Spectral representation of fingerprints
Xu, Haiyun; Bazen, Asker M.; Veldhuis, Raymond N.J.; Kevenaar, Tom A.M.; Akkermans, Anton H.M.
2007-01-01
Most fingerprint recognition systems are based on the use of a minutiae set, which is an unordered collection of minutiae locations and directions suffering from various deformations such as translation, rotation and scaling. The spectral minutiae representation introduced in this paper is a novel m
A spectral invariant representation of spectral reflectance
Ibrahim, Abdelhameed; Tominaga, Shoji; Horiuchi, Takahiko
2011-03-01
Spectral image acquisition as well as color image is affected by several illumination factors such as shading, gloss, and specular highlight. Spectral invariant representations for these factors were proposed for the standard dichromatic reflection model of inhomogeneous dielectric materials. However, these representations are inadequate for other characteristic materials like metal. This paper proposes a more general spectral invariant representation for obtaining reliable spectral reflectance images. Our invariant representation is derived from the standard dichromatic reflection model for dielectric materials and the extended dichromatic reflection model for metals. We proof that the invariant formulas for spectral images of natural objects preserve spectral information and are invariant to highlights, shading, surface geometry, and illumination intensity. It is proved that the conventional spectral invariant technique can be applied to metals in addition to dielectric objects. Experimental results show that the proposed spectral invariant representation is effective for image segmentation.
Spectral representation of Gaussian semimartingales
Basse-O'Connor, Andreas
2009-01-01
The aim of the present paper is to characterize the spectral representation of Gaussian semimartingales. That is, we provide necessary and sufficient conditions on the kernel K for X t =∫ K t (s) dN s to be a semimartingale. Here, N denotes an independently scattered Gaussian random measure...
Binary Representations of Fingerprint Spectral Minutiae Features
Xu, Haiyun; Veldhuis, Raymond N.J.
2010-01-01
A fixed-length binary representation of a fingerprint has the advantages of a fast operation and a small template storage. For many biometric template protection schemes, a binary string is also required as input. The spectral minutiae representation is a method to represent a minutiae set as a fixe
Complex Spectral Minutiae Representation For Fingerprint Recognition
Xu, Haiyun; Veldhuis, Raymond N.J.
2010-01-01
The spectral minutiae representation is designed for combining fingerprint recognition with template protection. This puts several constraints to the fingerprint recognition system: first, no relative alignment of two fingerprints is allowed due to the encrypted storage; second, a fixed-length featu
Spectral Representations of Fingerprint Minutiae Subsets
Xu, Haiyun; Veldhuis, Raymond N.J.
2009-01-01
The investigation of the privacy protection of biometric templates gains more and more attention. The spectral minutiae representation is a novel method to represent a minutiae set as a fixed-length feature vector, which is invariant to translation, and in which rotation and scaling become translati
From Local to Global Additive Representation
Wakker, P.P.; Chateauneuf, A.
1993-01-01
This paper studies continuous additive representations of transitive preferences on connected subdomains of product sets. Contrary to what has sometimes been thought, local additive representability does not imply global additive representability. It is shown that the result can nevertheless be
From local to global additive representation
A. Chateauneuf (Alain); P.P. Wakker (Peter)
1993-01-01
textabstractThis paper studies continuous additive representations of transitive preferences on connected subdomains of product sets. Contrary to what has sometimes been thought, local additive representability does not imply global additive representability. It is shown that the result can
Invariant representation for spectral reflectance images and its application
Ibrahim Abdelhameed
2011-01-01
Full Text Available Abstract Spectral images as well as color images observed from object surfaces are much influenced by various illumination conditions such as shading and specular highlight. Several invariant representations were proposed for these conditions using the standard dichromatic reflection model of dielectric materials. However, these representations are inadequate for other materials like metal. This article proposes an invariant representation that is derived from the standard dichromatic reflection model for dielectric and the extended dichromatic reflection model for metal. We show that a normalized surface-spectral reflectance by the minimum reflectance is invariant to highlights, shading, surface geometry, and illumination intensity. Here the illumination spectrum and the spectral sensitivity functions of the imaging system are measured in a separate way. As an application of the proposed invariant representation, a segmentation algorithm based on the proposed representation is presented for effectively segmenting spectral images of natural scenes and bare circuit boards.
Spatial, Temporal and Spectral Satellite Image Fusion via Sparse Representation
Song, Huihui
Remote sensing provides good measurements for monitoring and further analyzing the climate change, dynamics of ecosystem, and human activities in global or regional scales. Over the past two decades, the number of launched satellite sensors has been increasing with the development of aerospace technologies and the growing requirements on remote sensing data in a vast amount of application fields. However, a key technological challenge confronting these sensors is that they tradeoff between spatial resolution and other properties, including temporal resolution, spectral resolution, swath width, etc., due to the limitations of hardware technology and budget constraints. To increase the spatial resolution of data with other good properties, one possible cost-effective solution is to explore data integration methods that can fuse multi-resolution data from multiple sensors, thereby enhancing the application capabilities of available remote sensing data. In this thesis, we propose to fuse the spatial resolution with temporal resolution and spectral resolution, respectively, based on sparse representation theory. Taking the study case of Landsat ETM+ (with spatial resolution of 30m and temporal resolution of 16 days) and MODIS (with spatial resolution of 250m ~ 1km and daily temporal resolution) reflectance, we propose two spatial-temporal fusion methods to combine the fine spatial information of Landsat image and the daily temporal resolution of MODIS image. Motivated by that the images from these two sensors are comparable on corresponding bands, we propose to link their spatial information on available Landsat- MODIS image pair (captured on prior date) and then predict the Landsat image from the MODIS counterpart on prediction date. To well-learn the spatial details from the prior images, we use a redundant dictionary to extract the basic representation atoms for both Landsat and MODIS images based on sparse representation. Under the scenario of two prior Landsat
Wide-Band Multi-spectral Space for Color Representation
KONG Lingwang; ZHU Yuanhong; Kurt Muenger; ZHANG Xuliang
2003-01-01
This paper develops a wide-band multi-spectral space for color representation with Aitken PCA algorithm. This novel mathematical space using the broad-band spectra matching method aims at improving the accuracy of color representation as well as reducing costs for processing and storing multi-spectral images. The results show that the space can present our experimental original spectral spaces (i. e. Munsell color matt and DIN-6164 color chips) with high efficiency, and that the spanning space with three eigenvectors can present the original space at more than 98%CSCR, and when 5 eigenvectors are used it can cover almost the whole original spaces.
Enhanced representation of spectral contrasts in the primary auditory cortex
Nicolas eCatz
2013-06-01
Full Text Available The role of early auditory processing may be to extract some elementary features from an acoustic mixture in order to organize the auditory scene. To accomplish this task, the central auditory system may rely on the fact that sensory objects are often composed of spectral edges, i.e. regions where the stimulus energy changes abruptly over frequency. The processing of acoustic stimuli may benefit from a mechanism enhancing the internal representation of spectral edges. While the visual system is thought to rely heavily on this mechanism (enhancing spatial edges, it is still unclear whether a related process plays a significant role in audition. We investigated the cortical representation of spectral edges, using acoustic stimuli composed of multi-tone pips whose time-averaged spectral envelope contained suppressed or enhanced regions. Importantly, the stimuli were designed such that neural responses properties could be assessed as a function of stimulus frequency during stimulus presentation. Our results suggest that the representation of acoustic spectral edges is enhanced in the auditory cortex, and that this enhancement is sensitive to the characteristics of the spectral contrast profile, such as depth, sharpness and width. Spectral edges are maximally enhanced for sharp contrast and large depth. Cortical activity was also suppressed at frequencies within the suppressed region. To note, the suppression of firing was larger at frequencies nearby the lower edge of the suppressed region than at the upper edge. Overall, the present study gives critical insights into the processing of spectral contrasts in the auditory system.
Mixing of fermions and spectral representation of propagator
Kaloshin, A. E.; Lomov, V. P.
2016-03-01
We develop the spectral representation of propagator for n mixing fermion fields in the case of P-parity violation. The approach based on the eigenvalue problem for inverse matrix propagator makes possible to build the system of orthogonal projectors and to represent the matrix propagator as a sum of poles with positive and negative energies. The procedure of multiplicative renormalization in terms of spectral representation is investigated and the renormalization matrices are obtained in a closed form without the use of perturbation theory. Since in theory with P-parity violation the standard spin projectors do not commute with the dressed propagator, they should be modified. The developed approach allows us to build the modified (dressed) spin projectors for a single fermion and for a system of fermions.
Spectral Representation Theory for Dielectric Behavior of Nonspherical Cell Suspensions
HUANG Ji-Ping; YU Kin-Wah; LEI Jun; SUN Hong
2002-01-01
Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. The cell shape effect was simulated by an ellipsoidal cell model but the comparison between theory and experiment was far from being satisfactory. Prompted by the discrepancy, we proposed the use of spectral representation to analyze more realistic cell models. We adopted a shell-spheroidal model to analyze the effects of the cell membrane. It is found that the dielectric property of the cell membrane has only a minor effect on the dispersion magnitude ratio and the characteristic frequency ratio. We further included the effect of rotation of dipole induced by an external electric field, and solved the dipole-rotation spheroidal model in the spectral representation.Good agreement between theory and experiment has been obtained.
Geometrical Description in Binary Composites and Spectral Density Representation
Enis Tuncer
2010-01-01
Full Text Available In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based on a scaled permittivity approach, ξ = (εe − εm(εi − εm−1, where the subscripts e, m and i denote the dielectric permittivities of the effective, matrix and inclusion media, respectively [Tuncer, E. J. Phys.: Condens. Matter 2005, 17, L125]. This novel representation transforms the spectral density formalism to a form similar to the distribution of relaxation times method of dielectric relaxation. Consequently, I propose that any dielectric relaxation formula, i.e., the Havriliak-Negami empirical dielectric relaxation expression, can be adopted as a scaled permittivity. The presented scaled permittivity representation has potential to be improved and implemented into the existing data analyzing routines for dielectric relaxation; however, the information to extract would be the topological/morphological description in mixtures. To arrive at the description, one needs to know the dielectric properties of the constituents and the composite prior to the spectral analysis. To illustrate the strength of the representation and confirm the proposed hypothesis, the Landau-Lifshitz/Looyenga (LLL [Looyenga, H. Physica 1965, 31, 401] expression is selected. The structural information of a mixture obeying LLL is extracted for different volume fractions of phases. Both an in-house computational tool based on the Monte Carlo method to solve inverse integral transforms and the proposed empirical scaled permittivity expression are employed to estimate the spectral density function of the LLL expression. The estimated spectral functions for mixtures with different inclusion concentration compositions show similarities; they are composed of a couple of bell
Mixing of fermions and spectral representation of propagator
Kaloshin, A E
2015-01-01
We develop the spectral representation of propagator for $n$ mixing fermion fields in case of $\\mathsf{P}$-parity violation. Solving of the eigenstate problem for inverse matrix propagator allows to build the system of orthogonal projectors and to represent the matrix propagator as a sum of poles with positive and negative energy. The procedure of multiplicative renormalization is investigated, the renormalization matrices are obtained in a closed form without using of perturbation theory.
Baryon to meson transition distribution amplitudes and their spectral representation
Pire, Bernard; Szymanowski, Lech
2011-01-01
We consider the problem of construction of a spectral representation for nucleon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of nonlocal three quark light-cone operators between a nucleon and a meson states. We introduce the notion of quadruple distributions and generalize Radyshkin's factorized Ansatz for this issue. Modelling of baryon to meson TDAs in the complete domain of their definition opens the way to quantitative estimates of cross-sections for various hard exclusive reactions.
Vertical spectral representation in primitive equation models of the atmosphere
Mizzi, A.; Tribbia, J. [National Center for Atmospheric Research, Boulder, CO (United States); Curry, J. [Univ. of Colorado, Boulder, CO (United States)
1995-08-01
Attempts to represent the vertical structure in primitive equation models of the atmosphere with the spectral method have been unsuccessful to date. Linear stability analysis showed that small time steps were required for computational stability near the upper boundary with a vertical spectral representation and found it necessary to use an artificial constraint to force temperature to zero when pressure was zero to control the upper-level horizontal velocities. This ad hoc correction is undesirable, and an analysis that shows such a correction is unnecessary is presented. By formulating the model in terms of velocity and geopotential and then using the hydrostatic equation to calculate temperature from geopotential, temperature is necessarily zero when pressure is zero. The authors applied this technique to the dry-adiabatic primitive equations on the equatorial {beta} and tropical f planes. Vertical and horizontal normal modes were used as the spectral basis functions. The vertical modes are based on vertical normal modes, and the horizontal modes are normal modes for the primitive equations on a {beta} or f plane. The results show that the upper-level velocities do not necessarily increase, total energy is conserved, and kinetic energy is bounded. The authors found an upper-level temporal oscillation in the horizontal domain integral of the horizontal velocity components that is related to mass and velocity field imbalances in the initial conditions or introduced during the integration. Through nonlinear normal-mode initialization, the authors effectively removed the initial condition imbalance and reduced the amplitude of this oscillation. It is hypothesized that the vertical spectral representation makes the model more sensitive to initial condition imbalances, or it introduces imbalance during the integration through vertical spectral truncation. 20 refs., 12 figs.
Sparse representation-based spectral clustering for SAR image segmentation
Zhang, Xiangrong; Wei, Zhengli; Feng, Jie; Jiao, Licheng
2011-12-01
A new method, sparse representation based spectral clustering (SC) with Nyström method, is proposed for synthetic aperture radar (SAR) image segmentation. Different from the conventional SC, this proposed technique is developed by using the sparse coefficients which obtained by solving l1 minimization problem to construct the affinity matrix and the Nyström method is applied to alleviate the segmentation process. The advantage of our proposed method is that we do not need to select the scaling parameter in the Gaussian kernel function artificially. We apply the proposed method, k-means and the classic spectral clustering algorithm with Nyström method to SAR image segmentation. The results show that compared with the other two methods, the proposed method can obtain much better segmentation results.
Improved Spectral Representation for Birdcall Based on Fractional Fourier Transform
无
2008-01-01
A novel spectral representation based on fractional Fourier transform (FrFT) is proposed and applied to birdcall analysis. The FrFT-based spectrogram of a signal is derived and compared with its FT-based counterpart, and the spectrum gathering method is used to show the energy distribution related to the pitch frequency. The fixed transform order and adaptive orders for FrFT are tested. The fixed order can be obtained empirically or calculated according to the known chirp rate. The adaptive optimal orders are determined by using ambiguity function. Experimental results with birdcalls show that the FrFT-based spectrogram with an optimal transform order has higher resolution than its STFT-based counterpart, and the better performance can be achieved if adaptive orders are used.
Novel Spectral Representations and Sparsity-Driven Algorithms for Shape Modeling and Analysis
Zhong, Ming
respect to the dictionary comprising its Laplacian eigenbasis, and it is then possible to recover this sparse representation from partial measurements of the original shape. Taking advantage of the sparsity cue, we advocate a novel variational approach for surface inpainting, integrating data fidelity constraints on the shape domain with coefficient sparsity constraints on the transformed domain. Because of the powerful properties of Laplacian eigenbasis, the inpainting results of our method tend to be globally coherent with the remaining shape. Informative and discriminative feature descriptors are vital in qualitative and quantitative shape analysis for a large variety of graphics applications. We advocate novel strategies to define generalized, user-specified features on shapes. Our new region descriptors are primarily built upon the coefficients of spectral graph wavelets that are both multi-scale and multi-level in nature, consisting of both local and global information. Based on our novel spectral feature descriptor, we developed a user-specified feature detection framework and a tensor-based shape matching algorithm. Through various experiments, we demonstrate the competitive performance of our proposed methods and the great potential of spectral basis and sparsity-driven methods for shape modeling.
Automatic stellar spectral classification via sparse representations and dictionary learning
Díaz-Hernández, R.; Peregrina-Barreto, H.; Altamirano-Robles, L.; González-Bernal, J. A.; Ortiz-Esquivel, A. E.
2014-11-01
Stellar classification is an important topic in astronomical tasks such as the study of stellar populations. However, stellar classification of a region of the sky is a time-consuming process due to the large amount of objects present in an image. Therefore, automatic techniques to speed up the process are required. In this work, we study the application of a sparse representation and a dictionary learning for automatic spectral stellar classification. Our dataset consist of 529 calibrated stellar spectra of classes B to K, belonging to the Pulkovo Spectrophotometric catalog, in the 3400-5500Å range. These stellar spectra are used for both training and testing of the proposed methodology. The sparse technique is applied by using the greedy algorithm OMP (Orthogonal Matching Pursuit) for finding an approximated solution, and the K-SVD (K-Singular Value Decomposition) for the dictionary learning step. Thus, sparse classification is based on the recognition of the common characteristics of a particular stellar type through the construction of a trained basis. In this work, we propose a classification criterion that evaluates the results of the sparse representation techniques and determines the final classification of the spectra. This methodology demonstrates its ability to achieve levels of classification comparable with automatic methodologies previously reported such as the Maximum Correlation Coefficient (MCC) and Artificial Neural Networks (ANN).
Spectral Representation Analysis of Non Contact Acousto Thermal Signature Data (Preprint)
2017-07-07
the acoustic waves are absorbed into the material and converted to heat through the diffusion of transverse thermal currents, inter-crystalline...from Non-contact acousto-thermal signature (NCATS) experiments are considered. Spectral representation models are developed for general conductive...experiments are considered. Spectral representation models are developed for general conductive cooling physics. These models are subsequently used to
Representation of geographic terrain surface using global indexing
Kolar, Jan
2004-01-01
in the domain. Handling entire terrain is inherently coupled with global spatial index. This problem is overviewed and a solution is proposed. Afterwards the data representation of the essential surface in geography is introduced. The representation deals with the problem of LOD and is suitable for use...
Design of cloaking metamaterials using spectral representation theory
Lai Leung, Lai; Fung, Tai Hang; Yu, Kin Wah
2008-03-01
Controlling the propagation of electromagnetic (EM) waves, for instance in cloaking problem, has become an important topic in nanophotonics. So far, following the cloaking model proposed by Pendry et al. [1], the experimental realization was only limited to the microwave region [2]. Since practical application lies in the visible range, we have extended the investigation to that region by utilizing nanocomposites with reference to the material parameters proposed by Pendry et al. and Shalaev et al. [3]. The calculations can be made much simpler by invoking the spectral representation theory [4]. The loss and dispersion effects, as well as the propagation of EM waves are assessed for the designed cloaking models in order to investigate the cloaking performance. Further analyses show that our models can accomplish the desired cloaking effect in the visible range. Moreover, the loss and dispersion effects are found to be small and acceptable.[1] J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006). [2] D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, D. R. Smith Science 314, 5801 (2006). [3] Wenshan Cai, Uday K. Chettiar, Alexander V. Kildishev and Vladimir M. Shalaev, Nature photonics 1 (2007). [4] L. Dong, Mikko Karttunen, K. W. Yu, Phys. Rev. E 72, 016613 (2005).
Boyali, Ali
2015-01-01
In this study, we introduce a novel variant and application of the Collaborative Representation based Classification in spectral domain for recognition of the hand gestures using the raw surface Electromyography signals. The intuitive use of spectral features are explained via circulant matrices. The proposed Spectral Collaborative Representation based Classification (SCRC) is able to recognize gestures with higher levels of accuracy for a fairly rich gesture set. The worst recognition result...
Global and local aspects of spectral actions
Iochum, Bruno; Vassilevich, Dmitri
2012-01-01
The principal object in noncommutatve geometry is the spectral triple consisting of an algebra A, a Hilbert space H, and a Dirac operator D. Field theories are incorporated in this approach by the spectral action principle, that sets the field theory action to Tr f(D^2/\\Lambda^2), where f is a real function such that the trace exists, and \\Lambda is a cutoff scale. In the low-energy (weak-field) limit the spectral action reproduces reasonably well the known physics including the standard model. However, not much is known about the spectral action beyond the low-energy approximation. In this paper, after an extensive introduction to spectral triples and spectral actions, we study various expansions of the spectral actions (exemplified by the heat kernel). We derive the convergence criteria. For a commutative spectral triple, we compute the heat kernel on the torus up the second order in gauge connection and consider limiting cases.
Integrating Globality and Locality for Robust Representation Based Classification
Zheng Zhang
2014-01-01
Full Text Available The representation based classification method (RBCM has shown huge potential for face recognition since it first emerged. Linear regression classification (LRC method and collaborative representation classification (CRC method are two well-known RBCMs. LRC and CRC exploit training samples of each class and all the training samples to represent the testing sample, respectively, and subsequently conduct classification on the basis of the representation residual. LRC method can be viewed as a “locality representation” method because it just uses the training samples of each class to represent the testing sample and it cannot embody the effectiveness of the “globality representation.” On the contrary, it seems that CRC method cannot own the benefit of locality of the general RBCM. Thus we propose to integrate CRC and LRC to perform more robust representation based classification. The experimental results on benchmark face databases substantially demonstrate that the proposed method achieves high classification accuracy.
Dynamic representation of spectral edges in guinea pig primary auditory cortex.
Montejo, Noelia; Noreña, Arnaud J
2015-04-01
The central representation of a given acoustic motif is thought to be strongly context dependent, i.e., to rely on the spectrotemporal past and present of the acoustic mixture in which it is embedded. The present study investigated the cortical representation of spectral edges (i.e., where stimulus energy changes abruptly over frequency) and its dependence on stimulus duration and depth of the spectral contrast in guinea pig. We devised a stimulus ensemble composed of random tone pips with or without an attenuated frequency band (AFB) of variable depth. Additionally, the multitone ensemble with AFB was interleaved with periods of silence or with multitone ensembles without AFB. We have shown that the representation of the frequencies near but outside the AFB is greatly enhanced, whereas the representation of frequencies near and inside the AFB is strongly suppressed. These cortical changes depend on the depth of the AFB: although they are maximal for the largest depth of the AFB, they are also statistically significant for depths as small as 10 dB. Finally, the cortical changes are quick, occurring within a few seconds of stimulus ensemble presentation with AFB, and are very labile, disappearing within a few seconds after the presentation without AFB. Overall, this study demonstrates that the representation of spectral edges is dynamically enhanced in the auditory centers. These central changes may have important functional implications, particularly in noisy environments where they could contribute to preserving the central representation of spectral edges. Copyright © 2015 the American Physiological Society.
Representation of geographic terrain surface using global indexing
Kolar, Jan
2004-01-01
A global 3D geographic model a feasible solution for its visualization and management remains a challenging vision. The existence of a reusable platform would provide an unprecedented potential for development of applications related to geography and facilitate comprehension of geographic data...... visually in order to access information and data in the same geometric space as we navigate ourselves in our real environment. This article attempts to narrow down the overhead of problems in visualization of 3D geographic information and intends to identify fundamental issues common to other systems...... in the domain. Handling entire terrain is inherently coupled with global spatial index. This problem is overviewed and a solution is proposed. Afterwards the data representation of the essential surface in geography is introduced. The representation deals with the problem of LOD and is suitable for use...
Multi-Component NLS Models on Symmetric Spaces: Spectral Properties versus Representations Theory
Georgi G. Grahovski
2010-06-01
Full Text Available The algebraic structure and the spectral properties of a special class of multi-component NLS equations, related to the symmetric spaces of BD.I-type are analyzed. The focus of the study is on the spectral theory of the relevant Lax operators for different fundamental representations of the underlying simple Lie algebra g. Special attention is paid to the structure of the dressing factors in spinor representation of the orthogonal simple Lie algebras of B_r simeq so(2r+1,C type.
Ben-Nun, M; Mills, J D; Hinde, R J; Winstead, C L; Boatz, J A; Gallup, G A; Langhoff, P W
2009-07-02
Recent progress is reported in development of ab initio computational methods for the electronic structures of molecules employing the many-electron eigenstates of constituent atoms in spectral-product forms. The approach provides a universal atomic-product description of the electronic structure of matter as an alternative to more commonly employed valence-bond- or molecular-orbital-based representations. The Hamiltonian matrix in this representation is seen to comprise a sum over atomic energies and a pairwise sum over Coulombic interaction terms that depend only on the separations of the individual atomic pairs. Overall electron antisymmetry can be enforced by unitary transformation when appropriate, rather than as a possibly encumbering or unnecessary global constraint. The matrix representative of the antisymmetrizer in the spectral-product basis, which is equivalent to the metric matrix of the corresponding explicitly antisymmetric basis, provides the required transformation to antisymmetric or linearly independent states after Hamiltonian evaluation. Particular attention is focused in the present report on properties of the metric matrix and on the atomic-product compositions of molecular eigenstates as described in the spectral-product representations. Illustrative calculations are reported for simple but prototypically important diatomic (H(2), CH) and triatomic (H(3), CH(2)) molecules employing algorithms and computer codes devised recently for this purpose. This particular implementation of the approach combines Slater-orbital-based one- and two-electron integral evaluations, valence-bond constructions of standard tableau functions and matrices, and transformations to atomic eigenstate-product representations. The calculated metric matrices and corresponding potential energy surfaces obtained in this way elucidate a number of aspects of the spectral-product development, including the nature of closure in the representation, the general redundancy or
Regional fusion for high-resolution palmprint recognition using spectral minutiae representation
Wang, R.; Ramos, D.; Veldhuis, R.N.J.; Fierrez, J.; Spreeuwers, L.J.; Xu, Haiyun
2014-01-01
The spectral minutiae representation (SMC) has been recently proposed as a novel method to minutiae-based fingerprint recognition, which is invariant to minutiae translation and rotation and presents low computational complexity. As high-resolution palmprint recognition is also mainly based on minut
Sensitivity experiments to mountain representations in spectral models
U. Schlese
2000-06-01
Full Text Available This paper describes a set of sensitivity experiments to several formulations of orography. Three sets are considered: a "Standard" orography consisting of an envelope orography produced originally for the ECMWF model, a"Navy" orography directly from the US Navy data and a "Scripps" orography based on the data set originally compiled several years ago at Scripps. The last two are mean orographies which do not use the envelope enhancement. A new filtering technique for handling the problem of Gibbs oscillations in spectral models has been used to produce the "Navy" and "Scripps" orographies, resulting in smoother fields than the "Standard" orography. The sensitivity experiments show that orography is still an important factor in controlling the model performance even in this class of models that use a semi-lagrangian formulation for water vapour, that in principle should be less sensitive to Gibbs oscillations than the Eulerian formulation. The largest impact can be seen in the stationary waves (asymmetric part of the geopotential at 500 mb where the differences in total height and spatial pattern generate up to 60 m differences, and in the surface fields where the Gibbs removal procedure is successful in alleviating the appearance of unrealistic oscillations over the ocean. These results indicate that Gibbs oscillations also need to be treated in this class of models. The best overall result is obtained using the "Navy" data set, that achieves a good compromise between amplitude of the stationary waves and smoothness of the surface fields.
YANG Zhaoxia
2015-07-01
Full Text Available In order to avoid the problem of being over-dependent on high-dimensional spectral feature in the traditional hyperspectral image classification, a novel approach based on the combination of spatial-spectral feature and sparse representation is proposed in this paper. Firstly, we extract the spatial-spectral feature by reorganizing the local image patch with the first d principal components(PCs into a vector representation, followed by a sorting scheme to make the vector invariant to local image rotation. Secondly, we learn the dictionary through a supervised method, and use it to code the features from test samples afterwards. Finally, we embed the resulting sparse feature coding into the support vector machine(SVM for hyperspectral image classification. Experiments using three hyperspectral data show that the proposed method can effectively improve the classification accuracy comparing with traditional classification methods.
Fan, Jiayuan; Tan, Hui Li; Toomik, Maria; Lu, Shijian
2016-10-01
Spatial pyramid matching has demonstrated its power for image recognition task by pooling features from spatially increasingly fine sub-regions. Motivated by the concept of feature pooling at multiple pyramid levels, we propose a novel spectral-spatial hyperspectral image classification approach using superpixel-based spatial pyramid representation. This technique first generates multiple superpixel maps by decreasing the superpixel number gradually along with the increased spatial regions for labelled samples. By using every superpixel map, sparse representation of pixels within every spatial region is then computed through local max pooling. Finally, features learned from training samples are aggregated and trained by a support vector machine (SVM) classifier. The proposed spectral-spatial hyperspectral image classification technique has been evaluated on two public hyperspectral datasets, including the Indian Pines image containing 16 different agricultural scene categories with a 20m resolution acquired by AVIRIS and the University of Pavia image containing 9 land-use categories with a 1.3m spatial resolution acquired by the ROSIS-03 sensor. Experimental results show significantly improved performance compared with the state-of-the-art works. The major contributions of this proposed technique include (1) a new spectral-spatial classification approach to generate feature representation for hyperspectral image, (2) a complementary yet effective feature pooling approach, i.e. the superpixel-based spatial pyramid representation that is used for the spatial correlation study, (3) evaluation on two public hyperspectral image datasets with superior image classification performance.
Spectral Flow and Global Topology of the Hofstadter Butterfly.
Asbóth, János K; Alberti, Andrea
2017-05-26
We study the relation between the global topology of the Hofstadter butterfly of a multiband insulator and the topological invariants of the underlying Hamiltonian. The global topology of the butterfly, i.e., the displacement of the energy gaps as the magnetic field is varied by one flux quantum, is determined by the spectral flow of energy eigenstates crossing gaps as the field is tuned. We find that for each gap this spectral flow is equal to the topological invariant of the gap, i.e., the net number of edge modes traversing the gap. For periodically driven systems, our results apply to the spectrum of quasienergies. In this case, the spectral flow of the sum of all the quasienergies gives directly the Rudner-Lindner-Berg-Levin invariant that characterizes the topological phases of a periodically driven system.
Spectral Flow and Global Topology of the Hofstadter Butterfly
Asbóth, János K.; Alberti, Andrea
2017-05-01
We study the relation between the global topology of the Hofstadter butterfly of a multiband insulator and the topological invariants of the underlying Hamiltonian. The global topology of the butterfly, i.e., the displacement of the energy gaps as the magnetic field is varied by one flux quantum, is determined by the spectral flow of energy eigenstates crossing gaps as the field is tuned. We find that for each gap this spectral flow is equal to the topological invariant of the gap, i.e., the net number of edge modes traversing the gap. For periodically driven systems, our results apply to the spectrum of quasienergies. In this case, the spectral flow of the sum of all the quasienergies gives directly the Rudner-Lindner-Berg-Levin invariant that characterizes the topological phases of a periodically driven system.
A dedicated greedy pursuit algorithm for sparse spectral representation of music sound
Rebollo-Neira, Laura; Aggarwal, Gagan
2016-10-01
A dedicated algorithm for sparse spectral representation of music sound is presented. The goal is to enable the representation of a piece of music signal, as a linear superposition of as few spectral components as possible. A representation of this nature is said to be sparse. In the present context sparsity is accomplished by greedy selection of the spectral components, from an overcomplete set called a dictionary. The proposed algorithm is tailored to be applied with trigonometric dictionaries. Its distinctive feature being that it avoids the need for the actual construction of the whole dictionary, by implementing the required operations via the Fast Fourier Transform. The achieved sparsity is theoretically equivalent to that rendered by the Orthogonal Matching Pursuit method. The contribution of the proposed dedicated implementation is to extend the applicability of the standard Orthogonal Matching Pursuit algorithm, by reducing its storage and computational demands. The suitability of the approach for producing sparse spectral models is illustrated by comparison with the traditional method, in the line of the Short Time Fourier Transform, involving only the corresponding orthonormal trigonometric basis.
Hyperspectral image classification based on spatial and spectral features and sparse representation
Yang Jing-Hui; Wang Li-Guo; Qian Jin-Xi
2014-01-01
To minimize the low classification accuracy and low utilization of spatial information in traditional hyperspectral image classification methods, we propose a new hyperspectral image classification method, which is based on the Gabor spatial texture features and nonparametric weighted spectral features, and the sparse representation classification method (Gabor–NWSF and SRC), abbreviated GNWSF–SRC. The proposed (GNWSF–SRC) method first combines the Gabor spatial features and nonparametric weighted spectral features to describe the hyperspectral image, and then applies the sparse representation method. Finally, the classification is obtained by analyzing the reconstruction error. We use the proposed method to process two typical hyperspectral data sets with different percentages of training samples. Theoretical analysis and simulation demonstrate that the proposed method improves the classification accuracy and Kappa coefficient compared with traditional classification methods and achieves better classification performance.
Hyper-spectral remote sensing of global CO2
Wang, Ding Yi
2016-07-01
Monitoring of greenhouse gas CO2 on a basis of global scale, high precision, and real time has great significance for the understanding CO2 sources and sinks, as well as global climate change. In order to meet the urgent needs, several research projects are ongoing in China and in the world for retrieving CO2 from satellite-based hyper-spectral observations. In this talk, the projects are briefly introduced, the theory of atmospheric near-infrared remote sensing is discussed, and a forward model and inversion software system for near-infrared hyper-spectral measurements of CO2 is outlined. The validation of the software package against GOST-FTS observation are performed, and their relative error is less than 1.0%. Future cross-validation between the Chinese satellite and other observations is suggested.
A globally convergent matricial algorithm for multivariate spectral estimation
Ramponi, Federico; Pavon, Michele
2008-01-01
In this paper, we first describe a matricial Newton-type algorithm designed to solve the multivariable spectrum approximation problem. We then prove its global convergence. Finally, we apply this approximation procedure to multivariate spectral estimation, and test its effectiveness through simulation. Simulation shows that, in the case of short observation records, this method may provide a valid alternative to standard multivariable identification techniques such as MATLAB's PEM and MATLAB's N4SID.
Linear study of global microinstabilities using spectral and PIC methods
Brunner, S.; Fivaz, M.; Vaclavik, J.; Appert, K.; Tran, T.M. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1996-09-01
A spectral as well as a time evolution PIC code are presently being developed to solve the linearized gyrokinetic equations for studying global microinstabilities in toroidal geometry. In many ways these two methods are complementary and therefore allow for valuable cross-checking and validation of the different approximations made. This parallel approach forms a firm basis for future studies of non-linear evolution or higher dimensional systems. (author) 7 figs., 18 refs.
Wu, Bo; Zhu, Yong; Huang, Xin; Li, Jiayi
2016-10-01
Sparse representation classification (SRC) is becoming a promising tool for hyperspectral image (HSI) classification, where the Euclidean spectral distance (ESD) is widely used to reflect the fidelity between the original and reconstructed signals. In this paper, a generalized model is proposed to extend SRC by characterizing the spectral fidelity with flexible similarity measures. To validate the flexibility, several typical similarity measures-the spectral angle similarity (SAS), spectral information divergence (SID), the structural similarity index measure (SSIM), and the ESD-are included in the generalized model. Furthermore, a general solution based on a gradient descent technique is used to solve the nonlinear optimization problem formulated by the flexible similarity measures. To test the generalized model, two actual HSIs were used, and the experimental results confirm the ability of the proposed model to accommodate the various spectral similarity measures. Performance comparisons with the ESD, SAS, SID, and SSIM criteria were also conducted, and the results consistently show the advantages of the generalized model for HSI classification in terms of overall accuracy and kappa coefficient.
Gyrokinetic simulations of fusion plasmas using a spectral velocity space representation
Parker, Joseph Thomas
2016-01-01
Magnetic confinement fusion reactors suffer severely from heat and particle losses through turbulent transport, which has inspired the construction of ever larger and more expensive reactors. Numerical simulations are vital to their design and operation, but particle collisions are too infrequent for fluid descriptions to be valid. Instead, strongly magnetised fusion plasmas are described by the gyrokinetic equations, a nonlinear integro-differential system for evolving the particle distribution functions in a five-dimensional position and velocity space, and the consequent electromagnetic field. Due to the high dimensionality, simulations of small reactor sections require hundreds of thousands of CPU hours on High Performance Computing platforms. We develop a Hankel-Hermite spectral representation for velocity space that exploits structural features of the gyrokinetic system. The representation exactly conserves discrete free energy in the absence of explicit dissipation, while our Hermite hypercollision ope...
Spectral representation for u- and t-channel exchange processes in a partial-wave decomposition
Lutz, M F M; Korpa, C L
2015-01-01
We study the analytic structure of partial-wave amplitudes derived from u- and t-channel exchange processes. The latter plays a crucial role in dispersion-theory approaches to coupled-channel systems that model final state interactions in QCD. A general spectral representation is established that is valid in the presence of anomalous thresholds, decaying particles or overlapping left-hand and right-hand cut structures as it occurs frequently in hadron physics. The results are exemplified at hand of ten specific processes.
Ritschel, Gerhard; Eisfeld, Alexander
2014-09-01
We present a scheme to express a bath correlation function (BCF) corresponding to a given spectral density (SD) as a sum of damped harmonic oscillations. Such a representation is needed, for example, in many open quantum system approaches. To this end we introduce a class of fit functions that enables us to model ohmic as well as superohmic behavior. We show that these functions allow for an analytic calculation of the BCF using pole expansions of the temperature dependent hyperbolic cotangent. We demonstrate how to use these functions to fit spectral densities exemplarily for cases encountered in the description of photosynthetic light harvesting complexes. Finally, we compare absorption spectra obtained for different fits with exact spectra and show that it is crucial to take properly into account the behavior at small frequencies when fitting a given SD.
A global spectral library to characterize the world's soil
A. Viscarra Rossel, Raphael; Behrens, T.; Ben Dor, E.
2016-01-01
Soil provides ecosystemservices, supports human health and habitation, stores carbon and regulatesemissions of greenhouse gases. Unprecedented pressures on soil from degradation and urbanization are threatening agroecological balances and food security. It is important that we learn more about soil...... to sustainably manage and preserve it for future generations. To this end, we developed and analyzed a global soil visible–near infrared (vis–NIR) spectral library. It is currently the largest and most diverse database of its kind. We show that the information encoded in the spectra can describe soil composition...
Local and Global Gestalt Laws: A Neurally Based Spectral Approach.
Favali, Marta; Citti, Giovanna; Sarti, Alessandro
2017-02-01
This letter presents a mathematical model of figure-ground articulation that takes into account both local and global gestalt laws and is compatible with the functional architecture of the primary visual cortex (V1). The local gestalt law of good continuation is described by means of suitable connectivity kernels that are derived from Lie group theory and quantitatively compared with long-range connectivity in V1. Global gestalt constraints are then introduced in terms of spectral analysis of a connectivity matrix derived from these kernels. This analysis performs grouping of local features and individuates perceptual units with the highest salience. Numerical simulations are performed, and results are obtained by applying the technique to a number of stimuli.
Pire, Bernard; Szymanowski, Lech
2010-01-01
We construct a spectral representation for the transition distribution amplitudes (TDAs), i.e. matrix elements of three quark correlators which arise e.g. in the description of baryon to meson and baryon to photon transitions within the factorization approach to hard exclusive reactions. We generalize for these quantities the notion of double distributions introduced in the context of generalized parton distributions. We propose the generalization of A.Radyushkin's factorized Ansatz for the case of baryon to meson and baryon to photon TDAs. Our construction opens the way to modeling of baryon to meson and baryon to photon TDAs in their complete domain of definition and quantitative estimates of cross-sections for various hard exclusive reactions.
Spatial and Spectral Representations of the Geoid-to-Quasigeoid Correction
Tenzer, Robert; Hirt, Christian; Claessens, Sten; Novák, Pavel
2015-09-01
In geodesy, the geoid and the quasigeoid are used as a reference surface for heights. Despite some similarities between these two concepts, the differences between the geoid and the quasigeoid (i.e. the geoid-to-quasigeoid correction) have to be taken into consideration in some specific applications which require a high accuracy. Over the world's oceans and marginal seas, the quasigeoid and the geoid are identical. Over the continents, however, the geoid-to-quasigeoid correction could reach up to several metres especially in the mountainous, polar and geologically complex regions. Various methods have been developed and applied to compute this correction regionally in the spatial domain using detailed gravity, terrain and crustal density data. These methods utilize the gravimetric forward modelling of the topographic density structure and the direct/inverse solutions to the boundary-value problems in physical geodesy. In this article, we provide a brief summary of existing theoretical and numerical studies on the geoid-to-quasigeoid correction. We then compare these methods with the newly developed procedure and discuss some numerical and practical aspects of computing this correction. In global applications, the geoid-to-quasigeoid correction can conveniently be computed in the spectral domain. For this purpose, we derive and present also the spectral expressions for computing this correction based on applying methods for a spherical harmonic analysis and synthesis of global gravity, terrain and crustal structure models. We argue that the newly developed procedure for the regional gravity-to-potential conversion, applied for computing the geoid-to-quasigeoid correction in the spatial domain, is numerically more stable than the existing inverse models which utilize the gravity downward continuation. Moreover, compared to existing spectral expressions, our definition in the spectral domain takes not only the terrain geometry but also the mass density heterogeneities
Parker, Joseph T.
2015-02-03
Copyright © Cambridge University Press 2015. We study Landau damping in the 1+1D Vlasov-Poisson system using a Fourier-Hermite spectral representation. We describe the propagation of free energy in Fourier-Hermite phase space using forwards and backwards propagating Hermite modes recently developed for gyrokinetic theory. We derive a free energy equation that relates the change in the electric field to the net Hermite flux out of the zeroth Hermite mode. In linear Landau damping, decay in the electric field corresponds to forward propagating Hermite modes; in nonlinear damping, the initial decay is followed by a growth phase characterized by the generation of backwards propagating Hermite modes by the nonlinear term. The free energy content of the backwards propagating modes increases exponentially until balancing that of the forward propagating modes. Thereafter there is no systematic net Hermite flux, so the electric field cannot decay and the nonlinearity effectively suppresses Landau damping. These simulations are performed using the fully-spectral 5D gyrokinetics code SpectroGK, modified to solve the 1+1D Vlasov-Poisson system. This captures Landau damping via Hou-Li filtering in velocity space. Therefore the code is applicable even in regimes where phase mixing and filamentation are dominant.
Electromagnetic microinstabilities in tokamak plasmas using a global spectral approach
Falchetto, G. L
2002-03-01
Electromagnetic microinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. The code is the electromagnetic extension of an existing electrostatic global gyrokinetic spectral toroidal code, called GLOGYSTO. Ion dynamics is described by the gyrokinetic equation, so that ion finite Larmor radius effects are taken into account to all orders. Non adiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A low frequency electromagnetic perturbation is applied to a low -but finite- {beta}plasma (where the parameter {beta} identifies the ratio of plasma pressure to magnetic pressure); thus, the parallel perturbations of the magnetic field are neglected. The system is closed by the quasi-neutrality equation and the parallel component of Ampere's law. The formulation is applied to a large aspect ratio toroidal configuration, with circular shifted surfaces. Such a simple configuration enables one to derive analytically the gyrocenter trajectories. The system is solved in Fourier space, taking advantage of a decomposition adapted to the toroidal geometry. The major contributions of this thesis are as follows. The electromagnetic effects on toroidal Ion Temperature Gradient driven (ITG) modes are studied. The stabilization of these modes with increasing {beta}, as predicted in previous work, is confirmed. The inclusion of trapped electron dynamics enables the study of its coupling to the ITG modes and of Trapped Electron Modes (TEM) .The effects of finite {beta} are considered together with those of different magnetic shear profiles and of the Shafranov shift. The threshold for the destabilization of an electromagnetic mode is identified. Moreover, the global formulation yields for the first time the radial structure of this so-called Alfvenic Ion Temperature Gradient (AITG) mode. The stability of the
Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng
2004-01-01
Land surface albedo is an important parameter in describing the radiative properties of the earth s surface as it represents the amount of incoming solar radiation that is reflected from the surface. The amount and type of vegetation of the surface dramatically alters the amount of radiation that is reflected; for example, croplands that contain leafy vegetation will reflect radiation very differently than blacktop associated with urban areas. In addition, since vegetation goes through a growth, or phenological, cycle, the amount of radiation that is reflected changes over the course of a year. As a result, albedo is both temporally and spatially dependant upon global location as there is a distribution of vegetated surface types and growing conditions. Land surface albedo is critical for a wide variety of earth system research projects including but not restricted to remote sensing of atmospheric aerosol and cloud properties from space, ground-based analysis of aerosol optical properties from surface-based sun/sky radiometers, biophysically-based land surface modeling of the exchange of energy, water, momentum, and carbon for various land use categories, and surface energy balance studies. These projects require proper representation of the surface albedo s spatial, spectral, and temporal variations, however, these representations are often lacking in datasets prior to the latest generation of land surface albedo products.
Regional Densification of a Global VTEC Model Based on B-Spline Representations
Erdogan, Eren; Schmidt, Michael; Dettmering, Denise; Goss, Andreas; Seitz, Florian; Börger, Klaus; Brandert, Sylvia; Görres, Barbara; Kersten, Wilhelm F.; Bothmer, Volker; Hinrichs, Johannes; Mrotzek, Niclas
2017-04-01
The project OPTIMAP is a joint initiative of the Bundeswehr GeoInformation Centre (BGIC), the German Space Situational Awareness Centre (GSSAC), the German Geodetic Research Institute of the Technical University Munich (DGFI-TUM) and the Institute for Astrophysics at the University of Göttingen (IAG). The main goal of the project is the development of an operational tool for ionospheric mapping and prediction (OPTIMAP). Two key features of the project are the combination of different satellite observation techniques (GNSS, satellite altimetry, radio occultations and DORIS) and the regional densification as a remedy against problems encountered with the inhomogeneous data distribution. Since the data from space-geoscientific mission which can be used for modeling ionospheric parameters, such as the Vertical Total Electron Content (VTEC) or the electron density, are distributed rather unevenly over the globe at different altitudes, appropriate modeling approaches have to be developed to handle this inhomogeneity. Our approach is based on a two-level strategy. To be more specific, in the first level we compute a global VTEC model with a moderate regional and spectral resolution which will be complemented in the second level by a regional model in a densification area. The latter is a region characterized by a dense data distribution to obtain a high spatial and spectral resolution VTEC product. Additionally, the global representation means a background model for the regional one to avoid edge effects at the boundaries of the densification area. The presented approach based on a global and a regional model part, i.e. the consideration of a regional densification is called the Two-Level VTEC Model (TLVM). The global VTEC model part is based on a series expansion in terms of polynomial B-Splines in latitude direction and trigonometric B-Splines in longitude direction. The additional regional model part is set up by a series expansion in terms of polynomial B-splines for
Watson Gregg
2016-11-01
Full Text Available The importance of including directional and spectral light in simulations of ocean radiative transfer was investigated using a coupled biogeochemical-circulation-radiative model of the global oceans. The effort focused on phytoplankton abundances, nutrient concentrations and net primary production.The importance was approached by sequentially removing directional (i.e., direct vs. diffuse and spectral irradiance and comparing results of the above variables to a fully directionally and spectrally-resolved model.In each case the total irradiance was kept constant; it was only the pathways and spectral nature that were changed.Assuming all irradiance was diffuse had negligible effect on global ocean primary production. Global nitrate and total chlorophyll concentrations declined by about 20% each. The largest changes occurred in the tropics and sub-tropics rather than the high latitudes, where most of the irradiance is already diffuse. Disregarding spectral irradiance had effects that depended upon the choice of attenuation wavelength. The wavelength closest to the spectrally-resolved model, 500nm, produced lower nitrate (19% and chlorophyll (8% and higher primary production (2% than the spectral model. Phytoplankton relative abundances were very sensitive to the choice of non-spectral wavelength transmittance. The combined effects of neglecting both directional and spectral irradiance exacerbated the differences, despite using attenuation at 500nm. Global nitrate decreased 33% and chlorophyll decreased 24%. Changes in phytoplankton community structure were considerable, representing a change from chlorophytes to cyanobacteria and coccolithophores. This suggested a shift in community function, from light-limitation to nutrient limitation: lower demands for nutrients from cyanobacteria and coccolithophores favored them over the more nutrient-demanding chlorophytes. Although diatoms have the highest nutrient demands in the model, their relative
Europa: Characterization and interpretation of global spectral surface units
Nelson, M.L.; McCord, T.B.; Clark, R.N.; Johnson, T.V.; Matson, D.L.; Mosher, J.A.; Soderblom, L.A.
1986-01-01
The Voyager global multispectral mosaic of the Galilean satellite Europa (T. V. Johnson, L. A. Soderblom, J. A. Mosher, G. E. Danielson, A. F. Cook, and P. Kupferman, 1983, J. Geophys. Res. 88, 5789-5805) was analyzed to map surface units with similar optical properties (T. B. McCord, M. L. Nelson, R. N. Clark, A. Meloy, W. Harrison, T. V. Johnson, D. L. Matson, J. A. Mosher, and L. Soderblom, 1982, Bull Amer. Astron. Soc. 14, 737). Color assignments in the unit map are indicative of the spectral nature of the unit. The unit maps make it possible to infer extensions of the geologic units mapped by B. K. Lucchitta and L. A. Soderblom (1982, in Satellites of Jupiter, pp. 521-555, Univ. of Arizona Press, Tucson) beyond the region covered in the high-resolution imagery. The most striking feature in the unit maps is a strong hemispheric asymmetry. It is seen most clearly in the ultraviolet/violet albedo ratio image, because the asymmetry becomes more intense as the wavelength decreases. It appears as if the surface has been darkened, most intensely in the center of the trailing hemisphere and decreasing gradually, essentially as the cosine of the angle from the antapex of motion, to a minimum in the center of the leading hemisphere. The cosine pattern suggests that the darkening is exogenic in origin and is interpreted as evidence of alteration of the surface by ion bombardment from the Jovian magnetosphere. ?? 1986.
