The Experts below are selected from a list of 4974 Experts worldwide ranked by ideXlab platform
Tsuyoshi Ide - One of the best experts on this subject based on the ideXlab platform.
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Why Does Subsequence Time-Series Clustering Produce Sine Waves?
Control, 2006Co-Authors: Tsuyoshi IdeAbstract:The data mining and machine learning communities were surprised when\nKeogh et al. (2003) pointed out that the k-means cluster centers\nin subsequence time-series clustering become sinusoidal pseudo-patterns\nfor almost all kinds of input time-series data. Understanding this\nmechanism is an important open problem in data mining. Our new theoretical\napproach (based on spectral clustering and translational symmetry)\nexplains why the cluster centers of k-means naturally tend to form\nsinusoidal patterns.
Alan R Hemsley - One of the best experts on this subject based on the ideXlab platform.
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long period orbital climate forcing in the early palaeozoic
Journal of the Geological Society, 2013Co-Authors: Lesley Cherns, James R Wheeley, Ghobadi M Pour, Robert M. Owens, Leonid E Popov, Alan R HemsleyAbstract:Facies indicators and geochemical proxies of early Palaeozoic global climate cooling suggest episodes of fluctuating glacio-eustasy and severe cold or glaciation from the Mid–Late Cambrian to Silurian (c. 85 myr), with a mean frequency of 2.6 myr. Long-period orbital time series predicted through the Phanerozoic are used to generate Sine Waves to test against these data; the null hypothesis of no orbital influence is rejected with a high confidence level. Cooling episodes appear most frequent through the Late Ordovician leading up to the Hirnantian glacial maximum, but even ‘greenhouse’ intervals of the Early–Mid-Ordovician and early Silurian provide evidence for periodic cooling episodes.
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long period orbital climate forcing in the early palaeozoic
Journal of the Geological Society, 2013Co-Authors: Lesley Cherns, James R Wheeley, Ghobadi M Pour, Robert M. Owens, Leonid E Popov, Alan R HemsleyAbstract:Facies indicators and geochemical proxies of early Palaeozoic global climate cooling suggest episodes of fluctuating glacio-eustasy and severe cold or glaciation from the Mid–Late Cambrian to Silurian (c. 85 myr), with a mean frequency of 2.6 myr. Long-period orbital time series predicted through the Phanerozoic are used to generate Sine Waves to test against these data; the null hypothesis of no orbital influence is rejected with a high confidence level. Cooling episodes appear most frequent through the Late Ordovician leading up to the Hirnantian glacial maximum, but even ‘greenhouse’ intervals of the Early–Mid-Ordovician and early Silurian provide evidence for periodic cooling episodes.
Paul D Dresselhaus - One of the best experts on this subject based on the ideXlab platform.
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differential sampling measurement of a 7 v rms Sine wave with a programmable josephson voltage standard
IEEE Transactions on Instrumentation and Measurement, 2013Co-Authors: Alain Rufenacht, Paul D Dresselhaus, Charles J Burroughs, Samuel P BenzAbstract:A 10 V programmable Josephson voltage standard has enabled Sine Waves with voltages up to 7 V RMS to be accurately measured with a differential sampling measurement technique. Expanding the voltage range for this technique enables the direct calibration of the low-frequency ranges of commercial calibrators in the ac voltage mode. This paper reviews the practically achievable performance and challenges of the differential sampling measurement technique that arise when measuring RMS voltages greater than a few volts. A relative Type A uncertainty of 4 parts in $10^{7}$ was achieved with the technique when measuring a 7 V RMS Sine wave generated by a calibrator at 62.5 Hz.
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precision differential sampling measurements of low frequency synthesized Sine Waves with an ac programmable josephson voltage standard
IEEE Transactions on Instrumentation and Measurement, 2009Co-Authors: Alai Rufenach, Charles J Urroughs, Samuel P Enz, Paul D Dresselhaus, C Waltrip, T L NelsoAbstract:We have developed a precision technique to measure Sine-wave sources with the use of a quantum-accurate AC programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) Sine-wave voltages. We have performed a variety of measurements to evaluate this differential technique. After averaging, the uncertainty obtained in the determination of the amplitude of a 1.2 V Sine wave at 50 Hz is 0.3 muV/V (type A). Finally, we propose a dual-waveform approach for measuring two precision Sine Waves with the use of a single Josephson system. Currently, the National Institute of Standards and Technology (NIST) is developing a new calibration system for electrical power measurements based on this technique.
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precision differential sampling measurements of low frequency voltages synthesized with an ac programmable josephson voltage standard
Conference on Precision Electromagnetic Measurements, 2008Co-Authors: Alai Rufenach, Charles J Urroughs, Samuel P Enz, Paul D Dresselhaus, C Waltrip, T L NelsoAbstract:Sampling is a promising technique for comparing the stepwise-approximated Sine Waves synthesized by an AC Programmable Josephson Voltage Standard to the sinusoidal voltages of a secondary source at low frequencies (a few hundred hertz or less). This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high purity Sine wave voltages by comparing them to quantum-accurate waveforms.
