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1

Generic quantum Fourier transforms  

Microsoft Academic Search

The quantum Fourier transform (QFT) is the principal ingredient of most efficient quantum algorithms. We present a generic framework for the construction of efficient quantum circuits for the QFT by \\

Cristopher Moore; Daniel N. Rockmore; Alexander Russell

2004-01-01

2

Realization of quantum Fourier transform over ZN  

NASA Astrophysics Data System (ADS)

Since the difficulty in preparing the equal superposition state of amplitude is 1/?N, we construct a quantile transform of quantum Fourier transform (QFT) over ZN based on the elementary transforms, such as Hadamard transform and Pauli transform. The QFT over ZN can then be realized by the quantile transform, and used to further design its quantum circuit and analyze the requirements for the quantum register and quantum gates. However, the transform needs considerable quantum computational resources and it is difficult to construct a high-dimensional quantum register. Hence, we investigate the design of t-bit quantile transform, and introduce the definition of t-bit semiclassical QFT over ZN. According to probability amplitude, we prove that the transform can be used to realize QFT over ZN and further design its quantum circuit. For this transform, the requirements for the quantum register, the one-qubit gate, and two-qubit gate reduce obviously when compared with those for the QFT over ZN.

Fu, Xiang-Qun; Bao, Wan-Su; Li, Fa-Da; Zhang, Yu-Chao

2014-02-01

3

Semiclassical Fourier Transform for Quantum Computation  

Microsoft Academic Search

It is shown that the Fourier transform preceding the final measurement in Shor's algorithm for factorization on a quantum computer can be carried out in a semiclassical way by using the ``classical'' (macroscopic) signal resulting from measuring one bit to determine the type of measurement carried out on the next bit, and so forth. In this way all the two-bit

Robert B. Griffiths; Chi-Sheng Niu

1996-01-01

4

Secret sharing based on quantum Fourier transform  

NASA Astrophysics Data System (ADS)

Secret sharing plays a fundamental role in both secure multi-party computation and modern cryptography. We present a new quantum secret sharing scheme based on quantum Fourier transform. This scheme enjoys the property that each share of a secret is disguised with true randomness, rather than classical pseudorandomness. Moreover, under the only assumption that a top priority for all participants (secret sharers and recovers) is to obtain the right result, our scheme is able to achieve provable security against a computationally unbounded attacker.

Yang, Wei; Huang, Liusheng; Shi, Runhua; He, Libao

2013-07-01

5

Quantum computation of Fourier transforms over symmetric groups  

Microsoft Academic Search

Many algorithmic developments in quantum com- plexity theory, including Shor's celebrated algorithms for factoring and discrete logs, have made use of Fourier transforms over abelian groups. That is, at some point in the computation, the macline is in a superposition of states corresponding to elements of a finite abelian group G, and in quantum polynomial time (i.e., poly- nomial in

Robert Beals

1997-01-01

6

Limitations on continuous variable quantum algorithms with Fourier transforms  

NASA Astrophysics Data System (ADS)

We study quantum algorithms implemented within a single harmonic oscillator, or equivalently within a single mode of the electromagnetic field. Logical states correspond to functions of the canonical position, and the Fourier transform to canonical momentum serves as the analogue of the Hadamard transform for this implementation. This continuous variable version of quantum information processing has widespread appeal because of advanced quantum optics technology that can create, manipulate and read Gaussian states of light. We show that, contrary to a previous claim, this implementation of quantum information processing has limitations due to a position-momentum trade-off of the Fourier transform, analogous to the famous time-bandwidth theorem of signal processing.

Adcock, Mark R. A.; Høyer, Peter; Sanders, Barry C.

2009-10-01

7

A watermark strategy for quantum images based on quantum fourier transform  

NASA Astrophysics Data System (ADS)

We present a robust watermark strategy for quantum images. The watermark image is embedded into the fourier coefficients of the quantum carrier image, which will not affect the carrier image's visual effect. Before being embedded into the carrier image, the watermark image is preprocessed to be seemingly meaningless using quantum circuit, which further ensures the security of the watermark image. The properties of fourier transform ensure that the watermark embedded in the carrier image resists the unavoidable noise and cropping.

Zhang, Wei-Wei; Gao, Fei; Liu, Bin; Wen, Qiao-Yan; Chen, Hui

2013-02-01

8

Analysis and improvement of the watermark strategy for quantum images based on quantum Fourier transform  

NASA Astrophysics Data System (ADS)

We investigate the quantum watermark strategy for quantum images based on quantum Fourier transform proposed by Zhang et al.(Quantum Inf Process 12(2):793-803, 2013). It is aimed to embed the watermark image into the Fourier coefficients of the quantum carrier image without affecting the carrier image's visual effect. However, in our opinion the protocol is not clearly described and several steps are ambiguous. Moreover, we argue that the watermarking algorithm claimed by the authors is incorrect. At last, a possible improvement strategy is presented.

Yang, Yu-Guang; Jia, Xin; Xu, Peng; Tian, Ju

2013-08-01

9

Entanglement of periodic states, the quantum Fourier transform, and Shor's factoring algorithm  

SciTech Connect

The preprocessing stage of Shor's algorithm generates a class of quantum states referred to as periodic states, on which the quantum Fourier transform is applied. Such states also play an important role in other quantum algorithms that rely on the quantum Fourier transform. Since entanglement is believed to be a necessary resource for quantum computational speedup, we analyze the entanglement of periodic states and the way it is affected by the quantum Fourier transform. To this end, we derive a formula that evaluates the Groverian entanglement measure for periodic states. Using this formula, we explain the surprising result that the Groverian entanglement of the periodic states built up during the preprocessing stage is only slightly affected by the quantum Fourier transform.

Most, Yonatan; Biham, Ofer [Racah Institute of Physics, Hebrew University, Jerusalem IL-91904 (Israel); Shimoni, Yishai [Racah Institute of Physics, Hebrew University, Jerusalem IL-91904 (Israel); Department of Neurology, Mount Sinai School of Medicine, New York, New York (United States)

2010-05-15

10

Large quantum Fourier transforms are never exactly realized by braiding conformal blocks  

SciTech Connect

Fourier transform is an essential ingredient in Shor's factoring algorithm. In the standard quantum circuit model with the gate set {l_brace}U(2), controlled-NOT{r_brace}, the discrete Fourier transforms F{sub N}=({omega}{sup ij}){sub NxN}, i,j=0,1,...,N-1, {omega}=e{sup 2{pi}}{sup i} at {sup {approx}}{sup sol{approx}} at {sup N}, can be realized exactly by quantum circuits of size O(n{sup 2}), n=ln N, and so can the discrete sine or cosine transforms. In topological quantum computing, the simplest universal topological quantum computer is based on the Fibonacci (2+1)-topological quantum field theory (TQFT), where the standard quantum circuits are replaced by unitary transformations realized by braiding conformal blocks. We report here that the large Fourier transforms F{sub N} and the discrete sine or cosine transforms can never be realized exactly by braiding conformal blocks for a fixed TQFT. It follows that an approximation is unavoidable in the implementation of Fourier transforms by braiding conformal blocks.

Freedman, Michael H. [Microsoft Project Q, Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030 (United States); Wang, Zhenghan [Microsoft Project Q, Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030 (United States); Department of Mathematics, Indiana University, Bloomington, Indiana 47405 (United States)

2007-03-15

11

Applications of quantum Fourier transform in photon-added coherent state  

NASA Astrophysics Data System (ADS)

Quantum Fourier transform is realized by the Hadamard gate in a quantum computer, which can also be considered as a Hadamard transform. We introduce the Hadamard transformed photon-added coherent state (HTPACS), which is obtained by letting the photon-added coherent state (PACS) across the quantum Hadamard gate, from this result. It is found that the HTPACS can be considered as a coordinate—momentum mutual exchanging followed by a squeezing transform of the PACS. In addition, the non-classical statistical properties of HTPACS, such as squeezing coefficient, Mandel parameter, etc., are also discussed.

Ren, Gang; Du, Jian-Ming; Yu, Hai-Jun

2014-02-01

12

A ( t, n)-Threshold Scheme of Multi-party Quantum Group Signature with Irregular Quantum Fourier Transform  

NASA Astrophysics Data System (ADS)

A novel ( t, n)-threshold scheme for the multi-party quantum group signature is proposed based on the irregular quantum Fourier transform, in which every t-qubit quantum message needs n participants to generate the quantum group signature. All the quantum operation gates in the quantum circuit can be distributed and arranged randomly in the irregular QFT algorithm, which can increase the von Neumann entropy of the signed quantum message and the randomicity of the quantum signature generation significantly. The generation and verification of the quantum group signature can be both performed in quantum circuits with the parallel algorithm. Security analysis shows that an available and legal quantum ( t, n)-threshold group signature can be achieved.

Shi, Jinjing; Shi, Ronghua; Guo, Ying; Peng, Xiaoqi; Lee, Moon Ho; Park, Dongsun

2012-04-01

13

Unraveling quantum pathways using optical 3D Fourier-transform spectroscopy  

PubMed Central

Predicting and controlling quantum mechanical phenomena require knowledge of the system Hamiltonian. A detailed understanding of the quantum pathways used to construct the Hamiltonian is essential for deterministic control and improved performance of coherent control schemes. In complex systems, parameters characterizing the pathways, especially those associated with inter-particle interactions and coupling to the environment, can only be identified experimentally. Quantitative insight can be obtained provided the quantum pathways are isolated and independently analysed. Here we demonstrate this possibility in an atomic vapour using optical three-dimensional Fourier-transform spectroscopy. By unfolding the system’s nonlinear response onto three frequency dimensions, three-dimensional spectra unambiguously reveal transition energies, relaxation rates and dipole moments of each pathway. The results demonstrate the unique capacity of this technique as a powerful tool for resolving the complex nature of quantum systems. This experiment is a critical step in the pursuit of complete experimental characterization of a system’s Hamiltonian.

Li, Hebin; Bristow, Alan D.; Siemens, Mark E.; Moody, Galan; Cundiff, Steven T.

2013-01-01

14

Fractional finite Fourier transform  

NASA Astrophysics Data System (ADS)

We show that a fractional version of the finite Fourier transform may be defined by using prolate spheroidal wave functions of order zero. The transform is linear and additive in its index and asymptotically goes over to Namias's definition of the fractional Fourier transform. As a special case of this definition, it is shown that the finite Fourier transform may be inverted by using information over a finite range of frequencies in Fourier space, the inversion being sensitive to noise. Numerical illustrations for both forward (fractional) and inverse finite transforms are provided.

Khare, Kedar; George, Nicholas

2004-07-01

15

Optical two-dimensional Fourier transform spectroscopy of single GaAs quantum wells  

NASA Astrophysics Data System (ADS)

Optical two-dimensional Fourier transform spectroscopy is applied to study the coherent coupling between light-hole and heavy-hole excitons in single GaAs quantum wells instead of those consisted of ten or four periods of GaAs separated by Al0.3Ga0.7As barriers measured previously. The effect of the confinement energy as well as Coulomb and disorder correlation lengths on coherent coupling dynamics is discussed. The financial support from ARO, NSF, and Welch foundation is gratefully acknowledged.

Glinka, Yuri D.; Sun, Zheng; Li, Xiaoqin; Bracker, Allan

2011-03-01

16

Robustness of the quantum Fourier transform with respect to static gate defects  

NASA Astrophysics Data System (ADS)

The quantum Fourier transform (QFT) is one of the most widely used quantum algorithms, ranging from its primary role in finding the periodicity hidden in a quantum state to its use in constructing a quantum adder. Testing how the QFT performs under more realistic conditions, we find that the QFT, when used for period finding, shows extraordinary robustness with respect to static gate defects. For instance, replacing all rotation angles ? /2j of the controlled rotation gates in the QFT circuit by ?(1+r )/2j, where r is a uniformly distributed random variable taking values in the range [-1,1], effectively resulting in a QFT with random gates, the QFT performs well above the expected random result. However, it is important to keep the 2j terms in the denominators of the rotation angles, resulting in random, but hierarchically random, gates. Relaxing this hierarchical structure of the QFT circuit, we find that the performance of the QFT deteriorates significantly. This observation indicates that the hierarchical structure of the quantum circuit of the QFT is more important for the observed robustness in performance than the precise actions of individual gates. In addition to the specific example of the QFT circuit studied here, this observation also corroborates our experience with more general and more complex quantum circuits. Thus, backed by our detailed numerical and analytical results, we may condense the results of our research into the following general principle: The topology of a quantum circuit is more important than the precise actions of its gates.

Nam, Y. S.; Blümel, R.

2014-04-01

17

Fast Fourier Transform Fast Fourier Transformatie.  

National Technical Information Service (NTIS)

The fast Fourier transform (FFT), an efficient technique for evaluating the finite discrete Fourier transform (DFT) is dealt with. An explanation of the FFT algorithm is given, and two algorithms are presented for transforming real functions making use of...

E. H. J. Vermaas

1974-01-01

18

Matching-pursuit/split-operator Fourier-transform simulations of nonadiabatic quantum dynamics  

NASA Astrophysics Data System (ADS)

A rigorous and practical approach for simulations of nonadiabatic quantum dynamics is introduced. The algorithm involves a natural extension of the matching-pursuit/split-operator Fourier-transform (MP/SOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)] recently developed for simulations of adiabatic quantum dynamics in multidimensional systems. The MP/SOFT propagation scheme, extended to nonadiabatic dynamics, recursively applies the time-evolution operator as defined by the standard perturbation expansion to first-, or second-order, accuracy. The expansion is implemented in dynamically adaptive coherent-state representations, generated by an approach that combines the matching-pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting propagation method are demonstrated as applied to the canonical model systems introduced by Tully for testing simulations of dual curve-crossing nonadiabatic dynamics.

Wu, Yinghua; Herman, Michael F.; Batista, Victor S.

2005-03-01

19

Migration by Fourier transform  

Microsoft Academic Search

Wave equation migration is known to be simpler in principle when the horizontal coordinate or coordinates are replaced by their Fourier conjugates. Two practical migration schemes utilizing this concept are developed. One scheme extends the Claerbout finite difference method, greatly reducing dispersion problems usually associated with this method at higher dips and frequencies. The second scheme effects a Fourier transform

R. H. Stolt

1978-01-01

20

The quantum state vector in phase space and Gabor's windowed Fourier transform  

NASA Astrophysics Data System (ADS)

Representations of quantum state vectors by complex phase space amplitudes, complementing the description of the density operator by the Wigner function, have been defined by applying the Weyl-Wigner transform to dyadic operators, linear in the state vector and anti-linear in a fixed 'window state vector'. Here aspects of this construction are explored, and a connection is established with Gabor's 'windowed Fourier transform'. The amplitudes that arise for simple quantum states from various choices of windows are presented as illustrations. Generalized Bargmann representations of the state vector appear as special cases, associated with Gaussian windows. For every choice of window, amplitudes lie in a corresponding linear subspace of square-integrable functions on phase space. A generalized Born interpretation of amplitudes is described, with both the Wigner function and a generalized Husimi function appearing as quantities linear in an amplitude and anti-linear in its complex conjugate. Schrödinger's time-dependent and time-independent equations are represented on phase space amplitudes, and their solutions described in simple cases.

Bracken, A. J.; Watson, P.

2010-10-01

21

Fourier Transform Interferometry.  

National Technical Information Service (NTIS)

The basic Michelson interferometer, as used for Fourier transform spectroscopy, is analyzed in this report. The principles of operation are explained, and its inherent limitations are shown. An original analysis of apodization, for the case of an off-axis...

D. R. Hearn

1999-01-01

22

Exciton-exciton correlations revealed by two-quantum, two-dimensional fourier transform optical spectroscopy.  

PubMed

The Coulomb correlations between photoexcited charged particles in materials such as photosynthetic complexes, conjugated polymer systems, J-aggregates, and bulk or nanostructured semiconductors produce a hierarchy of collective electronic excitations, for example, excitons, and biexcitons, which may be harnessed for applications in quantum optics, light-harvesting, or quantum information technologies. These excitations represent correlations among successively greater numbers of electrons and holes, and their associated multiple-quantum coherences could reveal detailed information about complex many-body interactions and dynamics. However, unlike single-quantum coherences involving excitons, multiple-quantum coherences do not radiate; consequently, they have largely eluded direct observation and characterization. In this Account, we present a novel optical technique, two-quantum, two-dimensional Fourier transform optical spectroscopy (2Q 2D FTOPT), which allows direct observation of the dynamics of multiple exciton states that reflect the correlations of their constituent electrons and holes. The approach is based on closely analogous methods in NMR, in which multiple phase-coherent fields are used to drive successive transitions such that multiple-quantum coherences can be accessed and probed. In 2Q 2D FTOPT, a spatiotemporal femtosecond pulse-shaping technique has been used to overcome the challenge of control over multiple, noncollinear, phase-coherent optical fields in experimental geometries used to isolate selected signal contributions through wavevector matching. We present results from a prototype GaAs quantum well system, which reveal distinct coherences of biexcitons that are formed from two identical excitons or from two excitons that have holes in different spin sublevels ("heavy-hole" and "light-hole" excitons). The biexciton binding energies and dephasing dynamics are determined, and changes in the dephasing rates as a function of the excitation density are observed, revealing still higher order correlations due to exciton-biexciton interactions. Two-quantum coherences due to four-particle correlations that do not involve bound biexciton states but that influence the exciton properties are also observed and characterized. The 2Q 2D FTOPT technique allows many-body interactions that cannot be treated with a mean-field approximation to be studied in detail; the pulse-shaping approach simplifies greatly what would have otherwise been daunting measurements. This spectroscopic tool might soon offer insight into specific applications, for example, in detailing the interactions that affect how electronic energy moves within the strata of organic photovoltaic cells. PMID:19691277

Stone, Katherine W; Turner, Daniel B; Gundogdu, Kenan; Cundiff, Steven T; Nelson, Keith A

2009-09-15

23

ENVIRONMENTAL ANALYSIS BY AB INITIO QUANTUM MECHANICAL COMPUTATION AND GAS CHROMATOGRAPHY/FOURIER TRANSFORM INFRARED SPECTROMETRY.  

EPA Science Inventory

Computational chemistry, in conjunction with gas chromatography/mass spectrometry/Fourier transform infrared spectrometry (GC/MS/FT-IR), was used to tentatively identify seven tetrachlorobutadiene (TCBD) isomers detected in an environmental sample. Computation of the TCBD infrare...

24

Fourier Transforms, Fourier Series and the FFT  

NSDL National Science Digital Library

The goal of this module is to give students an understanding of the one-dimensional Fourier Transform, both mathematically and computationally, with a focus on finding periodicity in data. To motivate the study of the Fourier Transform, the students will be presented with certain application areas, such as searching for periodic patterns in CO2 data and differentiating between two sound signals using their power spectra. Students will explore some computational issues and challenges of the Discrete and Fast Fourier Transforms.

De Pillis, Lisette; Radunskaya, Ami

25

Enabling two-dimensional fourier transform electronic spectroscopy on quantum dots  

NASA Astrophysics Data System (ADS)

Colloidal semiconductor nanocrystals exhibit unique properties not seen in their bulk counterparts. Quantum confinement of carriers causes a size-tunable bandgap, making them attractive candidates for solar cells. Fundamental understanding of their spectra and carrier dynamics is obscured by inhomogeneous broadening arising from the size distribution. Because quantum dots have long excited state lifetimes and are sensitive to both air and moisture, there are many potential artifacts in femtosecond experiments. Two-dimensional electronic spectroscopy promises insight into the photo-physics, but required key instrumental advances. Optics that can process a broad bandwidth without distortion are required for a two-dimensional optical spectrometer. To control pathlength differences for femtosecond time delays, hollow retro-reflectors are used on actively stabilized delay lines in interferometers. The fabrication of rigid, lightweight, precision hollow rooftop retroreflectors that allow beams to be stacked while preserving polarization is described. The rigidity and low mass enable active stabilization of an interferometer to within 0.6 nm rms displacement, while the return beam deviation is sufficient for Fourier transform spectroscopy with a frequency precision of better than 1 cm -1. Keeping samples oxygen and moisture free while providing fresh sample between laser shots is challenging in an interferometer. A low-vibration spinning sample cell was designed and built to keep samples oxygen free for days while allowing active stabilization of interferometer displacement to ˜1 nm. Combining these technologies has enabled 2D short-wave infrared spectroscopy on colloidal PbSe nanocrystals. 2D spectra demonstrate the advantages of this key instrumentation while providing valuable insight into the low-lying electronic states of colloidal quantum dots.

Hill, Robert John, Jr.

26

Fourier Transform I  

NSDL National Science Digital Library

Created by Lang Moore for the Connected Curriculum Project, the purpose of this module is to study the Fourier transform and use it to describe solutions of the heat equation on an infinite rod. This is one of a much larger set of learning modules hosted by Duke University.

Moore, Lang

2010-07-02

27

Fourier transform deflection mapping  

Microsoft Academic Search

In a previous paper in 1992, we presented a flow visualization technique based on deflection mapping. We now present a new method for the interpretation of deflection mapping of small angles obtained by Ronchi gratings. In this method, a Fourier transform is operated on the transmission pattern of the Ronchi grating and the individual sine terms are then obtained by

Arie Dahan; Gabi Ben-Dor; Ezra Bar-Ziv

1993-01-01

28

Fourier Transform Mass Spectrometry.  

ERIC Educational Resources Information Center

Discusses the nature of Fourier transform mass spectrometry and its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. Examines its operation, capabilities and limitations, applications (ion storage, ion manipulation, ion chemistry), and future applications and developments. (JN)

Gross, Michael L.; Rempel, Don L.

1984-01-01

29

Fast quantum efficiency measurement of solar cells by Fourier transform photocurrent spectroscopy  

Microsoft Academic Search

Fourier Transform Photocurrent Spectroscopy (FTPS) was introduced four years ago as a method providing fast and highly sensitive evaluation of the spectral dependence of the photoconductive thin film optical absorption coefficient. Recently the method was also applied to the quality assessment of thin film silicon solar cells. In this contribution, we present the FTPS characterization of various thin film solar

L. Hod’áková; A. Poruba; R. Kravets; M. Vanecek

2006-01-01

30

Comment on: Novel image encryption/decryption based on quantum fourier transform and double phase encoding  

NASA Astrophysics Data System (ADS)

In this letter, we have pointed out some problems existed in (Yang et al. in Quantum Inf Process 12(11):3477-3493, 2013). Then, a new restricted quantum image color transformation method is proposed.

Song, Xian-Hua; Niu, Xia-Mu

2014-06-01

31

Rainbow Fourier Transform  

NASA Technical Reports Server (NTRS)

We present a novel technique for remote sensing of cloud droplet size distributions. Polarized reflectances in the scattering angle range between 135deg and 165deg exhibit a sharply defined rainbow structure, the shape of which is determined mostly by single scattering properties of cloud particles, and therefore, can be modeled using the Mie theory. Fitting the observed rainbow with such a model (computed for a parameterized family of particle size distributions) has been used for cloud droplet size retrievals. We discovered that the relationship between the rainbow structures and the corresponding particle size distributions is deeper than it had been commonly understood. In fact, the Mie theory-derived polarized reflectance as a function of reduced scattering angle (in the rainbow angular range) and the (monodisperse) particle radius appears to be a proxy to a kernel of an integral transform (similar to the sine Fourier transform on the positive semi-axis). This approach, called the rainbow Fourier transform (RFT), allows us to accurately retrieve the shape of the droplet size distribution by the application of the corresponding inverse transform to the observed polarized rainbow. While the basis functions of the proxy-transform are not exactly orthogonal in the finite angular range, this procedure needs to be complemented by a simple regression technique, which removes the retrieval artifacts. This non-parametric approach does not require any a priori knowledge of the droplet size distribution functional shape and is computationally fast (no look-up tables, no fitting, computations are the same as for the forward modeling).

Alexandrov, Mikhail D.; Cairns, Brian; Mishchenko, Michael I.

2012-01-01

32

Rainbow Fourier transform  

NASA Astrophysics Data System (ADS)

We present a novel technique for remote sensing of cloud droplet size distributions. Polarized reflectances in the scattering angle range between 135° and 165° exhibit a sharply defined rainbow structure, the shape of which is determined mostly by single scattering properties of cloud particles, and therefore, can be modeled using the Mie theory. Fitting the observed rainbow with such a model (computed for a parameterized family of particle size distributions) has been used for cloud droplet size retrievals. We discovered that the relationship between the rainbow structures and the corresponding particle size distributions is deeper than it had been commonly understood. In fact, the Mie theory-derived polarized reflectance as a function of reduced scattering angle (in the rainbow angular range) and the (monodisperse) particle radius appears to be a proxy to a kernel of an integral transform (similar to the sine Fourier transform on the positive semi-axis). This approach, called the rainbow Fourier transform (RFT), allows us to accurately retrieve the shape of the droplet size distribution by the application of the corresponding inverse transform to the observed polarized rainbow. While the basis functions of the proxy-transform are not exactly orthogonal in the finite angular range, this procedure needs to be complemented by a simple regression technique, which removes the retrieval artifacts. This non-parametric approach does not require any a priori knowledge of the droplet size distribution functional shape and is computationally fast (no look-up tables, no fitting, computations are the same as for the forward modeling).

Alexandrov, Mikhail D.; Cairns, Brian; Mishchenko, Michael I.

2012-12-01

33

Fast Fourier transform telescope  

NASA Astrophysics Data System (ADS)

We propose an all-digital telescope for 21 cm tomography, which combines key advantages of both single dishes and interferometers. The electric field is digitized by antennas on a rectangular grid, after which a series of fast Fourier transforms recovers simultaneous multifrequency images of up to half the sky. Thanks to Moore’s law, the bandwidth up to which this is feasible has now reached about 1 GHz, and will likely continue doubling every couple of years. The main advantages over a single dish telescope are cost and orders of magnitude larger field-of-view, translating into dramatically better sensitivity for large-area surveys. The key advantages over traditional interferometers are cost (the correlator computational cost for an N-element array scales as Nlog?2N rather than N2) and a compact synthesized beam. We argue that 21 cm tomography could be an ideal first application of a very large fast Fourier transform telescope, which would provide both massive sensitivity improvements per dollar and mitigate the off-beam point source foreground problem with its clean beam. Another potentially interesting application is cosmic microwave background polarization.

Tegmark, Max; Zaldarriaga, Matias

2009-04-01

34

Imaging Fourier Transform Spectrometer  

SciTech Connect

The operating principles of an Imaging Fourier Transform Spectrometer (IFTS) are discussed. The advantages and disadvantages of such instruments with respect to alternative imaging spectrometers are discussed. The primary advantages of the IFTS are the capacity to acquire more than an order of magnitude more spectral channels than alternative systems with more than an order of magnitude greater etendue than for alternative systems. The primary disadvantage of IFTS, or FTS in general, is the sensitivity to temporal fluctuations, either random or periodic. Data from the IRIFTS (ir IFTS) prototype instrument, sensitive in the infrared, are presented having a spectral sensitivity of 0.01 absorbance units, a spectral resolution of 6 cm{sup {minus}1} over the range 0 to 7899 cm{sup {minus}1}, and a spatial resolution of 2.5 mr.

Bennett, C.L.; Carter, M.R.; Fields, D.J.; Hernandez, J.

1993-04-14

35

Matching-pursuit/split-operator-Fourier-transform simulations of excited-state nonadiabatic quantum dynamics in pyrazine.  

PubMed

A simple approach for numerically exact simulations of nonadiabatic quantum dynamics in multidimensional systems is introduced and applied to the description of the photoabsorption spectroscopy of pyrazine. The propagation scheme generalizes the recently developed matching-pursuit/split-operator-Fourier-transform (MP/SOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)] to simulations of nonadiabatic quantum dynamics. The time-evolution operator is applied, as defined by the Trotter expansion to second order accuracy, in dynamically adaptive coherent-state expansions. These representations are obtained by combining the matching-pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting computational approach are demonstrated in calculations of time-dependent survival amplitudes and photoabsorption cross sections, using a model Hamiltonian that allows for direct comparisons with benchmark calculations. Simulations in full-dimensional potential energy surfaces involve the propagation of a 24-dimensional wave packet to describe the S(1)S(2) interconversion of pyrazine after S(0)-->S(2) photoexcitation. The reported results show that the generalized MP/SOFT method is a practical and accurate approach to model nonadiabatic reaction dynamics in polyatomic systems. PMID:17014180

Chen, Xin; Batista, Victor S

2006-09-28

36

Matching-pursuit/split-operator-Fourier-transform simulations of excited-state nonadiabatic quantum dynamics in pyrazine  

NASA Astrophysics Data System (ADS)

A simple approach for numerically exact simulations of nonadiabatic quantum dynamics in multidimensional systems is introduced and applied to the description of the photoabsorption spectroscopy of pyrazine. The propagation scheme generalizes the recently developed matching-pursuit/split-operator-Fourier-transform (MP/SOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)] to simulations of nonadiabatic quantum dynamics. The time-evolution operator is applied, as defined by the Trotter expansion to second order accuracy, in dynamically adaptive coherent-state expansions. These representations are obtained by combining the matching-pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting computational approach are demonstrated in calculations of time-dependent survival amplitudes and photoabsorption cross sections, using a model Hamiltonian that allows for direct comparisons with benchmark calculations. Simulations in full-dimensional potential energy surfaces involve the propagation of a 24-dimensional wave packet to describe the S1/S2 interconversion of pyrazine after S0-->S2 photoexcitation. The reported results show that the generalized MP/SOFT method is a practical and accurate approach to model nonadiabatic reaction dynamics in polyatomic systems.

Chen, Xin; Batista, Victor S.

2006-09-01

37

Matching-pursuit/split-operator-Fourier-transform simulations of excited-state nonadiabatic quantum dynamics in pyrazine.  

NASA Astrophysics Data System (ADS)

A simple approach for numerically exact simulations of nonadiabatic quantum dynamics in multidimensional systems is introduced and applied to the description of the photoabsorption spectroscopy of pyrazine. The propagation scheme generalizes the recently developed matching-pursuit/split-operator-Fourier-transform (MP/SOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)]. The time-evolution operator is applied, as defined by the Trotter expansion to second order accuracy, in dynamically adaptive coherent-state expansions. These representations are obtained by combining the matching-pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting computational approach are demonstrated in calculations of time-dependent survival amplitudes and photoabsorption cross sections, using a model Hamiltonian that allows for direct comparisons with benchmark calculations. Simulations in full-dimensional potential energy surfaces involve the propagation of a 24-dimensional wave packet to describe the S1 /S2 interconversion of pyrazine after after S0-S2 photoexcitation. The reported results show that the generalized MP/SOFT method is a practical and accurate approach to model nonadiabatic reaction dynamics in polyatomic systems.

Batista, Victor; Chen, Xin

2007-03-01

38

A Short Biography of Joseph Fourier and Historical Development of Fourier Series and Fourier Transforms  

ERIC Educational Resources Information Center

This article deals with a brief biographical sketch of Joseph Fourier, his first celebrated work on analytical theory of heat, his first great discovery of Fourier series and Fourier transforms. Included is a historical development of Fourier series and Fourier transforms with their properties, importance and applications. Special emphasis is made…

Debnath, Lokenath

2012-01-01

39

AIR POLLUTION MEASUREMENT BY FOURIER TRANSFORM SPECTROSCOPY  

EPA Science Inventory

Fourier transform spectroscopy substantially reduces the limitations on infrared methods of pollution measurement. EPA has used long path cells and Fourier transform spectrometers for pollutant measurement both in the laboratory and in the field. Labile pollutants are best measur...

40

Algo Procedures for the Fast Fourier Transform.  

National Technical Information Service (NTIS)

The report consists of six ALGOL procedures with comments. Procedure FASTTRANSFORM computes the complex finite Fourier transform or its inverse, using a modified version of the fast Fourier transform algorithm proposed by Cooley and Tukey. Procedure REALT...

R. C. Singleton

1966-01-01

41

Discrete integer Fourier transform in real space: elliptic Fourier transform  

NASA Astrophysics Data System (ADS)

The concept of the N-point DFT is generalized, by considering it in the real space (not complex). The multiplication by twiddle coefficients is considered in matrix form; as the Givens transformation. Such block-wise representation of the matrix of the DFT is effective. The transformation which is called the T-generated N-block discrete transform, or N-block T-GDT is introduced. For each N-block T-GDT, the inner product is defined, with respect to which the rows (and columns) of the matrices X are orthogonal. By using different parameterized matrices T, we define metrics in the real space of vectors. The selection of the parameters can be done among only the integer numbers, which leads to integer-valued metric. We also propose a new representation of the discrete Fourier transform in the real space R2N. This representation is not integer, and is based on the matrix C (2x2) which is not a rotation, but a root of the unit matrix. The point (1, 0) is not moving around the unite circle by the group of motion generated by C, but along the perimeter of an ellipse. The N-block C-GDT is therefore called the N-block elliptic FT (EFT). These orthogonal transformations are parameterized; their properties are described and examples are given.

Grigoryan, Artyom M.; Grigoryan, Merughan M.

2009-02-01

42

Fourier-transform laser spectroscopy.  

PubMed

The development of microphotonic sensors based on Fourier-transform laser spectroscopy (FT-LS) is discussed. The application demonstrated is for measurement of vapors from the hydrocarbon fuels JP-8, diesel fuel, and gasoline. The two-laser prototype FT-LS sensor used for our research employs distributed-feedback lasers in the near-infrared spectral region (1.3- and 1.7-microm wavelength). An extension of this research to multilaser arrays is discussed. We believe that this is the first measurement of middle-distillate fuel-vapor concentrations using this optical mixing technique. PMID:12716154

McNesby, Kevin L; Miziolek, Andrzej W

2003-04-20

43

Fourier Transform Mass Spectrometry Lab  

NSDL National Science Digital Library

This Web site discusses Boston University's Fourier Transform Mass Spectrometry (FTMS) Lab's devotion to the improvement of FTMS instrumentation and methods for its everyday biochemical functions. After discovering the importance of FTMS, visitors can find out about the lab's work in the enhancement of electrospray ion source and Cryogenic FTMS. Students can learn about the modern biochemistry's utilization of both traditional instrumentation such as gel electrophoresis and the latest devices including high performance chromatography, nuclear magnetic resonance, and X-ray crystallography. By downloading the Boston University Data Analysis (B.U.D.A.), researchers can participate in the development of analysis software for FTMS.

44

Fourier-transform optical microsystems  

NASA Technical Reports Server (NTRS)

The design, fabrication, and initial characterization of a miniature single-pass Fourier-transform spectrometer (FTS) that has an optical bench that measures 1 cm x 5 cm x 10 cm is presented. The FTS is predicated on the classic Michelson interferometer design with a moving mirror. Precision translation of the mirror is accomplished by microfabrication of dovetailed bearing surfaces along single-crystal planes in silicon. Although it is miniaturized, the FTS maintains a relatively high spectral resolution, 0.1 cm-1, with adequate optical throughput.

Collins, S. D.; Smith, R. L.; Gonzalez, C.; Stewart, K. P.; Hagopian, J. G.; Sirota, J. M.

1999-01-01

45

JPL Fourier transform ultraviolet spectrometer  

NASA Technical Reports Server (NTRS)

The Fourier Transform Ultraviolet Spectrometer (FTUVS) is a new high resolution interferometric spectrometer for multiple-species detection in the UV, visible and near-IR. As an OH sensor, measurements can be carried out by remote sensing (limb emission and column absorption), or in-situ sensing (long-path absorption or laser-induced fluorescence). As a high resolution detector in a high repetition rate (greater than 10 kHz) LIF system, OH fluorescence can be discriminated against non-resonant background emission and laser scatter, permitting (0, 0) excitation.

Cageao, R. P.; Friedl, R. R.; Sander, Stanley P.; Yung, Y. L.

1994-01-01

46

Fourier-Transform Infrared Spectrometer  

NASA Technical Reports Server (NTRS)

Fourier-transform spectrometer provides approximately hundredfold increase in luminosity at detector plane over that achievable with older instruments of this type. Used to analyze such weak sources as pollutants and other low-concentration substances in atmosphere. Interferometer creates fringe patterns on two distinct arrays of light detectors, which observe different wavelength bands. Objective lens focuses scene on image plane, which contains optical chopper. To make instrument less susceptible to variations in scene under observation, field and detector lenses focus entrance aperture, rather that image, onto detector array.

Schindler, R. A.

1986-01-01

47

Trim-to-Coherence Fourier Transform  

NASA Astrophysics Data System (ADS)

We introduce a discrete Fourier transform technique which extracts more spectral information from a given time series data set than conventional discrete Fourier transform (DFT). Valid information is obtained between the spectral bins of conventional DFT, scalloping error is greatly reduced, and amplitude and phase of Fourier components are more true to the process under study as with conventional DFT. We call the general idea Trim-to-Coherence Fourier Transform, and its particular embodiment 'Phase-Rotation Fourier Transform'. Treatment of the raw data is minimally invasive; e.g. there is no zero padding.

Böhm, M.; Tasche, M.; Seifert, B.; Mitschke, F.

2009-05-01

48

Laser Field Imaging Through Fourier Transform Heterodyne  

SciTech Connect

The authors present a detection process capable of directly imaging the transverse amplitude, phase, and Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LADAR systems, Fourier Transform Heterodyne incorporates transverse spatial encoding of the reference local oscillator for image capture. Appropriate selection of spatial encoding functions allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging may be accomplished with a single element detector/sensor requiring no additional scanning or moving components, (2) as detection is governed by heterodyne principles, near quantum limited performance is achievable, (3) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection, and (4) the concept is general with the applicable electromagnetic spectrum encompassing the RF through optical.

Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Galbraith, A.E.; Strauss, C.E.; Grubler, A.C.

1999-04-05

49

Quantum Algorithms, Symmetry, and Fourier Analysis  

NASA Astrophysics Data System (ADS)

I describe the role of symmetry in two quantum algorithms, with a focus on how that symmetry is made manifest by the Fourier transform. The Fourier transform can be considered in a wider context than the familiar one of functions on Rn or Z/nZ ; instead it can be defined for an arbitrary group where it is known as representation theory.. The first quantum algorithm solves an instance of the hidden subgroup problem—distinguishing conjugates of the Borel subgroup from each other in groups related to PSL(2; q). I use the symmetry of the subgroups under consideration to reduce the problem to a mild extension of a previously solved problem. This generalizes a result of Moore, Rockmore, Russel and Schulman by switching to a more natural measurement that also applies to prime powers. In contrast to the first algorithm, the second quantum algorithm is an attempt to use naturally continuous spaces. Quantum walks have proved to be a useful tool for designing quantum algorithms. The natural equivalent to continuous time quantum walks is evolution with the Schrödinger equation, under the kinetic energy Hamiltonian for a massive particle. I take advantage of quantum interference to find the center of spherical shells in high dimensions. Any implementation would be likely to take place on a discrete grid, using the ability of a digital quantum computer to simulate the evolution of a quantum system. In addition, I use ideas from the second algorithm on a different set of starting states, and find that quantum evolution can be used to sample from the evolute of a plane curve. The method of stationary phase is used to determine scaling exponents characterizing the precision and probability of success for this procedure.

Denney, Aaron

50

Temporal implementation of Fourier-related transforms  

Microsoft Academic Search

A class of Fourier-related functions such as the fractional Fourier transform, the Hartley and the fractional Hartley transform, the Mellin and the fractional Mellin transform, are implemented in the time-domain. To accomplish this task temporal analogue of beam splitters, cube corner prisms and holograms are found.

D. Dragoman; M. Dragoman

1998-01-01

51

Dual Comb Fourier Transform Spectroscopy  

NASA Astrophysics Data System (ADS)

The advent of laser frequency combs a decade ago has already revolutionized optical frequency metrology and precision spectroscopy. Extensions of laser combs from the THz region to the extreme ultraviolet and soft x-ray frequencies are now under exploration. Such laser combs have become enabling tools for a growing tree of applications, from optical atomic clocks to attosecond science. Recently, the millions of precisely controlled laser comb lines that can be produced with a train of ultrashort laser pulses have been harnessed for highly multiplexed molecular spectroscopy. Fourier multi-heterodyne spectroscopy, dual comb spectroscopy, or asynchronous optical sampling spectroscopy with frequency combs are emerging as powerful new spectroscopic tools. Even the first proof-of-principle experiments have demonstrated a very exciting potential for ultra-rapid and ultra-sensitive recording of complex molecular spectra. Compared to conventional Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. Longer recording times allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each laser comb line can be known with the accuracy of an atomic clock. The spectral structure of sharp lines of a laser comb can be very useful even in the recording of broadband spectra without sharp features, as they are e.g. encountered for molecular gases or in the liquid phase. A second frequency comb of different line spacing permits the generation of a comb of radio frequency beat notes, which effectively map the optical spectrum into the radio frequency regime, so that it can be recorded with a single fast photodetector, followed by digital signal analysis. In the time domain, a pulse train of a mode-locked femtosecond laser excites some molecular medium at regular time intervals. A second pulse train of different repetition frequency interferometrically samples the transient response or "free induction decay" of the medium, akin to an optical sampling oscilloscope.

Hänsch, T. W.; Picqué, N.

2010-06-01

52

The fractional Fourier transform and applications  

NASA Technical Reports Server (NTRS)

This paper describes the 'fractional Fourier transform', which admits computation by an algorithm that has complexity proportional to the fast Fourier transform algorithm. Whereas the discrete Fourier transform (DFT) is based on integral roots of unity e exp -2(pi)i/n, the fractional Fourier transform is based on fractional roots of unity e exp -2(pi)i(alpha), where alpha is arbitrary. The fractional Fourier transform and the corresponding fast algorithm are useful for such applications as computing DFTs of sequences with prime lengths, computing DFTs of sparse sequences, analyzing sequences with noninteger periodicities, performing high-resolution trigonometric interpolation, detecting lines in noisy images, and detecting signals with linearly drifting frequencies. In many cases, the resulting algorithms are faster by arbitrarily large factors than conventional techniques.

Bailey, David H.; Swarztrauber, Paul N.

1991-01-01

53

Fourier transform spectrometer instrument lineshape (ILS) retrieval by Fourier deconvolution  

NASA Astrophysics Data System (ADS)

This work presents a Fourier deconvolution (FD) technique for retrieving the instrument lineshape (ILS) function of high-resolution Fourier transform infrared (FTIR) spectrometers. The ILS retrieved by FD is compared with the results obtained using the LINEFIT technique of Hase. The effect of a non-ideal ILS function on quantitative analysis of HBr is explored and improvements in the results of quantitative analyses are demonstrated.

Bernardo, Cirilo; Griffith, David W. T.

2005-10-01

54

The Geostationary Fourier Transform Spectrometer  

NASA Technical Reports Server (NTRS)

The Geostationary Fourier Transform Spectrometer (GeoFTS) is an imaging spectrometer designed for a geostationary orbit (GEO) earth science mission to measure key atmospheric trace gases and process tracers related to climate change and human activity. GEO allows GeoFTS to continuously stare at a region of the earth for frequent sampling to capture the variability of biogenic fluxes and anthropogenic emissions from city to continental spatial scales and temporal scales from diurnal, synoptic, seasonal to interannual. The measurement strategy provides a process based understanding of the carbon cycle from contiguous maps of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and chlorophyll fluorescence (CF) collected many times per day at high spatial resolution (2.7kmx2.7km at nadir). The CO2/CH4/CO/CF measurement suite in the near infrared spectral region provides the information needed to disentangle natural and anthropogenic contributions to atmospheric carbon concentrations and to minimize uncertainties in the flow of carbon between the atmosphere and surface. The half meter cube size GeoFTS instrument is based on a Michelson interferometer design that uses all high TRL components in a modular configuration to reduce complexity and cost. It is self-contained and as independent of the spacecraft as possible with simple spacecraft interfaces, making it ideal to be a "hosted" payload on a commercial communications satellite mission. The hosted payload approach for measuring the major carbon-containing gases in the atmosphere from the geostationary vantage point will affordably advance the scientific understating of carbon cycle processes and climate change.

Key, Richard; Sander, Stanley; Eldering, Annmarie; Blavier, Jean-Francois; Bekker, Dmitriy; Manatt, Ken; Rider, David; Wu, Yen-Hung

2012-01-01

55

The Geostationary Fourier Transform Spectrometer  

NASA Technical Reports Server (NTRS)

The Geostationary Fourier Transform Spectrometer (GeoFTS) is an imaging spectrometer designed for an earth science mission to measure key atmospheric trace gases and process tracers related to climate change and human activity. The GeoFTS instrument is a half meter cube size instrument designed to operate in geostationary orbit as a secondary "hosted" payload on a commercial geostationary satellite mission. The advantage of GEO is the ability to continuously stare at a region of the earth, enabling frequent sampling to capture the diurnal variability of biogenic fluxes and anthropogenic emissions from city to continental scales. The science goal is to obtain a process-based understanding of the carbon cycle from simultaneous high spatial resolution measurements of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and chlorophyll fluorescence (CF) many times per day in the near infrared spectral region to capture their spatial and temporal variations on diurnal, synoptic, seasonal and interannual time scales. The GeoFTS instrument is based on a Michelson interferometer design with a number of advanced features incorporated. Two of the most important advanced features are the focal plane arrays and the optical path difference mechanism. A breadboard GeoFTS instrument has demonstrated functionality for simultaneous measurements in the visible and IR in the laboratory and subsequently in the field at the California Laboratory for Atmospheric Remote Sensing (CLARS) observatory on Mt. Wilson overlooking the Los Angeles basin. A GeoFTS engineering model instrument is being developed which will make simultaneous visible and IR measurements under space flight like environmental conditions (thermal-vacuum at 180 K). This will demonstrate critical instrument capabilities such as optical alignment stability, interferometer modulation efficiency, and high throughput FPA signal processing. This will reduce flight instrument development risk and show that the GeoFTS design is mature and flight ready.