A kernel representation for exponential splines with global tension
Barendt, Sven; Fischer, Bernd; Modersitzki, Jan
2009-02-01
Interpolation is a key ingredient in many imaging routines. In this note, we present a thorough evaluation of an interpolation method based on exponential splines in tension. They are based on so-called tension parameters, which allow for a tuning of their properties. As it turns out, these interpolants have very many nice features, which are, however, not born out in the literature. We intend to close this gap. We present for the first time an analytic representation of their kernel which enables one to come up with a space and frequency domain analysis. It is shown that the exponential splines in tension, as a function of the tension parameter, bridging the gap between linear and cubic B-Spline interpolation. For example, with a certain tension parameter, one is able to suppress ringing artefacts in the interpolant. On the other hand, the analysis in the frequency domain shows that one derives a superior signal reconstruction quality as known from the cubic B-Spline interpolation, which, however, suffers from ringing artifacts. With the ability to offer a trade-off between opposing features of interpolation methods we advocate the use of the exponential spline in tension from a practical point of view and use the new kernel representation to qualify the trade-off.
Spectral Invariants in Rabinowitz Floer homology and Global Hamiltonian perturbations
Albers, Peter
2010-01-01
Spectral invariant were introduced in Hamiltonian Floer homology by Viterbo, Oh, and Schwarz. We extend this concept to Rabinowitz Floer homology. As an application we derive new quantitative existence results for leaf-wise intersections. The importance of spectral invariants for the presented application is that spectral invariants allow us to derive existence of critical points of the Rabinowitz action functional even in degenerate situations where the functional is not Morse.
Provenance Representation in the Global Change Information System (GCIS)
Tilmes, Curt
2012-01-01
Global climate change is a topic that has become very controversial despite strong support within the scientific community. It is common for agencies releasing information about climate change to be served with Freedom of Information Act (FOIA) requests for everything that led to that conclusion. Capturing and presenting the provenance, linking to the research papers, data sets, models, analyses, observation instruments and satellites, etc. supporting key findings has the potential to mitigate skepticism in this domain. The U.S. Global Change Research Program (USGCRP) is now coordinating the production of a National Climate Assessment (NCA) that presents our best understanding of global change. We are now developing a Global Change Information System (GCIS) that will present the content of that report and its provenance, including the scientific support for the findings of the assessment. We are using an approach that will present this information both through a human accessible web site as well as a machine readable interface for automated mining of the provenance graph. We plan to use the developing W3C PROV Data Model and Ontology for this system.
Global representations of the Heat and Schrodinger equation with singular potential
Jose A. Franco
2013-07-01
Full Text Available The n-dimensional Schrodinger equation with a singular potential $V_lambda(x=lambda |x|^{-2}$ is studied. Its solution space is studied as a global representation of $widetilde{SL(2,mathbb{R}}imes O(n$. A special subspace of solutions for which the action globalizes is constructed via nonstandard induction outside the semisimple category. The space of K-finite vectors is calculated, obtaining conditions for $lambda$ so that this space is non-empty. The direct sum of solution spaces over such admissible values of $lambda$ is studied as a representation of the (2n+1-dimensional Heisenberg group.
Global cross-calibration of Landsat spectral mixture models
de Sousa, Daniel; Small, Christopher
2016-01-01
Data continuity for the Landsat program relies on accurate cross-calibration among sensors. The Landsat 8 OLI has been shown to exhibit superior performance to the sensors on Landsats 4-7 with respect to radiometric calibration, signal to noise, and geolocation. However, improvements to the positioning of the spectral response functions on the OLI have resulted in known biases for commonly used spectral indices because the new band responses integrate absorption features differently from prev...
Global cross-calibration of Landsat spectral mixture models
Sousa, Daniel
2016-01-01
Data continuity for the Landsat program relies on accurate cross-calibration among sensors. The Landsat 8 OLI has been shown to exhibit superior performance to the sensors on Landsats 4-7 with respect to radiometric calibration, signal to noise, and geolocation. However, improvements to the positioning of the spectral response functions on the OLI have resulted in known biases for commonly used spectral indices because the new band responses integrate absorption features differently from previous Landsat sensors. The objective of this analysis is to quantify the impact of these changes on linear spectral mixture models that use imagery collected by different Landsat sensors. The 2013 underflight of Landsat 7 and 8 provides an opportunity to cross calibrate the spectral mixing spaces of the ETM+ and OLI sensors using near-simultaneous acquisitions from a wide variety of land cover types worldwide. We use 80,910,343 pairs of OLI and ETM+ spectra to characterize the OLI spectral mixing space and perform a cross-...
Carrasco-Hernandez, Roberto; Smedley, Andrew R. D.; Webb, Ann R.
2016-05-01
Two radiative transfer models are presented that simplify calculations of street canyon spectral irradiances with minimum data input requirements, allowing better assessment of urban exposures than can be provided by standard unobstructed radiation measurements alone. Fast calculations improve the computational performance of radiation models, when numerous repetitions are required in time and location. The core of the models is the calculation of the spectral diffuse-to-global ratios (DGR) from an unobstructed global spectral measurement. The models are based on, and have been tested against, outcomes of the SMARTS2 algorithm (i.e. Simple Model of the Atmospheric Radiative Transfer of Sunshine). The modelled DGRs can then be used to partition global spectral irradiance values into their direct and diffuse components for different solar zenith angles. Finally, the effects of canyon obstructions can be evaluated independently on the direct and diffuse components, which are then recombined to give the total canyon irradiance. The first model allows ozone and aerosol inputs, while the second provides a further simplification, restricted to average ozone and aerosol contents but specifically designed for faster calculations. To assess the effect of obstructions and validate the calculations, a set of experiments with simulated obstructions (simulated canyons) were performed. The greatest source of uncertainty in the simplified calculations is in the treatment of diffuse radiation. The measurement-model agreement is therefore dependent on the region of the sky obscured and ranges from <5 % at all wavelengths to 20-40 % (wavelength dependent) when diffuse sky only is visible from the canyon.
Triviño Juan C
2010-04-01
Full Text Available Abstract Background Global studies of the protein repertories of organisms are providing important information on the characteristics of the protein space. Many of these studies entail classification of the protein repertory on the basis of structure and/or sequence similarities. The situation is different for metabolism. Because there is no good way of measuring similarities between chemical reactions, there is a barrier to the development of global classifications of "metabolic space" and subsequent studies comparable to those done for protein sequences and structures. Results In this work, we propose a vectorial representation of chemical reactions, which allows them to be compared and classified. In this representation, chemical compounds, reactions and pathways may be represented in the same vectorial space. We show that the representation of chemical compounds reflects their physicochemical properties and can be used for predictive purposes. We use the vectorial representations of reactions to perform a global classification of the reactome of the model organism E. coli. Conclusions We show that this unsupervised clustering results in groups of enzymes more coherent in biological terms than equivalent groupings obtained from the EC hierarchy. This hierarchical clustering produces an optimal set of 21 groups which we analyzed for their biological meaning.
The spectral-element method, Beowulf computing, and global seismology.
Komatitsch, Dimitri; Ritsema, Jeroen; Tromp, Jeroen
2002-11-29
The propagation of seismic waves through Earth can now be modeled accurately with the recently developed spectral-element method. This method takes into account heterogeneity in Earth models, such as three-dimensional variations of seismic wave velocity, density, and crustal thickness. The method is implemented on relatively inexpensive clusters of personal computers, so-called Beowulf machines. This combination of hardware and software enables us to simulate broadband seismograms without intrinsic restrictions on the level of heterogeneity or the frequency content.
Spectral estimation of global levels of atmospheric pollutants.
Fernández-Macho, Javier
2011-10-01
Underlying levels of atmospheric pollutants, assumed to be governed by smoothing mechanisms due to atmospheric dispersion, can be estimated from global emissions source databases on greenhouse gases and ozone-depleting compounds. However, spatial data may be contaminated with noise or even missing or zero-valued at many locations. Therefore, a problem that arises is how to extract the underlying smooth levels. This paper sets out a structural spatial model that assumes data evolve across a global grid constrained by second-order smoothing restrictions. The frequency-domain approach is particularly suitable for global datasets, reduces the computational burden associated with two-dimensional models and avoids cumbersome zero-inflated skewed distributions. Confidence intervals of the underlying levels are also obtained. An application to the estimation of global levels of atmospheric pollutants from anthropogenic emissions illustrates the technique which may also be useful in the analysis of other environmental datasets of similar characteristics.
Ceppi, Paulo [Department of Meteorology, University of Reading, Reading UK; Brient, Florent [Centre National de Recherches M?t?orologiques, M?t?o-France/CNRS, Toulouse France; Zelinka, Mark D. [Cloud Processes Research Group, Lawrence Livermore National Laboratory, Livermore CA USA; Hartmann, Dennis L. [Department of Atmospheric Sciences, University of Washington, Seattle WA USA
2017-05-11
Cloud feedback—the change in top-of-atmosphere radiative flux resulting from the cloud response to warming—constitutes by far the largest source of uncertainty in the climate response to CO2 forcing simulated by global climate models (GCMs). We review the main mechanisms for cloud feedbacks, and discuss their representation in climate models and the sources of intermodel spread. Global-mean cloud feedback in GCMs results from three main effects: (1) rising free-tropospheric clouds (a positive longwave effect); (2) decreasing tropical low cloud amount (a positive shortwave [SW] effect); (3) increasing high-latitude low cloud optical depth (a negative SW effect). These cloud responses simulated by GCMs are qualitatively supported by theory, high-resolution modeling, and observations. Rising high clouds are consistent with the fixed anvil temperature (FAT) hypothesis, whereby enhanced upper-tropospheric radiative cooling causes anvil cloud tops to remain at a nearly fixed temperature as the atmosphere warms. Tropical low cloud amount decreases are driven by a delicate balance between the effects of vertical turbulent fluxes, radiative cooling, large-scale subsidence, and lower-tropospheric stability on the boundary-layer moisture budget. High-latitude low cloud optical depth increases are dominated by phase changes in mixed-phase clouds. The causes of intermodel spread in cloud feedback are discussed, focusing particularly on the role of unresolved parameterized processes such as cloud microphysics, turbulence, and convection.
Global representation of tropical cyclone-induced short-term ocean thermal changes using Argo data
Cheng, L.; J. Zhu; R. L. Sriver
2015-01-01
Argo floats are used to examine tropical cyclone (TC) induced ocean thermal changes on the global scale by comparing temperature profiles before and after TC passage. We present a footprint method that analyzes cross-track thermal responses along all storm tracks during the period 2004–2012. We combine the results into composite representations of the vertical structure of the average thermal response for two different categories: tropical storms/tropical depressions (TS/TD)...
Friedman, Alinda; Montello, Daniel R
2006-03-01
The authors examined whether absolute and relative judgments about global-scale locations and distances were generated from common representations. At the end of a 10-week class on the regional geography of the United States, participants estimated the latitudes of 16 North American cities and all possible pairwise distances between them. Although participants were relative experts, their latitude estimates revealed the presence of psychologically based regions with large gaps between them and a tendency to stretch North America southward toward the equator. The distance estimates revealed the same properties in the representation recovered via multidimensional scaling. Though the aggregated within- and between-regions distance estimates were fitted by Stevens's law (S. S. Stevens, 1957), this was an averaging artifact: The appropriateness of a power function to describe distance estimates depended on the regional membership of the cities. The authors conclude that plausible reasoning strategies, combined with regionalized representations and beliefs about the location of these relative to global landmarks, underlie global-scale latitude and distance judgments.
How the public engages with global warming: A social representations approach.
Smith, Nicholas; Joffe, Helene
2013-01-01
The present study utilises social representations theory to explore common sense conceptualisations of global warming risk using an in-depth, qualitative methodology. Fifty-six members of a British, London-based 2008 public were initially asked to draw or write four spontaneous "first thoughts or feelings" about global warming. These were then explored via an open-ended, exploratory interview. The analysis revealed that first thoughts, either drawn or written, often mirrored the images used by the British press to depict global warming visually. Thus in terms of media framings, it was their visual rather than their textual content that was spontaneously available for their audiences. Furthermore, an in-depth exploration of interview data revealed that global warming was structured around three themata: self/other, natural/unnatural and certainty/uncertainty, reflecting the complex and often contradictory nature of common sense thinking in relation to risk issues.
Fukushima, Kenji
2014-01-01
We develop a formalism to describe the particle production out of equilibrium in terms of dynamical spectral functions, i.e. Wigner transformed Pauli-Jordan's and Hadamard's functions. We take an explicit example of a spatially homogeneous scalar theory under pulsed electric fields and investigate the time evolution of the spectral functions. In the out-state we find an oscillatory peak in Hadamard's function as a result of the mixing between positive- and negative-energy waves. The strength of this peak is of the linear order of the Bogoliubov mixing coefficient, whereas the peak corresponding to the Schwinger mechanism is of the quadratic order. Between the in- and the out-states we observe a continuous flow of the spectral peaks together with two transient oscillatory peaks. We also discuss the medium effect at finite temperature and density. We emphasise that the entire structure of the spectral functions conveys rich information on real-time dynamics including the particle production.
Finster, Felix
2015-01-01
A family of spectral decompositions of the spin-weighted spheroidal wave operator is constructed for complex aspherical parameters with bounded imaginary part. As the operator is not symmetric, its spectrum is complex and Jordan chains may appear. We prove uniform upper bounds for the length of the Jordan chains and the norms of the idempotent operators mapping onto the invariant subspaces. The completeness of the spectral decomposition is proven.
Rapisarda, P.; Trentelman, H.L.; Minh, H.B.
2013-01-01
We illustrate an algorithm that starting from the image representation of a strictly bounded-real system computes a minimal balanced state variable, from which a minimal balanced state realization is readily obtained. The algorithm stems from an iterative procedure to compute a storage function, bas
Spectral analysis of generators of representations of the group U(3)
Rozenblyum, A.V.
1988-06-01
In the space of an irreducible unitary representation of the group U(3) a basis consisting of eigenvectors of the generator of the Wigner d functions is constructed. The eigenvectors of the generator are described in terms of a certain class of orthogonal polynomials of two discrete variables; these generalize the Kravchuk polynomials. An expansion of the d functions with respect to exponential functions is obtained.
A Global Analytical Representation of the Potential Energy Surface of the FHF(-) Anion.
Cornaton, Yann; Marquardt, Roberto
2016-08-04
A global analytical representation of the potential energy hypersurface of the lowest adiabatic electronic state of the FHF(-) anion is derived from ab initio calculations at the coupled cluster level of theory with full single and double and perturbative triple excitations using explicitly correlated atomic basis functions. The new compact function of interatomic distances combines covalent short-range and long-range electrostatic interaction forms and assesses accurately both the lowest reaction channels between the F(-) and HF fragments, with reaction enthalpies to within 1 kJ mol(-1), as well as vibrational terms to within 1.5 cm(-1) deviation from experimental values.
Brunner, S.; Vaclavik, J. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1997-03-01
Considering the spectral problem of microinstabilities in a curved system, methods for solving the global gyrokinetic equation are presented for the simple case of a cylindrical plasma. They prove to be efficient for computing the full unstable spectrum of ITG-type modes and have shown to be applicable to the two-dimensional integral equation of tokamak configurations. (author) 5 figs., 22 refs.
Xu, Jian; Fan, Engui
2017-02-01
In a previous work, we show that the solution of the initial-boundary value problem for the two-component nonlinear Schrödinger equation on the finite interval can be expressed in terms of the solution of a 3 ×3 Riemann-Hilbert problem. The relevant jump matrices are explicitly given in terms of the three matrix-value spectral functions s(k), S(k), and SL(k), which in turn are defined in terms of the initial values, boundary values at x = 0, and boundary values at x = L, respectively. However, for a well-posed problem, only part of the boundary values can be prescribed, the remaining boundary data cannot be independently specified but are determined by the so-called global relation. Here, we use a Gelfand-Levitan-Marchenko representation to derive an expression for the generalized Dirichlet-to-Neumann map to characterize the unknown boundary values in physical domain, which is different from the approach, in fact it analyzed the global relation in spectral domain, used in the previous work. And, we can show that these two representations are equivalent.
STOCHASTIC HARMONIC FUNCTION AND SPECTRAL REPRESENTATIONS%随机过程的随机谐和函数表达
陈建兵; 李杰
2011-01-01
Stochastic harmonic functions and their properties are studied. In the paper, it is firstly proved that as the distributions of the random frequencies are consistent with the target power spectral density function,the power spectral density of the stochastic harmonic process is identical to the target power spectral density.Further, it is proved that the stochastic harmonic process is asymptotically Gaussian. The rate of approaching Gaussian distribution is discussed by adopting Pearson distribution to describe the one-dimensional distribution of the stochastic harmonic process. Compared to existing representations of stochastic process, very few stochastic harmonic components can capture the exact target power spectral density. This greatly reduces the number of the random variables and thus eases the difficulty of stochastic dynamics. Finally, linear and nonlinear responses of a multi-degree-of-freedom system subjected to random ground motions are carried out to exemplify the effectiveness and advantages of the stochastic harmonic representations.%研究了随机过程的随机谐和函数表达及其性质.首先证明了当随机谐和函数的频率分布与目标功率谱密度函数形状一致时,随机谐和函数过程的功率谱密度函数等于目标功率谱密度函数.进而,证明了随机谐和函数过程的渐进正态性,讨论了趋向正态分布的速率,并采用Pearson分布研究了一维概率密度函数的性质.与已有的随机过程谱表达方式相比,采用随机谐和函数表达,仅需要很少的展开项数,即可获得精确的目标功率谱密度函数,从而大大降低了与之相关的随机动力系统分析的难度.最后,以多自由度体系的线性和非线性响应分析为例,验证了随机谐和函数模型的有效性和优越性.
Demers, C.M.H.; Potvin, A.; Dubois, M.C. [Laval Univ., Quebec City, PQ (Canada). GRAP Groupe de recherche en ambiances physiques; Laval Univ., Quebec City, PQ (Canada). School of Architecture
2009-07-01
This paper presented a new graphical tool for architects. The Physical Ambience Rose (PAR) provides a record of the occupants' global environmental satisfaction and adaptability. A PAR representation takes into account all senses commonly at play in spatial perception, namely thermal, visual, acoustical and olfactory. Each of these 4 environmental stimuli can be qualified by the user to provide a representation of the perceived environmental satisfaction of a building. PAR can be generated for either individuals or groups of occupants and their interaction with the building. The satisfaction scale therefore varies from very pleasant, to neutral, and intolerable according to the level of quality, scale and duration of the thermal, luminous, visual and olfactory stimuli. The paper presents the methodology that led to the development of this representation tool. The tool was used in a post-occupancy evaluation of a bioclimatic administrative building in Montreal. The overall environmental conditions at the building were highly praised, ranging from neutral to very pleasant. 7 refs., 4 tabs., 6 figs.
Representation of the Antarctic circumpolar vortex mixing barrier in a Global Climate Model
Cameron, Chris; Conway, Jono; Bodeker, Greg; Renwick, James
2017-04-01
Dynamical processes that occur in the stratosphere between 15 and 50 km above Earth's surface can affect circulation in the troposphere and have an impact on weather and climate. The Antarctic Circumpolar Vortex (ACV) forms each winter and spring as a zone of strong stratospheric westerly winds surrounding Antarctica. The ACV presents a barrier to transport of air masses between middle and high-latitudes, and contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for ozone loss. The processes controlling the permeability of the ACV, and how they are likely to respond to a changing climate and a recovering ozone hole, have not been well studied, and as a result are not well simulated in Global Climate Models, particularly in terms of sub-grid scale turbulent diffusion which is parameterized in the models. The UK Met Office Unified Model (UM) is used to examine vortex permeability using both the "New Dynamics" and the upgraded "ENDGame" dynamical cores. Results are compared against reanalysis representations of vortex permeability using the MERRA-2 and ERA-Interim reanalyses data sets, which have been shown to have superior performance in the Southern Hemisphere stratosphere when compared against NCEP-CFSR, and MERRA reanalyses. Results are expected to lead to improved representation of ACV transport process in Global Climate Models and subsequent improvements in climate modelling.
Prospects for improving the representation of coastal and shelf seas in global ocean models
Holt, Jason; Hyder, Patrick; Ashworth, Mike; Harle, James; Hewitt, Helene T.; Liu, Hedong; New, Adrian L.; Pickles, Stephen; Porter, Andrew; Popova, Ekaterina; Icarus Allen, J.; Siddorn, John; Wood, Richard
2017-02-01
Accurately representing coastal and shelf seas in global ocean models represents one of the grand challenges of Earth system science. They are regions of immense societal importance through the goods and services they provide, hazards they pose and their role in global-scale processes and cycles, e.g. carbon fluxes and dense water formation. However, they are poorly represented in the current generation of global ocean models. In this contribution, we aim to briefly characterise the problem, and then to identify the important physical processes, and their scales, needed to address this issue in the context of the options available to resolve these scales globally and the evolving computational landscape.We find barotropic and topographic scales are well resolved by the current state-of-the-art model resolutions, e.g. nominal 1/12°, and still reasonably well resolved at 1/4°; here, the focus is on process representation. We identify tides, vertical coordinates, river inflows and mixing schemes as four areas where modelling approaches can readily be transferred from regional to global modelling with substantial benefit. In terms of finer-scale processes, we find that a 1/12° global model resolves the first baroclinic Rossby radius for only ˜ 8 % of regions state of the art.We quantify the benefit of improved resolution and process representation using 1/12° global- and basin-scale northern North Atlantic nucleus for a European model of the ocean (NEMO) simulations; the latter includes tides and a k-ɛ vertical mixing scheme. These are compared with global stratification observations and 19 models from CMIP5. In terms of correlation and basin-wide rms error, the high-resolution models outperform all these CMIP5 models. The model with tides shows improved seasonal cycles compared to the high-resolution model without tides. The benefits of resolution are particularly apparent in eastern boundary upwelling zones.To explore the balance between the size of a globally
Energy Content & Spectral Energy Representation of Wave Propagation in a Granular Chain
Shrivastava, Rohit; Luding, Stefan
2017-04-01
A mechanical wave is propagation of vibration with transfer of energy and momentum. Studying the energy as well as spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting) or non-destructive testing for the study of internal structure of solids. Wave propagation through granular materials is often accompanied by energy attenuation which is quantified by Quality factor and this parameter has often been used to characterize material properties, hence, determining the Quality factor (energy attenuation parameter) can also help in determining the properties of the material [3], studied experimentally in [2]. The study of Energy content (Kinetic, Potential and Total Energy) of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain can assist in understanding the energy attenuation due to disorder as a function of propagation distance. The spectral analysis of the energy signal can assist in understanding dispersion as well as attenuation due to scattering in different frequencies (scattering attenuation). The selection of one-dimensional granular chain also helps in studying only the P-wave attributes of the wave and removing the influence of shear or rotational waves. Granular chains with different mass distributions have been studied, by randomly selecting masses from normal, binary and uniform distributions and the standard deviation of the distribution is considered as the disorder parameter, higher standard deviation means higher disorder and lower standard deviation means lower disorder [1]. For obtaining macroscopic/continuum properties, ensemble averaging has been invoked. Instead of analyzing deformation-, velocity- or stress
Darup, Moritz Schulze; Mross, Stefan; Mönnigmann, Martin
2012-01-01
We compare two established and a new method for the calculation of spectral bounds for Hessian matrices on hyperrectangles by applying them to a large collection of 1522 objective and constraint functions extracted from benchmark global optimization problems. Both the tightness of the spectral bounds and the computational effort are assessed. Specifically, we compare eigenvalue bounds obtained with the interval variant of Gershgorin's circle criterion [2,6], Hertz and Rohn's [7,16] method for tight bounds of interval matrices, and a recently proposed Hessian matrix eigenvalue arithmetic [12], which deliberately avoids the computation of interval Hessians.
Matrix Representation of Global Power Energy Internet Topology%全球电力能源互联网拓扑的矩阵表述
苗新; 张东霞; 宋璇坤
2016-01-01
In order to solve the problem of network topology connectivity representation of the global power energy internet,by employing the network connection matrix analysis method,the earth”s continents,poles and their interconnections are abstracted as eight nodes and connection channels,which form a connected network and the corresponding connection matrix. Typical power system sectionalizing states and single/bidirectional connection types are selected.Then the spectral norms and spectral condition numbers of the corresponding connection matrixes are calculated and analyzed.The ill-conditioned connection matrixes are improved.The results show that the spectral norm and the spectral condition number can be used as the representation parameters of connection matrixes of the global power energy internet topology.The spectral norm can be used to characterize the complexity of the network topology connectivity.The stability or sensitivity of the corresponding system can be characterized by the spectral condition number.Analyzing system stability using the network connection matrix can serve as an analytical tool for the interconnection of bulk power networks.%为了解决全球电力能源互联网的连通性表述问题，应用网络连通矩阵分析方法，将全球各洲、两极及其互联抽象为8个节点和连接通道，组成连通网络及相应连通矩阵。选取出典型的系统解列状态及单/双向连接类型，计算分析相应连通矩阵的谱范数和谱条件数，改善其中的病态连通矩阵。结果表明，谱范数和谱条件数可以作为全球电力能源互联网拓扑连通矩阵的表述参数。谱范数可以表征其对应网络拓扑连通性的复杂程度。谱条件数可以表征其对应系统的稳定性或者敏感度。利用网络连通矩阵分析稳定性，可以作为大电网互联的一种分析手段。
Yang, Zhiguo; Rong, Zhijian; Wang, Bo; Zhang, Baile
2015-01-01
In this paper, we present an efficient spectral-element method (SEM) for solving general two-dimensional Helmholtz equations in anisotropic media, with particular applications in accurate simulation of polygonal invisibility cloaks, concentrators and circular rotators arisen from the field of transformation electromagnetics (TE). In practice, we adopt a transparent boundary condition (TBC) characterized by the Dirichlet-to-Neumann (DtN) map to reduce wave propagation in an unbounded domain to a bounded domain. We then introduce a semi-analytic technique to integrate the global TBC with local curvilinear elements seamlessly, which is accomplished by using a novel elemental mapping and analytic formulas for evaluating global Fourier coefficients on spectral-element grids exactly. From the perspective of TE, an invisibility cloak is devised by a singular coordinate transformation of Maxwell's equations that leads to anisotropic materials coating the cloaked region to render any object inside invisible to observe...
Robust Spectral Detection of Global Structures in the Data by Learning a Regularization
Zhang, Pan
2016-01-01
Spectral methods are popular in detecting global structures in the given data that can be represented as a matrix. However when the data matrix is sparse or noisy, classic spectral methods usually fail to work, due to localization of eigenvectors (or singular vectors) induced by the sparsity or noise. In this work, we propose a general method to solve the localization problem by learning a regularization matrix from the localized eigenvectors. Using matrix perturbation analysis, we demonstrate that the learned regularizations suppress down the eigenvalues associated with localized eigenvectors and enable us to recover the informative eigenvectors representing the global structure. We show applications of our method in several inference problems: community detection in networks, clustering from pairwise similarities, rank estimation and matrix completion problems. Using extensive experiments, we illustrate that our method solves the localization problem and works down to the theoretical detectability limits in...
Clearness index estimation for spectral composition of direct and global solar radiations
Rahoma, U.A. [National Research Inst. of Astronomy and Geophysics, Helwan, Cairo (Egypt)
2001-07-01
Measurements of cloudless direct, global, and diffuse solar radiations, taken over a one year period at Helwan, are analyzed in terms of global index and diffuse fraction for clear-sky conditions. The dependence of the diffuse fraction on the global index was represented by a polynomial. These results support the use of routine instantaneous surface meteorological data to calculate global and diffuse radiations on a horizontal surface in the absence of any other radiation measurements. The spectral composition of the global solar-radiation was found to be 4.3% UV band, 32.5% band range 250-630 nm, 13.74% red band, 52.75% infrared band and 29.7% diffuse solar-radiation. The spectral distribution of direct solar-radiation ratio of the extraterrestrial solar radiation was found to be: 0.69% green and blue band, 47.5% yellow and orange band 45% red band, and 52.7% infra-red band. (author)
Wissel, S.
2006-10-15
In this thesis we investigate thermal in-medium modifications of various mesonic correlation functions by lattice simulations of Quantum Chromodynamics for light valence quark masses and vanishing chemical potential. Mesonic properties are typically extracted from spatial correlation functions. The results presented are based on quenched gauge field configurations generated with the standard Wilson plaquette gauge action. Concerning the fermionic part of the action, we use the non-perturbative O(a) improved Sheikholeslami-Wohlert as well as the truncated hypercube perfect action. Furthermore we utilize the maximum entropy method in order to determine physically relevant pole masses and to investigate thermal modifications of physical states and possible lattice artefacts in the interacting case. The analyses of pole and screening masses, dispersion relations, wave functions, decay constants and spectral functions essentially yield no significant modifications of the zero-temperature behavior up to 0.55 T{sub c}. Close to the phase transition in-medium effects seem to appear, which lead inter alia to significant differences between pole and screening masses. The decay constants are in good agreement with the experimental values. We have simulated above T{sub c} at nearly zero quark masses. At 1.24 T{sub c}, the occurrence of topological effects, a sign for the presence of a still broken U(1){sub A} symmetry, prevent a more thorough analyses close to the phase transition. A complete continuum and infinite volume extrapolation of screening masses, guided by free lattice effective masses is done. It shows that the presence of collective phenomena at 1.5 and 3 T{sub c} cannot be explained by pure lattice artefacts. Unlike the vector meson the pion is far from being considered an unbound state. (orig.)
The automatic solution of partial differential equations using a global spectral method
Townsend, Alex; Olver, Sheehan
2015-10-01
A spectral method for solving linear partial differential equations (PDEs) with variable coefficients and general boundary conditions defined on rectangular domains is described, based on separable representations of partial differential operators and the one-dimensional ultraspherical spectral method. If a partial differential operator is of splitting rank 2, such as the operator associated with Poisson or Helmholtz, the corresponding PDE is solved via a generalized Sylvester matrix equation, and a bivariate polynomial approximation of the solution of degree (nx ,ny) is computed in O ((nxny) 3 / 2) operations. Partial differential operators of splitting rank ≥3 are solved via a linear system involving a block-banded matrix in O (min (nx3 ny ,nx ny3)) operations. Numerical examples demonstrate the applicability of our 2D spectral method to a broad class of PDEs, which includes elliptic and dispersive time-evolution equations. The resulting PDE solver is written in MATLAB and is publicly available as part of CHEBFUN. It can resolve solutions requiring over a million degrees of freedom in under 60 seconds. An experimental implementation in the JULIA language can currently perform the same solve in 10 seconds.
Representation of global and national conservation priorities by Colombia's Protected Area Network.
German Forero-Medina
Full Text Available BACKGROUND: How do national-level actions overlap with global priorities for conservation? Answering this question is especially important in countries with high and unique biological diversity like Colombia. Global biodiversity schemes provide conservation guidance at a large scale, while national governments gazette land for protection based on a combination of criteria at regional or local scales. Information on how a protected area network represents global and national conservation priorities is crucial for finding gaps in coverage and for future expansion of the system. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the agreement of Colombia's protected area network with global conservation priorities, and the extent to which the network reflects the country's biomes, species richness, and common environmental and physical conditions. We used this information to identify priority biomes for conservation. We find the dominant strategy in Colombia has been a proactive one, allocating the highest proportion of protected land on intact, difficult to access and species rich areas like the Amazon. Threatened and unique areas are disproportionately absent from Colombia's protected lands. We highlight six biomes in Colombia as conservation priorities that should be considered in any future expansion of Colombia's protected area network. Two of these biomes have less than 3% of their area protected and more than 70% of their area transformed for human use. One has less than 3% protected and high numbers of threatened vertebrates. Three biomes fall in both categories. CONCLUSIONS: Expansion of Colombia's Protected Area Network should consider the current representativeness of the network. We indicate six priority biomes that can contribute to improving the representation of threatened species and biomes in Colombia.
Mehmeti, Felix Ali; Régnier, Virginie
2010-01-01
We consider the Klein-Gordon equation on a star-shaped network composed of n half-axes connected at their origins. We add a potential which is constant but different on each branch. The corresponding spatial operator is self-adjoint and we state explicit expressions for its resolvent and its resolution of the identity in terms of generalized eigenfunctions. This leads to a generalized Fourier type inversion formula in terms of an expansion in generalized eigenfunctions. Further we prove the surjectivity of the associated transformation, thus showing that it is in fact a spectral representation. The characteristics of the problem are marked by the non-manifold character of the star-shaped domain. Therefore the approach via the Sturm-Liouville theory for systems is not well-suited. The considerable effort to construct explicit formulas involving the tunnel effect generalized eigenfunctions is justified for example by the perspective to study the influence of tunnel effect on the L-infinity-time decay.
Mautz, R.; Ping, J.; Heki, K.; Schaffrin, B.; Shum, C.; Potts, L.
2005-05-01
Wavelet expansion has been demonstrated to be suitable for the representation of spatial functions. Here we propose the so-called B-spline wavelets to represent spatial time-series of GPS-derived global ionosphere maps (GIMs) of the vertical total electron content (TEC) from the Earth’s surface to the mean altitudes of GPS satellites, over Japan. The scalar-valued B-spline wavelets can be defined in a two-dimensional, but not necessarily planar, domain. Generated by a sequence of knots, different degrees of B-splines can be implemented: degree 1 represents the Haar wavelet; degree 2, the linear B-spline wavelet, or degree 4, the cubic B-spline wavelet. A non-uniform version of these wavelets allows us to handle data on a bounded domain without any edge effects. B-splines are easily extended with great computational efficiency to domains of arbitrary dimensions, while preserving their properties. This generalization employs tensor products of B-splines, defined as linear superposition of products of univariate B-splines in different directions. The data and model may be identical at the locations of the data points if the number of wavelet coefficients is equal to the number of grid points. In addition, data compression is made efficient by eliminating the wavelet coefficients with negligible magnitudes, thereby reducing the observational noise. We applied the developed methodology to the representation of the spatial and temporal variations of GIM from an extremely dense GPS network, the GPS Earth Observation Network (GEONET) in Japan. Since the sampling of the TEC is registered regularly in time, we use a two-dimensional B-spline wavelet representation in space and a one-dimensional spline interpolation in time. Over the Japan region, the B-spline wavelet method can overcome the problem of bias for the spherical harmonic model at the boundary, caused by the non-compact support. The hierarchical decomposition not only allows an inexpensive calculation, but also
Representation of Dissolved Organic Carbon in the JULES Dynamic Global Vegetation Model
Nakhavali, Mahdi; Friedlingstein, Pierre; Guenet, Bertrand; Ciais, Philip
2017-04-01
Current global models of the carbon cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, hence not considering lateral transport of carbon from the continent to the oceans. This also means that such models implicitly consider that all the CO2 which is not respired to the atmosphere is stored on land, hence overestimating the land sink of carbon. Moving toward a boundless carbon cycle that is integrating the whole continuum from land to ocean to atmosphere is needed in order to better understand Earth's carbon cycle and to make more reliable projection of its future. Here we present an original representation of Dissolved Organic Carbon (DOC) processes in the Joint UK Land Environment Simulator (JULES). The standard version of JULES represent energy, water and carbon cycles and exchanges with the atmosphere, but only account for water run-off, not including export of carbon from terrestrial ecosystems to the aquatic environments. The aim of the project is to include in JULES a representation of DOC production in terrestrial soils, due to incomplete decomposition of organic matter, its decomposition to the atmosphere, and its export to the river network by leaching. In new developed version of JULES (JULES-DOCM), DOC pools, based on their decomposition rate, are classified into labile and recalcitrant within 3 meters of soil. Based on turnover rate, DOC coming from plant material pools and microbial biomass is directed to labile pool, while DOC from humus is directed to recalcitrant pool. Both of these pools have free (dissolved) and locked (adsorbed) form where just the free pool is subjected to decomposition and leaching. DOC production and decomposition are controlled by rate modifiers (moisture, temperature, vegetation fraction and decomposition rate) at each soil layer. Decomposed DOC is released to the atmosphere following a fixed carbon use efficiency. Leaching accounts for both surface (runoff) and
A Better Representation of European Croplands into a Global Biosphere Model
Gervois, S.; de Noblet, N.; Viovy, N.; Ciais, P.; Brisson, N.; Seguin, B.
2002-12-01
Croplands cover a quarter of Europe's surface (about an hundred million hectares), their impact on carbon and water fluxes must therefore be estimated. Global biosphere models such as ORCHIDEE (http://www.ipsl.jussieu.fr/~ssipsl/) were conceived to simulate natural ecosystems only, so croplands are often described as grasslands. Not only cropland productivity depends on climate and soil conditions but also on irrigations, fertilisers impact, date of sowing... In addition crop species are usually selected genetically to shorten and accelerate their growth. Agronomic models such as STICS (Brisson et al. 1998) give a more realistic picture of croplands as they are especially designed to account for this human forcing. On the other hand they can be used at the local scale only. First we evaluate the ability of the two models to reproduce the seasonal behaviour the leaf area index (LAI), the aerial biomass, and the exchanges of water vapour and CO2 with the atmosphere. For that we compare the model outputs with measurements performed at five sites that are representative of most common European crops (wheat, corn, soybean). As expected the agronomic STICS better behaves than the generic model ORCHIDEE in representing the seasonal cycle of the above variables. In order to get a realistic representation of croplands areas at the regional scale, we decided to couple ORCHIDEE with STICS. First we present the main steps of the coupling procedure. The principle consists in forcing ORCHIDEE with five more realistic outputs of STICS: LAI, date of harvest, nitrogen stress, root profile, and vegetation height. On the other hand, ORCHIDEE computes its own carbon and water balance. The allocation scheme was also modified in ORCHIDEE in order to conserve the coherence between LAI and leaf biomass, and we added a harvest module into ORCHIDEE. The coupled model was validated against carbon and water fluxes observed respectively at two fields (wheat and corn) in the US. We also
Fast and Parallel Spectral Transform Algorithms for Global Shallow Water Models
Jakob, Ruediger
1993-01-01
This dissertation examines spectral transform algorithms for the solution of the shallow water equations on the sphere and studies their implementation and performance on shared memory vector multiprocessors. Beginning with the standard spectral transform algorithm in vorticity divergence form and its implementation in the Fortran based parallel programming language Force, two modifications are researched. First, the transforms and matrices associated with the meridional derivatives of the associated Legendre functions are replaced by corresponding operations with the spherical harmonic coefficients. Second, based on the fast Fourier transform and the fast multipole method, a lower complexity algorithm is derived that uses fast transformations between Legendre and interior Fourier nodes, fast surface spherical truncation and a fast spherical Helmholtz solver. The first modification is fully implemented, and comparative performance data are obtained for varying resolution and number of processes, showing a significant storage saving and slightly reduced execution time on a Cray Y -MP 8/864. The important performance parameters for the spectral transform algorithm and its implementation on vector multiprocessors are determined and validated with the measured performance data. The second modification is described at the algorithmic level, but only the novel fast surface spherical truncation algorithm is implemented. This new multipole algorithm has lower complexity than the standard algorithm, and requires asymptotically only order N ^2log N operations per time step for a grid with order N^2 points. Because the global shallow water equations are similar to the horizontal dynamical component of general circulation models, the results can be applied to spectral transform numerical weather prediction and climate models. In general, the derived algorithms may speed up the solution of time dependent partial differential equations in spherical geometry. A performance model
A global low order spectral model designed for climate sensitivity studies
Hanna, A. F.; Stevens, D. E.
1984-01-01
A two level, global, spectral model using pressure as a vertical coordinate is developed. The system of equations describing the model is nonlinear and quasi-geostrophic. A moisture budget is calculated in the lower layer only with moist convective adjustment between the two layers. The mechanical forcing of topography is introduced as a lower boundary vertical velocity. Solar forcing is specified assuming a daily mean zenith angle. On land and sea ice surfaces a steady state thermal energy equation is solved to calculate the surface temperature. Over the oceans the sea surface temperatures are prescribed from the climatological average of January. The model is integrated to simulate the January climate.
Israel, F P; Raban, D; Reach, W T; Bot, C; Oonk, J B R; Ysard, N; Bernard, J P
2010-01-01
In order to reconstruct the global SEDs of the Magellanic Clouds over eight decades in spectral range, we combined literature flux densities representing the entire LMC and SMC respectively, and complemented these with maps extracted from the WMAP and COBE databases covering the missing the 23--90 GHz (13--3.2 mm) and the poorly sampled 1.25--250 THz (240--1.25 micron). We have discovered a pronounced excess of emission from both Magellanic Clouds, but especially the SMC, at millimeter and sub-millimeter wavelengths. We also determined accurate thermal radio fluxes and very low global extinctions for both LMC and SMC. Possible explanations are briefly considered but as long as the nature of the excess emission is unknown, the total dust masses and gas-to-dust ratios of the Magellanic Clouds cannot reliably be determined.
Brunner, S. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1997-08-01
Ion temperature gradient (ITG)-related instabilities are studied in tokamak-like plasmas with the help of a new global eigenvalue code. Ions are modelled in the frame of gyrokinetic theory so that finite Larmor radius effects of these particles are retained to all orders. Non-adiabatic trapped electron dynamics is taken into account through the bounce-averaged drift kinetic equation. Assuming electrostatic perturbations, the system is closed with the quasineutrality relation. Practical methods are presented which make this global approach feasible. These include a non-standard wave decomposition compatible with the curved geometry as well as adapting an efficient root finding algorithm for computing the unstable spectrum. These techniques are applied to a low pressure configuration given by a large aspect ratio torus with circular, concentric magnetic surfaces. Simulations from a linear, time evolution, particle in cell code provide a useful benchmark. Comparisons with local ballooning calculations for different parameter scans enable further validation while illustrating the limits of that representation at low toroidal wave numbers or for non-interchange-like instabilities. The stabilizing effect of negative magnetic shear is also considered, in which case the global results show not only an attenuation of the growth rate but also a reduction of the radial extent induced by a transition from the toroidal- to the slab-ITG mode. Contributions of trapped electrons to the ITG instability as well as the possible coupling to the trapped electron mode are clearly brought to the fore. (author) figs., tabs., 69 refs.
Fereidouni, F.; Bader, A.N.; Gerritsen, H.C.
2012-01-01
A new global analysis algorithm to analyse (hyper-) spectral images is presented. It is based on the phasor representation that has been demonstrated to be very powerful for the analysis of lifetime imaging data. In spectral phasor analysis the fluorescence spectrum of each pixel in the image is Fou
Fast Computation of Global Sensitivity Kernel Database Based on Spectral-Element Simulations
Sales de Andrade, Elliott; Liu, Qinya
2017-07-01
Finite-frequency sensitivity kernels, a theoretical improvement from simple infinitely thin ray paths, have been used extensively in recent global and regional tomographic inversions. These sensitivity kernels provide more consistent and accurate interpretation of a growing number of broadband measurements, and are critical in mapping 3D heterogeneous structures of the mantle. Based on Born approximation, the calculation of sensitivity kernels requires the interaction of the forward wavefield and an adjoint wavefield generated by placing adjoint sources at stations. Both fields can be obtained accurately through numerical simulations of seismic wave propagation, particularly important for kernels of phases that cannot be sufficiently described by ray theory (such as core-diffracted waves). However, the total number of forward and adjoint numerical simulations required to build kernels for individual source-receiver pairs and to form the design matrix for classical tomography is computationally unaffordable. In this paper, we take advantage of the symmetry of 1D reference models, perform moment tensor forward and point force adjoint spectral-element simulations, and save six-component strain fields only on the equatorial plane based on the open-source spectral-element simulation package, SPECFEM3D_GLOBE. Sensitivity kernels for seismic phases at any epicentral distance can be efficiently computed by combining forward and adjoint strain wavefields from the saved strain field database, which significantly reduces both the number of simulations and the amount of storage required for global tomographic problems. Based on this technique, we compute traveltime, amplitude and/or boundary kernels of isotropic and radially anisotropic elastic parameters for various (P, S, P_{diff}, S_{diff}, depth, surface-reflected, surface wave, S 660 S boundary, etc.) phases for 1D ak135 model, in preparation for future global tomographic inversions.
Uncertainty analysis in 3D global models: Aerosol representation in MOZART-4
Gasore, J.; Prinn, R. G.
2012-12-01
The Probabilistic Collocation Method (PCM) has been proven to be an efficient general method of uncertainty analysis in atmospheric models (Tatang et al 1997, Cohen&Prinn 2011). However, its application has been mainly limited to urban- and regional-scale models and chemical source-sink models, because of the drastic increase in computational cost when the dimension of uncertain parameters increases. Moreover, the high-dimensional output of global models has to be reduced to allow a computationally reasonable number of polynomials to be generated. This dimensional reduction has been mainly achieved by grouping the model grids into a few regions based on prior knowledge and expectations; urban versus rural for instance. As the model output is used to estimate the coefficients of the polynomial chaos expansion (PCE), the arbitrariness in the regional aggregation can generate problems in estimating uncertainties. To address these issues in a complex model, we apply the probabilistic collocation method of uncertainty analysis to the aerosol representation in MOZART-4, which is a 3D global chemical transport model (Emmons et al., 2010). Thereafter, we deterministically delineate the model output surface into regions of homogeneous response using the method of Principal Component Analysis. This allows the quantification of the uncertainty associated with the dimensional reduction. Because only a bulk mass is calculated online in Mozart-4, a lognormal number distribution is assumed with a priori fixed scale and location parameters, to calculate the surface area for heterogeneous reactions involving tropospheric oxidants. We have applied the PCM to the six parameters of the lognormal number distributions of Black Carbon, Organic Carbon and Sulfate. We have carried out a Monte-Carlo sampling from the probability density functions of the six uncertain parameters, using the reduced PCE model. The global mean concentration of major tropospheric oxidants did not show a
Analysis of global water vapour trends from satellite measurements in the visible spectral range
S. Mieruch
2008-02-01
Full Text Available Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data on MetOp.
Using linear and non-linear methods from time series analysis and standard statistics the trends of H_{2}O columns and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes from −5% per year to +5% per year. These significant trends are distributed over the whole globe. Increasing trends have been calculated for Greenland, East Europe, Siberia and Oceania, whereas decreasing trends have been observed for the northwest USA, Central America, Amazonia, Central Africa and the Arabian Peninsular.
The Soil Spectroscopy Group and the development of a global soil spectral library
Rossel, R. Viscarra Rossel; Soil Spectroscopy Group
2009-04-01
This collaboration aims to develop a global soil spectral library and to establish a community of practice for soil spectroscopy. This will help progress soil spectroscopy from an almost purely research tool to a more widely adopted and useful technique for soil analysis, proximal soil sensing, soil monitoring and digital soil mapping. The initiative started in April 2008 with a proposal for the project to be conducted in a number of stages to investigate the following topics: Global soil diversity and variation can be characterised using diffuse reflectance spectra. Soil spectral calibrations can be used to predict soil properties globally. Soil spectroscopy can be a useful tool for digital soil mapping. Currently, the soil spectral library is being developed using legacy soil organic carbon (OC) and clay content data and vis-NIR (350-2500 nm) spectra, but in future we aim to include other soil properties and mid-IR (2500-25000 nm) spectra. The group already has more than 40 collaborators from six continents and 20 countries and the library consists of 5223 spectra from 43 countries. The library accounts for spectra from approximately only 22% of the world's countries, some of which are poorly represented with only very few spectra. We would like to encourage participation from as many countries as possible, particularly, we would like contributions from counties in Central and South America, Mexico, Canada, Russia and countries in Eastern Europe, Africa and Asia. We are missing a lot of countries and for some, e.g. China we have only very few data! Do you want to join the group and contribute spectra to the global library? The requirements for contributing spectra to the global library are as follows: Spectra collected in the 350-2500 nm range every 1 nm. At least soil OC and clay content data but also any other soil chemical, physical, biological and mineralogical data, noting which analytical techniques were used. Coordinates (in WGS84 format) for each sample
Behrangi, Ali
In respond to the community demands, combining microwave (MW) and infrared (IR) estimates of precipitation has been an active area of research since past two decades. The anticipated launching of NASA's Global Precipitation Measurement (GPM) mission and the increasing number of spectral bands in recently launched geostationary platforms will provide greater opportunities for investigating new approaches to combine multi-source information towards improved global high resolution precipitation retrievals. After years of the communities' efforts the limitations of the existing techniques are: (1) Drawbacks of IR-only techniques to capture warm rainfall and screen out no-rain thin cirrus clouds; (2) Grid-box- only dependency of many algorithms with not much effort to capture the cloud textures whether in local or cloud patch scale; (3) Assumption of indirect relationship between rain rate and cloud-top temperature that force high intensity precipitation to any cold cloud; (4) Neglecting the dynamics and evolution of cloud in time; (5) Inconsistent combination of MW and IR-based precipitation estimations due to the combination strategies and as a result of above described shortcomings. This PhD dissertation attempts to improve the combination of data from Geostationary Earth Orbit (GEO) and Low-Earth Orbit (LEO) satellites in manners that will allow consistent high resolution integration of the more accurate precipitation estimates, directly observed through LEO's PMW sensors, into the short-term cloud evolution process, which can be inferred from GEO images. A set of novel approaches are introduced to cope with the listed limitations and is consist of the following four consecutive components: (1) starting with the GEO part and by using an artificial-neural network based method it is demonstrated that inclusion of multi-spectral data can ameliorate existing problems associated with IR-only precipitating retrievals; (2) through development of Precipitation Estimation
Mukherjee, Animesh; Kannan, Ravi
2009-01-01
Recent research has shown that language and the socio-cognitive phenomena associated with it can be aptly modeled and visualized through networks of linguistic entities. However, most of the existing works on linguistic networks focus only on the local properties of the networks. This study is an attempt to analyze the structure of languages via a purely structural technique, namely spectral analysis, which is ideally suited for discovering the global correlations in a network. Application of this technique to PhoNet, the co-occurrence network of consonants, not only reveals several natural linguistic principles governing the structure of the consonant inventories, but is also able to quantify their relative importance. We believe that this powerful technique can be successfully applied, in general, to study the structure of natural languages.
