Leavitt, M.A.; Lutz, I.C.
1958-08-01
An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.
Improved Tracking Of Square-Wave Subcarrier
NASA Technical Reports Server (NTRS)
Hurd, William J.; Aguirre, Sergio
1988-01-01
Variance of phase error reduced. Report discusses application of "windowing" concept to improve ability of telemetry receiver to track phase of square-wave phase-modulation subcarrier signal. Concept based on setting phase-tracking signal at zero outside narrow time "windows", reducing noise energy in processed signal. Result is increase in signal-to-noise ratio in tracking loop with consequent increase in accuracy of tracking and reduction in number of errors in telemetric data.
Thin-layer square wave voltametry and square wave stripping voltametry
Kumar, V.; Heineman, W.R.
1987-03-15
The feasibility of combining the highly sensitive techniques of square wave voltametry (SWV) and square wave stripping voltametry (SWSV) with a commercially available thin-layer electrochemical cell having a single-working electrode is demonstrated. The characteristics of thin-layer SWV were investigated by using ferri-/ferrocyanide and diazepam (Valium) systems. The calibration plot data for diazepam are linear between 10 and 60 ppm with a detection limit of 0.06 ppm. With a Hg-coated glassy carbon electrode, SWSV studies were carried out on 30-..mu..L aqueous solutions of In/sup 3 +/ and Pb/sup 2 +/ ions. The calibration curve for In/sup 3 +/ is linear up to 2000 ppb with a detection limit of 8 ppb. The detection limit for lead is 11 ppb.
Square wave jerks in parkinsonian syndromes.
Rascol, O; Sabatini, U; Simonetta-Moreau, M; Montastruc, J L; Rascol, A; Clanet, M
1991-01-01
The frequency of square wave jerks (SWJ) was compared in eight patients with progressive supranuclear palsy (PSP), 25 patients with multiple system atrophy or Parkinson's disease plus (MSA/PP), 85 patients with idiopathic Parkinson's disease (PD) and 20 age-matched normal volunteers. In the control group, the mean (SD) SWJ frequency (SWJ larger than 1 degree amplitude) was 2.3 (2.4)/min. Abnormal ocular fixation (SWJ frequency greater than 10/min) was observed in a large proportion of PSP patients (7/8) and of MSA/PP patients (16/25) but in few PD patients (13/85). In the group of PD patients with abnormal ocular fixation, freezing of gait, falls and instability were more severe than in the group of PD patients with normal fixation. The study of ocular fixation may help to differentiate PD clinically from other Parkinsonian syndromes. SWJ are probably not related to the central degeneration of the dopaminergic nigrostriatal pathway observed in PD. PMID:1895124
Analysis of cardamonin by square wave voltammetry.
Carvalho, Ana M; Gonçalves, Luís M; Valente, Inês M; Rodrigues, José A; Barros, Aquiles A
2012-01-01
Several biochemical studies have already shown that cardamonin has health promoting properties, such is in agreement with typical characteristics of chalcones. Although being a very promising compound for the nutraceutical field there is a lack of studies concerning its electroanalytical properties. To develop an electroanalytical methodology for the quantification of cardamonin in cardamom. Cardamonin was analysed electrochemically by means of a hanging mercury drop electrode (HMDE) using square wave voltammetry (SWV). It was extracted from cardamom spice and quantified thereafter using the standard additions method to overcome matrix effects. A limit of detection (LOD) of 0.15 mg/L and good linearity (r² = 0.9998) were obtained. Decoction using ethanol as the extraction solvent appears to be the simplest extraction technique. Spectrophotometric analysis (maximum absorbance peak was found in ethanol at 344 nm with a value of molar extinction coefficient of (2.8 ± 0.1) × 10⁴ L mol⁻¹ cm⁻¹) and mass spectrometry analysis by electrospray in the positive ion mode were also performed. Cardamonin was detected voltammetrically. The LOD and limit of quantification (LOQ) of the proposed voltammetric methodology are adequate for trace analysis of this compound in several phytochemical matrices. Copyright © 2011 John Wiley & Sons, Ltd.
Strongly asymmetric square waves in a time-delayed system.
Weicker, Lionel; Erneux, Thomas; D'Huys, Otti; Danckaert, Jan; Jacquot, Maxime; Chembo, Yanne; Larger, Laurent
2012-11-01
Time-delayed systems are known to exhibit symmetric square waves oscillating with a period close to twice the delay. Here, we show that strongly asymmetric square waves of a period close to one delay are possible. The plateau lengths can be tuned by changing a control parameter. The problem is investigated experimentally and numerically using a simple bandpass optoelectronic delay oscillator modeled by nonlinear delay integrodifferential equations. An asymptotic approximation of the square-wave periodic solution valid in the large delay limit allows an analytical description of its main properties (extrema and square pulse durations). A detailed numerical study of the bifurcation diagram indicates that the asymmetric square waves emerge from a Hopf bifurcation.
SNR degradation in square-wave subcarrier downconversion
NASA Technical Reports Server (NTRS)
Feria, Y.; Statman, J.
1992-01-01
This article presents a study of signal-to-noise ratio (SNR) degradation in the process of square-wave subcarrier downconversion. The study shows three factors that contribute to the SNR degradation: the cutoff of the higher frequency components in the data, the approximation of a square wave with a finite number of harmonics, and nonideal filtering. Both analytical and simulation results are presented.
Asymmetric electrowetting--moving droplets by a square wave.
Fan, Shih-Kang; Yang, Hanping; Wang, Tsu-Te; Hsu, Wensyang
2007-10-01
Here droplet oscillation and continuous pumping are demonstrated by asymmetric electrowetting on an open surface with embedded electrodes powered by a square wave electrical signal without control circuits. The polarity effect of electrowetting on an SU-8 and Teflon coated electrode is investigated, and it is found that the theta-V (contact angle-applied voltage) curve is asymmetric along the V = 0 axis by sessile drop and coplanar electrode experiments. A systematic deviation of measured contact angles from the theoretical ones is observed when the electrode beneath the droplet is negatively biased. In the sessile drop experiment, up to a 10 degrees increment of contact angle is measured on a negatively biased electrode. In addition, a coplanar electrode experiment is designed to examine the contact angles at the same applied potential but opposite polarities on two sides of one droplet at the same time. The design of the coplanar electrodes is then expanded to oscillate and transport droplets on square-wave-powered symmetric (square) and asymmetric (polygon) electrodes to demonstrate manipulation capability on an open surface. The frequency of oscillation and the speed of transportation are determined by the frequency of the applied square wave and the pitch of the electrodes. Droplets with different volumes are tested by square waves of varied frequencies and amplitudes. The 1.0 microl droplet is successfully transported on a device with a loop of 24 electrodes continuously at a speed up to 23.6 mm s(-1) when a 9 Hz square wave is applied.
Reconfigurable wave band structure of an artificial square ice
lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; Heinonen, Olle
2016-04-18
Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors. Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.
Reconfigurable wave band structure of an artificial square ice
lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; ...
2016-04-18
Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less
Reconfigurable wave band structure of an artificial square ice
lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; Heinonen, Olle
2016-04-18
Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors. Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.
Square-integrability of multivariate metaplectic wave-packet representations
NASA Astrophysics Data System (ADS)
Ghaani Farashahi, Arash
2017-03-01
This paper presents a systematic study for harmonic analysis of metaplectic wave-packet representations on the Hilbert function space {{L}2}≤ft({{{R}}d}\\right) . The abstract notions of symplectic wave-packet groups and metaplectic wave-packet representations will be introduced. We then present an admissibility condition on closed subgroups of the real symplectic group \\text{Sp}≤ft({{{R}}d}\\right) , which guarantees the square-integrability of the associated metaplectic wave-packet representation on {{L}2}≤ft({{{R}}d}\\right) .
High-frequency matrix converter with square wave input
Carr, Joseph Alexander; Balda, Juan Carlos
2015-03-31
A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.
Multi-electrodes in SAW with square wave ac power
Bunker, T.A.
1982-07-01
Examines the feasibility of using AC square wave power for multi-electrode submerged arc welding (SAW) by arranging 2 power sources for weld test using two-electrode submerged arc welding. Presents figures showing phase relationship between lead arc current and trail arc current for Scott connected multi-electrode SAW, and arc deflection vs. electrical degrees. Suggests that Scott connection is preferred because it balances the primary line draw. Concludes that the multielectrode submerged arc process with constant potential square wave power increases travel speed and deposition rates which can be added to the economies obtained from a narrow groove joint configuration and the SAW process.
Square wave voltammetry at the dropping mercury electrode: Experimental
Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.
1977-01-01
Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.
Integrated photonic threshold comparator based on square-wave synthesis.
Ehrlichman, Yossef; Amrani, Ofer; Ruschin, Shlomo
2013-06-17
A photonic threshold comparator is presented. A step-like electrical-to-optical (E/O) response is obtained by employing Fourier series synthesis in which a set of sine-wave responses of different amplitudes and phases are superimposed according to the Fourier series representation of a square-wave. The proposed comparator does not rely on optical material non-linearity; rather it consists of multimode interference (MMI) couplers and phase shifters.
Inverse free electron laser acceleration with a square wave wiggler
NASA Astrophysics Data System (ADS)
Parsa, Z.; Pato, M. P.
1997-02-01
We present an Inverse Free Electron Laser with a Square Wave Wiggler (IFELSW) as a new acceleration scheme and show Analytically and numerically about factor of 2 gain in the energy when compared to the standard IFEL with the Sinusoidal [1] field Wiggler.
Square wave voltammetry at the dropping mercury electrode: Theory
Christie, J.H.; Turner, J.A.; Osteryoung, R.A.
1977-01-01
The theoretical aspects of square wave voltammetry at the dropping mercury electrode are presented. The technique involves scanning the entire potential range of interest on a single drop of a DME. Asymmetries in the waveform as well as variations in current measurement parameters are discussed. Indications are that previous uses of the waveform may not have utilized all its capabilities.
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 14
Square-wave adsorptive cathodic stripping voltammetry of pantoprazole.
Radi, A
2003-11-24
Adsorption and reduction of pantoprazole were investigated by cyclic and square-wave voltammetry on a hanging mercury drop electrode in Britton-Robinson buffers at pH 2.0-11.0. The reduction process gave rise to a single peak within the entire pH range. Study of the variation of the reduction signal with solution variables such as pH and concentration of pantoprazole and instrumental variables such as accumulation time and potential, frequency, pulse height and pulse amplitude, has resulted in optimization of the reduction signal for analytical purposes. The voltammetric procedure was applied successfully to give a rapid and precise assay of pantoprazole in a tablet dosage form.
Standing wave brass-PZT square tubular ultrasonic motor.
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).
Evaluation of quasi-square wave inverter as a power source for induction motors
NASA Technical Reports Server (NTRS)
Guynes, B. V.; Haggard, R. L.; Lanier, J. R., Jr.
1977-01-01
The relative merits of quasi-square wave inverter-motor technology versus a sine wave inverter-motor system were investigated. The empirical results of several tests on various sizes of wye-wound induction motors are presented with mathematical analysis to support the conclusions of the study. It was concluded that, within the limitations presented, the quasi-square wave inverter-motor system is superior to the more complex sine wave system for most induction motor applications in space.
Determination of dipyridamole in pharmaceutical preparations using square wave voltammetry.
de Toledo, Renata Alves; Castilho, Marilza; Mazo, Luiz Henrique
2005-01-04
An analytical methodology using square wave voltammetry (SWV) at a hanging mercury drop electrode (HMDE) was developed for the quantitative determination of dipyridamole (DIP), a drug used for the treatment of several cardiovascular diseases, in pharmaceutical tablets and injections of Persantin in phosphate buffer (pH 3.0; 0.1M). After optimization of the parameters for SWV, analytical curves were obtained for application in the range of 1.28 x 10(-6)M to 7.02 x 10(-6)M. It was found a detection limit (DL) of 1.88 x 10(-8)M (9.50 ng/ml). The repeatability and the reproducibility of the method were determinated by successive measurements of DIP solutions on the range of the analytical curve with a coefficient variation of 0.97% (n=5) and 1.15%, respectively. The apparent recoveries were obtained by the IUPAC recommended procedure using the second reduction peak. Recoveries obtained by SWV were compared with the UV-vis spectrophotometric method. It was found that the determination of DIP in Persantin tablets gave a mean value of 75.6+/-0.4 mg (100.8%) and 68.9+/-0.3 mg (91.8%) for SWV and UV-vis spectrophotometry, respectively. In the case of injections, it was found 10.4+/-0.1 mg (103.4%) and 9.9+/-0.2 mg (99.9%) for SWV and UV-vis spectrophotometry. Both apparent recoveries for the two types of formulations are in good accordance with the declared value of 75 mg (tablets) and 10 mg (injections).
Chlorine Dioxide Gas Sterilization under Square-Wave Conditions
Jeng, David K.; Woodworth, Archie G.
1990-01-01
Experiments were designed to study chlorine dioxide (CD) gas sterilization under square-wave conditions. By using controlled humidity, gas concentration, and temperature at atmospheric pressure, standard biological indicators (BIs) and spore disks of environmental isolates were exposed to CD gas. The sporicidal activity of CD gas was found to be concentration dependent. Prehumidification enhanced the CD activity. The D values (time required for 90% inactivation) of Bacillus subtilis subsp. niger ATCC 9372 BIs were estimated to be 1.5, 2.5, and 4.2 min when exposed to CD concentrations of 30, 15, and 7 mg/liter, respectively, at 23°C and ambient (20 to 40%) relative humidity (RH). Survivor tailings were observed. Prehumidification of BIs to 70 to 75% RH in an environmental chamber for 30 min resulted in a D value of 1.6 min after exposure to a concentration of 6 to 7 mg of CD per liter at 23°C and eliminated survivor tailing. Prolonging prehumidification at 70 to 75% RH for up to 16 h did not further improve the inactivation rate. Prehumidification by ultrasonic nebulization was found to be more effective than prehumidification in the environmental chamber, improving the D value to 0.55 min at a CD concentration of 6 to 7 mg/liter. Based on the current observations, CD gas is estimated, on a molar concentration basis, to be 1,075 times more potent than ethylene oxide as a sterilant at 30°C. A comparative study showed B. subtilis var. niger BIs were more resistant than other types of BIs and most of the tested bacterial spores of environmental isolates. PMID:16348127
Henao-Escobar, W; Domínguez-Renedo, O; Alonso-Lomillo, M A; Arcos-Martínez, M J
2015-10-01
This work presents the simultaneous determination of cadaverine, histamine, putrescine and tyramine by square wave voltammetry using a boron-doped diamond electrode. A multivariate calibration method based on partial least square regressions has allowed the resolution of the very high overlapped voltammetric signals obtained for the analyzed biogenic amines. Prediction errors lower than 9% have been obtained when concentration of quaternary mixtures were calculated. The developed procedure has been applied in the analysis of ham samples, which results are in good agreement with those obtained using the standard HPLC method. Copyright © 2015 Elsevier B.V. All rights reserved.
Improved linear ultrasonic motor performance with square-wave based driving-tip trajectory
NASA Astrophysics Data System (ADS)
Le, Adam Y.; Mills, James K.; Benhabib, Beno
2015-03-01
This paper proposes the application of a non-sinusoidal periodic excitation voltage to induce a near-square-wave driving tip trajectory in linear ultrasonic motors (LUSMs). A square-wave-based trajectory can deliver superior frictional force to the moving stage in the forward stroke of the driving tip motion and reduced frictional force during the return stroke. This would reduce lost power in the periodic driving tip motion, thereby, increasing the output force and power of the LUSM. An implementation procedure is suggested to achieve the near-square-wave driving tip trajectory. The proposed approach is illustrated through realistic finite-element-based simulations using a bimodal LUSM configuration.
Square-wave oscillations in edge-emitting diode lasers with polarization-rotated optical feedback
NASA Astrophysics Data System (ADS)
Gavrielides, A.; Erneux, T.; Sukow, D. W.; Burner, G.; McLachlan, T.; Miller, J.; Amonette, J.
2006-04-01
The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied experimentally and theoretically. Square-wave self-modulated polarization intensities of a period close to twice the delay τ of the feedback gradually appear through a sequence of bifurcations starting with a Hopf bifurcation (Gavrielides et al, Proc. SPIE 6115, to appear, 2006). In Gavrielides et al (submitted, 2006), squarewave solutions were determined analytically from the laser equations in the limit of large τ. A condition on the laser parameters was derived explaining why square-wave oscillations are preferentially observed for suffciently large feedback strength. In this paper, we concentrate on the relaxation oscillations that always appear at each intensity jump between the plateaus of the square-wave. We show analytically that if the feedback strength is progressively decreased, a bifurcation to sustained relaxation oscillations is possible for one of the two plateaus.
Optical Square-Wave Clock Generation Based on an All-Optical Flip-Flop
Kaplan, A.M.; Agrawal, G.P.; Maywar, D.N.
2010-03-10
We demonstrate optical square-wave clock generation based on an all-optical flip-flop. The bistable output power from a resonant-type semiconductor optical amplifier (SOA) is switched ON and OFF by modulating its input with its output via cross-gain modulation in a traveling-wave SOA. All active components are driven by dc currents, and the wavelength and clock frequency are selectable. A clock frequency of 3.5 MHz is demonstrated, limited by the time of flight between bulk optical components. Optical square-wave clock signals are promising for applications in photonic integrated circuits and all-optical signal processing.
A method to remove odd harmonic interferences in square wave reference digital lock-in amplifier.
Li, Gang; Zhang, Shengzhao; Zhou, Mei; Li, Yongcheng; Lin, Ling
2013-02-01
Digital lock-in amplifier using square wave reference is much easier to be implemented compared to digital lock-in amplifier using sinusoidal wave reference. However, because of the odd harmonics containing in the square wave reference, the interferences at the odd harmonics of the reference cannot be removed with conventional algorithm. A new square wave digital lock-in algorithm is presented in this paper. It cannot only be capable of removing the interferences of the odd harmonics in the signal, but also can detect the amplitudes and the phases of the interferences. The real and imaginary parts of the frequency component of interest and those of the odd harmonic interferences are calculated simultaneously. The results of simulation experiments show the feasibility of the proposed algorithm. The algorithm is computationally efficient and thus suitable for weak signal detection implemented in the general microprocessor.
Nadeau, Kyle P; Rice, Tyler B; Durkin, Anthony J; Tromberg, Bruce J
2015-11-01
We present a method for spatial frequency domain data acquisition utilizing a multifrequency synthesis and extraction (MSE) method and binary square wave projection patterns. By illuminating a sample with square wave patterns, multiple spatial frequency components are simultaneously attenuated and can be extracted to determine optical property and depth information. Additionally, binary patterns are projected faster than sinusoids typically used in spatial frequency domain imaging (SFDI), allowing for short (millisecond or less) camera exposure times, and data acquisition speeds an order of magnitude or more greater than conventional SFDI. In cases where sensitivity to superficial layers or scattering is important, the fundamental component from higher frequency square wave patterns can be used. When probing deeper layers, the fundamental and harmonic components from lower frequency square wave patterns can be used. We compared optical property and depth penetration results extracted using square waves to those obtained using sinusoidal patterns on an in vivo human forearm and absorbing tube phantom, respectively. Absorption and reduced scattering coefficient values agree with conventional SFDI to within 1% using both high frequency (fundamental) and low frequency (fundamental and harmonic) spatial frequencies. Depth penetration reflectance values also agree to within 1% of conventional SFDI.
NASA Astrophysics Data System (ADS)
Hu, Hongsheng; Niu, Qunfeng; Pan, Yinqing; Wang, Li
A classification method of discriminate rice from different varieties with voltammetric electronic tongue based on square wave voltammetry is investigated. The rice samples are crushed and mixed with distilled water to get the rice solution, and the solution should be stirred and filtered before the experiment. In order to obtain the electrochemical response signals of the rice samples and extract the characteristic value of the singles, the electronic tongue which works respectively with titanium (Ti) electrode and tungsten electrode (W) to test the sample solution under square wave voltammetry. The Principal Component Analysis (PCA) and Clustering Analysis (CA) are adopted to classify and recognize the rice samples. Experimental results show that good classification and recognition results are got in this paper when using Principal Component Analysis and Cluster Analysis to analyze the response signals which are obtained by voltammetric electronic tongue worked with Ti electrode and W electrode under square wave potential.
Square-wave self-modulation in diode lasers with polarization-rotated optical feedback.
Gavrielides, Athanasios; Erneux, Thomas; Sukow, David W; Burner, Guinevere; McLachlan, Taylor; Miller, John; Amonette, Jake
2006-07-01
The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon.
Square-wave self-modulation in diode lasers with polarization-rotated optical feedback
NASA Astrophysics Data System (ADS)
Gavrielides, Athanasios; Erneux, Thomas; Sukow, David W.; Burner, Guinevere; McLachlan, Taylor; Miller, John; Amonette, Jake
2006-07-01
The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon.
NASA Astrophysics Data System (ADS)
Xiao, Lili; Ward, Steven N.; Wang, Jiajia
2015-12-01
We have developed a new method, named "Tsunami Squares", for modeling of landslides and landslide-generated waves. The approach has the advantages of the previous "Tsunami Ball" method, for example, separate, special treatment for dry and wet cells is not needed, but obviates the use of millions of individual particles. Simulations now can be expanded to spatial scales not previously possible. The new method accelerates and transports "squares" of material that are fractured into new squares in such a way as to conserve volume and linear momentum. The simulation first generates landslide motion as constrained by direct observation. It then computes induced water waves, given assumptions about energy and momentum transfer. We demonstrated and validated the Tsunami Squares method by modeling the 2008 Three Gorges Reservoir Gongjiafang landslide and river tsunami. The landslide's progressive failure, the wave generated, and its subsequent propagation and run-up are well reproduced. On a laptop computer Tsunami Square simulations flexibly handle a wide variety of waves and flows, and are excellent techniques for risk estimation.
Cathodic adsorptive stripping square-wave voltammetry of the anti-inflammatory drug meloxicam.
Radi, A E; Ghoneim, M; Beltagi, A
2001-10-01
The adsorptive behavior of the anti-inflammatory drug meloxicam was studied by cyclic, differentia-pulse and square-wave voltammetry on a hanging mercury drop electrode (HMDE). The drug was accumulated at HMDE and a well-defined stripping peak current was obtained at -1.42 V vs. Ag/AgCl (saturated KCl) electrode in acetate buffer solution (pH 5.0). A voltammetric procedure was developed for the determination of meloxicam using square-wave cathodic adsorptive stripping voltammetry (SW-CASV). The optimum working conditions for the determination of the drug were established. The analysis of meloxicam in human plasma was carried out satisfactorily.
Gubbiotti, G.; Tacchi, S.; Madami, M.; Carlotti, G.; Ding, J.; Adeyeye, A. O.
2015-06-29
The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.
Calvo, M Encarnación Burgoa; Renedo, Olga Domínguez; Martínez, M Julia Arcos
2007-02-19
A procedure for the determination of oxcarbazepine (OXC) by Square Wave Adsorptive Stripping Voltammetry (SWAdSV) has been optimized. Selection of the experimental parameters was made using experimental design methodology. The detection limit was 1.74 x 10(-7) mol dm(-3). This method was used to determine oxcarbazepine in pharmaceutical preparations.
Highly efficient square wave distant dipolar field and its application for in vivo MRI.
Cai, Congbo; Gao, Fenglian; Cai, Shuhui; Zhong, Jianhui; Chen, Zhong
2010-10-01
Intermolecular multiple quantum coherences generated by distant dipolar field (DDF) have some attractive properties, but the intrinsic weak signal intensity prevents their widespread applications. Recently, Branca et al. (J Chem Phys 2008;129:054502) suggested that square wave DDF was more efficient than conventional sinusoidal DDF because it could simultaneously produce intermolecular multiple quantum coherences signal with various major orders. In this article, instead of a series of adiabatic inversion pulses proposed previously, a more efficient composite adiabatic inversion pulse was applied to create square wave DDF. The square wave DDF was applied to in vivo MRI for the first time, and the corresponding simulations were performed. Both experimental and simulated results show that square wave DDF with composite adiabatic inversion pulse improves over the original Z-modulation enhanced to binary for self-refocused acquisition implementation and can enhance the signal intensity to about 2-fold of that from conventional correlation spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence for in vivo MRI, close to the theoretical prediction.
Improving noise resistance of intrinsic rhythms in a square-wave burster model.
Kohno, Takashi; Aihara, Kazuyuki
2013-06-01
The square-wave burster (Wang and Rinzel, 2003) is a class of autonomous bursting cells that share a bifurcation structure. It is known that this class of cells is involved in the generation of various life-supporting rhythms. In our research to realize an electronic circuit that mimics the rhythm generating mechanism in the square-wave burster, our circuit experimentally exhibited severe fluctuations in its rhythmic activity. We have found a noise-sensitive region in the phase portrait of the ideal model and have proposed modifications of the model that can reduce this fluctuation. A possible modification to ionic-conductance neuron models (Kohno and Aihara, 2011) was inspired by them. This modification, however, cannot be applied to a group of square-wave bursters, including the Butera-Rinzel-Smith model (Butera et al., 1999; Del Negro et al., 2001), which is a model of the pre-Bötzinger complex bursting neuron that plays a crucial role in the generation of respiration rhythms, because this modification premises that the slow dynamics originates from an activation gate variable of a hyperpolarizing ionic current. However, in some square-wave bursters, they are controlled by an inactivation gate variable of a depolarizing ionic current. In this study, we proposed a similar modification with a completely different mechanism that can be applied to this group of square-wave bursters. In the presence of noises, the modified Butera-Rinzel-Smith model can generate rhythmic activity that is more stable and similar to biological observations than the original model. The mechanisms underlying this modification are explained with noisy bifurcation diagrams. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Improved spherical wave least squares method for analyzing periodic arrays of spheres.
Xie, Huan; Lu, Ya Yan
2010-06-01
For analyzing plane wave scattering from a multilayer periodic structure where each layer consists of a two-dimensional periodic array of spheres, a spherical wave least squares method is developed which extends and improves the earlier work by Matsushima et al. [PIER 69, 305 (2007)]. A number of techniques are used to speed up the method and to reduce the memory requirement. Spherical wave expansions are used in one unit cell containing a sphere in each layer, and quasi-periodic conditions are imposed on lateral surfaces of the unit cell in the least squares sense. Unlike the layer-Korringa-Kohn-Rostoker method [Physica A 141, 575 (1987)], the method does not need lattice sums and it is relatively simple to implement.
Reliable Welding of HSLA Steels by Square Wave Pulsing Using an Advanced Sensing (EDAP) Technique.
1986-04-30
situation is the result of welding on A710 steel . (A similar effect on welding on HY80 ?) The following is offered by Woods and Milner (Ref. 12): "The...AD-R69 762 RELIABLE MELDING OF HSLA STEELS BY SQUARE MAVE PULSING 1/2 USING AN ADV NCED.. (U) APPLIED FUSION TECHNOLOGIES INC FORT COLLINS CO C...6 p . 0 Report 0001 AZ AD-A 168 762 I "RELIABLE WELDING OF HSLA STEELS BY SQUARE WAVE PULSING USING AN ADVANCED SENSING (EDAP) TECHNIQUE- Preliminary
Numerical simulation of shock wave emanating from a square shock tube
NASA Astrophysics Data System (ADS)
Abe, Akihisa; Itoh, Katsuhiro; Takayama, Kazuyoshi
1990-11-01
The flow field behind a shock wave emitted from a square shock tube was studied. Being 3-D, various phenomena were observed for axisymmetric flow such as distorted vortex ring structures generated from the shock tube exit, shock wave deformation, and a variety of flow structures behind the shock wave. If the generative mechanisms of distorted vortex ring and flows from the shock tube are clear, this also contributes to the technical advancement, regarding the mixture of different chemical species. The shock wave emanating from a square shock tube was studied in numerical simulation and shock tube experiment. In order to simulate these flow fields, a second order upwind Total Variation Diminishing (TVD) finite difference scheme was used. The TVD scheme, having been used for 2-D problems, was extended to 3-D and applied to Euler equations. The computational domain of 60 x 60 x 60 grid points covers a quarter of the shock tube cross section. As an initial configuration, a normal shock wave with Mach 1.5 was taken. The numerical results were compared with data from optical measurements. Good qualitative agreement was obtained between numerical and experimental results.
Determination of heavy metals by thin-layer chromatography-square-wave anodic stripping voltammetry
Aldstadt, J.H.; Dewald, H.D. )
1992-12-15
A square-wave anodic stripping voltammetric method is described for low parts per million determination of heavy metals separated by thin-layer chromatography (TLC). Heavy metal samples are separated on carboxymethyl cellulose TLC plates and detected by anodic stripping voltammetry (ASV) using a cellulose dialysis membrane-covered mercury film electrode (CM-MFE) placed directly on the TLC plate surface in a thin film of supporting electrolyte solution. The fast scan rates possible in square-wave voltammetry during the stripping step eliminate the need to deoxygenate the sample. Results are presented for a mixture of Pb(II), Cd(II), Cu(II), and Zn(II). Calibration curves for Pb(II) were linear over the range 10-500 ng, with a relative standard deviation of the peak current over a set of eight separate 100-ng Pb(II) samples of 16%. 25 refs., 7 figs.
Determination of Norfloxacin by square-wave adsorptive voltammetry on a glassy carbon electrode.
Ghoneim, M M; Radi, A; Beltagi, A M
2001-05-01
The adsorptive and electrochemical behavior of norfloxacin on a glassy carbon electrode were investigated by cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated that the process was irreversible and fundamentally controlled by adsorption. To obtain a good sensitivity, the solution conditions and instrumental parameters were studied using square-wave voltammetry. In acetate buffer of pH 5.0, norfloxacin gave a sensitive adsorptive oxidative peak at 0.920 V (versus Ag-AgCl). Applicability to measurement of norfloxacin at submicromolar levels in urine samples was illustrated. The peak current was linear with the norfloxacin concentration in the range 5-50 microg ml(-1) urine. The detection limit was 1.1 microg ml(-1) urine.
Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A
2014-08-19
Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.
Optimal decay rate for the wave equation on a square with constant damping on a strip
NASA Astrophysics Data System (ADS)
Stahn, Reinhard
2017-04-01
We consider the damped wave equation with Dirichlet boundary conditions on the unit square parametrized by Cartesian coordinates x and y. We assume the damping a to be strictly positive and constant for x<σ and zero for x>σ . We prove the exact t^{-4/3}-decay rate for the energy of classical solutions. Our main result (Theorem 1) answers question (1) of Anantharaman and Léautaud (Anal PDE 7(1):159-214, 2014, Section 2C).
Nouri-Nigjeh, Eslam; Permentier, Hjalmar P; Bischoff, Rainer; Bruins, Andries P
2011-07-15
Electrochemistry combined with mass spectrometry (EC-MS) is an emerging analytical technique in the imitation of oxidative drug metabolism at the early stages of new drug development. Here, we present the benefits of electrochemical oxidation by square-wave potential pulses for the oxidation of lidocaine, a test drug compound, on a platinum electrode. Lidocaine was oxidized at constant potential and by square-wave potential pulses with different cycle times, and the reaction products were analyzed by liquid chromatography-mass spectrometry [LC-MS(/MS)]. Application of constant potentials of up to +5.0 V resulted in relatively low yields of N-dealkylation and 4-hydroxylation products, while oxidation by square-wave potential pulses generated up to 50 times more of the 4-hydroxylation product at cycle times between 0.2 and 12 s (estimated yield of 10%). The highest yield of the N-dealkylation product was obtained at cycle times shorter than 0.2 s. Tuning of the cycle time is thus an important parameter to modulate the selectivity of electrochemical oxidation reactions. The N-oxidation product was only obtained by electrochemical oxidation under air atmosphere due to reaction with electrogenerated hydrogen peroxide. Square-wave potential pulses may also be applicable to modulate the selectivity of electrochemical reactions with other drug compounds in order to generate oxidation products with greater selectivity and higher yield based on the optimization of cycle times and potentials. This considerably widens the scope of direct electrochemistry-based oxidation reactions for the imitation of in vivo oxidative drug metabolism.
Square wave voltages-induced ON states of organic resistive memory devices
NASA Astrophysics Data System (ADS)
Qin, Jiajun; Chu, Ming; Peng, Huan; Zhang, Jiawei; Hou, Xiaoyuan
2016-10-01
In organic resistive memory device field, alternating current (AC) has seldom been studied systematically. In the present work, square wave voltage pulses are considered to obtain memory switching to the ON state with voltage amplitude lower than the threshold voltage of the device, even with less time. The ON states induced by such AC depend on both frequency and amplitude. A possible mechanism related to filamentary formation was proposed to explain the AC induced effect.
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.
Pentazocine transport by square-wave AC iontophoresis with an adjusted duty cycle.
Ogami, Saori; Hayashi, Shizuka; Shibaji, Takao; Umino, Masahiro
2008-03-01
So far, pentazocine iontophoresis has never been studied, although pentazocine is widely used in pain management. The purpose of this study was to determine whether pentazocine transportation through a cellophane membrane could be enhanced using square-wave alternating current (AC) iontophoresis with an adjusted duty cycle and dependence on the voltage and the duty cycle. Voltages of 10, 25 and 40 V with duty cycles of 50%, 51%, 52%, 53%, 54% and 55% were applied for 60 minutes at a high frequency of 1 MHz to diffusion cells on both sides of a cellophane membrane. The donor compartment was filled with a solution containing pentazocine. Square-wave AC iontophoresis with an adjusted duty cycle enhanced pentazocine transportation at higher voltages and duty cycles. These results suggested that the direct current (DC) component of the square-wave AC played an important role in enhancing pentazocine transportation despite changes in polarity at very high frequency of 1 MHz. The higher voltages and duty cycles induced a pH change. The practical electrical conditions that could be applied clinically were 25 V with a 54% duty cycle or 40 V with a 53% duty cycle.
Analysis of square-wave bouts to verify VO2max.
Sedgeman, D; Dalleck, L; Clark, I E; Jamnick, N; Pettitt, R W
2013-12-01
Submaximal and supramaximal square-wave bouts have been reported to consistently verify 'true' VO2max. Although a direct comparison between both protocols exists, knowledge on the statistical consistency between the protocols using the same group of participants is lacking. The purpose of this study was to conduct an analysis of the submaximal and supramaximal verification bout performed shortly subsequent to a graded exercise test (GXT). On 2 separate occasions, 6 males and 7 females (age: 29±9 years) completed a GXT protocol and an exhaustive, square-wave bout at either end-GXT power minus 2-stages or 105% end-GXT power. No differences (p>0.05) in VO2max were observed between the GXT and square-wave bouts. The typical error (ml/kg/min) for submaximal (1.09) and supramaximal (1.04) trials was similar. Likewise, similar relative measures of consistency were observed for the submaximal (ICC α=0.97, CV=2.4%) and supramaximal trials (ICC α=0.95, CV=2.3%). For a GXT lasting ~10-12 min, the submaximal or supramaximal protocols appear to be equally effective. © Georg Thieme Verlag KG Stuttgart · New York.
Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa.
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.
Magnetization reversal mechanism in patterned (square to wave-like) Py antidot lattices
NASA Astrophysics Data System (ADS)
Tahir, N.; Zelent, M.; Gieniusz, R.; Krawczyk, M.; Maziewski, A.; Wojciechowski, T.; Ding, J.; Adeyeye, A. O.
2017-01-01
The effects of shape and geometry of antidot (square, bi-component, and wave-like) lattices (ADLs) on the magnetization reversal processes and magnetic anisotropy has been systematically investigated by magneto-optical Kerr effect based microscopy. Our experimental results were reproduced by micromagnetic simulations, which highlight the qualitative agreement with the experimental results. We have demonstrated that a small antidot in the center of a unit cell in the square ADL is sufficient to induce additional easy axes with large coercive fields. In wave-like patterns, narrow channels connecting smaller and larger antidots (bi-component ADL) further drastically change the anisotropy map, creating the high coercive fields along a wide angular range (90°) of directions parallel to the channels. In simulated results, we have observed formation of periodic domain structures in all ADLs, however, in the case of a wave-like pattern it is most regular and moreover two different periodic patterns are stabilized at different applied magnetic field values. The formation of 360° domain walls were also observed in wave-like ADL where these domains are formed along the lines connecting adjacent larger and smaller antidots, perpendicular to the channels. These findings point out the possibility of exploiting ADLs with complex unit cells in magnonic or spintronic applications.
Multisource least-squares migration and prism wave reverse time migration
NASA Astrophysics Data System (ADS)
Dai, Wei
Least-squares migration has been shown to be able to produce high quality migration images, but its computational cost is considered to be too high for practical imaging. In this dissertation, a multisource least-squares migration algorithm (MLSM) is proposed to increase the computational efficiency by utilizing the blended sources processing technique. The MLSM algorithm is implemented with both the Kirchhoff migration and reverse time migration methods. In the last chapter, a new method is proposed to migrate prism waves separately to illuminate vertical reflectors such as salt flanks. Its advantage over standard RTM method is that it does not require modifying the migration velocity model. There are three main chapters in this dissertation. In Chapter 2, the MLSM algorithm is implemented with Kirchhoff migration and random time-shift encoding functions. Numerical results with Kirchhoff least-squares migration on the 2D SEG/EAGE salt model show that an accurate image is obtained by migrating a supergather of 320 phase-encoded shots. When the encoding functions are the same for every iteration, the I/O cost of MLSM is reduced by 320 times. Empirical results show that the crosstalk noise introduced by blended sources is more effectively reduced when the encoding functions are changed at every iteration. The analysis of the signal-to-noise ratio (SNR) suggests that an acceptable number of iterations are needed to enhance the SNR to an acceptable level. The benefit is that Kirchhoff MLSM is a few times faster than standard LSM, and produces much more resolved images than standard Kirchhoff migration. In Chapter 3, the MLSM algorithm is implemented with the reverse time migration method and a new parameterization, where the migration image of each shot gather is updated separately and an ensemble of prestack images is produced along with common image gathers. The merits of prestack plane-wave LSRTM are the following: (1) plane-wave prestack LSRTM can sometimes offer
Cyclic Square Wave Voltammetry of Surface-Confined Quasireversible Electron Transfer Reactions.
Mann, Megan A; Bottomley, Lawrence A
2015-09-01
The theory for cyclic square wave voltammetry of surface-confined quasireversible electrode reactions is presented and experimentally verified. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. These criteria were experimentally confirmed using two well-established surface-confined analytes. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.
Optimization of instrumental parameters for square-wave anodic stripping voltammetry.
Buchanan, E B; Soleta, D D
1983-07-01
Experimental parameters associated with the use of a square-wave potential waveform during the stripping procedure have been examined for their effect on the sensitivity of ASV. Voltamperograms for 10-ng ml solutions of lead and of cadmium were recorded under the various experimental conditions. Peak heights obtained experimentally were compared with those calculated from an equation describing the rate of decay of the measured current. Calibration graphs were constructed for lead and cadmium over the range 0.1-1.6ng ml , and the two metals were determined in samples of the local water supply.
Silicon-controlled-rectifier square-wave inverter with protection against commutation failure
NASA Technical Reports Server (NTRS)
Birchenough, A. G.
1971-01-01
The square-wave SCR inverter that was designed, built, and tested includes a circuit to turn off the inverter in case of commutation failure. The basic power stage is a complementary impulse-commutated parallel inverter consisting of only six components. The 400-watt breadboard was tested while operating at + or - 28 volts, and it had a peak efficiency of 95.5 percent at 60 hertz and 91.7 percent at 400 hertz. The voltage regulation for a fixed input was 3 percent at 60 hertz. An analysis of the operation and design information is included.
Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser.
Mei, Li; Chen, Guoliang; Xu, Lixin; Zhang, Xianming; Gu, Chun; Sun, Biao; Wang, Anting
2014-06-01
We have proposed and demonstrated a figure-8 dual-pump passively mode-locked fiber laser to generate square-wave pulse tunable by both width and amplitude. Just by simply adjusting the power of the pumps, both the amplitude and width of the output square-wave pulse can be tuned independently and continuously. One pump is used to tune the output pulsewidth while the other is used to tune amplitude.
2007-03-15
in Groundwater Development Of Novel Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled Monolayers On Mesoporous Supports...Sensors for Monitoring of Toxic Metals in Groundwater Development Of Novel Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled... Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled onolayers On Mesoporous Supports SI-1267 95440Zemanian, Thomas S., and Lin
Differentially-charged and sequentially-switched square-wave pulse forming network
North, George G. [Stockton, CA; Vogilin, George E. [Livermore, CA
1980-04-01
A pulse forming network for delivering a high-energy square-wave pulse to a load, including a series of inductive-capacitive sections wherein the capacitors are differentially charged higher further from the load. Each charged capacitor is isolated from adjacent sections and the load by means of a normally open switch at the output of each section. The switch between the load and the closest section to the load is closed to begin discharge of the capacitor in that section into the load. During discharge of each capacitor, the voltage thereacross falls to a predetermined potential with respect to the potential across the capacitor in the next adjacent section further from the load. When this potential is reached, it is used to close the switch in the adjacent section further from the load and thereby apply the charge in that section to the load through the adjacent section toward the load. Each successive section further from the load is sequentially switched in this manner to continuously and evenly supply energy to the load over the period of the pulse, with the differentially charged capacitors providing higher potentials away from the load to compensate for the voltage drop across the resistance of each inductor. This arrangement is low in cost and yet provides a high-energy pulse in an acceptable square-wave form.
Differentially-charged and sequentially-switched square-wave pulse forming network
North, G.G.; Vogilin, G.E.
1980-04-01
Disclosed is a pulse forming network for delivering a high-energy square-wave pulse to a load, including a series of inductive-capacitive sections wherein the capacitors are differentially charged higher further from the load. Each charged capacitor is isolated from adjacent sections and the load by means of a normally open switch at the output of each section. The switch between the load and the closest section to the load is closed to begin discharge of the capacitor in that section into the load. During discharge of each capacitor, the voltage thereacross falls to a predetermined potential with respect to the potential across the capacitor in the next adjacent section further from the load. When this potential is reached, it is used to close the switch in the adjacent section further from the load and thereby apply the charge in that section to the load through the adjacent section toward the load. Each successive section further from the load is sequentially switched in this manner to continuously and evenly supply energy to the load over the period of the pulse, with the differentially charged capacitors providing higher potentials away from the load to compensate for the voltage drop across the resistance of each inductor. This arrangement is low in cost and yet provides a high-energy pulse in an acceptable square-wave form. 5 figs.
Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.
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.
Canards in a minimal piecewise-linear square-wave burster
Desroches, M.; Krupa, M.; Fernández-García, S.
2016-07-15
We construct a piecewise-linear (PWL) approximation of the Hindmarsh-Rose (HR) neuron model that is minimal, in the sense that the vector field has the least number of linearity zones, in order to reproduce all the dynamics present in the original HR model with classical parameter values. This includes square-wave bursting and also special trajectories called canards, which possess long repelling segments and organise the transitions between stable bursting patterns with n and n + 1 spikes, also referred to as spike-adding canard explosions. We propose a first approximation of the smooth HR model, using a continuous PWL system, and show that its fast subsystem cannot possess a homoclinic bifurcation, which is necessary to obtain proper square-wave bursting. We then relax the assumption of continuity of the vector field across all zones, and we show that we can obtain a homoclinic bifurcation in the fast subsystem. We use the recently developed canard theory for PWL systems in order to reproduce the spike-adding canard explosion feature of the HR model as studied, e.g., in Desroches et al., Chaos 23(4), 046106 (2013).
On square-wave-driven stochastic resonance for energy harvesting in a bistable system
Su, Dongxu; Zheng, Rencheng; Nakano, Kimihiko; Cartmell, Matthew P
2014-11-15
Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.
Canards in a minimal piecewise-linear square-wave burster
NASA Astrophysics Data System (ADS)
Desroches, M.; Fernández-García, S.; Krupa, M.
2016-07-01
We construct a piecewise-linear (PWL) approximation of the Hindmarsh-Rose (HR) neuron model that is minimal, in the sense that the vector field has the least number of linearity zones, in order to reproduce all the dynamics present in the original HR model with classical parameter values. This includes square-wave bursting and also special trajectories called canards, which possess long repelling segments and organise the transitions between stable bursting patterns with n and n + 1 spikes, also referred to as spike-adding canard explosions. We propose a first approximation of the smooth HR model, using a continuous PWL system, and show that its fast subsystem cannot possess a homoclinic bifurcation, which is necessary to obtain proper square-wave bursting. We then relax the assumption of continuity of the vector field across all zones, and we show that we can obtain a homoclinic bifurcation in the fast subsystem. We use the recently developed canard theory for PWL systems in order to reproduce the spike-adding canard explosion feature of the HR model as studied, e.g., in Desroches et al., Chaos 23(4), 046106 (2013).
NASA Astrophysics Data System (ADS)
Meroño, P. A.; Gómez, F. C.; Marín, F.; Zaghar, L.
2017-02-01
One of the widely used processes to measure torsional vibration focuses on the analysis of a square signal from a device set in the machine shaft. The tools used for this purpose usually consist of a toothed wheel connected to an appropriate transducer, of an electromagnetic or optic type, which provides a square wave signal. If the rotation velocity is constant, the signal pulses are the same width, but when the velocity changes, the width of the pulses changes too, lengthening or shortening its width, resulting in a frequency modulated signal. When the shafts of the machines are misaligned angularly, the average speed changes due to variable torque action, so that spectral features of modulated signal show frequency components that are explained by the Bessel Functions. This work shows that these components are caused by a carrying (constant average speed) and a modulator signal (variable turning speed) between the harmonics surrounding the central frequency. Besides, it may also test their relationship with the presence of angular misalignment in the coupled-machine shafts. In addition, an iterative method is applied to construct the frequency spectral diagram of the induced square signal, once the appropriate modulation indices of the Bessel functions have been calculated. To compare and validate the method, different bench tests have been performed using pulse signal and laser interferometry.
Rabani, Amir
2016-01-01
The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications. PMID:27754324
Rabani, Amir
2016-10-12
The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications.
Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment
NASA Technical Reports Server (NTRS)
Walsh, E. J.; Vandemark, D. C.; Hines, D. E.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Jensen, J.; Lee, S.; Fandry, C.
1999-01-01
For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the 36 GHz (8.3 mm) NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 deg roll attitude, interrogating off-nadir incidence angles from -15 deg through nadir to +29 deg. The aircraft turned azimuthally through 810 deg in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 m to 65 m). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. A unique feature of this experiment was the use of a nadir-directed low-gain horn antenna (35 deg beamwidth) to acquire azimuthally integrated backscattered power data versus incidence angle before and after the turn data.
Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment
NASA Technical Reports Server (NTRS)
Walsh, E. J.; Vandemark, D. C.; Hines, D. E.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Jensen, J.; Lee, S.; Fandry, C.
1999-01-01
For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the 36 GHz (8.3 mm) NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 deg roll attitude, interrogating off-nadir incidence angles from -15 deg through nadir to +29 deg. The aircraft turned azimuthally through 810 deg in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 m to 65 m). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. A unique feature of this experiment was the use of a nadir-directed low-gain horn antenna (35 deg beamwidth) to acquire azimuthally integrated backscattered power data versus incidence angle before and after the turn data.
Otarola, Jessica; Garrido, Mariano; Correa, N Mariano; Molina, Patricia G
2016-08-04
A new, simple, and fast electrochemical (EC) method has been developed to determine the release profile of piroxicam, a nonsteroidal anti-inflammatory drug, loaded in a drug delivery system based on nanostructured lipid carriers (NLCs). For the first time, the samples were analyzed by using square wave voltammetry, a sensitive EC technique. The piroxicam EC responses allow us to propose a model that explains the experimental results and to subsequently determine the amount of drug loaded into the NLCs formulation as a function of time. In vitro drug release studies showed prolonged drug release (up to 5 days), releasing 60 % of the incorporated drug. The proposed method is a promising and stable alternative for the study of different drug delivery systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Flight Test of Orthogonal Square Wave Inputs for Hybrid-Wing-Body Parameter Estimation
NASA Technical Reports Server (NTRS)
Taylor, Brian R.; Ratnayake, Nalin A.
2011-01-01
As part of an effort to improve emissions, noise, and performance of next generation aircraft, it is expected that future aircraft will use distributed, multi-objective control effectors in a closed-loop flight control system. Correlation challenges associated with parameter estimation will arise with this expected aircraft configuration. The research presented in this paper focuses on addressing the correlation problem with an appropriate input design technique in order to determine individual control surface effectiveness. This technique was validated through flight-testing an 8.5-percent-scale hybrid-wing-body aircraft demonstrator at the NASA Dryden Flight Research Center (Edwards, California). An input design technique that uses mutually orthogonal square wave inputs for de-correlation of control surfaces is proposed. Flight-test results are compared with prior flight-test results for a different maneuver style.
Sensorimotor recovery following spaceflight may be due to frequent square-wave saccadic intrusions
NASA Technical Reports Server (NTRS)
Reschke, Millard; Somers, Jeffrey T.; Leigh, R. John; Krnavek, Jody M.; Kornilova, Ludmila; Kozlovskaya, Inessa; Bloomberg, Jacob J.; Paloski, William H.
2004-01-01
Square-wave jerks (SWJs) are small, involuntary saccades that disrupt steady fixation. We report the case of an astronaut (approximately 140 d on orbit) who showed frequent SWJs, especially postflight, but who showed no impairment of vision or decrement of postflight performance. These data support the view that SWJs do not impair vision because they are paired movements, consisting of a small saccade away from the fixation position followed, within 200 ms, by a corrective saccade that brings the eye back on target. Since many returning astronauts show a decrement of dynamic visual function during postflight locomotion, it seems possible that frequent SWJs improved this astronaut's visual function by providing postsaccadic enhancement of visual fixation, which aided postflight performance. Certainly, frequent SWJs did not impair performance in this astronaut, who had no other neurological disorder.
Mhammedi, M A El; Achak, M; Hbid, M; Bakasse, M; Hbid, T; Chtaini, A
2009-10-30
In this work, determination of cadmium(II) using square wave voltammetry (SWV) was described. The method is based on accumulation of these metal ions on kaolin platinum electrode (K/Pt). The K/Pt performance was optimized with respect to the surface modification and operating conditions. The optimized conditions were obtained in pH of 5.0 and accumulation time of 25 min. Under the optimal conditions, the relationship between the peak current versus concentration was linear over the range of 9 x 10(-8) to 8.3 x 10(-6) mol L(-1). The detection limit (DL, 3sigma) was 5.4 x 10(-9) mol L(-1). The analytical methodology was successfully applied to monitor the Cd(II) content in natural water. Interferences were also evaluated.
Torralba, E; Ortuño, J A; Molina, A; Serna, C; Karimian, F
2014-05-15
The transfer of the protonated forms of heptylamine, octylamine, decylamine, procaine and procainamide facilitated by dibenzo-18-crown-6 from water to a solvent polymeric membrane has been investigated by using cyclic square wave voltammetry. The experimental voltammograms obtained are in good agreement with theoretical predictions. The values of the standard ion transfer potential, complexation constant and diffusion coefficient in water have been obtained from these experiments, and have been used to draw some conclusions about the lipophilicity of these species and the relative stability of the organic ammonium complexes with dibenzo-18-crown-6. The results have been compared with those provided by linear sweep voltammetry. Calibration graphs were obtained with both techniques. An interesting chronoamperometric method for the determination of the diffusion coefficient of the target ion in the membrane has been developed and applied to all these protonated amines.
Towards optimum demodulation of bandwidth-limited and low SNR square-wave subcarrier signals
NASA Technical Reports Server (NTRS)
Feria, Y.; Hurd, W.
1995-01-01
The optimum phase detector is presented for tracking square-wave subcarriers that have been bandwidth limited to a finite number of harmonics. The phase detector is optimum in the sense that the loop signal-to-noise ratio (SNR) is maximized and, hence, the rms phase tracking error is minimized. The optimum phase detector is easy to implement and achieves substantial improvement. Also presented are the optimum weights to combine the signals demodulated from each of the harmonics. The optimum weighting provides SNR improvement of 0.1 to 0.15 dB when the subcarrier loop SNR is low (15 dB) and the number of harmonics is high (8 to 16).
Eberhard, J.W.; Hedengren, K.H.V.
1991-12-17
This paper describes a scanning and data acquisition method for three-dimensional computerized tomography (CT) imaging of a field of view containing at least a portion of an object illuminated by a cone beam source. It comprises: defining a source scanning trajectory as a path traversed by the source; employing the cone beam source fixed with reference to a two-dimensional array detector with both source and detector movably positioned relative to the object in order to scan about the object; specifying the source scanning trajectory as a square wave on a cylindrical surface surrounding the field of view such that each plane passing through the field of view intersects the scanning trajectory in at lease one point; and scanning at a plurality of positions along the source scanning trajectory to obtain cone beam projection data.
Properties of amorphous silicon thin films grown in square wave modulated silane rf discharges
NASA Astrophysics Data System (ADS)
Andújar, J. L.; Bertran, E.; Canillas, A.; Campmany, J.; Serra, J.; Roch, C.; Lloret, A.
1992-02-01
Hydrogenated amorphous silicon (a-Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2-4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a-Si:H from SQWM rf discharges through their influence on powder particle formation.
Symbol signal-to-noise ratio loss in square-wave subcarrier downconversion
NASA Technical Reports Server (NTRS)
Feria, Y.; Statman, J.
1993-01-01
This article presents the simulated results of the signal-to-noise ratio (SNR) loss in the process of a square-wave subcarrier down conversion. In a previous article, the SNR degradation was evaluated at the output of the down converter based on the signal and noise power change. Unlike in the previous article, the SNR loss is defined here as the difference between the actual and theoretical symbol SNR's for the same symbol-error rate at the output of the symbol matched filter. The results show that an average SNR loss of 0.3 dB can be achieved with tenth-order infinite impulse response (IIR) filters. This loss is a 0.2-dB increase over the SNR degradation in the previous analysis where neither the signal distortion nor the symbol detector was considered.
A submicron device to rectify a square-wave angular velocity.
Moradian, A; Miri, M F
2011-02-01
We study a system composed of two thick dielectric disks separated by a thin layer of an electrolyte solution. Initially both plates have the same surface charge distribution. The surface charge distribution has no rotational symmetry. We show that the top plate experiences a torque [Formula: see text]([Formula: see text]) if it rotates about its axis by an angle [Formula: see text] . The torque can be controlled by varying the electrolyte concentration, the separation and the surface charge density of the plates. For a specific example of charged rods attached to the plates, we find [Formula: see text]([Formula: see text]) [Formula: see text] sin(4[Formula: see text]) . We also study the dynamics of the system. We consider the case where the angular velocity of the bottom disk is a square-wave signal. We find that the average angular velocity of the top disk is not zero.
Tonello, Natalia; Moressi, Marcela Beatriz; Robledo, Sebastián Noel; D'Eramo, Fabiana; Marioli, Juan Miguel
2016-09-01
The simultaneous determination of eugenol (EU), thymol (Ty) and carvacrol (CA) in honey samples, employing square wave voltammetry (SWV) and chemometrics tools, is informed for the first time. For this purpose, a glassy carbon electrode (GCE) was used as working electrode. The operating conditions and influencing parameters (involving several chemical and instrumental parameters) were first optimized by cyclic voltammetry (CV). Thus, the effects of the scan rate, pH and analyte concentration on the electrochemical response of the above mentioned molecules were studied. The results show that the electrochemical responses of the three compounds are very similar and that the voltammetric traces present a high degree of overlap under all the experimental conditions used in this study. Therefore, two chemometric tools were tested to obtain the multivariate calibration model. One method was the partial least squares regression (PLS-1), which assumes a linear behaviour. The other nonlinear method was an artificial neural network (ANN). In this last case we used a supervised, feed-forward network with Levenberg-Marquardt back propagation training. From the accuracies and precisions analysis between nominal and estimated concentrations calculated by using both methods, it was inferred that the ANN method was a good model to quantify EU, Ty and CA in honey samples. Recovery percentages were between 87% and 104%, except for two samples whose values were 136% and 72%. The analytical methodology was simple, fast and accurate.
Masoller, C.; Sukow, D.; Gavrielides, A.
2011-08-15
We analyze the dynamics of two semiconductor lasers with so-called orthogonal time-delayed mutual coupling: the dominant TE (x) modes of each laser are rotated by 90 deg. (therefore, TM polarization or y) before being coupled to the other laser. Although this laser system allows for steady-state emission in either one or in both polarization modes, it may also exhibit stable time-periodic dynamics including square waveforms. A theoretical mapping of the switching dynamics unveils the region in parameter space where one expects to observe long-term time-periodic mode switching. Detailed numerical simulations illustrate the role played by the coupling strength, the mode frequency detuning, or the mode gain to loss difference. We complement our theoretical study with several experiments and measurements. We present time series and intensity spectra associated with the characteristics of the square waves and other waveforms observed as a function of the strength of the delay coupling. The experimental observations are in very good agreement with the analysis and the numerical results.
Ellison, Chad M.; Perricone, Matthew; Faraone, Kevin M. (Honeywell FM&T, Kansas City, MO); Roach, Robert Allen; Norris, Jerome T.
2007-02-01
Nd:YAG laser joining is a high energy density (HED) process that can produce high-speed, low-heat input welds with a high depth-to-width aspect ratio. This is optimized by formation of a ''keyhole'' in the weld pool resulting from high vapor pressures associated with laser interaction with the metallic substrate. It is generally accepted that pores form in HED welds due to the instability and frequent collapse of the keyhole. In order to maintain an open keyhole, weld pool forces must be balanced such that vapor pressure and weld pool inertia forces are in equilibrium. Travel speed and laser beam power largely control the way these forces are balanced, as well as welding mode (Continuous Wave or Square Wave) and shielding gas type. A study into the phenomenon of weld pool porosity in 304L stainless steel was conducted to better understand and predict how welding parameters impact the weld pool dynamics that lead to pore formation. This work is intended to aid in development and verification of a finite element computer model of weld pool fluid flow dynamics being developed in parallel efforts and assist in weld development activities for the W76 and future RRW programs.
Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment
NASA Technical Reports Server (NTRS)
Walsh, E. J.; Vandemark, D. C.; Wright, C. W.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Hines, D. E.; Jensen, J.; Lee, S.; Gerlach, John C. (Technical Monitor)
2001-01-01
For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The SRA sweeps a radar beam of P (two-way) half-power width across the aircraft ground track over a swath equal to 0.8 of the aircraft height, simultaneously measuring the backscattered power at its 36 GHz (8.3 mm) operating frequency and the range to the sea surface at 64 cross-track positions. In realtime, the slant ranges are multiplied by the cosine of the off-nadir incidence angles (including the effect of aircraft roll attitude) to determine the vertical distances from the aircraft to the sea surface. These distances are subtracted from the aircraft height to produce a sea-surface elevation map, which is displayed on a monitor in the aircraft to enable real-time assessments of data quality and wave properties. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 degree roll attitude, interrogating off-nadir incidence angles from -15 degrees through nadir to +29 degrees. The aircraft turned azimuthally through 810 degrees in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 meters to 65 meters). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. Data were collected over a wide range of wind and sea
Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment
NASA Technical Reports Server (NTRS)
Walsh, E. J.; Vandemark, D. C.; Wright, C. W.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Hines, D. E.; Jensen, J.; Lee, S.;
2001-01-01
For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The SRA sweeps a radar beam of P (two-way) half-power width across the aircraft ground track over a swath equal to 0.8 of the aircraft height, simultaneously measuring the backscattered power at its 36 GHz (8.3 mm) operating frequency and the range to the sea surface at 64 cross-track positions. In realtime, the slant ranges are multiplied by the cosine of the off-nadir incidence angles (including the effect of aircraft roll attitude) to determine the vertical distances from the aircraft to the sea surface. These distances are subtracted from the aircraft height to produce a sea-surface elevation map, which is displayed on a monitor in the aircraft to enable real-time assessments of data quality and wave properties. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 degree roll attitude, interrogating off-nadir incidence angles from -15 degrees through nadir to +29 degrees. The aircraft turned azimuthally through 810 degrees in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 meters to 65 meters). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. Data were collected over a wide range of wind and sea
Direct determination of molybdenum in seawater by adsorption cathodic stripping square-wave voltammetry.
Sun, Y C; Mierzwa, J; Lan, C R
2000-06-30
A reliable and very sensitive procedure for the determination of trace levels of molybdenum in seawater is proposed. The complex of molybdenum with 8-hydroxyquinoline (Oxine) is analyzed by cathodic stripping square-wave voltammetry based on the adsorption collection onto a hanging mercury drop electrode (HMDE). This procedure of molybdenum determination was found to be more favorable than differential pulse cathodic stripping voltammetry because of inherently faster scan rate and much better linearity obtained through the one-peak (instead of one-of-two peaks) calibration. The variation of polarographic peak and peak current with a pH, adsorption time, adsorption potential, and some instrumental parameters such as scan rate and pulse height were optimized. The alteration of polarographic wave and its likely mechanism are also discussed. The relationship between peak current and molybdenum concentration is linear up to 150 mug l(-1). Under the optimal analytical conditions, the determination limit of 0.5 mug l(-1) Mo was reached after 60 s of the stirred collection. The estimated detection limit is better than 0.1 mug l(-1) of Mo. The applicability of this method to analysis of seawater was assessed by the determination of molybdenum in two certified reference seawater samples (CASS-2 and NASS-2) and the comparison of the analytical results for real seawater samples (study on a vertical distribution of Mo in the seawater column) with the results obtained by Zeeman-corrected electrothermal atomization atomic absorption spectrometry (Zeeman ETAAS). A good agreement between two used methods of molybdenum determination was obtained.
Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms
NASA Technical Reports Server (NTRS)
Tang, I. H.; Murakami, D. M.; Fuller, C. A.
1999-01-01
Circadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P < 0.01) in LDSN than in LDSq and had a longer alpha-period (1.7 h; P < 0.05). The reactive Tb onset was 0.7 h earlier (P < 0.01) in LDSN. In LDSN, the predictive Act onset advanced by 0.3 h (P < 0.05), whereas the Tb predictive onset remained the same as in LDSq. The phase angle difference between Act and Tb predictive onsets decreased by 0.9 h (P < 0.05) in LDSN, but the offsets of both measures remained unchanged. In this study, animals exhibited different circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.
Atila, Alptug; Yilmaz, Bilal
2015-01-01
In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation.
Assay of dipyridamole in human serum using cathodic adsorptive square-wave stripping voltammetry.
Ghoneim, M M; Tawfik, A; Radi, A
2002-09-01
A rapid and sensitive square-wave voltammetric procedure was optimized for the determination of dipyridamole after its adsorption preconcentration onto a hanging mercury drop electrode. The peak current of the first of the two peaks developed for this drug in Britton-Robinson buffer at pH 8.0 has been considered for the present analytical study. An accumulation potential of -1.0 V versus Ag/AgCl/KCl(s), pulse amplitude a =100 mV, scan increment Delta E =10 mV, and frequency f =120 Hz were the optimal experimental parameters. Dipyridamole can be determined in the concentration range of 9.0 x 10(-9) to 5.0 x 10(-6) M using accumulation times of 30-300 s. A detection limit of 4.0 x 10(-11) M was achieved after a 300 s accumulation time. Applicability to serum samples was illustrated. The average recoveries for dipyridamole spiked to serum at 0.25-4.50 micro g ml(-1) were 96.0-102.0%, and the higher standard deviation was 2.9%. A detection limit of 0.06 micro g mL(-1) of serum was obtained.
Mirceski, Valentin; Hocevar, Samo B; Ogorevc, Bozidar; Gulaboski, Rubin; Drangov, Ivan
2012-05-15
A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface.
Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms
NASA Technical Reports Server (NTRS)
Tang, I. H.; Murakami, D. M.; Fuller, C. A.
1999-01-01
Circadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P < 0.01) in LDSN than in LDSq and had a longer alpha-period (1.7 h; P < 0.05). The reactive Tb onset was 0.7 h earlier (P < 0.01) in LDSN. In LDSN, the predictive Act onset advanced by 0.3 h (P < 0.05), whereas the Tb predictive onset remained the same as in LDSq. The phase angle difference between Act and Tb predictive onsets decreased by 0.9 h (P < 0.05) in LDSN, but the offsets of both measures remained unchanged. In this study, animals exhibited different circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.
Square Wave Voltammetric Determination of Diclofenac in Pharmaceutical Preparations and Human Serum.
Ciltas, Ulvihan; Yilmaz, Bilal; Kaban, Selcuk; Akcay, Bilge Kaan; Nazik, Gulsah
2015-01-01
In this study, a simple and reliable square wave voltammetric (SWV) method was developed and validated for determination of diclofenac in pharmaceutical preparations and human serum. The proposed method was based on electrooxidation of diclofenac at platinum electrode in 0.1 M TBAClO4/acetonitrile solution. The well-defined two oxidation peaks were observed at 0.87 and 1.27 V, respectively. Calibration curves that were obtained by using current values measured for second peak were linear over the concentration range of 1.5-17.5 μg mL(-1) and 2-20 μg mL(-1) in supporting electrolyte and serum, respectively. Precision and accuracy were also checked in all media. Intra- and inter-day precision values for diclofenac were less than 3.64, and accuracy (relative error) was better than 2.49%. Developed method in this study is accurate, precise and can be easily applied to Diclomec, Dicloflam and Voltaren tablets as pharmaceutical preparation. Also, the proposed technique was successfully applied to spiked human serum samples. No electroactive interferences from the endogenous substances were found in human serum.
Square Wave Voltammetric Determination of Diclofenac in Pharmaceutical Preparations and Human Serum
Ciltas, Ulvihan; Yilmaz, Bilal; Kaban, Selcuk; Akcay, Bilge Kaan; Nazik, Gulsah
2015-01-01
In this study, a simple and reliable square wave voltammetric (SWV) method was developed and validated for determination of diclofenac in pharmaceutical preparations and human serum. The proposed method was based on electrooxidation of diclofenac at platinum electrode in 0.1 M TBAClO4/acetonitrile solution. The well-defined two oxidation peaks were observed at 0.87 and 1.27 V, respectively. Calibration curves that were obtained by using current values measured for second peak were linear over the concentration range of 1.5-17.5 μg mL-1 and 2-20 μg mL-1 in supporting electrolyte and serum, respectively. Precision and accuracy were also checked in all media. Intra- and inter-day precision values for diclofenac were less than 3.64, and accuracy (relative error) was better than 2.49%. Developed method in this study is accurate, precise and can be easily applied to Diclomec, Dicloflam and Voltaren tablets as pharmaceutical preparation. Also, the proposed technique was successfully applied to spiked human serum samples. No electroactive interferences from the endogenous substances were found in human serum. PMID:26330859
Atila, Alptug; Yilmaz, Bilal
2015-01-01
In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation. PMID:25901151
Electrochemical behavior and square wave voltammetric determination of aristolochic acid-I.
Kim, Mi Sun; Hahn, Younghee
2007-02-01
Electroanalytical procedure for the determination of nephrotoxic aristolochic acid-I in the medicinal plant has been developed in the presence of potential interferences of lead and cadmium by square wave voltametry (SWV). Among the phosphate buffers of pH values at 5.0, 6.1, 6.5 and 7.0, the phosphate buffers of pH 6.1 yielded the most accurate analysis of AA-I in the presence of Pb2+ and Cd2+; Pb2+ was precipitated as Pb(HPO4) and did not appear in the SW voltammogram, while Cd2+ appeared at -0.564 V which was well resolved from AA-I at -0.416 V. When the Ip of AA-I was plotted vs. concentrations between 1.67 x 10(-8) M and 1.67 x 10(-6) M in the presence of Pb2+ and Cd2+, a linear calibration curve was obtained with a slope of 6 x 10(8) nA/M and a correlation coefficient of 0.9999. The present method was applied to determine AA in the dried natural products of Aristolochia contorta Bunge; Total AA in the dried root and the ripe fructus of Aristolochia contorta Bunge were found as 25 +/- 1 microg/g and 85 +/- 3 microg/g, respectively.
Vubangsi, M.; Tchoffo, M.; Fai, L. C.; Pisma’k, Yu. M.
2015-12-15
The problem of a particle with position and time-dependent effective mass in a one-dimensional infinite square well is treated by means of a quantum canonical formalism. The dynamics of a launched wave packet of the system reveals a peculiar revival pattern that is discussed. .
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.
Kergaravat, Silvina V; Pividori, Maria Isabel; Hernandez, Silvia R
2012-01-15
The electrochemical detection for horseradish peroxidase-cosubstrate-H(2)O(2) systems was optimized. o-Phenilendiamine, phenol, hydroquinone, pyrocatechol, p-chlorophenol, p-aminophenol and 3,3'-5,5'-tetramethylbenzidine were evaluated as cosubstrates of horseradish peroxidase (HRP) enzyme. Therefore, the reaction time, the addition sequence of the substrates, the cosubstrate:H(2)O(2) ratio and the electrochemical techniques were elected by one-factor optimization assays while the buffer pH, the enzymatic activity and cosubstrate and H(2)O(2) concentrations for each system were selected simultaneously by response surface methodology. Then, the calibration curves for seven horseradish peroxidase-cosubstrate-H(2)O(2) systems were built and the analytic parameters were analyzed. o-Phenilendiamine was selected as the best cosubstrate for the HRP enzyme. For this system the reaction time of 60s, the phosphate buffer pH 6.0, and the concentrations of 2.5×10(-4)molL(-1) o-phenilendiamine and of 1.25×10(-4)molL(-1) H(2)O(2) were chosen as the optimal conditions. In these conditions, the calibration curve of horseradish peroxidase by square wave voltammetry showed a linearity range from 9.5×10(-11) to 1.9×10(-8)molL(-1) and the limit of detection of 3.8×10(-11)molL(-1) with RSD% of 0.03% (n=3).
Brycht, Mariola; Nosal-Wiercińska, Agnieszka; Sipa, Karolina; Rudnicki, Konrad; Skrzypek, Sławomira
2017-01-01
In this paper, the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the veterinary drug closantel using a renewable silver amalgam film electrode (Hg(Ag)FE) is presented. As observed in SWAdSV, closantel provided one well-shaped reduction peak suitable for analytical purposes at potential ca. -1.4 V in the Britton-Robinson (B-R) buffer at pH 7.0. At optimal conditions, the SWAdSV response of Hg(Ag)FE for determining closantel was linear over two concentration ranges of 5.0 × 10(-8) to 2.0 × 10(-7) mol dm(-3) and 2.0 × 10(-7) to 1.2 × 10(-6) mol dm(-3) with a detection limit of 1.1 × 10(-8) mol dm(-3). In addition, a relevance of the developed SWAdSV method was successfully verified by the quantitative analysis of closantel in the commercial formulation Closamectin Pour-On with satisfactory results (RSD = 5.8%, recovery = 101.8%). The results showed that the developed procedure can be adequate for screening purposes. Also, the electrochemical behavior of closantel was characterized by cyclic voltammetry, and it was found that closantel exhibited a quasi-reversible behavior with cathodic peak on the forward scan at ca. -1.4 V and anodic peak on the reverse scan at ca. -1.35 V vs. Ag/AgCl in B-R buffer, pH 7.0. As the obtained results showed that the electrode mechanism of closantel is controlled by the adsorption, the effect of adsorption was studied using the electrochemical impedance spectroscopy technique.
Determination of tryptamine in foods using square wave adsorptive stripping voltammetry.
Costa, Daniel J E; Martínez, Ana M; Ribeiro, Williame F; Bichinho, Kátia M; Di Nezio, María Susana; Pistonesi, Marcelo F; Araujo, Mario C U
2016-07-01
Tryptamine, a biogenic amine, is an indole derivative with an electrophilic substituent at the C3 position of the pyrrole ring of the indole moiety. The electrochemical oxidation of tryptamine was investigated using glassy carbon electrode (GCE), and focusing on trace level determination in food products by square wave adsorptive stripping voltammetry (SWAdSV). The electrochemical responses of tryptamine were evaluated using differing voltammetric techniques over a wide pH range, a quasi-reversible electron-transfer to redox system represented by coupled peaks P1-P3, and an irreversible reaction for peak P2 were demonstrated. The proton and electron counts associated with the oxidation reactions were estimated. The nature of the mass transfer process was predominantly diffusion-limited for the oxidation process of P1, the most selective and sensitive analytical response (acetate buffer solution pH 5.3), being used for the development of SWAdSV method, under optimum conditions. The excellent response allowed the development of an electroanalytical method with a linear response range of from 4.7-54.5)×10(-)(8)molL(-1), low detection limit (0.8×10(-)(9)molL(-)(1)), and quantification limit (2.7×10(-9)molL(-1)), and acceptable levels of repeatability (3.6%), and reproducibility (3.8%). Tryptamine content was determined in bananas, tomatoes, cheese (mozzarella and gorgonzola), and cold meats (chicken sausage and pepperoni sausage), yielding recoveries above 90%, with excellent analytical performance using simple and low cost instrumentation.
Nicol, David S; Hamilton, Ruth; Shahani, Uma; McCulloch, Daphne L
2011-02-01
Steady-state VEPs to full-field flicker (FFF) using sinusoidally modulated light were compared with those elicited by square-wave modulated light across a wide range of stimulus frequencies with monocular and binocular FFF stimulation. Binocular and monocular VEPs were elicited in 12 adult volunteers to FFF with two modes of temporal modulation: sinusoidal or square-wave (abrupt onset and offset, 50% duty cycle) at ten temporal frequencies ranging from 2.83 to 58.8 Hz. All stimuli had a mean luminance of 100 cd/m(2) with an 80% modulation depth (20-180 cd/m(2)). Response magnitudes at the stimulus frequency (F1) and at the double and triple harmonics (F2 and F3) were compared. For both sinusoidal and square-wave flicker, the FFF-VEP magnitudes at F1 were maximal for 7.52 Hz flicker. F2 was maximal for 5.29 Hz flicker, and F3 magnitudes are largest for flicker stimulation from 3.75 to 7.52 Hz. Square-wave flicker produced significantly larger F1 and F2 magnitudes for slow flicker rates (up to 5.29 Hz for F1; at 2.83 and 3.75 Hz for F2). The F3 magnitudes were larger overall for square-wave flicker. Binocular FFF-VEP magnitudes are larger than those of monocular FFF-VEPs, and the amount of this binocular enhancement is not dependant on the mode of flicker stimulation (mean binocular: monocular ratio 1.41, 95% CI: 1.2-1.6). Binocular enhancement of F1 for 21.3 Hz flicker was increased to a factor of 2.5 (95% CI: 1.8-3.5). In the healthy adult visual system, FFF-VEP magnitudes can be characterized by the frequency-response functions of F1, F2 and F3. Low-frequency roll-off in the FFF-VEP magnitudes is greater for sinusoidal flicker than for square-wave flicker for rates ≤ 5.29 Hz; magnitudes for higher-frequency flicker are similar for the two types of flicker. Binocular FFF-VEPs are larger overall than those recorded monocularly, and this binocular summation is enhanced at 21.3 Hz in the mid-frequency range.
Width dependent transition of quantized spin-wave modes in Ni{sub 80}Fe{sub 20} square nanorings
Banerjee, Chandrima; Saha, Susmita; Barman, Saswati; Barman, Anjan; Rousseau, Olivier; Otani, YoshiChika
2014-10-28
We investigated optically induced ultrafast magnetization dynamics in square shaped Ni{sub 80}Fe{sub 20} nanorings with varying ring width. Rich spin-wave spectra are observed whose frequencies showed a strong dependence on the ring width. Micromagnetic simulations showed different types of spin-wave modes, which are quantized upto very high quantization number. In the case of widest ring, the spin-wave mode spectrum shows quantized modes along the applied field direction, which is similar to the mode spectrum of an antidot array. As the ring width decreases, additional quantization in the azimuthal direction appears causing mixed modes. In the narrowest ring, the spin-waves exhibit quantization solely in azimuthal direction. The different quantization is attributed to the variation in the internal field distribution for different ring width as obtained from micromagnetic analysis and supported by magnetic force microscopy.
Stivaktakis, Polychronis D; Giannakopoulos, Evangelos; Vlastos, Dimitris; Matthopoulos, Demetrios P
2017-02-01
The interaction of pesticides with environmental factors, such as pH, may result in alterations of their physicochemical properties and should be taken into consideration in regard to their classification. This study investigates the genotoxicity of methidathion and its alkaline hydrolysis by-products in cultured human lymphocytes, using the square-wave voltammetry (square wave-adsorptive cathodic stripping voltammetry (SW-AdCSV) technique) and the cytokinesis block micronucleus assay (CBMN assay). According to the SW-AdCSV data the alkaline hydrolysis of methidathion results in two new molecules, one non-electro-active and a second electro-active which is more genotoxic than methidathion itself in cultured human lymphocytes, inducing higher micronuclei frequencies. The present study confirms the SW-AdCSV technique as a voltammetric method which can successfully simulates the electrodynamics of the cellular membrane. Copyright © 2016 Elsevier B.V. All rights reserved.
Formation of noise-like square-wave pulses in a microfiber based topological insulator fiber laser
NASA Astrophysics Data System (ADS)
Liu, Jingmin; Zhang, Shumin; Li, Xingliang; Han, Mengmeng; Han, Huiyun; Yan, Dan; Shang, Ce; Feng, Yali
2016-11-01
We demonstrated the formation of noise-like square-wave pulses in an Er-doped fiber laser, using a microfiber based topological insulator as a saturated absorber (SA). The SA guaranteed both excellent saturable absorption and high nonlinearity. The pulse width can be increased ranging from 0.985 to 5.503 ns by increasing the pump power from 212 to 284 mW with the polarization state fixed. Moreover, with the adjustment of the polarization controllers in the cavity, the pulse width can be adjusted obviously. Worth mentioning, it was the first time that the noise-like square-wave pulse formed in a microfiber based topological insulator fiber laser.
Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser.
Zhang, Xianming; Gu, Chun; Chen, Guoliang; Sun, Biao; Xu, Lixin; Wang, Anting; Ming, Hai
2012-04-15
We report the generation of ultrawide tunable square-wave pulse in an erbium-doped mode-locked fiber laser. The pulse width can be tuned in an ultrawide range of more than 1700 ns by simply increasing the pump power. The pulse-width tuning is 5.1 ns/mW. To the best of our knowledge, this is the widest pulse-width tuning range of any square-wave pulse in an all-fiber passively mode-locked fiber laser. Experimental results show that the fiber nonlinearity plays an important role in the tuning range of the output pulse width. The high nonlinearity helps to increase the tuning range of the pulse width.
Horvatic, Vlasta; Michels, Antje; Ahlmann, Norman; Jestel, Günter; Veza, Damir; Vadla, Cedomil; Franzke, Joachim
2015-10-01
Helium capillary dielectric barrier discharge driven by the square wave-shaped high voltage was investigated spatially and temporally by means of optical emission spectroscopy. The finding of the previous investigation conducted with the sinusoidal-like high voltage was confirmed, i.e., the plasma in the jet and the plasma in the capillary constitute two temporally separated events. The plasma in the jet occurs prior to the discharge in the capillary and exists only during the positive half period of the applied high voltage. The time delay of the capillary discharge with respect to the discharge in the jet depended on the high voltage, and it was between 2.4 and 8.4 μs for the voltage amplitude change in the range from 1.96 to 2.31 kV, respectively. It was found that, compared to sinusoidal-like voltage, application of the square wave high voltage results with stronger (~6 times) He line emission in the jet, which makes the latter more favorable for efficient soft ionization. The use of the square wave high voltage enabled comparison of the currents (~1 mA) flowing in the capillary during the positive and negative high voltage periods, which yielded the estimation for the charge dissipated in the atmosphere ((4 ± 20 %) × 10(-11) C) through the plasma jet.
NASA Astrophysics Data System (ADS)
Wang, Gang; Zhang, Zhonghua; Lu, Yunfeng; Xu, Jinxin; Zhou, Kunli
2016-01-01
A programmable Josephson voltage standard (PJVS) can be used to generate a precision square wave for induced voltage compensation to measure the mutual inductance between the coils in a joule balance. In this paper, the influence of the transitions between quantized voltages in the synthesized square waves is analyzed in detail. The ratio of the time-integrated value of the transitions to the total waveform is reduced to several parts in 104 to improve the measurement accuracy. The influence of different configurations of the integrating digitizer is discussed. The result shows that when the voltages are in a quantum state, the time-integrated agreement between the measured and theoretical differences for two PJVS systems is within 4 × 10-9 V s V-1 s-1. For the total time integration of a voltage waveform larger than 2 V s, the combined relative uncertainty is less than 5.9 × 10-8 V s V-1 s-1. The result confirms the capability of the PJVS to generate a precision square wave for the joule balance.
Organic-crystal light-emitting field-effect transistors driven by square-wave gate voltages.
Yamao, Takeshi; Terasaki, Kohei; Shimizu, Yasuhiro; Hotta, Shu
2010-02-01
We have improved the operation method of organic light-emitting field-effect transistors by applying a square wave to the gate electrode. A thiophene/phenylene co-oligomer crystal was used as the organic layer. Compared with the sinusoidal wave gate bias application, the square-wave bias produces the emission intensity ten times as large as that of the former. The effective emissions take place through electrons injection from the source contact when the gate bias traverses 0 V so as to be positive. When asymmetric electrodes were used for the source and drain contacts, the resulting emission exhibited the narrowed spectral line at 491.5 nm with its FWHM approximately 1.1 nm. The line narrowing is expected to be a consequence of the emission intensity increment caused by the enhanced electrons injection from the Ag source contact. The location of the emission line is closely related to those of the multimodes due to the laser oscillation by cavity resonance.
Farghaly, Othman A; Ghandour, M A
2005-03-01
The application of square-wave voltammetry (SWV) for the determination of eight elements viz. Cd(II), Pb(II), Cu(II), Zn(II), Co(II), Ni(II), Cr(VI), and Mo(VI) in soil and indoor-airborne particulate matter has been examined and optimized. The cathodic and anodic types of the SWV technique were examined for the detection of these metal ions. It was found that the square-wave anodic stripping voltammetry is the conventional technique for the determination of Zn(II), Cd(II), Pb(II), and Cu(II), but square-wave adsorptive cathodic stripping voltammetric method is used for the determination of Co(II), Ni(II), Mo(VI) and Cr(VI). Various experimental parameters, which influenced the response of the mercury film electrode to these metal ions, were optimized. The detection limits of these metal ions were 0.03, 0.4, 0.04, 0.1, 0.15, 0.05, 0.2, and 3.2 microg/kg for Cd(II), Pb(II), Cu(II), Zn(II), Co(II), Ni(II), Cr(VI), and Mo(VI), respectively, with very good accuracy (standard deviation is below 2%). Interference from coexisting ions was successfully investigated. A comparison of analytical data for analyzing real samples was carried out between the SWV method and the graphite furnace atomic absorption spectrophotometric (GFAAS) method. By the standard addition method, the recoveries were 96.6-104% with SD of 0.75-2.5%. The great advantage of SWV is the simplicity, selectivity, sensitivity, and shortening analysis time over the GFAAS method.
NASA Technical Reports Server (NTRS)
Lee, F. C. Y.; Wilson, T. G.
1974-01-01
A family of four dc-to-square-wave LC tuned inverters are analyzed using singular point. Limit cycles and waveshape characteristics are given for three modes of oscillation: quasi-harmonic, relaxation, and discontinuous. An inverter in which the avalanche breakdown of the transistor emitter-to-base junction occurs is discussed and the starting characteristics of this family of inverters are presented. The LC tuned inverters are shown to belong to a family of inverters with a common equivalent circuit consisting of only three 'series' elements: a five-segment piecewise-linear current-controlled resistor, linear inductor, and linear capacitor.
NASA Technical Reports Server (NTRS)
Lee, F. C. Y.; Wilson, T. G.
1974-01-01
A family of four dc-to-square-wave LC tuned inverters are analyzed using singular point. Limit cycles and waveshape characteristics are given for three modes of oscillation: quasi-harmonic, relaxation, and discontinuous. An inverter in which the avalanche breakdown of the transistor emitter-to-base junction occurs is discussed and the starting characteristics of this family of inverters are presented. The LC tuned inverters are shown to belong to a family of inverters with a common equivalent circuit consisting of only three 'series' elements: a five-segment piecewise-linear current-controlled resistor, linear inductor, and linear capacitor.
NASA Technical Reports Server (NTRS)
Wilson, T. G.; Lee, F. C. Y.; Burns, W. W., III; Owen, H. A., Jr.
1974-01-01
A procedure is developed for classifying dc-to-square-wave two-transistor parallel inverters used in power conditioning applications. The inverters are reduced to equivalent RLC networks and are then grouped with other inverters with the same basic equivalent circuit. Distinction between inverter classes is based on the topology characteristics of the equivalent circuits. Information about one class can then be extended to another class using the basic oscillation theory and the concept of duality. Oscillograms from test circuits confirm the validity of the procedure adopted.
Gavrielides, Athanasios; Sukow, David W; Burner, Guinevere; McLachlan, Taylor; Miller, John; Amonette, Jake
2010-05-01
Numerical and experimental results are presented for an edge-emitting diode laser with delayed optical feedback, where the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. We examine the bifurcation structure and dynamics that give rise to a class of periodic, polarization-modulated solutions, the simplest of which is a square wave solution with a period related to but longer than twice the external cavity roundtrip time. Such solutions typically emerge when the feedback is strong and the differential losses in the normally unsupported polarization mode are small. We also observe more complex waveforms that maintain the same periodicity.
NASA Astrophysics Data System (ADS)
Gavrielides, Athanasios; Sukow, David W.; Burner, Guinevere; McLachlan, Taylor; Miller, John; Amonette, Jake
2010-05-01
Numerical and experimental results are presented for an edge-emitting diode laser with delayed optical feedback, where the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. We examine the bifurcation structure and dynamics that give rise to a class of periodic, polarization-modulated solutions, the simplest of which is a square wave solution with a period related to but longer than twice the external cavity roundtrip time. Such solutions typically emerge when the feedback is strong and the differential losses in the normally unsupported polarization mode are small. We also observe more complex waveforms that maintain the same periodicity.
NASA Technical Reports Server (NTRS)
Wilson, T. G.; Lee, F. C. Y.; Burns, W. W., III; Owen, H. A., Jr.
1974-01-01
A procedure is developed for classifying dc-to-square-wave two-transistor parallel inverters used in power conditioning applications. The inverters are reduced to equivalent RLC networks and are then grouped with other inverters with the same basic equivalent circuit. Distinction between inverter classes is based on the topology characteristics of the equivalent circuits. Information about one class can then be extended to another class using the basic oscillation theory and the concept of duality. Oscillograms from test circuits confirm the validity of the procedure adopted.
Smith, Eric Ryan; Farrow, Darcie A; Jonas, David M
2005-07-22
Four-wave-mixing nonlinear-response functions are given for intermolecular and intramolecular vibrations of a perpendicular dimer and intramolecular vibrations of a square-symmetric molecule containing a doubly degenerate state. A two-dimensional particle-in-a-box model is used to approximate the electronic wave functions and obtain harmonic potentials for nuclear motion. Vibronic interactions due to symmetry-lowering distortions along Jahn-Teller active normal modes are discussed. Electronic dephasing due to nuclear motion along both symmetric and asymmetric normal modes is included in these response functions, but population transfer between states is not. As an illustration, these response functions are used to predict the pump-probe polarization anisotropy in the limit of impulsive excitation.
Comments on 'Square-wave correlation phase detector with VLF atmospheric noise'
NASA Astrophysics Data System (ADS)
Kroenert, J. T.
1980-11-01
Calculated sine wave response data from Raab's paper (1979) are used to develop an algorithm for converting the outputs of a squarewave correlator into estimates of signal phase that is valid for all signal-to-noise ratios. The proposed algorithm is considerably simpler than three separate schemes suggested for low, intermediate, and high signal-to-noise ratio regions.
d-wave pairing in the doped static charge-density-wave state on a two-dimensional square lattice
NASA Astrophysics Data System (ADS)
Onozawa, Mikio; Fukumoto, Yoshiyuki; Oguchi, Akihide; Mizuno, Yukio
2000-10-01
The extended Hubbard model with nearest-neighbor (NN) Coulomb repulsion is used to study superconductivity in a static charge-density-wave (CDW) state. It is found that the doped carriers form a large Fermi surface and are condensed into the dxy-wave superconducting state from the 2×2 CDW state stabilized by the NN Coulomb repulsion. The superconductivity coexisting with a CDW order observed in YBa2Cu3O7-δ [S. Krämer and M. Mehring, Phys. Rev. Lett. 83, 396 (1999)] together with the superconductivity of Pr2-xCexCuO4-y [M. Brinkmann, H. Bach, and K. Westerholt, Physica C 292, 104 (1997)] may be important examples of this pairing mechanism.
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.
NASA Astrophysics Data System (ADS)
Marin, Bóris; Pinto, Reynaldo Daniel; Elson, Robert C.; Colli, Eduardo
2014-10-01
First return maps of interspike intervals for biological neurons that generate repetitive bursts of impulses can display stereotyped structures (neuronal signatures). Such structures have been linked to the possibility of multicoding and multifunctionality in neural networks that produce and control rhythmical motor patterns. In some cases, isolating the neurons from their synaptic network reveals irregular, complex signatures that have been regarded as evidence of intrinsic, chaotic behavior. We show that incorporation of dynamical noise into minimal neuron models of square-wave bursting (either conductance-based or abstract) produces signatures akin to those observed in biological examples, without the need for fine tuning of parameters or ad hoc constructions for inducing chaotic activity. The form of the stochastic term is not strongly constrained and can approximate several possible sources of noise, e.g., random channel gating or synaptic bombardment. The cornerstone of this signature generation mechanism is the rich, transient, but deterministic dynamics inherent in the square-wave (saddle-node and homoclinic) mode of neuronal bursting. We show that noise causes the dynamics to populate a complex transient scaffolding or skeleton in state space, even for models that (without added noise) generate only periodic activity (whether in bursting or tonic spiking mode).
Sayer, Martin D J; Azzopardi, Elaine; Sieber, Arne
2014-12-01
Dive computers are used in some occupational diving sectors to manage decompression but there is little independent assessment of their performance. A significant proportion of occupational diving operations employ single square-wave pressure exposures in support of their work. Single examples of 43 models of dive computer were compressed to five simulated depths between 15 and 50 metres' sea water (msw) and maintained at those depths until they had registered over 30 minutes of decompression. At each depth, and for each model, downloaded data were used to collate the times at which the unit was still registering "no decompression" and the times at which various levels of decompression were indicated or exceeded. Each depth profile was replicated three times for most models. Decompression isopleths for no-stop dives indicated that computers tended to be more conservative than standard decompression tables at depths shallower than 30 msw but less conservative between 30-50 msw. For dives requiring decompression, computers were predominantly more conservative than tables across the whole depth range tested. There was considerable variation between models in the times permitted at all of the depth/decompression combinations. The present study would support the use of some dive computers for controlling single, square-wave diving by some occupational sectors. The choice of which makes and models to use would have to consider their specific dive management characteristics which may additionally be affected by the intended operational depth and whether staged decompression was permitted.
El Hourch, Mohamed; Dudoit, Arnaud; Amiard, Jean-Claude
2004-02-01
Electrochemical determination of metallothionein (MT) is widely used for environmental studies. This article describes the development and optimization of the procedure for the quantification of metallothionein by square wave cathodic stripping voltammetry. The determination is based on the complexation of cisplatin and MT and the subsequent reduction of the complexes at the electrode. In order to achieve the highest possible sensitivity and resolution of the peak, an optimization of the experimental parameters has been carried out using experimental design methodology (response surface). Seven chemical and physical parameters, namely, pH, cisplatin concentration, buffer concentration, deposition potential, square wave frequency, amplitude of pulse, and step potential, have been optimized to give 9.0, 5.9 microM, 0.65 M, -0.2 mV, 229 Hz, 46 mV, and 2 mV, respectively. Method characterization has been performed, leading to a detection limit of 0.1 microg L(-1). Quantification of MT in polychaetes and comparison with the modified Brdicka procedure were also carried out.
Ioannides, X; Economou, A; Voulgaropoulos, A
2003-09-19
In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction current was related to the CPL concentration in the sample. The chemical and instrumental parameters affecting the response were investigated and optimized for the CPL determination. The calibration curve was linear from 0.5 to 180 microg l(-1) of CPL (depending on the preconcentration time), the limit of detection at a S/N ratio of 3 was 0.5 microg l(-1) with 300 s of preconcentration and the relative standard deviation was 3.2% at the 20 microg l(-1) level (with 120 s of preconcentration, n=8). The method was applied to the determination of CPL in two pharmaceutical formulations with recoveries of 97.9 and 98.8%. Finally, the potential for applying the proposed method to the determination of CPL in biological media is briefly discussed.