Key, Richard; Sander, Stanley; Eldering, Annmarie; Miller, Charles; Frankenberg, Christian; Natra, Vijay; Rider, David; Blavier, Jean-Francois; Bekker, Dmitriy; Wu, Yen-Hung

2012-01-01

56

FOURIER TRANSFORM INFRARED SPECTROMETRY OF AMBIENT AEROSOLS  

EPA Science Inventory

Fourier transform infrared (FTIR) spectrometry has been evaluated as a method for determining the concentration of selected species present in ambient aerosols collected on Teflon filters. The filters are analyzed by transmission measurements after collection of the fine fraction...

57

Numerical stability of nonequispaced fast Fourier transforms  

NASA Astrophysics Data System (ADS)

This paper presents some new results on numerical stability for multivariate fast Fourier transform of nonequispaced data (NFFT). In contrast to fast Fourier transform (of equispaced data), the NFFT is an approximate algorithm. In a worst case study, we show that both approximation error and roundoff error have a strong influence on the numerical stability of NFFT. Numerical tests confirm the theoretical estimates of numerical stability.

Potts, Daniel; Tasche, Manfred

2008-12-01

58

Fourier fringe processing using a regressive Fourier-transform technique  

NASA Astrophysics Data System (ADS)

Since the introduction of a fourier fringe algorithm by Takeda, it has been possible to determine the phase of a particular light source impinging on an object from one sole image. This has led to applications in many whole field optical measurement techniques such as ESPI, holography, profilometry and so on. However, the basic processing technique, in case of the 2D-Fourier transform, is subject to a major drawback. Because this technique supposes periodicity in a fringe image, the so-called leakage effects occur. This gives rise to non-negligible errors, which can be resolved by using a regressive Fourier transformation technique. In the method introduced in this article, the fringe signal is represented by a model using sines and cosines where the frequency is not fixed (which is the case for classical FFT-techniques). The coefficients of those sines and cosines together with the frequency components are then estimated locally by means of a frequency domain system identification technique. This allows the fringe pattern to be unwrapped without any distortion. This method will be applied in particular to Fourier-transform profilometry (determines object geometry using shifts of projected fringes) although it can be used in any of the techniques mentioned above. Moreover, it will be shown that the proposed method can deal with other distortions that occur in practice such as over-modulation and varying fringe visibility. The proposed technique will be validated on both simulations and on a profile measurement of a pipe section.

Vanherzeele, J.; Guillaume, Patrick; Vanlanduit, Steve

2005-06-01

59

Topics In Chemical Instrumentation: Fourier Transformations for Chemists Part I. Introduction to the Fourier Transform.  

ERIC Educational Resources Information Center

This paper explores how Fourier Transform (FT) mimics spectral transformation, how this property can be exploited to advantage in spectroscopy, and how the FT can be used in data treatment. A table displays a number of important FT serial/spectral pairs related by Fourier Transformations. A bibliography and listing of computer software related to…

Glasser, L.

1987-01-01

60

Ideal distortion-free transmission using optical Fourier transformation and Fourier transform-limited optical pulses  

Microsoft Academic Search

A new scheme for undistorted ideal pulse transmission is proposed that uses optical Fourier transformation (OFT) and transform-limited (TL) pulses. The technique focuses on the unchanged spectrum of the Fourier TL pulse after transmission, and at the output we convert the unchanged spectrum to the time domain using OFT. The transformed waveform in the time domain has no distortion. To

Masataka Nakazawa; Toshihiko Hirooka; Fumio Futami; Shigeki Watanabe

2004-01-01

61

A Primer of Fourier Transform NMR.  

ERIC Educational Resources Information Center

Fourier transform nuclear magnetic resonance (NMR) is a new spectroscopic technique that is often omitted from undergraduate curricula because of lack of instructional materials. Therefore, information is provided to introduce students to the technique of data collection and transformation into the frequency domain. (JN)

Macomber, Roger S.

1985-01-01

62

Pulse Testing Via the Fast Fourier Transform.  

National Technical Information Service (NTIS)

Subroutine REFFT accomplishes a fast, accurate transformation of time domain pulse response data to frequency response data using the real valued fast Fourier transform. The subroutine is written in Fortran IV and has been compiled and tested on a 7040, A...

C. R. Dollar C. L. Smith P. W. Murrill

1970-01-01

63

Geometric Representations for Discrete Fourier Transforms  

NASA Technical Reports Server (NTRS)

Simple geometric representations show symmetry and periodicity of discrete Fourier transforms (DFT's). Help in visualizing requirements for storing and manipulating transform value in computations. Representations useful in any number of dimensions, but particularly in one-, two-, and three-dimensional cases often encountered in practice.

Cambell, C. W.

1986-01-01

64

Fast Fourier Transform in the West (FFTW)  

NSDL National Science Digital Library

Despite its curious name, Fast Fourier Transform in the West (FFTW) is a powerful, free "C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of both real and complex data, and of arbitrary input size." Developed by researchers from the Massachusetts Institute of Technology, FFTW purportedly has outstanding performance when compared with other DFT algorithms. This statement is supported by experimental results from extensive speed and accuracy benchmarks. FFTW can be downloaded directly from this site, along with substantial documentation and three research papers stemming from its development.

Frigo, Matteo; Johnson, Steven G.

65

REMOTE FOURIER TRANSFORM INFRARED AIR POLLUTION STUDIES  

EPA Science Inventory

A commercial Fourier transform infrared interferometer system has been installed in a van and used to make longpath absorption and single-ended emission measurements of gaseous pollutant concentrations at a variety of pollutant sources. The interferometer system is described and ...

66

Fast and accurate Polar Fourier transform  

Microsoft Academic Search

In a wide range of applied problems of 2D and 3D imaging a continuous formulation of the problem places great emphasis on obtaining and manipulating the Fourier transform in Polar coordinates. However, the translation of continuum ideas into practical work with data sampled on a Cartesian grid is problematic. In this article we develop a fast high accuracy Polar FFT.

A. Averbuch; R. R. Coifmanb; D. L. Donoho; M. Elad; M. Israeli

2006-01-01

67

Fourier Transform and Reflective Imaging Pyrometry  

SciTech Connect

A stationary Fourier transform pyrometer was used to record mid-wavelength IR spectra in dynamic shock experiments. The gated-IR camera used with this system was also used to record images of light produced and light reflected from shocked metals in order to constrain the dynamic emissivity and provide temperature estimates. This technique will be referred to as reflective imaging pyrometry.

Stevens, G. D.

2011-07-01

68

Fourier Transform Spectroscopy, Eleventh International Conference. Proceedings  

SciTech Connect

These proceedings represent the papers presented at the Eleventh International Conference on Fourier Transform Spectroscopy held in August, 1997 in Athens, Georgia, USA. The Conference provided an atmosphere for people of diverse backgrounds to congregate and exchange information. The topics discussed included applications of Fourier transform spectroscopy to surface science, biological systems, atmospheric science, forensics and textiles, etc. Biochemical and biomedical studies utilizing Fourier Transform infrared spectroscopy formed a large section of the Conference Applications to semiconductor industry, namely monitoring of CVD processes and photoresists were also discussed. Most of the applications were in the near and mid infrared, with a few extending to the far infrared and visible regions of the electromagnetic spectrum. In the Keynote Address, Fourier Transform Ion Cyloctron Resonance Spectroscopy was reviewed by Professor Alan G. Marshall of the National High Magnetic Field Laboratory in Florida. Altogether 152 papers were presented at the Conference and out of these, 15 have been abstracted for the Energy, Science and Technology database. (AIP)

de Haseth, J.A. [Department of Chemistry, University of Georgia, Atlanta, GA 30602-2556 (United States)

1998-05-01

69

Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS)  

SciTech Connect

Lawrence Livermore National Laboratory is currently operating a hyperspectral imager, the Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS). This instrument is capable of operating throughout the infrared spectrum from 3 to 12.5 {mu}m with controllable spectral resolution. In this presentation we report on it`s operating characteristics, current capabilities, data throughput and calibration issues.

Carter, M.R.; Bennett, C.L.; Fields, D.J.; Lee, F.D.

1995-05-10

70

An algorithm for the basis of the finite Fourier transform  

NASA Technical Reports Server (NTRS)

The Finite Fourier Transformation matrix (F.F.T.) plays a central role in the formulation of quantum mechanics in a finite dimensional space studied by the author over the past couple of decades. An outstanding problem which still remains open is to find a complete basis for F.F.T. In this paper we suggest a simple algorithm to find the eigenvectors of F.T.T.

Santhanam, Thalanayar S.

1995-01-01

71

Discrete Fourier transforms of nonuniformly spaced data  

NASA Technical Reports Server (NTRS)

Time series or spatial series of measurements taken with nonuniform spacings have failed to yield fully to analysis using the Discrete Fourier Transform (DFT). This is due to the fact that the formal DFT is the convolution of the transform of the signal with the transform of the nonuniform spacings. Two original methods are presented for deconvolving such transforms for signals containing significant noise. The first method solves a set of linear equations relating the observed data to values defined at uniform grid points, and then obtains the desired transform as the DFT of the uniform interpolates. The second method solves a set of linear equations relating the real and imaginary components of the formal DFT directly to those of the desired transform. The results of numerical experiments with noisy data are presented in order to demonstrate the capabilities and limitations of the methods.

Swan, P. R.

1982-01-01

72

Trends in Fourier transform infrared spectroscopic imaging  

Microsoft Academic Search

Fourier transform infrared (FTIR) spectroscopic imaging is a relatively new method that has received great attention as a\\u000a new field of analytical chemistry. The greatest benefit of this technique lies in the high molecular sensitivity combined\\u000a with a spatial resolution down to a few micrometers. Another advantage is the ability to probe samples under native conditions,\\u000a which allows new insights

Gerald Steiner; Edmund Koch

2009-01-01

73

VLSI implementation of digital fourier transforms  

SciTech Connect

The construction of Fast Fourier Transform (FFT) processors is discussed. Pipeline and parallel-pipeline organizations are developed and are shown to meet the constraints imposed by VLSI. Various circuit technologies for the construction of these processors are compared, and the description of a set of NMOS chips are given. A technique for reducing the latency of the adders internal to the chips is also presented. Finally, a broad set of possible FFT organizations is discussed.

Despain, A.; Sequin, C.; Thompson, C.; Wold, E.; Lioupis, D.

1982-11-01

74

Acousto-Optic Fourier Transform Devices for Surveillance Signal Processing.  

National Technical Information Service (NTIS)

Acousto-optic techniques have been investigated for application to the Fourier-transform requirements of the Gemini surveillance concept. Acousto-optical computation of continuous and discrete Fourier transforms have been performed using a time-integratin...

J. N. Lee S. C. Lin A. B. Tveten

1983-01-01

75

Programs for high-speed Fourier, Mellin and Fourier-Bessel transforms  

NASA Technical Reports Server (NTRS)

Several FORTRAN program modules for performing one-dimensional and two-dimensional discrete Fourier transforms, Mellin, and Fourier-Bessel transforms are described along with programs that realize the algebra of high speed Fourier transforms on a computer. The programs can perform numerical harmonic analysis of functions, synthesize complex optical filters on a computer, and model holographic image processing methods.

Ikhabisimov, D. K.; Debabov, A. S.; Kolosov, B. I.; Usikov, D. A.

1979-01-01

76

Quantum transport efficiency and Fourier's law  

NASA Astrophysics Data System (ADS)

We analyze the steady-state energy transfer in a chain of coupled two-level systems connecting two thermal reservoirs. Through an analytic treatment we find that the energy current is independent of the system size, hence violating Fourier's law of heat conduction. The classical diffusive behavior in Fourier's law of heat conduction can be recovered by introducing decoherence to the quantum systems constituting the chain. We relate these results to recent discussions of energy transport in biological light-harvesting systems, and discuss the role of quantum coherence and entanglement.

Manzano, Daniel; Tiersch, Markus; Asadian, Ali; Briegel, Hans J.

2012-12-01

77

Comparative study of Hilbert–Huang transform, Fourier transform and wavelet transform in pavement profile analysis  

Microsoft Academic Search

This study employs the Hilbert–Huang transform (HHT), the wavelet transform and the Fourier transform to analyse the road surface profiles of three pavement profiles. The wavelet and Fourier transforms have been the traditional spectral analysis methods, but they are predicated on a priori selection of basis functions that are either of infinite length or have fixed finite widths. The central

A. Y. Ayenu-Prah; N. O. Attoh-Okine

2009-01-01

78

The PROSAIC Laplace and Fourier Transform  

SciTech Connect

Integral Transform methods play an extremely important role in many branches of science and engineering. The ease with which many problems may be solved using these techniques is well known. In Electrical Engineering especially, Laplace and Fourier Transforms have been used for a long time as a way to change the solution of differential equations into trivial algebraic manipulations or to provide alternate representations of signals and data. These techniques, while seemingly overshadowed by today`s emphasis on digital analysis, still form an invaluable basis in the understanding of systems and circuits. A firm grasp of the practical aspects of these subjects provides valuable conceptual tools. This tutorial paper is a review of Laplace and Fourier Transforms from an applied perspective with an emphasis on engineering applications. The interrelationship of the time and frequency domains will be stressed, in an attempt to comfort those who, after living so much of their lives in the time domain, find thinking in the frequency domain disquieting.

Smith, G.A.

1994-11-01

79

Noise figure of amplified dispersive Fourier transformation  

SciTech Connect

Amplified dispersive Fourier transformation (ADFT) is a powerful tool for fast real-time spectroscopy as it overcomes the limitations of traditional optical spectrometers. ADFT maps the spectrum of an optical pulse into a temporal waveform using group-velocity dispersion and simultaneously amplifies it in the optical domain. It greatly simplifies spectroscopy by replacing the diffraction grating and detector array in the conventional spectrometer with a dispersive fiber and single-pixel photodetector, enabling ultrafast real-time spectroscopic measurements. Following our earlier work on the theory of ADFT, here we study the effect of noise on ADFT. We derive the noise figure of ADFT and discuss its dependence on various parameters.

Goda, Keisuke; Jalali, Bahram [Electrical Engineering Department, University of California, Los Angeles, California 90095 (United States)

2010-09-15

80

Variant fractional Fourier transformer for optical pulses.  

PubMed

We demonstrate that it is possible to perform a fractional Fourier transform of an incident pulse with a continuously variable degree of fractionality, using a dispersive and nonlinear Kerr medium. This medium acts as a linear waveguide for the optical pulse if its intensity is small and if the refractive index is nonlinearly time-dependently modified by a simultaneously launched bright soliton. For optical pulses the dispersive and nonlinear medium is perfectly equivalent to a graded-index refractive medium for optical beams. PMID:18073900

Dragoman, D; Dragoman, M; Brenner, K H

1999-07-15

81

Fourier transform infrared spectroscopy of deuterated proteins  

NASA Astrophysics Data System (ADS)

We report on Fourier transform spectra of deuterated proteins: Bovine Serum Albumin, Leptin, Insulin-like Growth Factor II, monoclonal antibody to ovarian cancer antigen CA125 and Osteopontin. The spectra exhibit changes in the relative amplitude and spectral width of certain peaks. New peaks not present in the non-deuterated sample are also observed. Ways for improving the deuteration of proteins by varying the temperature and dilution time are discussed. We propose the use of deuterated proteins to increase the sensitivity of immunoassays aimed for early diagnostic of diseases most notably cancer.

Marcano O., A.; Markushin, Y.; Melikechi, N.; Connolly, D.

2008-08-01

82

Fourier transform infrared spectroscopy of peptides.  

PubMed

Fourier transform infrared (FTIR) spectroscopy provides data that are widely used for secondary structure characterization of peptides. A wide array of available sampling methods permits structural analysis of peptides in diverse environments such as aqueous solution (including optically turbid media), powders, detergent micelles, and lipid bilayers. In some cases, side chain vibrations can also be resolved and used for tertiary structure and chemical analysis. Data from several low-resolution spectroscopic techniques, including FTIR, can be combined to generate an empirical phase diagram, an overall picture of peptide structure as a function of environmental conditions that can aid in the global interpretation of large amounts of spectroscopic data. PMID:24146410

Bakshi, Kunal; Liyanage, Mangala R; Volkin, David B; Middaugh, C Russell

2014-01-01

83

Two-dimensional fourier transform spectrometer  

DOEpatents

The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

DeFlores, Lauren; Tokmakoff, Andrei

2013-09-03

84

Fourier Transforms Simplified: Computing an Infrared Spectrum from an Interferogram  

ERIC Educational Resources Information Center

Fourier transforms are used widely in chemistry and allied sciences. Examples include infrared, nuclear magnetic resonance, and mass spectroscopies. A thorough understanding of Fourier methods assists the understanding of microscopy, X-ray diffraction, and diffraction gratings. The theory of Fourier transforms has been presented in this "Journal",…

Hanley, Quentin S.

2012-01-01

85

Fourier transform methods in local gravity modeling  

NASA Technical Reports Server (NTRS)

New algorithms were derived for computing terrain corrections, all components of the attraction of the topography at the topographic surface and the gradients of these attractions. These algoriithms utilize fast Fourier transforms, but, in contrast to methods currently in use, all divergences of the integrals are removed during the analysis. Sequential methods employing a smooth intermediate reference surface were developed to avoid the very large transforms necessary when making computations at high resolution over a wide area. A new method for the numerical solution of Molodensky's problem was developed to mitigate the convergence difficulties that occur at short wavelengths with methods based on a Taylor series expansion. A trial field on a level surface is continued analytically to the topographic surface, and compared with that predicted from gravity observations. The difference is used to compute a correction to the trial field and the process iterated. Special techniques are employed to speed convergence and prevent oscillations. Three different spectral methods for fitting a point-mass set to a gravity field given on a regular grid at constant elevation are described. Two of the methods differ in the way that the spectrum of the point-mass set, which extends to infinite wave number, is matched to that of the gravity field which is band-limited. The third method is essentially a space-domain technique in which Fourier methods are used to solve a set of simultaneous equations.

Harrison, J. C.; Dickinson, M.

1989-01-01

86

Fourier transform methods in local gravity modeling  

NASA Astrophysics Data System (ADS)

New algorithms were derived for computing terrain corrections, all components of the attraction of the topography at the topographic surface and the gradients of these attractions. These algoriithms utilize fast Fourier transforms, but, in contrast to methods currently in use, all divergences of the integrals are removed during the analysis. Sequential methods employing a smooth intermediate reference surface were developed to avoid the very large transforms necessary when making computations at high resolution over a wide area. A new method for the numerical solution of Molodensky's problem was developed to mitigate the convergence difficulties that occur at short wavelengths with methods based on a Taylor series expansion. A trial field on a level surface is continued analytically to the topographic surface, and compared with that predicted from gravity observations. The difference is used to compute a correction to the trial field and the process iterated. Special techniques are employed to speed convergence and prevent oscillations. Three different spectral methods for fitting a point-mass set to a gravity field given on a regular grid at constant elevation are described. Two of the methods differ in the way that the spectrum of the point-mass set, which extends to infinite wave number, is matched to that of the gravity field which is band-limited. The third method is essentially a space-domain technique in which Fourier methods are used to solve a set of simultaneous equations.

Harrison, J. C.; Dickinson, M.

1989-06-01

87

Fourier transform ion cyclotron resonance mass spectrometry  

NASA Astrophysics Data System (ADS)

As for Fourier transform infrared (FT-IR) interferometry and nuclear magnetic resonance (NMR) spectroscopy, the introduction of pulsed Fourier transform techniques revolutionized ion cyclotron resonance mass spectrometry: increased speed (factor of 10,000), increased sensitivity (factor of 100), increased mass resolution (factor of 10,000-an improvement not shared by the introduction of FT techniques to IR or NMR spectroscopy), increased mass range (factor of 500), and automated operation. FT-ICR mass spectrometry is the most versatile technique for unscrambling and quantifying ion-molecule reaction kinetics and equilibria in the absence of solvent (i.e., the gas phase). In addition, FT-ICR MS has the following analytically important features: speed (~1 second per spectrum); ultrahigh mass resolution and ultrahigh mass accuracy for analysis of mixtures and polymers; attomole sensitivity; MSn with one spectrometer, including two-dimensional FT/FT-ICR/MS; positive and/or negative ions; multiple ion sources (especially MALDI and electrospray); biomolecular molecular weight and sequencing; LC/MS; and single-molecule detection up to 108 Dalton. Here, some basic features and recent developments of FT-ICR mass spectrometry are reviewed, with applications ranging from crude oil to molecular biology.

Marshall, Alan G.

1998-06-01

88

Compact Fourier transform spectrometer without moving parts  

NASA Astrophysics Data System (ADS)

Fourier transform spectroscopy (FTS) is a potent analytical tool for chemical and biological analysis, but is limited by system size, expense, and robustness. To make FTS technology more accessible, we present a compact, inexpensive FTS system based on a novel liquid crystal (LC) interferometer. This design is unique because the optical path difference (OPD) is controlled by voltage applied to the LC cell. The OPD is further improved by reflecting the polarized incident light through the LC several times before reaching the second polarizer and measurement. This paper presents the theoretical model and numerical simulations for the liquid crystal Fourier transform spectrometer (LCFTS), and experimental results from the prototype. Based on the experimental results, the LCFTS performs in accordance with the theoretical predictions, achieving a maximum OPD of 210?m and a resolution of 1nm at a wavelength of 630nm. The instrumental response refresh rate is just under 1 second. Absorbance measurements were conducted for single and mixed solutions of deionized water and isopropyl alcohol, demonstrating agreement with a commercial system and literature values. We also present the LCFTS transmission spectra for varying concentrations of potassium permanganate to show system sensitivity.

Huang, Chu-Yu; Estroff, B.; Wang, Wei-Chih

2012-03-01

89

Pseudo-log-polar Fourier transform for image registration  

Microsoft Academic Search

A new registration algorithm based on pseudo-log-polar Fourier transform (PLPFT) for estimating large translations, rotations, and scalings in images is developed. The PLPFT, which is calculated at points distributed at nonlinear increased concentric squares, approximates log-polar Fourier representations of images accurately. In addition, it can be calculated quickly by utilizing the Fourier separability property and the fractional fast Fourier transform.

Hanzhou Liu; Baolong Guo; Zongzhe Feng

2006-01-01

90

Geometric interpretations of the Discrete Fourier Transform (DFT)  

NASA Technical Reports Server (NTRS)

One, two, and three dimensional Discrete Fourier Transforms (DFT) and geometric interpretations of their periodicities are presented. These operators are examined for their relationship with the two sided, continuous Fourier transform. Discrete or continuous transforms of real functions have certain symmetry properties. The symmetries are examined for the one, two, and three dimensional cases. Extension to higher dimension is straight forward.

Campbell, C. W.

1984-01-01

91

Surface Inspection using fourier transform infrared spectroscopy  

SciTech Connect

The use of reflectance Fourier transform infrared (FTIR) spectroscopy as a tool for surface inspection is described. Laboratory instruments and portable instruments can support remote sensing probes that can map chemical contaminants on surfaces. Detection limits under the best of conditions are in the subnanometer range (i.e., near absolute cleanliness), excellent performance is obtained in the submicrometer range, and useful performance may exist for films tens of microns thick. Identifying and quantifying contamination such as mineral oils and greases, vegetable oils, and silicone oils on aluminum foil, galvanized sheet steel, smooth aluminum tubing, and gritblasted 7075 aluminum alloy and D6AC steel are described. The ability to map in time and space the distribution of oil stains on metals is demonstrated. Techniques for quantitatively applying oils to metals, subsequently verifying the application, and nonlinear relationships between reflectance and the quantity of oil are discussed.

Powell, G.L.; Smyrl, N.R.; Williams, D.M.; Meyers, H.M. III [Martin Marietta Energy Systems, Inc., TN (United States). Oak Ridge Y-12 Plant; Barber, T.E.; Marrero-Rivera, M. [Oak Ridge Institute for Science and Education, Oak Ridge, TN (United States)

1994-08-08

92

Advanced techniques for Fourier transform wavefront reconstruction  

NASA Astrophysics Data System (ADS)

The performance of Fourier transform (FT) reconstructors in large adaptive optics systems with Shack-Hartmann sensors and a deformable mirror is analyzed. FT methods, which are derived for point-based geometries, are adapted for use on continuous systems. Analysis and simulation show how to compensate for effects such as misalignment of the deformable mirror and wavefront sensor gain. Further filtering methods to reduce noise and improve performance are presented. These modifications can be implemented at the filtering stage, preserving the speed of FT reconstruction and providing flexibility by allowing on-the-fly filter adaptation. Simulation of a large system shows how compensated FT methods can have equivalent or better performance to slower vector-matrix-multiply methods. The best-performing FT method is the fastest to compute, has lower noise propagation and does not suffer from waffle errors.

Poyneer, Lisa A.

2003-02-01

93

Fourier transform spectrometer controller for partitioned architectures  

NASA Astrophysics Data System (ADS)

The current trend in spacecraft computing is to integrate applications of different criticality levels on the same platform using no separation. This approach increases the complexity of the development, verification and integration processes, with an impact on the whole system life cycle. Researchers at ESA and NASA advocated for the use of partitioned architecture to reduce this complexity. Partitioned architectures rely on platform mechanisms to provide robust temporal and spatial separation between applications. Such architectures have been successfully implemented in several industries, such as avionics and automotive. In this paper we investigate the challenges of developing and the benefits of integrating a scientific instrument, namely a Fourier Transform Spectrometer, in such a partitioned architecture.

Tamas-Selicean, D.; Keymeulen, D.; Berisford, D.; Carlson, R.; Hand, K.; Pop, P.; Wadsworth, W.; Levy, R.

94

Quantum indeterminism: a direct consequence of Fourier ontology  

NASA Astrophysics Data System (ADS)

Fourier ontology and consequent quantum indeterminism and the way to overcome it shall be discussed. Furthermore it shall be proven that recent experimental technology goes far beyond the limits imposed by Heisenberg indetermination relations. These experiments are perfectly integrated in the new causal nonlinear quantum physics. Keywords: Orthodox quantum mechanics, Fourier ontology, Heisenberg indetermination relations, nonlinear quantum physics, general uncertainty relations, beyond Heisenberg limits.

Croca, J. R.

2013-10-01

95

Determination of Fourier Transforms on an Instructional Analog Computer  

ERIC Educational Resources Information Center

An analog computer program to find and display the Fourier transform of some real, even functions is described. Oscilloscope traces are shown for Fourier transforms of a rectangular pulse, a Gaussian, a cosine wave, and a delayed narrow pulse. Instructional uses of the program are discussed briefly. (DT)

Anderson, Owen T.; Greenwood, Stephen R.

1974-01-01

96

DEFT: Direct electronic Fourier transforms of optical images  

Microsoft Academic Search

A family of novel devices for electronic imaging is described and several different realizations age presented. Direct electronic Fourier transform (DEFT) cameras employ coupling between surface strain waves, the image intensity, and electrical charge to produce electronic signals representing the spatial Fourier transform of the image at a single pair of terminals. This signal can be easily processed to accomplish

P. G. Kornreich; S. T. Kowel; D. J. Fleming; Neng-Tze Yang; A. Gupta; O. Lewis

1974-01-01

97

Fourier Transform based DS\\/FH Spread Spectrum Receiver  

Microsoft Academic Search

An approach towards an efficient implementation of a spread spectrum receiver for wireless non- cellular home-systems is presented. Whereas conventional receivers apply some filtering after despread- ing to recover the transmitted data, here a Discrete Fourier transform is applied and its output is redirected to an application specific processor (ASP). As mathematical operations (Fourier transforms) play a key role in

Jack P. F. Glas; Sándor E. Skolnik

1994-01-01

98

Polar Fourier transforms of radially sampled NMR data  

Microsoft Academic Search

Radial sampling of the NMR time domain has recently been introduced to speed up data collection significantly. Here, we show that radially sampled data can be processed directly using Fourier transforms in polar coordinates. We present a comprehensive theoretical analysis of the discrete polar Fourier transform, and derive the consequences of its application to radially sampled data using linear response

Brian E. Coggins; Pei Zhou

2006-01-01

99

Temporal Pulse Compression Beyond the Fourier Transform Limit  

Microsoft Academic Search

It is a generally known that the Fourier transform limit forbids a function and its Fourier transform to both be sharply localized. Thus, this limit sets a lower bound to the degree to which a band-limited pulse can be temporally compressed. However, seemingly counterintuitive waveforms have been theo- retically discovered, which, across finite time intervals, vary faster than their highest

Alex M. H. Wong; George V. Eleftheriades

2011-01-01

100

The fractional Fourier transform and time-frequency representations  

Microsoft Academic Search

The functional Fourier transform (FRFT), which is a generalization of the classical Fourier transform, was introduced a number of years ago in the mathematics literature but appears to have remained largely unknown to the signal processing community, to which it may, however, be potentially useful. The FRFT depends on a parameter ? and can be interpreted as a rotation by

Luis B. Almeida

1994-01-01

101

Application of Fourier Transform Infrared Spectrophotometry in Pharmaceutical Drugs Analysis  

Microsoft Academic Search

This review provides some background to infrared spectroscopy including Fourier transform infrared spectroscopy. It is not meant to be complete or exhaustive but to provide the reader with sufficient background for selected applications in pharmaceutical analysis. Fourier transform infrared spectroscopy (FTIR) is a fast and nondestructive analytical method. Associated with chemometrics, it can become a powerful tool for the pharmaceutical

Andrei A. Bunaciu; Hassan Y. Aboul-Enein; Serban Fleschin

2010-01-01

102

Mosaic imaging Fourier transform spectrometer applications  

NASA Astrophysics Data System (ADS)

A high-speed passive FTIR imaging spectrometer has been developed and tested in airborne flight tests on both fixed wing and helicopter platforms. This sensor was developed and flown from 2000 to 2005 in conjunction with various organizations, and is known as the Turbo FT. The Turbo FT is a laser-less rotary high speed Fourier Transform Infra-Red (FTIR) spectrometer capable of very high speed, spectral resolution to 1 cm-1, and operation in rugged environments. For these tests, the sensor was run at 8 cm-1 resolution and 50-100 scans per second with either a single element or a 2x8 element LWIR detector. An on-board auto-calibrating blackbody accessory was developed and automated chemical detection software was developed. These features allow in-flight calibration, facilitated detection of target gas clouds, and reported detections to an on-board targeting computer. This paper will discuss the system specifications, sensor performance, and field results from various experiments. Current work on development of an 8x8 pixel Turbo FT system will also be presented.

Wadsworth, Winthrop; Dybwad, Jens Peter; Stone, Drew

2005-06-01

103

Spectroscopic investigation of fluoroiodomethane, CH2FI: Fourier-transform microwave and millimeter-/submillimeter-wave spectroscopy and quantum-chemical calculations.  

PubMed

Guided by theoretical predictions, the rotational spectrum of fluoroiodomethane, CH(2)FI, has been recorded and assigned. Accurate values are reported for the ground-state rotational constants, all quartic, sextic, and two octic centrifugal-distortion constants. The hyperfine structure of the rotational spectrum was thoroughly investigated using a Fourier-transform microwave spectrometer and the Lamb-dip technique in the millimeter-/submillimeter-wave region, thus allowing the accurate determination of the complete iodine quadrupole-coupling tensor and of the diagonal elements of the iodine spin-rotation tensor. Relativistic effects turned out to be essential for the accurate theoretical prediction of the dipole moment and quadrupole-coupling constants and were accounted for by direct perturbation theory and a spin-free four-component treatment based on the Dirac-Coulomb Hamiltonian. The relativistic corrections to the dipole moment amount to up to 34% and to the iodine quadrupole-coupling tensor to about 15-16% of the total values. PMID:21548692

Puzzarini, Cristina; Cazzoli, Gabriele; López, Juan Carlos; Alonso, José Luis; Baldacci, Agostino; Baldan, Alessandro; Stopkowicz, Stella; Cheng, Lan; Gauss, Jürgen

2011-05-01

104

Cryogenic Scan Mechanism for Fourier Transform Spectrometer  

NASA Technical Reports Server (NTRS)

A compact and lightweight mechanism has been developed to accurately move a Fourier transform spectrometer (FTS) scan mirror (a cube corner) in a near-linear fashion with near constant speed at cryogenic temperatures. This innovation includes a slide mechanism to restrict motion to one dimension, an actuator to drive the motion, and a linear velocity transducer (LVT) to measure the speed. The cube corner mirror is double-passed in one arm of the FTS; double-passing is required to compensate for optical beam shear resulting from tilting of the moving cube corner. The slide, actuator, and LVT are off-the-shelf components that are capable of cryogenic vacuum operation. The actuator drives the slide for the required travel of 2.5 cm. The LVT measures translation speed. A proportional feedback loop compares the LVT voltage with the set voltage (speed) to derive an error signal to drive the actuator and achieve near constant speed. When the end of the scan is reached, a personal computer reverses the set voltage. The actuator and LVT have no moving parts in contact, and have magnetic properties consistent with cryogenic operation. The unlubricated slide restricts motion to linear travel, using crossed roller bearings consistent with 100-million- stroke operation. The mechanism tilts several arc seconds during transport of the FTS mirror, which would compromise optical fringe efficiency when using a flat mirror. Consequently, a cube corner mirror is used, which converts a tilt into a shear. The sheared beam strikes (at normal incidence) a flat mirror at the end of the FTS arm with the moving mechanism, thereby returning upon itself and compensating for the shear

Brasunas, John C.; Francis, John L.

2011-01-01

105

A discrete Fourier transform for virtual memory machines  

NASA Technical Reports Server (NTRS)

An algebraic theory of the Discrete Fourier Transform is developed in great detail. Examination of the details of the theory leads to a computationally efficient fast Fourier transform for the use on computers with virtual memory. Such an algorithm is of great use on modern desktop machines. A FORTRAN coded version of the algorithm is given for the case when the sequence of numbers to be transformed is a power of two.

Galant, David C.

1992-01-01

106

The conformational analysis of push-pull enaminoketones using Fourier transform IR and NMR spectroscopy, and quantum chemical calculations: II. ?-Dimethylaminoacrolein  

NASA Astrophysics Data System (ADS)

IR Fourier and 1H NMR spectra of ?-dimethylaminoacrolein (DMAA) were investigated in various pure solvents. Quantum chemical calculations by the method AM1 also was carried out to evaluate relative energy and dipole moment of each conformer. On the basis of NMR and IR-spectra we showed that the (DMAA) presented in solutions as equilibrium of two conformers, ( E- s- Z) ? ( E-s-E). Constant of this equilibrium, Keq = C( E- s- E)/ C( E- s- Z), depended strongly on the total (DMAA) concentration: ln K=ln K+a(1-e). Besides, ( E- s- Z) conformer of the (DMAA) was more polar and more stable than the ( E- s- E) conformer. Correlation of the out-of-phase ?˜(Cdbnd O) and in-phase ?˜(Cdbnd C) vibrations with solvatochromic parameters of Kamlet, Abbot, and Taft (KAT) revealed that the main contribution to the shift of the out-of-phase ?˜(Cdbnd O) vibrations of the both conformers made solvent's hydrogen bond acceptor (HBA) ( ?) term, whereas hydrogen bond donor (HBD) acidity ( ?) term influenced predominantly on the shift of the in-phase ?˜(Cdbnd C) vibrations of the conformers. Moreover, influence of these dominated terms was more pronounced for the ( E- s- Z) conformer in comparison with the ( E- s- E) conformer, hence the first conformer was more polarized than the last. Investigations of the enthalpies of the ( E- s- Z) ? ( E- s- E) equilibrium in carbon tetrachloride, 1,4-dioxane and their mixtures showed that these enthalpies depended predominantly on the solvent's atomic and electronic polarization and dispersive interactions.

Vdovenko, Sergey I.; Gerus, Igor I.; Fedorenko, Elena A.

2009-12-01

107

The conformational analysis of push-pull enaminoketones using Fourier transform IR and NMR spectroscopy, and quantum chemical calculations: II. Beta-dimethylaminoacrolein.  

PubMed

IR Fourier and (1)H NMR spectra of beta-dimethylaminoacrolein (DMAA) were investigated in various pure solvents. Quantum chemical calculations by the method AM1 also was carried out to evaluate relative energy and dipole moment of each conformer. On the basis of NMR and IR-spectra we showed that the (DMAA) presented in solutions as equilibrium of two conformers, (E-s-Z) <==> (E-s-E). Constant of this equilibrium, K(eq) = C(E-s-E)/C(E-s-Z), depended strongly on the total (DMAA) concentration: ln K(eq) = ln K(eq0) + a(1 - e(-bC) total). Besides, (E-s-Z) conformer of the (DMAA) was more polar and more stable than the (E-s-E) conformer. Correlation of the out-of-phase nu(C=O) and in-phase nu(C=C) vibrations with solvatochromic parameters of Kamlet, Abbot, and Taft (KAT) revealed that the main contribution to the shift of the out-of-phase nu(C=O) vibrations of the both conformers made solvent's hydrogen bond acceptor (HBA) (beta) term, whereas hydrogen bond donor (HBD) acidity (alpha) term influenced predominantly on the shift of the in-phase nu(C=C) vibrations of the conformers. Moreover, influence of these dominated terms was more pronounced for the (E-s-Z) conformer in comparison with the (E-s-E) conformer, hence the first conformer was more polarized than the last. Investigations of the enthalpies of the (E-s-Z) <==> (E-s-E) equilibrium in carbon tetrachloride, 1,4-dioxane and their mixtures showed that these enthalpies depended predominantly on the solvent's atomic and electronic polarization and dispersive interactions. PMID:19800286

Vdovenko, Sergey I; Gerus, Igor I; Fedorenko, Elena A

2009-12-01

108

Fourier and Schur-Weyl transforms applied to XXX Heisenberg magnet  

NASA Astrophysics Data System (ADS)

Similarities and differences between Fourier and Schur-Weyl transforms have been discussed in the context of a one-dimensional Heisenberg magnetic ring with N nodes. We demonstrate that main difference between them correspond to another partitioning of the Hilbert space of the magnet. In particular, we point out that application of the quantum Fourier transform corresponds to splitting of the Hilbert space of the model into subspaces associated with the orbits of the cyclic group, whereas, the Schur-Weyl transform corresponds to splitting into subspaces associated with orbits of the symmetric group.

Jakubczyk, P.; Lulek, T.; Jakubczyk, D.; Lulek, B.

2010-03-01

109

Theory and Implementation of Fast Fourier and Hadamard Transforms.  

National Technical Information Service (NTIS)

The purpose of this report is to develop general algorithms for the Fast Fourier Transform (FFT) and Hadamard transform from which optimum computer programs can be written as a signal analysis tool. The need for such discrete transforms is obvious from th...

B. K. Bhagavan E. R. McKee J. M. Carswell R. J. Polge

1973-01-01

110

Nonlinear inversion of a band-limited Fourier transform  

Microsoft Academic Search

We consider the problem of reconstructing a compactly supported function with singu- larities either from values of its Fourier transform available only in a bounded interval or from a limited number of its Fourier coefficients. Our results are based on several ob- servations and algorithms in (G. Beylkin, L. Monzón, On approximation of functions by exponential sums, Appl. Comput. Harmon.

Gregory Beylkin; Lucas Monzón

2009-01-01

111

Anamorphic fractional Fourier transform: optical implementation and applications  

Microsoft Academic Search

An additional degree of freedom is introduced to fractional-Fourier-transform systems by use of anamorphic optics. A different fractional Fourier order along the orthogonal principal directions is performed. Alaboratory experimental system shows preliminary results that demonstrate the proposed theory. Applications such as anamorphic fractional correlation and multiplexing in fractional domains are briefly suggested.

David Mendlovic; Yigal Bitran; Rainer G. Dorsch; Carlos Ferreira; Javier Garcia; Haldun M. Ozaktaz

1995-01-01

112

Grid based PHD filtering by Fast Fourier Transform  

Microsoft Academic Search

We propose an approach to calculate the Probability Hypothesis Density function on a numerical grid by using a method based on the convolution theorem and Fast Fourier transform. This approach provides a representation of the PHD over a discretized domain and, unlike other techniques, does not require Gaussian assumptions on the target and observation model. By using the Fast Fourier

Michele Pace; Huilong Zhang

2011-01-01

113

FT Digital Filtering and Simulating Fourier transform Apodization via Excel  

NSDL National Science Digital Library

This report presents an excel spreadsheet which simulates Fourier Transform apodization filtering on a noisy signal that contains either white or an environmental noise source. Users may download the report in PDF file format.

Overway, Ken

2008-02-04

114

Fourier transform infrared studies in solid egg white lysozyme.  

National Technical Information Service (NTIS)

Fourier Transform Infrared (FTIR) Spectroscopy is the most recent addition to the arsenal of bioanalytical techniques capable of providing information about the secondary structure of proteins in a variety of environments. FTIR spectra have been obtained ...

T. Z. Rivzi

1994-01-01

115

Collisional Detachment of Anions using Fourier Transform Mass Spectrometry.  

National Technical Information Service (NTIS)

Fourier Transform Mass Spectrometry (FTMS) is used to make energy resolved ion-neutral reaction measurements at high translational energies (up to several hundred eV). The technique is demonstrated for collisional detachment of anions, and should be easil...

K. B. Riehl

1992-01-01

116

Macdonald's Evaluation Conjectures, Difference Fourier Transform, and Applications  

Microsoft Academic Search

This paper contains the proof of Macdonald's duality and evaluation conjectures, the definition of the difference Fourier transform, the recurrence theorem generalizing Pieri rules, and the action of GL(2,Z) on the Macdonald polynomials at roots of unity.

Ivan Cherednik

1995-01-01

117

Determining cement composition by Fourier transform infrared spectroscopy  

Microsoft Academic Search

A diffuse reflectance mid-infrared Fourier transform spectroscopy (DRIFTS) method is described for obtaining high quality Fourier transform infrared (FTIR) spectra of cements. DRIFT spectra of synthetic C3S, C2S, C3A, and C4AF and of pure gypsum, bassanite, anhydrite, syngenite, and calcite are shown. Typical spectra of American Petroleum Institute class G and class A cements display characteristic features which can be

Trevor L. Hughes; Claire M. Methven; Timothy G. J. Jones; Sarah E. Pelham; Philip Fletcher; Christopher Hall

1995-01-01

118

Fourier transform differences and averaged similarities in diatoms.  

PubMed

Phase contrast photographs of diatoms are characterized from their Fourier transform taken through an optical diffractometer. The system output is placed on line to a PDP11/40 providing digital subtraction of two output spectral distributions due to different species. Differences obtained in this manner are used for characterizing various species. An average Fourier transform taken through coherent additions is also analyzed to find common features in a given set of diatoms. PMID:20212908

Almeida, S P; Fujii, H

1979-05-15

119

A general spectral transformation simultaneously including a Fourier transformation and a Laplace transformation  

NASA Technical Reports Server (NTRS)

A general spectral transformation is proposed and described. Its spectrum can be interpreted as a Fourier spectrum or a Laplace spectrum. The laws and functions of the method are discussed in comparison with the known transformations, and a sample application is shown.

Marko, H.

1978-01-01

120

Herz spaces and restricted summability of Fourier transforms and Fourier series  

NASA Astrophysics Data System (ADS)

A general summability method, the so-called [theta]-summability is considered for multi-dimensional Fourier transforms and Fourier series. A new inequality for the Hardy-Littlewood maximal function is verified. It is proved that if the Fourier transform of [theta] is in a Herz space, then the restricted maximal operator of the [theta]-means of a distribution is of weak type (1,1), provided that the supremum in the maximal operator is taken over a cone-like set. From this it follows that over a cone-like set a.e. for all . Moreover, converges to f(x) over a cone-like set at each Lebesgue point of if and only if the Fourier transform of [theta] is in a suitable Herz space. These theorems are extended to Wiener amalgam spaces as well. The Riesz and Weierstrass summations are investigated as special cases of the [theta]-summation.