ZHAO SongNian; YAO Li; JIN Zhen; XIONG XiaoYun; WU Xia; ZOU Qi; YAO GuoZheng; CAI XiaoHong; LIU YiJun
2008-01-01
In fMRI experiments on object representation in visual cortex, we designed two types of stimuli: one is the gray face image and its line drawing, and the other is the illusion and its corresponding completed illusion. Both of them have the same global features with different minute details so that the results of fMRI experiments can be compared with each other. The first kind of visual stimuli was used in a block design fMRI experiment, and the second was used in an event-related fMRI experiment. Comparing and analyzing interesting visual cortex activity patterns and blood oxygenation level dependent (BOLD)-fMRI signal, we obtained results to show some invariance of global features of visual images. A plau-sible explanation about the invariant mechanism is related with the cooperation of synchronized re-sponse to the global features of the visual image with a feedback of shape perception from higher cortex to cortex V1, namely the integration of global features and embodiment of sparse representation and distributed population code.
Leng, Kuangdai; Nissen-Meyer, Tarje; van Driel, Martin
2016-12-01
We present a new, computationally efficient numerical method to simulate global seismic wave propagation in realistic 3-D Earth models. We characterize the azimuthal dependence of 3-D wavefields in terms of Fourier series, such that the 3-D equations of motion reduce to an algebraic system of coupled 2-D meridian equations, which is then solved by a 2-D spectral element method (SEM). Computational efficiency of such a hybrid method stems from lateral smoothness of 3-D Earth models and axial singularity of seismic point sources, which jointly confine the Fourier modes of wavefields to a few lower orders. We show novel benchmarks for global wave solutions in 3-D structures between our method and an independent, fully discretized 3-D SEM with remarkable agreement. Performance comparisons are carried out on three state-of-the-art tomography models, with seismic period ranging from 34 s down to 11 s. It turns out that our method has run up to two orders of magnitude faster than the 3-D SEM, featured by a computational advantage expanding with seismic frequency.
A. Mahmud
2012-12-01
Full Text Available The secondary organic aerosol (SOA module in the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4 has been updated by replacing existing two-product (2p parameters with those obtained from two-product volatility basis set (2p-VBS fits, and by treating SOA formation from the following volatile organic compounds (VOCs: isoprene, propene and lumped alkenes. Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base-case and updated model versions. The base-case MOZART-4 predicted annual average SOA of 0.36 ± 0.50 μg m^{−3} in South America, 0.31 ± 0.38 μg m^{−3} in Indonesia, 0.09 ± 0.05 μg m^{−3} in the USA, and 0.12 ± 0.07 μg m^{−3} in Europe. Concentrations from the updated versions of the model showed a~marked increase in annual average SOA. Using the updated set of parameters alone (MZ4-v1 increased annual average SOA by ~8%, ~16%, ~56%, and ~108% from the base-case in South America, Indonesia, USA, and Europe, respectively. Treatment of additional parent VOCs (MZ4-v2 resulted in an even more dramatic increase of ~178–406% in annual average SOA for these regions over the base-case. The increases in predicted SOA concentrations further resulted in increases in corresponding SOA contributions to annual average total aerosol optical depth (AOD by <1% for MZ4-v1 and ~1–6% for MZ4-v2. Estimated global SOA production was ~6.6 Tg yr^{−1} and ~19.1 Tg yr^{−1} with corresponding burdens of ~0.24 Tg and ~0.59 Tg using MZ4-v1 and MZ4-v2, respectively. The SOA budgets predicted in the current study fall well within reported ranges for similar modeling studies, 6.7 to 96 Tg yr^{−1}, but are lower than recently reported observationally-constrained values, 50 to 380 Tg yr^{−1}. With MZ4-v2, simulated SOA concentrations at the surface were also in
A. Mahmud
2013-07-01
Full Text Available The secondary organic aerosol (SOA module in the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4 was updated by replacing existing two-product (2p parameters with those obtained from two-product volatility basis set (2p-VBS fits (MZ4-C1, and by treating SOA formation from the following additional volatile organic compounds (VOCs: isoprene, propene and lumped alkenes (MZ4-C2. Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base case and updated model simulations. Updates to the model resulted in significant increases in annual average SOA mass concentrations, particularly for the MZ4-C2 simulation in which the additional SOA precursor VOCs were treated. Annual average SOA concentrations predicted by the MZ4-C2 simulation were 1.00 ± 1.04 μg m−3 in South America, 1.57 ± 1.88 μg m−3 in Indonesia, 0.37 ± 0.27 μg m−3 in the USA, and 0.47 ± 0.29 μg m−3 in Europe with corresponding increases of 178, 406, 311 and 292% over the base-case simulation, respectively, primarily due to inclusion of isoprene. The increases in predicted SOA mass concentrations resulted in corresponding increases in SOA contributions to annual average total aerosol optical depth (AOD by ~ 1–6%. Estimated global SOA production was 5.8, 6.6 and 19.1 Tg yr−1 with corresponding burdens of 0.22, 0.24 and 0.59 Tg for the base-case, MZ4-C1 and MZ4-C2 simulations, respectively. The predicted SOA budgets fell well within reported ranges for comparable modeling studies, 6.7 to 96 Tg yr−1, but were lower than recently reported observationally constrained values, 50 to 380 Tg yr−1. For MZ4-C2, simulated SOA concentrations at the surface also were in reasonable agreement with comparable modeling studies and observations. Total organic aerosol (OA mass concentrations at the surface, however, were slightly over-predicted in Europe, Amazonian
Mahmud, A.; Barsanti, K.
2013-07-01
The secondary organic aerosol (SOA) module in the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) was updated by replacing existing two-product (2p) parameters with those obtained from two-product volatility basis set (2p-VBS) fits (MZ4-C1), and by treating SOA formation from the following additional volatile organic compounds (VOCs): isoprene, propene and lumped alkenes (MZ4-C2). Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base case and updated model simulations. Updates to the model resulted in significant increases in annual average SOA mass concentrations, particularly for the MZ4-C2 simulation in which the additional SOA precursor VOCs were treated. Annual average SOA concentrations predicted by the MZ4-C2 simulation were 1.00 ± 1.04 μg m-3 in South America, 1.57 ± 1.88 μg m-3 in Indonesia, 0.37 ± 0.27 μg m-3 in the USA, and 0.47 ± 0.29 μg m-3 in Europe with corresponding increases of 178, 406, 311 and 292% over the base-case simulation, respectively, primarily due to inclusion of isoprene. The increases in predicted SOA mass concentrations resulted in corresponding increases in SOA contributions to annual average total aerosol optical depth (AOD) by ~ 1-6%. Estimated global SOA production was 5.8, 6.6 and 19.1 Tg yr-1 with corresponding burdens of 0.22, 0.24 and 0.59 Tg for the base-case, MZ4-C1 and MZ4-C2 simulations, respectively. The predicted SOA budgets fell well within reported ranges for comparable modeling studies, 6.7 to 96 Tg yr-1, but were lower than recently reported observationally constrained values, 50 to 380 Tg yr-1. For MZ4-C2, simulated SOA concentrations at the surface also were in reasonable agreement with comparable modeling studies and observations. Total organic aerosol (OA) mass concentrations at the surface, however, were slightly over-predicted in Europe, Amazonian regions and Malaysian Borneo
Spectral nudging – a scale-selective interior constraint technique – is commonly used in regional climate models to maintain consistency with large-scale forcing while permitting mesoscale features to develop in the downscaled simulations. Several studies have demonst...
Global Source Parameters from Regional Spectral Ratios for Yield Transportability Studies
Phillips, W. S.; Fisk, M. D.; Stead, R. J.; Begnaud, M. L.; Rowe, C. A.
2016-12-01
We use source parameters such as moment, corner frequency and high frequency rolloff as constraints in amplitude tomography, ensuring that spectra of well-studied earthquakes are recovered using the ensuing attenuation and site term model. We correct explosion data for path and site effects using such models, which allows us to test transportability of yield estimation techniques based on our best source spectral estimates. To develop a background set of source parameters, we applied spectral ratio techniques to envelopes of a global set of regional distance recordings from over 180,000 crustal events. Corner frequencies and moment ratios were determined via inversion using all event pairs within predetermined clusters, shifting to absolute levels using independently determined regional and teleseismic moments. The moment and corner frequency results can be expressed as stress drop, which has considerable scatter, yet shows dramatic regional patterns. We observe high stress in subduction zones along S. America, S. Mexico, the Banda Sea, and associated with the Yakutat Block in Alaska. We also observe high stress at the Himalayan syntaxes, the Pamirs, eastern Iran, the Caspian, the Altai-Sayan, and the central African rift. Low stress is observed along mid ocean spreading centers, the Afar rift, patches of convergence zones such as Nicaragua, the Zagros, Tibet, and the Tien Shan, among others. Mine blasts appear as low stress events due to their low corners and steep rolloffs. Many of these anomalies have been noted by previous studies, and we plan to compare results directly. As mentioned, these results will be used to constrain tomographic imaging, but can also be used in model validation procedures similar to the use of ground truth in location problems, and, perhaps most importantly, figure heavily in quality control of local and regional distance amplitude measurements.
Power spectral density and scaling exponent of high frequency global solar radiation sequences
Calif, Rudy; Schmitt, François G.; Huang, Yongxiang
2013-04-01
The part of the solar power production from photovlotaïcs systems is constantly increasing in the electric grids. Solar energy converter devices such as photovoltaic cells are very sensitive to instantaneous solar radiation fluctuations. Thus rapid variation of solar radiation due to changes in the local meteorological condition can induce large amplitude fluctuations of the produced electrical power and reduce the overall efficiency of the system. When large amount of photovoltaic electricity is send into a weak or small electricity network such as island network, the electric grid security can be in jeopardy due to these power fluctuations. The integration of this energy in the electrical network remains a major challenge, due to the high variability of solar radiation in time and space. To palliate these difficulties, it is essential to identify the characteristic of these fluctuations in order to anticipate the eventuality of power shortage or power surge. The objective of this study is to present an approach based on Empirical Mode Decomposition (EMD) and Hilbert-Huang Transform (HHT) to highlight the scaling properties of global solar irradiance data G(t). The scale of invariance is detected on this dataset using the Empirical Mode Decomposition in association with arbitrary-order Hilbert spectral analysis, a generalization of (HHT) or Hilbert Spectral Analysis (HSA). The first step is the EMD, consists in decomposing the normalized global solar radiation data G'(t) into several Intrinsic Mode Functions (IMF) Ci(t) without giving an a priori basis. Consequently, the normalized original solar radiation sequence G'(t) can be written as a sum of Ci(t) with a residual rn. From all IMF modes, a joint PDF P(f,A) of locally and instantaneous frequency f and amplitude A, is estimated. To characterize the scaling behavior in amplitude-frequency space, an arbitrary-order Hilbert marginal spectrum is defined to: Iq(f) = 0 P (f,A)A dA (1) with q × 0 In case of scale
Mapping a part of Neuquen Basin in Argentina by global-phase H/V spectral ratio
Nishitsuji, Y.; Ruigrok, E.; Gomez, M.; Draganov, D.S.
2015-01-01
We investigated the applicability of global phases (epicentral distances of ≥ 120° and ≥ 150°) for the H/V spectral ratio to identify the fundamental resonance frequency. We applied the method to delineate a part of Neuquén basin in Argentina without the need for active seismic sources. We obtained
JIANG Yongsong; LIANG An; SUN Xiaofeng; JING Xiaodong
2012-01-01
This paper presents the extension of the global description approach of a discontinuous function,which is proposed in the previous paper,to a spectral domain decomposition method.This multi-domain spectral immersed interface method(IIM) divides the whole computation domain into the smooth and discontinuous parts.Fewer points on the smooth domains are used via taking advantage of the high accuracy property of the spectral method,but more points on the discontinuous domains are employed to enhance the resolution of the calculation.Two discontinuous problems are tested to verify the present method.The results show that the domain decomposition technique can reduce the error of the spectral IIM,especially when more collocation points are placed around the discontinuity.The present method is favorable for the reason that the same level of the accuracy can be reached,in spite of the enlarged computational domain.
Spectral Combination of Global and Regional Ionospheric Models Using Slepian Theory
Etemadfard, Hossein; Mashhadi Hossainali, Masoud
2016-04-01
This study suggests a new method for combining function-based regional and global ionospheric models, based on spherical Slepian theory. As the first step of this method, the Global Ionosphere Models (GIMs) of the International GNSS Service (IGS) are transformed to the Spherical Slepian Functions (SSFs), which are named modified GIMs. Then, the observations of the regional GPS networks are expanded in the same SSFs. The maximum degree of the regional model is 15, which is equal to the maximum degree of the GIMs. In the end, the modified GIM and the developed regional model are combined in the spectral domain. The new method is applied to the Arctic region. In the regional modeling, six GPS stations from the Canadian High Arctic Ionosphere Network (CHAIN) and four GPS station from the European Reference Frame (EUREF) network are used. The observation files belong to the day 334 in 2015. The models have been validated with three stations from the CHAIN and the EUREF as check stations. The check stations were used in neither the regional model nor the GIM. According to the obtained result, i the RMSE of GIM, modified GIM and the regional model are 3.7, 2.2 and 1.9 TECU (Total Electron Content Unit =1016electron/m2), respectively. However, the RMSE of the combined model is 1.4 TECU, which shows a significant improvement compare to the other models. The proposed method remarkably improves the quality of the ionospheric modeling in the Arctic region. This may lead to a better understanding of the ionospheric phenomena. Keywords: Regional Modeling, GIM, Spherical Slepian Functions
A Global Spectral Study of Stellar-Mass Black Holes with Unprecedented Sensitivity
Garci, Javier
There are two well established populations of black holes: (i) stellar-mass black holes with masses in the range 5 to 30 solar masses, many millions of which are present in each galaxy in the universe, and (ii) supermassive black holes with masses in the range millions to billions of solar masses, which reside in the nucleus of most galaxies. Supermassive black holes play a leading role in shaping galaxies and are central to cosmology. However, they are hard to study because they are dim and they scarcely vary on a human timescale. Luckily, their variability and full range of behavior can be very effectively studied by observing their stellar-mass cousins, which display in miniature the full repertoire of a black hole over the course of a single year. The archive of data collected by NASA's Rossi X-ray Timing Explorer (RXTE) during its 16 year mission is of first importance for the study of stellar-mass black holes. While our ultimate goal is a complete spectral analysis of all the stellar-mass black hole data in the RXTE archive, the goal of this proposal is the global study of six of these black holes. The two key methodologies we bring to the study are: (1) Our recently developed calibration tool that increases the sensitivity of RXTE's detector by up to an order of magnitude; and (2) the leading X-ray spectral "reflection" models that are arguably the most effective means currently available for probing the effects of strong gravity near the event horizon of a black hole. For each of the six black holes, we will fit our models to all the archived spectral data and determine several key parameters describing the black hole and the 10-million-degree gas that surrounds it. Of special interest will be our measurement of the spin (or rate of rotation) of each black hole, which can be as high as tens of thousands of RPM. Profoundly, all the properties of an astronomical black hole are completely defined by specifying its spin and its mass. The main goal of this
Fisenko, Anatoliy I
2015-01-01
The general analytical expressions for the thermal radiative and thermodynamic properties of a real-body are obtained in a finite range of frequencies at different temperatures. The frequency dependence of the spectral emissivity is represented as a power series. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible-near infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The g...
Thomas E. Rosmond
2000-01-01
Full Text Available The Navy Operational Global Atmospheric Prediction System (NOGAPS includes a state-of-the-art spectral forecast model similar to models run at several major operational numerical weather prediction (NWP centers around the world. The model, developed by the Naval Research Laboratory (NRL in Monterey, California, has run operational at the Fleet Numerical Meteorological and Oceanographic Center (FNMOC since 1982, and most recently is being run on a Cray C90 in a multi-tasked configuration. Typically the multi-tasked code runs on 10 to 15 processors with overall parallel efficiency of about 90%. resolution is T159L30, but other operational and research applications run at significantly lower resolutions. A scalable NOGAPS forecast model has been developed by NRL in anticipation of a FNMOC C90 replacement in about 2001, as well as for current NOGAPS research requirements to run on DOD High-Performance Computing (HPC scalable systems. The model is designed to run with message passing (MPI. Model design criteria include bit reproducibility for different processor numbers and reasonably efficient performance on fully shared memory, distributed memory, and distributed shared memory systems for a wide range of model resolutions. Results for a wide range of processor numbers, model resolutions, and different vendor architectures are presented. Single node performance has been disappointing on RISC based systems, at least compared to vector processor performance. This is a common complaint, and will require careful re-examination of traditional numerical weather prediction (NWP model software design and data organization to fully exploit future scalable architectures.
Fisenko, Anatoliy I.; Lemberg, Vladimir
2015-11-01
There are several classes of materials and space objects for which the frequency dependence of the spectral emissivity is represented as a power series. Therefore, the study of the properties of thermal radiation for these real bodies is an important task for both fundamental science and industrial applications. The general analytical expressions for the thermal radiative and thermodynamic functions of a real body are obtained in a finite range of frequencies at different temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The obtained general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible and near-infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The general analytical expressions obtained can easily be presented in the wavenumber domain.
Kwon, TaeKyu; Agrawal, Kunal; Li, Yunfeng; Pizlo, Zygmunt
2016-09-01
Finding the occluding contours of objects in real 2D retinal images of natural 3D scenes is done by determining, which contour fragments are relevant, and the order in which they should be connected. We developed a model that finds the closed contour represented in the image by solving a shortest path problem that uses a log-polar representation of the image; the kind of representation known to exist in area V1 of the primate cortex. The shortest path in a log-polar representation favors the smooth, convex and closed contours in the retinal image that have the smallest number of gaps. This approach is practical because finding a globally-optimal solution to a shortest path problem is computationally easy. Our model was tested in four psychophysical experiments. In the first two experiments, the subject was presented with a fragmented convex or concave polygon target among a large number of unrelated pieces of contour (distracters). The density of these pieces of contour was uniform all over the screen to minimize spatially-local cues. The orientation of each target contour fragment was randomly perturbed by varying the levels of jitter. Subjects drew a closed contour that represented the target's contour on a screen. The subjects' performance was nearly perfect when the jitter-level was low. Their performance deteriorated as jitter-levels were increased. The performance of our model was very similar to our subjects'. In two subsequent experiments, the subject was asked to discriminate a briefly-presented egg-shaped object while maintaining fixation at several different positions relative to the closed contour of the shape. The subject's discrimination performance was affected by the fixation position in much the same way as the model's.
Ahn, Kang-Hyun; Halpern, Howard J
2007-03-01
Spectral-spatial images reconstructed from a small number of projections suffer from streak artifacts that are seen as noise, particularly in the spectral dimension. Interpolation in projection space can reduce artifacts in the reconstructed images. The reduction of background artifacts improves lineshape fitting. In this work, we compared the performances of angular interpolation implemented using linear, cubic B-spline, and sinc methods. Line width maps were extracted from 4-D EPR images of phantoms using spectral fitting to evaluate each interpolation method and its robustness to noise. Results from experiment and simulation showed that the cubic B-spline, angular interpolation was preferable to either sinc or linear interpolation methods.
Spatially global representations in human primary visual cortex during working memory maintenance.
Ester, Edward F; Serences, John T; Awh, Edward
2009-12-02
Recent studies suggest that visual features are stored in working memory (WM) via sensory recruitment or sustained stimulus-specific patterns of activity in cortical regions that encode memoranda. One important question concerns the spatial extent of sensory recruitment. One possibility is that sensory recruitment is restricted to neurons that are retinotopically mapped to the positions occupied by the remembered items. Alternatively, specific feature values could be represented via a spatially global recruitment of neurons that encode the remembered feature, regardless of the retinotopic position of the remembered stimulus. Here, we evaluated these alternatives by requiring subjects to remember the orientation of a grating presented in the left or right visual field. Functional magnetic resonance imaging and multivoxel pattern analysis were then used to examine feature-specific activations in early visual regions during memory maintenance. Activation patterns that discriminated the remembered feature were found in regions of contralateral visual cortex that corresponded to the retinotopic position of the remembered item, as well as in ipsilateral regions that were not retinotopically mapped to the position of the stored stimulus. These results suggest that visual details are held in WM through a spatially global recruitment of early sensory cortex. This spatially global recruitment may enhance memory precision by facilitating robust population coding of the stored information.
Baba, H.; Kanayama, K.; Endo, N.; Koromohara, K.; Takayama, H. [Kitami Institute of Technology, Hokkaido (Japan)
1996-10-27
Use of global insolation for estimating the corresponding spectral distribution is proposed. Measurements of global insolation spectrum throughout a year were compiled for clear days and cloudy days, ranked by 100W/m{sup 2}, for the clarification of spectral distribution. Global insolation quantity for a clear day was subject mainly to sun elevation. The global insolation spectral distribution with the sun elevation not lower than 15{degree} was similar to Bird`s model. Under the cloudy sky, energy density was lower in the region of wavelengths longer than the peak wavelength of 0.46{mu}m, and the distribution curve was sharper than that under the clear sky. Values given by Bird`s model were larger than measured values in the wavelength range of 0.6-1.8{mu}m, which was attributed to absorption by vapor. From the standard spectral distribution charts for the clear sky and cloudy sky, and from the dimensionless spectral distributions obtained by dividing them by the peak values, spectral distributions could be estimated of insolation quantities for the clear sky, cloudy sky, etc. As for the characteristics of spectral solar radiation on a tilt surface obtained from Bird`s model, they agreed with actually measured values at an angle of inclination of 60{degree} or smaller. 6 refs., 10 figs., 1 tab.
MODES: open-access software for the normal-mode representation of the global 3D circulation
Zagar, Nedjeljka
2015-04-01
The goal of the talk is to present MODES, software for the normal-mode function representation of the 3D global datasets. The software, developed within the ERC project MODES, is now available to atmospheric research community as an open-access tool. MODES allows one to diagnose properties of balanced and inertio-gravity (IG) circulation across many scales by considering both mass and wind field and the whole model depth. In particular, the IG spectrum, which has only recently become observable in global datasets, can be studied simultaneously in the mass field and wind field and considering the whole model depth. The software can be used for the comparison of climate model outputs with the reanalysis datasets. The presentation will include theoretical background and basic technical details of the software that can be installed and used with a relatively modest effort. Example of the software outputs are available in real-time at http://meteo.fmf.uni-lj.si/MODES. Results from the modal analysis of the ERA Interim dataset as well as the ensemble prediction system of ECMWF are presented.
Bisinella, Valentina; Conradsen, Knut; Christensen, Thomas Højlund;
2016-01-01
Purpose: Identification of key inputs and their effect on results from Life Cycle Assessment (LCA) models is fundamental. Because parameter importance varies greatly between cases due to the interaction of sensitivity and uncertainty, these features should never be defined a priori. However...... and uncertainty in a Global Sensitivity Analysis (GSA) framework. Methods: The proposed analytical method based on the calculation of sensitivity coefficients (SC) is evaluated against Monte Carlo sampling on traditional uncertainty assessment procedures, both for individual parameters and for full parameter sets...... of additivity of variances and GSA is tested on results from both uncertainty propagation methods. Then, we examine the differences in discernibility analyses results carried out with varying numbers of sampling points and parameters. Results and discussion: The proposed analytical method complies...
Representation of Nucleation Mode Microphysics in a Global Aerosol Model with Sectional Microphysics
Lee, Y. H.; Pierce, J. R.; Adams, P. J.
2013-01-01
In models, nucleation mode (1 nmrepresentation of nucleation mode microphysics impacts aerosol number predictions in the TwO-Moment Aerosol Sectional (TOMAS) aerosol microphysics model running with the GISS GCM II-prime by varying its lowest diameter boundary: 1 nm, 3 nm, and 10 nm. The model with the 1 nm boundary simulates the nucleation mode particles with fully resolved microphysical processes, while the model with the 10 nm and 3 nm boundaries uses a nucleation mode dynamics parameterization to account for the growth of nucleated particles to 10 nm and 3 nm, respectively.We also investigate the impact of the time step for aerosol microphysical processes (a 10 min versus a 1 h time step) to aerosol number predictions in the TOMAS models with explicit dynamics for the nucleation mode particles (i.e., 3 nm and 1 nm boundary). The model with the explicit microphysics (i.e., 1 nm boundary) with the 10 min time step is used as a numerical benchmark simulation to estimate biases caused by varying the lower size cutoff and the time step. Different representations of the nucleation mode have a significant effect on the formation rate of particles larger than 10 nm from nucleated particles (J10) and the burdens and lifetimes of ultrafinemode (10 nm=Dp =70 nm) particles but have less impact on the burdens and lifetimes of CCN-sized particles. The models using parameterized microphysics (i.e., 10 nm and 3 nm boundaries) result in higher J10 and shorter coagulation lifetimes of ultrafine-mode particles than the model with explicit dynamics (i.e., 1 nm boundary). The spatial distributions of CN10 (Dp =10 nm) and CCN(0.2 %) (i.e., CCN concentrations at 0.2%supersaturation) are moderately affected, especially CN10 predictions above 700 hPa where nucleation contributes most strongly to CN10 concentrations. The lowermost-layer CN10 is substantially improved with the 3 nm boundary (compared to 10 nm) in most areas. The overprediction in CN10 with the 3 nm and 10 nm boundaries
Stochastic Harmonic Functions of Second Kind for Spectral Representations%随机过程的第二类随机谐和函数表达
孙伟玲; 陈建兵; 李杰
2011-01-01
The stochastic harmonic function of the second kind is proposed for representations of stochastic processes. It is firstly proved that, as long as the random phase angles and random circular frequencies are independent and uniformly distributed whereas the amplitudes are related to the target power spectral density function in a specified way, the power spectral density of the process represented by the stochastic harmonic function of the second kind is identical to the target power spectral density. Then, it is demonstrated that the process represented by the stochastic harmonic function of the second kind is asymptotically Gaussian. The rate of approaching Gaussian distribution is further studied by obtaining the one-dimensional distribution via Pearson distribution. The study reveals the similarities between the stochastic harmonic functions of the first kind and the second kind. However, the application of the stochastic harmonic function of the second kind is more convenient than that of the first kind because the random circular frequencies are uniformly distributed. Finally, linear and nonlinear responses of a multi-degree-of-freedom system subjected to random ground motions are analyzed to exemplify the effectiveness and superiorities of the proposed approach.%发展了随机过程的第二类随机谐和函数表达并研究了其性质.证明当随机频率与相位服从独立均匀分布而幅值由频率与目标功率谱密度决定时,随机谐和函数过程的功率谱密度函数精确地等于目标功率谱密度函数.研究第二类随机谐和函数过程的渐进正态性,讨论趋向正态分布的速率,并采用Pearson分布研究1维概率密度函数的性质.研究表明,第二类随机谐和函数同第一类随机谐和函数具有相似的性质,且由于第二类随机谐和函数频率为均匀分布,应用更为方便.以多自由度体系的线性和非线性响应分析为例,验证了随机谐和函数模型的有效性和优越性.
J. R. Melton
2014-02-01
period. Inclusion of LUC causes the estimates of the terrestrial C sink to differ by 15.2 Pg C (16% with values of 95.1 and 79.9 Pg C for the mosaic and composite approaches, respectively. Spatial differences in simulated vegetation and soil carbon and the manner in which terrestrial carbon balance evolves in response to LUC, in the two approaches, yields a substantially different estimate of the global land carbon sink. These results demonstrate that the spatial representation of vegetation has an important impact on the model response to changing climate, atmospheric CO2 concentrations, and land cover.
Richer, E.; Modolo, R.; Chanteur, G. M.; Hess, S.; Leblanc, F.
2012-10-01
The interaction of the solar wind (SW) with the magnetic field of Mercury is investigated by means of a three dimensional parallelized multispecies hybrid model. A comparison between two mathematical representations of Mercury's intrinsic magnetic field is studied. The first model is an Offset Dipole (OD) having the offset and dipolar moment reported by Anderson et al. (2011). The second model is a combination of a Dipole and a Quadrupole (DQ), the total field is fitted to the offset dipolar field, for northern latitudes greater than 50°. Simulations reproduce the features which characterize Mercury's interaction with the SW, encompassing the Bow Shock (BS), the magnetosheath, the magnetotail, the “cusps” region and the neutral current sheet. Global hybrid simulations of the Hermean magnetosphere run for the OD and DQ models demonstrate that the southern parts of the magnetospheres produced by the OD and DQ models differ greatly in topology and volume meanwhile their northern parts-are quite similar. In particular the DQ model exhibits a dome of closed field lines around the south pole in contrast to the OD. Without further information on the intrinsic magnetic field of the planet in the southern region which should be provided by BepiColombo after year 2020, we can only speculate on the influence of the different magnetic topologies on the magnetospheric dynamics.
Watson, Laura; Michou, Martine; Nabat, Pierre; Saint-Martin, David
2017-04-01
Aerosol radiative forcing is one of the greatest sources of uncertainty when projecting future climate change. Aerosols vary in time and in space and alter the Earth's radiative balance directly, by absorbing and scattering radiation, and indirectly, by interacting with clouds and altering cloud microphysics. A series of sensitivity tests were performed using the coupled ocean-atmosphere general circulation model CNRM-CM in order to investigate how the representation of aerosols within the model can affect climate. These tests included looking at the difference between using constant emissions versus using emissions that evolve over a period of thirty years; examining the impacts of including indirect effects from sea salt and organics; altering the aerosol optical properties; altering the vertical distribution of aerosols, and using an interactive aerosol scheme versus using 2-D climatologies. The results of these sensitivity tests show how modifying certain aspects of the aerosol scheme can significantly affect radiative flux, the cloud radiative effect and global surface temperatures. Of particular note is the importance of the indirect effect of sea salt aerosols, which has more of a significant impact upon climate than the direct radiative forcing of sea salt aerosols; and the impact of using an interactive aerosol scheme instead of 2-D climatologies, which results in more net radiative flux at the top of the atmosphere and slightly warmer temperatures at land surfaces.
Saad, Bilal M.
2017-09-18
This work focuses on the simulation of CO2 storage in deep underground formations under uncertainty and seeks to understand the impact of uncertainties in reservoir properties on CO2 leakage. To simulate the process, a non-isothermal two-phase two-component flow system with equilibrium phase exchange is used. Since model evaluations are computationally intensive, instead of traditional Monte Carlo methods, we rely on polynomial chaos (PC) expansions for representation of the stochastic model response. A non-intrusive approach is used to determine the PC coefficients. We establish the accuracy of the PC representations within a reasonable error threshold through systematic convergence studies. In addition to characterizing the distributions of model observables, we compute probabilities of excess CO2 leakage. Moreover, we consider the injection rate as a design parameter and compute an optimum injection rate that ensures that the risk of excess pressure buildup at the leaky well remains below acceptable levels. We also provide a comprehensive analysis of sensitivities of CO2 leakage, where we compute the contributions of the random parameters, and their interactions, to the variance by computing first, second, and total order Sobol’ indices.
Preliminary design of dynamic framework for global non-hydrostatic spectral model%全球非静力谱模式动力框架初步设计
吴建平; 赵军; 宋君强; 张卫民
2011-01-01
Based on the global hydrostatic spectral model for operational run, referring to the upgrade and design idea of ECMWF from hydrostatic spectral model to the non-hydrostatic one, a preliminary dry dynamic framework is designed for global non-hydrostatic spectral model, with the consideration of the select ion of the model equations, the linearization of the model equations, spectral representation in horizontal, finite difference in vertical, the scheme of integral in time, and the solution of the derived Helmholtz systems. The framework is provided for atmosphere with shallow approximation, and the Euler convection is exploited. Further, for the solution of the Helmholtz equations, a new computational scheme is provided based on the convection to the linear equations of block tri-diagonal form. The new scheme is clearly superior to the current one used in ECMWF for efficiency.%基于我国目前已在业务运行的全球静力谱模式,参考ECMWF从静力谱模式到非静力谱模式的升级设计思想,从模式方程组的选取、模式方程组的线性化、水平球谐谱离散、时间积分方法、垂直有限差分离散、Helmholtz方程的求解等几个方面出发,针对浅薄近似的大气,采用Euler对流,初步设计了一个全球非静力谱模式干动力框架,并针对Helmholtz方程的求解,给出了一种将其转化为块三对角线性方程组的计算方法,该方法从计算效率上明显优于ECMWF目前所用计算方法.
Terhoeven-Urselmans, T.; Vagen, T.G.; Spaargaren, O.; Shepherd, K.D.
2010-01-01
Globally applicable calibrations to predict standard soil properties based on infrared spectra may increase the use of this reliable technique. The objective of this study was to evaluate the ability of mid-infrared diffuse reflectance spectroscopy (4000-602 cm(-1)) to predict chemical and textural
The Flexible Global Ocean-Atmosphere-Land System Model,Spectral Version 2:FGOALS-s2
BAO Qing; LIN Pengfei; ZHOU Tianjun; LIU Yimin; YU Yongqiang; WU Guoxiong; HE Bian
2013-01-01
The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 (FGOALS-s2) was used to simulate realistic climates and to study anthropogenic influences on climate change.Specifically,the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 (CMIP5) to conduct coordinated experiments that will provide valuable scientific information to climate research communities.The performances of FGOALS-s2 were assessed in simulating major climate phenomena,and documented both the strengths and weaknesses of the model.The results indicate that FGOALS-s2 successfully overcomes climate drift,and realistically models global and regional climate characteristics,including SST,precipitation,and atmospheric circulation.In particular,the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean,and the main characteristic features of the Asian summer monsoon,which include a low-level southwestern jet and five monsoon rainfall centers.The simulated climate variability was further examined in terms of teleconnections,leading modes of global SST (namely,ENSO),Pacific Decadal Oscillations (PDO),and changes in 19th-20th century climate.The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate,and irregular ENSO periods.The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century.However,because the indirect effects of aerosols are not included in the model,the simulated global temperature change during the period 1850-2005 is greater than the observed warming,by 0.6℃.Some other shortcomings of the model are also noted.
Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott M.; Dong, Xiquan; Zhang, Guang J.; Chen, Qian; Ghan, Steven J.
2015-04-27
The ultimate goal of this study is to improve representation of convective transport by cumulus parameterization for meso-scale and climate models. As Part I of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in mid-latitude continent and tropical regions using the Weather Research and Forecasting (WRF) model with spectral-bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation, vertical velocity of convective cores, and the vertically decreasing trend of radar reflectivity than MOR and MY2, and therefore will be used for analysis of scale-dependence of eddy transport in Part II. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates radar reflectivity in convective cores (SBM predicts smaller radar reflectivity but does not remove the large overestimation); and (3) the model performs better for mid-latitude convective systems than tropical system. The modeled mass fluxes of the mid latitude systems are not sensitive to microphysics schemes, but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.
Rohaly, Gregg; Krishnamurti, T. N.
1991-01-01
Fundamental to improving the understanding of the total Earth system are increased and improved observations. In the coming decade several spaceborne instrumented platforms will be constructed and implemented. These platforms will, in large, be housing the NASA Earth Observing System (EOS) instrument suite. One of the proposed instruments is a wind profiling system which is currently referred to as the Laser Atmospheric Wind Sounder (LAWS). This instrument will use a CO2 Doppler lidar wind profiler to give wind measurements with a vertical and horizontal resolution which has yet to be seen globally. The LAWS instrument is now a candidate for launch on a NASA EOS-B platform and is fundamental to increasing our understanding of Earth system science. The LAWS data sets will form an integral component of the temporally continuous data base needed for research of the coupled climate systems. This instrument's observations will aid in giving an improved description of the atmospheric circulation, including the transports of energy, momentum, moisture, trace gases, and aerosols. Also, the wind data will be assimilated and used as the initial state for many global forecast models at various operational centers. Results of system simulation experiments are discussed, and future experiments are described.
1982-01-01
The geographical variability of short wavelength geoid power spectra (geoid roughness), was mapped for the world's oceans between latitudes 72 deg N and 72 deg S. A spectral analysis of SEASAT altimeter data, reduced to sea surface heights, was performed at 2 minute intervals for 15 consecutive days of the 3-day repeat orbit. The geoid roughness represented by these spectra for wavelengths shorter than about 220 km is separated from the total sea height variance and is displayed in the form of a global contour map. The global average geoid roughness is 32 cm RMS, varying from a high in excess of 2 m RMS near deep ocean trenches to a low of 2 cm RMS in the southeast Pacific near the East Pacific Rise. This average value agrees well with previous estimates based on gravimetry and GEOS-3 altimetry. In general, the smoothest areas in the marine geoid overlie relatively young seafloor adjacent mid-ocean spreading centers, where even short-wavelength topographic variations tend to be isostatically compensated.
Mitchell, David L. [Desert Research Institute, Reno, NV (United States)
2013-09-05
It is well known that cirrus clouds play a major role in regulating the earth’s climate, but the details of how this works are just beginning to be understood. This project targeted the main property of cirrus clouds that influence climate processes; the ice fall speed. That is, this project improves the representation of the mass-weighted ice particle fall velocity, V_{m}, in climate models, used to predict future climate on global and regional scales. Prior to 2007, the dominant sizes of ice particles in cirrus clouds were poorly understood, making it virtually impossible to predict how cirrus clouds interact with sunlight and thermal radiation. Due to several studies investigating the performance of optical probes used to measure the ice particle size distribution (PSD), as well as the remote sensing results from our last ARM project, it is now well established that the anomalously high concentrations of small ice crystals often reported prior to 2007 were measurement artifacts. Advances in the design and data processing of optical probes have greatly reduced these ice artifacts that resulted from the shattering of ice particles on the probe tips and/or inlet tube, and PSD measurements from one of these improved probes (the 2-dimensional Stereo or 2D-S probe) are utilized in this project to parameterize V_{m} for climate models. Our original plan in the proposal was to parameterize the ice PSD (in terms of temperature and ice water content) and ice particle mass and projected area (in terms of mass- and area-dimensional power laws or m-D/A-D expressions) since these are the microphysical properties that determine V_{m}, and then proceed to calculate V_{m} from these parameterized properties. But the 2D-S probe directly measures ice particle projected area and indirectly estimates ice particle mass for each size bin. It soon became apparent that the original plan would introduce more uncertainty in the V_{m} calculations
Mitchell, David L. [Desert Research Institute, Reno, NV (United States)
2013-09-05
It is well known that cirrus clouds play a major role in regulating the earth’s climate, but the details of how this works are just beginning to be understood. This project targeted the main property of cirrus clouds that influence climate processes; the ice fall speed. That is, this project improves the representation of the mass-weighted ice particle fall velocity, V_{m}, in climate models, used to predict future climate on global and regional scales. Prior to 2007, the dominant sizes of ice particles in cirrus clouds were poorly understood, making it virtually impossible to predict how cirrus clouds interact with sunlight and thermal radiation. Due to several studies investigating the performance of optical probes used to measure the ice particle size distribution (PSD), as well as the remote sensing results from our last ARM project, it is now well established that the anomalously high concentrations of small ice crystals often reported prior to 2007 were measurement artifacts. Advances in the design and data processing of optical probes have greatly reduced these ice artifacts that resulted from the shattering of ice particles on the probe tips and/or inlet tube, and PSD measurements from one of these improved probes (the 2-dimensional Stereo or 2D-S probe) are utilized in this project to parameterize V_{m} for climate models. Our original plan in the proposal was to parameterize the ice PSD (in terms of temperature and ice water content) and ice particle mass and projected area (in terms of mass- and area-dimensional power laws or m-D/A-D expressions) since these are the microphysical properties that determine V_{m}, and then proceed to calculate V_{m} from these parameterized properties. But the 2D-S probe directly measures ice particle projected area and indirectly estimates ice particle mass for each size bin. It soon became apparent that the original plan would introduce more uncertainty in the V_{m} calculations
Mizzi, A.P.
1994-12-31
The research examines the applicability of the spectral method to the vertical coordinate of atmoshperic models. Specifically, the authors use the vertical normal modes as basis functions in spectral expansion of the vertical structure of dependent variables in an equatorial beta-plane and a tropical f-plane model of the atmosphere.
Mungur, Amy
2014-01-01
This study is an examination of how two popular magazines, "National Geographic" and "Life" magazine, and one educational journal, "Social Education," perform the work of representation in general, and representing China more specifically. Drawing on postcolonial theorists (Blaut, 1993; Said, 1978; Tchen, 1999; wa…
朱勇; 吴波
2016-01-01
A novel sparse representation classification model with spectral-spatial sparsity properties is presented to improve the classification accuracy of hyperspectral images. Firstly, this method uses the wavelet dictionary as the core dictionary to extract spectral domain sparse information, and then the spectral dimension sparse representation classification is transformed into the wavelet domain (WSRC) by inverse wavelet transformation. After that, we actually extract the sparse spectral features of the hyper-spectral images and increase the recognition of the original dictionary. Secondly, considering the unity and diversity of the spatial adjacent object, we realize the sparse coding of the neighborhood pixels, and then accumulate the sparse codes. At the same time, we classify the hyperspectral images using a linear classifier that is based on the accumulated sparse codes. This method ensures that we extract the main sparse signal of the neighborhood pixels on the basis of the personality features of sparse encoding, and it performs better than the joint sparse representation model (JSRC) which is directly based on the neighborhood pixels. Finally, two commonly used hyperspectral images are utilized to validate the proposed model. The experimental results demonstrate that the pro-posed algorithm outperforms other models in terms of overall accuracy and kappa coefficient measurements.%高光谱遥感影像的稀疏分类是当前遥感信息处理的研究热点。本文提出一种光谱与空间双重稀疏表达的高光谱遥感影像分类方法（WSSRC）。首先利用小波字典对光谱维进行稀疏表示，将光谱维稀疏分类转化到小波域稀疏分类；其次，考虑空间邻域地物光谱的统一性和差异性，对邻域内像元分别进行稀疏编码，并对编码进行累加聚合；然后，利用聚合后的稀疏编码构造线性分类器对高光谱影像进行分类；最后，通过2幅标准的高光谱影像数据验证
Speech recognition from spectral dynamics
Hynek Hermansky
2011-10-01
Information is carried in changes of a signal. The paper starts with revisiting Dudley’s concept of the carrier nature of speech. It points to its close connection to modulation spectra of speech and argues against short-term spectral envelopes as dominant carriers of the linguistic information in speech. The history of spectral representations of speech is brieﬂy discussed. Some of the history of gradual infusion of the modulation spectrum concept into Automatic recognition of speech (ASR) comes next, pointing to the relationship of modulation spectrum processing to wellaccepted ASR techniques such as dynamic speech features or RelAtive SpecTrAl (RASTA) ﬁltering. Next, the frequency domain perceptual linear prediction technique for deriving autoregressive models of temporal trajectories of spectral power in individual frequency bands is reviewed. Finally, posterior-based features, which allow for straightforward application of modulation frequency domain information, are described. The paper is tutorial in nature, aims at a historical global overview of attempts for using spectral dynamics in machine recognition of speech, and does not always provide enough detail of the described techniques. However, extensive references to earlier work are provided to compensate for the lack of detail in the paper.
Hirt, Christian; Reußner, Elisabeth; Rexer, Moritz; Kuhn, Michael
2016-09-01
Over the past years, spectral techniques have become a standard to model Earth's global gravity field to 10 km scales, with the EGM2008 geopotential model being a prominent example. For some geophysical applications of EGM2008, particularly Bouguer gravity computation with spectral techniques, a topographic potential model of adequate resolution is required. However, current topographic potential models have not yet been successfully validated to degree 2160, and notable discrepancies between spectral modeling and Newtonian (numerical) integration well beyond the 10 mGal level have been reported. Here we accurately compute and validate gravity implied by a degree 2160 model of Earth's topographic masses. Our experiments are based on two key strategies, both of which require advanced computational resources. First, we construct a spectrally complete model of the gravity field which is generated by the degree 2160 Earth topography model. This involves expansion of the topographic potential to the 15th integer power of the topography and modeling of short-scale gravity signals to ultrahigh degree of 21,600, translating into unprecedented fine scales of 1 km. Second, we apply Newtonian integration in the space domain with high spatial resolution to reduce discretization errors. Our numerical study demonstrates excellent agreement (8 μGgal RMS) between gravity from both forward modeling techniques and provides insight into the convergence process associated with spectral modeling of gravity signals at very short scales (few km). As key conclusion, our work successfully validates the spectral domain forward modeling technique for degree 2160 topography and increases the confidence in new high-resolution global Bouguer gravity maps.
Joiner, J.; Gaunter, L.; Lindstrot, R.; Voigt, M.; Vasilkov, A. P.; Middleton, E. M.; Huemmrich, K. F.; Yoshida, Y.; Frankenberg, C.
2013-01-01
Globally mapped terrestrial chlorophyll fluorescence retrievals are of high interest because they can provide information on the functional status of vegetation including light-use efficiency and global primary productivity that can be used for global carbon cycle modeling and agricultural applications. Previous satellite retrievals of fluorescence have relied solely upon the filling-in of solar Fraunhofer lines that are not significantly affected by atmospheric absorption. Although these measurements provide near-global coverage on a monthly basis, they suffer from relatively low precision and sparse spatial sampling. Here, we describe a new methodology to retrieve global far-red fluorescence information; we use hyperspectral data with a simplified radiative transfer model to disentangle the spectral signatures of three basic components: atmospheric absorption, surface reflectance, and fluorescence radiance. An empirically based principal component analysis approach is employed, primarily using cloudy data over ocean, to model and solve for the atmospheric absorption. Through detailed simulations, we demonstrate the feasibility of the approach and show that moderate-spectral-resolution measurements with a relatively high signal-to-noise ratio can be used to retrieve far-red fluorescence information with good precision and accuracy. The method is then applied to data from the Global Ozone Monitoring Instrument 2 (GOME-2). The GOME-2 fluorescence retrievals display similar spatial structure as compared with those from a simpler technique applied to the Greenhouse gases Observing SATellite (GOSAT). GOME-2 enables global mapping of far-red fluorescence with higher precision over smaller spatial and temporal scales than is possible with GOSAT. Near-global coverage is provided within a few days. We are able to show clearly for the first time physically plausible variations in fluorescence over the course of a single month at a spatial resolution of 0.5 deg × 0.5 deg
Millar, Richard J.; Nicholls, Zebedee R.; Friedlingstein, Pierre; Allen, Myles R.
2017-06-01
Projections of the response to anthropogenic emission scenarios, evaluation of some greenhouse gas metrics, and estimates of the social cost of carbon often require a simple model that links emissions of carbon dioxide (CO2) to atmospheric concentrations and global temperature changes. An essential requirement of such a model is to reproduce typical global surface temperature and atmospheric CO2 responses displayed by more complex Earth system models (ESMs) under a range of emission scenarios, as well as an ability to sample the range of ESM response in a transparent, accessible and reproducible form. Here we adapt the simple model of the Intergovernmental Panel on Climate Change 5th Assessment Report (IPCC AR5) to explicitly represent the state dependence of the CO2 airborne fraction. Our adapted model (FAIR) reproduces the range of behaviour shown in full and intermediate complexity ESMs under several idealised carbon pulse and exponential concentration increase experiments. We find that the inclusion of a linear increase in 100-year integrated airborne fraction with cumulative carbon uptake and global temperature change substantially improves the representation of the response of the climate system to CO2 on a range of timescales and under a range of experimental designs.
Langmann, Elisabet
2011-01-01
In this article, I argue that any success a discourse on cosmopolitan hospitality might have in global citizenship education depends on how it deals with its own limits, and I propose a way of responding to these limits that takes the cosmopolitan commitment to openness to the other seriously. Following Jacques Derrida, my point is that to teach…
Lund, Marianne Tronstad; Eyring, Veronika; Fuglestvedt, Jan; Hendricks, Johannes; Lauer, Axel; Lee, David; Righi, Mattia
2012-08-21
We utilize a range of emission scenarios for shipping to determine the induced global-mean radiative forcing and temperature change. Ship emission scenarios consistent with the new regulations on nitrogen oxides (NO(x)) and sulfur dioxide (SO(2)) from the International Maritime Organization and two of the Representative Concentration Pathways are used as input to a simple climate model (SCM). Based on a complex aerosol-climate model we develop and test new parametrizations of the indirect aerosol effect (IAE) in the SCM that account for nonlinearities in radiative forcing of ship-induced IAE. We find that shipping causes a net global cooling impact throughout the period 1900-2050 across all parametrizations and scenarios. However, calculated total net global-mean temperature change in 2050 ranges from -0.03[-0.07,-0.002]°C to -0.3[-0.6,-0.2]°C in the A1B scenario. This wide range across parametrizations emphasizes the importance of properly representing the IAE in SCMs and to reflect the uncertainties from complex global models. Furthermore, our calculations show that the future ship-induced temperature response is likely a continued cooling if SO(2) and NO(x) emissions continue to increase due to a strong increase in activity, despite current emission regulations. However, such cooling does not negate the need for continued efforts to reduce CO(2) emissions, since residual warming from CO(2) is long-lived.
L.J. Pegler (Lee)
2009-01-01
textabstractThe co-ordination of global production and trade within value chains has amplified debates concerning the impact of globalisation on labour, especially for developing countries. Whilst many development agencies argue for value chain insertion and upgrading as optimistic development pathw
L.J. Pegler (Lee)
2009-01-01
textabstractThe co-ordination of global production and trade within value chains has amplified debates concerning the impact of globalisation on labour, especially for developing countries. Whilst many development agencies argue for value chain insertion and upgrading as optimistic development
Biega, A; Greenberg, D.A.; Mooers, A.O.
2017-01-01
Ambitious global conservation targets have been set to manage increasing threats to amphibians. Ex situ institutions (broadly, ‘zoos’) are playing an expanding role in meeting these targets. Here, we examine the extent to which zoos house species representing the greatest overall conservation pri...
Mátyus, Edit; Reiher, Markus
2012-07-14
We elaborate on the theory for the variational solution of the Schrödinger equation of small atomic and molecular systems without relying on the Born-Oppenheimer paradigm. The all-particle Schrödinger equation is solved in a numerical procedure using the variational principle, Cartesian coordinates, parameterized explicitly correlated Gaussian functions with polynomial prefactors, and the global vector representation. As a result, non-relativistic energy levels and wave functions of few-particle systems can be obtained for various angular momentum, parity, and spin quantum numbers. A stochastic variational optimization of the basis function parameters facilitates the calculation of accurate energies and wave functions for the ground and some excited rotational-(vibrational-)electronic states of H(2) (+) and H(2), three bound states of the positronium molecule, Ps(2), and the ground and two excited states of the (7)Li atom.
