Efficient Estimator for Moving Target Localization Using Multi-Station Dual-Frequency Radars.

PubMed

Huang, Jiyan; Zhang, Ying; Luo, Shan

2017-12-15

Localization of a moving target in a dual-frequency radars system has now gained considerable attention. The noncoherent localization approach based on a least squares (LS) estimator has been addressed in the literature. Compared with the LS method, a novel localization method based on a two-step weighted least squares estimator is proposed to increase positioning accuracy for a multi-station dual-frequency radars system in this paper. The effects of signal noise ratio and the number of samples on the performance of range estimation are also analyzed in the paper. Furthermore, both the theoretical variance and Cramer-Rao lower bound (CRLB) are derived. The simulation results verified the proposed method.

An Efficient Estimator for Moving Target Localization Using Multi-Station Dual-Frequency Radars

PubMed Central

Zhang, Ying; Luo, Shan

2017-01-01

Localization of a moving target in a dual-frequency radars system has now gained considerable attention. The noncoherent localization approach based on a least squares (LS) estimator has been addressed in the literature. Compared with the LS method, a novel localization method based on a two-step weighted least squares estimator is proposed to increase positioning accuracy for a multi-station dual-frequency radars system in this paper. The effects of signal noise ratio and the number of samples on the performance of range estimation are also analyzed in the paper. Furthermore, both the theoretical variance and Cramer–Rao lower bound (CRLB) are derived. The simulation results verified the proposed method. PMID:29244727

A multi-channel isolated power supply in non-equipotential circuit

NASA Astrophysics Data System (ADS)

Li, Xiang; Zhao, Bo-Wen; Zhang, Yan-Chi; Xie, Da

2018-04-01

A multi-channel isolation power supply is designed for the problems of different MOSFET or IGBT in the non-equipotential circuit in this paper. It mainly includes the square wave generation circuit, the high-frequency transformer and the three-terminal stabilized circuit. The first part is used to generate the 24V square wave, and as the input of the magnetic ring transformer. In the second part, the magnetic ring transformer consists of one input and three outputs to realize multi-channel isolation output. The third part can output different potential and realize non-equal potential function through the three-terminal stabilized chip. In addition, the multi-channel isolation power source proposed in this paper is Small size, high reliability and low price, and it is convenient for power electronic switches that operate on multiple different potentials. Therefore, the research on power supply of power electronic circuit has practical significance.

Power strain imaging based on vibro-elastography techniques

NASA Astrophysics Data System (ADS)

Wen, Xu; Salcudean, S. E.

2007-03-01

This paper describes a new ultrasound elastography technique, power strain imaging, based on vibro-elastography (VE) techniques. With this method, tissue is compressed by a vibrating actuator driven by low-pass or band-pass filtered white noise, typically in the 0-20 Hz range. Tissue displacements at different spatial locations are estimated by correlation-based approaches on the raw ultrasound radio frequency signals and recorded in time sequences. The power spectra of these time sequences are computed by Fourier spectral analysis techniques. As the average of the power spectrum is proportional to the squared amplitude of the tissue motion, the square root of the average power over the range of excitation frequencies is used as a measure of the tissue displacement. Then tissue strain is determined by the least squares estimation of the gradient of the displacement field. The computation of the power spectra of the time sequences can be implemented efficiently by using Welch's periodogram method with moving windows or with accumulative windows with a forgetting factor. Compared to the transfer function estimation originally used in VE, the computation of cross spectral densities is not needed, which saves both the memory and computational times. Phantom experiments demonstrate that the proposed method produces stable and operator-independent strain images with high signal-to-noise ratio in real time. This approach has been also tested on a few patient data of the prostate region, and the results are encouraging.

Lack of Association of Estrogen Receptor Alpha Gene Polymorphisms with Cardiorespiratory and Metabolic Variables in Young Women

PubMed Central

Rebelo, Ana Cristina; Verlengia, Rozangela; Kunz, Vandeni; Tamburus, Nayara; Cerda, Alvaro; Hirata, Rosario; Hirata, Mario; Silva, Ester

2012-01-01

This study examined the association of estrogen receptor alpha gene (ESR1) polymorphisms with cardiorespiratory and metabolic parameters in young women. In total, 354 healthy women were selected for cardiopulmonary exercise testing and short-term heart rate (HR) variability (HRV) evaluation. The HRV analysis was determined by the temporal indices rMSSD (square root of the mean squared differences of successive R–R intervals (RRi) divided by the number of RRi minus one), SDNN (root mean square of differences from mean RRi, divided by the number of RRi) and power spectrum components by low frequency (LF), high frequency (HF) and LF/HF ratio. Blood samples were obtained for serum lipids, estradiol and DNA extraction. ESR1 rs2234693 and rs9340799 polymorphisms were analyzed by PCR and fragment restriction analysis. HR and oxygen uptake (VO2) values did not differ between the ESR1 polymorphisms with respect to autonomic modulation. We not find a relationship between ESR1 T–A, T–G, C–A and C–G haplotypes and cardiorespiratory and metabolic variables. Multiple linear regression analysis demonstrated that VO2, total cholesterol and triglycerides influence HRV (p < 0.05). The results suggest that ESR1 variants have no effect on cardiorespiratory and metabolic variables, while HRV indices are influenced by aerobic capacity and lipids in healthy women. PMID:23202974

Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.

PubMed

Barus, C; Romanytsia, I; Striebig, N; Garçon, V

2016-11-01

A Square Wave Voltammetry electrochemical method is proposed to measure phosphate in seawater as pulse techniques offer a higher sensitivity as compared to classical cyclic voltammetry. Chronoamperometry cannot be either adapted for an in situ sensor since this method requires to have controlled convection which will be impossible in a miniaturised sensor. Tests and validation of Square Wave Voltammetry parameters have been performed using an open cell and for the first time with a small volume (<400µL) laboratory prototypes. Two designs of prototypes have been compared. Using high frequency (f=250Hz) allows to obtain a linear behaviour between 0.1 and 1µmolL(-1) with a very low limit of detection of 0.05 µmolL(-1) after 60min of complexation waiting time. In order to obtain a linear regression for a larger concentration range i.e. 0.25-4µmolL(-1), a lower frequency of 2.5Hz is needed. A limit of detection of 0.1µmolL(-1) is obtained in this case after 30min of complexation waiting time for the peak measured at E=0.12V. Changing the position of the molybdenum electrode for the complexation step and moving the detection into another electrochemical cell allow to decrease the reaction time down to 5min. Copyright © 2016 Elsevier B.V. All rights reserved.

Two-Stage Design Method for Enhanced Inductive Energy Transmission with Q-Constrained Planar Square Loops.

PubMed

Eteng, Akaa Agbaeze; Abdul Rahim, Sharul Kamal; Leow, Chee Yen; Chew, Beng Wah; Vandenbosch, Guy A E

2016-01-01

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.

Chi-square-based scoring function for categorization of MEDLINE citations.

PubMed

Kastrin, A; Peterlin, B; Hristovski, D

2010-01-01

Text categorization has been used in biomedical informatics for identifying documents containing relevant topics of interest. We developed a simple method that uses a chi-square-based scoring function to determine the likelihood of MEDLINE citations containing genetic relevant topic. Our procedure requires construction of a genetic and a nongenetic domain document corpus. We used MeSH descriptors assigned to MEDLINE citations for this categorization task. We compared frequencies of MeSH descriptors between two corpora applying chi-square test. A MeSH descriptor was considered to be a positive indicator if its relative observed frequency in the genetic domain corpus was greater than its relative observed frequency in the nongenetic domain corpus. The output of the proposed method is a list of scores for all the citations, with the highest score given to those citations containing MeSH descriptors typical for the genetic domain. Validation was done on a set of 734 manually annotated MEDLINE citations. It achieved predictive accuracy of 0.87 with 0.69 recall and 0.64 precision. We evaluated the method by comparing it to three machine-learning algorithms (support vector machines, decision trees, naïve Bayes). Although the differences were not statistically significantly different, results showed that our chi-square scoring performs as good as compared machine-learning algorithms. We suggest that the chi-square scoring is an effective solution to help categorize MEDLINE citations. The algorithm is implemented in the BITOLA literature-based discovery support system as a preprocessor for gene symbol disambiguation process.

Spatiotemporal frequency tuning of BOLD and gamma band MEG responses compared in primary visual cortex.

PubMed

Muthukumaraswamy, Suresh D; Singh, Krish D

2008-05-01

In this study, the spatial and temporal frequency tuning characteristics of the MEG gamma (40-60 Hz) rhythm and the BOLD response in primary visual cortex were measured and compared. In an identical MEG/fMRI paradigm, 10 participants viewed reversing square wave gratings at 2 spatial frequencies [0.5 and 3 cycles per degree (cpd)] reversing at 5 temporal frequencies (0, 1 6, 10, 15 Hz). Three-dimensional images of MEG source power were generated with synthetic aperture magnetometry (SAM) and showed a high degree of spatial correspondence with BOLD responses in primary visual cortex with a mean spatial separation of 6.5 mm, but the two modalities showed different tuning characteristics. The gamma rhythm showed a clear increase in induced power for the high spatial frequency stimulus while BOLD showed no difference in activity for the two spatial frequencies used. Both imaging modalities showed a general increase of activity with temporal frequency, however, BOLD plateaued around 6-10 Hz while the MEG generally increased with a dip exhibited at 6 Hz. These results demonstrate that the two modalities may show activation in similar spatial locations but that the functional pattern of these activations may differ in a complex manner, suggesting that they may be tuned to different aspects of neuronal activity.

Cardiovascular Autonomic Dysfunction in Patients with Morbid Obesity

PubMed Central

de Sant Anna Junior, Maurício; Carneiro, João Regis Ivar; Carvalhal, Renata Ferreira; Torres, Diego de Faria Magalhães; da Cruz, Gustavo Gavina; Quaresma, José Carlos do Vale; Lugon, Jocemir Ronaldo; Guimarães, Fernando Silva

2015-01-01

Background Morbid obesity is directly related to deterioration in cardiorespiratory capacity, including changes in cardiovascular autonomic modulation. Objective This study aimed to assess the cardiovascular autonomic function in morbidly obese individuals. Methods Cross-sectional study, including two groups of participants: Group I, composed by 50 morbidly obese subjects, and Group II, composed by 30 nonobese subjects. The autonomic function was assessed by heart rate variability in the time domain (standard deviation of all normal RR intervals [SDNN]; standard deviation of the normal R-R intervals [SDNN]; square root of the mean squared differences of successive R-R intervals [RMSSD]; and the percentage of interval differences of successive R-R intervals greater than 50 milliseconds [pNN50] than the adjacent interval), and in the frequency domain (high frequency [HF]; low frequency [LF]: integration of power spectral density function in high frequency and low frequency ranges respectively). Between-group comparisons were performed by the Student’s t-test, with a level of significance of 5%. Results Obese subjects had lower values of SDNN (40.0 ± 18.0 ms vs. 70.0 ± 27.8 ms; p = 0.0004), RMSSD (23.7 ± 13.0 ms vs. 40.3 ± 22.4 ms; p = 0.0030), pNN50 (14.8 ± 10.4 % vs. 25.9 ± 7.2%; p = 0.0061) and HF (30.0 ± 17.5 Hz vs. 51.7 ± 25.5 Hz; p = 0.0023) than controls. Mean LF/HF ratio was higher in Group I (5.0 ± 2.8 vs. 1.0 ± 0.9; p = 0.0189), indicating changes in the sympathovagal balance. No statistical difference in LF was observed between Group I and Group II (50.1 ± 30.2 Hz vs. 40.9 ± 23.9 Hz; p = 0.9013). Conclusion morbidly obese individuals have increased sympathetic activity and reduced parasympathetic activity, featuring cardiovascular autonomic dysfunction. PMID:26536979

Performance of High-frequency High-flux Magnetic Cores at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Gerber, Scott S.; Hammoud, Ahmad; Elbuluk, Malik E.; Patterson, Richard L.

2002-01-01

Three magnetic powder cores and one ferrite core, which are commonly used in inductor and transformer design for switch mode power supplies, were selected for investigation at cryogenic temperatures. The powder cores are Molypermalloy Core (MPC), High Flux Core (HFC), and Kool Mu Core (KMC). The performance of four inductors utilizing these cores has been evaluated as a function of temperature from 20 C to -180 C. All cores were wound with the same wire type and gauge to obtain equal values of inductance at room temperature. Each inductor was evaluated in terms of its inductance, quality (Q) factor, resistance, and dynamic hysteresis characteristics (B-H loop) as a function of temperature and frequency. Both sinusoidal and square wave excitations were used in these investigations. Measured data obtained on the inductance showed that both the MPC and the HFC cores maintain a constant inductance value, whereas with the KMC and ferrite core hold a steady value in inductance with frequency but decrease as temperature is decreased. All cores exhibited dependency, with varying degrees, in their quality factor and resistance on test frequency and temperature. Except for the ferrite, all cores exhibited good stability in the investigated properties with temperature as well as frequency. Details of the experimental procedures and test results are presented and discussed in the paper.

[Restoration filtering based on projection power spectrum for single-photon emission computed tomography].

PubMed

Kubo, N

1995-04-01

To improve the quality of single-photon emission computed tomographic (SPECT) images, a restoration filter has been developed. This filter was designed according to practical "least squares filter" theory. It is necessary to know the object power spectrum and the noise power spectrum. The power spectrum is estimated from the power spectrum of a projection, when the high-frequency power spectrum of a projection is adequately approximated as a polynomial exponential expression. A study of the restoration with the filter based on a projection power spectrum was conducted, and compared with that of the "Butterworth" filtering method (cut-off frequency of 0.15 cycles/pixel), and "Wiener" filtering (signal-to-noise power spectrum ratio was a constant). Normalized mean-squared errors (NMSE) of the phantom, two line sources located in a 99mTc filled cylinder, were used. NMSE of the "Butterworth" filter, "Wiener" filter, and filtering based on a power spectrum were 0.77, 0.83, and 0.76 respectively. Clinically, brain SPECT images utilizing this new restoration filter improved the contrast. Thus, this filter may be useful in diagnosis of SPECT images.

Analysis of the Magnitude and Frequency of Peak Discharges for the Navajo Nation in Arizona, Utah, Colorado, and New Mexico

USGS Publications Warehouse

Waltemeyer, Scott D.

2006-01-01

Estimates of the magnitude and frequency of peak discharges are necessary for the reliable flood-hazard mapping in the Navajo Nation in Arizona, Utah, Colorado, and New Mexico. The Bureau of Indian Affairs, U.S. Army Corps of Engineers, and Navajo Nation requested that the U.S. Geological Survey update estimates of peak discharge magnitude for gaging stations in the region and update regional equations for estimation of peak discharge and frequency at ungaged sites. Equations were developed for estimating the magnitude of peak discharges for recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years at ungaged sites using data collected through 1999 at 146 gaging stations, an additional 13 years of peak-discharge data since a 1997 investigation, which used gaging-station data through 1986. The equations for estimation of peak discharges at ungaged sites were developed for flood regions 8, 11, high elevation, and 6 and are delineated on the basis of the hydrologic codes from the 1997 investigation. Peak discharges for selected recurrence intervals were determined at gaging stations by fitting observed data to a log-Pearson Type III distribution with adjustments for a low-discharge threshold and a zero skew coefficient. A low-discharge threshold was applied to frequency analysis of 82 of the 146 gaging stations. This application provides an improved fit of the log-Pearson Type III frequency distribution. Use of the low-discharge threshold generally eliminated the peak discharge having a recurrence interval of less than 1.4 years in the probability-density function. Within each region, logarithms of the peak discharges for selected recurrence intervals were related to logarithms of basin and climatic characteristics using stepwise ordinary least-squares regression techniques for exploratory data analysis. Generalized least-squares regression techniques, an improved regression procedure that accounts for time and spatial sampling errors, then was applied to the same data used in the ordinary least-squares regression analyses. The average standard error of prediction for a peak discharge have a recurrence interval of 100-years for region 8 was 53 percent (average) for the 100-year flood. The average standard of prediction, which includes average sampling error and average standard error of regression, ranged from 45 to 83 percent for the 100-year flood. Estimated standard error of prediction for a hybrid method for region 11 was large in the 1997 investigation. No distinction of floods produced from a high-elevation region was presented in the 1997 investigation. Overall, the equations based on generalized least-squares regression techniques are considered to be more reliable than those in the 1997 report because of the increased length of record and improved GIS method. Techniques for transferring flood-frequency relations to ungaged sites on the same stream can be estimated at an ungaged site by a direct application of the regional regression equation or at an ungaged site on a stream that has a gaging station upstream or downstream by using the drainage-area ratio and the drainage-area exponent from the regional regression equation of the respective region.

47 CFR 87.145 - Acceptability of transmitters for licensing.

Code of Federal Regulations, 2014 CFR

2014-10-01

... square error which assumes zero error for the received ground earth station signal and includes the AES transmit/receive frequency reference error and the AES automatic frequency control residual errors.) The...

47 CFR 87.145 - Acceptability of transmitters for licensing.

Code of Federal Regulations, 2013 CFR

2013-10-01

... square error which assumes zero error for the received ground earth station signal and includes the AES transmit/receive frequency reference error and the AES automatic frequency control residual errors.) The...

47 CFR 87.145 - Acceptability of transmitters for licensing.

Code of Federal Regulations, 2012 CFR

2012-10-01

... square error which assumes zero error for the received ground earth station signal and includes the AES transmit/receive frequency reference error and the AES automatic frequency control residual errors.) The...

47 CFR 87.145 - Acceptability of transmitters for licensing.

Code of Federal Regulations, 2011 CFR

2011-10-01

... square error which assumes zero error for the received ground earth station signal and includes the AES transmit/receive frequency reference error and the AES automatic frequency control residual errors.) The...

Flip-Flop Digital Modulator

NASA Technical Reports Server (NTRS)

Eno, R. F.

1984-01-01

Clock switched on and off in response to data signal. Flip-flop modulator generates square-wave carrier frequency that is half clock frequency and turns carrier on and off. Final demodulator output logical inverse of data input.

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.

Source process and tectonic implication of the January 20, 2007 Odaesan earthquake, South Korea

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Ali K.; Kim, K. Y.; Fnais, M. S.; Al-Amri, A. M.

2014-04-01

The source process for the 20th of January 2007, Mw 4.5 Odaesan earthquake in South Korea is investigated in the low- and high-frequency bands, using velocity and acceleration waveform data recorded by the Korea Meteorological Administration Seismographic Network at distances less than 70 km from the epicenter. Synthetic Green functions are adopted for the low-frequency band of 0.1-0.3 Hz by using the wave-number integration technique and the one dimensional velocity model beneath the epicentral area. An iterative technique was performed by a grid search across the strike, dip, rake, and focal depth of rupture nucleation parameters to find the best-fit double-couple mechanism. To resolve the nodal plane ambiguity, the spatiotemporal slip distribution on the fault surface was recovered using a non-negative least-square algorithm for each set of the grid-searched parameters. The focal depth of 10 km was determined through the grid search for depths in the range of 6-14 km. The best-fit double-couple mechanism obtained from the finite-source model indicates a vertical strike-slip faulting mechanism. The NW faulting plane gives comparatively smaller root-mean-squares (RMS) error than its auxiliary plane. Slip pattern event provides simple source process due to the effect of Low-frequency that acted as a point source model. Three empirical Green functions are adopted to investigate the source process in the high-frequency band. A set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2.0-4.0 km/s. Although there is a small difference between the RMS errors produced by the two orthogonal nodal planes, the SW dipping plane gives a smaller RMS error than its auxiliary plane. The slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high-frequency analysis; indicating a complex rupture scenario for such moderate-sized earthquake, similar to those reported for large earthquakes.

Effect of ultrasonic cavitation on measurement of sound pressure using hydrophone

NASA Astrophysics Data System (ADS)

Thanh Nguyen, Tam; Asakura, Yoshiyuki; Okada, Nagaya; Koda, Shinobu; Yasuda, Keiji

2017-07-01

Effect of ultrasonic cavitation on sound pressure at the fundamental, second harmonic, and first ultraharmonic frequencies was investigated from low to high ultrasonic intensities. The driving frequencies were 22, 304, and 488 kHz. Sound pressure was measured using a needle-type hydrophone and ultrasonic cavitation was estimated from the broadband integrated pressure (BIP). With increasing square root of electric power applied to a transducer, the sound pressure at the fundamental frequency linearly increased initially, dropped at approximately the electric power of cavitation inception, and afterward increased again. The sound pressure at the second harmonic frequency was detected just below the electric power of cavitation inception. The first ultraharmonic component appeared at around the electric power of cavitation inception at 304 and 488 kHz. However, at 22 kHz, the first ultraharmonic component appeared at a higher electric power than that of cavitation inception.

Iterative MMSE Detection for MIMO/BLAST DS-CDMA Systems in Frequency Selective Fading Channels - Achieving High Performance in Fully Loaded Systems

NASA Astrophysics Data System (ADS)

Silva, João Carlos; Souto, Nuno; Cercas, Francisco; Dinis, Rui

A MMSE (Minimum Mean Square Error) DS-CDMA (Direct Sequence-Code Division Multiple Access) receiver coupled with a low-complexity iterative interference suppression algorithm was devised for a MIMO/BLAST (Multiple Input, Multiple Output / Bell Laboratories Layered Space Time) system in order to improve system performance, considering frequency selective fading channels. The scheme is compared against the simple MMSE receiver, for both QPSK and 16QAM modulations, under SISO (Single Input, Single Output) and MIMO systems, the latter with 2Tx by 2Rx and 4Tx by 4Rx (MIMO order 2 and 4 respectively) antennas. To assess its performance in an existing system, the uncoded UMTS HSDPA (High Speed Downlink Packet Access) standard was considered.

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

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less

Theoretical scaling law of coronal magnetic field and electron power-law index in solar microwave burst sources

NASA Astrophysics Data System (ADS)

Huang, Y.; Song, Q. W.; Tan, B. L.

2018-04-01

It is first proposed a theoretical scaling law respectively for the coronal magnetic field strength B and electron power-law index δ versus frequency and coronal height in solar microwave burst sources. Based on the non-thermal gyro-synchrotron radiation model (Ramaty in Astrophys. J. 158:753, 1969), B and δ are uniquely solved by the observable optically-thin spectral index and turnover (peak) frequency, the other parameters (plasma density, temperature, view angle, low and high energy cutoffs, etc.) are relatively insensitive to the calculations, thus taken as some typical values. Both of B and δ increase with increasing of radio frequency but with decreasing of coronal height above photosphere, and well satisfy a square or cubic logarithmic fitting.

SCINTILLATION ARCS IN LOW-FREQUENCY OBSERVATIONS OF THE TIMING-ARRAY MILLISECOND PULSAR PSR J0437–4715

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

Bhat, N. D. R.; Ord, S. M.; Tremblay, S. E.

2016-02-10

Low-frequency observations of pulsars provide a powerful means for probing the microstructure in the turbulent interstellar medium (ISM). Here we report on high-resolution dynamic spectral analysis of our observations of the timing-array millisecond pulsar PSR J0437–4715 with the Murchison Widefield Array (MWA), enabled by our recently commissioned tied-array beam processing pipeline for voltage data recorded from the high time resolution mode of the MWA. A secondary spectral analysis reveals faint parabolic arcs akin to those seen in high-frequency observations of pulsars with the Green Bank and Arecibo telescopes. Data from Parkes observations at a higher frequency of 732 MHz revealmore » a similar parabolic feature with a curvature that scales approximately as the square of the observing wavelength (λ{sup 2}) to the MWA's frequency of 192 MHz. Our analysis suggests that scattering toward PSR J0437–4715 predominantly arises from a compact region about 115 pc from the Earth, which matches well with the expected location of the edge of the Local Bubble that envelopes the local Solar neighborhood. As well as demonstrating new and improved pulsar science capabilities of the MWA, our analysis underscores the potential of low-frequency pulsar observations for gaining valuable insights into the local ISM and for characterizing the ISM toward timing-array pulsars.« less

Analysis and Optimization of Four-Coil Planar Magnetically Coupled Printed Spiral Resonators.

PubMed

Khan, Sadeque Reza; Choi, GoangSeog

2016-08-03

High-efficiency power transfer at a long distance can be efficiently established using resonance-based wireless techniques. In contrast to the conventional two-coil-based inductive links, this paper presents a magnetically coupled fully planar four-coil printed spiral resonator-based wireless power-transfer system that compensates the adverse effect of low coupling and improves efficiency by using high quality-factor coils. A conformal architecture is adopted to reduce the transmitter and receiver sizes. Both square architecture and circular architectures are analyzed and optimized to provide maximum efficiency at a certain operating distance. Furthermore, their performance is compared on the basis of the power-transfer efficiency and power delivered to the load. Square resonators can produce higher measured power-transfer efficiency (79.8%) than circular resonators (78.43%) when the distance between the transmitter and receiver coils is 10 mm of air medium at a resonant frequency of 13.56 MHz. On the other hand, circular coils can deliver higher power (443.5 mW) to the load than the square coils (396 mW) under the same medium properties. The performance of the proposed structures is investigated by simulation using a three-layer human-tissue medium and by experimentation.

Joint inversion of high-frequency surface waves with fundamental and higher modes

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Liu, Q.; Xu, S.

2007-01-01

Joint inversion of multimode surface waves for estimating the shear (S)-wave velocity has received much attention in recent years. In this paper, we first analyze sensitivity of phase velocities of multimodes of surface waves for a six-layer earth model, and then we invert surface-wave dispersion curves of the theoretical model and a real-world example. Sensitivity analysis shows that fundamental mode data are more sensitive to the S-wave velocities of shallow layers and are concentrated on a very narrow frequency band, while higher mode data are more sensitive to the parameters of relatively deeper layers and are distributed over a wider frequency band. These properties provide a foundation of using a multimode joint inversion to define S-wave velocities. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least-square method and the singular-value decomposition technique to invert high-frequency surface waves with fundamental and higher mode data simultaneously can effectively reduce the ambiguity and improve the accuracy of S-wave velocities. ?? 2007.

Characteristic analysis of diaphragm-type transducer that is thick relative to its size

NASA Astrophysics Data System (ADS)

Ishiguro, Yuya; Zhu, Jing; Tagawa, Norio; Okubo, Tsuyoshi; Okubo, Kan

2017-07-01

In recent years, high-performance piezoelectric micromachined ultrasonic transducers (PMUTs) have been fabricated by micro electro mechanical systems (MEMS) technology. For high-resolution imaging, it is important to broaden the frequency bandwidth. By reducing the diaphragm size to increase the resonance frequency, the film thickness becomes relatively larger and hence the transmitting and receiving characteristics may different from those of a usual thin diaphragm. In this study, we examine the performance of a square-diaphragm-type lead zirconate titanate (PZT) transducer through simulations. To realize the desired resonance frequency of 20 MHz, firstly, the diaphragm size and the thickness of the layers of PZT and Si constituting a PMUT are examined, and then, three PZT/Si models with different thicknesses are selected. Subsequently, using the models, we analyze the transmitting efficiency, transmitting bandwidth, receiving sensitivity (piezoelectric voltage/electric charge), and receiving bandwidth using an FEM simulator. It is found that the proposed models can transmit ultrasound independently of the diaphragm vibration and have wide bandwidth of the receiving frequency as compared with that of a typical PMUT.

Small-scale rotor test rig capabilities for testing vibration alleviation algorithms

NASA Technical Reports Server (NTRS)

Jacklin, Stephen A.; Leyland, Jane Anne

1987-01-01

A test was conducted to assess the capabilities of a small scale rotor test rig for implementing higher harmonic control and stability augmentation algorithms. The test rig uses three high speed actuators to excite the swashplate over a range of frequencies. The actuator position signals were monitored to measure the response amplitudes at several frequencies. The ratio of response amplitude to excitation amplitude was plotted as a function of frequency. In addition to actuator performance, acceleration from six accelerometers placed on the test rig was monitored to determine whether a linear relationship exists between the harmonics of N/Rev control input and the least square error (LSE) identification technique was used to identify local and global transfer matrices for two rotor speeds at two batch sizes each. It was determined that the multicyclic control computer system interfaced very well with the rotor system and kept track of the input accelerometer signals and their phase angles. However, the current high speed actuators were found to be incapable of providing sufficient control authority at the higher excitation frequencies.

Off-Resonance Acoustic Levitation Without Rotation

NASA Technical Reports Server (NTRS)

Barmatz, M. B.; Allen, J. L.

1984-01-01

Orthogonal acoustic-levitation modes excited at slightly different frequencies to control rotation. Rotation of object in square cross-section acoustic-levitation chamber stopped by detuning two orthogonal (x and y) excitation drivers in plane of square cross section. Detuning done using fundamental degenerate modes or odd harmonic modes.

Broad-band frequency references in the near-infrared: Accurate dual comb spectroscopy of methane and acetylene

NASA Astrophysics Data System (ADS)

Zolot, A. M.; Giorgetta, F. R.; Baumann, E.; Swann, W. C.; Coddington, I.; Newbury, N. R.

2013-03-01

The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm-1) and acetylene between 193 THz and 199 THz (6430-6630 cm-1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic standards. A least squares analysis of the measured absorbance and phase line shapes provides line center frequencies with absolute accuracy of 0.2 MHz, or less than one thousandth of the room temperature Doppler width. This accuracy is verified through comparison with previous saturated absorption spectroscopy of 37 strong isolated lines of acetylene. For the methane spectrum, the center frequencies of 46 well-isolated strong lines are determined with similar high accuracy, along with the center frequencies for 1107 non-isolated lines at lower accuracy. The measured methane line-center frequencies have an uncertainty comparable to the few available laser heterodyne measurements in this region but span a much larger optical bandwidth, marking the first broad-band measurements of the methane 2ν3 region directly referenced to atomic frequency standards. This study demonstrates the promise of dual comb spectroscopy to obtain high resolution broadband spectra that are comparable to state-of-the-art Fourier-transform spectrometer measurements but with much improved frequency accuracy.Work of the US government, not subject to US copyright.

Space-Time Joint Interference Cancellation Using Fuzzy-Inference-Based Adaptive Filtering Techniques in Frequency-Selective Multipath Channels

NASA Astrophysics Data System (ADS)

Hu, Chia-Chang; Lin, Hsuan-Yu; Chen, Yu-Fan; Wen, Jyh-Horng

2006-12-01

An adaptive minimum mean-square error (MMSE) array receiver based on the fuzzy-logic recursive least-squares (RLS) algorithm is developed for asynchronous DS-CDMA interference suppression in the presence of frequency-selective multipath fading. This receiver employs a fuzzy-logic control mechanism to perform the nonlinear mapping of the squared error and squared error variation, denoted by ([InlineEquation not available: see fulltext.],[InlineEquation not available: see fulltext.]), into a forgetting factor[InlineEquation not available: see fulltext.]. For the real-time applicability, a computationally efficient version of the proposed receiver is derived based on the least-mean-square (LMS) algorithm using the fuzzy-inference-controlled step-size[InlineEquation not available: see fulltext.]. This receiver is capable of providing both fast convergence/tracking capability as well as small steady-state misadjustment as compared with conventional LMS- and RLS-based MMSE DS-CDMA receivers. Simulations show that the fuzzy-logic LMS and RLS algorithms outperform, respectively, other variable step-size LMS (VSS-LMS) and variable forgetting factor RLS (VFF-RLS) algorithms at least 3 dB and 1.5 dB in bit-error-rate (BER) for multipath fading channels.

High frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings.

PubMed

Lu, Jian-Yu; Cheng, Jiqi; Wang, Jing

2006-10-01

A general-purpose high frame rate (HFR) medical imaging system has been developed. This system has 128 independent linear transmitters, each of which is capable of producing an arbitrary broadband (about 0.05-10 MHz) waveform of up to +/- 144 V peak voltage on a 75-ohm resistive load using a 12-bit/40-MHz digital-to-analog converter. The system also has 128 independent, broadband (about 0.25-10 MHz), and time-variable-gain receiver channels, each of which has a 12-bit/40-MHz analog-to-digital converter and up to 512 MB of memory. The system is controlled by a personal computer (PC), and radio frequency echo data of each channel are transferred to the same PC via a standard USB 2.0 port for image reconstructions. Using the HFR imaging system, we have developed a new limited-diffraction array beam imaging method with square-wave aperture voltage weightings. With this method, in principle, only one or two transmitters are required to excite a fully populated two-dimensional (2-D) array transducer to achieve an equivalent dynamic focusing in both transmission and reception to reconstruct a high-quality three-dimensional image without the need of the time delays of traditional beam focusing and steering, potentially simplifying the transmitter subsystem of an imager. To validate the method, for simplicity, 2-D imaging experiments were performed using the system. In the in vitro experiment, a custom-made, 128-element, 0.32-mm pitch, 3.5-MHz center frequency linear array transducer with about 50% fractional bandwidth was used to reconstruct images of an ATS 539 tissue-mimicking phantom at an axial distance of 130 mm with a field of view of more than 90 degrees. In the in vivo experiment of a human heart, images with a field of view of more than 90 degrees at 120-mm axial distance were obtained with a 128-element, 2.5-MHz center frequency, 0.15-mm pitch Acuson V2 phased array. To ensure that the system was operated under the limits set by the U.S. Food and Drug Administration, the mechanical index, thermal index, and acoustic output were measured. Results show that higher-quality images can be reconstructed with the square-wave aperture weighting method due to an increased penetration depth as compared to the exact weighting method developed previously, and a frame rate of 486 per second was achieved at a pulse repetition frequency of about 5348 Hz for the human heart.

Double-loop frequency selective surfaces for multi frequency division multiplexing in a dual reflector antenna

NASA Technical Reports Server (NTRS)

Wu, Te-Kao (Inventor)

1994-01-01

A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.

Combinatorial effect of nicotine and black tea on heart rate variability: Useful or harmful?

PubMed

Joukar, S; Sheibani, M

2017-06-01

The effect of nicotine on heart rate variability (HRV) is controversial. Autonomic nervous system is the main regulator of heart rhythm, and heart rate variability is an appropriate index to assessment of the effects of the autonomic system on heart. In this study, the combination effect of nicotine and black tea consumption on sympatho-vagal balance and heart rate variability was investigated in rats. Male Wistar rats were randomized into four groups as control, tea (2.5 g/100 cc, daily), nicotine (2 mg/kg/d) and tea plus nicotine groups which treated for 28 days, and in the 29th day, their electrocardiograms (lead II) were recorded. The mean of high-frequency power (HF) in tea, nicotine and tea plus nicotine groups was significantly more than control group (P < .05), and low-frequency power/high-frequency power (LF/HF) ratio in the nicotine and tea + nicotine groups was significantly less than control group (P < .05). LF values did not differ significantly among groups. Mean of standard deviation of normal RR intervals (SDNN) and square root of the mean squared differences of successive RR intervals (RMSSD) increased significantly in tea, nicotine and tea + nicotine groups in comparison with control group (P < .05) Overall, 4-week administration of black tea, nicotine or their combination with dosages used in this study can increase the heart rate variability and improve the sympatho-vagal balance in rat. © 2017 John Wiley & Sons Ltd.

Estimating the magnitude and frequency of floods in urban basins in Missouri

USGS Publications Warehouse

Southard, Rodney E.

2010-01-01

Streamgage flood-frequency analyses were done for 35 streamgages on urban streams in and adjacent to Missouri for estimation of the magnitude and frequency of floods in urban areas of Missouri. A log-Pearson Type-III distribution was fitted to the annual series of peak flow data retrieved from the U.S. Geological Survey National Water Information System. For this report, the flood frequency estimates are expressed in terms of percent annual exceedance probabilities of 50, 20, 10, 4, 2, 1, and 0.2. Of the 35 streamgages, 30 are located in Missouri. The remaining five non-Missouri streamgages were added to the dataset to improve the range and applicability of the regression analyses from the streamgage frequency analyses. Ordinary least-squares was used to determine the best set of independent variables for the regression equations. Basin characteristics selected for independent variables into the ordinary least-squares regression analyses were based on theoretical relation to flood flows, literature review of possible basin characteristics, and the ability to measure the basin characteristics using digital datasets and geographic information system technology. Results of the ordinary least-squares were evaluated on the basis of Mallow's Cp statistic, the adjusted coefficient of determination, and the statistical significance of the independent variables. The independent variables of drainage area and percent impervious area were determined to be statistically significant and readily determined from existing digital datasets. The drainage area variable was computed using the best elevation data available, either from a statewide 10-meter grid or high-resolution elevation data from urban areas. The impervious area variable was computed from the National Land Cover Dataset 2001 impervious area dataset. The National Land Cover Dataset 2001 impervious area data for each basin was compared to historical imagery and 7.5-minute topographic maps to verify the national dataset represented the urbanization of the basin at the time streamgage data were collected. Eight streamgages had less urbanization during the period of time streamflow data were collected than was shown on the 2001 dataset. The impervious area values for these eight urban basins were adjusted downward as much as 23 percent to account for the additional urbanization since the streamflow data were collected. Weighted least-squares regression techniques were used to determine the final regression equations for the statewide urban flood-frequency equations. Weighted least-squares techniques improve regression equations by adjusting for different and varying lengths in streamflow records. The final flood-frequency equations for the 50-, 20-, 10-, 4-, 2-, 1-, and 0.2-percent annual exceedance probability floods for Missouri provide a technique for estimating peak flows on urban streams at gaged and ungaged sites. The applicability of the equations is limited by the range in basin characteristics used to develop the regression equations. The range in drainage area is 0.28 to 189 square miles; range in impervious area is 2.3 to 46.0 percent. Seven of the 35 selected streamgages were used to compare the results of the existing rural and urban equations to the urban equations presented in this report for the 1-percent annual exceedance probability. Results of the comparison indicate that the estimated peak flows for the urban equation in this report ranged from 3 to 52 percent higher than the results from the rural equations. Comparing the estimated urban peak flows from this report to the existing urban equation developed in 1986 indicated the range was 255 percent lower to 10 percent higher. The overall comparison between the current (2010) and 1986 urban equations indicates a reduction in estimated peak flow values for the 1-percent annual exceedance probability flood.

A MHz speed wavelength sweeping for ultra-high speed FBG interrogation

NASA Astrophysics Data System (ADS)

Kim, Gyeong Hun; Lee, Hwi Don; Eom, Tae Joong; Jeong, Myung Yung; Kim, Chang-Seok

2015-09-01

We demonstrated a MHz speed wavelength-swept fiber laser based on the active mode locking (AML) technique and applied to interrogation system of an array of fiber Bragg grating (FBG) sensors. MHz speed wavelength sweeping of wavelength-swept fiber laser can be obtained by programmable frequency modulation of the semiconductor optical amplifier (SOA) without any wavelength tunable filter. Both static and dynamic strain measurement of FBG sensors were successfully characterized with high linearity of an R-square value of 0.9999 at sweeping speed of 50 kHz.

Potentials of the acousto-optical spectral data processing on a basis of a novel algorithm of the collinear wave heterodyning in a large-aperture KRS-5 crystalline cell

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Maximov, Jewgemij; Sanchez Lucero, Daniel

2010-02-01

Recently proposed modern technique of a precise spectrum analysis within an algorithm of the collinear wave heterodyning implies a two-stage integrated processing, namely, the wave heterodyning of a signal in a square-law nonlinear medium and then the optical processing in the same cell. Technical advantage of this approach is in providing a direct processing of ultra-high-frequency radio-wave signals with essentially improved frequency resolution. This algorithm can be realized on a basis of various physical principles, and we consider an opportunity of involving the potentials of modern acousto-optics for these purposes. From this viewpoint, one needs a large-aperture effective acousto-optical cell, which operates in the Bragg regime and performs the ultra-high-frequency co-directional collinear acoustic wave heterodyning. The technique under consideration imposes specific requirements on the cell's material, namely, a high optical quality of large-size crystalline boules, high-efficient acousto-optical and acoustic interactions, and low group velocity of acoustic waves together with square-low dispersive acoustic losses. We focus our attention on the solid solutions of thallium chalcogenides and take the TlBr-TlI (thallium bromine - thallium iodine) solution, which forms KRS-5 cubic-symmetry crystals with the mass-ratio 58% of TlBr to 42% of TlI. Analysis shows that the acousto-optical cell made of a KRS-5 crystal oriented along the [111] -axis and the corresponding longitudinal elastic mode for producing the dynamic diffractive grating in that crystal can be exploited. With the acoustic velocity of about 1.92 mm/μs and attenuation of approximately 10 dB/(cm GHz2), similar cell is capable to provide an optical aperture of 50 mm and one of the highest figures of acousto-optical merit in solid states in the visible range. Such a cell is rather desirable for applications to direct parallel multi-channel optical spectrum analysis with substantially improved frequency resolution.

Least-mean-square spatial filter for IR sensors.

PubMed

Takken, E H; Friedman, D; Milton, A F; Nitzberg, R

1979-12-15

A new least-mean-square filter is defined for signal-detection problems. The technique is proposed for scanning IR surveillance systems operating in poorly characterized but primarily low-frequency clutter interference. Near-optimal detection of point-source targets is predicted both for continuous-time and sampled-data systems.

APOE, MTHFR, LDLR and ACE polymorphisms among Angami and Lotha Naga populations of Nagaland, India.

PubMed

Murry, Benrithung; Vakha, Neikethono; Achoubi, Nongthombam; Sachdeva, M P; Saraswathy, K N

2011-12-01

Several common polymorphisms in the ApoE, ACE, MTHFR and LDLR genes have been implicated in the pathogenesis of common complex diseases across world populations. This study investigates the prevalence of five known and clinically important common polymorphisms in Angami and Lotha Naga populations. A total of 112 unrelated healthy volunteers (52 Lotha Nagas and 60 Angami Nagas) participated in the study. All the five genes were found to be polymorphic in the studied populations. The Lotha Nagas displayed higher mutant allele frequencies than the Angami Nagas except for the T allele frequency of the AvaII polymorphism of the LDLR gene, though chi square did not reveal any significant population differences by genotypes. In view of the relatively high mutant allele frequencies in both the populations, they are likely to be at a high risk of developing various complex diseases as they shift from an active and rigorous lifestyle to a more sedentary one.

Audible acoustics in high-shear wet granulation: application of frequency filtering.

PubMed

Hansuld, Erin M; Briens, Lauren; McCann, Joe A B; Sayani, Amyn

2009-08-13

Previous work has shown analysis of audible acoustic emissions from high-shear wet granulation has potential as a technique for end-point detection. In this research, audible acoustic emissions (AEs) from three different formulations were studied to further develop this technique as a process analytical technology. Condenser microphones were attached to three different locations on a PMA-10 high-shear granulator (air exhaust, bowl and motor) to target different sound sources. Size, flowability and tablet break load data was collected to support formulator end-point ranges and interpretation of AE analysis. Each formulation had a unique total power spectral density (PSD) profile that was sensitive to granule formation and end-point. Analyzing total PSD in 10 Hz segments identified profiles with reduced run variability and distinct maxima and minima suitable for routine granulation monitoring and end-point control. A partial least squares discriminant analysis method was developed to automate selection of key 10 Hz frequency groups using variable importance to projection. The results support use of frequency refinement as a way forward in the development of acoustic emission analysis for granulation monitoring and end-point control.

Peak-flow frequency for tributaries of the Colorado River downstream of Austin, Texas

USGS Publications Warehouse

Asquith, William H.

1998-01-01

Peak-flow frequency for 38 stations with at least 8 years of data in natural (unregulated and nonurbanized) basins was estimated on the basis of annual peak-streamflow data through water year 1995. Peak-flow frequency represents the peak discharges for recurrence intervals of 2, 5, 10, 25, 50, 100, 250, and 500 years. The peak-flow frequency and drainage basin characteristics for the stations were used to develop two sets of regression equations to estimate peak-flow frequency for tributaries of the Colorado River in the study area. One set of equations was developed for contributing drainage areas less than 32 square miles, and another set was developed for contributing drainage areas greater than 32 square miles. A procedure is presented to estimate the peak discharge at sites where both sets of equations are considered applicable. Additionally, procedures are presented to compute the 50-, 67-, and 90-percent prediction interval for any estimation from the equations.