Arantes, Tatiane M; Sardinha, André; Baldan, Mauricio R; Cristovan, Fernando H; Ferreira, Neidenei G
2014-10-01
Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 μg L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio.
Yilmaz, B.; Kaban, S.; Akcay, B. K.
2015-01-01
In this study, simple, fast and reliable cyclic voltammetry, linear sweep voltammetry, square wave voltammetry and differential pulse voltammetry methods were developed and validated for determination of etodolac in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of etodolac at platinum electrode in acetonitrile solution containing 0.1 M lithium perchlorate. The well-defined oxidation peak was observed at 1.03 V. The calibration curves were linear for etodolac at the concentration range of 2.5-50 μg/ml for linear sweep, square wave and differential pulse voltammetry methods, respectively. Intra- and inter-day precision values for etodolac were less than 4.69, and accuracy (relative error) was better than 2.00%. The mean recovery of etodolac was 100.6% for pharmaceutical preparations. No interference was found from three tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Etol, Tadolak and Etodin tablets as pharmaceutical preparation. PMID:26664057
NASA Astrophysics Data System (ADS)
Keefe, Laurence
2016-11-01
Parabolized acoustic propagation in transversely inhomogeneous media is described by the operator update equation U (x , y , z + Δz) =eik0 (- 1 +√{ 1 + Z }) U (x , y , z) for evolution of the envelope of a wavetrain solution to the original Helmholtz equation. Here the operator, Z =∇T2 + (n2 - 1) , involves the transverse Laplacian and the refractive index distribution. Standard expansion techniques (on the assumption Z << 1)) produce pdes that approximate, to greater or lesser extent, the full dispersion relation of the original Helmholtz equation, except that none of them describe evanescent/damped waves without special modifications to the expansion coefficients. Alternatively, a discretization of both the envelope and the operator converts the operator update equation into a matrix multiply, and existing theorems on matrix functions demonstrate that the complete (discrete) Helmholtz dispersion relation, including evanescent/damped waves, is preserved by this discretization. Propagation-constant/damping-rates contour comparisons for the operator equation and various approximations demonstrate this point, and how poorly the lowest-order, textbook, parabolized equation describes propagation in lined ducts.
New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation
Qin, Feng; Zhao, Hua; Cai, Wei; Duan, Qianqian; Zhang, Zhiguo; Cao, Wenwu
2013-11-15
A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 μs. CW Nd{sup 3+} lasers were used as examples to present the method. Upconversion dynamic process of Ho{sup 3+} was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb{sup 3+} to Yb{sup 3+} was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar{sup +} laser, Kr{sup +} laser, Ti:sapphire laser, etc.
New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation.
Qin, Feng; Zhao, Hua; Duan, Qianqian; Cai, Wei; Zhang, Zhiguo; Cao, Wenwu
2013-11-01
A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 μs. CW Nd(3+) lasers were used as examples to present the method. Upconversion dynamic process of Ho(3+) was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb(3+) to Yb(3+) was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar(+) laser, Kr(+) laser, Ti:sapphire laser, etc.
New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation
NASA Astrophysics Data System (ADS)
Qin, Feng; Zhao, Hua; Duan, Qianqian; Cai, Wei; Zhang, Zhiguo; Cao, Wenwu
2013-11-01
A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 μs. CW Nd3+ lasers were used as examples to present the method. Upconversion dynamic process of Ho3+ was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb3+ to Yb3+ was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar+ laser, Kr+ laser, Ti:sapphire laser, etc.
Friart, Gaetan; Verschaffelt, Guy; Danckaert, Jan; Erneux, Thomas
2014-11-01
We investigate the square-wave (SW) self-modulation output of an edge-emitting diode laser subject to polarization rotated optical feedback in detail, both experimentally and theoretically. Our experimental results show that the 2τ-periodic SW, where τ is the delay of the feedback, coexists with other SW oscillations of shorter periods. We have found that these new SWs are specific harmonics of the fundamental one and their periods are P(n)≃2τ/(1+2n), where n is an integer. Numerical simulations and analytical studies of laser rate equations confirm the multistability of SW solutions. By adding a weak conventional optical feedback, we show that the switching between the different periodic SWs can be easily controlled. The delay of this feedback control is the key parameter determining the harmonic that is stabilized. Numerical simulations corroborate the effectiveness of our experimental control scheme.
Rodrigues Filho, Guimes; Almeida, Flávia; Ribeiro, Sabrina D; Tormin, Thiago F; Muñoz, Rodrigo A A; Assunção, Rosana M N; Barud, Hernane
2016-01-01
In this paper, cellulose triacetate (CTA) was produced from sugarcane bagasse and used as matrices for controlled release of paracetamol. Symmetric and asymmetric membranes were obtained by formulations of CTA/dichloromethane/drug and CTA/dichloromethane/water/drug, respectively, and they were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Different morphologies of membranes were observed by SEM, and the incorporation of paracetamol was confirmed by lowering of the glass transition temperature (Tg) in the DSC curves. This indicates the existence of interactions between the matrix and the drug. The evaluation of drug release was based on the electrochemical monitoring of paracetamol through its oxidation at a glassy carbon electrode surface using square-wave voltammetry (SWV), which provides fast, precise and accurate in situ measurements. The studies showed a content release of 27% and 45% by the symmetric and asymmetric membranes, respectively, during 8 h.
Ikegami, Tomonori; Kageyama, Yoshiyuki; Obara, Kazuma; Takeda, Sadamu
2016-07-11
Building a bottom-up supramolecular system to perform continuously autonomous motions will pave the way for the next generation of biomimetic mechanical systems. In biological systems, hierarchical molecular synchronization underlies the generation of spatio-temporal patterns with dissipative structures. However, it remains difficult to build such self-organized working objects via artificial techniques. Herein, we show the first example of a square-wave limit-cycle self-oscillatory motion of a noncovalent assembly of oleic acid and an azobenzene derivative. The assembly steadily flips under continuous blue-light irradiation. Mechanical self-oscillation is established by successively alternating photoisomerization processes and multi-stable phase transitions. These results offer a fundamental strategy for creating a supramolecular motor that works progressively under the operation of molecule-based machines.
2012-01-01
A validated simple, rapid, sensitive and specific square-wave voltammetric technique is described for the determination of acebutolol (AC) following its accumulation onto a hanging mercury drop electrode in a Britton-Robinson universal buffer of pH 7.5. The optimal procedural conditions were: accumulation potential Eacc = - 0.8 V versus Ag/AgCl/KCl, accumulation duration tacc = 30 s, pulse-amplitude = 70 mV, scan rate = 100 mV/s, frequency = 30 Hz, surface area of the working electrode = 0.6 mm2 and the convection rate = 2000 rpm. Under these optimized conditions, the adsorptive stripping voltammetry (AdSV) peak current was proportional over the concentration range 5 × 10-7 - 6 × 10-6 M (r = 0.999). Recoveries for acebutolol from human plasma and urine were in the range 97-103% and 96-104% respectively. The method proved to be precise (intra-day precision expressed as %RSD in human plasma ranged from 2.9 - 3.2% and inter-day precision expressed as %RSD ranged from 3.4 - 3.8%) and accurate (intra-day accuracies expressed as % error in human urine ranged from -3.3 - 2.8% and inter-day accuracies ranged from -3.3 - 1.7%). The limit of quantitation (LOQ) and limit of detection (LOD) for acebutolol were 1.7 × 10-7 and 5 × 10-7 M, respectively. Possible interferences by substances usually present in the pharmaceutical formulations were investigated with a mean recovery of 101.6 ± 0.64%. Results of the developed square-wave adsorptive stripping voltammetry (SW-AdSV) method were comparable with those obtained by reference analytical method. PMID:22353684
Grate, J W; Patrash, S J; Kaganovet, S N; Abraham, M H; Wise, B M; Gallagher, N B
2001-11-01
In previous work, it was shown that, in principle, vapor descriptors could be derived from the responses of an array of polymer-coated acoustic wave devices. This new chemometric classification approach was based on polymer/vapor interactions following the well-established linear solvation energy relationships (LSERs) and the surface acoustic wave (SAW) transducers being mass sensitive. Mathematical derivations were included and were supported by simulations. In this work, an experimental data set of polymer-coated SAW vapor sensors is investigated. The data set includes 20 diverse polymers tested against 18 diverse organic vapors. It is shown that interfacial adsorption can influence the response behavior of sensors with nonpolar polymers in response to hydrogen-bonding vapors; however, in general, most sensor responses are related to vapor interactions with the polymers. It is also shown that polymer-coated SAW sensor responses can be empirically modeled with LSERs, deriving an LSER for each individual sensor based on its responses to the 18 vapors. Inverse least-squares methods are used to develop models that correlate and predict vapor descriptors from sensor array responses. Successful correlations can be developed by multiple linear regression (MLR), principal components regression (PCR), and partial least-squares (PLS) regression. MLR yields the best fits to the training data, however cross-validation shows that prediction of vapor descriptors for vapors not in the training set is significantly more successful using PCR or PLS. In addition, the optimal dimension of the PCR and PLS models supports the dimensionality of the LSER formulation and SAW response models.
Temerk, Y M; Kamal, M M; Ahmed, G A W; Ibrahim, H S M
2003-08-01
The surface activity of xanthine (Xan) and xanthosine (Xano) at a hanging mercury drop electrode (HMDE) was studied using out-of-phase ac and cyclic dc voltammetry. The results show that Xan and Xano were strongly adsorbed and chemically interacted with the charged mercury surface, which is the prerequisite step for applying the cathodic adsorptive stripping voltammetric determination of such biologically important compounds. Differential pulse cathodic adsorptive stripping voltammetry (DPCASV) and square-wave cathodic adsorptive stripping voltammetry (SWCASV) were applied for the ultratrace determination of Xan and Xano compounds. Moreover, a rapid and sensitive controlled adsorptive accumulation of Cu(II) complexes of both compounds provided the basis of a direct stripping voltammetric determination of such compounds to submicromolar and nanomolar levels. Operational and solution conditions for the quantitative ultratrace determination of Xan and Xano were optimized in absence and presence of Cu(II). The calibration curve data were subjected to least-squares refinements. The effects of several types of inorganic and organic interfering species on the determination of Xan or Xano were considered.
Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan
2016-03-01
Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.
Martínez-Llinàs, Jade; Colet, Pere
2015-09-21
We model two non-identical delay-line optoelectronic oscillators mutually coupled through delayed cross-feedback. The system can generate multi-stable nanosecond periodic square-wave solutions which arise through a Hopf instability. We show that for suitable ratios between self and cross delay times, the two oscillators generate square waves with different amplitude but synchronized in phase, out of phase or with a dephasing of a quarter of the period. We also show that the synchronization is robust to small mismatches in the delay times.
NASA Astrophysics Data System (ADS)
Laflorencie, Nicolas; Luitz, David J.; Alet, Fabien
2015-09-01
Using a modified spin-wave theory which artificially restores zero sublattice magnetization on finite lattices, we investigate the entanglement properties of the Néel ordered J1-J2 Heisenberg antiferromagnet on the square lattice. Different kinds of subsystem geometries are studied, either corner-free (line, strip) or with sharp corners (square). Contributions from the nG=2 Nambu-Goldstone modes give additive logarithmic corrections with a prefactor nG/2 independent of the Rényi index. On the other hand, π /2 corners lead to additional (negative) logarithmic corrections with a prefactor lqc which does depend on both nG and the Rényi index q , in good agreement with scalar field theory predictions. By varying the second neighbor coupling J2 we also explore universality across the Néel ordered side of the phase diagram of the J1-J2 antiferromagnet, from the frustrated side 0
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
Trammell, Scott A.; Zabetakis, Dan; Moore, Martin; Verbarg, Jasenka; Stenger, David A.
2014-01-01
Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (µA/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen. PMID:25549081
Ammar, Hafedh Belhadj; Brahim, Mabrouk Ben; Abdelhédi, Ridha; Samet, Youssef
2016-02-01
The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2μmolL(-1), with a detection limit of 0.065μmolL(-1). Copyright © 2015 Elsevier B.V. All rights reserved.
Parham, H; Rahbar, N
2010-05-15
A carbon paste electrode is modified with ZrO(2)-nanoparticles and its application for square wave voltammetric (SWV) detection of methyl parathion, MP (organophosphate pesticide) is reported. The nano-ZrO(2) shows a strong affinity toward the phosphate group on methyl parathion molecules, which provides sensitivity and selectivity of the modified carbon paste electrode. Instrumental and chemical parameters influencing the voltammetric response are optimized for MP determination. Under optimum experimental conditions the peak current is linear to MP concentration over the range of 5.0-3000.0 ng mL(-1) with a correlation coefficient of 0.9992. The limit of detection (LOD) and limit of quantification (LOQ) for MP based on three and ten times the standard deviation of the blank (3S(b), 10S(b)) were 2.0 and 5.7 ng mL(-1) (n=20) for MP, respectively. The recovery values from quality control (QC) samples of water solutions containing low, middle and high concentrations of MP (50, 100 and 800 ng mL(-1)) were 98.0+/-2.3%, 92.5+/-4.9% and 97.6+/-2.8%, respectively. The electrode is successfully applied for the determination of MP in different water samples.
Otero-Millan, Jorge; Schneider, Rosalyn; Leigh, R John; Macknik, Stephen L; Martinez-Conde, Susana
2013-01-01
During attempted visual fixation, saccades of a range of sizes occur. These "fixational saccades" include microsaccades, which are not apparent in regular clinical tests, and "saccadic intrusions", predominantly horizontal saccades that interrupt accurate fixation. Square-wave jerks (SWJs), the most common type of saccadic intrusion, consist of an initial saccade away from the target followed, after a short delay, by a "return saccade" that brings the eye back onto target. SWJs are present in most human subjects, but are prominent by their increased frequency and size in certain parkinsonian disorders and in recessive, hereditary spinocerebellar ataxias. Here we asked whether fixational saccades showed distinctive features in various parkinsonian disorders and in recessive ataxia. Although some saccadic properties differed between patient groups, in all conditions larger saccades were more likely to form SWJs, and the intervals between the first and second saccade of SWJs were similar. These findings support the proposal of a common oculomotor mechanism that generates all fixational saccades, including microsaccades and SWJs. The same mechanism also explains how the return saccade in SWJs is triggered by the position error that occurs when the first saccadic component is large, both in the healthy brain and in neurological disease.
Engelmann, W.; Hellrung, W.; Johnsson, A.
1996-05-01
Musca domestica flies that were exposed to a uniform vertical 10 Hz electric square-wave field of 1 kVm{sup {minus}1} changed the period length of their circadian locomotor activity rhythm. Under constant conditions, the clock of short-period flies was slowed down by the field, whereas the clock of long-period flies either was affected only scarcely (experiments at about 19 C) or ran faster (experiments at 25 C). It the field was applied for only 12 h daily, then 30--40% of the flies were synchronized. Thus, the field could function as a weak Zeitgeber (synchronizer). If the field was increased to 10 kVm{sup {minus}1}, then 50--70% of the flies were synchronized. Flies avoided becoming active around the onset of the 12 h period of exposure to a 10 Hz field. The results of these experiments are discussed with respect to similar experiments by Wever on the effects of exposure to a 10 Hz field on the circadian system of man.
Cittan, Mustafa; Koçak, Süleyman; Çelik, Ali; Dost, Kenan
2016-10-01
A multi-walled carbon nanotube modified glassy carbon electrode was used to prepare an electrochemical sensing platform for the determination of oleuropein. Results showed that, the accumulation of oleuropein on the prepared electrode takes place with the adsorption process. Electrochemical behavior of oleuropein was studied by using cyclic voltammetry. Compared to the bare GCE, the oxidation peak current of oleuropein increased about 340 times at MWCNT/GCE. Voltammetric determination of oleuropein on the surface of prepared electrode was studied using square wave voltammetry where the oxidation peak current of oleuropein was measured as an analytical signal. A calibration curve of oleuropein was performed between 0.01 and 0.70µM and a good linearity was obtained with a correlation coefficient of 0.9984. Detection and quantification limits of the method were obtained as 2.73 and 9.09nM, respectively. In addition, intra-day and inter-day precision studies indicated that the voltammetric method was sufficiently repeatable. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract. Microwave-assisted extraction of oleuropein had good recovery values between 92% and 98%. The results obtained with the proposed electrochemical sensor were compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Copyright © 2016 Elsevier B.V. All rights reserved.
Yi, Xiaoqing; Hao, Liling; Jiang, Fangfang; Xu, Lisheng; Song, Shaoxiu; Li, Gang; Lin, Ling
2017-08-01
Synchronous acquisition of multi-channel biopotential signals, such as electrocardiograph (ECG) and electroencephalograph, has vital significance in health care and clinical diagnosis. In this paper, we proposed a new method which is using single channel ADC to acquire multi-channel biopotential signals modulated by square waves synchronously. In this method, a specific modulate and demodulate method has been investigated without complex signal processing schemes. For each channel, the sampling rate would not decline with the increase of the number of signal channels. More specifically, the signal-to-noise ratio of each channel is n times of the time-division method or an improvement of 3.01×log2n dB, where n represents the number of the signal channels. A numerical simulation shows the feasibility and validity of this method. Besides, a newly developed 8-lead ECG based on the new method has been introduced. These experiments illustrate that the method is practicable and thus is potential for low-cost medical monitors.
Beltagi, A M
2003-04-10
A simple, rapid, reliable and fully validated square wave cathodic adsorptive stripping voltammetric procedure has been developed for the determination of the antibiotic pefloxacin drug in bulk form, tablets and human serum, based on its electrochemical reduction at a hanging mercury drop electrode. The Britton-Robinson buffer of pH 7.0 was found to be reasonable as a supporting electrolyte for assay of the drug. Pefloxacin drug, at the optimized conditions, showed a single 2-electron well-defined peak at -1.07 V (versus Ag/AgCl/KCl(s)) using an accumulation potential of -0.40 V. This peak may be attributed to the reduction of the C=O group. A mean recovery of 99.54%+/-0.23 and a detection limit of 1.65 x 10(-10) M pefloxacin were achieved. After being validated, the proposed procedure was successfully applied for the determination of the drug in tablets and human serum with mean recoveries of 99.57+/-0.48 and 98.55+/-0.78%, respectively. A detection limit of 4.50 x 10(-10) M was achieved for the determination of the drug in human serum. Results of the proposed procedure were comparable with those obtained by reported methods.
NASA Astrophysics Data System (ADS)
Wu, Xiaomao; Schelly, Z. A.; Vastano, John A.
1994-07-01
Results of studies of the limited Explodator model in a continuous-flow stirred tank reactor (CSTR) under square wave perturbation of the flow rate are reported. The perturbation is applied in such a way that the system is alternately attracted to two different periodic attractors in the parameter region close the Hopf bifurcation point. The system is shown to display a variety of entrainment bands, birhythmicity, quasiperiodicity, resonance-like phenomenon, period doubling and intermittency routes to chaos, and a complicated window structure of the chaotic region. In addition, a novel phenomenon, “intermittent alternative laminar oscillations”, was observed in a chaotic regime sandwiched between two entrainment bands. Transient chaos occurs in one of the entrainment bands, which intimates chaos in the adjacent regime. Positive Lyapunov exponents were found to be associated with the chaotic behavior. The folding and stretching property of the chaotic attractors was analyzed through stroboscopic representations. The deterministic nature of the chaotic behavior was confirmed by the quadratic-like curve formed in the one-dimensional map.
Lu, T H; Yang, H Y; Sun, I W
1999-06-01
A Nafion/mercury film electrode (NMFE) was used for the determination of trace thallium(I) in aqueous solutions. Thallium(I) was preconcentrated onto the NMFE from the sample solution containing 0.01 M ethylenediaminetetraacetate (EDTA), and determined by square-wave anodic stripping voltammetry (SWASV). Various factors influencing the determination of thallium(I) were thoroughly investigated. This modified electrode exhibits good resistance to interferences from surface-active compounds. The presence of EDTA effectively eliminated the interferences from metal ions, such as lead(II) and cadmium(II), which are generally considered as the major interferents in the determination of thallium at a mercury electrode. With 2-min preconcentration, linear calibration graphs were obtained over the range 0.05-100 ppb of thallium(I). An even lower detection limit, 0.01 ppb, were achieved with 5-min accumulation. The electrode is easy to prepare and can be readily renewed after each stripping experiment. Applicability of this procedure to various water samples is illustrated.
Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo
2016-10-27
Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.
NASA Astrophysics Data System (ADS)
Yi, Xiaoqing; Hao, Liling; Jiang, Fangfang; Xu, Lisheng; Song, Shaoxiu; Li, Gang; Lin, Ling
2017-08-01
Synchronous acquisition of multi-channel biopotential signals, such as electrocardiograph (ECG) and electroencephalograph, has vital significance in health care and clinical diagnosis. In this paper, we proposed a new method which is using single channel ADC to acquire multi-channel biopotential signals modulated by square waves synchronously. In this method, a specific modulate and demodulate method has been investigated without complex signal processing schemes. For each channel, the sampling rate would not decline with the increase of the number of signal channels. More specifically, the signal-to-noise ratio of each channel is n times of the time-division method or an improvement of 3.01 ×log2n dB, where n represents the number of the signal channels. A numerical simulation shows the feasibility and validity of this method. Besides, a newly developed 8-lead ECG based on the new method has been introduced. These experiments illustrate that the method is practicable and thus is potential for low-cost medical monitors.
Medeiros, Roberta Antigo; de Carvalho, Adriana Evaristo; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando
2008-07-30
A simple and highly selective electrochemical method was developed for the simultaneous determination of aspartame and cyclamate in dietary products at a boron-doped diamond (BDD) electrode. In square-wave voltammetric (SWV) measurements, the BDD electrode was able to separate the oxidation peak potentials of aspartame and cyclamate present in binary mixtures by about 400 mV. The detection limit for aspartame in the presence of 3.0x10(-4) mol L(-1) cyclamate was 4.7x10(-7) mol L(-1), and the detection limit for cyclamate in the presence of 1.0x10(-4) mol L(-1) aspartame was 4.2x10(-6) mol L(-1). When simultaneously changing the concentration of both aspartame and cyclamate in a 0.5 mol L(-1) sulfuric acid solution, the corresponding detection limits were 3.5x10(-7) and 4.5x10(-6) mol L(-1), respectively. The relative standard deviation (R.S.D.) obtained was 1.3% for the 1.0x10(-4) mol L(-1) aspartame solution (n=5) and 1.1% for the 3.0x10(-3) mol L(-1) cyclamate solution. The proposed method was successfully applied in the determination of aspartame in several dietary products with results similar to those obtained using an HPLC method at 95% confidence level.
Zhang, Shengzhao; Li, Gang; Lin, Ling; Zhao, Jing
2016-08-01
A digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. A technique that uses a square wave as the reference signal has an advantage over the one using a sinusoidal wave due to its easier implementation and higher computational efficiency. However, demodulating multiple-frequency composite signals using square wave reference may result in interference between channels. To avoid interference between channels and reduce the computational complexity, we modify the calculations and determine the optimal parameter settings of the low-pass filter and carrier frequency, as detailed in this paper. The results of our analysis show that when the length of the average filter and carrier frequencies are properly set, the interference between the channels is removed. This optimization produces the digital lock-in detection suitable for measuring multi-channel sensor signals.
NASA Astrophysics Data System (ADS)
Zhang, Shengzhao; Li, Gang; Lin, Ling; Zhao, Jing
2016-08-01
A digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. A technique that uses a square wave as the reference signal has an advantage over the one using a sinusoidal wave due to its easier implementation and higher computational efficiency. However, demodulating multiple-frequency composite signals using square wave reference may result in interference between channels. To avoid interference between channels and reduce the computational complexity, we modify the calculations and determine the optimal parameter settings of the low-pass filter and carrier frequency, as detailed in this paper. The results of our analysis show that when the length of the average filter and carrier frequencies are properly set, the interference between the channels is removed. This optimization produces the digital lock-in detection suitable for measuring multi-channel sensor signals.
Hammam, Essam
2002-10-15
Nitrofurnation is an antibacterial drug. It is used in the treatment of initial or recurrent urinary tract infections caused by susceptible organisms. The cyclic voltammogram of the drug in Britton-Robinson buffers (pH 2-11) exhibited a single well-defined cathodic peak at the hanging mercury drop electrode, that due to the reduction of its nitro group to the amine stage. A fully validated, sensitive, and reproducible developed procedure was described for determination of the drug in bulk form, pharmaceutical formulation, human serum and human urine using, square-wave cathodic adsorptive stripping voltammetry. The optimal experimental parameters for the drug assay were: accumulation potential = -0.4 V (vs. Ag/AgCl/ KCl(s)), accumulation time = 40 s, frequency = 120 Hz, pulse amplitude = 50 mV and scan increment = 10 mV in Britton-Robinson buffer (pH 10). A mean percentage recovery of 100.68 +/- 0.17 (n = 5) and a detection limit of 1.32 x 10(-10) M of bulk drug were achieved. Applicability to assay of the drug in pharmaceutical formulation, human serum and human urine was studied and illustrated. The mean percentage recoveries were found as: 101.49 +/- 0.65, 103.94 +/- 0.73 and 101.98 +/- 0.52 (n = 5) in pharmaceutical formulation, human serum and human urine, respectively. Detection limits of 2.86 x 10(-10) M and 5.77 x 10(-10) M nitrofurantoin were achieved in human serum and urine, respectively. Copyright 2002 Elsevier Science B.V.
Trevisani, M; Cecchini, M; Taffetani, L; Vercellotti, L; Rosmini, R
2011-02-01
A square-wave anodic-stripping voltammetric method for the analysis of lead and cadmium in chicken muscle and liver was developed and validated, and the results of a monitoring study relative to chicken and pigeon meat are reported. The voltammetric method allows the analysis of lead and cadmium at the same time in samples after acid digestion. The use of perchloric acid for digestion and of acetate buffer in the supporting electrolyte are suitable to reduce matrix interferences and obtain limits of quantification which were below 10 ng g⁻¹ for meat and liver samples. The regression between the analytical signal and the concentration of the target analytes in spiked samples and Certified Reference Materials proved to be linear within the 10-100 ng g⁻¹ range for meat and within the 50-500 ng g⁻¹ range for liver. The analytical method was verified using available Certified Reference Materials BCR-184 (cattle meat) and BCR-185R (cattle liver) as well as with spiked chicken samples. Precision (i.e. repeatability and intermediate precision) and accuracy (percentage recovery and bias) were of the order of 0.3-4.5% for both lead and cadmium The level of lead in muscle was in the range between 6.4 and 59.8 ng g⁻¹ in chickens and between 7.9 and 63.6 ng g⁻¹ in farmed pigeons, whereas it was between 8.0 and 84.4 ng g⁻¹ in chicken liver. The cadmium concentration was 0.4-10.4 ng g⁻¹ in chicken muscle, 10.4-90.6 ng g⁻¹ in chicken liver and 2.2-8.0 ng g⁻¹ in farmed pigeons.
Rahbar, Nadereh; Ramezani, Zahra; Babapour, Ahmad
2015-01-01
Background Lidocaine hydrochloride (LH) is one of the most extensively used local anesthetics and peripheral analgesics. Availability of a simple and sensitive assay method for this analyte in pharmaceutical preparations as well as development of new voltammetric detectors that can be applied in chromatographic systems for determination of this analyte in biological samples are of great importance. Objectives In this study, a square-wave voltammetric (SWV) determination of LH at a bare carbon-paste electrode (CPE) was reported. Moreover, the oxidation mechanism for LH molecule at this electrode was investigated. Materials and Methods The SW voltammogram of LH solution at CPE showed a well-defined peak between +0.80 and +0.88 V depending on a scan rate in potassium nitrate (KNO3) solution. Different chemical and instrumental parameters influencing the voltammetric response, such as the pH level and scan rate were optimized for LH determination. Results A linear range of 8.0 - 1000.0 μmol L-1 (r2 = 0.999) was obtained. The limit of detection (LOD) was 0.29 μmol L-1. The relative standard deviations of 2.1% obtained for 0.8 800 μmol L-1 solution of LH indicated a reasonable reproducibility of the method. Conclusions The results of this study show that LH in different pharmaceutical preparations could be determined with good reliability. In addition, the results reveal that the equal numbers of electrons and protons are involved in the oxidation of LH and the irreversible oxidation of an analyte was performed via amine groups of LH molecule. PMID:25866720
Rahbar, Nadereh; Parham, Hooshang
2013-01-01
Background Atrazine (ATZ) is a widely used herbicide in most countries because of its low cost and good selectivity. The concentration of ATZ that the EPA considers safe to consume in drinking water is 3 ppb. Therefore, recently, there have been concerns about its determination in trace levels. This compound is not electro-active, so in this research indirect electrochemical method for its detection in low levels was proposed. Objectives The main aim of this study is the indirect determination of ATZ in water samples by voltammetry using nano-particle modified electrode. Materials and Methods A nano-CuO modified carbon paste electrode (NMCPE) is constructed and its application for indirect square wave voltammetric (SWV) detection of ATZ is reported. The sensing performance mechanism of the nano-CuO modified carbon paste electrode toward atrazine is due to complexation of the analyte with Cu (II) ion. The peak current for copper (II) reduction decreases with increase in the ATZ concentration and is monitored for its determination. Instrumental and chemical parameters influencing the detection of ATZ were optimized. Results The results revealed that decrease in peak current was proportional to ATZ concentration over the range of 5-75 ng/mL. The limit of detection (LOD) and limit of quantification (LOQ) were 2 ng/mL and 5.6 ng/mL (n = 20), respectively. The relative standard deviation (n = 10) for the determination of 10 and 50 ng/mL of ATZ solution was estimated as 4.9% and 4.2 %, respectively. Conclusions This easily fabricated electrode together with the fast and sensitive SW voltammetry was successfully applied for the determination of concentration of ATZ at trace levels, in different water samples. PMID:24624200
Alghamdi, Ahmad H
2005-01-01
Square-wave adsorptive stripping voltammetric (AdSV) determinations of trace concentrations of the azo coloring agent Amaranth are described. The analytical methodology used was based on the adsorptive preconcentration of the dye on the hanging mercury drop electrode, followed by initiation of a negative sweep. In a pH 10 carbonate supporting electrolyte, Amaranth gave a well-defined and sensitive AdSV peak at -518 mV. The electroanalytical determination of this azo dye was found to be optimal in carbonate buffer (pH 10) under the following experimental conditions: accumulation time, 120 s; accumulation potential, 0.0 V; scan rate, 600 mV/s; pulse amplitude, 90 mV; and frequency, 50 Hz. Under these optimized conditions the AdSV peak current was proportional over the concentration range 1 x 10(-8)-1.1 x 10(-7) mol/L (r = 0.999) with a detection limit of 1.7 x 10(-9) mol/L (1.03 ppb). This analytical approach possessed enhanced sensitivity, compared with conventional liquid chromatography or spectrophotometry and it was simple and fast. The precision of the method, expressed as the relative standard deviation, was 0.23%, whereas the accuracy, expressed as the mean recovery, was 104%. Possible interferences by several substances usually present as food additive azo dyes (E110, E102), gelatin, natural and artificial sweeteners, preservatives, and antioxidants were also investigated. The developed electroanalyticals method was applied to the determination of Amaranth in soft drink samples, and the results were compared with those obtained by a reference spectrophotometric method. Statistical analysis (paired t-test) of these data showed that the results of the 2 methods compared favorably.
Adams, William C
2006-02-01
It has become increasingly well realized that laboratory simulations of air pollution risk assessment need to employ O(3) concentration profiles that more accurately mimic those encountered during summer daylight ambient air pollution episodes. The present study was designed to compare the pulmonary function and symptoms of breathing discomfort responses to a 6.6-h square-wave 0.08-ppm O(3) chamber exposure to those observed in a triangular O(3) exposure profile (mean of 0.08 ppm), as well as to both a 0.06-ppm square-wave and triangular mean 0.06-ppm exposure, and to those observed during a triangular mean 0.04-ppm exposure and to a filtered air (FA) square-wave exposure. Thirty young adults (15 of each gender) served as subjects, each completing all exposures. While the 6.6-h postexposure responses to the acute triangular exposure to a mean O(3) concentration of 0.08 ppm did not differ significantly from those observed in the square-wave exposure, forced expiratory volume in 1 s (FEV)(1.0) and total symptoms severity (TSS) were significantly different from preexposure at 4.6 h (when O(3) concentration was 0.15 ppm) in the triangular exposure, but not until 6.6 h in the square-wave exposure. Thus, significant pulmonary function and symptoms responses were observed over a longer period in the triangular exposure protocol at a mean O(3) concentration of 0.08 ppm. These results support previous evidence that O(3) concentration has a greater singular effect in the total inhaled O(3) dose than do V(E) and exposure duration. Subtracting pulmonary function effects consequent to O(3) exposure to existent 8-h average background levels (e.g., approximately 0.04 ppm, rather than those observed in FA exposures) from those observed at higher concentrations (e.g., approximately 0.08 ppm) represents a means of focusing the regulatory effort on effects that can be controlled. The greatest pulmonary function and symptoms responses observed for a 0.04-ppm triangular exposure were
Neto, M M; Rocha, M M; Brett, C M
1994-09-01
An adsorptive stripping voltammetry method for the determination of traces of molybdenum(VI) in flowing solution at a wall-jet electrode sensor has been developed. After adsorption of a molybdenum complex on a wall-jet mercury film electrode, the complex is reduced by a square wave scan. More satisfactory results were obtained using 8-hydroxyquinoline as a complexing agent in nitrate medium than using Toluidine Blue in oxalic acid. Enhanced sensitivity was achieved by optimizing adsorption time and square wave parameter values. The detection limit of Mo(VI) was found to be at the nanomolar level. Interference of some other metallic species in the determination of nanomolar Mo(VI) was also investigated: Cu(II), Zn(II), Mn(II) do not interfere at 10 muM, whereas 1 muM FeEDTA(-) causes an increase in peak current. This iron interference was removed effectively with citric acid.
Daneshgar, Parandis; Norouzi, Parviz; Ganjali, Mohammad Reza; Ordikhani-Seyedlar, Amin; Eshraghi, Hasan
2009-01-01
A new detection technique called the fast Fourier transform square-wave voltammetry (FFT-SWV) is based on the measurements of electrode admittance as a function of potential. The response of the detector (microelectrode) is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve better sensitivity. The response is generated by a redox processes. The redox property of L-dopa was used for determination of it in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for L-dopa determination was at 0.05 mol l(-1) acetate buffer pH 7.0. Synthesized dysprosium nanowires make more effective surface like nanotubes [P.M. Ajayan, S. Iijima, Nature 361 (1993) 333; I.A. Merkoc, Microchim. Acta 152 (2006) 157; F.H. Wu, G.C. Zhao, X.W. Wei, Z.S. Yang, Microchim. Acta 144 (2004) 243; L. Liu, J. Song, Anal. Biochem. 354 (2006) 22] so they are good candidates for using as a modifier for electrochemical reactions. The drug presented one irreversible oxidation peaks at 360 mV versus Ag/AgCl by modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential about 80 mV. Furthermore, signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensitivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, C(DL) of 4.0 x 10(-9)M and an LOQ of 7.0 x 10(-9) M were found for determination for L-dopa. A good recovery was obtained for assay spiked urine samples and a good quantification of L-dopa was achieved in a commercial formulation.
NASA Astrophysics Data System (ADS)
Laborda, Eduardo; Wang, Yijun; Henstridge, Martin C.; Martínez-Ortiz, Francisco; Molina, Angela; Compton, Richard G.
2011-08-01
The Marcus-Hush and Butler-Volmer kinetic electrode models are compared experimentally by studying the reduction of 2-methyl-2-nitropropane in acetonitrile at mercury microelectrodes using Reverse Scan Square Wave Voltammetry. This technique is found to be very sensitive to the electrode kinetics and to permit critical comparison of the two models. The Butler-Volmer model satisfactorily fits the experimental data whereas Marcus-Hush does not quantitatively describe this redox system.
Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A
2013-07-01
Conducted energy weapons (CEWs) (including the Advanced TASER(®) X26 model produced by TASER International, Inc.) incapacitate individuals by causing muscle contractions. In this study using anesthetized swine, the potential incapacitating effect of primarily monophasic, 19-Hz voltage imposed by the commercial CEW was compared with the effect of voltages imposed by a laboratory device that created 40-Hz square waves. Forces of muscle contraction were measured with the use of strain gauges. Stimulation with 40-Hz square waves required less pulse energy than stimulation with the commercial CEW to produce similar muscle contraction. The square-pulse stimulation, at the higher repetition rate, caused a more complete tetanus at a lower energy. Use of such a simple shape of waveform may be used to make future nonlethal weapon devices more efficient. © 2013 American Academy of Forensic Sciences Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.
Seaman, R.L. ); DeHaan, R.L. )
1993-03-15
Inter-beat intervals of aggregated cardiac cells from chicken embryos were studied during 190s exposures to 2.45 GHz microwaves in an open-ended coaxial device. Averaged specific-absorption rates (SARs) and modulation conditions were 1.2-86.9 W/kg continuous-wave (CW), 1.2-12.2 W/kg pulse modulation (PW, duty cycle [approximately] 11%), and 12.0-43.5 W/kg square-wave modulation (duty cycle = 50%). The inter-beat interval decreased during microwave exposures at 42.0 W/kg and higher when CW or square-wave modulation was used, which is consistent with established effects of elevated temperatures. However, increases in the inter-beat interval after PW exposures at 8.4-12.2 W/kg, are not consistent with simple thermal effects. Analysis of variance indicated that SAR, modulation, and the modulation-SAR interaction were all significant factors in altering the interbeat interval. The latter two factors indicated that the cardiac cells were affected by athermal as well as thermal effects of microwave exposure.
Helfrick, John C; Mann, Megan A; Bottomley, Lawrence A
2016-08-18
Theory for cyclic square wave voltammetry of electrode reactions with chemical reactions preceding the electron transfer is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Meisels, R; Gajic, R; Kuchar, F; Hingerl, K
2006-07-24
We report on a study of the wave propagation and refraction in a 2D square-lattice photonic crystal for the first two photonic bands as well as the coupling of the external waves and criteria for flat-lens focusing. Microwave experiments and numerical simulations are performed. Main results concern the transition from positive to negative refraction below the first band gap, the flat-lens focusing using a novel criterion, viz. the constancy of the ratio of the tangents of the incident and refracted angle. Focusing results for medium ( approximately 10) and ultra-large dielectric contrast ( approximately 100) are presented. In the latter case focusing with a spot size below one wavelength at distances several wavelengths behind the photonic crystal is achieved.
NASA Astrophysics Data System (ADS)
Méndez-Fragoso, Ricardo; Cabrera-Trujillo, Remigio
2015-05-01
The determination of the maximum number of atoms and the density profile of an ultra-cold wave-packet, under confinement conditions by an attractive impurity near the de-localization threshold, have been an open problem in ultra-cold atom physics. In this work, we study the effect of a wave-guide impurity on an ultra-cold matter wave-packet at the threshold of de-localization. The impurity is modeled by a 1-D square well potential with depth V 0 and length 2 R 0. Coupling of the square well potential to a contact impurity of strength β at the center is also considered. The time-independent non-linear Schrödinger equation describing a Bose-Einstein condensate at the delocalization threshold is exactly solved. The density profile, maximum non-linear coupling constant, g max, and maximum number of atoms, N max, prompt to be localized by the defect potential in the ground and first excited states are also reported. It is shown that g max and the density profiles become only functions of the reduced impurity size ξ = √ V 0 R 0. It is also found that the first excited state at the threshold of de-localization exists only for ξ ≥ π/(2√2), always holding a lower number of atoms than the corresponding ground state for the same reduced impurity size. Also, the addition of a repulsive contact impurity leads to a non-linear coupling constant at the de-localization threshold lower than that of the square well potential. In spite of the non-linear character of the Gross-Pitaevskii equation, it is found that a general scaling-law holds for defects with the same ξ, related with the same g max, having the same reduced density profile in the quasi-free direction. We report the full width at half maximum for the wave-function and density profile, finding a large spread for small reduced confining conditions. Implications of these results for the determination of the wave-packet properties under confinement in atom chip and Bose-Einstein condensates are presented with the
Fdez de Betoño, S; Arranz Garcia, A; Arranz Valentín, J F
1999-08-01
By using several electrochemical techniques, the study of electroanalytical behaviour of antihipertensive Doxazosin at Nafion modified carbon paste electrode (NMCPE) has been carried out. The voltammetric peak is very pH dependent, reaching the maximum i(p) at pH 6.8 (Ep -0.17 V), the reduction process being quasi-reversible and fundamentally controlled by adsorption. A method based on the control of adsorptive preconcentration of the Doxazosin on the NMCPE, before its voltammetric determination, is proposed. The detection limit reached using square wave voltammetry (SWV) as redissolution technique was 2.33x10(-11) M and the variation coefficient at 2x10(-9) M level was 3.54%. A spectrophotometric study of Doxazosin has also been made and two waves at 244 and 329 nm (pH 1.7), were obtained. The wave at 329 nm changes its height and position with the pH, allowing the pKa determination (6.94+/-0.21) using different methods. The obtained detection limit was 0.5x10(-6) M, and the variation coefficient at 1.5x10(-5) M level was 0.99%. The UV spectrophotometric method is sufficiently accurate and precise to be applied in the Carduran tablets assay, while the voltammetric method (AdS-SWV) can in addition be used to determine the drug at trace level in human urine samples with good recoveries.
Meucci, V; Laschi, S; Minunni, M; Pretti, C; Intorre, L; Soldani, G; Mascini, M
2009-01-15
An optimized digestion method coupled to electrochemical detection to monitor lead, copper, cadmium and mercury in fish tissues was developed. Square wave anodic stripping voltammetry (SWASV) coupled to disposable screen-printed electrodes (SPEs) was employed as fast and sensitive electroanalytical method for heavy metals detection. Different approaches in digestion protocols were assessed. The study was focused on Atlantic hake fillets because of their wide diffusion in the human nutrition. Best results were obtained by digesting fish tissue with hydrogen peroxide/hydrochloric acid mixture coupled to solid phase (SP) purification of the digested material. This combined treatment allowed quantitative extraction from fish tissue (muscle) of the target analytes, with fast execution times, high sensitivity and avoiding organic residues eventually affecting electrochemical measurements. Finally, the method has been validated with reference standard materials such as dogfish muscle (DORM-2) and mussel tissues (NIST 2977).
Zheng, Yu; Dou, Jun-Rong; Gao, Yang; Dong, Lei; Li, Gang
2017-04-01
Although magnetic fields have significant effects on neurons, little is known about the mechanisms behind their effects. The present study aimed to measure the effects of magnetic fields on ion channels in cortical pyramidal neurons. Cortical pyramidal neurons of Kunming mice were isolated and then subjected to 15 Hz, 1 mT square wave (duty ratio 50%) magnetic fields stimulation. Sodium currents (INa), transient potassium currents (IA) and delayed rectifier potassium currents (IK) were recorded by whole-cell patch clamp method. We found that magnetic field exposure depressed channel current densities, and altered the activation kinetics of sodium and potassium channels. The inactivation properties of INa and IA were also altered. Magnetic field exposure alters ion channel function in neurons. It is likely that the structures of sodium and potassium channels were influenced by the applied field. Sialic acid, which is an important component of the channels, could be the molecule responsible for the reported results.
Li, Meng; Xu, Su-Ying; Gross, Andrew J; Hammond, Jules L; Estrela, Pedro; Weber, James; Lacina, Karel; James, Tony D; Marken, Frank
2015-06-10
The interaction of ferrocene-boronic acid with fructose is investigated in aqueous 0.1 m phosphate buffer at pH 7, 8 and 9. Two voltammetric methods, based on 1) a dual-plate generator-collector micro-trench electrode (steady state) and 2) a square-wave voltammetry (transient) method, are applied and compared in terms of mechanistic resolution. A combination of experimental data is employed to obtain new insights into the binding rates and the cumulative binding constants for both the reduced ferrocene-boronic acid (pH dependent and weakly binding) and for the oxidised ferrocene-boronic acid (pH independent and strongly binding).
Turdean, Graziella L; Szabo, Gabriella
2015-07-15
A new modified electrode was realized in a simple way, consisting by the immobilization of a myoglobin (My) - single walled carbon nanotubes (SWCNT) mixture on the surface of a graphite electrode with a Nafion film. The cyclic voltammetry investigations realized with the obtained electrode (G/My-SWCNT/Nafion) showed a voltammetric signal due to a one-step redox reaction of the surface-confined myoglobin, in a deaerated 0.1 M phosphate buffer, pH 7. Also, the G/My-SWCNT/Nafion modified electrode demonstrated a great potential for the analytical determination of nitrite ions by square-wave voltammetry and an alternative for the already existing methods. The use of the sensor for the detection of nitrite ions in samples of meat products leads to comparable results with those obtained with the standard Griess spectrophotometric assay (ISO 2918/1975), proving the suitability of using immobilized myoglobin as electrocatalyst in the nitrite reduction process.
NASA Astrophysics Data System (ADS)
Sukow, David W.; Gilfillan, Taylor; Pope, Brenton; Torre, Maria S.; Gavrielides, Athanasios; Masoller, Cristina
2012-09-01
We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.
Shi, Changyan; Xie, Shaoai; Jia, Jinping
2008-01-01
A new method of indirect determination of Cu(2+) was developed based on square-wave voltammetry by the oxidation of iodide in organic solvent at the liquid/liquid (L/L) interface. The limit of detection for the determination of Cu(2+) in this method was found to be 5 x 10(-4) mol/L, and the concentration ranged up to 1 x 10(-2) mol/L gave a linear limiting current versus concentration response. For the same simulated wastewater, this method showed high accuracy compared with the result tested by sodium diethyldithiocarbamate extraction spectrophotometry. This approach could be applied to the indirect determination of the oxidative heavy metals in the industrial wastewater.