Friedrich, Johannes; Fetzer, Ingo; Cornell, Sarah
2016-04-01
The planetary boundaries framework is an approach to global sustainability that emphasises non-linear threshold behavior in anthropogenically perturbed Earth system processes. However, knowledge about the characteristics and positions of thresholds, and the scope for management of the boundaries is not well established. Global integrated models can help to improve this understanding, by reflecting the complex feedbacks between human and environmental systems. This study analyses the current state of integrated models with regard to the main processes identified as 'critical Earth system processes' in the planetary boundaries framework, and identifies gaps and suggests priorities for future improvements. Our approach involves creating a common ontology of model descriptions, and performing a network analysis on the state of system integration in models. The distinct clusters of specific biophysical and social-economic systems obviously has enabled progress in those specific areas of global change, but it now constrains analysis of important human-driven Earth system dynamics. The modeling process therefore has to be improved through technical integration, scientific gap-filling, and also changes in scientific institutional dynamics. Combined, this can advance model potentials that may help us to find sustainable pathways within planetary boundaries.
G. W. Mann
2012-05-01
Full Text Available In the most advanced aerosol-climate models it is common to represent the aerosol particle size distribution in terms of several log-normal modes. This approach, motivated by computational efficiency, makes assumptions about the shape of the particle distribution that may not always capture the properties of global aerosol. Here, a global modal aerosol microphysics module (GLOMAP-mode is evaluated and improved by comparing against a sectional version (GLOMAP-bin and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that the current values for two size distribution parameter settings in the modal scheme (mode widths and inter-modal separation sizes resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Annual mean surface-level mass of sulphate, sea-salt, black carbon (BC and organic carbon (OC are within 25% in the two schemes in nearly all regions. Surface level concentrations of condensation nuclei (CN, cloud condensation nuclei (CCN, surface area density and condensation sink also compare within 25% in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically 25–60% higher in the modal model, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2–4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin
Guenet, Bertrand; Esteban Moyano, Fernando; Peylin, Philippe; Ciais, Philippe; Janssens, Ivan A.
2016-03-01
Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURY-type soil decomposition model, whose decomposition equations are based only on first-order kinetics. We then compared the PRIM model and the standard first-order decay model incorporated into the global land biosphere model ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems). A test of both models was performed at ecosystem scale using litter manipulation experiments from five sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE-PRIM could simulate the observed priming (R2 = 0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the
G. W. Mann
2012-01-01
Full Text Available A global modal aerosol microphysics module (GLOMAP-mode is evaluated and improved by comparing against a sectional version (GLOMAP-bin and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that various size distribution parameter settings (mode widths and inter-modal separation sizes resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Surface mass of sulphate, sea-salt, black carbon (BC and organic carbon (OC are, on the annual mean, within 25 % in the two schemes in nearly all regions. On the annual mean, surface level concentrations of condensation nuclei (CN, cloud condensation nuclei (CCN, surface area density and condensation sink also compare within 25 % in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically higher in the modal scheme, by 25–60 %, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2–4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin-mode differences are much less than model-observation differences, although some processes are missing in these runs which may pose a bigger challenge to modal schemes (e.g. boundary layer nucleation, ultra-fine sea-spray. The findings here underline the need for a spectrum of complexity in global models, with size-resolved aerosol properties
Horwitz, James; Zeng, Wen
2008-10-01
As new methods of describing multiple fluid species and other advances enhance the capability of global magnetospheric models to simulate the dynamics of multiple ion species, they also allow more accurate incorporation of ionospheric plasma outflows as source populations into these large scale models. Here, we shall describe the distilled results of numerous physics-based simulations of ionospheric plasma outflows influenced by auroral driving agents in terms of compact analytic expressions in terms of precipitation electron energy flux levels, characteristic energy levels of the precipitating electrons, the peak spectral wave densities for low-frequency electrostatic waves which transversely heat ionospheric ions, and solar zenith angle. The simulations are conducted with the UT Arlington Dynamic Fluid Kinetic (DyFK) ionospheric plasma transport code. We present these analytic expressions for ionospheric origin O^+ and H^+ densities, temperatures and field-aligned flow velocities at the 3 RE altitude inner boundaries of typical magnetospheric models.
H. Wang
2013-01-01
Full Text Available Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5, have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold increase in the winter (summer months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold
Wang, Hailong; Easter, Richard C.; Rasch, Philip J.; Wang, Minghuai; Liu, Xiaohong; Ghan, Steven J.; Qian, Yun; Yoon, Jin-Ho; Ma, Po-Lun; Vinoj, V.
2013-06-05
Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5), have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF) that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC) due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold) increase in the winter (summer) months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold) increase in
H. Wang
2013-06-01
Full Text Available Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5, have large biases in predicting aerosols in remote regions such as the upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol–climate model that explicitly represents convection and aerosol–cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the subgrid-scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a 10-fold (5-fold increase in the winter (summer months, resulting in a much-better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold
G. Tang
2015-12-01
with very tight relative update tolerance. As some biogeochemical processes (e.g., methane and nitrous oxide production and consumption involve very low half saturation and threshold concentrations, this work provides insights for addressing nonphysical negativity issues and facilitates the representation of a mechanistic biogeochemical description in earth system models to reduce climate prediction uncertainty.
范玮丽
2008-01-01
This paper mainly talks about the currently hot topic-globalization. Firstly, it brings out the general trend about globalization and how to better understand its implication. Secondly, it largely focuses on how to deal with it properly, especially for international marketers. Then, facing with the overwhelming trend, it is time for us to think about seriously what has globalization brought to us. Last but not least, it summarized the author's personal view about the future of globalization and how should we go.
Hunter, J. R.; Woodworth, P. L.; Wahl, T.; Nicholls, R. J.
2017-09-01
The largest collection of tide gauge records assembled to date, called GESLA-2, has been used to provide reliable extreme sea level parameters at 655 locations around the world. This has enabled a rigorous assessment of the European Union-funded DINAS-COAST (D-C) data set of extreme sea level information for the global coastline that has been used in many published flood impact studies. We find the D-C extreme levels to be generally both too high, compared to those from GESLA-2, and too flat, when plotted as a function of return period. This leads to an over-estimation of the probability of extreme sea levels in the present day for most locations around the world, and also to an over-estimation of the probability of extreme sea levels in the future as sea level rises. A detailed impact study is conducted for the world's largest coastal cities following the approach of Hallegatte et al. (2013), resulting in similar conclusions for these particular locations. We suggest that most previous studies that have relied upon D-C information should be re-assessed in the light of these findings, using more recent modelling-based estimates of extreme sea level information.
Tulio Rosembuj
2006-12-01
Full Text Available There is no singular globalization, nor is the result of an individual agent. We could start by saying that global action has different angles and subjects who perform it are different, as well as its objectives. The global is an invisible invasion of materials and immediate effects.
K. Zhang
2012-10-01
Full Text Available This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation.
Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker in-cloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7 between accumulation mode and coarse mode emission fluxes of
Javier Sanchez-Rojas
2012-01-01
Full Text Available A new gravity data compilation for Venezuela was processed and homogenized. Gravity was measured in reference to the International Gravity Standardization Net 1971, and the complete Bouguer anomaly was calculated by using the Geodetic Reference System 1980 and 2.67 Mg/m3. A regional gravity map was computed by removing wavelengths higher than 200 km from the Bouguer anomaly. After the anomaly separation, regional and residual Bouguer gravity fields were then critically discussed in term of the regional tectonic features. Results were compared with the previous geological and tectonic information obtained from former studies. Gravity and topography data in the spectral domain were used to examine the elastic thickness and depths of the structures of the causative measured anomaly. According to the power spectrum analysis results of the gravity data, the averaged Moho depths for the massif, plains, and mountainous areas in Venezuela are 42, 35, and 40 km, respectively. The averaged admittance function computed from the topography and Free-Air anomaly profiles across Mérida Andes showed a good fit for a regional compensation model with an effective elastic thickness of 15 km.
Widjaja, Effendi; Garland, Marc
2002-07-15
A combination of singular value decomposition, entropy minimization, and simulated annealing was applied to a synthetic 7-species spectroscopic data set with added white noise. The pure spectra were highly overlapping. Global minima for selected objective functions were obtained for the transformation of the first seven right singular vectors. Simple Shannon type entropy functions were used in the objective functions and realistic physical constraints were imposed in the penalties. It was found that good first approximations for the pure component spectra could be obtained without the use of any a priori information. The present method out performed the two widely used routines, namely Simplisma and OPA-ALS, as well as IPCA. These results indicate that a combination of SVD, entropy minimization, and simulated annealing is a potentially powerful tool for spectral reconstructions from large real experimental systems. Copyright 2002 Wiley Periodicals, Inc.
Adjoint Functors and Representation Dimensions
Chang Chang XI
2006-01-01
We study the global dimensions of the coherent functors over two categories that are linked by a pair of adjoint functors. This idea is then exploited to compare the representation dimensions of two algebras. In particular, we show that if an Artin algebra is switched from the other, then they have the same representation dimension.
Someya, Yu; Imasu, Ryoichi; Ota, Yoshifumi; Saitoh, Naoko
2014-05-01
Global tropospheric cloud distribution was derived from thermal infrared band data observed by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse gases Observation SATellite (GOSAT). It is expected that this band has ability to detect optically thin clouds compared with Cloud and Aerosol Imager (CAI) which is the other sensor on GOSAT. In addition, polar stratospheric clouds (PSCs) which can be harder to detect than the tropospheric clouds because of high reflectivity or low temperature of the surface and their low optical thickness were also detected. We have modified CO2 slicing method which was developed as one of the cirrus cloud detection techniques using thermal infrared band data to detect thin clouds more stably. The pseudo spectral channels were defined as sets of several actual spectral channels between 700cm-1 and 750cm-1 which have weighting function peak height in a same height range for each 0.5km. These pseudo channels were optimized with simulation studies using a multi-scattering radiative transfer code, Polarized radiance System for Transfer of Atmospheric Radiation (Pstar) 3 for several temperature profile patterns prepared based on latitudes and temperature at 500hPa. GOSAT data was analyzed with the combination of these pseudo channels determined for each of observation points from these simulations and the results were compared with the observational results from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) / Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The comparisons about global cloud are based on the coincident observations in 2010. Monthly occurrences of Antarctic PSCs were compared for each grid area from June to September in 2010. As a result, the correlation coefficients in each month are 0.76, 0.71, 0.75, and 0.61 relatively. Though that is low value in September, it can be explained by decrease of occurrences.
Anatomy of the AGN in NGC 5548. I. A global model for the broadband spectral energy distribution
Mehdipour, M.; Kaastra, J. S.; Kriss, G. A.; Cappi, M.; Petrucci, P.-O.; Steenbrugge, K. C.; Arav, N.; Behar, E.; Bianchi, S.; Boissay, R.; Branduardi-Raymont, G.; Costantini, E.; Ebrero, J.; Di Gesu, L.; Harrison, F. A.; Kaspi, S.; De Marco, B.; Matt, G.; Paltani, S.; Peterson, B. M.; Ponti, G.; Pozo Nuñez, F.; De Rosa, A.; Ursini, F.; de Vries, C. P.; Walton, D. J.; Whewell, M.
2015-03-01
An extensive multi-satellite campaign on NGC 5548 has revealed this archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy absorption. Our observations taken in 2013-2014 with XMM-Newton, Swift, NuSTAR, INTEGRAL, Chandra, HST and two ground-based observatories have together enabled us to establish that this unexpected phenomenon is caused by an outflowing stream of weakly ionised gas (called the obscurer), extending from the vicinity of the accretion disk to the broad-line region. In this work we present the details of our campaign and the data obtained by all the observatories. We determine the spectral energy distribution of NGC 5548 from near-infrared to hard X-rays by establishing the contribution of various emission and absorption processes taking place along our line of sight towards the central engine. We thus uncover the intrinsic emission and produce a broadband continuum model for both obscured (average summer 2013 data) and unobscured (warm, optically-thick corona as part of the inner accretion disk. We then investigate the effects of the continuum on the ionisation balance and thermal stability of photoionised gas for unobscured and obscured epochs. Appendix A is available in electronic form at http://www.aanda.org
Anatomy of the AGN in NGC 5548: I. A global model for the broadband spectral energy distribution
Mehdipour, M; Kriss, G A; Cappi, M; Petrucci, P -O; Steenbrugge, K C; Arav, N; Behar, E; Bianchi, S; Boissay, R; Branduardi-Raymont, G; Costantini, E; Ebrero, J; Di Gesu, L; Harrison, F A; Kaspi, S; De Marco, B; Matt, G; Paltani, S; Peterson, B M; Ponti, G; Nuñez, F Pozo; De Rosa, A; Ursini, F; de Vries, C P; Walton, D J; Whewell, M
2015-01-01
An extensive multi-satellite campaign on NGC 5548 has revealed this archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy absorption. Our observations taken in 2013-2014 with XMM-Newton, Swift, NuSTAR, INTEGRAL, Chandra, HST and two ground-based observatories have together enabled us to establish that this unexpected phenomenon is caused by an outflowing stream of weakly ionised gas (called the obscurer), extending from the vicinity of the accretion disk to the broad-line region. In this work we present the details of our campaign and the data obtained by all the observatories. We determine the spectral energy distribution of NGC 5548 from near-infrared to hard X-rays by establishing the contribution of various emission and absorption processes taking place along our line of sight towards the central engine. We thus uncover the intrinsic emission and produce a broadband continuum model for both obscured (average summer 2013 data) and unobscured ($<$ 2011) epochs of NGC 5548. Our res...
Spectral geometry of spacetime
Kopf, T
2000-01-01
Spacetime, understood as a globally hyperbolic manifold, may be characterized by spectral data using a 3+1 splitting into space and time, a description of space by spectral triples and by employing causal relationships, as proposed earlier. Here, it is proposed to use the Hadamard condition of quantum field theory as a smoothness principle.
Plum, Maja
Globalization is often referred to as external to education - a state of affair facing the modern curriculum with numerous challenges. In this paper it is examined as internal to curriculum; analysed as a problematization in a Foucaultian sense. That is, as a complex of attentions, worries, ways...... of reasoning, producing curricular variables. The analysis is made through an example of early childhood curriculum in Danish Pre-school, and the way the curricular variable of the pre-school child comes into being through globalization as a problematization, carried forth by the comparative practices of PISA...
Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.
2012-06-01
Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. aerosol optical thickness (AOT) and Ångström exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) level 2.0 spectral observations. Additionally, temporal trends of coarse- and fine-mode dominant AOTs (CdAOT and FdAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström exponent difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation (σt) and (2) number of observations per month (nt). Temporal increase of FdAOTs (440 nm) prevails over newly industrializing countries in East Asia (weighted trends; +6.23% yr-1 at Beijing) and active agricultural burning regions in South Africa (+1.89% yr-1 at Mongu). On the other hand, insignificant or negative trends for FdAOTs are detected over Western Europe (+0.25% yr-1 at Avignon and -2.29% yr-1 at Ispra) and North America (-0.52% yr-1 for GSFC and -0.01% yr-1 at MD_Science_Center). Over desert regions, both increase and decrease of CdAOTs (+3.37% yr-1 at Solar_Village and -1.18% yr-1 at Ouagadougou) are observed depending on meteorological conditions.
Nakata, M
1987-03-01
EEG alterations after 5 or 10 minutes of global ischemia were investigated for 6 hours of postischemic period in 18 adult cats, together with biophysiological parameters such as cerebral blood flow, intracranial pressure, systemic blood pressure, heart rate, and blood gases. Our EEG analytical system is composed of high fidelity pre-amplifier, AA 6 MK II (Medelec Limited, England) and signal processor 7T 08 (NEC-SanEi, Japan). It is qualified to analyze frequencies up to 20 kHz within 3 dB cut-off. Particular features of our EEG analytical method are focused on Fourier analysis about broad frequency bands, frequency and amplitude spectra to be expressed on bi-logarithmic graph and direct EEG recordings from various structures of the brain. On the basis of fluctuation theory following 3 types were divided; Type f which corresponds to 1/f fluctuation, Type L which corresponds to Lorentzian fluctuation, Type f+L which is the sum of Type f and L. The distribution of these types in the central nervous system corresponds with cortical structures, spinal cord and brain stem respectively. In conclusion, there was a good correlation between EEG and blood flow in the motor cortex. The functional reversibility after ischemia was different according to the types. Type f structures, namely the motor cortex, hippocampus and amygdala were vulnerable and Type f+L structures namely ventrolateral nucleus of the thalamus and midbrain reticular formation tended to recover or stay in preservation.
Spectral Approaches to Learning Predictive Representations
2012-09-01
as a linear function of an indicator vector of the current observa- tion: PX+,AO| htP −1 AO,AO|hteao (4.10) where eao is an indicator vector that when...multiplied by PX+,AO| htP −1 AO,AO|ht , selects the column containing the correct Bayes’ rule update x(ht+1) = Maox(ht)/m>∞Maox(ht) at time t. In...Equation 4.10 is preserved: ΣX+,AO|htΣ −1 AO,AO|htφ AO t = PX+,AO|htΦ AO> ( ΦAO > )† P−1AO,AO|htΦ AO†ΦAOeao = PX+,AO| htP −1 AO,AO|hteao (4.13) Conversely
Spectral minutiae representations for fingerprint recognition
Xu, Haiyun
2010-01-01
The term biometrics refers to the technologies that measure and analyze human intrinsic physical or behavioral characteristics for authenticating individuals. Nowadays, biometric technology is increasingly deployed in civil and commercial applications. The growing use of biometrics is raising securi
Spectral representation of measured shallow water waves
SanilKumar, V.; Mandal, S.; Anand, N.M.; Nayak, B.U.
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D'Incecco, Piero; Helbert, Jörn; D'Amore, Mario; Ferrari, Sabrina; Head, James W.; Maturilli, Alessandro; Hiesinger, Harald
2016-11-01
In the present work, we expose procedures and results from a global scale geologically supervised spectral analysis of 121 impact craters on Mercury, selected on the basis of specific morphologic criteria. Using the capabilities of DFTs developed by PEL researchers at DLR, we combined MASCS spectra from the DLR database with MDIS high-resolution images. We use impact structures as a window for identifying vertical and horizontal compositional heterogeneities in the shallow crust of Mercury. Using specific GIS queries on a global scale, we defined five morphologic classes of units for each of the 121 impact craters, moving outward from the central peak to deposits at ten radii distance from the crater rim. We also used an external reference area as a term of comparison to represent intercrater plains. We then retrieved all the available MASCS spectra contained within each of those units. We analyzed the spectral slopes in the 350-450 nm and 450-650 nm ranges and reflectances in the 700-750 nm range using two different approaches, the first one being more conservative than the second one. The results indicate that the central peaks class is spectrally the most heterogeneous compared to all the other defined classes. As we move outward from the central peaks to external deposits, the other morphologic classes tend to get more and more spectrally and compositionally homogenous and more similar to intercrater plains. We identified a dependency of the spectral slopes from latitude. The spectral slopes of the analyzed deposits tend to decrease at increasing latitudes. This result might indicate the presence of a global N-S dichotomy in the composition of the shallow crust of Mercury. The detailed analysis of three impact craters with distinctive spectral characteristics revealed as well the occurrence of short-range horizontal heterogeneities in the composition of the shallow crust of Mercury.
Hirt, Christian; Rexer, Moritz; Claessens, Sten; Rummel, Reiner
2017-10-01
Comparisons between high-degree models of the Earth's topographic and gravitational potential may give insight into the quality and resolution of the source data sets, provide feedback on the modelling techniques and help to better understand the gravity field composition. Degree correlations (cross-correlation coefficients) or reduction rates (quantifying the amount of topographic signal contained in the gravitational potential) are indicators used in a number of contemporary studies. However, depending on the modelling techniques and underlying levels of approximation, the correlation at high degrees may vary significantly, as do the conclusions drawn. The present paper addresses this problem by attempting to provide a guide on global correlation measures with particular emphasis on approximation effects and variants of topographic potential modelling. We investigate and discuss the impact of different effects (e.g., truncation of series expansions of the topographic potential, mass compression, ellipsoidal versus spherical approximation, ellipsoidal harmonic coefficient versus spherical harmonic coefficient (SHC) representation) on correlation measures. Our study demonstrates that the correlation coefficients are realistic only when the model's harmonic coefficients of a given degree are largely independent of the coefficients of other degrees, permitting degree-wise evaluations. This is the case, e.g., when both models are represented in terms of SHCs and spherical approximation (i.e. spherical arrangement of field-generating masses). Alternatively, a representation in ellipsoidal harmonics can be combined with ellipsoidal approximation. The usual ellipsoidal approximation level (i.e. ellipsoidal mass arrangement) is shown to bias correlation coefficients when SHCs are used. Importantly, gravity models from the International Centre for Global Earth Models (ICGEM) are inherently based on this approximation level. A transformation is presented that enables a
Voitsekhovskaya, O. K.; Egorov, O. V.; Kashirskii, D. E.
2016-08-01
Nitrogen dioxide, 14N16O2, line positions and intensities calculated by us based on a "local" effective operator method are compared to the recent results of the "global" calculation. The comparison was made for theoretical absorption coefficients in the spectral range of 600-3700 cm- 1 using the measured data taken from the Pacific Northwest National Laboratory. In order to conduct the calculations, empirical parameters of the effective rotational Hamiltonian of the twenty-one vibrational states were applied from the most recent experimental works. The second order parameters of the dipole moment function of 14N16O2 were determined for the first time. The "local" line list in this research consists of one hundred and four bands and includes the line intensities of the v1 + v2 + v3 band of 14N16O2 that have not yet been investigated in the literature. Among these bands, only eleven bands are included in HITRAN2012. The reasons behind the disagreements between the theoretical and measured absorption coefficients of 14N16O2 are discussed.
Schiffler, Ralf
2014-01-01
This book is intended to serve as a textbook for a course in Representation Theory of Algebras at the beginning graduate level. The text has two parts. In Part I, the theory is studied in an elementary way using quivers and their representations. This is a very hands-on approach and requires only basic knowledge of linear algebra. The main tool for describing the representation theory of a finite-dimensional algebra is its Auslander-Reiten quiver, and the text introduces these quivers as early as possible. Part II then uses the language of algebras and modules to build on the material developed before. The equivalence of the two approaches is proved in the text. The last chapter gives a proof of Gabriel’s Theorem. The language of category theory is developed along the way as needed.
Wulf-Andersen, Trine Østergaard
2012-01-01
This article is based on a Danish research project with young people in vulnerable positions. Young people are involved throughout the research process, including the interpretation of material produced through interviews, and discussions on how reflections and conclusions from the research should......, and dialogue, of situated participants. The article includes a lengthy example of a poetic representation of one participant’s story, and the author comments on the potentials of ‘doing’ poetic representations as an example of writing in ways that challenges what sometimes goes unasked in participative social...
Rasmussen, Majken Kirkegaard; Petersen, Marianne Graves
2011-01-01
Stereotypic presumptions about gender affect the design process, both in relation to how users are understood and how products are designed. As a way to decrease the influence of stereotypic presumptions in design process, we propose not to disregard the aspect of gender in the design process......, as the perspective brings valuable insights on different approaches to technology, but instead to view gender through a value lens. Contributing to this perspective, we have developed Value Representations as a design-oriented instrument for staging a reflective dialogue with users. Value Representations...
An Enhanced Global Spectral Model
1992-02-27
dddtc e prod e = Kinetic energy/unit mass Eq. (5) ekh cpcnst diffusion coefficient for Z, T and W. ep pblvar epsl ipmn epsion ipmn epslr cpcnst eps...param List output ioterm param Terminal output ipdim grddim ipmn ipmn contains the constant parts of the PMNS computation. Refer to routines INIPMN and
Petersson, Dag; Dahlgren, Anna; Vestberg, Nina Lager
to the enterprises of the medium. This is the subject of Representational Machines: How photography enlists the workings of institutional technologies in search of establishing new iconic and social spaces. Together, the contributions to this edited volume span historical epochs, social environments, technological...
Integral representations and properties of operator fractional Brownian motions
Didier, Gustavo; 10.3150/10-BEJ259
2011-01-01
Operator fractional Brownian motions (OFBMs) are (i) Gaussian, (ii) operator self-similar and (iii) stationary increment processes. They are the natural multivariate generalizations of the well-studied fractional Brownian motions. Because of the possible lack of time-reversibility, the defining properties (i)--(iii) do not, in general, characterize the covariance structure of OFBMs. To circumvent this problem, the class of OFBMs is characterized here by means of their integral representations in the spectral and time domains. For the spectral domain representations, this involves showing how the operator self-similarity shapes the spectral density in the general representation of stationary increment processes. The time domain representations are derived by using primary matrix functions and taking the Fourier transforms of the deterministic spectral domain kernels. Necessary and sufficient conditions for OFBMs to be time-reversible are established in terms of their spectral and time domain representations. I...
Spectral Geometry and Causality
Kopf, T
1996-01-01
For a physical interpretation of a theory of quantum gravity, it is necessary to recover classical spacetime, at least approximately. However, quantum gravity may eventually provide classical spacetimes by giving spectral data similar to those appearing in noncommutative geometry, rather than by giving directly a spacetime manifold. It is shown that a globally hyperbolic Lorentzian manifold can be given by spectral data. A new phenomenon in the context of spectral geometry is observed: causal relationships. The employment of the causal relationships of spectral data is shown to lead to a highly efficient description of Lorentzian manifolds, indicating the possible usefulness of this approach. Connections to free quantum field theory are discussed for both motivation and physical interpretation. It is conjectured that the necessary spectral data can be generically obtained from an effective field theory having the fundamental structures of generalized quantum mechanics: a decoherence functional and a choice of...
Putman, William M.
2010-01-01
The Goddard Earth Observing System Model (GEOS-S), an earth system model developed in the NASA Global Modeling and Assimilation Office (GMAO), has integrated the non-hydrostatic finite-volume dynamical core on the cubed-sphere grid. The extension to a non-hydrostatic dynamical framework and the quasi-uniform cubed-sphere geometry permits the efficient exploration of global weather and climate modeling at cloud permitting resolutions of 10- to 4-km on today's high performance computing platforms. We have explored a series of incremental increases in global resolution with GEOS-S from irs standard 72-level 27-km resolution (approx.5.5 million cells covering the globe from the surface to 0.1 hPa) down to 3.5-km (approx. 3.6 billion cells).
Residual Representations of Spacetime
Saller, H
2001-01-01
Spacetime is modelled by binary relations - by the classes of the automorphisms $\\GL(\\C^2)$ of a complex 2-dimensional vector space with respect to the definite unitary subgroup $\\U(2)$. In extension of Feynman propagators for particle quantum fields representing only the tangent spacetime structure, global spacetime representations are given, formulated as residues using energy-momentum distributions with the invariants as singularities. The associatated quantum fields are characterized by two invariant masses - for time and position - supplementing the one mass for the definite unitary particle sector with another mass for the indefinite unitary interaction sector without asymptotic particle interpretation.
From De-Anglicization to Internationalisation: Cultural Representations of the UKand the USA in Global, Adapted and Local ELT Textbooks in Argentina
Enrique Alejandro Basabe
2006-10-01
Full Text Available It is generally acknowledged that the culture of English-speaking countries has abandoned its central role in recent ELT materials. However, this study suggests that representations of the Anglo-American culture are still favoured in ELT textbooks but that, in most cases, they have been transformed into “international” attitudes. This idea is tested by the compilation of lists of cultural references for four series of textbooks in use in Argentina, and by the application of the procedures of Critical Discourse Analysis (CDA to a selection of reading passages from them. The findings provide an answer as to what representations of English-speaking cultures are in current textbooks and open to debate the apparent fairness of English as an International Language (EIL.Existe un consenso casi generalizado en que la cultura de los países de habla inglesa ha abandonado su papel central en los textos de inglés como lengua extranjera. Sin embargo, se sugiere que las representaciones de la cultura Anglo-americana aun persisten sólo que transformadas en actitudes “internacionales”. Esta idea se pone a prueba mediante la compilación de listas de referencias culturales en cuatros series de libros en uso en Argentina y en el Análisis Crítico del Discurso (ACD de una serie de textos destinados a la lectura en dichos volúmenes. Los resultados determinan qué representaciones culturales subsisten en los textos y abren al debate la aparente neutralidad del inglés como lengua internacional (EIL, por sus siglas en inglés.
Temporal Lorentzian spectral triples
Franco, Nicolas
2014-09-01
We present the notion of temporal Lorentzian spectral triple which is an extension of the notion of pseudo-Riemannian spectral triple with a way to ensure that the signature of the metric is Lorentzian. A temporal Lorentzian spectral triple corresponds to a specific 3 + 1 decomposition of a possibly noncommutative Lorentzian space. This structure introduces a notion of global time in noncommutative geometry. As an example, we construct a temporal Lorentzian spectral triple over a Moyal-Minkowski spacetime. We show that, when time is commutative, the algebra can be extended to unbounded elements. Using such an extension, it is possible to define a Lorentzian distance formula between pure states with a well-defined noncommutative formulation.
D. Yamazaki
2009-07-01
Full Text Available This paper proposes an improved method to convert a fine-resolution flow direction map into a coarse-resolution river network map for the use in global river routing models. The proposed method attempts to preserve the river network structure of an original fine-resolution map in upscaling procedures, which has not been achieved by previous methods. It is found that the problem in previous methods is mainly due to the traditional way of describing downstream cells of a river network map with a direction toward one of the eight neighboring cells. Instead in the improved method, the downstream cell can be flexibly located onto any cells in the river network map. The improved method is applied to derive global river network maps at various resolutions. It succeeded to preserve the river network structure of the original flow direction map, and consequently realizes automatic construction of river network maps at any resolutions. This enables both higher-resolution approach in global river routing models and inclusion of sub-grid scale topographic features, such as realistic river meanderings and catchment boundaries. Those advantages of the proposed method are expected to enhance ability of global river routing models, providing ways to represent surface water storage and movement such as river discharge and inundated area extent in much finer-scale than ever modeled.
Mullins, Michael
elements into the process of design. Through its immersive properties, virtual reality allows access to a spatial experience of a computer model very different to both screen based simulations as well as traditional forms of architectural representation. The dissertation focuses on processes of the current......Contemporary communicational and informational processes contribute to the shaping of our physical environment by having a powerful influence on the process of design. Applications of virtual reality (VR) are transforming the way architecture is conceived and produced by introducing dynamic...... by ‘professionals’ to ‘laypeople’. The thesis articulates problems in VR’s current application, specifically the CAVE and Panorama theatres, and seeks an understanding of how these problems may be addressed. The central questions that have motivated this research project are thus: What is architectural VR...
Shen, Jie; Wang, Li-Lian
2011-01-01
Along with finite differences and finite elements, spectral methods are one of the three main methodologies for solving partial differential equations on computers. This book provides a detailed presentation of basic spectral algorithms, as well as a systematical presentation of basic convergence theory and error analysis for spectral methods. Readers of this book will be exposed to a unified framework for designing and analyzing spectral algorithms for a variety of problems, including in particular high-order differential equations and problems in unbounded domains. The book contains a large
Concepts, ontologies, and knowledge representation
Jakus, Grega; Omerovic, Sanida; Tomažic, Sašo
2013-01-01
Recording knowledge in a common framework that would make it possible to seamlessly share global knowledge remains an important challenge for researchers. This brief examines several ideas about the representation of knowledge addressing this challenge. A widespread general agreement is followed that states uniform knowledge representation should be achievable by using ontologies populated with concepts. A separate chapter is dedicated to each of the three introduced topics, following a uniform outline: definition, organization, and use. This brief is intended for those who want to get to know
Normalized neural representations of natural odors
Zwicker, David
2016-01-01
The olfactory system removes correlations in natural odors using a network of inhibitory neurons in the olfactory bulb. It has been proposed that this network integrates the response from all olfactory receptors and inhibits them equally. However, how such global inhibition influences the neural representations of odors is unclear. Here, we study a simple statistical model of this situation, which leads to concentration-invariant, sparse representations of the odor composition. We show that the inhibition strength can be tuned to obtain sparse representations that are still useful to discriminate odors that vary in relative concentration, size, and composition. The model reveals two generic consequences of global inhibition: (i) odors with many molecular species are more difficult to discriminate and (ii) receptor arrays with heterogeneous sensitivities perform badly. Our work can thus help to understand how global inhibition shapes normalized odor representations for further processing in the brain.
Cecconi, Jaures
2011-01-01
G. Bottaro: Quelques resultats d'analyse spectrale pour des operateurs differentiels a coefficients constants sur des domaines non bornes.- L. Garding: Eigenfuction expansions.- C. Goulaouic: Valeurs propres de problemes aux limites irreguliers: applications.- G. Grubb: Essential spectra of elliptic systems on compact manifolds.- J.Cl. Guillot: Quelques resultats recents en Scattering.- N. Schechter: Theory of perturbations of partial differential operators.- C.H. Wilcox: Spectral analysis of the Laplacian with a discontinuous coefficient.
Construct irreducible representations of quantum groups Uq(fm(K))
Xin TANG
2008-01-01
In this paper,we construct families of irreducible representations for a class of quantum groups Uq(fm(K)).First,we give a natural construction of irreducible weight representations for Uq(fm(K)) using methods in spectral theory developed by Rosenberg.Second,we study the Whittaker model for the center of Uq(fm(K)).As a result,the structure of Whittaker representations is determined,and all irreducible Whittaker representations are explicitly constructed.Finally,we prove that the annihilator of a Whittaker representation is centrally generated.
Spectral Theory and Mirror Symmetry
Marino, Marcos
2015-01-01
Recent developments in string theory have revealed a surprising connection between spectral theory and local mirror symmetry: it has been found that the quantization of mirror curves to toric Calabi-Yau threefolds leads to trace class operators, whose spectral properties are conjecturally encoded in the enumerative geometry of the Calabi-Yau. This leads to a new, infinite family of solvable spectral problems: the Fredholm determinants of these operators can be found explicitly in terms of Gromov-Witten invariants and their refinements; their spectrum is encoded in exact quantization conditions, and turns out to be determined by the vanishing of a quantum theta function. Conversely, the spectral theory of these operators provides a non-perturbative definition of topological string theory on toric Calabi-Yau threefolds. In particular, their integral kernels lead to matrix integral representations of the topological string partition function, which explain some number-theoretic properties of the periods. In this...
Spectral recognition of graphs
Cvetković Dragoš
2012-01-01
Full Text Available At some time, in the childhood of spectral graph theory, it was conjectured that non-isomorphic graphs have different spectra, i.e. that graphs are characterized by their spectra. Very quickly this conjecture was refuted and numerous examples and families of non-isomorphic graphs with the same spectrum (cospectral graphs were found. Still some graphs are characterized by their spectra and several mathematical papers are devoted to this topic. In applications to computer sciences, spectral graph theory is considered as very strong. The benefit of using graph spectra in treating graphs is that eigenvalues and eigenvectors of several graph matrices can be quickly computed. Spectral graph parameters contain a lot of information on the graph structure (both global and local including some information on graph parameters that, in general, are computed by exponential algorithms. Moreover, in some applications in data mining, graph spectra are used to encode graphs themselves. The Euclidean distance between the eigenvalue sequences of two graphs on the same number of vertices is called the spectral distance of graphs. Some other spectral distances (also based on various graph matrices have been considered as well. Two graphs are considered as similar if their spectral distance is small. If two graphs are at zero distance, they are cospectral. In this sense, cospectral graphs are similar. Other spectrally based measures of similarity between networks (not necessarily having the same number of vertices have been used in Internet topology analysis, and in other areas. The notion of spectral distance enables the design of various meta-heuristic (e.g., tabu search, variable neighbourhood search algorithms for constructing graphs with a given spectrum (spectral graph reconstruction. Several spectrally based pattern recognition problems appear in many areas (e.g., image segmentation in computer vision, alignment of protein-protein interaction networks in bio
Autoregressive Spectral Estimation and Functional Inference.
1982-06-01
spectral density function . Note that F(O) - 0, F(l) = 1, and (15) F(w) = f(w’) dw’, O<w<l...correlation function p(v) is summable, and its spectral density function f(w) is bounded above and below in the sense that the dynamic range of f(w) (2) DR...l The AR(-n) and MA(-) representations have important implications for spectral 6 analysis since they provide formulas for the spectral density function
张欣; 游雄; 张寅宝
2013-01-01
As a new digital earth reference model,discrete global grid system satisfies the need of efficient management and application of geospatial data.The representation models of spherical entities in discrete global hexagonal grid system were mainly discussed.With the method of cell coding and the relation of arrangement and contiguity of cells,the conception of the approach exponential of arrangement relation was brought forward,and the expression model of area spherical entity was optimized.The result showed that the optimized model could retrench storage space about 60％.%球面离散格网系统作为一种新的数字地球参考模型,能够满足对地理空间数据的高效管理和应用需求.本文主要研究了球面离散六角格网系统中点状、线状和面状3类空间实体的表达模型,并结合面状实体的空间连续特性,利用格元之间的层次关系和邻近关系,提出层次关系邻近指数的概念,对面状实体表达模型进行优化.实验结果表明,相对于直接存储格元地址码的方式,经过优化的模型能够节省约60％的存储空间.
Vigna, Sebastiano
2009-01-01
This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.
On the spectral formulation of Granger causality.
Chicharro, D
2011-12-01
Spectral measures of causality are used to explore the role of different rhythms in the causal connectivity between brain regions. We study several spectral measures related to Granger causality, comprising the bivariate and conditional Geweke measures, the directed transfer function, and the partial directed coherence. We derive the formulation of dependence and causality in the spectral domain from the more general formulation in the information-theory framework. We argue that the transfer entropy, the most general measure derived from the concept of Granger causality, lacks a spectral representation in terms of only the processes associated with the recorded signals. For all the spectral measures we show how they are related to mutual information rates when explicitly considering the parametric autoregressive representation of the processes. In this way we express the conditional Geweke spectral measure in terms of a multiple coherence involving innovation variables inherent to the autoregressive representation. We also link partial directed coherence with Sims' criterion of causality. Given our results, we discuss the causal interpretation of the spectral measures related to Granger causality and stress the necessity to explicitly consider their specific formulation based on modeling the signals as linear Gaussian stationary autoregressive processes.
Smartt, Heidi A. [Sandia National Laboratories (United States)
2003-05-01
This research examines the feasibility of spectral tagging, which involves modifying the spectral signature of a target, e.g. by mixing an additive with the target's paint. The target is unchanged to the human eye, but the tag is revealed when viewed with a spectrometer. This project investigates a layer of security that is not obvious, and therefore easy to conceal. The result is a tagging mechanism that is difficult to counterfeit. Uniquely tagging an item is an area of need in safeguards and security and non-proliferation. The powdered forms of the minerals lapis lazuli and olivine were selected as the initial test tags due to their availability and uniqueness in the visible to near-infrared spectral region. They were mixed with paints and applied to steel. In order to verify the presence of the tags quantitatively, the data from the spectrometer was input into unmixing models and signal detection algorithms. The mixture with the best results was blue paint mixed with lapis lazuli and olivine. The tag had a 0% probability of false alarm and a 100% probability of detection. The research proved that spectral tagging is feasible, although certain tag/paint mixtures are more detectable than others.
A Class of Modified Spectral Conjugate Gradient Method and Its Global Convergence%一种修正的谱共轭梯度法及其全局收敛性
汪丹戎
2015-01-01
In this paper , a spectral conjugate gradient method is proposed to solve unconstrained optimization problems.The method is proved to be sufficiently decent property under the Wolfe line search and the global con -vergence of the method with the standard wolfe in exact line search is proved .%提出了一种新的求解无约束优化问题的谱共轭梯度算法。该算法在标准Wolfe线性搜索条件就能满足充分下降性，在标准的Wolfe非精确线搜索下证明新算法的全局收敛性。
Representation as the representation of experience
Ankersmit, FR
This essay deals, mainly, with the notion of representation. Representation is associated with texts and, as such, is contrasted to the true singular statement. It is argued that the relationship between the text and what the text represents can never be modeled on the relationship between the true
Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.
2011-08-01
Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. Aerosol Optical Thickness (AOT) and Ångström Exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) spectral observations. Additionally, temporal trends of Coarse- and Fine-mode dominant AOTs (CAOT and FAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström Exponent Difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation and (2) Number of Observations (NO) per month. Temporal increase of FAOTs prevails over regions dominated by emerging economy or slash-burn agriculture in East Asia and South Africa. On the other hand, insignificant or negative trends for FAOTs are detected over Western Europe and North America. Over desert regions, both increase and decrease of CAOTs are observed depending on meteorological conditions.
Enhanced low-rank representation via sparse manifold adaption for semi-supervised learning.
Peng, Yong; Lu, Bao-Liang; Wang, Suhang
2015-05-01
Constructing an informative and discriminative graph plays an important role in various pattern recognition tasks such as clustering and classification. Among the existing graph-based learning models, low-rank representation (LRR) is a very competitive one, which has been extensively employed in spectral clustering and semi-supervised learning (SSL). In SSL, the graph is composed of both labeled and unlabeled samples, where the edge weights are calculated based on the LRR coefficients. However, most of existing LRR related approaches fail to consider the geometrical structure of data, which has been shown beneficial for discriminative tasks. In this paper, we propose an enhanced LRR via sparse manifold adaption, termed manifold low-rank representation (MLRR), to learn low-rank data representation. MLRR can explicitly take the data local manifold structure into consideration, which can be identified by the geometric sparsity idea; specifically, the local tangent space of each data point was sought by solving a sparse representation objective. Therefore, the graph to depict the relationship of data points can be built once the manifold information is obtained. We incorporate a regularizer into LRR to make the learned coefficients preserve the geometric constraints revealed in the data space. As a result, MLRR combines both the global information emphasized by low-rank property and the local information emphasized by the identified manifold structure. Extensive experimental results on semi-supervised classification tasks demonstrate that MLRR is an excellent method in comparison with several state-of-the-art graph construction approaches.
Ibarria, L; Lindstrom, P; Rossignac, J
2006-11-17
Many scientific, imaging, and geospatial applications produce large high-precision scalar fields sampled on a regular grid. Lossless compression of such data is commonly done using predictive coding, in which weighted combinations of previously coded samples known to both encoder and decoder are used to predict subsequent nearby samples. In hierarchical, incremental, or selective transmission, the spatial pattern of the known neighbors is often irregular and varies from one sample to the next, which precludes prediction based on a single stencil and fixed set of weights. To handle such situations and make the best use of available neighboring samples, we propose a local spectral predictor that offers optimal prediction by tailoring the weights to each configuration of known nearby samples. These weights may be precomputed and stored in a small lookup table. We show that predictive coding using our spectral predictor improves compression for various sources of high-precision data.
王彩玲; 王洪伟; 胡炳樑; 温佳; 徐君; 李湘眷
2016-01-01
Traditional hyperspectral image classification algorithms focus on spectral information application,however,with the increase of spatial resolution of hyperspectral remote sensing images,hyperspectral imaging presents clustering properties on spatial domain for the same category.It is critical for hyperspectral image classification algorithms to use spatial information in order to improve the classification accuracy.However,the marginal differences of different categories display more obviously.If it is introduced directly into the spatial-spectral sparse representation for image classification without the selection of neighbor-hood pixels,the classification error and the computation time will increase.This paper presents a spatial-spectral joint sparse representation classification algorithm based on neighborhood segmentation.The algorithm calculates the similarity with spectral angel in order to choose proper neighborhood pixel into spatial-spectral joint sparse representation model.With simultaneous subspace pursuit and simultaneous orthogonal matching pursuit to solve the model,the classification is determined by computing the minimum reconstruction error between testing samples and training pixels.Two typical hyperspectral images from AVIRIS and ROSIS are chosen for simulation experiment and results display that the classification accuracy of two images both improves as neighborhood segmentation threshold increasing.It concludes that neighborhood segmentation is necessary for joint sparse representation classification.%传统的高光谱遥感影像分类算法侧重于光谱信息的应用。随着高光谱遥感影像的空间分辨率的增加，高光谱影像中相同类别的地物在空间分布上呈现聚类特性，将空间特性有效地应用于高光谱遥感影像分类算法对分类精度的提升非常关键。但是，高光谱影像的高分辨率提供空间聚类特性的同时，在不同地物边缘处表现出的差异性更加明显
Mitigating noise in global manifold coordinates for hyperspectral image classification
Jin, Can; Bachmann, Charles M.
2016-09-01
Over the past decade, manifold and graph representations of hyperspectral imagery (HSI) have been explored widely in HSI applications. Among many data-driven approaches to deriving manifold coordinate representations including Isometric Mapping (ISOMAP), Local Linear Embedding (LLE), Laplacian Eigenmaps (LE), and Diffusion Kernels (DK), ISOMAP is the only global method that well represents the large scale nonlinear geometric structure of the data. In recent years, methods such as ENH-ISOMAP as well as its parallel computing accelerations makes ISOMAP practical for hyperspectral image dimensionality reduction. However, the noise problem in these methods has not been well addressed, which is critical to classification accuracy based on the manifold coordinates derived from these methods. While standard linear techniques to reduce the effects of noise can be applied as a preliminary step, these are based on global statistics and are applied globally across the entire data set, resulting in the risk of losing subtle nonlinear features before classification. To solve this problem, in this paper, we explore several approaches to modeling and mitigating noise in HSI in a local sense to improve the performance of the ENH-ISOMAP algorithm, aiming to reduce the noise effect on the manifold representations of the HSI. A new method to split data into local spectral subsets is introduced. Based on the local spectral subsets obtained with this method, a local noise model guided landmark selection scheme is proposed. In addition, a new robust adaptive neighborhood method using intrinsic dimensionality information to construct the k-Nearest Neighbor graph is introduced to increase the fidelity of the graph, based on the same framework of local spectral subsetting. The improved algorithm produces manifold coordinates with less noise, and shows a better classification accuracy using k-Nearest Neighbor classifier.
Spectral disentangling with Spectangular
Sablowski, Daniel P.; Weber, Michael
2017-01-01
The paper introduces the software Spectangular for spectral disentangling via singular value decomposition with global optimisation of the orbital parameters of the stellar system or radial velocities of the individual observations. We will describe the procedure and the different options implemented in our program. Furthermore, we will demonstrate the performance and the applicability using tests on artificial data. Additionally, we use high-resolution spectra of Capella to demonstrate the performance of our code on real-world data. The novelty of this package is the implemented global optimisation algorithm and the graphical user interface (GUI) for ease of use. We have implemented the code to tackle SB1 and SB2 systems with the option of also dealing with telluric (static) lines. Based in part on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC.
Spectral disentangling with Spectangular
Sablowski, Daniel P
2016-01-01
The paper introduces the software Spectangular for spectral disentangling via singular value decomposition with global optimisation of the orbital parameters of the stellar system or radial velocities of the individual observations. We will describe the procedure and the different options implemented in our program. Furthermore, we will demonstrate the performance and the applicability using tests on artificial data. Additionally, we use high-resolution spectra of Capella to demonstrate the performance of our code on real-world data. The novelty of this package is the implemented global optimisation algorithm and the graphical user interface (GUI) for ease of use. We have implemented the code to tackle SB1 and SB2 systems with the option of also dealing with telluric (static) lines.
Ren, Ruizhi; Gu, Lingjia; Fu, Haoyang; Sun, Chenglin
2017-04-01
An effective super-resolution (SR) algorithm is proposed for actual spectral remote sensing images based on sparse representation and wavelet preprocessing. The proposed SR algorithm mainly consists of dictionary training and image reconstruction. Wavelet preprocessing is used to establish four subbands, i.e., low frequency, horizontal, vertical, and diagonal high frequency, for an input image. As compared to the traditional approaches involving the direct training of image patches, the proposed approach focuses on the training of features derived from these four subbands. The proposed algorithm is verified using different spectral remote sensing images, e.g., moderate-resolution imaging spectroradiometer (MODIS) images with different bands, and the latest Chinese Jilin-1 satellite images with high spatial resolution. According to the visual experimental results obtained from the MODIS remote sensing data, the SR images using the proposed SR algorithm are superior to those using a conventional bicubic interpolation algorithm or traditional SR algorithms without preprocessing. Fusion algorithms, e.g., standard intensity-hue-saturation, principal component analysis, wavelet transform, and the proposed SR algorithms are utilized to merge the multispectral and panchromatic images acquired by the Jilin-1 satellite. The effectiveness of the proposed SR algorithm is assessed by parameters such as peak signal-to-noise ratio, structural similarity index, correlation coefficient, root-mean-square error, relative dimensionless global error in synthesis, relative average spectral error, spectral angle mapper, and the quality index Q4, and its performance is better than that of the standard image fusion algorithms.
Social representations of women
Álvaro Estramiana, José Luis
2006-05-01
Full Text Available Social Representations is one of the most important theories in contemporary social psychology. Since the social psychologist Serge Moscovici developed his theory of social representations to explain how a scientific theory such as the psychoanalysis turns into a common sense knowledge many studies have been done by different social psychologists. The analysis of the social representations of women as represented in myths and popular beliefs is an excellent opportunity to study how this theory can be applied to this representational field. At the same time it makes possible to understand the formation of attitudes towards women
Sparse Representations of Hyperspectral Images
Swanson, Robin J.
2015-11-23
Hyperspectral image data has long been an important tool for many areas of sci- ence. The addition of spectral data yields significant improvements in areas such as object and image classification, chemical and mineral composition detection, and astronomy. Traditional capture methods for hyperspectral data often require each wavelength to be captured individually, or by sacrificing spatial resolution. Recently there have been significant improvements in snapshot hyperspectral captures using, in particular, compressed sensing methods. As we move to a compressed sensing image formation model the need for strong image priors to shape our reconstruction, as well as sparse basis become more important. Here we compare several several methods for representing hyperspectral images including learned three dimensional dictionaries, sparse convolutional coding, and decomposable nonlocal tensor dictionaries. Addi- tionally, we further explore their parameter space to identify which parameters provide the most faithful and sparse representations.