Application of quadratic optimization to supersonic inlet control.

NASA Technical Reports Server (NTRS)

Lehtinen, B.; Zeller, J. R.

1972-01-01

This paper describes the application of linear stochastic optimal control theory to the design of the control system for the air intake, the inlet, of a supersonic air-breathing propulsion system. The controls must maintain a stable inlet shock position in the presence of random airflow disturbances and prevent inlet unstart. Two different linear time invariant controllers are developed. One is designed to minimize a nonquadratic index, the expected frequency of inlet unstart, and the other is designed to minimize the mean square value of inlet shock motion. The quadratic equivalence principle is used to obtain a linear controller that minimizes the nonquadratic index. The two controllers are compared on the basis of unstart prevention, control effort requirements, and frequency response. It is concluded that while controls designed to minimize unstarts are desirable in that the index minimized is physically meaningful, computation time required is longer than for the minimum mean square shock position approach. The simpler minimum mean square shock position solution produced expected unstart frequency values which were not significantly larger than those of the nonquadratic solution.

Amplitude-cyclic frequency decomposition of vibration signals for bearing fault diagnosis based on phase editing

NASA Astrophysics Data System (ADS)

Barbini, L.; Eltabach, M.; Hillis, A. J.; du Bois, J. L.

2018-03-01

In rotating machine diagnosis different spectral tools are used to analyse vibration signals. Despite the good diagnostic performance such tools are usually refined, computationally complex to implement and require oversight of an expert user. This paper introduces an intuitive and easy to implement method for vibration analysis: amplitude cyclic frequency decomposition. This method firstly separates vibration signals accordingly to their spectral amplitudes and secondly uses the squared envelope spectrum to reveal the presence of cyclostationarity in each amplitude level. The intuitive idea is that in a rotating machine different components contribute vibrations at different amplitudes, for instance defective bearings contribute a very weak signal in contrast to gears. This paper also introduces a new quantity, the decomposition squared envelope spectrum, which enables separation between the components of a rotating machine. The amplitude cyclic frequency decomposition and the decomposition squared envelope spectrum are tested on real word signals, both at stationary and varying speeds, using data from a wind turbine gearbox and an aircraft engine. In addition a benchmark comparison to the spectral correlation method is presented.

Differential sampling for fast frequency acquisition via adaptive extended least squares algorithm

NASA Technical Reports Server (NTRS)

Kumar, Rajendra

1987-01-01

This paper presents a differential signal model along with appropriate sampling techinques for least squares estimation of the frequency and frequency derivatives and possibly the phase and amplitude of a sinusoid received in the presence of noise. The proposed algorithm is recursive in mesurements and thus the computational requirement increases only linearly with the number of measurements. The dimension of the state vector in the proposed algorithm does not depend upon the number of measurements and is quite small, typically around four. This is an advantage when compared to previous algorithms wherein the dimension of the state vector increases monotonically with the product of the frequency uncertainty and the observation period. Such a computational simplification may possibly result in some loss of optimality. However, by applying the sampling techniques of the paper such a possible loss in optimality can made small.

Estimation of Flood-Frequency Discharges for Rural, Unregulated Streams in West Virginia

USGS Publications Warehouse

Wiley, Jeffrey B.; Atkins, John T.

2010-01-01

Flood-frequency discharges were determined for 290 streamgage stations having a minimum of 9 years of record in West Virginia and surrounding states through the 2006 or 2007 water year. No trend was determined in the annual peaks used to calculate the flood-frequency discharges. Multiple and simple least-squares regression equations for the 100-year (1-percent annual-occurrence probability) flood discharge with independent variables that describe the basin characteristics were developed for 290 streamgage stations in West Virginia and adjacent states. The regression residuals for the models were evaluated and used to define three regions of the State, designated as Eastern Panhandle, Central Mountains, and Western Plateaus. Exploratory data analysis procedures identified 44 streamgage stations that were excluded from the development of regression equations representative of rural, unregulated streams in West Virginia. Regional equations for the 1.1-, 1.5-, 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year flood discharges were determined by generalized least-squares regression using data from the remaining 246 streamgage stations. Drainage area was the only significant independent variable determined for all equations in all regions. Procedures developed to estimate flood-frequency discharges on ungaged streams were based on (1) regional equations and (2) drainage-area ratios between gaged and ungaged locations on the same stream. The procedures are applicable only to rural, unregulated streams within the boundaries of West Virginia that have drainage areas within the limits of the stations used to develop the regional equations (from 0.21 to 1,461 square miles in the Eastern Panhandle, from 0.10 to 1,619 square miles in the Central Mountains, and from 0.13 to 1,516 square miles in the Western Plateaus). The accuracy of the equations is quantified by measuring the average prediction error (from 21.7 to 56.3 percent) and equivalent years of record (from 2.0 to 70.9 years).

The basic thermodynamics of Earth's radiation budget

NASA Astrophysics Data System (ADS)

Ward, Peter L.

2015-04-01

The microscopic bonds that hold matter together oscillate about a potential energy minimum between attractive and repulsive electrostatic forces, giving rise to macroscopic temperature. When a body of matter reaches thermal equilibrium, the spectrum of frequencies and associated amplitudes of oscillation on the body's surface are described by Planck's empirical law, which shows that heating matter increases the amplitude of these oscillations at all frequencies and shifts the peak frequency to a higher value. The oscillating motion of charge on the surface of matter induces an electromagnetic field in air or space containing the same frequencies (colors) and amplitudes (brightness) flowing away from the surface just as a radio station transmits its frequency and amplitude. Numerous frequencies coexist in an electromagnetic field over a broad spectral range, but each frequency does not interact with any other frequencies and does not change as it propagates over galactic distances except for Doppler effects. Amplitudes (intensities, brightness), on the other hand, decrease by one over the square of the distance traveled as they spread out over the surface of an expanding sphere. Planck (1900) showed that in air and space radiant (thermal) energy at each frequency is equal to the frequency times a constant (E=hν), an expression used widely in photochemistry to designate the thermal energy required to cause a photochemical reaction. High-frequency ultraviolet radiation causes sunburn; lower frequency visible radiation powers photosynthesis; much lower frequency infrared radiation cannot cause either, no matter how large the amplitude or the amount. While many frequencies coexist in air or space, neither frequencies nor energies interact or are additive until in the presence of matter. According to E=hν, the solar, ultraviolet thermal energy that reaches Earth when ozone is depleted is at least 48 times more energetic (hotter) than infrared energy absorbed by greenhouse gases. There simply is not enough thermal energy absorbed by greenhouse gases to have a major effect on global warming. Computer programs used to quantify greenhouse-gas theory overestimate infrared energies because they assume that thermal energy travels in space as waves, for which energy is a function of amplitude squared, and that energies are additive over bandwidth, both properties that are very different from the observed behavior of radiation in the atmosphere. Heat only flows from hot to cold; it cannot flow from a colder layer in the atmosphere to a warmer Earth, as assumed in many radiation budgets (e.g. Wild et al., 2013); you cannot get warmer by standing next to a cold stove. According to Planck's Law, radiation from a body of matter does not have high enough frequencies or amplitudes to warm the same body, as is assumed by greenhouse-gas theory. Warming radiation must come from a warmer body. Detailed observations of global warming, including the recent hiatus, are explained much more directly and clearly by ozone depletion theory, where less ozone in the stratosphere allows more high-energy, solar ultraviolet radiation to reach Earth, cooling the stratosphere, warming the oceans. More details at ozonedepletiontheory.info plus a video at tinyurl.com/ozone-depletion-theory.

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks

PubMed Central

Al-Samman, A. M.; Rahman, T. A.; Azmi, M. H.; Hindia, M. N.; Khan, I.; Hanafi, E.

2016-01-01

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios. PMID:27654703

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks.

PubMed

Al-Samman, A M; Rahman, T A; Azmi, M H; Hindia, M N; Khan, I; Hanafi, E

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios.

Microwave response of hole and patch arrays

NASA Astrophysics Data System (ADS)

Taylor, Melita C.; Edmunds, James D.; Hendry, Euan; Hibbins, Alastair P.; Sambles, J. Roy

2010-10-01

The electromagnetic response of two-dimensional square arrays of perfectly conducting square patches, and their complementary structures, is modeled utilizing a modal matching technique and employing Babinet’s principle. This method allows for the introduction of progressively higher diffracted orders and waveguide modes to be included in the calculation, hence aiding understanding of the underlying causal mechanism for the observed response. At frequencies close to, but below, the onset of diffraction, a near-complete reflection condition is predicted, even for low filling fractions: conversely, for high filling fractions a near-complete transmission condition results. These resonance phenomena are associated with evanescent diffraction, which is sufficiently strong to reverse the step change in transmission upon establishment of electrical continuity; i.e., the connected structure demonstrates increased transmission with increasing filling fraction.

A Multi-Channel Method for Retrieving Surface Temperature for High-Emissivity Surfaces from Hyperspectral Thermal Infrared Images

PubMed Central

Zhong, Xinke; Labed, Jelila; Zhou, Guoqing; Shao, Kun; Li, Zhao-Liang

2015-01-01

The surface temperature (ST) of high-emissivity surfaces is an important parameter in climate systems. The empirical methods for retrieving ST for high-emissivity surfaces from hyperspectral thermal infrared (HypTIR) images require spectrally continuous channel data. This paper aims to develop a multi-channel method for retrieving ST for high-emissivity surfaces from space-borne HypTIR data. With an assumption of land surface emissivity (LSE) of 1, ST is proposed as a function of 10 brightness temperatures measured at the top of atmosphere by a radiometer having a spectral interval of 800–1200 cm−1 and a spectral sampling frequency of 0.25 cm−1. We have analyzed the sensitivity of the proposed method to spectral sampling frequency and instrumental noise, and evaluated the proposed method using satellite data. The results indicated that the parameters in the developed function are dependent on the spectral sampling frequency and that ST of high-emissivity surfaces can be accurately retrieved by the proposed method if appropriate values are used for each spectral sampling frequency. The results also showed that the accuracy of the retrieved ST is of the order of magnitude of the instrumental noise and that the root mean square error (RMSE) of the ST retrieved from satellite data is 0.43 K in comparison with the AVHRR SST product. PMID:26061199

Self-consistent modeling of terahertz waveguide and cavity with frequency-dependent conductivity

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

Huang, Y. J.; Chu, K. R., E-mail: krchu@yahoo.com.tw; Thumm, M.

The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, high-frequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequency-dependent complex quantity commonly used to treat electromagnetics of metals at opticalmore » frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of high-power THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a self-consistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DC-conductivity model. The reduction in Ohmic losses under the AC-conductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.« less

The Importance of High Frequency Observations for the SKA

NASA Astrophysics Data System (ADS)

Welch, William J.

2007-12-01

The plan for the Square Kilometer Array (SKA) is one or more very large arrays operating in two or more contiguous frequency bands: roughly 15 - 90 MHz, 120 - 500 MHz, and 500 MHz - 25 GHz. The last band may be further divided into roughly 500 MHz - 1.5 GHz and 1.5 - 25 GHz. Construction costs may delay or forgo one or more of these bands. We argue that the entire high frequency band is of special importance for astronomy both in the local universe and at great distances and early times. One of the Key Science Projects, the Cradle of Life, requires high sensitivity and resolution at frequencies up to 20 GHz for the study of forming disks around new stars with disk opacities too great for millimeter wave observations. The larger issue of star formation, a poorly understood area, will also benefit from high sensitivity observations at short cm wavelengths. Magnetic field measurements through the Zeeman effect in the densest star forming gas are best done using tracers such as CCS at frequencies of 11 and 22 GHz. The wide frequency range of the SKA permits the observation of multiple rotational transitions of long chain molecules, providing accurate measures of both gas densities and temperatures. The wide field of view will permit large scale surveys of entire star forming clouds revealing, at high resolution, the formation of clusters of pre-protostellar stars and class 0-2 protostars in line radiation. The continuum cm wave radiation will reveal the growth of grains in disks. On the larger scale, observations of CO at high redshifts will trace the evolution of star formation and the formation of metals back to the Epic of Reionization.

Direct comparison of low- and mid-frequency Raman spectroscopy for quantitative solid-state pharmaceutical analysis.

PubMed

Lipiäinen, Tiina; Fraser-Miller, Sara J; Gordon, Keith C; Strachan, Clare J

2018-02-05

This study considers the potential of low-frequency (terahertz) Raman spectroscopy in the quantitative analysis of ternary mixtures of solid-state forms. Direct comparison between low-frequency and mid-frequency spectral regions for quantitative analysis of crystal form mixtures, without confounding sampling and instrumental variations, is reported for the first time. Piroxicam was used as a model drug, and the low-frequency spectra of piroxicam forms β, α2 and monohydrate are presented for the first time. These forms show clear spectral differences in both the low- and mid-frequency regions. Both spectral regions provided quantitative models suitable for predicting the mixture compositions using partial least squares regression (PLSR), but the low-frequency data gave better models, based on lower errors of prediction (2.7, 3.1 and 3.2% root-mean-square errors of prediction [RMSEP] values for the β, α2 and monohydrate forms, respectively) than the mid-frequency data (6.3, 5.4 and 4.8%, for the β, α2 and monohydrate forms, respectively). The better performance of low-frequency Raman analysis was attributed to larger spectral differences between the solid-state forms, combined with a higher signal-to-noise ratio. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

PubMed

Lee, Chung Jun; Kim, Jip; Kim, Taegyu

2016-02-01

Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

High-Efficiency Microwave Power Amplifier

NASA Technical Reports Server (NTRS)

Sims, Williams H.

2005-01-01

A high-efficiency power amplifier that operates in the S band (frequencies of the order of a few gigahertz) utilizes transistors operating under class-D bias and excitation conditions. Class-D operation has been utilized at lower frequencies, but, until now, has not been exploited in the S band. Nominally, in class D operation, a transistor is switched rapidly between "on" and "off" states so that at any given instant, it sustains either high current or high voltage, but not both at the same time. In the ideal case of zero "on" resistance, infinite "off" resistance, zero inductance and capacitance, and perfect switching, the output signal would be a perfect square wave. Relative to the traditional classes A, B, and C of amplifier operation, class D offers the potential to achieve greater power efficiency. In addition, relative to class-A amplifiers, class-D amplifiers are less likely to go into oscillation. In order to design this amplifier, it was necessary to derive mathematical models of microwave power transistors for incorporation into a larger mathematical model for computational simulation of the operation of a class-D microwave amplifier. The design incorporates state-of-the-art switching techniques applicable only in the microwave frequency range. Another major novel feature is a transmission-line power splitter/combiner designed with the help of phasing techniques to enable an approximation of a square-wave signal (which is inherently a wideband signal) to propagate through what would, if designed in a more traditional manner, behave as a more severely band-limited device (see figure). The amplifier includes an input, a driver, and a final stage. Each stage contains a pair of GaAs-based field-effect transistors biased in class D. The input signal can range from -10 to +10 dBm into a 50-ohm load. The table summarizes the performances of the three stages

Automated segmentation of linear time-frequency representations of marine-mammal sounds.

PubMed

Dadouchi, Florian; Gervaise, Cedric; Ioana, Cornel; Huillery, Julien; Mars, Jérôme I

2013-09-01

Many marine mammals produce highly nonlinear frequency modulations. Determining the time-frequency support of these sounds offers various applications, which include recognition, localization, and density estimation. This study introduces a low parameterized automated spectrogram segmentation method that is based on a theoretical probabilistic framework. In the first step, the background noise in the spectrogram is fitted with a Chi-squared distribution and thresholded using a Neyman-Pearson approach. In the second step, the number of false detections in time-frequency regions is modeled as a binomial distribution, and then through a Neyman-Pearson strategy, the time-frequency bins are gathered into regions of interest. The proposed method is validated on real data of large sequences of whistles from common dolphins, collected in the Bay of Biscay (France). The proposed method is also compared with two alternative approaches: the first is smoothing and thresholding of the spectrogram; the second is thresholding of the spectrogram followed by the use of morphological operators to gather the time-frequency bins and to remove false positives. This method is shown to increase the probability of detection for the same probability of false alarms.

Lightweight, high-frequency transformers

NASA Technical Reports Server (NTRS)

Schwarze, G. E.

1983-01-01

The 25-kVA space transformer was developed under contract by Thermal Technology Laboratory, Buffalo, N. Y. The NASA Lewis transformer technology program attempted to develop the baseline technology. For the 25-kVA transformer the input voltage was chosen as 200 V, the output voltage as 1500 V, the input voltage waveform as square wave, the duty cycle as continuous, the frequency range (within certain constraints) as 10 to 40 kHz, the operating temperatures as 85 deg. and 130 C, the baseplate temperature as 50 C, the equivalent leakage inductance as less than 10 micro-h, the operating environment as space, and the life expectancy as 10 years. Such a transformer can also be used for aircraft, ship and terrestrial applications.

Theory of the high-frequency chiral optical response of a p(x) + ip(y) superconductor.

PubMed

Yakovenko, Victor M

2007-02-23

The optical Hall conductivity and the polar Kerr angle are calculated as functions of temperature for a two-dimensional chiral p(x) + ip(y) superconductor, where the time-reversal symmetry is spontaneously broken. The theoretical estimate for the polar Kerr angle agrees by the order of magnitude with the recent experimental measurement in Sr2RuO4 by Xia et al. [Phys. Rev. Lett. 97, 167002 (2006)10.1103/PhysRevLett.97.167002]. The theory predicts that the Kerr angle is proportional to the square of the superconducting energy gap and is inversely proportional to the cube of frequency, which can be verified experimentally.

Theoretical study of refraction effects on noise produced by turbulent jets

NASA Technical Reports Server (NTRS)

Graham, E. W.; Graham, B. B.

1975-01-01

The transmission of acoustic disturbances from the interior of a jet into the ambient air is studied. The jet is assumed infinitely long with mean velocity profile independent of streamwise location. The noise generator is a sequence of transient sources drifting with the local fluid and confined to a short length of the jet. In Part 1, supersonic jets are considered. Numerical results for mean-square pressure versus angle in the far-field show unexpected peaks which are very sharp. Analysis of simplified models indicates that these are complex quasi-resonant effects which appear to the stationary observer in a high frequency range. The peaks are real for the idealized model, but would be smoothed by mathematical integration over source position, velocity, and frequency. Subsonic jets were considered in part 2, and a preliminary study of the near-field was attempted. Mean-square radial displacements (or mean radial energy flow or space-time correlations of radial pressure gradient) are first found for very simple cases. The most difficult case studied is a sequence of transient sources at the center of a uniform-velocity circular cylindrical jet. Here a numerical triple integration is required and seems feasible although only preliminary results for mean square radial displacement are now available. These preliminary results show disturbances decreasing with increasing radial distance, and with increasing distance upstream and downstream from the source. A trend towards greater downstream disturbances appears even in the near field.

Quantum critical point revisited by dynamical mean-field theory

NASA Astrophysics Data System (ADS)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Quantum critical point revisited by dynamical mean-field theory

DOE PAGES

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-31

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less

High sensitivity field asymmetric ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

2017-03-01

A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

Frequency-doubled microwave waveforms generation using a dual-polarization quadrature phase shift keying modulator driven by a single frequency radio frequency signal

NASA Astrophysics Data System (ADS)

Zhu, Zihang; Zhao, Shanghong; Li, Xuan; Qu, Kun; Lin, Tao

2018-01-01

A photonic approach to generate frequency-doubled microwave waveforms using an integrated dual-polarization quadrature phase shift keying (DP-QPSK) modulator driven by a sinusoidal radio frequency (RF) signal is proposed. By adjusting the dc bias points of the DP-QPSK modulator, the obtained second-order and six-order harmonics are in phase while the fourth-order harmonics are complementary when the orthogonal polarized outputs of the modulator are photodetected. After properly setting the modulation indices of the modulator, the amplitude of the second-order harmonic is 9 times of that of the six-order harmonic, indicating a frequency-doubled triangular waveform is generated. If a broadband 90° microwave phase shifter is attached after the photodetector (PD) to introduce a 90° phase shift, a frequency-doubled square waveform can be obtained after adjusting the amplitude of the second-order harmonic 3 times of that of the six-order harmonic. The proposal is first theoretically analyzed and then validated by simulation. Simulation results show that a 10 GHz triangular and square waveform sequences are successfully generated from a 5 GHz sinusoidal RF drive signal.

Photonic microwave waveforms generation based on pulse carving and superposition in time-domain

NASA Astrophysics Data System (ADS)

Xia, Yi; Jiang, Yang; Zi, Yuejiao; He, Yutong; Tian, Jing; Zhang, Xiaoyu; Luo, Hao; Dong, Ruyang

2018-05-01

A novel photonic approach for various microwave waveforms generation based on time-domain synthesis is theoretically analyzed and experimentally investigated. In this scheme, two single-drive Mach-Zehnder modulators are used for pulses shaping. After shifting the phase and implementing envelopes superposition of the pulses, desired waveforms can be achieved in time-domain. The theoretic analysis and simulations are presented. In the experimental demonstrations, a triangular waveform, square waveform, and half duty cycle sawtooth (or reversed-sawtooth) waveform are generated successfully. By utilizing time multiplexing technique, a frequency-doubled sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can be obtained. In addition, a fundamental frequency sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can also be achieved by the superposition of square waveform and frequency-doubled sawtooth waveform.

Masking potency and whiteness of noise at various noise check sizes.

PubMed

Kukkonen, H; Rovamo, J; Näsänen, R

1995-02-01

The masking effect of spatial noise can be increased by increasing either the rms contrast or check size of noise. In this study, the authors investigated the largest noise check size that still mimics the effect of white noise in grating detection and how it depends on the bandwidth and spatial frequency of a grating. The authors measured contrast energy thresholds, E, for vertical cosine gratings at various spatial frequencies and bandwidths. Gratings were embedded in two-dimensional spatial noise. The side length of the square noise checks was varied in the experiments. The spectral density, N(0,0), of white spatial noise at zero frequency was calculated by multiplying the noise check area by the rms contrast of noise squared. The physical signal-to-noise ratio at threshold [E/N(0,0)]0.5 was initially constant but then started to decrease. The largest noise check that still produced a constant physical signal-to-noise ratio at threshold was directly proportional to the spatial frequency. When expressed as a fraction of grating cycle, the largest noise check size depended only on stimulus bandwidth. The smallest number of noise checks per grating cycle needed to mimic the effect of white noise decreased from 4.2 to 2.6 when the number of grating cycles increased from 1 to 64. Spatial noise can be regarded as white in grating detection if there are at least four square noise checks per grating cycle at all spatial frequencies.

Analogue solution for electrical capacity of membrane covered square cylinders in square array at high concentration.

PubMed

Cole, K S

1975-12-01

Analytical solutions of Laplace equations have given the electrical characteristics of membranes and interiors of spherical, ellipsoidal, and cylindrical cells in suspensions and tissues from impedance measurements, but the underlying assumptions may be invalid above 50% volume concentrations. However, resistance measurements on several nonconducting, close-packing forms in two and three dimensions closely predicted volume concentrations up to 100% by equations derived from Maxwell and Rayleigh. Calculations of membrane capacities of cells in suspensions and tissues from extensions of theory, as developed by Fricke and by Cole, have been useful but of unknown validity at high concentrations. A resistor analogue has been used to solve the finite difference approximation to the Laplace equation for the resistance and capacity of a square array of square cylindrical cells with surface capacity. An 11 x 11 array of resistors, simulating a quarter of the unit structure, was separated into intra- and extra-cellular regions by rows of capacitors corresponding to surface membrane areas from 3 x 3 to 11 x 11 or 7.5% to 100%. The extended Rayleigh equation predicted the cell concentrations and membrane capacities to within a few percent from boundary resistance and capacity measurements at low frequencies. This single example suggests that analytical solutions for other, similar two- and three-dimensional problems may be approximated up to near 100% concentrations and that there may be analytical justifications for such analogue solutions of Laplace equations.

A fast least-squares algorithm for population inference

PubMed Central

2013-01-01

Background Population inference is an important problem in genetics used to remove population stratification in genome-wide association studies and to detect migration patterns or shared ancestry. An individual’s genotype can be modeled as a probabilistic function of ancestral population memberships, Q, and the allele frequencies in those populations, P. The parameters, P and Q, of this binomial likelihood model can be inferred using slow sampling methods such as Markov Chain Monte Carlo methods or faster gradient based approaches such as sequential quadratic programming. This paper proposes a least-squares simplification of the binomial likelihood model motivated by a Euclidean interpretation of the genotype feature space. This results in a faster algorithm that easily incorporates the degree of admixture within the sample of individuals and improves estimates without requiring trial-and-error tuning. Results We show that the expected value of the least-squares solution across all possible genotype datasets is equal to the true solution when part of the problem has been solved, and that the variance of the solution approaches zero as its size increases. The Least-squares algorithm performs nearly as well as Admixture for these theoretical scenarios. We compare least-squares, Admixture, and FRAPPE for a variety of problem sizes and difficulties. For particularly hard problems with a large number of populations, small number of samples, or greater degree of admixture, least-squares performs better than the other methods. On simulated mixtures of real population allele frequencies from the HapMap project, Admixture estimates sparsely mixed individuals better than Least-squares. The least-squares approach, however, performs within 1.5% of the Admixture error. On individual genotypes from the HapMap project, Admixture and least-squares perform qualitatively similarly and within 1.2% of each other. Significantly, the least-squares approach nearly always converges 1.5- to 6-times faster. Conclusions The computational advantage of the least-squares approach along with its good estimation performance warrants further research, especially for very large datasets. As problem sizes increase, the difference in estimation performance between all algorithms decreases. In addition, when prior information is known, the least-squares approach easily incorporates the expected degree of admixture to improve the estimate. PMID:23343408

A fast least-squares algorithm for population inference.

PubMed

Parry, R Mitchell; Wang, May D

2013-01-23

Population inference is an important problem in genetics used to remove population stratification in genome-wide association studies and to detect migration patterns or shared ancestry. An individual's genotype can be modeled as a probabilistic function of ancestral population memberships, Q, and the allele frequencies in those populations, P. The parameters, P and Q, of this binomial likelihood model can be inferred using slow sampling methods such as Markov Chain Monte Carlo methods or faster gradient based approaches such as sequential quadratic programming. This paper proposes a least-squares simplification of the binomial likelihood model motivated by a Euclidean interpretation of the genotype feature space. This results in a faster algorithm that easily incorporates the degree of admixture within the sample of individuals and improves estimates without requiring trial-and-error tuning. We show that the expected value of the least-squares solution across all possible genotype datasets is equal to the true solution when part of the problem has been solved, and that the variance of the solution approaches zero as its size increases. The Least-squares algorithm performs nearly as well as Admixture for these theoretical scenarios. We compare least-squares, Admixture, and FRAPPE for a variety of problem sizes and difficulties. For particularly hard problems with a large number of populations, small number of samples, or greater degree of admixture, least-squares performs better than the other methods. On simulated mixtures of real population allele frequencies from the HapMap project, Admixture estimates sparsely mixed individuals better than Least-squares. The least-squares approach, however, performs within 1.5% of the Admixture error. On individual genotypes from the HapMap project, Admixture and least-squares perform qualitatively similarly and within 1.2% of each other. Significantly, the least-squares approach nearly always converges 1.5- to 6-times faster. The computational advantage of the least-squares approach along with its good estimation performance warrants further research, especially for very large datasets. As problem sizes increase, the difference in estimation performance between all algorithms decreases. In addition, when prior information is known, the least-squares approach easily incorporates the expected degree of admixture to improve the estimate.

High-frequency Electrocardiogram Analysis in the Ability to Predict Reversible Perfusion Defects during Adenosine Myocardial Perfusion Imaging

NASA Technical Reports Server (NTRS)

Tragardh, Elin; Schlegel, Todd T.; Carlsson, Marcus; Pettersson, Jonas; Nilsson, Klas; Pahlm, Olle

2007-01-01

Background: A previous study has shown that analysis of high-frequency QRS components (HF-QRS) is highly sensitive and reasonably specific for detecting reversible perfusion defects on myocardial perfusion imaging (MPI) scans during adenosine. The purpose of the present study was to try to reproduce those findings. Methods: 12-lead high-resolution electrocardiogram recordings were obtained from 100 patients before (baseline) and during adenosine Tc-99m-tetrofosmin MPI tests. HF-QRS were analyzed regarding morphology and changes in root mean square (RMS) voltages from before the adenosine infusion to peak infusion. Results: The best area under the curve (AUC) was found in supine patients (AUC=0.736) in a combination of morphology and RMS changes. None of the measurements, however, were statistically better than tossing a coin (AUC=0.5). Conclusion: Analysis of HF-QRS was not significantly better than tossing a coin for determining reversible perfusion defects on MPI scans.

Tunable microstrip SQUID amplifiers for the Gen 2 Axion Dark Matter eXperiment (ADMX)

NASA Astrophysics Data System (ADS)

O'Kelley, Sean; Hilton, Gene; Clarke, John; ADMX Collaboration

2016-03-01

We present a series of tunable microstrip SQUID (Superconducting Quantum Interference Device) amplifiers (MSAs) for installation in ADMX. The axion dark matter candidate is detected via Primakoff conversion to a microwave photon in a high-Q (~100,000) tunable microwave cavity cooled with a dilution refrigerator in a 7-tesla magnetic field. The microwave photon frequency ν is a function of the unknown axion mass, so both the cavity and amplifier must be scanned over a wide frequency range. An MSA is a linear, phase-preserving amplifier consisting of a square washer loop, fabricated from a thin Nb film, incorporating two Josephson tunnel junctions with resistive shunts to prevent hysteresis. The input is coupled via a microstrip made from a square Nb coil deposited over the washer with an intervening insulating layer. Tunability is achieved by terminating the microstrip with GaAs varactors that operate below 100 mK. By varying the varactor capacitance with a bias voltage, the resonant frequency is varied by up to a factor of 2. We demonstrate several devices operating below 100 mK, matched to the discrete operating bands of ADMX at frequencies ranging from 560 MHz to 1 GHz. The MSAs exhibit gains exceeding 20 dB and the associated noise temperatures, measured with a hot/cold load, approach the standard quantum limit (hν/kB) . Supported by DOE Grants DE - FG02 - 97ER41029, DE - FG02 - 96ER40956, DE - AC52 - 07NA27344, DE - AC03 - 76SF00098, and the Livermore LDRD program.

The Processing of High Temperature Ceramic Superconducting Devices. Volume 1.

DTIC Science & Technology

1992-01-31

assuming frequency squared dependence) for ease of comparison with other measurements. At the low power levels the surface resistance is I 200 micro ...transition temperature is 106K, where the measured resistivity becomes zero. The noimal state resistivity at the transition temperature, 100 micro -ohms...our films at temperatures down t o 4K. A four-point measurement is used, and the criterion of 1 micro -volt per millimeter is usedI to determine

Adaptive cancellation of motion artifact in wearable biosensors.

PubMed

Yousefi, Rasoul; Nourani, Mehrdad; Panahi, Issa

2012-01-01

The performance of wearable biosensors is highly influenced by motion artifact. In this paper, a model is proposed for analysis of motion artifact in wearable photoplethysmography (PPG) sensors. Using this model, we proposed a robust real-time technique to estimate fundamental frequency and generate a noise reference signal. A Least Mean Square (LMS) adaptive noise canceler is then designed and validated using our synthetic noise generator. The analysis and results on proposed technique for noise cancellation shows promising performance.

The use of heart rate variability in assessing precompetitive stress in high-standard judo athletes.

PubMed

Morales, J; Garcia, V; García-Massó, X; Salvá, P; Escobar, R; Buscà, B

2013-02-01

The objective of this study is to examine the sensitivity to and changes in heart rate variability (HRV) in stressful situations before judo competitions and to observe the differences among judo athletes according to their competitive standards in both official and unofficial competitions. 24 (10 male and 14 female) national- and international-standard athletes were evaluated. Each participant answered the Revised Competitive State Anxiety Inventory (CSAI-2R) and their HRV was recorded both during an official and unofficial competition. The MANOVA showed significant main effects of the athlete's standard and the type of competition in CSAI-2R, in HRV time domain, in HRV frequency domain and in HRV nonlinear analysis (p<0.05). International-standard judo athletes have lower somatic anxiety, cognitive anxiety, heart rate and low-high frequency ratio than national-standard athletes (p<0.05). International-standard athletes have a higher confidence, mean RR interval, standard deviation of RR, square root of the mean squared difference of successive RR intervals, number of consecutive RR that differ by more than 5 ms, short-term variability, long-term variability, long-range scaling exponents and short-range scaling exponent than national-standard judo athletes. In conclusion, international-standard athletes show less pre-competitive anxiety than the national-standard athletes and HRV analysis is sensitive to changes in pre-competitive anxiety. © Georg Thieme Verlag KG Stuttgart · New York.

Experimental power spectral density analysis for mid- to high-spatial frequency surface error control.

PubMed

Hoyo, Javier Del; Choi, Heejoo; Burge, James H; Kim, Geon-Hee; Kim, Dae Wook

2017-06-20

The control of surface errors as a function of spatial frequency is critical during the fabrication of modern optical systems. A large-scale surface figure error is controlled by a guided removal process, such as computer-controlled optical surfacing. Smaller-scale surface errors are controlled by polishing process parameters. Surface errors of only a few millimeters may degrade the performance of an optical system, causing background noise from scattered light and reducing imaging contrast for large optical systems. Conventionally, the microsurface roughness is often given by the root mean square at a high spatial frequency range, with errors within a 0.5×0.5  mm local surface map with 500×500 pixels. This surface specification is not adequate to fully describe the characteristics for advanced optical systems. The process for controlling and minimizing mid- to high-spatial frequency surface errors with periods of up to ∼2-3  mm was investigated for many optical fabrication conditions using the measured surface power spectral density (PSD) of a finished Zerodur optical surface. Then, the surface PSD was systematically related to various fabrication process parameters, such as the grinding methods, polishing interface materials, and polishing compounds. The retraceable experimental polishing conditions and processes used to produce an optimal optical surface PSD are presented.

[EMD Time-Frequency Analysis of Raman Spectrum and NIR].

PubMed

Zhao, Xiao-yu; Fang, Yi-ming; Tan, Feng; Tong, Liang; Zhai, Zhe

2016-02-01

This paper analyzes the Raman spectrum and Near Infrared Spectrum (NIR) with time-frequency method. The empirical mode decomposition spectrum becomes intrinsic mode functions, which the proportion calculation reveals the Raman spectral energy is uniform distributed in each component, while the NIR's low order intrinsic mode functions only undertakes fewer primary spectroscopic effective information. Both the real spectrum and numerical experiments show that the empirical mode decomposition (EMD) regard Raman spectrum as the amplitude-modulated signal, which possessed with high frequency adsorption property; and EMD regards NIR as the frequency-modulated signal, which could be preferably realized high frequency narrow-band demodulation during first-order intrinsic mode functions. The first-order intrinsic mode functions Hilbert transform reveals that during the period of empirical mode decomposes Raman spectrum, modal aliasing happened. Through further analysis of corn leaf's NIR in time-frequency domain, after EMD, the first and second orders components of low energy are cut off, and reconstruct spectral signal by using the remaining intrinsic mode functions, the root-mean-square error is 1.001 1, and the correlation coefficient is 0.981 3, both of these two indexes indicated higher accuracy in re-construction; the decomposition trend term indicates the absorbency is ascending along with the decreasing to wave length in the near-infrared light wave band; and the Hilbert transform of characteristic modal component displays, 657 cm⁻¹ is the specific frequency by the corn leaf stress spectrum, which could be regarded as characteristic frequency for identification.

A real-time sub-μrad laser beam tracking system

NASA Astrophysics Data System (ADS)

Buske, Ivo; Schragner, Ralph; Riede, Wolfgang

2007-10-01

We present a rugged and reliable real-time laser beam tracking system operating with a high speed, high resolution piezo-electric tip/tilt mirror. Characteristics of the piezo mirror and position sensor are investigated. An industrial programmable automation controller is used to develop a real-time digital PID controller. The controller provides a one million field programmable gate array (FPGA) to realize a high closed-loop frequency of 50 kHz. Beam tracking with a root-mean-squared accuracy better than 0.15 μrad has been laboratory confirmed. The system is intended as an add-on module for established mechanical mrad tracking systems.

A symmetrical method to obtain shear moduli from microrheology† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sm02499a

PubMed Central

Nishi, Kengo

2018-01-01

Passive microrheology typically deduces shear elastic loss and storage moduli from displacement time series or mean-squared displacements (MSD) of thermally fluctuating probe particles in equilibrium materials. Common data analysis methods use either Kramers–Kronig (KK) transformation or functional fitting to calculate frequency-dependent loss and storage moduli. We propose a new analysis method for passive microrheology that avoids the limitations of both of these approaches. In this method, we determine both real and imaginary components of the complex, frequency-dependent response function χ(ω) = χ′(ω) + iχ′′(ω) as direct integral transforms of the MSD of thermal particle motion. This procedure significantly improves the high-frequency fidelity of χ(ω) relative to the use of KK transformation, which has been shown to lead to artifacts in χ′(ω). We test our method on both model and experimental data. Experiments were performed on solutions of worm-like micelles and dilute collagen solutions. While the present method agrees well with established KK-based methods at low frequencies, we demonstrate significant improvement at high frequencies using our symmetric analysis method, up to almost the fundamental Nyquist limit. PMID:29611576

High N-Terminal Pro-B-Type Natriuretic Peptide Levels Are Associated with Reduced Heart Rate Variability in Acute Myocardial Infarction

PubMed Central

Lorgis, Luc; Moreau, Daniel; Mock, Laurent; Daumas, Bernadette; Potard, Daniel; Touzery, Claude; Cottin, Yves; Zeller, Marianne

2012-01-01

Aim We investigated the relationships between the autonomic nervous system, as assessed by heart rate variability (HRV) and levels of N-terminal Pro-B-type Natriuretic Peptide (Nt-proBNP) in patients with acute myocardial infarction (MI). Methods and Results The mean of standard deviation of RR intervals (SDNN), the percentage of RR intervals with >50 ms variation (pNN50), square root of mean squared differences of successive RR intervals (rMSSD), and frequency domain parameters (total power (TP), high frequency and low frequency power ratio (LF/HF)) were assessed by 24 h Holter ECG monitoring. 1018 consecutive patients admitted <24 h for an acute MI were included. Plasma Nt-proBNP (Elecsys, Roche) was measured from blood samples taken on admission. The median (IQR) Nt-proBNP level was 681(159–2432) pmol/L. Patients with the highest quartile of Nt-proBNP were older, with higher rate of risk factors and lower ejection fraction. The highest Nt-proBNP quartile group had the lowest SDNN, LF/HF and total power but similar pNN50 and rMSSD levels. Nt-proBNP levels correlated negatively with SDNN (r = −0.19, p<0.001), LF/HF (r = −0.37, p<0.001), and LF (r = −0.29, p<0.001) but not HF (r = −0.043, p = 0.172). Multiple regression analysis showed that plasma propeptide levels remained predictive of LF/HF (B(SE) = −0.065(0.015), p<0.001)), even after adjustment for confounders. Conclusions In conclusion, our population-based study highlights the importance of Nt-proBNP levels to predict decreased HRV after acute MI. PMID:23071500

Flexible All-Digital Receiver for Bandwidth Efficient Modulations

NASA Technical Reports Server (NTRS)

Gray, Andrew; Srinivasan, Meera; Simon, Marvin; Yan, Tsun-Yee

2000-01-01

An all-digital high data rate parallel receiver architecture developed jointly by Goddard Space Flight Center and the Jet Propulsion Laboratory is presented. This receiver utilizes only a small number of high speed components along with a majority of lower speed components operating in a parallel frequency domain structure implementable in CMOS, and can currently process up to 600 Mbps with standard QPSK modulation. Performance results for this receiver for bandwidth efficient QPSK modulation schemes such as square-root raised cosine pulse shaped QPSK and Feher's patented QPSK are presented, demonstrating the flexibility of the receiver architecture.

Faraday wave patterns on a square cell network

NASA Astrophysics Data System (ADS)

Peña-Polo, Franklin; Vargas, Carlos A.; Vásquez-González, Benjamín; Medina, Abraham; Trujillo, Leonardo; Klapp, Jaime; Sigalotti, Leonardo Di G.

2017-05-01

We present the experimental observations of the Faraday instability when the vibrated liquid is contained in a network of small square cells for exciting frequencies in the range 10≤ F≤ 24 Hz. A sweep of the parameter space has been performed to investigate the amplitudes and frequencies of the driving force for which different patterns form over the network. Regular patterns in the form of square lattices are observed for driving frequencies in the range 10≤ F<14 Hz, while ordered matrices of oscillons are formed for 1423 Hz, disordered periodic patterns appear within individual cells for a small range of amplitudes. In this case, the wave field is dominated by oscillating blobs that interact on the capillary-gravity scale. A Pearson correlation analysis of the recorded videos shows that for all ordered patterns, the surface waves are periodic and correspond to Faraday waves of dominant frequency equal to half the excitation frequency (i.e., f=F/2). In contrast, the oscillons formed for 1423 Hz are not subharmonic and correspond to periodic harmonic waves with f=nF/2 (for n=2,4,\\ldots ). We find that the experimentally determined minimum forcing necessary to destabilize the rest state and generate surface waves is consistent with a recent stability analysis of stationary solutions as derived from a new dispersion relation for time-periodic waves with nonzero forcing and dissipation.

Robust Nonrigid Multimodal Image Registration using Local Frequency Maps*

PubMed Central

Jian, Bing; Vemuri, Baba C.; Marroquin, José L.

2008-01-01

Automatic multi-modal image registration is central to numerous tasks in medical imaging today and has a vast range of applications e.g., image guidance, atlas construction, etc. In this paper, we present a novel multi-modal 3D non-rigid registration algorithm where in 3D images to be registered are represented by their corresponding local frequency maps efficiently computed using the Riesz transform as opposed to the popularly used Gabor filters. The non-rigid registration between these local frequency maps is formulated in a statistically robust framework involving the minimization of the integral squared error a.k.a. L2E (L2 error). This error is expressed as the squared difference between the true density of the residual (which is the squared difference between the non-rigidly transformed reference and the target local frequency representations) and a Gaussian or mixture of Gaussians density approximation of the same. The non-rigid transformation is expressed in a B-spline basis to achieve the desired smoothness in the transformation as well as computational efficiency. The key contributions of this work are (i) the use of Riesz transform to achieve better efficiency in computing the local frequency representation in comparison to Gabor filter-based approaches, (ii) new mathematical model for local-frequency based non-rigid registration, (iii) analytic computation of the gradient of the robust non-rigid registration cost function to achieve efficient and accurate registration. The proposed non-rigid L2E-based registration is a significant extension of research reported in literature to date. We present experimental results for registering several real data sets with synthetic and real non-rigid misalignments. PMID:17354721

Metamaterial composition comprising frequency-selective-surface resonant element disposed on/in a dielectric flake, methods, and applications

DOEpatents

Shelton, David; Boreman, Glenn; D'Archangel, Jeffrey

2015-11-10

Infrared metamaterial arrays containing Au elements immersed in a medium of benzocyclobutene (BCB) were fabricated and selectively etched to produce small square flakes with edge dimensions of approximately 20 .mu.m. Two unit-cell designs were fabricated: one employed crossed-dipole elements while the other utilized square-loop elements.

Seasonal contamination of public squares and lawns by parasites with zoonotic potential in southern Brazil.