Shi, Changyan; Xie, Shaoai; Jia, Jinping
2008-01-01
A new method of indirect determination of Cu2+ was developed based on square-wave voltammetry by the oxidation of iodide in organic solvent at the liquid/liquid (L/L) interface. The limit of detection for the determination of Cu2+ in this method was found to be 5 × 10−4 mol/L, and the concentration ranged up to 1 × 10−2 mol/L gave a linear limiting current versus concentration response. For the same simulated wastewater, this method showed high accuracy compared with the result tested by sodium diethyldithiocarbamate extraction spectrophotometry. This approach could be applied to the indirect determination of the oxidative heavy metals in the industrial wastewater. PMID:19096710
Wan, Qijin; Yang, Nianjun; Ye, Yongkang
2002-04-01
The electrochemical behavior of thiamine on a self-assembled electrode of L-cysteine (Cys/SAM/Au) has been investigated and Cys/SAM/Au can be used to detect thiamine using square-wave voltammetry (SWV). At pH 11.40 Britton-Robinson buffer, thiamine exhibits a well-defined anodic peak on Cys/SAM/Au. Under the optimized conditions, the anodic peak current of SWV was linear with the content of thiamine in the range of 1.1 x 10(-8) - 2.2 x 10(-6) mol/L; the detection limit was 5.5 x 10(-9) mol/L. The method was successfully applied to the determination of thiamine in pharmaceutical preparations.
King, Allen B
2009-04-01
To evaluate the effect of near-normal glucose control before initiation of pramlintide therapy and square-wave meal bolus on self-reported hypoglycemia and the percentage change in dosing parameters after attaining the maximum pramlintide dosage. In this prospective study, insulin pump-treated patients with type 1 diabetes had insulin dosages optimally titrated on the basis of daily continuous glucose monitoring (CGM). Pramlintide therapy was initiated, and the dosage was increased 15 mcg/meal per week. Insulin dosage was adjusted during 30-minute visits after review of self-monitored blood glucose records, adverse effects, and hypoglycemia diary. Within 2 weeks of achieving a pramlintide dosage of 60 mcg/meal, the second CGM-guided insulin dosage adjustment was done. The primary end point was the percentage change in total basal insulin dosage (TBD) from baseline. The secondary end points were the percentage change in the insulin to carbohydrate ratio (ICR) and the assessment of symptoms of nausea and hypoglycemia during the pramlintide dosing escalation. Nine patients were enrolled. The difference between before and during CGM-guided insulin dosing was a mean (+/- standard deviation) TBD change of -11.2 +/- 13.2% (P = 0.023) and mean ICR change of 7.8 +/- 13.4% (P = 0.053). Pramlintide was well tolerated and resulted in decrease in weight and hemoglobin A1c values. Hypoglycemia occurred in 6 patients during the study; the assistance of another person was not required in any of these cases. No hypoglycemia was reported in the first week of starting pramlintide. Mild to moderate nausea was reported in 6 patients during the titration phase. Patients with near-normal glucose control who use a square-wave bolus may not need initial bolus dosage reduction. With weight loss, small adjustments in both TBD and ICR may be required. Greater incidence of hypoglycemia seen in previous studies may in part be due to mismatched insulin dosing.
Sahlem, Gregory L.; Badran, Bashar W.; Halford, Jonathan J.; Williams, Nolan R.; Korte, Jeffrey E.; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L.; Runion, Jennifer; Bachman, David L.; Uhde, Thomas W.; Borckardt, Jeffery J.; George, Mark S.
2015-01-01
Background A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current wave form (square in our study, nearly sinusoidal in the original). Objective/Hypothesis Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Methods Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517mA/CM2, and oscillated between zero and maximal current at a frequency of 0.75Hz. Stimulation occurred during five-five minute blocks with one-minute inter-block intervals (25 minutes total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. Results There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1±3.0SD more associations) (sham = 3.8±3.1S.D more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6±2.7 S.D. correctly typed sequences) compared to
ERIC Educational Resources Information Center
DeTemple, Duane
2010-01-01
Purely combinatorial proofs are given for the sum of squares formula, 1[superscript 2] + 2[superscript 2] + ... + n[superscript 2] = n(n + 1) (2n + 1) / 6, and the sum of sums of squares formula, 1[superscript 2] + (1[superscript 2] + 2[superscript 2]) + ... + (1[superscript 2] + 2[superscript 2] + ... + n[superscript 2]) = n(n + 1)[superscript 2]…
ERIC Educational Resources Information Center
DeTemple, Duane
2010-01-01
Purely combinatorial proofs are given for the sum of squares formula, 1[superscript 2] + 2[superscript 2] + ... + n[superscript 2] = n(n + 1) (2n + 1) / 6, and the sum of sums of squares formula, 1[superscript 2] + (1[superscript 2] + 2[superscript 2]) + ... + (1[superscript 2] + 2[superscript 2] + ... + n[superscript 2]) = n(n + 1)[superscript 2]…
NASA Astrophysics Data System (ADS)
Griv, Evgeny; Lin, Chien-Cheng; Ngeow, Chow-Choong; Jiang, Ing-Guey
2014-05-01
The rotation about the Galactic center of open clusters belonging to the thin component of the Milky Way Galaxy is studied on the basis of line-of-sight velocities and positions for 169 nearby objects taken from the literature. The minor second-order effects caused by the Lin-Shu-type density waves are taken into account by using the least-squares numerical method. Even preliminary, the physical interpretation of the results obtained in this manner shows that (i) among several Fourier modes of collective oscillations developing in the solar neighborhood the one-armed m=1 spiral mode is the main one; the Galaxy has thus significant lopsidedness in the stellar distribution at large radii, (ii) the Sun is located between the major trailing spiral-arm segments in Carina-Sagittarius and Perseus, closer to the outer Perseus one, (iii) the local Cygnus-Orion segment is not a part of the dominant spiral arm but is a minor one, which is due to a secondary Fourier harmonic of the Galaxy’s oscillations, (iv) the pitch angle of the dominant density-wave pattern in the solar vicinity seems to be relatively small, of the order of 7°, and the wavelength (the radial distance between spiral arms) of the m=1 pattern is about 6 kpc, (v) the Galactocentric distance where the velocities of disk rotation and of the spiral density wave (the corotation radius) coincide is located outside of the solar circle; thus, a pattern angular speed lower than the local angular rotation velocity, and finally (vi) the spiral arms of the Galaxy do not represent small deviations of the surface density and gravitational potential from a basic distribution that is axisymmetric in the mean.
ERIC Educational Resources Information Center
Hubbard, Guy
2003-01-01
Discusses the role of the square in art and explains that students can study modern art. Includes background information and artwork by four artists: (1) Richard Anuszkiewicz; (2) Victor Vasarely; (3) Frank Stella; and (4) Bridget Riley. (CMK)
ERIC Educational Resources Information Center
Holton, Derek; Knights, Carol
2008-01-01
Here, we investigate what loci are produced when a square of side-length one is allowed to rotate around a square of side-length n, where n is a whole number. We find that if i = 1, 2, 3 or 4 (mod 4), the loci obtained for n [congruent to] i (mod 4) all have the same symmetry and we show how the perimeter of each class can be determined. We also…
Sahlem, Gregory L; Badran, Bashar W; Halford, Jonathan J; Williams, Nolan R; Korte, Jeffrey E; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L; Runion, Jennifer; Bachman, David L; Uhde, Thomas W; Borckardt, Jeffery J; George, Mark S
2015-01-01
A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current waveform (square in our study, nearly sinusoidal in the original). Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517 mA/cm(2), and oscillated between zero and maximal current at a frequency of 0.75 Hz. Stimulation occurred during five-five minute blocks with 1-min inter-block intervals (25 min total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1 ± 3.0 SD more associations) (sham = 3.8 ± 3.1 SD more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6 ± 2.7 SD correctly typed sequences) compared to sham stimulation (2.3 ± 2.2 SD correctly typed
Edwards, A W F
2012-03-01
The origin and development of Punnett's Square for the enumeration and display of genotypes arising in a cross in Mendelian genetics is described. Due to R. C. Punnett, the idea evolved through the work of the 'Cambridge geneticists', including Punnett's colleagues William Bateson, E. R. Saunders and R. H. Lock, soon after the rediscovery of Mendel's paper in 1900. These geneticists were thoroughly familiar with Mendel's paper, which itself contained a similar square diagram. A previously-unpublished three-factor diagram by Sir Francis Galton existing in the Bateson correspondence in Cambridge University Library is then described. Finally the connection between Punnett's Square and Venn Diagrams is emphasized, and it is pointed out that Punnett, Lock and John Venn overlapped as Fellows of Gonville and Caius College, Cambridge. Copious illustrations are given. Copyright © 2011 Elsevier Ltd. All rights reserved.
Tefera, Molla; Geto, Alemnew; Tessema, Merid; Admassie, Shimelis
2016-11-01
Poly(4-amino-3-hydroxynaphthalene sulfonic acid)-modified glassy carbon electrode (poly(AHNSA)/GCE) was prepared for simultaneous determination of caffeine and paracetamol using square-wave voltammetry. The method was used to study the effects of pH and scan rate on the voltammetric response of caffeine and paracetamol. Linear calibration curves in the range of 10-125μM were obtained for both caffeine and paracetamol in acetate buffer solution of pH 4.5 with a correlation coefficient of 0.9989 and 0.9986, respectively. The calculated detection limits (S/N=3) were 0.79μM for caffeine and 0.45μM for paracetamol. The effects of some interfering substances in the determination of caffeine and paracetamol were also studied and their interferences were found to be negligible which proved the selectivity of the modified electrode. The method was successfully applied for the quantitative determination of caffeine and paracetamol in Coca-Cola, Pepsi-Cola and tea samples.
Sýs, Milan; Švecová, Blanka; Švancara, Ivan; Metelka, Radovan
2017-08-15
A new electroanalytical method for determination of vitamin E in the form of the total content of tocopherols present in margarines and edible oils has been developed. The method is based on extraction of these biologically active compounds into silicone oil, acting as lipophilic binder of glassy carbon paste electrode, with subsequent electrochemical detection by square wave anodic stripping voltammetry (SWASV) in 0.1M HNO3. The values of vitamin E contents were expressed as mass equivalent of α-tocopherol known as the most active form of this lipophilic vitamin. The linear ranges for α-tocopherol determination were 5×10(-7)-4×10(-5) and 5×10(-8)-1×10(-5)molL(-1) with the detection limits of 1×10(-7) and 3.3×10(-9)molL(-1) for 5 and 15min accumulation, respectively. The results have shown that SWASV with extraction step is very sensitive method for the determination of vitamin E, being comparable to reversed-phase high performance liquid chromatography chosen as reference method. Copyright © 2017 Elsevier Ltd. All rights reserved.
Kong, Bo; Tang, Biyu; Liu, Xiaoying; Zeng, Xiandong; Duan, Haiyan; Luo, Shenglian; Wei, Wanzhi
2009-08-15
A novel method for the simultaneous determination of cadmium(II) and copper(II) during the adsorption process onto Pseudomonas aeruginosa was developed. The concentration of the free metal ions was successfully detected by square wave anodic stripping voltammetry (SWASV) on the mercaptoethane sulfonate (MES) modified gold electrode, while the P. aeruginosa was efficiently avoided approaching to the electrode surface by the MES monolayer. And the anodic stripping peaks of Cd(2+) and Cu(2+) appear at -0.13 and 0.34V respectively, at the concentration range of 5-50 microM, the peak currents of SWASV present linear relationships with the concentrations of cadmium and copper respectively. As the determination of Cd(2+) and Cu(2+) was in real time and without pretreatment, the kinetic characteristics of the adsorption process were studied and all the corresponding regression parameters were obtained by fitting the electrochemical experimental data to the pseudo-second-order kinetic model. Moreover, Langmuir and Freundlich models well described the biosorption isotherms. And there were some differences in the amount of metal ion adsorbed at equilibrium (q(e)) and other kinetics parameters when the two ions coexisted were compared with the unaccompanied condition, which were also discussed in this paper. The proposed electrode system provides excellent platform for the simultaneous determination of trace metals in complex biosorption process.
Zhang, Chang; Zhou, Yaoyu; Tang, Lin; Zeng, Guangming; Zhang, Jiachao; Peng, Bo; Xie, Xia; Lai, Cui; Long, Beiqing; Zhu, Jingjing
2016-01-01
The fabrication and evaluation of a glassy carbon electrode (GCE) modified with self-doped polyaniline nanofibers (SPAN)/mesoporous carbon nitride (MCN) and bismuth for simultaneous determination of trace Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV) are presented here. The morphology properties of SPAN and MCN were characterized by transmission electron microscopy (TEM), and the electrochemical properties of the fabricated electrode were characterized by cyclic voltammetry (CV). Experimental parameters, such as deposition time, pulse potential, step potential, bismuth concentration and NaCl concentration, were optimized. Under the optimum conditions, the fabricated electrode exhibited linear calibration curves ranging from 5 to 80 nM for Cd2+ and Pb2+. The limits of detection (LOD) were 0.7 nM for Cd2+ and 0.2 nM for Pb2+ (S/N = 3). Additionally, the repeatability, reproducibility, anti-interference ability and application were also investigated, and the proposed electrode exhibited excellent performance. The proposed method could be extended for other heavy metal determination.
Truzzi, Cristina; Lambertucci, Luca; Gambini, Gloria; Scarponi, Giuseppe
2002-03-01
Square wave anodic stripping voltammetry (SWASV) was optimized for the simultaneous determination of Cd, Pb and Cu in coastal seawater samples. Background subtraction was adapted to improve peak detection and quantification. Optimum background voltammograms were obtained by applying a 7.5 s equilibration potential at -975 mV (vs. Ag/AgCl, 3M KCl) before starting the background scan. Voltammetric scan parameters were optimized to obtain maximum sensitivity while retaining good peak resolution and discrimination from background. Optimal parameters were: frequency 100 Hz, pulse amplitude 25 mV, current sampling delay time 2 ms, step height 8 mV. The sensitivity of optimized SWASV proved to be more than double that of differential pulse anodic stripping voltammetry (DPASV), and analysis time was halved. Samples containing around 13 (Cd), 30 (Pb), 200 (Cu) ng/l (typical averages of the coastal area of the Marche region) can be analyzed using a 5 min deposition time and the total analysis time using three standard additions is about 1 h and half, excluding the mercury film preparation and the outgassing of the sample, which can be made in parallel using a second cell cup.
Li, Hongbo; Li, Jing; Yang, Zhanjun; Xu, Qin; Hou, Chuantao; Peng, Jinyun; Hu, Xiaoya
2011-07-15
An ultrasensitive electrochemical method for simultaneous determination of lead and cadmium was first developed using the novel bismuth-Nafion-medical stone doped disposable electrode (an improved wax-impregnated graphite electrode). Through the synergistic sensitization effect of the resulting composite material, the disposable electrode showed remarkable electrochemical responses to lead and cadmium. The oxidation of the two metals produced two well-defined and separated square wave peaks at about -0.62 V for Pb(2+) and -0.85 V for Cd(2+), respectively. The effects of the amount of medical stone, concentration of Nafion, thickness of bismuth, pH of buffer solution, deposition potential, accumulation time, voltammetric measurement and possible interferences were investigated in detail. Under the optimal conditions, the fabricated electrode exhibited linear ranges from 2.0 to 12.0 μg L(-1) with detection limit of 0.07 μg L(-1) for lead and 2.0-12.0 μg L(-1) with detection limit of 0.47 μg L(-1) for cadmium. The assay results of heavy metals in wastewater with the proposed method were in acceptable agreement with the atomic absorption spectroscopy method.
Sugita, Tomohiko; Hiramatsu, Kazuki; Ikeda, Shigeru; Matsumura, Michio
2013-02-01
By bringing an anodically biased needle electrode into contact with n-type Si at its tip in a solution containing hydrofluoric acid, Si is etched at the interface with the needle electrode and a pore is formed. However, in the case of p-type Si, although pores can be formed, Si is likely to be corroded and covered with a microporous Si layer. This is due to injection of holes from the needle electrode into the bulk of p-type Si, which shifts its potential to a level more positive than the potential needed for corrosion and formation of a microporous Si layer. However, by applying square-wave potential pulses to a Pt needle electrode, these undesirable changes are prevented because holes injected into the bulk of Si during the period of anodic potential are annihilated with electrons injected into Si during the period of cathodic potential. Even under such conditions, holes supplied to the place near the Si/metal interface are used for etching p-type Si, leading to formation of a pore at the place where the Pt needle electrode was in contact.
Laffont, Laure; Hezard, Teddy; Gros, Pierre; Heimbürger, Lars-Eric; Sonke, Jeroen E; Behra, Philippe; Evrard, David
2015-08-15
Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs-GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs-GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10(-2)M range. Finally, the AuNPs-GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM).
Jafari, Safiye; Faridbod, Farnoush; Norouzi, Parviz; Dezfuli, Amin Shiralizadeh; Ajloo, Davood; Mohammadipanah, Fatemeh; Ganjali, Mohammad Reza
2015-10-01
A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO2NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)3](2+/3+) redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)3](2+/3+) FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10(-15) to 1 × 10(-8) mol L(-1). The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL(-1) with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)3](2+/3+) interaction with ssDNA before and after hybridization.
Promraksa, Arwut; Chuang, Yu-Chen; Chen, Li-Jen
2014-03-15
A liquid droplet deposited on a hydrophobic surface with a square-array cosine wave-like pattern is simulated by using the Surface Evolver to study on the Cassie-Wenzel wetting transition. All the metastable states of a liquid drop with a fixed drop volume on the model surface are determined at different surface roughnesses. The maximum/minimum contact angles among the metastable states at each surface roughness correspond to the advancing/receding contact angles. It is interesting to find out that when the surface roughness is slightly smaller than the transition roughness (between the Wenzel and Cassie states) the drop under the condition of the advancing and receding contact angle would exhibit the Cassie and Wenzel state, respectively. Both experimental and simulation results demonstrate that a liquid droplet of a fixed volume on patterned substrates may exhibit either the Wenzel state or the Cassie state at a certain surface roughness. An increase in the surface roughness may induce the wetting transition from the Wenzel state to the Cassie state to occur. The slip-jump behavior of an advancing contact line with increasing drop volume at different viewing angles is carefully discussed to demonstrate the distorted three-phase contact line. Effect of surface roughness and drop size on liquid penetration into groove of the model surface is discussed. Copyright © 2013 Elsevier Inc. All rights reserved.
East, Gaston A; Marinho, Epitácio P
2005-03-01
A simple and reliable method for the determination of mercury in hair on a rotating gold disk electrode using subtractive anodic stripping voltammetry without removal of oxygen is reported. Voltammetric and microwave parameters were optimized to obtain the best analytical results. Parameters such as supporting electrolyte concentration, influence of chloride in the Hg peak, deposition potential, scan rate, accumulation time, rotation rate, square-wave amplitude, and electrode conditioning were studied. Pressurized microwave-assisted digestion of hair, suitable for the accurate voltammetric determination of Hg, was evaluated using six acid mixtures and several time-power programs. Under the optimized conditions, no interference by copper, cadmium, lead, nickel, manganese, iron, or zinc was found at concentrations corresponding to their occurrence in normal hair. A calibration plot between 6,67 and 46,69 microg/L was linear, with r(2) better than 0.999. The detection limit for a deposition time of 60 s at 254 g was calculated as 1.92 nM (3omega). Validation of the method was demonstrated with the use of a certified reference sample of hair. Eight real samples of hair (four unexposed children and four exposed persons) were also analyzed.
Viviana Tarditto, Lorena; Alicia Zon, María; García Ovando, Hugo; Roberto Vettorazzi, Nelio; Javier Arévalo, Fernando; Fernández, Héctor
2017-11-01
Diseases caused by enterotoxicogenic Escherichia coli F4 (K88) (ETEC F4) are a problem in swine production establishments. Due to the high rate of mortality and morbidity of E. coli infections, a rapid and accurate diagnosis is important in order to choose an appropriate treatment to reduce the economic impact. Therefore, an electrochemical magneto-immunosensor (EMI) was developed to detect and quantify ETEC F4 in swine feces samples through a direct non-competitive immunoassay. ETEC F4 was selectively captured by immunomagnetic separation. The detection principle was based on the activity of β-galactosidase endogenous enzyme (β-gal), which hydrolyses the p-aminophenyl-β-D-galactopyranoside (p-APG) producing p-aminophenol (p-AP), which was oxidized on a carbon screen printed electrode (CSPE) using square wave voltammetry (SWV). All parameters related to construction and electrochemical responses were optimized. The total analysis time to quantify ETEC F4 using the EMI was less than 2h and the limit of detection (LOD) was 33CFUmL(-1). The perceptual relative error (%Er) was 20%. The magneto-immunosensor was validated versus conventional method of culture and plate count, obtaining a very good agreement. The EMI is simple, fast and economical to detect and quantify ETEC F4 in swine feces samples, being thus a valuable tool in swine production. Copyright © 2017 Elsevier B.V. All rights reserved.
Bondarenko, E A
2014-04-28
For a laser gyro with a four-mirror square resonator we have developed a mathematical model, which allows one to simulate the temporal behaviour of the synchronisation zone parameters of the frequencies of counterpropagating waves in a situation when the device operates in the self-heating regime and is switched-on at different initial temperatures. (laser gyroscopes)
Gimenez, M; Servera, E; Salinas, W
1982-01-01
A new 45 min Square-Wave Endurance Exercise Test (SWEET) performed on a cycle ergometer and designed for endurance training was studied in 43 normal subjects: Untrained (U), twelve women and seven men and Trained (T), eight women and 16 men. Among them seven were elite sportsmen (E). Preliminary measurements were made of VO2 max by constant power and Maximal Tolerated Power (MTP) in a progressive test (+ 30 W/3 min). To the SWEET's base, established as a % of individual MTP, a peak of 1 min at MTP was added every 5 minutes. Maximum Intensity of Endurance during the SWEET (MIE45) is defined by both maximal heart rate (HR) at the end of the test and the impossibility of maintaining 5% above the percent MTP of the MIE45 for 45 min. Exhaustion was reached at the end of the MIE45, which could be expressed as % MTP, as total energy expenditure (TEE) in liters of O2, or as total mechanical work (TMW) in kiloJoules per kg of weight (kJ . kg-1). VE, VCO2, VO2 and HR were continuously measured. VO2 max, TMW and % MTP were significantly higher in T than in U subjects. The E subjects show the highest values of those parameters. TMW and TEE were well correlated (r = 0.992, p less than 0.001, n = 43) indicating good efficiency. TMW in T (r = 0.453) and in E men (r = 0.442) were however less well correlated to the VO2 max. MIE45 therefore gives different information in the evaluation of "endurance capacity" at the time of measurement than that provided by VO2 max. Because of the high TEE per session it could be useful for endurance training of T and U subjects.
dos Santos, Luciana B O; Masini, Jorge C
2008-01-14
This paper describes the development and evaluation of a sequential injection method to automate the determination of methyl parathion by square wave adsorptive cathodic stripping voltammetry exploiting the concept of monosegmented flow analysis to perform in-line sample conditioning and standard addition. Accumulation and stripping steps are made in the sample medium conditioned with 40 mmolL(-1) Britton-Robinson buffer (pH 10) in 0.25 molL(-1) NaNO3. The homogenized mixture is injected at a flow rate of 10 microLs(-1) toward the flow cell, which is adapted to the capillary of a hanging drop mercury electrode. After a suitable deposition time, the flow is stopped and the potential is scanned from -0.3 to -1.0V versus Ag/AgCl at frequency of 250 Hz and pulse height of 25 mV. The linear dynamic range is observed for methyl parathion concentrations between 0.010 and 0.50 mgL(-1), with detection and quantification limits of 2 and 7 microgL(-1), respectively. The sampling throughput is 25 h(-1) if the in line standard addition and sample conditioning protocols are followed, but this frequency can be increased up to 61 h(-1) if the sample is conditioned off-line and quantified using an external calibration curve. The method was applied for determination of methyl parathion in spiked water samples and the accuracy was evaluated either by comparison to high performance liquid chromatography with UV detection, or by the recovery percentages. Although no evidences of statistically significant differences were observed between the expected and obtained concentrations, because of the susceptibility of the method to interference by other pesticides (e.g., parathion, dichlorvos) and natural organic matter (e.g., fulvic and humic acids), isolation of the analyte may be required when more complex sample matrices are encountered.
Mladenov, Mitko; Mirceski, Valentin; Gjorgoski, Icko; Jordanoski, Blagoja
2004-12-01
The electrode reaction of glutathione (GSH) at the hanging mercury drop electrode is studied by means of square-wave voltammetry (SWV). At potentials more positive than -0.350 V (vs. Ag/AgCl (3 mol/l KCl)) the oxidation of the mercury electrode in the presence of GSH leads to creation of a sparingly soluble mercury-GSH complex that deposits onto the electrode surface. Under cathodic potential scan, the deposited complex acts as a reducible reactant, giving raise to a well-defined cathodic stripping reversible SW voltammetric response. The electrode reaction can be described by the scheme: Hg(SG)(2(s))+e(-)+2H((aq))(+) = Hg((l))+2GSH((aq)). Thus, the electrode reaction provides information on both thermodynamics and kinetics of the chemical interactions of GSH with mercury. An experimental methodology for measuring the kinetics of the electrode reactions, based on the property known as "quasireversible maximum", is developed. The standard redox rate constant is 5.09, 5.75 and 5.22 cm s(-1) in a phosphate buffer at pH 5.6, 7.0 and 8.5, respectively, with a precision of +/-10%. The high rate of the electrode reaction reflects the strong affinity of GSH towards chemical interaction with mercury. The electrode reaction is particularly sensitive to the presence of heavy metal ions such as Cu(2+), Cd(2+), and Zn(2+.) The rate of the electrode reaction decreases significantly in the presence of these ions due to simultaneous interactions of GSH with the respective ion and mercury.
Brycht, Mariola; Skrzypek, Sławomira; Guzsvány, Valéria; Berenji, Janoš
2013-12-15
A new square-wave adsorptive stripping voltammetric (SWAdSV) method was developed for the determination of the neonicotinoid insecticide clothianidin (Clo), based on its reduction at a renewable silver amalgam film electrode (Hg(Ag)FE). The key point of the procedure is the pretreatment of the Hg(Ag)FE by applying the appropriate conditioning potential (-1.70 V vs. Ag/AgCl reference electrode). Under the optimized voltammetric conditions, such pretreatment resulted in the peak for the Clo reduction in Britton-Robinson buffer pH 9.0 at about -0.60 V, which was used for the analytical purpose. The developed SWAdSV procedure made it possible to determine Clo in the concentration range of 6.0×10(-7)-7.0×10(-6) mol L(-1) (LOD=1.8×10(-7) mol L(-1), LOQ=6.0×10(-7) mol L(-1)) and 7.0×10(-6)-4.0×10(-5) mol L(-1) (LOD=1.3×10(-6) mol L(-1), LOQ=4.2×10(-6) mol L(-1)). The repeatability, precision, and the recovery of the method were determined. The effect of common interfering pesticides was also investigated. Standard addition method was successfully applied and validated for the determination of Clo in spiked Warta River water, corn seeds samples, and in corn seeds samples treated with the commercial formulation PONCHO 600 FS.
Guzmán-Vázquez de Prada, A; Loaiza, Oscar A; Serra, B; Morales, D; Martínez-Ruiz, P; Reviejo, A J; Pingarrón, J M
2007-05-01
A molecularly imprinted polymer was developed and used for solid-phase extraction (MISPE) of the antihelmintic fenbendazole in beef liver samples. Detection of the analyte was accomplished using square wave voltammetry (SWV) at a cylindrical carbon fibre microelectrode (CFME). A mixture of MeOH/HAc (9:1) was employed both as eluent in the MISPE system and as working medium for electrochemical detection of fenbendazole. The limit of detection was 1.9x10(-7) mol L-1 (57 microg L-1), which was appropriate for the determination of fenbendazole at the maximum residue level permitted by the European Commission (500 microg kg-1 in liver). Given that the SW voltammetric analysis could not be directly performed in the sample extract as a consequence of interference from some sample components, a sample clean-up with a MIP for selectively retaining fenbendazole was performed. The MIP was synthesized using a 1:8:22 template/methacrylic acid/ethylene glycol dimethacrylate ratio. A Britton-Robinson Buffer of pH 9.0 was selected for retaining fenbendazole in the MIP cartridges, and an eluent volume of 5.0 mL at a flow rate of 2.0 mL min-1 was chosen in the elution step. Cross-reactivity with the MIP was observed for other benzimidazoles. The synthesized MIP exhibited a good selectivity for benzimidazoles with respect to other veterinary drugs. The applicability of the MISPE-SWV method was tested with beef liver samples, spiked with fenbendazole at 5,000 and 500 microg kg-1. Results obtained for ten different liver samples yielded mean recoveries of (95+/-12)% and (96+/-11)% for the upper and lower concentration level, respectively.
Semaan, Georges; Ben Braham, Fatma; Salhi, Mohamed; Meng, Yichang; Bahloul, Faouzi; Sanchez, François
2016-04-18
We have experimentally demonstrated square pulses emission from a co-doped Er:Yb double-clad fiber laser operating in anomalous dispersion DSR regime using the nonlinear polarization evolution technique. Stable mode-locked pulses have a repetition rate of 373 kHz with 2.27 µJ energy per pulse under a pumping power of 30 W in cavity. With the increase of pump power, both the duration and the energy of the output square pulses broaden. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse.
(2 kF , 2 kF) density-wave orders of interacting p-orbital fermions in square optical lattice
NASA Astrophysics Data System (ADS)
Zhang, Zixu; Liu, W. Vincent
2011-03-01
We study instabilities of spinless fermionic atoms in the p- orbital bands in two dimensional optical lattices at non- integer filling against interactions. Stripe charge-density- wave or orbital-density-wave orders are found for attractive and repulsive interactions, respectively. A surprising result is that the superfluid phase, usually expected of attractively interacting fermions, is less energetically favored. Nesting quasi-one-dimensional Fermi surfaces in such systems are independent of filling, which ensures that the stripe density- wave orders occur in a large parameter regime. This work is supported by ARO (W911NF-07-1-0293) and ARO-DARPA-OLE (W911NF-07-1-0464). We also thank the KITP at UCSB for its hospitality where this research is supported in part by NSF Grant No. PHY05-51164.
Xia, J.; Miller, R.D.; Xu, Y.
2008-01-01
Inversion of multimode surface-wave data is of increasing interest in the near-surface geophysics community. For a given near-surface geophysical problem, it is essential to understand how well the data, calculated according to a layered-earth model, might match the observed data. A data-resolution matrix is a function of the data kernel (determined by a geophysical model and a priori information applied to the problem), not the data. A data-resolution matrix of high-frequency (>2 Hz) Rayleigh-wave phase velocities, therefore, offers a quantitative tool for designing field surveys and predicting the match between calculated and observed data. We employed a data-resolution matrix to select data that would be well predicted and we find that there are advantages of incorporating higher modes in inversion. The resulting discussion using the data-resolution matrix provides insight into the process of inverting Rayleigh-wave phase velocities with higher-mode data to estimate S-wave velocity structure. Discussion also suggested that each near-surface geophysical target can only be resolved using Rayleigh-wave phase velocities within specific frequency ranges, and higher-mode data are normally more accurately predicted than fundamental-mode data because of restrictions on the data kernel for the inversion system. We used synthetic and real-world examples to demonstrate that selected data with the data-resolution matrix can provide better inversion results and to explain with the data-resolution matrix why incorporating higher-mode data in inversion can provide better results. We also calculated model-resolution matrices in these examples to show the potential of increasing model resolution with selected surface-wave data. ?? Birkhaueser 2008.
All Square Chiliagonal Numbers
ERIC Educational Resources Information Center
A?iru, Muniru A.
2016-01-01
A square chiliagonal number is a number which is simultaneously a chiliagonal number and a perfect square (just as the well-known square triangular number is both triangular and square). In this work, we determine which of the chiliagonal numbers are perfect squares and provide the indices of the corresponding chiliagonal numbers and square…
All Square Chiliagonal Numbers
ERIC Educational Resources Information Center
A?iru, Muniru A.
2016-01-01
A square chiliagonal number is a number which is simultaneously a chiliagonal number and a perfect square (just as the well-known square triangular number is both triangular and square). In this work, we determine which of the chiliagonal numbers are perfect squares and provide the indices of the corresponding chiliagonal numbers and square…
NASA Astrophysics Data System (ADS)
Mounaix, Philippe; Collet, Pierre
2010-05-01
We study the divergence of the solution to a Schrödinger-type amplifier driven by the square of a Gaussian noise in presence of a random potential. We follow the same approach as Mounaix, Collet, and Lebowitz (MCL) in terms of a distributional formulation of the amplified field and the use of the Paley-Wiener theorem (Mounaix et al. in Commun. Math. Phys. 264:741-758, 2006, Erratum: ibid. 280:281-283, 2008). Our results show that the divergence is not affected by the random potential, in the sense that it occurs at exactly the same coupling constant as what was found by MCL without a potential. It follows a fortiori that the breakdown of the amplifier is not affected by the possible existence of a localized regime in the amplification free limit.
Discrete square root smoothing.
NASA Technical Reports Server (NTRS)
Kaminski, P. G.; Bryson, A. E., Jr.
1972-01-01
The basic techniques applied in the square root least squares and square root filtering solutions are applied to the smoothing problem. Both conventional and square root solutions are obtained by computing the filtered solutions, then modifying the results to include the effect of all measurements. A comparison of computation requirements indicates that the square root information smoother (SRIS) is more efficient than conventional solutions in a large class of fixed interval smoothing problems.
ERIC Educational Resources Information Center
Watson, Gale A.
2003-01-01
Demonstrates the transformations that are possible to construct a variety of magic squares, including modifications to challenge students from elementary grades through algebra. Presents an example of using magic squares with students who have special needs. (YDS)
ERIC Educational Resources Information Center
Watson, Gale A.
2003-01-01
Demonstrates the transformations that are possible to construct a variety of magic squares, including modifications to challenge students from elementary grades through algebra. Presents an example of using magic squares with students who have special needs. (YDS)
ERIC Educational Resources Information Center
Emanouilidis, Emanuel
2005-01-01
Latin squares have existed for hundreds of years but it wasn't until rather recently that Latin squares were used in other areas such as statistics, graph theory, coding theory and the generation of random numbers as well as in the design and analysis of experiments. This note describes Latin and diagonal Latin squares, a method of constructing…
ERIC Educational Resources Information Center
Emanouilidis, Emanuel
2005-01-01
Latin squares have existed for hundreds of years but it wasn't until rather recently that Latin squares were used in other areas such as statistics, graph theory, coding theory and the generation of random numbers as well as in the design and analysis of experiments. This note describes Latin and diagonal Latin squares, a method of constructing…
NASA Astrophysics Data System (ADS)
Terzian, Yervant; Lazio, Joseph
2006-06-01
The Square Kilometre Array (SKA) is the future centimeter- and meter-wavelength telescope with a sensitivity about 50 times higher than present instruments. Its Key Science Projects are (a) Astrobiology including planetary formation within protoplanetary disks; (b) Testing theories of gravitation using an array of pulsars to search for gravitational waves and relativistic binaries to probe the strong-field regime; (c) The origin and evolution of cosmic magnetism, both within the Galaxy and in intergalactic space, via an all-sky grid of magnetic field measurements; (d) The end of the Dark Ages, involving searches for a neutral hydrogen signature, the first supermassive black holes, and the first metal-rich systems; and (e) A hydrogen census to a redshift z greater than or equal to 1 from which to study the evolution of galaxies, dark matter, and dark energy. The SKA will operate at wavelengths from 1.2 cm to 3 m (0.1-25 GHz), providing milliarcsecond resolution at the shortest wavelengths. Its instantaneous field of view will be about 1° (20 cm wavelength), with many simultaneous beams on the sky. The Reference Design is composed of a large number of small dish antennas, building upon an original US proposal. In order to obtain these capabilities at a reasonable cost, significant engineering investments are being made in antennas, wideband feeds and receivers, and signal processing; aperture arrays (phased feeds) are also being investigated in Europe for the lower frequencies. Candidate sites are in Argentina, Australia, China, and South Africa, with a short list of acceptable sites anticipated late in 2006.
NASA Astrophysics Data System (ADS)
Ahmed, Salwa A.; Gaber, Ahmed A. Abdel; Rahim, Asmaa M. Abdel
2015-04-01
In this work, silica fume (SF) is used as a solid-phase extractor for extraction of Zn(II) and Cd(II) from aqueous solutions. Characterization of SF is performed by Fourier transform infrared, X-ray diffraction, transmission and scanning electron microscopy. The optimum experimental conditions for the two metal ions are investigated using batch and column techniques. The maximum adsorption capacity values are found to be 54.13 and 121.28 mg g-1 at the optimum pH 6.0 and 8.0 for Zn(II) and Cd(II), respectively. The equilibrium data are analyzed using the Langmuir, Freundlich, and Temkin isotherms by nonlinear regression analysis. Also, the kinetics analysis revealed that the overall adsorption process is successfully fitted with the pseudo-second-order model. The method is applied for determination of the target metal ions in pharmaceutical and environmental samples using square-wave anodic stripping voltammetry. The limit of detection (LOD) values are 0.102 and 1.43 × 10-3 mg L-1 for Zn(II) and Cd(II), respectively. The percentage recovery values are 98.8-100.5 % which indicate the success of the proposed method for determination of Zn(II) and Cd(II) without interfering effects.
Li, Zou; Chen, Li; He, Fang; Bu, Lijuan; Qin, Xiaoli; Xie, Qingji; Yao, Shouzhuo; Tu, Xinman; Luo, Xubiao; Luo, Shenglian
2014-05-01
Graphene oxide (GO)-thionine (TH) nanocomposite was prepared by π-π stacking. The nanocomposite was cast-coated on a glassy carbon electrode (GCE) to prepare an electroreduced GO (ERGO)-TH/GCE, then 2-mercaptoethanesulfonate (MES) was covalently tethered to ERGO-TH by potentiostatic anodization to form an ERGO-TH-MES/GCE. The thiolation reaction was monitored by electrochemical quartz crystal microbalance (EQCM). Square wave anodic stripping voltammetry (SWASV) was used to determine Cd(2+) and Pb(2+) at the ERGO-TH-MES/GCE further modified with Nafion and Bi. Under the optimal conditions, the linear calibration curves for Cd(2+) and Pb(2+) are from 1 to 40 μg L(-1), with limits of detection (S/N=3) of 0.1 μg L(-1) for Cd(2+) and 0.05 μg L(-1) for Pb(2+), respectively. The electrode was used for the simultaneous analysis of Cd(2+) and Pb(2+) in water samples with satisfactory recovery.
Chen, Haijie; Malliakas, Christos D.; Narayan, Awadhesh; ...
2017-07-17
We report a new two-dimensional compound Pb3–xSb1+xS4Te2-δ has a charge density wave (CDW) at room temperature. The CDW is incommensurate with q-vector of 0.248(6)a* + 0.246(8)b* + 0.387(9)c* for x = 0.29(2) and d = 0.37(3) due to positional and occupational long range ordering of Te atoms in the sheets. The modulated structure was refined from the single crystal X-ray diffraction data with a superspace group Pmore » $$\\bar{1}$$(αβγ)0 using (3 + 1)-dimensional crystallography. The resistivity increases with decreasing temperature, suggesting semiconducting behavior. The transition temperature (TCDW) of the CDW is ~ 345 K above which the Te square sheets become disordered with no q-vector. Lastly, first-principles density functional theory calculations on the undistorted structure and an approximate commensurate supercell reveal that the gap is due to the structure modulation.« less
Economou, Anastasios; Voulgaropoulos, Anastasios
2003-01-01
The development of a dedicated automated sequential-injection analysis apparatus for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) is reported. The instrument comprised a peristaltic pump, a multiposition selector valve and a home-made potentiostat and used a mercury-film electrode as the working electrodes in a thin-layer electrochemical detector. Programming of the experimental sequence was performed in LabVIEW 5.1. The sequence of operations included formation of the mercury film, electrolytic or adsorptive accumulation of the analyte on the electrode surface, recording of the voltammetric current-potential response, and cleaning of the electrode. The stripping step was carried out by applying a square-wave (SW) potential-time excitation signal to the working electrode. The instrument allowed unattended operation since multiple-step sequences could be readily implemented through the purpose-built software. The utility of the analyser was tested for the determination of copper(II), cadmium(II), lead(II) and zinc(II) by SWASV and of nickel(II), cobalt(II) and uranium(VI) by SWAdSV.
Chen, Haijie; Malliakas, Christos D.; Narayan, Awadhesh; ...
2017-08-16
We report a new two-dimensional compound Pb3-xSb1+xS4Te2-d has a charge density wave (CDW) at room temperature. The CDW is incommensurate with q-vector of 0.248(6)a* + 0.246(8)b* + 0.387(9)c* for x = 0.29(2) and d = 0.37(3) due to positional and occupational long range ordering of Te atoms in the sheets. The modulated structure was refined from the single crystal X-ray diffraction data with a superspace group P-1(αβγ)0 using (3 + 1)-dimensional crystallography. The resistivity increases with decreasing temperature, suggesting semiconducting behavior. The transition temperature (TCDW) of the CDW is ~ 345 K above which the Te square sheets become disorderedmore » with no q-vector. First-principles density functional theory calculations on the undistorted structure and an approximate commensurate supercell reveal that the gap is due to the structure modulation.« less
Ardila, Jorge Armando; Oliveira, Geiser Gabriel; Medeiros, Roberta Antigo; Fatibello-Filho, Orlando
2014-04-07
A highly sensitive method for bezafibrate determination using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film based on square-wave adsorptive stripping voltammetry (SWAdSV) is proposed. The electrochemical behaviour of bezafibrate has been studied by cyclic voltammetry, showing an irreversible anodic peak at a potential of 1.09 V in 0.1 mol L(-1) phosphate buffer solution (pH 2.0). A study of the scan rate showed that the oxidation of bezafibrate is an adsorptive-controlled process, involving the transfer of two electrons and two protons per molecule. The analytical curve was linear over a bezafibrate concentration range from 50 to 910 nmol L(-1), with a detection limit of 16 nmol L(-1). This analytical method was successfully applied for benzafibrate determination in pharmaceutical formulations, with results showing good agreement with those obtained using a comparative spectrophotometric method, and has the potential for field application.
NASA Astrophysics Data System (ADS)
Ahmed, Salwa A.; Gaber, Ahmed A. Abdel; Rahim, Asmaa M. Abdel
2017-05-01
In this work, silica fume (SF) is used as a solid-phase extractor for extraction of Zn(II) and Cd(II) from aqueous solutions. Characterization of SF is performed by Fourier transform infrared, X-ray diffraction, transmission and scanning electron microscopy. The optimum experimental conditions for the two metal ions are investigated using batch and column techniques. The maximum adsorption capacity values are found to be 54.13 and 121.28 mg g-1 at the optimum pH 6.0 and 8.0 for Zn(II) and Cd(II), respectively. The equilibrium data are analyzed using the Langmuir, Freundlich, and Temkin isotherms by nonlinear regression analysis. Also, the kinetics analysis revealed that the overall adsorption process is successfully fitted with the pseudo-second-order model. The method is applied for determination of the target metal ions in pharmaceutical and environmental samples using square-wave anodic stripping voltammetry. The limit of detection (LOD) values are 0.102 and 1.43 × 10-3 mg L-1 for Zn(II) and Cd(II), respectively. The percentage recovery values are 98.8-100.5 % which indicate the success of the proposed method for determination of Zn(II) and Cd(II) without interfering effects.
ERIC Educational Resources Information Center
Misiurewicz, Michal
2013-01-01
If students are presented the standard proof of irrationality of [square root]2, can they generalize it to a proof of the irrationality of "[square root]p", "p" a prime if, instead of considering divisibility by "p", they cling to the notions of even and odd used in the standard proof?
ERIC Educational Resources Information Center
Adams, Deborah
2006-01-01
This article describes an approach to teaching square dance that is advantageous for both the teacher and students. Lessons in dance become more meaningful to students when the music and vocabulary is consistent with experiences in their own lives. When students create their own squaring to the rap, lessons become more student-centered,…
ERIC Educational Resources Information Center
Adams, Deborah
2006-01-01
This article describes an approach to teaching square dance that is advantageous for both the teacher and students. Lessons in dance become more meaningful to students when the music and vocabulary is consistent with experiences in their own lives. When students create their own squaring to the rap, lessons become more student-centered,…
ERIC Educational Resources Information Center
Wagon, Stan; Cox, Barry
2009-01-01
A technique discovered in 1939 can be used to build a device that is driven by standard circular motion (as in a drill press) and drills exact square holes. This device is quite different from the classic design by Watts, which uses a Reuleaux triangle and drills a hole that is almost, but not exactly, square. We describe the device in detail,…
ERIC Educational Resources Information Center
Misiurewicz, Michal
2013-01-01
If students are presented the standard proof of irrationality of [square root]2, can they generalize it to a proof of the irrationality of "[square root]p", "p" a prime if, instead of considering divisibility by "p", they cling to the notions of even and odd used in the standard proof?
ERIC Educational Resources Information Center
Wagon, Stan; Cox, Barry
2009-01-01
A technique discovered in 1939 can be used to build a device that is driven by standard circular motion (as in a drill press) and drills exact square holes. This device is quite different from the classic design by Watts, which uses a Reuleaux triangle and drills a hole that is almost, but not exactly, square. We describe the device in detail,…
NASA Technical Reports Server (NTRS)
Argentiero, P. D.
1978-01-01
It is shown that the least squares collocation approach to estimating geodetic parameters is identical to conventional minimum variance estimation. Hence, the least squares collocation estimator can be derived either by minimizing the usual least squares quadratic loss function or by computing a conditional expectation by means of the regression equation. When a deterministic functional relationship between the data and the parameters to be estimated is available, one can implement a least squares solution using the functional relation to obtain an equation of condition. It is proved the solution so obtained is identical to what is obtained through least squares collocation. The implications of this equivalance for the estimation of mean gravity anomalies are discussed.
Square dielectric THz waveguides.