Spectral analysis by correlation; Analyse spectrale par correlation
Fauque, J.M.; Berthier, D.; Max, J.; Bonnet, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1969-07-01
The spectral density of a signal, which represents its power distribution along the frequency axis, is a function which is of great importance, finding many uses in all fields concerned with the processing of the signal (process identification, vibrational analysis, etc...). Amongst all the possible methods for calculating this function, the correlation method (correlation function calculation + Fourier transformation) is the most promising, mainly because of its simplicity and of the results it yields. The study carried out here will lead to the construction of an apparatus which, coupled with a correlator, will constitute a set of equipment for spectral analysis in real time covering the frequency range 0 to 5 MHz. (author) [French] La densite spectrale d'un signal qui represente la repartition de sa puissance sur l'axe des frequences est une fonction de premiere importance, constamment utilisee dans tout ce qui touche le traitement du signal (identification de processus, analyse de vibrations, etc...). Parmi toutes les methodes possibles de calcul de cette fonction, la methode par correlation (calcul de la fonction de correlation + transformation de Fourier) est tres seduisante par sa simplicite et ses performances. L'etude qui est faite ici va deboucher sur la realisation d'un appareil qui, couple a un correlateur, constituera un ensemble d'analyse spectrale en temps reel couvrant la gamme de frequence 0 a 5 MHz. (auteur)
Extensions of tempered representations
Opdam, E.; Solleveld, M.
2013-01-01
Let π, π′ be irreducible tempered representations of an affine Hecke algebra H with positive parameters. We compute the higher extension groups Ext nH(π,π′) explicitly in terms of the representations of analytic R-groups corresponding to π and π′. The result has immediate applications to the computa
Multiple sparse representations classification
E. Plenge (Esben); S.K. Klein (Stefan); W.J. Niessen (Wiro); E. Meijering (Erik)
2015-01-01
textabstractSparse representations classification (SRC) is a powerful technique for pixelwise classification of images and it is increasingly being used for a wide variety of image analysis tasks. The method uses sparse representation and learned redundant dictionaries to classify image pixels. In t
Embedded Data Representations.
Willett, Wesley; Jansen, Yvonne; Dragicevic, Pierre
2017-01-01
We introduce embedded data representations, the use of visual and physical representations of data that are deeply integrated with the physical spaces, objects, and entities to which the data refers. Technologies like lightweight wireless displays, mixed reality hardware, and autonomous vehicles are making it increasingly easier to display data in-context. While researchers and artists have already begun to create embedded data representations, the benefits, trade-offs, and even the language necessary to describe and compare these approaches remain unexplored. In this paper, we formalize the notion of physical data referents - the real-world entities and spaces to which data corresponds - and examine the relationship between referents and the visual and physical representations of their data. We differentiate situated representations, which display data in proximity to data referents, and embedded representations, which display data so that it spatially coincides with data referents. Drawing on examples from visualization, ubiquitous computing, and art, we explore the role of spatial indirection, scale, and interaction for embedded representations. We also examine the tradeoffs between non-situated, situated, and embedded data displays, including both visualizations and physicalizations. Based on our observations, we identify a variety of design challenges for embedded data representation, and suggest opportunities for future research and applications.
Ankersmit, F.R.
2010-01-01
This essay focuses on the historical text as a whole. It does so by conceiving of the historical text as representation - in the way the we may say of a photo or a painting that it represents the person depicted on it. It is argued that representation cannot be properly understood by modelling it on
Group and representation theory
Vergados, J D
2017-01-01
This volume goes beyond the understanding of symmetries and exploits them in the study of the behavior of both classical and quantum physical systems. Thus it is important to study the symmetries described by continuous (Lie) groups of transformations. We then discuss how we get operators that form a Lie algebra. Of particular interest to physics is the representation of the elements of the algebra and the group in terms of matrices and, in particular, the irreducible representations. These representations can be identified with physical observables. This leads to the study of the classical Lie algebras, associated with unitary, unimodular, orthogonal and symplectic transformations. We also discuss some special algebras in some detail. The discussion proceeds along the lines of the Cartan-Weyl theory via the root vectors and root diagrams and, in particular, the Dynkin representation of the roots. Thus the representations are expressed in terms of weights, which are generated by the application of the elemen...
Willett, Wesley; Jansen, Yvonne; Dragicevic, Pierre
2017-01-01
We introduce embedded data representations, the use of visual and physical representations of data that are deeply integrated with the physical spaces, objects, and entities to which the data refers. Technologies like lightweight wireless displays, mixed reality hardware, and autonomous vehicles...... are making it increasingly easier to display data in-context. While researchers and artists have already begun to create embedded data representations, the benefits, trade-offs, and even the language necessary to describe and compare these approaches remain unexplored. In this paper, we formalize the notion...... of physical data referents – the real-world entities and spaces to which data corresponds – and examine the relationship between referents and the visual and physical representations of their data. We differentiate situated representations, which display data in proximity to data referents, and embedded...
Local and Global Illumination in the Volume Rendering Integral
Max, N; Chen, M
2005-10-21
This article is intended as an update of the major survey by Max [1] on optical models for direct volume rendering. It provides a brief overview of the subject scope covered by [1], and brings recent developments, such as new shadow algorithms and refraction rendering, into the perspective. In particular, we examine three fundamentals aspects of direct volume rendering, namely the volume rendering integral, local illumination models and global illumination models, in a wavelength-independent manner. We review the developments on spectral volume rendering, in which visible light are considered as a form of electromagnetic radiation, optical models are implemented in conjunction with representations of spectral power distribution. This survey can provide a basis for, and encourage, new efforts for developing and using complex illumination models to achieve better realism and perception through optical correctness.
Orthogonal functions, discrete variable representation, and generalized gauss quadratures
Schneider, B. I.; Nygaard, Nicolai
2002-01-01
The numerical solution of most problems in theoretical chemistry involve either the use of a basis set expansion (spectral method) or a numerical grid. For many basis sets, there is an intimate connection between the spectral form and numerical quadrature. When this connection exists, the distinc......The numerical solution of most problems in theoretical chemistry involve either the use of a basis set expansion (spectral method) or a numerical grid. For many basis sets, there is an intimate connection between the spectral form and numerical quadrature. When this connection exists...... in the original representation. This has been exploited in bound-state, scattering, and time-dependent problems using the so-called, discrete variable representation (DVR). At the core of this approach is the mathematical three-term recursion relationship satisfied by the classical orthogonal functions...
The endoscopic classification of representations orthogonal and symplectic groups
Arthur, James
2013-01-01
Within the Langlands program, endoscopy is a fundamental process for relating automorphic representations of one group with those of another. In this book, Arthur establishes an endoscopic classification of automorphic representations of orthogonal and symplectic groups G. The representations are shown to occur in families (known as global L-packets and A-packets), which are parametrized by certain self-dual automorphic representations of an associated general linear group GL(N). The central result is a simple and explicit formula for the multiplicity in the automorphic discrete spectrum of G
Exploring the Structure of Spatial Representations.
Tamas Madl
Full Text Available It has been suggested that the map-like representations that support human spatial memory are fragmented into sub-maps with local reference frames, rather than being unitary and global. However, the principles underlying the structure of these 'cognitive maps' are not well understood. We propose that the structure of the representations of navigation space arises from clustering within individual psychological spaces, i.e. from a process that groups together objects that are close in these spaces. Building on the ideas of representational geometry and similarity-based representations in cognitive science, we formulate methods for learning dissimilarity functions (metrics characterizing participants' psychological spaces. We show that these learned metrics, together with a probabilistic model of clustering based on the Bayesian cognition paradigm, allow prediction of participants' cognitive map structures in advance. Apart from insights into spatial representation learning in human cognition, these methods could facilitate novel computational tools capable of using human-like spatial concepts. We also compare several features influencing spatial memory structure, including spatial distance, visual similarity and functional similarity, and report strong correlations between these dimensions and the grouping probability in participants' spatial representations, providing further support for clustering in spatial memory.
Multiple multiresolution representation of functions and calculus for fast computation
Fann, George I [ORNL; Harrison, Robert J [ORNL; Hill, Judith C [ORNL; Jia, Jun [ORNL; Galindo, Diego A [ORNL
2010-01-01
We describe the mathematical representations, data structure and the implementation of the numerical calculus of functions in the software environment multiresolution analysis environment for scientific simulations, MADNESS. In MADNESS, each smooth function is represented using an adaptive pseudo-spectral expansion using the multiwavelet basis to a arbitrary but finite precision. This is an extension of the capabilities of most of the existing net, mesh and spectral based methods where the discretization is based on a single adaptive mesh, or expansions.
New approach to the Dirac spectral density in lattice gauge theory applications
Fodor, Zoltan; Kuti, Julius; Mondal, Santanu; Nogradi, Daniel; Wong, Chik Him
2016-01-01
We report tests and results from a new approach to the spectral density and the mode number distribution of the Dirac operator in lattice gauge theories. The algorithm generates the spectral density of the lattice Dirac operator as a continuous function over all scales of the complete eigenvalue spectrum. This is distinct from an earlier method where the integrated spectral density (mode number) was calculated efficiently for some preselected fixed range of the integration. The new algorithm allows global studies like the chiral condensate from the Dirac spectrum at any scale including the cutoff-dependent IR and UV range of the spectrum. Physics applications include the scale-dependent mass anomalous dimension, spectral representation of composite fermion operators, and the crossover transition from the $\\epsilon$-regime of Random Matrix Theory to the p-regime in chiral perturbation theory. We present thorough tests of the algorithm in the 2-flavor sextet SU(3) gauge theory that we continue to pursue for its...
Spectral theory of ordinary differential operators
Weidmann, Joachim
1987-01-01
These notes will be useful and of interest to mathematicians and physicists active in research as well as for students with some knowledge of the abstract theory of operators in Hilbert spaces. They give a complete spectral theory for ordinary differential expressions of arbitrary order n operating on -valued functions existence and construction of self-adjoint realizations via boundary conditions, determination and study of general properties of the resolvent, spectral representation and spectral resolution. Special attention is paid to the question of separated boundary conditions, spectral multiplicity and absolutely continuous spectrum. For the case nm=2 (Sturm-Liouville operators and Dirac systems) the classical theory of Weyl-Titchmarch is included. Oscillation theory for Sturm-Liouville operators and Dirac systems is developed and applied to the study of the essential and absolutely continuous spectrum. The results are illustrated by the explicit solution of a number of particular problems including th...
On the spectral functions of scalar mesons
Giacosa, Francesco
2007-01-01
In this work we study the spectral functions of scalar mesons in one- and two-channel cases. When the propagators satisfy the K\\"allen-Lehman representation a normalized spectral function is obtained, allowing to take into account finite-width effects in the evaluation of decay rates. In the one-channel case, suitable to the light sigma and k mesons, the spectral function can deviate consistently from a Breit-Wigner shape. In the two-channel case with one subthreshold channel the evaluated spectral function is well approximated by a Flatte' distribution; when applying the study to the $a_0(980)$ and $f_0(980)$ mesons the three-level forbidden KK decay is analysed.
Spectral Decomposition Algorithm (SDA)
National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...
Chevrel, S. D.; Pinet, P. C.; Barreau, G.; Daydou, Y.; Richard, G.; Maurice, S.; Feldman, W. C.
1999-01-01
The Clementine mission (CLM) produced global multispectral data that resulted in a map of FeO and Ti02 concentrations of the lunar surface. The recent Lunar Prospector (LP) mission returned the first global data for the distribution of surface abundances of key elements in lunar rocks, using a gamma-ray spectrometer (GRS) and neutron spectrometer(NS). Integrating CLM mineralogical spectral reflectance and LP chemical data is important to enhance our view of lunar crust origin and evolution, lunar volcanism, and surface processes. Iron, Ti, and Th having relatively large compositional variation over the lunar surface, as well as strong isolated peaks in the GRS spectra, information concerning the distribution and concentration of these elements has been derived from maps of corrected (cosmic ray, nonsymmetric response of the instrument) counting rates only, without converting them into absolute abundances. Maps produced contain count rates in equal-area projection averaged into 5 x 5 degrees latitude/longitude bins, from -90 to +90 degrees latitude and -180 to +180 degrees longitude. In this work, we have used the CLM global FeO and Ti02 abundances (wt%) maps converted at the LP spatial resolution (about 150 km/pixel) to produce FeO and TiO2 GRS abundance maps, through a linear regression based on the analysis of the scatter distribution of both datasets. The regression coefficients have been determined from the data taken between -60 and +60 degrees latitude to avoid uncertainties in the CLM spectral data due to nonnominal conditions of observation at high latitudes. After a critical assessment of the validity of these coefficients for every class of absolute abundance, the LP data have been transformed into absolute abundances for the whole Moon. The Th LP data have been converted into abundances (ppm) using Th concentrations in average soils from the Apollo and Luna sites given. Values of Th abundances for these samples range between 0.5 and 13 ppm. A nonlinear
Hyperfinite Representation of Distributions
J Sousa Pinto; R F Hoskins
2000-11-01
Hyperfinite representation of distributions is studied following the method introduced by Kinoshita [2, 3], although we use a different approach much in the vein of [4]. Products and Fourier transforms of representatives of distributions are also analysed.
Income, Ideology, and Representation
Chris Tausanovitch
2016-11-01
Full Text Available Do legislators represent the rich better than they represent the poor? Recent work provides mixed support for this proposition. I test the hypothesis of differential representation using a data set on the political preferences of 318,537 individuals. Evidence of differential representation in the House of Representatives is weak. Support for differential representation is stronger in the Senate. In recent years, representation has occurred primarily through the selection of a legislator from the appropriate party. Although the preferences of higher-income constituents account for more of the variation in legislator voting behavior, higher-income constituents also account for much more of the variation in district preferences. In light of the low level of overall responsiveness, differential responsiveness appears small.
Ordering ambiguity versus representation
Souza de Dutra, A [Abdus Salam ICTP, Strada Costiera 11, 34014 Trieste (Italy); UNESP-Campus de Guaratingueta-DFQ , Av. Dr. Ariberto Pereira da Cunha, 333, C.P. 205, 12516-410 Guaratingueta SP (Brazil)
2006-01-06
In this work we show that the ordering ambiguity on quantization depends on the representation choice. This property is then used to solve unambiguously some particular systems. Finally, we speculate on the consequences for more involved cases.
MORPHOLOGICAL REPRESENTATION AND SEMANTIC ...
The morphological representation assigned to a complex word must provide the formal structure .... This brings us to the cases where, on Williams's (1981a:258) analysis, the compositional notion ...... Die en moda Ii tei t . Kaaps tad: Ba 1 kema.
Function, anticipation, representation
Bickhard, Mark. H.
2001-06-01
Function emerges in certain kinds of far-from-equilibrium systems. One important kind of function is that of interactive anticipation, an adaptedness to temporal complexity. Interactive anticipation is the locus of the emergence of normative representational content, and, thus, of representation in general: interactive anticipation is the naturalistic core of the evolution of cognition. Higher forms of such anticipation are involved in the subsequent macro-evolutionary sequence of learning, emotions, and reflexive consciousness.
$\\kappa$-Deformation and Spectral Triples
Iochum, B; Schücker, Th; Sitarz, A; 10.5506/APhysPolBSupp.4.305
2011-01-01
The aim of the paper is to answer the following question: does $\\kappa$-deformation fit into the framework of noncommutative geometry in the sense of spectral triples? Using a compactification of time, we get a discrete version of $\\kappa$-Minkowski deformation via $C^*$-algebras of groups. The dynamical system of the underlying groups (including some Baumslag--Solitar groups) is used in order to construct \\emph{finitely summable} spectral triples. This allows to bypass an obstruction to finite-summability appearing when using the common regular representation.
Effects of spectral modulation filtering on vowel identification.
Liu, Chang; Eddins, David A
2008-09-01
The goal of this study was to measure the effects of global spectral manipulations on vowel identification by progressively high-pass filtering vowel stimuli in the spectral modulation domain. Twelve American-English vowels, naturally spoken by a female talker, were subjected to varied degrees of high-pass filtering in the spectral modulation domain, with cutoff frequencies of 0.0, 0.5, 1.0, 1.5, and 2.0 cycles/octave. Identification performance for vowels presented at 70 dB sound pressure level with and without spectral modulation filtering was measured for five normal-hearing listeners. Results indicated that vowel identification performance was progressively degraded as the spectral modulation cutoff frequency increased. Degradation of vowel identification was greater for back vowels than for front or central vowels. Detailed acoustic analyses indicated that spectral modulation filtering resulted in a more crowded vowel space (F1xF2), reduced spectral contrast, and reduced spectral tilt relative to the original unfiltered vowels. Changes in the global spectral features produced by spectral modulation filtering were associated with substantial reduction in vowel identification. The results indicated that the spectral cues critical for vowel identification were represented by spectral modulation frequencies below 2 cycles/octave. These results are considered in terms of the interactions among spectral shape perception, spectral smearing, and speech perception.
Partial spectral analysis of hydrological time series
Jukić, D.; Denić-Jukić, V.
2011-03-01
SummaryHydrological time series comprise the influences of numerous processes involved in the transfer of water in hydrological cycle. It implies that an ambiguity with respect to the processes encoded in spectral and cross-spectral density functions exists. Previous studies have not paid attention adequately to this issue. Spectral and cross-spectral density functions represent the Fourier transforms of auto-covariance and cross-covariance functions. Using this basic property, the ambiguity is resolved by applying a novel approach based on the spectral representation of partial correlation. Mathematical background for partial spectral density, partial amplitude and partial phase functions is presented. The proposed functions yield the estimates of spectral density, amplitude and phase that are not affected by a controlling process. If an input-output relation is the subject of interest, antecedent and subsequent influences of the controlling process can be distinguished considering the input event as a referent point. The method is used for analyses of the relations between the rainfall, air temperature and relative humidity, as well as the influences of air temperature and relative humidity on the discharge from karst spring. Time series are collected in the catchment of the Jadro Spring located in the Dinaric karst area of Croatia.
Representation and prediction for locally harmonizable isotropic random fields
Randall J. Swift
1995-01-01
Full Text Available The class of harmonizable fields is a natural extension of the class of stationary fields. This paper considers fields whose increments are harmonizable and isotropic. Spectral representations are obtained for locally harmonizable isotropic fields. A linear least squares prediction for locally harmonizable isotropic fields is considered.
Hamhalter, Jan; Turilova, Ekaterina
2017-02-01
Quantum symmetries of spectral lattices are studied. Basic properties of spectral order on A W ∗-algebras are summarized. Connection between projection and spectral automorphisms is clarified by showing that, under mild conditions, any spectral automorphism is a composition of function calculus and Jordan ∗-automorphism. Complete description of quantum spectral symmetries on Type I and Type II A W ∗-factors are completely described.
Representation Elements of Spatial Thinking
Fiantika, F. R.
2017-04-01
This paper aims to add a reference in revealing spatial thinking. There several definitions of spatial thinking but it is not easy to defining it. We can start to discuss the concept, its basic a forming representation. Initially, the five sense catch the natural phenomenon and forward it to memory for processing. Abstraction plays a role in processing information into a concept. There are two types of representation, namely internal representation and external representation. The internal representation is also known as mental representation; this representation is in the human mind. The external representation may include images, auditory and kinesthetic which can be used to describe, explain and communicate the structure, operation, the function of the object as well as relationships. There are two main elements, representations properties and object relationships. These elements play a role in forming a representation.
Representation, interaction, and intersubjectivity.
Alterman, Richard
2007-09-10
What the participants share, their common "sense" of the world, creates a foundation, a framing, an orientation that enables human actors to see and act in coordination with one another. For recurrent activities, the methods the participants use to understand each other as they act change, making the intersubjective space in which actors operate richer and easier to produce. This article works through some of the issues that emerge from a close examination of intersubjectivity as it is managed through representation and interaction. The data that are presented document, in detail, a sequence of related interactions, within and across episodes of cooperation, where continuity and change can be observed. The emergence of conversational structure and coordinating representations are significant milestones in the long-term development of a representational practice that support the runtime co-construction of intersubjective space. Conversational structures emerge interactively to mediate recurrent points of coordination in the domain activity, and only secondarily the conversation itself. Coordinating representations change the representational practice of the participants by making it easier to manage their "shared view" of the collective work, enabling the participants to make progress, expand the field of the common activity, while exhibiting more control of if and when explicit grounding occurs.
Representation Discovery using Harmonic Analysis
Mahadevan, Sridhar
2008-01-01
Representations are at the heart of artificial intelligence (AI). This book is devoted to the problem of representation discovery: how can an intelligent system construct representations from its experience? Representation discovery re-parameterizes the state space - prior to the application of information retrieval, machine learning, or optimization techniques - facilitating later inference processes by constructing new task-specific bases adapted to the state space geometry. This book presents a general approach to representation discovery using the framework of harmonic analysis, in particu
The Spectral Shift Function and Spectral Flow
Azamov, N. A.; Carey, A. L.; Sukochev, F. A.
2007-11-01
At the 1974 International Congress, I. M. Singer proposed that eta invariants and hence spectral flow should be thought of as the integral of a one form. In the intervening years this idea has lead to many interesting developments in the study of both eta invariants and spectral flow. Using ideas of [24] Singer’s proposal was brought to an advanced level in [16] where a very general formula for spectral flow as the integral of a one form was produced in the framework of noncommutative geometry. This formula can be used for computing spectral flow in a general semifinite von Neumann algebra as described and reviewed in [5]. In the present paper we take the analytic approach to spectral flow much further by giving a large family of formulae for spectral flow between a pair of unbounded self-adjoint operators D and D + V with D having compact resolvent belonging to a general semifinite von Neumann algebra {mathcal{N}} and the perturbation V in {mathcal{N}} . In noncommutative geometry terms we remove summability hypotheses. This level of generality is made possible by introducing a new idea from [3]. There it was observed that M. G. Krein’s spectral shift function (in certain restricted cases with V trace class) computes spectral flow. The present paper extends Krein’s theory to the setting of semifinite spectral triples where D has compact resolvent belonging to {mathcal{N}} and V is any bounded self-adjoint operator in {mathcal{N}} . We give a definition of the spectral shift function under these hypotheses and show that it computes spectral flow. This is made possible by the understanding discovered in the present paper of the interplay between spectral shift function theory and the analytic theory of spectral flow. It is this interplay that enables us to take Singer’s idea much further to create a large class of one forms whose integrals calculate spectral flow. These advances depend critically on a new approach to the calculus of functions of non
Towards Multimodal Content Representation
Bunt, Harry
2009-01-01
Multimodal interfaces, combining the use of speech, graphics, gestures, and facial expressions in input and output, promise to provide new possibilities to deal with information in more effective and efficient ways, supporting for instance: - the understanding of possibly imprecise, partial or ambiguous multimodal input; - the generation of coordinated, cohesive, and coherent multimodal presentations; - the management of multimodal interaction (e.g., task completion, adapting the interface, error prevention) by representing and exploiting models of the user, the domain, the task, the interactive context, and the media (e.g. text, audio, video). The present document is intended to support the discussion on multimodal content representation, its possible objectives and basic constraints, and how the definition of a generic representation framework for multimodal content representation may be approached. It takes into account the results of the Dagstuhl workshop, in particular those of the informal working group...
Post-representational cartography
Rob Kitchin
2010-03-01
Full Text Available Over the past decade there has been a move amongst critical cartographers to rethink maps from a post-representational perspective – that is, a vantage point that does not privilege representational modes of thinking (wherein maps are assumed to be mirrors of the world and automatically presumes the ontological security of a map as a map, but rather rethinks and destabilises such notions. This new theorisation extends beyond the earlier critiques of Brian Harley (1989 that argued maps were social constructions. For Harley a map still conveyed the truth of a landscape, albeit its message was bound within the ideological frame of its creator. He thus advocated a strategy of identifying the politics of representation within maps in order to circumnavigate them (to reveal the truth lurking underneath, with the ontology of cartographic practice remaining unquestioned.
Learning network representations
Moyano, Luis G.
2017-02-01
In this review I present several representation learning methods, and discuss the latest advancements with emphasis in applications to network science. Representation learning is a set of techniques that has the goal of efficiently mapping data structures into convenient latent spaces. Either for dimensionality reduction or for gaining semantic content, this type of feature embeddings has demonstrated to be useful, for example, for node classification or link prediction tasks, among many other relevant applications to networks. I provide a description of the state-of-the-art of network representation learning as well as a detailed account of the connections with other fields of study such as continuous word embeddings and deep learning architectures. Finally, I provide a broad view of several applications of these techniques to networks in various domains.
Mobilities and Representations
Thelle, Mikkel
2016-01-01
, literature, and film. Moreover, we hope the authors of future reviews will reflect on the ways they approached those representations. Such commentaries would provide valuable methodological insights, and we hope to begin that effort with this interview. We have asked four prominent mobility scholars...... to consider how they and their peers are currently confronting representations of mobility. This is particularly timely given the growing academic focus on practices, material mediation, and nonrepresentational theories, as well as on bodily reactions, emotions, and feelings that, according to those theories...
Additive and polynomial representations
Krantz, David H; Suppes, Patrick
1971-01-01
Additive and Polynomial Representations deals with major representation theorems in which the qualitative structure is reflected as some polynomial function of one or more numerical functions defined on the basic entities. Examples are additive expressions of a single measure (such as the probability of disjoint events being the sum of their probabilities), and additive expressions of two measures (such as the logarithm of momentum being the sum of log mass and log velocity terms). The book describes the three basic procedures of fundamental measurement as the mathematical pivot, as the utiliz
Temporal shape analysis via the spectral signature.
Bernardis, Elena; Konukoglu, Ender; Ou, Yangming; Metaxas, Dimitris N; Desjardins, Benoit; Pohl, Kilian M
2012-01-01
In this paper, we adapt spectral signatures for capturing morphological changes over time. Advanced techniques for capturing temporal shape changes frequently rely on first registering the sequence of shapes and then analyzing the corresponding set of high dimensional deformation maps. Instead, we propose a simple encoding motivated by the observation that small shape deformations lead to minor refinements in the spectral signature composed of the eigenvalues of the Laplace operator. The proposed encoding does not require registration, since spectral signatures are invariant to pose changes. We apply our representation to the shapes of the ventricles extracted from 22 cine MR scans of healthy controls and Tetralogy of Fallot patients. We then measure the accuracy score of our encoding by training a linear classifier, which outperforms the same classifier based on volumetric measurements.
Elements of the representation theory of the Jacobi group
Berndt, Rolf
1998-01-01
The Jacobi group is a semidirect product of a symplectic group with a Heisenberg group. It is an important example for a non-reductive group and sets the frame within which to treat theta functions as well as elliptic functions - in particular, the universal elliptic curve. This text gathers for the first time material from the representation theory of this group in both local (archimedean and non-archimedean) cases and in the global number field case. Via a bridge to Waldspurger's theory for the metaplectic group, complete classification theorems for irreducible representations are obtained. Further topics include differential operators, Whittaker models, Hecke operators, spherical representations and theta functions. The global theory is aimed at the correspondence between automorphic representations and Jacobi forms. This volume is thus a complement to the seminal book on Jacobi forms by M. Eichler and D. Zagier. Incorporating results of the authors' original research, this exposition is meant for research...
Moment graphs and representations
Jantzen, Jens Carsten
2012-01-01
Moment graphs and sheaves on moment graphs are basically combinatorial objects that have be used to describe equivariant intersectiion cohomology. In these lectures we are going to show that they can be used to provide a direct link from this cohomology to the representation theory of simple Lie...
Compact Information Representations
2016-08-02
network traffic, information retrieval, and databases are faced with very large, inherently high-dimensional, or naturally streaming datasets. This...proposal aims at developing mathematically rigorous and general- purpose statistical methods based on stable random projections, to achieve compact...detections (e.g., DDoS attacks), machine learning, databases , and search. Fundamentally, compact data representations are highly beneficial because they
Representation and human reasoning
ter Meulen, Alice G.B.
2003-01-01
Interpretation and reasoning are two sides of sharing information. Representations of the context and common ground must capture the rich content of what has been said, by linking to situations in the world as well as to what has been said before, common sense and to the presuppositions and entailme
Moment graphs and representations
Jantzen, Jens Carsten
2012-01-01
Moment graphs and sheaves on moment graphs are basically combinatorial objects that have be used to describe equivariant intersectiion cohomology. In these lectures we are going to show that they can be used to provide a direct link from this cohomology to the representation theory of simple Lie...... algebras and of simple algebraic groups. The first section contains some background on equivariant cohomology....
Loddegaard, Anne
2009-01-01
out of place in a novel belonging to the serious combat literature of the Catholic Revival, and the direct representation of the supernatural is also surprising because previous Catholic Revival novelists, such as Léon Bloy and Karl-Joris Huysmans, maintain a realistic, non-magical world and deal...
Loddegaard, Anne
2012-01-01
out of place in a novel belonging to the serious combat literature of the Catholic Revival, and the direct representation of the supernatural is also surprising because previous Catholic Revival novelists, such as Léon Bloy and Karl-Joris Huysmans, maintain a realistic, non-magical world and deal...
Women and political representation.
Rathod, P B
1999-01-01
A remarkable progress in women's participation in politics throughout the world was witnessed in the final decade of the 20th century. According to the Inter-Parliamentary Union report, there were only eight countries with no women in their legislatures in 1998. The number of women ministers at the cabinet level worldwide doubled in a decade, and the number of countries without any women ministers dropped from 93 to 48 during 1987-96. However, this progress is far from satisfactory. Political representation of women, minorities, and other social groups is still inadequate. This may be due to a complex combination of socioeconomic, cultural, and institutional factors. The view that women's political participation increases with social and economic development is supported by data from the Nordic countries, where there are higher proportions of women legislators than in less developed countries. While better levels of socioeconomic development, having a women-friendly political culture, and higher literacy are considered favorable factors for women's increased political representation, adopting one of the proportional representation systems (such as a party-list system, a single transferable vote system, or a mixed proportional system with multi-member constituencies) is the single factor most responsible for the higher representation of women.
Sociocognitive Perspectives on Representation.
Jacob, Elin K.; Shaw, Debora
1998-01-01
Discusses research dealing with the cognitive aspects of formal systems of knowledge representation. Highlights include the origins and theoretical foundations of the cognitive viewpoint; cognition and information science; cognitivism, mentalism, and subjective individualism; categorization; mental models; and sociocognitive approaches to indexing…
Between Representation and Eternity
Atzbach, Rainer
2016-01-01
. At death, an indi- vidual’s corpse and burial primarily reflect the social act of representation during the funeral. The position of the arms, which have incorrectly been used as a chronological tool in Scandinavia, may indicate an evolution from a more collective act of prayer up to the eleventh century...
Sociocognitive Perspectives on Representation.
Jacob, Elin K.; Shaw, Debora
1998-01-01
Discusses research dealing with the cognitive aspects of formal systems of knowledge representation. Highlights include the origins and theoretical foundations of the cognitive viewpoint; cognition and information science; cognitivism, mentalism, and subjective individualism; categorization; mental models; and sociocognitive approaches to indexing…
Community-enhanced Network Representation Learning for Network Analysis
Tu, Cunchao; Zeng, Xiangkai; Liu, Zhiyuan; Sun, Maosong
2016-01-01
Network representation learning (NRL) aims to build low-dimensional vectors for vertices in a network. Most existing NRL methods focus on learning representations from local context of vertices (such as their neighbors). Nevertheless, vertices in many complex networks also exhibit significant global patterns widely known as communities. It's a common sense that vertices in the same community tend to connect densely, and usually share common attributes. These patterns are expected to improve NRL and benefit relevant evaluation tasks, such as link prediction and vertex classification. In this work, we propose a novel NRL model by introducing community information of vertices to learn more discriminative network representations, named as Community-enhanced Network Representation Learning (CNRL). CNRL simultaneously detects community distribution of each vertex and learns embeddings of both vertices and communities. In this way, we can obtain more informative representation of a vertex accompanying with its commu...
SPECTRAL PROPERTIES OF SECOND ORDER DIFFERENTIAL OPERATORS ON TWO-STEP NILPOTENT LIE GROUPS
Niu Pengcheng
2000-01-01
In this paper, spectral properties of certain left invariant differential operators on two-step nilpotent Lie groups are completely described by using the theory of unitary irreducible representations and the Plancherel formulae on nilpotent Lie groups.
A spectral formalism for computing three-dimensional deformations due to surface loads. 1: Theory
Mitrovica, J. X.; Davis, J. L.; Shapiro, I. I.
1994-01-01
We outline a complete spectral formalism for computing high spatial resolution three-dimensional deformations arising from the surface mass loading of a spherically symmetric planet. The main advantages of the formalism are that all surface mass loads are always described using a consistent mathematical representation and that calculations of deformation fields for various spatial resolutions can be performed by simpley altering the spherical harmonic degree truncation level of the procedure. The latter may be important when incorporating improved observational constraints on a particular surface mass load, when considering potential errors in the computed field associated with mass loading having a spatial scale unresolved by the observational constraints, or when treating a number of global surface mass loads constrained with different spatial resolutions. The advantages do not extend to traditional 'Green's function' approaches which involve surface element discretizations of the global mass loads. Another advantage of the spectral formalism, over the Green's function approach, is that a posteriori analyses of the computed deformation fields are easily performed. In developing the spectral formalism, we consider specific cases where the Earth's mantle is assumed to respond as an elastic, slightly anelastic, or linear viscoelastic medium. In the case of an elastic or slightly anelastic mantle rheology the spectral response equations incorporate frequency dependent Love numbers. The formalism can therefore be used, for example, to compute the potentially resonant deformational response associated with the free core nutation and Chandler wobble eigenfunctions. For completeness, the spectral response equations include both body forces, as arise from the gravitational attraction of the Sun and the Moon, and surface mass loads. In either case, and for both elastic and anelastic mantle rheologies, we outline a pseudo-spectral technique for computing the ocean
Alignment and integration of complex networks by hypergraph-based spectral clustering
Michoel, Tom
2012-01-01
Complex networks possess a rich, multi-scale structure reflecting the dynamical and functional organization of the systems they model. Often there is a need to analyze multiple networks simultaneously, to model a system by more than one type of interaction or to go beyond simple pairwise interactions, but currently there is a lack of theoretical and computational methods to address such problems. Here we introduce a framework for multi-network analysis based on hypergraph representations. Our main result is a generalization of the Perron-Frobenius theorem from which we derive spectral clustering algorithms for directed and undirected hypergraphs. We illustrate our approach with applications for tripartite community detection in folksonomies, for local and global alignment of protein-protein interaction networks between multiple species and for detecting clusters of overlapping regulatory pathways in directed networks.
高凤玲; 崔国民; 陶乐仁; 华泽钊; 黄晓璜
2014-01-01
In a one⁃dimensional radiation transfer model, energy distribution and spectral absorption mechanism of greenhouse effect under Pre⁃Industrial and current atmospheric compositions were analyzed. Coupling mechanism between greenhouse effect and surface temperature was investigated on the basis of greenhouse gas concentrations at current level. It shows that warm environment before Industrial Revolution is mainly due to three strong absorption bands of greenhouse gases, which are (100-370) cm-1 , (640-710) cm-1 and (1 370-2 000) cm-1 respectively. However, current global warming is originated from weak absorption bands of greenhouse gases, that is, radiation absorptions by (370-640) cm-1and (710-1 370) cm-1. Contributions to greenhouse effect increment of these weak bands after Industrial Revolution are 25% and 55% respectively. With rising temperature, contribution of right side of the earth’ s radiation peak wavenumber to total greenhouse effect shows positive change, while contribution of left side shows negative change.%利用一维辐射传递方程及LBLRTM逐线积分模式建立计算模型，对工业革命前与目前大气构成情况下温室效应的能量分布及其光谱吸收机理进行分析，在保持温室气体浓度为当前水平的基础上，研究温室效应能量分布与地表温度之间的相互耦合机理。结果表明：工业革命前地球的温暖环境主要来自于大气温室气体的（100～370） cm－1、（640～710） cm－1以及（1370～2000） cm－1三个强吸收带对于地球长波辐射的吸收，而地球当前的变暖则源自于大气的（370～640） cm－1和（710～1370） cm－1两个弱吸收带的作用，其对工业革命以来所额外增加的温室效应贡献分别达到了25％和55％；地表温度升高，温室效应在全波段范围内也会随之增强，但不同谱带处的温室效应贡献以地球平均温度所对应的辐射峰值波数为界线，峰值波数右侧的
Realizations of the Canonical Representation
M K Vemuri
2008-02-01
A characterisation of the maximal abelian subalgebras of the bounded operators on Hilbert space that are normalised by the canonical representation of the Heisenberg group is given. This is used to classify the perfect realizations of the canonical representation.
Standard model of knowledge representation
Yin, Wensheng
2016-09-01
Knowledge representation is the core of artificial intelligence research. Knowledge representation methods include predicate logic, semantic network, computer programming language, database, mathematical model, graphics language, natural language, etc. To establish the intrinsic link between various knowledge representation methods, a unified knowledge representation model is necessary. According to ontology, system theory, and control theory, a standard model of knowledge representation that reflects the change of the objective world is proposed. The model is composed of input, processing, and output. This knowledge representation method is not a contradiction to the traditional knowledge representation method. It can express knowledge in terms of multivariate and multidimensional. It can also express process knowledge, and at the same time, it has a strong ability to solve problems. In addition, the standard model of knowledge representation provides a way to solve problems of non-precision and inconsistent knowledge.
Representations of stem cell clinics on Twitter.
Kamenova, Kalina; Reshef, Amir; Caulfield, Timothy
2014-12-01
The practice of travelling abroad to receive unproven and unregulated stem cell treatments has become an increasingly problematic global phenomenon known as 'stem cell tourism'. In this paper, we examine representations of nine major clinics and providers of such treatments on the microblogging network Twitter. We collected and conducted a content analysis of Twitter posts (n = 363) by these establishments and by other users mentioning them, focusing specifically on marketing claims about treatment procedures and outcomes, discussions of safety and efficacy of stem cell transplants, and specific representations of patients' experiences. Our analysis has shown that there were explicit claims or suggestions of benefits associated with unproven stem cell treatments in approximately one third of the tweets and that patients' experiences, whenever referenced, were presented as invariably positive and as testimonials about the efficacy of stem cell transplants. Furthermore, the results indicated that the tone of most tweets (60.2 %) was overwhelmingly positive and there were rarely critical discussions about significant health risks associated with unproven stem cell therapies. When placed in the context of past research on the problems associated with the marketing of unproven stem cell therapies, this analysis of representations on Twitter suggests that discussions in social media have also remained largely uncritical of the stem cell tourism phenomenon, with inaccurate representations of risks and benefits for patients.
Harmonic Analysis and Group Representation
Figa-Talamanca, Alessandro
2011-01-01
This title includes: Lectures - A. Auslander, R. Tolimeri - Nilpotent groups and abelian varieties, M Cowling - Unitary and uniformly bounded representations of some simple Lie groups, M. Duflo - Construction de representations unitaires d'un groupe de Lie, R. Howe - On a notion of rank for unitary representations of the classical groups, V.S. Varadarajan - Eigenfunction expansions of semisimple Lie groups, and R. Zimmer - Ergodic theory, group representations and rigidity; and, Seminars - A. Koranyi - Some applications of Gelfand pairs in classical analysis.
Sannino, Francesco
2010-01-01
We uncover novel solutions of the 't Hooft anomaly matching conditions for scalarless gauge theories with matter transforming according to higher dimensional representations of the underlying gauge group. We argue that, if the duals exist, they are gauge theories with fermions transforming...... according to the defining representation of the dual gauge group. The resulting conformal windows match the one stemming from the all-orders beta function results when taking the anomalous dimension of the fermion mass to be unity which are also very close to the ones obtained using the Schwinger......-Dyson approximation. We use the solutions to gain useful insight on the conformal window of the associated electric theory. A consistent picture emerges corroborating previous results obtained via different analytic methods and in agreement with first principle lattice explorations....
Constructing visual representations
Huron, Samuel; Jansen, Yvonne; Carpendale, Sheelagh
2014-01-01
The accessibility of infovis authoring tools to a wide audience has been identified as a major research challenge. A key task in the authoring process is the development of visual mappings. While the infovis community has long been deeply interested in finding effective visual mappings......, comparatively little attention has been placed on how people construct visual mappings. In this paper, we present the results of a study designed to shed light on how people transform data into visual representations. We asked people to create, update and explain their own information visualizations using only...... tangible building blocks. We learned that all participants, most of whom had little experience in visualization authoring, were readily able to create and talk about their own visualizations. Based on our observations, we discuss participants’ actions during the development of their visual representations...
Representations of SARS in the British newspapers.
Washer, Peter
2004-12-01
In the Spring of 2003, there was a huge interest in the global news media following the emergence of a new infectious disease: severe acute respiratory syndrome (SARS). This study examines how this novel disease threat was depicted in the UK newspapers, using social representations theory and in particular existing work on social representations of HIV/AIDS and Ebola to analyse the meanings of the epidemic. It investigates the way that SARS was presented as a dangerous threat to the UK public, whilst almost immediately the threat was said to be 'contained' using the mechanism of 'othering': SARS was said to be unlikely to personally affect the UK reader because the Chinese were so different to 'us'; so 'other'. In this sense, the SARS scare, despite the remarkable speed with which it was played out in the modern global news media, resonates with the meanings attributed to other epidemics of infectious diseases throughout history. Yet this study also highlights a number of differences in the social representations of SARS compared with earlier epidemics. In particular, this study examines the phenomena of 'emerging and re-emerging infectious diseases' over the past 30 or so years and suggests that these have impacted on the faith once widely held that Western biomedicine could 'conquer' infectious disease.
MENTAL STATE REPRESENTATION: SPATIOTEMPORAL CHARACTERISTICS
Alexander Oktyabrinovich Prokhorov
2014-01-01
Full Text Available Since the time of statement of the problem of states in psychology, the study of “sensuous” tissue – the mental state representation-takes a fundamental meaning. The problem is concluded in the following questions: “How is mental state represented in the consciousness of an individual?”, “What is the specificity of the mental state representation as distinguished from the subject-matter representation?”, “What are the mechanisms of the mental state representation occurrence and the peculiarities of its dynamics? The study of the mental state representation will allow to explain its specificity and difference from the figurative representation, the peculiarities of state explication as a representation in the consciousness and its relation with other elements of consciousness, will allow to show the regularities of the mental state representation development and its dynamics, factors, which influence the specificity of its occurrence, the regulatory role of the state representation in the vital function. From these perspectives, the article presents the results of the study of spatiotemporal characteristics of the mental state representation; reveals the peculiar features of the spatiotemporal organization of mental state representations: Relieves, specificity, magnitude, variability of indicators, changes of structural characteristics in time spans; considers the age-specific peculiar features of the spatiotemporal organization of mental state representations in terms of organization, stability, coherence and differentiated nature of spatiotemporal structures with the representatives of certain age groups.
Comprehension and Representation in Translation
徐玉萍
2010-01-01
Transhfion is the faithful rcpresentation in one language of the thought, content, feeling and style written in another language. It involves two processes: comprehension and representation. Correct comprehension is the base for adequate representation. Criteria for good representation lies in two points: the version should be faithful to the original, and the version should be as intelligible as possible.
Learning Multisensory Representations
2016-05-23
AFRL-AFOSR-VA-TR-2016-0183 Learning Multisensory Representations Robert Jacobs UNIVERSITY OF ROCHESTER Final Report 05/23/2016 DISTRIBUTION A...DD-MM-YYYY) 16-05-2016 2. REPORT TYPE Final Performance Report 3. DATES COVERED (From - To) 01-09-2012 - 29-02-2016 4. TITLE AND SUBTITLE Learning ...perception; visual perception; haptic perception; auditory perception; perceptual learning ; perceptual decision making 16. SECURITY CLASSIFICATION OF
Jensen, Ole B.
2016-01-01
Dette kapitel gennemgår den såkaldte ”Non-Representational Theory” (NRT), der primært er kendt fra den Angelsaksiske humangeografi, og som særligt er blevet fremført af den engelske geograf Nigel Thrift siden midten af 2000 årtiet. Da positionen ikke kan siges at være specielt homogen vil kapitlet...
The field representation language.
Tsafnat, Guy
2008-02-01
The complexity of quantitative biomedical models, and the rate at which they are published, is increasing to a point where managing the information has become all but impossible without automation. International efforts are underway to standardise representation languages for a number of mathematical entities that represent a wide variety of physiological systems. This paper presents the Field Representation Language (FRL), a portable representation of values that change over space and/or time. FRL is an extensible mark-up language (XML) derivative with support for large numeric data sets in Hierarchical Data Format version 5 (HDF5). Components of FRL can be reused through unified resource identifiers (URI) that point to external resources such as custom basis functions, boundary geometries and numerical data. To demonstrate the use of FRL as an interchange we present three models that study hyperthermia cancer treatment: a fractal model of liver tumour microvasculature; a probabilistic model simulating the deposition of magnetic microspheres throughout it; and a finite element model of hyperthermic treatment. The microsphere distribution field was used to compute the heat generation rate field around the tumour. We used FRL to convey results from the microsphere simulation to the treatment model. FRL facilitated the conversion of the coordinate systems and approximated the integral over regions of the microsphere deposition field.
Translation between representation languages
Vanbaalen, Jeffrey
1994-01-01
A capability for translating between representation languages is critical for effective knowledge base reuse. A translation technology for knowledge representation languages based on the use of an interlingua for communicating knowledge is described. The interlingua-based translation process consists of three major steps: translation from the source language into a subset of the interlingua, translation between subsets of the interlingua, and translation from a subset of the interlingua into the target language. The first translation step into the interlingua can typically be specified in the form of a grammar that describes how each top-level form in the source language translates into the interlingua. In cases where the source language does not have a declarative semantics, such a grammar is also a specification of a declarative semantics for the language. A methodology for building translators that is currently under development is described. A 'translator shell' based on this methodology is also under development. The shell has been used to build translators for multiple representation languages and those translators have successfully translated nontrivial knowledge bases.
[Time perceptions and representations].
Tordjman, S
2015-09-01
Representations of time and time measurements depend on subjective constructs that vary according to changes in our concepts, beliefs, societal needs and technical advances. Similarly, the past, the future and the present are subjective representations that depend on each individual's psychic time and biological time. Therefore, there is no single, one-size-fits-all time for everyone, but rather a different, subjective time for each individual. We need to acknowledge the existence of different inter-individual times but also intra-individual times, to which different functions and different rhythms are attached, depending on the system of reference. However, the construction of these time perceptions and representations is influenced by objective factors (physiological, physical and cognitive) related to neuroscience which will be presented and discussed in this article. Thus, studying representation and perception of time lies at the crossroads between neuroscience, human sciences and philosophy. Furthermore, it is possible to identify several constants among the many and various representations of time and their corresponding measures, regardless of the system of time reference. These include the notion of movements repeated in a stable rhythmic pattern involving the recurrence of the same interval of time, which enables us to define units of time of equal and invariable duration. This rhythmicity is also found at a physiological level and contributes through circadian rhythms, in particular the melatonin rhythm, to the existence of a biological time. Alterations of temporality in mental disorders will be also discussed in this article illustrated by certain developmental disorders such as autism spectrum disorders. In particular, the hypothesis will be developed that children with autism would need to create discontinuity out of continuity through stereotyped behaviors and/or interests. This discontinuity repeated at regular intervals could have been
Pioneers of representation theory
Curtis, Charles W
1999-01-01
The year 1897 was marked by two important mathematical events: the publication of the first paper on representations of finite groups by Ferdinand Georg Frobenius (1849-1917) and the appearance of the first treatise in English on the theory of finite groups by William Burnside (1852-1927). Burnside soon developed his own approach to representations of finite groups. In the next few years, working independently, Frobenius and Burnside explored the new subject and its applications to finite group theory. They were soon joined in this enterprise by Issai Schur (1875-1941) and some years later, by Richard Brauer (1901-1977). These mathematicians' pioneering research is the subject of this book. It presents an account of the early history of representation theory through an analysis of the published work of the principals and others with whom the principals' work was interwoven. Also included are biographical sketches and enough mathematics to enable readers to follow the development of the subject. An introductor...
Dictionary-Based, Clustered Sparse Representation for Hyperspectral Image Classification
Zhen-tao Qin
2015-01-01
Full Text Available This paper presents a new, dictionary-based method for hyperspectral image classification, which incorporates both spectral and contextual characteristics of a sample clustered to obtain a dictionary of each pixel. The resulting pixels display a common sparsity pattern in identical clustered groups. We calculated the image’s sparse coefficients using the dictionary approach, which generated the sparse representation features of the remote sensing images. The sparse coefficients are then used to classify the hyperspectral images via a linear SVM. Experiments show that our proposed method of dictionary-based, clustered sparse coefficients can create better representations of hyperspectral images, with a greater overall accuracy and a Kappa coefficient.
Quantitative Analysis of Spectral Impacts on Silicon Photodiode Radiometers: Preprint
Myers, D. R.
2011-04-01
Inexpensive broadband pyranometers with silicon photodiode detectors have a non-uniform spectral response over the spectral range of 300-1100 nm. The response region includes only about 70% to 75% of the total energy in the terrestrial solar spectral distribution from 300 nm to 4000 nm. The solar spectrum constantly changes with solar position and atmospheric conditions. Relative spectral distributions of diffuse hemispherical irradiance sky radiation and total global hemispherical irradiance are drastically different. This analysis convolves a typical photodiode response with SMARTS 2.9.5 spectral model spectra for different sites and atmospheric conditions. Differences in solar component spectra lead to differences on the order of 2% in global hemispherical and 5% or more in diffuse hemispherical irradiances from silicon radiometers. The result is that errors of more than 7% can occur in the computation of direct normal irradiance from global hemispherical irradiance and diffuse hemispherical irradiance using these radiometers.
