Square Wave

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Young-doo Yoon - One of the best experts on this subject based on the ideXlab platform.

  • sensorless control for induction machines based on Square Wave voltage injection
    IEEE Transactions on Power Electronics, 2014
    Co-Authors: Young-doo Yoon
    Abstract:

    This paper presents a sensorless control for induction machines, using Square-Wave voltage injection. Multiple saliencies are considered, as well as saliency orientation shift according to loading conditions. These two nonideal phenomena severely degrade the performance of sensorless controls for induction machines. Multiple saliencies cause the position error signal to become distorted and make estimation of the rotor flux position difficult. Saliency orientation shift causes the estimated rotor flux position to drift from the actual rotor flux position, depending on the torque and speed. In this study, a sensorless algorithm based on Square-Wave voltage injection is adopted for induction machine control. When Square-Wave voltage is injected into the estimated synchronous reference frame, the harmonics of the error signal are lower than those of the conventional sinusoidal injection method. In addition, by injecting a Square Wave into the q-axis of the estimated synchronous reference frame instead of the d-axis, the saliency orientation shift is made smaller. Based on this study using Square-Wave voltage injection into the q-axis, the flux can be estimated with less error. Because of its enhanced rotor flux estimation performance, the proposed method provides better torque controllability than the conventional sinusoidal voltage injection method. Experimental results confirm the effectiveness of the proposed technique.

  • Sensorless control for induction machines using Square-Wave voltage injection
    2010 IEEE Energy Conversion Congress and Exposition, 2010
    Co-Authors: Young-doo Yoon
    Abstract:

    This paper presents a sensorless control for induction machines using a Square-Wave voltage injection. Multiple saliencies and a saliency orientation shift are considered in this paper. The multiple saliencies make the position error signal distorted and the estimation of the flux position difficult. And, due to the saliency orientation shift, the estimated rotor flux position drifts from the actual rotor flux position according to torque and speed. When the Square-Wave voltage is injected into the estimated synchronous reference d-q frame, the error signal has lower harmonics than that of the conventional sinusoidal injection method. In addition, by injecting the Square-Wave into q axis of the estimated synchronous reference frame, the flux can be estimated with less error compared to the injection into d axis. Because of the enhanced rotor flux estimation performance, the Square Wave injection into q axis reveals better torque controllability compared to the sine Wave injection into d axis.

S Balle - One of the best experts on this subject based on the ideXlab platform.

  • Square-Wave emission in vertical-cavity surface-emitting lasers
    2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE IQEC, 2013
    Co-Authors: M. Marconi, J. Javaloyes, S Barland, M Giudici, S Balle
    Abstract:

    This contribution numerically and experimentally illustrates how regular and robust Square Wave emission can be obtained in Vertical Cavity Surface Emitting Lasers (VCSELs) using the polarisation degrees of freedom of these devices. The scheme propose is based on crossed-polarization re-injection (XPR). In such scheme, the emission from the laser is split into its two linearly polarized components, LP-x and LP-y, and only one of these components (LP-x, say) is fed back into the laser after being rotated into the orthogonal polarization direction (LP-y). In this way, cross-saturation of the polarization states modifies the photon density in each LP component and may eventually lead to Square-Wave modulation of the power emitted in each of the LP components with a period close to 2τr. When the dichroism in the device is strong enough and the emission occurs on a single polarization mode, XPR above a critical level leads to Square-Wave modulation which is stable over large ranges of bias currents. The emission dynamics for different levels and delays of XPR and PSF (polarization-selective optical feedback) were experimentally characterized. An asymmetry in the effects of PSF for the two polarizations is found. The experimental observations are satisfactorily explained within the Spin-Flip Model supplemented with appropriate terms describing XPR and PSF.