Aflakian, N; Yang, N; LaFave, T; Henderson, R M; O, K K; MacFarlane, D L
2016-06-27
A holey cladding dielectric waveguide with square cross section is designed, simulated, fabricated and characterized. The TOPAS waveguide is designed to be single mode across the broad frequency range of 180 GHz to 360 GHz as shown by finite-difference time domain simulation and to robustly support simultaneous TE and TM mode propagation. The square fiber geometry is realized by pulling through a heat distribution made square by appropriate furnace design. The transmitted mode profile is imaged using a vector network analyzer with a pinhole at the receiver module. Good agreement between the measured mode distribution and the calculated mode distribution is demonstrated.
dos Santos, Vagner B; Fava, Elson L; de Miranda Curi, Newton S; Faria, Ronaldo C; Fatibello-Filho, Orlando
2014-08-01
In order to reduce the sample consumption and waste generation for electrochemical purposes, a screen-printed electrode (SPE) used for electrodeposition of bismuth film (SPE-BiFE) and a thermostated electrochemical flow cell (EFC) were developed. The SPE-BiFE with the EFC was employed to determine Cd(2+) and Pb(2+) ions in natural, wastewater and tap water samples by square-wave anodic stripping voltammetry (SWASV). For this, the flow-batch analysis (FBA) approach based on solenoid micro-pumps and three-way valves was developed to carry out a fully automated procedure with temperature control. Furthermore, the FBA and the SWASV parameters were optimized, on line simultaneous determination of Cd(2+) and Pb(2+) ions was performed and two analytical curves were linearly acquired in the concentration ranges from 6.30 to 75.6µg L(-1) and from 3.20 to 38.4µg L(-1), respectively. Moreover, limits of detection of 0.60µg L(-1) and 0.10µg L(-1) for Cd(2+) and Pb(2+), respectively, were obtained. Studies of precision for the same SPE-BiFE and repeatability for five built SPE-BiFE were carried out for Cd(2+) and Pb(2+) ion measurements and RSD of 4.1% and 2.9% (n=3) with repeatabilities (n=5) of 6.5% and 8.0% were respectively obtained for both analytes. Besides, a low consumption of 700µL of reagents and a sampling frequency of 13h(-1) were acquired. Simplicity, fast response, accuracy, high portability, robustness and suitability for in loco analyses are the main features of the proposed electroanalytical method.
Sun, Qianwen; Wang, Jikui; Tang, Meihua; Huang, Liming; Zhang, Zhiyi; Liu, Chang; Lu, Xiaohua; Hunter, Kenneth W; Chen, Guosong
2017-05-02
Here we describe a new and sensitive flow electrochemical detection system that employs a novel flow-field shaped solid electrode (FFSSE). The system was constructed with a 3D-printed thin-layer flow cell (TLFC) and a flat screen-printed FFSSE with USB connection. This interface facilitates continuous flow accumulation square-wave anodic stripping voltammetry (ASV). The flow distribution in the working space of TLFC was simulated using the finite element method (FEM) and the shape and configuration of electrodes were optimized accordingly. We demonstrated the electrochemical determination of Pb(2+) using this newly designed TLFC-FFSSE detection system without removal of oxygen from samples. This TLFC-FFSSE based system showed an attractive stripping voltammetric performance compared to a traditional ASV based method. A linear range for detection of Pb(2+) was found to be 0.5-100 μg/L (0.5 to 100 ppb) and a detection limit of 0.2 μg/L (0.2 ppb) was achieved in the presence of bismuth as codeposition metal. The system was further applied to detect Pb(2+) in biological broths of methane fermentation. The electrochemical detection results were consistent with that obtained from atomic fluorescence spectroscopy (AFS) analysis and the average recovery was found to be 95.5-106.5% using a standard addition method. This new flow electrochemical detection system showed better sensitivity and reproducibility compared to a traditional ASV based method. Such a system offers great potential for on-site and real-time detection of heavy metals where compact, inexpensive, robust, and low-volume analysis is required.
Spin configurations on a decorated square lattice
Mert, Gülistan; Mert, H. Şevki
2016-06-08
Spin configurations on a decorated square lattice are investigated using Bertaut’s microscopic method. We have obtained collinear and non-collinear (canted) modes for the given wave vectors in the ground state. We have found ferromagnetic and antiferromagnetic commensurate spin configurations. We have found canted incommensurate spin configurations.
ERIC Educational Resources Information Center
Hignite, Karla
2003-01-01
Details the $1 billion in facilities projects being undertaken by Georgia Institute of Technology, including the 8-acre Technology Square, which involve partnerships with its neighbors to accomplish urban revitalization. (EV)
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.
ERIC Educational Resources Information Center
Parker, Dan
2001-01-01
Presents design features of the Dawson Elementary School (Corpus Chriti, Texas) where an atmosphere of an old town square and the feeling of community have been created. Photos and a floor plan are provided. (GR)
Smoothed square well potential
NASA Astrophysics Data System (ADS)
Salamon, P.; Vertse, T.
2017-07-01
The classical square well potential is smoothed with a finite range smoothing function in order to get a new simple strictly finite range form for the phenomenological nuclear potential. The smoothed square well form becomes exactly zero smoothly at a finite distance, in contrast to the Woods-Saxon form. If the smoothing range is four times the diffuseness of the Woods-Saxon shape both the central and the spin-orbit terms of the Woods-Saxon shape are reproduced reasonably well. The bound single-particle energies in a Woods-Saxon potential can be well reproduced with those in the smoothed square well potential. The same is true for the complex energies of the narrow resonances.
Truzzi, C; Annibaldi, A; Illuminati, S; Bassotti, E; Scarponi, G
2008-09-01
Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution (approximately 0.55 mol L(-1) HF, pH approximately 1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L(-1), deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, DeltaE(step) 8 mV, t(step) 100 ms, t(wait) 60 ms, t(delay) 2 ms, t(meas) 3 ms. Under these conditions the metal peak potentials were Cd -654 +/- 1 mV, Pb -458 +/- 1 mV, Cu -198 +/- 1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to approximately 4 microg L(-1) for Cd and Pb and approximately 20 microg L(-1) for Cu. The detection limits were 5.8 ng L(-1), 3.6 ng L(-1), and 4.3 ng L(-1) for Cd, Pb, and Cu, respectively, with t(d) = 5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g(-1) to approximately 1 microg g(-1), depending on the metal considered and with significant differences between the two sponge species.
Asadpour-Zeynali, Karim; Mollarasouli, Fariba
2017-06-15
This work introduces a new electrochemical sensor based on polyvinyl pyrrolidone capped CoFe2O4@CdSe core-shell modified electrode for a rapid detection and highly sensitive determination of rifampicin (RIF) by square wave adsorptive stripping voltammetry. The new PVP capped CoFe2O4@CdSe with core-shell nanostructure was synthesized by a facile synthesis method for the first time. PVP can act as a capping and etching agent for protection of the outer surface nanoparticles and formation of a mesoporous shell, respectively. Another important feature of this work is the choice of the ligand (1,10-phenanthroline) for precursor cadmium complex that works as a chelating agent in order to increase optical and electrical properties and stability of prepared nanomaterial. The nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-vis, photoluminescence (PL) spectroscopy, FT-IR, and cyclic voltammetry techniques. The PL spectroscopy study of CoFe2O4@CdSe has shown significant PL quenching by the formation of CoFe2O4 core inside CdSe, this shows that CoFe2O4 NPs are efficient electron acceptors with the CdSe. It is clearly observed that the biosensor can significantly enhance electrocatalytic activity towards the oxidation of RIF, under the optimal conditions. The novelty of this work arises from the new synthesis method for the core-shell of CoFe2O4@CdSe. Then, the novel electrochemical biosensor was fabricated for ultra-trace level determination of rifampicin with very low detection limit (4.55×10(-17)M) and a wide linear range from 1.0×10(-16) to 1.0×10(-7)M. The fabricated biosensor showed high sensitivity and selectivity, good reproducibility and stability. Therefore, it was successfully applied for the determination of ultra-trace RIF amounts in biological and pharmaceutical samples with satisfactory recovery data
Annibaldi, A; Truzzi, C; Illuminati, S; Bassotti, E; Scarponi, G
2007-02-01
Eight PM10 aerosol samples were collected in the vicinity of the "Mario Zucchelli" Italian Antarctic Station (formerly Terra Nova Bay Station) during the 2000-2001 austral summer using a high-volume sampler and precleaned cellulose filters. The aerosol mass was determined by differential weighing of filters carried out in a clean chemistry laboratory under controlled temperature and humidity. A two-step sequential extraction procedure was used to separate the water-soluble and the insoluble (dilute-HCl-extractable) fractions. Cd, Pb and Cu were determined in the two fractions using an ultrasensitive square wave anodic stripping voltammetric (SWASV) procedure set up for and applied to aerosol samples for the first time. Total extractable metals showed maxima at midsummer for Cd and Pb and a less clear trend for Cu. In particular, particulate metal concentrations ranged as follows: Cd 0.84-9.2 microg g(-1) (average 4.7 microg g(-1)), Pb 13.2-81 microg g(-1) (average 33 microg g(-1)), Cu 126-628 microg g(-1) (average 378 microg g(-1)). In terms of atmospheric concentration, the values were: Cd 0.55-6.3 pg m(-3) (average 3.4 pg m(-3)), Pb 8.7-48 pg m(-3) (average 24 pg m(-3)), Cu 75-365 pg m(-3) (average 266 pg m(-3)). At the beginning of the season the three metals appear widely distributed in the insoluble (HCl-extractable) fraction (higher proportions for Cd and Pb, 90-100%, and lower for Cu, 70-90%) with maxima in the second half of December. The soluble fraction then increases, and at the end of the season Cd and Pb are approximately equidistributed between the two fractions, while for Cu the soluble fraction reaches its maximum level of 36%. Practically negligible contributions are estimated for crustal and sea-spray sources. Low but significant volcanic contributions are estimated for Cd and Pb (approximately 10% and approximately 5%, respectively), while there is an evident although not quantified marine biogenic source, at least for Cd. The estimated natural
Deng, Haiqiang; Huang, Xinjian; Wang, Lishi
2010-12-21
This paper describes a novel application of Fourier transformed large-amplitude square-wave voltammetry (FT-SWV) in combination with three-phase edge plane pyrolytic graphite (EPPG) electrode to investigate both the kinetics and thermodynamics of anion transfer across the liquid/liquid interface using a conventional three-electrode arrangement. The transfer of anion from aqueous phase to organic phase was electrochemically driven by reversible redox transformation of confined redox probe in the organic phase. The kinetics and thermodynamics of anion transfer were inspected by a so-called "quasi-reversible maximum" (QRM) emerged in the profile of even harmonic components of power spectrum obtained by Fourier transformation (FT) of time-domain total current response and formal potential E(f) of first harmonic voltammogram obtained by application of inverse FT on the power spectrum. Besides, a systematic study of patterns of behavior of a variety of anions at the same concentration and a specific anion at different concentrations on kinetics and thermodynamics and the effect of amplitude ΔE on QRM were also conducted, aiming to optimize the measurement conditions. The investigation mentioned above testified that the ion transfer across the liquid/liquid interface controls the kinetics of overall electrochemical process, regardless of either FT-SWV or traditional SWV investigation. Moreover, either the kinetic probe f(max) or the thermodynamic probe E(f) can be served as a way for analytical applications. Interestingly, a linear relationship between peak currents of the first harmonic components and concentrations of perchlorate anion in the aqueous solutions can be observed, which is somewhat in accordance with a finding obtained by Fourier transformed alternating current voltammetry (FT-ACV) [Bond, A. M.; Duffy, N. W.; Elton, D. M.; Fleming, B. D. Anal. Chem. 2009, 81, 8801-8808]. This may open a new door for analytical detection of a wide spectrum of
ERIC Educational Resources Information Center
Schulman, Steven M.
2014-01-01
In this article the author describes a problem posed to his class, "How many squares are there on a checkerboard?" The problem is deliberately vague so that the teacher can get the students to begin asking questions. The first goal is to come to an agreement about what the problem means (Identify the problem). The second goal is to get…
NASA Technical Reports Server (NTRS)
1940-01-01
This 1940s photo of the South side of Square in downtown Huntsville, Alabama, looking west, shows a historical bank in the background with cars parked just South of the Courthouse (not shown in photo). (Courtesy of Huntsville/Madison County Public Library)
ERIC Educational Resources Information Center
Smith, Scott G.
1993-01-01
A Reuleaux triangle is constructed by drawing an arc connecting each pair of vertices of an equilateral triangle with radius equal to the side of the triangle. Investigates the application of drilling a square hole using a drill bit in the shape of a Reuleaux triangle. (MDH)
Optimization of one-way wave equations.
Lee, M.W.; Suh, S.Y.
1985-01-01
The theory of wave extrapolation is based on the square-root equation or one-way equation. The full wave equation represents waves which propagate in both directions. On the contrary, the square-root equation represents waves propagating in one direction only. A new optimization method presented here improves the dispersion relation of the one-way wave equation. -from Authors
NASA Astrophysics Data System (ADS)
de Carvalho, R. Egydio; Leonel, Edson D.
2016-12-01
A periodic time perturbation is introduced in the logistic map as an attempt to investigate new scenarios of bifurcations and new mechanisms toward the chaos. With a squared sine perturbation we observe that a point attractor reaches the chaotic attractor without following a cascade of bifurcations. One fixed point of the system presents a new scenario of bifurcations through an infinite sequence of alternating changes of stability. At the bifurcations, the perturbation does not modify the scaling features observed in the convergence toward the stationary state.
Dory, R.A.; Uckan, N.A.; Ard, W.B.; Batchelor, D.B.; Berry, L.A.; Bryan, W.E.; Dandl, R.A.; Guest, G.E.; Haste, G.R.; Hastings, D.E.
1986-10-01
The ELMO Bumpy Square (EBS) concept consists of four straight magnetic mirror arrays linked by four high-field corner coils. Extensive calculations show that this configuration offers major improvements over the ELMO Bumpy Torus (EBT) in particle confinement, heating, transport, ring production, and stability. The components of the EBT device at Oak Ridge National Laboratory can be reconfigured into a square arrangement having straight sides composed of EBT coils, with new microwave cavities and high-field corners designed and built for this application. The elimination of neoclassical convection, identified as the dominant mechanism for the limited confinement in EBT, will give the EBS device substantially improved confinement and the flexibility to explore the concepts that produce this improvement. The primary goals of the EBS program are twofold: first, to improve the physics of confinement in toroidal systems by developing the concepts of plasma stabilization using the effects of energetic electrons and confinement optimization using magnetic field shaping and electrostatic potential control to limit particle drift, and second, to develop bumpy toroid devices as attractive candidates for fusion reactors. This report presents a brief review of the physics analyses that support the EBS concept, discussions of the design and expected performance of the EBS device, a description of the EBS experimental program, and a review of the reactor potential of bumpy toroid configurations. Detailed information is presented in the appendices.
Overlap Areas of a Square Box on a Square Mesh
2017-04-01
ARL-TN-0818 ● APR 2017 US Army Research Laboratory Overlap Areas of a Square Box on a Square Mesh by James U Cazamias...originator. ARL-TN-0818 ● APR 2017 US Army Research Laboratory Overlap Areas of a Square Box on a Square Mesh by James U Cazamias...no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control
Nonlinear least squares and regularization
Berryman, J.G.
1996-04-01
A problem frequently encountered in the earth sciences requires deducing physical parameters of the system of interest from measurements of some other (hopefully) closely related physical quantity. The obvious example in seismology (either surface reflection seismology or crosswell seismic tomography) is the use of measurements of sound wave traveltime to deduce wavespeed distribution in the earth and then subsequently to infer the values of other physical quantities of interest such as porosity, water or oil saturation, permeability, etc. The author presents and discusses some general ideas about iterative nonlinear output least-squares methods. The main result is that, if it is possible to do forward modeling on a physical problem in a way that permits the output (i.e., the predicted values of some physical parameter that could be measured) and the first derivative of the same output with respect to the model parameters (whatever they may be) to be calculated numerically, then it is possible (at least in principle) to solve the inverse problem using the method described. The main trick learned in this analysis comes from the realization that the steps in the model updates may have to be quite small in some cases for the implied guarantees of convergence to be realized.
Bayesian least squares deconvolution
NASA Astrophysics Data System (ADS)
Asensio Ramos, A.; Petit, P.
2015-11-01
Aims: We develop a fully Bayesian least squares deconvolution (LSD) that can be applied to the reliable detection of magnetic signals in noise-limited stellar spectropolarimetric observations using multiline techniques. Methods: We consider LSD under the Bayesian framework and we introduce a flexible Gaussian process (GP) prior for the LSD profile. This prior allows the result to automatically adapt to the presence of signal. We exploit several linear algebra identities to accelerate the calculations. The final algorithm can deal with thousands of spectral lines in a few seconds. Results: We demonstrate the reliability of the method with synthetic experiments and we apply it to real spectropolarimetric observations of magnetic stars. We are able to recover the magnetic signals using a small number of spectral lines, together with the uncertainty at each velocity bin. This allows the user to consider if the detected signal is reliable. The code to compute the Bayesian LSD profile is freely available.
NASA Astrophysics Data System (ADS)
Andrade, Miguel Ángel Gutiérrez; García, Eric Alfredo Rincón
The design of electoral zones is a complex problem in which democracy of the electoral processes is promoted by some constraints such as population balance, contiguity and compactness. In fact, the computational complexity of zone design problems has been shown to be NP-Hard. This paper propose the use of a new measure of compactness, which uses a mesh formed with square cells to measure the quality of the electoral zones. Finally, a practical real case was chosen, which topographical settings causes some traditional measures of compactness to give very poor quality results, and was designed an algorithm based on simulated annealing that realizes a search in the space of feasible solutions. The results show that the new measure favors the creation of zones with straight forms and avoids twisted or dispersed figures, without an important effect to the population balance, which are considered zones of high quality.
Generalized conjugate gradient squared
Fokkema, D.R.; Sleijpen, G.L.G.
1994-12-31
In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.
NASA Astrophysics Data System (ADS)
Cordes, James M.
2006-06-01
The SKA is an observatory for m/cm wavelengths that will provide quantum leaps in studies of the early universe, the high-energy universe, and astrobiology. Key science areas include:(1) Galaxy Evolution and Large-Scale Structure, including Dark Energy;(2) Probing the Dark Ages through studies of highly redshifted hydrogen and carbon monoxide;(3) Cosmic magnetism;(4) Probing Gravity with Pulsars and Black Holes; and(5) The Cradle of Life, including real-time images of protoplanetary disks, inventory of organic molecules, and the search for signals from extraterrestrial intelligence.From a phase-space point of view, the SKA will expand enormously our ability to discover new and known phenomena, including transient sources with time scales from nano-seconds to years. Particular examples include coherent emissions from extrasolar planets and gamma-ray burst afterglows, detectable at levels 100 times smaller than currently. Specifications needed to meet the science requirements are technically quite challenging: a frequency range of approximately 0.1 to 25 GHz; wide field of view, tens of square degrees (frequency dependent); high dynamic range and image fidelity; flexibility in imaging on scales from sub-mas to degrees; and sampling the time-frequency domain as demanded by transient objects. Meeting these specifications requires collaboration of a world-wide group of engineers and scientists. For this and other reasons, the SKA will be realized internationally. Initially, several concepts have been explored for building inexpensive collecting area that provides broad frequency coverage. The Reference Design now specifies an SKA based on a large number of small-diameter dish antennas with "smart feeds." Complementary to the dishes is a phased aperture array that will provide very wide-field capability. I will discuss the Reference Design, along with a timeline for developing the technology, building the first 10% of the SKA, and finishing the full SKA, along with the
Measurement of high frequency waves using a wave follower
NASA Technical Reports Server (NTRS)
Tang, S.; Shemdin, O. H.
1983-01-01
High frequency waves were measured using a laser-optical sensor mounted on a wave follower. Measured down-wind wave slope spectra are shown to be wind speed dependent; the mean square wave-slopes are generally larger than those measured by Cox and Munk (1954) using the sun glitter method.
NASA Astrophysics Data System (ADS)
Aso, N.; Ohta, K.; Ide, S.
2014-12-01
Deformation in a small volume of earth interior is expressed by a symmetric moment tensor located on a point source. The tensor contains information of characteristic directions, source amplitude, and source types such as isotropic, double-couple, or compensated-linear-vector-dipole (CLVD). Although we often assume a double couple as the source type of an earthquake, significant non-double-couple component including isotropic component is often reported for induced earthquakes and volcanic earthquakes. For discussions on source types including double-couple and non-double-couple components, it is helpful to display them using some visual diagrams. Since the information of source type has two degrees of freedom, it can be displayed onto a two-dimensional flat plane. Although the diagram developed by Hudson et al. [1989] is popular, the trace corresponding to the mechanism combined by two mechanisms is not always a smooth line. To overcome this problem, Chapman and Leaney [2012] developed a new diagram. This diagram has an advantage that a straight line passing through the center corresponds to the mechanism obtained by a combination of an arbitrary mechanism and a double-couple [Tape and Tape, 2012], but this diagram has some difficulties in use. First, it is slightly difficult to produce the diagram because of its curved shape. Second, it is also difficult to read out the ratios among isotropic, double-couple, and CLVD components, which we want to obtain from the estimated moment tensors, because they do not appear directly on the horizontal or vertical axes. In the present study, we developed another new square diagram that overcomes the difficulties of previous diagrams. This diagram is an orthogonal system of isotropic and deviatoric axes, so it is easy to get the ratios among isotropic, double-couple, and CLVD components. Our diagram has another advantage that the probability density is obtained simply from the area within the diagram if the probability density
ERIC Educational Resources Information Center
Emanouilidis, Emanuel
2008-01-01
Latin squares were first introduced and studied by the famous mathematician Leonhard Euler in the 1700s. Through the years, Latin squares have been used in areas such as statistics, graph theory, coding theory, the generation of random numbers as well as in the design and analysis of experiments. Recently, with the international popularity of…
From Square Dance to Mathematics
ERIC Educational Resources Information Center
Bremer, Zoe
2010-01-01
In this article, the author suggests a cross-curricular idea that can link with PE, dance, music and history. Teacher David Schmitz, a maths teacher in Illinois who was also a square dance caller, had developed a maths course that used the standard square dance syllabus to teach mathematical principles. He presents an intensive, two-week course…
ERIC Educational Resources Information Center
Emanouilidis, Emanuel
2008-01-01
Latin squares were first introduced and studied by the famous mathematician Leonhard Euler in the 1700s. Through the years, Latin squares have been used in areas such as statistics, graph theory, coding theory, the generation of random numbers as well as in the design and analysis of experiments. Recently, with the international popularity of…
NASA Astrophysics Data System (ADS)
Zhao, Haojiang; Liu, Rongqiang; Shi, Chuang; Guo, Hongwei; Deng, Zongquan
2015-07-01
Longitudinal vibration of thin phononic crystal plates with a hybrid square-like array of square inserts is investigated. The plane wave expansion method is used to calculate the vibration band structure of the plate. Numerical results show that rotated square inserts can open several vibration gaps, and the band structures are twisted because of the rotation of inserts. Filling fraction and material of the insert affect the change law of the gap width versus the rotation angles of square inserts.
Counting Triangles to Sum Squares
ERIC Educational Resources Information Center
DeMaio, Joe
2012-01-01
Counting complete subgraphs of three vertices in complete graphs, yields combinatorial arguments for identities for sums of squares of integers, odd integers, even integers and sums of the triangular numbers.
AKLSQF - LEAST SQUARES CURVE FITTING
NASA Technical Reports Server (NTRS)
Kantak, A. V.
1994-01-01
The Least Squares Curve Fitting program, AKLSQF, computes the polynomial which will least square fit uniformly spaced data easily and efficiently. The program allows the user to specify the tolerable least squares error in the fitting or allows the user to specify the polynomial degree. In both cases AKLSQF returns the polynomial and the actual least squares fit error incurred in the operation. The data may be supplied to the routine either by direct keyboard entry or via a file. AKLSQF produces the least squares polynomial in two steps. First, the data points are least squares fitted using the orthogonal factorial polynomials. The result is then reduced to a regular polynomial using Sterling numbers of the first kind. If an error tolerance is specified, the program starts with a polynomial of degree 1 and computes the least squares fit error. The degree of the polynomial used for fitting is then increased successively until the error criterion specified by the user is met. At every step the polynomial as well as the least squares fitting error is printed to the screen. In general, the program can produce a curve fitting up to a 100 degree polynomial. All computations in the program are carried out under Double Precision format for real numbers and under long integer format for integers to provide the maximum accuracy possible. AKLSQF was written for an IBM PC X/AT or compatible using Microsoft's Quick Basic compiler. It has been implemented under DOS 3.2.1 using 23K of RAM. AKLSQF was developed in 1989.
Polynomial integral for square and inverse-square potential systems
NASA Astrophysics Data System (ADS)
Virdi, Jasvinder Singh; Srivastava, A. K.; Ahmad, Muneer
2017-07-01
Classification and possibility of fourth order dynamical integral for some square and inverse-square potential in two-dimensional dynamical systems is searched out. It is based on the study of the quadratic algebras of the integrals of motion and on the equivalence of different systems under coupling constant metamorphosis. The determining equations for the existence of integrals of motion of arbitrary order are presented and partially solved for the case of fourth-order integrals. A systematic calculation is given of systems in two and higher dimensional pace that allow integrals of fourth order. The algebras of integrals of motions are not necessarily quadratic but close polynomially or rationally.
Dibrov, Sergey M.; McLean, Jaime; Parsons, Jerod; Hermann, Thomas
2011-12-22
The three-dimensional structures of noncoding RNA molecules reveal recurring architectural motifs that have been exploited for the design of artificial RNA nanomaterials. Programmed assembly of RNA nanoobjects from autonomously folding tetraloop-receptor complexes as well as junction motifs has been achieved previously through sequence-directed hybridization of complex sets of long oligonucleotides. Due to size and complexity, structural characterization of artificial RNA nanoobjects has been limited to low-resolution microscopy studies. Here we present the design, construction, and crystal structure determination at 2.2 {angstrom} of the smallest yet square-shaped nanoobject made entirely of double-stranded RNA. The RNA square is comprised of 100 residues and self-assembles from four copies each of two oligonucleotides of 10 and 15 bases length. Despite the high symmetry on the level of secondary structure, the three-dimensional architecture of the square is asymmetric, with all four corners adopting distinct folding patterns. We demonstrate the programmed self-assembly of RNA squares from complex mixtures of corner units and establish a concept to exploit the RNA square as a combinatorial nanoscale platform.
Science with the Square Kilometre Array
NASA Technical Reports Server (NTRS)
Lazio, Joseph; Huynh, Minh
2010-01-01
The Square Kilometre Array (SKA) is the centimeter- and meter-wavelength telescope for the 21st Century. Its Key Science Projects are (a) The end of the Dark Ages, involving searches for an H i signature and the first metalrich systems; (b) Testing theories of gravitation using an array of pulsars to search for gravitational waves and relativistic binaries to probe the strong-field regime; (c) Observations of H i to a redshift z 2 from which to study the evolution of galaxies and dark energy. (d) Astrobiology including planetary formation within protoplanetary disks; and (c) The origin and evolution of cosmic magnetism, both within the Galaxy and in intergalactic space. The SKA will operate over the wavelength range of at least 1.2 cm to 4 m (70 MHz to 25 GHz), providing milliarcsecond resolution at the shortest wavelengths.
Quantum mechanical streamlines. I - Square potential barrier
NASA Technical Reports Server (NTRS)
Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.
1974-01-01
Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.
A Weighted Least Squares Approach To Robustify Least Squares Estimates.
ERIC Educational Resources Information Center
Lin, Chowhong; Davenport, Ernest C., Jr.
This study developed a robust linear regression technique based on the idea of weighted least squares. In this technique, a subsample of the full data of interest is drawn, based on a measure of distance, and an initial set of regression coefficients is calculated. The rest of the data points are then taken into the subsample, one after another,…
A Solution to Weighted Sums of Squares as a Square
ERIC Educational Resources Information Center
Withers, Christopher S.; Nadarajah, Saralees
2012-01-01
For n = 1, 2, ... , we give a solution (x[subscript 1], ... , x[subscript n], N) to the Diophantine integer equation [image omitted]. Our solution has N of the form n!, in contrast to other solutions in the literature that are extensions of Euler's solution for N, a sum of squares. More generally, for given n and given integer weights m[subscript…
A Solution to Weighted Sums of Squares as a Square
ERIC Educational Resources Information Center
Withers, Christopher S.; Nadarajah, Saralees
2012-01-01
For n = 1, 2, ... , we give a solution (x[subscript 1], ... , x[subscript n], N) to the Diophantine integer equation [image omitted]. Our solution has N of the form n!, in contrast to other solutions in the literature that are extensions of Euler's solution for N, a sum of squares. More generally, for given n and given integer weights m[subscript…
Expedition 50 Red Square Visit
2016-10-26
Expedition 50 NASA astronaut Peggy Whitson, left, Russian cosmonaut Oleg Novitskiy of Roscosmos, center, and ESA astronaut Thomas Pesquet visit Red Square to lay roses at the site where Russian space icons are interred as part of traditional pre-launch ceremonies, Wednesday, Oct. 26, 2016, in Moscow. Photo Credit: (NASA/Bill Ingalls)
Expedition 52 Red Square Visit
2017-07-10
Expedition 52 flight engineers Paolo Nespoli of ESA, left, Sergey Ryazanskiy of Roscosmos, center, and Randy Bresnik of NASA visit Red Square to lay roses at the site where Russian space icons are interred as part of traditional pre-launch ceremonies, Monday, July 10, 2017 in Moscow. Photo Credit: (NASA/Bill Ingalls)
Expedition 52 Red Square Visit
2017-07-10
Expedition 52 flight engineers Paolo Nespoli of ESA, left, Sergey Ryazanskiy of Roscosmos, center, and Randy Bresnik of NASA visit Red Square prepare to lay roses at the site where Russian space icons are interred as part of traditional pre-launch ceremonies, Monday, July 10, 2017 in Moscow. Photo Credit: (NASA/Bill Ingalls)
C[squared] = Creative Coordinates
ERIC Educational Resources Information Center
McHugh, Shelley R.
2007-01-01
"C[squared] = Creative Coordinates" is an engaging group of tasks that fosters the integration of mathematics and art to create meaningful understanding. The project lets students illustrate of find an image, then plot points to map their design on a grid. The project usually takes about a week to complete. When it is finished, students who are…
Weighted total least squares formulated by standard least squares theory
NASA Astrophysics Data System (ADS)
Amiri-Simkooei, A.; Jazaeri, S.
2012-01-01
This contribution presents a simple, attractive, and flexible formulation for the weighted total least squares (WTLS) problem. It is simple because it is based on the well-known standard least squares theory; it is attractive because it allows one to directly use the existing body of knowledge of the least squares theory; and it is flexible because it can be used to a broad field of applications in the error-invariable (EIV) models. Two empirical examples using real and simulated data are presented. The first example, a linear regression model, takes the covariance matrix of the coefficient matrix as
Expedition 52 Red Square Visit
2017-07-10
Expedition 52 backup crew members Norishige Kanai of the Japan Aerospace Exploration Agency (JAXA), left, Alexander Misurkin of Roscosmos, center, and Mark Vande Hei of NASA pose for a photograph in front of Saint Basil's Cathedral as they visited Red Square to lay roses at the site where Russian space icons are interred as part of traditional pre-launch ceremonies, Monday, July 10, 2017 in Moscow. Photo Credit: (NASA/Bill Ingalls)
Expedition 52 Red Square Visit
2017-07-10
Expedition 52 flight engineers Paolo Nespoli of ESA, left, Randy Bresnik of NASA, Sergey Ryazanskiy of Roscosmos, and backup crew members, Alexander Misurkin of Roscosmos, Mark Vande Hei of NASA, and Norishige Kanai of the Japan Aerospace Exploration Agency (JAXA), right, pose for a group photograph in Red Square after having laid roses at the site where Russian space icons are interred as part of traditional pre-launch ceremonies, Monday, July 10, 2017 in Moscow. Photo Credit: (NASA/Bill Ingalls)
SUS Quality Assessment, SQUARE DEAL
1975-02-07
input it through a 1 /3 octave 800 Hz filter, square this output, and then sample the result. The shot shown in Figure (2) is shown again in Figure...ftef Dvma Emeoted)_ REPORT DOCUMENTATION PAGE .... FREAP INSTRUCTIONSBEFORE COMPLETING FORM 1 . REPORT NUMBER a. GOVT ACCESSION NO 3. RECIPIENT’S...Silver Spring, Md. 20910 (301) 589-1188 % YST EMS, Inc. TABLE OF CONTENTS Page No. Summary. . . . . . . . . . . . . . . .. . 1 Introduction
Fano resonances in prism-coupled multimode square micropillar resonators
NASA Astrophysics Data System (ADS)
Lee, Ho-Tong; Zhou, Linjie; Poon, Andrew W.
2005-06-01
We report Fano resonances in a multimode square glass micropillar resonator; the resonances were obtained by using angle-resolved prism coupling. Our experiments reveal characteristically asymmetric line shapes of high-Q resonances and of detuned low-Q resonances in multimode reflection spectra. The asymmetric resonance line shapes evolve for an approximately pi phase within a 0.5° range of reflection angles. We model our observed asymmetric multimode resonances by the far-field interference between a light wave that is evanescently coupled with a high-Q mode orbit and a coherent light wave that is refractively coupled with a detuned low-Q mode orbit.
Square ice in graphene nanocapillaries.
Algara-Siller, G; Lehtinen, O; Wang, F C; Nair, R R; Kaiser, U; Wu, H A; Geim, A K; Grigorieva, I V
2015-03-26
Bulk water exists in many forms, including liquid, vapour and numerous crystalline and amorphous phases of ice, with hexagonal ice being responsible for the fascinating variety of snowflakes. Much less noticeable but equally ubiquitous is water adsorbed at interfaces and confined in microscopic pores. Such low-dimensional water determines aspects of various phenomena in materials science, geology, biology, tribology and nanotechnology. Theory suggests many possible phases for adsorbed and confined water, but it has proved challenging to assess its crystal structure experimentally. Here we report high-resolution electron microscopy imaging of water locked between two graphene sheets, an archetypal example of hydrophobic confinement. The observations show that the nanoconfined water at room temperature forms 'square ice'--a phase having symmetry qualitatively different from the conventional tetrahedral geometry of hydrogen bonding between water molecules. Square ice has a high packing density with a lattice constant of 2.83 Å and can assemble in bilayer and trilayer crystallites. Molecular dynamics simulations indicate that square ice should be present inside hydrophobic nanochannels independently of their exact atomic nature.
Square ice in graphene nanocapillaries
NASA Astrophysics Data System (ADS)
Algara-Siller, G.; Lehtinen, O.; Wang, F. C.; Nair, R. R.; Kaiser, U.; Wu, H. A.; Geim, A. K.; Grigorieva, I. V.
2015-03-01
Bulk water exists in many forms, including liquid, vapour and numerous crystalline and amorphous phases of ice, with hexagonal ice being responsible for the fascinating variety of snowflakes. Much less noticeable but equally ubiquitous is water adsorbed at interfaces and confined in microscopic pores. Such low-dimensional water determines aspects of various phenomena in materials science, geology, biology, tribology and nanotechnology. Theory suggests many possible phases for adsorbed and confined water, but it has proved challenging to assess its crystal structure experimentally. Here we report high-resolution electron microscopy imaging of water locked between two graphene sheets, an archetypal example of hydrophobic confinement. The observations show that the nanoconfined water at room temperature forms `square ice'--a phase having symmetry qualitatively different from the conventional tetrahedral geometry of hydrogen bonding between water molecules. Square ice has a high packing density with a lattice constant of 2.83 Å and can assemble in bilayer and trilayer crystallites. Molecular dynamics simulations indicate that square ice should be present inside hydrophobic nanochannels independently of their exact atomic nature.
Analysis of viscous forces on square cylinders in complex kinematics
Scolan, Y.M.
1996-12-31
Viscous and separated flow effects are studied around square sections; this contributes to a better modelling of the dynamical behavior of Semisubmersible or TLP. The numerical results are compared to experimental ones for square cross sectional shapes with sharp or rounded edges. The numerical scheme is based on the two-dimensional Vortex-In-Cell Method which has been widely used and validated in many application cases. Much work has already been done for simple one-directional flows. However the flows occurring in nature are more complex. Typical examples are the combination of wave motion at high frequency and slow drift motion at low frequency. The forces acting on square sections placed in complex oscillating flows, are investigated in this paper.
A New Class of Pandiagonal Squares
ERIC Educational Resources Information Center
Loly, P. D.; Steeds, M. J.
2005-01-01
An interesting class of purely pandiagonal, i.e. non-magic, whole number (integer) squares of orders (row/column dimension) of the powers of two which are related to Gray codes and square Karnaugh maps has been identified. Treated as matrices these squares possess just two non-zero eigenvalues. The construction of these squares has been automated…
Highly Compact Circulators in Square-Lattice Photonic Crystal Waveguides
Jin, Xin; Ouyang, Zhengbiao; Wang, Qiong; Lin, Mi; Wen, Guohua; Wang, Jingjing
2014-01-01
We propose, demonstrate and investigate highly compact circulators with ultra-low insertion loss in square-lattice- square-rod-photonic-crystal waveguides. Only a single magneto- optical square rod is required to be inserted into the cross center of waveguides, making the structure very compact and ultra efficient. The square rods around the center defect rod are replaced by several right-angled-triangle rods, reducing the insertion loss further and promoting the isolations as well. By choosing a linear-dispersion region and considering the mode patterns in the square magneto-optical rod, the operating mechanism of the circulator is analyzed. By applying the finite-element method together with the Nelder-Mead optimization method, an extremely low insertion loss of 0.02 dB for the transmitted wave and ultra high isolation of 46 dB∼48 dB for the isolated port are obtained. The idea presented can be applied to build circulators in different wavebands, e.g., microwave or Tera-Hertz. PMID:25415417
ERIC Educational Resources Information Center
Dalton, Starrett
The amount of variance accounted for by treatment can be estimated with omega squared or with the squared multiple correlation coefficient. Monte Carlo methods were employed to compare omega squared, the squared multiple correlation coefficient, and the squared multiple correlation coefficient to which a shrinkage formula had been applied, in…
Intrinsic Mean Square Displacement in Proteins
NASA Astrophysics Data System (ADS)
Vural, Derya; Glyde, Henry R.
2012-02-01
The dynamics of biological molecules is investigated in neutron scattering experiments, in molecular dynamics simulations, and using analytical theory. Specifically, the mean square displacement (MSD),
Understanding Least Squares through Monte Carlo Calculations
ERIC Educational Resources Information Center
Tellinghuisen, Joel
2005-01-01
The method of least squares (LS) is considered as an important data analysis tool available to physical scientists. The mathematics of linear least squares(LLS) is summarized in a very compact matrix rotation that renders it practically "formulaic".
Understanding Least Squares through Monte Carlo Calculations
ERIC Educational Resources Information Center
Tellinghuisen, Joel
2005-01-01
The method of least squares (LS) is considered as an important data analysis tool available to physical scientists. The mathematics of linear least squares(LLS) is summarized in a very compact matrix rotation that renders it practically "formulaic".
Least-Squares Curve-Fitting Program
NASA Technical Reports Server (NTRS)
Kantak, Anil V.
1990-01-01
Least Squares Curve Fitting program, AKLSQF, easily and efficiently computes polynomial providing least-squares best fit to uniformly spaced data. Enables user to specify tolerable least-squares error in fit or degree of polynomial. AKLSQF returns polynomial and actual least-squares-fit error incurred in operation. Data supplied to routine either by direct keyboard entry or via file. Written for an IBM PC X/AT or compatible using Microsoft's Quick Basic compiler.
Multivariate Analog of Hays Omega-Squared.
ERIC Educational Resources Information Center
Sachdeva, Darshan
The multivariate analog of Hays omega-squared for estimating the strength of the relationship in the multivariate analysis of variance has been proposed in this paper. The multivariate omega-squared is obtained through the use of Wilks' lambda test criterion. Application of multivariate omega-squared to a numerical example has been provided so as…
ERIC Educational Resources Information Center
Richardson, Janessa; Bachman, Rachel M.
2017-01-01
This article describes a preservice teacher's imaginative exploration of completing the square through a process of reasoning and sense making. She recounts historical perspectives and her own discoveries in the process of completing the square. Through this process of sense making, she engaged with the content standard of completing the square to…
Using Least Squares for Error Propagation
ERIC Educational Resources Information Center
Tellinghuisen, Joel
2015-01-01
The method of least-squares (LS) has a built-in procedure for estimating the standard errors (SEs) of the adjustable parameters in the fit model: They are the square roots of the diagonal elements of the covariance matrix. This means that one can use least-squares to obtain numerical values of propagated errors by defining the target quantities as…
Story Squares. CATESOL Occasional Papers, No. 4.
ERIC Educational Resources Information Center
Sasaki, Ruth A.
A set of specific and practical ideas for teaching language skills are presented, centered around the use of charts or "squares" of pictures that represent ideas that can be expressed in basic English. The focus is a story square, a system of pictures tied together by a plot and presented to the class as a puzzle. Squares for pronunciation can be…
Using Least Squares for Error Propagation
ERIC Educational Resources Information Center
Tellinghuisen, Joel
2015-01-01
The method of least-squares (LS) has a built-in procedure for estimating the standard errors (SEs) of the adjustable parameters in the fit model: They are the square roots of the diagonal elements of the covariance matrix. This means that one can use least-squares to obtain numerical values of propagated errors by defining the target quantities as…
Deming's General Least Square Fitting
Rinard, Phillip
1992-02-18
DEM4-26 is a generalized least square fitting program based on Deming''s method. Functions built into the program for fitting include linear, quadratic, cubic, power, Howard''s, exponential, and Gaussian; others can easily be added. The program has the following capabilities: (1) entry, editing, and saving of data; (2) fitting of any of the built-in functions or of a user-supplied function; (3) plotting the data and fitted function on the display screen, with error limits if requested, and with the option of copying the plot to the printer; (4) interpolation of x or y values from the fitted curve with error estimates based on error limits selected by the user; and (5) plotting the residuals between the y data values and the fitted curve, with the option of copying the plot to the printer. If the plot is to be copied to a printer, GRAPHICS should be called from the operating system disk before the BASIC interpreter is loaded.
Equipment for the calibration of squareness standards
NASA Astrophysics Data System (ADS)
Hemming, Björn; Korhonen, Antti; Palosuo, Ilkka; Lassila, Antti
2012-09-01
In dimensional metrology, the measurement of squareness is a basic task for many purposes. At the Centre for Metrology and Accreditation (MIKES), a squareness measuring machine for traceable calibration of squares has been developed. The machine is able to measure a squareness standard of 1000 mm × 1000 mm maximum size. The system consists of a rotary table and a tactile displacement transducer with horizontal and vertical linear guides. The error sources of the developed equipment are presented together with a brief description of the calibration procedure. Implemented error compensation of the rotary table and one linear guide is described. The uncertainty estimate is presented for squareness angle measurement. The standard measurement uncertainty for steel or granite squares is 0.2″. We also present the results of an internal comparison of squareness measurements made with the developed machine and a high accuracy coordinate measuring machine. The results show good agreement.
Speckle evolution with multiple steps of least-squares phase removal
Chen Mingzhou; Dainty, Chris; Roux, Filippus S.
2011-08-15
We study numerically the evolution of speckle fields due to the annihilation of optical vortices after the least-squares phase has been removed. A process with multiple steps of least-squares phase removal is carried out to minimize both vortex density and scintillation index. Statistical results show that almost all the optical vortices can be removed from a speckle field, which finally decays into a quasiplane wave after such an iterative process.
Harmonic Forcing on the Stratified Square Lid Driven Cavity
NASA Astrophysics Data System (ADS)
Yalim, Jason; Welfert, Bruno; Lopez, Juan; Taylor, Stephanie
2016-11-01
Stratified fluids that are driven at an interface, such as oceans or seas, can be periodically driven by wind. As a canonical flow, the square lid driven cavity with a harmonic forcing and a linear temperature gradient serves as a idealized model. Resonances of the harmonic forcing with the internal modes of the system aide energy transfer from the surface to the bulk, leading to interesting dynamics. Using a numerical spectral collocation method, the internal waves of the system are investigated, including their possible interaction and annihilation.
Weighted conditional least-squares estimation
Booth, J.G.
1987-01-01
A two-stage estimation procedure is proposed that generalizes the concept of conditional least squares. The method is instead based upon the minimization of a weighted sum of squares, where the weights are inverses of estimated conditional variance terms. Some general conditions are given under which the estimators are consistent and jointly asymptotically normal. More specific details are given for ergodic Markov processes with stationary transition probabilities. A comparison is made with the ordinary conditional least-squares estimators for two simple branching processes with immigration. The relationship between weighted conditional least squares and other, more well-known, estimators is also investigated. In particular, it is shown that in many cases estimated generalized least-squares estimators can be obtained using the weighted conditional least-squares approach. Applications to stochastic compartmental models, and linear models with nested error structures are considered.
Generalized adjustment by least squares ( GALS).
Elassal, A.A.
1983-01-01
The least-squares principle is universally accepted as the basis for adjustment procedures in the allied fields of geodesy, photogrammetry and surveying. A prototype software package for Generalized Adjustment by Least Squares (GALS) is described. The package is designed to perform all least-squares-related functions in a typical adjustment program. GALS is capable of supporting development of adjustment programs of any size or degree of complexity. -Author
The Square Light Clock and Special Relativity
ERIC Educational Resources Information Center
Galli, J. Ronald; Amiri, Farhang
2012-01-01
A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45[degree] angle at each corner of a square of length L[subscript 0], shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By…
The Square Light Clock and Special Relativity
ERIC Educational Resources Information Center
Galli, J. Ronald; Amiri, Farhang
2012-01-01
A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45[degree] angle at each corner of a square of length L[subscript 0], shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By…
Sets of Mutually Orthogonal Sudoku Latin Squares
ERIC Educational Resources Information Center
Vis, Timothy; Petersen, Ryan M.
2009-01-01
A Latin square of order "n" is an "n" x "n" array using n symbols, such that each symbol appears exactly once in each row and column. A set of Latin squares is c ordered pairs of symbols appearing in the cells of the array are distinct. The popular puzzle Sudoku involves Latin squares with n = 9, along with the added condition that each of the 9…
Sets of Mutually Orthogonal Sudoku Latin Squares
ERIC Educational Resources Information Center
Vis, Timothy; Petersen, Ryan M.
2009-01-01
A Latin square of order "n" is an "n" x "n" array using n symbols, such that each symbol appears exactly once in each row and column. A set of Latin squares is c ordered pairs of symbols appearing in the cells of the array are distinct. The popular puzzle Sudoku involves Latin squares with n = 9, along with the added condition that each of the 9…
ERIC Educational Resources Information Center
Zelator, Konstantine
2006-01-01
We sometimes teach our students a method of finding all integral triples that satisfy the Pythagorean Theorem x[squared]+y[squared]=z[squared]. These are called Pythagorean triples. In this paper, we show how to solve the equation x[squared]+ky[squared]=z[squared], where again, all variables are integers.