Covariant representations of subproduct systems
Viselter, Ami
2010-01-01
A celebrated theorem of Pimsner states that a covariant representation $T$ of a $C^*$-correspondence $E$ extends to a $C^*$-representation of the Toeplitz algebra of $E$ if and only if $T$ is isometric. This paper is mainly concerned with finding conditions for a covariant representation of a \\emph{subproduct system} to extend to a $C^*$-representation of the Toeplitz algebra. This framework is much more general than the former. We are able to find sufficient conditions, and show that in important special cases, they are also necessary. Further results include the universality of the tensor algebra, dilations of completely contractive covariant representations, Wold decompositions and von Neumann inequalities.
Small automorphic representations and degenerate Whittaker vectors
Gustafsson, Henrik P A; Persson, Daniel
2014-01-01
We investigate Fourier coefficients of automorphic forms on split simply-laced Lie groups G. We show that for automorphic representations of small Gelfand-Kirillov dimension the Fourier coefficients are completely determined by certain degenerate Whittaker vectors on G. Although we expect our results to hold for arbitrary simply-laced groups, we give complete proofs only for G=SL(3) and G=SL(4). This is based on a method of Ginzburg that associates Fourier coefficients of automorphic forms with nilpotent orbits of G. Our results complement and extend recent results of Miller and Sahi. We also use our formalism to calculate various local (real and p-adic) spherical vectors of minimal representations of the exceptional groups E_6, E_7, E_8 using global (adelic) degenerate Whittaker vectors, correctly reproducing existing results for such spherical vectors obtained by very different methods.
Categorification and higher representation theory
Beliakova, Anna
2017-01-01
The emergent mathematical philosophy of categorification is reshaping our view of modern mathematics by uncovering a hidden layer of structure in mathematics, revealing richer and more robust structures capable of describing more complex phenomena. Categorified representation theory, or higher representation theory, aims to understand a new level of structure present in representation theory. Rather than studying actions of algebras on vector spaces where algebra elements act by linear endomorphisms of the vector space, higher representation theory describes the structure present when algebras act on categories, with algebra elements acting by functors. The new level of structure in higher representation theory arises by studying the natural transformations between functors. This enhanced perspective brings into play a powerful new set of tools that deepens our understanding of traditional representation theory. This volume exhibits some of the current trends in higher representation theory and the diverse te...
Compressive Spectral Renormalization Method
Bayindir, Cihan
2016-01-01
In this paper a novel numerical scheme for finding the sparse self-localized states of a nonlinear system of equations with missing spectral data is introduced. As in the Petviashivili's and the spectral renormalization method, the governing equation is transformed into Fourier domain, but the iterations are performed for far fewer number of spectral components (M) than classical versions of the these methods with higher number of spectral components (N). After the converge criteria is achieved for M components, N component signal is reconstructed from M components by using the l1 minimization technique of the compressive sampling. This method can be named as compressive spectral renormalization (CSRM) method. The main advantage of the CSRM is that, it is capable of finding the sparse self-localized states of the evolution equation(s) with many spectral data missing.
Spectral Camera based on Ghost Imaging via Sparsity Constraints
Liu, Zhentao; Wu, Jianrong; Li, Enrong; Shen, Xia; Han, Shensheng
2015-01-01
The information acquisition ability of conventional camera is far lower than the Shannon Limit because of the correlation between pixels of image data. Applying sparse representation of images to reduce the abundance of image data and combined with compressive sensing theory, the spectral camera based on ghost imaging via sparsity constraints (GISC spectral camera) is proposed and demonstrated experimentally. GISC spectral camera can acquire the information at a rate significantly below Nyquist, and the resolution of the cells in the three-dimensional (3D) spectral image data-cube can be achieved with a two-dimensional (2D) detector in a single exposure. For the first time, GISC spectral camera opens the way of approaching the Shannon Limit determined by Information Theory in optical imaging instruments.
Co-clustering Analysis of Weblogs Using Bipartite Spectral Projection Approach
Xu, Guandong; Zong, Yu; Dolog, Peter
2010-01-01
and content preference simultaneously. In this paper we will present an algorithm using bipartite spectral clustering to co-cluster Web users and pages. The usage data of users visiting Web sites is modeled as a bipartite graph and the spectral clustering is then applied to the graph representation of usage...
Superpixel sparse representation for target detection in hyperspectral imagery
Dong, Chunhua; Naghedolfeizi, Masoud; Aberra, Dawit; Qiu, Hao; Zeng, Xiangyan
2017-05-01
Sparse Representation (SR) is an effective classification method. Given a set of data vectors, SR aims at finding the sparsest representation of each data vector among the linear combinations of the bases in a given dictionary. In order to further improve the classification performance, the joint SR that incorporates interpixel correlation information of neighborhoods has been proposed for image pixel classification. However, SR and joint SR demand significant amount of computational time and memory, especially when classifying a large number of pixels. To address this issue, we propose a superpixel sparse representation (SSR) algorithm for target detection in hyperspectral imagery. We firstly cluster hyperspectral pixels into nearly uniform hyperspectral superpixels using our proposed patch-based SLIC approach based on their spectral and spatial information. The sparse representations of these superpixels are then obtained by simultaneously decomposing superpixels over a given dictionary consisting of both target and background pixels. The class of a hyperspectral pixel is determined by a competition between its projections on target and background subdictionaries. One key advantage of the proposed superpixel representation algorithm with respect to pixelwise and joint sparse representation algorithms is that it reduces computational cost while still maintaining competitive classification performance. We demonstrate the effectiveness of the proposed SSR algorithm through experiments on target detection in the in-door and out-door scene data under daylight illumination as well as the remote sensing data. Experimental results show that SSR generally outperforms state of the art algorithms both quantitatively and qualitatively.
Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio
1995-01-01
Recently we showed that the spectral flow acting on the N=2 twisted topological theories gives rise to a topological algebra automorphism. Here we point out that the untwisting of that automorphism leads to a spectral flow on the untwisted N=2 superconformal algebra which is different from the usual one. This "other" spectral flow does not interpolate between the chiral ring and the antichiral ring. In particular, it maps the chiral ring into the chiral ring and the antichiral ring into the antichiral ring. We discuss the similarities and differences between both spectral flows. We also analyze their action on null states.
Hermann Weyl and Representation Theory
2016-12-01
Weyl was a universal mathematician whose fundamental contributionsto mathematics encompassed all areas, and provideda unification seldom seen. His work on the theory ofLie groups was motivated by his life-long interest in quantummechanics and relativity. When Weyl entered Lie theory,it mostly focussed on the infinitesimal, and he strove to bringin a global perspective. Time and again, Weyl’s ideas arisingin one context have been adapted and applied to wholly newcontexts. In 1925–26, Weyl wrote four epochal papers in representationtheory of Lie groups which solved fundamentalproblems, and also gave birth to the subject of harmonic analysisof semisimple Lie groups. In these papers, Weyl provedcomplete reducibility theorems and introduced many techniqueswhich have become the standard way to study representationsof Lie groups and their various generalizationsin the last seven decades. Weyl’s work covers several parts ofmathematics, as well as parts of physics. In this article, wediscuss mainly his contributions to the representation theoryof Lie groups via the four papers mentioned above.
Representations of commonsense knowledge
Davis, Ernest
1990-01-01
Representations of Commonsense Knowledge provides a rich language for expressing commonsense knowledge and inference techniques for carrying out commonsense knowledge. This book provides a survey of the research on commonsense knowledge.Organized into 10 chapters, this book begins with an overview of the basic ideas on artificial intelligence commonsense reasoning. This text then examines the structure of logic, which is roughly analogous to that of a programming language. Other chapters describe how rules of universal validity can be applied to facts known with absolute certainty to deduce ot
Boot, Inge; Pecher, Diane
2011-01-01
In the present study we investigated whether the mental representation of the concept categories is represented by the container image schema (Lakoff & Johnson, 1980). In two experiments participants decided whether two pictures were from the same category (animal or vehicle). Pictures were presented inside or outside a frame that should activate the container schema. We found that performance to pictures was influenced by the frame in congruence with the metaphorical mapping (same category—inside bounded region; different category—not in same bounded region). These results show that the concept categories is metaphorically represented by containers.
Graham, Daniel J.; Friedenberg, Jay D.; Rockmore, Daniel N.
2009-02-01
An emerging body of research suggests that artists consistently seek modes of representation that are efficiently processed by the human visual system, and that these shared properties could leave statistical signatures. In earlier work, we showed evidence that perceived similarity of representational art could be predicted using intensity statistics to which the early visual system is attuned, though semantic content was also found to be an important factor. Here we report two studies that examine the visual perception of similarity. We test a collection of non-representational art, which we argue possesses useful statistical and semantic properties, in terms of the relationship between image statistics and basic perceptual responses. We find two simple statistics-both expressed as single values-that predict nearly a third of the overall variance in similarity judgments of abstract art. An efficient visual system could make a quick and reasonable guess as to the relationship of a given image to others (i.e., its context) by extracting these basic statistics early in the visual stream, and this may hold for natural scenes as well as art. But a major component of many types of art is representational content. In a second study, we present findings related to efficient representation of natural scene luminances in landscapes by a well-known painter. We show empirically that elements of contemporary approaches to high-dynamic range tone-mapping-which are themselves deeply rooted in an understanding of early visual system coding-are present in the way Vincent Van Gogh transforms scene luminances into painting luminances. We argue that global tone mapping functions are a useful descriptor of an artist's perceptual goals with respect to global illumination and we present evidence that mapping the scene to a painting with different implied lighting properties produces a less efficient mapping. Together, these studies suggest that statistical regularities in art can shed
Social Representations of Intelligence
Elena Zubieta
2016-02-01
Full Text Available The article stresses the relationship between Explicit and Implicit theories of Intelligence. Following the line of common sense epistemology and the theory of Social Representations, a study was carried out in order to analyze naive’s explanations about Intelligence Definitions. Based on Mugny & Carugati (1989 research, a self-administered questionnaire was designed and filled in by 286 subjects. Results are congruent with the main hyphotesis postulated: A general overlap between explicit and implicit theories showed up. According to the results Intelligence appears as both, a social attribute related to social adaptation and as a concept defined in relation with contextual variables similar to expert’s current discourses. Nevertheless, conceptions based on “gifted ideology” still are present stressing the main axes of Intelligence debate: biological and sociological determinism. In the same sense, unfamiliarity and social identity are reaffirmed as organizing principles of social representation. The distance with the object -measured as the belief in intelligence differences as a solve/non solve problem- and the level of implication with the topic -teachers/no teachers- appear as discriminating elements at the moment of supporting specific dimensions.
Knowledge representation with SOA
Daniela Gotseva
2013-01-01
Full Text Available This paper addresses the problem of supporting the software development process through the artificial intelligence. The expert systems could advise the Domain Engineer in programming without the detailed experience in programming languages. He will use and integrate, with the help of deductive database and domain knowledge, the previously developed software components to new complex functionalities. The objective of this document is to provide the knowledge representation about atomic Web Services which will be registered as the facts in the deductive database. The author proposes to use the decision rules in decision tables for representing the service model which consists of semantic specification, interface description, service quality (QoS, non-functional properties. Also the use of Domain Specific Languages (DSL for modeling Domain Engineers re-quests to the expert system will be considered within this document. As the illustrative use case for described knowledge representation the author proposes the domain of SOA-based geographic information systems (GIS which represent a new branch of information and communication technologies.
Global point signature for shape analysis of carpal bones
Chaudhari, Abhijit J.; Leahy, Richard M.; Wise, Barton L.; Lane, Nancy E.; Badawi, Ramsey D.; Joshi, Anand A.
2014-02-01
We present a method based on spectral theory for the shape analysis of carpal bones of the human wrist. We represent the cortical surface of the carpal bone in a coordinate system based on the eigensystem of the two-dimensional Helmholtz equation. We employ a metric—global point signature (GPS)—that exploits the scale and isometric invariance of eigenfunctions to quantify overall bone shape. We use a fast finite-element-method to compute the GPS metric. We capitalize upon the properties of GPS representation—such as stability, a standard Euclidean (ℓ2) metric definition, and invariance to scaling, translation and rotation—to perform shape analysis of the carpal bones of ten women and ten men from a publicly-available database. We demonstrate the utility of the proposed GPS representation to provide a means for comparing shapes of the carpal bones across populations.
Effective QED Actions Representations, Gauge Invariance, Anomalies and Mass Expansions
Deser, Stanley D; Seminara, D
1998-01-01
We analyze and give explicit representations for the effective abelian vector gauge field actions generated by charged fermions with particular attention to the thermal regime in odd dimensions, where spectral asymmetry can be present. We show, through $\\zeta-$function regularization, that both small and large gauge invariances are preserved at any temperature and for any number of fermions at the usual price of anomalies: helicity/parity invariance will be lost in even/odd dimensions, and in the latter even at zero mass. Gauge invariance dictates a very general ``Fourier'' representation of the action in terms of the holonomies that carry the novel, large gauge invariant, information. We show that large (unlike small) transformations and hence their Ward identities, are not perturbative order-preserving, and clarify the role of (properly redefined) Chern-Simons terms in this context. From a powerful representation of the action in terms of massless heat kernels, we are able to obtain rigorous gauge invariant...
Spectral compression algorithms for the analysis of very large multivariate images
Keenan, Michael R.
2007-10-16
A method for spectrally compressing data sets enables the efficient analysis of very large multivariate images. The spectral compression algorithm uses a factored representation of the data that can be obtained from Principal Components Analysis or other factorization technique. Furthermore, a block algorithm can be used for performing common operations more efficiently. An image analysis can be performed on the factored representation of the data, using only the most significant factors. The spectral compression algorithm can be combined with a spatial compression algorithm to provide further computational efficiencies.
On Longitudinal Spectral Coherence
Kristensen, Leif
1979-01-01
It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between...
SRD 115 Hydrocarbon Spectral Database (Web, free access) All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.
Optimal Segmentation Strategy for Compact Representation of Hyperspectral Image Cubes
Paglieroni, D; Roberts, R
2000-02-08
By producing compact representations of hyperspectral image cubes (hypercubes), image storage requirements and the amount of time it takes to extract essential elements of information can both be dramatically reduced. However, these compact representations must preserve the important spectral features within hypercube pixels and the spatial structure associated with background and objects or phenomena of interest. This paper describes a novel approach for automatically and efficiently generating a particular type of compact hypercube representation, referred to as a supercube. The hypercube is segmented into regions that contain pixels with similar spectral shapes that are spatially connected, and the pixel connectivity constraint can be relaxed. Thresholds of similarity in spectral shape between pairs of pixels are derived directly from the hypercube data. One superpixel is generated for each region as some linear combination of pixels belonging to that region. The superpixels are optimal in the sense that the linear combination coefficients are computed so as to minimize the level of noise. Each hypercube pixel is represented in the supercube by applying a gain and bias to the superpixel assigned to the region containing that pixel. Examples are provided.
Network Topology Inference from Spectral Templates
Segarra, Santiago; Mateos, Gonzalo; Ribeiro, Alejandro
2016-01-01
We address the problem of identifying a graph structure from the observation of signals defined on its nodes. Fundamentally, the unknown graph encodes direct relationships between signal elements, which we aim to recover from observable indirect relationships generated by a diffusion process on the graph. The fresh look advocated here permeates benefits from convex optimization and stationarity of graph signals, in order to identify the graph shift operator (a matrix representation of the graph) given only its eigenvectors. These spectral templates can be obtained, e.g., from the sample covariance of independent graph signals diffused on the sought network. The novel idea is to find a graph shift that, while being consistent with the provided spectral information, endows the network with certain desired properties such as sparsity. To that end we develop efficient inference algorithms stemming from provably-tight convex relaxations of natural nonconvex criteria, particularizing the results for two shifts: the...
Topographical scattering of waves: a spectral approach
Magne, R; Rey, V; Herbers, T H C; Magne, Rudy; Ardhuin, Fabrice; Rey, Vincent; Herbers, Thomas H. C.
2005-01-01
The topographical scattering of gravity waves is investigated using a spectral energy balance equation that accounts for first order wave-bottom Bragg scattering. This model represents the bottom topography and surface waves with spectra, and evaluates a Bragg scattering source term that is theoretically valid for small bottom and surface slopes and slowly varying spectral properties. The robustness of the model is tested for a variety of topographies uniform along one horizontal dimension including nearly sinusoidal, linear ramp and step profiles. Results are compared with reflections computed using an accurate method that applies integral matching along vertical boundaries of a series of steps. For small bottom amplitudes, the source term representation yields accurate reflection estimates even for a localized scatterer. This result is proved for small bottom amplitudes $h$ relative to the mean water depth $H$. Wave reflection by small amplitude bottom topography thus depends primarily on the bottom elevati...
Musical Instrument Timbres Classification with Spectral Features
Agostini Giulio
2003-01-01
Full Text Available A set of features is evaluated for recognition of musical instruments out of monophonic musical signals. Aiming to achieve a compact representation, the adopted features regard only spectral characteristics of sound and are limited in number. On top of these descriptors, various classification methods are implemented and tested. Over a dataset of 1007 tones from 27 musical instruments, support vector machines and quadratic discriminant analysis show comparable results with success rates close to 70% of successful classifications. Canonical discriminant analysis never had momentous results, while nearest neighbours performed on average among the employed classifiers. Strings have been the most misclassified instrument family, while very satisfactory results have been obtained with brass and woodwinds. The most relevant features are demonstrated to be the inharmonicity, the spectral centroid, and the energy contained in the first partial.
Musical Instrument Timbres Classification with Spectral Features
Agostini, Giulio; Longari, Maurizio; Pollastri, Emanuele
2003-12-01
A set of features is evaluated for recognition of musical instruments out of monophonic musical signals. Aiming to achieve a compact representation, the adopted features regard only spectral characteristics of sound and are limited in number. On top of these descriptors, various classification methods are implemented and tested. Over a dataset of 1007 tones from 27 musical instruments, support vector machines and quadratic discriminant analysis show comparable results with success rates close to 70% of successful classifications. Canonical discriminant analysis never had momentous results, while nearest neighbours performed on average among the employed classifiers. Strings have been the most misclassified instrument family, while very satisfactory results have been obtained with brass and woodwinds. The most relevant features are demonstrated to be the inharmonicity, the spectral centroid, and the energy contained in the first partial.
Snapshot spectral imaging system
Arnold, Thomas; De Biasio, Martin; McGunnigle, Gerald; Leitner, Raimund
2010-02-01
Spectral imaging is the combination of spectroscopy and imaging. These fields are well developed and are used intensively in many application fields including industry and the life sciences. The classical approach to acquire hyper-spectral data is to sequentially scan a sample in space or wavelength. These acquisition methods are time consuming because only two spatial dimensions, or one spatial and the spectral dimension, can be acquired simultaneously. With a computed tomography imaging spectrometer (CTIS) it is possible to acquire two spatial dimensions and a spectral dimension during a single integration time, without scanning either spatial or spectral dimensions. This makes it possible to acquire dynamic image scenes without spatial registration of the hyperspectral data. This is advantageous compared to tunable filter based systems which need sophisticated image registration techniques. While tunable filters provide full spatial and spectral resolution, for CTIS systems there is always a tradeoff between spatial and spectral resolution as the spatial and spectral information corresponding to an image cube is squeezed onto a 2D image. The presented CTIS system uses a spectral-dispersion element to project the spectral and spatial image information onto a 2D CCD camera array. The system presented in this paper is designed for a microscopy application for the analysis of fixed specimens in pathology and cytogenetics, cell imaging and material analysis. However, the CTIS approach is not limited to microscopy applications, thus it would be possible to implement it in a hand-held device for e.g. real-time, intra-surgery tissue classification.
A Framework of Semantic Information Representation in Distributed Environments
无
2006-01-01
An information representation framework is designed to overcome the problem of semantic heterogeneity in distributed environments in this paper. Emphasis is placed on establishing an XML-oriented semantic data model and the mapping between XML data based on a global ontology semantic view. The framework is implemented in Web Service, which enhances information process efficiency, accuracy and the semantic interoperability as well.
Integral geometry and representation theory
Gel'fand, I M; Vilenkin, N Ya
1966-01-01
Generalized Functions, Volume 5: Integral Geometry and Representation Theory is devoted to the theory of representations, focusing on the group of two-dimensional complex matrices of determinant one.This book emphasizes that the theory of representations is a good example of the use of algebraic and geometric methods in functional analysis, in which transformations are performed not on the points of a space, but on the functions defined on it. The topics discussed include Radon transform on a real affine space, integral transforms in the complex domain, and representations of the group of comp
Intentionality, Representation, and Anticipation
De Preester, Helena
2002-09-01
Both Brentano and Merleau-Ponty have developed an account of intentionality, which nevertheless differ profoundly in the following respect. According to Brentano, intentionality mainly is a matter of mental presentations. This marks the beginning of phenomenology's difficult relation with the nature of the intentional reference. Merleau-Ponty, on the other hand, has situated intentionality on the level of the body, a turn which has important implications for the nature of intentionality. Intentionality no longer is primarily based on having (re)presentations, but is rooted in the dynamics of the living body. To contrast those approaches enables us to make clear in what way intentionality is studied nowadays. On the one hand, intentionality is conceived of as a matter of formal-syntactical causality in cognitive science, and in particular in classical-computational theory. On the other hand, a interactivist approach offers a more Merleau-Ponty-like point of view, in which autonomy, embodiment and interaction are stressed.
Going beyond representational anthropology
Winther, Ida Wentzel
an education. There is a close connection between: 1) The dream and the desire for education; 2) Mobility (away from the family, home and friends in a very young age for getting an education; 3) Transforming a new and unknown site and space into a known place, where one can make one-self at home ('home one......Going beyond representational anthropology: Re-presenting bodily, emotional and virtual practices in everyday life. Separated youngsters and families in Greenland Greenland is a huge island, with a total of four high-schools. Many youngsters (age 16-18) move far away from home in order to get...... transformation work into the young people and their families. In this presentation I want to screen two sequences from the film, in order to show and clarify how mobility and transformation are made and dealt with both from the youngsters’ and their parents’ perspectives, but in asynchronous loups. I want...
Linear recursive distributed representations.
Voegtlin, Thomas; Dominey, Peter F
2005-09-01
Connectionist networks have been criticized for their inability to represent complex structures with systematicity. That is, while they can be trained to represent and manipulate complex objects made of several constituents, they generally fail to generalize to novel combinations of the same constituents. This paper presents a modification of Pollack's Recursive Auto-Associative Memory (RAAM), that addresses this criticism. The network uses linear units and is trained with Oja's rule, in which it generalizes PCA to tree-structured data. Learned representations may be linearly combined, in order to represent new complex structures. This results in unprecedented generalization capabilities. Capacity is orders of magnitude higher than that of a RAAM trained with back-propagation. Moreover, regularities of the training set are preserved in the new formed objects. The formation of new structures displays developmental effects similar to those observed in children when learning to generalize about the argument structure of verbs.
Computer aided surface representation
Barnhill, R.E.
1990-02-19
The central research problem of this project is the effective representation, computation, and display of surfaces interpolating to information in three or more dimensions. If the given information is located on another surface, then the problem is to construct a surface defined on a surface''. Sometimes properties of an already defined surface are desired, which is geometry processing''. Visualization of multivariate surfaces is possible by means of contouring higher dimensional surfaces. These problems and more are discussed below. The broad sweep from constructive mathematics through computational algorithms to computer graphics illustrations is utilized in this research. The breadth and depth of this research activity makes this research project unique.
Willberg, Martin; Lieb, Verena; Pail, Roland; Schmidt, Michael
2017-04-01
The analysis of the Earth's gravity field plays an important role in various disciplines of geosciences. While modern satellite gravity missions make it possible to define a globally consistent geoid with centimeter accuracy and a spatial resolution of 80-100km, it stays a major challenge to consistently combine global low-resolution data with regional high-resolution gravity information. Therefore, a variety of different regional gravity field modelling methods have been established during the last decades. In our analysis, we investigate the spectral combination of heterogeneous gravity data within two different calculation methods: First, the statistical approach of Least Squares Collocation (LSC) which uses the covariance information of input and output data to result in a full variance-covariance matrix. Second, the Multi-Resolution Representation (MRR) based on spherical radial basis functions. The MRR combines a low-pass filtered global geopotential model with satellite gradiometer and/or terrestrial gravity data by means of band-pass filtering. We examine the theoretical concepts and the computational differences and similarities between both approaches. Through fast changing topography, mountains as well as oceanic regions, our study area in the South American Andes is challenging and perfectly suitable for this examination. The use of synthetic data in closed-loop tests enables us to a very detailed investigation of predicted and actual accuracies of geoid determination. Furthermore, we point out respective advantages and disadvantages and link them to the calculation concepts of the two methods. The results contribute to the project "Optimally combined regional geoid models for the realization of height systems in developing countries (ORG4heights)" and, thus, aim to finally integrate the regional solutions into a global vertical reference frame.
Preschool Children's Participation in Representational and Non-Representational Activities
Braswell, Gregory S.
2017-01-01
The present study examined representational and non-representational activities in which children in a Head Start classroom participated. This was an investigation from the perspective of cultural-historical activity theory of how components (e.g. artifacts and division of labour) of classroom activities vary across and within types of activities.…
Linneweber, V.; Hartmuth, G.; Deising, S.; Fritsche, I.; Linneweber, A.
2001-04-01
At the example of the potential dangers of future changes in the climate threatening the island of Sylt, the authors deal with the question of how global changes in the environment, their causes and effects and possible measures taken by local groups to prevent them can be perceived and assessed in the context of general developments. To do this, 70 key persons of the ''Sylt social system'' who had been selected systematically were questioned at two different times in semi-structured, open interviews. The minutes of the interviews were categorized and evaluated quantitatively, analysing their contents. The goal was to find out the social representations of possible changes in the climate and to prove that these mental models are group-specific. It was found that to the persons questioned, tourism industry and construction activities on the island were far more important subjects than changes in the climate or the subject of protecting the shores. Climate changes were referred to with relation to their effects which were seen in connection with natural events. As far as causes were concerned, traffic turned out to be very important to the persons questioned. As for the measures, preventing changes in the climate was found to be more important than adapting to its consequences. Differences in the social representation of the groups mainly corresponded with the subjects focussed on and the interests of each group. As a supplement to the interview study, 54 tourists were interviewed regarding various aspects of the main study with a standardized questionnaire. [German] Am Beispiel der moeglichen Bedrohung Sylts durch zukuenftige Klimaaenderungen wird untersucht, wie globale Umweltveraenderungen, deren Ursachen und Auswirkungen sowie moegliche Gegenmassnahmen von lokalen Akteursgruppen im Kontext allgemeiner Entwicklungen wahrgenommen und bewertet werden. Dazu wurden 70 systematisch ausgewaehlte Schluesselpersonen des 'sozialen Systems Sylt
Spectrum recovery method based on sparse representation for segmented multi-Gaussian model
Teng, Yidan; Zhang, Ye; Ti, Chunli; Su, Nan
2016-09-01
Hyperspectral images can realize crackajack features discriminability for supplying diagnostic characteristics with high spectral resolution. However, various degradations may generate negative influence on the spectral information, including water absorption, bands-continuous noise. On the other hand, the huge data volume and strong redundancy among spectrums produced intense demand on compressing HSIs in spectral dimension, which also leads to the loss of spectral information. The reconstruction of spectral diagnostic characteristics has irreplaceable significance for the subsequent application of HSIs. This paper introduces a spectrum restoration method for HSIs making use of segmented multi-Gaussian model (SMGM) and sparse representation. A SMGM is established to indicating the unsymmetrical spectral absorption and reflection characteristics, meanwhile, its rationality and sparse property are discussed. With the application of compressed sensing (CS) theory, we implement sparse representation to the SMGM. Then, the degraded and compressed HSIs can be reconstructed utilizing the uninjured or key bands. Finally, we take low rank matrix recovery (LRMR) algorithm for post processing to restore the spatial details. The proposed method was tested on the spectral data captured on the ground with artificial water absorption condition and an AVIRIS-HSI data set. The experimental results in terms of qualitative and quantitative assessments demonstrate that the effectiveness on recovering the spectral information from both degradations and loss compression. The spectral diagnostic characteristics and the spatial geometry feature are well preserved.
2D Fourier series representation of gravitational functionals in spherical coordinates
Ghobadi-Far, Khosro; Sharifi, Mohammad Ali; Sneeuw, Nico
2016-09-01
2D Fourier series representation of a scalar field like gravitational potential is conventionally derived by making use of the Fourier series of the Legendre functions in the spherical harmonic representation. This representation has been employed so far only in the case of a scalar field or the functionals that are related to it through a radial derivative. This paper provides a unified scheme to represent any gravitational functional in terms of spherical coordinates using a 2D Fourier series representation. The 2D Fourier series representation for each individual point is derived by transforming the spherical harmonics from the geocentric Earth-fixed frame to a rotated frame so that its equator coincides with the local meridian plane of that point. In the obtained formulation, each functional is linked to the potential in the spectral domain using a spectral transfer. We provide the spectral transfers of the first-, second- and third-order gradients of the gravitational potential in the local north-oriented reference frame and also those of some functionals of frequent use in the physical geodesy. The obtained representation is verified numerically. Moreover, spherical harmonic analysis of anisotropic functionals and contribution analysis of the third-order gradient tensor are provided as two numerical examples to show the power of the formulation. In conclusion, the 2D Fourier series representation on the sphere is generalized to functionals of the potential. In addition, the set of the spectral transfers can be considered as a pocket guide that provides the spectral characteristics of the functionals. Therefore, it extends the so-called Meissl scheme.
Tajuddin, Wan Ahmad
1994-02-01
Ease in finding the configuration at the global energy minimum in a symmetric neural network is important for combinatorial optimization problems. We carry out a comprehensive survey of available strategies for seeking global minima by comparing their performances in the binary representation problem. We recall our previous comparison of steepest descent with analog dynamics, genetic hill-climbing, simulated diffusion, simulated annealing, threshold accepting and simulated tunneling. To this, we add comparisons to other strategies including taboo search and one with field-ordered updating.
Stevanovic, Dragan
2015-01-01
Spectral Radius of Graphs provides a thorough overview of important results on the spectral radius of adjacency matrix of graphs that have appeared in the literature in the preceding ten years, most of them with proofs, and including some previously unpublished results of the author. The primer begins with a brief classical review, in order to provide the reader with a foundation for the subsequent chapters. Topics covered include spectral decomposition, the Perron-Frobenius theorem, the Rayleigh quotient, the Weyl inequalities, and the Interlacing theorem. From this introduction, the
Sparse coding based feature representation method for remote sensing images
Oguslu, Ender
In this dissertation, we study sparse coding based feature representation method for the classification of multispectral and hyperspectral images (HSI). The existing feature representation systems based on the sparse signal model are computationally expensive, requiring to solve a convex optimization problem to learn a dictionary. A sparse coding feature representation framework for the classification of HSI is presented that alleviates the complexity of sparse coding through sub-band construction, dictionary learning, and encoding steps. In the framework, we construct the dictionary based upon the extracted sub-bands from the spectral representation of a pixel. In the encoding step, we utilize a soft threshold function to obtain sparse feature representations for HSI. Experimental results showed that a randomly selected dictionary could be as effective as a dictionary learned from optimization. The new representation usually has a very high dimensionality requiring a lot of computational resources. In addition, the spatial information of the HSI data has not been included in the representation. Thus, we modify the framework by incorporating the spatial information of the HSI pixels and reducing the dimension of the new sparse representations. The enhanced model, called sparse coding based dense feature representation (SC-DFR), is integrated with a linear support vector machine (SVM) and a composite kernels SVM (CKSVM) classifiers to discriminate different types of land cover. We evaluated the proposed algorithm on three well known HSI datasets and compared our method to four recently developed classification methods: SVM, CKSVM, simultaneous orthogonal matching pursuit (SOMP) and image fusion and recursive filtering (IFRF). The results from the experiments showed that the proposed method can achieve better overall and average classification accuracies with a much more compact representation leading to more efficient sparse models for HSI classification. To further
Restriction of complementary series representations of $O(1,N)$ to symmetric subgroups
Möllers, Jan; Oshima, Yoshiki
2012-01-01
We find the complete branching law for the restriction of complementary series representations of $O(1,n+1)$ to the symmetric subgroup $O(1,m+1)\\times O(n-m)$, $0\\leq m... the spectral decomposition of a certain hypergeometric type ordinary differential operator. The main tool connecting this differential operator with the representations are second order Bessel operators which describe the Lie algebra action in this realization....
Congruence properties of induced representations
Mayer, Dieter; Momeni, Arash; Venkov, Alexei
In this paper we study representations of the projective modular group induced from the Hecke congruence group of level 4 with Selberg's character. We show that the well known congruence properties of Selberg's character are equivalent to the congruence properties of the induced representations. ...
Representation of Fuzzy Symmetric Relations
1986-03-19
Std Z39-18 REPRESENTATION OF FUZZY SYMMETRIC RELATIONS L. Valverde Dept. de Matematiques i Estadistica Universitat Politecnica de Catalunya Avda...REPRESENTATION OF FUZZY SYMMETRIC RELATIONS L. "Valverde* Dept. de Matematiques i Estadistica Universitat Politecnica de Catalunya Avda. Diagonal, 649
Scientific Representation and Science Learning
Matta, Corrado
2014-01-01
In this article I examine three examples of philosophical theories of scientific representation with the aim of assessing which of these is a good candidate for a philosophical theory of scientific representation in science learning. The three candidate theories are Giere's intentional approach, Suárez's inferential approach and Lynch and…
$\\alpha$-Representation for QCD
Tuan, Richard Hong
1998-01-01
An $\\alpha$-parameter representation is derived for gauge field theories.It involves, relative to a scalar field theory, only constants and derivatives with respect to the $\\alpha$-parameters. Simple rules are given to obtain the $\\alpha$-representation for a Feynman graph with an arbitrary number of loops in gauge theories in the Feynman gauge.
International agreements on commercial representation
Slanař, Jan
2014-01-01
The purpose of the thesis is to describe the possibilities for fixing the position of a company in the market through contracts for commercial representation with a focus to finding legal and economic impact on the company that contracted for exclusive representation.
Scientific Representation and Science Learning
Matta, Corrado
2014-01-01
In this article I examine three examples of philosophical theories of scientific representation with the aim of assessing which of these is a good candidate for a philosophical theory of scientific representation in science learning. The three candidate theories are Giere's intentional approach, Suárez's inferential approach and Lynch and…
Teachers’ representations of school indiscipline
Joe Garcia
2015-11-01
Full Text Available In this article we analyze a set of teachers’ representations of school indiscipline and its implications for pedagogical practices, particularly related to the resolution of problems in the classroom. Initially we explore three teachers’ representations on the genesis of school indiscipline. The first representation attributes prominence to the student as the singular subject in the production of indiscipline and who will be the center of the pedagogical intervention. The second representation attributes the genesis of the indiscipline to the context of the relations among the subjects in the classroom. The third representation suggests that the indiscipline would be something socially constructed in the schools, where it is intrinsically related to its nature and social function, and is an intrinsic part of its institutional culture. This third representation is distant of the previous ones, and provides an understanding of the indiscipline as a cultural message. In the second part of this article we analyze a set of implications of the teachers’ representations in relation to their pedagogical practices. At the ending of the text, we present some notes that put in evidence some issues that seems to be at the center in the study of the representations regarding to school indiscipline, in relation to the roles teachers are supposed to taken in contexts of indiscipline.
Spectral analysis methods for the robust measurement of the flexural rigidity of biopolymers.
Valdman, David; Atzberger, Paul J; Yu, Dezhi; Kuei, Steve; Valentine, Megan T
2012-03-07
The mechanical properties of biopolymers can be determined from a statistical analysis of the ensemble of shapes they exhibit when subjected to thermal forces. In practice, extracting information from fluorescence microscopy images can be challenging due to low signal/noise ratios and other artifacts. To address these issues, we develop a suite of tools for image processing and spectral data analysis that is based on a biopolymer contour representation expressed in a spectral basis of orthogonal polynomials. We determine biopolymer shape and stiffness using global fitting routines that optimize a utility function measuring the amount of fluorescence intensity overlapped by such contours. This approach allows for filtering of high-frequency noise and interpolation over sporadic gaps in fluorescence. We use benchmarking to demonstrate the validity of our methods, by analyzing an ensemble of simulated images generated using a simulated biopolymer with known stiffness and subjected to various types of image noise. We then use these methods to determine the persistence lengths of taxol-stabilized microtubules. We find that single microtubules are well described by the wormlike chain polymer model, and that ensembles of chemically identical microtubules show significant heterogeneity in bending stiffness, which cannot be attributed to sampling or fitting errors. We expect these approaches to be useful in the study of biopolymer mechanics and the effects of associated regulatory molecules.
Spectral Analysis Methods for the Robust Measurement of the Flexural Rigidity of Biopolymers
Valdman, David; Atzberger, Paul J.; Yu, Dezhi; Kuei, Steve; Valentine, Megan T.
2012-01-01
The mechanical properties of biopolymers can be determined from a statistical analysis of the ensemble of shapes they exhibit when subjected to thermal forces. In practice, extracting information from fluorescence microscopy images can be challenging due to low signal/noise ratios and other artifacts. To address these issues, we develop a suite of tools for image processing and spectral data analysis that is based on a biopolymer contour representation expressed in a spectral basis of orthogonal polynomials. We determine biopolymer shape and stiffness using global fitting routines that optimize a utility function measuring the amount of fluorescence intensity overlapped by such contours. This approach allows for filtering of high-frequency noise and interpolation over sporadic gaps in fluorescence. We use benchmarking to demonstrate the validity of our methods, by analyzing an ensemble of simulated images generated using a simulated biopolymer with known stiffness and subjected to various types of image noise. We then use these methods to determine the persistence lengths of taxol-stabilized microtubules. We find that single microtubules are well described by the wormlike chain polymer model, and that ensembles of chemically identical microtubules show significant heterogeneity in bending stiffness, which cannot be attributed to sampling or fitting errors. We expect these approaches to be useful in the study of biopolymer mechanics and the effects of associated regulatory molecules. PMID:22404937
Embedding the global womb: Global child labour and the new policy agenda
Nieuwenhuys, O.
2007-01-01
Unevenly distributed symbolic resources misrecognize children's lifeworlds in favour of a mythical global order. As new policy agenda representations of child labour in the global south hold out the promise of a labour-free global childhood, children's day-to-day work routines are denied. These rout
Embedding the global womb: Global child labour and the new policy agenda
Nieuwenhuys, O.
2007-01-01
Unevenly distributed symbolic resources misrecognize children's lifeworlds in favour of a mythical global order. As new policy agenda representations of child labour in the global south hold out the promise of a labour-free global childhood, children's day-to-day work routines are denied. These
Unmixing of spectrally similar minerals
Debba, Pravesh
2009-01-01
Full Text Available -bearing oxide/hydroxide/sulfate minerals in complex mixtures be obtained using hyperspectral data? Debba (CSIR) Unmixing of spectrally similar minerals MERAKA 2009 3 / 18 Method of spectral unmixing Old method: problem Linear Spectral Mixture Analysis (LSMA...
Revealing children's implicit spelling representations.
Critten, Sarah; Pine, Karen J; Messer, David J
2013-06-01
Conceptualizing the underlying representations and cognitive mechanisms of children's spelling development is a key challenge for literacy researchers. Using the Representational Redescription model (Karmiloff-Smith), Critten, Pine and Steffler (2007) demonstrated that the acquisition of phonological and morphological knowledge may be underpinned by increasingly explicit levels of spelling representation. However, their proposal that implicit representations may underlie early 'visually based' spelling remains unresolved. Children (N = 101, aged 4-6 years) were given a recognition task (Critten et al., 2007) and a novel production task, both involving verbal justifications of why spellings are correct/incorrect, strategy use and word pattern similarity. Results for both tasks supported an implicit level of spelling characterized by the ability to correctly recognize/produce words but the inability to explain operational strategies or generalize knowledge. Explicit levels and multiple representations were also in evidence across the two tasks. Implications for cognitive mechanisms underlying spelling development are discussed.
Fuzzy Morphological Polynomial Image Representation
Chin-Pan Huang
2010-01-01
Full Text Available A novel signal representation using fuzzy mathematical morphology is developed. We take advantage of the optimum fuzzy fitting and the efficient implementation of morphological operators to extract geometric information from signals. The new representation provides results analogous to those given by the polynomial transform. Geometrical decomposition of a signal is achieved by windowing and applying sequentially fuzzy morphological opening with structuring functions. The resulting representation is made to resemble an orthogonal expansion by constraining the results of opening to equate adapted structuring functions. Properties of the geometric decomposition are considered and used to calculate the adaptation parameters. Our procedure provides an efficient and flexible representation which can be efficiently implemented in parallel. The application of the representation is illustrated in data compression and fractal dimension estimation temporal signals and images.
Representational gain in cortical area underlies increase of memory strength.
Bieszczad, Kasia M; Weinberger, Norman M
2010-02-23
Neuronal plasticity that develops in the cortex during learning is assumed to represent memory content, but the functions of such plasticity are actually unknown. The shift in spectral tuning in primary auditory cortex (A1) to the frequency of a tone signal is a compelling candidate for a substrate of memory because it has all of the cardinal attributes of associative memory: associativity, specificity, rapid induction, consolidation, and long-term retention. Tuning shifts increase the representational area of the signal in A1, as an increasing function of performance level, suggesting that area encodes the magnitude of acquired stimulus significance. The present study addresses the question of the specific function of learning-induced associative representational plasticity. We tested the hypothesis that specific increases in A1 representational area for an auditory signal serve the mnemonic function of enhancing memory strength for that signal. Rats were trained to bar-press for reward contingent on the presence of a signal tone (5.0 kHz), and assessed for memory strength during extinction. The amount of representational area gain for the signal frequency band was significantly positively correlated with resistance to extinction to the signal frequency in two studies that spanned the range of task difficulty. These findings indicate that specific gain in cortical representational area underlies the strength of the behaviorally-relevant contents of memory. Thus, mnemonic functions of cortical plasticity are determinable.
Vowel Inherent Spectral Change
Assmann, Peter
2013-01-01
It has been traditional in phonetic research to characterize monophthongs using a set of static formant frequencies, i.e., formant frequencies taken from a single time-point in the vowel or averaged over the time-course of the vowel. However, over the last twenty years a growing body of research has demonstrated that, at least for a number of dialects of North American English, vowels which are traditionally described as monophthongs often have substantial spectral change. Vowel Inherent Spectral Change has been observed in speakers’ productions, and has also been found to have a substantial effect on listeners’ perception. In terms of acoustics, the traditional categorical distinction between monophthongs and diphthongs can be replaced by a gradient description of dynamic spectral patterns. This book includes chapters addressing various aspects of vowel inherent spectral change (VISC), including theoretical and experimental studies of the perceptually relevant aspects of VISC, the relationship between ar...
Time and spectral domain relative entropy: A new approach to multivariate spectral estimation
Ferrante, Augusto; Pavon, Michele
2011-01-01
The concept of spectral relative entropy rate is introduced for jointly stationary Gaussian processes. Using a classical result of Marc Pinsker, we establish a remarkable connection between time and spectral domain relative entropy rate. This naturally leads to a new multivariate spectral estimation technique. The latter may be viewed as an extension of the approach, called THREE, introduced by Byrnes, Georgiou and Lindquist in 2000 which, in turn, followed in the footsteps of the Burg-Jaynes Maximum Entropy Method. Spectral estimation is here recast in the form of a constrained spectrum approximation problem where the distance is equal to the processes relative entropy rate. The corresponding solution entails a complexity upper bound which improves on the one so far available in the multichannel framework. Indeed, it is equal to the one featured by THREE in the scalar case. The solution is computed via a globally convergent matricial Newton-type algorithm. Simulations suggest the effectiveness of the new tec...
Archival Representation in the Digital Age
Zhang, Jane
2012-01-01
This study analyzes the representation systems of three digitized archival collections using the traditional archival representation framework of provenance, order, and content. The results of the study reveal a prominent role of provenance representation, a compromised role of order representation, and an active role of content representation in…
Archival Representation in the Digital Age
Zhang, Jane
2012-01-01
This study analyzes the representation systems of three digitized archival collections using the traditional archival representation framework of provenance, order, and content. The results of the study reveal a prominent role of provenance representation, a compromised role of order representation, and an active role of content representation in…
Simulating PACE Global Ocean Radiances
Gregg, Watson W.; Rousseaux, Cecile S.
2017-01-01
The NASA PACE mission is a hyper-spectral radiometer planned for launch in the next decade. It is intended to provide new information on ocean biogeochemical constituents by parsing the details of high resolution spectral absorption and scattering. It is the first of its kind for global applications and as such, poses challenges for design and operation. To support pre-launch mission development and assess on-orbit capabilities, the NASA Global Modeling and Assimilation Office has developed a dynamic simulation of global water-leaving radiances, using an ocean model containing multiple ocean phytoplankton groups, particulate detritus, particulate inorganic carbon (PIC), and chromophoric dissolved organic carbon (CDOC) along with optical absorption and scattering processes at 1 nm spectral resolution. The purpose here is to assess the skill of the dynamic model and derived global radiances. Global bias, uncertainty, and correlation are derived using available modern satellite radiances at moderate spectral resolution. Total chlorophyll, PIC, and the absorption coefficient of CDOC (aCDOC), are simultaneously assimilated to improve the fidelity of the optical constituent fields. A 5-year simulation showed statistically significant (P leaving radiances at 1 nm for the spectral range 250-800 nm. These unassimilated radiances were within 0.074 mW/sq cm/micron/sr of MODIS-Aqua radiances at 412, 443, 488, 531, 547, and 667 nm. This difference represented a bias of 10.4% (model low). A mean correlation of 0.706 (P leaving radiances, biogeochemical model, radiative transfer model
NONE
1998-08-01
Spectrally selective glazing is window glass that permits some portions of the solar spectrum to enter a building while blocking others. This high-performance glazing admits as much daylight as possible while preventing transmission of as much solar heat as possible. By controlling solar heat gains in summer, preventing loss of interior heat in winter, and allowing occupants to reduce electric lighting use by making maximum use of daylight, spectrally selective glazing significantly reduces building energy consumption and peak demand. Because new spectrally selective glazings can have a virtually clear appearance, they admit more daylight and permit much brighter, more open views to the outside while still providing the solar control of the dark, reflective energy-efficient glass of the past. This Federal Technology Alert provides detailed information and procedures for Federal energy managers to consider spectrally selective glazings. The principle of spectrally selective glazings is explained. Benefits related to energy efficiency and other architectural criteria are delineated. Guidelines are provided for appropriate application of spectrally selective glazing, and step-by-step instructions are given for estimating energy savings. Case studies are also presented to illustrate actual costs and energy savings. Current manufacturers, technology users, and references for further reading are included for users who have questions not fully addressed here.
Thermophotovoltaic Spectral Control
DM DePoy; PM Fourspring; PF Baldasaro; JF Beausang; EJ Brown; MW Dashiel; KD Rahner; TD Rahmlow; JE Lazo-Wasem; EJ Gratrix; B Wemsman
2004-06-09
Spectral control is a key technology for thermophotovoltaic (TPV) direct energy conversion systems because only a fraction (typically less than 25%) of the incident thermal radiation has energy exceeding the diode bandgap energy, E{sub g}, and can thus be converted to electricity. The goal for TPV spectral control in most applications is twofold: (1) Maximize TPV efficiency by minimizing transfer of low energy, below bandgap photons from the radiator to the TPV diode. (2) Maximize TPV surface power density by maximizing transfer of high energy, above bandgap photons from the radiator to the TPV diode. TPV spectral control options include: front surface filters (e.g. interference filters, plasma filters, interference/plasma tandem filters, and frequency selective surfaces), back surface reflectors, and wavelength selective radiators. System analysis shows that spectral performance dominates diode performance in any practical TPV system, and that low bandgap diodes enable both higher efficiency and power density when spectral control limitations are considered. Lockheed Martin has focused its efforts on front surface tandem filters which have achieved spectral efficiencies of {approx}83% for E{sub g} = 0.52 eV and {approx}76% for E{sub g} = 0.60 eV for a 950 C radiator temperature.
Spectral Duality in Integrable Systems from AGT Conjecture
Mironov, A; Zenkevich, Y; Zotov, A
2012-01-01
We describe relationships between integrable systems with N degrees of freedom arising from the AGT conjecture. Namely, we prove the equivalence (spectral duality) between the N-cite Heisenberg spin chain and a reduced gl(N) Gaudin model both at classical and quantum level. The former one appears on the gauge theory side of the AGT relation in the Nekrasov-Shatashvili (and further the Seiberg-Witten) limit while the latter one is natural on the CFT side. At the classical level, the duality transformation relates the Seiberg-Witten differentials and spectral curves via a bispectral involution. The quantum duality extends this to the equivalence of the corresponding Baxter-Schrodinger equations (quantum spectral curves). This equivalence generalizes both the spectral self-duality between the 2x2 and NxN representations of the Toda chain and the famous AHH duality.
Automated spectral classification and the GAIA project
Lasala, Jerry; Kurtz, Michael J.
1995-01-01
Two dimensional spectral types for each of the stars observed in the global astrometric interferometer for astrophysics (GAIA) mission would provide additional information for the galactic structure and stellar evolution studies, as well as helping in the identification of unusual objects and populations. The classification of the large quantity generated spectra requires that automated techniques are implemented. Approaches for the automatic classification are reviewed, and a metric-distance method is discussed. In tests, the metric-distance method produced spectral types with mean errors comparable to those of human classifiers working at similar resolution. Data and equipment requirements for an automated classification survey, are discussed. A program of auxiliary observations is proposed to yield spectral types and radial velocities for the GAIA-observed stars.
Spectral emissivity of cirrus clouds
Beck, Gordon H.; Davis, John M.; Cox, Stephen K.