PubMed

Tiyo, R; Guedes, T A; Falavigna, D L M; Falavigna-Guilherme, A L

2008-03-01

The presence of helminths and protozoans in public squares and lawns of the city of Maringá, southern Brazil, during winter and summer was assessed in order to evaluate their seasonal fluctuations in relation to edaphic and climatic factors. Samples were collected from January 2003 through June 2004 in 90% (13) of all public squares covered by sand, and in 30% (4) of all lawns used as leisure areas. The samples were analysed quantitatively by modified centrifugal-flotation and sedimentation in water techniques, and qualitatively by a method based on positive larval thermo-hydrotropism. Meteorological data were recorded, and physical, chemical and structural characteristics of the soil were analysed. One hundred and thirty samples of sand from squares, 65 in summer and 65 in winter, and 40 samples of grass from lawns, 20 in each season, were collected. All samples from lawns, 62 (95.38%) from squares in winter and 45 (69.23%) in summer, contained protozoans and/or helminths. Eggs of Toxocara spp. were the most frequently observed parasites in both winter and summer in squares (P < 0.0001) and in lawns (P = 0.6142), being equally distributed among the different locations (P = 0.2038). Species diversity was lower in winter; fewer parasites were found in summer. This region, with a tropical climate and a mild winter dry season, has favourable edaphic and climatic conditions for soil contaminants to persist year-round. In addition, the high frequency of animals such as dogs and cats and the poor sanitary measures in force made it possible for zoonoses to be transmitted in the public spaces.

Quasi-elastic light scattering of carnauba wax in the liquid phase: dynamics 2.

PubMed

de Almeida, F J; Barbosa, G A

1983-12-01

Quasi-elastic light scattering of carnauba wax in the liquid phase is obtained in a heterodyne setup, and dynamic processes are analyzed through electrophoresis. Nonspherical polar clusters are found, containing a net electrical charge. An applied square-wave electric field induces drift and rotation of these clusters.These effects are dependent on strength and frequency of the applied electric field. At 373 K and in the low frequency limit the local electric field strength is approximately 70 times the strength of the applied one. This enhancement is believed to be caused by collective orientation of the clusters. The electrophoretic mobility is 1.1 X 10(-12) m2/V sec in the high frequency limit and 7.4 X 10(-11) m2/V sec in the low frequency limit. The electric dipole moment is 6.3 X 10(-16) N(-1/2) m(-1/2) where N is the cluster density/cubic meter and the net charge is about one or two elementary charges.

Similitude relations for buffet and wing rock on delta wings

NASA Astrophysics Data System (ADS)

Mabey, D. G.

1997-08-01

Vortex flow phenomena at high angles of incidence are of great interest to the designers of advanced combat aircraft. The steady phenomena (such as steady lift and pitching moments) are understood fairly well, whereas the unsteady phenomena are still uncertain. This paper addresses two important unsteady phenomena on delta wings. With regard to the frequency parameter of the quasi-periodic excitation caused by vortex bursting, a new correlation is established covering a range of sweep back from 60 to 75°. With regard to the much lower frequency parameter of limit-cycle rigid-body wing-rock, a new experiment shows conclusively that although the motion is non-linear, the frequency parameter can be predicted by quasi-steady theory. As a consequence, for a given sweep angle, the frequency parameter is inversely proportional to the square root of the inertia in roll. This is an important observation when attempting to extrapolate from model tests in wind tunnels to predict the wing-rock characteristics of aircraft.

Multi-Scale Complexity in Linear Dispersive Pulse Propagation Phenomena

DTIC Science & Technology

2011-02-01

ǫ(0)/ǫ0, the single resonance frequency ω0 Lorentz-model dielectric ǫ(ω)/ǫ0 = 1− b2 ω2 − ω20 + 2iδω (63) with b2 ≡ Nq2e/me the square of the plasma ...ω20 + 2iδω) 2 , (74) where b2 ≡ Nq2e/me is the square of the plasma frequency with number density N . In the singular dispersion limit as δ → 0, n′r(ω...International Symposium and USNC/ CNC /URSI National Radio Science Meeting, Toronto, Canada (2010). 11. K. E. Oughstun, “Beer’s Law and the Unique

Circularly Polarized S Band Dual Frequency Square Patch Antenna Using Glass Microfiber Reinforced PTFE Composite

PubMed Central

Samsuzzaman, M.; Islam, M. T.; Arshad, Haslina; Mandeep, J. S.; Misran, N.

2014-01-01

Circularly polarized (CP) dual frequency cross-shaped slotted patch antenna on 1.575 mm thick glass microfiber reinforced polytetrafluoroethylene (PTFE) composite material substrate is designed and fabricated for satellite applications. Asymmetric cross-shaped slots are embedded in the middle of the square patch for CP radiation and four hexagonal slots are etched on the four sides of the square patch for desired dual frequency. Different substrate materials have been analysed to achieve the desired operating band. The experimental results show that the impedance bandwidth is approximately 30 MHz (2.16 GHz to 2.19 GHz) for lower band and 40 MHz (3.29 GHz to 3.33 GHz) for higher band with an average peak gain of 6.59 dBiC and 5.52 dBiC, respectively. Several optimizations are performed to obtain the values of the antenna physical parameters. Moreover, the proposed antenna possesses compactness, light weight, simplicity, low cost, and circularly polarized. It is an attractive candidate for dual band satellite antennas where lower band can be used for uplink and upper band can be used for downlink. PMID:24982943

Evaluation of arch form between Vietnamese and North American Caucasians using 3-dimensional virtual models.

PubMed

Trang, Vu Thi Thu; Park, Jae Hyun; Bayome, Mohamed; Shastry, Shruti; Mellion, Alex; Kook, Yoon-Ah

2015-01-01

The purpose of this study was to investigate the three-dimensional (3D) morphologic differences in the mandibular arch of Vietnamese and North American White subjects. The sample included 113 Vietnamese subjects (41 Class I, 37 Class II and 35 Class III) and 96 White subjects (29 Class I, 30 Class II and 37 Class III). The samples were regrouped according to arch form types (tapered, ovoid, and square) to compare the frequency distribution of the three arch forms between ethnic groups in each angle classification. The facial axis point of each tooth was digitized on 3D virtual models. Four linear and two ratio variables were measured. In comparing arch dimensions, the intercanine and intermolar widths were wider in Vietnamese than in Whites (p < 0.001, p = 0.042, respectively). In the White group, there was even frequency distribution of the three arch forms. However, in the Vietnamese group, the square arch form was the most frequent followed by tapered and ovoid arch forms. The arch forms of Whites were narrower than Vietnamese. In North American Whites, the distribution of the arch form types showed similar frequency. In Vietnamese, the square arch form was more frequent.

Microwave energy harvesting based on metamaterial absorbers with multi-layered square split rings for wireless communications

NASA Astrophysics Data System (ADS)

Karaaslan, Muharrem; Bağmancı, Mehmet; Ünal, Emin; Akgol, Oguzhan; Sabah, Cumali

2017-06-01

We propose the design of a multiband absorber based on multi-layered square split ring (MSSR) structure. The multi-layered metamaterial structure is designed to be used in the frequency bands such as WIMAX, WLAN and satellite communication region. The absorption levels of the proposed structure are higher than 90% for all resonance frequencies. In addition, the incident angle and polarization dependence of the multi-layered metamaterial absorber and harvester is also investigated and it is observed that the structure has polarization angle independent frequency response with good absorption characteristics in the entire working frequency band. The energy harvesting ratios of the structure is investigated especially for the resonance frequencies at which the maximum absorption occurs. The energy harvesting potential of the proposed MSSRs is as good as those of the structures given in the literature. Therefore, the suggested design having good absorption, polarization and angle independent characteristics with a wide bandwidth is a potential candidate for future energy harvesting applications in commonly used wireless communication bands, namely WIMAX, WLAN and satellite communication bands.

Optical Quantification of Harmonic Acoustic Radiation Force Excitation in a Tissue-Mimicking Phantom.

PubMed

Suomi, Visa; Edwards, David; Cleveland, Robin

2015-12-01

Optical tracking was used to characterize acoustic radiation force-induced displacements in a tissue-mimicking phantom. Amplitude-modulated 3.3-MHz ultrasound was used to induce acoustic radiation force in the phantom, which was embedded with 10-μm microspheres that were tracked using a microscope objective and high-speed camera. For sine and square amplitude modulation, the harmonic components of the fundamental and second and third harmonic frequencies were measured. The displacement amplitudes were found to increase linearly with acoustic radiation force up to 10 μm, with sine modulation having 19.5% lower peak-to-peak amplitude values than square modulation. Square modulation produced almost no second harmonic, but energy was present in the third harmonic. For the sine modulation, energy was present in the second harmonic and low energy in the third harmonic. A finite-element model was used to simulate the deformation and was both qualitatively and quantitatively in agreement with the measurements. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

A Novel Photonic Clock and Carrier Recovery Device

NASA Technical Reports Server (NTRS)

Yao, X. Steve; Lutes, George; Maleki, Lute

1996-01-01

As data communication rates climb toward ten Gb/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. We present in this article experimental results of a high speed clock and carrier recovery using a novel device called a photonic oscillator that we recently developed in our laboratory. This device is capable of recovering clock signals up to 70 GHz. To recover the clock, the incoming data is injected into the photonic oscillator either through the optical injection port or the electrical injection port. The free running photonic oscillator is tuned to oscillate at a nominal frequency equal to the clock frequency of the incoming data. With the injection of the data, the photonic oscillator will be quickly locked to clock frequency of the data stream while rejecting other frequency components associated with the data. Consequently, the output of the locked photonic oscillator is a continuous periodical wave synchronized with the incoming data or simply the recovered clock. We have demonstrated a clock to spur ratio of more than 60 dB of the recovered clock using this technique. Similar to the clock recovery, the photonic oscillator can be used to recover a high frequency carrier degraded by noise and an improvement of about 50 dB in signal-to-noise ratio was demonstrated. The photonic oscillator has both electrical and optical inputs and outputs and can be directly interfaced with a photonic system without signal conversion. In addition to clock and carrier recovery, the photonic oscillator can also be used for (1) stable high frequency clock signal generation, (2) frequency multiplication, (3) square wave and comb frequency generation, and (4) photonic phase locked loop.

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.

Estimation of peak-discharge frequency of urban streams in Jefferson County, Kentucky

USGS Publications Warehouse

Martin, Gary R.; Ruhl, Kevin J.; Moore, Brian L.; Rose, Martin F.

1997-01-01

An investigation of flood-hydrograph characteristics for streams in urban Jefferson County, Kentucky, was made to obtain hydrologic information needed for waterresources management. Equations for estimating peak-discharge frequencies for ungaged streams in the county were developed by combining (1) long-term annual peakdischarge data and rainfall-runoff data collected from 1991 to 1995 in 13 urban basins and (2) long-term annual peak-discharge data in four rural basins located in hydrologically similar areas of neighboring counties. The basins ranged in size from 1.36 to 64.0 square miles. The U.S. Geological Survey Rainfall- Runoff Model (RRM) was calibrated for each of the urban basins. The calibrated models were used with long-term, historical rainfall and pan-evaporation data to simulate 79 years of annual peak-discharge data. Peak-discharge frequencies were estimated by fitting the logarithms of the annual peak discharges to a Pearson-Type III frequency distribution. The simulated peak-discharge frequencies were adjusted for improved reliability by application of bias-correction factors derived from peakdischarge frequencies based on local, observed annual peak discharges. The three-parameter and the preferred seven-parameter nationwide urban-peak-discharge regression equations previously developed by USGS investigators provided biased (high) estimates for the urban basins studied. Generalized-least-square regression procedures were used to relate peakdischarge frequency to selected basin characteristics. Regression equations were developed to estimate peak-discharge frequency by adjusting peak-dischargefrequency estimates made by use of the threeparameter nationwide urban regression equations. The regression equations are presented in equivalent forms as functions of contributing drainage area, main-channel slope, and basin development factor, which is an index for measuring the efficiency of the basin drainage system. Estimates of peak discharges for streams in the county can be made for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals by use of the regression equations. The average standard errors of prediction of the regression equations ranges from ? 34 to ? 45 percent. The regression equations are applicable to ungaged streams in the county having a specific range of basin characteristics.

A simple model for strong ground motions and response spectra

USGS Publications Warehouse

Safak, Erdal; Mueller, Charles; Boatwright, John

1988-01-01

A simple model for the description of strong ground motions is introduced. The model shows that response spectra can be estimated by using only four parameters of the ground motion, the RMS acceleration, effective duration and two corner frequencies that characterize the effective frequency band of the motion. The model is windowed band-limited white noise, and is developed by studying the properties of two functions, cumulative squared acceleration in the time domain, and cumulative squared amplitude spectrum in the frequency domain. Applying the methods of random vibration theory, the model leads to a simple analytical expression for the response spectra. The accuracy of the model is checked by using the ground motion recordings from the aftershock sequences of two different earthquakes and simulated accelerograms. The results show that the model gives a satisfactory estimate of the response spectra.

Comparison of arch forms between Egyptian and North American white populations.

PubMed

Bayome, Mohamed; Sameshima, Glenn T; Kim, Yoonji; Nojima, Kunihiko; Baek, Seung-Hak; Kook, Yoon-Ah

2011-03-01

The aim of this study was to evaluate the morphologic differences in the mandibular arches of Egyptian and North American white subjects. The sample included 94 Egyptian subjects (35 Class I, 32 Class II, and 27 Class III) and 92 white subjects (37 Class I, 29 Class II, and 26 Class III). The subjects were grouped according to arch form types (tapered, ovoid, and square) to compare their frequency distribution between ethnic groups in each Angle classification. The most facial portions of 13 proximal contact areas were digitized on scanned images of mandibular casts to estimate the corresponding clinical bracket point for each tooth. Four linear and 2 proportional measurements were taken. In comparing arch dimensions, intermolar width was narrower in Egyptians than in the whites (P = 0.001). There was an even frequency distribution of the 3 arch forms in the Egyptian group. On the other hand, the most frequent arch form was ovoid followed by tapered and square in the white group; the square arch form was significantly less frequent than the tapered and ovoid arch forms (P = 0.029). The arch forms of Egyptians are narrower than those of whites. The distribution of the arch form types in Egyptians showed similar frequency, but the square arch form was less frequent in whites. It is recommended to select narrower archwires from the available variations to suit many Egyptian patients. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Effect of Frequency and Waveform on Inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in Salsa by Ohmic Heating

PubMed Central

Lee, Su-Yeon; Ryu, Sangryeol

2013-01-01

The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform. PMID:23023752

Effect of frequency and waveform on inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in salsa by ohmic heating.

PubMed

Lee, Su-Yeon; Ryu, Sangryeol; Kang, Dong-Hyun

2013-01-01

The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform.

Fast frequency acquisition via adaptive least squares algorithm

NASA Technical Reports Server (NTRS)

Kumar, R.

1986-01-01

A new least squares algorithm is proposed and investigated for fast frequency and phase acquisition of sinusoids in the presence of noise. This algorithm is a special case of more general, adaptive parameter-estimation techniques. The advantages of the algorithms are their conceptual simplicity, flexibility and applicability to general situations. For example, the frequency to be acquired can be time varying, and the noise can be nonGaussian, nonstationary and colored. As the proposed algorithm can be made recursive in the number of observations, it is not necessary to have a priori knowledge of the received signal-to-noise ratio or to specify the measurement time. This would be required for batch processing techniques, such as the fast Fourier transform (FFT). The proposed algorithm improves the frequency estimate on a recursive basis as more and more observations are obtained. When the algorithm is applied in real time, it has the extra advantage that the observations need not be stored. The algorithm also yields a real time confidence measure as to the accuracy of the estimator.

Low-cost, high-fidelity, adaptive cancellation of periodic 60 Hz noise.

PubMed

Wesson, Kyle D; Ochshorn, Robert M; Land, Bruce R

2009-12-15

A common method to eliminate unwanted power line interference in neurobiology laboratories where sensitive electronic signals are measured is with a notch filter. However a fixed-frequency notch filter cannot remove all power line noise contamination since inherent frequency and phase variations exist in the contaminating signal. One way to overcome the limitations of a fixed-frequency notch filter is with adaptive noise cancellation. Adaptive noise cancellation is an active approach that uses feedback to create a signal that when summed with the contaminated signal destructively interferes with the noise component leaving only the desired signal. We have implemented an optimized least mean square adaptive noise cancellation algorithm on a low-cost 16 MHz, 8-bit microcontroller to adaptively cancel periodic 60 Hz noise. In our implementation, we achieve between 20 and 25 dB of cancellation of the fundamental 60 Hz noise component.

Infrared radiometer for measuring thermophysical properties of wind tunnel models

NASA Technical Reports Server (NTRS)

Corwin, R. R.; Moorman, S. L.; Becker, E. C.

1978-01-01

An infrared radiometer is described which was developed to measure temperature rises of wind tunnel models undergoing transient heating over a temperature range of -17.8 C to 260 C. This radiometer interfaces directly with a system which measures the effective thermophysical property square root of rho ck. It has an output temperature fluctuation of 0.26 C at low temperatures and 0.07 C at high temperatures, and the output frequency response of the radiometer is from dc to 400 hertz.

Polarization Maintaining, Very-Large-Mode Area, Er Fiber Amplifier for High Energy Pulses at 1572.3 nm

NASA Technical Reports Server (NTRS)

Nicholoson, J. W.; DeSantolo, A.; Yan, M. F.; Wisk, P.; Mangan, B.; Puc, G.; Yu, A.; Stephen, M.

2016-01-01

We demonstrate the first polarization maintaining, very-large-mode-area Er-doped fiber amplifier with 1000 square micron effective area. The amplifier is core pumped by a Raman fiber laser and is used to generate single frequency one microsecond pulses with pulse energy of 368 microJoules, M2 of 1.1, and polarization extinction greater than 20 dB. The amplifier operates at 1572.3 nm, a wavelength useful for trace atmospheric CO2 detection.

A comparison of etched-geometry and overgrown silicon permeable base transistors by two-dimensional numerical simulations

NASA Astrophysics Data System (ADS)

Vojak, B. A.; Alley, G. D.

1983-08-01

Two-dimensional numerical simulations are used to compare etched geometry and overgrown Si permeable base transistors (PTBs), considering both the etched collector and etched emitter biasing conditions made possible by the asymmetry of the etched structure. In PTB devices, the two-dimensional nature of the depletion region near the Schottky contact base grating results in a smaller electron barrier and, therefore, a larger collector current in the etched than in the overgrown structure. The parasitic feedback effects which result at high base-to-emitter bias levels lead to a deviation from the square-law behavior found in the collector characteristics of the overgrown PBT. These structures also have lower device capacitances and smaller transconductances at high base-to-emitter voltages. As a result, overgrown and etched structures have comparable predicted maximum values of the small signal unity short-circuit current gain frequency and maximum oscillation frequency.

A digital optical phase-locked loop for diode lasers based on field programmable gate array.

PubMed

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382∕MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad(2) and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

A digital optical phase-locked loop for diode lasers based on field programmable gate array

NASA Astrophysics Data System (ADS)

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad2 and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

Potential damage to DC superconducting magnets due to the high frequency electromagnetic waves

NASA Technical Reports Server (NTRS)

Gabriel, G. J.

1977-01-01

Experimental data are presented in support of the hypothesis that a dc superconducting magnet coil does not behave strictly as an inductor, but as a complicated electrodynamic device capable of supporting electromagnetic waves. Travel times of nanosecond pulses and evidence of sinusoidal standing waves were observed on a prototype four-layer solenoidal coil at room temperature. Ringing observed during switching transients appears as a sequence of multiple reflected square pulses whose durations are related to the layer lengths. With sinusoidal excitation of the coil, the voltage amplitude between a pair of points on the coil exhibits maxima at those frequencies such that the distance between these points is an odd multiple of half wavelength in free space. Evidence indicates that any disturbance, such as that resulting from switching or sudden fault, initiates multiple reflections between layers, thus raising the possibility for sufficiently high voltages to cause breakdown.

Light amplification by seeded Kerr instability

NASA Astrophysics Data System (ADS)

Vampa, G.; Hammond, T. J.; Nesrallah, M.; Naumov, A. Yu.; Corkum, P. B.; Brabec, T.

2018-02-01

Amplification of femtosecond laser pulses typically requires a lasing medium or a nonlinear crystal. In either case, the chemical properties of the lasing medium or the momentum conservation in the nonlinear crystal constrain the frequency and the bandwidth of the amplified pulses. We demonstrate high gain amplification (greater than 1000) of widely tunable (0.5 to 2.2 micrometers) and short (less than 60 femtosecond) laser pulses, up to intensities of 1 terawatt per square centimeter, by seeding the modulation instability in an Y3Al5O12 crystal pumped by femtosecond near-infrared pulses. Our method avoids constraints related to doping and phase matching and therefore can occur in a wider pool of glasses and crystals even at far-infrared frequencies and for single-cycle pulses. Such amplified pulses are ideal to study strong-field processes in solids and highly excited states in gases.

Quantum Critical Point revisited by the Dynamical Mean Field Theory

NASA Astrophysics Data System (ADS)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.

Investigating the mechanism of aggregation of colloidal particles during electrophoretic deposition

NASA Astrophysics Data System (ADS)

Guelcher, Scott Arthur

Charged particles deposited near an electrode aggregate to form ordered clusters in the presence of both dc and ac applied electric fields. The aggregation process could have important applications in areas such as coatings technology and ceramics processing. This thesis has sought to identify the phenomena driving the aggregation process. According to the electroosmotic flow developed by Solomentsev et al. (1997), aggregation in dc electric fields is caused by convection in the electroosmotic flow about deposited particles, and it is therefore an electrokinetic phenomenon which scales linearly with the electric field and the zeta-potential of the particles. Trajectories of pairs of particles aggregating to form doublets have been shown to scale linearly with the electric field and the zeta-potential of the particles, as predicted by the electroosmotic flow model. Furthermore, quantitative agreement has been demonstrated between the experimental and calculated trajectories for surface-to-surface separation distances between the particles ranging from one to two radii. The trajectories were calculated from the electroosmotic flow model with no fitting parameters; the only inputs to the model were the mobility of the deposited particles, the zeta- potential of the particles, and the applied electric field, all of which were measured independently. Clustering of colloidal particles deposited near an electrode in ac fields has also been observed, but a suitable model for the aggregation process has not been proposed and quantitative data in the literature are scarce. Trajectories of pairs of particles aggregating to form doublets in an ac field have been shown to scale with the root-mean-square (rms) electric field raised to the power 1.4 over the range of electric fields 10-35 V/cm (100-Hz sine and square waves). The aggregation is also frequency dependent; the doublets aggregate fastest at 30 Hz (square wave) and slowest at 500 Hz (square wave), while the interaction is repulsive at 1 kHz (square wave). The advantage of ac fields is that the process can operated at frequencies sufficiently high to avoid the negative effects of electrochemical reactions.

Adaptive Modal Identification for Flutter Suppression Control

NASA Technical Reports Server (NTRS)

Nguyen, Nhan T.; Drew, Michael; Swei, Sean S.

2016-01-01

In this paper, we will develop an adaptive modal identification method for identifying the frequencies and damping of a flutter mode based on model-reference adaptive control (MRAC) and least-squares methods. The least-squares parameter estimation will achieve parameter convergence in the presence of persistent excitation whereas the MRAC parameter estimation does not guarantee parameter convergence. Two adaptive flutter suppression control approaches are developed: one based on MRAC and the other based on the least-squares method. The MRAC flutter suppression control is designed as an integral part of the parameter estimation where the feedback signal is used to estimate the modal information. On the other hand, the separation principle of control and estimation is applied to the least-squares method. The least-squares modal identification is used to perform parameter estimation.

Consensus structures of the Mo(v) sites of sulfite-oxidizing enzymes derived from variable frequency pulsed EPR spectroscopy, isotopic labelling and DFT calculations.

PubMed

Enemark, John H

2017-10-10

Sulfite-oxidizing enzymes from eukaryotes and prokaryotes have five-coordinate distorted square-pyramidal coordination about the molybdenum atom. The paramagnetic Mo(v) state is easily generated, and over the years four distinct CW EPR spectra have been identified, depending upon enzyme source and the reaction conditions, namely high and low pH (hpH and lpH), phosphate inhibited (P i ) and sulfite (or blocked). Extensive studies of these paramagnetic forms of sulfite-oxidizing enzymes using variable frequency pulsed electron spin echo (ESE) spectroscopy, isotopic labeling and density functional theory (DFT) calculations have led to the consensus structures that are described here. Errors in some of the previously proposed structures are corrected.

Magnetic and microwave properties of U-type hexaferrite films with high remanence and low ferromagnetic resonance linewidth

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

Su, Zhijuan; Bennett, Steven; Hu, Bolin

2014-05-07

U-type barium hexaferrite films (Ba{sub 4}Ni{sub 1.4}Co{sub 0.6}Fe{sub 36}O{sub 60}) were deposited on (0001) sapphire substrates by pulsed laser deposition. Microstructure and magnetic properties of the films were characterized by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. Ferromagnetic resonance (FMR) measurements were performed at X-band. The results indicate an anisotropy field of ∼8 kOe, and the saturation magnetization (4πM{sub s}) of ∼3.6 kG. An optimal post-deposition annealing of films results in a strong (0 0 n) crystallographic texture and a high hysteresis loop squareness (M{sub r}/M{sub s} = 92%) leading to self biased properties. Furthermore, the highly self-biased ferrite films exhibitedmore » an FMR linewidth of ∼200 Oe. The U-type hexaferrite films having low microwave loss, low magnetic anisotropy field, and high squareness are a suitable alternative to Sc or In doped BaM ferrites that have been the choice material for self-biased microwave devices at X-band frequencies.« less

Relativistic Tennis with Photons: Frequency Up-Shifting, Light Intensification and Ion Acceleration with Flying Mirrors

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

Bulanov, S. V.; Esirkepov, T. Zh.; Kando, M.

2011-01-04

We formulate the Flying Mirror Concept for relativistic interaction of ultra-intense electromagnetic waves with plasmas, present its theoretical description and the results of computer simulations and laboratory experiments. In collisionless plasmas, the relativistic flying mirrors are thin and dense electron or electron-ion layers accelerated by the high intensity electromagnetic waves up to velocity close to the speed of light in vacuum; in nonlinear-media and in nonlinear vacuum they are the ionization fronts and the refraction index modulations induced by a strong electromagnetic wave. The reflection of the electromagnetic wave at the relativistic mirror results in its energy and frequency changemore » due to the double Doppler effect. In the co-propagating configuration, in the radiation pressure dominant regime, the energy of the electromagnetic wave is transferred to the ion energy providing a highly efficient acceleration mechanism. In the counter-propagation configuration the frequency of the reflected wave is multiplied by the factor proportional to the gamma-factor squared. If the relativistic mirror performs an oscillatory motion as in the case of the electron motion at the plasma-vacuum interface, the reflected light spectrum is enriched with high order harmonics.« less

Classification of a Driver's cognitive workload levels using artificial neural network on ECG signals.

PubMed

Tjolleng, Amir; Jung, Kihyo; Hong, Wongi; Lee, Wonsup; Lee, Baekhee; You, Heecheon; Son, Joonwoo; Park, Seikwon

2017-03-01

An artificial neural network (ANN) model was developed in the present study to classify the level of a driver's cognitive workload based on electrocardiography (ECG). ECG signals were measured on 15 male participants while they performed a simulated driving task as a primary task with/without an N-back task as a secondary task. Three time-domain ECG measures (mean inter-beat interval (IBI), standard deviation of IBIs, and root mean squared difference of adjacent IBIs) and three frequencydomain ECG measures (power in low frequency, power in high frequency, and ratio of power in low and high frequencies) were calculated. To compensate for individual differences in heart response during the driving tasks, a three-step data processing procedure was performed to ECG signals of each participant: (1) selection of two most sensitive ECG measures, (2) definition of three (low, medium, and high) cognitive workload levels, and (3) normalization of the selected ECG measures. An ANN model was constructed using a feed-forward network and scaled conjugate gradient as a back-propagation learning rule. The accuracy of the ANN classification model was found satisfactory for learning data (95%) and testing data (82%). Copyright © 2016 Elsevier Ltd. All rights reserved.

High-frequency Rayleigh-wave method

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

2009-01-01

High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

Statistical analysis of multivariate atmospheric variables. [cloud cover

NASA Technical Reports Server (NTRS)

Tubbs, J. D.

1979-01-01

Topics covered include: (1) estimation in discrete multivariate distributions; (2) a procedure to predict cloud cover frequencies in the bivariate case; (3) a program to compute conditional bivariate normal parameters; (4) the transformation of nonnormal multivariate to near-normal; (5) test of fit for the extreme value distribution based upon the generalized minimum chi-square; (6) test of fit for continuous distributions based upon the generalized minimum chi-square; (7) effect of correlated observations on confidence sets based upon chi-square statistics; and (8) generation of random variates from specified distributions.

Microwave Photonic Architecture for Direction Finding of LPI Emitters: Post-Processing for Angle of Arrival Estimation

DTIC Science & Technology

2016-09-01

mean- square (RMS) error of 0.29° at ə° resolution. For a P4 coded signal, the RMS error in estimating the AOA is 0.32° at 1° resolution. 14...FMCW signal, it was demonstrated that the system is capable of estimating the AOA with a root-mean- square (RMS) error of 0.29° at ə° resolution. For a...Modulator PCB printed circuit board PD photodetector RF radio frequency RMS root-mean- square xvi THIS PAGE INTENTIONALLY LEFT BLANK xvii

A new method for finding and characterizing galaxy groups via low-frequency radio surveys

NASA Astrophysics Data System (ADS)

Croston, J. H.; Ineson, J.; Hardcastle, M. J.; Mingo, B.

2017-09-01

We describe a new method for identifying and characterizing the thermodynamic state of large samples of evolved galaxy groups at high redshifts using high-resolution, low-frequency radio surveys, such as those that will be carried out with LOFAR and the Square Kilometre Array. We identify a sub-population of morphologically regular powerful [Fanaroff-Riley type II (FR II)] radio galaxies and demonstrate that, for this sub-population, the internal pressure of the radio lobes is a reliable tracer of the external intragroup/intracluster medium (ICM) pressure, and that the assumption of a universal pressure profile for relaxed groups enables the total mass and X-ray luminosity to be estimated. Using a sample of well-studied FR II radio galaxies, we demonstrate that our method enables the estimation of group/cluster X-ray luminosities over three orders of magnitude in luminosity to within a factor of ˜2 from low-frequency radio properties alone. Our method could provide a powerful new tool for building samples of thousands of evolved galaxy groups at z > 1 and characterizing their ICM.

Effect of laser frequency noise on fiber-optic frequency reference distribution

NASA Technical Reports Server (NTRS)

Logan, R. T., Jr.; Lutes, G. F.; Maleki, L.

1989-01-01

The effect of the linewidth of a single longitude-mode laser on the frequency stability of a frequency reference transmitted over a single-mode optical fiber is analyzed. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation (square root of the Allan variance) of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit of the ultimate stability possible for frequency reference transmission on optical fiber, but is not a serious limitation to present system performance.

High-order boundary integral equation solution of high frequency wave scattering from obstacles in an unbounded linearly stratified medium

NASA Astrophysics Data System (ADS)

Barnett, Alex H.; Nelson, Bradley J.; Mahoney, J. Matthew

2015-09-01

We apply boundary integral equations for the first time to the two-dimensional scattering of time-harmonic waves from a smooth obstacle embedded in a continuously-graded unbounded medium. In the case we solve, the square of the wavenumber (refractive index) varies linearly in one coordinate, i.e. (Δ + E +x2) u (x1 ,x2) = 0 where E is a constant; this models quantum particles of fixed energy in a uniform gravitational field, and has broader applications to stratified media in acoustics, optics and seismology. We evaluate the fundamental solution efficiently with exponential accuracy via numerical saddle-point integration, using the truncated trapezoid rule with typically 102 nodes, with an effort that is independent of the frequency parameter E. By combining with a high-order Nyström quadrature, we are able to solve the scattering from obstacles 50 wavelengths across to 11 digits of accuracy in under a minute on a desktop or laptop.

Ultra-wideband high-efficiency reflective linear-to-circular polarization converter based on metasurface at terahertz frequencies.

PubMed

Jiang, Yannan; Wang, Lei; Wang, Jiao; Akwuruoha, Charles Nwakanma; Cao, Weiping

2017-10-30

The polarization conversion of electromagnetic (EM) waves, especially linear-to-circular (LTC) polarization conversion, is of great significance in practical applications. In this study, we propose an ultra-wideband high-efficiency reflective LTC polarization converter based on a metasurface in the terahertz regime. It consists of periodic unit cells, each cell of which is formed by a double split resonant square ring, dielectric layer, and fully reflective gold mirror. In the frequency range of 0.60 - 1.41 THz, the magnitudes of the reflection coefficients reach approximately 0.7, and the phase difference between the two orthogonal electric field components of the reflected wave is close to 90° or -270°. The results indicate that the relative bandwidth reaches 80% and the efficiency is greater than 88%, thus, ultra-wideband high-efficiency LTC polarization conversion has been realized. Finally, the physical mechanism of the polarization conversion is revealed. This converter has potential applications in antenna design, EM measurement, and stealth technology.

Thermal Considerations of Space Solar Power Concepts with 3.5 GW RF Output

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2000-01-01

This paper presents the thermal challenge of the Space Solar Power (SSP) design concepts with a 3.5 GW radio-frequency (RF) output. High efficiency klystrons are thermally more favored than solid state (butterstick) to convert direct current (DC) electricity to radio-frequency (RF) energy at the transmitters in these concepts. Using klystrons, the heat dissipation is 0.72 GW. Using solid state, the heat dissipation is 2.33 GW. The heat dissipation of the klystrons is 85% at 500C, 10% at 300C, and 5% at 125C. All the heat dissipation of the solid state is at 100C. Using klystrons, the radiator area is 74,500 square m Using solid state, the radiator area is 2,362,200 square m Space constructable heat pipe radiators are assumed in the thermal analysis. Also, to make the SSP concepts feasible, the mass of the heat transport system must be minimized. The heat transport distance from the transmitters to the radiators must be minimized. It can be accomplished by dividing the radiator into a cluster of small radiators, so that the heat transport distances between the klystrons and radiators can be minimized. The area of each small radiator is on the order of 1 square m. Two concepts for accommodating a cluster of small radiators are presented. If the distance between the transmitters and radiators is 1.5 m or less, constant conductance heat pipes (CCHPs) are acceptable for heat transport. If the distance exceeds 1.5 m, loop heat pipes (LHPs) are needed.

The Square Kilometre Array Epoch of Reionisation and Cosmic Dawn Experiment

NASA Astrophysics Data System (ADS)

Trott, Cathryn M.

2018-05-01

The Square Kilometre Array (SKA) Epoch of Reionisation and Cosmic Dawn (EoR/CD) experiments aim to explore the growth of structure and production of ionising radiation in the first billion years of the Universe. Here I describe the experiments planned for the future low-frequency components of the Observatory, and work underway to define, design and execute these programs.

14 CFR Appendix G to Part 25 - Continuous Gust Design Criteria

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Values of Ā (ratio of root-mean-square incremental load root-mean-square gust velocity) must be... gust velocity, ft./sec. Ω=reduced frequency, radians per foot. L=2,500 ft. (3) The limit loads must be... velocity Uσ: (i) At speed Vc: Uσ=85 fps true gust velocity in the interval 0 to 30,000 ft. altitude and is...

14 CFR Appendix G to Part 25 - Continuous Gust Design Criteria

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Values of Ā (ratio of root-mean-square incremental load root-mean-square gust velocity) must be... gust velocity, ft./sec. Ω=reduced frequency, radians per foot. L=2,500 ft. (3) The limit loads must be... velocity Uσ: (i) At speed Vc: Uσ=85 fps true gust velocity in the interval 0 to 30,000 ft. altitude and is...

14 CFR Appendix G to Part 25 - Continuous Gust Design Criteria

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Values of Ā (ratio of root-mean-square incremental load root-mean-square gust velocity) must be... gust velocity, ft./sec. Ω=reduced frequency, radians per foot. L=2,500 ft. (3) The limit loads must be... velocity Uσ: (i) At speed Vc: Uσ=85 fps true gust velocity in the interval 0 to 30,000 ft. altitude and is...

The Design of a Four Square Gear Tester for Noise and Vibration Measurements.

DTIC Science & Technology

1986-12-01

Four Square Gear Tester ...... . 25 2.3 The Speed-Torque Relationship of Contraves Blower Ventilated Motor ....... ..................... ... 31 2.4...The Speed-Torque Relationship of Contraves Self- Ventilated Motor ....... ..................... ... 32 2.5 The Contraves Motor...34 2.6 The Contraves Motor Mounted Blower ... ............ ... 35 2.7 The Fixed-Fixed End Condition (to determine the natural frequency of the

The origin of high frequency radiation in earthquakes and the geometry of faulting

NASA Astrophysics Data System (ADS)

Madariaga, R.

2004-12-01

In a seminal paper of 1967 Kei Aki discovered the scaling law of earthquake spectra and showed that, among other things, the high frequency decay was of type omega-squared. This implies that high frequency displacement amplitudes are proportional to a characteristic length of the fault, and radiated energy scales with the cube of the fault dimension, just like seismic moment. Later in the seventies, it was found out that a simple explanation for this frequency dependence of spectra was that high frequencies were generated by stopping phases, waves emitted by changes in speed of the rupture front as it propagates along the fault, but this did not explain the scaling of high frequency waves with fault length. Earthquake energy balance is such that, ignoring attenuation, radiated energy is the change in strain energy minus energy released for overcoming friction. Until recently the latter was considered to be a material property that did not scale with fault size. Yet, in another classical paper Aki and Das estimated in the late 70s that energy release rate also scaled with earthquake size, because earthquakes were often stopped by barriers or changed rupture speed at them. This observation was independently confirmed in the late 90s by Ide and Takeo and Olsen et al who found that energy release rates for Kobe and Landers were in the order of a MJ/m2, implying that Gc necessarily scales with earthquake size, because if this was a material property, small earthquakes would never occur. Using both simple analytical and numerical models developed by Addia-Bedia and Aochi and Madariaga, we examine the consequence of these observations for the scaling of high frequency waves with fault size. We demonstrate using some classical results by Kostrov, Husseiny and Freund that high frequency energy flow measures energy release rate and is generated when ruptures change velocity (both direction and speed) at fault kinks or jogs. Our results explain why super shear ruptures are only observed when faults are relatively flat and smooth, and why complex geometry inhibits fast ruptures.

Equivalent circuit parameters of nickel/metal hydride batteries from sparse impedance measurements

NASA Astrophysics Data System (ADS)

Nelatury, Sudarshan Rao; Singh, Pritpal

In a recent communication, a method for extracting the equivalent circuit parameters of a lead acid battery from sparse (only three) impedance spectroscopy observations at three different frequencies was proposed. It was based on an equivalent circuit consisting of a bulk resistance, a reaction resistance and a constant phase element (CPE). Such a circuit is a very appropriate model of a lead-acid cell at high state of charge (SOC). This paper is a sequel to it and presents an application of it in case of nickel/metal hydride (Ni/MH) batteries, which also at high SOC are represented by the same circuit configuration. But when the SOC of a Ni/MH battery under interrogation goes low, The EIS curve has a positive slope at the low frequency end and our technique yields complex values for the otherwise real circuit parameters, suggesting the need for additional elements in the equivalent circuit and a definite relationship between parameter consistency and SOC. To improvise the previous algorithm, in order that it works reasonably well at both high and low SOCs, we propose three more measurements—two at very low frequencies to include the Warburg response and one at a high frequency to model the series inductance, in addition to the three in the mid frequency band—totally six measurements. In most of the today's instrumentation, it is the user who should choose the circuit configuration and the number of frequencies where impedance should be measured and the accompanying software performs data fitting by complex nonlinear least squares. The proposed method has built into it an SOC-based decision-making capability—both to choose the circuit configuration and to estimate the values of the circuit elements.

The safety assessment of saffron (Crocus sativus L.) on sympathovagal balance and heart rate variability; a comparison with amiodarone.

PubMed

Joukar, Siyavash; Dehesh, Mohammad-Moein

2015-12-01

Dry stigmas of the Crocus sativus L. (Saffron) are well known in world as a popular flavouring and therapeutic agent. The anxiolytic, antidepressant, anticonvulsant and antiarrhythmic effects of saffron suggest that it may affect the autonomic control of the heart. This study assessed its safety on cardiac sympathovagal balance and heart rate variability in rat. Experimental groups were control, Saf50, Saf100, Saf200 (received saffron at dosages of 50 and 100 and 200 mg/kg/d, orally, respectively) and Amio (received 30 mg/mL/kg/d of amiodarone, orally, for 7 days) groups. On day 8, the frequency domain and time domain indices of animals' electrocardiograms were calculated. The heart rate decreased and RR interval increased in Saf200 and Amio groups (P<.05 vs other groups). Square root of the mean squared differences of successive RR intervals enhanced in all treated groups, however, was only significant in Amio group (P<.05). The SD1/SD2 ratio was higher in Saf200 and Amio groups. Both low-frequency (LF) and high-frequency (HF) parameters were higher, and the LF/HF ratio was non-significantly lower in treated groups. The findings suggest that saffron not only has no harmful effect on activity of cardiac autonomic nervous system, but it may improve the stability of heart sympathovagal balance in normal rat. © 2016 John Wiley & Sons Ltd.

Genetic influences on heart rate variability

PubMed Central

Golosheykin, Simon; Grant, Julia D.; Novak, Olga V.; Heath, Andrew C.; Anokhin, Andrey P.

2016-01-01

Heart rate variability (HRV) is the variation of cardiac inter-beat intervals over time resulting largely from the interplay between the sympathetic and parasympathetic branches of the autonomic nervous system. Individual differences in HRV are associated with emotion regulation, personality, psychopathology, cardiovascular health, and mortality. Previous studies have shown significant heritability of HRV measures. Here we extend genetic research on HRV by investigating sex differences in genetic underpinnings of HRV, the degree of genetic overlap among different measurement domains of HRV, and phenotypic and genetic relationships between HRV and the resting heart rate (HR). We performed electrocardiogram (ECG) recordings in a large population-representative sample of young adult twins (n = 1060 individuals) and computed HRV measures from three domains: time, frequency, and nonlinear dynamics. Genetic and environmental influences on HRV measures were estimated using linear structural equation modeling of twin data. The results showed that variability of HRV and HR measures can be accounted for by additive genetic and non-shared environmental influences (AE model), with no evidence for significant shared environmental effects. Heritability estimates ranged from 47 to 64%, with little difference across HRV measurement domains. Genetic influences did not differ between genders for most variables except the square root of the mean squared differences between successive R-R intervals (RMSSD, higher heritability in males) and the ratio of low to high frequency power (LF/HF, distinct genetic factors operating in males and females). The results indicate high phenotypic and especially genetic correlations between HRV measures from different domains, suggesting that >90% of genetic influences are shared across measures. Finally, about 40% of genetic variance in HRV was shared with HR. In conclusion, both HR and HRV measures are highly heritable traits in the general population of young adults, with high degree of genetic overlap across different measurement domains. PMID:27114045

Influence of skin peeling procedure in allergic contact dermatitis.

PubMed

Kim, Jung Eun; Park, Hyun Jeong; Cho, Baik Kee; Lee, Jun Young

2008-03-01

The prevalence of allergic contact dermatitis in patients who have previously undergone skin peeling has been rarely studied. We compared the frequency of positive patch test (PT) reactions in a patient group with a history of peeling, to that of a control group with no history of peeling. The Korean standard series and cosmetic series were performed on a total of 262 patients. 62 patients had previously undergone peeling and 200 patients did not. The frequency of positive PT reactions on Korean standard series was significantly higher in the peeling group compared with that of the control group (P < 0.05, chi-square test). However, the most commonly identified allergens were mostly cosmetic-unrelated allergens. The frequency of positive PT reactions on cosmetic series in the peeling group was higher than that of the control group, but lacked statistical significance. The frequency (%) of positive PT reactions on cosmetic series in the high-frequency peel group was higher than that of the low-frequency group, but lacked statistical significance. It appears peeling may not generally affect the development of contact sensitization. Further work is required focusing on the large-scale prospective studies by performing a PT before and after peeling.