Optical NOR logic gate design on square lattice photonic crystal platform
D’souza, Nirmala Maria Mathew, Vincent
2016-05-06
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.
Optical NOR logic gate design on square lattice photonic crystal platform
NASA Astrophysics Data System (ADS)
D'souza, Nirmala Maria; Mathew, Vincent
2016-05-01
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.
Laboratory observation of elastic waves in solids
NASA Astrophysics Data System (ADS)
Rossing, Thomas D.; Russell, Daniel A.
1990-12-01
Compressional, torsional, and bending waves in bars and plates can be studied with simple apparatus in the laboratory. Although compressional and torsional waves show little or no dispersion, bending waves propagate at a speed proportional to (f)1/2. Reflections at boundaries lead to standing waves that determine the vibrational mode shapes and mode frequencies. Boundary conditions include free edges, simply supported edges, and clamped edges. Typical mode shapes and mode frequencies for rectangular bars, circular plates, and square plates are described.
Neyman's Restricted Chi-Square Tests.
ERIC Educational Resources Information Center
Timm, Neil H.
Pearson's unrestricted chi-square procedure is reviewed, and an historical presentation of Neyman's restricted chi-square test is introduced with a discussion of its theory and applicability to education. An example of the Neyman procedure is discussed in detail to familiarize researchers with this useful technique for analyzing contingency…
Infant perception of the rotating Kanizsa square.
Yoshino, Daisuke; Idesawa, Masanori; Kanazawa, So; Yamaguchi, Masami K
2010-04-01
This study examined the perception of the rotating Kanizsa square by using a fixed-trial familiarization method. If the Kanizsa square is rotated across the pacmen, adult observers perceive not only a rotating illusory square, but also an illusory expansion/contraction motion of this square. The phenomenon is called a "rotational dynamic illusion". In experiments 1 and 2, we investigated whether infants perceived the rotational dynamic illusion, finding that 3-8-month-old infants perceived the rotational dynamic illusion as a simple rotation of the Kanizsa square. In experiment 3, we investigated whether infants perceived the rotational dynamic illusion as a rotation of the Kanizsa square or as a deformation of shape, finding that 3-4-month-old infants did perceive the rotational dynamic illusion as a rotation of the Kanizsa square. Our results show that while 3-8-month-old infants perceive the rotating Kanizsa square, however, it is difficult for the infants to extract expansion/contraction motion from the rotational dynamic illusion. Copyright 2010 Elsevier Inc. All rights reserved.
Enhancing Students' Understanding of Square Roots
ERIC Educational Resources Information Center
Wiesman, Jeff L.
2015-01-01
Students enrolled in a middle school prealgebra or algebra course often struggle to conceptualize and understand the meaning of radical notation when it is introduced. For example, although it is important for students to approximate the decimal value of a number such as [square root of] 30 and estimate the value of a square root in the form of…
Discovering the Magic of Magic Squares
ERIC Educational Resources Information Center
Semanisinova, Ingrid; Trenkler, Marian
2007-01-01
The purpose of this article is to present a collection of problems that allow students to investigate magic squares and Latin squares, formulate their own conjectures about these mathematical objects, look for arguments supporting or disproving their conjectures, and finally establish and prove mathematical assertions. Each problem is completed…
On the Magic Square and Inverse
ERIC Educational Resources Information Center
Elzaidi, S. M.
2005-01-01
In this note, we give a method for finding the inverse of a three by three magic square matrix without using the usual methods for finding the inverse of a matrix. Also we give a method for finding the inverse of a three by three magic square matrix whose entries are also matrices. By using these ideas, we can construct large matrices whose…
Discovering the Magic of Magic Squares
ERIC Educational Resources Information Center
Semanisinova, Ingrid; Trenkler, Marian
2007-01-01
The purpose of this article is to present a collection of problems that allow students to investigate magic squares and Latin squares, formulate their own conjectures about these mathematical objects, look for arguments supporting or disproving their conjectures, and finally establish and prove mathematical assertions. Each problem is completed…
On the Magic Square and Inverse
ERIC Educational Resources Information Center
Elzaidi, S. M.
2005-01-01
In this note, we give a method for finding the inverse of a three by three magic square matrix without using the usual methods for finding the inverse of a matrix. Also we give a method for finding the inverse of a three by three magic square matrix whose entries are also matrices. By using these ideas, we can construct large matrices whose…
Enhancing Students' Understanding of Square Roots
ERIC Educational Resources Information Center
Wiesman, Jeff L.
2015-01-01
Students enrolled in a middle school prealgebra or algebra course often struggle to conceptualize and understand the meaning of radical notation when it is introduced. For example, although it is important for students to approximate the decimal value of a number such as [square root of] 30 and estimate the value of a square root in the form of…
Collinearity in Least-Squares Analysis
ERIC Educational Resources Information Center
de Levie, Robert
2012-01-01
How useful are the standard deviations per se, and how reliable are results derived from several least-squares coefficients and their associated standard deviations? When the output parameters obtained from a least-squares analysis are mutually independent, as is often assumed, they are reliable estimators of imprecision and so are the functions…
On the Denesting of Nested Square Roots
ERIC Educational Resources Information Center
Gkioulekas, Eleftherios
2017-01-01
We present the basic theory of denesting nested square roots, from an elementary point of view, suitable for lower level coursework. Necessary and sufficient conditions are given for direct denesting, where the nested expression is rewritten as a sum of square roots of rational numbers, and for indirect denesting, where the nested expression is…
Collinearity in Least-Squares Analysis
ERIC Educational Resources Information Center
de Levie, Robert
2012-01-01
How useful are the standard deviations per se, and how reliable are results derived from several least-squares coefficients and their associated standard deviations? When the output parameters obtained from a least-squares analysis are mutually independent, as is often assumed, they are reliable estimators of imprecision and so are the functions…
Three Perspectives on Teaching Least Squares
ERIC Educational Resources Information Center
Scariano, Stephen M.; Calzada, Maria
2004-01-01
The method of Least Squares is the most widely used technique for fitting a straight line to data, and it is typically discussed in several undergraduate courses. This article focuses on three developmentally different approaches for solving the Least Squares problem that are suitable for classroom exposition.
On the Topological Classification of Fractal Squares
NASA Astrophysics Data System (ADS)
Rao, Feng; Wang, Xiaohua; Wen, Shengyou
A fractal square is a nonempty compact set in the plane satisfying F = (F + D)/n, where n > 1 is an integer and D ⊂{0, 1, 2,…,n - 1}2 is nonempty. We give the topological classification of fractal squares with n = 3 and Card(D) = 6.
Measurement of Helmholtz wave fields
Alonso
2000-07-01
A simple formalism is found for the measurement of wave fields that satisfy the Helmholtz equation in free space. This formalism turns out to be analogous to the well-known theory of measurements for quantum-mechanical wave functions: A measurement corresponds to the squared magnitude of the inner product (in a suitable Hilbert space) of the wave field and a field that is associated with the detector. The measurement can also be expressed as an overlap in phase space of a special form of the Wigner function that is tailored for Helmholtz wave fields.
BIOMECHANICS. Why the seahorse tail is square.
Porter, Michael M; Adriaens, Dominique; Hatton, Ross L; Meyers, Marc A; McKittrick, Joanna
2015-07-03
Whereas the predominant shapes of most animal tails are cylindrical, seahorse tails are square prisms. Seahorses use their tails as flexible grasping appendages, in spite of a rigid bony armor that fully encases their bodies. We explore the mechanics of two three-dimensional-printed models that mimic either the natural (square prism) or hypothetical (cylindrical) architecture of a seahorse tail to uncover whether or not the square geometry provides any functional advantages. Our results show that the square prism is more resilient when crushed and provides a mechanism for preserving articulatory organization upon extensive bending and twisting, as compared with its cylindrical counterpart. Thus, the square architecture is better than the circular one in the context of two integrated functions: grasping ability and crushing resistance. Copyright © 2015, American Association for the Advancement of Science.
Single-polarization hollow-core square photonic bandgap waveguide
Eguchi, Masashi; Tsuji, Yasuhide
2016-07-15
Materials with a periodic structure have photonic bandgaps (PBGs), in which light can not be guided within certain wavelength ranges; thus light can be confined within a low-index region by the bandgap effect. In this paper, rectangular-shaped hollow waveguides having waveguide-walls (claddings) using the PBG have been discussed. The design principle for HE modes of hollow-core rectangular PBG waveguides with a Bragg cladding consisting of alternating high- and low-index layers, based on a 1D periodic multilayer approximation for the Bragg cladding, is established and then a novel single-polarization hollow-core square PBG waveguide using the bandgap difference between two polarized waves is proposed. Our results demonstrated that a single-polarization guiding can be achieved by using the square Bragg cladding structure with different layer thickness ratios in the mutually orthogonal directions and the transmission loss of the guided mode in a designed hollow-core square PBG waveguide is numerically estimated to be 0.04 dB/cm.
Evidence for stable square ice from quantum Monte Carlo
NASA Astrophysics Data System (ADS)
Chen, Ji; Zen, Andrea; Brandenburg, Jan Gerit; Alfè, Dario; Michaelides, Angelos
2016-12-01
Recent experiments on ice formed by water under nanoconfinement provide evidence for a two-dimensional (2D) "square ice" phase. However, the interpretation of the experiments has been questioned and the stability of square ice has become a matter of debate. Partially this is because the simulation approaches employed so far (force fields and density functional theory) struggle to accurately describe the very small energy differences between the relevant phases. Here we report a study of 2D ice using an accurate wave-function based electronic structure approach, namely diffusion Monte Carlo (DMC). We find that at relatively high pressure, square ice is indeed the lowest enthalpy phase examined, supporting the initial experimental claim. Moreover, at lower pressures, a "pentagonal ice" phase (not yet observed experimentally) has the lowest enthalpy, and at ambient pressure, the "pentagonal ice" phase is degenerate with a "hexagonal ice" phase. Our DMC results also allow us to evaluate the accuracy of various density functional theory exchange-correlation functionals and force field models, and in doing so we extend the understanding of how such methodologies perform to challenging 2D structures presenting dangling hydrogen bonds.
Stratified spin-up in a sliced, square cylinder
Munro, R. J.; Foster, M. R.
2014-02-15
We previously reported experimental and theoretical results on the linear spin-up of a linearly stratified, rotating fluid in a uniform-depth square cylinder [M. R. Foster and R. J. Munro, “The linear spin-up of a stratified, rotating fluid in a square cylinder,” J. Fluid Mech. 712, 7–40 (2012)]. Here we extend that analysis to a “sliced” square cylinder, which has a base-plane inclined at a shallow angle α. Asymptotic results are derived that show the spin-up phase is achieved by a combination of the Ekman-layer eruptions (from the perimeter region of the cylinder's lid and base) and cross-slope-propagating stratified Rossby waves. The final, steady state limit for this spin-up phase is identical to that found previously for the uniform depth cylinder, but is reached somewhat more rapidly on a time scale of order E{sup −1/2}Ω{sup −1}/log (α/E{sup 1/2}) (compared to E{sup −1/2}Ω{sup −1} for the uniform-depth cylinder), where Ω is the rotation rate and E the Ekman number. Experiments were performed for Burger numbers, S, between 0.4 and 16, and showed that for S≳O(1), the Rossby modes are severely damped, and it is only at small S, and during the early stages, that the presence of these wave modes was evident. These observations are supported by the theory, which shows the damping factors increase with S and are numerically large for S≳O(1)
Eta Squared, Partial Eta Squared, and Misreporting of Effect Size in Communication Research.
ERIC Educational Resources Information Center
Levine, Timothy R.; Hullett, Craig R.
2002-01-01
Alerts communication researchers to potential errors stemming from the use of SPSS (Statistical Package for the Social Sciences) to obtain estimates of eta squared in analysis of variance (ANOVA). Strives to clarify issues concerning the development and appropriate use of eta squared and partial eta squared in ANOVA. Discusses the reporting of…
Investigating bias in squared regression structure coefficients.
Nimon, Kim F; Zientek, Linda R; Thompson, Bruce
2015-01-01
The importance of structure coefficients and analogs of regression weights for analysis within the general linear model (GLM) has been well-documented. The purpose of this study was to investigate bias in squared structure coefficients in the context of multiple regression and to determine if a formula that had been shown to correct for bias in squared Pearson correlation coefficients and coefficients of determination could be used to correct for bias in squared regression structure coefficients. Using data from a Monte Carlo simulation, this study found that squared regression structure coefficients corrected with Pratt's formula produced less biased estimates and might be more accurate and stable estimates of population squared regression structure coefficients than estimates with no such corrections. While our findings are in line with prior literature that identified multicollinearity as a predictor of bias in squared regression structure coefficients but not coefficients of determination, the findings from this study are unique in that the level of predictive power, number of predictors, and sample size were also observed to contribute bias in squared regression structure coefficients.
Investigating bias in squared regression structure coefficients
Nimon, Kim F.; Zientek, Linda R.; Thompson, Bruce
2015-01-01
The importance of structure coefficients and analogs of regression weights for analysis within the general linear model (GLM) has been well-documented. The purpose of this study was to investigate bias in squared structure coefficients in the context of multiple regression and to determine if a formula that had been shown to correct for bias in squared Pearson correlation coefficients and coefficients of determination could be used to correct for bias in squared regression structure coefficients. Using data from a Monte Carlo simulation, this study found that squared regression structure coefficients corrected with Pratt's formula produced less biased estimates and might be more accurate and stable estimates of population squared regression structure coefficients than estimates with no such corrections. While our findings are in line with prior literature that identified multicollinearity as a predictor of bias in squared regression structure coefficients but not coefficients of determination, the findings from this study are unique in that the level of predictive power, number of predictors, and sample size were also observed to contribute bias in squared regression structure coefficients. PMID:26217273
Spacecraft inertia estimation via constrained least squares
NASA Technical Reports Server (NTRS)
Keim, Jason A.; Acikmese, Behcet A.; Shields, Joel F.
2006-01-01
This paper presents a new formulation for spacecraft inertia estimation from test data. Specifically, the inertia estimation problem is formulated as a constrained least squares minimization problem with explicit bounds on the inertia matrix incorporated as LMIs [linear matrix inequalities). The resulting minimization problem is a semidefinite optimization that can be solved efficiently with guaranteed convergence to the global optimum by readily available algorithms. This method is applied to data collected from a robotic testbed consisting of a freely rotating body. The results show that the constrained least squares approach produces more accurate estimates of the inertia matrix than standard unconstrained least squares estimation methods.
Spacecraft inertia estimation via constrained least squares
NASA Technical Reports Server (NTRS)
Keim, Jason A.; Acikmese, Behcet A.; Shields, Joel F.
2006-01-01
This paper presents a new formulation for spacecraft inertia estimation from test data. Specifically, the inertia estimation problem is formulated as a constrained least squares minimization problem with explicit bounds on the inertia matrix incorporated as LMIs [linear matrix inequalities). The resulting minimization problem is a semidefinite optimization that can be solved efficiently with guaranteed convergence to the global optimum by readily available algorithms. This method is applied to data collected from a robotic testbed consisting of a freely rotating body. The results show that the constrained least squares approach produces more accurate estimates of the inertia matrix than standard unconstrained least squares estimation methods.
Shoaling internal solitary waves
NASA Astrophysics Data System (ADS)
Sutherland, B. R.; Barrett, K. J.; Ivey, G. N.
2013-09-01
The evolution and breaking of internal solitary waves in a shallow upper layer as they approach a constant bottom slope is examined through laboratory experiments. The waves are launched in a two-layer fluid through the standard lock-release method. In most experiments, the wave amplitude is significantly larger than the depth of the shallow upper layer so that they are not well described by Korteweg-de Vries theory. The dynamics of the shoaling waves are characterized by the Iribarren number, Ir, which measures the ratio of the topographic slope to the square root of the characteristic wave slope. This is used to classify breaking regimes as collapsing, plunging, surging, and nonbreaking for increasing values of Ir. For breaking waves, the maximum interface descent, Hi
NASA Astrophysics Data System (ADS)
Montagnino, Lee J.; Cassabaum, Mary L.; Halversen, Shawn D.; Hebert, Christina L.; Rupp, Chad T.; Young, Matthew T.; Ku, Neilson
2008-04-01
A multi-stage Synthetic Aperture Radar (SAR) Automatic Target Recognition (ATR) system is analyzed across images of various pixel areas achieved by both square and non-square resolution. Non-square resolution offers the ability to achieve finer resolution in the range or cross-range direction with a corresponding degradation of resolution in the cross-range or range direction, respectively. The algorithms examined include a standard 2-parameter Constant False Alarm Rate (CFAR) detection stage, a discrimination stage, and a template-based classification stage. Performance for each stage with respect to both pixel area and square versus non-square resolution is shown via cascaded Receiver Operating Characteristic (ROC) curves. The results indicate that, for fixed pixel areas, non-square resolution imagery can achieve statistically similar performance to square pixel resolution imagery in a multi-stage SAR ATR system.
A spectral mimetic least-squares method
Bochev, Pavel; Gerritsma, Marc
2014-09-01
We present a spectral mimetic least-squares method for a model diffusion–reaction problem, which preserves key conservation properties of the continuum problem. Casting the model problem into a first-order system for two scalar and two vector variables shifts material properties from the differential equations to a pair of constitutive relations. We also use this system to motivate a new least-squares functional involving all four fields and show that its minimizer satisfies the differential equations exactly. Discretization of the four-field least-squares functional by spectral spaces compatible with the differential operators leads to a least-squares method in which the differential equations are alsomore » satisfied exactly. Additionally, the latter are reduced to purely topological relationships for the degrees of freedom that can be satisfied without reference to basis functions. Furthermore, numerical experiments confirm the spectral accuracy of the method and its local conservation.« less
A spectral mimetic least-squares method
Bochev, Pavel; Gerritsma, Marc
2014-09-01
We present a spectral mimetic least-squares method for a model diffusion–reaction problem, which preserves key conservation properties of the continuum problem. Casting the model problem into a first-order system for two scalar and two vector variables shifts material properties from the differential equations to a pair of constitutive relations. We also use this system to motivate a new least-squares functional involving all four fields and show that its minimizer satisfies the differential equations exactly. Discretization of the four-field least-squares functional by spectral spaces compatible with the differential operators leads to a least-squares method in which the differential equations are also satisfied exactly. Additionally, the latter are reduced to purely topological relationships for the degrees of freedom that can be satisfied without reference to basis functions. Furthermore, numerical experiments confirm the spectral accuracy of the method and its local conservation.
Filling Squares: Variations on a Theme.
ERIC Educational Resources Information Center
Senteni, Alain
1986-01-01
Four methods of filling a square using programing with Logo are presented, with comments on children's solutions. Analysis of the mathematical or programing concepts underlying a few simple algorithms is the focus. (MNS)
Elmo bumpy square plasma confinement device
Owen, L.W.
1985-01-01
The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.
Anomalous structural transition of confined hard squares.
Gurin, Péter; Varga, Szabolcs; Odriozola, Gerardo
2016-11-01
Structural transitions are examined in quasi-one-dimensional systems of freely rotating hard squares, which are confined between two parallel walls. We find two competing phases: one is a fluid where the squares have two sides parallel to the walls, while the second one is a solidlike structure with a zigzag arrangement of the squares. Using transfer matrix method we show that the configuration space consists of subspaces of fluidlike and solidlike phases, which are connected with low probability microstates of mixed structures. The existence of these connecting states makes the thermodynamic quantities continuous and precludes the possibility of a true phase transition. However, thermodynamic functions indicate strong tendency for the phase transition and our replica exchange Monte Carlo simulation study detects several important markers of the first order phase transition. The distinction of a phase transition from a structural change is practically impossible with simulations and experiments in such systems like the confined hard squares.
Applications of square-related theorems
NASA Astrophysics Data System (ADS)
Srinivasan, V. K.
2014-04-01
The square centre of a given square is the point of intersection of its two diagonals. When two squares of different side lengths share the same square centre, there are in general four diagonals that go through the same square centre. The Two Squares Theorem developed in this paper summarizes some nice theoretical conclusions that can be obtained when two squares of different side lengths share the same square centre. These results provide the theoretical basis for two of the constructions given in the book of H.S. Hall and F.H. Stevens , 'A Shorter School Geometry, Part 1, Metric Edition'. In page 134 of this book, the authors present, in exercise 4, a practical construction which leads to a verification of the Pythagorean theorem. Subsequently in Theorems 29 and 30, the authors present the standard proofs of the Pythagorean theorem and its converse. In page 140, the authors present, in exercise 15, what amounts to a geometric construction, whose verification involves a simple algebraic identity. Both the constructions are of great importance and can be replicated by using the standard equipment provided in a 'geometry toolbox' carried by students in high schools. The author hopes that the results proved in this paper, in conjunction with the two constructions from the above-mentioned book, would provide high school students an appreciation of the celebrated theorem of Pythagoras. The diagrams that accompany this document are based on the free software GeoGebra. The author formally acknowledges his indebtedness to the creators of this free software at the end of this document.
Deflection And Stress In Preloaded Square Membrane
NASA Technical Reports Server (NTRS)
Hermida, Alfonso
1991-01-01
Theoretical analysis yields equations for transverse deflection of, and stresses in, square membrane subject to both uniform transverse load and tension preloads applied uniformly along the edges. Follows energy/virtual-displacement approach. Basic equation expresses strain energy in membrane as double integral, over x and y coordinates of square, of function of longitudinal strains, shear strain, thickness of membrane, and Young's modulus and Poissons's ratio of membrane material.
The effect of wave breaking on wave spectrum in water of finite depth
NASA Technical Reports Server (NTRS)
Tung, C. C.; Huang, N. E.
1987-01-01
An approximate method is devised to compute the energy-containing portion of the spectrum of waves in water of finite depth, taking into account the effect of wave breaking. It is assumed that there exists a linear and Gaussian ideal wave train whose spectrum is first calculated using the wave energy flux balance equation without considering wave breaking. The Miche wave-breaking criterion for waves in water of finite depth is then applied to limit the wave elevation and establish an expression for the breaking wave elevation in terms of the elevation and elevation's second time derivative of the ideal waves. Simple expressions for the mean value, the mean square value, and the spectrum of the breaking waves are then obtained, and numerical results are presented graphically.
Vertex micromagnetic energy in artificial square ice
NASA Astrophysics Data System (ADS)
Perrin, Yann; Canals, Benjamin; Rougemaille, Nicolas
2016-10-01
Artificial arrays of interacting magnetic elements provide an uncharted arena in which the physics of magnetic frustration and magnetic monopoles can be observed in real space and in real time. These systems offer the formidable opportunity to investigate a wide range of collective magnetic phenomena with a lab-on-chip approach and to explore various theoretical predictions from spin models. Here, we study artificial square ice systems numerically and use micromagnetic simulations to understand how the geometrical parameters of the individual magnetic elements affect the energy levels of an isolated square vertex. More specifically, we address the question of whether the celebrated square ice model could be made relevant for artificial square ice systems. Our work reveals that tuning the geometry alone should not allow the experimental realization of the square ice model when using nanomagnets coupled through the magnetostatic interaction. However, low-aspect ratios combined with small gaps separating neighboring magnetic elements of moderated thickness might permit approaching the ideal case where the degeneracy of the ice rule states is recovered.
Ultrasonic Lamb wave tomography
NASA Astrophysics Data System (ADS)
Leonard, Kevin R.; Malyarenko, Eugene V.; Hinders, Mark K.
2002-12-01
Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our recent work using ultrasonic Lamb wave tomography to address this pressing NDE technology need. Lamb waves are ultrasonic guided waves, which allow large sections of aircraft structures to be rapidly inspected for structural flaws such as disbonds, corrosion and delaminations. Because the velocity of Lamb waves depends on thickness, for example, the travel times of the fundamental Lamb modes can be converted into a thickness map of the inspection region. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. Our work focuses on tomographic reconstruction to produce quantitative maps that can be easily interpreted by technicians or fed directly into structural integrity and lifetime prediction codes. Laboratory measurements discussed here demonstrate that Lamb wave tomography using a square perimeter array of transducers with algebraic reconstruction tomography is appropriate for detecting flaws in aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this paper.
Dual negative refraction in a two dimension square photonic crystal
NASA Astrophysics Data System (ADS)
Derbali, J.; AbdelMalek, F.
2015-09-01
Dual refraction effect based on the overlapping bands in a two dimensional (2D) photonic crystal (PhC) is demonstrated. The PhC consists of alumina rods with a dielectric constant ε=8.9, arranged in a square lattice in air. To disperse light which has special excitation frequency and a specific incident angle, by this PhC we optimize his structural parameters such as the radius of dielectric rods). It is shown that two focusing phenomena are formed in the PhC image plan; the degeneracy of modes can be applied to realize optical interference and wave front division. The simulation results are obtained by employing the PWM for analyzing bands structure and the finite-difference time-domain (FDTD) to predict the evolution of the electric fields.
Highly Anisotropic Dirac Fermions in Square Graphynes.
Zhang, L Z; Wang, Z F; Wang, Zhiming M; Du, S X; Gao, H-J; Liu, Feng
2015-08-06
We predict a family of 2D carbon (C) allotropes, square graphynes (S-graphynes) that exhibit highly anisotropic Dirac fermions, using first-principle calculations within density functional theory. They have a square unit-cell containing two sizes of square C rings. The equal-energy contour of their 3D band structure shows a crescent shape, and the Dirac crescent has varying Fermi velocities from 0.6 × 10(5) to 7.2 × 10(5) m/s along different k directions. Near the Fermi level, the Dirac crescent can be nicely expressed by an extended 2D Dirac model Hamiltonian. Furthermore, tight-binding band fitting reveals that the Dirac crescent originates from the next-nearest-neighbor interactions between C atoms. S-graphynes may be used to build new 2D electronic devices taking advantages of their highly directional charge transport.
Rhombic preordering on a square substrate.
Neuhaus, T; Marechal, M; Schmiedeberg, M; Löwen, H
2013-03-15
A competition of incommensurate symmetries occurs whenever a system is forced to conform to an ordering that is different from the intrinsically preferred structure of the system itself. As a model system of such a competition, we study the rivalry between the triangular ordering of hard disks and the square symmetry induced by a periodic square substrate. By using density functional theory as well as Monte Carlo computer simulations, we determine the full phase behavior for the case of one particle per minimum. We observe a rhombic preordering structure preceding the hexagonal solid as a direct consequence of the competing symmetries. Furthermore, the square-rhombic transition is reentrant with increasing substrate interaction. Our predictions can be verified in experiments of colloids in laser fields.
William Wilde and 1 Merrion Square.
McEntegart, R
2016-05-01
William Wilde spent the final third of his life, from 1855 to 1876, in 1 Merrion Square. During the first half of his occupancy of the house his career blossomed to its fullest; the second decade, on the other hand, was marked by scandal, personal tragedy, and an unhappy professional and social decline. This paper considers the background to the development of Merrion Square, the architectural history of 1 Merrion Square from its building in 1762 to the arrival of the Wildes in 1855, the attractions and possibilities which the house offered for William Wilde, the major architectural expansion of the building which he commissioned in 1859, and aspects of his and his family's life in the house.
The chi-square test of independence.
McHugh, Mary L
2013-01-01
The Chi-square statistic is a non-parametric (distribution free) tool designed to analyze group differences when the dependent variable is measured at a nominal level. Like all non-parametric statistics, the Chi-square is robust with respect to the distribution of the data. Specifically, it does not require equality of variances among the study groups or homoscedasticity in the data. It permits evaluation of both dichotomous independent variables, and of multiple group studies. Unlike many other non-parametric and some parametric statistics, the calculations needed to compute the Chi-square provide considerable information about how each of the groups performed in the study. This richness of detail allows the researcher to understand the results and thus to derive more detailed information from this statistic than from many others. The Chi-square is a significance statistic, and should be followed with a strength statistic. The Cramer's V is the most common strength test used to test the data when a significant Chi-square result has been obtained. Advantages of the Chi-square include its robustness with respect to distribution of the data, its ease of computation, the detailed information that can be derived from the test, its use in studies for which parametric assumptions cannot be met, and its flexibility in handling data from both two group and multiple group studies. Limitations include its sample size requirements, difficulty of interpretation when there are large numbers of categories (20 or more) in the independent or dependent variables, and tendency of the Cramer's V to produce relative low correlation measures, even for highly significant results.
On the Classification of Fractal Squares
NASA Astrophysics Data System (ADS)
Luo, Jun Jason; Liu, Jing-Cheng
2016-01-01
In the previous paper [K. S. Lau, J. J. Luo and H. Rao, Topological structure of fractal squares, Math. Proc. Camb. Phil. Soc. 155 (2013) 73-86], Lau, Luo and Rao completely classified the topological structure of so called fractal square F defined by F = (F + 𝒟)/n, where 𝒟 ⊊ {0, 1,…,n - 1}2,n ≥ 2. In this paper, we further provide simple criteria for the F to be totally disconnected, then we discuss the Lipschitz classification of F in the case n = 3, which is an attempt to consider non-totally disconnected sets.
Linear Least Squares for Correlated Data
NASA Technical Reports Server (NTRS)
Dean, Edwin B.
1988-01-01
Throughout the literature authors have consistently discussed the suspicion that regression results were less than satisfactory when the independent variables were correlated. Camm, Gulledge, and Womer, and Womer and Marcotte provide excellent applied examples of these concerns. Many authors have obtained partial solutions for this problem as discussed by Womer and Marcotte and Wonnacott and Wonnacott, which result in generalized least squares algorithms to solve restrictive cases. This paper presents a simple but relatively general multivariate method for obtaining linear least squares coefficients which are free of the statistical distortion created by correlated independent variables.
Square sugars: challenges and synthetic strategies.
Hazelard, Damien; Compain, Philippe
2017-03-31
Square sugars (4-membered ring carbohydrate mimetics) are at the intersection of several important topics concerning the recent emergence, in medicinal chemistry, of glycomimetic drugs and small ring systems. Monosaccharide mimetics containing oxetane, azetidine, thiethane or cyclobutane rings present a number of synthetic challenges that are a powerful driving force for innovation in organic synthesis. In addition to the inherent issues associated with 4-membered rings, the high density of functional groups and asymmetric centres found in glycomimetics further complicates the matter and requires efficient stereoselective methodologies. The purpose of this review is to present an overview of the elegant strategies that have been developed to synthesize the different types of square sugars.
Disclinations in square and hexagonal patterns.
Golovin, A A; Nepomnyashchy, A A
2003-05-01
We report the observation of defects with fractional topological charges (disclinations) in square and hexagonal patterns as numerical solutions of several generic equations describing many pattern-forming systems: Swift-Hohenberg equation, damped Kuramoto-Sivashinsky equation, as well as nonlinear evolution equations describing large-scale Rayleigh-Benard and Marangoni convection in systems with thermally nearly insulated boundaries. It is found that disclinations in square and hexagonal patterns can be stable when nucleated from special initial conditions. The structure of the disclinations is analyzed by means of generalized Cross-Newell equations.
Modal decomposition method for acoustic impedance testing in square ducts.
Schultz, Todd; Cattafesta, Louis N; Sheplak, Mark
2006-12-01
Accurate duct acoustic propagation models are required to predict and reduce aircraft engine noise. These models ultimately rely on measurements of the acoustic impedance to characterize candidate engine nacelle liners. This research effort increases the frequency range of normal-incidence acoustic impedance testing in square ducts by extending the standard two-microphone method (TMM), which is limited to plane wave propagation, to include higher-order modes. The modal decomposition method (MDM) presented includes four normal modes in the model of the sound field, thus increasing the bandwidth from 6.7 to 13.5 kHz for a 25.4 mm square waveguide. The MDM characterizes the test specimen for normal- and oblique-incident acoustic impedance and mode scattering coefficients. The MDM is first formulated and then applied to the measurement of the reflection coefficient matrix for a ceramic tubular specimen. The experimental results are consistent with results from the TMM for the same specimen to within the 95% confidence intervals for the TMM. The MDM results show a series of resonances for the ceramic tubular material exhibiting a monotonic decrease in the resonant peaks of the acoustic resistance with increasing frequency, resembling a rigidly-terminated viscous tube, and also evidence of mode scattering is visible at the higher frequencies.
Science with ASKAP. The Australian square-kilometre-array pathfinder
NASA Astrophysics Data System (ADS)
Johnston, S.; Taylor, R.; Bailes, M.; Bartel, N.; Baugh, C.; Bietenholz, M.; Blake, C.; Braun, R.; Brown, J.; Chatterjee, S.; Darling, J.; Deller, A.; Dodson, R.; Edwards, P.; Ekers, R.; Ellingsen, S.; Feain, I.; Gaensler, B.; Haverkorn, M.; Hobbs, G.; Hopkins, A.; Jackson, C.; James, C.; Joncas, G.; Kaspi, V.; Kilborn, V.; Koribalski, B.; Kothes, R.; Landecker, T.; Lenc, E.; Lovell, J.; Macquart, J.-P.; Manchester, R.; Matthews, D.; McClure-Griffiths, N.; Norris, R.; Pen, U.-L.; Phillips, C.; Power, C.; Protheroe, R.; Sadler, E.; Schmidt, B.; Stairs, I.; Staveley-Smith, L.; Stil, J.; Tingay, S.; Tzioumis, A.; Walker, M.; Wall, J.; Wolleben, M.
2008-12-01
The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries. The SKA will be 50 times more sensitive than any existing radio facility. A majority of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from 300 MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is aimed squarely in this frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phase-array feed systems on parabolic reflectors. This large field-of-view makes ASKAP an unprecedented synoptic telescope poised to achieve substantial advances in SKA key science. The central core of ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of the sites selected by the international community as a potential location for the SKA. Following an introductory description of ASKAP, this document contains 7 chapters describing specific science programmes for ASKAP. In summary, the goals of these programmes are as follows: The detection of a million galaxies in atomic hydrogen emission across 75% of the sky out to a redshift of 0.2 to understand galaxy formation and gas evolution in the nearby Universe.
Eta Squared and Partial Eta Squared as Measures of Effect Size in Educational Research
ERIC Educational Resources Information Center
Richardson, John T. E.
2011-01-01
Eta squared measures the proportion of the total variance in a dependent variable that is associated with the membership of different groups defined by an independent variable. Partial eta squared is a similar measure in which the effects of other independent variables and interactions are partialled out. The development of these measures is…
Products of square-zero operators
NASA Astrophysics Data System (ADS)
Novak, Nika
2008-03-01
We characterize matrices that can be written as a product of two or three square-zero matrices. We also consider the same questions for (bounded) operators on an infinite-dimensional, separable, complex Hilbert space and in the Calkin algebra.
Iterative methods for weighted least-squares
Bobrovnikova, E.Y.; Vavasis, S.A.
1996-12-31
A weighted least-squares problem with a very ill-conditioned weight matrix arises in many applications. Because of round-off errors, the standard conjugate gradient method for solving this system does not give the correct answer even after n iterations. In this paper we propose an iterative algorithm based on a new type of reorthogonalization that converges to the solution.
Very Large Least Squares Problems and Supercomputers,
1984-12-31
structures) Purdue University Ahmed Sameh (supercomputers) University of Illinois 6. REFERENCES Abad-Zapatero, C., Abdel-Meguid, S.S., Johnson, J.E...pp. 784-811. Sameh , A., Solving the linear least squares problem on a linear array of proces- sors, In: Purdue Workshop on Algorithmically
Least-squares fitting Gompertz curve
NASA Astrophysics Data System (ADS)
Jukic, Dragan; Kralik, Gordana; Scitovski, Rudolf
2004-08-01
In this paper we consider the least-squares (LS) fitting of the Gompertz curve to the given nonconstant data (pi,ti,yi), i=1,...,m, m≥3. We give necessary and sufficient conditions which guarantee the existence of the LS estimate, suggest a choice of a good initial approximation and give some numerical examples.
Least squares estimation of avian molt rates
Johnson, D.H.
1989-01-01
A straightforward least squares method of estimating the rate at which birds molt feathers is presented, suitable for birds captured more than once during the period of molt. The date of molt onset can also be estimated. The method is applied to male and female mourning doves.
BLS: Box-fitting Least Squares
NASA Astrophysics Data System (ADS)
Kovács, G.; Zucker, S.; Mazeh, T.
2016-07-01
BLS (Box-fitting Least Squares) is a box-fitting algorithm that analyzes stellar photometric time series to search for periodic transits of extrasolar planets. It searches for signals characterized by a periodic alternation between two discrete levels, with much less time spent at the lower level.
Inverse-Square Orbits: A Geometric Approach.
ERIC Educational Resources Information Center
Rainwater, James C.; Weinstock, Robert
1979-01-01
Presents a derivation of Kepler's first law of planetary motion from Newtonian principles. Analogus derivations of the hyperbolic and parabolic orbits of nonreturning comets and the hyperbolic orbit for a particle in a repulsive inverse-square field are also presented. (HM)
Exemplifying Definitions: A Case of a Square
ERIC Educational Resources Information Center
Zazkis, Rina; Leikin, Roza
2008-01-01
In this study we utilize the notion of learner-generated examples, suggesting that examples generated by students mirror their understanding of particular mathematical concepts. In particular, we explore examples generated by a group of prospective secondary school teachers for a definition of a square. Our framework for analysis includes the…
Least squares polynomial fits and their accuracy
NASA Technical Reports Server (NTRS)
Lear, W. M.
1977-01-01
Equations are presented which attempt to fit least squares polynomials to tables of date. It is concluded that much data are needed to reduce the measurement error standard deviation by a significant amount, however at certain points great accuracy is attained.
Non-Circular Wheels: Reuleaux and Squares
ERIC Educational Resources Information Center
Mills, Allan
2011-01-01
Circular wheels are so familiar on vehicles of all types that it is seldom realized that alternatives do exist. This short non-mathematical article describes Reuleaux and square wheels that, rolling along appropriate tracks, can maintain a moving platform at a constant height. Easily made working models lend themselves to demonstrations at science…
Non-Circular Wheels: Reuleaux and Squares
ERIC Educational Resources Information Center
Mills, Allan
2011-01-01
Circular wheels are so familiar on vehicles of all types that it is seldom realized that alternatives do exist. This short non-mathematical article describes Reuleaux and square wheels that, rolling along appropriate tracks, can maintain a moving platform at a constant height. Easily made working models lend themselves to demonstrations at science…
Inverse-Square Orbits: A Geometric Approach.
ERIC Educational Resources Information Center
Rainwater, James C.; Weinstock, Robert
1979-01-01
Presents a derivation of Kepler's first law of planetary motion from Newtonian principles. Analogus derivations of the hyperbolic and parabolic orbits of nonreturning comets and the hyperbolic orbit for a particle in a repulsive inverse-square field are also presented. (HM)
Squaring Matrices: Connecting Mathematics and Science
ERIC Educational Resources Information Center
Horton, Robert M.; Wiegert, Elaine M.; Marshall, Jeff C.
2008-01-01
This article shows how a matrix can be used to represent a food chain and how the square of this matrix represents the indirect food sources for each animal in the chain. By exploring, through mathematics, the implications when the bottom of the food chain is destroyed, students will see an important connection between mathematics and science.…
Meshless Galerkin least-squares method
NASA Astrophysics Data System (ADS)
Pan, X. F.; Zhang, X.; Lu, M. W.
2005-02-01
Collocation method and Galerkin method have been dominant in the existing meshless methods. Galerkin-based meshless methods are computational intensive, whereas collocation-based meshless methods suffer from instability. A new efficient meshless method, meshless Galerkin lest-squares method (MGLS), is proposed in this paper to combine the advantages of Galerkin method and collocation method. The problem domain is divided into two subdomains, the interior domain and boundary domain. Galerkin method is applied in the boundary domain, whereas the least-squares method is applied in the interior domain.The proposed scheme elliminates the posibilities of spurious solutions as that in the least-square method if an incorrect boundary conditions are used. To investigate the accuracy and efficiency of the proposed method, a cantilevered beam and an infinite plate with a central circular hole are analyzed in detail and numerical results are compared with those obtained by Galerkin-based meshless method (GBMM), collocation-based meshless method (CBMM) and meshless weighted least squares method (MWLS). Numerical studies show that the accuracy of the proposed MGLS is much higher than that of CBMM and is close to, even better than, that of GBMM, while the computational cost is much less than that of GBMM.
On Least Squares Fitting Nonlinear Submodels.
ERIC Educational Resources Information Center
Bechtel, Gordon G.
Three simplifying conditions are given for obtaining least squares (LS) estimates for a nonlinear submodel of a linear model. If these are satisfied, and if the subset of nonlinear parameters may be LS fit to the corresponding LS estimates of the linear model, then one attains the desired LS estimates for the entire submodel. Two illustrative…
Squaring Matrices: Connecting Mathematics and Science
ERIC Educational Resources Information Center
Horton, Robert M.; Wiegert, Elaine M.; Marshall, Jeff C.
2008-01-01
This article shows how a matrix can be used to represent a food chain and how the square of this matrix represents the indirect food sources for each animal in the chain. By exploring, through mathematics, the implications when the bottom of the food chain is destroyed, students will see an important connection between mathematics and science.…
Latin square three dimensional gage master
Jones, Lynn L.
1982-01-01
A gage master for coordinate measuring machines has an nxn array of objects distributed in the Z coordinate utilizing the concept of a Latin square experimental design. Using analysis of variance techniques, the invention may be used to identify sources of error in machine geometry and quantify machine accuracy.
A Limitation with Least Squares Predictions
ERIC Educational Resources Information Center
Bittner, Teresa L.
2013-01-01
Although researchers have documented that some data make larger contributions than others to predictions made with least squares models, it is relatively unknown that some data actually make no contribution to the predictions produced by these models. This article explores such noncontributory data. (Contains 1 table and 2 figures.)
Kendall Square multiprocessor: Early experiences and performance
Dunigan, T.H.
1992-04-01
Initial performance results and early experiences are reported for the Kendall Square Research multiprocessor. The basic architecture of the shared-memory multiprocessor is described, and computational and I/O performance is measured for both serial and parallel programs. Experiences in porting various applications are described.
Square waveforms in edge-emitting diode laser subject to polarization-rotated optical feedback
NASA Astrophysics Data System (ADS)
Gavrielides, A.; Erneux, T.; Sukow, D. W.; Burner, G.; McLachlan, T.; Miller, J.; Amonette, J.
2006-02-01
The response of a diode laser resulting from an incoherent delayed optical feedback is considered from numerical and experimental perspectives. We concentrate on a class of solutions that appear as regular square waveforms. A two-field model is used and the bifurcation diagram of these square-wave regimes is studied. Conditions under which they typically appear are determined. The roles of various parameters are examined, particularly with regard to the gains and losses of the two polarization modes. Numerical results are in close agreement with experiments.
Mathematical Construction of Magic Squares Utilizing Base-N Arithmetic
ERIC Educational Resources Information Center
O'Brien, Thomas D.
2006-01-01
Magic squares have been of interest as a source of recreation for over 4,500 years. A magic square consists of a square array of n[squared] positive and distinct integers arranged so that the sum of any column, row, or main diagonal is the same. In particular, an array of consecutive integers from 1 to n[squared] forming an nxn magic square is…
Mathematical Construction of Magic Squares Utilizing Base-N Arithmetic
ERIC Educational Resources Information Center
O'Brien, Thomas D.
2006-01-01
Magic squares have been of interest as a source of recreation for over 4,500 years. A magic square consists of a square array of n[squared] positive and distinct integers arranged so that the sum of any column, row, or main diagonal is the same. In particular, an array of consecutive integers from 1 to n[squared] forming an nxn magic square is…
Least Squares Estimation Without Priors or Supervision
Raphan, Martin; Simoncelli, Eero P.
2011-01-01
Selection of an optimal estimator typically relies on either supervised training samples (pairs of measurements and their associated true values) or a prior probability model for the true values. Here, we consider the problem of obtaining a least squares estimator given a measurement process with known statistics (i.e., a likelihood function) and a set of unsupervised measurements, each arising from a corresponding true value drawn randomly from an unknown distribution. We develop a general expression for a nonparametric empirical Bayes least squares (NEBLS) estimator, which expresses the optimal least squares estimator in terms of the measurement density, with no explicit reference to the unknown (prior) density. We study the conditions under which such estimators exist and derive specific forms for a variety of different measurement processes. We further show that each of these NEBLS estimators may be used to express the mean squared estimation error as an expectation over the measurement density alone, thus generalizing Stein’s unbiased risk estimator (SURE), which provides such an expression for the additive gaussian noise case. This error expression may then be optimized over noisy measurement samples, in the absence of supervised training data, yielding a generalized SURE-optimized parametric least squares (SURE2PLS) estimator. In the special case of a linear parameterization (i.e., a sum of nonlinear kernel functions), the objective function is quadratic, and we derive an incremental form for learning this estimator from data. We also show that combining the NEBLS form with its corresponding generalized SURE expression produces a generalization of the score-matching procedure for parametric density estimation. Finally, we have implemented several examples of such estimators, and we show that their performance is comparable to their optimal Bayesian or supervised regression counterparts for moderate to large amounts of data. PMID:21105827
Deformation of square objects and boudins
NASA Astrophysics Data System (ADS)
Treagus, Susan H.; Lan, Labao
2004-08-01
Some geological objects, such as clasts and boudins, may have had original shapes close to square, that have been modified by ductile deformation. We demonstrate through finite element models presented here and in earlier papers that square objects in a matrix with contrasting viscosity can deform to a variety of curved shapes. The maximum shape change is where the square edges are parallel to the principal bulk strains. Competent objects with viscosity ratio to matrix ( m) of 2-20 become barrel shaped, showing concave 'fish mouth' shortened edges. Incompetent objects ( m<1) show a narrower variety of shapes with m, all becoming smoothed to bone, dumb-bell or lobate shapes, and losing the original corners. We compare the results for square objects with linear and non-linear rheology (power law, stress exponent n=1, 3 or 10), and with previous modelling with different object-matrix proportions. Competent objects with higher n values deform slightly less, and more irregularly, than linearly viscous ( n=1) objects, but the distinctions between n=3 and 10 are only slight. The differences are even slighter (in the opposite sense) for incompetent objects. The proportion of object to matrix is as important, if not more, in controlling the deformation and shape of these objects. The results are compared via graphs of object strain and concavity versus bulk strain. The concavity graph for competent square objects with linear viscosity up to very high strain can be compared with examples of ductile boudins with barrel or fish mouth shapes. Subject to a number of assumptions, this provides a method of estimating boudin-matrix viscosity ratios and post-boudinage ductile strain, of potential use in highly deformed rocks lacking other strain markers. The approach may also be suitable for deformed porphyroblasts, but is more difficult to apply to single clasts in breccias and conglomerates.