1993-01-01
The inference of cirrus cloud properties has many important applications including global climate studies, radiation budget determination, remote sensing techniques and oceanic studies from satellites. Data taken at the Parsons Kansas site during the FIRE II project are used for this study. On November 26 there were initially clear sky conditions gradually giving way to a progressively thickening cirrus shield over a period of a few hours. Interferometer radiosonde and lidar data were taken throughout this event. Two techniques are used to infer the downward spectral emittance of the observed cirrus layer. One uses only measurements and the other involves measurements and FASCODE III calculations. FASCODE III is a line-by line radiance/transmittance model developed at the Air Force Geophysics Laboratory.
Islam and Media Representations
Mohamed Bensalah
2006-04-01
Full Text Available For the author of this article, the media’s treatment of Islam has raised numerous polymorphous questions and debates. Reactivated by the great scares of current events, the issue, though an ancient one, calls many things into question. By way of introduction, the author tries to analyse the complex processes of elaboration and perception of the representations that have prevailed during the past century. In referring to the semantic decoding of the abundant colonial literature and iconography, the author strives to translate the extreme xenophobic tensions and the identity crystallisations associated with the current media orchestration of Islam, both in theWest and the East. He then evokes the excesses of the media that are found at the origin of many amalgams wisely maintained between Islam, Islamism and Islamic terrorism, underscoring their duplicity and their willingness to put themselves, consciously, in service to deceivers and directors of awareness, who are very active at the heart of the politico-media sphere. After levelling a severe accusation against the harmful drifts of the media, especially in times of crisis and war, the author concludes by asserting that these tools of communication, once they are freed of their masks and invective apparatuses, can be re-appropriated by new words and bya true communication between peoples and cultures.
Horwitz, J. L.; Zeng, W.
2009-01-01
Extensive systematic dynamic fluid kinetic (DyFK) model simulations are conducted to obtain advanced simulation-based formula representations of ionospheric outflow parameters, for possible use by global magnetospheric modelers. Under F10.7 levels of 142, corresponding to solar medium conditions, we obtain the H+ and O+ outflow densities, flow velocities, and perpendicular and parallel temperatures versus energy fluxes and characteristic energies of soft electron precipitation, wave spectral densities of ion transverse wave heating, and F region level solar zenith angle in the high-latitude auroral region. From the results of hundreds of DyFK simulations of auroral outflows for ranges of each of these driving agents, we depict the H+ and O+ outflow density and flow velocity parameters at 3 R E altitude at the ends of these 2-h simulation runs in spectrogram form versus various pairs of these influencing parameters. We further approximate these results by various distilled formula representations for the O+ and H+ outflow velocities, densities, and temperatures at 3 R E altitude, as functions of the above indicated four ``driver'' parameters. These formula representations provide insight into the physics of these driven outflows, and may provide a convenient set of tools to set the boundary conditions for ionospheric plasma sources in global magnetospheric simulations.
Rapid spectral analysis for spectral imaging.
Jacques, Steven L; Samatham, Ravikant; Choudhury, Niloy
2010-07-15
Spectral imaging requires rapid analysis of spectra associated with each pixel. A rapid algorithm has been developed that uses iterative matrix inversions to solve for the absorption spectra of a tissue using a lookup table for photon pathlength based on numerical simulations. The algorithm uses tissue water content as an internal standard to specify the strength of optical scattering. An experimental example is presented on the spectroscopy of portwine stain lesions. When implemented in MATLAB, the method is ~100-fold faster than using fminsearch().
On Spectral Triples in Quantum Gravity I
Aastrup, Johannes; M. Grimstrup, Jesper; Nest, Ryszard
2009-01-01
This paper establishes a link between Noncommutative Geometry and canonical quantum gravity. A semi-finite spectral triple over a space of connections is presented. The triple involves an algebra of holonomy loops and a Dirac type operator which resembles a global functional derivation operator....... The interaction between the Dirac operator and the algebra reproduces the Poisson structure of General Relativity. Moreover, the associated Hilbert space corresponds, up to a discrete symmetry group, to the Hilbert space of diffeomorphism invariant states known from Loop Quantum Gravity. Correspondingly......, the square of the Dirac operator has, in terms of canonical quantum gravity, the form of a global area-squared operator. Furthermore, the spectral action resembles a partition function of Quantum Gravity. The construction is background independent and is based on an inductive system of triangulations...
Irreducible representations of Birman-Wenzl algebras
潘峰
1995-01-01
Irreducible representations of Birman-Wenzl algebras are constructed by using the induced representation and the linear equation method. Self-adjoint representations of Birman-Wenzl algebras Cf (r, q) with f≤4 are presented.
SVD analysis of Aura TES spectral residuals
Beer, Reinhard; Kulawik, Susan S.; Rodgers, Clive D.; Bowman, Kevin W.
2005-01-01
Singular Value Decomposition (SVD) analysis is both a powerful diagnostic tool and an effective method of noise filtering. We present the results of an SVD analysis of an ensemble of spectral residuals acquired in September 2004 from a 16-orbit Aura Tropospheric Emission Spectrometer (TES) Global Survey and compare them to alternative methods such as zonal averages. In particular, the technique highlights issues such as the orbital variation of instrument response and incompletely modeled effects of surface emissivity and atmospheric composition.
Functional Representations for Fock Superalgebras
Kupsch, J; Kupsch, Joachim; Smolyanov, Oleg G.
1997-01-01
The Fock space of bosons and fermions and its underlying superalgebra are represented by algebras of functions on a superspace. We define Gaussian integration on infinite dimensional superspaces, and construct superanalogs of the classical function spaces with a reproducing kernel -- including the Bargmann-Fock representation -- and of the Wiener-Segal representation. The latter representation requires the investigation of Wick ordering on Z2-graded algebras. As application we derive a Mehler formula for the Ornstein-Uhlenbeck semigroup on the Fock space.
Multi-parameter Burau representations
Mohammad N. Abdulrahim; Madline Al- Tahan; Samer S. Habre
2013-01-01
We consider the multi-parameter representation of Artin's braid group introduced by D. D. Long and J. P. Tian, namely $\\alpha: B_{n}\\rightarrow GL_{m}(C)$, where $m=n!n$ . First, we show that there exists a complex specialization of the multi-parameter representation that does not arise from any Hecke algebra. Second, we find conditions under which the images of the generators of the braid group on three strings under the multi-parameter representation are unitary relative to a nonsingular he...
Thinking together with material representations
Stege Bjørndahl, Johanne; Fusaroli, Riccardo; Østergaard, Svend
2014-01-01
How do material representations such as models, diagrams and drawings come to shape and aid collective, epistemic processes? This study investigated how groups of participants spontaneously recruited material objects (in this case LEGO blocks) to support collective creative processes in the context......, the material representations were experimented on and physical attributes were explored resulting in discoveries of new meaning potentials and creative solutions. We discuss these different ways in which material representations do their work in collective reasoning processes in relation to ideas about top...
The Fundamental k-Form and Global Relations
Anthony C.L. Ashton
2008-03-01
Full Text Available In [Proc. Roy. Soc. London Ser. A 453 (1997, no. 1962, 1411-1443] A.S. Fokas introduced a novel method for solving a large class of boundary value problems associated with evolution equations. This approach relies on the construction of a so-called global relation: an integral expression that couples initial and boundary data. The global relation can be found by constructing a differential form dependent on some spectral parameter, that is closed on the condition that a given partial differential equation is satisfied. Such a differential form is said to be fundamental [Quart. J. Mech. Appl. Math. 55 (2002, 457-479]. We give an algorithmic approach in constructing a fundamental k-form associated with a given boundary value problem, and address issues of uniqueness. Also, we extend a result of Fokas and Zyskin to give an integral representation to the solution of a class of boundary value problems, in an arbitrary number of dimensions. We present an extended example using these results in which we construct a global relation for the linearised Navier-Stokes equations.
Computer aided surface representation
Barnhill, R.E.
1989-02-09
The central research problem of this project is the effective representation and display of surfaces, interpolating to given information, in three or more dimensions. In a typical problem, we wish to create a surface from some discrete information. If this information is itself on another surface, the problem is to determine a surface defined on a surface,'' which is discussed below. Often, properties of an already constructed surface are desired: such geometry processing'' is described below. The Summary of Proposed Research from our original proposal describes the aims of this research project. This Summary and the Table of Contents from the original proposal are enclosed as an Appendix to this Progress Report. The broad sweep from constructive mathematics through algorithms and computer graphics displays is utilized in the research. The wide range of activity, directed in both theory and applications, makes this project unique. Last month in the first Ardent Titan delivered in the State of Arizona came to our group, funded by the DOE and Arizona State University. Although the Titan is a commercial product, its newness requires our close collaboration with Ardent to maximize results. During the past year, four faculty members and several graduate research assistants have worked on this DOE project. The gaining of new professionals is an important aspect of this project. A listing of the students and their topics is given in the Appendix. The most significant publication during the past year is the book, Curves and Surfaces for Computer Aided Geometric Design, by Dr. Gerald Farin. This 300 page volume helps fill a considerable gap in the subject and includes many new results on Bernstein-Bezier curves and surfaces.
Representation of identities and the politics of representation in cognition
Kanavillil Rajagopalan
2001-02-01
Full Text Available
In this paper, I make a plea for viewing representation as first and foremost a political matter. I argue that by so doing we may avoid the many of pitfalls of contemporary theories of cognition as they attempt to tackle the issue of representation. Most of these problems have to do with the fact that representation is treated exclusively as a mimetic or theatrical question. The fact of the matter is however that representation also has a political dimension. Indeed it has always had this political dimension which, counterintuitive though it may seem at first glimpse, manifests itself even in very the attempt to aestheticise the whole issue of representation (as in some versions of postmodernism or to deny its role altogether as a tertium quid between the external world and the cognising mind (as in contemporary neo-pragmatism. I also contend that, by recognising the political nature of representation, we also pave the way for endorsing the thesis that the mind is a social construct, thereby taking some steam out of the thesis of "mind-brain identity" (so-called "identity theory of mind".
Bipolar spectral associative memories.
Spencer, R G
2001-01-01
Nonlinear spectral associative memories are proposed as quantized frequency domain formulations of nonlinear, recurrent associative memories in which volatile network attractors are instantiated by attractor waves. In contrast to conventional associative memories, attractors encoded in the frequency domain by convolution may be viewed as volatile online inputs, rather than nonvolatile, off-line parameters. Spectral memories hold several advantages over conventional associative memories, including decoder/attractor separability and linear scalability, which make them especially well suited for digital communications. Bit patterns may be transmitted over a noisy channel in a spectral attractor and recovered at the receiver by recurrent, spectral decoding. Massive nonlocal connectivity is realized virtually, maintaining high symbol-to-bit ratios while scaling linearly with pattern dimension. For n-bit patterns, autoassociative memories achieve the highest noise immunity, whereas heteroassociative memories offer the added flexibility of achieving various code rates, or degrees of extrinsic redundancy. Due to linear scalability, high noise immunity and use of conventional building blocks, spectral associative memories hold much promise for achieving robust communication systems. Simulations are provided showing bit error rates for various degrees of decoding time, computational oversampling, and signal-to-noise ratio.
Teutsch, J
2007-01-01
It is possible to enumerate all computer programs. In particular, for every partial computable function, there is a shortest program which computes that function. f-MIN is the set of indices for shortest programs. In 1972, Meyer showed that f-MIN is Turing equivalent to 0'', the halting set with halting set oracle. This paper generalizes the notion of shortest programs, and we use various measures from computability theory to describe the complexity of the resulting "spectral sets." We show that under certain Godel numberings, the spectral sets are exactly the canonical sets 0', 0'', 0''', ... up to Turing equivalence. This is probably not true in general, however we show that spectral sets always contain some useful information. We show that immunity, or "thinness" is a useful characteristic for distinguishing between spectral sets. In the final chapter, we construct a set which neither contains nor is disjoint from any infinite arithmetic set, yet it is 0-majorized and contains a natural spectral set. Thus ...
Photon propagation function: spectral analysis of its asymptotic form.
Schwinger, J
1974-08-01
The physical attitudes of source theory, displacing those of renormalized, perturbative, operator field theory, are used in a simple discussion of the asymptotic behavior of the photon propagation function. A guiding principle is the elementary consistency requirement that, under circumstances where a physical parameter cannot be accurately measured, no sensitivity to its precise value can enter the description of those circumstances. The mathematical tool is the spectral representation of the propagation function, supplemented by an equivalent phase representation. The Gell-Mann-Low equation is recovered, but with their function now interpreted physically as the spectral weight function. A crude inequality is established for the latter, which helps in interpolating between the initial rising behavior and the ultimate zero at infinite mass. There is a brief discussion of the aggressive source theory viewpoint that denies the existence of a "bare charge".
(Self)-representations on youtube
Simonsen, Thomas Mosebo
This paper examines forms of self-representation on YouTube with specific focus on Vlogs (Video blogs). The analytical scope of the paper is on how User-generated Content on YouTube initiates a certain kind of audiovisual representation and a particular interpretation of reality that can...... be distinguished within Vlogs. This will be analysed through selected case studies taken from a representative sample of empirically based observations of YouTube videos. The analysis includes a focus on how certain forms of representation can be identified as representations of the self (Turkle 1995, Scannell...... 1996, Walker 2005) and further how these forms must be comprehended within a context of technological constrains, institutional structures and social as well as economical practices on YouTube (Burgess and Green 2009, Van Dijck 2009). It is argued that these different contexts play a vital part...
Computer representation of molecular surfaces
Max, N.L.
1981-07-06
This review article surveys recent work on computer representation of molecular surfaces. Several different algorithms are discussed for producing vector or raster drawings of space-filling models formed as the union of spheres. Other smoother surfaces are also considered.
Semantic Knowledge Representation (SKR) API
U.S. Department of Health & Human Services — The SKR Project was initiated at NLM in order to develop programs to provide usable semantic representation of biomedical free text by building on resources...
Integral representation of Skorokhod reflection
Anantharam, Venkat
2010-01-01
We show that a certain integral representation of the one-sided Skorokhod reflection of a continuous bounded variation function characterizes the reflection in that it possesses a unique maximal solution which solves the Skorokhod reflection problem.
Probability representation of classical states
Man'ko, OV; Man'ko, [No Value; Pilyavets, OV
2005-01-01
Probability representation of classical states described by symplectic tomograms is discussed. Tomographic symbols of classical observables which are functions on phase-space are studied. Explicit form of kernel of commutative star-product of the tomographic symbols is obtained.
Parametric Explosion Spectral Model
Ford, S R; Walter, W R
2012-01-19
Small underground nuclear explosions need to be confidently detected, identified, and characterized in regions of the world where they have never before occurred. We develop a parametric model of the nuclear explosion seismic source spectrum derived from regional phases that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low-strength) with increased spectral slope. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source.
Photovoltaic spectral responsivity measurements
Emery, K.; Dunlavy, D.; Field, H.; Moriarty, T. [National Renewable Energy Lab., Golden, CO (United States)
1998-09-01
This paper discusses the various elemental random and nonrandom error sources in typical spectral responsivity measurement systems. The authors focus specifically on the filter and grating monochrometer-based spectral responsivity measurement systems used by the Photovoltaic (PV) performance characterization team at NREL. A variety of subtle measurement errors can occur that arise from a finite photo-current response time, bandwidth of the monochromatic light, waveform of the monochromatic light, and spatial uniformity of the monochromatic and bias lights; the errors depend on the light source, PV technology, and measurement system. The quantum efficiency can be a function of he voltage bias, light bias level, and, for some structures, the spectral content of the bias light or location on the PV device. This paper compares the advantages and problems associated with semiconductor-detector-based calibrations and pyroelectric-detector-based calibrations. Different current-to-voltage conversion and ac photo-current detection strategies employed at NREL are compared and contrasted.
Khushaba, Rami N; Takruri, Maen; Miro, Jaime Valls; Kodagoda, Sarath
2014-07-01
Recent studies in Electromyogram (EMG) pattern recognition reveal a gap between research findings and a viable clinical implementation of myoelectric control strategies. One of the important factors contributing to the limited performance of such controllers in practice is the variation in the limb position associated with normal use as it results in different EMG patterns for the same movements when carried out at different positions. However, the end goal of the myoelectric control scheme is to allow amputees to control their prosthetics in an intuitive and accurate manner regardless of the limb position at which the movement is initiated. In an attempt to reduce the impact of limb position on EMG pattern recognition, this paper proposes a new feature extraction method that extracts a set of power spectrum characteristics directly from the time-domain. The end goal is to form a set of features invariant to limb position. Specifically, the proposed method estimates the spectral moments, spectral sparsity, spectral flux, irregularity factor, and signals power spectrum correlation. This is achieved through using Fourier transform properties to form invariants to amplification, translation and signal scaling, providing an efficient and accurate representation of the underlying EMG activity. Additionally, due to the inherent temporal structure of the EMG signal, the proposed method is applied on the global segments of EMG data as well as the sliced segments using multiple overlapped windows. The performance of the proposed features is tested on EMG data collected from eleven subjects, while implementing eight classes of movements, each at five different limb positions. Practical results indicate that the proposed feature set can achieve significant reduction in classification error rates, in comparison to other methods, with ≈8% error on average across all subjects and limb positions. A real-time implementation and demonstration is also provided and made available
Spectral integration of linear boundary value problems
Viswanath, Divakar
2012-01-01
Spectral integration is a method for solving linear boundary value problems which uses the Chebyshev series representation of functions to avoid the numerical discretization of derivatives. It is occasionally attributed to Zebib (J. of Computational Physics vol. 53 (1984), p. 443-455) and more often to Greengard (SIAM J. on Numerical Analysis vol. 28 (1991), p. 1071-1080). Its advantage is believed to be its relative immunity to errors that arise when nearby grid points are used to approximate derivatives. In this paper, we reformulate the method of spectral integration by changing it in four different ways. The changes consist of a more convenient integral formulation, a different way to treat and interpret boundary conditions, treatment of higher order problems in factored form, and the use of piecewise Chebyshev grid points. Our formulation of spectral integration is more flexible and powerful as show by its ability to solve a problem that would otherwise take 8192 grid points using only 96 grid points. So...
Number line representations of fractions
Behr, Merlyn J.; Bright, George W.; Wachsmuth, Ipke; Wagner, Sigrid
1982-01-01
The study explored students' interpretations of representations of fractions on number lines and the effect of instruction on those interpretations. Subjects were five fourth-graders, and instruction was a four-day unit on the use of number lines. A 16-item, multiple-choice pre- and posttest was used along with videotaped interviews. Performance improved except when students had to associate a reduced fraction symbol with an equivalent, unreduced fraction representation on a number line. The ...
The Fifth Mode of Representation
Behrendt, Poul; Krogh Hansen, Per
2011-01-01
“The fifth mode of representation: Ambiguous voices in unreliable third person narration”. Sammen med Poul Behrendt. In Per Krogh Hansen, Stefan Iversen, Henrik Skov Nielsen og Rolf Reitan (red.): Strange Voices. Walter de Gruyter, Berlin & New York......“The fifth mode of representation: Ambiguous voices in unreliable third person narration”. Sammen med Poul Behrendt. In Per Krogh Hansen, Stefan Iversen, Henrik Skov Nielsen og Rolf Reitan (red.): Strange Voices. Walter de Gruyter, Berlin & New York...
Lee, J.; Kim, J.; Yang, P.
2011-12-01
New over-ocean aerosol models are developed by integrating extensive AERONET inversion data and a database of the optical properties of tri-axial ellipsoidal dust particles. These models allow more accurate retrieval of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) for high AOD cases. Spectral AOD, single scattering albedo (SSA), and phase function, which are used to calculate a lookup table (LUT), are archived by combining inversion data from Aerosol Robotic Network (AERONET) Sun/sky radiometers and single-scattering properties from the tri-axial ellipsoidal dust database. The aerosol models are categorized from the AERONET data using the fine-mode fraction (FMF) at 550 nm and the SSA at 440 nm to resolve a variety of aerosol types throughout the globe. For each aerosol model, the changes in aerosol optical properties (AOP) are included as functions of AOD. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the new aerosol models improve correlation compared to the MODIS Collection 5 products with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85, respectively, for the MODIS operational algorithm. Moreover, use of the new algorithms increases the percentage of data within an expected error of ± (0.03 + 0.05 × AOD) from 62 to 64% overall and from 39 to 51% for high AOD cases (AOD > 0.3). Errors in the retrieved AOD are characterized further with respect to the Ångström exponent (AE), scattering angle (Θ), and air mass factor (AMF). Overall, the new aerosol models reduce systematic errors in AOD retrieval compared with the Collection 5 data due to realistic AOP assumptions. In particular, the scattering angle dependence of the retrieved AOD for dust cases is significantly mitigated due to improved treatment of the nonsphericity of dust particles by the new algorithm.
Gaiotto, Davide; Neitzke, Andrew
2012-01-01
We apply and illustrate the techniques of spectral networks in a large collection of A_{K-1} theories of class S, which we call "lifted A_1 theories." Our construction makes contact with Fock and Goncharov's work on higher Teichmuller theory. In particular we show that the Darboux coordinates on moduli spaces of flat connections which come from certain special spectral networks coincide with the Fock-Goncharov coordinates. We show, moreover, how these techniques can be used to study the BPS spectra of lifted A_1 theories. In particular, we determine the spectrum generators for all the lifts of a simple superconformal field theory.
Spectral library searching in proteomics.
Griss, Johannes
2016-03-01
Spectral library searching has become a mature method to identify tandem mass spectra in proteomics data analysis. This review provides a comprehensive overview of available spectral library search engines and highlights their distinct features. Additionally, resources providing spectral libraries are summarized and tools presented that extend experimental spectral libraries by simulating spectra. Finally, spectrum clustering algorithms are discussed that utilize the same spectrum-to-spectrum matching algorithms as spectral library search engines and allow novel methods to analyse proteomics data.
Paley-Wiener Theorems with respect to the spectral parameter
Dann, Susanna
2010-01-01
One of the important questions related to any integral transform on a manifold M or on a homogeneous space G/K is the description of the image of a given space of functions. If M=G/K, where (G,K) is a Gelfand pair, then the harmonic analysis is closely related to the representations of G and the direct integral decomposition of L^2(M) into irreducible representations. We give a short overview of the Fourier transform on such spaces and then ask if one can describe the image of the space of smooth compactly supported functions in terms of the spectral parameter, i.e., the parameterization of the set of irreducible representations in the support of the Plancherel measure for L^2(M). We then discuss the Euclidean motion group, semisimple symmetric spaces, and some limits of those spaces.
Representation of Ethiopian Wet Spells in Global and Nested Models
Mark R. Jury
2014-01-01
Full Text Available Weather forecast and reanalysis models exhibit different performance in daily rainfall estimation over the Ethiopian highlands, 2000–2012, with ECMWF closer to observations than other models. Background is given to illustrate the Hadley circulation and easterly jets over Ethiopia, using sections on 37°E in July–August 2011. ECMWF reanalysis has a narrow band of rainfall >15 mm/day on 10°N, consistent with TRMM satellite estimates, associated with a steep gradient in meridional wind. MERRA and GFS models have a wider band of rainfall and weaker gradients in meridional winds. The contrasting background states influence a nested WRF model simulation of heavy rain in the upper Nile Valley on 29 July, 2011. The GFS (ECMWF initialization yields stronger northerly (southerly winds north (south of Ethiopia, while aircraft observations are southerly at 850 mb and northerly at 700 mb. ECMWF produces heavy and widespread rainfall consistent with observations, with a potentially more realistic simulation of the Hadley circulation.
Representation of nucleation mode microphysics in global aerosol microphysics models
Y. H. Lee
2013-02-01
Full Text Available In models, nucleation mode (1 nm Dp J10 and the burdens and lifetimes of ultrafine mode (10 nm Dp J10 and shorter coagulation lifetimes of ultrafine mode particles than the model with explicit dynamics (i.e. 1 nm boundary. The spatial distributions of CN10 (Dp > 10 nm and CCN(0.2% (i.e. CCN concentrations at 0.2% supersaturation are moderately affected, especially CN10 predictions above ~ 700 hPa where nucleation contributes most strongly to CN10 concentrations. The lowermost layer CN10 is substantially improved with the 3 nm boundary (compared to 10 nm in most areas. The overprediction in CN10 with the 3 nm and 10 nm boundaries can be explained by the overprediction of J10 or J3 with the parameterized microphysics possibly due to the instantaneous growth rate assumption in the survival and growth parameterization. The errors in CN10 predictions are sensitive to the choice of the lower size boundary but not to the choice of the time step applied to the microphysical processes. The spatial distribution of CCN(0.2% with the 3 nm boundary is almost identical to that with the 1 nm boundary, but that with the 10 nm boundary can differ more than 10–40% in some areas. We found that the deviation in the 10 nm simulations is partly due to the longer time step (i.e. 1-h time step used in the 10 nm simulations compared to 10-min time step used in the benchmark simulations but, even with the same time step, the 10 nm cutoff showed noticeably higher errors than the 3 nm cutoff. In conclusion, we generally recommend using a lower diameter boundary of 3 nm for studies focused on aerosol indirect effects but down to 1 nm boundary for studies focused on CN10 predictions or nucleation.
Tary, J. B.; Herrera, R. H.; van der Baan, M.
2014-01-01
Recent studies show that the frequency content of continuous passive recordings contains useful information for the study of hydraulic fracturing experiments as well as longstanding applications in volcano and global seismology. The short-time Fourier transform (STFT) is usually used to obtain the time-frequency representation of a seismic trace. Yet, this transform has two main disadvantages, namely its fixed time-frequency resolution and spectral leakage. Here, we describe two methods based on autoregressive (AR) models: the short-time autoregressive method (ST-AR) and the Kalman smoother (KS). These two methods allow for the AR coefficients to vary over time in order to follow time-varying frequency contents. The outcome of AR methods depends mainly on the number of AR coefficients. We use a robust approach to estimate the optimum order of the AR methods that best matches the spectral comparison between Fourier and AR spectra. Comparing the outcomes of the three methods on a synthetic signal, a long-period volcanic event, and microseismic data, we show that the STFT and both AR methods are able to track fast changes in frequency content. The STFT provides reasonable results even for noisy data using a simple and effective algorithm. The coefficients of the AR filter are defined at all time in the case of the KS. However, its better time resolution is slightly offset by a lower frequency resolution and its computational complexity. The ST-AR has a high spectral resolution and the lowest sensitivity to background noises, facilitating the identification of the various frequency components. The estimated AR coefficients can also be used to extract parts of the signal. The study of long-term phenomena, such as resonance frequencies, or transient events, such as long-period events, could help to gain further insight on reservoir deformation during hydraulic fracturing experiments as well as global or volcano seismological signals.
Schunck, Franz E
2008-01-01
We reconsider the nonlinear second order Abel equation of Stewart and Lyth, which follows from a nonlinear second order slow-roll approximation. We find a new eigenvalue spectrum in the blue regime. Some of the discrete values of the spectral index n_s have consistent fits to the cumulative COBE data as well as to recent ground-base CMB experiments.
Large Spectral Library Problem
Chilton, Lawrence K.; Walsh, Stephen J.
2008-10-03
Hyperspectral imaging produces a spectrum or vector at each image pixel. These spectra can be used to identify materials present in the image. In some cases, spectral libraries representing atmospheric chemicals or ground materials are available. The challenge is to determine if any of the library chemicals or materials exist in the hyperspectral image. The number of spectra in these libraries can be very large, far exceeding the number of spectral channels collected in the ¯eld. Suppose an image pixel contains a mixture of p spectra from the library. Is it possible to uniquely identify these p spectra? We address this question in this paper and refer to it as the Large Spectral Library (LSL) problem. We show how to determine if unique identi¯cation is possible for any given library. We also show that if p is small compared to the number of spectral channels, it is very likely that unique identi¯cation is possible. We show that unique identi¯cation becomes less likely as p increases.
Mocsy, Agnes [Department of Mathematics and Science, Pratt Institute, Brooklyn, NY 11205 (United States)
2009-11-01
In this talk I summarize the progress achieved in recent years on the understanding of quarkonium properties at finite temperature. Theoretical studies from potential models, lattice QCD, and effective field theories are discussed. I also highlight a bridge from spectral functions to experiment.
SURFACE ALBEDO AND SPECTRAL VARIABILITY OF CERES
Li, Jian-Yang; Reddy, Vishnu; Corre, Lucille Le; Sykes, Mark V.; Prettyman, Thomas H. [Planetary Science Institute, 1700 E. Ft. Lowell Road, Suite 106, Tucson, AZ 85719 (United States); Nathues, Andreas; Hoffmann, Martin; Schaefer, Michael [Max Planck Institute for Solar System Research, Göttingen (Germany); Izawa, Matthew R. M.; Cloutis, Edward A. [University of Winnipeg, Winnipeg, Manitoba (Canada); Carsenty, Uri; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Schröder, Stefan E. [German Aerospace Center (DLR), Institute of Planetary Research, Berlin (Germany); Castillo-Rogez, Julie C. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Schenk, Paul [Lunar and Planetary Institute, Houston, TX 77058 (United States); Williams, David A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Smith, David E. [Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Zuber, Maria T. [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); and others
2016-02-01
Previous observations suggested that Ceres has active, but possibly sporadic, water outgassing as well as possibly varying spectral characteristics over a timescale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, as well as the newly acquired images by the Dawn Framing Camera, to search for spectral and albedo variability on Ceres, on both a global scale and in local regions, particularly the bright spots inside the Occator crater, over timescales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in the Occator crater by >15%, or the global albedo by >3% over the various timescales that we searched. Recently reported spectral slope variations can be explained by changing Sun–Ceres–Earth geometry. The active area on Ceres is less than 1 km{sup 2}, too small to cause global albedo and spectral variations detectable in our data. Impact ejecta due to impacting projectiles of tens of meters in size like those known to cause observable changes to the surface albedo on Asteroid Scheila cannot cause detectable albedo change on Ceres due to its relatively large size and strong gravity. The water vapor activity on Ceres is independent of Ceres’ heliocentric distance, ruling out the possibility of the comet-like sublimation process as a possible mechanism driving the activity.
2010-05-01
Global Security & Engineering Solutions Division 1300-B Floyd Avenue Rome, NY 13440-4615 8. PERFORMING ORGANIZATION REPORT NUMBER...18 1 1. BACKGROUND This report is being submitted by L-3 Global Security...tasks. Utilized the Avid Xpress video enhancement system to process the Group 2, Phase II competency test A. This was done to attempt to recreate
Weighted-Fusion-Based Representation Classifiers for Hyperspectral Imagery
Bing Peng
2015-11-01
Full Text Available Spatial texture features have been demonstrated to be very useful for the recently-proposed representation-based classifiers, such as the sparse representation-based classifier (SRC and nearest regularized subspace (NRS. In this work, a weighted residual-fusion-based strategy with multiple features is proposed for these classifiers. Multiple features include local binary patterns (LBP, Gabor features, and the original spectral signatures. In the proposed classification framework, representation residuals for a testing pixel from using each type of features are weighted to generate the final representation residual, and then the label of the testing pixel is determined according to the class yielding the minimum final residual. The motivation of this work is that different features represent pixels from different perspectives and their fusion in the residual domain can enhance the discriminative ability. Experimental results of several real hyperspectral image datasets demonstrate that the proposed residual-based fusion outperforms the original NRS, SRC, support vector machine (SVM with LBP, and SVM with Gabor features, even in small-sample-size (SSS situations.
Meenakshi, R.
2017-01-01
FTIR, FT-Raman, UV, NMR and quantum chemical calculation studies are performed on 5-chloro-2-nitroanisole, in order to gain the insights of its structural, spectroscopic and electronic properties (Fukui indices, HOMO and LUMO energy gap, MESP and Global reactivity descriptors). A complete vibrational analysis of 5-chloro-2-nitroanisole is performed by HF/B3LYP methods using 6-31G(d,p) basis set. To estimate the electronic transitions, the UV spectra of title compound are predicted in gas phase and ethanol. The obtained absorption maxima at 389.94 nm (in ethanol) is predicted possibly due to HOMO→LUMO transition with 85% contribution and assigned as π-π*. The MESP map shows that the negative potential sites are localized on oxygen atom (O10) as well as the positive potential sites are identified around the hydrogen and ring carbon atoms. The analysis of Fukui indices is also carried out to distinguish the nucleophilic and electrophiic centers. The prediction of reactive sites by MESP is well supported by this Fukui indices analysis. The correlations between the statistical thermodynamics and temperature are also obtained. It is seen that the heat capacities, entropies and enthalpies increase with increasing the intensities of the molecular vibrations. Furthermore, the first hyperpolarizability of 5-chloro-2-nitroanisole is calculated and the results are discussed. This result indicates that 5-chloro-2-nitroanisole is a good candidate of nonlinear optical materials.
32 CFR 724.215 - Military representation.
2010-07-01
... 32 National Defense 5 2010-07-01 2010-07-01 false Military representation. 724.215 Section 724.215... BOARD Authority/Policy for Departmental Discharge Review § 724.215 Military representation. Military... consult legal counsel before undertaking such representation. Such representation may be prohibited by 18...
Spectral-collocation variational integrators
Li, Yiqun; Wu, Boying; Leok, Melvin
2017-03-01
Spectral methods are a popular choice for constructing numerical approximations for smooth problems, as they can achieve geometric rates of convergence and have a relatively small memory footprint. In this paper, we introduce a general framework to convert a spectral-collocation method into a shooting-based variational integrator for Hamiltonian systems. We also compare the proposed spectral-collocation variational integrators to spectral-collocation methods and Galerkin spectral variational integrators in terms of their ability to reproduce accurate trajectories in configuration and phase space, their ability to conserve momentum and energy, as well as the relative computational efficiency of these methods when applied to some classical Hamiltonian systems. In particular, we note that spectrally-accurate variational integrators, such as the Galerkin spectral variational integrators and the spectral-collocation variational integrators, combine the computational efficiency of spectral methods together with the geometric structure-preserving and long-time structural stability properties of symplectic integrators.
Taşkin, Gülşen
2016-05-01
Recently, information extraction from hyperspectral images (HI) has become an attractive research area for many practical applications in earth observation due to the fact that HI provides valuable information with a huge number of spectral bands. In order to process such a huge amount of data in an effective way, traditional methods may not fully provide a satisfactory performance because they do not mostly consider high dimensionality of the data which causes curse of dimensionality also known as Hughes phenomena. In case of supervised classification, a poor generalization performance is achieved as a consequence resulting in availability of limited training samples. Therefore, advance methods accounting for the high dimensionality need to be developed in order to get a good generalization capability. In this work, a method of High Dimensional Model Representation (HDMR) was utilized for dimensionality reduction, and a novel feature selection method was introduced based on global sensitivity analysis. Several implementations were conducted with hyperspectral images in comparison to state-of-art feature selection algorithms in terms of classification accuracy, and the results showed that the proposed method outperforms the other feature selection methods even with all considered classifiers, that are support vector machines, Bayes, and decision tree j48.
Closing the Learning-Planning Loop with Predictive State Representations
Boots, Byron; Gordon, Geoffrey J
2009-01-01
A central problem in artificial intelligence is that of planning to maximize future reward under uncertainty in a partially observable environment. In this paper we propose and demonstrate a novel algorithm which accurately learns a model of such an environment directly from sequences of action-observation pairs. We then close the loop from observations to actions by planning in the learned model and recovering a policy which is near-optimal in the original environment. Specifically, we present an efficient and statistically consistent spectral algorithm for learning the parameters of a Predictive State Representation (PSR). We demonstrate the algorithm by learning a model of a simulated high-dimensional, vision-based mobile robot planning task, and then perform approximate point-based planning in the learned PSR. Analysis of our results shows that the algorithm learns a state space which efficiently captures the essential features of the environment. This representation allows accurate prediction with a smal...
Shaping ideal cities: the graph representation of the urban utopia
D'Autilia, Roberto
2016-01-01
The ideal Renaissance city is designed as a star-shaped fortress, where the streets and squares are organized to speed the movement of people and soldiers. Symmetry and accessibility represent the key features for the organization of the urban space. The resulting city is hierarchized and does not always guarantee an optimal degree of connectivity. Taking the baton from the work done by space syntax in the definition of properties of spatial graph representation, we introduce a method to compute urban graphs from the Euclidean representation, the corresponding line graph and the contraction of nodes with the same urban function. We analyze the urban graphs of five historic cities: Vitry le Fran\\c{c}ois, Avola, Neuf Brisach, Grammichele and Palmanova and compare the analysis restults with the corresponding results from space syntax. Analysis of the spectral gap and the relative asymmetry distribution show a similar structure for these cities. The irregular or reticular housing structure seems to ensure connect...
Conformal-Based Surface Morphing and Multi-Scale Representation
Ka Chun Lam
2014-05-01
Full Text Available This paper presents two algorithms, based on conformal geometry, for the multi-scale representations of geometric shapes and surface morphing. A multi-scale surface representation aims to describe a 3D shape at different levels of geometric detail, which allows analyzing or editing surfaces at the global or local scales effectively. Surface morphing refers to the process of interpolating between two geometric shapes, which has been widely applied to estimate or analyze deformations in computer graphics, computer vision and medical imaging. In this work, we propose two geometric models for surface morphing and multi-scale representation for 3D surfaces. The basic idea is to represent a 3D surface by its mean curvature function, H, and conformal factor function λ, which uniquely determine the geometry of the surface according to Riemann surface theory. Once we have the (λ, H parameterization of the surface, post-processing of the surface can be done directly on the conformal parameter domain. In particular, the problem of multi-scale representations of shapes can be reduced to the signal filtering on the λ and H parameters. On the other hand, the surface morphing problem can be transformed to an interpolation process of two sets of (λ, H parameters. We test the proposed algorithms on 3D human face data and MRI-derived brain surfaces. Experimental results show that our proposed methods can effectively obtain multi-scale surface representations and give natural surface morphing results.
Real Representation in Chiral Gauge Theories on the Lattice
Suzuki, H
2000-01-01
The Weyl fermion belonging to the real representation of the gauge group provides a simple illustrative example for L\\"uscher's gauge-invariant lattice formulation of chiral gauge theories. We can explicitly construct the fermion integration measure globally over the gauge-field configuration space in the arbitrary topological sector; there is no global obstruction corresponding to the Witten anomaly. It is shown that this Weyl formulation is equivalent to a lattice formulation based on the Majorana (left--right-symmetric) fermion, in which the fermion partition function is given by the Pfaffian with a definite sign, up to physically irrelevant contact terms. This observation suggests a natural relative normalization of the fermion measure in different topological sectors for the Weyl fermion belonging to the complex representation.
A Framework for Coxeter Spectral Classification of Finite Posets and Their Mesh Geometries of Roots
2013-01-01
Following our paper [Linear Algebra Appl. 433(2010), 699–717], we present a framework and computational tools for the Coxeter spectral classification of finite posets J≡(J,⪯). One of the main motivations for the study is an application of matrix representations of posets in representation theory explained by Drozd [Funct. Anal. Appl. 8(1974), 219–225]. We are mainly interested in a Coxeter spectral classification of posets J such that the symmetric Gram matrix GJ:=(1/2)[CJ+CJtr]∈J(ℚ) is posi...
Simulating PACE Global Ocean Radiances
Gregg, Watson W.; Rousseaux, Cecile S.
2017-01-01
The NASA PACE mission is a hyper-spectral radiometer planned for launch in the next decade. It is intended to provide new information on ocean biogeochemical constituents by parsing the details of high resolution spectral absorption and scattering. It is the first of its kind for global applications and as such, poses challenges for design and operation. To support pre-launch mission development and assess on-orbit capabilities, the NASA Global Modeling and Assimilation Office has developed a dynamic simulation of global water-leaving radiances, using an ocean model containing multiple ocean phytoplankton groups, particulate detritus, particulate inorganic carbon (PIC), and chromophoric dissolved organic carbon (CDOC) along with optical absorption and scattering processes at 1 nm spectral resolution. The purpose here is to assess the skill of the dynamic model and derived global radiances. Global bias, uncertainty, and correlation are derived using available modern satellite radiances at moderate spectral resolution. Total chlorophyll, PIC, and the absorption coefficient of CDOC (aCDOC), are simultaneously assimilated to improve the fidelity of the optical constituent fields. A 5-year simulation showed statistically significant (P Ocean-Atmosphere Spectral Irradiance Model, OASIM) to estimate normalized water-leaving radiances at 1 nm for the spectral range 250-800 nm. These unassimilated radiances were within 0.074 mW/sq cm/micron/sr of MODIS-Aqua radiances at 412, 443, 488, 531, 547, and 667 nm. This difference represented a bias of 10.4% (model low). A mean correlation of 0.706 (P ocean color, water-leaving radiances, biogeochemical model, radiative transfer model
Representations Of The Super-virasoro Algebra fock Representations
Polychronidis, V J
1999-01-01
In this dissertation the complete classification of the Super- Virasoro modules M (h, c) of the Neveu-Schwarz and Ramond algebras is constructed. A family of representations F p, po of the Neveu- Schwarz and Ramond algebras, which generalize the Fock representations of the Virasoro algebra, is constructed. The Felder's construction of Fock space resolutions for the Virasoro minimal models is generalized in the Super-Virasoro minimal models case. In particular, a two-sided resolution of the irreducible Super-Verma module L( h, c) of the Neveu- Schwarz algebra is provided. --- 8 --- AN
On Representation in Information Theory
Joseph E. Brenner
2011-09-01
Full Text Available Semiotics is widely applied in theories of information. Following the original triadic characterization of reality by Peirce, the linguistic processes involved in information—production, transmission, reception, and understanding—would all appear to be interpretable in terms of signs and their relations to their objects. Perhaps the most important of these relations is that of the representation-one, entity, standing for or representing some other. For example, an index—one of the three major kinds of signs—is said to represent something by being directly related to its object. My position, however, is that the concept of symbolic representations having such roles in information, as intermediaries, is fraught with the same difficulties as in representational theories of mind. I have proposed an extension of logic to complex real phenomena, including mind and information (Logic in Reality; LIR, most recently at the 4th International Conference on the Foundations of Information Science (Beijing, August, 2010. LIR provides explanations for the evolution of complex processes, including information, that do not require any entities other than the processes themselves. In this paper, I discuss the limitations of the standard relation of representation. I argue that more realistic pictures of informational systems can be provided by reference to information as an energetic process, following the categorial ontology of LIR. This approach enables naïve, anti-realist conceptions of anti-representationalism to be avoided, and enables an approach to both information and meaning in the same novel logical framework.
Wavelength conversion based spectral imaging
Dam, Jeppe Seidelin
There has been a strong, application driven development of Si-based cameras and spectrometers for imaging and spectral analysis of light in the visible and near infrared spectral range. This has resulted in very efficient devices, with high quantum efficiency, good signal to noise ratio and high...... resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art...... visible or near infrared cameras and spectrometers to include other spectral regions of interest....
Solar spectral irradiance variability in cycle 24: observations and models
Marchenko Sergey V.
2016-01-01
Full Text Available Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI, we characterize both short-term (solar rotation and long-term (solar cycle changes of the solar spectral irradiance (SSI between 265 and 500 nm during the ongoing cycle 24. We supplement the OMI data with concurrent observations from the Global Ozone Monitoring Experiment-2 (GOME-2 and Solar Radiation and Climate Experiment (SORCE instruments and find fair-to-excellent, depending on wavelength, agreement among the observations, and predictions of the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI2 and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S models.
PRECONDITIONED SPECTRAL PROJECTED GRADIENT METHOD ON CONVEX SETS
Lenys Bello; Marcos Raydan
2005-01-01
The spectral gradient method has proved to be effective for solving large-scale unconstrained optimization problems. It has been recently extended and combined with the projected gradient method for solving optimization problems on convex sets. This combination includes the use of nonmonotone line search techniques to preserve the fast local convergence. In this work we further extend the spectral choice of steplength to accept preconditioned directions when a good preconditioner is available. We present an algorithm that combines the spectral projected gradient method with preconditioning strategies to increase the local speed of convergence while keeping the global properties. We discuss implementation details for solving large-scale problems.
Indoor and Outdoor Spectroradiometer Intercomparison for Spectral Irradiance Measurement
Habte, A.; Andreas, A.; Ottoson, L.; Gueymard, C.; Fedor, G.; Fowler, S.; Peterson, J.; Naranen, R.; Kobashi, T.; Akiyama, A.; Takagi, S.
2014-05-01
This report details the global spectral irradiance intercomparison using spectroradiometers that was organized by the National Renewable Energy Laboratory's Solar Radiation Research Laboratory. The intercomparison was performed both indoors and outdoors on September 17, 2013. Five laboratories participated in the intercomparison using 10 spectroradiometers, and a coordinated measurement setup and a common platform were employed to compare spectral irradiances under both indoor and outdoor conditions. The intercomparison aimed to understand the performance of the different spectroradiometers and to share knowledge in making spectral irradiance measurements. This intercomparison was the first of its kind in the United States.
Endoscopic classification of representations of quasi-split unitary groups
Mok, Chung Pang
2015-01-01
In this paper the author establishes the endoscopic classification of tempered representations of quasi-split unitary groups over local fields, and the endoscopic classification of the discrete automorphic spectrum of quasi-split unitary groups over global number fields. The method is analogous to the work of Arthur on orthogonal and symplectic groups, based on the theory of endoscopy and the comparison of trace formulas on unitary groups and general linear groups.
Sparsity based target detection for compressive spectral imagery
Boada, David Alberto; Arguello Fuentes, Henry
2016-09-01
Hyperspectral imagery provides significant information about the spectral characteristics of objects and materials present in a scene. It enables object and feature detection, classification, or identification based on the acquired spectral characteristics. However, it relies on sophisticated acquisition and data processing systems able to acquire, process, store, and transmit hundreds or thousands of image bands from a given area of interest which demands enormous computational resources in terms of storage, computationm, and I/O throughputs. Specialized optical architectures have been developed for the compressed acquisition of spectral images using a reduced set of coded measurements contrary to traditional architectures that need a complete set of measurements of the data cube for image acquisition, dealing with the storage and acquisition limitations. Despite this improvement, if any processing is desired, the image has to be reconstructed by an inverse algorithm in order to be processed, which is also an expensive task. In this paper, a sparsity-based algorithm for target detection in compressed spectral images is presented. Specifically, the target detection model adapts a sparsity-based target detector to work in a compressive domain, modifying the sparse representation basis in the compressive sensing problem by means of over-complete training dictionaries and a wavelet basis representation. Simulations show that the presented method can achieve even better detection results than the state of the art methods.
Spectral decomposition of fractional operators and a reflected stable semigroup
Patie, P.; Zhao, Y.
2017-02-01
In this paper, we provide the spectral decomposition in Hilbert space of the C0-semigroup P and its adjoint P ˆ having as generator, respectively, the Caputo and the right-sided Riemann-Liouville fractional derivatives of index 1 operators, which are non-local and non-self-adjoint, appear in many recent studies in applied mathematics and also arise as the infinitesimal generators of some substantial processes such as the reflected spectrally negative α-stable process. Our approach relies on intertwining relations that we establish between these semigroups and the semigroup of a Bessel type process whose generator is a self-adjoint second order differential operator. In particular, from this commutation relation, we characterize the positive real axis as the continuous point spectrum of P and provide a power series representation of the corresponding eigenfunctions. We also identify the positive real axis as the residual spectrum of the adjoint operator P ˆ and elucidate its role in the spectral decomposition of these operators. By resorting to the concept of continuous frames, we proceed by investigating the domain of the spectral operators and derive two representations for the heat kernels of these semigroups. As a by-product, we also obtain regularity properties for these latter and also for the solution of the associated Cauchy problem.
Surface Albedo and Spectral Variability of Ceres
Li, Jian-Yang; Nathues, Andreas; Corre, Lucille Le; Izawa, Matthew R M; Clouts, Edward A; Sykes, Mark V; Carsenty, Uri; Castillo-Rogez, Julie C; Hoffmann, Martin; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Prettyman, Thomas H; Schaefer, Michael; Schenk, Paul; Schröder, Stefan E; Williams, David A; Smith, David E; Zuber, Maria T; Konopliv, Alexander S; Park, Ryan S; Raymond, Carol A; Russell, Christopher T
2016-01-01
Previous observations suggested that Ceres has active but possibly sporadic water outgassing, and possibly varying spectral characteristics in a time scale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, and the newly acquired images by Dawn Framing Camera to search for spectral and albedo variability on Ceres, in both a global scale and local regions, particularly the bright spots inside Occator crater, over time scales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in Occator crater by >15%, or the global albedo by >3% over various time scales that we searched. Recently reported spectral slope variations can be explained by changing Sun-Ceres-Earth geometry. The active area on Ceres is less than 1 km$^2...
Digital models for architectonical representation
Stefano Brusaporci
2011-12-01
Full Text Available Digital instruments and technologies enrich architectonical representation and communication opportunities. Computer graphics is organized according the two phases of visualization and construction, that is modeling and rendering, structuring dichotomy of software technologies. Visualization modalities give different kinds of representations of the same 3D model and instruments produce a separation between drawing and image’s creation. Reverse modeling can be related to a synthesis process, ‘direct modeling’ follows an analytic procedure. The difference between interactive and not interactive applications is connected to the possibilities offered by informatics instruments, and relates to modeling and rendering. At the same time the word ‘model’ describes different phenomenon (i.e. files: mathematical model of the building and of the scene; raster representation and post-processing model. All these correlated different models constitute the architectonical interpretative model, that is a simulation of reality made by the model for improving the knowledge.
Executive control influences linguistic representations.
Lev-Ari, Shiri; Keysar, Boaz
2014-02-01
Although it is known that words acquire their meanings partly from the contexts in which they are used, we proposed that the way in which words are processed can also influence their representation. We further propose that individual differences in the way that words are processed can consequently lead to individual differences in the way that they are represented. Specifically, we showed that executive control influences linguistic representations by influencing the coactivation of competing and reinforcing terms. Consequently, people with poorer executive control perceive the meanings of homonymous terms as being more similar to one another, and those of polysemous terms as being less similar to one another, than do people with better executive control. We also showed that bilinguals with poorer executive control experience greater cross-linguistic interference than do bilinguals with better executive control. These results have implications for theories of linguistic representation and language organization.
FUNSTAT and statistical image representations
Parzen, E.