4th Generation ECR Ion Sources

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

Lyneis, Claude M.; Leitner, D.; Todd, D.S.

2008-12-01

The concepts and technical challenges related to developing a 4th generation ECR ion source with an RF frequency greater than 40 GHz and magnetic confinement fields greater than twice Becr will be explored in this paper. Based on the semi-empirical frequency scaling of ECR plasma density with the square of operating frequency, there should be significant gains in performance over current 3rd generation ECR ion sources, which operate at RF frequencies between 20 and 30 GHz. While the 3rd generation ECR ion sources use NbTi superconducting solenoid and sextupole coils, the new sources will need to use different superconducting materialsmore » such as Nb3Sn to reach the required magnetic confinement, which scales linearly with RF frequency. Additional technical challenges include increased bremsstrahlung production, which may increase faster than the plasma density, bremsstrahlung heating of the cold mass and the availability of high power continuous wave microwave sources at these frequencies. With each generation of ECR ion sources, there are new challenges to be mastered, but the potential for higher performance and reduced cost of the associated accelerator continue to make this a promising avenue for development.« less

Method and apparatus for frequency spectrum analysis

NASA Technical Reports Server (NTRS)

Cole, Steven W. (Inventor)

1992-01-01

A method for frequency spectrum analysis of an unknown signal in real-time is discussed. The method is based upon integration of 1-bit samples of signal voltage amplitude corresponding to sine or cosine phases of a controlled center frequency clock which is changed after each integration interval to sweep the frequency range of interest in steps. Integration of samples during each interval is carried out over a number of cycles of the center frequency clock spanning a number of cycles of an input signal to be analyzed. The invention may be used to detect the frequency of at least two signals simultaneously. By using a reference signal of known frequency and voltage amplitude (added to the two signals for parallel processing in the same way, but in a different channel with a sampling at the known frequency and phases of the reference signal), the absolute voltage amplitude of the other two signals may be determined by squaring the sine and cosine integrals of each channel and summing the squares to obtain relative power measurements in all three channels and, from the known voltage amplitude of the reference signal, obtaining an absolute voltage measurement for the other two signals by multiplying the known voltage of the reference signal with the ratio of the relative power of each of the other two signals to the relative power of the reference signal.

Implanted Silicon Resistor Layers for Efficient Terahertz Absorption

NASA Technical Reports Server (NTRS)

Chervenak, J. A.; Abrahams, J.; Allen, C. A.; Benford, D. J.; Henry, R.; Stevenson, T.; Wollack, E.; Moseley, S. H.

2005-01-01

Broadband absorption structures are an essential component of large format bolometer arrays for imaging GHz and THz radiation. We have measured electrical and optical properties of implanted silicon resistor layers designed to be suitable for these absorbers. Implanted resistors offer a low-film-stress, buried absorber that is robust to longterm aging, temperature, and subsequent metals processing. Such an absorber layer is readily integrated with superconducting integrated circuits and standard micromachining as demonstrated by the SCUBA II array built by ROE/NIST (1). We present a complete characterization of these layers, demonstrating frequency regimes in which different recipes will be suitable for absorbers. Single layer thin film coatings have been demonstrated as effective absorbers at certain wavelengths including semimetal (2,3), thin metal (4), and patterned metal films (5,6). Astronomical instrument examples include the SHARC II instrument is imaging the submillimeter band using passivated Bi semimetal films and the HAWC instrument for SOFIA, which employs ultrathin metal films to span 1-3 THz. Patterned metal films on spiderweb bolometers have also been proposed for broadband detection. In each case, the absorber structure matches the impedance of free space for optimal absorption in the detector configuration (typically 157 Ohms per square for high absorption with a single or 377 Ohms per square in a resonant cavity or quarter wave backshort). Resonant structures with -20% bandwidth coupled to bolometers are also under development; stacks of such structures may take advantage of instruments imaging over a wide band. Each technique may enable effective absorbers in imagers. However, thin films tend to age, degrade or change during further processing, can be difficult to reproduce, and often exhibit an intrinsic granularity that creates complicated frequency dependence at THz frequencies. Thick metal films are more robust but the requirement for patterning can limit their absorption at THz frequencies and their heat capacity can be high. patterned absorber structures that offer low heat capacity, absence of aging, and uniform, predictable behavior at THz frequencies. We have correlated DC electrical and THz optical measurements of a series of implanted layers and studied their frequency dependence of optical absorption from .3 to 10 THz at cryogenic temperatures. We have modeled the optical response to determine the suitability of the implanted silicon resistor as a function of resistance in the range 10 Ohms/sq to 300 Ohms/sq.

Terahertz Bandpass Frequency Selective Surfaces on Glass Substrates Using a Wet Micromachining Process

NASA Astrophysics Data System (ADS)

Ramzan, Mehrab; Khan, Talha Masood; Bolat, Sami; Nebioglu, Mehmet Ali; Altan, Hakan; Okyay, Ali Kemal; Topalli, Kagan

2017-08-01

This paper presents terahertz (THz) frequency selective surfaces (FSS) implemented on glass substrate using standard microfabrication techniques. These FSS structures are designed for frequencies around 0.8 THz. A fabrication process is proposed where a 100-μm-thick glass substrate is formed through the HF etching of a standard 500-μm-thick low cost glass wafer. Using this fabrication process, three separate robust designs consisting of single-layer FSS are investigated using high-frequency structural simulator (HFSS). Based on the simulation results, the first design consists of a circular ring slot in a square metallic structure on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of approximately 0.07 THz, which remains nearly constant till 30° angle of incidence. The second design consists of a tripole structure on top of a 100-μm-thick Pyrex glass substrate with 65% transmission bandwidth of 0.035 THz, which remains nearly constant till 30° angle of incidence. The third structure consists of a triangular ring slot in a square metal on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of 0.051 THz, which remains nearly constant up to 20° angle of incidence. These designs show that the reflections from samples can be reduced compared to the conventional sample holders used in THz spectroscopy applications, by using single layer FSS structures manufactured through a relatively simple fabrication process. Practically, these structures are achieved on a fabricated 285-μm-thick glass substrate. Taking into account the losses and discrepancies in the substrate thickness, the measured results are in good agreement with the electromagnetic simulations.

Spectro-temporal characteristics of speech at high frequencies, and the potential for restoration of audibility to people with mild-to-moderate hearing loss.

PubMed

Moore, Brian C J; Stone, Michael A; Füllgrabe, Christian; Glasberg, Brian R; Puria, Sunil

2008-12-01

It is possible for auditory prostheses to provide amplification for frequencies above 6 kHz. However, most current hearing-aid fitting procedures do not give recommended gains for such high frequencies. This study was intended to provide information that could be useful in quantifying appropriate high-frequency gains, and in establishing the population of hearing-impaired people who might benefit from such amplification. The study had two parts. In the first part, wide-bandwidth recordings of normal conversational speech were obtained from a sample of male and female talkers. The recordings were used to determine the mean spectral shape over a wide frequency range, and to determine the distribution of levels (the speech dynamic range) as a function of center frequency. In the second part, audiometric thresholds were measured for frequencies of 0.125, 0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, and 12.5 kHz for both ears of 31 people selected to have mild or moderate cochlear hearing loss. The hearing loss was never greater than 70 dB for any frequency up to 4 kHz. The mean spectrum level of the speech fell progressively with increasing center frequency above about 0.5 kHz. For speech with an overall level of 65 dB SPL, the mean 1/3-octave level was 49 and 37 dB SPL for center frequencies of 1 and 10 kHz, respectively. The dynamic range of the speech was similar for center frequencies of 1 and 10 kHz. The part of the dynamic range below the root-mean-square level was larger than reported in previous studies. The mean audiometric thresholds at high frequencies (10 and 12.5 kHz) were relatively high (69 and 77 dB HL, respectively), even though the mean thresholds for frequencies below 4 kHz were 41 dB HL or better. To partially restore audibility for a hearing loss of 65 dB at 10 kHz would require an effective insertion gain of about 36 dB at 10 kHz. With this gain, audibility could be (partly) restored for 25 of the 62 ears assessed.

Impact of Primary Spherical Aberration, Spatial Frequency and Stiles Crawford Apodization on Wavefront determined Refractive Error: A Computational Study

PubMed Central

Xu, Renfeng; Bradley, Arthur; Thibos, Larry N.

2013-01-01

Purpose We tested the hypothesis that pupil apodization is the basis for central pupil bias of spherical refractions in eyes with spherical aberration. Methods We employed Fourier computational optics in which we vary spherical aberration levels, pupil size, and pupil apodization (Stiles Crawford Effect) within the pupil function, from which point spread functions and optical transfer functions were computed. Through-focus analysis determined the refractive correction that optimized retinal image quality. Results For a large pupil (7 mm), as spherical aberration levels increase, refractions that optimize the visual Strehl ratio mirror refractions that maximize high spatial frequency modulation in the image and both focus a near paraxial region of the pupil. These refractions are not affected by Stiles Crawford Effect apodization. Refractions that optimize low spatial frequency modulation come close to minimizing wavefront RMS, and vary with level of spherical aberration and Stiles Crawford Effect. In the presence of significant levels of spherical aberration (e.g. C40 = 0.4 µm, 7mm pupil), low spatial frequency refractions can induce −0.7D myopic shift compared to high SF refraction, and refractions that maximize image contrast of a 3 cycle per degree square-wave grating can cause −0.75D myopic drift relative to refractions that maximize image sharpness. Discussion Because of small depth of focus associated with high spatial frequency stimuli, the large change in dioptric power across the pupil caused by spherical aberration limits the effective aperture contributing to the image of high spatial frequencies. Thus, when imaging high spatial frequencies, spherical aberration effectively induces an annular aperture defining that portion of the pupil contributing to a well-focused image. As spherical focus is manipulated during the refraction procedure, the dimensions of the annular aperture change. Image quality is maximized when the inner radius of the induced annulus falls to zero, thus defining a circular near paraxial region of the pupil that determines refraction outcome. PMID:23683093

A Kalman Filter Clock Algorithm for Use in the Presence of Flicker Frequency Modulation Noise

DTIC Science & Technology

2004-09-01

40, S335-S341. [5] P. M. Harris, J. A. Davis, M. G. Cox, and S. L. Shemar, 2003, “ Least - squares analysis of time series data and its application to two - way satellite time and frequency transfer measurements ,” Metrologia

Pursuit gain and saccadic intrusions in first-degree relatives of probands with schizophrenia.

PubMed

Clementz, B A; Sweeney, J A; Hirt, M; Haas, G

1990-11-01

Oculomotor functioning of 26 probands with schizophrenia, 12 spectrum and 46 nonspectrum first-degree relatives, and 38 nonpsychiatric control subjects was evaluated. Spectrum relatives had more anticipatory saccades (ASs) and lower pursuit gain than nonspectrum relatives, who had more ASs and lower pursuit gain than control subjects. Probands also had lower pursuit gain than nonspectrum relatives and control subjects but did not differ from other groups on AS frequency. Control subjects had more globally accurate pursuit tracking (root mean square [RMS] error deviation) than both relative groups, whereas probands had the poorest RMS scores. Square wave jerk frequency did not differentiate the groups. Attention enhancement affected the frequency of ASs but did not affect either the other intrusive saccadic event or RMS scores. These results offer evidence that eye-movement dysfunction may serve as a biological marker for schizophrenia.

Optical frequency comb generation based on the dual-mode square microlaser and a nonlinear fiber loop

NASA Astrophysics Data System (ADS)

Weng, Hai-Zhong; Han, Jun-Yuan; Li, Qing; Yang, Yue-De; Xiao, Jin-Long; Qin, Guan-Shi; Huang, Yong-Zhen

2018-05-01

A novel approach using a dual-mode square microlaser as the pump source is demonstrated to produce wideband optical frequency comb (OFC). The enhanced nonlinear frequency conversion processes are accomplished in a nonlinear fiber loop, which can reduce the stimulated Brillouin scattering threshold and then generate a dual-mode Brillouin laser with improved optical signal-to-noise ratio. An OFC with 130 nm bandwidth and 76 GHz repetition rate is successfully generated under the four-wave mixing, and the number of the comb lines is enhanced by 26 times compared with the system without fiber loop. In addition, the repetition rate of the comb can be adjusted by changing the injection current of the microlaser. The pulse width of the comb spectrum is also compressed from 3 to 1 ps with an extra amplification-nonlinear process.

Proposed square spiral microfabrication architecture for large three-dimensional photonic band gap crystals.

PubMed

Toader, O; John, S

2001-05-11

We present a blueprint for a three-dimensional photonic band gap (PBG) material that is amenable to large-scale microfabrication on the optical scale using glancing angle deposition methods. The proposed chiral crystal consists of square spiral posts on a tetragonal lattice. In the case of silicon posts in air (direct structure), the full PBG can be as large as 15% of the gap center frequency, whereas for air posts in a silicon background (inverted structure) the maximum PBG is 24% of the center frequency. This PBG occurs between the fourth and fifth bands of the photon dispersion relation and is very robust to variations (disorder) in the geometrical parameters of the crystal.

Control of the permeability loss-peak frequency of Ni81Fe19 thin films through laser ablation of triangular and square cluster geometries

NASA Technical Reports Server (NTRS)

Grimes, C. A.; Lumpp, J. K.

2000-01-01

Laser ablation arrays of triangular and square shaped clusters, comprised of 23 micrometers diam circular holes, are defined upon 100 nm thick Ni81Fe19 films used to control the rf permeability spectra. Cluster-to-cluster spacing is varied from 200 to 600 micrometers. For each geometry it is found that the loss peak frequency and permeability magnitude shift lower, in a step-wise fashion, at a cluster-to-cluster spacing between 275 and 300 micrometers. The nonlinear shift in the behavior of the permeability spectra correlates with a dramatic increase in domain wall density. c2000 American Institute of Physics.

Monolithic Superconducting Emitter of Tunable Circularly Polarized Terahertz Radiation

NASA Astrophysics Data System (ADS)

Elarabi, A.; Yoshioka, Y.; Tsujimoto, M.; Kakeya, I.

2017-12-01

We propose an approach to controlling the polarization of terahertz (THz) radiation from intrinsic Josephson-junction stacks in a single crystalline high-temperature superconductor Bi2Sr2CaCu2O8 . Monolithic control of the surface high-frequency current distributions in the truncated square mesa structure allows us to modulate the polarization of the emitted terahertz wave as a result of two orthogonal fundamental modes excited inside the mesa. Highly polarized circular terahertz waves with a degree of circular polarization of more than 99% can be generated using an electrically controlled method. The intuitive results obtained from the numerical simulation based on the conventional antenna theory are consistent with the observed emission characteristics.

Preliminary evaluation of flood frequency relations in the urban areas of Memphis, Tennessee

USGS Publications Warehouse

Boning, Charles W.

1977-01-01

A storm-runoff relation for streams in the urban areas of Memphis was determined by a statistical evaluation of 59 flood discharges from 19 gaging stations. These flood discharges were related to drainage area, percent imperviousness of the drainage basin, and rainfall occuring over 120-minute periods. The defined relation is Q=m3A*777A - .02 tI,,,,P + 1j-227 (1120).539(t120).40 where Q is flood discharge in cfs, A is drainage area in square miles, IMP is percent imperviousness in the basin, and I120 is rainfall in inches, over 120 minute time period. The defined relation was used to synthesize sets of annual flood peaks for drainage basins ranging from .05 square miles to 10 square miles and imperviousness ranging from 0 to 80 percent for the period of rainfall record at Memphis. From these series of flood peaks, frequency relations were defined and presented for 2, 5, 10, 25, 50 and 100 year recurrent intervals.

Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

NASA Astrophysics Data System (ADS)

Zhu, Hui; Chen, Yueyuan; Chu, Daping; Feng, Shiwei; Zhang, Yingqiao; Wang, Pengfei

2016-09-01

The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V 0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V 0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

Characterization of the polarization and frequency selective bolometric detector architecture

NASA Astrophysics Data System (ADS)

Leong, Jonathan Ryan Kyoung Ho

2009-01-01

The Cosmic Microwave Background (CMB) has been a wonderful probe of fundamental physics and cosmology. In the future, we look towards using the polarization information encoded in the CMB for investigating the gravity waves generated by inflation. This is a daunting task as it requires orders of magnitude increases in sensitivity as well as close attention to systematic rejection and astrophysical foreground removal. We have characterized a novel detector architecture which is aimed at making these leaps towards gravity wave detection in the CMB. These detectors are called the Polarization and Frequency Selective Bolometers (PFSBs). They attempt to use all the available photon information incident on a single pixel by selecting out the two orthogonal polarizations and multiple frequency bands into separately stacked detectors in a smooth-walled waveguide. This approach is inherently multimoded and thus solves problems with downlink and readout throughput by catching more photons per detector at the higher frequencies where the number of detectors required is prohibitively large. We have found that the PFSB architecture requires the use of a square cross-section waveguide. A simulation we developed has illuminated the fact that the curved field lines of the higher order modes can be eliminated by degeneracies which exist only for a square guide and not a circular one. In the square guide configuration, the PFSBs show good band selection and polarization efficiency to a level of about 90% over the beam out to at least 20° from on-axis.

Mechanical design of a single-axis monolithic accelerometer for advanced seismic attenuation systems

NASA Astrophysics Data System (ADS)

Bertolini, Alessandro; DeSalvo, Riccardo; Fidecaro, Francesco; Francesconi, Mario; Marka, Szabolcs; Sannibale, Virginio; Simonetti, Duccio; Takamori, Akiteru; Tariq, Hareem

2006-01-01

The design and mechanics for a new very-low noise low frequency horizontal accelerometer is presented. The sensor has been designed to be integrated in an advanced seismic isolation system for interferometric gravitational wave detectors. The motion of a small monolithic folded-pendulum (FP) is monitored by a high resolution capacitance displacement sensor; a feedback force actuator keeps the mass at the equilibrium position. The feedback signal is proportional to the ground acceleration in the frequency range 0-150 Hz. The very high mechanical quality factor, Q≃3000 at a resonant frequency of 0.5 Hz, reduces the Brownian motion of the proof mass of the accelerometer below the resolution of the displacement sensor. This scheme enables the accelerometer to detect the inertial displacement of a platform with a root-mean-square noise less than 1 nm, integrated over the frequency band from 0.01 to 150 Hz. The FP geometry, combined with the monolithic design, allows the accelerometer to be extremely directional. A vertical-horizontal coupling ranging better than 10-3 has been achieved. A detailed account of the design and construction of the accelerometer is reported here. The instrument is fully ultra-high vacuum compatible and has been tested and approved for integration in seismic attenuation system of japanese TAMA 300 gravitational wave detector. The monolithic design also makes the accelerometer suitable for cryogenic operation.

Experimental study of a very high frequency, 162 MHz, segmented electrode, capacitively coupled plasma discharge

NASA Astrophysics Data System (ADS)

Sirse, Nishant; Harvey, Cleo; Gaman, Cezar; Ellingboe, Bert

2016-09-01

Radio-frequency capacitively coupled plasma (CCP) discharge operating at a very high frequency, 30-300 MHz, offers many advantages over standard 13.56 MHz CCP. However, there is a limited flexibility on the choice of driving frequency and substrate size due to plasma non-uniformity caused by the standing wave effect and edge effect. To overcome this issue segmented electrode CCP's are proposed and researched. Despite its numerous advantages the power coupling mechanism and plasma chemistry in this type of discharge are not fully understood due to lack of experimental data. In this paper, we present the experimental study of a segmented electrode, 3x4 tile array (10x10 cm square tile with 1 cm tile-to-tile separation), CCP discharge driven at 162 MHz. We measured plasma uniformity and gas temperature using hairpin probe and optical emission spectroscopy respectively. A homemade RF compensated Langmuir probe is employed to measure the Electron Energy Distribution Function (EEDF) by second harmonic technique. Energy resolved quadrupole mass spectrometer is utilized to measure the ion energy distribution. Discharge/plasma properties are investigated for several operating conditions and for power coupling mode in both washer board and checker board configuration. The experimental results show that the uniform plasma density can be maintained over a large area along with highly non-equilibrium condition to produce unique gas phase plasma chemistry.

Simulation Study Using a New Type of Sample Variance

NASA Technical Reports Server (NTRS)

Howe, D. A.; Lainson, K. J.

1996-01-01

We evaluate with simulated data a new type of sample variance for the characterization of frequency stability. The new statistic (referred to as TOTALVAR and its square root TOTALDEV) is a better predictor of long-term frequency variations than the present sample Allan deviation. The statistical model uses the assumption that a time series of phase or frequency differences is wrapped (periodic) with overall frequency difference removed. We find that the variability at long averaging times is reduced considerably for the five models of power-law noise commonly encountered with frequency standards and oscillators.

Quantum gates by periodic driving

PubMed Central

Shi, Z. C.; Wang, W.; Yi, X. X.

2016-01-01

Topological quantum computation has been extensively studied in the past decades due to its robustness against decoherence. One way to realize the topological quantum computation is by adiabatic evolutions—it requires relatively long time to complete a gate, so the speed of quantum computation slows down. In this work, we present a method to realize single qubit quantum gates by periodic driving. Compared to adiabatic evolution, the single qubit gates can be realized at a fixed time much shorter than that by adiabatic evolution. The driving fields can be sinusoidal or square-well field. With the sinusoidal driving field, we derive an expression for the total operation time in the high-frequency limit, and an exact analytical expression for the evolution operator without any approximations is given for the square well driving. This study suggests that the period driving could provide us with a new direction in regulations of the operation time in topological quantum computation. PMID:26911900

Quantum gates by periodic driving.

PubMed

Shi, Z C; Wang, W; Yi, X X

2016-02-25

Topological quantum computation has been extensively studied in the past decades due to its robustness against decoherence. One way to realize the topological quantum computation is by adiabatic evolutions-it requires relatively long time to complete a gate, so the speed of quantum computation slows down. In this work, we present a method to realize single qubit quantum gates by periodic driving. Compared to adiabatic evolution, the single qubit gates can be realized at a fixed time much shorter than that by adiabatic evolution. The driving fields can be sinusoidal or square-well field. With the sinusoidal driving field, we derive an expression for the total operation time in the high-frequency limit, and an exact analytical expression for the evolution operator without any approximations is given for the square well driving. This study suggests that the period driving could provide us with a new direction in regulations of the operation time in topological quantum computation.

A physical optics/equivalent currents model for the RCS of trihedral corner reflectors

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polycarpou, Anastasis C.

1993-01-01

The scattering in the interior regions of both square and triangular trihedral corner reflectors is examined. The theoretical model presented combines geometrical and physical optics (GO and PO), used to account for reflection terms, with equivalent edge currents (EEC), used to account for first-order diffractions from the edges. First-order, second-order, and third-order reflection terms are included. Calculating the first-order reflection terms involves integrating over the entire surface of the illuminated plate. Calculating the second- and third-order reflection terms, however, is much more difficult because the illuminated area is an arbitrary polygon whose shape is dependent upon the incident angles. The method for determining the area of integration is detailed. Extensive comparisons between the high-frequency model, Finite-Difference Time-Domain (FDTD) and experimental data are used for validation of the radar cross section (RCS) of both square and triangular trihedral reflectors.

Least square regularized regression in sum space.

PubMed

Xu, Yong-Li; Chen, Di-Rong; Li, Han-Xiong; Liu, Lu

2013-04-01

This paper proposes a least square regularized regression algorithm in sum space of reproducing kernel Hilbert spaces (RKHSs) for nonflat function approximation, and obtains the solution of the algorithm by solving a system of linear equations. This algorithm can approximate the low- and high-frequency component of the target function with large and small scale kernels, respectively. The convergence and learning rate are analyzed. We measure the complexity of the sum space by its covering number and demonstrate that the covering number can be bounded by the product of the covering numbers of basic RKHSs. For sum space of RKHSs with Gaussian kernels, by choosing appropriate parameters, we tradeoff the sample error and regularization error, and obtain a polynomial learning rate, which is better than that in any single RKHS. The utility of this method is illustrated with two simulated data sets and five real-life databases.

The collisional drift mode in a partially ionized plasma. [in the F region

NASA Technical Reports Server (NTRS)

Hudson, M. K.; Kennel, C. F.

1974-01-01

The structure of the drift instability was examined in several density regimes. Let sub e be the total electron mean free path, k sub z the wave-vector component along the magnetic field, and the ratio of perpendicular ion diffusion to parallel electron streaming rates. At low densities (k sub z lambda 1) the drift mode is isothermal and should be treated kineticly. In the finite heat conduction regime square root of m/M k sub z Lambda sub 1) the drift instability threshold is reduced at low densities and increased at high densities as compared to the isothermal threshold. Finally, in the energy transfer limit (k sub z kambda sub e square root of m/M) the drift instability behaves adiabatically in a fully ionized plasma and isothermally in a partially ionized plasma for an ion-neutral to Coulomb collision frequency ratio.

Design and numerical analysis of a THz square porous-core photonic crystal fiber for low flattened dispersion, ultrahigh birefringence.

PubMed

Luo, Jianfeng; Tian, Fengjun; Qu, Hongkun; Li, Li; Zhang, Jianzhong; Yang, Xinhua; Yuan, Libo

2017-08-20

We propose a kind of square porous-core photonic crystal fiber (PCF) for polarization-maintaining terahertz (THz) wave guidance. An asymmetry is introduced by implementing rectangular array air holes in the porous core of the PCF, and ultrahigh birefringence and low effective material loss (EML) can be achieved simultaneously. The properties of THz wave propagation are analyzed numerically in detail. The numerical results indicate that the proposed fiber offers a high birefringence of 0.063 and a low EML of 0.081  cm -1 at 1 THz. Moreover, a very low flattened dispersion profile is observed over a wide frequency domain of 0.85-1.9 THz. The zero flattened dispersion can be controlled. It is predicted that this PCF would be used potentially in polarization maintaining and dispersion management of THz waves.

Dynamic response of an artificial square spin ice

DOE PAGES

Jungfleisch, M. B.; Zhang, W.; Iacocca, E.; ...

2016-03-02

Magnetization dynamics in an artficial square spin-ice lattice made of Ni80Fe20 with magnetic field applied in the lattice plane is investigated by broadband ferromagnetic resonance spectroscopy. The experimentally observed dispersion shows a rich spectrum of modes corresponding to different magnetization states. These magnetization states are determined by exchange and dipolar interaction between individual islands, as is confirmed by a semianalytical model. In the low field regime below 400 Oe a hysteretic behavior in the mode spectrum is found. Micromagnetic simulations reveal that the origin of the observed spectra is due to the initialization of different magnetization states of individual nanomagnets.more » Our results indicate that it might be possible to determine the spin-ice state by resonance experiments and are a first step towards the understanding of artificial geometrically frustrated magnetic systems in the high-frequency regime.« less

Dynamic response of an artificial square spin ice

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

Jungfleisch, M. B.; Zhang, W.; Iacocca, E.

Magnetization dynamics in an artficial square spin-ice lattice made of Ni80Fe20 with magnetic field applied in the lattice plane is investigated by broadband ferromagnetic resonance spectroscopy. The experimentally observed dispersion shows a rich spectrum of modes corresponding to different magnetization states. These magnetization states are determined by exchange and dipolar interaction between individual islands, as is confirmed by a semianalytical model. In the low field regime below 400 Oe a hysteretic behavior in the mode spectrum is found. Micromagnetic simulations reveal that the origin of the observed spectra is due to the initialization of different magnetization states of individual nanomagnets.more » Our results indicate that it might be possible to determine the spin-ice state by resonance experiments and are a first step towards the understanding of artificial geometrically frustrated magnetic systems in the high-frequency regime.« less

Study on THz wave generation from air plasma induced by quasi-square Airy beam

NASA Astrophysics Data System (ADS)

Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin

2018-01-01

Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.

Stability Criteria Analysis for Landing Craft Utility

DTIC Science & Technology

2017-12-01

Square meter m/s Meters per Second m/s2 Meters per Second Squared n Vertical Displacement of Sea Water Free Surface n3 Ship’s Heave... Displacement n5 Ship’s Pitch Angle p(ξ) Rayleigh Distribution Probability Function POSSE Program of Ship Salvage Engineering pk...Spectrum Constant γ JONSWAP Wave Spectrum Peak Factor Γ(λ) Gamma Probability Function Δ Ship’s Displacement Δω Small Frequency

Ultrasonic attenuation in superconducting molybdenum-rhenium alloys.

NASA Technical Reports Server (NTRS)

Ashkin, M.; Deis, D. W.; Gottlieb, M.; Jones, C. K.

1971-01-01

Investigation of longitudinal sound attenuation in superconducting Mo-Re alloys as a function of temperature, magnetic field, and frequency. Evaporated thin film CdS transducers were used for the measurements at frequencies up to 3 GHz. The normal state attenuation coefficient was found to be proportional to the square of frequency over this frequency range. Measurements in zero magnetic field yielded a value of the energy gap parameter close to the threshold value of 3.56 kTc, appropriate to a weakly coupled dirty limit superconductor.

Effect of plasma actuator control parameters on a transitional flow

NASA Astrophysics Data System (ADS)

Das Gupta, Arnob; Roy, Subrata

2018-04-01

This study uses a wall-resolved implicit large eddy simulation to investigate the effects of different surface dielectric barrier discharge actuator parameters such as the geometry of the electrodes, frequency, amplitude of actuation and thermal effect. The actuator is used as a tripping device on a zero-pressure gradient laminar boundary layer flow. It is shown that the standard linear actuator creates structures like the Tollmien-Schlichting wave transition. The circular serpentine, square serpentine and spanwise actuators have subharmonic sinuous streak breakdown and behave like oblique wave transition scenario. The spanwise and square actuators cause comparably faster transition to turbulence. The square actuator adds energy into the higher spanwise wavenumber modes resulting in a faster transition compared to the circular actuator. When the Strouhal number of actuation is varied, the transition does not occur for a value below 0.292. Higher frequencies with same amplitude of actuation lead to faster transition. Small changes (<4%) in the amplitude of actuation can have a significant impact on the transition location which suggests that an optimal combination of frequency and amplitude exists for highest control authority. The thermal bumps approximating the actuator heating only shows localized effects on the later stages of transition for temperatures up to 373 K and can be ignored for standard actuators operating in subsonic regimes.

Reference layer adaptive filtering (RLAF) for EEG artifact reduction in simultaneous EEG-fMRI.

PubMed

Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R

2017-04-01

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) combines advantages of both methods, namely high temporal resolution of EEG and high spatial resolution of fMRI. However, EEG quality is limited due to severe artifacts caused by fMRI scanners. To improve EEG data quality substantially, we introduce methods that use a reusable reference layer EEG cap prototype in combination with adaptive filtering. The first method, reference layer adaptive filtering (RLAF), uses adaptive filtering with reference layer artifact data to optimize artifact subtraction from EEG. In the second method, multi band reference layer adaptive filtering (MBRLAF), adaptive filtering is performed on bandwidth limited sub-bands of the EEG and the reference channels. The results suggests that RLAF outperforms the baseline method, average artifact subtraction, in all settings and also its direct predecessor, reference layer artifact subtraction (RLAS), in lower (<35 Hz) frequency ranges. MBRLAF is computationally more demanding than RLAF, but highly effective in all EEG frequency ranges. Effectivity is determined by visual inspection, as well as root-mean-square voltage reduction and power reduction of EEG provided that physiological EEG components such as occipital EEG alpha power and visual evoked potentials (VEP) are preserved. We demonstrate that both, RLAF and MBRLAF, improve VEP quality. For that, we calculate the mean-squared-distance of single trial VEP to the mean VEP and estimate single trial VEP classification accuracies. We found that the average mean-squared-distance is lowest and the average classification accuracy is highest after MBLAF. RLAF was second best. In conclusion, the results suggests that RLAF and MBRLAF are potentially very effective in improving EEG quality of simultaneous EEG-fMRI. Highlights We present a new and reusable reference layer cap prototype for simultaneous EEG-fMRI We introduce new algorithms for reducing EEG artifacts due to simultaneous fMRI The algorithms combine a reference layer and adaptive filtering Several evaluation criteria suggest superior effectivity in terms of artifact reduction We demonstrate that physiological EEG components are preserved.

Reference layer adaptive filtering (RLAF) for EEG artifact reduction in simultaneous EEG-fMRI

NASA Astrophysics Data System (ADS)

Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R.

2017-04-01

Objective. Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) combines advantages of both methods, namely high temporal resolution of EEG and high spatial resolution of fMRI. However, EEG quality is limited due to severe artifacts caused by fMRI scanners. Approach. To improve EEG data quality substantially, we introduce methods that use a reusable reference layer EEG cap prototype in combination with adaptive filtering. The first method, reference layer adaptive filtering (RLAF), uses adaptive filtering with reference layer artifact data to optimize artifact subtraction from EEG. In the second method, multi band reference layer adaptive filtering (MBRLAF), adaptive filtering is performed on bandwidth limited sub-bands of the EEG and the reference channels. Main results. The results suggests that RLAF outperforms the baseline method, average artifact subtraction, in all settings and also its direct predecessor, reference layer artifact subtraction (RLAS), in lower (<35 Hz) frequency ranges. MBRLAF is computationally more demanding than RLAF, but highly effective in all EEG frequency ranges. Effectivity is determined by visual inspection, as well as root-mean-square voltage reduction and power reduction of EEG provided that physiological EEG components such as occipital EEG alpha power and visual evoked potentials (VEP) are preserved. We demonstrate that both, RLAF and MBRLAF, improve VEP quality. For that, we calculate the mean-squared-distance of single trial VEP to the mean VEP and estimate single trial VEP classification accuracies. We found that the average mean-squared-distance is lowest and the average classification accuracy is highest after MBLAF. RLAF was second best. Significance. In conclusion, the results suggests that RLAF and MBRLAF are potentially very effective in improving EEG quality of simultaneous EEG-fMRI. Highlights We present a new and reusable reference layer cap prototype for simultaneous EEG-fMRI We introduce new algorithms for reducing EEG artifacts due to simultaneous fMRI The algorithms combine a reference layer and adaptive filtering Several evaluation criteria suggest superior effectivity in terms of artifact reduction We demonstrate that physiological EEG components are preserved

Multi-frequency Phase Unwrap from Noisy Data: Adaptive Least Squares Approach

NASA Astrophysics Data System (ADS)

Katkovnik, Vladimir; Bioucas-Dias, José

2010-04-01

Multiple frequency interferometry is, basically, a phase acquisition strategy aimed at reducing or eliminating the ambiguity of the wrapped phase observations or, equivalently, reducing or eliminating the fringe ambiguity order. In multiple frequency interferometry, the phase measurements are acquired at different frequencies (or wavelengths) and recorded using the corresponding sensors (measurement channels). Assuming that the absolute phase to be reconstructed is piece-wise smooth, we use a nonparametric regression technique for the phase reconstruction. The nonparametric estimates are derived from a local least squares criterion, which, when applied to the multifrequency data, yields denoised (filtered) phase estimates with extended ambiguity (periodized), compared with the phase ambiguities inherent to each measurement frequency. The filtering algorithm is based on local polynomial (LPA) approximation for design of nonlinear filters (estimators) and adaptation of these filters to unknown smoothness of the spatially varying absolute phase [9]. For phase unwrapping, from filtered periodized data, we apply the recently introduced robust (in the sense of discontinuity preserving) PUMA unwrapping algorithm [1]. Simulations give evidence that the proposed algorithm yields state-of-the-art performance for continuous as well as for discontinues phase surfaces, enabling phase unwrapping in extraordinary difficult situations when all other algorithms fail.

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

PubMed Central

Hettich, Mike; Jacob, Karl; Ristow, Oliver; Schubert, Martin; Bruchhausen, Axel; Gusev, Vitalyi; Dekorsy, Thomas

2016-01-01

We investigate the viscoelastic properties of confined molecular nano-layers by time resolved optical pump-probe measurements. Access to the elastic properties is provided by the damping time of acoustic eigenmodes of thin metal films deposited on the molecular nano-layers which show a strong dependence on the molecular layer thickness and on the acoustic eigen-mode frequencies. An analytical model including the viscoelastic properties of the molecular layer allows us to obtain the longitudinal sound velocity as well as the acoustic absorption coefficient of the layer. Our experiments and theoretical analysis indicate for the first time that the molecular nano-layers are much more viscous than elastic in the investigated frequency range from 50 to 120 GHz and thus show pronounced acoustic absorption. The longitudinal acoustic wavenumber has nearly equal real and imaginary parts, both increasing proportional to the square root of the frequency. Thus, both acoustic velocity and acoustic absorption are proportional to the square root of frequency and the propagation of compressional/dilatational acoustic waves in the investigated nano-layers is of the diffusional type, similar to the propagation of shear waves in viscous liquids and thermal waves in solids. PMID:27633351

Sub-Frequency Interval Approach in Electromechanical Impedance Technique for Concrete Structure Health Monitoring

PubMed Central

Yang, Yaowen; Divsholi, Bahador Sabet

2010-01-01

The electromechanical (EM) impedance technique using piezoelectric lead zirconate titanate (PZT) transducers for structural health monitoring (SHM) has attracted considerable attention in various engineering fields. In the conventional EM impedance technique, the EM admittance of a PZT transducer is used as a damage indicator. Statistical analysis methods such as root mean square deviation (RMSD) have been employed to associate the damage level with the changes in the EM admittance signatures, but it is difficult to determine the location of damage using such methods. This paper proposes a new approach by dividing the large frequency (30–400 kHz) range into sub-frequency intervals and calculating their respective RMSD values. The RMSD of the sub-frequency intervals (RMSD-S) will be used to study the severity and location of damage. An experiment is carried out on a real size concrete structure subjected to artificial damage. It is observed that damage close to the PZT changes the high frequency range RMSD-S significantly, while the damage far away from the PZT changes the RMSD-S in the low frequency range significantly. The relationship between the frequency range and the PZT sensing region is also presented. Finally, a damage identification scheme is proposed to estimate the location and severity of damage in concrete structures. PMID:22163548

Poroelastic finite difference modeling of seismic attenuation and dispersion due to mesoscopic-scale heterogeneity

NASA Astrophysics Data System (ADS)

Masson, Y. J.; Pride, S. R.

2007-03-01

Seismic attenuation and dispersion are numerically determined for computer-generated porous materials that contain arbitrary amounts of mesoscopic-scale heterogeneity in the porous continuum properties. The local equations used to determine the poroelastic response within such materials are those of Biot (1962). Upon applying a step change in stress to samples containing mesoscopic-scale heterogeneity, the poroelastic response is determined using finite difference modeling, and the average strain throughout the sample computed, along with the effective complex and frequency-dependent elastic moduli of the sample. The ratio of the imaginary and real parts of these moduli determines the attenuation as a function of frequency associated with the modes of applied stress (pure compression and pure shear). By having a wide range of heterogeneity present, there exists a wide range of relaxation frequencies in the response with the result that the curves of attenuation as a function of frequency are broader than in existing analytical theories based on a single relaxation frequency. Analytical explanations are given for the various high-frequency and low-frequency asymptotic behavior observed in the numerical simulations. It is also shown that the overall level of attenuation of a given sample is proportional to the square of the incompressibility contrasts locally present.

Harvesting Low-Frequency (<5 Hz) Irregular Mechanical Energy: A Possible Killer Application of Triboelectric Nanogenerator.

PubMed

Zi, Yunlong; Guo, Hengyu; Wen, Zhen; Yeh, Min-Hsin; Hu, Chenguo; Wang, Zhong Lin

2016-04-26

Electromagnetic generators (EMGs) and triboelectric nanogenerators (TENGs) are the two most powerful approaches for harvesting ambient mechanical energy, but the effectiveness of each depends on the triggering frequency. Here, after systematically comparing the performances of EMGs and TENGs under low-frequency motion (<5 Hz), we demonstrated that the output performance of EMGs is proportional to the square of the frequency, while that of TENGs is approximately in proportion to the frequency. Therefore, the TENG has a much better performance than that of the EMG at low frequency (typically 0.1-3 Hz). Importantly, the extremely small output voltage of the EMG at low frequency makes it almost inapplicable to drive any electronic unit that requires a certain threshold voltage (∼0.2-4 V), so that most of the harvested energy is wasted. In contrast, a TENG has an output voltage that is usually high enough (>10-100 V) and independent of frequency so that most of the generated power can be effectively used to power the devices. Furthermore, a TENG also has advantages of light weight, low cost, and easy scale up through advanced structure designs. All these merits verify the possible killer application of a TENG for harvesting energy at low frequency from motions such as human motions for powering small electronics and possibly ocean waves for large-scale blue energy.

Investigating the performance of reconstruction methods used in structured illumination microscopy as a function of the illumination pattern's modulation frequency

NASA Astrophysics Data System (ADS)

Shabani, H.; Sánchez-Ortiga, E.; Preza, C.

2016-03-01

Surpassing the resolution of optical microscopy defined by the Abbe diffraction limit, while simultaneously achieving optical sectioning, is a challenging problem particularly for live cell imaging of thick samples. Among a few developing techniques, structured illumination microscopy (SIM) addresses this challenge by imposing higher frequency information into the observable frequency band confined by the optical transfer function (OTF) of a conventional microscope either doubling the spatial resolution or filling the missing cone based on the spatial frequency of the pattern when the patterned illumination is two-dimensional. Standard reconstruction methods for SIM decompose the low and high frequency components from the recorded low-resolution images and then combine them to reach a high-resolution image. In contrast, model-based approaches rely on iterative optimization approaches to minimize the error between estimated and forward images. In this paper, we study the performance of both groups of methods by simulating fluorescence microscopy images from different type of objects (ranging from simulated two-point sources to extended objects). These simulations are used to investigate the methods' effectiveness on restoring objects with various types of power spectrum when modulation frequency of the patterned illumination is changing from zero to the incoherent cut-off frequency of the imaging system. Our results show that increasing the amount of imposed information by using a higher modulation frequency of the illumination pattern does not always yield a better restoration performance, which was found to be depended on the underlying object. Results from model-based restoration show performance improvement, quantified by an up to 62% drop in the mean square error compared to standard reconstruction, with increasing modulation frequency. However, we found cases for which results obtained with standard reconstruction methods do not always follow the same trend.

Cardiovascular and stress responses to short-term noise exposures-A panel study in healthy males.

PubMed

Walker, Erica D; Brammer, Anthony; Cherniack, Martin G; Laden, Francine; Cavallari, Jennifer M

2016-10-01

While previous epidemiological studies report adverse effects of long-term noise exposure on cardiovascular health, the mechanisms responsible for these effects are unclear. We sought to elucidate the cardiovascular and stress response to short-term, low (31.5-125Hz) and high (500-2000Hz) frequency noise exposures. Healthy male (n=10) participants were monitored on multiple visits during no noise, low- or high-frequency noise exposure scenarios lasting 40min. Participants were fitted with an ambulatory electrocardiogram (ECG) and blood pressure measures and saliva samples were taken before, during and after noise exposures. ECGs were processed for measures of heart rate variability (HRV): high-frequency power (HF), low-frequency power (LF), the root of the mean squared difference between adjacent normal heart beats (N-N) intervals (RMSSD), and the standard deviation of N-N intervals (SDNN). Systolic blood pressure (SBP), diastolic blood pressure (DPB), and pulse were reported and saliva was analyzed for salivary cortisol and amylase. Multivariate mixed-effects linear regression models adjusted for age were used to identify statistically significant difference in outcomes by no noise, during noise or after noise exposure periods and whether this differed by noise frequency. A total of 658, 205, and 122, HRV, saliva, and blood pressure measurements were performed over 41 person days. Reductions in HRV (LF and RMSSD) were observed during noise exposure (a reduction of 19% (-35,-3.5) and 9.1% (-17,-1.1), respectively). After adjusting for noise frequency, during low frequency noise exposure, HF, LF, and SDNN were reduced (a reduction of 32% (-57,-6.2), 34% (-52,-15), and 16% (-26,-6.1), respectively) and during high frequency noise exposure, a 21% (-39,-2.3) reduction in LF, as compared to during no noise exposure, was found. No significant (p<0.05) changes in blood pressure, salivary cortisol, or amylase were observed. These results suggest that exposure to noise, and in particular, to low-frequency noise, negatively impacts HRV. The frequencies of noise should be considered when evaluating the cardiovascular health impacts of exposure. Copyright © 2016 Elsevier Inc. All rights reserved.