Fractional excitations in the square-lattice quantum antiferromagnet
Dalla Piazza, Bastien; Mourigal, M.; Christensen, N. B.; Nilsen, G. J.; Tregenna-Piggott, P.; Perring, T. G.; Enderle, M.; McMorrow, D. F.; Ivanov, D. A.; Ronnow, H. M.
2014-12-15
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). Here, we use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experiments reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Lastly, our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration.
Fractional excitations in the square lattice quantum antiferromagnet
Christensen, N. B.; Nilsen, G. J.; Tregenna-Piggott, P.; Perring, T. G.; Enderle, M.; McMorrow, D. F.; Ivanov, D. A.; Rønnow, H. M.
2014-01-01
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). We use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experiments reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration. PMID:25729400
Fractional excitations in the square-lattice quantum antiferromagnet
Dalla Piazza, Bastien; Mourigal, M.; Christensen, N. B.; ...
2014-12-15
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). Here, we use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experimentsmore » reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Lastly, our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration.« less
Fractional excitations in the square lattice quantum antiferromagnet.
Piazza, B Dalla; Mourigal, M; Christensen, N B; Nilsen, G J; Tregenna-Piggott, P; Perring, T G; Enderle, M; McMorrow, D F; Ivanov, D A; Rønnow, H M
2015-01-01
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). We use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experiments reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration.
NASA Astrophysics Data System (ADS)
Nazarenko, Sergey
2015-07-01
Wave turbulence is the statistical mechanics of random waves with a broadband spectrum interacting via non-linearity. To understand its difference from non-random well-tuned coherent waves, one could compare the sound of thunder to a piece of classical music. Wave turbulence is surprisingly common and important in a great variety of physical settings, starting with the most familiar ocean waves to waves at quantum scales or to much longer waves in astrophysics. We will provide a basic overview of the wave turbulence ideas, approaches and main results emphasising the physics of the phenomena and using qualitative descriptions avoiding, whenever possible, involved mathematical derivations. In particular, dimensional analysis will be used for obtaining the key scaling solutions in wave turbulence - Kolmogorov-Zakharov (KZ) spectra.
Wave-equation dispersion inversion
NASA Astrophysics Data System (ADS)
Li, Jing; Feng, Zongcai; Schuster, Gerard
2017-03-01
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
Sutton, G W; Weiner, M M; Mani, S A
1976-09-01
Theoretical Fraunhofer diffraction patterns are presented for uniformly illuminated square apertures with noncentered square obscurations. The energy within a given subtended solid angle in the far field is calculated. It is shown that the cornered-off-axis obscuration provides much more far-field energy in a given spot size than the centered obscuration for the same clear aperture area and total energy, for example, 82% more far-field energy in the first Airy square for 50% obscuration, thus providing superior performance for practical systems.
Operations concept for the Square Kilometre Array
NASA Astrophysics Data System (ADS)
Davis, Gary R.; Bock, Douglas C.; Chrysostomou, Antonio; Taljaard, Cornelius
2016-07-01
The Square Kilometre Array (SKA) is an ambitious project to build the world's largest radio telescope, eventually reaching one square kilometre in collecting area. The first phase of the project, SKA1, will consist of two telescopes: SKA1-LOW, comprising 131,000 dipole antennas at the Murchison Radio Observatory in Western Australia covering the range 50-350 MHz, and SKA1-MID, comprising 200 x 15-m dishes in the Karoo desert in South Africa covering the range 0.35-13.8 GHz. SKA1 is scheduled to commence operations in 2023 and, in order to appropriately influence the design of the system, operational planning has commenced. This paper presents an overview of the operational concept for SKA1.
Hybrid least squares multivariate spectral analysis methods
Haaland, David M.
2002-01-01
A set of hybrid least squares multivariate spectral analysis methods in which spectral shapes of components or effects not present in the original calibration step are added in a following estimation or calibration step to improve the accuracy of the estimation of the amount of the original components in the sampled mixture. The "hybrid" method herein means a combination of an initial classical least squares analysis calibration step with subsequent analysis by an inverse multivariate analysis method. A "spectral shape" herein means normally the spectral shape of a non-calibrated chemical component in the sample mixture but can also mean the spectral shapes of other sources of spectral variation, including temperature drift, shifts between spectrometers, spectrometer drift, etc. The "shape" can be continuous, discontinuous, or even discrete points illustrative of the particular effect.
Optical inverse-square displacement sensor
Howe, Robert D.; Kychakoff, George
1989-01-01
This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R+.DELTA.R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as ##EQU1##
Optical inverse-square displacement sensor
Howe, R.D.; Kychakoff, G.
1989-09-12
This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R + [Delta]R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as given in an equation. 10 figs.
Dielectric square resonator investigated with microwave experiments.
Bittner, S; Bogomolny, E; Dietz, B; Miski-Oglu, M; Richter, A
2014-11-01
We present a detailed experimental study of the symmetry properties and the momentum space representation of the field distributions of a dielectric square resonator as well as the comparison with a semiclassical model. The experiments have been performed with a flat ceramic microwave resonator. Both the resonance spectra and the field distributions were measured. The momentum space representations of the latter evidenced that the resonant states are each related to a specific classical torus, leading to the regular structure of the spectrum. Furthermore, they allow for a precise determination of the refractive index. Measurements with different arrangements of the emitting and the receiving antennas were performed and their influence on the symmetry properties of the field distributions was investigated in detail, showing that resonances with specific symmetries can be selected purposefully. In addition, the length spectrum deduced from the measured resonance spectra and the trace formula for the dielectric square resonator are discussed in the framework of the semiclassical model.
Least Squares Moving-Window Spectral Analysis.
Lee, Young Jong
2017-01-01
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.
Least squares restoration of multichannel images
NASA Technical Reports Server (NTRS)
Galatsanos, Nikolas P.; Katsaggelos, Aggelos K.; Chin, Roland T.; Hillery, Allen D.
1991-01-01
Multichannel restoration using both within- and between-channel deterministic information is considered. A multichannel image is a set of image planes that exhibit cross-plane similarity. Existing optimal restoration filters for single-plane images yield suboptimal results when applied to multichannel images, since between-channel information is not utilized. Multichannel least squares restoration filters are developed using the set theoretic and the constrained optimization approaches. A geometric interpretation of the estimates of both filters is given. Color images (three-channel imagery with red, green, and blue components) are considered. Constraints that capture the within- and between-channel properties of color images are developed. Issues associated with the computation of the two estimates are addressed. A spatially adaptive, multichannel least squares filter that utilizes local within- and between-channel image properties is proposed. Experiments using color images are described.
Solution of Nonlinear Least-Squares Problems.
1987-07-01
Computation Building 460, Room 313 Stanford University Stanford, California 94305-2140 0 87 i4 3 4 SOLUTION OF NONLINEAR LEAST-SQUARES PROBLEMS A...Performance on a Well-Conditioned Zero -Residual Problem ............. 84 4.7 Num erical Results...termination conditions A superscspt o following a problem number indicates a zero -residual problem A superscipt following a problem number denotes a
Natural convective heat transfer from square cylinder
Novomestský, Marcel Smatanová, Helena Kapjor, Andrej
2016-06-30
This article is concerned with natural convective heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable.
Subset selection circumvents the square root law
NASA Astrophysics Data System (ADS)
Craver, Scott; Yu, Jun
2010-01-01
The square root law holds that acceptable embedding rate is sublinear in the cover size, specifically O(square root of n), in order to prevent detection as the warden's data and thus detector power increases. One way to transcend this law, at least in the i.i.d.case, is to restrict the cover to a chosen subset whose distribution is close to that of altered data. Embedding is then performed on this subset; this replaces the problem of finding a small enough subset to evade detection with the problem of finding a large enough subset that possesses a desired type distribution. We show that one can find such a subset of size asymptotically proportional to n rather than the square root of n. This works in the case of both replacement and tampering: Even if the distribution of tampered data depends on the distribution of cover data, one can find a fixed point in the probability simplex such that cover data of that distribution yields stego data of the same distribution. While the transmission of a subset is not allowed, this is no impediment: wet paper codes can be used, else in the worst case a maximal desirable subset can be computed from the cover by both sender and receiver without communication of side information.
Square spiral photonic crystal with visible bandgap
NASA Astrophysics Data System (ADS)
Krabbe, Joshua D.; Leontyev, Viktor; Taschuk, Michael T.; Kovalenko, Andriy; Brett, Michael J.
2012-03-01
Nanoimprint lithography was combined with glancing angle deposition (GLAD) of titanium dioxide to fabricate a square spiral columnar film with a bandgap in the visible spectral range. Nanoimprint stamps were fabricated with seed spacing ranging from 80 to 400 nm, and four periods of square spiral film were deposited on top of the 320 nm array of seeds. The ratio of lattice spacing, vertical pitch and spiral arm swing was chosen as a : P : A = 1 : 1.35 : 0.7 and the deposition angle was fixed at 86° to maximize the square spiral film's bandgap. Reflectivity measurements show that the fabricated structure exhibit a pseudo-gap centered at around 600 nm wavelength, in good agreement with finite difference electromagnetic simulations. The absence of a full 3D bandgap is due the deviation of GLAD columns' cross-section from the optimal one, which has to be highly elongated in the deposition plane. However, simulations show that a geometry close to the fabricated one will produce a full 3D bandgap, if the structure is inverted. The material refractive index in such an inverted photonic crystal can be as low as n = 2.15.
NASA Astrophysics Data System (ADS)
Shakouri, Amir; Xu, Feifei; Fan, Zheng
2017-07-01
The propagation of acoustic waves in hierarchical sonic crystals is studied computationally and experimentally. These sonic crystals are composed of a hierarchical order of square inclusions rotated 45° with respect to the square lattice structure. It is shown that these hierarchical sonic crystals are capable of confining acoustic energy over a broad frequency range and at multiple lattice points inside the sonic crystal based on Bragg's scattering effect. Fused deposition modeling additive manufacturing is applied to prepare a finite-sized sample of the hierarchical sonic crystal. Acoustic measurements are conducted on the hierarchical sonic crystal sample in a direct and closely plane-wave field inside an anechoic room. The experimental measurements are in good agreement with the band structure calculated using the finite element method. Potential applications of the hierarchical sonic crystals for acoustic energy harvesting and noise measurements are discussed.
Fast Algorithms for Structured Least Squares and Total Least Squares Problems
Kalsi, Anoop; O’Leary, Dianne P.
2006-01-01
We consider the problem of solving least squares problems involving a matrix M of small displacement rank with respect to two matrices Z1 and Z2. We develop formulas for the generators of the matrix M HM in terms of the generators of M and show that the Cholesky factorization of the matrix M HM can be computed quickly if Z1 is close to unitary and Z2 is triangular and nilpotent. These conditions are satisfied for several classes of matrices, including Toeplitz, block Toeplitz, Hankel, and block Hankel, and for matrices whose blocks have such structure. Fast Cholesky factorization enables fast solution of least squares problems, total least squares problems, and regularized total least squares problems involving these classes of matrices. PMID:27274922
Fast Algorithms for Structured Least Squares and Total Least Squares Problems.
Kalsi, Anoop; O'Leary, Dianne P
2006-01-01
We consider the problem of solving least squares problems involving a matrix M of small displacement rank with respect to two matrices Z 1 and Z 2. We develop formulas for the generators of the matrix M (H) M in terms of the generators of M and show that the Cholesky factorization of the matrix M (H) M can be computed quickly if Z 1 is close to unitary and Z 2 is triangular and nilpotent. These conditions are satisfied for several classes of matrices, including Toeplitz, block Toeplitz, Hankel, and block Hankel, and for matrices whose blocks have such structure. Fast Cholesky factorization enables fast solution of least squares problems, total least squares problems, and regularized total least squares problems involving these classes of matrices.
NASA Astrophysics Data System (ADS)
Liu, Dan; Hu, Sen; Gao, Yihua
2017-07-01
A 2D orthogonal square-lattice photonic crystal (PC) heterojunction consisting of circular and square air holes in silicon is presented. Band structures are calculated using the plane wave expansion method, and the transmission properties are investigated by the finite-different time-domain simulations. Thanks to the higher diffraction orders excited when the circular and square holes are interlaced along the interface, one-way transmission phenomena can exist within wide frequency regions. The higher order diffraction is further enhanced through two different interface optimization designs proposed by modifying the PC structure of the hetero-interface. An orthogonal PC heterojunction for wide-band and efficient one-way transmission is constructed, and the maximum transmissivity is up to 78%.
NASA Astrophysics Data System (ADS)
Hayata, Kazuya
2003-08-01
Properties of several extremely squeezed configurations (ESCs) are described through rank-ordering statistics of the area data of their elements. The validity of a regression calculus is confirmed with a residual analysis followed by Durbin-Watson testing. As specific ESC systems two perfect squared squares and selected Japanese prefectures containing many cities are considered. The results are explained by a competitive effect, which could arise among elements being closely packed in a constrained domain.
XAFS study of copper(II) complexes with square planar and square pyramidal coordination geometries
NASA Astrophysics Data System (ADS)
Gaur, A.; Klysubun, W.; Nitin Nair, N.; Shrivastava, B. D.; Prasad, J.; Srivastava, K.
2016-08-01
X-ray absorption fine structure of six Cu(II) complexes, Cu2(Clna)4 2H2O (1), Cu2(ac)4 2H2O (2), Cu2(phac)4 (pyz) (3), Cu2(bpy)2(na)2 H2O (ClO4) (4), Cu2(teen)4(OH)2(ClO4)2 (5) and Cu2(tmen)4(OH)2(ClO4)2 (6) (where ac, phac, pyz, bpy, na, teen, tmen = acetate, phenyl acetate, pyrazole, bipyridine, nicotinic acid, tetraethyethylenediamine, tetramethylethylenediamine, respectively), which were supposed to have square pyramidal and square planar coordination geometries have been investigated. The differences observed in the X-ray absorption near edge structure (XANES) features of the standard compounds having four, five and six coordination geometry points towards presence of square planar and square pyramidal geometry around Cu centre in the studied complexes. The presence of intense pre-edge feature in the spectra of four complexes, 1-4, indicates square pyramidal coordination. Another important XANES feature, present in complexes 5 and 6, is prominent shoulder in the rising part of edge whose intensity decreases in the presence of axial ligands and thus indicates four coordination in these complexes. Ab initio calculations were carried out for square planar and square pyramidal Cu centres to observe the variation of 4p density of states in the presence and absence of axial ligands. To determine the number and distance of scattering atoms around Cu centre in the complexes, EXAFS analysis has been done using the paths obtained from Cu(II) oxide model and an axial Cu-O path from model of a square pyramidal complex. The results obtained from EXAFS analysis have been reported which confirmed the inference drawn from XANES features. Thus, it has been shown that these paths from model of a standard compound can be used to determine the structural parameters for complexes having unknown structure.
Simulated sawing of squares: a tool to improve wood utilization
R. Bruce Anderson; Hugh W. Reynolds
1981-01-01
Manufacturers of turning squares have had difficulty finding the best combination of bolt and square sizes for producing squares most efficiently. A computer simulation technique has been developed for inexpensively detemining the best combination of bolt and square size. Ranges of bolt dimeters to achieve a stated level of yield are given. The manufacturer can choose...
Exact, zero-energy, square-integrable solutions of a model related to the Maxwell's fish-eye problem
Makowski, Adam J.
2009-12-15
A model, which admits normalizable wave functions of the Schroedinger equation at the energy of E = 0, is exactly solved and the solutions are compared to the corresponding classical trajectories. The wave functions are proved to be square-integrable for discrete (quantized) values of the coupling constant of the used potential. We also show that our model is a specific version of the well-known Maxwell's fish-eye. This is performed with the help of a suitably chosen conformal mapping.
1982-09-23
Similarity in the asymptotic behavior of collision-free hydromagnetic waves and water waves, New York Univ., Courant Inst. Math. Sci., Res. Report NYO -90 L...Long solitary waves in lakes and • estuaries, propagating on the thermocline separating two shallow layers of fluid of almost equal densities, are
Atmospheric Science Data Center
2013-04-19
article title: Gravity Waves Ripple over Marine Stratocumulus Clouds ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ... that occur when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air ...
NASA Astrophysics Data System (ADS)
Higashira, Takaya; Kageyama, Tomoaki; Kashiwagi, Kouhei; Miyashita, Hidetoshi; Takano, Keisuke; Nakajima, Makoto; Lee, Sang-Seok
2017-09-01
In this study, we investigated the influence of the distance between metal squares in self-complementary metal checkerboard patterns (CPs) on the transmittance characteristics in the infrared (IR) region. Transmittance characteristics of CPs in the IR region are rarely studied. Here, to clarify experimentally the influence of reactance variation in CPs on the transmittance in the IR region, we fabricated self-complementary metallic CPs with differing distances between the metal squares, and their transmittances were measured. Initially, two types of capacitive CPs (C-CPs) and three types of inductive CPs (I-CPs) were fabricated, and their IR transmittances were measured. The CPs were configured to have different gaps or overlapping distances between the metal squares for the C-CPs and I-CPs, respectively. Furthermore, we investigated the influence of the distance configuration of CPs consisting of both C-CPs and I-CPs, on the transmittances of x- and y-polarized incident IR electromagnetic waves. The evaluated hybrid CPs, referred to as anisotropic CPs (A-CPs), were fabricated with horizontal metal patterns in contact with each other and separated vertical components. The results demonstrated that the transmittance depends on sensitively to the gap or the overlapping distance between the metal squares of the self-complementary metallic CPs. Moreover, we observed remarkable changes in the transmittance associated with the A-CPs, resulting from the polarization of the incident IR electromagnetic waves.
NASA Astrophysics Data System (ADS)
Binfeng, Yun; Hu, Guohua; Zhang, Ruohu; Yiping, Cui
2016-05-01
A coupled plasmonic waveguide resonator system which can produce sharp and asymmetric Fano resonances was proposed and analyzed. Two Fano resonances are induced by the interactions between the narrow discrete whispering gallery modes in a plasmonic square cavity resonator and the broad spectrum of the metal-insulator-metal stub resonator. The relative peak amplitudes between the 1st and 2nd order Fano resonances can be adjusted by changing the structure parameters, such as the square cavity size, the stub size and the center-to-center distance between the square cavity and the stub resonators. And the 1st order Fano resonant peak, which is a standing-wave mode, will split into two resonant peaks (one standing-wave mode and one traveling-wave mode) when it couples with the 2nd Fano resonance. Also, the potential of the proposed Fano system as an integrated slow-light device and refractive index sensor was investigated. The results show that a maximum group index of about 100 can be realized, and a linear refractive index sensitivity of 938 nm/RIU with a figure of merit of about 1.35 × 104 can be obtained.
Propagation of waves along an impedance boundary
NASA Technical Reports Server (NTRS)
Wenzel, A. R.
1974-01-01
A theoretical analysis of the scalar wave field due to a point source above a plane impedance boundary is presented. A surface wave is found to be an essential component of the total wave field. It is shown that, as a result of ducting of energy by the surface wave, the amplitude of the total wave near the boundary can be greater than it would be if the boundary were perfectly reflecting. Asymptotic results, valid near the boundary, are obtained both for the case of finite impedance (the soft-boundary case) and for the limiting case in which the impedance becomes infinite (the hard-boundary case). In the latter, the wave amplitude in the farfield decreases essentially inversely as the horizontal propagation distance; in the former (if the surface-wave term is neglected), it decreases inversely as the square of the horizontal propagation distance.
The Square-Shoulder-Asakura-Oosawa model
NASA Astrophysics Data System (ADS)
Fantoni, Riccardo
2016-09-01
A new model for a colloidal size-asymmetric binary mixture is proposed: The Square-Shoulder-Asakura-Oosawa. This belongs to the larger class of non-additive hard-spheres models and has the property that its effective pair formulation is exact whenever the solvent particle fits inside the interstitial region of three touching solute particles. Therefore one can study its properties from the equivalent one-component effective problem. Some remarks on the phase diagram of this new model are also addressed.
Iterative least squares functional networks classifier.
El-Sebakhy, Emad A; Hadi, Ali S; Faisal, Kanaan A
2007-05-01
This paper proposes unconstrained functional networks as a new classifier to deal with the pattern recognition problems. Both methodology and learning algorithm for this kind of computational intelligence classifier using the iterative least squares optimization criterion are derived. The performance of this new intelligent systems scheme is demonstrated and examined using real-world applications. A comparative study with the most common classification algorithms in both machine learning and statistics communities is carried out. The study was achieved with only sets of second-order linearly independent polynomial functions to approximate the neuron functions. The results show that this new framework classifier is reliable, flexible, stable, and achieves a high-quality performance.
An Overview of the Square Kilometre Array
NASA Technical Reports Server (NTRS)
Huynh, Minh T.; Lazio, Joseph
2013-01-01
The Square Kilometre Array (SKA) will be the premier instrument to study radiation at centimetre and metre wavelengths from the cosmos, and in particular 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, astrobiology and cosmology. Phase 1, which will be about 10% of the full SKA collecting area, will be built in Australia and South Africa. This paper describes the key science drivers of the SKA, provides an update on recent SKA Organisation activities and summarises the baseline design for Phase 1.
Uranyl peroxide closed clusters containing topological squares
Unruh, Daniel K.; Burtner, Alicia; Pressprich, Laura; Sigmon, Ginger E.; Burns, Peter C
2010-01-01
Four self-assembling clusters of uranyl peroxide polyhedra have been formed in alkaline aqueous solutions and structurally characterized. These clusters consist of 28, 30, 36 and 44 uranyl polyhedra and exhibit complex new topologies. Each has a structure that contains topological squares, pentagons and hexagons. Analysis of possible topologies within boundary constraints indicates a tendency for adoption of higher symmetry topologies in these cases. Small angle X-ray scattering data demonstrated that crystals of one of these clusters can be dissolved in ultrapure water and that the clusters remain intact for at least several days.
[Partial lease squares approach to functional analysis].
Preda, C
2006-01-01
We extend the partial least squares (PLS) approach to functional data represented in our models by sample paths of stochastic process with continuous time. Due to the infinite dimension, when functional data are used as a predictor for linear regression and classification models, the estimation problem is an ill-posed one. In this context, PLS offers a simple and efficient alternative to the methods based on the principal components of the stochastic process. We compare the results given by the PLS approach and other linear models using several datasets from economy, industry and medical fields.
Algorithms for Nonlinear Least-Squares Problems
1988-09-01
Newton meth - ods using these problems, and observes that the Jacobian is well-conditioned at every iteration. A difficulty with the Gauss-Newton method...QTf, (4.10) and ( TITTI + T T 21 )pI + (T’TI 2 + T2 T2 )p + ZTBp - (T1 , T2 )QTf. (4.11) 19 As in the earlier version, the term YTBp is ignored in...Algorithms", Math- ematical Programming 7 (1974) 351-367. Osborne, M. R., "Some Aspects of Non-linear Least Squares Calculations", in Numerical Meth - ods for
Protecting Spin Squeezing with Square Noise
NASA Astrophysics Data System (ADS)
Zhang, Ji-Ying; Zhang, Yong-Chang; Wu, Shan; Li, Xing; Lu, Wang-Ting; Chen, Hong-Mei; Zheng, Chun-Hong
2017-02-01
Here we provide two schemes to eliminate the square noise in the collective angular momentum during the generation of one-axis twisting (OAT) squeezed spin states (SSSs) by using the Radio frequency (RF) pulses. The first scheme can effectively overcome the detrimental noise and gives us a bare OAT Hamiltonian at last. The second one may also remove the noise well enough and finally offers us a two-axis twisting (TAT) Hamiltonian. In other words, it can both protect and enhance the OAT Hamiltonian. The corresponding theoretical analysis and numerical simulations are presented in the paper.
Exceptional supergravity theories and the magic square
NASA Astrophysics Data System (ADS)
Günaydin, M.; Sierra, G.; Townsend, P. K.
1983-12-01
We derive the magic square of Freudenthal, Rozenfeld, and Tits from the geometry of a special class of N=2 Maxwell-Einstein supergravity theories. We also show that all of these theories are obtainable by truncation of N=8 supergravity theories in various spacetime dimensions d, except for an ``exceptional'' subclass, unique for a given d, which is associated with with the exceptional Jordan algebra of 3 × 3 hermitian octonionic matrices. Laboratoire Propre du Centre National de la Recherche Scientifique, associé à l'Ecole Normale Supérieure et à l'Université de Paris-Sud.
Vibration and buckling of uniaxially loaded square plates with square holes
Sabir, A.B.; Djoudi, M.S.; Davies, G.T.
1996-11-01
The finite element method of analysis is used to determine the natural frequencies and elastic buckling loads of flat square plates containing centrally located square holes. The lateral bending stiffness matrix used was the nonconforming rectangular element having a total of twelve degrees of freedom, three at each of the four corner nodes. To determine the inplane geometric matrix a strain based element is used. This element is rectangular in shape, has two degrees of freedom at each of the four corner nodes and its displacement fields satisfy the exact requirements of rigid body displacements. The natural frequencies of the plates with central square holes were first determined to show the influence of the size of the hole. These plates were then subjected to uniaxial compressive forces to determine the effect of these forces on the natural frequencies. The results show that the natural frequencies of the simply supported and clamped square plates with central square holes decrease with increasing compressive forces, and that the frequencies become zero when the axial compressive forces are equal to the elastic buckling loads of the plates.
Total least squares for anomalous change detection
Theiler, James P; Matsekh, Anna M
2010-01-01
A family of difference-based anomalous change detection algorithms is derived from a total least squares (TLSQ) framework. This provides an alternative to the well-known chronochrome algorithm, which is derived from ordinary least squares. In both cases, the most anomalous changes are identified with the pixels that exhibit the largest residuals with respect to the regression of the two images against each other. The family of TLSQ-based anomalous change detectors is shown to be equivalent to the subspace RX formulation for straight anomaly detection, but applied to the stacked space. However, this family is not invariant to linear coordinate transforms. On the other hand, whitened TLSQ is coordinate invariant, and furthermore it is shown to be equivalent to the optimized covariance equalization algorithm. What whitened TLSQ offers, in addition to connecting with a common language the derivations of two of the most popular anomalous change detection algorithms - chronochrome and covariance equalization - is a generalization of these algorithms with the potential for better performance.
Least-squares Gaussian beam migration
NASA Astrophysics Data System (ADS)
Yuan, Maolin; Huang, Jianping; Liao, Wenyuan; Jiang, Fuyou
2017-02-01
A theory of least-squares Gaussian beam migration (LSGBM) is presented to optimally estimate a subsurface reflectivity. In the iterative inversion scheme, a Gaussian beam (GB) propagator is used as the kernel of linearized forward modeling (demigration) and its adjoint (migration). Born approximation based GB demigration relies on the calculation of Green’s function by a Gaussian-beam summation for the downward and upward wavefields. The adjoint operator of GB demigration accounts for GB prestack depth migration under the cross-correlation imaging condition, where seismic traces are processed one by one for each shot. A numerical test on the point diffractors model suggests that GB demigration can successfully simulate primary scattered data, while migration (adjoint) can yield a corresponding image. The GB demigration/migration algorithms are used for the least-squares migration scheme to deblur conventional migrated images. The proposed LSGBM is illustrated with two synthetic data for a four-layer model and the Marmousi2 model. Numerical results show that LSGBM, compared to migration (adjoint) with GBs, produces images with more balanced amplitude, higher resolution and even fewer artifacts. Additionally, the LSGBM shows a robust convergence rate.
Augmented classical least squares multivariate spectral analysis
Haaland, David M.; Melgaard, David K.
2004-02-03
A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra. Also, since the various ACLS methods are based on CLS, they can incorporate the new prediction-augmented CLS (PACLS) method of updating the prediction model for new sources of spectral variation contained in the prediction sample set without having to return to the calibration process. The ACLS methods can also be applied to alternating least squares models. The ACLS methods can be applied to all types of multivariate data.
Augmented Classical Least Squares Multivariate Spectral Analysis
Haaland, David M.; Melgaard, David K.
2005-07-26
A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra. Also, since the various ACLS methods are based on CLS, they can incorporate the new prediction-augmented CLS (PACLS) method of updating the prediction model for new sources of spectral variation contained in the prediction sample set without having to return to the calibration process. The ACLS methods can also be applied to alternating least squares models. The ACLS methods can be applied to all types of multivariate data.
Augmented Classical Least Squares Multivariate Spectral Analysis
Haaland, David M.; Melgaard, David K.
2005-01-11
A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra. Also, since the various ACLS methods are based on CLS, they can incorporate the new prediction-augmented CLS (PACLS) method of updating the prediction model for new sources of spectral variation contained in the prediction sample set without having to return to the calibration process. The ACLS methods can also be applied to alternating least squares models. The ACLS methods can be applied to all types of multivariate data.
Gravity as the square of gauge theory
Bern, Zvi; Dennen, Tristan; Huang Yutin; Kiermaier, Michael
2010-09-15
We explore consequences of the recently discovered duality between color and kinematics, which states that kinematic numerators in a diagrammatic expansion of gauge-theory amplitudes can be arranged to satisfy Jacobi-like identities in one-to-one correspondence to the associated color factors. Using on-shell recursion relations, we give a field-theory proof showing that the duality implies that diagrammatic numerators in gravity are just the product of two corresponding gauge-theory numerators, as previously conjectured. These squaring relations express gravity amplitudes in terms of gauge-theory ingredients, and are a recasting of the Kawai, Lewellen, and Tye relations. Assuming that numerators of loop amplitudes can be arranged to satisfy the duality, our tree-level proof immediately carries over to loop level via the unitarity method. We then present a Yang-Mills Lagrangian whose diagrams through five points manifestly satisfy the duality between color and kinematics. The existence of such Lagrangians suggests that the duality also extends to loop amplitudes, as confirmed at two and three loops in a concurrent paper. By ''squaring'' the novel Yang-Mills Lagrangian we immediately obtain its gravity counterpart. We outline the general structure of these Lagrangians for higher points. We also write down various new representations of gauge-theory and gravity amplitudes that follow from the duality between color and kinematics.
Update on the Square Kilometer Array
NASA Astrophysics Data System (ADS)
Tarter, Jill
2002-01-01
In August 2000 representatives of 24 groups in 10 countries signed a memorandum of understanding to continue cooperative technology development on five different antenna concepts intended to enable the cost-effective construction of a radio telescope array with one million square meters of collecting area; the Square Kilometer Array (SKA). The goal of this MOA is to find innovative ways of solving the many technical challenges posed by this mammouth array, and to drive down the costs so that this can realistically be afforded as a groundbased, international project for radio astronomy. The science drivers for this large instrument are diverse and very exciting; SETI being one of them. However, this means that the technical specifications are extremely challenging. There is historical reason to believe that these goals can be met. For the past six decades, the capability of radio astronomy facilities has been improving exponentially, and the SKA represents the logical extrapolation of this trend. In 2005 a selection of one or more of the current antenna concepts will be made, along with the choice of a suitable site and configuration for the array. Final detailed designs and prototyping will follow. Construction could start by the end of this decade. The SKA will permit SETI observations over a wider range of frequencies, and will offer a sensitivity that is two orders of magnitude better than current arrays. This improved performance justifies all the effort needed to overcome the technological, political, and bureaucratic challenges inherent in this international mega-science project.
NASA Astrophysics Data System (ADS)
Hamer, C. J.
2009-06-01
The energy spectra of the two-magnon bound states in the Heisenberg-Ising antiferromagnet on the square lattice are calculated using series expansion methods. The results confirm an earlier spin-wave prediction of Oguchi and Ishikawa that the bound states vanish into the continuum before the isotropic Heisenberg limit is reached.
Measured and predicted root-mean-square errors in square and triangular antenna mesh facets
NASA Technical Reports Server (NTRS)
Fichter, W. B.
1989-01-01
Deflection shapes of square and equilateral triangular facets of two tricot-knit, gold plated molybdenum wire mesh antenna materials were measured and compared, on the basis of root mean square (rms) differences, with deflection shapes predicted by linear membrane theory, for several cases of biaxial mesh tension. The two mesh materials contained approximately 10 and 16 holes per linear inch, measured diagonally with respect to the course and wale directions. The deflection measurement system employed a non-contact eddy current proximity probe and an electromagnetic distance sensing probe in conjunction with a precision optical level. Despite experimental uncertainties, rms differences between measured and predicted deflection shapes suggest the following conclusions: that replacing flat antenna facets with facets conforming to parabolically curved structural members yields smaller rms surface error; that potential accuracy gains are greater for equilateral triangular facets than for square facets; and that linear membrane theory can be a useful tool in the design of tricot knit wire mesh antennas.
Cichocki, A; Unbehauen, R
1994-01-01
In this paper a new class of simplified low-cost analog artificial neural networks with on chip adaptive learning algorithms are proposed for solving linear systems of algebraic equations in real time. The proposed learning algorithms for linear least squares (LS), total least squares (TLS) and data least squares (DLS) problems can be considered as modifications and extensions of well known algorithms: the row-action projection-Kaczmarz algorithm and/or the LMS (Adaline) Widrow-Hoff algorithms. The algorithms can be applied to any problem which can be formulated as a linear regression problem. The correctness and high performance of the proposed neural networks are illustrated by extensive computer simulation results.
Wave-particle interaction in the Faraday waves.
Francois, N; Xia, H; Punzmann, H; Shats, M
2015-10-01
Wave motion in disordered Faraday waves is analysed in terms of oscillons or quasi-particles. The motion of these oscillons is measured using particle tracking tools and it is compared with the motion of fluid particles on the water surface. Both the real floating particles and the oscillons, representing the collective fluid motion, show Brownian-type dispersion exhibiting ballistic and diffusive mean squared displacement at short and long times, respectively. While the floating particles motion has been previously explained in the context of two-dimensional turbulence driven by Faraday waves, no theoretical description exists for the random walk type motion of oscillons. It is found that the r.m.s velocity ⟨μ̃(osc)⟩(rms) of oscillons is directly related to the turbulent r.m.s. velocity ⟨μ̃⟩(rms) of the fluid particles in a broad range of vertical accelerations. The measured ⟨μ̃(osc)⟩(rms) accurately explains the broadening of the frequency spectra of the surface elevation observed in disordered Faraday waves. These results suggest that 2D turbulence is the driving force behind both the randomization of the oscillons motion and the resulting broadening of the wave frequency spectra. The coupling between wave motion and hydrodynamic turbulence demonstrated here offers new perspectives for predicting complex fluid transport from the knowledge of wave field spectra and vice versa.
Square or Sine: Finding a Waveform with High Success Rate of Eliciting SSVEP
Teng, Fei; Chen, Yixin; Choong, Aik Min; Gustafson, Scott; Reichley, Christopher; Lawhead, Pamela; Waddell, Dwight
2011-01-01
Steady state visual evoked potential (SSVEP) is the brain's natural electrical potential response for visual stimuli at specific frequencies. Using a visual stimulus flashing at some given frequency will entrain the SSVEP at the same frequency, thereby allowing determination of the subject's visual focus. The faster an SSVEP is identified, the higher information transmission rate the system achieves. Thus, an effective stimulus, defined as one with high success rate of eliciting SSVEP and high signal-noise ratio, is desired. Also, researchers observed that harmonic frequencies often appear in the SSVEP at a reduced magnitude. Are the harmonics in the SSVEP elicited by the fundamental stimulating frequency or by the artifacts of the stimuli? In this paper, we compare the SSVEP responses of three periodic stimuli: square wave (with different duty cycles), triangle wave, and sine wave to find an effective stimulus. We also demonstrate the connection between the strength of the harmonics in SSVEP and the type of stimulus. PMID:21941529
Analytic wave model of Stark deceleration dynamics
Gubbels, Koos; Meijer, Gerard; Friedrich, Bretislav
2006-06-15
Stark deceleration relies on time-dependent inhomogeneous electric fields which repetitively exert a decelerating force on polar molecules. Fourier analysis reveals that such fields, generated by an array of field stages, consist of a superposition of partial waves with well-defined phase velocities. Molecules whose velocities come close to the phase velocity of a given wave get a ride from that wave. For a square-wave temporal dependence of the Stark field, the phase velocities of the waves are found to be odd-fraction multiples of a fundamental phase velocity {lambda}/{tau}, with {lambda} and {tau} the spatial and temporal periods of the field. Here we study explicitly the dynamics due to any of the waves as well as due to their mutual perturbations. We first solve the equations of motion for the case of single-wave interactions and exploit their isomorphism with those for the biased pendulum. Next we analyze the perturbations of the single-wave dynamics by other waves and find that these have no net effect on the phase stability of the acceleration or deceleration process. Finally, we find that a packet of molecules can also ride a wave which results from an interference of adjacent waves. In this case, small phase stability areas form around phase velocities that are even-fraction multiples of the fundamental velocity. A detailed comparison with classical trajectory simulations and with experiment demonstrates that the analytic 'wave model' encompasses all the longitudinal physics encountered in a Stark decelerator.
Effective theory of interacting fermions in shaken square optical lattices
NASA Astrophysics Data System (ADS)
Keleş, Ahmet; Zhao, Erhai; Liu, W. Vincent
2017-06-01
We develop a theory of weakly interacting fermionic atoms in shaken optical lattices based on the orbital mixing in the presence of time-periodic modulations. Specifically, we focus on fermionic atoms in a circularly shaken square lattice with near-resonance frequencies, i.e., tuned close to the energy separation between the s band and the p bands. First, we derive a time-independent four-band effective Hamiltonian in the noninteracting limit. Diagonalization of the effective Hamiltonian yields a quasienergy spectrum consistent with the full numerical Floquet solution that includes all higher bands. In particular, we find that the hybridized s band develops multiple minima and therefore nontrivial Fermi surfaces at different fillings. We then obtain the effective interactions for atoms in the hybridized s band analytically and show that they acquire momentum dependence on the Fermi surface even though the bare interaction is contactlike. We apply the theory to find the phase diagram of fermions with weak attractive interactions and demonstrate that the pairing symmetry is s +d wave. Our theory is valid for a range of shaking frequencies near resonance, and it can be generalized to other phases of interacting fermions in shaken lattices.
The Square Kilometer Array: Key Science and Technology Development
NASA Astrophysics Data System (ADS)
Cordes, J. M.
2005-12-01
This paper summarizes the science goals for the Square Kilometer Array and its possible implementation. The SKA is the next generation radio telescope that will revolutionize our knowledge of the universe. The SKA will enable massive surveys of many kinds at meter and centimeter wavelengths. It is being designed to probe fundamental questions in physics, such as the nature of dark energy and dark matter and the properties of gravity in the strong-field limit. The SKA will also lead to a better understanding of complexity in the universe, viz. the origins of magnetic fields, galaxies, stars, planets and life. Currently the purpose and specifications of the SKA are defined in terms of five key science areas, which are summarized here, along with the enormous discovery space that will be opened up by the SKA. The key ``axes of discovery'' for the SKA include a huge boost in sensitivity combined with high angular resolution and wide field of view (FoV). These innovations, combined with those developed in radio astronomy contexts over the last few decades, will open new windows to the universe. It will also provide numerous synergistic studies with telescopes that span the electromagnetic spectrum as well as with non-electromagnetic telescopes, especially gravitational wave detectors.
Science with the Australian Square Kilometre Array Pathfinder (ASKAP)
NASA Astrophysics Data System (ADS)
Johnston, S.; Feain, I. J.; Gupta, N.
2009-09-01
The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries that will be 50 times more sensitive than any existing radio facility. Most of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from a few hundred MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is a technology demonstrator aimed in the mid-frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phased-array feed systems on parabolic reflectors. The large field-of-view makes ASKAP an unprecedented synoptic telescope that will make substantial advances in SKA key science. ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of two sites selected by the international community as a potential location for the SKA. In this paper, we outline the ASKAP project and summarise its headline science goals as defined by the community at large.
Experiments on supersonic turbulent flow development in a square duct
NASA Technical Reports Server (NTRS)
Gessner, F. B.; Ferguson, S. D.; Lo, C. H.
1986-01-01
The nature of supersonic, turbulent, adiabatic-wall flow in a square duct is investigated experimentally over a development length of x/D between 0 and 20 for a uniform flow, Mach 3.9 condition at the duct inlet. Initial discussion centers on the duct configuration itself, which was designed specifically to minimize wave effects and nozzle-induced distortion in the flow. Total pressure contours and local skin friction coefficient distributions are presented which show that the flow develops in a manner similar to that observed for the incompressible case. In particular, undulations exist in total pressure contours within the cross plane and in transverse skin friction coefficient distributions, which are indicative of the presence of a well-defined secondary flow superimposed upon the primary flow. The results are analyzed to show that local law-of-the-wall behavior extends well into the corner region, which implies that wall functions conventionally applied in two-equation type turbulence models, when suitably defined for compressible flow, may also be applied to supersonic streamwise corner flows.
2015-10-13
Scientists spotted a rare wave in Jupiter North Equatorial Belt that had been seen there only once before in this false-color close-up from NASA Hubble Telescope. In Jupiter's North Equatorial Belt, scientists spotted a rare wave that had been seen there only once before. It is similar to a wave that sometimes occurs in Earth's atmosphere when cyclones are forming. This false-color close-up of Jupiter shows cyclones (arrows) and the wave (vertical lines). http://photojournal.jpl.nasa.gov/catalog/PIA19659
NASA Astrophysics Data System (ADS)
Kruse, Karsten
2017-01-01
Traveling waves propagating along surfaces play an important role for intracellular organization. Such waves can appear spontaneously in reaction-diffusion systems, but only few general criteria for their existence are known. Analyzing the dynamics of the Min proteins in Escherichia coli, Levine and Kessler (2016 New J. Phys. 18 122001) now identified a new mechanism for the emergence of traveling waves that relies on conservation laws. From their analysis one can expect traveling waves to be a generic feature of systems made of proteins that have a cytoplasmic and a membrane-bound state.
Dark Matter, Waves, and Identification
NASA Astrophysics Data System (ADS)
Wagner, Orvin
2011-10-01
In 1994 I wrote article for Physics Essays (Waves in Dark Matter) showing how the solar system is organized and stabilized by dark matter standing waves from the dark matter oscillating sun. Wave velocity is apparently inversely proportional to the square root of the dark matter density. At the sun's surface the wave velocity is near 1.25 m/s. More recently I have found local dark matter waves that appear to travel near 25 m/s near April 1 and appear to organize plants. They travel between plants and artificial transmitters and receivers, and penetrate my local hill. From my measurements the local dark matter density is a function of the time of year. The data indicate that dark matter interacts much more than just with gravity as others have surmised. I present experimental proofs and a local dark matter density equation in terms of the measured velocity. The waves and the earth's location may be very important for nature's organization. The observed behavior appears to go a long way towards dark matter identification. These waves also may explain the rings of the gaseous planets in terms of oscillating layers. See the ring article on the web site Darkmatterwaves.com.
NASA Astrophysics Data System (ADS)
Wang, Da; Wang, Wan-Sheng; Wang, Qiang-Hua
2015-11-01
In phonon mediated conventional s -wave superconductors, higher-frequency phonon (or smaller atomic mass) leads to a higher superconducting transition temperature, known as the isotope effect. However, in correlated systems, various competing electronic order (such as spin-density-wave, charge-density-wave, and unconventional superconductivity) arises and the effect of electron-phonon coupling on these orders is a long-standing problem. Using the functional renormalization group, here we investigated the interplay between the electron correlation and electron-phonon coupling in the Hubbard-Holstein model on a square lattice. At half-filling, we found spin-density-wave and charge-density-wave phases and the transition between them, while no superconducting phase arises. Upon finite doping, d -wave/s -wave superconductivity emerges in proximity to the spin-density-wave/charge-density-wave phase. Surprisingly, lower-frequency Holstein phonons are either less destructive or even beneficial to the various phases, resulting in a negative isotope effect. For the superconducting phases, such an effect is apparently beyond the Bardeen-Cooper-Schrieffer theory.
Vehicle detection using partial least squares.
Kembhavi, Aniruddha; Harwood, David; Davis, Larry S
2011-06-01
Detecting vehicles in aerial images has a wide range of applications, from urban planning to visual surveillance. We describe a vehicle detector that improves upon previous approaches by incorporating a very large and rich set of image descriptors. A new feature set called Color Probability Maps is used to capture the color statistics of vehicles and their surroundings, along with the Histograms of Oriented Gradients feature and a simple yet powerful image descriptor that captures the structural characteristics of objects named Pairs of Pixels. The combination of these features leads to an extremely high-dimensional feature set (approximately 70,000 elements). Partial Least Squares is first used to project the data onto a much lower dimensional sub-space. Then, a powerful feature selection analysis is employed to improve the performance while vastly reducing the number of features that must be calculated. We compare our system to previous approaches on two challenging data sets and show superior performance.
Resistant hypertension and the Birmingham Hypertension Square.
Felmeden, D C; Lip, G Y
2001-06-01
Recent guidelines for the treatment of hypertension place great emphasis on tighter blood pressure control, especially in the presence of hypertensive target organ damage and diabetes. In order to achieve these treatment targets, more patients will require a combination of antihypertensive medications. However, resistant hypertension may have many possible underlying causes, and clinicians should appreciate how to detect and tackle these potential problems. Effective and synergistic combinations are therefore of vital importance, especially in patients with resistant hypertension. The choice of rational first- and second-line drugs that act in synergy could lead to better blood pressure management as well as significant financial savings for health care resources. The use of the Birmingham Hypertension Square for the optimum choice of add-in drugs for the treatment of resistant hypertension may aid management.
Hybrid least squares multivariate spectral analysis methods
Haaland, David M.
2004-03-23
A set of hybrid least squares multivariate spectral analysis methods in which spectral shapes of components or effects not present in the original calibration step are added in a following prediction or calibration step to improve the accuracy of the estimation of the amount of the original components in the sampled mixture. The hybrid method herein means a combination of an initial calibration step with subsequent analysis by an inverse multivariate analysis method. A spectral shape herein means normally the spectral shape of a non-calibrated chemical component in the sample mixture but can also mean the spectral shapes of other sources of spectral variation, including temperature drift, shifts between spectrometers, spectrometer drift, etc. The shape can be continuous, discontinuous, or even discrete points illustrative of the particular effect.
Object tracking via partial least squares analysis.