  • robust Square Wave polarization switching in vertical cavity surface emitting lasers
    Physical Review A, 2013
    Co-Authors: Mathias Marconi, J. Javaloyes, S Barland, M Giudici, S Balle
    Abstract:

    We study theoretically and experimentally the combined effects of polarization-selective optical feedback and of crossed-polarization reinjection in a vertical-cavity surface-emitting laser. We show that the application of polarization-selective optical feedback, which induces an effective dichroism in the system, allows one to generate a robust and regular Square-Wave output signal in each polarization component. The period of the Square-Wave signal is determined by twice the reinjection delay. We analyze the regularity of the induced modulation as a function of laser bias current, dichroism, and of the levels and delays of reinjection and feedback, thus revealing the robustness of the Square-Wave emission in the parameter space. We also show that the feedback is more effective when acting on the long-Wavelength polarization mode, which can be traced to the asymmetry of the bistable region of the vertical-cavity surface-emitting lasers for low dichroism.

Gregorio Castañeda - One of the best experts on this subject based on the ideXlab platform.

  • Voltammetric determination of Imatinib (Gleevec) and its main metabolite using Square-Wave and adsorptive stripping Square-Wave techniques in urine samples.
    Talanta, 2004
    Co-Authors: Juana Rodríguez, J.j. Berzas, Gregorio Castañeda, Noel Rodriguez
    Abstract:

    Abstract The voltammetric behaviour of Imatinib (STI 571) and its main metabolite (N-demethylated piperazine derivative) were studied by Square-Wave techniques, resulting in to two methods for their determination in aqueous and urine samples at pH 2. The application of the Square-Wave (SW) without the adsorptive accumulation and voltammetric stripping (AdSV) exhibit a peak at a reduction potential of −0.70 V for an accumulation potential of −0.45 V. The sensitivity was higher for the stripping technique because a signal four times higher than that provided by the Square-Wave method without the previous accumulation was obtained. Due to the fact that Imatinib and its metabolite show the same voltammetric reduction process, some experiments were performed in order to compare the voltammetric response of Imatinib and its main metabolite in a similar ratio than that of the therapeutic concentration. The calibration curve for Imatinib in urine was linear in the range from 1.9 × 10−8 to 1.9 × 10−6 M in stripping mode with an accumulation time (tacc) of 10 s. The relative standard deviations obtained for concentration levels of Imatinib as low as 2.0 × 10−7 M for Square-Wave was 2.17% (n = 9) and for stripping Square-Wave was 2.65% (n = 9) in the same day. The limits of detection for Square-Wave and stripping Square-Wave were 5.55 × 10−9 and 5.19 × 10−9 M, respectively. Thus, the presented method are straightforward, rapid and sensitive and has been applied to the determination of Imatinib and its main metabolite altogether in urine samples from real patients.

  • Voltammetric behavior of sildenafil citrate (Viagra) using Square Wave and adsorptive stripping Square Wave techniques: Determination in pharmaceutical products
    Analytica Chimica Acta, 2000
    Co-Authors: J.j. Berzas, Juana Rodríguez, Gregorio Castañeda, M.j. Villaseñor
    Abstract:

    Abstract The behavior of sildenafil citrate (SC) was studied by Square Wave technique, leading to two methods for its determination in aqueous samples (pH 2.0) and pharmaceutical formulations. The application of the Square Wave (SW) without the adsorptive accumulation shows the maximum response at –1.03 V. Besides, SC gave two adsorptive stripping voltammetric (AdSV) peaks at –1.03 and −1.15 V using an accumulation potential of −0.80 V. The effect of experimental parameters that affect this determination are discussed. For the stripping technique, SC proved to be more sensitive, yielding signals three or four times larger than those obtained by applying a Square Wave scan without the previous accumulation. The calibration graph to determine SC was linear in the range 5×10 −9 to 9×10 −7  M by stripping mode with a time of accumulation t acc of 10 s. The relative standard deviations obtained for concentration levels of SC as low as 1.0×10 −7  M with Square Wave was 2.5% ( n =10) and for 1.0×10 −7  M with stripping Square Wave was 3.1% ( n =10) in the same day. The two proposed methods (SW and SWAdSV) were applied to the determination of SC in three pharmaceutical products (Viagra 25, Viagra 50 and Viagra 100) with very good recoveries with respect to the labelled values.