Weisz, Ferenc

2008-08-01

121

Reaction Dynamics of O(1D,3P) + OCS Studied with Time-Resolved Fourier Transform Infrared Spectroscopy and Quantum Chemical Calculations  

NASA Astrophysics Data System (ADS)

Time-resolved infrared emission of CO2 and OCS was observed in reactions O(3P) + OCS and O(1D) + OCS with a step-scan Fourier transform spectrometer. The CO2 emission involves ??3 = -1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0°, 1) ? (0, 0°, 0); the latter derives its energy via near-resonant V-V energy transfer from highly excited CO2. Rotationally resolved emission lines of CO (v ? 4 and J ? 30) were also observed in the reaction O(1D) + OCS. For O(3P) + OCS, weak emission of CO2 diminishes when Ar is added, indicating that O(3P) is translationally hot to overcome the barrier for CO2 formation. The band contour of CO2 agrees with a band shape simulated on the basis of a Dunham expansion model of CO2; the average vibrational energy of CO2 in this channel is 49% of the available energy. This vibrational distribution fits with that estimated through a statistical partitioning of energy E* ? 18 000 ± 500 cm-1 into all vibrational modes of CO2. For the reaction of O(1D) + OCS, approximately 51% of the available energy is converted into vibrational energy of CO2, and a statistical prediction using E* ? 30 000 ± 500 cm-1 best fits the data. The mechanisms of these reactions are also investigated with the CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) method. The results indicate that the triplet O(3P) + OCS(X1?+) surface proceeds via direct abstraction and substitution channels with barriers of 27.6 and 36.4 kJ mol-1, respectively, to produce SO(X3?-) + CO(X1?+) and S(3P) + CO2(X1A1), whereas two intermediates, OSCO and SC(O)O, are formed from the singlet O(1D) + OCS(X1?+) surface without barrier, followed by decomposition to SO(a1?) + CO(X1?+) and S(1D) + CO2(X1A1), respectively. For the ground-state reaction O(3P) + OCS(X1?+), the singlet-triplet curve crossings play important roles in the observed kinetics and chemiluminescence.

Chiang, Hung-Chu; Wang, Niann-Shiah; Tsuchiya, Soji; Chen, Hsin-Tsung; Lee, Yuan-Pern; Lin, M. C.

2009-07-01

122

A comparative image analysis of discrete radial Fourier transforms  

Microsoft Academic Search

Fourier transform is not often applied to pattern and object recognition, because of its inefficiency in image description and calculation. In order to solve this problem, a bi-discrete radial cosine transform is proposed. This new transform has two superior properties. Firstly, by using Mukundan’s square-to-circular transformation, it projects images in square to images in discrete circle girds. Secondly, different from

Guojun Zhang; Bo Li; Bo Fu; Li Li; Gaoxiang Liu

2010-01-01

123

The Fast Fourier and Hilbert-Huang Transforms: A Comparison  

Microsoft Academic Search

The conversion of time domain data via the fast Fourier (FFT) and Hilbert-Huang (HHT) transforms is compared. The FFT treats amplitude vs. time information globally as it transforms the data to an amplitude vs. frequency description. The HHT is not constrained by the assumptions of stationarity and linearity, required for the FFT, and generates both amplitude and frequency information as

Denis Donnelly

2006-01-01

124

Inverse Fourier Transform in the Gamma Coordinate System  

PubMed Central

This paper provides auxiliary results for our general scheme of computed tomography. In 3D parallel-beam geometry, we first demonstrate that the inverse Fourier transform in different coordinate systems leads to different reconstruction formulas and explain why the Radon formula cannot directly work with truncated projection data. Also, we introduce a gamma coordinate system, analyze its properties, compute the Jacobian of the coordinate transform, and define weight functions for the inverse Fourier transform assuming a simple scanning model. Then, we generate Orlov's theorem and a weighted Radon formula from the inverse Fourier transform in the new system. Furthermore, we present the motion equation of the frequency plane and the conditions for sharp points of the instantaneous rotation axis. Our analysis on the motion of the frequency plane is related to the Frenet-Serret theorem in the differential geometry.

Wei, Yuchuan; Yu, Hengyong; Wang, Ge

2011-01-01

125

Designing the Fourier Space with Transformation Optics.  

National Technical Information Service (NTIS)

We show that transformation optics can be applied to extend the functionalities of conventional optical devices. In particular, geometrically compressing the input facet of any conventional optical elements can extend the input spatial frequency bandwidth...

G. Bartal J. Li S. Han S. Zhang X. Zhang

2009-01-01

126

Imaging Fourier Transform Spectroscopy from a Space Based Platform -- The Herschel/SPIRE Fourier Transform Spectrometer  

NASA Astrophysics Data System (ADS)

The Herschel Space Observatory (Herschel), a flagship mission of the European Space Agency (ESA), is comprised of three cryogenically cooled instruments commissioned to explore the far-infrared/submillimetre universe. Herschel's remote orbit at the second Lagrangian point (L2) of the Sun-Earth system, and its cryogenic payload, impose a need for thorough instrument characterization and rigorous testing as there will be no possibility for any servicing after launch. The Spectral and Photometric Imaging Receiver (SPIRE) is one of the instrument payloads aboard Herschel and consists of a three band imaging photometer and a two band imaging spectrometer. The imaging spectrometer on SPIRE consists of a Mach-Zehnder (MZ)-Fourier transform spectrometer (FTS) coupled with bolometric detector arrays to form an imaging FTS (IFTS). This thesis presents experiments conducted to verify the performance of an IFTS system from a space based platform, Le. the use of the SPIRE IFTS within the Herschel space observatory. Prior to launch, the SPIRE instrument has undergone a series of performance verification tests conducted at the Rutherford Appleton Laboratory (RAL) near Oxford, UK. Canada is involved in the SPIRE project through provision of instrument development hardware and software, mission flight software, and support personnel. Through this thesis project I have been stationed at RAL for a period spanning fifteen months to participate in the development, performance verification, and characterization of both the SPIRE FTS and photometer instruments. This thesis discusses Fourier transform spectroscopy and related FTS data processing (Chapter 2). Detailed discussions are included on the spectral phase related to the FTS beamsplitter (Chapter 3), the imaging aspects of the SPIRE IFTS instrument (Chapter 4), and the noise characteristics of the SPIRE bolometer detector arrays as measured using the SPIRE IFTS (Chapter 5). This thesis presents results from experiments performed both on site at the RAL Space Science and Technology Department (SSTD) Assembly Integration Verification (AIV) instrument test facility as well as from the Astronomical Instrumentation Group (AIG) research laboratories within the Department of Physics & Astronomy at the University of Lethbridge.

Spencer, Locke Dean

127

Electro-Optical Imaging Fourier-Transform Spectrometer  

NASA Technical Reports Server (NTRS)

An electro-optical (E-O) imaging Fourier-transform spectrometer (IFTS), now under development, is a prototype of improved imaging spectrometers to be used for hyperspectral imaging, especially in the infrared spectral region. Unlike both imaging and non-imaging traditional Fourier-transform spectrometers, the E-O IFTS does not contain any moving parts. Elimination of the moving parts and the associated actuator mechanisms and supporting structures would increase reliability while enabling reductions in size and mass, relative to traditional Fourier-transform spectrometers that offer equivalent capabilities. Elimination of moving parts would also eliminate the vibrations caused by the motions of those parts. Figure 1 schematically depicts a traditional Fourier-transform spectrometer, wherein a critical time delay is varied by translating one the mirrors of a Michelson interferometer. The time-dependent optical output is a periodic representation of the input spectrum. Data characterizing the input spectrum are generated through fast-Fourier-transform (FFT) post-processing of the output in conjunction with the varying time delay.

Chao, Tien-Hsin; Zhou, Hanying

2006-01-01

128

A class of fractional integral transforms: a generalization of the fractional Fourier transform  

Microsoft Academic Search

The paper presents a systematic and unified approach to fractional integral transforms. We introduce a new class of fractional integral transforms that includes the fractional Fourier and Hankel transforms and the fractional integration and differentiation operators as special cases. These fractional transforms may also be viewed as angular transforms, indexed by an angular parameter ?, since their kernels are obtained

Ahmed I. Zayed

2002-01-01

129

[Spatially modulated Fourier transform imaging spectrometer data compression research].  

PubMed

Fourier transform imaging spectrometer is a new technic, and has been developed very fast in recent ten years. When it is used in satellite, because of the limit by the data transmission, the authors need to compress the original data obtained by the Fourier transform imaging spectrometer, then, the data can be transmitted, and can be incepted on the earth and decompressed. Then the authors can do data process to get spectrum data which can be used by user. Data compression technic used in Fourier transform imaging spectrometer is a new technic, and few papers introduce it at home and abroad. In this paper the authors will give a data compression method, which has been used in EDIS, and achieved a good result. PMID:20302132

Huang, Min; Xiangli, Bin; Yuan, Yan; Shen, Zhong; Lu, Qun-bo; Wang, Zhong-hou; Liu, Xue-bin

2010-01-01

130

Photonic fractional Fourier transformer with a single dispersive device.  

PubMed

In this work we used the temporal analog of spatial Fresnel diffraction to design a temporal fractional Fourier transformer with a single dispersive device, in this way avoiding the use of quadratic phase modulators. We demonstrate that a single dispersive passive device inherently provides the fractional Fourier transform of an incident optical pulse. The relationships linking the fractional Fourier transform order and scaling factor with the dispersion parameters are derived. We first provide some numerical results in order to prove the validity of our proposal, using a fiber Bragg grating as the dispersive device. Next, we experimentally demonstrate the feasibility of this proposal by using a spool of a standard optical fiber as the dispersive device. PMID:23571945

Cuadrado-Laborde, C; Carrascosa, A; Díez, A; Cruz, J L; Andres, M V

2013-04-01

131

Blind digital watermarking method in the fractional Fourier transform domain  

NASA Astrophysics Data System (ADS)

In this paper, we proposed a novel blind digital image watermarking algorithm based on the fractional Fourier transform (FRFT), which is a generalization of the ordinary Fourier transform and its output has the mixed time and frequency components of the signal. The original image is segmented into non-overlapping blocks for watermarking, and each block is transformed by the two dimensional fractional Fourier transform with two fractional orders. Then each pixel value of binary watermark is embedded by modifying the back-diagonal FRFT coefficients of each image block at the same location with a random array. After perform an inverse two dimensional fractional Fourier transform, we can obtain the watermarked image and the transform orders can be consider as the encryption keys in this method. A series of attacking experiments are performed on the proposed method. The experiments results show that the proposed algorithm not only is of good imperceptibility and security and is very robust to JPEG compression noise attacks and image manipulation operations, but also can provide protection even under compound attacks.

Lang, Jun; Zhang, Zheng-guang

2014-02-01

132

Fourier Transform Microwave Spectroscopy of the Hoso Radical  

NASA Astrophysics Data System (ADS)

Molecules closely-related to SO_2 are of considerable interest because of the important role this triatomic or its surrogates play in the atmospheric and combustion chemistry of sulfur-containing compounds. Previous coupled-cluster quantum chemical calculations of the [HSO_2] potential energy surface conclude that a cis-isomer is the ground state, the trans isomer is a transition state, and that a C2v HSO_2 isomer lies considerably higher in energy (˜ 20 kcal/mol). Using Fourier Transform microwave spectroscopy, the rotational spectrum of the cis-HOSO radical has been precisely characterized for the first time by applying a DC discharge to a mixture of water and sulfur dioxide heavily diluted in neon. The fundamental rotational transition was detected near 17 GHz, in good agreement (within ˜ 1%) of the calculated value derived from the equilibrium structure. Microwave-microwave double resonance techniques have been used to extend the dataset to higher frequencies and to provide confirmation of the spectroscopic assignments. D. Binns, and P. Marshall, Journal of Chemical Physics 95, 4940, (1991) B. Napolion, and J. D. Watts, Chemical Physics Letters 421, 562, (2006)

Lattanzi, Valerio; McCarthy, M. C.; Tamassia, Filippo

2011-06-01

133

Parallel fast Fourier transforms for non power of two data  

SciTech Connect

This report deals with parallel algorithms for computing discrete Fourier transforms of real sequences of length N not equal to a power of two. The method described is an extension of existing power of two transforms to sequences with N a product of small primes. In particular, this implementation requires N = 2{sup p}3{sup q}5{sup r}. The communication required is the same as for a transform of length N = 2{sup p}. The algorithm presented is intended for use in the solution of partial differential equations, or in any situation in which a large number of forward and backward transforms must be performed and in which the Fourier Coefficients need not be ordered. This implementation is a one dimensional FFT but the techniques are applicable to multidimensional transforms as well. The algorithm has been implemented on a 128 node Intel Ipsc/860.

Semeraro, B.D.

1994-09-01

134

Fourier-transform and global contrast interferometer alignment methods  

DOEpatents

Interferometric methods are presented to facilitate alignment of image-plane components within an interferometer and for the magnified viewing of interferometer masks in situ. Fourier-transforms are performed on intensity patterns that are detected with the interferometer and are used to calculate pseudo-images of the electric field in the image plane of the test optic where the critical alignment of various components is being performed. Fine alignment is aided by the introduction and optimization of a global contrast parameter that is easily calculated from the Fourier-transform.

Goldberg, Kenneth A. (Berkeley, CA)

2001-01-01

135

Fractional Fourier transform of Lorentz-Gauss beams.  

PubMed

Lorentz-Gauss beams are introduced to describe certain laser sources that produce highly divergent beams. The fractional Fourier transform (FRFT) is applied to treat the propagation of Lorentz-Gauss beams. Based on the definition of convolution and the convolution theorem of the Fourier transform, an analytical expression for a Lorentz-Gauss beam passing through an FRFT system has been derived. By using the derived expression, the properties of a Lorentz-Gauss beam in the FRFT plane are graphically illustrated with numerical examples. PMID:19183688

Zhou, Guoquan

2009-02-01

136

Gas Analysis by Fourier Transform Mm-Wave Spectroscopy  

NASA Astrophysics Data System (ADS)

Molecular rotational spectroscopy of low pressure, room temperature gases offers high chemical selectivity and sensitivity with the potential for a wide range of applications in gas analysis. A strength of the technique is the potential to identify molecules that have not been previously studied by rotational spectroscopy by comparing experimental results to predictions of the spectroscopic parameters from quantum chemistry -6 so called library-free detection. The development of Fourier transform mm-wave spectrometers using high peak power (30 mW) active multiplier chain mm-wave sources brings new measurement capabilities to the analysis of complex gas mixtures. Strategies for gas analysis based on high-throughput mm-wave spectroscopy and arbitrary waveform generator driven mm-wave sources are described. Several new measurement capabilities come from the intrinsic time-domain measurement technique. High-sensitivity double-resonance measurements can be performed to speed the analysis of a complex gas sample containing several species. This technique uses a "pi-pulse" to selectively invert the population of two selected rotational energy levels and the effect of this excitation pulse on all other transitions in the spectrometer operating range is monitored using segmented chirped-pulse Fourier transform spectroscopy. This method can lead to automated determination of the molecular rotational constants. Rapid pulse duration scan experiments can be used to estimate the magnitude and direction of the dipole moment of the molecule from an unknown spectrum. Coherent pulse echo experiments, using the traditional Hahn sequence or two-color population recovery methods, can be used to determine the collisional relaxation rate of the unknown molecule. This rate determination improves the ability to estimate the mass of the unknown molecule from the determination of the Doppler dephasing rate. By performing a suite of automated, high-throughput measurements, there is the potential to determine the shape (via the rotational constant), electric properties (the dipole moments and its direction in the principal axis system), and the mass of the molecule to aid its identification.

Harris, Brent J.; Steber, Amanda L.; Lehmann, Kevin K.; Pate, Brooks H.

2013-06-01

137

Fractional cosine and sine transforms in relation to the fractional Fourier and Hartley transforms  

Microsoft Academic Search

The fractional cosine and sine transforms-closely related to the fractional Fourier transform, which is now actively used in optics and signal processing, and to the fractional Hartley transform-are introduced and their main properties and possible applications as elementary fractional transforms of causal signals are discussed.

T. Alieva; M. J. Bastiaans

2003-01-01

138

FRACTIONAL COSINE AND SINE TRANSFORMS IN RELATION TO THE FRACTIONAL FOURIER AND HARTLEY TRANSFORMS  

Microsoft Academic Search

The fractional cosine and sine transforms - closely related to the fractional Fourier transform, which is now actively used in optics and signal processing, and to the fractional Hartley transform - are introduced and their main properties and possible applications as elementary fractional transforms of causal signals are discussed.

Tatiana Alieva; Martin J. Bastiaans

2002-01-01

139

Discrete Fourier Transform Analysis in a Complex Vector Space  

NASA Technical Reports Server (NTRS)

Alternative computational strategies for the Discrete Fourier Transform (DFT) have been developed using analysis of geometric manifolds. This approach provides a general framework for performing DFT calculations, and suggests a more efficient implementation of the DFT for applications using iterative transform methods, particularly phase retrieval. The DFT can thus be implemented using fewer operations when compared to the usual DFT counterpart. The software decreases the run time of the DFT in certain applications such as phase retrieval that iteratively call the DFT function. The algorithm exploits a special computational approach based on analysis of the DFT as a transformation in a complex vector space. As such, this approach has the potential to realize a DFT computation that approaches N operations versus Nlog(N) operations for the equivalent Fast Fourier Transform (FFT) calculation.

Dean, Bruce H.

2009-01-01

140

The conformational analysis of push-pull enaminones using Fourier transform IR and NMR spectroscopy, and quantum chemical calculations. V. ?-Methyl-, fluorine-?-N,N-dimethylaminovinyl trifluoromethyl ketones.  

PubMed

IR Fourier spectra of two enaminoketones with general formula F3CCOCRCHN(CH3)2, R=F (DMTFBN); R=CH3, (DMTMBN) were studied in various pure solvents. For comparison results of earlier investigated enaminoketone R=H (DMTBN) was also presented. On the basis of NMR and IR spectra it was shown that enaminoketones DMTBN, DMTFBN and DMTMBN presented in solutions as equilibrium of two conformers, (E-s-Z)?(E-s-E) (for DMTFBN these conformers are denoted as (Z-s-Z) and (Z-s-E), respectively). DFT calculations were carried out to evaluate relative energy and dipole moment of each spatial form. It was shown that 'closed-ring' complex formation between (E-s-Z) and (E-s-E) conformers of DMTBN accounts for discrepancies between DFT calculations of conformer relative energies and experimentally evaluated enthalpies of (E-s-Z)?(E-s-E) equilibrium. In ?-substituted DMTFBN and DMTMBN, where formation of 'closed-ring' complex was impossible we did not observe such discrepancies. For both (E-s-Z) and (E-s-E) conformers of the DMTBN and DMTMBN the main influence on the ??(CO) vibrations has the solvent's hydrogen bond donor (HBD) acidity, whereas for the DMTFBN an influence of the solvent's polarity/polarizability dominated. PMID:24820327

Vdovenko, Sergey I; Gerus, Igor I; Zhuk, Yuri I; Kukhar, Valery P; Röschenthaler, Gerd-Volker

2014-10-15

141

Calibration of optical detectors using discrete Fourier transform techniques  

NASA Technical Reports Server (NTRS)

A method for determining the detector electrooptical transfer function (DEOTF) at different discrete frequencies simultaneously is presented. It involves simulation of the detector with a waveform of unknown frequency composition, such as a square wave or impulse function. The DEOTF is calculated as the ratio of the discrete Fourier transform of the detector output to the transform of the input waveform. This technique was successfully applied to Golay cell and bolometer detectors and can be used for other linear detector systems.

Hagopian, John G.; Eichhorn, William

1990-01-01

142

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging  

Microsoft Academic Search

Fourier transform infrared (FT-IR) imaging allows simultaneous spectral characterization of large spatial areas due to its multichan- nel detection advantage. The acquisition of large amounts of data in the multichannel coné guration results, however, in a poor tem- poral resolution of sequentially acquired data sets, which limits the examination of dynamic processes to processes that have character- istic time scales

Rohit Bhargava; Ira W. Levin

2003-01-01

143

APPLICATION OF FOURIER TRANSFORM SPECTROSCOPY TO AIR POLLUTION PROBLEMS  

EPA Science Inventory

The nature of information that can be retrieved from spectra obtained with Fourier transform spectroscopy is discussed. Nonlinear, least-squares analysis of spectra is capable of retrieving information that is beyond the reach of conventional methods and has improved precision an...

144

Applications of Fourier transforms in digital magnetic recording theory  

Microsoft Academic Search

In this paper we present a unified treatment of many problems in digital pulse recording. The physics appropriate to each problem is characterized by a reciprocal-space transfer function, which may be abstracted from published studies of sine wave recording. Over twenty-five transfer functions are given in appendices. Given the transfer functions, an inverse Fourier transformation completes each problem. The fields,

J. Mallinson; I. A. Stegun

1974-01-01

145

Fourier transform infrared spectroscopy (FTIR) of laser-irradiated cementum  

Microsoft Academic Search

Utilizing Fourier Transform Infrared Spectroscopy (FTIR) in specular reflectance mode chemical changes of root cement surfaces due to laser radiation were investigated. A total of 18 samples of root cement were analyzed, six served as controls. In this study laser energies were set to those known for removal of calculus or for disinfection of periodontal pockets. Major changes in organic

Peter Rechmann; Joel M. White; Silvia C. M. Cecchini; Thomas Hennig

2003-01-01

146

Fourier transform-iteration for antenna pattern synthesis  

Microsoft Academic Search

A method for the synthesis of antenna patterns is developed in which a specified beam is approached by Fourier transform-iteration under the condition of retaining the side lobe level below its allowable level. It is found that this method is suitable for the simultaneous synthesis of the modulus and the phase of the pattern. The method is particularly effective for

K. Y. Feng

1981-01-01

147

Signal estimation from modified short-time Fourier transform  

Microsoft Academic Search

In this paper, we present an algorithm to estimate a signal from its modified short-time Fourier transform (STFT). This algorithm is computationally simple and is obtained by minimizing the mean squared error between the STFT of the estimated signal and the modified STFT. Using this algorithm, we also develop an iterative algorithm to estimate a signal from its modified STFT

DANIEL W. GRIFFIN; JAE S. LIM

1984-01-01

148

Robust Watermarking Scheme Based on Multiresolution Fractional Fourier Transform  

Microsoft Academic Search

In this paper, a new robust watermarking scheme is proposed in multiresolution fractional Fourier transform domain using singular value decomposition. The watermark is embedded in the high frequency sub-band of the host image at coarsest level. Although the schemes based on SVD are robust but fail under ambiguity attacks. In this attack, both the owner and attacker can extract their

Gaurav Bhatnagar; Balasubramanian Raman

2008-01-01

149

Fourier transform photoacoustic visible spectroscopy of solids and liquids  

SciTech Connect

Fourier transform photoacoustic spectroscopy (FTPAS) can be carried out in the visible using either a piezoelectric crystal or a microphone to detect the interferogram produced in a sample when the latter is illuminated by white light passed through a Michelson interferometer. Spectra of lanthanide oxides and whole human blood are reported that illustrate benefits and limitations of visible FTPAS.

Lloyd, L.B. (Univ. of Utah, Salt Lake City); Burnham, R.K.; Chandler, W.L.; Eyring, E.M.; Farrow, M.M.

1980-09-01

150

Approximate Fast Fourier Transform Technique for Vernier Spectral Analysis.  

National Technical Information Service (NTIS)

An approximate and quick fast Fourier transform technique for vernier spectral analysis is derived and tested for several candidate time-and delay-weightings, and for overlaps of the time weightings. For 50 percent overlap, the use of a simple cosine lobe...

A. H. Nuttall

1974-01-01

151

Sample rotation in diffuse reflectance Fourier transform infrared spectroscopy  

Microsoft Academic Search

An apparatus for the rotation of sample and blank in diffuse reflectance Fourier transform infrared spectroscopy has been designed and fabricated. Spectra taken with sample rotation give data with better precision by a factor of 4 than without rotation. Additionally, sample rotation saves time by eliminating the need for taking three to five spectra followed by spectrum averaging as has

Rance A. Velapoldi; Jan E. Tvedt; Alfred A. Christy

1987-01-01

152

Initial Results From the USNO Dispersed Fourier Transform Spectrograph.  

National Technical Information Service (NTIS)

We have designed and constructed a dispersed Fourier transform spectrometer (dFTS), consisting of a conventional FTS followed by a grating spectrometer. By combining these two devices,we negate a substantial fraction of the sensitivity disadvantage of a c...

A. R. Hajian A. T. Cenko B. B. Behr D. Mozurkewich R. P. Olling

2007-01-01

153

Discrete fourier transform (DFT) analysis for applications using iterative transform methods  

NASA Technical Reports Server (NTRS)

According to various embodiments, a method is provided for determining aberration data for an optical system. The method comprises collecting a data signal, and generating a pre-transformation algorithm. The data is pre-transformed by multiplying the data with the pre-transformation algorithm. A discrete Fourier transform of the pre-transformed data is performed in an iterative loop. The method further comprises back-transforming the data to generate aberration data.

Dean, Bruce H. (Inventor)

2012-01-01

154

A Unified Method of Finding Laplace Transforms, Fourier Transforms, and Fourier Series. [and] An Inversion Method for Laplace Transforms, Fourier Transforms, and Fourier Series. Integral Transforms and Series Expansions. Modules and Monographs in Undergraduate Mathematics and Its Applications Project. UMAP Units 324 and 325.  

ERIC Educational Resources Information Center

This document contains two units that examine integral transforms and series expansions. In the first module, the user is expected to learn how to use the unified method presented to obtain Laplace transforms, Fourier transforms, complex Fourier series, real Fourier series, and half-range sine series for given piecewise continuous functions. In…

Grimm, C. A.

155

On uncertainty principle of the local polynomial Fourier transform  

NASA Astrophysics Data System (ADS)

In this article, a comprehensive study on uncertainty principle of the local polynomial Fourier transform (LPFT) is presented. It shows that the uncertainty product of the LPFT of an arbitrary order is related to the parameters of the signal and the window function, in addition to the errors of estimating the polynomial coefficients. Important factors that affect resolutions of signal representation, such as the window width, the length of overlap between signal segments, order mismatch and estimation errors of polynomial coefficients, are discussed. The effects of minimizing computational complexities on signal representation by reducing the order of the transform and the overlap length between signal segments are also examined. In terms of the signal concentration, comparisons among the short-time Fourier transform, the Wigner-Ville distribution and the second order LPFT are presented. The LPFT is shown to be an excellent candidate providing better representations for time-varying signals.

Li, Xiumei; Bi, Guoan; Li, Shenghong

2012-12-01

156

A VLSI architecture for simplified arithmetic Fourier transform algorithm  

NASA Technical Reports Server (NTRS)

The arithmetic Fourier transform (AFT) is a number-theoretic approach to Fourier analysis which has been shown to perform competitively with the classical FFT in terms of accuracy, complexity, and speed. Theorems developed in a previous paper for the AFT algorithm are used here to derive the original AFT algorithm which Bruns found in 1903. This is shown to yield an algorithm of less complexity and of improved performance over certain recent AFT algorithms. A VLSI architecture is suggested for this simplified AFT algorithm. This architecture uses a butterfly structure which reduces the number of additions by 25 percent of that used in the direct method.

Reed, Irving S.; Shih, Ming-Tang; Truong, T. K.; Hendon, E.; Tufts, D. W.

1992-01-01

157

Fourier transforms and fractals in the food and agricultural industry  

NASA Astrophysics Data System (ADS)

Links between the fractal Hausdorff-dimension, the Fourier transform of 2D scenes and image segmentation by texture are discussed. It is shown that the fractal Hausdorff-dimension can be derived by integration of the intensity of the spatial frequency domain (i.e. the Fourier plane) over a set of different band-limited spatial filters. The difference between a computational and optical approach to determine the Hausdorff-dimension are shown, with advantages of both methods discussed. Possible future directions of research/improvements are mentioned. Natural and simulated scenes are considered which apply to a wide range of situations in the agricultural and food industry.

Zwiggelaar, Reyer; Bull, Christine R.

1994-11-01

158

Novel fringe scanning/Fourier transform method of synthetic imaging  

SciTech Connect

We have developed a one-dimensional theory and a computer model for synthetically imaging scenes using a novel fringe scanning/Fourier transform technique. Our method probes a scene using two interfering beams of slightly different frequency. These beams form a moving fringe pattern which scans the scene and resonates with any spatial frequency components having the same spatial frequency as the scanning fringe pattern. A simple, non-imaging detector above the scene observes any scattered radiation from the scene falling onto it. If a resonance occurs between the scanning fringe pattern and the scene, then the scattered radiation will be modulated at the difference frequency between the two probing beams. By changing the spatial period of the fringe pattern and then measuring the amplitude and phase of the modulated radiation that is scattered from the scene, the Fourier amplitudes and phases of the different spatial frequency components making up the scene can be measured. A synthetic image of the scene being probed can be generated from this Fourier amplitude and phase data by taking the inverse Fourier transform of this information. This technique could be used to image objects using light, ultrasonic, or other electromagnetic or acoustic waves.

Crawford, T.M.; Albano, R.K.

1993-08-01

159

Application of Fourier transforms for microwave radiometric inversions  

NASA Technical Reports Server (NTRS)

Existing microwave radiometer technology now provides a suitable method for remote determination of the ocean surface's absolute brightness temperature. To extract the brightness temperature of the water from the antenna temperature, an unstable Fredholm integral equation of the first kind is solved. Fourier transform techniques are used to invert the integral after it is placed into a cross correlation form. Application and verification of the methods to a two-dimensional modeling of a laboratory wave tank system are included. The instability of the ill-posed Fredholm equation is examined and a restoration procedure is included which smooths the resulting oscillations. With the recent availability and advances of fast Fourier transform (FFT) techniques, the method presented becomes very attractive in the evaluation of large quantities of data.

Holmes, J. J.; Balanis, C. A.; Truman, W. M.

1975-01-01

160

Fourier transform digital holographic adaptive optics imaging system  

PubMed Central

A Fourier transform digital holographic adaptive optics imaging system and its basic principles are proposed. The CCD is put at the exact Fourier transform plane of the pupil of the eye lens. The spherical curvature introduced by the optics except the eye lens itself is eliminated. The CCD is also at image plane of the target. The point-spread function of the system is directly recorded, making it easier to determine the correct guide-star hologram. Also, the light signal will be stronger at the CCD, especially for phase-aberration sensing. Numerical propagation is avoided. The sensor aperture has nothing to do with the resolution and the possibility of using low coherence or incoherent illumination is opened. The system becomes more efficient and flexible. Although it is intended for ophthalmic use, it also shows potential application in microscopy. The robustness and feasibility of this compact system are demonstrated by simulations and experiments using scattering objects.

Liu, Changgeng; Yu, Xiao; Kim, Myung K.

2013-01-01

161

Target Image Enhancement in Radar Imaging Using Fractional Fourier Transform  

NASA Astrophysics Data System (ADS)

This paper presents a new Range-Doppler Algorithm based on Fractional Fourier Transform (RDA-FrFT) to obtain High-Resolution (HR) images for targets in radar imaging. The performance of the proposed RDA-FrFT is compared with the classical RDA algorithm, which is based on the Fast Fourier Transform (FFT). A closed-form expression for the range and azimuth compression of the proposed RDA-FrFT is mathematically derived and analyzed from the HR Synthetic Aperture Radar (SAR) imaging point of view. The proposed RDA-FrFT takes its advantage of the property of the FrFT to resolve chirp signals with high precision. Results show that the proposed RDA-FrFT gives low Peak Side-Lobe (PSL) and Integrated Side-Lobe (ISL) levels in range and azimuth directions for detected targets. HR images are obtained using the proposed RDA-FrFT algorithm.

El-Mashed, M. G.; Dessouky, M. I.; El-Kordy, M.; Zahran, O.; Abd El-Samie, F. E.

2012-03-01

162

Fourier transform digital holographic adaptive optics imaging system.  

PubMed

A Fourier transform digital holographic adaptive optics imaging system and its basic principles are proposed. The CCD is put at the exact Fourier transform plane of the pupil of the eye lens. The spherical curvature introduced by the optics except the eye lens itself is eliminated. The CCD is also at image plane of the target. The point-spread function of the system is directly recorded, making it easier to determine the correct guide-star hologram. Also, the light signal will be stronger at the CCD, especially for phase-aberration sensing. Numerical propagation is avoided. The sensor aperture has nothing to do with the resolution and the possibility of using low coherence or incoherent illumination is opened. The system becomes more efficient and flexible. Although it is intended for ophthalmic use, it also shows potential application in microscopy. The robustness and feasibility of this compact system are demonstrated by simulations and experiments using scattering objects. PMID:23262541

Liu, Changgeng; Yu, Xiao; Kim, Myung K

2012-12-10

163

Fourier transform infrared and Raman spectral investigations of 5-aminoindole  

Microsoft Academic Search

Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectra of 5-aminoindole has been recorded and analysed. The FT-IR spectrum of the compound was recorded in a BrukerIFS 66V spectrometer in the range 4000–400cm?1 and the FT-Raman spectrum was also recorded in the same instrument in the region 3500–100cm?1. Observed frequencies for normal modes are compared with those calculated form normal co-ordinate

V. Arjunan; N. Puviarasan; S. Mohan

2006-01-01

164

Apparatus and methods for continuous beam fourier transform mass spectrometry  

DOEpatents

A continuous beam Fourier transform mass spectrometer in which a sample of ions to be analyzed is trapped in a trapping field, and the ions in the range of the mass-to-charge ratios to be analyzed are excited at their characteristic frequencies of motion by a continuous excitation signal. The excited ions in resonant motions generate real or image currents continuously which can be detected and processed to provide a mass spectrum.

McLuckey, Scott A. (Oak Ridge, TN); Goeringer, Douglas E. (Oak Ridge, TN)

2002-01-01

165

Nonlinear effects of phase blurring on Fourier transform holograms  

Microsoft Academic Search

Liquid-crystal light valves can have intensity-dependent resolution. We find for a nematic liquid-crystal light valve that this effect is well modeled as a phase that has been blurred by a linear space-invariant filter. The phase point-spread function is measured and is used in simulations to demonstrate that it introduces inter- modulation products to the diffraction patterns of computer-generated Fourier transform

Markus Duelli; Li Ge; Robert W. Cohn

2000-01-01

166

Gas Chromatography\\/Fourier Transform Infrared Spectroscopy Applications  

Microsoft Academic Search

The past few years have seen a marked increase in interest in the use of combined gas-liquid chromatography and infrared spectroscopy (GC\\/IR). This increase in interest is primarily due to the advent of Fourier transform infrared spectroscopy (FTIR). The combination. GC\\/FTIR. provides the sensitivity and scanning speed which have hindered the wide applicability of GC\\/IR using dispersive instruments.

M. D. Erickson

1979-01-01

167

Path Integrals, Fourier Transforms, and Feynman's Operational Calculus  

Microsoft Academic Search

.    The disentangling process is the key to Feynman's operational calculus for noncommuting operators. The main result of his\\u000a heuristic calculations deals with disentangling an exponential factor. We use the Wiener and Feynman integrals to make this\\u000a disentangling (or time-ordering) mathematically rigorous in the case where the analytic functions from earlier work are replaced\\u000a by Fourier transforms of complex-valued

Byung Moo Ahn; G. W. Johnson

1998-01-01

168

Properties of the Multidimensional Generalized Discrete Fourier Transform  

Microsoft Academic Search

In this work the generalized discrete Fourier transform (GFT), which includes the DFT as a particular case, is considered. Two pairs of fast algorithms for evaluating a multidimensional GFT are given (T-algorithm, F-algorithm, and T?-algorithm, F?-algorithm). It is shown that in the case of the DFT of a vector, the T-algorithm represents a form of the classical FFT algorithm based

Paolo Corsini; Graziano Frosini

1979-01-01

169

Pulsed Nozzle Fourier Transform Microwave Spectrometer: Advances and Applications  

Microsoft Academic Search

The pulsed nozzle Fourier transform microwave (PNFTMW) spectrometer was developed by Balle and Flygare [A new method for observing the rotational spectra of weak molecular complexes: KrHCl. J. Chem. Phys. 1979, 71 (6), 2723–2724 and 1980, 72 (2), 922–932] in 1979. The design, fabrication, and operation of this spectrometer are complicated and it has largely remained a research laboratory tool

E. Arunan; Sagarika Dev; Pankaj K. Mandal

2004-01-01

170

An Orthogonally Multiplexed QAM System Using the Discrete Fourier Transform  

Microsoft Academic Search

An orthogonally multiplexed QAM (O-QAM) system is a multichannel system with a baud rate spacing between adjacent carrier frequencies; this property is desirable to digitally implement the system using the discrete Fourier transformation (DFT). This paper provides a novel digital signal processing method based on anN\\/2-point DFT processing in the O-QAM system. A complexity comparison between a digital O-QAM system

BOTARO HIROSAKI

1981-01-01

171

Fourier transform holography using a quasimonochromatic incoherent source.  

PubMed

Fourier transform hologram of an object is recorded using a quasimonochromatic incoherent source. The object lies in the far field of the incoherent source and is illuminated in partially coherent light. The hologram is constituted by a large number of elementary holograms, each one reconstructing only a small region of the object. The hologram as a whole reconstructs the complete object. The bias problem encountered in incoherent holography is partly resolved though at the expense of resolution. PMID:20094495

Mallick, S; Roblin, M L

1971-03-01

172

Interferometric Fourier transform coherent anti-Stokes Raman microscopy  

NASA Astrophysics Data System (ADS)

We present a time domain Fourier transform coherent Raman microscopy. We show that with an added local electric field, the signal can be amplified by an order of magnitude through homodyne detection. Our approach requires a single broadband pulse to modulate, probe and amplify Raman coherence with passive phase stability to obtain high-resolution coherent anti-Stokes Raman (CARS) spectra for microscopy and microspectroscopy applications.

Cui, M.; Skodack, J.; Ogilvie, J. P.

2007-03-01

173

Fourier spectroscopy with a one-million-point transformation  

NASA Technical Reports Server (NTRS)

A new type of interferometer for use in Fourier spectroscopy has been devised at the Aime Cotton Laboratory of the National Center for Scientific Research (CNRS), Orsay, France. With this interferometer and newly developed computational techniques, interferograms comprising as many as one million samples can now be transformed. The techniques are described, and examples of spectra of thorium and holmium, derived from one million-point interferograms, are presented.

Connes, J.; Delouis, H.; Connes, P.; Guelachvili, G.; Maillard, J.; Michel, G.

1972-01-01

174

Fourier transform infrared and Raman microspectroscopy of materials in tissue.  

PubMed

Fourier transform infrared and Raman (FT-IR and FT-Raman) microspectroscopy were used to study materials found in human tissue. Individual cases involving cholesterol, calcium stearate, and a polystyrenesulfonate ion exchange resin demonstrate the utility of the spectroscopic data. Characteristic spectral bands for these materials were compared with those of authentic chemical species to confirm their identities. The role of vibrational spectroscopy in pathologic diagnoses is discussed. PMID:9551646

Kalasinsky, V F; Johnson, F B; Ferwerda, R

1998-02-01

175

Fourier transform mass spectrometry: A powerful tool for toxin analysis  

Microsoft Academic Search

The crude venom of Conus virgo was analyzed by Fourier transform mass spectrometry (FTMS) using both nano-electrospray ionization and MALDI. The analyses were performed directly on the crude venom, without chromatographic separation. The mass fingerprinting of the venom yielded 64 distinct molecular masses in the range 500–4500Da with two major components at 1328.5142 and 1358.5592Da. To facilitate the de novo

Loïc Quinton; Jean-Pierre Le Caër; Joëlle Vinh; Nicolas Gilles; Julia Chamot-Rooke

2006-01-01

176

Wavelet transform-based Fourier deconvolution for resolving oscillographic signals.  

PubMed

Fourier self-deconvolution is an effective means of resolving overlapped bands, but this method requires a mathematical model to yield deconvolution and it is quite sensitive to noises in unresolved bands. Wavelet transform is a technique for noise reduction and deterministic feature capturing because its time-frequency localization or scale is not the same in the entire time-frequency domain. In this work, wavelet transform-based Fourier deconvolution was proposed, in which a discrete approximation (such as A(2)) obtained from performing wavelet transform on the original data was substituted for the original data to be deconvolved and another discrete appropriate approximation (such as A(5)) was used as a lineshape function to yield deconvolution. Again, instead of the apodization function, the B-spline wavelet was used to smooth the deconvolved data to enhance the signal-to-noise ratio. As a consequence, this method does not suffer as badly as Fourier self-deconvolution from noises in the original data. Thus, resolution enhancement can be increased significantly, especially for signals with higher noise level. Furthermore, this method does not require a mathematical model to yield deconvolution; it is very convenient to deconvolve electrochemical signals. PMID:18968359

Zhang, X; Zheng, J; Gao, H

2001-08-01

177

Construction of high frame rate images with Fourier transform  

NASA Astrophysics Data System (ADS)

Traditionally, images are constructed with a delay-and-sum method that adjusts the phases of received signals (echoes) scattered from the same point in space so that they are summed in phase. Recently, the relationship between the delay-and-sum method and the Fourier transform is investigated [Jian-yu Lu, Anjun Liu, and Hu Peng, ``High frame rate and delay-and-sum imaging methods,'' IEEE Trans. Ultrason. Ferroelectr. Freq. Control (submitted)]. In this study, a generic Fourier transform method is developed. Two-dimensional (2-D) or three-dimensional (3-D) high frame rate images can be constructed using the Fourier transform with a single transmission of an ultrasound pulse from an array as long as the transmission field of the array is known. To verify our theory, computer simulations have been performed with a linear array, a 2-D array, a convex curved array, and a spherical 2-D array. The simulation results are consistent with our theory. [Work supported in part by Grant 5RO1 HL60301 from NIH.

Peng, Hu; Lu, Jian-Yu

2002-05-01

178

Computation of Fourier Transform Quantities in Hartree-Fock Calculations for Simple Crystals.  

National Technical Information Service (NTIS)

An efficient method is presented to compute the Fourier transforms of lattice sums over Slater-type orbital products that arise in crystal Hartree-Fock calculations. Introduction of one-dimensional integral representations for the Fourier transforms of th...

A. Graovac H. J. Monkhorst M. L. Glasser

1974-01-01

179

Improved digital filters for evaluating Fourier and Hankel transform integrals  

USGS Publications Warehouse

New algorithms are described for evaluating Fourier (cosine, sine) and Hankel (J0,J1) transform integrals by means of digital filters. The filters have been designed with extended lengths so that a variable convolution operation can be applied to a large class of integral transforms having the same system transfer function. A f' lagged-convolution method is also presented to significantly decrease the computation time when computing a series of like-transforms over a parameter set spaced the same as the filters. Accuracy of the new filters is comparable to Gaussian integration, provided moderate parameter ranges and well-behaved kernel functions are used. A collection of Fortran IV subprograms is included for both real and complex functions for each filter type. The algorithms have been successfully used in geophysical applications containing a wide variety of integral transforms

Anderson, Walter L.

1975-01-01

180

An improved fast Radon transform algorithm for two-dimensional discrete Fourier and Hartley transform  

Microsoft Academic Search

Presents a novel algorithm for the computation of the two-dimensional discrete Fourier transform and discrete Hartley transform. By using the discrete Radon transform (DRT), the algorithm essentially converts the two-dimensional transforms into a number of one-dimensional ones. By totally eliminating all redundant operations during the computation of the DRT, the algorithm can give an average of 20% reduction in the

Daniel Pak-Kong LUN; Wan-Chi SIU

1992-01-01

181

Partial differential equation transform -- Variational formulation and Fourier analysis  

PubMed Central

Nonlinear partial differential equation (PDE) models are established approaches for image/signal processing, data analysis and surface construction. Most previous geometric PDEs are utilized as low-pass filters which give rise to image trend information. In an earlier work, we introduced mode decomposition evolution equations (MoDEEs), which behave like high-pass filters and are able to systematically provide intrinsic mode functions (IMFs) of signals and images. Due to their tunable time-frequency localization and perfect reconstruction, the operation of MoDEEs is called a PDE transform. By appropriate selection of PDE transform parameters, we can tune IMFs into trends, edges, textures, noise etc., which can be further utilized in the secondary processing for various purposes. This work introduces the variational formulation, performs the Fourier analysis, and conducts biomedical and biological applications of the proposed PDE transform. The variational formulation offers an algorithm to incorporate two image functions and two sets of low-pass PDE operators in the total energy functional. Two low-pass PDE operators have different signs, leading to energy disparity, while a coupling term, acting as a relative fidelity of two image functions, is introduced to reduce the disparity of two energy components. We construct variational PDE transforms by using Euler-Lagrange equation and artificial time propagation. Fourier analysis of a simplified PDE transform is presented to shed light on the filter properties of high order PDE transforms. Such an analysis also offers insight on the parameter selection of the PDE transform. The proposed PDE transform algorithm is validated by numerous benchmark tests. In one selected challenging example, we illustrate the ability of PDE transform to separate two adjacent frequencies of sin(x) and sin(1.1x). Such an ability is due to PDE transform’s controllable frequency localization obtained by adjusting the order of PDEs. The frequency selection is achieved either by diffusion coefficients or by propagation time. Finally, we explore a large number of practical applications to further demonstrate the utility of proposed PDE transform.