Wang, Qing; Chen, Feng; Xu, Wenli; Yang, Ming-Hsuan
2012-10-01
We propose an object tracking algorithm that learns a set of appearance models for adaptive discriminative object representation. In this paper, object tracking is posed as a binary classification problem in which the correlation of object appearance and class labels from foreground and background is modeled by partial least squares (PLS) analysis, for generating a low-dimensional discriminative feature subspace. As object appearance is temporally correlated and likely to repeat over time, we learn and adapt multiple appearance models with PLS analysis for robust tracking. The proposed algorithm exploits both the ground truth appearance information of the target labeled in the first frame and the image observations obtained online, thereby alleviating the tracking drift problem caused by model update. Experiments on numerous challenging sequences and comparisons to state-of-the-art methods demonstrate favorable performance of the proposed tracking algorithm.
Testing Newton's Gravitational Inverse-Square Law
NASA Astrophysics Data System (ADS)
Hagedorn, Charles
2015-04-01
Newton's inverse-square law of gravitation is the oldest standing mathematical description of a fundamental interaction. Experimental tests of gravity's distance-dependence define a frontier between our understanding of gravity and many proposed forms of new physics. These experiments constrain the size of possible extra dimensions, bound attempted resolution of the cosmological-constant problem, search for self-interacting chameleons, make direct measurements at the dark-energy length-scale, and more. As gravity is ~1040 times weaker than electromagnetism, gravity remains hidden by experimental backgrounds at distances smaller than the diameter of a fine human hair. This talk will survey the past, present, and near-future of the experimental field, with substantial emphasis on precision sub-millimeter laboratory experiments.
Classical least squares multivariate spectral analysis
Haaland, David M.
2002-01-01
An improved classical least squares multivariate spectral analysis method that adds spectral shapes describing non-calibrated components and system effects (other than baseline corrections) present in the analyzed mixture to the prediction phase of the method. These improvements decrease or eliminate many of the restrictions to the CLS-type methods and greatly extend their capabilities, accuracy, and precision. One new application of PACLS includes the ability to accurately predict unknown sample concentrations when new unmodeled spectral components are present in the unknown samples. Other applications of PACLS include the incorporation of spectrometer drift into the quantitative multivariate model and the maintenance of a calibration on a drifting spectrometer. Finally, the ability of PACLS to transfer a multivariate model between spectrometers is demonstrated.
Square lattice photonic crystal surface mode lasers.
Lu, Tsan-Wen; Lu, Shao-Ping; Chiu, Li-Hsun; Lee, Po-Tsung
2010-12-06
In this report, we propose a square lattice photonic crystal hetero-slab-edge microcavity design. In numerical simulations, three surface modes in this microcavity are investigated and optimized by tuning the slab-edge termination τ and gradual mirror layer. High simulated quality (Q) factor of 2.3 × 10(5) and small mode volume of 0.105 μm(3) are obtained from microcavity with τ = 0.80. In experiments, we obtain and identify different surface modes lasing. The surface mode in the second photonic band gap shows a very-low threshold of 140 μW and high Q factor of 5,500, which could be an avenue to low-threshold optical lasers and highly sensitive sensor applications with efficient light-matter interactions.
Flexible least squares for approximately linear systems
NASA Astrophysics Data System (ADS)
Kalaba, Robert; Tesfatsion, Leigh
1990-10-01
A probability-free multicriteria approach is presented to the problem of filtering and smoothing when prior beliefs concerning dynamics and measurements take an approximately linear form. Consideration is given to applications in the social and biological sciences, where obtaining agreement among researchers regarding probability relations for discrepancy terms is difficult. The essence of the proposed flexible-least-squares (FLS) procedure is the cost-efficient frontier, a curve in a two-dimensional cost plane which provides an explicit and systematic way to determine the efficient trade-offs between the separate costs incurred for dynamic and measurement specification errors. The FLS estimates show how the state vector could have evolved over time in a manner minimally incompatible with the prior dynamic and measurement specifications. A FORTRAN program for implementing the FLS filtering and smoothing procedure for approximately linear systems is provided.
Tensor hypercontraction. II. Least-squares renormalization
NASA Astrophysics Data System (ADS)
Parrish, Robert M.; Hohenstein, Edward G.; Martínez, Todd J.; Sherrill, C. David
2012-12-01
The least-squares tensor hypercontraction (LS-THC) representation for the electron repulsion integral (ERI) tensor is presented. Recently, we developed the generic tensor hypercontraction (THC) ansatz, which represents the fourth-order ERI tensor as a product of five second-order tensors [E. G. Hohenstein, R. M. Parrish, and T. J. Martínez, J. Chem. Phys. 137, 044103 (2012)], 10.1063/1.4732310. Our initial algorithm for the generation of the THC factors involved a two-sided invocation of overlap-metric density fitting, followed by a PARAFAC decomposition, and is denoted PARAFAC tensor hypercontraction (PF-THC). LS-THC supersedes PF-THC by producing the THC factors through a least-squares renormalization of a spatial quadrature over the otherwise singular 1/r12 operator. Remarkably, an analytical and simple formula for the LS-THC factors exists. Using this formula, the factors may be generated with O(N^5) effort if exact integrals are decomposed, or O(N^4) effort if the decomposition is applied to density-fitted integrals, using any choice of density fitting metric. The accuracy of LS-THC is explored for a range of systems using both conventional and density-fitted integrals in the context of MP2. The grid fitting error is found to be negligible even for extremely sparse spatial quadrature grids. For the case of density-fitted integrals, the additional error incurred by the grid fitting step is generally markedly smaller than the underlying Coulomb-metric density fitting error. The present results, coupled with our previously published factorizations of MP2 and MP3, provide an efficient, robust O(N^4) approach to both methods. Moreover, LS-THC is generally applicable to many other methods in quantum chemistry.
1. WASHINGTON SQUARE IN CENTER, LOOKING SOUTHWEST. CURTIS PUBLISHING COMPANY ...
1. WASHINGTON SQUARE IN CENTER, LOOKING SOUTHWEST. CURTIS PUBLISHING COMPANY IS AT RIGHT. THE BUILDING IN FRONT OF PHOTO IS THE PENN MUTUAL LIFE INSURANCE COMPANY - Washington Square Area Study, Sixth, Seventh, Walnut & Locust Streets, Philadelphia, Philadelphia County, PA
A Simple Parameterization of 3 x 3 Magic Squares
ERIC Educational Resources Information Center
Trenkler, Gotz; Schmidt, Karsten; Trenkler, Dietrich
2012-01-01
In this article a new parameterization of magic squares of order three is presented. This parameterization permits an easy computation of their inverses, eigenvalues, eigenvectors and adjoints. Some attention is paid to the Luoshu, one of the oldest magic squares.
The Magic of Balanced Groups: Educational Applications of Magic Squares
ERIC Educational Resources Information Center
Bosse, Michael J.; Nandakumar, N. R.; Ore, Melanie L.
2007-01-01
This paper provides students with many interesting observations regarding the nature of magic squares, magic rectangles, and quasi-magic squares and provides tools for teachers to group students into ability-balanced cooperative learning groups.
1. General view of the Moody Hotel, Tremont Square. The ...
1. General view of the Moody Hotel, Tremont Square. The hotel was built by William Emerson in 1890-92. - Claremont Village Industrial District, Moody Hotel, Tremont Square, Claremont, Sullivan County, NH
The Magic of Balanced Groups: Educational Applications of Magic Squares
ERIC Educational Resources Information Center
Bosse, Michael J.; Nandakumar, N. R.; Ore, Melanie L.
2007-01-01
This paper provides students with many interesting observations regarding the nature of magic squares, magic rectangles, and quasi-magic squares and provides tools for teachers to group students into ability-balanced cooperative learning groups.
A Simple Parameterization of 3 x 3 Magic Squares
ERIC Educational Resources Information Center
Trenkler, Gotz; Schmidt, Karsten; Trenkler, Dietrich
2012-01-01
In this article a new parameterization of magic squares of order three is presented. This parameterization permits an easy computation of their inverses, eigenvalues, eigenvectors and adjoints. Some attention is paid to the Luoshu, one of the oldest magic squares.
Multiplier less high-speed squaring circuit for binary numbers
NASA Astrophysics Data System (ADS)
Sethi, Kabiraj; Panda, Rutuparna
2015-03-01
The squaring operation is important in many applications in signal processing, cryptography etc. In general, squaring circuits reported in the literature use fast multipliers. A novel idea of a squaring circuit without using multipliers is proposed in this paper. Ancient Indian method used for squaring decimal numbers is extended here for binary numbers. The key to our success is that no multiplier is used. Instead, one squaring circuit is used. The hardware architecture of the proposed squaring circuit is presented. The design is coded in VHDL and synthesised and simulated in Xilinx ISE Design Suite 10.1 (Xilinx Inc., San Jose, CA, USA). It is implemented in Xilinx Vertex 4vls15sf363-12 device (Xilinx Inc.). The results in terms of time delay and area is compared with both modified Booth's algorithm and squaring circuit using Vedic multipliers. Our proposed squaring circuit seems to have better performance in terms of both speed and area.
View of south elevation of Building No. 34. Corto Square ...
View of south elevation of Building No. 34. Corto Square in foreground and Building No. 22 at right rear. Looking northeast - Easter Hill Village, Building No. 34, East side of Corto Square, Richmond, Contra Costa County, CA
Simple pulse counting circuit computes sum of squares
NASA Technical Reports Server (NTRS)
Schaefer, D. H.
1965-01-01
Pulse counting circuit with an extra chain of flip-flops, delay lines, and gates computes the sum of the squares of the pulse sequences. A pulse train and the sum of the squares of the pulses are simultaneously completed.
Vibration and buckling of square plates with square holes subjected to biaxial and shear loads
Sabir, A.B.; Davies, G.T.
1996-11-01
The finite element method of analysis is used to determine the elastic buckling loads and natural circular frequencies of flat square plates. The square plates contain centrally located square holes that vary in size. The plates are subjected to inplane biaxial compression, tensile loads and uniform shear. In all cases the load is distributed uniformly along the simply supported or clamped outer edges. The finite element used for calculating the inplane stiffness matrix is based on an assumed strain rather than displacement field, and is rectangular in shape. The out of plane finite element used is the nonconforming rectangular bending element having a total of twelve degrees of freedom, three at each of the four corner nodes. Square plates with centrally located holes are initially subjected to inplane biaxial compression, and the effect of this load on the natural frequency is examined for different sizes of hole. Similar analysis was carried out when inplane biaxial tension and uniform shear was applied. For both cases of biaxial compression and shear, the natural frequency decreased towards zero, as the applied force increased towards the elastic buckling load. When biaxial tension was applied the natural frequency increased with increasing tensile loads.
NASA Astrophysics Data System (ADS)
Huang, Wen-Min; Lai, Chen-Yen; Shi, Chuntai; Tsai, Shan-Wen
2013-08-01
We study the phase diagram of the extended Hubbard model on a two-dimensional square lattice, including on-site (U) and nearest-neighbor (V) interactions, at weak couplings. We show that the charge-density wave phase that is known to occur at half filling when 4V>U gives way to a dxy-wave superconducting instability away from half filling, when the Fermi surface is not perfectly nested, and for sufficiently large repulsive V and a range of on-site repulsive interaction U. In addition, when nesting is further suppressed and in the presence of a nearest-neighbor attraction, a triplet time-reversal breaking (px+ipy)-wave pairing instability emerges, competing with the dx2-y2 pairing state that is known to dominate at fillings just slightly away from half. At even smaller fillings, where the Fermi surface no longer presents any nesting, the (px+ipy)-wave superconducting phase dominates in the whole regime of on-site repulsions and nearest-neighbor attractions, while dxy pairing occurs in the presence of on-site attraction. Our results suggest that zero-energy Majorana fermions can be realized on a square lattice in the presence of a magnetic field. For a system of cold fermionic atoms on a two-dimensional square optical lattice, both an on-site repulsion and a nearest-neighbor attraction would be required, in addition to rotation of the system to create vortices. We discuss possible ways of experimentally engineering the required interaction terms in a cold atom system.
Novel itinerant transverse spin waves
NASA Astrophysics Data System (ADS)
Feldmann, John Delaney
wavelengths, or can lead to spin waves that are characterized by a square root dependence on the wave number at long wavelength. The author also presents new results for spin waves in a fermi liquid that has a spin density wave in its ground state. A spin density wave is characterized by a spiral magnetization in the ground state, and is observed to occur in materials such as MnSi.
Asymptotic Linear Stability of Solitary Water Waves
NASA Astrophysics Data System (ADS)
Pego, Robert L.; Sun, Shu-Ming
2016-12-01
We prove an asymptotic stability result for the water wave equations linearized around small solitary waves. The equations we consider govern irrotational flow of a fluid with constant density bounded below by a rigid horizontal bottom and above by a free surface under the influence of gravity neglecting surface tension. For sufficiently small amplitude waves, with waveform well-approximated by the well-known sech-squared shape of the KdV soliton, solutions of the linearized equations decay at an exponential rate in an energy norm with exponential weight translated with the wave profile. This holds for all solutions with no component in (that is, symplectically orthogonal to) the two-dimensional neutral-mode space arising from infinitesimal translational and wave-speed variation of solitary waves. We also obtain spectral stability in an unweighted energy norm.
Square tubing reduces cost of telescoping bridge crane hoist
NASA Technical Reports Server (NTRS)
Bernstein, G.; Graae, J.; Schraidt, J.
1967-01-01
Using standard square tubing in a telescoping arrangement reduces the cost of a bridge crane hoist. Because surface tolerances of square tubing need not be as accurate as the tubing used previously and because no spline is necessary, the square tubing is significantly less expensive than splined telescoping tubes.
Going Off-the-Pegs: Revisiting Geoboard Squares
ERIC Educational Resources Information Center
Canada, Daniel L.; Ciancetta, Matthew A.; Blair, Stephen D.
2014-01-01
How many squares can be found on a typical 5 × 5 geoboard? Teachers who are unfamiliar with this question may wish to stop here and reflect a bit. The question can lead to wonderful student discourse: How can someone tell if something is a square? Should squares be counted that are the same size (but in a different location) or just different…
Structural and dynamic characteristics in monolayer square ice
NASA Astrophysics Data System (ADS)
Zhu, YinBo; Wang, FengChao; Wu, HengAn
2017-07-01
When water is constrained between two sheets of graphene, it becomes an intriguing monolayer solid with a square pattern due to the ultrahigh van der Waals pressure. However, the square ice phase has become a matter of debate due to the insufficient experimental interpretation and the slightly rhomboidal feature in simulated monolayer square-like structures. Here, we performed classical molecular dynamics simulations to reveal monolayer square ice in graphene nanocapillaries from the perspective of structure and dynamic characteristics. Monolayer square-like ice (instantaneous snapshot), assembled square-rhombic units with stacking faults, is a long-range ordered structure, in which the square and rhombic units are assembled in an order of alternative distribution, and the other rhombic unit forms stacking faults (polarized water chains). Spontaneous flipping of water molecules in monolayer square-like ice is intrinsic and induces transformations among different elementary units, resulting in the structural evolution of monolayer square ice in dynamics. The existence of stacking faults should be attributed to the spontaneous flipping behavior of water molecules under ambient temperature. Statistical averaging results (thermal average positions) demonstrate the inherent square characteristic of monolayer square ice. The simulated data and insight obtained here might be significant for understanding the topological structure and dynamic behavior of monolayer square ice.
Structural and dynamic characteristics in monolayer square ice.
Zhu, YinBo; Wang, FengChao; Wu, HengAn
2017-07-28
When water is constrained between two sheets of graphene, it becomes an intriguing monolayer solid with a square pattern due to the ultrahigh van der Waals pressure. However, the square ice phase has become a matter of debate due to the insufficient experimental interpretation and the slightly rhomboidal feature in simulated monolayer square-like structures. Here, we performed classical molecular dynamics simulations to reveal monolayer square ice in graphene nanocapillaries from the perspective of structure and dynamic characteristics. Monolayer square-like ice (instantaneous snapshot), assembled square-rhombic units with stacking faults, is a long-range ordered structure, in which the square and rhombic units are assembled in an order of alternative distribution, and the other rhombic unit forms stacking faults (polarized water chains). Spontaneous flipping of water molecules in monolayer square-like ice is intrinsic and induces transformations among different elementary units, resulting in the structural evolution of monolayer square ice in dynamics. The existence of stacking faults should be attributed to the spontaneous flipping behavior of water molecules under ambient temperature. Statistical averaging results (thermal average positions) demonstrate the inherent square characteristic of monolayer square ice. The simulated data and insight obtained here might be significant for understanding the topological structure and dynamic behavior of monolayer square ice.
Delayed ripple counter simplifies square-root computation
NASA Technical Reports Server (NTRS)
Cliff, R.
1965-01-01
Ripple subtract technique simplifies the logic circuitry required in a binary computing device to derive the square root of a number. Successively higher numbers are subtracted from a register containing the number out of which the square root is to be extracted. The last number subtracted will be the closest integer to the square root of the number.
NASA Astrophysics Data System (ADS)
Trautman, Andrzej
2017-07-01
Historical remarks on early theoretical work on the subject. Very early on, Einstein introduced the notion of gravitational waves, but later became convinced that they did not exist as a physical phenomenon. Exact solutions of Einstein’s equations representing waves were found by a number of authors, contributing to their final acceptance as part of physics.
1989-06-15
following surprising situation. Namely associated with the integrable nonlinear Schrodinger equations are standard numerical schemes which exhibit at...36. An Initial Boundary Value Problem for the Nonlinear Schrodinger Equations , A.S. Fokas, Physica D March 1989. 37. Evolution Theory, Periodic... gravity waves and wave excitation phenomena related to moving pressure distributions; numerical approximation and computation; nonlinear optics; and
Utz, Marcel; Begley, Matthew R.; Haj-Hariri, Hossein
2012-01-01
The propagation of pressure waves in fluidic channels with elastic covers is discussed in view of applications to flow control in microfluidic devices. A theory is presented which describes pressure waves in the fluid that are coupled to bending waves in the elastic cover. At low frequencies, the lateral bending of the cover dominates over longitudinal bending, leading to propagating, non-dispersive longitudinal pressure waves in the channel. The theory addresses effects due to both the finite viscosity and compressibility of the fluid. The coupled waves propagate without dispersion, as long as the wave length is larger than the channel width. It is shown that in channels of typical microfluidic dimensions, wave velocities in the range of a few 10 m s−1 result if the channels are covered by films of a compliant material such as PDMS. The application of this principle to design microfluidic band pass filters based on standing waves is discussed. Characteristic frequencies in the range of a few kHz are readily achieved with quality factors above 30. PMID:21966667
ERIC Educational Resources Information Center
Reed, Chris
2000-01-01
Third Wave is a Christian charity based in Derby (England) that offers training in vocational skills, preindustrial crafts, horticultural and agricultural skills, environmental education, and woodland survival skills to disadvantaged people at city and farm locations. Third Wave employs a holistic approach to personal development in a community…
African Astronomy and the Square Kilometre Array
NASA Astrophysics Data System (ADS)
MacLeod, Gordon
2010-02-01
We highlight the growth of astronomy across Africa and the effect of hosting the Square Kilometer Array (SKA) will have on this growth. From the construction of a new 25m radio telescope in Nigeria, to new university astronomy programmes in Kenya, the HESS in Namibia and the Mauritian Radio Telescope, to the world class projects being developed in South Africa (Southern African Large Telescope and Karoo Array Telescope) astronomy is re-emerging across the continent. The SKA will represent the pinnacle of technological advancement in astronomy when constructed; requiring ultra high speed data transmission lines over 3000 km baselines and the World's fastest computer for correlation purposes. The investment alone to build the SKA on African soil will be of great economic benefit to its people, but the required network connectivity will significantly drive commercial expansion far beyond the initial value of the SKA investment. The most important consequence of hosting the SKA in Africa would be the impact on Human Capital Development (HCD) on the continent. Major HCD projects already underway producing excellent results will be presented. )
Review of the Generalized Least Squares Method
NASA Astrophysics Data System (ADS)
Menke, William
2014-09-01
The generalized least squares (GLS) method uses both data and prior information to solve for a best-fitting set of model parameters. We review the method and present simplified derivations of its essential formulas. Concepts of resolution and covariance—essential in all of inverse theory—are applicable to GLS, but their meaning, and especially that of resolution, must be carefully interpreted. We introduce derivations that show that the quantity being resolved is the deviation of the solution from the prior model and that the covariance of the model depends on both the uncertainty in the data and the uncertainty in the prior information. On face value, the GLS formulas for resolution and covariance seem to require matrix inverses that may be difficult to calculate for the very large (but often sparse) linear systems encountered in practical inverse problems. We demonstrate how to organize the computations in an efficient manner and present MATLAB code that implements them. Finally, we formulate the well-understood problem of interpolating data with minimum curvature splines as an inverse problem and use it to illustrate the GLS method.
Review of the Generalized Least Squares Method
NASA Astrophysics Data System (ADS)
Menke, William
2015-01-01
The generalized least squares (GLS) method uses both data and prior information to solve for a best-fitting set of model parameters. We review the method and present simplified derivations of its essential formulas. Concepts of resolution and covariance—essential in all of inverse theory—are applicable to GLS, but their meaning, and especially that of resolution, must be carefully interpreted. We introduce derivations that show that the quantity being resolved is the deviation of the solution from the prior model and that the covariance of the model depends on both the uncertainty in the data and the uncertainty in the prior information. On face value, the GLS formulas for resolution and covariance seem to require matrix inverses that may be difficult to calculate for the very large (but often sparse) linear systems encountered in practical inverse problems. We demonstrate how to organize the computations in an efficient manner and present MATLAB code that implements them. Finally, we formulate the well-understood problem of interpolating data with minimum curvature splines as an inverse problem and use it to illustrate the GLS method.
Estimating errors in least-squares fitting
NASA Technical Reports Server (NTRS)
Richter, P. H.
1995-01-01
While least-squares fitting procedures are commonly used in data analysis and are extensively discussed in the literature devoted to this subject, the proper assessment of errors resulting from such fits has received relatively little attention. The present work considers statistical errors in the fitted parameters, as well as in the values of the fitted function itself, resulting from random errors in the data. Expressions are derived for the standard error of the fit, as a function of the independent variable, for the general nonlinear and linear fitting problems. Additionally, closed-form expressions are derived for some examples commonly encountered in the scientific and engineering fields, namely ordinary polynomial and Gaussian fitting functions. These results have direct application to the assessment of the antenna gain and system temperature characteristics, in addition to a broad range of problems in data analysis. The effects of the nature of the data and the choice of fitting function on the ability to accurately model the system under study are discussed, and some general rules are deduced to assist workers intent on maximizing the amount of information obtained form a given set of measurements.
Seismic Sensor orientation by complex linear least squares
NASA Astrophysics Data System (ADS)
Grigoli, Francesco; Cesca, Simone; Krieger, Lars; Olcay, Manuel; Tassara, Carlos; Sobiesiak, Monika; Dahm, Torsten
2014-05-01
Poorly known orientation of the horizontal components of seismic sensors is a common problem that limits data analysis and interpretation for several acquisition setups, including linear arrays of geophones deployed in borehole installations, ocean bottom seismometers deployed at the sea-floor and surface seismic arrays. To solve this problem we propose an inversion method based on complex linear least squares method. Relative orientation angles, with respect to a reference sensor, are retrieved by minimizing the l2-norm between the complex traces (hodograms) of adjacent pairs of sensors in a least-squares sense. The absolute orientations are obtained in a second step by the polarization analysis of stacked seismograms of a seismic event with known location. This methodology can be applied without restrictions, if the plane wave approximation for wavefields recorded by each pair of sensors is valid. In most cases, it is possible to satisfy this condition by low-pass filtering the recorded waveform. The main advantage of our methodology is that, finding the estimation of the relative orientations of seismic sensors in complex domain is a linear inverse problem, which allows a direct solution corresponding to the global minimum of a misfit function. It is also possible to use simultaneously more than one independent dataset (e.g. using several seismic events simultaneously) to better constrain the solution of the inverse problem itself. Furthermore, by a computational point of view, our method results faster than the relative orientation methods based on waveform cross-correlation. Our methodology can be also applied for testing the correct orientation/alignment of multicomponent land stations in seismological arrays or temporary networks and for determining the absolute orientation of OBS stations and borehole arrays. We first apply our method to real data resembling two different acquisition setups: a borehole sensor array deployed in a gas field located in the
Dynamics of paramagnetic squares in uniform magnetic fields
NASA Astrophysics Data System (ADS)
Du, Di; He, Peng; Zeng, Yongchao; Biswal, Sibani Lisa
2016-11-01
The magnetic forces between paramagnetic squares cannot be calculated using a classic dipolar model because the magnetic field distribution is not uniform within square particles. Here, we present the calculation of magnetic forces and torques on paramagnetic squares in a uniform 2-D magnetic field using a Laplace's equation solver. With these calculations, we simulate the variations in equilibrium configurations as a function of number of interacting squares. For example, a single square orients with its diagonal directed to the external field while a system of multiple squares will assemble into chain-like structures with their edges directed to the external field. Unlike chains of spherical magnetic particles, that easily stagger themselves to aggregate, chains consisting of magnetic squares are unable to aggregate due to interchain repulsion.
Numerous but rare: an exploration of magic squares.
Kitajima, Akimasa; Kikuchi, Macoto
2015-01-01
How rare are magic squares? So far, the exact number of magic squares of order n is only known for n ≤ 5. For larger squares, we need statistical approaches for estimating the number. For this purpose, we formulated the problem as a combinatorial optimization problem and applied the Multicanonical Monte Carlo method (MMC), which has been developed in the field of computational statistical physics. Among all the possible arrangements of the numbers 1; 2, …, n(2) in an n × n square, the probability of finding a magic square decreases faster than the exponential of n. We estimated the number of magic squares for n ≤ 30. The number of magic squares for n = 30 was estimated to be 6.56(29) × 10(2056) and the corresponding probability is as small as 10(-212). Thus the MMC is effective for counting very rare configurations.
Numerous but Rare: An Exploration of Magic Squares
Kitajima, Akimasa; Kikuchi, Macoto
2015-01-01
How rare are magic squares? So far, the exact number of magic squares of order n is only known for n ≤ 5. For larger squares, we need statistical approaches for estimating the number. For this purpose, we formulated the problem as a combinatorial optimization problem and applied the Multicanonical Monte Carlo method (MMC), which has been developed in the field of computational statistical physics. Among all the possible arrangements of the numbers 1; 2, …, n2 in an n × n square, the probability of finding a magic square decreases faster than the exponential of n. We estimated the number of magic squares for n ≤ 30. The number of magic squares for n = 30 was estimated to be 6.56(29) × 102056 and the corresponding probability is as small as 10−212. Thus the MMC is effective for counting very rare configurations. PMID:25973764
NASA Technical Reports Server (NTRS)
Fritts, David
1987-01-01
Gravity waves contributed to the establishment of the thermal structure, small scale (80 to 100 km) fluctuations in velocity (50 to 80 m/sec) and density (20 to 30%, 0 to peak). Dominant gravity wave spectrum in the middle atmosphere: x-scale, less than 100 km; z-scale, greater than 10 km; t-scale, less than 2 hr. Theorists are beginning to understand middle atmosphere motions. There are two classes: Planetary waves and equatorial motions, gravity waves and tidal motions. The former give rise to variability at large scales, which may alter apparent mean structure. Effects include density and velocity fluctuations, induced mean motions, and stratospheric warmings which lead to the breakup of the polar vortex and cooling of the mesosphere. On this scale are also equatorial quasi-biennial and semi-annual oscillations. Gravity wave and tidal motions produce large rms fluctuations in density and velocity. The magnitude of the density fluctuations compared to the mean density is of the order of the vertical wavelength, which grows with height. Relative density fluctuations are less than, or of the order of 30% below the mesopause. Such motions may cause significant and variable convection, and wind shear. There is a strong seasonal variation in gravity wave amplitude. Additional observations are needed to address and quantify mean and fluctuation statistics of both density and mean velocity, variability of the mean and fluctuations, and to identify dominant gravity wave scales and sources as well as causes of variability, both temporal and geographic.
NASA Technical Reports Server (NTRS)
2007-01-01
With its Multispectral Visible Imaging Camera (MVIC), half of the Ralph instrument, New Horizons captured several pictures of mesoscale gravity waves in Jupiter's equatorial atmosphere. Buoyancy waves of this type are seen frequently on Earth - for example, they can be caused when air flows over a mountain and a regular cloud pattern forms downstream. In Jupiter's case there are no mountains, but if conditions in the atmosphere are just right, it is possible to form long trains of these small waves. The source of the wave excitation seems to lie deep in Jupiter's atmosphere, below the visible cloud layers at depths corresponding to pressures 10 times that at Earth's surface. The New Horizons measurements showed that the waves move about 100 meters per second faster than surrounding clouds; this is about 25% of the speed of sound on Earth and is much greater than current models of these waves predict. Scientists can 'read' the speed and patterns these waves to learn more about activity and stability in the atmospheric layers below.
NASA Technical Reports Server (NTRS)
Thompson, B. J.
1999-01-01
"Moreton waves," named for the observer who popularized them, are a solar phenomenon also known in scientific literature as "Moreton-Ramsey wave," "flare waves," "flare-associated waves," "MHD blast waves," "chromospheric shock fronts" and various other combinations of terms which connote violently propagating impulsive disturbances. It is unclear whether all of the observations to which these terms have been applied pertain to a single physical phenomenon: there has perhaps been some overlap between the observations and the assumed physical properties of the observed occurrence. Moreton waves are ideally observed in the wings of H alpha, and appear as semi-circular fronts propagating at speeds ranging from several hundred to over a thousand km/sec. They form an arc, or "brow shape" which can span up to 180 degrees. Extrapolating the speed and locations of the arc indicates that the phenomenon's origin intersects well with the impulsive phase of the associated H alpha flare (if the flare exhibits an impulsive phase). However, the arc may not form or may not be observable until it is tens of megameters from the flaring region, and subsequently can propagate to distances exceeding 100 megameters. The high speeds and distances of propagation, plus the associated radio and energetic particle observations, provided strong evidence of a coronal, rather than a chromospheric origin. The H alpha manifestation of the wave is assumed to be the "ground track" or "skirt" of a three-dimensional disturbance.
NASA Technical Reports Server (NTRS)
Poole, L. R.
1975-01-01
A study of the effects of using different methods for approximating bottom topography in a wave-refraction computer model was conducted. Approximation techniques involving quadratic least squares, cubic least squares, and constrained bicubic polynomial interpolation were compared for computed wave patterns and parameters in the region of Saco Bay, Maine. Although substantial local differences can be attributed to use of the different approximation techniques, results indicated that overall computed wave patterns and parameter distributions were quite similar.
NASA Astrophysics Data System (ADS)
Mohapatra, S. K.; Maity, K. P.
2016-02-01
The effect of various process parameters for determining extrusion load has been studied for square to square extrusion of Al-6061 alloy, a most used aluminium alloy series in forming industries. Parameters like operating temperature, friction condition, ram velocity, extrusion ratio and die length have been chosen as an input variable for the above study. Twenty five combinations of parameters were set for the investigation by considering aforementioned five parameters in five levels. The simulations have been carried out by Deform-3D software for predicting maximum load requirement for the complete extrusion process. Effective stress and strain distribution across the billet has been checked. Operating temperature, extrusion ratio, friction factor, ram velocity and die length have the significant effect in decreasing order on the maximum load requirement.
Broad-Band FMR of Patterned Square Arrays of Square Permalloy Antidots
NASA Astrophysics Data System (ADS)
Bhat, Vinayak; Sklenar, Joseph; Ketterson, John; Delong, Lance
2011-03-01
We have used electron beam lithography to pattern 25-nm-thick Permalloy films with square arrays of square antidots of size D = 300, 400, 500 and 700 nm and same lattice constant d = 1000 nm, using a lift-off technique. Broadband FMR was used to observe localized modes , showing four-fold rotational symmetry for in-plane DC magnetic field. We have studied FMR spectra spanning the ferromagnetic hysteresis regime around 250 MHz, up to the saturation regime ending near 14 GHz, and observe the appearance and disappearance of various FMR modes, especially at frequencies below 7 GHz. We have observed history-dependent modes below 3 GHz that may be associated with domain walls. UK research supported by U.S. DoE Grant No. DE-FG02-97ER45653.
NASA Astrophysics Data System (ADS)
Patel, Shobhit K.; Kosta, Y. P.
2013-11-01
A square multiband truncated microstrip patch antenna was investigated using a square-tooth split ring resonator for multiband applications in both S- and C-bands. The square-tooth split ring resonator is formed from metallic inclusions in a substrate to create a metamaterial. We introduce a new square-tooth split ring resonator which increases the radiation of the antenna as well as the bandwidth. This new design creates a slow wave structure. The square-tooth addition to the split ring resonator works like a slow wave structure. The square-tooth split ring resonator design is compared with the simple split ring resonator design. The square-tooth design has four bands with center frequencies of 3.88, 4.81, 5.4, and 5.62 GHz, whereas design with the simple split ring resonator has just three bands with center frequencies of 3.88, 4.74, and 5.50 GHz. The bandwidth is increased by 20% to 30% using the square-tooth split ring resonator compared to the simple split ring resonator.
2000-10-06
The pattern on the right half of this image of the Bay of Bengal is the result of two opposing wave trains colliding. This ASTER sub-scene, acquired on March 29, 2000, covers an area 18 kilometers (13 miles) wide and 15 kilometers (9 miles) long in three bands of the reflected visible and infrared wavelength region. The visible and near-infrared bands highlight surface waves due to specular reflection of sunlight off of the wave faces. http://photojournal.jpl.nasa.gov/catalog/PIA02662
Identification for a Nonlinear Periodic Wave Equation
Morosanu, C.; Trenchea, C.
2001-07-01
This work is concerned with an approximation process for the identification of nonlinearities in the nonlinear periodic wave equation. It is based on the least-squares approach and on a splitting method. A numerical algorithm of gradient type and the numerical implementation are given.
Stress Wave Propagation in Two-dimensional Buckyball Lattice
Xu, Jun; Zheng, Bowen
2016-01-01
Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices. PMID:27892963
Stress Wave Propagation in Two-dimensional Buckyball Lattice
NASA Astrophysics Data System (ADS)
Xu, Jun; Zheng, Bowen
2016-11-01
Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices.
Generation of microseconds-duration square pulses in a passively mode-locked fiber laser
NASA Astrophysics Data System (ADS)
Liu, Tonghui; Jia, Dongfang; Liu, Ying; Wang, Zhaoying; Yang, Tianxin
2015-12-01
An ultra-wide tunable square pulse operating in dissipative soliton resonance (DSR) region has been experimentally investigated in a passively mode-locked figure-of-eight fiber laser. In our experiment, by simply increasing the pump power, the pulse width can be tuned in an ultra-wide range from 135 ns to 2272 ns without wave-breaking while the peak power remains almost constant. The maximum output single pulse energy is 236.8 nJ at the pump power of 508 mW. A 960 m highly nonlinear fiber (HNLF) is employed to realize widely tunable square pulse in the DSR region. To the best of our knowledge, this is the widest tunable range of pulse width in any all-fiber passively mode-locked fiber laser.
Flextensional ultrasonic motor using the contour mode of a square piezoelectric plate.
Leinvuo, Joni T; Wilson, Stephen A; Whatmore, Roger W
2004-08-01
This paper presents the design, fabrication, and characterization of a new type of standing wave piezoelectric ultrasonic motor. The motor uses a metallic flextensional amplifier, or cymbal, to convert the contour mode vibrations of a square piezoelectric ceramic plate into flexural oscillations, which are further converted to produce rotary actuation by means of an elastic-fin friction drive. The motor operates on a single-phase electrical supply. A beryllium copper rotor design with three-fin configuration was adopted, and the geometry was varied to include different material thicknesses, fin lengths, and inclinations. The best stall torque and no load speed for a 25-mm square motor were 0.72 Nmm and 895 r/minute, respectively. The behavior of the stator structure was analyzed by ANSYS finite element software using harmonic and modal analyses. The vibration mode estimated by finite element modeling (FEM) was confirmed by laser Doppler vibration measurements.
Dirac-like point at the high symmetric M point in a square phononic crystal
NASA Astrophysics Data System (ADS)
Gao, Han-Feng; Zhang, Xin; Wu, Fu-Gen; Yao, Yuan-Wei; Li, Jing
2016-05-01
Using the accidental degeneracy of a doubly degenerate state and a single state, a new Dirac-like point was constructed at the high symmetric M point in a two-dimensional phononic crystal (PnC) that consists of a square array of square rods in water. When a plane wave at a frequency near the Dirac-like point impinges on the PnC slab from the left, the spatial phase experiences a minor change in the regions located near the incident interface, but this phase remains uniform in the far field. We also demonstrate two important properties that are correlated to these special field patterns: acoustic cloaking and wavefront reshaping.
NASA Astrophysics Data System (ADS)
El-Hawary, Ferial
1989-09-01
This paper treats the problem of source dynamic motion evaluation in underwater applications using recursive weighted least squares estimation. The issue of compensating for underwater motion effects arises in a number of areas of current interest such as control and operations of autonomous remotely operated vehicles, underwater seismic exploration, and buoy wave data analysis. Earlier treatments of the problem relied on frequency response methods and Kalman filtering. The present paper discusses the compensation problem using an alternative discrete model of the process and proposes use of the recursive weighted least squares algorithm for its solution. The algorithm is simpler than Kalman filtering in terms of the required knowledge of noise statistics and provides an attractive alternative to Kalman Filtering. Emphasis is given practical implementation using parallel processing and systolic array methodologies.
Sea surface mean square slope from Ku-band backscatter data
NASA Technical Reports Server (NTRS)
Jackson, F. C.; Walton, W. T.; Hines, D. E.; Walter, B. A.; Peng, C. Y.
1992-01-01
A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.
A MEMS square Chladni plate resonator
NASA Astrophysics Data System (ADS)
Pala, Sedat; Azgın, Kıvanç
2016-10-01
This paper presents the design, fabrication and tests of a micro-fabricated MEMS ‘Chladni’ plate resonator. The proposed MEMS resonator has a square plate geometry having a side length of 1400 µm and a height of 35 µm. Its geometry and electrode layout are designed to analyze and test as many modes as possible. The MEMS plate is fabricated using a silicon-on-insulator process with a 35 µm thick < \\text{1} \\text{1} \\text{1}> silicon layer on a glass substrate. Transverse vibration of the plate is investigated to obtain closed form natural frequencies and mode shapes, which are derived using the Rayleigh-Ritz energy method, with an electrostatic softening effect included. Closed form equations for the calculation of effective stiffness’, masses and natural frequencies of the two modes (mode (1,1) and mode (2,0)-(0,2)) are presented, with and without electrostatic softening. The analytical model is verified for those modes by finite-element simulations, frequency response tests in vacuum and laser Doppler vibrometer (LDV) experiments. The derived model deviates from the finite-element analysis by 3.35% for mode (1,1) and 6.15% for mode (2,0)-(0,2). For verification, the frequency responses of the plates are measured with both electrostatic excitation-detection at around 20 mTorr vacuum ambient and LDV at around 0.364 mTorr vacuum ambient. The resonance frequency and Q-factor of mode (1,1) are measured to be 104.2 kHz and 14 300, respectively. For mode (2,0)-(0,2), the measured resonance frequency and Q-factor are 156.68 kHz and 10 700, respectively. The presented LDV results also support both natural frequencies of interest and corresponding mode shapes of the plate structure.
Square Kilometre Array Science Data Processing
NASA Astrophysics Data System (ADS)
Nikolic, Bojan; SDP Consortium, SKA
2014-04-01
The Square Kilometre Array (SKA) is planned to be, by a large factor, the largest and most sensitive radio telescope ever constructed. The first phase of the telescope (SKA1), now in the design phase, will in itself represent a major leap in capabilities compared to current facilities. These advances are to a large extent being made possible by advances in available computer processing power so that that larger numbers of smaller, simpler and cheaper receptors can be used. As a result of greater reliance and demands on computing, ICT is becoming an ever more integral part of the telescope. The Science Data Processor is the part of the SKA system responsible for imaging, calibration, pulsar timing, confirmation of pulsar candidates, derivation of some further derived data products, archiving and providing the data to the users. It will accept visibilities at data rates at several TB/s and require processing power for imaging in range 100 petaFLOPS -- ~1 ExaFLOPS, putting SKA1 into the regime of exascale radio astronomy. In my talk I will present the overall SKA system requirements and how they drive these high data throughput and processing requirements. Some of the key challenges for the design of SDP are: - Identifying sufficient parallelism to utilise very large numbers of separate compute cores that will be required to provide exascale computing throughput - Managing efficiently the high internal data flow rates - A conceptual architecture and software engineering approach that will allow adaptation of the algorithms as we learn about the telescope and the atmosphere during the commissioning and operational phases - System management that will deal gracefully with (inevitably frequent) failures of individual units of the processing system In my talk I will present possible initial architectures for the SDP system that attempt to address these and other challenges.
Robust Variable Selection with Exponential Squared Loss.
Wang, Xueqin; Jiang, Yunlu; Huang, Mian; Zhang, Heping
2013-04-01
Robust variable selection procedures through penalized regression have been gaining increased attention in the literature. They can be used to perform variable selection and are expected to yield robust estimates. However, to the best of our knowledge, the robustness of those penalized regression procedures has not been well characterized. In this paper, we propose a class of penalized robust regression estimators based on exponential squared loss. The motivation for this new procedure is that it enables us to characterize its robustness that has not been done for the existing procedures, while its performance is near optimal and superior to some recently developed methods. Specifically, under defined regularity conditions, our estimators are [Formula: see text] and possess the oracle property. Importantly, we show that our estimators can achieve the highest asymptotic breakdown point of 1/2 and that their influence functions are bounded with respect to the outliers in either the response or the covariate domain. We performed simulation studies to compare our proposed method with some recent methods, using the oracle method as the benchmark. We consider common sources of influential points. Our simulation studies reveal that our proposed method performs similarly to the oracle method in terms of the model error and the positive selection rate even in the presence of influential points. In contrast, other existing procedures have a much lower non-causal selection rate. Furthermore, we re-analyze the Boston Housing Price Dataset and the Plasma Beta-Carotene Level Dataset that are commonly used examples for regression diagnostics of influential points. Our analysis unravels the discrepancies of using our robust method versus the other penalized regression method, underscoring the importance of developing and applying robust penalized regression methods.
Ha, Yong H; Han, Byung H; Lee, Soo Y
2010-02-01
We introduce a square coil system for remote magnetic navigation of a magnetic device without any physical movements of the coils. We used three square-Helmholtz coils and a square-Maxwell coil for magnetic propulsion of a small magnet along the desired path. All the square coils are mountable on a cubic frame that has an opening to accommodate a living subject. The square-Helmholtz coils control the magnetic propulsion direction by generating uniform magnetic field along the desired direction while the square-Maxwell coil controls the propulsion force by generating magnetic gradient field. We performed magnetic propulsion experiments with a down-scaled coil set and a three-channel coil driver. Experimental results demonstrate that we can use the square coil set for magnetic navigation of a magnetic device without any physical movements of the coils.
Least-squares reverse time migration in elastic media
NASA Astrophysics Data System (ADS)
Ren, Zhiming; Liu, Yang; Sen, Mrinal K.
2017-02-01
Elastic reverse time migration (RTM) can yield accurate subsurface information (e.g. PP and PS reflectivity) by imaging the multicomponent seismic data. However, the existing RTM methods are still insufficient to provide satisfactory results because of the finite recording aperture, limited bandwidth and imperfect illumination. Besides, the P- and S-wave separation and the polarity reversal correction are indispensable in conventional elastic RTM. Here, we propose an iterative elastic least-squares RTM (LSRTM) method, in which the imaging accuracy is improved gradually with iteration. We first use the Born approximation to formulate the elastic de-migration operator, and employ the Lagrange multiplier method to derive the adjoint equations and gradients with respect to reflectivity. Then, an efficient inversion workflow (only four forward computations needed in each iteration) is introduced to update the reflectivity. Synthetic and field data examples reveal that the proposed LSRTM method can obtain higher-quality images than the conventional elastic RTM. We also analyse the influence of model parametrizations and misfit functions in elastic LSRTM. We observe that Lamé parameters, velocity and impedance parametrizations have similar and plausible migration results when the structures of different models are correlated. For an uncorrelated subsurface model, velocity and impedance parametrizations produce fewer artefacts caused by parameter crosstalk than the Lamé coefficient parametrization. Correlation- and convolution-type misfit functions are effective when amplitude errors are involved and the source wavelet is unknown, respectively. Finally, we discuss the dependence of elastic LSRTM on migration velocities and its antinoise ability. Imaging results determine that the new elastic LSRTM method performs well as long as the low-frequency components of migration velocities are correct. The quality of images of elastic LSRTM degrades with increasing noise.
Least-squares reverse time migration in elastic media
NASA Astrophysics Data System (ADS)
Ren, Zhiming; Liu, Yang; Sen, Mrinal K.
2016-11-01
Elastic reverse time migration (RTM) can yield more subsurface information (e.g. PP and PS reflectivity) by imaging the multi-component seismic data. However, the existing RTM methods are still insufficient to provide satisfactory results because of the finite recording aperture, limited bandwidth and imperfect illumination. Besides, the P- and S-wave separation and the polarity reversal correction are indispensable in conventional elastic RTM. Here, we propose an iterative elastic least-squares RTM (LSRTM) method, in which the imaging accuracy is improved gradually with iteration. We first use the Born approximation to formulate the elastic de-migration operator, and employ the Lagrange multiplier method to derive the adjoint equations and gradients with respect to reflectivity. Then, an efficient inversion workflow (only four forward computations needed in each iteration) is introduced to update the reflectivity. Synthetic and field data examples reveal that the proposed LSRTM method can obtain higher-quality images than the conventional elastic RTM. We also analyze the influence of model parameterizations and misfit functions in elastic LSRTM. We observe that Lamé parameters, velocity and impedance parameterizations have similar and plausible migration results when the structures of different models are correlated. For an uncorrelated subsurface model, velocity and impedance parameterizations produce fewer artifacts caused by parameter crosstalk than the Lamé coefficient parameterization. Correlation- and convolution-type misfit functions are effective when amplitude errors are involved and the source wavelet is unknown, respectively. Finally, we discuss the dependence of elastic LSRTM on migration velocities and its anti-noise ability. Imaging results determine that the new elastic LSRTM method performs well as long as the low-frequency components of migration velocities are correct. The quality of images of elastic LSRTM degrades with increasing noise.