Cardiovascular and Stress Responses to Short-Term Noise Exposures—A Panel Study in Healthy Males

PubMed Central

Walker, Erica D; Brammer, Anthony; Cherniack, Martin G; Laden, Francine; Cavallari, Jennifer M

2016-01-01

Background While previous epidemiological studies report adverse effects of long-term noise exposure on cardiovascular health, the mechanisms responsible for these effects are unclear. We sought to elucidate the cardiovascular and stress response to short-term, low (31.5-125 Hz) and high (500 – 2000 Hz) frequency noise exposures. Methods Healthy male (n = 10) participants were monitored on multiple visits during no noise, low- or high-frequency noise exposure scenarios lasting 40 minutes. Participants were fitted with an ambulatory electrocardiogram (ECG) and blood pressure measures and saliva samples were taken before, during and after noise exposures. ECGs were processed for measures of heart rate variability (HRV): high-frequency power (HF), low-frequency power (LF), the root of the mean squared difference between adjacent normal heart beats (N-N) intervals (RMSSD), and the standard deviation of N-N intervals (SDNN). Systolic blood pressure (SBP), diastolic blood pressure (DPB), and pulse were reported and saliva was analyzed for salivary cortisol and amylase. Multivariate mixed-effects linear regression models adjusted for age were used to identify statistically significant difference in outcomes by no noise, during noise or after noise exposure periods and whether this differed by noise frequency. Results A total of 658, 205, and 122, HRV, saliva,and blood pressure measurements were performed over 41 person days. Reductions in HRV (LF and RMSSD) were observed during noise exposure (a reduction of 19%(−35,−3.5) and 9.1%(−17,−1.1), respectively). After adjusting for noise frequency, during low frequency noise exposure, HF, LF, and SDNN were reduced (a reduction of 32%(−57,−6.2), 34%(−52,−15), and 16%(−26,−6.1), respectively and during high frequency noise exposure, a 21%(−39,−2.3) reduction in LF, as compared to during no noise exposure was found. No significant (p>0.05) changes in blood pressure,salivary cortisol or amylase were observed. Conclusions These results suggest that exposure to noise, and in particular, to low-frequency noise negatively impacts HRV. The frequencies of noise should be considered when evaluating the cardiovascular health impacts of exposure. PMID:27371930

Patterns of multi-drug resistant bacteria at first culture from patients admitted to a third level University hospital in Calabria from 2011 to 2014: implications for empirical therapy and infection control.

PubMed

Reale, Mariaconcetta; Strazzulla, Alessio; Quirino, Angela; Rizzo, Claudia; Marano, Vito; Postorino, Maria Concetta; Mazzitelli, Maria; Greco, Giuseppe; Pisani, Vincenzo; Costa, Chiara; Cesana, Bruno Mario; Liberto, Maria Carla; Torti, Carlo; Focà, Alfredo

2017-06-01

Surveillance of antimicrobial drug resistance is fundamental to guide empirical treatment. However, the European Antimicrobial Resistance Surveillance Network provides a general picture, which might not be applicable to clinical settings that are excluded from this survey. We evaluated resistance patterns of ESKAPE isolates over a four-year period in a third level University hospital in the province of Catanzaro (Southern Italy). In this retrospective study, we evaluated the frequency of ESKAPE isolates with different resistance patterns (group 1=low-resistant bacteria; group 2=multi-drug and extremely drug-resistant bacteria; group 3=pan-resistant bacteria), stratified by year (2011, 2012, 2013 and 2014), hospital units (intensive care units, medical and surgical units) and by sample type (urine, blood, wound swabs, respiratory samples, other samples). Chi square test was applied to find differences between isolates with different resistance patterns by hospital unit and by organs and systems. Cochran-Armitage trend test was applied to assess the trend in resistance patterns during the four years analyzed. Amongst 2385 isolates, Escherichia coli (38%) was the most frequent, followed by Pseudomonas aeruginosa (15%), Klebsiella pneumoniae (14%), Staphylococcus aureus (13%), Acinetobacter baumannii (9%), Enterococcus faecalis (8%) and Enterococcus faecium (3%). From 2011 to 2014, frequency of isolates in group 2 plus 3 decreased from 23% to 14% (chi square=55.093; p<0.0001), particularly for E. coli and K. pneumoniae, but the trend increased for S. aureus (from 5% in 2011 to 10% in 2014), and remained stable for the other species. Frequency of isolates in group 2 plus 3 was higher in intensive care units for K. pneumoniae (chi square =32.292; p<0.0001), A. baumannii (chi square =6.947; p<0.0001) and S. aureus (chi square =22.079; p<0.0001). It was also higher from blood than from different sources for most species.

The clarinet: how blowing pressure, lip force, lip position and reed "hardness" affect pitch, sound level, and spectrum.

PubMed

Almeida, Andre; George, David; Smith, John; Wolfe, Joe

2013-09-01

Using an automated clarinet playing system, the frequency f, sound level L, and spectral characteristics are measured as functions of blowing pressure P and the force F applied by the mechanical lip at different places on the reed. The playing regime on the (P,F) plane lies below an extinction line F(P) with a negative slope of a few square centimeters and above a pressure threshold with a more negative slope. Lower values of F and P can produce squeaks. Over much of the playing regime, lines of equal frequency have negative slope. This is qualitatively consistent with passive reed behavior: Increasing F or P gradually closes the reed, reducing its equivalent acoustic compliance, which increases the frequency of the peaks of the parallel impedance of bore and reed. High P and low F produce the highest sound levels and stronger higher harmonics. At low P, sound level can be increased at constant frequency by increasing P while simultaneously decreasing F. At high P, where lines of equal f and of equal L are nearly parallel, this compensation is less effective. Applying F further from the mouthpiece tip moves the playing regime to higher F and P, as does a stiffer reed.

Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa.

PubMed

Phillipou, Andrea; Rossell, Susan Lee; Castle, David Jonathan; Gurvich, Caroline; Abel, Larry Allen

2014-12-02

The factors contributing to the cause and maintenance of anorexia nervosa (AN) are poorly understood, though increasing interest surrounds the neurobiological underpinnings of the condition. The examination of saccadic eye movements has proven useful in our understanding of the neurobiology of some other psychiatric illnesses, as they utilize identifiable brain circuits. Square wave jerks (SWJs), which describe an involuntary saccade away and back to fixation, have been observed to occur at abnormally high rates in neurodegenerative disorders and some psychiatric illnesses, but have not been examined in AN. Therefore, the aim of this study was to investigate whether individuals with AN and healthy control (HC) individuals differ in SWJ rate during attempted fixation. Square wave jerk frequency was compared across 23 female participants with AN and 22 HC participants matched for age, sex, and premorbid intelligence. Anorexia nervosa participants were found to make SWJs at a significantly higher rate than HC participants. The rate of SWJs in AN was also found to negatively correlate with anxiety. Square wave jerk rate and anxiety were found to correctly classify groups, with an accuracy of 87% for AN participants and 95.5% for HCs. Given our current understanding of saccadic eye movements, the findings suggest a potential role of γ-aminobutyric acid (GABA) in the superior colliculus, frontal eye fields, or posterior parietal cortex in the psychopathology of AN. © ARVO.

Magnitude and frequency of floods in western Oregon

USGS Publications Warehouse

Harris, David Dell; Hubbard, Larry L.; Hubbard, Lawrence E.

1979-01-01

A method for estimating the magnitude and frequency of floods is presented for unregulated streams in western Oregon. Equations relating flood magnitude to basin characteristics were developed for exceedance probabilities of 0.5 to 0.01 (2- to 100-year recurrence intervals). Separate equations are presented for four regions: Coast, Willamette, Rogue-Umpqua, and High Cascades. Also presented are values of flood discharges for selected exceedance probabilities and of basin characteristics for all gaging stations used in the analysis. Included are data for 230 stations in Oregon, 6 stations in southwestern Washington, and 3 stations in northwestern California. Drainage areas used in the analysis range from 0.21 to 7,280 square miles. Also included are maximum discharges for all western Oregon stations used in the analysis. (Woodard-USGS)

Dielectric properties of benzylamine in 1,2,6-hexanetriol mixture using time domain reflectometry technique

NASA Astrophysics Data System (ADS)

Swami, M. B.; Hudge, P. G.; Pawar, V. P.

The dielectric properties of binary mixtures of benzylamine-1,2,6-hexantriol mixtures at different volume fractions of 1,2,6-hexanetriol have been measured using Time Domain Reflectometry (TDR) technique in the frequency range of 10 MHz to 30 GHz. Complex permittivity spectra were fitted using Havriliak-Negami equation. By using least square fit method the dielectric parameters such as static dielectric constant (ɛ0), dielectric constant at high frequency (ɛ∞), relaxation time τ (ps) and relaxation distribution parameter (β) were extracted from complex permittivity spectra at 25∘C. The intramolecular interaction of different molecules has been discussed using the Kirkwood correlation factor, Bruggeman factor. The Kirkwood correlation factor (gf) and effective Kirkwood correlation factor (geff) indicate the dipole ordering of the binary mixtures.

Relativistic mirrors in laser plasmas (analytical methods)

NASA Astrophysics Data System (ADS)

Bulanov, S. V.; Esirkepov, T. Zh; Kando, M.; Koga, J.

2016-10-01

Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort x-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. We present an overview of theoretical methods used to describe relativistic flying, accelerating, oscillating mirrors emerging in intense laser-plasma interactions.

Personal coronary risk profiles modify autonomic nervous system responses to air pollution.

PubMed

Chen, Jiu-Chiuan; Stone, Peter H; Verrier, Richard L; Nearing, Bruce D; MacCallum, Gail; Kim, Jee-Young; Herrick, Robert F; You, Jinhong; Zhou, Haibo; Christiani, David C

2006-11-01

We investigated whether PM2.5-mediated autonomic modulation depends on individual coronary risk profiles. Five-minute average heart rate (HR) and heart rate variability (HRV, including standard deviation of normal-to-normal intervals [SDNN], square root of the mean squared differences of successive NN intervals [rMSSD], high frequency [HF]) were measured from 24-hour ambulatory electrocardiograms, and personal PM(2.5) exposures were monitored in a prospective study of 10 male boilermakers (aged 34.3 +/- 8.1 years). We used the Framingham score to classify individuals into low (score = 1-3) and high (score = 5-6) risk categories. Mixed-effect models were used for statistical analyses. Each 1-mg/m(3) increase in the preceding 4-hour moving average PM(2.5) was associated with HR increase (5.3 beats/min) and HRV reduction (11.7%, confidence interval [CI] = 6.2-17.1% for SDNN; 11.1%, CI = 3.1-19.1% for rMSSD; 16.6%, CI = 1.5-31.7% for HF). Greater responses (2- to 4-fold differences) were observed in high-risk subjects than in low-risk subjects. Our study suggests that adverse autonomic responses to metal particulate are aggravated in workers with higher coronary risk profiles.

The Stochastic X-Ray Variability of the Accreting Millisecond Pulsar MAXI J0911-655

NASA Technical Reports Server (NTRS)

Bult, Peter

2017-01-01

In this work, I report on the stochastic X-ray variability of the 340 hertz accreting millisecond pulsar MAXI J0911-655. Analyzing pointed observations of the XMM-Newton and NuSTAR observatories, I find that the source shows broad band-limited stochastic variability in the 0.01-10 hertz range with a total fractional variability of approximately 24 percent root mean square timing residuals in the 0.4 to 3 kiloelectronvolt energy band that increases to approximately 40 percent root mean square timing residuals in the 3 to 10 kiloelectronvolt band. Additionally, a pair of harmonically related quasi-periodic oscillations (QPOs) are discovered. The fundamental frequency of this harmonic pair is observed between frequencies of 62 and 146 megahertz. Like the band-limited noise, the amplitudes of the QPOs show a steep increase as a function of energy; this suggests that they share a similar origin, likely the inner accretion flow. Based on their energy dependence and frequency relation with respect to the noise terms, the QPOs are identified as low-frequency oscillations and discussed in terms of the Lense-Thirring precession model.

Low-flow characteristics of streams on the Kitsap Peninsula and selected adjacent islands, Washington

USGS Publications Warehouse

Cummans, J.E.

1976-01-01

Low-flow-frequency data are tabulated for 90 streamflow sites on the Kitsap Peninsula and adjacent islands, Washington. Also listed are data for 56 additional sites which have insufficient measurements for frequency analysis but which have been observed having no flow at least once during the low-flow period. The streams drain relatively small basins; only three streams have drainage areas greater than 20.0 square miles, and only nine other streams have drainage areas greater than 10.0 square miles. Mean annual precipitation during the period 1931-60 ranged from about 25 inches near Hansville to about 70 inches near Tahuya. Low-flow-frequency curves plotted from records of streamflow at eight long-term gaging stations were used to determine data for low-flow durations of 7, 30, 60, 90, and 183 days. Regression techniques then were used to estimate low flows with frequencies up to 20 years for stations with less than 10 years of record and for miscellaneous sites where discharge measurements have been made. (Woodard-USGS)

Noninvasive Diagnosis of Coronary Artery Disease Using 12-Lead High-Frequency Electrocardiograms

NASA Technical Reports Server (NTRS)

Schlegel, Todd T.; Arenare, Brian

2006-01-01

A noninvasive, sensitive method of diagnosing certain pathological conditions of the human heart involves computational processing of digitized electrocardiographic (ECG) signals acquired from a patient at all 12 conventional ECG electrode positions. In the processing, attention is focused on low-amplitude, high-frequency components of those portions of the ECG signals known in the art as QRS complexes. The unique contribution of this method lies in the utilization of signal features and combinations of signal features from various combinations of electrode positions, not reported previously, that have been found to be helpful in diagnosing coronary artery disease and such related pathological conditions as myocardial ischemia, myocardial infarction, and congestive heart failure. The electronic hardware and software used to acquire the QRS complexes and perform some preliminary analyses of their high-frequency components were summarized in Real-Time, High-Frequency QRS Electrocardiograph (MSC- 23154), NASA Tech Briefs, Vol. 27, No. 7 (July 2003), pp. 26-28. To recapitulate, signals from standard electrocardiograph electrodes are preamplified, then digitized at a sampling rate of 1,000 Hz, then analyzed by the software that detects R waves and QRS complexes and analyzes them from several perspectives. The software includes provisions for averaging signals over multiple beats and for special-purpose nonrecursive digital filters with specific low- and high-frequency cutoffs. These filters, applied to the averaged signal, effect a band-pass operation in the frequency range from 150 to 250 Hz. The output of the bandpass filter is the desired high-frequency QRS signal. Further processing is then performed in real time to obtain the beat-to-beat root mean square (RMS) voltage amplitude of the filtered signal, certain variations of the RMS voltage, and such standard measures as the heart rate and R-R interval at any given time. A key signal feature analyzed in the present method is the presence versus the absence of reduced-amplitude zones (RAZs). In terms that must be simplified for the sake of brevity, an RAZ comprises several cycles of a high-frequency QRS signal during which the amplitude of the high-frequency oscillation in a portion of the signal is abnormally low (see figure). A given signal sample exhibiting an interval of reduced amplitude may or may not be classified as an RAZ, depending on quantitative criteria regarding peaks and troughs within the reduced-amplitude portion of the high-frequency QRS signal. This analysis is performed in all 12 leads in real time.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Synchronization of tunable asymmetric square-wave pulses in delay-coupled optoelectronic oscillators.

PubMed

Martínez-Llinàs, Jade; Colet, Pere; Erneux, Thomas

2015-03-01

We consider a model for two delay-coupled optoelectronic oscillators under positive delayed feedback as prototypical to study the conditions for synchronization of asymmetric square-wave oscillations, for which the duty cycle is not half of the period. We show that the scenario arising for positive feedback is much richer than with negative feedback. First, it allows for the coexistence of multiple in- and out-of-phase asymmetric periodic square waves for the same parameter values. Second, it is tunable: The period of all the square-wave periodic pulses can be tuned with the ratio of the delays, and the duty cycle of the asymmetric square waves can be changed with the offset phase while the total period remains constant. Finally, in addition to the multiple in- and out-of-phase periodic square waves, low-frequency periodic asymmetric solutions oscillating in phase may coexist for the same values of the parameters. Our analytical results are in agreement with numerical simulations and bifurcation diagrams obtained by using continuation techniques.

[Study on anti-hyperlipidemia mechanism of high frequency herb pairs by molecular docking method].

PubMed

Jiang, Lu-di; He, Yu-su; Chen, Xi; Tao, Ou; Li, Gong-Yu; Zhang, Yan-ling

2015-06-01

Traditional Chinese medicine (TCM) has definitely clinical effect in treating hyperlipidemia, but the action mechanism still need to be explored. Based on consulting Chinese Pharmacopoeia (2010), all the lipid-lowering Chinese patent medicines were analyzed by associated rules data mining method to explore high frequency herb pairs. The top three couplet medicines with high support degree were Puerariae Lobatae Radix-Crataegi Fructus, Salviae Miltiorrhizae Radix et Rhizoma-Crataegi Fructus, and Polygoni Multiflori Radix-Crataegi Fructus. The 20 main ingredients were selected from the herb pairs and docked with 3 key hyperlipidemia targets, namely 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), peroxisome proliferator activated receptor-α (PPAR-α ) and niemann-pick C1 like 1 (NPC1L1) to further discuss the molecular mechanism of the high frequency herb pairs, by using the docking program, LibDock. To construct evaluation rules for the ingredients of herb pairs, the root-mean-square deviation (RMSD) value between computed and initial complexes was first calculated to validate the fitness of LibDock models. Then, the key residues were also confirmed by analyzing the interactions of those 3 proteins and corresponding marketed drugs. The docking results showed that hyperin, puerarin, salvianolic acid A and polydatin can interact with two targets, and the other five compounds may be potent for at least one of the three targets. In this study, the multi-target effect of high frequency herb pairs for lipid-lowering was discussed on the molecular level, which can help further researching new multi-target anti-hyperlipidemia drug.

Assessment of the Vibrations Effects Caused by Technical Seismicity Due to the Railway traffic on High-sensitivity Machinery

NASA Astrophysics Data System (ADS)

Papán, Daniel; Valašková, Veronika; Demeterová, Katarína

2016-10-01

The numerical and experimental approach in structural dynamics problems is more and more current nowadays. This approach is applied and solved in many research and developing institutions of the all the world. Vibrations effect caused by passing trains used in manufacturing facilities can affect the quality of the production activity. This effect is possible to be solved by a numerical or an experimental way. Numerical solution is not so financially and time demanding. The main aim of this article is to focus on just experimental measurement of this problem. In this paper, the case study with measurement due to cramped conditions realized in situ is presented. The case study is located close to railway. The vibration effect caused by passing trains on the high-sensitivity machinery contained in this object were observed. The structure was a high-sensitivity machine that was placed in a construction process. For the measurements, the high-sensitivity standard vibrations equipment was used. The assessments of measurements’ results were performed for the technological conditions and Slovak Standard Criteria. Both of these assessments were divided to amplitude and frequency domain. The amplitude criterion is also divided to peak particle velocity and RMS (Root Mean Square). Frequency domain assessment were realised using the frequency response curves obtained from high-sensitivity machinery manufacturer. The frequency limits are established for each axis of triaxle system. The measurement results can be predicted if the vibration have to be reduced. Measurement implemented in the production hall should obtain materials to determine the seismic loading and response of production machinery caused by technical seismicity.

Improvement of Frequency Locking Algorithm for Atomic Frequency Standards

NASA Astrophysics Data System (ADS)

Park, Young-Ho; Kang, Hoonsoo; Heyong Lee, Soo; Eon Park, Sang; Lee, Jong Koo; Lee, Ho Seong; Kwon, Taeg Yong

2010-09-01

The authors describe a novel method of frequency locking algorithm for atomic frequency standards. The new algorithm for locking the microwave frequency to the Ramsey resonance is compared with the old one that had been employed in the cesium atomic beam frequency standards such as NIST-7 and KRISS-1. Numerical simulations for testing the performance of the algorithm show that the new method has a noise filtering performance superior to the old one by a factor of 1.2 for the flicker signal noise and 1.4 for random-walk signal noise. The new algorithm can readily be used to enhance the frequency stability for a digital servo employing the slow square wave frequency modulation.

Inhibition of Salmonella typhi growth using extremely low frequency electromagnetic (ELF-EM) waves at resonance frequency.

PubMed

Fadel, M A; Mohamed, S A; Abdelbacki, A M; El-Sharkawy, A H

2014-08-01

Typhoid is a serious disease difficult to be treated with conventional drugs. The aim of this study was to demonstrate a new method for the control of Salmonella typhi growth, through the interference with the bioelectric signals generated from the microbe during cell division by extremely low frequency electromagnetic waves (ELF-EMW-ELF-EM) at resonance frequency. Isolated Salmonella typhi was subjected to square amplitude modulated waves (QAMW) with different modulation frequencies from two generators with constant carrier frequency of 10 MHz, amplitude of 10 Vpp, modulating depth ± 2 Vpp and constant field strength of 200 V m(-1) at 37°C. Both the control and exposed samples were incubated at the same conditions during the experiment. The results showed that there was highly significant inhibition effect for Salm. typhi exposed to 0·8 Hz QAMW for a single exposure for 75 min. Dielectric relaxation, TEM and DNA results indicated highly significant changes in the molecular structure of the DNA and cellular membrane resulting from the exposure to the inhibiting EM waves. It was concluded that finding out the inhibiting resonance frequency of ELF-EM waves that deteriorates Salm. typhi growth will be promising method for the treatment of Salm. typhi infection either in vivo or in vitro. This new non-invasive technique for treatment of bacterial infections is of considerable interest for the use in medical and biotechnological applications. © 2014 The Society for Applied Microbiology.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

NASA Technical Reports Server (NTRS)

Armano, M.; Audley, H.; Auger, G.; Baird, J. T.; Bassan, M.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Thorpe, J. I.

2016-01-01

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 +/- 0.1 fm s(exp -2)/square root of Hz, or (0.54 +/- 0.01) x 10(exp -15) g/square root of Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 +/- 0.3) fm square root of Hz, about 2 orders of magnitude better than requirements. At f less than or equal to 0.5 mHz we observe a low-frequency tail that stays below 12 fm s(exp -2)/square root of Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

A compact and accurate semi-global potential energy surface for malonaldehyde from constrained least squares regression

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

Mizukami, Wataru, E-mail: wataru.mizukami@bristol.ac.uk; Tew, David P., E-mail: david.tew@bristol.ac.uk; Habershon, Scott, E-mail: S.Habershon@warwick.ac.uk

2014-10-14

We present a new approach to semi-global potential energy surface fitting that uses the least absolute shrinkage and selection operator (LASSO) constrained least squares procedure to exploit an extremely flexible form for the potential function, while at the same time controlling the risk of overfitting and avoiding the introduction of unphysical features such as divergences or high-frequency oscillations. Drawing from a massively redundant set of overlapping distributed multi-dimensional Gaussian functions of inter-atomic separations we build a compact full-dimensional surface for malonaldehyde, fit to explicitly correlated coupled cluster CCSD(T)(F12*) energies with a root mean square deviations accuracy of 0.3%–0.5% up tomore » 25 000 cm{sup −1} above equilibrium. Importance-sampled diffusion Monte Carlo calculations predict zero point energies for malonaldehyde and its deuterated isotopologue of 14 715.4(2) and 13 997.9(2) cm{sup −1} and hydrogen transfer tunnelling splittings of 21.0(4) and 3.2(4) cm{sup −1}, respectively, which are in excellent agreement with the experimental values of 21.583 and 2.915(4) cm{sup −1}.« less

The Square Kilometre Array

NASA Technical Reports Server (NTRS)

Huynh, Minh; Lazio, Joseph

2011-01-01

The Square Kilometre Array (SKA) will be the premier instrument to study radiation at centimetre and metre wavelengths from the cosmos, and in particular neutral hydrogen, the most abundant element in the universe. The SKA will probe the dawn of galaxy formation as well as allow advances in many other areas of astronomy, such as fundamental physics, astro-biology and cosmology. The SKA will have a collecting area of up to one million square metres spread over at least 3000 km, providing a collecting area more than twenty times greater than the current largest radio telescope. Its field of view on the sky will be several tens of square degrees with potentially several large (100 square degrees) independent beams at the lower frequencies, providing a survey speed many thousands of times greater than current facilities. This paper summarises the key science drivers of the SKA and provides an update on the international project.

Investigation of Dual-Mode Microstrip Bandpass Filter Based on SIR Technique

PubMed Central

Mezaal, Yaqeen S.; Ali, Jawad K.

2016-01-01

In this paper, a new bandpass filter design has been presented using simple topology of stepped impedance square loop resonator. The proposed bandpass filter has been simulated and fabricated using a substrate with an insulation constant of 10.8, thickness of 1.27mm and loss tangent of 0.0023 at center frequency of 5.8 GHz. The simulation results have been evaluated using Sonnet simulator that is extensively adopted in microwave analysis and implementation. The output frequency results demonstrated that the proposed filter has high-quality frequency responses in addition to isolated second harmonic frequency. Besides, this filter has very small surface area and perceptible narrow band response features that represent the conditions of recent wireless communication systems. Various filter specifications have been compared with different magnitudes of perturbation element dimension. Furthermore, phase scattering response and current intensity distribution of the proposed filter have been discussed. The simulated and experimental results are well-matched. Lastly, the features of the proposed filter have been compared with other designed microstrip filters in the literature. PMID:27798675

North Atlantic storm track variability and its association to the North Atlantic oscillation and climate variability of northern Europe

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

Rogers, J.C.

The primary mode of North Atlantic track variability is identified using rotated principal component analysis (RPCA) on monthly fields of root-mean-squares of daily high-pass filtered (2-8-day periods) sea level pressures (SLP) for winters (December-February) 1900-92. It is examined in terms of its association with (1) monthly mean SLP fields, (2) regional low-frequency teleconnections, and (3) the seesaw in winter temperatures between Greenland and northern Europe. 32 refs., 9 figs.

Aperture shape dependencies in extended depth of focus for imaging camera by wavefront coding

NASA Astrophysics Data System (ADS)

Sakita, Koichi; Ohta, Mitsuhiko; Shimano, Takeshi; Sakemoto, Akito

2015-02-01

Optical transfer functions (OTFs) on various directional spatial frequency axes for cubic phase mask (CPM) with circular and square apertures are investigated. Although OTF has no zero points, it has a very close value to zero for a circular aperture at low frequencies on diagonal axis, which results in degradation of restored images. The reason for close-to-zero value in OTF is also analyzed in connection with point spread function profiles using Fourier slice theorem. To avoid close-to-zero condition, square aperture with CPM is indispensable in WFC. We optimized cubic coefficient α of CPM and coefficients of digital filter, and succeeded to get excellent de-blurred images at large depth of field.

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters

PubMed Central

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-01-01

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies. PMID:26552584

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters.

PubMed

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-11-10

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies.

Enhanced diffusion with abnormal temperature dependence in underdamped space-periodic systems subject to time-periodic driving

NASA Astrophysics Data System (ADS)

Marchenko, I. G.; Marchenko, I. I.; Zhiglo, A. V.

2018-01-01

We present a study of the diffusion enhancement of underdamped Brownian particles in a one-dimensional symmetric space-periodic potential due to external symmetric time-periodic driving with zero mean. We show that the diffusivity can be enhanced by many orders of magnitude at an appropriate choice of the driving amplitude and frequency. The diffusivity demonstrates abnormal (decreasing) temperature dependence at the driving amplitudes exceeding a certain value. At any fixed driving frequency Ω normal temperature dependence of the diffusivity is restored at low enough temperatures, T

Internet search trends analysis tools can provide real-time data on kidney stone disease in the United States.

PubMed

Willard, Scott D; Nguyen, Mike M

2013-01-01

To evaluate the utility of using Internet search trends data to estimate kidney stone occurrence and understand the priorities of patients with kidney stones. Internet search trends data represent a unique resource for monitoring population self-reported illness and health information-seeking behavior. The Google Insights for Search analysis tool was used to study searches related to kidney stones, with each search term returning a search volume index (SVI) according to the search frequency relative to the total search volume. SVIs for the term, "kidney stones," were compiled by location and time parameters and compared with the published weather and stone prevalence data. Linear regression analysis was performed to determine the association of the search interest score with known epidemiologic variations in kidney stone disease, including latitude, temperature, season, and state. The frequency of the related search terms was categorized by theme and qualitatively analyzed. The SVI correlated significantly with established kidney stone epidemiologic predictors. The SVI correlated with the state latitude (R-squared=0.25; P<.001), the state mean annual temperature (R-squared=0.24; P<.001), and state combined sex prevalence (R-squared=0.25; P<.001). Female prevalence correlated more strongly than did male prevalence (R-squared=0.37; P<.001, and R-squared=0.17; P=.003, respectively). The national SVI correlated strongly with the average U.S. temperature by month (R-squared=0.54; P=.007). The search term ranking suggested that Internet users are most interested in the diagnosis, followed by etiology, infections, and treatment. Geographic and temporal variability in kidney stone disease appear to be accurately reflected in Internet search trends data. Internet search trends data might have broader applications for epidemiologic and urologic research. Copyright © 2013 Elsevier Inc. All rights reserved.

Optimal secondary source position in exterior spherical acoustical holophony

NASA Astrophysics Data System (ADS)

Pasqual, A. M.; Martin, V.

2012-02-01

Exterior spherical acoustical holophony is a branch of spatial audio reproduction that deals with the rendering of a given free-field radiation pattern (the primary field) by using a compact spherical loudspeaker array (the secondary source). More precisely, the primary field is known on a spherical surface surrounding the primary and secondary sources and, since the acoustic fields are described in spherical coordinates, they are naturally subjected to spherical harmonic analysis. Besides, the inverse problem of deriving optimal driving signals from a known primary field is ill-posed because the secondary source cannot radiate high-order spherical harmonics efficiently, especially in the low-frequency range. As a consequence, a standard least-squares solution will overload the transducers if the primary field contains such harmonics. Here, this is avoided by discarding the strongly decaying spherical waves, which are identified through inspection of the radiation efficiency curves of the secondary source. However, such an unavoidable regularization procedure increases the least-squares error, which also depends on the position of the secondary source. This paper deals with the above-mentioned questions in the context of far-field directivity reproduction at low and medium frequencies. In particular, an optimal secondary source position is sought, which leads to the lowest reproduction error in the least-squares sense without overloading the transducers. In order to address this issue, a regularization quality factor is introduced to evaluate the amount of regularization required. It is shown that the optimal position improves significantly the holophonic reconstruction and maximizes the regularization quality factor (minimizes the amount of regularization), which is the main general contribution of this paper. Therefore, this factor can also be used as a cost function to obtain the optimal secondary source position.

Improving surface EMG burst detection in infrahyoid muscles during swallowing using digital filters and discrete wavelet analysis.

PubMed

Restrepo-Agudelo, Sebastian; Roldan-Vasco, Sebastian; Ramirez-Arbelaez, Lina; Cadavid-Arboleda, Santiago; Perez-Giraldo, Estefania; Orozco-Duque, Andres

2017-08-01

The visual inspection is a widely used method for evaluating the surface electromyographic signal (sEMG) during deglutition, a process highly dependent of the examiners expertise. It is desirable to have a less subjective and automated technique to improve the onset detection in swallowing related muscles, which have a low signal-to-noise ratio. In this work, we acquired sEMG measured in infrahyoid muscles with high baseline noise of ten healthy adults during water swallowing tasks. Two methods were applied to find the combination of cutoff frequencies that achieve the most accurate onset detection: discrete wavelet decomposition based method and fixed steps variations of low and high cutoff frequencies of a digital bandpass filter. Teager-Kaiser Energy operator, root mean square and simple threshold method were applied for both techniques. Results show a narrowing of the effective bandwidth vs. the literature recommended parameters for sEMG acquisition. Both level 3 decomposition with mother wavelet db4 and bandpass filter with cutoff frequencies between 130 and 180Hz were optimal for onset detection in infrahyoid muscles. The proposed methodologies recognized the onset time with predictive power above 0.95, that is similar to previous findings but in larger and more superficial muscles in limbs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Crosstalk Reduction for High-Frequency Linear-Array Ultrasound Transducers Using 1–3 Piezocomposites With Pseudo-Random Pillars

PubMed Central

Yang, Hao-Chung; Cannata, Jonathan; Williams, Jay; Shung, K. Kirk

2013-01-01

The goal of this research was to develop a novel diced 1–3 piezocomposite geometry to reduce pulse–echo ring down and acoustic crosstalk between high-frequency ultrasonic array elements. Two PZT-5H-based 1–3 composites (10 and 15 MHz) of different pillar geometries [square (SQ), 45° triangle (TR), and pseudo-random (PR)] were fabricated and then made into single-element ultrasound transducers. The measured pulse–echo waveforms and their envelopes indicate that the PR composites had the shortest −20-dB pulse length and highest sensitivity among the composites evaluated. Using these composites, 15-MHz array subapertures with a 0.95λ pitch were fabricated to assess the acoustic crosstalk between array elements. The combined electrical and acoustical crosstalk between the nearest array elements of the PR array sub-apertures (−31.8 dB at 15 MHz) was 6.5 and 2.2 dB lower than those of the SQ and the TR array subapertures, respectively. These results demonstrate that the 1–3 piezocomposite with the pseudo-random pillars may be a better choice for fabricating enhanced high-frequency linear-array ultrasound transducers; especially when mechanical dicing is used. PMID:23143580

An inductorless multi-mode RF front end for GNSS receiver in 55 nm CMOS

NASA Astrophysics Data System (ADS)

Yanbin, Luo; Chengyan, Ma; Yebing, Gan; Min, Qian; Tianchun, Ye

2015-10-01

An inductorless multi-mode RF front end for a global navigation satellite system (GNSS) receiver is presented. Unlike the traditional topology of a low noise amplifier (LNA), the inductorless current-mode noise-canceling LNA is applied in this design. The high-impedance-input radio frequency amplifier (RFA) further amplifies the GNSS signals and changes the single-end signal path into fully differential. The passive mixer down-converts the signals to the intermediate frequency (IF) band and conveys the signals to the analogue blocks. The local oscillator (LO) buffer divides the output frequency of the voltage controlled oscillator (VCO) and generates 25%-duty-cycle quadrature square waves to drive the mixer. Our measurement results display that the implemented RF front end achieves good overall performance while consuming only 6.7 mA from 1.2 V supply. The input return loss is better than -26 dB and the ultra low noise figure of 1.43 dB leads to high sensitivity of the GNSS receiver. The input 1 dB compression point is -43 dBm at the high gain of 48 dB. The designed circuit is fabricated in 55 nm CMOS technology and the die area, which is much smaller than traditional circuit, is around 220 × 280 μm2.

Exceptional points enhance sensing in an optical microcavity

NASA Astrophysics Data System (ADS)

Chen, Weijian; Kaya Özdemir, Şahin; Zhao, Guangming; Wiersig, Jan; Yang, Lan

2017-08-01

Sensors play an important part in many aspects of daily life such as infrared sensors in home security systems, particle sensors for environmental monitoring and motion sensors in mobile phones. High-quality optical microcavities are prime candidates for sensing applications because of their ability to enhance light-matter interactions in a very confined volume. Examples of such devices include mechanical transducers, magnetometers, single-particle absorption spectrometers, and microcavity sensors for sizing single particles and detecting nanometre-scale objects such as single nanoparticles and atomic ions. Traditionally, a very small perturbation near an optical microcavity introduces either a change in the linewidth or a frequency shift or splitting of a resonance that is proportional to the strength of the perturbation. Here we demonstrate an alternative sensing scheme, by which the sensitivity of microcavities can be enhanced when operated at non-Hermitian spectral degeneracies known as exceptional points. In our experiments, we use two nanoscale scatterers to tune a whispering-gallery-mode micro-toroid cavity, in which light propagates along a concave surface by continuous total internal reflection, in a precise and controlled manner to exceptional points. A target nanoscale object that subsequently enters the evanescent field of the cavity perturbs the system from its exceptional point, leading to frequency splitting. Owing to the complex-square-root topology near an exceptional point, this frequency splitting scales as the square root of the perturbation strength and is therefore larger (for sufficiently small perturbations) than the splitting observed in traditional non-exceptional-point sensing schemes. Our demonstration of exceptional-point-enhanced sensitivity paves the way for sensors with unprecedented sensitivity.

The Autogram: An effective approach for selecting the optimal demodulation band in rolling element bearings diagnosis

NASA Astrophysics Data System (ADS)

Moshrefzadeh, Ali; Fasana, Alessandro

2018-05-01

Envelope analysis is one of the most advantageous methods for rolling element bearing diagnostics but finding a suitable frequency band for demodulation has been a substantial challenge for a long time. Introduction of the Spectral Kurtosis (SK) and Kurtogram mostly solved this problem but in situations where signal to noise ratio is very low or in presence of non-Gaussian noise these methods will fail. This major drawback may noticeably decrease their effectiveness and goal of this paper is to overcome this problem. Vibration signals from rolling element bearings exhibit high levels of second-order cyclostationarity, especially in the presence of localized faults. The autocovariance function of a 2nd order cyclostationary signal is periodic and the proposed method, named Autogram, takes advantage of this property to enhance the conventional Kurtogram. The method computes the kurtosis of the unbiased Autocorrelation (AC) of the squared envelope of the demodulated signal, rather than the kurtosis of the filtered time signal. Moreover, to take advantage of unique features of the lower and upper portions of the AC, two modified forms of kurtosis are introduced and the resulting colormaps are called Upper and Lower Autogram. In addition, a thresholding method is also proposed to enhance the quality of the frequency spectrum analysis. A new indicator, Combined Squared Envelope Spectrum, is employed to consider all the frequency bands with valuable diagnostic information and to improve the fault detectability of the Autogram. The proposed method is tested on experimental data and compared with literature results so to assess its performances in rolling element bearing diagnostics.

Characterization of an electrochemical mercury sensor using alternating current, cyclic, square wave and differential pulse voltammetry.

PubMed

Guerreiro, Gabriela V; Zaitouna, Anita J; Lai, Rebecca Y

2014-01-31

Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

Illumination Modulation for Improved Propagation-Based Phase Imaging

NASA Astrophysics Data System (ADS)

Chakraborty, Tonmoy

Propagation-based phase imaging enables the quantitative reconstruction of a light beam's phase from measurements of its intensity. Because the intensity depends on the time-averaged square of the field the relationship between intensity and phase is, in general, nonlinear. The transport of intensity equation (TIE), is a linear equation relating phase and propagated intensity that arises from restricting the propagation distance to be small. However, the TIE limits the spatial frequencies that can be reliably reconstructed to those below some cutoff, which limits the accuracy of reconstruction of fine features in phase. On the other hand, the low frequency components suffer from poor signal to noise ratio (SNR) unless the propagation distance is sufficiently large, which leads to low frequency artifacts that obscure the reconstruction. In this research, I will consider the use of incoherent primary sources of illumination, in a Kohler illumination setup, to enhance the low-frequency performance of the TIE. The necessary steps required to design and build a table-top imaging setup which is capable of capturing intensity at any defocused position while modulating the source will be explained. In addition, it will be shown how by employing such illumination, the steps required for computationally recovering the phase, i.e. Fourier transforms and frequency-domain filtering, may be performed in the optical system. While these methods can address the low-frequency performance of the TIE, they do not extend its high-frequency cutoff. To avoid this cutoff, for objects with slowly varying phase, the contrast transfer function (CTF) model, an alternative to the TIE, can be used to recover phase. By allowing the combination of longer propagation distances and incoherent sources, it will be shown how CTF can improve performance at both high and low frequencies.

High-Level, First-Principles, Full-Dimensional Quantum Calculation of the Ro-vibrational Spectrum of the Simplest Criegee Intermediate (CH2OO).

PubMed

Li, Jun; Carter, Stuart; Bowman, Joel M; Dawes, Richard; Xie, Daiqian; Guo, Hua

2014-07-03

The ro-vibrational spectrum of the simplest Criegee intermediate (CH2OO) has been determined quantum mechanically based on nine-dimensional potential energy and dipole surfaces for its ground electronic state. The potential energy surface is fitted to more than 50 000 high-level ab initio points with a root-mean-square error of 25 cm(-1), using a recently proposed permutation invariant polynomial neural network method. The calculated rotational constants, vibrational frequencies, and spectral intensities of CH2OO are in excellent agreement with experiment. The potential energy surface provides a valuable platform for studying highly excited vibrational and unimolecular reaction dynamics of this important molecule.

Cooperation of a Dissatisfied Adaptive Prisoner's Dilemma in Spatial Structures

NASA Astrophysics Data System (ADS)

Zhang, Wen; Li, Yao-Sheng; Du, Peng; Xu, Chen

2013-10-01

We study the cooperative behavior of a dissatisfied adaptive prisoner's dilemma via a pair updating rule. We compare two kinds of relationship among the competing agents, one is the well-mixed population and the other is the two-dimensional square lattice. It is found that the cooperation emerges in both the cases and the frequency of cooperation is enhanced in the square lattice. Though it is impossible for the cooperators to have a higher average payoff than that of the defectors in the well-mixed case, the cooperators in the spatial square lattice could have higher average payoffs in certain regions of the game parameters. We theoretically analyze the well-mixed case exactly and the square lattice by pair approximation. The theoretic results are in agreement with the simulation data.

An assessment of a conical horn waveguide to represent the human eardrum

NASA Astrophysics Data System (ADS)

Fields, Taylor N.; Schnetzer, Lucia; Brister, Eileen; Yates, Charles W.; Withnell, Robert H.

2018-05-01

This study examined a model of the acoustic input impedance of the ear that includes a waveguide model of the eardrum. The eardrum was modeled as a lossless conical-horn with rigid walls. The ear canal was modeled as a one-dimensional lossy transmission line. The output impedance of the eardrum, the middle ear, and the cochlea, was modeled as a circuit analog. The model was fit to acoustic input impedance data from human ears using a nonlinear least-squares fit. The impact of a conical-horn shape for the eardrum was quantified by comparison with the eardrum modeled as a near-flat surface. The model provided a good match to the data over the frequency range examined. A conical-horn model of the human eardrum provided gain at high frequencies, most notably above 1–2 kHz, with a broader middle-ear frequency response. This finding may suggest that eardrum shape plays an important role in sound transmission to the cochlea.

Inflammatory cytokine response and reduced heart rate variability in newborns with hypoxic-ischemic encephalopathy.

PubMed

Al-Shargabi, T; Govindan, R B; Dave, R; Metzler, M; Wang, Y; du Plessis, A; Massaro, A N

2017-06-01

To determine whether systemic inflammation-modulating cytokine expression is related to heart rate variability (HRV) in newborns with hypoxic-ischemic encephalopathy (HIE). The data from 30 newborns with HIE were analyzed. Cytokine levels (IL-2, IL-4, IL-6, IL-8, IL-10, IL-13, IL-1β, TNF-α, IFN-λ) were measured either at 24 h of cooling (n=5), 72 h of cooling (n=4) or at both timepoints (n=21). The following HRV metrics were quantified in the time domain: alpha_S, alpha_L, root mean square (RMS) at short time scales (RMS_S), RMS at long time scales (RMS_L), while low-frequency power (LF) and high-frequency power (HF) were quantified in the frequency domain. The relationships between HRV metrics and cytokines were evaluated using mixed-models. IL-6, IL-8, IL-10, and IL-13 levels were inversely related to selected HRV metrics. Inflammation-modulating cytokines may be important mediators in the autonomic dysfunction observed in newborns with HIE.