Wang, Yang; Wei, Guo-Wei; Yang, Siyang

2011-01-01

182

Coherent electromagnetic field imaging through Fourier transform heterodyne  

SciTech Connect

The authors present a detection process capable of directly imaging the transverse amplitude, phase, and if desired, Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LIDAR systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding of the local oscillator for image capture. Appropriate selection of spatial encoding functions, or basis set, allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging is accomplished on a single element detector requiring no additional scanning or moving components, and (2) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection. In this paper, they introduce the underlying principles governing FTH imaging, followed by demonstration of concept via a simple experimental setup based on a HeNe laser and a 69 element spatial phase modulator.

Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Goeller, R.M.; Cafferty, M.; Briles, S.D. [Los Alamos National Lab., NM (United States); Galbraith, A.E. [Los Alamos National Lab., NM (United States)]|[Univ. of Arizona, Tucson, AZ (United States). Electrical and Computer Engineering Dept.; Grubler, A.C. [Los Alamos National Lab., NM (United States)]|[Naval Academy, Annapolis, MD (United States)

1998-12-31

183

The gridding method for image reconstruction by Fourier transformation  

SciTech Connect

This paper explores a computational method for reconstructing an n-dimensional signal f from a sampled version of its Fourier transform {cflx f}. The method involves a window function {cflx w} and proceeds in three steps. First, the convolution {cflx g} = {cflx w} * {cflx f} is computed numerically on a Cartesian grid, using the available samples of {cflx f}. Then, g = wf is computed via the inverse discrete Fourier transform, and finally f is obtained as g/w. Due to the smoothing effect of the convolution, evaluating {cflx w} * {cflx f} is much less error prone than merely interpolating {cflx f}. The method was originally devised for image reconstruction in radio astronomy, but is actually applicable to a broad range of reconstructive imaging methods, including magnetic resonance imaging and computed tomography. In particular, it provides a fast and accurate alternative to the filtered backprojection. The basic method has several variants with other applications, such as the equidistant resampling of arbitrarily sampled signals or the fast computation of the Radon (Hough) transform.

Schomberg, H. [Philips Research Lab., Hamburg (Germany)] [Philips Research Lab., Hamburg (Germany); Timmer, J. [Philips Medical Systems, Best (Netherlands)] [Philips Medical Systems, Best (Netherlands)

1995-09-01

184

Transfer Function Identification Using Orthogonal Fourier Transform Modeling Functions  

NASA Technical Reports Server (NTRS)

A method for transfer function identification, including both model structure determination and parameter estimation, was developed and demonstrated. The approach uses orthogonal modeling functions generated from frequency domain data obtained by Fourier transformation of time series data. The method was applied to simulation data to identify continuous-time transfer function models and unsteady aerodynamic models. Model fit error, estimated model parameters, and the associated uncertainties were used to show the effectiveness of the method for identifying accurate transfer function models from noisy data.

Morelli, Eugene A.

2013-01-01

185

Nonuniform sampled scalar diffraction calculation using nonuniform fast Fourier transform.  

PubMed

Scalar diffraction calculations, such as the angular spectrum method (ASM) and Fresnel diffraction, are widely used in the research fields of optics, x rays, electron beams, and ultrasonics. It is possible to accelerate the calculation using fast Fourier transform (FFT); unfortunately, acceleration of the calculation of nonuniform sampled planes is limited due to the property of the FFT that imposes uniform sampling. In addition, it gives rise to wasteful sampling data if we calculate a plane having locally low and high spatial frequencies. In this Letter, we developed nonuniform sampled ASM and Fresnel diffraction to improve the problem using the nonuniform FFT. PMID:24281527

Shimobaba, Tomoyoshi; Kakue, Takashi; Oikawa, Minoru; Okada, Naohisa; Endo, Yutaka; Hirayama, Ryuji; Ito, Tomoyoshi

2013-12-01

186

Chirped-Pulse Fourier Transform Microwave Spectroscopy of 3-VINYLBENZALDEHYDE  

NASA Astrophysics Data System (ADS)

The pure rotational spectrum of 3-vinylbenzaldehyde (3VBA) has been measured and assigned. Coker College's chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer was used to measure the rotational spectrum of 3VBA in the 7.5 - 18.5 GHz region of the microwave spectrum. The results have been analyzed to discover the rotational constants and centrifugal distortion constants of four distinct conformations of 3VBA: cis,cis-, cis,trans-, trans,cis-, and trans,trans-3VBA. The experimental rotational constants have been compared to the results of ab initio calculations. The performance of Coker's CP-FTMW spectrometer will also be discussed.

Smith, Miranda; Brown, Gordon G.

2013-06-01

187

Fourier transform spectrometry for fiber-optic sensor systems  

NASA Technical Reports Server (NTRS)

An integrated-optic Mach-Zehnder interferometer is used as a Fourier transform spectrometer to analyze the input and output spectra of a temperature-sensing thin-film etalon. This type of spectrometer has an advantage over conventional grating spectrometers because it is better suited for use with time-division-multiplexed sensor networks. In addition, this spectrometer has the potential for low cost due to its use of a component that could be manufactured in large quantities for the optical communications industry.

Beheim, Glenn; Tuma, Margaret L.; Sotomayor, Jorge L.; Flatico, Joseph M.

1993-01-01

188

Optical fiber interferometer array for scanless Fourier-transform spectroscopy.  

PubMed

We report a spatial heterodyne Fourier-transform spectrometer implemented with an array of optical fiber interferometers. This configuration generates a wavelength-dependent stationary interferogram from which the input spectrum is retrieved in a single shot without scanning elements. Furthermore, fabrication and experimental deviations from the ideal behavior of the device are corrected by spectral inversion algorithms. The spectral resolution of our system can be readily scaled up by incorporating longer optical fiber delays, providing a pathway toward surpassing current spectroscopy resolution limits. PMID:23811896

Velasco, Aitor V; Cheben, Pavel; Florja?czyk, Miros?aw; Schmid, Jens H; Bock, Przemek J; Lapointe, Jean; Delâge, André; Janz, Siegfried; Vachon, Martin; Calvo, María L; Xu, Dan-Xia; Civiš, Svatopluk

2013-07-01

189

Laser and Fourier Transform Spectroscopy of Gas Phase Molecules  

Microsoft Academic Search

Laser and Fourier transform spectroscopy were used to study a variety of gas phase molecules. A series of calcium and strontium monoalkoxides, CaOR and SrOR (R=H, CH_3, CH _2CH_3, CH(CH _3)_2, CH_2CH _2CH_3, CH _2(CH_2)_2 CH_3, CH_2 (CH_3)CH_2 CH_3 and C(CH_3) _3) was studied by laser induced fluorescence and laser excitation techniques. The A - X and B - X

Leah Christine O'Brien

1987-01-01

190

Fiber-optic thermometer using Fourier transform spectroscopy  

NASA Technical Reports Server (NTRS)

An integrated-optic Mach-Zender interferometer is used as a Fourier transform spectrometer to analyze the input and output spectra of a temperature-sensing thin-film etalon. This configuration provides a high degree of immunity to the effects of changes in the source spectrum, and it readily permits the interrogation of a number of different sensors using a single spectrometer. In addition, this system has a potentially low cost because it uses optical communications hardware that may in the future be manufactured in large quantities.

Beheim, Glenn; Sotomayor, Jorge L.; Flatico, Joseph M.; Azar, Massood T.

1991-01-01

191

Fourier-transform Raman spectroscopic study of human hair  

NASA Astrophysics Data System (ADS)

Fourier-transform Raman microscopic spectra of normal, untreated and bleached hair fibres are presented. Vibrational assignments are made and differences are ascribed to the production of cysteic acid from cysteine. Changes in conformation associated with the disulphide bond in the keratotic component are noted from the ?(CSSC) vibrational modes at wave numbers near 500 cm -1. Raman spectra of hair root ends have also been investigated with a diminution in cysteine content being observed. Application of the technique to the biomedical investigation of healthy and diseased hair is proposed.

Akhtar, W.; Edwards, H. G. M.; Farwell, D. W.; Nutbrown, M.

1997-07-01

192

Particle field holography data reduction by Fourier transform analysis  

NASA Technical Reports Server (NTRS)

The size distribution of a particle field hologram is obtained with a Fourier transformation of the Fraunhofer diffraction pattern of the reconstructed hologram. Off-axis absorption holograms of particle fields with known characteristics were obtained and analyzed with a commercially available instrument. The mean particle size of the reconstructed hologram was measured with an error of + or - 5 percent, while the distribution broadening was estimated within + or - 15 percent. Small sections of a pulsed laser hologram of a synthetic fuel spray were analyzed with this method thus yielding a spatially resolved size distribution. The method yields fast and accurate automated analysis of particle field holograms.

Hess, Cecil F.; Trolinger, James D.

1987-01-01

193

Fourier transform vibrational circular dichroism of small pharmaceutical molecules  

NASA Astrophysics Data System (ADS)

Fourier transform vibrational circular dichroism (FT-VCD) spectra of the small pharmaceutical molecules propanolol, ibuprofen and naproxen have been measured in the hydrogen stretching and mid-infrared regions to obtain information on solution conformation and to identify markers for absolute configuration determination. Ab initio molecular orbital calculations of low energy conformations, vibrational frequencies and VCD intensities for fragments of the drugs were utilized in interpreting the spectra. Features characteristic of five conformers of propranolol were identified. The weak positive CH stretching VCD signal in ibuprofen and naproxen is characteristic of the S-configuration of the chiral center common to these two analgesics.

Long, Fujin; Freedman, Teresa B.; Nafie, Laurence A.

1998-06-01

194

Fourier Transform Infrared Spectroscopy of Trifluoroiodomethane ICP Discharge  

NASA Astrophysics Data System (ADS)

Trifluoroiodomethane (CF3I) is an experimental gas that currently is being considered for semiconductor etching. We will report the breakdown characteristics of CF3I in an ICP plasma. In this study, the gas chemistry was examined through the use of Fourier transform infrared (FTIR) spectroscopy. This allowed us to identify the fraction of CF3I remaining in the discharge as well as some of the daughter species produced. Our results indicate that the major multi-atomic species found in the system include Tetrafluoromethane (CF4) and Trifluoromethyl (CF3). Mass balance examination also suggests the creation of atomic and molecular Iodide.

Fagioli, Cassius; Urrabazo, David; Goeckner, Matthew

2012-10-01

195

Hard X-Ray Fourier Transform Holography with Zone Plates  

SciTech Connect

Using two zone plates, a hard x-ray lens-less Fourier transform holographic microscope with cone-beam illumination was investigated at SPring-8 BL20XU. One zone plate was placed on the optical axis, and another zone plate was placed 16 mm downstream and 9 {mu}m off the optical axis. The diverging x-rays from the focus of the upstream zone plate illuminated a specimen where the focus of the downstream zone plate was placed. A hologram of a copper mesh of 12.7 {mu}m pitch could be obtained. The intensity and the phase could be successfully reconstructed with sub-micron resolution.

Watanabe, Norio; Yokosuka, Hiroki; Ohigashi, Takuji; Aoki, Sadao [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573 (Japan); Takano, Hidekazu; Takeuchi, Akihisa; Suzuki, Yoshio [SPring-8, Mikazuki, Hyogo 679-5198 (Japan)

2004-05-12

196

Information reduction using lensless Fourier transform digital composite holography  

NASA Astrophysics Data System (ADS)

An optical hologram contains substantially more information than necessary for some specific applications. Practical methodology of handling huge information contents in these holograms for such applications is cumbersome. In this paper, a method of information reduction, which aims at efficient storage and transmission of holograms, is investigated using digital composite holography in lensless Fourier transform configuration. The maximum information reduction factor obtained in our experiment is ˜105. The advantages/disadvantages of this method over an earlier method used in optical holography [Lin LH. A method of hologram information reduction by spatial frequency sampling. Appl Opt 1968;7:545] are also discussed.

Mosarraf Hossain, Md.; Singh Mehta, Dalip; Shakher, Chandra

2008-02-01

197

Tests of a compact static Fourier-transform imaging spectropolarimeter.  

PubMed

A compact Fourier-transform imaging spectropolarimeter covering a 450-1000 nm spectral range is presented. The sensor, which is based on two birefringent retarders and a Wollaston interferometer, offers significant advantages over previous implementations. Specifically, with no internal moving parts, electrically controllable or micro polarization components, the full wavelength-dependent state of polarization, spectral and spatial information of a scene can be acquired simultaneously. Outdoor measurements of several cars and plants demonstrate the sensor's potential for color measurement, target identification, and agriculture monitoring applications. PMID:24921497

Li, Jie; Gao, Bo; Qi, Chun; Zhu, Jingping; Hou, Xun

2014-06-01

198

Zernike aberration coefficients transformed to and from Fourier series coefficients for wavefront representation  

Microsoft Academic Search

The set of Fourier series is discussed following some discussion of Zernike polynomials. Fourier transforms of Zernike polynomials are derived that allow for relating Fourier series expansion coefficients to Zernike polynomial expansion coefficients. With iterative Fourier reconstruction, Zernike representations of wavefront aberrations can easily be obtained from wavefront derivative measurements.

Guang-Ming Dai

2006-01-01

199

Zernike aberration coefficients transformed to and from Fourier series coefficients for wavefront representation.  

PubMed

The set of Fourier series is discussed following some discussion of Zernike polynomials. Fourier transforms of Zernike polynomials are derived that allow for relating Fourier series expansion coefficients to Zernike polynomial expansion coefficients. With iterative Fourier reconstruction, Zernike representations of wavefront aberrations can easily be obtained from wavefront derivative measurements. PMID:16496900

Dai, Guang-Ming

2006-02-15

200

Fast Fourier Transform Co-processor (FFTC), towards embedded GFLOPs  

NASA Astrophysics Data System (ADS)

Many signal processing applications and algorithms perform their operations on the data in the transform domain to gain efficiency. The Fourier Transform Co-Processor has been developed with the aim to offload General Purpose Processors from performing these transformations and therefore to boast the overall performance of a processing module. The IP of the commercial PowerFFT processor has been selected and adapted to meet the constraints of the space environment. In frame of the ESA activity "Fast Fourier Transform DSP Co-processor (FFTC)" (ESTEC/Contract No. 15314/07/NL/LvH/ma) the objectives were the following: • Production of prototypes of a space qualified version of the commercial PowerFFT chip called FFTC based on the PowerFFT IP. • The development of a stand-alone FFTC Accelerator Board (FTAB) based on the FFTC including the Controller FPGA and SpaceWire Interfaces to verify the FFTC function and performance. The FFTC chip performs its calculations with floating point precision. Stand alone it is capable computing FFTs of up to 1K complex samples in length in only 10?sec. This corresponds to an equivalent processing performance of 4.7 GFlops. In this mode the maximum sustained data throughput reaches 6.4Gbit/s. When connected to up to 4 EDAC protected SDRAM memory banks the FFTC can perform long FFTs with up to 1M complex samples in length or multidimensional FFT-based processing tasks. A Controller FPGA on the FTAB takes care of the SDRAM addressing. The instructions commanded via the Controller FPGA are used to set up the data flow and generate the memory addresses. The paper will give an overview on the project, including the results of the validation of the FFTC ASIC prototypes.

Kuehl, Christopher; Liebstueckel, Uwe; Tejerina, Isaac; Uemminghaus, Michael; Witte, Felix; Kolb, Michael; Suess, Martin; Weigand, Roland; Kopp, Nicholas

2012-10-01

201

Data Transmission by Frequency-Division Multiplexing Using the Discrete Fourier Transform  

Microsoft Academic Search

The Fourier transform data communication system is a realization of frequency-division multiplexing (FDM) in which discrete Fourier transforms are computed as part of the modulation and demodulation processes. In addition to eliminating the bunks of subcarrier oscillators and coherent demodulators usually required in FDM systems, a completely digital implementation can be built around a special-purpose computer performing the fast Fourier

S. B. WEINSTEIN; PAUL M. EBERT

1971-01-01

202

Soft x-ray microscope using Fourier transform holography  

SciTech Connect

A Fourier transform holographic microscope with an anticipated resolution of better than 100 nm has been built. Extensive testing of the apparatus has begun. Preliminary results include the recording of interference fringes using 3.6 nm x-rays. The microscope employs a charge-coupled device (CCD) detector array of 576 {times} 384 elements. The system is illuminated by soft x-rays from a high brightness undulator. The reference point source is formed by a Fresnel zone plate with a finest outer zone width of 50 nm. Sufficient temporal coherence for hologram formation is obtained by a spherical grating monochromator. The x-ray hologram intensities at the recording plane are to be collected, digitized and reconstructed by computer. Data acquisition is under CAMAC control, while image display and off-line processing takes place on a VAX graphics workstation. Computational models of Fourier transform hologram synthesis, and reconstruction in the presence of noise, have demonstrated the feasibility of numerical methods in two dimensions, and that three-dimensional information is potentially recoverable. 13 refs., 3 figs.

McNulty, I.; Kirz, J.; Jacobsen, C.; Anderson, E.; Howells, M.R.; Rarback, H. (State Univ. of New York, Stony Brook, NY (USA). Dept. of Physics; Lawrence Berkeley Lab., CA (USA); Brookhaven National Lab., Upton, NY (USA))

1989-01-01

203

Integrated optics in an electrically scanned imaging Fourier transform spectrometer  

NASA Technical Reports Server (NTRS)

An efficient, lightweight and stable, Fourier transform spectrometer was developed. The mechanical slide mechanism needed to create a path difference was eliminated by the use of retro-reflecting mirrors in a monolithic interferometer assembly in which the mirrors are not at 90 degrees to the propagation vector of the radiation, but rather at a small angle. The resulting plane wave fronts create a double-sided inteferogram of the source irradiance distribution which is detected by a charge-coupled device image sensor array. The position of each CCD pixel in the array is an indication of the path difference between the two retro-reflecting mirrors in the monolithic optical structure. The Fourier transform of the signals generated by the image sensor provide the spectral irradiance distribution of the source. For imaging, the interferometer assembly scans the source of irradiation by moving the entire instrument, such as would occur if it was fixedly mounted to a moving platform, i.e., a spacecraft. During scanning, the entrace slot to the monolithic optical structure sends different pixels to corresponding interferograms detected by adjacent columns of pixels of the image sensor.

Breckinridge, James B. (inventor); Ocallaghan, Fred G. (inventor)

1982-01-01

204

Ultrafast and versatile spectroscopy by temporal Fourier transform  

PubMed Central

One of the most remarkable and useful properties of a spatially converging lens system is its inherent ability to perform the Fourier transform; the same applies for the time-lens system. At the back focal plane of the time-lens, the spectral information can be instantaneously obtained in the time axis. By implementing temporal Fourier transform for spectroscopy applications, this time-lens-based architecture can provide orders of magnitude improvement over the state-of-art spatial-dispersion-based spectroscopy in terms of the frame rate. On the other hand, in addition to the single-lens structure, the multi-lens structures (e.g. telescope or wide-angle scope) will provide very versatile operating conditions. Leveraging the merit of instantaneous response, as well as the flexible lens structure, here we present a 100-MHz frame rate spectroscopy system – the parametric spectro-temporal analyzer (PASTA), which achieves 17 times zoom in/out ratio for different observation ranges.

Zhang, Chi; Wei, Xiaoming; Marhic, Michel E.; Wong, Kenneth K. Y.

2014-01-01

205

Fourier synthesis of optical potentials for atomic quantum gases  

SciTech Connect

We demonstrate a scheme for the Fourier synthesis of periodic optical potentials with asymmetric unit cells for atoms. In a proof of principle experiment, an atomic Bose-Einstein condensate is exposed to either symmetric or sawtooth-like asymmetric potentials by superimposing a conventional standing wave potential of {lambda}/2 spatial periodicity with a fourth-order lattice potential of {lambda}/4 periodicity. The high periodicity lattice is realized using dispersive properties of multiphoton Raman transitions. Future applications of the demonstrated scheme could range from the search for novel quantum phases in unconventionally shaped lattice potentials up to dissipationless atomic quantum ratchets.

Ritt, Gunnar; Geckeler, Carsten; Cennini, Giovanni [Physikalisches Institut der Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Salger, Tobias; Weitz, Martin [Physikalisches Institut der Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Institut fuer Angewandte Physik der Universitaet Bonn, Wegelerstrasse 8, 53115 Bonn (Germany)

2006-12-15

206

Discrete Fourier transforms when the number of data samples is prime  

Microsoft Academic Search

The discrete Fourier transform of a sequence of N points, where N is a prime number, is shown to be essentially a circular correlation. This can be recognized by rearranging the members of the sequence and the transform according to a rule involving a primitive root of N. This observation permits the discrete Fourier transform to be computed by means

C. M. Rader

1968-01-01

207

Comparison of the cosine and Fourier transforms of Markov1 signals  

Microsoft Academic Search

This correspondence compares the effectiveness of the discrete cosine and Fourier transforms in decorrelating sampled signals with Markov-1 statistics. It is shown that the discrete cosine transform (DCT) offers a higher (or equal) effectiveness than the discrete Fourier transform (DFT) for all values of the correlation coefficient. The mean residual correlation is shown to vanish as the inverse square root

M. Hamidi; J. Pearl

1976-01-01

208

Calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS)  

NASA Technical Reports Server (NTRS)

The NASA New Millennium Program's Geostationary Imaging Fourier Transform Spectrometer (GIFTS) requires highly accurate radiometric and spectral calibration in order to carry out its mission to provide water vapor, wind, temperature, and trace gas profiling from geostationary orbit. A calibration concept has been developed for the GIFTS Phase A instrument design. The in-flight calibration is performed using views of two on-board blackbody sources along with cold space. A radiometric calibration uncertainty analysis has been developed and used to show that the expected performance for GIFTS exceeds its top level requirement to measure brightness temperature to better than 1 K. For the Phase A GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric calculations.

Best, F. A.; Revercomb, H. E.; Bingham, G. E.; Knuteson, R. O.; Tobin, D. C.; LaPorte, D. D.; Smith, W. L.

2001-01-01

209

A Fourier transform spectrometer for site testing at Dome A  

NASA Astrophysics Data System (ADS)

Observations in tera-hertz astronomy can only be done at a site with good atmospheric transmission at millimeter and submillimeter wavelengths. With extremely dry weather and calm atmosphere resulted by high altitude and cold temperature, Dome A (or Dome Argus), Antarctica, is possibly the best site on this earth for THz astronomy. To evaluate the site condition there, we are constructing a Fourier Transform Spectrometer (FTS) based on Martin-Puplett interferometer to measure the atmospheric transmission in the frequency range of 0.75~15THz. The whole FTS system is designed for unattended and outdoor (temperatures even below -70 degrees Celsius) operation. Its total power consumption is estimated to be approximately 200W. This contribution will give a brief overview of this FTS development.

Li, Xin-Xing; Paine, Scott; Yao, Qi-Jun; Shi, Sheng-Cai; Matsuo, Hiroshi; Yang, Ji; Zhang, Qi-Zhou

2009-07-01

210

Denoising and deblurring of Fourier transform infrared spectroscopic imaging data  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FT-IR) spectroscopic imaging is a powerful tool to obtain chemical information from images of heterogeneous, chemically diverse samples. Significant advances in instrumentation and data processing in the recent past have led to improved instrument design and relatively widespread use of FT-IR imaging, in a variety of systems ranging from biomedical tissue to polymer composites. Various techniques for improving signal to noise ratio (SNR), data collection time and spatial resolution have been proposed previously. In this paper we present an integrated framework that addresses all these factors comprehensively. We utilize the low-rank nature of the data and model the instrument point spread function to denoise data, and then simultaneously deblurr and estimate unknown information from images, using a Bayesian variational approach. We show that more spatial detail and improved image quality can be obtained using the proposed framework. The proposed technique is validated through experiments on a standard USAF target and on prostate tissue specimens.

Nguyen, Tan H.; Reddy, Rohith K.; Walsh, Michael J.; Schulmerich, Matthew; Popescu, Gabriel; Do, Minh N.; Bhargava, Rohit

2012-02-01

211

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer  

NASA Astrophysics Data System (ADS)

Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz.

Finneran, Ian A.; Holland, Daniel B.; Carroll, P. Brandon; Blake, Geoffrey A.

2013-08-01

212

Charge Reversal Fourier Transform Ion Cyclotron Resonance Mass Spectrometry  

NASA Astrophysics Data System (ADS)

We report the first charge reversal experiments performed by tandem-in-time rather than tandem-in-space MS/MS. Precursor odd-electron anions from fullerene C60, and even-electron ions from 2,7-di- tert-butylfluorene-9-carboxylic acid and 3,3'-bicarbazole were converted into positive product ions (-CR+) inside the magnet of a Fourier transform ion cyclotron resonance mass spectrometer. Charge reversal was activated by irradiating precursor ions with high energy electrons or UV photons: the first reported use of those activation methods for charge reversal. We suggest that high energy electrons achieve charge reversal in one step as double electron transfer, whereas UV-activated -CR+ takes place stepwise through two single electron transfers and formally corresponds to a neutralization-reionization (-NR+) experiment.[Figure not available: see fulltext.

Lobodin, Vladislav V.; Savory, Joshua J.; Kaiser, Nathan K.; Dunk, Paul W.; Marshall, Alan G.

2013-02-01

213

Fractional Fourier transform of Lorentz-Gauss vortex beams  

NASA Astrophysics Data System (ADS)

An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge.

Zhou, GuoQuan; Wang, XiaoGang; Chu, XiuXiang

2013-08-01

214

Solar radiometry at millimeter wavelengths. [Fast Fourier Transformation solutions  

NASA Technical Reports Server (NTRS)

In the area of resolution enhancement, the use of Fast Fourier Transform programs was investigated for possible application to millimeter wavelength maps of the sun. A difficulty arises with the La Posta maps in that they are limited to 35 arc-minutes square while the smeared out solar image is larger than that. A list of possible cometary emission lines near 13 millimeters is presented. Although preparation of the list was inspired by the appearance of Comet Kohoutek, the results are applicable to any future comet. The brightness temperature of the sun at 8.6 millimeters was measured using the moon as a calibration source. The result does not confirm a deep absorption feature as apparently observed by earlier workers.

Henze, W.

1974-01-01

215

Solving Molodensky's series by fast Fourier transform techniques  

NASA Astrophysics Data System (ADS)

The use of the fast Fourier transform algorithm in the evaluation of the Molodensky series terms is demonstrated in this paper. The solution by analytical continuation to point level has been reformulated to obtain convolution integrals in planar approximation which can be efficiently evaluated in the frequency domain. Preliminary results show that the solution by Faye anomalies is not sufficient for highly accurate deflections of the vertical and height anomalies. The Molodensky solution up to at least the second-order term must be carried out. Part of the unrecovered deflection and height anomaly signal appears to be due to density variations, verifying the essential role of density modelling. A remove-restore technique for the terrain effects can improve the convergence of the series and minimize the interpolation errors.

Sideris, M. G.; Schwarz, K. P.

1986-03-01

216

[Influence of collimation system on static Fourier transform spectrometer].  

PubMed

Collimation system provides collimated light for the static Fourier-transform spectroscopy (SFTS). Its quality is crucial to the signal to noise ratio (SNR) of SFTS. In the present paper, the physical model of SFTS was established based on the Fresnel diffraction theory by means of numerical software. The influence of collimation system on the SFTS was discussed in detail focusing on the aberrations of collimation lens and the quality of extended source. The results of simulation show that the influences of different kinds of aberrations on SNR take on obvious regularity, and in particular, the influences of off-axis aberrations on SNR are closely related to the location of off-axis point source. Finally the extended source's maximum radius allowed was obtained by simulation, which equals to 0.65 mm. The discussion results will be used for the design of collimation system. PMID:24783575

Jiang, Cheng-Zhi; Liang, Jing-Qiu; Liang, Zhong-Zhu; Sun, Qiang; Wang, Wei-Biao

2014-01-01

217

Structural Characterization of Carbohydrates by Fourier Transform Tandem Mass Spectrometry  

PubMed Central

Fourier transform tandem mass spectrometry (MS/MS) provides high mass accuracy, high sensitivity, and analytical versatility and has therefore emerged as an indispensable tool for structural elucidation of biomolecules. Glycosylation is one of the most common posttranslational modifications, occurring in ~50% of proteins. However, due to the structural diversity of carbohydrates, arising from non-template driven biosynthesis, achievement of detailed structural insight is highly challenging. This review briefly discusses carbohydrate sample preparation and ionization methods, and highlights recent developments in alternative high-resolution MS/MS strategies, including infrared multiphoton dissociation (IRMPD), electron capture dissociation (ECD), and electron detachment dissociation (EDD), for carbohydrates with a focus on glycans and proteoglycans from mammalian glycoproteins.

Zhou, Wen; Hakansson, Kristina

2012-01-01

218

Two-dimensional Fourier-transform spectroscopy of potassium vapor  

SciTech Connect

Optical two-dimensional Fourier-transform (2DFT) spectroscopy is used to study the coherent optical response of potassium vapor in a thin transmission cell. Rephasing and nonrephasing spectra of the D{sub 1} and D{sub 2} transitions are obtained and compared to numerical simulations. Non-perturbative calculations using the optical Bloch equations give very good agreement with the experimental peak strengths and line shapes. Nonradiative Raman-like coherences are isolated using a different 2DFT projection. Comparison between the optical and Raman linewidths shows that dephasing is due to partially correlated energy fluctuations. Density-dependent measurements show distortion of 2DFT spectra due to pulse propagation effects.

Dai, X.; Bristow, A. D.; Karaiskaj, D.; Cundiff, S. T. [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)

2010-11-15

219

Fourier transform millimeter-wave spectroscopy of chlorocarbene (HCCl)  

NASA Astrophysics Data System (ADS)

The 101-000 and 202-101 rotational transitions of HC35Cl and HC37Cl in the X~ 1A' ground vibronic state have been observed with a Fourier transform millimeter-wave spectrometer. The HCCl molecule is produced by discharging a gaseous sample of CH2Cl2 diluted in Ar with a pulsed discharge nozzle. The effective rotational constant (B+C)/2, the centrifugal distortion constant ?J, the nuclear quadrupole interaction constants, and the nuclear-spin rotation interaction constant are determined for each isotopic species. The nuclear-spin rotation interaction is found to make a significant contribution to the hyperfine structure of this molecule, which originates from the relatively low-lying electronic excited state. The nuclear quadrupole interaction tensor is highly asymmetric, indicating a significant ? character of the C-Cl bond. This can be interpreted in terms of the backdonation of ? electrons from the chlorine atom to the carbon atom.

Yamamoto, Satoshi; Habara, Hideta; Kim, Eunsook; Nagasaka, Hiroyuki

2001-10-01

220

Wavenumber scanning-based Fourier transform white-light interferometry.  

PubMed

Fourier transform white-light interferometry recovers the optical path difference of an interferometer by measuring the phase change caused by scanning wavelength. However, the optical spectrum, obtained by wavelength scanning method (?-method), contains a chirp in period. The chirp would induce deviation and decrease the measurement accuracy. An improved method, the wavenumber scanning method (k-method), is proposed and experimentally demonstrated, in which there is no chirp in the optical spectrum. The measurement results using the k-method and the ?-method are compared experimentally. The experimental results show that the standard deviation of the measurement results decreases from 0.015 to 0.004 ?m, when an extrinsic Fabry-Perot interferometer with a cavity length of 387 ?m is interrogated. PMID:22859041

Wang, Zhen; Jiang, Yi

2012-08-01

221

High throughput full Stokes Fourier transform imaging spectropolarimetry.  

PubMed

A complete full Stokes imaging spectropolarimeter is proposed. Four separate polarized spectra are fed into the Sagnac Fourier transform spectrometer without slit using different angle combinations of the polarized elements. The four polarized spectra are separated without spatial aliasing. And the system has a good performance to resist the instrument noise due to its high light throughput. The mathematical model for the approach is derived and an optimization of the retardance is discussed. For acquiring the four spectra simultaneously, an improved robust polarization modulator using aperture division is outlined. Then the system is discussed in detail including the imaging principle and spectral resolution. Lastly, two proven experiments are carried out and the experimental results in visible light are outlined. PMID:24514802

Meng, Xin; Li, Jianxin; Xu, Tingting; Liu, Defang; Zhu, Rihong

2013-12-30

222

On the abstracted dataflow complexity of Fast Fourier Transforms  

SciTech Connect

In this paper we develop and analyze the simulated performance of codes for the Fast Fourier Transform written in If and targeted for execution on Motorola's dataflow machine Monsoon. The FFT application is of interest because of its computational parallelism, its requirement for global communications, and its array element data dependences. We use the parallel profiling simulator Id World to study the dataflow performance of various implementations. Our approach is comparative. We study two approaches, a recursive and an iterative one, and in each version we examine the effect of a variety of implementations. We contend that only through such comparative evaluations can significant insight be gained in understanding the computational and structural details of functional algorithms.

Boehm, A.P.W. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Computer Science); Hiromoto, R.E.; Kelly, K.A. (Los Alamos National Lab., NM (United States)); Ashley, J.M. (Indiana Univ., Bloomington, IN (United States). Dept. of Computer Science)

1992-01-01

223

On the abstracted dataflow complexity of Fast Fourier Transforms  

SciTech Connect

In this paper we develop and analyze the simulated performance of codes for the Fast Fourier Transform written in If and targeted for execution on Motorola`s dataflow machine Monsoon. The FFT application is of interest because of its computational parallelism, its requirement for global communications, and its array element data dependences. We use the parallel profiling simulator Id World to study the dataflow performance of various implementations. Our approach is comparative. We study two approaches, a recursive and an iterative one, and in each version we examine the effect of a variety of implementations. We contend that only through such comparative evaluations can significant insight be gained in understanding the computational and structural details of functional algorithms.

Boehm, A.P.W. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Computer Science; Hiromoto, R.E.; Kelly, K.A. [Los Alamos National Lab., NM (United States); Ashley, J.M. [Indiana Univ., Bloomington, IN (United States). Dept. of Computer Science

1992-05-01

224

Surface analysis by Fourier-transform infrared (FTIR) spectroscopy  

SciTech Connect

A diffuse-reflectance capability for the Fourier transform infrared spectrometer at the Y-12 Plant Laboratory has been implemented. A sample cell with a 25 to 400/sup 0/C temperature-controlled sample stage and an ultrahigh-vacuum-to-atmospheric pressure gas-handling capability has been developed. Absorbance of light from the spectrometer beam, resulting from the beam being scattered from a powder sample, can be measured. This capability of detecting molecular species on and in powders is to be used to study chemisorption on actinide and rare-earth metals, alloys, and compounds. Cell design is described along with experiments demonstrating its performance in detecting moisture absorption on uranium oxide, moisture and carbon dioxide absorption on the lithium hydride/hydroxide system, and carbon dioxide absorption on potassium borohydride. 13 figures.

Powell, G.L.; Smyrl, N.R.; Fuller, E.L.

1981-08-12

225

Color image encryption based on joint fractional Fourier transform correlator  

NASA Astrophysics Data System (ADS)

In this paper, an optical color image encryption/decryption technology based on joint fractional Fourier transform correlator and double random phase encoding (DRPE) is developed. In this method, the joint fractional power spectrum of the image to be encrypted and the key codes is recorded as the encrypted data. Different from the case with classical DRPE, the same key code was used both in the encryption and decryption. The security of the system is enhanced because of the fractional order as a new added key. This method takes full advantage of the parallel processing features of the optical system, and could optically realize single-channel color image encryption. The experimental results indicate that the new method is feasible.

Lu, Ding; Jin, Weimin

2011-06-01

226

Fourier domain target transformation analysis in the thermal infrared  

NASA Technical Reports Server (NTRS)

Remote sensing uses of principal component analysis (PCA) of multispectral images include band selection and optimal color selection for display of information content. PCA has also been used for quantitative determination of mineral types and abundances given end member spectra. The preliminary results of the investigation of target transformation PCA (TTPCA) in the fourier domain to both identify end member spectra in an unknown spectrum, and to then calculate the relative concentrations of these selected end members are presented. Identification of endmember spectra in an unknown sample has previously been performed through bandmatching, expert systems, and binary classifiers. Both bandmatching and expert system techniques require the analyst to select bands or combinations of bands unique to each endmember. Thermal infrared mineral spectra have broad spectral features which vary subtly with composition. This makes identification of unique features difficult. Alternatively, whole spectra can be used in the classification process, in which case there is not need for an expert to identify unique spectra. Use of binary classifiers on whole spectra to identify endmember components has met with some success. These techniques can be used, along with a least squares fit approach on the endmembers identified, to derive compositional information. An alternative to the approach outlined above usese target transformation in conjunction with PCA to both identify and quantify the composition of unknown spectra. Preprocessing of the library and unknown spectra into the fourier domain, and using only a specific number of the components, allows for significant data volume reduction while maintaining a linear relationship in a Beer's Law sense. The approach taken here is to iteratively calculate concentrations, reducing the number of endmember components until only non-negative concentrations remain.

Anderson, D. L.

1993-01-01

227

Quantization maps, algebra representation, and non-commutative Fourier transform for Lie groups  

SciTech Connect

The phase space given by the cotangent bundle of a Lie group appears in the context of several models for physical systems. A representation for the quantum system in terms of non-commutative functions on the (dual) Lie algebra, and a generalized notion of (non-commutative) Fourier transform, different from standard harmonic analysis, has been recently developed, and found several applications, especially in the quantum gravity literature. We show that this algebra representation can be defined on the sole basis of a quantization map of the classical Poisson algebra, and identify the conditions for its existence. In particular, the corresponding non-commutative star-product carried by this representation is obtained directly from the quantization map via deformation quantization. We then clarify under which conditions a unitary intertwiner between such algebra representation and the usual group representation can be constructed giving rise to the non-commutative plane waves and consequently, the non-commutative Fourier transform. The compact groups U(1) and SU(2) are considered for different choices of quantization maps, such as the symmetric and the Duflo map, and we exhibit the corresponding star-products, algebra representations, and non-commutative plane waves.

Guedes, Carlos; Oriti, Daniele [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Potsdam (Germany)] [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Potsdam (Germany); Raasakka, Matti [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Potsdam (Germany) [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Potsdam (Germany); LIPN, Institut Galilée, Université Paris-Nord, 99, av. Clement, 93430 Villetaneuse (France)

2013-08-15

228

a Fourier Transform Technique for Estimating Bioelectric Currents from Magnetic Field Measurements  

Microsoft Academic Search

This dissertation presents a new noniterative technique for estimating current densities from magnetic field measurements. This Fourier-transform technique starts by forming a set of linear equations from the Fourier-transformed Maxwell equations. The set of equations is sampled according to the Whittaker-Shannon sampling theorem and solved by matrix methods. Two variations of the technique are extensions of a Fourier-transform method developed

Heidi Anne Schlitt

1992-01-01

229

Fundamental properties of spatial light modulators for Fourier transform applications  

NASA Astrophysics Data System (ADS)

The performance of Fourier transform optical processors, e.g. optical correlators, beam steering systems, associative memories, etc., depends intimately both on the physical characteristics of the particular spatial light modulator (SLM) and on the particular algorithms that map the signal into the available modulation range of the device. For the most general Fourier systems the information/signal is complex-valued. This is an essential requirement for multi- spot beam steering systems and composite pattern recognition filters. Since practical and/or affordable SLM's only represent a limited range of values in the complex plane (e.g. phase-only or quantized phase), numerous approaches have been proposed and demonstrated for representing, approximating, encoding or mapping complex values to the available SLM states. The best approach depends on the space bandwidth product of the signal, the number of SLM pixels, the computation time of the encoding algorithm, the time available for the application, and the quality of the optical processor, as measured by an application-specific performance metric. Based on the low pixel count and the high cost per pixel of most current SLM's we argue for encoding algorithms that map one signal value to one pixel value, as opposed to group-oriented encoding. This maximized the usable area of the frequency plane. We also recommend algorithms that maximize the fidelity over the entire frequency range as opposed to maximum diffraction efficiency/minimum mean squared error design. These ideas are illustrated with several simulated and experimental results for pseudorandom, minimum Euclidean distance, error diffusion and hybrid/blended encoding algorithms.

Cohn, Robert W.

2000-11-01

230

Transformative effects of higher magnetic field in Fourier transform ion cyclotron mass spectrometry  

PubMed Central

The relationship of magnetic field strength and Fourier transform ion cyclotron resonance mass spectrometry performance was tested using three instruments with the same designs but different fields of 4.7, 7 and 9.4 tesla. We found that the theoretically predicted “transformative” effects of magnetic field are indeed observed experimentally. The most striking effects were that mass accuracy demonstrated approximately 2nd–3rd-order improvement with the magnetic field, depending upon the charge state of the analyte, and that peak splitting, which prohibited automated data analysis at 4.7 T, was not observed at 9.4 T.

Karabacak, N. Murat; Easterling, Michael L.; Agar, N.Y.R.; Agar, Jeffrey N.

2010-01-01

231

Advantages of Karhunen Loève transform over fast Fourier transform for planetary radar and space debris detection  

NASA Astrophysics Data System (ADS)

The present article describes that the range of any radiotelescope (and radar in general) may be increased by virtue of software, if one replaces the fast Fourier transform by the Karhunen Loève transform. The range increases with the inverse of the fourth root of the signal-to-noise ratio when this ratio decreases. Thus, the range on any radiotelescope (and radar) may be increased without changing the hardware at all, but by changing the software only. This improvement in the range of the radiotelescope is currently implemented at the 32-m antenna located at Medicina, near Bologna, in Italy, for both SETI and general radioastronomy.

Maccone, Claudio

2007-04-01

232

An Introduction to Fast Fourier Transforms through the Study of Oscillating Reactions.  

ERIC Educational Resources Information Center

Discusses an experiment designed to introduce students to the basic principles of the fast Fourier transform and Fourier smoothing through transformation of time-dependent optical absorption data from an oscillating reaction. Uses the Belousov-Zhabotinskii reaction. Describes the experimental setup and data analysis techniques.

Eastman, M. P.; And Others

1986-01-01

233

Rapid screening of the fermentation profiles of wine yeasts by Fourier transform infrared spectroscopy  

Microsoft Academic Search

A rapid screening method for the evaluation of the major fermentation products of Saccharomyces wine yeasts was developed using Fourier transform infrared spectroscopy and principal component factor analysis. Calibration equations for the quantification of volatile acidity, glycerol, ethanol, reducing sugar and glucose concentrations in fermented Chenin blanc and synthetic musts were derived from the Fourier transform infrared spectra of small-scale

Hélène H. Nieuwoudt; Isak S. Pretorius; Florian F. Bauer; Daniel G. Nel; Bernard A. Prior

2006-01-01

234

Iterative Fourier transform algorithm: different approaches to diffractive optical element design  

Microsoft Academic Search

This contribution focuses on the study and comparison of different design approaches for designing phase-only diffractive optical elements (PDOEs) for different possible applications in laser beam shaping. Especially, new results and approaches, concerning the iterative Fourier transform algorithm, are analyzed, implemented, and compared. Namely, various approaches within the iterative Fourier transform algorithm (IFTA) are analyzed for the case of phase-only

Marek Skeren; Ivan Richter; Pavel Fiala

2002-01-01

235

The applications of fractional Fourier transform in underwater acoustic trajectory tracking  

Microsoft Academic Search

As an important kind of non-stationary signals, the linear frequency modulation signals have been widely used in underwater acoustic communication systems and signal detection systems. The fractional Fourier transform is an effective transform manner to analyse non-stationary signals especially to detect linear frequency modulation signals. The time measurement manner can be changed into frequency measurement manner by employing fractional Fourier

Yilin Wang; Xiaoxue Wang; Ping Cai

2010-01-01

236

A new polar Fourier transform for computer-aided tomography and spotlight synthetic aperture radar  

Microsoft Academic Search

An algorithm for calculating the Fourier transform of certain discrete measures supported on a two-dimensional polar grid is described. The algorithm utilizes a modified Bluestein chirp algorithm to directly calculate the Fourier transform values over a rectangular grid. Applications to computer-aided tomography and spotlight synthetic aperture radar are described

Wayne Lawton

1988-01-01

237

Investigation of the enzymatic digestion of plant cell walls using reflectance Fourier Transform Infrared spectroscopy  

Microsoft Academic Search

A method has been developed to determine the reflectance Fourier Transform Infrared spectra of plant cells grown in vitro and of the protoplasts released from such cells by enzymatic digestion. It is demonstrated that there is a smooth and reproducible transition in spectral detail as enzymatic digestion procedes. Reflectance Fourier Transform Infrared spectroscopy has been used to monitor the progress

J. Hopkinson; C. Moustou; K. A. Charlwood; J. E. Newbery; B. V. Charlwood

1985-01-01

238

The Numerical Solution of Waveguide Problems by Fast Fourier Transforms (Correspondence)  

Microsoft Academic Search

Ab.vtract-Tbe classical method of boundary matching in conjunction with “fast Fourier transforms” permits many wavegnide problems to be easily solved. The nse of fast Fourier transforms in tbe analysis of wavegrdde problems is described. The method is illustrated by analyzing a section of waveguide containing two identical irises. The susceptances obtained for single inductive and capacitive irises and tbe magnetic

C. T. Carson

1968-01-01

239

An analogue of a theorem of Titchmarsh for Walsh-Fourier transformations  

SciTech Connect

Let f-hat{sub c} be the Fourier cosine transform of f. Then, as proved for functions of class L{sup p}(R{sub +}) in Titchmarsh's book 'Introduction to the theory of Fourier integrals' (1937), the Hardy operator and the Hardy-Littlewood operator can be defined. In the present paper similar equalities are proved for functions of class L{sup p}(R{sub +}), 1Fourier transformation.

