A Fast Spectrum-Recovery Method for Hadamard Transform Spectrometers Having Nonideal Masks

1989 ◽  
Vol 43 (3) ◽  
pp. 435-440 ◽  
Author(s):  
S. A. Dyer ◽  
B. K. Harms ◽  
J. B. Park ◽  
T. W. Johnson ◽  
R. A. Dyer
Keyword(s):  
Point Spectrum ◽  
Hadamard Transform ◽  
Arithmetic Operations ◽  
Inexpensive Method ◽  
Recovery Method ◽  
Conventional Procedure ◽  
Preliminary Work ◽  
Spectrum Recovery

A computationally inexpensive method is presented for the recovery of spectra from measurements obtained with Hadamard transform spectrometers having nonideal masks. Normally, N measurements are required in order to recover an N-point spectrum; this method requires N + N0 measurements to be taken, where, typically, N0 ≤ 10. Once the additional measurements have been taken, only O( N[log2 N + 2]) arithmetic operations—mostly additions or subtractions—are needed in order to recover the spectrum; a conventional procedure requires O(2 N2) operations. Preliminary work for this method is minimal, requiring O( N) operations as opposed to O( N3) for a conventional procedure; this work needs to be done only once for a given spectrometer. The spectrum-estimate obtained is unbiased.

An Efficient Method for Recovering the Optimal Unbiased Linear Spectrum-Estimate from Hadamard Transform Spectrometers Having Nonideal Masks

1989 ◽  
Vol 43 (5) ◽  
pp. 746-750 ◽  
Author(s):  
T. W. Johnson ◽  
J. B. Park ◽  
S. A. Dyer ◽  
B. K. Harms ◽  
R. A. Dyer
Keyword(s):  
Spectral Resolution ◽  
Efficient Method ◽  
Hadamard Transform ◽  
Computationally Efficient ◽  
Arithmetic Operations ◽  
Recovery Method ◽  
Linear Spectrum ◽  
Recovery Techniques ◽  
Spectrum Recovery ◽  
Conventional Methods

A spectrum-recovery method is presented which efficiently computes an optimal unbiased linear spectrum-estimate for measurements obtained with Hadamard transform (HT) spectrometers having nonideal masks. This method has the following advantages over other spectrum-recovery techniques: it is computationally efficient, it requires no additional measurements, and it computes an optimal spectrum-estimate. In the method presented, after the mask of the HT spectrometer has been characterized, approximately 3 N preliminary arithmetic operations are performed once for a given spectrometer, where N is both the number of spectral resolution-elements desired and the number of measurements required. Each spectrum-estimate to be recovered then requires only an additional O[ N(log2 N + 4)] arithmetic operations. In contrast, conventional methods for obtaining an optimal unbiased linear spectrum-estimate require O( N3) preliminary operations, and O(2 N2) operations during each spectrum-recovery.

Spectrum Recovery Method for Hyperspectral Imaging Based on Symmetric Wedgy Interferometric Cavity

2016 ◽  
Vol 36 (2) ◽  
pp. 0230004
Author(s):  
柏财勋 Bai Caixun ◽  
李建欣 Li Jianxin ◽  
孟鑫 Meng Xin ◽  
周建强 Zhou Jianqiang ◽  
沈燕 Shen Yan ◽  
...  
Keyword(s):  
Hyperspectral Imaging ◽  
Recovery Method ◽  
Spectrum Recovery

On the Mean-Square Error of Various Spectrum-Recovery Techniques in Hadamard Transform Spectrometry

1990 ◽  
Vol 44 (2) ◽  
pp. 219-228 ◽  
Author(s):  
J. B. Park ◽  
T. W. Johnson ◽  
S. A. Dyer ◽  
B. K. Harms ◽  
R. A. Dyer
Keyword(s):  
Mean Square Error ◽  
Hadamard Transform ◽  
Mean Square ◽  
Recovery Techniques ◽  
Spectrum Recovery ◽  
The Mean

On the Use of Fast Hadamard Transforms for Spectrum Recovery in Hadamard Transform Spectroscopy

1992 ◽  
Vol 46 (9) ◽  
pp. 1358-1361 ◽  
Author(s):  
B. K. Harms ◽  
J. B. Park ◽  
S. A. Dyer
Keyword(s):  
Equivalence Class ◽  
Efficient Method ◽  
Hadamard Matrix ◽  
Hadamard Matrices ◽  
Hadamard Transform ◽  
Spectrum Recovery ◽  
Hadamard Transforms ◽  
Permutation Scheme

The spectrum-recovery step in Hadamard transform spectroscopy is commonly implemented with a fast Hadamard transform (FHT). When the Hadamard or simplex matrix corresponding to the mask does not have the same ordering as the Hadamard matrix corresponding to the FHT, a modification is required. When the two Hadamard matrices are in the same equivalence class, this modification can be implemented as a permutation scheme. This paper investigates permutation schemes for this application. The investigation clarifies inaccurate claims about the applicability of existing methods; reveals a new, more efficient method; and leads to an extension that allows a permutation scheme to be applied to any Hadamard or simplex matrix in the appropriate equivalence class.

TEM study of very thin InGaAsP layers grown by liquid-phase epitaxy

1990 ◽  
Vol 48 (4) ◽  
pp. 672-673
Author(s):  
N.A. Bert ◽  
A.O. Kosogov
Keyword(s):  
Liquid Phase ◽  
Liquid Phase Epitaxy ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Dark Field ◽  
Organic Chemical ◽  
Simple Liquid ◽  
Cross Sectional ◽  
Conventional Procedure ◽  
Double Heterostructures

The very thin (<100 Å) InGaAsP layers were grown not only by molecular beam epitaxy and metal-organic chemical vapor deposition but recently also by simple liquid phase epitaxy (LPE) technique. Characterization of their thickness, interfase abruptness and lattice defects is important and requires TEM methods to be used.The samples were InGaAsP/InGaP double heterostructures grown on (111)A GaAs substrate. The exact growth conditions are described in Ref.1. The salient points are that the quarternary layers were being grown at 750°C during a fast movement of substrate and a convection caused in the melt by that movement was eliminated. TEM cross-section specimens were prepared by means of conventional procedure. The studies were conducted in EM 420T and JEM 4000EX instruments.The (200) dark-field cross-sectional imaging is the most appropriate TEM technique to distinguish between individual layers in 111-v semiconductor heterostructures.

Conscious and Unconscious Reward Cues Can Affect a Critical Component of Executive Control

2011 ◽  
Vol 58 (5) ◽  
pp. 370-375 ◽  
Author(s):  
Rémi L. Capa ◽  
Gaëlle M. Bustin ◽  
Axel Cleeremans ◽  
Michel Hansenne
Keyword(s):  
Correct Response ◽  
Executive Control ◽  
Critical Component ◽  
Arithmetic Operations ◽  
Component Process

The present study investigates whether updating an important function of executive control can be driven by unconscious reward cues. Participants had to memorize several numbers and update those numbers independently according to a sequence of arithmetic operations. At the beginning of each trial, a reward (1 euro or 5 cents) was presented, either subliminally or supraliminally. Participants could earn the reward if they found the correct response on the updating task. Results showed better performance when a high (conscious or unconscious) reward was at stake compared to a low reward. This suggests that subliminal information can influence a component process of executive control traditionally thought to require consciousness.

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