Modal analysis of graphene-based structures for large deformations, contact and material nonlinearities

NASA Astrophysics Data System (ADS)

Ghaffari, Reza; Sauer, Roger A.

2018-06-01

The nonlinear frequencies of pre-stressed graphene-based structures, such as flat graphene sheets and carbon nanotubes, are calculated. These structures are modeled with a nonlinear hyperelastic shell model. The model is calibrated with quantum mechanics data and is valid for high strains. Analytical solutions of the natural frequencies of various plates are obtained for the Canham bending model by assuming infinitesimal strains. These solutions are used for the verification of the numerical results. The performance of the model is illustrated by means of several examples. Modal analysis is performed for square plates under pure dilatation or uniaxial stretch, circular plates under pure dilatation or under the effects of an adhesive substrate, and carbon nanotubes under uniaxial compression or stretch. The adhesive substrate is modeled with van der Waals interaction (based on the Lennard-Jones potential) and a coarse grained contact model. It is shown that the analytical natural frequencies underestimate the real ones, and this should be considered in the design of devices based on graphene structures.

A New Strategy for ECG Baseline Wander Elimination Using Empirical Mode Decomposition

NASA Astrophysics Data System (ADS)

Shahbakhti, Mohammad; Bagheri, Hamed; Shekarchi, Babak; Mohammadi, Somayeh; Naji, Mohsen

2016-06-01

Electrocardiogram (ECG) signals might be affected by various artifacts and noises that have biological and external sources. Baseline wander (BW) is a low-frequency artifact that may be caused by breathing, body movements and loose sensor contact. In this paper, a novel method based on empirical mode decomposition (EMD) for removal of baseline noise from ECG is presented. When compared to other EMD-based methods, the novelty of this research is to reach the optimized number of decomposed levels for ECG BW de-noising using mean power frequency (MPF), while the reduction of processing time is considered. To evaluate the performance of the proposed method, a fifth-order Butterworth high pass filtering (BHPF) with cut-off frequency at 0.5Hz and wavelet approach are applied. Three performance indices, signal-to-noise ratio (SNR), mean square error (MSE) and correlation coefficient (CC), between pure and filtered signals have been utilized for qualification of presented techniques. Results suggest that the EMD-based method outperforms the other filtering method.

LONGITUDINAL IMPEDANCE OF THE SQUID GIANT AXON

PubMed Central

Cole, Kenneth S.; Baker, Richard F.

1941-01-01

Longitudinal alternating current impedance measurements have been made on the squid giant axon over the frequency range from 30 cycles per second to 200 kc. per second. Large sea water electrodes were used and the inter-electrode length was immersed in oil. The impedance at high frequency was approximately as predicted theoretically on the basis of the poorly conducting dielectric characteristics of the membrane previously determined. For the large majority of the axons, the impedance reached a maximum at a low frequency and the reactance then vanished at a frequency between 150 and 300 cycles per second. Below this frequency, the reactance was inductive, reaching a maximum and then approaching zero as the frequency was decreased. The inductive reactance is a property of the axon and requires that it contain an inductive structure. The variation of the impedance with interpolar distance indicates that the inductance is in the membrane. The impedance characteristics of the membrane as calculated from the measured longitudinal impedance of the axon may be expressed by an equivalent membrane circuit containing inductance, capacity, and resistance. For a square centimeter of membrane the capacity of 1 µf with dielectric loss is shunted by the series combination of a resistance of 400 ohms and an inductance of one-fifth henry. PMID:19873252

Structural-Vibration-Response Data Analysis

NASA Technical Reports Server (NTRS)

Smith, W. R.; Hechenlaible, R. N.; Perez, R. C.

1983-01-01

Computer program developed as structural-vibration-response data analysis tool for use in dynamic testing of Space Shuttle. Program provides fast and efficient time-domain least-squares curve-fitting procedure for reducing transient response data to obtain structural model frequencies and dampings from free-decay records. Procedure simultaneously identifies frequencies, damping values, and participation factors for noisy multiple-response records.

Relative sideband amplitudes versus modulation index for common functions using frequency and phase modulation. [for design and testing of communication system

NASA Technical Reports Server (NTRS)

Stocklin, F.

1973-01-01

The equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either square wave, sine wave, sawtooth or triangular modulating functions are presented. Spectral photographs and computer generated tables of modulation index vs. relative sideband amplitudes are also included.

Deterministic ion beam material adding technology for high-precision optical surfaces.

PubMed

Liao, Wenlin; Dai, Yifan; Xie, Xuhui; Zhou, Lin

2013-02-20

Although ion beam figuring (IBF) provides a highly deterministic method for the precision figuring of optical components, several problems still need to be addressed, such as the limited correcting capability for mid-to-high spatial frequency surface errors and low machining efficiency for pit defects on surfaces. We propose a figuring method named deterministic ion beam material adding (IBA) technology to solve those problems in IBF. The current deterministic optical figuring mechanism, which is dedicated to removing local protuberances on optical surfaces, is enriched and developed by the IBA technology. Compared with IBF, this method can realize the uniform convergence of surface errors, where the particle transferring effect generated in the IBA process can effectively correct the mid-to-high spatial frequency errors. In addition, IBA can rapidly correct the pit defects on the surface and greatly improve the machining efficiency of the figuring process. The verification experiments are accomplished on our experimental installation to validate the feasibility of the IBA method. First, a fused silica sample with a rectangular pit defect is figured by using IBA. Through two iterations within only 47.5 min, this highly steep pit is effectively corrected, and the surface error is improved from the original 24.69 nm root mean square (RMS) to the final 3.68 nm RMS. Then another experiment is carried out to demonstrate the correcting capability of IBA for mid-to-high spatial frequency surface errors, and the final results indicate that the surface accuracy and surface quality can be simultaneously improved.

Effect of oxygen at high pressure on spontaneous transmitter release.

PubMed

Colton, J S; Colton, C A

1978-11-01

The effect of oxygen at high pressure (OHP) on resting membrane properties (effective membrane resistance (Reff) and membrane potential (Vm)) and the spontaneous release of excitatory transmitter were examined at the lobster neuromuscular junction. Pressurization with 100% oxygen to 150 pounds per square inch gauge pressure (psig) or with nitrogen to 150 psig (7,000 mmHg nitrogen and 135 mmHg oxygen) produced a decrease in Reff associated with a hyperpolarization of Vm. These changes, however, returned to control values within 20--30 min after completion of pressurization. Spontaneous release of excitatory transmitter was shown to increase dramatically in the presence of 100% oxygen at 150 psig. The increase in miniature end-plate potential (MEPP) frequency persisted beyond the transient changes seen with Reff and Vm. This effect was selective to oxygen, as pressurization with nitrogen did not produce an increase in MEPP frequency. No change in average MEPP amplitude was seen with either OHP or pressure alone. An OHP-induced increase in MEPP frequency was also seen at the frog neuromuscular junction. The results indicate that both glutamate-mediated and acetylcholine-mediated synaptic transmission are altered by OHP.

Vertical array measurements of humpback whale songs

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Lammers, Marc O.; Pack, Adam A.; Herman, Louis

2004-05-01

The songs of eight male humpback whales were recorded at ranges varying from 20 to 40 m with a vertical array of hydrophones that had a flat frequency response to 24 kHz. The songs consisted of bursts of sounds called units. Units were organized into phrases and phrases into themes. Most of the units had mean duration between 1 and 2 s and mean silent periods between units between 1 and 2 s. Many of the recorded songs contained units that had high-frequency harmonics that extended beyond 22 kHz. These harmonic results suggest that humpback whale songs have a broadband quality not previously reported and may provide some insights on the high-frequency limit of hearing in these whales. The source levels of the songs were also estimated by considering the root-mean-square sound-pressure level referenced to 1 m for the unit with the largest level for different phrase within a song. Source levels varied between 171 to 189 dB re: 1 μPa. Singing escorts have been regularly observed within two whale lengths of females and these observations and knowledge of source levels provide estimates of sound-pressure levels that male humpback whales expose female whales to.

Month-to-Month and Year-to-Year Reproducibility of High Frequency QRS ECG signals

NASA Technical Reports Server (NTRS)

Batdorf, Niles; Feiveson, Alan H.; Schlegel, Todd T.

2006-01-01

High frequency (HF) electrocardiography analyzing the entire QRS complex in the frequency range of 150 to 250 Hz may prove useful in the detection of coronary artery disease, yet the long-term stability of these waveforms has not been fully characterized. We therefore prospectively investigated the reproducibility of the root mean squared (RMS) voltage, kurtosis, and the presence versus absence of reduced amplitude zones (RAzs) in signal averaged 12-lead HF QRS recordings acquired in the supine position one month apart in 16 subjects and one year apart in 27 subjects. Reproducibility of RMS voltage and kurtosis was excellent over these time intervals in the limb leads, and acceptable in the precordial leads using both the V-lead and CR-lead derivations. The relative error of RMS voltage was 12% month-to-month and 16% year-to-year in the serial recordings when averaged over all 12 leads. RAzs were also reproducible at a rate of up to 87% and 8 1 %, respectively, for the month-to-month and year-to-year recordings. We conclude that 12-lead HF QRS electrocardiograms are sufficiently reproducible for clinical use.

Liquid density analysis of sucrose and alcoholic beverages using polyimide guided Love-mode acoustic wave sensors

NASA Astrophysics Data System (ADS)

Turton, Andrew; Bhattacharyya, Debabrata; Wood, David

2006-02-01

A liquid density sensor using Love-mode acoustic waves has been developed which is suitable for use in the food and drinks industries. The sensor has an open flat surface allowing immersion into a sample and simple cleaning. A polyimide waveguide layer allows cheap and simple fabrication combined with a robust chemically resistant surface. The low shear modulus of polyimide allows thin guiding layers giving a high sensitivity. A dual structure with a smooth reference device exhibiting viscous coupling with the wave, and a patterned sense area to trap the liquid causing mass loading, allows discrimination of the liquid density from the square root of the density-viscosity product (ρη)0.5. Frequency shift and insertion loss change were proportional to (ρη)0.5 with a non-linear response due to the non-Newtonian nature of viscous liquids at high frequencies. Measurements were made with sucrose solutions up to 50% and different alcoholic drinks. A maximum sensitivity of 0.13 µg cm-3 Hz-1 was achieved, with a linear frequency response to density. This is the highest liquid density sensitivity obtained for acoustic mode sensors to the best of our knowledge.

E-beam high voltage switching power supply

DOEpatents

Shimer, Daniel W.; Lange, Arnold C.

1997-01-01

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360.degree./n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

E-beam high voltage switching power supply

DOEpatents

Shimer, D.W.; Lange, A.C.

1997-03-11

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360{degree}/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load. 7 figs.

The effect of ultrasonic nanocrystalline surface modification on the high-frequency fretting wear behavior of AISI304 steel.

PubMed

Cho, In-Shik; Lee, Chang-Soon; Amanov, Auezhan; Pyoun, Young-Shik; Park, In-Gyu

2011-01-01

The fact that one of fundamental characteristics of fretting is the very small sliding amplitude dictates the unique feature of wear mechanism. Ultrasonic Nanocrystalline Surface Modification (UNSM) technology was applied in order to investigate its effect on the high-frequency fretting wear behavior of AISI304 steel. Its influence on the fretting wear is also reported in this paper with these treated and untreated samples. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. UNSM creates homogenous nanocrystalline structures as well on the surface. UNSM process is expected to eliminate or significantly retard the formation of fretting wear. Nanocrystalline structure generation after UNSM has been reported to produce its unique structure and to offer a variety of beneficial properties compared to conventionally treated materials. A deformed layer of 220 microm exhibits high dislocation density, where top layer transformed to a nanostructure of the grain size in 23 nm and mechanical twins were observed. Deformation-induced martensite was observed to form at the intersections of mechanical twins, whose volume fraction has increased up to 38.4% and wear loss rate at 800,000 cycles has decreased by 40%. In this paper, experimental results are discussed to elucidate potential mechanism of high-frequency fretting wear.

A digital optical phase-locked loop for diode lasers based on field programmable gate array

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

Xu Zhouxiang; Zhang Xian; Huang Kaikai

2012-09-15

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat notemore » line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.« less

A//r//m//s AND SEISMIC SOURCE STUDIES.

USGS Publications Warehouse

Hanks, T.C.; ,

1984-01-01

This paper briefly summarizes some recent developments in studies of seismic source parameter estimation, emphasizing the essential similarities between mining-induced seismogenic-failure and naturally occurring, tectonically driven earthquakes. The root-mean-square acceleration, a//r//m//s, shows much promise as an observational measure of high-frequency ground motion; it is very stable observationally, is insensitive to radiation pattern, and can be related linearly to the dynamic stress differences arising in the faulting process. To interpret a//r//m//s correctly, however, requires knowledge of f//m//a//x, the high-frequency band-limitation of the radiated field of earthquakes. As a practical matter, f//m//a//x can be due to any number of causes, but an essential ambiguity is whether or not f//m//a//x can arise from source properties alone. The interaction of the aftershocks of the Oroville, California, earthquake illustrates how a//r//m//s stress drops may be connected to detailed seismicity patterns.

High-resolution time-frequency representation of EEG data using multi-scale wavelets

NASA Astrophysics Data System (ADS)

Li, Yang; Cui, Wei-Gang; Luo, Mei-Lin; Li, Ke; Wang, Lina

2017-09-01

An efficient time-varying autoregressive (TVAR) modelling scheme that expands the time-varying parameters onto the multi-scale wavelet basis functions is presented for modelling nonstationary signals and with applications to time-frequency analysis (TFA) of electroencephalogram (EEG) signals. In the new parametric modelling framework, the time-dependent parameters of the TVAR model are locally represented by using a novel multi-scale wavelet decomposition scheme, which can allow the capability to capture the smooth trends as well as track the abrupt changes of time-varying parameters simultaneously. A forward orthogonal least square (FOLS) algorithm aided by mutual information criteria are then applied for sparse model term selection and parameter estimation. Two simulation examples illustrate that the performance of the proposed multi-scale wavelet basis functions outperforms the only single-scale wavelet basis functions or Kalman filter algorithm for many nonstationary processes. Furthermore, an application of the proposed method to a real EEG signal demonstrates the new approach can provide highly time-dependent spectral resolution capability.

Robust Timing Synchronization in Aeronautical Mobile Communication Systems

NASA Technical Reports Server (NTRS)

Xiong, Fu-Qin; Pinchak, Stanley

2004-01-01

This work details a study of robust synchronization schemes suitable for satellite to mobile aeronautical applications. A new scheme, the Modified Sliding Window Synchronizer (MSWS), is devised and compared with existing schemes, including the traditional Early-Late Gate Synchronizer (ELGS), the Gardner Zero-Crossing Detector (GZCD), and the Sliding Window Synchronizer (SWS). Performance of the synchronization schemes is evaluated by a set of metrics that indicate performance in digital communications systems. The metrics are convergence time, mean square phase error (or root mean-square phase error), lowest SNR for locking, initial frequency offset performance, midstream frequency offset performance, and system complexity. The performance of the synchronizers is evaluated by means of Matlab simulation models. A simulation platform is devised to model the satellite to mobile aeronautical channel, consisting of a Quadrature Phase Shift Keying modulator, an additive white Gaussian noise channel, and a demodulator front end. Simulation results show that the MSWS provides the most robust performance at the cost of system complexity. The GZCD provides a good tradeoff between robustness and system complexity for communication systems that require high symbol rates or low overall system costs. The ELGS has a high system complexity despite its average performance. Overall, the SWS, originally designed for multi-carrier systems, performs very poorly in single-carrier communications systems. Table 5.1 in Section 5 provides a ranking of each of the synchronization schemes in terms of the metrics set forth in Section 4.1. Details of comparison are given in Section 5. Based on the results presented in Table 5, it is safe to say that the most robust synchronization scheme examined in this work is the high-sample-rate Modified Sliding Window Synchronizer. A close second is its low-sample-rate cousin. The tradeoff between complexity and lowest mean-square phase error determines the rankings of the Gardner Zero-Crossing Detector and both versions of the Early-Late Gate Synchronizer. The least robust models are the high and low-sample-rate Sliding Window Synchronizers. Consequently, the recommended replacement synchronizer for NASA's Advanced Air Transportation Technologies mobile aeronautical communications system is the high-sample-rate Modified Sliding Window Synchronizer. By incorporating this synchronizer into their system, NASA can be assured that their system will be operational in extremely adverse conditions. The quick convergence time of the MSWS should allow the use of high-level protocols. However, if NASA feels that reduced system complexity is the most important aspect of their replacement synchronizer, the Gardner Zero-Crossing Detector would be the best choice.

Optical NOR logic gate design on square lattice photonic crystal platform

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

D’souza, Nirmala Maria, E-mail: nirmala@cukerala.ac.in; Mathew, Vincent, E-mail: vincent@cukerala.ac.in

We numerically demonstrate a new configuration of all-optical NOR logic gate with square lattice photonic crystal (PhC) waveguide using finite difference time domain (FDTD) method. The logic operations are based on interference effect of optical waves. We have determined the operating frequency range by calculating the band structure for a perfectly periodic PhC using plane wave expansion (PWE) method. Response time of this logic gate is 1.98 ps and it can be operated with speed about 513 GB/s. The proposed device consists of four linear waveguides and a square ring resonator waveguides on PhC platform.

E-beam high voltage switching power supply

DOEpatents

Shimer, D.W.; Lange, A.C.

1996-10-15

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 figs.

E-beam high voltage switching power supply

DOEpatents

Shimer, Daniel W.; Lange, Arnold C.

1996-01-01

A high-power power supply produces a controllable, constant high voltage put under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

Effects of frequency and duration on psychometric functions for detection of increments and decrements in sinusoids in noise.

PubMed

Moore, B C; Peters, R W; Glasberg, B R

1999-12-01

Psychometric functions for detecting increments or decrements in level of sinusoidal pedestals were measured for increment and decrement durations of 5, 10, 20, 50, 100, and 200 ms and for frequencies of 250, 1000, and 4000 Hz. The sinusoids were presented in background noise intended to mask spectral splatter. A three-interval, three-alternative procedure was used. The results indicated that, for increments, the detectability index d' was approximately proportional to delta I/I. For decrements, d' was approximately proportional to delta L. The slopes of the psychometric functions increased (indicating better performance) with increasing frequency for both increments and decrements. For increments, the slopes increased with increasing increment duration up to 200 ms at 250 and 1000 Hz, but at 4000 Hz they increased only up to 50 ms. For decrements, the slopes increased for durations up to 50 ms, and then remained roughly constant, for all frequencies. For a center frequency of 250 Hz, the slopes of the psychometric functions for increment detection increased with duration more rapidly than predicted by a "multiple-looks" hypothesis, i.e., more rapidly than the square root of duration, for durations up to 50 ms. For center frequencies of 1000 and 4000 Hz, the slopes increased less rapidly than predicted by a multiple-looks hypothesis, for durations greater than about 20 ms. The slopes of the psychometric functions for decrement detection increased with decrement duration at a rate slightly greater than the square root of duration, for durations up to 50 ms, at all three frequencies. For greater durations, the increase in slope was less than proportional to the square root of duration. The results were analyzed using a model incorporating a simulated auditory filter, a compressive nonlinearity, a sliding temporal integrator, and a decision device based on a template mechanism. The model took into account the effects of both the external noise and an assumed internal noise. The model was able to account for the major features of the data for both increment and decrement detection.

Optimal Frequency-Domain System Realization with Weighting

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Maghami, Peiman G.

1999-01-01

Several approaches are presented to identify an experimental system model directly from frequency response data. The formulation uses a matrix-fraction description as the model structure. Frequency weighting such as exponential weighting is introduced to solve a weighted least-squares problem to obtain the coefficient matrices for the matrix-fraction description. A multi-variable state-space model can then be formed using the coefficient matrices of the matrix-fraction description. Three different approaches are introduced to fine-tune the model using nonlinear programming methods to minimize the desired cost function. The first method uses an eigenvalue assignment technique to reassign a subset of system poles to improve the identified model. The second method deals with the model in the real Schur or modal form, reassigns a subset of system poles, and adjusts the columns (rows) of the input (output) influence matrix using a nonlinear optimizer. The third method also optimizes a subset of poles, but the input and output influence matrices are refined at every optimization step through least-squares procedures.

Detection of main tidal frequencies using least squares harmonic estimation method

NASA Astrophysics Data System (ADS)

Mousavian, R.; Hossainali, M. Mashhadi

2012-11-01

In this paper the efficiency of the method of Least Squares Harmonic Estimation (LS-HE) for detecting the main tidal frequencies is investigated. Using this method, the tidal spectrum of the sea level data is evaluated at two tidal stations: Bandar Abbas in south of Iran and Workington on the eastern coast of the UK. The amplitudes of the tidal constituents at these two tidal stations are not the same. Moreover, in contrary to the Workington station, the Bandar Abbas tidal record is not an equispaced time series. Therefore, the analysis of the hourly tidal observations in Bandar Abbas and Workington can provide a reasonable insight into the efficiency of this method for analyzing the frequency content of tidal time series. Furthermore, applying the method of Fourier transform to the Workington tidal record provides an independent source of information for evaluating the tidal spectrum proposed by the LS-HE method. According to the obtained results, the spectrums of these two tidal records contain the components with the maximum amplitudes among the expected ones in this time span and some new frequencies in the list of known constituents. In addition, in terms of frequencies with maximum amplitude; the power spectrums derived from two aforementioned methods are the same. These results demonstrate the ability of LS-HE for identifying the frequencies with maximum amplitude in both tidal records.

Design and characterization of a high-power ultrasound driver with ultralow-output impedance

NASA Astrophysics Data System (ADS)

Lewis, George K.; Olbricht, William L.

2009-11-01

We describe a pocket-sized ultrasound driver with an ultralow-output impedance amplifier circuit (less than 0.05 Ω) that can transfer more than 99% of the voltage from a power supply to the ultrasound transducer with minimal reflections. The device produces high-power acoustical energy waves while operating at lower voltages than conventional ultrasound driving systems because energy losses owing to mismatched impedance are minimized. The peak performance of the driver is measured experimentally with a PZT-4, 1.54 MHz, piezoelectric ceramic, and modeled using an adjusted Mason model over a range of transducer resonant frequencies. The ultrasound driver can deliver a 100 Vpp (peak to peak) square-wave signal across 0-8 MHz ultrasound transducers in 5 ms bursts through continuous wave operation, producing acoustic powers exceeding 130 W. Effects of frequency, output impedance of the driver, and input impedance of the transducer on the maximum acoustic output power of piezoelectric transducers are examined. The small size, high power, and efficiency of the ultrasound driver make this technology useful for research, medical, and industrial ultrasonic applications.

Design and characterization of a high-power ultrasound driver with ultralow-output impedance.

PubMed

Lewis, George K; Olbricht, William L

2009-11-01

We describe a pocket-sized ultrasound driver with an ultralow-output impedance amplifier circuit (less than 0.05 ohms) that can transfer more than 99% of the voltage from a power supply to the ultrasound transducer with minimal reflections. The device produces high-power acoustical energy waves while operating at lower voltages than conventional ultrasound driving systems because energy losses owing to mismatched impedance are minimized. The peak performance of the driver is measured experimentally with a PZT-4, 1.54 MHz, piezoelectric ceramic, and modeled using an adjusted Mason model over a range of transducer resonant frequencies. The ultrasound driver can deliver a 100 V(pp) (peak to peak) square-wave signal across 0-8 MHz ultrasound transducers in 5 ms bursts through continuous wave operation, producing acoustic powers exceeding 130 W. Effects of frequency, output impedance of the driver, and input impedance of the transducer on the maximum acoustic output power of piezoelectric transducers are examined. The small size, high power, and efficiency of the ultrasound driver make this technology useful for research, medical, and industrial ultrasonic applications.

Precision Isotope Shift Measurements in Calcium Ions Using Quantum Logic Detection Schemes.

PubMed

Gebert, Florian; Wan, Yong; Wolf, Fabian; Angstmann, Christopher N; Berengut, Julian C; Schmidt, Piet O

2015-07-31

We demonstrate an efficient high-precision optical spectroscopy technique for single trapped ions with nonclosed transitions. In a double-shelving technique, the absorption of a single photon is first amplified to several phonons of a normal motional mode shared with a cotrapped cooling ion of a different species, before being further amplified to thousands of fluorescence photons emitted by the cooling ion using the standard electron shelving technique. We employ this extension of the photon recoil spectroscopy technique to perform the first high precision absolute frequency measurement of the 2D(3/2)→2P(1/2) transition in calcium, resulting in a transition frequency of f=346 000 234 867(96)  kHz. Furthermore, we determine the isotope shift of this transition and the 2S(1/2)→2P(1/2) transition for 42Ca+, 44Ca+, and 48Ca+ ions relative to 40Ca+ with an accuracy below 100 kHz. Improved field and mass shift constants of these transitions as well as changes in mean square nuclear charge radii are extracted from this high resolution data.

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.

[Burnout syndrome in teachers from two universities in Popayán, Colombia].

PubMed

Correa-Correa, Zamanda; Muñoz-Zambrano, Isabel; Chaparro, Andrés F

2010-08-01

Evaluating professional exhaustion or burnout syndrome: background, syndrome and consequences amongst half-time and full-time staff working in two private universities in the city of Popayán during 2008. The study population included 44 male and female participants aged 20 to 40 who were evaluated by using a brief burnout questionnaire (BBQ). This questionnaire had been validated for Latin-American and for teachers. It was not exclusively focused on the structure of the syndrome itself but rather included background elements and consequences. The study was quantitative and cross-sectional, having a deductive hypothetical methodological focus. Descriptive statistics and the Chi-square test were used for data analysis, accepting p<0.05 statistical significance. The analysis was univariate and bivariate. The results indicated low burnout syndrome frequency in the study population. However, 9.1 % high depersonalization frequency was found (i.e. teachers had developed negative attitudes and were insensitive to those receiving their services) and 15.9 % and 9.1 % frequencies for high physical and social consequences, respectively. Bivariate analysis revealed significant association of several factors. The results indicated low burnout syndrome frequency in this population. However, factors which were highly associated with physical and social consequences were: being male, aged 20 to 40, having a marital relationship with a habitual partner, working full-time, working at home and spending more than 75 % of the working day interacting with the beneficiaries of the services being provided.

Experimental evaluation of leaky least-mean-square algorithms for active noise reduction in communication headsets.

PubMed

Cartes, David A; Ray, Laura R; Collier, Robert D

2002-04-01

An adaptive leaky normalized least-mean-square (NLMS) algorithm has been developed to optimize stability and performance of active noise cancellation systems. The research addresses LMS filter performance issues related to insufficient excitation, nonstationary noise fields, and time-varying signal-to-noise ratio. The adaptive leaky NLMS algorithm is based on a Lyapunov tuning approach in which three candidate algorithms, each of which is a function of the instantaneous measured reference input, measurement noise variance, and filter length, are shown to provide varying degrees of tradeoff between stability and noise reduction performance. Each algorithm is evaluated experimentally for reduction of low frequency noise in communication headsets, and stability and noise reduction performance are compared with that of traditional NLMS and fixed-leakage NLMS algorithms. Acoustic measurements are made in a specially designed acoustic test cell which is based on the original work of Ryan et al. ["Enclosure for low frequency assessment of active noise reducing circumaural headsets and hearing protection," Can. Acoust. 21, 19-20 (1993)] and which provides a highly controlled and uniform acoustic environment. The stability and performance of the active noise reduction system, including a prototype communication headset, are investigated for a variety of noise sources ranging from stationary tonal noise to highly nonstationary measured F-16 aircraft noise over a 20 dB dynamic range. Results demonstrate significant improvements in stability of Lyapunov-tuned LMS algorithms over traditional leaky or nonleaky normalized algorithms, while providing noise reduction performance equivalent to that of the NLMS algorithm for idealized noise fields.

Performance enhanced miniaturized and electrically tunable patch antenna with patterned permalloy based magneto-dielectric substrate

NASA Astrophysics Data System (ADS)

Peng, Yujia; Farid Rahman, B. M.; Wang, Xuehe; Wang, Guoan

2014-05-01

Perspective magneto-dielectric materials with high permeability are potential substrates to miniaturize the patch antenna without deteriorating its performance. Besides its high permeability at high frequency, patterned Permalloy (Py) also presents tunable permeability by applying DC current. A performance enhanced miniaturized and electrically tunable patch antenna with patterned Py thin film is first presented and developed in this paper. To suppress the magnetic loss, the Py thin film layer is consisted of an array of 2 μm × 2 μm square Py patterns between the copper patch antenna and dielectric substrate. The DC current could be applied directly on Py patterns through the copper strip lines beneath the Py patterns along the length of patch antenna. The copper strip lines are specially designed with the same width of Py patterns and the thickness much less than the skin depth at the operating frequency, which can reduce their deteriorating effects to the performance of antenna. The structure of the antenna is presented and simulated with high frequency structure simulator. The results show that compared with non-magnetic antenna, the performance of Py thin film based antenna is improved with 50% bandwidth increase from 4 MHz to 8 MHz and 1.2 dB gain enhancement from 1.16 dB to 2.36 dB. The resonant frequency of the antenna could be continuously tuned from 937 MHz to 911 MHz with the permeability of Py thin film changing from 1750 to 1 900 by applying the DC current.

Autonomic cardiovascular modulation in masters and young cyclists following high-intensity interval training.

PubMed

Borges, Nattai R; Reaburn, Peter R; Doering, Thomas M; Argus, Christos K; Driller, Matthew W

2017-04-01

This study aimed at examining the autonomic cardiovascular modulation in well-trained masters and young cyclists following high-intensity interval training (HIT). Nine masters (age 55.6 ± 5.0 years) and eight young cyclists (age 25.9 ± 3.0 years) completed a HIT protocol of 6 x 30 sec at 175% of peak power output, with 4.5-min' rest between efforts. Immediately following HIT, heart rate and R-R intervals were monitored for 30-min during passive supine recovery. Autonomic modulation was examined by i) heart rate recovery in the first 60-sec of recovery (HRR 60 ); ii) the time constant of the 30-min heart rate recovery curve (HRRτ); iii) the time course of the root mean square for successive 30-sec R-R interval (RMSSD 30 ); and iv) time and frequency domain analyses of subsequent 5-min R-R interval segments. No significant between-group differences were observed for HRR 60 (P = 0.096) or HRR τ (P = 0.617). However, a significant interaction effect was found for RMSSD 30 (P = 0.021), with the master cyclists showing higher RMSSD 30 values following HIT. Similar results were observed in the time and frequency domain analyses with significant interaction effects found for the natural logarithm of the RMSSD (P = 0.008), normalised low-frequency power (P = 0.016) and natural logarithm of high-frequency power (P = 0.012). Following high-intensity interval training, master cyclists demonstrated greater post-exercise parasympathetic reactivation compared to young cyclists, indicating that physical training at older ages has significant effects on autonomic function.

An open-loop system design for deep space signal processing applications

NASA Astrophysics Data System (ADS)

Tang, Jifei; Xia, Lanhua; Mahapatra, Rabi

2018-06-01

A novel open-loop system design with high performance is proposed for space positioning and navigation signal processing. Divided by functions, the system has four modules, bandwidth selectable data recorder, narrowband signal analyzer, time-delay difference of arrival estimator and ANFIS supplement processor. A hardware-software co-design approach is made to accelerate computing capability and improve system efficiency. Embedded with the proposed signal processing algorithms, the designed system is capable of handling tasks with high accuracy over long period of continuous measurements. The experiment results show the Doppler frequency tracking root mean square error during 3 h observation is 0.0128 Hz, while the TDOA residue analysis in correlation power spectrum is 0.1166 rad.

Anderson localization and ''universal'' degradation of T/sub c/ in high-temperature superconductors

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

Leavens, C.R.

Anderson, Muttalib, and Ramakrishnan (AMR) showed that strong disorder leads to a frequency (..omega..) dependent increase of the Coulomb repulsion in a three-dimensional superconductor. Their one-free-parameter theory agrees nicely with the experimentally observed decrease in T/sub c/ but only for a fitted critical resistivity (rho/sub c/) that is very much smaller than the free-electron-gas estimate (rho/sup f//sub c/). We reexamine the effect of AMR's disorder-enhanced Coulomb repulsion using the Eliashberg equations for T/sub c/ rather than the simple two-square-well aproximation to them which is suspect when there are more than two characteristic frequencies involved. The most important modification of themore » original calculation is the inclusion of the Coulomb contribution to the renormalization function Z(..omega..).« less

Distribution of rain height over subtropical region: Durban, South Africa for satellite communication systems

NASA Astrophysics Data System (ADS)

Olurotimi, E. O.; Sokoya, O.; Ojo, J. S.; Owolawi, P. A.

2018-03-01

Rain height is one of the significant parameters for prediction of rain attenuation for Earth-space telecommunication links, especially those operating at frequencies above 10 GHz. This study examines Three-parameter Dagum distribution of the rain height over Durban, South Africa. 5-year data were used to study the monthly, seasonal, and annual variations using the parameters estimated by the maximum likelihood of the distribution. The performance estimation of the distribution was determined using the statistical goodness of fit. Three-parameter Dagum distribution shows an appropriate distribution for the modeling of rain height over Durban with the Root Mean Square Error of 0.26. Also, the shape and scale parameters for the distribution show a wide variation. The probability exceedance of time for 0.01% indicates the high probability of rain attenuation at higher frequencies.

The V3, V4 and V6 bands of formaldehyde: A spectral catalog from 900 cm(-1) to 1580 cm(-1)

NASA Technical Reports Server (NTRS)

Nadler, Shachar; Reuter, D. C.; Daunt, S. J.; Johns, J. W. C.

1988-01-01

The results of a complete high resolution study of the three vibration-rotation bands v sub 3, v sub 4, and V sub 6 using both TDLs and FT-IR spectroscopy are presented. The reults are given in terms of a table of over 8000 predicted transition frequencies and strengths. A plot of the predicted and calculated spectra is shown. Over 3000 transitions were assigned and used in the simultaneous analysis of the three bands. The simultaneous fit permitted a rigorous study of Coriolis and other type iterations among bands yielding improved molecular constants. Line intensities of 28 transitions measured by a TDL and 20 transitions from FTS data were used, along with the eigenvectors from the frequency fitting, in a least squares analysis to evaluate the band strengths.

Performance evaluation of coherent free space optical communications with a double-stage fast-steering-mirror adaptive optics system depending on the Greenwood frequency.

PubMed

Liu, Wei; Yao, Kainan; Huang, Danian; Lin, Xudong; Wang, Liang; Lv, Yaowen

2016-06-13

The Greenwood frequency (GF) is influential in performance improvement for the coherent free space optical communications (CFSOC) system with a closed-loop adaptive optics (AO) unit. We analyze the impact of tilt and high-order aberrations on the mixing efficiency (ME) and bit-error-rate (BER) under different GF. The root-mean-square value (RMS) of the ME related to the RMS of the tilt aberrations, and the GF is derived to estimate the volatility of the ME. Furthermore, a numerical simulation is applied to verify the theoretical analysis, and an experimental correction system is designed with a double-stage fast-steering-mirror and a 97-element continuous surface deformable mirror. The conclusions of this paper provide a reference for designing the AO system for the CFSOC system.

A channel estimation scheme for MIMO-OFDM systems

NASA Astrophysics Data System (ADS)

He, Chunlong; Tian, Chu; Li, Xingquan; Zhang, Ce; Zhang, Shiqi; Liu, Chaowen

2017-08-01

In view of the contradiction of the time-domain least squares (LS) channel estimation performance and the practical realization complexity, a reduced complexity channel estimation method for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) based on pilot is obtained. This approach can transform the complexity of MIMO-OFDM channel estimation problem into a simple single input single output-orthogonal frequency division multiplexing (SISO-OFDM) channel estimation problem and therefore there is no need for large matrix pseudo-inverse, which greatly reduces the complexity of algorithms. Simulation results show that the bit error rate (BER) performance of the obtained method with time orthogonal training sequences and linear minimum mean square error (LMMSE) criteria is better than that of time-domain LS estimator and nearly optimal performance.

Site-specific estimation of peak-streamflow frequency using generalized least-squares regression for natural basins in Texas

USGS Publications Warehouse

Asquith, William H.; Slade, R.M.

1999-01-01

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, has developed a computer program to estimate peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency refers to the peak streamflows for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Peak-streamflow frequency estimates are needed by planners, managers, and design engineers for flood-plain management; for objective assessment of flood risk; for cost-effective design of roads and bridges; and also for the desin of culverts, dams, levees, and other flood-control structures. The program estimates peak-streamflow frequency using a site-specific approach and a multivariate generalized least-squares linear regression. A site-specific approach differs from a traditional regional regression approach by developing unique equations to estimate peak-streamflow frequency specifically for the ungaged site. The stations included in the regression are selected using an informal cluster analysis that compares the basin characteristics of the ungaged site to the basin characteristics of all the stations in the data base. The program provides several choices for selecting the stations. Selecting the stations using cluster analysis ensures that the stations included in the regression will have the most pertinent information about flooding characteristics of the ungaged site and therefore provide the basis for potentially improved peak-streamflow frequency estimation. An evaluation of the site-specific approach in estimating peak-streamflow frequency for gaged sites indicates that the site-specific approach is at least as accurate as a traditional regional regression approach.

Active Control of the Forced and Transient Response of a Finite Beam. M.S. Thesis

NASA Technical Reports Server (NTRS)

Post, John Theodore

1989-01-01

When studying structural vibrations resulting from a concentrated source, many structures may be modelled as a finite beam excited by a point source. The theoretical limit on cancelling the resulting beam vibrations by utilizing another point source as an active controller is explored. Three different types of excitation are considered, harmonic, random, and transient. In each case, a cost function is defined and minimized for numerous parameter variations. For the case of harmonic excitation, the cost function is obtained by integrating the mean squared displacement over a region of the beam in which control is desired. A controller is then found to minimize this cost function in the control interval. The control interval and controller location are continuously varied for several frequencies of excitation. The results show that control over the entire beam length is possible only when the excitation frequency is near a resonant frequency of the beam, but control over a subregion may be obtained even between resonant frequencies at the cost of increasing the vibration outside of the control region. For random excitation, the cost function is realized by integrating the expected value of the displacement squared over the interval of the beam in which control is desired. This is shown to yield the identical cost function as obtained by integrating the cost function for harmonic excitation over all excitation frequencies. As a result, it is always possible to reduce the cost function for random excitation whether controlling the entire beam or just a subregion, without ever increasing the vibration outside the region in which control is desired. The last type of excitation considered is a single, transient pulse. A cost function representative of the beam vibration is obtained by integrating the transient displacement squared over a region of the beam and over all time. The form of the controller is chosen a priori as either one or two delayed pulses. Delays constrain the controller to be causal. The best possible control is then examined while varying the region of control and the controller location. It is found that control is always possible using either one or two control pulses. The two pulse controller gives better performance than a single pulse controller, but finding the optimal delay time for the additional controllers increases as the square of the number of control pulses.

Prediction of STN-DBS Electrode Implantation Track in Parkinson's Disease by Using Local Field Potentials

PubMed Central

Telkes, Ilknur; Jimenez-Shahed, Joohi; Viswanathan, Ashwin; Abosch, Aviva; Ince, Nuri F.

2016-01-01

Optimal electrophysiological placement of the DBS electrode may lead to better long term clinical outcomes. Inter-subject anatomical variability and limitations in stereotaxic neuroimaging increase the complexity of physiological mapping performed in the operating room. Microelectrode single unit neuronal recording remains the most common intraoperative mapping technique, but requires significant expertise and is fraught by potential technical difficulties including robust measurement of the signal. In contrast, local field potentials (LFPs), owing to their oscillatory and robust nature and being more correlated with the disease symptoms, can overcome these technical issues. Therefore, we hypothesized that multiple spectral features extracted from microelectrode-recorded LFPs could be used to automate the identification of the optimal track and the STN localization. In this regard, we recorded LFPs from microelectrodes in three tracks from 22 patients during DBS electrode implantation surgery at different depths and aimed to predict the track selected by the neurosurgeon based on the interpretation of single unit recordings. A least mean square (LMS) algorithm was used to de-correlate LFPs in each track, in order to remove common activity between channels and increase their spatial specificity. Subband power in the beta band (11–32 Hz) and high frequency range (200–450 Hz) were extracted from the de-correlated LFP data and used as features. A linear discriminant analysis (LDA) method was applied both for the localization of the dorsal border of STN and the prediction of the optimal track. By fusing the information from these low and high frequency bands, the dorsal border of STN was localized with a root mean square (RMS) error of 1.22 mm. The prediction accuracy for the optimal track was 80%. Individual beta band (11–32 Hz) and the range of high frequency oscillations (200–450 Hz) provided prediction accuracies of 72 and 68% respectively. The best prediction result obtained with monopolar LFP data was 68%. These results establish the initial evidence that LFPs can be strategically fused with computational intelligence in the operating room for STN localization and the selection of the track for chronic DBS electrode implantation. PMID:27242404

High-frequency envelope inversion analysis of the 2003 Tokachi-Oki, JAPAN, earthquake (Mw8.0)

NASA Astrophysics Data System (ADS)

Nakahara, H.

2004-12-01

The 2003 Tokachi-Oki earthquake (Mw 8.0) took place on September 26, 2003 at the plate interface between the subducting Pacific plate and the Hokkaido island, northern Japan. The focal depth is around 30km and the focal mechanism is thrust type. This earthquake caused 2 missings, more than 100 injures, 2000 collapsed houses, and so on. Slip distribution on the fault plane was already estimated by inversion analyses of low-frequency seismograms. However, source characteristics for the earthquake in frequencies higher than 1 Hz is not so far clarified. In this study, we execute an envelope inversion analysis based on the method by Nakahara et al. (1998) and clarify the spatial distribution of high-frequency seismic energy radiation on the fault plane of this earthquake. We use three-component sum of mean squared velocity seismograms multiplied by a density of earth medium, which is called envelopes here, for the envelope inversion analysis. Three frequency bands of 1-2, 2-4, and 4-8 Hz are adopted. We use envelopes in the time window from the onset of S waves to the lapse time of 128 sec. Green functions of envelopes representing the energy propagation process through a scattering medium are calculated based on the radiative transfer theory, which are characterized by parameters of scattering attenuation and intrinsic absorption. We use the values obtained for eastern Hokkaido (Hoshiba, 1993). We assume the fault plane as follows: strike=249o, dip=15o, rake=130o, length=150km, width=165km with reference to a waveform inversion analysis in low frequencies (e.g. Yagi, 2003). We divide this fault plane into 110 subfaults, each of which is a 15km x 15km square. Rupture velocity is assumed to be constant. Seismic energy is radiated from a point source as soon as the rupture front passes the center of each subfault. Time function of energy radiation is assumed as a box-car function. The amount of seismic energy from all the subfaults and site amplification factors for all the stations are estimated by the envelope inversion method. Rupture velocity and the duration time of a box-car function should be estimated by a grid search. Theoretical envelopes calculated with best-fit parameters generally fit to observed ones. The rupture velocity and duration time were estimated as 3.0 km/s and 6 sec, respectively. The high-frequency seismic energy was found to be radiated mainly from two spots on the fault plane: The first one is the deeper part beneath the initial rupture point and the second is the southern shallow part of the fault plane. Radiated energy was estimated to be 7.2 × 1016J in the 1-8Hz band. Acknowledgements: We used strong-motion seismograms recorded by the K-NET and KiK-net of NIED, JAPAN.