  • Voltammetric behavior of sulfadimetoxol using SquareWave and adsorptive stripping SquareWave techniques
    Electroanalysis, 1997
    Co-Authors: J.j. Berzas, Juana Rodríguez, José M. Lemus, Gregorio Castañeda
    Abstract:

    The voltammetric behavior of sulfadimetoxol (SDX) was studied by Square-Wave techniques, leading to two methods for its determination in aqueous samples and veterinary formulations. The application of the Square-Wave mode shows the determination of SDX between 1 × 10−7 M and 2 × 10−6 M at −0.60 V and for the stripping voltammetry of adsorbed SDX with an accumulation step of 15 s proved to be more sensitive, yielding signals five times larger than those obtained without the accumulation. The determination of SDX was done between 2 × 10−8 M and 5 × 10−7 M by stripping mode. The relative standard deviations obtained for concentration levels of SDX as low as 3 × 10−7 M with Square-Wave was 3.4 % (n = 8) and for 2 × 10−7 M with stripping Square-Wave was 3.1 % (n = 8). The methods were satisfactorily applied for determining SDX in four veterinary products.

  • Voltammetric behavior of pyrimethamine in veterinary formulations using SquareWave and adsorptive SquareWave techniques
    Electroanalysis, 1995
    Co-Authors: J.j. Berzas, Juana Rodríguez, José M. Lemus, Gregorio Castañeda
    Abstract:

    The voltammetric behavior of pyrimethamine (PMT) was studied by Square-Wave (SW) and Square-Wave stripping (SWS) techniques, leading to two methods for its determination [in presence of sulfaquinoxaline (SQX)] in aqueous samples and veterinary formulations. Due to overlapping response of SQX and PMT the first derivative was used for the simultaneous determination of these two components. The relative standard deviations obtained for concentration levels of PMT as low as 3 × 10−6 M (SW) and 5 × 10−7 M (SWS) were 2.2% and 2.7% (n = 10), respectively.

J.j. Berzas - One of the best experts on this subject based on the ideXlab platform.

  • Voltammetric determination of Imatinib (Gleevec) and its main metabolite using Square-Wave and adsorptive stripping Square-Wave techniques in urine samples.
    Talanta, 2004
    Co-Authors: Juana Rodríguez, J.j. Berzas, Gregorio Castañeda, Noel Rodriguez
    Abstract:

    Abstract The voltammetric behaviour of Imatinib (STI 571) and its main metabolite (N-demethylated piperazine derivative) were studied by Square-Wave techniques, resulting in to two methods for their determination in aqueous and urine samples at pH 2. The application of the Square-Wave (SW) without the adsorptive accumulation and voltammetric stripping (AdSV) exhibit a peak at a reduction potential of −0.70 V for an accumulation potential of −0.45 V. The sensitivity was higher for the stripping technique because a signal four times higher than that provided by the Square-Wave method without the previous accumulation was obtained. Due to the fact that Imatinib and its metabolite show the same voltammetric reduction process, some experiments were performed in order to compare the voltammetric response of Imatinib and its main metabolite in a similar ratio than that of the therapeutic concentration. The calibration curve for Imatinib in urine was linear in the range from 1.9 × 10−8 to 1.9 × 10−6 M in stripping mode with an accumulation time (tacc) of 10 s. The relative standard deviations obtained for concentration levels of Imatinib as low as 2.0 × 10−7 M for Square-Wave was 2.17% (n = 9) and for stripping Square-Wave was 2.65% (n = 9) in the same day. The limits of detection for Square-Wave and stripping Square-Wave were 5.55 × 10−9 and 5.19 × 10−9 M, respectively. Thus, the presented method are straightforward, rapid and sensitive and has been applied to the determination of Imatinib and its main metabolite altogether in urine samples from real patients.