Golubov, B I [Moscow Engineering Physics Institute (State University), Moscow (Russian Federation)

1998-06-30

240

Fourier transform infrared spectroscopy for Kona coffee authentication.  

PubMed

Kona coffee, the variety of "Kona typica" grown in the north and south districts of Kona-Island, carries a unique stamp of the region of Big Island of Hawaii, U.S.A. The excellent quality of Kona coffee makes it among the best coffee products in the world. Fourier transform infrared (FTIR) spectroscopy integrated with an attenuated total reflectance (ATR) accessory and multivariate analysis was used for qualitative and quantitative analysis of ground and brewed Kona coffee and blends made with Kona coffee. The calibration set of Kona coffee consisted of 10 different blends of Kona-grown original coffee mixture from 14 different farms in Hawaii and a non-Kona-grown original coffee mixture from 3 different sampling sites in Hawaii. Derivative transformations (1st and 2nd), mathematical enhancements such as mean centering and variance scaling, multivariate regressions by partial least square (PLS), and principal components regression (PCR) were implemented to develop and enhance the calibration model. The calibration model was successfully validated using 9 synthetic blend sets of 100% Kona coffee mixture and its adulterant, 100% non-Kona coffee mixture. There were distinct peak variations of ground and brewed coffee blends in the spectral "fingerprint" region between 800 and 1900 cm(-1). The PLS-2nd derivative calibration model based on brewed Kona coffee with mean centering data processing showed the highest degree of accuracy with the lowest standard error of calibration value of 0.81 and the highest R(2) value of 0.999. The model was further validated by quantitative analysis of commercial Kona coffee blends. Results demonstrate that FTIR can be a rapid alternative to authenticate Kona coffee, which only needs very quick and simple sample preparations. PMID:19646032

Wang, Jun; Jun, Soojin; Bittenbender, H C; Gautz, Loren; Li, Qing X

2009-06-01

241

Liquid chromatography/Fourier transform IR spectrometry interface flow cell  

DOEpatents

A zero dead volume (ZDV) microbore high performance liquid chromatography (..mu.. HPLC)/Fourier transform infrared (FTIR) interface flow cell includes an IR transparent crystal having a small diameter bore therein through which a sample liquid is passed. The interface flow cell further includes a metal holder in combination with a pair of inner, compressible seals for directly coupling the thus configured spectrometric flow cell to the outlet of a ..mu.. HPLC column end fitting to minimize the transfer volume of the effluents exiting the ..mu.. HPLC column which exhibit excellent flow characteristics due to the essentially unencumbered, open-flow design. The IR beam passes transverse to the sample flow through the circular bore within the IR transparent crystal, which is preferably comprised of potassium bromide (KBr) or calcium fluoride (CaF/sub 2/), so as to minimize interference patterns and vignetting encountered in conventional parallel-plate IR cells. The long IR beam pathlength and lensing effect of the circular cross-section of the sample volume in combination with the refractive index differences between the solvent and the transparent crystal serve to focus the IR beam in enhancing sample detection sensitivity by an order of magnitude.

Johnson, C.C.; Taylor, L.T.

1985-01-04

242

Liquid chromatography/Fourier transform IR spectrometry interface flow cell  

DOEpatents

A zero dead volume (ZDV) microbore high performance liquid chromatography (.mu.HPLC)/Fourier transform infrared (FTIR) interface flow cell includes an IR transparent crystal having a small diameter bore therein through which a sample liquid is passed. The interface flow cell further includes a metal holder in combination with a pair of inner, compressible seals for directly coupling the thus configured spectrometric flow cell to the outlet of a .mu.HPLC column end fitting to minimize the transfer volume of the effluents exiting the .mu.HPLC column which exhibit excellent flow characteristics due to the essentially unencumbered, open-flow design. The IR beam passes transverse to the sample flow through the circular bore within the IR transparent crystal, which is preferably comprised of potassium bromide (KBr) or calcium fluoride (CaF.sub.2), so as to minimize interference patterns and vignetting encountered in conventional parallel-plate IR cells. The long IR beam pathlength and lensing effect of the circular cross-section of the sample volume in combination with the refractive index differences between the solvent and the transparent crystal serve to focus the IR beam in enhancing sample detection sensitivity by an order of magnitude.

Johnson, Charles C. (Fairfield, OH); Taylor, Larry T. (Blacksburg, VA)

1986-01-01

243

External Second Gate-Fourier Transform Ion Mobility Spectrometry.  

SciTech Connect

Ion mobility spectrometry (IMS) is recognized as one of the most sensitive and versatile techniques for the detection of trace levels of organic vapors. IMS is widely used for detecting contraband narcotics, explosives, toxic industrial compounds and chemical warfare agents. Increasing threat of terrorist attacks, the proliferation of narcotics, Chemical Weapons Convention treaty verification as well as humanitarian de-mining efforts has mandated that equal importance be placed on the analysis time as well as the quality of the analytical data. (1) IMS is unrivaled when both speed of response and sensitivity has to be considered. (2) With conventional (signal averaging) IMS systems the number of available ions contributing to the measured signal to less than 1%. Furthermore, the signal averaging process incorporates scan-to-scan variations decreasing resolution. With external second gate Fourier Transform ion mobility spectrometry (FT-IMS), the entrance gate frequency is variable and can be altered in conjunction with other data acquisition parameters to increase the spectral resolution. The FT-IMS entrance gate operates with a 50% duty cycle and so affords a 7 to 10-fold increase in sensitivity. Recent data on high explosives are presented to demonstrate the parametric optimization in sensitivity and resolution of our system.

Tarver, Edward E., III

2005-01-01

244

Fourier transform infrared spectroscopy (FTIR) of laser-irradiated cementum  

NASA Astrophysics Data System (ADS)

Utilizing Fourier Transform Infrared Spectroscopy (FTIR) in specular reflectance mode chemical changes of root cement surfaces due to laser radiation were investigated. A total of 18 samples of root cement were analyzed, six served as controls. In this study laser energies were set to those known for removal of calculus or for disinfection of periodontal pockets. Major changes in organic as well as inorganic components of the cementum were observed following Nd:YAG laser irradiation (wavelength 1064 nm, pulse duration 250 ?s, free running, pulse repetition rate 20 Hz, fiber diameter 320 ?m, contact mode; Iskra Twinlight, Fontona, Slovenia). Er:YAG laser irradiation (wavelength 2.94 ?m, pulse duration 250 ?s, free running, pulse repetition rate 6 Hz, focus diameter 620 ?m, air water cooling 30 ml/min; Iskra Twinlight, Fontona, Slovenia) significantly reduced the Amid bands due to changes in the organic components. After irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, q-switched, pulse repetition rate 20 Hz, beam diameter 800 ?m, contact mode, water cooling 30 ml/min; laboratory prototype) only minimal reductions in the peak intensity of the Amide-II band were detected.

Rechmann, Peter; White, Joel M.; Cecchini, Silvia C. M.; Hennig, Thomas

2003-06-01

245

Continued Development of a Planetary Imaging Fourier Transform Spectrometer (PIFTS)  

NASA Technical Reports Server (NTRS)

This report describes continued efforts to evaluate a breadboard of a Planetary Imaging Fourier Transform Spectrometer (PIFTS). The PIFTS breadboard was developed under prior PIDDP funding. That effort is described in the final report for NASA Grant NAG5-6248 and in two conference papers (Sromovsky et al. 2000; Revercomb et al. 2000). The PIFTS breadboard was designed for near-IR (1-5.2 micrometer imaging of planetary targets with spectral resolving powers of several hundred to several thousand, using an InSb detector array providing at least 64x64 pixels imaging detail. The major focus of the development effort was to combine existing technologies to produce a small and low power design compatible with a very low mass flyable instrument. The objective of this grant (NAG5-10729) was further characterization of the breadboard performance, including intercomparisons with the highly accurate non-imaging Advanced Emitted Radiance Interferometer (AERI) (Revercomb et al. 1994; Best et al. 1997).

Sromovsky, L. A.

2002-01-01

246

Toward a soft x-ray Fourier-transform spectrometer  

SciTech Connect

The use of Fourier transform spectroscopy (FTS) in the soft x-ray region is advocated as a possible route to spectral resolution superior to that attainable with a grating system. A technical plan is described for applying FTS to the study of the absorption spectrum of helium in the region of double ionization around 60--80 eV. The proposed scheme includes a Mach-Zehnder interferometer deformed into a rhombus shape to provide grazing incidence reflections. The path difference between the interfering beams is to be tuned by translation of a table carrying four mirrors over a range {+-}1 cm which, in the absence of errors generating relative tilts of the wave fronts, would provide a resolving power equal to the number of waves of path difference: half a million at 65 eV, for example. The signal-to-noise ratio of the spectrum is analyzed and for operation on an Advanced Light Source bending magnet beam line should be about 330.

Howells, M.R.; Frank, K.; Hussain, Z.; Moler, E.J. [Lawrence Berkeley Lab., CA (US); Reich, T. [Lawrence Berkeley Lab., CA (US)]|[Pennsylvania State Univ., University Park, PA (US); Moeller, D. [Fairleigh Dickenson Univ., Teaneck, NJ (US). Dept. of Physics and Chemistry; Shirley, D.A. [Pennsylvania State Univ., University Park, PA (US)

1993-10-29

247

Ivory and simulated ivory artefacts: Fourier transform Raman diagnostic study  

NASA Astrophysics Data System (ADS)

The Fourier transform Raman spectrum of ivory is reported and assignments are proposed for the major spectroscopic features. Application of the FT Raman technique to the non-destructive diagnostic identification of ivory and simulated ivory artefacts is illustrated with reference to several specimens, both modern and aged. Although the FT Raman spectrum of ivory is similar to that of other bone samples, the characteristic vibrational modes are identified and it is suggested that the relative intensity ratio of the ?(CH) stretching bands near 2930 cm -1 and the hydroxyapatite ?(PO) stretching band at 960 cm -1 is a good diagnostic parameter for ivory. Other modes, such as ?(NH) near 3300 cm -1, the ?(CH 2) profile near 1250 cm -1 and ?(CC) symmetric ring stretching intensity at 1002 cm -1 are also good confirming indicators to distinguish ivory from bone and synthetic specimens. Modern specimens of "ivory" using synthetic polymers and polymer-inorganic composites are easily distinguished spectroscopically from genuine ivory, particularly close textural specimens, which involved a synthetic blending of poly(methylmethacrylate), polystyrene and calcite.

Edwards, H. G. M.; Farwell, D. W.

1995-11-01

248

[Study on spectrum inversion of spatially modulated Fourier transform spectrometer].  

PubMed

The sampling mode of static Fourier transform spectrometer is spatial domain sampling. The interferogram function is sampled by two orthogonal stepped mirrors and the interference irradiance is received by the detector. The interferogram image is a planar spatial array which consists of MXM interferogram units. After image segmentation, the interferogram image is divided into M x M interferogram units according to comparability criterion. By means of addressing location, the sampled interferogram sequence which matches up to the discrete optical path difference sequence could be gained. Using over-zero sampling technique, the big single side interferogram sequence and the small double side interferogram sequence are apodizated by different window functions. For the sake of correcting phase error, the frequency-domain spectrum correction and space-domain interferogram correction are researched and improved. The simulation result shows that the two methods can both gain the perfect spectrum line shape, and the effect of space-domain interferogram correction is better than others with the spectrum standard deviation only 0.012 088. PMID:22870669

Lü, Jin-Guang; Liang, Jing-Qiu; Liang, Zhong-Zhu

2012-06-01

249

Fourier Transform Infrared Emission Spectroscopy of SeH  

NASA Astrophysics Data System (ADS)

The infrared vibration-rotation bands of SeH have been measured in the X2? ground state using a Fourier transform spectrometer. The bands were observed in a microwave discharge of a mixture of H 2 and Se in the presence of He. The rotational structure of the 1-0, 2-1, 3-2 bands of the X2? 3/2 spin component and the 1-0 band of X2? 1/2 spin component has been observed in the 1800-2600 cm -1 region. The principal ground state molecular constants obtained are ? e = 2421.7153(234) cm -1, ? exe = 44.6012(110) cm -1, ? eye = 0.20697(236) cm -1, Be = 7.899187(696) cm -1, ? e = 0.220749(399) cm -1, and re = 1.464319(64) Å. This work is the first determination of the equilibrium molecular constants of the X2? state of SeH.

Ram, R. S.; Bernath, P. F.

2000-09-01

250

Remote detection of organics using Fourier transform infrared spectroscopy  

SciTech Connect

Fourier transform infrared (FTIR) spectroscopy is an ideal technique for remote detection of organic emissions. There is an atmospheric window in the 1200 to 800 cm{sup {minus}1} region, which corresponds to the fingerprint'' region for organic molecules. Virtually all organic molecules have a unique absorption/emission pattern in the fingerprint region. A remote-passive FTIR relies on ambient emission of infrared energy from organics to obtain spectra. The instrumentation consists of inlet optics, and interferometer, a mercury cadmium telluride (MCT) detector, and an on-board computer. The transportable unit measures 40 cm by 50 cm and has been used to collect data while mounted on a helicopter or ground vehicle. Through the use of this FTIR combined with least squares software, it is possible to analyze qualitatively and quantitatively for organic vapors from either the air or ground. The data presented will include quantitative releases of common organics present in incinerator stacks, hazardous wastes, and illegal laboratories. Data will be presented for pure compounds, mixtures, and target analytes in the presence of interfering compounds. The sensitivity, reproducibility, and the potential of the technique will be discussed. 1 ref., 8 figs., 6 tabs.

Demirgian, J.C.; Spurgash, S.M.

1990-01-01

251

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer.  

PubMed

Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz. PMID:24007050

Finneran, Ian A; Holland, Daniel B; Carroll, P Brandon; Blake, Geoffrey A

2013-08-01

252

Fourier transform infrared phase shift cavity ring down spectrometer  

NASA Astrophysics Data System (ADS)

OPTRA has developed a novel approach to phase shift cavity ring down spectroscopy (PS-CRDS) using a Fourier transform infrared (FTIR) modulator to impose the spectrally-dependent amplitude modulation on a broadband IR light source. As with previous PS-CRDS measurements, we excite a resonant cavity with amplitude modulated energy and measure the phase shift of the modulated signal exiting the cavity which is proportional to the ring down time and inversely proportional to the losses of the cavity including those due to molecular absorption. In contrast to previous efforts, we impose the amplitude modulation with the FTIR interferometer instead of an external electro-optical modulator and extract the phase from each interferogram thereby enabling broadband FTIR-PS-CRDS measurements at greater than 1 Hz update rates. The measured phase spectra can then be used for multicomponent analysis. The combined measurement can be viewed as a resonant cavity enhancement to traditional FTIR spectroscopy or a broadband enhancement to CRDS. In our paper we present the theory behind this measurement and describe the breadboard and test results from our feasibility study.

Rentz Dupuis, Julia; Engel, James R.

2012-05-01

253

Fourier transform spectrum of the torsional band of hydrazine  

NASA Astrophysics Data System (ADS)

The far-infrared torsional band of hydrazine has been studied by Fourier transform spectroscopy with an apodized resolution of 0.011 cm -1. As a result of torsional as well as inversion tunneling, large splittings are observed in this b-type band. About 700 rRK and pPK transitions of 22 subbands with ? K· K? from -10 to +11 were assigned. The A- B, B- A, and E- E transitions were assigned for all subbands except for the ? K· K? = -2 and -1 subbands, for which only the nondegenerate transitions were observed. A global fitting, which includes all available ground state microwave data, was made using Hougen's group theoretical formalism. Several fitting constants, i.e., B- C, the trans torsional tunneling constant h3 vt, and the inversion tunneling constant h5 v, were found to exhibit large changes upon torsional excitation. The values of these constants in the torsional fundamental state are: B- C = 184.52(30) MHz, h3 vt = -912.0(21) MHz, and h5 v = 1994.1(16) MHz, where the numbers in parentheses are 1 ?.

Ohashi, Nobukimi; Lafferty, Walter J.; Olson, W. Bruce

1986-05-01

254

Compliant MEMS mechanism to extend resolution in Fourier transform spectroscopy  

NASA Astrophysics Data System (ADS)

A complaint mechanism to extend resolution in the Fourier Transform Spectroscopy (FTS) technique has been designed, fabricated and tested. The mechanism based on the complaint mechanical design strategy has not mobile parts and was fabricated in MEMS technology in a Bosch Process. When this mechanism is used to displacing the mobile mirror in a FTS setup, an extended range travel for the reference mirror is achieved; thus, the optical path difference and hence the resolving power of the FTS system is increased. The fabricated device has dimensions of 5400x4200x400 Microns at the large, width and thickness respectively, with an aspect ratio about 10. Numerical simulations with ANSYS Software were developed to get the Stress limits and the input and output displacements, the mechanical gain and the resonance frequency of the device. Experimental results in both the forced and dynamical regime are presented. It is found that in the dynamical regime when the device is operated at its resonance frequency it exhibits a higher mechanical gain several times its gain in the forced regime.

Sauceda-Carvajal, A.; Kennedy-Cabrera, H. D.; Hernández-Torres, J.; Herrera-May, A. L.; Mireles, José

2014-03-01

255

High-resolution wide-band fast Fourier transform spectrometers  

NASA Astrophysics Data System (ADS)

We describe the performance of our latest generations of sensitive wide-band high-resolution digital fast Fourier transform spectrometer (FFTS). Their design, optimized for a wide range of radio astronomical applications, is presented. Developed for operation with the GREAT far infrared heterodyne spectrometer on-board SOFIA, the eXtended bandwidth FFTS (XFFTS) offers a high instantaneous bandwidth of 2.5 GHz with 88.5 kHz spectral resolution and has been in routine operation during SOFIA's Basic Science since July 2011. We discuss the advanced field programmable gate array (FPGA) signal processing pipeline, with an optimized multi-tap polyphase filter bank algorithm that provides a nearly loss-less time-to-frequency data conversion with significantly reduced frequency scallop and fast sidelobe fall-off. Our digital spectrometers have been proven to be extremely reliable and robust, even under the harsh environmental conditions of an airborne observatory, with Allan-variance stability times of several 1000 s. An enhancement of the present 2.5 GHz XFFTS will duplicate the number of spectral channels (64k), offering spectroscopy with even better resolution during Cycle 1 observations.

Klein, B.; Hochgürtel, S.; Krämer, I.; Bell, A.; Meyer, K.; Güsten, R.

2012-06-01

256

Fourier transform infrared spectroscopic analysis of cell differentiation  

NASA Astrophysics Data System (ADS)

Stem cells and its differentiations have got a lot of attentions in regenerative medicine. The process of differentiations, the formation of tissues, has become better understood by the study using a lot of cell types progressively. These studies of cells and tissue dynamics at molecular levels are carried out through various approaches like histochemical methods, application of molecular biology and immunology. However, in case of using regenerative sources (cells, tissues and biomaterials etc.) clinically, they are measured and quality-controlled by non-invasive methods from the view point of safety. Recently, the use of Fourier Transform Infrared spectroscopy (FT-IR) has been used to monitor biochemical changes in cells, and has gained considerable importance. The objective of this study is to establish the infrared spectroscopy of cell differentiation as a quality control of cell sources for regenerative medicine. In the present study, as a basic study, we examined the adipose differentiation kinetics of preadipocyte (3T3-L1) and the osteoblast differentiation kinetics of bone marrow mesenchymal stem cells (Kusa-A1) to analyze the infrared absorption spectra. As a result, we achieved to analyze the adipose differentiation kinetics using the infrared absorption peak at 1739 cm-1 derived from ester bonds of triglyceride and osteoblast differentiation kinetics using the infrared absorption peak at 1030 cm-1 derived from phosphate groups of calcium phosphate.

Ishii, Katsunori; Kimura, Akinori; Kushibiki, Toshihiro; Awazu, Kunio

2007-03-01

257

Optimal Padding for the Two-Dimensional Fast Fourier Transform  

NASA Technical Reports Server (NTRS)

One-dimensional Fast Fourier Transform (FFT) operations work fastest on grids whose size is divisible by a power of two. Because of this, padding grids (that are not already sized to a power of two) so that their size is the next highest power of two can speed up operations. While this works well for one-dimensional grids, it does not work well for two-dimensional grids. For a two-dimensional grid, there are certain pad sizes that work better than others. Therefore, the need exists to generalize a strategy for determining optimal pad sizes. There are three steps in the FFT algorithm. The first is to perform a one-dimensional transform on each row in the grid. The second step is to transpose the resulting matrix. The third step is to perform a one-dimensional transform on each row in the resulting grid. Steps one and three both benefit from padding the row to the next highest power of two, but the second step needs a novel approach. An algorithm was developed that struck a balance between optimizing the grid pad size with prime factors that are small (which are optimal for one-dimensional operations), and with prime factors that are large (which are optimal for two-dimensional operations). This algorithm optimizes based on average run times, and is not fine-tuned for any specific application. It increases the amount of times that processor-requested data is found in the set-associative processor cache. Cache retrievals are 4-10 times faster than conventional memory retrievals. The tested implementation of the algorithm resulted in faster execution times on all platforms tested, but with varying sized grids. This is because various computer architectures process commands differently. The test grid was 512 512. Using a 540 540 grid on a Pentium V processor, the code ran 30 percent faster. On a PowerPC, a 256x256 grid worked best. A Core2Duo computer preferred either a 1040x1040 (15 percent faster) or a 1008x1008 (30 percent faster) grid. There are many industries that can benefit from this algorithm, including optics, image-processing, signal-processing, and engineering applications.

Dean, Bruce H.; Aronstein, David L.; Smith, Jeffrey S.

2011-01-01

258

Fast Registration of Tabular Document Images Using the Fourier-Mellin Transform  

Microsoft Academic Search

A new technique is presented for quickly identifying global affine transformations applied to tabular document images, and to correct for those transformations. This technique, based on the Fourier-Mellin transform, is used to register (align) a set of tabular documents to each other. Each component of the affine transform is handled separately, which dramatically reduces the total parameter space of the

Luke A. D. Hutchison; William A. Barrett

2004-01-01

259

Complexation of chitosan with acetic acid according to Fourier transform Raman spectroscopy data  

NASA Astrophysics Data System (ADS)

The results of the interaction between the protonated chitosan (CHI) macromolecule and the acetate ion in dilute acetic acid solutions were studied by Fourier transform Raman spectroscopy and quantum-chemical modeling. The complexation of CHI with the acetate ion showed itself as the 934 cm-1 band in the Raman spectrum, which suggests the formation of [CHI+ · CH3COO-] type ion pairs. It was concluded that a comparative analysis of the integrated intensities of the Raman bands in the range 880-940 cm-1 makes it possible to judge about the relative content of hydrated acetate ions, CHI macromolecules of the [CHI+ · CH3COO-] complex, and acetic acid molecules not involved in CHI protonation.

Mikhailov, G. P.; Tuchkov, S. V.; Lazarev, V. V.; Kulish, E. I.

2014-06-01

260

Far infrared Fourier-transform spectroscopy of mono-deuterated hydrogen peroxide HOOD  

NASA Astrophysics Data System (ADS)

We present the gas phase spectrum of singly deuterated hydrogen peroxide, HOOD, in its vibrational ground state, recorded by the high resolution Fourier-transform interferometer located at the AILES synchrotron beamline connected to SOLEIL. More than 1000 transitions in the range from 20 to 143 cm-1 were assigned, leading to a set of preliminary rotational and centrifugal distortion constants determined by least squares fit analysis. All transitions are split by the tunneling motion of a hindered internal rotation. The splitting has been determined to be 5.786(13) cm-1 in the torsional ground state and it shows a dependence on the rotational quantum number Ka. Some perturbations were not treated yet, but the present analysis permits to obtain a preliminary set of parameters.

Herberth, Doris; Baum, Oliver; Pirali, Olivier; Roy, Pascale; Thorwirth, Sven; Yamada, Koichi M. T.; Schlemmer, Stephan; Giesen, Thomas F.

2012-07-01

261

Analyzing Real Vector Fields with Clifford Convolution and Clifford-Fourier Transform  

NASA Astrophysics Data System (ADS)

Postprocessing in computational fluid dynamics and processing of fluid flow measurements need robust methods that can deal with scalar and vector fields. While image processing of scalar data is a well-established discipline, there is a lack of similar methods for vector data. This paper surveys a particular approach defining convolution operators on vector fields using geometric algebra. This includes a corresponding Clifford-Fourier transform including a convolution theorem. Finally, a comparison is tried with related approaches for a Fourier transform of spatial vector or multivector data. In particular, we analyze the Fourier series based on quaternion holomorphic functions of Gürlebeck et al. (Funktionentheorie in der Ebene und im Raum, Birkhäuser, Basel, 2006), the quaternion Fourier transform of Hitzer (Proceedings of Function Theories in Higher Dimensions, 2006) and the biquaternion Fourier transform of Sangwine et al. (IEEE Trans. Signal Process. 56(4),1522-1531, 2007).

Reich, Wieland; Scheuermann, Gerik

262

SPICA/SAFARI Fourier transform spectrometer mechanism evolutionary design  

NASA Astrophysics Data System (ADS)

TNO, together with its partners, have designed a cryogenic scanning mechanism for use in the SAFARI1 Fourier Transform Spectrometer (FTS) on board of the SPICA mission. SPICA is one of the M-class missions competing to be launched in ESA's Cosmic Vision Programme2 in 2022. JAXA3 leads the development of the SPICA satellite and SRON is the prime investigator of the Safari instrument. The FTS scanning mechanism (FTSM) has to meet a 35 mm stroke requirement with an Optical Path Difference resolution of less then 15 nm and must fit in a small volume. It consists of two back-to-back roof-top mirrors mounted on a small carriage, which is moved using a magnetic bearing linear guiding system in combination with a magnetic linear motor serving as the OPD actuator. The FTSM will be used at cryogenic temperatures of 4 Kelvin inducing challenging requirements on the thermal power dissipation and heat leak. The magnetic bearing enables movements over a scanning stroke of 35.5 mm in a small volume. It supports the optics in a free-floating way with no friction, or other non-linearities, with sub-nanometer accuracy. This solution is based on the design of the breadboard ODL (Optical Delay Line) developed for the ESA Darwin mission4 and the MABE mechanism developed by Micromega Dynamics. During the last couple of years the initial design of the SAFARI instrument, as described in an earlier SPIE 2010 paper5, was adapted by the SAFARI team in an evolutionary way to meet the changing requirements of the SPICA payload module. This presentation will focus on the evolution of the FTSM to meet these changing requirements. This work is supported by the Netherlands Space Office (NSO).

van den Dool, Teun C.; Kruizinga, Bob; Braam, Ben C.; Hamelinck, Roger F. M. M.; Loix, Nicolas; Van Loon, Dennis; Dams, Johan

2012-09-01

263

Libyan Desert Glass: New field and Fourier transform infrared data  

NASA Astrophysics Data System (ADS)

Results are presented of new geological observations and laboratory analyses on Libyan Desert Glass (LDG), a unique kind of impact glass found in Egypt, probably 28.5-29.4 million years in age. A new LDG occurrence has been discovered some 50 km southward of the main LDG occurrences in the Great Sand Sea. From Fourier transform infrared (FTIR) analysis, the molecular structure of LDG is refined and significant differences are shown between LDG specimens and other pure silica glasses (fulgurite, industrial fused quartz, and amorphous biogenic silica) that are related to differences in their structures. The slight variations observed here for the mean Si-O-Si angle between the different glasses are attributed to their thermal histories. With regard to the other glasses analyzed, the LDG infrared spectral parameters point to a higher ratio of discontinuities and defects in the tetrahedral (SiO4) network. The quantitative mineralogical constitutions of sandstones and quartzites from the LDG geological setting were analyzed by FTIR. Cretaceous sandstones have a specific composition (about 90 wt% quartz, 10% dickite), clearly different from the Paleozoic ones (about 90 wt% quartz, but ?7% kaolinite). It is shown that the reddish silts bearing the LDG are constituted mainly of microquartz enriched with dickite, whose particle size distribution is characteristic of fluvio-lacustrine deposits, probably Oligocene to Miocene in age. The target rocks, most probably quartz sand, resulted from the weathering (loss of the cementing microquartz) of the Cretaceous sandstones from the Gilf Khebir Plateau with deposition in a high-energy environment.

Fröhlich, F.; Poupeau, G.; Badou, A.; Le Bourdonnec, F. X.; Sacquin, Y.; Dubernet, S.; Bardintzeff, J. M.; Véran, M.; Smith, D. C.; Diemer, E.

2013-12-01

264

Calibration of the Herschel SPIRE Fourier Transform Spectrometer  

NASA Astrophysics Data System (ADS)

The Herschel Spectral and Photometric REceiver (SPIRE) instrument consists of an imaging photometric camera and an imaging Fourier Transform Spectrometer (FTS), both operating over a frequency range of ˜450-1550 GHz. In this paper, we briefly review the FTS design, operation, and data reduction, and describe in detail the approach taken to relative calibration (removal of instrument signatures) and absolute calibration against standard astronomical sources. The calibration scheme assumes a spatially extended source and uses the Herschel telescope as primary calibrator. Conversion from extended to point-source calibration is carried out using observations of the planet Uranus. The model of the telescope emission is shown to be accurate to within 6 per cent and repeatable to better than 0.06 per cent and, by comparison with models of Mars and Neptune, the Uranus model is shown to be accurate to within 3 per cent. Multiple observations of a number of point-like sources show that the repeatability of the calibration is better than 1 per cent, if the effects of the satellite absolute pointing error (APE) are corrected. The satellite APE leads to a decrement in the derived flux, which can be up to ˜10 per cent (1 ?) at the high-frequency end of the SPIRE range in the first part of the mission, and ˜4 per cent after Herschel operational day 1011. The lower frequency range of the SPIRE band is unaffected by this pointing error due to the larger beam size. Overall, for well-pointed, point-like sources, the absolute flux calibration is better than 6 per cent, and for extended sources where mapping is required it is better than 7 per cent.

Swinyard, B. M.; Polehampton, E. T.; Hopwood, R.; Valtchanov, I.; Lu, N.; Fulton, T.; Benielli, D.; Imhof, P.; Marchili, N.; Baluteau, J.-P.; Bendo, G. J.; Ferlet, M.; Griffin, M. J.; Lim, T. L.; Makiwa, G.; Naylor, D. A.; Orton, G. S.; Papageorgiou, A.; Pearson, C. P.; Schulz, B.; Sidher, S. D.; Spencer, L. D.; Wiel, M. H. D. van der; Wu, R.

2014-06-01

265

First Observations with the LLNL Optical Imaging Fourier Transform Spectrometer  

NASA Astrophysics Data System (ADS)

We present the results of the first observing run with an optical imaging Fourier transform spectrometer (FTS). We have designed and fabricated this FTS for low-background astronomical use as a testbed for a proposed imaging FTS for the Next Generation Space Telescope (NGST). The relatively low background in the optical allows us to mimic the long dwell, step-scan operation of the proposed infrared NGST FTS. In this first data set, we have demonstrated the operation of the system as a multi-band camera and as a medium-resolution 3D spectrometer. Our testbed FTS reflects our current design for the NGST FTS (IFIRS). It is a four-port (two input, two output) Michelson interferometer with two 45 degree, self-compensating beamsplitters and cube-corner retro-reflectors. This system was taken to the 1.5-m McMath-Pierce Solar Observatory (MPSO) in March 1999. MPSO provides a good facility for prototyping astronomical instruments with a horizontal focal plane projected onto a (de)rotating table. We collected data from one output port with an off-the-shelf PixelVision CCD camera with a 1024x1024, thinned SITe chip thermoelectrically cooled to 235K. Our final platescale was about 0.5 arcsec/pixel with an unvignetted field of about 4x4 arcmin. We collected imaging spectroscopy with resolutions of a few to 500 of well-known objects including globular clusters, open clusters, spiral galaxies, elliptical galaxies, and nebular regions. We describe our data reduction procedures with emphasis on the unique aspects of imaging FTS data. We present color-magnitude diagrams of star clusters to demonstrate the utility of the imaging FTS as a camera and compare the signal-to-noise performance with theoretical models and filter-based camera performance. Finally, we present datacubes demonstrating the ability of the imaging FTS to yield ``a spectrum for every pixel''.

Wurtz, R.; Abrams, M. C.; Bennett, C. L.; Bixler, J. V.; Carr, D. J.; Carr, J.; Cook, K. H.; Dey, A.; Graham, J. R.; Hertel, R. J.; Macoy, N. H.; Morris, S. L.; Najita, J. R.; Villemaire, A.; Wickham, D. R.; Wishnow, E.

1999-05-01

266

Continuously tunable optical multidimensional Fourier-transform spectrometer  

NASA Astrophysics Data System (ADS)

A multidimensional optical nonlinear spectrometer (MONSTR) is a robust, ultrastable platform consisting of nested and folded Michelson interferometers that can be actively phase stabilized. The MONSTR provides output pulses for nonlinear excitation of materials and phase-stabilized reference pulses for heterodyne detection of the induced signal. This platform generates a square of identical laser pulses that can be adjusted to have arbitrary time delays between them while maintaining phase stability. This arrangement is ideal for performing coherent optical experiments, such as multidimensional Fourier-transform spectroscopy. The present work reports on overcoming some important limitations on the original design of the MONSTR apparatus. One important advantage of the MONSTR is the fact that it is a closed platform, which provides the high stability. Once the optical alignment is performed, it is desirable to maintain the alignment over long periods of time. The previous design of the MONSTR was limited to a narrow spectral range defined by the optical coating of the beam splitters. In order to achieve tunability over a broad spectral range the internal optics needed to be changed. By using broadband coated and wedged beam splitters and compensator plates, combined with modifications of the beam paths, continuous tunability can be achieved from 520 nm to 1100 nm without changing any optics or performing alignment of the internal components of the MONSTR. Furthermore, in order to achieve continuous tunability in the spectral region between 520 nm and 720 nm, crucially important for studies on numerous biological molecules, a single longitudinal mode laser at 488.5 nm was identified and used as a metrology laser. The shorter wavelength of the metrology laser as compared to the usual HeNe laser has also increased the phase stability of the system. Finally, in order to perform experiments in the reflection geometry, a simple method to achieve active phase stabilization between the signal and the reference beams has been developed.

Dey, P.; Paul, J.; Bylsma, J.; Deminico, S.; Karaiskaj, D.

2013-02-01

267

Fourier transform infrared studies of ammonia photochemistry in solid parahydrogen.  

PubMed

We present 193 nm in situ photochemical studies of NH3 isolated in solid parahydrogen (pH2) at 1.8 K using Fourier Transform Infrared (FTIR) spectroscopy. By recording FTIR spectra during and after irradiation we are able to identify and assign a number of rovibrational transitions to ortho-NH2(X(2)B1) and NH(X(3)?(-)). Spectroscopic analysis shows that these two radical species rotate freely in solid pH2 and that effects of the unpaired electron spin remain essentially unchanged from the gas phase. We provide detailed mechanistic studies that show the nascent ortho-NH2 photoproduct is rapidly cooled within the pH2 matrix to the ground vibrational and rotational state before (1) subsequent photodissociation or (2) tunneling-driven reaction (k(tun) = 1.88(17) min(-1)) with the pH2 host to produce ortho-NH3 in a defect site. Once the ortho-NH3 is produced in this defect site it slowly converts (k(conv) = 7.72(51) × 10(-3) min(-1)) back to a single substitution site even at 1.8 K. We demonstrate the in situ photolysis of NH3 can be utilized to generate NH doped pH2 solids that are relatively stable at low temperature. However, the ortho-NH2 + pH2 ? ortho-NH3 + H back reaction substantially limits the sequential two-photon conversion of NH3 to NH. These studies also reveal that extended photolysis of the NH3/pH2 system results in the generation of high concentrations of orthohydrogen that must result from repeated cycles of photodissociation and NH2 back reaction within the pH2 host. PMID:24063591

Ruzi, Mahmut; Anderson, David T

2013-12-19

268

Far-field radiation patterns of aperture antennas by the Winograd Fourier transform algorithm  

NASA Technical Reports Server (NTRS)

A more time-efficient algorithm for computing the discrete Fourier transform, the Winograd Fourier transform (WFT), is described. The WFT algorithm is compared with other transform algorithms. Results indicate that the WFT algorithm in antenna analysis appears to be a very successful application. Significant savings in cpu time will improve the computer turn around time and circumvent the need to resort to weekend runs.

Heisler, R.

1978-01-01

269

A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers  

NASA Technical Reports Server (NTRS)

A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.

Campbell, Joel

2008-01-01

270

Optical correlator performance of binary phase-only filters using Fourier and Hartley transforms.  

PubMed

Theoretical studies of the performance capabilities of binary phase-only filters (BPOFs), constructed using both Fourier and Hartley transforms, are presented. A thorough analysis of the Fourier BPOF is given. We show that, although BPOFs constructed using Fourier transforms perform well in optical correlator systems, they are also subject to additional noise sources and have the possibility of generating large false correlation signals. We then present an analysis of BPOFs constructed using the Hartley transform. We show that BPOFs made using the Hartley transform provide superior false correlation rejection and more uniformly sized correlation signals for heavily multiplexed BPOFs, compared with those made using the Fourier transform. We also present a technique for constructing Hartley BPOFs. Therefore, although it is well known that the quality of the correlation signal depends on the object, this work demonstrates that the quality of the correlation signal can also depend on the technique used in the synthesis of the BPOF. PMID:20490138

Cottrell, D M; Lilly, R A; Davis, J A; Day, T

1987-09-15

271

Split manageable efficient algorithm for Fourier and Hadamard transforms  

Microsoft Academic Search

In this paper, a general, efficient, manageable split algorithm to compute one-dimensional (1-D) unitary transforms, by using the special partitioning in the frequency domain, is introduced. The partitions determine fast transformations that split the N-point unitary transform into a set of Ni-point transforms i=1: n(N1+...N n=N). Here, we introduce a class of splitting transformations: the so-called paired transforms. Based on

Artyom M. Grigoryan; Sos S. Agaian

2000-01-01

272

A fast algorithm for nonequispaced Fourier transforms on the rotation group  

NASA Astrophysics Data System (ADS)

In this paper we present algorithms to calculate the fast Fourier synthesis and its adjoint on the rotation group SO(3) for arbitrary sampling sets. They are based on the fast Fourier transform for nonequispaced nodes on the three-dimensional torus. Our algorithms evaluate the SO(3) Fourier synthesis and its adjoint, respectively, of B-bandlimited functions at M arbitrary input nodes in or even flops instead of . Numerical results will be presented establishing the algorithm's numerical stability and time requirements.

Potts, Daniel; Prestin, Jürgen; Vollrath, Antje

2009-11-01

273

Fast Fourier transform based image compression algorithm optimized for speckle interferometer measurements  

Microsoft Academic Search

In the framework of European Space Agency (ESA) FluidPac satellite mission, we have developed a fast, lossy image compression algorithm (ICA) based on a slight variation of the classical 2-D fast Fourier transform (FFT). In essence, given a monochrome picture, the ICA calculates (almost) its Fourier spectrum. It then applies a low-pass filter to eliminate all Fourier coefficients beyond a

Jorge L. Vago; Herman C. Vermeulen; Antonio Verga

1997-01-01

274

Generalized Fourier transform and its application to the volume integral equation for elastic wave propagation in a half space  

Microsoft Academic Search

In the present study, a generalized Fourier transform for time harmonic elastic wave propagation in a half space is developed. The generalized Fourier transform is obtained from the spectral representation of the operator derived from the elastic wave equation. By means of the generalized Fourier transform, a volume integral equation method for the analysis of scattered elastic waves is presented.

Terumi Touhei

2009-01-01

275

Midwave infrared imaging Fourier transform spectrometry of combustion plumes  

NASA Astrophysics Data System (ADS)

A midwave infrared (MWIR) imaging Fourier transform spectrometer (IFTS) was used to successfully capture and analyze hyperspectral imagery of combustion plumes. Jet engine exhaust data from a small turbojet engine burning diesel fuel at a low rate of 300 cm3/min was collected at 1 cm -1 resolution from a side-plume vantage point on a 200x64 pixel window at a range of 11.2 meters. Spectral features of H2O, CO, and CO2 were present, and showed spatial variability within the plume structure. An array of thermocouple probes was positioned within the plume to aid in temperature analysis. A single-temperature plume model was implemented to obtain spatially-varying temperatures and plume concentrations. Model-fitted temperatures of 811 +/- 1.5 K and 543 +/- 1.6 K were obtained from plume regions in close proximity to thermocouple probes measuring temperatures of 719 K and 522 K, respectively. Industrial smokestack plume data from a coal-burning stack collected at 0.25 cm-1 resolution at a range of 600 meters featured strong emission from NO, CO, CO2, SO 2, and HCl in the spectral region 1800-3000 cm-1. A simplified radiative transfer model was employed to derive temperature and concentrations for clustered regions of the 128x64 pixel scene, with corresponding statistical error bounds. The hottest region (closest to stack centerline) was 401 +/- 0.36 K, compared to an in-stack measurement of 406 K, and model-derived concentration values of NO, CO2, and SO2 were 140 +/- 1 ppmV, 110,400 +/- 950 ppmV, and 382 +/- 4 ppmV compared to in-stack measurements of 120 ppmV (NOx), 94,000 ppmV, and 382 ppmV, respectively. In-stack measurements of CO and HCl were not provided by the stack operator, but model-derived values of 19 +/- 0.2 ppmV and 111 +/- 1 ppmV are reported near stack centerline. A deployment to Dugway Proving Grounds, UT to collect hyperspectral imagery of chemical and biological threat agent simulants resulted in weak spectral signatures from several species. Plume detection of methyl salicilate was achieved from both a stack release and explosive detonation, although spectral identification was not accomplished due to weak signal strength.

Bradley, Kenneth C.

276

Phase demodulation using adaptive windowed Fourier transform based on Hilbert-Huang transform.  

PubMed

The phase demodulation method of adaptive windowed Fourier transform (AWFT) is proposed based on Hilbert-Huang transform (HHT). HHT is analyzed and performed on fringe pattern to obtain instantaneous frequencies firstly. These instantaneous frequencies are further analyzed based on the condition of AWFT to locate local stationary areas where the fundamental spectrum will not be interfered by high-order spectrum. Within each local stationary area, the fundamental spectrum can be extracted accurately and adaptively by using AWFT with the background, which has been determined previously with the presented criterion during HHT, being eliminated to remove the zero-spectrum. This method is adaptive and unconstrained by any precondition for the measured phase. Experiments demonstrate its robustness and effectiveness for measuring the object with discontinuities or complex surface. PMID:23038397

Wang, Chenxing; Da, Feipeng

2012-07-30

277

EVALUATION OF THE FOURIER TRANSFORM INFRARED SPECTROMETER FOR PARTICLE-ASSOCIATED AMMONIUM SULFATE DETERMINATION  

EPA Science Inventory

A commercial Fourier transform infrared (FTIR) spectrometer, modified for automated analysis of particulate-associated sulfate, was used to obtain transmission spectra samples of particulate matter collected from the ambient air onto Teflon filters. n evaluation of this instrumen...

278

HIGH SENSITIVITY FOURIER TRANSFORM NMR. INTERMOLECULAR INTERACTIONS BETWEEN ENVIRONMENTAL TOXIC SUBSTANCES AND BIOLOGICAL MACROMOLECULES  

EPA Science Inventory

This project explored the feasibility of developing new techniques for evaluation of the effects of environmental toxic materials on complex biopolymer systems using high sensitivity Fourier transform nuclear magnetic resonance (nmr) spectroscopy. Commercial instrumentation avail...

279

Discrete Fourier Transform Identities for Testing the Accuracy of Digital Data Processing Systems and Procedures.  

National Technical Information Service (NTIS)

Analytical expressions are developed for the discrete Fourier transforms (DFTs) of three classes of theoretical time series that often occur in physical and engineering investigations. The DFTs are expressed in terms of arbitrary parameters specifying the...

R. A. Saenger

1974-01-01

280

Application of Liquid Core Fiber Fourier Transform Raman Spectroscopy to Low Concentration Detection  

NASA Astrophysics Data System (ADS)

Fourier transform Raman system integrating liquid core fiber technique got high quality Raman spectra at low concentrations from 10^-7-10^-12 M. The extreme sensitivity makes it a potential analytical tool in low concentration environment monitoring.

Yin, J. H.

2014-06-01

281

The Fourier Transform in Chemistry. Part 1. Nuclear Magnetic Resonance: Introduction.  

ERIC Educational Resources Information Center

Using fourier transformation methods in nuclear magnetic resonance has made possible increased sensitivity in chemical analysis. This article describes these methods as they relate to magnetization, the RF magnetic field, nuclear relaxation, the RF pulse, and free induction decay. (CW)

King, Roy W.; Williams, Kathryn R.