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systematic error analysis of stepwise approximated ac waveforms generated by a programmable josephson voltage standard
Conference on Precision Electromagnetic Measurements, 2008Co-Authors: Charles J Burroughs, Alain Rufenacht, Samuel P Benz, Paul D DresselhausAbstract:We have measured stepwise-approximated Sine Waves generated by a programmable Josephson voltage standard (PJVS) with several different output configurations. These data are analyzed to characterize the dominant error mechanisms for RMS applications, such as AC-DC difference measurements of thermal voltage converters (TVCs). We present detailed explanations of the fundamental causes and consequences of systematic errors that arise from transitions and consider the overall uncertainties for PJVS ac metrology using this synthesis method. We show that timing-related errors are sufficient to make this waveform synthesis approach impractical for RMS audio-frequency applications. The implications of providing the load current required by devices of low input impedance, such as TVCs, are also discussed.
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error and transient analysis of stepwise approximated Sine Waves generated by programmable josephson voltage standards
IEEE Transactions on Instrumentation and Measurement, 2008Co-Authors: Charles J Burroughs, Paul D Dresselhaus, Alain Rufenacht, Samuel P Benz, B C Waltrip, T L NelsonAbstract:We are developing a quantum-based 60 Hz power standard that exploits the precision sinusoidal reference voltages synthesized by a programmable Josephson voltage standard (PJVS). PJVS systems use series arrays of Josephson junctions as a multibit digital-to-analog converter to produce accurate quantum-based dc voltages. Using stepwise-approximation synthesis, the system can also generate arbitrary ac waveforms [i.e., an ac programmable Josephson voltage standard (ACPJVS)] and, in this application, produces Sine Waves with calculable root mean square (rms) voltage and spectral content. The primary drawback to this ACPJVS synthesis technique is the uncertainty that results from switching between the discrete voltages due to finite rise times and transient signals. In this paper, we present measurements and simulations that elucidate some of the error sources that are intrinsic to the ACPJVS when used for rms measurements. In particular, we consider Sine Waves synthesized at frequencies up to the audio range, where the effect of these errors is more easily measured because the fixed transition time becomes a greater fraction of the time in each quantized voltage state. Our goal for the power standard is to reduce all error sources and uncertainty contributions from the PJVS-synthesized waveforms at 60 Hz to a few parts in 107 so that the overall uncertainty in an ac power standard will be a few parts in 106.
Arye Nehorai - One of the best experts on this subject based on the ideXlab platform.
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newton algorithms for conditional and unconditional maximum likelihood estimation of the parameters of exponential signals in noise
IEEE Transactions on Signal Processing, 1992Co-Authors: David Starer, Arye NehoraiAbstract:The authors present polynomial-based Newton algorithms for maximum likelihood estimation (MLE) of the parameters of multiple exponential signals in noise. This formulation can be used in the estimation, for example, of the directions of arrival of multiple noise-corrupted narrowband plane Waves using uniform linear arrays and the frequencies of multiple noise-corrupted complex Sine Waves. The algorithms offer rapid convergence and exhibit the computation efficiency associated with the polynomial approach. Compact, closed-form expressions are presented for the gradients and Hessians. Various model assumptions concerning the statistics of the underlying signals are considered. Numerical simulations are presented to demonstrate the algorithms' performance. >
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asymptotic cramer rao bounds for estimation of the parameters of damped Sine Waves in noise
IEEE Transactions on Signal Processing, 1991Co-Authors: Torbjorn Wigren, Arye NehoraiAbstract:The problem of estimating the parameters of a signal composed of several damped Sine Waves in noise has applications, for example, in transient signal analysis. Explicit, closed-form expressions are derived for the Cramer-Rao bound of this problem in the case of low damping, low spectral interference between the signal components, and a sufficiently large number of samples. Among several conclusions which are drawn from the expressions, it is found that the estimation problem is much more sensitive to errors in the damping factor and frequency than to errors in amplitude and phase. >
R L Geiger - One of the best experts on this subject based on the ideXlab platform.
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low distortion Sine wave generation using a novel harmonic cancellation technique
IEEE Transactions on Circuits and Systems, 2013Co-Authors: Bharath K Vasan, Siva Kumar Sudani, Degang J Chen, R L GeigerAbstract:A novel technique is proposed to generate robust, low distortion Sine Waves. In this method, outputs of a phase shift oscillator (PSO) are weighted and summed to obtain multiple outputs with very low distortion and precise phase relationship. The method allows a programmable number of harmonic distortion components to be cancelled over a wide frequency range. This work derives the condition for the weights on the outputs of the PSO to be a real quantity, and demonstrates how this can be used to generate low distortion Sine Waves. With the proposed method, in an N-stage PSO, harmonics up to N-2th can be canceled. Simulation results using commercial operational amplifier spice models are presented to demonstrate low distortion Sine wave generation over 2 kHz-180 kHz frequency range. The method has been experimentally verified using extremely low-cost, discrete components to produce 100 dB total harmonic distortion (THD) Sine wave.