MIMO system identification using frequency response data

NASA Technical Reports Server (NTRS)

Medina, Enrique A.; Irwin, R. D.; Mitchell, Jerrel R.; Bukley, Angelia P.

1992-01-01

A solution to the problem of obtaining a multi-input, multi-output statespace model of a system from its individual input/output frequency responses is presented. The Residue Identification Algorithm (RID) identifies the system poles from a transfer function model of the determinant of the frequency response data matrix. Next, the residue matrices of the modes are computed guaranteeing that each input/output frequency response is fitted in the least squares sense. Finally, a realization of the system is computed. Results of the application of RID to experimental frequency responses of a large space structure ground test facility are presented and compared to those obtained via the Eigensystem Realization Algorithm.

Frequency analysis via the method of moment functionals

NASA Technical Reports Server (NTRS)

Pearson, A. E.; Pan, J. Q.

1990-01-01

Several variants are presented of a linear-in-parameters least squares formulation for determining the transfer function of a stable linear system at specified frequencies given a finite set of Fourier series coefficients calculated from transient nonstationary input-output data. The basis of the technique is Shinbrot's classical method of moment functionals using complex Fourier based modulating functions to convert a differential equation model on a finite time interval into an algebraic equation which depends linearly on frequency-related parameters.

Waveguide Photonic Choke Joint with Wide Out-of-Band Rejection

NASA Technical Reports Server (NTRS)

U-yen, Kongpop; Wollack, Edward J.

2015-01-01

A photonic choke joint structure with a wide-stop-band is proposed for use as a waveguide flange interface. The structure consists of arrays of square metal pillars arranged in a periodic pattern to suppress the dominant-mode wave propagation in parallel-plate waveguide over a wide frequency bandwidth. The measurement results at microwave frequencies confirm that the structure can provide broadband suppression of more than 56dB over 6.25 times its operating frequency. Applications at millimeter wavelength are discussed.

Waveguide Photonic Choke Joint with Wide Out-of-Band Rejection

NASA Technical Reports Server (NTRS)

U-yen, Kongpop; Wollack, Edward J.

2015-01-01

A photonic choke joint structure with a wide- stop-band is proposed for use as a waveguide flange interface. The structure consists of arrays of square metal pillars arranged in a periodic pattern to suppress the dominant-mode wave propagation in parallel-plate waveguide over a wide frequency bandwidth. The measurement results at microwave frequencies confirm the structure can provide broadband suppression, more than 56 dB over 6.25 times its operating frequency. Applications at millimeter wavelength are discussed.

Iterative design of one- and two-dimensional FIR digital filters. [Finite duration Impulse Response

NASA Technical Reports Server (NTRS)

Suk, M.; Choi, K.; Algazi, V. R.

1976-01-01

The paper describes a new iterative technique for designing FIR (finite duration impulse response) digital filters using a frequency weighted least squares approximation. The technique is as easy to implement (via FFT) and as effective in two dimensions as in one dimension, and there are virtually no limitations on the class of filter frequency spectra approximated. An adaptive adjustment of the frequency weight to achieve other types of design approximation such as Chebyshev type design is discussed.

High resolution NMR imaging using a high field yokeless permanent magnet.

PubMed

Kose, Katsumi; Haishi, Tomoyuki

2011-01-01

We measured the homogeneity and stability of the magnetic field of a high field (about 1.04 tesla) yokeless permanent magnet with 40-mm gap for high resolution nuclear magnetic resonance (NMR) imaging. Homogeneity was evaluated using a 3-dimensional (3D) lattice phantom and 3D spin-echo imaging sequences. In the central sphere (20-mm diameter), peak-to-peak magnetic field inhomogeneity was about 60 ppm, and the root-mean-square was 8 ppm. We measured room temperature, magnet temperature, and NMR frequency of the magnet simultaneously every minute for about 68 hours with and without the thermal insulator of the magnet. A simple mathematical model described the magnet's thermal property. Based on magnet performance, we performed high resolution (up to [20 µm](2)) imaging with internal NMR lock sequences of several biological samples. Our results demonstrated the usefulness of the high field small yokeless permanent magnet for high resolution NMR imaging.

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

Cheng, Ke; Wang, Xiaoyun; Liu, Jingjing

Highlights: • Cu/In bilayer was fabricated by BMSMW deposition technique. • High quality CIS film was successfully fabricated. • A preferable ratio of Cu:In:S close to 1:1:2 was approached. • The SPV response as high as 6 mV was achieved. - Abstract: High-quality CuInS{sub 2} (CIS) thin films have been fabricated by sulfurization of electrodeposited copper–indium bilayer. A novel bell-like wave modulated square wave (BWMSW) electrodeposition technique is employed for the deposition of copper thin film. Three independent parameters (current or potential, frequency, duty cycle) are available for the BWMSW electrodeposition, which is different from the traditional electrodeposition technique withmore » only one adjustable parameter (current or potential). The influences of deposition parameters such as frequency, duty cycle and the concentration of complexing agent are investigated. Benefited from the high quality copper film obtained by the BWMSW technique, the indium film is electrodeposited successfully on the copper layer to form a compact copper–indium alloy bilayer. After sulfurized at 600 °C for 60 min, the phase pure CIS film is obtained with better crystallinity. The structures, morphologies and optoelectronic properties of the CIS film are also characterized.« less

A robust signal processing method for quantitative high-cycle fatigue crack monitoring using soft elastomeric capacitor sensors

NASA Astrophysics Data System (ADS)

Kong, Xiangxiong; Li, Jian; Collins, William; Bennett, Caroline; Laflamme, Simon; Jo, Hongki

2017-04-01

A large-area electronics (LAE) strain sensor, termed soft elastomeric capacitor (SEC), has shown great promise in fatigue crack monitoring. The SEC is able to monitor strain changes over a mesoscale structural surface and endure large deformations without being damaged under cracking. Previous tests verified that the SEC is able to detect, localize, and monitor fatigue crack activities under low-cycle fatigue loading. In this paper, to examine the SEC's capability of monitoring high-cycle fatigue cracks, a compact specimen is tested under cyclic tension, designed to ensure realistic crack opening sizes representative of those in real steel bridges. To overcome the difficulty of low signal amplitude and relatively high noise level under high-cycle fatigue loading, a robust signal processing method is proposed to convert the measured capacitance time history from the SEC sensor to power spectral densities (PSD) in the frequency domain, such that signal's peak-to-peak amplitude can be extracted at the dominant loading frequency. A crack damage indicator is proposed as the ratio between the square root of the amplitude of PSD and load range. Results show that the crack damage indicator offers consistent indication of crack growth.

Effect of Temperature on Heart Rate Variability in Neonatal ICU Patients With Hypoxic-Ischemic Encephalopathy.

PubMed

Massaro, An N; Campbell, Heather E; Metzler, Marina; Al-Shargabi, Tareq; Wang, Yunfei; du Plessis, Adre; Govindan, Rathinaswamy B

2017-04-01

To determine whether measures of heart rate variability are related to changes in temperature during rewarming after therapeutic hypothermia for hypoxic-ischemic encephalopathy. Prospective observational study. Level 4 neonatal ICU in a free-standing academic children's hospital. Forty-four infants with moderate to severe hypoxic-ischemic encephalopathy treated with therapeutic hypothermia. Continuous electrocardiogram data from 2 hours prior to rewarming through 2 hours after completion of rewarming (up to 10 hr) were analyzed. Median beat-to-beat interval and measures of heart rate variability were quantified including beat-to-beat interval SD, low and high frequency relative spectral power, detrended fluctuation analysis short and long α exponents (αS and αL), and root mean square short and long time scales. The relationships between heart rate variability measures and esophageal/axillary temperatures were evaluated. Heart rate variability measures low frequency, αS, and root mean square short and long time scales were negatively associated, whereas αL was positively associated, with temperature (p < 0.01). These findings signify an overall decrease in heart rate variability as temperature increased toward normothermia. Measures of heart rate variability are temperature dependent in the range of therapeutic hypothermia to normothermia. Core body temperature needs to be considered when evaluating heart rate variability metrics as potential physiologic biomarkers of illness severity in hypoxic-ischemic encephalopathy infants undergoing therapeutic hypothermia.

The reliability of nonlinear least-squares algorithm for data analysis of neural response activity during sinusoidal rotational stimulation in semicircular canal neurons.

PubMed

Ren, Pengyu; Li, Bowen; Dong, Shiyao; Chen, Lin; Zhang, Yuelin

2018-01-01

Although many mathematical methods were used to analyze the neural activity under sinusoidal stimulation within linear response range in vestibular system, the reliabilities of these methods are still not reported, especially in nonlinear response range. Here we chose nonlinear least-squares algorithm (NLSA) with sinusoidal model to analyze the neural response of semicircular canal neurons (SCNs) during sinusoidal rotational stimulation (SRS) over a nonlinear response range. Our aim was to acquire a reliable mathematical method for data analysis under SRS in vestibular system. Our data indicated that the reliability of this method in an entire SCNs population was quite satisfactory. However, the reliability was strongly negatively depended on the neural discharge regularity. In addition, stimulation parameters were the vital impact factors influencing the reliability. The frequency had a significant negative effect but the amplitude had a conspicuous positive effect on the reliability. Thus, NLSA with sinusoidal model resulted a reliable mathematical tool for data analysis of neural response activity under SRS in vestibular system and more suitable for those under the stimulation with low frequency but high amplitude, suggesting that this method can be used in nonlinear response range. This method broke out of the restriction of neural activity analysis under nonlinear response range and provided a solid foundation for future study in nonlinear response range in vestibular system.

Phase-aberration correction with a 3-D ultrasound scanner: feasibility study.

PubMed

Ivancevich, Nikolas M; Dahl, Jeremy J; Trahey, Gregg E; Smith, Stephen W

2006-08-01

We tested the feasibility of using adaptive imaging, namely phase-aberration correction, with two-dimensional (2-D) arrays and real-time, 3-D ultrasound. Because of the high spatial frequency content of aberrators, 2-D arrays, which generally have smaller pitch and thus higher spatial sampling frequency, and 3-D imaging show potential to improve the performance of adaptive imaging. Phase-correction algorithms improve image quality by compensating for tissue-induced errors in beamforming. Using the illustrative example of transcranial ultrasound, we have evaluated our ability to perform adaptive imaging with a real-time, 3-D scanner. We have used a polymer casting of a human temporal bone, root-mean-square (RMS) phase variation of 45.0 ns, full-width-half-maximum (FWHM) correlation length of 3.35 mm, and an electronic aberrator, 100 ns RMS, 3.76 mm correlation, with tissue phantoms as illustrative examples of near-field, phase-screen aberrators. Using the multilag, least-squares, cross-correlation method, we have shown the ability of 3-D adaptive imaging to increase anechoic cyst identification, image brightness, contrast-to-speckle ratio (CSR), and, in 3-D color Doppler experiments, the ability to visualize flow. For a physical aberrator skull casting we saw CSR increase by 13% from 1.01 to 1.14, while the number of detectable cysts increased from 4.3 to 7.7.

The reliability of nonlinear least-squares algorithm for data analysis of neural response activity during sinusoidal rotational stimulation in semicircular canal neurons

PubMed Central

Li, Bowen; Dong, Shiyao; Chen, Lin; Zhang, Yuelin

2018-01-01

Although many mathematical methods were used to analyze the neural activity under sinusoidal stimulation within linear response range in vestibular system, the reliabilities of these methods are still not reported, especially in nonlinear response range. Here we chose nonlinear least-squares algorithm (NLSA) with sinusoidal model to analyze the neural response of semicircular canal neurons (SCNs) during sinusoidal rotational stimulation (SRS) over a nonlinear response range. Our aim was to acquire a reliable mathematical method for data analysis under SRS in vestibular system. Our data indicated that the reliability of this method in an entire SCNs population was quite satisfactory. However, the reliability was strongly negatively depended on the neural discharge regularity. In addition, stimulation parameters were the vital impact factors influencing the reliability. The frequency had a significant negative effect but the amplitude had a conspicuous positive effect on the reliability. Thus, NLSA with sinusoidal model resulted a reliable mathematical tool for data analysis of neural response activity under SRS in vestibular system and more suitable for those under the stimulation with low frequency but high amplitude, suggesting that this method can be used in nonlinear response range. This method broke out of the restriction of neural activity analysis under nonlinear response range and provided a solid foundation for future study in nonlinear response range in vestibular system. PMID:29304173

Use of Sine Shaped High-Frequency Rhythmic Visual Stimuli Patterns for SSVEP Response Analysis and Fatigue Rate Evaluation in Normal Subjects

PubMed Central

Keihani, Ahmadreza; Shirzhiyan, Zahra; Farahi, Morteza; Shamsi, Elham; Mahnam, Amin; Makkiabadi, Bahador; Haidari, Mohsen R.; Jafari, Amir H.

2018-01-01

Background: Recent EEG-SSVEP signal based BCI studies have used high frequency square pulse visual stimuli to reduce subjective fatigue. However, the effect of total harmonic distortion (THD) has not been considered. Compared to CRT and LCD monitors, LED screen displays high-frequency wave with better refresh rate. In this study, we present high frequency sine wave simple and rhythmic patterns with low THD rate by LED to analyze SSVEP responses and evaluate subjective fatigue in normal subjects. Materials and Methods: We used patterns of 3-sequence high-frequency sine waves (25, 30, and 35 Hz) to design our visual stimuli. Nine stimuli patterns, 3 simple (repetition of each of above 3 frequencies e.g., P25-25-25) and 6 rhythmic (all of the frequencies in 6 different sequences e.g., P25-30-35) were chosen. A hardware setup with low THD rate (<0.1%) was designed to present these patterns on LED. Twenty two normal subjects (aged 23–30 (25 ± 2.1) yrs) were enrolled. Visual analog scale (VAS) was used for subjective fatigue evaluation after presentation of each stimulus pattern. PSD, CCA, and LASSO methods were employed to analyze SSVEP responses. The data including SSVEP features and fatigue rate for different visual stimuli patterns were statistically evaluated. Results: All 9 visual stimuli patterns elicited SSVEP responses. Overall, obtained accuracy rates were 88.35% for PSD and > 90% for CCA and LASSO (for TWs > 1 s). High frequency rhythmic patterns group with low THD rate showed higher accuracy rate (99.24%) than simple patterns group (98.48%). Repeated measure ANOVA showed significant difference between rhythmic pattern features (P < 0.0005). Overall, there was no significant difference between the VAS of rhythmic [3.85 ± 2.13] compared to the simple patterns group [3.96 ± 2.21], (P = 0.63). Rhythmic group had lower within group VAS variation (min = P25-30-35 [2.90 ± 2.45], max = P35-25-30 [4.81 ± 2.65]) as well as least individual pattern VAS (P25-30-35). Discussion and Conclusion: Overall, rhythmic and simple pattern groups had higher and similar accuracy rates. Rhythmic stimuli patterns showed insignificantly lower fatigue rate than simple patterns. We conclude that both rhythmic and simple visual high frequency sine wave stimuli require further research for human subject SSVEP-BCI studies. PMID:29892219

Use of Sine Shaped High-Frequency Rhythmic Visual Stimuli Patterns for SSVEP Response Analysis and Fatigue Rate Evaluation in Normal Subjects.

PubMed

Keihani, Ahmadreza; Shirzhiyan, Zahra; Farahi, Morteza; Shamsi, Elham; Mahnam, Amin; Makkiabadi, Bahador; Haidari, Mohsen R; Jafari, Amir H

2018-01-01

Background: Recent EEG-SSVEP signal based BCI studies have used high frequency square pulse visual stimuli to reduce subjective fatigue. However, the effect of total harmonic distortion (THD) has not been considered. Compared to CRT and LCD monitors, LED screen displays high-frequency wave with better refresh rate. In this study, we present high frequency sine wave simple and rhythmic patterns with low THD rate by LED to analyze SSVEP responses and evaluate subjective fatigue in normal subjects. Materials and Methods: We used patterns of 3-sequence high-frequency sine waves (25, 30, and 35 Hz) to design our visual stimuli. Nine stimuli patterns, 3 simple (repetition of each of above 3 frequencies e.g., P25-25-25) and 6 rhythmic (all of the frequencies in 6 different sequences e.g., P25-30-35) were chosen. A hardware setup with low THD rate (<0.1%) was designed to present these patterns on LED. Twenty two normal subjects (aged 23-30 (25 ± 2.1) yrs) were enrolled. Visual analog scale (VAS) was used for subjective fatigue evaluation after presentation of each stimulus pattern. PSD, CCA, and LASSO methods were employed to analyze SSVEP responses. The data including SSVEP features and fatigue rate for different visual stimuli patterns were statistically evaluated. Results: All 9 visual stimuli patterns elicited SSVEP responses. Overall, obtained accuracy rates were 88.35% for PSD and > 90% for CCA and LASSO (for TWs > 1 s). High frequency rhythmic patterns group with low THD rate showed higher accuracy rate (99.24%) than simple patterns group (98.48%). Repeated measure ANOVA showed significant difference between rhythmic pattern features ( P < 0.0005). Overall, there was no significant difference between the VAS of rhythmic [3.85 ± 2.13] compared to the simple patterns group [3.96 ± 2.21], ( P = 0.63). Rhythmic group had lower within group VAS variation (min = P25-30-35 [2.90 ± 2.45], max = P35-25-30 [4.81 ± 2.65]) as well as least individual pattern VAS (P25-30-35). Discussion and Conclusion: Overall, rhythmic and simple pattern groups had higher and similar accuracy rates. Rhythmic stimuli patterns showed insignificantly lower fatigue rate than simple patterns. We conclude that both rhythmic and simple visual high frequency sine wave stimuli require further research for human subject SSVEP-BCI studies.

Soft sensor modelling by time difference, recursive partial least squares and adaptive model updating

NASA Astrophysics Data System (ADS)

Fu, Y.; Yang, W.; Xu, O.; Zhou, L.; Wang, J.

2017-04-01

To investigate time-variant and nonlinear characteristics in industrial processes, a soft sensor modelling method based on time difference, moving-window recursive partial least square (PLS) and adaptive model updating is proposed. In this method, time difference values of input and output variables are used as training samples to construct the model, which can reduce the effects of the nonlinear characteristic on modelling accuracy and retain the advantages of recursive PLS algorithm. To solve the high updating frequency of the model, a confidence value is introduced, which can be updated adaptively according to the results of the model performance assessment. Once the confidence value is updated, the model can be updated. The proposed method has been used to predict the 4-carboxy-benz-aldehyde (CBA) content in the purified terephthalic acid (PTA) oxidation reaction process. The results show that the proposed soft sensor modelling method can reduce computation effectively, improve prediction accuracy by making use of process information and reflect the process characteristics accurately.

Forensic Discrimination of Latent Fingerprints Using Laser-Induced Breakdown Spectroscopy (LIBS) and Chemometric Approaches.

PubMed

Yang, Jun-Ho; Yoh, Jack J

2018-01-01

A novel technique is reported for separating overlapping latent fingerprints using chemometric approaches that combine laser-induced breakdown spectroscopy (LIBS) and multivariate analysis. The LIBS technique provides the capability of real time analysis and high frequency scanning as well as the data regarding the chemical composition of overlapping latent fingerprints. These spectra offer valuable information for the classification and reconstruction of overlapping latent fingerprints by implementing appropriate statistical multivariate analysis. The current study employs principal component analysis and partial least square methods for the classification of latent fingerprints from the LIBS spectra. This technique was successfully demonstrated through a classification study of four distinct latent fingerprints using classification methods such as soft independent modeling of class analogy (SIMCA) and partial least squares discriminant analysis (PLS-DA). The novel method yielded an accuracy of more than 85% and was proven to be sufficiently robust. Furthermore, through laser scanning analysis at a spatial interval of 125 µm, the overlapping fingerprints were reconstructed as separate two-dimensional forms.

Sugar and acid content of Citrus prediction modeling using FT-IR fingerprinting in combination with multivariate statistical analysis.

PubMed

Song, Seung Yeob; Lee, Young Koung; Kim, In-Jung

2016-01-01

A high-throughput screening system for Citrus lines were established with higher sugar and acid contents using Fourier transform infrared (FT-IR) spectroscopy in combination with multivariate analysis. FT-IR spectra confirmed typical spectral differences between the frequency regions of 950-1100 cm(-1), 1300-1500 cm(-1), and 1500-1700 cm(-1). Principal component analysis (PCA) and subsequent partial least square-discriminant analysis (PLS-DA) were able to discriminate five Citrus lines into three separate clusters corresponding to their taxonomic relationships. The quantitative predictive modeling of sugar and acid contents from Citrus fruits was established using partial least square regression algorithms from FT-IR spectra. The regression coefficients (R(2)) between predicted values and estimated sugar and acid content values were 0.99. These results demonstrate that by using FT-IR spectra and applying quantitative prediction modeling to Citrus sugar and acid contents, excellent Citrus lines can be early detected with greater accuracy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rapid estimation of frequency response functions by close-range photogrammetry

NASA Technical Reports Server (NTRS)

Tripp, J. S.

1985-01-01

The accuracy of a rapid method which estimates the frequency response function from stereoscopic dynamic data is computed. It is shown that reversal of the order of the operations of coordinate transformation and Fourier transformation, which provides a significant increase in computational speed, introduces error. A portion of the error, proportional to the perturbation components normal to the camera focal planes, cannot be eliminated. The remaining error may be eliminated by proper scaling of frequency data prior to coordinate transformation. Methods are developed for least squares estimation of the full 3x3 frequency response matrix for a three dimensional structure.

Laser frequency stabilization and control through offset sideband locking to optical cavities.

PubMed

Thorpe, J I; Numata, K; Livas, J

2008-09-29

We describe a class of techniques whereby a laser frequency can be stabilized to a fixed optical cavity resonance with an adjustable offset, providing a wide tuning range for the central frequency. These techniques require only minor modifications to the standard Pound-Drever-Hall locking techniques and have the advantage of not altering the intrinsic stability of the frequency reference. We discuss the expected performance and limitations of these techniques and present a laboratory investigation in which both the sideband techniques and the standard, on-tunable Pound-Drever- Hall technique reached the 100Hz/square root(Hz) level.

Temperature and frequency dependent mean free paths of renormalized phonons in nonlinear lattices

NASA Astrophysics Data System (ADS)

Li, Nianbei; Liu, Junjie; Wu, Changqin; Li, Baowen

2018-02-01

Unraveling general properties of renormalized phonons are of fundamental relevance to the heat transport in the regime of strong nonlinearity. In this work, we directly study the temperature and frequency dependent mean free path (MFP) of renormalized phonons with the newly developed numerical tuning fork method. The typical 1D nonlinear lattices such as Fermi-Pasta-Ulam β lattice and {φ }4 lattice are investigated in detail. Interestingly, it is found that the MFPs are inversely proportional to the frequencies of renormalized phonons rather than the square of phonon frequencies predicted by existing phonon scattering theory.

Is stress level related to Dengue Hemorrhagic fever cases in Semarang?

NASA Astrophysics Data System (ADS)

Purdianingrum, Julliana; Adib Mubarok, Muhammad; Putri Sunarno, Rahmah; Khairunisa, Ummi; Endah Wahyuningsih, Nur; Murwani, Retno; Budiharjo, Anto

2018-05-01

Dengue Hemorrhagic Fever (DHF) is transmitted to humans by dengue virus harboring Aedes aegypti. Immune response against viral infection can be influenced by stress as stress could weaken immune response. Stress can cause illness through physiological changes and changes in immune function. The immunological changes associated with stress were adapted from the immunological changes in response to infection. The purpose of this study was to determine the relationship between DHF cases with stress level._We used a case control study with DHF sample cases from three hospitals in Semarang city (n=27) from the period of March to May 2017 and the control groups from healthy respondents with matched age, sex, and district location (n=27). The data was processed by Chi-Square test._Levels of stress were categorized into two namely high and low tress levels. The data was normally distributed. The frequency distribution in case group at high stress category were 15 respondents (55.6%) and low stress were 12 respondents (44.4%). Meanwhile, in control group there were 8 respondents (29.6%) at high stress category and 19 respondents (70.4%) at low stress category. The Chi Square Test revealed that the p value was 0,054 and OR was 2,969. In conclusion there was no relation between stress level and Dengue Hemorrhagic Fever cases.

Voltammetric detection of the α-dicarbonyl compound: methylglyoxal as a flavoring agent in wine and beer.

PubMed

Chatterjee, Sanghamitra; Chen, Aicheng

2012-11-02

A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were cast on a glassy carbon electrode (GCE) substrate, is presented in this paper. This modified electrode exhibited excellent catalytic activity in the electroreduction of methylglyoxal, showing much higher peak currents than those measured on an unmodified GCE. The effects of different experimental and instrumental parameters, such as solution pH and square wave frequency, were examined. The reduction peak current showed a linear range of from 0.1×10(-6) to 100×10(-6)M with a 0.9979 correlation coefficient; and a low detection limit of 2.8×10(-9)M was also obtained. The proposed methodology was successfully applied to the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal. Copyright © 2012 Elsevier B.V. All rights reserved.

Maximum known stages and discharges of New York streams and their annual exceedance probabilities through September 2011

USGS Publications Warehouse

Wall, Gary R.; Murray, Patricia M.; Lumia, Richard; Suro, Thomas P.

2014-01-01

Maximum known stages and discharges at 1,400 sites on 796 streams within New York are tabulated. Stage data are reported in feet. Discharges are reported as cubic feet per second and in cubic feet per second per square mile. Drainage areas range from 0.03 to 298,800 square miles; excluding the three sites with larger drainage areas on the St. Lawrence and Niagara Rivers, which drain the Great Lakes, the maximum drainage area is 8,288 square miles (Hudson River at Albany). Most data were obtained from U.S. Geological Survey (USGS) compilations and records, but some were provided by State, local, and other Federal agencies and by private organizations. The stage and discharge information is grouped by major drainage basins and U.S. Geological Survey site number, in downstream order. Site locations and their associated drainage area, period(s) of record, stage and discharge data, and flood-frequency statistics are compiled in a Microsoft Excel spreadsheet. Flood frequencies were derived for 1,238 sites by using methods described in Bulletin 17B (Interagency Advisory Committee on Water Data, 1982), Ries and Crouse (2002), and Lumia and others (2006). Curves that “envelope” maximum discharges within their range of drainage areas were developed for each of six flood-frequency hydrologic regions and for sites on Long Island, as well as for the State of New York; the New York curve was compared with a curve derived from a plot of maximum known discharges throughout the United States. Discharges represented by the national curve range from at least 2.7 to 4.9 times greater than those represented by the New York curve for drainage areas of 1.0 and 1,000 square miles. The relative magnitudes of discharge and runoff in the six hydrologic regions of New York and Long Island suggest the largest known discharges per square mile are in the southern part of western New York and the Catskill Mountain area, and the smallest are on Long Island.

Metamaterial-based "sabre" antenna

NASA Astrophysics Data System (ADS)

Hafdallah Ouslimani, Habiba; Yuan, Tangjie; Kanane, Houcine; Priou, Alain; Collignon, Gérard; Lacotte, Guillaume

2014-05-01

The "sabre" antenna is an array of two monopole elements, vertically polarized with omnidirectional radiation patterns, and placed on either side of a composite material on the tail of an airplane. As an in-phase reflector plane, the antenna uses a compact dual-layer high-impedance surface (DL-HIS) with offset mushroom-like Sivenpiper square shape unit cells. This topology allows one to control both operational frequency and bandgap width, while reducing the total height of the antenna to under λ0/36. The designed antenna structure has a wide bandwidth higher than 24% around 1.4 GHz. The measurements and numerical simulations agree very well.

Generation of tunable plasma photonic crystals in meshed dielectric barrier discharge

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

Wang, Yongjie; Dong, Lifang, E-mail: donglfhbu@163.com; Liu, Weibo

2014-07-15

Tunable superlattice plasma photonic crystals are obtained in a meshed dielectric barrier discharge. These plasma photonic crystals are composed of thin artificial lattices and thick self-organized lattices, and can be tuned easily by adjusting the applied voltage. A plasma photonic crystal with self-organized hexagonal lattice coupled to artificial square lattice is first realized. The dispersion relations of the square sublattices with different radii, which are recorded by an intensified charge-coupled device camera, are calculated. The results show that the thick square sublattice has the higher band edge frequencies and wider band widths. Band gaps of superlattice plasma photonic crystals aremore » actually temporal integrations of those of transient sublattices.« less

A Phonocardiographic-Based Fiber-Optic Sensor and Adaptive Filtering System for Noninvasive Continuous Fetal Heart Rate Monitoring.

PubMed

Martinek, Radek; Nedoma, Jan; Fajkus, Marcel; Kahankova, Radana; Konecny, Jaromir; Janku, Petr; Kepak, Stanislav; Bilik, Petr; Nazeran, Homer

2017-04-18

This paper focuses on the design, realization, and verification of a novel phonocardiographic- based fiber-optic sensor and adaptive signal processing system for noninvasive continuous fetal heart rate (fHR) monitoring. Our proposed system utilizes two Mach-Zehnder interferometeric sensors. Based on the analysis of real measurement data, we developed a simplified dynamic model for the generation and distribution of heart sounds throughout the human body. Building on this signal model, we then designed, implemented, and verified our adaptive signal processing system by implementing two stochastic gradient-based algorithms: the Least Mean Square Algorithm (LMS), and the Normalized Least Mean Square (NLMS) Algorithm. With this system we were able to extract the fHR information from high quality fetal phonocardiograms (fPCGs), filtered from abdominal maternal phonocardiograms (mPCGs) by performing fPCG signal peak detection. Common signal processing methods such as linear filtering, signal subtraction, and others could not be used for this purpose as fPCG and mPCG signals share overlapping frequency spectra. The performance of the adaptive system was evaluated by using both qualitative (gynecological studies) and quantitative measures such as: Signal-to-Noise Ratio-SNR, Root Mean Square Error-RMSE, Sensitivity-S+, and Positive Predictive Value-PPV.

A Phonocardiographic-Based Fiber-Optic Sensor and Adaptive Filtering System for Noninvasive Continuous Fetal Heart Rate Monitoring

PubMed Central

Martinek, Radek; Nedoma, Jan; Fajkus, Marcel; Kahankova, Radana; Konecny, Jaromir; Janku, Petr; Kepak, Stanislav; Bilik, Petr; Nazeran, Homer

2017-01-01

This paper focuses on the design, realization, and verification of a novel phonocardiographic- based fiber-optic sensor and adaptive signal processing system for noninvasive continuous fetal heart rate (fHR) monitoring. Our proposed system utilizes two Mach-Zehnder interferometeric sensors. Based on the analysis of real measurement data, we developed a simplified dynamic model for the generation and distribution of heart sounds throughout the human body. Building on this signal model, we then designed, implemented, and verified our adaptive signal processing system by implementing two stochastic gradient-based algorithms: the Least Mean Square Algorithm (LMS), and the Normalized Least Mean Square (NLMS) Algorithm. With this system we were able to extract the fHR information from high quality fetal phonocardiograms (fPCGs), filtered from abdominal maternal phonocardiograms (mPCGs) by performing fPCG signal peak detection. Common signal processing methods such as linear filtering, signal subtraction, and others could not be used for this purpose as fPCG and mPCG signals share overlapping frequency spectra. The performance of the adaptive system was evaluated by using both qualitative (gynecological studies) and quantitative measures such as: Signal-to-Noise Ratio—SNR, Root Mean Square Error—RMSE, Sensitivity—S+, and Positive Predictive Value—PPV. PMID:28420215

Experimental investigation about the effect of non-axisymmetric wake impact on a low speed axial compressor

NASA Astrophysics Data System (ADS)

Liu, Jianyong; Lu, Yajun; Li, Zhiping

2010-05-01

Non-axisymmetric wake impact experiments were carried out after the best exciting frequency for a low speed axial compressor had been found by axisymmetric wake impact experiments. When the number and circumferential distribution of inlet guide vanes (IGV) are logical the wakes of non-axisymmetric IGVs can exert beneficial unsteady exciting effect on their downstream rotor flow fields and improve the compressor’s performance. In the present paper, four non-axisymmetric wake impact plans were found working better than the axisymmetric wake impact plan. Compared with the base plan, the best non-axisymmetric plan increased the compressor’s peak efficiency, and the total pressure rise by 1.1 and 2%, and enhanced the stall margin by 4.4%. The main reason why non-axisymmetric plans worked better than the axisymmetric plan was explained as the change of the unsteady exciting signal arising from IGV wakes. Besides the high-frequency components, the non-axisymmetric plan generated a beneficial low-frequency square-wave exciting signal and other secondary frequency components. Compared with the axisymmetric plan, multi-frequency exciting wakes arising from the non-axisymmetric plans are easier to get coupling relation with complex vortices such as clearance vortices, passage vortices and shedding vortices.

Standing wave brass-PZT square tubular ultrasonic motor.

PubMed

Park, Soonho; He, Siyuan

2012-09-01

This paper reports a standing wave brass-PZT tubular ultrasonic motor. The motor is composed of a brass square tube with two teeth on each tube end. Four PZT plates are attached to the outside walls of the brass tube. The motor requires only one driving signal to excite vibration in a single bending mode to generate reciprocating diagonal trajectories of teeth on the brass tube ends, which drive the motor to rotate. Bi-directional rotation is achieved by exciting different pairs of PZT plates to switch the bending vibration direction. Through using the brass-PZT tube structure, the motor can take high magnitude vibration to achieve a high output power in comparison to PZT tube based ultrasonic motors. Prototypes are fabricated and tested. The dimension of the brass-PZT tube is 3.975mm×3.975mm×16mm. Measured performance is a no-load speed of >1000RPM, a stall torque of 370μNm and a maximum output power of 16 mW when a sinusoidal driving voltage of 50V is applied. The working frequencies of the motor are 46,050Hz (clockwise) and 46,200Hz (counter-clockwise). Copyright © 2012. Published by Elsevier B.V.

Correlated environmental corrections in TOPEX/POSEIDON, with a note on ionospheric accuracy

NASA Technical Reports Server (NTRS)

Zlotnicki, V.

1994-01-01

Estimates of the effectiveness of an altimetric correction, and interpretation of sea level variability as a response to atmospheric forcing, both depend upon assuming that residual errors in altimetric corrections are uncorrelated among themselves and with residual sea level, or knowing the correlations. Not surprisingly, many corrections are highly correlated since they involve atmospheric properties and the ocean surface's response to them. The full corrections (including their geographically varying time mean values), show correlations between electromagnetic bias (mostly the height of wind waves) and either atmospheric pressure or water vapor of -40%, and between atmospheric pressure and water vapor of 28%. In the more commonly used collinear differences (after removal of the geographically varying time mean), atmospheric pressure and wave height show a -30% correlation, atmospheric pressure and water vapor a -10% correlation, both pressure and water vapor a 7% correlation with residual sea level, and a bit surprisingly, ionospheric electron content and wave height a 15% correlation. Only the ocean tide is totally uncorrelated with other corrections or residual sea level. The effectiveness of three ionospheric corrections (TOPEX dual-frequency, a smoothed version of the TOPEX dual-frequency, and Doppler orbitography and radiopositioning integrated by satellite (DORIS) is also evaluated in terms of their reduction in variance of residual sea level. Smooth (90-200 km along-track) versions of the dual-frequency altimeter ionosphere perform best both globally and within 20 deg in latitude from the equator. The noise variance in the 1/s TOPEX inospheric samples is approximately (11 mm) squared, about the same as noise in the DORIS-based correction; however, the latter has its error over scales of order 10(exp 3) km. Within 20 deg of the equator, the DORIS-based correction adds (14 mm) squared to the residual sea level variance.

Imaging electrical conductivity, permeability, and/or permittivity contrasts using the Born Scattering Inversion (BSI)

NASA Astrophysics Data System (ADS)

Darrh, A.; Downs, C. M.; Poppeliers, C.

2017-12-01

Born Scattering Inversion (BSI) of electromagnetic (EM) data is a geophysical imaging methodology for mapping weak conductivity, permeability, and/or permittivity contrasts in the subsurface. The high computational cost of full waveform inversion is reduced by adopting the First Born Approximation for scattered EM fields. This linearizes the inverse problem in terms of Born scattering amplitudes for a set of effective EM body sources within a 3D imaging volume. Estimation of scatterer amplitudes is subsequently achieved by solving the normal equations. Our present BSI numerical experiments entail Fourier transforming real-valued synthetic EM data to the frequency-domain, and minimizing the L2 residual between complex-valued observed and predicted data. We are testing the ability of BSI to resolve simple scattering models. For our initial experiments, synthetic data are acquired by three-component (3C) electric field receivers distributed on a plane above a single point electric dipole within a homogeneous and isotropic wholespace. To suppress artifacts, candidate Born scatterer locations are confined to a volume beneath the receiver array. Also, we explore two different numerical linear algebra algorithms for solving the normal equations: Damped Least Squares (DLS), and Non-Negative Least Squares (NNLS). Results from NNLS accurately recover the source location only for a large dense 3C receiver array, but fail when the array is decimated, or is restricted to horizontal component data. Using all receiver stations and all components per station, NNLS results are relatively insensitive to a sub-sampled frequency spectrum, suggesting that coarse frequency-domain sampling may be adequate for good target resolution. Results from DLS are insensitive to diminishing array density, but contain spatially oscillatory structure. DLS-generated images are consistently centered at the known point source location, despite an abundance of surrounding structure.

Observations of shallow water marine ambient sound: the low frequency underwater soundscape of the central Oregon coast.

PubMed

Haxel, Joseph H; Dziak, Robert P; Matsumoto, Haru

2013-05-01

A year-long experiment (March 2010 to April 2011) measuring ambient sound at a shallow water site (50 m) on the central OR coast near the Port of Newport provides important baseline information for comparisons with future measurements associated with resource development along the inner continental shelf of the Pacific Northwest. Ambient levels in frequencies affected by surf-generated noise (f < 100 Hz) characterize the site as a high-energy end member within the spectrum of shallow water coastal areas influenced by breaking waves. Dominant sound sources include locally generated ship noise (66% of total hours contain local ship noise), breaking surf, wind induced wave breaking and baleen whale vocalizations. Additionally, an increase in spectral levels for frequencies ranging from 35 to 100 Hz is attributed to noise radiated from distant commercial ship commerce. One-second root mean square (rms) sound pressure level (SPLrms) estimates calculated across the 10-840 Hz frequency band for the entire year long deployment show minimum, mean, and maximum values of 84 dB, 101 dB, and 152 dB re 1 μPa.

Lumbar multifidus and erector spinae electromyograms during back bridge exercise in time and frequency domains.

PubMed

Mello, Roger Gomes Tavares; Carriço, Igor Rodrigues; da Matta, Thiago Torres; Nadal, Jurandir; Oliveira, Liliam Fernandes

2016-01-01

Muscle activity is studied during trunk stabilization exercises using electromyograms (EMG) in time domain. However, the frequency domain analysis provides information that would be important to understand fatigue process. To assess EMG of lumbar multifidus (LM) and erector spinae (ES) muscles, in time and frequency domains, during back bridge exercise. Nineteen healthy young men performed the exercise for one minute and EMG was monitored by surface electromyography. Normalized root mean square (RMS) value and spectral median frequency (MF) were compared between beginning and final epochs of test. The dynamics of the MF during whole test was also obtained by short-time Fourier transform. RMS values were about 30% of maximum voluntary contraction, and LM muscle showed greater MF than ES, which did not decrease at the final of exercise. However, the slope of MF was significant mainly for LM. Muscle activation of 30% is sufficient to keep lumbar stability and is suitable to improve muscular endurance. The significance of MF slope without decreasing at the final of exercise indicates challenging muscular endurance without imply on high fatigability. Due to lower muscular demand, this exercise might be recommended for trunk stabilizing for low back pain patients.

Quantitative color measurement of pH indicator paper using trichromatic LEDs and TCS230 color sensor

NASA Astrophysics Data System (ADS)

Ghorude, T. N.; Chaudhari, A. L.; Shaligram, A. D.

2008-11-01

Quantitative analysis of pH indicator paper color is needed in the various fields. An indigenously developed Tristimulus colorimeter is used in this work for pH Indicator paper color measurement. The colorimeter uses Trichromatic RGB LEDs and a programmable color light to frequency converter (TCS230), combining configurable silicon photodiodes and a current to frequency converter on a single monolithic CMOS integrated circuit. The output is a square wave (50% duty cycle) with frequency directly proportional to light intensity. Digital input and digital output allow directly to a microcontroller. The light to frequency converter reads an 8*8 array of photodiodes. Sixteen photodiodes have red filters, 16 photodiodes have green filters, 16 photodiodes have blue filters, and 16 photodiodes are clear with no filters. All 16 photodiodes of the same colors are connected in parallel and type of photodiode the device uses during operation is pin selectable. Solutions having different standard pH were prepared and indicator paper was dipped in solution, it shows change in color. Using the developed RGB colorimeter chromaticity coordinates were measured and compared with the chromaticity coordinates measured using Ocean Optics HR-4000 high resolution spectrophotometer.

Human Commercial Models' Eye Colour Shows Negative Frequency-Dependent Selection.

PubMed

Forti, Isabela Rodrigues Nogueira; Young, Robert John

2016-01-01

In this study we investigated the eye colour of human commercial models registered in the UK (400 female and 400 male) and Brazil (400 female and 400 male) to test the hypothesis that model eye colour frequency was the result of negative frequency-dependent selection. The eye colours of the models were classified as: blue, brown or intermediate. Chi-square analyses of data for countries separated by sex showed that in the United Kingdom brown eyes and intermediate colours were significantly more frequent than expected in comparison to the general United Kingdom population (P<0.001). In Brazil, the most frequent eye colour brown was significantly less frequent than expected in comparison to the general Brazilian population. These results support the hypothesis that model eye colour is the result of negative frequency-dependent selection. This could be the result of people using eye colour as a marker of genetic diversity and finding rarer eye colours more attractive because of the potential advantage more genetically diverse offspring that could result from such a choice. Eye colour may be important because in comparison to many other physical traits (e.g., hair colour) it is hard to modify, hide or disguise, and it is highly polymorphic.

Conductivity tomography based on pulsed eddy current with SQUID magnetometer

NASA Astrophysics Data System (ADS)

Panaitov, G. I.; Krause, H.-J.; Zhang, Y.

2002-05-01

Pulsed eddy current (EC) techniques have the advantage of potentially covering a broader depth range than standard single frequency EC testing. We developed a novel pulsed EC technique using a liquid-nitrogen cooled SQUID magnetometer. For two reasons, SQUID magnetometers are particularly well suited as sensors: first they constitute an extremely sensitive magnetic field sensor, second they measure the field directly which decays more slowly than its time derivative picked up by induction coils. A square waveform transmitter signal was used, with alternating slopes in order to eliminate drift effect, and stacking synchronous to the power line frequency in order to improve signal-to-noise. The early time (high frequency) data of the recorded transient correspond to the upper layers of the conducting medium, while late time data or low frequencies deliver information on deep layers. Measurements of cracks at different depths in a stacked aluminum sample are presented. From the measured data, the apparent conductivity of the sample was calculated for each position and depth by applying a technique known from geophysical data interpretation. Thus, the position and depth of the crack was determined from the tomographic conductivity image of the sample.

High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

DOEpatents

Shimer, D.W.; Lange, A.C.

1995-05-23

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

DOEpatents

Shimer, Daniel W.; Lange, Arnold C.

1995-01-01

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

A comparative study of clock rate and drift estimation

NASA Technical Reports Server (NTRS)

Breakiron, Lee A.

1994-01-01

Five different methods of drift determination and four different methods of rate determination were compared using months of hourly phase and frequency data from a sample of cesium clocks and active hydrogen masers. Linear least squares on frequency is selected as the optimal method of determining both drift and rate, more on the basis of parameter parsimony and confidence measures than on random and systematic errors.

Stabilization of a system with saturating, non-monotone hysteresis and frequency dependent power losses by a PD controller

NASA Astrophysics Data System (ADS)

Ekanayake, D. B.; Iyer, R. V.