1989-01-01

282

Quantitative Gas Analysis of Sulfur Dioxide in Nitrogen by Fourier Transform Infrared Spectrophotometer.  

National Technical Information Service (NTIS)

A method for quantitative gas analysis of sulfur dioxide contained in nitrogen using the Fourier transform infrared spectrophotometer has been established. On account of the strong adsorption properties of sulfur dioxide, the measuring method adopted is o...

Y. Koga M. Sugie S. Kondo S. Saeki

1979-01-01

283

QUANTITATIVE FOURIER TRANSFORM INFRARED SPECTROSCOPIC INVESTIGATION OF HUMIC SUBSTANCE FUNCTIONAL GROUP COMPOSITION  

EPA Science Inventory

Infrared (IR) spectroscopy has been widely used for the structural investigation of humic substances. Although Fourier Transform Infrared (FTIR) instrumentation has been available for sometime, relatively little work with these instruments has been reported for humic substances,...

284

Simple Example of Track Finding by Fourier Transform and Possibilities for Vector or Optical Processors.  

National Technical Information Service (NTIS)

Simple examples of finding tracks by Fourier transform with filter or correlation function are presented. Possibilities for using this method in more complicated real situations and the processing times which might be achieved are discussed. The method im...

D. Underwood

1986-01-01

285

Fast Wavefront Reconstruction in Large Adaptive Optics Systems Using the Fourier Transform.  

National Technical Information Service (NTIS)

Wavefront Reconstruction using the Fast Fourier Transform and spatial filtering is shown to be computationally tractable and sufficiently accurate for use in large Shack Hartmann-based adaptive optics systems (up to at least 10,000 actuators). This method...

L. A. Poyneer D. T. Gavel J. M. Brase

2002-01-01

286

Polarized fourier transform infrared microscopy as a tool for structural analysis of adsorbates in molecular sieves  

Microsoft Academic Search

This report tries to determine whether polarized fourier transform infrared microscopy could be useful in the analysis of the adsorbate structure in zeolites. Measurements on p-xylene loaded single crystals of silicalite I were performed.

F. Schueth

1992-01-01

287

Fourier Transform Infrared Spectroscopy: Part II. Advantages of FT-IR.  

ERIC Educational Resources Information Center

This is Part II in a series on Fourier transform infrared spectroscopy (FT-IR). Described are various advantages of FT-IR spectroscopy including energy advantages, wavenumber accuracy, constant resolution, polarization effects, and stepping at grating changes. (RH)

Perkins, W. D.

1987-01-01

288

Particulate Matter Measurements using Open-Path Fourier Transform Infrared Spectroscopy.  

National Technical Information Service (NTIS)

Open-path Fourier transform infrared (OP-FTIR) spectroscopy is an accepted technology for measuring gaseous air contaminants. OP-FTIR absorbance spectra acquired during changing aerosols conditions reveal related changes in very broad baseline features. U...

R. A. Hashmonay D. B. Harris

2001-01-01

289

Gaseous effluent monitoring and identification using an imaging Fourier transform spectrometer.  

National Technical Information Service (NTIS)

We are developing an imaging Fourier transform spectrometer for chemical effluent monitoring. The system consists of a 2-D infrared imaging array in the focal plane of a Michelson interferometer. Individual images are coordinated with the positioning of a...

M. R. Carter C. L. Bennett D. J. Fields J. Hernandez

1993-01-01

290

Instrument Line Shape Modeling and Correction for Off-Axis Detectors in Fourier Transform Spectrometry  

NASA Technical Reports Server (NTRS)

Spectra measured by off-axis detectors in a high-resolution Fourier transform spectrometer (FTS) are characterized by frequency scaling, asymmetry and broadening of their line shape, and self-apodization in the corresponding interferogram.

Bowman, K.; Worden, H.; Beer, R.

1999-01-01

291

Surface hydration of aqueous calcium minerals as studied by Fourier transform Raman and infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Rapid hydration reactions of several calcium minerals are studied using Fourier transform (FT) Raman and infrared (IR) spectroscopy. Oleate adsorption over aqueous synthetic fluorite, calcite and gypsum (pH 9) is investigated and adsorption mechanisms are discussed.

Holmgren, Allan; Wu, Liuming; Forsling, Willis

1994-10-01

292

Multiple Internal Reflection Fourier Transform Infrared Spectroscopy Studies of Thiocyanate Adsorption on Silver and Gold.  

National Technical Information Service (NTIS)

Conducting silver and gold coatings on silicon Attenuated Total Reflectance (ATR) plates have been employed as transparent electrodes to monitor in situ surface electrochemistry. The multiple internal reflection Fourier transform infrared spectroscopy (MI...

D. B. Parry J. M. Harris K. Ashley

1989-01-01

293

Investigation of the enzymatic digestion of plant cell walls using reflectance Fourier Transform Infrared spectroscopy.  

PubMed

A method has been developed to determine the reflectance Fourier Transform Infrared spectra of plant cells grown in vitro and of the protoplasts released from such cells by enzymatic digestion. It is demonstrated that there is a smooth and reproducible transition in spectral detail as enzymatic digestion procedes. Reflectance Fourier Transform Infrared spectroscopy has been used to monitor the progress of protoplast release during enzymatic digestion of cell wall material. PMID:24254073

Hopkinson, J; Moustou, C; Charlwood, K A; Newbery, J E; Charlwood, B V

1985-12-01

294

Compact Fourier-transform volume holographic spectrometer for diffuse source spectroscopy.  

PubMed

We present a new idea for diffuse source spectroscopy using a Fourier-transform volume holographic spectrometer formed by a Fourier-transform lens, a volume hologram, and a CCD. We show that this spectrometer can operate well under spatially incoherent light illumination. Furthermore, this spectrometer is less bulky, less sensitive to input alignment, and potentially more appropriate for implementation of highly sensitive spectrometers than conventional spectrometers. PMID:15865371

Hsieh, Chaoray; Momtahan, Omid; Karbaschi, Arash; Adibi, Ali

2005-04-15

295

Digital optoelectronic processor for fast Fourier transform in binary sign-bit-system  

Microsoft Academic Search

A novel structure of an optoelectronic multiprocessor digital Fourier-computer which uses Hartley transform and representation of operands in the form of a binary sign-bit numbers is proposed. The dynamic circulator fiber-optic storage device is taken as a random access memory. The use of Hartley transform in the proposed Fourier-computer and representation of operands in the binary sign-bit number system in

V. A. Pilipovich; A. K. Esman; V. K. Kuleshov; I. F. Solonovich

1994-01-01

296

Fourier transform-based optical waveguide filters and WDMs  

Microsoft Academic Search

Summary form only given. We have introduced a new type of optical filter comprising a chain of couplers and differential delays based on Fourier expansion. We have demonstrate a 1.31\\/1.55-?m WDM with a rectangular response and an EDFA gain equalization filter as two examples.

Y. P. Li; C. H. Henry; E. J. Laskowski; H. H. Yaffe

1996-01-01

297

Note: Phase sensitive detection of photoluminescence with Fourier transform spectroscopy.  

PubMed

Although known for more than twenty years, there is limited information in the literature regarding the experimental parameters of lock-in based phase sensitive emission detection in conjunction with Fourier spectrometers. For this technique - also known as double modulation spectroscopy - we present a guideline for parameter optimization by measuring the photoluminescence of InSb:Te at cryogenic temperatures. PMID:22300001

Ullrich, B; Brown, G J

2012-01-01

298

Structrural Determination of Silacyclobutane and Silacyclopentane Using Fourier Transform Microwave (ftmw) and Chirped Pulse Fourier Transform Microwave (cp-FTMW) Spectroscopy  

Microsoft Academic Search

The pure rotational spectra of the ground states of silacyclobutane (SCB) and silacyclopentane (SCP) were measured in a supersonic jet in the 6-24 GHz range using Fourier transform microwave spectroscopy and the chirped-pulse variant of this technique. Heavy atom isotopic substitution for the silicon and each of the carbon atoms within the rings enabled the accurate determination of the RS

Ziqiu Chen; Cody Van Dijk; Jennifer Van Wijngaarden

2011-01-01

299

Operational and convolution properties of three-dimensional Fourier transforms in spherical polar coordinates.  

PubMed

For functions that are best described with spherical coordinates, the three-dimensional Fourier transform can be written in spherical coordinates as a combination of spherical Hankel transforms and spherical harmonic series. However, to be as useful as its Cartesian counterpart, a spherical version of the Fourier operational toolset is required for the standard operations of shift, multiplication, convolution, etc. This paper derives the spherical version of the standard Fourier operation toolset. In particular, convolution in various forms is discussed in detail as this has important consequences for filtering. It is shown that standard multiplication and convolution rules do apply as long as the correct definition of convolution is applied. PMID:20922005

Baddour, Natalie

2010-10-01

300

Digital optoelectronic processor for fast Fourier transform in binary sign-bit-system  

NASA Astrophysics Data System (ADS)

A novel structure of an optoelectronic multiprocessor digital Fourier-computer which uses Hartley transform and representation of operands in the form of a binary sign-bit numbers is proposed. The dynamic circulator fiber-optic storage device is taken as a random access memory. The use of Hartley transform in the proposed Fourier-computer and representation of operands in the binary sign-bit number system in conjunction with the use of fiber-optic memory devices make it possible to compute coefficients of Fourier-series in practically real time.

Pilipovich, Vladimir A.; Esman, Alexander K.; Kuleshov, V. K.; Solonovich, Ivan F.

1994-01-01

301

Fourier transform of the Boltzmann collision integral for a bimodal distribution function  

NASA Astrophysics Data System (ADS)

The Fourier transform of the Boltzmann collision integral for a gas of Maxwell molecules is calculated explicitly for the bimodal distribution proposed by Mott-Smith for the shock wave structure. The results of Bobylev's approach of Fourier transforming of the Boltzmann equation were used as the starting point. Pour le modèle d'onde de choc de Mott-Smith correspondant à des interactions Maxwelliennes, la transformée de Fourier du terme de collision est calculée. La méthode utilisée est celle qui a été donnée par Bobylev pour l'équation de Boltzmann.

Orlov, Alexander

1993-03-01

302

Photoreflectance spectroscopy with a step-scan Fourier-transform infrared spectrometer: technique and applications.  

PubMed

We report on a new technique of realizing photoreflectance (PR) spectroscopy with a step-scan Fourier-transform infrared spectrometer. The experimental configuration is briefly described and a detailed theoretical analysis is conducted. The results reveal two distinct features of this PR technique that (i) the PR related signal is enhanced by a factor of at least 100 relative to those of the conventional PR techniques and (ii) the unwanted spurious signal introduced by either diffuse reflected pump beam or pump-beam induced material's photoluminescence reaching the photodetector of the PR configuration is eliminated without any special consideration of normalization for deducing the final PR spectrum. Applications are given as examples in the study of GaNAs/GaAs single quantum wells and GaInP/AlGaInP multiple quantum wells, respectively, under different pump-beam excitation energy and/or power. The experimental results approve the theoretically predicted features and illustrate the possibility of investigating weak PR features by using high pump-beam power. A brief comparison of this technique with the conventional PR techniques is given, and the extendibility of this technique to long-wavelength spectral regions is pointed out. PMID:17503911

Shao, Jun; Lu, Wei; Yue, Fangyu; Lü, Xiang; Huang, Wei; Li, Zhifeng; Guo, Shaoling; Chu, Junhao

2007-01-01

303

Shifted Fourier transform-based tensor algorithms for the 2-D DCT  

Microsoft Academic Search

In this paper, tensor algorithms for calculating the two-dimensional (2-D) discrete cosine transform (DCT) are presented. The tensor approach is based on the concept of the covering revealing the transforms, which yields in particular the splitting of the shifted 2 r×2r-point Fourier and cosine transforms into 2r-13 one-dimensional (1-D) incomplete 2r-point transforms. The multiplicative complexity of the 2-D 2r×2r-point discrete

Artyom M. Grigoryan; Sos S. Agaian

2001-01-01

304

Factoring and Fourier transformation with a Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

The scheme of Clauser and Dowling [Phys. Rev. A 53, 4587 (1996)] for factoring N by means of an N-slit interference experiment is translated into an experiment with a single Mach-Zehnder interferometer. With dispersive phase shifters, the ratio of the coherence length to wavelength limits the numbers that can be factored. A conservative estimate permits N~107. It is furthermore shown that sine and cosine Fourier coefficients of a real periodic function can be obtained with such an interferometer.

Summhammer, Johann

1997-11-01

305

Local quaternion Fourier transform and color image texture analysis  

Microsoft Academic Search

Color images can be treated as two-dimensional quaternion functions. For analysis of quaternion images, a joint space-wavenumber localized quaternion S transform (QS) is presented in this study for a simultaneous determination of the local color image spectra. The QS transform uses a two-dimensional Gaussian localizing window that scales with wavenumbers. Rotation invariance, invertibility and computational aspects of the QS transform

Dawit Assefa; Lalu Mansinha; Kristy F. Tiampo; Henning Rasmussen; Kenzu Abdella

2010-01-01

306

High Accuracy Evaluation of the Finite Fourier Transform Using Sampled Data  

NASA Technical Reports Server (NTRS)

Many system identification and signal processing procedures can be done advantageously in the frequency domain. A required preliminary step for this approach is the transformation of sampled time domain data into the frequency domain. The analytical tool used for this transformation is the finite Fourier transform. Inaccuracy in the transformation can degrade system identification and signal processing results. This work presents a method for evaluating the finite Fourier transform using cubic interpolation of sampled time domain data for high accuracy, and the chirp Zeta-transform for arbitrary frequency resolution. The accuracy of the technique is demonstrated in example cases where the transformation can be evaluated analytically. Arbitrary frequency resolution is shown to be important for capturing details of the data in the frequency domain. The technique is demonstrated using flight test data from a longitudinal maneuver of the F-18 High Alpha Research Vehicle.

Morelli, Eugene A.

1997-01-01

307

The complete iodine and nitrogen nuclear electric quadrupole coupling tensors for fluoroiodoacetonitrile determined by chirped pulse Fourier transform microwave spectroscopy.  

PubMed

Molecular pulsed jet, chirped-pulse Fourier transform microwave spectroscopy has been used to record 499 transitions for the title molecule. Measurements have been made in the 8-16 GHz regions. Vibrational and electronic ground state rotational constants A, B, and C have been obtained, together with centrifugal distortion terms. The complete iodine and nitrogen nuclear quadrupole coupling tensors have been determined for the first time. Quantum chemical calculations have been performed to aid with analyses and, in particular, to aid in determining the signs of the off-diagonal components of the nuclear quadrupole coupling tensors. An experimentally determined relative electronegativity scale for several polyhalomethyl groups is proposed. PMID:20095677

Grubbs, G S; Kadiwar, G; Bailey, W C; Cooke, S A

2010-01-14

308

A Graphical Presentation to Teach the Concept of the Fourier Transform  

ERIC Educational Resources Information Center

A study was conducted to visualize the reason why the Fourier transform technique is useful to detect the originating frequencies of a complicated superposition of waves. The findings reveal that students respond well when instructors adapt pictorial presentation to show how the time-domain function is transformed into the frequency domain.

Besalu, E.

2006-01-01

309

A Nonrecursive Equation for the Fourier Transform of a Walsh Function  

Microsoft Academic Search

Convolution of a discrete Walsh function with a rectangular pulse simplifies the derivation of an expression for the Fourier transform of a Walsh function. The nonrecursive transform equation that is developed is a function of the bits of the Gray code number for the order of the Walsh function.

Karl Siemens; Reuven Kitai

1973-01-01

310

Development of out-of-core fast Fourier transform software for the connection machine. Final report  

SciTech Connect

This report describes the algorithm and implementation of an out-of-core Fast Fourier Transform routine for the Thinking Machines Corp. CM-5 parallel computer. The software has the capability of transforming multi-dimensional arrays that are both real and complex.

Sweet, R.; Wilson, J. [Univ. of Colorado, Denver, CO (United States). Center for Computational Mathematics

1995-10-01

311

Evaluation of Fourier cosine/sine transforms using exponentially positioned samples  

NASA Astrophysics Data System (ADS)

The digital filter technique using exponentially positioned samples has been widely used in evaluating Hankel transforms. However it is not so widely used in evaluating Fourier transforms (FT). Published actual filters for FT evaluation are rather limited. We therefore present filters in lengths: 21, 61 and 101, which may be useful in evaluating FT for calculating e.g., the electromagnetic fields from a line source and from a dipole source, etc. It is shown that the filter technique can be more efficient (i.e., using fewer samples) than using digital Fourier transform (DFT) in evaluating FT related to 2D and 3D Green's functions.

Kong, F. N.

2012-04-01

312

Detection of magnification, rotation, and parallel translation using Hough and Fourier-Mellin transforms  

NASA Astrophysics Data System (ADS)

Let a reference image and an input image that is magnified, rotated, and parallel-translated from the reference image be given. This paper discusses a method of computing the scale of magnification, the angle of rotation, and the quantity of parallel translation with a Hough transform of O'Gorman- Clowes version and a Fourier-Mellin transform. Differently from known methods using Fourier or Hough transforms, the discussed method can compute uniquely the angle of rotation. Moreover, the discussed method can process even low quality images since it does not require extracting feature points differently from known methods. Experiments were applied to actual images of bills.

Onishi, Hiroyuki; Suzuki, Hisashi

1997-03-01

313

Does the entorhinal cortex use the Fourier transform?  

PubMed Central

Some neurons in the entorhinal cortex (EC) fire bursts when the animal occupies locations organized in a hexagonal grid pattern in their spatial environment. Place cells have also been observed, firing bursts only when the animal occupies a particular region of the environment. Both of these types of cells exhibit theta-cycle modulation, firing bursts in the 4–12 Hz range. Grid cells fire bursts of action potentials that precess with respect to the theta cycle, a phenomenon dubbed “theta precession.” Various models have been proposed to explain these phenomena, and how they relate to navigation. Among the most promising are the oscillator interference models. The bank-of-oscillators model proposed by Welday et al. (2011) exhibits all these features. However, their simulations are based on theoretical oscillators, and not implemented entirely with spiking neurons. We extend their work in a number of ways. First, we place the oscillators in a frequency domain and reformulate the model in terms of Fourier theory. Second, this perspective suggests a division of labor for implementing spatial maps: position vs. map layout. The animal's position is encoded in the phases of the oscillators, while the spatial map shape is encoded implicitly in the weights of the connections between the oscillators and the read-out nodes. Third, it reveals that the oscillator phases all need to conform to a linear relationship across the frequency domain. Fourth, we implement a partial model of the EC using spiking leaky integrate-and-fire (LIF) neurons. Fifth, we devise new coupling mechanisms, enlightened by the global phase constraint, and show they are capable of keeping spiking neural oscillators in consistent formation. Our model demonstrates place cells, grid cells, and phase precession. The Fourier model also gives direction for future investigations, such as integrating sensory feedback to combat drift, or explaining why grid cells exist at all.

Orchard, Jeff; Yang, Hao; Ji, Xiang

2013-01-01

314

Continuous Fourier transform method and apparatus. [for the analysis of simultaneous analog signal components  

NASA Technical Reports Server (NTRS)

An input analog signal to be frequency analyzed is separated into N number of simultaneous analog signal components each identical to the original but delayed relative to the original by a successively larger time delay. The separated and delayed analog components are combined together in a suitable number of adders and attenuators in accordance with at least one component product of the continuous Fourier transform and analog signal matrices to separate the analog input signal into at least one of its continuous analog frequency components of bandwidth 1/N times the bandwidth of the original input signal. The original analog input signal can be reconstituted by combining the separate analog frequency components in accordance with the component products of the continuous Fourier transform and analog frequency component matrices. The continuous Fourier transformation is useful for spectrum analysis, filtering, transfer function synthesis, and communications.

Munoz, R. M. (inventor)

1974-01-01

315

The \\mathfrak {su}(2)_\\alpha Hahn oscillator and a discrete Fourier-Hahn transform  

NASA Astrophysics Data System (ADS)

We define the quadratic algebra \\mathfrak {su}(2)_\\alpha which is a one-parameter deformation of the Lie algebra \\mathfrak {su}(2) extended by a parity operator. The odd-dimensional representations of \\mathfrak {su}(2) (with representation label j, a positive integer) can be extended to representations of \\mathfrak {su}(2)_\\alpha. We investigate a model of the finite one-dimensional harmonic oscillator based upon this algebra \\mathfrak {su}(2)_\\alpha. It turns out that in this model the spectrum of the position and momentum operator can be computed explicitly, and that the corresponding (discrete) wavefunctions can be determined in terms of Hahn polynomials. The operation mapping position wavefunctions into momentum wavefunctions is studied, and this so-called discrete Fourier-Hahn transform is computed explicitly. The matrix of this discrete Fourier-Hahn transform has many interesting properties, similar to those of the traditional discrete Fourier transform.

Jafarov, E. I.; Stoilova, N. I.; Van der Jeugt, J.

2011-09-01

316

Windowed Fourier transform as an essential digital interferometry tool to study coupled heat and mass transfer  

NASA Astrophysics Data System (ADS)

Series of thermodiffusion experiments using optical digital interferometry (ODI) have been conducted onboard the International Space Station. Conventionally, the two-dimensional (2D) fast Fourier transform (FFT) fringe analysis technique has been applied as a fast and reliable technique to extract data. In this study, for the first time, the windowed Fourier transform (WFT) method is used to analyze the same experiments. In this method, a Fourier transformation is applied on the fringes at two different stages: initially, during the filtration of the non-zero peaks and then on the wrapped phase image. We provide a detailed comparison between FFT and WFT results of binary and ternary mixtures for ODI thermodiffusion experiments. The substantial enhancements of this method are presented and discussed for different experiments conducted for both binary and ternary mixtures. We show that while disturbances in the phase fringe pattern can cause significant error in FFT techniques, if the windowed Fourier filtration (WFF) parameters are properly chosen this type of noise can be eliminated during WFF analysis. The importance of replacing the FFT method becomes more pronounced for the ternary system, as this method fails to reconcile reliable concentration profiles. The results of this work can show that the application of the windowed Fourier transform in optical digital interferometry investigations show improved results over the same experiments analyzed using FFT methods, especially for experiments involving very small heat and mass fluxes such as the Soret effect in multicomponent mixtures.

Ahadi, Amirhossein; Khoshnevis, Ahmad; Saghir, M. Ziad

2014-04-01

317

Automated charge state determination of complex isotope-resolved mass spectra by peak-target Fourier transform  

Microsoft Academic Search

This study describes a new algorithm for charge state determination of complex isotope-resolved mass spectra. This algorithm\\u000a is based on peak-target Fourier transform (PTFT) of isotope packets. It is modified from the widely used Fourier transform\\u000a method because Fourier transform may give ambiguous charge state assignment for low signal-to-noise ratio (S\\/N) or overlapping\\u000a isotopic clusters. The PTFT algorithm applies a

Li Chen; Yee Leng Yap

2008-01-01

318

Application of Fourier transform to MHD flow over an accelerated plate with partial-slippage  

NASA Astrophysics Data System (ADS)

Magneto-Hydrodynamic (MHD) flow over an accelerated plate is investigated with partial slip conditions. Generalized Fourier Transform is used to get the exact solution not only for uniform acceleration but also for variable acceleration. The numerical solution is obtained by using linear finite element method in space and One-Step-?-scheme in time. The resulting discretized algebraic systems are solved by applying geometric-multigrid approach. Numerical solutions are compared with the obtained Fourier transform results. Many interesting results related with slippage and MHD effects are discussed in detail through graphical sketches and tables. Application of Dirac-Delta function is one of the main features of present work.

Ahmad, Salman; Hussain, Shafqat; Siddiqui, Abuzar Abid; Ali, Asad; Aqeel, Muhammad

2014-06-01

319

Performance of portable high-resolution Fourier transform spectrometer for trace gas remote sensing  

NASA Astrophysics Data System (ADS)

Fourier Transform Spectrometer (FTS), with its throughput, multiplex, and spectra resolution advantages, has become one of the most promising atmospheric remote-sensing instruments for the research on the global climax change and air quality evaluation. In this paper, the instrument concept and performances of a compact, portable, high resolution Fourier transform spectrometer, named B3M-FTS are reported. Sample atmospheric absorption spectra and corresponding retrieval results measured by the FTS are given. The success of atmospheric composition profile retrieval using the FTS measurements provides a useful way to understand the atmospheric chemistry, and validates the feasibility of atmospheric composition remote sensing using high resolution FTS.

Wei, Haoyun; Ren, Libing; Fan, Dongdong; Soucy, Marc-André

2012-12-01

320

Reflections on the q-Fourier transform and the q-Gaussian function  

NASA Astrophysics Data System (ADS)

The standard q-Fourier Transform (qFT) of a constant diverges, which begs for a better treatment. In addition, Hilhorst has conclusively proved that the ordinary qFT is not of a one-to-one character for an infinite set of functions [H.J. Hilhorst, J. Stat. Mech. (2010) P10023]. Generalizing the ordinary qFT analyzed in [S. Umarov, C. Tsallis, S. Steinberg, Milan J. Math. 76 (2008) 307], we appeal here to a complex q-Fourier transform, and show that the problems above mentioned are overcome.

Plastino, A.; Rocca, M. C.

2013-09-01

321

[Research on spatially modulated Fourier transform imaging spectrometer data processing method].  

PubMed

Fourier transform imaging spectrometer is a new technic, and has been developed very rapidly in nearly ten years. The data catched by Fourier transform imaging spectrometer is indirect data, can not be used by user, and need to be processed by various approaches, including data pretreatment, apodization, phase correction, FFT, and spectral radicalization calibration. No paper so far has been found roundly to introduce this method. In the present paper, the author will give an effective method to process the interfering data to spectral data, and with this method we can obtain good result. PMID:20496726

Huang, Min; Xiangli, Bin; Lü, Qun-Bo; Zhou, Jin-Song; Jing, Juan-Juan; Cui, Yan

2010-03-01

322

The Los Alamos Fourier-transform spectrometer: Applications to molecular spectroscopy  

SciTech Connect

We outline design considerations and operating characteristics of the Los Alamos Fourier-transform spectrometer, a state-of-the-art instrument operating from 200 nm to 20 ..mu..m with a resolution of 0.0026 cm/sup /minus/1/ and very high wave number and intensity accuracy. Recent work in molecular spectroscopy carried out with this instrument will be discussed, including N/sub 2//sup +/ spectra obtained in inductively-coupled plasmas; high-temperature spectra of diatomic molecules of astrophysical interest; high-resolution rovibrational fine structure; and Fourier-transform Raman spectroscopy of species in expansion-cooled gases. 8 refs., 5 figs., 4 tabs.

Palmer, B.A.; McDowell, R.S.

1989-01-01

323

Feasibility breadboard demonstration of an imaging Fourier transform spectrometer using solid state time delay  

NASA Astrophysics Data System (ADS)

JPL has developed an innovative electro-optic time delay line and utilize it to build a prototype proof-of-principle completely non-mechanical Electro-optic Hyperspectral Imaging Fourier Transform Spectrometer (EOHIFTS). Due to the use of the EO time delay line, the EOHIFTS is lightweight, broad spectral band, hyperspectral resolution that cannot be achieved simultaneously by any of the Imaging Fourier Transform Spectrometers (IFTS) developed to date. We will report the recent progress in the development of a feasibility breadboard and its feasibility demonstration.

Chao, Tien-Hsin; Lu, Thomas T.

2011-04-01

324

Phase-shifting algorithm via wavelength tuning based on temporal Fourier transform  

NASA Astrophysics Data System (ADS)

The phase-shifting algorithm via wavelength tuning based on temporal Fourier transform is according to the Fourier transform technique and the difference technique to realize the processing of the interferogram. This algorithm is applied to test some course profiles or the topography with high steps. The paper describes its main idea and presents the shortcoming of the algorithm proposed by Takeda. Then it puts forward the improved algorithml. The pape describes the realization processing and the errors of the new algorithm. Finally, it supplies the measurement result.

Yu, Yingjie; Zhang, Benhao; Jiao, Yunfang

2003-11-01

325

Use of the fractional Fourier transform in {pi}/2 converters of laser modes  

SciTech Connect

The possibility of using the fractional Fourier transform (FrFT) in optical schemes for astigmatic {pi}/2 converters of Hermite-Gaussian modes to donut Laguerre-Gaussian modes is considered. Several schemes of converters based on the FrFT of the half-integer and irrational orders are presented. The lowest FrFT order than can be used in astigmatic mode converters is found. The properties of converters based on the fractional and ordinary Fourier transforms are compared. (laser beams)

Malyutin, A A [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2004-02-28

326

Introduction to Quantum Simulation  

NASA Technical Reports Server (NTRS)

This viewgraph presentation addresses the problem of efficiently simulating the evolution of a quantum system. The contents include: 1) Quantum Simulation; 2) Extracting Answers from Quantum Simulations; 3) Quantum Fourier Transform; 4) Eigenvalue Estimation; 5) Fermionic Simulations.

Williams, Colin P.

2005-01-01

327

Studies on mechanism of phase transformation of carboxylated poly(phenylene oxide) and polystyrene blend by Fourier transform infrared spectrometry  

Microsoft Academic Search

The thermally-induced phase transformation behaviors of carboxylated poly(phenylene oxide)(CPPO)\\/polystyrene(PS), and PPO\\/PS blends were studied by using a difference-spectrum method of Fourier Transform Infrared Spectrometry (FTIR). The difference intensities(µ) and vibration frequency shifts(??) of the characteristic infrared absorption bands in both CPPO\\/PS and PPO\\/PS increased with raising temperature. A linear temperature dependence in the band frequency vs. temperature plots was observed

Bing Liao; Yuhui Huang; Mincai Cheng; Guangmin Cong

1996-01-01

328

Progress Towards Chirped-Pulse Fourier Transform Thz Spectroscopy  

NASA Astrophysics Data System (ADS)

New opportunities are provided by the development of higher power THz frequency multiplier sources, the development of a broadband Chirped-Pulse FTMW spectroscopy technique at microwave and mm Wave frequencies, and recently demonstrated heterodyne hot electron bolometer detection technology in the THz frequency region with near quantum noise-limited performance and high spectral resolution. Combining these three technologies and extending the chirped-pulse technique to 0.85 THz enables a host of new applications. NIST is currently pursing applications as a point sensor for greenhouse gases, volatile organic compounds, and potentially human breath. The generation and detection of phase stable chirped pulses at 850 GHz will be demonstrated. A description of the experimental setup and preliminary data will be presented for nitrous oxide. G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S. Shipman and B.H. Pate, Rev.Sci.Instrum. 79 (2008) 053103. E. Gerecht, D. Gu, L. You, K.S. Yngvesson, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. 56, (2008) 1083.

Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

2010-06-01

329

Localized Fourier transform filter for noise removal in electronic speckle pattern interferometry wrapped phase patterns  

NASA Astrophysics Data System (ADS)

This article is concerned with frequency filtering for electronic speckle pattern interferometry wrapped phase patterns. We propose a robust localized Fourier transform filter which is an extension of the root filtering method (RFM). We improve the RFM from a simple technical process and a filter function in the frequency domain. In our method, the proposed filter function is taken as the power spectrum of the convolution of an image and a Gaussian function to the power ?. We test the proposed method on two computer-simulated wrapped phase fringe patterns and one experimentally obtained wrapped phase pattern, and compare our models with the widely used, well-known RFM and windowed Fourier filtering (WFF). The experimental results have demonstrated that our localized Fourier transform filter outperforms the RFM and is comparable to WFF. Our method depends on fewer parameters, as compared with WFF, and can achieve a better balance between the computational complexity and the filtered results.

Li, Cancan; Tang, Chen; Yan, Haiqing; Wang, Linlin; Zhang, Hao

2011-08-01

330

Localized Fourier transform filter for noise removal in electronic speckle pattern interferometry wrapped phase patterns.  

PubMed

This article is concerned with frequency filtering for electronic speckle pattern interferometry wrapped phase patterns. We propose a robust localized Fourier transform filter which is an extension of the root filtering method (RFM). We improve the RFM from a simple technical process and a filter function in the frequency domain. In our method, the proposed filter function is taken as the power spectrum of the convolution of an image and a Gaussian function to the power ?. We test the proposed method on two computer-simulated wrapped phase fringe patterns and one experimentally obtained wrapped phase pattern, and compare our models with the widely used, well-known RFM and windowed Fourier filtering (WFF). The experimental results have demonstrated that our localized Fourier transform filter outperforms the RFM and is comparable to WFF. Our method depends on fewer parameters, as compared with WFF, and can achieve a better balance between the computational complexity and the filtered results. PMID:21857715

Li, Cancan; Tang, Chen; Yan, Haiqing; Wang, Linlin; Zhang, Hao

2011-08-20

331

Multi-dimensional option pricing using radial basis functions and the generalized Fourier transform  

NASA Astrophysics Data System (ADS)

We show that the generalized Fourier transform can be used for reducing the computational cost and memory requirements of radial basis function methods for multi-dimensional option pricing. We derive a general algorithm, including a transformation of the Black-Scholes equation into the heat equation, that can be used in any number of dimensions. Numerical experiments in two and three dimensions show that the gain is substantial even for small problem sizes. Furthermore, the gain increases with the number of dimensions.

Larsson, Elisabeth; Ahlander, Krister; Hall, Andreas

2008-12-01

332

Efficient architectures for implementing the prime-factor Fourier transform modules  

Microsoft Academic Search

Memory intensive architectures are highly suited to VLSI technology. In this paper we present efficient architectures for implementing the discrete Fourier transform (DFT) and the discrete Hartley transform (DHART) based on prime factor decomposition. We use the multiplier-less distributed arithmetic in our architecture. But the look-up table sizes needed for implementing the short DFT\\/DHART modules are minimized by judiciously decomposing

R. Kumaresan

1985-01-01

333

Mirror Symmetry of Fourier-Mukai transformation for Elliptic Calabi-Yau manifolds  

Microsoft Academic Search

Mirror symmetry conjecture identi…es the complex geometry of a Calabi- Yau manifold with the symplectic geometry of its mirror Calabi-Yau man- ifold. Using the SYZ mirror transform, we argue that (i) the mirror of an elliptic Calabi-Yau manifold admits a twin Lagrangian …bration structure and (ii) the mirror of the Fourier-Mukai transform for dual elliptic …bra- tions is a symplectic

Naichung Conan Leung; Shing Tung Yau

334

A Weak Formulation of the Boltzmann Equation Based on the Fourier Transform  

NASA Astrophysics Data System (ADS)

In this article we present an alternative formulation of the spatially homogeneous Boltzmann equation. Rewriting the weak form of the equation with shifted test functions and using Fourier techniques, it turns out that the transformed problem contains only a three-fold integral. Explicit formulas for the transformed collision kernel are presented in the case of VHS models for hard and soft potentials. For isotropic Maxwellian molecules, a classical result by Bobylev is recovered, too.

Kirsch, R.; Rjasanow, S.

2007-11-01

335

FOURIER TRANSFORM SPECTROSCOPY AS A CONTINUOUS MONITORING METHOD: A SURVEY OF APPLICATIONS AND PROSPECTS  

EPA Science Inventory

Several field tests of a Fourier transform infrared (FTIR) spectrometer have been conducted. he results indicate that effective use of this type of instrument in the field of continuous emissions monitoring (CEM) is possible under the proper conditions, and within limits currentl...

336

Fourier Transform Infrared Spectrometric Analysis of Protein Conformation: Effect of Sampling Method and Stress Factors  

Microsoft Academic Search

Changes in the amide bands in Fourier transform infrared spectra of proteins are generally attributed to alterations in protein secondary structure. In this study spectra of five different globular proteins were compared in the solid and solution states recorded with several sampling techniques. Spectral differences for each protein were observed between the various sampling techniques and physical states, which could

Marco van de Weert; Parvez I. Haris; Wim E. Hennink; Daan J. A. Crommelin

2001-01-01

337

Recent Applications of Fourier Transform Infrared Spectrophotometry in Herbal Medicine Analysis  

Microsoft Academic Search

Fourier transform infrared spectroscopy (FTIR) is a fast and nondestructive analytical method. Associated with chemometrics, it is a powerful tool for the pharmaceutical industry. It is becoming a suitable technique for analysis of herbal medicine. This review focuses on the recent developments and updates for the qualitative and quantitative analysis of herbal medicine using FTIR. Moreover, it can be implemented

Andrei A. Bunaciu; Hassan Y. Aboul-Enein; Serban Fleschin

2011-01-01

338

Probing natural product biosynthetic pathways using Fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

Two natural products, diazepinomicin (1) and dioxapyrrolomycin (2), containing stable isotopic labels of 15N or deuterium, were used to demonstrate the utility of Fourier transform ion cyclotron resonance mass spectrometry for probing natural product biosynthetic pathways. The isotopic fine structures of significant ions were resolved and subsequently assigned elemental compositions on the basis of highly accurate mass measurements. In most

Xidong Feng; Anokha S. Ratnayake; Romila D. Charan; Jeffrey E. Janso; Valerie S. Bernan; Gerhard Schlingmann; Haiyin He; Mark Tischler; Frank E. Koehn; Guy T. Carter

2009-01-01

339

Modeling fourier transform infrared spectroscopic imaging of Prostate and Breast Cancer tissue specimens  

Microsoft Academic Search

Fourier transform infrared (FT-IR) spectroscopic imaging is an emerging technique that provides both spatially and chemically resolved information. The rich chemical content of data may be utilized for computer-aided determinations of structure and pathologic state (cancer diagnosis) in histological tissue sections for Prostate and Breast Cancer. Recent results show that tissue type (histological) classification can be performed to an accuracy

Rohith Reddy; Brynmor Davis; Paul Scott Carney; Rohit Bhargava

2011-01-01

340

Practical protocols for fast histopathology by Fourier transform infrared spectroscopic imaging  

Microsoft Academic Search

Fourier transform infrared (FT-IR) spectroscopic imaging is an emerging technique that combines the molecular selectivity of spectroscopy with the spatial specificity of optical microscopy. We demonstrate a new concept in obtaining high fidelity data using commercial array detectors coupled to a microscope and Michelson interferometer. Next, we apply the developed technique to rapidly provide automated histopathologic information for breast cancer.

Frances N. Keith; Rohith K. Reddy; Rohit Bhargava

2008-01-01

341

The Kinetics of Mo(Co)6 Substitution Monitored by Fourier Transform Infrared Spectrophotometry.  

ERIC Educational Resources Information Center

Describes a physical chemistry experiment that uses Fourier transform (FTIR) spectrometers and microcomputers as a way of introducing students to the spectral storage and manipulation techniques associated with digitized data. It can be used to illustrate FTIR spectroscopy, simple kinetics, inorganic mechanisms, and Beer's Law. (TW)

Suslick, Kenneth S.; And Others

1987-01-01

342

A program for 2D modeling (cross) correlogram tables using fast Fourier transform  

Microsoft Academic Search

An alternative to the traditional fitting of analytical correlogram models or of a linear model of coregionalization has been recently proposed, whereby the conditions for permissibility of a set of (cross) correlogram tables are imposed on their Fourier transforms, that is on the corresponding set of (cross) spectrum tables. The resulting model is entirely non-parametric and consists of a set

Xianlin Ma; Tingting Yao

2001-01-01

343

Planetary infrared astronomy using a cryogenic postdisperser on Fourier transform spectrometers  

Microsoft Academic Search

High resolution infrared spectra of planets from ground-based observatories were analyzed and instrumentation to improve sensitivity was developed. A cryogenic postdisperser (a narrow bandpass spectral filter) for use with Fourier transform spectrometers (FTS's) at facility observatories was constructed. This instrument has improved the sensitivity of FTS observations at 8 to 20 microns by about an order of magnitude. Spectra of

D. E. Jennings; V. G. Kunde; R. A. Hanel; W. C. Maguire; G. M. Lamb

1986-01-01

344

The generation of correlated Rayleigh random variates by inverse discrete Fourier transform  

Microsoft Academic Search

A number of different algorithms are used for the generation of correlated Rayleigh random variates. This paper presents an analysis of the statistical properties of methods based on the inverse discrete Fourier transform (IDFT). A modification of the algorithm of Smith (1975) is presented, the new method requiring exactly one-half the number of IDPT operations and roughly two-thirds the computer

David J. Young; Norman C. Beaulieu

2000-01-01

345

Real-Time Fourier Transformer Using One Acousto-Optical Cell.  

National Technical Information Service (NTIS)

Document describes an optical Fourier transformer comprising an acousto-optical cell such as a Bragg cell upon which is impressed a chirp signal, a laser which is modulated by the signal to be analyzed, optical means for dividing the laser beam into two b...

S. S. C. Lin

1983-01-01

346

Fourier Transform Infrared and Raman Spectroscopy for Characterization of Listeria monocytogenes Strains  

Microsoft Academic Search

The purpose of this study was to characterize the variation in biochemical composition of 89 strains of Listeria monocytogenes with different susceptibilities towards sakacin P, using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The strains were also analyzed using amplified fragment length polymorphism (AFLP) analysis. Based on their susceptibilities to sakacin P, the 89 strains have previously been divided

Astrid Oust; T. Moretro; Kristine Naterstad; Ganesh D. Sockalingum; Isabelle Adt; Michel Manfait; Achim Kohler

2006-01-01

347

Copyright protection of vector map using digital watermarking method based on discrete Fourier transform  

Microsoft Academic Search

In this paper, a new digital watermarking method for vector maps is proposed, where the watermark can be embedded in a set of polylines by using the discrete Fourier transform (DFT). The robustness against external attacks and visual degradation caused by embedding were evaluated, and the effectiveness of the watermarking was confirmed. Our watermarking method is especially robust against vertex

I. Kitamura; S. Kanai; T. Kishinami

2001-01-01

348

ATMOSPHERIC MEASUREMENTS OF TRACE POLLUTANTS; LONG PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY  

EPA Science Inventory

Described are the results of a four-year study to measure trace pollutant concentrations in polluted atmospheres by kilometer pathlength Fourier transform infrared (FT-IR) absorption spectroscopy. The study covers selected smog episodes during the years 1976 to 1979. During 1976 ...

349

Sensorless speed detection of inverter fed induction motors using rotor slot harmonics and fast Fourier transform  

Microsoft Academic Search

A novel approach to sensorless speed detection for adjustable-speed AC drives is described. No a priori knowledge is required about the motor construction, electrical parameters, or load condition. In addition, no external tuning is needed for the system. The technique is based on instantaneous spectral estimation using the fast Fourier transform, whereby the speed-dependent slot ripple harmonic frequency is determined.

A. Ferrah; K. G. Bradley; G. M. Asher

1992-01-01

350

Multiple internal reflection Fourier transform infrared spectroscopic studies of thiocyanate adsorption on silver and gold  

SciTech Connect

Conducting silver and gold coatings on silicon attenuated total reflectance (ATR) plates have been employed as transparent electrodes to monitor in situ surface electrochemistry. The multiple internal reflection Fourier transform infrared spectroscopy (MIRFTIRS) techniques, is applied in this work to the study of adsorption processes in the double-layer region, in particular, the adsorption of thiocyanate on silver and gold.

Parry, D.B.; Harris, J.M. (Univ. of Utah, Salt Lake City (USA)); Ashley, K. (San Jose State Univ., CA (USA))

1990-01-01

351

Millimeter and Submillimeter Wave Dielectric Measurements of Household Powders Using Fourier Transform Spectroscopy  

Microsoft Academic Search

High resolution millimeter and submillimeter wave measurements of solids and powders are very difficult to acquire and have taken on a growing significance for security reasons. Utilizing a two-beam polarizing interferometer, the dielectric properties of household powders were obtained through Dispersive Fourier Transform Spectroscopy. The refractive index, absorption coefficient, real and imaginary permittivity, and loss tangent for talc, confectioner sugar,

Usman Khan; M. N. Afsar; Nicholas Nguyen

2006-01-01

352

Waveguide Chirped-Pulse Fourier Transform Microwave Spectroscopy of 2-ETHOXYETHANOL  

NASA Astrophysics Data System (ADS)

The pure rotational spectrum of 2-ethoxyethanol was recorded from 8.7 to 26.5 GHz at 250 K with a waveguide chirped-pulse Fourier transform microwave spectrometer. The full spectrum contains contributions from multiple vibrational states. Preliminary assignments have been made with a combination of ab initio calculations and an automated spectral fitting program that accelerates the initial fitting process.

Phillips, Maria A.; Shipman, Steven T.

2013-06-01

353

Determination of diosmin in pharmaceutical formulations using Fourier transform infrared spectrophotometry  

PubMed Central

A Fourier transform infrared (FT-IR) spectrometric method was developed for the rapid, direct measurement of diosmin in different pharmaceutical drugs. Conventional KBr-spectra were compared for best determination of active substance in commercial preparations. The Beer–Lambert law and two chemometric approaches, partial least squares (PLS) and principal component regression (PCR+) methods, were tried in data processing.

Bunaciu, Andrei A.; Udristioiu, Gabriela Elena; Ruta, Lavinia L.; Fleschin, Serban; Aboul-Enein, Hassan Y.