  • Voltammetric behavior of sildenafil citrate (Viagra) using Square Wave and adsorptive stripping Square Wave techniques: Determination in pharmaceutical products
    Analytica Chimica Acta, 2000
    Co-Authors: J.j. Berzas, Juana Rodríguez, Gregorio Castañeda, M.j. Villaseñor
    Abstract:

    Abstract The behavior of sildenafil citrate (SC) was studied by Square Wave technique, leading to two methods for its determination in aqueous samples (pH 2.0) and pharmaceutical formulations. The application of the Square Wave (SW) without the adsorptive accumulation shows the maximum response at –1.03 V. Besides, SC gave two adsorptive stripping voltammetric (AdSV) peaks at –1.03 and −1.15 V using an accumulation potential of −0.80 V. The effect of experimental parameters that affect this determination are discussed. For the stripping technique, SC proved to be more sensitive, yielding signals three or four times larger than those obtained by applying a Square Wave scan without the previous accumulation. The calibration graph to determine SC was linear in the range 5×10 −9 to 9×10 −7  M by stripping mode with a time of accumulation t acc of 10 s. The relative standard deviations obtained for concentration levels of SC as low as 1.0×10 −7  M with Square Wave was 2.5% ( n =10) and for 1.0×10 −7  M with stripping Square Wave was 3.1% ( n =10) in the same day. The two proposed methods (SW and SWAdSV) were applied to the determination of SC in three pharmaceutical products (Viagra 25, Viagra 50 and Viagra 100) with very good recoveries with respect to the labelled values.

  • Voltammetric behavior of sulfadimetoxol using SquareWave and adsorptive stripping SquareWave techniques
    Electroanalysis, 1997
    Co-Authors: J.j. Berzas, Juana Rodríguez, José M. Lemus, Gregorio Castañeda
    Abstract:

    The voltammetric behavior of sulfadimetoxol (SDX) was studied by Square-Wave techniques, leading to two methods for its determination in aqueous samples and veterinary formulations. The application of the Square-Wave mode shows the determination of SDX between 1 × 10−7 M and 2 × 10−6 M at −0.60 V and for the stripping voltammetry of adsorbed SDX with an accumulation step of 15 s proved to be more sensitive, yielding signals five times larger than those obtained without the accumulation. The determination of SDX was done between 2 × 10−8 M and 5 × 10−7 M by stripping mode. The relative standard deviations obtained for concentration levels of SDX as low as 3 × 10−7 M with Square-Wave was 3.4 % (n = 8) and for 2 × 10−7 M with stripping Square-Wave was 3.1 % (n = 8). The methods were satisfactorily applied for determining SDX in four veterinary products.

  • Voltammetric behavior of pyrimethamine in veterinary formulations using SquareWave and adsorptive SquareWave techniques
    Electroanalysis, 1995
    Co-Authors: J.j. Berzas, Juana Rodríguez, José M. Lemus, Gregorio Castañeda
    Abstract:

    The voltammetric behavior of pyrimethamine (PMT) was studied by Square-Wave (SW) and Square-Wave stripping (SWS) techniques, leading to two methods for its determination [in presence of sulfaquinoxaline (SQX)] in aqueous samples and veterinary formulations. Due to overlapping response of SQX and PMT the first derivative was used for the simultaneous determination of these two components. The relative standard deviations obtained for concentration levels of PMT as low as 3 × 10−6 M (SW) and 5 × 10−7 M (SWS) were 2.2% and 2.7% (n = 10), respectively.

Rubin Gulaboski - One of the best experts on this subject based on the ideXlab platform.

  • Square-Wave voltammetry of Ofloxacin
    2020
    Co-Authors: Rubin Gulaboski, Blagoja Jordanoski
    Abstract:

    Adsorption phenomena of ofloxacin at a hanging mercury drop electrode in Britton Robinson buffer solution with pH of 8.36 were studied by means of Square-Wave voltammetry.