1983-01-01
General ideas of functional statistical inference analysis of one sample and two samples, univariate and bivariate are outlined. ONESAM program is applied to analyze the univariate probability distributions of multi-spectral image data.
Spectral structure and decompositions of optical states, and their applications
Rohde, P P; Silberhorn, C; Rohde, Peter P.; Mauerer, Wolfgang; Silberhorn, Christine
2006-01-01
We discuss the spectral structure and decomposition of multi-photon states. Ordinarily `multi-photon states' and `Fock states' are regarded as synonymous. However, when the spectral degrees of freedom are included this is not the case, and the class of `multi-photon' states is much broader than the class of `Fock' states. We discuss the criteria for a state to be considered a Fock state. We then address the decomposition of general multi-photon states into bases of orthogonal eigenmodes, building on existing multi-mode theory, and introduce an occupation number representation that provides an elegant description of such states that in many situations simplifies calculations. Finally we apply this technique to several example situations, which are highly relevant for state of the art experiments. These include Hong-Ou-Mandel interference, spectral filtering, finite bandwidth photo-detection, homodyne detection and the conditional preparation of Schr\\"odinger Kitten and Fock states. Our techniques allow for ver...
Fast Selection of Spectral Variables with B-Spline Compression
Rossi, Fabrice; Wertz, Vincent; Meurens, Marc; Verleysen, Michel
2007-01-01
The large number of spectral variables in most data sets encountered in spectral chemometrics often renders the prediction of a dependent variable uneasy. The number of variables hopefully can be reduced, by using either projection techniques or selection methods; the latter allow for the interpretation of the selected variables. Since the optimal approach of testing all possible subsets of variables with the prediction model is intractable, an incremental selection approach using a nonparametric statistics is a good option, as it avoids the computationally intensive use of the model itself. It has two drawbacks however: the number of groups of variables to test is still huge, and colinearities can make the results unstable. To overcome these limitations, this paper presents a method to select groups of spectral variables. It consists in a forward-backward procedure applied to the coefficients of a B-Spline representation of the spectra. The criterion used in the forward-backward procedure is the mutual infor...
Knowledge Discovery in Spectral Data by Means of Complex Networks
Stefano Boccaletti
2013-03-01
Full Text Available In the last decade, complex networks have widely been applied to the study of many natural and man-made systems, and to the extraction of meaningful information from the interaction structures created by genes and proteins. Nevertheless, less attention has been devoted to metabonomics, due to the lack of a natural network representation of spectral data. Here we define a technique for reconstructing networks from spectral data sets, where nodes represent spectral bins, and pairs of them are connected when their intensities follow a pattern associated with a disease. The structural analysis of the resulting network can then be used to feed standard data-mining algorithms, for instance for the classification of new (unlabeled subjects. Furthermore, we show how the structure of the network is resilient to the presence of external additive noise, and how it can be used to extract relevant knowledge about the development of the disease.
Knowledge Discovery in Spectral Data by Means of Complex Networks
Zanin, Massimiliano; Papo, David; Solís, José Luis González; Espinosa, Juan Carlos Martínez; Frausto-Reyes, Claudio; Anda, Pascual Palomares; Sevilla-Escoboza, Ricardo; Boccaletti, Stefano; Menasalvas, Ernestina; Sousa, Pedro
2013-01-01
In the last decade, complex networks have widely been applied to the study of many natural and man-made systems, and to the extraction of meaningful information from the interaction structures created by genes and proteins. Nevertheless, less attention has been devoted to metabonomics, due to the lack of a natural network representation of spectral data. Here we define a technique for reconstructing networks from spectral data sets, where nodes represent spectral bins, and pairs of them are connected when their intensities follow a pattern associated with a disease. The structural analysis of the resulting network can then be used to feed standard data-mining algorithms, for instance for the classification of new (unlabeled) subjects. Furthermore, we show how the structure of the network is resilient to the presence of external additive noise, and how it can be used to extract relevant knowledge about the development of the disease. PMID:24957895
Biologically-inspired data decorrelation for hyper-spectral imaging
Ghita Ovidiu
2011-01-01
Full Text Available Abstract Hyper-spectral data allows the construction of more robust statistical models to sample the material properties than the standard tri-chromatic color representation. However, because of the large dimensionality and complexity of the hyper-spectral data, the extraction of robust features (image descriptors is not a trivial issue. Thus, to facilitate efficient feature extraction, decorrelation techniques are commonly applied to reduce the dimensionality of the hyper-spectral data with the aim of generating compact and highly discriminative image descriptors. Current methodologies for data decorrelation such as principal component analysis (PCA, linear discriminant analysis (LDA, wavelet decomposition (WD, or band selection methods require complex and subjective training procedures and in addition the compressed spectral information is not directly related to the physical (spectral characteristics associated with the analyzed materials. The major objective of this article is to introduce and evaluate a new data decorrelation methodology using an approach that closely emulates the human vision. The proposed data decorrelation scheme has been employed to optimally minimize the amount of redundant information contained in the highly correlated hyper-spectral bands and has been comprehensively evaluated in the context of non-ferrous material classification
Adaptable Multivariate Calibration Models for Spectral Applications
THOMAS,EDWARD V.
1999-12-20
Multivariate calibration techniques have been used in a wide variety of spectroscopic situations. In many of these situations spectral variation can be partitioned into meaningful classes. For example, suppose that multiple spectra are obtained from each of a number of different objects wherein the level of the analyte of interest varies within each object over time. In such situations the total spectral variation observed across all measurements has two distinct general sources of variation: intra-object and inter-object. One might want to develop a global multivariate calibration model that predicts the analyte of interest accurately both within and across objects, including new objects not involved in developing the calibration model. However, this goal might be hard to realize if the inter-object spectral variation is complex and difficult to model. If the intra-object spectral variation is consistent across objects, an effective alternative approach might be to develop a generic intra-object model that can be adapted to each object separately. This paper contains recommendations for experimental protocols and data analysis in such situations. The approach is illustrated with an example involving the noninvasive measurement of glucose using near-infrared reflectance spectroscopy. Extensions to calibration maintenance and calibration transfer are discussed.
Aspiring to Spectral Ignorance in Earth Observation
Oliver, S. A.
2016-12-01
Enabling robust, defensible and integrated decision making in the Era of Big Earth Data requires the fusion of data from multiple and diverse sensor platforms and networks. While the application of standardised global grid systems provides a common spatial analytics framework that facilitates the computationally efficient and statistically valid integration and analysis of these various data sources across multiple scales, there remains the challenge of sensor equivalency; particularly when combining data from different earth observation satellite sensors (e.g. combining Landsat and Sentinel-2 observations). To realise the vision of a sensor ignorant analytics platform for earth observation we require automation of spectral matching across the available sensors. Ultimately, the aim is to remove the requirement for the user to possess any sensor knowledge in order to undertake analysis. This paper introduces the concept of spectral equivalence and proposes a methodology through which equivalent bands may be sourced from a set of potential target sensors through application of equivalence metrics and thresholds. A number of parameters can be used to determine whether a pair of spectra are equivalent for the purposes of analysis. A baseline set of thresholds for these parameters and how to apply them systematically to enable relation of spectral bands amongst numerous different sensors is proposed. The base unit for comparison in this work is the relative spectral response. From this input, determination of a what may constitute equivalence can be related by a user, based on their own conceptualisation of equivalence.
K\\"all\\'en-Lehmann representation of noncommutative quantum electrodynamics
Bufalo, R; Pimentel, B M
2014-01-01
Noncommutative (NC) quantum field theory is the subject of many analyses on formal and general aspects looking for deviations and, therefore, potential noncommutative spacetime effects. Within of this large class, we may now pay some attention to the quantization of NC field theory on lower dimensions and look closely at the issue of dynamical mass generation to the gauge field. This work encompasses the quantization of the two-dimensional massive quantum electrodynamics and three-dimensional topologically massive quantum electrodynamics. We begin by addressing the problem on a general dimensionality making use of the perturbative Seiberg-Witten map to, thus, construct a general action, to only then specify the problem to two and three dimensions. The quantization takes place through the K\\"all\\'en-Lehmann spectral representation and Yang-Feldman-K\\"all\\'en formulation, where we calculate the respective spectral density function to the gauge field. Furthermore, regarding the photon two-point function, we disc...
Alternative coherent-mode representation of a random source
Ostrovsky, A S; Zemliak, A M; Olvera, M A; Romero, P C, E-mail: andreyo@fcfm.buap.mx [Facultad de Ciencias Fisico Matematicas, Universidad Autonoma de Puebla, Puebla 72000 (Mexico)
2011-01-01
The coherent-mode representation (CMR) of an optical random source is a very powerful tool in contemporary optics. However, the practical value of the CMR is essentially restricted because of the complexity of solving the Fredholm integral equation with the field cross-spectral density as a kernel. Moreover, in practice, the analytical expression for the cross-spectral density of the field, as a rule is unknown, a fact that makes this solution impossible in general. Here we propose a technique for determination of the field CMR that does not involve solving the Fredholm integral equation but is based on usual radiometric measurement. We illustrate the proposed technique with the results of mathematical simulation.
Context Dependent Spectral Unmixing
2014-08-01
International Geoscience and Remote Sensing Symposium (IGARSS), Cape Town, South Africa , July 2009. HONORS AND AWARDS: 1. IEEE Outstanding CECS Student Award...COMMEND on the Usgs1C2M3 data across the 25 runs and at all noise levels: (a) SME , (b) SMAE, (c) AME. . . . . . . . . . . . . . 59 6.10 True (solid lines...identifying multiple sets of endmembers. In other words, the unmixing process is adapted to different regions of the spectral space. Another challenge with most
Spectral functions for composite fields and viscosity in hot scalar field theory
Wang, E; Heinz, Ulrich W; Wang, Enke; Zhang, Xiaofei; Heinz, Ulrich
1995-01-01
We derive a spectral representation for the two-point Green function for arbitrary composite field operators in Thermo Field Dynamics (TFD). A simple way for calculating the spectral density within TFD is pointed out and compared with known results from the imaginary time formalism. The method is applied to hot \\phi^4 theory. We give a compact derivation of the one-loop contribution to the shear viscosity and show that it is dominated by low-momentum plasmons.
Two-time Green's functions and spectral density method in nonextensive quantum statistical mechanics
Cavallo, A.; Cosenza, F.; De Cesare, L.
2007-01-01
We extend the formalism of the thermodynamic two-time Green's functions to nonextensive quantum statistical mechanics. Working in the optimal Lagrangian multipliers representation, the $q$-spectral properties and the methods for a direct calculation of the two-time $q$% -Green's functions and the related $q$-spectral density ($q$ measures the nonextensivity degree) for two generic operators are presented in strict analogy with the extensive ($q=1$) counterpart. Some emphasis is devoted to the...
Global nuclear material control model
Dreicer, J.S.; Rutherford, D.A.
1996-05-01
The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of a disposition program for special nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool that treats the nuclear fuel cycle as a complete system. Such a tool must represent the fundamental data, information, and capabilities of the fuel cycle including an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, and a framework supportive of national or international perspective. They have developed a prototype global nuclear material management and control systems analysis capability, the Global Nuclear Material Control (GNMC) model. The GNMC model establishes the framework for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material.
Rotation-independent representations for haptic movements
Shioiri, Satoshi; Yamazaki, Takanori; Matsumiya, Kazumichi; Kuriki, Ichiro
2013-01-01
The existence of a common mechanism for visual and haptic representations has been reported in object perception. In contrast, representations of movements might be more specific to modalities. Referring to the vertical axis is natural for visual representations whereas a fixed reference axis might be inappropriate for haptic movements and thus also inappropriate for its representations in the brain. The present study found that visual and haptic movement representations are processed independently. A psychophysical experiment examining mental rotation revealed the well-known effect of rotation angle for visual representations whereas no such effect was found for haptic representations. We also found no interference between processes for visual and haptic movements in an experiment where different stimuli were presented simultaneously through visual and haptic modalities. These results strongly suggest that (1) there are separate representations of visual and haptic movements, and (2) the haptic process has a rotation-independent representation. PMID:24005481
Simultaneous Spectral-Spatial Feature Selection and Extraction for Hyperspectral Images.
Zhang, Lefei; Zhang, Qian; Du, Bo; Huang, Xin; Tang, Yuan Yan; Tao, Dacheng
2016-09-12
In hyperspectral remote sensing data mining, it is important to take into account of both spectral and spatial information, such as the spectral signature, texture feature, and morphological property, to improve the performances, e.g., the image classification accuracy. In a feature representation point of view, a nature approach to handle this situation is to concatenate the spectral and spatial features into a single but high dimensional vector and then apply a certain dimension reduction technique directly on that concatenated vector before feed it into the subsequent classifier. However, multiple features from various domains definitely have different physical meanings and statistical properties, and thus such concatenation has not efficiently explore the complementary properties among different features, which should benefit for boost the feature discriminability. Furthermore, it is also difficult to interpret the transformed results of the concatenated vector. Consequently, finding a physically meaningful consensus low dimensional feature representation of original multiple features is still a challenging task. In order to address these issues, we propose a novel feature learning framework, i.e., the simultaneous spectral-spatial feature selection and extraction algorithm, for hyperspectral images spectral-spatial feature representation and classification. Specifically, the proposed method learns a latent low dimensional subspace by projecting the spectral-spatial feature into a common feature space, where the complementary information has been effectively exploited, and simultaneously, only the most significant original features have been transformed. Encouraging experimental results on three public available hyperspectral remote sensing datasets confirm that our proposed method is effective and efficient.
Recursive definition of global cellular-automata mappings
Feldberg, Rasmus; Knudsen, Carsten; Rasmussen, Steen
1994-01-01
A method for a recursive definition of global cellular-automata mappings is presented. The method is based on a graphical representation of global cellular-automata mappings. For a given cellular-automaton rule the recursive algorithm defines the change of the global cellular-automaton mapping as...
Embedding the global womb: Global child labour and the new policy agenda
Nieuwenhuys, O.; Aitken, S.; Lund, R.; Kjørholt, T.
2008-01-01
This paper seeks to understand how representations of child labour shape children’s lifeworlds globally. I use the term lifeworld to qualify the social world, which unevenly distributed symbolic resources contribute to misrecognize in favour of a mythical global order (cf. Couldry, 2003, 41 ff). My
Dunford-Shore, Brian H
2007-01-01
An analysis using a composition of currently-accepted theories is given. Starting with a synthesis of what may be generically termed ``paths'', analysis of representations for these ``paths'' is developed. Foreground and background interactions are explicitly treated by using a local representation that treats the two representations equally and symmetrically. A restriction coupling from the global space-time representation to local interaction source terms is treated in terms of mass and charge couplings. Rewriting the connection in terms of the global manifold and the coupled terms yields compatibility with Dirac and Klein-Gordan equations for electro-weak coupled particles and fields. Compatibility with currently-accepted theories that includes standard charge assignments, SU(3) confinement, and a definition for particle flavour generations is used to constrain and validate the composition and the analysis.
Ethier, Wilfred J.
2002-01-01
This paper addresses a complex of globalization issues: the effect of globalization on the skill premium; the effect of globalization on unemployment; the relative importance of globalization and exogenous technical change; the effect of globalization on the ability of national governments to conduct independent social policies. Thinking about these topics has been dominated by a large empirical literature concluding that trade has played a relatively minor role in the rise of the skill premi...
Philipsen, Lotte; Baggesgaard, Mads Anders
2013-01-01
In order to understand globalization, we need to consider what globalization is not. That is, in order to understand the mechanisms and elements that work toward globalization, we must, in a sense, read against globalization, highlighting the limitations of the concept and its inherent conflicts....... Only by employing this as a critical practice will we be analytically able to gain a dynamic understanding of the forces of globalization as they unfold today and as they have developed historically....
Quantum mechanics using Fradkin's representation
Shajesh, K V; Milton, Kimball A.
2005-01-01
Fradkin's representation is a general method of attacking problems in quantum field theory, having as its basis the functional approach of Schwinger. As a pedagogical illustration of that method, we explicitly formulate it for quantum mechanics (field theory in one dimension) and apply it to the solution of Schrodinger's equation for the quantum harmonic oscillator.
Adaptive representations for reinforcement learning
Whiteson, S.
2010-01-01
This book presents new algorithms for reinforcement learning, a form of machine learning in which an autonomous agent seeks a control policy for a sequential decision task. Since current methods typically rely on manually designed solution representations, agents that automatically adapt their own r
Acquired Equivalence Changes Stimulus Representations
Meeter, M.; Shohamy, D.; Myers, C. E.
2009-01-01
Acquired equivalence is a paradigm in which generalization is increased between two superficially dissimilar stimuli (or antecedents) that have previously been associated with similar outcomes (or consequents). Several possible mechanisms have been proposed, including changes in stimulus representations, either in the form of added associations or…
Octonionic matrix representation and electromagnetism
Chanyal, B. C. [Kumaun University, S. S. J. Campus, Almora (India)
2014-12-15
Keeping in mind the important role of octonion algebra, we have obtained the electromagnetic field equations of dyons with an octonionic 8 x 8 matrix representation. In this paper, we consider the eight - dimensional octonionic space as a combination of two (external and internal) four-dimensional spaces for the existence of magnetic monopoles (dyons) in a higher-dimensional formalism. As such, we describe the octonion wave equations in terms of eight components from the 8 x 8 matrix representation. The octonion forms of the generalized potential, fields and current source of dyons in terms of 8 x 8 matrix are discussed in a consistent manner. Thus, we have obtained the generalized Dirac-Maxwell equations of dyons from an 8x8 matrix representation of the octonion wave equations in a compact and consistent manner. The generalized Dirac-Maxwell equations are fully symmetric Maxwell equations and allow for the possibility of magnetic charges and currents, analogous to electric charges and currents. Accordingly, we have obtained the octonionic Dirac wave equations in an external field from the matrix representation of the octonion-valued potentials of dyons.
Minimal Surfaces for Hitchin Representations
Li, Qiongling; Dai, Song
2016-01-01
Given a reductive representation $\\rho: \\pi_1(S)\\rightarrow G$, there exists a $\\rho$-equivariant harmonic map $f$ from the universal cover of a fixed Riemann surface $\\Sigma$ to the symmetric space $G/K$ associated to $G$. If the Hopf differential of $f$ vanishes, the harmonic map is then minimal...
Reusable Lexical Representations for Idioms
Odijk, J.E.J.M.
2004-01-01
In this paper I introduce (1) a technically simple and highly theory-independent way for lexically representing flexible idiomatic expressions, and (2) a procedure to incorporate these lexical representations in a wide variety of NLP systems. The method is based on Structural EQuivalence Classes
Empirical studies on word representations
Suster, Simon
2016-01-01
One of the most fundamental tasks in natural language processing is representing words with mathematical objects (such as vectors). The word representations, which are most often estimated from data, allow capturing the meaning of words. They enable comparing words according to their semantic simila
Reusable Lexical Representations for Idioms
Odijk, J.E.J.M.
2004-01-01
In this paper I introduce (1) a technically simple and highly theory-independent way for lexically representing flexible idiomatic expressions, and (2) a procedure to incorporate these lexical representations in a wide variety of NLP systems. The method is based on Structural EQuivalence Classes for
Correct Representation of Conformational Equilibria.
Fulop, F.; And Others
1983-01-01
In representing conformational equilibria of compounds having only one chiral center, erroneous formulas showing different antipodes on the two sides of the equilibrium are rare. In contrast, with compounds having two or more chiral centers especially with saturated heterocycles, this erroneous representation occurs frequently in the chemical…
Representational Momentum in Older Adults
Piotrowski, Andrea S.; Jakobson, Lorna S.
2011-01-01
Humans have a tendency to perceive motion even in static images that simply "imply" movement. This tendency is so strong that our memory for actions depicted in static images is distorted in the direction of implied motion--a phenomenon known as representational momentum (RM). In the present study, we created an RM display depicting a pattern of…
Digital Image Representation and Access.
Mostafa, Javed
1994-01-01
Reviews the literature relating to the development and application of modern imaging technology between 1987 and 1993. Highlights include image representation, including image data, compression, and image formats; and image access, including indexing and modeling, user interface design, and distributed access. (143 references) (LRW)
Measurable representation of biconjugate integrands
Ottavio Caligaris
1986-11-01
Full Text Available We find here a representation of convex regularization of a non convex proper function and of a non convex proper normal integrand by means of a suitable multifunction which reveals to be very useful in existence theorems for non convex problems of calculus of variations.
Mental Representations of Social Status
Chiao, Joan Y.; Bordeaux, Andrew R.; Ambady, Nalni
2004-01-01
How do people think about social status? We investigated the nature of social status and number representations using a semantic distance latency test. In Study 1, 21 college students compared words connoting different social status as well as numbers, which served as a control task. Participants were faster at comparing occupations and numbers…
Bryan, Frank [Univ. of Washington, Seattle, WA (United States); Dennis, John [Univ. of Washington, Seattle, WA (United States); MacCready, Parker [Univ. of Washington, Seattle, WA (United States); Whitney, Michael [Univ. of Washington, Seattle, WA (United States)
2016-10-20
This project aimed to improve long term global climate simulations by resolving and enhancing the representation of the processes involved in the cycling of freshwater through estuaries and coastal regions. This was a collaborative multi-institution project consisting of physical oceanographers, climate model developers, and computational scientists. It specifically targeted the DOE objectives of advancing simulation and predictive capability of climate models through improvements in resolution and physical process representation.
Bryan, Frank [Univ. of Connecticut, Storrs, CT (United States); Dennis, John [Univ. of Connecticut, Storrs, CT (United States); MacCready, Parker [Univ. of Connecticut, Storrs, CT (United States); Whitney, Michael M. [Univ. of Connecticut, Storrs, CT (United States)
2016-09-30
This project aimed to improve long term global climate simulations by resolving and enhancing the representation of the processes involved in the cycling of freshwater through estuaries and coastal regions. This was a collaborative multi-institution project consisting of physical oceanographers, climate model developers, and computational scientists. It specifically targeted the DOE objectives of advancing simulation and predictive capability of climate models through improvements in resolution and physical process representation.
Reflections on the concept of representation and its application to China
Heberer, Thomas (Ed.)
2016-01-01
This paper presents both a literature review on the issue of political representation and the preliminary framework of a sub-project on new political claims of representation in China. It is primarily concerned with portraying and typing diverse schools of thought in both a "Western" and a Chinese context, while the sub-project is part of the French-German Joint Cooperation Project "New Political Representative Claims: A Global View: France, Germany, Brazil, China, India". The paper is organi...
Improved spectral vector error diffusion by dot gain compensation
Nyström, Daniel; Norberg, Ole
2013-02-01
Spectral Vector Error Diffusion, sVED, is an interesting approach to achieve spectral color reproduction, i.e. reproducing the spectral reflectance of an original, creating a reproduction that will match under any illumination. For each pixel in the spectral image, the colorant combination producing the spectrum closest to the target spectrum is selected, and the spectral error is diffused to surrounding pixels using an error distribution filter. However, since the colorant separation and halftoning is performed in a single step in sVED, compensation for dot gain cannot be made for each color channel independently, as in a conventional workflow where the colorant separation and halftoning is performed sequentially. In this study, we modify the sVED routine to compensate for the dot gain, applying the Yule-Nielsen n-factor to modify the target spectra, i.e. performing the computations in (1/n)-space. A global n-factor, optimal for each print resolution, reduces the spectral reproduction errors by approximately a factor of 4, while an n-factor that is individually optimized for each target spectrum reduces the spectral reproduction error to 7% of that for the unmodified prints. However, the improvements when using global n-values are still not sufficient for the method to be of any real use in practice, and to individually optimize the n-values for each target is not feasible in a real workflow. The results illustrate the necessity to properly account for the dot gain in the printing process, and that further developments is needed in order to make Spectral Vector Error Diffusion a realistic alternative for spectral color reproduction.
Interactive Global Illumination Effects Using Deterministically Directed Layered Depth Maps
Aalund, F. P.; Frisvad, Jeppe Revall; Bærentzen, Jakob Andreas
2015-01-01
A layered depth map is an extension of the well-known depth map used in rasterization. Multiple layered depth maps can be used as a coarse scene representation. We develop two global illumination methods which use said scene representation. The first is an interactive ambient occlusion method...
Leaf optical properties shed light on foliar trait variability at individual to global scales
Shiklomanov, A. N.; Serbin, S.; Dietze, M.
2016-12-01
Recent syntheses of large trait databases have contributed immensely to our understanding of drivers of plant function at the global scale. However, the global trade-offs revealed by such syntheses, such as the trade-off between leaf productivity and resilience (i.e. "leaf economics spectrum"), are often absent at smaller scales and fail to correlate with actual functional limitations. An improved understanding of how traits vary within communities, species, and individuals is critical to accurate representations of vegetation ecophysiology and ecological dynamics in ecosystem models. Spectral data from both field observations and remote sensing platforms present a potentially rich and widely available source of information on plant traits. In particular, the inversion of physically-based radiative transfer models (RTMs) is an effective and general method for estimating plant traits from spectral measurements. Here, we apply Bayesian inversion of the PROSPECT leaf RTM to a large database of field spectra and plant traits spanning tropical, temperate, and boreal forests, agricultural plots, arid shrublands, and tundra to identify dominant sources of variability and characterize trade-offs in plant functional traits. By leveraging such a large and diverse dataset, we re-calibrate the empirical absorption coefficients underlying the PROSPECT model and expand its scope to include additional leaf biochemical components, namely leaf nitrogen content. Our work provides a key methodological contribution as a physically-based retrieval of leaf nitrogen from remote sensing observations, and provides substantial insights about trait trade-offs related to plant acclimation, adaptation, and community assembly.
Spectral community detection in sparse networks
Newman, M E J
2013-01-01
Spectral methods based on the eigenvectors of matrices are widely used in the analysis of network data, particularly for community detection and graph partitioning. Standard methods based on the adjacency matrix and related matrices, however, break down for very sparse networks, which includes many networks of practical interest. As a solution to this problem it has been recently proposed that we focus instead on the spectrum of the non-backtracking matrix, an alternative matrix representation of a network that shows better behavior in the sparse limit. Inspired by this suggestion, we here make use of a relaxation method to derive a spectral community detection algorithm that works well even in the sparse regime where other methods break down. Interestingly, however, the matrix at the heart of the method, it turns out, is not exactly the non-backtracking matrix, but a variant of it with a somewhat different definition. We study the behavior of this variant matrix for both artificial and real-world networks an...
Spectral signatures of chirality
Pedersen, Jesper Goor; Mortensen, Asger
2009-01-01
We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...
Minfeng Gu; Y. L. Ai
2011-03-01
The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may be responsible for the spectral behaviour.
Spectrally encoded confocal microscopy
Tearney, G.J.; Webb, R.H.; Bouma, B.E. [Wellman Laboratories of Photomedicine, Massachusetts General Hospital, 50 Blossom Street, BAR 703, Boston, Massachusetts 02114 (United States)
1998-08-01
An endoscope-compatible, submicrometer-resolution scanning confocal microscopy imaging system is presented. This approach, spectrally encoded confocal microscopy (SECM), uses a quasi-monochromatic light source and a transmission diffraction grating to detect the reflectivity simultaneously at multiple points along a transverse line within the sample. Since this method does not require fast spatial scanning within the probe, the equipment can be miniaturized and incorporated into a catheter or endoscope. Confocal images of an electron microscope grid were acquired with SECM to demonstrate the feasibility of this technique. {copyright} {ital 1998} {ital Optical Society of America}
A spectral characterization of nonlinear normal modes
Cirillo, G. I.; Mauroy, A.; Renson, L.; Kerschen, G.; Sepulchre, R.
2016-09-01
This paper explores the relationship that exists between nonlinear normal modes (NNMs) defined as invariant manifolds in phase space and the spectral expansion of the Koopman operator. Specifically, we demonstrate that NNMs correspond to zero level sets of specific eigenfunctions of the Koopman operator. Thanks to this direct connection, a new, global parametrization of the invariant manifolds is established. Unlike the classical parametrization using a pair of state-space variables, this parametrization remains valid whenever the invariant manifold undergoes folding, which extends the computation of NNMs to regimes of greater energy. The proposed ideas are illustrated using a two-degree-of-freedom system with cubic nonlinearity.
Architecture design in global and model-centric software development
Heijstek, Werner
2012-01-01
This doctoral dissertation describes a series of empirical investigations into representation, dissemination and coordination of software architecture design in the context of global software development. A particular focus is placed on model-centric and model-driven software development.
Architecture design in global and model-centric software development
Heijstek, Werner
2012-01-01
This doctoral dissertation describes a series of empirical investigations into representation, dissemination and coordination of software architecture design in the context of global software development. A particular focus is placed on model-centric and model-driven software development.
Li, Peter Ping
2013-01-01
Global strategy differs from domestic strategy in terms of content and process as well as context and structure. The content of global strategy can contain five key elements, while the process of global strategy can have six major stages. These are expounded below. Global strategy is influenced...... by rich and complementary local contexts with diverse resource pools and game rules at the national level to form a broad ecosystem at the global level. Further, global strategy dictates the interaction or balance between different entry strategies at the levels of internal and external networks....
Simulated annealing spectral clustering algorithm for image segmentation
Yifang Yang; and Yuping Wang
2014-01-01
The similarity measure is crucial to the performance of spectral clustering. The Gaussian kernel function based on the Euclidean distance is usual y adopted as the similarity mea-sure. However, the Euclidean distance measure cannot ful y reveal the complex distribution data, and the result of spectral clustering is very sensitive to the scaling parameter. To solve these problems, a new manifold distance measure and a novel simulated anneal-ing spectral clustering (SASC) algorithm based on the manifold distance measure are proposed. The simulated annealing based on genetic algorithm (SAGA), characterized by its rapid conver-gence to the global optimum, is used to cluster the sample points in the spectral mapping space. The proposed algorithm can not only reflect local and global consistency better, but also reduce the sensitivity of spectral clustering to the kernel parameter, which improves the algorithm’s clustering performance. To efficiently ap-ply the algorithm to image segmentation, the Nystr¨om method is used to reduce the computation complexity. Experimental re-sults show that compared with traditional clustering algorithms and those popular spectral clustering algorithms, the proposed algorithm can achieve better clustering performances on several synthetic datasets, texture images and real images.
Multipolar representation of protein structure
Bourne Philip E
2006-05-01
Full Text Available Abstract Background That the structure determines the function of proteins is a central paradigm in biology. However, protein functions are more directly related to cooperative effects at the residue and multi-residue scales. As such, current representations based on atomic coordinates can be considered inadequate. Bridging the gap between atomic-level structure and overall protein-level functionality requires parameterizations of the protein structure (and other physicochemical properties in a quasi-continuous range, from a simple collection of unrelated amino acids coordinates to the highly synergistic organization of the whole protein entity, from a microscopic view in which each atom is completely resolved to a "macroscopic" description such as the one encoded in the three-dimensional protein shape. Results Here we propose such a parameterization and study its relationship to the standard Euclidian description based on amino acid representative coordinates. The representation uses multipoles associated with residue Cα coordinates as shape descriptors. We demonstrate that the multipoles can be used for the quantitative description of the protein shape and for the comparison of protein structures at various levels of detail. Specifically, we construct a (dissimilarity measure in multipolar configuration space, and show how such a function can be used for the comparison of a pair of proteins. We then test the parameterization on a benchmark set of the protein kinase-like superfamily. We prove that, when the biologically relevant portions of the proteins are retained, it can robustly discriminate between the various families in the set in a way not possible through sequence or conventional structural representations alone. We then compare our representation with the Cartesian coordinate description and show that, as expected, the correlation with that representation increases as the level of detail, measured by the highest rank of multipoles
The extended loop representation of quantum gravity
Di Bartolo, C; Griego, J R
1995-01-01
A new representation of Quantum Gravity is developed. This formulation is based on an extension of the group of loops. The enlarged group, that we call the Extended Loop Group, behaves locally as an infinite dimensional Lie group. Quantum Gravity can be realized on the state space of extended loop dependent wavefunctions. The extended representation generalizes the loop representation and contains this representation as a particular case. The resulting diffeomorphism and hamiltonian constraints take a very simple form and allow to apply functional methods and simplify the loop calculus. In particular we show that the constraints are linear in the momenta. The nondegenerate solutions known in the loop representation are also solutions of the constraints in the new representation. The practical calculation advantages allows to find a new solution to the Wheeler-DeWitt equation. Moreover, the extended representation puts in a precise framework some of the regularization problems of the loop representation. We sh...
FILMIC REPRESENTATION IN POSTCOLONIAL DISCOURSE: A ...
implicated in the public debate about representation. Representations come in .... A mapping of the dominant discourse, a reading and expressing of its .... This relationship, not only boosted Europe and developed. America, also, Africa was ...
Representation learning for cross-modality classification
G. van Tulder (Gijs); M. de Bruijne (Marleen)
2017-01-01
textabstractDifferences in scanning parameters or modalities can complicate image analysis based on supervised classification. This paper presents two representation learning approaches, based on autoencoders, that address this problem by learning representations that are similar across domains. Bot
The communicative constitution of representation and exclusion
Wessel, van M.G.J.
2014-01-01
In the light of current debate on representation, specifically engaging with literature showing how representation is communicatively constituted, this paper empirically shows how exclusion also can be seen as communicatively constituted. The interpretive approach toward communication employed in th
Multiple Interactive Representations for Fractions Learning
Feenstra, Laurens; Aleven, Vincent; Rummel, Nikol; Taatgen, Niels; Aleven,; Kay, J; Mostow, J
2010-01-01
Multiple External Representations (MERs) have been used successfully in instructional activities, including fractions However, students often have difficulties making the connections between the MERs spontaneously We argue that interactive fraction representations may help students in discovering re
The communicative constitution of representation and exclusion
Wessel, van M.G.J.
2014-01-01
In the light of current debate on representation, specifically engaging with literature showing how representation is communicatively constituted, this paper empirically shows how exclusion also can be seen as communicatively constituted. The interpretive approach toward communication employed in th
Some Representations of Unified Voigt Functions
M. KAMARUJJAMA; Dinesh SINGH
2005-01-01
The authors derive a set of unified representations of the Voigt functions in terms of familiar special functions of Mathematical Physics. Some deductions from these representations are also considered.
A geometric representation for the Proca model
Camacaro, J; Leal, L C; Camacaro, Jaime; Gaitan, Rolando; Leal, Lorenzo
1996-01-01
The Proca model is quantized in an open-path dependent representation that generalizes the Loop Representation of gauge theories. The starting point is a gauge invariant Lagrangian that reduces to the Proca Lagrangian when certain gauge is selected.
Attitudes, social representations and social attitudes
Farr, Robert, M.
1994-01-01
This paper plays the role of the devil's advocate in relation to Colin Fraser's paper "attitudes, social representations and widespread beliefs". It argues for the alternative perspective which Colin identifies that social representations and social attitudes are epistemologically incompatible theories.
Kernel representations for behaviors over finite rings
Kuijper, M.; Pinto, R.; Polderman, J.W.; Yamamoto, Y.
2006-01-01
In this paper we consider dynamical systems finite rings. The rings that we study are the integers modulo a power of a given prime. We study the theory of representations for such systems, in particular kernel representations.
Multiple External Representations: Bridges or Barriers to Climate Literacy?
Holzer, M. A.
2012-12-01
The continuous barrage of science related headlines and other media sources warn us of the need to heed the imperative for a science literate society. Climate change, genetics, evolution are a few of the charged and complex scientific topics requiring public understanding of the science to fully grasp the enormous reach of these topics in our daily lives. For instance, our global climate is changing as evidenced by the analysis of Earth observing satellite data, in-situ data, and proxy data records. How we as a global society decide to address the needs associated with a changing climate are contingent upon having a population that understands how the climate system functions, and can therefore make informed decisions on how to mitigate the effects of climate change. Communication in science relies heavily on the use of multiple representations to support the claims presented. However, these multiple representations require spatial and temporal skills to interpret information portrayed in them, and how a person engages with complex text and the multiple representations varies with the level of expertise one has with the content area. For example, a climatologist will likely identify anomalous data more quickly than a novice when presented with a graph of temperature change over time. These representations are used throughout textbooks as well as popular reading materials such as newspapers and magazines without much consideration for how a reader engages with complex text, diagrams, images, and graphs. If the ability to read and interact with scientific text found in popular literature is perceived as a worthy goal of scientific literacy, then it is imperative that readers understand the relationship between multiple representations and the text while interacting with the science literature they are reading. For example, in climate related articles multiple representations not only support the content, but they are part of the content not to be overlooked by a
A 3-layer coding scheme for biometry template protection based on spectral minutiae
Shao, X.; Xu, H.; Veldhuis, Raymond N.J.; Slump, Cornelis H.
2011-01-01
Spectral Minutiae (SM) representation enables the combination of minutiae-based fingerprint recognition systems with template protection schemes based on fuzzy commitment, but it requires error-correcting codes that can handle high bit error rates (i.e. above 40%). In this paper, we propose a
Representation of Islam and Muslims' Image in Computer Games
Fereidoon Najafi Shabankareh
2015-01-01
Full Text Available At the digital era, mass media have sensibly altered the social spheres through broadcasting and promoting various thoughts and different life styles. The computer games industry also acts as an influential medium in changing user behavior so as to form our cognition and perception of the world by constructing, transferring and recurring a variety of representations. In reviewing media texts, the ideological elements existing beyond them and the way they affect the audience's insight must be seriously addressed. In recent years, we have been witnessing a critical focus on Moslems' image in Western Media and computer games, in specific. This article has an attempt to investigate figurative representation of Arabs and Moslems, narrative structure and games stages in order for studying the methods of imaging of Arabs and Moslems in computer games. So, 7 ideological computer games produced in recent years regarding Moslems and Islam were examined using semiotic analysis qualitative method. Here, an integrative approach is conducted in which Stewart Hall's representation theories are at the center of theoretical debates and then Edward Said's insight into Orientalism is presented as an instance of representation theory application. We conclude that-in a complex integrative movement-Global Imperialism tries to create a sort of Islam-phobia in public opinion across the world and represents its own desirable image of Islam and Islamic civilization in mind of the audience.
Transfinite tree quivers and their representations
Enochs, E; Özdemir, S
2012-01-01
The idea of "vertex at the infinity" naturally appears when studying indecomposable injective representations of tree quivers. In this paper we formalize this behavior and find the structure of all the indecomposable injective representations of a tree quiver of size an arbitrary cardinal $\\kappa$. As a consequence the structure of injective representations of noetherian $\\kappa$-trees is completely determined. In the second part we will consider the problem whether arbitrary trees are source injective representation quivers or not.
PHISHING WEB IMAGE SEGMENTATION BASED ON IMPROVING SPECTRAL CLUSTERING
Li Yuancheng; Zhao Liujun; Jiao Runhai
2011-01-01
Abstract This paper proposes a novel phishing web image segmentation algorithm which based on improving spectral clustering.Firstly,we construct a set of points which are composed of spatial location pixels and gray levels from a given image.Secondly,the data is clustered in spectral space of the similar matrix of the set points,in order to avoid the drawbacks of K-means algorithm in the conventional spectral clustering method that is sensitive to initial clustering centroids and convergence to local optimal solution,we introduce the clone operator,Cauthy mutation to enlarge the scale of clustering centers,quantum-inspired evolutionary algorithm to find the global optimal clustering centroids.Compared with phishing web image segmentation based on K-means,experimental results show that the segmentation performance of our method gains much improvement.Moreover,our method can convergence to global optimal solution and is better in accuracy of phishing web segmentation.
Narula, Rajneesh
Technology and globalization are interdependent processes. Globalization has a fundamental influence on the creation and diffusion of technology, which, in turn, affects the interdependence of firms and locations. This volume examines the international aspect of this interdependence at two levels...
... globalhealth/what/default.htm) CDC protects Americans through global health. frame support disabled and/or not supported ... Public Health Emergencies More stories Infographic More infographics Global Health & You OUTBREAKS DISEASES & CONDITIONS TRAVEL CDC JOBS ...
Hamiltonian indices and rational spectral densities
Byrnes, C. I.; Duncan, T. E.
1980-01-01
Several (global) topological properties of various spaces of linear systems, particularly symmetric, lossless, and Hamiltonian systems, and multivariable spectral densities of fixed McMillan degree are announced. The study is motivated by a result asserting that on a connected but not simply connected manifold, it is not possible to find a vector field having a sink as its only critical point. In the scalar case, this is illustrated by showing that only on the space of McMillan degree = /Cauchy index/ = n, scalar transfer functions can one define a globally convergent vector field. This result holds both in discrete-time and for the nonautonomous case. With these motivations in mind, theorems of Bochner and Fogarty are used in showing that spaces of transfer functions defined by symmetry conditions are, in fact, smooth algebraic manifolds.
Paired structures in knowledge representation
Montero, J.; Bustince, H.; Franco de los Ríos, Camilo;
2016-01-01
In this position paper we propose a consistent and unifying view to all those basic knowledge representation models that are based on the existence of two somehow opposite fuzzy concepts. A number of these basic models can be found in fuzzy logic and multi-valued logic literature. Here it is clai......In this position paper we propose a consistent and unifying view to all those basic knowledge representation models that are based on the existence of two somehow opposite fuzzy concepts. A number of these basic models can be found in fuzzy logic and multi-valued logic literature. Here...... of paired structures, generated from two paired concepts together with their associated neutrality, all of them to be modeled as fuzzy sets. In this way, paired structures can be viewed as a standard basic model from which different models arise. This unifying view should therefore allow a deeper analysis...
Representation theory of finite monoids
Steinberg, Benjamin
2016-01-01
This first text on the subject provides a comprehensive introduction to the representation theory of finite monoids. Carefully worked examples and exercises provide the bells and whistles for graduate accessibility, bringing a broad range of advanced readers to the forefront of research in the area. Highlights of the text include applications to probability theory, symbolic dynamics, and automata theory. Comfort with module theory, a familiarity with ordinary group representation theory, and the basics of Wedderburn theory, are prerequisites for advanced graduate level study. Researchers in algebra, algebraic combinatorics, automata theory, and probability theory, will find this text enriching with its thorough presentation of applications of the theory to these fields. Prior knowledge of semigroup theory is not expected for the diverse readership that may benefit from this exposition. The approach taken in this book is highly module-theoretic and follows the modern flavor of the theory of finite dimensional ...
Berry phase in Heisenberg representation
Andreev, V. A.; Klimov, Andrei B.; Lerner, Peter B.
1994-01-01
We define the Berry phase for the Heisenberg operators. This definition is motivated by the calculation of the phase shifts by different techniques. These techniques are: the solution of the Heisenberg equations of motion, the solution of the Schrodinger equation in coherent-state representation, and the direct computation of the evolution operator. Our definition of the Berry phase in the Heisenberg representation is consistent with the underlying supersymmetry of the model in the following sense. The structural blocks of the Hamiltonians of supersymmetrical quantum mechanics ('superpairs') are connected by transformations which conserve the similarity in structure of the energy levels of superpairs. These transformations include transformation of phase of the creation-annihilation operators, which are generated by adiabatic cyclic evolution of the parameters of the system.
Representations of mad cow disease.
Washer, Peter
2006-01-01
This paper examines the reporting of the story of Bovine Spongiform Encephalopathy (BSE) and its human derivative variant Creutzfeld-Jacob Disease (vCJD) in the British newspapers. Three 'snapshots' of newspaper coverage are sampled and analysed between the period 1986 and 1996 focusing on how representations of the disease evolved over the 10-year period. Social representations theory is used to elucidate how this new disease threat was conceptualised in the newspaper reporting and how it was explained to the UK public. This paper examines who or what was said to be at risk from the new disease, and whether some individuals or groups held to blame for the diseases' putative origins, the appearance of vCJD in human beings, and its spread.
Time representations in social science.
Schulz, Yvan
2012-12-01
Time has long been a major topic of study in social science, as in other sciences or in philosophy. Social scientists have tended to focus on collective representations of time, and on the ways in which these representations shape our everyday experiences. This contribution addresses work from such disciplines as anthropology, sociology and history. It focuses on several of the main theories that have preoccupied specialists in social science, such as the alleged "acceleration" of life and overgrowth of the present in contemporary Western societies, or the distinction between so-called linear and circular conceptions of time. The presentation of these theories is accompanied by some of the critiques they have provoked, in order to enable the reader to form her or his own opinion of them.
Time representations in social science
Schulz, Yvan
2012-01-01
Time has long been a major topic of study in social science, as in other sciences or in philosophy. Social scientists have tended to focus on collective representations of time, and on the ways in which these representations shape our everyday experiences. This contribution addresses work from such disciplines as anthropology, sociology and history. It focuses on several of the main theories that have preoccupied specialists in social science, such as the alleged “acceleration” of life and overgrowth of the present in contemporary Western societies, or the distinction between so-called linear and circular conceptions of time. The presentation of these theories is accompanied by some of the critiques they have provoked, in order to enable the reader to form her or his own opinion of them. PMID:23393420
Sparse representation of astronomical images.
Rebollo-Neira, Laura; Bowley, James
2013-04-01
Sparse representation of astronomical images is discussed. It is shown that a significant gain in sparsity is achieved when particular mixed dictionaries are used for approximating these types of images with greedy selection strategies. Experiments are conducted to confirm (i) the effectiveness at producing sparse representations and (ii) competitiveness, with respect to the time required to process large images. The latter is a consequence of the suitability of the proposed dictionaries for approximating images in partitions of small blocks. This feature makes it possible to apply the effective greedy selection technique called orthogonal matching pursuit, up to some block size. For blocks exceeding that size, a refinement of the original matching pursuit approach is considered. The resulting method is termed "self-projected matching pursuit," because it is shown to be effective for implementing, via matching pursuit itself, the optional backprojection intermediate steps in that approach.
Vivi Triana
2008-03-01
Full Text Available Pemanasan global (global warming pada dasarnya merupakan fenomena peningkatan temperature global dari tahun ke tahun karena terjadinya efek rumah kaca (greenhouse effect yang disebabkan oleh meningkatnya emisi gas-gas seperti karbondioksida (CO2, metana (CH4, dinitrooksida (N2O dan CFC sehingga energy matahari terperangkap dalam atmosfer bumi. Berbagai literatur menunjukkan kenaikan temperatur global termasuk Indonesia yang terjadi pada kisaran 1,5 – 40 °C pada akhir abad 21.
Representation of the Alpine snowpack in CMIP5 models
Terzago, Silvia; Palazzi, Elisa; von Hardenberg, Jost; Provenzale, Antonello
2016-04-01
Global Climate Models (GCMs) still have too coarse spatial resolution to adequately reproduce the small-scale variability of precipitation and snowpack in orographically complex areas but increasingly higher resolutions are currently being introduced for the next generation of models. As a preliminary step a comparative assessment of the performances of the current, state-of-art GCMs in the representation of the snowpack characteristics is needed. Our study investigates how the GCMs participating in the Coupled Models Intercomparison Project phase 5 (CMIP5) represent the snow water equivalent and snow depth climatology over the Greater Alpine Region (4-19°E, 43-49°N) during the historical period 1980-2005. We compare the CMIP5 model outputs to the available satellite and reanalysis products, including Global Monthly EASE-Grid Snow Water Equivalent Climatology, Climate Forecast System Reanalysis, Modern Era-Retrospective analysis for Research and Applications, ERA-Interim/Land and 20th Century reanalyses, highlighting common features and discrepancies. We also explore the models spread in the representation of the snow seasonal cycle and its projected changes for the XXI century in RCP4.5 and RCP8.5 scenarios, discussing the results in the frame of the latest literature studies. The present analysis aims at providing a comprehensive picture of the current uncertainties in the representation of snowpack by the major gridded snow datasets derived from remote sensing, reanalyses and model simulations, in condition of complex orography.
Phases of stable representations of quivers
Engenhorst, Magnus
2015-01-01
We consider stable representations of non-Dynkin quivers with respect to a central charge. On one condition the existence of a stable representation with self-extensions implies the existence of infinitely many stables without self-extensions. In this case the phases of the stable representations approach one or two limit points. In particular, the phases are not dense in two arcs.
On Nambu-Lie 3-algebra representations
Sochichiu, Corneliu
2008-01-01
We propose a recipe to construct matrix representations of Nambu--Lie 3-algebras in terms of irreducible representations of underlying Lie algebra. The case of Euclidean four-dimensional 3-algebra is considered in details. We find that representations of this 3-algebra are not possible in terms of only Hermitian matrices in spite of its Euclidean nature.
37 CFR 350.2 - Representation.
2010-07-01
... 37 Patents, Trademarks, and Copyrights 1 2010-07-01 2010-07-01 false Representation. 350.2 Section... ROYALTY JUDGES RULES AND PROCEDURES GENERAL ADMINISTRATIVE PROVISIONS § 350.2 Representation. Individual... representation that the attorney is a member of the bar, in one or more states, in good standing. ...
24 CFR 180.305 - Representation.
2010-04-01
... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Representation. 180.305 Section 180... Representation. (a) HUD is represented by the General Counsel. (b) Any party may appear on his/her/its own behalf... State. The attorney's representation that he/she is in good standing before any of these courts is...
2010-01-01
... 4 Accounts 1 2010-01-01 2010-01-01 false Representation. 28.25 Section 28.25 Accounts GOVERNMENT... Parties, Practitioners and Witnesses § 28.25 Representation. (a) All parties to a petition may be..., in the petition or responsive pleading. Any subsequent changes in representation shall also be in...
75 FR 32273 - Representation Election Procedure
2010-06-08
... 29 CFR Parts 1202 and 1206 RIN 3140-ZA00 Representation Election Procedure AGENCY: National Mediation... delaying the effective date of its rule regarding representation election procedures from June 10, 2010 to... Representation Election Procedure Rule have been made. The NMB will notify participants if there are any further...
33 CFR 20.301 - Representation.
2010-07-01
... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Representation. 20.301 Section 20... Motions § 20.301 Representation. (a) A party may appear— (1) Without counsel; (2) With an attorney; or (3... United States. A personal representation of membership is sufficient proof, unless the ALJ orders more...