2009-01-01

354

Amplified Dispersive FourierTransform Imaging for Ultrafast Displacement Sensing and Barcode Reading  

Microsoft Academic Search

Dispersive Fourier transformation is a powerful technique in which the spectrum of an optical pulse is mapped into a time-domain waveform using chromatic dispersion. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector. This simplifies the system and, more importantly, enables fast real-time measurements. Here we describe a novel ultrafast barcode reader and displacement

Keisuke God; Kevin K. Tsi; Bahram Jalali

355

Fourier transform infrared spectroscopic study of thermal degradation of sugar cane bagasse  

Microsoft Academic Search

Thermal degradation of sugar cane bagasse has been studied between 200 and 800 °C under a nitrogen gas flow. Different experimental parameters of the pyrolysis have been investigated, including holding temperature, time duration of pyrolysis, and heating rate. The solid residues obtained were then analyzed by classical elemental analysis and Fourier transform infrared (FTIR) spectroscopy.The most important structure modifications appeared

Ketty Bilba; Alex Ouensanga

1996-01-01

356

GRAZING-ANGLE FOURIER TRANSFORM INFRARED SPECTROSCOPY FOR ONLINE SURFACE CLEANLINESS VERIFICATION. YEAR 1  

EPA Science Inventory

As part of the Online Surface Cleanliness Project, the Naval Facilities Engineering Service Center (NFESC) conducted a study of grazing-angle reflectance Fourier Transform Infrared (FTIR) Spectroscopy as a tool for online cleanliness verification at Department of Defense (DoD) cl...

357

Applications of advanced technologies to space-based Fourier transform spectrometers for atmospheric remote sensing  

Microsoft Academic Search

A design for a miniaturized high resolution Fourier transform spectrometer (FTS) system for space based applications is proposed which will combine new advanced technologies and the proven advantages of the FTS to deliver a new class of remote sensing instruments with more than an order of magnitude reduction in mass, volume, power, and telemetry rate relative to existing instrumentation. For

D. E. Hinton; I. G. Nolt; J. H. Park; W. L. Smith; M. C. Abrams

1998-01-01

358

New Pair of Mutually Conjugate 3-Mode Entangled State Representations and the Corresponding Fractional Fourier Transformation  

NASA Astrophysics Data System (ADS)

Based on constructing a new pair of mutually conjugate 3-mode entangled state representations (ESR), we find new 3-mode bosonic operator realization of angular momentum. Using the properties of 3-mode ESR we formulate the new fractional Fourier transformation in entangled form. The method of integration within an ordered product of operators plays an important role in establishing the ESR.

Dao-Ming, Lu

2014-03-01

359

A VLSI chip for the winograd\\/Prime factor algorithm to compute the discrete Fourier transform  

Microsoft Academic Search

There is an extensive literature about computing the discrete Fourier transform and the hardware implementations of the different algorithms. In this paper, we propose a radically different approach based on the so-called small n algorithms and several different iteration methods. Our approach will result in fully pipelined bit serial architectures which require no control units. The area is about the

R. Owens

1986-01-01

360

Discrete chirp-Fourier transform and its application to chirp rate estimation  

Microsoft Academic Search

The discrete Fourier transform (DFT) has found tremendous applications in almost all fields, mainly because it can be used to match the multiple frequencies of a stationary signal with multiple harmonics. In many applications, wideband and nonstationary signals, however, often occur. One of the typical examples of such signals is chirp-type signals that are usually encountered in radar signal processing,

Xiang-Gen Xia

2000-01-01

361

Pulsed nozzle Fourier transform microwave spectrometer: Ideal to define hydrogen bond radius  

Microsoft Academic Search

A pulsed nozzle Fourier transform microwave (PNFTMW) spectrometer has been recently fabri- cated at the Indian Institute of Science. The basic design is the same as that of Balle and Flygare. How - ever, recent advances in microwave and computer technologies have helped in designing a state -of-the- art PNFTMW spectrometer. The range of the spectro- meter is from 2

E. Arunan; A. P. Tiwari; P. K. Mandal; P. C. Mathias

362

Petroleomics Applications of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Crude Oil and Bitumen Analysis  

Microsoft Academic Search

The ultra-high mass resolving power and high mass accuracy of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have been shown to be well suited for the characterization of highly complex mixtures. Petroleum mixtures, arguably the most complex on the planet, have been extensively characterized by FT-ICR MS. This new field of \\

Donald Francis Smith

2007-01-01

363

Quantitative Fourier Transform Infrared Analysis of Gas Phase Cigarette Smoke and Other Gas Mixtures  

Microsoft Academic Search

A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. the method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time.Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and

Rafael Cueto; Daniel R. Church; William A. Piyor

1989-01-01

364

Topics in Chemical Instrumentation: Fourier Transform-Infrared Spectroscopy: Part I. Instrumentation.  

ERIC Educational Resources Information Center

Discusses: (1) the design of the Fourier Transform-Infrared Spectroscopy (FT-IR) spectrometer; (2) the computation of the spectrum from the interferogram; and (3) the use of apodization. (Part II will discuss advantages of FT-IR over dispersive techniques and show applications of FT-IR to difficult spectroscopic measurements.) (JN)

Perkins, W. D.

1986-01-01

365

A practical implementation of de-Pake-ing via weighted Fourier transformation  

PubMed Central

We provide an NMRPipe macro to meet an increasing need in membrane biophysics for facile de-Pake-ing of axially symmetric deuterium, and to an extent phosphorous, static lineshapes. The macro implements the development of McCabe & Wassall (1997), and is run as a simple replacement for the usual Fourier transform step in an NMRPipe processing procedure.

Sani, Marc-Antoine; Weber, Daniel K.; Delaglio, Frank; Separovic, Frances

2013-01-01

366

Authentication of Olive Oil Adulterated with Vegetable Oils Using Fourier Transform Infrared Spectroscopy  

Microsoft Academic Search

Determination of the authenticity of extra virgin olive oils has become more important in recent years following some infamous adulteration and contamination scandals. The study focused on application of Fourier transform infrared spectroscopy to identify the adulteration of olive oils. Single-bounce attenuated total reflectance measurements were made on pure olive oil and olive oil samples adulterated with varying concentrations of

A Tay; R. K Singh; S. S Krishnan; J. P Gore

2002-01-01

367

Review of finite fields: Applications to discrete Fourier, transforms and Reed-Solomon coding  

NASA Technical Reports Server (NTRS)

An attempt is made to provide a step-by-step approach to the subject of finite fields. Rigorous proofs and highly theoretical materials are avoided. The simple concepts of groups, rings, and fields are discussed and developed more or less heuristically. Examples are used liberally to illustrate the meaning of definitions and theories. Applications include discrete Fourier transforms and Reed-Solomon coding.

Wong, J. S. L.; Truong, T. K.; Benjauthrit, B.; Mulhall, B. D. L.; Reed, I. S.

1977-01-01

368

Signal-to-noise ratio in the Mesooptical Fourier-Transform Microscope.  

National Technical Information Service (NTIS)

The character of the noise in the Mesooptical Fourier-Transform Microscope (MFTM) is analyzed and new techniques of amelioration of the signal-to-noise ratio in the MFTM for searching for particle tracks of minimum ionization are treated. Two models of no...

A. Kisvaradi I. Molnar L. M. Soroko V. V. Tereschchenko I. Torma

1989-01-01

369

Chemical ionization Fourier transform mass spectrometry of chemical warfare agent simulants using laser produced metal ions  

Microsoft Academic Search

In an initial investigation of the potential utility of chemical ionization (CI) mass spectrometry of selected analogs of chemical warfare agents using metal ions, the reactions of manganese ions with chloroalkyl sulfides and organophosphonates have been followed in a Fourier transform mass spectrometer. Mn{sup +} ions, produced by UV laser radiation focused on a stainless steel target, react rapidly with

Chih-Cong Chou; S. Randolph Long

1990-01-01

370

Minimum-Bias Windows for Spectral Estimation by Means of Overlapped Fast Fourier Transform Processing.  

National Technical Information Service (NTIS)

The time-limited nonnegative data windows that minimize the bias in auto- and cross-spectral estimation of stationary random processes by means of overlapped Fast Fourier Transform (FFT) processing are derived for a variety of constraints. The author cons...

A. H. Nuttall

1973-01-01

371

Aspects of Fast Fourier Transform Application for Analysis of Electrical Systems with Wind Generation  

Microsoft Academic Search

One of the most powerful tools in spectral analysis is the Fast Fourier Transform (FFT). Since the sixties it has been successfully installed in many electrical engineering applications. Nowadays, the engineer needs to press a button to get results. Nevertheless, meaningful analysis of measurements requires in- depth knowledge of the FFT algorithms. Sometimes the engineer would be forced to use

P. Janik

372

Polyphase-Discrete Fourier Transform Spectrum Analysis for the Search for Extraterrestrial Intelligence Sky Survey.  

National Technical Information Service (NTIS)

The sensitivity of a matched filter-detection system to a finite-duration continuous wave (CW) tone is compared with the sensitivities of a windowed discrete Fourier transform (DFT) system and an ideal bandpass filter-bank system. These comparisons are ma...

G. A. Zimmerman S. Gulkis

1991-01-01

373

Lossless compression of the geostationary imaging Fourier transform spectrometer (GIFTS) data via predictive partitioned vector quantization  

Microsoft Academic Search

The Geostationary Imaging Fourier Transform Spectrometer (GIFTS), as part of NASA's New Millennium Program, is an advanced instrument to provide high-temporal-resolution measurements of atmospheric temperature and water vapor, which will greatly facilitate the detection of rapid atmospheric changes associated with destructive weather events, including tornadoes, severe thunderstorms, flash floods, and hurricanes. The Committee on Earth Science and Applications from Space

Bormin Huang; Shih-Chieh Wei; Allen H.-L. Huang; Maciek Smuga-Otto; Robert Knuteson; Henry E. Revercomb; William L. Smith Sr.

2007-01-01

374

RETRIEVAL OF LINE PARAMETERS FROM HIGH RESOLUTION FOURIER TRANSFORM LABORATORY SPECTRA IN SUPPORT OF ATMOSPHERIC SPECTROSCOPY  

Microsoft Academic Search

Fourier transform infrared (FTIR) spectroscopy has become a powerful tool for the detection and measurement of gas emissions (or absorption) in terrestrial and planetary atmospheric remote sensing. Besides the improving quality of current instruments (signal to noise ratio, spectral resolution, sensors' response…) and the advances in computational facilities, one needs precise knowledge of molecular spectroscopic line parameters to deduce accurate

M. Badaoui; F. Schreier; G. Wagner; M. Birk

2007-01-01

375

On the use of windows for harmonic analysis with the discrete Fourier transform  

Microsoft Academic Search

This paper makes available a concise review of data windows and their affect on the detection of harmonic signals in the presence of broad-band noise, and in the presence of nearby strong harmonic interference. We also call attention to a number of common errors in the application of windows when used with the fast Fourier transform. This paper includes a

FREDRIC J. HARRIS

1978-01-01

376

Fourier transform infrared spectroscopy in high-pressure studies on proteins  

Microsoft Academic Search

Several aspects of the application of Fourier transform infrared spectroscopy (FTIR) in high-pressure studies on proteins are reviewed. Basic methodological considerations regarding spectral band assignments, quantitative analysis, and choice of pressure calibrants are also placed within the scope of this paper. This work attempts to evaluate recent developments in the field of high-pressure FTIR of proteins and its prospects for

Wojciech Dzwolak; Minoru Kato; Yoshihiro Taniguchi

2002-01-01

377

PARTICULATE MATTER MEASUREMENTS USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY  

EPA Science Inventory

Open-path Fourier transform infrared (OP-FT1R) spectroscopy is an accepted technology for measuring gaseous air contaminants. OP-FT1R absorbance spectra acquired during changing aerosols conditions reveal related changes in very broad baseline features. Usually, this shearing of ...

378

Measurement of ferrocyanides and oxyanions in waste sludges by Fourier transform infrared reflection methods  

NASA Astrophysics Data System (ADS)

Simulated waste sludges with compositions similar to some of the actual waste sludges stored in carbon steel tanks at the Hanford Site were measured for their ferrocyanide and oxyanion contents by Fourier transform infrared (FT-IR) reflection methods. The results indicated the viability of these methods to chemically characterize highly radioactive waste sludges.

Rebagay, Teofila V.; Dodd, D. A.; Jeppson, David W.

1994-01-01

379

A procedure to predict the spectral resolution requirements of a Fourier Transform Infrared spectrometer  

Microsoft Academic Search

The DSTO employs a Bomem MR series Fourier Transform Infrared (FTIR) spectrometer for a variety of thermal signature measurements, passive remote sensing and spectroscopic applications. These measurements are often performed at the maximum resolution of the instrument with associated overheads in extended acquisition times and increased data size and storage issues. With many of the passive remote sensing and target

T. Bubner; S. Frost; V. Devrelis

2001-01-01

380

Determination of the total unsaturation in vegetable oils by Fourier transform Raman spectroscopy and multivariate calibration  

Microsoft Academic Search

In this paper multivariate calibration was used in conjunction with NIR-Fourier transform Raman spectroscopy for determination of the total degree of unsaturation in vegetable oils. For this purpose, different vegetable oils and some mixtures were employed as calibration standards. A calibration model based on partial least squares (PLS) was constructed and used to analyse oils with iodine values ranging from

Rosangela C Barthus; Ronei J Poppi

2001-01-01

381

Learning applications of multi-tasking signal analysis of Fourier transform based on smart mobile devices  

Microsoft Academic Search

This paper presents a viable approach and a new teaching and learning paradigm to enhance the effectiveness of teaching fast Fourier transform [1] and significantly improve the learning outcomes. By using the smart mobile devices, this approach establishes the links among concepts, abstract representations, and realistic applications which are often lacking in traditional instruction. Several mobile apps for real time

Zhengzhe Li; Teng Zhao; Dong Ren; Yang Zhang; Lei Wang

2012-01-01

382

Predicting bovine milk protein composition based on Fourier transform infrared spectra  

Microsoft Academic Search

Phenotypic information on individual protein composition of cows is important for many aspects of dairy processing with cheese production as the center of gravity. However, measuring individual protein composition is expensive and time consuming. In this study, we investigated whether protein composition can be predicted based on inexpensive and routinely measured milk Fourier transform infrared (FTIR) spectra. Based on 900

M. J. M. Rutten; H. Bovenhuis; J. M. L. Heck; J. A. M. van Arendonk

2011-01-01

383

Fourier transform Raman spectral measurements of powdered quaternary mixtures of organic compounds  

Microsoft Academic Search

Fourier transform Raman spectra of eight mixtures of four organic solids, namely dicyandiamide, melamine, acetamide and urea were measured. Matrices formed from these spectra were first subjected to singular value decomposition to obtain the right singular vectors. The right singular vectors were then subjected to blind source separation using band-target entropy minimization (BTEM), thus no a priori information (i.e. involving

Chilukoti Srilakshmi; Effendi Widjaja; Bruce G. Anderson; Marc Garland

2007-01-01

384

Fidelities for transformations of unknown quantum states  

SciTech Connect

We present a general theoretical formalism to compute the fidelity of transformations of unknown quantum states, and we apply our theory to Gaussian transformations of continuous variable quantum systems. For the case of a Gaussian distribution of displaced coherent states, the theory is readily tractable by a covariance matrix formalism, and a wider class of states, exemplified by Fock states, can be treated efficiently by the Wigner function formalism. Given the distribution of input states, the optimum feedback gain is identified, and analytical results for the fidelities are presented for recently implemented teleportation and memory storage protocols for continuous variables.

Madsen, Lars Bojer [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark); Moelmer, Klaus [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark); Department of Physics and Astronomy, QUANTOP-Danish National Research Foundation Center for Quantum Optics, University of Aarhus, 8000 Aarhus C (Denmark)

2006-03-15

385

Synthesis of Arbitrary Unitary Transformations in Quantum Systems by Householder Reflections  

SciTech Connect

We demonstrate that Householder reflections emerge naturally in the propagator of a coherently driven degenerate two-level system. Such reflections are a very powerful tool for constructing arbitrary unitary transformations of an N-state quantum system. We present examples for construction of discrete Fourier transforms, superposition-to-superposition navigation between pure states, engineering of arbitrary mixed states, and entanglement of trapped ions.

Ivanov, P. A.; Vitanov, N. V. [Department of Physics, Sofia University, James Bourchier 5 blvd, 1164 Sofia (Bulgaria)

2007-12-26

386

Modified radon-Fourier transform for reflective tomography laser radar imaging  

NASA Astrophysics Data System (ADS)

This paper presents imaging result of computer simulation using a modified Radon-Fourier transform algorithm to reconstruct images from reflective tomography data. Since the signal returned is reflected off the illuminated outer surface of an opaque target, only information about the exterior of the target can be obtained, and the images reconstructed using reflective tomography techniques is an outline view of the target cross section. The projection p(r,? ) and p(r,? + 180°) contain different information about the target surface, and will lead different Fourier estimates along the same line through the origin based on the standard Fourier-Slice tomography theorem. Here, using the functional similarity between transmission tomography and reflective tomography, we add the collinear reflective projections to become corresponding transmissive projections before Fourier transform. Then the target can be reconstructed from the Fourier domain using the same operations in transmission tomography. The computer simulation result demonstrates the effectiveness of this modified algorithm to reconstruct image in reflective tomography using the diffuse reflection model (lamberts body). Future research will include the development of image reconstruction based on this modified algorithm for targets with much more complicated reflective characters.

Jin, Xiaofeng; Sun, Jianfeng; Yan, Yi; Zhou, Yu; Liu, Liren

2011-06-01

387

Implementation of quantum search algorithm using classical Fourier optics  

Microsoft Academic Search

We report on an experiment on Grover's quantum search algorithm showing that\\u000a{\\\\em classical waves} can search a $N$-item database as efficiently as quantum\\u000amechanics can. The transverse beam profile of a short laser pulse is processed\\u000aiteratively as the pulse bounces back and forth between two mirrors. We\\u000adirectly observe the sought item being found in $\\\\sim\\\\sqrt{N}$ iterations, in

N. Bhattacharya; Linden van den Heuvell van H. B; R. J. C. Spreeuw

2002-01-01

388

Fourier-Transform Raman and Fourier-Transform Infrared Spectroscopy (An Investigation of Five Higher Plant Cell Walls and Their Components).  

PubMed Central

Infrared and Raman spectra of sequentially extracted primary cell walls and their pectic polymers were obtained from five angiosperm plants. Fourier-transform Raman spectrometry was shown to be a powerful tool for the investigation of primary cell-wall architecture at a molecular level, providing complementary information to that obtained by Fourier-transform infrared microspectroscopy. The use of an extraction procedure using imidazole instead of cyclohexane trans-1,2-N,N,N[prime],N[prime]-diaminotetraacetate allows the extension of the infrared spectral window for data interpretation from 1300 to 800 cm-1, to 2000 to 800 cm-1, and allows us to obtain Raman spectra from extracted cell-wall material. Wall constituents such as pectins, proteins, aromatic phenolics, cellulose, and hemicellulose have characteristic spectral features that can be used to identify and/or fingerprint these polymers without, in most cases, the need for any physical separation. The Gramineae (rice [Oryza sativa], polypogon [Polypogon fugax steud], and sweet corn [Zea mays]) are spectroscopically very different from the nongraminaceous monocotyledon (onion [Allium cepa]) and the dicotyledon (carrot [Daucus carota]); this reflects differences in chemical composition and cross-linking of the walls. The possibility of a taxonomic classification of plant cell walls based on infrared and Raman spectroscopies and the use of spectral fingerprinting for authentication and detection of adulteration of products rich in cell-wall materials are discussed.

Sene, CFB.; McCann, M. C.; Wilson, R. H.; Grinter, R.

1994-01-01

389

Fourier transform IR and Fourier transform Raman spectroscopy studies of metallothionein-III: amide I band assignments and secondary structural comparison with metallothioneins-I and -II.  

PubMed

The secondary structures of porcine brain Cu(4)Zn(3)-metallothionein (MT)-III and Cd(5)Zn(2)MT-I, Cd(5)Zn(2)MT-II, and Zn(7)MT-I from rabbit livers in the solid state are investigated by Fourier transform IR spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT-Raman). The Cu(4)Zn(3)MT-III contains 26-28% beta-turns and half-turns, 13-14% 3(10)-helices, 47-49% random coils, and 11-12% beta-extended chains. The structural comparison of porcine brain Cu(4)Zn(3)MT-III with rabbit liver Cd(5)Zn(2)MT-I (II) and Zn(7)MT-I shows that the contents of the random coil structure are obviously increased. The results indicate that the insert of an acidic hexapeptide in the alpha domain of Cu(4)Zn(3)MT-III possibly forms an alpha helix. However, because the bands assigned to the alpha-helix and random coil structures are overlapped in the spectra, the content of random coil structures in Cu(4)Zn(3)MT-III is therefore higher than those in Cd(5)Zn(2)MT-I, Cd(5)Zn(2)MT-II, and Zn(7)MT-I. PMID:12209458

Shi, Yan-Bo; Fang, Jiang-Lin; Liu, Xiao-Yu; Du, Liang; Tang, Wen-Xia

2002-10-15

390

A Study of Derivative Filters Using the Discrete Fourier Transform. Final Report M. S. Thesis  

NASA Technical Reports Server (NTRS)

Important properties of derivative (difference) filters using the discrete Fourier transform are investigated. The filters are designed using the derivative theorem of Fourier analysis. Because physical data are generally degraded by noise, the derivative filter is modified to diminish the effects of the noise, especially the noise amplification which normally occurs while differencing. The basis for these modifications is the reduction of those Fourier components for which the noise most dominates the data. The various filters are tested by applying them to find differences of two-dimensional data to which various amounts of signal dependent noise, as measured by a root mean square value, have been added. The modifications, circular and square ideal low-pass filters and a cut-off pyramid filter, are all found to reduce noise in the derivative without significantly degrading the result.

Ioup, G. E.

1980-01-01

391

Program for the analysis of time series. [by means of fast Fourier transform algorithm  

NASA Technical Reports Server (NTRS)

A digital computer program for the Fourier analysis of discrete time data is described. The program was designed to handle multiple channels of digitized data on general purpose computer systems. It is written, primarily, in a version of FORTRAN 2 currently in use on CDC 6000 series computers. Some small portions are written in CDC COMPASS, an assembler level code. However, functional descriptions of these portions are provided so that the program may be adapted for use on any facility possessing a FORTRAN compiler and random-access capability. Properly formatted digital data are windowed and analyzed by means of a fast Fourier transform algorithm to generate the following functions: (1) auto and/or cross power spectra, (2) autocorrelations and/or cross correlations, (3) Fourier coefficients, (4) coherence functions, (5) transfer functions, and (6) histograms.

Brown, T. J.; Brown, C. G.; Hardin, J. C.

1974-01-01

392

Displacement estimation by the phase-shiftings of Fourier transform in present white noise  

NASA Astrophysics Data System (ADS)

Displacement estimation is a fundamental problem in Real-time video image processing. It can be typically approached by theories based on features in spatial domain. This paper presents an algorithm which improves the theory for estimating the moving object's displacement in spatial domain by its Fourier transform frequency spectrum. Because of the characters of Fourier transform, the result is based on all the features in the image. Utilizing shift theorem of Fourier transform and auto-registration, the algorithm employs the phase spectrum difference in polar coordinate of two frame images sequence with the moving target.The method needn't transform frequency spectrum to spatial domain after calculation comparing with the traditional algorithm which has to search Direc peak, and it reduces processing time. Since the technique proposed uses all the image information, including all the white noise in the image especially, and it's hard to overcome the aliasing from noises, but the technique can be an effective way to analyze the result in little white noise by the different characters between high and low frequency bands. It can give the displacement of moving target within 1 pixel of accuracy. Experimental evidence of this performance is presented, and the mathematical reasons behind these characteristics are explained in depth. It is proved that the algorithm is fast and simple and can be used in image tracking and video image processing.

Wu, Yuan-hao; Yu, Qian-yang

2006-01-01

393

Tropical Forest Biomass Estimation from Vertical Fourier Transforms of Lidar and InSAR Profiles  

NASA Astrophysics Data System (ADS)

Structural forest biomass estimation from lidar or interferometric SAR (InSAR) has demonstrated better performance than radar-power-based approaches for the higher biomasses (>150 Mg/ha) found in tropical forests. Structural biomass estimation frequently regresses field biomass to some function of forest height. With airborne, 25-m footprint lidar data and fixed-baseline C-band InSAR data over tropical wet forests of La Selva Biological Station, Costa Rica, we compare the use of Fourier transforms of vertical profiles at a few frequencies to the intrinsically low-frequency “average height”. RMS scatters of Fourier-estimated biomass about field-measured biomass improved by 40% and 20% over estimates base on average height from lidar and fixed-baseline InSAR, respectively. Vertical wavelengths between 14 and 100 m were found to best estimate biomass. The same airborne data acquisition over La Selva was used to generate many 10’s of repeat-track L-band InSAR baselines with time delays of 1-72 hours, and vertical wavelengths of 5-100 m. We will estimate biomass from the Fourier transforms of L-band radar power profiles (InSAR complex coherence). The effects of temporal decorrelation will be modeled in the Fourier domain to try to model and reduce their impact. Using L-band polarimetric interferometry, average heights will be estimated as well and biomass regression performance compared to the Fourier transform approach. The more traditional approach of using L-band radar polarimetry will also be compared to structural biomass estimation.

Treuhaft, R. N.; Goncalves, F.; Drake, J.; Hensley, S.; Chapman, B. D.; Michel, T.; Dos Santos, J. R.; Dutra, L.; Graca, P. A.

2010-12-01

394

A Discussion of the Discrete Fourier Transform Execution on a Typical Desktop PC  

NASA Technical Reports Server (NTRS)

This paper will discuss and compare the execution times of three examples of the Discrete Fourier Transform (DFT). The first two examples will demonstrate the direct implementation of the algorithm. In the first example, the Fourier coefficients are generated at the execution of the DFT. In the second example, the coefficients are generated prior to execution and the DFT coefficients are indexed at execution. The last example will demonstrate the Cooley- Tukey algorithm, better known as the Fast Fourier Transform. All examples were written in C executed on a PC using a Pentium 4 running at 1.7 Ghz. As a function of N, the total complex data size, the direct implementation DFT executes, as expected at order of N2 and the FFT executes at order of N log2 N. At N=16K, there is an increase in processing time beyond what is expected. This is not caused by implementation but is a consequence of the effect that machine architecture and memory hierarchy has on implementation. This paper will include a brief overview of digital signal processing, along with a discussion of contemporary work with discrete Fourier processing.

White, Michael J.

2006-01-01

395

Image hiding in Fourier domain by use of joint transform correlator architecture and holographic technique.  

PubMed

Based on joint transform correlator (JTC) architecture and holographic techniques, a new method for image hiding is presented. A hidden image encrypted by JTC architecture is embedded in the Fourier hologram of the host image. Inverse Fourier transform can be used to obtain the watermarked image, and JTC architecture is used to decode the hidden image from the watermarked hologram. Unlike other watermarking techniques, by prechoosing information, the noise added to the recovered hidden image by the host can be reduced. Unlike other watermarking systems based on double random-phase encoding, no conjugate key is used to recover the hidden image. Theoretical analyses have shown the system's feasibility. Computer simulations are presented to verify the system's validity and efficiency. Numerical simulations also show that the proposed system is robust enough to resist attacks, such as occlusion, noise, and filtering. PMID:21343999

Shi, Xiaoyan; Zhao, Daomu

2011-02-10

396

Data reconstructing for windowing broom Fourier transform imaging spectrometers based on multi-core techniques  

NASA Astrophysics Data System (ADS)

The windowing broom Fourier transform imaging spectrometer, based on space-time modulation, has the characteristics of high luminous flux, static interference part etc. However, the large amount of raw data and the data reconstruction increase the difficulty of the whole data processing and extend the computing time. In this paper, a parallel calculation algorithm for reconstruction of raw data is proposed. The proposed algorithm is achieved by using Task Parallel Library (TPL), which is provided by .NET framework, and a visualized processing system is further established. A set of data collected from a windowing broom Fourier transform imaging spectrometer is processed using both the proposed method and the ordinary serial algorithm. The scalability of this presented algorithm is verified by employing it on computers with different number of cores. The experimental results show that, compared to the serial algorithm, the proposed method can greatly speed up the processing with the same hardware condition, and it also has ideal scalability with different hardware.

Dong, Zhi-gang; Liao, Ning-fang; Qu, Liang; Lv, Hang

2013-08-01

397

Gaseous effluent monitoring and identification using an imaging Fourier transform spectrometer  

SciTech Connect

We are developing an imaging Fourier transform spectrometer for chemical effluent monitoring. The system consists of a 2-D infrared imaging array in the focal plane of a Michelson interferometer. Individual images are coordinated with the positioning of a moving mirror in the Michelson interferometer. A three dimensional data cube with two spatial dimensions and one interferogram dimension is then Fourier transformed to produce a hyperspectral data cube with one spectral dimension and two spatial dimensions. The spectral range of the instrument is determined by the choice of optical components and the spectral range of the focal plane array. Measurements in the near UV, visible, near IR, and mid-IR ranges are possible with the existing instrument. Gaseous effluent monitoring and identification measurements will be primarily in the ``fingerprint`` region of the spectrum, ({lambda} = 8 to 12 {mu}m). Initial measurements of effluent using this imaging interferometer in the mid-IR will be presented.

Carter, M.R.; Bennett, C.L.; Fields, D.J.; Hernandez, J.

1993-10-01

398

Automatic procedure for non-coplanar aberration compensation in lensless Fourier transform digital holography  

NASA Astrophysics Data System (ADS)

As the lensless Fourier transform digital holography is applied into the microscopic phase-contrast imaging on the live cells, the motion of the cells will lead to the non-coplanarity phenomena between the object and the reference source. This could result in the imaging aberration. An effective and robust autofocus procedure based on the phase distribution is presented in the paper. With the initial measurement of the distance between the reference source and the hologram, the optimum parameters corresponding to the phase-contrast image can be achieved by a single hologram, combined with the linearity fitting. The lensless Fourier transform digital holographic system is built and the experiments on the phase-contrast imaging of the live cervical carcinoma cells are performed. Finally, the good experiment results are demonstrated. Both the theoretical analysis and the experimental investigation verify the feasibility and validity of the automatic procedure for the non-coplanar aberration compensation.

Cui, Huakun; Wang, Dayong; Wang, Yunxin; Liu, Changgeng; Zhao, Jie; Li, Yan

2010-05-01

399

High-speed spectral domain optical coherence tomography using non-uniform fast Fourier transform  

PubMed Central

The useful imaging range in spectral domain optical coherence tomography (SD-OCT) is often limited by the depth dependent sensitivity fall-off. Processing SD-OCT data with the non-uniform fast Fourier transform (NFFT) can improve the sensitivity fall-off at maximum depth by greater than 5dB concurrently with a 30 fold decrease in processing time compared to the fast Fourier transform with cubic spline interpolation method. NFFT can also improve local signal to noise ratio (SNR) and reduce image artifacts introduced in post-processing. Combined with parallel processing, NFFT is shown to have the ability to process up to 90k A-lines per second. High-speed SD-OCT imaging is demonstrated at camera-limited 100 frames per second on an ex-vivo squid eye.

Chan, Kenny K. H.; Tang, Shuo

2010-01-01

400

Tabletop single-shot extreme ultraviolet Fourier transform holography of an extended object.  

PubMed

We demonstrate single and multi-shot Fourier transform holography with the use of a tabletop extreme ultraviolet laser. The reference wave was produced by a Fresnel zone plate with a central opening that allowed the incident beam to illuminate the sample directly. The high reference wave intensity allows for larger objects to be imaged compared to mask-based lensless Fourier transform holography techniques. We obtain a spatial resolution of 169 nm from a single laser pulse and a resolution of 128 nm from an accumulation of 20 laser pulses for an object ~11x11?m(2) in size. This experiment utilized a tabletop extreme ultraviolet laser that produces a highly coherent ~1.2 ns laser pulse at 46.9 nm wavelength. PMID:23609701

Malm, Erik B; Monserud, Nils C; Brown, Christopher G; Wachulak, Przemyslaw W; Xu, Huiwen; Balakrishnan, Ganesh; Chao, Weilun; Anderson, Erik; Marconi, Mario C

2013-04-22

401

Fatal extensive bone cement embolism: histological findings confirmed by Fourier transform infrared spectroscopy.  

PubMed

We herein report the first case of fatal extensive bone cement embolism appearing in pulmonary arterioles following surgical vertebral screw augmentation, which histological evidence of bone cement emboli was confirmed by Fourier transform infrared spectroscopy. A 47-year-old woman has accepted multilevel spine fusion and pedicle screw augmentation with totally 4 ml bone cement infusion. She suddenly developed low blood pressure, dyspnoea, and unconsciousness approximately 1 h post anaesthetic recovery, and then she was dead. It was shown both lungs were edematous in autopsy, and bluish emboli were appeared in extensive pulmonary arterioles in H&E stained sections. Negative information was shown in Molybdenum target X-ray imaging, but the emboli were confirmed to be PMMA bone cement by Fourier transform infrared spectroscopy. The present case indicated it might be effective to confirm the dubious trace component in histology by FTIR. PMID:23821787

Zheng, Na; Liang, Man; Zhang, Hai Dong; Zhu, Shao Hua; Yang, Tian Tong; Zhuo, Luo; Wang, Gui Feng; Liu, Hong Xia; Liu, Liang

2013-06-10

402

Mix ratio measurements of pozzolanic blends by Fourier transform infrared-attenuated total reflectance method  

SciTech Connect

The disposal of low-level radioactive liquid wastes at the Hanford Site near Richland, Washington, involves mixing the wastes with pozzolanic grout-forming solid blends. Checking the quality of each blend component and its mix ratio will ensure processibility of the blend and the long-term performance of the resulting waste grout. In earlier work at Hanford laboratories, Fourier transform infrared-transmission method (FTIR-TR) using KBr pellet was applied successfully in the analysis of blends consisting of cement, fly ash, and clays. This method involves time-consuming sample preparation resulting in slow turnaround for repetitive sampling. Because reflection methods do not require elaborate sample preparation, they have the potential to reduce turnaround analysis time. Neat samples may be examined making these methods attractive for quality control. This study investigates the capability of Fourier transform infrared-attenuated total reflectance method (FTIR-ATR) to analyze pozzolanic blends.

Rebagay, T.V.; Dodd, D.A.

1992-07-01

403

Subwavelength Fourier-transform imaging without a lens or a beamsplitter  

NASA Astrophysics Data System (ADS)

The fourier-transform patterns of an object are usually observed in the far-field region or obtained in the near-field region with the help of lenses. Here we propose and experimentally demonstrate a scheme of Fourier-transform patterns in the Fresnel diffraction region with thermal light. In this scheme, neither a lens nor a beamsplitter is used, and only one single charge coupled device (CCD) is employed. It means that dividing one beam out of a light source into signal and reference beams is not as necessary as the one done by the use of a beamsplitter in usual ghost interference experiments. Moreover, the coincidence measurement of two point detectors is not necessary and data recorded on a single CCD are sufficient for reconstructing the ghost diffraction patterns. The feature of the scheme promises a great potential application in the fields of X-ray and neutron diffraction imaging processes.

Liu, Rui-Feng; Yuan, Xin-Xing; Fang, Yi-Zhen; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fu-Li

2014-05-01

404

Rotation of Achernar and Regulus through Fourier Transform Analysis of High Resolution Spectra  

NASA Astrophysics Data System (ADS)

Projected rotational velocity parameter V_{e} sin i for selected stars has been determined using high-resolution spectroscopic observations from UVES and ELODIE databases and FEROS spectra. Applying the Fourier Transform Method this parameter can be precisely measured since (under classical approximations) the position of first minimum is determined only by rotational broadening, providing an estimate which is fairly insensitive to the assumptions about intrinsic line profile, micro and macro turbulence, eventually pulsational broadening and emission from circumstellar envelope, which is crucial for accurate determination of V_{e} sin i in Be stars (Neiner et al. 2002). We study in particular Achernar (? Eri) and Regulus (? Leo A), two stars in which the extreme oblateness has been recently discovered by interferometry. Since the Fourier Transform Method allows the detection of deviations from solid body rotation, rotational oblateness and gravity darkening (Reiners 2003), we discuss the extent to which our measurements reflect the actual projected equatorial rotation velocities.

Gavrilovi?, N.; Jankov, S.

2007-03-01

405

Prediction of ?-lactoglobulin genotypes based on milk Fourier transform infrared spectra.  

PubMed

?-Lactoglobulin (?-LG) genotypes are associated with differences in bovine milk protein composition. Therefore, ?-LG genotypes are of direct relevance for the dairy industry. In this study, we predicted ?-lactoglobulin genotypes based on routinely recorded milk Fourier transform infrared spectra using 500 calibration samples. The results show that 76% of the cows carrying the ?-LG AA genotype, 80% of the cows carrying the ?-LG AB genotype, and 66% of the cows carrying the ?-LG BB genotype were predicted correctly. Furthermore, the prediction of ?-LG genotypes based on Fourier transform infrared spectra showed a repeatability of 0.85. We discuss how the combined use of predicted ?-LG genotypes, pedigree information, and ?-LG genotypes derived using other methods could lead to further improvement in the percentage of correctly predicted ?-LG genotypes. The presented methodology is easy and inexpensive and could ultimately provide ?-LG genotypes at the individual cow level. PMID:21787953

Rutten, M J M; Bovenhuis, H; Heck, J M L; van Arendonk, J A M

2011-08-01

406

Simulation of micromechanical behavior of polycrystals: finite elements vs. fast Fourier transforms  

SciTech Connect

In this work, we compare finite element and fast Fourier transform approaches for the prediction of micromechanical behavior of polycrystals. Both approaches are full-field approaches and use the same visco-plastic single crystal constitutive law. We investigate the texture and the heterogeneity of the inter- and intragranular, stress and strain fields obtained from the two models. Additionally, we also look into their computational performance. Two cases - rolling of aluminium and wire drawing of tungsten - are used to evaluate the predictions of the two mode1s. Results from both the models are similar, when large grain distortions do not occur in the polycrystal. The finite element simulations were found to be highly computationally intensive, in comparison to the fast Fourier transform simulations.

Lebensohn, Ricardo A [Los Alamos National Laboratory; Prakash, Arun [IWM FREIBURG

2009-01-01

407

Discrete Fourier preprocessing transforms for the binary phase-only filter  

NASA Astrophysics Data System (ADS)

Two useful discrete Fourier preprocessing transforms (DFPTs), say, class 1 and class 2, are applied to the binary phase-only filter. The class-1 DFPT is very close to the discrete Fourier transform (DFT); therefore it preserves the properties similar to those for the DFT. The Class-2 DFPT's are location sensitive and are able to recognize the partial-shape-like input pattern that is the partial set of the pattern in the filter. The Class-2 DFPT's generate a delta-function-like correlation peak whose intensity is larger than that obtained by the DFT. These are different from the DFT-based binary phase-only filter. The elements of the DFPT's are very simple, containing only +/-1 and 0; some even contain sparse +/-1 values and plenty of zeros. Therefore the DFPT's are suitable for either optical or electrical implementation.

Hu, Neng-Chung; Su, Chia-Hsien

1995-03-01

408

Studies of Atmospherically Relevant Reactions Using Differentially Pumped Mass Spectrometer and Fourier Transform Infrared Spectroscopy  

Microsoft Academic Search

This article describes recent studies of atmospherically relevant reactions using spectroscopic techniques by our group at the Wadsworth Center. Heterogeneous reactions of SO2 with either HOBr or HOCl on ice have been studied using a coated-wall flow reactor coupled with differentially pumped quadrupole mass spectrometer, and the reaction of NO2+HI has been investigated using Fourier transform infrared spectroscopy (FTIR). Reaction

Hui Yan; Liang T. Chu; Ronghua Jin; Guowang Diao

2009-01-01

409

Joint-Detection using Fast Fourier Transforms in TD-CDMA based Mobile Radio Systems  

Microsoft Academic Search

Third generation mobile radio systems will employ TD-CDMA in their TDD mode. In a TD-CDMA mobile radio system, joint- detection is equivalent to solving a least squares problem with a block-Toeplitz sys- tem matrix. By extending this matrix to a block-circulant matrix, it is possible to block- diagonalize the matrix with Fast Fourier Transforms. For the typical system scenario of

Marius Vollmer; Jurgen Gotze; Martin Haardt

410

Reorganizational dynamics of multilamellar lipid bilayer assemblies using continuously scanning Fourier transform infrared spectroscopic imaging  

Microsoft Academic Search

We employ an implementation of rapid-scan Fourier transform infrared (FT-IR) microspectroscopic imaging to acquire time-resolved images for assessing the non-repetitive reorganizational dynamics of aqueous dispersions of multilamellar lipid vesicles (MLVs) derived from distearoylphosphatidylcholine (DSPC). The spatially and temporally resolved images allow direct and simultaneous determinations of various physical and chemical properties of the MLVs, including the main thermal gel to

Scott W Huffman; Sebastian Schlücker; Ira W Levin

2004-01-01

411

Theory and Application of Gain Ranging to Fourier Transform Infrared Spectroscopic Imaging  

Microsoft Academic Search

Gain ranging is incorporated into the data acquisition and process- ing protocol for a Fourier transform infrared (FT-IR) imaging spec- trometer employing a focal plane array (FPA) detector. A model for predicting the signal, noise, and signal-to-noise ratio (SNR) for an FPA in terms of the dynamic range of the analog-to-digital con- verter (ADC) is presented. Conventional gain ranging theory,

Rohit Bhargava; Daniel C. Fernandez; Michael D. Schaeberle; Ira W. Levin

2001-01-01

412

Generalized Implementation of Rapid-Scan Fourier Transform Infrared Spectroscopic Imaging  

Microsoft Academic Search

We describe a novel, generalized data acquisition sequence to allow rapid-scan Fourier transform infrared (FT-IR) spectroscopic im- aging using focal plane array (FPA) detectors. This technique de- rives its applicability from the reproducible performance of modern FT-IR instrumentation and the availability of FPAs with simulta- neous, full array acquisition, or snapshot electronics. Instead of sampling the entire interferogram in one

Scott W. Huffman; Rohit Bhargava; Ira W. Levin

2002-01-01

413

Optimal recovery of values of functions and their derivatives from inaccurate data on the Fourier transform  

SciTech Connect

The problems of the optimal recovery of the derivatives of functions from inaccurate information about the Fourier transforms of these functions on a finite interval or the entire number line are considered. The Stechkin problem of the approximation of derivatives by bounded linear functionals, which is closely connected to this range of problems, is also studied. Precise Kolmogorov-type inequalities for derivatives corresponding to these problems are obtained.