2015-02-01

We prove the closed loop stability of a PD controller for certain systems with saturating, non-monotone hysteresis and frequency dependent power losses. Most controllers use inverse compensators to cancel out actuator hysteresis nonlinearity. We show that we can achieve stability of the closed-loop system without an explicit inverse computation (using least squares minimization or otherwise).

Modified fast frequency acquisition via adaptive least squares algorithm

NASA Technical Reports Server (NTRS)

Kumar, Rajendra (Inventor)

1992-01-01

A method and the associated apparatus for estimating the amplitude, frequency, and phase of a signal of interest are presented. The method comprises the following steps: (1) inputting the signal of interest; (2) generating a reference signal with adjustable amplitude, frequency and phase at an output thereof; (3) mixing the signal of interest with the reference signal and a signal 90 deg out of phase with the reference signal to provide a pair of quadrature sample signals comprising respectively a difference between the signal of interest and the reference signal and a difference between the signal of interest and the signal 90 deg out of phase with the reference signal; (4) using the pair of quadrature sample signals to compute estimates of the amplitude, frequency, and phase of an error signal comprising the difference between the signal of interest and the reference signal employing a least squares estimation; (5) adjusting the amplitude, frequency, and phase of the reference signal from the numerically controlled oscillator in a manner which drives the error signal towards zero; and (6) outputting the estimates of the amplitude, frequency, and phase of the error signal in combination with the reference signal to produce a best estimate of the amplitude, frequency, and phase of the signal of interest. The preferred method includes the step of providing the error signal as a real time confidence measure as to the accuracy of the estimates wherein the closer the error signal is to zero, the higher the probability that the estimates are accurate. A matrix in the estimation algorithm provides an estimate of the variance of the estimation error.

Experiments on Laser Beam Jitter Control with Applications to a Shipboard Free Electron Laser

DTIC Science & Technology

2007-12-01

factor one half converts from peak to rms values. This psd was then converted to units of ( mrms /s2)2/Hz by dividing by the square of the given voltage...the root mean square value in units of mrms for a given frequency range. (3) Vibration Measurement Results. The total displacement from 1-400 Hz...The mass may represent, for example, a component of an FEL. The support, s, is harmonically excited at a peak displacement amplitude of xs. The

Response functions for sine- and square-wave modulations of disparity.

NASA Technical Reports Server (NTRS)

Richards, W.

1972-01-01

Depth sensations cannot be elicited by modulations of disparity that are more rapid than about 6 Hz, regardless of the modulation amplitude. Vergence tracking also fails at similar modulation rates, suggesting that this portion of the oculomotor system is limited by the behavior of disparity detectors. For sinusoidal modulations of disparity between 1/2 to 2 deg of disparity, most depth-response functions exhibit a low-frequency decrease that is not observed with square-wave modulations of disparity.

HAMP - the microwave package on the High Altitude and LOng range research aircraft (HALO)

NASA Astrophysics Data System (ADS)

Mech, M.; Orlandi, E.; Crewell, S.; Ament, F.; Hirsch, L.; Hagen, M.; Peters, G.; Stevens, B.

2014-12-01

An advanced package of microwave remote sensing instrumentation has been developed for the operation on the new German High Altitude LOng range research aircraft (HALO). The HALO Microwave Package, HAMP, consists of two nadir-looking instruments: a cloud radar at 36 GHz and a suite of passive microwave radiometers with 26 frequencies in different bands between 22.24 and 183.31 ± 12.5 GHz. We present a description of HAMP's instrumentation together with an illustration of its potential. To demonstrate this potential, synthetic measurements for the implemented passive microwave frequencies and the cloud radar based on cloud-resolving and radiative transfer model calculations were performed. These illustrate the advantage of HAMP's chosen frequency coverage, which allows for improved detection of hydrometeors both via the emission and scattering of radiation. Regression algorithms compare HAMP retrieval with standard satellite instruments from polar orbiters and show its advantages particularly for the lower atmosphere with a root-mean-square error reduced by 5 and 15% for temperature and humidity, respectively. HAMP's main advantage is the high spatial resolution of about 1 km, which is illustrated by first measurements from test flights. Together these qualities make it an exciting tool for gaining a better understanding of cloud processes, testing retrieval algorithms, defining future satellite instrument specifications, and validating platforms after they have been placed in orbit.

HAMP - the microwave package on the High Altitude and LOng range research aircraft HALO

NASA Astrophysics Data System (ADS)

Mech, M.; Orlandi, E.; Crewell, S.; Ament, F.; Hirsch, L.; Hagen, M.; Peters, G.; Stevens, B.

2014-05-01

An advanced package of microwave remote sensing instrumentation has been developed for the operation on the new German High Altitude LOng range research aircraft (HALO). The HALO Microwave Package, HAMP, consists of two nadir looking instruments: a cloud radar at 36 GHz and a suite of passive microwave radiometers with 26 frequencies in different bands between 22.24 and 183.31 ± 12.5 GHz. We present a description of HAMP's instrumentation together with an illustration of its potential. To demonstrate this potential synthetic measurements for the implemented passive microwave frequencies and the cloud radar based on cloud resolving and radiative transfer model calculations were performed. These illustrate the advantage of HAMP's chosen frequency coverage, which allows for improved detection of hydrometeors both via the emission and scattering of radiation. Regression algorithms compare HAMP retrieval with standard satellite instruments from polar orbiters and show its advantages particularly for the lower atmosphere with a reduced root mean square error by 5 and 15% for temperature and humidity, respectively. HAMP's main advantage is the high spatial resolution of about 1 km which is illustrated by first measurements from test flights. Together these qualities make it an exciting tool for gaining better understanding of cloud processes, testing retrieval algorithms, defining future satellite instrument specifications, and validating platforms after they have been placed in orbit.

GNSS Ephemeris with Graceful Degradation and Measurement Fusion

NASA Technical Reports Server (NTRS)

Garrison, James Levi (Inventor); Walker, Michael Allen (Inventor)

2015-01-01

A method for providing an extended propagation ephemeris model for a satellite in Earth orbit, the method includes obtaining a satellite's orbital position over a first period of time, applying a least square estimation filter to determine coefficients defining osculating Keplarian orbital elements and harmonic perturbation parameters associated with a coordinate system defining an extended propagation ephemeris model that can be used to estimate the satellite's position during the first period, wherein the osculating Keplarian orbital elements include semi-major axis of the satellite (a), eccentricity of the satellite (e), inclination of the satellite (i), right ascension of ascending node of the satellite (.OMEGA.), true anomaly (.theta.*), and argument of periapsis (.omega.), applying the least square estimation filter to determine a dominant frequency of the true anomaly, and applying a Fourier transform to determine dominant frequencies of the harmonic perturbation parameters.

Modulation characteristics of a high-power semiconductor Master Oscillator Power Amplifier (MOPA)

NASA Technical Reports Server (NTRS)

Cornwell, Donald Mitchell, Jr.

1992-01-01

A semiconductor master oscillator-power amplifier was demonstrated using an anti-reflection (AR) coated broad area laser as the amplifier. Under CW operation, diffraction-limited single-longitudinal-mode powers up to 340 mW were demonstrated. The characteristics of the far-field pattern were measured and compared to a two-dimensional reflective Fabry-Perot amplifier model of the device. The MOPA configuration was modulated by the master oscillator. Prior to injection into the amplifier, the amplitude and frequency modulation properties of the master oscillator were characterized. The frequency response of the MOPA configuration was characterized for an AM/FM modulated injection beam, and was found to be a function of the frequency detuning between the master oscillator and the resonant amplifier. A shift in the phase was also observed as a function of frequency detuning; this phase shift is attributed to the optical phase shift imparted to a wave reflected from a Fabry-Perot cavity. Square-wave optical pulses were generated at 10 MHz and 250 MHz with diffraction-limited peak powers of 200 mW and 250 mW. The peak power for a given modulation frequency is found to be limited by the injected power and the FM modulation at that frequency. The modulation results make the MOPA attractive for use as a transmitter source in applications such as free-space communications and ranging/altimetry.

The Engineering Development Array: A Low Frequency Radio Telescope Utilising SKA Precursor Technology

NASA Astrophysics Data System (ADS)

Wayth, Randall; Sokolowski, Marcin; Booler, Tom; Crosse, Brian; Emrich, David; Grootjans, Robert; Hall, Peter J.; Horsley, Luke; Juswardy, Budi; Kenney, David; Steele, Kim; Sutinjo, Adrian; Tingay, Steven J.; Ung, Daniel; Walker, Mia; Williams, Andrew; Beardsley, A.; Franzen, T. M. O.; Johnston-Hollitt, M.; Kaplan, D. L.; Morales, M. F.; Pallot, D.; Trott, C. M.; Wu, C.

2017-08-01

We describe the design and performance of the Engineering Development Array, which is a low-frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased array. The Engineering Development Array was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array precursor technology and expertise, specifically from the Murchison Widefield Array radio telescope. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the Engineering Development Array's receiver temperature as a function of frequency. The Engineering Development Array is shown to be sky-noise limited over most of the frequency range measured between 60 and 240 MHz. By using the Engineering Development Array in interferometric mode with the Murchison Widefield Array, we used calibrated visibilities to measure the absolute sensitivity of the array. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature. The results demonstrate the practicality and feasibility of using Murchison Widefield Array-style precursor technology for Square Kilometre Array-scale stations. The modular architecture of the Engineering Development Array allows upgrades to the array to be rolled out in a staged approach. Future improvements to the Engineering Development Array include replacing the second stage beamformer with a fully digital system, and to transition to using RF-over-fibre for the signal output from first stage beamformers.

Frequency of orthodontic extraction

PubMed Central

Dardengo, Camila de S.; Fernandes, Luciana Q. P.; Capelli, Jonas

2016-01-01

Introduction: The option of dental extraction for orthodontic purposes has been debated for more than 100 years, including periods when it was widely used in treatment, including the present, during which other methods are used to avoid dental extractions. The objective was to analyze the frequency of tooth extraction treatment performed between 1980 and 2011 at the Orthodontic Clinic of Universidade Estadual do Rio de Janeiro (UERJ). Material and Methods: The clinical records of 1484 patients undergoing orthodontic treatment were evaluated. The frequency of extractions was evaluated with regard to sex, Angle's classification, the different combinations of extractions and the period when orthodontic treatment began. Chi-square test was used to determine correlations between variables, while the chi-square test for trends was used to assess the frequency of extractions over the years. Results: There was a reduction of approximately 20% in the frequency of cases treated with tooth extraction over the last 32 years. The most frequently extracted teeth were first premolars. Patients with Class I malocclusion showed fewer extractions, while Class II patients underwent a higher number of extraction treatment. There were no statistically significant differences with regard to sex. Conclusion: New features introduced into the orthodontic clinic and new esthetic concepts contributed to reducing the number of cases treated with dental extractions. However, dental extractions for orthodontic purposes are still well indicated in certain cases. PMID:27007762

Small impact craters in the lunar regolith - Their morphologies, relative ages, and rates of formation

USGS Publications Warehouse

Moore, H.J.; Boyce, J.M.; Hahn, D.A.

1980-01-01

Apparently, there are two types of size-frequency distributions of small lunar craters (???1-100 m across): (1) crater production distributions for which the cumulative frequency of craters is an inverse function of diameter to power near 2.8, and (2) steady-state distributions for which the cumulative frequency of craters is inversely proportional to the square of their diameters. According to theory, cumulative frequencies of craters in each morphologic category within the steady-state should also be an inverse function of the square of their diameters. Some data on frequency distribution of craters by morphologic types are approximately consistent with theory, whereas other data are inconsistent with theory. A flux of crater producing objects can be inferred from size-frequency distributions of small craters on the flanks and ejecta of craters of known age. Crater frequency distributions and data on the craters Tycho, North Ray, Cone, and South Ray, when compared with the flux of objects measured by the Apollo Passive Seismometer, suggest that the flux of objects has been relatively constant over the last 100 m.y. (within 1/3 to 3 times of the flux estimated for Tycho). Steady-state frequency distributions for craters in several morphologic categories formed the basis for estimating the relative ages of craters and surfaces in a system used during the Apollo landing site mapping program of the U.S. Geological Survey. The relative ages in this system are converted to model absolute ages that have a rather broad range of values. The range of values of the absolute ages are between about 1/3 to 3 times the assigned model absolute age. ?? 1980 D. Reidel Publishing Co.

Luminaire layout: Design and implementation

NASA Technical Reports Server (NTRS)

Both, A. J.

1994-01-01

The information contained in this report was presented during the discussion regarding guidelines for PAR uniformity in greenhouses. The data shows a lighting uniformity analysis in a research greenhouse for rose production at the Cornell University campus. The luminaire layout was designed using the computer program Lumen-Micro. After implementation of the design, accurate measurements were taken in the greenhouse and the uniformity analysis for both the design and implementation were compared. A study of several supplemental lighting installations resulted in the following recommendations: include only the actual growing area in the lighting uniformity analysis; for growing areas up to 20 square meters, take four measurements per square meter; for growing areas above 20 square meters, take one measurement per square meter; use one of the uniformity criteria and frequency graphs to compare lighting uniformity amongst designs; and design for uniformity criterion of a least 0.75 and the fraction within +/- 15% of the average PAR value should be close to one.

a Unified Matrix Polynomial Approach to Modal Identification

NASA Astrophysics Data System (ADS)

Allemang, R. J.; Brown, D. L.

1998-04-01

One important current focus of modal identification is a reformulation of modal parameter estimation algorithms into a single, consistent mathematical formulation with a corresponding set of definitions and unifying concepts. Particularly, a matrix polynomial approach is used to unify the presentation with respect to current algorithms such as the least-squares complex exponential (LSCE), the polyreference time domain (PTD), Ibrahim time domain (ITD), eigensystem realization algorithm (ERA), rational fraction polynomial (RFP), polyreference frequency domain (PFD) and the complex mode indication function (CMIF) methods. Using this unified matrix polynomial approach (UMPA) allows a discussion of the similarities and differences of the commonly used methods. the use of least squares (LS), total least squares (TLS), double least squares (DLS) and singular value decomposition (SVD) methods is discussed in order to take advantage of redundant measurement data. Eigenvalue and SVD transformation methods are utilized to reduce the effective size of the resulting eigenvalue-eigenvector problem as well.

Analysis of the Magnitude and Frequency of Peak Discharge and Maximum Observed Peak Discharge in New Mexico and Surrounding Areas

USGS Publications Warehouse

Waltemeyer, Scott D.

2008-01-01

Estimates of the magnitude and frequency of peak discharges are necessary for the reliable design of bridges, culverts, and open-channel hydraulic analysis, and for flood-hazard mapping in New Mexico and surrounding areas. The U.S. Geological Survey, in cooperation with the New Mexico Department of Transportation, updated estimates of peak-discharge magnitude for gaging stations in the region and updated regional equations for estimation of peak discharge and frequency at ungaged sites. Equations were developed for estimating the magnitude of peak discharges for recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years at ungaged sites by use of data collected through 2004 for 293 gaging stations on unregulated streams that have 10 or more years of record. Peak discharges for selected recurrence intervals were determined at gaging stations by fitting observed data to a log-Pearson Type III distribution with adjustments for a low-discharge threshold and a zero skew coefficient. A low-discharge threshold was applied to frequency analysis of 140 of the 293 gaging stations. This application provides an improved fit of the log-Pearson Type III frequency distribution. Use of the low-discharge threshold generally eliminated the peak discharge by having a recurrence interval of less than 1.4 years in the probability-density function. Within each of the nine regions, logarithms of the maximum peak discharges for selected recurrence intervals were related to logarithms of basin and climatic characteristics by using stepwise ordinary least-squares regression techniques for exploratory data analysis. Generalized least-squares regression techniques, an improved regression procedure that accounts for time and spatial sampling errors, then were applied to the same data used in the ordinary least-squares regression analyses. The average standard error of prediction, which includes average sampling error and average standard error of regression, ranged from 38 to 93 percent (mean value is 62, and median value is 59) for the 100-year flood. The 1996 investigation standard error of prediction for the flood regions ranged from 41 to 96 percent (mean value is 67, and median value is 68) for the 100-year flood that was analyzed by using generalized least-squares regression analysis. Overall, the equations based on generalized least-squares regression techniques are more reliable than those in the 1996 report because of the increased length of record and improved geographic information system (GIS) method to determine basin and climatic characteristics. Flood-frequency estimates can be made for ungaged sites upstream or downstream from gaging stations by using a method that transfers flood-frequency data at the gaging station to the ungaged site by using a drainage-area ratio adjustment equation. The peak discharge for a given recurrence interval at the gaging station, drainage-area ratio, and the drainage-area exponent from the regional regression equation of the respective region is used to transfer the peak discharge for the recurrence interval to the ungaged site. Maximum observed peak discharge as related to drainage area was determined for New Mexico. Extreme events are commonly used in the design and appraisal of bridge crossings and other structures. Bridge-scour evaluations are commonly made by using the 500-year peak discharge for these appraisals. Peak-discharge data collected at 293 gaging stations and 367 miscellaneous sites were used to develop a maximum peak-discharge relation as an alternative method of estimating peak discharge of an extreme event such as a maximum probable flood.

Investigation of a nanostrip patch antenna in optical frequencies

NASA Astrophysics Data System (ADS)

Kashyap, Nitesh; Wani, Zamir Ahmad; Jain, Rishi; Khusboo; Dinesh Kumar, V.

2014-08-01

This is the first report and investigation of a patch antenna in optical frequency range. Variety of plasmonic nanoantenna reported so far is good at enhancing the local field intensity of light by orders of magnitude. However, their far-field radiation efficiency is very poor. The proposed patch antenna emits a directional beam with high efficacy in addition to enhancing the intensity of near field. The nano-patch antenna (NPA) consists of a square patch of gold film of dimension 480 nm2, placed on a substrate of dielectric constant \\varepsilon_{{r}} = 3.9 and thickness 150 nm with a ground plane of gold film of dimension 1,080 nm2. The NPA resonates at 210 THz and has gain nearly 2 dB and radiation efficiency 45.18 %. The NPA might be useful in variety of applications such as optical communication, nano-photonics, biosensing, and spectroscopy.

Measurements of the spectrum and energy dependence of X-ray transition radiation

NASA Technical Reports Server (NTRS)

Cherry, M. L.

1978-01-01

The results of experiments designed to test the theory of X-ray transition radiation and to verify the predicted dependence of the characteristic features of the radiation on the radiator dimensions are presented. The X-ray frequency spectrum produced by 5- to 9-GeV electrons over the range 4 to 30 keV was measured with a calibrated single-crystal Bragg spectrometer, and at frequencies up to 100 keV with an NaI scintillator. The interference pattern in the spectrum and the hardening of the radiation with increasing foil thickness are clearly observed. The energy dependence of the total transition-radiation intensity was studied using a radiator with large dimensions designed to yield energy-dependent signals at very high particle energies, up to E/mc-squared approximately equal to 100,000. The results are in good agreement with the theoretical predictions.

SU-D-204-05: Quantitative Comparison of a High Resolution Micro-Angiographic Fluoroscopic (MAF) Detector with a Standard Flat Panel Detector (FPD) Using the New Metric of Generalized Measured Relative Object Detectability (GM-ROD)

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

Russ, M; Ionita, C; Bednarek, D

Purpose: In endovascular image-guided neuro-interventions, visualization of fine detail is paramount. For example, the ability of the interventionist to visualize the stent struts depends heavily on the x-ray imaging detector performance. Methods: A study to examine the relative performance of the high resolution MAF-CMOS (pixel size 75µm, Nyquist frequency 6.6 cycles/mm) and a standard Flat Panel Detector (pixel size 194µm, Nyquist frequency 2.5 cycles/mm) detectors in imaging a neuro stent was done using the Generalized Measured Relative Object Detectability (GM-ROD) metric. Low quantum noise images of a deployed stent were obtained by averaging 95 frames obtained by both detectors withoutmore » changing other exposure or geometric parameters. The square of the Fourier transform of each image is taken and divided by the generalized normalized noise power spectrum to give an effective measured task-specific signal-to-noise ratio. This expression is then integrated from 0 to each of the detector’s Nyquist frequencies, and the GM-ROD value is determined by taking a ratio of the integrals for the MAF-CMOS to that of the FPD. The lower bound of integration can be varied to emphasize high frequencies in the detector comparisons. Results: The MAF-CMOS detector exhibits vastly superior performance over the FPD when integrating over all frequencies, yielding a GM-ROD value of 63.1. The lower bound of integration was stepped up in increments of 0.5 cycles/mm for higher frequency comparisons. As the lower bound increased, the GM-ROD value was augmented, reflecting the superior performance of the MAF-CMOS in the high frequency regime. Conclusion: GM-ROD is a versatile metric that can provide quantitative detector and task dependent comparisons that can be used as a basis for detector selection. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

Generalizing Terwilliger's likelihood approach: a new score statistic to test for genetic association.

PubMed

el Galta, Rachid; Uitte de Willige, Shirley; de Visser, Marieke C H; Helmer, Quinta; Hsu, Li; Houwing-Duistermaat, Jeanine J

2007-09-24

In this paper, we propose a one degree of freedom test for association between a candidate gene and a binary trait. This method is a generalization of Terwilliger's likelihood ratio statistic and is especially powerful for the situation of one associated haplotype. As an alternative to the likelihood ratio statistic, we derive a score statistic, which has a tractable expression. For haplotype analysis, we assume that phase is known. By means of a simulation study, we compare the performance of the score statistic to Pearson's chi-square statistic and the likelihood ratio statistic proposed by Terwilliger. We illustrate the method on three candidate genes studied in the Leiden Thrombophilia Study. We conclude that the statistic follows a chi square distribution under the null hypothesis and that the score statistic is more powerful than Terwilliger's likelihood ratio statistic when the associated haplotype has frequency between 0.1 and 0.4 and has a small impact on the studied disorder. With regard to Pearson's chi-square statistic, the score statistic has more power when the associated haplotype has frequency above 0.2 and the number of variants is above five.

Oriented modulation for watermarking in direct binary search halftone images.

PubMed

Guo, Jing-Ming; Su, Chang-Cheng; Liu, Yun-Fu; Lee, Hua; Lee, Jiann-Der

2012-09-01

In this paper, a halftoning-based watermarking method is presented. This method enables high pixel-depth watermark embedding, while maintaining high image quality. This technique is capable of embedding watermarks with pixel depths up to 3 bits without causing prominent degradation to the image quality. To achieve high image quality, the parallel oriented high-efficient direct binary search (DBS) halftoning is selected to be integrated with the proposed orientation modulation (OM) method. The OM method utilizes different halftone texture orientations to carry different watermark data. In the decoder, the least-mean-square-trained filters are applied for feature extraction from watermarked images in the frequency domain, and the naïve Bayes classifier is used to analyze the extracted features and ultimately to decode the watermark data. Experimental results show that the DBS-based OM encoding method maintains a high degree of image quality and realizes the processing efficiency and robustness to be adapted in printing applications.

Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

PubMed

Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

2016-04-01

In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser.

High temperature superconductor analog electronics for millimeter-wavelength communications

NASA Technical Reports Server (NTRS)

Romanofsky, R. R.; Bhasin, K. B.

1991-01-01

The performance of high temperature superconductor (HTS) passive microwave circuits up to X-band was encouraging when compared to their metallic counterparts. The extremely low surface resistance of HTS films up to about 10 GHz enables a reduction in loss by as much as 100 times compared to copper when both materials are kept at about 77 K. However, a superconductor's surface resistance varies in proportion to the frequency squared. Consequently, the potential benefit of HTS materials to millimeter-wave communications requires careful analysis. A simple ring resonator was used to evaluate microstrip losses at Ka-band. Additional promising components were investigated such as antennas and phase shifters. Prospects for HTS to favorable impact millimeter-wave communications systems are discussed.

A high resolution soil moisture radiometer

NASA Technical Reports Server (NTRS)

Dod, L. R.

1980-01-01

The design of an L-band high resolution soil moisture radiometer is described. The selected system is a planar slotted waveguide array at L-band frequencies. The square aperture is 74.75 m by 74.75 m subdivided into 8 tilted subarrays. The system has a 290 km circular orbit and provides a spatial resolution of 1 km. The aperture forms 230 simultaneous beams in a cross-track pattern which covers a swath 420 km wide. A revisit time of 6 days is provided for an orbit inclination of 50 deg. The 1 km resolution cell allows an integration time of 1/7 second and sharing this time period sequentially between two orthogonal polarization modes can provide a temperature resolution of 0.7 K.

Sonoporation generator design and performance evaluation

NASA Astrophysics Data System (ADS)

Svilainis, L.; Chaziachmetovas, A.; Jurkonis, R.; Kybartas, D.

2012-05-01

We propose to perform the sonoporation by use of direct excitation employing the square wave pulser. Addition of the arbitrary waveform generator and programmable high voltage power supply to the pulser should allow for more economical experiment arrangement. Excitation stage has to be capable of transmitting high voltage signal into capacitive load. This paper reports the generator topology and performance evaluation experimental results. Transformer push-pull topology was suggested. Thanks to proposed pulser structure both unipolar and bipolar pulses can be obtained. Energy per pulse was suggested as performance parameter: any combination of achievable bust duration and repetition frequency can be estimated. Comparison of experimental results to Pspice modeling and energy delivered to load is presented. Energy per pulse at 300 V (600 Vpp) 2.7 MHz output into 3000 pF load was 1.1 mJ. Using 5 W power supplies this would allow for 3 kHz pulse repetition frequency single pulse of 100 Hz pulse repetition at 40 pulses burst. Focused 2.7 MHz center frequency transducer was targeted as load. Transducer impedance was measured to estimate the load and power delivery efficiency. It was found that 5 Ω is the optimal generator output impedance at 2.7 MHz. Using 2.7 MHz transducer we were able to achieve 1 MPa peak negative pressure at 250 V power supply.

Methods for estimating the magnitude and frequency of floods for urban and small, rural streams in Georgia, South Carolina, and North Carolina, 2011

USGS Publications Warehouse

Feaster, Toby D.; Gotvald, Anthony J.; Weaver, J. Curtis

2014-01-01

Reliable estimates of the magnitude and frequency of floods are essential for the design of transportation and water-conveyance structures, flood-insurance studies, and flood-plain management. Such estimates are particularly important in densely populated urban areas. In order to increase the number of streamflow-gaging stations (streamgages) available for analysis, expand the geographical coverage that would allow for application of regional regression equations across State boundaries, and build on a previous flood-frequency investigation of rural U.S Geological Survey streamgages in the Southeast United States, a multistate approach was used to update methods for determining the magnitude and frequency of floods in urban and small, rural streams that are not substantially affected by regulation or tidal fluctuations in Georgia, South Carolina, and North Carolina. The at-site flood-frequency analysis of annual peak-flow data for urban and small, rural streams (through September 30, 2011) included 116 urban streamgages and 32 small, rural streamgages, defined in this report as basins draining less than 1 square mile. The regional regression analysis included annual peak-flow data from an additional 338 rural streamgages previously included in U.S. Geological Survey flood-frequency reports and 2 additional rural streamgages in North Carolina that were not included in the previous Southeast rural flood-frequency investigation for a total of 488 streamgages included in the urban and small, rural regression analysis. The at-site flood-frequency analyses for the urban and small, rural streamgages included the expected moments algorithm, which is a modification of the Bulletin 17B log-Pearson type III method for fitting the statistical distribution to the logarithms of the annual peak flows. Where applicable, the flood-frequency analysis also included low-outlier and historic information. Additionally, the application of a generalized Grubbs-Becks test allowed for the detection of multiple potentially influential low outliers. Streamgage basin characteristics were determined using geographical information system techniques. Initial ordinary least squares regression simulations reduced the number of basin characteristics on the basis of such factors as statistical significance, coefficient of determination, Mallow’s Cp statistic, and ease of measurement of the explanatory variable. Application of generalized least squares regression techniques produced final predictive (regression) equations for estimating the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probability flows for urban and small, rural ungaged basins for three hydrologic regions (HR1, Piedmont–Ridge and Valley; HR3, Sand Hills; and HR4, Coastal Plain), which previously had been defined from exploratory regression analysis in the Southeast rural flood-frequency investigation. Because of the limited availability of urban streamgages in the Coastal Plain of Georgia, South Carolina, and North Carolina, additional urban streamgages in Florida and New Jersey were used in the regression analysis for this region. Including the urban streamgages in New Jersey allowed for the expansion of the applicability of the predictive equations in the Coastal Plain from 3.5 to 53.5 square miles. Average standard error of prediction for the predictive equations, which is a measure of the average accuracy of the regression equations when predicting flood estimates for ungaged sites, range from 25.0 percent for the 10-percent annual exceedance probability regression equation for the Piedmont–Ridge and Valley region to 73.3 percent for the 0.2-percent annual exceedance probability regression equation for the Sand Hills region.

Design and Test of a Soil Profile Moisture Sensor Based on Sensitive Soil Layers

PubMed Central

Liu, Cheng; Qian, Hongzhou; Cao, Weixing; Ni, Jun

2018-01-01

To meet the demand of intelligent irrigation for accurate moisture sensing in the soil vertical profile, a soil profile moisture sensor was designed based on the principle of high-frequency capacitance. The sensor consists of five groups of sensing probes, a data processor, and some accessory components. Low-resistivity copper rings were used as components of the sensing probes. Composable simulation of the sensor’s sensing probes was carried out using a high-frequency structure simulator. According to the effective radiation range of electric field intensity, width and spacing of copper ring were set to 30 mm and 40 mm, respectively. A parallel resonance circuit of voltage-controlled oscillator and high-frequency inductance-capacitance (LC) was designed for signal frequency division and conditioning. A data processor was used to process moisture-related frequency signals for soil profile moisture sensing. The sensor was able to detect real-time soil moisture at the depths of 20, 30, and 50 cm and conduct online inversion of moisture in the soil layer between 0–100 cm. According to the calibration results, the degree of fitting (R2) between the sensor’s measuring frequency and the volumetric moisture content of soil sample was 0.99 and the relative error of the sensor consistency test was 0–1.17%. Field tests in different loam soils showed that measured soil moisture from our sensor reproduced the observed soil moisture dynamic well, with an R2 of 0.96 and a root mean square error of 0.04. In a sensor accuracy test, the R2 between the measured value of the proposed sensor and that of the Diviner2000 portable soil moisture monitoring system was higher than 0.85, with a relative error smaller than 5%. The R2 between measured values and inversed soil moisture values for other soil layers were consistently higher than 0.8. According to calibration test and field test, this sensor, which features low cost, good operability, and high integration, is qualified for precise agricultural irrigation with stable performance and high accuracy. PMID:29883420

Design and Test of a Soil Profile Moisture Sensor Based on Sensitive Soil Layers.

PubMed

Gao, Zhenran; Zhu, Yan; Liu, Cheng; Qian, Hongzhou; Cao, Weixing; Ni, Jun

2018-05-21

To meet the demand of intelligent irrigation for accurate moisture sensing in the soil vertical profile, a soil profile moisture sensor was designed based on the principle of high-frequency capacitance. The sensor consists of five groups of sensing probes, a data processor, and some accessory components. Low-resistivity copper rings were used as components of the sensing probes. Composable simulation of the sensor’s sensing probes was carried out using a high-frequency structure simulator. According to the effective radiation range of electric field intensity, width and spacing of copper ring were set to 30 mm and 40 mm, respectively. A parallel resonance circuit of voltage-controlled oscillator and high-frequency inductance-capacitance (LC) was designed for signal frequency division and conditioning. A data processor was used to process moisture-related frequency signals for soil profile moisture sensing. The sensor was able to detect real-time soil moisture at the depths of 20, 30, and 50 cm and conduct online inversion of moisture in the soil layer between 0⁻100 cm. According to the calibration results, the degree of fitting ( R ²) between the sensor’s measuring frequency and the volumetric moisture content of soil sample was 0.99 and the relative error of the sensor consistency test was 0⁻1.17%. Field tests in different loam soils showed that measured soil moisture from our sensor reproduced the observed soil moisture dynamic well, with an R ² of 0.96 and a root mean square error of 0.04. In a sensor accuracy test, the R ² between the measured value of the proposed sensor and that of the Diviner2000 portable soil moisture monitoring system was higher than 0.85, with a relative error smaller than 5%. The R ² between measured values and inversed soil moisture values for other soil layers were consistently higher than 0.8. According to calibration test and field test, this sensor, which features low cost, good operability, and high integration, is qualified for precise agricultural irrigation with stable performance and high accuracy.

Characterizing the relative contributions of large vessels to total ocean noise fields: a case study using the Gerry E. Studds Stellwagen Bank National Marine Sanctuary.

PubMed

Hatch, Leila; Clark, Christopher; Merrick, Richard; Van Parijs, Sofie; Ponirakis, Dimitri; Schwehr, Kurt; Thompson, Michael; Wiley, David

2008-11-01

In 2006, we used the U.S. Coast Guard's Automatic Identification System (AIS) to describe patterns of large commercial ship traffic within a U.S. National Marine Sanctuary located off the coast of Massachusetts. We found that 541 large commercial vessels transited the greater sanctuary 3413 times during the year. Cargo ships, tankers, and tug/tows constituted 78% of the vessels and 82% of the total transits. Cargo ships, tankers, and cruise ships predominantly used the designated Boston Traffic Separation Scheme, while tug/tow traffic was concentrated in the western and northern portions of the sanctuary. We combined AIS data with low-frequency acoustic data from an array of nine autonomous recording units analyzed for 2 months in 2006. Analysis of received sound levels (10-1000 Hz, root-mean-square pressure re 1 microPa +/- SE) averaged 119.5 +/- 0.3 dB at high-traffic locations. High-traffic locations experienced double the acoustic power of less trafficked locations for the majority of the time period analyzed. Average source level estimates (71-141 Hz, root-mean-square pressure re 1 microPa +/- SE) for individual vessels ranged from 158 +/- 2 dB (research vessel) to 186 +/- 2 dB (oil tanker). Tankers were estimated to contribute 2 times more acoustic power to the region than cargo ships, and more than 100 times more than research vessels. Our results indicate that noise produced by large commercial vessels was at levels and within frequencies that warrant concern among managers regarding the ability of endangered whales to maintain acoustic contact within greater sanctuary waters.

A new method for gravity field recovery based on frequency analysis of spherical harmonics

NASA Astrophysics Data System (ADS)

Cai, Lin; Zhou, Zebing

2017-04-01

All existing methods for gravity field recovery are mostly based on the space-wise and time-wise approach, whose core processes are constructing the observation equations and solving them by the least square method. It's should be pointed that the least square method means the approximation. On the other hand, we can directly and precisely obtain the coefficients of harmonics by computing the Fast Fourier Transform (FFT) when we do 1-D data (time series) analysis. So the question whether we directly and precisely obtain the coefficients of spherical harmonic by computing 2-D FFT of measurements of satellite gravity mission is of great significance, since this may guide us to a new understanding of the signal components of gravity field and make us determine it quickly by taking advantage of FFT. Like the 1-D data analysis, the 2-D FFT of measurements of satellite can be computed rapidly. If we can determine the relationship between spherical harmonics and 2-D Fourier frequencies and the transfer function from measurements to spherical coefficients, the question mentioned above can be solved. So the objective of this research project is to establish a new method based on frequency analysis of spherical harmonic, which directly compute the confidents of spherical harmonic of gravity field, which is differ from recovery by least squares. There is a one to one correspondence between frequency spectrum and the time series in 1-D FFT. The 2-D FFT has a similar relationship to 1-D FFT. Owing to the fact that any degree or order (higher than one) of spherical function has multi frequencies and these frequencies may be aliased. Fortunately, the elements and ratio of these frequencies of spherical function can be determined, and we can compute the coefficients of spherical function from 2-D FFT. This relationship can be written as equations and equivalent to a matrix, which is solid and can be derived in advance. Until now the relationship has be determined. Some preliminary results, which only compute lower degree spherical harmonics, indicates that the difference between the input (EGM2008) and output (coefficients from recovery) is smaller than 5E-17, while the minimal precision of computer software (Matlab) is 2.2204E-16.

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.

Anther response to high-temperature stress during development and pollen thermotolerance heterosis as revealed by pollen tube growth and in vitro pollen vigor analysis in upland cotton.

PubMed

Song, Guicheng; Wang, Miaomiao; Zeng, Bin; Zhang, Jing; Jiang, Chenliang; Hu, Qirui; Geng, Guangtao; Tang, Canming

2015-05-01

Pollen tube growth in styles was strongly inhibited by temperature above 35 °C, and the yield of cotton decreased because of the adverse effect of high temperatures during square development. High-temperature stress during flowering influences the square development of upland cotton (Gossypium hirsutum L.) and cotton yield. Although it is well known that square development is sensitive to high temperature, high-temperature sensitive stages of square development and the effects of high temperature on pollen tube growth in the styles are unknown. The effect of high temperature on anther development corresponding to pollen vigor is unknown during anther development. The objectives of this study were to identify the stages of square development that are sensitive to high temperatures (37/30 and 40/34 °C), to determine whether the abnormal development of squares influenced by high temperature is responsible for the variation in the in vitro germination percent of pollen grains at anthesis, to identify the effect of high temperature on pollen germination in the styles, and to determine pollen thermotolerance heterosis. Our results show that the stages from the sporogenous cell to tetrad stage (square length <6.0 mm) were the most sensitive to high temperature, and the corresponding pollen viability at anthesis was consistent with the changes in the square development stage. Pollen tube growth in the styles was strongly inhibited by temperature above 35 °C, and the yield of cotton decreased because of the effect of high temperature during square development. The thermotolerance of hybrid F1 pollen showed heterosis, and pollen viability could be used as a criterion for screening for high-temperature tolerance cultivars. These results can be used in breeding to develop new cotton cultivars that can withstand high-temperature conditions, particularly in a future warmer climate.

Post-processing of auditory steady-state responses to correct spectral leakage.

PubMed

Felix, Leonardo Bonato; de Sá, Antonio Mauricio Ferreira Leite Miranda; Mendes, Eduardo Mazoni Andrade Marçal; Moraes, Márcio Flávio Dutra

2009-06-30

Auditory steady-state responses (ASSRs) are electrical manifestations of brain due to high rate sound stimulation. These evoked responses can be used to assess the hearing capabilities of a subject in an objective, automatic fashion. Usually, the detection protocol is accomplished by frequency-domain techniques, such as magnitude-squared coherence, whose estimation is based on the fast Fourier transform (FFT) of several data segments. In practice, the FFT-based spectrum may spread out the energy of a given frequency to its side bins and this escape of energy in the spectrum is called spectral leakage. The distortion of the spectrum due to leakage may severely compromise statistical significance of objective detection. This work presents an offline, a posteriori method for spectral leakage minimization in the frequency-domain analysis of ASSRs using coherent sampling criterion and interpolation in time. The technique was applied to the local field potentials of 10 Wistar rats and the results, together with those from simulated data, indicate that a leakage-free analysis of ASSRs is possible for any dataset if the methods showed in this paper were followed.

Internal tides in the Northern Gulf of California

NASA Astrophysics Data System (ADS)

Filonov, Anatoliy E.; LavíN, M. F.

2003-05-01

The characteristics of the internal tide in the Northern Gulf of California are described using data from two moored arrays of temperature and current sensors, one for summer and one for winter, located between Angel de la Guarda Island and the mainland. From the summer six-sensor mooring it was found that: (1) the current fluctuations are dominated by the semidiurnal frequency band, while the quarterdiurnal frequency dominated the temperature fluctuations. (2) The baroclinic semidiurnal horizontal current fluctuations are aligned with the gulf axis, and have amplitudes of 10-15 cm s-1; the vertical displacements reached 4 m in this frequency band. (3) The vertical modal structure for the temperature and velocity oscillations was dominated by the first and third modes. (4) The energy of the semidiurnal internal tide is 45% of that of the barotropic tide. (5) Vertical wave number spectra showed slightly asymmetric peaks in the high wave number components, indicating that their downflowing energy is larger than that flowing upward. From the winter two-sensor mooring, it was found that the vertical oscillations were mainly semidiurnal, with root mean square amplitudes of 7 m.

Determination of Prevalence of Dental Erosion in 12 - 14 Years School Children and Its Relationship with Dietary Habits.

PubMed

Shahbaz, Uzma; Quadir, Fauzia; Hosein, Tasleem

2016-07-01

To determine the frequency of dental erosion in 12-14 years school children and its association with dietary habits. Observational cross-sectional analytical study. Fatima Jinnah Dental College, Karachi, from January to June 2010. School children aged between 12 - 14 years were included in this study. Dental erosion was detected by visual examination. Aself-developed questionnaire was used to assess the dietary habits of children. Acidic diet was considered a diet that has an acidic pH. The amount of consumption of acidic drinks and food per week was categorized into low consumption (1 - 7 times / week) and medium consumption (8 - 21 times / week). Chi-square test was applied to see any statistical difference between diet and tooth erosion at 95% CI. The results showed a high frequency of (46%) dental erosion in children, which was significantly higher (p < 0.001) in children with more acidic diet. This study highlights the impact of dietary habits on the prevalence of dental erosion in children. Acidic diets need to be controlled in frequency to prevent dental erosion.

Fluid mechanical model of the Helmholtz resonator

NASA Technical Reports Server (NTRS)

Hersh, A. S.; Walker, B.

1977-01-01

A semi-empirical fluid mechanical model of the acoustic behavior of Helmholtz resonators is presented which predicts impedance as a function of the amplitude and frequency of the incident sound pressure field and resonator geometry. The model assumes that the particle velocity approaches the orifice in a spherical manner. The incident and cavity sound fields are connected by solving the governing oscillating mass and momentum conservation equations. The model is in agreement with the Rayleigh slug-mass model at low values of incident sound pressure level. At high values, resistance is predicted to be independent of frequency, proportional to the square root of the amplitude of the incident sound pressure field, and virtually independent of resonator geometry. Reactance is predicted to depend in a very complicated way upon resonator geometry, incident sound pressure level, and frequency. Nondimensional parameters are defined that divide resonator impedance into three categories corresponding to low, moderately low, and intense incident sound pressure amplitudes. The two-microphone method was used to measure the impedance of a variety of resonators. The data were used to refine and verify the model.

Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

PubMed

El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

2017-06-26

Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

An experimental-theoretical study of free vibrations of plates on elastic point supports

NASA Technical Reports Server (NTRS)

Leuner, T. R.

1972-01-01

A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. A theoretical model is developed using a Rayleigh-Ritz analysis which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modelled both as massless translational springs, and springs with tip masses. The tip masses are included to better represent the experimental supports. An experiment is constructed using the bending stiffness of horizontal beams to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured, and compared with the theoretical results. The plate mode shapes for rigid supports are analyzed using holographic interferometry. There is excellent agreement between the theoretical and experimental results, except for high plate modes where the theoretical model is demonstrated to be inadequate.

Analog circuit for the measurement of phase difference between two noisy sine-wave signals

NASA Technical Reports Server (NTRS)

Shakkottai, P.; Kwack, E. Y.; Back, L. H.

1989-01-01

A simple circuit was designed to measure the phase difference between two noisy sine waves. It locks over a wide range of frequencies and produces an output proportional to the phase difference of rapidly varying signals. A square wave locked in frequency and phase to the first signal is produced by a phase-locked loop and is amplified by an operational amplifier.

Monte Carlo calculation of dynamical properties of the two-dimensional Hubbard model

NASA Technical Reports Server (NTRS)

White, S. R.; Scalapino, D. J.; Sugar, R. L.; Bickers, N. E.

1989-01-01

A new method is introduced for analytically continuing imaginary-time data from quantum Monte Carlo calculations to the real-frequency axis. The method is based on a least-squares-fitting procedure with constraints of positivity and smoothness on the real-frequency quantities. Results are shown for the single-particle spectral-weight function and density of states for the half-filled, two-dimensional Hubbard model.