  • Differential Square-Wave Voltammetry.
    Analytical Chemistry, 2019
    Co-Authors: Valentin Mirčeski, Leon Stojanov, Dariusz Guziejewski, Rubin Gulaboski
    Abstract:

    A new voltammetric technique designed as a hybrid between differential pulse and Square-Wave voltammetry is proposed for the purpose of unifying the advantages of both techniques, i.e., the ability to provide mechanistic information, studying electrode kinetics of both sluggish and very fast electrode reactions, and the ability to suppress effectively residual background current. Voltammetric modulation of the hybrid technique consists of a staircase potential combined with Square-Wave potential modulation superimposed at the end of each potential step. By measuring the current at the end of each potential step and pulse, differential forward and backward voltammetric components can be composed, which is a unique ability of the hybrid technique. In addition, by analogy to Square-Wave voltammetry, a net differential component can be contracted with improved analytical performances compared to Square-Wave voltammetry. The proposed technique opens a new avenue for an advanced analysis of electrochemical proc...

  • RECENT ACHIEVEMENTS IN Square-Wave VOLTAMMETRY (A REVIEW)
    Macedonian Journal of Chemistry and Chemical Engineering, 2014
    Co-Authors: Valentin Mirčeski, Rubin Gulaboski
    Abstract:

    Recent advances in Square-Wave voltammetry for analytical purposes as well as for studying electrode mechanisms and kinetics are reviewed, mainly covering results published in the last decade. Analyzing only some typical analytically oriented studies, one confirms the well-known fact that the technique is attributed with superior analytical performance in the family of advance pulse voltammetric techniques. Covering all analytical studies where Square-Wave voltammetry is the working technique is hardly possible. For this reason, we decided to cover the relevant studies in Square-Wave voltammetry, mainly published in the last five to seven years. The reviewed period is marked with remarkable contributions in the theory of complex electrode mechanisms, revealing that Square-Wave voltammetry is one of the most powerful voltammetric techniques for both mechanistic and kinetic characterizations of electrode processes. Finally, a brief consideration is given to several methodologically oriented studies, referring mainly to cyclic-Square voltammetry as well as methods based on the analysis of electrode processes by varying the amplitude of the potential modulation, which is expected to expand the scope and application of the technique in coming years.

  • Square-Wave Voltammetric Determination of Sulpiride
    Portugaliae Electrochimica Acta, 1999
    Co-Authors: Blagoja Jordanoski, Valentin Mirčeski, Rubin Gulaboski
    Abstract:

    The basic redox properties of sulpiride are investigated by means of cyclic voltammetry and Square-Wave voltammetryat a hanging mercury drop electrode. Sulpiride undergoes electrochemical reaction in basic media. The voltammetric response of sulpiride strongly depends on pH of the medium. A Square-Wave method for quantitative determination of sukpiride was developed.

  • Adsorptive Stripping Square-Wave Voltammetry of Creatine
    Analytical Letters, 1999
    Co-Authors: Kornelija Stojanova, Rubin Gulaboski, Valentin Mirečeski, Simka Petrovska-jovanović
    Abstract:

    ABSTRACT An adsorptive stripping Square-Wave voltammetric method for quantitative determination of creatine is developed. The basic redox properties of creatine are investigated by means of Square-Wave and cyclic staircase voltammetry. Creatine undergoes an irreversible reduction in neutral and acidic medium at a hanging mercury drop electrode. The Square-Wave voltammetric response of creatine depends on the parameters of the SW excitation signal as well as on the concentration and type of the supporting electrolyte, the accumulation time and the potential and pH of the medium. The optimal experimental conditions for quantitative determination of creatine are as follows: supporting electrolyte 0.1 mol/L KNO3 buffered with 0.1 mol/L acetate buffer to pH = 4 and accumulation potential -1.2 V. The optimal SW parameters found are: frequency f = 120 Hz, amplitude E sw = 30 mV, and scan increment dE = 4 mV. A detection limit of 6.6 x 10−8 mol/L creatine was obtained after 30 s preconcentration period at accumul...