Magaril-Il'yaev, G G [Moscow State Institute of Radio Engineering, Electronics and Automatics (Technical University), Moscow (Russian Federation); Osipenko, K Yu [Moscow State Aviation Technological University (MATI), Moscow (Russian Federation)

2004-10-31

414

Identification of solvents of abuse using gas chromatography\\/Fourier transform infrared spectrometry after headspace sampling  

Microsoft Academic Search

Summary  After experimental intoxication of rats, gas chromatography — Fourier transform infrared spectrometry with headspace sampling (HS\\/GC\\/FT-IR) was used to identify solvents of abuse in biological material (blood, liver, lungs and brain). Limits of detection were measured for acetone, 2-butanone, ether, toluene and trichlorethylene with standard solutions. All the solvents have been identified in the organs of the intoxicated rats. For

M. Deveaux; J.-P. Huvenne

1987-01-01

415

Serially interfaced gas chromatography\\/Fourier transform infrared spectrometer\\/ion trap mass spectrometer system  

Microsoft Academic Search

A serial gas chromatography\\/Fourier transform infrared spectrometer\\/mass spectrometer (GC\\/FTIR\\/MS) system has been developed with an ion trap detector or mass analyzer that is interfaced to the light pipe in the FTIR spectrometer. A modification of the manufacturer-supplied open-split interface to the ion trap was required to obtain chromatographic results free of discrimination and activation effects. The flow rate of the

Edwin S. Olson; John W. Diehl

1987-01-01

416

Determination of doubly labeled water by gas-phase fourier transform infrared spectroscopy  

Microsoft Academic Search

Both 2H (deuterium) and 18O (oxygen 18) in isotopically enriched water have been detected by gas-phase Fourier transform infrared (FTIR) spectroscopy at 2,720 and 3,661.8 cm?1, respectively. A linear relationship between varying concentrations of each of these isotopes and their absorbance at the above frequencies indicates that gas-phase FTIR may provide a rapid and potentially less expensive approach to measure

M. A. Khaled; C. L. Krumdieck; J. L. Ong

1995-01-01

417

Pattern recognition techniques screening for drugs of abuse with gas chromatography–Fourier transform infrared spectroscopy  

Microsoft Academic Search

As many drugs of abuse are relatively volatile substances, gas chromatography–mass spectrometry (GC–MS), and more recently gas chromatography–Fourier transform infrared spectroscopy (GC–FTIR) became the most powerful techniques applied for their identification. We are presenting a combination of pattern recognition techniques discriminating illicit amphetamines according to the substitution pattern associated with the psychotropic activity (stimulants and hallucinogens) for which they are

M. Praisler; I. Dirinck; J. Van Bocxlaer; A. De Leenheer; D. L. Massart

2000-01-01

418

Gas chromatography\\/Fourier transform infrared spectroscopy for determining traces of methane from biodegradation of methylmercury  

Microsoft Academic Search

A sensitive and specific technique, gas chromatography\\/Fourier transform infrared spectroscopy (GC\\/FTIR), has been used to detect traces of methane from the biodegradation of methylmercury due to the detoxification process of Pseudomonas putida strain FB1, which was isolated from cinnabar mines in southern Tuscany (Italy). The cured strain FB4 was used together with uninoculated samples as controls for the experiment. The

Franco Baldi; Ermanno Cozzani; Marco Filippelli

1988-01-01

419

ANALYSIS OF ORGANIC VAPORS IN THE WORKPLACE BY REMOTE SENSING FOURIER TRANSFORM INFRARED SPECTROSCOPY  

Microsoft Academic Search

A Remote Sensing-Fourier Transform Infrared (RS-FTIR) system was applied to identify and quantify air contaminants along the beam, ranging from single compounds to mixtures, in various workplaces. Gas chromatography (GC) was used to provide information of point concentration variation by means of analyzing charcoal tube samples placed along the beam path. The results indicated a correlation between the charcoal tube-GC

Hongkui Xiao; Steven P. Levine; Julie Nowak; Mark Puskar; Robert C. Spear

1993-01-01

420

Fast classification and compositional analysis of cornstover fractions using Fourier transform near-infrared techniques  

Microsoft Academic Search

The objectives of this research were to determine the variation of chemical composition across botanical fractions of cornstover, and to probe the potential of Fourier transform near-infrared (FT-NIR) techniques in qualitatively classifying separated cornstover fractions and in quantitatively analyzing chemical compositions of cornstover by developing calibration models to predict chemical compositions of cornstover based on FT-NIR spectra. Large variations of

X. Philip Ye; Lu Liu; Douglas Hayes; Alvin Womac; Kunlun Hong; Shahab Sokhansanj

2008-01-01

421

An introduction to combined Fourier-wavelet transform and its application to convectively coupled equatorial waves  

NASA Astrophysics Data System (ADS)

Convectively coupled equatorial waves (CCEWs) are major sources of tropical day-to-day variability. The majority of CCEWs-related studies for the past decade or so have based their analyses, in one form or another, on the Fourier-based space-time spectral analysis method developed by Wheeler and Kiladis (WK). Like other atmospheric and oceanic phenomena, however, CCEWs exhibit pronounced nonstationarity, which the conventional Fourier-based method has difficulty elucidating. The purpose of this study is to introduce an analysis method that is able to describe the time-varying spectral features of CCEWs. The method is based on a transform, referred to as the combined Fourier-wavelet transform (CFWT), defined as a combination of the Fourier transform in space (longitude) and wavelet transform in time, providing an instantaneous space-time spectrum at any given time. The elaboration made on how to display the CFWT spectrum in a manner analogous to the conventional method (i.e., as a function of zonal wavenumber and frequency) and how to estimate the background noise spectrum renders the method more practically feasible. As a practical example, this study analyzes 3-hourly cloud archive user service (CLAUS) cloudiness data for 23 years. The CFWT and WK methods exhibit a remarkable level of agreement in the distributions of climatological-mean space-time spectra over a wide range of space-time scales ranging in time from several hours to several tens of days, indicating the instantaneous CFWT spectrum provides a reasonable snapshot. The usefulness of the capability to localize space-time spectra in time is demonstrated through examinations of the annual cycle, interannual variability, and a case study.

Kikuchi, Kazuyoshi

2013-09-01

422

FourierTransform Infrared Spectroscopy Studies of the Interaction of Functionalized Siloxane Polymers with Porous Silica  

Microsoft Academic Search

Adsorption behavior of the siloxane polymer, cyanopropylmethyl-phenyl-methyl-siloxane, in contact with a mesoporous silica has been investigated by Fourier-transform infrared spectroscopy (FT-IR) using a series of physically modified materials with different coating levels up to 20 w\\/w%. The nitrile stretch bands, which are observed in the 2150–2350 cm1 range, exhibited complex profiles due to a variety of interactions of the cyano

Anima Bose; Roger K. Gilpin; Mietek Jaroniec

2000-01-01

423

First-Derivative FourierTransform Infrared Determination of Oxadiazon in Commercial Herbicide Formulations  

Microsoft Academic Search

A Fourier?transform infrared (FTIR) method has been developed for the quantification of oxadiazon in herbicide formulations. The method involves the extraction of the active ingredient by sonication of the samples with CHCl3 and direct measurement of the peak area values in first?order derivate spectra from 1770 cm to 1774 cm corrected with a baseline point located at 1950 cm and after a 5?point

Javier Moros; Guillermo Quintás; Sergio Armenta; Salvador Garrigues; Miguel de La Guardia

2008-01-01

424

Fourier-transform infrared spectroscopy of hopping oscillations of electrons in vanadium oxide nanotubes  

NASA Astrophysics Data System (ADS)

We have employed Fourier-transform infrared spectroscopy in order to study the phase transitions and charge dynamics in vanadium oxide nanotubes with alternating organic and inorganic layers. The structural phase transitions accompanied by conformational changes in the organic layer were identified. Besides, a phase transition around 343 K from an insulator phase to a metal-like one that arises from electron delocalization was observed in the inorganic layers, manifesting an electron hopping oscillation between the V4+ and V5+ sites.

Ha Oh, Min; Jung Kim, Hyo; Won Lee, Kyu; Eui Lee, Cheol

2013-03-01

425

Initial implementation of an electrodynamic ion funnel with fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has become a widely used method to study biopolymers.\\u000a The method, in combination with an electrospray ionization (ESI) source has demonstrated the highest resolution and accuracy\\u000a yet achieved for characterization of biomolecules and their noncovalent complexes. The most common design for the ESI interface\\u000a includes a heated capillary inlet followed by a

Mikhail E. Belov; Michael V. Gorshkov; Harold R. Udseth; Gordon A. Anderson; Aleksey V. Tolmachev; David C. Prior; Richard Harkewicz; Richard D. Smith

2000-01-01

426

Room-Temperature Chirped-Pulse Fourier Transform Microwave Cp-Ftmw Spectrum of 2-METHYLFURAN  

Microsoft Academic Search

The microwave spectrum of 2-methylfuran has been measured at temperatures between 0°C and 50°C from 8.7--18.3 GHz with waveguide chirped-pulse Fourier transform microwave spectroscopy (CP-FTMW). Using the enhanced sensitivity of this technique relative to that of prior measurements from Stark-modulated instruments, we have been able to extend the assignments of the lowest energy A- and E-states from Norris and Krisher

Ian A. Finneran; Steven T. Shipman

2011-01-01

427

a Study of 4,4-DIMETHYLAMINOBEZONITRILE by Chirped-Pulsed Fourier Transform Microwave Spectroscopy  

Microsoft Academic Search

The ground state rotational spectrum of 4,4-dimethylaminobenzonitrile (DMABN) was studied using chirped-pulsed Fourier transform microwave spectroscopy (CP-FTMW). The rotational spectrum from 6.5 to 18 GHz was collected using a compilation of 250 MHz chirped pulses and pieced together. DMABN is widely known as an important model for excited state twisted intramolecular charge transfer dynamics. It has been previously studied in

Ryan G. Bird; Valerie J. Alstadt; David W. Pratt; Justin L. Neill; Brooks H. Pate

2010-01-01

428

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy  

Microsoft Academic Search

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5–18.5GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2GS\\/s arbitrary waveform generator as a frequency source and a 12GHz digital

Gordon G. Brown; Brian C. Dian; Kevin O. Douglass; Scott M. Geyer; Brooks H. Pate

2006-01-01

429

Microsolvation of beta-PROPIOLACTONE as Revealed by Chirped-Pulse Fourier Transform Microwave Spectroscopy  

Microsoft Academic Search

Microwave spectra of water clusters of beta-propiolactone with up to five water molecules attached are presented. Helium or neon carrier gas with 3 atm of backing pressure is flowed over a room-temperature water reservoir, then over a room-temperature sample of beta-propiolactone before being expanded into a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating between 6.5 and 18.5 GHz. A very

Justin L. Neill; Matt T. Muckle; Brooks H. Pate; I. Pena; C. Perez; J. L. Alonso

2010-01-01

430

Room temperature chirped-pulse Fourier transform microwave spectroscopy of anisole  

Microsoft Academic Search

The room-temperature rotational spectrum of anisole from 8.7 to 18.3GHz was collected with a waveguide-based chirped-pulse Fourier transform microwave spectrometer whose operating principles are described. Three spectra were assigned, corresponding to the vibrational ground state and the first and second excited states of the lowest frequency torsional mode. Results for the ground state and first excited state are in agreement

B. Reinhold; I. A. Finneran; S. T. Shipman

431

Waveguide Chirped-Pulse Fourier Transform Microwave Cp-Ftmw Spectrum of Allyl Chloride  

Microsoft Academic Search

The microwave spectrum of allyl chloride at 0° C was measured from 8.7--18.3 GHz with waveguide chirped-pulse Fourier transform microwave spectroscopy (CP-FTMW). The spectrum consists of contributions from 35Cl and 37Cl isotopomers of the cis and skew isomers. As the vibrational partition function for each of these conformers is approximately 4, the microwave spectrum contains a few thousand transitions with

Erin B. Kent; Morgan N. McCabe; Maria A. Phillips; Brittany P. Gordon; Steven T. Shipman

2011-01-01

432

a KA-BAND Chirped-Pulse Fourier Transform Microwave Spectrometer  

Microsoft Academic Search

The design and performance of a new chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating from 25-40 GHz will be discussed. A 10.5-3 GHz linear frequency sweep, generated by a 24 GS\\/s arbitrary waveform generator, is upconverted by a 23.00 GHz phase-locked oscillator, then fed into an active doubler to create a 25-40 GHz chirped pulse. After amplification with a 60-80

Daniel P. Zaleski; Justin L. Neill; Matthew T. Muckle; Brooks H. Pate; P. Brandon Carroll; Susanna L. Widicus Weaver

2010-01-01

433

Waveguide Chirped-Pulse Fourier Transform Microwave Cp-Ftmw Spectrum of Ortho-Fluorotoluene  

Microsoft Academic Search

The microwave spectrum of o-fluorotoluene has been measured at 0°C from 8.7--18.3 GHz with waveguide chirped-pulse Fourier transform microwave spectroscopy (CP-FTMW). We have extended previous assignments of the lowest energy A- and E-states by Susskind and Mäder and report on preliminary assignments of vibrationally excited states. This molecule also serves as a proof-of-principle for ``coarse\\

Ian A. Finneran; Steven T. Shipman

2011-01-01

434

Ion trapping and manipulation in a tandem time-of-flight-Fourier transform mass spectrometer  

Microsoft Academic Search

An external source tandem time-of-flight-Fourier transform mass spectrometer which provides programmed ion kinetic energy manipulation and trapping control is described. Design considerations are discussed and a detailed description of the instrument is provided. Typical ion injection efficiencies of 80-90% are obtained over an injection energy range of 30-500 eV. The instrument is capable of sensitive time-of-flight analysis of ions which

S. C. Beu; D. A. Laude

1991-01-01

435

Local Polynomial Fourier Transform Receiver for Nonstationary Interference Excision in DSSS Communications  

Microsoft Academic Search

The problem treated in this paper is monocomponent nonstationary interference excision in direct sequence spread spectrum (DSSS) communication systems by means of the local polynomial Fourier transform (LPFT). First, the interference is optimally concentrated in the time-frequency (t-f) plane and then its t-f signature is removed via a binary mask. The LPFT receiver is derived in matrix form and its

Slobodan Djukanovic; Ljubisa A. Stankovic

2008-01-01

436

Nontargeted metabolome analysis by use of Fourier transform ion cyclotron mass spectrometry  

Microsoft Academic Search

Advanced functional genomic tools now allow the parallel and high-throughput analyses of gene and protein expression. Although this information is crucial to our understanding of gene function, it offers insufficient insight into phenotypic changes associated with metabolism. Here we introduce a high-capacity Fourier Transform Ion Cyclotron Mass Spectrometry (FTMS)¿based method, capable of nontargeted metabolic analysis and suitable for rapid screening

Asaph Aharoni; Vos de C. H; C. A. Maliepaard; G. Kruppa; R. J. Bino; D. Goodenough; Dayan B. Goodenowe

2002-01-01

437

Determination of pectin degree of esterification by diffuse reflectance Fourier transform infrared spectroscopy  

Microsoft Academic Search

A diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) method was developed to measure the degree of esterification (DE) of commercial pectin samples. The relationship between infrared spectroscopy data and titrimetrically determined DE values was investigated. The ester carbonyl band area (C?O) occurring at a mean frequency of 1756 cm?1 had the highest correlation (R2=0.822) with the mean DE of the

Ravin Gnanasambandam; A Proctor

2000-01-01

438

Estimation of Cellulose Crystallinity Using Fourier Transform-Infrared Spectroscopy and Dynamic Thermogravimetry  

Microsoft Academic Search

Dynamic thermogravimetry (tga), differential thermogravimetry (dtg), and Fourier Transform-Infrared Spectroscopy (FT-IR) were performed on a variety of celluloses with different cyr3tallinities. The data were compared to the crystallinlty indices (C.I.) determined by X-ray diffraction. Highly significant correlations (99.9%) included: a positive linear correlation of the maximum dtg value; a logarithmic relation of the temperature at which the initial 10% weight

T. P. Schultz; G. D. McGinnis; M. S. Bertran

1985-01-01

439

Penetration of compounds through human stratum corneum as studied by Fourier transform infrared photoacoustic spectroscopy  

Microsoft Academic Search

The penetration of the lipophilic model permeant, 1-cyanodecane, into isolated human stratum corneum (SC) was followed nondestructively by step-scan Fourier transform infrared (FTIR) photoacoustic spectroscopy (PAS) with phase modulation technique. The uptake of the compound in the SC was quantified by monitoring the alterations in the spectra in the course of the penetration using multivariate analysis. Step-scan technique in conjunction

Bui D. Hanh; Reinhard H. H. Neubert; Siegfried Wartewig; Jürgen Lasch

2001-01-01

440

Color holographic image by using digital lensless Fourier transform holography with optical fiber  

NASA Astrophysics Data System (ADS)

A new method of lensless Fourier transform holography for color reconstruction image is presented. With this method, the recording distance can be kept invariant in recording process. The resolutions of reconstruction images can be adjusted in the same recording distance. Three lasers with different wavelengths are used in an experimental setup to synthesize a color image in a reconstruction process. An optical fiber is used effectively, and the quality of the reconstruction image is improved after filter operation.

Chen, Li; Ma, Xiao; Wang, Qu

2012-04-01

441

Speziesdifferenzierung von Hefen der Gattung Malassezia mittels Fourier-Transform-Infrarot-Spektroskopie  

Microsoft Academic Search

ZusammenfassungHintergrund und Methoden  Insgesamt 83 Malassezia-Stämme, darunter 18 Referenzstämme — konventionell mit biochemischen Methoden identifiziert und verschiedenen Spezies zugeordnet — wurden mittels Fourier-Transform-Infrarot-Spektroskopie (FT-IRS) analysiert.Ergebnisse  Die FT-IRS-Analyse ermöglichte eine klare Abgrenzung der Malassezia-Isolate mit für jede Spezies spezifischer Clusterbildung. Die größten Unterschiede fanden sich zwischen Malassezia furfur und den restlichen Malassezia-Spezies. Darüber hinaus gibt es innerhalb der Spezies Malassezia furfur eine Untergliederung in 2

A. Kalinowska-Pujdak; A. Schmalreck; U.-F. Haustein; P. Nenoff

2006-01-01

442

A low-complexity architecture of inverse fast Fourier transform for XDS  

Microsoft Academic Search

In this work, a low-complexity architecture of the inverse fast Fourier transform (IFFT) using the serial-input-parallel-output data flow is designed for digital subscriber line for any class (XDSL). Since input data in the XDSL are symmetric, the computation of the IFFT can be reduced to multiplication accumulation operations in the real part. Furthermore, consideration is taken to process all multiplication

Hsin-Horng Chen; O. T.-C. Chen; Heng-Cheng Yeh; Cheng-Shing Wu

2004-01-01

443

Effect of the fringe visibility on spectrum SNR of Fourier transform imaging spectrometer  

NASA Astrophysics Data System (ADS)

The principle of Fourier transform spectrometer is based on the relationship of Fourier-Transform between interferogram and spectrum. The spectral information of Fourier transform imaging spectrometer (FTIS) reconstructed from raw interferogram by data processing. So there are two kinds of signal-to-noise ratio (SNR) to evaluate instrument performance, one regarding interferogram and the other regarding reconstructed spectrum. Because the raw interferogram is intuitive, the interferogram SNR is studied usually. On the contrary, the spectrum SNR is studied less because of the complexity of the data processing from interferogram to spectrum. The research about the effect of the interference fringe visibility on the spectrum SNR is especially few. This paper present a research work on the relations between the interference fringe visibility and the spectrum SNR. Firstly, the reduction of fringe visibility caused by imaging lens defocus was analyzed. Secondly, the changes of the average spectrum signal and noise caused by the reduction of fringe visibility were calculated. For average spectrum signal, the math deductions are done base on Fourier transform theory. The average noise with different input signal optic-electrons number are simulated. the results show that the average spectrum signal is directly proportional to the fringe visibility, and the effect of fringe visibility on the noise related to signal can be ignorable. Finally, In order to demonstrate above results, the imaging experiment was done with white-light source, using LASIS (Large aperture static imaging spectrometer) based on Sagnac Interferometer. The average spectrum SNRs under different fringe visibility are calculated and analyzed. The experimental results show that: the average spectrum SNRs increase from 42.7 to 62.4.along with the fringe visibility increasing from 0.5051 to 0.687. the reconstructed spectrum SNR is directly proportional to the fringe visibility. As a result, the interferogram fringe visibility can be used to estimate the reconstructed spectrum SNR, and evaluate the performance of FTIS before data processing.

Wang, Shuang; Bin, Xiangli; Jing, Juanjuan; Pi, Haifeng

2013-08-01

444

Data processing pipeline for a time-sampled imaging Fourier transform spectrometer  

Microsoft Academic Search

ABSTRACT Imaging Fourier transform spectrometers ,(IFTS) are becoming ,the preferred systems ,for remote ,sensing spectral imaging applications because of their ability to provide, simultaneously, both high spatial and spectral resolution images ofa scene. IFTS can be operated in either step-and-integrate or rapid-scan modes, where it is common practice to sample interferograms at equal optical path difference intervals. The step-and-integrate mode

David A. Naylor; Trevor R. Fulton; Peter W. Davis; Ian M. Chapman; Brad G. Gom; D Locke; John V. Lindner; Nathan E. Nelson-fitzpatrick; Margaret K. Tahic; Gary R. Davis

445

A 64-point Fourier transform chip for video motion compensation using phase correlation  

Microsoft Academic Search

Details of a new low power fast Fourier transform (FFT) processor for use in digital television applications are presented. This has been fabricated using a 0.6-?m CMOS technology and can perform a 64 point complex forward or inverse FFT on real-time video at up to 18 Megasamples per second. It comprises 0.5 million transistors in a die area of 7.8×8

Colin Chiu; Wing Hui; Tiong Jiu Ding; J. V. McCanny

1996-01-01

446

Cross-Range Scaling Algorithm for ISAR Images Using 2-D Fourier Transform and Polar Mapping  

Microsoft Academic Search

This paper proposes a new method that solves the problem of inverse synthetic aperture radar image cross-range scaling by estimating the rotational velocity (RV) using the expansion-rotation-scale relationship between two range-Doppler (RD) images. This method is composed of three steps. The first step is preprocessing to construct 2-D Fourier transform images and initial polar-mapped images. In this step, two RD

Sang-Hong Park; Hyo-Tae Kim; Kyung-Tae Kim

2011-01-01

447

High pressure crystal phases of solid CH4 probed by Fourier transform infrared spectroscopy  

Microsoft Academic Search

High pressure infrared spectra of solid CH4 are reported in the range 0.8–30 GPa at room temperature, coupling a Fourier transform infrared spectrometer to a membrane diamond–anvil cell by means of a high efficiency beam condensing optical system. Two crystal phases, A and B, have been investigated. The phase transition is affected by hysteresis and occurs at 9±0.5 GPa during

Roberto Bini; Lorenzo Ulivi; Hans J. Jodl; Pier R. Salvi

1995-01-01

448

Fast wave-front reconstruction in large adaptive optics systems with use of the Fourier transform  

Microsoft Academic Search

Wave-front reconstruction with the use of the fast Fourier transform (FFT) and spatial filtering is shown to be computationally tractable and sufficiently accurate for use in large Shack-Hartmann-based adaptive optics systems (up to at least 10,000 actuators). This method is significantly faster than, and can have noise propa- gation comparable with that of, traditional vector-matrix-multiply reconstructors. The boundary problem that

Lisa A. Poyneer; Donald T. Gavel; James M. Brase

2002-01-01

449

Open-path Fourier transform infrared studies of large-scale laboratory biomass fires  

Microsoft Academic Search

A series of nine large-scale, open fires was conducted in the Intermountain Fire Sciences Laboratory (IFSL) controlled-environment combustion facility. The fuels were pure pine needles or sagebrush or mixed fuels simulating forest-floor, ground fires; crown fires; broadcast burns; and slash pile burns. Mid-infrared spectra of the smoke were recorded throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy

Robert J. Yokelson; David W. T. Griffith; Darold E. Ward

1996-01-01

450

The transport of water in a tetrafunctional epoxy resin by near-infrared Fourier transform spectroscopy  

Microsoft Academic Search

An epoxy resin formulation composed of tetraglycidyl-4,4?-diamino diphenylmethane (TGDDM) and 4,4?diamino diphenyl sulfone (DDS) was investigated by Fourier transform near infrared (FT-NIR) spectroscopy and dynamic-mechanical analysis. Both techniques have demonstrated the essentially complete cure state of the resin with the adopted curing schedule. A novel feature of this work is the possibility of monitoring the transport of water into the

P Musto; L Mascia; G Ragosta; G Scarinzi; P Villano

2000-01-01

451

Investigation of UV matrix-assisted laser desorption fourier transform mass spectrometry for peptides  

Microsoft Academic Search

Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA Ultraviolet matrix-assisted laser\\u000a desorption can be used to enhance formation of [M + H]+, [M + Na]+, and [M + K)+ ions from small peptides for Fourier transform mass spectrometry (FTMS). In accord with laser desorption (LD) time-of-flight\\u000a experiments, matrices such as nicotinic acid and 2-pyrazinecarboxylic acid exhibit strong

R. L. Hettich; M. V. Buchanan

1991-01-01

452

Techniques for Handling and Removal of Spectral Channels in Fourier Transform Synchrotron-Based Spectra  

SciTech Connect

Channel spectra are a big problem for those attempting to use synchrotron-based Fourier transform spectra for spectral lineshape studies. Due to the layout of the optical system at the CLS far-infrared beamline, the synchrotron beam undergoes unavoidable multiple reflections on the steering mirrors, beam splitter, several sets of windows, and filters. We present a method for eliminating channel spectra and compare the results of our technique with other methods available in the literature.

Ibrahim, Amr; Predoi-Cross, Adriana; Teillet, Philippe M. [University of Lethbridge, Department of Physics and Astronomy, 4401 University Drive, Lethbridge, AB, T1K 3M4 (Canada)

2010-02-03

453

Coherent transfer function of Fourier transform spectral interferometric coherent anti-Stokes Raman scattering microscopy.  

PubMed

We analyze the optical resolution of Fourier transform spectral interferometric-coherent anti-Stokes Raman scattering microscopy, which extracts the complex amplitude of an image by using a spectral interferometric effect. Image-formation formulas are presented that describe the properties of the image observed by the apparatus. The image-formation properties represented by the coherent transfer function are different depending on the mode (transmission, reflection, etc.) of the microscopy. PMID:21811331

Fukutake, Naoki

2011-08-01

454

Fast Fourier transform admittance analysis method applied to thickness-shear-mode acoustic wave sensors  

Microsoft Academic Search

A fast Fourier transform admittance analysis (FFT-AA) method, applied to thickness-shear-mode (TSM) acoustic wave sensors, is first proposed and the corresponding theory is presented. Based on the FFT-AA, an oscillatory waveform with the feature of a damped free oscillation is obtained experimentally. It can illustrate dynamically and directly the vibratory characteristics of TSM sensors, which can be considered as an

Huwei Tan; Jinhua Chen; Ronghui Wang; Xiaoli Su; Lihua Nie; Shouzhuo Yao

1997-01-01

455

VUV Fourier Transform Spectroscopy of the δ(0,0) band of NO  

Microsoft Academic Search

Using the VUV Fourier Transform Spectrometer (FTS) at Imperial College we have observed the γ(0,0) and γ(1,0) bands of NO, at 191 nm and 183 nm respectively, in absorption. A high current hydrogen lamp was used as the background continuum source with a 0.3 in Czerny-Turner spectrometer as a bandpass filter. The absorption spectrum was observed at various pressures of

J. E. Murray; K. Yoshino; J. R. Esmond; W. H. Parkinson

1993-01-01

456

Diffuse reflectance Fourier transform infrared spectroscopy of oleic acid adsorption on silicic acid  

Microsoft Academic Search

Diffuse reflectance Fourier transform infrared spectroscopy was used to observe adsorption complexes of oleic acid and isopropanol\\u000a (IPA) on silicic acid in hexane. The spectra provide definite evidence of the molecular nature of the surface interaction.\\u000a In addition, the effect on oleic acid adsorption of modifying the solvent with IPA, which competes for adsorption sites and\\u000a modifies the solvent polarity,

C. Adhikari; A. Proctor; G. D. Blyholder

1994-01-01

457

Multiconjugate adaptive optics with plenoptic cameras and the Fourier transform reconstructor  

NASA Astrophysics Data System (ADS)

Multi-Conjugate Adaptive Optics (MCAO) will play a key role in future astronomy. Every Extremely Large Telescope (ELT) is being designed with its MCAO module, and most of their instruments will rely on that kind of correction for their optimum performance. Many technical challenges have to be solved in order to develop MCAO systems. One of them, related to its use on ELT's, is to find fast algorithms to perform the reconstruction at the required speed. For that reason we have been studying the application of the Fourier Transform Reconstructor (FTR) to MCAO. We use the Fourier Slice Theorem in order to reconstruct the atmospheric volume. The process consists on reconstructing "slices" of atmosphere, taking 1D-FFT's of the different projections to build a 2D Fourier space that is inverse-transformed to build the reconstructed slice. The advantage of using the FTR is that this algorithm gives us directly the Fourier Transform of the projections, speeding up the process. To do a good reconstruction it is necessary to know the height at which the laser guide star is focused, and we propose to use a plenoptic camera to get this information, that we use together with the available information relative to the atmosphere we are reconstructing, C2n, to weight the inverse-transforms and obtain a better estimate. The height is obtained in real-time, a very important advantage for the reconstruction. We present the preliminary results of our MCAO simulations and the configuration of the plenoptic camera that could be applied to an ELT

Montilla, I.; Reyes, M.; Femenía, B.; Rodríguez-Ramos, J. M.

2010-07-01

458

High-resolution Fourier-transform infrared chemical imaging with multiple synchrotron beams  

PubMed Central

Conventional Fourier-transform infrared (FTIR) microspectroscopic systems are limited by an inevitable trade-off between spatial resolution, acquisition time, signal-to-noise ratio (SNR) and sample coverage. We present an FTIR imaging approach that substantially extends current capabilities by combining multiple synchrotron beams with wide-field detection. This advance allows truly diffraction-limited high-resolution imaging over the entire mid-infrared spectrum with high chemical sensitivity and fast acquisition speed while maintaining high-quality SNR.

Nasse, Michael J; Walsh, Michael J; Mattson, Eric C; Reininger, Ruben; Kajdacsy-Balla, Andre; Macias, Virgilia; Bhargava, Rohit; Hirschmugl, Carol J

2013-01-01

459

Analysis of Soil Chemical Properties of Sand-Based Turfgrass Rootzone Using Fourier Transform Infrared Spectroscopy  

Microsoft Academic Search

To evaluate diffuse reflectance Fourier transform infrared (DRIFT) in near-infrared (NIR) and mid-infrared (MIR) regions in conjunction with partial least square regression analysis for sand-based turfgrass soils, soil samples were collected from greens 6 to 9-yr-old, composed of two rootzone mixtures and two establishment fertilization regimes, and different depths (surface to 7.6 cm in 12 layers). Mid-infrared and NIR spectroscopy

Lei Han; Deying Li; Wenjuan Fang; Yichun Wang; Roch Gaussoin

2012-01-01

460

Thermogravimetric coupled with Fourier transform infrared analysis study on thermal treatment of monopotassium phosphate residue  

Microsoft Academic Search

In China, safe disposal of hazardous waste is more and more a necessity, urged by rapid economic development. The pyrolysis\\u000a and combustion characteristics of a residue from producing monopotassium phosphate (monopotassium phosphate residue), considered\\u000a as a hazardous waste, were studied using a thermogravimetric, coupled with Fourier transform infrared analyzer (TG-FTIR).\\u000a Both pyrolysis and combustion runs can be subdivided into three

Yuheng Feng; Xuguang Jiang; Yong Chi; Xiaodong Li; Hongmei Zhu

2011-01-01

461

High-Throughput Metabolic Fingerprinting of Legume Silage Fermentations via Fourier Transform Infrared Spectroscopy and Chemometrics  

Microsoft Academic Search

Silage quality is typically assessed by the measurement of several individual parameters, including pH, lactic acid, acetic acid, bacterial numbers, and protein content. The objective of this study was to use a holistic metabolic fingerprinting approach, combining a high-throughput microtiter plate-based fermentation system with Fourier transform infrared (FT-IR) spectroscopy, to obtain a snapshot of the sample metabolome (typically low-molecular-weight compounds)

Helen E. Johnson; David Broadhurst; Douglas B. Kell; Michael K. Theodorou; Roger J. Merry; Gareth W. Griffith

2004-01-01

462

Quantitative analysis of palm carotene using fourier transform infrared and near infrared spectroscopy  

Microsoft Academic Search

?-Carotene content is usually determined by using ultraviolet (UV)-visible spectrophotometry at 446 nm. In this study, two\\u000a spectroscopic techniques, namely, Fourier transform infrared (FTIR) and near infrared (NIR) spectroscopy, have been investigated\\u000a and compared to UV-visible spectrophotometry to measure the ?-carotene content of crude palm oil (CPO). Calibration curves\\u000a ranging from 200 to 800 ppm were prepared by extracting ?-carotene

M. H. Moh; Y. B. Che Man; B. S. Badlishah; S. Jinap; M. S. Saad; W. J. W. Abdullah

1999-01-01

463

The Characterisation of Pluripotent and Multipotent Stem Cells Using Fourier Transform Infrared Microspectroscopy  

PubMed Central

Fourier transform infrared (FTIR) microspectroscopy shows potential as a benign, objective and rapid tool to screen pluripotent and multipotent stem cells for clinical use. It offers a new experimental approach that provides a holistic measurement of macromolecular composition such that a signature representing the internal cellular phenotype is obtained. The use of this technique therefore contributes information that is complementary to that acquired by conventional genetic and immunohistochemical methods.

Cao, Julie; Ng, Elizabeth S.; McNaughton, Donald; Stanley, Edouard G.; Elefanty, Andrew G.; Tobin, Mark J.; Heraud, Philip

2013-01-01

464

A Fourier transform method for powder diffraction based on the Debye scattering equation.  

PubMed

A fast Fourier transform algorithm is introduced into the method recently defined for calculating powder diffraction patterns by means of the Debye scattering equation (DSE) [Thomas (2010). Acta Cryst. A66, 64-77]. For this purpose, conventionally used histograms of interatomic distances are replaced by compound transmittance functions. These may be Fourier transformed to partial diffraction patterns, which sum to give the complete diffraction pattern. They also lead to an alternative analytical expression for the DSE sum, which reveals its convergence behaviour. A means of embedding the DSE approach within the reciprocal-lattice-structure-factor method is indicated, with interpolation methods for deriving the peak profiles of nanocrystalline materials outlined. Efficient calculation of transmittance functions for larger crystallites requires the Patterson group symmetry of the crystals to be taken into account, as shown for ?- and ?-quartz. The capability of the transmittance functions to accommodate stacking disorder is demonstrated by reference to kaolinite, with a fully analytical treatment of disorder described. Areas of future work brought about by these developments are discussed, specifically the handling of anisotropic atomic displacement parameters, inverse Fourier transformation and the incorporation of instrumental (diffractometer) parameters. PMID:22011464

Thomas, Noel William

2011-11-01

465

Reservoir information extraction using a fractional fourier transform and a smooth pseudo Wigner-Ville distribution  

NASA Astrophysics Data System (ADS)

Currently, it is difficult for people to express signal information simultaneously in the time and frequency domains when analyzing acoustic logging signals using a simple-time or frequency-domain method. It is difficult to use a single type of time-frequency analysis method, which affects the feasibility of acoustic logging signal analysis. In order to solve these problems, in this paper, a fractional Fourier transform and smooth pseudo Wigner-Ville distribution (SPWD) were combined and used to analyze array acoustic logging signals. The time-frequency distribution of signals with the variation of orders of fractional Fourier transform was obtained, and the characteristics of the time-frequency distribution of different reservoirs under different orders were summarized. Because of the rotational characteristics of the fractional Fourier transform, the rotation speed of the cross terms was faster than those of primary waves, shear waves, Stoneley waves, and pseudo Rayleigh waves. By choosing different orders for different reservoirs according to the actual circumstances, the cross terms were separated from the four kinds of waves. In this manner, we could extract reservoir information by studying the characteristics of partial waves. Actual logging data showed that the method outlined in this paper greatly weakened cross-term interference and enhanced the ability to identify partial wave signals.

Wang, Zhu-Wen; Wang, Xiao-Li; Xiang, Min; Liu, Jing-Hua; Zhang, Xue-Ang; Yang, Chuang

2012-12-01

466

Infrared small target enhancement via phase spectrum of Quaternion Fourier Transform  

NASA Astrophysics Data System (ADS)

Small target enhancement is one of the crucial stages in infrared small target detection. In this paper, we propose a new method using phase spectrum of Quaternion Fourier Transform to enhance small targets while suppressing backgrounds for infrared images. This is inspired by the property that regularly Gaussian-like shape small targets could be considered as attractively salient signal in infrared images and the location information of such signal is implicitly contained in the phase spectrum from frequency domain. Formally, in the proposed method, we adopt the phase spectrum of Quaternion Fourier Transform instead of using traditional Fourier Transform to enhance the targets since the quaternion provides at most four data channels than only one for the latter, which could be helpful to broad types of background clutters by adding more information. For the construction of the quaternion, we present a second-order directional derivative filter via facet model to compute four second order directional derivative maps from four directions respectively as the four data channels. This filter is used to suppress noises and distinguish the targets and backgrounds into separably different textures so that it would boost the robustness of small target enhancement. In experiments, some typical infrared images with various scenes are tested to validate the effectiveness of the proposed method. The results demonstrate that our method actually has good performance and outperforms several state-of-the-art methods, which can be further used for infrared small target detection and tracking.

Qi, Shengxiang; Ma, Jie; Li, Hang; Zhang, Shuiping; Tian, Jinwen

2014-01-01

467

Single-channel color image encryption based on iterative fractional Fourier transform and chaos  

NASA Astrophysics Data System (ADS)

A single-channel color image encryption is proposed based on iterative fractional Fourier transform and two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and permuted by a sequence of chaotic pairs which is generated by two-coupled logistic map. Firstly, the permutation image is decomposed into three components again. Secondly, the first two components are encrypted into a single one based on iterative fractional Fourier transform. Similarly, the interim image and third component are encrypted into the final gray scale ciphertext with stationary white noise distribution, which has camouflage property to some extent. In the process of encryption and description, chaotic permutation makes the resulting image nonlinear and disorder both in spatial domain and frequency domain, and the proposed iterative fractional Fourier transform algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.

Sui, Liansheng; Gao, Bo

2013-06-01

468

Transformation of Zernike coefficients: a Fourier-based method for scaled, translated, and rotated wavefront apertures.  

PubMed

This paper studies the effects on Zernike coefficients of aperture scaling, translation, and rotation, when a given aberrated wavefront is described on the Zernike polynomial basis. It proposes an analytical method for computing the matrix that enables the building of transformed Zernike coefficients from the original ones. The technique is based on the properties of Zernike polynomials and Fourier transform, and, in the case of a full aperture without central obstruction, the coefficients of the matrix are given in terms of integrals of Bessel functions. The integral formulas are exact and do not depend on any specific ordering of the polynomials. PMID:23595334

Tatulli, Eric

2013-04-01

469

Fourier-Domain Holography in Photorefractive Quantum-Well Films  

NASA Astrophysics Data System (ADS)

Fourier-domain holography (FDH) is investigated as a candidate for holographic optical coherence imaging to produce real-time images of structure inside living tissue and turbid media. The effects of spatial filtering, the background intensity distributions, and the role of background noise in determining dynamic range are evaluated for both FDH and image-domain holography (IDH). The grating washout effect in FDH (edge enhancement) is removed by use of a vibrating diffuser that consequently improves the image quality. By comparing holographic images and background images of FDH and IDH we show that FDH provides a higher dynamic range and a higher image quality than IDH for this specific application of imaging diffuse volumetric objects.

Jeong, Kwan; Peng, Leilei; Nolte, David D.; Melloch, Michael R.

2004-07-01

470

The parallel implementation of the one-dimensional Fourier transformed Vlasov Poisson system  

NASA Astrophysics Data System (ADS)

A parallel implementation of an algorithm for solving the one-dimensional, Fourier transformed Vlasov-Poisson system of equations is documented, together with the code structure, file formats and settings to run the code. The properties of the Fourier transformed Vlasov-Poisson system is discussed in connection with the numerical solution of the system. The Fourier method in velocity space is used to treat numerical problems arising due the filamentation of the solution in velocity space. Outflow boundary conditions in the Fourier transformed velocity space removes the highest oscillations in velocity space. A fourth-order compact Padé scheme is used to calculate derivatives in the Fourier transformed velocity space, and spatial derivatives are calculated with a pseudo-spectral method. The parallel algorithms used are described in more detail, in particular the parallel solver of the tri-diagonal systems occurring in the Padé scheme. Program summaryTitle of program:vlasov Catalogue identifier:ADVQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Operating system under which the program has been tested: Sun Solaris; HP-UX; Read Hat Linux Programming language used: FORTRAN 90 with Message Passing Interface (MPI) Computers: Sun Ultra Sparc; HP 9000/785; HP IPF (Itanium Processor Family) ia64 Cluster; PCs cluster Number of lines in distributed program, including test data, etc.:3737 Number of bytes in distributed program, including test data, etc.:18 772 Distribution format: tar.gz Nature of physical problem: Kinetic simulations of collisionless electron-ion plasmas. Method of solution: A Fourier method in velocity space, a pseudo-spectral method in space and a fourth-order Runge-Kutta scheme in time. Memory required to execute with typical data: Uses typically of the order 10 5-10 6 double precision numbers. Restriction on the complexity of the problem: The program uses periodic boundary conditions in space. Typical running time: Depends strongly on the problem size, typically few hours if only electron dynamics is considered and longer if both ion and electron dynamics is important. Unusual features of the program: No

Eliasson, Bengt

2005-08-01

471

Quantum Affine Transformation Group and Covariant Differential Calculus  

NASA Astrophysics Data System (ADS)

We discuss quantum deformation of the affine transformation group and its Lie algebra in one-dimensional space. It is shown that the quantum algebra has a non-cocommutative Hopf algebra structure, simple realizations and quantum tensor operators. It is also shown that the quantum algebra does not have a universal R-matrix. We present a new method to construct the quantum deformation of the affine transformation group. The method is based on the quantum algebra and the adjoint representation. Furthermore, we construct a differential calculus which is covariant with respect to the action of the quantum affine transformation group.

Aizawa, N.; Sato, H.

1994-06-01

472

Quantum polarization transformations in anisotropic dispersive media  

NASA Astrophysics Data System (ADS)

Based on the concept of ? -matrix and Choi-Jamiólkowski states we develop the approach of quantum process reconstruction. The key part of the work is devoted to the adequacy of applied reconstruction models. The approach is tested with the statistical reconstruction of the polarization transformations in anisotropic and dispersive media realized by means of quartz plates and taking into account the spectral structure of input polarization states.

Bogdanov, Yu I.; Kalinkin, A. A.; Kulik, S. P.; Moreva, E. V.; Shershulin, V. A.

2013-03-01

473

Continuous wavelet transform in quantum field theory  

NASA Astrophysics Data System (ADS)

We describe the application of the continuous wavelet transform to calculation of the Green functions in quantum field theory: scalar ?4 theory, quantum electrodynamics, and quantum chromodynamics. The method of continuous wavelet transform in quantum field theory, presented by Altaisky [Phys. Rev. D 81, 125003 (2010)] for the scalar ?4 theory, consists in substitution of the local fields ?(x) by those dependent on both the position x and the resolution a. The substitution of the action S[?(x)] by the action S[?a(x)] makes the local theory into a nonlocal one and implies the causality conditions related to the scale a, the region causality [J. D. Christensen and L. Crane, J. Math. Phys. (N.Y.) 46, 122502 (2005)]. These conditions make the Green functions G(x1,a1,…,xn,an)=??a1(x1)…?an(xn)? finite for any given set of regions by means of an effective cutoff scale A=min?(a1,…,an).

Altaisky, M. V.; Kaputkina, N. E.

2013-07-01

474

Fast continuous Fourier and Haar transforms of rectilinear polygons from very-large-scale integration layouts  

NASA Astrophysics Data System (ADS)

We propose two new fast algorithms for the computation of the continuous Fourier series and the continuous Haar transform of rectilinear polygons such as those of mask layouts in optical lithography. These algorithms outperform their discrete counterparts traditionally used. Not only are continuous transforms closer to the underlying continuous physical reality, but they also avoid the inherent inaccuracies introduced by the sampling or rasterization of the polygons in the discrete case. Moreover, massive amounts of data and the intense processing methods used in lithography require efficient algorithms at every step of the process. We derive the complexity of each algorithm and compare it to that of the corresponding discrete transform. For the practical very-large-scale integration (VLSI) layouts, we find significant reduction in the complexity because the number of polygon vertices is substantially smaller than the corresponding discrete image. This analysis is completed by an implementation and a benchmark of the continuous algorithms and their discrete counterparts. We run extensive experiments and show that on tested VLSI layouts the pruned continuous Haar transform is 5 to 25 times faster, while the fast continuous Fourier series is 1.5 to 3 times faster than their discrete counterparts.

Scheibler, Robin; Hurley, Paul; Chebira, Amina

2013-10-01

475

Fourier Transform Microwave Spectroscopy of Multiconformational Molecules and Van Der Waals Complexes.  

NASA Astrophysics Data System (ADS)

With the use of a Fourier transform microwave (FTM) spectrometer, structural determinations of two types of species; multiconformational molecules and van der Waals complexes, have been performed. Presented in this thesis are three sections summarizing this research effort. The first section contains a detailed explanation of the FTM instrument. In Section II, the study of three multiconformational molecules is presented as two chapters. Finally, three chapters in Section III outline the work still in progress on many van der Waals complexes. Section I was written to be a "manual" for the FTM spectrometer and to aid new additions to the group in their understanding of the instrument. An instruction guide is necessary for home-built instruments such as this one due to their unique design and application. Vital techniques and theories are discussed and machine operation is outlined. A brief explanation of general microwave spectroscopy as performed on an FTM spectrometer is also given. Section II is composed of two chapters pertaining to multiconformational molecules. In Chapter 2, a complete structural analysis of dipropyl ether is reported. The only conformer assigned had C_{rm s} symmetry. Many transitions are yet unassigned. Chapter 3 summarizes an investigation of two nitrosamines; methyl ethyl and methyl propyl nitrosamine. Only one conformer was observed for methyl ethyl nitrosamine, but two were assigned to methyl propyl nitrosamine. Nuclear hyperfine structure and internal methyl rotation complicated the spectra. The final section, Section III, contains the ongoing progress on weakly bound van der Waals complexes. The analysis of the OCS--HBr complex identified the structure as quasi-linear with large amplitude bending motions. Five separate isotopomers were assigned. Transitions originating from the HBr--DBr complex were measured and presented in Chapter 5. Although early in the analysis, the structure was determined to be bent and deuterium bonded. The final chapter of this section is meant to be a permanent record of transition frequencies whose molecular carrier is still in question. Two different groups of transitions from two different samples are listed. Further work is needed to unambiguously assign the frequencies with a carrier and quantum numbers, however the complexes (H_2 O)--(HCl)_2 and NO--H _2O are considered possible suspects.

Hight Walker, Angela Renee